Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
iO~35~;~
This invention relates to glass toughening methods
and in particular to the toughening of glass sheets by
quenching in a chilling medium, e.g. a chilling liquid.
One use of such sheets is in the manufacture of windows
for vehicles, for example motor vehicle windscreens and
aircraft windscreens.
A glass sheet toughened by the method of the present
invention may be used alone as a vehicle windscreen, or
may be either used as one of the laminates of a composite
laminated glass windscreen.
It is customary to laminate two thin sheets of glass
together to form a windscreen using an interlayer of trans-
parent plastics material, for example polyvinylbutyral.
In such a windscreen both sheets may be of annealed glass
or both of toughened glass and in a current proposal a
laminated windscreen having a dual fracture characteristic
is fabricated using a sheet of annealed glass as the outer
sheet and a sheet of toughened glass as the inner sheet.
With such a windscreen visibility is retained even
if the outer annealed sheet is fractured by a sharp flying
stone, while the inner toughened sheet fragments rapidly
when struck by the head of an occupant of the vehicle.
Usually in the manufacture of a toughened glass sheet
for a windscreen the sheet of flat glass is first cut to
the shape appropriate to the styling of the vehicle in
which the windscreen is to be fitted and the cut edges
of the sheets are then polished to remove defects resulting
from the cutting operation. Then the glass is heated to
a temperature suitable for bending, during traverse through
a heating furnace while suspended by tongs from an overhead
conveyor which then conveys the glass between vertical
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bending dies which close on to the glass sheet and bend ,
the sheet to the desired curvature.
Thereafter the bending dies are opened and the glass
is conveyed between blowing frames where the glass is
toughened, or the glass is conveyed from the bending dies
through an annealing lehr when an annealed sheet is required.
Throughout this process the glass i5 suspended from tongs
which grip the upper edge of the sheet.
In a process for bending two sheets of glass which
are to have accurately matching curvature for subsequent
lamination it has been customary to bend the glass by a
sag-bending process in which the two sheets lying one on
top of the other are placed horizontally on a sag-bending
mould and then conveyed through an oven where the glass
sheets are heated and sag together to the desired matching
curvature,
In a more recently developed process for the toughen-
ing of glass, a sheet of flat glass cut to the desired
shape is suspended by tongs in a heating furnace having
an open mouth in the floor of the furnace, and when heated
to bending temperature is lowered to a location between
bending dies which close on to the suspended sheet and
bend it to a desired curvature before the sheet is further
lowered through a pre-cooling stage in which cooling air
is blown on to the glass surfaces, followed immediately
by quenching in a quenching liquid, which may for example
be a mineral oil or a mineral oil with a minor amount of
low boiling point additive. Toluene or carbon tetra-
chloride are suitable additives. This process has been
particularly effective for the production of high strength
glass for aircraft windscreens, and bent and toughened
'-'``` 10~35~
glass of thickness 1~5 to 3 ~m fox use in the manufacture of
laminated w~ndscreens ~or motor vehicles.
It has been found to be advantageous in terms of maintaining
optical quality standards of the toughened glass and in order
to minimise glass fracture during quenching, to have the part
of the glass which contacts the chilling medium first, at a
higher temperature than the opposite margin of the glass, it is
a main object of the present invention to provide an improved
method which employs this discovery.
According to the invention there is provided a glass
toughening method in which a glass sheet is advanced through a
heating zone into a chilling medium to quench the sheet,
characterised by, prior to quenching, heating the leading edge
of the sheet which contacts the chilling medium first, to a
higher temperature than the trailing edge of the sheet.
The speed of the glass sheet through the heating zone may
be varied so that the leading edge of the sheet has a longer
time in the heating zone than the trailing edge.
The heating of the glass sheet can also be handled so that
its leading edge is 5C to 40C hotter than the trailing edge,
and so that a substantially linear temperature gradient exists
from the leading edge to the trailing edge of the sheet.
An embodiment of the invention will now be described,
by way of example, with reference to the accompanying drawings
in which:-
Figure 1 is an elevation, partly in section, of
apparatus for operating the invention
including a loading station for flat glass
sheets, a heating furnace, bending apparatus
and liquid quenching apparatus.
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Figure 2 is a side elevation of the loading.
station and the inlet end of the
furnace of Figure 1, partly broken
away to illustrate upright support
rollers and associated bottom rollers
at the loading station and in the
furnace,
Figure 3 is a section on line V-V of Figure 2,
showing the disposition of heaters in
the furnace,
Figure 4 is a front elevation of a carriage on
which a glass sheet is supported for
transportation through the furnace,
Figure 5 is a section on line X-X of Figure 4
also illustrating the disposition of
the carriage and the glass sheet relative
to the upright rollers and the bottom
stub rollers of the furnace,
Figure 6 illustrates an arrangement of electrical
heaters on one side wall of the furnace,
Figure 7 shows schematically a thyristor-controlled
circuit for controlling current supply to
a group of heaters of Figure 6,
Figure 8 illustrates an arrangement of electrical
heaters on the opposite side wall of the
furnace, appearing with Fig. 4,
Figure 9 is a more detailed view of part of Figure
1 illustrating generally a tilting box
which encloses male and female bending
dies and is mounted to be tilted from an
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~435ti9
angle matching the angle of the upright
rollers in the furnace to a horizontal
disposition above thermal treatment
apparatus through which bent glass sheets
are lower-ed,
Figures lOA and lOB together constitute a part-
sectional view of the tilting box on
line XVIII-XVIII of Figure 9,
Figure 11 is a horizontal cross-section through
the male bending die,
Figures 12A, 12B and 12C together form an overall
view in elevation of a tong bar from
which tongs are suspended for gripping
the upper edge of a glass sheet between
the male and female bending dies, and
of the hoist mechanism from which the
tong bar is suspended,
Figures 13A, 13B and 13C together show an end elevation
of a part of the hoist mechanism and the
tong bar suspension,
Figure 14 is a vertical section through panels of
boost heaters which are located beneath
the tilting box and between which a bent
glass sheet is lowered for heating prior
to toughening,
Figure 15 is a generalised sectional view through
the lower part of the pit below the
tilting box showing a pre-cooling sta-~e
and a tank of chilling liquid in more
detail,
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Figure 16 is a diagrammatic hydraulic control
circuit for the tilting box, the
bending dies and the tong bar suspension
system,
Figure 17 is a diagrammatic~pneumatic circuit
for operating the tong opening mechanism,
brakes on the hoist mechanism, and speed
control of the hoist motor, and
Figures 18, 19 and 20 are circuit diagrams of switch-
ing circuits for operating the hydraulic
and pneumatic circuits of Figures 16 and 17.
Figure 1 illustrates the general arrangement of
apparatus for carrying out the invention, for heating, bending
and toughening glass sheets which are conveyed through the
apparatus throughout that operation in an upright disposition,
that is in a near-vertical disposition during heating, and
in ~ vertical disposition after bending and when being quenched
in a chilling liquid.
The furnace chamber is indicated generally at 1 and
has a cross-section of rectangular form with a specially
shaped floor as will be described, and is supported at an angle
to th~ vertical of about 5 in a basic girder framework which
includes base girders 2 which are joined at their ends by
cross girders 3. From the ends of the base girders there
extend upright girders 4 which are at an angle of for example
5 to the vertical as more clearly shown in Figures 4 and 5.
The upper ends of the upright girders 4 are connected to-
gether by cross girders 5 which are inclined at an angle of
about 5 below the horizontal.
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10~;~5~
The floor of the furnace is supported by cross
girders 6 which extend below the lower ends of the
upright girders 4 and are shaped to support the shaped
floor of the furnace. The downwardly sloping step in
the furnace floor which slopes towards the bottom of
one side wall permits any cullet which falls to the
floor to be collected at outlets near the bottom of
the side walls, which outlets are closed by hinged
doors.
- 10 The furnace 1 is a refractory-lined, metal struc-
ture having side walls which extend upwardly from the
floor and an integral roof construction which is hung
from the upper girders 5. Longitudinal girders 7 fixed
along the top of the furnace provide support for gear
boxes housing the upper ends of a plurality of spaced-
apart, upright, near-vertical rollers 8 which define an
in~lined support for sheets of glass 9 which are to be
conveyed through the furnace 1 for bending and subsequent
liquid-quench toughening or annealing.
The rollers 8 are asbestos-covered or of heat-
resisting stainless steel and are each mounted at an
angle of from 2 to 10 to the vertical e.g. 5, and
form part of a conveyor for the sheets 9 which extends
right through the furnace 1 from a loading station
indicated generally at 10 to a bending station 11.
The rollers are 6.5 cm in diameter and are spaced 19
cm apart in the furnace. The spacing between rollers
may be up to 30 cm in the region of the outlet end of
the furnace where the glass reaches its final temperature.
At the inlet end of the furnace where the glass is at a
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low temperature, the spacing may be greater, for example
38 cm or more providing there are sufficient rollers to
support the whole length of the glass sheet in a stable
condition.
The conveyor includes a movable support in the form
of a carriage 12 on which the lower edge of the glass
sheet 9 is seated, and bottom stub rollers 13 which
project through spaces between the upright rollers 8
near the bottom of those rollers both at the loading
station 10 and in the furnace 1, and driving means for
advancing the carriage 12 through the furnace with the
glass sheet 9 leaning against the upright rollers 8.
The bottom stub rollers 13, which are also of heat-
resistant stainless steel or asbestos covered, are mounted,
in the embodiment illustrated, at acute angle of 50 to
the upright rollers 8.
The carriage 12 is shown in more detail in Figures
4 and 5 and is of V-section having faces which are at an
angle to each other matching the acute angle between the
axes of the upright rollers 8 and the stub rollers 13.
These faces of the carriage engage frictionally both the
rollers 8 and 13, which are driven at the same speed as
will be described, so that the carriage carrying the sheet
is advanced through the furnace by the frictional engagement
with both the bottom rollers 13 and the upright rollers 8.
Initially, only the upper edge of the sheet rests on the
surface of the upright rollers 8 but as the sheet is
heated during its advance through the furnace the sheet
tends to relax against the transient support for the
sheet provided by the rotating surfaces of the rollers 8.
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~0435~5~
The bottom edge of the sheet is seated on specially
shaped supports on the carriage and is slightly offset
on the carriage 12 from the roller surfaces, so that
a certain relaxation with deformation only below a
predetermined limit can take place while ensuring that
the sheet remains in its upright disposition and that
the lower edge of the sheet does not become displaced
from the carriage.
In operation thermal conditions in the furnace are
set and the time taken by the carriage carrying the
glass sheet to traverse the heating zone is also set,
in dependence on the glass thickness, the height of
the glass sheet, the angle of the support rollers to
the vertical and the amount of offset of the lower edge
of the glass sheet from the support rollers so as to
achieve a predetermined temperature condition of the
glass, the thermal and time settings being such as to
permit the glass sheet as it is heated to relax against
the support rollers only by an amount less than the
maximum deformation of the glass sheet which is acceptable
prior to bending. The heating of the glass sheet ~s
it traverses the heating zone is described in Canadian
Patent Application Serial No. 204,721.
Usually the offset distance is about 2 mm to 4 mm
and the maximum acceptable amount of deformation depends
on the quality, particularly the optical quality required
in the final product. In *he case of glass sheets which
are to be incorporated in vehicle windscreens, for which
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10~;~5~i~
the optical requirements are stringent, it may only be
acceptable to permit deformation of the glass sheets
up to a point in the initial relaxation before the
appearance of the bulge. A bulge of up to 0.5 mm
may be acceptable.
Where the quality requirements are less critical
a bulge greater than 0.5 mm may be permissible, for
example up to 4.0 mm.
It has been found that the near vertical angle at
which the sheet is initially supported when leaning
against the rollers 8 may be in the range 2 to 10
for the heating of sheets of soda-lime-silica glass
of thickness in the range 1.5 mm to 15 mm to a temperature
in the range 580C to 680C or even 700C which
temperature range encompasses the usual temperature to
which soda-lime-silica glass is heated prior to bending
or toughening.
The upright, near-vertical rollers 8 are supported
at their lower ends by self-aligning bearing blocks
which are carried by parallel girders which run beneath
the furnace floor and are supported on the specially
shaped cross-girders 6.
The first ten upright rollers 8 of the plurality
of upright rollers constitute the loading station 10,
and five bottom stub rollers 13 are respectively located
between alternate spaces between the upright rollers 8.
At the bending station there are horizontally
disposed bending dies 15 and 16 which are shown more
particularly in Figures 9, lOA and lOB. The female
die 15 is a ring frame die which co-operates with a male
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die 16 having a continuous bending surface, indicated
in more detail in Figure 11. The dies illustrated
are rigid dies but articulated wing dies with pivoting
mechanism of known kind may be employed for bending
complex windscreen shapes. The dies are located in
a tilting box 17 which is a refractory lined metal
structure defining a heated chamber enclosing the
bending dies, and through which there extends a
conveyor comprising upright rollers 8 and bottom stub
rollers 13 similar to those in the furnace and forming
an extension of the conveyor. The upright rollers 18
in the tilting box 17 in the area occupied by the bending
dies have short support surfaces so that the female die
ring frame can move through and beyond the rollers.
Beyond the outlet from the tilting box 17 there
are further upright rollers 8 and bottom stub rollers
13 ~hich form an extension of the conveyor for receiving
each carr~age 12 after the sheet which it supported has
been lifted from the carriage for bending between the
bending dies.
The drive to all the rollers at the loading station,
in the furnace and in the tilting box is from the same
motor. The rollers beyond the outlet from the tilting
box have a separate drive and all the drives are controlled
in the manner which will be described so that a glass
sheet 9 can be fed slowly from the loading station towards
the entrance to the furnace 1, thereafter accelerated
into the furnace and is advanced through the furnace at
an appropriate lower furnace creep speed as the glass is
heated. At the end of the set heating time in the furnace
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10435~
the glass is accelerated from the furnace on to the
short upright rollers 18 between the bending dies where
the carriage is brought to rest with the hot glass sheet
exactly located between the dies.
The tilting box is heated by gas burners, shown
in Figure 9, to the same temperature as the glass achieves
during its passage through the furnace so that the bending
dies are at the same temperature as the glass when it is
presented to the dies for bending.
The tilting box 17 is mounted on a massive rocking
girder frame including bottom beams 20 which are mounted
on central pivots 21. An hydraulic ram attached centrally
to one end girder of the rocking frame is operable to
tilt the frame from an angle of about 5 to the horizontal,
in which position the rollers 18 are aligned at the same
angle to the vertical as the rollers 8 in the furnace,
to a horizontal position of the frame in which the rollers
18 are vertical.
Initially the box is in its tilted position and the
male bending die is moved into position as the carriage
carrying a glass sheet enters the tilting box and as soon
as a hot glass is located between the dies the female die
15 moves through the rollers 18 to press the sheet against
the male die and the rocking frame is tilted to its hori-
zontal position as bending of the sheet proceeds. Duringmovement of the female die the glass sheet is lifted from
the carriage by fingers on the female die which pass
beneath the lower edge of the glass sheet and lift the
sheet. When the rocking frame is horizontal, a tong bar
23 carrying glass-gripping tongs 22 is lowered from a
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hoist mechanism indicated at 25 which can itself be
raised and lowered.
Provision is made for the tongs 22 to engage in
recesses in the upper edges of the dies 15 and 16,
so that they can grip the upper edge of the glass sheet
as it is held between the bending dies.
When the glass sheet has been lifted from the
carriage 12, the carriage is accelerated out of the
tilting box on to the exit conveyor 8 before the roc~ing
frame is rocked to its horizontal position when the
dies open and the glass, now suspended vertically from
the tongs, is lowered through a mouth in the bottom of
the box for further treatment.
During its traverse through the furnace l the
glass is heated to bending temperature for example 610C
at which temperature the glass can be satisfactorily
bent and engaged by the tongs 22 without having become
so soft as to endanger the finish of the glass surfaces
during the bending operation.
When the bent glass is to be toughened, especially
when a high strength glass is required, it is desirable
to quench the glass from a higher glass te~perature,
e.g. 680C, and in the embodiment illustrated in Figure
1 the bent glass is reheated before it is quenched in a
chilling liquid contained in a quench tank 26 which is
located in a pit beneath the tilting box 17.
Just beneath the exit mouth in the bottom of the
tilting box the glass passes between two banks of electric
heaters 27 mounted in a pattern as illustrated facing
both surfaces of the glass. During the passage of the
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_~ ~04;~5~i~
glass downwardly between these heaters the glass at
its bendin~ temperature, e.g. 610C, is heated through-
out its thickness to a pre-quenching temperature nearer
to the softening point of the glass e.g. 680C. The
bent glass may be lowered at uniform speed so as to
ma,intain as near as practically possible uniform temperat-
ure throughout the whole ~lass sheet. Alternatively
the gl~$s may be accelerated as it is lowered between
the he~ters to produce in the glass a uniform temperature
la gradient from a high temperature at the bottom of the
sheet to a lower temperature at the top of the sheet.
Such a temperature gradient may be induced in the
glass sheet prior to bending by running lower sections
of heaters on the furnace walls hotter than upper sections,
or by locat~n~ the lower sections of heaters in closer
proximity to the glass as described with reference to
Figures 3 and lQ~. For exa,mple the bottom of the furnace
may ~e at 80QC, middle areas of the furnace walls at
75QC and the upper part of the furnace at 700C. The
male ~ending die 16, Figure 11, is then heated by means
of internal heaters 511 mounted internally to have a
temperature distribution matching that induced in the
glas$ sheet by such a furnace, as will be described with
reference to Figure 11~
Below the boost heaters 27 are two blowing boxes
28 both of which are supplied with cooling air at ambient
temperature, for example about 30C, which is projected
thro~h nozzles 29 in the boxes uniformly towards both
surfaces of t~e glass sheet, This pre cooling of the
glass surfaces after boost heating produces immediate
- lS -
5~S~
temperature gradients from the central core to the
surfaces of the glass. The core of the glass remains
at about the temperature achieved between the boost
heaters, and the pre-cooling of the glass surfaces is
such that while the glass temperature is still above
the strain point of the glass, the glass sheet is
immediately quenched in a chilling liquid before these
temperature gradients decay.
As the glass is being lowered from the bending
dies the tank 26 of chilling liquid is raised on a
scissors-lift platform 30 which stands in the bottom
of the pit. The tank 26 is raised until the top of
the tank is located just below the bottom of the blowing
boxes 28 with the surfaces of the chilling liquid in the
tank at a predetermined small distance from the bottom
nozzles 29 of the blowing boxes. The bent glass sheet
in which core-to-surface temperature gradients exist as
just described is immediately quenched in the chilling
liquid as it passes from the ambience of the cooling air
into the surface of the chilling liquid.
The chilling liquid is usually a mineral oil for
example CYLREX FM (Trade Mark) and may have added to
it a minor proportion of a low boiling point additive
for example up to 1% by weight of toluene or carbon
tetrachloride.
As the glass is immersed in the liquid in the tank
26 it comes to rest on a frame immersed in the tank,
which frame is attached to the bottom one of the blowing
boxes. The tongs are opened to release the glass on to
the frame and after a time to permit the glass to cool
- 16 -
in the liquid the tank is lowered, the glass is removed
from the frame and degreased, and the toughened glass
is stacked in a rack to complete its cooling to ambient
temperature.
In another method of operation the tank 26 is not
raised, the bent glass sheet comes to rest in the frame
and remains in the frame for cooling in ambient air to
produce an annealed glass sheet. An annealing enclosure
may be moved on a horizontal track into position to
receive a hot bent glass sheet.
Provision may be made for alternatively annealing
and quenching sheets in succession as they are lowered
from the bending dies so that successive sheets of a
pair are respectively annealed and toughened. These
sheets have been heated and bent under identical conditions
and have matching dimensions and are emminently suitable
for laminating together in the manufacture of a laminated
windscreen.
Figures 2 and 3 illustrate in more detail the con-
struction and operation of the loading station and the
furnace.
The first ten upright rollers 8 of the conveyor
constitute the loading station as illustrated at the
right hand end of Figure 2. These rollers are of heat-
resisting stainless steel and are mounted at 20 cm
intervals between upper horizontal girders 35 and lower
horizontal girders 36 which form extensions of the
girder construction supporting the furnace 1. The
girders 35 and 36 at the loading station are connected
to an end frame comprising a base girder 2 and an upright
- 17 -
la~s~3
which is inclined to the vert~cal at the same angle
of about 5 as the rollers 8 and whi~ch is supported
by struts. The end wall of the furnace at the loading
station is indicated at 39 and an entrance mouth 40 to
the furnace is formed through the end wall 39 in align-
ment with the upright rollers 8 and includes an enlarge-
ment at the bottom of the mouth 40 and aligned with the
stub rollers 13 to permit passage of the carriage 12
on the conveyor into the furnace. Flexible asbestos
cloth sealing strips, not shown, are mounted in the
upright edges of the furnace mouth 40.
Side walls 42 and 43 of the furnace 1 carry banks
of electrical heaters 44 and 45, Figure 3, which heater
banks are illustrated in greater detail in Figures 6
and 8. These heaters face opposite sides of the path
of travel of each glass sheet 9 through the furnace and
are connected together in groups which are individually
controlled as will be described.
At the loading station, Figure 2, the carriage 12
is located in position by a retractable carriage stop
47 against which the front end of the carriage 12 bears
so that the carriage is held in sliding engagement with
the rollers which are being driven at an initial slow
speed and when the stop 47 is retracted movement of the
carriage commences from the loading station into the
furnace. A cold flat glass sheet 9 loaded on to the
carriage 12 leans against the upright rollers 8 at the
loading station. The sheet, being cold is not deformable
and the necessity for exact alignment of the rollers 8 and
13 at the loading station is not as critical as is the
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need for their exact alignment in the furnace and the
tilting box. Therefore the rollers 8 which are mounted
between the beams 35 and 36 at the loading station are
not angularly adjustable but are set in fixed bearing
blocks at the angle of the conveyor, in this en~odiment
5 to the vertical.
The lower ends of the upright rollers 8 at the
loading station are formed with stub shafts 48 which
extend downwardly between the girders 36 and through
apertures in a plate 50 which is bolted to the bottom
of girders 36. Beneath the plate 50 there are carried
self-aligning bearing blocks 51, one for each of the
rollers 8. The bearing blocks 51 have lugs which are
bolted to the plate 50 and the stub shafts 48 extend
downwardly into and through the bearing blocks 51.
At their upper ends the upright rollers 8 at the
loading station are formed as integral elongated stub
shafts 53 which extend upwardly between the beams 35
and are each housed in a self-aligning bearing block 54.
The bearing blocks 54 are bolted by lugs to a support
plate 55 which is fixed on top of the girders 35. Each
of the shafts 53, except that of the roller 8 nearest to
the entrance to the furnace, extends upwardly through its
bearing block 54 and carries a sprocket wheel block comp-
rising two sprocket wheels 56 and 57. The sprocketwheels for adjacent rollers are connected together by
means of drive chains 59.
The elongated stub shaft 53 of the roller 8 nearest
to the inlet end wall 39 of the furnace is longer than
the stub shaft 53 of the other rollers of the loading station,
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l()~;~S~;5
and carries a single sprocket wheel 56 and on its upper
end a main drive sprocket 60 which is connected by a
drive chain 61 to a sprocket 62 on the upper end of the
first of the upright rollers 8 within the furnace. The
rollers 8 at the loading stat~on are thus driven from the
same drive as the rollers 8 constituting the rest of the
conveyor in the furnace.
Within the furnace it is important to ensure
accurate alignment of the surfaces of the rollers 8
relative to each other so that the surfaces of the
rollers which provide transient support for the glass
sheet all lie in the same plane which is inclined to the
vertical at the preset angle, for example 5. In order to
effect this, and as described in the above mentioned co-
pending Application Serial No. 204,721, the rollers 8
within the furnace are mounted in alternating groups of
four and three rollers each, with the rollers spaced about
20 cm. apart, and the exact location of the lower bearings
of each group of adjacent rollers is adjustable horizontally
at right angles to the direction of the conveyor. The upper
ends of the rollers of each group are mounted in a gear box
whose position is also adjustable horizontally at right
angles to the direction of advance of sheets of glass along
the conveyor. The adjustment of the disposition of the
bearing blocks and the gear boxes relative to each other
permits alignment of all the upright rollers 8 in the
furnace at the required angle to the vertical.
The lower end of each roller 8 in the furnace is
formed as a stub shaft 63, which is supported in a self-
aligning bearing block 64 which is fixed in a plate 65
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35~
which is carried by dove tail slides which slide in slide
beds 67 which are fixed beneath parallel girders 68 which
run longitudinally beneath the furnace floor and are
supported on the specially shaped cross girders 6 which
support the furnace floor. This arrangement is shown
in Figure 3.
Each of the dove-tail slides has an end
lug 72 which is drilled and threaded to receive the
threaded end of an adjusting shaft 74 whose other end
extends through an apertured locating block which is
bolted to a cross girder 76 extending between the lower
ends of the upright girders 4 along one side of the
furnace. The outer end of the shaft is threaded and ;
is fitted with lock nuts on either side of the loading
block. Each of the plates 65 carrying the bearing
blocks 64 for a group of rollers has two V-slides and
the adjustment of the two shafts 74 permits adjustment
of the disposition of the lower ends of that group of
rollers.
The upper ends of the group of rollers 8 are of
reduced diameter and the elongated stub shafts 78,
Figure 3, extend into a gear box 79 mounted by anti-
vibration mountings on dove-tail slides which are located
in slide beds 82 which are mounted on top of the longitu-
dinally extending girders 7. In the same way as the
slides for the lower bearings of the rollers, each of
the dove-tail slides has an end lug 83 which is drilled
and threaded to receive the threaded end of an adjustment
shaft 85. The other end of the shaft 85 extends through
an apertured locating plate 86 which is mounted on a girder
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1()~35~5~
87 ~hiCh runs lo.ng~tud~nally~of the.furnace beneath
the cross girders 5. The outer end of the shaft 8~
is threaded and is f~tted with lock nuts 88 on either
side of the locating plate 86.
Each of the gear boxes 79 is seated on two such
slides and rotation of the shafts 85 of the gear box
moves the dove-tail slides in their slide beds 82
so that the position of the gear boxes 79 can be adjusted,
as required relative to the adjustment of the bearing
blocks 64 for the lower ends of the rollers to ensure
that the rollers 8 driven by that gear box are at the
required predetermined angle to the vertical.
The position of the gear box 79 for each group of
rollers is adjustable in conjunction with adjustment of
the plate 65 carryir.g the bearing blocks for the lower
ends of the rollers so that in setting up the furnace all
the rollers 8 of the conveyor extending througll the furnace
can be accurately aligned so that the glass supporting
surface of each of the rollers 8 is at the same angle to
the vertical, for example 5.
The bottom stub rollers 13 define a track for the
movable carriage 12 which carries the glass sheet 9 through
the furnace and these bottom stub rollers project througl
spaces between the upright rollers 8 along tlle whole longtl
of the conveyor and are mounted at an acute angle, in this
embodiment 50, to the upright rollers 8.
The five bottom stub rollers 13 which support the
carriage 12 at the loading station are shorter than those
that project inwardly into the furnace, and are located in
alternate spaces between the upright rollers 8.
~43S~
~GL~S~SUp~O~T C~RIAGE
The carriage 12 which constitutes the movable
support for a sheet of glass 9 is illustrated in more
detail in Figures 4 and 5. The carriage is made of
sheet steel bent to an angle so as to provide two faces
which match the acute angle between the upright rollers
8 and the stub rollers 13. The upright face 148 of
the carriage is the longer face and carries two support
plates 149, the upper edge of each of which is widened
to provide a support shoulder 150 whose upper surface
151 is provided with a non-slip refractory coating.
The rear edge of the upper surface 151 of each shoulder
150 is formed with an upstanding land 152 of width which
predetermines the minimum offset distance of the lower
edge 153 of the glass sheet 9 from the supporting surface
of the upright rollers 8 when the carriage is in position
for conveying the sheet through the furnace with the face
148 of the carriage bearing against the supporting surfaces
of the rollers 8 and with the lower shorter face 154 of
the carriage supported on the bottom stub rollers 13.
Figure 5 illustrates how the upper edge 155 of the glass
sheet rests against the rollers 8 when the glass is loaded
at the loading station and Figure 4 shows how the support
shoulders are adapted to the partic~llar shape of the sheet
of glass to be bent. The shape of the glass sheet matches
the styling of the vehicle in which the sheet is to be
embodied.
By reason of common drive to the rollers 8 alld 13
from a single hydraulic motor, and by choice of
suitable gearing with similar frictional engagement of
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43S~i~
the faces 148 and 154 of the carriage with the upright
rollers and the stub rollers 13 respectively, the
movable carriage is always advancing with the same
linear speed as the surface linear speed of the upright
rollers 8 against which the sheet of glass rests and
which provide transient support for the upper edge of
the glass sheet.
The carriage also carries a stop member 156 at its
front end for abutment against the retractable carriage
stop 47 at the loading station as shown in Figure 2 and
for eventual abutment against a second carriage stop in
the tilting box 17 when the glass sheet is correctly
located between the bending dies. Also mounted on the
carriage is striker 157 near the front end of the carriage
for engaging a limit switch Sl mounted just outside the
furnace at the loading station. A further striker 158
is mounted on the carriage at about a midway location to
engage an actuating member in the furnace for a second
limit switch which forms a part of a control system for
regulation of the speed of travel of the carriage through
the furnace when the whole of the glass sheet is within
the furnace.
FURNACE HEATERS
Figure 6 illustrates the way in which the electric
heaters indicated at 44 in Figure 3 are mounted on the
furnace side wall 42 facing the back of the upright
rollers 8. Each of the heaters is an electric resistance
wire heater 159 the wire being wound on a ceramic rod
which is carried by two connection rods 160 which extend
through the side wall 42 of the furnace. Current is
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`` 104;~5~
~
supplied through these connection rods 160. The heaters
159 are arranged in a chevron pattern and the heaters
are connected together in series in groups which groups
are de-limited by the chain lines in Figure 6. For
example the upper group of heaters first encountered by
the glass which is advanced into the furnace in the
direction of the arrow 161, is indicated at 162 and
comprises ten heaters 159 which are connected together
in series as illustrated in Figure 7. One end 163 of
the series connection of the heaters is connected to one
line 164 of a power supply. The other supply line 165
of the power supply is connected to a thyristor control
circuit 166 of conventional design which controls the
flow of current through the series connected group of
heaters 159 in response to firing pulses supplied to the
trigger electrodes of the thyristors on lines indicated
by the firing pulse line 167 which is connected to a
firing pulse generating circuit 168 which is also supplied
with power from the lines 164 and 165.
A control thermocouple 169 is mounted in the furnace
within the limits of the group of heaters 162. This
thermocouple is connected into a temperature control
circuit 170 of conventional design and controls a simple
on/off switch indicated by the two way switch 171 to
switch into the blocking oscillator of the firing pulse
generator circuit 168, control by one or other of two
potentiometers 172 and 173.
The setting of the potentiometers 172 and 173 are
such as to give, in known manner, respectively high and
low levels of power dissipation in the group of heaters
-25-
10~35bi~
162 so that in response to the temperature in that
part of the furnace within the limits of the group
of heaters 162 as sensed by the thermocouple 169, the
level of power dissipation can be switched between
S the high and low levels in order to maintain the
sensed temperature at a desired value set by a set
point adjustment provided in known manner by adjust-
ment of a potentiometer in the control circuit 170.
Eight series connected heaters are arranged in
chevron fashion in a second group 174 at the inlet
end of the furnace lying below the group 162. There-
after the heaters are arranged in two sets of three
groups, each group consisting of nine heaters connected
together in the series and each having an associated
control thermocouple 169 and being supplied through a
thyristor control circuit under the control of the
appropriate thermocouple 169 and temperature control
circuit as illustrated in Figure 7.
Operation of each group of heaters can be set
indi~idually by the set point adjustment in the associated
temperature control circuit. For example for heating
a sheet of glass 2 mm thick to a bending temperature of
590C, which is attained substantially uniformly through-
out the whole of the glass sheet, the set points of the
temperature control circuits may be such that the
temperature at the thermocouple 169 within the group of
heaters 162 is 700C, and the temperature at the thermo-
couple 169 within the group 174 is 750C. Of the
subsequent groups of heaters the temperatures at the
thermocouples 169 are 700C for the upper groups, 725C
1(~ 5~i~
for the middle groups, and 750C for the lower groups.
Figure 8 illustrates the electrical heaters 45
which are mounted on the side wall 43 of the furnace
facing the glass sheet leaning against the rollers 8.
In this drawing the direction of glass movement 161
is shown from the left hand end of the Figure. The
heaters 159 are wire-wound heaters on ceramic tubes of
the same kind as illustrated in Figure 6 and are mounted
on connection rods 160 which extend through the side
wall 43 of the furnace. The heaters are divided up
into groups which are indicated by chain lines and are
similar to the groups of heaters in Figure 6 with the
addition of a further group of heaters 177 each with a
control thermocouple 178. This additional group of
heaters comprises a row of six heaters extending along
the bottom of the longer side wall ~3 of the furnace
just above the cullet clearance exit passages. Each
group of heaters is controlled by a thyristor control
circuit of the kind illustrated in Figure 7 with a
simple on/off switching arrangement. The temperature
at the thermocouple 178 in the upper group of the two
groups at the entrance end of the furnace is maintained
at 700C and the lower group at 750C when heating a
2 mm glass sheet to 590C for bending as described above.
The bottom temperature at the control thermocouple 178
in the bottom row of heaters 177 is at 750C, and in the
upper, middle and lower groups of heaters of the further
arrangements of groups of heaters as illustrated the
temperatures at the control thermocouples 178 are
respectively controlled at 700C and 750C.
~04;~5~i~
An alternative arrangement for the middle and
lower groups of heaters is indicated at 44a, 44b;
45a and 45b in Figure 3~ The close proximity of the
lower groups 44b and 45b to the glass and the median
position of the middle groups 44a and 45a produces a
top-to-bottom temperature gradient in each sheet with
the lower edge of the sheet at a higher temperature
than the upper edge.
Control of the speed of traverse of the carriage
carrying a glass sheet through the furnace is described
in detail in the above mentioned co-pending Application
Serial No. 204,721.
Figure 5 illustrates how the upper edge 155 of the
glass sheet rests against the near-vertical support
rollers 8 when the cold sheet 9 is loaded on to the
support carriage 12 at the loading station and during
the initial part of the heating of the glass. As the
glass is heated during its travel through the furnace
and the glass approaches the temperature in the range
580C to 660C to which it is to be heated, the glass
becomes sufficiently softened to relax against the support
rollers 8, and could become unacceptably deformed if it
were maintained at that temperature for too long.
Initially the upper part of the sheet relaxes against
the rollers 8 and the length of effective supporting
surface of the rollers 8 which extends downwardly below
the top edge of the glass sheet must always be sufficient
to accommodate permissible relaxation.
A timer in the control circuit for the roller drive
is set so that the glass has reached its desired temperature
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1()4;~5tj9
which, in one ma~ner of operation, is substantially
uniform over the whole sheet and through its thickness
by the time the hot sheet is accelerated out of the
furnace into the tilting box, before the amount of
deformation of the sheet by initial relaxation of the
upper part of the sheet against the rollers 8, followed,
if acceptable, by outward bulging of the lower part of
the sheet, exceeds the limits of acceptable deformation
of the sheet.
Settings of furnace temperature may be employed as
set out in Table 1.
TABLE 1
_ .
Heater Sections Temperature Mean Furnace Temperature
(C) (C)
~ - 710
700 725 750 730
720_ 1 745 770 750
780 805 830 810
. _ .
At any particular mean furnace temperature the time
taken for a sheet to reach a required final temperature is
dependent on its thickness, and examples of operation for
a range of glass thicknesses from 2.2 mm to 15 nml and o:~
heatlng times required to achieve a final glass temperature
in the range 580C to 700C, are described in detail in the
above mentioned co-pending Application Serial No. 204,721.
TILTING BOX
The tilting box 17 which is illustrated in Figures 9,
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~V435t~3
lOA and lOB, defines a chamber in which the bending dies
are enclosed, and comprises the inlet end wall 248, an
exit end wall 253, a roof 254 formed with a step 255
leading down to the top of the inlet end wall 248 and a
step 256 leading down to the top of the outlet end wall
253. The depth of each of the steps is adjustable to
accommodate adjustments of the hoist mechanism for different
h.eights of glass sheets as will be described with reference
to Figures 12 and 13.
The tilting box furth.er comprises a rear wall 257
~nd a front wall 258 and floor parts 259 extending rear-
wardly from the bottom of the front wall 258, and 260
extending forwardly from the bottom of the rear wall 257.
There is a vertical elongated entrance to the chamber
for~ed in the inlet end wall 248 and an exit 262 formed
in the outlet end wall 253 through which exit the carriage
12 is discharged after the glass sheet being bent has been
lifted off the carriage and is being bent between the
bending dies.. The exit 262 leads to the extension 8 of
the conve~or sh.own at the left hand side of Figure 1.
The roof 254 is suspended by hangers 264 from a
support structure including a cross beam 265 e~tendinq
between vertical pillars 266.
The parts 259 and 260 of the floor are supported on
floor support girders 267 and 268, and define between them
a mouth 269 in the floor of the furnace through which a
bent glass sheet can be lowered, The walls, roof and
floor parts of the tilting box are fabricated with an
outer steel shell lined with refractory material.
Th,e chamber defined within the tilting box 17 is
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5~i~
heated to the temperature o the glass which enters the
tilting box from the furnace so that the bending dies
which are enclosed within the tilting bo~ are at the
temper~ture of th.eir environment and are therefore at
about th.e same temperature as that of the glass sheet
~hen it enters the tiltin~ box, The temperature within
the tilting box is maintai~ed by gas burners indicated
at 27Q which are connected by ducts to inlet slots 271
formed in the front and rear walls 257 and 258 of the
tilting box~ There a,re four gas burners 270 feeding
four slots 271, two in each o~ the front and back walls
and each of the burners is controlled by a thermocouple
fi~xed in the male die as near to its bending surface as
possIble~ to ensure the mainten~nce o~ a uniform bending
tempe.rature, in the range 580C to 650C for example 610C,
w~thin the t~lting box. The burners 270 are connected by
flexible ducts to gas and combustion air supplies, including
meanS. controlled by the thermocouDle in the male die to
v~ry the air:gas ratio fed to the burners.
The ~as burners .mainta~in ~ positive pressure of hot
~ses in the tilting box and hot gases flow downwardly
throug~ the exit'mouth beneath the box and meet uprising
gases~ ~ pressure balance usuall~ exists just below the
boost h.eaters 27,
The massive rocking frame, on which the tilting box
IS mounted~ which frame is indica,ted at 20 in Figure 1,
co~prises side girders 272 and end girders 273 welded to
th.e end of the side girders 272, Each of the side girders
272 is seated on and welded to a pivot block 274 wllich
ca,~r~es trunnions 275 wh.ich are mounted in bearina blocks
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~435tiS~
276 which are seated on a base support plate 277 which
provides the upper surface of a ledge 278 which is cut
into the side walls of the pit. The rocking frame is
balanced on the trunnions 275 as is the whole of the
tilting box construction and its associated equipment
carried by the rocking frame so that the frame 272, 273
can be readily tilted from horizontal to the tilted
position at about 5 to the horizontal which is illust-
rated in Figure 10.
Cross girders 279 and 280 extend across and above
the rocking frame between the side girders 272 being
mounted on the side girders by end brackets 281.
A cross girder 282 is seated directly on the side
girders 272 of the rocking frame and the floor support
girders 267 are seated on the cross girder 282.
At the left-hand end of the rocking frame as viewed
in Figure 10, a plate 283 is supported by spacer blocks
284 on the end girder 273. The plate 283 is a short
plate centrally mounted on the end girder 273, and
stiffening girders 285 extend from the plate 283 to the
cross beam 279.
Mounted above the plate 283 and the cross beam 279
are a pair of parallel support beams 286 which are
respectively mounted by support blocks 287 and 288 on
the plate 283 and the cross beam 279. The parallel
support beams 286 support an actuator unit 289 for the
male die 16 which is mounted on a die mounting assembly
291.
Similarly at the right-hand end of the rocking frame
a central plate 292 is mounted by support blocks 293 on
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104;~5~
the upper face of the end girder 273. The plate 292 is
fi~.xed by stiffening beams 294 which extend between the
plate 2~2 and the cross beam 280, and a pair of parallel
support beams 2~6 for an actuator unit 297 for the female
dIe 15 are carried on the cross beam 280 and the plate
2~2 by support blocks 298 and 29~.
The female die 15 is mounted on a die mounting
assem,bly 300~ which is carried on the die actuating unit
297,
The rocking fra~e 272, 273 ~s rocked by means of a
single hydraulic cylinder 301, Eigure lO~A which is mounted
by means of trunnions 3Q2 between brackets 303 which are
~xed to a beam 304 extending across one end face of the
p~t, Th.e cyl.inder 3Ql has a ram 305 which extends up-
wa~dly and h.as a head 306 w,h.~ch carries trunnions
wh~ch p~Vot in bearings in be~ring support brackets 3Q9
~h~.ch are fixed beneath.the centre of the end girder 273.
The. hor~zontal positIon of the rocking frame and the
angle of tilt of the frame is settable by stop means.
~ear ei.ther end of the end girder 273 to which the ram
3Q5 ~s atta~hed there are U-shaped stirrups 310 extending
belo~ the bea,m. Each stirrup 31Q is welded to the beam
and strengthened by brackets, With.in each stirrup and
mounted on the beam 304 fixed to the end wall of the pit
th.ere ~s a stop block 311 of rectangular cross-section,
and a second stop block 311 is mounted on the beam 304
below the stirrup, Adjustable $top bolts are secured
the base of the sti.rrup and respectively extend upwardly
and downwardly from the base to engage the blocks 311.
Adju$tment of the bolts e.nsures that the frame is returned
104;~S~3
to a horizontal position, and provides an adjustment of
the setting of the angle of tilt of the rocking frame
bringing the upright rollers 8 in the tilting box 17 into
exact alignment with the upright rollers in the furnace
to receive a hot sheet of glass for bending.
At either end of the other end girder 273 of the
rocking frame there is an hydraulic shock absorber 314
having a ram which bears against the shelf 278 which extends
along the sides of the pit. These shock absorbers steady
the rocking frame as it nears the end of its tilting move-
ment.
Also carried on the rocking frame there is a support
structure indicated at 315, for supporting the gas burners
270.
The rollers 8, 13 and 18 in the tilting box 17 are
driven by the same drive as the furnace rollers taken
from the hydraulic motor. The upright rollers 8 and
18 are driven from their upper ends by gear boxes 317,
Figures 9 and 10, of similar construction to the gear
boxes 79 which drive the upright rollers 8 in the furnace.
The gear boxes 317 are mounted above cross-girders 318
which are fixed between the cross-members 265, being
adjustably mounted on the cross-girders 318 by means of
V-slides in the same way as the mounting of the gear boxes
79 of the furnace.
The drive to the gear boxes 317 is by a shaft 319
coupled by a flexible coupling 320 to an intermediate
shaft 321 which is coupled by a further flexible coupling
322 to an output shaft 323 of a right angle drive unit 324
which is mounted on one of the upright girders 266. The
~ 34 -
1~)43~
drive to the right angled drive unit 324 through a flexible
coupling 325 is by a transmission shaft 326 which is held
in bearings 327 on the upright girder 266 and the lower
end of which.is coupled by a flexible coupling 328 to a
further right angled drive unit 329 which is mounted on the
cross girder 280.
The lower end of each of the upright rollers 8 and
18 in the tilting box is formed as a stub shaft 330 which
is supported in a self-aligning bearing block 331 fixed
to a plate 332 which is mounted by brackets, one of which
is shown at 333 on the ends of girders 334 which cantilever
out from the centre web of the cross-girder 280. The
plate 332 is adjustable laterally with respect to the
brackets 333, The free end of each of the cantilever
girders 334 i5 supported by a prop girder, not shown,
which extends upwardly from a cross-girder, omitted from
the drawing for clarity, spanning the two side girders
272 of the rocking frame. Supports for the floor support
girders 268 beneath the floor part 260 of the tilting box
are also provided from that cross girder.
A box ~irder 336 extending transversely of the girders
334 is mounted on the upper faces of the girders 334. The
box girder 336 provides a mounting support for the bottom
stub rollers 13 and their drive means.
Both. the angle of inclination of the stub rollers 13
relative to the upright rollers 8 and 18 and the extent of
projection of the rollers 13 between the rollers 8 and 18
i5 adjustable in the same manner as for the bottom stub
rollers 13 in the furnace. The drive to the bottom stub
rollers 13 is by means of a shaft 338 which extends parallel
- 35 -
10435~
to the box girder 336 and is mounted in bearings carried
by brackets fixed to the girder 336. The drive from
the shaft 338 to the bottom stub rollers 13 is through
right angle drive units 339 which are also mounted by
brackets on the box girder 336. Each right angle drive
unit 339 drives the corresponding stub roller 13 throu-31l
an intermediate shaft 340, which through a further flexible
coupling 341 drives a right angled drive unit 342 which
drives a shaft 343 on which the ferrule of the roller 13
is mounted. The shaft 343 extends through a cylindrical
bearing assembly 344 whose body has integral sleeves
which are bolted to an adjustable mounting.
The shaft 338 is driven from the bottom gear box
which drives the bottom stub rollers 13 at the exit end
of the furnace adjacent the tilting die box 17. A
conventional articulated coupling, not shown, couples an
output drive shaft from the bottom gear box with the
end of the shaft 338 adjacent the exit end of the furnace.
The other end of the shaft 338 is connected through a
right angle drive unit and a flexible coupling to the
input shaft of the drive unit 329 thus providing the drive
to the rollers 18 through the gear boxes 317.
The female die actuator unit 297 comprises two parallel
box section girders 400 which are joined near their ends
by cross members which are fixed beneath the girders.
The two parallel beams 296 are tied together by four cross-
girders, not shown, the ends of which are welded to the
beams 296. The upper surface of each of the support beams
is fitted with two bed plates 405 which extend for some
distance along the upper surface of both beams 296 in the
- 36 -
~Q~35~
region of both ends of the beams. Running on these bed
plates 405 are recirculating ball bearing pads each fixed
to the side of one of the girders 400 by brackets 407.
The ball bearing pads support the box girders 400 and the
female die actuating mechanism 300 on the main beams 296.
Mounted on a plate 422 fixed to the side of one of
the support beams 296 are four limit switches S9, S10, Sll
and S12. The switches are staggered at right angles to
the plate 422 so as to be operated as appropriate by
strikers 423 which are fixed beneath a plate 424 which is
cantilevered out from the side of one of the box girders
400.
These switches and their strikers are located so as
to give the following indications
S9 - female die partly out
S10 - female die in
Sll - female die partly in
S12 - female die out.
MALE DIE
The male die 16 is mounted on a male die support unit
291, itself mounted on an actuator unit 289 of similar
construction to the support unit and actuator unit for
the female die.
The male die construction is shown in more detail in
Figure 11 and comprises a contlnuous die face 490 of sheet
steel which is perforated as indicated at 491 and is provided
with a coating of refractory material for engagin~ one face
of the hot glass sheet which is bent against that surface
by the open frame of the female die construction. A shaped
frame 492 provides a mounting for the die face 490 and is
104;~5~
connected to a back frame 493 by adjustable struts of
known kind indicated at 494.
An inner wall 495 is mounted on stays within the
back frame 493 and the upper edge of the wall 495 is
connected to the shaped frame 492 by a flexible seal 497.
The back frame 493 has a back plate 498 sealed to it which
plate is recessed to receive pneumatic ducts 499 which
lead into a chamber formed by the die face 490, the inner
wall 495 and the back plate 498, from a manifold 500 which
is connected through a valve 501 to a pressure duct 502
and through a valve 503 to a vacuum line 504. The flexible
seal 497 permits adjustment of the location of the male
die face 490 relative to the back frame 493.
Opening of the valve 503 connects the chamber within
the die to the vacuum line and is effective through the
perforations 491 in the die face to help such a sheet
being bent against the surface of the die.
When bending is complete, with the valve 503 shut,
opening of the valve 501 provides a puff of air through
the perforations 491 to help release the bent glass sheet
from the surface of the male die upon opening of the dies.
A support frame 510 is fixed on the back plate 498
within the die chamber near to the bottom of the die, and
carried electric heating elements indicated at 511, and
also shown in Figure 10A, which are employed to heat the
lower part of the die when a temperature gradient is
required from top to bottom of the surface 490 of the male
die to match a temperature gradient already put into the
sheet as it passes through the furnace with the alternative
arrangement of heaters 44a, 44b, 45a and 45b of Figure 3.
- 38 -
~04~5~i~
Electric supplies to the elements 511 are connected through
the back of the die in conventional manner.
The back plate 498 of the male die is hung from the
main die support using an adjustable locating and clamping
arrangement, and angular rotation about a horizontal axis
generally at right angles to the back plate 498 of the die
is possible since the male die support unit 291 is adjustably
connected to the male die actuator unit 289.
Two limit switches S13 and S14 are mounted on a plate
506, Figure 10A, fixed to the side of one of the support
beams 285 which support the male die actuator unit. The
switches are actuated by stri~ers fixed beneath a plate
507 cantilevered from the side of one of the box girders
400 of the male die actuator unit. These switches and
strikers are located so as to give the following indications
S13 - male die partly out
S14 - male die in
TONG BAR AND HOIST
The tong bar 23 from which six tongs 22 are suspended
and the hoist mechanism from which the tong bar is suspended
are illustrated in more detail in Figures 12 and 13. Each
of the tongs 22 is movable to a location exactly positioned
over the upper edge of the bent glass sheet between the
bending dies before the tongs close onto the upper edge
of the sheet, and each of the tongs is loosely mounted in
a tong gate structure which is described in detail in the
Canadian Patent Application Serial No. 204,722,
and which is mounted above a vertical pivot secured to or
cantilevered from the tong bar.
The tong bar 23 is a straight bar which is suspended
- 39 -
from two hoists each of which is mounted on an overhead
beam structure 570 which is supported on pillars 571
which structure straddles the tilting box as shown in
Figure 12. A hoist is provided for each end of the
tong bar 23 and each hoist comprises a fixed head frame
572 which is an open cuboid structure including vertical
supports and cross supports and having a cross head 573
on the upper surface of which are fixed trunnion brackets
574 in which the head of an hydraulic cylinder, respectively
575a and 575_ is mounted by pivots 576. The piston rod
577 of the piston which is slidable in the cylinder 575
extends downwardly through the head of the cylinder and
is pivotally linked at 578 to massive lu~s 579 which are
fixed to a cross head member 580 of a movable frame
structure 581 also of open cuboid form which is movable
vertically within the fixed head structure 572 by actuation
of the cylinder 575. The movable frame structure is
fixed to vertical shafts 581a which slide in bearings
which are in lugs 572a on the head frame 572.
The piston rod 577 extends through the upper end of
the cylinder as indicated at 582 and carries on its upper
end a switch actuating member 583 which co-operates with
two limit switches S16 and S17 which are actuated when the
piston in the cylinder 575 reaches the limits of its upward
and downward movement which moves the frame 581 up and down
within the fixed head frame 572.
The frame 581 includes a horizontal base structure
586 which provides a mounting for bearing brackets 587
which carry a shaft 588 on which are mounted two winding
drums 589 and 590 both of which are coupled to the shaft
- 40 -
s~
588 by a slipping clutch.
A brake disc 591 is also journalled to the shaft
and braking caliper arms 592 are fixed to a support on
the base structure 586. The calipers 592 co-operate
with the disc 591 for braking the hoist drums as will
be described.
Fixed below the movable frame 581 is a lower frame
indicated generally at 593. The lower frame comprises
four suspension girders 594 which extend downwardly froni
a frame 595 of the movable head 581. The lower end of
each of the suspension girders 594 is fixed to a bottom
plate 596. There are four girders 594 respectively to
the corners of the upper frame 595 and the bottom plate
596.
Two shafts 597, the lower parts of which are threaded
as indicated at 598, extend between and are fixed to the
upper frame 595 and the lower plate 596. The shafts 597
carry a centre frame which comprises two vertical members
599 which are joined at their upper ends by a bridge plate
600 and at their lower ends by a cross member 601. The
centre frame is mounted on the shafts 597 by lugs 602
positioned at the ends of the bridge member 600 and which
are fitted with bearing sleeves. The lugs 602 support
the centre frame on the shafts 597 while permitting vertical
movement of the centre frame relative to the shafts 597.
Further lugs 603 are fixed to the lower ends of the side
members 599 and are located on the threaded parts 598 of
the rods 597 by means of nuts 604.
Adjustment of the nuts 604 adjusts the vcrtical position
of the centre frame with respect to the frame 593 which is
-41-
la~s~
suspended beneath the movable frame structure 581.
The centre frame carries two guide tubes 606 which
serve to guide lifting cables 607 and 608 which are
respectively wound on to the hoist drums 589 and 590.
Both the cables 607 and 608 pass over jockey guide
pulleys 609 which are mounted on spindles 610 supported
on a mounting bar 611 which is suspended by struts 612
beneath the movable frame 581. The two jockey pulleys
609 are offset with respect to each other as shown in
Figure 13b. The two tubes 606 are similarly offset so
that the lower ends of the tubes can respectively engage
the upper face of the tong bar 23 near to the back and
front edges of the upper face of the tong bar. The
cables 607 are connected to the front edge of the tong
bar 23 and the cables 608 are connected to the back edges
of the tong bar.
Figure 13B shows how the upper ends of the guide
tubes 606 are fixed to the cross member 601 of the centre
frame. The upper ends of the guide tubes 606 pass througl
apertures in the cross member 601 and are fixed to the
cross member 601 by captive nuts. The guide tubes 606
pass through bearing bushes, now shown, fixed in the bottom
plate 596 of the movable frame, to permit vertical adjust-
ment of the guide tubes within the movable frame 593 when
the position of the lu~s 603 on the rods 597 is adjusted.
In this way the vertical position of the centre frame with
the guide tubes 606 is adjustable to accommodate the upper-
most position and the lowered position of the tong bar 23
to suit different heights of the glass sheets being
processed. Appropriate adjustment of the depth of the
1()435ti~
steps 255, 256 in the roof of the tilting box to accommod-
ate these adjustments of the hoist mechanisms is also
made as described with reference to Figure 16.
The shaft 588 of the hoist drums 589 and 590 shown
in Figure 12A is connected by a flexible drive coupling
615 to an hydraulic drive motor 616 which is mounted
the cross beam 570 of the overhead support structure.
The shaft is extended right along the top of the beam 570
to the right-hand hoist unit where it is supported in
further bearing bushes 587 and has fixed to it the hoist
cable drums 589 and 590 for the right-hand hoist unit
: for the tong bar 23 which is identical in every respect
to the left-hand hoi~t unit.
The guide tubes 606 which are made of heat resisting
stainless steel extend downwardly through glands 617 in
the roof 254 of the tilting box and locate the upper face
of the tong bar 23 which is suspended within the tilting
box by the cables 607 and 608.
In the position illustrated in the drawin-J the
pistons are retracted in the cylinders 575 so that the
movable frames 581 are in their uppermost position re-
tracted upwardly within the fixed frames 572 and the
cables 607 and 608 are wound up on the drums 589 and
590 so that the upper face of the tong bar 23 is located
against the lower end of the tubes 606 which are themselves
in their uppermost position.
The lower parts of the lifting cables 607 and 608
are fitted with sleeves 620 which are located in bushings
fitted in the upper and lower ends of the guide tubes 606.
The tong bar 23 is fixed to the lower ends of the sleeves
-43-
1(~4;~5~
620 and in the upwardly retracted position as illustrated
the upper ends of the sleeves 620 project upwardly out of
the upper ends of the guide tubes 606.
The location of the tong bar 23 in its raised position
as illustrated is assisted by a roller 621 mounted on the
back face of the tong bar 23 which roller engages in a
guideway 622 which depends through the roof of the tilting
box from the overhead beam 570.
In the upwardly retracted position of the tong bar
which is illustrated the jaws of the tongs 22 are spaced
above the position of the upper edge of the bending dies.
The lowering of the tong bar to bring the tong jaws astride
the upper edge of a bent glass sheet when it is held between
the bending dies is effected by simultaneous actuation of
the two cylinders 575 to push the movable frames 581 and
593 downwardly with the tong bar still tightened against
the lower ends of the guide tubes 606 by the hoist cables
607 and 608. The whole of the movable hoist arrangement
moves downwardly to reposition the tong bar 23 at a location
where the open jaws of the tongs straddle the upper edge
of the bent glass sheet held between the bending dies.
The tongs are so located on the tong bar that they are
lowered into the spaces between the sections of the ring
frame female die, Figure 9, and into corresponding recesses
cut into the upper edge of the male bending die to accommo-
date the jaws of the tongs. As the tong bar is lowered
the tongs are guided into exact location above the upper
edges of the glass sheet.
The guide tubes 606 through which the cables 607 and
608 pass are shown in detail in Figures 13B and 13C. The
~o~;~s~
sleeve 620 which is fitted on the end of the cable 607
passes through a bush 623 welded into the top of the
guide tube 606 and through a specially shaped bush 624
which is fitted into the bottom end of the guide tube.
The lower end of the cable sleeve 620 is welded to
an upper adaptor plate 626 which rests on the upper face
of a plate 628 of the tong bar and has a hemi-cylindrical
boss 626a on its upper surface. The end of the cable
607 which projects from the lower end of the cable sleeve
620 passes through the plate 628 and through a lower
adaptor plate 627 below the plate 628. A ferrule is
welded to the lower end of the cable beneath the adaptor
plate.
The lower face of the bushing 624 is formed with a
surface 62~ of inverted V-section which receives the hemi-
cylindrical boss 626a of the upper adaptor plate 626 when
the cable 607 is taut clamping the tong bar plate 628
against the bottom of the guide tubes.
A push rod 630 is housed in the guide tube 606, and
extends through a vertical hole drilled in the bush 624.
The lower pointed end 631 of the push rod rests on the
upper face of the adaptor plate 626 when the tong bar is
drawn against the guide tubes. The upper end of the push
rod 630 is guided by a lug 632 inside the guide tube 606
and fixed to the rod 630 near its upper end is a radially
extending striker arm 633 which passes through a slot 634
cut into the wall of the guide tube. An adjustable screw
635 on the arm 633 engages with a pressure-operated swit`ch
S18 which is mounted by a bracket 637 on the outside of the
guide tube 606. When the tong bar is in its raised position
-45-
104;~5~i~
as indicated in the drawings the rod 630 is pushed
upwardly so that the screw 635 disengages from the
switch S18. When the tong bar is lowered relative
to the guide tube 606 the lower support for the pointed
end 631 of the rod 630 falls away, the pin is pulled
down by action of a spring 638 which connects the
striker arm 633 to the bracket 637, and the switch S18
is operated to indicate that the tong bar is being
lowered as the cables 607 and 608 unwind.
The other guide tube 606 through which the cable
608 is threaded has differently shaped bushing 639 fixed
in the lower end of the guide tube 606 and extending
below the tube end without a conically formed internal
face, thereby providing a lower flat abutment face 640
against which the flat upper face of the adaptor plate
626 abuts when the tong bar plate 628 is drawn upwardly
against the lower end of the guide tubes. The adaptor
plate 627 for fixing the lower end of the cable 608 to
the front edge of the tong bar plate 628 includes a
cable clamp clamped to the end of the cable 608 beneath
the tong bar. The clamp can be adjusted on the cable
to permit adjustment of the angle of tilt of the tong
bar by pivoting about the hemi-cylindrical boss 626a of
the adaptor plate 626. This permits exact adjustment
of the tong bar when the hoist mechanism is being set up.
The tong bar is steadied and guided during an upward
and downward movement by means of two guide wires 645.
The upper end of each of the guide wixes 645 is held in
a clamp 646, Figure 13B, attached to a lower member 647
of the fixed head frame. The guide wires 645 extend
-46-
1()4;~5~
vertically right through the tilting box and down the
sides of the pit beneath the tilting box. At the
bottom of the pit the lower end of each guide wire 6g5
which passes beneath a guide pulley, not shown, terminates
in a shackle which is attached to the shaft of a hydraulic
cylinder by means of which the wire 645 is maintained at
a required tension.
Attached to each of the top plates 628 at the ends
of the tong bar, there is a pair of rollers 649 extending
parallel to the tong bar. The guide wires 645 passes
between these rollers 649.
At both ends of the tong bar there are welded to
the side plates 641 near their lower end side extension
plates 652 which extend inwardly of the tong bar and
carry a pivot pin 653 on which is pivoted a frame compris-
ing two side arms 654 which are pivoted on the ends of
the pin 653 which project through the outside faces of
the ends of the extension plates 652. One of the side
arms 654 has a rearward extension which is fitted with
a striker plate 655 to be engaged by a pusher rod for
rocking the frame. The arms 654 are connected together
at their outer ends by bolts and fixed to each Qf the
arms and extending at right angles thereto in the re~Jioll
of the pivot pin 653 are upstanding plates 657 the upper
ends of which are connected by a rod 659 in which there
engage screw clamps 660 in which there are clamped the
ends of three actuator cables 661 which open and close
- 47 -
104;~5~
three of the tongs. Three of the tongs are actuated
from each end of the tong bar.
Each of the tongs is preferably constructed so
that the tong jaws close under the weight of sliding weights
forming a part of the tong construction.
Each of the striker plates 655 is engaged by a
pusher rod 662, which, as shown in Figure 12 is slidable
in a bracket 663 fixed to one of the vertical members 594
positioned beneath a pneumatic cylinder 664 which is also
fixed to the member 594 and whose downwardly extending
ram 665 can, when extended, press the pusher rod 662
downwardly to engage the striker plate 655 and cause the
arms 654 to rotate thereby tensioning the cables 661 and
opening the tong jaws.
A striker plate 666 engages a limit switch Sl9 when
the ram 665 is withdrawn into the cylinder and the tong
jaws are closed. Identical pusher rod arrangements are
provided associated with the two ends of the tong bar,
each having a pneumatic cylinder 664 and limit switch Sl9.
Also mounted on the tong bar 23 near each end are
downwardly depending bracket arms 667 carrying square
metal plates 668 which are employed for sensing photo-
electrically the location of the tong bar during its
downward travel below the tilting box.
TONG AND TONG SUSPENSION
Six pairs of tongs 22 are suspended Erom the tong
bar 23 and the suspension for the tongs is such that
when a bent glass sheet is held between the dies, the
- tong bar descends with the tongs positioned with their
jaws open to straddle accurately the upper edge of the
- 48 -
104~5~5~
bent glass sheet.
Each of the outermost tongs 22 is suspended in
a tong gate which is pivoted on an arm 670 mounted at
right angles to the tong bar which cantilevers the pivot out
from the tong bar 23 towards the male die. The next inner-
most pair of tongs 22 are suspended in tong gates whose
pivots are directly connected to the tong bar. The inner-
most tongs 22 are suspended in gates which are pivoted on the
ends of the cantilever arms 672 which are cantilevered at
right angles to the tong bar 23 backwardly towards the
female die.
Means are provided for guiding the tongs into exact
location with the tong jaws straddling the upper edge of
the glass sheet as the tong bar 23 is lowered. I~hen the
lower position of the tong bar 23 is reached, that is thc
lower position of the pistons in the cylinders 575a and
575b, the cables 661 are relaxed and the jaws close onto
the glass sheet.
The male and female bending dies, which are at the
temperature of their environment within the tilting box
which is maintained as nearly as possible the same as
that of the glass sheet leaving the furnace, remain
closed on the sheet for the period of, for example, five
seconds during which period bending stresses which are
induced in the glass by the bending operation are permitted
to relax and inhomogeneities within the glass are reduced
due to the contact of the glass with the hot bending dies.
When the tongs grip the upper edge of the glass sheet the
lifting fingers are lowered, and retracting of the female
die begins and the bent glass sheet, suspended from the
- 49 -
1~4;~5~;~
/
tongs/ is still in contact with the continuous surface
of the male die.
The valve 501, Figure 11, is opened and air puffed
through the perforations 491 in the male die releases the
bent sheet from the male die surface and retraction of
the male die begins.
The bent glass sheet is now freely suspended vertic-
ally from the tongs and the lowering of the glass sheet
for further processing commences. The rocking of the
box back to its tilted position begins ready for receiving
the next sheet to be bent, and the retraction of male and
female dies to their initial positions is completed.
BOOST IIEATING
The temperature to which the glass sheet heated
during its advance through the furnace which temperature
is related to the time of heating of the glass in the
furnace so as to heat the glass without unacceptable
deformation as it relaxes against the upright rollers
of the furnace, is also the temperature at which the
glass is bent and this temperature in the range 550C to
650C, e.g. 610C is the temperature of the bent sheet
of glass released from the bending dies and suspended
by the tongs within the tilting box.
It is often desirable, particularly when producing
a high strength glass sheet, that the initial temperature
of a glass sheet before toughening should be greater than
the bending temperature, e.g. 680C and prior to the
quenching of the sheet in the tank 26 of quenching liquid,
the sheet, as it is lowered, passes between boost heaters
which heat the sheet to a higher initial temperature from
- 50 -
10435~i~
which it undergoes a preliminary surface cooling prior
to immersion in the chilling li~uid.
After bending of the glass, the rams 577 in the
cylinders 575 of the hoists are extended downwardl~ so
that the movable frames 593 are at their lowermost
position relative to the fixed head frames. Further
lowering of the tong bar during continued processing of
the glass takes place by operation of the hoist motor
616 which, through the flexible drive 615, drives the
shaft 588 and the cable drums 589 and 590 to unwind
the cables 607 and 608 which suspend both ends of the
tong bar. Vertical descent of the tong bar along the
guide wires 645 commences and the glass passes between
the two banks of boost heaters 27, Figure 1, which are
shown in more detail in Figure 14. The top of the
boost heaters 27 is about 60 cm below the bottom edges
of the dies, and the boost heater panels are 90 cm deep.
The banks of boost heaters each comprises a refrac-
tory panel 790 which carries a pattern of heating elements
27. The refractory panels 790 form walls of an elongated
chamber having an open entrance mouth 791 lying below the
exit mouth 269 from the tiltin~ box. Sealing asbestos
curtains 792 hang downwardly from the sides of the
elongated mouth 269 against members defining the mouth
791 into the refractory boost heating assembly. The
refractory panels are fixed vertically and the flexible
asbestos curtains 792 provide a flexible seal between
the mouth 269 of the tilting box and the fixed entrance
mouth 791,
Each of the refractory panels has a metal support
- 51 -
1~3StiS~
backing structure 793. The heater elements 7 are in
the form of wire wound elements on ceramic tubes which
are mounted on steel connector rods 794 which are fixed
through the refractory panels 790 and are mounted in
insulators held by the metal backing structure 793.
The electrical supplies to the boost heater elements
27 are such as to maintain the heater elements at a
temperature in the range 750C to 1600C, for example
1000C to 1200C. During the downward passage of the
bent glass sheet between the heaters the glass may be
heated to 60C or more above the temperature at which
it leaves the bending dies, for example the glass at
620C may be heated to a pre-quenching temperature of
680C
If the glass passes downwardly at uniform speed
between the heater elements it is heated substantially
uniformly throughout its thickness. The surface
temperature may be raised slightly higher than that of
the core of the glass but at worst a temperature difference
of about 12C is produced between the surfaces and the
core of the glass.
Alternatively, and in order to heat the lower edge
of the glass sheet to a higher temperature than the upper
edge of the glass sheet, the glass may be accelerated
when the lower edge of the glass sheet is at the level
of the bottom of the heater panels for e~ample, from a
lowering hoist speed of 15 cm/sec. to a lowering speed
of 30 cm/sec. The heating time for the upper part of
the glass sheet between the boost heater panels is there-
fore less and so, while each part of the glass sheet is
s~ ~
heated so that there is substantially no temperaturegradient through its thickness or at most about 12C
as just described, a linear temperature gradient is
set up from,a high temperature of for example, 700C
at the lower edge of the bent glass sheet to a lower
temperature of for exampl,e, 680C at the upper edge
of the glass sheet as it passes between the bottom of
the boost heaters 27 to a pre-cooling sta~e prior to
quenching in the o~l tank 26.
lQ The control equipment to be described permits
the setting up of a select.ed veloc~ty profile for
the hoist motor 616 from initiation of its operation
to the time the hot ben.t sheet of glass is brought
to rest in the ~uench tank,
A maximum lowering speed of 100 cm/sec. can be
achievedr and some further examples will be given.
Some more detailed examples of operation will
now be given in Table IX which gives the temperature
at ,wh,ich the glass is bent as well as times between
the boost heaters to heat the glass to a desired pre-
quenching temperature and values of hoist speed necessary
to ach.ieve the desired temperature.
- 53 -
10~
TABLE IX
_
Glass Bendin~ Boost HeatFinal Glass Time in Hoist
Thickness Temp. Furnace Temperature Boost Speed
mm o Temperature o Heatcm/sec.
C C C(~ec~nd~l
2.0 580 750 650 22 4.1
2.0 620 750 630 3.0 30
2.0 620 750 680 25 3.5
2.0 580 1000 630 4.0 23
2.Q 580 1000 720 12.6 7.1
2.0 620 1000 720 9.3 10
2.0 620 1600 720 2.1 43
3.0 580 750 630 20 4.6
3.0 580 75Q 650 30 3
3,0 62Q 750 630 5 18.3
3~0 620 750 680 35 2.5
3.0 580 1000 630 5.6 15.5
3.0 580 1000 720 17.3 5.3
3.0 620 1000 720 12.9 7.1
- 54 -
104~5~9
TABLE IX (Continued)
~ .
Glass Bending Boost Heat Final Glass Time Hoist
Thickness Temp. Furnace Temperature in Boost Speed
. mm C Temperature o Heat cm/sec.
_ C C (seconds) .
3.0 580 1600 630 1.3 71
3.o 580 1600 ?20 3- 9 23
3.0 620 1600 720 2.9 31.5
4. o 580 750 630 26.3 3.6
4. o 620 750 630 6.3 14.5
4.0 650 750 670 16 5.8
4.0 580 1000 630 7.2 12.7
4.0 580 1000 720 22.2 4.1
4.0 620 1000 630 1.4 65
4. o 620 1000 720 16.6 5.6
4. o 650 1000 680 5.0 1 8.3
4.0 650 1000 720 12.0 7.3
4.0 580 1600 630 1.7 54
4.0 580 1600 720 7.9 19
4. o 620 1600 720 3.62 25
4.0 650 1600 720 2.6 ~ 36
- 55 -
5~
Some further examples of operation are given in
Tables X, XI and XII which show the production of a linear
temperature gradien-t of from 10C to 30C from a higher
temperature of the lower edge of the sheet to a lower
temperature of the upper edge of the sheet. These
tables are based on a glass sheet 25 cm in height which
is being lowered through banl~s of boost heaters 27 which
are 90 cm deep. The acceleration of the glass sheet
takes place from the initial speed to the final speed
when the lower edge of the glass sheet has reached the
bottom of the furnace. The hoist speed gives the
a~proximate transit times of the top and bottom edges
of the glass sheet between the boost heaters.
- 56 -
104;~S~i~
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- 59 -
1(14;~56i~
PRE COOLI`NG STAGE.
The two blowing boxes 28 are each elongated boxes
which extend from side to side of the pit below the
boost heaters. Each of the boxes 28 with its nozzles
29 extending from the front face of the box is mounted
on side wheels 800, Fig.15, which run on tracks 801
which extend longitudinally along the side walls of the
pit. EacA of the blowing boxes 28 is connected by a
duct 802 to a centrifugal blower 803 mounted near one of
tAe end walls of the pit and each of the blowing boxes 28
has an indivi~dual supply from its own centrifugal blower
803 at a pressure of 38 cm water gauge. The wheels 800
are tAe wheels of carriages on which the blowing boxes
and their connection ducts are mounted and the blowing
boxes can be moved in and out on the tracks 801 to adjust
the spacing of the ends of the nozzles 29 from the path
taken by the hot bent glass sheet as it is lowered through
the bottom of the boost heater elements. A usual separa-
ti`on of the ends of the nozzles i`s 10.5 cm. The front
faces of the blowing boxes 28 may be flat as shown in the
drawi`ng or may be curved to a shape more nearly matchin~
that of the bent glass sheets whi~ch are to be pre-cooled
by cooli`ng air directed from the blowi`ng boxes.
The faces of the boxes are in one embodiment 22 cm.
TAe nozzle orifices are 3 mm in diameter and there are
arranged in a "DOMINO 5" pattern with a pitch of 18 mm.
The nozzles are staggered so that they do not face each
other across the interspace through which the glass is
lowered.
Attached to the carriage for the right hand blowin~
-60-
1()43S~s~
box 28 a~ shown i~n Fig~e 15 i~ a downwardly dependi~g
frame 80-6 whi~c~ carri~s~at i~sllower end support shoes
8a7 onto whfch the hot glass sheet i`s lowered. The
shoes 807 extend right across the lowering path of the
glass and are steadied by stays 808 which are clamped
to the track 801 when the blowing box is in desired
locati~on. The frame 806 and the stays 808 are suffi-
ci`ently long to ensure that when the bottom edge of the
glass rests i`n the shoes 807 the upper edge of the glass
i`s just below the bottom nozzles of the blowing boxes.
The supply of cooling air to the boxes 28 is reg-
ulated so that the surfaces of the reheated glass are
cooled by, for example 50C while the core of the glass
thi`ckness does not cool appreciably below the pre-quench-
~n~ temperature achieved by reheating by the boost heaters.
~n thi`s ~ay temperature gradients of about 50C exists
from the core to the surfaces of the glass as the glass
leaves the ambience of the cooling air supplied through
the nozzles 29 and the glass is then immediately quenched
2a in the quench tank 26.
QUENCH TANK
The quenching tank 26 ~s illustrated diagrammatically
i~ Fi`gure 15 and contains a body of chilling liquid main-
tai`ned for example at 240C. The tank 26 is seated on a
table whi`ch stands on the lifting platform 30 which is the
upper platform of the scissors-lift table 30. The table
~s operated hydraulically and lifts the quenching tank 26
at a ti~me relati~ve to the operation of the bending dies
whic~ ensures that the quench tank has been raised to a
3Q posi`tion just below the blowing boxes 28 before the glass
-61-
356~
sheet descends through the~blowing boxes i~to the
chi`lli`ng li~ui~ i~n the quench tank. Provi`si`on i`s made
for t~e frame 806 with the shoes 807 to be fully
i~mersed i~n the quench~ng li`quid before the glass enters
tHe tank.
T~e exact location of the surface of the liquid in
vhi`ch the glass i`s quenched, relative to the bottom
nozzles of the blowing boxes 28 is of importance in order
to ensure a minimum decay of the centre-to-surface temp-
~a e~ature gradi~ents produced through the thickness of theglass by the pre cooli~ng stage, before the glass surfaces
~ecome severely quenched by contact with the chilling
ll~qui`d. It i`s the temperature gradients existing through
the glass- thickness as the core of the glass cools through
the strai`n point of the glass which influences generation
of desi`red surface compressive stress and central tensile
stress i`n the glass by the time the glass has cooled to
roo~ temperature.
Accurate defini`tion of the exact location of the
2Q surface of the chilling liquid, for example 2.5 cm below
the bottom of the blowing boxes 28, is provided by
causi`n~ c~i`lli~ng liqui`d to flow continuously over a weir,
not shown, i`n the upper part of the quench tank 26,
At the appropri~ate ti`me in the operation of the
apparatus t~e platform 30 is lifted to carry the quencl
tanR 26 to i`ts raised quench position ready to receive
a hot glass sheet. The quench tank remains in position
wi~h the hot glass resti~ng i~n the shoes 807 for a time,
for example 20 seconds, to ensure that the whole of the
glass has cooled to a temperature well below its strain
-62-
1()4;~St~
poi~nt before the platfor~ 3Q i~ lo~exqd which the~y
lowe~s the quench tank from alound the supported L~nt
glass~sheet wAi~ch i~s i~ndi~cated at 856 in Figure 15 and
re~ai~n~ seated on the shoes 8a7.
Duri~ng quenchi~ng, as soon as the whole of the
glass i~s i~mersed in the chilling liquid and the lower
edge of the glass 856 is seated on the shoes 807 the
tonys are opened by actuati`ng means in the pit engaging
the stri`ker plate 655, Figure 12, thereby tensioning
the tong operating cables, and the tong bar 23 with the
ton~s 22 i`s then raised by operation of the hoist
~echani`sm so that the tong bar i`s in position above
the di~es before the di`es are closed onto the next glass
sheet to ~e bent.
After the quench tank has been lowered the bent
~lass i`s removed manually to a degreasing tank and after
degreasing the glass is cooled to room temperature.
When a seri`es of bent annealed sheets of glass are
to be produced the quenc~ tank 26 remains in its lowered
2a posi`ti`on, tAe boost heating section is switched off and
tAe al~r supply to the pre-cooling section is turned off.
The frame 806 i`s mounted in an annealing enclosure
whi~h i`s~oved horizontally i`nto position to receive
each sheet i`n turn as it is lowered through the inoper-
atl~ye boost heating and pre-cooling sections. The frame
i`9 spri`n~ loaded to accommodate the highest speed of the
glass whi~ch will not have been damped by immersion of
the glass i`n a chilli`ng liquid. The shoes 807 of the
frame are provi~ded wi`th greater thermal insulation.
3a EacH sheet i`n turn rests on the shoes 807 in the
~()4;~Stj~
annealing condi~tions within th~ enclosure so that when
the glass i`s~cool only relati`vely small stresses are
present, as represented for example by a central tensile
stress of 7 MN/m2. When the sheet has cooled the
annealing enclosure is moved away horizontally, the
annealed sheet is removed from the frame, and the
anneal;`ng enclosure is returned into position around
the frame ready to receive the next sheet.
In some circumstances an annealed sheet is manu-
factured ~n success;~on to a toughened sheet, for example
w~en those two sheets are to be laminated together to
produce a laminated windscreen. The boost heating section
and the pre-cooling section remain operative. Up to the
ti~e at which the bending dies open both sheets have
i`dentical thermal histories and the bent shapes of the
sheets match for lamination. T~ese matching bent shapes
must be preserved during subsequent processing. The way
in whi`ch this ;s achieved is described in the above-
mentioned co-pending Application Serial No. 204,722.
The overall deformation index of the toughened and
annealed s~eet is similarly matched when they are
proces~sed so as to have a top to bottom temperature
~rad~ent, by consi~dering the condition reached by the
top edge of the glass sheet. This ensures physical
~atching of the top edges of the sheets which is the
most cri`ti`cal region ;n the lamination process.
TILTING BOX
HYDRAU1IC CONTROL CIRCUITS
Figure 16 i~llustrates di`agrammatical~y the hydraulic
ci`rcui`ts for operation of the femaleand male die
-64-
S~i~
actuati`ng cylinders 411 and 411a, the rocki~ng frame
actuating cylinder 3al, the cylinders 575_ and 575~
for raising and lowering the movable frames which carry
the tong bar suspension system, and the cylinder 849
operating the scissors-lift table. The control of the
motor 616 which operates the hoists from which the ends
of tfie tong bar are suspended, is also shown.
A main supply line 183 of hydraulic fluid under
pressure, provides the supply of hydraulic fluid for
these cylinders. The ends of the female die actuating
cyli`nder 411 are connected ~y lines 870 and 871 to a
solenoi~d operated spool valve 872 which is also of the
"locked centre" type and has operating solenoids 873
and 874. When both the solenoids 873 and 874 are de-
energi`sed, the spool of the valve is locked in a central
posi`t~on ~locking fluid flow and maintaining the cylinder
under wfiatever conditions currently prevail in the
cyli`nder. Inlets to the valve 872 are connected to the
pressure line 183 and the return line 193.
2a The ends of the male die operating cylinder 411a
are connected by lines 875 and 876 to a "locke~ centre"
- dl~recti~onal spool valve 877 having operating solenoids
878 and 879. The inlets to the valve 877 are connected
to bot~ the pressure line 183 and the return line 193.
Th~ ends of the rocking frame cylinder 301 are
connected ~y lines 880 and 881 to outlets from another
"loc~ed centre" directional spool valve 882 which has
operat~ng solenoids 883 and 884 and which is connected
to both the pressure li~ne 183 and the return line 193.
3n A further "locked centre" directional spool valve
-65
35~9
887, haYin~ operating solenoids, 888 and 889, an input
li`ne connected to the pressure li`ne 183 and a,n e~haus.t
line connected to the return line 193, has a line 890
connected to the upper end of the left-hand vertical
cylinder of the hoist mechanism of Figure 12A, dosi.~llated
575a i`n Figure 16. The.lower end of the cylinder 575_
i`s connected by a line 891 to a compensating spool valve
892 having operating solenoids 893 and 899 and a pressure
li`ne 8g5 connected to the pressure line 183 and an
exhaust li~ne 896 connected to the return line. 193.
The ~pper end of the right-hand cylinder of the
hoi`st mechanism, here designated 575_ is connected by a
line 897 to one input of the spool valve 892, which
~alve i`s operable to connect the lines-891 and 897 in
seri`es ~n circumstances to be described to ensure that
both ends of the tong bar are brought down together. The
lower end of the cylinder 575_ is connected by a line
898 to the val-ve 887.
The ends of an operating cylinder 849 for the
2Q sci`ssPrs~lift table are respectively connected by lines
89g and g00 to a further and si`mi`lar spool valve 901
having operating solenoids 902 and 903, which valve is
also connected to tKe pressure line 183 and the return
li`ne 193.
The hoi`st motor 616, Figure 12A, is connected to
the press~re li~ne 183 and the return line 193 by a
di`recti`onal spool valve 904 having operating solenoids
ga5 and ga6. One output from the valve 904 on line 907
is press~uri`sed to dri`ve the motor 616 in a direction to
3Q lp~er the tong bar. The other output from the valve 904
66-
104;~5~9
is connected by a line 908 to the other side of the
motor, and when pressurised drives the hoist motor 616
in a direction to raise the tong bar. The speed of the
motor is controlled by a shunt circuit connecting the
valve 904 to the return line 193 and including a tappet-
operated flow control valve 909 connected in parallel
with a by-pass valve 910 which is operable to regulate
creep speed of the motor.
Variation of the setting of the valve 909 to
control the speed of the motor 616 is achieved pneumat-
ically as described with reference to Figure 17.
TILTING BOX PNEUMATIC CIRCUITS
Pneumatic control circuits associated with the
tilting box are illustrated diagrammatically in Figure 17.
The upper and lower ends of the two cylinders 664,
Figures 12A and 12C, which depress the pusher rods 662 to
open the tongs, are connected in parallel to a solenoid
operated spool valve 911 which has an input connected by
a line 912 to an air pressure line 913 as described below
with reference to Figure 17.
The valve 911 has operating solenois 914 and 915.
When air under pressure is switched the tops of both
cylinders 664 the pusher rods 662 are depressed and the
tong jaws open, and vice versa when pressure air is
switched to the bottoms of the cylinders downward force
ls removed from the pusher and the tongs open.
Figure 17 also shows one pneumatic circuit for
operating the disc brake 591 associated with the hoist
drum 590, Figure 12. Pneumatically operated caliper arms
592 for engaging the brake disc 591 are connected by a
line 916 to an air reservoir 917 which is supplied through
- 67 -
10~5~i~
a regulator 918 from parallel high pressure and low
pressure ci`rcui`ts whose i~nputs are connected to the
pressure line 913.
The high pressure circuit, whose function is to
engage the brakes and hold the hoists in wound-up
condition until the gripped glass is to be lowered from
the bending dies, comprises a pressure regulator 919 and
a spool valve 920 having an operating solenoid 921
energisation of which releases the brake.
T~e low pressure circuit is similar, having a low
pressure regulator 922 and a solenoid-operated spool
valve 923 hav~ng a solenoid 924 energised for a low
pressure condit~on and a solenoid 925 energised for a
zero pressure condi~tion as will be described. The
function of the low pressure circuit is to prevent
"snatchrng" of the hoist winding gear when lowering a
bent glass sheet.
The speed control hydraulic valve 909 for the hoist
~otor 616, Figure 16, is operated by a lever arm 926
whi`ch can assume three positions, marked A, B and C in
Fl~u~e 17, each setting a motor speed, under control of
a double acting cylinder assembly comprising two cylinders
927 and g28 which are joined end-to-end and slidable
as a w~ole i`n a fixed housi`ng 929.
The cyli~nder 927 has a piston 930 mounted on à
pi`ston rod 931 whose outer end carries a domed head 932
whi`ch engages the lever arm 926 of the speed control
~alye 909.
The cylinder 928 has a piston 933 on a piston rod
3~ 934 whose outer end is fixed to a fixed bracket 935.
-68-
1~3.~
The i~nner and outer ends o.~ the cylinde~r 927 are
respecti~ely connected th~ouyh flow control valves 936
and g37 to a solenoid operated spool valve 939 having
a si`ngle operating solenoid 940 and connected to the
pressure air line 913. Energisation of solenoid 940
sets the pneumatic circuït to determine a first motor
speed. The inner and outer ends of the cylinder 928
are similarly connected by flow control valves 941 and
942 to a further spool valve 943 having a single operating
solenoid g44. The valve 943 is also connected to the
pressure line 913, and energ;sation of the solenoid 944
sets a second speed of the hoist motor 616 as will be
described.
BENDING AND TOUGHENING OPERATION
When a previous die bending operation has finished,
tKe di`es are fully withdrawn, the tilting box is in its
i`ncli`ned position to receive the next hot glass sheet,
lower;ng of the glass has begun, and contacts R122
and R123 of the hoist lower relay R12, Figure 20, close.
2a. A cl~rcui~t l~s operated including a solenoid which removes
the: carri`age stop 242, and the carriage is accelerated
o~t of the ti~lti~ng box.
Mean~hi~le all the rollers 8 and 13 in the furnace
and i`n the ti~lti~ng box are all now being driven at creep
s.peed; and at the same time contacts open to disengage
the clutc~ dri~i`ng the rollers of the exit conveyor which
are then brought to rest so that the carriage is stationary
on th.e exi`t section of the conveyor and can be removed and
tak.en back to the inlet end for reloading. The reset push
31 B~tton swi`tch is then closed to start up the whole operation
-69-
1()4;~S~
for processing of the n~xt sheet.
The initial condi`ti`on of the apparatus is that both
the male die and the female die are withdrawn, the tong
bar is raised and the tilting box is inclined, e.g. at a
5 angle.
The male die actuating cylinder 411_, Figure 16, has
~een operated to retract the male die by energisation of
solenoi`d 878 of the valve 877, Figures 16 and 18, through
normally closed contacts R73 of a male die relay R7 which
also has holding contacts R71 and normally open contacts
R72 in series wi~th solenoid 879 of the valve 877. Energi-
sat~on of solenoid 878 normally holds the male die out.
Si`milarly the female die actuating cylinder 411 lS
operated ~y female die relay R8 having holding contacts
R81 normally open contacts R82 in series with the solenoid
874 of the valve 872, and normally closed contacts R83 in
seri`es wi`th the coil 873 of valve 872. Ener~isation of
solenoid 873 normally holds the female die out.
The ti`lting of the tilting die box is controlled by
a roller vertical relay R9 having holding contacts R91
normally closed contacts Rg3 in series with solenoid 883
of the cy-linder 301, and normally open contacts R92 in
seri`es wi~th solenoid 884 of the valve 882. Normally the
solenoi~d 883 i`s energised so that the cylinder 301 main-
tains the frame in its inclined position.
A tong ~ar relay R10 is in series with the hoist
rai`sed switches S16, Figure 12, and rollers ver-tical
swi`tch S8 and the female die in switch S10. The relay
R10 has holdi`ng contacts R101, and normally closed contacts
Rla2 i~n seri~es wi~th solenoid 883 of the valve 887, Ei~ure 16.
-70-
~1()4;:~5~5
In parallel with the solenoid 889 is the solenoid 893 of
the compensating valve 892, which solenoid 893 is in
series with two parallel hoist raised switches S16 which
are respectively on the left-hand and right-hand hoist
mechanisms of Figures 12A and 12C.
Relay R10 also has normally-open contacts R103 in
series with solenoid 888 o~ the valve 887. In parallel
with solenoid 888 is solenoid 894 of the compensating
valve 892 which solenoid 894 is connected in series with
two parallel hoist lowered switches S17.
With the tong bar rising in a mid-position coil 889
is energized and the hydraulic circuits for the two
cylinders 575 are connected in series with pressure fluid
fed on line 898 of valve 887 to the bottom of cylinder
575_. Fluid under pressure from the top of cylinder
575b passes on line 897 and through the compensating valve
892 on to line 891 connected to the bottom of cylinder 575_.
The two pistons in the cylinders 575a and 575_ rise
together but may not reach the top of their stroke together.
~hichever hoist raised switch S16 closes first energises
solenoid 893 of the compensating valve 892 which changes
over to connect pressure fluid directly to the bottom of
cylinder 575a thereby ensuring that both hoist frames are
in their raised position as nearly as possible at the same
time.
When the tong bar is being lowered, the tong bar
relay R10 is energised to open contacts R102 and close
contacts R103 which energises coil 888. The compensating
valve 892 is in position to connect the two cylinders 575
1()~35~9
in series. Pressure fluid is fed on line 890 to the
top of cylinder 575_ and from the bottom of that cylin~er
on line 891 through the valve 892 to the top of cylinder
575_. When one of the cylinders reaches the bottom of
its stroke one of the hoist lowered switches S17 is
closed to energise solenoid 894 to switch over the
compensating valve 892 so that pressure fluid is fed
from line 895 to line 897 to the top of cylinder 575_
and both the cylinders 575 are brought down together to
bring the tong bar horizontally into position above the
closed bending dies.
The male die timer which was actuated when the sheet
was in the furnace now commences the actuation of the male
die and after a delay, closes the contacts T31, Figure 18
which are connected in series with the female die partly
out switch S9 and the coil of the male die relay R7 whose
holding contacts R71 are in parallel with the switch T31.
Actuation of the relay R7 causes contacts R73 to open
and contact R72 to close so that solenoid 878 of valve 877,
Figure 16, is de-energised and solenoid 879 is energised,
and pressure fluid is fed on line 876 to the cylinder
411a to cause inward movement of the male die.
When the male die i5 fully in, the male dies in
switch S14 closes. While the male die is moving in, a
carriage 12 carrying a glass sheet 9 is still moving and
operates switch S4 before it comes to rest against the
carriage stop 242. Operation of switch S4 initiates the
inward movement of the female die, so that the lifting
fingers on the bottom of the female die lift the hot glass
sheet 9 from the carriage 12 before the carriage is brought
- 72 -
5~5
to rest against the carriage stop so that the impact
of the carriage against carriage stop is not transmitted
to the hot glass sheet.
With the male die in and the switch S4 closed as
the carriage 12 approaches the carriage stop 242 the
female die relay R8 is energised through a closed reset
switch S15 on the lifting finger mechanism.
By this time the male die has moved in to bending
position and the male die in switch S14 is closed so that
when the switch S4 is closed as the carriage is conveyed
into the tilting box the female die relay R8 is energised
and is latched in by its holding contacts R81. The
normally-closed contacts R83 open and normally-open contacts
R82 close so that solenoid 874 of the female die actuating
valve 872, Figure 16 is energised and solenoid 873 is de-
energised and inward movement of the female die begins.
Contacts R84 on the fe~ale die relay R8 also close and
start operation cf the timer T4 which after a time delay
closes contacts T41 which actuate the solenoid 503_ of
the valve 503, Figure 11, to apply vacuum to the male die
in order to assist bending by drawing the hot glass sheet
against the male die surface 490.
The contacts T41 close to apply the vacuum at a time
when the bending operation is almost complete and th~
female die is just reaching the end of its inward movement.
At a later time after bending and when the female die is
being retracted and the upper edge of the sheet has already
been gripped by the tongs, contacts T41 open and contacts
T42 of timer T4 close to energise operating solenoid 501a
of the pressure valve 501 to supply air under pressure to
- 73 -
~(~4;~S~
the male die to assist in releasing the bent glass sheet
~rom the male die surface.
As the female die moves in the lifting fingers pick
up the hot glass sheet from the carriage and the sheet
is engaged by the female die sections as they move through
the rollers 8 in the tilting box. The hot sheet is then
carried forwardly from the rollers 8 towards the male die.
The female dies partly in switch Sll closes which switch
i5 in series with the normally closed female die out switch
S12 and with~ the coil of the rollers vertical relay R9
which is energised and closes holding contacts R91 to latch
the relay through normally-closed male die part out switch
S13. The normally closed contacts R93 open and the normally-
open contacts R92 close so that solenoid 883 of valve 882,
Figure 16, is de-energised and solenoid 884 is energised
and the cyllnder 301 is operated to tilt the frame to its
horizontal position which brings the rollers 8 in the
tilting box vertical. It is during this tilting movement
of the tilting box that the inward movement of the female
die is completed to complete the bending of the glass bet-~een
the dies, the bent glass is then being held on the lifting
fingers between the closed dies~
When the female die is fully in, the female die in
switch ~10 closes, Figure 19~ This switch S10 is in series
with the rollers vertical switch S8, the hoist raised
switches S16~ which are closed in the condition in which
the hoist frames 581 are raised, and with the coil of the
ton~ bar relay R10. In parallel with the female die in
switch S10 and the rollers vertical switch S8 is holding
contact R101 of the relay R10, and a normally closed contact
- 74 -
5~9
Rlll o a hoist raised relay ~11, Figure 20 is in parallel
with the hoist raised switches S16. When the female die
in switch S10 closes the relay~R10 is actuated, contacts
R102 open and contacts R103 close, the valves 887 and 892,
Figure 16, supply pressure fluid to the cylinders 575a and
575_ and lowering of the ho;st frames 581 begins, Figure
12, to begin the lowering of the tong bar 23 towards the
upper edge of the bent glass sheet held between the dies.
While the tong bar 23 is raised contacts S211 and S212
on a tong bar raised switch are closed and solenoid 914
of the pneumatic spool valve 911, Figure 17, is energised
to supply pressure air to the tops of the cylinders 664,
Figures 12A and 12C, so that the pusher rods 662 are depressed
and the tong jaws open. As the tong bar is lowered the open
tong jaws become positioned exactly above the upper edge of
the glass sheet which is held between the bending dies the
tong jaws having moved downwardly into the recesses formed
in the upper edge of the male die and between the sections
of the female die.
When the tong bar is lowered switch contacts S221
and S222 close and the solenoid 915 of valve 911 is
energised to cause the valve to change over so that the
pusher rods 662 are retracted and the tong jaws close under
the weight of their sliders, onto the upper edge of the
glass sheet.
When the pusher rods 662 are retracted the two switches
Sl9 close to actuate a timer T5 which is set to the shortest
possible time delay, up to 5 seconds, to allow the tong
points to grip into the upper edge of the glass sheet so
that the sheet is securely suspended from the tongs when
the dies open. Contacts T51 of the timer T5 then close
- 75 -
A
lW;~5~5~
to energise solenoid 952 of a ~neumatic valve~ which is
operable to drop the l~ft~ng fingers. Normally closed
contacts S15 are opened and the female die relay R8 is de-
energised. The contacts R82 open and the contacts R83
close, solenoid 874 of valve 872 is de-energised and
solenoid 873 is energised and the retraction of the female
die begins. The time of closure of the dies to bend the
glass sheet may be for example 8 seconds.
When the female die is partly out the female die
partly out switch S9 opens to de-energise the male die
relay R7 so that contacts R73 open and contacts R72 close,
solenoid 879 of valve 877 is energised and solenoid 878
is de-energised and retraction of the male die begins.
When the female die is fully out the female die out
1~ switch S12 opens, and at this time the male die is partly
out and the male die partly out switch S13 opens and when
both switches have been opened the rollers vertical relay
R9 is de-energised, contacts R92 open and contacts R93 close,
and the solenoid 884 of valve 882 is de-energised and the
solenoid 883 is energised so that pressure fluid is supplied
to the bottom of the cylinder 301 to tilt the rocking frame
back to its inclined position with the upright rollers 8 in
the tilting box and their preset angle, e.g. 5, to the
vertical, ready for receiving the next glass sheet from the
furnace. The retraction of the male die continues until it
is fully out. The bent glass sheet is left freely suspended
in the tongs between the open bending dies ready for lowering
through the boost heat section and the pre-cooling section
into the chilling liquid,
- 76 -
,~
S~S~
~ hen the rocking frame is tilted to its inclined
position the rollers tilted switch S7, Figure 20, closes.
This switch $7 is in series with closed contacts R104 of the
tong bar relay R10, normally closed contacts PEl of a photo
electrically operated switch which is operated by the
pla,tes 668 on the hoist as will be described, normally
closed contact~ R112 of the hoist raise relay Rll, and
with. the~coil of a hoist lower relay R12 and with a hoist
lower time T6, The relay coil R12 and the time T6 are
connected in parallel,
~ oldi~ng contacts R122 of the hoist lower relay R12
close to latch the relay~ Contacts R12 3 close to energise
a solenoid 955 which lowers the exit stop 242 to permit
the carriage 12 to be conveyed out of the tilting box.
The hoist lower timer T6 immediately closes contacts
T61 to energise the solenoid 906 of the valve 904 control-
lin~ supply of pressure fluid to the hoist motor 616. At
the same time contacts R124 of the hoist lower relay R12 arc
closed to ener~ise the solenoid 940 of valve 939, Figure 17,
to $uppl~ press~re air through the valve 937 to the cylinder
927 so tha~t the pi,ston 930 i$ extended and the lever arm 926
of valve 909 moves from position A corresponding to zero
speed o~ the motor 616 to posi.tion s which determines a
first s~eed of the hoist motor 616. At this time the drums
of th.e hoists are held stationary by engagement of the disc
brake, the slipping clutch of each drum permitting this
although th.e motor is being driven.
~fter a set time delay, for example 2 seconds, the
contacts T62 of the hoist lower timer T6 close to energise
the bra~e release solenoid 921 of the valve 920 in the bra~e
1()4;~5~i~
operating circuit, to take high pressure off the brake
caliper arms and at the same time energises the lowcr
pressure solenoid 924 of the valve 923 through contacts
R125 of the hoist lower relay R12. After a further
time delay, up to 20 seconds, the contacts T63 of the
timer T6 close to energise the solenoid 944 of the
pneumatic valve 943 which switches pressure air through
the flow control valve 941 to the inner end of the
cylinder 928 causing that cylinder to move in the housing
929, towards the right as shown in Figure 17, and cause
movement of the lever arm to position C to determine a
second faster speed of the hoist motor 616.
~; This acceleration of the hoist motor 616 to a second
speed takes place at the appropriate time when it is
required to accelerate part of the glass sheet through
the boost heat section to achieve a temperature gradient
in the glass as described with reference to Figure 14.
; The acceleration takes place for example when the lower
edge of the glass sheet reaches the bottom of the boost
heater panels.
The plates 668 on the tong bar 23 now cut off light
beams to photoelectric cells not shown, which are connected
to switching circuits which open the contacts PEl to de-
energise the hoist lower relay R12 and the hoist lower time
T6 which instantaneously releases switches R124 and T63 to
de-energise the solenoids 940 and 944, thereby retracting
the double cylinder system 927, 928 and causing the lever
arm 926 of valve 909 to return to position A so that the
speed of the hoist motor returns to zero.
After a delay to permit deceleration of the hoist
- 78 -
1()435~9
system the switch T62 opens and the brake release solenoid
921 is de-energised, this operates in the brake circuit
to put the high pressure back on to the brake caliper arms
to brake the hoist motor when the lower edge of the glass
sheet is just reaching the shoes 807, Figure 15, in which
the glass rests. The contacts T61 open after a delay to
de-energise the hoist lower solenoid 906, the motor 616
then being stationary.
When the glass is being heated in the furnace prior
to entry into the tilting box for bending, a push button
switch S24 is closed, and operates solenoid 902, Figure 16,
of the valve 901 operating the scissors lift table, through
normally-closed contacts S201 to supply pressure to the
bottom of cylinder 849 to raise the table 30 carrying the
quench tank 26 to the raised position ready to receive
the hot bent glass. When the tank 26 reaches its raised
position the contacts S201 open and the valve 901 maintains
pressure on the cylinder to maintain the tank 26 in its
raised position.
A few seconds after the hoist motor 616 has stopped
and the glass is quenched in the tank, a push button switch
S25 is operated to energise solenoid 903 of valve 901
through closed contacts S202, which switches pressure
fluid to the top of cylinder 849 to lower the scissors
lift table which leaves the quenched glass 856 in the
rack 807, 808 as the quench tank 26 moves downwardly.
The contacts 202 open when the tank reaches its lowermost
position and de-energises the solenoid 903.
The glass is now supported in the rack 807, 808 and
is still gripped by the tongs. To open the tongs a tong
- 79 -
10435~
release switch S26 is operated to energise a solenoid
957 which causes pusher members, not shown, in the pit,
to engage the striker plates 655 on the arms 654 to tension
the cables 661 and open all the tongs. The glass sheet
then settles on to the rack, the tong points then being
just clear of the upper edge of the sheet and the tongs
can close again prior to being lifted by the hoist.
A further push button switch S27 is then pressed
and energises through closed contacts R105 of the tong
bar relay ~lQ the hoist rai$e relay Rll and the hoist
raise timer T7.
The relay Rll is latched by its holding contacts
R113 and instantaneously the timer T7 closes contacts
T71 to energise the solenoid 905 of valve 904, and sole-
noid 958 of the by pass valve 9.10 in the hoist motor
supply circ~it~
~t the same t~me contacts ~114 of the hoist raise
relay Rll close to energise a solenoid 959 which raises
the carriage stop 242, The contacts R115 and R116 close
to energise, through normally-closed contacts T73 of timer
- T7~ th.e speed control solenoids 940 and 944 so that the
leve~ ar~ 926 is moved to position C and the hoist motor
616 is accelerated up to top speed determined by fluid
flow through the fully open~valve 909 and the open by-
pass valve ~10 in parallel~
The tong bar is thus returned auickly before the
next glass sheet moves between the dies and when near the
top of its upward travel the contacts T73 of the hoist
raise tim.er T7 open to de-energise the speed control sole-
~oids 94Q an.d 944. The motor 616 decelerates to a creep
- 80 -
la~3s~
speed determined by the by-pass valve 910 and continues
to raise the tong bar at creep speed.
The hoist raise timer T7 has further contacts T72
which close ater a delay to energise the brake release
solenoid 921 which causes the valve 920 to remove the
high pressure from the brake calipers and at the same
time through closed contacts R127 energises the zero
pressure solenoid 925 of the brake circuit. The brake
is right off the hoist motor 616 at this stage.
The normally closed contacts Rlll of the hoist raise
relay Rll open when that relay is energised and when the
hoist raised switches S16 are all open the tong bar relay
R10 is de-energised, switch R102 closes and switch R103
opens to raise the hoist frames 581 by actuation of the
valves 887 and 892 to raise the pistons in the cylinders
575. Contacts R105 also open to de-energise the hoist
raise relay Rll and the hoist raise timer T7. After a
time delay to permit the motor 616 to wind up any slack
and to ensure that the wires have all been raised together
and to make sure that there is just enough tension on the
slipping clutch on each drum to make sure that the wires
are up together, the switch T71 opens to de-energise the
solenoids 905 and 958 of the valves in the motor circuit,
so that the hoist motor 616 is brought to rest. At the
same time the contacts T72 open to put full pressure back
onto the brake caliper arms.
~hen the tong bar is fully raised the switches S211
and S212 close to energise solenoid 914 and open the tongs.
The processing sequence then restarts for the next
sheet to be bent and toughened.
- 81 -
A subs-ta~tially linear temperature gradient may be
induced over the height of the glass sheet with the
leading edge of the sheet hotter than the trailing edge
of the s~leet by lowering the sheet through the boost
heaters 27 with constant acceleration. The space
between the bottom of the boost heaters 27 and the
top of the blowing boxes 28 is at least equal to the
height of the glass sheets being processed so as to
allow each sheet to be brought to a constant speed
before it passes between the blowing boxes. Any
loss o~ heat in this space can be compensated for
by providing a secondary heating zone in-the space
which is maintained at the average temperature of
the glass sheet leaving the boost heaters.
Some examples of operation in this way are set
out in Tables XIII, XIV, XV and XVI.
In each of these examples a glass sheet 61 c~l
in height is lowered through banks of boost heaters
27 which are 90 cm deep.
- 82 ~
~OL~35~9
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-- 83 --
la4;~s~
In each of these examples the top edge of the
glass sheet leaves the boost heaters~27 at a speed of
30.5 cm/sec. When the entry speed of the bottom edge
of the sheet between the top of the panels of boost
heaters is 2.5 cm/sec the constant acceleration of
the sheet is 3.08 cm/sec2. When the entry speed is
10.2 cm/sec the constant acceleration is 2.77 cm/sec2.
When the entry speed is 20.4 cm/sec the constant
acceleration is 1.73 cm/sec2.
When the temperature of the boost heaters is high,
e.g. 1600C it is pre~erred that the glass sheet shall
move between the panels of boost heaters at high ~n~
Some examples are given in ~h~
, . -.
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- 85
1~35~
When the entry speed is 30.5 cm/sec the constant
acceleration is 9.3 cm/sec2, and when the entry speed
is 46 cm/sec the constant acceleration is 5.3 cm/sec2.
Table XV sets out results achieved with glass
S sheets 3 mm thick and 61 cm in height.
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-- 87 --
In order to achieve the exit speed of 30.5 cm/sec,
the values of constant acceleration from the stated
entry speeds are as follows:-
. . _
Entry Speed Constant
Acceleration
cm/sec cm/sec2
_ _
2.5 3.08
5.1 3.01
10.5 2.77
. 15 2.35
: lO 21 1.73
1.02
Similar results obtained with glass sheets 4 mmthick and 61 cm in height are set out in Table XVI;
'~
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-- 89 --
:
1043S~;g
The values of constant acceleration of the glass
sheet are as set out above in connection with Table XV.
A linear temperature gradient can be produced in
the glass sheet by lowering the hot sheet with constant
acceleration between panels of boost heaters whose
depth is less than the height of the glass sheet.
Some examples of operation for different glass
thicknesses are set out in the following Table.
- 90 -
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--91--
~0~35ti9
The values of constant acceleration of the glass
sheet are also as set out above in connection with
Table XV.
- 92 -
