Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to the snapping of sheets of
glass and in particular to a method of and apparatus for
snapping a sheet of glass having a score line extendlng along
the sheet.
U.K. Patent No 1,110,764 describes a method of
snapping a sheet of glass having a score line extending along
the sheet, which method is characterised by applying to
opposite faces of the sheet uniformly curved bending members
of complementary form which members extend across the sheet
' 10 and each comprise a plurality of contacting elements, to
i impose on the sheet a curvature which is sufficient to snap' the sheet along any score line parallel to the axis of the
curvature but is insufficient to break any unscored area of
! the sheet. In this known method, the snapped portions of the
¦ sheet are usually conveyed along a common conveyor in spaced
¦ relationship to one another. The separated snapped portions
¦ are subsequently stacked on to pallets.
According to the present invention there is provided
a method of snapping a sheet of glass having at least one
1 20 score line extending along the sheet and separating the
¦ snapped portions by a predetermined amount, comprising
advancing at least the leading edge of the sheet over
conveying means, exerting on at least the leading edge of
the sheet a plurality of forces diverging away from one
another in the direction of advance, raising the trailing
edge of the sheet above the leading edge and imposing on
the sheet at its trailing edge a bending moment about its
direction of advance which is sufficient to snap the sheet
along any score line parallel to the direction of advance
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but is insufficient to break any unscored area of the sheet,
and continuing to advance the snapped portions of the sheet
so formed over the conveying means while maintaining the
diverging forces, thereby effecting a lateral separation
between the snapped portions of the sheet.
The present invention also provides an apparatus for
snapping a sheet of glass along a score line extending along
the sheet, comprising conveyor means arranged to exert on a
conveyed sheet a plurality of forces diverging away from one
another along the direction of advance, means for raising the
trailing edge of the sheet above the leading edge and for
imposing on the sheet at its trailing edge a bending moment
about its direction of advance whilst the sheet is passing
over the conveyor means, the bending moment being sufficient
~ ` to snap the sheet along any score line parallel to the
¦ direction of advance but insufficient to break any unscored
¦ area of the sheet.
Preferably the conveyor means comprises a plurality
of conveyors diverging away from one another along the
direction of advance.
The imposition of the bending moment on the trailing
edge of the sheet has been found to give a more precise and
cleaner break than bending at another portion of the sheet.
Also the use of the diverging conveyors in conjunction with
snapping by bending at the trailing edge results in a more
precise and reproducible positioning of the separated
snapped portions of the sheet.
Preferably the bending moment is produced by imposing
a curvature on the trailing edge of the sheet by pressing
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the trailing edge of the sheet between raised ends of the
diverging conveyors and an overhead contacting member having a
complementary shape to the imposed curvature. Alternatively
the overhead contacting member could be of variable shape
and arranged to adapt itself to the shape formed by the ends
of the diverging conveyors, both when in their lowered and
when in their raised positions. The overhead contacting mem-
ber may comprise a set of rollers, either freely rotatable or
i driven at the forward speed of the glass sheets, disposed in
! 10 a curved line and adjustably mounted to allow the curvature
of the overhead contacting member to be altered.
Advantageously, two freely rotatable rollers are
! positioned on opposite sides of, and at the same level as,
the upstream end of each conveyor. These rollers are lifted
together with the upstream end of the conveyor and serve as
additional support beneath the moving sheet as it is lifted
into engagement with the overhead contacting member. The
additional support provided by the rollers is particularly
important when the score line is located over the gap bet-
ween adjacent conveyors. In the latter instance the addition-
I al support rollers prevent vertical relative movement or
i~ shearing between snapped portions of the glass at the moment
of snapping. The overall effect of tne additional support
beneath the glass is to allow the glass sheet to adopt a
more uniform curvature when it is sandwiched between the
overhead supporting member and the conveyors.
Advantageously sensing means are provided for detect-
ing when the trailing edge of the sheet is over the upstream
ends of the conveyors, and means are provided, responsive
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to the sensing means, for raising the upstream ends of the
conveyors and the additional supporting rollers relative to
the downstream ends of the conveyors. The means for raising
the upstream ends of the conveyors and the additional support-
' ing rollers may take the form of a series of spaced torque
arms, rigidly attached to a transverse torque shaft. Each of
the torque arms has a defined length and its end remote from
the torque shaft can cooperate with a respective conveyor and
pair of supporting rollers to raise them a predetermined
ve,rtical distance. The rotation of the torque shaft can be
effected either by a motor or by an hydraulically or pneu-
matically operated piston and cylinder assembly, the piston
being connected to one or more of the torque arms. Alter-
natively the raising and lowering of the upstream ends of the
conveyors and supporting rollers can be effected by a plura-
lity of spaced eccentric cams mounted on the rotatable torque
~, arm, each cam being associated with a respective conveyor
I and pair of supporting rollers.
7 A specific embodiment of the invention will be
, 20 described further by way of example with reference to the
'I accompanying drawings in which:-
Figure 1 is a schematic plan view of an apparatus
I constituting an embodiment of the present invention installed
¦ in a conveyor line having diverging conveyors,
j Figure 2 is a section through the leading portion
of the diverging conveyors taken along the line II-II of
Figure 4,
Figure 3 is an enlarged plan view of the diverging
conveyors, and
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Figure 4 is a side view of one of the conveyors and a
lifting mechanism.
Referring to Figure 1, a portion of a conveyor line
consists of upstream and downstream roller conveyors 2, 6
between which is a set 4 of diverging belt conveyors. The
diverging belt conveyors are in the form of ten endless
flexible belts (e.g. V-belts shown in Figure 2). The two
central belt conveyors 10,12 are parallel to one another and
to the direction of advance; but the outer belt conveyors
diverge away from one another along their direction of advance,
the angles between adjacent conveyors being equal. Although
only ten flexible belts are illustrated in Figure 1, the
number of diverging conveyors can be more or less, dependent
¦ on the size of glass sheets to be snapped.
¦ In operation, a sheet of glass 1 having a longitudinal
. I .
score line 3 is conveyed from the upstream conveyor 2 on -to
the set 4 of diverging conveyors. The glass sheet 1 is then
sensed by a sensor 9 and snapped along the score line in a
manner to be described later, and two snapped portions 7,8
j 20 are formed. The two snapped portions are separated on the
diverging conveyors and proceed along parallel paths on the
downstream conveyor 6.
`I Figure 2 shows a section through the upstream portions
of two of the endless V-belt conveyors 10,12 of Figure 1,
j the V-belts 10,12 being located on opposite sides of the
centre line through the set 4 of diverging conveyors. On
each side of each V-belt is located a rubber roller 14 so
that two rollers 14 are associated with each V-belt. The
V-belts and their associated roller pairs are mounted on,
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and for vertical movement with, respective supporting frame-
- worksgenerally indicated by numerals 20,22. The roller pairs
14 and the upstream portions of the V-belts can be raised or
lowered with their respective supporting frameworks in a
manner -to be described below with reference to Figures 3 and
4.
Above -the V-belts is an overhead contacting member
comprising a set of driven or freely rotatable rollers 16
adjustably mounted on supports 18, on a curved line A-A.
Referring to Figure 4, the endless V-belt conveyor
12 passes around a drive wheel 24 and a free wheel 26 and
¦ moves along a V-shaped channel 13 defined by the periphery of
a supporting structure 15 (Figure 2). The drive wheel 24
and an end portion of the supporting structure 15 are attached
to a framework 32 which is pivotally mounted to a fixed point
34. The drive wheel 24 is rotated by a belt 28 which is it-
self driven by a pulley 30 on a drive shaft of a motor (not
shown).
The free wheel 26 and the other end portion of the
supporting structure 15 are attached to the vertically
movable supporting framework 22.
A downward projec-tion on the supporting framework 22
is rigidly fixed at a point 36 to the end of a vertical rod
38 which is arranged to reciprocate in a vertically disposed
guide member 40 which fits closely around it. The rod 38 and
guide member 40 serve as a guidance system to maintain the
belt conveyor 12 in a vertical plane when the end of the
belt conveyor 12 is raised and lowered.
The supporting framework 22 cooperates by means of a
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S~ thrust pad 42 with a roller 44. The roLler 44 i s mounted
! on a torque arm 46 which is supported on a transverse torque
j shaft 48, the weigh-t of the torque arm being balanced by a
weight 50. A downward projection on the end portion of the
torque arm 46 is connected to a lifting piston and cylinder
assembly 52. The top of the torque arm 46 is connected to
the undersurface of the supporting framework 22 by a spring
i 54 which biasses the torque arm away from the supporting
framework 22.
Torque arms of different lengths are arranged to
cooperate with the different diverging belt conveyors, to
impart differing heights of lift for a given movement of the
torque shaft 48. Thus Figure 4 shows in chain lines a torque
arm 56 which is smaller in overall dimens.ions than the torque
arm 46. The torque arm 56 cooperates with another belt
I conveyor, for example belt conveyor 11 in Figure 1, in an
¦ analogous manner to that described for torque arm 44.
In operation, a sheet of glass having at least one
score line 3 along its length is advanced along direction B
¦ 20 over the diverging conveyors until its trailing edge is
about to pass between the rollers 16 and 14. The trailing
edge is sensed by the sensor ~ which transmits a signal
to actuate an hydraulic or pneumatic system (not shown)
operably connected to the piston and cylinder assembly 52.
The piston of the assembly 52 is forced upwardly and effects
clockwise rotation of the torque arm 46. Rotation of the
torque arm 46 effects rotation of the torque shaft 48 which
; in turn effects simultaneous clockwise rotation of all the
¦ torque arms attached in spaced relationship to the torque
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shaft 48 along its length. The roller 44 mounted on the top
of each torque arm abuts upwardly against the respective
supporting framework (such as 22) attached to the upstream
portion of the respective diverging belt conveyor. In this
way the upstream portion of each belt conveyor is raised
relative to the trailing end of the conveyor which pivots
about point 34. Each conveyor is maintained in its vertical
plane during lifting by means of the respective guidance
system constituted by rod 38 and guide member 40, and the
height to which each belt conveyor is lifted is dependent on
the dimensions of the respective torque arm and the angle
at which it is mounted on the torque shaft. The height is
preset to bring the top of the trailing edge of the sheet
of glass in-to engagement with the rollers 16. Each pair of
rollers 14 being mounted on the respective supporting frame-
work 20,22, is lifted through the same height as the upstream
end of the respective conveyor. In this manner the upstream
portions of the diverging conveyors are pivoted upwardly and
the ends of the conveyors present a transverse curvature
complementary to that of the set of rollers 16. By imposing
the curvature on the trailing edge of the glass sheet as it
is advancing over the diverging conveyors between the rollers
16 and the rollers 14, a bending moment is created about the
score line 3. The size of the bending moment is dependent
on the curvature imposed on the sheet, the curvature being
adjusted so that the sheet is snapped along the score line
but not along any unscored area of the sheet. After the
score line has been snapped the piston and cylinder assemblies
52 lower the diverging conveyors. As a safety device, each
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spring 54 first urges the torque arm away from the framework
22 and then goes into tension to aid the retraction of the
torque arm and lowering-of the belt conveyors before the next
glass sheet arrives.
Other means than a piston and cylinder assembly can be
used to raise the diverging belt conveyors. For example, the
torque shaft can have a number of eccentric cams or linkages
mounted along its length, each cam or linkage cooperating
¦ with a respective belt conveyor to raise and lower them.
¦ 10 The angle of inclination, in a horizontal plane,
¦ between each diverging belt conveyor and the direction of
advance determines the extent t~ which the snapped portions
of the glass sheet are separated. In Figure 3, the central
pair of conveyors 10,12 are parallel, but on each side of
this pair the angles of inclination between adjacent conveyors
¦ vary in ~ steps. However, the angles of inclina-tion between
¦ adjacent conveyors can be set to vary at angles less than or
greater than ~.
- In a typical system, twenty-two diverging belt
conveyors are employed, eleven conveyors on each side of
the centre line and having angles of inclination between
adjacent conveyors of 2. The set of rollers 16 are set
at a fixed radius of curvature of 516 inches and the torque
arms each have varying radii so that the ends of the
diverging conveyors, when raised, lie on a curve having a
radius of curvature of 516 inches.
An advantage of the diverging conveyors is that
opposing transverse forces are applied to each portion of
the sheet at the moment of snapping. The opposing forces
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I apply a tensional force across the score line in the plane
¦ of the glass sheet and separate the snapped portions as soon
I as they are formed. It is for this reason that the belts
¦ are located in grooves. In this manner the snapping of the
glass sheet is assisted and shear forces between the opposing
faces of the snapped portions are reduced. Likewise adjacent
sheets are prevented from damaging one another by mutual
. contact.
A further advantage is that the snapped portions of
the glass sheet can be moved into precis~ defined positions
on the downstream conveyor 6, in correctly squared relation-
ship thereto, i.e. with their side edges parallel to, and
their leading and trailing edges perpendicular to, the
centre line of the conveyor system; whereas a previous
j system of using skewed rollers to separate snapped portions
of the glass sheet tended to result in unpredictable position-
ing of the snapped portions. In addition, because only one
end of the device is actuated, the cycle time between each
glass sheet passing along the conveyor line can be reduced
to a low figure, e.g. approximately one second.
It is to be understood that, although the above
description describes the imposition of a uniform transverse
curvature on the glass sheet for snapping it, the invention
also covers the concept of using non-uniform curvatures.
It will further be understood that, although the
specific embodiment of apparatus is shown and described
above as acting on a sheet having a single score line along
its length to form two snapped portions, the apparatus can
act on sheets each having a plurality of longitudinal score
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lines, for example having two score lines to form three
snapped portions or three score lines to form four snapped
portions.
It will be appreciated that it is advantageous to
drive the downstream wheel 24 of the conveyor 12 (as described
above) rather than the upstream wheel 26 as this simplifies
the engineering in avoiding the need for drive means in the
region of the upstream end of the conveyor where the lifting
mechanism is located. It will further be appreciated that
instead of providing a separate drive belt 28 for the wheel 24
as shown and described, the drive to this wheel could if
desired be transmitted by the conveyor belt 12 itself, the
belt 12 being lengthened and arranged to pass from the wheel
24 round the drive pulley 30 and then over a suitable ten-
sioning device at a position along its return run to the
upstream wheel 26.
Yet further it will be appreciated that instead of
providing torque arms of different lengths as described
above and as illustrated by the torque arms 46 and 56 in
Figure 4, the torque arms could all be of the same length
(for purposes of ease of manufacture) and the respective
rollers 44 would then be mounted at different positions
along the torque arms, i.e. at different distances from the
torque shafts 48, so as -to provide the differing heights
of lift of the ups-tream ends of the respective belt conveyors
required to achieve the desired transverse curvature. It
will also be appreciated that the arrangement of a roller 44
which ac-ts against a thrust pad 42 as shown and described
could, if desired, be replaced by a suitable pivoted linkage
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between the framework 22 and the torque arm 46.
In some embodiments the rollers 14 shown in Figure 2
may be itted.
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