Note: Descriptions are shown in the official language in which they were submitted.
WO95/283G0 ~ t 6 4 8 ~ ~ PCT~S95/04434
TITLE
CONTROL SYSTEM FOR GLASS BENDING PLATEN
BACRGROUND OF T~ lNV~llON
1. Cross-Reference to Related Ap~lication
The present application is a continuation in part of
co-pending United States Letters Patent Application Serial
Number 08/228,121, filed April 15, 1994 in the names of
Jennifer R. Wolfe, Allen T. Enk, and Robert G. Revells, and
entitled "Control System for Gla~s R~n~ ~ ~g Platen." The
specification of said co-pending application, to the extent
not repeated herein, is specifically incorporated by
reference.
2. Field of the Inven~ion
The present invention pertains broadly to press
bending of glass sheets, and more particularly to a press
bending device utilizing a hydraulically actuated platen
incorporating a closed loop hydraulic control system.
3. Descri~tion of the Prior Art
Bent or curved glas~ sheets are commonly employed as
glazing closures in present day vehicles ~uch as
automobiles and the~like. Such glass sheets must be bent
to precisely defined curvatures dictated by the
configuration and size of the openings in the vehicle body
in order to meet the strict quality st~n~Ards of automobile
manufacturers. In addition, the bent sheets must be of
consistently high optical quality in accordance with
established government and industry stAn~Ards. Such curved
glass sheets intended for use as automobile side and rear
windows are generally thermally tempered to increase their
resistance to damage due to impact and to cause the glass,
if broken, to fragment into relatively small harmless
particles as opposed to the large, jagged pieces normally
WO 95/28360 2 1 6 4 8 2 2 PCT~US95/n4434
resulting from the breaking of untempered glass.
Alternatively, if the glass sheets are to be used in the
production of automobile windshields, for example, the
glass is subjected to a suitable annealing procedure
5- following bending.
In accordance with a procedure currently widely used
in producing such curved sheets of glass, flat sheets of
glass are heated to their softening temperature, and the
heat-softened sheets are then press bent to the desired
curvature between complemental shaping surfaces. Following
bending, the bent sheets may be rapidly cooled in a
controlled manner to a temperature below the annealing
range of glass for tempering purposes, or they may be
gradually cooled in a controlled manner to a temperature
below the annealing range for annealing the bent sheets.
In either case the operations are preferably carried out in
succession, while the sheets of glass are being advanced
substantially continuously on a conveyor system along a
horizontal path including, in succession, a heat area, a
bending area and a tempering or annealing area. The heat
initially imported to each sheet to bring it to the proper
bending temperature is thus also utilized in the final heat
treating operation.
The complemental shaping surfaces between which the
sheets are formed to the desired curvature are provided on
opposed upper and lower press members or platens, normally
located above and below the horizontal path of movement of
the glass sheets on the conveyor system. The sheets are
conveyed into position between the upper and lower press
members, and the opposed press members are movable
relatively toward and away from each other for pressing the
sheets into the desired shape. A hydraulic cylinder of
WO95/283G0 2 1 6 4 ~ 2 2 PCT~S95/04434
generally conventional construction is preferably employed
for raising the lower press member upwardly to engage and
lift a suitably positioned heated glass sheet from the
conveyor system, out of the horizontal path, and press it
against the complemental shaping surface of the opposed or
upper press member. The cylinder then retracts the lower
press member to deposit the bent sheet upon the conveyor
system for advancement out of the bending area.
In production it is necessary that as the sheets are
bent one after another they consistently achieve a uniform
shape and be free of objectionable defects which might
result from inconsistent operation of the press bender.
The upper and lower press members may be frequently changed
to produce sheets o~ different configurations, and it is
desirable to minimize the time required to make the
changeover and begin production of the different parts so
as to minimize down time and lost production. The movement
of the mold needs to be smooth and of controlled velocity
from cycle to cycle to assure that the sheets are subjected
to equivalent gravitational and pressing forces from cycle
to cycle.
In the hydraulic system conventionally employed
heretofore for operating the bending press, the hydraulic
cylinder operatively coupled to the lower platen is
incorporated in a so-called open loop system. The system
may comprise a circuit including a pump connected to the
cylinder through solenoid controlled "platen up" and
"platen down" flow regulating valves, with a
cam-and-plunger operated flow control valve in the upside
of the circuit. To begin a pressing cycle a programmable
controller sends a signal to the platen-up solenoid, and
full hydraulic pressure is delivered to the platen
w~s~l283Go PCI`/US95/04434
- 21 64822
cylinder. The upstroke speed is determined by the flow
control valve in the platen-up circuit. It is important
that the sheet not be moving at an excessive speed as it is
pressed against the upper mold, and that the lower platen
not be jolted by coming to an abrupt stop from high speed
as it reaches its upmost position. To that end, at a
selected point in the upstroke the cam operates the plunger
on the flow reducing valve which, in turn, reduces the rate
of flow of hydraulic fluid being delivered to the platen
cylinder. The platen continues its upward movement at a
reduced velocity until it reaches the end of the cylinder
stroke.
When pressing has been completed the platen-down
solenoid is energized by the programmable controller. This
delivers full hydraulic pressure to the platen cylinder and
the platen moves downwardly until it reaches a down-normal
position on a programmable limit switch. The limit switch
then sends a signal for the down solenoid to close. Once
the solenoid is closed the platen tends to continue its
downward movement for a brief period due to the hysteresis
of the system, until it comes to rest at some position
below the "down normal" position. This position is
generally constant for a given temperature, and hence
viscosity, of the hydraulic fluid, but may vary as the
fluid temperature changes. The upper dwell position of the
lower platen, that is, the upper limit of the stroke at
which the sheet is pressed against the upper press member
by the lower press member, is constant since this position
is at the end of the platen cylinder stroke.
As the heated sheet advances into the bending station
on the conveyor rolls, its forward edge is engaged by
retractable stops which restrain the sheet in position to
wo 95/28360 2 1 6 4 8 2 2 PcT~ss5/o4434
be lifted from the conveyor rolls by the lower press
member. In order to minimize potential damage during the
dwell time of the stopped sheet upon the spaced conveyor
rolls, it is important that cycling of the lower press
member be closely coordinated with movement of the sheet
into position by the conveyor rolls. With the prior system
the down or lower dwell position of the lower platen is
subject to positioning variations due to errors of the
programmable limit switch and changes in hydraulic oil
temperature as pointed out above. In addition, adjustment
of the various flow controls and the cam position are
matters of subjective judgment and will vary from setup for
production of one part to another, and even from one shift
to another as an operator makes changes in accordance with
his or her perception of the operation. These factors
cause variations in the positioning of the lower platen in
its lower, rest position, which result in undesirable
variable dwell times of the glass on the rolls. A lower
down position, of course, results in a longer dwell time
while a higher down position results in a shorter dwell
time.
SUMMARY OF THE INVENTION
The aforementioned problems of the prior art are
addressed in accordance with the present invention by
utilization of a closed loop hydraulic control system.
Flow of hydraulic fluid supplied to the cylinder operating
the lower platen is controlled through a servo solenoid
valve. A linear displacement transducer associated with
the lower press platen continuously monitors the position
and velocity of the platen and sends appropriate signals
indicative of the position and velocity to a programmable
wos~l2836o 2 1 6 4 8 2 2 PCT~S95/04434
. _
motion controller. The motion controller is programmed
through an operator interface to cause the lower platen to
cycle through a predetermined sequence in accordance with
the motion control program. To that end the motion
controller commands a position module which is operatively
coupled to the spool of the servo solenoid valve. The
servo solenoid valve in turn regulates the flow of
hydraulic fluid from a hydraulic pump to the hydraulic
cylinder or actuator. The linear displacement transducer
feeds lower platen position and velocity information to the
programmable motion controller, which utilizes the
information for making any necessary corrections to insure
that the platen and lower press member thereon cycle in
accordance with the predetermined program.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a fragmentary side elevational view of a
bending and tempering apparatus embodying the invention,
and schematically illustrating the hydraulic control
system;
Fig. 2 is a diagrammatic view of Fig. 1 showing
additional components which are added in a second
embodiment of the invention;
Fig. 3 is a more detailed diagrammatic view of the
magnetic pickup shown in Fig. 2 and the associated
apparatus for controlling the speed of the conveyor rolls;
Fig. 4 is a graph showing a plot of a press cycle
performed in accordance with the method of the present
invention;
Fig. 5 is a flow chart showing a series of steps used
in the method of the present invention;
Fig. 6 is a flow chart showing additional steps used
in the method of the present invention;
wossl2836o 2 1 6 4 8 2 2 PCT~S951~4434
Fig. 7 is a flow chart showing a series of steps
involved in the step of checking the speed and position of
the lower platen member shown in Fig. 6; and
Fig. 8 is a flow chart showing a series of steps
involved in the step of checking position and timer value
shown in Figure 6.
It is to be understood that the invention is not
limited in its application to the details of construction
and arrangement of parts illustrated in the accompanying
drawings, since the invention is capable of other
embodiments, and of being practiced or carried out in
various ways within the scope of the claims. Also, it is
to be understood that the phraseology and terminology
employed herein is for the purpose of description, and not
of limitation.
DESCRIPTION OF T~E PREFERRED EMBODIMENT
Referring now in detail to the illustrative embodiment
depicted in the accompanying drawing, there is shown
generally at 10 a bending and tempering apparatus for
producing bent and tempered glass sheets by a generally
continuous process. Glass sheets to be bent are advanced
along a predetermined path successively through a heating
area, a bending area and a thermal conditioning area, with
the areas being contiguous so that a sheet passes
immediately from one area to the next succeeding area. To
that end the apparatus 10 includes a conveyor system 12
adapted to support a series of sheets S for movement one
after another along a predetermined horizontal path through
a heating section 14, a bending station 16 and a thermal
conditioning station 18, in this case a tempering section.
The sections 14, 16 and 18 are disposed end-to-end along
Woss;283Go 2 1 6 4 8 2 2 PCT~S95/04434
the path so that residual heat remaining in the sheets
following bending may be utilized for thermal conditioning
purposes. A programmable operating system, shown
schematically at 20, is provided for the bending station.
While the invention has been illustrated in
conjunction with a tempering section adjacent the bending
station 16, it will be appreciated that it may as well be
utilized with an annealing section in place of the
tempering section as the thermal conditioning station 18
where annealed bent sheets are to be produced.
Typically, the glass sheets S are heated in a
controlled manner while being conveyed through a furnace 22
comprising the heating section 14 on aligned conveyor rolls
24 forming part of the conveyor system 12. The furnace may
be of any suitable construction and conventionally, as
illustrated, may be a tunnel-type furnace having a heating
chamber 26 defined by a roof 28, a bottom wall or floor 30,
opposite side walls 32 and an end wall 34. The heating
chamber 26 is heated by suitable heating means such as gas
burners or electrical resistance heaters (not shown)
disposed in the top, bottom and side walls and suitably
regulated to provide a desired heating pattern for the
~lass sheets moving therethrough. The sheets S are carried
through the heating chamber 26 on the conveyor rolls 24 of
the conveyor system 12, which extend from the entrance end
(not shown) of the furnace through an opening 36 in the end
wall 34. The sheets are heated to substantially their
softening point as they are conveyed through the controlled
temperature environment of the furnace. Upon exiting the
furnace through the opening 36, the heated sheets are
received upon a second series o~ conveyor rolls 3~ for
movement into and within the bending station 16. The
Wo~)s/28360 2 1 6 4 8 2 2 PCT~S95/04434
~,
heated sheets are conveyed upon the rolls 38 between
opposed upper and lower press members 40 and 42,
respectively, which impart the desired curvature thereto as
will be hereinafter described.
Following bending the sheets are advanced along the
conveyor 12 on a further ~eries of rolls 44 through the
adjacent thermal conditioning station 18. While the rolls
38 and 44 have been illustrated as being of linear or
straight configuration, it i8 contemplated that they may as
well be of the curved mandrel and rotating sleeve type
conventionally employed in conveying bent sheets as
disclosed, for example, in U.S. Patents Nos. 4,015,968 and
4,167,997. In the tempering station the bent glass sheets
pass between upper and lower blastheads 46 and 48,
respectively. The blastheads have a plurality of tubes 50
and 52 operably disposed to direct opposed streams of
cooling fluid, generally air or the like, towards and
against the opposite sur~aces of the sheets moving along
the conveyor.
The press bending station 16 more particularly
comprises a skeletal framework 54 generally of rectangular
parallel piped form. The framework includes upstanding
corner posts 56 interconnected at their top and bottom by
longitudinal beams 58 and transverse beams 60. The rolls
3~ and 44 of the bending station are drivingly mounted upon
the framework in a conventional manner (not shown). Upper
and lower press members 40 and 42, respectively, are
mounted within the framework 54 for reciprocating relative
movement toward and away from each other. The press
members are provided with opposed complemental shaping
members conforming to the curvature to which the sheets are
to be bent.
WO ~)51283G(~ 2 1 6 4 8 2 2 rcT/usg~/04434
The upper or male press member 40 typlcally comprises
a shaping element 62 carried upon a platen frame 64. While
not limited thereto the upper male shaping element as
illustrated is of the so-called solid or continuous type,
and includes a continuous glass contacting surface having a
configuration complementary to that o~ the lower female
shaping rail of the lower press member 42. The platen
frame is preferably constructed to be adjustable to
selected vertical positions in order to accommodate glass
parts bent to varying degrees of curvature between the
opposed press members. To that end the platen frame 64 is
operatively coupled at each of its corners within the
framework 54 to the lower ends of screw jack shafts 66.
The jack shafts are threadably received within rotatable
collars 68 of screw jack bases 70 carried on a framework
comprised by the beams 58 and 60 atop the framework 54.
Also carried atop the framework is a motorized dri~e unit
72 adapted to rotatably drive the collars 68 in unison for
retracting or extending the shafts 66 to correspondingly
raise or lower the platen frame 64 and the shaping element
62 carried thereby.
The lower or female press member 42 is mounted for
vertical reciprocating movement upon each bending cycle,
that is, as each glass sheet is lifted from the rollers 38
and pressed against the upper shaping element 62. To that
end the press member 42 comprises a carriage, identified
generally at 74, including a bed 76 upon which a base plate
78 is mounted. A shaping rail 80 is mounted upon and
spaced from the base plate by means of connecting rods 82.
The shaping rail as illustrated is of the so-called
peripheral ring-type, conforming in outline to the glass
sheets S to be bent, and is formed to include a series of
W095/283Go 2 1 6 4 8 2 2 PCT~S~5/04434
_ .
11
spaced segments across its ends so as to be able to pass
upwardly between the rollers 38 and lift a sheet from the
conveyor. of course, the rollers may as well be of other
well-known configurations such as the curved rollers of
U.S. Patent No. 5,178,660 which curve downwardly beneath
the ends of the shaping rail so that the shaping rail may
be a continuous ring. Also, as will be readily appreciated
a shuttle transfer mechanism (not shown) such as disclosed
and described in U.S. Patent No. 4,883,526 may be
lo incorporated in the bending and thermal conditioning
apparatus for receiving and transferring the bent sheets.
The shaping rail 80 is provided on its upwardly
directed face with a generally concave shaping surface 84
complementary to the shaping surface of the ~pper shaping
element 62 in opposed relationship thereto. In order to
insure that the platen frame 64 and the carriage 74 move
freely up and down along a precise vertical path within the
framework 54, they may be provided at each of their corners
with roller guide members 86. The guide members include
brackets 88 affixed to the corners of the platen frame 64
and the carriage 74. Each bracket carries spaced pairs o~
rollers 90 mounted perpendicularly to one another and
adapted to rollingly engage track plates 92 affixed to
adjacent angularly disposed faces of the associated corner
posts 56. The platen framè and carriage are thus held
firmly against lateral movement while being ~ble to move
freely up and down along a vertical path.
As heretofore explained the lower press member 42
carries a shaping rail 80 which is of outline or ring-type
construction and which normally resides in a rest position
beneath the rolls 38. A heated sheet S can the be advanced
on the rolls into position over the press member so that
W~95/28360 2 1 6 4 8 2 2 PCT~S95104434
_,
12
the sheet can be lifted from the rolls by the lower press
member, pressed against the upper shaping element 62, and
then returned to the rolls 38 and 44, or otherwise advanced
out of the bending station 16 as by the aforementioned
shuttle transfer mechanism (not shown).
For purposes of accurately positioning each sheet
between the upper and lower press members 40 and 42, there
is provided in the path of the advancing sheets between
adjacent ones of the rolls 38 and 44 a pair of laterally
lo spaced locator stops 94. Each of the locator stops is
affixed to the distal end of a piston rod 96 of a fluid
actuated cylinder 98 mounted as on the base plate 78 of the
carriage 74. The cylinders are operable to selectively
move the stops 94 between an upper raised position at which
they protrude above the conveyor rolls 38 into the path of
an advancing glass sheet S, and a lowered position beneath
the path. The base plate 78 is carried on the bed 76 of
the carriage 74 so as to move up and down therewith.
A hydraulic cylinder 100 is suitably mounted beneath
the carriage 74 upon the beams 58. The cylinder includes a
piston rod 102 connected at its distal end to the bed 76 of
the carriage 74. The axially extensible and retractable
piston rod is thus operable to reciprocally move the lower
female press member 42 between its retracted or lowered and
raised positions. In the retracted position the shaping
rail 80 is disposed beneath the rolls 38 so that a sheet
may advance into position thereabove and into engagement
with the locator stops 94. Upon extension of the piston
rod the shaping rail 80 moves upwardly through the bed of
rolls 38 to lift the heated sheet S from the rolls and
press it against the upper press member 40 between the
complementary shaping surfaces of the male element 62 and
WO 95/283G0 2 1 6 4 8 2 2 PCT~S95104434
the shaping surface 84 of the shaping rail 80 to form it to
a predetermined curvature. Upon completion of bending, the
piston rod 96 is retracted to lower the carriage 74,
thereby retracting the shaping rail 80 thereon and
depositing the bent sheet on the conveyor rolls 38 or other
transfer mechanism such as the aforementioned chuttle
transfer system for removal from the bending station 16.
As shown diagrammatically in Fig. 1, the programmable
system 20 for operating the lower press member 42 includes
a suitably driven hydraulic pump 104 adapted to receive
hydraulic fluid through a conduit 106 from a reservoir 10~.
The pump 104 provides hydraulic fluid under pressure
through a pressure supply conduit 110 to a servo solenoid
valve 112. The servo solenoid valve may be of the type
available commercially from the Parker Hannifin
Corporation, Hydraulic Valve Division, Elyria, Ohio 44035,
under the designation Series D3lFH.
The valve 112 controllably regulate5 flow of hydraulic
fluid to and from the press cylinder 100 through conduits
114 and 116 connected the cylinder at the proximal and
distal ends, respectively. More particularly, hydraulic
fluid is supplied through the conduit 114 to the proximal
end of the cylinder beneath the piston (not shown)
connected to the piston rod 102 for raising the lower press
member 42. At the same time hydraulic fluid is expelled
from the cylinder above the piston at the distal end and
returned through the conduit 116 to the solenoid valve and
thence through a return conduit 118 to the reservoir 108.
For retracting the lower press member the servo solenoid
valve 112 directs hydraulic fluid through the conduit 116
to the distal end of the press cylinder 100 above the
piston, and fluid returns from beneath the piston through
wo g5/283Go 2 1 6 4 8 2 2 PCT~S95/04434
14
the conduit 114 and the solenoid valve to the reservoir
108.
In order to continuously monitor the position and
velocity of the lower carriage or platen 74 and send
approprlate indicative signals to the control system, a
linear displacement transducer, identified generally at
120, is provided. The linèar displacement transducer, by
way of example, may suitably be a TEMPOSONICS II model,
commercially available from MTS Systems Corporation, Box
13218, Research Triangle Park, North Carolina 27709. More
specifically, the linear displacement transducer comprises
a stationary sensing unit 122 carried upon a bracket 124
affixed as to a corner post 56 of the framework 54. A
linear probe 126 of the sensing unit is adapted to project
axially through a ring magnet 128 affixed to a bracket 130
carried by the carriage 74. Thus, as the carriage or lower
platen 74 reciprocates vertically the linear probe 126
correspondingly moves axially back and forth through the
magnet 128, generating a signal indicative of the position,
direction of movement and velocity of the lower carriage.
The linear displacement transducer is capable of
consistently determining the position and velocity of the
lower carriage with great accuracy, for example, its
position within one thousandth of an inch. The signal from
the sensing unit 122 is transmitted by a line 132 to a
programmable motion controller 134. The motion controller
may suitably be a model designated TMC 188/40, available
from Delta computer Systems, Inc., Industrial Electronics
Controls, 11719 NE 95th Street, Suite D, Vancouver, WA
98682-2444. The motion controller interfaces through a
line 136 with a conventional interface unit 138 including
an operator console and programming entry system .
woss/28360 2 1 6 4 8 2 2 PCT~S95/04434
A position module 140 receives velocity command
signals from the motion controller 134 through a line 142,
and sends appropriate spool position command signals
through a line 144 to the servo solenoid valve 112.
Feedback ~ignals indicatlve of the actual 5ervo valve spool
position are sent from the valve 112 through a line 145 to
the position module 140.
With the closed loop system of the invention the
setpoint, that is, the predetermined program for the lower
carriage or platen operation, is entered through the
operator interface unit 138,and the press unit is ready for
operation. A heated sheet S advances into position upon
the rolls 3~ and the up command is i55ued by the computer
unit 138. The servo-valve is positioned to move the lower
carriage or platen 74 upwardly at a predetermined speed
commanded by the motion controller 134. The position of
the servo solenoid valve 112, which determines the velocity
of the platen, is monitored by the computer 134 and this
target velocity is compared to the actual velocity of the
platen 74 as determined by the linear displacement
transducer 120. Adjustments to the position of the servo
solenoid valve are made as necessary in response to signals
from the motion controller 134 by the position module 140
to insure that the platen moves at the predetermined speed
in accordance with the program.
When the upwardly moving platen reaches the slow-down
position in its cycle as determined by the linear
displacement transducer 120, the motion controller 134
signals the position module 140 to set the servo solenoid
valve for reducing the rate of flow of fluid to the
cylinder lOo, and hence the platen speed, to the
predetermined level. The platen speed is continuously
wossl2836o 2 1 6 4 8 2 2 PCT~S95/04434
16
monitored and corrected as appropriate by the linear
displacement transducer and programmed motion controller.
When the platen reaches the upper dwell position, again as
determined by the linear motion transducer, its motion is
stopped. Due to the degree of precision of the transducer,
the platen is consistently able to achieve a dwell position
within a high degree of accuracy, on the order of 0.001
inch (0.025 mm), without bottoming of the piston within the
cylinder. Upon elapse of a selected dwell time, the motion
controller signals the position module to set the servo
solenoid valve for retracting the piston rod lOZ and moving
the platen downwardly at a selected speed. The platen
speed and position are monitored by the linear transducer
120, and the platen is stopped precisely at a predetermined
lower rest position in response to appropriate signals from
the linear motion transducer to await the beginning of the
next cycle.
The advantages of close loop hydraulic system
described above have been found to be particularly
advantageous when used in a second embodiment of the
invention which involves combining the closed loop
hydraulic system for the operation of the upper or lower
platen member with increased control and accountability of
the movement of the glass sheet S on the aligned conveyor
roles 24 forming a part of the variable speed conveyor
system 12.
Referring to ~ig. 2, a second embodiment of a
construction embodying the present invention is shown in
diagrammatic form. In this embodiment of the invention the
operator interface 138 is connected to programmable logic
controller (PLC) 135. It is pre~erable to use a
programmable logic controller due to the additional tasks
WO95/283Go 2 1 6 4 8 2 2 PCT~S95/04434
which need to be performed. As before, the hydraulic
cylinder 100 is hydraulically connected to servo valve 112,
which is connected to servo controller 146. The stop means
94 are again operated by the PLC 134. In addition a
photoelectric eye 144 is connected to the PLC.
A variable speed drive motor (Fig. 3) 148 is connected
by way of shaft 150 to at least one of the second conveyor
rolls 38. Mounted to the output shaft 150 is an indicator
means, such as gear 38A having fine teeth (indicated
diagrammatically in Fig. 3). The teeth moving past
magnetic pickup 156 produce pulses which are supplied to
motor speed controller 158, which may be such as the "M-
Trim" manufactured by Fenner Industrial Controls of Maple
Grove, Minnesota. The motor controller 158 is then
connected to motor drive 159. The motor drive 159 is, in
turn, connected to motor 148 to form a control loop.
The gear 38A has a predetermined number of teeth on
it, and the magnetic pickup 156 produces a pulse each time
one of the gear teeth passes by the pickup. Since the
spacing of the gear teeth is precisely known, the number of
teeth can be related to angular position, and the rate at
which they are counted can be related to the angular
velocity or speed of the second conveyor rolls 38. With
this information, the motor speed controller 158, in
combination with the PLC 135, can control the speed of the
conveyor rolls 38 very precisely.
The pulse from the magnetic pickup 156, in addition to
being supplied to the motor speed controller 158, is
supplied to counting means including a counter card (not
shown) in the PLC 135 for purposes to be described
hereinafter. Likewise the PLC 135 can supply signals to
the motor speed controller 158.
WO95/~83Go 2 1 6 4 8 2 2 rcT~s9slo4434
18
Alternately, other variable speed drive means, such as
a servo drive control, could be used to drive the conveyor
rolls.
In this embodiment of the invention, the servo
solenoid valve 112 is a zero overlap valve, which may be
such as the Bosch Racine servo solenoid valve model number
NG-6 manufactured by the Bosch Racine Group of Racine,
wisconsin. The use of the zero overlap valve is preferred
in the second embodiment of the invention because the
pulsating effect which is produced by other valves is
eliminated. However, other servo solenoid valves,
including that previously described, could be used, if
desired. The servo controller 146 may be the same as the
programmable motion controller 134 if desired.
Referring now to Fig. 4, there is shown a graph of one
of the almost infinite number of cycles of the platen or
lower press member 42 which may be preprogrammed in-to the
PLC 135 throu~h the operator interface 138. The particular
cycle shown is for bending windshield, and is a plot of
milliseconds of time versus milliinches of position of the
lower press member 42. The operator will have entered into
the PLC 134, through the operator interface 138, the "wait"
positions or first predetermined position (A), the CAM or
slow down or second predetermined position (B), the Dwell 1
or third predetermined position (C,D) a Dwell 2 or fourth
predetermined position (E,F). The operator will have also
entered through operator interface ~38 a first
predetermined, or up, speed or velocity, a second
predetermined, or CAM speed, or Dwell 1 speed or velocity,
~ third predetermined-, or Dwell 2 speed or velocity, and a
fourth predetermined down speed or velocity. Also ~or
purposes to be described, a first number of pulses, or
WO 95/28360 2 1 6 4 8 2 2 PCT/USgSI04434
19
"operator preset 1", and a second number, or "operator
preset 2" will be entered.
It should be understood by those skilled in the art
that this press cycle, which is by way of example for press
bending a windshield, is only one of an almost infinite
variety of cycles which may be preprogrammed by the
operator. Additional positions or velocities may be
programmed as desired. For example, when certain types of
parts are bent, the platen or lower press member may be
lowered to a below home or "wait" position, while a shuttle
removes the windshield from under the upper press member
after bending. When some shuttles are in use, the lower
press member does not have to go to a below home position.
When parts other than winflshields are being bent, a Dwell 2
position and Dwell 2 speed may not be used. Thus it can be
understood by those skilled in the art that this
programming capability makes for a construction of extreme
versatility in the glass bending art.
Referring now to Figs. 5-6 the operation of the
present method and apparatus will be explained in greater
detail. When the press cycle is started (box 200) several
things happen substantially simultaneously. The computer
will check to see if the system is initialized (box 205).
If the system is not initialized, the servo system will be
initialized (box 210), and the lower platen or press member
42 will be moved to the first predetermined or "wait"
position (box 215).
While this is happening, the computer will be checking
(box 220) to see if a sheet S of glass has been detected by
the photoelectric eye 144 while travelling along the
conveyor rolls 38 at a first predetermined speed. When the
photo eye 144 detects a sheet S of glass, it will send a
WO 951283CU 2 1 6 4 8 2 2 rcrlus9slo4434
signal to the PLC 135. The PLC will then cause the stops
94 to be raised (box 225) and the counter card (not shown)
in the PLC 135 to begin counting pulses from the magnetic
pickup 156.
~s previously explained with regard to Fig. 3, the
magnetic pickup 156 counts a pulse every time one of the
teeth on gear 138A passes in proximity thereto. These
pulses are supplied to the motor speed controller 158 as
well as being supplied to the counter card in the PLC 135.
As shown in Fig. 5, a decision is being made as to whether
to change the speed of the second conveyor rolls 38 from
the first predetermined speed to the second determined
speed or "creep" speed. The counter card is continuously
comparing the number of counts counted to the "operator
preset 1" value. The second conveyor rolls 38 will
continue to rotate at the speed of the conveyor rolls 24
until the "operator preset 1" value is reached (box 240).
~t tllis time the PLC 135 5upplles a signal to the
primary/secondary mode switch of the motor speed controller
158. The controller will automatically start to decelerate
the rolls in accordance with the program the operator has
entered into the motor speed controller 158. This is
accomplished through the motor drive 159 supplying a signal
to the motor 148, which turns the shaft 150 connected to
the second conveyor roll or rollers 38.
While this deceleration is taking place, the motor
speed controller is operating independently of the PLC 135,
but pulses are still being supplied to the counter card by
the magnetic pickup 156. The computer is continuously
checking (box 268) to see if the "operator preset 2" value
for counter pulses has been reached. When the "operator
preset 2" value is reached, the press cycle will be
WO95/283Go 2 1 6 4 8 2 2 PCT~S95/04434
21
initiated (box 255). It is up to the judgment of the
operator to choose the "operator preset 2" value such that
the "creep" speed is just being reached, and the glass
sheet is just coming into registry between the upper and
lower platen member, when the press cycle is initiated.
This requires some judgement on the part of the operator.
When the counter card has the required number of
counts it initiates the press cycle (box 255) which starts
the press program (260). At the same time the press cycle
is initiated, the stops 94 will be lowered and the counter
will be reset (box 23~). The press program is described in
greater detail in Fig. 6.
~ s previously described, at the initiation of the
cycle (box 200) the system was initialized (box 205) and
the platen was moved to the "wait" position (box 215) by
the hydraulic cylinder loO. The closed loop control system
previously described has been continuously comparing the
desired "wait" position with the actual "wait" position
(box 284) utilizing information being supplied to the servo
controller 146 by the linear transducer 122 (box 2~3). The
servo controller 146 continually inquires if the position
is correct (box 286), and will initiate the press cycle
(box 260) if both the position is correct and a proper
signal is received indicating that the number of pulses
counted by the counter card in the PLC 135 is equal to the
"operator preset 2" value. If the position is not correct,
the system will loop through boxes 215, 284, 286 until the
platen is in the correct position.
In accordance with the values preprogrammed by the
operator into the operator interface 138 to accomplish the
program shown in Fig. 4, lower press member 42 will be
rapidly advanced by the hydraulic cylinder lOo under
wos5l283G(l 2 1 6 4 8 2 2 Pcl~ss5to4434
22
control of the servo valve 112 and servo controller 146 at
the up or f irst predetermined velocity until it reaches the
f irst predetermined slow down or CAM position indicated at
point B on Fig. 3. While the lower press member 42 is
moving to the CAM position at up speed, the closed loop
hydraulic control system is continually checking the speed
and position of the platen.
The servo controller 146 continually inquires: "Is
the speed correct?" by monitoring the position data being
supplied to the servo controller 146 by the measuring
device associated with the servo solenoid valve 112. If
the speed is not correct, an adjustment will be made and
the inquiry repeated. As shoWn in Fig. 7, the system will
make the loop of checking speed (box 270A), inquiring if
the speed is correct (box 270B), adjusting speed if the
speed is not correct (box 270c) until the inquiry can be
answered yes, at which time the servo controller 146 will
make a check of position (box 270D) by inquiring: "Is the
position correct?" (270E). If the position is not correct,
the system loops to Box 270A where the speed will again be
checked.
This will continue to occur until the speed and
position check indicate that the lower press member 42 has
arrived at position B. At this time the servo controller
146 will begin decelerating the lower press member 42 at
the so called CAM speed, second predetermined velocity or
"Dwell 1" velocity (box 275). The same speed and position
check (box 270) are again made while this is occurring
until it is determined that the lower press member 42 has
decelerated to a stop and is at the "Dwell 1" (C) position.
At this time a dwell timer (not shown) will be started
(box 285). The servo controller 146 will continue to check
WO 95/2X3C0 2 1 6 4 8 2 2 Pcrlus~sl()4434
-
23
on the position of the lower press member 42, while the PLC
135 is checking the time remaining on the dwell timer.
This will continue throughout the period of time which the
operator has programmed as the "Dwell 1" time through the
operator interface 138. This operation, to be described in
more detail hereinafter, is identified as Box 290.
Once the dwell timer has timed out, the press member
142 will move at a predetermined "Dwell 2" velocity to the
"Dwell 2" position or "E" position (Box 295) while the
speed and position of the lower platen is checked (Box
270). At the conclusion of this portion of the cycle, the
lower platen 42 will have decelerated to a stop at the
"Dwell 2" position (box 300).
The "Dwell 2" timer (not shown) is started (box 305)
and the position of the lower platen member and the time
remaining on the timer, is again continually checked (box
290) until the "Dwell 2" timer times out, at which time the
lower platen will move at the down speed or velocity toward
the "wait" position (box 305). Again, its' speed and
position is constantly being checked (box 270) until it
reaches the "wait position" (box 310). At this time a
signal will be supplied, as shown at Box 255-, indicating
that one press cycle has been completed and another is
ready to be initiated.
The manner in which the "check position" operation
(box 290) is carried out is shown in Fig. 8. It is
desirable that the lower press member 42 remain in the
correct position and not "creep" while the dwell is being
held, as this will effect the quality of the glass product
being manufactured. For this reason, while the "Dwell 1"
or "Dwell 2" timer is timing out, the system will be
continually looping. The position will be checked (box
W095/28360 2 1 6 4 8 2 2 PCT~S~5/04434
.
24
290A) by inquiring: "Is the position correct?" (box 290B).
If the position is correct (box 290B) the timer will
then be checked (box 290C). If the timer has not timed
out, the program will continue to loop through (box 290A),
290B and 290C) until the timer has timed out and the
program moves to the next step. If at any time the
position has not been found to be correct the program will
then again check the timer (box 290D) and, as long as the
timer has not timed out, will adjust the position (290E)
and then recheck the position (box 290A). If the position
is still not correct (box 290B) the timer will again be
checked (box 290D), and if there is time remaining, the
position will again be adjusted (box 290E). This loop
through boxes 290A, 290B, 290D, and 290E will continue as
long as the timer has not timed out and the position is
incorrect. Once the position is corrected, the program
will use the loop (290A, 290B and 290C) previously
described. It is to be noted that the timer is dominant,
and the program will continue to run even if the exact
predetermined desired position has not been reached by the
time the Dwell timer has timed out.
When the press program (box 260) is completed, a
signal will be sent to reset the servo valve (box 320) and
to reset the second conveyor rolls 38 to the fast speed to
be in a readiness state to receive the next sheet S of
glass from the first set of conveyor rolls 24 (box 325).
21 64822
woss/283Go PCT~S95/04434
It is to be understood that the form of the invention
herewith shown and described is to be taken as an
illustrative embodiment only of the preferred mode of the
invention, and that various changes in the shape, size and
arrangement of parts, as well as various procedural
changes, may be resorted to without departing from the
spirit of the invention.
