Differential pressure forming machine with variable mold closed cycle

• US 4,377,377 A
• Filed: 12/15/1980
• Issued: 03/22/1983
• Est. Priority Date: 05/10/1978
• Status: Expired due to Fees

• Current Assignee: John Brown Industries Limited
• Original Assignee: Leesona Corp.
• Inventors: Russell, Edward J., Arends, Albert W., Pickard, George L., West, George A.
• Primary Examiner(s): Anderson, Philip E.
• Application Number:
  US06/216,317
• Time in Patent Office: 827 Days
• Field of Search: 425/451.4, 425/155, 425/451.2, 425/394, 264/322
• US Class Current: 425/155
• CPC Class Codes: B29C 51/38 Opening, closing or clamping means

Abstract

A thermoforming machine having opposed mold platens includes a linkage system driven in cyclic movement by rotary cam mechanism to cyclically shift the platens between their open and closed position. The cam mechanism is driven by a variable speed motor which is controlled in a manner such that the rotary speed of the cam mechanism during different portions of a cam revolution may be set to a speed which is different than the rotary speed of the cam mechanism during other portions of each revolution. By adjusting the speed differential or by adjusting the angular extent of that portion of a revolution of the cam mechanism over which the different speed is maintained the time duration of any chosen portion of the cycle may be adjusted independently of the time duration of other portions of the cycle.

Claims

1. In a thermoforming machine having a frame;

a pair of mold carrying platens mounted on said frame for movement toward and away from each other between a mold open and a mold closed position, and motor driven means including cam and cam follower means operable when driven to cyclically drive said platens between said mold open and mold closed position, the improvement wherein said motor driven cam and cam follower means comprises a cam for each platen mounted on said frame for rotation about an axis, each cam having a dwell portion of given angular extent lying at a constant radius from the axis about which it rotates, said follower means including a cam follower for each platen engaged with each cam and operable to maintain the mold platen it drives in mold closed position when the cam follower is engaged with the dwell portion of its cam, variable speed motor means for driving said cams in rotation, and control means for selectively controlling the speed of said motor means during that portion of the rotary cycle of said cams when said cam followers are engaged with said dwell portions to thereby adjustably vary the times during which said mold platens are held in said mold closed position.

2. The machine defined in claim 1 wherein the mold carrying platens carry a female mold having mold cavity configurations and a male mold having plug assist configurations;

and the female mold carrying platen reaches closed position slightly before the male mold carrying platen.

30. The invention defined in claim 2 wherein said motor is a hydraulic motor and a hydraulic system including a pump drivingly connected with the motor.

3. In a thermoforming machine having a frame, a pair of mold carrying platens mounted on said frame for movement toward and away from each other between a mold open and a mold closed position, and variable speed drive means for driving each of said platens in intermittent motion through a cycle wherein each of said platens are shifted from said mold open position to said mold closed position and subsequently returned to said mold open position;

the improvement comprising control means operable for varying the speed of drive of said drive means driving each platen during said cycle to cause said drive means to drive each platen at different speeds during different portions of the same cycle.

4. The machine defined in claim 3 in which said control means is operable to select a slower speed setting for a stage of each platen which includes the mold closed stage of each platen than for the remaining portions of the cycle.

5. In a thermoforming machine having a frame, a pair of mold carrying platens mounted on said frame for movement toward and away from each other between a mold open and a mold closed position, and a motor operable when driven to cyclically drive said platens between said mold open and mold closed position, the improvement wherein drive elements driven by said motor are connected with each of said platens and are operable to maintain each of said mold platens in mold closed position during a dwell period, and control means is provided for varying the speed of said motor during a portion of the cycle of said drive elements for each platen which includes the time when each platen is in mold closed position.

6. A method of operating a thermoforming machine having a pair of mold carrying platens mounted on a frame for movement toward and away from each other between a mold open and a mold closed position, a motor operable when driven to cyclically drive said platens between said mold open and mold closed position, and drive elements driven by said motor connected with each of said platens and operable to maintain each of said mold platens in mold closed position during a dwell period, comprising varying the speed of drive of said motor during a portion of the cycle of said drive elements for each platen which includes the time when each platen is in mold closed position.

7. In a differential pressure thermoforming machine having a frame, a pair of mold carrying platens mounted on said frame for relative movement in which at least one moves between a mold open and a mold closed position;

mating molds carried by said platens; and

motor driven means including cam mechanism and cam follower means connected to and operable when driven to cyclically drive at least one of said platens between said mold open and mold closed position;

the improvement wherein said motor driven cam mechanism and cam follower means comprises at least one cam mounted on said frame for rotation about a first axis and having a dwell portion of given angular extent lying at a constant radius from said axis, said follower means including a cam follower engaged with said cam and operable to drive said platen through a cycle from mold open to mold closed position and back to said mold open position in which it maintains at least one of said mold platens in said mold closed position when said cam follower is engaged with said dwell portion of said cam, and a motor assembly having control means for driving said cam continuously in rotation about said axis, and adapted for driving it at a different constant speed than it drives the cam in another portion of said cycle, during at least some of that portion of the rotary cycle of said cam when said cam follower is engaged with said dwell portion.

8. The invention defined in claim 7 wherein said control means comprises speed setting means operable in a first position to drive said motor assembly at a first constant speed and operable in a second position to drive said motor assembly at a second constant speed, and actuating means operable to shift said speed setting means between said first and said second positions at selected rotative positions of said cam.

9. The invention defined in claim 8 wherein said cam is formed with a constant radius dwell section of fixed angular extent about the axis of rotation of said cam, said follower means when engaged with said dwell section being operable to hold said molds in said mold closed position, said control means being operable to selectively adjust the time interval during which said molds remain in said closed position by establishing a selected speed of rotation of said cam over all or a selected portion of the rotary movement of said cam wherein said follower means is engaged with said dwell section.

10. The invention defined in claim 8 wherein said cam is formed with a closure section of fixed angular extent about the axis of rotation of said cam, said follower means when traversing said closure section being operable to move said molds relatively from said mold open to said mold closed position, said control means being operable to selectively adjust the rate of closure by establishing a selected speed of rotation of said cam over all or a selected portion of the rotary movement of said cam wherein said follower means is traversing said closure section.

16. The invention defined in claim 7 in which the control means is programmed to drive said motor at one speed of revolution during the time when the molds are in mold closed position and another speed of revolution when the molds are moving relatively from mold closed to mold open position.

11. In a thermoforming machine having a frame, a mold and platen assembly mounted on said frame and including a pair of mating molds mounted for relative movement between a mold open and a mold closed position, and a continuously driven motor operable when driven to cyclically drive said assembly and to effect the mold open and mold closed positions, the improvement wherein drive elements driven by said motor in continuously consecutive cycles are connected with said assembly and operable to drive said assembly through consecutive cycles effecting said relative movement and in which said molds are maintained in said mold closed position during a dwell period, and control means is provided for varying the speed of revolution of said motor during selected portions of the same cycle of the assembly to drive the motor at a different speed during a portion of each cycle which includes at least part of the dwell period.

12. The invention defined in claim 11 in which the control means is programmed to drive said motor at a maximum speed of revolution during the period the molds are in mold open position and are relatively moving from mold closed to mold open position, a lesser speed of revolution when the molds are relatively moving from mold open position to mold closed position, and a still lesser speed of revolution when the molds are in mold closed position.

13. The invention defined in claim 11 in which the control means is programmed to drive said motor at one speed of revolution during the time when the molds are in mold closed position and another speed of revolution when the molds are in mold open position.

14. The invention defined in claim 11 in which the motor comprises a rotary hydraulic motor driven by a hydraulic system including a pump, and the control means is operable to vary the output of the pump during selected portions of the same cycle.

15. The invention defined in claim 14 in which the output of said pump is controlled by an electrical signal, and the control means includes a shaft angle sensing device.

17. A thermoforming machine having a frame;

a mold and platen assembly mounted on said frame and including a pair of mating molds, at least one being mounted for movement between a mold open and a mold closed position;

a drive motor;

driving elements, driven by said motor, connected with said one mold, said motor being operable when driven to cyclically drive said one mold relatively between mold open and mold closed position, and operable to maintain said one mold in said mold closed position during a dwell period, and control means for varying the speed of revolution of said motor during each cycle of said drive elements and driving said one mold at predetermined different speeds during each cycle from mold open to mold closed position and back.

18. The invention defined in claim 17 in which the control means is programmed to drive said motor at a maximum speed of revolution during the period the molds are in mold open position and said one mold is relatively moving from mold closed to mold open position, a lesser speed of revolution when said one mold is relatively moving from mold open position to mold closed position, and a still lesser speed of revolution when the molds are in mold closed position.

19. The invention defined in claim 17 in which the control means is programmed to drive said motor at one speed of revolution during the time when the molds are in mold closed position and another speed of revolution when the molds are in mold open position.

20. The invention defined in claim 17 in which the motor comprises a rotary hydraulic motor driven by a hydraulic system including a pump, and the control means is operable to vary the output of the pump during selected portions of the same cycle.

21. The invention defined in claim 20 in which the output of said pump is controlled by an electrical signal, and the control means includes a shaft angle sensing device.

22. A thermoforming machine having a frame, a mold and platen assembly mounted on said frame and including a pair of mating molds mounted for relative movement between a mold open and a mold closed position;

a continuously driven, rotary hydraulic motor, operable when driven to drive said assembly to effect the mold open and mold closed positions;

drive elements, driven by said motor, connected with said assembly and operable to drive said assembly through consecutive cycles effecting said relative movement and in which said molds are maintained in said mold closed position during a dwell period;

a hydraulic system including a pump connected with the motor; and

control means operable to vary the output of the pump during selected portions of the same cycle of the assembly to drive the motor at a different speed during a portion of each cycle of the assembly which includes a portion of the dwell period.

23. The invention as defined in claim 22 wherein said drive elements comprise at least one cam driven in rotation and follower means engaged between said cam and said assembly for moving said assembly in response to rotation of said cam, one revolution of said cam corresponding to one cycle of said assembly, and said control means includes means for establishing a selected constant speed of rotation of said cam over a selected angular portion of one revolution of said cam and for driving the assembly at independently selected different speeds during independently selected different portions of one revolution of said cam.

24. The invention defined in claim 23 wherein said control means comprises speed setting means operable in a first position to operate said pump to drive said motor at a first constant speed and operable in a second position to operate said pump to drive said motor at a second constant speed, and actuating means operable to shift said speed setting means between said first and said second positions at selected rotative positions of said cam.

25. The invention defined in claim 23 wherein said second speed is slower than said first speed, and said actuating means maintains said speed setting means in said second position throughout a selected range of rotative positions of said cam during which said dwell portion is engaged with said cam follower.

26. The invention defined in claim 25 wherein said speed setting means permits adjustably selecting the angular positions of said cam at which said actuating means is operable to shift said speed setting means between said first and said second positions.

27. The invention defined in claim 22 in which the control means is programmed to drive said motor at a maximum speed of revolution during the period the molds are in mold open position and are relatively moving from mold closed to mold open position, a lesser speed of revolution when the molds are relatively moving from mold open position to mold closed position, and a still lesser speed of revolution when the molds are in mold closed position.

28. The invention defined in claim 22 in which the output of said pump is controlled by an electrical signal, and the control means includes a motor driven shaft and shaft angle sensing device.

29. In a thermoforming machine having a frame, a mold and platen assembly mounted on said frame and including a pair of mating molds mounted for relative movement between a mold open and a mold closed position;

a continuously driven, rotary motor, operable when driven to drive said assembly to effect the mold open and mold closed positions;

drive elements driven by said motor, connected with said assembly and operable to drive said assembly through consecutive cycles effecting said relative movement and in which said molds are maintained in said mold closed position during a dwell period;

the improvement wherein a variable input energy transmission system is provided to drive said motor at at least two different constant speeds; and

control means, comprising speed setting means operable in a first position to vary the energy input from said energy transmission system to said motor to drive it at a first constant speed and operable in a second position to vary the energy input from said energy transmission system to said motor to drive it at a second constant speed, is provided to drive said motor at at least each of said two speeds during each said cycle and at one of such constant speeds during a portion of each cycle of the assembly which includes a portion of the dwell period.