Thermoforming machine with automatically mechanically operated web stripping element

• US 4,255,382 A
• Filed: 03/20/1980
• Issued: 03/10/1981
• Est. Priority Date: 03/20/1980
• Status: Expired due to Term

• Current Assignee: John Brown Industries Limited
• Original Assignee: Leesona Corp.
• Inventors: Arends, Albert W., Henke, Ronald E.
• Primary Examiner(s): Flint, Jr., J. Howard
• Application Number:
  US06/131,880
• Time in Patent Office: 355 Days
• Field of Search: 425/387.1, 425/388, 425/394, 425/398, 425/406, 425/410, 425/411, 425/436, 425/451.4, 425/451.2, 425/416, 425/422, 425/214, 264/544
• US Class Current: 264/544
• CPC Class Codes: B29C 51/38 Opening, closing or clamping means
• CPC Class Codes: B29C 51/44 Removing or ejecting moulded articles

Abstract

In differential pressure synthetic plastics thermoforming machinery, mold support assemblies mounted on a frame have relative movement between a mold open and a mold closed position. Power operated mechanism is provided for axially moving at least the female mold support assembly, and the female mold on the assembly which carries a stripper element mounted for relative movement with the mold. Mechanism is provided for automatically latching the stripper element to the frame as the female mold moves toward mold closed position, and abutments are provided on the mold support assembly and latch for automatically unlatching it only after the female mold has withdrawn a predetermined distance in its movement toward mold open position.

Claims

1. In a differential pressure thermoforming machine having a frame;

mold assemblies mounted thereon for relative movement along an axis between a mold open and a mold closed position;

one of said assemblies having a female mold with a mold cavity;

means for feeding a heated deformable plastic web to be formed between said mold assemblies and adjacent said mold when the latter are in a mold open position;

a stripper element for the female mold for restraining the web from moving with the female mold when the latter is moved toward mold open position;

a stop supported by said frame;

a latch carried by said stripper and movable through a path of travel from a withdrawn position to a stop engaging position in which the latch and stripper are initially prevented by the stop from moving in the withdrawal path of the female mold; and

mechanism carried by the female mold assembly operable to effect movement of the latch to withdrawn position after a predetermined axial withdrawal of the female mold wherein the web is stripped from the mold to permit the stripped element to commence to move with the female mold assembly.

2. The invention defined in claim 1 wherein the latch is a bell crank mounted for pivotal movement in the plane of the stop from a latched position underlying said stop to a withdrawn position out of axial alignment with the stop.

3. The invention defined in claim 2 wherein the latch has a roller for engaging under the stop and the stop has an outwardly inclined surface engaged by the roller when the latch and mold are moving toward mold closed position for pivoting the latch outwardly and then releasing it so the roller can swing in under the stop to locked position.

4. The invention defined in claim 3 wherein means is provided to normally urge the latch to locked position.

5. The invention defined in claim 2 wherein the mechanism operable for withdrawing the latch includes an abutment on said latch and an abutment on said female mold assembly which are in axially spaced apart relation when the mold assemblies are in mold closed position, and which pivot said latch to withdrawn position when the abutment on the female mold assembly engages the latch abutment to pivot the latch to a withdrawn position wherein the stripper element is released to move with the female mold assembly and the latch is free to move axially with the stripper element to an axial position withdrawn axially from said stop.

6. The invention defined in claim 5 wherein said abutment on the female mold assembly comprises an axially adjustable pin extending axially from the female mold assembly.

7. The invention defined in any of claims 1-5 wherein the female mold carries the stripper element which comprises a stripper frame mounted for relative axial movement with the female mold;

and means reacting between the stripper frame and mold mormally urges the stripper frame to a position flush with the web confronting face of the female mold and opposes axial withdrawal movement of the mold relative to the stripper frame.

8. In a differential pressure thermoforming machine having a frame;

mold support assemblies, at least one of which is movable on the frame and carries a female mold having a plastic web confronting face, mounted for relative movement between a mold open and a mold closed position along an axis of movement;

means for supporting a heated deformable synthetic plastic material between said mold support assemblies and adjacent the said mold face when the assemblies are in mold closed position; and

a stripper element for the female mold for restraining the plastic material when the female mold is moved toward mold open position;

the improvement wherein a first abutment is provided on the female mold support assembly and a second abutment is provided, the said abutments being in predetermined axially spaced position when the mold support assemblies are in mold closed position and moving into engagement when the said assemblies move relatively to mold open position, and one of said abutments is movable to normally restrain movement of the stripper element with the female mold and to release the stripper element to travel with the mold when the abutments engage.

9. The invention defined in claim 8 wherein one of said abutments includes a latch actuator and the other includes a latch, and a third abutment cooperating with the latch to function as a latch lock is provided on the frame.

10. For use in a differential pressure thermoforming machine having a frame;

mold support assemblies mounted for relative movement thereon along an axis of movement between an open and a closed position;

means for feeding a web of synthetic plastic material between the platen assemblies; and

means for moving at least one of the said assemblies axially, the combination comprising;

a female mold adapted to be mounted on the latter support assembly carrying a stripper element mounted for relative movement therewith;

a first abutment;

a second abutment adapted to be mounted on the said latter support assembly at a predetermined distance from the first abutment when the support assemblies are in closed position to engage the first abutment when the support assemblies are moved relatively to open position;

one of said abutments including a latch connected to restrain movement of the stripper element with the mold when the mold is withdrawn and cooperating with the other abutment to release the stripper element to travel with the mold when the abutments engage.

11. The combination as set forth in claim 10 wherein a lock element is adapted to be carried by the frame in a position to cooperate with the latch to lock the stripper element to the frame when the support assemblies are in the mold closed position.

12. A method of aiding the stripping process in a differential pressure thermoforming machine having a frame, mold support assemblies mounted for relative movement thereon along an axis of movement between an open and closed position;

mechanism for feeding a web of synthetic plastic between the mold support assemblies when the latter are in open position, power operated mechanism for moving at least one of the mold support assemblies axially and a female mold on the latter assembly carrying a stripper element mounted for relative movement therewith;

the steps of;

moving the female mold toward mold closed position and, as the mold approaches said position, latching the stripper element to the frame;

differential pressurizing the plastic web to cause it to conform to the contour of the mold cavity;

withdrawing the female mold from closed position while keeping the stripper element locked to the frame and thereby helping to strip the portion of the plastic web deformed into the mold cavity from the mold cavity; and

after a predetermined interval engaging abutments on the mold support assembly and latch as the mold moves to open position to effect unlatching of the stripper element from the frame.