Thermoforming Apparatus Having Deformation Sensor and Method

• US 20190322030A1
• Filed: 04/24/2018
• Published: 10/24/2019
• Est. Priority Date: 04/24/2018
• Status: Active Grant

• Current Assignee: Irwin Research and Development, Inc.
• Original Assignee: Irwin Research and Development, Inc.
• Inventors: Vantrease, Dale L.
• Granted Patent: US 11,478,977 B2
• Time in Patent Office: Days
• CPC Class Codes: B29C 51/082 by shaping between complementary mould parts
• CPC Class Codes: B29C 51/10 Forming by pressure difference, e.g. vacuum
• CPC Class Codes: B29C 51/38 Opening, closing or clamping means
• CPC Class Codes: B29C 51/46 Measuring, controlling or regulating
• CPC Class Codes: B30B 1/26 by cams, eccentrics, or cranks
• CPC Class Codes: B30B 15/0094 Press load monitoring means B30B15/281 takes precedence
• CPC Class Codes: B30B 15/34 Heating or cooling presses or parts thereof

Abstract

A thermoforming apparatus is provided having a pair of coacting platens, a load bearing structural member, a force applicator, and a deformation sensor. The pair of coacting platens and respective dies are configured to mate on opposed surfaces of a heated sheet of thermoformable material to form articles. The load bearing structural member is configured to carry the coacting platens and the dies in complementary closed relationship about the sheet during an article forming operation. The force applicator is carried by the structural member and configured to impart a forming load between the pair of opposed dies and platens and across the structural member during a forming operation. The deformation sensor is configured to span a first location and a second location on the structural member to detect deformation indicative of separation between the dies resulting from deformation. A method is also provided.

Claims

1. A thermoforming apparatus, comprising:

a pair of coacting platens and respective dies configured to mate on opposed surfaces of a heated sheet of thermoformable material to form articles;

a load bearing structural member configured to carry the coacting platens and the dies in complementary closed relationship about the sheet during an article forming operation;

a force applicator carried by the structural member and configured to impart a forming load between the pair of opposed dies and platens and across the structural member during a forming operation; and

a deformation sensor configured to span a first location and a second location on the structural member to detect deformation indicative of separation between the dies resulting from deformation.

2. The apparatus of claim 1, wherein the deformation sensor is affixed at one end to the first location and at another end to the second location, the first location proximate a coupling between one platen and respective one die and the second location proximate a coupling between another platen and respective another die.

3. The apparatus of claim 1, wherein the deformation sensor comprises an elongate rod affixed at one end to the structural member at the first location and a displacement sensor communicating with another end of the rod affixed to the structural member at the second location.

4. The apparatus of claim 3, wherein the sensor comprises a linear variable differential transformer (LVDT) sensor.

5. The apparatus of claim 3, wherein the rod comprises a thermally stable material.

6. The apparatus of claim 5, wherein the rod is a carbon fiber rod.

7. The apparatus of claim 1, wherein the detected deformation of the structural member is elastic deformation of at least one of the frame, the platens, the dies, and the drive mechanism responsive to the differential closing load.

8. The apparatus of claim 1, wherein the structural member is a frame, and a pair of deformation sensors are provided, one on each side of the frame.

9. A thermoforming apparatus, comprising:

a load path configured to carry a load between a first location and a second location and across a counteracting load path;

a pair of opposed platens and dies respectively provided along the first location and the second location configured to engage opposed faces of a heated web of thermoformable material; and

a sensor carried across the load path and configured to detect deformation between the first location and the second location from loads imparted between the dies during a forming operation.

10. The thermoforming apparatus of claim 9, wherein the detected structural deformation is elastic deformation of at least one of the frame, the platens, the dies, and the drive mechanism responsive to the differential closing load.

11. The thermoforming apparatus of claim 9, wherein the load path is a frame member of a frame.

12. The thermoforming apparatus of claim 11, wherein a plurality of sensors are provided spaced apart on opposed sides of the frame.

13. The thermoforming apparatus of claim 11, wherein four sensors are provided spaced apart on each corner of the frame.

14. The thermoforming apparatus of claim 9, wherein the motion sensor comprises a thermally stable elongate member affixed to one of the first frame location and the second frame location and a linear motion detector interposed between another of the first frame location and the second frame location configured to detect motion between a distal end of the elongate member and the another frame member.

15. A method for detecting deformation in a thermoforming apparatus, comprising:

providing a deformation sensor between a first location and a second location across a load path;

imparting a forming load between platens and dies coacting along the first location and the second location while engaged together; and

detecting deformation between the first location and the second location indicative of load path deformation of the apparatus.

16. The method of claim 15, wherein the deformation sensor is an optical sensor.

17. The method of claim 16, wherein the optical sensor detects movement between the first location and the second location.

18. The method of claim 15, wherein the deformation sensor is a physical deflection detector.

19. The method of claim 18, further comprising physically detecting at least one of stress and strain of one or more of a frame member, a bearing assembly, a linkage, a platen, a platen lock, and a die plate.

20. The method of claim 15, after detecting deformation, moving the first platen towards the second platen an amount of the detected deformation prior to applying a forming load between coacting dies.