Magnetic force sensor assembly for workholding fixtures

• US 20060174713A1
• Filed: 02/08/2005
• Published: 08/10/2006
• Est. Priority Date: 02/08/2005
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Lin, Yhu-Tin, Shen, Chi-Hung
• Granted Patent: US 7,201,059 B2
• Time in Patent Office: Days
• US Class Current: 73/779
• CPC Class Codes: B23Q 17/005 by measuring a force, a pressure or a deformation
• CPC Class Codes: B25B 11/00 Work holders not covered by any preceding group in the subclass, e.g. magnetic work holders, vacuum work holders for holding or positioning work for welding, soldering, or cutting by applying heat locally B23K37/04; specially adapted to machine tools B23Q3/00
• CPC Class Codes: G01L 5/0076 Force sensors associated with manufacturing machines G01L5/0066, G01L5/0071 and B23Q17/09 take precedence; for the specific machine or operation involved see relevant class, e.g. B21 - B42

Abstract

A magnetic force sensor assembly for a workholding fixture includes a magnetic force switch operatively supported by a base of a component disposed on the workholding fixture. The magnetic force sensor assembly also includes a sensor operatively supported by the base of the component to sense a position change of the magnetic force switch and inform a controller that there is sufficient magnetic force between the workholding fixture and the base.

Claims

1. A magnetic force sensor assembly for a workholding fixture comprising:

a magnetic force switch operatively supported by a base of a component disposed on the workholding fixture; and

a sensor operatively supported by the base of the component to sense a position change of said magnetic force switch and inform a controller that there is sufficient magnetic force between the workholding fixture and the base.

2. A magnetic force sensor assembly as set forth in claim 1 wherein said magnetic force switch comprises a post at least partially disposed in an instrumentation cavity of the base.

3. A magnetic force sensor assembly as set forth in claim 2 wherein said post is fixed relative to the base.

4. A magnetic force sensor assembly as set forth in claim 2 wherein said post is movable relative to the base.

5. A magnetic force sensor assembly as set forth in claim 2 wherein said post is made of a non-ferrous material.

6. A magnetic force sensor assembly as set forth in claim 2 wherein said post is made of a ferrous material.

7. A magnetic force sensor assembly as set forth in claim 2 wherein said post has a head portion extending radially and a shaft portion extending axially from said head portion.

8. A magnetic force sensor assembly as set forth in claim 7 wherein said shaft portion has a threaded end portion threadably engaging a threaded portion of the instrumentation cavity.

9. A magnetic force sensor assembly as set forth in claim 7 wherein said shaft portion has a cavity extending axially therein.

10. A magnetic force sensor assembly as set forth in claim 9 including a spring at least partially disposed in said cavity between a top of said cavity and a bottom of the instrumentation cavity.

11. A magnetic force sensor assembly as set forth in claim 10 wherein said spring comprises a coil spring

12. A magnetic force sensor assembly as set forth in claim 7 including a sensing plate cooperating with said shaft portion.

13. A magnetic force sensor assembly as set forth in claim 12 wherein said sensing plate is disposed about said shaft portion and movable relative to said shaft portion.

14. A magnetic force sensor assembly as set forth in claim 12 wherein said sensing plate is attached to said shaft portion and fixed relative to said shaft portion.

15. A magnetic force sensor assembly as set forth in claim 12 wherein said sensing plate is made of a ferrous material.

16. A magnetic force sensor assembly as set forth in claim 12 including a spring disposed about said shaft portion between said sensing plate and a bottom of the instrumentation cavity.

17. A magnetic force sensor assembly as set forth in claim 12 wherein said sensing plate has a diameter greater than a diameter of the instrumentation cavity.

18. A magnetic force sensor assembly as set forth in claim 7 including a sleeve disposed in the instrumentation cavity and about a portion of said shaft portion, said shaft portion being movable relative to said sleeve.

19. A magnetic force sensor assembly as set forth in claim 18 wherein said sleeve is made of a non-ferrous material.

20. A magnetic force sensor assembly as set forth in claim 1 wherein said magnetic force switch comprises a spacer supported by the base.

21. A magnetic force sensor assembly as set forth in claim 20 including a spring having a first end supported by said spacer and a second end cantilevered over the base.

22. A magnetic force sensor assembly as set forth in claim 21 wherein said spring is a leaf spring.

23. A magnetic force sensor assembly as set forth in claim 21 wherein said spring is a made of a carbon steel.

24. A magnetic force sensor assembly as set forth in claim 21 including a contact tip supported by said second end of said spring.

25. A magnetic force sensor assembly as set forth in claim 24 wherein said contact tip is a made of a carbon steel.

26. A magnetic force sensor assembly as set forth in claim 21 including a fastener extending through said first end of said spring and said spacer to secure said spring and said spacer to the base.

27. A magnetic force sensor assembly as set forth in claim 1 wherein said sensor is disposed in a recess in a top surface of the base.

28. A magnetic force sensor assembly as set forth in claim 1 wherein said sensor is a proximity sensor.

29. A workholding fixture comprising:

a magnetic chuck;

a component disposed on a surface of said magnetic chuck and having a base held by a magnetic field to the surface of said magnetic chuck;

a magnetic force switch operatively supported by said base; and

a sensor operatively supported by said base to sense a position change of said magnetic force switch and inform a controller that there is sufficient magnetic force between said magnetic chuck and said base.

30. A magnetic force sensor assembly for a workholding fixture comprising:

a magnetic force switch operatively supported by a base of a component disposed on the workholding fixture, said magnetic force switch comprising a post at least partially disposed in an instrumentation cavity of the base;

said post being made of a non-ferrous material and having a head portion extending radially and a shaft portion extending axially from said head portion, said shaft portion having a threaded end portion threadably engaging a threaded portion of the instrumentation cavity;

a sensing plate made of a ferrous material disposed about said shaft portion and movable relative to said shaft portion;

a spring disposed about said shaft portion between said sensing plate and a bottom of the instrumentation cavity; and

a proximity sensor operatively supported by the base of the component to sense a position change of said magnetic force switch and inform a controller that there is sufficient magnetic force between the workholding fixture and the base.

31. A magnetic force sensor assembly for a workholding fixture comprising:

a magnetic force switch operatively supported by a base of a component disposed on the workholding fixture, said magnetic force switch comprising a post at least partially disposed in an instrumentation cavity of the base;

said post being made of a non-ferrous material and having a head portion extending radially and a shaft portion extending axially from said head portion, said shaft portion having a cavity extending axially therein;

a sleeve made of a non-ferrous material disposed in the instrumentation cavity and about a portion of said shaft portion, said shaft portion being movable relative to said sleeve;

a spring at least partially disposed in said cavity between a top of said cavity and a bottom of the instrumentation cavity;

a proximity sensor operatively supported by the base of the component to sense a position change of said magnetic force switch and inform a controller that there is sufficient magnetic force between the workholding fixture and the base.

32. A magnetic force sensor assembly for a workholding fixture comprising:

a magnetic force switch operatively supported by a base of a component disposed on the workholding fixture, said magnetic force switch comprising a spacer supported by the base, a leaf spring having a first end supported by said spacer and a second end cantilevered over the base, and a contact tip supported by said second end of said spring;

a fastener extending through said first end of said spring and said spacer to secure said spring and said spacer to the base; and

a proximity sensor operatively supported by the base of the component to sense a position change of said magnetic force switch and inform a controller that there is sufficient magnetic force between the workholding fixture and the base.