Load cell for monitoring torsion and having over load protection

• US 8,161,828 B1
• Filed: 09/29/2009
• Issued: 04/24/2012
• Est. Priority Date: 09/29/2009
• Status: Active Grant

• Current Assignee: Interface Incorporated
• Original Assignee: Interface Incorporated
• Inventors: Clegg, Lavar, Burrow, Lawrence J.
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): DUNLAP, JONATHAN M
• Application Number:
  US12/586,996
• Time in Patent Office: 938 Days
• Field of Search: 738/626.32, 738/626.21, 738/626.22, 738/626.25, 738/626.27, 738/626.28, 738/620.8, 738/621.91, 738/622.1, 738/622.3, 738/623.21, 738/623.25, 738/623.38, 73862041-862045
• US Class Current: 73/862.338
• CPC Class Codes: G01L 3/1457 involving resistance strain gauges

Abstract

A load cell structure for receiving strain gages to monitor applied torsional forces wherein the opposing force-receiving ends have a plurality of sensing beams spaced about an axis of rotation. Limit posts located between the ends each have a discontinuity therein that includes a U-shaped gap to limit relative rotation about the axis and thereby providing overload protection.

Claims

1. A load cell structure for receiving strain gages thereon to monitor torsional forces applied to said structure which comprises:

(a) a first force-receiving end having a first central region bounded by a first peripheral region;

(b) a second force-receiving end having a second central region bounded by a second peripheral region, said first and second ends being spaced along an axis of rotation;

(c) a plurality of sensing beams extending between the first and second peripheral regions, said beams having strain gage receiving surfaces thereon;

(d) at least one limit post attached to the second force-receiving end and aligned with the axis of rotation, said at least one limit post having a free end spaced from the first force-receiving end; and

(e) a pair of contact surfaces formed on the free end, said pair of contact surfaces being oriented in alignment with the axis of rotation to establish a pair of overload gaps between the free end and the force-receiving end, the application of torsional force to the structure causing relative rotation of the first and second force-receiving ends limited by the engagement of a contact surface with the first force-receiving end.

2. The load cell structure of claim 1 wherein said at least one limit post has a plurality of pairs of contact surfaces, each pair being oriented in alignment with the axis of rotation thereby establishing a like plurality of overload gaps between the first and second force-receiving ends.

3. The load cell structure of claim 2 wherein said plurality of pairs of contact surfaces are spaced about the axis of rotation.

4. The load cell structure of claim 3 wherein said plurality of pairs of contact surfaces are spaced outwardly from the axis of rotation and located adjacent to the first peripheral region in the first force-receiving end.

5. The load cell structure of claim 4 wherein said first force-receiving end has an opening in the first central region, the free end of said having at least one limit post extending into said opening, said free end being adjacently spaced from the first force-receiving end.

6. The load cell structure of claim 5 wherein said first force-receiving end includes a plurality of recesses spaced outwardly from the axis of rotation for receiving said pairs of contact surfaces therein.

7. The load cell structure of claim 6 wherein each of said plurality of recesses is aligned with a sensing beam.

8. The load cell structure of claim 7 wherein said first force-receiving end has elevated contact regions located between adjacent recesses therein.

9. The load cell structure of claim 8 wherein mounting holes are located in the elevated contact regions.

10. The load cell structure of claim 9 wherein said second force-receiving end has elevated contact regions in substantial alignment with the contact regions of said first force-receiving end.

11. The load cell structure of claim 10 wherein a plurality of limit posts are affixed to the second force-receiving end and further comprising a plurality of engaging posts affixed to the first force-receiving end and in alignment with said limit posts, the engaging posts being spaced from the free ends of the limit posts whereby overload gaps are established therebetween.

12. The load cell structure of claim 11 wherein the engaging posts each terminate with a pair of engaging surfaces spaced from the pair of contact surfaces formed on the free end of the limit post, the overload gaps are established therebetween.

13. The load cell structure of claim 12 wherein the sensing beams and limit posts are substantially equally spaced about the axis of rotation with the limit posts angularly displaced from the sensing beams.

14. The load cell structure of claim 13 wherein said first and second force-receiving ends are provided with mounting holes in the peripheral regions thereby.

15. The load cell structure of claim 14 wherein said first and second force-receiving ends have mounting holes located in their respective peripheral regions.

16. The load cell structure of claim 15 wherein said first and second force-receiving ends each have an opening in the central region thereof.

17. A load cell structure for receiving strain gages thereon to monitor torsional forces applied thereto, said structure comprising:

(a) first and second force-receiving ends, said ends each being spaced along an axis of rotation;

(b) a plurality of sensing beams affixed to the first and second force-receiving ends and having strain gage receiving surfaces thereon, said sensing beams being oriented substantially parallel to the axis of rotation; and

(c) a plurality of limit posts positioned between said first and second force-receiving ends and aligned with the axis of rotation, each of said plurality of limit posts having a discontinuity therein, each said discontinuity permitting limited relative rotation of said first and second force-receiving ends.

18. The load cell structure of claim 17 wherein each said discontinuity includes at least one overload gap having spaced contact surfaces aligned with the axis of rotation.

19. The load cell structure of claim 18 wherein each said discontinuity includes a pair of spaced contact surfaces to provide bidirectional overload protection.