Load Cell for Sensing Supporting Forces in a Support Element

• US 20100251831A1
• Filed: 04/02/2010
• Published: 10/07/2010
• Est. Priority Date: 04/03/2009
• Status: Active Grant

• Current Assignee: WIKA Alexander Wiegand SE & Company KG
• Original Assignee: Tecsis GmbH
• Inventors: Haerle, Klaus, Amendt, Stefan, Hose von Wolfframsdorff, Joachim, Jost, Oliver
• Granted Patent: US 8,661,916 B2
• Time in Patent Office: Days
• US Class Current: 73/862.45
• CPC Class Codes: G01G 19/12 having electrical weight-sensitive devices
• CPC Class Codes: G01G 3/14 measuring variations of electrical resistance G01G3/13 takes precedence
• CPC Class Codes: G01L 1/2231 the supports being disc- or ring-shaped, adapted for measuring a force along a single direction

Abstract

A load cell for detecting the supporting force transmitted by a load-bearing support element is provided. The load cell forms a measuring portion of the support element, which deforms under the supporting force and transverse forces in a direction deviating from the supporting force to form part of the support element with the same. A plurality of thin-film resistors are arranged at the measuring portion, and exhibit a reaction proportional to strain and whose reactions proportional to transverse forces cancel each other.

Claims

1. A load cell for detecting the supporting force transmitted by a load-bearing support element, the load cell forming a measuring portion of the support element and comprising:

a plurality of thin-film resistors, arranged at the measuring portion, for indicating a reaction proportional to strain, wherein reactions proportional to transverse forces of which cancel each other, and

wherein the measuring portion deforms under the supporting force and transverse forces in a direction deviating from the supporting force.

2. The load cell according to claim 1, wherein the thin-film resistors are connected to an evaluation unit for detecting the resistances of the individual thin-film resistors and for generating a signal corresponding to the change of each thin-film resistor.

3. The load cell according to claim 2, wherein the evaluation unit offsets signals to be assigned to measured transverse forces against each other in accordance with their sign.

4. The load cell according to claim 1, wherein the thin-film resistors are arranged at the measuring portion such that they are strained each in pairs in opposite direction in the case of transverse force and moment loading.

5. The load cell according to claim 4, wherein the thin-film resistors are arranged at the measuring portion such that they are strained each in pairs in opposite direction and to an equal amount in the case of transverse force and/or moment loading.

6. The load cell according to claim 1, wherein the thin-film resistors are formed on a carrier member.

7. The load cell according to claim 1, wherein the measuring portion comprises a membrane-like deformation member to which a hollow cylinder is adjacent at one side at the outer membrane edge and to which a hollow cylinder or a solid cylinder is adjacent at the other side at the inner membrane edge.

8. The load cell according to claim 1, wherein the measuring portion comprises a deformation member consisting of a corrosion-resistant material.

9. The load cell according to claim 6, wherein the measuring portion comprises a deformation member, wherein the thin-film resistors are formed on an end face of the carrier member, and wherein the carrier member is welded to the deformation member.

10. The load cell according to claim 1, wherein the thin-film resistors are interconnected in the form of plural similar Wheatstone bridges the output signals of which are separately evaluated and are assessed by an electronic comparator circuit.

11. The load cell according to claim 6, wherein the thin-film resistors are formed in a layer monolithically applied to the carrier member.

12. The load cell according to claim 6, wherein temperature-sensitive resistors applied to the carrier member are provided which compensate the thermal effect on zero and the range of the output signal.

13. The load cell according to claim 6, wherein the measuring portion comprises a deformation member, and the carrier member forms a standard sensor element ready for connection having a welding flange that is welded onto the deformation member.

14. The load cell according to claim 13, wherein the carrier member of the standard sensor element carries temperature-sensitive resistors.

15. The load cell according to claim 13, wherein the deformation member deforms under a preset nominal load such that the standard sensor element transmits a signal of predetermined magnitude.

16. The load cell according to claim 15, wherein standard sensor elements of identical construction are adapted for use in differently dimensioned deformation members so as to provide load cells for different nominal load ranges.

17. The load cell according to claim 7, wherein the diameters or wall thicknesses of the two cylinders adjacent to the deformation member are adapted by the design of the deformation member.

18. The load cell according to claim 15, wherein load cells for nominal loads of from 300 to 6000 kN are provided by the standard sensor element of identical construction making use of adapted deformation members.

19. The load cell according to claim 1, adapted for installation in support elements of a mobile crane, lifting gear, drilling vehicle or a self-propelled gun carriage.

20. The load cell according to claim 1, wherein the thin-film resistors are glued to the measuring portion in the form of strain gauges.