Compensated load cell

• US 4,453,609 A
• Filed: 03/15/1982
• Issued: 06/12/1984
• Est. Priority Date: 03/15/1982
• Status: Expired due to Term

• Current Assignee: Mettler-Toledo Incorporated (Mettler-Toledo International Inc.)
• Original Assignee: Reliance Electric Company (ABB Limited)
• Inventors: Griffen, Neil C., Behrman, David M.
• Primary Examiner(s): MILLER JR, GEORGE
• Application Number:
  US06/358,195
• Time in Patent Office: 820 Days
• Field of Search: 177/211, 73/862.65
• US Class Current: 177/211
• CPC Class Codes: G01G 3/1402 Special supports with preselected places to mount the resistance strain gauges; Mounting of supports

Abstract

This invention relates to new and improved single beam load cells which are compensated for both longitudinal and lateral displacement of the load; to new and improved scale arrangements incorporating such load cells; and to methods of compensating such single beam load cells. In one embodiment of the invention strain gages are attached to only one side of the beam and the beam is honed or filed to compensate for both longitudinal and lateral displacement of the load. In another embodiment of the invention strain gages are placed on both sides of the single beam and the strain gages are placed on the beam at a slight angle from the longitudinal axis of the beam. In this embodiment the beam may be honed to compensate for both lateral and longitudinal displacement of the load. In addition, with the strain gages displaced at a small angle with respect to the longitudinal axis of the beam, the load cell may be compensated for both longitudinal and transverse displacement of the load by placing resistors in parallel with two or more of the strain gages.

The single beam is mounted or supported at one end thereof and the other end supports the platter or platform of the scale arrangement. The platter or platform mounting arrangements may be arranged to provide moment insensitive arrangements, and in one exemplary embodiment the platform or platter is supported by one end of the single beam load cell at or near an edge thereof.

Claims

1. An improved method of compensating a weighing mechanism having a single beam load cell member, comprising the steps of mounting a first strain gage on one side of the beam member near an end thereof, mounting a second strain gage on the other side of the beam near the same end, positioning said first and second strain gages at opposite angles to the longitudinal axis of the beam to increase the sensitivity of said gages to off-center loading of the beam, mounting third and fourth strain gages near the other end of the beam, arranging the gages in an electrical bridge circuit, and connecting a resistor network to one or more of the gages to make the output of the bridge circuit substantially independent of the position of a weight along at least one direction of the weighing mechanism.

2. An improved weighing mechanism comprising, in combination, a single beam member, first and second strain gages mounted on the beam member at angles to the longitudinal axis of the beam member to increase the sensitivity of said gages to off-center loading of the beam member, and a resistor network connected in circuit with at least one of said strain gages to make the output of the weighing mechanism substantially independent of the position of a weight along at least one of two mutually perpendicular directions on the weighing mechanism.

3. A weighing mechanism according to claim 2 wherein said gages are mounted at opposite angles to the longitudinal axis of the beam.

4. A weighing mechanism according to claim 2 wherein said gages are mounted on opposite sides and near the same end of the beam.

5. A weighing mechanism in accordance with claim 2 wherein said gages are mounted on the same side and near opposite ends of the beam.

6. A weighing mechanism according to claim 2 further comprising a base member, a weight receiving member, means for supporting one end of the beam member on the base member, and means for supporting the weight receiving member at one edge thereof by the other end of the beam member.

7. A weighing mechanism in accordance with claim 6 wherein the load cell beam member is substantially the same length as one dimension of the weight receiving member.

8. A weighing mechanism in accordance with claim 2 wherein said beam member comprises a flat beam having a reduced section near each end formed by notches in the edges, said strain gages being mounted on the beam near the reduced sections.

9. A weighing mechanism in accordance with claim 8 wherein one strain gage is mounted on one side of the beam near the reduced section at one end at a clockwise angle relative to the longitudinal axis of the beam and the other strain gage is mounted at a counter-clockwise angle on the same side at the other end of the beam.

10. A weighing mechanism in accordance with claim 8 wherein a strain gage is mounted on one side of the beam near the reduced section at one end at a clockwise angle relative to the longitudinal axis of the beam and another strain gage is mounted at a counter-clockwise angle on the other side at the same end of the beam.

11. A weighing mechanism in accordance with claim 2 further comprising third and fourth strain gages mounted on the beam, said gages being arranged in an electrical bridge circuit, the output of the bridge circuit being substantially independent of the position of a weight along at least said one direction.

12. A weighing mechanism in accordance with claim 11 wherein said first and second strain gages are mounted on the same third and fourth strain gages are mounted on the other side near opposite ends of the beam.

13. A weighing mechanism in accordance with claim 11 wherein said third and fourth strain gages are rotated at mutually opposite angles with respect to the longitudinal axis of the beam.

14. A weighing mechanism in accordance with claim 11 wherein said first and second strain gages are mounted on opposite sides of the beam near the same end thereof and said third and fourth strain gages are mounted on opposite sides of the beam near the other end thereof.

15. A weighing mechanism in accordance with claim 11 including resistor networks connected to two of the strain gages to make the output of the bridge circuit substantially independent of the position of a weight along said one direction.

16. A weighing mechanism in accordance with claim 11 including resistor networks connected to three of the strain gages to make the output of the bridge circuit substantially independent of the position of a weight on the weighing mechanism.

17. A method of compensating a weighing mechanism having a single beam load cell member with longitudinal and lateral axes, comprising the steps of mounting first and second strain gages on the beam member at opposite angles to the longitudinal axis of the beam to increase the sensitivity of said gages to off-center loading of the beam, mounting third and fourth strain gages on the beam, arranging the gages in an electrical bridge circuit, and connecting a resistor network to one or more of the gages to make the output of the bridge circuit substantially independent of the position of a weight along at least one of said axes.

18. A weighing mechanism comprising a single beam member having longitudinal and lateral axes, first and second strain gages mounted on said beam at opposite angles to the longitudinal axis to increase the sensitivity of said gages to off-center loading of said beam, third and fourth strain gages mounted on said beam, said strain gages being arranged in an electrical bridge circuit, and a resistor network connected to one or more of the gages to make the output of the bridge circuit substantially independent of the position of a weight along at least one of said axes.

19. A weighing mechanism in accordance with claim 18 wherein said third and fourth strain gages are mounted on said beam at mutually opposite angles to the longitudinal axis of the beam.

20. An improved weighing mechanism comprising, in combination, a single bending beam member for producing bending strain in response to loads applied thereto, first and second strain gages mounted on opposite sides of said beam near the same end thereof, said gages being rotated at opposite angles relative to the longitudinal axis of said beam to increase the sensitivity of said gages to off-center loading of said beam, third and fourth strain gages mounted on the other end of said beam, said gages being arranged in an electrical bridge circuit, and a resistor network connected to one or more of said gages to make the output of the bridge circuit substantially independent of the position of a weight along at least one direction of the weighing mechanism.