Load cell and weighing foot

Patent metadata

Field	Value
Publication number	US-10935446-B2
Application number	US-201916723056-A
Country	US
Kind code	B2
Filing date	Dec 20, 2019
Priority date	Dec 20, 2018
Publication date	Mar 2, 2021
Grant date	Mar 2, 2021

Abstract

The invention relates to a load cell with a spring body formed rotationally symmetrically about a center axis, and a plurality of strain gauges arranged on a lower side of the membrane for detecting a stretching and/or compressive deformation of the spring body, wherein the strain gauges are electrically connected to a Wheatstone bridge or as a part thereof, with at least one first strain gauge. The spring body has an outer support ring, an upwardly projecting inner force introduction element, and an annular deformation section that is formed as an annular membrane and with which the support ring and the force introduction element are fixedly connected to one another. The mean thickness of the annular membrane in the region of the first strain gauge or gauges is larger than the mean thickness in the region of a second strain gauge or gauges.

First claim

The invention claimed is:

1. A load cell comprising
a spring body formed rotationally symmetrically about a center axis, the spring body comprising an outer support ring, an upwardly projecting inner force introduction element, and an annular deformation section that is formed as an annular membrane, wherein the outer support ring and the force introduction element are fixedly connected to one another with the annular membrane; and
a plurality of strain gauges arranged on a lower side of the annular membrane configured for detecting a stretching and/or compressive deformation of the spring body, wherein the plurality of strain gauges are electrically connected to form at least a part of a Wheatstone bridge,
wherein at least one first strain gauge of the plurality of strain gauges is disposed on a first circle having a first radius about the center axis of the spring body and at least one second strain gauge of the plurality of strain gauges is disposed on a second circle having a second radius that is greater than the first radius about the center axis of the spring body,
wherein a first mean thickness of the annular membrane in a first region of the at least one first strain gauge is larger than a second mean thickness of the annular membrane in a second region of the at least one second strain gauge, and
wherein the at least one first strain gauge overlaps the inner force introduction element and the annular membrane and the at least one second strain gauge is overlaps the outer support ring and the annular membrane.

2. The load cell in accordance with claim 1 ,
wherein the at least one first strain gauge comprises two first strain gauges, wherein the two first strain gauges are disposed on the first circle.

3. The load cell in accordance with claim 1 ,
wherein the at least one second strain gauge comprises two second strain gauges, wherein the two second strain gauges are disposed on the second circle.

4. The load cell in accordance with claim 1 ,
wherein the annular membrane is formed as planar at its lower side.

5. The load cell in accordance with claim 1 ,
wherein the annular membrane has a rounded extent at its upper side in at least one of its transition region to the outer support ring and its transition region to the inner force introduction element.

6. The load cell in accordance with claim 1 ,
wherein the force introduction element has an undercut at its lower end.

7. The load cell in accordance with claim 1 ,
wherein the thickness of the annular membrane monotonously decreases from the inside to the outside.

8. The load cell in accordance with claim 1 ,
wherein the thickness of the annular membrane decreases from the inside to the outside in the region of the at least one first strain gauge and increases from the inside to the outside in the region of the at least one second strain gauge.

9. The load cell in accordance with claim 1 ,
wherein the plurality of strain gauges each have a measurement grid oriented in a radial direction.

10. The load cell in accordance with claim 1 ,
wherein a first strain gauge of the at least one first strain gauge and a second strain gauge of the at least one second strain gauge are respectively arranged on two mutually oppositely disposed sides of the force introduction element.

11. The load cell in accordance with claim 10 ,
wherein the plurality of strain gauges comprises four strain gauges arranged along a common line through the center axis of the spring body.

12. The load cell in accordance with claim 1 ,
wherein two strain gauges of the at least one first strain gauges are arranged along a first line through the center axis of the spring body and two strain gauges of the at least one second strain gauges are arranged along a second line through the center axis of the spring body, with the two lines being rotated with respect to one another by an angle from 5° to 20°.

13. The load cell in accordance with claim 1 ,
wherein the annular membrane is provided in a central region with a peripheral annular web at an upper side.

14. The load cell in accordance with claim 1 ,
wherein the load cell comprises an evaluation circuit that is electrically connected to the plurality of strain gauges and that is configured to generate an output signal corresponding to a weight acting on the force introduction element.

15. The load cell in accordance with claim 14 , further comprising an external interface electrically connected to the evaluation circuit and configured to output the output signal generated by the evaluation circuit to a device external to the load cell.

16. The load cell in accordance with claim 1 ,
wherein the force introduction element is configured as a force introduction pipe; and/or wherein the spring body is configured in monolithic form.

17. A weighing foot having a load cell, the load cell comprising:
a spring body formed rotationally symmetrically about a center axis, the spring body comprising an outer support ring, an upwardly projecting inner force introduction element, and an annular deformation section that is formed as an annular membrane, wherein the outer support ring and the force introduction element are fixedly connected to one another with the annular membrane; and
a plurality of strain gauges arranged on a lower side of the annular membrane configured for detecting a stretching and/or compressive deformation of the spring body, wherein the plurality of strain gauges are electrically connected to form at least a part of a Wheatstone bridge,
wherein at least one first strain gauge of the plurality of strain gauges is disposed on a first circle having a first radius about the center axis of the spring body and at least one second strain gauge of the plurality of strain gauges is disposed on a second circle having a second radius that is greater than the first radius about the center axis of the spring body,
wherein a first mean thickness of the annular membrane in a first region of the at least one first strain gauge is larger than a second mean thickness of the annular membrane in a second region of the at least one second strain gauge, and
wherein the at least one first strain gauge overlaps the inner force introduction element and the annular membrane and the at least one second strain gauge is overlaps the outer support ring and the annular membrane.

18. The weighing foot in accordance with claim 17 ,
wherein the force introduction element comprises an external thread at an upper end of the force introduction element.

19. The weighing foot in accordance with claim 17 ,
wherein the weighing foot comprises a lower part on which the outer support ring of the load cell is supported.

20. A weighing system comprising a plurality of weighing feet, and a load carrier supported on the plurality of weighing feet, wherein each weighing foot comprising a load cell, wherein each load cell comprises:
a spring body formed rotationally symmetrically about a center axis, the spring body comprising an outer support ring, an upwardly projecting inner force introduction element, and an annular deformation section that is formed as an annular membrane wherein the outer support ring and the force introduction element are fixedly connected to one another with the annular membrane; and
a plurality of strain gauges arranged on a lower side of the annular membrane configured for detecting a stretching and/or compressive deformation of the spring body, wherein the plurality of strain gauges are electrically connected to form at l

Assignees

• Bizerba Se & Co Kg

Inventors

• Fritsch Andreas
• Gutmacher Annika
• Eschment Jens
• Metzger Frank

Classifications

• G01G3/141 Primary

  the supports being disc or ring shaped · CPC title

• G01L1/2231 Primary

  the supports being disc- or ring-shaped, adapted for measuring a force along a single direction · CPC title

• G01G3/1408

  the supports being of the column type, e.g. cylindric · CPC title

• G01L1/04

  by measuring elastic deformation of gauges, e.g. of springs · CPC title