FORKLIFT SCALE, LOAD CELL THEREOF AND METHOD OF MEASURING A FORKLIFT LOAD

• US 20140262550A1
• Filed: 03/14/2014
• Published: 09/18/2014
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Larry D. Santi
• Original Assignee: Larry D. Santi
• Inventors: Santi, Larry D.
• Granted Patent: US 9,562,804 B2
• Time in Patent Office: Days
• US Class Current: 177/1
• CPC Class Codes: B66F 17/003 for fork-lift trucks
• CPC Class Codes: B66F 9/12 Platforms; Forks; Other load supporting or gripping members
• CPC Class Codes: G01G 19/083 lift truck scale
• CPC Class Codes: G01G 19/12 having electrical weight-sensitive devices

Abstract

A forklift scale to measure a load carried by a pair of forks of a forklift that includes a fork carriage to movably position the forks. The forklift scale includes a pair of load cells that are configured to mount to the fork carriage independent of each other and to removably receive a respective fork of the forklift. Each load cell includes a structural arrangement that couples the respective fork to the fork carriage during operation such that an entirety of the load carried by the forks during operation is transmitted to the carriage via the pair of load cells. Other related forklift scales, load cells thereof and methods of measuring a forklift load are also provided.

Claims

1. A forklift scale to measure a load carried by a pair of forks of a forklift that includes a fork carriage to movably position the forks, the forklift scale comprising:

a pair of load cells, each load cell configured to mount to the fork carriage independent of the other and to removably receive a respective fork of the forklift, and wherein each load cell includes a structural arrangement that couples the respective fork to the fork carriage during operation such that an entirety of the load carried by the forks is transmitted to the fork carriage via the pair of load cells.

2. The forklift scale of claim 1 wherein a base of the respective fork to be received by each load cell defines a fork base width, a fork base depth and a fork base height, and wherein the structural arrangement of each load cell is configured such that the entirety of the structural arrangement falls within a reference rectangular prism defined by a reference width of one and one-half times the fork base width, a reference depth of two times the fork base depth and a reference height of one and one-quarter times the fork base height.

3. The forklift scale of claim 1 wherein, when the forklift scale is installed for use, each load cell spaces the respective fork to which the load cell is attached from a mounting face of the carriage by a distance less than or equal to twice a thickness of a base of the fork.

4. The forklift scale of claim 1 wherein the structural arrangement of each load cell comprises an elongated structural member that is configured to deform elastically in response to a load carried by the forks of the forklift when using the forklift scale, the amount of deformation indicative of a portion of the load carried by each respective fork.

5. The forklift scale of claim 4 wherein the elongated structural member includes an elongated aperture extending a majority of a height of the elongated structural member.

6. The forklift scale of claim 5 wherein the elongated aperture is I-shaped and extends through a width of the elongated structural member.

7. The forklift scale of claim 5 wherein the elongated aperture is oriented generally parallel to opposing sides of the load cell.

8. The forklift scale of claim 4 wherein the structural arrangement further comprises a bearing member coupled to the elongated structural member, the bearing member including engagement features to couple with corresponding features of the fork.

9. The forklift scale of claim 8 wherein the bearing member includes a notch to align with a locking aperture in the fork when the fork is attached to the load cell.

10. The forklift scale of claim 4 wherein the elongated structural member includes engagement features integral therewith to couple with corresponding features of the fork.

11. The forklift scale of claim 4 wherein the elongated structural member includes engagement features integral therewith to couple with corresponding features of the fork carriage.

12. The forklift scale of claim 4 wherein the elongated structural member includes at least one aperture extending through a width thereof to at least partially define at least one thin-walled structural portion adjacent to the aperture.

13. The forklift scale of claim 12 wherein the thin-walled structural portion is generally planar and includes opposing surfaces that are generally parallel to a horizontal reference plane of the respective load cell.

14. The forklift scale of claim 13 wherein each load cell further comprises a plurality of strain gauges, and wherein, for each load cell, at least some of the strain gauges are located on the at least one thin-walled structural portion thereof.

15. The forklift scale of claim 4 wherein the elongated structural member includes a plurality of distinct apertures extending through a width thereof in series to define at least one thin-walled structural portion between the apertures.

16. The forklift scale of claim 1 wherein each load cell further includes a lock to lock each load cell and respective fork to the carriage during use.

17. A forklift scale to measure a load carried by a pair of forks of a forklift having a fork carriage to movably position the forks, the forklift scale comprising:

a first load cell having a deformable body configured to mount directly to the fork carriage and being configured to removably receive one of the pair of forks of the forklift; and

a second load cell having a deformable body configured to mount directly to the fork carriage and being configured to removably receive the other one of the pair of forks of the forklift, and

wherein the first load cell and the second load cell are independently attachable to the fork carriage.

18. A load cell to measure a portion of a load carried by a pair of forks of a forklift that includes a fork carriage to movably position the forks, the load cell comprising:

an elongated structural member including opposing portions separated by a primary aperture extending at least a majority of a height of the elongated structural member, the elongated structural member further including at least one pair of parallel offset horizontal strain gauge mounting surfaces at each of opposing ends thereof;

carriage engagement features configured to removably attach to complementary features of the fork carriage; and

fork engagement features configured to removably attach to complementary features of one of the forks.

19. The load cell of claim 18 wherein at least one of the carriage engagement features and the fork engagement features are integrally formed with the elongated structural member.

20. The load cell of claim 18 wherein a base of the fork to be attached to the load cell defines a fork base width, a fork base depth and a fork base height, and wherein an entirety of a load bearing structure of the load cell is configured such that the load bearing structure falls within a reference rectangular prism defined by a reference width of one and one-half times the fork base width, a reference depth of two times the fork base depth and a reference height of one and one-quarter times the fork base height.

21. The load cell of claim 18, further comprising:

a first bridge arrangement of strain gauges including one pair of strain gauges mounted on one of the parallel offset horizontal mounting surfaces located at one of the opposing ends of the load cell and one pair of strain gauges mounted on one of the parallel offset horizontal mounting surfaces located at the other one of the opposing ends of the load cell; and

a second bridge arrangement of strain gauges including one pair of strain gauges mounted on one of the parallel offset horizontal mounting surfaces located at one of the opposing ends of the load cell and one pair of strain gauges mounted on one of the parallel offset horizontal mounting surfaces located at the other one of the opposing ends of the load cell.

22. The load cell of claim 21 wherein the first bridge arrangement of strain gauges includes a first set of strain gauges located on one of the parallel offset horizontal mounting surfaces at an upper end of the elongated structural member and a second set of strain gauges located on one of the parallel offset horizontal mounting surfaces at a lower end of the elongated structural member, and wherein the second bridge arrangement of strain gauges includes a first set of strain gauges located on one of the parallel offset horizontal mounting surfaces at the upper end of the elongated structural member and a second set of strain gauges located on one of the parallel offset horizontal mounting surfaces at the lower end of the elongated structural member.

23. The load cell of claim 22 wherein the first set of strain gauges of the first bridge arrangement is positioned generally opposite the first set of strain gauges of the second bridge arrangement.

24. The load cell of claim 23 wherein the first set of strain gauges of the first bridge arrangement is located further away from a central horizontal reference plane of the load cell than the first set of strain gauges of the second bridge arrangement, and wherein a spread of the first set of strain gauges of the first bridge arrangement is greater than a spread of the first set of strain gauges of the second bridge arrangement.

25. The load cell of claim 21 wherein the strain gauges are arranged such that a load value indicative of the load shared by the pair of forks is maintained below a threshold accuracy of about 0.5 percent irrespective of a position of the load along a length of the forks, and wherein, for each load cell, the first bridge arrangement of strain gauges exhibits a signal increase when the load is positioned on the forks with increasing distance from the load cell and the second bridge arrangement of strain gauges exhibits a signal decrease when the load is positioned on the forks with increasing distance from the load cell.

26. The load cell of claim 25 wherein a magnitude of the signal increase exhibited by the first bridge arrangement when the load is positioned on the forks with increasing distance from the load cell is about equal to a magnitude of the corresponding signal decrease exhibited by the second bridge arrangement such that a summation of the magnitudes of the signals of the first and the second bridge arrangements remains generally constant with changing position of the load along the forks.

27. A method of measuring a load carried by a pair of forks of a forklift that includes a fork carriage to movably position the forks, the method comprising:

obtaining strain gauge signals from a pair of independently mountable load cells that are each positioned between the fork carriage and a respective one of the forks; and

processing the signals to obtain a load value indicative of a load shared by the pair of forks.

28. The method of claim 27 wherein obtaining strain gauge signals from the pair of independently mountable load cells includes obtaining, for each load cell, strain gauge signals from a respective first bridge arrangement of strain gauges mounted on parallel mounting surfaces located at each of opposing ends of the load cell and strain gauge signals from a respective second bridge arrangement of strain gauges mounted on parallel mounting surfaces located at each of opposing ends of the load cell.

29. The method of claim 27 wherein obtaining strain gauge signals from the pair of independently mountable load cells includes obtaining, for each load cell, strain gauge signals from a respective first bridge arrangement of strain gauges mounted on parallel horizontal mounting surfaces located at each of opposing ends of the load cell and strain gauge signals from a respective second bridge arrangement of strain gauges mounted on parallel horizontal mounting surfaces located at each of opposing ends of the load cell.

30. The method of claim 29 wherein the first bridge arrangement of strain gauges includes a first set of strain gauges located on one of parallel offset horizontal mounting surfaces at an upper end of the load cell and a second set of strain gauges located on one of parallel offset horizontal mounting surfaces at a lower end of the load cell, and wherein the second bridge arrangement of strain gauges includes a first set of strain gauges located on another one of the parallel offset horizontal mounting surfaces at an upper end of the load cell and a second set of strain gauges located on another one of the parallel offset horizontal mounting surfaces at a lower end of the load cell.

31. The method of claim 30 wherein the first set of strain gauges of the first bridge arrangement is positioned generally opposite the first set of strain gauges of the second bridge arrangement, and wherein the second set of strain gauges of the first bridge arrangement is positioned generally opposite the second set of strain gauges of the second bridge arrangement.

32. The method of claim 31 wherein the first set of strain gauges of the first bridge arrangement is located further away from a central horizontal reference plane of the load cell than the first set of strain gauges of the second bridge arrangement, and wherein a spread of the first set of strain gauges of the first bridge arrangement is greater than a spread of the first set of strain gauges of the second bridge arrangement.

33. The method of claim 29 wherein the strain gauges are arranged such that the load value indicative of the load shared by the pair of forks is maintained below a threshold accuracy of about 0.5 percent irrespective of a position of the load along a length of the forks, and wherein, for each load cell, the first bridge arrangement of strain gauges exhibits a signal increase when the load is positioned on the forks with increasing distance from the load cell and the second bridge arrangement of strain gauges exhibits a signal decrease when the load is positioned on the forks with increasing distance from the load cell.

34. The method of claim 33 wherein a magnitude of the signal increase exhibited by the first bridge arrangement of strain gauges when the load is positioned on the forks with increasing distance from the load cell is about equal to a magnitude of the corresponding signal decrease exhibited by the second bridge arrangement of strain gauges such that a summation of the magnitudes of the signals of the first and the second bridge arrangements remains generally constant with changing position of the load along the forks.

35. The method of claim 29, further comprising:

obtaining, for each load cell, a supplemental signal from a third bridge arrangement of strain gauges that comprises a first and a second set of strain gauges located on opposing sides of a central horizontal reference plane of the load cell and located on opposing sides of a vertical reference plane of the load cell that is generally parallel to a mounting face thereof.