Force measuring load pin having at least one sensor and a slot that divides the load pin into upper and lower portions

Abstract

A load pin configured for measuring a force, the load pin including two sensors spaced apart from each other for measuring stress or tension. An axis includes a lateral surface configured to be subjected to a load from an upside in an area of the axis between the two sensors. A slot divides the axis into a lower portion and an upper portion, the slot extending essentially in an axial direction of the axis.

Claims

1. A load pin configured for measuring a force, the load pin comprising: two sensors spaced apart from each other for measuring stress or tension, an axis including a lateral surface configured to be subjected to a load from above in an area of the axis between the two sensors; and a slot dividing the axis into a lower portion and an upper portion, the slot extending essentially in an axial direction of the axis, wherein the axis comprises a center portion adapted to be subjected to the load, wherein the center portion is a spherical segment, and wherein the upper portion is larger than the lower portion.

2. The load pin according to claim 1, wherein the upper portion comprises recesses arranged at least in an upper area of the lateral surface to concentrate stress or tension to the sensors.

3. The load pin according to claim 2, wherein a first one of the two sensors is located in the axis in a position that aligns with a first end of the slot and a second one of the two sensors is located in the axis in a position that aligns with a second end of the slot, and wherein a first one of the recesses arranged at least in the upper area of the lateral surface is aligned with the first one of the two sensors and the first end of the slot and a second one of the recesses arranged at least in the upper area of the lateral surface is aligned with the second one of the two sensors and the second end of the slot.

4. The load pin according to claim 1, wherein the center portion is raised from the lateral surface.

5. The load pin according to claim 1, wherein the center portion surrounds the lateral surface of the axis in the area configured to be subjected to the load.

6. The load pin according to claim 1, wherein a length of the slot in an axial direction of the axis substantially equals a length of a distance between the two sensors.

7. The load pin according to claim 1, wherein the slot has two endings and comprises a semicircular shape on the endings.

8. The load pin according to claim 1, wherein the slot extends through the axis from one side of the lateral surface to another side of the lateral surface or extends from one side of the lateral surface into the axis to a defined depth.

9. The load pin according to claim 1, wherein a channel is provided inside the axis for connecting the sensors with a cable coming from one face side of the axis.

10. The load pin according to claim 1, wherein the center portion surrounds the axis.

11. A load pin configured for measuring a force, the load pin comprising: two sensors spaced apart from each other for measuring stress or tension, an axis including a lateral surface configured to be subjected to a load from above in an area of the axis between the two sensors; and a slot dividing the axis into a lower portion and an upper portion, the slot extending essentially in an axial direction of the axis, wherein the upper portion is larger than the lower portion.

12. A load pin configured for measuring a force, the load pin comprising: an axis with at least one sensor for measuring stress or tension, the axis including a lateral surface configured to be subjected to a load from an area above the at least one sensor; and a recess dividing the axis into a lower portion and an upper portion, the recess extending essentially in an axial direction of the axis, wherein the axis comprises a center portion adapted to be subjected to the load, wherein the center portion is a spherical segment, and wherein the upper portion is larger than the lower portion.

13. The load pin according to claim 12, wherein the recess is a sink from one side of a lateral surface into the axis; two sinks from two sides of the lateral surface into the axis; or a slot.

14. The load pin according to claim 12, wherein the recess is milled.

15. The load pin according to claim 12, wherein the recess has at least two endings and comprises a semicircular shape on the endings.

16. The load pin according to claim 12, wherein the center portion surrounds the axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus, are not limitative of the present invention, and wherein:

(2) FIG. 1 is a schematic view of applications of a load pin;

(3) FIG. 2A is a schematic sectional view of an arrangement with a load pin according to the conventional art in an unloaded condition;

(4) FIG. 2B is a schematic sectional view of the arrangement shown in FIG. 2A in a loaded condition;

(5) FIG. 2C is a schematic sectional view of an arrangement with a load pin in a loaded condition;

(6) FIG. 3A is a schematic sectional view of an arrangement with a load pin in an unloaded condition;

(7) FIG. 3B is a schematic sectional view of the arrangement shown in FIG. 3A with a load pin in a loaded condition;

(8) FIG. 4A is a schematic plan view on a lateral surface of a load pin;

(9) FIG. 4B is a schematic perspective view of a section of the load pin shown in FIG. 4A;

(10) FIG. 4C is a schematic perspective view of a section of the load pin shown in FIG. 4A; and

(11) FIG. 4D is a schematic perspective view of a section of the load pin shown in FIG. 4A.

DETAILED DESCRIPTION

(12) FIG. 1 shows a schematic view of applications of a load pin 1. For example, the load pin 1 is used on cranes 50, mobile cranes 50, container spreaders, harbor cranes 50 or other applications that use a pin, for example structural joints in bridges and buildings, hydraulic actuators, and aircraft landing gears.

(13) A load is measured via the load pin which is integrated in a crane construction. For example the load of a rope, chain, or cable 20 is transmitted via a wheel 2 to the load pin 1.

(14) Any other applications are possible where a load of a rope, chain, or cable 20 or a construction should be monitored on an axis A of a load pin 1.

(15) FIG. 2A shows a schematic sectional view of an arrangement with a load pin 1 according to the conventional the art in an unloaded condition.

(16) The load pin 1 is configured for measuring a force and comprises an axis A with two sensors S spaced apart from each other for measuring stress or tension. The axis A includes a lateral surface A1 configured to be subjected to load from an upside in an area B of the axis A between the two sensors S. Further, the axis comprises two surrounding recesses 4 in an area of the sensors S to concentrate stress or tension to the sensors S.

(17) On an underside the axis A is mounted with its endings 9 on two bearings 21.

(18) FIG. 2B shows a schematic sectional view of the arrangement shown in FIG. 2A in a loaded condition, wherein in the loaded condition a force F acts on the wheel 2 and on the axis A.

(19) Due to the force F, the axis is bent and the sensors S measure a shear force which is combined with rotation, which has bad influence on measured values.

(20) Due to the bending a gap G1 between the wheel 2 and the axis A and further gaps G2 between the ends 9 and the bearings 21 are generated. These gaps G1, G2 also create errors. Bending, rotation and changes in load conditions, also created from the recesses 4, create errors and peaks in measured values at the sensors S. The load pin 1 is thus prone to large errors from small variations in load conditions such as differences in surface roughness, change in position and differences in surface hardness.

(21) FIG. 2C shows a schematic sectional view of an arrangement with an exemplary embodiment of a load pin 1 according to an aspect of the invention in a loaded condition.

(22) In contrast to the load pin 1 according to the conventional art shown in FIGS. 2A and 2B, the exemplary embodiment of the load pin 1 shown in FIG. 2C comprises the axis A with a slot 3, which divides the axis A into a lower portion 6 and an upper portion 7, wherein the slot 3 extends essentially in an axial direction of the axis A. Further the slot 3 extends through the axis A from one side of the lateral surface B to another side of the lateral surface B and has two endings and comprises a semicircular shape on the endings. In other exemplary embodiments, the slot 3 extends from one side of the lateral surface B into the axis A to a defined depth. In the shown embodiment, for example, the upper portion 7 is larger than the lower portion 6. Due to this separation of the axis A only the upper portion 7 is bent under load by the force F. The lower portion 6 is less or nearly not bent under load by the force F. Thus, shear force and less rotation is transmitted to the sensors S. Therefore, in the gaps G1, G2, errors or measuring peaks are not possible or at least reduced.

(23) The force F is introduced from the rope wheel 2 via a center portion 8 to the axis A. The center portion 8 is raised from the lateral surface A1 of the axis A and surrounds the lateral surface A in the area B configured to be subjected to load from the upside. The center portion 8 is designed as a spherical segment. This added raised center portion reduces the influence of the bending still occurring in the center portion. The spherical radius to this surface further reduces change in load conditions.

(24) Furthermore, the upper portion 7 of the axis comprises recesses 5 arranged in an upper area of the lateral surface B in an alignment with the sensors S to concentrate stress or tension to the sensors S.

(25) Additionally, the axis A comprises a recess 15 for fixing the load pin 1 against turning in the application. Other anti-rotation mechanisms well known to those skilled in the art of load pin 1 design could also be used.

(26) The center portion 8 and the ends 9 of the axis can be modified in many ways known to those skilled in the art of load cell design.

(27) In exemplary embodiments the recesses 5, 15, undercuts, reliefs and other structures may only be milled in the upper portion of the load pin 1. Consequently, recesses at the bearings 21 are minimized. This allows fewer changes in changing loading conditions, so that the lower portion 6 is more rigid.

(28) FIG. 3A shows a schematic sectional view of an arrangement with an exemplary embodiment of a load pin 1 according to an aspect of the invention in an unloaded condition. FIG. 3B shows this arrangement in a loaded condition.

(29) In addition to the load pin 1 shown in FIG. 2C, the load pin 1 of FIG. 3A includes a channel 10 inside the axis A for connecting the sensors S with a cable 11 coming from one face side C1 of the axis A. The channel 10 is arranged on the lateral surface B or is integrated completely inside the axis A.

(30) The rope, chain, or cable 20 introduces a load force F via the wheel 2 to the axis A of the load pin 1 over the raised center portion 8, which completely surrounds the axis A.

(31) The slot 3 separates the axis A in the lower portion 6 and the upper portion 7, which has more deflection under load than the lower portion.

(32) A length D of the slot 3 in an axial direction of the axis A between two face sides C1, C2 equals a distance d between the two sensors S or the distance d between the two sensors S is longer or shorter in a region of about 5 mm-10 mm. The diameter of the axis A of the load pin 1 could be as small as 7 mm. There is no inherent limit on the maximum size.

(33) In an exemplary embodiment, the sensors S are constructed as conventional bonded foil strain gauges. Each sensor S contains one or more strain gauges. Other types of strain/stress gauges could also be incorporated such as silicon or thin film technology. Other known methods of force measuring based on principles such as fiber optics, magneto-elastic effects or piezo-resistivity can also be used.

(34) In other exemplary embodiments there is only one sensor S to measure the force F.

(35) In other exemplary embodiments, a recess (not shown) divides the axis A into a lower portion 6 and an upper portion 7, wherein the recess extends essentially in the axial direction of the axis A. The recess is one of a sink from one side of the lateral surface B into the axis S and two sinks from two sides of the lateral surface B into the axis A. The recess can be milled. In one embodiment, the recess has at least two endings and comprises a semicircular shape on the endings.

(36) FIG. 4A to 4D show different views of an exemplary embodiment of a load pin 1 according to an aspect of the invention.

(37) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.