FORCE SENSING LINKAGE CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to, and claims priority from, U.S. Provisional Patent Application Serial No. 60/895,239 filed on March 16, 2007, which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable. BACKGROUND OF THE INVENTION

The present invention is related generally to a system and method for measuring the weight, force, and moments on the load-lifting assembly of a utility vehicle, and in particular, to a linkage assembly for coupling the load- lifting assembly of a utility vehicle to an actuating mechanism which incorporates a sensor for measuring forces exerted on the load-lifting assembly during operation there of. Utility vehicles commonly known as skid-steers or front-end loaders, are commonly utilized in a wide range of applications in the landscaping, construction, and load-lifting environments. These vehicles are characterized by a very short wheelbase, and are often steered by locking or braking wheels on one side of the vehicle, facilitating turning in a very tight radius. The operator is generally seated in a protective cage in the middle of the vehicle, with an engine and counterweight being disposed at the rear, to offset the weight of any load carried by hydraulically powered implements such as buckets or forks, which are coupled to the front of the vehicle.

Generally, the implements coupled to the front of the vehicle are interchangeable, and are coupled and uncoupled to the vehicle via an attachment assembly. Given the very short wheelbase commonly found on these vehicles, and the nature of their use, there is a high risk of vehicle rollover or tipping when picking up or transporting heavy loads via the front- mounted implements such as buckets. Often, an operator may have difficulty in gauging the weight of a load before or after it is picked up with the front-

mountθd implements. The hydraulic power which can be directed to the front- mounted implements to lift or move loads is often considerable, and it is possible for an operator to lift a load which may not be safely moved at a high rate of speed. Accordingly, it would be advantageous to provide a linkage component for use in the attachment assembly of such a utility vehicle which incorporates sensors capable of providing an indication of the forces acting on the attached implements during operation of the vehicle. It would be further advantageous to provide such a linkage which is sensitive to forces acting along a specific axis of the linkage, and which is relatively decoupled from the effects of forces acting perpendicular to the specific axis. BRIEF SUMMARY OF THE INVENTION

Briefly stated, the present disclosure provides an improved linkage for use in an implement attachment assembly of a utility vehicle. The improved linkage assembly is configured to have compliance along a selected axis, and to incorporate at least one sensor for measuring the effect of forces in the improved linkage along the selected axis. Placement of the sensor, and the configuration of the improved linkage, are selected to decouple the sensor from the effects of forces which are exerted perpendicular to the selected axis.

In an embodiment of the present invention, an improved linkage for use in an implement attachment assembly of a front-end loader is provided with end couplings at opposite ends of a longitudinal X-axis, configured for attachment between components of the front-end loader and the implement attachment. A central transverse opening passes through the improved linkage parallel to the Z-axis, and has a width parallel to the Y-axis, which is less than the width of the improved linkage. A displacement sensor is centrally disposed across the central transverse opening on the longitudinal X-axis of the improved linkage. A plurality of side openings passing through the improved linkage parallel to the Z-axis each extend inward from the

peripheral edge of the improved linkage. Each side opening has a transverse length parallel to the Y-axis, which is less than half the transverse width of the improved linkage, and is displaced longitudinally from, and parallel to, the central opening. Optionally, each opening may be filled with an elastomeric compound and/or enclosed within a protective cover. Forces acting on the improved linkage along the longitudinal X-axis vary the width of the central opening, and are measured by the displacement sensor. Lateral forces acting on the improved linkage along the Y-axis and the Z-axis are decoupled from the displacement sensor by the side openings. The foregoing features, and advantages set forth in the present disclosure as well as presently preferred embodiments will become more apparent from the reading of the following description in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS In the accompanying drawings which form part of the specification:

Figure 1 illustrates a linkage assembly of the present invention, the linkage is shown without an optional protective covering;

Figure 2 illustrates the linkage assembly of Fig. 1 with an optional protective covering; Figure 3 illustrates the linkage assembly of Fig. 1 , incorporating additional displacement sensors, the linkage is shown without an optional protective covering;

Figure 4 illustrates the improved linkage of Figs. 1 -3 installed on an implement attachment assembly of a utility vehicle; and Figure 5 is a close-up illustration of the installed improved linkage of

Fig. 3.

Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. It is to be understood that the drawings are for illustrating the concepts set forth in the present disclosure and are not to scale.

-A-

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description illustrates the invention by way of example and not by way of limitation. The description enables one skilled in the art to make and use the present disclosure, and describes several embodiments, adaptations, variations, alternatives, and uses of the present disclosure, including what is presently believed to be the best mode of carrying out the present disclosure.

Turning to Figures 1 and 2, an improved linkage for use in an implement attachment assembly of a utility vehicle is shown generally at 10. The improved linkage assembly 10 has a planar rectangular body 1 OA, and is configured with a set of transverse openings 12 and 14 to have compliance along a selected longitudinal X-axis, and to incorporate at least one displacement sensor 100 for measuring the effect of forces in the improved linkage 10 along the selected X-axis. Placement of the displacement sensor 100, and the configuration of the transverse openings 12 and 14 in the improved linkage 10, are selected to decouple the displacement sensor 100 from the effects of forces which are exerted perpendicular to the selected longitudinal X-axis. It will be recognized that the displacement sensor 100 may be configured to communicate output to an associated electronic controller via either a wired connection or a wireless communications link. Furthermore, the displacement sensor 100 may be replaced with a variety of similarly suitable sensors configured to provide an output signal which is responsive to the forces exerted on the improved linkage assembly 100, such as a strain gauge. In an embodiment of the present invention, the improved linkage 10 is shown in one exemplary embodiment for use in an implement attachment assembly of a utility vehicle such as a skid-steer or front-end loader in Figures 4 and 5. However, it will be recognized that the improved linkage 10 may be used in a variety of applications wherein loads or forces will be conveyed between two or more connections coupled by the improved linkage 10.

Thθ improved linkage 10 is provided with a linkage body 1 OA. The thickness and specific dimensions of the linkage body 1 OA may be varied depending upon the structural requirements for the particular application in which the improved linkage 10 is to be utilized, and may be coated to prevent corrosion or other environmental damage as required. End couplings 1 1 and 13 at opposite ends of a longitudinal X-axis of the improved linkage body 1 OA are configured for securing the improved linkage 10 between components of the utility vehicle and the implement attachment mechanisms, such as seen in Figures 4 and 5. Those of ordinary skill in the art will recognize that the end couplings 1 1 and 13 may be varied depending upon the particular requirements for securing the improved linkage 10 in place without departing from the scope of the invention. Furthermore, it will be recognized that excess material may be removed from the rectangular configuration of the improved linkage body 10A to reduce weight, provided such removal of material does not compromise the structural integrity of the improved linkage 10 or alter the characteristic response of the improved linkage 10 to incident forces from that which is described below.

Preferably, as seen best in Figures 1 and 3, the central body portion 1 OA of the improved linkage 10 is configured to provide a mechanical reaction to forces exerted along the longitudinal X-axis of the improved linkage 10. A central transverse opening 14 passes through the improved linkage body 10A parallel to the Z-axis, and has a width parallel to the Y-axis, which is less than the width of the improved linkage body 10A. A displacement sensor 100 is centrally disposed across the central transverse opening 14 parallel to the longitudinal X-axis of the improved linkage 10. The sensor 100 may be disposed on an outer surface of the linkage body 10A, as seen in Figures 1 and 3, may be disposed within a recess in the surface, or may be disposed within an internal cavity within the linkage body 10A so long as the sensor 100 is disposed to acquire measurements as set forth here in.

An extension (compression) force (Fx) applied to the improved linkage 10 along the x-direction will increase (decrease) the width of the central opening 14 in proportion to the force. The displacement sensor 100 is disposed to measure displacements across the central opening 14 (in the x- direction), which are a function of the applied force along the x-axis of the improved linkage 10. Any suitable type of displacement sensor 100 can be used (e.g., capacitive, inductive, optical, etc.). Those of ordinary skill in the art will recognize that if the improved linkage 10 is to be used for measurements along a single axis, (i.e., compression or tension), then the linkage assembly 10 may be optionally pre-stressed oppositely (i.e., tension or compression) in order to increase the operating range.

A plurality of side openings 12 pass through the improved linkage body 1 OA parallel to the Z-axis, each extend inward from the peripheral edge of the improved linkage body 1 OA, as best seen in Figures 1 and 3. Each side opening 12 has a transverse length, which is less than half the transverse width of the improved linkage body 10A. Each side opening 12 is displaced longitudinally from, and parallel to, the central opening 14, such that a total of at least two side openings 12 are present in the improved linkage body 10A on each side of the central opening 14. In addition to increasing the compliance of the improved linkage 10, the side openings 12 help to decouple the displacement sensor 100 from the effects of lateral forces (Fy and Fz) and moments applied about the x-, y-, and z-axes of the improved linkage 10. Optionally, each side or central opening 12, 14 may be filled with an elastomeric compound and/or enclosed within a protective cover 16. Similarly, mechanical stops may be provided within the openings 12, 14, or external thereto, which prevent excessive movement of the improved linkage 10 which may result in damage.

It will be recognized that more than one sensor 100 may be utilizes on the linkage assembly 10 to provide multiple measures of the forces transferred through the linkage assembly 10. For example, as shown in

Figure 3, additional sensors 102a through 102f may be disposed across openings 12 and disposed on the linkage body 1 OA. As with sensor 100, the additional sensors 102 may be disposed on an outer surface of the linkage body 1 OA, as seen in Fig. 3, may be disposed within a recess in the outer surface, or may be disposed within an internal cavity within the linkage body 10A so long as each sensor 102 is disposed to acquire measurements as set forth here in. With the sensor arrangement illustrated in Fig. 3, various additional measurements may be acquired when the end couplings 1 1 and 13 transmit forces and torques through the linkage assembly 10. For example, the output from sensors 102a through 102d, when configured to measure displacements in the X-axis direction across openings 12, may be summed to provide a measure of force along the X-axis, while the difference of signals from sensors 102a and 102b, and/or 102c and 102d can provide a measure of the torque about the Z-axis. Alternatively, the output from sensors 102a through 102d, when configured to measure displacements in the Z-axis direction across openings 12, can provide a measure of the torque about the X-axis by observing the difference of signals from sensors 102a and 102b, and/or 102c and 102d.

A measure of torque about the X-axis axis may further be acquired by providing sensors 102e and 102f as shear strain sensors on the surface of the linkage body 10a, between openings 12 on opposite sides of the X-axis.

In a further alternate embodiment, with sensors 102a-102d disposed on as shown in Figure 3, on a front surface of the linkage assembly 10, a second set of sensors 104a-104d may be disposed in mirror image from sensors 102a-102d, on the opposite surface of the linkage assembly 10. With sensors 104a-104d configured to acquire the same force and torque measurements as sensors 102a-102d, the resulting measurements may be used to measure torque about the Y-axis by determining the difference in displacement along the X-axis from sensor pairs 102a with 104a, 102b with 104b, 102c with 104c, and/or 102d with 104d.

As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.