Attachments for industrial material handling equipment

Abstract

An attachment assembly for industrial material handling equipment is shown and disclosed. In some embodiments, the attachment assembly includes a carriage assembly having a carriage and a linear actuator attached to the carriage. The carriage is mountable to the industrial material handling equipment. The linear actuator includes a body and longitudinally opposed piston rods slidably received within the body. Each piston rod has an end. The attachment assembly further includes a frame assembly slidably coupled to the carriage. The frame assembly has upper and lower transverse frame members and end vertical frame members that connect the upper and lower transverse frame members in a spaced-apart relationship to define a central frame cavity between the upper and lower transverse frame members. The linear actuator is positioned within the central frame cavity such that the ends of the piston rods contact the end vertical frame members, allowing the linear actuator to slide the frame assembly laterally relative to the carriage assembly.

Description

[Background technology]

[0001] [background]

[0002]

[0001] The subject matter of this application relates to attachments for industrial material handling equipment for lifting, moving, and / or weighing loads. Examples of industrial material handling equipment include lift trucks, automated guided vehicles (AGVs), and other transport and movement devices for a variety of loads.

[0003]

[0002] When used with lift trucks, attachments are typically added to a standard carriage that carries the lift forks to provide added range of motion and / or other functionality. However, the attachments offset the position of the lift forks further away from the front axle of the lift truck, thereby reducing the lifting and lowering capabilities of the lift truck. What is desired, therefore, is an attachment assembly that allows for nesting of components to provide the desired added range of motion and other functionality, while also reducing the distance from the front axle of the industrial material handling equipment, thereby increasing the capacity of the industrial material handling equipment. [Brief description of the drawings]

[0004] For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: [Figure 1] FIG. 1 is a perspective view of an exemplary embodiment of an attachment assembly for industrial material handling equipment shown mounted to a lift truck with lift forks attached to fork positioners of the attachment assembly. [Diagram 2] FIG. 2 is a side view of the attachment assembly of FIG. [Diagram 3] 3 is a front perspective view of a faceplate assembly of the attachment assembly of FIG. 1; [Figure 4]4 is a rear perspective view of a faceplate assembly of the attachment assembly of FIG. 1; [Diagram 5] FIG. 5 is a front view of the attachment assembly of FIG. 1 with the lift forks shown apart. [Figure 6] FIG. 6 is a front view of the attachment assembly of FIG. 1 shown with the lift forks moved together. [Figure 7] 7 is a perspective view of a frame assembly of the attachment assembly of FIG. 1. FIG. [Figure 8] 8 is a partial cross-sectional view of the attachment assembly of FIG. 1 taken along line 8-8 of FIG. 1 and showing the fasteners and load cell assembly for securing the faceplate assembly of FIGS. 3-4 to the frame assembly of FIG. [Figure 9] 9 is a perspective view of a carriage assembly of the attachment assembly of FIG. 1. FIG. [Figure 10] FIG. 10 is a perspective view of the attachment assembly of FIG. 1 shown without the faceplate assembly. [Figure 11] FIG. 11 is a front view of the attachment assembly of FIG. 1 with the frame assembly and faceplate assembly moved to one side and with a portion of the faceplate assembly not moved to illustrate movement of the piston end of the linear actuator of the carriage assembly. [Figure 12] 12 is a front view of the attachment assembly of FIG. 1 with the frame assembly and faceplate assembly moved to the opposite side of FIG. 11 to show movement of the piston end of the linear actuator of the carriage assembly without moving a portion of the faceplate assembly. [Figure 13] 13 is a perspective view of a load cell of the attachment assembly of FIG. 1. FIG. [Figure 14] FIG. 14 is a front view of the load cell of FIG. [Figure 15] FIG. 15 is a side view of the load cell of FIG. [Figure 16] FIG. 16 is a plan view of the load cell of FIG. [Figure 17] 17 is a rear perspective view of an alternative embodiment of a faceplate assembly of the attachment assembly of FIG. 1 showing a center tie bar. [Figure 18] FIG. 18 is a perspective view of the center tie bar of FIG.

[0005] Detailed Description

[0006]

[0022] 1-2, an exemplary embodiment of an attachment assembly 20 for industrial material handling equipment is shown. In the embodiment of FIGS. 1-2, the attachment assembly is shown mounted to a lift truck. However, other embodiments of the attachment assembly 20 may be configured to mount to automated guided vehicles (AGVs) and other carriers and / or movers. The attachment assembly may be integral with the industrial material handling equipment and / or removably mounted thereto.

[0007]

[0023] In the embodiment of Figures 1-2, an attachment assembly 20 is shown received within a mast channel 22 of a lift truck and supporting a lift fork 24. The lift truck attachment assembly 20 includes a faceplate assembly 26, a frame assembly 28, and a carriage assembly 30. As shown in Figure 2, at least a substantial portion of each of the faceplate assembly, frame assembly, and carriage assembly resides within separate faceplate FP, frame FR, and carriage CR surfaces, respectively, that are spaced apart and parallel to one another.

[0008]

[0024] 3-4, the faceplate assembly 26 includes parallel, coplanar and spaced apart upper and lower cross-plate members 32, 34. End vertical faceplate members 36, 38 are disposed between and connect the cross-plate members to define a faceplate central cavity 40 therebetween. The end vertical faceplate members are spaced apart and parallel to each other and are coplanar with the upper and lower cross-plate members. If weighing capability is desired, one or more load cell assemblies 42 are received in one or more faceplate holes 44. The load cell assemblies include one or more load cells 43 that measure the weight of a load supported by the lift forks 24 or, when attached to other industrial material handling equipment, by a support member other than the lift forks. Measurements may be made in any suitable manner, such as by measuring the deflection of the faceplate assembly and / or frame assembly and converting the deflection to a weight measurement. In the embodiment shown in Figures 3-4, the faceplate assembly includes four load cell assemblies 42. However, the faceplate assembly may include more or less than four load cell assemblies. The faceplate assembly is designed to lift truck carriage dimensional standards or other industrial material handling equipment dimensional standards. When the faceplate assembly includes one or more load cell assemblies, the faceplate assembly may be referred to as an "external weighing faceplate."

[0009]

[0025] In the embodiment shown in Figures 3-4, the faceplate assembly 26 includes a fork positioner 46 disposed within the faceplate central cavity 40. The fork positioner includes a pair of elongated bi-directional hydraulic piston and cylinder assemblies 48 and 50, each having a respective cylinder 52, 54 having a respective base portion 56, 58 at one end and a respective rod end portion 60, 62 at the other end from which a respective piston rod 64, 66 can extend. A cylinder connector 68 is configured to rigidly connect the rod end 60 of one cylinder to the rod end portion 62 of the other cylinder such that the longitudinal axes of the piston rods are parallel to one another.

[0010]

[0026] A pair of fork positioning guide members 70, 72 are each coupled to a respective piston rod 64, 66 via a respective rod connector 74, 76 and slidably and guideably engage a respective cylinder 52, 54 of an opposing piston and cylinder assembly by a respective sliding bushing 78, 80. In the embodiment shown in Figures 3-4, the piston and cylinder assemblies 48 and 50 are attached to the end face plate members 36 and 38 via fasteners 82. The cylinder connector 68 includes one or more hydraulic fluid line connectors 84, 86 that communicate with the interior of the respective cylinder 52, 54. The fork positioning guide members 70, 72 receive the forks and are moved by the piston rods 64, 66 to move the forks toward or away from one another as shown in Figures 5-6. Although the fork positioning guide members are shown to receive forks, these guide members can receive and move other accessories.

[0011]

[0027] Examples of fork positioners 46 are further described in U.S. Patent No. 7,909,563, the complete disclosure of which is incorporated herein by reference for all purposes. The nesting of the fork positioner within the faceplate central cavity reduces the thickness (i.e., the thickness measured in the fore-aft direction) of the lift truck attachment assembly 20, as best seen in FIG. 2. Although the faceplate assembly 26 is shown including the fork positioner 46, other embodiments of the faceplate assembly may exclude the fork positioner. In these embodiments, the forks or other support members may be attached to the faceplate assembly by other means, such as notches in the upper cross faceplate member. In some embodiments, the faceplate assembly 26 may not include any devices or structures within the faceplate central cavity.

[0012]

[0028] 7, the frame assembly 28 includes parallel, coplanar and spaced apart upper and lower transverse frame members 92, 94. End vertical frame members 96, 98 are disposed between and connect the transverse frame members to define a central frame cavity 100 therebetween. The end vertical frame members are spaced apart, parallel and coplanar with the upper and lower transverse frame members. Additionally, the end vertical frame members have a thickness greater than that of the upper and lower transverse frame members (as best seen in FIG. 2), thereby providing mounting points for the load cell assemblies (if included) and reducing deflection of the faceplate assembly.

[0013]

[0029] The upper cross frame member 92 includes a lower hook portion 102 that extends substantially or the entire length of the frame member and extends toward the carriage assembly when slidably received by the carriage assembly. The lower hook portion includes a groove 104 that receives a sliding support of the upper cross carriage member of the carriage assembly, as described below. In the embodiment shown in FIG. 2, an upper plain bearing 106 is disposed in the groove 104. Additionally, a lower plain bearing 108 is attached to the rear surface of the lower cross frame member (i.e., the surface facing the lower cross carriage member of the carriage assembly). The upper and lower plain bearings reduce friction to facilitate sliding movement of the frame and faceplate assembly relative to the carriage assembly. In the embodiment shown in FIG. 7, the upper cross frame member includes a grease fixture 109 that allows a user to inject grease adjacent to and along the upper plain bearing.

[0014]

[0030] The end vertical frame members 96, 98 and the lower transverse frame member 94 include one or more frame holes 110 corresponding to the faceplate holes 44 of the faceplate assembly. If the attachment assembly 20 includes one or more load cell assemblies 42, the protruding portions 112 on the housings 113 of these load cell assemblies may be received in the faceplate holes and frame holes and may be fixedly or stably attached to the frame assembly and faceplate assembly via fasteners 114 that secure the faceplate assembly to the frame assembly. The protruding portions of the load cell assemblies include threaded portions 116 that receive the fasteners 114 in the form of nuts, as shown in Figures 2, 4 and 8. In some embodiments, the faceplate assembly is secured to the frame assembly only via the loadcell assemblies and fasteners. In other words, the remainder of the faceplate assembly may be supported by the loadcell assemblies. Thus, the frame assembly allows lateral movement relative to the carriage assembly and serves as an anchor point for the weight load sensing components.

[0015]

[0031] Referring to FIG. 9, the carriage assembly 30 includes a carriage 118 and a lateral or linear actuator 120 attached to the carriage. The carriage includes an upper transverse carriage member 122 and a lower transverse carriage member 124 arranged parallel and spaced apart from one another. End vertical carriage members 126, 128 are attached to the rear surfaces of the transverse carriage members and connect the transverse carriage members to define a carriage central cavity 130 therebetween. The end vertical carriage members are arranged parallel and spaced apart from one another. In addition, the end vertical carriage members include posts 132 that are received in the mast channels of the lift truck (as shown in FIG. 1). The upper transverse carriage member 122 includes a base portion 134 that is flush with the lower transverse carriage member, a raised portion or upper lateral sliding support 135 that is received in a groove 104 of the frame assembly, and an extension portion or shelf 136 that extends vertically from the base portion toward the frame assembly. The upper transverse carriage member carries both front / rear and vertical loads, thus enabling central cavities in the various assemblies of the mounting assembly 20 to support such loads without any central support structure. The lower transverse carriage member 124 is sometimes referred to as the "lower lateral sliding support."

[0016]

[0032] In the embodiment shown in FIG. 9, the linear actuator 120 is mounted to the underside of the shelf 136. The linear actuator is configured to move the frame assembly and faceplate assembly laterally relative to the carriage assembly. The linear actuator includes a body or cylinder 138 and piston rods 140, 142 slidably received within the cylinder. The piston rods move along longitudinally opposed or common longitudinal axles. The carriage assembly 130 further includes a bracket 144 attached to the lower cross carriage member 124. The bracket includes a slot 146 that receives a lip 148 of the frame assembly. The carriage assembly 130 is sometimes referred to as a "stationary frame."

[0017]

[0033] Referring to FIG. 10, the upper transverse carriage member and / or shelf of the linear actuator are sized such that the linear actuator is received within the frame center cavity 100 of the frame assembly. The nesting of the linear actuator within the plane of the frame assembly substantially reduces the thickness of the attachment assembly 20. The ends of the piston rods of the linear actuators are received in reaction blocks or rod connectors 150 stably attached to the end vertical faceplate members 96, 98 of the frame assembly. In other words, the piston rods of the linear actuators contact the end vertical faceplate members. Extension and retraction of the piston rods moves the frame assembly and faceplate assembly laterally or transversely (or parallel to the common longitudinal axis of the piston rods) relative to the carriage assembly as shown in FIGS. 11-12. Movement of the frame and faceplate assembly by the linear actuator is within the plane of the frame and faceplate assembly (i.e., the plane of the faceplate FP and frame FR as shown in FIG. 2).

[0018]

[0034] 13-16, one embodiment of the load cell 43 is shown. The load cell includes a base 152, a body 154, and a coupler 156. In the embodiment shown in FIGS. 13-16, the base 152 is disk-shaped or cylindrical and includes a plurality of openings 158 that receive connectors for mounting the load cell to a faceplate assembly. The body 154 is elongated and includes opposing side portions 160 and 162. The side portions 162 are substantially wider than the side portions 160, as shown in FIGS. 13-16. A strain gauge 164 is mounted on an outer surface of one or both narrow side portions 160. Additionally, a strain gauge 166 is mounted on an outer surface of one or both wide side portions 162. Thus, the strain gauges 164 and 166 are mounted or positioned perpendicular (90 degrees) or nearly perpendicular to one another such that the gauges can measure both vertical and horizontal forces during operation. In particular, strain gauge 164 measures horizontal force and strain gauge 166 measures vertical force. Coupler 156 includes a threaded portion 168 that receives a nut for attaching the faceplate assembly to the frame assembly, as described above.

[0019]

[0035] Four spaced load cell assemblies 42, each having a load cell with a strain gauge positioned to measure horizontal and vertical forces, provide various information to the operator of the attachment. For example, the measured weight from the load cell assemblies can be used by a controller (such as a controller of an industrial material handling equipment) to calculate the lateral offset of the center of gravity by comparing the difference between the weight measurements of the left and right load cells. When the lateral offset is greater than or equal to a predetermined amount or outside of a window of a predetermined amount, the controller can shut down operation of the attachment or industrial material handling equipment. Additionally, the horizontal force measurements can alert the operator of an unexpected horizontal force, such as contacting a trailer wall or another load when engaging a pallet. The controller can shut down operation of the attachment or industrial material handling equipment if a horizontal force is measured outside of a predetermined area or greater than or equal to a predetermined amount.

[0020]

[0036] 17-18, another embodiment of the face plate assembly 26 is shown and generally designated 226. Unless expressly excluded, the face plate assembly 226 may include one or more of the structures and components of the face plate assembly 26. Unlike the face plate assembly 26, the face plate assembly 226 includes a central tie element or central tie bar 227. The central tie bar includes first and second end portions 229 and 231 and a central portion 233 disposed therebetween. The first end portion 229 and the second end portion 231 are attached to the upper and lower cross plate members 232 and 234, respectively, and span the face plate central cavity 240 between the face plate members. The central portion 223 arches away from the upper and lower cross plate members to accommodate the components of the fork positioner 46. The central tie bar is important because it stiffens the face plate assembly and reduces measurement errors from the load cells of the load cell assembly attached to the face plate assembly.

[0021]

[0037] While a particular embodiment of the attachment assembly 20 is shown, other embodiments may modify, add, omit, and / or omit one or more components. For example, a standard carriage without linear actuators may be used in place of the carriage assembly shown in FIG. 10. The frame assembly and faceplate assembly may be stably mounted to a standard carriage to provide metering and / or fork positioning capabilities (if the faceplate assembly includes a fork positioner). Additionally or alternatively, the frame assembly 28 and carriage assembly 30 may include slides, rollers, and / or other components that allow the frame assembly to move relative to the carriage assembly.

[0022]

[0038] It will be understood that the present invention is not limited to the particular embodiments described, and that modifications may be made to the claims without departing from the scope of the invention as defined therein. Such modifications are to be interpreted in accordance with general legal principles, including the doctrine of equivalents or other principles that extend beyond interpretation in accordance with such principles. Unless the context dictates otherwise, a reference in a claim to the number of instances of an element, whether a reference to one instance or to two or more instances, requires at least the recited number of instances of the element, but is not intended to exclude from the scope of the claim a structure or method having more than the recited instances of the element. The word "comprises" or its derivatives, when used in the claims, is used in a non-exclusive sense that is not intended to exclude the presence of other elements or steps in the claimed structure or method.

Claims

1. An attachment assembly comprising a carriage assembly, a frame assembly, and a faceplate assembly, The carriage assembly includes a carriage and a linear actuator attached to the carriage, the carriage being mountable to an industrial material handling device, the linear actuator including a body and longitudinally opposed piston rods, the piston rods each having an end; the frame assembly is slidably coupled to the carriage, the frame assembly having an upper transverse frame member, a lower transverse frame member and an end vertical frame member, the end vertical frame member connecting the upper and lower transverse frame members in spaced apart relationship to define a central frame cavity between the upper and lower transverse frame members, the linear actuator being disposed within the central frame cavity such that the end of the piston rod contacts the end vertical frame member, the linear actuator enabling the frame assembly to slide laterally relative to the carriage assembly; the faceplate assembly is stably attached to the frame assembly and configured to receive one or more support members; the faceplate assembly including one or more load cells configured to measure a weight of a load when supported by the one or more support members; an attachment assembly, the face plate assembly including upper and lower cross-face plate members and end vertical face plate members, the end vertical face plate members connecting the upper and lower cross-face plate members in spaced apart relationship to define a face plate central cavity between the upper and lower cross-face plate members;

2. 2. The attachment assembly of claim 1, wherein the one or more support members are a pair of forks, and the faceplate assembly further includes a fork positioner disposed within a faceplate central cavity, the fork positioner configured to selectively move the pair of forks toward or away from each other.

3. 2. The attachment assembly of claim 1, wherein the faceplate assembly includes at least one faceplate hole, the frame assembly includes at least one frame hole, the frame hole corresponding to the at least one faceplate hole, and the at least one load cell is contained within at least one housing, the at least one housing being received in the at least one faceplate hole and the at least one frame hole.

4. 4. The attachment assembly of claim 3, wherein the frame assembly includes at least one fastener that secures the at least one housing to the at least one face plate hole and the at least one frame hole and secures the face plate assembly to the frame assembly.

5. 2. The attachment assembly of claim 1, wherein a substantial portion of the carriage is in a carriage plane, a substantial portion of the frame assembly is in a frame plane parallel to the carriage plane, and the faceplate assembly is in a faceplate plane parallel to the frame plane.

6. 2. The attachment assembly of claim 1, wherein the carriage includes an upwardly protruding portion and the upper cross frame member includes a lower hook portion having a groove, the protruding portion being received within the groove to allow the frame assembly to slide laterally relative to the carriage assembly.

7. 2. The attachment assembly of claim 1, wherein a substantial portion of the carriage lies in a first plane and a substantial portion of the frame assembly lies in a second plane parallel to the first plane.

8. An attachment assembly comprising a carriage assembly, a frame assembly and a faceplate assembly, The carriage assembly includes a carriage and a linear actuator attached to the carriage, the carriage being mountable to a lift truck, the linear actuator including a body and longitudinally opposed piston rods slidably received within the body, each piston rod having an end; a frame assembly slidably coupled to the carriage, the frame assembly having an upper transverse frame member, a lower transverse frame member and an end vertical frame member, the end vertical frame member connecting the upper transverse frame member and the lower transverse frame member in spaced apart relationship to define a central frame cavity between the upper transverse frame member and the lower transverse frame member, the linear actuator disposed within the central frame cavity such that the end of the piston rod contacts the end vertical frame member, the linear actuator enabling the frame assembly to slide laterally relative to the carriage assembly, the carriage including an upwardly protruding portion, the upper transverse frame member including a lower hook portion having a groove, the protruding portion being received within the groove to enable the frame assembly to slide laterally relative to the carriage assembly, 11. An attachment assembly, wherein the face plate assembly is stably mounted to the frame assembly, the face plate assembly configured to receive one or more forks, the face plate assembly including one or more load cells configured to measure a weight of a load when supported by the one or more forks, the face plate assembly including upper and lower cross plate members and end vertical face plate members, the end vertical face plate members connecting the upper and lower cross plate members in spaced apart relationship to define a face plate central cavity between the upper and lower cross plate members, the face plate assembly further including a fork positioner disposed within the face plate central cavity, the fork positioner configured to selectively move a pair of forks toward or away from each other.

9. An attachment assembly comprising a carriage assembly, a frame assembly, and a faceplate assembly, the carriage assembly includes a carriage, the carriage being mountable to an industrial material handling device; the frame assembly is slidably coupled to the carriage; the frame assembly includes upper and lower transverse frame members and end vertical frame members connecting the upper and lower transverse frame members in spaced apart relationship to define a faceplate central cavity between the upper and lower transverse frame members; the faceplate assembly is stably mounted to the frame assembly, the faceplate assembly configured to receive one or more support members to support a load, the faceplate assembly including one or more load cells configured to measure horizontal and vertical forces applied to the one or more support members; the face plate assembly including upper and lower cross plate members and end vertical face plate members connecting the upper and lower cross plate members in spaced apart relationship to define a face plate central cavity between the upper and lower cross plate members, the face plate assembly including a central tie bar spanning between the upper and lower cross plate members across the face plate central cavity.

10. 10. The attachment assembly of claim 9, wherein the carriage assembly includes a linear actuator having a body and longitudinally opposed piston rods slidably received within the body, each of the piston rods having an end, the frame assembly being slidably coupled to the carriage, the frame assembly having upper and lower transverse frame members and end vertical frame members connecting the upper and lower transverse frame members in spaced apart relationship to define a central frame cavity therebetween, the linear actuator being disposed within the central frame cavity such that ends of the piston rods contact the end vertical frame members, the linear actuator enabling the frame assembly to slide laterally relative to the carriage assembly.

11. 11. The attachment assembly of claim 10, wherein the faceplate assembly further includes a fork positioner disposed within the faceplate central cavity, the fork positioner configured to selectively move a pair of forks toward or away from each other.

12. 10. The attachment assembly of claim 9, wherein the faceplate assembly includes at least one faceplate hole, the frame assembly includes at least one frame hole corresponding to the at least one faceplate hole, and the at least one load cell is included within at least one housing, the at least one housing being received in the at least one faceplate hole and the at least one frame hole.

13. 13. The attachment assembly of claim 12, wherein the frame assembly includes at least one fastener for securing the at least one housing to the at least one face plate hole and the at least one frame hole and for securing the face plate assembly to the frame assembly.

14. 10. The attachment assembly of claim 9, wherein a substantial portion of the carriage is in a carriage plane, a substantial portion of the frame assembly is in a frame plane parallel to the carriage plane, and the faceplate assembly is in a faceplate plane parallel to the frame plane.

15. 10. The attachment assembly of claim 9, wherein the carriage includes an upwardly protruding portion and the upper cross frame member includes a lower hook portion having a groove, the protruding portion being received within the groove to allow the frame assembly to slide laterally relative to the carriage assembly.

16. 10. The attachment assembly of claim 9, wherein a substantial portion of the carriage lies in a first plane and a substantial portion of the frame assembly lies in a second plane parallel to the first plane.

17. 10. The attachment assembly of claim 9, wherein the one or more load cells each include one or more first strain gauges and one or more second strain gauges, the one or more second strain gauges perpendicular to the one or more first strain gauges.

18. An attachment assembly comprising a carriage assembly, a frame assembly, and a faceplate assembly, The carriage assembly includes a carriage and a linear actuator attached to the carriage, the carriage being mountable to an industrial material handling device, the linear actuator including a body and longitudinally opposed piston rods, the piston rods each having an end; the frame assembly is slidably coupled to the carriage, the frame assembly having an upper transverse frame member, a lower transverse frame member and an end vertical frame member, the end vertical frame member connecting the upper and lower transverse frame members in spaced apart relationship to define a central frame cavity between the upper and lower transverse frame members, the linear actuator being disposed within the central frame cavity such that the end of the piston rod contacts the end vertical frame member, the linear actuator enabling the frame assembly to slide laterally relative to the carriage assembly; 11. An attachment assembly, comprising: a face plate assembly stably mounted to the frame assembly, the face plate assembly configured to receive one or more support members to support a load, the face plate assembly including upper and lower cross plate members and end vertical face plate members, the end vertical face plate members connecting the upper and lower cross plate members in spaced apart relationship to define a face plate central cavity between the upper and lower cross plate members, the face plate assembly including a central tie bar spanning between the upper and lower cross plate members across the face plate central cavity, the face plate assembly including one or more first strain gauges and one or more second strain gauges for measuring horizontal and vertical forces applied to one or more support members, the one or more second strain gauges being perpendicular to the one or more first strain gauges.

19. An attachment assembly as described in claim 1, wherein the upper and lower transverse frame members are coplanar with the end vertical frame members.

20. An attachment assembly as described in claim 1, wherein the end vertical frame members have a thickness greater than the thicknesses of the upper transverse frame members and the lower transverse frame members.

Images