Tandem wheel assembly with reaction downforce center pivot

Abstract

A tandem wheel assembly includes a tandem wheel housing having a central opening extending along a pivot axis, and a wheel end opening extending along an associated wheel axis. A pivot bracket is configured to be fixedly mounted to a chassis of a vehicle and disposed about the pivot axis at the central opening. A central sprocket is disposed inside the pivot bracket and is rotatable relative to the pivot bracket. A wheel end assembly is disposed at each wheel end opening and has a wheel end sprocket, a wheel end gear train, and a wheel end hub. Each wheel end gear train is coupled to rotate through the wheel end sprocket and to rotate the wheel end hub about a wheel end axis. A pair of reaction links are pivotally coupled at one end to the pivot bracket and at the other end to a component of the wheel end gear train.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to work vehicles, and more particularly to a tandem wheel assembly for a work vehicle. BACKGROUND

[0002] Work vehicles, such as those used in forestry, construction, agriculture, mining, and other industries, can utilize a tandem wheel assembly (also known as a bogie axle) to support a substantial load across four or more ground-engaging wheels or tracks with a single axle that allows the wheels to pivot together to maintain ground contact over varying terrain without significantly displacing other areas of the work vehicle including the cab and work implements such as cranes. Such a tandem wheel assembly can also be driven (e.g., from the work vehicle powertrain through a transmission or can be self-powered). One work vehicle that often utilizes a tandem wheel assembly is a skidder used in tree harvesting operations. Various applications can require a skidder to provide high torque and possibly low speed power to the ground-engaging wheels, which is achieved through high gear reduction of the wheels. Different applications can be suited for different skidder or other machine platforms with different load carrying capabilities. SUMMARY

[0003] The present disclosure provides a work vehicle tandem wheel assembly having a central pivot axle carrier with reaction bars to achieve downforce on the wheels.

[0004] In one aspect, the present disclosure provides a tandem wheel assembly for a work vehicle having a chassis and wheels. The tandem wheel assembly includes a tandem wheel housing having an inner side wall and an outer side wall, both of which at least partially define an interior, both of which define a center opening extending along a pivot axis and a wheel end opening extending along an associated wheel axis. A pivot mount is configured to be fixedly mounted to the chassis and disposed at the center opening of the tandem wheel housing about the pivot axis. The pivot mount has an annular body extending between an inner side end and an outer side end. The inner side wall and the outer side wall of the tandem wheel housing are pivotably mounted to the pivot mount at the inner side end and the outer side end of the annular body, respectively. A center sprocket is disposed within the pivot mount and is rotatable relative to the pivot mount. A wheel end assembly is disposed at each of the wheel end openings. Each wheel end assembly has a wheel end sprocket, a wheel end gear train, and a wheel end hub, each wheel end sprocket being supported within the tandem wheel housing for rotation by at least one chain coupled to the center sprocket. Each wheel end gear train is coupled for rotation by the associated wheel end sprocket and is configured to effect a change in drive ratio and rotate the associated wheel end hub about the associated wheel end axis. A pair of reaction links are included, with each reaction link being pivotably coupled at one end to the annular body of the pivot mount and pivotably coupled at an opposite end to a component of the wheel end gear train.

[0005] In another aspect, the present disclosure provides a tandem wheel assembly for a work vehicle having a chassis and wheels. The tandem wheel assembly includes a tandem wheel housing having an inner side wall and an outer side wall, both of which at least partially define an interior, both of which define a central opening extending along a pivot axis and a wheel end opening extending along an associated wheel axis. A pivot bracket is configured to be fixedly mounted to the chassis and disposed at the central opening of the tandem wheel housing about the pivot axis. The pivot bracket has an annular body extending between an inner side end and an outer side end. The inner side wall and the outer side wall of the tandem wheel housing are pivotably mounted to the pivot bracket at the inner side end and the outer side end of the annular body, respectively. A central sprocket is disposed within the pivot bracket and rotatable relative to the pivot bracket. A wheel end assembly is disposed at each of the wheel end openings. Each wheel end assembly has a wheel end sprocket, a wheel end gear train, and a wheel end hub, each wheel end sprocket being supported within the tandem wheel housing for rotation by at least one chain coupled to the central sprocket. Each wheel end gear train is coupled for rotation by the associated wheel end sprocket and is configured to effect a change in drive ratio and rotate the associated wheel end hub about the associated wheel end axis. Reaction rods extend within the interior of the tandem wheel housing. Each reaction rod is pivotably coupled at one end to the annular body of the pivot bracket and at an opposite end to a component of the wheel end gear train.

[0006] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will become apparent from the description, the drawings, and the claims. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a simplified perspective view of an exemplary work vehicle in the form of a tree harvesting forwarder in which a tandem wheel assembly according to the present disclosure can be used;

[0008] Figure 2 is an isometric view of an exemplary tandem wheel assembly for the exemplary forwarder;

[0009] Figure 3 is a top sectional view taken through plane 3-3 of the exemplary tandem wheel assembly of Figure 2 ;

[0010] Figure 4 is an exploded isometric view of the exemplary tandem wheel assembly;

[0011] Figure 5 is a side view of a tandem wheel housing of the exemplary tandem wheel assembly;

[0012] Figure 6is an isometric view of a pivot bracket of an exemplary tandem wheel assembly;

[0013] Figure 7 is a top view of the pivot bracket;

[0014] Figure 8 is a bottom view of the pivot bracket;

[0015] Figure 9 is an isometric view of a reaction rod support of an exemplary tandem wheel assembly;

[0016] Figure 10 and Figure 11 is a partial top view of an exemplary tandem wheel assembly, with the tandem wheel housing shown separated; and

[0017] Figure 12 and 13 is a partial cross-sectional view of an exemplary tandem wheel assembly, showing Figure 2 region 12-12 and 13-13, respectively, of

[0018] The same reference numbers in the various drawings indicate the same elements. DETAILED DESCRIPTION

[0019] The following description describes one or more exemplary embodiments of the disclosed tandem wheel assembly, as shown in the drawings of the figures, which were briefly described above. Those skilled in the art will appreciate that various modifications can be made to the exemplary embodiments.

[0020] As used herein, unless otherwise limited or modified, a list of items preceded by “one or more of the a disjunctive (e.g., “and” or “or”) with the limitation at the end of the list of items (e.g., “or the like”) indicates an inclusive or, that is, at least one, but also including any and all combinations of the items in the list. For example, a list of “at least one of A, B, and C” or “one or more of A, B, and C” indicates that A, B, or C alone can be the correct answer, or that any combination of A, B, and C can be the correct answer, such as A and B, B and C, A and C, or A, B, and C.

[0021] Furthermore, in describing the present disclosure, directional and orientational terms can be used, such as, for example, “longitudinal,” “inner,” “outer,” “radial,” “axial,” “circumferential,” “lateral,” and “transverse.” These terms, at least in part, are defined relative to an axle, a pivot axis, and / or a work vehicle. As used herein, the term “longitudinal” refers to an orientation along a length of the device; the term “lateral” refers to an orientation along a width of the device and orthogonal to the longitudinal orientation; and the term “transverse” refers to an orientation along a height of the device and orthogonal to the longitudinal and lateral orientations. These orientations can be relative to a work vehicle or direction of travel of the work vehicle to which a component can be attached. In other examples, the components to which these terms refer can be reversed in accordance with the present disclosure.

[0022] SUMMARY

[0023] Work vehicles, such as tree harvesting skidders, generally include components such as a chassis, a powertrain (e.g., an engine and a powertrain system), a suspension, and a work implement (e.g., a crane) that perform tasks in a variety of terrains and conditions. Often, the work vehicle can perform tasks that require consistent positioning of the work implement (e.g., a crane to grab and move felled trees). The axle region can be subjected to considerable static weight loads from the on-board components (e.g., the engine, transmission, axles, work implement, etc.) and encounter considerable operational loads (e.g., via the attached work implement and through impacts / loads by the wheels and suspension). Thus, the work vehicle must accommodate changing terrain, static loads, and operational loads resulting from the work task while maintaining the required implement positioning. Tandem wheel assemblies can accommodate such loads or grade changes by mounting the wheel assemblies (often rear wheel assemblies) together to pivot relative to the work vehicle, which provides ground contact for the wheels without significantly hindering placement of the work implement.

[0024] In the case of a skidder, the work implement is often a crane that lifts large felled trees onto a loading space of the skidder during operation. The skidder carries a large amount of felled trees and must travel at a speed sufficient to increase productivity while preventing unnecessary bouncing and swaying; for example, the skidder can operate at a speed range from low speeds (e.g., 1-10 miles per hour (mph)) to higher speed ranges (e.g., 40 mph or higher during transport and other operational states). During use, the skidder experiences load forces of the weight of the felled trees and impacts of ground obstacles encountered during travel. The corresponding operational loads are transferred to and through the chassis and powertrain system to the wheels, which transfer the loads to the ground. Thus, the powertrain system and wheels can improve the performance of the skidder by maintaining ground contact for consistent traction.

[0025] The present disclosure provides a tandem wheel assembly having a pivot bracket non-rotatably secured to a chassis of a vehicle, the pivot bracket nested or seated within a tandem wheel housing of the tandem wheel assembly, the tandem wheel assembly having a set of tandem wheels mounted thereto. Bushings are provided at inboard and outboard locations between the pivot bracket and the tandem wheel housing and at inboard and outboard of the center sprocket, which increases the overall rotational moment extending through the bushings. Additionally, ground forces pushing upward on the wheels cause a moment to be created at the outward end of the tandem wheel housing, and by providing a more conforming or consistent outboard bushing, the moment arm is reduced, thereby reducing the moment created at the outward end of the tandem wheel housing to improve overall load capacity.

[0026] The present disclosure provides a tandem wheel assembly configured to provide improved downforce distribution to a set of tandem wheels during operation of a work vehicle, particularly during acceleration and deceleration of the work vehicle, the disclosed arrangement responsive to input torque changes with a reaction force or moment to maintain both wheels in engagement with the ground during operation of the work vehicle, particularly during acceleration and deceleration of the work vehicle. The tandem wheel assembly distributes torque between the wheels with a reaction bar coupled to the pivot bracket.

[0027] One or more exemplary embodiments of the disclosed tandem wheel housing are described below. While the discussion herein can at times focus on exemplary applications of the tandem wheel assembly to tree harvesting skidders, the disclosed tandem wheel assembly can also be applicable to bogie or tandem axles in other types of work vehicles, including self-propelled or towed work vehicles and various other agricultural machines (e.g., articulated tractors, utility tractors, motor graders, front end loaders, harvesters, etc.), various construction and forestry machines (e.g., skidders, etc.), and transport vehicles (e.g., semi-trailers).

[0028] Exemplary embodiments of the tandem wheel assembly

[0029] Reference Figure 1In some embodiments, the disclosed work vehicle 10 can be a tree harvesting forwarder, although as noted above, the tandem wheels described herein can be suitable for use in various machines, such as motor graders, skidders, other engineering vehicles, agricultural vehicles (including articulated tractors), other forestry vehicles, and transport vehicles (such as semi-trailers). As shown, the work vehicle 10 can be considered to include a chassis 12, which is made up of a rear frame 14 having a loading space 16 formed for transport of felled trees, and a front frame 18 having a cab 20. The rear frame 14 and the front frame 18 can be connected by an articulation joint. A crane 22 for maneuvering felled trees into the loading space 16 is mounted on the rear frame 14 behind the cab 20. At the head of the crane 22, a loading grapple 23 is provided, which is equipped with known gripping members that are turned towards or away from each other by actuators provided therein, wherein the loading grapple 23 can be used to grip one or more tree trunks to be hauled to a desired location. The loading grapple 23 can also be turned so that felled trees in the loading grapple 23 can be brought to the right place as they are, for example, loaded into or unloaded from the loading space 16. The crane 22 is selectively positioned or adjusted in position by a drive system 24. The work vehicle 10 can also be considered to include a powertrain 26, a control system 28, and a hydraulic system 30. The work vehicle 10 includes a tandem wheel assembly 32 on the rear frame 14 for mounting two wheels 36, 38 on the left side of the work vehicle 10 and two wheels 42, 44 on the right side of the work vehicle 10, and the work vehicle 10 can also have a similar tandem wheel assembly on the front frame 18 for mounting two wheels on the left side of the work vehicle 10 and for mounting two wheels on the right side of the work vehicle 10. Each wheel 36, 38, 42, 44 is mounted on the tandem wheel assembly 32 by a wheel end hub 46. The wheels 36, 38, 42, 44 include a pair of left wheels defined by a first left wheel 36 and a second left wheel 38, and a pair of right wheels defined by a first right wheel 42 and a second right wheel 44 (also collectively referred to as, for example, “four tandem wheels 36, 38, 42, 44”). It should be noted that any left / right wheel pair can be arranged as dual wheels on either left / right side (e.g., both sides in the x-direction) of the work vehicle 10. Figure 1

[0030] ​Generally, the powertrain 26 includes a propulsion source 50, such as an engine, that provides power to the work vehicle 10 as direct mechanical power or after being converted to electrical power (e.g., via a battery) or hydraulic power. In one example, the engine can be an internal combustion engine, such as a diesel engine, that is controlled by an engine control module (not shown) of the control system 28. It should be noted that the use of an internal combustion engine is by way of example only, as the propulsion source 50 can be a fuel cell, an electric motor, a hybrid gas electric motor, or other power generating device. A transmission 52 transmits power from the propulsion source 50 to one or more of the wheels 36, 38, 42, 44. In addition, the powertrain 26 has wheel steering components 54, including various devices (e.g., power steering pumps and lines, steering mechanisms, etc.) that couple manual (e.g., operator steering controls or steering wheel) and / or automatic (via the control system 28) steering inputs to one or more sets of wheels.

[0031] In addition to providing tractive power to propel the work vehicle 10, the propulsion source 50 can also provide power or power to various on-board subsystems of the work vehicle 10, including various electrical and hydraulic components of the work vehicle 10, and to provide off-board power or power to other subsystems remote from the work vehicle 10. For example, the propulsion source 50 can provide mechanical power that is converted into electrical power form to operate the electronics of the control system 28 and one or more electrically powered devices of the work vehicle 10. Accordingly, the powertrain 26 can have mechanical to electrical power or power conversion components 56, one or more batteries 58 and associated electronics, including various alternators, generators, voltage regulators, rectifiers, inverters, etc. The propulsion source 50 can also provide mechanical power that is converted into hydraulic form to power various pumps and compressors that pressurize fluid to drive various actuators of the hydraulic system 30 in order to power wheel steering and braking and various work implements on the work vehicle 10. The hydraulic system 30 can include other components (e.g., valves, flow lines, pistons / cylinders, seals / gaskets, etc.) so that control of various devices can be utilized and based on hydraulic, mechanical, or other signals and actions.

[0032] The control system 28 can be configured as a computing device with associated processor and memory architecture, configured as one or more hardwired computing circuits, configured as programmable circuits, and configured as a hydraulic, electric, or electro-hydraulic controller. The control system 28 can be configured to perform various computational and control functions related to the work vehicle 10 (including various devices associated with the powertrain 26, hydraulic system 30, drive system 24, and various additional components of the work vehicle 10). In some embodiments, the control system 28 can be configured to receive input signals in multiple formats (e.g., as hydraulic signals, voltage signals, current signals, etc.) and to output command signals in multiple formats (e.g., as hydraulic signals, voltage signals, current signals, mechanical motion, etc.).

[0033] As described above, the hydraulic system 30 can be controlled by the control system 28 (automatically, via operator input, or both). The hydraulic system 30 can be powered by the thruster 50 and configured in various arrangements to suit multiple hydraulic functions (e.g., powering the drive system 24). Therefore, the hydraulic system 30 can have a variety of components (not shown), including a pump for supplying pressurized hydraulic fluid, a reservoir for storing the hydraulic fluid, and various valves (e.g., control valves) associated with each function.

[0034] In the illustrated example, when the work vehicle 10 is traveling in the forward direction ( Figure 1 When (as indicated in the diagram), the tandem wheel assembly 32 follows behind the connection between the crane 22 and the rear frame 14 and supports most of the weight on the rear frame 14. The tandem wheel assembly 32 is pivotable about a pivot axis 60. Specifically, each of the pair of left wheels 36, 38 and the pair of right wheels 42, 44 can pivot independently about the pivot axis 60 relative to the work vehicle 10. In use, if the work vehicle 10 encounters an obstacle or uneven surface, the tandem wheel assembly 32 adapts to this situation by pivoting relative to the chassis 12 of the work vehicle 10, and the reaction assembly 34, forming a walking beam configuration, counteracts the forces that cause the tandem wheel assembly 32 to pivot. As a result, during the operation of the work vehicle 10, especially during the acceleration and deceleration of the work vehicle 10, the reaction assembly 34 provides an improved downforce distribution to each of the pair of left wheels 36, 38 and the pair of right wheels 42, 44. The reaction assembly 34 responds to changes in input torque with a reaction force or torque to keep each of the pair of left wheels 36, 38 and the pair of right wheels 42, 44 engaged with the ground. Thus, the transmission of bumps or changes in terrain are mitigated or eliminated, keeping the crane 22 and cab 20 in a relatively stable position that maintains traction and weight distribution.

[0035] The tandem wheel assembly 32 mounts the four tandem wheels 36, 38, 42, 44 below the rear frame 14. The exemplary tandem wheel assembly 32 Figure 2 ) can include a differential housing 62, first and second mounting arms 64, 66, first and second pivot mounts 68, and first and second tandem wheel housings 70 in which the reaction assemblies 34 are respectively mounted. The pivot mounts 68 are rigidly fixed relative to the rear frame 14 about the pivot axis 60 and partially function as a central pivot about which the tandem wheel assembly 32 and the four tandem wheels 36, 38, 42, 44 pivot relative to the work vehicle 10. The differential housing 62 is rigidly fixed to the first and second mounting arms 64, 66, which are fixed to the chassis 12 of the work vehicle 10 (e.g., via bolts through arm holes of the mounting arms 64, 66). Thus, the differential housing 62 and the pivot mounts 68 are fixed in place relative to one another, and one or both of the first and second tandem wheel housings 70 are independently pivotable relative to the differential housing 62 and the respective first and second pivot mounts 68.

[0036] As also noted above, the tandem wheel assembly 32 includes components of the powertrain 26 for transmitting power to each of the four wheels 36, 38, 42, 44 Figure 3 ). A differential 74 is mounted in the differential housing 62 and is connected to a drive shaft 76 that is driven by the transmission 52. The differential 74 includes gear components to split the rotation of the drive shaft 76 and transfer the rotation of the drive shaft 76 laterally outward toward the first and second tandem wheel housings 70. A pinion gear 78 at an end of the drive shaft 76 is in meshing engagement with a differential ring gear 80 mounted in a differential housing 82 that is coupled to first and second axles 84, 86 (via a side gear 88). The differential 74 can be a limited slip differential with a clutch assembly 90 for slip prevention. Although not shown in detail, the differential housing 62 can house additional components of the differential 74, including brakes, U-joints, ring gears, pinion shaft(s), pinion gears, planetary gears, side gears, clutch plates, bearings, etc. Any type of differential can be implemented within the tandem wheel assembly 32, including an open differential, a limited slip differential, etc. The differential housing 62 also mounts portions of the drive shaft 76 and portions of the first and second axles 84, 86. Hydraulic brake-type brakes 72 can be provided in engagement with the axles 84, 86, as is known in the art.

[0037] Reference is also made to Figures 6-8Each pivot bracket 68 has an annular body 110 disposed about the pivot axis 60 and extending between an inner side end 112 of the pivot bracket and an outer side end 114 of the pivot bracket. Each pivot bracket 68 also has an extension body portion 116 extending from the inner side end 112 and coupled to the chassis 12 by the brake 72 and the differential housing 62. A cavity 118 extends from an inner end 120 of the extension body portion 116 to an outer end 122 of the annular body 110 at the outer side end 114. An inner side flange 124 extends radially outward from the annular body 110 at the inner side end 112, and an outer side flange 126 extends radially outward from the annular body 110 at the outer side end 114. The outer side flange 126 can be provided as a separate component and attached to the annular body 110. At least one opening is provided through the annular body 110 between the flanges 124, 126 and in communication with the cavity 118. As shown, the at least one opening is provided by a forward upper opening 128, a rearward upper opening 130, a forward lower opening 132, and a rearward lower opening 134. As shown, each of the upper openings 128, 130 is generally T-shaped, having a lower portion 128a, 130a that is wider than an upper portion 128b, 130b. The upper portions 128b, 130b are laterally offset from one another, and the lower portions 128a, 130a are aligned with one another in the forward-rearward direction. As shown, the upper portion 128b of the forward upper opening 128 is outward of the upper portion 130b of the rearward upper opening 130, however, the upper portion 128b of the forward upper opening 128 can be inward of the upper portion 130b of the rearward upper opening 130. This reduces the size of the pivot bracket 68. In one embodiment, the upper portions 128b, 130b are aligned with one another in the forward-rearward direction. The lower portion 128a is laterally aligned with the forward lower opening 132; the lower portion 130a is laterally aligned with the rearward lower opening 134. The lower openings 132, 134 are aligned with one another in the forward-rearward direction. The first and second pivot brackets 68 can be formed of cast metal or other suitable structural material.

[0038] Each tandem axle wheel housing 70( Figure 2 and Figure 5) is a generally hollow component having an inner sidewall 140 and an outer sidewall 142 that define an interior space 144 that extends from a front wall 146 to a rear wall 148 and between an upper wall 150 and a lower wall 152. A longitudinal axis 154 of the tandem wheel housing 70 is defined between the front wall 146 and the rear wall 148 and is perpendicular to the pivot axis 60. The tandem wheel housing 70 can be formed of cast metal or other suitable structural material. The inner sidewall 140 and the outer sidewall 142 have shoulders 156, 158 that define aligned central openings 160, 162 about the pivot axis 60 that are in communication with the interior volume 144, and the annular body 110 of the respective pivot bracket 68 is nested or seated in the central openings 160, 162 so that the tandem wheel housing 70 can pivot about the pivot bracket 68 and relative to the chassis 12. The shoulder 156 is outward of the inner flange 124 and the shoulder 158 is inward of the outer flange 126. A portion of the outer sidewall 142 can be formed by a separate cover 142a that can be removed to expose the opening 162. Each tandem wheel housing 70 can be made in modular form; as shown, each tandem wheel housing 70 has three parts that are secured together.

[0039] A plurality of circular bushings 164, 166 and bearings 168, 170 Figure 12 are disposed between the pivot bracket 68 and the tandem wheel housing 70 to facilitate pivoting of the tandem wheel housing 70 relative to the pivot bracket 68. An inner bushing 164 is disposed between an inner surface of the shoulder 156 facing the annular body 110 of the pivot bracket 68 and an outer surface of the annular body 110 and inward of the openings 128, 130, 132, 134. An inner thrust bearing 168 is disposed between an outer surface of the inner flange 124 and an inner surface of the inner shoulder 156. An outer bushing 166 is disposed between an inner surface of the shoulder 158 facing the annular body 110 of the pivot bracket 68 and an outer surface of the annular body 110 and outward of the openings 128, 130, 132, 134. An outer thrust bearing 170 is disposed between an inner surface of the outer flange 126 and an outer surface of the outer shoulder 158.

[0040] The components in each tandem wheel housing 70 can be identical mirror images. Each tandem wheel housing 70 has a central sprocket 172 mounted for co-rotation with the respective axle 84, 86, a first chain 174 connecting the central sprocket 172 to a front wheel end assembly 176 on a first side of the central sprocket 172, and a second chain 178 connecting the central sprocket 172 to a rear wheel end assembly 180 on a second side of the central sprocket 172 Figure 12). In some embodiments, the center sprocket 172 is a double sprocket that mounts the first chain 174 that extends to the front wheel end assembly 176 and the second chain 178 that extends to the rear wheel end assembly 180. The center sprocket 172 is positioned laterally outward of the inboard bushing 164 and laterally inward of the outboard bushing 166.

[0041] Each wheel end assembly 176, 180 Figure 13 ) includes a wheel end sprocket 182 mounted on a shaft 184 for co-rotation with the shaft 184, a wheel end gear train 188 coupled to the shaft 184, a wheel end housing 190, and the wheel end hub 46. The wheel end housing 190 is fixedly mounted on the outboard wall 142 of the tandem wheel housing 70. The shaft 184 is rotatably mounted to the inboard wall 140, extends through a wheel end opening 192 in the outboard wall 142, and extends laterally outward from the outboard wall 142. The shaft 184 extends laterally outward from the outboard wall 142 and is coupled to the wheel end gear train 188. A wheel end axis 194 is defined by the shaft 184.

[0042] The wheel end sprocket 182 of the front wheel end assembly 176 is aligned with and connected by the first chain 174 to one of the double rings of the center sprocket 172. The first chain 174 passes through the lower portion 128a of the forward upper opening 128 in the pivot bracket 68, around the center sprocket 172, through the forward lower opening 132 in the pivot bracket 68, and around the wheel end sprocket 182 of the front wheel end assembly 176. The wheel end sprocket 182 of the rear wheel end assembly 180 is aligned with and connected by the second chain 178 to the other of the double rings of the center sprocket 172. The second chain 178 passes around the center sprocket 172 through the lower portion 130a of the rearward upper opening 130 in the pivot bracket 68, around the center sprocket 172, through the rearward lower opening 134 in the pivot bracket 68, and around the wheel end sprocket 182 of the rear wheel end assembly 180. Although the first chain 174 is illustrated as being mounted inboard relative to the second chain 178, these relative positions can be reversed. The wheel end sprockets 182 will have the same size (e.g., the same number of teeth) to drive the corresponding first left wheel 36 and second left wheel 38 (or first right wheel 42 and second right wheel 44) to rotate at substantially equal speeds. The first chain 174 and the second chain 178 can be plate chains, roller chains, or other suitable drive chains for heavy-duty construction applications. The chains 174, 178 can be continuous chains without breakaway links or “master” links to improve the torque handling capacity of the chains 174, 178. In some embodiments, the openings 128, 132 are continuous, and the openings 130, 134 are continuous. In some embodiments, the openings 128, 130 are continuous, and the openings 132, 134 are continuous. In some embodiments, all of the openings 128, 132, 130, 134 are continuous.

[0043] The wheel end gear train 188 includes a ring gear 196 and a planetary gear carrier 198 coupled to the ring gear 196. A shaft 200 of the wheel end hub 46 extends through a wheel end opening 202 in the wheel end housing 190 and is coupled to the planetary gear carrier 198. The shaft 200 supports the wheel end hub 46 of the corresponding wheel 36, 38, 42, 44 for common rotation about the wheel end axis 194 with the wheel end hub 46. The wheel end gear train 188 is mounted within the wheel end housing 190 and effects a gear ratio change to rotate the associated wheel end hub 46 and its shaft 200 about the associated wheel end axis 194. As described herein, the ring gear 196 is rotatable relative to the wheel end housing 190. Other configurations of the wheel end gear train 188 can be incorporated without departing from the scope of the present disclosure.

[0044] Each wheel end housing 190 extends laterally outward from the outer side wall 142 and has a wheel end opening 202 at an end thereof that supports at least a portion of the wheel end hub 46. The wheel end housing 190 can be conical in shape. The shaft 200 of the wheel end hub 46 extends through the wheel end housing 190 and the wheel end opening 202, the shaft 200 and its wheel end hub 46 being supported in the wheel end housing 190 by a rotational bearing 204. The wheel end housing 190 can mount various additional support components (not shown), such as roller bearings.

[0045] The wheel end shaft 184 of the front wheel end assembly 176 defines a front wheel end axis 194 that is a rotational axis of the front wheel end hub 46 and wheel 36 (or wheel 42 on the right side of the work vehicle 10), the front wheel end shaft 184 and the front wheel end sprocket 182 when driven by the central sprocket 172 through the first chain 174. This front wheel end axis 194 is substantially parallel to the pivot axis 60. The wheel end shaft 184 of the rear wheel end assembly 180 defines a rear wheel end axis 194 that is a rotational axis of the rear wheel end hub 46 and wheel 38 (or wheel 44 on the right side of the work vehicle 10), the rear wheel end shaft 184 and the rear wheel end sprocket 182 when driven by the central sprocket 172 through the second chain 178. This rear wheel end axis 194 is substantially parallel to the pivot axis 60. Thus, when the central sprocket 172 is rotated, the chains 174, 178 provide for common rotation of the wheel end sprockets 182 of the wheel end assemblies 176, 180, and rotation of the wheels 36, 38, 42, 44.

[0046] Each reaction assembly 34( Figure 4) including a pivot bracket 68, a front reaction rod support 210, a rear reaction rod support 212, a front reaction rod 214, and a rear reaction rod 216, the front reaction rod support 210 being attached to an inboard end of the ring gear 196 of the wheel end gear train 188 of the front wheel end assembly 176 for co-rotation with the ring gear 196, the rear reaction rod support 212 being attached to an inboard end of the ring gear 196 of the wheel end gear train 188 of the rear wheel end assembly 180 for co-rotation with the ring gear 196, the front reaction rod 214 being coupled between the front reaction rod support 210 and the pivot bracket 68, the rear reaction rod 216 being coupled between the rear reaction rod support 212 and the pivot bracket 68.

[0047] Each reaction rod support 210, 212 Figure 9 ) includes a ring body portion 218 having a central bore 220 therethrough that is slightly larger than the bore through the ring gear 196. An outboard end of the ring body portion 218 is attached to an inboard end of the ring gear 196 for co-rotation with the ring gear 196. A hook portion 222 extends from the inboard end of the body portion 218 and has a recess 224 therein. The recess 224 of the front reaction rod support 210 faces rearward and the recess 224 of the rear reaction rod support 212 faces forward. Each recess 224 can be generally square in shape. The hook portion 222 of the reaction rod supports 210, 212 extends through a respective arcuate receiving opening 226, 228 Figure 5 ) in the outboard wall 142 of the tandem wheel housing 70 that is proximate the wheel end opening 192 at the opposite end of the tandem wheel housing 70. The receiving opening 226 is vertically spaced above the respective wheel end opening 192. Each receiving opening 226, 228 has a length in the fore-aft direction that is greater than the length of the hook portion 222. The receiving openings 226, 228 communicate the interior space of the wheel end housing 190 with the interior space 144 of the tandem wheel housing 70.

[0048] Each reaction rod 214, 216 Figure 4 ) is an elongated and rigid member. The front reaction rod 214 includes a front end 214a that is seated in the recess 224 of the front reaction rod support 210 Figure 11) and is pivotably coupled to the hook portion 222 of the front reaction rod support 210 by a pivot pin 230 that extends through the front end 214a and is seated within a hole in the wall forming the recess 224 of the reaction rod support 210, and the front reaction rod 214 includes a rear end 214b that is seated within the forward upper opening 128 of the pivot bracket 68 and is pivotably coupled to the annular body 110 of the pivot bracket 68 by a pivot pin 232 that extends through the rear end 214b and is seated within a hole in the wall forming the upper portion 128b of the forward upper opening 128 Figure 10 ). The front reaction rod 214 is laterally offset from the chain 174 and is positioned laterally inboard of the chain 174 as shown. The front reaction rod 214 can pivot relative to the pivot bracket 68 and relative to the front reaction rod support 210. The rear reaction rod 216 includes a rear end 216a that is seated in the recess 224 of the rear reaction rod support 212 and is pivotably coupled to the hook portion 222 of the reaction rod support 212 by a pivot pin 234 that extends through the rear end 216a and is seated within a hole in the wall forming the recess 224 of the rear reaction rod support 212, and the rear reaction rod 216 includes a front end 216b that is seated in the rearward upper opening 130 of the pivot bracket 68 and is pivotably coupled to the annular body 110 of the pivot bracket 68 by a pivot pin 236 that extends through the front end 216 and is seated within a hole in the wall forming the upper portion 130b of the rearward upper opening 130. The rear reaction rod 216 is laterally offset from the chain 178 and is positioned laterally outboard of the chain 178 as shown. The rear reaction rod 216 can pivot relative to the pivot bracket 68 and relative to the rear reaction rod support 212. The front and rear reaction rods 214, 216 can pivot relative to each other. The reaction rods 214, 216 are seated within the interior space 144 of the tandem wheel housing 70. This provides a very compact design compared to prior art designs that have exposed reaction rods. In addition, disposing the reaction rods 214, 216 within the interior volume 144 prevents exposure of moving parts to external elements that can damage the reaction rods 214, 216.

[0049] In some embodiments, the working elements of the tandem wheel assembly 32 can be partially or fully immersed in a lubricant (e.g., lubricating oil and cooling oil), thereby providing a "wet" environment. The lubricant can be provided in the interior space 144 of the tandem wheel housing 70 and the cavity 118 of the pivot mount 68. Such lubricant helps to keep the moving parts therein in good working order. To prevent leakage of the lubricant from the connection near the shoulder 156 between the tandem wheel assembly 32 and the pivot mount 68, and from the surfaces of the annular body 110 and the flanges 124, 126, at least one seal 238 is disposed between the inner side wall 140 on the inner side of the shoulder 156 and the outer surface of the inner side flange 124. The inner side flange 124 has an outer circumference and the inner side wall of the tandem wheel housing 70 has an inner circumference at the central opening 160, and the at least one seal 238 is disposed between the outer circumference of the inner side flange 124 and the inner circumference of the inner side wall 140. The at least one seal 238 provides a fluid-tight seal therebetween to substantially prevent leakage of the lubricant therefrom. The seals 238 can be V-shaped.

[0050] To propel the work vehicle 10, a propulsion source 50 provides power to a transmission 52, which drives the differential 74 and the axle 84, which in turn drives the central sprocket 172 in each tandem wheel housing 70. The central sprocket 172 drives the first and second chains 174, 178, which in turn rotate the first and second wheel end sprockets 182 and their axles 200 to ultimately rotate a pair of right wheels 36, 38 mounted on the wheel end assemblies 176, 180 (or to ultimately rotate a pair of left wheels 36, 38 mounted on the wheel end assemblies 176, 180 in the left tandem wheel housing 70). The transmission 52 typically includes one or more gear arrangements and / or clutches (not shown) to modify the input speed from the propulsion source 50 to one or more speeds suitable for the tandem wheel assembly 32. Rotation of the axle 200 of the front wheel end assembly 176 rotates the wheel end gear train 188, including rotating the ring gear 196 and the front reaction rod support 210 relative to the wheel end housing 190. The amount of rotation of the ring gear 196 and the front reaction rod support 210 is limited by the length of the receiving opening 226. Likewise, rotation of the axle 200 of the rear wheel end assembly 180 rotates the wheel end gear train 188, including rotating the ring gear 196 and the rear reaction rod support 212 relative to the wheel end housing 190. The amount of rotation of the ring gear 196 and the rear reaction rod support 212 is limited by the length of the receiving opening 228.

[0051] Positioning of the center sprocket 172 between the bushings 164, 166 serves to center the center sprocket 172 across the tandem wheel housing 70 and to balance and distribute loads on the tandem wheel housing 70 as the tandem wheel housing 70 pivots relative to the pivot mount 68. The provision of the outboard bushing 166 improves the overall moment of rotation through the bushings 164, 166. Further, the ground pushing upward on the wheels 36, 38, 42, 44 causes a moment to be created at the outward end of the tandem wheel housing 70. By providing the outboard bushing 166 on the outboard side of the center sprocket 172 more in line or more consistent with the wheels 36, 38 or 40, 42, the force arm is reduced, which reduces the moment created at the outward end of the tandem wheel housing 70 to improve overall load capacity.

[0052] In some cases, an increase in power or force from the propulsion source 50 can tend to rotate the reaction assembly 34 about the pivot axis 60, lifting the front wheels 36 or 42 off the ground while increasing the downward pressure on the rear wheels 38 or 44. To counteract this tendency, the reaction bars 214, 216 provide opposing forces that transfer torque directly to the chassis 12. Further, a sudden decrease in power or force from the propulsion source 50 can reverse the direction of rotation of the reaction assembly 34 about the pivot axis 60; however, these forces can be counteracted by the reaction bars 214, 216. Thus, the rotation of the reaction assembly 34 relative to the chassis 12 can be limited, and the torque delivered to the wheels 36, 38 or 42, 44 can be substantially equal.

[0053] The foregoing describes one or more exemplary tandem wheel assemblies in detail. Various other configurations are possible within the scope of the present disclosure. For example, the disclosed dual ring, two-chain drive in the tandem wheel housing can be replaced by a single ring center sprocket and a single chain coupling the center sprocket to two wheel end sprockets.

[0054] Enumerated Examples

[0055] Further, the following examples are provided, numbered for easier reference.

[0056] 1. A tandem wheel assembly for a work vehicle having a chassis and wheels, the tandem wheel assembly comprising: a tandem wheel housing having an inner side wall and an outer side wall, both of which at least partially define an interior, both of which define a central opening extending along a pivot axis and a wheel end opening extending along an associated wheel end axis; a pivot bracket configured to be fixedly mounted to the chassis and disposed at the central opening of the tandem wheel housing about the pivot axis, the pivot bracket having an annular body extending between an inner side end and an outer side end, the inner side wall and the outer side wall of the tandem wheel housing being pivotably mounted to the pivot bracket at the inner side end and the outer side end, respectively, of the annular body; a central sprocket disposed within the pivot bracket and rotatable relative to the pivot bracket; a plurality of wheel end assemblies, each disposed at one of the wheel end openings, each wheel end assembly having a wheel end sprocket, a wheel end gear train, and a wheel end hub, each wheel end sprocket being supported within the tandem wheel housing for rotation by at least one chain coupled to the central sprocket, each wheel end gear train being coupled for rotation by the associated wheel end sprocket and configured to effect a change in drive ratio and rotate the associated wheel end hub about the associated wheel end axis; and a pair of reaction rods, each reaction rod being pivotably coupled at one end to the annular body of the pivot bracket and pivotably coupled at an opposite end to a component of the wheel end gear train.

[0057] 2. The tandem wheel assembly of example 1, wherein the reaction rods extend within the interior of the tandem wheel housing.

[0058] 3. The tandem wheel assembly of example 1, wherein the annular body of the pivot bracket has at least one opening through the annular body between the inner side end and the outer side end; and wherein the reaction rods extend through the at least one opening of the annular body of the pivot bracket.

[0059] 4. The tandem wheel assembly of example 1, wherein the pivot bracket includes an inner side flange at the inner side end of the annular body; and the tandem wheel assembly further comprises at least one inner side seal disposed between the inner side flange and the inner side wall of the tandem wheel housing.

[0060] 5. The tandem wheel assembly of example 4, wherein the inner side flange has an outer circumference and the inner side wall of the tandem wheel housing has an inner circumference at the central opening, the at least one inner side seal being disposed between the outer circumference of the inner side flange and the inner circumference of the inner side wall.

[0061] 6. The tandem wheel assembly of example 4, further comprising a lubricant in an interior space of the tandem wheel housing and in an interior space of the pivot mount.

[0062] 7. The tandem wheel assembly of example 1, wherein the pivot mount comprises an inboard flange at an inboard end of the annular body and an outboard flange at an outboard end of the annular body; wherein the inboard wall and the outboard wall of the tandem wheel housing define an inboard shoulder and an outboard shoulder, the inboard shoulder being outboard of the inboard flange and the outboard shoulder being inboard of the outboard flange; and the tandem wheel assembly further comprising: an inboard bushing disposed between the inboard shoulder and the annular body of the pivot mount; and an outboard bushing disposed between the outboard shoulder and the annular body of the pivot mount.

[0063] 8. The tandem wheel assembly of example 7, further comprising: an inboard thrust bearing disposed between the inboard flange and the inboard shoulder; and an outboard thrust bearing disposed between the outboard flange and the outboard shoulder.

[0064] 9. The tandem wheel assembly of example 1, wherein each of the reaction rods is pivotably coupled to one of the wheel end gear trains and pivotably coupled to the pivot mount by a pivot pin.

[0065] 10. The tandem wheel assembly of example 1, wherein the annular body of the pivot mount comprises one or more upper openings and one or more lower openings, the at least one chain extends through the upper openings, the at least one chain extends through the lower openings, and wherein each reaction rod is pivotably attached to the pivot mount above the one or more upper openings.

[0066] 11. The tandem wheel assembly of example 1, wherein the inboard wall and the outboard wall of the tandem wheel housing define an inboard shoulder and an outboard shoulder; and the tandem wheel assembly further comprises: an inboard bushing disposed between the inboard shoulder and the annular body of the pivot mount; and an outboard bushing disposed between the outboard shoulder and the annular body of the pivot mount; and wherein the reaction rods extend within the interior of the tandem wheel assembly.

[0067] 12. The tandem wheel assembly of example 11, wherein the reaction rods are pivotably coupled to the annular body between the inboard bushing and the outboard bushing; and wherein one of the reaction rods is outboard of the other reaction rod.

[0068] 13. The tandem wheel assembly of example 12, wherein the pivot bracket includes upper openings and lower openings; and wherein the at least one chain includes a first chain and a second chain, the first chain being coupled between one of the wheel end sprockets and the center sprocket and extending through a first one of the upper openings and a first one of the lower openings, and the second chain being coupled between the other wheel end sprocket and the center sprocket and extending through a second one of the upper openings and a second one of the lower openings.

[0069] 14. The tandem wheel assembly of example 1, wherein each wheel end gear train is a planetary set including a ring gear; and wherein the reaction bar is pivotably coupled to the ring gear.

[0070] 15. The tandem wheel assembly of example 1, wherein the center sprocket has a double chain loop; and wherein the at least one chain includes a first chain and a second chain, the first chain being coupled between one of the wheel end sprockets and the center sprocket, and the second chain being coupled between the other wheel end sprocket and the center sprocket.

[0071] CONCLUSION

[0072] The examples discussed above produce a variety of benefits of the disclosed tandem wheel assembly. For example, the reaction bar is pivotably coupled at one end to the ring body of the pivot bracket and at an opposite end to a component of the wheel end gear train to provide the transfer and distribution of forces between the wheels when the work vehicle is in motion. The placement of the reaction bar within the interior space of the tandem wheel housing protects the reaction bar from damage and maintains a good working condition. The outboard bushings move the torque arm outward toward the wheels of the work vehicle, making the assembly more stable.

[0073] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0074] The description of the present disclosure is presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art, without departing from the scope and spirit of the disclosure. The embodiments specifically recited herein are chosen for purposes of illustration and description, to best explain the principles of the disclosure and its practical application, and to enable others skilled in the art to understand the disclosure and to recognize its applicability to various situations, one or more of the examples described. Therefore, various different embodiments and implementations are contemplated within the scope of the claims that follow.

Claims

1. A tandem wheel assembly for a work vehicle (10) having a chassis and wheels, the tandem wheel assembly comprising: A tandem train wheel housing (70) having an inner sidewall (140) and an outer sidewall (142) that at least partially define an interior (144), and that define a central opening (160) extending along a pivot axis (60) and a wheel end opening (192) extending along an associated wheel end axis (194). A pivot frame (68) is configured to be fixedly mounted to the chassis and disposed around the pivot axis (60) at the central opening (160) of the train wheel housing (70). The pivot frame (68) has an annular body (110) extending between an inner end (112) and an outer end (114). The inner wall (140) and the outer wall (142) of the train wheel housing (70) are pivotally mounted to the pivot frame (68) at the inner end (112) and the outer end (114) of the annular body (110), respectively. A central sprocket (172) is disposed within the pivot (68) and is rotatable relative to the pivot (68); Wheel end assemblies (176, 180), each wheel end assembly being disposed at one of the wheel end openings (192), each wheel end assembly (176, 180) having a wheel end sprocket (182), a wheel end gear train (188) and a wheel end hub (46), each wheel end sprocket (182) being supported within a train wheel housing (70) for rotation by at least one chain (174, 178) connected to the central sprocket (172), each wheel end gear train (188) being connected to rotate by the associated wheel end sprocket (182) and being configured to achieve a change in gear ratio and to rotate the associated wheel end hub (46) about the associated wheel end axis (194); and A pair of reaction rods (214, 216), each reaction rod (214, 216) is pivotally connected at one end to the annular body (110) of the pivot (68) and at the opposite end to a component of the wheel-end gear train (188). The annular body (110) of the pivot (68) has at least one opening (128, 130) passing through the pivot (68) between the inner end (112) and the outer end (114); and The reaction rods (214, 216) extend through at least one opening (128, 130) of the annular body (110) of the pivot (68).

2. The tandem train wheel assembly according to claim 1, wherein, The reaction rods (214, 216) extend within the interior (144) of the train wheel housing (70).

3. The tandem train wheel assembly according to claim 1, wherein, The pivot (68) includes an inner flange (124) at the inner end (112) of the annular body (110); and The tandem wheel assembly also includes at least one inner seal (238) disposed between the inner flange (124) and the inner wall (140) of the tandem wheel housing (70).

4. The tandem train wheel assembly according to claim 3, wherein, The inner flange (124) has an outer circumference and the inner wall (140) of the train wheel housing (70) has an inner circumference at the central opening (160), and the at least one inner seal (238) is disposed between the outer circumference of the inner flange (124) and the inner circumference of the inner wall (140).

5. The tandem wheel assembly according to claim 3, further comprising lubricant in the interior space of the tandem wheel housing (70) and the interior space of the pivot (68).

6. The tandem train wheel assembly according to claim 1, wherein, The pivot (68) includes an inner flange (124) at the inner end (112) of the annular body (110) and an outer flange (126) at the outer end (114) of the annular body (110). The inner wall (140) and outer wall (142) of the train wheel housing (70) define an inner shoulder (156) and an outer shoulder (158), the inner shoulder (156) being outside the inner flange (124) and the outer shoulder (158) being inside the outer flange (126); and The train wheel assembly further includes: An inner bushing (164) disposed between the inner shoulder (156) and the annular body (110) of the pivot (68); and An outer bushing (166) is disposed between the outer shoulder (158) and the annular body (110) of the pivot (68).

7. The tandem train wheel assembly according to claim 6, further comprising: An inner thrust bearing (168) is disposed between the inner flange (124) and the inner shoulder (156); and An outer thrust bearing (170) is disposed between the outer flange (126) and the outer shoulder (158).

8. The tandem train wheel assembly according to claim 1, wherein, Each of the reaction rods (214, 216) is pivotally connected to one of the wheel-end gear trains (188) and pivotally connected to the pivot frame (68) via pivot pins (232, 236).

9. The tandem train wheel assembly according to claim 1, wherein, The annular body (110) of the pivot (68) includes one or more upper openings (128, 130) and one or more lower openings (132, 132), with at least one chain (174, 178) extending through the one or more upper openings (128, 130) and the at least one chain (174, 178) extending through the one or more lower openings (132, 132).

10. The tandem train wheel assembly according to claim 1, wherein, The inner wall (140) and outer wall (142) of the train wheel housing (70) define an inner shoulder (156) and an outer shoulder (158); and The train wheel assembly also includes: An inner bushing (164) is disposed between the inner shoulder (156) and the annular body (110) of the pivot (68); and An outer bushing (166) is disposed between the outer shoulder (158) and the annular body (110) of the pivot (68).

11. The tandem train wheel assembly according to claim 10, wherein, The reaction rods (214, 216) extend within the interior (144) of the train wheel housing (70).

12. The tandem train wheel assembly according to claim 11, wherein, The reaction rods (214, 216) are pivotally connected to the annular body (110) between the inner bushing (164) and the outer bushing (166); and In this configuration, one of the reaction rods (214) is located outside the other reaction rod (216).

13. The tandem train wheel assembly according to claim 1, wherein, Each wheel-end gear train (188) is a planetary gear set including a ring gear; and The reaction rods (214, 216) are pivotally connected to the ring gear.

14. The tandem sprocket assembly of claim 1, wherein the central sprocket (172) has a double chain ring; and The at least one chain (174, 178) includes a first chain and a second chain, the first chain being connected between a wheel end sprocket and the center sprocket (172), and the second chain being connected between another wheel end sprocket and the center sprocket (172).

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