Patent Publication Number: US-2015084309-A1

Title: Work vehicle chassis articulation joint

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     Not applicable. 
     STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FIELD OF THE DISCLOSURE 
     This disclosure relates to articulation joints for articulated heavy duty work vehicles. 
     BACKGROUND OF THE DISCLOSURE 
     Many types of construction and forestry machines and other work vehicles have wide chasses and wheelbases, and consequently tend to track in a straight-ahead direction. To improve the cornering and turning capabilities of such large-bodied vehicles the chasses can be constructed with an articulation joint between separate front and rear frame sections. Typically, these articulated work vehicles include an engine frame that carries a prime mover, typically a gasoline or diesel engine, and an equipment frame that carries a task specific implement. The articulation joint connects the equipment frame to the engine frame and permits relative rotation of the chassis frames on the order of 90 degrees, such as 45 degrees to either side of the chassis centerline. 
       FIG. 1  illustrates an example articulation joint of the type commonly used in articulated work vehicles.  FIG. 1  shows a typical clevis-type connection  20  that connects an equipment frame  24  to an engine frame  28 . The clevis-type connection  20  includes an equipment frame clevis structure  32  rigidly connected to an upper surface of the equipment frame  24  and an engine frame tab structure  36  rigidly connected to an upper surface of the equipment frame  28 . The engine frame tab structure  36  is straddled by the equipment frame clevis structure  32  and maintained therein by a pin  40 . A bearing  44  is arranged to enable rotation of the equipment frame  24  relative to the engine frame  28  about the pin  40 . A second clevis-type connection  48  is arranged at the bottom of the equipment frame  24  and engine frame  28 . The second clevis-type connection  48  cab be similar to the clevis-type connection  20  or can have a single or multiple ball bushing arrangement. The two clevis-type connections  20  and  48  cooperate to provide an articulating joint between the equipment frame  24  and the engine frame  28 . 
     Prior articulation joints of this type suffer from a number of shortcomings. For one thing, the prior art articulation joints are generally complex and costly to manufacturing due to the number of components involved. Clevis-type joints of this kind also can significantly affect the construction of the work vehicle in other aspects. For example, the articulation joint must be sufficiently robust to connect the large frame components of the chassis together and withstand the heavy loading of the machine components as well as impact loading realized during operation. It must also be located along the centerline of the chassis. Consequently, the articulation joint can interfere with the placement of drive shafts, and electrical or plumbing lines that extend between the engine and the work implement or other components carried by the engine and equipment frames. The double clevis-type connections of prior art articulation joints, such as shown in  FIG. 1 , are bulky and can significantly reduce the useable volume of space within the joint through which shafts and lines can be routed. Often such interconnecting components must be routed around the joint, which is less than optimal placement, can impede articulation, and leaves the lines vulnerable to damage or pinching as the chassis is articulated, or due to debris. 
     Other important considerations for large work vehicles of this type are ground clearance and overall vehicle height. It is often very important for the operation of these work vehicles to have high ground clearance in order to perform as needed on off-road terrain. High ground clearance is particularly important for forestry machines, such as skidders and the like, which are often required to drive over stumps and logs during operation. At the same time, over the road hauling of these work vehicles may require the overall height of the vehicles to be under a prescribed or regulated maximum height. Thus, in light of these considerations it may not be practical, or even possible, to position and size the articulation joint as needed to accommodate the interconnecting components within and through the joint while also meeting the overall height and ground clearance requirements of the vehicle. For example, simply enlarging the joint, such as by increasing the vertical spacing between the upper and lower connections, could reduce ground clearance or raise the overall height of the vehicle, or both. Furthermore, if the resulting height of the vehicle is raised, it can also have adverse affects on vehicle stability and operator access to the vehicle cabin. 
     An improved articulation joint for work vehicles is thus needed. 
     SUMMARY OF THE DISCLOSURE 
     This disclosure addresses the aforementioned issues common in many articulated chassis work vehicles by reducing or avoiding clevis-connections in the articulation joint. One or both of the upper and lower joint assemblies of the articulation joint are constructed of a single lug or tab-like structure extending from each frame. Thus, the articulation joint is less complex and the space available within the articulation joint between the upper and lower joint assemblies is not reduced by more lug and bearing components than needed. 
     More specifically, one aspect of this disclosure pertains to an articulation joint for a work vehicle having a chassis including a first frame coupled to a second frame by the articulation joint. Each frame can include two spaced apart single lugs that mate with corresponding lugs of the other frame. The articulation joint can be formed by two joint assemblies spaced apart along a pivot axis. A first joint assembly can include a first bearing assembly coupled between mating first lugs of the two frames. A second joint assembly can include a second bearing assembly coupled between the second lugs of the two frames. 
     In one arrangement, the first frame first lug is positioned at a side of the first joint assembly opposite the second joint assembly, such that the space within the articulation joint defined between the second frame first lug and the second joint assembly is uninterrupted by the first joint assembly. In another arrangement, the first frame second lug is positioned at a side of the second joint assembly opposite the first joint assembly such that the space within the articulation joint defined between the second frame second lug and the first joint assembly is uninterrupted by the second joint assembly. In yet another arrangement, the first frame second lug is positioned at a side of the second joint assembly nearest the first joint assembly, such that the space within the articulation joint defined between the first frame second lug and the first joint assembly is uninterrupted by the second joint assembly. These arrangements thus define example articulation joints in which at least one joint assembly is formed of by mating single lugs from each frame, as well as both joint assemblies being formed by mating single lugs, either with the two lugs of one frame being to the outside of the lugs of the other frame or by interleaving the lugs the two frames. 
     Another aspect of this disclosure provides an example construction of the individual joint assemblies of the articulation joint. In particular, a joint assembly can include a pin having a bearing portion and that is received in and fastened to a frame lug aperture. The bearing portion of the pin can engage a bearing cone defining a cone raceway. A second frame lug aperture can receive a bearing cup defining a cup raceway. A plurality of rollers can be arranged between the cone raceway and the cup raceway. The pin can be configured to extend into but not through the second frame lug aperture. Further, the articulation joint can have an upper joint with an upper bearing assembly and a lower joint having a lower bearing assembly. Each upper and lower bearing can be of the like construction. 
     Another aspect of the disclosure provides an articulated chassis work vehicle. The work vehicle can have an engine frame that carries the prime mover of the vehicle and an equipment frame that carries the functional implement of the machine. An articulation joint as described above rotationally couples the engine frame to the equipment frame. 
     Additional aspects and advantages of the disclosure can be found in the description and drawings referenced below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial side elevational view of a prior art articulation joint. 
         FIG. 2  is a side elevational view of a work vehicle including an articulation joint according to one construction of this disclosure. 
         FIG. 3  is a top view of the chassis of the vehicle of  FIG. 2 . 
         FIG. 4  is a partial perspective view showing the articulation joint according to the example construction of this disclosure connecting engine and equipment frames of the work vehicle chassis. 
         FIG. 5  is a partial perspective view thereof with portions of the engine frame removed. 
         FIG. 6  is a detailed perspective view of the articulation joint as taken from arc  6 - 6  of  FIG. 4 . 
         FIG. 7  is another partial perspective view of the example articulation joint. 
         FIG. 8  is an enlarged partial sectional view of the example articulation joint taken along line  8 - 8  in  FIG. 7 . 
         FIGS. 9  is an enlarged detail views of the example articulation joint taken within the bounds of arc  9 - 9  in  FIG. 8 . 
         FIG. 10  is an enlarged detail view of the example articulation joint taken within the bounds of line  10 - 10  in  FIG. 9 . 
         FIG. 11  is an enlarged partial perspective view showing shims of the example articulation joint. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in the accompanying figures of the drawings described above, the following describes one or more example constructions of an articulation joint for an articulated chassis work vehicle. Various modifications to the example construction(s) may be contemplated by one of skill in the art. 
       FIGS. 2 and 3  show an example work vehicle in the form of an articulated forestry vehicle  52 , commonly called a “skidder”, that includes an articulated chassis formed by an engine frame  56  coupled to an equipment frame  60  by an example articulation joint  64 . An engine  68  and other components are mounted to the engine frame  56 , and a task specific implement  72 , such as a boom-mounted grapple in the case of the illustrated skidder, is coupled to the equipment frame  60  and in communication with the engine  68 . Four wheels  76  support the chassis of the forestry vehicle  52  and are coupled to drivetrain components driven by the engine  68  for movement over the ground. The articulation joint  64  would ordinarily be expected to provide for non-cyclical, low-speed, high-load relative rotation of the engine and equipment frames  56 ,  60  through approximately 90 degrees, such as approximately 45 degrees of movement to each side of the centerline of the vehicle chassis. 
     Those skilled in the art will readily understand the wide array of components that may be arranged on such work vehicles. Further, the articulation joint  64  may be implemented in work vehicles of other kinds, such as an earth mover, scraper, or other construction machinery. Depending on the specific arrangement of the work vehicle, the equipment frame  60  or the engine frame  56  may be arranged at the front or rear of the vehicle, as desired. Also, the vehicle may include more than four wheels  76 , and may include other components or equipment, as desired. 
       FIGS. 4 and 5  show the example articulation joint  64  with a drive shaft  80 , actuators  84 , hoses and wires  88 , and other components passing therethrough. The articulation joint  64  includes an upper joint assembly  92  (shown in  FIGS. 4-6 ) and a lower joint assembly  96  (see  FIGS. 7 and 8 ). The upper and lower joint assemblies  92 ,  96  can be identical, but inverted, and arranged to be spaced apart along a main pivot axis  98  of the chassis (see  FIGS. 3 and 8 ). Thus, the description of the joint assemblies  92 ,  96  will be made primarily with reference to the upper joint assembly  92  and a cursory description of the lower joint assembly  96  will be made thereafter. 
     Turning now to  FIG. 9 , the upper joint assembly  92  includes an engine frame lug  100 , which can be a single tab-like structure in the form of an integral extension of the engine frame  56  and to which a spacer plate  102  is welded, and an equipment frame lug  104 , which can also be a single tab-like integral extension of the equipment frame  60  and to which another spacer plate  106  is welded. In other constructions, the lugs  100 ,  104  may be bolted or welded to the respective frame  56 ,  60 , either with or without the spacers plates  102 ,  106 . The lugs  100 ,  104  are sized such that, under the predetermined preload of the joint assembly  92 , as described below, the lugs  100 ,  104  resist bending and undergo only a very minimal deflection so as to maintain an essentially parallel alignment between the lugs  100 , 104  of the two frames  56 ,  60 . To achieve this stiffness the lugs  100 ,  104  are made of sufficiently thick plate material and are supported by vertical gussets  114 , which are themselves of sufficient thickness and rigidity. This joint stiffness further leads to a minimal axial or angular misalignment of the joint assembly  92 . 
     The engine frame lug  100  defines an engine frame lug aperture  108  and a depression  112  formed in a top surface  116  thereof. A plurality of threaded apertures  120  are arranged about the engine frame lug aperture  108 . The equipment frame lug  104  defines an equipment frame lug aperture  124  and a grease fitting aperture  128 . 
     Positioned in the depression  112  is one or more shims  132 . The shims  132  are shown in more detail in  FIG. 11  and each includes a first half  136  and a second half  140 . Each half has bolt cutouts  144  arranged to align with the threaded apertures  120  of the engine frame lug  100 . The shims  132  also define jack screw cutouts  148  whose purpose will be described below. 
     Turning back to  FIG. 9 , a pin  152  includes an upper flange  156  arranged to engage an upper surface of the top shim  132  and including a plurality of countersunk apertures  160  arranged to align with the threaded apertures  120  of the engine frame lug  100 . The pin  152  further includes a frame portion  164  with a diameter sized to be received within the engine frame lug aperture  108  via a tight slip fit, and a bearing portion  168 . Threaded jack screw apertures  170  are formed in the flange  156  and are arranged to align with the jack screw cutouts  148  of the shim  132 . A top depression  172  is formed in a top surface of the pin  152  and a bottom depression  176  is formed in a bottom surface of the pin  152  and a plug aperture  180  is formed therebetween. A seal groove  184  is formed in the pin  152  between the frame portion  164  and the bearing portion  168 . 
     A bearing cup  188  defines an outer diameter sized to be received via an interference fit in the equipment frame lug aperture  124 . The bearing cup  188  defines a cup raceway  192 . A bearing cone  196  defines an inner diameter sized to be received on the bearing portion  168  of the pin  152  via interference fit. The bearing cone  196  defines a cone raceway  200  and a shoulder  204 . 
     When assembled, the upper joint assembly  92  includes fasteners  208  that pass through the countersunk apertures  160  of the pin  152 , the bolt cutouts  144  of the shims  132  and thread into the threaded apertures  120  of the engine frame lug  100  to securely hold the pin thereto. A plug  212  is threaded into the plug aperture  180 , a grease fitting  216  is threaded into the grease fitting aperture  128 , a grease seal  220 , such as conventional urethane-based compliant seal, is installed in the seal groove  184 , and a plurality of rollers  224  are arranged between the bearing cup  188  and the bearing cone  196 . The illustrated rollers  224  are tapered pin type rollers and support the upper joint assembly  92  in both the axial and radial directions. 
     The lower joint assembly  96  is substantially identical to the upper joint assembly  92 , however install in an inverted fashion relative to the upper joint assembly  92 . Components of the lower joint assembly  96  have been labeled with prime numbers corresponding to the above description of the upper joint assembly  92 . 
     The manufacture and assembly of the articulation joint  64  will now be described with further reference to  FIG. 9 . First, the frames  56 ,  60 , and in particular the lugs  100 ,  104 , can be machined to improve the accuracy and fit of the articulation joint  64 . Machining these components aids in achieving a close and controlled fit of the components of the joint assemblies  92 ,  96  and thereby in reducing relative inclination of the lugs  100 ,  104  at the joint assemblies  92 ,  96  and possible damage to, or excessive wear of, the joint  64 . 
     To assemble, the bearing cup  188  can be press fit into the blind equipment frame lug aperture  124 . Temperature differential may be used to aid in effecting the press fit. For example, the bearing cup  188  may be cooled and the lug  104  may be heated prior to the press fit operation, although cooling the bearing cup  188  without also heating the lug  104  is also suitable. As an example, the bearing cup may be cooled to about negative 40 degrees Celsius and the lug  104  may be heated to about 120 degrees Celsius. Next, with the grease seal  220  mounted to the seal groove  184 , the bearing cone  196  along with the rollers  224  are press fit onto the bearing portion  168  of the pin  152 . Again a temperature differential may be utilized. Then, the pin  152  is installed through the engine frame lug aperture  108  with the shims  132  arranged between the depression  112  and the upper flange  156 . The fasteners  208  are then tightened to a predetermined torque setting to maintain the pin  152  installed with the engine frame lug  100 . With the pin  152  installed, the rollers  224  are engaged between the cup raceway  192  and the cone raceway  200  and maintained therebetween by the shoulder  204 . The bearing cup  188 , the bearing cone  196 , and the rollers  224  together define a bearing assembly  228 . The illustrated bearing assembly  228  is a single row tapered bearing assembly. 
     The bearings can be preloaded to a predetermined load rating. The preload can be selected to be the highest predicted load that each joint assembly  92 ,  96  is predicted to encounter. In one construction, the preload may be about 180 kilonewtons (180 kN). The preload reduces galling and other detriments to the joint assembly  92 . The preload may be increased by decreasing the thickness or count of the shims  132  and may be decreased by increasing the thickness or count of the shims  132 . 
     In the illustrated construction, each shim  132  includes a first half  136  and a second half  140  such that the shim  132  may be installed beneath the upper flange  156  of the pin  152  without full removal of the fasteners  208 . To further aid in the adjustment of the shims  132  and the preload of the joint assembly  92 , jack screws (not shown) may be threaded through the jack screw apertures  170  and into contact with the depression  112 . With the fasteners  208  loosened, the jack screws may be used to manipulate the pin  152  away from the depression  112  thereby making room for the addition or removal of shims  132 , should it be needed. 
     Finally, the plug  212  and the grease fitting  216  are installed. Then grease is pumped through the grease fitting and fills the bearing assembly  228  as shown in  FIG. 10 . The grease seal  220  maintains the grease within the bearing assembly  228  during use and inhibits contaminants from fouling the grease or bearing assembly. 
     As mentioned above, ground clearance and overall vehicle height are important considerations for large work vehicles of this type, such as the forestry vehicle  52  illustrated in  FIG. 2 . Such work vehicles typically operate off road and thus require high ground clearance. High ground clearance is particularly important for forestry machines, which typically drive over stumps and logs during operation. Limiting the overall height of the vehicle is also important in order to meet the over the road hauling maximum height regulations of various states or municipalities. It is also important to control the height of the chassis from the ground in order to balance the benefits of high ground clearance with the adverse affects on vehicle stability and operator access to the vehicle cabin that can arise if the chassis is elevated excessively. By way of example, work vehicles, such as the forestry vehicle  52  shown in  FIG. 2 , can require a minimum ground clearance of 2 feet (0.6 meters) and the total height of the vehicle  52  may be no larger than 11 feet (3.4 meters). In other words the upper bounds for the articulation joint  64  can be 5 feet (1.5 meters) and the minimum bounds can be 2 feet (0.6 meters). 
     As also mentioned, it is often desired to mount the interconnecting components that span the two chassis frames  56 ,  60  along the centerline of the vehicle chassis so as not to interfere with the articulation of the chassis or otherwise comprising such components when the vehicle articulates. Thus, the driveshaft  80 , actuators  84 , hoses and wires  88 , and other components are desired to pass through the articulation joint  64 . Therefore, it is desirable to maximize the space available within the bounds. 
     The inventive articulation joint  64  provides a relatively larger interior space when compared to the previously employed clevis-type connection. Clevis-type connections require a relatively large amount of space and a greater number of parts. Maximizing the space between the upper joint assembly  92  and the lower joint assembly  96  also minimizes the radial load rating required of the bearings. The greater the number of parts, often the greater the cost and complexity of the system. 
     Moreover, in prior art articulation joints, ground clearance has been reduced or components have been routed outside the articulation joint. The inventive articulation joint  64  provides an increased ground clearance while routing all system components through the center of the articulation joint  64  thereby protecting the components. 
     The above-described example articulation joint  64  can provide a work vehicle that meets the aforementioned overall height and ground clearance requirements while providing an increased volume of usable space within the articulation joint  64 . By way of example, the forestry vehicle  52  shown in  FIG. 6 , can have a usable interior space with a vertical dimension of approximately 20 inches (50 centimeters). 
     The foregoing detailed description describes the subject of this disclosure in one or more examples. A skilled person in the art to which the subject matter of this disclosure pertains will recognize many alternatives, modifications and variations to the described example(s). For example, the above-described articulation joint  64  provides an example in which the articulation joint has no clevis-type connections, specifically at both the upper and lower joint assemblies the two frames of the chassis mate at single tab-like lugs, that is one lug from each frame at both the upper and lower sections of the joint. However, the articulation joint could be constructed with only one joint assembly being formed of by mating single lugs from each frame. In addition, the articulation joint  64  described is constructed with the two upper and lower lugs of the engine frame from being outside of, that is above and below, the lugs of the equipment frame. However, this could be reversed so that the equipment frame lugs are to the outside of the engine frame lugs. 
     Thus, the following claims should be referenced with regard to the scope of the invention.