Patent Application
20140306426
The present disclosure relates generally to a steering linkage arrangement and, more particularly, to a steering linkage arrangement for an articulated mobile machine.
Articulated mobile machines, for example haul trucks, scrapers, wheel loaders, motor graders, and other machines, generally include a tool (e.g., a non-engine) section and a tractor (e.g., an engine) section that are coupled together by way of a hitch. A conventional hitch is configured to swivel about an articulation joint and thereby allow the tool section to move in a direction different from the tractor section. This articulation facilitates steering of the machine.
An exemplary mobile machine is disclosed on page 3 of a product brochure entitled “988H Wheel Loader” that published in 2010 and can be found at the internet website: http://xml.catmms.com/servlet/ImageServlet?imageId=C609127&imageType=2. In this brochure, the machine (known commonly as a 6-bar machine) is shown with a single and centrally-located box boom that is pivotally connected to a front tool section. The machine also includes a pair of hydraulic cylinders located at opposing sides of an articulation hitch. The hydraulic cylinders are connected at a forward end near an axle of the front tool section and outboard of the box boom, and at a rear end near the articulation hitch. The hydraulic cylinders are used to pivot the front tool section relative to a rear tractor section.
Another exemplary mobile machine is disclosed on page 4 of a product brochure entitled “990H Wheel Loader” that published in 2012 and can be found at the internet website: http://xml.catmms.com/servlet/ImageServlet?imageId=C743073&imageType=2. In this brochure, the machine (known commonly as a Z-bar machine) is shown with a boom consisting of dual, spaced-apart lift arms that are pivotally connected to a front tool section. The machine also includes a pair of hydraulic cylinders located at opposing sides of an articulation hitch. The hydraulic cylinders are connected at a forward end near the articulation hitch, and at a rear end near an axle in an open structure of a rear tractor section.
The rear tractor section of the 6-bar machine has proven to be durable in high-stress applications due to its generally closed-in configuration. The closed-in configuration in the rear tractor section of the 6-bar machine may be possible because the associated steering cylinders do not require an open structure for attachment. The steering linkage of the 6-bar machine has historically been preferred by customers over the steering linkage of the Z-bar machine, because steering loads may be smaller and more controllable with the associated outboard-location of the steering cylinders. In contrast, the lift arm cost, durability, productivity, and/or strength of the Z-bar machine linkage may be superior to the box boom linkage of the 6-bar machine, in some applications. Due to space constraints associated with the dual, spaced-apart lift arms of the Z-bar linkage, however, it has not previously been possible to apply the rear tractor section and steering linkage of the 6-bar machine to a Z-bar machine.
The disclosed steering linkage arrangement is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.
In one aspect, the present disclosure is directed to a front frame for use with steering linkage of an articulated machine. The front frame may include a central tilt structure having two spaced apart parallel plates, at least one web member disposed between and connecting the parallel plates, and an articulation hitch hinge component connected to the at least one web member at a base of the parallel plates. The front frame may also include mounting lugs connected to the at least one web member at a point opposite the base. The mounting lugs may be configured to receive a pivot pin of a tilt cylinder. The front frame may further include two substantially identical lift structures located at opposing sides of the central tilt structure. The lift structures may be configured to receive spaced apart lift arms. The front frame may additionally include an axle mounting pad connected at a base of each of the lift structures and configured to engage a front axle of the articulated machine, and a bearing bore located adjacent the axle mounting pad and configured to receive a pivot pin of a steering cylinder.
In another aspect, the present disclosure is directed to a steering linkage arrangement. The steering linkage arrangement may include a front frame having axle mounting pads configured to engage a front axle of an articulated machine, and parallel lift arms pivotally connected at first ends to the front frame and configured to connect to a work tool of the articulated machine at opposing second ends. The steering linkage arrangement may further include a pair of lift cylinders connected between sides of the front frame and the lift arms, a bell crank connected at a center to the parallel lift arms and configured to connect to the work tool, and a tilt cylinder pivotally connected to a center of the front frame and an end of the bell crank. The steering linkage arrangement may also include a pair of steering cylinders connected at first ends to the front frame adjacent the axle mounting pads and configured to connect to a rear frame at second ends. The pair of steering cylinders may be located outboard of the front frame and below the parallel lift arms.
Tractor section 14, in the disclosed embodiment, is located at a rear of machine 10 and configured to support a power source. Specifically, tractor section 14 may include a rear frame 20, a rear axle 22, a powertrain 24, and an operator station 26. Rear frame 20 may rotatably receive rear axle 22 and be configured to support powertrain 24 and operator station 26. Powertrain 24 may be configured to drive rear axle 22 and provide electrical and/or hydraulic power to other components of machine 10. Operator station 26 may facilitate manual control of machine 10.
Tool section 16 may include a front structures assembly 28 that supports work tool 12 at the front end of machine 10. In the disclosed example, work tool 12 is a loader bucket that is vertically supported by a front axle 30, such that work tool 12 may be raised, lowered, and tilted relative to a ground surface. It should be noted, however, that other types of work tools 12 may alternatively be utilized in connection with machine 10. In some embodiments, front axle 30 may also be driven by powertrain 24, for example via hitch assembly 18. In these embodiments, front axle 30 may be substantially identical to rear axle 22.
Hitch assembly 18 may be an assembly of components that cooperate to connect tractor section 14 with tool section 16, while still allowing some relative rotational movement therebetween. In particular, hitch assembly 18 may include a pivot joint having separate hinge components 32 that are rigidly connected to each of tractor and tool sections 14, 16, and one or more pivot pins 34 that are received within and join hinge components 32. With this configuration, each of hinge components 32, along with the connected portions of tractor and tool sections 14, 16, may swivel about pivot pins 34, thereby allowing machine 10 to steer about a vertical axis 36.
Front structures assembly 28 may include structural components that support movement of work tool 12 and steering of machine 10. In particular, front structures assembly 28 may include a tool linkage arrangement 38 that is pivotally mounted to a front frame 40. Front frame 40, in turn, may be rigidly mounted to front axle 30 and pivotally joined to rear frame 20 at articulation hitch 18.
As shown in
One or more hydraulic cylinders (or other steering actuators) 68 may connect rear frame 20 to front frame 40, and function to pivot tool section 16 relative to tractor section 14. In the disclosed embodiment, two hydraulic cylinders 68 are utilized for this purpose; one located at each side of hitch assembly 18. Each hydraulic cylinder 68 may be connected at a rod-end to rear frame 20 adjacent hitch assembly 18, and at a head-end to front frame 40 adjacent front axle 30. With this configuration, a retraction of hydraulic cylinder 68 located at a left side of machine 10 (relative to an operator's perspective), combined with an extension of hydraulic cylinder 68 located at a right side of machine 10 may function to articulate tool section 16 counterclockwise relative to tractor section 14 (as viewed from above machine 10). The opposite may also be true.
Each hydraulic cylinder 68 may be connected to rear frame 20 and to front frame 40 by way of vertically-oriented pivot pins (not shown). In particular, the head-end of hydraulic cylinder 68 may be connected to rear frame 20 via a vertical pivot pin that passes through a mounting arm 70. Mounting arm 70 may extend forward and outward from a front corner of rear frame 20, at a height about equal to the height of an axis of front axle 30 (e.g., equal to or just higher than the axis, but lower than a hub portion of front axle 30). In one embodiment, the pivot pin at the head-end of hydraulic cylinder 68 maybe generally aligned with axis 36 of hitch assembly 18 in a fore/aft direction of machine 10. The rod-end of hydraulic cylinder 68 may be similarly connected to front frame 40 via a vertical pivot pin that is located just rearward of front axle 30 (e.g., rearward of the axis of front axle 30, but within a hub diameter of front axle 30). Hydraulic cylinders 68 may be generally horizontally oriented and located in general transverse alignment with lift arms 42.
An exemplary embodiment of front frame 40 is shown in
Central tilt structure 72 may include two parallel plates 76 that are joined to each other at least one intermediate web member 78 to form a generally hollow or box-like enclosure. Each of plates 76 and web members 78 may be fabricated from steel stock having about the same thickness, and joined to each other via welding. Plates 76 may be generally triangularly shaped, and have a first bearing bore 80 located at an apex to receive pivot pins 44, and a second bearing bore 82 located at a rear base corner near an upper one of hinge components 32 to receive pivot pins 60. Hinge components 32 may extend rearward from web members 78, between plates 76. One or more holes 84 may be formed within web members 78 to reduce a weight and/or cost of machine 10, while also allowing debris to fall through central tilt structure 72 to the ground surface below. Holes 84 may also provide service access to components (e.g., hoses, fasteners, wiring harnesses, etc.) that may be housed within central tilt structure 72.
A pair of mounting lugs 86 may be integral with central tilt structure 72, and extend upward away from web members 78. Mounting lugs 86 may be located higher than (i.e., further away from the ground surface upon which machine 10 is operating) and forward of bearing bores 80. Mounting lugs 86 may themselves each include a bearing bore 88 configured to receive pivot pin 45 that is connected to the head-end of hydraulic cylinder 64. With this configuration, central tilt structure 72 may support tilting of work tool 12 caused by extension and retraction of hydraulic cylinder 64.
Each of lift structures 74 may include an outer plate 90 that is separated from and joined to plates 76 of central tilt structure 72 via at least one intermediate web member 92. Plates 90 may be generally parallel with plates 76, joined to web members 92 via welding, and generally triangularly shaped. Like plates 76, plates 90 may each include a bearing bore 94 at its apex that is configured to receive pivot pin 44, and a bearing bore 96 at its rear base corner that is configured to receive pivot pin 60. Web members 92 may include one or more cutouts 98 that provide clearance for lift arms 42 and/or hydraulic cylinders 58. One or more gussets 100 may be provided to connect outer plates 90 and/or web members 92 of lift structure 74 to plate 76 of central tilt structure 72.
An axle mounting pad 102 may be located at a lower front corner of each lift structure 74 and used to connect front frame 40 to front axle 30. Axle mounting pad 102 may be connected to outer plate 90 of lift structure 74, web members 92, and/or plate 76 of central tilt structure 72. Axle mounting pad 102 may be connected to any one or all of these components, for example, by welding. Each axle mounting pad 102 may be configured to rest on top of a generally flat upper surface of front axle 30, and include a plurality of holes 103 (only one shown) that accommodate fasteners clamping the two components together.
An adapter 104 may be formed within a lowest portion of each lift structure 74 and configured to receive the vertical pivot pin of a corresponding hydraulic cylinder 68. Adapter 104 may be integral with axle mounting pad 102 and, in the disclosed embodiment, formed through a casting process and later joined to lift structure 74 via welding. Adapter 104 may have a vertically oriented bearing bore 106 configured to receive the pivot pin of hydraulic cylinder 68. Bearing bore 106 may be located immediately rearward of axle mounting pad 102, just below axle mounting pad 102, but above the axis of front axle 30.
The disclosed steering linkage arrangement may be applicable to any articulated mobile machine where improved steering and durability is desired. However, the disclosed steering linkage arrangement may be particularly beneficial to mobile machines known as Z-bar machines, where packaging difficulties associated with parallel lift arms normally preclude the use of front-located steering cylinders. The disclosed steering linkage arrangement may be adapted to the tool linkage of a Z-bar machine via a unique front structures assembly, which locates the corresponding steering cylinders low on the machine, near the front axle, and out of the way of the associated lift arms. With this arrangement, the historically durable rear tractor section and highly desirable steering linkage of a 6-bar machine may be used together with the low-cost, durable Z-bar tool linkage.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed steering linkage arrangement without departing from the scope of the disclosure. Other embodiments of the steering linkage arrangement will be apparent to those skilled in the art from consideration of the specification and practice of the steering linkage arrangement disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
