BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of steering systems for land vehicles. More particularly, the present invention relates to steering systems wherein the steerable wheels are selectively movable inboard and outboard of the vehicle frame, and wherein the distance between the steerable wheels is selectively adjustable. 
     2. Background 
     Most all land vehicles include steerable wheels which are rotatable about a generally vertical steering axis, typically generally perpendicular to the wheels axis of rotation, for turning the wheels and thereby directing the vehicle in a desired direction. In this regard, many steering systems have been devised and are currently in use. For example, the steerable wheels can be mounted to wheel ends such as driven wheel motors and non-driven stub axles or spindles which are pivotally supported on a yoke with a king pin. By rotating the wheel ends about the king pin/steering axis, the steerable wheels can be turned for directing the vehicle as desired. Of course, in vehicles having a pair of spaced apart steerable wheels, one on each of the left and right sides of the vehicle, the left and right wheel ends are simultaneously turned in the desired direction. 
     In most vehicles, the steerable wheels are fixed relative to the vehicle frame or chassis. That is, the steerable wheels cannot be moved inboard or outboard and the distance between the left and right steerable wheels is fixed. 
     It is oftentimes desirable to adjust the steerable wheels inboard/outboard position and/or the distance between the left and right steerable wheels. For example, in construction and off road vehicles, it may be desirable to sometimes increase the distance between the steerable wheels and thereby increase the stability of the vehicle. In agricultural vehicles such as combines and chemical spraying vehicles, it may be desirable to adjust the steerable wheels inboard/outboard location and/or the distance between the left and right steerable wheels so as to place the wheels between the crop rows. 
     Although steering apparatus have been devised for adjusting the distance between the left and right steerable wheels, a need exists for an improved steering system capable of adjusting the steerable wheels inboard/outboard locations and/or the distance between the left and right steerable wheels. 
     SUMMARY OF THE INVENTION 
     The steering system of the present invention is capable of selectively independently moving the left and right steerable wheels inboard and outboard of the vehicle and selectively adjusting the distance between the left and right steerable wheels. 
     In one form thereof, the present invention is directed to a steering system including left and right steering assemblies for a land vehicle. Each steering assembly includes a pivot arm pivotally secured to the vehicle about a first pivot axis. A first selectively extendable and retractable mechanism is secured between the pivot arm and the vehicle. A wheel end is pivotally secured to the pivot arm about a steering axis whereupon a steerable wheel is mountable. A second selectively extendable and retractable mechanism is secured between the wheel end and the pivot arm. Accordingly, actuation of the first mechanism rotates the pivot arm about the first pivot axis and moves the wheel end inboard and outboard of the vehicle, and actuation of the second mechanism rotates the wheel end relative to the pivot arm for steering the vehicle. 
     Preferably, the steering assembly selectively extendable and retractable mechanisms are hydraulic cylinders; and, the steering assembly wheel end is a hydraulically driven wheel motor or a non-driven stub axle. 
     Also preferably, the steering assembly includes a suspension means. In this regard, the steering assembly pivot arm includes a first control arm pivotally secured about the first pivot axis and a second control arm pivotally secured to the upper control arm about a suspension axis. An air spring is provided between the first control arm and the second control arm. The wheel end is pivotally secured to the second control arm, and the second mechanism is secured between the wheel end and the second control arm. Also, the steering assembly first mechanism is secured between the second control arm and the vehicle. Preferably, the suspension axis is generally perpendicular to the first pivot axis. 
     In another form thereof, the present invention is directed to a steering system including left and right steering assemblies for a land vehicle. Each steering assembly includes a pivot arm pivotally secured to the vehicle about a first pivot axis whereby the pivot arm is moveable between inboard and outboard positions. A wheel end is pivotally secured to the pivot arm about a steering axis whereupon a steerable wheel is mountable. A selectively extendable and retractable steering mechanism is secured between the wheel end and the pivot arm. Accordingly, rotation of the pivot arm about the first pivot axis moves the wheel end inboard and outboard of the vehicle, and actuation of the steering mechanism rotates the wheel end relative to the pivot arm for steering the vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a land vehicle steering system constructed in accordance with the principles of the present invention and shown as would be secured to a land vehicle, but with the land vehicle removed for better illustrating the steering system; 
         FIG. 2  is a top plan view of the steering system shown in  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the steering system shown in  FIG. 1 ; 
         FIG. 4  is an exploded perspective view similar to  FIG. 3  and further showing the driven wheel ends detached from the pivot arm; 
         FIG. 5  is a perspective view depicting a lower control arm of the pivot arm of the steering system shown in  FIG. 1 ; 
         FIG. 6  is another perspective view depicting a lower control arm of the pivot arm of the steering system shown in  FIG. 1 ; 
         FIG. 7  is a perspective view depicting the upper control arm of the pivot arm of the steering assembly shown in  FIG. 1 ; 
         FIG. 8  is a top plan view diagrammatically depicting a land vehicle comprising the steering system of  FIG. 1  and wherein the pivot arms are in their retracted inboard positions and the steerable wheels are in their inboard positions; 
         FIG. 9  is a top plan view similar to  FIG. 8  but wherein the wheel ends have been turned to the left; 
         FIG. 10  is a top plan view similar to  FIG. 8  but wherein the wheel ends have been turned to the right; 
         FIG. 11  is a top plan view similar to  FIG. 8  but wherein the pivot arms are in their extended outboard positions and the steerable wheels are in their outboard positions; 
         FIG. 12  is a top plan view similar to  FIG. 11  but wherein the wheel ends have been turned to the left; 
         FIG. 13  is a top plan view similar to  FIG. 11  but wherein the wheel ends have been turned to the right; 
         FIG. 14  is an exploded perspective view of the steering system shown in  FIG. 1  but wherein the wheel ends are non-driven spindles; 
         FIG. 15  is an exploded perspective view similar to  FIG. 14  and further showing the non-driven spindle wheel ends detached from the pivot arm; and, 
         FIG. 16  is a top plan view similar to  FIG. 8  but wherein the wheel ends are non-driven stub axles. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout several views. Although the exemplification set out herein illustrates embodiments of the invention, in several forms, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise forms disclosed. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A land vehicle steering system constructed in accordance with the principles of the present invention is shown in the drawings and generally designated by the numeral  10 . Steering system  10  includes left and right steering assemblies  12  which are essentially identical mirror images of one another and are mounted to the left and right sides of a vehicle frame or chassis  14 . Steering assemblies  12  each include a wheel end  16 . Steerable wheels  18  are mounted onto the wheel ends  16  and are steerable as seen in  FIGS. 8-14 and 16 . 
     As more fully described hereinbelow, steering assemblies  12  are each also adapted to selectively move the steerable wheels  18  between their inboard or retracted positions as shown in  FIGS. 8-10  and their outboard or extended positions as shown in  FIGS. 11-13 . That is, steering assemblies  12  are adapted to move the steerable wheels  18  between their inboard positions whereat the left and right steerable wheels are spaced a shorter distance DI from one another ( FIG. 8 ), and their outboard positions whereat the left and right steerable wheels are spaced a greater distance DO and further apart from one another ( FIG. 11 ). The steerable wheels  18  are selectively movable and can be located anywhere between their fully retracted inboard and fully extended outboard positions and, indeed, each left or right steerable wheel  18  is selectively movable between its inboard and outboard positions independent of the other left or right steerable wheel  18 . 
     In  FIGS. 8-14 and 16 , the steering system  10  is mounted to and supports the rear end  22  of a land vehicle  20  such as, for example, a combine. The front end  24  of the vehicle  20  is supported by wheels  26 . Steering system  10  can, of course, also be used at the front end  24  of the land vehicle  20 . It can also be used on all types of steerable land vehicles including, but not limited to, trucks, construction vehicles, automobiles, recreational vehicles, etc. 
     For simplicity and clarity purposes, the several components and elements of the left and right steering assemblies  12  are identified and referred to herein using the same reference numerals, regardless of whether such components or elements are in a left steering assembly or a right steering assembly. 
     Referring now more particularly to  FIGS. 1-7 , steering assemblies  12  include a pivot arm  28  pivotally secured to the vehicle frame  14 , such as with bracket ears  30  attached to the frame  14 , and is adapted to pivot about a generally vertical first pivot axis  32 . A first selectively extendable and retractable mechanism such as a hydraulic cylinder  34  is pivotally secured at one end  36  thereof to the vehicle frame  14 , such as with a bracket ear  38  attached to the frame  14 . The other end  40  of the first hydraulic cylinder  34  is pivotally secured to the pivot arm  28  such as with a bracket ear  42  which is attached to the pivot arm  28 . Accordingly, by retracting and extending the first hydraulic cylinder  34 , the pivot arm  28  is selectively pivotable about the first pivot axis  32 . By retracting first hydraulic cylinder  34 , the pivot arm  28  can be pulled to its retracted inboard position as seen in  FIGS. 8-10  whereas, by extending first hydraulic cylinder  34 , the pivot arm  28  can be pushed to its extended outboard position as shown in  FIGS. 11-13 . 
     The wheel end  16  of each of the steering assemblies  12  is pivotally secured to the pivot arm  28 , such as with a yoke or C-shaped bracket  46  attached to the pivot arm  28 , and is adapted to pivot about a generally vertical second or steering pivot axis  44 . A second selectively extendable and retractable mechanism such as a hydraulic cylinder  48  is pivotally secured at one end  50  thereof to the pivot arm  28 , such as with a bracket ear  52  attached to the pivot arm  28 . The other end  54  of the second hydraulic cylinder  48  is pivotally secured to the wheel end  16  such as with a bracket ear  56  which is attached to the wheel end  16 . Accordingly, by retracting and extending the second hydraulic cylinder  48 , wheel end  16  is selectively pivotable about the second pivot axis  44  and a steerable wheel  18  mounted thereon is thereby selectively pivotable/steerable between its left and right directions as shown in  FIGS. 8-13 . 
     The wheel ends  16  can be hydraulically or electrically driven wheel motors  58  as depicted in  FIGS. 1-4 and 8-13  or non-driven stub axles  60  as depicted in  FIGS. 14-16 . In either case, of course, the steerable wheels  18  are mounted thereto and the wheel ends  16  and wheels  18  are adapted to rotate about a generally horizontal wheel axis of rotation  62 . 
     The pivot arm  28  can be a simple cantilevered arm pivotally secured at one end thereof to the vehicle frame  14  about the first pivot axis  32  and simply having the wheel end  16  pivotally secured thereto about the second pivot axis  44  as described hereinabove. Preferably, however, the pivot arm  28  is constructed having suspension means incorporated therewith as described hereinafter and shown in the drawings. In this regard, the pivot arm  28  is constructed with a first or upper rigid control arm  64  pivotally secured to the vehicle frame  14  about the first pivot axis  32 , and a second or lower rigid control arm  66  pivotally secured to the upper control arm  64  about a generally horizontal suspension pivot axis  68 . Because the suspension pivot axis  68  is generally perpendicular to the first pivot axis  32  and the lower control arm  66  is pivotally secured to and carried by the upper control arm  64 , both the upper and lower control arms  64 ,  66  are adapted to simultaneously/together pivot about the first vertical axis  32 . A spring, preferably in the form of an air spring  70 , is provided between the upper and lower control arms  64 ,  66 . Accordingly, the vehicle  20  weight/load is carried from the upper control arm  64  through the spring  70  to the lower control arm  66  and to the wheel end  16  and steerable wheel  18 . The upper control arm  64  is thereby insulated from sudden impacts or shocks experienced by the wheel  18 . It is noted that a shock absorber/dampener (not shown) can also be provided between the upper and lower control arms  64 ,  66 . 
     As best seen if  FIG. 7 , the upper control arm includes a shaft portion  72  including an upper pin  74  at its upper end thereof and a lower pin  76  at its lower end thereof. Upper pin  74  is rotatably received within a bore extending into the upper bracket ear  30  and lower pin  76  is rotatably received within a bore extending into the lower bracket ear  30 . Accordingly, shaft portion  72  thereby rotates about the first pivot axis  32 . A cantilevered arm  78  is preferably integrally formed with and extends radially/perpendicularly from the shaft portion  72 . An upper spring seat  80  is provided at the terminal end of the cantilevered arm  78 . A horizontal bore  82  extends through the shaft portion  72  between end faces  84 . Horizontal bore  82  is collinear with the horizontal suspension pivot axis  68  and is adapted to rotatably receive a pivot pin  86  therethrough. 
     As best seen in  FIGS. 8 and 9 , the lower control arm  66  includes a body or frame  88 . A pair of parallel blades  90  extend from the lower control arm body  88  and are provided with aligned holes  92 . As best seen in  FIG. 1 , the upper arm shaft portion  72  is received between the parallel blades  90  with the end faces  84  thereof abutting a perspective blade  90  and with the upper control arm horizontal bore  82  aligned with the blades holes  92 . The pivot pin  86  is received through the aligned horizontal bore  82  and blades holes  92  thereby pivotally securing the lower control arm body  88  to the upper control arm shaft portion  72 . 
     A lower spring seat  94  is provided on the lower control arm body  88  and is generally aligned with the upper spring seat  80 . The air spring  70  is secured to and between the upper and lower seats  80 ,  94  in a known and customary manner. 
     An attachment plate  96  is provided on the lower control arm body  88  whereat the C-shaped bracket  46  is attached with fasteners as shown or other suitable means. Alternatively, a C-shaped bracket or yoke can be formed directly into the body  88  for pivotally securing a wheel end  16  thereto. The bracket ear  42  having a hole  98  is provided on the attachment plate  46  for pivotally securing the end  40  of the hydraulic cylinder  34 . The bracket ear  42  can, of course, be located elsewhere on the lower control arm body  88  as may be needed. Bracket ear  52  having a hole  100  is also provided on the lower control arm body  88  as shown. 
     As should be appreciated by one skilled in the art, the lower control arm body  88  can take on various shapes so as to accommodate the various vehicles and the desired design criteria. However, it will essentially include a pivotal connection to the upper control arm  64 , a spring seat  94 , a bracket ear  42  or other means for pivotally attaching to the hydraulic cylinder  34 , a bracket ear  52  or other means for pivotally attaching to the hydraulic cylinder  48 , and a C-shaped bracket  46  secured thereto or other means for pivotally attaching the wheel end  16  thereto. Similarly, the upper control arm  64  can take on various shapes but will, essentially, include a pivotal connection to the vehicle so as to rotate about pivot axis  32 , a horizontal bore  82  or other means for pivotally attaching the lower control arm  66  thereto, and a spring seat  80 . 
     The wheel ends  16  shown in  FIGS. 1-4  are hydraulically driven motors  58 . Motors  58  are pivotally secured between the upper and lower legs  102 ,  104  of the C-shaped bracket  46 . In this regard, a pivot plug  106  extends through the hole  108  in the lower leg  104  and into a bore (not shown) in the housing of the driven motor  58 . Similarly, a pivot plug  110  extends through the hole  112  in the upper leg  102  and into the bore  114  in the housing of the driven motor  58 . Preferably, pivot plug  110  includes hydraulic ports  116  for providing hydraulic oil and powering the driven motor  58  in a known and customary manner. The pivot plugs  106 ,  110  essentially function similar to a king pin for pivotally securing the wheel end motor  58  to the lower control arm  66  of the pivot arm  58 . 
     As mentioned hereinabove, wheel ends  16  can also be non-driven stub axles  60  as shown in  FIGS. 14-16 . In this embodiment, a yoke  118  is attached to the attachment plate  96  of the lower control arm body  88  with fasteners or other suitable means. A steering knuckle  120  is pivotally secured to the yoke  118  with a king pin  122  in a known and customary manner. A spindle  124  is rigidly secured to the steering knuckle  120  with fasteners or other suitable means. The bracket ear  56 , in this embodiment, is secured to the steering knuckle  120 /spindle  124  and the end  54  of the second hydraulic cylinder  48  is pivotally secured thereto. A wheel hub  126  is rotatably secured to the spindle  124  in a known and customary manner for attaching the steerable wheels  18  thereto. Accordingly, the non-driven stub axle  60  and wheels  18  mounted thereon are carried on the lower control arm  66  of the pivot arm  28  and are selectively rotatable about the steering pivot axis  44  by selectively extending and retracting the second hydraulic cylinder  48 . 
     As should now be appreciated, each of the left and right steering assemblies  12  can be operated independent of one another, although typically the deployment of the pivot arms  28  will be coordinated so as to maintain the vehicle  20  centered between the wheels  18 . Similarly, the rotational position of the left and right wheel ends  18  about their steering pivot axes  44  will be coordinated so as to steer the vehicle  20  in the desired direction. In this regard, the pivot arms  28  can be moved between their retracted inboard positions and their extended outboard positions, and anywhere in between, by retracting and extending the hydraulic cylinders  34  and rotating the pivot arms  28  about the first pivot axis  32 . Simultaneously, the wheel ends  16  carried on each of the pivot arms  28  can be rotated about their steering pivot axis  44  by retracting and extending the hydraulic cylinders  48  for thereby placing the steerable wheels  18  thereof in the desired angle/position for steering the vehicle  20  as may be desired. 
     While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles.
A land vehicle steering system capable of selectively moving the left and right steerable wheels inboard and outboard of the vehicle, and selectively adjusting the distance between the left and right steerable wheels. The steering system includes left and right steering assemblies. Each assembly includes: a pivot arm pivotally secured to the vehicle about a first pivot axis; a first hydraulic cylinder secured between the pivot arm and the vehicle; a wheel end pivotally secured to the pivot arm about a steering axis; and, a second hydraulic cylinder secured between the wheel end and the pivot arm. Actuation of the first hydraulic cylinders rotates the pivot arms about their first pivot axes and moves the wheel ends inboard and outboard of the vehicle. Actuation of the second hydraulic cylinders rotates the wheel ends and steerable wheels thereon relative to their pivot arm for steering the vehicle.