Abstract:
For an implement, a caster wheel assembly including a tubular member connected to reciprocate as the caster wheel swivels. An adjustable brake assembly resists movement of the tubular member to eliminate caster wheel wobble as the implement is transported. A plurality of caster wheel assemblies permit the implement to crab between the towing vehicle and a trailing implement. The brake assemblies provide convenient locking and control of selective wheels for the desired swivel action in numerous operating situations.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to an implement supported on caster wheels, and more specifically to a device for controlling caster wheel motion. 
     Caster wheels are commonly used on agricultural equipment to prevent skidding of a wheel or wheels when the implement is turned. These wheels can cause a problem when transporting the machine at higher than field-operating speeds by wobbling or attempting to rotate about their caster frame vertical spindle. This action can cause such problems as tire wear, structural damage or loss of control of the machine. In some previously available implements with caster wheels, the caster wheels have been rigidly pinned to prevent oscillation, but such an arrangement causes the wheel to skid and results in high stresses in the structural members when the implement is turned. 
     Other previously available devices, such as the caster wheel assembly shown in U.S. Pat. No. 2,761,692 include a friction disk fixed to the spindle and engaging a friction plate interlocked with the framework and spring-urged downwardly. Such a device is relatively expensive, since it requires special castings or the like. Swivel wheel dampers for the caster wheels of aircraft 20 have also been available for some time, but these devices are also relatively complicated and expensive to manufacture. Examples of such aircraft devices are shown in U.S. Pat. Nos. 2,367,993; 2,482,961; 2,508,057; 2,693,003 and 2,770,832. U.S. Pat. No. 2,388,874 shows a caster wheel with an arm that is spring-loaded to restore the wheel to its operating position from any castered position. At transport speeds, wobbling would still be present with such a device. 
     In certain applications, such as when a seeder is towed behind a grain cart, and the grain cart, in turn, is towed behind a tractor or the like, the cart is supported on four caster wheels spaced fore-and-aft in pairs. In some situations it is desirable that all the wheels be able to caster freely, while in other situations it is necessary to limit the castering of a front or rear pair of wheels while permitting the remaining wheels to caster freely. Heretofore, devices for selectively locking the caster wheel in position or alternately adjustably braking the caster action have been relatively expensive or ineffective and often have been difficult to adjust for the proper caster wheel action. 
     BRIEF SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide an improved caster wheel assembly for an implement. 
     It is a further object of the invention to provide an improved caster wheel assembly for an implement for preventing wobble from starting when the vehicle is towed at higher than field-operating speeds. It is another object to provide such an assembly which is relatively inexpensive and easy to adjust. 
     It is a further object of the invention to provide an improved damping device for a caster wheel which allows the caster wheel to pivot freely 180 degrees when turning or backing, but prevents wobble or oscillation of the caster wheel at transport speeds. It is a further object to provide such an assembly wherein the resistance to swiveling of the caster wheel is easily adjusted. 
     It is still another object of the invention to provide a caster wheel assembly with an elongate member which reciprocates in response to castering of the wheel and which has a braking device which adjustably resists the reciprocating motion of the member. 
     It is yet another object of the invention to provide a cart or similar implement with a plurality of supporting caster wheels which includes a plurality of caster wheel control devices which may be quickly and easily adjusted to resist or prevent castering of preselected combinations of the wheels. 
     In accordance with the above objects, a control arm is rigidly connected to the caster wheel frame vertical spindle. An elongated tubular member or brake tube is pivotally connected to the end of the control arm and reciprocates as the caster wheel casters about its vertical axis. The break tube slides between a pair of brake pads mounted in a support carried by the cart frame. A threaded handle in the support allows adjustment of the pressure exerted by the brakes against the brake tube. With proper adjustment of the brake pads, the caster wheel is free to pivot 180 degrees when turning or backing the machine, but the resistance provided by the brake prevents wobble or oscillation of the caster wheel at transport speeds. One or more of the caster wheels can be locked in position by inserting pins in the brake tube to prevent relative reciprocation between the tube and the support. The device is relatively simple and inexpensive to manufacture and provides for easy adjustment of the resistance to castering of the caster wheels. The braking action prevents tire wear and structural damage during transporting of the machine by preventing wobbling of the caster wheel. With proper adjustment of the braking device, the wheel can still caster during turns to prevent skidding action of the wheel and eliminate high stresses in the structural members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an implement utilizing the device of the present invention. 
     FIG. 2 is a perspective view of one of the rear caster wheel assemblies utilized with the implement of FIG. 1 with the wheel in position for forward movement. 
     FIG. 3 is an exploded view of a portion of the assembly shown in FIG. 2. 
     FIG. 4 is a detailed view of the brake support assembly shown in FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, therein is shown an implement 10 supported for forward movement over the ground by a plurality of caster wheels 12. The implement 10 is shown as a grain drill cart for an air seeder, but it is to be understood that the present invention may be utilized with other implements. Each caster wheel 12 is rotatably mounted on a horizontal axle 14 of a caster wheel frame assembly 16 having a vertical spindle 18 offset in the forward direction from the axle 14. The vertical or upright spindle 18 is journalled in a bearing member 20 carried by a fore-and-aft extending beam 22 of cart frame assembly 24. As seen in FIG. 1, the cart frame assembly includes a pair of transversely spaced and generally parallel fore-and-aft beams 22, and each beam supports a pair of caster wheel assemblies at its opposite ends. 
     The vertical spindle 18 of each caster wheel assembly extends upwardly through its associated bearing member 20 and terminates in an upper end located above the beam 22. A control arm member 30 which is part of a caster wheel control assembly is rigidly attached to the upper end by a set screw 28 and rotates with the spindle 18 as the caster wheel swivels. In the preferred embodiment, the control arm 30 is fixed such that its axis is substantially parallel to the axis of the caster wheel 12 so that as the wheel pivots 90 degrees in either direction from the forward direction, the arm member approaches a position generally parallel to the beam 22. A guide member or bracket 34 is welded to the beam 22 at a position offset from the axis of the vertical spindle 18. The bracket 34 is located outside of the arc that the end of the control arm 30 traverses as the caster wheel swivels. 
     The bracket 34 includes a generally U-shaped outer portion having upright sidelegs 36 welded to the beam 22 and a transverse bight portion 38 extending between the sidelegs. A lower support plate 40 is welded to the sidelegs 36 and extends parallel to the bight portion 38. 
     A brake support assembly 44 having a generally open-ended box structure is pivotally supported inside the bracket 34. The assembly 44 includes parallel and substantially horizontal top and bottom plates 46 and 48, respectively, with central pivot-receiving apertures 50 and 52. Side plates 54 and 56 are welded to and space the plates 46 and 48. The plates 54 and 56 include centrally located apertures 58 and 60, respectively. A nut 62 is welded to the plate 54 in alignment with the aperture 58. The aperture 50 in the plate 46 is aligned with a hole 64 in the bight 38 of the bracket 34, and a vertical pivot assembly 66 is inserted through the aperture and hole. Likewise, a pivot assembly 67 is inserted through the aperture 52 and a corresponding axially aligned hole 69. The pivot assemblies 66 and 67 maintain the brake support assembly 44 within the bracket 34 while allowing the assembly 44 to pivot about an upright axis. 
     A pair of U-shaped brake pad members 70 are supported in the assembly 44 with leg portions 72 extending outwardly beyond the sides of the plates 54 and 56. Brake pads 74 are supported generally parallel to the plates 54 and 56. A pin 76 is inserted through a pair of opposed thrust washers 78 and through the hole 60 in the side of plate 56 to urge the corresponding brake pad member 70 inwardly from the sidewall 56. A threaded handle member 80 is screwed into the nut 62 to urge the opposite brake pad member 70 inwardly in the direction of the first mentioned pad member. 
     An elongated rod member or brake tube 82 having a rectangular cross section is connected at one end by a pivot pin assembly 84 to the outer end of the control arm member 30. The brake tube 82 extends through the support member 34 between the opposed brake pads 74 and between the upper and lower plates 46 and 48. The handle 80 is screwed inwardly to increase the pressure of the pads 74 against the sides of the brake tube 82 and, thereby, adjust the pressure applied by the brake pads 74 to the opposite sides of the brake tube 82. 
     As the caster wheel 12 swivels back and forth, the control arm member 30 pivots with the spindle 18 to recriprocate the brake tube 82 within the bracket 34. The recriprocating motion of the brake tube 82 is resisted by the brake pad members 70 with the amount of resistance provided depending upon the adjustment of the handle 80. As the angle of the brake tube 82 changes with the position of the control arm 30, the brake support assembly 44 pivots within the bracket 34 about the upright axis so that the brake pads 74 are maintained flatly against the sides of the tube 82. Apertures 90 are provided in the top and bottom surfaces of the tube 82 which, when the caster wheel is positioned for forward movement over the ground, (FIG. 2) are located on opposite sides of the bracket 34. To lock the caster wheel in this position, pins 92 are inserted in the holes to prevent the tube from recriprocating within the bracket. 
     When the cart 10 is operating in the field behind a towing vehicle and forwardly of a towed implement such as a grain drill or a seeder 100 (FIG. 1), the brake pads 74 are adjusted away from the brake tube 82 by turning the handle 80 so that all four caster wheels 12 can freely caster in any direction. When the cart 10 is pulled at transport speeds with the rear implement attached, the brake pads 74 are tightened against the brake tube 82 so that there is sufficient resistance or drag to prevent the caster wheel from oscillating. This adjustment is accomplished by turning the handle 80 until the brake pads 74 contact the sides of the brake tube 82 and, thereafter, turning the handle an additional fraction of a turn. All four caster wheel brakes are adjusted in the same manner. However, when the cart 10 is being towed by the tractor without an implement attached behind the cart, it is desirable that the front wheels be able to pivot while the rear wheels are held firmly in a straight line for forward movement. In this situation, the pins 92 are inserted through each rear wheel brake tube 82 on each side of the corresponding brackets 34 when the rear wheels are in position for forward movement (FIG. 2). The front wheel brake pads 74 are adjusted as described above so there is sufficient drag on the associated brake tubes 82 to prevent the wheels from oscillating while traveling at transport speeds. Therefore, the caster wheel control assemblies can be utilized to switch between a first situation where the cart is towing an implement and a crabbing action is required to a second situation where the cart is pulled like a trailer and only the front wheels 12 need to caster. The braking action of each caster wheel control assembly can be easily adjusted to prevent oscillations or wobble from starting while permitting the desired wheels to caster during turns. 
     As best seen in FIG. 2, maximum resistance to swivel occurs when the wheel is positioned for movement in the forward direction because of the angle of the control arm 30. Once the wheel begins to swivel, the effective moment arm acting to resist swivel decreases. Therefore, when the cart 10 is being towed at transport speeds with the brake pads 70 tightened against the brake tube 82, any tendancy of the wheel to begin to wobble is resisted with maximum force. However, resistance decreases as the caster wheel swivels from the forward direction to reduce side loading on the assembly during turns. 
     Having described the preferred embodiment, it will be apparent that modifications can be made without departing from the scope of the invention as defined in the accompanying claims.