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TECHNICAL FIELD OF THE INVENTION  
         [0001]    The present invention relates to utility vehicles, such as industrial or agricultural tractors. Particularly, the invention relates to tractors utilizing a rockshaft or three point hitch and an attachable rear-mounted implement.  
         BACKGROUND OF THE INVENTION  
         [0002]    Utility vehicles typically include an internal combustion engine, which delivers power to a transmission and ultimately to a wheel for traction, and also delivers power to pressurize hydraulic fluid, via one or more pumps, to operate hydraulic tools or implements.  
           [0003]    In this regard, it is known to provide three hydraulic pumps driven from the engine. A first pump generates pressurized hydraulic fluid to charge a steering cylinder of the vehicle. A second pump generates pressurized hydraulic fluid to charge a power takeoff clutch pack and at least one hydraulic cylinder which operates a three point hitch or “rockshaft.” The power takeoff is a shaft that is rotated by the vehicle transmission and is used for supplying rotational power to tools, such as mower decks, where rotation is required. The first and second pumps are driven by an auxiliary drive of the engine.  
           [0004]    The third pump is usually fixed directly to the crankshaft of the engine and is used to charge pressurized hydraulic fluid to the loader and the backhoe hydraulic cylinders.  
           [0005]    Typically, the first pump requires 1.4˜8 horsepower, depending on steering demand and 6 GPM of hydraulic fluid. The second pump requires 1˜9.5 horsepower, depending on demand from the auxiliary circuit, and 5.4 GPM of hydraulic fluid. The third pump requires 3.2˜21.3 horsepower, depending on demand from loader or backhoe circuits and 12 GPM of hydraulic fluid. The engine typically delivers 42 horsepower.  
           [0006]    When a backhoe is attached to the utility vehicle, the rockshaft is not needed, nor is it practically operable. The present inventors have recognized the desirability of disabling the rockshaft when a backhoe is attached to the utility vehicle. The present inventors have recognized the desirability of diverting hydraulic fluid that would otherwise supply the rockshaft, when the backhoe attachment is attached. Furthermore, the present inventors have recognized the desirability of using the circulating hydraulic fluid otherwise available to the rockshaft, to improve the effectiveness and efficiency of the utility vehicle.  
           [0007]    The present inventors have recognized that a proper balance of available engine horsepower directed to the various tractor functions at the proper time is required for best operation of the machine. While the loader is in use, the transmission must necessarily also be in use simultaneously. As such, it is desirable to limit the available horsepower consumed in the operation of the loader while demands are placed on the transmission, to prevent engine stalling.  
           [0008]    Conversely, the inventors have recognized that the backhoe is used without demand on the loader, transmission, rockshaft, or steering circuits. Furthermore, the backhoe has very high hydraulic power requirements. This is because in normal operation, 3 or more hydraulic cylinders (of a typical 7 total cylinders) may be in motion at any given time For this reason, the inventors have recognized that it would be desirable to utilize additional flow from tractor systems which are sitting idle while the backhoe is in use.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention provides a method and apparatus for diverting pressurized hydraulic fluid, otherwise available to a utility vehicle rockshaft system, to be used by another hydraulic fluid powered implement on the utility vehicle. Particularly, the invention provides a method and apparatus for diverting pressurized hydraulic fluid from the rockshaft hydraulic system to be available to a backhoe attachment hydraulic system.  
           [0010]    The method and apparatus of the invention are advantageously accomplished by use of a rockshaft disable switch. The switch is placed in a position such that installation of the backhoe attachment on the utility vehicle automatically changes the state of the switch.  
           [0011]    The switch is connected to a solenoid operator that moves a valve spool to divert pressurized hydraulic fluid from a rockshaft control valve to other hydraulically operated tools, such as to the backhoe attachment. Additional hydraulic fluid available to the backhoe attachment allows for faster movements of the backhoe attachment operating hydraulic cylinders, and thus faster manipulations of the backhoe arms and backhoe bucket.  
           [0012]    Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a fragmentary elevational view of a tractor incorporating the present invention with a foreground rear wheel removed to view portions behind the wheel;  
         [0014]    [0014]FIG. 2 is an enlarged fragmentary elevational view of a backhoe attachment being installed on the tractor of FIG. 1;  
         [0015]    [0015]FIG. 3 is a schematic diagram of a hydraulic fluid system of the tractor shown in FIG. 1;  
         [0016]    [0016]FIG. 3A is a schematic diagram of a rockshaft control system of FIG. 3; and  
         [0017]    [0017]FIG. 4 is an enlarged diagrammatic view of a rockshaft disable switch mounted to a surface of a tractor. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.  
         [0019]    [0019]FIG. 1 illustrates a utility vehicle  20  with an attachable rear-mounted implement, such as a backhoe attachment  24 . The utility vehicle  20  includes a cab or operator&#39;s station  28  including a seat  32 , a steering wheel  34 , and loader controls  36 . The cab is supported on a chassis  42  which is supported on front wheels  44  and larger rear wheels  46 . The utility vehicle  20  can be equipped with a front mounted loader assembly  48 .  
         [0020]    The backhoe attachment  24  includes a bucket  54 , a distal arm or dipperstick  58 , an intermediate arm or boom arm  62 , a swivel arm or swivel tower  66  and a base assembly or mainframe  67 . The distal arm  58  can be pivoted about a point  58   a  with respect to the intermediate arm  62  by a hydraulic cylinder  70 . The intermediate arm  62  can be pivoted about a point  62   a  with respect to the swivel arm  66  by a boom cylinder  74 . The swivel arm  66  can be swung about a vertical axis with respect to the base assembly  67 . The bucket  54  can be rotated about a point  54   a  with respect to the first arm  58  by a hydraulic cylinder  76  and linkages  54   b,    54   c.  The operation of the hydraulic cylinders is by rear-mounted controls  82 .  
         [0021]    The backhoe base assembly  67  includes laterally directed, laterally spaced apart, round bars  92  (one shown) extending on opposite sides of the base assembly  67  on a bottom thereof. The base assembly  67  further includes laterally spaced apart cylinder bosses  102  (one shown) located substantially above the round bars  92  and extending laterally on opposite sides of the base assembly. The bars  92  and bosses  102  are arranged in mirror image symmetrical fashion across a longitudinal vertical plane.  
         [0022]    The utility vehicle chassis  42  includes a mounting structure  42   a  comprising hooks or seats  106  (one shown) opened upwardly and located on opposite lateral sides of the rear portion of the chassis  42 . The seats  106  are sized and shaped to each receive a round bar  92  therein. The mounting structure  42   a  further includes two laterally spaced apart receivers  112  (one shown) which are sized and shaped to receive the bosses  102  therein. The receivers  112  are open substantially horizontally toward the backhoe attachment. The mounting structure  42   a  is configured in mirror image symmetrical fashion across a longitudinal vertical plane.  
         [0023]    [0023]FIG. 2 illustrates, in an enlarged view, the base assembly  67  of the backhoe attachment  24  partially engaged to the utility vehicle  20 . The round bars  92  are already fit into the seats  106 . The boss cylinders  102  are then rotated up to engage the receivers  112 ,  114 . The receivers  112  each include a semi-circular rim portion  112   a  and a pin receiving cylinder  112   b  having a base  112   c.  Each boss  102  includes a central bore  102   a.  When a boss  102  is fit into the receiver rim portions  112   a  the bore  102   a  aligns with the bore  112   c  as the boss  102  fits coaxially against the cylinder portion  112   b.  Two cylindrical connector pins  115  are fit through the central bores  102   a  of the bosses  102 , respectively, and through the adjacent bores  112   c  of the cylinder portions  112   b  of the receivers  112  to lock the backhoe attachment  24  to the utility vehicle  20 . Means, such as a radial locking pin  117  that penetrates the cylinder  112  or the boss  102  and the connector pin  115 , can be provided to lock the connector pins  115  in place.  
         [0024]    The backhoe attachment is removeable by removing the connector pins  115  when it is desired to install a different rear attachment, such as a mower deck, or a tiller.  
         [0025]    [0025]FIG. 3 illustrates a hydraulic system  120  of the invention. The hydraulic system  120  is charged by three pumps. A first pump  124  and a second pump  126  are driven by the auxiliary drive of an engine  130 . A third pump  134  is driven by the crankshaft of the engine  130 . The first pump  124  charges the power steering system  142  and ultimately powers a steering cylinder  144 . Hydraulic fluid out of the steering system  142  charges a hydrostatic transmission  148  which transfers power from the engine to the utility vehicle gear train. The second pump  126  charges a power takeoff system clutch pack  156 , and a rockshaft system  162 , particularly directing hydraulic fluid through a rockshaft selective control valve  163  (shown in FIG. 3A) which powers at least one rockshaft hydraulic cylinder  164  (shown in FIG. 3A). The hydraulic cylinder(s)  164  controls vertical and/or attitude and/or pitch adjustment of the three-point hitch.  
         [0026]    The third pump  134  charges a loader selective control valve  166  and a backhoe selective control valve  168 . The selective control valves  166 ,  168  each include an operation control lever for precise manipulation of hydraulic cylinders which control movements of the associated implement.  
         [0027]    According to the invention, a diverter valve in the form of a spool valve or cartridge valve  174  is hydraulically connected to pressurized hydraulic fluid from the second pump  126 . In the absence of the backhoe attachment, a solenoid  176  of the valve  174  is normally energized, to overcome spring force, to deliver pressurized hydraulic fluid to the clutch pack  156  and to the rockshaft system  162 . When the backhoe attachment is subsequently installed onto the utility vehicle  20 , the backhoe attachment  24  makes contact with, and trips a switch  178  such that power is disconnected from the solenoid  176  and spring force moves a spool  180  of the valve  174  to connect the backhoe system to pressurized hydraulic fluid from the second pump  126 , and to simultaneously disconnect pressurized hydraulic fluid to the rockshaft system  162 .  
         [0028]    By causing this diversion of hydraulic fluid, the third pump  134  can be made correspondingly smaller, having less fluid capacity. The second pump  126 , which is needed for rockshaft operation, but heretofore represented unused capacity during backhoe operation, can now be used to increase total pump capacity to the backhoe attachment.  
         [0029]    The size of the pump  134  is typically selected to correspond to the total horsepower demand of the front loader, via the valve  166 . The engine is typically sized to provide reserve power over the horsepower demand of the loader to power the hydrostatic transmission  148  during loader work, when the backhoe is not in use. Thus, sufficient engine horsepower is available to drive both pumps  126 ,  134  to supply the backhoe with increased hydraulic capacity. The invention is therefore particularly advantageous to retrofit existing utility vehicles or existing designs for utility vehicles.  
         [0030]    [0030]FIG. 3A illustrates a rockshaft or three point hitch control scheme including the rockshaft control valve  163  having an operator controlled lever  163   a  for manipulating a valve spool  163   b.  The spool  163   b  communicates pressurized hydraulic fluid through a system of valves to the hydraulic cylinder  164 . The hydraulic cylinder  164  includes a rod that is configured to extend or retract to pivot a hitch arm  165  to adjust the rockshaft. Although one cylinder  164  is shown, plural cylinders  164  can be used to adjust height, attitude, pitch, etc. Other rockshaft or three point hitch systems are disclosed in U.S. Pat. Nos. 6,216,072; 5,152,347; 4,216,975; and 3,990,520, all herein incorporated by reference.  
         [0031]    [0031]FIG. 4 illustrates the switch  178  in more detail. The switch includes a switch component  184  which can be a commercially available switch. The component  84  can be mounted on or in a frame or box  185 . The switch component  184  includes a switch button or trigger  186 . The trigger can be a momentary switch which must be continuously depressed to maintain an actuated state. A resilient switch lever  190  is mounted to the frame  185  at an attachment point  192 . The switch  190  includes a button engaging portion  194 , an extending portion  196 , and a roller portion  198  mounted to the extending portion  196 .  
         [0032]    When the backhoe is installed, a surface  67   a  of the backhoe attachment base assembly  67  presses the roller portion  198  in the direction A, which pivots the extending portion  196  and the engaging portion  194  about the attachment point  192  to press the button  186  inwardly, to change the state of the switch component  184 , i.e. to open (or alternatively to close) the switch component  184 . An electrical signal is thus sent to the solenoid  176  and hydraulic fluid is thus diverted from the rockshaft to the backhoe attachment. When the backhoe attachment is removed, the lever  190  springs away from the button  186  to change the state of the switch component, i.e. to close (or alternably to open) the switch component  184 , and hydraulic fluid is diverted back to the rockshaft system.  
         [0033]    From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.

Summary:
A hydraulic fluid diverting arrangement for a utility vehicle provides additional pressurized hydraulic fluid supply to an installed backhoe attachment by diverting hydraulic fluid from the unused rockshaft or three-point hitch of the utility vehicle. A solenoid operated valve manifold is switch actuated by contact from the backhoe during installation of the backhoe to the utility vehicle and diverts hydraulic fluid flow from rockshaft hydraulic cylinders to backhoe hydraulic cylinders. The system increases the available horsepower to the backhoe by using hydraulic fluid otherwise dedicated to the idle rockshaft.