Abstract:
A work attachment for a commercial work vehicle such as a skid steer loader has a unique hydraulic circuit that splits hydraulic working flow between two hydraulic functions without the need for electronic solenoids. The commercial work vehicle has hydraulic flow through two hydraulic hoses to the work attachment which can be reversed by the operator of the vehicle to provide two different hydraulic signals. During normal operation, hydraulic working output flow is directed toward a first function, such as the rotary motor of a rotary broom or rotary snow blower. To provide for the second function, the circuit includes a diversion valve that may take the form of a check valve that diverts the flow in response to one of the hydraulic signals (e.g. when flow is reversed). The diversion valve directs flow toward the second hydraulic function such as a hydraulic cylinder for positioning a portion of the attachment (e.g. to effect a selected engaging angle of a rotary broom). A hydraulic switch is used to direct the working output flow for both expansion and contraction of the hydraulic cylinder. The hydraulic switch automatically switches due to increased pressure when the hydraulic cylinder reaches the end of its movement such that the cylinder continuously reciprocates back and forth until the hydraulic signal is terminated and hydraulic flow is again directed to the first function.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to hydraulic controls and more specifically to the hydraulic controls for attachments to skid steers, loader tractors and other work vehicles. 
     BACKGROUND OF THE INVENTION 
     Skid steers, loader tractors and other commercial work vehicles are commonly used for many industrial, agricultural, and landscaping operations. These work vehicles typically have two laterally spaced loader arms that extend in front of the vehicle that are adapted to attach to a wide variety of attachments. Commercial work vehicles may also have a three point hitch at their back end. A number of attachments can be selectively attached and detached from the loader arms or the three point hitch to make these work vehicles applicable to a wide variety of applications. For example, a bucket is commonly provided to dig, dump and transport loose materials such as dirt, sand and gravel. The loader arms are hydraulically driven to raise and lower the attachment and pivot the attachment about a horizontal axis. 
     Skid steer loaders and other work vehicles commonly have a single hydraulic hook-up which comprise a pair of couplings (one for pressurized hydraulic flow and the other for rated flow) that can be utilized by the attachment for any desired purpose. A control lever is provided in the operator cab for controlling the hydraulic flow to the attachment through the hydraulic couplings. The common uses of the hydraulic pump include tilting the attachment left or right about a vertical axis to effect a windrow and/or to direct dirt, gravel or debris, or alternatively hydraulically driving an engaging device such the rotary rake of a as a rock raking attachment. 
     Although a single hydraulic hook up is sufficient for many of the applications, it is often insufficient for certain attachments where it is required or desirable to have hydraulic control over more than one function, such as rotary broom attachments. Rotary broom attachments often include: (1) a hydraulic cylinder for tilting the broom left or right about a vertical axis to direct swept debris or effect a windrow and (2) a hydraulically driven motor that rotates the broom to sweep material. Heretofore, the prior approach of controlling two separate hydraulic functions with a single power source has been to use an electronically operated solenoid that switches between the two functions. However, this approach has significant drawbacks. One drawback is that electrical wiring, electrical hook-ups and electrical couplings are necessary to operate the solenoid. These electrical components increase the time and difficulty of attaching and detaching attachments. Loose wires can also break or sever when not properly secured or when not properly located out of the way when not in use. Due to the environment at which attachments operate, these electrical components are also often subject to wear, poor connections and the like. In view of the foregoing, electrical hook-ups, wiring and couplings have lead to much aggravation for work vehicle operators, require frequent replacement and are not desirable. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to eliminate or reduce the need for electrical wiring hook ups, electrical couplings, and electrical wiring on attachments for work vehicles that have more than one hydraulically powered function. 
     In accordance with this objective the present invention provides an attachment that has a hydraulic circuit that is responsive to hydraulic signals (e.g. as result of hydraulic flow being reversed) that selectively operates one of the hydraulic functions when one signal is received and the other hydraulic function when the other hydraulic signal is received. 
     According to one aspect, the present invention is directed toward an attachment for selective attachment to and detachment from a work vehicle. As is conventional, the work vehicle has a hydraulic pump for generating a working output and a hydraulic sump and the working output controlled by the operator of the work vehicle to selectively provide two different hydraulic signals. The attachment includes a mounting structure adapted to attach and detach the attachment to the work vehicle. The attachment further includes a first hydraulic actuator performing a first work operation a second hydraulic actuator performing a second work operation (thus two hydraulic functions). A hydraulic circuit connects the working output of the work vehicle with the first and second hydraulic actuators. The hydraulic circuit including a primary circuit directing the working output to the first hydraulic actuator and a secondary circuit directing the working output to the second hydraulic actuator. To control flow between hydraulic function, the hydraulic circuit further comprises a diversion valve (in the preferred form of a check valve) diverting working output through the secondary circuit in response to one of the hydraulic signals. 
     It is a further aspect of the present invention that the second hydraulic actuator is a hydraulic cylinder requiring flow to it to be reversed in order to have a reciprocating stroke. To switch or reverse the flow, a hydraulic switch is provided that is responsive to hydraulic pressures in the hydraulic circuit to control hydraulic flow to the hydraulic cylinder and expand or retract the cylinder as desired. 
     According to a preferred implementation, the hydraulic circuit comprises a pair of hoses for hydraulic coupling to the work vehicle and a hydraulic sequencing block. One of the hoses is directly connected to the first actuator in the form of a hydraulic rotary motor (that may power a rotary broom for example). The hydraulic sequencing block comprises 
     (a) a first port hydraulically connected with the first hydraulic hose, 
     (b) a second port hydraulically connected with the rotary motor; 
     (c) a pair of third and fourth ports hydraulically connected to the hydraulic cylinder for reciprocating the hydraulic cylinder; 
     (d) a diversion valve arranged between the first and second ports adapted to divert hydraulic working flow through a bypass conduit to one of the third and fourth ports for operating the hydraulic cylinder; 
     (e) a hydraulic switch arranged in the bypass conduit adapted to switch the working flow between the third and fourth ports, the hydraulic switch adapted to be responsive to increased hydraulic pressure in the working output as a result of the hydraulic cylinder reaching ends of its linear reciprocating movement; and 
     (f) a vent conduit venting to the second port, routed through the switch to one of the third and fourth ports for venting flow from the hydraulic cylinder out through the second port. 
     Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings: 
     FIG. 1 is a side elevation view of a rotary broom attachment according to an embodiment of the present invention attached to an exemplary work vehicle shown in the form of a skid steer loader. 
     FIG. 2 is an isometric view of the rotary broom attachment shown in FIG. 1 with a portion of the attachment being cut away to expose the hydraulic block. 
     FIG. 3 is an exploded assembly drawing of a hydraulic circuit used for the rotary broom attachment shown in FIG. 2 according to an embodiment of the present invention. 
     FIG. 4 is a schematic diagram of a hydraulic circuit in a static state according to an embodiment of the present invention. 
     FIG. 5 is a schematic diagram of the hydraulic circuit shown in FIG. 4 shown in a first mode for driving the rotary broom. 
     FIGS. 6 a - 6   e  are schematic diagrams of the hydraulic circuit shown in FIG. 4 shown in a second mode for reciprocating a hydraulic cylinder with various states shown in sequence. 
     FIG. 7 is an isometric view of a hydraulic sequencing block used in an embodiment of the present invention. 
     FIGS. 8-12 are top, bottom, front side, first end and second end views of the hydraulic sequencing block shown in FIG.  7 . 
    
    
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings and specifically to FIG. 1, it can be seen that the present invention generally relates to the field of commercial work vehicles such as a skid steer  10  as shown, or other loader tractors, tractors or other commercial work vehicles. A skid steer loader  10  is adapted for use in many industrial, agricultural and landscaping applications wherein easy maneuverability, power lifting and transporting capabilities are required. The skid steer loader  10  is provided with a pair of laterally spaced loader arms  12  that are driven along an arcuate path by hydraulic cylinders  14 . The loader arms  12  are pivotally attached to main body of the skid steer loader  10  on each side of the operator cab  16 . 
     Toward the front end of the loader arms  22  there is provided a mounting structure which takes the form in this embodiment as a quick attach mechanism  18  as is well known in the art. The quick attach mechanism  18  allows for selective attachment and detachment of the skid steer loader  10  to a wide variety of attachments for industrial, agricultural, construction, landscaping, commercial and other applications. 
     The specific attachment to which the illustrated embodiment is directed is a rotary broom attachment  20  as shown in FIGS. 1-3. The rotary broom attachment  20  includes a mounting support structure  21  including quick attach plate  22 , a broom support frame  24 , and a rotary broom  26 . The quick attach plate  22  is adapted to be quickly attached and detached from the quick attach mechanism  18  of the skid steer loader  10  in a conventional manner. The rotary broom  26  is mounted for rotation to the broom support frame  24  in a conventional manner. A first hydraulic actuator, namely a hydraulic rotary motor  28 , is mounted to an end for broom support frame  24  and drives the rotary broom  26  about its axis of rotation to provide for sweeping of dirt, debris, gravel and other material. The broom support frame  24  is pivotably mounted about a vertical axis to the mounting support structure  21  such that the rotary broom  26  may be pivoted left or right to direct dirt, debris, gravel and other material being swept by the rotary broom  26 . To control the tilt position of the broom  26 , a second hydraulic actuator shown in the form of a hydraulic cylinder  30  is mounted between the support structure  21  and the broom support frame  24  such that expansion and contraction of the hydraulic cylinder  30  pivots the broom to the desired angle. A pair of stabilizer spring supports  32  are also connected between the support structure  21  and the broom support frame  24 . 
     From the foregoing and referring to FIGS. 4-6 e,  it will be apparent that the disclosed embodiment includes two different hydraulic functions, including a tilt function and a broom rotation function. With this being said, only one hydraulic working output is typically available from the hydraulic system  33  of the skid steer loader  10 , through a pair of hydraulic couplings  34  from the hydraulic system  33  having quick connect hydraulic couplings at their ends. During operation, one of the hydraulic couplings  34  carries high pressure hydraulic fluid from the skid steer&#39;s hydraulic pump  36  while the other coupling vents the return flow of low pressure hydraulic fluid to the skid steer&#39;s hydraulic sump  38 . A control lever  39  is provided in the operator cab  16  that allows manual control over a 4-way, three position, blocked over center, control valve  40 . Thus, there is a single control provided in the operator cab  16  for control over two hydraulic functions. The skid steer&#39;s control valve  40  has a first position shown schematically in FIG. 5 in which hydraulic flow is direct in one direction, a second position as shown schematically in FIG. 6 a - 6   d  in which hydraulic flow is in the reverse direction and a third position as shown schematically in FIG. 4 which prevents hydraulic flow to the rotary broom attachment  20 . 
     Recalling that prior rotary broom attachments (and other similar attachments having two different hydraulic functions) have used a second additional control in the form of electrically operated solenoid to switch between the hydraulic functions, the illustrated embodiment departs from the prior art by providing a rotary broom attachment  20  with two different hydraulic functions (hydraulic rotary motor  28  and hydraulic cylinder  30 ) using the single hydraulic control of the skid steer loader  10  without the need for an electrically operated solenoid. The described embodiment of the rotary broom attachment  20  achieves the foregoing by featuring a hydraulic circuit  42  that is responsive to the direction of the hydraulic flow (in which flow in one direction provides a first hydraulic signal and flow in the reverse direction provides a second hydraulic signal). Details of how this is accomplished and advantages will be detailed further below after a first describing structurally how the described embodiment of the circuit  42  is arranged. 
     In the described embodiment, the hydraulic circuit  42  is connected to the hydraulic system  33  of the skid steer loader  10  by a pair of hoses  46 ,  47  that include quick attach couplings at their ends for quick hydraulic attachment and detachment from the skid steer. The first hose  46  is connected to a hydraulic sequencing block  50  while the second hose  47  is connected directly to the hydraulic motor  28 . A third hose  48  connects the hydraulic motor  28  to the hydraulic sequencing block  50  as well. The first three hoses  46 - 48  and internal plumbing of the hydraulic sequencing block  50  complete a primary circuit (shown in bold lines and arrows in FIG. 5) for operational mode of the hydraulic rotary motor  28  as shown in the schematic illustration FIG.  5 . The hydraulic circuit  42  also includes a secondary circuit (shown in bold lines and arrows in FIG. 6 a - 6   d ) for operating the hydraulic cylinder  30  that further includes a pair of fourth and fifth hoses  53 ,  54  connecting the hydraulic sequencing block  50  with the hydraulic cylinder  30 . This secondary circuit is illustrated in the schematic illustrations of FIGS. 6 a - 6   d  (each different figure showing a different state or transition between states). 
     From the foregoing, it should be apparent that the hydraulic sequencing block  50  includes four different external ports  56 - 59 . The first port  56  is connected directly to the skid steer&#39;s hydraulic system  33  via hose  46 . The second port  57  is connected directly to the hydraulic rotary motor  28  via hose  48 . The third and fourth ports  58 ,  59  are connected directly to the hydraulic cylinder  30  via hoses  53 ,  54 . The internal plumbing of the hydraulic sequencing block includes a direct conduit  62  connecting the first two ports  56 ,  57 . A check valve  64  is arranged in the direct conduit  62  to only allow one directional return flow from the hydraulic rotary motor  28  to flow along the direct conduit path en route to the sump  38  as shown in FIG.  5 . When hydraulic flow is reversed, the check valve  64  closes thus blocking flow and in turn cause causes flow to pressurize and enter a bypass inlet conduit  66  which diverts flow through the secondary circuit, first through shut-off valve  68  and then through an array of four two-position valves  70 - 73 , the combination of which provides a hydraulic switch generally indicated at  75 . The hydraulic switch  75  is operable to reverse the direction hydraulic flow to the hydraulic cylinder  30 . As shown in FIGS. 6 a ,  6   b , the hydraulic switch  75  includes a first state in which pressurized working fluid is channeled to a first chamber  78  of the hydraulic cylinder  30  and the second chamber  80  is vented to the sump  38 . This causes the piston of the hydraulic cylinder  30  to retract. As shown in FIGS. 6 c ,  6   d , the hydraulic switch  75  includes a second state in which pressurized working fluid is channeled to a second chamber  80  of the hydraulic cylinder  30  and the first chamber  78  is vented to the sump  38 . This causes the piston of the hydraulic cylinder  30  to expand. Vented hydraulic fluid from the hydraulic cylinder  30  is evacuated on vent line  82  en route to the second port  57  for return to the hydraulic sump  38 . A pressure relief valve  84  (or check valve) is arranged along vent line  82  to ensure that flow does not reverse through vent line  82  and that the hydraulic cylinder  30  is vented only when desired. 
     It is a feature that the hydraulic switch  75  is responsive to hydraulic feedback from the hydraulic cylinder  30  as a result of the cylinder reaching the end of its expansion or retraction stroke. In particular, when the hydraulic cylinder  30  reaches the end of its stroke (either expansion or retraction), the pressure increases to the full working pressure from the skid steer&#39;s hydraulic system  33  which in turn is used to switch states of certain valves to reverse the direction of flow and cause the hydraulic cylinder  30  to reverse direction. With this configuration, the hydraulic cylinder  30  continuously reciprocates back and forth when the cab operator places the skid steer&#39;s control valve  40  in the reverse flow position shown in FIGS. 6 a - 6   d.  Once the control valve  40  is moved via the control lever  39  to either the over center position shown in FIG. 4 or the broom operation position shown in FIG. 5, the flow to the hydraulic cylinder  30  ceases and the hydraulic cylinder  30  and thus the pivoted/tilted position of the broom  26  is hydraulically locked into position. 
     Referring to the preferred construction of the hydraulic sequencing block  50  and the hydraulic switch  75 , the third and fourth two-position valves  72 ,  73  of the hydraulic switch  75  function as control gates connecting the respective cylinder chambers  78 ,  80  to either the high pressure hydraulic working flow in working line  86  (connected to the high pressure hydraulic working flow through bypass shut-off valve  68  ) or to the low pressure vent line  82 . The other two valves  70 ,  71  of the hydraulic switch  75  function as pilots adapted to control high pressure pilot flow through pilot line  88  to the gate valves  72 ,  73 . The first pilot valve  70  is also responsive to hydraulic feedback from the hydraulic pressure between the hydraulic cylinder  30  and one of the gate valves  73  via pilot line  90 . 
     Operation of how the switch works can be seen with reference to FIGS. 6 a - 6   d.  As shown in FIG. 6 a  when the cylinder  30  is retracting, hydraulic working flow is routed through the working line  86  and gate valve  72  to the hydraulic cylinder  30  causing it to retract. The other gate valve  73  vents the hydraulic fluid from the cylinder  30  through the vent line  82 . The second pilot valve  71  which is piloted by pressure in the pilot line  88  remains closed as the pressure is reduced sufficiently in the pilot line  88  to maintain the closed position due to the active outflow of the hydraulic working flow to the cylinder  30 . 
     However, once the hydraulic cylinder  30  reaches the end of its retracting stroke, the hydraulic working flow stops, thus increasing the pressure in pilot line  88  as can be seen in viewing FIGS. 6 b ,  6   c , which in turn switches the state of the second pilot valve  71  allowing flow through the pilot line  88  to simultaneously switch the states of both gate valves  72 ,  73 . This reverse the direction of hydraulic flow causing the hydraulic working flow to now work the hydraulic cylinder  30  through the other gate valve  73  causing the cylinder to expand as shown in FIG. 6 c . The other gate valve  72  now allows hydraulic fluid from the hydraulic cylinder  30  to vent through the vent line  82 . It should be noted that valve  72  is a direct acting, spool-type, hydraulic sequence valve with internal pilot and spring chamber drain, designed to direct flow to a second circuit once a first predetermined pressure is attained in the first circuit. The valve  72  will remain shifted until the pressure in the second circuit falls below a second lower predetermined pressure set by a second spring. 
     Now, once the hydraulic cylinder  30  fully expands and reaches the end of its expanding stroke, pressure builds up in feedback line  90  causing the first pilot valve  70  to shift allowing the second pilot valve  71  to vent the pilot lines from the two gate valves  72 ,  73  to the vent line  82 , which in turn causes the gate valves to simultaneously switch states again back to the state shown n FIG. 6 a.    
     Assuming a commercial work vehicle that has a hydraulic system pressure of between about 2000-3500 PSI, the following valves in the sequencing block  50  may be actuated and shifted at the following pilot pressures: 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Valve 
                 Actuating Pressure 
               
               
                   
                   
               
             
             
               
                   
                 Shut off valve 68 
                  450 PSI 
               
               
                   
                 Pressure Relief Valve 84 
                  400 PSI 
               
               
                   
                 1 st  Pilot Valve 70 
                 1400 PSI 
               
               
                   
                 2 nd  Pilot Valve 71 
                 1800 PSI (in one direction) and 
               
               
                   
                   
                  450 PSI (in opposite direction) 
               
               
                   
                   
               
             
          
         
       
     
     Referring to other hydraulic structures for the sake of completeness, the hydraulic sequencing block  50  also includes screens/filters  94 ,  96  at selected locations to prevent plugging of the hydraulic sequencing block  50  and a restriction  98  to control flow rate to the hydraulic cylinder  30 . 
     A further feature of the present invention is a second check valve  100  arranged in parallel circuit with the broom&#39;s hydraulic rotary motor  28  that has a closed position during flow through the primary circuit shown in FIG. 5 when hydraulic flow powers the motor and drives the broom. The check valve opens when flow is reversed venting returning flow from the hydraulic sequencing block  50  when the hydraulic cylinder  30  is being driven as shown in FIGS. 6 a - 6   d.  The second check valve  100  serves the purpose of preventing shock loads from being induced on the hydraulic rotary motor  28  when the hydraulic flow is reversed. This allows the rotary broom  26  to free wheel and naturally come to a stop and prevents hydraulic flow from reversing through the motor  28 . 
     In normal operation as shown in FIG. 5, hydraulic working output of the skid steer&#39;s hydraulic system  33  is directed to the hydraulic rotary motor  28  which rotates the broom  26  for sweeping operation. The operator in the cab  16  may turn the broom  26  off by positioning the control valve  40  in the blocked over center position as shown in FIG.  4 . When it is desired to tilt or pivot the rotary broom  26  left or right, the operator of the cab reverses the hydraulic flow which causes the hydraulic cylinder  30  to continuously reciprocate back and forth until the operator shuts off flow through this secondary circuit. 
     All the illustrated embodiment takes the form of a rotary broom attachment  20 , it will be appreciated that the present invention is applicable to and covers other embodiments. In particular, the present invention may be incorporated in a snowblower attachment (functions of engaging/blowing snow and direction the snow or the attachment), a cold planner attachment, a rock saw attachment, a stump grinder attachment, a rotary landscape rake, and other similar attachments where control over two hydraulic functions is desirable or necessary. Other embodiments may attach to the rear end of the vehicle (eg. via a three point hitch) or may be part of the hydraulic system of the commercial work vehicle or other hydraulic system of other work apparatus. 
     The foregoing description of various preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.