Abstract:
A cartridge valve assembly ( 19 ) including a sleeve valve ( 49 ) fixed within a valve housing ( 17 ), and a spool valve ( 47 ) moveable both axially and rotatably within the sleeve valve. Rotation of an input ( 35,39 ) causes rotation of a cam member ( 43 ) and the spool valve, and the engagement of the cam member ( 43 ) with a cam surface ( 57 ) results in axial movement of the spool valve within the sleeve valve. The spool and sleeve valves define a neutral axial and rotational position (FIG.  5 ), and rotation from neutral in a first direction (FIG.  6 ) communicates fluid from an inlet port ( 21 ) to a first actuator port ( 25 ), and rotation from neutral in a second direction (FIG.  7 ) communicates fluid from the inlet port to a second actuator port ( 27 ). In either case, the axial movement of the spool valve ( 47 ), relative to the sleeve valve ( 49 ) is the same. The spool valve defines a load holding land ( 97 ) which, in the neutral position (FIG.  5 ) engages a seat ( 99 ) defined by the interior of the sleeve valve ( 49 ), to block the flow of fluid from the first actuator port ( 25 ), and provide an integral load holding capability, with no extra valving or plumbing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     MICROFICHE APPENDIX 
     Not Applicable. 
     BACKGROUND OF THE DISCLOSURE 
     The present invention relates to cartridge valve assemblies, and more particularly, to such cartridge valve assemblies for use in raising and lowering accessories in vehicle hydraulic systems. 
     On many vehicles, such as lawn and garden tractors, there is a hydraulic system which may include one or more priority functions, such as a power steering system, and one or more ancillary (or auxiliary) hydraulic functions, such as driving a rotary actuator to wind up a winch, or raising and lowering a cylinder to control some portion of the vehicle. For example, on turf equipment, it is common to have a hydraulic cylinder associated with the mower deck, and operable to raise and lower the mower deck, in response to movement of a main control valve. 
     In most vehicle hydraulic systems of the type described above, conventional spool type direction and flow control valves have been used to control flow to and from such hydraulic accessories. Unfortunately, a typical spool valve assembly adds substantially to the overall cost of the vehicle hydraulic system. This is especially true in the case wherein the auxiliary hydraulic function is a cylinder or some other actuator which requires “load holding” capability. An example would be a lift cylinder for a mower deck, wherein the control valve assembly must be capable of maintaining the lift cylinder at a desired position so that the weight of the mower deck does not cause fluid leakage, thus permitting the mower deck to move downward from its desired position. 
     In the case of hydraulic functions which require load holding capability, it is typical to provide the control valve assembly with pilot operated check valves. Such check valves are normally effective to provide the load holding capability, but add substantially to the overall cost and complexity, and even the physical size, of the total control valve assembly. This is especially true if the vehicle manufacturer purchases pilot operated check valves which are separate from the main control spool, and must be separately plumbed into the system. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved control valve assembly, especially for use in vehicle hydraulic systems, which overcomes the disadvantages of the prior art. 
     It is a more specific object of the present invention to provide such a control valve assembly in the form of a cartridge valve assembly, which is able to provide the necessary flow control functions in response to a somewhat conventional manual input. 
     It is another object of the present invention to provide such an improved cartridge valve assembly which has, integral therewith, load holding capability, but without the need for a separate check valve arrangement. 
     The above and other objects of the invention are accomplished by the provision of a cartridge valve assembly adapted to be disposed in a valve housing defining a cartridge bore, an inlet port, a tank port, and first and second actuator ports. The cartridge valve assembly includes a sleeve valve fixed within the cartridge bore and a spool valve disposed within the sleeve valve for movement therein. 
     The improved cartridge valve assembly is characterized by the spool valve being moveable both axially and rotatably within the sleeve valve. The assembly includes means biasing the spool valve toward a neutral axial and rotational position within the sleeve valve, in which the inlet port is blocked from fluid communication with the first actuator port. There is means operable to displace the spool valve in a first rotational direction, away from the neutral rotational position, in response to an input in the first direction, and in a second rotational direction, away from the neutral rotational position, in response to an input in the second direction. The means operable to displace the spool valve includes cam means whereby rotation of the spool valve in the first direction results in axial movement of the spool valve from the neutral axial position toward an axial operating position, and rotation of the spool valve in the second direction results in axial movement of the spool valve from the neutral axial position toward the axial operating position. The spool valve and the sleeve valve, when the spool valve is displaced in the first rotational direction, and is in the axial operating position, provide fluid communication from the inlet port to the first actuator port and from the second actuator port to the tank port. The spool valve and the sleeve valve, when the spool valve is displaced in the second rotational direction, and is in the axial operating position, provide fluid communication from the inlet port to the second actuator port, and from the first actuator port to the tank port. 
     In accordance with another aspect of the invention, the improved cartridge valve assembly is characterized by the spool valve defining a load holding land in sealing engagement with a seat surface disposed within the valve sleeve. When the spool valve is in the neutral axial and rotational position, the engagement of the load holding land and the seat surface block fluid communication from the first actuator port to any of the inlet port, the tank port and the second actuator port. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a somewhat simplified hydraulic schematic of the portion of the overall vehicle hydraulic system to which the present invention relates, including the cartridge valve assembly of the present invention. 
     FIG. 2 is an axial cross-section of a valve housing, and disposed therein, the cartridge valve assembly of the present invention, in external plan view. 
     FIG. 3 is an axial cross-section of the cartridge valve assembly shown in external plan view if FIG. 2, and on about the same scale. 
     FIG. 4 is an enlarged, fragmentary, axial cross-section similar to FIG.  3 . 
     FIG. 5 is a layout view of the spool and sleeve valving, illustrating the neutral axial and rotational position. 
     FIGS. 6,  7  and  8  are layout views, similar to FIG. 5, illustrating three different operating positions of the spool and sleeve valving of the cartridge valve assembly. 
     FIG. 6A is an enlarged, fragmentary, axial cross-section similar to FIG. 4, but with the spool and sleeve valving in a position corresponding to that of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, which are not intended to limit the invention, FIGS. 1 and 2 illustrate a vehicle hydraulic system for controlling fluid flow from a source, such as a pump  11  to a vehicle auxiliary device, shown herein as a hydraulic cylinder  13 . As is shown schematically in FIG. 1, the cylinder  13  is used to raise and lower a load L which, by way of example only, may comprise a mower deck on a lawn tractor. 
     The control of fluid flow from the pump  11  to the cylinder  13  is accomplished by means of a control valve assembly, generally designated  15  (see FIG. 2) which includes a valve housing  17  and a cartridge valve assembly, generally designated  19 . The valve housing  17  defines an inlet port  21 , for connection to the pump  11 , and a return port  23 , for connection to a low pressure fluid source, such as a system reservoir R. The valve housing  17  also defines a pair of actuator ports  25  and  27 , for connection to the opposite ends of the cylinder  13  in a manner generally well known to those skilled in the art. 
     The valve housing  17 , which may be formed integrally with the housing of some other vehicle hydraulic component, defines a multi-step bore  29 , and disposed within the bore  29  is the valving portion of the cartridge valve assembly  19 , as will be described in (greater detail subsequently. 
     Referring now primarily to FIGS. 2 and 3, the cartridge valve assembly  19  includes a main body  31 , having an externally threaded portion  33  which is in threaded engagement with the left end of the bore  29  in FIG. 2, thus retaining the assembly  19  in a fixed position relative to the valve housing  17 . Partially surrounding the left end of the main body  31  is a generally cylindrical knob  35  which, in the subject embodiment, comprises the manual input to the cartridge valve assembly  19 . Preferably, such manual input may be facilitated by providing an elongated lever (not shown herein), extending radially out of a bore  37  defined by the knob  35 . An input shaft  39  extends axially through the knob  35  and through a central opening in the main body  31 , and is preferably fixed to rotate with the knob  35 , such as by means of a taper on the left end of the shaft  39 , and also by means of a set screw  41 . The right end (in FIG. 3) of the input shaft  39  extends into the valving portion of the cartridge valve assembly  19 , and has a dowel pin  43  extending diametrically therethrough, and also extending through diametrically opposed circular openings  45  defined by a spool valve  47 . The spool valve  47  is moveable both axially and rotationally within a sleeve valve  49 , the sleeve valve  49  being fixed relative to the main body  31 , and therefore, being stationary within the bore  29 . 
     Referring now to FIGS. 2,  3  and  4  together, it may be seen that the sleeve valve  49  is provided with three O-ring seals  51 ,  52  and  53  which sealingly engage the bore  29  to isolate the various fluid ports from each other. It should be noted by comparing FIGS. 3 and 4 with FIG. 2 that the interior of the spool valve  47 , generally designated  55  in FIG. 4, is in open fluid communication with the return port  23 . 
     Referring again primarily to FIG. 3, in conjunction with FIG. 5, it may be seen that the left end of the sleeve valve  49  defines a cam surface  57 , which typically would be provided at only one location on the sleeve valve  49 . Disposed radially between the input shaft  39  and the main body  31  is a cylindrical compression spring  59  (also shown schematically in FIG.  1 ). The function of the spring  59  is to bias the spool valve  47  to the right in FIG. 3 (or in the schematic of FIG. 1, to the neutral position), thus biasing the dowel pin  43  into engagement with the cam surface  57 . It should be noted that in the schematic of FIG. 1, above certain sections (positions) of the schematic are the reference numerals “ 5 ”, “ 6 ”, “ 7 ” and “ 8 ”, those sections of the schematic corresponding to the valve layout views shown in FIGS. 5 through 8, respectively. As will be understood by those skilled in the art, the other schematic positions in FIG. 1 are merely intermediate positions, intended to show all of the various communication paths as the valving progressively moves from one position to another. 
     Referring now primarily to FIGS. 4 and 5, the spool valve  47  and sleeve valve  49  will be described in greater detail. It should be noted that what is shown in the layout views of FIGS. 5 through 8 is the actual valving interface, i.e., the ports and slots on the outer surface of the spool valve  47  (in dashed lines), and the ports at the inner surface of the sleeve valve  49  (in solid lines). 
     The spool valve  47  defines three ports  61 ; three ports  63 ; three ports  65 ; three ports  67 ; three ports  69 ; three ports  71 ; three ports  73 ; and six ports  75 . All of the ports  61  through  75  defined by the spool valve  47  extend through the entire radial extent of the spool valve  47 , i.e., they interconnect the valving interface with the interior  55 , and therefore, all of the ports  61  through  75  are in communication with the return port  23 . 
     Referring now primarily to FIG. 5, but not FIG. 4, the spool valve  47  also defines three axial slots  77  and three axial slots  79 . The slots  77  and  79  are formed only on the outer surface of the spool valve  47 , and therefore are not in communication with the interior  55 , and are not in communication with the return port  23 . As will become apparent subsequently, the function of the slots  77  and  79  is to permit communication between different groups of ports defined by the sleeve valve  49 . 
     Referring again to FIGS. 4 and 5, in conjunction with FIG. 2, the sleeve valve  49  defines three ports  81  and three ports  83 , the ports  81  being in open communication with the actuator port  25 , and the ports  83  being indirectly in communication with the actuator port  25 , past a seat  99  (to be described subsequently) and through the ports  81 . The sleeve valve  49  defines three ports  85  and three ports  87 , the ports  85  and  87  being in open communication with the inlet port  21 . Finally, the sleeve valve  49  defines three ports  89  and three ports  91 , the ports  89  and  91  being in open communication with the actuator port  27 . Those skilled in the art will understand that the specific number of each of the ports and slots recited above is by way of example only, and is not essential to the present invention. 
     Referring now primarily to FIG. 5, when the manual input to the knob  35  is released, and the spring  59  returns the valving to its neutral position (position “ 5 ” in FIG.  1 ), the relationship of the spool valve  47  and sleeve valve  49  is as illustrated in FIG.  5 . With the valving in neutral, pressurized flow entering the inlet port  21  flows through the ports  85  and  87 , which, in the neutral position, are overlapping the spool valve ports  63  and  67 , respectively. Therefore, inlet fluid flows through the ports  63  and  67  to the interior  55  of the spool valve  47 , and then to the return port  23 . Also when the valving is in neutral, the ports  89  and  91  in the sleeve valve overlap the ports  71  and  73  in the spool valve, such that the upper chamber (rod end) of the cylinder  13  is in communication through the actuator port  27 , and through the ports  89  and  91  and  71  and  73 , with the return port  23 . It should be noted in FIG. 5 that, in neutral, the dowel pin  43  engages the “lowest” portion of the cam surface  57 , i.e., the spool valve  47  is in its rightward-most position relative to the sleeve valve  49 . The significance of this will become apparent subsequently. 
     Referring now primarily to FIG. 6, when the vehicle operator wishes to raise the load, the lever and the knob  35  may be rotated in a clockwise direction as viewed from the left end in any one of FIGS. 2 through 8. The result is that the dowel pin  43  rides up one portion of the cam surface  57 , moving the spool valve  47  to the left, relative to the sleeve valve  49 , and “downward” from the position shown in FIG. 5 to that shown in FIG.  6 . With the valving in the Raise position (position “ 6 ” in FIG.  1 ), the ports  85  and  87  in the sleeve valve  49  receive pressurized fluid from the inlet port  21 , but the ports  85  and  87  are no longer in communication with the ports  63  and  67  in the spool valve. Instead, the port  85  is now in communication with the adjacent axial slot  77 , the other end of the axial slot  77  being in communication with one of the ports  83 . As may best be seen in FIGS. 4 and 6A, each of the ports  83  is plugged with a ball  101 , such that fluid in the axial slots  77  enters the ports  83 , but then flows to the ports  81  in a manner to be described subsequently. Thus, pressurized fluid flows from the inlet port  21  through the sleeve ports  85 , through the axial slots  77  and out the sleeve ports  81  to the actuator port  25 , and then to the lower chamber (head end) of the cylinder  13 . At the same time, fluid being expelled from the rod end of the cylinder  13  is communicated back through the actuator port  27  and through the sleeve ports  91 , which are now overlapping adjacent ports  75  in the spool valve  47 . Thus, fluid expelled from the rod end of the cylinder  13  is communicated to the return port  23 . 
     In accordance with one important aspect of the present invention, the relative position of the spool and sleeve as shown in FIGS. 3,  4  and  5  comprises the neutral position, axially, wherein, as mentioned previously, the spool valve  47  is in its rightward-most position, relative to the sleeve valve  49 . Referring again primarily to FIG. 5, in order to raise the cylinder  13 , the knob  35  and dowel pin  43  are moved clockwise, as was described above in connection with FIG. 6, and such clockwise rotation of the pin  43  and spool valve  47  results in axial movement of the spool valve  47  to the left from the position shown in FIG.  5 . In order to lower the cylinder  13 , i.e., by directing pressurized fluid from the inlet port  21  to the actuator port  27 , the spool valve  47  and pin  43  are rotated counterclockwise (as viewed from the left in any one of FIGS.  2  through  8 ). However, in accordance with an important aspect of the invention, such movement of the spool valve  47  in the “opposite” direction, to thereby move the cylinder  13  in the opposite direction, still involves axial movement by the spool valve  47  toward the left, from the neutral axial position shown in FIG. 5. A particular advantage of this feature will now be described. 
     Referring now primarily to FIG. 6A, in conjunction with FIG. 6, it may be seen that the spool valve  47  defines an annular groove  93 , generally aligned with the ports  83 , and an annular groove  95 , generally aligned with the ports  81 . The annular grooves  93  and  95  intersect to form an annular land surface  97 , and disposed adjacent thereto, the sleeve valve  49  defines an internal, annular seat surface  99 . Thus, with each of the ports  83  being plugged by the ball plug  101  as shown in FIG. 4, pressurized inlet fluid in the axial slots  77  flows into each of the ports  83 , and from there into the annular groove  93 , then between the surfaces  97  and  99  and into the annular groove  95 , then out through the ports  81  to the actuator port  25 . 
     After the spool valve  47  has been in the raised position shown in FIG. 6, when the handle is released and the spool valve  47  returns to the neutral position of FIG. 5, the spool valve  47  returns to its neutral axial position of FIGS. 3 and 4, and the land surface  97  engages the seat surface  99 , under the biasing force of the spring  59 . As is well known to those skilled in the art, a typical load on the cylinder  13  would generate sufficient pressure in the conduit and the actuator port  25  that, if the piece of equipment were left for a period of time with the cylinder in the raised position, the pressurized fluid in the port  25  would begin to leak back through the ports  81 , and then through the radial clearance between the spool valve  47  and sleeve valve  49 , then leak through the ports  61  to the interior  55  and back to the return port  23 . Such leakage with the cylinder under load would result in a gradual lowering of the cylinder over a period of time which is considered extremely undesirable from the standpoint of the customer and the vehicle operator. 
     Therefore, in accordance with another aspect of the invention, the land surface  97  and seat surface  99  have been provided as a load holding check valve. Thus, when the spool valve  47  returns to the neutral position of FIG. 5, the force of the biasing spring  59  biases the land surface  97  into tight sealing engagement with the seat surface  99 . Thereafter, regardless of the load on the cylinder  13 , pressurized fluid in the actuator port  25  and in the ports  81  can enter the annular groove  95 , but is prevented by the load holding check surfaces  97  and  99  from flowing into the annular groove  93  and therefore, is prevented from leaking down in the manner previously described. The way in which the load holding capability is provided illustrates the importance of having the spool valve  47  move axially in the same direction (to the left) whether the inlet port  21  is to be communicated with the actuator port  25 , or is to be communicated with the actuator port  27 . 
     Referring now primarily to FIG. 7, when the operator wishes to power the cylinder  13  in a downward direction, the dowel pin  43  and the spool valve  47  may be rotated counterclockwise from the position shown in FIG. 5 to that shown in FIG. 7 (position “ 7 ” in FIG.  1 ). With the valving in the Lower position shown in FIG. 7, pressurized fluid entering the inlet port  21  flows through the sleeve ports  85  and  87 , but the ports  85  are now blocked from communication with any of the ports or passages in the spool valve  47 . However, each of the ports  87  is now in communication with the left end of the adjacent axial slot  79 , the right end of the slot  79  being in communication with one of the sleeve ports  89 , such that pressurized fluid flows out through the ports  89  to the actuator port  27 , and then to the rod end of the cylinder  13 . As the piston within the cylinder  13  moves downward, return fluid exhausted from the head end of the cylinder flows back through the actuator port  25 , through the ports  81 , then through the annular grooves  95  and  93  (see FIG.  6 A). The return fluid in the groove  93  then enters the ports  83  which, in the position shown in FIG. 7, now overlap the spool ports  61  such that the return fluid flows through the ports  61  to the interior  55 , and then to the return port  23 . It should be understood that the Lower position represented in FIG. 7 is not merely one discrete position of the spool valve  47  and sleeve valve  49 , but instead, as is shown schematically in FIG. 1, the Lower position is a range of relative positions of the spool valve and sleeve valve. 
     Referring now primarily to FIG. 8, when the operator wishes to permit the vehicle accessory to “Float”, as that term is well understood in the hydraulic control art, whereby the cylinder  13  is free to move upward and downward in response to imposed loads, the operator rotates the dowel pin  43  and spool valve  47  counterclockwise, to the position shown in FIG.8 (position “ 8 ” in FIG.  1 ). With the valving in the Float position of FIG. 8, pressurized fluid entering the inlet port  21  flows through the sleeve ports  85  and  87 , which are partially overlapping the spool ports  65  and  67 , respectively, such that the inlet port  21  is in communication with the interior  55  and the return port  23 . At the same time, fluid in the actuator port  25  is in communication through the ports  81  with the ports  83 , in the manner described preciously, and the ports  83  are overlapping the spool ports  61 , and thus, are in communication with the interior  55  and the return port  23 . Finally, fluid in the actuator port  27  flows through the sleeve ports  89  and  91 , which are in communication with the axial slots  79  and the spool ports  75 , respectively. The fluid in the axial slots  79  flows through the sleeve ports  87  and into the spool ports  69 , as described previously, while the fluid in the spool ports  75  merely flows to the interior  55  and to the return port  23 . Thus, with all of the ports  21 ,  23 ,  25  and  27  interconnected, the cylinder  13  is free to move upward and downward under the influence of external forces. 
     From the foregoing description, it may be seen that the present invention provides a cartridge valve assembly which may be used to control the flow of fluid, in response to a generally conventional manual input, in the manner of a three-position, four-way flow control, wherein the valve assembly includes integral load holding capability, without the need for added structure and plumbing. 
     The invention has been described in great detail in the foregoing specification, and it is believed that various alterations and modifications of the invention will become apparent to those skilled in the art from a reading and understanding of the specification. It is intended that all such alterations and modifications are included in the invention, insofar as they come within the scope of the appended claims.