Abstract:
A hydraulic pressure device valve having an outer circumferential support to a surrounding housing journal is constructed of a series of flat plates brazed together to form a unitary member containing substantially all of the valving passages of the entire device.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    Hydraulic pressure devices are efficient at producing high torque from relatively compact units. Their ability to provide low speed and high torque make them adaptable for numerous applications. U.S. Pat. Nos. 4,285,643, 4,357,133, 4,697,997 and 5,173,043 are examples of hydraulic motors.  
           [0002]    Low speed high torque gerotor motors are well represented in agriculture and commercial usages. Examples include scissorlifts, wenches, grain elevators and other applications requiring well controlled remote power. Examples include the U.S. Pat. Nos. 3,572,983, 4,390,329 and 4,480,972. These devices use a powder metal rotating valve in order to connect the expanding and contracting gerotor cells to the pressure and return feeds. One perennial problem with these motors is that they are prone to stall due to the separation of the valve from either the manifold or the balancing ring that biases the rotary valve in contact with the manifold. Over the years, companies such as Eaton have struggled to develop a commercial device which does not present this particular problem. Efforts are continuing within the industry to accomplish this result.  
           [0003]    In addition to the above, prior art rotary valve motors have contained powder metal valves which necessitated complicated dies for the manufacturer thereof. In addition, there are inherent manufacturing inaccuracies to this construction, particularly in the main valve drive spline interconnection, which inaccuracies cause timing errors in addition to other problems. In use, the wear between the valve and the balancing ring, cause leakage to occur bypassing the valve, thus significantly reducing the volumetric efficiency of the hydraulic motor.  
           [0004]    The valve in the present invention solves these particular problems in an efficient compact easy to manufacture unit.  
           [0005]    These prior art units, however, require extensive machining of the housing and include many parts.  
           [0006]    The present invention eliminates these problems.  
         OBJECTS AND SUMMARY OF THE INVENTION  
         [0007]    It is the object of the present invention to provide for a high speed high flow hydraulic motor having a rotational speed valve;  
           [0008]    It is an object of this invention to improve the service life of hydraulic motors;  
           [0009]    It is another object of the present invention to increase the volumetric efficiency of hydraulic motors;  
           [0010]    It is a further object of the invention to reduce the parasitic bypassing of fluid about the valve;  
           [0011]    It is another object of the present invention to eliminate the need for a separate case drain for the hydraulic motor by incorporating same into the main valve;  
           [0012]    It is an object of this invention to reduce the complexity of gerotor motor housings;  
           [0013]    It is still another object of the present invention to reduce the cost of and manufacturing time for hydraulic motors;  
           [0014]    It is yet another object of the present invention to increase the adaptability of hydraulic motors;  
           [0015]    Other objects and a more complete understanding of the invention may be had by referring to the drawings in which: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a longitudinal cross-sectional view of a hydraulic pressure device incorporating the invention of the application;  
         [0017]    [0017]FIG. 2 is a lateral cross-sectional view through the hydraulic pressure generating gerotor structure of FIG. 1 taken substantially along the lines  2 - 2  in such figure;  
         [0018]    FIGS.  3 - 7  are selective cross-sectional views of the plates in the rotating valve of the gerotor device of FIG. 1 of these figures;  
         [0019]    [0019]FIG. 8 is a perspective drawing showing the plates of the value separated in proper order and number;  
         [0020]    [0020]FIG. 9 is a see-through view of the valve taken substantially from lines  9 - 9  in FIG. 1;  
         [0021]    [0021]FIG. 10 is an enlarged view of an angular section of FIG. 9 highlighting the cooperation of the drain passages;  
         [0022]    [0022]FIG. 11 is a cross-sectional side view of the rotating valve of FIG. 9 taken generally along lines  11 - 11  therein highlighting the seating of the ball check valves;  
         [0023]    [0023]FIG. 12 is a face view of the wear plate of the embodiment of FIG. 1 taken generally from line  12 - 12  in that figure;  
         [0024]    [0024]FIG. 13 is a representational view of the gerotor structure of FIG. 2 super imposed on the wear plate of FIG. 12 with a top dead center rotor positioning;  
         [0025]    [0025]FIG. 14 is a representational view like FIG. 12 of the gerotor structure of FIG. 2 with with lubrication fluid passages in the rotor instead of the wear plate;  
         [0026]    [0026]FIG. 15 is a modified enlargement of FIG. 13 highlighting the preferred parameters of the leakage passages disclosed therein;  
         [0027]    [0027]FIG. 16 is a surface view of the biasing piston of the device of FIG. 1 taken generally along lines  16 - 16  therein;  
         [0028]    [0028]FIG. 17 is a cross-sectional view of the biasing piston of FIG. 16 taken generally along lines  17 - 17  therein;  
         [0029]    [0029]FIG. 18 is a surface view of the manifold of FIG. 1; and,  
         [0030]    [0030]FIG. 19 is a cross-sectional view like FIG. 1 of an alternate embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    This invention relates to an improved pressure device having a multiplate valve (FIGS.  3 - 11 ). The invention will be described in its preferred embodiment of a low speed high flow gerotor pressure device having a rotating valve separate from the gerotor structure. As understood this device will operate as a motor or pump depending on the nature of its fluidic and mechanical connections. It is designed for up to 35 gallons per minute at 4000 PSI.  
         [0032]    The gerotor pressure device  10  includes a bearing housing  20 , a drive shaft  30 , a gerotor structure  40 , a manifold  60 , a valving section  80  and a port plate  110 .  
         [0033]    The bearing housing  20  serves to physically support and locate the drive shaft  30  as well as typically mounting the gerotor pressure device  10  to its intended use (such as a cement mixer, mowing deck, winch or other application).  
         [0034]    The particular bearing housing of FIG. 1 includes a central cavity  25  having two roller bearings  21  rotatively supporting the drive shaft therein. A shaft seal  22  is incorporated between the bearing housing and the drive shaft in order to contain the operative hydraulic fluid within the bearing housing  20 . Due to the later described integral drain for the cavity  25  within the bearing housing  20  this shaft seal  22  can be a relatively low pressure seal. The reason for this is that the case drain invention of this application reduces the pressure of the fluid within the cavity  25  from full operational pressure, typically 2,000-4,000 PSI, down to a more manageable number, typically 100-200 PSI. The use of tapered roller bearings  21  in the pressure device encourages the flow of fluid within the cavity  25  due to the fact that the bearings  21  inherently will move fluid from their small diameter section to their large diameter section. This facilitates in the lubrication and cooling of these critical components. Two large diameter holes  23 , some ⅝″ in diameter, between the bearings  21  allow fluid to pass to the inside of the drive shaft  30  near to the drive connection to the later described wobblestick. In addition to the above, a series of radial holes  32  in the drive shaft further facilitates the movement of fluid within the cavity  25  across the bearings  21  (see U.S. Pat. No. 4,285,653 for a further explanation).  
         [0035]    A wear plate  27  completes the bearing housing  20  (FIG. 12). This wear plate is a separate part from the bearing housing  20 . As such, it can be made of different materials than the housing proper. Further, the wear plate  27  has an axial length slightly greater than the length  28  of the cavity within which it is inserted (0.003″ greater in the embodiment disclosed). This distance is selected in such that the stator  41  of the later described gerotor structure  40  is in contact with the bearing housing  20  outside of the wear plate upon the application of torque to the longitudinal assembly bolts holding the device  10  together. This allows the wear plate  27  to be axially clamped between the later described gerotor structure  40  and the remainder of the bearing housing  20 , thus serving to reduce the leakage from the pressure cells of the gerotor structure. This improves the efficiency of the gerotor motor. A single seal can be utilized at this location to seal the stator  41  to the bearing housing  20 , thus simplifying the manufacture of a three part assembly. The wear plate  27  in addition serves to lock the bearings  21  in place in respect to the bearing housing  20 .  
         [0036]    In the particular embodiment disclosed, the bearing housing  20  is made of machine cast metal while the wear plate  27  is a powder metal part. The inherent porosity of the wear plate allows oil impregnation so as to reduce friction and increase the service life of the unit.  
         [0037]    The drive shaft  30  is rotatively supported within the bearing housing  20  by the bearings  21 . This drive shaft serves to interconnect the later described gerotor structure  40  to the outside of the gerotor pressure device  10 . This allows rotary power to be generated (if the device is used as a motor) or fluidic power to be produced (if the device is used as a pump). As previously described the radial holes  23  and the radial hole  32  facilitate the movement of fluid throughout the cavity  25  thus to further facilitate the lubrication and cooling of the components contained therein.  
         [0038]    The drive shaft  30  includes a central axially located hollow which has internal teeth  35  cut therein. The hollow provides room for the wobblestick  36  while the internal teeth  35  drivingly interconnect the drive shaft  30  with such wobblestick  36 . Additional teeth  37  on the other end of the wobblestick drivingly interconnect the wobblestick  36  to the rotor  45  of the later described gerotor structure, thus completing the power drive connection for the device. A central hole drilled through the longitudinal axis of the wobblestick  36  is a possible addition to further facilitate fluid communication through the device.  
         [0039]    The gerotor structure  40  is the main power generation apparatus for the pressure device  10 .  
         [0040]    The particular gerotor structure  40  disclosed includes a stator  41  and a rotor  45  which together define gerotor cells  47  (FIG. 2). As these cells  47  are subjected to varying pressure differential by the later described valve, the power of the pressure device  10  is generated. This occurs because the axis of rotation  46  of the rotor is displaced from the central axis  42  of the stator (the wobblestick  36  accommodates this displacement).  
         [0041]    A case drain is designed to remove fluid from the central cavity  25  of the device. This serves to lower the pressure in such cavity (thus lowering the pressure requirements for seals and increasing tolerances) as well as removing fluid (thus assisting in lubrication and cooling of the components therein). The case drain is utilizable with any system that has some sort of way of introducing fluid into the cavity  25 , with such fluid having a relatively higher pressure than the outlet side of the later described case drain mechanism. This would include devices that, while having no special passage, naturally have leakage from high pressure areas (for example due to inherent tolerances as in U.S. Pat. No. 4,362,479), devices with dedicated bleed passages (such as U.S. Pat. No. 3,862,814, U.S. Pat. No. 4,390,329 or in U.S. Pat. No.  4,533,302)  or otherwise.  
         [0042]    In the particular embodiment herein disclosed dedicated leakage passages are utilized along at least one flat surface of the orbiting rotor  45  and/or an adjoining part (such as the wear plate  27 ) so as to provide a connection between at least one relatively pressurized gerotor cell and the central area of the device (FIG. 12). Relatively pressurized means that the fluid pressure is sufficiently greater than that of the central area of the device that fluid will flow from the cell thereinto. This leakage path can be located on either or both of the adjoining surfaces. As the rotor  45  moves, due to the orbiting motion of the rotor about the central axis  42  of the stator, the inner valleys  48  between the lobes of the rotor define an inner limit circle  49  on the adjoining part (see FIG. 15). Note that this inner limit circle  49  (FIGS.  1 - 18 ) is shown substantially equal to the diameter of the central opening  51  of the wear plate  27  (see FIG. 1). The reason for this is that the actual difference between the two in the embodiment disclosed is only 0.018″ (1.298″ vs. 1.280″). In other devices, the two might be more markedly different (see FIG. 15). This inner circle  49  defines the innermost extension swept by the valleys  48  between the rotor lobes (and thus the gerotor cells  47 ). In the present application, there are fluid passages  50  which extend from at least this inner circle  49  to the central area  52  within the pressure device  10 . This allows an amount of fluid to be parasitically drawn off of the relatively higher pressure cells  47  to pass into the central area  52 . This serves simultaneously to lubricate the critical moving components of the pressure device  10  in addition to providing a cooling function therefor.  
         [0043]    Preferably there is a leakage path from at least one relatively higher pressure gerotor cell  47  (further preferably a plurality in sequence) to an opening no larger than this inner circle  49 . While any higher pressure cell could be selected, it is preferred that a cell  47  located adjacent to a dead cell be utilized (a dead cell is a cell connected to neither port, a cell that if previously connected to higher pressure would retain such until connected to lower pressure). This provides a more predictable fluid flow than the dead cell without significant loss in volumetric efficiency.  
         [0044]    If the controlled leakage path is located in a stationary part (such as the wear plate), the path must extend outwards to at least the dead cell with the rotor located top dead center (the top center cell shown uppermost in FIG. 15). Ideally the outer extension of this leakage path extends for a distance less than that swept by the outer tips of the rotor lobes  44  so as to provide a seal for most of the high pressure in the device. The reason for this is to reduce the loss of volumetric efficiency that would occur if all cells were fluidically connected to the central area of the device (and also to each other via other leakage paths), although under certain circumstances such a connection may be desirable (for example small leakage paths and/or need for higher fluid flow).  
         [0045]    It is preferred that the leakage path also extend into an adjacent cell so as to insure a continual source of relatively higher pressure lubrication fluid (the cell at 10:30 in the bidirectional pressure device of FIGS. 1 and 15 assuming it is the next pressurized) (in a known unidirectional pressure device only one would be needed). It is further preferred that the path extend such that with the rotor located bottom dead center (FIG. 13) adjacent paths extend into the cell in transition  54  (at 11:00 in FIG. 13), with the crossover to a further cell  55  just starting to leak (at 9:30 in FIG. 13) (again assuming next pressurized). These additional connections, though not mandatory, facilitate the lubrication function of the device. Note that the inward extension of the leakage paths in a stationary part is not critical as long as it is sufficient to extend into the central cavity of the pressure device at the time that the leakage path is active. Additional inward extensions would not compromise the operation of the device.  
         [0046]    In this preferred embodiment only 0.2 to 0.5 gallon per minute are being utilized. The number of cells having leakage paths are thus kept to a minimum to provide a continuous input flow. This continuous flow provides a constant input lubrication function without a significant parasitical volumetric efficiency loss.  
         [0047]    The parameters behind this leakage path are set forth in example form in FIG. 15. This figure is a top dead center orientation of the structure of FIG. 13 with the diameter  51 A of the central area  52  reduced for clarity of explanation. The first parameter is the radius  1  of the inner limit circle  49  defined by the valleys  48  between rotor lobes  44 . This radius  1  defines the inward extension of the gerotor cells  47  towards the central longitudinal axis  42  of the gerotor pressure device  10 . The second parameter is the radius  2  of the central opening  51  defining the outer extent of the central area  52 . This radius  2  defines the location to which the leakage passage  50  must extend to provide lubrication for such area  52 . This radius  2  will vary considerably depending on the device. The leakage passage  50  itself extends from  49  to  51  ( 51 A in FIG. 15) across distance  3  (i.e., radius  1  minus radius  2 ). Further extension outward from the inner limit circle  49  connects that leakage passage to its respective gerotor cell sooner and for a longer time (subject to a continual leakage if extended beyond the outer position of the rotor lobes  44 ). An example of this would be the extension of the passage  50  along vector  4 . With this extension the respective gerotor cell would be interconnected to the central area  52  before becoming a dead pocket, and would be interconnected longer than it would have been had the extension along this vector  4  stopped at the inner limit circle  49 . It is preferred to increase the lateral extension  56  (or to use multiple passages per cell) in combination with a moderate further outward extension so as to optimize lubrication without unduly compromising volumetric efficiency. (A similar factor could be adjusted by not having a passage for every gerotor cell.)  
         [0048]    The design technique is similar for the later described leakage passages in the rotor (FIG. 14). The only difference is that the passages extend inward in the rotor from the rotor valleys  48  to central opening  51  ( 51 A) to contact same. Preferably this is accomplished in the center of the valleys  48  so as to provide symmetrical bidirectional operation.  
         [0049]    In the preferred embodiment disclosed in FIGS. 1 and 12, these passages  50  are “T” slots cut into the wear plate  27  (see FIG. 12). With the slots so positioned, there is one slot interconnected to the dead pocket in a top dead center position rotor (FIG. 15) with a second more active slot  53  (higher pressure rotation direction assumed) leaking to the central area  52  of the pressure device. In a corresponding bottom dead center position (FIG. 13), there would be one leakage path going to the almost dead pocket and a further slot just starting to have leakage to the central area  52  (again pressure direction assumed).  
         [0050]    Due to the fact that these cells are pressurized at full operating pressure, some 2,000-4,000 PSI, while the central area  52  of the gerotor device is at a lower pressure, perhaps 200 PSI, fluid will readily flow through the passages  50  from this gerotor cell to the central area  52 , thus providing the desired lubrication and cooling fluid. The radial extension  56  at the outer end of the passages  50  allow for an increased amount of leakage over a longer period of time than would be possible with a straight laterally extending passage  50  (i.e., without the radial extension  56 ). This facilitates the continuity of the flow of the lubrication fluid into the central area  52  of the device.  
         [0051]    The location of the passages  50  in the wear plate  27  is preferred to a location in the later described manifold due to its axial separation from the later described pressure release case drain mechanism in the rotating valve of the valving section  80 . Note that although the passages  50  are shown located in a non-moving part, the wear plate  27 , they could also be located in the rotor  45  as long as the same conditions are met (i.e., there is a leakage path from the gerotor cells  47  into the central area  52  of the device). This would be accomplished by placing a small inwardly extending passages within the rotor  45 , preferably at the base of the lobes thereof, sufficiently long enough to extend into the central hole of the wear plate  27  or later described manifold  60  thus to provide for the desired leakage.  
         [0052]    The particular wear plate disclosed is 3″ in diameter and 0.650″ thick. It includes a central opening of substantially 1.280″ in diameter in addition to a surrounding bearing clearance groove of substantially 2″ in diameter. There are seven recesses  29  substantially 0.375″ in diameter and from 0.030-0.040″ deep equally spaced around the diameter on a 2.3″ diameter circle aligned with the central axis of the rolls  43  of the gerotor structure  40 . There are in addition, seven balancing recesses  30  some 0.40″ in width and 0.25″ in depth equally spaced around the wear plate on the same diameter as the recesses  29 . The depth of these balancing recesses  30  is the same as the recesses  29 . In addition to the above, the passages  50  extend some 0.25″ from the central opening in the wear plate some 0.020″ in width and 0.020-0.025″ in depth. The “T” section  56  at the top of these passages  50  extend for 0.260″ in radial width and 0.020″ in axial width. Again, the depth of these passages  50  is from 0.020-0.025″ in depth. In differing devices with differing parameters, these dimensions would change.  
         [0053]    The manifold  60  in the port plate  110  serves to fluidically interconnect the later described valve to the gerotor cells  47  of the gerotor structure  40 , thus to generate the power for the pressure device  10  (FIG. 18).  
         [0054]    In the particular embodiment disclosed, since the valve is a rotating valve, phase compensation is not necessary. As such, the valving passages  62  can extend straight through the manifold  60 . The particular manifold disclosed includes recesses  64  directly centered on the rolls  43  of the stator  41 . These serve to reduce the axial pressure on such rolls  43  (corresponding recesses  29  in the wear plate  27  provide a similar function at the other end of the rolls  43 ). In addition, the manifold openings are expanded at their interconnection with the gerotor cells  47  relative to the openings of the through valving passages  62  on the other side of such manifold. (Balancing recesses  30  in the wear plate  27  serve to equalize the pressure on alternate sides of the rotor  45 ). As with the wear plate  27 , the axial length of the manifold  60  is greater than the axial length  65  of the cavity in the port plate within which it is contained, again some 0.003″ in the preferred embodiment disclosed. This serves to clamp the gerotor structure  40  with substantially equal pressure on both sides thereof, thus to reduce leakage and improve the overall efficiency of the pressure device the same parameters as the wear plate  27  apply to selection of distances. Similarly with the wear plate, the manifold  60  is of powder metal construction for reasons as previously explained. A pin  66  in combination with a slot  67  in the manifold and a hole  112  in the port plate  110  retains the manifold in rotary alignment with the gerotor structure  40  and valve  80  during assembly and use.  
         [0055]    The manifold  60  in the port plate  110  also can serve as a location for an additional/alternate dedicated leakage path (FIG. 19). Although not preferred as a location for a leakage path (due to its proximity to the case drain in the valve) it was discovered that the area  71  immediately surrounding the manifold  60  was subjected to high pressure when the outer port  113  pressurized, primarily via leakage past the outer surface of the valve  80 . This provided a relatively convenient source or lubrication fluid for a leakage path. In addition a leakage path at this location would lower the relative pressure at this location (and on the seal  73 ). The inclusion of a hole  72 , or series of holes  72 , from this area  71  to the center  70  of the manifold  60  provides this. (If the outer port  113  is connected to low pressure, since the later described case drain in the valve would be also, the hole  72  is relatively pressure balanced between its inner and outer ends. It would thus not compromise the volumetric efficiency of the device under this alternate connection.) This hole  72  may be included in addition to or instead of the previously described first dedicated leakage passage.  
         [0056]    The second fluid leakage passage  72  in the manifold  60  could also form part of a separate case drain for the hydraulic device (for use with or instead of the later set forth valve case drain). This would be attractive for applications wherein a separate drain line isolated from the valve  80  or ports  110 ,  113  is desired. To provide for this separate case drain a drain port  75  would be located extending from the area  71  to the outside of the device, preferably directly radially outwards so as to simplify its manufacture. The drain port  75  would be threaded or otherwise rendered into a form for an external drainline (not shown). Multiple holes  72  would be preferred on an outer circumferential groove so as to increase the connection dwell time between the port  75  and the center  70  of the manifold  60  (via holes  72 ). This drain port  75  would simultaneously lower the unit pressure on the area  71  (especially if port  113  is pressurized) while also providing for a case drain for the center  52  of the device  10 . Towards this end if the first set of dedicated leakage paths is eliminated it is preferred that longitudinal hole  31  be included in the wobblestick  36  (FIG. 19). This hole  31  allows movement of fluid down the center of the wobblestick towards the drive connection  35 , such movement assisted by the centripetal radial forces on the fluid provided by hole  32  and the previously described pumping action of the front bearing  21 . The holes  23  and the back bearing  21  further encourage movement of fluid in the center of the device and across the back drive connection  37 . These connections are cooled and lubricated by this fluid flow.  
         [0057]    The valving section  80  selectively valves the gerotor structure to the pressure and return ports.  
         [0058]    The particular valve  81  disclosed is a rotary valve of multiplate construction including a selective compilation of five plates (FIGS.  3 - 11 ).  
         [0059]    The particular valve  81  is an eleven plate compilation of a two communication plates  82 , five transfer plates  83 ,  84 , a single radial transfer plate  85  and three valving plates  86 . Due to the use of a multiplicity of plates, the cross-sectional area of each opening available for fluid passage is increased over that which would be available if only a single plate of each type was utilized. The plates themselves are brazed together so as to form an integral multiplate valve.  
         [0060]    The communication plate  82  contains a segmented inner area  88  which communicates directly to the inside port  111  in the port plate  110 . The communication plate  82  also contains six outer areas  89  which are in communication with the outside port  113 . The plate thus serves primarily to interconnect the valve  81  to the pressure and return ports of the gerotor pressure device  10 . The communication plate  82 , in addition, contains three sets of three holes  120 ,  130  and  150  (To avoid confusion and duplication, only one set of holes is numbered in the drawings).  
         [0061]    The hole  120  serves to interconnect part of the case drain to the port  111 , thus serving as one half of the later described case drain. The hole  130  interconnects with the recessed areas on the later described balancing ring, thus to interconnect same to the central area  52  of the hydraulic device  10 . The hole  150  interconnects to the port  113 , thus forming the second half of the case drain. The middle holes  130  are included to equalize fluid pressure on the later described balancing piston. It is preferred that the number of middle holes  130  differ in number than any blocking lands on the adjoining balancing ring (3 holes vs. 4 lands shown).  
         [0062]    The particular communication plate  82  is 2.48″ in diameter and 0.042″ deep. The inner area  88  is formed of three segments separated by three lands 0.250″ in width. These lands are large in order to provide for the three through holes  120 ,  130 ,  150  that serve as the pressure release mechanism. The outer hole  150  of this mechanism sweeps an area radially outside of the balancing ring and thus connects the outside port  113 . This outer hole  150  is an arched oval some 0.200″ in straight section length and 0.130″ in width with 0.130″ diameter ends (0.330″ in total length). The central radial axis of the outer hole  150  is spaced from the center  100  of the valve  81  by 1.013″ arching about such center. The middle hole  130  of this mechanism is 0.130″ in diameter with a location substantially matching the center land of the later described balancing piston (0.815″ radius) (3 total). The inner hole  120  of this mechanism is key slot shaped, with a head  121  some 0.130″ in diameter having a center spaced 0.615″ from the center  100  of the valve. A leg  122  some 0.185″ in center to center length and 0.080″ in width extends inward off the head  121 . The center to center leg  122  off of the inner hole  120  and width of the outer hole  150  allows for a bypassing movement of the fluid past the sealing check balls contained therein. This lowers the forces on the check balls and increases the longevity of the pressure release mechanism.  
         [0063]    In order to provide for the necessary alternating passages  105 ,  106  in the valving plate  86 , the first  83 , second  84  and third  85  transfer plates shift the fluid from the inner  88  and outer  89  areas in the communication plate  82 .  
         [0064]    The first transfer plate  83  contains a series of three first intermediate passages  90  which serve to begin to transfer fluid from the inner area  88  outwards. It also includes a series of six second outward passages  91  which communicate with the outer areas  89  in the communication plate to laterally transfer fluid. Since the outside port  113  directly surrounds the valve  81 , these passages  91  also serve to interconnect to the outside port  113 .  
         [0065]    As with the communication plate  82 , the particular first transfer plate  83  is 2.48″ in diameter and 0.041″ in depth. The three large symmetrically oriented intermediate passages  90  comprise the majority of this plate, such passages  90  extending in aggregate some 345° separated by three lands some 0.240″ in width. An enlarged hole  151  some 0.180″ in diameter connects to the outer hole  150 . The center of this hole is spaced 1.038″ from the center  100  of the valve. The middle hole  131  is reduced in diameter to 0.100″ to allow more room for hole  123 . Its center is spaced 0.780″ from the center  100  of the valve. The hole  123  in this plate is a key shaped slot with a substantially oval head some 0.150″ in diameter having centers space 0.040″ from each other. The innermost center is spaced 0.565″ from the center  100  of the valve. The leg  125  is some 0.220″ in center to center length having a width some 0.080″ extends inward off of the head  123 .  
         [0066]    A second transfer plate  84  completes the movement of the fluid from the inner and outer areas of the communication plate  82 . It accomplishes this by a series of three second intermediate passages  93  which serve to complete the radial movement of fluid from the inner area  88  of the communication plate  82 . A set of third outer passages  94  interconnect with the second outward passage  91  in the transfer plate  83  to complete the lateral movement of fluid therefrom. Again, since the outside port  113  surrounds the valve, the third outer passages  94  also directly interconnects to the outside port  113 .  
         [0067]    The particular transfer plate  84  is 2.48″ in diameter and 0.082″ in depth. The increased depth is incorporated to provide for good sealing between the central cavity of the device and the inner port  111  as well as a bearing surface for valve end of the valve stick. Three radially spaced passages  93  extend some 115° each to complete the shifting of the fluid of the inside port. The inner radius of these passages  93  is some 0.630″ with separating wall width of 0.350″ and 0.485″ respectively. The walls have three holes  152 ,  132  and  126  some 0.080″ in diameter therein. The outer hole  152  is spaced 1.050″ from the center  100  of the valve  81  and the inner hole  126  is spaced 0.565″ from such center. These dimensions allow for the seating of the check balls  107  without interference notwithstanding the slight radial offset of these holes from their respective companions in plate  83 . The center hole  132  is spaced 0.750″ from the center of the valve (since there is no seating of a ball check in respect to this passage, location is not critical). The check balls  107  in the holes  151  and  131  in plates  82 ,  83  seal on these holes  152  and  132  respectively when subjected to an inward higher relative pressure.  
         [0068]    The radial transfer plate  85  segments the second intermediate passages  93  so as to provide for the alternating valving passages in the valving plate  86 . This is provided by cover sections  96  for the middle of such passages  93 . This separates the two passages  97 ,  98  therein to initiate alternate placement thereof. Two passages  155 ,  135  extend outwards from the central opening so as to interconnect the holes  120 ,  130 ,  150  thereto (and thus the cavity  25 ).  
         [0069]    The particular radial transfer plate  85  is 2.55″ in diameter and 0.060″ in depth. The central opening is a spline having  12  teeth on a pitch diameter of some 1.10″ and a major diameter of some 1.20″. The passages  97  are substantially identical to the valving passages  105  in the valving plate  86  with an inner radius of 0.800″, an outer radius of 1.125″, 60° on center to the next passage  105 . The passages  98  have an inner radius of 0.800″ and alternate with passages  97  separated therefrom by triangular lands varying from 0.080″ to substantially 0.200″ in width. Passage  155  is some 0.079″ wide extending 1.050″ from the center of the plate  85 . The outer end  156  of this passage is aligned with hole  152  in plate  84 . Passage  135  is 0.079″ wide some 30° offset from passage  155  and extending 0.750″ from the center of the plate  85 . The outer end  136  of this passage is aligned with hole  132  in plate  84 . Hole  126 , being inward of hole  132 , is also connected to this passage  135 .  
         [0070]    The valving plate  86  contains a series of alternating passages  105 ,  106  which terminate the inner  88  and outer  89  areas of the communication plate  82  to complete the passages necessary for the accurate placement of the valving openings in the device. In the valving plate  86  the first  105  of the alternating valving passages are thus interconnected to the inside port  111  while the second  106  of the alternating passages are connected to the outside port  113  by the previously described passages. The use of four valving plates  86  allows for a solid, reliable connection to the valve stick that rotates the valve.  
         [0071]    The particular valving plate  86  is 2.55″ in diameter and 0.082″ thick. The central drive opening is a  12  tooth spline having a 1.10″ pitch diameter, a 1.20″ major diameter and a 1.01″ minor diameter. The outer radius of the alternating passages  105 ,  106  is 1.125″ and the inner radius 0.800″. The passages are located 30° on center separated from adjoining passages by lands 0.200″ wide.  
         [0072]    In the valving plate  86  the first of the alternating valving passages  105  is interconnected to the inside port  111  while the second of the alternating passages  106  is connected to the outside port  113  by the previously described passages in the communication plate and transfer plates as previously described.  
         [0073]    Two check balls  107 , some 0.125″ in diameter are located in the holes  151 ,  124  so as to provide for a check valve assembly. The diameter of the check balls are chosen such that the plates  82 - 86  of the valve  80  can be fully assembled and brazed together prior to the insertion of the check balls  107 . This allows for the uncompromised assembly of the valve  80  in addition to allowing larger check balls relative to their respective holes (and thus also good closure on their respective seats). Note that the dimension of the passages in the valve must include consideration of any offset between passages (i.e., the check balls  107  should drop into their respective passages from the outside of an assembled valve to the extent of fully seating on their respective seats). Further the passages themselves are designed in cooperation with the check balls  107  so as to provide for a relatively unimpeded smooth laminar flow about the balls when the respective passage is functioning as a case drain. This is particularly important at the check balls  107  outermost position in plate  82  adjacent to the balancing ring  180 . In the preferred embodiment two techniques are utilized (FIGS. 10 and 11). In respect to passage  150  (shown open in FIG. 11), the check ball  107  passes into hole  150  in plates  82 . As these plates aggregate 0.084″ in depth, the side edges of hole  151  in plate  83  localizes the ball  107  near the center of hole  150 , thus allowing a flow of fluid past the ball  107  on either side thereof (the hole  150  is 0.330″ in total length while the ball  107  has a maximum diameter of 0.125″ leaving 0.205″ for fluid passage, ignoring the circularity of the ball  107 ). In respect to passage  120  (shown closed in FIG. 11), the check ball  107  would pass into head  121  in plate  82  (the leg  122  is only 0.080″ in width). This leaves the full extent of the leg  122  for fluid passage bypassing the ball  107  (the leg  122  is 0.185″ in center to center length and 0.080″ in width, again ignoring the circularity of the ball  107 ). As the upstream check holes  152 ,  126  in plate  84  are only 0.080″ in diameter, the areas in hole  150  and leg  122  being greater in diameter are non-restrictive, thus reducing the fluidic forces on the balls  107  when in their respective open positions. Other methods of reducing the outward forces on the check ball  107  could also/instead be utilized. Examples include press in cages, stop plates, sidewards extending passages bypassing the balls and other techniques.  
         [0074]    The check balls  107  in the valve  80  are relatively unrestrained in their respective passages. For this reason they are very fast actuating check valves, unseating quickly. This is especially so in contrast with spring loaded housing located check balls (such as that found in U.S. Pat. No. 3,572,983). Further the check valves are located directly between the cavity  25  and the port  111 ,  113  having lower relative pressure. This again provides a faster acting check valve than those devices containing complicated passages (such as U.S. Pat. No. 3,572,983, U.S. Pat. No. 4,390,329 and U.S. Pat. No. 4,480,972). The present check valves are much more efficient to manufacture and assemble, not needing the machining of the housing and numerous additional parts such as seals, springs, plugs, etc. used in the above art. The present check valves are also more efficient.  
         [0075]    The later described balancing piston  180  retains the balls  107  in their respective holes.  
         [0076]    The cooperation of the case drain passages in the valve is detailed in FIGS. 9, 10 and  11 . When either passage  120 ,  150  is connected to a port  111 ,  113  respectively having a lower relative pressure than the center area  52  of the device, its respective ball  107  unseats from its seat  152 ,  126  so as to allow for the relatively unimpeded movement of fluid thereby. The other passage  120 ,  150 , presumably connected to a higher pressure remains closed by its respective check ball  107 , thus preventing the inadvertent cross-connection of ports  111 ,  113 .  
         [0077]    As is apparent from the above in addition to valving the gerotor structure  40 , the valve  81  also serve as a pressure release/case drain mechanism. This is accomplished by the interconnection of the three holes  120 ,  130  and  150  in the communication plate  82  to the central area  52 . This is accomplished by two passages  135 ,  155  in the preferred embodiment.  
         [0078]    The first passage  155  extends radially outward of the valve, thus to interconnect the central area  52  to the hole  150  and thus the outside port  113  if such port has a lower relative pressure that such area  52 .  
         [0079]    The second passage  135  extends radially to the second and third holes  120 ,  130 , thus connecting the central area  52  to the lands of the balancing piston  180  as well as the inside port  111  (again if the port has a lower relative pressure than the area  52 ). In any event the sizing of the valve seats and check valves for both passages is selected in combination with the rest of the device to control the volume of lubrication passing therethrough. This volume is about 0.2 to 0.5 gallon a minute in the preferred embodiment disclosed. The location of most restriction to fluid flow controls this volume. It is preferred that this restriction not be created by the check balls  107 . In the embodiment disclosed, the passages  50  of the leakage path in the wear plate  27  control the volume of fluid.  
         [0080]    The valving section  80  thus also includes a pressure release mechanism for the central area  52  of the gerotor pressure device. This pressure release mechanism includes the previously described two through holes  120 ,  150 , each containing a ball check  107 , in combination with their respective valve seats  126 ,  152 . The balls  107  themselves cooperate with valve seats in order to interconnect the central area  52  to the inside port  111  or outside port  113  having the lowest relative pressure. This provides for a self-contained case drain for the cavity  25  of the hydraulic device, thus allowing the circulation of fluid therein as well as lowering the pressure thereof. By integrating these pressure release valves with the rotating valve, the overall complexity and cost of the gerotor pressure device is reduced.  
         [0081]    The valve  81  is itself rotated by a valve stick interconnected to the rotor  45  and thus through the wobblestick  36  to the drive shaft. This provides for the accurate timing and rotation of the valve  81 .  
         [0082]    A balancing ring  180  on the port plate  110  side of the valve  81  separates the inside port  111  from the outside port  113 , thus allowing for the efficient operation of the device (FIGS. 16, 17). This balancing ring is substantially similar to that shown in the Eaton U.S. Pat. No. 3,572,983, Fluid Operated Motor. Four recessed areas  181  in the balancing ring  180  are aligned with the three unvalved holes  130  in the valve  80  so as to intermittently interconnect both the adjacent grooves  182  and the backside of the piston (via holes  183 ) to the central area of  52  of the device. This equalizes the pressure of these two areas through efficient intermittent pulses along the three unvalved holes  130  in the valve  80  (the pulses are intermittent due to the spacing differential between the holes  130  in the valve  80  (three in number) and the recessed areas  181  in the balancing ring  180  (four in number)). A series of springs located in pockets behind the balancing ring bias such piston against the valve  81  so as to reduce the chances of axial separation of the valve  81  from either the manifold  60  or the piston  120 .  
         [0083]    The radial and circumferential extensions of the holes  120 ,  150  in plates  82  and  83  reduce the check ball chattering against the later described balancing ring by allowing fluid to bypass the balls  107  when such are not seated on the valve plate  84 . This increases the longevity of the balancing ring while also reducing any unusual noises from the hydraulic pressure device.  
         [0084]    The particular balancing ring  180  has a 1.050″ outer and 0.565″ inner radius with a depth of 0.420″. The outer land  184  has an outer radius of 0.980″ and the inner land  185  has a 0.565″ radius. Since the outer hole  150  in the adjoining valve  80  is spaced 1.014″ and the inner hole  130  is spaced 0.615″ from the center  100  of the valve and the check balls  107  have a diameter of 0.125″, the balancing ring  180  serves to retain the check balls  107  in the holes  130  and  150 . The reason for this is the lack of room for such balls to bypass such ring  180  (i.e., 1.079″ minus 0.980″ and 0.565″ minus 0.55″ are both less than 0.125″ ). This simplifies the device. The holes  183  in the balancing ring  180  are 0.100″ in diameter centered on the inner land  184 . The land itself is centered on a 0.817″ radius from the center of the balancing ring. The particular balancing ring  180  has a hardened face adjacent to the valve  80  and its contained check balls  107 . This hardening increases the service life of the device by reducing the speed of physical damage at this location.  
         [0085]    The port plate  110  serves as the physical location for the valving section  80  in addition to providing a location for the pressure and return connections, typically a threaded opening (not shown). It thus completes the structure of the gerotor pressure device  10 .  
         [0086]    Although the invention has been described in its preferred form with a certain degree of particularity, it is to be understood that numerous changes can be made without deviating from the invention as hereinafter claimed. For example the valve is shown with three sets of three holes  120 ,  130 ,  150 . This is primarily due to the design and sizing of the leakage path in the wear plate  27 . This could be modified if desired, for example by eliminating the radial extension  56  or reducing the cross-section of the leakage paths one could use only one set of holes  120 ,  130 ,  150 , producing a lower fluid flow. Similarly if the holes  72  and separate case drain  75  are included, the case drain holes  120 ,  150  might be omitted (in certain parameter designs). Alternate numbers and locations could thus be utilized without deviating from the invention herein.