Abstract:
A hydraulic brake is interconnected to two ports of a hydraulic motor, the pressurization of either port will act on a unitary brake piston to deactivate a spring loaded brake.

Description:
BACKGROUND OF THE INVENTION 
     Hydraulic pressure devices are efficient at producing high torque from relatively compact devices. However, the ability of an unaided hydraulic motor alone to retain an associated shaft in a certain preset braking position is limited due primarily to volumetric fluid bypass. Therefore typically if hydraulic pressure devices are going to be utilized in applications necessitating braking forces on a shaft, a separate brake is utilized. 
     DESCRIPTION OF THE PRIOR ART 
     Hydraulic pressure devices with auxiliary brakes are well known in the art. Examples include U.S. Pat. No. 3,960,470, U.S. Pat. No. 3,536,230, U.S. Pat. No. 3,616,822, U.S. Pat. No. 4,981,423, U.S. Pat. No. 3,969,950 and ACT/US/83/01683. 
     These brakes, while serviceable, necessitate complicated housing parts, a separation of the brake from the hydraulic motor and/or auxiliary brake actuation lines. Each of these additional components adds to the complexity of the overall device, increasing the manufacturing, maintenance and other cost potentates to the brakes. In addition, frequently additional auxiliary components are necessary in order to provide for the desired braking function. 
     The present invention is designed to provide a simple hydraulic brake which is more adaptable than that of the prior art. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to simplify the construction of hydraulic brakes. 
     It is another object of the present invention to increase the reliability of hydraulic brakes. 
     It is a further object of the present invention to strengthen hydraulic brakes. 
     It is still another object of the present invention to reduce the cost of hydraulic braking mechanisms and their controllers. 
     It is yet another object of the present invention to increase the adaptability of hydraulic motors. 
    
    
     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 
     FIG. 1 is a longitudinal cross-sectional view of a spring applied pressure release hydraulic pressure device incorporating the invention of the application. 
     FIG. 2 is a lateral view of the back of the housing of FIG. 1; 
     FIG. 3 is a cross sectional view of the activating piston of FIG. 1; 
     FIG. 4 is a cross sectional view of the back of the housing of FIG. 2; 
     FIG. 5 is a comparative view of the surface areas of the two activation cavities of the piston of FIG. 3; 
     FIG. 6 is a lateral view of the front of the housing of FIG. 1; 
     FIG. 7 is an end view of a reaction disk utilized with the brake of FIG. 1; 
     FIG. 8 is an end view of a brake disk utilized with the brake of FIG. 1; and, 
     FIG. 9 is a partial view of a pressure applied spring release pressure device. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention relates to an improved hydraulic brake. The invention will be described in its preferred embodiment of a hydraulic brake utilized with a hydraulic gerotor motor. 
     The brake includes a housing  10 , a driveshaft  60 , a braking mechanism  100 , and, in the preferred embodiment disclosed, a power mechanism  200 . 
     The housing  10  serves to physically support and locate the driveshaft  60  and the braking mechanism  100 , as well as typically mounting the power mechanism  200  to its intended use such as a mower, a scissorlift, a winch or other application. 
     The particular housing of FIG. 1 includes a central cavity  11  having two needle bearings  21 ,  41  rotatively supporting the driveshaft therein. A shaft seal  24  is incorporated between the cavity  11  and the driveshaft  60  in order to contain the operative fluid within the housing  10 . Due to the fact that the cavity surrounding the shaft  40  in the housing  10  may be subjected to relatively high pressure fluid, a thrust bearing  22  is incorporated between the shaft  60  and the housing  10  to absorb any forces axially of the shaft  60 . 
     The particular housing  10  disclosed is constructed of a front part  20  and a back part  40 . 
     The front part  20  of the brake in the embodiment disclosed utilized to interconnect the housing  10  to the mechanism with which it will be utilized. This could be a frame, flange or other typically fixed member. The front part  20  of the housing  10  also serves as the reaction member for the later described brake mechanism  100 . 
     The front  20  of the housing has substantially all its machined surfaces formed therein from one side thereof. This facilitates the alignment of the machined surfaces thereby reducing the cost of the brake assembly  100  as well as increasing service life. The major concentric surface which is machined in the front of the housing shown include the area surrounding the oil seal  24  and the surface  26  on one side of the activating piston for the brake mechanism  100 . The additional lateral end  30  of the front  20  of the housing where it abuts the back  40  of the housing is also machined. The remainder of the surfaces of the front  20 , except for the front bearing  21 , have clearances to any adjoining part, thus removing the necessity of any machining thereof. 
     The oil seal  24  itself is located directly next to the main bearing  21  in a seal cavity formed in the front  20  of the housing  10 . 
     On the other side of the main oil seal  24  a small protrusion  23 , extending inwardly of the inner rest of the front of the housing, that locates the seal  24  axially in the housing while also aiding in retaining the shaft  60  in location in respect to the remainder of the brake assembly  100  via the thrust bearing  22  off of the end of a shoulder on the drive shaft  60 . 
     The back part  40  of the housing  10  serves to contain most of the operative members of the brake mechanism  100 . The particular back part  40  disclosed in addition contains both ports  31 ,  51  for the brake as well as serving as the location for interconnection of the later described power mechanism  200 . 
     In respect to the back  40  of the housing, the major areas which are machined include the surfaces adjoining the cavity seals  47 ,  49  (later described), the surface of the main housing seal  25  and the rear bearing  41 . A reduced area  45  in combination with aggregate clearances about such reduced area  45  eliminates the need to machine most of the inner-surface of the back  40  of the housing while also providing for an integral reservoir for the oil which is contained in the cavity  11  of the housing. 
     The driveshaft  60  is rotatively supported to the housing  10  by bearings  21 ,  41 . This driveshaft serves to interconnect the later described power mechanism  200  at the other end of the shaft  60  to the outside of the device. 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). The particular driveshaft  60  includes an axially located hollow which has internal teeth  63  cut therein. This hollow provides room for the wobblestick of the later described power mechanism  200  while the internal teeth  63  drivingly interconnect the driveshaft  60  with such wobblestick  201 . Additional teeth  202  at the other end of the wobblestick  201  drivingly interconnect the wobblestick to the rotor of the later described power mechanism, thus completing the power generating drive connection for the device. 
     The brake mechanism  100  can be utilized by itself or in combination with a power mechanism  200 . 
     The preferred particular shaft  50  is interconnected to a brake mechanism  100  and a drive mechanism  200 . 
     In the preferred embodiment disclosed, the drive mechanism  200  is a modification of the White Model RE Rotor Valved Motor, disclosed with a more complete explanation in White U.S. Pat. No. 4,697,997, the contents of which are incorporated by reference. Other example drive mechanisms include the Eaton Rotary Valve Motors (disclosed in U.S. Pat. No. 3,572,983), the TRW Orbiting Valve Motors (disclosed in U.S. Pat. No. 3,452,680) and Shaft Valved Gerotor Motors (disclosed by example in U.S. Pat. No. 4,285,643). Vane motors or piston motors could also be utilized. If no drive is provided, a plate (not shown) would be utilized to seal the opening in the back  56  of the housing, thus preventing internal contamination while also allowing for the selective pressurization of the later described deactivation cavity  32 . The White Hydraulics&#39; Closed Center Hydraulic Power Unit (such as that in White U.S. Pat. No. 4,877,383), an electric motor, or other power unit could also be utilized, the contents all of which are incorporated by reference. Note that in certain of these devices separate external piping may be appropriate between the brake ports  31 ,  51  and the associated devices. This would allow for a single brake unit to be utilized with many differing manufacturer&#39;s units with no extensive redesign of either. It would also allow filters, coolers, valves, and other ancillary parts to be easily incorporated as well as infield non-evasive repairs. 
     The brake mechanism  100  is the main braking device for the shaft  60 . The particular brake mechanism  100  disclosed includes a spring activated piston  102 , a spring  108 , braking plates  110 , and reaction plates  120 . 
     The brake mechanism  100  preferably surrounds the shaft  60  located between the two bearings  21  and  41 . This allows the bearings to primarily absorb any radial forces on the shaft  60 . 
     The brake assembly shown is spring activated and hydraulic pressure released (FIG.  1 ). If desired, alternate activation mechanism can be utilized such as pressure applied spring released brakes (FIG.  9 ), mechanical activation, and other systems. 
     The activating piston  102  is the main operation control for the brake mechanism  100 . The activating piston  102  itself is located in a stepped recess  13  in the housing  10 . The activating piston and stepped recess together define two fluidic cavities  32 ,  52  on a single side of the activating piston. Opposing these cavities  32 ,  52  is a set of actuation springs  108  located on the opposing side of the piston  102  between such piston and the front part  20  of the housing. 
     In the embodiment disclosed, a number of actuation springs  108  are located substantially equally spaced about the shaft  60  within a concentric activation cavity in the front  20  of the housing. The springs are retained radially and circumferentially located in position by small pockets  109  formed in the piston  102  of the brake mechanism  100 . Alternately the activation springs  108  could be located by pins in either or both of the front  20  of the housing or the piston  102 , or other means. The total force of the springs  108  are chosen sufficient to provide the main braking force for the brake mechanism. 
     The piston  102  is the major operating mechanism for the disclosed embodiment. Typically, the actuation springs  108  bias the piston  102  against the brake  110 /reaction  120  disks stack to the opposite side  43  of the housing  10 , thus to prevent the rotation of the shaft  60 . However, upon selective interconnection of either the port  31 ,  51  to a source of high pressure, a deactivation cavity  32 ,  52  is pressurized, thus overcoming the force of the actuation springs  108  so as to release the brake. Two seals  27 ,  29  located between the piston  102  and the housing  10  (seal  27  to the front  20  and seal  29  to the back  40 ) retain the pressure in deactivation cavity  32  while two seals  47 ,  49  located between the piston  102  and the back  40  of the surrounding housing  10  retain the pressure in the deactivation cavity  52 , thus allowing for the deactivation of the piston  102 . Note in the embodiment disclosed the seals  29 ,  49  are coextensive. This reduces the cost and complexity of the device. Optionally, the seals could be separate with or without a second activating piston (i.e., one piston for each cavity). 
     In the preferred embodiment disclosed, the selective pressurization of the cavities  32 ,  52  between the housing  10  and the piston  102  are designed to selectively operate the brake and release same. 
     In the embodiment disclosed, the first cavity  32  is connected to one fluid port  31  while the second cavity  52  is interconnected to the other port  51 . Due to this interconnect the selective pressurization of either or both ports  31 ,  51  will activate the piston  102  and thus release the brake. 
     In the preferred embodiment disclosed, the first cavity  32  is located radially displaced from the second cavity  52  substantially radially inward thereof. This provides for a shorter device than would be possible without this radial displacement and axial overlap. This orientation is therefore preferred. 
     The deactivation cavities have many unique properties. 
     For example, there are two cavities, either or both of which will release the braking mechanism. Further these cavities can accomplish this function connected with an allied device fluid connection (for example the two fluid ports of a gerotor pressure device as shown in the preferred embodiment), to one or the other, or even independently thereof. Further, both parallel or series connections could be utilized. This provides for a very flexible brake. 
     A further example, the pin  122  serves both to interconnect the reaction disks  120  to a surrounding member (the piston  102 ) while in addition preventing the rotation of the piston  102  (and thus the reaction disks  120 ) in respect to the housing  10 . This further simplifies the construction of the brake. 
     Additional example since one cavity is located radially outward of another cavity, the braking mechanism is shorter than it otherwise would be. This also allows for multiple use of parts (i.e., the piston  102  and seal  49 ). This further simplifies the construction and operation of the brake. The location of the pins  122  overlapping both cavities further shorten the unit. 
     As previously set forth, the ports  31 ,  51  may or may not be coextensive with the pressure and return ports of an hydraulic drive mechanism. If coextensive (as shown), operation of the hydraulic drive mechanism in either direction would automatically release the brake. This coextensive connection could be provided externally or internally of the housing. 
     If the ports  31 ,  51  are not coextensive (or if no drive mechanism is provided) separate control of the brake is possible by one, the other, or both ports. This provides for a very flexible brake. 
     Further to above, the surface area of the cavities  32 ,  52  are designed to be substantially equal, irrespective of their radial displacement. This provides for a substantially equal movement of the piston  102  for a given pressure no matter which cavity  32 ,  52  happens to be pressurized. As the preferred embodiment disclosed is utilized in a device having substantially equal forward and/or reverse capabilities of the power mechanism  200 , this substantial equalization is preferred. 
     For example in FIG. 5, the inside cavity  32  has an outer radius of some 2.31″ and an inner radius of some 1.26″, leaving a total surface area of some 11.78 square inches while the outside cavity  52  has an outer radius of some 3.0″ and an inner radius of some 2.31″ leaving a total surface area of some 11.5 square inches, an insignificant difference of less than 2%. 
     If differential action is desired, this can be easily accomplished by providing for the selected differential of surface area between the two cavities  32 ,  52 . For example, if the manufacturer wanted a quick (or slow) release of the brake for pressurization of one port, the surface area for the cavity of such port would be increased (or decreased respectively). Some spring adjustment might also be appropriate. Additional example, if the manufacturer wanted the brake to release only if both ports were pressurized, each cavity would be sized insufficient to overcome the activation springs alone. The area  129  behind the piston  102  can also be used for brake control differential. 
     The particular brake mechanism  100  disclosed is spring actuated/pressure released. 
     To accomplish the actuation a series of springs  108  are located circumferentially about the activating piston  102  extending between such piston and the front part  20  of the housing  10 . These springs  108  together serve to bias the activating piston  102  in brake activated position against the side  43  of the back of the housing  10 . Thus the default position of the brake mechanism  100  is in a braking condition. 
     The particular braking plates  110  are a series of braking plates interconnected to the shaft  60  interleaved with a series of reaction plates  120  which are interconnected to the housing  10 . 
     The braking disks  110  as shown have a series of projections or tabs  112  extending into the inner hole  113  of the disk  110 . These tabs  112 , preferably 3 to 15 in number, cooperate with a series of tabways  62  extending longitudinally inwardly in the outer circumference of the shaft  60 . The cooperation between the tabs  112  and the tabways  62  solidly interconnect the braking disks  110  to the shaft for rotation therewith. This construction is simple while at the same time providing for an accurate interconnection between the braking disks  100  and the drive shaft  60 , this in contrast with the more conventional triangular splines normally used for this interconnection. Further, the significant width of the tabs  112  efficiently pass the torque between the braking disks  110  and the shaft  60  on which the braking disks  110  are mounted. 
     In the particular preferred embodiment disclosed, the braking disks  110  are substantially 4″ in diameter having a 1.9″ inner hole  113  formed therein. There are six tabs  112  some 0.38″ long and 0.15″ thick leaving a spacing of 1.59″ between opposing tabs. The disks themselves are 0.072″ thick. There are six tabs  112  and four braking disks  110  utilized in the preferred embodiment disclosed. The spline has a pressure angle of substantially 30° (20° to 40° range) and an inner extension of 0.07″. Both sides of the disks  110  include a 0.5″ band of friction material such as sintered bronze. 
     The drive shaft  60  and the tabways  62  therein are sized to substantially match the dimensions of the inner hole  113  and the tabs  112  respectively with a 0.01″ to 0.015″ radial and circumferential clearance. 
     Alternating with the braking disks  110  are a series of reaction disks  120  (FIG.  7 ). These reaction disks are interconnected with a fixed surrounding part in a non-rotative manner. The number of reaction disks is preferably substantially the same as the number of braking disks. Since any rotation of the reaction disks  120  in respect to the housing  10  would allow for some lash, it is preferred that the reaction disks  120  are supported solidly against rotation to a fixed surrounding part, typically directly or indirectly to the housing. In the preferred embodiment, this solid connection is provided by a series of a number of pins  122  pressed into holes in a part about the reaction disks  120 . These pins  122  interconnect with corresponding grooves  108  cut into extended areas  121  about the outer diameter of the reaction disk  120 . The number of pins and grooves can vary as necessary or desired. Three to eight are preferred; four are shown. This construction allows for the accurate location of the reaction disk  120  in respect to the adjoining part via four accurately drilled holes for the pins  122 , thus for more precisely locating the reaction disk  120  while avoiding brake lash. Further, this is accomplished without the necessity of machining the adjoining part of the brake assembly  100  about the disks  120  thus keeping cost at a minimum. 
     In the particular preferred embodiment disclosed, the reaction disk  120  is substantially 4″ in diameter having a 2.2″ inner hole formed therein. There are four extended areas  121  some 0.17″ long extending off of the outer circumference of the disk  125 . Four 0.31″ semi-circular grooves  123  are centered on the extended areas  121  at a 4.35″ diameter bolt circle. The disks themselves are approximately 0.07″ thick. They are coated with a reaction material such as iron phosphate on both sides. 
     The pins  122  are sized to substantially match the grooves  123 . The opening in the adjoining part containing the disks has a diameter slightly greater than the 4.35″ diameter of the disks. 
     The braking plates  110 , being indexed to the shaft  60 , rotate equally with the shaft  60 . The reaction plates  120  remain in a stationary position due to the contact of the series of positioning pins  122  with the grooves  108  in the reaction plates  120 . 
     In cooperation with the activating piston  102  (FIG.  1 ), the pins  122  serve both to affix the reaction disks  120  to the piston  102  and also serve to retain the activating piston  102  (and hence the reaction disks  120 ) in position in respect to the housing  10 . 
     In respect to the former, a semi-circular groove  103  in the piston  102  captures the pins  122  against any circumferential movement, thus tying the reaction disks  120  to such piston. This interconnection is strengthened by the pins  122  axial extension  124  within the main body of the piston. This extension  124  further ties the pins  122  to the piston by holding the pins  122  in the groove  103  as well as resisting any angular shifting of the pins  122  in respect to the piston  102 . 
     In respect to the latter, the small stub extension  127  of the pin  122  extending beyond the piston  102  cooperates with holes  28  in the front  20  of the housing  10  to locate the piston and prevent rotation of the piston  102  (and thus the reaction disks  120 ) in respect to the housing. For the former the pins  122 , being captured in the holes  28  in the housing, do not allow rotary movement of the reaction disks  120  in respect to the housing. For the latter the holes  28  are slightly (0.01-0.05″) larger in diameter than the pins  122 . This allows some motion between the pins  122  and the housing  10  in line with the longitudinal axis of such pins  122 . This allows for the unimpeded actuation/deactuation movement of the piston  102  along such axis. 
     In the embodiment shown, as the pins  122  are subjected to relatively high pressures (for example during the pressurization of the deactivation cavity  32 ) the pins  122  are sealed to the piston  102  at least somewhere in the extension  124 . This prevents fluid flow by therebetween. In the example shown, this seal is provided by utilizing a press-type fit between the pin and piston (a 0.312″ diameter pin is pressed into a 0.281″ hole). A separate seal or other fluid retention means could also be utilized in addition/instead of this press fit type seal if desired and/or appropriate. 
     In cooperating with the piston  102 , the pins  122  serve to affix the reaction disks  120  directly to the housing  10 . The pins  122  otherwise function as previously described. 
     The particular pins  122  disclosed are some 1.625″ in length and 0.313″ in diameter. As previously set forth, these pins are pressed into four 0.281″ diameter holes in the piston on a 4.35″ diameter bolt circle. The free ends  127  of the pins extend some 0.3″ beyond the face of the piston  102 . The ends  127  of the pins themselves are located in four 0.35″ diameter holes  28  in the front  20  of the housing, again on a 4.35″ diameter bolt circle. The pins  122  thus cooperate with the housing to allow axial but not rotary movement of the piston  102  (and with it the reaction disks  120  to release the brake). 
     In this brake mechanism  100 , the pressurization of either cavity  32 ,  52  will cause the activating piston  102  to move differentially in respect to the springs  108  and thus release the contact between the braking plates and reaction plates, thus deleting the braking function of the device. 
     In the preferred embodiment disclosed, the ports  31 ,  51  also serve to provide pressure and return to the power mechanism  200 . Therefore, upon pressurization of a pertinent port  31 ,  51  to operate the power mechanism  200 , the brake mechanism  100  will also be deactivated. This eliminates the needs for any braking valves, external fluidic connections, or other more complicated parts to provide for an integrated motor/brake operation (unless such connections, parts, etc. are desired). In this operation, since the cross-sectional area of the cavities  32 ,  52  (as shown) are substantially equal the braking release/actuation operations will be substantially identical no matter how the power mechanism  200  is operated. With differing cross sections, alternate actuation times and strengths can be provided. 
     In addition to the activating side of the piston  102  there is also an area  129  behind the piston  102  which is sealed off from the pressure/return fluid of ports  31 ,  51 . This area  129  behind the piston thus provides for an additional control element over the brake mechanism  100 —control which can be operated irrespective of the control provided by the rest of the brake mechanism  100 . 
     The additional control includes plain operation, vented operation, charge compensation and/or a separate additional brake actuator. 
     In the plain operation of the area  129  behind the piston, this area would not be subject to any additional interconnections. Thus the control of the brake would be subject entirely to the pressurization of the cavities  32 ,  52 . (Note that in certain instances, it may be advantageous to provide a bleed off path for this area  129  behind the piston so as to prevent any high pressure build-up due to incidental leakage past the seals for the cavities  32 ,  52 . Such a bleed off could be provide by extending a small hole from the area  129  to the area around the driveshaft  60  inward of the bearing  21 . This would allow any incidental high pressure fluid to pass through the bearing  21  and associated dust seal. As this bypass fluid would be minimal, the overall operation of the device would not be compromised by its addition.) 
     In the venting operation of this area  129  behind the piston, a dedicated venting mechanism would interconnect the area behind the piston in a controlled manner to an area of lower pressure. This venting could be provided through a dual action valve to the return port, or otherwise as desired. A separate line  130  is shown in representational form. Some sort of mechanism in this interconnection would allow for control of the degree of venting. This could provide, for example, a control of the speed of the braking mechanism  100  by impeding the passage of fluid through the vent. 
     Note, however, that in the preferred embodiment disclosed the overall movement of the piston  102  is sufficiently small that precise control would be difficult. 
     In the charged compensation mode, it is possible under certain circumstances that both ports  31 ,  51  would be actuated (i.e. both ports would be subjected to pressure above return pressure up to and including equal pressure on both ports). Under these circumstances, an additional port (again numbered  130 ) connected to the area  129  behind the piston can modify the operation of the brake mechanism  100  to other than the brake release action which could otherwise be provided by the pressurization of the two cavities  32 ,  52 . This is especially true since the total area behind the piston  102  in the embodiment disclosed is substantially equal to the sum of the cross-sectional areas of the two activating cavities  32 ,  52 . 
     The area  129  behind the piston can, in addition, be used as a separate brake actuator. In this embodiment, a port  130  would again be provided for interconnection via a separate valve to the source of high pressure. As the area  129  behind the piston is substantially equal to the first and second cavities combined area, upon full pressurization of all three ports  31 ,  51  and  130 , the brake mechanism will remain in a braked condition—the pressure on both sides of the piston would cancel out allowing the spring  108  to continue to apply the brake. However, upon reduction of the pressure of the area  129  behind the piston, the brake would be released—the pressurization in the first and second cavities  32 ,  52  would be greater than the forces of the springs  108  in combination with the fluidic pressure in the area  129  behind the piston. For this reason, the brake can be activated via the port  130  totally separately of the pressure of the two ports  31 ,  51 . 
     The pressure mechanism  200  is a device associated with the brake to provide for selective rotation of the shaft  60 . The particular pressure mechanism disclosed operates according to the principles of U.S. Pat. No. 4,697,997 entitled Multiplate Manifold and U.S. Pat. No. 4,717,320 entitled Balancing Plate the contents of which are incorporated by reference. 
     In this power mechanism, one port  31  is interconnected to the area about the wobblestick  201  while the other port  51  is interconnected through a passage in the housing  20  and passages in the multiplate manifold to the valving groove  204  in the rotor of the device. With this internal connection upon pressurization of the port  31 , the deactivation cavity  32  and the center opening of the rotor will be pressurized. This in turn will release the brake mechanism and allow the shaft to rotate in one direction. With this same setup, on pressurization of the other port  51 , the deactivation cavity  52 , and the outer valving groove  204  of the rotor would be pressurized. This would also release the brake mechanism and allow the shaft to rotate in the opposite direction. 
     Note in certain applications an automatic brake release might be desired in one but not both directions. Under this type of application, one fluid connection to a cavity would be interrupted by a valve. This would also allow for a feathered brake release. 
     Other pressure mechanisms and connections could be substituted if desired. For example, if the power mechanism  200  was a closed center motor, such as that shown in White U.S. Pat. No. 4,877,383 issued Oct. 31, 1989, there would be a series of four ports for fluidic interconnection (two for the brake mechanism  100  and two for the gerotor motor pressure mechanism  200 ). These ports could be connected in parallel (for simultaneous brake release/rotation as previously described). Two ports in parallel and two independent (this would allow brake release and rotation for the parallel port pressurization while allowing independent control for the outer ports), using the port  130  further increases the adaptability of the device from slowing brake release time to actively overriding the two other ports. 
     Although the invention has been described in its preferred embodiment 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.