Patent Abstract:
A variable capacity pump/motor has a meshing internal and external gear set disposed between an upper mandrel and a lower mandrel, each including a flange extending towards the gears to divide a pump/motor chamber into suction and discharge chambers. The outer gear is fixed and the internal gear is axially moveable with respect thereto. The inner gear and the upper mandrel move in response to changing pressures in the casing, allowing the motor to vary displacement and the pump to vary its output based on supplied fluid pressure or based on the speed of the prime mover. An external configuration includes a pair of meshing gears mounted on separate shafts in a casing. One gear is fixed and the other is axially moveable with respect thereto and moves in response to changing pressures in the casing. Each of the gears is sealed by a seal/bushing on a free end thereof.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. provisional patent application Ser. No. 60/560,897 filed Apr. 9, 2004. 

   BACKGROUND OF THE INVENTION 
   The present invention relates generally to geared pumps and motors and, in particular, to a variable capacity geared apparatus usable as either a pump or a motor. 
   Numerous types of variable volume gear pumps and motors are found in the prior art. For example, the U.S. Pat. No. 2,293,126 shows a gear pump or motor having a gear housing movable by a lever secured to a stub shaft. 
   The U.S. Pat. No. 2,754,765 shows a variable displacement pump that includes a drive gear and a follower gear that displaces radially when a fluid pressure on an accumulator exceeds a predetermined value. 
   The U.S. Pat. No. 3,110,265 shows a gear type fluid handling device that includes an upper gear movable with respect to a lower gear via a lever. 
   The U.S. Pat. No. 3,588,295 shows a variable output gear pump or motor apparatus that includes an output gear assembly movable relative to an input gear assembly via a control output assembly that diverts fluid to the input side of the pump. 
   The U.S. Pat. No. 4,740,142 shows a variable capacity gear pump with pressure balance for transverse forces that includes a fixed gear and a gear axially movable relative to the fixed gear alternatively via a spring, via hydraulic pressure through bores, and via a controller. 
   The U.S. Pat. No. 5,184,947 shows a fully variable output hydraulic gear pump having an axially translatable gear and a fixed gear. The translatable gear is movable through a gear sleeve via hydraulic pressure controlled by a hydraulic cylinder or a motorized screw. 
   The U.S. Pat. No. 5,306,127 shows a fluid pump with axially adjustable gears having telescoping first and second cylindrical housings and mounted in the pump housing. 
   The U.S. Pat. No. 5,620,315 shows a gear pump for feeding of fluids that includes a fixed gear and a gear that is axially movable between a pair of shiftable walls. 
   The U.S. Pat. No. 5,724,812 shows a variable displacement apparatus that includes housing parts that are interconnected for relative axial movement. 
   The U.S. Pat. No. 6,283,735 shows a variable-delivery external gear pump that includes a steel compression spring that moves one of the gears axially with respect to the other gear based on pressure in the pump casing. 
   The U.S. Patent Application No. 2001/0024618 shows an adjustable displacement gear pump having a follower assembly that is operable to move an idler gear within a pump housing relative to a pump gear in order to vary the output of the pump. The pump gear includes a gear complement and the idler gear includes a gear complement for providing a seal for the gears. The displacement of the pump is varied by moving the follower assembly from a proximal end to a distal end of the pump. The follower assembly moves both the pump gear and the idler gear to vary a pump chamber length. 
   The U.S. Pat. No. 2,484,789 shows a variable displacement pump and motor that includes an outer gear and an inner gear mounted on a shaft and disposed between a pair of bulkheads. Displacement of the pump/motor is varied by moving the bulkhead axially along a shaft. Fluid is introduced to the gears via radial ports formed in the outer gear. 
   The U.S. Pat. No. 3,805,526 shows an embodiment of a variable displacement rotary hydraulic machine having a gerotor assembly that includes an inner element, an outer element, a plug that rotates with the inner element, and a plug that rotates with the outer element. The capacity and/or displacement of the pump or motor are varied by mechanical movement of a locating ring. Fluid is supplied to the elements through ducts. 
   The U.S. Pat. No. 4,492,539 shows a variable displacement gerotor pump having a housing that achieves variable displacement by positioning an axis of an outer rotor eccentric to the axis of an inner rotor by movement of a variator in the housing. The movement of the variator is alternately manual or hydraulic. 
   The U.S. Pat. No. 4,493,622 shows a variable displacement motor that includes an outer gerotor gear and an inner gerotor gear that transmits torque to an output shaft via a wobble shaft. The displacement of the motor is varied by varying the eccentricity between the meshing gears of the gerotor gears. A second embodiment of the motor includes a pair of gerotor gear sets. 
   The U.S. Pat. No. 4,812,111 shows a variable displacement apparatus usable as a pump or motor that includes an inner rotor movable relative to an outer rotor for varying the displacement of the apparatus. A distributor plate guides and directs flow from inlet and outlet ports through integral chambers and to the pump or motor displacement chambers. The distributor plate is fixed axially with respect to the inner rotor. 
   The U.S. Pat. No. 6,244,839 shows a pressure compensated variable displacement internal gear pump that includes an inner gerotor, a port plug, and an outer gerotor axially aligned on a drive shaft. The inner gerotor and the port plug slide inside the outer gerotor and vary displacement of the pump by opening and closing various intake and discharge ports defined by the outer gerotor. 
   The U.S. Pat. No. 6,758,656 shows a multi-stage internal gear/turbine fuel pump that includes a gear pumping module having an internal gear and an external gear and a turbine pumping module attached on a shaft. 
   The U.S. Pat. No. RE 31,067, and the U.S. Pat. Nos. 4,426,199, 4,545,748, 4,563,136, and 4,824,347 show gerotor or internal gear pumps or motors. 
   It remains desirable, therefore, to provide an efficient variable capacity internal or external gear pump. 
   SUMMARY OF THE INVENTION 
   The internal gear pump in accordance with the present invention utilizes a meshing internal and external gear set. The gears are disposed between an upper mandrel and a lower mandrel, each of which mandrels includes a flange extending towards the gears to divide a pump/motor chamber into suction and discharge chambers. The upper mandrel includes spaced apart bores for supplying the suction and discharge chambers. The internal gear is fixed and the outer gear is axially moveable with respect to the fixed internal gear. The moveable outer gear and the upper mandrel move in response to changing pressures in the casing, allowing the motor or engine to vary its displacement and the pump to vary its output based on supplied fluid pressure or based on the speed of the prime mover. 
   The external gear pump in accordance with the present invention is a variable volume motor/engine/pump that includes a pair of meshing gears mounted on separate shafts in a casing. One of the gears is fixed and the other of the gears is axially moveable with respect to the fixed gear and moves in response to changing pressures in the casing, allowing the motor or engine to vary its displacement and the pump to vary its output based on supplied fluid pressure or based on the speed of the prime mover. Each of the gears is sealed by a gear seal/bushing on a free end thereof. 

   
     DESCRIPTION OF THE DRAWINGS 
     The above, as well as other advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
       FIG. 1  is a schematic block diagram of the apparatus according to the present invention operating as a motor; 
       FIG. 2  is a schematic block diagram of the apparatus according to the present invention operating as a pump; 
       FIG. 3  is an exploded perspective view of an internal gear pump/motor in accordance with the present invention; 
       FIG. 4  is a partial cross sectional perspective view of the assembled internal gear pump/motor of  FIG. 3 : 
       FIG. 5  is an partial exploded perspective view of an external gear pump/motor in accordance with the present invention; and 
       FIG. 6  is an exploded partial cross sectional perspective view of the external gear pump of  FIG. 5 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   U.S. provisional patent application Ser. No. 60/560,897 is incorporated herein by reference. 
   There is shown in  FIG. 1  a pump/motor unit  10  according to the present invention operating as a motor. A source of pressured fluid  11  is connected to an inlet of the unit  10  by a line  12  to supply pressured fluid to drive the unit  10  as a motor. A return line  13  is connected to an outlet of the unit  10  to return the fluid to the source  11 . The unit  10  has an output shaft  14  coupled to a load  15 . Pressured fluid from the source  11  causes the unit  10  to rotate the shaft  14  and drive the load  15  which can be, for example, one or more drive wheels of a vehicle. 
   There is shown in  FIG. 2  the pump/motor unit  10  according to the present invention operating as a pump. A source of fluid  21  is connected to the inlet of the unit  10  by the line  12  to supply fluid to be pumped by the unit  10 . The return line  13  is connected to an outlet of the unit  10  to return the fluid to the source  21 . The shaft  14  is coupled to a prime mover such as a combustion engine or electric motor  20 . The prime mover  20  drives the unit  10  via the shaft  14  to generate pressured fluid to a load  22  connected in the return line  13 . 
   Referring now to  FIGS. 3 and 4 , an internal gear apparatus in accordance with the present invention is indicated generally at  100 . The apparatus  100  may be configured to operate as the motor  10  of  FIG. 1  or the pump  10  of  FIG. 2  as will be appreciated by those skilled in the art, but will be referred to as a motor in the following description of the present invention. The internal gear motor  100  includes a hollow housing  102  having a base portion  104  and an end cap  106 . The base portion  104  defines a recess or cavity  108  therein that is sized to receive a first mandrel  110  and a first piston member  112 . The end cap  106  includes at least two ports  107  (only one is shown) that each extend between an internal and an external surface thereof, preferably on opposite sides of the end cap  106 . One of the ports  107  is connected to a high pressure segment of a fluid system (not shown) such as the pressured fluid source  11  of  FIG. 1 , and another of the ports  107  is connected to a return line such as the line  13  of  FIG. 1 . 
   The first mandrel  110  defines an aperture  114  extending through a base portion  111  thereof and includes a first outer flange  116  and a plurality of spaced apart second outer flanges  118  extending upwardly from an upper surface  113  of the base portion  111 . An inner flange  120  extends upwardly from the base portion  111  of the first mandrel  110  and is located adjacent the aperture  114 . The first outer flange  116  is located adjacent the aperture  114 . The second outer flanges  118  are spaced apart from both the aperture  114  and the inner flange  120 . A first seal bushing  122  is sized to rotatably fit in the aperture  114  and is preferably substantially equal in height to the base portion  111  of the first mandrel  110  such that when the bushing  122  is placed in the aperture  114 , an upper surface of the bushing  122  is substantially flush with the upper surface  113  of the base portion  111 . 
   An external gear  124  that is substantially circular in cross section is adapted to be placed atop the upper surface  113  of the base portion  111  wherein a curved outer surface of the gear  124  is adjacent the respective curved inner surfaces of the outer flanges  116  and  118 . The external gear  124  includes a plurality of teeth  126  formed on an inner surface thereof. When placed on the upper surface  113 , the gear  124  is fixed axially between the outer flanges  118  and the inner flange  120 . 
   An internal gear  128  that is substantially circular in cross section includes a plurality of teeth  130  formed on an outer surface thereof and defines an aperture  132  extending therethrough. The teeth  130  are operable to mesh with the teeth  126  formed on the inner surface of the external gear  124 . A lower surface of the gear  128  extends into and rotates with the bushing  122 , wherein the teeth  130  cooperate with corresponding teeth on the bushing  122  when the motor  100  is assembled and operated, as discussed in more detail below. The respective outer surfaces of the teeth  130  of the internal gear  128  are adjacent the inner surface of the inner flange  120 . The aperture  132  is adapted to receive a free end of a drive or output shaft  134  when the motor  100  is assembled. The internal gear  128  is fixed on the shaft  134 . The drive shaft  134  is rotatably supported in the end cap  106  by a bearing  135 , such as a ball bearing, a roller bearing or the like. The free end of the drive shaft  134  extends a predetermined distance beyond the upper surface of the end cap  106  and acts as an output shaft for the motor  100  such as the shaft  14  of  FIG. 1 . 
   A second piston member  136  defines an aperture  138  on an interior portion thereof and is adapted to be mounted on respective upper surfaces of the outer flanges  116  and  118  of the first mandrel  110 . The second piston  136  and the first piston  112 , therefore, are mounted on the upper surface and the lower surface, respectively of the lower mandrel  110 . 
   A second mandrel  140  is adapted to be disposed in the aperture  138  of the second piston member  136  and defines an aperture  142  on an interior portion thereof for receiving the drive shaft  134 . The second mandrel  140  includes a downwardly extending flange  144  that cooperates with the upwardly extending inner flange  120  of the first mandrel  110  when the motor  100  is assembled. The upper mandrel  140  includes a pair of bores  146  extending therethrough for fluid communication with the gears  122  and  124  during operation of the motor  100 . 
   A second seal bushing  148  includes a plurality of teeth  150  formed on an exterior surface thereof and defines an aperture  152  extending therthrough. The second seal bushing  148  is adapted to receive the upper mandrel  140  in the aperture  152  and be received in the external gear  124  and rotates therewith, wherein the teeth  126  cooperate with the teeth  150  on the bushing  148  when the motor  100  is assembled and operated, as discussed in more detail below. 
   When the motor  100  is assembled, the first mandrel  110  and the first piston  112  are placed in the base portion  104  of the housing  102 , the first seal bushing  122  is placed in the mandrel  110 , and the external gear  124  is placed on the mandrel  110 . The internal gear  132  and the second mandrel  138  are mounted on the drive shaft  134  and assembled such that the respective teeth  126  and  130  of the gears  132  and  124  rotatably mesh and the internal gear  132  engages with the first seal bushing  122 . The second piston  136  is attached to the upper surface of the mandrel  110 , and the second seal bushing  148  is placed on the second mandrel  138  and engages with the external gear  124 . The downwardly extending flange  144  cooperates with the upwardly extending inner flange  120  to divide the interior of the external gear into an inlet chamber and discharge chamber of the motor  100  and the upper end cap  106  is attached to the base portion  104  to enclose the housing  102 . The flanges  120  and  144  extend radially between the teeth  126  and the teeth  130  to form the inlet chamber on one side of the flanges and the discharge chamber on the other side of the flanges. 
   In operation, the shaft  134  is connected to a load (not shown), such as a wheel of a vehicle or the like. Pressured fluid is introduced from the fluid system through one of the ports  107 , is routed to the inlet chamber side of the gears  124  and  128  through the bores  146 , acts against the meshing teeth  126  and  130  to rotate the gears and the shaft, flows between the teeth to the discharge chamber and is discharged through the other the bores  146  to the other of the ports  107 . The first seal bushing  122  provides a rotating seal between the internal gear  128  and the first mandrel  110  and the second seal bushing  148  provides a rotating seal between the external gear  124  and the second mandrel  140  to ensure the integrity of the inlet and discharge chambers. The motor  100  in accordance with the present invention requires only the seals  122  and  148  to maintain a fluid seal and allow for efficient operation of the motor  100 . 
   The normal or default spatial relationship between the teeth  126  and  130  of the gears  124  and  128  is such that the teeth  126  and  130  engage substantially all of the axial area of the teeth. In such a relationship, the motor  100  produces its maximum volume flow or maximum output. The motor  100  in accordance with the present invention may advantageously vary from its maximum displacement because the gear  124  is axially movable along the shaft  134 . When the gear  124  moves towards the first mandrel  110 , less of the axial area of the teeth  126  and  130  engage, which reduces the volume flow or displacement of the motor  100 . 
   When the unit  100  is configured as a motor, an external source of pressure, such as hydraulic fluid from an external hydraulic pump, compressed air from an air compressor or the like, provides a volume flow to the ports  107  to spin the gears  124  and  128  and produce an output torque on the shaft  134 . As the pressure is varied, the gear  124  will move along the axis of the shaft  134  in order to vary the output horsepower of the motor  100 . The motor  100  may be advantageously utilized to control output rpm under widely changing output loads including, but not limited to automotive vehicles, turrets, large machinery, earth movers, large well drills, ships, farm equipment, or the like. 
   When the unit  100  is configured as a pump and the prime mover rotates the shaft  134  at a lower speed or with a lower torque, the pump  100  will react to the reduced input speed or input torque by varying its output based on the internal pressures in the pump housing  102 . In this condition, the output port  107  will create a higher back pressure in the discharge chamber, and the gear  124  will move along the axis of the shaft  134  to a point along the axis where the gear  124  is at or near equilibrium to continue operation. The pump  100 , therefore, can vary from a maximum output or displacement where the gear  124  is substantially adjacent the upper mandrel  140  to a minimum displacement where the gear  124  is substantially adjacent the lower mandrel  110 . 
   Referring now to  FIGS. 5 and 6 , an external gear apparatus in accordance with the present invention is indicated generally at  200 . The apparatus  200  may be configured to operate as a pump or a motor as will be appreciated by those skilled in the art, but will be referred to as a pump in order to simplify the description of the present invention. The external gear pump  200  includes a hollow housing  202  having a first end cap  204  and an second end cap  206  connected by a body portion  208 . Preferably, the first end cap  204  and the second end cap  206  are attached to the body portion  208  by a plurality of fasteners  210 , such as high strength bolts or the like. The body portion  208  defines a recess  212  therein. 
   A first gear  214  having a plurality of teeth  216  formed on an external surface thereof and a second gear  218  having a plurality of teeth  220  formed on an external surface thereof are adapted to be disposed in the recess  212  of the housing  202 . The teeth  216  and  220  of the respective gears  214  and  218  are operable to rotatably mesh in the recess or pump cavity  212  during operation of the pump  200 . The first gear  214  has a shaft  222  extending therefrom and the second gear  218  has a stepped shaft  224  extending therefrom. The first gear  214  is fixed on the shaft  222  and the second gear  218  is fixed on the shaft  224 . The shafts  222  and  224  extend in opposite axial directions and the shaft  224  is greater in length than the shaft  222 . A first seal sleeve  226  having internal teeth receives the first gear  214  and a second seal sleeve  228  having internal teeth receives an end of the second gear  218 . 
   A plate fitting  230  includes a flange  232  extending downwardly therefrom and is attached to a first thrust plate  234  on a planar upper surface thereof. Preferably, the thrust plate  234  is attached to the fitting  230  by a plurality of fasteners  236 , such as high strength bolts or the like. A free end of the shaft  222  extends through an opening formed in the fitting  230  and the thrust plate  234 . The free end of the shaft  222  is rotatably secured in the fitting  230  and the thrust plate  234  by a pair of nuts  238  and is rotatably supported by a bearing  240 , such as a ball bearing, a roller bearing or the like. The second seal sleeve  228  is operable to be received in a recess in the fitting  230  adjacent the flange  232 . When the shaft  222  is mounted in the fitting  230  and the thrust plate  234 , the gear  214  and the fitting  230  are movable axially with respect to the housing  202 . 
   A second thrust plate  242  is attached to an upper surface  205  of the first end cap  204  by a plurality of fasteners  244 , such as high strength bolts or the like. The plate  242  includes an aperture for receiving a free end of the shaft  224  and a larger aperture for receiving and locating the first seal sleeve  226  adjacent the upper surface of the first end cap  204 . The free end of the shaft  224  extends through the aperture in the plate  242 , threadably engages a pair of nuts  246  at the step and is rotatably supported by a bearing  248 , such as a ball bearing, a roller bearing or the like. The bearing  248  is preferably disposed in a cavity  250  formed in the upper surface  205  of the first end cap  204  while the nuts  246  attach the shaft  224  to the end cap on a lower surface opposite the upper surface  205 . The free end of the shaft  224  extends a predetermined distance beyond the lower surface of the end cap  204  and acts as a drive shaft or output shaft for the pump  200 . 
   The body portion  208  defines a first port  252  and a second port  254  that each extend between an internal and an external surface thereof. One of the ports  252  and  254  is connected to a low pressure segment of a fluid system (not shown) such as a reservoir or the like, and another of the ports  252  and  254  is connected to a high pressure or pressurized segment of a fluid system. 
   In operation, the shaft  224  is connected to a prime mover (not shown), such as an electric motor or the like. When the prime mover rotates the shaft  224 , the gear  218  rotates and causes the gear  214  to rotate. Fluid is introduced from the fluid system through one of the ports  252  or  254 , is trapped between the meshing teeth  216  and  220  as is well known in the art and is discharged through the other of the ports  252  or  254 . Suitable passages are formed in the housing  202  to ensure that the fluid is routed correctly during operation of the pump  200 . The first seal sleeve  226  provides a rotating seal between the first gear  214  and the upper surface  205  and the second seal sleeve  228  provides a rotating seal between the second gear  218  and the fitting  230  to ensure the integrity of the pump cavity  212 . The pump  200  in accordance with the present invention requires only the seal sleeves  226  and  228  to maintain a seal and allow for efficient operation of the pump  200 . 
   The normal or default spatial relationship between the teeth  216  and  220  of the gears  214  and  218  is such that the teeth  216  and  220  engage substantially all of the axial area of the teeth. In such a relationship, the pump  200  produces its maximum volume flow or maximum displacement. The pump  200  in accordance with the present invention may advantageously vary from its maximum displacement because the first gear  214  is axially movable. When the first gear  214  moves towards the lower thrust plate  242 , less of the axial area of the teeth  216  and  220  engage, which reduces the volume flow or displacement of the pump  200 . Typically, this will occur when the prime mover rotates the shaft  224  at a lower speed or with a lower torque and the pump  200  will react to the reduced input speed or input torque by varying its output based on the internal pressures in the pump housing  202 . In this condition, the output port  252  or  254  will create a higher back pressure in the recess  212 , and the first gear  214  together with the fitting  230  will move along the axis of the shaft  224  to a point along the axis where the gear  214  is at or near equilibrium to continue operation. The pump  200 , therefore, can vary from a maximum output or displacement where the gear  214  is substantially adjacent the gear  218  to a minimum displacement where the gear  214  is substantially adjacent the lower thrust plate  242 . 
   When the apparatus  200  is configured as a motor, an external source of pressure, such as hydraulic fluid from an external hydraulic pump, compressed air from an air compressor or the like, provides a volume flow to the ports  252  and  254  to spin the gears  214  and  218  and produce an output torque on the shaft  224 . As the pressure is varied, the first gear  214  will move along the axis of the shaft  224  in order to vary the output horsepower of the motor  200 . The motor  200  may be advantageously utilized to control output rpm under widely changing output loads including, but not limited to automotive vehicles, turrets, large machinery, earth movers, large well drills, ships, farm equipment, or the like. 
   In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.

Technology Classification (CPC): 5