Abstract:
Rotary seals in a telescoping gear pump/motor a feature that allows the seal to shift radially relative to other components while maintaining the seal integrity and without compromising the function of the bearings or the bushings needed to bear the load.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of the U.S. patent application Ser. No. 11/101,837 filed Apr. 8, 2005. 
   This application claims the benefit of U.S. provisional patent application Ser. No. 60/725,555 filed Oct. 11, 2005. 

   BACKGROUND OF THE INVENTION 
   The present invention relates generally to telescoping gear pumps and motors and, in particular, to a sealing apparatus for such pumps and motors. 
   Gear pumps and motors provide variable displacement capabilities to some of the most hostile environments. The sealing however on these functionally durable pumps with variable displacement has been an issue. The rotary seals on the gears have to be maintained by even as the internal components shift as the pressure in the pump increases. The gears shift away from the pressure causing many of the other pump/motor technologies with telescoping. The present invention provides a method of and apparatus for eliminating this shortcoming in an otherwise robust technology. 
   SUMMARY OF THE INVENTION 
   The rotary pump and motor described in U.S. Pat. No. 815,522 probably worked at the relatively low pressures needed for irrigation. The pressure required to maintain these seals in today&#39;s applications however can be extremely high; so high that the seal may fail completely as the components inside the pump/motor begin to distort even slightly under the operating pressure. The rotary seals of the pump/motor according to the present invention have a feature added to them that allows the seal so shift with the other components while maintaining the seal integrity and without compromising the function of the bearings or the bushings needed to bear the load. 

   
     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 cross section of an internal gear pump/motor according to the present invention; 
       FIG. 2  is a perspective view of the internal gear pump/motor shown in  FIG. 1  with portions in cutaway; 
       FIG. 3  is a cross section of an external gear pump/motor according to the present invention; and 
       FIG. 4  is a perspective view of the external gear pump/motor shown in  FIG. 3  with portions in cutaway. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   U.S. patent application Ser. No. 11/101,837, filed Apr. 8, 2005, is hereby incorporated by reference. U.S. provisional patent application Ser. No. 60/725,555, filed Oct. 11, 2005, is hereby incorporated herein by reference. 
   In the drawings, the components of the external gear pump/motor shown in  FIGS. 3 and 4  are identified with reference numerals that are twenty numbers higher than the reference numerals for similar components of the internal gear pump/motor shown in  FIGS. 1 and 2 . 
   The internal gear pump/motor  10  shown in  FIGS. 1 and 2  includes a hollow seal housing  4  closed at one end by a cap  1 . A tubular rotary seal  3  has a radially outwardly extending flange  3   c  including a downwardly facing annular pressure shift surface  3   a  and an outwardly facing peripheral shift riser  3   b.    
   In order to maintain a seal as the pressure develops in the pump/motor  10 , the seal  3  will shift away from the applied fluid pressure toward the low pressure side of the pump/motor. At low pressures this shifting in minimal and prior art telescoping gear pumps/motors can maintain the seals by simply controlling the tolerance at the interface points between the moving parts. However, as the pressure increases the materials of the pump/motor begin to distort. The pressure distortion forms a gap that runs the length of the seal causing the pump/motor to leak internally. 
   The shift surface  3   a  nests into a matching feature in the seal housing  4  so that the amount of radial distortion that can be tolerated before a leak can begin is the width of the shift surface  3   a.    
   The external gear pump/motor  30  shown in  FIGS. 3 and 4  includes a hollow seal housing  24  closed at one end by a cap  21 . A pair of gears  22  having pluralities of meshing teeth are disposed in the hollow teal housing  24 . The hollow seal housing  24  further includes a first port (not shown) and a second port (not shown) that extend between an internal surface and an external surface thereof. One of the ports is connected to a low pressure segment of fluid system (not shown) such as a reservoir or the like, and another of the ports is connected to a high pressure or pressurized segment of the fluid system. 
   In operation, a shaft of the external gear pump/motor  30  is connected to a prime mover (not shown), such as an electric motor or the like. When the prime mover rotates the shaft, one of the gears  22  rotates and causes the other of the gears  22  to rotate. Fluid is introduced from the fluid system through one of the ports, is trapped between the pluralities of meshing teeth of the gears  22 , and is discharged through the other of the ports. Suitable passages are formed in the hollow seal housing  24  to ensure that the fluid is routed correctly during operation of the external gear pump/motor  30 . Each of the two tubular rotary seals  23  provides a rotating seal between each of the gears  22  and inner surfaces of the hollow seal housing  24  to ensure the integrity of the cavity of the external gear pump/motor  30 . The external gear pump/motor  30  in accordance with the present invention requires only the tubular rotary seals  23  to maintain a seal and allow for efficient operation of the extending gear pump/motor  30 . Each of two tubular rotary seals  23  has a radially inwardly extending step  23   c  including an annular pressure shift surface  23   a  and an outwardly facing peripheral shift riser  23   b . The steps  23   c  face one another and cooperate to permit radial distortion before a leak can begin. 
   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.