Abstract:
The invention concerns a fluid pump with a cylinder, piston and check valve for compressing the fluid having a high-pressure seal for precluding leakage of pressurized fluid. Any leakage from the high-pressure seal feeds back into an inlet area of the pump and recycles through the pump instead of leaking externally.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to the field of pumps and more particularly to a pump with an enhanced high-pressure seal. 
   2. Description of the Related Art 
   High pressure pumps are used in many applications including hydraulic systems, pressure washers and presses. A high-pressure pump is described in U.S. Pat. No. 6,092,370 to Tremoulet, Jr. et al., issued on Jul. 25, 2000 and is hereby incorporated by reference in its entirety. 
   Often, high pressure pumps are used in applications where leaks are a problem. For example, a leaking pump in an airplane may cause the loss of hydraulic fluid. Furthermore, the lost fluid may create an environmental issue or, at least, may create a stain or a slippery area that may contribute to falling or slipping danger. 
   One problem area in high pressure pumps is the high pressure seal which helps keep pressurize fluids inside the pump. At high pressures, some exceeding 100,000 psi, high pressure seals often fail. It is believed that leaking of the high pressure seal may be the most common problems in high pressure pumps. The failure usually begins with a slow leak, wherein the pump is fully functional and only a small amount of fluid is lost. Furthermore, beyond a slight loss in output pressure, leaks from the high pressure seal can also impact other parts of the pump through loss of lubrication, fatigue and corrosion. 
   This problem is known in the industry and has been addressed by many solutions including placing a higher, more even force on the seal. For example, US Publication 2005/0074350A1 to Raghavan, et al., published Apr. 7, 2005, describes a “Device and Method for Maintaining a Static Seal of a High Pressure Pump,” and is hereby incorporated by reference. A pump is described in U.S. Pat. No. 3,966,360 to Greene, issued Jun. 29, 1976. This pump has an outer casing forming a reservoir. Such solutions may improve the performance of such seals, but they do not prevent the problem and, when a seal leaks, the loss of fluid or the resulting spill may cause problems. 
   What is needed is a pump with a high pressure seal in which any leaking in the high pressure seal feed back into the input chamber of the pump. 
   SUMMARY OF THE INVENTION 
   In one embodiment, a pump is disclosed including a cylinder in which a fluid is compressed, an inlet for accepting a fluid into the pump, an inlet area connected to the inlet for transporting the fluid across the pump and a feed tube for transporting the fluid from the inlet area to the cylinder. A check valve is provided to allow the fluid to flow from the feed tube and into the cylinder while blocking the flow of the fluid from the cylinder back into the feed tube. A piston is configured within the cylinder for compressing the fluid and a piston rod is coupled to the piston for exerting force on the piston. The piston is held within the cylinder by a high pressure seal. A high-pressure output port is connected to the cylinder for outputting the fluid under pressure. The high pressure seal interfaces with the inlet area so that any leakage of the fluid through the high pressure seal leaks back into the inlet area. 
   In another embodiment, a method of reducing leakage in a pump is disclosed including providing a fluid into an inlet of a pump, the fluid flowing through an inlet area and flowing through a feed tube and flowing through a check valve and into a cylinder; then applying force to the piston within the cylinder to pressurize the fluid. The check valve prevents the fluid from leaving the cylinder back into the feed tube. The piston and cylinder are sealed using a high pressure seal and potential leakage is captured from the high pressure seal by interfacing the high pressure seal with the inlet area. 
   In another embodiment, a pump is disclosed including a cylinder having a bore in which a fluid may be compressed with an inlet for accepting the fluid into the pump and an inlet area connected to the inlet for conducting fluid across the pump. A feed tube for transports the fluid from the inlet area to a first end of the cylinder and a check valve allows the fluid to flow in one direction into the first end of the cylinder from the feed tube. A piston within the cylinder compresses the fluid whereby a piston rod coupled to the piston exerts force on the piston. A high pressure seal is provided for retaining the piston within the cylinder while retarding the fluid from leaking from the cylinder under pressure and a high-pressure output port is connected to a second end of the cylinder for outputting the fluid under pressure. The high pressure seal interfaces with the inlet area such that any leakage of the fluid through the high pressure seal feeds back into the inlet area. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: 
       FIG. 1  illustrates a pictorial view of a pump of a first embodiment of the present invention. 
       FIG. 2  shows a cross section along line  2 - 2  of  FIG. 1 . 
       FIG. 3  shows a cross section along line  2 - 2  of  FIG. 1 . 
       FIG. 4  shows a cross section along line  2 - 2  of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures. 
   Referring to  FIG. 1 , a pictorial view of a pump present invention is shown. Shown is the pump  10  with inlet  11  providing a source of fluids to the pump. A mounting plate  34  is provided with mounting bolts  32 . Tie rods  24  are provided to maintain pressure on the seals. A piston rod adapter  24  provides reciprocating motion to a piston within the pump  10 , pressurizing the fluid. 
   Referring now to  FIG. 2 , the components of the pump  10  will be described. A mounting plate  34  has mounting bolts  32  for mounting the pump  10  to other equipment. A piston rod  25  couples the piston rod adapter  24  to the piston  26  so that reciprocating motion applied to the piston rod adapter  24  causes the piston  26  to move in and out of the cylinder  27  formed by cylinder walls  29 . An inlet  11  is provided for allowing fluid to enter the pump  10  through the inlet area  13 , where it flows through to a feed tube  24  and enters the cylinder  27  through a first check valve  16  which restricts the direction of flow of the fluid in a direction into the cylinder. In some embodiments, the check valve  16  is a ball  16  made of a hard material such as steel. In some embodiments, the ball  16  prevents a reverse flow of fluids by seating against a seat  19  when reverse pressure is applied. In some embodiments, gravity or fluid pressure seats the ball  16 . In some embodiments, a spring  17  maintains pressure on the ball  16  to reduce back pressure. 
   In some embodiments, a second check valve  18  is adapted within the piston  26 , restricting the direction of flow of fluid, allowing flow from within the cylinder  27  below the piston  26  into the cylinder  27  above the piston  26 . A high pressure seal  14  helps prevent fluid under a high pressure from leaking while a low-pressure seal  12  helps prevent low pressure fluid from leaking. A guide bushing  9  keeps the low pressure seal  12  in place. To prevent external leakage of fluid, the high pressure seal  14  is interfaced and enclosed by the fluid inlet area  13  such that leakage through the high pressure seal  14  will seep into the fluid inlet area  13  and re-circulate through the pump  10  instead of exiting the pump  10 . 
   Referring now to  FIGS. 3 and 4 , the operation of the pump will be described.  FIG. 3  describes the operation of the pump during an up stroke of the piston rod  25 . During this, as the piston  26  moves up within the cylinder  27 , the space vacated by the piston  26  is replaced by fluid entering through the check valve  16  from the feed tube  24 , which receives fluid through an inlet  11 , passing through inlet area  13 . During this movement, fluid from a previous stroke  31  in the cylinder above the piston  26  is prevented from flowing back below the piston  26  by a second check valve  18 , thereby forcing the fluid under high pressure to exit the outlet  29 .  FIG. 4  describes the operation of the pump during a down stroke of the piston rod  25 . During this, the piston  26  moves down within the cylinder  27 , placing a pressure on the fluid already within the cylinder  27 . The check valve  16  prevents the fluid from exiting through the feed tube  24 . Being that the volume of the lower part of the cylinder  27  is greater than the volume of the cylinder above  31  the piston  26 , the fluid is forced through the second check valve  18  and into the upper portion of the cylinder and out the outlet  29  under pressure. 
   Being that the fluid is under a very high pressure, a high pressure seal  14  helps prevent the high pressure liquid from leaking out of the pump. A low pressure seal  12  is provided to help keep low pressure fluids from leaking out of the pump  10 . A guide bushing  9  keeps the low pressure seal  12  in place. Being that the high pressure seal interfaces with the fluid inlet area  13 , any fluid leaking through the high pressure seal  14  will re-circulate through the inlet area  13  and mix with low pressure fluid, flowing back through the feed tube  24  into the pump  10  instead of exiting the pump. 
   Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result. Although the above description describes a double acting pump, in that a symmetrical pressure is created on both the up stroke and the down stroke, the same high-pressure seal and fluid inlet area interface can be equally applied to a single action pump without veering from the present invention. 
   It is believed that the system and method of the present invention and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.