Patent Publication Number: US-2005133095-A1

Title: Ball check for pressure test port

Description:
FIELD OF THE INVENTION  
      This invention relates generally to ball check valves and more particularly to ball check valves wherein the ball is translated to a sealed position by fluid pressure across the ball.  
     BACKGROUND  
      Hydraulic devices, such as automatic transmissions for vehicles, have fluid passages interconnecting various operating elements, such as pistons and valves. It is desirable to provide a test port for connecting fluid test equipment to these passages while the hydraulic equipment is being tested. It is desirable that the test port provides a simple means for fluid connection between a test probe and a fluid passage. It is also desirable that the test port reliably seals air and debris from the fluid passage once testing is complete.  
     SUMMARY OF THE INVENTION  
      Accordingly, an aspect of the present invention is to provide a test port which reliably seals air and debris from a fluid passage and facilitates measuring pressure within the fluid passage.  
      In accordance with these aspects, a ball-check assembly is provided which has a ball in a conical retaining chamber with an open proximate end having an inner diameter greater than the diameter of the ball and an open distal end having an inner diameter less than the diameter of the ball, and a conical wall extending between the proximate and distal ends. The ball is located in the conical retaining chamber and becomes wedged against the conical wall as the ball is moved from the proximate end toward the distal end. A seal is thereby provided between the open proximate and open distal ends of said conical retaining chamber.  
      Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross-section diagram of a prior art ball check; and  
       FIG. 2  is a cross section diagram of a redesigned ball check. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Turning now to  FIG. 1 , a cross section diagram of a prior-art ball check is shown. A hydraulic device  1  has a housing  10 . The housing  10  contains a fluid passage  16  in communication with a test passage  18 . The fluid and test passages  16 ,  18  are covered by a plate  12 , which may include a fluid passage  14  for fluid communication with other passages (not shown). The test passage  18  is in fluid communication with a retaining chamber  19 , which retains a ball  20 . The ball  20  rests upon an annular ball seat  26  to seal test passage  18  from a proximate end of probe passage  24 . A conical test probe lead-in  22  is provided at a distal end of probe passage  24 . The test probe lead-in  22 , test passage  24 , annular ball seat  26 , and retaining chamber  19  are coaxially aligned along an axis substantially normal to exterior surface plane  15 . The exterior surface  15  is generally exposed to the environment.  
      During a test period, a test probe (not shown) is pressed against the probe lead-in  22 . A stylus, which is integral to the probe, protrudes through the probe passage  24  and lifts ball  20  from the annular ball seat  26 . The fluid port  16  is thereby in fluid communication with the probe passage  24 , and fluid pressure within the passage  16  is measured by the test probe at test passage  24 .  
      The test probe and stylus are withdrawn at the end of the test period, allowing the ball  20  to seat against the annular ball seat  26 . The ball is urged against the seat by a difference in fluid pressure between test passage  18  and probe passage  24 .  
      When the difference in fluid pressure is minimal, such as when passage  16  is unpressurized, ball  20  may vibrate and lift from the annular ball seat  26 . With the ball  20  lifted, and test passage  18  exposed to the environment, an undesirable opportunity arises for foreign material, such as debris, air, or water, to pass between the ball  20  and annular ball seat  26  and compromising the fluid within fluid passage  16 .  
      Turning to  FIG. 2 , a hydraulic device  2  having an improved check ball assembly is shown in cross section. A hydraulic device  2  has a housing  30 . The housing  30  contains a fluid passage  36  in communication with a test passage  38 . The fluid and test passages  36 ,  38  are covered by a plate  12 , which may include a second fluid passage  14  for fluid communication with other passages (not shown). The test passage  38  is in fluid communication with an end  44 ′ of a conical retaining chamber  44 . At end  44 ′, the conical retaining chamber  44  has a diameter larger than the diameter of ball  20 . The ball  20  is located within the conical retaining chamber  20  and restrained therein at the end  44 ′ by plate  12 . At an opposite end  44 ″ of the conical retaining chamber, the chamber has a diameter less than the diameter of ball  20 . The end  44 ″ of the conical retaining chamber is in fluid communication with a test probe lead-in  42 . The test probe lead-in  42  and conical retaining chamber  44  are coaxially aligned along an axis substantially normal to exterior surface plane  45 . The exterior surface  45  can be generally exposed to the environment.  
      During a test, a test probe (not shown) is pressed against the probe lead-in  42 . The probe&#39;s stylus protrudes through the end  44 ″ of conical retaining chamber  44  and forces ball  20  towards the end  44 ′ as illustrated by dashed ball  20 ′. As the ball  20  traverses to position  20 ′, a clearance  21  is created between the fixed diameter of ball  20  and the increasing diameter of the proximate end  44 ′. The clearance  21  places the fluid port  36  in fluid communication with the test probe, and fluid pressure within the passage  36  is effectively measured by the probe.  
      The test probe and stylus are withdrawn at the end of the test period, thereby allowing the ball  20  to be urged toward end  44 ″ of conical retaining chamber  44 . The ball  20  is urged by a difference in fluid pressure between test passage  38  and end  44 ″ of conical retaining chamber  44 , and resultantly becomes wedged against conical wall  46 . The wedged ball  20  is retained in position by a frictional force parallel with the conical wall  46 . The frictional force is dependent upon the force P exerted on the conical wall  46  by the wedged ball  20 .  
      When the difference in fluid pressure is minimal, such as when passage  36  is unpressurized, ball  20  remains wedged against the conical wall  46 . The wedged ball  20  prevents an undesirable opportunity for foreign material to pass between ball  20  and conical wall  46 , thereby compromising the fluid within fluid passage  16 . However, the frictional force exhibited on the dedged ball is such that it can be overcome by insertion of a test probe. An angle of the tapered wall  46  with respect to an axial centerline of conical retaining chamber  44  is preferably selected between 3 and 15 degrees. A lower angle improves reliability of the wedging seal; however it also requires greater dimensional control in the diameter of the ball and diameters of the conical retaining chamber. Conversely, a higher angle reduces reliability of the wedging seal; however it also increases the dimensional tolerances of both the ball  20  and the diameters of the conical retaining chamber  44 .  
      The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.