Abstract:
An inlet check valve is mountable to a valve body that, in turn, is mounted to a high pressure pump. The inlet check valve has a removable inlet seat with a first through-hole forming an inlet path and functioning as a valve seat. A valve is positionable over the first through-hole. An inlet guide has first, second, third and fourth through-holes alignable with respective first, second, third and fourth through-holes of the inlet seat. The third and fourth through-holes receive fasteners to mount the inlet check valve to the valve body.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to the field of check valves and, more particularly, to an improved inlet check valve for use with a high pressure waterjet intensifier. 
   BACKGROUND OF THE INVENTION 
   A waterjet intensifier has a high pressure cylinder of, for example, up to 40,000 psi or greater; and fluid to the high pressure cylinder is supplied via an inlet check valve that also must be capable of operating reliably at such high pressures. One example of an inlet check valve assembly is described in U.S. Pat. No. 6,021,810, which discloses an inlet valve mounted on the end of a projecting portion of a generally cylindrical check valve body. The inlet check valve has a ball valve element that is mounted over an inlet passage. Such a check valve functions well in service, however, the design does have an opportunity for an improvement. The valve body is made of a steel material that is not as hard as the ball valve. After some time in service, the repetitive action of the ball valve being pushed against the valve body seat by the high pressure liquid results in wear on the valve body where the ball valve seats. After continued use, the inlet check valve should be serviced, which requires that the valve body be machined or replaced to restore a high quality inlet valve seat. Such a servicing process is costly and labor intensive. Consequently, there is the need for an improved inlet check valve that has a longer useful life. 
   SUMMARY OF THE INVENTION 
   The present invention provides an inlet check valve that provides a long, highly reliable service life. In addition, the inlet check valve of the present invention isolates all wear parts; and while such isolation requires extra static seals, additional sealing components are not required, which would otherwise reduce the service life of the inlet check valve. Further, the inlet check valve of the present invention permits all wear parts to be easily and quickly replaced in the field, thereby substantially reducing the cost of servicing the inlet check valve. Thus, the inlet check valve of the present invention is especially useful in high pressure cylinders that require a long service life. 
   In accordance with the principles of the present invention and in accordance with the described embodiments, the present invention provides an inlet check valve mounted with first and second fasteners to an end surface of a projection extending from one end of a valve body. The valve body has inlet and outlet passages intersecting the projection end surface, and the valve body is mounted to a high pressure pump for conducting a low pressure liquid via the inlet passage to the high pressure pump and conducting a high pressure liquid via the outlet passage from the high pressure pump. The inlet check valve has an inlet seat with first and second through-holes locatable adjacent the inlet passage and the outlet passage, respectively, and third and fourth through-holes receiving the first and second fasteners, respectively. A first surface on the inlet seat is locatable against the projection end surface and forms a liquid tight seal therewith. 
   A valve is positionable over the first through-hole to define a closed valve position blocking a flow of liquid past the valve and through the inlet passage. An inlet guide has first and second through-holes alignable with respective first and second through-holes of the inlet seat. Third and fourth through-holes of the inlet guide are locatable adjacent the third and fourth through-holes of the inlet seat, respectively, and also receive the first and second fasteners, respectively. A cavity in the inlet guide is aligned with the first through-hole of the inlet seat and maintains the valve between the cavity and the first through-hole of the inlet seat. The valve is positionable in the cavity away from the closed valve position to define an open valve position permitting the flow of liquid past the valve and through the inlet passage. 
   In one aspect of the invention, the end surface and the first surface are lapped surfaces. In another aspect of the invention, an alignment component extends into the inlet seat, the end surface and the inlet guide for aligning the inlet guide and the inlet seat with the end surface. 
   These and other objects and advantages of the present invention will become more readily apparent during the following detailed description together with the drawings herein. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevation view partially in cross-section of a portion of a check valve body illustrating a valve element of an inlet check valve in its closed position in accordance with the principles of the present invention. 
       FIG. 2  is cross-sectional top view of the inlet check valve taken generally along line  2 - 2  of  FIG. 1 . 
       FIG. 3  is cross-sectional top view of the inlet check valve taken generally along line  3 - 3  of  FIG. 1 . 
       FIG. 4  is cross-sectional top view of the inlet check valve taken generally along line  4 - 4  of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , a check valve assembly  20  of the present invention includes a generally cylindrical check valve body  22 . The check valve body  22  has a centrally located cylindrical projection  24  that extends beyond a larger diameter flange  26  into the bore  28  of a high pressure hydraulic cylinder or pump  30 . The flange  26  has an annular surface  32  that bears against an end surface  34  of the cylinder  30 . An annular seal  36  fills the gap between the outer surface of the projection  24  and the inner surface of the bore  28 . The check valve body  22  is secured to the end of a high pressure hydraulic cylinder  30  by means of an end cap  38  screwed onto the cylinder  30  in a known manner. 
   Referring to  FIGS. 1 and 2 , an inlet check valve  70  is mounted on the end surface  52  of the projection  24 . The inlet check valve  70  includes a valve  72  having an outer surface with a curved or spherical shape and cross-sectional profile. The valve  72  is often a ball disposed above an inlet  53  formed at one end of a fluid inlet path  55  within an inlet seat  59 . The inlet fluid path  55  intersects an off-center, low pressure fluid inlet passage  50  on an end surface  52  on the end of the projection  24 , and the inlet fluid passage  50  is fluidly connected with a source of low pressure fluid (not shown) in a known manner. 
   Above the valve  72  is a cavity  83  of an inlet guide  61 . The inlet guide  61  has an upper side or surface  79  with an arcuate or circular periphery extending approximately parallel to the surface  52  of the projection  24 . A portion of the upper side  79  forms a flange  80 , and an opening or hole  81  is located in the flange  80 . The cavity  83  is disposed in an inner or a lower side  87  of the inlet guide flange  80 . The cavity  83  has a curved and preferably spherical shape and cross-sectional profile. Thus, the valve  72  is able to move freely in the cavity  83  and in a direction generally parallel to a centerline  63  of the valve body  22 . The displacement or lift of the valve  72  is fixed by the height of the cavity  83  above the end surface  52  and the size of the valve  72 , for example, the diameter of the valve  72 . The hole  81  is radially displaced from the centerline  63  of the valve body  22  and is concentric with the fluid inlet path  55  in the inlet seat  59 , which, in turn, is concentric with, and intersects, the valve body fluid inlet passage  50 . 
   Referring to  FIGS. 1 and 3 , in this embodiment, an alignment or locating pin  86  is press fit into hole  65  of the inlet seat  59  and extends beyond an upper surface  104  and lower surface  106 . Referring to  FIG. 2 , the inlet guide  61  has a first alignment or locating element  84 , for example, a locating hole, sized to receive the locating pin  86 . As shown in  FIG. 4 , the locating pin  86  extends into a second alignment or locating element  67 , for example, a locating hole in the projection surface  52 . The locating holes  84 ,  67  and locating pin  86  provide a first mechanism for locating the inlet guide  61  and the inlet seat  59  with respect to the valve body  22 , so that the fluid inlet passage  50  and the fluid inlet path  55  can be properly aligned. 
   Referring to  FIGS. 2-4 , first clearance holes  69 ,  71  extend through the inlet guide  61  and inlet seat  59 , respectively; and second clearance holes  73 ,  75  also pass through the inlet guide  61  and inlet seat  59 , respectively. A first fastener  88 , for example, a machine screw, passes through the first clearance holes  69 ,  71  and engages with a threaded hole  91  ( FIG. 4 ) in the surface  52  of the projection  24 . A second fastener  89 , for example, a machine screw, passes through the second clearance holes  73 ,  75  and engages with a threaded hole  92  also in the surface  52  of the projection  24 . Thus, the clearance holes  69 ,  71 ,  73 ,  75 , threaded holes  91 ,  92  and fasteners  88 ,  89  provide a second mechanism for properly aligning the inlet guide  61  and inlet seat  59  with the valve body projection  24 . The fasteners  88 ,  89  also securely fix the position of the inlet guide  61  and inlet seat  59  with respect to valve body projection  24  to maintain the valve  72  centrally over the fluid inlet path  55  and fluid inlet passage  50 . 
   The inlet guide  61  further includes an off-center, high pressure fluid outlet path  93  that is concentrically alignable with a fluid outlet bore  94  in the inlet seat  59 , which, in turn, is concentrically alignable with an outlet fluid passage  96  within the valve body  22 . The outlet fluid passage  96  provides a fluid exit from the valve body  22  in a known manner via an outlet check valve (not shown). 
   The valve body projection surface  52  and its opposing surface  106  on the inlet seat  59  are made with a lapped finish. Therefore, lapped surfaces  52 ,  106 , when brought together, form a liquid-tight static seal around the fluid outlet bore  94  and the outlet fluid passage  96 . Thus, even though the addition of the inlet seat  59  increases the number of static seals required, such static seal is provided by the contacting lapped surfaces  52 ,  106  without the use of separate sealing components, for example, O-rings. 
   In use, referring to  FIG. 1 , during an intake stroke, a piston  101  within the cylinder  30  moves away from the projection  24 , thereby creating a pressure differential across the inlet check valve  70  such that the fluid in the inlet fluid passage  50  and the inlet fluid path  55  are under a relatively small positive pressure. That positive fluid pressure is applied against the outer surface of the valve  72  and pushes the valve  72  away from the end surface  52  of the projection  24  and the closed position illustrated in  FIG. 1  to an open position. When in the open position, fluid readily flows from the fluid source (not shown) through the inlet fluid passage  50  and the inlet fluid path  55  to fill the bore  28  of the cylinder  30 . When the piston  101  in the cylinder  30  reverses direction, a very high fluid pressure is applied via the opening  81  to an upper portion  78  of the outer surface (as viewed in  FIG. 1 ) of the valve  72 , thereby creating a pressure differential. That pressure differential pushes the valve  72  to a closed position in which the outer surface of the valve  72  partially extends past the end surface  104  and seats itself in the inlet orifice  53  of the inlet seat  59 , thereby sealing the inlet orifice  53  as illustrated in  FIG. 1 . In the sealing position, the valve  72  has an annular area, that is, a thin circular line, of bearing contact with an annular portion of the orifice  53 . Thus, fluid is prevented from passing through the inlet  53  into the inlet fluid path  55 . The high pressure fluid passes through the outlet fluid path  93  in the inlet guide  61 , the outlet bore  94  in the inlet seat  59  and through the outlet passage  96 . During the operation of the cylinder pump  30 , it is believed that the valve  72  continuously rotates, to some extent, to provide a different outer surface area against the annular sealing area around the inlet  53 . Therefore, the valve  72  wears evenly during use, is less subject to overheating and provides a highly repeatable fill cycle. 
   The operation of the valve described herein provides superior performance. It is believed that the curved shape of the outer surface of the valve  72  provides less resistance in the closing process; and therefore, the valve  72  is more responsive and closes faster than other valves. Normally, the piston  101  is powered by a reciprocating pump which creates significant pressure spikes in reversing direction. An accumulator is used to absorb the changes in pressure, but the hydraulic system still experiences pressure spikes. The faster response of the valve  72  minimizes those pressure spikes and provides a generally improved and smoother operation. 
   The inlet seat  59  is made from a hard stainless steel, for example, a 0.812ø 15-5 PH H900 stainless steel, which is harder than the material used to make the valve body  22 . The inlet guide  61  is also made from a stainless steel, for example, a 300 series stainless steel. With such materials, the inlet  53  provides a valve seat that has a substantially longer service life than valve seats located in the end surface  52  of the projection  24  as is done in comparable known valves. 
   However, when it is desired to service the inlet check valve  70 , the end cap  38  is unscrewed from the end  40  of the cylinder  30 ; and the valve body  22  is removed from the end of the cylinder  30 . Removing the screws  88 ,  89  releases the inlet guide  61 , valve  72  and inlet seat  59  from the valve body projection  24 . A new inlet valve seat  59  is installed by inserting the locating pin  86  extending from the surface  106  into the locating hole  67  of the valve body projection  24 . A new valve  72  is placed on the inlet  53 , and the locating hole  84  in the inlet guide  61  is placed over the locating pin  86  extending from the surface  104  of the inlet seat  59 . The screws  88 ,  89  are inserted through respective clearance holes  69 ,  71 ,  73 ,  75  and into respective threaded holes  91 ,  92 . The curved or spherical shape of the outer surface of the valve  72  automatically aligns the valve  72  in its desired concentric position with respect to the inlet  53 , and the screws  88 ,  89  are tightened to complete assembly of the check valve  70 . Further, if the screws  88 ,  89  are not fully tightened or loosen during operation, the valve  72  cannot move but maintains its desired concentric relationship with the inlet  53 . 
   The inlet check valve  70  described herein has several advantages. First, the use of the harder inlet seat  59  provides the inlet check valve  70  with a substantially longer service life than comparable known valves. Second, the additional static seals required by the inlet seat  59  are achieved without requiring separate sealing components such as O-rings, which also contributes to the increased service life of the inlet check valve  70 . Third, the valve  72  and inlet seat  59  are not permanently connected to any other components and therefore, can be individually replaced, thereby substantially reducing the cost of servicing the inlet check valve  70 . Thus, the inlet check valve  70  provides a long, highly reliable operation, can be easily and quickly serviced in the field and is especially adaptable for use in high pressure cylinders. 
   While the invention has been set forth by a description of the preferred embodiment in considerable detail, it is not intended to restrict or in any way limit the claims to such detail. Additional advantages and modifications will readily appear to those who are skilled in the art. For example, while the cavity  83  is shown as being a mating partial spherical shape, the cavity may be conical or any other shape that is effective to receive and maintain a valve in its desired operating position with respect to the inlet  53 . Further, in the disclosed embodiment, the valve  72  is spherical; however, as will be appreciated, the valve can be any shape that can be held captured by the cavity  83  and provides a circular line of contact with the inlet  53  when the valve is in the closed position. For example, the valve could be conical in shape, have a bull nose shape or be curved but not spherical. As will be appreciated, in an alternative embodiment, the valve  72  can be a poppet that covers the inlet fluid path  55 . In addition, the orifice illustrated as being the opening  81  is shown as a single cylindrical hole; however, an opening or openings of any size, shape and number may be used to facilitate the application of a closing pressure force onto the valve  72 . 
   As will be appreciated, the locations of one or both of the locating holes  84 ,  67  and the locating pin  86  may be reversed such that the locating hole extends through the inlet valve seat  59  and locating pins are attached to the inlet guide  61  and projection  24 , respectively. Further, in the disclosed embodiment, the major cross-sectional profile of the inlet guide  61 , that is, the cross-sectional profile taken right below the upper surface  79 , is generally arcuate and specifically circular. However, the inlet guide  61  may have a noncircular shape such that the major cross-sectional profile is octagonal, hexagonal or an irregular shape. Further, it is not required that the inlet guide  61  and inlet seat  59  cover the outlet fluid passage  96 . For example, an inlet guide  61  may be made that eliminates the portion of the mounting plate shown to the left of the phantom line  107  in  FIG. 2 . In the described embodiment, the screws  88 ,  89  have respective pressure relieving bores  108 ,  110 . 
   Therefore, the invention in its broadest aspects is not limited to the specific detail shown and described. Consequently, departures may be made from the details described herein without departing from the spirit and scope of the claims which follow.