Abstract:
A high-pressure fluid pump is operable to pressurize a fluid and includes a hollow stud including a first end, a second end, and a cylindrical space extending between the first end and the second end and a housing fixedly coupled to the first end of the hollow stud. A high pressure cylinder is disposed within the cylindrical space of the hollow stud. The high pressure cylinder includes a bore that extends from a first end to a second end of the high pressure cylinder. A seal head is engaged with the first end of the high pressure cylinder to define a seal therebetween and an end cap is coupled to the second end of the hollow stud and the seal head. The end cap is operable to apply a compressive force to the seal head to compress the seal head against the cylinder and to apply a tensile load to the hollow stud. A plunger is movable within the bore to pressurize the fluid in a space defined by the piston, the seal head, and the high pressure cylinder.

Description:
RELATED APPLICATION DATA 
       [0001]    This application claims priority to co-pending provisional patent application No. 61/381,742 filed Sep. 10, 2010, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to high pressure fluid pumps, and more particularly to head attachment assemblies for high pressure fluid pumps. 
         [0003]    High pressure pumps can be used in a variety of applications such as providing a high pressure fluid for a water jet cutting device. The high pressure (in excess of 50 ksi) required to produce a cutting jet necessitates the use of high pressure sealing systems and other high strength components. 
       SUMMARY 
       [0004]    In one embodiment, the invention provides a high-pressure fluid pump that is operable to pressurize a fluid. The pump includes a hollow stud including a first end, a second end, and a cylindrical space extending between the first end and the second end and a housing fixedly coupled to the first end of the hollow stud. A high pressure cylinder is disposed within the cylindrical space of the hollow stud. The high pressure cylinder includes a bore that extends from a first end to a second end of the high pressure cylinder. A seal head is engaged with the first end of the high pressure cylinder to define a seal therebetween and an end cap is coupled to the second end of the hollow stud and the seal head. The end cap is operable to apply a compressive force to the seal head to compress the seal head against the cylinder and to apply a tensile load to the hollow stud. A plunger is movable within the bore to pressurize the fluid in a space defined by the piston, the seal head, and the high pressure cylinder. 
         [0005]    In another embodiment, the invention provides a high-pressure fluid pump operable to pressurize a fluid. The pump includes a high pressure cylinder including a bore and a high pressure end, a plunger positioned at least partially within the bore, a power source operable to produce a reciprocating motion of the plunger within the bore, and a housing. A hollow stud has a first end fixedly coupled to the housing and a cylindrical space that extends between the first end and a second end of the hollow stud. The high pressure cylinder is disposed at least partially within the cylindrical space. A seal head is positioned adjacent the high pressure end of the high pressure cylinder such that the seal head, the high pressure cylinder and the plunger cooperate to define a variable volume space that receives the fluid to be pressurized. An end cap is coupled to the second end of the hollow stud and is operable to apply a compressive force to the seal head and the high pressure cylinder to maintain a seal therebetween at operating pressures in excess of 30,000 psi (2,069 bars) and to apply a tensile force to the hollow stud. 
         [0006]    In yet another embodiment the invention provides a high-pressure fluid pump that is operable to pressurize a fluid. The pump includes a power cylinder having a hydraulic drive member disposed therein, a first housing coupled to a first end of the power cylinder and cooperating with the power cylinder and the drive member to define a first space, and a second housing coupled to a second end of the power cylinder and cooperating with the power cylinder and the drive member to define a second space. A first hollow stud has a first end connected to the first housing and a second end, a first head assembly is coupled to the second end of the first hollow stud, and a first high pressure cylinder is disposed within the first hollow stud and has a first cylindrical bore that at least partially defines a space. The first head assembly is adjustable to apply a tensile load to the first hollow stud and to compress the first high pressure cylinder between the first head assembly and the first housing. A first plunger is disposed within the first cylindrical bore, a second hollow stud has a first end connected to the second housing and a second end, and a second head assembly is coupled to the second end of the second hollow stud. A second high pressure cylinder is disposed within the second hollow stud and has a second cylindrical bore. The second head assembly is adjustable to apply a tensile load to the second hollow stud and to compress the second high pressure cylinder between the second head assembly and the second housing. A second plunger is disposed within the second cylindrical bore. The first plunger and the second plunger are movable in response to movement of the drive member and in opposition to one another to pressurize the fluid to a pressure in excess of 30,000 psi (2,069 Bar). 
         [0007]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of a portion of a high pressure pump. 
           [0009]      FIG. 2  is a section view of an end cap taken along line  9 - 9  of  FIG. 1 . 
           [0010]      FIG. 3  is a section view of a sealing head taken along line  9 - 9  of  FIG. 1 . 
           [0011]      FIG. 4  is a section view of a hollow stud taken along line  9 - 9  of  FIG. 1 . 
           [0012]      FIG. 5  is a section view of a high pressure cylinder taken along line  9 - 9  of  FIG. 1 . 
           [0013]      FIG. 6  is a section view of a hydraulic cylinder head taken along line  9 - 9  of  FIG. 1   
           [0014]      FIG. 7  is a section view of a power cylinder taken along line  9 - 9  of  FIG. 1 . 
           [0015]      FIG. 8  is a section view of the pump of  FIG. 1  taken along line  9 - 9  of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
         [0017]    It should be noted that “high pressure” as used herein refers to pressure in excess of 30,000 psi (2,069 bar). One of ordinary skill in the art will realize that unique problems occur at these high pressures. Thus, solutions common to lower pressure pumps are not necessarily applicable in systems operating at pressures in excess of 30,000 psi (2,069 bar). 
         [0018]      FIG. 1  is a perspective view of a double acting high pressure pump  10 . The embodiment described herein is a double acting high pressure pump, however, the invention can also be applied to a single acting high pressure pump or a mechanically actuated pump if desired. The pump  10  includes a power cylinder  12 , a pump head  14  disposed on a first end  16  of the pump  10  and another pump head  14  disposed on a second end  18  of the pump  10 . The first end  16  and second end  18  are substantially identical and capable of delivering high-pressure fluid during pump operation. As the first end  16  and second end  18  are substantially identical, only one end  16  will be described in detail. 
         [0019]    As is best illustrated in  FIG. 8 , the end  16  includes a sealing head  50  partially disposed inside an end cap  22 . One end of a hollow stud  24  is connected to the end cap  22  and the opposite end of the hollow stud is coupled to a hydraulic cylinder head  26 . The hydraulic cylinder head  26  is coupled to the power cylinder  12 . 
         [0020]    As illustrated in  FIG. 2 , a first end of the end cap  22  includes an opening  44  of cylindrical shape and a second end of the end cap  22  includes a threaded opening  46  of cylindrical shape. The threaded opening  46  is sized to receive one end of the hollow stud  24  as will be discussed. The threaded opening  46  cooperates with the first end of the end cap to define a shoulder  47 . The first end of the end cap  22  includes a plurality of holes  48  (only one hole shown in  FIG. 3 ) arranged such that a central axis of a hole  48  is substantially parallel to the central axis of the end cap  22 . Each of the holes  48  includes threads and passes through the first end of the end cap  22  such that one end of the hole passes through the shoulder  47 . In the illustrated construction, the opening  44  includes a pair of grooves that are sized to receive a sealing member. In other constructions, other arrangements are employed to define a seal in the opening  44 . 
         [0021]      FIG. 3  illustrates a sealing head  50  that includes a first portion  52 , a middle portion  54 , and a boss  56  that cooperate to define a central axis. The middle portion defines a shoulder  51  that is radially larger than the remainder of the sealing head  50 . The boss  56  is a substantially cylindrical projection that extends from the middle portion  54 . A chamfered seal surface  57  extends between the middle portion  54  and the boss  56 . In addition, two flow paths  59   a ,  59   b  are formed in the sealing head  50  and include a first end that terminates at the end of the boss. One of the flow paths  59   a  is a discharge flow path and is operable to direct high pressure fluid out of the pump  10 , while the second flow path  59   b  is an inlet flow path that provides for the flow of fluid into the pump  10  before it is pressurized by the pump  10 . The second flow path  59   b  includes a check valve  61  positioned within the sealing head  50  that is operable to inhibit flow in one direction, while allowing substantially free flow in the opposite direction. 
         [0022]    A discharge check valve  20  having a fluid check valve  36  disposed therein connects to the sealing head  50  through a check-valve seat  51  and operates to inhibit flow in one direction, while allowing high pressure fluid flow in the opposite direction. In the illustrated construction, the discharge check valve  20  is threadably connected to the sealing head  50 . However, other constructions may employ other connection arrangements or may integrate the check valve  20  and the sealing head  50  into a single component. 
         [0023]    As illustrated in  FIG. 4 , the hollow stud  24  has a central axis about which the hollow stud  24  is generally cylindrical. In the illustrated construction, the first end  60  of the hollow stud  24  and the second end  62  of the hollow stud  24  have a smaller interior diameter than a middle portion  64  of the hollow stud  24  with other constructions having a uniform bore. Each end of the hollow stud  24  includes external threads sized to be received within the threaded opening  46  of the end cap  22  or a threaded opening  82  of a hydraulic cylinder head  26 . In preferred constructions, multi-start thread arrangements are used. For example, in one preferred construction, quad threads are disposed on the exterior of the first end  60  and the second end  62  of the hollow stud  24 . The quad threads include four separate threads that facilitate the desired alignment of the threaded components during assembly. In another preferred arrangement dual threads are disposed on the exterior of the first end  60  and the second end  62  of the hollow stud  24  to allow for thread engagement at two different starting locations. In alternative embodiments, single, triple or other numbers of start threads may be used in place of quad threads or dual threads. A thread undercut is disposed on the exterior of the hollow stud  24  next to the threads on the first end  60  and the second end  62 . In another construction, the hollow stud  24  is fixed to the hydraulic cylinder head  26  via a flange that threads onto the hollow stud  24  and then is bolted to the hydraulic cylinder head  26 . In this construction, the cylinder head  26  would not need to be threaded. 
         [0024]      FIG. 5  illustrates a high pressure cylinder  66  which includes a central axis about which the high pressure cylinder  66  is generally cylindrical. The interior of the high pressure cylinder  66  includes a cylindrical opening  68  which extends throughout the full length of the high pressure cylinder  66 . The outside diameter of the high pressure cylinder  66  is sized to fit within the hollow stud  24 . In preferred constructions, a close fit is provided between the outer surface of the high pressure cylinder  66  and the inner surface of the hollow stud  24  to inhibit lateral movement of the high pressure cylinder  66 . The cylinder opening  68  includes a chamfer  63  on both ends to facilitate assembly and sealing. 
         [0025]    As illustrated in  FIG. 6 , a hydraulic cylinder head  26  includes a central axis and a main receiving bore  82  that is sized to receive one end of the hollow stud  24 . The main receiving bore  82  includes threads that match the threads of the hollow stud  24 . In addition, several cylindrical bores  84 ,  86  are formed in the hydraulic cylinder head and are sized to receive seal members to assure that hydraulic fluid does not leak past the hydraulic cylinder head  26 . 
         [0026]    With reference to  FIG. 1 , the hydraulic cylinder head  26  includes a plurality of apertures  104  arranged around the central axis of the cylinder head  26 . The apertures  104  extend through the hydraulic cylinder head  26  and are sized to receive bolts  90  that facilitate the attachment of the hydraulic cylinder head  26  to the power cylinder  12 . In the illustrated construction, six apertures  104  and six bolts  90  are provided with more or fewer apertures  104  and bolts  90  being possible. 
         [0027]    As illustrated in  FIG. 7 , the power cylinder  12  has a central axis about which the power cylinder  12  is generally cylindrical. The interior of the power cylinder  12  includes a hollow opening of cylindrical shape which exists throughout the power cylinder  12 . A plurality of openings  95  extend through a sidewall of the power cylinder  12  with each opening  95  having an axis which is substantially perpendicular to the central axis of the power cylinder  12 . The openings provide for hydraulic fluid flow into and out of the power cylinder  12  as well as access for proximity switches which are required to produce the desired reciprocating movement of a double-sided piston  100  (shown in  FIG. 8 ) disposed within the cylinder  12 . 
         [0028]    With reference to  FIG. 8 , the assembly and operation of the high pressure pump  10  (sometimes referred to as an attenuator or attenuator pump) will be described. The double-sided piston  100  is positioned within the bore of the power cylinder  12  and a plunger  98  is attached to each side of the double-sided piston  100 . Seal members are positioned within the two hydraulic cylinder heads  26  such that the two plungers  98  can pass through the seal members and form a seal. The hydraulic seal heads  26  are then bolted to the hydraulic cylinder  12 . The seal members and the seal between the hydraulic seal heads  26  and the power cylinder  12  should be adequate to inhibit leakage of hydraulic fluid out of the power cylinder  12 . 
         [0029]    Each of the hollow studs  24  is then threaded into one of the two hydraulic seal heads  26  and each of the high pressure cylinders  66  is positioned within one of the hollow studs  24 . Once positioned, the central bore  68  of each of the high pressure cylinders  66  receives the associated plunger  98  for reciprocation. Each of the seal heads  50  is positioned on one end of one of the high pressure cylinders  66  such that a seal is defined between the chamfer of the high pressure cylinder  66  and the chamfer  57  of the seal head  50 . The seal must be such that it inhibits unwanted flow at the maximum operating pressure of the pump  10 . To assure that the seal is capable of inhibiting leakage, the end cap  22  is threaded onto the hollow stud  24  to apply a compressive force on the seal head  50  and thereby increase the contact force at the seal between the seal head  50  and the high pressure cylinder  66  on each end of the pump  10 . 
         [0030]    The shoulder  51  of the seal head  50  is disposed adjacent the shoulder  47  of the end cap  22  when the end cap  22  is threaded onto the hollow stud  24 . To apply the desired force to the seal head  50 , a plurality of jack bolts  102  are threaded into the apertures  48  of the end cap  22 . As the jack bolts  102  are turned, the ends engage the shoulder  51  of the seal head  50  and push the seal head  50  into the high pressure cylinder  66 . The result is a large compressive force and preload on the high pressure cylinder  66 . In addition, the hollow stud  24  is placed in tension and remains in tension throughout pump operation. 
         [0031]    In operation, hydraulic fluid is directed to the power cylinder  12  to induce reciprocating movement of the double-sided piston  100 . As illustrated in  FIG. 8 , high pressure hydraulic fluid has been forced into the space to the left of the double-sided piston  100 , thereby moving the piston  100  to the right. The space to the right of the double-sided piston  100  is connected to a drain to allow the desired movement. To reverse the movement of the piston  100 , the space to the left of the piston  100  is connected to the drain and the space to the right is connected to the high pressure hydraulic fluid source. Because the surface area of the piston  100  is significantly larger than the surface area of the plungers  98 , the pressure of the hydraulic fluid can be substantially less than the operating pressure of the pump  10 . As the pump  10  moves toward the position illustrated in  FIG. 8 , the intake check valve  61  in the left side seal head  50  opens to allow relatively low pressure fluid to enter the high pressure cylinder  66  on the left side. The discharge check valve  36  on the right side opens to allow the plunger  98  and high pressure cylinder  66  to discharge compressed fluid at the operating pressure of the pump  10 . When the direction reverses, the open check valves on either side close and the closed check valves on either side open such that the right side cylinder  66  and plunger  98  cooperate to draw fluid in and the left side pump compresses fluid within the cylinder  66 . No matter the position in the cycle, both hollow studs  24  remain in tension and both high pressure cylinders  66  remain in compression. 
         [0032]    Thus, the invention provides, among other things, a high pressure pump  10  where there is tension on the end cap  22 , hollow stud  24 , and hydraulic cylinder head  26  when the pump  10  is not compressing a fluid. Various features and advantages of the invention are set forth in the following claims.