Abstract:
A sealing system for a high pressure pump, in which the pump includes a vessel defining a vessel bore and having an end portion, the vessel bore having a first engagement face and defining a central longitudinal axis, and in which the pump further includes a plunger cooperative with the vessel to increase the pressure of a fluid within the bore, includes a seal member at least partially received within the bore and defining a second engagement face. The sealing system further includes a retaining member in operative contact with the seal member to mate the first engagement face with the second engagement face to inhibit fluid leakage from the bore. The first engagement face includes a first contacting surface having a non-linear cross-section. The second engagement face includes a second contacting surface having a non-linear cross-section in contact with the first contacting surface.

Description:
RELATED APPLICATION DATA 
     The present application claims priority under 35 U.S.C. §119 to Provisional Patent Application No. 61/545,236, filed Oct. 10, 2011, the disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     The present invention relates to a gasketless high pressure connection for an ultrahigh pressure fluid pump. 
     Precision cutting for industrial and commercial purposes is often accomplished through the use of a waterjet system that directs a high speed stream of water at a material surface to be cut. Waterjet systems pressurize water to about 30,000 psi and convert that pressure to a fluid stream traveling at speeds in excess of Mach 2. This high velocity stream, often mixed with an abrasive, is capable of slicing through hard materials such as metal and granite with thicknesses of more than a foot. 
     SUMMARY 
     The pumps operating within a waterjet system require sealing connections able to contain the high pressures generated. Seal gaskets positioned between the sealing surfaces in such an environment are typically constructed of a softer material than that of the surrounding components and tend to rapidly break down, requiring frequent replacement. A sealing assembly for these purposes should therefore effectively seal the high pressure side from a low pressure side without premature failure or necessitating unreasonable maintenance. 
     In one embodiment of a sealing system for a high pressure pump, the pump includes a vessel defining a vessel bore and having an end portion. The vessel bore has a first engagement face and defines a central longitudinal axis. The pump further includes a plunger cooperative with the vessel to increase the pressure of a fluid within the bore. The sealing system includes a seal member at least partially received within the bore and defining a second engagement face, and a retaining member in operative contact with the seal member to mate the first engagement face with the second engagement face to inhibit fluid leakage from the bore. The first engagement face includes a first contacting surface having a non-linear cross-section. The second engagement face includes a second contacting surface having a non-linear cross-section in contact with the first contacting surface. 
     A high pressure pumping system for fluid in excess of 15,000 psi defines a longitudinal axis. A first component includes a first engagement face having a first contacting surface with a first non-linear cross-section that is convex. A second component includes a second engagement face having a second contacting surface with a second non-linear cross section that is concave. A retaining member is coupled to one of the first component and the second component to sealingly connect the first engagement face to the second engagement face to inhibit fluid leakage therebetween. 
     A high pressure pump for producing fluid pressure in excess of 15,000 psi includes a vessel including an end portion having a first engagement face. The vessel includes a vessel bore that defines a central longitudinal axis and is in communication with a source of fluid. A plunger is cooperative with the vessel to increase the pressure of a fluid within the bore. A seal member is at least partially received within the bore and defines a second engagement face. A retaining member is in operative contact with the seal member and with the vessel to mate the first engagement face with the second engagement face to inhibit fluid leakage from the bore. The first engagement face includes a convex contacting surface with a variable radius continuously increasing with increasing distance from the longitudinal axis. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an abrasive waterjet cutting system. 
         FIG. 2  is a perspective view of the intensifier pump of the abrasive waterjet cutting system of  FIG. 1 . 
         FIG. 3  is a cross sectional view of the intensifier pump of  FIG. 2  taken along line  3 - 3 . 
         FIG. 4  is a partial cross sectional view of an end portion of the intensifier pump of  FIG. 3 . 
         FIG. 5  is a partial cross sectional view of the end portion of  FIG. 4 , showing a portion of the seal head engaging the cylindrical vessel. 
         FIG. 6  is a partial cross sectional view of another embodiment of the end portion of  FIG. 4 , showing a portion of the seal head engaging the cylindrical vessel. 
         FIG. 7  is a partial cross sectional view of another embodiment of the end portion of  FIG. 4 , showing a portion of the seal head engaging the cylindrical vessel. 
         FIG. 8  is a partial cross sectional view of another embodiment of the end portion of  FIG. 4 , showing a portion of the seal head engaging the cylindrical vessel. 
     
    
    
     DETAILED DESCRIPTION 
     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. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. And as used herein and in the appended claims, the terms “upper”, “lower”, “top”, “bottom”, “front”, “back”, and other directional terms are not intended to require any particular orientation, but are instead used for purposes of description only. 
     It should be noted that “ultrahigh” or ‘high pressure” as used herein refers to fluid pressure in excess of 15,000 psi. 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 to systems operating at pressures in excess of 30,000 psi and in fact can produce results contrary to those seen in low pressure operation. 
       FIG. 1  illustrates an abrasive waterjet cutting system  10  for cutting a particular material with a high pressure stream of water mixed with abrasive. The cutting system  10  includes a cutting table  20  with a material supporting surface  22  and a cutting head assembly  30  that includes a cutting head  40 . The cutting head assembly  30  is controlled through a computer  50  and is functionally movable via the arms  24 ,  26  in a manner known to those of skill in the art to provide cutting at any required operable location on the surface  22 . A pumping system  60  generates high pressure fluid, typically water, for the cutting process and provides that water through a high pressure tube (not shown) to the cutting head assembly  30 . A feed system  70  supplies an abrasive material, such as garnet, that is combined with the water stream at the cutting head  40 . An abrasive removal system  80  filters the wastewater produced in the process to recover the abrasive for further use. The wastewater can be disposed of through a drain or recycled to minimize overall water usage. 
       FIGS. 2 and 3  illustrate a double acting high pressure pump  100  of the pumping system  60 . As is well known to those of skill in the art, this type of pump, also referred to as an intensifier pump, includes a power cylinder  110  defining a hydraulic fluid chamber  114 . A double-sided piston  118  coupled to opposing plungers  122  alternates back and forth within the chamber  114  in response to pressurized hydraulic fluid directed into and out of the chamber  114 . One or more proximity switches  126  detect the piston  118 , and when detected, send a signal to a controller such as a PLC to switch a 4-way valve on the hydraulic pump, thus directing hydraulic oil to the other side of the piston  118  through the ports  128  at the bottom of the power cylinder  110 . The piston/plunger assembly acts as a pressure multiplier to increase the pressure of a fluid, such as water, drawn into the bores  130  of two opposing cylindrical vessels  134 . The vessels  134  are coupled to the power cylinder  110  through hydraulic cylinder heads  138 . A pump head  140  is disposed on the ends  142 ,  144  of each cylindrical vessel  134 . The pump head  140  includes a seal head  146  partially disposed inside an end cap  150 . Each end  142 ,  144  is substantially identical and capable of delivering high pressure fluid to the waterjet cutting system. 
     As shown in  FIGS. 3 and 4 , the seal head assembly  146  includes an inlet check valve  154  configured to allow low pressure water to enter the bore  130  as the plunger  122  is retracted, and an outlet check valve  158  to direct high pressure fluid to the outlet  162  as the plunger  122  advances within the bore  130 . Referring to  FIG. 4 , the end cap  150  in the illustrated embodiment includes female threads  166  for mating with male threads  170  on an outer surface of a hollow stud  174 . In other embodiments, the end cap  150  can be secured to the hollow stud  174  with an alternative removable connection. For example, tie rods (not shown) may extend the length of the vessel  134  and couple the hydraulic cylinder head  138  to the end cap  150 . A plurality of jack bolts  180  threaded into apertures  184  of the end cap  150  each include end faces  190  that engage the shoulder  194  of the seal head  146  and provide a compressive force to press the seal head  146  into sealing relationship with an end portion  200  of the cylindrical vessel  134 . As will be further described below, the seal head  146  includes an engagement face  208  proximate an engagement face  212  of the end portion  200  of the cylindrical vessel  134 . The secured cylindrical vessel  134 , seal head  146 , and end cap  150  are all concentric with a longitudinal axis  215  through the center of the bore  130 . 
     Referring to  FIG. 5 , the engagement face  208  includes a generally curved contacting surface  216 . The curved contacting surface  216  in the illustrated embodiment is concave and has a radius R 1  of approximately 0.5″ (17.8 mm), with other radii being possible. In the illustrated construction, the surface  216  is defined by a continuous circular curve that extends the full length of the surface  208 , with other curves such as ellipses, ovals, variable radius curves and the like also being possible. 
     The engagement face  212  includes a substantially linear surface  218  and a blend radius  220  formed between the linear surface  218  and the bore  130 . Thus, the engagement face  212  is defined in part by the linear surface  218  and the convex blend radius  220 . The blend radius  220  has a radius R 2  of about 0.08″ (2.0 mm) in preferred constructions, with larger and smaller radii being possible. 
     The engagement of the concave surface  216  and the blend radius  220  provides for a wider seal area than would be achieved if the concave surface  216  were linear. During operation, the cylinder expands radially which can allow the seal head  146  and the concave surface  216  to move inward slightly relative to the blend radius  220 . During this cyclic process, the convex blend radius  220  can rock on the surface  216  such that the amount of sliding between the surfaces is reduced. The reduction in sliding can reduce the likelihood of surface damage, thereby improving the life of the components. The engagement of surfaces  216  and  220 , when forcibly exerted against each other, exhibits a variable contact angle as they form a pressure-tight seal. The contact angle when the pieces are first mated provides a somewhat shallow contact angle α with respect to the longitudinal axis  215  that allows the seal head  146  to be wedged into the bore  130  of cylinder  134 , thus quickly forming a pressure-tight seal with relatively low jack bolt force. As jack bolts  180  are tightened further to exert the proper preload on the joint, the contact angle α changes such that the wedging action on the bore  130  of the cylinder  134  is reduced, which slows the introduction of additional tensile circumferential stresses in the bore, and the contact loading of the seal head  146  on the end of the cylinder  134  becomes more axial. 
     In other constructions, the engagement face  212  includes a convex curved surface  224  that extends along at least a portion of the engagement face  212  and may or may not blend into a linear surface, as shown in  FIG. 6 . The surface  224  can be defined by a simple curve such as a circle, ellipse, oval, or the like. Alternatively, the surface  224  is defined by a complex curve, which defines a radius that varies as a function of the distance from the longitudinal axis  215 . The radius of the surface  224  can vary continuously from a point having a designated radius R 3  to another point having a designated radius R 4 , or can vary non-continuously from R 3  to R 4 . Specifically, the radius of the surface  224  can vary continuously such that an infinite number of radii exist between R 3  and R 4 . Alternatively, the radius of the surface  224  can vary non-continuously such that a discrete number of distinct radii (e.g., one, two, three, etc.) exist between R 3  and R 4 , and in some constructions the surface  224  may be limited to a discrete number of distinct radii linearly connected. In the construction of  FIG. 6 , the curve radius R 3  is smallest near the axis, for example, approximately 0.060″ (1.5 mm), and increases as the distance from the axis increases. As illustrated, the radius along the surface  224  smoothly transitions from R 3  to a larger radius R 4  that ranges from approximately ¼″ (6.4 mm) to approximately ⅜″ (9.5 mm). In addition, the concave contacting surface  216  in such an embodiment can have a radius R 1  ranging from approximately ⅓″ (8.5 mm) to approximately ½″ (12.7 mm). The concave surface  216  can be similarly arranged such that it can be defined by a simple curve or by a complex curve that can vary continuously or non-continuously from R 5  to R 1  in the same manner as previously described for R 3  and R 4 . 
     In another embodiment, the engagement face  208  includes a generally convex curved surface  228  that extends the full length of the surface  208 . Referring to  FIG. 7 , the convex curved surface  228  is shown proximate the linear surface  218  and the blend radius  220  of the engagement face  212  of the construction illustrated in  FIG. 5 . In this construction, the curved surface  228  contacts the blend radius  220  to form a seal therebetween. In alternative constructions, the linear surface  218  and the blend radius  220  are replaced with a convex curved surface, to include any of the aforementioned surfaces  224  of  FIG. 6 . 
     The engagement of the convex surface  228  and the blend radius  220  (or curved surface) provides for a narrower seal area than would be achieved if the convex surface  228  were linear. The narrower seal increases the contact pressure per unit of length when compared to other designs. During operation, the cylinder expands radially, which can allow the seal head  146  and the convex surface  228  to move inward slightly relative to the blend radius  220 . During this cyclic process, the convex blend radius  220  can rock on the surface  228  such that the amount of sliding between the surfaces is reduced. The reduction in sliding can reduce the likelihood of surface damage, thereby improving the life of the components. 
     Referring to  FIG. 8 , another construction includes a seal formed between an engagement face  212  defined by a continuous concave curved surface  232  and the previously identified convex curved surface  228 . 
     Rather than define the surface  232  with a simple curve such as a circle, ellipse, oval, or the like, the surface  232  is defined by a complex curve. Specifically, the complex curve defines a radius that varies as a function of the distance from the longitudinal axis  215 . In the illustrated construction, the curve radius is largest near the axis and continuously decreases as the distance from the axis increases. Thus, the radius of the curve at a point  236  of the surface  232  is greater than the radius of the curve at a point  240 . 
     The construction of  FIG. 8  provides benefits similar to those described for the construction of  FIG. 5 . In addition, the use of a variable radius curve or spiral to define the surface  232  improves the sealing of the joint. As the seal head  146  is assembled into the cylinder  134  a wedging action occurs. The wedging action tends to widen the opening at the end of the cylinder and is a function of the contact angle α between the surfaces. As the angle gets smaller, the wedging action increases. However, the arrangement of  FIG. 8  is such that as the seal head  146  moves further into the cylinder  134 , the contact angle α increases slightly, thereby reducing the wedging action as the forces on the seal head  146  are increased. The reduction in wedging can produce a joint that provides an adequate seal with less force than would be required with another arrangement. 
     In other constructions, other curves or combinations of curves could be employed to form the surfaces of the engagement faces  208 ,  212 . For example, ovals, ellipses, other conic sections, etc. could be used alone or in combination to define the engagement faces  208 ,  212 . In still other constructions, other complicated or compound curves could be employed for the surfaces of the engagement faces  208 ,  212 . It should also be noted that the examples illustrated herein could be combined or changed such that aspects of one illustrated construction could be applied to other constructions illustrated or described herein. 
     When urged together by the fastening of the end cap  150  to the hollow stud  174  and the action of the jack bolts  180 , the aforementioned surfaces of the engagement faces  208 ,  212  illustrated in  FIGS. 5-8  engage each other at a point of contact  250 , the tangent line to which forms a contact angle α with respect to the longitudinal axis  215  (also illustrated locally to the point of contact  250  in  FIGS. 5-8 ). In some constructions, the contact angle α ranges from approximately 30° to approximately 60°. In one construction, the contact angle α can be about 37°. In another construction, the contact angle α can be about 45°. In still another construction, the contact angle α can be about 55°. 
     In operation, the end cap  150  is fastened to the hollow stud  174  to properly align and provide a first amount of compressive force between the seal head  146  and the end portion  200  of the cylindrical vessel  134 . In the case of the construction of  FIGS. 3 and 4 , the end cap  150  is fastened to the hollow stud  174  which is anchored in the hydraulic cylinder head  138 . The jack bolts  180  are rotated to engage the end faces  190  with the shoulder  194  of the seal head assembly  146  until a desired final amount of compressive force is obtained. When the jack bolts  180  are rotated, the hollow stud  174  is placed in tension and the cylindrical vessel  134  is placed in compression due to the axial load. During rotation of the jack bolts  180 , the end faces  190  push the seal head  146  and the engagement faces  208 ,  212  together. The engagement faces  208 ,  212  interface at the point of contact  250  as previously described to form a seal that inhibits unwanted flow leakage from the bore  130  throughout the operational pressure fluctuations of the pumping cycle. In other designs, the hollow stud  174  and the cylindrical vessel  134  are combined into one piece and another tensioning method such as tie rods are employed to provide the necessary compression between the cylindrical vessel  134  and the seal head  146 . In still another design, the end cap  150  is fastened directly to the cylindrical vessel  134  using mating female and male threads, without the need for the hollow stud  174 . 
     It has been unexpectedly determined that the seal engagement configurations illustrated and described result in a more effective seal between the seal head  146  and the cylindrical vessel  134  than identified in previous engagement configurations having alternative geometries. As an example, the point of contact  250  of the configurations of  FIGS. 5-8  is in closer proximity to the longitudinal axis  215  than in previous configurations. The high pressure fluid being sealed therefore acts on a smaller surface area of the seal head  146 , resulting in a lower force tending to separate the seal head from the cylinder  134 . For this and other reasons, the engagement of the seal head  146  and the cylindrical vessel  134 , as illustrated in any of  FIGS. 5-8  and further described herein, has been found to provide a satisfactory seal connection at a lower required value of compressive force while concurrently reducing the incidence of galling and spalling between the contacting surfaces. The reduced galling and spalling increases the re-sealability of the components, thereby increasing the life of the components. 
     In all of the aforementioned embodiments, it is to be understood that all operational sealing contact of the cylinder  134  with the seal head  146  occurs between two curved surfaces, as described herein. 
     Various features and advantages of the invention are set forth in the following claims.