Abstract:
A mounting assembly for mounting a pump to a fluid cylinder comprising a tie rod threaded at one end and providing a second end drivingly engageable with a sleeve-like threaded connection for clamping attachment directly into the cylinder block by the direct thread engagement of the connector internally of the cylinder block. The invention eliminates the requirement of machining a fluid cylinder block to provide engageable flanges and form nut pockets, thereby minimizing fabrication time and costs, while increasing strength, stability and alignment accuracy between pump pony rods and plunger assemblies of fluid cylinders generally of the type used for high pressure industrial applications.

Description:
BACKGROUND OF THE INVENTION 
     The invention generally relates to multipurpose pumps useful for various applications, such as oil well servicing, oil well stimulation, water blasting, and various industrial uses. The invention is more specifically directed to the mounting of a fluid cylinder to the power end assembly of a pump. 
     The prior art techniques for mounting a fluid cylinder to a pump require the machining of flanges in the fluid cylinder block in order to create nut pockets for affixing nuts to the threaded ends of stay rods passing through the flanges. The creation of these flanges requires extensive machining time and further demands the accurate alignment of through bores cut through the flanges for passages of stay rods to be affixed thereto and aligned axially with corresponding bores in the pump frame. At the opposite ends of the stay rods, threaded portions threadingly engage the threaded bores of the pump frame. 
     Typically, pumps of the kind primarily envisioned for the present invention are high pressure devices, often reaching pressures in the range of 10-20,000 psi (703 Kg/cm 2 -1406 Kg/cm 2 ). Such are often used as oil stimulation pumps well known in the petroleum industry. In these arrangements, pony rods driven by crank shaft drives within the pump&#39;s power end assembly are drivingly cooperative with reciprocating plungers communicating within the fluid cylinder for providing high pressure fluid discharge. High stresses can be created with pumps operating normally in the range of 350-2000 BHP for driving plungers that are typically from about 4″ to 8″ in diameter. 
     Normally, each pony rod and an associated plunger have four stay rod assemblies therearound for interconnecting the frame of the pump to machined flanged portions of the fluid cylinder block. The machining required to create the flanged portions inherently eliminates valuable stabilizing mass and strength from the block of steel forming the fluid cylinder. Zones of weakness are created by this procedure. Machining the steel block also requires a significant amount of labor cost and time. Built in to the machining process is potential stay rod alignment inaccuracy by cutting bores in the flanges for accommodating the stay rods and forming nut pockets for fastening the rods to the flanges. This prior art method can also affect the alignment of the pony rods and plungers. With the high pressures developed by the pumps and resultant dynamic forces, coupled with the concurrent rapid reciprocation times of the pony rods, even slight misalignments can cause early machine part wear, breakdowns, loss of power, and the requirement to check and retighten connections. 
     It is therefore a goal of the present invention to eliminate the expensive and strength reducing process of forming flanges and nut pockets in a fluid cylinder block. Because of the special performance requirements of high pressure pumps, the fluid cylinder blocks are not cast but are forged from special heat treated steels. Accordingly, it is an adjunct goal of the invention to maintain the full stabilizing mass of the forged fluid cylinder block for retaining strength, eliminating weakened zones, and maximizing pump-to-fluid cylinder pony rod/plunger alignments. 
     It is a concomitant object of the invention to eliminate the prior art techniques of creating weakened flange sections which have been required to be made in order to provide through-bores necessary to connect nuts to the stay rods extending therethrough from the pump frame. 
     It is an allied objective of the invention to provide for a direct attachment to the fluid cylinder block internally of the steel mass forming the fluid cylinder block. 
     SUMMARY OF THE INVENTION 
     The invention replaces the bolted stay rod technique of the prior art and provides a unique tie rod and exteriorly threaded connector assembly to clampingly embed the tie rods directly into the steel block forming the fluid cylinder and co-axially aligning them with corresponding engageable bores in the pump frame. 
     A plurality of tie rods are provided with either a short or long sleeve-like threaded connector for attachment to the fluid cylinder block. The short and long connectors facilitate a captive and anchored clamping of shouldered heads of the tie rods within at least partially threaded bores in the fluid cylinder block. Usually with multiple pump pony rods, each pony rod is associated with a fluid cylinder plunger and four tie rods and connectors. The short and long connectors preferably are arranged, respectively, at upper and lower adjacent tie rods to permit for the direct passage of a tightening wrench to reach and facilely engage a hex head of a connector at the correct 90° relation for accurate threading rotation for clamping the tie rod to the fluid cylinder. The opposite end of the tie rod is threaded and forms a shoulder relief portion for accommodating a pump frame spacer, which spacer is pressed against the pump frame as the threaded end of the tie rod threadingly engages a threaded bore in the pump frame. A grippable surface of the tie rod is created along the tie rod, such as by knurling, to facilitate the sure grip of a pipe wrench for tightening to the pump frame. Optionally, the shouldered head of the tie rod is provided with an axial hex bore, which facilitates the initial starting of the threaded connection at the other end to the pump frame, such as by means of a drill and bit spinning the tie rod, leaving only the final tightening of the threaded engagement to the pump frame by, for example, a torque wrench gripping the knurled surface. 
     The shouldered head of the tie rod has an abuttable annular shoulder surface forcefully contacted by a short or long connector as the connector is tightened into a fluid cylinder threaded bore, thereby inserting and clamping the shouldered head into the bore of the fluid cylinder. The leading, or terminal, end of the shouldered head is preferably provided with a circumferential chamfer, which bottoms out generally at the drill point bottom wall of the threaded bore. 
     In a standard configuration for an oil well stimulation pump, three pony rods driven by the pump power end assembly are drivingly associated with three fluid cylinder plungers. The invention provides a method for the quick connection of twelve tie rods (four tie rods around each plunger), having sleeve-like short or long connectors slidingly placed thereon, which tie rods are subsequently rotated by means of a power drill, or the like, engaging the hex end bores of the tie rods and spinning them for preliminary attachment of the opposite threaded ends to twelve threaded bores in the pump frame. The tie rods are then finally tightened by means of a torque wrench or the like. The fluid cylinder is then brought adjacent to the power end assembly of the pump having the attached tie rods, and the tie rod shouldered heads are inserted into twelve threaded bores in the fluid cylinder block. The connectors are then wrench-tightened at hex bolt heads thereof to force the connectors against the shouldered heads and embeddingly clamp the tie rods inside the bores to thereby securely mount the fluid cylinder on the pump frame. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a power end assembly of a pump and a fluid cylinder connected thereto by means of the mounting assembly of the present invention; 
     FIG. 2 is a top plan view of the pump and fluid cylinder of FIG. 1; 
     FIG. 3 is a front elevational view of the pump and fluid cylinder of FIG. 1; 
     FIG. 4 is a vertical cross-sectional view taken through two vertically adjacent tie rod assemblies of the present invention and showing the connection of the fluid cylinder to the power end assembly of the pump as in FIG. 1; 
     FIG. 4 a  is a vertical cross-sectional view like FIG. 4 but showing a prior art stay rod mounting assembly; 
     FIG. 5 is a plan view of the tie rod of the mounting assembly; 
     FIG. 6 is a end view looking at the left end of the tie rod of FIG. 5; 
     FIG. 7 is an end view looking at the right end of the tie rod of FIG. 5; 
     FIG. 8 is a plan view of a short connector for connecting a tie rod to a fluid cylinder; 
     FIG. 9 is a plan view of a long connector for connecting a tie rod to a fluid cylinder; 
     FIG. 10 is an end view showing the identical hex bolt head of the short and long connectors of FIGS. 8 and 9; 
     FIG. 11 is a spacer mountable at a recessed spacer shoulder of the tie rod located substantially adjacent the threaded end of the tie rod as shown in FIG. 5; and, 
     FIG. 12 is a side view of the spacer of FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In reference to the attached figures, like reference numerals are used to refer to the same elements throughout. 
     In reference to FIGS. 1-3, it will be seen that the invention is directed to the mounting of a pump  10  to a fluid cylinder  20  of generally known constructions. One commercial pump that may be used in practicing the invention is a Series OPI 2000 well stimulation pump manufactured and sold by Gardner Denver, Inc. An example of a fluid cylinder also useful in practicing the invention is a 1515 GPM cylinder block having a one-piece design, also sold by the same manufacturer. The invention comprises a mounting assembly  30  therebetween. It will be observed that in the illustrative embodiment, the pump  10 , which is also referred to in the industry as the power end assembly, drives three pony rods  11 ,  12  and  13 , which operably communicate with the fluid cylinder  20 . The fluid cylinder  20  is also referred to in the industry as the fluid end assembly. The fluid cylinder  20  has discharge outlets  21  and a suction manifold  22 . The fluid cylinder  20  in the exemplary embodiment is made of a special forged heat-treated steel alloy, which meets ASTM standard No. 4330. Forged cylinder blocks are normally required because of the pressures developed in these industrial type pumps that typically can range from about 10,000 psi (703 Kg/cm 2 ) to over 20,000 psi (1406 Kg/cm 2 ). The fluid cylinder  20  has three plungers  23 ,  24  and  25 , which are driven by the pony rods  11 ,  12  and  13 , respectively. The pump  10  includes crank shaft and cross-head assemblies well-known in the industry for reciprocally driving the pony rods. Horsepower ratings of such high pressure pumps are typically in the range of from about 350 BHP to about 2000 BHP. In operation, considerable force is thus exerted whereby vibratory effects should be minimized to maintain the alignment of the pump pony rods  11 - 13  with the fluid cylinder plungers  23 - 25  and keep mounting assembly connections tight. 
     With reference now to FIGS. 4 and 4 a,  the inventive mounting assembly  30  and prior art assembly  60  will be seen in greater detail. The mounting assembly  30  joins a fluid cylinder block  26  of the fluid cylinder  20  to a plate  14  of pump housing  15  of the pump  10 . 
     The mounting assembly  30  comprises a plurality of tie rods  31  each associated with a sleeve-like hollow connector  32  or  33 . Said tie rods  31  each having a threaded end  34  opposite a second end having a shouldered head  35 , preferably ending in a circumferential chamfer. In the disclosed embodiment, each of the pony rods  11 - 13  and plungers  23 - 25  are associated with four tie rods, whereby twelve tie rods  31  join the pump  10  to the fluid cylinder  20 , as shown in FIGS. 1-3. The connections of the ties rods  31  to the plate  14  are made possible by machining complementary threaded bores  16  into the plate  14  to be thread engageable with the threaded end  34  of each tie rod  31 . At the other side, the fluid cylinder block  26  is machined to have at least partially threaded bores  27  engageable by threaded shafts  36  of the connectors  32  and  33 . The bores  27  in the preferred embodiment have extending non-threaded portions  28 , which need not be threaded as they are for the clamping receipt therein of the shouldered heads  35  of the tie rods  31 . The shouldered heads  35  are not rotationally thread-engaged but are longitudinally forced bore-inward. The bores  26  are machine drilled, threaded and bored, and terminate in drill point bottom walls  29  against which the shouldered heads  35  abut. 
     The threaded ends  34  of the tie rods  31  are cut to have a smaller diameter than the adjacent major diameter of the tie rods  31  thereby forming annular spacer shoulders  37  for accommodating washer-like spacers  38 , which abut against, and distribute tightening forces onto, the plate  14 . 
     The threading attachment of the tie rods  31  to the plate  14  is initially achieved by means of optional hex bores  39  that are axially machined into the leading ends of the shouldered heads  35 . The hex bores  39  facilitate a time-saving initial starting of the threading engagement of the tie rods  31  into the plate  14  by means of using a drill with a complementary hex bit for engaging the hex bores  39  to screw the threaded ends  34  into the bores  16 . To accomplish complete tightening to a prescribed torque level, the tie rods  31  are further provided with knurling  40 , which offer a grippable surface for applying a torque wrench to finally tighten the connection between the tie rods  31  and the plate  14 . 
     It will be observed from FIG. 4 that the connectors  32  are short connectors and connectors  33  are longer by virtue of having a longer shank portion  41  between a bolt-like hex head  42  and the threading  36 . By providing vertically adjacent short and long connectors, a wrench can be introduced between the pump  10  and the fluid cylinder  20 , so that each vertically adjacent pair of long and short connectors can be reached by the mechanic to be tightened into the fluid cylinder  20 . Because the longer connectors hex heads  42  project further from the fluid cylinder  20 , the shorter and longer connector hex heads  42  are tightenable in different parallel vertical planes, thus providing clearance for a wrench to correctly approach them all at 90° to the axes of the connectors  32  and  33 . 
     With reference to FIG. 4 a,  a prior art mounting assembly  60  is shown for comparison. In this prior art technique, the assembly  60  is provided with a plurality of hex-shaped stay rods  61 , which are connected by means of nuts  62  to a fluid cylinder block  200 . In this common prior art technique, the fluid cylinder block  200  is machined to provide nut pockets  201  and flanges  202 , which flanges are bored therethrough at  203  for the receipt therein of a smooth shaft  63  of the stay rods  61 . The stay rods  61  terminate in threaded ends  64  for engagement by the nuts  62 . The creation of the nut pockets  201  results in weakened zones in the flanges  202  adjacent to the connections of the stay rods  61 . The machining also eliminates considerable mass from the steel cylinder block, which can lead to fatigue cracking due to pressure pulsations. The phantom lines L and LL show the original block shape and indicate the amount of steel machined from the fluid cylinder block  200 , without which machining the fluid cylinder block  200  would have the construction and mass of the fluid cylinder block  20 . This may amount to hundreds of pounds of lost mass. For a 1515 GPM fluid cylinder, this can amount to a loss of about 400 pounds. 
     Because of clearance inherently required to insert the shafts  63  into the bores  203 , axial misalignments can occur between the pump pony rods and fluid cylinder plungers. At the other end of the stay rods  61 , lesser diameter stay rod shafts  65  terminate in abutment shoulders  66  at threaded end stubs  67  that are thread engageable with bores  16 ′ made in a plate  14 ′ of a pump  10 ′. The pump  10 ′ and plate  14 ′ being substantially identical to the pump  10  and plate  14  of the illustrative embodiment shown in FIGS. 1-4. 
     In achieving a more secure mounting than the prior art, the connection of the tie rods  31  to the fluid cylinder block  20  by means of the connectors  32  and  33 , and the clamping of the shouldered heads  35  within the bores  27  to abut against the bottom walls  29 , establish a direct embedment internally of the fluid cylinder block mass. This provides a very stable unweakened joinder contrary to the external bolted connection of stay rods  61  passed through bores  203  in a flange  202  of the fluid cylinder  200  shown in FIG.  4 a. The connectors  32 ,  33  of the invention threadably clamp the tie rods inside the mass of the cylinder block versus the prior art technique of externally bolting them onto a flange. Additionally, the provisions of a grippable knurling surface  40  for tightening the threaded end of the tie rods and pressing the shoulders  37  against spacers  38  to create an even abutting force against the plate  14  achieve stronger connections over the prior art. 
     Previously known mounting assemblies have not provided means to facilitate a fast efficient preliminary connection of stay rods to the pump plates. In the present invention, the tie rods  31  having the optional hex bores  39  greatly improve attachment efficiency, which is highly desirable when connections, for example, in an oil field, must be made under varying weather conditions, uneven terrain and other deleterious environmental conditions. 
     With reference to FIGS. 5-12, details of the tie rod  31 , connectors  32 ,  33  and spacer  38  are shown. FIG. 5 illustrates the tie rod  31  having the smaller diameter threaded end  34  joining the tie rod  31  at a shoulder  37 , which forms an annular seat for the spacer  38  shown in FIGS. 11-12. The knurling  40  allows for grippable attachment of a wrench to tighten threading  34  into a pump plate threaded bore. 
     At the opposite end of the tie rod  31 , the hex bore  39  is machined into the end face of the shouldered head  35 . An end view of the hex bore  39  is shown in FIG. 6 facilitating the insertion of a drill bit for the preliminary threading engagement of the threaded end  34  into a threaded bore  16  of the plate  14 . Other polygonal, geometric, or non-geometrically shaped bores could also be formed for driving engagement by a drill bit shaped to engage the particular bore configuration. 
     The shouldered head  35  provides a shoulder  43  for the short or long connector  32  or  33  to press against when the threads  36  are screwed into threaded bore  27  for clamping a chamferred end  44  of the shouldered head  35  into the non-threaded portion  28  of the bore  27  bored into the fluid cylinder block  23 . The chamfered end  44  is driven against the drill point bottom wall  29  of the bore  27 . 
     FIG. 8 illustrates a short connector  32  having a hex head  42 , shank  41 , and threading  36 . In FIG. 9, a long connector  33  is shown having the identical hex head  42  and threading  36  but having a longer shank  41  extending between the threading and the hex head. The connector  33  is made longer by an amount that allows for wrench clearance within the space between the pump  10  and the fluid cylinder assembly  20  for the purpose of correctly gripping all the hex heads  42  of the connectors  32  and  33  at 90° to the long axis of the connectors. As shown in dashed lines, the connectors  32 ,  33  are hollow and sleeve-like with an internal passageway P sized to slide over the tie rods  31 . FIG. 10 is an end view of the hex heads  42  and having a typical bolt configuration. 
     In the disclosed embodiment the tie rods  31  are comprised of a standard ASTM 4340 heat treated steel alloy. For the example disclosed, when utilizing a 2000 BHP pump and 1515 GPM fluid cylinder, the tie rods  31  have a length of about 19 inches and nominal diameter of about 2¼ inches. These dimensions will vary with pump sizes, numbers of plungers, fluid cylinder capacities, fluid pressures, and the like, as would be understood by one skilled in the art. The illustrative connectors  32  and  33  are made of stainless steel and the spacers  38  are made of a heat treated ASTM 4140 steel alloy. Equivalent materials are useable for practicing the invention. 
     The foregoing is a description of a preferred embodiment of the invention but it will be understood that the claims appended hereto are not limited thereto and have a broad range of equivalents thereof.