Patent Abstract:
A reciprocating pump assembly has a pump within a housing. The pump has a crankshaft that rotates and a crosshead that is connected to a plunger via a pony rod. The plunger pumps fluid through cylinders in the pump. A connecting rod connects at one end to the crankshaft and at another end to the crosshead to translate the crankshaft&#39;s rotational movement into linear movement of the crosshead and thereby the plunger. The end connected to the crosshead is secured to the crosshead by a bushing located within the crosshead that allows the connecting rod end to pivot during operation. The bushing extends more than 180 degrees, retaining the connecting rod with the crosshead without the need for a wrist pin. The end secured by the bushing can be retained within the bushing by a lock plate, and retainers without the need for a wrist pin.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to provisional application No. 61/143,300 filed Jan. 8, 2009. 
    
    
     FIELD OF THE INVENTION 
     This invention relates in general to connecting rods used in reciprocating pump crankshafts, and, in particular, to a connecting rod that does not require a wrist pin to link it to the crosshead. 
     BACKGROUND OF THE INVENTION 
     Connecting rods are used in various kinds of pumps used in oilfield operations. A connecting rod can be used, for example, in a reciprocating pump. The reciprocating pump can be used to pump fluid such as chemicals, cement, or other media into a well. Reciprocating pumps typically increase the pressure within a cylinder by reciprocating a plunger longitudinally within the cylinder. The connecting rod typically has a body and two ends. The crosshead end has a hole that allows the end to be connected to a crosshead, which is connected to a pony rod, which in turn is connected to the plunger. The other end secures to a crankshaft that rotates. 
     The crosshead reciprocates within a crosshead housing and has a concave cavity that receives the crankshaft end of the connecting rod. To secure the end of the connecting rod to the crosshead, a wrist pin is inserted through the hole formed in the crosshead end of the connecting rod. The wrist pin thus pivotally secures the end of the connecting rod to the crosshead and allows for the translation of the crankshaft&#39;s rotational movement into linear movement of the crosshead and thereby the plunger. The wrist pin is an additional part that may need to be replaced during the life of the pump. Further, the wrist pin adds weight to the overall pump weight, which can make the transportation of reciprocating pumps more difficult and expensive. Also, disconnecting the connecting rod from the crosshead requires driving the wrist pin out. 
     Thus, it would be desirable to provide a connecting rod for use in reciprocating pumps that does not require a wrist pin to secure an end of the connecting rod to a crosshead. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present invention, a reciprocating pump assembly has a pump located inside a housing. The pump has a crankshaft that rotates and a crosshead that is connected to a plunger via a pony rod. The plunger pumps fluid through cylinders in the pump when it is moved longitudinally within the cylinder. A connecting rod has a body and connects at one endpiece to the crankshaft and at another endpiece to the crosshead to thereby translate the crankshaft&#39;s rotational movement into linear movement of the crosshead and thereby energize the plunger. 
     In this embodiment, the endpiece connected to the crosshead is secured to the crosshead by a bushing located within the crosshead. The bushing extends more than 180 degrees around the connecting rod&#39;s endpiece. The crosshead bushing allows the connecting rod&#39;s endpiece to pivot within the bushing during pump operation. To retain the connecting rod&#39;s endpiece within the bushing, a lock plate, support blocks, and retainers may be used. This eliminates the need for a wrist pin, resulting in one less part to service and repair. Further, the body and the endpiece of the connecting rod may be fabricated with hollow portions to lighten the weight of the connecting rod and thereby the weight of the pump assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a reciprocating pump constructed in accordance with the invention; 
         FIG. 2  is a schematic illustration of the connecting rod location within the reciprocating pump crankshaft housing, and is constructed in accordance with the invention; 
         FIG. 3  an enlarged sectional view of one embodiment of the connecting rod without a wrist pin, and is constructed in accordance with the invention; 
         FIG. 4  an enlarged sectional view of one embodiment of the connecting rod without a wrist pin, and is constructed in accordance with the invention. 
         FIG. 5  is a sectional view of the crosshead of  FIG. 3 , taken along the line  5 - 5  of  FIG. 3 , but with the crosshead housing and the connector rod not shown. 
         FIG. 6  is a sectional view of the crosshead of  FIG. 3 , taken along the line  6 - 6  of  FIG. 3 , but with the crosshead housing and the connector rod not shown. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , reciprocating pump assembly or pump  12  includes a crankshaft housing  13  that comprises a majority of the outer surface of reciprocating pump  12 . Stay rods  15  connect crankshaft housing  13  to a set of cylinders  17 . Each cylinder  17  is in communication with a fluid inlet  19  and a fluid outlet  21 . As shown in  FIGS. 1 and 2 , a suction cover plate  22  connects to an end of each cylinder  17  opposite the plunger rod housing  15 . Pump  12  can be free-standing on the ground, can be mounted to a trailer that can be towed between operational sites, or mounted to a skid such as for offshore operations. 
     Referring to  FIG. 2 , a portion of reciprocating pump  12  housed within crankshaft housing  13  is shown. Crankshaft housing  13  houses a crankshaft  25 , which is typically mechanically connected to a motor (not shown). The motor rotates crankshaft  25  in order to drive reciprocating pump  12  ( FIG. 1 ). In one embodiment, crankshaft  25  is cammed so that fluid is pumped from each cylinder  17  at alternating times. As is readily appreciable by those skilled in the art, alternating the cycles of pumping fluid from each of cylinders  17  helps minimize the primary, secondary, and tertiary (et al.) forces associated with reciprocating pump  12  ( FIG. 1 ). 
     A gear  24  is mechanically connected to crankshaft  25  and is rotated by the motor through gears  26  and  24 . A connecting rod  27  is shown as a substantially solid piece and shown connected to the crankshaft  25  at one end by an endpiece. The connecting rod  27  is pivotally secured by a bushing  34  within the crosshead  29 , which holds connecting rod  27  longitudinally relative to crosshead  29 . Crosshead  29  reciprocates within a crosshead housing  37 . Crosshead  29  may have flat and parallel sides. Alternatively, the crosshead  29  may be cylindrical, as shown in  FIGS. 5 and 6 . The connecting rod  27  pivots within the crosshead bushing  34  as crankshaft  25  rotates with the other end of connecting rod  27 . A pony rod  33  extends from crosshead  29  in a longitudinally opposite direction from crankshaft  25 . Connecting rod  27  and crosshead  29  convert rotational movement of crankshaft  25  into longitudinal movement of pony rod  33 . 
     A plunger  35  is connected to pony rod  33 , which may be considered an extended portion of plunger  35 , for pumping the fluid passing through cylinder  17 . Cylinder  17  includes an interior or cylinder chamber  39 , which is where plunger  35  pressurizes the fluid being pumped by reciprocating pump  12  ( FIG. 1 ). Cylinder  17  also typically includes an inlet valve  41  and an outlet valve  43 . Valves  41  and  43  are usually spring-loaded valves and are actuated by a predetermined differential pressure. Inlet valve  41  actuates to control fluid flow through fluid inlet  19  into cylinder chamber  39 , and outlet valve  43  actuates to control fluid flow through fluid outlet  21  from cylinder chamber  39 . 
     Plunger  35  reciprocates, or moves longitudinally toward and away from cylinder  17 , as crankshaft  25  rotates. As plunger  35  moves longitudinally away from cylinder chamber  39 , the pressure of the fluid inside chamber  39  decreases, creating a differential pressure across inlet valve  41 , which actuates valve  41  and allows the fluid to enter cylinder chamber  39  from fluid inlet  19 . The fluid being pumped enters cylinder chamber  39  as plunger  35  continues to move longitudinally away from cylinder  17  until the pressure difference between the fluid inside chamber  39  and the fluid in fluid inlet  19  is small enough for inlet valve  41  to actuate to its closed position. As plunger  35  begins to move longitudinally towards cylinder  17 , the pressure on the fluid inside of cylinder chamber  39  begins to increase. Fluid pressure inside cylinder chamber  39  continues to increase as plunger  35  approaches cylinder  17  until the differential pressure across outlet valve  43  is large enough to actuate valve  43  and allow the fluid to exit cylinder  17  through fluid outlet  21 . In one embodiment, fluid is only pumped across one side of plunger  35 , therefore reciprocating pump  12  is a single-acting reciprocating pump. 
     Referring to  FIG. 3 , an embodiment of the connecting rod  27  is shown. The connecting rod  27  comprises a body  57  made of steel, or other suitable metallic material, that attaches to the crankshaft  25  ( FIG. 2 ) on one end via an endpiece. An outermost semicircular retainer  58  is placed over the crankshaft  25  and fastened by bolts to the innermost semicircular portion of the endpiece  60 , which is integral with the body  57 . The body  57  optionally may have a hollow interior that extends approximately the length of the body  57 . Alternatively, material may be removed from both sides along the body  57  to leave a thin web of material within the body  57 . 
     The front end of the connecting rod  27  is a steel cylindrical endpiece  59  with an optional hole  31  to lighten the weight of the rod  27 . Alternatively, material may be removed from both sides of the steel endpiece  59  to leave a thin wall of material within the endpiece  59 . Endpiece  59  may be integrally formed with connecting rod  27  or attached by bolts  62 . Endpiece  59  has a cylindrical exterior surface  64  pivotally secured within a concave bushing  34  in the crosshead  29 . Cylindrical exterior surface  64  slides relative to bushing  34  as connecting rod  27  pivots up and down. A neck  66  of reduced diameter is located by the cylindrical portion of endpiece  59  and the portion that joins connecting rod  57 . 
     Bushing  34  may comprise a single curved piece of metal that extends circumferentially greater than 180 degrees and less than 360 degrees. Alternately, bushing  34  may comprise three separate pieces  34   a ,  34   b  and  34   c , as will be described subsequently. The circumferential ends  68  of bushing  34  are spaced apart from each other, defining a gap  71 , shown also in  FIG. 6 . In  FIG. 3 , gap  71  extends about 70 degrees from one circumferential end  68  to the other and faces the crankshaft  25  ( FIG. 2 ). In the example of  FIG. 3 , crosshead  29  has one portion that contains about 180 degrees of the partially cylindrical receptacle for bushing  34 . Upper and lower retainer blocks  32  attach to this portion and form a part of crosshead  29 . Each retainer block  32  continues the partially cylindrical receptacle for bushing  34  for another 55 degrees or so. Bushing portion  34   a  extends 180 degrees, and bushing portions  34   b  and  34   c  extend 55 degrees each in this example. Upper and lower lock plates  28  are located on the sides of retainer blocks  32  opposite crosshead  29 . Bolts  30  extend through holes in lock plates  28  and retainer blocks  32  into crosshead  29 . Because gap  71  is smaller than the cylindrical portion of endpiece  59 , connecting rod  27  is retained within the bushing  34  by lock plate  28 , support blocks  32 , and bolts  30 . The bushing  34  extends more than 180 degrees around the endpiece  59  of the connecting rod  27 , so the bushing  34  has enough contact surface to secure the endpiece  59  when the rod is retracted. Gap  71  may extend completely across the width of crosshead  29 , thus resulting in a rectangular configuration for gap  71 , as shown in  FIG. 6 . Alternately, lock plates  28  could have semi-circular holes that fit around neck  66 , giving gap  71  a circular configuration. 
     Connecting rod endpiece  59  can be installed and removed from bushing  34  without removing crosshead  29  from crosshead housing  37 . To remove it from the position in  FIG. 3 , the operator releases the bolts fastening lock plates  28  and retainer blocks  34 , then removes lock plates  28  and retainer blocks  34 . If bushing  34  is in three separate pieces  34   a ,  34   b  and  34   c , this removal leaves only the 180 degree portion  34   a  of bushing  34 . The operator can simply pull endpiece  59  to the left as shown in the drawing to detach it from crosshead  29 . 
     A lubrication port  36  communicates the periphery of the crosshead  29  to the interior of the crosshead  29  to provide lubricant between the pivoting endpiece  59  and the bushing  34 . This arrangement between the bushing  34  and the endpiece  59  of the connecting rod  27  translates the rotational movement of the crankshaft  25  into longitudinal movement of the plunger  35 . The connecting rod  27  that does not require a wrist pin and thus is unlike connecting rods in the prior art that are secured to the crosshead  29  via a wrist pin. 
     In another embodiment (not shown), the lubrication port  36  is located on the endpiece  59  of the connecting rod  27 . 
     In another embodiment shown in  FIG. 4 , the connecting rod  27  is retained within the bushing  34  by lock plate  28 , and bolts  30 . The support blocks  32  used in  FIG. 3  are omitted in this embodiment. Instead, crosshead  80  contains the full extent of bushing  34 , rather than just 180 degrees as in  FIG. 3 . Connecting rod endpiece  59  is installed in bushing  34  from one side while crosshead  80  is removed from crosshead housing  37 . Endpiece  59  would be inserted into bushing  34  in a direction along an axis of bushing  34 . 
     Reciprocating pumps  12  are large, and complex pieces of equipment with many parts that may have to be replaced as they wear out. Minimizing the number of parts by eliminating the need for a wrist pin to connect the endpiece  59  of the connecting rod  27  to the cross head  29  is thus desirable because it makes pump  12  more reliable and simpler. By using a bushing  34  that extends more than 180 degrees around the cylindrical endpiece  59  of the connecting rod  27 , the need for a wrist pin is eliminated. The optional hole  31  at the endpiece  59  further provides a lighter weight for the connecting rod  27 . 
     This written description uses examples to disclose the invention, including the best mode, and also enable a person of ordinary skill in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. These embodiments are not intended to limit the scope of the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Technology Classification (CPC): 5