GB1572632A - Drive rod coupling for positive displacement pump - Google Patents

Description

(54) DRIVE ROD COUPLING FOR POSITIVE DISPLACEMENT PUMP (71) We, VAPOR CORPORATION, a corporation organized under the laws of the State of Delaware, United States of America, located at 6420 W. Howard Street, Chicago, Illinois, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to a new and improved coupling that functions as a preloaded member coupling two reciprocating elements. More specifically, the present invention is directed to a new and improved drive rod coupling member for coupling the plunger and piston rod of a gas operated positive displacement pump while maintaining sufficient contact between the two to prevent damage due to separation.

Producing portions of the oil and gas industry. i.e., oilfields have many activities which involve frequent transfer of crude oil and other associated liquids often at high pressures. These operations include transfer of mixtures of oil and water from accumulation tanks located at various points in the producing field. Exotic chemicals are also mixed and or injected on a controlled ratio basis for altering the characteristics of crude oil which varies greatly from place to place and time to time.

Oilfield operating conditions require equipment which is rugged and requires little maintenance. Liquids pumped are often highly contaminated and contain a high percentage of dissolved gases and undissolved solids. Pumps must be capable of withstanding "ganging" or multiple parallel operation. Often the source of operating energy is highly contaminated natural gas from the same well, producing the pumped oil. Compressed air is also available.

Current pumps employed in the oil field utilize a fluid drive piston connected to a high pressure fluid plunger. Both of these driven components of these pumps are alignment sensitive, since they operate at rapid rates and at high forces. Accordingly, if a slight misalignment between the driven and drive components occurs, excessive plunger and packing wear is caused resulting in rapid deterioration of these elements.

Typically, the piston rod and the plunger of these prior art pumps are rigidly connected requiring precision boring and extreme care in assembly in order to accomplish a high degree of accuracy in axial alignment. A slight misalignment during fabrication or assembly results in rapid deterioration of the plunger, piston rod and the packing for each.

Moreover, any misalignment between the piston rod and the plunger of the pump that is not continuously absorbed by the coupling apparatus, whether it be rigid or otherwise, results in excessive movement of both the piston rod in the drive cylinder packing and the pump plunger in the pump cylinder packing. This excessive movement greatly reduces the life of the packing and if continued over sufficiently long periods of time, can result in piston rod and plunger interference in their respective confinements and eventual destruction thereof.

Typically, gas operated, positive displacement pumps are employed for general fluid handling in producing oil fields. Such applications require an extremely rugged construction, since the pumps are used in the field and often use natural gas directly from the well as the working fluid.

Gas operated reciprocating high pressure pumps employ a drive piston that is rigidly connected to a piston rod. During operation of the pump, the piston is reciprocated within the piston cylinder of the pump. Reciprocation of the pump is accomplished by utilization of switch valves and a conventional reversing spool spool valve. In this manner, fluid flows into the piston cylinder through ports. This flow is alternated in direction by the spool valve causing a reciprocating motion of the piston, and accordingly, a similar movement is imparted to the piston rod.

To pump water or similar fluid at a high pressure into pipelines, tanks, or refinery processes, a high pressure fluid plunger is used in the pump. The plunger must be connected to the piston rod to be reciprocated thereby, so that in one direction the plunger draws fluid into a chamber and in the reverse direction forces the fluid at a high pressure to the high pressure system.

In one aspect the present invention provides, in a reciprocating pump of the type including a pair of reciprocating elements, one reciprocating element being a piston rod driven by a pressure operated piston and the other being a fluid plunger slidably mounted in a plunger cylinder for pumping fluid, the improvement comprising.

a coupling device connecting said rod to said plunger, including, a retainer on one of said members, a head on the other of said members, and means resilently maintaining said head in said retainer to inhibit separation of said head and said retainer.

The coupling device allows the power piston rod and the fluid plunger to be less alignmentsensitive and therefore reduces the precision boring and extreme care in assembly required in the prior art pumps.

In another aspect the present invention provides a coupling assembly for coupling first and second elongated members during reciprocal movement of said members along their longitudinal axes, said assembly comprising a retainer having an open end and an internal cavity, said retainer secured to said first member, a concave part-spherical bearing face within said retainer, a head having a convex part-spherical face secured to said second member and positioned within said retainer wherein said convex face abuts and mates with said concave face, a backup member positioned within said retainer between said open end and said head, and at least one biasing element positioned within said retainer and acting between said backup member and said retainer thereby maintaining the said faces in contact.

Such a coupling allows relative angular misalignment, while maintaining sufficient contact between the members at the point of coupling to prevent damage to either due to impact during the reversal of the reciprocating stroke. It allows efficient force transfer between the members travelling in noncooperating paths without appreciable relative motion or loss of pump delivery. This compliant coupling is conveniently disconnectable.

The connector head is fabricated preferably of stainless steel or similar material. It is rigidly secured to either the piston rod or the fluid plunger. Attached to the other member is the retainer.

Preferably between a closed end of the retainer and the connector head is a bearing fabricated of steel or similar material. The bearing surface abutting the connector face is of a mating configuration allowing slight angular movement of the head relative to the bearing along the curved abutting surfaces.

Opposite the part-spherical face of the connector head and separated therefrom is a backup plate secured within the retainer.

Positioned behind the backup plate is a cap that is secured e.g. threadably within the retainer and serves to lock the bearing head and backup plate within the retainer.

Mounted between the backup plate and the cap are several dished or "Belleville" spring washers. These washers serve to bias the backup plate and connector head against the bearing within the retainer. In this manner, the connector head is allowed to rotate through the interac tion of its hemispherical face against the bearing while the Belleville washers provide sufficient force to maintain contact between the two points of coupling - to point of contact between the bearing and head.

The contact maintained by the "Belleville" washers prevents damage to either the piston rod or the plunger that may result from impact on reversal of stroke of the pump. The coupling also prevents excessive movement of either the piston rod or the plunger in their respective packings. thereby extending the life of the pump.

The above and other objects and advantages and novel features of the present invention will become apparent from the following detailed description of the preferred embodiment of the invention illustrated in the accompanying drawings wherein: Figure 1 is a perspective view of a gas operated, positive displacement pump including a coupling constructed in accordance with the present invention; Figure 2 is an enlarged, sectional view of the device of the present invention illustrated in Figure 1; and Figure 3 is an enlarged, sectional view of the coupling device illustrated in Figure 1.

With reference to Figs 1-3, therein is disclosed a conventional gas operated, positive displacement pump 10. The pump 10 includes a drive cylinder 12 rigidly secured between the caps 14 and 16 by a plurality of studs or bolts 18.

The pump 10 employs a typical reversing spool valve 20 that functions to direct high pressure fluid alternately through the conduits 22 and 24 (Fig 2). The conduits 22 and 24 direct fluid into alternate ends of the piston drive chamber 26. In this manner, the piston 28 is influenced by high pressure fluids on alternate sides thereof causing reciprocating motion. Reciprocation of the pump stroke is accomplished by the piston 28 abutting either of the switch valves 30 and 32. These valves 30 and 32 relieve spool valve 20 thereby allowing it to shift, thus alternating the fluid flow to drive chamber 26.

Rigidly attached to piston 28 is a piston rod 34. To prevent fluid leakage from the drive cylinder 26 around the rod 34, a drive cylinder packing 38 is employed. This drive cylinder packing 38 includes packing 40, a bushing and Boring 42, and wiper 48.

The pump 10 (Fig 1) may be employed in oil fields for pumping large quantities of fluid such as water under high pressure into storage tanks, pipelines or other refinery processes, involved in oil production. To accomplish its pumping function, the pump 10 includes a fluid inlet 50 and a fluid outlet 52 fabricated in the plunger cylinder 53.

Fluid is drawn through the inlet 50 by the reciprocation or withdrawal of the fluid plunger 54 out of the chamber 58 (Fig 2). During withdrawal of the fluid plunger 54, fluid is drawn into inlet 50 through a one-way check valve 56. Reverse flow is prevented by the interaction of ball 60 in its seat 62.

During the alternate reciprocal movement of the plunger 54, a fluid is forced through outlet 52 from the chamber 58 by passing through the one-way check valve 64. The reversal of fluid through outlet 52 is prevented by the interaction of ball 66 in its seat 68.

Leakage of fluid around the fluid plunger 54 is prevented by a pump cylinder packing 70 similar to the drive cylinder packing 38.

The plunger cylinder 53 is secured to a coupling cylinder 72 by bolts 73. The coupling cylinder 72 is in turn attached to end cap 16 by a series of bolts 74.

In order to reduce the precision boring and assembly necessary in prior art pumps, compensation for the resultant axial and angular misalignment must be made. This can be obtained by a coupling that allows axial and angular misalignment at the point of connection, but not at the point of contact of the rod 34 and plunger 54 with their respective packings 38 and 70. To connect the piston rod 34 to the plunger 54 in a manner to provide a connection tolerant of angular and axial misalignment, there is provided a coupling or connector 75 (Fig 3). The coupling 75 includes a retainer 77 rigidly secured, in this embodiment, to the fluid plunger 54 through the utilization of a set screw 79. A connector head 76 is rigidly secured to the piston rod 34 by a set screw 78 and threads 80 on the tapered end of the piston rod 34. It should be noted that the retainer 77 may be secured to the rod 34 and the head 76 may be secured to the plunger 54. It is of no significance to which elements 34 or 54 each is attached.

Axial and angular movement of the connector head 76 is allowed relative to the retainer 77 through the utilization of the head 76 and its substantially hemispherical face 82. This face 82 abuts against and is complementary to the concave face 84 of the bearing 86. This bearing 86 is positioned between the closed end 88 of the retainer 77 and the hemispherical face 82 of the connector 76. The hemispherical configuration of the face 82 and the bearing face 84 allows slight axial and angular movement relative to each other.

This movement obviates the need for precision boring, but introduces possible damage to the rod 34 and plunger 54 due to impact on reversal of the stroke of the piston 28.

In order to allow this angular or axial misalignment while preventing separation and the subsequent impact, a plurality of "Belleville" dished spring washers 92 are employed. These washers 92 are positioned within the retainer 77 and behind a backup plate 90. Sufficient compression is imparted to the "Belleville" washers 92 against the backup plate 90 and, consequently, against the connector 76 and bearing 86 by threadably inserting a closure member 94 into the threaded opened end 96 of the retainer 77.

In this manner, sufficient compressible force can be imparted to the "Belleville" washers 92, and, thus, to the point of connection for the constant contact of the faces 82 and 84. This compressible force must be sufficient to prevent the separation of the faces 84 and 82 during reversal of the stroke of the piston 28 thereby preventing damage to either the rod 34 and plunger 54 and to their respective packings 38 and 70.

The operation of the pump 10 can be summarized as follows.

Gas is alternately introduced into chamber 26 through the interaction of the switches 30 and 32 and spool valve 20. The movement of the piston 28 reciprocates the piston rod 34 within the packing 38.

The piston rod 34 is connected to the plunger 54 by the connector 75. Accordingly, the reciprocating motion of piston rod 34 is also imparted to plunger 54 causing it to reciprocate in its packing 70. Upon the retraction of the plunger 54 out of the chamber 58, fluid is drawn into the chamber 58 through the inlet 50. Upon reversal of the plunger 54, fluid is pressurized in the chamber 58 and passes through the valve 64 and the outlet 52 to a high pressure system or the like.

During the reciprocating motion of the rod 34 and plunger 54, there may be slight angular misalignment of the piston rod 34 relative to the plunger 54. However, the coupling 75 compensates for this angular or axial misalignment preventing the plunger 54 or the piston 34 from moving improperly through the packings 70 and 38, respectively, thus resulting in possible destruction thereof. This is accomplished by interaction of the hemispherical face 82 and complementary face 84.

Moreover, though angular misalignment of the piston rod 34 and the plunger 54 is allowed, longitudinal separation these elements is prevented by the "Belleville" washers 92 and the closure member 94. Accordingly, during reversal of the stroke of the piston 28, plunger 54 and piston rod 34 are prevented from being longitudinally separated and brought together thereby preventing damage.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. Thus, it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described above.

WHAT WE CLAIM IS: 1. In a reciprocating pump of the type including a pair of reciprocating elements, one reciprocating element being a piston rod driven by a pressure operated piston and the other being a fluid plunger slidably mounted in a plunger cylinder for pumping fluid, the improvement comprising a coupling device connecting said rod to said plunger, including a retainer on one of said members, a head on the other of said members, and means resiliently maintaining said head in said retainer to inhibit separation of said head and said retainer.

2. A reciprocating pump as claimed in claim 1 in which the resilient maintaining means is a plurality of dished spring washers secured in said retainer.

3. A reciprocating pump as claimed in claim 2 further including a bearing in said retainer abutting a face of said head, said face being of a part-pherical configuration and said bearing having a face of a complementary configuration to said face of said head, said bearing face and said head face held in abutting relationship by said washers.

4. A pump as claimed in claim 1, 2 or 3 including a piston drive chamber, a piston reciprocably mounted within said chamber, valve means for alternately introducing pressurized fluid within said chamber on alternate sides of said piston to reciprocate said piston within said chamber, and a housing secured to said chamber into which housing the piston rod attached to said piston extends, the plunger cylinder being secured to said housing, said plunger cylinder including a fluid chamber having a fluid inlet and outlet adapted to be connected to a fluid system.

5. A coupling assembly for coupling first and second elongated members during reciprocal movement of said members along their longitudinal axes, said assembly comprising a retainer having an open end and an internal cavity, said retainer secured to said first member, a concave part-spherical bearing face within said retainer, a head having a convex part-spherical face secured to said second member and positioned within said retainer wherein said convex face abuts and mates with said concave face, a backup member positioned within said retainer between said open end and said head, and at least one biasing element positioned within said retainer and acting between said backup member and said retainer thereby maintaining the said faces in contact.

6. A coupling assembly as claimed in claim 5 including a closure member secured in the said open end and having a central aperture through which the second elongated member extends.

7. A coupling assembly as claimed in claim 5 or 6 in which the at least one biasing element comprises at least one compression spring seated between the closure member and the back-up member.

8. A coupling assembly as claimed in claim 5, 6 or 7 in which the concave face is on a bearing member in the retainer.

9. A coupling assembly as claimed in any of claims 5 to 8 in which the at least one biasing element comprises at least one dished spring washer.

10. A coupling assembly substantially as herein described with reference to Fig. 3 of the accompanying drawings.

11. A pump as claimed in claims 1, 2, 3 or 5 in which the coupling device is a coupling assembly as claimed in any of claims 5 to 10.

12. A reciprocating pump substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. closure member 94. Accordingly, during reversal of the stroke of the piston 28, plunger 54 and piston rod 34 are prevented from being longitudinally separated and brought together thereby preventing damage. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. Thus, it is to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described above. WHAT WE CLAIM IS:

1. In a reciprocating pump of the type including a pair of reciprocating elements, one reciprocating element being a piston rod driven by a pressure operated piston and the other being a fluid plunger slidably mounted in a plunger cylinder for pumping fluid, the improvement comprising a coupling device connecting said rod to said plunger, including a retainer on one of said members, a head on the other of said members, and means resiliently maintaining said head in said retainer to inhibit separation of said head and said retainer.

2. A reciprocating pump as claimed in claim 1 in which the resilient maintaining means is a plurality of dished spring washers secured in said retainer.

3. A reciprocating pump as claimed in claim 2 further including a bearing in said retainer abutting a face of said head, said face being of a part-pherical configuration and said bearing having a face of a complementary configuration to said face of said head, said bearing face and said head face held in abutting relationship by said washers.

4. A pump as claimed in claim 1, 2 or 3 including a piston drive chamber, a piston reciprocably mounted within said chamber, valve means for alternately introducing pressurized fluid within said chamber on alternate sides of said piston to reciprocate said piston within said chamber, and a housing secured to said chamber into which housing the piston rod attached to said piston extends, the plunger cylinder being secured to said housing, said plunger cylinder including a fluid chamber having a fluid inlet and outlet adapted to be connected to a fluid system.

5. A coupling assembly for coupling first and second elongated members during reciprocal movement of said members along their longitudinal axes, said assembly comprising a retainer having an open end and an internal cavity, said retainer secured to said first member, a concave part-spherical bearing face within said retainer, a head having a convex part-spherical face secured to said second member and positioned within said retainer wherein said convex face abuts and mates with said concave face, a backup member positioned within said retainer between said open end and said head, and at least one biasing element positioned within said retainer and acting between said backup member and said retainer thereby maintaining the said faces in contact.

6. A coupling assembly as claimed in claim 5 including a closure member secured in the said open end and having a central aperture through which the second elongated member extends.

7. A coupling assembly as claimed in claim 5 or 6 in which the at least one biasing element comprises at least one compression spring seated between the closure member and the back-up member.

8. A coupling assembly as claimed in claim 5, 6 or 7 in which the concave face is on a bearing member in the retainer.

9. A coupling assembly as claimed in any of claims 5 to 8 in which the at least one biasing element comprises at least one dished spring washer.

10. A coupling assembly substantially as herein described with reference to Fig. 3 of the accompanying drawings.

11. A pump as claimed in claims 1, 2, 3 or 5 in which the coupling device is a coupling assembly as claimed in any of claims 5 to 10.

12. A reciprocating pump substantially as herein described with reference to the accompanying drawings.