CA1077731A

CA1077731A - Drive rod coupling for positive displacement pump

Info

Publication number: CA1077731A
Application number: CA270,406A
Authority: CA
Inventors: Robert R. Bell
Original assignee: Vapor Corp
Current assignee: Vapor Corp
Priority date: 1976-02-25
Filing date: 1977-01-25
Publication date: 1980-05-20
Also published as: CH610629A5; IT1192171B; JPS52148801A; AU2178677A; NL7701804A; AR216644A1; BR7701137A; FR2342412A1; AU515893B2; DE2708309A1; MX4203E; GB1572632A; FR2342412B1; BE851744A

Abstract

DRIVE ROD COUPLING
FOR POSITIVE DISPLACEMENT PUMP
Abstract of the Disclosure A coupling device for use in a gas operated posit-ive displacement reciprocating pump, which disconnectably accomodates two rigid, elongated reciprocating elements while maintaining contact between the elements and eliminating relative longitudinal movement. Included is a hemispherically faced connector head connected to one of the elements. The coupling device further includes a retainer connected to the other of said elements into which the head is positioned. The connector head is contained in the retainer by a retaining member and biased against a bearing within the retainer by a plurality of Belleville washers. The force developed by the washers is sufficient to maintain the hemispherically faced connector head in contact with the connector bearing to insure that the connector head and bearing do not separate relative to each other during reciprocation of the rigid elements.

Description

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i Background of the Invention ;
, A. Field oE the Invention The present invention relates to a new and improved il coupling that functions as a preloaded member coupling two i~ 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.
,' B. Description of the Prior Art i -- .
i 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.

Il These operations include transfer of mixtures of oil and water lr) ' 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 charac-teristics of crude oil which varies greatly from place to l; 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 1~ must be capable of withstanding "ganying" or multiple parallel 1, operation. Often the source of operating energy is highly `~ contaminated natural gas from the same wellOproducing the pumped oil. Compressed air is also available.

The invention of the application is a gas operated ~,~ reciprocating positve displacement pump which fulfills the 1 requirements for successful operation in the producing oil ~ Eields discribed above.

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, Current pumps employed in the oil field utilize , a fluid drive piston connected to a high pressure fluid plunger.
~i Bo-th of these driven components of these pumps are alignment ~1 ~ensiti~e, since they operate at rapid rates and at high ,', forces. Accordingly, if a slight misaIignment between the driven 'j and drive componentsoccurs,excessiveplunger and packing wear is caused resulting in ra,pid deterioration of these elements.
Typically, the piston rod and -the plunger of these , prior art pumps are rigidly connected requiring precision 1~ ; boring and extreme care in assembly in order to accomplish a high degree cf accuracy in axial alignment. A slight misalignment during fabrication or assembly results in rapid ~I deterioration oE the plunger, piston rod and the packiny 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 ;l life of the packing and if continued over sufficiently lony periods of time, can result in piston rod and plunger inter- ;
' ference in their respective confinements and eventual destruct-~1~ ion thereof.
, Summary of the Invention ,; ' .
An ohject of the present invention is to provide I a new and improved device fcr COnneCtiQg reciprocating " elongated members.

'' Another object of the present invention is to ~ provide a new and improved device for coupling two elongated ~ ' 7~731 reciprocating members allowing relative angular and axia]misalignment, while maintaining sufEicient contact between the members at the point of coupling to prevent damage to either due to impact during the reversal of the reciprocating stroke.
Moreover, another object of the present invention is to provide a new and improved device for coupling the piston rod to the fluid plunger of a gas operated positive displacement pump.
A further object of the invention is to provide a coupling for the piston rod and fluid plunger of a gas operated fluid pump which allows efficien-t force transfer between members traveling in noncooperating paths without appreciable relative motion or loss of pump delivery.
]5 A still further object of the invention is to provide a compliant coupling for the piston rod and fluid plunger of a gas operated fluid pump which is conveniently disconnectable~
Briefly, the present invention is a new and improved 211 ~ coupliny device for connecting the piston rod of a fluid operated, hlgh pressure pump to an elongated plunger member -to allow the reciprocating motion of the piston rod to be imparted to the plunger. The reciprocation of the plunger functions to pump fluid to a desired location at a high pressuret 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 pump is used in the field and often use natural gas directly from the well as the workincJ fluid.

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Gas operated reciprocatinghigh pressure pumps employ a drive piston that is rigidly connected to a piston rod. During operation of -the pump, the piston is recipro-¦ ca-ted within the piston cylinder of the pump. Reciprocation ¦ of the pump is accomplished by utilization of switch valves and a conventional reversing spool valve. In this manner, fluid flows into the piston cylinder through ports. This flow is alternated in direction by the spool val~e causing a reciprocating motion of the piston, and, accordingly, a ln ¦ similar rnovement 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 flwid plunger is used in the pump. The plunger must be conn~cted 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 order to allow the power piston rod and the fluid plunger to be less alignment sensitive and therefore reduce the precision boring and extreme care in assembly required in the prior art pumps, the coupling of the present invcrltion is used. This coupling includes a connector head fabricated of stainless steel or similar material that is rigidly secured to elther the piston rod or the fluid plunger.
Attached to the other memher is a retainer. The connec~or head is positioned into this retainer.
The connector head has a substantially hemispherical face. Abutting this face and located between a closed end of the retainer and the connec-tor head is a bearing fabrica-ted ~0 of steel or similar material. The bearing surface abutting the connector face is of a mating configuration allowing I

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slight angular movement of the head relative to the bearing along the curved abutting surfaces.
Opposite the hemispherical 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 threadably secured 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 ]o ~ several Belleville washers. These washers serve to bias ' the backup plate and connector head agains-t the bearing within the retainer. In this manner, the connector head ~ is allowed to rotate through the interaction of its hemis-`, pherical face against the bearing while the Belleville ,, washers provide suficient force to maintain contact between the two points of coupling - the point o contact between j the bearing and head.
' The contact maintained by the Belleville washers ~; prevents damage to either the piston rod or the plunger l~ that may result Erom 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.
I~ Brief Description of -the Drawings , The above and other objects and advantages and novel features o the present invention will become apparent from the ollowing detailed description oF the preferred embodiment of the inven-tion illustrated in the accompanying ,', drawings wherein:
, FIG. 1 is a perspective view of a gas operated, l~ positive displacement pump including a couplina constructed "

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in accordance with the principles of the present invention;
FIG. 2 is an enlarged, sectional view of the ,, device of the present inventi,on illustrated in FIG. l; and ; F'IG. 3 is an enlarged, sectional view of the coupling device illustrated in FIG. 1.
~ Description of the Preferred Embodiment , . ..
With reference to FIGS. 1-3, therein is disclosed a conventional gas operated, positive displacemen-t pump 10.
, The pump 10 includes a drive cylinder 12 rigidly secured .~ hetween end 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 1.5 ~,' and 24 direct fluid into alternate ends of the piston drive chamber 26. In this manner, the piston 28 is influenced by h.igh 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.
~j To prevent fluid leakage from the drive cylinder 26 around 2S ', the rod 34, a drive cylinder packing 38 is employed. This drive cylinder packing 38 includes packing 40, a bushing and O-ring 42, and wiper 48.
The pump 10 (FIG.l) may be employed in oil ~, fields for pumping large quantities of fluid such as water Ij under high pressure into storage tanks, pipelines or other !, ~ ' ~C~7~73~

I refinery processes, involved in o.il production. To accom-plish 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 re-'~ ciprocation 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 flui.d is forced throuyh outlet 52 from the ,: chamber 58 by passing through the one-way check valve 64.
i The reversal of fluid through outlet 52 is prevented by the ;i 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 '' cyllnder 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 ,j the resultant axial and angular misaligmnent must be made.
~ This can be obtained by a coupling that allows axial and i 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 33 and 70. To connect the piston I rod 34 to the plunger 54 in a manner to provide a connection 3() ~ tolerant of angular and axial misalignment, the~ is provided 1, a coupling or connector 75 (FIG. 3). The coupling 75 :includes , 1 i,.
1~ , ~ ` ~
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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 pis-ton rod 34 by a set screw 78 and threads 80 on the tapered end of the piston rod 3g. 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 movment of the connector head 76 is allowed relative to the retainer 77 through the i 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 xeversal of the stroke of the piston 28.
In order to allow this angular or axial misalign-ment while preventing separation and the subsequent impact, ~; a plurality of Belleville 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.

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~ In this manner, sufficient compressible force can ¦ be imparted to the Belleville washers 92, and, thus, to the ¦I 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 a.nd 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 i p~ckings 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. ~he 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 pistonrod 34isa~so 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 i.s drawn in-to 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 inlet 52 to an 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 misalign-ment preventing the plunger 54 or the ~iston 34 from moving improperly through the packings 70 and 38, respectively, thus resulting in possible destruction thereof. This is accom-~ _g_ ~77~3~

~ plished by interaction of the hemispherical face 82 and ¦ complementary face 84.
Moreover, through angular misalignment oE the piston rod 34 and the plunger 54 is allowed, longitudinal separation oE these elements is prevented by the Belleville washers 92 and the closure member 94 Accordinqly, during re-versal o the strokeofthe piston28,and plunqer 54 and piston rod 34 are prevented from being longitudinally separated and brought together thereby preventing damage.
Obviously, many modifications and variations of i th~ present invention are possible in light of the above teachings. Thus, it is to be understood that,within t:he scope of the appended claims, the invention may be practiced l otherwise than as specifically described above.
¦ What i5 claimed and desired to be secured by Letters Patent of the United States is:

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a reciprocating pump of the type including a pair of coaxial and rectilinearly moving reciprocating elements for pumping incompressible fluids, one reciprocating elements being a piston rod driven by a pressure operated piston and the other being an incompressible fluid plunger slideably mounted in a plunger cylinder for pumping fluid, the improvement comprising:
a coupling device for connecting said rod and said plunger, including a retainer on one of said members, said retainer comprising a body including a first open end and a second closed end and a side wall defined therebetween, said side wall and said second end defining a chamber within said body, a head on the other of said members, a plurality of Belleville washers for resiliently maintaining said head secured in said retainer to prevent separation of said head and said retainer through the entire stroke of said rod and said plunger, and a bearing positioned within said chamber between said second end of said body and said head, said bearing being of substantially the same cross-sectional configuration and transverse dimension as said chamber, said bearing in-cluding a planar first end abutting a complementary portion of said second end of said retainer, said bearing also including a second end abutting a face of said head, said abutting relationship being the sole means supporting said bearing, said face being of a substantially hemispherical configuration and said second end of 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 throughout said stroke by said Belleville washers.

2. An apparatus for coupling at least two elongated elements for rectilinear motion said elements being employed to pump incompressible fluids through rectilinear motion, said apparatus allowing relative angular movement and preventing relative longitudinal movement, said apparatus comprising:
a retaining member secured to one of said elements, said retaining member including a body having a first open end and a second closed end and a cavity defined therebetween, a coupling head secured to a second one of said elements and positioned within said cavity, a bearing mounted within said cavity and abutting said second end of said body, said bearing being of substan-tially the same cross-sectional configuration as said cavity, said head including a substantially hemispherical face that abuts against said bearing, said bearing having a face complementary to said hemispherical face, said bearing positioned between said head and said second end of said body so that said faces abut thereby allowing relative angular movement of said elongated elements, a plurality of biasing members in said cavity positioned behind said head for applying an axial load on said head to bias said head into engagement with said bearing and prevent separation of said head and said bearing element during the entire stroke of said two elongated elements, and a tension member threadably secured to said first end of said retainer body for adjusting the axial load provided by said biasing members.

3. In combination a pump for incompressible fluids including a piston drive chamber, a piston reciprocally 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, a housing secured to said chamber into which a piston rod attached to said piston extends, a plunger cylinder secured to said housing into which a pump plunger coupled to said piston rod by a coupling assembly extends, said plunger cylinder including a fluid chamber having a fluid inlet and outlet valve means adapted to be connected to a fluid system, said coupling assembly comprising a retainer defined by a cylindrical body having an open end and a closed end, and a cavity defined therebetween, said body being affixed to an end of said plunger, a head having a hemispherical face secured to an end of said piston rod, said head positioned within said body, a bearing positioned within said body between said closed end of said body and said face of said head, said bearing a planar front end abutting a complementary portion of said closed end, said bearing being of substantially the same cross-sectional configuration and transverse dimension as said body, a second end of said bearing have a concave face mating with said hemispherical face of said head, said abutting and mating relationships being the sole means supporting said bearing, a retaining plate positioned within said body and between said head and said open end of said body, a plurality of biasing elements positioned within said body between said open end of said body and said retaining plate to bias said head against said bearing, and a closure member threadably secured in the open end of said body.

4. The combination of claim 3 wherein said biasing elements are Belleville washers.

5. The apparatus claimed in claim 2 further comprising a back-up plate positioned in said cavity and between said head and said biasing members.

6. The improvement claimed in claim 1 further comprising a tension member threadably secured in said open end of said chamber for adjusting the axial load applied by said Belleville washers.

7. The improvement claimed in claim 1 further comprising a backing member mounted in said chamber between said resilient means and said head.