US3030117A - Pumping rod and packing assembly - Google Patents

Description

April 17, 1962 J. H. COOPER 3,030,117

PUMPING ROD AND PACKING ASSEMBLY Filed Jan. 27, 1960 2 Sheets-Sheet 1 jummm m W3 U W HUM I z/ /7 hf ('00 er j a ,7 INVENfZQ.

I BY

QM Qwm April 1962 J. H. COOPER 3,030,117

PUMPIN G ROD AND PACKING ASSEMBLY l m \H H H H \H M dab/7 (00 0 er IN V EN TOR.

BY QOQM W NW ATTORNEY tres My invention relates. to the art of reciprocating pumps for fluids and is particularly adapted for use in high pressure pumps of the type employed in the drilling and production phases of the petroleum industry.

In reciprocating pumps for fluids, conventional designs are either single acting or double acting. In the former, a plunger reciprocates within a fluid chamber having an inlet and outlet valve so as to pull fluid thereinto on its intake stroke and force fluid therefrom on its power stroke. In the latter type, a rod driven piston reciprocates inside a fluid cylinder which is positioned within a fluid chamber. There is an inlet valve and an outlet valve associated with each end of the chamber so that movement of the piston in one direction brings fluid into one end of the chamber and cylinder as it forces fluid from the other end, and movement in the opposite direction reverses these operations. In both designs, there is an opening in the end wall of the fluid chamber through which the reciprocating member or pumping rod extends for attachment to a source of power such as a crankshaft. At the opening, a packing or sealing means must be provided to prevent leakage around the pumping rod as it moves into and out of the chamber.

In recent years, the demand for increased capacity and operating pressure in pumping has created an urgent need for a sealing means which will provide long and troublefree service. Indeed, it may be stated that the primary weakness in present equipment and the chief bar to advanced design in the field is in this area. Thus, my invention is directed to the solution of this problem, and its primary object is'to provide a pumping rod and packing assembly which coact to insure an effective seal of increased service life with wearing elements which may be renewed or reconditioned quickly and economically.

It is also an object of my invention to provide a pumping rod and packing assembly which is readily adaptable to pumps presently in service to increase their efficiency and reduce the cost of maintenance.

More specifically, it is an object of my invention to provide a replaceable wearing surface of unique design for the pumping rod, whether a plunger or piston rod, to aid in sealing efficiency and eliminate the expensive practice of replacing the entire member at frequent intervals.

It is a further object of my invention to provide a surface on the pumping rod which is corrugated, spirally grooved, or otherwise provided with convenient recesses to carry fluids from the pumping chamber to the heart of the packing for cooling and lubrication.

It is a further object of my invention to provide a packing assembly which is adapted to seal against a corrugated or grooved pumping rod to prevent leakage of fluids therethrough, while it allows introduction of a small amount of'fluid thereinto for cooling and lubrication.

In carrying out these objectives, my invention contemplates the provision of a continuous spirally wound member surrounding the reciprocating member so that the exposed wearing surface is corrugated or grooved to provide small recesses in the surface. As the member projects into the fluid chamber during its inward movement, the fluid medium is picked up in the recesses, to be carried into the packing assembly during the return or outward stroke. The packing means comprises a series of O-rings or similar sealing members which are arranged 3,3,117 i atented Apr. l7, 1982 in abutting relationship over a considerable distance so that each tends to wipe a small portion of the entrapped fluid from the rod as it moves therethrough, and the progressive wiping action of the rings will cool and lubricate the entire assembly without allowing any appreciable leakage.

Two preferred embodiments of my invention and two of its applications are shown in the attached drawings in which:

FIG. 1 is a partially cut away view of the fluid chamher and plunger of a single acting pump incorporating my invention;

FIG. 2 is a partially cut away view of the fluid chamber, cylinder, piston and piston rod of a double acting pump incorporating my invention;

FIG. 3 is an elevational view, partly in section, of a plunger covered with a spirally wound hard surfaced wire which is retained in position by an alternate means of attachment; and

FIG. 4 is an enlarged view in section of a plunger rod and packing assembly as employed in my invention.

Referring first to FIG. 1, reference numeral 11 designates generally one pumping chamber of a conventional single acting pump. It is to be understood that such a pump usually has two or more such chambers, and my invention is intended for employment in each. A reciprocating plunger 12 is connected at one end to a source of power, not shown, which imparts reciprocating movement thereto. The opposite end extends into the fluid chamber 13 defined by the casting l4, and as the plunger moves thereinto, fluid within the chamber is driven through the outlet valve 15 into the discharge line 16. Upon completion of the pumping stroke, the plunger begins to move in the opposite direction on its intake stroke to pull fluid from the inlet line 17 into the fluid chamber 13 through inlet'valve 18.

The plunger 12 is covered with a hard or hard sur faced, spirally wound wire 19 over a portion of itslength at least equal to and preferably somewhat greater than its stroke plus the length of the stuffing box, the winding being restrained at each end by a removable collar 20 which is held in position by a set screw 20a. At the end wall of the casting 14 through which the plunger projects, a packing casing 21 is secured to the casting by bolts 22 through the outturned flange 23. There is an inturned shoulder 24 at the inward end of the casing, against which a series of abutting rubber O-ring-s 25 rest. The rings 25 are held within the housing and lightly compressed by end member 26 which is attached to the flange 23 by means of bolts 27. FIG. 2 represents one pumping cylinder 28 of a double acting pump which is similar in many regards to the single acting unit of FIG. 1. Consequently, the reference numerals of FIG. 1 are employed to designate those elements which occur in both figures. There are two outlet valves 15 and two inlet valves 18 with a cylinder 39 positioned therebetween. The piston 31 reciprocates within the cylinder responsive to the movement of piston rod 32, which member is covered with a spirally wound wire 33, the rod 32 and wire 33 being a counterpart of plunger 12 and wire 19 for purposes of my invention. A suitable collar 34 with set screw 34a may be employed to retain the wire wrapping in position toward the power end of the rod, and a shoulder 35 adjacent the piston provides a stop at the opposite end. The packing assembly is identical to that of FIG. 1, except that it is of proper size to accommodate the piston rod rather than the substantially larger plunger.

In each of the embodiments of FIGS. 1 and 2, the spiral wrapping on the reciprocating rod provides recesses about the exposed surface thereof, and fluid within the chamber or cylinder is collected therein and transported into the packing assembly. When convenient, the coil of wire may extend throughout the length of the pumping rod, although it need be no longer than the length of the packing plus the length of stroke.

By design, the O-rings are of proper diameter to em brace and lightly squeeze the surface of the rod so that it is wiped clean as it travels therethrough. Ideally, the packing casing 21 is of suflicient length to effectively remove all of the entrapped fluid from the surface of the rod, the last portion of such fluid being removed at or near the O-ring which is most remote from the the fluid chamber itself.

Although the O-ring seal is particularly suitable for use in my invention, it will be apparent that any other conventional type sealing ring could be employed. Th-us, chevron rings or similar elements having flexible lips or sealing surfaces to wipe fluid from the plunger rod might be substituted.

The hard or hard surfaced wire employed in the protective member 19 and 33 preferably is circular in cross section, but an elliptical or other shape may be used so long as a groove or recess is provided between adjacent windings.

Referring now to FIG. 3, a plunger 40 is fitted with a hard wearing surface such as the wire 41, but in lieu of the collars of FIG. 1, the coil of wire is held in position by threading it onto the plunger where it is accommodated by precut spiral threads 42. The two ends of the wire are welded to the adjacent windings of the coil by a spot weld 43 to prevent the wire from uncoiling or working its way out of position by moving along the threads 42.

In the embodiments of FIGS. 1 and 2, it is contemplated that the surface of the plunger 12 or piston rod 32 will be smooth and the prewound wire sleeve will be attached by sliding it onto the receiving member. To insure a firm embrace, the wire will be wound to an inside diameter somewhat less than the outside diameter of the rod to produce an interference fit therebetween. The problem of forcing the undersized coil onto the somewhat larger rod is solved by attaching a tapered mandrel to the end of the rod so that the wire sleeve will be gradually enlarged as it is forced along the mandrel and onto the rod. The inherent resilience of the wire will allow it to deform and firmly grasp the rod, and the collars 20 on the plunger and the collar 34 on the piston rod will hold the coil in proper position.

In the FIG. 3 embodiment, the surface of the receiving member will be threaded on the same pitch as the wire is wound. Thus the coil will be screwed onto the receiving member, i.e., the plunger or piston rod, and when it is at the desired location, the ends of the wire will be spot welded to the adjacent windings of the coil so as to prevent unscrewing.

FIG. 4 illustrates the design of the plunger and packing assembly of FIG. lin detail, the plunger 12 being covered with the wire wrapping 19 and equipped with collars 26. The O-rings are carried within the casing 21 and surround the wire coating to progressively wipe the fluid therefrom as the rod moves therethrough. In the event the wire wrapping becomes sufliciently worn to require replacement, the plunger may be detached from the power driving means which imparts movement thereto and withdrawn from the fluid chamber. Then the wire can be stripped from the plunger and replaced in any convenient manner such as by use of the mandrel described above. At the same time, the packing casing 21 can be removed entirely by unscrewing bolts 22 from the casting 14. Thereafter, or if desired, without removing the rod or casing, the bolts 27 may be unscrewed from the flange 23 of the casing to allow removal of the end member 26 so that new rings or packing material can be inserted within the casing.

One of the primary advantages of my invention is the avenue which it provides for cooling and lubricating the packing means. It may be desirable in some installations to increase this effect by cutting small openings or slots into the packing casing. Where such alteration is to be made, the size and shape will be readily ascertainable by one skilled in the art.

Each rod and packing assembly comprises a unit, and they can be removed and replaced together or separately. If it is desired to substitute a larger or smaller rod, a new packing assembly which is dimensioned for the new rod can be inserted.

My invention is readily adapted for use in virtually all conventional pumps. It is necessary only to remove the old plunger or piston rod along with its stufling box and substitute the new units which embody the invention. I have chosen to illustrate and describe two environments in which my invention can be employed, and two types of structure which embody the invention. However, it is apparent that several additional alterations might occur to one skilled in the art without departing from the spirit of my invention. Thus its scope is to be determined by reference to the following claims:

1. In a pump having a fluid chamber with an inlet valve and an outlet valve and a wall with an opening therethrough, the combination comprising a reciprocating plunger projecting into said fluid chamber through said opening, a packing housing releasably secured to said wall around said opening and surrounding said plunger, a group of annular sealing elements within said packing housing, spiral threads about the exterior of said plunger over a portion of its length, and a spirally wound coil of continuous, relatively hard wire surrounding said plunger and secured thereto by mating engagement with said threads.

2. The combination of claim 1 in which said sealing elements are O-rings disposed coaxially and in abutting relationship to surround said plunger over the length of said packing housing.

3. The combination of claim 1 in which said threads and said coil extend over a length at least equal to the length of said packing housing plus the length of the stroke of said plunger.

4. The combination of claim 1 and a removable annular cap on the end of said packing housing most remote from said fluid chamber to allow replacement of said sealing elements.

References Cited in the file of this patent UNITED STATES PATENTS 425,569 Gare Apr. 15, 1890 1,278,853 Caverno Sept. 17, 1918 1,832,493 Marsilius Nov. 17, 1931 1,854,773 Tannehill Apr. 19, 1932 2,056,687 Moseley Oct. 6, 1936 2,726,886 Thomas Dec. 13, 1955 2,893,789 Heinz July 7, 1959

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