US 3075474 A
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Description (OCR text may contain errors)
Jan. 29, 1963 V. A. KELLEY PLUNGER SEALING CUP Filed DSG. 12. 1960 Fizz-3 INVENToR. l/erJe/zz A. /fe//ey Arron/fr United States Patent Oihce 3,0%,474 Patented dan. Z9, 1963 honra Filed Dec. 12, 1960, Ser. No. 75,371 3 Claims. (Cl. lr03- 179) The present invention relates to improvements in fluid pumps and more particularly, but not by way `of limitation, to improvements in subsurface oil well pumps.
One type of subsurface lift pump presently in use employs a plurality of resilient sealing elements in the form of cups to maintain a substantially fluid-tight annular seal between a plunger and a working barrel within which the plunger reciprocates. The working barrel is vertically disposed in the bottom of the hole and has a conventional standing valve associated therewith. The plunger is normally tubular and has a traveling valve to prevent tluid from passing downwardly through the plunger. As the plunger travels upwardly on what is termed the working stroke, the traveling valve is closed and the entire column of fluid extending to the surface is lifted. A pressure corresponding to the weight of the column of fluid is exerted on the plunger and sealing cups associated therewith. Simultaneously, fluid is pulled into the lower part of the working barrel through the standing valve. The sealing cups on the plunger are so constructed that the differential in pressure between the high pressure labove the plunger and the low pressure below the plunger and within the barrel exerts a force tending to expand the cups into positive sealing engage` ment with the barrel. The first or uppermost sealing cup, by virtue of its position, receives substantially all of the high pressure and resulting expansive force. The second, third and subsequent cups are subjected only to such pressure as may leak by the iirst cup. The high pressure on the uppermost cup generally exerts a force on the cup far greater than is necessary to expand the cup into effective sealing engagement with the barrel. The excessive expanding force results in an excessive rate of wear of the uppermost cup. The pressure differential is sometimes so great as to distort the cup out of round-which, in addition to excessive wear of the cup, also results in scouring of the barrel, a permanent and costly damage to the pump. Ater the iirst cup is quickly worn out, the high pressure is applied to the second cup and so on, therefby wearing out each cup in rapid succession. The pump must then be removed from the hole and the sealing cups replaced; and the cost of pulling the pump from the hole is far greater than the cost of the cups.
In accordance with the present invention, an orice means is provided in each sealing cup to pass a small volume of uid from above to below the sealing cup to decrease the differential in pressure across the sealing cup.
The `object of the present invention is to reduce the rate of wear of sealing cups u-sed in connection with reciprocating plungers, thereby prolonging the service life of the sealing cups.
Another object of this invention is to establish a means to gradually reduce the dierential pressure across any type dynamic sealing unit.
Another object of the present invention is to reduce 1an unnecessarily large differential sealing pressure across any one of several sealing cups -use-d on a reciprocating plunger.
Still another object of the present invention is to more evenly distribute the total lluid force acting on a reciprocating plunger -among the several sealing cups connected to the plunger.
A further object of the present invention is to provide a subsurface iluid pump having a longer service life and therefore greater economy of operation.
Additional objects [and advantages will be readily apparent to those skilled in the art from the following detailed description and drawings wherein:
.FIGURE l is a sectional view taken along the longitudinal axis of a pump device constructed in accordance with the present invention.
FIGURE 2 is a top view of a sealing cup constructed in accordance with the present invention.
FiGURE 3 is a side view of the device of FIG. 2.
Referring now to the drawings, a tubular working 1barrel l@ has a chamber 1l and is threaded onto a tubular hold-down body 12. The hold-down body can be provided with conventional seating cup rings to anchor the hold-down body and workin-g barrel in the bottom of the production string or casing, as the case may be. The seating cups and the production string or casing are not shown for convenience of illustration. A standing valve comprised of ball ltd and seat 16 is retained by a valve cage 158 which is threaded onto a neck 26 of the hold-down body. The seat i6 is clamped between an annular shoulder i9 within the valve cage and the upper surface of the neck Ztl as shown.
A tubular plunger body 22 having a bore 23 is disposed within the barrel tu and is threaded into a valve cage 24. A valve seat 2a is clamped between an annular shoulder 25 within the valve cage 24 and the upper end of the plunger body. A ball 28 is retained Within the cage. The ball 23 and seat 26 with associated structure constitute what is referred to as a traveling valve and permits fluid to pass upwardly through the plunger 22 but checks return flow downwardly. A rod 3i) is threaded into the upper part of the valve cage 24. The rod 39 is the lowermost ot a rod string extending to the surface. The string is connected to a pump jack (not shown) which reciprocates the rod string, the traveling valve and the plunger body.
Four duplicate sealing cups 32 encircle the plunger body 22 and are maintained at spaced intervals by duplicate spacer sleeves 34. Each sealing cup 32 is comprised of a sleeve slightly tapered outwardly at the upper end 32a and having an annular inturned shoulder 32]; at the lower end dimensioned to closely t the plunger body. The internal diameter of the cup 32 is greater than the outer diameter of spacer sleeve 34 to provide a cavity 33. The largest outer diameter oi the cup sleeve at the upper end 32a is dimensioned to slidably engage the internal surface of the working barrel lil. The upper face of each spacer sleeve 34 is concave to mate with the rounded lower face of shoulder 32b of each of the sealing cups. An annular depending shoulder 35 on the lower end of each of the spacer sleeves is adapted to seat in an annular groove in the Lipper Aface of inturned shoulder 32h. A retainer ring 35 slides over the plunger body and also has a. concave upper face which mates with the bottom of the lowermost sealing cup 32.
A rst nut 33 is threaded onto the lower end of the plunger body and tightened until the spacer sleeves and retainer ring compress each of the resilient sealing cups therebetween to form a fluid-tight plunger comprised of the cups, the spacer sleeves and plunger body. A lock nut 4l@ is then tightened against nut 38 to secure it against loosening.
The structure, insofar as it is described above, is old within the art and in extensive use. In the operation of the above-described conventional pump, the plunger 22 and structure connected thereto is raised to its up position, and fluid from the well bore passes upwardly through the standing valve ltd-16 into the working barrel 10 and into the bore 23 of the plunger body 22. When the plunger is lowered on the return stroke, a portion of the uid within the working barrel l@ is displaced by the plunger and passes upwardly through the traveling valve 26-28. When the reciprocating plunger 22 starts upwardly on the working stroke, the traveling valve -28 prevents the fluid above the plunger from passing back through the plunger bore 23. The fluid above the plunger passes through the annular space between the plunger body 22 and the working barrel l@ and fills the chamber 33 within the uppermost sealing cup 32. Pressure due to the weight of the fiuid above the cups tends to expand the cup sleeve outwardly and seat the circumference of the sealing cup against the working barrel to provide a substantially Vfluid-tight seal. The pressure immediately below the first sealing cup 32 is Virtually zero due to the partial vacuum created below the plunger on the working stroke. Therefore7 the pressure differential between the high pressure above the sealing cup and the low pressure below the cup readily expands the resilient sleeve to form a seal with the working barrel l0. When the pressure above the plunger is great due to a high column of iluid extending to the surface, the rst cup 3-2 is expanded with great `force and very effectively seals the high pressure from the lower cups 32. The lower cups 32 are subjected only to pressure created by uid which by chance leaks past the next higher cup. As a result, the high pressure exerts an expanding force far in excess of that required merely to effectively seat the cup against the barrel, and the high pressure greatly increases the rate of wear of the circumference of the cup 32 due to abrasion with the Working barrel. After the uppermost cup 32 is worn out, each successive cup is in turn rapidly worn out as it is subjected to the high pressure which passes around the worn-out cup.
ln accordance with the present invention, a restricted orifice 50 is provided in each of the sealing cups 32 at a point where a restricted volume of fluid will be passed to the next lower chamber 33 above and within the next lower sealing cup 32. Pressure is quickly built up between the uppermost or rst sealing cup 32 and the next lower or second sealing cup. Each cup 32 in turn passes uid to the chamber 33 of the next lower cup with the last cup passing a restricted volume of fluid to the working ybarrel chamber l1 below the plunger. The plunger, taken as a whole, then becomes a fluid conduit having a very tortuous, high resistance flow path with a high pressure at the upper end and virtually no pressure at the lower end. The difference in the pressure above and below each sealing cup is equal to the pressure drop across the cup due to the ow of uid through the orifice in that cup. It is this pressure differential which exerts the expanding force on the resilient cup to seat it against the working barrel. The pressure drop across each cup is therefore a function of the resistance in the orifice and, 4by properly sizing the orifice in the cup, the expansive force of the uid can be controlled to exert suicient pressure to substantially seat the sealing cup against the working barrel, but eliminate excessive pressure which causes excessive wear.
While a reduced pressure differential across a sealing cup will reduce the circumferential sealing efficiency of the cup, by using a number of sealing cups each subjected to a substantial pressure differential, the overall efficiency of the plunger to seal off circumferential bypass of fluid is not materially reduced and, in fact, in most cases is increased. Due to the short duration of the pumping stroke, the small volume of fluid passed through the orifice of the last or lowermost cup on the plunger, when compared-with the large volume pumped, is negligible.
The high fluid pressure which has previously been applied almost entirely to the top sealing cup resulted in very great pressure forces per unit area between the circumference of the sealing cup and the working barrel. This great force per area quickly wore the resilient, relatively soft cup out. In accordance with the present invention, high huid pressure is distributed more evenly to all of the cups with the resulting force per unit area of circumferential contact between the several sealing cups and the working barrel being greatly reduced due to the increased contact area of all the cups. As is well known, when the force pressing two relatively sliding surfaces together is reduced, the rate of wear of the contacting surfaces is reduced at a much greater rate. Therefore, by reducing the expanding force on the cup, the life of each of the cups is greatly increased and the operation period greatly prolonged before it is necessary to pull the pump from the well and replace the scaling cups.
Sealing cups for reciprocating plungers are standard replacement items. Therefore, l prefer to adopt a standard orifice size for each type and size of sealing cup, of which there are many for the various makes and models of pumps. For example, a 3/lg-inch diameter orifice is acceptable for a 2%inch diameter sealing cup.
It will be apparent from the foregoing description that the invention will ellectively reduce the differential pressure across the uppermost sealing cup on a reciprocating plunger, reducing the rate of wear of the cup and prolonging its service life. Further, the total tiuid force acting on the plunger is removed from any one sealing cup and distributed among all of the sealing cups on the plunger so that each sealing cup contributes to the total circumferential sealing effect between the reciprocating plunger and the working barrel. The reduced seating pressure between each of the several cups and the working barrel greatly reduces the rate of wear of each sealing cup. The rate of wear is reduced to the extent that the total operating time required to simultaneously wear all of the cups is appreciably greater than the total time required to wear through the series of cups one at a time, as was previously the case. Of course, this means that a pump in the bottom of a well has a much longer service life and therefore greater economy of operation because the pump does not have to be removed as often to replace worn and ineicient sealing cups.
While the preferred form of this invention is that herein described in detail in which the resrictive orifice means is located in the resilient sealing cups, it will be apparent that the restrictive orifice means for passing a restricted volume of uid by each sealing cup could, if preferred, be located either in the plunger body 22, spacing sleeves 34 or the sealing cups or any combination thereof so long as the orice means bypasses a restricted volume of fluid by each cup to control the sealing pressure differential across each sealing cup. It will also be apparent that the cups could be secured around the inner periphery of a working barrel and dynamically seal around the plunger, if desired.
While I have fully described preferred embodiments of my invention, it is to be understoodthat I do not wish to be limited to the details heretofore set forth, but that my invention is of the full scope of vthe appended claims.
l. ln a fluid pump having a vertically disposed barrel, a plunger reciprocally located within the barrel having a plurality of resilient `sealing cups at spaced intervals therealong, each of said sealing cups being expandable into circumferential sealing engagement with said` barrel by the pressure differential lbetween a greater pressure above the sealing cup anda lesser pressure below the sealing cup caused by said plunger moving upwardly in said barrel, the improvement comprising orifice means in each of said sealing cups for passing a restricted volume of uid from above to below the cup to decrease the differential in pressure across the sealing cup thereby decreasing the rate of wear of the sealing cup.
2. In combination with a fluid pump having a vertically disposed barrel, a plunger reciprocally located within the barrel, a standing valve in the bottom of the barrel and a traveling valve associated with the plunger, an improved sealing cup comprising a resilient sleeve dimensioned to encircle said plunger and slide within said barrel and having means adjacent one end adapted to be connected to said plunger to form e fluid seal with said plunger whereby the dierential `between the pressure above and within the sleeve as the plunger moves upwardly and the pressure below the sleeve will expand and press the sleeve into substantially sealing engagement with said barrel, said sealing cup having orifice means therein exposed at its opposite ends to the pressure in the barrel above and below the sealing cup for passing a restricted volume of fluid from above the cup to below the cup to reduce the dierentiel between the pressure above and below the cup thereby reducing the rate of wear of the sleeve.
3. ln a fluid pump having `a vertically disposed barrel with a standing valve in the bottom thereof, the improvement comprising a plunger member reciproeally located within the barrel, a traveling valve associated with `seid plunger member, `a plurality of sealing cup members encircling said plunger member, a spacer member rdisposed between each sealing cup member, means for clamping said spacer members and said sealing cup members together to form a fluid Seal between the sealing cup members, the spacer members and the plunger member, each `of said sealing cup members being deformed by a pressure differential between a greater pressure above each sealing cup member and a lesser pressure below each sealing cup member to form substantially a circumferential uid seal between the sealing cup members and the barrel, and restricted orifice means in each of said sealing cup members to pass a restricted volume of fluid by each of said sealing cup members from the greater to the lesser pres sure to reduce the pressure differential across the members thereby reducing the rate of Wear of the members.
References Cited in the le of this patent UNITED STATES PATENTS 251,523 Chipley Dec. 27, 1881 655,954 Brooks Aug. 14, 1900 1,930,839 Kater et al Oct. 17, 1933 2,175,000 Schlesinger Oct. 3, 1939 2,193,020 Collins Mar. 12, 1940 2,300,648 Carlberg Nov. 3, 1942 2,309,339 Calaway Ian. 26, 1943