US2719768A - Well tools and sealing means therefor - Google Patents

Description

Oct 4, 1955 J. c. wl-:BBER

WELL TOOLS AND SEALING MEANS THEREF'OR Filed Nov. 15, 1952 United States Patent WELL TOOLS AND SEALING MEANS THEREFOR Jack C. Webber, Houston, Tex. Application November 15, 1952, Serial No. 320,750 5 Claims. (Cl. 309-33) This invention relates to new and useful improvements in well tools and sealing means therefor, and is an improvement on my co-pending application, Serial No. 51,173, filed September 25, 1948, for Well Tools and Sealing Means Therefor, now Patent No. 2,633,808, April 7, 1953.

It has been found in practice that, when well tools such as swabs or the like are positioned and used in a well ilow conductor, only a single one of the cups or packing sleeves commonly used on such tools carries nearly all the load and hence wears rapidly. Swabs commonly in use at the present time are usually provided with two or more sealing elements, each of which is individually capable of carrying a very large fluid pressure load. Examination of the sealing elements of used swabs has disclosed by comparative wear that one of the two or more sealing elements does carry nearly all the fluid load, and hence when the first sealing element has become so worn that its sealing capacity is destroyed by such wear, or by damage otherwise caused, the iluid load is` transferred to another intact sealing element. Thus, in eiect, thecustomary swab may be regarded as a tool having only one effective sealing cup or sleeve. Furthermore, since the sealing elements of the customary swab are capable of carrying very large fluid loads, itis a commonoccurrence for such swabs to be lowered suilciently deep below the surface of the liquid in the well bore to prevent the swab from being lifted. Or, such a great load applied to a single cup or packing sleeve of the swab may cause the cup or sleeve to be cut or stripped off when said cup or sleeve passes an irregularity or coupling recess in the flow con-- ductor while carrying such heavy load. Also, when heavy loads are applied to a single cup or sleeve, it wears rapidly due to the heavy frictional engagement of the cup with the bore wall of the flow conductor, and such heavy loads also impose an increased frictional load resisting lifting of the swab.

It is, therefore, one object of this invention to provide improved sealing means for well tools such as swabs, such means including a plurality of uniformly spaced re-v silient substantially annular sealing `rings carried by the well tool or swab which are arranged to move into sealing engagement with the bore wall of the llow conductor upon the application of iluid pressure thereagainst for maintaining a seal between the well tool or swab and the conductor.

It is a particular object of the invention to provide, in a well tool, sealing means including a plurality of spaced annular sealing rings which will each carry only a predetermined maximum pressure differential and which are arranged so that a pressure in excess of such fixed or predetermined maximum differential will pass the individual sealing ring to act against the next adjacent sealing ring, whereby each sealing ring bears a proportionate share of the total load and cannot carry a load greater than the maximum predetermined load for which the sealing ring is designed, but a plurality of spaced rings will carry or absorb a desired total amount of fluid lee pressure; and wherein each of the sealing rings is provided with an annular wear surface engageable with the bore wall of the conductor through which the well tool is moved for lengthening the service life of said sealing rings.

Another object of the invention is to provide a swab of the character described wherein the sealing rings are so disposed that the swab will support only a predetermined pressure load, the sealing means being arranged to by-pass any iluid load in excess of such predetermined load to the well bore therebelow, whereby the possibility of overloading and sticking the Vswab is eliminated.

An important object of the invention is to provide sealing means of the character described wherein the bearing pressure between the sealing means and the bore wall of the pipe is maintained at a minimum under maximum conditions of load, whereby the wear of the sealing means is minimized under maximum load conditions; and, wherein the wear surface on the upper outer annular edge of each of the sealing rings provides the contact between the sealing means and the bore wall of the pipe.

Still another object of the invention is to provide a sealing element which will be deflected upwardly and inwardly by the action of Well iluids when lowered thereinto and thus provide by-pass area around the sealingelement for the passage of well fluids in order that the swab may be lowered more rapidly and without wear on the sealing element.

It is a particularly important object of the invention to provide in a swab sealing means which is so constructed and arranged that the load carried by the swab is distributed substantially uniformly over a plurality of separate ilexible sealing rings rather than applied solely against a single cup or sleeve, whereby wear and damage to the sealing elements are reduced and substantially eliminated and light loads may be lifted from great depths with minimum leakage or slippage, and heavy loads may be lifted with minimum wear.

A further object of the invention is to providea sealing means which is simple to manufacture, has a minimum number of parts, and is designed for maximum life and minimum wear, and which is designed for maximum ease of replacement of worn parts when required.

f Additional objects and advantages of ythe invention will readily be apparent from thereading of the Vfollowing description of devices constructed in accordance with the invention, and reference to the accompanying drawings thereof, wherein:

Figure 1 is a side view, partly in elevation and partly in section, of a well swab having sealing means constructed in accordance with the invention provided thereon,

Figure 2 is a view similar to Figure 1 showing the sealing means deflected into lluid lifting position, i

Figure 3 is a fragmentary view, partly in elevation and partly in section, of several of the sealing rings of Figure 1 showing the rings in position by-passing fluids downwardly past the packing,

Figure 4 is a horizontal cross-sectional view taken on the line 4 4 of Figure 1,

Figure 5 is an enlarged fragmentary vertical sectional view of the sealing rings of Figure 1, showing a part of the wear surface worn away.

Figure 6 is a fragmentary side view, partly in elevation and partly in section, illustrating a modified form sealing means mounted on a mandrel in a well conductor.

Figure 7 is a fragmentary view ofthe sealing means of Figure 6 showing theY sealing rings deflected downwardly into sealing position, with the wear surfaces in engage-` ment with the bore wall of the conductor,

Figure 8' is a view similar to Figure 6 showing a further modied form of the sealing means, i

Figure '9 is a view Ysimilar tFigure 7 showing the sealing means of Figure 8 in downwardly deflected sealing position with the wear surfaces in engagement with the bore wall of the conductor,

Figure 10' is a view similar to Figure S showing aY still` further modification of the sealing means, and

Figure ll is a fragmentary, vertical sectional view similar to Figure 9 showing the sealing means of Figure l0J deflected downwardly into sealing position with the wear surfaces in engagement with the bore wall ofl the conductor.

In the drawings, the numeral lil designates an elongate cylindrical mandrel of a well tool, such as aswab, and having an axialfbore 11 therethrough. A guide shoe 12 having vertical external flow courses 12a is screwthreadedonto the lower end of the mandrel for guiding the same in its vertical movement in a wellilow conductor C. Fthe guide shoe has an axial flow passageway 13 therethrough which communicates with the bore 11 of the mandrel andis flared outwardly therebelow. A valve cage 15 is secured to the upper end of the mandrel by means of screwthreads or in any other suitable` manner, and said valve cage provides means for retaining a ball check valve 16 in position to engage an upwardly facing valve seat 17- formed in the upper end of the bore of the mandrel 10, whereby the ball valve will engage the seat to close the bore of the mandrel against downward flow. Lateral flow openings 1S are provided in the valve cage for permitting fluids` flowing through the bore of the mandrel' to pass outwardly to the bore of the well conductor thereabove. A sinker bar 19 isscrewthreaded to an upstanding pin 20 carried by the upper end of the valve cage, and a cable socket 21 at the upper end of the sinker bar provides means for connecting a flexible cable 22 to the mandrel. It is believed obvious that the valve may be positioned elsewhere than at the upper end of the mandrel, if desired.

Mounted on the exterior of the cylindrical mandrel 10 between the valve cage 15 and the guide shoe 12 is an elongate sealing member 25 for sealing between the mandrel and the bore wall of the well flow conductor C, as will be hereinafter explained. The sealing member includes an elongate cylindrical sleeve 26, formed of rubber, synthetic rubber, or like resilient sealing material, and preferably molded on the exterior cylindrical surface of a reinforcing tube 27 so as to be fixed* against movement. The tube 27 has a slidable fit on the exterior of the mandrel 10'. A plurality of uniformly spaced inverted substantially frusto-conical annular sealing rings 2S are carried by the sleeve 26, said sealing rings being preferably formed integral with the. sleeve. The cross-sectional thickness of the rings projecting outwardly from the sleeve is preferably substantialy uniform throughout, and each ring is moldedin the form shown in Figure l, wherein the ring extends outwardly and upwardly in substantially an inverted frusto-conical shape. The outer peripheral edges of the sealingirings are normallysubstantially cylindrical inshape; and the upper surfaces of the rings extend outwardly thereto so asto providewear surfaces or extensions 29 at their upper outer annular edge, for a purpose which will be hereinafter more fully explained.

The diameter of the sealing rings 23, in the normal undeformed position shown in Figure l, is substantially equal to the diameter of the bore of the well conductor C. However, due to the fact that the sealing rings are formed in the inverted frusto-conical shape, it will be seen that when the swab mandrel is lowered into the bore of the well conductor the sealing rings will readily flex upwardly to permitluid to pass exteriorly of the mandrel between the sealing rings and the bore wall of the conductor. Also, the ball valve 16 will lift off the upwardly facing seat 17 at the upper end of the mandrel and permits fluids to flow upwardly through the bore of the mandrel as the swab is lowered through the' liquid in the well conductor.

Y Whenthe swab. is raised. by' lifting the cableI 22, the

ball check valve 16 engages the upwardly facing seat 17 to close the bore of the mandrel and trap liquid in the bore of the flow conductor above the mandrel. The liquid trapped above the mandrel will act downwardly upon the uppermost sealing ring 2S and will deform the ring downwardly to substantially the position shown in Figure 2, wherein the ring extends downwardly and outwardly in substantially a frusto-conical shape. The wear surface or extension 29 on the upper outer edge of the ring then engages the bore wall of the conductor to form a seal therewith, and it is this wear surface 29 which rubs against the wall of the conductor as the swab is lifted.

Since the uppermost sealing ring 28 is made of rubber or other similar flexible sealing material and is relatively thin, it will be seen that such sealing ring will support or lift only a predetermined column of fluids, for example, a column which weighs approximately 8 to 25 pounds per square inch, andany pressure in excess of that amount will deflect suchuppermost sealing ring downwardly out of sealing engagement withl the bore wall of the conductorV to permit fluid to flow past such uppermost cup to the sealingring next below it. The second sealing ring will then likewise be deformed downwardly in the same manner as was theuppermost sealing ring, whereby the peripheral wear` sur-face at the upper outer edge of the second sealing ring engages and seals against the bore wallk ofthe conductor and supports a column of liquid there-above.

Since all of the sealing rings are of substantially the same dimensions, ity will be seen that each sealing ring will support substantially the same fluid pressure differential thereacross, and any differential in excess of such predetermined value will cause the sealing ring to be deflected downwardly to permit the liquid to pass said ring to the ring next below it. Therefore, the total load of liquid to be supported by the swab will be borne in predetermined increments by each of the sealing rings 28, each sealing ring bearing its proportionate share of the load; and no one sealing ring will carry a greater load than the pressure differential which will deform or deflect said ring downwardly to permit liquids to pass downwardly. below it.

It is to be clearly understood that it is not necessary that a sufllcient space be provided between the sealing rings to permit the accumulation of a column of liquid above each sealing ring equal to the differential which said sealing ring-will support. Instead, only enough space -must be, provided to permit each sealing ring to move independently of the other rings. The major portion of the column of liquid may be supported above the uppermost sealing ring, but each sealing ring will support and carry a predetermined pressure differential portion of the total load. Thusif each sealing ring is so constructed that it will support, without leaking, a differential pressure of, l0 poundsper square inch, then ten rings would support acolurnnof; fluidexerting ay downward force due toits weight equal to substantially pounds per square inch. rlghe uppermost ring would absorb or support l0 pounds per square inch of the total load, thus by bypassing a. 9,0-pounds per square inchl pressure to the second ring, Which would in turn support l0 pounds per square inch differential of the total load and pass to the third ring 8() pounds, and so on until the total load of l0() pounds per square inch had been absorbed by or distributed over the 1'0 sealing rings, each of which carries a l0 pounds per square inch share of the total load.

Since each sealing ring will support` only a predetermined-pressure differential without leakage, and any pressureinl excess of such predetermined value acts to deform or. force the sealing rings downwardly out of contacty withl the bore. wall of the conductor; then, if the swabv is lowered too deeply into the. liquid in the well conductor, so. that a column of fluid in excess of the Y capacity of the sealing rings is trapped above the swab, the sealing' rings will simply: leak until the load above the swab has been reduced to a column which the seal-r ing rings will support. This provides `for' automatically controlling the column of liquid which can be carried by the swab and eliminates the possibility of lowering the swab so deep in the liquid that the swab is caused to stick. It will be seen that it is impossible to trap a liquid load above the swab which would prevent the swab from being lifted or pulled upwardly through the bore of the conductor. Therefore, the swab cannot be overloaded and stuck in the well.

Since the pressure load on each sealing ring tends to reduce the force of contact or bearing pressure between the sealing ring and the bore wall of the conductor by deilecting the sealing ring downwardly, it will be seen that the bearing pressure between the sealing rings and the bore wall of the conductor will be a minimum under maximum load conditions, hence the wear of the sealing rings will be a minimum when lifting the maximum load for which the swab is designed. Conversely, when the load is light the sealing rings will have a maximum bearing pressure against the pipe and thus reduce uid slippage to a minimum.

It will be seen, therefore, that the lift of the sealing element of the swab should be increasingly long for increasingly heavier loads up to the maximum for the swab. Therefore, since the bearing pressure between the sealing rings and the bore wall of the conductor will be low under heavy loads, and since the rate of wear is a function of bearing pressure, the rate of wear of the sealing rings under heavy fluid loads will be a minimum and the wear life of the sealing rings correspondingly long. Furthermore, so long as bearing pressures are low, it isalmost impossible to cut rubber or like resilient material, and the sealing rings will thus pass irregularities and projections without material damage; As a result, the damage which occurs when conventional swabs kpass coupling recesses under a heavy load is eliminated by the sealing element described herein, since `the bearing pressure of the individual sealing rings against the bore wall ofthe conductor is relatively low and the edge portions of the sealing rings may pass coupling recesses with practically no damage or Wear. l

Furthermore, since only the outer upper peripheral wear surfaces or extensions 29 of .the sealing rings engage the bore wall of the conductor, it Will be seen that only such wear surfaces of therings will be worn, and hence there is no way in which substantial chunks of the material of which the sealing rings are made can be torn off or stripped from the swab to remain in the bore of the conductor to foul therethrough.

In Figure 5 is shown an enlarged view illustrating the manner in which the Wear surface 29 of the sealing rings will be worn away by heavy use. The portion of the wear surface which has been worn away is shown in dotted lines, while the portion of the wear surface remaining and engaging the bore wall of theconductor is shown in full lines. Obviously, a substantial portion of the upper outer cylindrical peripheral edge and wear surface 29 of the sealing ring must beworn away before the effectiveness of the sealing ring is diminished to any substantial degree.

lt is believed manifest that the Wearing surface 29 of the sealing member 25 may be formed in manners differing from that just described.v Several modifications of the wear surface ofthe sealing member are illustrated in Figures 6 through l1.

In Figure 6, a sealing member 30 is shown assembled on a portion of a tubular mandrel 31, which sealing member is formed with anelongate cylindrical sleeve 32, similar to the sleeve 26 of the form rst described, and formed of rubber, syntheticfrubber, or the like resilient sealing material, and preferably molded on the exterior cylindrical surface of a reinforcing tube 33 so as to be fixed against movement-of said tube. The tube is slidable onto the exterior of the mandrel 31. A plurality of uniextending the life of the sealing element 40 withoutV 6 formly spaced inverted substantially frusto-coni'cal annular sealing rings 34 are carried by the sleeve 32, said sealing rings being preferably formed integral with the sleeve. The cross-sectional thickness of the rings projecting outwardly from the sleeves is preferablyvsubstantially uniform throughout andthe annular outer edge surface of each ring is cylindrical. Also, eachring is provided at its outer upper peripheral edge with an up standing bead or wear surface 35,.-as clearly shown in Figure 6, for the purpose of increasing-the life of the sealing element in the manner already described.

The diameter of the sealing rings 34, in the normal undeformed position shown in Figure 6, is substantially equal to the diameter of the bore wall of the well conductor C. The sealing rings will readily flex upwardly in the manner already described to permit fluid to pass exteriorly of the mandrel between the sealing member and the bore wall of the conductor when the lswab mandrel is lowered into the lbore of the wellV conductor. When the swab is lifted, liquid trapped above the mandrel will act downwardly upon the uppermost sealing ring 34 and deform the ring downwardly to the manner shownin Figure 7, wherein the beaded wear ange 35 of the ring engages against the bore wall of the conductor to form a seal therewith. The sealing rings will each support or lift only a predetermined column of Afluid, so that the total load of liquid tor be supported bythe swab will be borne in equal increments by the sealing ring which bears its proportionate share of the total load in the manner already described. The wear surfaces or beads 35 on the sealing rings will wear away, similarly to the wear surface 29 of the form rst described, runtil the outer annular cylindrical surfaces of the rings have been substantially worn away, the rings functioning without loss of efficiency until such wear surface has been worn away. Y l

A further modification of the sealing member is illustrated in Figures 8 and 9, wherein a sealing member 40 ismounted on a mandrel 41, said sealing member including an elongated tubular sleeve 42, similar to lthat of the form first described, made of rubber, synthetic rubber or other suitable flexible material, molded on the exterior cylindrical surface of a supportingtube 43 which is slidable onto the mandrel 41. A plurality of .uniformly spaced inverted substantially frusto-conical annular sealing rings 44 are carried by the sleeve 42, said sealing rings being preferably substantially uniform throughout, and the annular outer edge surface of the rings is substantially cylindrical. Each ring is provided with an annular wear flange 45, which is angular in crosssection, on its outer upper peripheral edge. As is shown in Figure 9, when the rings flex downwardly under load as the swab is lifted, the wear `surfaces or flanges 45 engage against the bore wall of the Well flow conductor to form a seal therewith. The wear surfaces 45 will wear away gradually until the -outer annular cylindrical surface of each ring is substantially worn off, thus greatly diminishing its effectiveness. v

; A still further modicationof the sealing element is illustrated in Figures l0 and ll, wherein the element is mounted on a mandrel 51, said sealing element including an elongated cylindrical sleeve 52, preferably formed of rubber, synthetic rubber or the like resilient sealing material, similar to the sealing elements previously described, and preferably molded on the exterior cylindrical surface of a reinforcing tube 53 which is slidable onto the mandrel 51 of the swab. A plurality of uniformly spaced inverted substantially frusto-conical annular sealing rings 54 are carried by the sleeve 52, said sealing rings being preferably formed integral with the sleeve. The cross-sectional thickness of the rings projecting outwardly from the sleeve is preferably substantially uniform throughout, and the outer annular edge surface' of the rings is substantially cylindrical. Each ring is pro- 7 vided witiranl upstanding annular substantially triangular wear an'ge 55 at its outer upper peripherall edge, as clearly shown in Figure l0; These wear flanges 55 are adapted' to engage the bore wall of the tiow conductorV C as the swab is' lifted therein and the sealing rings are deected under loadY to the positionshownv in Figure l1. The wear surfaces provided by the wear anges 55 will' gradually wear in use until the cylindrical portion of the ring is substantially eliminated, without reducing to any substantial extentthe effectiveness of the sealing rings for lifting uid; as has already been explained;

In all forms of the invention illustrated herein, it will be seenV that the outer upper peripheral edge of the sealing ring ofthe sealing member is formed with an annular wear surface providing for an extended wear life for such wiping edges of the sealing ringsY as the rings are deectedinto engagement with the bore wall ofthe conductor C in use in lifting fluid. In all forms each of the sealing rings will support only predetermined" maximum pressure differential without leaking, and any pressure in excess of such predetermined value actsto force or deform the sealing ring downwardly out or" contact with the bore wall of the conductor to permit uid trapped above such ring to flow downwardly therepast. Tghe sealing rings` are all arranged to move into sealing engagement with the bore wall of the conductor upon thev application of iiuid pressure thereagainst for maintaining a seal between the mandrel andl the bore wallof the conductor. arranged to carry only a predetermined maximum pressure differential, so that a pressure differential in excess of such` predetermined maximum differential" will pass the individual sealing ring to act againstv the next adjacent ring, whereby each sealing ring bears a proportionate share of the'total load, and will not carry a loadV greater than the maximum predetermined valuefor which the sealingring is designed. Furthermore, it is believed manifest that the sealing rings are so constructed thatV the bearing pressure between the outer peripheral lip portions of the ring in the bore wall of the conductor ismaintained at a minimum under maximum conditions of load, whereby the wear of the rings is` minimized under such maximum load conditions. It is also believed manifestV that a light load appliedY to the sealingring does not deliect the rings downwardly to so great an extent, whereA by greater bearing pressure is exerted against the wall of the well conductor and light loads may be lifted atr great depths with minimum leakage or slippage. Furthermore, the wear surfaces or anges provided on the upper outer peripheral edges of the sealing ring provide for an' extended life of the sealing rings in use without decreased4 efficiency. lt is also believed manifest thatth'e sealing rings of each form of the invention disclosed will by-pass excess fluid pressures, so that the swabs cannot be stuck or overloaded in the well flow conductor an'd caused to' stick therein.

The foregoing description of the invention is explanatory only, and'changesin the details of the construction illustrated may be made by those skilled in the art, within the" scope of the appended claims, without departing from the spirit of the invention.

What I claim and desire to secure by Letters Patent is'.

l. A wellv swabk adapted to be lowered and raised in a well structure to elevate well liquid and including, a support, a plurality of annular sealing elements mounted on the support in` axially spaced relationship, each'sealing element' beingconstructed of elastic material and being upwardly and outwardly inclined with its peripheral edge substantially cylindrical in shape and in non-sealing engagement'with the wall of the well conductor when the element is in a normal undistorted position, each sealing element being capable of flexing in a downward direction under a predetermined load of liquid to effect a sealing engagement of the peripheral edge of the element with the wall'of the conductor, whereby said element may be Furthermore, each sealing ring is S utilized to lift the predetermined loadl of liquid, increase of! the liquidl load beyond the predetermined load causing further' flexing of! said element inl a downward direction to move. the` peripheral edge thereof out of sealing engagement withf thewall of the conductor to.`

permit escape of liquids downwardly past the element and reduce ther liquidi loadl thereabove to the predetermined'I load, the upperI peripheral edgel of the sealing elements' each1 having an upward projecting portion forming a wear surface for engaging the wall of the conductor when the sealing element is flexed downwardly into sealing engagementwith the wall of thel conductor, said wear surface providing an a-rea of Contact between the edges of the sealing element-s and the wall of the well conductor lesswt-hanf the cross-sectional thickness of the sealing element' when said sealing element is in sealing engagement with they wall ofthe conductor.

2. A- sealing member! for a welltool for use in well' tubing comprising: asleeve member mountable on the well tool, and a pluralityof axially` spaced inverted substantially truste-conical flangeV like sealing rings projecting from said sleeve, each of` said'sealing rings being upwardly andoutwardly inclined, said rings being constructed and arranged to iiex under a predetermined load of liquid thereon to a downwardly and outwardly inclined posit-ion such that the outerv perphery of the ring first moves downwardly and' outwardly to seal with the well tubingv interior surface and then further downwardly and inwardly to a leakage position to eventually move out of engaging contact with the well tubing interior surface so long as; the load on the ring exceeds such predetermined load, the outer peripheral surface of each ring being substantially cylindrical, each of said rings having an upwardly projecting portion 'f' forming a wear surface at its upper outerperipheral edge,

theV wear surface of' each of' said sealing rings providing an area ofcontactbetween the edges of the sealing rings and the wall? of the wellA conductor less than the crosssectional thickness of the sealing ring when said sealing ring is in sealing engagement with the wall of the conductor.

n 3. A sealing member for a well swabV for use in well tubinglincluding-z a sleeve member mountable on the well tool, and a sealing member carried by the sleeve mem-v ber for sealing between theV sleeve and the bore wall of the well tubing, said sea-lingmember being upwardly and outwardly inclined in substantially an inverted frustoconical shape and having a` substantially cylindrical outer peripheraly edge surface, an upward and outward extension of the upper surface of' said sealing member fornn ing a wear surface at the upper outer peripheral edge of,k said sealing member, said sealing member being initially deformable downwardly from above a horizontal plane' to bring' therwear `surface into sealing engagement with the bore'wall of the tubing and'being further downwardly deformableV upon the' application of a fluid pressurev load' thereacross in excess of a predetermined uid pressure diere'ntial to move the sealing means out of sealing engagement with' the bore Wall of the tubing to permit fluid pressure to' flow downwardly past the sealing member, the wear surface of said sealing member providing an area of contact between' the edge of the sealing member and the wall of the well conductor less than the' cross-sectional thickness ofthe sealing member when said sealing member is in sealing engagement with of said sealing rings having an upwardly projecting wear ange at its upper outer peripheral edge for engaging the bore wall of the flow conductor, the wear surface of each of said sealing rings providing an area of contact between the edges of the sealing rings and the wall of the well conductor less than the cross-sectional thickness of the sealing ring when said sealing ring is in sealing engagement with the wall of the conductor.

5. A Well swab adapted to be lowered and raised in a well structure to elevate well liquid and including, a support, a plurality of annular sealing elements mounted on the support in axially spaced relationship, each sealing element being constructed of elastic material and being upwardly and outwardly inclined with its peripheral edge substantially cylindrical in shape and in non-sealing engagement with the wall of the Well conductor when the element is in a normal undstorted position, each sealing element being capable of flexing in a downward direction under a predetermined load of liquid to eiect a sealing engagement of the peripheral edge of the element with the wall of the conductor, whereby said element may be utilized to lift the predetermined load of liquid, increase of the liquid load beyond the predetermined load causing further flexing of said element in a downward direction to move the peripheral edge thereof out of sealing engagement with the wall of the conductor to permit escape of liquids downwardly past the element and reduce the liquid load thereabove to the predetermined load, the upper peripheral edge of the sealing elements forming a wear surface for engaging the wall of the conductor when the sealing element is exed downwardly into sealing engagement with the wall of the conductor, said wear surface providing an area of contact between the edges of the sealing elements and the wall of the well conductor less than the cross-sectional thickness of the sealing element when said sealing element is in sealing engagement with the wall of the conductor.

References Cited in the file of this patent UNITED STATES PATENTS 1,634,891 Trout July 5, 1927 2,018,205 Evans Oct. 22, 1935 2,283,460 Pumphrey May 19, 1942 2,417,349 Colbaugh Mar. 11, 1947 2,633,808 Webber Apr. 7, 1953

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