US3085627A - Inflatable packer or element - Google Patents

Description

April 16, 1963 E. o. SODICH 3,085,627

INFLATABLE PACKER OR ELEMENT Filed Aug. 15, 1958 3 Sheets-Sheet 1 i I I i I z A4 45, s M

ATTOR/VE VJ April 16, 1963 E. o. SODICH 3,

INFLATABLE PACKEZR OR ELEMENT Filed Aug. 15, 1958 5 Sheets-Sheet 3 J 0 a c fi INVENTOR Ernesf 0.

BY y M 3,085,627 INFLATABLE PACKER R ELEMENT Ernest 0. Sodich, Houston, Tex, assignor to Lynes, Inc, a corporation of Texas Filed Aug. 15, N58, Ser. No. 755,177 7 Qlairns. (Cl. 166-120) The present invention relates to an inflatable element.

When packers or inflatable elements are lowered into well bores in order to seal off a portion of the well bore, there is sometimes a tendency for the packer to move or slide along the well bore wall as a result of fluid pressure acting thereon. Such conditions arise where the well bore is cased, so that-the bore wall is relatively uniform and has no surface irregularities which might aid in anchoring the hydraulic packer in position after it has been inflated. Also, many holes drilled into the earths formation are smooth and slick even without casing so that the problem is prevalent whether the hole is cased or not.

Noninflatable types of packers are generally provided with suitable hold-down means such as slips or the like, which are adapted to frictionally engage the wall of the well pipe, whereupon the packer can thereafter be expanded to sealing position within the well pipe. It is undesirable to provide a hold-down tool for maintaining the packer in position in the .well pipe whether the packer be a squeeze type of packer which is adapted to be expanded by exerting a force or squeeze on a large mass of rubber as distinguished from inflatable packers, which are adapted to be expanded by fluid pressure applied internally thereof.

It may also be desirable to seal off a flow line while repairs are made therein, or to seal off a tubular member to test for leaks, and in various other situations it is desirable at times to seal oil. in an annulus.

An object of the present invention is to provide an inflatable packer which will remain seated in either a cased or open hole, even under high differential pressures.

Another object of the present invention is to provide an inflatable element construction which is provided with a friction area on the body thereof so as to maintain the element seated in position in an annular member;

Still a further object of the present invention is to provide an inflatable element which is adapted to be expanded in a well bore to seal with the well bore wall, which element includes force concentrating means thereon to concentrate and thereby magnify the sealing or seating pressure of the packer against the -well bore wall so as to anchor the packer firmly in the well bore.

Still a further object of the present invention is to provide a packer including spaced annular heads, a packer body extending therebetween, reinforcing in said body and secured to each of said heads, and particles positioned on the exterior of said body which are adapted to frictionally engage the -well bore wall and concentrate the inflating pressure within the packer on said particles to aid in seating the packer within the well bore.

Still a further object of the present invention is to provide an inflatable element for a well bore including means to concentrate and magnify the inflating pressure of the element so as to aid in seating and maintaining the packer seated in position in the well bore.

Yet a further object of the present invention is to provide an inflatable packer construction which is constructed and arranged so that it will remain seated within a well pipe, or tubular object.

A further object of the present invention is to provide spaced friction areas on the external periphery of a fluid inflatable packer body, so that after the packer has been inflated and seated within well pipe, it will maintain its original seated position.

Still a further object is to provide an inflatable packer body having recessed friction areas thereon which engage the wall in a well bore when the packer is inflated so as to properly seat, and maintain the packer seated within the well even though substantial differential pressure within the well is effective to act on the packer.

Other and further objects of the present invention will become more readily apparent from a consideration of the following description and drawings, wherein:

FIG. 1 is a view illustrating a form of the inflatable packer of the present invention in deflated position and being lowered into well pipe, with a well pipe shown in section;

FIG. 2 is a view somewhat similar to FIG. 1, but showing the inflatable packer expanded or inflated and in seated position within the well;

FIG. 3 is a sectional view on .the line 3-3 of FIG. 2 showing in more detail the construction of a form of the friction areas or force concentrating means on the packer body and its relationship to the internal periphery of the well pipe when the packer is expanded and seated within the well pipe;

FIG. 3A is an enlarged view illustrating one particle of the abrasive material which is embedded in the packer body;

FIG. 4 is a side view, illustrating an alternate modification of the friction means or force concentrating means for use on the packer body;

FIG. 5 is a sectional view on the line 5-5 of FIG. 4, illustrating in more detail, the structural arrangement of the friction, or force concentrating means of the FIG. 4 modification and its arrangement on the packer body;

FIG. 6 is a side view of still another modification of the friction or force magnifying means for use on the packer body;

FIG. 7 is a sectional view on theline 7-7 of FIG. 6 to show in more detail, the structural arrangement of the friction means of the FIG. 6 modification;

FIG. 8 is an elevational view, partly in section, wherein an alternate arrangement of the force concentrating and magnifying means of the invention is illustrated, and also illustrating in more detail the preferred embodiment of the internal structural arrangement of the packer or element;

FIG. 9 is a sectional view on the line 9-9 of FIG. 8;

FIG. 10 is a sectional view on the same line as FIG. 9 but showing the arrangement or relationhip of the element components when the element is inflated; and

FIG. 11 is an enlarged schematic representation to illustr-ate the function of the force concentrating means of the present invention.

The present invention will be described in detail as it may be used for positioning in a well pipe in a well bore. However, it should be understood that such description is purely for purposes of explanation, and that the present invention may be as easily used in any annular member wherein it is desired to seal off the member, either to test it, for repairs, or for other reasons.

Attention is directed to FIG. 1 of the drawings wherein a Well pipe is illustrated at 2, which well pipe is positioned within the well bore 3 formed in the earth 4. The packer or element forming the present invention is illustrated generally by the numeral 5 and is adapted to be lowered within the Well pipe 2 by any suitable means such as by connecting a male adapter 6 threadedly to the packer as shown in P16. 4, and then connecting the well string 6 to the fitting 6, as shown in FIG. 1. The well string ex.- tends upwardly to the earth's surface and, if desired, the well string 6 may extend below the packer as illustrated at 7 in FIG. 1, depending upon what the packer or packers are to accomplish within the well bore 3.

After the packer has reached the elevation within the well pipe 2 at which it is desired to expand the packer in sealing engagement with the well pipe, the packer may be inflated by discharging fluid from the well string 6 through a port therein (not shown) internally into the packer 5. Suitable mechanism, shown in the prior art, may be connected to the well string and packer in order that it may be inflated, as desired. As the packer inflates, it will expand radially until the packer engages the internal periphery of the pipe 2 as illustrated at 8 so as to seal off a portion of the well bore 3.

It will be noted that the present invention is described with regard to only one packer; however, a plurality of packers can be provided in order to treat or test the well, as desired, in which event all of the packers may be provided, if necessary, with friction areas as described here inafter.

The details of the packer arrangement on the well pipe 6 and the operating mechanism for inflating the packers are not described herein, since such construction and arrangement on the well pipe are Well known in the art, for example, as shown in Patent No. 2,824,612, issued to John Lynes on February 25, 1958. The representation in the drawings is merely illustrative and the above patent, as well as others may be referred to for details of connection and arrangement of the packers on the well string 6. The prior art also illustrates means whereby the packer may be inflated and, therefore, the details of inflating and deflating the packers 5 are not described herein.

The packer designated generally by the numeral 5 in FIG. 1 is shown in more detail in the modification illustrated in FIG. 8. The packer or inflatable element 5 includes annular heads 9 and arranged in spaced relation to each other to form the ends of the packer and the body 11 extending therebetween. The packer body represented generally at 11 which extends between the heads 9 and 10 is secured thereto by any suitable means as disclosed in Patent No. 2,611,437, issued to John Lynes on September 23, 1952.

The body 11 includes resilient material 11' and suitable reinforcing as shown at 11" therein to withstand the internal and external pressure-s applied thereto during inflating and the external and internal pressures applied thereto during functioning of the packer in the well bore. The reinforcing 11" is shown as being formed by a plurality of strips 11" which extend longitudinally of the body 11 of the packer 5 and are secured to each head 9 and 10, as will be described in more detail hereinafter. The longitudinally extending strips 11" of reinforcing 11 are arranged within the packer body 11 so that adjacent strips overlie each other longitudinally between the heads 9 and 16.

FIG. 9 shows the packer 5 in deflated position and FIG. 10 represents the packer or inflatable element 5 inflated. As shown in FIG. 10, the longitudinally extending strips 11" of the reinforcing 11 remain in overlapped relation although the degree of the overlapping is not as great as it is when the packer is deflated as shown in FIG. 9. Thus, the reinforcing which is formed of material of relatively great tensile strength serves to reinforce the body 11 of resilient material and aids in retaining the inflating fluid even when the packer is inflated.

Each annular head may be provided with a recess as illustrated at 9' on the outer periphery and at the inner end so that the body 11 may fit closely about each of the heads. Serrations or a knurled surface 9" is provided on the inside of each head which engages the ends 11a of the strips 11" to aid in securing the reinforcing 11" to each of the heads 9 and 10. A member 11b may be provided for fitting within each of the heads 9 and 10 to engage the ends 11a of the reinforcing strips 11 in order to anchor the ends 1111 of the longitudinally extending reinforcing strips 11" in position in each of the heads 9 and 10. It will be noted that serrations 11c are provided on the lower end of the member 1112 which are adapted to engage the ends 11a of the reinforcing strips 11' and as the member 11b is driven by pressure into a tight fit with each of the heads 9 and 10, the serrations 11c thereon will engage against the ends 11a of the strips 11" to firmly secure the reinforcing 11" in position in each of the heads 9 and 10. It will be noted that a portion of the resilient material 11' of the packer body 11 extends upwardly within the member 11!) and this portion of the packer body may be retained in position therein by suitable means such as the brass or bronze ring 11:] which may be expanded by pressure to seat within the member 1112 as shown in FIG. 8 of the drawings.

The packer body 11, including the heads, the reinforcing 11", and the arrangement of the resilient material 11 of the packer body serve to retain the inflating fluid within the packer when the packer is expanded. The reinforcing 11" and the heads 9 and 10 also provide additional strength to the packer 5 to aid in withstanding the high pressures necessary to a proper functioning of the packer when it is expanded to seat or seal within the well bore 3.

In the FIG. 8 modification, it will be noted that a friction area or force concentrating means represented generally by the numeral 15 is provided on the packer or inflatable element 5, which extends throughout the length of the resilient material 11 between the heads 9 and 10 of the body 11 of the packer.

The FIGS. 1 and 2 modification show packer body 11 as being provided with annular recesses 13 and 14 which are spaced relative to each other on the periphery of the resilient material 11' and adjacent the heads 9 and It The recesses 13 and 14 are formed in the resilient material 11 in any suitable fashion, as, for example, the recesses 13 and 14 may be formed by suitable cutting means which cuts the recesses 13 and 14 in the resilient material 11' after the packer body 11 has been formed.

It will be noted that each recess 13 and 14 of the FIGS. 1 and 2 modifications, as well as the entire body 11 of the FIG. 8 modification, is provided with a coating of abrasive particles 17 or material to form the friction areas or force concentrating means 15 on the packer or inflatable element 5. The particles 17 are bonded on the body 11 of the FIG. 8 modification and are embedded within the recesses 13 and 14 of the body 11 in the FIGS. 1 and 2 form. The abrasive particles 17 are of a hard substance such as metal or the like, and each particle has a plurality of edges and surfaces which are irregular and protrude outwardly relative to the body 11 of the packer 5 to aid in frictionally gripping the inner periphery 8 of the well bore when the packer '5 is expanded or inflated as shown in FIG. 2 of the drawings. More particularly, the abrasive particles 17 may be formed of cracked metal shot, carborundum or aluminum oxide grit, or may be in the form of the circular buttons at shown in FIG. 4, or the jaw segments as shown in FIG. 6. Additionally, other forms of frictional areas or force concentrating means may be provided on the packer without departing from the scope of the invention.

It has been further discovered that the arbrasive coating of particles 17 may be applied to the annular recesses or grooves 13 and 14 by wrapping the recesses 13 and 14 with uncured resilient material or synthetic rubber and then providing a surface on the uncured material with a suitable cement which is sticky in nature. The particles 17 may then be placed manually on the sticky surface within the grooves 13 and 14, and the packer or element 5 then subjected to suitable heat so as to cure the material, whereupon the hard particles become firmly embedded within and bonded to the cured rubber in the recesses 13 and 14 and are thereby integrally formed with the packer body 11.

If the resilient material is synthetic or natural rubber, the portion within the recesses 13 and 14 of the FIGS. 1 and 2 modification may be softened with methyl ethyl ketone or ethylene dichloride, either of which softens syn thetic or natural rubber and makes it sticky, whereupon the particles 17 may be placed in each of the recesses. Of course, in the FIG. 8 modification, the entire body '11, between the heads 9 and 10 would be correspondingly treated so as to retain the particles 17 thereon, while the resilient material is cured.

In order to aid in bonding the particles 17 on the packer body 11, either in the FIGS. 1 and 2 modification, or in the FIG. 8 modification, they should be coated with a suitable material prior to placing them on the packer body 11 in order to facilitate bonding of the particles to the resilient body 11.

It has been further discovered that the metallic or hard particles 17 forming the abrasive friction surface or force concentrating means need only be one layer thick, in order to perform the desirable function of firmly gripping and concentrating a force against the inner periphery 8 of the well pipe 2.

In FIG. 2 the packer construction 5 is illustrated as having been inflated, and it will be noted that the packer body '11 has been expanded and the grooveslfi and 14 therein also expand radially with the resilient body 11' to engage the inner periphery 8 of the well bore. Since the grooves 13 and 14, and the abrasive particles 17 therein, are arranged adjacent each end of the packer, and in spaced relation, the packer is thus firmly held in position in the well pipe 2, so that any tendency from pressure acting above or below the packer which tends to move the packer in the well pipe is resisted. Thus, the packer is firmly seated within the well pipe 2, and treating or testing operations, as desired, can be carried out without running the risk of having the expanded packer slip or move along the well pipe.

FIG. 3 illustrates the inflated position of the packet, and it will be noted that the particles 17 have a plurality of sharp edges and irregular surfaces thereon and tend to dig into the inner periphery 8 of the well pipe 2 to aid in gripping the well pipe and transmitting a concentrated force from the packer to the pipe or Well bore.

FIG. 3A represents in enlarged form one of the particles 17 embedded in the recesses 13 and 14 on the packer body 11. Of course, each particle will be of different configuration and shape, but it will be noted that as shown in FEG. 3A, the particle 17 includes many edges '18, '19, 2t 21 and 22 which are, of course, joined by their respective surfaces, which are irregular as represented by the numeral 23. The lack of uniformity of the particles 17, as well as their irregular surfaces and edges aids in providing a plurality of smaller individual surfaces which define the friction surface 15 that positively grips the pipe 2 or the well bore wall to prevent movement of the packer 5 therealong.

The particles 17 also form a means so that the force of the inflating pressure of the well packer may be concentrated and magnified to aid in retaining the packer in position in the well, and to prevent slipping thereof, even though the pressure differentials within the well may become great. For example, attention is directed again to FIGS. 3 and 3A, and as previously mentioned, the particles 17 are provided with a plurality of edges joined by irregular surfaces. The particles 17 are embedded and bonded within the packer body 11 and protrude therefrom so that as the packer body llexpands to engage the wall of the well bore, the inflating pressure within the packer is transmitted through the resilient body 11' of the inflatable element 5 to the surrounding formation against which the element 5 is seated. Since the particles '17 protrude relative to the resilient body 11' of the packer 5, the exposed surfaces of the particles 17 bear against the adjacent well wall. isting within the packer, instead of being uniformly distributed along what would normally be a smooth outer periphery of the resilient body 11' of the packer 5, is transmitted to the protruding edges of each of the particles 17. These edges, being much smaller in total area than Therefore, the fluid pressure exwithin the resilient packer body 11.

the edge of the button 25'.

the total area of the resilient body 11 therefore serve to concentrate the force from the inflatable element or packer 5 and tend to magnify the pressure along each edge so that a greater force is exerted by the packer 5 than would otherwise be the case to aid in seating it properly within the well bore. As previously mentioned, the force concentrating means 15 shown in FIGS. 1, 2 and 8 as being in the form of the particles 17 is harder than the pipe in a well bore, and is harder than the wall of a well bore so that the force applied from the inflating element to the sharp edges of the particles tend to dig into the pipe or into the wall of the well bore because of the force magnified thereon. The resilient material 11' in the body '11 of the inflatable element or packer 5 is such that it will elongate, but its hardness preferably is such that the resilient material will not always contact the wall of the well or pipe when it is expanded. In other words, the major portion of the force transmitted to the wall of the well bore or to the pipe in which the packer is positioned, will be that force concentrated through the force concentrating means on the edges of each of the protruding particles 17, while only a portion of the force is transmitted by the resilient'material directly to the surrounding wall of the annulus in which the element is positioned. In FIG. 4 the packer construction is again represented generally by the numeral 5, and it will be noted that the packer body 11 is provided with a plurality of members designated generally by the numeral 25 within the resilient material 11' to form friction are-as or force concenrating means 15 adjacent each end of the packer. The members 25 are shown as being in the form of circular buttons 25 which are arranged in rows as shown at 26, which rows may be in staggered circumferential relationship to each other, if desired, as shown at 27. The buttons 25' may be embedded in the resilient material 11 in any suitable manner, such as by integrally forming the members therein at the'time that the packer body 11 is formed with uncured rubber and thereafter cured by heating.

In FIG. 5, the details of the buttons 25 are shown as well as their circumferential relationship to each other It Will be noted that thebuttons 25 are providedwith the surface 30 thereon which is tapered inwardly and annularly as shown at 31 to form the edge 32 where the tapered surface 31 meets Therefore, when the packer body 11 is inflated to expand it, the edge 32 of each button is exposed to engage with the periphery 8 of the well, and tends to dig into the periphery of the well to inhibit movement of the packer therealong. It will be further noted that the buttons 25' are grouped adjacent each end of the packer body 11 to form friction areas 15 adjacent each end of the packer in a manner as described with regard to the FIGS. 1 and 2 modification.

In FIG. 6, the members 25 are represented as being in the form of jaw segments 33, which segments may be arranged in rows 34 on the'packer body 11, and in staggered circumferential relationship as shown at 35, if desired. The segments 33 are provided with serrations or other irregular surface areas thereon as shown at 36 so that when the packer body 11 is expanded, the jaw segments engage with the inner periphery 8 of the well. Jaw segments 33-are shown as being grouped adjacent eachend of the packer in the FIG. 6 construction in a manner similar to the buttons 25' of the FIG. 4 modification, to form friction areas or force concentrating means 15 in the packer body 11.

It will be noted with regard to the FIGS. 4 and 6; modification, that the force concentrating the force magnification means 15 is illustrated as being in the form of the spectively, For example, in the form of the force magniflcation means 15 illustrated in FIG. 5, the edges 32 of the buttons 25' will be exposed as the packer is inflated so that the inflating force within the packer is transmitted through the body 11 to the edges 32 of each of the elements 25'. In the FIG. 6 modification, the force transmitted from the packer is concentrated and magnified by means of the serrations, or irregular surface areas, on the jaw segments 33.

From the foregoing it can be appreciated that other forms of force magnification and concentration means could be provided other than that illustrated in the present drawings and description without departing from the scope of the present invention.

It will be further noted that in FIGS. 1-6 inclusive, there is illustrated a form of the invention wherein the friction areas or force magnification means is provided at spaced locations adjacent the ends of the packer or inflatable element 5, whereas in the FIG. 8 modification, it will be noted that the means 15 extends substantially throughout the length of the resilient material 11' of the body 11 of the inflatable element 5. Either form will work quite satisfactorily; however, by using two friction areas as illustrated in the preferred embodiment shown in FIGS. 1-6 inclusive, the maximum resistance against sliding or slipping of the packer within the well bore in either direction is provided with a maximum sealing effect between the spaced areas.

In FIG. 11, an enlarged representation of the force magnification means 15 is shown as being in the form of the particles 17. A portion of the packer body 11 is shown and it will be noted that the resilient material 11 of the packer body does not contact the wall of the adjacent well bore in which the packer is expanded. Therefore, the inflating pressure represented by the arrow 60 is transmitted to the protruding edges 61 of the particles 17 which contact the well bore wall. Thus, the inflating pressure is concentrated on the contacting edges 61 instead of along the exterior 62 of the packer body 11. This magnifies the force, since the pressure must be distributed over the smaller areas of the contacting edges 61 so that the resistance to slipping of the packer is thereby greatly multiplied.

The function and operation of the present invention in any other situation is similar to that previously described with regard to the example in the well bore. If the device is to be used in an annulus of a well bore to seal against the well bore wall, the force magnification means will act to concentrate the force against the well bore wall in a manner as previously described with regard to concentrating the force against the periphery of the well pipe. Also, where the device is to be used in any annulus, or in a tubular object, for purposes of testing, or for any other use, the force magnification means functions in the manner as described with regard to the force magnification means in the same manner as previously described with regard to the use of the invention in well pipe in a well bore.

Broadly the invention relates to an inflatable packer or element, and more particularly to an inflatable packer which is provided with a friction surface area or force magnification means for aiding in gripping the well bore wall when the packer element is inflated and seated therein, or for gripping the surrounding wall in any annulus in which it is positioned.

What is claimed is:

1. An inflatable packer construction including spaced annular heads, an annular body of resilient material extending between and secured to each of said heads, a pair of spaced recesses on the external periphery of said body, and abrasive material embedded within said recesses to form friction areas on the packer when inflated to aid in anchoring the packer in inflated position, said abrasive material forming the friction area being in the form of a coating of particles on said body recess having protruding edges and surfaces.

2. An inflatable element adapted to be inflated and seated in a tubular object including a support head adjacent each end of the element, an annular body of resilient material extending between and secured to each of said heads, said body including a reinforcing sheath extending between and secured by each of said heads, at least one recess on the external periphery of said body, and force concentrating means embedded in said recess on said annular body of resilient material to aid in anchoring said body in the well bore.

3. An inflatable element adapted to be inflated and seated in an annulus including a support head adjacent each end of the element, an annular body of resilient material extending between and secured to each of said heads, said body including a reinforcing sheath extending between and secured to each of said heads, and force concentrating means embedded in said annular body of resilient material to aid in anchoring said body in the well bore.

4. An inflatable element adapted to be inflated and seated in an annulus including a support head adjacent each end of the element, an annular body of resilient material extending between said heads, said body including a reinforcing sheath extending between and secured to each of said heads, and means forming a friction area embedded in said annular body of resilient material to aid in anchoring said body in the Well bore.

5. An inflatable element adapted to be inflated and seated in an annulus including a support head adjacent each end of the element, an annular body of resilient material extending between said heads, said body including a reinforcing sheath extending between and secured to each of said heads, and means forming a friction area on said annular body of resilient material to aid in anchoring said body in the well bore, said last named means including particles of abrasive material which tend to dig into the well bore wall when said element is expanded to anchor it.

6. An inflatable element adapted to be inflated and seated in an annulus including a support head adjacent each end of the element, an annular body of resilient material extending between and secured to each of said heads, said body including a reinforcing sheath extending between and secured to each of said heads, means on said annular body of resilient material to aid in anchoring said body in the well bore, said last named means including particle means which concentrate and thereby magnify the pressure of the inflating body element against the well bore wall to anchor said body in the well bore.

7. In an inflatable element which is adapted to be expanded in a tubular bore to seal with the tubular bore wall, said element including an annular body of resilient material, friction means on said body to aid in anchoring said element in the tubular bore, said friction means including particles embedded in said element, said particles having irregular edges and surfaces which protrude outwardly relative to said element to concentrate and thereby magnify pressure of the inflating element against the tubular bore Wall to anchor the element in the tubular bore.

References Cited in the file of this patent UNITED STATES PATENTS 2,019,418 Lang Oct. 29, 1935 2,084,784 Stahl June 22, 1937 2,171,438 Tarbox Aug. 29, 1939 2,194,331 Strom Mar. 19, 1940 2,370,832 Baker Mar. 6, 1945 2,656,891 Toelke Oct. 27, 1953 2,778,432 Allen Ian. 22, 1957 2,800,186 Tausch July 23, 1957 2,835,329 True May 20, 1958 2,970,649 Brown Feb. 7, 1961

Claims (1)

1. 7. IN AN INFLATABLE ELEMENT WHICH IS ADAPTED TO BE EXPANDED IN A TUBULAR BORE TO SEAL WITH THE TUBULAR BORE WALL, SAID ELEMENT INCLUDING AN ANNULAR BODY OF RESILIENT MATERIAL, FRICTION MEANS ON SAID BODY TO AID IN ANCHORING SAID ELEMENT IN THE TUBULAR BORE, SAID FRICTION MEANS INCLUDING PARTICLES EMBEDDED IN SAID ELEMENT, SAID PARTICLES HAVING IRREGULAR EDGES AND SURFACES WHICH PROTRUDE OUTWARDLY RELATIVE TO SAID ELEMENT TO CONCENTRATE AND THEREBY MAGNIFY PRESSURE OF THE INFLATING ELEMENT AGAINST THE TUBULAR BORE WALL TO ANCHOR THE ELEMENT IN THE TUBULAR BORE.

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