US3109490A

US3109490A - Slidable latching seal assembly

Info

Publication number: US3109490A
Application number: US83187A
Authority: US
Inventors: John R Baker
Original assignee: Baker Oil Tools Inc
Current assignee: Baker Hughes Oilfield Operations LLC
Priority date: 1961-01-17
Filing date: 1961-01-17
Publication date: 1963-11-05
Anticipated expiration: 1980-11-05

Description

Nov. 5, 1963 J. R. BAKER SLIDABLE LAIV'CHING SEAL ASSEMBLY Filed Jan. 17; 1961 INVENTOR (fa/10v J9 BAA/1? Arraemzrs.

United States Patent 3,109,490 SLIDABLE LATCHING SEAL ASSEMBLY John R. Baker, Mexico City, Mexico, assignor .150 Baker Oil Tools, Inc, Los Augeles, Caliltl, a corporation of California Filed Jan. 17, 1961, Ser. No. 83,187 17 Claims. (Cl. 166-114) The present invention relates to subsurface well bore apparatus, and more particularly to the obtaining and maintaining of a proper seal relationship between a tubular member disposed in the well bore and a companion well packer, or other barrier device in the well bore.

Tubing is disposed in a well bore in sealing relation to a well packer for the purpose of conducting fluids through the tubing and packer without such fluids leaking between them. Heretofore, under some well conditions, the tubing shrinks or elongates substantially due to thermal changes, with the possibility of disrupting the sealing relation between the tubing and the packer. The same adverse result might pertain upon subjecting the tubing to high pressure, which tends to elevate the tubing in the packer and disrupt the sealing relationship therebetween. Elongation of the tubing due to temperature increase or its being subjected to upwardly directed hydraulic force can induce buckling of the tubing which might cause its failure.

An object of the present invention is to provide an improved seal assembly between tubing and a well packer, or other barrier in a well bore, that permits the tubing to move longitudinally in the well packer over a relatively wide range without disrupting their sealing relation, and without requiring the use of an extended length of seals on the tubing.

Another object of the invention is to provide a seal assembly between tubing and a well packer, or other barrier in a well bore, capable of being run in the Well bore on the tubing and coupled to the packet, the tubing being movable longitudinally of the packer over an extended length without disrupting its sealing relation to the packer.

An additional object of the invention is toprovide a seal assembly between tubing and a well packer, or other barrier in a well bore, that is run in the well bore on the tubing and coupled to the packer and releasable therefrom without requiring the tubing to be rotated, the tubing being movable longitudinally of the packer through a substantial distance without disrupting its sealing relation to the packer.

A further object of the invention is to provide a seal assembly between tubing and a well packer, or other barrier in a well bore, that is run in a well bore on the tubing and coupled to the packer, the effect of hydraulic force on the tubing tending to elevate it in the packer being reduced considerably.

Yet another object of the invention is to provide a seal assembly between tubing and a well packer, or other barrier in a well bore, adapted to be releasably locked to the well packer so that it cannot be moved in either direction by hydraulic pressure.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

FIGURE 1 is a combined side elevational view and longitudinal section through a tubing and seal assembly, to

be used in conjunction with a well packer or other barrier in a well bore;

FIG. 2 is a diagrammatic view in longitudinal section of the assembly disclosed in FIG. 1 being inserted within a well packer;

FIG. 3 is a view similar to FIG. 2 disclosing the seal device fully assembled within the well packer.

The invention is illustrated in the drawings with specific reference to a well packer A anchored in packed-off condition in a string of well casing B disposed in a well bore. The Well packer is disclosed diagrammatically in the drawings, since it is of any known type. For example, it may comprise the specific construction illustrated in U.S. Patent 2,507,262 or U.S. Patent 2,683,492. The bodies of the well packer disclosed in such patents have a central passage 19 therethrough of cylindrical shape, there being a lower shoulder 11 on the body 13 inclined in a downward and outward direction, and also an upper shoulder 12 against which a companion member can bear.

A tubular string C, which is usually tubing, is lowered in the Well casing to the location of the Well packer A and is adapted to be inserted in its central bore or passage 10 in sealing relation to the body of the packer. This tubing string may extend to the top of the well bore, or may be suitably connected to an upper device, such as another packer (not shown), lowered in the well bore and set in the casing at a particular location above the packer A, as desired. The tubing string C includes a tubular inner body member 14 having an upper head 15, and which may be of an extended length. This tubular inner body member 14 is threadedly attached to an adjacent tubing section 16 thereabove, with its lower threaded pin 17 threadedly attached to a threaded box portion 18 on a lower sub 19, which may have a lower threaded pin 20 for attachment to a tail pipe D, or other tubular extension of the inner body member 14. l The periphery of the inner body member 14 is smooth and has a diameter substantially less than the inside diameter of the passage .10 through the well packer A, or other barrier disposed in the well bore, The inner tubular member 14 is to be placed in leak-proof relation to the body 13 of the packer by means of a seal assembly 21 mounted on the inner body member, and which. is adapted to be releasably coupled to the well packer A, or other barrier, anchored in the well casing B. As shown, the seal assembly includes an outer tubular body member 22 slida-ble on the inner tubular body member 14 and consisting of a plurality of sections. Thus, the outer body member includes an upper section 23 having an upper head portion 24 adapted to engage the upwardly facing shoulder 12 of the packer body 13. Provided in this upper portion is an internal groove 25 containing a pliant, elastic seal ring 26 adapted to slidably seal against the periphery 27 of the inner tubular member 1-4. The lower end of the upper section 23 is threadedly secured to an intermediate body section 28, there. being a groove 29 formed between these sections in which a suitable side seal device .30 is mounted adapted to seal against the inner wall 10 of the packer body 13. The lower end of the intermediate section is threadedly attached to a lower section 31, there being a peripheral groove 32 formed between these sections in which a packing or seal assembly 33 is mounted, also for sealing engagement with the wall 10 of the Well packer body. The

seals

30, 33 may be of any suitable type. As shown specifically in FIG. 1 by way of example, they may consist of upwardly and downwardly facing chevron seals .34, 35 with metallic spacers 36 therebetween. The inner lips of the chevron seals are adapted to bear and seal against the periphery of the body sections 23, 28 and the outer lips against the inner wall 10 of the packer body 13.

The lower section 31 of the outer body member 22 terminates in a latching, locking or coupling device, in the form of latch legs 37 terminating in lower latch feet 38. The latch legs and feet are formed by providing circumferentially spaced longitudinal slots or cuts 39 in the lower portion of the lower body section 31, the latch feet having inwardly projecting portions 40 adapted to be received within a peripheral groove 41 in the lower portion of the inner body member 14 above the bottom inner body sub 19. The upper side 42 ofrthis groove is tapered in a downward and inward direction and is adapted to engage companion tapered surfaces 43 at the upper inner portions of the latch feet 38. The latch feet extend outwardly from the groove 41 and are provided with upwardly tacing shoulders 44 inclined in an upward and inward direction, and also downward and inwardly tapering or beveled outer surfaces 45 at their lower corners which are adapted to be engaged by the downwardly tapering end 46 or the threaded box .18.

When the latch feet 38 are disposed in the inner body groove 41, they are adapted to pass through the well packer passage 10. When disposed laterally out of the groove 41, in the manner described hereinbelow, they will extend outwardly to an eifect-ive diameter substantially greater than the internal diameter of the packer body passage 10 and are then adapted to fit under the lower body shoulder 11 and be held in engagement therewith to prevent upward movement of the outer body member 22 in the well packer A. 7

Initially, the outer body member 22 is held in a fixed position on the inner body member 1 4, and with the latch feet 38 disposed in the lower inner body groove 41, by a releasable device in the form of a frangible or shear ring 47 mounted in a groove '48 in the inner body member and held within an opposed groove 49 formed between the lower endof the intermediate outer body section 28 and the lower body section 31. With the parts in this initial position, the tubing string C is lowered through the fluid in the well casing toward the well packer A, which has previously been anchored in packed-01f condition in the well casing. The entire assembly can pass into the well packer body 13 (FIG. 2), the latch feet 38 being disposed in the inner body groove 41, until the entire outer body member 22 is extending within the well packerwith the latch feet 38 disposed below the lower packer body shoulder .11. Such position of the latch feet is insured and is definitely determined by virtue of the engagement of the outer body member head 24 with the upper packer body shoulder v12, which will preclude further downward movement of the outer body member 22 within the well packer A. During entry of the assembly 'in the well packer, the

seal ring members

30, 33 are forced into the packer body passage 10 and will make a fluid tight seal with the inner wall of the packer body 13, preventing leakage of fluid between the outer body member 22 and the packer body 13 in both longitudinal directions.

Suitable downweight is now imposed on the tubing string C. Since the outer body member 22 cannot move downwardly, the shear ring 47 is disrupted (for example, a force of approximately 3,000 pounds may be required to disrupt the shear ring), which then permits the inner body member. 14 to be lowered within the outer body member 122, the latch feet 38 being cammed outwardly by the tapered side 4210f the body groove and disposed outwardly under the lower latch shoulder 11 on the packer body 13;. The tubing string C and the inner body member 14 attached thereto may then be lowered, the per-iphery 27 of the body then being disposed behind the latchteet 38 to prevent their retraction tfrom latching engagemen-t under the lower packer body shoulder 11 (FIG.

3). The tubing string C and inner body member 14 forming a part thereof can now be lowered to the required extent, limited by engagement of the upper tubing sub or head 15 with the upper end of the packer body v13. I! desired, weight can be imposed downwardly on the tubing string C on the packer A, or the tubing C can be held in a freely suspended condition with the top sub 15 disposed to any desired distance above the top of the packer, so long as the groove '41 at the bottom of the inner body member 14 is below the latched feet or. fingers 38 of the latch device.

The inner body member '14 with its smooth or slick periphery 27 may be of any desired length between its groove 41 and its top sub 1*5,'which is preferably considerably greater than the length of the outer body member 22 and its latching or locking portion. The inner seal 26 prevents leakage of fluid in both longitudinal directions between the inner body member 14 and the outer body member 22, and such seal is maintained regardless of the longitudinal position of theinner body member within the outer body member. In the event that the tubing were to shrink or elongate, due to a substantial thermal change, the inner seal 26 would still be maintained against the smooth periphery 27 of theinner body member 1 4. The shrinkage can be of considerable extent and the apparatus would still remain assembled with respect to the well packer A, so long as the lower groove 41 does not become disposed opposite the latch feet or fingers 38. Elongation of the tubing C can occur as the result of temperature change, the seal relationship being undisturbed and maintained to the extent at which the top sub .15 may engage the upper end of the packer body 13. Even where such engagement does occur, the seal relationship is still retained, since further elongation results in the imposition of additional downweight on the well packer A, which is anchored in the well casing B.

In the event that substantial hydraulic pressure exists below the Well packer, it acts in an upward direction over the outer body member 22 and tends to shift it upwardly of the packer body 13. This action, however, cannot occur since the latch feet 38 are maintained under the packer body shoulder 11. Similarly, if hydraulic pressure above the apparatus tends to shift the outer body member 22 downwardly, such action is resisted and prevented by engagement of the upper head 24 with the up per shoulder 12 of the pack-er body '13. Thus, the outer body member 22 is locked within and to the well packer A against removal from its passage 10.

In the event that hydraulic pressure is present below the apparatus, it tends to elevate the inner body member 14 with rsepect to the outer body member 22. The tubing C can move to a substantial extent under the influence of the elevating force of the hydraulic pressure, the inner seal 26 still maintaining its leakproof engagement against the periphery 27 of the inner body member. The force 7 available for lifting action on the inner tubing member 14 and on the tubing string C connected thereto'is re duced substantially compared to the prior device. Ordinarily, the end area over which such hydraulic lifting force can act is the area between the inside diameter of the inner body member 14 and the inside diameter of the well packer body 13. In the present case, the end area is much less than the area just referred to since the pressure can act only over an area of the inner body member 14 which extends between its inner diameter and its outer diameter 27 engaged by the upper inner seal 26. It is evident from a comparison between the two areas that the last-mentioned area is considerably less than the firstm entioned area. In fact, in a typical device, it is about one-half that area.

When it is desired to release theseal assembly 21 and remove it from the Well packer, it is only necessary to elevate the tubing string C, which will raise the inner gages the beveled lower ends 45 of the latch feet to hold them in the groove 4-1, causing continued upward movement of the tubing string C and inner body member 14 to move the outer body member 22 upwardly with it, the assembly 21 moving up through the packer body 13 and to a position above the upper end of the latter, whereupon the entire apparatus can be removed from the well bore, if desired.

It is, accordingly, evident that the seal assembly 21 is placed in proper sealing relation to the well packer, or other corresponding barrier device in the well casing, without rotation of any parts being required. This is also true of the removal of the apparatus from the well packer, which occurs, as described above, merely by elevating the tubing string C in the well bore, and without rotating it.

It is to be noted that the

latching mechanism

37, 38 is located below the

seals

30, 33, which precludes the latches from becoming fouled by sand or mud weighting material that might settle out of the fluid on top of the packer. The inner body member 14 is always free to move upwardly within the outer body member 22 until its groove 4 1 is opposite the latch feet 38, whereupon the latter move inwardly from engagement with the lower packer shoulder 11.

I claim:

1. In combination: a well packer adapted to be set in packed-elf condition in a well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; seal means between said outer member and well packer to prevent leakage of fluid therebetween; and a seal on said outer member slidably sealing with the exterior of said inner member to prevent leakage of fluid therebetween while allowing longitudinal movement of said inner member in said outer member.

2. In combination: a well packer adapted to be set in packedofl condition in a well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; seal means between said outer member and well packer to prevent leakage of fluid therebetween; a seal on said outer member slidably sealing with the exterior of said inner member to prevent leakage of fluid therebetween while allowing longitudinal movement of said inner member in said outer member; and means for securing said outer member to said well packer in its sealed relation thereto.

3. In combination: a well packer adapted to be set in packed-off condition in a well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; seal means between said outer member and well packer to prevent leakage of fluid therebetween; a seal on said outer member slidably sealing with the exterior of said inner member to prevent leakage of fluid therebetween while allowing longitudinal movement of said inner member in said outer member; and coengaging means on said inner and outer members enabling said inner member to move said outer member in said passage.

4. In combination: a well packer adapted to be set in packed-off condition in a well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; seal means between said outer member and well packer to prevent leakage of fluid therebetween; a seal on said outer member slidably sealing with the exterior of said inner member to prevent leakage of fluid therebetween while allowing longitudinal movement of said inner member in said outer member; coengaging means on said inner and outer members enabling said inner member to move said outer member in said passage; and means for securing said outer member to said well packer in its sealed relation thereto.

5. In combination: a barrier adapted to be disposed in a Well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; seal means between said outer member and barrier to prevent leakage of fluid therebetween; and a seal on said outer member slidably sealing with the "exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member.

6. In combination: a barrier adapted to be disposed in a well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; a seal on said outer member disposed in said passage and sealing against said barrier to prevent fluid leakage between said outer member and barrier; and a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member.

7. In combination: a barrier adapted to be disposed in a well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; a seal on said outer member disposed in said passage and sealing against said barrier to prevent fluid leakage between said outer member and barrier; a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member; and means on said outer member releasably engaging said barrier to secure said outer member to said barrier.

8. In combination: a barrier adapted to be disposed in a well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; a seal on said outer member disposed in said passage and sealing against said barrier to prevent fluid leakage between said outer member and barrier; a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member; means on said outer member releasably engaging said barrier to secure said outer member to said barrier; and means on said inner member engaging said securing means to prevent release of said securing means from said barrier,

9. In combination: a barrier adapted to be disposed in a well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; a seal on said outer member disposed in said passage and sealing against said barrier to prevent fluid leakage between said outer member and barrier; a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member; means on said outer member engageable with said barrier to limit downward movement of said outer member in said barrier; and releasable means on said outer member releasably engaging said barrier to prevent upward movement of said outer member from said barrier.

10. In combination: a barrier adapted to be disposed in a well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; a seal on said outer member disposed in said passage and sealing against said barrier to prevent fluid leakage between said outer member and barrier; a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member; means on said outer member engageable with said barrier to limit downward movement of said outer member in said barrier; releasable means on said outer member releasably engaging said barrier to prevent upward movement or" said outer member from said barrier; and means on said inner member engaging said releasable means to prevent its release from said barrier.

11. In combination: a barrier adapted to be disposed in a well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; a seal on said outer member disposed in said passage and sealing against said barrier to prevent fluid leakage between said outer member and barrier; a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member; means on said outer member engageable with said barrier to limit downward movement of said outer member in said barrier; laterally movable latch means on said outer member releasably coupled to said barrier to prevent upward movement of said outer member irom said barrier; said inner member having a groove adapted to receive said latch means to permit inward movement of said latch means and its uncoupling from said barrier; said inner member having means above said groove engageable with said latch means to hold said latch means laterally outwardly coupled to said barrier.

12. In combination: a barrier adapted to be disposed in a Well bore and having a passage therethrough; an inner tubular member movable into said passage; an outer tubular member movable relatively longitudinally on said inner member and movable into said passage; a seal on said 7 outer member disposed in said passage and sealing against said barrier to prevent fluid leakage between said outer member and barrier; a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member; means on said outer member engageable with said barrier to limit downward movement of said outer member in said barrier; laterally movable latch means on said outer member releasably coupled to said barrier to prevent up ward movement of said outer member from said barrier; said inner member having a groove adapted to receive said latch means to permit inward movement of said latch means and its uncoupling from said barrier; said inner member having means above said groove engageable with said latch means to hold said latch means laterally outwardly coupled to said barrier; and means releasably securing said inner and outer members together with said latch means in said groove.

13. In combination: a barrier adapted to be disposed in a well bore and having a passage therethrough', said barrier having an upper shoulder and a lower shoulder; an inner tubular member movable into said passage; anouter tubular member movable relatively longitudinally on said inner member and movable 'into said passage;a seal on said outer member disposed'in said passage and sealing against said barrier to prevent fluid leakage between said outer member and barrier; a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said.

inner member in said outer member; means on said outer member engageable with said upper shoulder to limit downward movement of said outer member in said barrier; laterally movable latch means on said outer member engageable with said lower shoulder to prevent upward movement of said outer member from said barrier; said inner member having a groove adapted to receive said latch means to permit inward movement of said latch means from engagement with said lower shoulder; said inner member having means above said groove engageable with said latch means to hold said latch means laterally outwardly below said lower shoulder for engagement therewith.

14. In a seal assembly adapted to be placed in a passage in a barrier disposed in a well bore and in sealing relation therewith: an inner tubular member movable into the passage; an outer tubular member movable relatively longitudinally on said inner member and movable into the passage; a seal on said outer member for sealing against the barrier; and a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member.

15. In a seal assembly, adapted to be placed in a passage in a barrier disposed in a well bore and in sealing relation therewith: an inner tubular member movable into the passage; an outer tubular member movable relatively longitudinally on said inner member and movable into the passage; a seal on said outer member for sealing against the barrier; a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member; means on said outer member engageable with the barrier to limit downward movement of the outer member in the barrier; and releasable means on said outer member releasably engageable with the barrier to I passage in a barrier disposed in a well bore and in sealprevent upward movement of the outer member from the barrier;

16. In a seal assembly adapted to be placed in a passage in a barrier disposed in a well bore and in seal ing relation therewith: an inner tubular member movable into the passage; an outer tubular member movable relatively longitudinally on said inner member and movable into the passage; a seal on said outer member for sealing against the barrier; a seal on said outer member slidably sealing with the exterior of said inner member to prevent fluid leakage therebetween while allowing 3 longitudinal movement of said inner member in said outer member; means on said outer member engageable with the barrier to limit downward movement of the outer member in the barrier; laterally movable latch means on said outer member adapted to be releasably coupled to the barrier to prevent upward movement of the outer member from the barrier; said inner member having a groove adapted to receive said latch means to prevent its inward lateral movement and uncoupling from the barrier; said inner member having means above said groove engeable with said latch means to hold said latch means laterally outwardly and coupled to the barrier.

17. In a seal assembly adapted to be placed in a ing relation therewith: an inner tubular member movable into the passage; an outer tubular member movable relatively longitudinally on said inner member and movable into the passage; a seal on said outer member for sealing against the barrier; a seal on said outer member slidably sealing with the exterior of said inner member vto prevent fluid leakage therebetween while allowing longitudinal movement of said inner member in said outer member; means on said outer member engageable with the barrier to limit downward movement of the outer member in the barrier; laterally movable atch means on said outer member adapted to be releasably coupled to the barrier to prevent upward movement of the outer member from the barrier; said inner member having a groove adapted to receive said latch means to prevent its inward lateral movement and un- 9 10 coupling from the barrier; said inner member having References Cited in the file of this patent means above said groove engageable with said latch means to hold said latch means laterally outwardly and UNITED STATES PATENTS coupled to the barrier; and means releasably securing said U inner and outer members together with said latch means 5 fi g g in said groove. g or

Claims

1. IN COMBINATION: A WELL PACKER ADAPTED TO BE SET IN PACKED-OFF CONDITION IN A WELL BORE AND HAVING A PASSAGE THERETHROUGH; AN INNER TUBULAR MEMBER MOVABLE INTO SAID PASSAGE; AN OUTER TUBULAR MEMBER MOVABLE RELATIVELY LONGITUDINALLY ON SAID INNER MEMBER AND MOVABLE INTO SAID PASSAGE; SEAL MEANS BETWEEN SAID OUTER MEMBER AND WELL PACKER TO PREVENT LEAKAGE OF FLUID THEREBETWEEN; AND A SEAL ON SAID OUTER MEMBER SLIDABLY SEALING WITH THE EXTERIOR OF SAID INNER MEMBER TO PREVENT LEAKAGE OF FLUID THEREBETWEEN WHILE ALLOWING LONGITUDINAL MOVEMENT OF SAID INNER MEMBER IN SAID OUTER MEMBER.