US2302856A - Releasable joint for rotary well strings - Google Patents

Description

Nov. 24, 1942.

w. M. HAMQN RELEASABLE JOINT FOR ROTARY WELL STRINGS Filed Aug. l0, 1940 Patented Nov. 24, 1942 UNlTED "STATES" PATENTv l OFFICE RELEASABLE JOINT'FOR IROTA-RY WELL STRINGS -Y Weslie M. Hamon, .East Los Angeles, Calif.

Application August 10, 1940, Serial No. 352,106

I(Cl.V Z55-,28)

9 Claims.

rI'his invention is a releasable joint for a rotary well string.

It is an object of the invention to provide a joint which is adapted for release by relative rotation of proximate lengths of the well string and which includes driving means normally engaged for positively xing the proximate lengths of the well string against relative rotation, the driving means being adapted for disengagement at the will of the operator to permit relative rotation of the proximate lengths of the well string for releasing the joint.

It is a further object of the invention to provide a threaded jointwhich is normally locked against unscrewing by the engaged driving means, and which upon disengagement of the driving means (to permit relative rotation of the proximate lengths of the well string) is adapted for 'unscrewing by rotating the'well string in the vsame direction as employed during drilling or other operative'rotation of the string.

It is a still further object of the invention to provide a driving means which when engaged provides a sturdy and positive drive between proximate lengths of the well string, and which when disengaged maintains a driving connection between one of the proximate lengths of the well stringand one oi the cooperating elements of the threaded joint, for unscrewing the ljoint by rela,-

tive rotation of the proximate lengths o'f the well string.

Further objects of the invention will be readily understood from the following description of the accompanying drawing, in which:

li'ig. l is an axial section through the releasab-le joint, showing `it in operative position between proximate lengths of a well string.

Fig. 2 is a similar view, showing the parts vin position for relatively rotating the proximate lengths of the well string for releasing the joint.

Figs. 3, 4 and 5 are transverse sections on the lines i-li and 5--5 respectively of Fig. v1.

Fig. 6 is a fragmentary view similar to Fig. 1, showing a modified construction.

The invention is applicable to any tool string adapted for rotation in a well and wherein it is desired to release and withdraw the upper portion of the string in the event of its lower lportion becoming stuck in the well bore.` The invention is particularly applicable and is therefore described with reference to a rotary drill string and its associated drill. The improved jointV is preferably incorporated in the drill string immediately above the drill, whereby the proximate lengths of the well string which are connected by the joint respectively comprise the drill and its operating string which yextends from the drill to the earths surface.

Duri-ng drilling operation, with the joint connecting the drill and the drill string, driving means incorporated in the joint provides a positive drive for rotating the drill with the drill string. The driving means thus relieves the joint of torsional strain and `locks the joint against release. In vthe event of the drill becoming stuck the driving means is disengaged, thereby releasing the drill Ystring for rotation relative Ytothe stuck drill; and when the driving means is thus disengaged it maintains a driving connection between the drill 'string and one of the cooperating elements 4of the joint, whereby rotation of the drill string relative tothe stuck drill disconnects the joint for release and withdrawal of the drill string.

The connection between the cooperating elements of the joint is preferably a threaded connection, yand is threaded for unscrewing by rotating the drill string relative to the stuck drill in the `same direction in which the drill string is rotated during drilling operation. In other words, if the connections between the lengths of the drill string (other than at the improved joint) have usual right-hand threads for normal right-hand drilling, the improved joint has left-hand threads. While drilling, this lefthand joint is vlocked against unscrewing 4by the driving 'means which yprevents relative rotation at this threaded joint; and in the event of the drill becoming stuck and after disengaging the driving means, the 'drill string 'is again rotated in normal right-hand direction, thereby unscrewing 'the left-hand joint ,by the driving connection which is vmaintained between the drill string and one of the cooperating elements of this left-hand joint.

As an instance of this arrangement, the improved joint comprises `joint-sections lhaving a threaded connection 3. The lower portion of the well string, which inthe villustrated embodiment of the invention is lthe drill 5, is suspended from the joint-section 2 by a coupling 4. A mandrel B is adapted for ltelescopic reception in the connected Vjoint-section I-2, vand is suspended by a coupling 8 from the upper portion of the well string, which in the illustrated embodiment of the invention is the drill string 1 extending to the earths surface. The couplings 4 and 8, and the couplings '(not shown) between lengths of the drill string, preferably have usual right-hand 'threads adapting the drill string for normal right-hand drilling rotation; and the threaded-connection 3 is preferably oppositely threaded, i. e. it has a left-hand thread.

As shown at Fig. 1, when the drill string is ready for drilling, the mandrel 6 is telescoped in the connected joint-sections I-2 so that the coupling 8 abuts the joint-section I and the lower end of the mandrel seats in a recess 9 in the coupling 4. The mandrel 6 is releasably held in this normal operative position.

For this purpose, and as shown in Fig. 1, locking dogs I are pivotally mounted in the bore of the joint-section I; and an annulus I I is yieldably longitudinally projected by a spring I2, so as to engage the dogs and swing the same into locking engagement with a recess I3 in the mandrel Ii when the mandrel is telescopically contracted relative to the connected joint I-v-2.

A modication of this releasable holding means is shown at Fig. 6. In this instance, a collar Ia is adapted for sliding reception on the mandrel En and in the bore of the joint-section I, and is yieldably tensioned by a spring I2a so as to seat on a shoulder I3a of the mandrel 6a when the mandrel is telescopcally contracted relative to the connected joint I-2.

The tension or" the spring I2 or I2a is adjusted by a follower I4 or I4a so that as long as the drill is not stuck in the well bore the drill string may be withdrawn without yielding of the spring, thereby maintaining engagement at Ill- I3 or at Illa-i3d, for preventing telescopic expansion of the mandrel relative to the connected joint I-2. The drill stringand its suspended drill are thus adapted for withdrawal as a unit. In the event of the drill becoming stuck in the well bore, strain exert-ed on the drill string causes the spring I2 to yield for longitudinal retraction of the annulus II so that the dogs IEI may swing clear of the recess I3, or causes the spring I2a to yield for upward displacement of the collar Ia and the shoulder I3a relative to the joint-section I. The mandrel 6 or 6a is thus released for telescopic expansion relative to the connected joint I2, as shown at Fig. 2.

When the mandrel 6 or 6a is telescopically contracted in the connected joint I-2, it provides a driving means xing the joint-sections against relative rotation and against rotation relative to the mandrel, so that rotation of the mandrel by the drill string rotates the connected joint I-2 and the suspended drill 5. As an instance, the bores of the joint-sections I-2 are splined adjacent their threaded connection 3 as shown at I6-I 'I, with the splines IB-I'I adapted for longitudinal alinement when the joint-sections I-2 are screwed together; and the mandrel 6 or Ea has cooperating splines I8, operatively engaging the splines II-I'I when the mandrel is telescopically contracted as shown at Fig. l.

When the mandrel 6 or Sais telescopically expanded relative to the connected joint I-2, its longitudinal displacement is arrested when it reaches the position shown at Fig. 2, with the splines IS clear of the splines I'I of the joint-section 2 but still operatively engaged with the splines IB of the joint-section I. The drill string and the suspended mandrel are thus free for rotation relative to the joint-section 2 (which is connected to the drill which has become stuck) while maintaining a rotary driving connection between the mandrel and the joint-section I. By rotating the drill string, the joint-sections I-2 are thus adapted for relative rotation for unscrewing their threaded connection 3.

As an instance for means for thus arresting telescopic expansion of the mandrel, abutment means 23 may project into the bore of the jointsection 2 below its splines I'I, and a length of the mandrel 6 or 6a is of reduced diameter below its splines I8 as shown at 6b, with a collar 2I at the lower end of this reduced mandrel length. The collar 2| is adapted for rotation and longitudinal play in the bore of the joint-section 2 below its abutment means 23, and is adapted to longitudinally engage the abutment means for limiting telescopic expansion of the mandrel relative to the joint-section 2.

To permit assembly, the collar 2l is cut away at diametrically opposite at surfaces 24 and the abutment means 23 are shoulders which project into the bore of the joint-section 2 and dei-lne diametrically opposite iiat surfaces 25. The flat surfaces 24-25 are circumferentially positioned relative to the splines I8-I`I, as shown at Figs. 4 and 5. The drill 5 having been suspended from the joint-section 2 by the coupling II, the mandrel 6 or 6a is inserted in the joint-section 2 with the mandrel turned so that the fiat surfaces 24-25 are longitudinally alined. The collar 2I may thus be longitudinally projected through the bore which isl defined by the abutment means 23, so as to longitudinally clear the abutment means when insertion of the mandrel is arrested by the splines I8 longitudinally abutting the upper end of the splines I'I.

The joint-section I is then lowered over the upper end of the mandrel so as to operatively engage the splines IS-IS while the joint-section I is still disconnected from the joint-section 2; the dogs III being retracted and sliding on the mandrel 6 below its recess I3 when employing that form of the invention which is shown at Figs. 1 and 2, and the collar Ia sliding on the mandrel 6a until seated on its shoulder I3a when employing that modiiication of the invention which is shown at Fig. 6. The mandrel is then suspended from the drill string I by the coupling 8. The drill string and the mandrel,

,n together with the joint-section I, are then rotated relative to the joint-section 2 and the suspended drill, as permitted by the splines I8 being still longitudinally clear of operative engagement with the splines I1 and the collar 2| freely rotating in they bore of the joint-section 2 below its abutment means 23.

By this relative rotation the joint-sections I-2 are screwed together at their threaded connection 3, with the joint-section I longitudinally displaced relative to the mandrel while this threaded connection is being made, as permitted by the retracted dogs I0 sliding along the mandrel 6 below its recess I3, or as permitted by yielding of the spring I2a for upward displacement the collar Illa in the bore of the joint-section I. When the threaded connection between the joint-sections I-2 has been made, the jointsections will have been relatively turned so that the splines I6-II are longitudinally alined; and the mandrel will thus have been turned relative to the joint-section 2 so that it may be projected an additional distance into this joint-section for operatively engaging the splines I'I-I8 and at the same time maintaining the splined engagement at IE5-I8. The position to which the mandrel will have been turned, also longitudinally alines the cellar 2I with the abutment means. 23, in spaced relation below said abutment means. The releasable joint is thus in operative position with its mandrel telescopically contracted relative to the connected joint as shown at Fig. 1, with the dogs I seating in the recess I3, or the collar Illa longitudinally projected by the spring |2a'and seating on the shoulder I 3a.

The drill being thus operatively suspended from the drill string, the latter may be lowered into a well bore for usual drilling. If the. drill becomes. stuck so that it is desired to release the connected joint |-2, upward strain is exerted on the drill string, thereby causing. the spring I2 or I2a to yield. The mandrel is thus telescopically expanded relative to the connected joint I-Z, as permitted by retraction of the dogs I0 and their disengagement from the recess I3, or as permitted by upward ydisplacement of the collar lila, in Vthe bore of the joint-section I. This telescopic expansion of the mandrel is limited by the collar 2| longitudinally engaging the abutment means 23 as shown at Fig. 2. The splines I8 being then longitudinally clear of the splines but still operatively engaged with the splines I6, the threaded connection `3 may be unscrewed by relatively rotating the joint-section |-2 by rotating the drill string and its suspended mandrel. Y When the joint-sections I-Z have been thus disengaged, the mandrel is turned to position longitudinally alining the .flat surfaces 26| with the flat surfaces 25, so that the collar 2| may be withdrawn through the bore which is defined by the abutment means 23. The drill string and the mandrel, together with the joint-section I, may thus be withdrawn as a unit from the well bore, the joint-section I being supported, on the mandrelv 6 or 5a by a shoulder I9 at the upper end of the splines I6 resting upon the upper end of the splines I8. After withdrawal of the drill string, any desired shing or washing procedure may be followed for recovering the stuck drill and the joint-section 2 which have been left in the well.

When the joint is in operative position as shown at Fig. 1, driving meansin addition to the splined engagement ||-|8 is preferably provided between the mandrel and the joint-section 2. As an instance, a mandrel length 6c may be provided between the splines I8 and the reduced mandrel length 6b; and this mandrel length 6c is cut away at diametrically oppositelat surfaces 30 which are adapted for reception between the flat` surfaces of the abutment means 23. The flat surfaces 2li-3&1 are relatively circumferentially offset, preferably 90 as shown at Figs. 4 and 5.

When assembling, the mandrel is initially inserted in the joint-section 2 and the joint-section I is mounted on the mandrel as previously described, i. e. the collar 2| is projected through and longitudinally beyond the bore which is defined by the abutment means 23, with the splines I8 longitudinally abutting theupper end of the splines I'l and the threaded connection 3 disengaged. The mandrel length 6c is then in the bore which is defined by the splines I1, free for rotation in said bore. The drill string and the mandrel, together with the joint-section I, `are then rotated relative to the joint-section 2 as previously described, for screwing the joint-sections together at their threaded connection 3.

As above noted, when this threaded connection has been made the joint-section I and the mandrel will have been turned relative to the jointsection 2 so that the splines .I6- Il are longitudinally alined and the collar 2| is longitudinally.

alined with the abutment means 23. The flat surfaces of the mandrel length 6c will also have beenturned 'so as to longitudinally aline with the Jflat surfaces 25.1 The mandrel is thus adapted for projecting its additional distance into the joint-section 2 as shown at Fig. 1, for operativelyengaging. the splines ||-|8 and'projecting the mandrel length 6c into the bore which is definedv by the abutment means 23, with the fiat surfaces 30 between and operatively engaging the'at surfaces 25 so as to provide additional driving eonnection between the mandrel and the joint-section 2.

When the mandrel is teleseopically expanded relative to the connected joint |-2, as limited by the collar 2| engaging the abutment means 23, the splines I8 are shifted longitudinally clear of the splines ||`as previously described, and the mandrely length 6c is withdrawn from the bore which is defined by the abutment means 23, for free rotation in the bore which is defined by the splines I l. The parts being then in the position shown atk Fig. 2, the mandrel and the jointsection I may be rotated relative to the jointsection 2 as previously described, for unscrewing the joint-sections at their threaded connection 3.

As an instance of additional driving connection which may be provided between the mandrel and the joint-section 2, the mandrel may be splined below its collar 2| as shown at 35, with these splines adapted for longitudinal projection through the bore which is dened by the abutment means 23 and adapted to operatively engage cooperating splines which are provided in the bore or" the joint-section 2 in spaced rrelation below the abutment means 23. The splines 35--36 are circumferentially positioned relative to the flat surfaces 2li-25, as shown at Figs. 4 and 5.

When assembling, initial insertion of the mandrel into the joint-section 2 until arrested by the splines i8 engaging the upper end of the splines' projects the collar A2| and the splines 35 through the bore which vis defined by the abutment' means 23,*and into the bore of the jointsection .21 below the abutment means, with the splines 35 longitudinally clear of the splines 36. Thecollar 2| and the splines 35 are thus free for 'rotationin the bore of the joint-section 2, so that the mandrel and the joint-section may be rotated-relative to the joint-section 2 as previously described, for screwing the joint-sections together at their threaded connection 3.

As above noted, when this threaded connectio11=has been made the mandrel and the joint- -section `will haveV been turned relative to the joint-section 2 for projecting the mandrel its additionalr distance.` into the bore of the jointsection-2 so as to operatively engage the splines |'|-|8 andthe flat surfaces 30-25. The splines 35 will also have been turned to position whereby this additional projection of the mandrel into the joint-section 2 operatively engages kthe splines 35-36 as :shown at Fig. 1, thereby providing additional driving connection between the mandrel and the joint-section 2.

When the .mandrel is telescopically expanded relative to the connected joint |-2, the splines 28 are-:shifted longitudinally clear of the splines and the mandrel length 6c is withdrawn from the bore which is defined by the abutment means 23, as. previously described; and the splines 35 are shifted longitudinally clear of the splines 36 for free rotation in the bore of the joint-section 2 below the abutment means 23. The parts beingl thus inv the 'position shown at Fig. 2, the

mandrel and the joint-section I may be rotated relative to the joint-section 2 as previously described, for unscrewing the joint-sections at their threaded connection 3.

When employing -the holding means Ill-I3 (Figs. 1 and 2), the cooperating splines which constitute the driving means are' preferably nontapering splines, with telescopic contraction of the mandrel 6 into the connected joint I-2 limited by the dogs I seating in the recess I3. When employing the holding means IIJa-I3a (Fig. 6), the splines I8 preferably have tapering sides as indicated at I8a, and the sides of the auxiliary splines 35 (which are not shown at Fig. 6) preferably have similar tapering sides. The cooperating splines in the joint-section 2 have corresponding tapering sides; and the parts are relatively arranged so that telescopic contraction of the mandrel Scinto the connected joint I-2 is limited by wedging engagement of the cooperating tapering splines, thereby insuring snug operative engagement so as to eliminate back lash at the driving connection Which is formed by the cooperating splines.

When the joint I-2 is operatively connected as shown at Fig. l, it preferably provides for circulation via the bore of the drill string. For this purpose, the coupling 8 is bored as shown at 40 and communicates with a bore 4I of the mandrel 6 or 6a; and the bore 4I communicates with a bore 42 of the coupling 4. Telescopic reception of the lower end of the mandrel in the coupling 4 is preferably packed off; and for this purpose packing 43 surrounds the lower end of the mandrel in the bore of the joint-section 2, with the packing longitudinally engaged by the upper end of the coupling 4 fo11 longitudinally compressing the packing against an abutment annulus 44.

I claim:

l. In a releasable joint for a well string, jointsections adapted for connection and release by relative rotation, a mandrel adapted for telescopic expansion or construction relative to the connected joint-sections, one of proximate lengths of the well string being connected to one of the joint-sections, the other of proximate lengths of the well string being connected to the mandrel, spring-urged means normally retaining the mandrel telescopically contracted relative to the connected joint-sections to yield for telescopic expansion of the mandrel responsive to longitudinal strain on said other of proximate lengths of the well string, and a rotary driving connection between the mandrel and the jointsections, said driving connection fixing the jointsections against rotation relative to the mandrel when the latter is telescopically contracted relative to the connected joint-sections,Y and said driving connection releasing the mandrel for rotation relative to said one of the joint-sections and maintaining the other joint-Section xed against rotation relative to the mandrel when the latter is telescopically expanded relative to the connected joint-sections.

2. In a releasable joint for a well string, jointsections adapted for connection and release by relative rotation, a mandrel adapted for telescopic expansion or contraction relative to the connected joint-sections, one of proximate lengths of the well string being connected to one of the joint-sections, the other of proximate lengths of the well string being connected to the mandrel, means for releasably retaining the mandrel telescopically contracted relative to the con- Anected joint-sections, a spline on the mandrel, and splines on the respective joint-sections longitudinally alined when the joint-sections are connected, the respective ends of the spline on the mandrel operatively engaging the longitudinally alined splines of the respective joint-sections when the mandrel is telescopically contracted relative to the connected joint-sections, and the spline on the mandrel being shifted longitudinally clear of the spline of said one of the joint-sections and remaining operatively engaged with the spline of the other joint-section when the mandrel is telescopically expanded relative to the connected joint-sections.

3. In a releasable joint for a well string, jointsections having a threaded connection, a mandrel adapted for telescopic expansion or contraction relative to the connected joint-sections, one of proximate lengths of the well string having a threaded connection with one of the joint-sections, the other of proximate lengths of the well string having a threaded connection with the mandrel, the threaded connection between the joint-sections being threaded opposite to the other threaded connections of the well string, and a rotary driving connection between the mandrel and the joint-sections, said driving connection xing the joint-sections against rotation relative to the mandrel when the latter is telescopically contracted relative to the connected joint-sections, and said driving connection releasing the mandrel for rotation relative to said one of the joint-sections and maintaining the other joint-section xed against rotation relative to the mandrel when the latter is telescopically expanded relative to the connected joint-sections.

4. In a releasable joint for a well string, jointsections adapted for connection and release by relative rotation, a mandrel adapted for telescopic expansion or contraction relative to the connected joint-sections, one of proximate lengths oi the well string being connected to one of the joint-sections, the other of proximate lengths of the well string being connected to the mandrel, means for releasably retaining the mandrel telescopically contracted relative to the connected joint-sections, abutment means between the mandrel and said one of the jointsections for limiting telescopic expansion of the mandrel relative to the connected joint-sections, and a rotary driving connection between the mandrel and the joint-sections, said driving connection fixing the joint-sections against rotation relative to the mandrel when the latter is telescopically contracted relative to the connected joint-sections, and said driving connection releasing the mandrel for rotation relative to said one of the joint-sections and maintaining the other contracted relative to the connected joint-sections, a rotary driving connection between the mandrel and the joint-sections, said driving connection fixing the joint-sections against rotation relative to the mandrel when the latter is telescopically contracted relative to the connected joint-sections, and said driving connection releasing the mandrel for rotation relative to said one of the joint-sections and maintaining the other joint-section fixed against rotation relative to the mandrel when the latter is telescopically expanded relative to the connected joint-sections, abutment means in the bore of said one of the joint-sections, and a collar on the mandrel, the abutment means defining a non-circular bore and the collar being correspondingly non-circular for projection of the collar through the bore of and beyond the abutment means when the mandrel is telescopically contracted and for then longitudinally alining the collar with the abutment means byturning the mandrel to a second position, so that the collar is adapted for longitudinal engagement with the abutment means for limiting telescopic expansion of the mandrel relative to the connected joint-sections.

6. In a releasable joint for a well string, jointsections adapted for connection and release by relative rotation, a mandrel adapted for telescopic expansion or contraction relative to the connected joint-sections, one of proximate lengths of the well string being connected to one of the joint-sections, the other of proximate lengths of the well string being connected to the mandrel, means for releasably retaining the mandrel telescopically contracted relative to the connected joint-sections, a rotary driving connection between the mandrel and the joint-sections, said driving connection fixing the jointsections against rotation relative to the mandrel when the latter is telescopically contracted relative to the connected joint-sections, and said driving connection releasing the mandrel for rotation relative to said one of the joint-sections and maintaining the other joint-section fixed against, rotation relative to the mandrel when the latter is telescopically expanded relative to the connected joint-sections, and a second rotary driving connection between the mandrel and said one of the joint-sections, said second driving connection xing said one of the joint-sections against rotation relative to the mandrel when the latter is telescopically contracted relative to the connected joint-sections, and releasing the mandrel for rotation relative to said one s of the joint-sections when the mandrel is telescopically expanded relative to the connected joint-sections.

7. In a releasable joint for a well string, jointsections -adapted for connection and release by relative rotation, a mandrel adapted for telescopic expansion or contraction relative to the connected joint-sections, one of proximate lengths of the well string being connected to one of the joint-sections, the other of proxivmate lengths of the well string being connected to the mandrel, means for releasably retaining the mandrel telescopically contracted relative to the connected joint-sections, abutment means between the mandrel and said one of the jointsections for limiting telescopic expansion of the mandrel relative to the connected joint-sections, a rotary driving connection between the mandrel and the joint-sections, said driving connection xing the joint-sections against rotation relative to the mandrel when the latter is telescopically contracted relative to the connected joint-sections, and said driving connection releasing the mandrel for rotation relative to said one of the joint-sections and maintaining the other joint-section xed against rotation relative to the mandrel when the latter is telescopically expanded relative to the connected joint-sections, and a second rotary driving connection between the mandrel and said one of the joint-sections, said second driving connection fixing said one of the joint-sections against rotation relative to the mandrel when the latter is telescopically contracted relative to the connected joint-sections, and releasing the mandrel for rotation relative to said one of the jointsections when the mandrel is telescopically expanded relative to the connected joint-sections.

8. In a releasable joint for a well string, jointsections adapted for connection and release by relative rotation, a mandrel adapted for tele-` scopic expansion or contraction relative to the connected joint-sections, one of proximate lengths of the well string being connected to one of the joint-sections, the other of proximate lengths of the well string being connected t0 the mandrel, a spring-urged dog on the other of the joint-sections, said dog normally engaging the mandrel for retaining the mandrel telesccpically contracted Iand adapted for yielding ci its spring for releasing the dog responsive to longitudinal strain on said other of the proximate lengths of the well string, and a rotary driving connection between the mandrel and the joint-sections, said driving connection xing the joint-sections against rotation relative to the mandrel when the latter is telescopically contracted relative to the connected joint-sections, and said driving connection releasing the mandrel for rotation relative to said one of the joint-sections and maintaining the other jointsection fixed against rotation relative to the mandrel when the latter is telescopically expanded relative to the connected joint-sections.

9. In a releasable joint for a well string, jointsections adapted for connection and release by relative rotation, a mandrel adapted for telescopic expansion or contraction relative to the connected joint-sections, one of proximate lengths or" the well string being connected to one of the joint-sections, the other of proximate lengths of the well string being connected to the mandrel, a spring urging telescopic contraction of the mandrel and 4adapted to yield for telescopic expansion of the mandrel responsive to longitudinal strain on said other of proximate lengths of the well string, and a rotary driving connection between the mandrel and the jointsections, said driving connection providing a longitudinally wedging engagement and fixing the joint-sections against rotation relative to the mandrel when the latter is telescopically contracted relative to the connected joint-sections, and said driving connection releasing said wedging engagement and releasing the mandrel for rotation relative to said one of the jointsections and maintaining the other joint-section xed against rotation relative to the mandrel when the latter is telescopically expanded relative to the connected joint-sections.

kWESLIE M. HAMON.

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