US3727967A - Universal overshot - Google Patents

Abstract

A universal overshot or fishing tool (adapted to enter a well or borehole) has a tubular body with a mouth adapted to receive a drill string or sucker rod (fish). A plurality of axially aligned bushings are received in the body and each has an inner wall tapering toward the mouth with a set of slips disposed in each of the bushings. The slips are each longitudinally slidable along and wedgingly engageable between the respective inner wall and the drill string or rod. A spring bearing on a sleeve in turn acting on the set of slips furthest from the mouth (uppermost slip) urges all of the slips axially toward the mouth. The set of slips have increasingly large diameters away from the mouth.

Description

Unite ates let 91 Anastasiu et al. 1 Apr. 17, 1973 [5 1 UNIVERSAL OVERSHOT 1,646,965 10/1927 Johnson 294/8631 x inventors: Eugeniu vasiie Anastasiu, l,529,734 3/1925 Barbour et al ..294/86.3 X

B h' t' T d h h uc fi ea or G eorg e Primary ExaminerEvon C. Blunk tescu, Nlcollae Stefan Farcas, both of i Assistant Examiner-Johnny D. Cherry Cimpma, all of Romama Att0rneyl(arl F. Ross [73] Assignee: llnstitulul De Proiectari Si Cerceiari Pentru Utilaj Peta-tiller, Bucharest, [57] ABSTRACT Romania i A universal overshot or fishing tool (adapted to enter Fllcdi J n 1971 a well or borehole) has a tubular body with a mouth [2i] Appi NO: i54i48 adapted to receive a drill stringer sucker rod (fish). A plurality of axially aligned bushings are received in the body and each has an inner wall tapering toward the [52] U.S. Cl ..294/86.3l,294/l02 mouth with a set f Slips disposed in each f the [51] lnLCl. ..E2lb 31/02 bushings. The Slips are each longitudinally slidable Fleld of Search. along and engageable between [he regpee- 294/96, 86-31; 24/263 DF; 166/98 99 tive inner wall and the drill string or rod. A spring 6 I bearing on a sleeve in turn acting on the set of slips [56] References cued furthest from the mouth (uppermost slip) urges all of UNITED STATES PATENTS the slips axially toward the mouth. The set of slips have increasingly large diameters away from the 1,532,979 4/l925 Barbour .v294/86.3l mouth. l,58l,()l() 4/1926 Murrayu. 294/863 R23,557 9/I952 Siracusa ..294/86.3 X 5 Claims, 2 Drawing Figures UNIVERSAL OVERSHOT FIELD OF THE INVENTION The present invention relates to a universal overshot having a plurality of sets of slips arranged in an outer bowl and specifically used for fishing in oil wells or the like, for catching and drawing out of wells sucker rods, drill strings, or tubes which have broken off in the hole.

BACKGROUND OF THE INVENTION Universal overshots having only one set of slips are known for use as fishing tools. Such devices have a low gripping force so that the sucker rods or tubes are often dropped as they are being pulled out of the well.

Other universal overshots with several sets of slips are known, with each set having a different inner diameter so that various diameters of tubular material or rod can be tightly grasped. However, such overshots are quite complicated and the distance between the lowest set of slips and the highest set is relatively great which, in combination with the customary downwardly increasing slip diameter, often makes it impossible to grasp a fish of short length, such as a drill string which has broken just above the tooljoint or collar.

OBJECTS OF THE INVENTION It is, therefore, an object of the present invention to provide an improved universal overshot.

Another object is the provision of an overshot which overcomes the above-given disadvantages.

SUMMARY OF THE INVENTION The above objects are attained according to the present invention by an overshot having a cylindrical tubular body receiving a series of axially aligned bushings each having an inner wall which tapers toward a mouth formed at the end of the body and adapted to receive a drill string or other fish. A set of slips is disposed in each of the bushings and is longitudinally slidable along and wedgingly engageable with its respective inner wall. The slips axially abut and are all urged toward the mouth of the tube by a spring and sleeve.

According to further features of this invention, the bushings are axially fixed in the tube or sleeve and the slips are nonrotatable about the tube axis. These sets of slips are formed with left-hand threads of sawtooth profile on their inner faces so that removal of the drill string from the fishing tool, according to the present invention, is a simple task. The sawtooth profile provides a ramp along the flanks of the threads facing downwardly to promote entry of the fish, and flanks facing upwardly which are transverse to the overshot axis.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages will become apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a longitudinal section through an overshot, according to the present invention, specially adapted for fishing sucker rods; and

FIG. 2 is a longitudinal section through an overshot according to this invention for drill pipes and tubing.

SPECIFIC DESCRIPTION As shown in FIG. 1, an overshot has an outer cylindrical body 1 formed with a conical mouth 1a at its lower end and with a collar lb at its upper end into which a sub 2 for sucker rods, tubing or drill pipes is screwed by means of right-hand threads. This sub 2 is formed at its lower end with a threaded male projection or boss 2a received in the collar lb and having a circular lower rim 2b which serves along with a shoulder 1c of the sleeve 1 to clamp a stack of bushings 3. The bushings 3 are all identical, with cylindrical outer walls and bowl-forming downwardly-tapered inner walls 3a. A set of slips 4 prevented from rotation within the sleeve 1 by a stop 5 in the form of an axially extending key is disposed in each bushing. Each set of such sector wedge-like slips 4 defines a downwardly tapering outer wall complementary and slidable along the wall 3a to reduce the inner diameter of the set. In addition, the inside of the individual sets of slips is machined on its cylindrical inner wall with left-hand threads with the inside diameters increasing away from the mouth la of the sleeve 1. When the sleeve 1 is screwed onto sub 2, the end face 2b clamps the sleeves 3 axially against one another and against the inwardly extending shoulder 1c directly or via a further ring.

A spring 7 braced against a seat 20 formed in the sub 2 pushes a sleeve 6 against the uppermost set of slips 4, thereby driving all of the slips downwardly and consequently inwardly. This sub 2 is also formed with laterally opening apertures 2d to allow mud compressed therein to escape during fishing of a drill string or the like to introduce drilling mud.

In order to fish a broken sucker rod or other type of fish, the sub 2 is screwed onto a fishing string, or even a conventional drill string, and lowered into the bore. Its outwardly and downwardly open mouth la is fitted over the broken rod end, which forces its way up through the sets of slips 4. This causes the slips to rise until they can fit around the rod; in any case, a set can rise no further than the base of the next upper bushing. Since the lower set of slips defines the smallest aperture, the broken rod will be tightly gripped as soon as it has passed partly through this set. If it is longer, it can rise all the way up through the sleeve 6 and even into contact with the sub 2 forcing dirt and mud out through the apertures 2d. It is preferable that the fish diameter correspond roughly to the inner diameter of at least one of the sets of slips since only in this manner is the best possible clamping attained. The provision of several sets here insures this while provision of the smallest diameter set at the mouth insures some holding even with partial penetration. The overshot can then be rotated counterclockwise, as seen from the top, to complete the attachment. Once the fish is fully engaged, the whole device is lifted with the slips 4 tightly and wedgingly engaging the fish. The fish is freed from the tool by displacing this tool downwardly relative to the fish, which is advantageously clamped in a spider, and rotating the overshot clockwise relative to the fish to unscrew the overshot from the fish.

FIG. 2 shows an embodiment of the fishing tool, according to the present invention, used as described above but intended for catching tubing or drill pipes. To this end, the stack of bushings bear on a base bushing 9 continuing the inner bowl shape of the lowermost bushing 3 and itself bearing on an annular resilient seal 8 adapted to compress on lifting of the fish and receiving said bushings, said sub being formed with sealingly engage its side to prevent leakage. a passage communicating with the interior of said We claim: casing, said casing being formed at its lower end Aunivel'salovershot Comprisingi with a downwardly widening mouth and an ina tubular y having a mouth adapted to receive a wardly extending annular shoulder immediately drill string or rod;

a plurality of axially aligned bushings received in said body and each having an inner wall tapering toward said mouth;

a respective set of slips disposed in each of said 10 bushings and longitudinally slidable along and wedgingly engageable between the respective inner wall and the drill string or rod, said slips being axially abutting;

a sleeve bearing axially on the set of slips furthest from said mouth,

a spring bearing on said sleeve and urging all of said slips toward said mouth, said body being formed with a sub threadedly engageable with a fishing string and having a threaded axially extending boss I receiving Said Spring and forming a Seat therefore, of slips are each formed on their lnner wall with leftand a unitary cylindrical casing threaded onto said handed threads boss flush with the outer periphery of said sub and above said mouth, said bushings being clamped between said boss and said shoulder; and

a resilient sealing ring clamped between said bushings and said shoulder and engagable with the periphery of the string or rod.

2. The overshot defined in claim 1 wherein said body comprises a pair of screw-threadedly interengaged parts clamping said bushing in a stack.

3. The overshot defined in claim 2 wherein said sleeve is tubular.

4. The overshot defined in claim 3 wherein each of said sets of slips has a downwardly and outwardly widening mouth.

5. The overshot defined in claim 2 wherein said sets

Claims (5)

1. A universal overshot comprising: a tubular body having a mouth adapted to receive a drill string or rod; a plurality of axially aligned bushings received in said body and each having an inner wall tapering toward said mouth; a respective set of slips disposed in each of said bushings and longitudinally slidable along and wedgingly engageable between the respective inner wall and the drill string or rod, said slips being axially abutting; a sleeve bearing axially on the set of slips furthest from said mouth; a spring bearing on said sleeve and urging all of said slips toward said mouth, said body being formed with a sub threadedly engageable with a fishing string and having a threaded axially extending boss receiving said spring and forming a seat therefore, and a unitary cylindrical casing threaded onto said boss flush with the outer periphery of said sub and receiving said bushings, said sub being formed with a passage communicating with the interior of said casing, said casing being formed at its lower end with a downwardly widening mouth and an inwardly extending annular shoulder immediately above said mouth, said bushings being clamped between said boss and said shoulder; and a resilient sealing ring clamped between said bushings and said shoulder and engagable with the periphery of the string or rod.

2. The overshot defined in claim 1 wherein said body comprises a pair of screw-threadedly interengaged parts clamping said bushing in a stack.

3. The overshot defined in claim 2 wherein said sleeve is tubular.

4. The overshot defined in claim 3 wherein each of said sets of slips has a downwardly and outwardly widening mouth.

5. The overshot defined in claim 2 wherein said sets of slips are each formed on their inner wall with left-handed threads.

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