BACKGROUND OF INVENTION

1. Field of the Invention

[0001] This invention is directed to a release mechanism for a mandrel of a jarring device commonly referred to as a jar. Jars are used in the well drilling industry to free downhole tools that may become lodged in a well. An upward or downward force can be supplied to a tubular string which includes the affected tool in order to break free the tool from the well bore.

2. Description of Related Art

[0002] Typically, a release mechanism in the form of an annular collet is provided which normally prevents axial movement of the mandrel. The mandrel is spring biased to move with significant force in an upward or downward direction. If a sufficient force is placed on the mandrel, the collet will release.

[0003] U.S. Patent No. 5,022,473 discloses a release assembly which comprises a plurality of angular segments 62 and 162 that engage in slots 86 and 88, and 186 and 188 respectively. It has been found that this arrangement can result in the segments 62 and 162 becoming out of alignment which could result in the failure of the release mechanism. As disclosed in the patent, the jar requires two sets of release lugs to withstand the anticipated tensile load. In this design the two lug assemblies must be spaced further apart than the total travel of the jar to prevent the lower lug from inadvertently engaging the groove of the upper lug assembly. If a third lug assembly were necessary it would have to be spaced a distance greater than the jar stroke from the lower set. This would significantly increase the total length of the jar and also the cost.

BRIEF SUMMARY OF THE INVENTION

[0004] The present invention solves the above noted problem by providing a plurality of angular lug segments each of which has two or more projections that engage corresponding grooves in the mandrel.

[0005] In order to avoid misalignment or a jarring situation, the projections having either a differing width or are spaced at different distances. The grooves on the mandrel have a complimentary configuration as will be explained below. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0006] FIG. 1 is a cross-sectional view of a first embodiment of the release lugs as shown in a neutral position.

[0007] FIG. 2 is a cross-sectional view of the first embodiment of the release lugs just prior to release of the mandrel.

[0008] FIG. 3 is a cross-sectional view of the release lugs of FIG. 1 in a release position with the mandrel initially moving.

[0009] FIG. 4 is a cross-sectional view of the mandrel in a completely released position.

[0010] FIG. 5 is a perspective view of a release lug according to a first embodiment of the invention.

[0011] FIG. 6 is a perspective view of a plurality of release lugs forming a release mechanism according to a first embodiment of the invention.

[0012] FIG. 7 is a cross-sectional view of a second embodiment of the release lugs shown in a neutral position.

[0013] FIG. 8 is a cross-sectional view of the release lugs of the second embodiment in a fully released mode.

[0014] FIG. 9 is a segmented cross-sectional view of an entire jar including the release lugs of FIG. 7.

[0015] FIG. 10 is a cross-sectional view taken along line 10-10 of FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

[0016] FIG. 1 illustrates a release mechanism including a plurality of release lugs 17 surrounding mandrel 21 of the jar such as that shown in FIG. 9.

[0017] The jar includes a central housing 11, a Belleville spring stack 12, a restrictor orifice 14 and one or more check valves 13, an annular sleeve 15 surrounding mandrel 21 and an annular trigger sleeve 16 having an inwardly projecting lip 33. Annular trigger sleeve 16 is spring biased against a shoulder 9 provided in housing 11 by a spring 19 at lip 33. A lubricant fitting housing 151 is threadedly coupled to the downhole portion of housing 11.

[0018] As shown in FIG. 5, each release lug 17 includes a plurality of projections 18 of varying width on its interior surface. Projections 18 in this embodiment are evenly spaced from each other. The exterior surface of the release lug includes a plurality of grooves 37 which are adapted to receive projections 36 of the trigger sleeve 16 as shown in FIG. 4. A plurality of smaller grooves 41, 42, 43 and 44 are also provided on the exterior surface of release lugs 17 and are adapted to hold garter springs 38 as shown in FIG.6. A plurality of the release lugs are used to form a release mechanism as shown in FIG. 6 having spaces 43 between the release lugs. Although six release lugs are shown any number of segments for example, 2 thru 12 may be used.

[0019] In the rest position shown in FIG. 1, surfaces 35 of the release lugs are in contact with the interior surface of trigger sleeve 16 and projections 18 are located within grooves 32 provided on the outer surface of mandrel 21. As an upward force is applied to mandrel 21 which would be from the left as shown in FIG. 1, mandrel 21 and release lugs 17 will travel to the left, thereby compressing Belleville spring stack 12. As the surfaces 35 align with grooves 31 of the trigger sleeve 16, the beveled surfaces of the projections and grooves of the trigger sleeve, release lugs and mandrel grooves will allow the surfaces to be forced outwardly into grooves 31 resulting in projections 18 disengaging from grooves 32 in the mandrel. The mandrel then is free to move in an upward direction or to the left as shown in FIG. 4. The overall operation of a hydraulic jar is well known and explained in U.S. Patent No. 6,290,004 and 7,510,008, the entire contents of which are expressly incorporate herein by reference thereto.

[0020] In order to reload the jar, a downward force is placed on the mandrel which will move the mandrel downward. The garter springs 38 will cause the release lugs to return to their original position with the projections 18 in grooves 32.

[0021] Spring 19 which is now compressed will move trigger sleeve 16 back to the neutral position shown in FIG. 1. In the embodiment of FIGS. 7 and 8, the release lugs 57 have been changed to include a plurality of projections 58 that are non-uniformly spaced apart from each other rather than having varying widths. The grooves 59 in the mandrel are also spaced apart accordingly to receive projections 59 in the neutral position as shown in FIG. 7. The outer surfaces of the release lugs are formed in the same fashion as the lugs shown in FIG. 5 so that in the released position of FIG. 8, surfaces 35 of the release lug are located within grooves 31 of the trigger sleeve 16.

[0022] FIG. 9 illustrates an embodiment of a complete jarring tool that incorporates the release lugs of the embodiment shown in FIGS. 7 and 8. The jar includes a connector 100 for connecting the jar to a tubular string, upper housing members 102 and 103, lubricating fitting 104, central housing 11, a lower lubricating fitting 151, lower housing member 152 and lower connector 141. The jar also includes a Bellville spring stack 12. The housing members are threadably connected to each other at 130, 131, 132, 133, 134 and 135. The mandrel of the jar includes an upper portion 160 which is threadedly connected to connector 100, a central portion 21 and a lower portion 153. The mandrel portions are connected together by threads at 136 and 158. Suitable seals are provided at 121, 122, 123, 124, 125, 126, 129 and 139. A floating piston 127 surrounds the lower portion of mandrel 153. A lubricating material is introduced into the housing through fittings 140 and 141. The upper portion of the mandrel 160 includes an annular raised portion 138 which acts as a hammer against an anvil shoulder 137 on housing upper end member 102. As shown in FIG. 10, upper housing member 103 may comprise a hexagon surface 171 which received a hexagon outer surface 172 on the mandrel portion 160.

[0023] The jarring tool of FIG. 9 may incorporate the release lugs shown in the embodiments of FIG. 5 or that of the embodiment of FIGS. 7 and 8.

[0024] Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.