US3776258A

US3776258A - Well pipe valve

Info

Publication number: US3776258A
Authority: US
Inventors: R Dockins
Original assignee: B&W Inc
Current assignee: B&W Inc
Priority date: 1972-03-20
Filing date: 1972-03-20
Publication date: 1973-12-04
Anticipated expiration: 1990-12-04

Abstract

A valve for use in a well pipe string including an apertured diaphragm for producing a variable restriction in fluid flow through the valve for controlled filling while running the well pipe and an expandable tapered valve seat for cooperating with a ball to allow the ball to pass downwardly through the valve seat to convert the valve to a reverse flow check valve to prevent subsequent upward flow of fluid through the valve.

Description

United States Patent [191 Dockins, Jr.

[4 Dec.4,1973

[ WELL PIPE VALVE [75] Inventor: Roy Raymond Dockins, Jr.,

Anaheim, Calif.

[73] Assignee: B & W Incorporated, Torrance,

Calif.

[22] Filed: Mar. 20, 1972 [21] App]. No.: 235,909

[52] US. Cl. 137/269, l37/525.3, 137/5l9.5,

l37/533.1l [51] Int. Cl. Fl6k 51/00 [58] Field of Search 137/268, 269, 525,

[56] References Cited UNITED STATES PATENTS 2,829,719 4/1958 Clark, Jr. 137/269 X Primary Examiner-Henry T. Klinksiek Assistant Examiner-Robert J. Miller Attorney-Charles G. Lyon et a1.

[ 5 7 ABSTRACT A valve for use in a well pipe string including an apertured diaphragm for producing a variable restriction in fluid flow through the valve for controlled filling while running the well pipe and an expandable tapered valve seat for cooperating with a ball to allow the ball to pass downwardly through the valve seat to convert the valve to a reverse flow check valve to prevent subsequent upward flow of fluid through the valve.

16 Claims, '10 Drawing Figures PATENTEDuEn 4mm 3,776,258

Era 9.

WELL PIPE VALVE This invention relates to a valve used in a well pipe string for controlling the fluid flow in the stringand, in

particular, is directed to a valve for automatically controlling the filling of the well pipe string while running the string into the well and that may be converted to a float valve for preventing reverse fluid flow upwardly through the well pipe string.

The use of valves of various configurations in oil well drill pipe or casing strings for accomplishing various flow controlling purposes is well known. The valve or valves are mounted at any desired location along the string'including the bottom or shoe end. One such valve device is commonly called fill'up equipment which allows the pipe string to fill up with fluid as it is lowered into the well and certain types of such valves also serve to control the rate of fill up. By permitting filling of the pipe string while running into the well, hydraulic pressure surges onthe well bore are reduced thereby allowing faster running of the pipe string. In addition some of these valves serve to control the quantity of fill up whereby a given length of dry pipe string is always maintained at the surface for convenient running of the pipe string.

Another conventional type of well pipe valve device is commonly called float equipment and it essentially comprises a check valve that allows free downward flow of fluid through the pipe string but prevents any reverse upward fluid flow. The many uses and advantages of float equipment are well known as for example in allowing the cement slurry to be pumped downwardly through a well casing but preventing its return upwardly in the well casing upon completion of the cementing.

In some situations and applications in oil well drilling and completion it is desirable to employ the features of both fill-up equipment and float equipment. As a result, combined valves have been developed that operate as fill-up equipment during the lowering of the well pipe string in the well bore. and then can be selectively converted to float equipment by the use of some actuating procedure such as imposing a high hydraulic pressure or dropping an actuating ball. Heretofore the combined convertible valves have had various deficiencies or undesirable qualities such as high cost, lack of dependability, premature and unintended actuation to float equipment, inadequate sealing as float equipment, inability to use in deep wells, etc. While the more complex combination valves have been relatively dependable they have the obvious drawback of being expensive and often are of a construction that inhibits or prevents drilling therethrough for subsequent operations and procedures in the well.

Accordingly in summary it is a principal object of this invention to provide a novel form of well pipe valve that employs a novel diaphragm member for both producing controlled fill up and preventing reverse flow upon the passage of a valve ball therethrough wherein return upward passage of the ball is mechanically prohibited to insure against failure.

Another object of this invention is to provide a novel form of combined fill-up and float valve for well pipe strings in which a flexible diaphragm serves both .to

control fill up rate and as the valve seat for the conthrough the diaphragm. Still another object of this invention is to provide such a combination valve in which the flexible diaphragm is molded to the split ring collet for providing a reinforcing and mounting support for the diaphragm.

A still further object of this invention is to provide a novel form of fill-up and float valve for well pipe strings in which an integral diaphragm and'split ring collet combine to serve both intended functions and cooperate with each other whereby the ring both supports and reinforces the diaphragm and the diaphragm resiliently maintains the split ring in the desired dimensional .condition. Still another object is to provide such a valve wherein the split ring collet has an external tapered surface cooperating with a mating supportingsurface for allowing expansion of the ring collet upon downward axial movement thereby allowing anactuating ball to only pass downwardly through the ring collet. Still another object of this invention is to provide such a valve wherein the split ring collet is normally constrained in a position having a minor diameterless than and a major diameter slightlygreater than the diameter of the actuating ball.

Other and more detailed objects and advantages of this invention will appear from the following description and the accompanying drawings wherein:

FIG. 1 is a sectional elevation of the preferred form of the valve of this invention illustrated as incorporated in the shoe of the well pipe string.

FIG. 2 is a fragmentary enlargedelevation view of a portion of that which is shown in FIG. 1.

FIG. 3 is a view similar to FIG. 2 illustratingthe actuating ball in the transitory state of passing through the valve diaphragm.

FIG. 4 is a view similar to FIGS. 2 and 3 and illustrating the further position of the actuating ball upon the occurrence of reverse fluid pressure as resisted bythe ball.

FIG. 5 is a plan view of the ring and diaphragm element of the valve in its normal configuration such as illustrated in FIGS. 1 and 2.

FIG. 6 is a plan view of the ring and diaphragm element similar to FIG. 5 but illustrating the expanded condition of the element as caused by the actuating ball such as occurs in the condition illustrated in FIG. 3.

FIG. 7 is an enlarged fragmentary sectional view taken on the lines 7-7 in FIG. 5.

FIG. 8 isan enlarged fragmentary section taken on the line 8-8 in FIG. 5.

FIG.'9 is a sectional elevation illustrating the valve of this invention located between two joints of the well pipewithin the connecting pipe collar.

FIG. 10 is a fragmentary perspective view partially in section illustrating a modification of the valve of this invention for supporting and retaining the actuating ball at the valve assembly.

Referring now in detail to the drawings, it is to be noted at the outset from a consideration of FIGS. 5, 7 and 8 that the ring and diaphragm element in.the preferred form of this invention is not entirely symmetrical, particularly as tothe location and lack of cencentricity of the ring within the surrounding rubber. Specifically it is to be noted that the rubber is thicker at the exterior of the ring in FIG. 7 and at the interior of the ring in FIG. 8. The importance of this asymmetrical an rangement will appear more fully hereinafter but for convenience and clarity of illustration this difference has been omitted from FIGS. 1, 2, 3, 4 and 9.

Referring specifically to FIG. 1, the valve of this invention, generally designated 10, is supported by concrete 11 in a tubular casing 12 to comprise the shoe joint of the well pipe string 13. As is conventional, the upper end of the tubular element 12 of the shoe joint is internally threaded at 14 for connecting to the well pipe string.

The valve has a tubular body comprised of an upper member 15 and a lower cage portion 16 which are joined together in any convenient manner such as threads and/or pins 17. The upper end of both the tubular member 15 and the concrete 11 are tapered at 18 and 19, respectively, to provide a smooth downward entrance for the ball 20. As is conventional, the lower end of the shoe joint is open by reason of aligned

holes

21 and 22 in the concrete l1 and cage portion 16, respectively. It is preferred that the

valve body elements

15 and 16 be comprised of a readily drillable material such as aluminum to permit subsequent drilling through the shoe joint if desired.

Means are provided for functioning as both a fill-up control orifice and a valve seat and as shown in the drawings these means may include the valve member, generally designated 23, mounted between the upper tubular member 15 and the lower cage portion 16 of the valve 10. The valve member is comprised of a flexible diaphragm 24 and a split ring 25 integrally molded together. While various materials may be acceptable, I prefer using aluminum for the ring 25 and neoprene rubber of about 70 shore hardness for the diaphragm 24. The valve member 23 has a frusto-conical external surface 26 that mates with a like internal surface 27 on the lower end of the valve tubular member 15. The diaphragm 24 is formed essentially on the bottom of the ring 25 and has a substantial thickness in the axial direction. The upper end 28 of the cage portion 16 of the valve captures and provides a support for the bottom of the diaphragm portion of the valve member 23. The diaphragm 24 subtends the opening through the valve and has a central orifice 29. The upper surface of the diaphragm within the ring 25 may be flat while it is preferred that the lower surface have a flatly tapered or dished portion 30 against which the actuating ball will seat when urged upwardly from beneath the diaphragm thereby assuring a seal between the diaphragm and the ball. It is preferred that the tapered portion be at an angle of about 15 from the radius and that the

conical surfaces

26 and 27 be at an angle of about 20 relative to the axis.

Referring more particularly to FIGS. 5, 7 and 8, the split ring is preferably comprised of two semicircular portions die cast or machined to the desired shape and dimensions prior to being molded to the diaphragm 24. The radius of curvature on the inwardly facing surface 31 of split ring 25 is preferably only slightly larger than the radius of curvature of the ball 20, as for example perhaps only 0.010 inch to 0.015 inch larger radius than the ball radius. However it is also preferable that the two semicircular portions of the split ring 25 be positioned diametrically closer to each other than their natural diameter whereby the split ring 25 is not concentric with the otherwise symmetrical valve member 23. In other words the minor diameter D between internal surfaces 31 of a split ring 25 as shown in FIG. 5 is less than the machined diameter of the split ring as represented by the dimension D". As illustrated by FIGS; 7 and 8, this results in a thicker layer 32 of neoprene on the exterior frusto-conical surface 26 at the mid-point of each half of the split ring than at the ends thereof and conversely a thicker layer 33 of neoprene on the internal surface 31 at the ends of the split rings. By way of example and without limitation as to the scope of this invention. for a ball of 2 1% inch diameter the major or machined diameter D" of split ring 25 is preferably 2.520 inches while the spacing or minor diameter D between the two rings is preferably about 2.437 inches. Thus it may be seen in the preferred dimensional relationship among the components, that the two halves of the split ring 25 must spread radially away from each other to allow the ball 20 to pass therethrough but no deformation or bending of the split ring is required.

In the embodiment of FIG. 9 the valve of this invention, generally designated 10A is positioned in a conventional well pipe collar 34 which may be located anywhere along the well pipe string 13 as required by the particular well conditions. In this embodiment, the cage portion 16 and valve member 23 may be identical to those heretofore described with respect to the valve of FIG. 1 but the upper portion of the valve is in the form of a flange 15A of somewhat different shape but similar function. Cage portion 16 and flange 15A may be joined together as previously described with respect to FIG. 1. Flange 15A is provided with the same internal, downwardly facing frusto-conical surface 27 for mating with the like surface 26 on the valve member 23. Flange 15A has a similar but obviously larger and flatter tapered surface 18 than in FIG. 1 and a neoprene lip 32A overlaps said surface. The external periphery of flange 15A is provided with a thread 35 for engaging the internal threads of collar 34 just above the midpoint of the collar. The valve 10A is actually installed with the collar 34 already assembled to the top of the joint of well pipe therebelow by threading the valve 10A in from the open upper end of the collar. A gasket 36 is positioned immediately below the threads 35 and has a ring 37 for engaging the upper end of the well pipe within the collar. The next joint of well pipe is then threadedly installed from above and, as shown in FIG. 9, captures the flange 15A with the gasket 36 and ring 37 between the two ends of the well pipes within the collar which location is commonly referred to as the .11.

The embodiments of the

valves

10 and 10A illustrated in FIGS. 1 and 9, respectively, function identically to first serve as fill-up equipment and when desired may be converted to float equipment. While lowering the well pipe 13 into the well bore the orifice 29 in the diaphragm 24 serves to control the rate of flow of fluid past the

valve

10 or 10A. The orifice 29 will dialate by virtue of the flexure of diaphragm 24 in direct response to the differential pressure across the diaphragm. Thus if the well pipe 13 is lowered into the well bore rapidly the immediate effect would be a substantial pressure differential between the outside and the inside of the well pipe causing the well fluid to flow upwardly through the orifice 29 and this dynamic condition in turn causes a flexing of diaphragm 24 to temporarily enlargen orifice 29 and allow a greater volumetric rate of fluid flow through the valve than would otherwise be possible if the orifice was of a fixed size. This serves the beneficial function of rapidly relieving the hydraulic pressure imposed on the well bore by this dynamic condition of lowering the well pipe. However as the differential pressure across the dipahragm and the rate of fluid flow therethrough diminishes, the orifice 29 will tend to return to its original size and therefore the rate of flow will slowly be reduced whereby overfilling of the well pipe will be prevented that might otherwise occur by reason of this dynamic condition. Of course at any time fluid may be circulated through the valves and 10A in either direction such as is sometimes required as an intermediate step during the lowering of the well pipe into a well bore and the valve does not present any objectionable restriction.

When the well pipe 13 has reached its desired depth or for any other reason it is desired to convert the

valve

10 or 10A from fill up equipment to float equipment, the ball is dropped from the surface and either by circulation or gravity will eventually approach the valve as illustrated in FIGS. 1 and 9. Oncethe ball 20 reaches the upper surface of the diaphragm 24 is illustrated in FIG. 2, the ball forms a seal with the orifice 29 restricting further downward flow of fluid through the orifice. Thus by pumping fluid down the well pipe 13 the ball 20 will be urged downwardly against the diaphragm and urge the diaphragm to flex downwardly. Since the ball diameter D is slightly larger than the valve minor diameter D and only slightly smaller than the valve major diameter D", the ball will virtually fit the cylindrical internal surface of the valve 23 as formed by the inner layer 33 of neoprene. The continuing downward hydraulic force on the ball and the top of the valve member 23 will urge the valve member passage of the ball 20 through the valve, it is possible to use the valve of this invention in deep wells in which other conventional flexible diaphragm valves are unacceptable.

A modification of the valve of this invention that is applicable to either the shoe form of FIG. 1 or the collar 1.! form of FIG. 9 (with appropriate modifications) is the arrangement illustrated in FIG. 10 wherein the ball 20 is retained immediately above the valve member 23 while running the equipment rather than dropping the ball from the surface when desired. This may be accomplished in any convenient manner such as by a spring retainer 40 comprising two arms joined at their apex 41 and having loops 42 at their free ends. An internal groove 43 is provided in the upper tubular member 15 of the valve and the apex 41 and loop ends 42 engage the groove with the arms tending to resiliently expand outwardly thereby holding the spring retainer 40 in position.- By this arrangement the ability to circulate fluid downwardly through the valve is eliminated since the ball 20 will seal against theorifice 29 but upward circulation, as in filling the well pipe while running it in, is still possible. When it is desired to convert the valve to a float valve it is merely necessary to create an increased hydraulic pressure on the inside of the well pipe to force the ball 20 down through the diaphragm as previously described.

Having fully described my invention in connection with the presently preferred embodiment together with modifications thereof, it is to be understood that my in vention is not limited to said embodiment or modifications but rather is of the full scope of the appended downwardly against the upwardly facing shoulder 28 ball 20 passes therethrough. The ball will come to rest in cage portion 16 on three fins 39 as shown by the phantom lines in FIG. 3 whereby subsequently fluid may flow downwardly past the ball 20 and out the hole 22 in the bottom of the cage. However upon reverse upward fluid flow the ball 20 will engage and seal with the dished surface on the bottom of the diaphragm 24 to prevent reverse flow whereby the

valve

10 or 10A becomes so called float equipment. The elasticity of the neoprene causes the valve member 23 to return to its original condition as illustrated in FIG. 5 and in turn the upward hydraulic force on the ball 20 and diaphragm 24 will cause the split ring 25 to collapse to its minimum possible diameter. In this condition, the minor diameter D of the split ring 25 is smaller than the ball thereby positively assuring that the ball will not pass upwardly through the valve member 23. Moreover the thickness of the diaphragm itself as it is urged upwardly by the ball 20 will be supported by the inner wall of the split ring 25 and preclude upward passage of the ball. Thus, as illustrated in FIG. 4,'the ball and valve member 23 form and effective back pressure shut off valve against the reverse flow of fluid as required. Due to the positive mechanical prevention of upward claims.

I claim:

1. A valve for well pipe comprising, a tubular body adapted to be mounted in the well pipe, a ball for selectively modifying the function of the valve, a diaphragm means mounted in and extending across said tubular body and having an expandable orifice, an expandable split metal ring mounted immediately above said diaphragm means in said tubular body for allowing the ball to pass downwardly through the orifice of said diaphragm means but preventing upward return therethrough whereby said ball forms a seal against said diaphragm means, and cage means below said diaphragm means for retaining said ball.

2- The valve of claim 1 wherein said metal ring has a frusto-conical outer surface converging in the upward direction, and said tubular body has a mating frustoconical inner surface supporting said metal ring for allowing said ring to expand in response to downward relative movement and'for causing said ring to contract in response to upward relative movement.

3. The valve of claim 2 wherein said metal ring is resiliently mounted in said tubular body for allowing said relative movements and returning said ring to a neutral position.

4. The valve of claim 1 wherein said expandable split metal ring has anormal minimum internal diameter across at least one point that is less than the diameter of said ball.

5. The valve of claim 4 wherein said split metal ring forms a positive mechanical support against excessive upward flexure of said diaphragm.

6. The valve of claim 5 wherein said metal ring has a frusto-conical outer surface converging in the upward direction, and said tubular body has a mating frustoconical inner surface supporting said metal ring for allowing said ring to expand in response to downward relative movement and for causing said ring to contract in response to upward relative movement.

7. A valve for well pipecomprising, a tubular body adapted to be mounted in the well pipe, a ball for selectively modifying the function of the valve, a diaphragm means mounted in and extending across said tubular body and having an expandable orifice, expandable ring means mounted in said tubular body for allowing the ball to pass downwardly through the orifice of said diaphragm means but preventing upward return therethrough whereby said ball forms a seal against said diaphragm means, said diaphragm means and expandable ring means being an integrally molded component with said expandable ring means located immediately above said diaphragm means, and cage means below said diaphragm means for retaining said ball.

8. The valve of claim 7 wherein said expandable ring means comprises a resilient split metal ring a normal internal diameter in at least one location less than the diameter of said ball.

9. The valve of claim 7 wherein said expandable ring is comprised of two semi-circular metal rings resiliently supported in opposed relationship by said diaphragm in a normal position with the diametric distance between the mid-points of said two semi-circular rings being less than the diameter of said ball.

10. The valve of claim 9 wherein said two semicircular rings have frusto-conical outer surfaces converging upwardly, and said tubular body has a mating frusto-conical surface for causing contraction of said rings in response to upward force for positive mechanical prevention of said ball upwardly therethrough.

11. A valve for well pipe comprising, a tubular body adapted to be mounted in the well pipe, a ball adapted to selectively modify the function of the valve, a diaphragm means mounted insaid tubular body and having an expandable orifice for controlling the rate of fluid flow therethrough in response to varyir ig fluid pressure thereacross and allowing the ball to pass therethrough, an expandable split metal ring integrally formed with and on top of said diaphragm means for allowing the ball to pass downwardly through said diaphragm means but preventing upward return whereby said ball forms a seal against said diaphragm means,

said ring having at least one internal diametric dimension less than said ball diameter, and cage means below said diaphragm means for retaining said ball.

12. The valve of claim 1 I wherein said metal ring has a frusto-conical outer surface converging in the upward direction, and said tubular body has a mating frustoconical inner surface supporting said metal ring for allowing said ring to expand in response to downward relative movement and for causing said ring to contract in response to upward relative movement.

13. The valve of claim 12 wherein said ring is split into two semi-circular havles with an internal cylindrical surface having a radius of curvature slightly greater than the diameter of said ball, and said ring halves appropriately spaced to produce said internal diameter dimension at approximately the mid-points of said halves. 7

14. A valve for well pipe comprising, a tubular body having means for mounting in the well pipe and a spherical ball adapted to selectively modify the operation of the valve, said body having a frusto-conical internal surface tapering outwardly in the downward direction, a valve member mounted in said body and having a frusto-conical outer surface engaging said body internal surface, said valve member having a central flexible diaphragm portion subtending the body with an orifice through said diaphragm, said orifice allowing restricted fluid flow therethrough and dilating by flexure of said diaphragm for varying the restriction in inverse proportion to the fluid pressure differential thereacross, said valve member including a split ring having an internal diameter in at least one direction which is less than the diameter of said ball, said body having a cage portion below said valve member for receiving and retaining said ball in a supported position allowing downward fluid flow, and said ball forcing said split ring downwardly and expanding the split ring outwardly when the ball is urged downwardly by fluid pressure thereby allowing the ball to pass through said valve member by also expanding said orifice, said ball being restrained from subsequent upward movement by said split ring cooperating with said internal frusto-conical mately between the mid-points of said ring halves.

Claims

2. The valve of claim 1 wherein said metal ring has a frusto-conical outer surface converging in the upward direction, and said tubular body has a mating frusto-conical inner surface supporting said metal ring for allowing said ring to expand in response to downward relative movement and for causing said ring to contract in response to upward relative movement.

4. The valve of claim 1 wherein said expandable split metal ring has a normal minimum internal diameter across at least one point that is less than the diameter of said ball.

6. The valve of claim 5 wherein said metal ring has a frusto-conical outer surface converging in the upward direction, and said tubular body has a mating frusto-conical inner surface supporting said metal ring for allowing said ring to expand in response to downward relative movement and for causing said ring to contract in response to upward relative movement.

7. A valve for well pipe comprising, a tubular body adapted to be mounted in the well pipe, a ball for selectively modifying the function of the valve, a diaphragm means mounted in and extending across said tubular body and having an expandable orifice, expandable ring means mounted in said tubular body for allowing the ball to pass downwardly through the orifice of said diaphragm means but preventing upward return therethrough whereby said ball forms a seal against said diaphragm means, said diaphragm means and expandable ring means being an integrally molded component with said expandable ring means located immediately above said diaphragm means, and cage means below said diaphragm means for retaining said ball.

10. The valve of claim 9 wherein said two semi-circular rings have frusto-conical outer surfaces converging upwardly, and said tubular body has a mating frusto-conical surface for causing contraction of said rings in response to upward force for positive mechanical prevention of said ball upwardly therethrough.

11. A valve for well pipe comprising, a tubular body adapted to be mounted in the well pipe, a ball adapted to selectively modify the function of the valve, a diaphragm means mounted in said tubular body and having an expandable orifice for controlling the rate of fluid flow therethrough in response to varying fluid pressure thereacross and allowing the ball to pass therethrough, an expandable split metal ring integraLly formed with and on top of said diaphragm means for allowing the ball to pass downwardly through said diaphragm means but preventing upward return whereby said ball forms a seal against said diaphragm means, said ring having at least one internal diametric dimension less than said ball diameter, and cage means below said diaphragm means for retaining said ball.

12. The valve of claim 11 wherein said metal ring has a frusto-conical outer surface converging in the upward direction, and said tubular body has a mating frusto-conical inner surface supporting said metal ring for allowing said ring to expand in response to downward relative movement and for causing said ring to contract in response to upward relative movement.

13. The valve of claim 12 wherein said ring is split into two semi-circular havles with an internal cylindrical surface having a radius of curvature slightly greater than the diameter of said ball, and said ring halves appropriately spaced to produce said internal diameter dimension at approximately the mid-points of said halves.

14. A valve for well pipe comprising, a tubular body having means for mounting in the well pipe and a spherical ball adapted to selectively modify the operation of the valve, said body having a frusto-conical internal surface tapering outwardly in the downward direction, a valve member mounted in said body and having a frusto-conical outer surface engaging said body internal surface, said valve member having a central flexible diaphragm portion subtending the body with an orifice through said diaphragm, said orifice allowing restricted fluid flow therethrough and dilating by flexure of said diaphragm for varying the restriction in inverse proportion to the fluid pressure differential thereacross, said valve member including a split ring having an internal diameter in at least one direction which is less than the diameter of said ball, said body having a cage portion below said valve member for receiving and retaining said ball in a supported position allowing downward fluid flow, and said ball forcing said split ring downwardly and expanding the split ring outwardly when the ball is urged downwardly by fluid pressure thereby allowing the ball to pass through said valve member by also expanding said orifice, said ball being restrained from subsequent upward movement by said split ring cooperating with said internal frusto-conical surface to tend to contract and said ball forming a fluid seal with the underside of said diaphragm.

15. The valve of claim 14 wherein said split ring has an external frusto-conical surface mating with said body internal frusto-conical surface.

16. The valve of claim 15 wherein said split ring is comprised of two semi-circular halves with said internal diameter less than said ball diameter being approximately between the mid-points of said ring halves.