APPLICATION FOR PATENT Title: Release Mechanism for Downhole Tool FIELD OF THE INVENTION The field of this invention is releasable locking mechanisms for downhole tools. Various 5 embodiments rely on expansion or radial movement to effect release of components previously held together. BACKGROUND OF THE INVENTION Downhole tools frequently involve mechanisms to hold one portion of the tool to another. This is sometimes accomplished using shearable members such as shear pins or similar devices such as 0 spring loaded collets. Typically pistons are used with such locking elements to respond to built up pressure after landing a ball on a seat and adding pressure from above. Some of the problems with these designs lead to premature failure of the locking device creating a problem downhole. If the tool is a disconnect, for example, it may release prematurely forcing a fishing operation to retrieve the lowermost portion that falls in the wellbore. One of the reasons for the premature failure of the shear pins is the 5 weight of the piston that has to ultimately move to break the shear pin or release a collet. Due to cyclical loading during run in or from operation of adjacent downhole equipment such as downhole pumps the shock loads on the piston combined with its weight can be sufficient to shear a pin or otherwise allow relative movement of tool components at an inopportune time. Other limitations of prior designs is that the locking members that were used to hold the 20 components fixed to each other provided only discrete areas of contact about the periphery of the components causing elevated stress levels due to the minimal contact areas and creating another weakness that has in the past lead to premature failure. The prior art release tools that suffered from the limitations described above are represented by the following list of U.S. Patents, presented as some examples of the issues affecting the prior art 25 designs of hydraulic disconnects: 5,526,888; 6,527,048; 6,439,305; 6,408,946; 6,349,767; 6,318,470; 6,053,262; 6,053,250; 5,984,029; 5,960,884; 5,787,982; 5,718,291 and 4,984,632. Also of interest is U.S. Application 2004/0045704. It is not admitted that any of the information in this specification is common general knowledge, or that the person skilled in the art could reasonably be expected to have ascertained, understood, 30 regarded it as relevant or combined it in any way at the priority date. 1 SUMMARY OF THE INVENTION What is needed is a design to eliminate or at least reduce the incidence of premature failures, preferably with a design that does not become even more complex than the prior designs sought to be upgraded. At least preferred embodiments of the present invention offer solutions that meet this need. 5 The invention provides a releasable locking mechanism for a downhole tool. The mechanism has a longitudinal axis and includes a first body, and a second body, and a lock which is discrete from the first and second bodies to selectively hold the first and second bodies together without a shearing member. An actuator is selectively movable radially with respect to the longitudinal axis and in contact with the lock, to operate the lock. 0 According to preferred forms of the invention, the shear pin or collet designs that were prone to failure in the past are eliminated. In an embodiment of the invention locking components offer as much as 360 degree support to minimize shear failure. Unlocking is accomplished by radial movement of the locking members to release the grip between the members initially held together. Once the release is accomplished a lockout feature can be provided to prevent re-engagement. Radial movement can be 5 accomplished in a variety of ways with pistons or a sleeve that bends responsive to applied internal pressure or by other mechanisms. The design that provides as much as full circumferential contact prior to unlocking can also take on a variety of forms. The application can be for a host of downhole tools although aspects of the preferred embodiment will be described in the context of a hydraulic release tool. Also disclosed is a release mechanism for a downhole tool which is actuated by radial .0 movement of a locking member. The locking member provided as much as full circumferential support in the locked position and once released can be prevented from re-gripping the previously connected elements. Illustrative examples of the mechanism for radial movement for release comprise sleeves that expand and radially oriented pistons. Shear pins or collets are not used to hold the components together in the preferred embodiment. 25 Internal pressure fluctuations before initiating the release sequence will not cause unwanted release. The mechanism is applicable to a variety of downhole tools and is illustrated in the context of a hydraulic release. Those skilled in the art will appreciate the varied applications of the present invention and its advantages from a detailed discussion of two embodiments and the claims, which appear below.
As used herein, except where the context requires otherwise the term 'comprise' and variations of the term, such as 'comprising', 'comprises' and 'comprised', are not intended to exclude other additives, components, integers or steps. DETAILED DESCRIPTION QF THE DRAWINGS 5 [0008] Figures la-lb show the run in position of the preferred embodiment in a half section view; [0009] Figures 2a-2b are the view of Figures I a-l b but in the beginning to release position; [0010] Figures 3a-3b are the view of Figures 2a-2b but in the fully released position; [00 11] Figures 4a-4b are a half section view of an alternative embodiment in the run in position; 0 [0012] Figure 5 is a section view along lines 5-5 of Figure 4b. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0013] Referring to Figures la-Ib, the upper body 10 is secured releaseably to lower body 12 through locking ring 14. Preferably, locking ring 14 is made of segments that are held against the upper body 10 by band springs 16 or other biasing member or members. The number and placement of the 5 band springs 16 is variable with the application. In the preferred embodiment the band springs 16 straddle the first projection-depression mating profile 18 that is disposed between the upper body 10 and the locking ring 14. A second projection-depression mating profile 20 is disposed between the locking ring 14 and the lower body 12. Profiles 18 and 20 can take a variety of configurations. Those skilled in the art will appreciate that the greater the number of undulations the smaller the shear load on each 20 undulation. Similarly, the greater the height from valley to peak the smaller the shear load on each undulation. To the extent the locking ring 14 is in segment, the segments can take the full circumference for run in to reduce the shear load on each undulation. While the locking ring 14 is a complete WO 2007/073378 PCT/US2005/046679 sleeve that either expands for release or breaks into segments in response to a radial force, there again the shear load on each undulation is reduced. In fact, any form of locking profile that will resist shear loading can be used for profiles 18 and 20. To hold the profiles 18 and 20 together during run in and to prevent chatter that can cause premature wear, a spring 22 is supported off the lower body 12 to push against sleeve 24 that bears against the upper body 10. A wiper ring 26 prevents debris from reaching cavity 28 where spring 22 resides while letting pressure in passage 30 pass to the back side of expansion sleeve or actuator 32. Along the same lines one or more ports 34 are covered by a flexible ring 36 to handle pressure surges in passage 30 by lifting off ports 34 to equalize pressure on both sides of expansion sleeve 32. [0014] Upper body 10 has a seat 38 to catch an object (not shown) to allow pressure buildup through ports 40. Upper seals 42 have preferably a greater diameter than lower seals 44 so that pressure directed through ports 40 bows out the sleeve 32, as shown in Figure 2a. Since the upper end of the locking ring 14 overlays the expanding portion of sleeve 32, outward movement of sleeve 32 spreads apart profile 18 and narrows any gap in profile 20 with the result being release of the lower body 12 from the upper body 10. The locking ring 14 moves radially a sufficient distance so that a shoulder 46 moves away from shoulder 48 at the lower end of sleeve 32. Since the diameter of seals 42 is greater than seals 44 the pressure entering ports 40 puts a net downward force on sleeve 32 as well as pushing a part of it out to move the locking ring 14 radially outwardly. As soon as shoulder 46 clears shoulder 48 the net downward force moves sleeve 32 down until it lands on travel stop 50, as shown in Figure 3b. In this position, the sleeve 32 prevents the locking ring 14 from moving radially inwardly to reconnect profile 18. In this preferred design, once release occurs the tool is prevented from reconnecting to the run in position. [0015] It should be noted that a rupture disc or equivalent removable barrier 52 is used to open a circulation port if for any reason an emergency circulation path is needed prior to dropping the flow blockage device. A fishing neck 54 on the lower body 12 becomes exposed after tool separation to facilitate fishing out the lower body 12 and anything attached to it, if desired. Seal 56 keeps out annulus pressure and allows 4 WO 2007/073378 PCT/US2005/046679 pressurizing into ports 40 when seat 38 is obstructed. One or more matched flats 58 can be provided where the lower body 12 overlaps upper body 10 to allow torque transmission through the tool when the components are attached as in the run in position shown in Figures lIa-b. [00161 In operation, the tool stays together until an object is dropped to obstruct seat 38. Pressure buildup in passages 40 flex the sleeve 32 radially outwardly to the point where locking ring 14 is forced radially outwardly as well. The profile 18 disengages and shoulder 46 moves radially and clear of shoulder 48 at the lower end of sleeve 32. A net force downwardly exists on sleeve 32 because the diameter of seals 42 exceeds the diameter of seals 44. As a result the sleeve 32 is forced under the now expanded locking ring 14 to prevent band springs 16 from reconnecting profile 18. [0017] An alternative embodiment is shown in Figures 4 and 5. An upper body 60 is connected to a lower body 62 by a locking ring 64 that has a profile 66 to engage the lower body 62 and a profile 68 to engage the upper body 60. One or more band springs 70 bias the locking ring 64 inwardly closing the profile 68. At least one port 72 leads from passage 74 to a piston or actuator 76. Piston 76 has a seal ring 78 and a retainer 80 to hold it in a retracted position shown in Figure 4b. Preferably retainer 80 is a flexible c-ring. Port 82 extends from passage 74 to annular space 84 sealed by locking sleeve 86 and seals 88 and 90. Due to the diameter of seal 88 being larger than the diameter of seal 90 a net downward force is applied to sleeve 86 from pressure in port 82. Pressure in port 72 pushes the piston 76 out against the force of the retainer 80 and forces the locking ring 64 radially outwardly to undo the profile 68 for a release. As that happens sleeve 86 is pushed down and under the locking ring 64 preventing it from moving back in radially. [0018] Other features of this embodiment include a rupture plug or equivalent removable barrier 92 for the same purpose previously stated. A fishing neck 94 and a seal 96 to isolate annulus pressure. A passage 98 is for equalizing pressure surges in passage 74 across the piston 76. A seat 100 catches an object and allows pressure buildup in 5 WO 2007/073378 PCT/US2005/046679 passages 72 and 82. A spring similar to 22 can also be employed in this embodiment for the same purpose. [0019] Those skilled in the art will appreciate the wide application of the present invention to downhole tools of many types. The disadvantage of the prior designs featuring longitudinally shifting pistons that are movable after a shear or breakable element is removed and replaced with an actuating member that moves radially. The piston or actuating member does not need a restraint primarily because of its radial direction of movement. Longitudinal movement of the actuating member is simply precluded from the manner in which the parts are assembled. Pressure surges internally do not cause premature release because the actuator for release is pressure balanced and will not move until the desired time. The engagement between the components against shear forces tending to separate them can be a majority to as much as full 360 degree contact in one or multiple layers such that contact stresses in a particular location are minimized. Lower circumferential contact lengths are also envisioned. A positive lock feature is incorporated to prevent re-engagement of the components once they are released from each other. The radial movement of the actuating member can occur by expansion of a sleeve, radial movement of one or more pistons or by other equivalent structures. Because this movement is radial shock loading from running in and stopping is not an issue as the manner in which the parts are assembled and subsequently move prevents them from actuation under shock loading in an uphole or downhole direction. [0020] While the preferred embodiment has been set forth above, those skilled in art will appreciate that the scope of the invention is significantly broader and as outlined in the claims which appear below. 6