Patent Application
20110016998
Common in the downhole drilling and completion arts is the traditional body lock ring. The ring is well known and includes a finely threaded section commonly referred to as “wicker threads” or “wickers” on an inside dimension of the body lock ring that are configured to be engageable with a set of wickers on an outside dimension surface of another component. The body lock ring may be urged along the other component under an applied force to ratchet into a final set position. Because there is a finite distance between adjacent peaks of wicker threads, there is necessarily a potential backlash. In the event that the applied force brings the wickers to very close but not quite the next wicker trough, the device being actuated will relax in backlash by the distance between the wickers. It is possible to reduce backlash by reducing the peak-to-peak distance between adjacent wickers. A reduction in this dimension, however, is often accompanied by a reduction in every tooth dimension including height and flank surface area as well. A reduction in tooth flank surface area tends to reduce the “holding ability” of such flanks. While the backlash is necessarily reduced in this type of construction, the potential for slippage of the body lock so constructed is increased. Since slippage is unquestionably undesirable, wickers with reduced peak-to-peak dimensions are not often the selected solution to the backlash problem.
In some situations the backlash is inconsequential while in others it can be catastrophic to the function of the particular tool or device. For example, if the device is a sealing tool, the backlash may allow sufficient energy in the seal to relax that the seal function is substantially lost. In other devices, while the entire or any substantial part of the functionality may not be lost, it clearly would be better for the ring to retain the input energy than to lose energy. Hence, it is axiomatic that the art would well receive improved apparatus where backlash is reduced or eliminated.
A spiral body lock including a mandrel; a sleeve; and at least one of the mandrel and sleeve including a male component, the other of the mandrel and the sleeve including a recess receptive to the male component at least one of the recess and the male component being helically configured.
A method for maintaining a set force in a tool including imparting an actuation force to a tool including a spiral body lock; spirally advancing the body lock; and converting axial backlash to spiral movement.
A body lock configured to translate axial movement to helical movement, thereby reducing backlash.
Referring now to the drawings wherein like elements are numbered alike in the several Figures:
Referring to
Because each of the recess 20 and male component 16 include wickers 18 and 22, whether the pitch and length and spacing be the same or different, respectively, movement of one relative to the other can be controlled. The wickers 18 and 22 are in one embodiment unidirectional teeth that facilitate movement of the spiral body lock 10 in one direction while inhibiting movement in the opposite direction. The wickers may also be configured to allow movement in either direction in which case such movement would be based upon a threshold force being achieved in that direction. It should also be noted that the sleeve 12 or the mandrel 14 may be the component rotating and that the rotation may be imparted as rotation input or as axial movement input that is translated to rotational movement by the helical or spiral construction.
Returning to direction of movement and whether or not that movement is unidirectionally configured, as one of ordinary skill in the art will clearly appreciate one important direction of movement facilitation will be that of setting a tool, in one iteration. For example, where the downhole tool is a compression set packer, the direction of facilitation of movement is the direction that compresses the packer and the opposite direction would be the direction of release of the compressive force on the packer. This is similar to the prior art insofar as one direction is for setting and the other for unsetting but as noted above the prior art suffers greatly from the backlash associated with the axial distance between adjacent wicker teeth. With the spiral body lock embodiments, because the teeth are arranged in a spiral pattern, and the spiral body lock 10 operates spirally, the actual distance between adjacent teeth is measured spirally and not axially. The effective axial distance between those teeth is accordingly much smaller than that of the prior art. Because of this condition, the backlash experienced by the system in which the spiral body lock 10 is employed is much smaller than what the prior art could have provided. Another way of visualizing the same thing is to stand a stick with graduations on it vertically and provide a distance value to the graduations measured normal to the surface upon which the stick is standing. Then, support the stick at a 45-degree angle to the same surface and measure the distance to the graduations normal to the surface. The distances have become smaller. Consequently, while the actual distance between graduations or wickers is the same, the vertical or axial distance of movement becomes smaller and accordingly so does the relevant backlash.
In the embodiment of
In another embodiment, referring to
It is to be appreciated that while the illustrated embodiment of
In each case, the lock 100 may be actuated by an axial load placed on the sleeve or the mandrel depending upon which component is to be moved toward the tool to be set, tooth direction being appropriate for the selection, or may be actuated by a rotational input, the other considerations remaining the same. In the event that the lock 100 will be axially actuated, a bearing 142 at an uphole end of the device and a bearing 144 at a downhole end of the device allow rotational freedom of the components of the device that must follow the helical path. It is to be appreciated that the term “bearing” is used very generically to indicate any configuration that allows rotational freedom. Upon axial (or rotational) actuation of one of the sleeve 130 or mandrel 134, the teeth or wickers are ratcheted past one another and the tool attached to the lock 100 is set. Upon release of the input load, the teeth or wickers hold and prevent unintended unsetting of the tool attached thereto.
In yet another embodiment, referring to
While preferred embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.
