BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective of the slip ring;
FIG. 2 is an elevation view of another embodiment; and
FIG. 3 is a plan view of one row of slots showing the tabs of FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows a unitary, or made of one piece, slip ring 10 in perspective. It features external serrations 12 that are shown as a series of axially spaced rings but other patterns can be used to enhance grip or even random distribution of projections that act as grip enhancers without departing from the invention. The slip ring 10 has opposed ends 14 and 16. A longitudinal axis 18 is shown in the embodiment of FIG. 2. As shown in FIG. 1 a series of openings 20, 22 and 24 are preferably generally aligned with each other in rows and with longitudinal axis 18. Each opening such as 20 is preferably axially aligned and circumferentially spaced from the other openings 20. In the preferred embodiment the openings are equally spaced circumferentially at a given axial location. In the preferred embodiment the other openings 22 and 24 are similarly oriented with regard to like openings adjacent to them. The openings are preferably elongated slots with rounded ends such as 26 and 28 at opposed ends of each opening. While there are three openings 20, 22 and 24 illustrated, other numbers in generally aligned rows are also contemplated. Between rounded ends 26 and 28 are narrow segments 30 that optionally can further feature notches 32 to further weaken them. The operation of the slip ring 10 when expansion occurs from end 14 to end 16 is such that narrow segment 34 will spread first under an expansion force. Segments 34 being at an end can be cut clean through or simply notched at 36 or some combination around the circumference, recognizing that the preferred embodiment has the narrow segments 36 of uniform strength so they will all break or separate at nearly the same rate and at nearly the same time. However when that happens the narrow segments 30, 38 and 40 will still be intact so that the dimensional growth of the slip ring 10 as a swage advances through a tubular that it is mounted to (not shown) is more predictable and uniform. The desired effect is that as the swage advances axially, the segments break with the advancements of the swage so that some structural integrity of the slip ring 10 is maintained during the expansion process. Thus thin segments break in the following order when the expansion progresses from end 14 to end 16: 34, 30, 38, and 40. The reverse order is achieved if the expansion is in the opposite direction.
The overall structure is sounder than the prior designs described above when the slip ring 10 is in storage and not mounted to a tubular or when it is on a tubular and run in the hole. As a result, it is less likely to deform or get damages in storage or during run in. Whereas the prior designs provided resistance to hoop stresses circumferentially only near the opposed ends and only on an alternating basis at opposed ends of elongated elements, the design of FIG. 2 has resistance to hoop stresses along several axially displaced locations between what could be considered elongated elements such as 42 and 44. As a result, the structural integrity is enhances while in storage or during run in but the resistance to expansion is not significantly increased while attaining the benefit of more uniform expansion as the swage is advanced within a tubular on which the slip ring 10 is mounted. While a symmetrical design of elongated slots is illustrated, other opening shapes and arrangements are contemplated if they produce the result of at least retaining part of the integrity of the structure of ring 10 as the expansion takes place. In essence, there need to be narrow or weaker segments properly situated to reduce expansion resistance while leaving the ring 10 some strength to retain its cylindrical shape during storage and run in. FIG. 1 shows using narrow segments and also optionally adding notches like 32.
Other alternatives are seen in FIGS. 2 and 3. Unlike FIG. 1 they are not unitary. FIG. 2 shows half a cylindrical shape that can be held to a mating half with tabs 46 that are preferably aligned axially with narrow segments such as 48 that are for example between elongated slots 50 and 52. The tabs can be of the same or different material than the segments they hold together and can be designed to break at close to the same degree of expansion as the narrow segments 48. As with the variations discussed with regard to FIG. 1 the same discussion applied to the design of FIGS. 2 and 3. Tabs 46 can be integral or mounted to a half section 52 by mechanical, chemical welding or other techniques. They can be an overlay on the inside or outside of the half section 52 or abutting its end. Narrow segments such as 48 in FIG. 2 can also be notched or otherwise weakened, as is illustrated in FIG. 1. This can be applied to some narrow segments or all of them.
While the breaking of the narrow segments 34, 30, 38 and 40 during expansion is contemplated, an elongation without physical disconnection at some to all of said locations is also possible as an alternative. In this respect, the material will stretch within its elastic limit and could experience some plastic deformation short of a physical break.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
Patent Application
20080047704
