Self Locking Tensioner

FIELD OF THE INVENTION

[0001] The present invention is directed to a self locking tensioner that can be used to place a piston or stud in tension. The present invention is directed to a tensioner comprising slip wedges positioned between a piston and a body which houses the piston and the slip wedges.

BACKGROUND OF THE INVENTION

[0002] Prior art tensioners typically apply hydraulic forces to tension a stud. Prior art hydraulic tensioners typically involve the use of a nut which must be positioned on the stud while hydraulic pressure is applied. In many applications using a remotely operated vehicle ("ROV"), it is inconvenient to use a tensioner which requires simultaneous positioning of the stud and application of hydraulic pressure.

[0003] Prior art tensioners comprising hydraulic nuts require an extra operation to hold the stretched stud. For subsea applications where remotely controlled ROV manipulator arms are used to tension such nuts, this extra operation increases the difficulty of using such tensioners.

[0004] The present invention provides a self locking tensioner, which may be tensioned using hydraulic pressure, and which has greater position setting flexibility than do prior art hydraulic tensioners. In another embodiment, the present invention provides a tensioner comprising a fluid operated nut that will automatically hold whatever position the nut is stretched to without an extra operation, as discussed above.

[0005] In one preferred embodiment, the present invention provides for tensioning or detensioning of a piston or stud in whatever increment of tensioning or detensioning is desired. The term "detensioning" as used herein, means movement of a tensioned member to reduce the magnitude of tensile force on the member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure IA is a side cross sectional of a first preferred embodiment of the present invention in the untensioned mode.

[00071 Figure IB is a side cross sectional of a first preferred embodiment of the present invention in the tensioned mode.

[0008] Figure 1C is an exploded isometric view of the first preferred embodiment of the present invention.

[0009] Figure 2A is a side cross sectional of a second preferred embodiment of the present invention in the untensioned mode.

[0010] Figure 2B is a side cross sectional of a second preferred embodiment of the present invention in the tensioned mode.

[0011] Figure 2C is an exploded isometric view of the second preferred embodiment of the present invention.

[0012] Figure 3A is a side cross sectional of a third preferred embodiment of the present invention in the untensioned mode.

[0013] Figure 3B is a side cross sectional view of a third preferred embodiment of the present invention in the tensioned mode.

[0014] Figure 3C is an exploded isometric view of the third preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A first preferred embodiment of the present invention is directed toward a tensioner comprising a body 10 comprising a central channel 12 comprising an upper cylindrical section 14 and a lower conical section 16. This embodiment is depicted in Figures IA, IB and 1C. This preferred embodiment further comprises a piston member 18 centrally located in the central channel. The piston member comprises a longitudinal shaft 20 and a top region 22 comprising an upper lip 24. In a preferred embodiment, the invention further comprises an elastomeric sealing member 29 positioned to form a fluid tight seal between the piston member and the body.

[0016] This preferred embodiment further comprises at least two slip wedges 26 extending into the conical section of the central channel adjacent to the piston and a wedge piston 28 mounted above the slip wedges in the central channel. In a preferred embodiment, each slip wedge comprises a flat top surface. In another preferred embodiment, the wedge piston comprises a flat bottom surface. In yet another preferred embodiment, a wedged piston is mounted above each slip wedge. In another preferred embodiment, the invention

comprises an outer elastomeric sealing member 31a positioned to form a fluid tight seal between the wedge piston and the body and an inner elastomeric sealing member 31b positioned to form a seal between the wedge piston and the piston member.

[0017] This first preferred embodiment of the invention is shown in the untensioned mode in Figure IA and in the tensioned mode in Figure IB. The wedge pistons 28 and the slip wedges 26 move downward as this embodiment of the invention is placed in the tensioned mode. As the slip wedges move downward into the conical section of the central channel, they exert a tensile or tensioning force on piston member 18.

[0018] This preferred embodiment of the invention further comprises a first fluid flowpath 30 extending through the upper lip to a pressurization region 32 of the upper cylindrical section above the wedge piston. In one preferred embodiment, the fluid flowpath is adapted to receive hydraulic fluid. In another preferred embodiment, the fluid flowpath is adapted to receive a gas.

[0019] Another preferred embodiment of the present invention is depicted in Figures 2A, 2B, and 2C. This preferred embodiment comprises the body, piston member, two slip wedges, wedge piston, and first fluid flowpath, as described above. Additionally, the second preferred embodiment comprises a spring 36 inserted between each slip wedge and the piston member, and a second fluid flowpath 38 extending through the piston to a region between a slip wedge and a wedge piston. The spring facilitates detensioning of the piston member. In a preferred embodiment, the second fluid flowpath is radially opposite the first fluid flowpath.

[0020] This second preferred embodiment of the invention is shown in the untensioned mode in Figure 2A and in the tensioned mode in Figure 2B. The wedge pistons 28 and the slip wedges 26 move downward as this embodiment of the invention is placed in the tensioned mode. As the slip wedges move downward into the conical section of the central channel, they exert a tensile or tensioning force on piston member 18.

[0021] This preferred embodiment of the invention further comprises a seal 35 located in the body below the lower conical section. This seal is positioned in a sealing relationship between the piston member and the body. In a preferred embodiment, the seal is elastomeric.

[0022] Another preferred embodiment of the present invention is depicted in Figures 3A, 3B, and 3C. This preferred embodiment comprises the body 10, comprising a central

channel 12 which, comprises an upper cylindrical section 14 and a lower conical section 16, as described above. This preferred embodiment further comprises a stud 40 which is centrally located in the central channel. The stud comprises a longitudinal shaft 42 and a top region 44. This preferred embodiment further comprises a nut 46 which is integral with the stud and located within the central channel.

[0023] This preferred embodiment further comprises at least two slip wedges 26 extending into the conical section of the central channel and a wedge piston 28 mounted above the slip wedges in the central channel. In a preferred embodiment, each slip wedge comprises a flat top service. In yet another preferred embodiment, the wedge piston comprises a flat bottom surface.

[0024] The invention further comprises a fluid flowpath 30 extending through the stud to a pressurized region 32 of the upper cylindrical section, above the wedge piston. In one preferred embodiment, the fluid flowpath is adapted to receive hydraulic fluid. In another preferred embodiment, the fluid flowpath is adapted to receive a gas.

[0025] This third preferred embodiment of the invention is shown in the untensioned mode in Figure 3 A and in the tensioned mode in Figure 3B. The wedge pistons 28 and the slip wedges 26 move downward as this embodiment of the invention is placed in the tensioned mode. As the slip wedges move downward into the conical section of the central channel, they exert a tensile or tensioning force on stud 40.

[0026] In another preferred embodiment, the invention further comprises an elastomeric sealing member 41 positioned to form a fluid tight seal between the stud and the body. In another preferred embodiment, the invention further comprises an outer elastomeric sealing member 43a positioned to form a fluid tight seal between the wedge piston and the body and an inner elastomeric sealing member 43b positioned to form a fluid tight seal between the wedge piston and the stud.

[0027] The foregoing disclosure and description of the inventions are illustrative and explanatory. Various changes in the size, shape, and materials, as well as in the details of the illustrative construction and/or an illustrative method may be made without departing from the spirit of the invention.