Abstract:
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.

Description:
PRIORITY INFORMATION 
       [0001]    This application is a divisional application claiming priority from U.S. patent application Ser. No. 11/332,439, filed on Jan. 13, 2006. 
     
    
     FIELD OF THE INVENTION 
       [0002]    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 
       [0003]    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. 
         [0004]    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. 
         [0005]    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. 
         [0006]    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 
         [0007]      FIG. 1A  is a side cross sectional of a first preferred embodiment of the present invention in the untensioned mode. 
           [0008]      FIG. 1B  is a side cross sectional of a first preferred embodiment of the present invention in the tensioned mode. 
           [0009]      FIG. 1C  is an exploded isometric view of the first preferred embodiment of the present invention. 
           [0010]      FIG. 2A  is a side cross sectional of a second preferred embodiment of the present invention in the untensioned mode. 
           [0011]      FIG. 2B  is a side cross sectional of a second preferred embodiment of the present invention in the tensioned mode. 
           [0012]      FIG. 2C  is an exploded isometric view of the second preferred embodiment of the present invention. 
           [0013]      FIG. 3A  is a side cross sectional of a third preferred embodiment of the present invention in the untensioned mode. 
           [0014]      FIG. 3B  is a side cross sectional view of a third preferred embodiment of the present invention in the tensioned mode. 
           [0015]      FIG. 3C  is an exploded isometric view of the third preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    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 . In a preferred embodiment, the central channel defines a longitudinal axis  19 . This embodiment is depicted in  FIGS. 1A ,  1 B and  1 C. This preferred embodiment further comprises a piston member  18  centrally located in the central channel. In the embodiment shown in  FIGS. 1A-1C , the cross sectional area of the conical section decreases as the distance from the upper cylindrical section increases. 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. 
         [0017]    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. As shown in  FIGS. 1A-1C , each of the slip wedges becomes narrower as the distance from the upper cylindrical section increases; In a preferred embodiment, each slip wedge comprises a flat top surface. In another preferred embodiment, each slip wedge comprises an inner surface that is substantially parallel to the longitudinal axis, and an outer surface that is oriented at an acute angle to the inner surface, such that each of the slip wedges becomes narrower as the distance from the upper cylindrical section increases. In another preferred embodiment, the outer surface is substantially parallel to the lower conical section, as shown in  FIGS. 1A-1B . 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  31   a  positioned to form a fluid tight seal between the wedge piston and the body and an inner elastomeric sealing member  31   b  positioned to form a seal between the wedge piston and the piston member. 
         [0018]    This first preferred embodiment of the invention is shown in the untensioned mode in  FIG. 1A  and in the tensioned mode in  FIG. 1B . 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 . 
         [0019]    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. As shown in  FIGS. 1A and 1B , in a preferred embodiment, the fluid flowpath is oriented substantially parallel to the longitudinal axis. 
         [0020]    Another preferred embodiment of the present invention is depicted in  FIGS. 2A ,  2 B, and  2 C. 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. 
         [0021]    This second preferred embodiment of the invention is shown in the untensioned mode in  FIG. 2A  and in the tensioned mode in  FIG. 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 . 
         [0022]    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. 
         [0023]    Another preferred embodiment of the present invention is depicted in  FIGS. 3A ,  3 B, and  3 C. 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. 
         [0024]    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. 
         [0025]    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. As shown in  FIG. 3A , the fluid flowpath comprises an upper region substantially parallel to the central channel and a lower region that is oriented diagonally to the upper region. 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. 
         [0026]    This third preferred embodiment of the invention is shown in the untensioned mode in  FIG. 3A  and in the tensioned mode in  FIG. 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 . 
         [0027]    In another preferred embodiment, the invention further comprises an upper 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  43   a  positioned to form a fluid tight seal between the wedge piston and the body and an inner elastomeric sealing member  43   b  positioned to form a fluid tight seal between the wedge piston and the stud. 
         [0028]    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.