Gripping or clamping mechanisms

Abstract

A clamping mechanism having two or more jaws ( 1, 2 ) which may be opened to allow a tubular ( 5 ) to be introduced within the jaws and closed to retain the tubular ( 5 ) therewithin. Rollers 4 are located within concave recesses 3 and maintained in spaced apart relationship by biasing means 6 . Rotation of tubular 5 may cause the rollers 4 to be wedged between a wall of the recess and tubular 5 to grip tubular 5 within jaws 1 and 2 . The clamping mechanism may be utilised as an oil field tubular clamp, a slip, a pipe clamp etc. There is also disclosed a clutch comprising an outer race 33 , a cage 34 and an inner ring 35 . Recesses 36 are provided in outer race 33 and accommodate rollers 37 therewithin maintained in spaced apart relationship by cage 34 . Cage 34 may be moved by an actuator to selectively allow free wheeling or prevent rotation in one or other direction. A socket ratchet 44 incorporating such a clutch is also disclosed.

1 . A clamping mechanism including: a plurality of jaws which may be moved apart to allow an object to be positioned within the jaws and moved together to substantially encompass the object; and a plurality of rollers retained about the mouths of the jaws between the jaws and the object, the arrangement being such that when the jaws are closed about an object, rotation of the rollers against the object enclosed within the jaws may cause the rollers to move into positions in which they are wedged between the jaws and the object so that the object is gripped by the clamping mechanism.  
     
     
         2 . A clamping mechanism as claimed in  claim 1  wherein the jaws are pivotally connected together at a proximal end of each jaw and secured together by locking means at the distal ends thereof.  
     
     
         3 . A clamping mechanism as claimed in  claim 2  wherein the distal ends of the jaws have interengaging fingers and the locking means consists of pin sections passing through adjacent apertures in the fingers when engaged.  
     
     
         4 . A clamping mechanism as claimed in  claim 1  wherein the jaws are opened and closed by driving means causing lateral separation and closure.  
     
     
         5 . A clamping mechanism as claimed in  claim 1  wherein the jaws are opened and closed by one or more hydraulic ram.  
     
     
         6 . A clamping mechanism as claimed in  claim 1  including three or more pivotably connected jaws lockable at distal ends thereof.  
     
     
         7 . A clamping mechanism as claimed in  claim 6  wherein further jaw sections are insertable between the jaws.  
     
     
         8 . A clamping mechanism as claimed in  claim 6  wherein the proximal ends of two jaws are pivotally connected to a handle and arranged so that rotation of the handle relative to the jaws draws the distal ends of the jaws together.  
     
     
         9 . A clamping mechanism as claimed in  claim 1  wherein the rollers consist of a plurality of cylindrical rollers circumferentially spaced apart about the mouths of the jaws.  
     
     
         10 . A clamping mechanism as claimed in  claim 9  wherein the axis of the cylindrical rollers are substantially parallel with the axis of the mouths of the jaws.  
     
     
         11 . A clamping mechanism as claimed in  claim 1  wherein a plurality of concave recesses are provided about the circumference of the mouths of the jaws which accommodate gripping elements.  
     
     
         12 . A clamping mechanism as claimed in  claim 11  wherein the concave recesses are substantially V-shaped.  
     
     
         13 . A clamping mechanism as claimed in  claim 1  wherein the rollers are retained by positioning means which is movable relative to the jaws by actuation means.  
     
     
         14 . A clamping mechanism as claimed in  claim 13  wherein the positioning means is formed in a plurality of sections corresponding to the jaw sections.  
     
     
         15 . A clamping mechanism as claimed in  claim 1  wherein the rollers have an asymmetric cross section along an axis parallel to the mouths of the jaws.  
     
     
         16 . A clamping mechanism as claimed in  claim 1  comprising two jaws having semi-circular jaw mouths which are off-set in a closed position having rollers of progressively different sizes provided adjacent the jaw mouths to define a substantially cylindrical opening to receive a tubular member.  
     
     
         17 . A clamping mechanism as claimed in  claim 1  wherein the rollers are disposed transversely to the axis of the mouth of the jaws.  
     
     
         18 . A clamping mechanism as claimed in  claim 17  wherein the rollers are circumferentially spaced apart within a plurality of axially spaced apart circumferential groves.  
     
     
         19 . A clamping mechanism as claimed in  claim 18  wherein the rollers are retained by a cage which is axially movable by actuation means to selectively position the rollers adjacent walls of the grooves.  
     
     
         20 . A clamping mechanism as claimed in  claim 19  wherein the jaws have a tapered outer profile which is accommodated within a body having a tapered bore.  
     
     
         21 . A clamping mechanism as claimed in  claim 17  wherein the clamping mechanism is a slip.  
     
     
         22 . A clamping mechanism as claimed in  claim 1  suitable for gripping a downhole tubular.  
     
     
         23 . A clamping mechanism as claimed in  claim 1  wherein the rollers taper axially from a relatively narrow end to a relatively wide end; and the jaws together define a cam surface which is shaped so as to urge the rollers against the object, when in use, when the rollers translate axially with respect to the cam surface, and which is also shaped so as to urge the rollers against the object when the rollers roll along the cam surface.  
     
     
         24 . A method of clamping an object with a clamping mechanism, the method including: moving a plurality of jaws apart; positioning the object within the jaws; moving the jaws together to substantially encompass the object; and rotating a plurality of rollers against the object enclosed within the jaws so as to cause the rollers to move into positions in which they are wedged between the jaws and the object so that the object is gripped by the clamping mechanism.  
     
     
         25 . A method according to  claim 24  wherein the object is a downhole tubular.  
     
     
         26 . Gripping apparatus comprising a plurality of rollers which taper axially from a relatively narrow end to a relatively wide end; and a body having a cam surface which is shaped so as to urge the rollers against a gripped member, when in use, when the rollers translate axially with respect to the cam surface, and which is also shaped so as to urge the rollers against the gripped member when the rollers roll along the cam surface.  
     
     
         27 . Apparatus according to  claim 26  further comprising an actuator for generating relative movement between the rollers and the cam surface to urge the rollers against the gripped member.  
     
     
         28 . Apparatus according to  claim 27  wherein the actuator is configured to generate relative axial movement between the rollers and the cam surface.  
     
     
         29 . Apparatus according to  claim 27  wherein the actuator is configured to generate relative rolling movement between the rollers and the cam surface.  
     
     
         30 . Apparatus according to  claim 27  wherein the actuator engages the rollers.  
     
     
         31 . Apparatus according to  claim 27  wherein the actuator comprises a plurality of resilient members, each coupled with a respective roller.  
     
     
         32 . Apparatus according to  claim 26  wherein the angle of taper of the rollers is approximately constant along the length of the rollers.  
     
     
         33 . Apparatus according to  claim 26  wherein the rollers are substantially circular in cross-section.  
     
     
         34 . Apparatus according to  claim 26  wherein the rollers are substantially frustoconical.  
     
     
         35 . Apparatus according to  claim 26  wherein the direction of taper of the rollers alternates between successive rollers.  
     
     
         36 . Apparatus according to  claim 26  wherein the cam surface is formed with a plurality of recesses, each recess receiving a respective roller.  
     
     
         37 . Apparatus according to  claim 26  wherein the body comprises a plurality of jaws which can be moved apart to allow the gripped member to be positioned within the jaws and moved together to substantially encompass the object.  
     
     
         38 . Apparatus according to claims  26 , wherein the rollers are spaced axially with respect to each other.  
     
     
         39 . Apparatus according to  claim 26  wherein the rollers are arranged in two or more axially spaced rows.  
     
     
         40 . Apparatus according to  claim 26  suitable for gripping a downhole tubular.  
     
     
         41 . Apparatus according to  claim 40  wherein the apparatus is a power tong for gripping and rotating the downhole tubular.  
     
     
         42 . Apparatus according to  claim 40  wherein the apparatus is a backup for gripping and securing the downhole tubular against rotational movement.  
     
     
         43 . Apparatus according to  claim 40  wherein the apparatus is an elevator for securing the downhole tubular against axial and rotational movement.  
     
     
         44 . Apparatus according to  claim 26  wherein the body comprises two or more jaws which can be moved apart to admit the gripped member.  
     
     
         45 . A socket wrench comprising gripping apparatus according to  claim 26 .  
     
     
         46 . A method of handling a downhole tubular, the downhole tubular having an elastic deformation limit, the method comprising gripping the tubular with a plurality of gripping members arranged circumferentially around the pipe; and transferring rotational and/or longitudinal forces to or from the tubular, wherein the tubular is gripped in such a manner so as not to exceed the elastic deformation limit of the tubular while the forces are being transferred.  
     
     
         47 . The method of  claim 46  further comprising the step of urging the gripping members against the tubular by a wedging action.  
     
     
         48 . The method of  claim 46  wherein the gripping member comprises a roller.  
     
     
         49 . The method of  claim 46  wherein the roller is tapered.  
     
     
         50 . The method of  claim 46  further comprising the step of coupling the downhole tubular to an additional length of downhole tubular.  
     
     
         51 . The method of  claim 46  wherein the maximum deformation of the tubular lies in a range greater than 10% of the elastic limit of the tubular and less than 100% of the elastic limit of the tubular.  
     
     
         52 . The method of  claim 46 , comprising gripping the tubular with three or more gripping members.  
     
     
         53 . The method of  claim 46 , wherein the gripping members are metallic.  
     
     
         54 . A method of handling a downhole tubular comprising gripping the tubular with a plurality of rollers arranged circumferentially around the tubular; and transferring rotational and/or longitudinal forces to or from the tubular.  
     
     
         55 . The method of  claim 54  wherein the rollers are tapered.  
     
     
         56 . The method of  claim 54  further comprising the step of coupling the downhole tubular to an additional length of downhole tubular.  
     
     
         57 . The method of  claim 54 , comprising gripping the tubular with three or more rollers.  
     
     
         58 . The method of  claim 54 , wherein the rollers are metallic.  
     
     
         59 . Apparatus for gripping a downhole tubular comprising a plurality of rollers; and a body having a cam surface which is shaped so as to urge the rollers against a downhole tubular, when in use, when the rollers roll along the cam surface.