Tool for gripping a pipe or rod

Abstract

A tool for gripping the circumferential outer surface of a pipe or rod and comprising a pair of diametrically opposed arcuate shoes each with a ball cage having a plurality of balls retained by the cage. The shoes have ramped surfaces upon which the balls will run so that when the shoes are rotated about the central longitudinal axis of the pipe or rod the balls become trapped between the ramp surfaces and the surface of the pipe or rod, to grip same. Reverse rotation releases the tool. The rolling action imposed by the balls on the pipe or rod, whilst gripping same, avoids the creation of sharp burrs on the surface of the pipe or rod thus helping to prevent corrosion.

1 . A tool for gripping a pipe or rod, comprising at least one arcuate shoe adapted to contact the circumferential surface of a pipe or rod to be gripped by the tool, the or each arcuate shoe comprising an arcuate body enclosing and retaining a ball/roller cage and having a plurality of ramp surfaces over which a plurality of balls or rollers retained by the ball/roller cage may run upon relative rotational movement of the shoe and the pipe or rod, thus to cause the balls or rollers to become trapped between the ramp surfaces of the shoe and the surface of the pipe or rod, to grip the surface thereof.  
   
   
       2 . A tool according to  claim 1 , wherein a pair of arcuate shoes is provided and located so as to lie in diametrically opposed locations with respect to a pipe or rod to be gripped, thus simultaneously to engage diametrically opposed surface regions thereof.  
   
   
       3 . A tool according to  claim 1 , including a plurality of pairs of arcuate shoes with ramp surfaces directed collectively to cause a pipe or rod to be gripped in opposed directions of rotation of the shoes relative to the pipe or rod.  
   
   
       4 . A tool according to  claim 1 , wherein the or each arcuate shoe has ramp surfaces inclined in two opposed directions to cause a pipe or rod to be gripped selectively in both directions of rotation of the or each shoe relative to the pipe or rod.  
   
   
       5 . A tool according to  claim 1 , wherein the ramp surfaces are flat.  
   
   
       6 . A tool according to  claim 1 , wherein the ramp surfaces are spirally directed relative to a central longitudinal axis of the tool and thus of a pipe or rod to be gripped thereby.  
   
   
       7 . A tool according to  claim 1 , wherein the ball or roller cage of the or each arcuate shoe is spring biased towards a condition in which the balls or rollers are in a non-gripping relationship with a pipe or rod to be gripped.  
   
   
       8 . A tool according to  claim 1 , wherein the ramp surfaces are provided as individual ramps of tear-drop shape.  
   
   
       9 . A tool according to  claim 8 , wherein the ramp surfaces are of reducing width from one end to the other thereof and whose narrower end represents the innermost extremity of the ramp surface at which the associated ball has reached its maximum engagement with the rod.  
   
   
       10 . A tool according to  claim 1 , wherein the tool comprises a pair of diametrically opposed arcuate shoes, only one of which has ramped surfaces, the other serving as a support against which a pipe or rod is forced by the opposed shoe having ramp surfaces.  
   
   
       11 . A tool according to  claim 1 , wherein the or each arcuate shoe encloses a rollercage having a plurality of rollers retained therein upon a corresponding plurality of ramp surfaces.