Apparatus for tightening threaded fasteners

Abstract

According to a first aspect of the invention we provide an apparatus for coupling a shank of a threaded fastener and a torque device including: —a first coupling member having an external surface portion defined by more than two steps that forms a taper; a second coupling member having an inversely tapered internal surface portion non-rotatably engagable with the tapered external surface of the first coupling member; wherein the steps of the first coupling member and the second coupling member are shaped either as angled cylinders, frustums of an angled stepped cone or frustums of an angled curved solid; and wherein the diameters of the steps of the first coupling member and the second coupling member are less than the diameter of the shank. Advantageously, this aspect of the invention allows for an increased load bearing surface area between the coupling members without increasing the overall diameter of the apparatus; a three dimensional load bearing surface area rather than a conventional two dimensional plane; more efficiently and evenly distributed load stress distribution over the load bearing surface area; higher torsion strength; and apparatus with lower mass, dimensions and volume.

What is claimed is: 
     
         1 . An apparatus for coupling a shank of a threaded fastener and a torque device including:—
 a first coupling member having an external surface portion defined by more than two steps that forms a taper; 
 a second coupling member having an inversely tapered internal surface portion non-rotatably engagable with the tapered external surface of the first coupling member; 
 wherein the steps of the first coupling member and the second coupling member are shaped either as angled cylinders, frustums of an angled stepped cone or frustums of an angled curved solid; and 
 wherein the diameters of the steps of the first coupling member and the second coupling member are less than the diameter of the shank. 
 
     
     
         2 . An apparatus according to  claim 1  wherein the steps of the first coupling member and the second coupling member are shaped as solids not limited to particular step quantities, dimensions, geometries, angles and/or intervals. 
     
     
         3 . An apparatus according to  claim 1  wherein the internal surface portion of the second coupling member substantially surrounds the external surface portion of the first coupling member. 
     
     
         4 . An apparatus according to  claim 1  wherein the first coupling member is non-rotatably engagable with an action portion of the torque device. 
     
     
         5 . An apparatus according to  claim 1  wherein the second coupling member, when rotated by an action portion of the torque device, applies a load to the threaded fastener. 
     
     
         6 . An apparatus according to  claim 1  wherein the first coupling member is formed on a reaction shaft of the torque device and wherein the second coupling member is formed on the shank of the threaded fastener. 
     
     
         7 . An apparatus according to  claim 6  wherein the first coupling member is formed as an axial protrusion and wherein the second coupling member is formed as an axial bore. 
     
     
         8 . An apparatus according to  claim 1  wherein the first coupling member is formed on a shank of the threaded fastener and wherein the second coupling member is formed on a reaction shaft of the torque device. 
     
     
         9 . An apparatus according to  claim 8  wherein the first coupling member is formed as an axial bore and wherein the second coupling member is formed as an axial protrusion. 
     
     
         10 . An apparatus according to  claim 1  having an infinite number of steps such that the external surface portion of the first coupling member is smoothly tapered and the inversely tapered internal surface portion of the second coupling member is smoothly tapered. 
     
     
         11 . A system for fastening objects including a combination of a torque power tool either pneumatically, electrically, hydraulically or manually driven and a threaded fastener having an apparatus according to either  claim 1 - 10 .