Screw tensioning device

Abstract

The screw tensioning device comprises a support tube ( 12 ), a cylinder member ( 15 ) and a piston section ( 17 ). The piston section serves for moving a tensioning bolt ( 20 ) screwed onto the thread of a threaded bolt ( 31 ). Provided according to the invention is a depth measuring device ( 35 ), which presents an externally visible indication of the screw-in depth (ET) of the threaded bolt ( 31 ). This ensures that, when the threaded bolt ( 31 ) undergoes extension under strain, there is a threaded engagement with the tensioning bolt ( 20 ) along a sufficiently long distance. This avoids the hazard that the screw tensioning device might break off from the threaded bolt.

1 - 6 . (canceled) 
     
     
         7 . A screw tensioning device for stretching a threaded bolt carrying a nut, said screw tensioning device comprising a support tube and a cylinder member provided in the axial extension of the support tube, said cylinder member surrounding an axially moveable piston section, and comprising a tensioning bolt extending through the piston section and arranged in engagement with the piston section so as to be axially entrained, wherein
 the tensioning bolt comprises an axial channel provided with a depth measurement device for indicating the axial position of the end of the threaded bolt relative to the tensioning bolt.   
     
     
         8 . The screw tensioning device of  claim 7 , wherein the tensioning bolt comprises an axial threaded bore for screwing the threaded bolt thereinto, and that the threaded bore terminates at and end-side edge of the tensioning bolt. 
     
     
         9 . The screw tensioning device of  claim 7 , wherein the depth measuring device comprises a measurement rod arranged to be axially movable in said channel of the tensioning bolt, said measurement rod on one end thereof being provided with an abutment portion and on the other end being provided with a marking adapted to project from a casing of the screw tensioning device. 
     
     
         10 . The screw tensioning device of  claim 9 , wherein the tensioning bolt is provided with a spring biasing the measurement rod toward said second end. 
     
     
         11 . The screw tensioning device of  claim 7 , wherein that the depth measuring device is configured to present an acceptance marking when the end of the threaded bolt has a distance at least equal to D from the abutment face, D being the thread diameter of the threaded bolt. 
     
     
         12 . The screw tensioning device of  claim 7 , wherein that the depth measuring device emits an optical and/or acoustic signal when the screw-in depth of the threaded bolt is in a predetermined range.