Expansion tool for cold expansion of holes

Abstract

A tool ( 10 ) for cold expansion of holes comprises a body ( 14 ) which has at least a cylindrically shaped part ( 16 ) having an inner hole ( 24 ) in axial direction of the body ( 14 ). The body ( 14 ) comprises along the circumferential direction a plurality of members ( 18, 18 a , 18 b , 18 c ) which are movable in radial direction of the body ( 14 ), such that the outer diameter of the cylindrically shaped part ( 16 ) of the body ( 14 ) can be changed. Furthermore a core ( 26, 26 c ) is provided which is insertable into the inner hole ( 24 ), wherein at least one of the core ( 26, 26 c ) and the inner hole ( 24 ) comprises a portion ( 28 ) of changing diameter and the inner hole ( 24 ) and the core ( 26, 26 c ) get into contact with each other upon insertion of the core, such that in dependency of the depth of the insertion of the core ( 26, 26 c ) into the inner hole ( 24 ) in axial direction the members ( 18, 18 a , 18 b , 18 c ) move radially outwardly and the outer diameter of the cylindrically shaped part ( 16 ) of the body ( 14 ) increases.

1 . A tool for cold expansion of holes, comprising
 a body comprising at least a cylindrically shaped part having an inner hole in axial direction of the body, wherein the body further comprises along its circumferential direction a plurality of members which are movable in radial direction of the body, such that the outer diameter of the cylindrical part of the body can be changed; and   a core, which can be inserted into the inner hole, wherein at least one of the core or the inner hole comprises a portion having changing diameter and the inner hole and the core get into contact with respect to each other upon insertion of the core, such that in dependency of the insertion depth of the core into the inner hole in axial direction the members move in radial direction outwardly and the outer diameter of the cylindrical part of the body increases.   
     
     
         2 . The tool according to  claim 1 , wherein the inner hole has a conically tapering shape in insertion direction of the core. 
     
     
         3 . The tool according to  claim 1 , wherein the core has a conically tapering face as a contact face. 
     
     
         4 . The tool according to  claim 1 , further comprising an elastical bias configured to bias the members of the body into a position, in which said members assume a minimal diameter. 
     
     
         5 . The tool according to  claim 4 , wherein the elastic bias is an elastic cap or ring member, that encompasses the body from outside. 
     
     
         6 . The tool according to  claim 1 , wherein the cylindrical part of the body has a circular cross section. 
     
     
         7 . The tool according to  claim 1 , further comprising a means for monitoring the insertion depth of the core into the inner hole. 
     
     
         8 . The tool according to  claim 7 , wherein the means for monitoring the insertion depth comprises a thread at the core, and a thread at a device for relatively positioning the core and the body in axial direction. 
     
     
         9 . The tool according to  claim 1 , wherein separation lines of the members of the cylindrically shaped part run through a longitudinal axis of the cylindrical part. 
     
     
         10 . The tool according to  claim 9 , wherein the cylindrical part is evenly split in a plurality of members, which form in their positions of minimal diameter a closed cylinder contour as outer contour. 
     
     
         11 . The tool according to  claim 1 , wherein the cylindrical part is formed by members of different shape, which form in their position of maximal diameter a closed cylinder contour as outer contour. 
     
     
         12 . The tool according to  claim 11 , wherein contact surfaces of the members are at an angle with respect to the radial direction of the cylindrical part. 
     
     
         13 . The tool according to  claim 1 , wherein the inner hole and the core have a polygonal cross section in a direction perpendicular to the longitudinal axis. 
     
     
         14 . The tool according to  claim 13 , wherein the polygonal cross-section has a square shape. 
     
     
         15 . The tool according to  claim 13 , wherein the body is formed of a number of members corresponding to the number of sides of a polygonal shape of the inner hole and the core, such that a planar surface of each member corresponds to one surface of the polygonal shape of the inner hole. 
     
     
         16 . The tool according to  claim 1 , wherein said members are slidable from an initial configuration into an expanded configuration, said members being separated by gaps in said expanded configuration. 
     
     
         17 . The tool according to  claim 16 , wherein, in said expanded configuration, outside surfaces of said members define collectively a circle interrupted by said gaps, said circle having a diameter greater than an initial diameter of said cylindrical part in said initial configuration. 
     
     
         18 . The tool according to  claim 1 , further comprising a cap configured to position the body and the core with respect to each other in an initial position with respect to an axial direction of said tool.