Eccentric cones for rock cutting

Abstract

A backreaming assembly having an elongate rotatable tool shaft and a plurality of cutting elements. The tool shaft is disposed on a tool axis and has a first end and a second end. Each cutting element is supported on the shaft in side-to-side relationship. Each cutting element is rotatable with respect to the shaft and with respect to each other. Each cutting element has a center offset from the tool axis.

What is claimed is: 
     
         1 . A tool, comprising:
 an elongate rotatable tool shaft disposed on a tool axis and having a first end and a second end; and   a plurality of cutting elements supported on the shaft in side-to-side relationship, each cutting element rotatable with respect to the shaft and with respect to each other and having a center offset from the tool axis.   
     
     
         2 . The tool of  claim 1  in which each cutting element is rotatable about a bit axis that is not parallel to the tool axis. 
     
     
         3 . The tool of  claim 2  in which each bit axis is tilted by an angle of less than about 30 degrees from parallel relationship to the tool axis. 
     
     
         4 . The tool of  claim 2  in which each bit axis is tilted by an angle of about 3 degrees from parallel relationship to the tool axis. 
     
     
         5 . The tool of  claim 1  in which each cutting element is shaped as a conical frustum and in which cutters are formed on the side walls of the frustum. 
     
     
         6 . The tool of  claim 4 , in which each cutting element has its maximum cross-sectional dimension adjacent the second end of the tool shaft. 
     
     
         7 . The tool of  claim 1  in which the cutting elements are situated intermediate the first and second ends of the tool shaft and in which a threaded connection is formed at the first end of the tool shaft and a towing connection is formed at the second end of the tool shaft. 
     
     
         8 . The tool of  claim 7  in which the towing connection is a towing eye formed on a swivel that is maintained in a non-rotating configuration when the tool shaft is under rotation. 
     
     
         9 . The tool of  claim 1  in which each cutting element is angularly offset about the tool axis relative to its adjacent cutting elements. 
     
     
         10 . The tool of  claim 9  in which the angular spacing of adjacent cutting elements is uniform. 
     
     
         11 . A system comprising:
 the tool of  claim 1 ;   an underground drill stem attached to the tool adjacent the first end of the shaft; and   a product pipe attached to the tool adjacent the second end of the shaft.   
     
     
         12 . A tool, comprising:
 an elongate rotatable tool shaft disposed on a tool axis and having a first end and a second end; and   a plurality of cutting elements supported on the shaft in side-to-side relationship, each cutting element rotatable with respect to the shaft and with respect to each other and having a center offset from the tool axis; and   a product pipe towing connection formed at the second end of the elongate rotatable tool shaft.   
     
     
         13 . The tool of  claim 12  in which the towing connection is maintained in a non-rotating configuration when the tool shaft is under rotation. 
     
     
         14 . The tool of  claim 12  in which each cutting element is shaped as a conical frustum and in which cutters are formed on the side walls of the frustum 
     
     
         15 . The tool of  claim 12  in which each cutting element is angularly offset about the tool axis relative to its adjacent cutting elements. 
     
     
         16 . The tool of  claim 15  in which the angular spacing of adjacent cutting elements is uniform. 
     
     
         17 . The tool of  claim 12  in which each cutting element is rotatable about a bit axis that is not parallel to the tool axis. 
     
     
         18 . The tool of  claim 17  in which each bit axis is tilted by an angle of less than about 30 degrees from parallel relationship to the tool axis. 
     
     
         19 . The system of  claim 12  having a central bore formed in the tool shaft and a radial fluid passage in fluid communication with the central bore formed in each of the cutting elements.