Extendable cyclinder, drill head and method

Abstract

The invention relates to an extendable cylinder ( 10 ), in particular an extendable cylinder for a drill head ( 2000 ), a drill head comprising an extendable cylinder, and a method of operating a drill head. The extendable cylinder comprises a shaft ( 100 ) with a shaft ring volume ( 101 ) between an inner part ( 110 ) and an outer part ( 120 ) of the shaft; a piston ( 200 ) with a piston ring volume ( 201 ) between an inner part ( 120 ) and an outer part ( 220 ) of the piston; the piston being moveable with respect to the shaft along a longitudinal axis (LX); a proximal end of the outer part of the piston being arranged between the inner and outer part of the shaft; and a distal end of the inner part of the shaft being arranged between the inner and outer part of the piston; and wherein the extendable cylinder is extendable and/or retractable along the longitudinal axis.

1 . An extendable cylinder for a drill head, comprising:
 a shaft having a shaft ring volume disposed between an inner part and an outer part of the shaft; and   a piston having a piston ring volume disposed between an inner part and an outer part of the piston, the piston being moveable with respect to the shaft along a longitudinal axis, a proximal end of the outer part of the piston being arranged between the inner and outer part of the shaft, and a distal end of the inner part of the shaft being arranged between the inner and outer part of the piston; wherein the extendable cylinder is extendable and/or retractable along the longitudinal axis.   
     
     
         2 . The extendable cylinder according to  claim 1 , wherein the piston and the shaft are connected by a torsionally rigid coupling. 
     
     
         3 . The extendable cylinder according to  claim 2 , wherein the torsionally rigid coupling is realized by a connection of the outer part of the piston and the inner part of the shaft. 
     
     
         4 . The extendable cylinder according to  claim 2 , wherein the torsionally rigid coupling is a spline coupling and/or a latch coupling. 
     
     
         5 . The extendable cylinder according to  claim 1 , wherein the extendable cylinder is extendable and/or retractable by provision of hydraulic fluid to the shaft ring volume and/or the piston ring volume. 
     
     
         6 . The extendable cylinder according to  claim 1 , wherein the proximal end of the outer part of the piston is sealed against the outer part of the shaft, and the proximal end of the inner part of the piston is sealed against the inner part of the shaft. 
     
     
         7 . The extendable cylinder according to  claim 1 , wherein the shaft ring volume and the piston ring volume are in fluid communication with each other, via the coupling between the outer part of the piston and the inner part of the shaft. 
     
     
         8 . The extendable cylinder according to  claim 1 , further comprising an intermediary ring volume located between the outer part of the piston and the outer part of the shaft, wherein the extendable cylinder is retractable by provision of hydraulic fluid to the intermediary ring volume. 
     
     
         9 . The extendable cylinder according to  claim 1 , further comprising at least one force transmission element disposed between the outer part of the piston and the outer part of the shaft for transmitting lateral forces in at least one direction different from a direction parallel to the longitudinal axis. 
     
     
         10 . The extendable cylinder according to the  claim 9 , wherein the at least one force transmission element is a ring-shaped element with an axial extension which exceeds its radial extension by at least a factor of two, and which is form-fitted to the outer part of the piston. 
     
     
         11 . The extendable cylinder according to  claim 1 , further comprising a supply channel forming a central cavity for supplying a fluid to the piston. 
     
     
         12 . The drill head, comprising an extendable cylinder according to  claim 1 ;
 a drive for rotationally driving the shaft of the extendable cylinder;   an extending union arranged to extend and/or retract the extendable cylinder along the longitudinal axis; and   a connector at a distal end of the piston for connecting a functional drill element thereto.   
     
     
         13 . The drill head according to  claim 12 , wherein the extending union is a rotating union in fluid communication with the shaft ring volume and/or the piston ring volume and/or the intermediary ring volume, the rotating union being arranged to provide and/or discharge hydraulic fluid to and/or from the shaft ring volume and/or the piston ring volume and/or the intermediary ring volume. 
     
     
         14 . The method of operating a drill head comprising:
 providing a drill head, the drill head including an extendable cylinder according to  claim 1 ;   connecting a functional drill element to the connector at the distal end of the piston;   rotating the extendable cylinder by rotationally driving the shaft;   extending and/or retracting the extendable cylinder along the longitudinal axis.   
     
     
         15 . The method according to  claim 14 , further comprising removing the functional drill element from the connector and connecting another functional drill element to the connector.