Steering system tension control devices

Abstract

A steerable shaft of a medical instrument is steered by one or more control cables. The control cables are in contact with a steering system tension control device that reduces the tension in the control cables caused by bends in the shaft.

1 . A steering system tension control device for a medical instrument having a shaft, comprising: 
 (a) a control cable disposed within the shaft of the medical instrument that is selectively tensioned to steer a tip of the medical instrument, the control cable having a core wire surrounded by an outer sheath; and    (b) a spring disposed to relieve tension in the control cable at a predetermined tension threshold caused by bends in the shaft.    
   
   
       2 . The steering system tension control device of  claim 1 , wherein the spring is a compression spring that relieves tension in the control cable by compressing.  
   
   
       3 . The steering system tension control device of  claim 1 , wherein the spring is disposed to act against a proximal end of the outer sheath.  
   
   
       4 . The steering system tension control device of  claim 1 , wherein the spring is disposed to act against a distal end of the outer sheath.  
   
   
       5 . The steering system tension control device of  claim 1 , wherein the spring is disposed to act against ends in the outer sheath of the cable that are between a proximal end of the outer sheath and a distal end of the outer sheath.  
   
   
       6 . The steering system tension control device of  claim 1 , comprising first and second control cables and first and second springs, wherein the first spring is disposed to act against an end of the outer sheath of the first cable and the second spring is disposed to act against an end of the outer sheath of the second cable.  
   
   
       7 . The steering system tension control device of  claim 1 , comprising first, second, third, and fourth control cables, wherein the spring is disposed to act against the ends of the outer sheaths of the four cables.  
   
   
       8 . The steering system tension control device of  claim 1 , comprising two or more cables, each cable having a core wire surrounded by an outer sheath, wherein the spring is disposed to act against the outer sheath of each of the two or more control cables.  
   
   
       9 . The steering system tension control device of  claim 1 , further comprising a cam follower disposed on the end of the spring, wherein the cam follower is in contact with a cam, wherein rotation of the cam changes the compression of the spring.  
   
   
       10 . The steering system tension control device of  claim 1 , wherein the outer sheath comprises a spiral wound material.  
   
   
       11 . The steering system tension control device of  claim 10 , wherein the spring is formed from the spiral wound material that also forms the outer sheath.  
   
   
       12 . The steering system tension control device of  claim 1 , wherein the spring is coupled to the cable at the core wire of the cable, wherein the spring expands to relieve the tension of the core wire caused by bends in the shaft.  
   
   
       13 . A medical instrument having a steerable shaft, comprising: 
 (a) a shaft having a distal end and a proximal end;    (b) a handle connected to the proximal end of the shaft;    (c) a control cable having an outer sheath and a core wire that is connected to or adjacent a distal location of the shaft such that the distal end of the shaft is oriented in a desired direction by tensioning the core wire of the control cable; and    (d) a spring positioned to relieve the tension of the control cable by being compressed by the tension created in the cable as the shaft of the medical instrument is bent.    
   
   
       14 . The medical instrument of  claim 13 , wherein the spring is disposed to act against a proximal end of the outer sheath of the cable.  
   
   
       15 . The medical instrument of  claim 13 , wherein the spring is disposed to act against a distal end of the outer sheath of the cable.  
   
   
       16 . The medical instrument of  claim 13 , wherein the spring is disposed to act against ends in the outer sheath of the cable that are between a proximal end of the outer sheath and a distal end of the outer sheath.  
   
   
       17 . The medical instrument of  claim 13 , comprising first and second control cables and first and second springs, each cable having a core wire surrounded by an outer sheath, wherein the first spring is disposed to act against an end of the outer sheath of the first cable and the second spring is disposed to act against an end of the outer sheath of the second cable.  
   
   
       18 . The medical instrument of  claim 13 , comprising first, second, third, and fourth control cables, each cable having a core wire surrounded by an outer sheath, wherein the spring is disposed to act against the ends of the outer sheaths of the four cables.  
   
   
       19 . The medical instrument of  claim 13 , comprising two or more cables, each cable having a core wire surrounded by an outer sheath, wherein the spring is disposed to act against the outer sheath of each of the two or more control cables.  
   
   
       20 . The medical instrument of  claim 13 , further comprising a cam follower disposed on the end of the spring, wherein the cam follower is in contact with a cam, wherein rotation of the cam changes the compression of the spring.  
   
   
       21 . The medical instrument of  claim 13 , wherein the outer sheath comprises a spiral wound material.  
   
   
       22 . The medical instrument of  claim 21 , wherein the spring is formed from the spiral wound material that also forms the outer sheath.  
   
   
       23 . The medical instrument of  claim 13 , wherein the spring is coupled to the cable at the core wire of the cable, wherein the spring expands to relieve the tension of the core wire caused by bends in the shaft.  
   
   
       24 . A steering system tension control device for a medical instrument having a shaft and a control cable disposed within the shaft, wherein the control cable includes a core wire surrounded by an outer sheath, comprising a spring disposed to compress by the action of the outer sheath caused by bends in the control cable.  
   
   
       25 . The steering system tension control device of  claim 24 , further comprising a pressure transfer member that receives the outer sheath and allows the core wire to pass through, wherein the pressure transfer member abuts against the spring.  
   
   
       26 . The steering system tension control device of  claim 24 , further comprising a cam system disposed against the spring to change the compression of the spring.  
   
   
       27 . A medical instrument having a steerable shaft, comprising: 
 (a) a control cable having a core wire and an outer sheath surrounding the core wire;    (b) a spring disposed to relieve tension in the control cable by compressing at a predetermined tension threshold caused by bends in the shaft.    
   
   
       28 . The medical instrument of  claim 27 , further comprising a pressure transfer member, wherein the spring and a proximal end of the outer sheath abut against the pressure transfer member from opposite sides.  
   
   
       29 . The medical instrument of  claim 27 , further comprising first and second pressure transfer members, first and second springs, and first and second control cables with first and second core wires and outer sheaths, wherein the first spring and a proximal end of the outer sheath of the first control cable abut against the first pressure transfer member from opposite sides and the second spring and a proximal end of the outer sheath of the second control cable abut against the second pressure transfer member from opposite sides.  
   
   
       30 . The medical instrument of  claim 27 , further comprising a pressure transfer member and first, second, third, and fourth control cables, each cable having a core wire surrounded by an outer sheath, wherein the spring and proximal ends of the outer sheaths of the four cables abut against the pressure transfer member from opposite sides.  
   
   
       31 . The medical instrument of  claim 27 , further comprising a pressure transfer member and two or more cables, each cable having a core wire surrounded by an outer sheath, wherein the spring and proximal ends of the outer sheaths of each of the two or more control cables abut against the pressure transfer member from opposite sides.  
   
   
       32 . The medical instrument of  claim 27 , further comprising a cam follower disposed on the end of the spring, wherein the cam follower is in contact with a cam, wherein rotation of the cam changes the compression of the spring.  
   
   
       33 . The medical instrument of  claim 27 , wherein the outer sheath comprises a spiral wound material.  
   
   
       34 . The medical instrument of  claim 33 , wherein the spring is formed from the spiral wound material that also forms the outer sheath.  
   
   
       35 . The medical instrument of  claim 27 , wherein the spring is coupled to the cable at the core wire of the cable, wherein the spring expands to relieve the tension of the core wire caused by bends in the shaft.