Geared roll drive for medical instrument

Abstract

A medical instrument includes a roll mechanism that rotates an instrument shaft. The roll mechanism may include a first gear coupled to the instrument shaft and meshed with a second gear. One of gears may be a spur gear while the other gear may be a beveloid gear. Further, the spur gear and the beveloid gear may be in a gear train containing a compressible gear, e.g., a gear with an inner center piece, an outer ring, and a flexible interconnecting structure between the inner center piece and the outer ring. With a compressible gear, an interference fit of in the gear train may be within manufacturing variations of the gear train, and the compressible gear may deflect radially away from the interference fit.

1 . A medical instrument comprising:
 an instrument shaft; and   a roll mechanism coupled to rotate the instrument shaft, the roll mechanism comprising a first gear coupled to the instrument shaft and a second gear meshed with the first gear;   wherein one of the first gear and the second gear is a beveloid gear.   
     
     
         2 . The medical instrument of  claim 1 , wherein the second gear is the beveloid gear. 
     
     
         3 . The medical instrument of  claim 2 , further comprising:
 a third gear mounted on a common shaft with the second gear; and   a fourth gear meshed with the third gear;   wherein the third gear is a spur gear.   
     
     
         4 . The medical instrument of  claim 3 , wherein the second gear and the third gear are formed as a single monolithic piece. 
     
     
         5 . The medical instrument of  claim 1 , wherein one or both of the first gear and the second gear is a compressible gear. 
     
     
         6 . The medical instrument of  claim 1 , wherein the roll mechanism further comprises:
 an input spindle shaped to engage an actuator, the input spindle having a rotation axis at a non-zero angle relative to a central axis of the instrument shaft; and   a third gear on the input spindle and coupled to rotate the second gear.   
     
     
         7 . The medical instrument of  claim 6 , wherein one or more of the first gear, the second gear, and the third gear is a compressible gear. 
     
     
         8 . The medical instrument of  claim 6 , further comprising:
 a fourth gear that acts as an idler gear between the third gear and the second gear.   
     
     
         9 . The medical instrument of  claim 8 , wherein one or more of the first gear, the second gear, the third gear, and the fourth gear is a compressible gear. 
     
     
         10 . The medical instrument of  claim 8 , further comprising:
 a fifth gear mounted on a common axis with the second gear;   wherein the third gear meshes with the fourth gear; and   wherein the fourth gear meshes with the fifth gear.   
     
     
         11 . The medical instrument of  claim 5 , wherein the compressible gear comprises:
 an inner hub piece;   an outer ring surrounding the inner hub piece; and   a flexible interconnecting member that connects the inner hub piece to the outer ring and allows the outer ring to radially compress inward.   
     
     
         12 . The medical instrument of  claim 1 , wherein teeth of the beveloid gear differ between a toe of the beveloid gear and a heel of the beveloid gear such that variation in an axial position of the second gear does not change a backlash between the first gear and the second gear. 
     
     
         13 . The medical instrument of  claim 1 , wherein teeth of the beveloid gear have a helix angle that accommodates a skew of a shaft of the beveloid gear relative to a shaft of a spur gear meshed with the beveloid gear. 
     
     
         14 . The medical instrument of  claim 1 , wherein the second gear is the beveloid gear, and the first gear is selected from a group consisting of a spur gear, a cylindrical gear, a helical cylindrical gear, and a second beveloid gear. 
     
     
         15 . A mechanism comprising a compressible gear, wherein the compressible gear comprises:
 an inner piece;   an outer ring surrounding the inner piece; and   an interconnecting member that connects the inner piece to the outer ring and allows the outer ring to radially compress inward in response to a force that results from meshing with an adjacent gear.   
     
     
         16 . The mechanism of  claim 15 , wherein the interconnecting member comprises:
 a middle ring;   a plurality of first spokes connecting the inner piece to the middle ring; and   a plurality of second spokes connecting the middle ring to the outer ring, wherein the second spokes are not radially aligned with the first spokes.   
     
     
         17 . The mechanism of  claim 15 , wherein:
 the interconnecting member comprises a plurality of spokes that extend between the inner piece and the outer ring; and   each spoke of the plurality of spokes comprises:
 a first portion attached to the inner piece; 
 a second portion attached to the outer ring; and 
 a cantilever extending circumferentially between the first portion of the spoke and the second portion of the spoke. 
   
     
     
         18 . The mechanism of  claim 15 , wherein the compressible gear is a molded part. 
     
     
         19 . The mechanism of  claim 15 , wherein:
 the mechanism comprises a gear train including the compressible gear;   an interference fit of the compressible gear in the gear train is within manufacturing variations of the gear train; and   flexibility of the outer ring allows teeth of the compressible gear to deflect radially away from the interference fit.   
     
     
         20 . The mechanism of  claim 15 , wherein:
 the outer ring comprises a supported edge and an unsupported edge;   the interconnecting member connects the inner piece to the outer ring only along the supported edge of the outer ring; and   the unsupported edge of the outer ring is radially compressible inward in response to the force that results from meshing with the adjacent gear.   
     
     
         21 . (canceled) 
     
     
         22 . The medical instrument of  claim 1 , further comprising a gear train, the gear train comprising the first and second gears, and one or more gears of the gear train being compressible. 
     
     
         23 . The medical instrument of  claim 22 , the gear train comprising a third gear, the first and second gears being incompressible, and the third gear being compressible.