Adjustable dental tool drive arrangement

Abstract

The invention relates to an improved dental tool drive arrangement for a hand-piece with a drive head, the tool drive arrangement permitting length adjustment of the tool in the drive head by concentrically supporting the tool in the drive head at any position from a fully inserted position to a maximum retracted position. The tool drive arrangement preferably includes a tool and a rotatable tool supporting element for concentrically supporting the tool from the fully inserted to the maximum retracted position, the tool preferably including a maximum retraction indicator for indicating to a user when the tool has been retracted to the maximum retraction position. This provides a significant advantage over the prior art by allowing a user to adjust the exposed length of a rotatable tool, preferably a dental bur, without exceeding safe operating limits. The invention also relates to an improved drive spindle which allows depth adjustment of a tool in a dental handpiece while maintaining efficient torque transfer and concentricity during high speed rotation.

1 - 52 . (canceled) 
   
   
       53 . A rotatable tool drive assembly for use with a dental or medical handpiece having a drive head with an axis of rotation, the assembly comprising:
 a rotatable tool; and   a tool drive arrangement for releasably supporting the tool, the tool drive arrangement being insertable into the drive head for coaxial rotation in the drive head; the tool having a tool body with an axis of rotation, a driven portion with a driven end for insertion into the tool drive arrangement and a working portion for projecting from the drive head during use; the tool drive arrangement having a tool passage for coaxially receiving the driven portion of the tool at different insertion depths, the tool passage including a first tool seat for concentrically supporting the driven end of the tool and a second tool seat for concentrically supporting the driven portion of the tool at a location intermediate the driven end and the working portion; the first tool seat being axially elongated for concentrically supporting the driven end at any position from a maximum insertion depth wherein the drive end is fully inserted into the tool passage to a maximum retraction depth wherein the tool is retracted from the maximum insertion depth and the drive end is still engaged in the first tool seat.   
   
   
       54 . The rotatable tool drive assembly of  claim 53 , wherein the tool includes a maximum retraction indicator for indicating to a user when the tool has been retracted to the maximum retraction depth. 
   
   
       55 . The rotatable tool drive assembly of  claim 54 , wherein the tool drive arrangement includes a drive spindle for being fittingly received in a drive spindle socket of the drive head, the drive spindle having a drive torque receiving portion for receiving drive torque from the drive head, a tool supporting portion connected with the drive torque receiving portion and having the tool passage with first and second tool seats, the drive spindle further including a tool retaining member for releasably retaining the driven portion in the tool passage; and the axial length of the first tool seat being selected for the tool retaining member to engage the driven portion at any position of the tool from the maximum insertion position to the maximum retraction position. 
   
   
       56 . A rotatable dental tool for use in a tool drive arrangement having a tool passage for coaxially receiving the tool and including first and second tool seats for concentrically supporting the tool, the first tool seat being axially elongated for concentrically supporting the tool at different insertion depths, the tool comprising:
 a tool body having an axis of rotation, the tool body divided into a driven portion with a driven end for insertion into the tool passage of the tool drive arrangement and a working portion with a working end for projection from the tool drive arrangement during use; and a maximum retraction indicator on the driven portion for indicating to a user when the tool is retracted from the supporting portion to a maximum retraction depth wherein the drive end is only partially inserted in the first tool seat.   
   
   
       57 . The tool of  claim 56 , wherein the maximum retraction indicator is a mechanical indicia located on the driven portion for engagement by a portion of the tool supporting element when the maximum retraction depth is reached. 
   
   
       58 . The tool of  claim 57 , wherein the mechanical indicia is a stop on the driven portion for mechanical interaction with the supporting element when the tool is retracted to the maximum retraction depth. 
   
   
       59 . The tool of  claim 56 , for use in an air turbine driven handpiece. 
   
   
       60 . The tool of  claim 59 , wherein the tool is a dental bur. 
   
   
       61 . The rotatable tool drive assembly according to  claim 53 , wherein the tool drive arrangement is a drive spindle comprising:
 a torque receiving element for receiving rotational torque from the drive;   a tool supporting element connected with the torque receiving element and having the tool passage for receiving the driven portion of the tool coaxial with an axis of rotation of the spindle; and   a tool retaining member connected to the tool supporting element for releasably engaging the driven portion of the tool to releasably retain the tool in the supporting element; whereby in the maximum retracted position at which the tool is retracted from the maximum insertion depth and the drive end is still engaged in the first tool seat, the tool retaining member still engages the driven portion.   
   
   
       62 . The drive spindle of  claim 61 , wherein the axial length of the first tool seat is 7 mm. 
   
   
       63 . A drive spindle for rotatably supporting a tool in a dental handpiece having a rotational torque generating drive, the tool having a body divided into a driven portion with a driven end for insertion into the handpiece and a working portion for extending from the handpiece during use, the drive spindle comprising:
 a driving element for receiving drive torque from the torque generating drive;   a tool supporting element connected with the driving element and having a tool passage for receiving the driven portion of the tool coaxial with an axis of rotation of the spindle, the tool passage including a first tool seat for supporting the driven end of the tool and a second tool seat for supporting the driven portion at a location intermediate the driven end and the working portion; the first tool seat having an axial length for concentrically supporting the driven end when the tool is retracted from a maximum insertion depth at which the driven portion is fully inserted into the tool passage to a reduced insertion depth at which the tool retaining member still engages the driven portion; the driving element being a generally cylindrical sleeve for receiving the driven portion of the tool and the supporting element being a chuck coaxial with the sleeve; and   a tool engaging member for releasably engaging the driven portion to releasably retain the tool in the tool passage between an engagement depth at which depth the contact between the tool engaging member and the driven portion is initiated and the maximum insertion depth; the tool engaging member being positioned in the spindle for engagement of the driven portion of the tool at a location closer to the working portion than the driven end.   
   
   
       64 . The drive spindle of  claim 63 , wherein the tool engaging member is located on an inner surface of a wall portion of the chuck, the wall portion being expandable upon insertion of the driven portion, such that insertion of the driven portion into the bore forces the wall portion to expand radially outward, the expanded wall portion applying force radially inward against the driven portion such that the tool engaging member frictionally engages the driven portion for torque transfer and to prevent axial movement of the driven portion relative to the chuck. 
   
   
       65 . The drive spindle of  claim 63 , wherein the tool engaging member comprises one or more protrusions extending radially inward from the inner surface of the wall portion, the tool engaging member either continuously or discontinuously extending annularly about the axis of rotation. 
   
   
       66 . The drive spindle of  claim 64 , wherein the wall portion further comprises a pair of diametrically opposed axial retaining arms and wherein a portion of the tool engaging member is located on an inner surface of one or both of the retaining arms extending into the bore. 
   
   
       67 . The drive spindle of  claim 66 , wherein the retaining arms are formed by two semi-circular wall portions of the chuck separated by axial slits. 
   
   
       68 . The drive spindle of  claim 66 , wherein the tool engaging member is a tab or a discontinuous annularly extending ridge. 
   
   
       69 . The drive spindle of  claim 63 , further comprising a ram axially aligned with and adjacent to the chuck in the drive spindle, the ram operatively engaging the chuck in a torque transfer arrangement. 
   
   
       70 . The drive spindle of  claim 69 , wherein the torque transfer arrangement consists of a pair of diametrically opposed lugs for engaging the axial slits in the adjacent wall portion of the chuck. 
   
   
       71 . The drive spindle of  claim 63 , wherein the ram is fitted into the sleeve for drive torque transfer from the sleeve to the ram. 
   
   
       72 . The drive spindle of  claim 63 , wherein the chuck is in direct contact with the drive for torque transfer to rotate the tool in the handpiece. 
   
   
       73 . The drive spindle of  claim 63 , further comprising a locking socket of non-circular cross-section for engaging a complementary non-circular cross-sectional portion of the driven portion to lock the tool against rotation in the drive spindle, and a tool aligning member positioned in the tool receiving bore near a tool insertion end of the drive spindle for aiding in pre-alignment of the locking portion with the locking socket, the tool aligning member being complementary in shape and orientation with the locking socket.