Adjustable tool drive arrangement

A rotatable tool drive assembly having a first axis of rotation for use with a dental handpiece including a drive head having a drive producing rotational torque, the rotatable tool drive assembly comprising:

• a rotatable tool including a tool body having a second axis of rotation coaxial with the first axis of rotation, the tool body having a driven portion with a driven end and a working portion with a working end;
• a sleeve adapted for insertion into the drive assembly;
• a chuck disposed in the sleeve and movable axially relative thereto, the chuck extending between a driven chuck end and a tool receiving end, the chuck including a tool passage receiving the driven portion of the rotatable tool therein, the driven chuck end including a torque key adapted for fitting engagement with the drive and receiving rotational torque therefrom, the driven chuck end defining a first tool seat concentrically supporting the driven end of the rotatable tool, the tool receiving end including at least two retaining arms engaging the driven portion of the rotatable tool and releasably retaining the rotatable tool against axial movement;
• and
• a ram secured to the sleeve directly adjacent the tool receiving end of the chuck, the ram having a central tool opening receiving the driven portion of the rotatable tool therein, the ram defining a second tool seat axially spaced apart from the first tool seat concentrically supporting the driven portion of the rotatable tool at a location intermediate the driven end and the working portion, the ram including at least two lugs extending axially towards the tool receiving end of the chuck, the at least two lugs adapted for engaging the chuck causing the at least two retaining arms to disengage with the driven portion of the rotatable tool in response to moving the chuck toward the ram;
• wherein the first tool seat being axially elongated and concentrically supporting the driven end of the rotatable tool at any position from a maximum insertion depth wherein the rotatable tool is fully inserted into the chuck to a maximum retraction depth wherein the rotatable tool is retracted from the maximum insertion depth and the driven end is still engaged in the first tool seat.