Drive system for interconnecting attachment devices and handheld rotary power tools

A drive system for releasably interconnecting a motor shaft of a rotary hand held power tool and an input shaft of an attachment device that is mounted thereon, said system comprising:

• an elongated flexible drive shaft connected to the input shaft of the attachment device, said flexible drive shaft having an outer end portion with a non-circular cross-section configured to engage a complementarily shaped cavity of an output shaft operatively attached to the power tool motor shaft;
• an elongated output shaft operatively connected to the motor shaft of the power tool, said output shaft having a generally cylindrical outer configuration along its length and having a rearward mounting portion for attachment to said motor shaft, an intermediate portion having said complementarily shaped cavity for receiving said flexible drive shaft and a forward portion with an enlarged concentric opening for receiving and guiding the outer end portion of said flexible drive shaft into said cavity during mounting the attachment device on the power tool;
• wherein:
• the rotary tool comprises an elongated housing with a nose portion having an opening concentric for accessing said output shaft, the nose portion including a transition portion with an inclined outer surface extending radially inwardly toward the motor shaft and a generally cylindrically shaped wall extending from the transition portion concentrically and forwardly and having a plurality of screw threads formed in an outer surface of the wall,
• the attachment device has a screw threaded collar rotatably attached thereto for mounting the attachment device to the nose portion of the power tool, wherein the collar is screwed onto the screw threads of the wall of the nose portion to secure the same thereto, the outer end portion of said flexible drive shaft extending forwardly of the attachment device a distance sufficient to enter said enlarged concentric opening of said forward portion of said output shaft before the collar is screwed onto the screw threads of the wall of the rotary tool;
• and
• said intermediate portion has an outside diameter that is larger than the outside diameter of said threaded outside surface and said mounting portion has an outside diameter that is larger than the outside diameter of said intermediate portion to form an annular shoulder at the interface between said portions, said system further comprising a bearing having inner and outer races, said inner race of which fits on said outside surface of said intermediate portion and bears against said shoulder, said outer race of which fits within an inside surface of said cylindrically shaped wall, said bearing providing stability countering side forces applied to said output shaft.