High speed grinding tool

Claim 1

In a portable lightweight angle grinder comprising a motor housing, a motor spindle journaled for rotation in said housing, a rotary air motor in said housing having a fixed stator and a rotor within the stator and mounted on said spindle, said air motor having air inlet and exhaust openings and means for supplying compressed air to the inlet openings, manually operated valve means for controlling the flow of air to the air motor, and outer housing spaced from and carried by said motor housing, a work spindle journaled for rotation in said outer housing, means at the end of the work spindle for detachably mounting the shaft of a cutting or grinding tool, and drive means operably connecting said motor spindle to said work spindle to drive the same, the improvement wherein said drive means comprises a pair of wheels of small diameter and a flexible endless band mounted on the wheels to effect rotation of the work spindle at a speed in excess of 20,000 revolutions per minute, said wheels comprise replaceable upper and lower pulleys with external teeth regularly spaced around the periphery, said band comprises a molded belt of elastomeric material having teeth which mesh with the teeth of said pulleys, an axially elongated tubular extension is provided between said motor housing and said outer housing to support said outer housing, adjustable means are provided for mounting said tubular extension whereby the distance between the motor spindle and the work spindle can be changed to adjust the tension in the belt, said tubular extension is rigidly connected to said outer housing and has a lower end detachably mounted on one end of said motor housing, and screw means for holding said extension in adjusted positions on said motor housing, said tubular extension comprising a muffler housing enclosing said belt and the lower pulley and having a multiplicity of small exhaust openings, said air motor having exhaust passages discharging air to the interior of said muffler housing.