Patent ID: 8307959

Claim:
In a device having a portion of a shaft mounted for rotation within a housing, the improvement which comprises: a shaft brake adapted to be selectively engaged to prevent rotation of said shaft relative to said housing and adapted to be selectively disengaged to permit rotation of said shaft relative to said housing, said brake including: a collar mounted on said housing by a helical connection for combined axial and rotative movement relative thereto; a first interlock portion mounted on said shaft; an annular member surrounding said shaft and mounted on said housing for axial but not rotative movement relative thereto, said member having a second interlock portion arranged to face toward said first interlock portion; a spring acting between said member and said shaft and urging said second interlock portion to move toward said first interlock portion; and wherein said collar is adapted to be selectively moved relative to said housing between a first position at which said first and second interlock portions are interlocked with one another to prevent rotation of said shaft relative to said housing, and a second position at which said first and second interlock portions are physically separated from one another to permit said shaft to rotate relative to said housing.