Patent attributes
The hand tool has a chuck with a central axial opening through which bits or other tool elements are selectively moved from a retracted position to an extended operative position. A mechanical element automatically engages the tool element, such that as the tool element reaches its operative position, it is automatically locked in place, such that it cannot be retracted without user intervention to retract the mechanical element and thereby permit retraction of the tool element. In a specific preferred embodiment the mechanical element is at least one pivotally mounted cam, biased to engage the tool element once the tool element is extended to its operative position. A user-operable mechanism such as a collar for example, spring-biased against retraction, is arranged to contact the cam when retracted against the force of the spring, to rotate the cam so that it no longer engages the tool element, thus allowing the tool element to be retracted to its storage position.
