Torque limiting wrench

Claim 2

A power tool having a motor, an output shaft for transmitting rotation to a tool bit; and a torque-limiting assembly comprising adjustable torque transmitting means with a driving member, a co-axial driven member, a helical spring frictionally connecting said driving member and said driven member, the wire size of the spring varying from end-to-end, means for adjusting the position of said spring axially, and automatic shut-off means for interrupting the supply of power to said motor.

Claim 3

A manually operable power tool having a motor, means for manual control of power to said motor, automatic shut-off means for interrupting the supply of power to said motor, a torque-limiting assembly for transmitting torque to the output shaft of said tool, said torque-limiting assembly comprising a driving spindle connected to the output of said motor, a driven spindle co-axial with and abutting said driving spindle, said driven spindle connected to said output shaft, and a helical spring frictionally connecting said driving member and said driven member, said torque-limiting assembly having means for operating said automatic shut-off means.

Claim 4

A manually operable power tool having a motor, means for manual control of power to said motor, automatic shut-off means for interrupting the supply of power to said motor, a torque-limiting assembly for transmitting torque to the output shaft of said tool, said torque-limiting assembly comprising a driving spindle connected to the output of said motor, a driven spindle co-axial with and abutting said driving spindle, said driven spindle connected to said output shaft, and a helical spring frictionally connecting said driving member and said driven member, said torque-limiting assembly having means for operating said automatic shut-off means.

Claim 5

The power tool of claim 2, in which said helical spring cross-sectional area uniformly increases in size from one end towards the other.

Claim 6

The power tool of claim 3 in which means is provided for adjusting axially the position of said helical spring connecting said driving member and said driven member.

Claim 7

The power tool of claim 4 wherein said means for adjusting the position of said helical spring comprises a threaded adjusting nut.

Claim 8

A manually operable power tool comprising a motor, operator control means for control of power to said motor, automatic shut-off means for interrupting the supply of power to said motor, said shut-off means remaining operable after initial automatic actuation until interruption of power by said operator control means, after which said automatic shut-off means resets for the next cycle of operation, an adjustable torque-limiting assembly for transmitting torque to the output shaft of said tool, said torque-limiting assembly comprising a driving spindle, connected to the output of said motor, a driven spindle co-axial with and abutting said driving spindle, said driven spindle being connected to said output shaft, a helical spring frictionally coupling said driving spindle and said driven spindle and being axially adjustable along said driving and driven spindles, said helical spring cross-sectional area increasing from the end over the output spindle towards the other end of said spring; and means connecting said torque-limiting assembly and said automatic shut-off means, whereby said torque-limiting assembly actuates said automatic shut-off means upon attaining the pre-set limit of torque.

Claim 9

A manually operable power tool comprising a motor, operator control means for control of power to said motor, automatic shut-off means for interrupting the supply of power to said motor, said shut-off means remaining operable after initial automatic actuation until interruption of power by said operator control means, after which said automatic shut-off means resets for the next cycle of operation, an adjustable torque-limiting assembly for transmitting torque to the output shaft of said tool, said torque-limiting assembly comprising a driving spindle, connected to the output of said motor, a driven spindle co-axial with and abutting said driving spindle, said driven spindle being connected to said output shaft, a helical spring frictionally coupling said driving spindle and said driven spindle and being axially adjustable along said driving and driven spindles, said helical spring cross-sectional area increasing from the end over the output spindle towards the other end of said spring; and means connecting said torque-limiting assembly and said automatic shut-off means, whereby said torque-limiting assembly actuates said automatic shut-off means upon attaining the pre-set limit of torque.

Claim 10

The power tool of claim 6 wherein said helical spring is axially adjusted by a torque adjusting nut enclosing said helical spring.

Claim 11

The power tool of claim 6 wherein said helical spring is wound so that increasing resistance to rotation tends to loosen said spring coils on said driven spindle.