Tools – Wrench – screwdriver – or driver therefor – Responsive to torque on work
Patent
1988-09-28
1989-12-19
Smith, James G.
Tools
Wrench, screwdriver, or driver therefor
Responsive to torque on work
173 12, B25B 2351
Patent
active
048874990
ABSTRACT:
The instant invention relates to a power screwdriver with torque limiter, with a drive unit and a secondary transmission, with an output shaft for the attachment of a keyed bit. According to the invention the drive unit is a pneumatic motor (2) with a compressed-air intake (13) and a compressed-air outlet (14), whereby the differential pressure between the compressed-air intake (13) and the compressed-air outlet (14) (measuring circuits 19 and 20) is taken as the measure of the torque produced by the power screwdriver (1). The differential pressure is measured in a differential pressure measuring device (21) and the measure signal is transmitted to a control unit (23). The control unit (23) contains a comparator unit which compares the measured differential pressure signal with a set value of differential pressure (adjusting potentiometer 24) and transmits a switching signal to a switch unit (solenoid valve 19) to switch off the power screwdriver when the compared values become equal. In this manner a simple calculation of torque is achieved by means of a differential pressure measurement in combination with a simple switch-off possibility. In further embodiments the rotational speed of the pneumatic motor is usedr additionally in the determination of torque.
REFERENCES:
patent: 3939920 (1976-02-01), Hardiman et al.
patent: 4023627 (1977-05-01), Clapp et al.
patent: 4081037 (1978-03-01), Johnson
patent: 4552041 (1985-11-01), Coyle, Sr.
patent: 4631992 (1986-12-01), Eckman
Flint Cort
Smith James G.
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