Abstract A screw tightening apparatus comprises a motor-driven screwdriver bit supported on a base for tightening a screw with a torque which is detected as a reactive force acting on the base by a torque detector. An output signal from the torque detector is amplified and delivered to a comparator in which the signal is compared with a signal from a torque setting device which is indicative of a desired torque with which the screw is to be tightened. When the signals agree with each other in the comparator, the latter produces an output signal which is supplied to a switch which in turnde-energizes an electric or pneumatic motor of the screw tightening apparatus. An adjustable time-delay circuit is connected between the comparator and the switch to delay the signal from the comparator for a period of time which may be varied dependent on the material into which the screw is to be driven and the pitch and material of the screw in use. The screwdriver bit is coupled to an output shaft of the motor through an electromagnetic clutch which is de-energizable by the switch simultaneously with the de-energization of the motor.
Inventors
👤 Takashi Mori
👤 Shuuji Hosokawa
👤 Takao Naito
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-11-02 15:29
CPC Classifications
B; B25; B25B; B25B23/00; B25B23/14
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
134 words
A power-driven screwdriver comprising: a base; a motor mounted on said base; a screwdriver bit mounted on said base and rotatably drivable by said motor to tighten a screw with a tightening torque; a torque detector mounted on said base for producing a signal representative of said tightening torque; a torque setting device for generating a signal indicative of a desired tightening torque with which the screw is to be tightened; a comparator for generating a comparator output signal when said torque representative signal is within a range defined by the signal from said torque setting device; a switch responsive to said comparator output signal for de-energizing said motor; and a time-delay circuit interposed between said comparator and said switch for introducing a delay time to said comparator output signal applied to said switch.
Claim 2
Dependent Claim
134 words
A power-driven screwdriver comprising: a base; a motor mounted on said base; a screwdriver bit mounted on said base and rotatably drivable by said motor to tighten a screw with a tightening torque; a torque detector mounted on said base for producing a signal representative of said tightening torque; a torque setting device for generating a signal indicative of a desired tightening torque with which the screw is to be tightened; a comparator for generating a comparator output signal when said torque representative signal is within a range defined by the signal from said torque setting device; a switch responsive to said comparator output signal for de-energizing said motor; and a time-delay circuit interposed between said comparator and said switch for introducing a delay time to said comparator output signal applied to said switch.
Claim 3
Dependent Claim
48 words
A power-driven screwdriver according to claim 1, said motor having an output shaft, further including an electromagnetic clutch coupled between said output shaft and said screwdriver bit and de-energizable by said switch to disconnect said screwdriver bit from said output shaft simultaneously with the de-energization of said motor.
Claim 4
Dependent Claim
31 words
A power-driven screwdriver according to claim 2, said motor comprising an electric motor, further including an electric power supply connected through said switch to said electric motor and said electromagnetic clutch.
Claim 5
Dependent Claim
45 words
A power-driven screwdriver according to claim 2, said motor comprising a pneumtic actuator, further including a source of compressed air connected to said pneumatic actuator and a solenoid-operated valve interposed between said source of compressed air and said pneumatic actuator and de-energizable by said switch.
Claim 6
Dependent Claim
30 words
A power-driven screwdriver according to claim 1, including an analog-to-digital converter for converting said torque representative signal into a digital signal, and a display unit for displaying said digital signal.
Claim 7
Dependent Claim
17 words
A power-driven screwdriver according to claim 1, said time-delay circuit being adjustable to vary said delay time.