Power-driven screwdriver with a torque control
First Claim
1. 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.
1 Assignment
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Accused Products
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.
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Citations
6 Claims
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1. A power-driven screwdriver comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification
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- Resources
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Current AssigneeMatsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
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Original AssigneeMatsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
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InventorsNaito, Takao, Mori, Takashi, Hosokawa, Shuuji
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Primary Examiner(s)Meister, James M.
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Application NumberUS06/338,996Time in Patent Office693 DaysField of Search173/12, 81/469, 81/470, 73/761US Class Current173/182CPC Class CodesB25B 23/14 Arrangement of torque limit...
