Patent ID: 6471106
Filing Date: 2002-10-29
Classification: B25C

Abstract:
A device for discharging fastening elements comprising:a body having a location at which the fastening elements are discharged; and a sensor circuit supported by the body, the sensor circuit including a conductive coil proximate the location and further including: a capacitive element connected in parallel with the conductive coil so that the capacitive element and the conductive coil form a resonant tank circuit; a frequency detector connected to the resonant tank circuit, the frequency detector detecting a frequency of oscillation of the resonant tank circuit as affected by a material proximate the conductive coil and outputting a frequency signal indicative thereof; an oscillator having an output terminal and a control terminal, wherein the output terminal is connected to the resonant tank circuit, wherein the oscillator drives the resonant tank circuit at the resonant frequency of the resonant tank circuit as affected by the material proximate the conductive coil; an amplitude control circuit coupled to the oscillator, the amplitude control circuit receiving an electrical signal from the output terminal and in response generating a control signal that is provided to the control terminal of the oscillator; and a processor that receives the frequency signal and an additional signal that is functionally related to the control signal, wherein the processor provides an output signal that prevents the device from discharging at least one of the fastening elements when the processor determines that the frequency signal and the additional signal indicate that the material proximate the conductive coil is a particular material into which the fasteners should not be discharged.