초록 ▼

A sensor, especially for detecting misfeeds in a stream of sheets of paper, comprises a pair of sensing plates sensing changes in the capacitance between the plates, a first oscillator providing an output signal at a frequency representative of the capacitance, a second oscillator set to a reference

A sensor, especially for detecting misfeeds in a stream of sheets of paper, comprises a pair of sensing plates sensing changes in the capacitance between the plates, a first oscillator providing an output signal at a frequency representative of the capacitance, a second oscillator set to a reference frequency which is the same as or close to that frequency generated by the first oscillator when no object is between the sensing plates, gating means to produce an output representative of the frequency difference between the oscillator outputs, a low-pass filter, and a microprocessor which responds to changes in the difference frequency.

대표청구항 ▼

Sheet feeding sensing apparatus for detecting a change in number of at least one sheet and subject to undesirable influences, comprising a pair of spaced parallel sensing plates which are energized to create electric field lines and which define a sensing zone therebetween, feed means to direct a pl

Sheet feeding sensing apparatus for detecting a change in number of at least one sheet and subject to undesirable influences, comprising a pair of spaced parallel sensing plates which are energized to create electric field lines and which define a sensing zone therebetween, feed means to direct a plurality of sheets in succession through said sensing zone, sensing means to sense a parameter of at least one of said sheets when located in the sensing zone, a first oscillator connected to receive the sensed parameter information from the sensing zone and to provide an output signal at a frequency which varies in response to changes in the parameter, a second oscillator set to a reference frequency, said reference frequency being within a predetermined range about the output frequency of said first oscillator which is generated in response to a predetermined steady-state condition in the sensing zone, gating means arranged to receive the outputs of the two oscillators and to provide a signal representative of the frequency difference between said outputs, screening means associated with one of said sensing plates and arranged to reduce disturbance of the electric field lines between the sensing plates caused by said undesirable influences, and processor means arranged to detect and respond to changes in said frequency difference signal.