Abstract: A rip detector system having electrically conductive antennae imbeddedly spaced along the direction of movement of the belt and extending from edge to edge of the belt for carrying signals thereacross to detect rips in the belt. The system includes inserts of rubber made electrically conductive by having 10% to 30% by weight of electrically conductive carbon black within the inserts extending from the surface of the belt to a point adjacent the edges of the belt where the antennas are positioned.

Abstract: A circuit for generating plural AC signals, at least two of which may be relatively shifted in phase by a selected amount, includes a frequency divider for dividing the frequency of an AC input signal to derive a first AC signal at a relatively reduced second frequency, and a digital phase shifter responsive to the progress of the frequency divider for producing a second AC signal shifted in phase a selected amount from such first AC signal. The circuit is especially suited for use in a conveyor belt rip detector in which input and output coupling means couple an AC transmitter signal to antennas carried by the conveyor belt and receive an AC transmitter signal transmitted by respective antennas, and a detector monitors such AC signals received by said output coupling means and an AC reference signal to detect the integrity of the conveyor belt, for the circuit of the invention may be used to generate such AC signal and such reference signal relatively shifted in phase by a selected amount.

Abstract: The frequency of the AC signal used to detect the integrity or lack of same in a conveyor belt is reduced to be in the 25 KHz. to about less than 200 KHz. and most preferably in the 50 KHz. to 100 KHz. frequency range. When such AC signals are capacitively coupled to antennas carried by a conveyor belt past a rip detector station, the ratio of the magnitude of such signal relative to that of the cross coupled noise, in particular, and other electrical noise in general is significantly increased. The invention relates to an apparatus and method in which signals in such frequency range are used.

Abstract: Existing conveyor belt rip detection systems presently incorporate a synchronous detector circuit for increasing the rejection of electrical noise. In order for the detector circuit to work at peak efficiency, the input signal occurring when an antenna is over the detector probes must be tuned in phase with the reference signal. The circuit to effect such tuning includes a light emitting diode as an indicator for determining the optimum phase tuning of the oscillator signal through the probes and antennae to a related synchronous detector for achieving maximum signal to noise ratio. A thumb wheel switch is employed to shift the phase of one of the signals with respect to the other to effect the tuning while the light emitting diode is utilized to detect when the thumbwheel switch has shifted the signals into an optimum synchronous relationship.

Abstract: A detection circuit accurately monitors an AC signal, which is pulse modulated by information characteristic or indicative of the integrity of a conveyor belt or the like, to provide a distinguishable output representative of such integrity. Such distinguishable output may be utilized for display purposes and/or for control purposes to stop a ripped conveyor belt.The detection circuit includes a combination circuit of a voltage doubler with high pass filters utilizing full wave rectifiers, RC filters, and a common summing junction. The detection circuit also includes a DC level detector with an automatic gain response adjustment.