Conveyor band monitoring arrangement

Claim 2

An arrangement for continuously determining the presence of tears and breaks in a conveyor band, comprising, in combination, a plurality of tuned circuits spaced along the length of the conveyor band and moving therewith, each of said tuned circuits being resonant at at least approximately the same frequency; a respective inductive shorting loop connected in parallel with each tuned circuit to short the latter, said inductive shorting loop tuning said tuned circuit and having a first resonant frequency when said loop is continuously conductive, said tuned circuit having a second resonance frequency when said loop is open and nonconductive, the shorting loops being spaced along the length of the conveyor band and moving therewith, each said shorting loop extending transversely of the conveyor band so as to cover at least a part of the width of the band; and stationary circuit monitoring means spaced from the conveyor band so that said plurality of tuned circuits, during operation of the conveyor band, one by one pass by said circuit monitoring means, for producing an electric signal whenever a respective tuned circuit passes by and said shorting loop thereof is open thereby indicating a break or tear in the conveyor band at that position.

Claim 3

The arrangement as defined in claim 1, wherein said circuit monitoring means includes means for producing an alternating current electromagnetic field varying at a frequency at least approximately equal to the resonant frequency of said plurality of tuned circuits, said circuit monitoring means and a respective tuned circuit being electromagnetically coupled together when the latter passes by the former, the former being damped when the shorting loop of the respective tuned circuit is open.

Claim 4

The arrangement as defined in claim 2, wherein said means of said circuit monitoring meanS includes an oscillator of which the frequency is at least approximately the resonant frequency of said plurality of tuned circuits.

Claim 5

The arrangement as defined in claim 3, further including a threshold and switching amplifier, said amplifier being connected to the output of said oscillator for providing said electric signal whenever the output of said oscillator falls due to an open shorting loop.

Claim 6

The arrangement as defined in claim 4, further including switch means connected to the output of said threshold and switching amplifier and operated by said electric signal for shutting down the conveyor and/or turning on a warning signal.

Claim 7

The arrangement as defined in claim 3, wherein said circuit monitoring means further includes means for wobbling the output frequency of said oscillator through a predetermined range of frequencies, which range includes the resonant frequency of said plurality of tuned circuits.

Claim 8

The arrangement as defined in claim 3, wherein said oscillator is a high frequency oscillator.

Claim 9

The arrangement as defined in claim 3, wherein said shorting loops are embedded in the conveyor band.

Claim 10

The arrangement as defined in claim 3, wherein said shorting loops are located on the conveyor band.

Claim 11

The arrangement as defined in claim 1, wherein said plurality of tuned circuits is embedded in the conveyor band.

Claim 12

The arrangement as defined in claim 3, wherein said plurality of tuned circuits is located on the conveyor band.

Claim 13

The arrangement as defined in claim 3, further including switch means operated by said electric signal for shutting down the conveyor and/or turning on a warning signal.

Claim 14

The arrangement as defined in claim 1, wherein each said shorting loop covers at least the major part of the width of the conveyor band.

Claim 15

An arrangement for continuously determining the presence of tears and breaks in a conveyor band comprising, in combination, a plurality of tuned circuits spaced along the length of the conveyor band and moving therewith, each of said tuned circuits being resonant at at least approximately the same frequency; a respective shorting loop connected to each tuned circuit to short the latter, the shorting loops being spaced along the length of the conveyor band and moving therewith, each said shorting loop extending transversely of the conveyor band so as to cover at least a part of the width of the band; stationary circuit monitoring means spaced from the conveyor band so that said plurality of tuned circuits, during operation of the conveyor band, one by one passes by said circuit monitoring means, for producing an electric signal whenever a respective tuned circuit passes by and said shorting loop thereof is open thereby indicating a break or tear in the conveyor band at that position, said circuit monitoring means including means for producing an alternating current electromagnetic field varying at a frequency at least approximately equal to the resonant frequency of said plurality of tuned circuits, said circuit monitoring means and a respective tuned circuit being electromagnetically coupled together when the latter passes by the former, the former being damped when the shorting loop of the respective tuned circuit is open, said means of said circuit monitoring means including an oscillator of which the frequency is at least approximately the resonant frequency of said plurality of tuned circuits, said circuit monitoring means further including means for wobbling the output frequency of said oscillator through a predetermined range of frequencies, which range includes the resonant frequency of said plurality of tuned circuits, said oscillator including a tuned circuit, and said means for wobbling the output frequency of said oscillator including a saw tooth generator and a capacitance diode of which latter the capacity varies in dependence on the voltage across it, said capacitance diode being connected between said tuned circuit of the oscillator and the output of said generatoR so as to vary the resonant frequency of said tuned circuit in dependence on the voltage supplied to said capacitance diode by said saw tooth generator.

Claim 16

An arrangement for continuously determining the presence of tears and breaks in a conveyor band comprising, in combination, a plurality of tuned circuits spaced along the length of the conveyor band and moving therewith, each of said tuned circuits being resonant at at least approximately the same frequency; a respective shorting loop connected to each tuned circuit to short the latter, the shorting loops being spaced along the length of the conveyor band and moving therewith, each said shorting loop extending transversely of the conveyor band so as to cover at least a part of the width of the band; stationary circuit monitoring means spaced from the conveyor band so that said plurality of tuned circuits, during operation of the conveyor band, one by one passes by said circuit monitoring means, for producing an electric signal whenever a respective tuned circuit passes by and said shorting loop thereof is open thereby indicating a break or tear in the conveyor band at that position, said circuit monitoring means including means for producing an alternating current electromagnetic field varying at a frequency at least approximately equal to the resonant frequency of said plurality of tuned circuits, said circuit monitoring means and a respective tuned circuit being electromagnetically coupled together when the latter passes by the former, the former being damped when the shorting loop of the respective tuned circuit is open, said means of said circuit monitoring means including an oscillator of which the frequency is at least approximately the resonant frequency of said plurality of tuned circuits, said circuit monitoring means further including means for wobbling the output frequency of said oscillator through a predetermined range of frequencies, which range includes the resonant frequency of said plurality of tuned circuits, said oscillator including a tuned circuit, and said means for wobbling the output frequency of said oscillator including a saw tooth generator and a capacitance diode of which latter the capacity varies in dependence on the voltage across it, said capacitance diode being connected between said tuned circuit of the oscillator and the output of said generatoR so as to vary the resonant frequency of said tuned circuit in dependence on the voltage supplied to said capacitance diode by said saw tooth generator.

Claim 17

The arrangement as defined in claim 1, wherein said first resonant frequency is higher than said second resonant frequency.