US3656137A

US3656137A - Conveyor band monitoring arrangement

Info

Publication number: US3656137A
Application number: US878374A
Authority: US
Inventors: Walter Ratz
Original assignee: Bergwerksverband GmbH
Current assignee: Bergwerksverband GmbH
Priority date: 1968-11-22
Filing date: 1969-11-20
Publication date: 1972-04-11
Anticipated expiration: 1989-04-11
Also published as: AT292553B; JPS5032514B1; FR2023843A1; BE740536A; FR2023843B1; DE1810387A1; GB1234315A; CH502935A

Abstract

An arrangement for monitoring the operating condition of conveyor bands by providing them with conductive loops spaced along the conveying path of the band. Each of the conductive loops short-circuits a respective tuned circuit which can transmit through a receiver situated outside of the conveyor. When a conductive loop ceases to short circuit the tuned circuit because of a tear, for example, the receiver emits a signal directed to a warning circuit and/or a control circuit through which the drive of the conveyor may be stopped. The tuned circuit is comprised of a capacitor and inductor connected in parallel, and the receiver frequency is wobbled to compensate for any variations in the characteristics of the electrical components, for maintaining the monitoring equipment in operation under such variations in the circuit components.

Description

United States Patent Ratz [151 3,656,137 [4 1 Apr. 11,1972

[54] CONVEYOR BAND MONITORING ARRANGEMENT [72] Inventor: Walter Ratz, Gelsenkirchen, Germany {73] Assignee: Bergwerksverband GmbH, Essen, Germany [22] Filed: Nov. 20, 1969 [21] Appl. No.: 878,374

[30] Foreign Application Priority Data Nov. 22, 1968 Germany ..P 18 10 387.2

US. Cl. ..340/259, 340/258 C 2,932,382 4/1960 James ..340/259X Primary ExaminerJohn W. Caldwell Assistant Examiner-Michael Slobasky Attorney-Michael S. Striker 5 7] ABSTRACT An arrangement for monitoring the operating condition of conveyor bands by providing them with conductive loops spaced along the conveying path of the band. Each of the con ductive loops short-circuits a respective tuned circuit which can transmit through a receiver situated outside of the conveyor. When a conductive loop ceases to short circuit the tuned circuit because of a tear, for example, the receiver emits a signal directed to a warning circuit and/or a control circuit through which the drive of the conveyor may he stopped. The tuned circuit is comprised of a capacitor and inductor connected in parallel, and the receiver frequency is wobbled to compensate for any variations in the characteristics of the electrical components, for maintaining the monitoring equipment in operation under such variations in the circuit components.

15 Claims, 1 Drawing Figure i emu CONVEYOR BAND MONITORING ARRANGEMENT BACKGROUND OF THE INVENTION Monitoring arrangements for conveyor bands serve for sensing longitudinal tears in conveyor bands, through the application of electrical signals by which a warning signal may be transmitted and/or the conveyor bands may be immediately stopped from operating.

Arrangements of the preceding species are known in the art, in which closed conductive loops are inserted in the conveyor band, and every conductive loop is associated with a voltage source. A transmitter, furthermore, is associated and fed with such voltage source, and the transmitter has a frequency which differs from the frequency of the current flowing through the conductive loop. A transmitter operates in conjunction with a stationary receiver situated outside the conveyor band. Such an arrangement is considerably complex.

Accordingly, it is an object of the present invention to provide a simple monitoring arrangement in which only conductive loops are inserted into the conveyor band. The arrangement is such that the fabrication of the conveyor bands, in this manner, is significantly simplified, and the conveyor bands can be readily monitored in operation.

The monitoring arrangement of the present invention consists of conductive loops which extend for the entire width of the band and are inserted in the conveyor band. A high frequency tuned circuit is, furthermore, short-circuited by each one of the conductive loops in the conveyor band, and this tuned circuit is also inserted in the conveyor band. A stationary monitor outside of the conveyor band is located within the electromagnetic operative region of the tuned circuit in or on the conveyor band. When the tuned circuit is not short-circuited by the conductive loop, the monitor is actuated, and the driving motor for the conveyor band may be correspondingly controlled by, for example, stopping operation and thereby holding the conveyor band stationary. At the same time, the actuation of the monitor may be used to produce a warning signal.

A high frequency oscillator serves as the electrical monitor, and comprises a capacitor and an inductance which constitute a tuned circuit. Thisoscillating circuit in the monitoring unit, is damped by the high frequency tuned circuit in the conveyor band, as soon as a tear in the short-circuiting loop opens the circuit and permits, thereby, both tuned circuits to be in mutal each other. This feature is based on the condition that both tuned circuits are tuned to the same frequency. The amplitude of the voltage signal fromthe oscillator decreases, thereby, and as a result of being applied to a switching amplifier, a relay is used to disconnect the motor which drives the conveyor, when this amplitude drops below a predetermined level. At the same time, the actuation of the relay may be used to actuate further a warning arrangement. Electrical monitoring units may be advantageously placed at where the conveyor band turns; however such monitoring units or further monitoring units may also be placed along the length of the band.

In accordance with a preferred embodiment of the present invention, the frequency of the oscillator circuit is wobbled in the conventional manner, by approximately plus or minus l percent of its nominal frequency. Assurance is thereby had that even when the resonent frequency of the tuned circuit in the conveyor band deviates from the designated frequency, the desired coupling or influence between the tuned circuit of the conveyor band and that of the monitoring unit outside of the conveyor band is maintained. In this manner, the feature is also achieved that even when the characteristics of the electrical components vary, the tuned circuits, which mutually act on each other when the conductive loop is open, will always be in resonance.

SUMMARY OF THE INVENTION An arrangement for monitoring the operability of conveyor bands. Conductive loops are spaced along the band and traverse the entire width of the band. These conductive loops short-circuit respective tuned circuit comprised of a capacitor and inductor. One tuned circuits is provided for each conductive loop. External to the conveyor is a receiver tuned to the frequency of the tuned circuits. Whenever one of the conductive loops is opened through, for example, a tear in the conveyor band, the receiver provides a signal to either a warning circuit or a control circuit, which stops the conveyor from moving further. The frequency of the receiver is wobbled in order to compensate for any changes in characteristics of the electrical components used in the tuned circuits.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims.

The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING A functional schematic diagram showing a portion of the conveyor band with conductive loops installed thereon for the purpose of detecting any tears in the conveyor band through interaction between the tuned circuits on the band and a receiver outside of the band, in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, a conveyor band I has regularly spaced tuned circuits 18 located in proximity of one of its conveyor band edges. These tuned circuits are selectively spaced from each other by, for example, 25 meters, and consist of the capacitor 2 and the inductance 3. These elements are shortcircuited through the conductiveloops 4 which extend for. the entire width of the conveyor band.

When a short-circuiting loop 4 becomes destroyed or tom, the tuned circuit 18 acts upon a tuned circuit 19 arranged outside of the conveyor band and is electromagnetically coupled with the tuned circuit 18 The tuned circuit 19, which consists of a capacitor 5 andinductance 6, determines the frequency of the oscillator 7. The inductance 6 forms the monitoring head which, when the shorting loop 4 is open, interacts with the inductance on the conveyor band, when an inductance 3 passes by the inductance 6. The electromagnetic coupling between the tuned circuits 18 and 19 damps the latter, reducing the amplitude of the output of the tuned circuit 19. This amplitude becomes measured with the: aid of a diode 17, and the signal is then applied to a threshold and switching amplifier 8. When the voltage amplitude of this signal drops below a predetermined level, the amplifier 8 actuates, in a known manner, the coil of a relay 9 which, in turn, operates the switch 10 associated with the relay to turn on a warning signal and/or to turn off the conveyor band. The warning signal device and/or the conveyor motor control are connected to the terminals 11 and 12. To ensure that the arrangement of the invention functions properly when the resonant frequency of the tuned circuits 18 or 19 changes, the output voltage of a saw tooth generator 13 is connected by a decoupling resistor 14 and by a high frequency bypass capacitor 15 to a capacitance diode 16, this output voltage, so changing the capacitance of the latter that the oscillator 7, the frequency of which is determined by the tuned circuit 19, is also influenced by the capacitance of the capacitance diode 16 so as to wobble the oscillator frequency through a certain range. Asa result of this feature, it is assured that even though variations take place in the characteristics of the elements 2 or 3 on the conveyor band 1, the resonant frequency of the oscillating circuit 18 is determined by the oscillator 7.

It will be understood that each of the elements described above, or ,two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in conveyor band monitoring arrangement, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended 1. 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.

2. 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,

3. 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.

4. 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.

5. 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.

6. 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.

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

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

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

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

11. The arrangement as defined in claim 3, wherein said pluralifi lof tuned circuits is located on the conve or band. I

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

13. 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.

14. 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.

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

Claims

1. 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.

2. 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.

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

12. 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.