JPH045136B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention automatically detects vertical tears that occur during operation of a conveyor belt used for transporting ore, lime, coal, etc. without contacting the belt. This invention relates to a device that tests whether the device is functioning normally during operation.

Prior Art and Problems In conveyor belts that transport ore, lime, coal, etc., vertical cracks may occur due to the sharp edges of the ore, etc. The tear develops over the entire length of the belt, not only hindering the conveying function of the conveyor in question, but also
This makes the entire belt unusable.
Therefore, it is desirable to detect and repair longitudinal tears as soon as possible, but it is impossible to constantly monitor longitudinal tears with the naked eye in belts that are several hundred meters or more in length. Therefore, there is a need for a device that automatically detects vertical tears in conveyor belts, and various devices have been developed and devised in the past.

A plurality of loop coils are buried in the width direction of the belt at predetermined intervals in the longitudinal direction of the belt, and a detection end equipped with a detection coil that electromagnetically couples with the loop coils is arranged opposite to the conveyor belt, and when the belt is normal, the loop coils are shot rings. When a belt tears vertically, the loop coil breaks and becomes a mere open conductor, so one example is a device that uses the change in impedance of the detection coil that is electromagnetically coupled to it to detect whether the belt is normal or abnormal based on the change. It is.

FIG. 1 is a schematic diagram showing the conveyor belt 10 made of rubber or the like, 12 a reinforcing steel cord, and 14 the loop coil. a
is a schematic plan view, and b is a cross-sectional view of the same. As shown in cross-sectional view b, the steel cord 12 and the loop coil 14 are buried in different layers, and the former is the belt surface on which loads such as ore are placed. side, the latter is placed on the back side of the belt. A plurality of steel cords 12 extend linearly in the longitudinal direction of the belt, and are arranged at approximately equal intervals in the width direction of the belt. The loop coil 14 is a one-turn or multiple-turn short-circuit coil with a winding axis oriented perpendicular to the belt surface, and the rectangular coil extends over substantially the entire width of the belt. Although only two loop coils 14 are shown in FIG. 1, they are actually arranged at a predetermined pitch (for example, 30 m) in the belt length direction.
A large number of them are buried. The reinforcing steel cord 12 and the loop coil 14 are electrically insulated.

FIG. 2 shows a state in which a load 16 is conveyed by such a conveyor belt 10. 18 and 20 are pulleys. 22 is a detection end equipped with a detection coil,
This detection coil serves as the primary winding of the transformer, and the loop coil serves as the secondary winding of the transformer, and disconnection of the loop coil due to vertical tearing of the belt is detected as a change in impedance of the detection coil.

There is a method to detect the impedance change of the detection coil by its magnitude, that is, Z = R + jX, which is √ ² + ² , but it is better to detect it by the change in phase angle φ = tan ^-1 Accurate detection unaffected by interval fluctuations becomes possible. This method was previously proposed by the applicant (Japanese Patent Application No. 181463, 1983).
The method is summarized as follows. FIG. 3 shows the impedance change characteristics of the detection coil, where the horizontal axis shows the resistance change ΔR and the vertical axis shows the reactance change. Vector V ₁ indicates the impedance change ΔZ = ΔR + jΔX when the detection coil faces the loop coil 14 when the belt is normal,
V ₁ ′ is the case when the distance between the detection coil and the loop coil becomes large, and V ₁ ″ is the case when the distance becomes even larger. The vector V ₂ faces the portion of the belt 10 other than the loop coil 14. _The phase angle clearly differs from the vector V ₁ due to the impedance change of the detection coil when the loop coil 14 is disconnected. There is almost no difference.

Therefore, we monitor the change in the phase angle of the impedance of the detection coil, and at the position where the loop coil should be,
V ₁ , V ₃ outside the above position means the belt is normal, and V ₂ at the position where the loop coil should be (this is
If it is the same as V ₃ ), it can be determined that the belt is longitudinally torn. These vectors can be easily calculated by shifting the whole so that V ₂ and V ₃ match the vertical axis, and monitoring the horizontal axis, that is, whether there is a resistance component.
It is possible to identify whether V ₁ is V ₂ or V ₃ . In addition, if the loop coil 14 is inserted into the belt 10 at regular intervals and the belt speed is constant, the vector V ₁ will appear at a constant cycle. Therefore, a retriggerable monomulti is prepared, and it is inserted into the belt ₁₀ at regular intervals. When triggered, if the belt is normal, the mono-multi is repeatedly triggered at a certain period and does not change the output state, but in places where there is a vertical tear, it is not triggered and changes the output state, so it is possible to detect a vertical belt tear. . Of course, longitudinal tearing of the belt may be detected by separately detecting the position of the loop coil of the belt and checking whether the vector is _V1 at that position. This phase angle method has the great advantage of not being affected by variations in the distance between the belt and the detection coil.

Incidentally, although vertical tearing of conveyor belts may occur frequently, it is generally an extremely rare accident.
The vertical tear detection device that monitors this needs to operate stably over a long period of time. However, there are generally limits to the reliability of devices that are made up of a large number of parts.
The vertical tear detection device is no exception. Therefore, it is desired to develop a means to conduct regular functional tests and easily check whether or not the device is operating normally.

Conventionally, there has been no simple means of testing the functionality of vertical tear detection equipment during its service life, and testing has only been carried out using methods that require specialized knowledge of the equipment, such as observing signal waveforms in each part of the equipment, and thus have not been performed manually. ,
For economic reasons, the interval between functional tests has to be one to two years, so when a vertical tear occurs, the vertical tear detection device happens to be out of order and does not issue an alarm.
There have been cases where unforeseen circumstances have arisen.

OBJECTS OF THE INVENTION The invention can therefore be tested during service life very simply and without requiring any expertise regarding the equipment. The present invention aims to provide a functional test device for a belt longitudinal tear detection device.

Structure of the Invention The present invention provides a conveyor belt in which a plurality of loop coils that extend in the width direction of the belt and are disconnected when the belt is longitudinally torn are buried in the longitudinal direction of the belt, and a detection end equipped with a detection coil is arranged to face the loop coil. In a functional test device for a device that detects longitudinal tearing of a belt by an impedance change caused in a detection coil due to electromagnetic coupling of The device is characterized in that it is provided with a drive mechanism that is inserted between the end and the end to break the electromagnetic coupling, and is moved back from the drive mechanism to restore the electromagnetic coupling.This will be described below with reference to embodiments.

Embodiments of the invention FIGS. 4 and 5 show embodiments of the invention,
The same parts as in FIGS. 1 and 2 are given the same reference numerals. 24 is a shielding plate that connects the belt 10 and the detection end 2.
2 as shown by the dotted line to break the electromagnetic coupling between the loop coil and the detection coil, and retreat to the solid line position to restore the electromagnetic coupling. 2
6 is a motor, rack and pinion mechanism 28, fulcrum 3
The shielding plate is inserted and removed via a lever 30 that rotates around 0a.

The detection end 22 of the vertical tear detection device is equipped with a detection circuit 32, a monomulti 34, and a gate circuit 36 as shown in FIG.
And so on. The detection circuit 32 detects the aforementioned vector V ₁
This circuit detects ΔR and ΔX components by detecting the phase of the voltage proportional to the coil impedance generated in the detection coil, a constant current source that drives the detection coil, and a detector disclosed in the above-mentioned application. ,
A circuit such as a phase rotation circuit that shifts the phase and extracts only the resistance change component can be used, but other circuits may of course be used. The retriggerable monomulti 34 is triggered by the vector V ₁ detection output S ₁ and produces a pulse output S ₂ of a predetermined width T. FIG. 6 illustrates these pulses. The predetermined width T is
The value is selected depending on the generation cycle of the vector _V1 detection output _S1 . Therefore, if the belt is normal, the output _S2 of the monomulti 34 is retriggered one after another before it falls, maintaining the H (high) level output, but if a vertical tear in the belt or a loop coil break occurs, the broken loop coil Since there is no detection output S ₁ for the vector V ₁ , the monomulti 34 lowers the output S ₂ to the L (low) level after the predetermined time period has elapsed, and this becomes the vertical tear detection output.

The gate circuit 36, timer 38, etc. are used when the conveyor is started. That is, even if the conveyor drive motor (not shown) is powered on and the conveyor is started, the conveyor operating speed is not immediately reached, so the loop coil detection time interval, that is, the period of the output _S1 of the detection circuit 32, is large. Yes, Mono Multi S ₁
Even if the output _S2 is triggered to the H level, it will be dropped to the L level after a time period T, and there is a possibility that the vertical tear detection output will be temporarily generated. In this circuit, the gate 36 is closed during the time τ from the start of the conveyor belt until it reaches the operating speed, so that the vertical tear detection output is not generated. That is, when the conveyor drive motor is started, the contact 40 closes and inputs the H level signal S ₄ from the power supply V to the timer 38 which produces an H level output S ₅ after a time τ and opens the gate 36. At this time, the output S ₂ of the mono multi 34
is repeatedly triggered and is at H level, its inverted signal becomes L, and the inhibit gate 36
The output S ₃ of is L. Output S ₁ when loop coil is disconnected
When the cycle of becomes longer, the output S ₂ of the monomulti 34 becomes L
The inverted output is H, and the output of gate 36 is
_S3 becomes H, which becomes the vertical tear detection output.

Vertical tear detection devices are tested while the conveyor is running. That is, when the motor 26 is started by operating a switch (not shown) while the conveyor is in operation, the shielding plate 30 moves to the dotted line position and interrupts the electromagnetic coupling between the loop coil of the conveyor and the detection coil at the detection end. Assuming that the time point at which the shielding plate is inserted is t ₁ , the shielding plate is a kind of shot ring, so it operates in the same way as a loop coil, and the detection circuit 32 produces an output S ₁ . However, since there is no change in the state after that and the loop coil is shielded, there is no output S ₁ from the detection circuit 32, and after the time interval T, the monomulti 34 makes the output S ₂ L level. This is similar to the case of a broken loop coil,
A vertical tear detection output S ₃ is generated from the gate 36 .

In other words, according to this device, if the output _S3 occurs after a while after pressing the button, it is normal, and if it does not occur, it is abnormal, and any person other than a specialized staff member can perform a functional test of the vertical tear detection device at any time. .

The shielding plate insertion mechanism can be modified as appropriate. Since what is required is to insert the shield plate and remove it after the test is completed, this series of operations may be automated or may be performed manually. In the case of manual operation, for example, a forward rotation switch for the motor 26, a limit switch for stopping the motor 26 at the end of insertion, a reverse switch for the motor 26, and a limit switch for stopping the motor 26 at the end of withdrawal are provided. In the case of automation, simply pressing the push button switch temporarily starts the motor 26, inserts the shielding plate 24, and after a predetermined time, for example, several tens of seconds, during which an alarm should be issued, the motor 26 reverses and moves the shielding plate 24 back. , a mechanism for returning may be used.

Vertical tear detection output _S3 sounds a buzzer, lights a lamp,
Furthermore, it can be used to automatically stop the conveyor. If the conveyor is to be automatically stopped, a switch is inserted into the automatic stop circuit, and during testing, the switch is operated to disable the automatic stop function.

Effects of the Invention As explained above, according to the present invention, the belt longitudinal tear detection device can be tested very easily at any time during conveyor operation, and is extremely effective.

[Brief explanation of drawings]

1 to 3 are explanatory diagrams of a belt longitudinal tear detection device, FIGS. 4 and 5 are explanatory diagrams and block diagrams showing an embodiment of the present invention, and FIG. 6 is an explanatory diagram of its operation. In the drawing, 10 is a belt, 14 is a loop coil,
22 is a detection end, 24 is a shielding plate, 26, 28, 30
is the shielding plate drive mechanism.

Claims (1)

[Claims] 1. A conveyor belt in which a plurality of loop coils that extend in the width direction of the belt and are disconnected when the belt is longitudinally torn are buried in the longitudinal direction of the belt, and a detection end equipped with a detection coil is arranged so as to face the loop coil. In a functional test device for a device that detects longitudinal tearing of a belt by an impedance change caused in a detection coil due to electromagnetic coupling, a shield plate is provided to break the electromagnetic coupling between the conveyor belt and the detection end, and the shield plate is used to detect the conveyor belt. 1. A functional test device for a vertical belt tear detection device, comprising: a drive mechanism inserted between the ends of the belt to break the electromagnetic coupling, and retreated from the drive mechanism to restore the electromagnetic coupling.