Conveyor belt and belt conveyor device

Provided are a conveyor belt further enhancing the durability of loop coils embedded in the conveyor belt so as to detect vertical tears in the conveyor belt; and a belt conveyor system using the conveyor belt. A conveyor belt includes a core layer having a plurality of metal cords extending in the belt longitudinal direction arranged in parallel in the belt width direction; an upper cover rubber and a lower cover rubber disposed so as to interpose a core layer from above and below; a plurality of loop coils embedded at intervals in the belt longitudinal direction in the lower cover rubber; and protective layers being disposed between the core layer above and each of the loop coils below and embedded in the lower cover rubber at intervals in the belt longitudinal direction.

TECHNICAL FIELD

The present technology relates to a conveyor belt and belt conveyor system and particularly relates to a conveyor belt further improving the durability of loop coils embedded in the conveyor belt so as to detect vertical tears in the conveyor belt; and a belt conveyor system using this conveyor belt.

BACKGROUND ART

In order to detect a vertical tear of a conveyor belt (cracks continuous in the belt longitudinal direction), a conveyor belt in which loop coils are embedded is known (see Japan Unexamined Patent Publication Nos. 2014-31241 and 2015-71493). In such a conveyor belt, a sensor arranged adjacent to the conveyor belt senses the induced current occurring in loop coils passing near the sensor. If a sharp object or the like to be conveyed pierces the conveyor belt and a vertical tear is generated, the loop coils are damaged, so no induced current is generated in the loop coils. In this case, the sensor does not detect the induced current even though the loop coils have passed through the vicinity. Thus, it is possible to determine whether a vertical tear has occurred in the conveyor belt depending on whether the induced current is detected by the sensor. If it is determined that a vertical tear has occurred on the basis of the detection of the sensor, the operation of the conveyor is stopped in order to prevent expansion of the vertical tear.

Local impacts and external forces are exerted on conveyor belts due to objects to be conveyed or the like to be loaded. Even if a vertical tear does not occur in the conveyor belt due to the impact or external force, the loop coils may be damaged. If loop coils are damaged in this way, the sensors do not detect the induced current even if the loop coils passing through the vicinity. Thus, if judged based on the detection of the sensor, it will be erroneously recognized that vertical tears occur in the conveyor belt.

Japan Unexamined Patent Publication No. 2015-71493 proposes loop coils comprising a metal part and a stretchable conductive material. In this proposal, the durability of the loop coils is improved by mitigating the impact or the like acting on the conveyor belt with the stretchable conductive material. However, in the case where a large impact or stress locally acts on the conveyor belt, it is difficult to prevent damage to the loop coils even if a part of the stretchable conductive material is provided. In addition, when a large impact or stress directly acts on the metal part, the mitigating effect by the stretchable conductive material can hardly be obtained and damage to loop coils cannot be prevented. Therefore, there is room for improvement in improving the durability of loop coils.

SUMMARY

The present technology provides a conveyor belt which can further improve the durability of loop coils embedded in the conveyor belt and detect vertical tears of the conveyor belt; and a belt conveyor system using this conveyor belt.

A conveyor belt according to the present technology includes a core layer having a plurality of metal cords extending in the belt longitudinal direction arranged in parallel in the belt width direction; an upper cover rubber and a lower cover rubber respectively disposed so as to interpose the core layer from above and below; a plurality of loop coils embedded at intervals in the belt longitudinal direction in the lower cover rubber; and a plurality of protective layers disposed between the core layer above and each of the loop coils below and embedded in the lower cover rubber at intervals in the belt longitudinal direction.

The belt conveyor system according to the present technology comprises the conveyor belt, a magnetic field generating unit disposed adjacent to the lower cover rubber to generate a magnetic field for producing an induced current in each of the loop coils, and a sensor disposed adjacent to the lower cover rubber and detecting induced current.

According to the present technology, since the protective layers are disposed between the core layer above and each of the loop coils below; and embedded in the lower cover rubber, the protective layers absorb and mitigate a localized impact or external force from objects to be conveyed acting on the conveyor belt. Specifically, since the metal cords arranged in parallel are constrained by the protective layers, impact and external force acting are widely dispersed in the metal cords. Thus, even if a large impact or external force acts locally on the conveyor belt, the loop coils are hardly damaged and its durability is further enhanced. Along with this, it is advantageous to avoid the situation that the loop coils are damaged even if vertical tears do not occur in the conveyor belt.

Additionally, since the respective protective layers are embedded in the lower cover rubber at intervals in the belt longitudinal direction, a weight increase in the conveyor belt due to the provision of the protective layers can be suppressed, and deterioration of flexibility can also be avoided.

DETAILED DESCRIPTION

A conveyor belt and a belt conveyor system according to the present technology will be described below with reference to the drawings.

A conveyor belt1according to the present technology is illustrated inFIGS. 1 and 2. The conveyor belt1is provided with a core layer2, and an upper cover rubber3and a lower cover rubber4disposed so as to interpose the core layer2from above and below. These components are integrally formed with one another via a vulcanization process. The conveyor belt1may also include edge rubber disposed on each end portion in the belt width direction or other constituents as appropriate.

In the core layer2, a plurality of metal cords2a(steel cords, for example) extending in the belt longitudinal direction are arranged in parallel with each other in the belt width direction. Specifically, the core layer2is covered with cushion rubber, and the cushion rubber is bonded to the upper cover rubber3and the lower cover rubber4via vulcanization bonding.

For the upper cover rubber3and the lower cover rubber4, a rubber composition may be used that contains at least a diene rubber including natural rubber; and carbon black to achieve good wear resistance. The layer thicknesses of the upper cover rubber3and the lower cover rubber4are determined as appropriate according to the performance required of the conveyor belt1, within a range of, for example, from 5 mm to 30 mm. The cushion rubber is a rubber with excellent adhesion.

A plurality of loop coils5are embedded in the lower cover rubber4at intervals in the belt longitudinal direction. The loop coils5are, for example, a conductive wire5aformed in an annular shape, and a known one may be used. The conductive wire5amay be formed into a wavy shape or a non-wavy shape. The loop coils5is not limited to a double quadrilateral shape, and various shapes such as a circular shape and an elliptical shape may be adopted. The loop coil5embedded position in a plane is within a region including the central portion in the belt width direction.

The embedding depth position of each of the loop coils5is preferably from 30% to 80% the rubber thickness T of the lower cover rubber4from the bottom surface of the core layer2, more preferably from 50% to 60% (rubber thickness t=from 30% to 80% of T). The upper to lower interval between the bottom surface of the core layer2and the top surface of the loop coils5(rubber thickness t) may be 5 mm or more.

Protective layers6are disposed between the core layer2above and each of the loop coils5below. Namely, the protective layers6are embedded in the lower cover rubber4at intervals in the belt longitudinal direction. The protective layers6are specified to have less elongation (higher modulus) than the rubber used for the conveyor belt1under the same conditions. The thickness of the protective layers6may be 0.2 mm to 3.0 mm.

Each of the protective layers6is disposed so as to cover the entire range of the corresponding loop coils5(loop coils5disposed closest to each protective layer6) in a plan view as viewed from the upper cover rubber3side. It is possible to set the protective layers6so as to cover at least the center portion of the corresponding loop coils5in the belt width direction in a plan view as viewed from the upper cover rubber3. However, in order to reliably protect the loop coils5, it is preferable that the specification is such that the protective layers6are disposed so as to cover the entire range of the loop coils5, as in the present embodiment. Furthermore, although the metal cords2aare indicated by dot-dash lines in the middle ofFIG. 2in order to make it easier to understand the internal structure of the conveyor belt1, they are omitted in the illustration of the first and second protective layers6from the top. In addition, inFIG. 2, the second protective layer6from the top is partially cut out, and the third protective layer6from the top is omitted.

The protective layers6can be formed of various materials including natural fibers, resins, metals, and the like. Various structures such as a woven structure and a film shape can be adopted for the protective layers6. As the woven structure, a plain weave structure, a cord weave structure, a twill weave structure, a sateen weave structure, or the like can be exemplified.

In this embodiment, the protective layers6are formed by a plurality of wires6a. As the wires6a, a desired wires6asuch as natural fibers, resin fibers metal fibers or the like can be used. This protective layers6have a plain weave structure, and thus a plurality of wires6aextending in the belt width direction are disposed in parallel in the belt longitudinal direction. Thus, the wires6aextending in the belt width direction intersect with the metal cords2adisposed in parallel in the belt width direction.

Although the metal cords2adisposed in parallel are joined by the cushion rubber interposed in the mutual gap between them, the cushion rubber elastically deforms, so the force for constraining displacement of the metal cords2ain the belt width direction is weak. However, in the present embodiment, the protective layers6are disposed so as to cover the metal cords2adisposed in parallel, so the protective layers6restrain and bundle the metal cords2aadjacent to each other in the belt width direction. Thus, in the present technology, the displacement of the metal cords2ain the belt width direction is suppressed as compared with a conventional conveyor belt.

As illustrated inFIG. 3, a belt conveyor system7of the present technology is provided with the conveyor belt1, a magnetic field generating unit10, and a sensor11. The conveyor belt1is stretched between pulleys8,8. As illustrated inFIG. 4, the conveyor belt1is supported on the carrier side in a trough shape projecting downward by support rollers9, so that the loaded objects to be conveyed C are placed mainly at the center in the belt width direction.

The magnetic field generating unit10is disposed adjacent to the lower cover rubber4. The magnetic field generating unit10transmits, for example, an electromagnetic wave to each of the loop coils5passing near the magnetic field generating unit10. An induced current is induced in each of the loop coils5due to this electromagnetic wave. If the loop coils5are disconnected, no induced current is induced.

The sensor11is disposed adjacent to the lower cover rubber4. The sensor11is arranged slightly downstream of the magnetic field generating unit10in the forward direction of the conveyor belt1. The sensor11detects whether any induced current is generated for each of the loop coils5passing near the sensor11. Detection data from the sensor11are transmitted to a control unit12. On the basis of the detection data from the sensor11, the control unit12determines that a vertical tear has not occurred in the conveyor belt1if an induced current is generated, and if no induced current is generated, the control unit12determines that a vertical tear has occurred in the conveyor belt1. If it is determined that a vertical tear occurs in the conveyor belt1, the operation of the conveyor belt1is stopped, and a warning or the like is issued.

As illustrated inFIG. 6, when an object for conveyance C is fed from a chute part13onto a conventional conveyor belt14in which the protective layers6are not embedded, the metal cords2atries to be displaced in the belt width direction due to the impact caused by the object for conveyance C and the external force. Specifically, in the local portion of a conveyor belt14receiving impact or external force, the interval between the metal cords2ain the belt width direction is widened. Thus, the impact or external force is easily transmitted to the loop coils5embedded below the core layer2. Namely, in the structure of the conventional conveyor belt14, a local impact or external force received by the conveyor belt14acts greatly on the loop coils5, so the loop coils5are easily damaged.

On the other hand, in the conveyor belt1according to the present technology illustrated inFIG. 5, the metal cords2adisposed in parallel are constrained by the protective layers6, therefore displacement of the metal cords2ain the belt width direction is suppressed even if a local impact or external force acts on the conveyor belt1due to an object for conveyance C. Thereby, the impact and the external force acting are widely dispersed among the metal cords2a. In addition, the impact and the external force are absorbed or lessened by the protective layers6. Thus, even if a large impact or an external force acts locally on the conveyor belt1, the loop coils5are not easily damaged, and its durability is further enhanced. Therefore, the advantage is avoiding damage to loop coils5even if no vertical tears occur in the conveyor belt1, making it possible to more accurately detect vertical tears in the conveyor belt1. Furthermore,FIG. 5omits the protective layers6.

When the object for conveyance C is loaded from the upper cover rubber3side under the same conditions onto the conveyor belt having the same specifications except for the presence or absence of the protective layers6illustrated inFIGS. 1 and 2, the principal stress generated in the loop coils5and the amount of deformation were simulated. The protective layers6were embedded at a position 60% the thickness T of the lower cover rubber4from the bottom surface of the core layer2and were set to a plain weave structure made of nylon fibers. As a result, it has been found that when the protective layers6are present, the principal stress generated in the loop coils5and the amount of deformation are approximately 60% of those in the absence of the protective layers6.

Additionally, since the respective protective layers6are embedded in the lower cover rubber4at intervals in the belt longitudinal direction, the weight increase in the conveyor belt1due to provision of the protective layers6can be suppressed, and it is also possible to avoid deterioration of flexibility (ease of bending when traveling around the pulley8). These facts greatly affect reducing the energy required for operating the conveyor belt1, which contributes to energy-saving.

Furthermore, in order to satisfy the specification of embedding the protective layers6in the lower cover rubber4at intervals in the belt longitudinal direction, each loop coil5may be disposed together with each protective layer6in the lower cover rubber4in the forming process for the conveyor belt1. Thus, it is unnecessary to substantially increase the number of steps in manufacturing according to this specification as compared with the case of the specification not embedding the protective layers6.

If the protective layers6have a specification in which a plurality of wires6aextending in the belt width direction are disposed in parallel in the belt longitudinal direction, displacement of the metal cords2ain the belt width direction can be further suppressed by the wire6a. Thus, it is advantageous to avoid damage to the loop coils5.

When a cord fabric structure (woven structure wherein wires6ain one direction are of significantly lower disposition density than perpendicular wires6ain another direction) is used for the protective layers6, the wires6awith a higher disposition density are extended in the belt width direction. Thereby, it is possible to realize the effect of avoiding deterioration of flexibility of the conveyor belt1; and the effect of suppressing the displacement of the metal cords2ain the belt width direction at a high level.

If the loop coils5are embedded at a position from 30% to 80% the rubber thickness T of the lower cover rubber4from the bottom surface of the core layer2, more preferably at a position from 50% to 60%, it is advantageous to protect the loop coils5from impact or external force due to an object for conveyance C to be loaded. In the case where the loop coils5are embedded at a position less than 30% the rubber thickness T from the bottom surface of the core layer2, impact or external force is easily transmitted to the loop coils5, which is disadvantageous for preventing damage to the loop coils5. In addition, when the loop coils5are embedded at a position greater than 80% the rubber thickness T from the bottom surface of the core layer2, since the distance between the loop coils5and the surface of the lower cover rubber4becomes too small, the impact or external force will be easily transmitted from the lower cover rubber4side to the loop coils5, which is not preferable.