Electrically conductive structure as a conductor loop

Abstract

Conductor loop (15) which is completely embedded in a body (10a, 10b), wherein the body (10a, 10b) comprises a polymeric material with elastic properties, wherein an electrically conductive structure (20) forms the conductor loop (15) after its endless closure, wherein the conductor loop (15) is embedded in the body (10a, 10b) surrounded by an insulation (25), characterized in that the endless closure of the conductor loop (15) at the connection point (30) is carried out by means of splicing and / or clamping, wherein at least the connection point (30) of the endlessly closed conductor loop (15) is surrounded by at least one shrunk shrink tube (35).

Description

[0001] The invention relates to a conductor loop according to the preamble of claim 1.

[0002] Monitoring for longitudinal slits in conveyor belts has long been known. For this purpose, conductor loops can be inserted into the conveyor belt and checked for damage using a slit protection system, e.g., a transmitter / receiver combination, using electromagnetic induction. This is intended to stop a conveyor system if a longitudinal slit or other major belt damage occurs in the conveying direction A.

[0003] A conductor loop is an arrangement consisting of one or more continuously connected (short-circuited) contours of any shape, such as meandering, figure-eight, straight, etc. The contours can have different materials and construction elements, such as steel wire, steel cable, conductive textile thread, conductive braid, conductive elastomer material, etc. The conductor loops can be vulcanized directly or embedded in an elastomer package during the production of a conveyor belt, or subsequently into the upper or lower cover plate of the conveyor belt, for example at a distance d of approx. 50 m to 200 m.

[0004] A slot protection system is an electronic device comprising a transmitter / receiver pair that interacts with a conductor loop of the conveyor belt according to the principle of electromagnetic induction and thereby determines whether the conductor loop is closed (undamaged) or open (damaged / destroyed).

[0005] For example, a slot protection system can have a scanning station (a combination of transmitter and receiver), possibly proximity sensors (or transponders), and a monitoring station (scanner). During operation of the conveyor belt system, the conductor loops are scanned by the scanning station. When a conductor loop passes the scanning station, an electromagnetic signal is transmitted from the transmitter via the conductor loop to the receiver (assuming the conductor loop is intact). The transmitter generates an alternating magnetic field, which generates a current in the conductive, closed contours of the conductor loop. This current, in turn, generates a magnetic field that is registered by the receiver (principle of electromagnetic induction).

[0006] If the conveyor belt is slit in the conveying direction, causing the contours of the conductor loop to be damaged or destroyed, thereby interrupting the transmitter / receiver transmission path, no signal is transmitted from the transmitter to the receiver. This allows the longitudinal slit to be detected. In this case, the conveyor belt is stopped by the slit protection system to limit the extent of damage. The maximum possible length of the slit is thus limited to the distance d between two adjacent conductor loops.

[0007] Various contours made from different materials and construction elements are known for use as conductor loops. A conductor loop often consists of meandering metal cables, particularly steel cables. The cables, in turn, usually consist of at least five strands or wires. A 7x7 cable structure with an individual wire diameter of approximately 0.2 mm and a total diameter of 1.5 mm to 2 mm is preferred. There are also variants consisting of a mixed structure of copper strands and steel strands, with the steel strands in particular covering the copper strands. A version consisting of a solid copper wire covered by steel strands is also known. Instead of cables, twisted yarns or threads can also be used. A twisted yarn is a linear textile structure made from two or more yarns twisted together. Each yarn consists of several twisted filaments or fibers.

[0008] DE 10 2009 025 848 A1 describes a conductor loop referred to as a hybrid conductor loop. The hybrid conductor loop comprises at least one hybrid thread, which in turn consists of at least a textile first material and a conductive second material, and which, after being endlessly closed, forms the conductor loop. Preferably, at least two hybrid threads form a thread composite, in particular in the form of a cord or twisted yarn.

[0009] In all of these variants, the contours must be connected to form a continuous conductor loop. Depending on the number of contours to be used for the closed conductor loop, a corresponding number of connection points may be required. For example, a 7x7 cable structure may require up to seven connection points. These connection points can be designed in different ways. For example, cable strands are often spliced ​​and soldered, or simply soldered.

[0010] A disadvantage of using such slot protection systems is that, after extended use of the conveyor belts, false alarms become increasingly frequent. These are triggered by conductor loops being damaged or destroyed without a longitudinal slot occurring in the conveyor belt. This can have various causes: Conventional conductor loops are exposed to the risk of corrosion. For example, water or moisture can penetrate the conveyor belt through damage, particularly its cover plate, and upon contact with the conductor loops, damage or destroy them through corrosion, at least rendering them unusable for signal transmission within a slot protection system. Both conventional conductor loops made of steel cables, for example, and hybrid conductor loops, which contain at least one corrodible material, are exposed to this corrosion risk.

[0011] Also, known steel conductor loops can be destroyed when the conveyor belt is folded during a conveyor belt turnaround, e.g. due to an accident.

[0012] Likewise, the impact and fatigue strength of conventional conductor loops is insufficient when the conveyor belt is subjected to alternating bending or impact loads. For example, strong local expansion and compression during bulk material impact, particularly in a steel cable contour, cannot be adequately compensated for by, for example, a meandering contour design.

[0013] Furthermore, the manufacturing processes for the connection points of conventional conductor loops are very complex. This is particularly the case with steel cable contours, where each individual steel cable contour or multiple strands of a steel cable contour must be spliced ​​separately and then soldered.

[0014] US 6,352,149 B1 describes a conveyor belt with a microcoil spring wire sensor, a method for manufacturing the same, and a conveyor belt crack detection system incorporating this sensor for monitoring the integrity of the conveyor belt. The system uses an external transmitter and an external receiver, the microcoil sensor being configured in a substantially signal-inverting configuration and located substantially in a single plane within the conveyor belt, the microcoil wire sensor having loops connected to the external transmitter and to the external receiver. The microcoil wire crosses itself at at least one location such that the microcoil wire lies substantially in a single plane across the entire sensor, including the crossing points. Means may be provided to prevent short-circuiting of the conductor at the crossing points.These materials include: adhesive, insulation covering the conductor, a tee with two grooves, and a tee with a first, second, third, and fourth cylindrical dowel. The adhesive is also used to attach the conductor to the tees.

[0015] US 4,621,727 A describes an improved form of conductor wire using a sheath for incorporation into a conveyor belt. Sheaths with a low coefficient of friction form small cavities in the carcass of the conveyor belt, allowing the conductors to move freely as the belt flexes during operation. This movement minimizes stress and conductor breakage. The belt, with an array of these conductors distributed along the length of the belt, can be used in electrical or magnetic crack detection systems for detecting cracks in long-distance conveyor belts. If a field is damaged, the conveyor system can be shut down to minimize the length of the longitudinal cracks.

[0016] DE 101 00 249 A1 describes a conveyor belt comprising: a carrying side for the conveyed material and a running side, each made of an elastomeric material; a tension member embedded between the carrying side and the running side, in particular in the form of steel cables running in the longitudinal direction; and at least one conductor loop formed from a conductive cord, in particular from a metallic cord; embedded in the carrying side and / or running side; extending substantially across the entire width of the conveyor belt; arranged in one plane; free of crossing points and preferably having only one connection, which is located in particular in the less vulnerable edge region of the conveyor belt. The conductor loop has a higher cord mass within the edge region of the conveyor belt than in the central region of the conveyor belt.

[0017] The object of the present invention is to provide a conductor loop of the type described above which has improved protection against external influences.

[0018] The object is achieved according to the invention by the features of the characterizing part of claim 1. Advantageous further developments are described in the subclaims.

[0019] Thus, the present invention relates to a conductor loop that is completely embedded in a body. The body comprises a polymeric material with elastic properties. An electrically conductive structure forms the conductor loop after its continuous closure. The conductor loop is characterized in that the conductor loop is embedded in the body and surrounded by insulation.

[0020] The invention is based on the finding that the contours of a conductor loop, in particular a textile conductor loop or a hybrid conductor loop embedded in an elastic body, can be chemically or mechanically attacked and damaged or even destroyed by the components of the elastomeric material.

[0021] For example, the conductive materials of the conductor loop can oxidize or corrode due to sulfur when vulcanized without insulation from the elastomeric material. Over time, the elastomeric material can also migrate between the filaments or fibers of the conductor loops and push them apart, reducing their mechanical stability or potentially causing them to tear. In other words, the elastomeric material can separate the filaments or fibers of the conductor loops due to dynamic loads, thus disrupting the yarns.

[0022] This can be avoided according to the invention in that by means of this insulation a separation of the contours of the conductor loop from the flowing polymeric material with elastic properties (elastomeric material) can be achieved during vulcanization and also during operation.

[0023] Another advantage is that the insulation of the conductor loop increases its elongation at break and thus the stress and fatigue strength when the conductor loop is subjected to alternating bending stress.

[0024] Another advantage is that the insulation additionally protects the conductor loop from external influences such as water, dirt, oil, and the like, which can occur due to a damaged cover plate of a conveyor belt. Penetration of water, for example, into the cover plate of the conveyor belt down to the depth of the conductor loops could cause corrosion, which could lead to damage or even destruction of the conductor loops.

[0025] All of these advantages, individually or together, increase the service life of the conductor loop.

[0026] The insulation can be provided by a plastic coating or sheath, e.g., TPU, or by an elastomer tube or heat-shrink tubing, e.g., polyolefin. The insulation is applied around the conductor loop before it is embedded in the elastomer material and subsequently vulcanized.

[0027] The conductor loop is made of an electrically conductive structure, which can be a metallic material such as copper or steel, or a polyamide (PA), aramid, polyester (PES), polyvinyl acetal (PVA), polyimide (PI), polyetheretherketone (PEEK), polyphenylene, or a copolymer, or a combination of two or more of these materials. Of particular importance among the polyphenylene group is polyphenylene sulfide (PPS).

[0028] According to one aspect of the invention, the insulation comprises a coating or sheath.

[0029] The advantage here is that the electrical conductivity of a conductor loop is not impaired. Furthermore, the sheathing thickness is usually in the micrometer range, e.g., between 100 µm and 200 µm, so the overall thickness of a textile conductor loop increases only slightly due to the insulation. This is very important because the overall thickness of a conductor loop influences the selection of the minimum cover thickness of a conveyor belt.

[0030] The sheathing can, for example, comprise thermoplastic polyurethane (TPU), preferably made of TPU.

[0031] According to a further aspect of the invention, the insulation comprises an elastomer tube or shrink tube.

[0032] It is advantageous that such hoses are available as commercially available products at low cost and can be easily handled in order to produce an insulation according to the invention.

[0033] According to the invention, the endless closure of the conductor loop at the connection point is carried out by means of splicing and / or clamping.

[0034] The advantage here is that the continuous closure of the conductor loop is simplified. This allows for faster and more cost-effective production. Furthermore, a spliced ​​and / or clamped connection point can offer greater strength than conventional solutions, thus increasing the service life of the conductor loop.

[0035] Whereas it has previously been customary to splice and solder or simply solder such connection points, for example in rope strands, the connection in the electrically conductive textile structure is achieved by providing a splice and / or clamp across the entire width of the conductive textile structure or by multiple splices and / or clamps across multiple yarns or across each individual yarn separately. Before splicing and / or clamping, the yarns to be joined are preferably twisted together or otherwise guided around each other in order to create an overlap of the respective yarn ends in the area of ​​the splice and / or clamping. If insulation is already provided around the electrically conductive textile structure, this must be removed at least in the area of ​​the yarn ends in which the splice and / or clamping is to take place.A shrink-wrapped tube is preferably used as the clamp, which also serves to insulate the connection point from the surrounding elastomer material. Furthermore, a sleeve clamp, such as a crimp sleeve, can be used to provide additional reinforcement for the connection point.

[0036] According to the invention, at least the connection point of the endlessly closed conductor loop is surrounded by at least one shrunken shrink tube.

[0037] The advantage here is that the splicing and / or clamping by means of at least one overlying shrink-wrapped heat-shrink tube eliminates the need for costly and time-consuming splicing and soldering connections or soldering connections of the strands of a steel cable at multiple points, as is currently the case with reliable, commercially available steel conductor loops. This significantly increases the service life of the conductor loop.

[0038] According to a further aspect of the invention, the conductor loop has a textile transverse reinforcement.

[0039] The advantage here is that a textile cross-armor, also known as a breaker, can be used to reinforce the conductor loop against impacts. This increases the impact resistance of the entire conductor loop and thus also its service life. Polyester polyamide (EP) fabrics, for example, can be used as textile cross-armor.

[0040] The invention further relates to a conveyor belt having a body comprising a polymeric material with elastic properties, a strength member arranged in the body, and at least one conductor loop according to one of claims 1 to 6, which is completely embedded in the body.

[0041] In this way, the advantageous properties of the conductor loop according to the invention can be used in a conveyor belt within the framework of slot protection monitoring.

[0042] According to one aspect of the invention, the body has a support-side cover plate and / or a running-side cover plate of the conveyor belt, in which at least one conductor loop is embedded.

[0043] The advantage here is that in this arrangement the conductor loop can be provided in the area of ​​the conveyor belt that is to be monitored for slot formation.

[0044] According to a further aspect of the invention, the connection point of the conductor loop is arranged outside the material loading area of ​​the conveyor belt.

[0045] The advantage here is that stress on the connection points of the conductor loops caused by the material loading can be avoided or at least reduced. This benefits the durability of the connection points and thus the service life of the conductor loops. The connection points are preferably located as close as possible to the lateral edge of the conveyor belt, so as to be outside the material loading area and at the greatest possible distance from it.

[0046] According to a further aspect of the invention, a first connection point of a first conductor loop and a second connection point of a second conductor loop are located diagonally opposite each other across the area enclosed by the conductor loops in the plane of the conveying direction A.

[0047] The advantage here is that if the material is loaded on one side beyond the loading area, only one connection point is subjected to stress. In other words, an off-center bulk material feed at a feed or transfer point, or any other asymmetrical mechanical damage to a conveyor belt that can be caused by a conveyor system, does not simultaneously stress both connection points, but only one connection point.

[0048] An embodiment and further advantages of the invention are explained below in conjunction with the following figures. Fig. 1 a perspective schematic representation of a conveyor belt system with slot protection system; Fig. 2 a perspective schematic sectional view of a conveyor belt; Fig. 3 a schematic plan view of a cut-open conductor loop package with two conductor loops; Fig. 4 a schematic plan view of a cut-open conductor loop package with a conductor loop; Fig. 5 a schematic sectional view of an electrically conductive structure with insulation embedded in an elastomer material; Fig. 6 a schematic sectional view of a connection point of an electrically conductive structure; Fig. 7 a perspective schematic sectional view of a conveyor belt with an electrically conductive structure with a textile transverse reinforcement; and Fig. 8 a schematic plan view of a cut-open conveyor belt with two conductor loops with diagonally opposite connection points.

[0049] Fig. 1 shows a perspective schematic representation of a conveyor belt system 1 with slot protection system 13, 14, 16, 17. Fig. Figure 2 shows a perspective schematic sectional view of a conveyor belt 10. The conveyor belt system 1 comprises a closed conveyor belt 10 with a supporting-side cover plate 10a for receiving or transporting conveyed material and a running-side cover plate 10b for rolling on guide, support, or drive elements 11, 12. A strength member 18 in the form of steel cables is embedded between these two cover plates 10a, 10b.

[0050] The conveyor belt 10 is driven at one end in the conveying direction A (belt running direction) by a drive drum 11, which rotates in the direction of rotation U. The other end of the conveyor belt 10 is tensioned and held in a rotating manner by a reversing drum 12. At a material loading position G of the conveyor belt system 1, material can be loaded onto the support-side cover plate 10a of the conveyor belt 10 and moved in the conveying direction A.

[0051] Embedded in the supporting-side cover plate 10a of the conveyor belt 10 are several conductor loops 15 at a distance d. These conductor loops 15 can comprise only a single conductor loop 15 or an arrangement of several conductor loops 15a, 15b.

[0052] Fig. Figure 3 shows a schematic plan view of a cut-open conductor loop package 15 with two conductor loops 15a, 15b, which run concentrically in a meandering manner in the plane of the conveyor belt 10. The first conductor loop 15a runs around the second conductor loop 15b.

[0053] Fig. Figure 4 shows a schematic top view of a cut-open conductor loop package 15 with a conductor loop 15a. This conductor loop 15a extends in a figure-eight shape in the plane of the conveyor belt 10. The contours of the conductor loops 15a intersect without short-circuiting.

[0054] The slot protection system 13, 14, 16, 17 has a transmitter 16 that transmits an electromagnetic signal in the direction of the conveyor belt 10. The position of the conductor loops 15 can be determined absolutely or relative to the adjacent conductor loops 15, independent of the rotational speed U and the conveying direction A, for example, using proximity sensors located, for example, on the reversing drum 12. Solutions for position determination based on a transponder are also known. Furthermore, the position of the conductor loops 15 can be detected by means of corresponding markings on the conveyor belt 10.

[0055] If the contour of the conductor loop 15 is intact, the electromagnetic signal from the transmitter 16 generates an alternating magnetic field around the contour of the conductor loop 15, which in turn induces a current in the contour of the conductor loop 15. This current, in turn, generates a magnetic field around the contour of the conductor loop 15, which is registered by a receiver 17.

[0056] If a magnetic signal is registered by the receiver 17 at a position on the conveyor belt 10 where a conductor loop 15 is present, it is concluded that this conductor loop 15 must be intact and undamaged at least to the extent that sufficient electromagnetic induction can occur between the transmitter 16 and the receiver 17 via the contour of the conductor loop 15. Consequently, no damage to the conveyor belt 10 due to a longitudinal slit is suspected in this area.

[0057] However, if no magnetic signal is received by the receiver 17 at this position, this conductor loop 15 must be damaged or destroyed to such an extent that sufficient electromagnetic induction cannot occur between the transmitter 16 and the receiver 17 via the contour of the conductor loop 15. This can be caused by a longitudinal slot in the conveyor belt 10.

[0058] To generate this electromagnetic interaction, transmitter 16 and receiver 17 are controlled and monitored by an evaluation unit 13. The evaluation unit 13 can also be supplied with, for example, the rotational speed U of the drive drum 11 or the reversing drum 12 in order to determine the position of the conductor loops 15 therefrom. The evaluation unit 13 can output a signal, for example to a central unit 14, to indicate whether the respective conductor loops 15 are intact and the conveyor belt system 1 can continue to operate, or whether a failure of at least one conductor loop 15 has been detected and the conveyor belt system 1 should be stopped for safety reasons. For this purpose, the central unit 14 can be connected to the drive drum 11.

[0059] Fig. 5 shows a schematic sectional view of an electrically conductive structure 20 with insulation 25 embedded in the elastomer material. In this exemplary embodiment, the electrically conductive structure 20 is a thread surrounded by insulation 25 and embedded in the elastomer material of the conveyor belt 10 to form the conductor loop 15. In this exemplary embodiment, the insulation 25 is a plastic coating or sheath, e.g., made of TPU (thermoplastic polyurethane).

[0060] Fig. Figure 6 shows a schematic sectional view of a connection point 30 of an electrically conductive structure 20. The two ends 21, 22 of the electrically conductive structure 20 are connected to one another by a splice 30 as a connection point 30 to form an endless conductor loop 15. For this purpose, the two ends 21, 22 are not surrounded by the insulation 25 or have been exposed by it. The connection point 30 is covered by a shrink tube 35 in such a way that the ends 21, 22 of the electrically conductive structure 20 up to the areas of the electrically conductive structure 20 covered by the insulation 25 are also surrounded by the shrink tube. The shrink tube 35 is in the Fig. 6 is shown in the unshrunken state; after shrinking, it contracts essentially radially, so that the connection point 30 is protected and reinforced by the shrunken shrink tube 35. The overlap of the shrink tube 35 and the insulation 25 is selected such that the electrically conductive structure 20 or the closed conductor loop 15 is continuously enclosed by either the shrunken shrink tube 35, the insulation 25, or their overlap and is insulated from the elastomer material of the conveyor belt 10.

[0061] Fig. 7 shows a perspective schematic sectional view of a conveyor belt 10 with an electrically conductive structure 20 with a textile transverse reinforcement 28. This serves to reinforce the conductor loop 15 against impact and is arranged between the conductor loop 15 and the supporting-side cover plate 10a of the conveyor belt 10.

[0062] Fig. Figure 8 shows a schematic plan view of a cut-open conveyor belt 10 with two conductor loops 15a, 15b with diagonally opposite connection points 30a, 30b. The conductor loops 15a, 15b run, as in Fig. 3, concentrically meandering in the plane of the conveyor belt 10. The material loading area G is provided in the middle of the conveyor belt 10. Outside the material loading area G, the diagonally opposite connection points 30a, 30b are arranged. List of reference symbols A Conveyor direction of the conveyor belt system 1 d Distance between two adjacent conductor loops 15 G Material loading position of the conveyor belt 10 U Direction of rotation of the drive drum 11 1 conveyor belt system 10 conveyor belt 10a supporting cover plate of the conveyor belt 10 10b Running-side cover plate of the conveyor belt 10 11 Drive drum 12 reversing drum 13 Evaluation unit 14 Central unit 15 conductor loop package(s) 15a first conductor loop 15b second conductor loop 16 channels 17 recipients 18 Strength members of the conveyor belt 10 20 electrically conductive structure 21 first end area of ​​a conductor loop 22 second end area of ​​a conductor loop 25 Insulation of the electrically conductive textile fabric 28 textile cross reinforcement 30 connection point 30a Connection point of the first conductor loop 15a 30b Connection point of the second conductor loops 15b 35 shrink tubing around the connection point 30

Claims

[1] Conductor loop (15) which is completely embedded in a body (10a, 10b), wherein the body (10a, 10b) comprises a polymeric material with elastic properties, wherein an electrically conductive structure (20) forms the conductor loop (15) after its endless closure, wherein the conductor loop (15) is embedded in the body (10a, 10b) surrounded by an insulation (25), characterized by , that the endless closure of the conductor loop (15) at the connection point (30) is carried out by means of splicing and / or clamping, wherein at least the connection point (30) of the endlessly closed conductor loop (15) is surrounded by at least one shrunk shrink tube (35). [2] Conductor loop (15) according to claim 1, wherein the insulation (25) has a coating or sheath. [3] Conductor loop (15) according to claim 1 or 2, wherein the insulation (25) comprises an elastomer tube or shrink tube. [4] Conductor loop (15) according to one of the preceding claims, wherein the conductor loop (15) has a textile transverse reinforcement (28). [5] Conveyor belt (10), with a body (10a, 10b) comprising a polymeric material with elastic properties, a strength member (18) arranged in the body (10a, 10b), and at least one conductor loop (15) according to one of claims 1 to 4, which is completely embedded in the body (10a, 10b). [6] Conveyor belt (10) according to claim 5, wherein the body (10a, 10b) has a support-side cover plate (10a) and / or a running-side cover plate (10b) of the conveyor belt (10), in which at least one conductor loop (15) is embedded. [7] Conveyor belt (10) according to claim 5 or 6, wherein the connection point (30) of the conductor loop (15) is arranged outside the material loading area (G) of the conveyor belt (10). [8] Conveyor belt (10) according to one of claims 5 to 7, wherein a first connection point (30a) of a first conductor loop (15a) and a second connection point (30b) of a second conductor loop (15b) are located diagonally opposite one another across the area enclosed by the conductor loops (15a, 15b) in the plane of the conveying direction A.

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