Abstract:
A conveyor belt with a microcoil springwire sensor, a method for manufacturing same, and a conveyor belt rip detection system incorporating same for monitoring the integrity of the conveyor belt. The system employs an external transmitter and an external receiver, the microcoil sensor configured substantially in a signal inverting configuration residing substantially in a single plane within the conveyor belt, said microcoil springwire sensor having loops coupled to the external transmitter, and to the external receiver. The microcoil springwire crosses through itself in at least one place such that the microcoil springwire resides substantially in a single plane throughout the sensor including the crossing places. Means may be provided to prevent short-circuiting of the conductor at the crossing places, the means including: adhesive, insulation coating the conductor, a tee having two grooves, and a tee having a first, second, third and fourth cylindrical dowel. Adhesive is also used to secure the conductor to the tees.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The invention relates to conveyor belts having electrical conductors, which are sensor loops embedded therein, and more particularly to belts having signal inverting type sensor loops. 
     BACKGROUND OF THE INVENTION 
     It is known to transport bulk materials, such as metallic ore and the like, with a heavy duty conveyor belt. These belts may be on the order of miles (1 mile=1.6 kilometers) long. Sharp edges of the material being transported may become lodged in such a position in the conveyor belt mechanism that they can cause a rip (slit, cut or tear) in the belt. When such a rip or tear commences, if the belt is not stopped, the rip can propagate longitudinally for a substantial distance along the belt. Ripped or torn portions of the belt must then be repaired. The costs can be quite formidable for repairing such heavy duty conveyor belts, as well as the cost of cleaning up material which has spilled off of the conveyor belt. It is therefore generally well known to detect and locate a rip in the belt as quickly as possible after it commences, thereby minimizing the extent of the damage to the belt. 
     It is therefore known to employ sensors within the conveyor belts as part of a rip detection system. These sensors may take the form of loops of conductive wire, and operate in conjunction with an overall rip detection system. Generally, the rip detection system functions by ‘inferentially’ determining whether a sensor (sensor loop) has been damaged, i.e., is an open circuit rather than a closed circuit, as a result of a rip or tear in the belt. Typically an electrical energy source external to the belt is inductively or capacitively coupled to a sensor in the belt. For example, a transmitter/receiver (exciter/detector) external to the belt and which is inductively or capacitively coupled to the sensor is used to detect a break in the conductive wire loop of the sensor. A plurality of such sensors may be disposed at a corresponding plurality of intervals along the length of the conveyor belt. Also, a plurality of exciter/detectors may be disposed at various locations adjacent the length of the belt. In this manner, the damage from rips or tears can be minimized. 
     U.S. Pat. No. 3,742,477 (Enabnit; 1973) discloses a conveyor belt condition monitoring apparatus for monitoring the open-circuited or close-circuited condition of electrical conductors associated with the conveyor belt. The electrical conductors comprise sensor loops, and are embedded in the conveyor belt. Generally, the monitoring apparatus comprises a detector circuit including an oscillator disposed so as to detect the proximate passage of a close-circuited (i.e., undamaged) sensor loop. The sensor loops disclosed in this patent each employ a single wire which passes (crosses) over (or under) itself in at least two places in order to form a pair of inverted coils. As a general proposition, an elongate element (e.g., a conductor), which is used to form a pair of inverted coils can be described as a “figure-eight sensor loop” will have at least one “crossover”. 
     U.S. Pat. No. 4,621,727 (Strader; 1986) discloses a conveyor belt damage sensor in which conductors freely move during flexing of the belt by enclosing the conductors in low coefficient of friction jacketing envelopes. As illustrated in FIG. 5 of this patent, a (sensor) conductor is disclosed which comprises a coiled conductor ( 62 ) surrounded by an extruded thermoplastic resin envelope ( 60 ). Multiple formations of figure-eight sensor loops are disclosed wherein the conductor contained within its envelope passes (crosses) over/under itself multiple times. 
     U.S. Pat. No. 4,854,446 (Strader; 1989;“&#39;446 Patent”) discloses electrical conductors formed into a “figure-eight” pattern embedded in a conveyor belt. The electrical conductors of the sensor loops may be “wavy”, in the form of a repeating flat sinusoidal wave form, to accommodate flexure of the belt without losing continuity (close-circuitness). A typical conveyor belt construction is shown in FIG. 6 of the patent. The belt ( 90 ) has a top layer ( 92 ) which has an outer load carrying surface or “cover”, and a bottom layer ( 94 ) which has an outer pulley engaging surface or cover. The bottom layer is sometimes referred to as a “pulley cover”. Reinforcing cables ( 98 ) are disposed between the top and bottom layers. Each of the top and bottom layers has a layer ( 100 ) of insulation gum on an inner surface thereof, for engaging with each other and with the cables ( 98 ). The electrical conductors (sensor loops) ( 108 ) are shown as being disposed between the bottom layer ( 94 ) and the cables ( 98 ), with an insulation layer ( 104 ) and an optional fabric layer ( 106 ) lying between the conductors ( 108 ) and the cables ( 98 ). 
     FIG. 1, comparable to FIG. 1 of the &#39;446 patent, illustrates the prior art rip detection system as set forth in the &#39;446 patent to Strader. A belt rip detection system is shown generally by reference numeral  100 . An elastomeric conveyor belt  104  is driven around/over rollers or pulleys  102  and  103 . A motor  110  provides the power to drive roller  103  which in turn drives the conveyor belt  104  in a direction of travel as indicated by arrow  111 . Of course, the motor could also drive the belt in the opposite direction. 
     A plurality of conductors  105  (sensor loops or sensors) are embedded in the elastomeric belt  104  transverse to the direction of travel. The conductors  105  are arranged generally in a signal inverting format. 
     The conductors/sensors  105  may be used in connection with a rip detection system which may use either magnetic or electric fields for excitation/detection. The conductors  105  carry a current flow therein when subjected to an electrical or magnetic field. A rip in the belt  104  will eventually propagate far enough to cause one of the conductors  105  to be broken. A transmitter  106  emits an electrical or magnetic field which is communicated by conductors  105  to a receiver  107  provided that the conductor  105  is intact. Receiver  107  provides a signal to control circuitry  101  which can process the signal and indicate a rip. The rip signal may result in an alarm and/or a signal  108  to the motor controller  109  to automatically stop motor  110  and shut down the conveyor belt  104 . 
     The electrical conductors  105  are embedded within a conveyor belt  104  which comprises an elastomeric body having a load carrying surface (cover) and a parallel pulley engaging cover with a reinforcement ply disposed within the elastomeric body. The electrical conductors  105  can be embedded into either the load carrying or the pulley engaging surfaces, located between reinforcing plies, or between a reinforcing ply and either load carrying or pulley engaging surface. The electrical conductors can be located either longitudinally or transversely with respect to the belt. The electrical conductors are arranged in a pattern such as a loop, oval, polygon, or in substantially a figure-eight. 
     FIG. 2, comparable to FIG. 6 in the &#39;446 patent, illustrates the installation of a conductor in the prior art belt construction. Reference numeral  200  denotes a conveyor belt. Load bearing surface  202  is secured to reinforcing cables  204  by gum  203 . Conductor assembly  205  is comprised of insulation  206 , fabric  207  and wire  208 . Tie gum  209  secures the conductor assembly  205  to the cables  204  and to a bottom pulley cover  210 . Compactor  201  compresses the assembly together prior to the belt being fed to a press and finally vulcanized. 
     FIG. 3 illustrates the crossover of the insulated coated fabric and wire of the conductor caused by forming the figure eight sensor loop configuration as disclosed in the &#39;446 patent. The total thickness of the crossover of insulated fabric  207  and wire portions  301  and  302  of a sensor loop  105  conductor assembly  205  is represented by reference numeral  303  and is twice the diameter of the wire plus the thickness of the fabric. 
     Although details of the conductor crossovers are not discussed in the prior art patents hereinabove, it should be apparent to those skilled in the art that the disclosed rip detection systems (e.g.,  100 ) having sensor loops incorporating crossovers will not function properly unless the conductors (e.g.,  105 ,  301 ,  302 ) are insulated or otherwise prevented from touching themselves (short-circuiting) wherever they cross over. In other words, a portion  301  of a sensor loop  105  must not be allowed to touch an other portion  302  of the same sensor loop  105 . 
     It is desirable to minimize the thickness of conveyor belt sensors, while at the same time preventing short circuiting at sensor conductor crossovers, and also providing sensor conductors which will resist breakage due to flexure. 
     SUMMARY OF THE INVENTION 
     This invention concerns the use of microcoil springwire for conductors utilized for sensors in conveyor belt rip detection systems in order to achieve the objectives of minimizing the thickness of conveyor belt sensors, while at the same time preventing short circuiting at sensor conductor crossovers, and also providing sensor conductors which will resist breakage due to flexure. 
     According to the invention, a rip detection sensor for incorporation within a conveyor belt comprises a conductor formed in an endless loop arranged in a signal inverting configuration wherein the conductor crosses itself in at least one crossing place. The conductor is formed as microcoil springwire. The conductor crosses itself by crossing through itself such that the microcoil springwire resides substantially in a single plane throughout the sensor including the crossing places, and means are provided to prevent short-circuiting of the conductor at the crossing places. 
     According to the invention, the conveyor belt is characterized in that the short-circuit prevention means comprise insulation coating the conductor, or comprise adhesive applied between the microcoil conductor portions where they cross-through each other. 
     According to the invention, the conveyor belt is characterized in that the short-circuit prevention means comprise a tee having two grooves in which an elongated portion of the microcoil springwire conductor can reside to form a cross-through for the conductor, wherein the grooves are on opposite faces of the tee and are oriented substantially orthogonally to each other. 
     According to the invention, the conveyor belt is characterized in that the short-circuit prevention means comprise a tee having a first, second, third, and fourth cylindrical dowel, wherein the first and third dowels are on opposed sides of the tee, and the second and fourth dowels are on opposed sides of the tee; such that a first crossing portion of the microcoil springwire conductor can be wrapped around the first dowel, elongated to traverse a first side of the tee, and then wrapped around the opposing third dowel; and such that a second crossing portion of the microcoil springwire conductor can be wrapped around the second dowel, elongated to traverse a second side of the tee, and then wrapped around the opposing fourth dowel. The microcoil springwire conductor can be affixed to the tee with an adhesive. 
     According to the invention, the conveyor belt is characterized in that the microcoil springwire conductor comprises plated or coated high-tensile strength steel. Furthermore, the microcoil springwire comprises a coiled conductor with a pitch of between one to four conductor diameters, and a coil diameter of between 0.025 to 0.175 inches and preferably between 0.050 to 0.10 inches. 
     According to the invention, the conveyor belt comprises a top load bearing surface, a middle carcass layer, and a pulley cover, characterized in that the sensor is embedded within any of the three layers. 
     According to the invention, the conveyor belt is characterized in that the sensor includes loops configured for use in connection with a belt rip detection system which includes external transmitter/exciters, and receiver/detectors. 
     An aspect of the invention is a method of manufacturing a conveyor belt incorporating within it a rip detection sensor comprising a conductor formed in an endless loop arranged in a substantially figure-eight configuration wherein the conductor crosses itself in at least one crossing place, characterized by: forming the conductor as a microcoiled springwire; forming the crossing places such that the microcoil springwire conductor crosses through itself and resides substantially in a single plane throughout the sensor including the crossing places; and preventing short-circuiting of the conductor at the crossing places. 
     According to the invention, the method is characterized by insulating the conductor to prevent short-circuiting, or by providing adhesive between the conductor portions at the crossing places. 
     According to the invention, the method may be characterized by providing tees at the crossing places. The method further includes elongating portions of the conductor in the crossing places, wrapping the elongated portions of the conductor around the tees, and possibly affixing the conductor to the tees with adhesive. 
     A further aspect of the invention is a conveyor belt rip detection system, comprising a conveyor belt incorporating within it a rip detection sensor comprising a conductor formed in an endless loop arranged in a signal inverting configuration wherein the conductor crosses itself in at least one crossing place, and the sensor has loops. The system further comprises a drive motor, a driven roller driven by the drive motor, a following roller, an external transmitter and receiver coupled with the sensor loops, and control circuitry controllably connected between the external receiver and a motor controller for controlling the action of the drive motor. The conveyor belt rip detection system is characterized in that the conductor is formed as microcoil springwire; the conductor crosses itself by crossing through itself such that the microcoil springwire resides substantially in a single plane throughout the sensor including the crossing places; and means are provided to prevent short-circuiting of the conductor at the crossing places. 
     According to the invention, the conveyor belt rip detection system is characterized in that the means to prevent short circuiting is selected from the group consisting of adhesive, insulation coating the conductor, a tee having two grooves, and a tee having a first, second, third, and fourth cylindrical dowel or other non-conductive material positioned to prevent the two or more sections of microcoil from contacting each other. 
     Additional objects of the invention will be understood when reference is made to the Brief Description of the Drawings, Description of the Invention and Claims which follow hereinbelow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference will be made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawing figures. The figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these preferred embodiments, it should be understood that it is not intended to limit the spirit and scope of the invention to these particular embodiments. 
     Certain elements in selected ones of the figures may be illustrated to a different scale than other elements in the same drawing, or elements of other figures. The cross-sectional views, if any, presented herein may be in the form of “slices”, or “near-sighted” cross-sectional views, omitting certain lines which would otherwise be visible in a true cross-sectional view. 
     Elements of the figures are typically numbered as follows. The most significant digits (hundreds) of the reference number corresponds to the figure number. Elements of FIG. 1 are typically numbered in the range of 100-199. Elements of FIG. 2 are typically numbered in the range of 200-299. Similar elements throughout the figures may be referred to by similar reference numerals. For example, the element  199  in a figure may be similar, and possibly identical to the element  299  in an other figure. In some cases, similar (including identical) elements may be referred to with similar numbers in a single drawing. For example, each of a plurality of elements  199  may be referred to individually as  199   a ,  199   b ,  199   c , etc. Such relationships, if any, between similar elements in the same or different figures will become apparent throughout the specification, including, if applicable, in the claims and abstract. 
     The structure, operation, and advantages of the present preferred embodiment of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a schematic of the prior art rip detection system; 
     FIG. 2 is a cross-sectional exploded view of the prior art conveyor belt construction; 
     FIG. 3 is a cross-sectional view illustrating the spatial relationship of conductors in a crossover according to the prior art; 
     FIG. 4 is a cross-sectional view of the cross-through of microcoil springwire conductors according to the present invention; 
     FIG. 5 is a schematic of the conveyor belt rip detection system according to the present invention; 
     FIG. 6 is a cross-sectional exploded view of the conveyor belt construction according to the present invention; 
     FIG. 7 is a perspective view of the microcoil springwire employed in the sensor according to the present invention; 
     FIG. 8 is a cross sectional view of the microcoil springwire of FIG. 7 illustrating a rubber coated wire according to the present invention; 
     FIG. 9 is a perspective view of the cross-through of microcoil springwire conductors according to the present invention; 
     FIG. 10 is a diagrammatic representation of the microcoil springwire arranged in multiple loops for a sensor according to the present invention; 
     FIG. 11 is a cross sectional view of a first embodiment of the conveyor belt taken along the lines  13 — 13  of FIG. 15 according to the present invention; 
     FIG. 12 is a cross sectional view of the first embodiment of the conveyor belt similar to that of FIG. 11 with the addition of an external energy source and an external receiver in proximity to the conveyor belt according to the present invention; 
     FIG. 13 is a cross-sectional view of another embodiment of the conveyor belt taken along the lines  13 — 13  of FIG. 15 according to the present invention; 
     FIG. 14 is a cross-sectional view of the embodiment of the conveyor belt of FIG. 13 with the addition of an external energy source and an external receiver in proximity to the conveyor belt according to the present invention; 
     FIG. 15 is a plan view of the conveyor belt with the sensors embedded therein (not shown) according to the present invention; 
     FIG. 16 is a schematic view of the conveyor belt of FIG. 15 with the sensor loops exposed so as to illustrate their relative positions along the length of the belt according to the present invention; 
     FIG. 17 is a cross sectional view of a cross-through such as that illustrated in FIG. 9 with epoxy shown separating the microcoil springwire portions according to the present invention; 
     FIG. 18 is a top view illustrating the approximate orthogonal nature of the cross-through of two elongated sections of the microcoil springwire according to the present invention; 
     FIG. 19 is a top perspective view of a tee with a groove in which an elongated portion of the microcoil springwire resides according to the present invention; 
     FIG. 20 is an enlarged side view of a portion of the microcoil springwire illustrating the pitch and diameter of the microcoil springwire according to the present invention; 
     FIG. 21 is a plan view of the preferred embodiment of a microcoil springwire cross-through wherein the springwire has been wrapped around a tee according to the present invention; 
     FIG. 22 is a front view of the tee of FIG. 21 according to the present invention; 
     FIG. 23 is a view similar to FIG. 22 with wire wrapped around the cylindrical dowels or protrusions according to the present invention; 
     FIG. 24 is a view similar to FIG. 21 illustrating the epoxy/adhesive affixing the springwire to the tee according to the present invention; and 
     FIG. 25 is a view similar to FIG. 23 illustrating the epoxy/adhesive affixing the springwire to the tee according to the present invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     The present invention is directed to a conveyor belt rip detection system, as shown in FIG. 5, which incorporates signal inverting sensors  130 ,  140  and  150  of a conductor  301 ,  302  (generally a wire), as shown in FIG.  3 . An important feature of the invention is to use microcoil springwire  701 , as illustrated in FIG. 7, for the conductor in the sensors  130 ,  140 ,  150 . Another important feature of the invention relates to the manner in which the conductors cross over (or through) each other as shown in FIG. 4, which illustrates the cross-through of the conductor portions  401 ,  402  of the sensors  130 ,  140 ,  150  of the present invention. Reference numeral  401  indicates one portion of a sensor loop conductor made of microcoil springwire  701 , and reference numeral  402  indicates another portion of the same sensor loop conductor crossing-through within the total height  403  of the microcoil. Various embodiments of the present invention are disclosed hereinbelow which provide various means of insulating the conductor portions  401 ,  402  from each other where the portions cross through each other. 
     FIG. 5 illustrates the conveyor belt rip detection system of the present invention. Sensors  130 ,  140  and  150  are spaced apart from each other and are embedded in a conveyor belt  540 . Conveyor belt  540  moves in the direction of arrow  535  and is driven by roller (or pulley)  538  and roller  539  follows. Typical systems incorporate multiple un-driven rollers  539  for long belts  540 , and may also include multiple driven rollers  538 . Sensors  130 ,  140 ,  150  pass over transmitter/exciter  1232  and receiver/detector  1233 . Receiver  1233  communicates with control circuitry  534 . If the control circuitry  534  senses a discontinuity in any of the sensors  130 ,  140  and  150 , it then signals motor controller  536  to stop motor  537 . Transmitter/exciters and receiver/detectors are known in the art, as generally described in the U.S. Pat. No. 4,854,446. 
     FIG. 6 illustrates the process for manufacturing the conveyor belt  540  wherein a section  600  of conveyor belt is shown prior to vulcanization. A load carrying cover  602  has a layer of tie gum  603  affixed thereto. Reinforcing cables  604  running the length of the conveyor belt  540  are disposed between the gum layer  603  and a gum layer  606  on the inner side of a pulley cover  607 . After the sensors  130 ,  140 ,  150  are placed within the conveyor belt, such as the sensor made of microcoil springwire  701 , as shown in FIG.  7  and discussed in more detail below, the belt is disposed in a compactor  601  that applies pressure to the load carrying cover  602  and the pulley cover  607  to compress the components of the conveyor belt together. Then the completed conveyor belt assembly  600  is vulcanized. 
     FIG. 7 is a perspective view of a section of a springwire conductor  712  formed into a microcoil springwire  701  which is employed as sensors  130 ,  140 ,  150  to detect rips in the conveyor belt  540 . The use of the microcoil springwire  701  for conveyor belt rip detection system sensor conductors is a feature of this invention, intended to provide flexibility and fracture resistance, as well as enabling thinner overall sensors  130 ,  140 ,  150  due to the methods described hereinbelow of crossing-through where the conductors cross (as illustrated in FIG.  4 ). 
     Referring to FIG. 8, there is shown a cross sectional view of the microcoil springwire  701  illustrating an electrical insulator  835  (e.g., rubber) coating the springwire conductor  834 , which is preferably brass or copper plated steel. The gauge of the springwire can typically be in the range of 0.005 to 0.030 inches and preferably in the range of 0.010 to 0.020 inches and the diameter  2024  (see FIG. 20) of the microcoil  701  is in the range of 0.025 to 0.175 inches and preferably in the range of 0.050 to 0.10 inches. The insulation or rubber coating  835  is optional. 
     FIG. 9 is a perspective view of the microcoil springwire  701  illustrating the springwire conductors  712  disposed in a cross-through  905  of a sensor  130 ,  140 ,  150 . 
     FIG. 10 is a diagrammatic representation of the microcoil springwire  701  arranged in multiple loops  1002  and  1015  to form a signal inverting type of sensor  130 ,  140 ,  150 . Reference numerals  1003  and  1004  each indicate a dashed circle indicating three crossing places which are cross-throughs. Reference numeral  905  indicates a single cross-through such as in FIG.  9 . Preferably the tee  2125  of FIG. 21 is used at each cross-through  905  to prevent short-circuiting of the conductor  712  where it crosses through itself. The microcoil springwire  701  is formed into a signal inverting pattern and comprises just one springwire conductor  712  with its two ends joined together as indicated by reference numeral  1006  to form an endless loop. The joint  1006  can be made, for example, by braiding, soldering or by a mechanical connector, all of which are known in the electrical trades. The microcoil springwire  701  is arranged to cross through (as in FIG. 4) rather than over or under itself (as in prior art FIG.  3 ), so that the two crossing portions of microcoil springwire conductor  701  are in substantially the same plane. 
     FIG. 11 is a cross sectional view of a first embodiment of the conveyor belt taken along the lines  13 — 13  of FIG.  15 . Conveyor belt  1107  is comprised of three sections: a top section  1108  which is a load carrying surface which is affixed by known technology to a middle section  1109  comprising tie gum and a fabric carcass or reinforcing cables  1110 . Those skilled in the art may refer to the middle section  1109  as the carcass section. Middle section  1109  includes plies of fabric or reinforcing steel cables  1110  which typically run longitudinally within the conveyor belt  1107 . Pulley cover  1111  is affixed to the middle section  1109  as is known in the art. Cross-sections of -the micro-coiled springwire conductor  712  of the microcoil springwire  701  are shown vulcanized into the pulley cover  1111 . Coiled conductor portions  712  illustrated in cross-section in FIG. 11 reside in substantially the same plane. The plane in which the conductor  712  microcoils reside is approximately the thickness (0.10″) of the diameter  2024  of the microcoils as illustrated in FIG.  20 . FIG. 20 is an enlarged side view of a portion of the microcoil springwire  701  illustrating the pitch  2023  and diameter  2024  (0.10″) of the microcoil springwire. 
     It is highly desirable to provide the sensor  130 ,  140 ,  150  loops and cross-throughs of the microcoil springwire  701  in substantially a single plane so as to minimize the thickness of the pulley cover  1111 . Using the microcoil springwire  701  provides flexure capability so as to protect against inadvertent fracturing of the sensor  130 ,  140 ,  150 . There are substantial cost savings in using a thinner pulley cover  1111  which is enabled by the use of a flexible microcoil springwire  701  with cross-throughs in a single plane. The microcoil springwire  701  is designed to flex and rotate without permanent deformation or fracture. 
     FIG. 12 is a cross sectional view of the conveyor belt  1107  of FIG. 11 with the addition of an external energy source  1232  (sometimes called an exciter or transmitter) and an external receiver  1233  (sometimes called a detector) in proximity to the pulley cover  1111  of the conveyor belt  1107 . Also, see FIG. 5 for a schematic view of the belt rip detection system, and see FIG. 10 for a top view of the sensor  130 ,  140 ,  150  loops made of microcoil springwire conductor  712  which are illustrated in cross-section in FIG.  12 . In operation, the sensor loops  1002 ,  1015  pass in proximity to the external energy source  1232  and the external receiver  1233 . The loops  1002  and  1015  are exposed so as to illustrate their positions across the width of the belt relative to the external detector  1233  and external exciter  1232 . The schematic drawing of FIG. 10 indicates that the loops  1002  and  1015  are generally arranged in a signal inverting pattern. FIG. 10 illustrates three loops in each side  1002  and  1015 . However, those skilled in the art will recognize that a different number of loops may be used without departing from the spirit and scope of the invention as claimed. Further, those skilled in the art will recognize that a different pattern of loops may be employed without departing from the spirit and scope of the claimed invention. 
     FIG. 13 is a cross-sectional view of the preferred embodiment of the conveyor belt  1307  (compare to the first embodiment  1107 ) taken along the lines  13 — 13  of FIG.  15 . Cross-sections of the micro-coiled springwire conductor  712  of the microcoil springwire  701  are shown vulcanized into tie gum which surrounds steel reinforcing cables  1310  in the middle section or carcass  1309 . Coiled conductor portions  712  illustrated in cross-section in FIG. 13 reside in substantially the same plane. The plane in which the conductor  712  microcoils reside is approximately the thickness (0.10″) of the diameter  2024  of the microcoils as illustrated in FIG.  20 . An optional insulating spacer (not shown) such as a fabric layer may be positioned between the springwire conductors  712  and the reinforcing cables  1310 . Pulley cover  1311  can be made of a thinner construction in this preferred embodiment  1307 . Reference numeral  1308  denotes the load carrying surface of the conveyor belt  1307 . 
     FIG. 14 is a cross-sectional view of the preferred embodiment of the conveyor belt  1307  of FIG. 13 with the addition of an external energy source  1232  and an external receiver  1233  in proximity to the conveyor belt  1307 . If there is a break in the springwire conductor  712 , it is sensed by receiver  1233  and control circuitry  534  signals the motor controller  536  to stop motor  537  (also see FIG.  5 ). 
     FIG. 16 is a top view of a conveyor belt  1107  with the sensors embedded therein. Reference numerals  130 ,  140  and  150  represent three of the many sensors typically employed in a belt, and are typically spaced approximately 25 to 250 feet from each other. Also see FIG.  5 . Referring to FIGS. 12 and 14, as the belt  1107 ,  1307  moves, it passes over an external pair comprising an exciter  1232  and a receiver  1233  which then interrogates the microcoil springwire  712  of the sensor (e.g.,  130 ,  140 ,  150 ) for continuity. If a discontinuity is detected the belt is automatically shut down and inspected and/or repaired. Various control schemes may be employed to detect a damaged belt. For instance, the spacing between sensors may be varied and/or multiple open circuits (i.e., open sensors) may be detected before the belt is shut down. 
     FIG. 17 is a cross sectional view of a cross-through such as the cross-through  905  illustrated in FIG.  9 . Note that FIG. 9 does not illustrate adhesive  1716  (e.g., epoxy) between the elongated portions of the microcoil  701  in the cross-through  905 , but there is a space between the microcoil springwire conductors  712  in the elongated portions of the microcoil  701 . Epoxy/adhesive  1716  is used to separate the portions of springwire conductor  712  from each other, thereby preventing short-circuiting. If a tee  2125  as illustrated in FIG. 21 is not used to assist in the separation of the conductor portions  712 , then epoxy  1716  should be used to ensure that they are insulated each from the other. Although the springwire conductor  712  itself may be insulated (as shown in FIG.  8 ), if two portions of the springwire conductor  712  happen to be in engagement, there is a possibility that the insulation (e.g.,  835 ) may wear away. In this instance the detector/receiver  1233  may not receive correct information as to the integrity of the belt. 
     FIG. 18 is a top view illustrating the approximate orthogonal nature of the cross-through of two elongated portions of the microcoil springwire  712 . In an elongated helical arrangement the helix approximates a sine wave enabling the microcoil springwire conductors  712  to pass through each other, and at this cross-through the orientation of the conductors  712  are approximately orthogonal each to the other. 
     FIG. 19 is a top perspective view of a tee  1921  with a groove  1922  in which an elongated portion of the microcoil springwire conductor  712  can reside to form a cross-through such as those illustrated in FIGS. 9 and 18, with the tee  1921  providing insulation between the microcoil springwire conductor portions  712 . A reciprocal groove (not shown) is located on the bottom (opposite face) of the tee  1921 . An adhesive (not shown) may be applied to affix the conductor  712  in the grooves  1922  and onto the tee  1921 . 
     FIG. 20 is an enlarged side view of a portion of the microcoil springwire (e.g.,  701 ) illustrating the pitch  2023  and coil diameter  2024  of the microcoil springwire in its normal configuration (not elongated for a cross-through). The coil diameter  2024  of the microcoil is in the range of 0.025 to 0.175 inches and preferably in the range of 0.050 to 0.10 inches. It is this configuration that the microcoil springwire  701  takes at places where it does not cross-through itself. The wire has a pitch  2023  of between one to four diameters and can stretch out in length to several times its original length. The springwire conductor  712  is electrically conductive and is suitably plated high-tensile strength steel which exhibits good mechanical strength and resistance to corrosion when vulcanized into a pulley cover  1111 ,  1311 , top cover  1108 ,  1308  or into the tie gum of the carcass  1109 ,  1309  of a conveyor belt  1107 ,  1307 . 
     FIG. 21 is a plan view of the preferred embodiment of a microcoil springwire  701  cross-through wherein the microcoil springwire conductor  712  has been wrapped around a tee  2125  made of a non-conductive material such as plastic. FIG. 22 is a front view of the tee  2125  of FIG.  21 . The conductor  712  in the individual coils of the microcoil springwire  701  is elongated to wrap around the first cylindrical dowel  2127 , the second cylindrical dowel  2128 , the third cylindrical dowel  2129  and the fourth cylindrical dowel  2130 . Further elongation or straightening is necessary to traverse the tee  2125  which ensures separation of conductor portion  2126  which traverses the top of tee  2125  and conductor portion  2131  which traverses the bottom of tee  2125 . Reference numerals  2126  and  2131  have been assigned to those portions of springwire conductor  712  wherein the helical microcoil has been substantially elongated to traverse tee  2125 . 
     FIG. 23 is a view similar to FIG. 22 illustrating the springwire conductor  712  wrapped around the cylindrical dowels or protrusions  2127 ,  2128 , and  2130 . Reference numerals  2126  and  2131  indicate the elongated portions of the springwire conductor  712  which traverse the tee  2125 . 
     FIG. 24 is a view similar FIG. 21 illustrating an adhesive  1716  (e.g., epoxy) affixing the springwire to the tee. The adhesive  1716  ensures that the conductors  712  stay firmly affixed to the tee. Where there are multiple cross-throughs, multiple tees  2125  are used, one tee  2125  per cross-through. FIG. 25 is a view similar to FIG. 23 illustrating adhesive  1716  affixing the springwire  712  to the tee  2125 . 
     It will be understood by those skilled in the art that many changes and modifications may be made to the described invention without departing from the spirit and scope of the claims which are appended below.