Abstract:
A conveyer belt abrasion detecting apparatus which can automatically detect a conveyer belt abrasion quantity easily and accurately during operation. A plurality of magnet sheets (M 1 -M 5 ) magnetized in a thickness direction are arranged so that polarities on the surface are in the same direction and are embedded deeper stepwise in a longitudinal direction of a belt main body ( 2 ). A magnetic sensor ( 4 ) for detecting changes of the magnetic forces of the magnet sheets (M 1 -M 5 ) is arranged at a position where the magnet sheets (M 1 -M 5 ) pass through.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a National Stage of International Application No. PCT/JP2006/307728 filed on Apr. 12, 2006, claiming priority based on Japanese Patent Application Nos. 2005-115626, filed Apr. 13, 2005 and 2005-306603, filed Oct. 21, 2005, the contents of all of which are incorporated herein by reference in their entirely. 
   TECHNICAL FIELD 
   The present invention relates to a conveyor-belt wear detector for detecting wear of a conveyor belt without contact. 
   BACKGROUND OF THE INVENTION 
   JP2004-35115A discloses a conveyor-belt wear detector in which a wear-detecting layer having a color different from that of an elastic layer of a belt body is embedded in a belt body, the colored wear-detecting layer being exposed with wear of the elastic layer to allow the wear to be found. 
   As another measure for detecting wear, thickness of a conveyor belt is periodically determined by an ultrasonic-wave thickness meter to find wear while the conveyor belt stops. 
   In DE19525326C1 a number of transponders are embedded at different depths from the surface in a belt. Destruction or dropout of any one of the transponders with wear of the belt is detected by an antenna comprising a transmission coil and a sensor coil to allow wear of the belt to be found. 
   However, in the detector of JP2004-35115A and the ultrasonic wave thickness meter, it is very difficult to determine the amount of the wear automatically. Wear has to be determined visually by a person while the conveyor belt stops, so that its efficiency is poor. 
   In DE19525326C1, a number of transponders have to be embedded over a broad range to make the device itself larger, which requires a high cost. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide a conveyor-belt wear detector for detecting wear of a conveyor belt during operation automatically, readily and exactly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevational view of the first embodiment of a conveyor-belt wear detector according to the present invention; 
       FIG. 2  is an enlarged sectional view of the part II in  FIG. 1 ; 
       FIG. 3  is an enlarged view seen from the line III-III in  FIG. 1 ; 
       FIG. 4  is a block diagram of a control; 
       FIG. 5  is a sectional view showing wear of a belt; 
       FIG. 6  shows the second embodiment of the present invention, similar to  FIG. 3 ; 
       FIG. 7  is a sectional view taken along the line VII-VII in  FIG. 6 ; 
       FIG. 8  is a view showing local wear of a belt body in the second embodiment; 
       FIG. 9  is a bottom plan view of the third embodiment of the present invention, similar to  FIG. 3 ; 
       FIG. 10  is a sectional view taken along the line X-X in  FIG. 9 ; 
       FIG. 11  is a bottom plan view showing the fourth embodiment of the present invention, similar to  FIG. 3 ; and 
       FIG. 12  is a sectional view taken along the line XII-XII in  FIG. 11 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   The first embodiment of a conveyor-belt wear detector comprises a magnet-sheet group  3  comprising a plurality of magnet sheets M 1 ,M 2 ,M 3 ,M 4 ,M 5  in a belt body  2  wound on a pulley  1 ; and a magnetic sensor  4  for detecting magnetic force from the magnet sheet group  3  near the belt body  2 . 
   In each of the magnetic sheets M 1 -M 5  of the magnet sheet group  3 , a sheet-like magnetic substance is magnetized along thickness of the belt body  2  or vertically in  FIG. 2 , and magnet powder is dispersed and mixed in a rubber matrix, which is molded like a sheet and magnetized along thickness of the belt body  2  to form a bonded magnet. Other permanent magnets may be used. 
   Along a running direction P of the belt body  2 , the magnet sheet are embedded to become deeper, but may be embedded shallower. The number of the magnet sheets M 1 -M 5  may be more than one. 
   The magnet sheets M 1  to M 5  can be embedded in the belt body  2  when a belt is manufactured, but may preferably be embedded in a joined portion  5  at which one end of the belt body  2  is joined to the other end because it is easier to embed it. Where to embed it is not limited thereto. 
   In the illustrated embodiment, in any of the magnet sheets M 1 -M 5 , N poles are in an outer side, while S-poles are in an inner side, but N-poles may be in an inner side, while S-poles may be in an outer side. 
   The magnetic sensor  4  is well-known such as a loop coil or a hole element and located as close as possible with respect to a running position of the magnet sheets M 1 -M 5 . In  FIGS. 1 and 2 , the magnetic sensor  4  may preferably be positioned near the returning belt body  2 . Cleaned part which conveyed material is taken off by a scraper  6  can be detected in the belt body  1 . 
   In  FIG. 3 , a width guide  7  is provided to limit a width of the belt body  2  passing through the guide  7 , while a thickness guide  8  is provided to keep a relation of the belt body  2  with the magnetic sensor  4  at the other side of the magnetic sensor  4 . The magnetic sheets M 1 -M 5  having the same length are embedded in the belt body  2  along width of the belt body  2 . 
     FIG. 4  shows one example of a conveyor-belt wear detector. A control comprises a site control portion  10  which receives a detected signal from the magnetic sensor  4 , operates wearing degree of the belt and transmits the result from a transmitting portion  9 ; and a central control portion  13  in which a receiving portion  11  receives a transmitted signal, outputs an operated result to an output terminal  12  and taking required actions such as giving a warning or stopping the belt conveyor if the wear exceeds a critical value. 
   The site control portion  10  or the central control portion  13  comprises a digital control unit (not shown) which counts a peak number of magnetic force of the magnet sheets M 1 -M 5  detected by the magnet sensor  4 , finds dropout of the magnet sheets M 1 -M 5  owing to decrease in the counted number and detects wear of the belt body  2  digitally; and an analogue control unit (not shown) which detects wear of the belt body  2  analoguely based on change in peak values of magnetic force of the magnetic sheets M 1 -M 5  detected by the magnetic sensor  4 . 
   Operation of the embodiment of a wear detector will be described. 
   Whenever the magnet sheets M 1 -M 5  pass near the magnet sensor  4  as the belt body  2  moves in a direction of an arrow P, the magnet sensor  4  detects magnetic force and a signal of wave form in  FIG. 2  is outputted. A signal from the nearest magnet sheet M 1  is an output wave form H 1  having the highest peak value and a signal of the second stage magnet sheet M 2  is slightly lower peak value. Signals of the magnet sheets M 3 ,M 4  are output waveforms H 3 ,H 4  of lower peak values. A signal from the deepest magnet sheet M 5  is an output waveform H 5  of the lowest peak value. 
     FIG. 5  shows wear of the conveyor belt. Wear of the belt body  2  starts from the face on which material is conveyed, and the first magnet sheet M 1  which is the shallowest starts to wear. In  FIG. 5(   a ), the first magnet sheet M 1  drops out with wear of the belt body  2 , so the output waveform H 1  disappears. 
   Furthermore, the second, third and fourth magnet sheets M 2 , M 3 , M 4  drop out, so that the output waveforms H 1 -H 4  disappear and the output waveform H 5  from the magnet sheet M 5  only remains. 
   A signal from the magnetic sensor  4  is inputted into the site control portion  10 , and the number of peak values of the output waveforms H 1 -H 5  is counted by a counter therein and determines the magnet sheets M 1 -M 5  dropped out, so that wear of the belt body  2  can exactly be detected digitally. 
   The peak values of the present output waveforms H 1 -H 5  are deducted from the peak values of the initial output waveforms H 1 -H 5  of the belt body  2 , so that wear degree is detected analoguely until each of the magnet sheets M 1 -M 5  drops out. 
     FIGS. 6-8  show the second embodiment of the invention. 
   Each of magnet sheets M 1 -M 6  of a magnet sheet group  3  is magnetized along thickness of the belt body  2  similar to the first embodiment. In the second embodiment, each of the magnet sheets M 1 -M 6  in the magnet sheet group  3  is embedded at the same depth from the face of the belt body  2  having the same direction of magnetic pole, shifting along width and length to form an oblique arrangement. 
   The magnetic sensor  4  comprises a gate-shape loop coil which can cover the whole width of the belt body  2 , close to the surface of the belt body  2 . 
   Whenever the belt body  2  moves in a direction of an arrow P to allow the magnet sheets M 1 -M 6  to pass close to the magnetic sensor  4 , the magnetic sensor  4  detects the magnetic force and signals of output waveforms H 1 -H 6  having substantially the same peak values 4 are outputted from the magnetic sensor  4  in  FIG. 6 . 
   In  FIG. 8 , local wear  14  occurs in the belt body  2 , and the second magnet sheet M 2  drops out, so that the second output waveform H 4  disappears, which is detected by a site control portion  10  to find out a position of the wear similar to the first embodiment. 
   Peak value of each of the output waveforms H 1 -H 6  is deducted from peak value of the initial output waveforms H 1 -H 6  of the belt body  2 , thereby analoguely detecting wear until each of the magnet sheets M 1 -M 6  drops out or wear of the belt body  2  where each of the magnet sheets M 1 -M 6  is disposed. 
     FIGS. 9 and 10  show the third embodiment of the present invention. 
   A belt body  2  is divided longitudinally to provide three detection areas A-C in which magnet sheet groups  3 A- 3 C are embedded respectively. The number of the detection areas is optional. 
   The magnet sheet groups  3 A- 3 C of the detection areas A-C are shifted stepwise along width and length of a conveyor belt to form an oblique arrangement over the whole width while magnetic pole is in the same direction. In  FIG. 10 , the magnet sheet group  3 A of the detection area A is the shallowest and the magnet sheet group  3 B and the magnet sheet group  3 C become deeper in order. 
   Whenever the belt body  2  moves in a direction of P to make the detection areas A-C closer to the magnetic sensor  4 , the magnetic sensor  34  detects magnetic force, and the magnetic sensor  4  outputs waveforms Ha-Hc which have substantially the same strength in the same detection area and become smaller in order of the detection areas A-C. 
   For example, local worn portion  15  occurs in the detection area A and a magnetic sheet M 2  drops out, so that the second output waveform Ha 2  in the detection area disappears. Similar to the second embodiment, it is detected by a site control portion  10  to allow where to wear and how deep to wear to be detected at the same time. As well as in the other detection areas B, C, if the belt is worn to the depth of the magnet sheet groups  3 B, 3 C, local wear in the detection area B,C can be detected under the same principle. 
     FIGS. 11 and 12  show the fourth embodiment of the present invention. 
   In this embodiment, a belt body  2  comprises three layers of a reinforcement layer  2   c  such as cloth between a face layer  2   a  and a back layer  2   b . A plurality of magnet sheets M 1 -M 5  magnetized along thickness becomes deeper or shallower stepwise along length of the belt body  2  to form one unit U. A plurality of units U 1 -U 5  are arranged to shift along length or width of the belt body  2 . 
   N-poles of the magnet sheets M 1 -M 5  are toward the face side of the belt body  2 . 
   In front of the first unit U 1  close to the reinforcement layer  2   c  in the face layer  2   a , a magnet sheet MS for calculating the head and detecting elongation is embedded. 
   The magnetic pole of the magnet sheet MS is reverse to those of the other magnet sheets M 1 -M 5  and S-pole is toward the face of the belt body  2 . The others are the same as in the first embodiment. 
   In the fourth embodiment, when the belt body  2  moves in a direction of the arrow P in a normal condition, the magnet sheet MS outputs a single cycle output waveform Hx comprising a negative peak value and a positive peak value, and the magnet sheets M 1 -M 5  of the first unit U 1  output a single cycle output waveform comprising a positive peak value and a negative peak value. Then, each of the units U 2 -U 5  outputs similar output waveforms HU 2 -HU 3  repeatedly. HU 4  and HU 5  are not shown. 
   In the output waveform Hx, when the magnet sheet MS meets a loop-coil magnetic sensor  4  to allow a downward line of magnetic force toward the S-pole of the magnet sheet MS to go through a coil, the output waveform shows a negative peak value. When the magnet sheet MS leaves the magnetic sensor  4  to allow the line of magnetic force of the magnet sheet MS to go out of the coil, the output waveform shows a positive peak value. 
   In the output waveforms HU 1 -HU 5 , the magnet sheets M 1 -M 5  of each of the units U 1 -U 5  constitute one mass to form a distribution of the line of magnetic force. When the head of the mass of the magnet sheets M 1 -M 5  passes by the loop-coil magnetic sensor  4  to allow an upward line of magnetic force from the N-pole of the magnet sheet M 1 -M 5  to get into the coil, the output waveform shows a positive peak value. When the end of the mass of the magnet sheets M 1 -M 5  leaves the magnetic sensor  4  to allow the line of magnetic force of the magnet sheets M 1 -M 5  to get out of the coil, the output waveform shows a negative peak value. 
   The magnet sheets M 1 -M 5  are embedded so that the sheets are embedded gradually deeper. Thus, the line of magnetic force passing through the magnetic sensor  4  is the strongest from the magnet sheet M 1  and gradually decreases to allow the magnet sheet M 5  to be the weakest. So the negative peak value at the end of each of the output waveforms HU 1 -HU 5  is smaller than the positive peak value at the head. 
   In  FIGS. 11 and 12 , a local worn portion  16  in the belt body  2  occurs to allow the first magnet sheet M 1  of the second unit U 2  to drop out, so that the head peak value P 1  of the second output waveform HU 2  disappears as shown by a dotted line in  FIG. 11 . Similar to the first embodiment, change of peak distance and lowering of the peak value are detected by a site control portion  10  so that we can find a position and a degree of the wear of the local worn portion  16  exactly. 
   While the belt body  2  runs at a fixed velocity, time from the output waveform Hx to the next waveform Hx is measured. With extension of the time, elongation of the belt body  2  can be detected. 
   The foregoing merely relate to embodiments of the invention. Various changes and modifications may be made by a person skilled in the art without departing from the scope of claims. 
   For example, the magnet sheets M 1 -M 6  need not to be arranged stepwise in  FIGS. 2 ,  6  and  9 , but may be arranged at random.