Abstract:
A device for monitoring a conveyor belt in which a sensor can be fixed easily to the body without using any special fixing means and the properties of the conveyor belt can be detected with high precision. The device for monitoring the conveyor belt comprises a body to be detected embedded in a conveyor belt ( 6 ) running endlessly, and a sensor ( 7 ) provided oppositely thereto in the body. The sensor ( 7 ) detects the variation in properties of the conveyor belt by detecting variation of the body to be detected due to the variation in properties of the conveyor belt ( 6 ). The sensor ( 7 ) is secured to a shaft ( 5 ) which supports a hollow roller ( 4 ) for guiding the conveyor belt ( 6 ) in the conveyance direction rotatably on the body in the roller ( 4 ) thus making the sensor ( 7 ) itself nonrotatable.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a device for monitoring a conveyor belt. 
         [0002]    In such a device for monitoring a conveyor belt, an object to be detected is embedded in or attached on the conveyor belt. A sensor for detecting the object is fixed to a stationary object close to the moving object to the conveyor belt. Owing to variation in information detected by the sensor, variations in the shape of the conveyor belt such as meandering, a crack and wear can be detected. JP6-48533A discloses magnets as object to be detected. A sensor detects magnetic force, so that the conditions of a conveyor belt can be grasped with variation in magnetic force 
         [0003]    A gauss meter, a loop coil and a MI sensor (magnetic-impedance sensor) are used as sensor. 
         [0004]    JP6-48533A discloses that the sensor is provided in a roller or a pulley. 
         [0005]    JP6-48533A merely discloses that the sensor is provided in the roller and pulley, but there is no detailed structure on how to fix the sensor in the rotating roller or how to pull out a cable extending from the sensor. 
         [0006]    In the publication, the belt does not always contact the roller. The distance between the sensor and the belt varies when the roller contacts the belt and when the roller does not contact the belt. Meandering of the belt can be detected, but it would be very difficult to exactly detect other variations in shape of the belt such as wear. 
       SUMMARY OF THE INVENTION 
       [0007]    In view of the disadvantages in the prior art, it is an object of the invention to provide a device for monitoring a conveyor belt, a sensor being easily mounted to a stationary structure without special mounting means, the shape of the belt being detected with high accuracy. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a vertical sectional front view of a conveyor belt comprising the first embodiment of a device for monitoring the conveyor belt according to the present invention with a monitor for the conveyor belt. 
           [0009]      FIG. 2  is an enlarged partially cutaway view showing the section A in  FIG. 1 . 
           [0010]      FIG. 3  is a vertical sectional view taken along the line III-Ill in  FIG. 2 . 
           [0011]      FIG. 4  is an exploded perspective view showing parts in the section A in  FIG. 1 . 
           [0012]      FIG. 5  is a schematic side view of a tubular conveyor belt to which the present invention applies. 
           [0013]      FIG. 6  is an enlarged vertical sectional view taken along the line VI-VI in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0014]      FIGS. 1-4  show a conveyor belt comprising the first embodiment of the present Invention. 
         [0015]    In  FIG. 1 , at plural positions along the length of a horizontal support frame  1  of the conveyor belt, there are a pair of lower inner brackets  2 , 2  and a pair of higher outer brackets  3 , 3  in the middle and side of the support frame  1  respectively. 
         [0016]    Between the inner bracket  2  and the inner bracket  2 , a guide roller  4  is rotatively mounted around a shaft  5 , and between the inner bracket  2  and the outer bracket  3 , a roller  4  is rotatively mounted around a shaft  5  and tilted to rise sideward. 
         [0017]    The roller  4  may be made of HDPE (high density polyethylene), PP and ABS which are excellent in processing capability, strength, sliding performance and cost. 
         [0018]    The roller may be made of POM (polyacetal) which is better than HDPE, PP and ABS in sliding performance. 
         [0019]    PA66 and PA6 may be used and is better than HDPE, PP and ABS in heat resistance and sliding performance. 
         [0020]    Magnetized electric conductors such as Al alloy may be used. 
         [0021]    An endless trough-like conveyor belt  6  is placed on the rollers  4  and runs smoothly by rotating the rollers  4  around the shaft  5 . 
         [0022]    The conveyor belt  6  is wound between a driving pulley and a driven pulley (not shown). Materials are held on the middle of the upper surface of the conveyor belt  6 , conveyed along a going path from one end to the other end and thrown away onto a hopper. Then, the conveyor belt  6  is guided through guide rollers (not shown) under the support frame  1  along a returning path. 
         [0023]    In  FIGS. 2-6 , the roller  4  is hollow and has an elongate sensor  7  on the shaft  5  therein. The detecting surface of the sensor  6  faces the lower surface of the conveyor belt  6 . 
         [0024]    A cable  8  coupled at one end to the sensor  7  extends from the axial end of the shaft  5  and is connected to a signal processor  9 . The sensor  7  may be a magnetic sensor such as a gauss meter, a loop coil and an MI sensor if magnets are used as object to be detected. 
         [0025]    A signal detected by the sensor  7  is converted to an electric signal by a signal processor  9  and fed to a monitor  11  via a cable  10 . Thus, the conveyor belt  6  can be monitored continuously along the width of the belt  6 . 
         [0026]      FIGS. 2-4  show an internal structure of the roller  4  in detail. The roller  4  comprises a hollow roller body  12  and an end plate  13  fixed to each end of the roller body  12 . An outward flange  13   a  of the end plate  13  is fixed to the inner surface of the roller body  4  by shrinkage fit and a tubular portion  13   b  is provided in the middle. A hole  13   c  is formed in the middle of the tubular portion  13   b.    
         [0027]    The roller  4  is rotatively mounted around the shaft  5  via a ball bearing  14 . A combined labyrinth seal  15  over the ball bearing  14  provides water resistance on the bearing part. 
         [0028]    A cavity  5   a  is formed at one end of the shaft  5 . A closure  16  engages in a thread bore  5   b  of the cavity  5   a.    
         [0029]    The closure  16  projecting outward from the shaft  5  is not circular in a vertical cross section with a pair of flat surfaces  16   a , 16   a  on the outer circumferential surface. The noncircular closure  16  engages in a noncircular axial hole  2   a  of the bracket  2 , so that the shaft  5  is positioned with respect to the bracket  2  to allow the sensor  7  mounted on the shaft  5  to face the conveyor belt  6  anytime. 
         [0030]    Specifically, the closure  16  at the end of the shaft  5  is noncircular and engages in the noncircular axial hole  2   a  of the bracket  2  to allow the sensor  7  to face the conveyor belt  6  anytime. 
         [0031]    A flat surface  5   c  is formed on the outer circumferential surface of the shaft  5 . A rectangular case  7   a  including the sensor  7  is placed on the flat surface  5   c  along the length of the shaft  5 . A U-like piece  17  engages on the shaft  5 , and the ends of the U-like piece  17  pass through an outward flange  7   b  at the lower end of the case  7   a . The ends of the U-like piece  17  are tightened with nuts  18 . So the sensor  5  is firmly fixed to the shaft  5 . 
         [0032]    At the end of the shaft  5 , there is formed a through hole  5   d  which communicates with the cavity  5   a  and opens in the outer circumferential surface of the shaft  5 . A water-proof grommet  19  fits in the through hole  5   d.    
         [0033]    The cable  8  from one end of the case  7   a  extends through the through hole  5   d , the grommet  19 , the cavity  5   a , the through hole  16   b  at the center of the closure  16  and a grommet  20  fitting in the opening end of the through hole  16   b , and is pulled out. 
         [0034]    For assembling, the case  7   a  for the sensor  7  is mounted to the shaft  5  with a mounting tool  17 . After the cable and the closure  16  are mounted as above, they are inserted in the roller  4  via the mounting hole  13   c  of the roller  4  and the sensor  7  is placed at a desired position in the roller  4 . The ball bearing  14  and the seal  15  are mounted in the tubular portion  13   b  at each end of the roller  4 . The ball bearing  14  and seal  15  may have been provided at one end of the roller  4  in advance. 
         [0035]    Only the horizontal roller  4  is shown in detail in the drawings, but the tilted roller  4  is provided at different posture with structure similar to the horizontal roller  4 . 
         [0036]    In  FIG. 3 , a lower non-conveying surface  6   b  of the conveyor belt  6  that conveys materials on the upper surface goes on the roller  4  as shown in an arrow. A magnet M embedded in the conveyor belt  6  is detected by the sensor  7 , and a detected signal is sent to the signal processor  9  via the cable  8 . It is converted into an electric signal which is fed into the monitor  11  via the cable  10 , so that meandering, a crack or wear is detected certainly. 
         [0037]    Besides the magnet M including magnetic rubbers, what transmits sound, light, vibration, magnetic force or electromagnetic wave may be used, and a detector that receives such a signal may be used. 
         [0038]    The present invention may apply not only to a flat conveyor belt in  FIG. 1 , but also to a tubular conveyor belt in  FIGS. 5 and 6 . 
         [0039]    In the tubular conveyor belt, an endless conveyor belt  21  is wound around a front end pulley  22  and a rear end pulley  23 . Between the front end pulley  22  and the rear end pulley  23 , the conveyor belt  21  is rolled up into a tube with an overlapped portion  28  by passing though a number of guide frames  25 , 26 , 27  in which a plurality of guide rollers  24  is arranged like a circle or a trough. Materials are enclosed in the conveyor belt  21  and conveyed with the closed overlapped portion  28 . 
         [0040]    In  FIG. 6 , the intermediate guide frame  26  comprises an upper chamber  26   b  and a lower chamber  26   c  each having an opening  26   a  in the middle through which the conveyor belt  21  goes. The plurality of guide rollers  24  is arranged around the opening  26   a  in each of the chambers  26   b , 26   c.    
         [0041]    A going belt  21   a  of the conveyor belt  21  passes through the opening  26   a  in the upper chamber  26   b , and a returning belt  21   b  passes through the opening  26   a  in the lower chamber  26   c , so that the belts  21   a , 21   b  are kept like a tube. 
         [0042]    In the guide roller  24  of the tubular conveyor belt, there is provided a shaft  31  for rotatively mounting the guide roller  24  to a bracket  31  in the guide frame  26 . A detector (not shown) similar to the sensor  7  in the first embodiment may be provided as well as those in the first embodiment.