Abstract:
The conveyor belt monitor includes sensors and motion detectors for monitoring the condition of the conveyor belt of a conveyor belt system. The monitor includes upper and lower sensors respectively positioned above and below the lower belt of the conveyor to transmit warning of belt damage or other problem(s) while allowing the conveyor to continue operation. An additional switch above the upper sensor detects extreme belt damage, and shuts down the conveyor if such damage or condition(s) is/are detected. A motion sensor may also be provided to detect rotation of the upper roller and to transmit a warning of material carried on the lower or return belt surface that causes the roller to rotate. The monitor thus automatically warns of an anomalous condition while allowing the conveyor to continue to operate, or shuts down the conveyor in the event of an extreme condition(s).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/140,412, filed Mar. 30, 2015. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to conveyor systems and the like, and particularly to a conveyor belt monitor incorporating several sensors monitoring the condition of the belt and the load on the belt to provide the operator with sufficient time to correct the problem prior to belt breakage or other damage. 
     2. Description of the Related Art 
     Conveyor belt systems are used for relatively local transport of a wide variety of goods and materials, and operations are generally highly dependent upon the reliable and continuous operation of such conveyor belt systems. Many such conveyor systems have extensive lengths. Some conveyor systems used in the coal mining industry have lengths on the order of a mile from the face of the coal seam to a point where the loose coal can be loaded into a mine vehicle for further transport. When such a conveyor belt system breaks down for whatever reason, e.g., a broken belt or belt splice, spillage of loose coal onto the lower or return belt and corresponding accumulation of coal at the tail roller at the coal seam face (known in the mining industry as a “gob-out”), delivery of coal from the face of the seam comes to a complete halt, and often many hours are lost due to the time required to repair or perhaps replace the belt. 
     In many cases a relatively minor problem may occur that requires monitoring of the condition, with the system still being functional so long as the problem does not worsen. For example, a “gob-out” may be remedied by clearing the accumulated coal from the lower belt at the tail roller, or a slight delamination can be monitored to allow the system to continue in operation so long as the delamination does not worsen. In such cases it is far more efficient to continue operation of the conveyor belt system, rather than shutting down the entire system unnecessarily. 
     Thus a conveyor belt monitor solving the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     The conveyor belt monitor includes various sensors for detecting the condition of the belt and/or material(s) improperly carried on the belt. The monitor includes a housing that installs upon the conventional lateral members of a conveyor frame. Upper and lower rollers extend across the housing and capture the lower or return portion of the conveyor belt therebetween. Upper and lower sensor switches are installed respectively at the axles of the upper and lower rollers. These switches provide a warning signal to the operator in the event of an anomalous condition such as a minor belt tear or minor damage at a belt splice or material being carried improperly on the lower or return belt, etc. A third sensor switch is installed somewhat higher above the upper roller and serves to detect more extreme damage to the conveyor belt, and automatically shuts down the conveyor system if such extreme damage is detected. The upper and lower sensor switches and the third sensor can comprise mechanical switches or magnetically actuated switches. 
     A fourth switch comprises a motion detector set to detect rotation of the upper roller. Neither roller is normally in contact with the belt; thus neither roller will normally rotate. Rotation of the upper roller is indicative of material being carried atop the lower or return portion of the belt, which is indicative of a twisted or otherwise damaged belt that allows the spillage of material onto the return portion of the belt. This motion detector transmits an alarm or warning even though the belt may not have shifted sufficiently to move the rollers in order to activate either of the first two sensor switches. The system can incorporate a programmable logic controller (PLC) that senses the duration of any alarm signal from the various warning sensor switches. The PLC will allow the conveyor to continue to operate in the event of receipt of a short or intermittent alarm or warning signal. However, in the event of receipt of a longer duration signal, the PLC will shut down the conveyor to prevent further damage and/or loss of material being carried on the conveyor. 
     These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an environmental, perspective view of a conveyor system and conveyor belt monitor according to the present invention, illustrating its basic structure and features. 
         FIG. 2  is an environmental end elevation view in section of the conveyor system and conveyor belt monitor according to the present invention, illustrating further details thereof 
         FIG. 3  is a detailed schematic side elevation view of one sensor switch array of the conveyor belt monitor according to the present invention, illustrating various details thereof. 
         FIG. 4  is a perspective view of one side and door of an alternative housing of the conveyor belt monitor according to the present invention. 
         FIG. 5  is a block diagram of the conveyor belt monitor according to the present invention, illustrating the relationship between various components of the system. 
       Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The conveyor belt monitor essentially comprises a frame with upper and lower rollers extending thereacross, respectively beneath the conventional upper and lower portions of an endless conveyor belt. A series of sensors monitor the rollers to actuate an alarm and/or shut down the conveyor system in the event that either of the rollers is displaced, which displacement would indicate some adverse condition in the conveyor system. 
       FIG. 1  of the drawings provides an environmental perspective view of a portion of a conventional conveyor system C, with its endless belt B comprising an upper belt portion UB and lower belt portion LB and extending around the tail roller TR and an opposite distal head roller (not shown). The belt B with its upper and lower portions UB and LB and tail roller TR are supported by the laterally opposed first and second sides S 1  and S 2  of a conveyor frame F. (The conveyor frame F is not shown in other Figs., for clarity in the drawing Figs.) This structure is conventional and known in the art. Such conveyor systems C are used in a wide variety of industries, e.g., the coal mining industry to transport loose coal from the face of the coal seam to other transport means to remove the coal from the mine 
     The conveyor belt monitor  10  essentially comprises a housing  12  having mutually laterally opposed first and second sides, respectively  14   a  and  14   b , connected by a crossmember  16 . The housing  12 , and more specifically the upper ends of the two sides  14   a  and  14   b , includes respective first and second hangers  18   a ,  18   b  that extend from the upper ends of the sides  14   a ,  14   b  to rest atop the respective sides S 1  and S 2  of the conveyor frame S when the conveyor belt monitor  10  is installed thereon. An upper roller  20  extends between the first and second sides  14   a ,  14   b  of the housing  12 , and is positioned above the lower belt portion LB when the monitor  10  is installed on the conveyor system C. Similarly, a lower roller  22  extends between the first and second sides  14   a ,  14   b  of the housing  12  and is positioned below the lower belt portion LB when the monitor  10  is installed on the conveyor system C, i.e., the lower belt LB passes between the upper and lower rollers  20  and  22 . The two rollers  20  and  22  are positioned sufficiently far apart that they do not contact the lower belt LB during normal operation. They are not a part of the conveyor system C and do not provide support for the lower belt LB, or any other portion of the belt B, during normal operation of the conveyor system. 
       FIGS. 2 and 3  illustrate the various sensors incorporated with the present conveyor monitor  10 . A pair of upper warning sensors  24   a  and  24   b  is installed respectively with the first and second sides  14   a  and  14   b  of the housing  12 . The contact elements (e.g., wheels or rollers, etc.)  26   a ,  26   b  of these sensors or switches are in contact with the underside of the axle  28  of the upper roller  20  and communicate with the upper roller. Similarly, a pair of lower warning sensors  30   a  and  30   b  is installed respectively with the first and second sides  14   a  and  14   b  of the housing  12 . The contact elements (e.g., wheels or rollers, etc.)  32   a ,  32   b  of these sensors or switches are in contact with the upper side of the axle  34  of the lower roller  22  and communicate with the lower roller. 
     The upper roller axle  28  is disposed within first and second upper guide slots  36   a,    36   b  formed respectively in the two housing sides  14   a ,  14   b , and normally rests at the bottoms of these slots but is free to slide up and down within these slots. Thus, debris or other matter remaining on the upper surface of the lower belt LB (known as a “gob-out” in the coal mining industry), or perhaps a bad belt splice or delamination or other belt damage, will lift the upper roller  20  and its axle  28  upward within its guide slots  36   a ,  36   b , thereby displacing the upper sensor contacts  26   a ,  26   b  and actuating the respective upper sensors  24   a ,  24   b.    
     Similarly, the lower roller axle  34  is disposed within first and second lower guide slots  38   a ,  38   b  formed respectively in the two housing sides  14   a ,  14   b , and is free to slide up and down within these slots. However, it will be seen that due to gravity, the lower roller axle  34  would tend to drop away from the lower sensor switch contacts  32   a ,  32   b  to the bottom of its slots  38   a ,  38   b , if it were not supported in some manner. Accordingly, the lower roller axle  34  is resiliently supported within its two lower guide slots  38   a ,  38   b  by respective springs  40   a  and  40   b . The springs  40   a ,  40   b  are in turn supported in brackets  42   a ,  42   b  ( FIG. 2 ) and may be adjusted by means of threaded adjusters  44   a  and  44   b  that thread into the bottoms of the brackets  42   a ,  42   b  and bear against the bottom ends of the springs  40   a ,  40   b . The springs  40   a,    40   b  are preferably adjusted to hold the lower roller axle  34  just within the upper ends of the lower slots  38   a ,  38   b , without exerting any noticeable or significant pressure against the upper ends of the two slots  38   a ,  38   b . Thus, debris or other matter remaining on the lower or outer surface of the lower belt LB, or perhaps a bad belt splice or delamination or other belt damage, will push the lower roller  22  and its axle  34  downward within its lower guide slots  38   a ,  38   b , thereby displacing the lower sensor contacts  32   a ,  32   b  and actuating the respective lower sensors  30   a ,  30   b.    
     It will be noted that the above configuration duplicates the upper and lower sensors and their contacts in each of the housing sides  14   a  and  14   b . It is possible to save some complexity and expense by providing only one set of sensors and their contacts in one of the housing sides. Preferably, however, two laterally opposed upper and lower sensors and associated components are provided to provide for detection of any laterally offset anomaly in or on the lower belt portion LB. If only one set of sensors were provided, e.g., on the first housing side  14   a , it is possible that some anomaly of the opposite side of the lower belt LB might fail to displace the first housing side sensor(s) sufficiently to trigger an alarm. However, a single set of sensors installed on one of the housing sides might be acceptable in some circumstances, e.g., a relatively narrow belt with some additional lateral span between the belt edges and the sensor contacts. 
     The upper and lower warning sensors  24   a ,  24   b ,  30   a , and  30   b  can utilize any of various known operating principles, e.g., electromechanical, magnetic proximity, hydraulic or pneumatic, etc., as desired. In any event, it is preferred that some protection from contamination and/or physical damage be provided to these switches. Accordingly, the two housing sides  14   a ,  14   b  are provided with cover plates, respectively  46   a  and  46   b . The cover plates  46   a ,  46   b  can be bolted to the underlying housing sides  14   a ,  14   b , as shown in the drawings, or otherwise attached, e.g., hinge and latch, etc. The second side cover plate  46   b  is shown partially broken away in  FIG. 3 , to more clearly show the various elements below. Debris protection is also provided by resilient seals  48  disposed along each side of each of the slots  36   a ,  36   b ,  38   a , and  38   b . The seals  48  deflect around the upper and lower axles  28  and  34 , and fold closed beyond the axles. 
       FIG. 4  of the drawings is a perspective view of an alternative housing side  114   b  and access door  146   b . The door  146   b  is attached to the housing side  114   b  by hinges  148   b  along one edge thereof A latch  150   b  is provided on or in the door  146   b , selectively engaging a cooperating latch receptacle  152   b  in the housing side  114   b . A seal(s), not shown, can be provided at the juncture of the door  146   b  with the housing side  114   b . The assembly is supported on the second side S 2  of the conveyor frame ( FIG. 1 ) by its hanger  118   b . It will be noted that the opposite side of the assembly can include a similar arrangement in mirror image to that shown in  FIG. 4 . 
     The above-described upper and lower warning sensors  24   a ,  24   b ,  30   a , and  30   b  are positioned to provide immediate warning or notification of even a slight displacement of either of the roller axles  28  or  34  due to corresponding displacement of their rollers  20  or  22 . While these warning sensors may be connected to the conventional conveyor drive to cause the drive to shut down in the event of actuation of these sensors, it is preferred that these four sensors only provide an announcement, warning, or alarm of some anomalous condition of the conveyor belt B. The relatively slight displacement required to trigger such an announcement or alarm might be due to a relatively minor problem that would allow the conveyor system C to continue to operate for some period of time, or some condition that may be cleared while the system is in operation. 
     However, it is possible that a more serious problem might occur that would result in serious damage and lost time if it were allowed to continue. In such a case, it would be better to shut down the conveyor system C immediately, rather than allowing it to continue in operation. Generally, such serious problems will manifest themselves by relatively large displacements of the conveyor belt B, and particularly the lower belt portion LB. Accordingly, a pair of conveyor shutdown switches  50   a  and  50   b  is provided in the two housing sides  14   a ,  14   b , installed at some vertical distance above the upper roller axle  28 . A relatively large upward displacement of the lower belt portion LB will result in the upper roller  20  and its axle  28  being lifted in the upper guide slots  36   a ,  36   b  to the point that the axle  28  displaces the two contacts  52   a ,  52   b  of the shutdown switches  50   a  and  50   b , thereby actuating these two switches. These two shutdown switches  50   a ,  50   b  are preferably connected to the conventional conveyor drive to shut down the conveyor drive immediately. They are also preferably connected to an annunciator or alarm system, to alert the operator of the system of such an extreme displacement of the upper roller  20 . As in the cases of the upper and lower warning sensors  24   a ,  24   b ,  30   a , and  30   b , a single such shutdown switch may be provided in limited conveyor configurations, although two such switches  50   a ,  50   b  installed respectively in the two laterally opposed sides  14   a ,  14   b  of the housing  12  are preferred. The shutdown switches  50   a ,  50   b  may be of the same type or principle of operation as described further above for the warning sensors, i.e., electromechanical, hydraulic, pneumatic, magnetic proximity, etc. 
     An additional motion sensor warning switch  54  is also preferably installed in the housing  12 , as shown in the end elevation view of  FIG. 2 . This switch  54  preferably comprises an electromagnetic switch, i.e., infrared, photoelectric, etc., and is situated adjacent the upper roller  20  to detect rotary motion of the upper roller axle  28 . Thus, even in the event that the upper roller is not displaced vertically, or not displaced sufficiently to actuate one or both of the upper warning sensors  24   a ,  24   b , any contact of material residing upon the upper or inner surface of the lower belt portion LB with the upper roller  20  that is sufficient to cause the roller  20  and its axle  28  to rotate, will result in the actuation of the motion sensor warning switch  54  to trigger an announcement, warning, or alarm. It will be seen that only a single such motion sensor warning switch  54  is needed, as rotation of the roller axle  28  will be uniform throughout the length of the axle. Thus, the single motion sensor warning switch  54  may be located anywhere that it may detect rotary motion of the axle  28 , or its roller  20 . This motion sensor warning switch  54  is preferably not connected to the drive of the conveyor system C. Thus, the conveyor system C will continue to operate after actuation of the motion sensor warning switch  54 , but will alert the operator that some problem has occurred that may require attention or correction. 
       FIG. 5  is a flow chart that describes the basic steps in the operation of the conveyor belt monitor  10 . It will be seen in  FIG. 5  that the upper and lower roller warning sensors  24   a ,  24   b ,  30   a , and  30   b , as well as the upper roller axle motion sensor or warning switch  54 , all communicate electronically with an annunciator system  56 . The annunciator system  56  can comprise any of various annunciating means, e.g., voice alert, siren or other audial alert, visual, etc., or a combination thereof, as desired. However, the sensors  24   a ,  24   b,    30   a ,  30   b , and  54  are preferably not connected to any conveyor shutdown system or means. Thus, the conveyor C will continue to operate in the event that any of the sensors  24   a ,  24   b,    30   a ,  30   b , and  54  detect an anomaly and send a signal to the annunciator  56 . However, the limit switches  50   a  and  50   b , being positioned to detect much greater belt displacements, communicate electronically with a conveyor shutdown system or means  58 . Thus, if either or both of the limit switches  50   a ,  50   b  are displaced, they will cause the conveyor system to shut down completely, as indicated by the conveyor shutdown position  58  of  FIG. 5 . A signal is also sent to the annunciator  56  in the event of conveyor shutdown, or alternatively directly to the annunciator  56  from the limit switches  54   a ,  54   b , although it will be obvious to the operator that the conveyor system C has shut down in such an event. When the conveyor monitor is used in an underground mine, the system can be connected to the conventional programmable logic controller (PLC) commonly used in such mines, with the monitor reporting the belt status and/or condition to the main belt control room of the mine. Alternatively, the controls can be incorporated into a separate control box where a PLC is not used in the system. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.