Abstract:
A communication system for use in a mine to provide two-way communication between a conveyance which moves in a mine and a communication network located in the mine. The system comprising: means for producing a signal indicative of the location of the conveyance in the mine; a plurality of repeaters situated in the mine and being coupled to the communication network; and a controller for controlling the repeaters and the controller being responsive to the signal and having means for activating the repeater which is proximate to the conveyance so that a communication link is provided between the conveyance and the communication network.

Description:
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright whatsoever. 
     FIELD OF THE INVENTION 
     This invention relates to communication systems. More particularly, it relates to a communication system which is suitable for use in an underground mine. 
     BACKGROUND OF THE INVENTION 
     Communication in a mine is vital, not only to ensure the safety of the miners, but also to coordinate the work effort. Because of the nature of an underground mine, there is a need for a reliable and satisfactory communication system. It will be appreciated that the environment of an underground mine system places considerable demands on a communication system. 
     In the prior art, there are known mine communication systems which are based on radio transmission. While it is possible to provide a working communication system, a radio-based system has its limitations. Firstly, a radio system is one-way, and therefore, communication between a miner and the surface is limited and can be broken. In addition, the characteristics of a mine, e.g. type of ore body and tunnelling, can affect the propagation of radio frequencies, thereby limiting the number of available channels for communication and accessibility of the communication system to the miners. 
     Furthermore, the communication system at the surface of a mine typically comprises a telephone system. A telephone system provides two-way communication and also provides a gateway to any number of emergency/rescue agencies. In practical terms this means that there are two communication systems operating on a mine site and while integrating the two systems is desirable, it can be expensive. 
     Another consideration for a communication system for use in an underground mine is the potential effect of electromagnetic radio waves propagating through the shafts. Since blasting caps can be ignited by radio signals having certain frequencies and/or power levels, the power level and frequency of signals utilized in a mine communication system must be a consideration. 
     Therefore, it is desirable to provide a communication system for use in a mine which can be integrated with the existing telephone system of the mine. It also desirable to provide the communication system with a two-way communication capability for full telephone service. Lastly, the transmission characteristics, e.g. power level and frequency range, of the system should provide optimum performance without any dangerous consequences in the mining environment. 
     BRIEF SUMMARY OF THE INVENTION 
     In a first aspect the present provides a communication system for use in a mine to provide two-way communication between a conveyance which moves in a mine and a communication network located in the mine, the system comprising: (a) means for producing a signal indicative of the position of the conveyance in the mine; (b) a plurality of repeater means situated in the mine and being coupled to said communication network; (c) controller means for controlling said repeater means and said controller means being responsive to said signal and having means for activating said repeater means which is proximate to the conveyance so that a two-way communication link is provided between the conveyance and the communication network. 
     In a second aspect, the present invention provides a method for controlling the operation of a communication system for use in a mine having a telephone set located in a conveyance which moves in a mine shaft, and a plurality of repeater stations located adjacent the mine shaft and coupled to the communication system, said method including the steps of: (a) determining the position of the conveyance in the mine shaft; (b) determining the repeater station which is proximate to the conveyance and activating said proximate repeater station so that a communication link is provided between the telephone set in the conveyance and the communication network; and (c) deactivating said other repeater stations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, and to show more dearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: 
     FIG. 1 shows in block diagram form a communication system for use in a mine according to the present invention; 
     FIG. 2 shows in diagrammatic form the operation of the communication system of FIG. 1 as a conveyance moves through the mine; 
     FIG. 3 shows in block diagram form the central and remote controllers for the system of FIG. 1; and 
     FIG. 4 shows in flow chart the decision steps embodied in the control of the communication system of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference is first made to FIG. 1 which shows in block diagram a communication system 10 according to the present invention. The communication system 10 is suitable for use in an underground mine and provides a two-way communication link between a conveyance 12 which moves in a mine shaft 14 and a mine telephone system 16. The conveyance 12 has a telephone 13 and as will be explained below, the communication system 10 according to the present invention couples the telephone 13 into the mine telephone system 16. Thus, the miners travelling in the conveyance 12 can stay in full contact with the rest of mine. In addition, the system 10 provides an extra level of safety for inspection of the mine shaft 14 and &#34;in-shaft&#34; maintenance. 
     As shown in FIG. 1, the communication system 10 comprises a central controller rack 18 and a number of remote controller racks 20. The remote controller racks 20 are located at various levels through mine. Each of the remote controllers 20 is connected to a repeater 21. Each repeater 21 includes an antenna 23 and can comprise a known cordless phone station which has been industrially hardened to withstand the harsh environment of a mine. As will be explained below, the repeater 21 is used to couple the conveyance telephone 13 into the mine telephone system 16. The mine telephone system 16 includes surface telephones 17 and field telephones 19. The telephones 17,19 can be wired into the system 16 or can comprise conventional portable or cordless telephone sets. The conveyance telephone 13 can also comprise a cordless or portable telephone unit which preferably has been industrially hardened for use in a mining environment. A portable set 13 in the conveyance provides a miner with mobility to do shaft inspections, for example. As shown in FIG. 1, the first remote controller 20 and repeater 21 are located at the top of the mine shaft 14. 
     The remote controller racks 20 are coupled to the central controller rack 18 through a bus 22. The bus 22 allows the central controller 18 to send commands and status requests to any one or all of the remote controllers 20. The central controller 18 uses the bus 22 to control the remote controllers 20. 
     In known manner, the conveyance 12 is raised and lowered in the mine shaft 14 by a hoist 24. The hoist 24 typically comprises a drum and cable 26, which are located in a hoist room, indicated generally by reference 28. The central controller rack 18 is typically located in the &#34;hoist&#34; room 28 for convenience. The central controller 18 is coupled to the hoist 24 through a conveyance position indicator 30. The conveyance position indicator 30 provides the central controller 18 with a signal that is indicative of the position of the conveyance 12 in the mine shaft 14. The central controller 18 uses the position of the conveyance 12 to determine which repeater 21 to turn on. This ensures that there is a strong signal between the conveyance telephone 13 and the mine telephone system 16 with minimum interference from the other repeaters. 
     To verify the position of the conveyance 12 (and ensure the integrity of the system 10), position reference switches 32 are located at known positions in the mine shaft 14. These reference switches 32 are coupled to a respective remote controller 20. As will be explained in detail below, when the conveyance 12 passes a reference switch 32 a signal is produced which is read by the remote controller 20 and sent to the central controller 18. The central controller 18 uses this signal to verify the position of the conveyance 12 as determined from the conveyance position indicator 30. 
     Reference is next made to FIG. 2 which provides an overview of the operation of the communication system 10 according to the present invention. For this example, there are three base stations or levels along the mine shaft 14, each comprising a repeater 21 and remote controller rack 20. Base station #1 (reference 101) is located at the surface level of the mine shaft 14 as indicated by reference 110. Base station #2 is located at a first level which in this example is 2000 feet below the surface, as indicated by reference 120. Base station #3 is located at the second level below the surface, e.g. 4000 feet, as indicated by reference 130. When the conveyance 12 is at the surface 110, the central controller rack 20 activates the repeater 21 which is closest, in this case, base station #1 (101). The other repeaters 21 (i.e. Base Stations #2 and #3) are deactivated to ensure a strong signal between the conveyance telephone 13 and the mine telephone system 16 and also to minimize the interference from the other repeaters (i.e. Base Stations #2 and #3). 
     Referring still to FIG. 2, as the conveyance 12 moves down the mine shaft 14, the central controller 18 uses the position indicator 30 to determine the position of the conveyance 12. For example, when the conveyance 12 moves within the range of the repeater 21 located at the first level below the surface 120, the central controller 18 activates the repeater 21 at Base Station #2 and deactivates the repeaters 21 at Base Stations #1 and #3. Similarly, when the conveyance 12 moves further down the mine shaft 14 to the second level 130 (e.g. 4000 feet), the central controller 18 activates the repeater 21 at Base Station #3 and deactivates the repeaters 21 at Base Stations #2 and #3. The same procedure, except in reverse, is followed as the conveyance 12 returns to the surface level 110. 
     Reference is next made to FIG. 3 which shows in more detail the elements of the communication system 10 of FIG. 1. The central controller rack 20 comprises a programmable controller 40 and a local interface module 42. 
     The programmable controller 40 is used to run a computer program 41 which is used to control the system 10 as will be explained with reference to FIG. 4. A suitable device for the programmable controller 40 is the SY/MAX* Model 400 processor which is available from the Square D Company in the United States. (The Specification Sheets for the Model 400 Processor and other SY/MAX* devices referred to are incorporated herein by reference.) The Model 400 Processor includes an instruction set which is suited for control applications and can be readily programmed by one skilled in the art. The Model 400 processor is a module which can be plugged into the SY/MAX* Class 8030 Type HRK-150 Register/Digital Rack Assembly which is also available from the Square D Company. The Rack Assembly includes a number of slots which accept modules (e.g. controller, input, output or interface modules). The Rack Assembly provides power and a backplane (or bus) for the plugged-in modules. 
    
     As shown in FIG. 3, the conveyance position indicator 30 comprises a digital encoder 44 and a high speed counter module 46. In known manner, the digital encoder 44 is mechanically attached to a drive shaft (not shown) off the hoist drum 24 (FIG. 1). The digital encoder 44 is coupled to the high speed counter module 46 and produces a number value in the form of digital pulses for every increment (e.g foot) that the conveyance 12 actually moves up or down the mine shaft 14. 
     The high speed counter module 46 accepts the pulses from the digital encoder 44 and &#34;counts&#34; the number of pulses. It will be appreciated that the number of pulses corresponds to the position of the conveyance 12 in the shaft 14. The high speed counter module 46 is coupled to the programmable controller 40 and the programmable controller 40 uses the pulse count to determine the position of the conveyance 12. A suitable commercially available device for the counter module 46 is the SY/MAX* Class 8030 Type RIM-131 High Speed Counter Module which is also available from the Square D Company in the United States. The Type RIM-131 Counter Module is compatible with the Class 8020 Processor and can be plugged in the Rack Assembly (see above). The RIM-131 Counter Module is configured to run in single count pulse train with direction signal mode as will be understood by one skilled in the art. 
     Referring still to FIG. 3, the local interface module 42 provides the interface between the programmable controller 40 and the remote controller racks 20. A suitable commercially available device for the local interface module 42 is the SY/MAX* Class 8030 Local Interface which is available from the Square D Company. The local interface module 42 allows the programmable controller 40 to communicate with the remote controller racks 20 over a two-pair twisted shielded cable (i.e. bus 22 in FIG. 1). The local interface module 42 is mounted in the Rack Assembly and coupled to the programmable controller 40 through the backplane bus (not shown). 
     The remote controller rack 20 includes a remote interface module 48, an input module 50 and an output module 52. The remote interface module 48 is coupled to the programmable controller 40 through the bus 22 and local interface module 42 to provide the link between the central controller rack 18 and the remote controller racks 20. A suitable assembly for the remote controller rack 20 is the SY/MAX* Class 8030 Type HRK-100 I/O Rack Assembly which is also available from the Square D Company. Similar to the central controller rack (see above), the Type HRK-100 Rack provides a rugged assembly into which the interface module 48, input module 50 and output module 52 can be plugged. 
     A suitable commercially available unit for the remote interface module 48 is the SY/MAX* Class 8030 Remote Interface which is also available from the Square D Company. The Class 8030 Remote Interface provides the communication interface between the programmable processor 40 and the input and output modules 50,52 in the remote controller racks 20. 
     As shown in FIG. 3, the output module 52 is coupled to the repeater 21. Under the control of the programmable controller 40, the output module 52 is used to activate/deactivate the repeater 21 (as determined by the position of the conveyance 12 in the mine shaft 14). A suitable commercially available device for the output module is the SY/MAX* Class 8030 Type HOM-251 Output Module which is also available from the Square D Company. The HOM-251 Output Module contains eight optically isolated outputs, each of which is capable of driving a load. In the system 10, the programmable controller 40 uses one of these optically isolated outputs to drive the power feed line for the associated repeater 21, which allows the repeater 21 to be turned on and off by the programmable controller 40. 
     Lastly in reference to FIG. 3, the input module 50 couples the position reference switch 32 to the remote interface 48 (and the central controller rack 18). The position reference switch 32 is used to verify the position of the conveyance 12 in the mine shaft 14. In the preferred embodiment of the present invention, the reference switch 32 comprises a Triac Magnetic Proximity Switch such as the CR 9440-QST2 which is manufactured by Canadian General Electric. The CR 9440-QST2 is contact-making device with one normally open Triac circuit which is arranged to become conductive when the device is placed in a magnetic field. When the magnetic field is removed (or reduced sufficiently), the Triac circuit reverts to the non-conducting state. The Triac circuit (in the proximity switch 32) is connected to an input on the input module 50 which is used by the programmable controller 40 to read the state of the proximity switch, i.e. open or closed. 
     A suitable device for the input module 42 is the SY/MAX* Class 8030 Type HIM-101 Input Module which is also available from the Square D Company. The HIM-101 Input Module is compatible with the HRK-150 Register/Digital Rack Assembly and the other SY/MAX* family modules. 
     As shown in FIG. 3, the conveyance 12 includes a magnet 33 of suitable field strength to trip the proximity switch 32 when the conveyance 12 passes by the switch 32. When the proximity switch 32 is tripped or closed this will generate a signal for the programmable controller 40. Since the proximity switch 32 is located at a fixed location in the mine shaft 14, the signal which is generated by the switch provides a reference that the programmable controller 40 uses to check the position of conveyance as determined by the counter module 46. 
     Reference is next made to FIG. 4 which shows in flow chart the method steps embodied in the computer program 41 which is run by the programmable controller 40 for controlling the activation/deactivation of the repeaters 21. The program 41 is implemented in a &#34;Programmable Logic Controller&#34; format using the instruction set of the SY/MAX* Model 400 Processor. A code listing for the computer program 41 is included as an Appendix to this document. 
     The first logic step involves initializing the communication system 10 when power is first turned (as indicated by block 200). The initialization 200 can involve a number of operations such as performing a memory check for the programmable controller 40 (FIG. 2) and turning all the repeaters 21 off, for example. 
     Once the communication system 10 has been initialized, the central controller 18 is ready to receive inputs from the conveyance position indicator 30 (i.e. high speed counter module 46). As explained above, the &#34;count&#34; from the counter module 46 is responsive to the movement of the conveyance 12 and indicative of the position of the conveyance 12 (block 202). (The programmable controller 40 can read the count from the counter module 46 using an appropriate ladder diagram program as will be within the understanding of one skilled in art and the reader is referred to the Appendix.) If the conveyance 12 has moved into another &#34;repeater zone&#34;, then the repeater 21 must be turned on (block 204). If a repeater 21 is to be turned on (206), then the central controller 18 sends an appropriate command to the respective remote controller 20 instructing it to turn on the repeater 21 (block 208). Similarly, the central controller 18 sends another command to the remote controller 20 for the repeater 21 which was on telling it to turn off the previously active repeater 21 (block 210). 
     Referring still to FIG. 4, if the conveyance 12 passes a proximity switch 32, then a signal is generated which is received by the central controller 18 (via the remote interface 48 and the input module 50) as indicated by block 212. When this signal is received, the program 41 can verify the position of the conveyance 12 in block 214. The location (i.e. fixed position) of the proximity switch 32 in the mine shaft 14 can be compared to the position of the conveyance 12 as calculated from the &#34;count&#34; received from the counter module 46. For example, the depth or location corresponding to each physical proximity switch 32 can be stored as a &#34;look-up table&#34; in memory. 
     Although various preferred embodiments of the present invention have been described in detail, it will be appreciated by those skilled in the art, that variations may be made without departing from the spirit of the invention or the scope of the appended claims. * Trademark ##SPC1##