Patent GB-1100464-A (GB)
Title: Improvements in and relating to control arrangements
Inventor: EDMONDS PETER HICKS
IPC: E21D23/14
Filed: 1964-05-04
Abstract: 1,100,464. Coal cutting machinery. ELECTRIC & MUSICAL INDUSTRIES Ltd. May 4, 1965 [May 4, 1964], No. 18490/64. Heading F1P. Coal cutting machinery capable of cutting coal when travelling in either direction along the coal face is associated with a system for advancing the coal conveyer supports and the roof supports which system is operable in either direction of travel of the cutting machinery. The system is sequentially operative and is self checking so that if a given operation fails to be completed the sequence of operations is terminated. The coal conveyer supports and the roof supports are hydraulically operated and are controlled by an electrical system which includes such elements as transistors, AND gates, OR gates, bi-stable circuit and limit switches. The supports are arranged in assemblies known as chocks, each chock comprising a conveyer support and two roof supports, one a master support and one a slave support connected together by a frame. When it is necessary to advance a chock the slave support is retracted from the roof, pushed forward hydraulically and then reset to the roof. When the slave support is taking load a limit switch operates whereupon the conveyer support is advanced. Thereafter the master roof support is retracted from the roof, pushed forward and then reset to the roof. When this support is taking load a further limit switch operates to reset the circuitry for a succeeding cycle of events. The chocks are divided into groups along the coal face, a convenient number of chocks per group being twenty. Each chock is provided with a local control box which determines that the conditions are correct for the supports to advance and these control boxes are provided with manually operated push buttons. When the coal cutting apparatus is travelling say from left to right, along the coal face the slave support associated with any given push button is that of the chock itself but when the coal cutting apparatus is travelling in the opposite direction along the coal face the push button controls the slave support of the chock two behind the push button. Each group of chocks is further provided with a group control box with a push button which is effective, when operated, to cause all the slave supports in a group to advance sequentially, then the conveyer supports in sequence and finally the master supports. The system further ensures that no more than three conveyer supports operating rams can be operated simultaneously and a conveyer support operating ram cannot be operated unless the slave support in the eighth chock ahead has advanced. Loud speakers give a warning note whenever a chock is operating and whenever a slave or master support is operating a signal is transmitted to a central board indicating the chock which is being operated. Delay circuits are incorporated in the circuitry operating the master supports but not in the circuitry for the slave supports. Alarm circuits giving signals of different types are provided to give warning of different types of faults in the system and control units are provided at the ends of the coal face to ensure that the chock advance sequences start and terminate at the beginning and end of a coal cutting operation.