Electrical transmission or interconnection systems – Personnel safety or limit control features
Reexamination Certificate
2000-07-07
2003-01-28
Fleming, Fritz (Department: 2836)
Electrical transmission or interconnection systems
Personnel safety or limit control features
Reexamination Certificate
active
06512312
ABSTRACT:
The present invention relates to a method for use in underground mining for detecting the presence of persons in mining faces supported by support frames in which detection sensors are provided on at least some of the support frames, and which are coupled to control units for the support frames, whereby the detection sensors sample at least the working and operating area of a support frame to which they are assigned and bring that frame to a standstill or do not permit its movement, if the presence of a person is established in a detection area. The present invention further relates to a device for use in underground mining for the detection of the presence of persons in mining faces supported by support frames, whereby detection sensors are provided on at least some of the support frames, and are coupled to control units for the support frames, and which sample at least the working and operating areas of the associated support frames.
In modern mining of coal or other minerals by underground mining, extraction is commonly effected using a coal-extraction machine operating back and forth between two headings, for instance a shearing machine or an extraction plough. The roof of the face is underpinned and supported by a multiplicity of support frames arranged alongside each other, which are normally all attached to a conveyor for the removal of the coal or materials extracted onto it, to which the extraction machine also leads. Following the passage of the extraction machine the conveyor and the support frames are moved forward in the direction of the mining face, to which end following the pushing forward of the conveyor, the individual support frames are retracted (withdrawn) a little, then, with the aid of an advancing cylinder, are drawn forward (advanced) in the direction of the conveyor, and then the roof caps of the support frames are extended, until the prescribed support pressure is reached and the roof is again safely underpinned (setting). This method of operation of such an advancing support frame is well known.
In modern mining, each support frame is commonly provided with its own electrical or electro-hydraulic control unit, can be connected together for the exchange of information with each other, by means of which also dependent movement sequences can be performed by several support frames arranged alongside each other. The various movements of a support frame can be initiated automatically from a supervising control monitor and independently performed; it is also possible, however, to move a selected support frame manually via the keyboard of a control unit, whereby in this case the manual operation is not carried out from the control unit arranged on the support frame to be moved, but from the control unit on an adjacent support frame, which is connected by a control line to the control unit of the support frame to be moved (Isleworth safe distance support advance control).
A movement of a support frame, i.e. the retraction of the roof cap (withdrawal), advancing in the direction towards the face conveyor and re-extension of the roof cap (setting), should only occur when there is no person in the working and operating area of the individual support frame, so as to avoid accidents involving personal injury. The working and operational area of a support frame is to be understood to be that area bounded by the roof cap, the ground shoes, the rear gob shield and the face conveyor arranged in front of it, that is, that section of a face which is supported by the support frame. In order to avoid a movement of the support frame, whilst persons are to be found in this area, monitoring devices and procedures are installed, which only permit withdrawal, advancing and setting of the frame if no persons are put in danger thereby.
A method and a device of the construction described in the opening paragraph of the present specification are proposed in DE-OS 36 27 174, in which detection sensors are arranged on the support frames such that each sensor transmits a continuous signal in order to monitor an individual detection area. The method requires that each individual person at the face carries a transponder, which is a small transmitting and receiving device, which works with the detection sensors on the individual support frames, and is located by a sensor if the person is within the detection area of that individual sensor. As soon as a sensor receives a signal from the transponder, it passes a control signal to the control unit of the support frame, following which the control unit puts the normal control function of the support frame out of action and prevents movement of the support frame as long as the person is within the working and operational area of the support frame.
This device and this method have the disadvantage that all the detection sensors at the face are permanently active, which results in a relatively heavy current usage, which must be covered by expensive and intrinsically safe power circuits. Owing to the permanent activation of all the sensors at the face, the transponders carried by the individual persons are also permanently active and have a large energy requirement, which must be covered by transportable energy supplies such as batteries or accumulators and which, with a minimum operating duration of ten hours are relatively large and heavy. Furthermore, the detection sensors transmit permanent electromagnetic signals, which lead to a non-negligible electro-smog at the face, which can affect the health of the persons working at the face, and possibly influences their concentration, which can endanger the safety of the miners. Furthermore, false switching can easily occur owing to the permanent activation of all the -sensors and the electromagnetic waves transmitted by them, if the electromagnetic signal transmitted by one sensor is distorted, possibly after multiple reflections or similar, and is misinterpreted as the signal of a transponder by another detection sensor, and can lead to the immobilisation of a support frame in whose working and operating area there is no miner and which therefore could be moved without danger.
It is an aim of the present invention to address one or more of these disadvantages, and to produce a method and a device of the construction described at the beginning of the present specification, in which electro-smog at the face owing to the detection sensors is avoided and by which the current requirement not only of the detection sensors, but also of the transponders carried by the supervising personnel is small.
Accordingly the present invention is a method according to the opening paragraph of the present specification in which the detection sensors can be activated by the control units of the support frame and are activated before a planned movement of the support frame and de-activated after the completion of the movement.
Advantageously each support frame is provided with at least one detection sensor. It is alternatively possible to provide detection sensors only on alternate support frames and having the detection area of the sensors is large enough such that the working and operating areas of two adjacent support frames can be monitored together.
Preferably the detection sensor of a support frame to be moved is activated at a time before the planned support frame movement, and then the working and operating area of at least the support frame concerned is sampled, and a stop signal is transmitted to the control unit if the presence of a person is established during the sampling, or a release signal is transmitted if no person is established in the detection area during the sampling. Thus detection sensors at the face are thus only activated by the control units of the support frame to which the sensors are allocated when a movement of the support frame is shortly to occur. Normally a movement of the support frame is announced by a warning signal some five seconds before the start of the movement sequence. At about the same time the detection sensors assigned to the support frame to be moved are activated, wh
Herkenrath Peter
Richter Bernhard
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
DBT Automation GmbH
Fleming Fritz
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