The instant application should be granted the priority date of Feb. 19, 2008, the filing date of the corresponding International patent application PCT/EP2008/001268.
The invention relates to a method for automatically producing a defined face opening in the case of longwall operations, comprising a face conveyor, at least one plow guided on the face conveyor as an extraction machine, and a hydraulic shield support, in underground mining.
A problem in the automatic control of longwall operations both in the mining direction and also in the extraction direction of the extraction machine used is, inter alia, producing a sufficiently large face opening to ensure the passage of the longwall equipment without collisions between extraction machine and shield support frames as the extraction machine travels past, for example, on the one hand, and keeping the rock collapse during the extraction work as limited as possible, and accordingly restricting the extraction work to the coal layer as much as possible, without also cutting excessive country rock, on the other hand. The mineral deposit data which is essentially available before the extraction about seam thickness, level of footwall or overlying stratum, and the presence of saddles and/or troughs both in the mining direction and also in the longitudinal direction of the longwall equipment, i.e. in the extraction direction of the extraction machine, are too imprecise to be able to support automated control of the extraction and support work thereon.
This problem results in particular in the case of so-called plow operations, during which a plow moves back and forth along the longwall front on a fixed guide attached to the face conveyor. The plow, which is equipped with chisels, has a setting-related fixed cutting height and a comparatively low cutting depth in a magnitude of approximately 60 mm, so that in contrast to an extraction with a disc shearer loader, the cutting height is not variable during extraction travel in any case. In plow operations, a height control of the plow is set up as a so-called boom or delivery controller via a control cylinder situated between the face conveyor as a fixed guide to the plow and the shield support frame attached thereon. Via the inclination of the face conveyor, which is changeable using the boom controller, in addition to a level-neutral control, a plunging movement in the mining direction can thus also be given to the face conveyor and thus the plow guided thereon, even during the extraction travel, in which the plow tilts into the footwall by cutting of its floor chisels, or also a climbing movement, in which the plow executes a rising extraction.
In that damage to the footwall by the plow is to be avoided as much as possible during the extraction work, the height control of the plow is essentially performed according to the known method of boundary layer plowing on the footwall. In this method, it is ascertained by a sensor carried at the level of the floor chisel of the plow whether the floor chisel of the plow cuts into the country rock, i.e. into the footwall, or into the coal. This method is primarily fragile on its hardware side, because the relevant sensor and the associated evaluation computer are installed in an extremely rough environment in or on the plow and are thus subject to corresponding stresses and/or occurring defects. Furthermore, the mobility of the plow requires a power supply of the hardware via battery and a data transmission via radio using multiple transponders situated in the longwall, the radio conditions being very difficult to control in particular in low longwalls having higher proportions of ferromagnetic components of the longwall equipment. In addition, this method is also subject to uncertainties in its information and/or also causes a corresponding time delay in the case of possibly required regulation, because a somewhat reliable statement about the material cut by the plow is only to be made after several plow passes, i.e., after it travels past a shield support frame several times, typically approximately 5 times.
The invention is therefore based on the object of disclosing a method of the type cited at the beginning, using which automation of the extraction and support work with respect to the production of a defined face opening is possible even in plowing operation.