Tool driving or impacting – Automatic control of power operated means – Tool advance causing or controlling means
Reexamination Certificate
1999-05-18
2001-04-10
Vo, Peter (Department: 3721)
Tool driving or impacting
Automatic control of power operated means
Tool advance causing or controlling means
C173S001000, C173S002000, C173S032000, C173S034000, C173S036000
Reexamination Certificate
active
06213223
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an arrangement in a rock drilling apparatus comprising a feed for feeding a rock drill during the drilling; at least one rear support connected to the feed substantially parallel to and rearward of the feed, the support being moveable by its own support cylinder to rest on a surface rearward of the feed; and means for supplying pressure fluid to the support cylinder.
When holes are drilled in rock, the drill apparatus is usually supported by hydraulically-driven supports at its front and/or rear end. When the drill apparatus is directed, it is first adjusted in the correct direction, and the supports are then moved outward at the end of the drill apparatus by hydraulic cylinders until the supports rest against a surface in that direction. This is usually done before the drilling is started, and the bracing is usually not corrected in any way. During the drilling both the vibration and the feed capacity of the rock drill typically make the supports sink in the support surface, for example as the chippings in the surface yield. As a result, the direction of the drill apparatus changes and has to be corrected, which is at present usually performed by different angle gauges and very often by automatic adjustment.
In extension rod drilling, it is of prime importance to keep the direction during the drilling. Even a minor lateral change or change of angle to the effect that the drill axis of the drill apparatus and the centre axis of the hole do not coincide causes problems, for example, as regards disassembly of the drill equipment, since the threaded joints of drill pipes then no longer open in the correct order. A directing error of even half a degree is known to hinder automatic disassembly of the drill equipment. Another drawback resulting from the known methods of adjustment is that the drill apparatus, although in correct direction, is displaced laterally from the axis of the drill hole, which causes similar problems.
U.S. Pat. No. 5,129,464 teaches a solution in which the anchoring force of the feed of a rock drilling apparatus against a rock surface is to be maintained constant by adjusting the force that pushes the feed in proportion to the feed force of the rock drill in such a way that the difference of the forces and thereby the anchoring force remain constant. The solution does in no way eliminate the above problem concerning the changing of the direction and the resulting change of direction or lateral displacement that make it more difficult to disengage the drill rods.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide an arrangement for a rock drilling apparatus by which the above drawbacks can be eliminated and the drilling and the disassembly of the extension rod equipment can be performed simply and correctly.
The arrangement of the invention is characterized by comprising means for setting the pressure value of the pressure fluid in the support cylinder; a pressure detector for detecting the pressure of the support cylinder; and a control unit, controlled by the pressure detector, for controlling the supply of the pressure fluid to the support cylinder so as to maintain the pressure in the support cylinder during the drilling at substantially a pre-set pressure value.
The essential idea of the invention is that one or more rear supports are driven into the support surface before the drilling starts by supplying pressure fluid to the support cylinders, and that the pressure detector detects the pressure prevailing in the support cylinder, and the control unit controls the supply of the pressure fluid to the support cylinder or cylinders so as to maintain the pressure substantially at the set value. The supports press firmly against the support surface even before the drilling operation is started and, if the support surface yields so that the support is pushed outward in the support cylinder and the pressure subsequently tends to drop below the set pressure level, then more pressure fluid is supplied to the cylinder to maintain the pressure level substantially constant. The bracing compensates for any yielding of the ground and maintains the feed direction of the rock drilling apparatus with a sufficient accuracy as originally set. Experiments have shown that in this way the direction can be maintained the same with the accuracy of about 0.1°, and so the above problems relating to stress in the equipment and to unthreading in the disassembly step can be eliminated. A lateral displacement between the drill axis of the rock drilling apparatus and the longitudinal axis of the hole can be simultaneously avoided.
The advantage of the invention is that the drilling direction and the position of the drill apparatus can be maintained substantially unchanged in a simple and effective manner without any extra changes of angle, and without any extra equipment for angle measurement and automatic adjustment. A further advantage is that in most cases it is possible avoid the use of extra front supports and the drilling can be performed merely on the rear supports, using two rear supports spaced from each other.
REFERENCES:
patent: 2979320 (1961-04-01), Adams
patent: 3106257 (1963-10-01), Helm
patent: 3721094 (1973-03-01), Elders et al.
patent: 3951216 (1976-04-01), Crawshay et al.
patent: 4109733 (1978-08-01), Dummer
patent: 4537263 (1985-08-01), Bjor
patent: 4676322 (1987-06-01), Rajakallio et al.
patent: 4848485 (1989-07-01), Piipponen et al.
patent: 5129464 (1992-07-01), Richier
patent: 5131475 (1992-07-01), Beney
Calve Jim
Sandvick Tamrock Oy
Smith-Hill and Bedell
Vo Peter
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