Mining or in situ disintegration of hard material – Processes – Breaking down by direct contact with fluid
Patent
1991-05-06
1993-10-26
Bagnell, David J.
Mining or in situ disintegration of hard material
Processes
Breaking down by direct contact with fluid
239128, 175424, E21B 1060, E21C 2560
Patent
active
052559599
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention is directed to a method of and an apparatus for cutting, drilling and similar material-removing treatment of rock, ore, coal, concrete or other hard objects by means of a pressure medium.
BACKGROUND OF THE INVENTION
Such a method and such an apparatus have already been known (DE-A-3,739,825). In the nozzle head of this apparatus, individual nozzles are arranged at a setting angle relative to the direction of the main jet of the nozzle head so as to achieve a comparatively wide "scattering" of the bundle of discrete jets before the same "fan out" to such an extent that the marginal areas of the discrete jets will overlap.
In this connection it has also been known with other apparatus of similar species (DE-B-3,410,981 and 3,516,572) to employ cutting metal inserts for the nozzles and to anchor the same in the nozzle head by screwing-down or push-fitting.
Moreover, apparatus for drilling holes in concrete and rock have been known (MACHINE DESIGN 57/1985, pp.114-117), in which water jets mixed with abrasive particles are highly pressurized and are used for drilling by means of a rotating nozzle head, wherein a water pressure of approximately up to 100 bar is used.
Finally, it has also been known (CH-A-370,717 and GB-A-718,735) to atomize a liquid by means of air for the treatment of surfaces; here, too, rotary nozzles are employed by means of which the inner wall of the bore in a workpiece is treated to cause said bore to adopt the final fine-machining condition. Hence, a proper material-removing cutting effect is not obtained thereby.
SUMMARY OF THE INVENTION
It is the object of the invention to improve the machining especially of hard objects by removing material to form grooves or channels at a high removal rate without any bulky auxiliary units; it is particularly desirable to increase the "advance rate" when channelling the hard material.
Surprisingly, it has been found that by the method according to the invention, in which together with at least one jet of pressure medium at least one directional jet of a coolant is directed to the removal site of the object, a cooling effect acts on said object whereby the removal rate is substantially increased over the rate possible without such a cooling medium. The cooling medium need not necessarily be cooler than the pressure medium; it will suffice for the cooling medium to cause a strong cooling effect at the point of impact within the area of impact of the pressure medium jet on the object to be channelled. The removal rate will be improved for instance by the factor 3-4 relative to the absence of cooling medium even if water is used as pressure medium and air is used as cooling medium provided the water pressure is at least 1500 bar. It is assumed that due to the combination of the high-pressure water and the directional jet or several directional jets of air, respectively, sufficient heat is absorbed from the water already before the water impacts hard granite, for example, so that any substantial heating of the granite may be prevented. Investigations have shown that in the absence of the cooling medium the granite at the bottom of the channel formation will be heated to such an extent that a vitreous or ceramic-like coating is formed thereon whereby the removal rate is significantly reduced. The invention prevents the formation of such a coating on the granite top surface, which coating offers high resistance to removal. Moreover, the interaction between the point-like pressure-medium jets, which cause considerable heating of the rock upon impact, and the directional jet which cools the same part of the rock during oscillatory movement thereover promotes the formation of cracks in the rock and helps to break it up and crush it to particles.
The object of the invention is solved in a particularly advantageous way when the pressure medium is ejected from a nozzle head at the high pressure of up to 2000 bar and more in the form of plural narrow discrete jets and when the discrete narrow jets are not arranged in par
REFERENCES:
patent: 4074858 (1978-02-01), Burns et al.
patent: 4708214 (1987-11-01), Krawza et al.
patent: 4795217 (1989-01-01), Hilaris
patent: 5052756 (1991-10-01), Wada et al.
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