Mining or in situ disintegration of hard material – Expansible breaking-down devices – Fluid-pressed element
Reexamination Certificate
1999-03-05
2001-10-23
Bagnell, David (Department: 3673)
Mining or in situ disintegration of hard material
Expansible breaking-down devices
Fluid-pressed element
C102S328000
Reexamination Certificate
active
06305752
ABSTRACT:
The present invention relates to a blasting device for use in rock blasting, particularly, although not exclusively, open cast mining.
Most conventional operations of rock blasting employ nitroprill as the explosive. Currently, in open cast mining, the blasting is carried out by firstly drilling a pattern of bores into a “bench” of rock to be blasted. Open cast mines are blasted in a step formation, the section of the step to be blasted being known as a “bench”. Each bore is then loaded with the explosive, then the immediate area must be cleared of all personnel and machinery that could be damaged, before blasting may commence. After blasting, the area must be cleared of all rock and debris which could damage the machinery used on the site. In addition to the inherent dangers involved, these conventional methods of blasting have many drawbacks, including high labour costs in loading the holes, and high costs in the provision and transportation of the explosive used. The cessation of mining operations during blasting and clearing of the immediate area subsequent to the blasting, all add to the expense and time involved in such operations.
It is accordingly an object of the present invention to provide a device and method which at least partly overcomes the above-mentioned drawbacks.
In accordance with a first aspect of the present invention there is provided a blasting device for connection to a source of compressed gas, the device being insertable in a previously prepared bore and comprising one or more air guns contained within a housing each air gun being provided with an associated aperture in the housing through which gas exhausted from the gun is directed at a high pressure and velocity to create a blasting effect.
Preferably, the housing is of tubular form having a plurality of apertures or exhaust ports arranged down one side thereof. A rubber-like sheath may be located within the housing with openings in register with the or each of said aperture(s). The apertures may be ovoid in shape although other shapes may be found suitable. In particular, it has been noted that a T-shaped aperture is advantageous in that it reduces the damping effect on the air gun caused by air being unable to escape rapidly enough from the air gun exhaust chamber.
In accordance with a further aspect of the invention there is provided a method of blasting, employing at least one blasting device as defined above, and in which a bore or an array of bores is drilled into a section to be blasted, said device is lowered into a bore and the air gun(s) fired, causing the compressed air from the source to be released from the gun(s) and pass through the aperture(s), to create a blasting effect on the section surrounding the bore.
In accordance with a still further aspect of the present invention, there is provided a blasting device as previously described for insertion in a previously prepared bore which device further includes at least one packer located at one end of the device, the arrangement being such that the packer forms a seal between the bore and the device so that liquid introduced into said bore before operation of the device is retained within the bore and thereby amplifies the blasting effect of the air gun(s) when fired.
Preferably the packer takes the form of an inflatable collar, whilst the liquid, conveniently water, is introduced to the bore via a cascade provided within the device. Advantageously, the cascade is positioned to ensure that liquid emerging from the cascade washes the housing in the region of the apertures to prevent the accumulation of debris from the bore reducing the efficiency of the device.
It will be recognised that the packer or packers may be positioned anywhere on the housing of the device to suit a particularly blasting technique. For example, where it is desired to blast rock away from the lower portion of a bench, a packer may further be fitted at the lower end of the device to retain liquid which would otherwise drain into the undercut portion of the bench.
REFERENCES:
patent: 2636437 (1953-04-01), Loving
patent: 3018731 (1962-01-01), Filstrup
patent: 3172361 (1965-03-01), Thouzeau
patent: 4301731 (1981-11-01), Fitzgerald
patent: 564144 (1958-02-01), None
patent: 1298483 (1969-07-01), None
patent: 3610149 (1987-10-01), None
patent: 1208365 (1970-10-01), None
patent: 2124681 (1984-02-01), None
patent: WO 94/03707 (1984-02-01), None
PTO translation of Auslegeschrift 1298483; PTO 2000-3253, Jul. 2000.
Bagnell David
Kinney & Lange , P.A.
Kreck John
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