Improvements in Apparatus or Machinery for Drilling Rocks and other Hard Substances.
Year: 1896

page_text: Date of Application, 23rd Jan., 1896
Complete Specification Left, 14th Oct.. 1895-Accepted, 9th Jan., 1897
MOVISIONA
Improvements in Apparatus or Machinery for Drilling Rocks and
other Hard Substances.
We, RICHARD STEPHENS and WILLIAM CHARLES STEPHENS, both of Carn
Brea, in the County of Cornwall, Engineers, do hereby declare the nature of this
invention to be as follows:-
Our invention relates to percussive drills of the kind wherein the valve is
operated by the pressure of the motive fluid and wherein such fluid, after having
completed its work on the valve, is allowed to escape through a circumferential
passage in the main piston to the atmosphere.
In such drills as heretofore constructed considerable difficulty has been
experienced in preventing the leakage of the air into the main cylinder before
the piston has arrived in the proper position relatively with the valve. Now the
chief object of our invention is to overcome this difficulty and to this end we
arrange in conjunction with the port or passage, through which the air escapes
from the valve chest into the circumferential groove in the piston, a bushing or
plug which we term an "auxiliary valve," and which may be composed of leather,
fibre, asbestos, wood or other suitable elastic or compressible material. This
bushing is maintained in permanent contact with the piston and in order to
compensate for any wear of the latter and of the auxiliary valve we advantageously
make the valve chest removable and introduce packing pieces upon the back end
of the auxiliary valve so that when the face is replaced the said auxiliary valve
will be pressed forward into contact with the piston.
Or we may compensate for the wear of the piston and auxiliary valve by flanging
the said auxiliary valve and arranging it so that the air acts on it and forces it
down into contact with the piston.
Dated this 22nd der of Ian 180R
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.
Improvements in Apparatus or Machinery for Drilling Rocks and
other Hard Substances.
We, RICHARD STEPHENS and WILLIAM CHARLES STEPHENS, both of Carn
Brea, in the County of Cornwall, Engineers, do hereby declare the nature of this
invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
Our invention relates to percussive drills of the kind wherein the valve is
operated by the pressure of the motive fluid and wherein such fluid, after having
completed its work on the valve, is allowed to escape through a circumferential
passage in the main piston to the atmosphere.

page_text: In such drills as heretofore constructed difficulty has been experienced in
preventing the leakage of the air into the main cylinder before the piston has
arrived in the proper position relatively with the valve. Now the chief object of
our invection is to overcome this difficulty and to this end we arrange in con-
junction with each port or passage, through which the air escapes from the valve
chest into the circumferential groove in the piston, a bushing or plug which we
term an "auxiliary valve," and which may be composed of leather, fibre, asbestos,
wood or other suitable elastic or compressible material. This bushing is maintained
in permanent contact with the piston and in order to compensate for any wear of the
latter and of the auxiliary valve we advantageously make the valve chest removable
and introduce packing pieces upon the back end of the auxiliary valve so that when
the face is replaced the said auxiliary valve will be pressed forward into contact
with the piston.
Or we may compensate for the wear of the piston and auxiliary valve by flanging
the said auxiliary valve and arranging it so that the air acts on it and forces it down
into contact with the piston.
In lieu of the usual split front cover of the cylinder we employ a solid cover
having a hole through which a leather or other packing ring can be inserted and
which is provided with an air-tight plug or stopper.
To enable our invention to be fully understood we will describe it by reference
to the accompanying drawing, in which :-
Figure 1 is a longitudinal section of a rock drill having our improvements applied
thereto :
.
Figure 2 is a vertical section of the bushing or auxiliary valve:
Figure 3 is a plan of the same:
Figure 4 is a vertical section of a modified form of bushing or auxiliary valve.
Figure 5 is a section of the solid front cover on the line 5-5 Figure 1.
a is the cradle, b the cylinder which slides in the cradle, and c the screw by
means of which the cylinder is moved in the cradle a; d is the piston-rod,
e, e' are the two pistons or piston heads, and the circumferential passage in the
same. g is the twist bar for rotating the drill. These parts are all of known
construction.
h is the valve-chest bolted to the cylinder by bolts, and having an inlet i
for the compressed air or other motive fluid and outlet ports j, j into the cylinder
for the escape of the same. k is the piston valve having an annular groovel for
the distribution of the compressed air to either end of the valve-chest through the
grooves m, m¹.
n, n are the bushings or auxiliary valves, the said bushings being, as shewn
clearly in Figure 1, inserted in the ports j, j in the cylinder wall. The bushings
are held in place by their conical shape or by means of a flange o as shewn in
Figure 4 or by other suitable means.
It will be obvious that these auxiliary valves n, n which are pressed down on to
the piston by the valve-chest, act as packing to the piston at the openings of the
ports j, j into the cylinder 6 so as to prevent the motive fluid escaping into the
latter except when the passage f comes opposite one of the said openings when
the fluid escapes into the passage and thence into the atmosphere through one of
the holes p, p arranged in the cylinder opposite the openings of the ports j, j.
When the pistons e, e' or the bushings n, n have become worn, the valve-chest
is removed and packing-pieces are placed on the backs of the said bushings so that
when the valve-chest is again bolted to the cylinder the bushings are pressed on to
the pistons so as to again make tight joints.
In Figure 4 the bushing is made cylindrical and flanged on the back or valve
side and is provided with a circumferential groove q. With this construction the
air pressure on the back of the bushings will tend to press the said bushings
towards the pistons and so compensate for the wear of the pistons and valves or
bushings the groove giving the necessary elasticity for allowing the body of the
bushing to be pressed forward whilst the flange remains upon its seat.

page_text: is the solid front cover of the cylinder 6 and is a groove in the same for the
reception of a split leather or other packing ring is the hole through which
the packing ring is passed into the groover and is the screw plug for closing
the said hole air tight. By this construction of solid front cover it will be obvious
that a worn packing ring can be easily and quickly renewed without disturbing the
front cover which was necessary with covers as heretofore made.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. In apparatus or machinery for drilling rocks and other hard substances,
wherein apertures or ports in the cylinder are designed to be closed by the pistons,
compressible bushings arranged in the said apertures or ports, substantially as, and
for the purpose, described.
2. In percussive drills of the kind wherein the valve is operated by the pressure
of motive fluid which, after operating the valve, is allowed to escape through a
circumferential groove in the piston, bushings arranged in conjunction with the
exhaust ports of the motive fluid from the valve-chest, substantially as, and for the
purpose, described.
3. The combination with apparatus or machinery for drilling rocks and other
hard substances having apertures or ports in the cylinder designed to be closed by
the pistons in which apertures or ports compressible bushings are arranged as
claimed in Claim 1, of a solid front cylinder cover having a hole for the insertion
of the packing ring and a plug or stopper for the said hole, substantially as, and
for the purpose, herein before described.
4. In a percussive drill having openings or ports j, j between the valve-chest
and the cylinder, bushings n, n arranged in the said openings or ports, substantially
as described.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.