Improvements in Rock Drilling Machines.
Year: 1894

page_text: Date of Application, 15th Mar., 1894-Accepted, 21st Apr., 1894
..
COMPLETE SPECIFICATION.
Improvements in Rock Drilling Machines.
We, JAMES WILLIAM LARMUTH and ROBERT BIRKEN HOWARTH both of
Todleben Iron Works, Unwin Street, Cross Lane, Salford in the County of
Lancaster, 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 compound rock drilling machines and consists in an
improved arrangement or construction of a compound rock drilling machine and
parts thereof operated in a similar manner as the not compounded rock drilling
machine for which Letters Patent Number 10050 dated the 13th June 1891 have
been granted to us, the object of our improvements being mainly to obtain the
advantages of operating the rock drill by expanding the motive fluid in a larger
cylinder for effecting the return stroke after. it has acted in a smaller cylinder for
the working stroke, in a simple and reliable manner with few working parts in the
machine.
Our improvements are hereinafter particularly described with reference to the
accompanying sheet of drawings on which
Figure 1 is a central longitudinal vertical section of our improved compound rock
drill.
Fig. 2 is a plan showing an exterior view of the same.
Figures. 3 and 4 are cross sections on lines A B and C D Figure 1.
Figure 5 is a plan of the rockdrill cylinder showing the receiver pipe and
connecting port from the high pressure exhaust to the low pressure inlet valve
chamber, the receiver pipe being partly shewn in section.
Like letters indicate the same parts throughout the drawings.
According to our invention we provide a compound cylinder A', Figure 1, formed
of a larger cylinder at the front or piston rod end and a smaller cylinder at the back
end, the larger or low pressure cylinder being formed with exhaust port B', inlet
port C, receiver port D' and a small escape port E, Figs. 1 and 3, at the end of
the enlarged or low pressure part of the cylinder, and with the inlet port F and
exhaust port G at the high pressure end of the cylinder. On the top of this
cylinder we form or attach by means of bolts a valve box H provided with screwed
plugs or covers J and J at the ends, into which valve box we place a piston
valve K having chambers L, L' and L' formed therein, also a central recess M to
receive the nose of the threearmed tappet N arranged in a similar manner as
described in our Patent Specification No. 10050 A.D. 1891.
Into the cylinder A' we fit a double piston having an enlarged piston face P and
a reduced piston Q Q and piston rod, O, the reduced part being formed with a
recess and curved shoulders R and R' as described in our Specification aforesaid and
by means of which the piston valve receives a reciprocating motion and alternately
opens and closes the ports B, C, D, E, F and G.
We further form on the side of the drill cylinder the receiver pipe S and
connecting the ports D¹ and G, for conducting the pressure fluid exhausted from.
the reduced cylinder end to the inlet chamber L, Figs. 1 and 3.
Our rock drill operates as follows: The drawing Figure 1 shows the piston valve
admitting pressure fluid to the small or high pressure end Q1 of the piston, causing
the piston to make its outwards or boring stroke the enlarged or low pressure end
of the cylinder being open to the atmosphere through the ports B and C and
chamber L in the piston valve K. When the piston has travelled two thirds of its
stroke, the curved shoulder R' begins to operate the tappet N and shifts the piston

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valve K to the left, opening the exhaust port G through which the pressure fluid
escapes into the receiver or connecting pipe or port S and passes through the
port D₁, chamber L' and port C' into the enlarged end of the cylinder and causes
the piston P to make its return stroke. When during the return stroke the curved
shoulder R operates the tappet N, the piston valve is returned to the position
shewn on the drawing and the fluid in the large end of the cylinder exhausts
into the atmosphere, while at the same time pressure fluid is admitted to the
high pressure end, and so on. The small port E is provided to prevent during
the return stroke the compression of air in the annular space T formed
by the large cylinder and smaller piston, and the retardation of the return stroke
thereby.
1
.
A further improvement in the rock drill consists in the arrangement and
construction of an automatically closing starting valve. It is evident that if the
rockdrill has been used for drilling holes downwards in the rock in á vertical or
angular direction, the piston and rod after the drill is stopped will slide down to the
bottom or outward position and shift the piston valve to the position in which
the two ends of the cylinder communicate and so prevent the pressure fluid from
entering the large or low pressure end when the fluid is again admitted to the valve
chamber, and thus the drill cannot start. To overcome this difficulty we form in
the rear plug J' of the valve box a double seated valve having two faces U and U'
and provided with a shank and knob V, which valve is kept on its seat by means of
a light helical spring assisted by the fluid pressure in the end of the valve box, the
fluid being admitted to the end of the valve box by means of a port or flat cut in
the top of the piston valve at W. The starting valve operates as follows: When
the knob is pushed fluid is admitted to the chamber X between the valve
seating and by means of small holes X¹ into the exhaust ports G and S allowing
the pressure to enter the low pressure end of the cylinder and move the piston and
rod into the positions shewn on the drawings and ready for starting the drilling.
As soon as the knob,is released the valve will close automatically by means of the
pressure in the valve box assisted by the spring aforesaid. When boring holes
vertically or at an upward angle the starting valve does not require using as then
the piston and valve will be in the positions shewn on the drawings ready for
starting on admission of the fluid to the valve box H.
Another improvement applied to the piston valve of our improved rock drill
consists in a device to counteract the tendency of the piston valve K to lift
in consequence of the pressure in the chambers, more particularly in chamber L¹
acting on the surface of the valve box at Y. For this purpose we cut a flat in the
top of the piston valve K at W of such an area that the pressure of the motive fluid
in the valve box H on the top of the valve will have a slight excess over the lifting
pressure, and prevent the tendency of the valve to lift in consequence of the
pressure on its underside. This port or flat also allows the fluid to pass freely to
each end of the piston valve and so produce an equilibrium of pressure on the ends
of the piston valve K.
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:
Firstly. In a percussive rock drilling machine the arrangement, of pistons,
cylinders and ports thereof, piston valve and ports and chambers thereof and tappet
for operating the valve substantially as hereinbefore described and illustrated and
for the purposes set forth.
Secondly. In a compound rock drilling machine the use and arrangement of a
starting valve for admitting the motive fluid to the low pressure end of the
cylinder constructed substantially as hereinbefore described and illustrated.
Thirdly. The arrangement of a flat part or its equivalent on the top of the
piston valve for preventing the lifting of the piston valve and admitting the
motive fluid to the ends of the piston valve, substantially as hereinbefore described.

page_text: Fourthly. The general arrangement or construction of a rockdrilling machine
substantially as hereinbefore described and illustrated.
Dated the 13th day of March 1894.
R. J. URQUHART,
57, Barton Arcade, Manchester, and 5, Clayton Square, Liverpool,
Consulting Engineer and Patent Agent.