Improvements in Rock Drilling Machines.
Year: 1891

page_text: Date of Application, 13th June, 1891-Accepted, 22nd Aug.. 1891
COMPLETE SPECIFICATION.
Improvements in Rock Drilling Machines.
We JAMES WILLIAM LARMUTII, and ROBERT BIRKEN HOWARTH both of
Todleben Ironworks, Pendleton 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 percussive rock drilling machines operated by steam,
compressed air or other fluids and consists in improved arrangements of the ports
and valves of the same and the mechanism for moving the valves and improved
means for taking up the slackness of the feed screws and nuts, the object of our
invention being to economise the consumption of compressed air or other fluid and
to remove or reduce the destructive shocks to which the valve gear and feed screws
and nuts of ordinary rock drills are subject.
On the 2 sheets of drawings appended hereunto :
Fig. 1 shows a central longitudinal vertical section of our improved rock drill
with improved arrangement of ports and valve.
Figure 2, a similar view showing the application of our improvements except
that relating to the arrangement of ports to a rock drill with the usual long inlet
ports.
Figure 3. is a plan of the rock drill.
Figures 4, 5 and 6 show cross-sections on lines A. B, C D', and E F of
Figure 1.
:
Figures 7, 8 and 9 show cross-sections on lines G. H, I J and K L of
Figure 2:
Figure 10 is an enlarged central longitudinal vertical section of a cylinder and
valve box showing our improvements in the same.
Like letters indicate the same parts on all the figures.
In carrying out our improvement in the arrangement of the ports, we bolt to the
cylinder B. Figure 1 a valve chambér A equal in length to the main cylinder B.
The valve chamber A contains a piston valve, which works over the inlet ports D
and D and the exhaust ports E and E' leading to the interior of the cylinder B.
The length of these inlet ports D and D₁ being equal only to the thickness of the
flat faces cast upon the cylinder and the thickness of the ports; the length
of the inlet ports is much shortened by this arrangement and consequently a
great saving of the pressure fluid employed for driving the rock-drilling machine is
effected.
Another improvement connected with the piston valve C consists in arrange-
ments for assisting the action of the tappet F which shifts the valve by making the
fluid pressure act alternately at each end of the piston stroke upon said piston
valve in the same direction as the tappet F.
In carrying out this part of our invention we form the piston valve C with
enlarged ports or pistons at each end and form flats G and G or equivalent ports
or passages on each end piston, and corresponding passages or ports H and H' in
the valve box A. The ports are so arranged that the ports G and G¹ in the piston
valve C overlap the ports H and H' alternately. We also form small ports I
and I communicating with the exhaust ports E and E¹. The action of this
arrangement is as follows: As soon as the valve C has been shifted by the
tappet Fin the manner hereinafter described into the position shewn on the
drawings, the port G¹ in the piston valve overlaps the port H' in the valve casing.
while the port I' is closed by the valve, so that the pressure fluid passes through
D

page_text: ports G'H' into the space J' and fills the same. At the same time the ports G
and H at the other end are put out of communication with each other and the
port I is opened so that the pressure fluid previously contained in the space J
escapes into the exhaust. In consequence of this the fluid contained in J¹ presses
the valve to the left and as soon as the nose K of the tappet F passes off the
cylindrical part Q of the main piston to the curved part O, the fluid pressure
assists the tappet in shifting the valve to the left. Arriving at the other end of its
stroke, the valve opens ports G H and closes port I, and the fluid pressure
entering into space serves to cushion the piston valve C and prevents the nose K
of the tappet F striking the recessed part L of the piston. At the return stroke of
the piston valve the pressure in space J assists the movement of the valve and the
pressure fluid let into the space J' towards the end of the stroke cushions the
valve. By these means the piston valve C is operated without the shocks which
are so destructive to the tappets of ordinary rock drills.
Another improvement consists in an arrangement for locking the tappet Fat
each end of the stroke of the piston so as to prevent the position of the piston
valve C being disturbed by the shock resulting from the blow on the drill. For
this purpose the central part of the main piston P in cylinder B is recessed in
its middle part L, curved shoulders O and O₁ connecting the recessed part L
to the cylindrical parts Q and Q₁ fitting the cylinder B. The central part of
the piston valve is recessed for the central tail M of the tappet F, which tappet
oscillates on the pivot N fixed to cylinder B. The curved shoulders O and O' act
alternately upon each of the two lower arms or noses K and K' of the tappet F
and cause it to rock upon its pivot N and by means of the central tail M cause the
piston to make a reciprocating motion, which is preferably assisted by the fluid
pressure in the manner hereinbefore described. In executing this movement the
noses K and K of the tappet alternately slide up the curved shoulders O and O¹
and rest upon the circumference Q and Q₁ at the end of the stroke, while the other
nose is depressed against the recessed part L of the piston. The tappet is then
held immovable and prevents any shifting of the piston valve C while the blow is
delivered. This arrangement of tappet and piston is applicable to machines
with the ordinary arrangement of valve and where arrangements for assisting
the movement of the piston valve by fluid pressure hereinbefore described are not
used.
Our further improvement relates to means for taking up any slackness in the
feed screws and nut of a rock drilling machine arising from wear. In carrying
out this part of our invention, we cast on the underside of the cylinder B to pro-
jecting lugs R and S between which the feed screw nut T is fitted as usual, and
fit a second nut U in the enlarged hole in the lug of such length that a space V
is left between the nut T and the second or binding nut U. Into this space we
preferably place a helical spring X which automatically increases the distance
between the nuts T and U as wear takes place in the threads of said nuts and of
the feed screw Y, as by pushing out the nut U, which is prevented from turning by
means of a flat on the collar of the nut held in position by the cylinder cover, it
presses the threads of the same against those of the feed screw and draws the
latter out of the nut T until the threads of the latter bear tightly against those of
the feed screw Y. Instead of a spring, we adjust the nut U in some cases by
means of bolts passing through a flange cast upon the nut and a flange on the lug S,
or by equivalent means.
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 actuated by fluid pressure the
arrangement of short inlet ports and a valve box equal in length to the cylinder
substantially as hereinbefore described and illustrated and for the purpose set
forth.

page_text: Secondly. The method of and arrangements for assisting the action of the tappet
operating the piston valve of a percussive rock-drilling machine by means of fluid
pressure admitted alternately behind each end of said piston valve through small
ports or their equivalent and exhausted from the opposite end through a small port
communicating with the exhaust ports of the cylinder substantially as hereinbefore
described and illustrated.
Thirdly. The arrangement of the piston of a percussive rock-drilling machine
with a recess and curved shoulders for actuating the tappet and locking the same
in its position at the end of the stroke, substantially as hereinbefore described and
illustrated.
Fourthly. In rock drilling machines the arrangement of a second or binding nut
for the feed screw in addition to the usual nut in combination with a spring, bolts
or equivalent means for adjusting the distance between said nuts substantially as
and for the purpose herein before specified.
Fifthly. The combination in a rock drilling machine of the short inlet ports,
arrangements for assisting the action of the valve operating tappet by fluid
pressure, locking the tappet at the end of the stroke of the valve and taking up the
wear on the feed screw and nut hereinbefore specified.
Sixthly. The general arrangement or combination of parts of rock drilling
machines substantially as hereinbefore described and illustrated by the drawings.
Dated this 10th day of June 1891.
W. T. EMMOTT,
Agent for the Applicants.