IMPROVEMENTS IN PER- CUSSIVE ROCK DRILLS
Year: 1875

page_text: LETTERS PATENT to Thomas Brown, of No. 96, Newgate Street, in
•
the Oity of London, for the Invention of "IMPROVEMENTS IN PER-
CUSSIVE ROCK DRILLS."—A communication from abroad by Charles
Burleigh, of Fitchburg, Massachusetts, United States of America.
PROVISIONAL SPECIFICATION left by the said Thomas Brown at
the Office of the Commissioners of Patents, with his Petition, on
the 12th May 1875.
I, THOMAS BROWN, of No. 96, Newgate Street, in the City of London,
5 do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN PERCUSSIVE ROCK DRILLS," to be as follows :-
This Invention relates to improvements in rock drills of the kind in
which the drill is attached to the rod_of_a_piston caused_to_reciprocate-
in a cylinder by the pressure of steam, compressed air, or other fluid
under pressure. The present improvements having for their object a
compact and simple arrangement of the mechanism, particularly of that

page_text: whereby the motion of the piston is utilised to effect the alternation of
the slide and the intermittent rotation of the drill, as well as to give
reciprocating movement to the drill itself. For this purpose the piston is
made of considerable length and is rounded at its edges and fitted with
one or more packing rings in the middle. The slide is made with a rod
projecting from it both ways, parallel to the axis of the cylinder; and to
this rod are connected the arms of two bell-crank tappet levers which are
mounted on pivots and work within the ports opening into the cylinder,
the other arms of these cranks being somewhat sloped or curved and
projecting into the cylinder near each end thereof. When the piston 1
moves in either direction, just before reaching the end of its stroke, its
rounded edge bearing against and pushing aside the one or the other of
the said bell-crank arms causes the slide to be moved so as to reverse the
direction of the acting fluid through the cylinder ports, and so to reverse
the direction of the piston's movement. On the stem or rod of the piston 1
is an inclined or helical groove (or there may be two or more such
grooves), and this rod is arranged to slide through a ratchet wheel pro-
vided with a spring pawl, and having a feather which projects into the
said helical groove, so that at every stroke of the piston it, with the drill
which is attached to it, is partially rotated in the manner described in
the Specification of a Patent granted to G. Haseltine as a communica-
tion from the said Charles Burleigh, on the 22nd November 1866,
No. 3065.

page_text: .
nistrators, and assigns, or such others as I, the said Thomas Brown,
my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN PERCUSSIVE ROCK DRILLS," a communication to me
from abroad by Charles Burleigh, of Fitchburg, Massachusetts, United
States of America, upon the condition' (amongst others) that I, the
said Thomas Brown, my executors or administrators, by an instrument
in writing under my, or their, or one of their hands and seals, should
particularly describe and ascertain the nature of the said Invention,
and in what manner the same was to be performed, and cause the
same to be filed in the Great Seal Patent Office within six calendar
5 months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Thomas Brown, do hereby declare
the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by
the following statement thereof, reference being had to the accom-
panying Sheet of Drawings, and to the figures and letters marked
thereon, that is to say :—
This Invention relates to improvements in rock drills of the kind in
which the drill is attached to the rod of a piston caused to reciprocate
in a cylinder by the pressure of steam, compressed air, or other fluid
5 under pressure. The present improvements having for their object a
compact and simple arrangement of the mechanism, particularly of that
whereby the motion of the piston is utilised to effect the alternation of
the slide and the intermittent rotation of the drill, as well as to give
reciprocating movement to the drill itself. For this purpose the piston is
O made of considerable length and is rounded at its edges and fitted with
one or more packing rings in the middle. The slide is made with a rod
projecting from it both ways, parallel to the axis of the cylinder; and
to this rod are-connected the arms of two bell-crank tappet lovers which
are mounted on pivots and work within the ports opening into tho
5 cylinder, the other arms of these cranks being somewhat sloped or curved-
and projecting into the cylinder near each end thereof. When the piston
moves in either direction, just before reaching the end of its stroke, its
rounded edge bearing against and pushing aside the one or the other of
"

page_text: the said bell-crank arms causes the slide to be moved so as to reverse
the direction of the acting fluid through the cylinder ports and so to
reverse the direction of the piston's movement. On the stem or rod of
the piston is an inclined or helical groove (or there may be two or more
such grooves), and this rod is arranged to slide through a ratchet wheel
provided with a spring pawl, and having a feather which projects into
the said helical groove, so that at every stroke of the piston it with the
drill which is attached to it, is partially rotated in the manner described
in the Specification of a Patent granted to G. Haseltine, as a commu-
nication from the said Charles Burleigh, on the 22nd November 1866,
No. 8065.
DESCRIPTION OF THE DRAWINGS.
Fig. 1 is a plan, and Fig. 2, a longitudinal section of the working
cylinder and frame of a rock drill constructed and arranged according to
this Invention; Fig. 3 is a traverse section on the line 2, 5, of Fig. 2.
A is the piston made of considerable length with rounded edges, and
with one or more packing rings a about its middle; B is the slide
having its rod extended both ways, as indicated at 6 and b', with gabs
receiving the arms of two bell-crank levers C, O', the tails of which c, c',
are made to pass through the cylinder ports at each end, so that as the
piston A approaches the end of its stroke in either direction its rounded
edge bears against one or other of the tails c, c³, and pushing it outwards
moves the slide so as to alter the direction of the working fluid, and
thereby reverse the movement of the piston. On the piston rod is
formed an inclined or helical groove D, or two or more such grooves ?
into which fit feathers d, d, in a ratchet wheel E, through which the
rod passes. This ratchet wheel is provided with a pawl e to prevent it
from turning backwards, and along with the pawl and piston rod is
enclosed in an extension of the cylinder so that there is no escape of the
working fluid. As the piston makes its back stroke the ratchet wheel a
being prevented by the pawl from turning backwards, the piston itself
and drill are partly turned round by the feathers d, d, acting in the
helical slots D, but during the forward stroke the ratchet wheel being
free to turn forwards is partly turned round by the action of the inclined
slots D on the feathers d, d, the piston and drill themselves advancing a
without turning. F is tho clamp for securing the drill to the piston rod
in the usual manner. The cylinder is fitted to slide on a frame G, being

page_text: moved by a screw H worked by hand as described in the Specification
above referred to.
Having thus described the nature of this Invention, and in what
manner the same is to performed, as communicated to me by my
foreign correspondent, I claim,―
First. The use for working the slide for the cylinder of a percussive
rock drill of two tappet bell-crank levers having tails projecting through
the cylinder ports, so as to be acted on by the piston as it approaches
each end of its stroke, substantially as herein described.
Second. The use in combination with the piston, cylinder, and slide of
a percussive rock drill operating in the manner referred to in the pre-
ceding claim, of a ratchet wheel and pawl, the piston rod passing
through the ratchet wheel and having an inclined slot or slots fitting
feathers in the wheel, substantially as and for the purpose herein set
forth
forth
In witness whereof, I, the said Thomas Brown, have hereunto
set my hand and seal, this Fifth day of November, in the
year of our Lord One thousand eight hundred and seventy-
five.