Improvements in Rock Drills.
Year: 1896

page_text: Improvements in Rock Drills.
We, Joux HENRY HOLMAN, and JAMES MINERS HOLMAN, carrying on business as
Holman Brothers, of Camborne, in the County of Cornwall, Engineers, do hereby
declare the nature of this invention to be as follows:-
This invention relates to improvements in rock drills.
In carrying out our invention we employ a quadrant shaped valve working
in a semicircular slide or guide with elongated or bevelled ends and adapted to be
actuated by the piston striking the said ends alternately thereby driving the valve
the required distance to open the ports and enabling us to dispense with the use of
springs, bolts, studs and the like.
By this arrangement the piston in travelling the length of its forward stroke
drives the valve to one end of its path thereby uncovering the port to the front end
of the cylinder so as to allow the air to pass from the valve chest through this port
to the said front end of the cylinder to drive back the piston. At the same time
the valve uncovers the port from the back end of the cylinder allowing the air to
pass through the said port to the exhaust port; the piston then making its back-
ward stroke drives the valve to the opposite end of its path uncovering the port to
the back end of the cylinder admitting the air from the valve chest through the
said port so as to again drive the piston forward, communication at the same time
being opened between the front end of the cylinder and the exhaust port and so
on alternately.
1000
We, JOHN HENRY HOLMAN, and JAMES MINERS HOLMAN, carrying on business as
Holman Brothers, of Camborne, in the County of Cornwall, Engineers, do hereby
declare the nature of this invention and in what manner the same is to be per
formed to be particularly described and ascertained in and by the following
statement:-
This invention relates to improvements in rock drills.
In carrying out our invention we employ a quadrant shaped valve working in a
corresponding circular guide and adapted to be actuated by the piston striking its
ends alternately, and without the use of springs, bolts, studs and the like.

page_text: To enable our invention to be fully understood we will describe the same by
reference to the accompanying drawing, in which:-
Figure 1 is a longitudinal section of part of a rock drill having our improved
distributing valve applied thereto;
Figure 2 is a plan of the same;
Figure 3 is a section on the line 3-3 Figure 1; and,
Figure 4 is a section on the line 4-4 Figure 1.
a is the cylinder of the drill, b is the piston, c is the passage establishing com-
munication between the port el in the valve face and the front end of the cylinder
and d is the passage establishing communication between the port and the rear
end of the cylinder. c is the air inlet passage and f is the exhaust passage which
communicates with the port f' in the valve face.
g is our quadrant shaped valve which slides in a correspondingly shaped channel
cut in the downwardly projecting portion of the cover i the said cover with its
downwardly projecting portion having also formed in it portions of the passages c
and d and also the exhaust passage f. The said valve has formed through it two
ports c and d and the recess f, the said ports and being designed to alter-
nately establish communication between the air inlet e and the ports c¹ and
and the recess f to alternately place the ports c and d in communication with the
exhaust port f'. The lower corners or angles of the valve g project into the path
of the piston so that the surfaces at the ends of the recess formed in the centre
of the piston will alternately impinge against the valve to operate it.
The operation of the valve mechanism herein before described will be undersmod.
from the following:-
Assume the piston to have nearly completed its forward stroke and the surface j
to have acted against the valve g so that the valve closes all the ports c, as
shewn in Figure 4. The further movement of the piston towards the front end
of the cylinder under the expansion of the air which has just been cut off from the
rear end of the cylinder causes the further movement of the valve so that the
ports therein comes opposite to the port e whilst the ports d', flare placed in
communication by the recess f. The result of this movement of the valve is to
allow the air which enters the valve chest through the aperture e to flow through
the ports and c and the passage e to the front end of the cylinder thereby driving
the niston back in the cylinder the air behind the piston at the same time escaping
through the passage d, the port d', the recess f, and the port f¹ to the exhaust
passage f during this backward movement of the piston the surface i thereon strikes
against the adjacent angle of the valve and moves the valve to place the
ports d, din communication and the ports f, c' in communication and so on.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
A rock drill having a quadrant shaped valve constructed, arranged and operating
substantially in the manner hereinbefore described and illustrated in the accom-
panying drawing.
Datad this 21st love of Tune 100%
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.