Improvements in Rock Drills.
Year: 1897

page_text: Date of Application, 10th Aug., 1897-Accepted, 23rd July, 1898
COMPLETE SPECIFICATION.
Improvements in Rock Drills.
A communication from abroad by ANTHONY JOHN BANT, of Johannesburg, South
African Republic, Engineer.
I, JOHN CORRY FELL, of the firm of Fell and James, of 1, Queen Victoria Street,
in the City of London, Chartered Patent Agents, do hereby declare the nature
of this invention to be as follows:-
This invention relates to reciprocating rock drills driven by steam or compressed
air, and consists in improvements, whereby the surfaces of the drill piston, operated
upon by the motive power are duplicated, in conjunction with a suitable valve
and ports, giving reduction of weight compared with other drills of the same
power, economy of working, and greater adaptability to various kinds of work;
and further by a special spring re-action, or compensation upon the feed screw,
the slack or wear in the screw is always taken up, giving increased durability to
the drill as compared with others.
And in order that this invention may be the better understood, I now proceed to
describe the same with reference to the drawings hereto annexed, and to the letters,
and figures marked thereon.
Fig. 1 is a longitudinal section through the drill, and cradle.
Fig. 2 is an outside plan of the same with valve box removed.
Fig. 3 is an end view of the same.
The drill cylinder A is mounted so as to slide freely on ways in the cradle B
and is controlled as to its relative position to the cradle by the feed screw C, and
bandle C¹.
The compressed air or steam enters the valve box D by an inlet port d, and is
admitted to the required ports as hereinafter more fully described by the reciproca-
tion of the piston valve E actuated by a rocking tappet e which is moved at either
end of the stroke by the shoulders f of a recess in the main piston F.
An interchangeable valve face G is introduced between the valve box D) and
the cylinder A to facilitate renewal of the wearing parts.
The chief item of improvement in this drill lies in the arrangement of duplicate
piston heads H and H₁ provided with junk rings h, to make them steam, or air
tight; and in the arrangement of duplicate ports K, k, and L, l, from each end of
the valve chest D, so that when the piston valve E is at one extremity of its stroke,
the ports K, k, admit air, or steam simultaneously to the two faces b b of the
duplicate piston heads H, H'. The opposite faces of these heads a a are at the
same time in communication by the duplicate ports L, l, with the central exhaust
port and exit M, in the same position of the valve E.
Upon reversal of the valve E the opposite effects of air or steam supply to the
faces a a and exhaust from the faces 66 take place as regards the duplicate piston
heads.
This double action of piston is effected by the introduction of a fixed abutment
or diaphragm N, provided with spring packing rings n, and which is conveniently

page_text: and cheaply introduced and fixed into the plain cylinder bore, by a bush P holding
the said abutment against a shoulder in the bore.
The end of the piston body F is bored to receive a rifled bar Q, which works in
a rifled bush or nut q screwed or otherwise fixed into the head of the piston
body F.
On the end of the rifled bar Q is keyed a ratchet wheel R into the teeth of
which spring pressed pawls r engage. By this arrangement the inertia and
momentum of the piston body cause a partial rotation of the rifled-bar, at each
outward stroke, causing a continued intermittent rotation of the piston head and
drill at each double stroke.
The drill is fed forwards by the feed screw C operated by the handle C¹. The
feed screw engages with a nut S carried by a lug cast on the bottom of the
cylinder A.
The essential improvement upon this feeding device is the introduction of a
spiral spring T upon the feed screw, reacting between the nut S and lug, and a
nut V, upon the feed screw; thus taking up any slack or wear in the threads of
the feed screw and nut S.
The advantages gained by these improvements are;-great reduction in weight
compared with other drills of the same power; economy of labour;-greater
adaptability for all kinds of work; -and increase of durability by the compensat-
ing spring on the feed screw removing continuous vibrations, which would other-
wise arise from slack between the feed screw and feed nut.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1st. In a rock drill, the combination with duplicate piston heads of an inter-
mediate fixed diaphragm or abutment through which the piston rod works air-
tight, and duplicate ports from the end ports of a three-ported valve face; and a
piston D-valve; to permit simultaneous action of steam or air on two faces at
each stroke, substantially as described.
2nd. In a rock drill, the combination with a feed screw of a compensating spring
surrounding same, and a lock or re-action nut thereon, to take up slack or wear
between feed screw and nut, to prevent continuous vibration, substantially as
described.
3rd. The combination and arrangement of parts, forming a duplex acting rock
drill, substantially as described and illustrated herewith.
D: 10th day of Au 1807
FELL & JAMES,
1 Queen Victoria Street, E.C.. Agents for the Applicant.