Improvements in Electric Rock Drills.
Year: 1899

page_text: Date of Application, 5th Sept., 1399-Accepted, 18th Nov., 1899
COMPLETE SPECIFICATION.
Improvements in Electric Rock Drills.
I, GEORGE BARKER, Fellow of the Chartered Institute of Patent Agents, of
77, Colmore Row, Birmingham, in the County of Warwick, Consulting Engineer,
do hereby declare the nature of the said invention as communicated to me from
abroad by Samuel Lesem, Insurance Agent, of 1532, Race Street, Denver,
Colorado, and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:—
It is the object of my present invention to produce a simple, durable and
efficient apparatus to be operated by electricity for drilling rock, and my inven-
tion consists in the combination of devices hereinafter described and referred to
in the claims.
In the drawings, Figure 1, is a side elevation of a drilling apparatus con-
structed according to my invention, showing the supporting frame and the casing
and the general arrangement of the parts;
Fig. 2 is a side elevation, partly in section and with the supporting frame
and part of the casing removed to show the internal working parts:
Fig. 3 is a front elevation (looking from the right in Figs. 1 and 2) partly in
section and with the frame and part of the casing removed;
Fig. 4 is a top view, partly in section;
Fig. 5 is an enlarged view of the hammer and its actuating lever and eccentrics
detached from the rest of the apparatus, and Figs. 6 to 15 are detail views of
different parts of the apparatus, as will be more fully explained below.
The same letters of reference designate the same parts in all the drawings.
The apparatus consists of three general parts, a drilling mechanism of the type
in which a drill supported in a suitable holder is struck a rapid series of blows
by a hammer, an electric motor, and mechanism interposed between the two by
means of which the rotation of the armature of the motor actuates the hammer
and at the same time retracts and turns the drill after each blow.
The general arrangement of the parts is best shown in Figs. 1, 2 and 3, in
which I have for convenience shown the apparatus in position for drilling a hole
vertically downward. It will of course be understood, however, that it may be
adjusted so as to work in any direction. 1, is a drill of the usual construction,
supported by a drill holder, 2. The drill holder is enclosed and held in position
by a casing 3, which is firmly secured as a bracket to the main casing of the
machine. The drill is loosely supported in the holder and held in position by
keys, 4. 4. The key-ways in the drill are made somewhat wider than the keys
so as to permit a certain amount of longitudinal movement of the drill in the
holder.
6 is the
5 is a hammer arranged to strike the head of the drill.
armature, and 7, 7 are the field magnets of an electric motor, which may be of
any of the ordinary types. The armature shaft, 8, of the motor is connected
by gear wheels, 9, 10 and 11, to the shaft 12, which actuates the hammer, 5, and
the mechanism for retracting and turning the drill, 1.
The working parts of the apparatus are enclosed in a casing, 13, which serves
as the main frame of the machine. This casing is in turn supported by a frame
or bed piece. 14, upon which it has a longitudinal movement controlled by the
screw, 15.
As is shown in Fig. 4, the two parts are held together by longitudinal
splines or rails, 16, on the casing, 18, working in channels or grooves in the
frame 14. The screw 15 is attached to the frame 14 and works in a nut 17 attached
Price R71

page_text: to the casing 13, so that by turning the screw by means of the crank 18 the
casing 13, and with it the drill 1, may be advanced or retracted by the operator
at will. The frame 14 is provided with a lug or trunnion, 19, and with adjustable
legs, 20, so that it may be clamped to a column or fixed directly to the walls of
a shaft or tunnel in any desired position in the usual way.
As has been stated the shaft 12 actuates the mechanism by which the hammer 5
is operated. This mechanism is best shown in Fig. 5 and it is also shown in
Fig. 2 and to greater or less extent in other drawings. It consists essentially
of two pairs of eccentrics mounted on the shaft and of actuating levers operated
by the joint action of these eccentrics and imparting a reciprocating movement to
a pivoted arm or handle on which the hammer is mounted. One set of these
eccentrics and levers is shown in Fig. 5. As will be seen, there are two eccen-
trics, 21 and 22, preferably but not necessarily of unequal size mounted on the
shaft 12 at right angles to each other. The details of construction of these parts
are shown more fully in Figs. 6, 7, 8 and 9. As is shown in these figures, ball
bearings are interposed between the eccentrics and their straps to diminish the
friction. The hammer 5 is mounted upon a curved arm or handle, 23, which is
pivoted at 24 to the strap of the eccentric 22. The arm is preferably curved so
as to clear the shaft 12, but it may be made straight and is preferably made of
a steel rod or bar doubled back upon itself and shaped as shown for engagement
with the rollers carried by the actuating levers 25. One of these levers detached
from the rest of the apparatus is shown in Figs. 10 and 11, and in Fig. 5 it is
shown in connection with the eccentrics 21 and 22 and the hammer arm 23.
will be seen, the lever is triangular in shape, and is provided with journals or
pins, 26 and 27, for pivoting it to the straps of the eccentrics 21 and 22 and
with bearing 28 and 29, for the rollers, 30 and 31, engaging with the hammer
arm 23. As is shown in Figure 5, the lever is pivoted at 27 to the strap of the
eccentric 22 and at 26 to the strap of the eccentric 21. The strap of the eccen-
tric 22 is restrained from rotary movement by the link, 32, (see Fig. 2) which is
pivoted at 33 to the casing and at 34 to the tail piece or extension, 35, of the
eccentric strap, so that the strap has merely an oscillating movement about the
centre 33.
As
I have for convenience described the hammer actuating mechanism as con-
sisting of one set of eccentrics, 21 and 22, and one actuating lever, 25, operated
by them, and it may be constructed in this way. I prefer, however, to use two
sets of eccentrics and two actuating levers, and this is the construction illustrated
in the drawings, as will more clearly appear from Figs. 3 and 4. The corre
sponding eccentrics, 21 and 22, of each set are placed parallel to each other on
the shaft 12, and each set is connected in the same manner with an actuating
lever 25. The rollers 30 and 31 are journaled at one end in one of the levers
and at the other end in the other. I find that great advantages are secured by
this arrangement as the levers and rollers are kept in sufficiently accurate align-
ment without any very accurate mechanical fit of the various bearings, and the
wear of the parts and the liability to breakage are greatly reduced. In fact I
find that with this construction the machine works more effectively with a certain
amount of lost motion in the bearings of the levers and rollers, than with the
parts accurately fitted. Simple bars may be used in place of the rollers 30 and
31, but I prefer to use the rollers to diminish the friction.
In order to relieve the gearing and the motor from the shocks due to the
sudden starting and stopping of the hammer at the end of the stroke, which at
high speeds are very severe. I interpose between the gear wheel 11 and the
shaft 12 a friction clutch, which is so adjusted as to work without slip during
the greater part of the stroke of the hammer, but to slip or vield somewhat at
the times when the hammer is at or near the end of its stroke and the shocks
due to its stopping and starting produce a sudden or violent variation in torque
that would put undue strain upon the gearing or the motor. The construction
of this device is shown in Figs. 14 and 15. The rim of the gear wheel 11 is not

page_text: connected directly to the hub 36 which is keyed to the shaft 12, but is made in a
separate piece and surrounds, and is carried by, the two semi circular pieces 37
and 38. These pieces are connected to the hub 36 through the bar 39 by sliding
pins 41 which are pressed outward by springs, of which one is shown at 42. The
springs 42 are so adjusted as to produce the required amount of friction between
the semi-circular pieces 37 and 38 and the interior surface of the rim carrying
the gears for transmitting the torque necessary for actuating the hammer properly,
but to allow the rim to slip upon such sudden or violent variation in the torque
as is caused by the stopping and starting of the hammer. I have found that,
although it is impracticable to operate the apparatus with a rigid connection of
the gearing between the motor and the shaft 12 on account of the frequent break-
ing of the gears, even when made very heavy, a very small amount of slip during
each revolution, at the times when the hammer is stopping and starting, is
sufficient entirely to obviate the difficulty. The springs 42 should, therefore,
be so adjusted as to prevent any considerable amount of slip between the parts.
The outer surfaces of the pieces 37 and 38 may be made of any suitable material
with reference to uniformity of friction and durability, and the grooves or
recesses, 43 in the rim may be filled with lead or similar material to secure
greater uniformity in the friction between the parts.
I have described the friction clutch as applied between the gear wheel 11 and
the shaft 12, but it is obvious that it may be applied at any other part of the gear-
ing between the armature shaft and the shaft 12, and it is also obvious that the
details of construction of the clutch are not material so long as the object set
forth is accomplished.
In order to prevent the drill from jamming in the hole and to bring its cutting
edges into a new position for each stroke, the oscillating movement of the tail
pieces 35 of the straps of the eccentrics 22 is utilized to retract and turn the
drill after each blow of the hammer, as follows: A retractor rod, 44, is pivoted
to the tail pieces at 34 and carries at its lower end a yoke or fork, 45, entering
a circumferential recess, 46, in the drill holder 2. A spring, 47 is interposed
between the retractor rod and the yoke to relieve the working parts from tension
when the drill is fed forward by the screw 15. The drill holder is mounted in
the casing 3 so as to have free movement both of rotation and longitudinally,
except as restrained by the yoke 45 and the other parts now described. 48 is
a ratchet through which the drill holder moves freely longitudinally but not
rotatively, and 49 is a pawl (see Fig. 13) permitting the ratchet to move only
from right to left. The lower end of the drill holder has a set of spiral grooves 50,
cut in its surface, and 51 is a nut carried by lugs, 52, on the interior of the
casing 3 and having on its interior surface spiral splines or lugs fitted into the
grooves 50. The nut 51 has a ratchet on its outer surface and a pawl, 53, pre-
vents it from turning except from left to right as shown in Fig. 12.
When the drill holder is lifted by the upward movement of the retractor
rod 44 the pawl 49 prevents it from turning backward, and the nut 51 is con-
sequently turned forward, or from left to right, by the action of the grooves 50
on the splines on its inner surface; and when it is lowered by the downward
movement of the retractor, the nut being restrained from moving backward by
the pawl 53, the drill holder is rotated from right to left an amount corresponding
to the previous rotation of the nut.
The operation of the apparatus will be understood from the foregoing description
of its construction. When the current is supplied to the electric motor, its
armature is rotated at substantially uniform speed in the same direction, and
the chaft 12 is driven by it through the gearing connecting them. The eccen-
tries 21 and 22, being set at an angle with each other on the shaft and being of
unequal throw impart an oscillating movement to the levers 25 which are pivoted
to their straps. This movement is produced by the conjoint action of the two
pairs of eccentrics, and is at certain parts of their revolution due to their com
bined action in the same direction and at other parts of the revolution to their

page_text: differential action. The parts are so arranged as to give the levers a gradually
accelerated motion on the forward stroke, especially toward the end of it, which
gives the hammer a very efficient stroke such as is required for enabling it to
strike a sharp and effective blow on the head of the drill. This is aided by the
curve 54, in the upper member of the hammer arm 23 against which the actuating
roller 30 bears. This curve also facilitates the clearance of the roller from the
hammer arm after the blow is struck so as to prevent the arm from striking the
roller violently on the rebound. As will be seen, the two rollers, 30 and 31, are
adjusted so as to provide for a certain amount of lost motion between them and
the hammer arm so as to leave the hammer free to swing by its own momentum
for a short distance at each end of the stroke, and especially at the forward end.
This greatly relieves the levers and eccentrics from the shocks that would other-
wise be imparted to them by the inertia of the hammer.
In Fig. 2, I have shown by dotted lines at the left the position of the parts
at the end of the back stroke, and by full lines at the right their position at the
completion of the forward stroke. Since the hammer arm 23 does not swing
about a fixed centre but about a pivot on the strap of the eccentric 22, the hammer
does not follow the same path on its forward and return stroke and the dotted
line 55, indicates its path on the forward stroke and the dotted line, 56, its path
on the return stroke."
It is obvious that the hammer-actuating apparatus may be applied with advan-
tage to reciprocating the drill and its holder instead of a hammer striking the
head of the drill, but I prefer the type of drilling mechanism shown as more
efficient and more readily managed.
When the apparatus is in use, the frame or bed piece 14 is firmly clamped to
a column by the trunnion 19, or fixed directly to the walls of the working by
means of the adjustable legs 20, with the drill turned in the direction in which
it is desired to drill the hole, and the drill is advanced by means of the screw 15
until its point is in contact with the rock. Current is then admitted to the
motor, and the hammer 5 is reciprocated rapidly and strikes a sharp blow on the
head of the drill at each stroke, and, as the hammer is drawn back for each stroke,
the drill is retracted and rotated part of a revolution so as to bring its cutting
edge into a new position in the hole. As the rock is cut away, the drill is
advanced by the operator by means of the feed screw 15, and the spring 47 keeps
its point firmly in contact with the rock at the time when the hammer strikes the
head of the drill. It is obvious that a switch for stopping and starting the motor
and a rheostat or any of the common devices for controlling the speed of electric.
motors may be placed in a position convenient to the hand of the operator so
that he may stop and start the drill and control its speed at will.
This apparatus is cheap to construct, since accuracy of mechanical fit is not
necessary for most of the working parts, and they may be made of simple castings.
It is easily managed and not liable to get out of order, and may be readily
repaired by any ordinary workman when it does get out of order by the use of
duplicate parts. It is also highly efficient in operation. I have found that it
will do a given amount of work in cutting rock with a much smaller amount of
power than the ordinary compressed air drill.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:
1: In a rock-drilling apparatus, the combination of drilling mechanism having
a reciprocating movement of its rock-cutting parts, an electric motor having a
rotary movement of its armature in one direction, and gearing connecting the
armature shaft of the motor with the drilling mechanism and provided with a
friction clutch adjusted so as to transmit the power of the motor to the drilling
mechanism but to slip or yield at or about the times when the movement of the
reciprocating parts is reversed, substantially as described.

page_text: 2: In a rock-drilling apparatus the combination of a drill supported in a
holder and having longitudinal movement therein, a reciprocating hammer
arranged to strike the head of the drill, mechanism for reciprocating the hammer,
an electric motor, and connecting gearing between the motor and the hammer-
operating mechanism provided with a friction clutch adjusted so as to transmit
the power of the motor to the hammer-operating mechanism but to slip or yield
at or about the times when the movement of the reciprocating hammer is reversed,
substantially as described.
3: In a rock-drilling apparatus, the combination of a drill supported by a
holder in which it is capable of longitudinal movement, a reciprocating hammer
arranged to strike the head of the drill, mechanism for reciprocating the hammer
consisting essentially of two eccentrics set at right angles to each other on the
same shaft and having their straps pivoted to an actuating lever which imparts
a reciprocating movement to a pivoted arm carrying the hammer, an electric
motor, and gearing connecting the armature shaft of the motor with the shaft
carrying the eccentrics, substantially as described.
4: In a rock-drilling apparatus, the combination of a drill supported in a
holder in which it is capable of longitudinal movement, a reciprocating hammer
arranged to strike the head of the drill, mechanism for reciprocating the hammer con-
sisting essentially of two pairs of eccentrics set at right angles to each other on the
same shaft with two actuating levers, each pivoted to the straps of two eccentrics
(one of each pair) and carrying rollers or bars between their outer ends which
actuate a pivoted arm carrying the hammer, an electric motor and gearing con-
necting the armature shaft of the motor with the eccentric shaft, substantially
as described.
5: In a rock-drilling apparatus, a drill supported in a holder so as to be
capable of longitudinal movement therein, a reciprocating hammer for striking
the head of the drill, a shaft driven by power, two eccentrics mounted on the
shaft at an angle to each other an arm pivoted at one end to the strap of one
of the eccentrics and carrying the hammer at its other end, and a lever actuating
the hammer arm and pivoted to the straps of both eccentrics so as to receive an
oscillating movement from their conjoint action, substantially as described.
6: In a rock-drilling apparatus of the type described, in which the drill is
operated by blows of a hammer, the combination of a shaft, two pairs of eccentrics
mounted on the shaft with those of each pair parallel to each other but at an
angle to the other pair, two actuating levers each of which is pivoted to the
straps of two eccentrics (one of each pair), a pivoted arm carrying the hammer,
and rollers engaging with the hammer arm and carried by the outer ends of the
two actuating levers, substantially as described.
7: In a rock-drilling apparatus of the type described in which the drill is
operated by blows of a hammer, the combination of a shaft, two pairs of eccentrics
mounted on the shaft with those of each pair parallel to each other but at an
angle to the other pair, two actuating levers each of which is pivoted to the
straps of two eccentrics (one of each pair), an arm carrying the hammer and
pivoted to the straps of one pair of eccentrics, and rollers or bars engaging with
the hammer arm and carried by the outer ends of the two actuating levers, sub-
stantially as described.
S: The combination of the eccentrics 21 and 22 mounted at an angle to each
other on the shaft 12, the actuating lever 25 pivoted to the straps of the eccen-
tries, the hammer arm 23, having the curve 54 and the rollers 30 and 31 carried by
the lever 25 and engaging with the hammer arm, substantially as described.
41 .
Labo 1900