Improvements in Hand Rock Drills.
Year: 1890

page_text: Date of Application, 1st July, 1890-Accepted, 2nd Aug., 1890
COMPLETE SPECIFICATION.
Improvements in Hand Rock Drills.
I, HERBERT JOHN ALLISON, of 52 Chancery Lane, London, in the County of
Middlesex, Patent Agent, do hereby declare the nature of this invention, which has
been communicated to me from abroad by Edward Thomas Bromfield, of Glenbrook,
Township of Stamford, Fairfield County, Connecticut, U.S.A., Gentleman, and in what
manner the same is to be performed to be particularly described and ascertained in
and by the following statement :-
My invention has for its general object to simplify and improve the construction
of this class of rock drills, the special object being to do away with friction on
the drill bar, to avoid friction in the feed movement, and to so apply spring power to
the drill bar that the pressure shall be increased rather than diminished as the bar
descends. In other words, instead of starting the drill bar and drill downward under
heavy-pressure and then having the pressure relieved as the drill strikes the rock, I
provide that the downward movement of the drill bar and drill shall begin under a
moderate pressure which shall constantly increase as the bar and drill move downward, so
that the pressure is greatest at the instant that the blow is struck. I am thus enabled to
strike as heavy a blow as the drill will stand, to greatly improve the operation of the
drill and increase its results, and, furthermore, to avoid the necessity of weighting the
legs or framework to cause the drill to stand firmly on the rock.
With these ends in view, I have devised the simple and novel construction of which
the following description, in connection with the accompanying drawings, is a
specification, numbers being used to denote the several parts.
Figure 1 is a front elevation of the drill complete ;
Fig. 2, a section on the line a x in Fig. 1;
Fig. 2a, a detail view showing in full lines the position of the drill bar, spring, etc.
at the instant the downward movement commences, and in dotted lines the position
of said parts at the instant the blow is struck, the dotted position corresponding with
that shown in Fig. 2;
Fig. 3, a rear elevation ;
Fig. 4, a detail sectional view on the line y y in Fig. 1 ;
Fig. 5, a detail sectional view on the line z in Fig. 1, said views illustrating
the drill turning and the feeding mechanism; and
Fig. 6 is a detail view of the operating lever detached.
1 denotes framework which may be of any suitable or preferred construction, and
which is supported by legs 2 pivoted thereto. 3 denotes a carrier which slides upon
the framework and carries all of the operative parts of the machine. 4 denotes the drill
bar which is provided with a longitudinal groove 5, and with collars 6, the functions
of which will presently be explained. 7 denotes the drill which is attached to the
8 denotes arms which project
drill bar in the usual or any preferred manner.
forward from the carriage; 9, a shaft journaled in said arms; and 10, balance
wheels at the ends of said shaft, one or both of which are provided with crank
handles 11, by which power is applied to the machine. The drill bar is suitably
journaled in boxes 12 upon the carriage, and is actuated by means of an operating
lever 13, the inner end of which is provided with inwardly turned arms 14 which
engage between collars 6 on the drill bar, and by which the latter is raised and
5 lowered as will be more fully explained. At the outer end of lever 13 is a cross
piece 15 which is journaled between the outer ends of arms 8. by means of pointed
screws 16 which pass through said arms and engage the ends of the cross piece as is
clearly shown in Fig. 1. The shaft is provided with a belt pulley 17 and with a rigid
cross arm 18 preferably provided at its ends with rollers 19, said rollers being in
line with each other on opposite sides of the shaft, and equi-distant from the center

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of the shaft. 20 is an arm which projects outward from cross piece 15 being preferably
adjustably secured thereto by means of a set screw or in any suitable manner.
21 denotes a strong spring, the end of which is attached to the end of arm 20, the
inner end of said spring being attached to the short arm 22ª of the bell crank lever 22.
This lever is pivoted to any convenient portion of the carriage, and its long arm 22°
extends outward and is provided with a pin 23 which is adapted to engage any one
of a series of teeth 24 in a rack 25 which is journaled in any suitable manner so as
to turn freely. In the present instance, see Fig. 1, I have shown one of the pointed
screws 16 as passing through the base of the rack before engaging the end of the
cross piece. This construction gives a thoroughly practical adjustment to the spring.
The operation of this portion of my invention is as follows: As seen in Figs. 2
and 2, the shaft, balance wheel, cross arm, etc. are rotated from left to right. Each
end of the cross arm as it moves upward engages the under side of lever 13, and
raises said lever, and with it the drill bar, against the power of spring 21, the posi-
tion of said parts while the drill bar is at the raised position being clearly shown in
Fig. 2. It will be seen that as lever 13 is raised, arm. 20 will be moved outward,
so that while the tension of the spring will be greatly increased, the line of tension
will be moved downward so as to be at half the distance, more or less, from the
pivotal point of said arm to the line of tension at the instant the blow is struck, all of
which is clearly illustrated in Fig. 2. While the spring has decreased slightly in
length at the end of the stroke, it has about doubled its leverage upon the shaft 16
by reason of the changed position of arm 20 which now lies at substantially right
angles to the spring, so that the decreased tension of the spring is more than
compensated for. It will be seen, therefore, that while the tension of the spring bas
a perceptible effect upon the drill bar at the instant the downward movement
commences, the power exerted thereby will continue to increase until the instant the
blow is struck. This is a reversal of the principles of every rock drill, so far as I
am aware, that has heretofore been placed upon the market. It will be seen in
Fig. 2, that as the end of the cross arm moves upward, lever 13 will be raised until
the end of said cross arm, in the present instance a roller, shall have passed the
abrupt shoulder 26 on the under side of said lever, the lever being curved upward
beyond said shoulder, so as to leave the lever, drill bar, drill, etc. free to descend
without obstruction until the blow of the drill is delivered. Almost instantly after-
ward, lever 13 is raised again by the other end of the cross arm, two blows of the
drill being caused to be delivered by each revolution of the shaft. Should it be
desired to lessen the force of the blow of the drill, pin 23 upon the long arm of the
bell crank lever is engaged with a higher tooth in rack 25. Should it be desired to
increase the force of the blow, the long arm of said lever is pressed downward and
pin 23 is engaged with a tooth further down the rack. It will be seen that this
movement will swing the short arm of the bell crank lever toward the left, as seen
in Fig. 2, thereby increasing the tension of the spring. It is found in practice that
the drill will operate and do good work without any spring to assist in the down-
ward movement of the drill bar. As it is desirable to increase the force of the blows
in order to make the drill cut faster, I ordinarily use a spring. It will of course be
understood that various styles and arrangements of springs may be used to accomplish
this purpose. I preferably, however, so adjust the spring as to force the drill bar
downward with accelerated velocity, and have illustrated a style of spring that I have
found to accomplish the purpose admirably.
The drill bar is given a partial rotation, ordinarily one-eighth turn during each
upward movement in the manner which I will now describe: 27 is a shaft journaled
in ears 28 projecting forward from the carriage. This shaft is provided with a'
worm 29 and a belt pulley 30. 31 is a crossed belt extending over belt pulleys 17
and 30 by which reverse motion is communicated to shaft 27 from shaft 9. 32 is a
gear having inclined teeth for engagement with the worm. The drill bar passes
through this gear which is provided with a spline 33 engaging the longitudinal
groove 5 in the drill bar. This gear is supported in position upon the carriage in

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any suitable manner.
In the present instance I have shown it as supported by a
block 34, said block being provided with a recess to receive the gear, and being
firmly secured to the carriage by screws or bolts 35. It will be seen that the drill
bar is thus left free to move vertically independently of the gear, and that the rotary
movement of the gear is imparted to the drill bar by the spline. The drill bar may
be given greater or less rotation at each upward movement.by increasing or decreasing
the size of the belt pulleys relatively to each other.
The feed may be by hand, although I preferably use an automatic feed which I will
now describe: 36 is a ratchet having a central opening screw threaded to receive the
feed screw 37. This ratchet is held in position by a plate 38 which is secured to or
made integral with the carriage. The feed screw engages the ratchet and fits in a
bearing or bearings in the carriage 3 but without engaging the latter with its screw
thread. At the upper end of the feed screw is a crank handle 39 for convenience in
operation. When the automatic feed is in use, the feed screw is locked in position
by means of a pin 40 engaging the top of the framework against which the crank
handle rests. 41 denotes the feed lever which is pivoted to a stump 42 projecting
, backward from the framework. At the upper end of this lever is a pawl 43, the
inner end of which engages the feed ratchet, being held in contact therewith by a
spring 44, see dotted lines in Fig. 4. The lower end of this lever is branched as
:shown in Fig. 2, one branch denoted by 41" extending inward in position to be
engaged and pressed, downward by one of the arms.14 of lever 13 at each downward
movement of said lever. The other branch of the feed lever denoted by 41 extends
downward and is provided with a set screw 45, the inner end of which engages the
framework each time the lever is, oscillated and acts to limit and adjust the oscillation
thereof. 46 is a spring, the end of which is secured to any suitable portion of the
carriage, the free end thereof bearing against the feed lever and acting to throw its
upper end outward,, which moves pawl 43 to its retracted position, and to throw
branch 41 inward in position to be engaged by one of the arms 14 of lever 13, when
the downward movement of said lever takes place. This movement of the lever acts
to throw the lower end of the feed lever outward, consequently throwing the upper
end inward against the power of spring 46, moving pawl 43 forward and carrying
ratchet, 36 forward one or more teeth according to the rapidity with which the drill
penetrates, the rock, it being understood of course that penetration depends upon th
hardness of the rock, the action of the feed being purely automatic. It will be readily
understood that as the feed screw is rigidly held in position and that the ratchet is
threaded to engage said screw, forward movement of the ratchet as seen in Fig. 3
must necessarily move the carriage downward.
191
When it is desired to feed the drill by hand, the feed lever is removed from the
machine and the carriage_fed downward by turning crank handle 39. The carriage,
drill bar and drill are, in practice, raised by turning said handle backward, no matter
whether the feed is performed automatically or by hand. The pressure of pawl 43
upon the feed ratchet is sufficient to hold the latter in position when the carriage is
raised or lowered by turning the feed screw.
It will of course be understood that my invention is not limited to the exact details
of construction which I have shown, as they may obviously be varied within reason-
able limits without departing from the principles of my invention.
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 drill, the combination with the drill holder, means for retracting the
same, and an actuating spring connected with the holder for driving the same, of a
compensating lever mechanism whereby a decreased tension of the spring is partly or
wholly compensated for by a more effective application of the power of the spring,
substantially as set forth.
2. The combination with the sliding carriage, the drill bar, the shaft having a cross
arm 18, and lever 13 engaging the drill bar and engaged by the cross arm, of an

page_text: arm 20 rigidly connected to lever 13, a bell crank lever, a spring, the ends of which
are connected respectively to one arm of the bell crank lever and to arm 20, and
means, as a rack, engaging the other arm of the bell crank lever, whereby the spring
may be adjusted to increase or diminish the power exerted upon the drill bar.
3. The combination with the sliding carriage having arms extending therefrom, the
drill bar, the shaft journaled in said arms and having a cross arm, and a lever 13
having a cross piece journaled at the outer ends of said arms, of an arm 20 rigidly
secured to said cross piece, a rack 25, a bell crank lever having a pin on one arm
adapted to engage said rack, and a spring, the ends of which are connected respec-
tively to the other arm of the bell crank lever, and to arm 20, whereby the power of
said spring upon the drill bar is increased as the drill bar descends.
4. The sliding carriage, the drill bar, shaft 9 having cross arm 18, and lever 13
connected to the drill bar, said drill bar, lever and shaft being journaled in the
carriage, in combination with an arm rigidly secured to the outer end of lever 13,
and a spring, one end of which is connected to said arm whereby, when the drill bar
is raised, said arm is swung outward, which increases the tension of the spring, but
carries the line of tension downward toward the pivotal point of said lever so that
the power exerted upon the drill bar is increased as the arm swings inward and the
drill bar moves downward.
5. The combination with the framework, the carriage having ratchet 36, the feed
screw threaded to engage the ratchet, and a feed lever carrying a pawl, of a drill
bar having a longitudinal groove, gear 32 supported in the carriage and having a
spline engaging said groove, lever 13 which actuates the drill bar and the feed lever,
shaft 9 having a cross arm which actuates lever 13, a shaft 27 having a worm
engaging gear 32, and a belt connecting said shafts.
6. In a rock drill, a sliding carriage carrying a drill bar and a ratchet 36, in
combination with a feed screw threaded to engage the ratchet, a feed lever having
a pawl engaging said ratchet, and a pin 40, whereby the feed screw is held against
rotation so that movement of the ratchet will feed the carriage downward.
7. In a rock drill, the combination with the drill holder, and a lever and rock
shaft connected therewith whereby said holder is actuated, of a spring connected with
said lever operating to force the holder forward, and carried by the forward move-
ment of the lever away from the center of said rock shaft, whereby the operative
leverage of the spring is increased during the stroke of the drill, substantially as set
forth.
Din 1 1
T.1 1000
ALLISON BROS.,
Agents for the Applicant.