Improvements in Direct Acting Percussion Drills.
Year: 1896

page_text: Date of Application, 28th Dec., 1896
Complete Specification Left, 27th Sept., 1897-Accepted, 30th Oct., 1897
DIEMENS & ITALSKE, 34, Markgrafenstrasse,
Berlin, in the German Empire, Electrical Engineors.]
Improvements in Direct Acting Percussion Drills.
We, SIEMENS BROS. & Co. LIMITED, of 12 Queen Anne's Gate, Westminster, in
the County of London, Electrical Engineers, do hereby declare the nature of this
invention to be as follows:-
In percussion drills, the to and fro motion of the drill or of the rod actuating
the same is effected either through the medium of mechanical gear, or, without
such gear, directly by the motive power, such as steam, compressed air or electro-
magnetic force.
In the second case, the motive force is made to act in both directions for pro-
ducing the reciprocating motion of the drill, but as the drill has to operate with
a percussive action in the forward direction only, a buffer spring or air cushion
is employed which stores up the energy of the backward stroke and gives it out
again during the forward stroke as an addition to the energy imparted by the
driving motive force.
For normally working drills, this arrangement suffices, but if the drill jams in
the bore hole, a considerably increased backward acting force is required for
withdrawing the drill, if the machine is not to be thrown out of work, and such
increase of power is not generally available.
This drawback of existing percussion drills, in particular those worked by elec-
trical energy, is entirely obviated by the present invention, the essential feature
of which consists in providing, in addition to the ordinary rear buffer spring, a
second or front spring which is so arranged as to act against the percussive for-
ward motion of the drill rod but which differs from similar forward springs here-
tofore employed in that it resists the forward motion of the piston in its normal
stroke, whereas the springs heretofore employed only come into action when the
motion of the piston extends beyond the normal. It might at first sight appear
that by this arrangement the forward percussive stroke would be weakened;
this is however not the case, as the front spring after compression on the for-
ward stroke of the drill, will throw the drill backward with the same expenditure
of force as that employed for compressing it, and will consequently compress the
rear spring to a correspondingly greater extent than if there were no front spring,
so that the compressed back spring will throw the drill forward with a corres-
pondingly increased energy, the only difference in the action being that the
stroke of the drill will be somewhat increased.
If on the other hand the drill jams in the bore hole, the front compressed
spring wil afford the necessary power for overcoming the frictional resistance of
the drill, and its energy being thus more or less expended it will not accelerate
the backward stroke of the drill to such an extent as before so that the following
forward stroke will be somewhat weaker.

page_text: Various arrangements may be employed for carrying out this invention; thus
according to one construction the drill rod; part of which is made of soft iron,
passes through two solenoids so as to be moved alternately in opposite directions
by the alternate excitement of the solenoids and carries in a front part of the drill
cylinder, a collar on each side of which is a helical spring bearing with its one end
against the collar and with the other end against an abutment in the cylinder, so
that the two springs act in the before described manner. For adjusting the action
of the springs so as to hold the drill rod, when not working; with its soft iron part
exactly centrally between the two solenoids, the two springs are held in a frame
which is made longitudinally adjustable in the drill casing, so that by adjusting
the frame, the drill rod will be correspondingly adjusted through the medium of
the springs. The frame may also be so constructed that, by a screw adjustment,
it may be made to put any desired amount of initial compression on the springs.
In this case the collar on the drill rod will be gripped between the two springs so
that it cannot readily turn, whereas it is necessary to partially rotate the drill
rod at each stroke in the usual manner; to provide for this, the collar is formed'
on a sleeve which is free to rotate upon the drill rod, but is held between collars
thereon, one of which is secured by screwing.
According to another modification, the above described action of the two springs
may be combined in a single spring, one end of which is fixed to the drill casing
while the other is fixed to the collar of the drill spindle, and which is so propor-
tioned that, say, during the forward stroke it is expanded so as to act by tension
while at the back stroke it acts by compression.
According to another construction applicable more particularly to powerful
drills, we employ in place of helical springs two sets of bow or coach springs,
which would in that case be arranged at the rear end of the drill casing and be
connected to a rear extension of the drill rod; or to a separate yoke, which is
pivotally connected to the rear end of the drill rod.
Dated this 28th day of December 1896.
-
ABEL & IMRAY,
Agents for the Applicants.
Improvements in Direct Acting Percussion Drills.
We SIEMENS BROTHERS & CO. LIMITED, of 12 Queen Anne's Gate, Westminster, in
the County of London, Electrical Engineers, do hereby declare the nature of this
invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:
In percussion drills, the to and fro motion of the drill or of the rod actuating
the same is effected either through the medium of mechanical gear, or, without
such gear, directly by the motive power, such as steam, compressed air or electro-
maguetic force.
In the second case, the motive force is made to act in both directions for pro-
ducing the reciprocating motion of the drill, but as the drill has to operate with
a percussive action in the forward direction only; a buffer spring or air cushion
is employed which stores up the energy of the backward stroke and gives it out
again during the forward stroke as an addition to the energy imparted by the
driving motive force.
For normally working drills, this arrangement suffices, but if the drill jams in
the bore hole, a considerably increased backward acting force is required for

page_text: withdrawing the drill, if the machine is not to be thrown out of work, and such
increase of power is not generally available.
This drawback of existing percussion drills, in particular those worked by elec-
trical energy, is entiroly obviated by the present invention, the essential feature
of which consists in providing, in addition to the ordinary rear buffer spring, a
second or front spring which is so arranged as to act against the percussive for-
ward motion of the drill rod but which differs from similar forward springs here-
tofore employed in that it resists the forward motion of the piston in its normal
stroke, whereas the springs heretofore employed only come into action when the
motion of the piston extends beyond the normal. It might at first sight appear
that by this arrangement the forward percussive stroke would be weakened;
this is however not the case, as the front, spring after compression on the for-
ward stroke of the drill, will throw the drill backward with the same expenditure
of force as that employed for compressing it, and will consequently compress the
rear spring to a correspondingly greater extent than if there were no front spring,
so that the compressed back spring will throw the drill forward with a corre-
sponding increased energy, the only difference in the action being that the
stroke of the drill will be somewhat increased.
If on the other hand the drills jams in the bore hole, the front compressed
spring will afford the necessary power for overcoming the frictional resistance of
the drill, and its energy being thus more or less expended it will not accelerate
the backward stroke of the drill to such an extent as before so tliat the following
forward stroke will be somewhat weaker.
Various arrangements may be employed for carrying out this invention, some of
which are shewn by way of example on the accompanying drawing.
Fig. 1 shews a longitudinal section of an electromagnetic percussion drill with
the above described invention applied thereto.
The drill rod K is of non-magnetic material with a part E of soft iron, working
within two solenoids P¹ P, the currents passing through which impart a recipro
cating motion to the drill rod in the known manner. The rod K has a collar G,
which during the normal stroke bears against and compresses the helical spring Fi
during the forward stroke, and the spring Fa during the back stroke.
The spring F has its front end fixed to the cover of the drill casing, and the
spring F is fixed by its rear end to an annular projection H of the casing.
If the spring F were removed, or were so arranged that it would only come
into action in the case of an excessively long stroke of the drill rod, then, as there
would only be produced a comparatively small backward pull, the drill cutter
would jam after a very slight wear thereof, thus stopping the action of the drill.
With a withdrawing spring arranged according to the present invention, on the
other hand, the drill cutter will work without jamming, even when worn to a
very considerable extent, so that it is only by the use of such a spring that the
drill is rendered practically useful.
The action of the spring will of course be the greater, the more it is compressed
by the collar of the drill rod; consequently the greatest effect will be produced if
the withdrawing spring F, as also the propelling spring F reach up to the collar G
of the drill rod when in the middle position as shewn in the modification at
Figure 2 In this case, as the springs determine the middle position of the drill
rod and its soft iron core E, it is desirable that such position should be capable
of adjustment, so as to make it coincide with the most favourable middle position
of the core E relatively to the solenoids P' P².
For this purpose, the springs are in this case iot fixed directly to the drill
casing, but to a separate supporting frame the position of which can be adjusted
by means of screw devices S S..
The said frame may consist of the two rings R¹ and R connected by rods Z¹, Z³,
as shewn, or it may be otherwise arranged.
".
This construction may also be so arranged that the two springs FF, when
mounted in the frame will each be subject to a certain amount of compression

page_text: when the other spring is fully compressed at the end of the out or instroke;
this may be effected by screwing up the nuts M M of the rods Z' 7³ to a greater
or less extent.
This arrangement enables special devices for fixing the springs to the rings R¹ R³
to be dispensed with; also, the springs can be considerably weaker than if they
have no initial compression, as their spring-power is increased to a corresponding
extent by such compression. Fig. 2 shews one of the springs of Fig. 2 separately,
in the uncompressed condition.
As the drill rod requires to be turned partially round after each stroke, and
this would be prevented with the above arrangement by the collar B thereof being
nipped between the springs, it is necessary to arrange the collar so as to be rota-
table upon the drill rod, for which purpose it is formed on a loose sleeve which
can rotate between a fixed and a screwed abutment on the drill rod, as shown.
The above described arrangement can also be so modified that the withdrawing
spring and the rcpelling spring are both combined in one, such spring being
made to act in compression in the one direction, and in tensiou m the other direc-
tion. Such an arrangement is shewn at Fig. 3; in this case the spring requires
to be fixed at beth onds, namely at the one end to a ring R, male adjustable as
at Fig. 2, and at the other end to a rotatable collar B on the drill rod
In all the above arrangements the kind of spring employed is of course
generally immaterial; in the above described arrangements helical springs are
shewn, Fig. 2 shewing single springs formed in the usual manner with round steel
rod.
While in Figs. 1 and 3, as the springs have to be fixed by means of screws or
other means, a special construction of double springs is employed, of the form
shewn separately at Fig. 3*; such springs can be conveniently formed by cutting
from a steel cylinder.
Under certain circumstances in particular for large drills the helical springs
may advantageously be replaced by blade springs. Such a construction is shewn
respectively in elevation, longitudinal section and plan at Figs. 4, 5 and 6. The
arrangement is here substantially the same as described with reference to l'ig. 2;
the springs FF of that arrangement are replaced by blade springs ff
and v² 2.8
By means of this construction a considerable extent of stroke can be obtained
with a comparatively small amount of flexure of the individual springs.
The rings R of Fig. 2 are in this case replaced by cross bars "T; the
rods 7 and 7 and screw nuts Ms are arranged substantially the same as
before, with the exception that the entire spring device is situated outside, at the
rear end of the drill casing. The spring frame is here shewn non-adjustable but
it may, of course readily be made adjustable; the collar B is rotatable on the drill
rod and is connected to the springs by forked arms and a cross bar.
All other details of the above described percussion drills may be of any known
construction and are therefore not shewn on the drawing.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed we declare that what we
claim is:-
1. In a direct acting percussion drill a spring or springs for withdrawing the
drill from the bore hole, so arranged as to act against the forward motion of the
drill rod during its normal stroke.
2. In a direct acting peroussion drill, a withdrawing spring or springs such as
referred to in the first claim, arranged in combination with a propelling spring or
springs in such manner as to hold the drill rod in a definite middle position sub-
stantially as described.
3. In a direct acting percussion drill with withdrawing and propelling springs
such as referred to in the preceding claims the use of a single spring or set of
springs that acts both as a propelling and as a withdrawing spring, being made

page_text: to operate under compression in the one direction and under tension in the other
direction substantially as described..
4. Arranging combined propelling and withdrawing springs such as are referred
to in the second and third claims, in a frame that is capable of longitudinal
adjustment, for adjusting the middle position of the drill rod, substantially as
described.
01: 1
1007
ABEL & IMRAY,
Agents for the Applicants.