Improvements in Electrically Driven Percussive Tools and in the Means of Operating the same.
Year: 1890

page_text: Date of Application, 21st June, 1890
Complete Specification Left, 23rd Mar, 1891-Accepted, 20th June, 1891
PROVISIONAL SPECIFICATION.
Improvements in Electrically Driven Percussive Tools and in the
Means of Operating the same.
I, LLEWELYN BIRCHALL ATKINSON, of the firm of Messrs. T. W. Goollen & Co.,
of Woodfield Road, Harrow Road, in the County of Londen, Civil Engineer, do
hereby declare the nature of this invention to be as follows:-
My invention relates to improvements in the construction of electrically driven
percussive tools, such as rock drills, rivetters, stamps, or hammers, and in the
means of operating the same.
The improvements consist in constructing such percussive tools in such a manner
that a reciprocating or oscillating movement is obtained directly from the action,
and reaction of magnetic fields, instead of from a revolving electrical motor pro-
ducing the reciprocating action by mechanical means, such as cranks, or cams, as is
at present known.
To carry my invention into effect I use essentially a fixed, and a moving
magnetic part (the latter connected direct to a reciprocating tool, or drill)
corresponding to the armature and electro-magnet of an ele tric motor, but with an
end longitudinal motion one to another, as in a double solenoid, and either the part
corresponding to the armature may move, and the magnet remain stationary, or
(preferably) vice-versa.
The part corresponding to the field magnet, where the magnetism is constant,
may be made of solid iron, but the part corresponding to the armature should
preferably be built of laminated, or divided iron, so as to avoid heating from
reversals or variations of magnetism.
The two parts form a magnetic system magnetized by a continuous current
passing through a coil, or coils embracing the magnet core which may be wound on
the internal magnet core but preferably surrounds it so that the core is free to
move in the coil.
In the spaces between the internal field magnet poles, and the surrounding
armature, are wound coils and the current passing through these coils is reversed,
or started and stopped alternatively, thus producing a reversing magnetic force
tending to produce a reciprocating relative motion between the said fixed armature
coils, and the central magnetic core.
I provide necessary guides, stops, or spiral spring attachment for regulating or
controlling the motion of the moving magnetic core in performing the said
reciprocating movement.
The reversals of the current in the armature, or solenoid coils may be obtained
from a direct current by a commutator, or switch, or contact maker, moved or
shifted automatically by the reciprocating motion of the central core, but the
following method of electrically operating such reciprocating movement is that
which I prefer.
Two separate circuits are provided from a generator, one of which conveys
a continuous current to the magnetic core, and the other an alternating current to
the fixed armature coils, having a period corresponding to the number of oscil-
lations which it is desired to produce in the core and tool attached thereto.
The continuous current circuit is connected to the coil magnetizing the core, and
the alternating current system is connected to the coils forming the armature coils
of the system.
By these means all reversing apparatus in the tool itself is done away with,
making the tool applicable to purposes where such reversing gear would be
troublesome

page_text: The two circuits may be united in a common return.
Any suitable forms of generator may be used with my reciprocating tool or drill
apparatus as above described but I prefer to construct a special generator for the
purpose as follows:-
An ordinary two poled dynamo is provided with the armature having only one
large coil wound on it, the pole angles containing only 90° between them, the coil
thus covers in all, half, or 180° of the surface of the armature.
Such an armature when revolved will produce an alternating current having
as many complete phases per minute as the machine makes revolutions per minute.
In order to utilize the whole surface of the armature a second coil may be
wound at right angles to the first, and connected to a second circuit for similarly
driving reciprocating, or percussive tools.
The continuous current for the magnetising circuit, before described in the
reciprocating tool, and for magnetising the above alternating generator, may be
produced either by a separate continuous current dynamo on the same shaft, or
otherwise, or by rectifying the alternating current produced as above, or by
winding an ordinary continuous winding over or amongst the alternating windings
already described, and connecting it to an ordinary collector in the usual
manner.
Dated this 21st day of June 1890.
FELL & WILDING,
Per R. A. Hoffmann,
1, Queen Victoria Street, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Electrically Driven Percussive Tools and in the
Means of Operating the same.
1, LLEWELYN BIRCHALL ATKINSON of the firm of Messrs. W. T. Goolden & Co.
of Woodfield Road, Harrow Road in the County of London, Civil Engineer, 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 :-
My invention relates to improvements in the construction of electrically driven
percussive tools such as rock drills, rivetters, stamps or hammers; and in the
means of operating the same.
The improvements consist in constructing such percussive tools in such a manner
that a reciprocating or oscillating movement is obtained, directly from the action
& reaction of magnetic fields instead of from a revolving electrical motor producing
the reciprocating action by mechanical means, such as cranks or cams as is at
present known,
Hitherto in inventions designed to produce this result, solenoids have been used
and by varying the currents in the solenoids either as to their position or
magnitude, an iron core or bar is moved to & fro. This method of working has the
defect of necessitating the variation of current in a circuit or circuits of large
self induction, with a result of small output of power for given weight or
dimensions of material and destructive sparking at the commutating apparatus with
consequent low efficiency.
My invention consists in the arrangement of apparatus so that the magnetism is
maintained constant or nearly so by a continuous current, or current in one
direction, whilst the motive power is obtained from the reaction on the constant
magnetic field of a variable or alternating current passing through another coil or
coils. These coils may have a relatively weak magnetising effect in themselves
and hence their self induction is small, and the output of the whole apparatus large
for its weight, and the efficiency high.

page_text: To carry my invention into effect I use essentially a fixed and a moving magnetic
part (the latter connected direct to a reciprocating tool or drill) corresponding to
the armature & field magnet of an electric motor, but with an end longitudinal
motion, one to another and either the part corresponding to the armature may
move, and the magnet remain stationary or (preferably) vice-versi.
The part corresponding to the field magnet, where the magnetism is constant may
be made of solid iron, but the part corresponding to the armature should preferably
be built of laminated or divided iron, so as to avoid heating from reversals or
variations of magnetism.
The two parts form a magnetic system, magnetized by a continuous current
passing through a coil or coils embracing the magnet core and which may be wound
on the internal magnet core but preferably surrounds it so that the core is free to
move in the coil.
In the spaces between the internal field magnet poles and the surrounding
armature are wound coils, and the current passing through these coils is reversed
or started and stopped alternatively, thus producing a reversing magnetic force
tending to produce a reciprocating relative motion between the said fixed armature
coils and the central magnetic core.
I may provide necessary guides, stops, or spiral spring attachment for regulating
or controlling the motion of the moving magnetic core in performing the said
reciprocating movement, as is usual in percussive drills, but 1 prefer to use an
electromagnetic spring or buffer as follows:-
By so constructing the parts that at the end of the stroke the magnetic resistance
of the circuit increases, the motion is arrested and the energy of motion is converted
into electrical energy in the continuous current circuit. This energy is given back
to the moving part on its return stroke, and thus the effect of a spring is obtained
without the difficulties attending its use.
The reversals of the current in the armature or solenoid coils may be obtained
from a direct current by a commutator, switch or contact maker moved or shifted
automatically by the reciprocating motion of the central core; but the following
method of electrically operating such reciprocating movement is that which 1
prefer :-
:-
Two separate circuits are provided from a generator, one of which conveys a
continuous current to the magnetizing coil on the magnetic core, and the other an
alternating current to the fixed armature coils having a period corresponding to the
number of oscillations which it is desired to produce in the core and tool attached
thereto.
The continuous current circuit is connected to the coil magnetizing the core, and
the alternating current system is connected to the coils forming the armature coil
of the system.
By these means all reversing apparatus in the tool itself is done away with,
making the tool applicable to purposes where such reversing gear would be
troublesome.
The two circuits may be united in a common return.
As a practical method of dealing with these three circuits, I prefer to use
a double concentric cable having an outside armouring of iron wire. This latter
forms the return circuit for both currents, and is earthed as also is the framework
of the tool. By this means the men operating the tool cannot possibly receive a
shock even when using high potentials.
Any suitable forms of generator may be used with my reciprocating tool, or drill
apparatus, as above described, but I prefer to construct a special generator for the
purpose as follows:-
--
An ordinary two poled dynamo is provided with an armature having only ong
large coil wound on it the pole angles containing only 90° between them, the coil
thus covers in all half or 180° of the surface of the armature.
Such an armature, when revolved, will produce an alternating current having as
many complete phases per minute as the machine makes revolutions per minute.

page_text: In order to utilise the whole surface of the armature, a second coil may be wound
at right angles to the first, and connected to a second circuit for similarly driving
reciprocating, or percussive tools.
If it is desired to drive the tool by an alternating or varying current derived
from an ordinary continuous current generator, 1 use a commutator driven by or
connected to, or forming part of such generator. This commutator is of a con-
struction used for such purposes having brushes or connectors which are connected
to the two poles of the dynamo, and having brushes or connectors which are
connected to the two ends of the circuit which conveys the alternating or varying
current.
The revolution of the commutator brings metal pieces connected to the two
dynamo poles alternately in contact with the two circuit ends thus reversing the
current. In order to avoid the spark caused by thus breaking the circuit when
a current is flowing, additional brushes may be provided, connected to a circuit of
small self induction & of proper resistance forming an alternating path for the
current.
The continuous current for the magnetizing circuit, before described in the
reciprocating tool, and for magnetizing the alternating generator when such is used
may be produced either by a separate continuous-current dynamo on the same shaft
or otherwise, or by rectifying the alternating current produced as above or by
winding an ordinary continuous winding over or amongst the alternating windings,
already described & connecting it to an ordinary collector in the usual manner.
In order that my invention may be the better understood I now proceed to
describe the same in relation to the drawings hereunto annexed, reference being had
to the letters and figures marked thereon.
Like letters refer to like parts in the various figures.
Fig. 1. shows a single magnetizing coil & double armature coil arrangement.
The central core moves.
Fig. 2. shows a double magnetizing coil and single armature coil arrangement.
The central core moves.
Fig. 3. is equivalent to one half of Fig. 2. The central core moves.
Fig. 4. is the same as 3 but instead of the whole core moving the polar expansion,
of the central core is modified into an annular ring which moves the rest of the
core being stationary.
Fig. 5. shews a further development where the armature coil C is wound on the
inner bar.
These arrangements are typical but other forms embodying the same principle
may be adopted.
Fig. 6. shews the arrangement of circuits used for operating these percussive
tools.
Fig. 7. shews the same arrangement with a common return wire.
Fig. 8 shews an arrangement of single coil generator for the production of the
slow period alternating current necessary.
The dotted lines indicate the second coil on the armature which may be con-
nected to a separate tool or series of tools.
Figures 9 & 10 shew the arrangement of commutator for producing an alternating
current from a continuous current dynamo, D, E. are the brushes from the two poles
of the dynamo & press on the continuous rings K, K',
H, H, are semicircular segments connected respectively to K, K, and on these
press the brushes F, G. connected to the circuit leading to the armature coil.
The Figs. 123 4 & 5 which shew diagramatically some of the forms and
arrangements of magnetic parts & of coils, in accordance with my invention, it
these figures A, A, A', A', represent the magnetic circuit; A, A, being the par
corresponding to the field magnet; A', A', the part corresponding to the armature
of a dynamo or motor; B, B, represent the coil or coils which carry the con
tinuous current magnetizing the whole system.
The path of the magnetic induction is indicated by the arrows. Crepresents the

page_text: coll or coils corresponding to the armature coil of a dynamo or motor, in which the
current varies or alternates.
In order to apply the mechanism described for the purpose of a percussive rock
drill use the following construction. An outer cylindrical casing formed of
wrought iron tube has a wrought or cast iron back plate inserted, and a central core
of wrought iron, bored hollow up its centre to take the drill spindle and divided
parallel to the axis by saw. cuts forming a magnetic system as shewn Fig. 5.
On this core is wound the magnetizing coil, and on the front, end of the core
is wound the armature coil or coils, preferably in notches or grooves turned in the
core to receive the coils. The front end of the tube or barrel is closed by a brass,
aluminium, delta metal or other suitable non-magnetic core, which is corrugated or
webbed to give it strength. The front end of the core forms the front bearing of
the drill spindle. The drill spindle is of steel or delta metal, preferably hollow,
& has a taper screwed part which carries a hollow bell or cone also ribbed or
corrugated, attached to the circular pole piece, or shoe oscillating over the armature
coils. The front end of the drill spindle is provided with a suitable drill holder.
The back end has a nut or guide in which slides a rifled rod to the back end of
which is attached a racket wlicel, held & checked by two pawls or plungers
allowing it to rotate on the forward stroke of the drill, but to hold & rotate the
drill on its backward stroke. The whole drill thus formed slides into a cast iron or
steel shell, which increases the sectional area of the outer tube, and which is
properly formed to fix into slides guides on the support or carriage of the usual
description.
1
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1st. An electrically driven percussive tool in which there is a nearly closed
magnetic circuit having a fixed and movable part in combination with a coil or
coils producing a constant or uni-directional magnetic force in the said magnetic
circuit, and a second coil or set of coils (called the armature coils) carrying a
varying, reversing, or alternating current to produce a relatively reciprocating
motion between the said fixed and movable parts of the said magnetic circuit..
2nd. An electrically driven percussive tool as claimed in Claim 1 in combination
with a source of supply of continuous-or-uni-directional current connected to the
said constantly magnetizing coil or coils, and a current reverser operated by the
reciprocation of the moving parts of the said magnetic circuit connected to the said
armature coil or coils and the source of supply of the continuous or, uni-directional
current substantially as and for the purposes described.
3rd. An electrically driven percussive tool as claimed in Claim 1 in combination
with a source of supply of continuous or uni-directional current connected to the
said constantly magnetizing coil or coils and a source of supply of varying
reversing or alternating current connected to the said armature coil or coils
forming two independent electric circuits.
4th. The arrangement and combination of parts as claimed in Claim 3 in
combination with a common return conductor uniting the two separate sources of
supply.
5th. An electrically driven percussive tool as claimed in Claim 1 operated by two
separate sources of supply of electric current, in combination with a dynamo
forming a source of supply of alternating currents with a period corresponding to
the required period of reciprocation of the tool substantially as described in
reference to and illustrated in Fig. 8.
6th. An electrically driven percussive tool as claimed in Claim 1 operated by two
separate sources of supply of electric current in combination with a commutator
driven by or in connection with a dynamo giving continuous or uni-directional
current, and electrically connected to the said dynamo, and the said armature coil
or coils in order to form a source of supply of reversing or varying current to the

page_text: said armature coil or coils in addition to part uni-directional current connected to
the magnetizing coil substantially as described.
7th. An electrically driven percussive tool as claimed in Claim 1 operated by two
circuits connected respectively to sources of alternating, varying or reversing, and
continuous currents in combination with a common return consisting of a
bi-concentric cable having for its outer conductor or sheathing an iron or other
stranded conductor, earthed, forming the return circuit substantially as and for the
purposes set forth.
8th. The construction and arrangement of parts of an electrically driven per-
cussive tool substantially as described.
Dated this 23rd day of March 1891.
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.