improvements in Electro magnets, and in the Application of the same to the Control of Electric Currents.
Year: 1885

page_text: improvements in Electro magnets, and in the Application of the
same to the Control of Electric Currents.
I HENRY WILLOCK RAVENSHAW of Bull Green Works, Halifax in the County
of York Electrical Engineer do hereby declare the nature of my invention for
"IMPROVEMENTS IN ELECTRO MAGNETS AND IN THE APPLICATION OF THE SAME TO
THE CONTROL OF ELECTRIC CURRENTS," to be as follows:→
The present invention relates to improvements in electro magnets whereby a
better control over the armature than heretofore is effected, and to the application
of such electro magnets for controlling electric currents.
According to my invention I employ a pair of separate electro magnets and a
pair of keepers or armatures of which one is in delicate adjustment and the other
does the work, and I so arrange them with respect to the electro magnets that
when the current passing around the coils exceeds the desired strength, the keeper
in delicate adjustment or as it may be called the "floating" keeper is attracted and,
by reducing their magnetic resistance, converts the separate electro magnets into a
single horse shoe magnet of greater power than that exerted by the pair of separate
magnets.
The result of this is that a strong and decided pull can be obtained through the
armature of the electro magnet with a current which, alone, passing round the two
separate magnets and without the increase of magnetism due to the attraction of
the floating keeper, would have been impossible, and electro magnets of this new
and improved construction may be applied to a variety of useful purposes where a
strong and decided pull is required to be exerted at a given moment such for
instance as the automatic regulation of the brushes of arc light dynamos and the
regulation of the feed mechanism of electric lamps. The same combination of
magnets and keepers can also be used for effecting slow beating vibrating move-
ments in electric bells and telegraph instruments where a strong positive pull is
required with a comparatively feeble current.
It may also be used as a cut out for batteries, or in other cases where a delicately
adjusted keeper restrained by a spring has to be attracted up to a certain point,
and yet where strong and decided work is required, the one keeper being in
delicate adjustment, and the other doing the work.
Where a repetition of the movement effected by the armature of my improved
electro magnet, is required, a short circuiting arrangement may be added-but if

page_text: the armature is arranged to break the circuit as in the electric bell, this will not be
necessary.
When my improved electro magnet is applied as a regulator of the current from
a dynamo machine, I arrange its armature to operate a pawl so as to partially
rotate a ratchet wheel fast on the axis of a worm which shifts the brush holder, so
that in the event of the current from the dynamo becoming too strong, the floating
keeper will be attracted and convert the separate magnets into one, reducing the
magnetic resistance and increasing their total effective power, or pull, upon the
armature. When this is done and the armature is attracted the ratchet wheel will
be rotated and the brushes slightly shifted so that the current is diminished.
The armature is arranged to short circuit the coils so that both keepers fall
back; the operation being repeated if the current is still too strong.
A similar arrangement of electro magnet is adopted for shifting the brushes
when the current is too weak, the spring of the floating keeper in this case being
attached to the core of a solenoid whose position will vary, and with it the tension
of the spring, according to the current strength. When the core is released
sufficiently to allow the keeper to be attracted, the magnets will be so re-inforced
in strength that they will attract the armature and cause the rotation of the
ratchet wheel in the opposite direction.
When this new form of electro magnet is used as a cut out, its action is precisely
the same as in the preceding case, but in this application it secures an important
advantage over ordinary cut out devices, inasmuch as if the increase of current
has been accidental and momentary, it may be turned on again by simply touching
Should there
the appropriate contact button, without having to go to the cut out.
however, be a permanent increase of current, the fact can be ascertained at once,
since it cannot be restored by pressing in the contact button.
When used as a cut out my improved electro magnet, or combination of electro
magnets and pair of keepers, hereinabove described, is especially suited for use
with the magnetic switch for which a Patent was obtained by Mr Edmunds dated
29th March 1884 N° 5670.

page_text: same to the Control of Electric Currents:
I HENRY WILLOCK RAVENSHAW of Bull Green Works, Halifax in the County
of York, Electrical 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:—
The present invention relates to improvements in electro magnets, whereby a
better control over the armature than heretoforo is effected, and to the application
of such electro-magnets for controlling electric currents.
According to my invention I employ a pair of separate electro-magnets and a
pair of keepers or armatures, of which one is in delicate adjustment and the other
does the work; and I so arrange them with respect to the electro magnets, that
when the current passing around the coil exceeds the desired strength, the keeper
in delicate adjustment, or as it may be called the "floating keeper," is attracted,
and by reducing their magnetic resistance, converts the separate electro magnets
into a single horse shoe magnet of greater power than that exerted by the pair
of separate magnets.
In the accompanying drawing, Fig. 1 shows in diagram my new arrangement of
electro-magnets and armatures, both armatures being out of contact.
A B are the electro-magnets wound in reverse directions by the same wire,
which may be in the main line, or a shunt from the main line, according to the
requirements of the case. C is the "floating armature," which is held out of
contact with the magnets A B, of opposite polarity, by means of a light coiled
spring D, and E is what may be termed the working armature.
When a current is passed through the coils of the electro magnets, or when a •
current above the normal strength is passed through the coils, the floating
armature C will, according to its adjustment, be attracted by the magnets as
shown in the diagram Fig. 2, and convert the magnets A. B. into a single horse
shoe magnet.
The result of this conversion is, that a strong and decided pull can be obtained
through the armature E of the electro-magnet, with a current which, alone, passing
round the two separate magnets, and without the increase of magnetism due to
the attraction of the floating armature C, would have been impossible. Electro
magnets of this new and improved construction, it is obvious, may be applied to a
variety of useful purposes, where a strong and decided pull is required to be
exerted at a given moment, such, for instance, as tho automatic regulation of the
brushes of arc-light dynamos, and the regulation of the feed mechanism of electric
lamps. The same combination of magnets and keepers can also be used for
effecting slow beating vibrating movements in electric bells and telegraph instru-
ments, where a strong positive pull is required with a comparatively feeble
current.
Fig. 3 shows in diagram the mode of applying my invention to the shifting, in
either direction, of the brushes of of a dynamo-electrical machine, when the electric
current yaries from its normal state in either direction. In this figure, two pairs

page_text: of electro magnets A. B. and A¹, B¹, are represented, their use being to turn the
axle F intermittently in opposite directions as the normal state of the electric
current varies, and thereby to transmit, through a worm and worm wheel or
equivalent mechanism, a rocking axial motion to the brush holders of the dynamo
machine.
Mounted loosely on the axle F-is a pair of arms G G³, to the free ends of which
are pivotted respectively the bell crank levers g g¹. The lower limbs of these bell
crank levers form pawls, which take into the teeth of a wheel F¹ keyed on the
axle F.
Pendent from the horizontal arms of these levers are rods which carry respec- 1
tively the working armatures E and E'. The floating or coupling armatures are
shown at C. C².
The spring o, which holds back the arimature C, is secured to a fixed adjustable
point, and it is when the current rises above its normal strength, that the spring c
yields, and allows the armature C to convert its electro magnets A B into a horse 1
shoe magnet of increased power.
The spring o¹, instead of being connected to a fixed point, is weighted by the
core h of a solenoid H, the action of which solenoid is to put tension on the spring c
and hold back the armature C₁ until the electric current has fallen below its
normal strength.
A branch or shunt wire from the main circuit of the dynamo electric machine
passes around the magnets A. B, thence to the magnets A B¹, and is connected to
one end of the solenoid H, the opposite end of the solenoid wire being carried back
to the main circuit.
It will now be understood that when the floating armature C is attracted, its
horse shoe- magnet A B will draw down the working armature E, and through
the-pawl and toothed wheel, turn the axle F in its bearings in the direction of the
arrow 1,
'
This movement of the armature E will short circuit the current passing through
the coils of the horse shoe magnets A. B, and thereby allow a coiled spring e to
raise the armature E clear of the magnet. This action will be repeated as often
as is required to enable the worm gearing to shift the brushes of the dynamo
machine to the required extent.
Similarly, when the current falls below its normal strength, the attraction of the
solenoid will be weakened, and will consequently put less tension on the spring
of the floating armature C¹-This floating armature will therefore, under the
attraction of the magnets A¹ B¹, be caused to rise, thereby forming them into a
⚫ horse shoe magnet of sufficient power to draw down the armature E¹, and turn the
toothed wheel. F in the direction of the arrow 2, so as to shift the brushes of the
dynamo machine in the reverse direction. In like manner the armature E will, in
its turn, short circuit the current flowing through. the coils of the horse shoe
magnet A¹ B¹, and allow the spring e¹ to lift the armature E¹ clear of the magnet,
ready for a repetition of the action of the pawl upon the toothed wheel F¹.
Fig. 4 illustrates the application of the invention to the sounding of an electric
bell. A weak current being passed through the coils of the magnets A. B, will
attract the floating armature C, and draw down the armature. E carried on the
hammer shank. This movement of the armature E will cause the hammer to
strike the bell, and at the same time break the circuit. A repetition of this
action will be maintained so long as the current is allowed to flow through the
magnet coils.
This new form of electro magnet may be used as a cut out, when its action will
be precisely the same as in the preceding cases, but, in this application, it secures
an important advantage over ordinary cut-out devices, inasmuch as, if the increase.
of current has been accidental and momentary, it may be turned on again by
simply touching the appropriate contact button, without having to go to the cut
out. Should there, however, be a permanent increase of current, the fact can be
ascertained at once, since it cannot be restored by pressing in the contact button,

page_text: When used as a cut out, my improved electro magnet, or combination of electro
magnets, and pair of keepers, hereinabove described, is especially suited for use
with the magnetic switch for which a patent was granted to Henry Edmunds
dated 29th March 1884 N° 5670.
This application of the invention is illustrated at Figs. 5 and 6,-Fig. 5 showing
the circuit closed, and Fig. 6 showing the circuit opened. As in the preceding
figures, A. B. is the pair of electro magnets, C the floating armature, and E the
working armature, which, being attracted, will lift the fork I out of the mercury
cups KK, and break the circuit. The raised position of the fork I is maintained
by a catch i, until the catch is withdrawn by the attraction of the electro magnet L,
set in action by the pressing of a button 7. To allow of the breaking of the
circuit by the attendant, a second push button is provided, for setting in action
an electro magnet L¹, which will lift the fork I from the mercury cups.
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. Constructing together electro-magnets by means of a floating armature, for
the purpose of increasing the effective power or pull of the magnets on the working
armature, as above set forth.
2. The application of my improved arrangement of electro-magnets to the
various uses above set forth.