Improvements in Electro Magnets.
Year: 1892

page_text: Date of Application, 22nd Oct., 1892
Complete Specification Left, 22nd July, 1893-Accepted, 26th Aug., 1893
PROVISIONAL SPECIFICATION.
Improvements in Electro Magnets.
I ILLIUS AUGUSTUS TIMMIS of No. 2 Great George Street, Westminster
London S.W. Civil and Electrical Engineer, do hereby declare the nature of this
invention to be as follows:-
The objects of my improvements are to give a maximum of initial pull or
attraction, with a given E.M.F. and current, between the bobbin and armature
of an electro magnet when at a given distance apart; and a great holding power
with a very small reduced current when the armature and bobbin have been drawn
together (ie. are "home").
It is well known that a solenoid gives a long pull to an iron rod inserted in it
when an electric current is sent through the solenoid coil but when the rod is
pulled into the centre of the coil (ie. when its centre of gravity is on the line of
the centre of attracting forces) it is in equilibrium but there is no practical holding
power.
Many devices have been invented and tried to give a magnet with a long pull
and some to give a strong holding power economically but none have been successful
so far in combining these two features.
The most successful one was patented in 1882, No. 3712 by S. C. C. Currie and
this was more or less perfected by him and the undersigned the latter of whom it
now belongs to. The principles worked out and claimed in that invention are the
putting of an inner and outer metal tube to a helix of insulated wire and joining
them by a common base plate thus forming the bobbin of the magnet. Then
making an armature of a flat piece of suitable metal the same diameter as the
outer tube of the bobbin and putting a central rod and outer rim to it. The rod
first being magnetically attracted by the inner tube (it approaching nearest) then
the outer rim being attracted by the outer rim of the bobbin and lastly the flat
armature plate being attracted by both tubes and when the armature and bobbin
are together (the armature being in contact with the inner and outer tubes of the
bobbin) an enormous holding power is effected.
But though the range of power or practical pull is great yet that pull is not
satisfactory and with a moderate sized magnet say 6" x 5" and with an E.M.F. of
40 volts and a current of 5 ampères the effective pull is very little at over 2" and
not enough at that distance to place much reliance on it for rough practical work.
The holding power however of the Currie magnet is great and with a very small
expenditure of electricity.
I bave however discovered after years of work and experiments that I can as
hereinafter described make a magnet with a very long and powerful pull and also a
strong holding power and do this with efficiency and economy.
This double quality is especially valuable in actuating railway signals where a
long and strong pull (with a great reserve of power) is requisite to actuate the
arms &c. in bad weather, and where a minimum holding electric current must be
used to hold signals at "line clear" often for many hours during the day. These
With these objects
conditions are obvious for economy, safety and convenience.
in view and with the above explanation I make an electro magnet as follows:-
For the bobbin I make a helix or coil (or more than one coil) of insulated wire
(copper or other suitable metal) and outside I put a tube (of any suitable metal)
and inside it I put another tube (it may be a rod) and at the bottom I join them
by a common metal base plate.
The centre tube may be a rod bored out or it may be solid but these
tubes, one
or both, are not extended to the top of the helix for reasons
hereinafter stated

page_text: The tubes may be bevelled or square with the central axis, or partly bevelled
and partly square.
The armature is made with a top plate of any suitable shape and metal and
with an inner rod (it may be a tube) which extends towards the bobbin and is
made to fit into the helix and the central tube of the bobbin the helix exercises a
powerful pull or attraction on it and then it comes within the attraction of the
central tube. Also there is (or may or may not be) an outer rim which extends
towards the bobbin and is attracted by the helix and fits into or onto the outer
rim of the bobbin.
The shapes of the armature and bobbin are so arranged that when they are
coming together the surfaces of the magnetisable parts exercise the maximum of
attraction and when they are together the holding power between them is a
maximum with an exceedingly small current of electricity flowing. I may thicken
up the top of the outer tube and widen the armature and give greater mass of
magnetisable metal and contact and thus increase the holding power.
The plane or planes of contact between the armature and bobbin should be above
the plane of maximum magnetic force in the bobbin.
The outer rim of the bobbin may extend to the top of the helix instead of
having an outside rim to the armature. And in any case a tube may run up
outside all and beyond the armature and attached or joined to the bobbin base
plate.
The helix of wire may be covered or protected, where it is not protected by
magnetisable metal by means of non-magnetisable metal.
Where I use the words "
metal.
copper or wire" I mean any suitable conducting
The bobbin metal case and the armnature may be in any convenient number of
pieces and of any metal that magnetises and demagnetises quickly and the surfaces
that come in contact may be of any suitable form.
By these several means a very powerful pull or suck is given to the central
core, and, or, outer rim of the armature by the helix of wire where not encased
in magnetisable metal. The central core and outer rim (if there are both) may be
at different distances (perhaps adjustable) and thus the attractive force or pull
may be varied.
It is possible to arrange several rods, or, and, rims on the armature and corre-
sponding parts on the bobbin for them to approach or come in contact with,
and there may be a tube from the base plate outside all to any suitable height.
It will be seen that the objects I have are to utilize the great magnetic
attractive forces exercised by a coil or coils of copper (or other suitable) wire
having a current of electricity flowing through them when they are not encased in,
or surrounded by, magnetisable metal such as soft iron &c., on an armature of
suitable shape and metal. And then when that pull or suck is in action and the
armature and bobbin are coming together the pull is increased as the magnetisable
surfaces come closer and then when these surfaces of the armature and bobbin are
in contact (or practically so) the holding power between the armature and bobbin
is very great with a minimum current of electricity.
Dated: 11
1
1000
COMPLETE SPECIFICATION.
Improvements in Electro Magnets.
1 ILLIUS AUGUSTUS TIMMIS of No. 2 Great George Street, Westminster 50
London S. W. Civil and 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 objects of my improvements are to give a maximum of initial pull or

page_text: attraction, with a given E.M.F. and current, between the bobbin and armature of
an electro magnet when at a given distance apart; and a great holding power with
a very small reduced current when the armature and bobbin have been drawn
together (ie. are "home").
It is well known that a solenoid gives a long pull to an iron rod inserted in it
when an electric current is sent through the solenoid coil but when the rod is
pulled into the centre of the coil (ie. when its centre of gravity is on the line of
the centre of attracting forces) it is in equilibrium but there is practically no
holding power.
Many devices have been invented and tried to give a magnet with a long pull
and some to give a strong holding power economically but none have been successful
so far in combining these two features.
The most successful one was patented in 1882 No. 3712 by S. C. C. Currie and
this was more or less perfected by him and the undersigned the latter of whom it
now belongs to. The principles worked out and claimed in that invention are the
putting of an inner and outer metal tube to a helix of insulated wire and joining
them by a common base plate thus forming the bobbin of the magnet. Then
making an armature of a Hat piece of suitable metal the same diameter as the
outer tube of the bobbin and putting a central rod and outer rim to it. The rod
first being magnetically attracted by the inner tube (it approaching nearest) then
the outer rim being attracted by the outer rim of the bobbin and lastly the flat
armature plate being attracted by both tubes and when the armature and bobbin
are together (the armature being in contact with the inner and outer tubes of the
bobbin) an enormous holding power is effected.
But though the range of power or practical pull is great yet that pull is not
satisfactory and with a moderate sized magnet say 6" x 5" and with an E.M. F. of
40 volts and a current of 5 ampères the effective pull is very little at over 2" and
not enough at that distance to place much reliance on it for rough practical work.
The holding power however of the Currie magnet is great and with a very small
expenditure of electricity.
I have however discovered after years of work and experiments that I can as
hereinafter described make a magnet with a very long and powerful pull also a
strong holding power and do this with efficiency and economy.
This double quality is especially valuable in actuating railway signals where a
long and strong pull (with a great reserve of power) is requisite to actuate the
arms &c. in bad weather and where a minimum holding electric current must be
used to hold signals at "line clear" often for many hours during the day. These
conditions are obvious for economy, safety and convenience. With these objects
in view and with the above explanation I make an electro magnet as follows:
For the bobbin I make a helix or coil (or more than one coil) of insulated wire
(copper or other suitable material) and outside I put a tube (of any suitable
metal) and inside it I put another tube (it may be a rod) and at the bottom I join
them by a common metal base plate.
The centre tube may be a rod bored out or it may be a solid but these tubes,
one or both, are not extended to the top of the helix for reasons hereinafter stated.
The tubes may be bevelled or square with the central axis, or partly bevelled
and partly square.
The armature is made with a top plate of any suitable shape and metal and with
an inner rod (it may be a tube) which extends towards the bobbin and is made to
fit into the helix and the central tube of the bobbin-the helix exercises a powerful
pull or attraction on it and then it comes within the attraction of the central tube.
Also there is (or may or may not be) an outer rim which extends towards the
bobbin and is attracted by the helix and fits into or on to the outer rim of the
bobbin.
The shapes of the armature and bobbin are so arranged that when they are
coming together the surfaces of the magnetisable parts exercise the maximum of
attraction and when they are together the holding power between them is a

page_text: maximum with an exceedingly small current of electricity flowing. I may thicken
up the top, of the outer tube and widen the armature and give a greater mass of
magnetisable metal and contact and thus increase the holding power.
The plane or planes of contact between the armature and bobbin should be above
the plane of maximum magnetic force in the bobbin that is to get the greatest
pull.
The outer rim of the bobbin may extend to the top of the helix instead of having
an outside rim to the armature. And in any case a tube may run up outside all
and beyond the armature and attached or joined to the bobbin base plate.
The helix of wire may be covered or protected, where it is not protected by
magnetisable metal, by means of non-magnetisable metal.
Where I use the words "copper" or "wire" I mean any suitable conducting
metal.
The bobbin metal case and the armature may be in any convenient number of
pieces and of any metal that magnetises and demagnetises quickly and the surfaces
that come in contact may be of any suitable form.
By these several means a very powerful pull or suck is given to the central core,
and, or, outer rim of the armature by the helix of wire where not encased in
magnetisable metal. The central core and outer rim (if there are both) may be at
different distances (perhaps adjustable) and thus the attractive force or pull may
be varied.
It is possible to arrange several rods, or, and, rims on the armature and
corresponding parts on the bobbin for them to approach or come in contact
with and there may be a tube from the base plate outside all to any suitable
height.
It will be seen that the objects that I have are to utilize the great magnetic
attractive forces exercised by a coil or coils of copper (or other suitable) wire
having a current of electricity flowing through them when they are not encased in,
or surrounded by, magnetisable metal such as soft iron &c. on an armature of
suitable shape and metal. And then when that pull or suck is in action and the
armature and bobbin are coming together the pull is increased as the magnetisable
surfaces come closer and then when these surfaces of the armature and bobbin are
in contact (or practically so) the holding power between the armature and bobbin
is very great with a minimum current of electricity.
This invention is best understood by reference to the accompanying drawing.
Fig. 1 is an electro-magnet with only one kind of uniform winding.
Fig. 2 is a modified form of the foregoing with double winding, the purpose of
which will be explained hereinafter.
Fig. 3 is a modified form of the electro-magnet shown in Fig. 2.
Fig. 4 shows a modified form of the armature.
Fig. 5 shows another modification of both armature and central core.
Fig. 6 represents a combination of three electro-magnets of which Fig. 7 is
a plan.
The same letters of reference refer to all the figures of the drawings. a is the
armature of the electro-magnet: a brass bobbin on which the coils of wire H
and Hare wound. c is a central core which forms part of armature a, in Fig. 5 it
is done away with. i in Fig. 1 is a rod of non-magnetisable metal attached to
centre core c of armature a, its purpose is to actuate some electrical or mechanical
device when the armature a is attracted.
"
H is a helix of thick wire.
Hin Figs. 2 & 3 is a helix of fine wire the purpose of which is to act as
additional resistance and therefore decrease the current when the armature a has
come down against or very near the top face of the brass bobbin b. p is a cast or
wrought iron base plate provided with a central hollow tube fitting exactly into
the central part or tube of brass bobbin b. o is a rim attached to or forming part
of armature a. t is a cast or wrought iron casing attached to base plate t as shown
in Figs. 1, 2, 4,5, and 6,

page_text: It will be seen that in all these figures the armature a and its rim o, casing and
base plate p form a complete magnetic circuit when the amature is down. The
pull is due to the combined attraction of the central core c and tuber and of the
armature a and casing t.
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:
First. An electro-magnet, consisting of the tuber having a base plate pof
magnetisable metal, and the bobbin & of non-magnetisable provided with one or
more coils of wire H and H arranged around the said bobbin with its flanges
wholly covering the ends of the wires, in combination with an armature consisting
of a plate a provided with a rim o adapted to slide over the top of the coil, and a
central portion c adapted to slide within the said bobbin, substantially as set
forth.
Second. An electro-magnet, consisting of the tuber having a base plate p, and
the outer casing t, all of magnetisable metal, and the bobbin 6 of non-magnetisable
metal provided with one or more coils of wire H and arranged between the said
tube and casing, in combination with an armature consisting of a plate a provided
with a rim o adapted to slide over the top of the said coil, a central portion
adapted to slide within the said bobbin, and a rod i adapted to pass through the said
tube, substantially as set forth.
G
Third. An electro-magnet consisting of an armature of magnetisable metal
constructed as and for the purposes set forth in the Specification together with a
bobbin consisting of a helix of one or more coils of insulated wire protected where
necessary by non-magnetisable material and encased partially by magnetisable
metal so that one or more parts of the armature are first attracted by the wire helix
where it is not encased in magnetisable metal (when a current of electricity is
running through it) and then as the armature approaches the bobbin the former
comes within the attractive force of the magnetisable parts of the latter substantially
as set forth.
Fourth. A compound electro-magnet consisting of several helices of wire with
suitably shaped casing and a corresponding armature substantially as set forth.
Dated this 22nd day of July 1893.
1. A. TIMMIS.