IMPROVEMENTS IN ELECTRO-MAGNETIC MOTORS
Year: 1881

page_text: LETTERS PATENT to Sydney Pitt, of Sutton, in the County of Surrey, for an
Invention of "IMPROVEMENTS IN ELECTRO-MAGNETIC MOTORS." A com-
munication from abroad by Moses Gerrish Farmer, of the City and County
of Newport and State of Rhode Island, one of the United States of
America.
COMPLETE SPECIFICATION filed by the said Sydney Pitt at the Office of the
Commissioners of Patents on the 5th July 1881.
SYDNEY PITT, of Sutton, in the County of Surrey.
"IMPROVEMENTS IN
ELECTRO-MAGNETIC MOTORS." A communication from abroad by Moses Gerrish
Farmer, of the City and County of Newport and State of Rhode Island, one of
the United States of America.
This Invention relates to certain improvements in electro magnetic motors, in
which the ends of an electro-magnetic coil or helix are united just before the
connection between the helix and the electrical generator is broken, whereby the
spark due to the discharge of the extra or induced current from the coil is
prevented.
The result of the Invention is greatly to diminish or destroy the effects of the
induced current, by virtue of which the efficiency of the said motors is greatly
increased, and the expense of operating the same diminished.
The Invention consists in making use of one or more pairs of helices, arranged
to act upon a soft iron armature or moveable core, and in connecting the said
helices with the generator by means of an automatic commutator operated by the
movement of said core or armature in such a manner that during the movement
of the latter in either direction, the two helices which are thus simultaneously in
action are included in the same circuit, and exert their attractive forces in the
same direction upon the core or armature; while at the completion of the stroke
the terminals of the pair of helices are first united so as to form a closed circuit
before the battery current is cut off from them, and the commutator is so arranged
with reference to the terminals of the helices, that when thus united the connections
are such that the induced current generated within them by the magnetic discharge
of the core or armature tends to traverse the respective helices in opposite
directions. Thus the current of induction set up in each helix of the pair
neutralizes that in the other, and the total effect upon the armature becomes
inappreciable.

page_text: In the accompanying Drawings Figures 1 and 2 are plan views, partly in section
of an electro-magnetic motor embodying the improvements shown in two different
positions; Figure 3 is a side elevation of the same; Figures 4 and 5 are theoretical
diagrams illustrating the circuit connections in different positions of the motor.
In the Figures, A, a, A¹, a', represent four helices or coils of insulated wire of
the usual construction. These are grouped in two pairs in such a manner, that the
pairs are capable of acting alternately upon a cylindrical armature of soft iron B,
which is itself enveloped in a coil of insulated wire, as hereinafter described. The
armature B, which also forms the core of the four helices hereinbefore referred to, is
mounted upon a horizontal rod b, which slides freely to and fro in suitable
guides C, C. The armature B moves freely within the central opening of the
helices, which latter are arranged in two groups or pairs, A and a being at one end
of the armature, and A¹ and a at the other end, the whole arrangement forms in
fact a compound axial magnet. The armature B is caused to move to and fro by
the alternate magnetic attraction of the helices A and A', in a manner which will
hereinafter be explained. Attached to the sliding rod b is a pitman c_which takes
hold of the crank D on the end of a horizontal axis or shaft E, E, which
is mounted in suitable bearings e, e. Upon this axis is fixed a fly wheel F, the
whole arrangement being somewhat similar to that of the cylinder, piston, crank,
and fly wheel of a horizontal steam engine. Upon the shaft E are mounted a
sèries of commutators G, H, I, J, K, L, and M, the function of which is to
automatically control the distribution of the electric current from the generator to
the four helices A, a, A¹, a¹, as hereinafter set forth. Each commutator consists
of a section of a metallic cylinder or ring mounted concentrically upon the
shaft E, E, and each of the rings is insulated from the shaft and from the other
rings. The series of insulated contact springs g, g, h, h¹, etc., are mounted upon
the base of the machine, and press against the cylinder sections or commutators
upon the shaft and thus form electrical contact with the latter as they revolve.
The adjacent ends of the commutator cylinders or rings are provided with recesses
and projections arranged with reference to each other in a manner which will be
best understood by inspection of Figures 1 and 2, so that parts of two different
rings may be brought in contact with one and the same contact spring during
different portions of one revolution. The several contact springs which press
against the revolving commutator rings constitute the terminals of wires leading
respectively to the poles of the electric generator and to the helices which act
upon the movable armature to impel the machine; and the function of the revolving
commutator rings is to form the required connections and disconnections between
these two sets of conductors. The coil which is wound directly upon the
armature B is traversed by a constant current of electricity from a suitable battery
or other generator o, the respective poles of which are connected with the binding
screws 1, n. The electric current is conducted from the binding screw p by a
wire q to a standard s, thence by a spiral wire r to the terminal t of the coil
surrounding the core or armature B, thence by terminal and spiral wire v to a
standard w, from which a wire x leads to the other binding screw n.
armature B thus becomes a permanent or constantly polarized magnet by virtue of
the constant current passing round it from the generator o.
The
In Figure 1 the armature is represented as in a position midway of its stroke
and moving in the direction indicated by the arrow. The course of the actuating
electric current may be traced as follows:-
○○ represents a battery, dynamo-electric machine, or other suitable electric
generator, the positive and negative poles of which are respectively connected with
the binding screws P and N upon the base of the electro-motor. Commencing
at the positive pole of the generator O, the current goes first to the binding
post P, and thence by the wire 2 to the contact spring 7, through the commutator
ring L to the spring, thence by the wire 13 to the helix A', passing through
said helix, and thence by the wire 10 to the commutator spring i, thence to the
ring I, spring i', and wire 11 to the other helix a' of the pair, through said helix,

page_text: and thence by wire 5 to contact spring j, commutator ring J, and spring j¹, and
thence by wire 4 to the binding screw N, and negative pole of the generator. It
will be observed that the organization of the circuits is such that the current whose
course bas just been described traverses the helices A¹, a¹, in the same direction.
The effect of this. arrangement is that both helices act in this same manner upon
the adjacent end of the polarized armature B, exerting a powerful attraction upon
it, and tending to pull it in the direction indicated by the arrow until the fly
wheel F has been caused to revolve by means of the crank D through one fourth
of a revolution. At this moment the direction of the electric circuits is changed
throughout by the action of the commutators upon the shaft E, E, which then
assume the position shown in Figure 2. In the new position of the commutators
the course of the circuit is as follows:-From the positive pole of the generator O
to the binding screw P, thence by the wire 2, contact spring Z, commutator ring L,
spring, and wire 12 to the helix A, thence by wire 6, contact spring ³, commutator
ring H, contact spring h, and wire 7, to helix a, thence by wire 9, contact spring g,
commutator ring G, contact spring gl, and wire 8, to the binding screw N, and negative
pole of the generator. Thus it will be understood that by this movement of the com-
mutator the helices A' and a' are disconnected from the generator, and the helices A
and a are connected with it, while by the same operation the terminals of the
helices A' and a¹ are united by the commutator, as will be understood by tracing the
connections in Figures 2 and 5 from the helix A¹ by the wire 10, contact spring i,
commutator I, contact spring j, and wire 5 to helix a', thence by wire 11, contact
spring, commutator ring J, contact spring j', wire 4, binding screw N, wire 1,
contact spring m, commutator ring M, contact spring 1, and wire 13, to
the other terminal of the helix A. This latter circuit is in fact completed
immediately before the disconnection of the generator, as the construction of the
commutator is such that the springs are in contact momentarily with two com-
mutator rings at the same time while passing from one to the other. The effect
of this arrangement is that the closed circuit which is formed by uniting the
terminals of the two helices A¹ and a' traverses them in opposite directions after
the generator has been detached. Therefore the inductive action which is set up
in each helix upon the disappearance of the magnetism of the core is precisely
equal and opposite to that in the other end, and the two induced currents therefore
reciprocally neutralize or destroy each other, so that by this improved organization
the action of the induced current upon the core, which seriously impairs the
efficiency of ordinary electro motors, is entirely done away with.
It will sometimes be found advantageous in practice to set the commutator a
little in advance of the movement of the armature, giving it as it is technically
termed a "lead." In such case the terminals of each pair of helices would be
united and the generator disconnected just before the completion of the stroke.
The connections of the circuits in the two positions of the commutators during
the direct and the return stroke respectively will be more readily understood by
reference to the diagrams Figures 4 and 5, in which the two positions of the
commutators are respectively illustrated. The full lines show the circuits traversed
by the electric current from the generator, while the dotted lines show the circuits
in which the terminals of the coils are united after the disconnection of the
generator. The arrows in these Figures indicate the direction in which the core or
armature is supposed to be moving.
It is obvious that many changes may be made in the construction and arrange-
ment of the details of the apparatus without departing from the spirit of the
Invention. Various well known forms of commutators might be advantageously
employed in order to produce the effects which I have described. So also a
permanently polarized steel bar might be employed for the reciprocating armature,
or even a non-polarized soft iron bar, but neither of these would be as efficient in
practice as the construction which I have described.
•
I claim as the Invention of improvements in electro magnetic motors,-
First. The herein before described method of neutralizing or destroying the

page_text: induced current generated in the helix of the electro magnet upon the cessation of
the primary current traversing the same, which consists in uniting with each other
the respective opposing terminals of the two sections of the divided helix, and
thereby forming a closed circuit immediately upon the disconnection of the
generator.
Second. The combination, substantially as hereinbefore set forth, of two helices
included in the same circuit and acting in unison upon the same core or armature,
a commutator automatically operated by the movement of said core or armature,
and circuit connections, substantially such as described, whereby the connections of
the terminals of the respective helices are reversed, so that a current is made to
traverse said helices alternately in the same and in an opposite direction with
reference to each other.
Third. The combination, substantially as hereinbefore set forth, of a movable core
or armature, two helices or coils arranged to act simultaneously upon said core or
armature to impel it in a given direction, a commutator automatically operated by
the movement of said core or armature, and circuit connections, substantially such
as described, from the commutator to the helices, whereby the opposing or like
terminals of said coils are united at the termination of the stroke to form a closed
circuit before the disconnection of the generator.
In witness whereof, I, the said Sydney Pitt, have hereunto set my hand and
seal, this Eleventh day of June, in the year of our Lord One thousand
eight hundred and eighty one.