An Improved Method of Reciprocating the Anchor of an Electric Apparatus.
Year: 1891

page_text: Date of Application, 16th July, 1891-Accepted, 19th Sept., 1891
COMPLETE SPECIFICATION.
[Communicated from abroad by KARL FERDINARD SCHÖLLER, Manufacturer, and
RUDOLPH HERMAN JAHR, Engineer, both of Opladen, Germany.]
An Improved Method of Reciprocating the Anchor of an Electric
Apparatus.
I, HUGH DONALD FITZPATRICK, of '70 Wellington Street, Glasgow, Registered
Patent Agent, 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 the methods of producing the to-and-fro motion of the anchor of an electric
apparatus, as hitherto used, there must be a considerable space between the anchor
and the poles of the magnet.
The magnetic power decreasing in inverse proportion to the square of tho
distance, one has to use magnets of large dimensions to produce the motion from
the beginning, as the greater distance off that the anchor is a larger magnetio
power will be required to affect it. The drawback resulting, is, that the power
becomes too great when the anchor approaches the poles, and, as a consequence,
the anchor strikes the stop-pins with a force ofttimes sufficient to injure the
apparatus.
The task of the inventor, is, for such an apparatus, to produce a magnetic
power as constant as possible, so that the use of magnets of large dimensions is
obviated.
This new and original effect is produced by the combination of one or more
magnets having an even number of poles with one or more having an odd number;
and by changing the direction of the currents so as to produce a change in the
polarity of one, or one set, of the magnets.
A method of carrying out my invention is illustrated on the drawing annexed.
The fixed electro-magnet A has the three poles a, b, c, of which the outward
ones a and c have a different polarity from the inner one b.
For a movable anchor I adopt an electromagnet B with its centre of motion at o
and having two poles d and e. The stop-scrows or pins s prevent the poles of the
movable anchor B from covering or overlapping the corresponding poles of the
magnet A for-more than about a third of their width. This overlapping may be
compared to the lap of the slide valve of a steam engine.
As shown on the drawing the current flows from both poles through the fixed
magnet A to the commutator C which may be of any construction and from thence
to the anchor B.
It is evident that the polarity of A will always remain the same as the direction
of the current is never changed whilst the polarity of B may be changed by the
commutator which latter may be operated either by hand or automatically.
Now, suppose the poles a and c of the magnet are positive and the inner pole b
negative, if the current is changed so that the pole d of the anchor B is positive
and the pole e negative then the pole a will, with great force, repel the pole d and
the pole & will repel the pole e as these poles (a and d and band e) are near to
each other. This repelling action causes the anchor to move in the direction of
the arrow as the overlapping of the poles of the anchor is at the right hand side
of the poles a and b of the fixed magnet. As the movement to the right hand
continues the poles b and d and caude, which have different polarities, attract
each other, and, as this attraction increases with the movement of the anchor and
the approach of the poles, d, and c, e, to each other, it compensates for the loss of
repelling force due to the increasing distance between the poles a, d, and b, e.

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By this method of compensation the task of producing a constant moving power
is fulfilled.
By operating the commutator the direction of the current and consequently the
polarity of the anchor B can be changed so that the attractive and repelling forces
of the poles will act in a reverse manner and produce a reverse motion of the
anchor.
The invention can, without departing from its principle; be carried out in various
other ways besides that illustrated, such as, making the magnet A movable and the
magnet B fixed; or making the polarity of B. constant. and that of A changable' or
by using a horse-shoe or other magnet (A) with permanent polarity instead of an
electromagnet with constant polarity; or by using magnets with an increased
number of poles.
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
.
The method of working electric apparatuses of any kind by an anchor motion
produced by the combination of a magnet or magnets having an even number of
poles with one or more corresponding magnets having an odd number of poles,
substantially as herein before set forth.
Dated this 15th day of July 1891.
H. D. FITZPATRICK,
70, Wellington Street, Glasgow.