IMPROVEMENTS IN ELECTRO-MAGNETS
Year: 1868

page_text: PROVISIONAL SPECIFICATION left by Alexander Melville Clark at
the Office of the Commissioners of Patents, with his Petition, on
the 16th September 1868.-A communication from abroad by Félix
Gruet and Frédéric Gruet, both of 13, Boulevart St. Martin,,
Paris.
I, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN ELECTRO-MAGNETS," to bo as
follows:-
The principle on which the improvements of this Invention are based is
as follows:-In winding a circuit round a certain number of single electro-
magnets they possess, when taken separately, but very slight magnetic
power if the battery which feeds the circuit is composed of only a few
elements. Further, these electro-magnets, when acting in combination
on a plate presented thereto, will produce but an inconsiderable effect if
they rest on any other substance than iron. However, if these same
clectro-magnets be placed on an iron plate it is found that in applying
the first the force attraction on the face is considerably augmented,
and if two be applied and an iron plate be brought near the face of the

page_text: one the magnetism of the face of the other will be augmented, while if
the plate be brought at the same time in proximity to both faces the
force of attraction will be still further increased, especially if care be
taken to place the opposite poles of the two electro-magnets on the plate.
Further, if all the electro-magnets be placed on the plate with their poles
disposed alternately as above, the attractive force developed by the whole
of their faces will be very considerable on bringing an iron plate in
proximity therewith. The following is a description of apparatus based
on the principles above enunciated, reference being had to the accom-
panying Drawing. :-
The number of the magnets may vary, seven being shown in this
instance, but there may be fewer or a larger number if desired. The
effect is produced more particularly by the contact of the opposite poles
of the electro-magnets with the iron. It is preferable to arrange the
magnets in the way shown, which, however, is not absolutely requisite.
The apparatus is composed of a soft iron plate A, Figures 1, 2, and 3,
united by ties B, B, to a copper plate C parallel with A; D, electro-
magnets formed of coils on a soft iron cylindrical core resting on, plate A,
and supported in position thereon by pins d, d, as seen, their other ends
being mounted in the copper plate C. The apparatus is arranged so that
four of the electro-magnets shall have their south poles in the plate A,
for example, and their north poles in plate C, the other three magnets
being placed in the reverse position. The attractive power of the
electro-magnet thus composed is shown by applying the soft iron plate E
to the face of, C; said. plate E having a hook eat its centre, from, which
weights may be suspended for counterbalancing the force; of attraction..
The difference in the power of attraction, may be.at, once ascertained by
adding a similar electro-magnet to that described and supplied, by, the
same circuit, but, isolated from the plate.
The apparatus being, thus arranged, the following modes of action, may
be adopted: 1st, an iron plate may be simply made to act on the face C
of the apparatus, or the face of a similar, apparatus may be presented
thereto;. 2ndly, several apparatus may be superposed so as to cause the
same elements, as, in the preceding instance, to. act, on, the face C, care
being taken in, this case to substitute copper for the soft iron plates A,
as shown in Figure 4, and to make the opposite poles to coincide; or
the iron plates.may be retained if one face, C be kept at one end of the
superposed apparatus, at which end,also the superposed apparatus before
described may act.

page_text: One mode of combining two apparatus is shown in Figure 4. Usually
the same circuit is coiled round the whole of the electro-magnets,
but several circuits may be employed and several currents, and the
arrangement and number of the electro-magnets may also be varied,
the poles being alternately placed as nearly equal as possible.
The advantages of the apparatus are that the current is completely
utilized considerable attractive power may be obtained from a weak
current, and consequently very great economy may be effected in
apparatus requiring but slight power, as in the case of telegraphs.
Considerable power may be also produced when the force of the current
and the number and dimensions of the electro-magnets are increased.
The Invention consists in combining any suitable number of electro-
magnets with their poles disposed in the manner described for effecting
contact at one or both ends with soft iron plates, such improved electro-
magnets being applicable to scientific and other purposes.