IMPROVEMENTS IN APPARATUS FOR CONNECTING AND DISCONNECTING ELECTRICAL CIRCUITS AND LIMITING AND PROVISIONAL SPECIFICATION
Year: 1883

page_text: LETTERS PATENT to Henry Hardinge Cunynghame of Paper Buildings
Temple in the County of Middlesex, Otway Edward Woodhouse and
Frederick Lawrence Rawson both of No 11 Queen Victoria Street in the
City of London for an Invention of "IMPROVEMENTS IN APPARATUS FOR
CONNECTING AND DISCONNECTING ELECTRICAL CIRCUITS AND LIMITING AND
PROVISIONAL
SPECIFICATION left by the said Henry Hardinge
Cunynghame, Otway Edward Woodhouse, and Frederick Lawrence Rawson
at the Office of the Commissioners of Patents on the 7th June 1883.
HENRY HARDINGE CUNYNGHAME of Paper Buildings Temple in the County of
Middlesex, OTWAY EDWARD WOODHOUSE and FREDERICK LAWRENCE RAWSON
both of No 11 Queen Victoria Street in the City of London, "IMPROVEMENTS IN
APPARATUS FOR CONNECTING AND DISCONNECTING ELECTRICAL CIRCUITS AND
LIMITING AND MEASURING CURRENTS PASSING THROUGH THEM
"
Our invention relates to apparatus whereby electrical circuits are connected and
disconnected by hand, or automatically according to the strength of current, that
strength being limited by the adjustment of the apparatus and measured by
additional apparatus which may be used separately. For this purpose we introduce
into the circuit an electromagnet which has an armature so mounted that it can
pass to either side of the pole of the magnet being strained by a tumbling weight
or spring so as to be held with certain force on one side of the pole or in another
position. In its one attitude it closes the circuit by making contact either with a
metallic surface or with mercury, in passing to the other attitude it opens the
circuit. Thus when the strength of current is such that the attraction of the
electromagnet overcomes the strain of the tumbling weight or spring, the armature
is drawn from its contact making attitude, and when it has passed a certain point
in its course at which contact is broken and the electromagnet therefore ceases to
ID 77

page_text: act, the effect of the tumbling weight or spring is to carry the armature over to its
other attitude, and to retain it there leaving the circuit open. The armature may
be moved by hand so as to act simply as a means of opening or closing a circuit,
or its position may be adjusted relatively to the force of the tumbling weight or
spring in such a way that when the current attains a certain strength, it will
automatically open the circuit, thus operating as a safety plug or junction, limiting
the current strength according as it inay be adjusted. In order to adjust it for
this purpose, we employ an instrument by which we can ascertain the current
strength, this instrument being also available generally for such measurement, as we
will now describe. It consists of an electromagnet with an iron core that can be
slid more or less out or in the coil, and in front of this is an armature needlo
mounted on a torsion spring and carrying an index. The torsion spring can be
adjusted by hand to an extent determined by an index, until its torsion exactly
balances the attractive force on the needle, the position of the adjusting index on
a dial then indicating the strength of current. For convenience of indication, we
prefer to graduate the dial with divisious proportional to the successive squares,
so as to follow the law according to which the strength of current acts. By
drawing out or pushing in the magnet core the scale of these divisions can be
varied at pleasure. In connecting the circuit wires to the apparatus above
described we use contact screws of the following kind. We cut a longitudinal or
oblique notch in a screw bolt and into this we insert the wire and screw down
Such contact screws may
upon it a nut which holds the wire firmly in the notch.
obviously be used for electrical connections generally.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Henry Hardinge Cunynghame, Otway Edward Woodhouse, and
Frederick Lawrence Rawson in the Great Seal Patent Office
7th December 1883.
on the
HENRY HARDINGE CUNYNGHAME of Paper Buildings Temple in the County of
Middlesex, OTWAY EDWARD WOODHOUSE and FREDERICK LAWRENCE RAWSON
both of No 11 Queen Victoria Street, in the city of London "IMPROVEMENTS IN
APPARATUS FOR CONNECTING AND DISCONNECTING ELECTRICAL CIRCUITS AND
LIMITING AND MEASURING CURRENTS PASSING THROUGH THEM "
Our invention relates to apparatus whereby electrical circuits are connected and
disconnected by hand or automatically, according to the strength of the current,
that strength being limited by the adjustment of the apparatus, and measured by
additional apparatus which may be used separately. For this purpose, we introduce
into the circuit an electromagnet, which has an armature so mounted that it can
pass to either side of the pole of the magnet, being strained by a tumbling weight
or spring, so as to be held with certain force on one side of the pole or in another
position. In its one attitude it closes the circuit by making contact either with a
inetallic surface or with mercury, in passing to the other attitude, it opens the
circuit. Thus, when the strength of the current is such that the attraction of the
electromagnet overcomes the strain of the tumbling weight or spring, the armature
is drawn from its contact making attitude, and when it has passed a certain point
in its course at which contact is broken and the electromagnet thus ceases to act,
the effect of the tumbling weight or spring is to carry the armature over to its
other attitude, and to retain it there, leaving the circuit open.
The armature may
be moved by hand, so as to act simply as a means of opening or closing a circuit,
or its position may be adjusted relatively to the force of the tumbling weight or
spring in such a way that when the current attains a certain strength, it will
automatically open the circuit, thus operating as a safety plug or junction, limiting
the current strength according as it may be adjusted. In order to adjust it for
this purpose, we employ an instrument by which we can ascertain the current
strength, this instrument being also available generally for such measurement, as
we will now describe. It consists of an electromagnet with an iron core that can
be slid more or less out or in the coil, and in front of this is an armature needle
mounted on a torsion spring and carrying an index. The torsion spring can be
adjusted by hand to an extent determined by an index, until its torsion exactly
balances the attractive force on the needle, the position of the adjusting index on a
dial then indicating the strength of current. For convenience of indication, we
prefer to graduate the dial with divisions proportional to the successive squares, so
as to follow the law according to which the strength of current acts. By drawing
out or pushing in the magnet core, the scale of these divisions can he varied at
pleasure. In connecting the circuit wires to the apparatus above described, we use
contact screws of the following kind. We cut a longitudinal or oblique notch in
a screw bolt, and into this we insert the wire, and screw down upon it a nut,
which holds the wire firmly in the notch. Such contact screws may obviously be
used for electrical connections generally.

page_text: electrical circuit. The apparatus shewn is of such a form that it can be conve-
niently fixed against a wall or upright by screwing thereto a plate of wood A
which forms its framing. From this plate projects a bracket B having in it two
cavities C containing mercury. On the bracket is fixed an electromagnet D, having
one end of the wire of its coils connected to one of the two circuit wires W, and
the other end of its wire connected with one of the mercury cups C into which dips
a wire attached to an iron yoke E which is pivotted at its lower end to the
bracket B, and has projecting from its arms two bent wires F which dip into the
mercury in the two mercury cups. One of the mercury cups is connected to the
other wire W' of the circuit, the other mercury cup is connected to one end of the
wire wound on the electro-magnet D. While the circuit is closed, the yoke E
leans against an adjustable screw stop G, the electricity passing from W through
the coil of the magnet into one of the mercury cups, thence into the yoke E, its
wire F and the mercury in C to W'. The binding screws at W W' may be made
of common round headed screws passing through loose brass washers. When the
current is of such power that the attraction of the upper end of the magnet D on
the head of E overcomes the weight of the yoke, the yoke turns on its pivots until
it is stopped by its lower ends e bearing against the face of the bracket B, and thus,
the wire F being withdrawn from the mercury, the circuit between W and W¹
is opened. In this way, the apparatus operates automatically as a safety plug
opening the circuit when the electrical current is in excess. Obviously the yoke E
may be moved by hand to open and close the circuit, and so act as a contact key.
By adjusting the screw G, the instrument may be set to act at any required
strength of current. The end of one of the wires F may be made forked, with one
prong slightly longer than the other, one of these prongs dipping into a third
mercury cup, so that the sparking takes place at this cup, the true contact being
made at the other. The effect of oxydation incident to the use of mercury is thus
much diminished. A small partition across one of the cups would have the same
effect, one prong dipping on each side of the partition.
Obviously, by means of suitable connections, the movement of the yoke E may
be made to close a circuit as well as to open one, by causing bent wires attached
to it to be immersed in mercury.
In order to ascertain the current strength, we employ an instrument or Ammeter
of which fig. 3 represents a vertical section. Fig. 4 is a sectional plan and fig. 5 is
a plan of the dial graduated by divisions, the lengths of which are preferably made
as shewn, proportional to the squares of the numbers with which they are marked.
A is a horse-shoe electro-magnet having its coils in the circuit. From its two limbs
project two adjustable iron screws B, which constitute poles presented towards an
armature C of elliptical form. This armature is fixed on a vertical axis, and has
attached to it one end of a coiled spring D, the other end of which is attached to a
disc E. This disc is on a stem extending upwards and terminating in a button F,
by which it can be turned by hand so as to give the spring D greater or less
torsion. The stem carries the index G which moves over the graduated dial H
under a glass I. From the armature C, a light index K bends upwards and
presents its point through a slot L cut through the dial H. When the magnet A
is excited by the current passing through its coils, the attraction of its poles B on
the armature C brings it into such a position that the index K bears against one
end of the slot L.
By then turning the button F, the operator changes the torsive force of the
spring D until it balances the attractive force of the magnet on the armature,
as indicated by the point of the index K moving to the middle of the slot L.
The position of the index G then shews on the dial the current strength. It
is of advantage to attach to the armature C a wire M, projecting between two
wires arranged in circuit of an electric bell, so that when the armature moves in
either direction from its normal attitude, M makes a contact, which causes the
bell to sound and so gives notice of a change of the current strength. The bell
circuit may be made by joining both the wires to one end of the bell and its

page_text: battery, and the case of the instrument to the other end, or a wire may lead from
each of the two wires to two bells of different sound, so that one rings if the
current passing through the main coils of the ammeter becomes too great, and
another if it becomes too small, thus warning the assistant in charge.
Figs. 3 and 4 shew in vertical section and sectional plan another form of the
ainmeter. In this, the case A A is a soft iron cylinder with projections pointing
inwards, which may be of soft iron, or of wood or other non-magnetic material, on
which are wound coils of insulated wire, and within which are soft iron screws B B.
In other respects, the instrument resembles that shewn in figs. 3 and 4. The iron
casing serves to complete the magnetic circuit, and also acts as a magnetic screen
against the influence of magnetic forces in the vicinity.
Fig. 6 shews diagrammatically how the instrument above described may be
connected in the circuit to which it is applied L L' being the leads of the circuit,
A the ammeter, and B B' two contact slides. When the one slide B is slid
forwards, the current is sent through the ammeter as shewn, or when B is retracted
and B slid forwards, the ammeter is cut out of the circuit. Contact slides such
as B B may be arranged in any required numbers on a base as shewn in elevation
at fig 7 and in fig 8 which is a plan of three such slides arranged on one base in
conjunction with safety plugs. Each of the slides B has at its end a bent spring C,
which, on advancing the slide, is pushed into a notch in a metallic piece D. This
piece is connected to another piece E by a safety plug F which is held in position
by setting screws G. The guide H through which the slides B are fitted to slide,
and each of the pieces E is provided with a contact screw according to our
invention. It consists of a screw K, which has a slot M cut through it and is
fitted with a nut N. This nut may be of the kind shewn in fig. 7 which can be
screwed down by a wrench or spanner, or it may be a nut made with wings or a
projecting handle, or with a milled edge, so that it can be turned by hand. The
circuit wire is inserted in the slot M and is pinched therein by screwing down the
nut N. Contact screws of this kind are obviously applicable for making electrical
contacts generally.
Having thus described the nature of our invention and in what manner the
same is to be performed, we claim:
-
First For connecting and disconnecting electrical circuits, the construction of
apparatus substantially as described with reference to figs 1 and 2.
Second The construction of Ammeter or instrument for ascertaining current
strength, substantially as described with reference to figs. 3, 4, 5, 6, and Figs. 3ª
and 4ª
Third For connecting wires of electric circuits, the use of slotted contact screws
and nuts, substantially as herein described.
In Witness whereof I the said Henry Hardinge Cunynghame have hereunto set
my hand and seal this Seventh day of December, in the year of our Lord, One
thousand eight hundred and eighty-three
TENDY HILDRINGE ARVVVCUTT
וחתת.
זזזמm
(cm)