Improved Device for Deriving Weak Currents from Main Current Conductors.
Year: 1897

page_text: Date of Application, 23rd Sept., 1897
Complete Specification Left, 28th June, 1898-Accepted, 30th July,
1898
PROVISIONAL SPECIFICATION.
Improved Device for Deriving Weak Currents from Main Current
Conductors.
I, MAX SICHEL, of 75, St. Mark's Road, North Kensington, in the County of
London, Merchant, do hereby declare the nature of this invention to be as
follows:-
The object of the present invention is to provide means for deriving weak
currents, such as are sufficient for operating bells and other signals, from the
main current conductors and at the same time preventing any possibility of the strong
current from the main conductors passing to the conductors for the weak current.
This enables the circuit for the weak current to be arranged in the ordinary
manner, and the same may consequently be fitted up much more cheaply than
heretofore, because hitherto the circuits of the weak current, when the latter is
derived from a main line wire have been similarly arranged to those of the main
conductors, as far as the insulation of the same is concerned, in order, as
far as possible, to prevent accidents in the case of the strong current passing into
the conductors of the weak current.
According to the present invention, a branch circuit is taken from the main
circuit and in this circuit a resistance is arranged, the terminals of a shunt
circuit for the weak current being applied to the resistance at a point in the same
corresponding to the intensity of the current required for the said weak circuit.
The bell or other signalling device is arranged in the shunt circuit. The latter
circuit and also the branch circuit from the main conductors are normally broken,
and a double switch device is provided, which when operated first closes the branch
circuit and then the shunt circuit, when the bell or other signalling device will be
set at work. On releasing the switch button the shunt circuit of the weak current
will be first broken and then the branch circuit from the main conductors.
The particular construction of the switch device is of no importance the same
may consist of a button spring pressed in the usual manner and having two
contacting tongues, the first being adapted to close the branch circuit, the terminals
of which are mounted in proximity to the said button, and then on further
depressing the button, the shunt circuit should be closed by the second contacting
tongue.
The advantages of the present system are that there will be no danger of the main
current passing into the conductors of the weak circuit and secondly both the
branch circuit and the shunt circuit will be broken or open normally, only being
closed when it is required to ring the bell, or to operate the other signalling
device in connection with the weak circuit.
1007
CASTLE SMITH,
<
Invention" Office, Mitre Court, Fleet Street, London, E.C.,
Agent for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improved Device for Deriving Weak Currents from Main Current
Conductors.
.1
I, MAX SICHEL, of 75, St Mark's Road, North Kensington, London, Merchant,
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:
-
This invention relates to an improved device for deriving weak currents from
main current conductors and is characterized by arranging the several operating
devices (buttons, levers, or the like) employed for calling and signalling purposes
in the weak current circuit in such a manner that each of the same is ready to be
connected separately with the main circuit, the said devices forming simultaneously
shunt and branch line switches. Thus the device consists of a combined main line
switch and a switch for the weak current circuit connected to a resistance, and is
so constructed that the weak line system or circuit is only connected up to the main
line wires for the time being i.e. whilst it is actually in operation. One form of
carrying the invention into practice will be described first; according to this
arrangement the branch circuit can only be switched in or out of the system' after
the main line circuit has been closed.
And in order to render the present invention more easily intelligible reference is
had to the accompanying drawing, in which similar letters of reference denote
similar parts throughout the several views:
Fig. 1 is a diagram, showing the circuit open,
Fig. 1 shows the circuit closed,
Fig. 2 is a diagram of the ordinary telegraphic system of any house and
Fig. 2 a diagram showing the telegraphic system of the present invention.
For the purpose of illustrating the present invention the button of an ordinary
house telegraph system has been chosen. The shunt circuit is connected with the
main circuit at L1 and L2. The resistance W is circuited in the shunt line by
means of a brush contact at M and the contacts or terminals at L', L2 and is of such
proportions that the current derived from the terminals A1 and A2 will have the
necessary tension (for instance 10 volt) for the weak current. The brush contact
at M is closed by pressing in the button K to a certain extent and on continuing to
depress the button (Fig. 1) the metallic connection of A¹ and A2 with the weak
current circuit will be effected, in that the contact springs touch those c³ct.
The weak current thus passes from 131 132 into its circuit. On releasing the button
the shunt circuit will be first switched out at the branch points and then the
main current cut off; the springs s¹² spring back and effect first, the breaking of
the contacts at clc and c² and then the switching out of the brush contact at M.
In this manner the induced high-tension currents generated on switching the main
current out or in are effectually prevented from passing on to the weak current lines,
since the latter are only in metallic connection as long as a constant main circuit
current obtains at the points of juncture of the shunt and branch lines.
If this point need not be taken into consideration, the switch may simply be
provided with two contacts (such as M) one at each side of the branch line re-
sistance W and the weak current contacts c¹³ and may be omitted. If the
main wires are fed with a constant current, the main line terminals of the shunt
switch (in the drawing the brush contacts M) may be omitted and the two weak
current contacts and only retained.
The device above described possesses the following advantages:
:-
a). The resistance, main conductor switch and weak current operating device
Chutton or the like) are all combined.
3:1

page_text: 6). The weak current circuit is only in metallic connection with the main unes
during the time it is actually in employment.
In the case of ground leakage i.e. if the main current finds its way through the
ground into the weak current conductors one part of the resistance W will still
be in the circuit thus formed and will be sufficient to prevent the current in the
weak current conductors from attaining dangerous proportions. Since the weak
current circuit is only in metallic connection with the main lines whilst it is in
use, no percepticle amount of current will be lost. The danger of the formation
of sparks is reduced by the present device to a practically harmless minimum.
There is no danger of ground leakage in connection with the present system so that
cheap weak current circuits with very simple insulating means may be employed
in spite of the connection with the main line wires.
The system has been
In Figures and 2 s designates the shunt switches.
described in connection with house telegraphy, but may of course be employed for
any other purpose in which a weak current is used.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1: Shunt switch for deriving weak current from main line wires, which serves
simultaneously as operating means (calling device) for the weak current circuit said
switch being so constructed that the weak current circuit is in metallic connection
with the main line circuit during its operative period only, the device being con-
nected to a resistance W in the manner and for the purpose substantially as
described.
2: A special form of the switch covered by Claim 1 which consists of the com-
bination of main current and weak current switches in such manner that, on
operating the same, the main line circuit will first be closed and thereafter the
weak current circuit whilst on throwing the weak current circuit out of operation the
same will first be interrupted and then the main circuit, substantially as described.
n
1 ilis 09-1 dor of June 1898.
CASTLE SMITH,
"Invention!" Office, Mitre Court, Fleet Street, London, E.C.,
Agent for the Applicant.