Improvements in and relating to Telegraphic Relays.
Year: 1894

page_text: Date of Application, 31st Oct., 1894-Accepted, 1st Dec.,
1894
Improvements in and relating to Telegraphic Relays.
I, ARCHIBALD DAVID MACDONALD, of Sun Building, Queen Street,
Melbourne, in the Colony of Victoria, Telegraph Operator under the Victorian
Government, 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 ordinary forms of telegraphic relay, the principal drawback is the necessity
for frequent re-adjustment of the instrument, because the strength of the current
varies from time to time, owing to meteorological or other influences. Further, it
is found in practice that the current often becomes so weak that even when adjusted
to its limit the relay will not work so as to produce intelligible signals.
Relays which are in most general use have the cores, armature levers, armatures
and regulating springs arranged in a manner requiring unnecessarily strong currents
to work them. Such currents are as a general rule supplied by means of galvanic
cells, which in considerable numbers are costly to maintain, so that the reduction of
the expenses for current becomes a desideratum.
My improvements are designed to obviate the necessity for frequent re-adjustment,
and to render feasible the employment of much weaker currents than usual, in this
way effecting considerable economy. In consequence of the mechanism I employ
being adapted to continue the working whether the current be strong or weak, my
With weak
instruments will give signals when ordinary ones would fail to do so.
currents, which I prefer, the induction troubles hitherto common practically
disappear. Among the economies effected by my invention are the abolition of
repeating stations on long lines.
The method of regulating my mechanism is by increasing or decreasing the
tension of a specially arranged spring operating a suitably constructed armature
lever. I have also invented a method of causing relays when they are found non-
responsive to very weak currents to become sensitive to the same, and thus enable
working to be carried on. This method is applicable to relays generally, and is
only employed when the current has become abnormally weak.
My improved mechanism may be applied to relays of various kinds, but by way
of example I will now describe a simple non-polarized instrument embodying my
invention.
In the accompanying drawings,
Fig. 1 represents in perspective a relay containing my improvements. Fig. 2 is
a plan of the same instrument. Fig. 3 is a corresponding rear elevation.
Fig. 4 is a diagram (not to scale) showing my improved method of working
relays.
A is the armature. In the construction illustrated, the core and coils B are
upright and the armature lever is extended on each side of its axis or fulcrum H
and is so arranged that its arms C and D lie horizontally when at rest.' To secure
this horizontal position, 1 make the weight of the extension C almost but not quite
sufficient to act (when the instrument is free from electrical or magnetic influence)
as a counterpoise to the arm D carrying the armature A. The arm D is extended
considerably beyond the contact points F, and at or near its extremity E is con-
nected to the lower end of a vertical spiral spring G the upper end of which is
connected by a thread or its equivalent to a micrometer or regulating screw J, this
screw enabling the tension of the spring to be adjusted. M is a hollow post in
which the bar M' carrying the screw J slides; this bar being held in any desired

page_text: position by means of the set-screw N. The spring G differs from those ordinarily
used because it is so arranged that its weight is not a factor in the pull it gives
upon the armature, and it is so delicate that a pull of less than one grain may be
exerted by it on the end of the armature lever. A pull of about two grains when
there is no current should cause the spring to raise the end E of the arm D until
the contact point at F is up against the back stop. The instrument should be set
for work with a two grain pull lifting the end E of the arm D. It is necessary to
see that the armature lever is horizontal and when up against the back stop barely
opening the local circuit so that while the local circuit is closed the armature shall
be as close to the cores as practicable without touching them.
As work proceeds there is little residual magnetism so long as the current
remains weak, but when the current strengthens the residual magnetism increases
and necessitates a tightening of the vertical spring G until the pull is as great as
may be required.
In a polarized relay, I place the coils horizontally, one core being above the
other, so as to allow the armature lever to oscillate vertically between them. The
armature or lever for such relay may be constructed and arranged, in respect to
pivoting and counterpoising, as above described for an ordinary relay, with the
agate or back stop uppermost, and may be furnished with a special spring also
arranged as above set forth.
My improvements thus avoid mechanical impediments to working with weak
currents and make the receiving instruments extremely sensitive so that the speed
of signalling is increased.
It will be observed that various known parts of relay mechanism are shown in
the drawings but are not described. Their use will, however, be well understood
by persons versed in the art of telegraphy.
K are binding screws for the local circuit, L are binding screws for the
connection of the main line wires, P is the bed-plate and O is an upright or
supporting frame for various parts.
I will now describe in detail my improved method applicable to the working of
relays generally.
When a main line current is too weak to work a relay, the sensitiveness of the
relay is greatly increased in the following manner :-The weak main line current is
cut off and the electro magnet of the relay momentarily short-circuited with say
one Lechanche cell having the same polarity as the main line current.
RR' (Fig. 4) are points where the main line is entirely disconnected from the
relay. S are wires joining one cell T to the relay X, the latter connection or
circuit being made only after the main line has been disconnected at R R¹. An
important point is that the currents from the main line and the lines S through the
relay shall both have the same polarity. This is shown in the diagram by the
arrows and the arrangement of cells T and Y, the former being near and the latter
remote from the relay X. The current thus passed through the coils is of about
six milliampères, four to six being adequate. The telegraph operator should then
work his key and set the adjustment low; and afterwards take off the short circuit
cell T and reconnect the main line, when it will be found easy to adjust for and
work with a weak current.
A modification of this method would be to introduce a number of cells such as T
in the short circuit without disconnecting the main line current, but this course is
not so simple, it might require many cells to be used, and, if the ordinarily proper
number of cells be employed, it might still not be attended with such favourable
results as the one current method above described. In some cases, however, this
double current method answers, such current being made to pass through the relay
with a combined strength of about four to six milliampères.
When relays are worked after having been at rest sufficiently to enable their
residual magnetism to be discharged, I find that my method is greatly superior in
its effectiveness to what it would be if it were applied to a relay which had not had
such rest and which contained residual magnetism.

page_text: Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed, I claim :-
1. In a relay, the combination, with an electromagnet, of a lever having on one
side of its fulcrum in successive order an armature, contact points and a tension
spring, the last vertically set above the end of the lever, and on the other side of
its fulcrum an arm or extension heavy enough to act as a counterpoise to the
weight on the armature side of the lever and allow the lever to rise against the
back stop under the influence of the tension spring, which is regulated to exert
the desired upward pull, substantially as and for the purposes herein set forth.
2. In a relay, the employment of a horizontally arranged armature lever having
the arm carrying the armature extending beyond said armature, such extended arm
being connected to a vertical spring set above the same and serving to raise said
arm against the back stop when pulling it with the predetermined force, the said
arm and armature falling by their own weight to form the local circuit, substantially
as and for the purposes herein set forth.
3. In a polarized relay, the employment of a horizontally arranged pivoted
armature lever adapted to oscillate vertically between cores placed one above
another, the lever having on one side contact points and a tension spring, the
spring being vertically set above the end of the lever, and on the other side an arm
or extension heavy enough to act as a counterpoise to cause the lever to rise up
against the back stop under the influence of the spring, which is regulated to exert
the predetermined upward pull, substantially as and for the purposes herein set
forth.
4. In a polarized relay having its cores set above one another, the employment
of a horizontally arranged pivoted armature lever adapted to oscillate vertically
between the cores and having the arm carrying the armature extended beyond said
cores, such extended arm being connected to a vertical spring set above the same
and serving to raise said arm against the back stop when pulling it with the
predetermined force, the said arm falling by its own weight to form the local
circuit, substantially as and for the purposes herein set forth.
5. In a telegraphic relay, the improved mechanism substantially as described
with reference to the accompanying drawings.
6. The herein-described method of rendering relays workable with weak currents,
the same consisting in momentarily introducing through the relay (when the main
line current is disconnected therefrom) a current having the same direction and
polarity as the weak current, subsequently reconnecting the weak current and using
this current in working the relay.
7. The herein-described method of rendering relays workable with weak currents,
the same consisting in leaving the weak current in circuit through the relay and of
momentarily combining therewith an additional current of the same polarity and of
sufficient strength.
D