Improvements in Variable Resistance Devices for Relays, Telephones, and the like.
Year: 1891

page_text: Date of Application, 15th Dec., 1891-Accepted, 16th Jan., 1892
[Communicated from abroad by CHARLES CUTTRISs, of Drexel Building, New
York, United States of America, Electrician.]
Improvements in Variable Resistance Devices for Relays, Telephones,
and the like.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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, is primarily, an improvement in relay instruments of that class
which in response to impulses of current over a line with which they are or may be
connected, produce in a local circuit or in branches of the same a variation of
electrical resistance as distinguished from an actual make and break and by such
means control the amount of current flowing through a suitable receiving
instrument.
The invention involves a device which may be regarded as a rheostat, and
which consists of a resilient body in the form of a wire or strip, preferably of a
resistant material such as carbon, and which is bent or wound upon itself so that
different parts or convolutions may lie in the same lines or planes such as in the
case of a solenoid, volute or spiral. In practice a true spiral form is preferred,
so that as the wire or strip is distended or compressed, different parts of its con-
volutions or spires will be drawn out of or forced into contact to a greater or less
extent depending upon the degree of distension or compression.
Such a device included in an electric circuit between a fixed point of resistance
and a body movable in response to electric or other waves or impulses may be
utilized to vary the resistance of such circuit for the control of a relay instrument
or for other purposes, and constitutes for such purpose a most sensitive and delicate
instrument, well adapted for use in telephones, cable relays and the like. For, in
such applications, the vibrating diaphragm or oscillating armature or coil may be
caused to distend or compress the spiral to a sufficient extent to produce marked
variations in its total electrical resistance without encountering any sensible
opposition or resistance to movement.
In the accompanying drawing the invention is shown as applied to a cable relay,
but it will be understood than in lieu of an armature or coil for imparting movements
to the resistant conductor corresponding to electrical impulses or waves, that a
diaphragm vibrated by sound waves may be employed.
Figure 1 is a plan view, partly diagrammatic, of a cable relay embodying my
improvements.
Figure 2 is an enlarged view of the rheostat or variable resistance detached and
in a modified form.
A designates a permanent magnet provided with concentrating pole-pieces B,
between which a coil of fine wire C is suspended by the usual torsional or similar
supports. The normal position of the coil is that shown, in which the convolutions
lie in planes parallel to the lines of the field of force created by the magnet.
D is a non-magnetic bar that supports a magnetic block or core E, that extends
between the convolutions of the coil and the poles of the magnet A, for the purpose
of concentrating the lines of force.
The coil C is connected with the cable or signalling line of conductors F, and a
current impulse or rise of potential in such line tends to turn said coil out of
parallelism with the magnetic lines. Such deflections, in one direction or the other
according to the direction of the current, are employed to operate the relay
instrument, in the following manner.

page_text: To each side of the coil C is connected by a fibre one end of a carbon spiral G, G¹.
The opposite ends of these spirals are connected in a similar manner with
adjusting stops or screws H, by means of which the tension of the spiral may be
adjusted.
The spiral Gis connected electrically by a wire K with one of the poles of
a local battery L, and the other end is connected with the opposite pole of
the battery through a wire K', an adjustable resistance R, and a wire M. The
spiral G has one end connected to the battery L by wire N, and the other
end to the opposite pole of the same by wire N¹, adjustable resistance R' and
wire M.
The receiving instrument S is connected up in a bridge between the wires K'
and N¹.
In the operation or use of this instrument a rise of potential on the main line
will deflect the coil C in a direction, say, to distend the spiral G and permit
a closer contact of the spires of C. The resistance of the branch of the local
circuit including the spiral G, the wire K', and resistance R, will, therefore, be
considerably increased, while the resistance of the other and corresponding branch
will be reduced so that the previously adjusted balance on the bridge P being
disturbed, current will flow through the same from N₁ to the battery through
resistance R.
The opposite effect will obviously be produced by a line current of opposite
direction, and the receiving instrument, of whatever character it may be, will
respond immediately to all impulses or variations of potential on the main line.
In lieu of the suspended or pivoted coil C, an armature or bar actuated by an
electro-magnet may be employed. This is indicated in Figure 2, in which
T designates an armature and Van adjustable support.
In such cases it is
desirable to attach buttons or studs W to both the armature and the adjustable
support which enter the ends of the carbon spiral W and are secured thereto.
The spirals are made by winding a carbonized strip spirally around a suitable
former or mandril and carbonizing the same in a muffle, in a manner similar to
that followed in the manufacture of carbons for incandescent lamps.
It may,
however, be prepared in any other way, it being only necessary that it should have
a certain degree of elasticity or resiliency, and so that under the influence of the coil
or other device moved by electric or other waves it may be distended or compressed
so that its spires, or in general the different parts of its surface, may close upon
themselves or be forced into more or less intimate contact, whereby the resistance
of the strip as a whole will be varied in accordance with such movements or
vibrations.
The spirals may be composed of other materials such as are known in the art to
be capable of producing the same or similar results, and it is desirable in most cases
that they be square or rectangular in cross-section in order to secure as broad and
even a surface of contact as possible between the different parts. A very excellent
conductor for this purpose may be produced by carbonizing a strip of vulcanized
fibre.
The main feature which distinguishes this rheostat or variable resistance device
from the solid carbon buttons, or the cushion electrodes composed of agglomerated
pieces or particles of conducting material heretofore used in such instruments is
that by the movement imparted to it the extent as well as character of superficial
contact is varied and such variation is attended by a true short-circuiting of the
intermediate conductor, gradual in character. A further feature and one of
importance is that the movement of one part of the conductor with respect to
another is effected with little or no opposition.
It is evident, since the function of the fixed or stationary support for the spiral,
aside from its capability of adjustment, is merely to oppose the movement of the
coil or equivalent moving part, that when such means of securing greater range of
movement, as two coils or the like moved in opposite directions by the same
electric or other impulse, is employed, that the ends of the spiral may be connected

page_text: to the two coils respectively, and the stationary support becomes an imaginary
point.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed as communicated by my
foreign correspondent I declare that what I claim is :-
First. A sensitive rheostat or device for varying the resistance of an electric
circuit, composed of a resilient conducting strip included in the circuit to be varied
and wound or bent in symmetrical convolutions or spires, in combination with a
stationary support and a body movable in response to current or other waves or
impulses, the ends of said conducting strip being respectively connected to the
stationary support and movable body, as set forth.
Second. The combination, with a moving coil or other device capable of moving
or vibrating in response to current or other waves, of a carbon spiral connected
therewith and included in the circuit of a receiving instrument and adapted to be
compressed and released by such movements.
Third. The combination, with a device such as a coil adapted to be moved in
response to current waves or impulses in an electric circuit, of a local circuit, a
receiving instrument therein and one or more resilient resistant conductors included
in the local circuit and connected to the said coil and to a stationary support
respectively, said strip being bent or wound in spiral form, as herein set forth.
Fourth A relay instrument, comprising in combination a coil or device to be
moved by currents in the main line, of a carbon strip wound spirally upon itself and
adapted to be distended or compressed by the moving coil and included in the local
circuit for varying the resistance in the same, as set forth.
Fifth. The combination with a coil movable in response to currents in a main
circuit, of a divided local circuit, a distensible carbon spiral in each branch of the
same connected with the movable coil on opposite sides of the axis of the same, and
a receiving instrument in a bridge between the divisions of the local circuit.
Sixth. In a relay instrument, the combination with a permanent magnet and a
suspended coil movable on an axis between the poles of said magnet, of two spirally
wound carbon strips connected at opposite ends to adjustable supports and to the
coils on opposite sides of its axis respectively, and included in branches of a local
circuit and a receiving instrument in a bridge between the same, as set forth.
Dated this 15th day of December 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.