Breaking of Circuits Conveying Electric Currents.
Year: 1886

page_text: Breaking of Circuits Conveying Electric Currents.
We, CHARLES MARK DORMAN of 24, Brazenose Street, Manchester in the County
of Lancaster, Electrical Engineer and REGINALD ARTHUR SMITH of 24, Brazenose
Street Manchester in the County of Lancaster, Electrical Engineer 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:-
Our invention relates to that class of switch or contact breaker in which a revolving
arm makes and breaks contact between two plates or springs or between a central
boss in which the arm is pivotted and plates or springs.
Our invention consists in an improved method of actuacting the arm and restricting
the positions in which it can be left by the operator and also in improvements in the
arrangement of the parts of the switch embodying the said controlling arrangement.
by which a switch convenient to fix and use and elegant in appearance can be
constructed either of the materials generally in use or entirely of metal and earthen-
ware or other incombustible nonconductor of electricity.
In switches of the nature described it is desirable that when the arm is turned by
the operator to that position in which it establishes contact it shall be firmly held
there by a spring or other means and when turned so that the contact is broken it is
also similarly held. It is also desirable that at the moment the arm breaks contact
a force shall be exerted on it by a spring or other means tending to carry it away to a
safe non-sparking distance.
In our switch these forces are brought to bear on the arm by means of a spring,
which is of such a form that it embraces the spindle to which the arm is fixed and by
acting on a cam or projections at opposite or approximately opposite points on the
spindle exerts a force of the nature of a mechanical couple tending to turn the spindle
and with it the arm in the desired direction.
Referring to the drawings accompanying this specification Fig. 1. shows the switch
in sectional elevation, Fig. 2. is the plan of complete switch, Fig. 3. is the plan with
cover and handle removed. The rest of the figures show the various parts of the
switch detached.

page_text: a. is a spring of steel or other suitable material coiled as shown round the peg or
pillar p. This spring is coiled in such a manner as to act compressively on the
projections c. c. of the spindle b. d is a metallic arm rigidly attached to the
spindle b. which when in the position shown in Fig. 3 makes contact between the
metal plates e and, but when turned round against the stop y ceases to do so. The
relative positions of the spring a and the projections c. c. of the spindle bare such
that when the arm d is fully over in the contact making direction a force of the
nature of a mechanical couple is exerted tending to hold it there; but when the arm d
is turned to the extreme "off" position a couple is exerted tending to hold it against
the stop g; also at the instant when the arm d breaks contact with the plate fa strong
couple exists tending to carry the arm rapidly away to a safe non-sparking position.
A handle or thumb-nut h preferably of some insulating material is attached to the
spindle whereby the switch is operated. When the switch is used for small currents
we prefer to make contact by means of the arm d between the plates e and fas shown
in the drawing but when used for currents so large that there would be a possibility
of an arc forming between the plates e and we prefer to cut off a part of the
plate e at the line y Fig. 5, and ensure a good contact between the arm d and the
plate e through the spring a by clamping the spiral part of it down on the plate e
by means of a projection on the peg p, in any case leaving the central spindle free
from the friction which would be caused were a good electrical contact made directly
between it and the plate e. a. a. Figs. 10 and 11 show elevation and plan of another
form of spring we prefer to use in some cases. The spring in this case is held in
position by two pegs on the plate e. kis a small metallic plate to which one of
the conductors is attached. Between this plate and the plate e a connection is made
by means of a fuzible wire l.
The other leading wire is attached to the plate f. The
screws m₁, m2, m, m₁, m, are preferably passed through clearance holes in the base
from the underside and screwed into their respective plates, nuts and washers being
fitted for the attachment of the various wires as shown.
The case and handle may be made of any suitable material, the one shown in the
figures being designed for manufacture in earthenware. We prefer to form a recess
on the underside of the base as shown in order that the wires may be conveniently
led into the switch.
.
Having now particularly described and ascertained the nature of our said invention,
and in what manner the same is performed, we declare that what we claim is :-
Firstly The combination of a spring with a spindle having a cam or projections
and carrying an arm or arms for the purpose of making and breaking an electric
circuit, the spring being so arranged that it embraces the spindle and by pressing on
the cam or projections at opposite or approximately opposite points exerts a force of
the nature of a mechanical couple tending to urge the arm round in a direction varying
with its position substantially as and for the purposes described.
Secondly The improved switch as a whole substantially as described and shown
in the accompanying drawings.