Improvements in Electrical Switches.
Year: 1896

page_text: Improvements in Electrical Switches.
ROOKES EVELYN BELL CROMPTON, Electrical Engineer, and EDMUND ARTHUR
NORMAN POCHIN, Electrical Engineer, both of Arc Works, Chelmsford, Essex, do
hereby declare the nature of this invention to be as follows:-
Our Invention relates to Improvements in Electrical Switches, and has for its
object the prevention of the burning of the contacts by removing the spark which
occurs on breaking contact to a subsidiary contact so made as to be easily renew-
able. We may also minimise the spark occurring at the subsidiary contacts by a
device for giving a quick break.
In carrying out our Invention we take any of the ordinary forms of electrical
switches, for instance those in which the contacts are arranged in a plane and
usually on a flat base of some non-conducting material and over which contacts
a switch arm, or contact lever, passes, either with a circular or straight line motion,
and our Improvement consists in attaching to each of these contacts a subsidiary
contact and attaching to the switch arm, a subsidiary arm. The subsidiary arm
and the subsidiary contacts are so placed with reference to the main contacts and
their switch arm, that on using the switch, the metallic circuit or connection
between each main contact and the switch arm, is broken, before the metallic
circuit or connection between the corresponding subsidiary contact and subsidiary
arm; and that as the motion of the switch is continued, the metallic circuit
between the subsidiary contact and its subsidiary arm, is then broken. Until this
latter break occurs, the circuit, although broken at the main contact, is still main-
tained through the subsidiary contact, but when this break occurs the circuit is
interrupted completely and a spark occurs on breaking.
This Improvement is applicable to switches having one or any number of con-
tacts, and from the description above it will be seen that the sparking which occurs
in switching off, or in passing from one contact to another, in the case of a multiple
contact switch, is not suppressed, but is removed from the main contacts to the
subsidiary contacts. The subsidiary contacts and the subsidiary arm are made 30
as to be easily renewable.
To minimise the sparking which occurs at the subsidiary contacts, the switch is
so constructed that by means of a spring or springs, a very rapid break is obtained.
One method of applying this Improvement is as follows:-
We take a switch of the ordinary multiple contact type in which the contacts are
flat segmental shaped pieces of metal attached to a plane slate base and arranged in
a circle, so that a switch arm pivoted at the centre of this circle can travel over all
the contacts. To each of these contacts and a little beyond the reach of the switch.
arm, we attach a stout metal pin standing up at right angles to the plane of motion
of the switch arm. The subsidiary switch arm is attached to the main switch arm
and carries a spring-controlled metal contact finger. The position of this finger,
is so adjusted with reference to the other parts of the switch, that the main switch

page_text: arm leaves its contact before the contact finger leaves the subsidiary contact, and
that as the motion of the switch is continued the contact finger leaves the sub-
sidiary contact with a rapid action and completes the disruption of the circuit.
It will be seen that this Invention is applicable to other forms of switch than
that described, and also that a rapid break can be obtained by attaching a spring
finger to each contact instead of to the subsidiary arm.
ROOKES EVELYN BELL CROMPTON.
EDMUND ARTHUR NORMAN POCHIN.
ROOKES EVELYN BELL CROMPTON, Mansion House Buildings, Queen Victoria
Street, London, E.C., Engineer, and EDMUND ARTHUR NORMAN POCHIN, Are
Works, Chelmsford, Essex, Engineer, do hereby declare the nature of this inven-
tion 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 Improvements in Electrical Switches, and has for its
object the prevention of the burning of the contacts, by removing the spark which
occurs on breaking contact to a subsidiary contact, so made as to be easily renew-
able. We may also minimise the spark occurring at the subsidiary contacts by a
device for giving a quick break.
In carrying out our invention we take any of the ordinary forms of electrical
switches, for instance, those in which the contacts, are arranged in a plane, and
usually on a flat base of some non-conducting material, and over which contacts
a switch-arm or contact-lever passes, either with a circular or straight line motion,
and our improvement consists in attaching to each of these contacts a subsidiary
contact, and attaching to the switch-arm a subsidiary arm. The subsidiary arm
and the subsidiary contacts are so placed with reference to the main contacts and
their switch-arm, that on using the switch, the metallic circuit or connection
between each main contact and the switch-arm is broken before the metallic cir-
cuit or connection between the corresponding subsidiary contact and subsidiary
arm; and that as the motion of the switch is continued, the metallic circuit
between the subsidiary contact and its subsidiary arm, is then broken.
latter break occurs, the circuit, although broken at the main contact, is still main-
tained through the subsidiary contact, but when this break occurs the circuit is
interrupted completely, and a spark occurs on breaking.
This improvement is applicable to switches having one, or any number of con-
tacts, and from the description above it will be seen that the sparking which
occurs in switching off, or in passing from one contact to another in the case of a
multiple contact switch is not suppressed, but is removed from the main contacts
to the subsidiary contacts. The subsidiary contacts, and the subsidiary arm, are
made so as to be easily renewable.
To minimise the sparking which occurs at the subsidiary contacts the switch is
so constructed that, by means of a spring or springs, a very rapid break is obtained.
One method of applying this improvement is shown in the drawing:-
We take a switch of the ordinary multiple contact type, in which the
contacts "A.A.A. are flat segmental shaped pieces of metal, attached to a plane
slate base, and arranged in a circle, so that a switch-arm "D" pivoted at the centre
of the circle, can travel over all the contacts. To each of these contacts, and a
little beyond the reach of the switch-arm, we attach a stout metal pin "C" stand-

page_text: The
ing up at right angles to the plane of motion of the switch-arm. To facilitate the
renewal of these pins they are preferably screwed into the switch contacts and secured
in position by means of a lock nut, as shown. The subsidiary switch-arm is attached
to the main switch-arm, and carries a spring controlled metal finger "B."
position of this finger is so adjusted in reference to the other parts of the switch
that the main switch-arm leaves its contact before the contact finger leaves the
subsidiary contact, and that as the motion of the switch is continued the contact
finger leaves the subsidiary contact with a rapid action, and completes the disrup-
tion of the circuit. This action is shown in the drawing by the dotted position of
the switch-arm and finger. The main switch-arm has been moved over from the
central to the left-hand contact, but the continuity of the circuit has been main-
tained with the central contact by means of the spring finger and peg.
The
finger in the dotted position is shown just on the point of breaking circuit with
the central subsidiary contact.
It will be seen that this invention is applicable to other forms of switch than
that described, and also that a rapid break can be obtained by attaching a spring
finger to each contact, instead of to the subsidiary arm.
Having now particularly described and ascertained the nature of our said in-
vention, and in what manner the same is to be performed, we declare that what
we claim is:
The use of an electrical switch, when provided with a detachable pivoted spring
finger acting in connection with renewable sparking pieces, or subsidiary contacts
substantially as herein described, whether the switch be of the radial or rectilinear
type, either single or multiple contact, and without making special claim to any
particular form of switch.
11
T1907
ROOKES EVELYN BELL CROMPTON.
EDMUND ARTHUR NORMAN POCHIN.