Improvements in Switches for Electrical Purposes.
Year: 1890

page_text: Date of Application, 13th Nov., 1890-Accepted, 20th Dec., 1890
COME DETE DI MULETUATION.
Improvements in Switches for Electrical Purposes.
We BERNARD MERVYN DRAKE and JOHN MARSHALL GORHAM Electrical Engineers,
both of No. 66 Victoria Street in the City of Westminster S.W. 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 :-
The object of our invention is to provide an improved form of contact for electric
light switches.
In our Specification No. 15658 of Dec. 19th 1885 we described a contact formed
by a severed ring, the contact being formed by the insertion of a metal bar into the
aperture cut in the ring. We find however that under certain conditions we are
unable to obtain a sufficiently elastic action with this form of contact, and our present
invention relates to a new form of "spring" contact which enables any required
amount of elasticity to be obtained.
The spring contact is of U section the ends being bent outwards to form the contact
& a screw is arranged between the two sides of the U to press them outwards for
adjustment.
The contact bar of the above section may be either cast or built up of a number of
laminated sheets pressed or stamped to the desired shape. In some cases it is more
convenient to sever the contact bar at the back & screw it in two halves on to a handle
or a lever
Referring now to the accompanying drawings, (shews the special form of the
spring contact which is carried by a bolt E and when pressed down by the handle F
mounted on the same centre a circuit is completed between the contacts B. B. which
are fitted with the usual terminals or sockets arranged to carry away the current.
An adjusting screw D enables the spring contact bar to be adjusted so as to provide
for any wear.
An additional advantage of the arrangement shewn is that the current is carried by a
continuons conductor instead of through contacts on a spindle which are liable to cause
a bad contact & heating.
The switch is also titted with a spring G arranged to push the lever upwards into
the dotted position shewn. When pressed downwards by the handle the friction is
sufficient to overcome the force exerted by the spring providing the contacts are
properly adjusted.
Should however, there be any wear & a loose contact be made the switch will refuse
to stop on, and the attendants attention will be drawn to the fact that the friction
must be increased by the adjusting screw. The arrangement also renders it impossible
for the switch to be left partly on.
Having now particularly described & ascertained the nature of our said inven-
tion & in what manner the same is to be performed we declare that what we
claim is:
1. In an electrical switch a spring contact bar of the special section shewn, the
ends being turned outwards substantially as hereinbefore described.
2. In an electrical switch having a spring contact bar or bars as described; the
method of mounting the bar on a spindle passed through both sides so as to provide a
continuous conductor between the two contacts of the switch; the arrangement and

page_text: combination of parts in the switch as hereinbefore described & illustrated by the
accompanying drawings.
Dated this 12th day of November 1890.
BERNARD MERVYN DRAKE.
JOHN MARSHALL GORHAM.