Improvements in Electrical Switches.
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improvements in Electrical Switches.
I, EDWARD WILLIAM LANCASTER of Albert Works, Graham Street,
Birmingham 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 :-
The object of this invention is to provide a means whereby the sparking which
usually accompanies the breaking of a circuit is diminished, and the tendency to
form arcs overcome. On a circuit of high voltage (say three hundred or four
hundred volts) such as a four or five wire system there is much difficulty in
obtaining a switch of reasonably small dimensions to break a current of more than
a few amperes without forming an arc. My method of overcoming this difficulty
is to break the circuit at four points a b c d simultaneously on one pole the
contacts a being insulated from the contacts c d. This is carried into effect in
two forms as illustrated in the drawings. In the first form Figs. 1, 2 & 3 I employ
a metal contact bar (squared on to a spindle) but insulated from it by fibre porcelain
ebonite or other suitable insulating material to bridge the contacts a & b. Then
on the other side of the insulating base I fix a similar contact bar on to the same
spindle bridging the contacts c d of which c is connected to by means of a screw
or pin passing through the upper side of the base. The contact d also has a terminal
pin passing through the upper side of the base. The leading wires are connected to
this terminal and to a screw on the contact a so that the course of the current is
from a across the contact bar to d and finally to the other terminal. All these parts
are so arranged that the contact bars leave the pieces a b c & d simultaneously.
A spiral spring encloses and is attached to the spindle and is compressed when
the switch is on the pressure at the contacts being sufficient to prevent the spring
operating but as soon as the bars are forced out of the contacts by means of the
loose handle the spring acts and the bars fly off.
In the second form Figs. 4 5 & 6 I use a large H shaped insulating piece leaving
the two contact bridges on two of its legs. The four contacts are as in the case
before described except that the fixed pieces b c are merged into one and the
cranked contact bars are replaced by shaped pieces embracing the legs of the
insulating H piece. This insulating piece turns on a horizontal pin passing
through a shaped metal piece fixed to the base of the switch. An arched metal
piece carries the handle to which is attached a lever that forces the switch into
contact. The lever in being moved back catches a curved metallic horn on
the H piece the break being made rapid by means of a spring passing round the
spindle and under the H piece. The terminals are solid metal pieces connected to
the outer contacts a d.
In the drawings corresponding parts of the two forms of switch are similarly
lettered.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. The combination of an insulating base and metal pieces for making or
breaking an electric circuit at four points as herein described and illustrated.
Dated this Third day of August 1893.
EDWARD W. LANCASTER.