Improvements in Electrical Switches.
Year: 1897

page_text: Date of Application, 5th Mar., 1897-Accepted, 24th Apr., 1897
COMPLETE SPECIFICATION.
Improvements in Electrical Switches.
We CHARLES MARK DORMAN of Ordsal Electrical Works Salford in the
County of Lancaster, Electrical Engineer, and REGINALD ARTHUR SMITH of
Ordsal Electrical Works Salford 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:-
The object of our improvements is to obtain an increased break and greater
clearance when the switch is in the off position than is usually obtained in switches
of similar size. By means of our improvements we are also able to construct our
long break switch entirely of an incombustible insulator such as porcelain or slate
and metal without the use of vulcanite or fibre. Our improved switch is specially
applicable for use in connection with lamps requiring a pressure of two hundred to
three hundred volts.
Referring to the drawings
Fig. 1 is a side elevation of the switch with the cover in section and the switch
in the on position.
Fig. 2 is a longitudinal section of the switch on the centre line with cover
removed and the switch in the off position.
Fig. 3 is a section of the handle lever and attachments through the centre at
right angles with Fig. 2.
Fig. 4 is a plan of the switch with cover removed and switch in the on position.
Fig. 5 is an end elevation of the switch with cover removed and switch in the
off position.
-
Fig. 6 is a section of part of the base of the switch on the line XX showing
the method of fixing the terminals to the base.
Fig. 7 shows the spring gear detached from the switch.
A is the lever or handle by means of which the switch is actuated. This lever
or handle is made of an insulating material and is enlarged at the end nearest the
switch into a sphere or ball in order that when a cover is used on the switch the
circular hole in the centre of the cover may be always approximately filled up by
the sphere, whatever the position of the handle may be. A metal shaft B passes
through the centre of the sphere forming pivots on which the handle revolves.
The shaft B is pivotted and turns in holes in the metallic brackets or
standards C 1. C 2. These brackets or standards are fixed to the base of the
switch by means of nuts and studs D 1. D 2 as described in our Specification
No. 11143-1893. The shaft B passes through a metallic nut E which is sunk in
the insulating handle as shown. F is a metallic fork. A screw G passes through
the fork F into the nut E and binds the fork F and the shaft B together gripping
them both firmly to the insulating handle A. Instead of the sunk nut E a sunk
stud may be used with a hole in it for the shaft B to pass through and provided
with a screwed end which projects through the hole in the fork F a nut being
screwed on the projecting end to bind the fork F and the shaft B firmly to the
insulating handle A. H1, H2 are the terminals of the switch consisting of
metallic angle plates which are placed at a wide distance apart on the base of the
switch as shown and are clamped down on the base by means of hollow screws
which pass through holes in the angle plates and through part of the insulating

page_text: base into nuts K1 K2 which are inserted into recesses formed in the base from
the side as clearly shown in Fig. 6. The leading wires or cables are led in through
holes from the back of the switch into the holes in the hollow screws where they
are clamped by means of pinching screws. A projection on the angle plates is
turned downwards into a small recess provided in the base to prevent the angle
plates from turning round under the head of the hollow screws. The advantages
of this form of terminal are that it is very firm, no metal parts are exposed at the
back of the base, and the terminal as a whole is compact and does not occupy
much space on the base. L is the moving contact maker which makes and breaks
electrical contact between the terminal plates of the switch H 1. H2. This
contact maker is formed somewhat after the maurer of a fork or sugar tong the
arms of which are at a wide distance apart at the free ends and have a permanent
tendency to open slightly outwards. When the contact maker is forced between
the terminal plates this outward tendency maintains a good electrical contact
between the contact maker and the terminal plates. The sugar-tong contact maker
is hinged on a shaft or spindle M which is supported in holes made in extensions
of the standards C 1. C 2. which are carried downwards for the purpose. As
shown by the drawings the pivotted end of the contact maker is sunk considerably
below the general surface of the insulating base in a recess formed in the insulating
base for the purpose. The object of this is to allow the arms of the contact maker to
turn right outwards from the base of the switch until they are approximately at right
angles to it without fouling the shaft B which carries the handle lever. The arms of
the sugar-teng contact maker L are curved into the form of an are as seen in Figs. 1
and 2. The edges of the standards C 1. C 2 nearest the terminals are also curved in
such a manner as to approximately coincide with the curve of the arms of the contact
maker when in the off position. The result of the whole arrangement is that when
the switch is in the off position there is a very large amount of clearance between
the terminals of the switch and also between the terminals of the switch and the
contact maker or any other metallic parts of the switch. N is a spiral spring
which is coiled round a rod and is held in a state of compression between the
spindles O and P. The rod on which the spring is coiled is free to slide through
a hole in the spindle but is fixed, in the spindle P. The spindle O is pivotted in
holes in the standards C 1. C 2. The spindle P is pivotted in slots in the sugar-
tong contact maker. When the switch is in the on position the spindles O and P
and the spindle M on which the contact maker is pivotted are all approximately in
one line, and the compression spring does not tend to move the contact maker out
from between the terminal plates but as soon as the contact maker is moved round
so as to bring the arms just clear of the terminal plates the spindle P has moved so
far out of line with the spindles O and M that the compression spring has a strong
tendency to turn the arms of the contact maker rapidly away from the terminal
plates into the off position. R is a roller which is pirotted in holes in the arms of
the sugar-tong contact maker. The fork F engages with the roller R and when
the handle lever is pushed backwards and forwards round the spindle B the contact
maker is moved, backwards and forwards in the reverse direction round the
spindle M. The arms of the fork F are so shaped that at the moment when the
contact maker is pushed by the handle just clear of the terminal plates there is a
great amount of, back lash between the fork F and the roller Rand- the contact
maker is consequently free to fly rapidly under the influence of the spring N to a
considerable distance from the terminal plates. The gear in our improved switch
between the handle level and the contact maker consists in principle of a pair of
spur-wheels of very course pitch having a great amount of back-lash between them,
the spur wheel on the contact maker being all cut away with the exception of one
tooth which is represented by the roller R, and the spur wheel on the handle lever
being all cut away with the exception of two teeth with one space between them
which, two teeth and one space are represented by the fork F. The object of
replacing the solid tooth on the contact maker by the roller R is to reduce friction
in working. S is a cross stay which is held by screws or rivets between the

page_text: standards C 1. C 2. This cross stay serves to bind the standards together and
make them more rigid and also acts as a stop to prevent the contact maker
moving too far in the off direction under the influence of the spring N.
The base and handle lever of our improved switch are made of an incombustible
insulating material preferably porcelain. The cover is also preferably made of
porcelain as shown in drawings but can if desired be made of metal of plain or
ornamental design.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
(1.) The improved handle lever constructed of incombustible insulator with
metallic parts attached substantially as and for the purposes described.
(2.) The combination of the improved sugar-tong contact maker with curved
arms and the spiral compression spring substantially as and for the purposes.
described.
(3.) The method of holding down the terminal plate by means of a hollow screw
tapped into a nut inserted in the insulating base substantially as and for the
purposes described.
(4.) The improved switch as a whole substantially as described and shown.
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