Improvements in Electrical Switches.
Year: 1896

page_text: Date of Application, 9th June. 1896
Complete Specification Left, 22nd Mar., 1897-Accepted, 24th Apr., 1897
PROVISIONAL SPECIFICATION.
Improvements in Electrical Switches.
GEORGE SENIOR Junr. Instrument Maker 30, Caithness Road Brook Green, W.
THOMAS DUNCAN DUNDAS Electrical Engineer Manager of the British Elec.
Mfg. & Eng. Co. Ltd. 44, Blythe Road London W. do hereby declare the nature
of this invention to be as follows:-
This invention relates to a form of switch for electrical purposes so designed as
to ensure an absolutely quick break without a "loose handle" & a definite on & off
position.
The movable contact is so designed that it is held by a spring between the two
arms of a hollow sector-shaped lever which is capable of motion radially, being
pivotted at its smaller end to which is fixed the end of the spring carrying the
movable contact. Suitable jaw contacts are arranged which are short circuited by
the movable contact mentioned above.
Thus when the lever is rotated in the action of switching on, it carries with it
the movable contact & this being forced in between the above jaw contacts, is in a
fixed position, the spring exerting no influence.
And when the lever is rotated in the action of switching off, it gradually draws
away the movable contact, but the friction offered by the jaw contacts produces a
tension in the spring, which (tension) enables the movable contact to fly out as soon
as it overcomes the friction.
When in this position a spring working against a flat on the heel of the lever
locks it in a fixed position.
Deted this 20th day of April.
G. SENIOR, JNR.
T. DUNCAN DUNDAS.
GEORGE SENIOR, Junr., Instrument Maker 30, Caithness Road Brook Green, W.
THOMAS DUNCAN DUNDAS Electrical Engineer, Manager-the British Electrical
Mfg. & Eng. Co. Ld. 44 Blythe Road 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:-
This invention relates to improvements in electrical switches. Switches made in
accordance with this invention are so constructed that they have an absolutely
quick break without a loose handle, & a fixed "on" & "off" position.
The better to explain this invention reference is made to the accompanying
drawings, Fig. I being a side elevation; Fig. Il a plan; Fig. III a front elevation;
& Fig. IV a detail of sector-shaped lever & movable contact.

page_text: Fig. I shows the sector shaped lever "A," to which is firmly secured at "B" a
spring "C" carrying the movable contact "G."
Now the position of the lever "A" (which is pivotted at "F") as shown in the
full lines of the drawing Fig. I, represents the switch in the "on" position, i.e. the
movable contact "G" (Fig. III) has short circuited the fixed contacts "H," "H"
& the switch is in a fixed "on" position the spring "C" exerting no force on the
movable contact "G" (Fig. III).
And when the lever "A" is rotated in the action of switching off & takes up
the dotted position shown in Fig. I., it carries with it the spring "C"; but the
motion is imparted at once (by the rotation of the lever "A") to the movable
contact "G," yet the friction offered by the fixed contacts "H," "H" (Fig. III)
retards the movable contact "G" till it is overcome by the tension produced in the
spring "C." Should the tension be insufficient to throw the novable contact out;
the lever "A" must draw the contact "G" out & an absolutely quick break is
obtained.
When the switch is in the "off" position Fig. I a spring "S" working against
a flat "I" on the heel of the sector shaped lever "A" holds the switch in a fixed
"off" position.
Having now particularly described and 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. The use of a sector-shaped lever as described.
2. The combination of a sector-shaped lever with a spring & movable contact as
described.
3. The improved electrical switch, substantially as described & set forth in the
accompanying specification & drawings.
Dated thie 22nd dex of March 1897
GEORGE SENIOR, JNR.
THOMAS DUNCAN DUNDAS.