Improvements in Electrical Switches.
Year: 1894

page_text: Date of Application, 11th July, 1894-Accepted, 11th Aug., 1894
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:-
Our improvements relate to that class of switch consisting of a lever pivoted in.
the centre, one end of the lever forming a handle and the other end carrying a
contact device for making and breaking an electric circuit.
Our improvements consist of a new arrangement of spring for controlling the
position of the lever, also of improved methods of constructing the lever with
insulated contact pieces, and also in an improved arrangement of the parts as a
whole.
Referring to the drawings
Fig. 1, 2, and 3 are diagrammatic views of three forms of lever switch with our
improved arrangement of spring.
Figs. 4, 5, 6, 7, 8, 9, 10, 11 shew various forms of spring suitable for our improved
arrangement.
Figs. 12 and 13 shew a complete switch fitted with our improved arrangement of
spring and improved lever.
Figs. 14, 15, 16 and 17 shew our improved levers.
Referring to Fig. 1. A. is a lever which turns on a pivot B. The lower end of
the lever carries a contact device which completes the circuit between two terminal
plates C1. C 2. one behind the other in the drawings with the contact maker between
them. D is a spring of a V form the arms of which bave a permanent tendency to
open outwards. The two ends of the spring E1 E 2. form or are provided with
bearings or pivots round which they can turn in the same plane, or in a plane
parallel to that in which the lever A moves. One end E 1 of the spring is pivoted
on the lever A. at the same side of the fulcrum as the contact device and the other
end E2. of the spring is pivoted to a fixed point near the contact end of the lever.
The part of the spring from which the arms radiate is unconstrained except by the
pivoted ends and when the lever is moved travels in a circular path round the fixed
pivot E 2. It will be seen that when the lever is moved into such a position that
the point E 1. lies on a line drawn between the pivot B. and the point E 2, owing
to the outward pressure of the arms of the spring the lever is in a state of unstable
equilibrium.
If the lever is moved so that the point E 1 is slightly on that side of the same
line next the contact terminals the spring at once exerts a pressure tending to
carry the contact end of the lever between the terminals, but if the lever is moved
so that the point E 1. is slightly on the other side of the same line the spring at
once exerts a pressure tending to carry the contact end of the lever away clear of
the terminals. The best position for the points E1 and E2 is such that at the
moment when the contact end of the lever is leaving the terminals the point El is
well over the line joining B and E 2 on the side furthest from the terminals and
the spring consequently tends to produce a very quick break, but when the contact
end of the lever is right home between the terminals the point E 1 is slightly over

page_text: on the opposite side of the line so that the spring has a tendency to hold the lever
between the terminals.
Fig. 2 shews the application of our improved spring arrangement to a modified
form of lever. In this case the lever is formed in two parts A 1 forming the handle
and A 2 carrying the contact device, both hinged on the same pivot B. either end
of the lever being free to turn through a certain arc without the other. The
length of the arc is determined by stops. The effect of this arrangement is that
when the contact end of the lever is pulled clear of the terminals it is free to dart
rapidly away under the influence of the spring however slowly the handle is turned,
as described in, Holmes' Specification 3256-1884.
Fig. 3. shews the application of our improved spring arrangement to another
modified form of lever. In this case the lever is also formed in two parts A 1.
forming the handle and A 2. carrying the contact device, both hinging on the same
pivot B. either end of the lever being free to turn through a certain arc without
the other. The two parts of the lever overlap one another at the side of the pivot
next the contact device, and are both pierced with a slot in the form of an arc,
both struck at the same distance from the centre of the pivot B. The end E 1 of
the arm of the spring is pivoted through these two slots and is both free to turn
round in the same plane, or in a plane parallel to that in which the lever turns, and
also to move from end to end of the slots. A slide block or other suitable
arrangement can, if desired, be inserted in the slots for the pivot to turn in. It
will be seen that the effect of this arrangement is that the pivot E1 can be pushed
across the line joining B and E 2. by means of the handle end of the lever in
advance of the contact end of the lever and that the contact end of the lever will
then be free to fly rapidly either in the "on" or "off" direction according to the
motion of the handle through an arc regulated by the length of the slots or if
preferred by fixed stops.
Any kind of spring is suitable for our improved arrangement either formed from
one piece of metal or built up of several parts, providing that when looked at in
the same direction as in Figs. 1. 2. and 3. it is of a bowed or U or V form and that
the pivoted ends have a tendency to fly apart.
If desired one or both of the arms
can be formed in duplicate. Figs. 10 and 11 shew a form of spring with one of the
arms in duplicate, for duplicate bearing.
Figs. 14 and 15 shew our improved method of building up the lever for a switch
of the type shewn in Fig. 1. It will be seen that the lever is formed of a piece of
flat metal twisted round at one end through an angle of ninety degrees to form a
handle or palm which may be operated by the thumb or finger. The contact
pieces F 1. F 2. are formed of two metallic plates connected by a screw or rivet and
insulated from the other parts of the lever by means of an insulating bush and
washers.
Figs. 16 and 17 shew our improved method of building up the lever for a switch
of the type shewn in Fig. 2. It will be seen that the end of the lever A 1 forming
the handle is turned or formed of a round section and suitable shape for handling
and is slotted to receive the end of the lever A 2 which is formed of flat sheet
metal with insulated contact plates same as the lever shewn in Figs. 14 and 15.
The contact end of the lever A 2 can turn on the pivot B through a certain arc
regulated by the stops H 1. H 2. independently from the handle end.
Our improved spring arrangement is applicable to any form of lever generally in
use or of ordinary construction with any form of contact device with or without
insulating device as well as to the improved forms of lever described in this
Specification.
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Fig. 12 is a sectional elevation and Fig. 13. is a plan with cover removed of our
improved lever switch with improved spring arrangement and the improved lever
shown in Figs. 14 and 15.
It will be seen that the improved arrangement as a whole is particularly
applicable to switches of small size which are covered by metal domes the handle
end of the lever only projecting through the cover.

page_text: 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. A lever one end of which forms a handle and the other end is provided with a
suitable contact device for making and breaking an electric circuit the fulcrum
being between the handle and the contact device combined with a spring of a
bowed or U or V form the arms of which have a permanent tendency to open
outwards the two ends of the spring forming or being provided with bearings
or pivots round which they can turn in the same plane, or in a plane parallel
to that in which the lever moves one end of the spring being pivoted on the
lever at the same side of the fulcrum as the contact device and the other end
being pivoted to a fixed point near the contact end of the lever in such a position
that the outward pressure of the arms of the spring tends to hold the lever
over both in the "on" and "off" position but at the moment of breaking contact
tends to draw the contact end of the lever rapidly away from the fixed terminal
or terminals the middle part of the spring being unconstrained except by the
pivoted ends substantially as described and shewn in diagrammatic Figure No. 1.
2. The modification of the above arrangement substantially as described and
shewn in diagrammatic Figure No. 2.
3. The modification of the above arrangement substantially as described and
shewn in diagrammatic Figure No. 3.
4. The improved methods of building up the levers with insulated contact plates
substantially as described and shewn in Figures 14, 15, 16 and 17.
5. The switch as a whole substantially as described and shewn in Figures 12. 13.
14. 15. 16 and 17.
Dated this 10th day of July 1894.
CHARLES MARK DORMAN.
REGINALD ARTHUR SMITH.