Year: 1885

page_text: I, FRANK WYNNE of 112, Belvedere Road, Lambeth, in the County of Surrey,
Electrical Engineer, do hereby declare the nature of this invention, to be as
follows:-
:-
My invention relates to that class of electrical switches or contact apparatus in
which a spring toggle joint is employed to retain a contact piece in either of its
two extreme positions, and to provide that it is in unstable equilibrium or out of
equilibrium in any intermediate position.
The principal feature of my invention consists in obtaining this toggle-action by
the alternate greater or less compression of a continous helical spring placed
across the line of motion of the contact piece or pull or push piece and fixed or
secured at both ends.
In the following description reference will be made to the accompanying
drawings which illustrate various forms of switches embodying my invention.
Fig. 1 is a vertical section of a switch as applied to an electric incandescent lamp.
Fig. 2 is a side elevation of the same after removal of the attachment pieces and
ornamental cover. Fig. 3 is a face view, Fig. 4 a horizontal cross section and
Fig. 5 a vertical cross section of a switch provided with glass cover and adapted
to be attached to a wall (or table).
Fig. 6 is a face view and Fig. 7 a cross section of a switch similar to Fig 3, 4
and 5 but provided with different contact pieces. Fig. 8 is a front elevation,
partly in section, and Fig. 9 a horizontal section of a switch in which the helical
spring, instead of being directly controlled by a pull piece or push piece, is actuated
by a tap or key provided with a lever arm acting on the helical spring through
suitable mechanism. Figs 10 and 11 are detail views of Fig. 3.
In all figures the same letters designate identical or corresponding parts.
A and B are a pair of fixed metallic contact pieces or plates connected with the
terminals of the conducting wires; C is a movable metallic contact piece serving
to establish electric connection between the stationary pieces A and B when the
circuit is to be closed. c is a pusher, hereinafter called " contact rod". preferably of
insulating material and serving to put the movable piece C in and out of contact
TD 031
•

page_text: with the stationary pieces A and B. D is the helical spring resting at both
ends d, d, on abutments or pivots or in recesses of the switch casing, and forming
in the centre with the contact rod c a spring toggle joint adapted to push or pull
the latter in the direction of its length. In its middle position the spring is
perpendicular to the contact rod and compressed. But when brought out of this
state of unstable equilibrium, either to the right or to the left, it will expand by its
reaction so as to be less compressed and form a bow, thereby throwing the contact
rod c into one or other of its extreme positions and retaining it therein until the
switch is reversed by an external force acting on the contact rod or movable
contact piece.
In the drawings the spring D is shown as passing through a perforation of the
contact rod, but instead of this arrangement I may employ two parallel springs
acting on the sides of the contact rod, or the arrangement illustrated by Fig* 8
and 9.
The contact rod may be guided in a straight line, preferably by allowing it to
pass diametrically through the walls of the casing E, so as to form a double push
and pull switch.
The shape and arrangement of the contact pieces, the means for operating the
movable contact piece from the outside, the shape and construction of the casing,
may vary to suit individual requirements. The same helical spring and contact
rod may also be adapted to open and close alternately two different circuits.
In Fig 1 and 2 the stationary contact plates A B are situated on the same side
of the contact rod and provided with facings a, b which touch the movable contact
piece C when the latter is in one of its extreme positions.
The ends of the contact rod cc may be made of non-conducting material screwed
on to the metallic piece C and projecting through the walls of the casing.
In Fig 3 and 4, the contact piece is a wedge-shaped metallic sleeve or shoe
mounted on the rod c. The stationary contact pieces A and B are situated right
and left of the rod c. They are provided with symmetrically inclined contact
faces a, b placed so that the shoe or block C fits between them like a wedge. c¹ is
preferably an inclined projection at the base of the shoe C, the object of which will
be described later on. e, e are slots formed in the casing E diametrically opposite
each other and serving to guide the contact rod c in a straight line. F and G are
terminals each of which is connected with one of the contact plates A, B and one
of the conducting wires. His a glass plate and I a ring screwed on to the casing E
and serving to hold the glass plate.
The contact plates A and B have projections a¹ and 61 placed so, that in closing
the circuit, contact is first made through the projections a¹, b¹ and c¹, (before the
wedge-shaped surfaces come in contact with each other) and that in breaking the
circuit, the said projections remain in contact for a moment after the contact
between the principal contact surfaces a, b and C has already ceased. The
advantage of this arrangement is, that sparks and the accompanying roughening of
the metal do not take place on the principal contact surfaces, but between the
temporary or auxiliary contact surfaces a¹ b¹ aud c, the latter thus protecting the
surfaces a, b and C from destruction. Fig. 10 and 11 are detail views of a switch
as shown by Fig. 3, the former with and the latter without the projections a¹, b¹
and c¹.
In Figs 6 and 7 the stationary contact pieces are formed by dished or corrugated
springs A and B, and instead of a movable contact piece, there are two spherical
contact pieces C mounted or formed on a metallic contact rod c. The latter is
guided in the insulated casing E and conducts the current from A to B, when the
spherical pieces C are bedded in the springs A. B.
This arrangement shares to a certain extent the advantages obtained by the
projections a, b and c described with reference to Fig. 3 and 10, the points of
the dished springs A and B corresponding to the projections a¹ and b¹.
In Figs 8 and 9 the stationary contact pieces A and B are again situated on the
same side of the movable contact piece C. The contact rod is replaced by a key J

page_text: adapted to turn on its axis and provided with a radial arm j passing through a
ring c fixed in the side of the contact piece C.
The contact piece C is moved to and fro by turning the key. K and L are a pair
of springs serving as terminals, each being connected with one of the pieces A, B.
One of the fixed contact pieces may be omitted, and the corresponding terminal
joined to the movable contact piece by a flexible wire or equivalent connection.
I am aware, that switches, in which two springs are symmetrically placed on
opposite sides of a contact rod, have been constructed before, but I am not aware
that switches with symmetrical spring toggle action produced by a continuous
spring and so arranged as to force the contact piece into or away from its contact
as required, have been made or known.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
1. In a switch for making and breaking electric contacts, a continuous helical
spring in more or less compression held at its extremities and arranged so that in
the middle position or when the axis of the spring forms a straight line the spring
is in compression and in a state of unstable equilibrium, and that any deviation to
the right or to the left (the axis of the spring forming a slight curve) will cause
the spring to assume one or the other of two extreme positions, where the spring is
in stable equilibrium and forms a curve, the said spring carrying at or near its
centre a contact piece which in one of the extreme positions of the spring makes
contact with one or more stationary contact pieces and thereby closes an electric
circuit..
2. The combination of a continuous helical spring D in a state of greater or less
compression fixed at both ends and adapted to operate as described, with a contact
rod c and one or more movable contact pieces C, guided in a straight line perpen-
dicular to the axis of the spring, and one or more fixed contact pieces A, B
substantially as described and illustrated by Fig 1 to 7.
3. The combination of a continuous belical spring D fixed at both ends and
adapted to operate as described, with a movable contact piece C carried in or near
the centre of the spring, one or more fixed contact pieces A B, and a key J adapted
to act on the movable contact piece from the outside, substantially as described
and illustrated by Figs 8 and 9.
4. In a switch adapted to operate by spring-toggle action, contact pieces having
wedge-shaped or inclined surfaces, substantially as described and illustrated by
Figs 3 and 4.
5. In a switch, adapted to operate by spring toggle action, contact pieces
provided with temporary or auxilary contact surfaces for the purpose of preventing
destruction of the principal contact surfaces, substantially as described and
illustrated by Fig 3, 6, 7 and 10.