Improvements in Electric Switches.
Year: 1892

page_text: Date of Application, 14th June, 1892-Accepted, 16th July, 1892
COMPLETE SPECIFICATION.
Improvements in Electric Switches.
I, FRANCIS BROADNAX, Engineer, a citizen of the United States, residing at
No. 221 West 133rd Street, in the City of New York, in the County and State of
New York, do hereby declare that 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:---
"
My invention relates more especially to that variety of electric switches known as
"double-pole switches by which both poles of the circuit are simultaneously
disrupted or closed. The novel features of my invention will be separately pointed
out in the claims concluding this Specification.
Referring to the accompanying drawings,
Fig. 1 is a transverse vertical section through a switch embodying my present
invention, taken on the dotted line of Fig. 2.
Fig. 2 is a horizontal section through the switch, on the dotted line ¹¹ Fig. 1.
Fig. 3 is a plan of the switch turned bottom side up.
Fig. 4 is an elevation of one pair of contact plates and the conductor uniting
them.
Fig. 5 is an elevation of the rotating cam carrying the contact plates.
Fig. 6 is a perspective of a coupling piece and. attendant parts.
I will now describe the structure illustrated in the accompanying drawings,
which show a good practical form of double pole switch involving all the novel
features of my present invention.
A is the body or base piece of the switch. It is made wholly of glass and has
attached to it the coupling pieces c, each of which is fitted with a binding screw d.
These coupling pieces are bored and screwthreaded both horizontally and
vertically, so that the line wire e may be introduced and clamped therein either from
the sides or bottom. The binding screw d¹ fits both screwthreaded perforations.
It will be seen that on the left hand side of Fig. 1 the line wire e enters from the
side and is held by a binding screw inserted in the vertical screwthreaded hole
from above while on the right hand side of said figure the conductor enters from
beneath and is held in place by the binding screw. inserted horizontally from the
side. It is plain from the drawings that the conductor on the left hand side might
be inserted and clamped as shown on the right hand side and that the conductor on
the right hand side might be inserted and clamped as shown on the left hand side of
Fig. 1; or that both conductors might enter from the sides or both from below.
This feature is. very advantageous as by a simple device it permits the conductors
approaching the switch vertically or horizontally to be clamped therein without
bending.
The coupling piece has mounted upon it a standard c to which the contact
brush F is attached in any suitable way. This is shown in detail in Figure 6.
D is a rotating cam. It is attached to the base in the ordinary manner by a spindle
which permits the cam to be freely rotated on its axis, said spindle being provided
with, a thumb piece S taking on the upper screwthreaded end thereof. G is a
cover also preferably made of glass which may be removed when: the thumb piece.S
is unscrewed.
The rotating cam D is also made of glass and into or onto it are set the contact
pieces E. As shown in Fig. 4 these plates are arranged in pairs electrically
connected together. The conductor which connects them is curved so as to avoid
making contact with the spindle of the cam. The connecting conductor of one
pair of plates is at the top and the connecting conductor of the other pair at the
bottom, so that they may cross without touching. The standards. c projecting

page_text: from the coupling pieces c, carry the contact brushes F. The cam D is preferably
made in a mould into which the contact plates are first set in position, the glass being
then cast around and upon them. In this way they are firmly held in position,
without the use of screws or other equivalent devices; and extending as the
connecting conductors do through the body of the cam piece itself they cannot be
detached therefrom while the cam remains intact.
A
The rotating cam D has its periphery cut into eight separate faces. Each
alternate face is fashioned in the arc of a circle, the center of which is the line
about which the cam revolves, and is provided with a contact plate E. The
contact plate docs not extend the entire width of the face on which it is set.
small ledge 2 of the conducting material of which the body of the cam is formed
projects beyond it. This ledge which is flush with the face of the contact plate,
prevents the brush cutting and making irregular the edge of the contact plate as it
leaves it, not only increasing the life of the parts, but also diminishing sparking at
this point. It also prevents the establishment of an arc between the brush and
contact plate when they are separated without increasing the depth of the step, by
interposing between the two a barrier of solid insulating material. Every alternate
face is of non-conducting material, in this case being the material of which the
body of the cam is made. Each insulating face is fashioned so that at one end it is
a greater distance from the centre of the cam than at the other end. The brushes F
are preferably curved so that they bear for a considerable distance upon the
contact plates, and as these plates are a segment of a circle of which the spindle of
the cam is the centre, the brushes present an equal surface in contact with the
plates during a considerable rotation of the cam and there is no force exerted
tending to cause the cam to revolve in either direction when the brushes rest upon
the contact pieces. The intermediate insulating faces being inclined permit the
periphery with its contact surfaces formed as described to be cut into a series of
steps dividing contiguous surfaces. The ledge of insulating material 2 prevents
accidental contact between a brush and a contact plate when the cam has been
rotated to break circuit.
In switches of this character it is desirable to have as much of the conducting
material enclosed in insulating material as possible and to have the contact pieces
of a given pair remote from each other, to avoid short circuiting and uncertain
insulation and to obtain absolute certainty in simultaneously closing and disrupting
both poles of the circuit. By the arrangement above described I am able to
provide a switch in which only the actual contact surfaces of the plates are
exposed, the conductors joining the plates of each pair being completely
surrounded by and imbedded in insulating material. As the conductors joining
the plates of each pair are of irregular shape, being in the form of a loop, the
metal parts of the switch are held more securely in position by the glass itself
when moulded upon and around them. A consideration of Fig. 2 will show that
the contact plates on the cam in electrical connection with each other are on
opposite sides of the cam and are separated from each other on both sides by three
faces, the connecting link between the two passing directly through the body of the
cam as described.
Having thus particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, what I claim is :-
1. In a double pole switch, a rotating cam provided with a series of faces of
conducting material-such as metal-and non-conducting material-such as glass-
in the form of steps, the contact plates of each set being placed diametrically
opposite each other and connected together by a conductor upon and around which
the insulating material of which the cam is formed is moulded.
2. In an electric switch, a rotating cam provided with a series of faces of con-
ducting and non-conducting material in the form of steps, the conducting faces
being provided with an insulating ledge 2 extending beyond and flush with the
conducting plate.

page_text: 3. In an
electric switch, a coupling piece provided with a plurality of
intersecting screwthreaded apertures having an angular relation to each other,
combined with a suitable set screw.
4. In a double-pole switch, & rotating cam provided with a series of faces of
conducting material-such as metal-and non-conducting material-such as glass-
in the form of steps, the contact plates of each set being placed diametrically
opposite each other and connected together by a conductor of irregular form upon
and around which the insulating material of which the cam is formed is moulded.
Dated this 14th day of June 1892.
CHEESBROUGH & ROYSTON, Fels. Chart. Inst. P.A.,
15, Water Street, Liverpool, Applicant's Patent Agents.