IMPROVEMENTS IN ELECTRICAL SWITCHES
Year: 1884

page_text: FRANK WYNNE of Palace Chambers in the City of Westminster, in the County
of Middlesex, Engineer and GEORGE CAMERON SILLAR of Kingswood Lodge, in
the Parish of Bexley in the County of Kent Engineer, do hereby declare the
nature of our invention for IMPROVEMENTS IN ELECTRICAL SWITCHES to be as
follows:-
The type of switches or contact makers & breakers to which our Invention
relates, is that in which the electrical contacts are made by means of metallic
surfaces, sliding on one another, for use in electrical circuits in which a novel
arrangement of parts is employed and in which the main contact surfaces are kept
distinct from the parts which are exposed to the destructive action of the sparking
due to the making & breaking of the circuit, and the contacts between the con-
necting wires of the circuit and the parts of the switch are made certain.
In order more clearly to explain the nature of our Invention we premise that an
electrical switch of the sort to which our Invention refers consists essentially of
two metallic terminals which we prefer to refer to as "contact pieces" attached
respectively, by the method we shall hereafter describe to the positive and negative
wires of the electrical circuit and that a metallic tongue, which we shall hereinafter
refer to as a "tongue," moveable on a pivot electrically connects these two or dis-
connects them at will by movement on this pivot. In some cases the pivot is in
permanent electrical connection with the one terminal in which case there is only
one contact piece in the sense in which we herein use it, in other cases the pivot is
separate from either terminal and there are two " contact pieces."
In the switches at present in use the sparking which takes place on making or
breaking the circuit, tends to materially roughen & thus injure the metallic parts
which first come in contact or as we prefer to call them "contact points" in closing
an electric circuit, or which are last in contact in opening the circuit. If then
these contact points which are exposed to this action are allowed to form part of
the main metallic circuit or as we prefer to call "main contact" when the switch
is closed, an element of uncertainty & risk is introduced.
To overcome this, we arrange that our contact points shall be on projecting
pieces which are so arranged and disposed that they come into contact with the
"tongue" before the main contact is made and we arrange that the contact point
or points shall, on completion of the main contact, form no part of this latter and

page_text: "
we also arrange that that part of the tongue which first touched the contact point,
and which we prefer to refer to as the tongue contact, shall form no part of the
main contact and this we do by arranging the contact points so that they shall be
situated on a radius from the pivot of the tongue, which radius is different (either
greater or less) than that of any part of the main contact. The " contact points
shall be of such limited area that the contact of the tongue with the contact points
shall take place (when closing the circuit) so much in advance of the completion of
the main circuit, that when this latter is completed the "tongue contact" shall
have passed completely over the contact points..
In arranging the certain electrical contact, between the leading wires of the
Electrical circuit and the contact pieces, we employ a device which we prefer to
refer to as an "eel grip" & and which consists in inserting the end of the wire in
a slot in a bolt, the said bolt passing freely through a hole in one of the contact
pieces & beyond this and being furnished in this projecting part with a screwed
thread & nut, by means of which, the nut being screwed down on the contact
piece, the bolt is drawn through the latter, as far as the wire which is thereby
pressed against the other side of the contact piece, will allow; the effect of which
is, that by one & the same movement of a screwed nut the wire may be forced into
good electrical connection with the contact piece & with the bolt & the bolt through
the screwed nut forced into good electrical connection with the contact piece.

page_text: COMPLETE SPECIFICATION.
We, FRANK WYNNE of 4, Palace Chambers Westminster, in the County of
Middlesex, Engineer and GEORGE CAMERON SILLAR of Kingswood Lodge, Bexley
in the County of Kent, Engineer do hereby declare the nature of our invention
for IMPROVEMENTS IN ELECTRICAL SWITCHES and in what manner the same is to
be performed, to be particularly described and ascertained in and by the
following statement :-
Our Invention relates to Improvements in switches or contact makers & breakers
in which the electrical contacts are made by means of metallic surfaces sliding on
one another, for use in electrical circuits, in which a novel arrangement of parts is
employed and in which the main contact surfaces are kept distinct from the parts
which are exposed to the destructive action of the sparking due to the making &
breaking of the circuit and the contacts between the connecting wires of the
circuit and the parts of the switch are made certain.
"
Our Invention will be readily understood on reference being made to the drawings
accompanying & forming part of this Specification, in which Figs. i & ii illustrate,
in elevation and plan, respectively, a switch consisting essentially of two metallic
terminals " a. a," which we prefer to refer to as "contact pieces," which are respec-
tively attached in the manner hereinafter described, to the "positive" & "negative
wires of the circuit and consisting also of a metallic tongue "b," hereinafter referred
to as the "tongue," moveable on a pivot, which electrically connects or disconnects
these contact pieces "a. a," at will, by being moved on this pivot. In cases where
we employ only one contact piece "a," we cause the pivot on which the tongue "b"
works, to be in permanent electrical contact with one of the conducting wires or
terminals of the switch, but in most cases the pivot is insulated from the terminals
and two or more contact pieces a. a are employed.
"
In the switches at present in use, the sparking which takes place on making or
breaking the circuit tends to materially roughen & injure those parts, which wo
call contact points or pieces, which first come into contact with one another, in
closing the circuit, or, which are last in contact in opening the circuit. Hence, it is
essential that these parts of the contact pieces or points should not form part of
the electrical circuit; when the switch is closed. In our improved switch, therefore,
we furnish the contact pieces "a. a" with lugs or projecting contact points, "c. c"
and preferably arrange them on the base of the switch, so that they shall be
situated on a radius, from the pivot of the tongue "b," which radius is either
greater or less than that of any part of the main contacts "a. a." Hence, on the
tongue "b" being turned on its pivot, it first makes contact with the projecting
contact points "c. c," at which points the destructive sparking takes place, so much
in advance of the completion of the main circuit, that when this latter is com-
pleted, the tongue "b" shall have passed completely over the projecting contact
points " c. c."
In the sides of the tongue "b," we make recesses, "k. ¹," so that the burr formed
on the projecting contact points, "c. c," by the sparking will not raise the
tongue "b" from its proper position, in which it makes good contact with the
contact pieces:

page_text: .
For making & maintaining an efficient electrical connection between the contact
points "a.a" & the tongue "b," we usually fasten by suitable means, upon the
contact points, springs "f.f" the tendency of which is to grip & clamp tightly the
ends of the tongue, when they rest on the main contact points. In order to pull
the tongue "b" from the contact points." a. a," very suddenly & so obviate the
chance of heating or destructive sparking owing to partial connection, we attach
a spring of some convenient form to the switch such as is shewn in Figs. i. & ii,
where "d" represents a cam &-"e" an ordinary gun lock spring. Another
arrangement which we have found convenient is shewn in Fig: iv, in this case any
suitable spring may be used, in the present instance a spiral spring is shewn and
in this the effect of the attachment is shewn that the spring shall. tend to both
hold the tongue "b" in contact and in breaking the contact, before this is quite
completed, the spring passes a dead point, after passing which its tendency is to
pull the tongue away from the contact.
.
The manner in which we arrange the certain electrical connection between the
leading wires & the contact pieces, by means of what we prefer to term the "eel"
grip, which forms an important part of our Invention, will be readily understood
on reference being made to Fig: iii of the drawings, which shews a section
through A. B. Fig: ii. The leading wire "g" is shewn threaded through the hole
or slot "h" of the bolt "i" which passes through a hole in the contact pieces "a,"
having beyond this a screw thread cut, on to which a running nut "j" having
a slot in its head "Z" fits.
On the wire being inserted in the slot "h" the nut ".
"
j on being screwed down
on the spring "f" & contact piece "a" causes the bolt "i" to be drawn through
the latter, as far as the leading wire "g" will permit, which is thereby pressed
against the other side of the contact piece, the effect of this, is, that by one & the
same movement of a screwed nut "j" the wire "g" may be forced into good
electrical connection with the contact piece "a" & with the bolt "," & the
bolt ""through the screwed nut "j" forced with good electrical connection with
the contact piece "a."
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed, we declare that
what we claim is
(i). In an electrical switch, the combination of a tongue with contact points and
projecting contact points, so arranged that the points which are first brought into
contact in closing the electrical circuit shall not form part of the closed circuit,
when this is properly completed, substantially as hereinbefore described.
(ii). The employment of an arrangement for connecting the wire of the circuit
to the contact pieces and termed herein the "cel" joint, substantially as described.
(iii). The combination of parts in Fig: iv. & consisting of a tongue, contact
points & spring, which spring is so arranged that its tendency shall be to keep the
circuit closed when the circuit is closed and keep it open, when the circuit is open,
substantially as described. .