Year: 1888

page_text: We, CHARLES MARK DORMAN of 24, Brazenose Street Manchester in the County
of Lancaster, Electrical Engineer, and REGINALD ARTHUR SMITH, of 24, Brazenose
Street, Manchester, in the County of Lancaster, Electrical Engineer do hereby
declare the nature of this invention and in what manner the same is to be performel,
to be particularly described and ascertained in and by the following statement :-
Our invention relates to that class of Electrical Switches, Cut-outs, Ceiling and
Wall Connectors which are mounted on Porcelain, slate or other incombustible bases,
and refers principally to the method of attaching the cover to the base, and also in
the case of switches to an improved method of pivoting the contact arm.
Our invention consists principally in enclosing the switch, fuse, connector or other
similar fitting in a light metallic box or case which is preferably stamped, pressed or
spun out of sheet metal. The base of this box is generally held to the wall, ceiling,
or other surface to which the fitting is attached by screws which pass through the
insulating base. A large central hole is usually pierced out of the flat bottom of the
metallic base for convenience in leading in the wires. The lid of the case fits on
to the base like that of an ordinary canister and in the case of switches, connectors
and similar fittings has a central hole through which the handle, connecting plug, or
wire passes.
In the case of ordinary ceiling connectors this hole is plugged with an
insulator where the wires pass through.
We sometimes altogether dispense with the metallic base of the case, the lid then
being attached to the insulating base by bayonet slots in the lid gearing with flat
springs projecting beyond the edge of the insulating base into the said slots. These

page_text: springs generally resolve themselves into a single flat spring girder passing under the
insulating base and attached thereto by means of screws, rivets or bolts.
Referring to the drawings accompaning this specification Fig. 1 is a section on
the line X. X. and Fig. 2. a plan of a cut-out enclosed in our improved canister case;
Fig. 3 is a section on the line Y. Y. and Fig. 4 a plan of our improved switch
enclosed in our improved canister case; Fig. 5 is a section on the line Z. Z. Fig. 6
an outside elevation, and Fig. 7 a plan of a cut-out having its cover held on by a
flat spring and bayonet slots.
In Figures 1 and 2 the insulating base A of the cut-out is shown held down by
screws B. B. which also secure the metallic baso C'of the canister. The lid D of the
case fits the base C as clearly shown.
In Fig. 3 is shown the same arrangement applied to a switch, a hole being made
in the cover D through which the handle C can pass.
To prevent the base C. from turning round when the lid D is put on or taken off
wo form a tab by turning up a small tongue F of the base C and let it project in a
recess made in the insulating base for its reception.
We do not always rely on the lid and base of the cannister being a good fit, some-
times preferring to attach the lid to the base by means of screws or a bayonet joint.
In Figures 5, 6, and 7 is shown a cut-out.
In this case the metallic base C shown in Fig. 1 is entirely dispensed with. The
cover has bayonet slots H into which enter the ends of the spring girder K
attached to the insulating base by the screw L.
In the switch shown in Figures 3 and 4, which is similar to that described in our
specification No. 16578 A.D. 1886 we have introduced an improvement in the
manner in which the revolving contact arm M takes its bearing. To lesson the cost
of construction we now crect pillars to form the cam on the stamped sheet metal
contact arm, allowing the said contact arm M to take its bearing on a peg or rivet N
fixed or revolving in the base-plate of the switch, instead of as formerly casting in
one solid piece the contact arm, cam, and peg which took its bearing in a hole in the
base-plate of the switch.
We have found in the above mentioned fittings that it is difficult when they are
subject to vibration to maintain a good contact between the leading in wires and their
terminals.
This is especially the case in combined switches and cut-outs where the percussive
action of the switch tends to shake loose the nuts or screws of the terminals.
This
action is more prevalent with the soft fuse wire terminals than with those for the
copper leading in wires.
To get over this difficulty we have invented a locking nut device, which is shown in
Fig. 8 in section and in Fig. 9 in elevation. In this terminal a round nut P is turned
conical at its inside end, this tapered part fitting into a conical recess in the washer G.
The nut P has a saw-gate R cut right through its longitudinal axis for more than half
its length. After the washer has been screwed home on the wire the taper part of
the nut enters further into the washer, the lower part of the nut being thereby
squeezed in, effectually locking the nut on the screw.
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-
1. In electrical switches, cut-outs, wall and ceiling connectors having insulating
bases of porcelain, slate or other incombustible material, the method of attaching the
metallic cover to the insulator by fitting it to a light metallic base surrounding the
insulating base, the said metallic lid and base together forming a canister substantially
as described and represented in the drawings.
2. The improved cut-out shown in Figures 1 and 2 as a whole substantially as
described and shown..
3. The improved cut-out shown in Figures 5, 6, and 7 as a whole substantially as
described and shown.

page_text: 4. In the form of switch described in our specification No. 16578 A.D. 1886 the
improved method of pivoting the contact arni or arms with their attached cams or
projections on a separate spindle or rivet rigidly fixed or turning loosely in the base
of the switch.
5. In electrical terminals the method of locking a nut which holds a conducting
wire or fuse by allowing the nut, which is sawn through its longitudinal axis from its
inside end, to enter a conical recess in a washer and thereby become squeezed in and
grip the screw substantially as described and shown in Figures 8 and 9.
Dated this 5th day of November 1888.
CHARLES MARK DORMAN.
REGINALD ARTHUR SMITH.