Improvements in or relating to Electrical Switches Plugs and the like.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in or relating to Electrical Switches Plugs and
the like.
I, FRANCIS GIBSON BAILY, of 11, Ramsay Garden, Edinburgh, N.B., Professor
of Electrical Engineering, do hereby declare the nature of this invention to be as
follows:-
This invention relates to improvements in electrical switches, plugs and the
like, its primary object being to obviate the danger of "short-circuiting" while
inserting and removing the plug in the various types of plug and socket fittings,
as hitherto constructed.
In switches constructed according to this invention it is impossible to insert
or remove the plug until the circuit has been broken, and further in some cases,
it is arranged that after the plug has been inserted the circuit cannot be com-
pleted until the plug is fully home, thus ensuring that a thoroughly good
electrical connection is made.
One construction of a device according to this invention is as follows:-
A plug-fitting of the type commonly known as a wall socket and plug and a
switch of the Tumler" form, are mounted side by side. A lever or arm is
attached to the handle of the switch in such manner that it moves in suitablo
guides over the top of the central opening in the socket. An opening is made in
the lever large enough to easily admit the plug and at such a point that it
coincides with the central opening in the socket only when the circuit is opened
by the "Tumler" switch. From one side of the opening in the lever a smaller
opening or slot extends, and when the plug is inserted, and the circuit completed
by the. switch, the motion of the lever brings this smaller opening into such a
position that the sides of it enter an annular recess formed in the plug and thus
prevent the withdrawal of the latter, until the circuit is broken."
It will be seen that if the annular recess in the plug is made sufficiently
narrow, it is necessary to push the plug completely home in the socket before the
lever can be moved sufficiently far to complete the circuit.
In order to completely close the central opening in the socket, when the
switch is not in use, and to effectually prevent the insertion of the plug when the
switch is closed, a block of insulating material is provided sliding freely between
the inner and outer contacts of the socket; it is pressed upwards by a spring, and
its motion limited and controlled by guides, and it is provided with a neck or
annular recess similar to that formed in the plug. When the plug is removed,
this block springs up and fills the central opening of the socket, and if the
"Tumler" switch should be closed before the insertion of the plug, the sides of
the smaller opening in the lever, enter the neck in the block and lock it, thus
absolutely closing the central opening of the socket and rendering it impossible
to insert the plug.
Another means for closing the mouth of the socket would be to provide the
lever with a sliding joint and a spring so that if the switch is closed after the
plug has been withdrawn, part of the lever itself completely covers the central

page_text: opening. In this case the spring would cause the edges of the opening in the
lever to move into the recess in the plug, when in position.
socket.
The above construction is only given by way of example, and it is obvious
that similar devices may be fitted to many types of switches and sockets. It will
be readily seen for instance, that this invention could be applied to that form of
socket in which two pins of the plug are inserted into corresponding holes in the
In this case the lever may have two small openings which coincide with
the contact holes, only when the circuit is open. On closing the switch, the con-
tact holes are covered. In this construction the pins may have nicks or grooves
cut in them, into which the sides or ends of the slots fit, when the switch is 1
closed, in order to prevent the withdrawal of the plug.
Dated this 16th day of August 1898.
BOULT & WADE,
Agents for the Applicant.
Improvements in or Relating to Electrical Switches, Plugs and
the like.
I, FRANCIS GIBSON BAILY, of 11, Ramsay Garden, Edinburgh, N.B., Professor
of Electrical Engineering, 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:-
This invention relates to improvements in electrical switches, plugs and the
like, its primary object being to obviate the danger of "short-circuiting" while
inserting and removing the plug in the various types of plug and socket fittings,
as hitherto constructed, or by accidental contact with other bodies.
In sockets constructed according to this invention it is impossible to insert
or remove the plug until the circuit has been broken, and further in some cases,
it is arranged that after the plug has been inserted the circuit cannot be com-
pleted until the plug is fully home, thus ensuring that a thoroughly good
electrical connection is made.
In the accompanying drawings,
Figure 1 is a plan showing a socket-fitting and
Tumler" switch inter-
connected according to one construction of this invention.
Figure 2 is an elevation partly in section on the line 2-2 of Figure 1.
Figure 3 is an elevation of a plug suitable for use in the socket shown in
Figures 1 and 2.
Figures 4, 5 and 6 are views similar to Figures 1, 2 and 3 respectively show-
ing another form of wall socket inter-connected according to this invention with
a Tumler" switch.
Like letters indicate like parts throughout the drawings.
With reference first to Figures 1, 2 and 3, A is a socket fitting of the " con-
centric" type having a central contact A¹ and a second contact A2 concentric with
it. The base and cover of the socket may be of the ordinary type and need no
description. The upper portion A3 of the socket is grooved or slotted as at A4 so
that a plate B can move therein, when actuated by the handle C¹ of a "Tumler"
switch C, to which the plate B is attached by means of an arm B¹.
In the plate B is a circular hole B2 of a size to admit the plug D, Figure 3,
and a smaller opening B3 extends at one side of the hole 132 and is shaped so that
when the plug D) is in position in the socket, the smaller opening B³ will, when
moved by the switch handle C¹, fit into a recess D' in the plug and thus prevent.

page_text: its removal. It is to be understood that the plug D is of the type usually employed
with a concentric wall socket, except that it is furnished with an annular
recess D¹. If the plug is not pushed fully home in the socket the sides of the
opening B will come into contact with the lower and larger portion of the plug
when the switch handle is moved, and thus prevent the closing of the circuit
by the switch C until the plug is properly inserted.
In order to close the mouth of the socket when the plug is not in use and to
prevent the insertion of the plug or any other object when the socket contacts
are "alive," an annular block of insulating material E is placed between the
inner and outer contacts A', A2, of the socket sliding freely between them and
projecting above them, when the plug is removed. When the plug is inserted the
block is pressed down into the space in the lower part of the socket. The block
is pressed upwards by a spring F and its motion is controlled by two pins or
projections which move in vertical slots F2 in the outer contact piece A². These
pins stop the upward movement of the block E at the position when an annular
recess E' in it comes opposite to the plate B, so that when the switch is put over,
the sides of the smaller opening B fit into the recess in the block and prevent its
motion, thus closing and locking the opening.
As shown in Figures 1 and 2 the switch C is "off" i.c., one or both of the con-
nections between the contacts A and A2 and the conductors, is broken at the
switch. The block E closes the entrance to the socket but is not locked, con-
sequently the plug D may be inserted and will depress the block E. When the
plug D is fully home, the switch handle C is moved into the position shown in
dotted lines in Figure 2, this movement having the effect of closing the circuit to
the socket contacts A1 and A2 and locking the plug D so that it cannot be with-
drawn until the switch is once more in its "off" position.
"
Figures 4, 5 and 6 show a device according to this invention applied to a
socket fitting of the kind in which the contacts are made between two pins D²,
Figure 6, on the plug, and tubes A5 in the socket. The sliding plate B is in
this construction made of insulating material and is provided with two open-
ings B, which, when the switch C is in the "off" position as shown in Figures 4
and 5, lie opposite the tubes A and admit the pins D2 of the plug 1). A smaller
opening B extends from each of the openings B2, the function of the smaller
openings being to engage with grooves D in the pins D, in a similar way to that
previously described with reference to Figures 1, 2 and 3.
When the switch handle is moved into the
on position, if the plug D has
not been inserted, the top of the contact tubes A are covered by solid portions of
the plate B. If however, the plug D is in position, the plate B is only moved far
enough to engage the openings B with the grooves D). This latter movement is
less than the full travel of the arm B₁ attached to the switch handle C¹ and
therefore a sliding joint is provided between the arm B and the plate B. A
tubular socket B is attached to the plate B, in which a reduced portion of the
arm B slides, a spring B is placed as shown, (Figure 5), between the socket B
and the arm B, so that when the motion of the plate B is stopped by the pins D²
the further movement of the switch handle C₁ compresses the spring B5. A pin B6
attached to the arm 13¹ and moving in a slot 137 in the socket B4, serves to bring
the plate B back when the switch handle C' is returned to its off" position.
<<
The constructions herein described and illustrated are merely given by way of
example, it being obvious that various types of switches and sockets may be used
for carrying out this invention, suitable alterations being made in the covering
plate and lever to suit the motion of the handle of the switch, and the shape of
the contacts in the socket employed.
my said
Having now particularly described and ascertained the nature of
invention and in what manner the same is to be performed, I declare that what
I claim is: -
1. The combination with a socket-fitting of a separate switch so arranged that

page_text: the plug of the socket-fitting cannot be inserted or withdrawn when the switch
is closed.
2. The combination with a socket-fitting and a switch of a plate or equivalent
operated by the switch and controlling the entrance to the socket substantially
as described.
3. The combination with a socket-fitting having a recessed plug of a switch
operating a sliding plate or equivalent substantially as described.
4. The combination with a socket-fitting of a spring controlled block such
as E and a sliding plate or equivalent operated by a switch substantially as
described.
5. The combined socket-fitting and switch substantially as described and illus-
trated in Figures 1, 2 and 3 or Figures 4, 5 and 6 of the accompanying drawings.
1011
JM 1900
FRANCIS G. BAILY.
Boult & Wade,
Agents for the Applicant.
FRANCIS G. BAILY.
Boult & Wade,
Agents for the Applicant.