Improvements in Electrical Switching Apparatus.
Year: 1898

page_text: Improvements in Electrical Switching Apparatus.
I, HENRY EDMUNDS, of 39, Victoria Street, in the City of Westminster, Elec-
trical Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to an electric switch for slowly switching on through
resistance coils, a large current to arc lamps, motors and the like, so that the
current be gradually introduced, and also for gradually switching off the same
but with a very quick break off the last contact. It is also applicable to simple
switches without resistances.
A switch, according to my invention, comprises an arm actuated through a
worm and worm wheel, a short arm and spring which give it a very slow motion.
The contact arm closes the circuit preferably by one of its ends sliding between
a strip of metal on one side and contact pieces on the other side. The strip of
metal I generally make positive and the first contact piece is connected on to
the greatest resistance. The other end of the contact arm works on the same
stud as the worm wheel, but they are not rigidly fastened together. To the
outside of the worm wheel a short arm is fastened so that it extends not parallel
with the contact arm but at an angle of say about 50° to it. To the free end of
this arm I secure a rod shaped as an arc passing through a hole in the contact
arm and having on its end a nut or stop. On this rod between the contact arm
and short arm-is mounted a spiral spring.
The switch is actuated as follows:-Supposing the contact arm to be off, and
it be desired to switch the current on. The handle which actuates the worm is
turned in such a direction that the short arm begins to travel between the con-
tact pieces and worm wheel, now the arc-shaped rod being attached at one end
to this arm will also travel up, and as it has a nut or stop on its other end which
cannot pass through the hole in the contact arm it will slowly carry the latter
along with it, which will in consequence "make" contact, and gradually cut
the resistances out, until a stop is reached at the correct height. The current is
now full on.
In switching off, the worm is turned in the opposite direction, with the result
that the short arm is forced down by the worm-wheel revolving in that direction.
Now the arc-shaped rod will also be forced down through the hole in the contact
arm, and the spring in consequence will be compressed between the two arms
until it is able to overcome the resistance of the contact arm due to its friction
with the contact pieces and contact strip. When that happens the contact arm
will begin to move down, cutting out, the resistances gradually in doing so, but
when it finally passes off the first contact piece, it will no longer be restrained
by friction and therefore the compressed spring will violently regain its normal
condition causing the contact arm to shoot forward and thus make a very quick
break.
When my improvements are applied to an ordinary switch only one contact
piece is necessary and no resistances are required, the current being in this case

page_text: introduced instantaneously and not cut off gradually and in the previously
described example.
Dated this 22nd day of April 1898.
"
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
Improvements in Electrical Switching Apparatus.
I, HENRY EDMUNDS, of 39, Victoria Street, in the City of Westminster, Elec-
trical Engineer, 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 an electric switch for slowly switching on, through
resistance coils, a large current to arc lamps, motors and the like, so that the
current be gradually introduced, and also for gradually switching off the same,
but with a very quick break off the last contact. It is also applicable to simple
switches without resistances.
I will describe my invention by reference to the accompanying drawings in
which:—Figure 1 is a front elevation of one of my improved switches, and
Figure 2 is a sectional view thereof as seen from the underside.
The switch as shewn in the drawings comprises an arm A actuated through
a worm B and worm wheel B₁, a contact arm C, and spring D.
The contact arm C closes the circuit preferably by one of its ends sliding
between a strip of metal E on one side, and contact pieces F1, F2, F3, F4, F5, on
the other side. The strip of metal E I generally make positive and the first
contact piece F1 is connected on to the greatest resistance. The other end of
the contact arm C works preferably on the same stud b as the worm wheel B₁
but they are not rigidly fastened together. The arm A is rigidly secured to
the worm wheel B₁ and extends, not parallel with the contact arm C, but, except
during the opening or turning off of the switch, at an angle of say about 50°
to it as shewn in Figure 1. To the free end of this arm A I secure a rod d shaped
as an are passing freely through a hole c in the contact arm C and having on
its end a nut or stop d¹. On this rod-between the contact arm and short arm--
is mounted the before mentioned spring D.
The switch is actuated as follows:-Supposing the contact arm to be off, and
it be desired to switch the current on. The handle 61 which actuates the worm B
is turned in such a direction that the short arm A begins to ascend and raise
the arc-shaped rod d which, by means of the nut or stop d¹ thereon (which nut
or stop cannot pass through the hole c in the contact arm C) will slowly carry
the said contact arm along with it. The contact arm C will in consequence
"make" contact with the strip of metal E and successively with the contact
pieces F1 F2 F3 F4 F5 and thereby gradually cut the resistances out, until a
stop G is reached at the correct height, which is the position in which the switch
is shewn in Figure 1. The current is now full on.
In switching off, the worm B is turned in the opposite direction, with the
result that the short arm A is moved downwards by the worm wheel B¹ revolving
in that direction. Now the arc-shaped rod d will be forced down through the
hole c in the contact arm C and the spring D in consequence will be compressed
between the two arms A and C until it is able to overcome the resistance of the
contact arm C due to its friction with the contact strip E and contact pieces F
F2 F3 F¹ F³, When that happens the contact arm C will begin to move down,

page_text: cutting out the resistances gradually in doing so, but when it finally passes off
the first contact piece F1, it will no longer be restrained by friction and there-
fore the then-compressed spring D will violently regain its normal condition,
causing the contact arm C to shoot forward and thus make a very quick break.
When my improvements are applied to an ordinary switch only one contact
piece is necessary (instead of the several contact pieces F F F F F³) and no
resistances are required, the current being in this case introduced instantaneously
and not cut off gradually as in the previously described example.
Although I have described the switch as though operated in the position in
which it is shewn in the drawings, which is the preferred arrangement, it may
if desired be used in other positions.
Having now particularly described and ascertained the nature of this in-
vention and in what manner the same is to be performed, I declare that what
I claim is―
1. In an electric switch the combination with an arm such as A, and a contact
arm such as C, of a yielding connection and spring to make a quick break, sub-
stantially as herein before described with reference to the accompanying drawings.
2. The combination and arrangement of parts constituting the electric switch,
substantially as hereinbefore described and illustrated in the accompanying
drawings.
Dad 41 02nd day of January 1899
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.