Improvements in Switching Apparatus, more especially adapted for use with Electric Motors.
Year: 1897

page_text: Date of Application, 19th Mar., 1897
Complete Specification Left, 20th Dec., 1897- Accepted, 5th Feb., 1898
PROVISIONAL SPECIFICATION.
Improvements in Switching Apparatus, more especially adapted for
use with Electric Motors.
I, HENRY EDMUNDS, of 39, Victoria Street, in the City of Westminster, Electrical
Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to electrical switches more especially intended for use with
electric motors in which it is desirable to put on the current or start the motor
slowly but to enable the current to be discontinued or the motor stopped with
rapidity. According to my invention I provide a contact maker which makes
contact successively with the contact terminals of a resistance inserted
in the circuit supplying current to the armature of the motor and
which also makes a contact which commences to supply current to the
field of the motor before the current is supplied to the armature. This contact
maker is operated by a worm and worm wheel or equivalent gear by which
only a slow motion can be given to the said contact maker. When the said contact
maker has been moved into such a position that the current is full on to the motor
a contact is made whereby an electro-magnet is energised to act to retain the
contact maker in the position to which it has been brought. When the supply of
current ceases from any cause or should any accident happen to the motor such as to
disturb the normal conditions which prevail whilst the motor is properly at work
the said electro-magnet becomes demagnetized and the contact maker being
released, the switch, under the action of a spring or its equivalent, immediately
returns to the off position.
The apparatus is preferably arranged as follows:-
The contact arm is secured to the axis of a worm wheel which is operated by a
worm in a carrier bracket which is normally raised out of engagement with the
worm wheel by a spring or its equivalent. This bracket is provided with a pro-
jection by which it can be moved so that the worm engages with the worm wheel.
This projection and the handle by which the worm is operated will of course project
from the casing in which the apparatus is enclosed. The contact arm is arranged
to make contact with a series of contact pieces in connection with a variable resist-
ance by which the current is led to the armature of the motor which the switch
controls, and the said contact arm also makes contact with a contact piece leading
to the field magnets of the said motor. In proximity to an iron armature on or
connected with the bracket which carries the worm is an electro-magnet so con-
nected that when the contact arm at the end of its travel to put on the current
comes into contact with a contact piece provided for the purpose the electro-magnet
is energised and attracts the said armature and so holds the worm in engagement
with the worm wheel. The apparatus is operated as follows:-When the switch
is in its off position the contact arm is not in contact with either of the aforesaid
contact pieces and the worm is not in engagement with the worm wheel. By the
operator moving the projection from the bracket which carries the worm the worm
is put in engagement with the worm wheel and by operating the worm the worm
wheel and consequently the contact arm can be operated. The contact arm first

page_text: comes in contact with the contact piece putting on the current to the field magnets
of the motor and then comes into contact with the first contact piece of the resistance
through which the current is put onto the armature of the motor. As the contact
arm is moved onwards the resistance contacts are successively made so that the
resistance is decreased until finally it is cut out and by then the contact arm has
also made contact with the contact piece by which the current is caused to energise
the aforesaid electro-magnet which by keeping the worm engaged with the worm
wheel maintains the switch in its on position. Should, from any cause, the
current be discontinued or so disturbed as to cause the electro-magnet to be demag-
netized the bracket which carries the worm will at once move so as to cause the
worm to leave the worm wheel and the contact arm will fly back and the switch
be instantly brought to its off position. It will be seen that as the electro-magnet
which keeps the switch on is not energised till the resistance is fully cut out the
switch cannot be left in an intermediate position as, on the operator releasing the
projection from the bracket carrying the worm, the worm will at once leave its
engagement with the worm wheel and the contact arm will fly back to its off
position, the aforesaid electro-magnet retaining it in its on position only when the
resistance is fully cut out.
Although I have described the invention as applied to electric motors it can be
similarly applied in any case where a switch is to be arranged so as to put on a
current gradually and yet allow of its being returned rapidly to its off position.
Dated this 19th day of March 1897.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
Improvements in Switching Apparatus, more especially adapted for
use with Electric Motors.
I, HENRY EDMUNDS, of 39, Victoria Street, in the City of Westminster, Electrical
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;-
My invention relates to electrical switches more especially intended for use with
electric motors in which it is desirable to put on the current or start the motor
slowly but to enable the current to be discontinued or the motor stopped with
rapidity.
According to my invention I provide a contact maker which makes contact
successively with the contact terminals of a resistance inserted in the circuit
supplying current to the armature of the motor and which also makes a contact
which commences to supply current to the field of the motor before the current is
supplied to the armature. This contact maker is operated by a worm and worm
wheel or equivalent gear by which only a slow motion can be given to the
said contact maker. When the said contact maker has been moved into such a
position that the current is full on to the motor a contact is made whereby an
electro-magnet is energised to act to retain the contact maker in the position to
which it has been brought. When the supply of current ceases from any cause,
or should any accident happen to the motor such as to disturb the normal conditions
which prevail whilst the motor is properly at work, the said electro-magnet becomes
demagnetised and the contact maker being released, the switch, under the action
of a spring or its equivalent, immediately returns to the off position.
The apparatus may be arranged as illustrated in views at right angles to each
other in Figures 1 and 2.

page_text: The contact arm A is secured to the axis a of a worm wheel B which is operated
by a worm C in a carrier bracket D which is centred at and is normally raised
out of engagement with the worm wheel B by a spring for its equivalent. This
bracket D is provided with a projection d by which it can be moved so that the
worm C engages with the worm wheel B. This projection d and the handle c by
which the worm C is operated, will of course project from the casing in which the
apparatus is enclosed. The contact arm A is arranged to make contact with a
series of contact pieces ġ in connection with a variable resistance by which the -
current is led to the armature of the motor which the switch controls, and the
said contact arm A also makes contact with a contact piece J2 leading to the field
magnets of the said motor. In proximity to an iron armature J on, or connected
with the bracket D which carries the worm C, is an electro-magnet H so connected
that when the contact arm A, at the end of its travel to put on the current, comes
into contact with a contact piece J³ provided for the purpose, the electro-magnet H
is energised and attracts the said armature J and so holds the worm C in engage-
ment with the worm wheel B. The apparatus is operated as follows:--When the
switch is in its off position the contact arm A is not in contact with either of the
aforesaid contact pieces g and the worm C is not in engagement with the worm
wheel B. By the operator moving the projection d from the bracket D which
carries the worm C, the worm is put in engagement with the worm wheel B and
by operating the worm, the worm wheel and consequently the contact arm A are
operated. The contact arm A first comes in contact with the contact piece J2
putting on the current to the field magnets of the motor and then comes into contact
with the first contact piece of the resistance through which the current is put onto
the armature of the motor. As the contact arm is moved onwards the resistance
contacts are successively made, so that the resistance is decreased until finally it is
cut out and by then the contact. arm A has also made contact with the contact
piece Ja by which the current is caused to energise the aforesaid electro-magnet H,
which, by keeping the worm C engaged with the worm wheel B maintains the
switch in its on position. Should, from any cause, the current be discontinued or
so disturbed as to cause the electro-magnet H to be demagnetised the bracket D
which carries the worm C will, under the action of the spring f, at once move so
as to cause the worm to leave the worm wheel B and the contact arm. A will fly
back by the action of the spring f, and the switch be instantly brought to its off
position. It will be seen that as the electromagnet H which keeps the switch on,
is not energised till the resistance is fully cut out, the switch cannot be left in an
intermediate position as, on the operator releasing the projection d from the
bracket D carrying the worm C, the worm will at once leave its engagement with
the worm wheel and the contact arm A will fly back to its off position, the afore-
said electro-magnet retaining it in its on position only when the resistances are
fully cut out.
Although I have described the invention as applied to electric motors it can be
similarly applied in any case where a switch is to be arranged so as to put on a
current gradually and yet allow of its being returned rapidly to its off position.
Figures 3 and 4 are respectively a front elevation and an inverted horizontal
section of a modified arrangement.
The contact arm A is suspended from the same axis or centre bolt a as a worm
wheel B which is operated by a worm C carried by a bracket D placed preferably
under the worm wheel, but which normally is not in gear. This bracket D is
provided with a projection d by which it can be moved, so that the worm C engages
with the worm wheel B. This projection d and the handle e by which the worm
is operated will of course project from the casing E in which the apparatus is
enclosed. The arm F is secured at one end to the side of the worm wheel, and
near the other end has attached to it a weight f. The contact, arm A is arranged
to make contact with a series of contact pieces g in connection with a variable
resistance by which the current is led to the armature of the motor which the
switch controls, and the said contact arm A being in series with the circuit of the

page_text: switch magnet H and with the field magnets of the motor, energises them imme-
diately contact is made by it with the bar I connected to the positive terminal of
the switch. The switch magnet H is at some little distance above the last of the
contact picces g and a small iron bar J which is pivotted so that it swings against
the poles of the magnet H forms its keeper or armature. This keeper or arma-
ture J has a lip or projection j at the bottom which comes in contact with the end
of the weighted arm F when the said arm has been wound up nearly to the end of
its travel, so that the said arm has to force the lip or projection j, and with it the
keeper or armature J to which it is attached, away from the magnet H in order to
pass, but the latter of course immediately pulls the said armature J back when the
end of the arm F has reached the top side of the lip or projection j. The arm F
can get no higher than this as it is arrested by a stop k. The contact arm A
consequently will now also be at its highest point, and the current will be full on
to the motor, all the resistances having been cut out. Should the worm gear be
now allowed to disengage, the end of the weighted arm F is held up by the lip or
projection j.
The apparatus is operated as follows:-
When the switch is in its off position the contact. arm A is not touching either
the bar I or any of the contact pieces 7 and the worm C is not engaged with the
worm wheel B. When the operator moves down the projection d of the bracket D
the worm C and worm wheel B are engaged together and if the
worm C be now turned by the handle C in the right direction the
worm
F
wheel B will turn upon its axis, carrying the weighted arm
round also. When the said arm F has moved the predetermined distance
(say three inches) the stud b on the worm wheel B engages with the contact arm A
and carries it round also. The contact arm A first comes against the bar I and
current passes along the said arm and through the axis or centre bolt a to a
terminal at the back from whence it passes round the switch magnet H and on to
the motor field magnets. The contact arm A next comes against the first contact
piece of the resistance through which the current is led in to the armature of the
motor. As the contact arm A is moved still further the resistance contacts are
successively made so that the resistance is gradually decreased until finally it is
all cut out, by which time the weighted arm F will have come in contact with and
have passed the lip or projection j. If the operator releases his hold on the exten-
sion from the bracket D of the worm gear, the weighted arm F will be held
up by the small projection or lip on the end of the armature J of the switch
magnet H. Should from any cause the current be discontinued, or so disturbed
as to cause the electro-magnet to be de-magnetised, the projection or lip will no
longer be held by the magnet H in its position under the end of the weighted
arm F but will be pushed aside by the said arm which will, in consequence strike,
by means of its pin 3, the contact arm A which will carry it to the off-position.
The magnet armature J extends through the casing which encloses the switch,
terminating in an insulated handle, and as it is pivotted, the other end can be.
pulled away from the magnet, so that the weighted arm F will fall and stop the
motor whenever it may be desired. It will be seen that as the weighted arm F
is not supported by the projection or lip until the contact arm A has cut out
out all the resistances, the switch cannot be left on in an intermediate position, as
the moment the operator takes his hand off the projecting end of the bracket, the
other end of the said bracket drops down by gravity is withdrawn by a spring
allowing the worm C to disengage from the worm wheel B, with the result that the
unsupported weighted arm F will drop and carry the contact arm A to the off-
position.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is-

page_text: with the switch by a magnetic device and a spring or its equivalent which rapidly.
operates to cut off the current when the magnetic device is demagnetised so as to
release the said gear substantially as hereinbefore described.
2. In combination with an electric switch for motors, a gear by which the
switch can be slowly operated, and a magnetic device energised by an electric
current supplied to the motor and acting normally to retain the gear in engage-
ment and a spring or its equivalent to rapidly operate the switch to cut off current
when the magnetic device demagnetised substantially as hereinbefore described.
3. In combination with an electric switch and operating gear a magnetic device
which can be inserted in the field circuit of a motor in such a way that a short
circuit in the armature will cause the magnetic device to cut off the current from
the motor substantially as herein before described.
4. A switching apparatus constructed substantially as hereinbefore described and
illustrated in Figures 1 and 2 of the accompanying drawings.
5. A switching apparatus constructed substantially as herein before described
and illustrated in Figures 3 and 4 of the accompanying drawings.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.