Year: 1899

page_text: I, WALTER FREDERICK JONES, of Albert Works, Hanımersmith, in the County of
Middlesex, Engineer, do hereby declare the nature of this invention to be as
follows:
My invention relates to electric switches and in particular to switches for
starting and stopping electric motors.
One object of my invention is to construct a switch for use with electric motors
in such a manner that if the current supply stops, or if the current in the supply
circuit to the motor becomes greater than a predetermined maximum, the switch
will be automatically operated to break the motor circuit.
A further object of my invention is to provide for rupturing the are formed
when the circuit is broken.
According to my invention I so arrange the switch that the movement of the
hand-wheel or lever is transmitted to the switch arm or arms through an electro-
magnetic clutch which is magnetised by a coil in series with the field coils
of the motor.
The portion of the clutch which is secured to the hand-wheel or lever is held in
the position to which it is turned by a pawl or other suitable stop, but since the
other part of the clutch is held in this position by electromagnetic means alone,
as soon as the current ceases this portion of the clutch will be released and operate
the switch to break the circuit.
In order to break the circuit at any time when desired, I provide for short-
circuiting the coil which magnetises the clutch by means of a suitable press-button
or key, and in case where it is desired to prevent the switch being operated by
unauthorised persons, I provide a lock which is arranged to secure the short-cir-
cuiting key in either of its positions and prevent the same being altered.
For automatically opening the circuit when the current supply becomes exces-
sive I provide an electro-magnetic device operated by a coil in the circuit which is
adapted to short-circuit the clutch electro-magnet and thereby demagnetise the
clutch and cause the switch to break the circuit. With this switch it is therefore
impossible to turn on the current if there is any defect in the circuit which
would permit an excessive current to pass when the circuit is made because the
clutch can not in such case be magnetised, whereas with switches of the ordinary
type the circuit breaking or overload magnet cannot act while the handle or
handle-wheel of the switch is being operated.
The power for operating the switch to break the circuit is obtained from a weight
or spring arranged in connection with the switch so that when the handle is
operated to make the circuit energy is stored in said weight or spring. Since
when the circuit is broken the clutch is demagnetised and the switch therefore
cannot be operated I arrange that the first movement of the handle shall cause
á circuit to be made temporarily or otherwise which magnetises the clutch.
In order that the movement of the switch when making the circuit shall be slow.

page_text: I provide a dash-pot connected with the spindle or lever of the switch; said
dash pot is so arranged that its piston moves quickly in the cylinder when the
circuit is broken and at a suitable point in its movement opens a valve through
which the compressed air escapes and is conducted to the point where. the circuit
is broken so as to form a blast and blow out the spark on breaking.
The dashpot arrangement above described adapted to rupture the are on breaking
the circuit is clearly applicable to non-automatic switches as well as to switches
such as described in the Specification.
001
1. 1900
I, WALTER FREDERICK JONES, of Albert Works, Hammersmith, in the County of
Middlesex, Engineer, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:--
My invention relates to electric switches and in particular to switches for
starting and stopping regulating and reversing electric motors.
The main object of my invention is to construct a switch for use with electric
motors in such a manner that if the current supply stops, or if the current in
the supply circuit to the motor becomes greater than a predetermined maximum,
the switch will be automatically operated to break the motor circuit.
According to my invention I so arrange the switch that the movement of the
hand-wheel or lever is transmitted to the switch arm or arms through an electro-
magnetic clutch which is magnetized by a coil in series with the field coils of the
motor or by a separate circuit from the source supplying current to the motor.
The portion of the clutch which is secured to the hand-wheel or lever is held in
the position to which it is turned by a pawl or other suitable stop or by friction,
but since the other part of the clutch is held in this position by electromagnetic
means alone, as soon as the current ceases this portion of the clutch will be
released and operate the switch to break the circuit.
In order that my invention may be the better understood I will now proceed to
describe the same with reference to the accompanying drawings, in which the same
letters refer to the same parts in the different figures.
Figure 1 is a front elevation of my improved switch.
Figure 2 is a side elevation partly sectional looking from the left hand of
Figure 1, the switch being in a position at right angles to that shewn in said figure.
Figure 3 shows a convenient method of connecting up the various circuits when
the switch is used with a shunt motor.
The switch is actuated by a lever or by a hand-wheel A fixed on the spindle B
which passes through the switch board or base C of slate or other suitable insulating
material and carries at its further end the armature D of the clutch electro-
magnet E.
The clutch magnet E as shewn in section in Figure 2 is of the iron
clad type but may be of other suitable design and is secured to one end of the
sleeve Floosely carried on the spindle B. This sleeve finds a bearing in the
sleeve G fixed to the switch board C and carries at its other end the switch arm H
which is insulated from the sleeve I by the insulating piece I. The switch arm H
is provided at its two ends with contact pieces J Jadapted to engage with the

page_text: contact blocks K, K¹
K on the switch board. Resistances r ...
are inserted between the blocks K¹ K¹.
r Figure 3
It will thus be seen that the switch arm H is driven by the hand-wheel A
through the electromagnetic clutch consisting of the armature D and the magnet E
containing the coil L which is connected in series with the field coil of the motor
or any other way to the source of electric supply. When the motor has been
switched on by turning the hand-wheel the armature D is held by the pawl while
the electromagnet E and consequently the switch arm H are held in position by
the electromagnetic clutch alone against the reaction of a spring or weight
attached to the cord V which is wound on the outside of the magnet E as it is turned
or a spring may be attached direct to its hub. When the electromagnet E is not
magnetized by a current the spring M Figure 2 surrounding the spindle B main-
tains the armature D'out of engagement with the electromagnet, the pin N
connecting the armature to the spindle B permitting a slight movement parallel
to the axis of the spindle. Projections and depressions on the armature face
and magnet may also be shaped, as in some tapping apparatus, so as to cause
the magnet to shear the armature back, when the clutch is demagnetized and
weight or spring on cord V is acting. In this case the spring M can be very weak.
This disengagement of the two parts of the clutch when the clutch is not mag-
netized permits the switch arm under the influence of the spring or weight
attached to the cord V to return to its original position.
Since when the circuit is broken the clutch is demagnetized and the switch
therefore cannot be operated I arrange that the first movement of the handle shall
cause a circuit to be made temporarily or otherwise which magnetizes the clutch.
I effect this by means of an elbow lever l' pivoted at the back of the switch board,
provided with a projection Q which rests on the edge of the circular armature D.
One end of said lever is connected by the spring R to the detent which is
adapted to engage with recesses on the edge of the armature to hold said armature
after the switch has been actuated. On the edge of the clutch armature D there are
also formed depressions $ which when the armature is turned allow the projection
Q to fall and the elbow lever P to turn on its pivot under the influence of the
spring R, temporarily causing contact to be made between the contact on the
shorter arm U of the elbow lever and a spring T. A current thus flows through
the coils L magnetising the clutch, see Figures 1 and 3. Consequently on further
turning the hand-wheel the switch arm is caused to complete the motor circuit so
that the clutch remains magnetized by the current of the field coils of the motor
after the contact at T has been broken by the lever P returning to its original
position after the depression S has moved away from the projection Q. The
switch arm can thus be turned until all the resistances between the blocks K' K'
have been cut out, in which position the detent will hold the clutch armature D
and the clutch magnet, being magnetized by the field current of the motor, will
hold the switch arm H against the reaction of the spring or weight at the end of
the cord V.
In order to prevent current being supplied to the motor armature when the
temporary contact is made the connection between the end of the clutch coil and
the motor armature is made through a switch formed by a bar K2 with which the
switch arm H engages as soon as it is rotated from its zero position.
"
It is essential in switches where the switch arm must only be left in the "full
on position as in a starting switch where the resistances are only sufficiently
large to carry the current for a short period. or where the switch is used with one
contact only for simply making a circuit when joining dynamos in parallel for
example or for other purposes, that the clutch armature and magnet should engage
when they are in a certain relative position in order to ensure the arm being
at the position of "full on " when the detent engages. In view of this the sur-
face of the armature D has one or more projections D¹ formed upon it to engage
with one or more depressions E¹ on the electromagnet E to prevent slipping. To

page_text: ensure that the electromagnet shall engage only at the right place provide a stop f
on the lever Padapted to engage with stop. pins'e on the clutch armature D when
the projection Q falls into a depression S. The stop f. thus prevents any further
movement of the switch hand-wheel A until the clutch has become magnetized
when the armature D is attracted to the electromagnet E against the action of the
spring M. This inward motion of the armature D allows the stop pin e to escape
from engagement with the stop f and thus the hand wheel can be turned further
round moving the switch arm with it.
If the current supply to the motor ceases from any reason, the clutch will
become demagnetized and the motor will be automatically switched out of circuit
by the switch arm returning to its original position under the action of the
spring or weight at the end of the cord V.
Carbon sparking contacts Ware provided as shewn in Fig. 1.
For automatically opening the circuit when the current supply becomes exces-
sive I provide an electromagnet X Figures 1 and 3 operated by a coil in series
with the motor. The armature Y of this electromagnet forms one arm of a
pivoted lever, the other arm carrying an adjustable weight Z. When the current
rises above the predetermined amount for which the position of the weight Z has
been adjusted the armature is attracted upwards and a contact piece a on the
armature makes contact with another fixed piece b short-circuiting the clutch
coil L and causing the automatic switching off of the motor through the switch
arm returning to its original position as herein before described. Any suitable
form of electromagnetic short-circuiting device may be employed for the purpose
of rendering the clutch coil L inoperative when an excessive current passes.
With this switch it is therefore impossible to switch on motor if there is any
defect in the circuit which would permit an excessive current to pass when the
eircuit is made because the clutch cannot in such case be magnetized, whereas
with switches of some of the ordinary type circuit-breaking or overload magnet
cannot act while the handle or handle-wheel of the switch is being operated.
In order to switch off at any time when desired I make contact at a and b by
means of a press button or push bar e which actuates the elbow lever and raises
the armature carrying the contact a against the contact 6 whereby the clutch
becomes demagnetized.
I have described the switch as applied to the circuit of a shunt motor, but the
switch may be used for many other purposes the connections of the switch being
altered as required to suit each particular case; for example with a series motor
the switch is arranged so that the motor armature is short-circuited when the
temporary contact is on and until the switch arm reaches the first contact.
When the switch is to be used as a regulating switch a spring catch is employed
in place of the detent or the hand-wheel is fixed by friction so that the switch
arm will remain in any position to which it is turned or can be moved backwards
or forwards. The switch can also when somewhat modified be employed for
reversing and it is clear that provided movement be given to the switch arm by
properly arranging the contacts such movement may be caused to make any
desired changes in a circuit. By connecting the armature of the clutch magnet or
the switch spindle to a chain the switch contacts may be arranged in a straight
line to co-operate with a switch arm having a rectilinear motion only.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what
1 claim is:-
-
1. A switch in which the motion of the actuating hand-wheel or lever is
transmitted to the switch arm or arms through an electromagnetic clutch, either
with or without the device for short-circuiting the clutch electromagnet when the
current supply becomes excessive, substantially as described.
2. In a switch of the kind described means whereby the first movement of the
hand wheel or lever causes a circuit to be made temporarily or otherwise which

page_text: magnetizes the clutch before the switch arm or arms have been moved, for the
purpose specified.
3. An electric switch constructed and operating substantially as described
with reference to the accompanying drawings.
Dated the 26th day of January 1900.
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham.