Improvements relating to the Starting Switches of Electro-motors.
Year: 1897

page_text: :PROVISIONAL SPECIFICATION.
Improvements relating to the Starting Switches of Electro-motors.
I, FREDERICK. GEORGE ROBINSON, of 9, Strand Street, in the City of Liverpool,
Electrical Engineer, do hereby declare the nature of the said invention to be as
follows:-
This invention relates to that type, of starting switch, for electro-motors, in
which a radial arm or-switch is caused to travel over a series of contacts, arranged
in a sector of a circle. The said contacts are connected in series by resistance
coils, in such a manner that the potential of the current gradually increases as the
switch passes from the off" to the "
on position.
وو
The object, of the present invention is, firstly, to provide means whereby the
switch must pass comparatively slowly over the, contacts, so that an appreciable
period of time must elapse between its making contact with the first, or low
potential contact,, and with the final or high potential contact, of the series of
contacts. Provision is thus made for the motor to commence revolving before the
full potential is supplied to it. Another object is to provide means whereby such
switch may be instantly returned, or fly back, from the on", to the "off". position.
Such return action may be automatic, and take place when a failure of the electric
main, or other source of supply, takes place, or may be due to a mechanical device
operated by hand.
In practice I mount the switch upon a spur wheel, which latter has also a series
of ratchet teeth. Gearing with the spur wheel is a train of wheels,similar to the
hour and minute train of clock-work, which train is put in motion by a hand
wheel or its equivalent, which forms the starting handle of the motor. Assuming
the series of contacts to occupy one third of, a, circle, the switch must travel a
like distance; and to cause the spur wheel which carries it to make one third of a
revolution, I prefer that the hand wheel must make three, four or more revolu-
tions. A comparatively slow motion of the switch is, thus ensured.
22
on
"
37
In order that the switch may be quickly returned over the contacts from the
to the "off" position, I provide the tooth wheel which carries it with a spring,
preferably a volute spiral or clock spring, which is wound up in the operation of
moving the switch. forward to the on position. The switch and wheel, are pre-
vented from returning by a pawl which enters the, ratchet teeth of the spur, wheel
when the pawl is attracted by an electro-magnet. The coils of this magnet are in
series with the coils of the field magnets of the electro-motor which is being
controlled. Thus, so long as the said field magnets are supplied with current, the
electro-magnet is energised and keeps the pawl in gear with the said ratchet teeth
and prevents, the switch from being returned by the clock spring. In case,..how-
ever, the field magnet current fails, the electro-magnet is no longer energised, and
an adjustable spring now causes the pawl to release the spur wheel and radial

page_text: switch, which latter is then instantly returned to the " off" position by the clock
spring. In this way the switch automatically flies back to the "off" position upon
the failure of the supply of current from the main or other source, and the danger
when the current is renewed-of a high potential being put upon the motor
suddenly, is averted.
"
In order that the switch may be instantly returned to the off" position by
hand, I arrange a press button or handle which acts mechanically upon the pawl,
and acting against the pull of the electro-magnet-removes it from the ratchet
teeth of the spur wheel, whereupon the latter and the switch are returned, by the
action of the clock spring, to the off" position.
66
J. A. COUBROUGH,
Registered Patent Agent (Qual. by Exam.),
10, St. George's Crescent, Liverpool, Agent for the Applicant.
Improvements relating to the Starting Switches of Electro-motors.
I, FREDERICK GEORGE ROBINSON, of 9, Strand Street, in the City of Liverpool,
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 :-
This invention relates to that type of starting switch, for electro-motors, in
which a radial arm or switch is caused to travel over a series of contacts arranged
in an arc of a circle. The said contacts are connected in series by resistance coils
in such a manner that the potential of the current gradually increases as the switch
passes from the off" to the on" position.
*
The object of the present invention is, firstly, to provide means whereby the
switch must pass comparatively slowly over the contacts, so that an appreciable
period of time must elapse between its making contact with the first or low
potential contact, and with the final or high potential contact, of the series of
contacts. Provision is thus made for the motor to commence revolving before
the full potential is supplied to it. Another object is to provide means whereby
such switch may be instantly returned, or fly back, from any position, to the "off"
position. Such return action may be automatic, and take place when a failure
of the electric main, or other source of supply takes place, or may be due to a
mechanical device operated by hand and disposed on the switch or at a distance
away from it.
In the drawings hereto annexed Figure 1 is a front view of a starting switch
according to my invention, Figure 2 being a side view. Figure 3 is a detail
section of Figure 1. Figures 4 and 5 illustrate modifications of Figure 1. Figure 6
is a diagrammatic view of the switch and its electrical connections.
Referring to Figures 1 2 and 3, I mount the switch a upon a spur wheel_b.
Gearing with the spur wheel b is an idle wheel c, and gearing with the wheel c
is a pinion wheel & mounted on the spindle e which is rotated by the hand wheel
or knob f, the latter being the starting handle of the motor. g are a series of
contact pieces which are electrically connected in series by means of the resis
tances h. i is a continuous metallic plate in rear of the contacts 9 and separated
from them by the insulation k. The plate i and contacts g form terminals in the
circuit between the source of electrical energy and the motor to be driven, and are
bridged by the switch arma, the latter being forked and split to ensure a good

page_text: metallic rubbing contact. As the switch a travels over the contacts g the
resistances are cut out one after the other and the potential of the current
supplied to the motor gradually increases until the switch a reaches the final
contact piece, g¹, when it is at its maximum. In order that the switch a must
travel comparatively slowly over the contacts g, the pinion wheel dis of such a
size relative to the size of the spur wheel 6 that the starting handle must be
revolved a number of times before the switch a reaches the final contact g'. An
appreciable period of time thus elapses between the contact of the switch with the
first or low potential contact of the series of contacts g and the final or high
potential contact, gl. Provision is thus made for the motor to commence revolving
before the full potential is supplied to it.
In order that the switch a may be quickly returned from any contact g to the
"off" position, I employ a volute spiral or clock spring 1, one end of which is
attached to the sleeve of the spur wheel b and its other end to the frame, the spring
being wound up in the operation of moving the switch forward over the contacts y
to the "on" position. The switch a is prevented from returning by a pawl m
which engages with the ratchet wheel upon the spindle e so long as the arm m
of the pawl is attracted by the electro-magnets o. The coils of these magnets are
in series with the coils of the field-magnets of the electro-motor which is being
controlled. Therefore, so long as the said field-magnets are supplied with current,
the electro-magnets o are energised and keep the pawl m in gear with the ratchet
wheel and prevent the switch a from being returned by the spring 1. In case
however the field-magnet current fails, the electro-magnets o are no longer
energised and an adjustable spring now causes the pawl m to release the ratchet
wheel which allows the switch a to be instantly returned to the "off" position
off"
by the spring 1. In this way the switch automatically flies back to the "
position upon the failure of the supply of current from the main or other source,
and the danger-when the current is renewed-of a high potential being put
upon the motor suddenly is averted.
In order that the switch a may be instantly returned to the off" position by
hand, I arrange a press button or handle y whose spindle carries a cone q' which
presses against the lower limb m² of the pawl m and-acting against the pull
of the magnets 0-removes the pawl from the teeth of the ratchet wheel n, where-.
upon the switch a is returned by the spring to the "off" position.
is a pointer which indicates the position of the switch a upon a suitable dial.
To enable a machinist or other person at some distance from the switch to
return it to the "off" position, as for instance in case of accident, disarrangement,
or other emergency, I provide the electro-magnets r. On reference to Figure 1 it
will be seen that these magnets r are opposed to the magnets o, and when
energised they overcome the pull which the magnets exercise on the arm m¹ of
the pawl m and remove the latter from the ratchet wheel n, being assisted in this
action by the spring p.
When the magnets are employed, the switch a and its contacts are arranged
as shewn in Figs. 4 or 5. On reference to Figure 4 it will be seen that a second
continuous contact plate is added, and that the switch a is doubly forked, one
pair of forks bridging the contacts and the live plate i and the other forks
bridging the live plate i and the secondary plate . On reference to Figure 5
it will be seen that I arrange the contacts and the secondary plate in concen-
tric circles upon an insulation h, the single forked switch a carrying springs a¹
which rub against the contacts g and plate respectively.
Figure 6 is a diagrammatic view of the electrical connections of the switch a
when constructed as shewn in Figure 4 and when the "distance" magnets are
used, the motor being one in which current is supplied to the armature thereof as
well as to the field-magnets. The armature circuit leads from the source P to
the live plate i thence through the switch a to the contacts g and through the resis-
tances to the brushes of the armature A. The field magnet circuit leads from the
source P to the live plate i thence through the switch a to the secondary plate i¹

page_text: and thence through the coils of the magnets o (which hold the pawl m engaged
with the ratchet wheel n) and thence through the field magnets FM of the motor,
to N or earth. To energise the distance or emergency magnets (which with
draw the pawl m from the wheel) a shunt is taken from the secondary plate z¹.
The circuit of this shunt which passes through the coils of the magnets r and
thence to the field-magnets F M, is normally broken at D, which represents a
press-button contact or other suitable switch disposed at a distance from the
switch a, as for instance at a loom, lathe, or other machine which is being driven
by the motor.
It must be understood that the apparatus described with reference to Figures 1,
2 and 3 may be employed without the magnets r. and that where the magnets r
are employed it is necessary to use the contact plate ¹.
I am aware that a radially moving switch has heretofore been used with
contacts such as g and i and that means for giving a slow motion to such a switch
have also been employed, but to neither of these features broadly do I lay
any claim.
The present invention relates to the combination of means for con-
trolling such radial switch, as set forth in the following claiming clauses.
Having now particularly described and ascertained the nature of my invention,
and in what manner the same is to be performed, I declare that what I claim is :-
1. The combination in a motor starting switch of the type described, of the radial
arma, the slow motion tooth. wheel gearing c d for rotating the same, the spring
upon the spindle of said arm for returning same to the off" position, the
ratchet and pawl m operated by electro-magnets whose coils are energised by
the motor currents, for retaining same in the "on" position, and the push q for re-
"leasing the pawl, whereby the arm a is caused to travel slowly forward over the
switch contacts, thus gradually increasing the potential of the current supplied,
and to instantly return from any position to the "off" position when the motor
current fails or the push q is pressed, substantially as and for the purposes herein
described with reference to the drawings.
2. The employment in combination with the apparatus specified in the preceding
claim, of the electro-magnets r adapted to overcome the magnets and to release
the pawl m from the wheel n when the circuit of their coils is completed by a
press button or similar switch which may be disposed at a distance from the
switch, whereby the switch arm may be instantly returned from any position to
the "off" position in case of emergency, substantially as described witli reference
to the drawings.
3 The construction, arrangement and disposition of parts, and the electrical
connections thereof, forming a starting switch for electro motors, substantially as.
described with reference to the drawings.
J. A. COUBROUGH,
Registered Patent Agent (Qual. by Exam.),
10, St. George's Crescent, Liverpool, Agent for the Applicant.