Improvements in Switches for use with Rheostats for Starting and Controlling Electric Motors for Lifts or the like.
Year: 1899

page_text: Improvements in Switches for use with Rheostats for Starting and
Controlling Electric Motors for Lifts or the like.
We, HUGO HIRST, of 69, 71, 88, 92, Queen Victoria Street, in the City and
County of London, Electrical Engineer, and FREDERIC OSMOND HUNT, of 21,
Mount Vale, York, Electrical Engineer, do hereby declare the nature of this
invention to be as follows:-
Our invention relates to switches for starting and controlling electric motors
for driving the winding gear of lifts or the like, or any apparatus so driven
in which it is desirable that the rate of the switch movement shall be controlled
by the mechanism or apparatus so driven.
For this purpose we use a multiple-contact switch operated by means of a
ratchet and pawl.
In carrying our invention into practice we use a reciprocating arm supporting
the working pawl, actuated by a connecting rod attached to an eccentric, or
crank, or by a lever and cam, the eccentric, crank or cam being placed upon
any convenient shaft of the driven machinery, or upon an auxiliary counter-
shaft geared and driven by said machinery. The throw of the pawl may be
regulated to take up one or more teeth of the ratchet on each stroke as may
be required.
There is no OFF position on the switch the position of rest being that
in which the whole resistance of the rheostat is in circuit. The switching ON
or OFF for either direction of rotation is accomplished by a separate reversing
switch of any of the well known types. The pawls are thrown out of the ratchet
teeth by the action of a curved piece, operated by springs or by gravity, when
no current is passing. When the current is switched on, the curved piece is
forced towards the centre of the ratchet wheel by the core of a solenoid, or
armature of an electro magnet, the pawls thus being allowed to drop into the
teeth. The electric motor may, therefore automatically cut out the resistance
between the studs of the switch gradually and so attain its full speed. When
all the resistance is thus cut-out, and full speed attained, the switch does not
advance since there are no teeth in the ratchet for the pawl to engage with.
We may modify this by causing the releasing device to be mechanically con-
nected to the brake lever of the winding gear, or to a special lever operated
by a cam on the spindle of the reversing switch. In the first case the release
is effected by the application of the brake, and in the second by the action of
said reversing switch, but in both methods of mechanical release the pawls
are thrown out of gear before the reversing switch breaks the circuit. This

page_text: causes the whole of the starting resistance to be inserted before the circuit is
broken, thereby ensuring a gentle stoppage, and saving said reversing switch
from destructive arcing.
The force necessary to return the switch to the starting position when
released as aforesaid, may be provided by a coiled or other spring, or a weight
acting by gravity on a lever or on a cord or chain passed over a suitable pulley
on the switch spindle.
In cases where a limit is fixed for the amount of current to be taken from the
mains at starting, an additional device is provided in all cases where the motor
requires current beyond the aforesaid limit for starting at full load.
In such cases the resistance in the circuit is sufficiently high to keep the
initial current within the prescribed limit, and the cutting out of the first
sections of resistance is accomplished by means of a multiple contact switch
controlled by a dash pot. The contacts are arranged in a straight line vertically,
and a contact bar slides over these in succession. Attached to one side of the
bar, but insulated from it, is the piston rod of the dash pot. On the other side
is attached a flexible cord or chain passing over a floating pulley and so to a
counterweight which is sufficiently heavy to counterbalance the weight and
frictional resistance of the contact bar upon the studs. The frame of the float-1
ing pulley is attached by a flexible wire or chain to a stud on a wheel on the
spindle of the reversing switch. In the condition of rest the reversing switch
is in the OFF position, and the contact bar on the first stud, and the counter-
weight rests on the base of the apparatus. When the reversing switch. is
turned on in either direction, the floating pulley is pulled, thus raising the
counterweight the contact bar being meanwhile held almost stationary by the
action of the dash pot. After the movement of the reversing switch is com-
. pleted the dash pot will gradually allow the counterweight to fali, and draw
the contact bar over the other studs, cutting out the sections of resistance con-
nected between them.
The dash pot piston is fitted with a cup leather so as to form an air tight fit
when being drawn out of its cylinder but to pass freely back. To regulate the
speed of yielding of the dashpot a leak is provided in the base of the cylinder
by means of a screw threaded hole into which a special screw is fitted. This
screw has part of the thread on one side filed away, so that at the point all
thread is removed but near the head full thread remains. The piston and its
adjuncts are made sufficiently heavy to return promptly to the starting position
as soon as the reversing switch is turned to the OFF position.
For motors of small power the dash pot device may perform the entire con-
trolling functions without the intervention of a ratchet and pawls.
Dated this 13th day of November 1899.
FREDK. WALKER,
73, St. Stephen's Road, Upton Park, London, E.,
Agent for the Applicants.
Improvements in Switches for use with Rheostats for Starting and
Controlling Electric Motors for Lifts or the like.
We, HUGO HIRST, of 69, 71, 88, and 92, Queen Victoria Street, in the City and
County of London, Electrical Engineer, and FREDERIC OSMOND HUNT, of 21,
Mount Vale, York, Electrical Engineer, do hereby declare the nature of this

page_text: invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
Our invention relates to switches for starting and controlling electric motors
for driving the winding gear of lifts or the like, or any apparatus so driven
in which it is desirable that the rate of the switch movement shall be controlled
by the mechanism or apparatus so driven.
For this purpose we use a multiple contact switch operated by means of a
ratchet and pawl.
In the annexed six explanatory sheets of drawings Figure 1, Sheet 1 is a
horizontal sectional plan and Figure 2, Sheet, 2 a vertical sectional elevation
of our improvements, Figures 3 to 14, Sheet 3 being merely details of Figures 1
and 2 shewn separately for clearness. Sheets 4 5 and 6 are views of the dashpot
arrangement hereinafter more fully referred to, Figure 1, Sheet 4 being a ver-
tical section and Figures 2 to 8 details; whilst Figure 9, Sheet 5 is an elevation
of Figure 1, Sheet 4, Figures 10 to 13 being details. Figure 14, Sheet 6 is a
plan view of the dashpot arrangement shewn in Figure 1, Sheet 4 and Figure 9,
Sheet 5, whilst Figures 15 to 17 inclusive shew details.
In carrying our invention into effect we use an arm A, Figure 1, Sheet 1 and
Figure 2, Sheet 2, which has a reciprocatory movement imparted to it by means
of a rod B (shown broken and swung round for clearness) attached to an eccen-
tric strap, crank, or cam lever, said eccentric, crank or cam being attached to
any convenient part of the driving mechanism of the lift or the like, or to an
auxiliary countershaft, so that a synchronous movement is imparted thereto.
The range of the pawl C is adapted to take up one or more teeth of the ratchet
wheel D upon each movement of A and B as may be predetermined, thereby
moving the contact brush E over the contact bars or studs F, which are con-
nected to a rheostat or set of resistance coils, thus allowing of a graduated cur-
rent in the motor circuit. These coils are of the ordinary platinoid, German
silver, or other alloy of high resistance and are not necessarily shewn by the
drawings, but simply indicated by the contacts F.
The switch in all modifications is continuous, having no "switch on and off"
positions, this being accomplished by a separate switch of any type, preferably
a reversing switch.
The pawl C is thrown out of action upon the ratchet or detent wheel D by a
curved lever G, operated by spiral springs or by gravity when no current is
passing. Said pawl C is carried within a slots and a pin p engaging with G and
controlled by its action as aforesaid. When the current is switched on by the
independent switch herein before referred to, the curved lever G is forced towards
the centre of the ratchet wheel D by a solenoid or electro magnet in shunt with
the main circuit or in circuit with the shunt field winding of motor) and not
shewn by the drawings, the pawl C then engaging with the teeth of the ratchet D.
Thus when the rod B is operated by the motor shaft or any countershaft con-
nected thereto, the motor automatically cuts out the resistances between the
contact studs F of the switch gradually until full speed is attained, when the
ratchet D no longer advances since the teeth are segmental and a plain part of
the periphery prevents the pawl C from further action.
We may modify the above arrangement by causing the releasing device G
to be mechanically connected to the brake lever of the winding gear, or to a
special lever operated by a cam on the spindle of the reversing switch. The
release lever G in the drawing is intended for operation by the latter arrange-
ment. In the first case the release is effected by the application of the brake,
and in the second by the action of the said reversing switch, but in both methods
of mechanical release the pawls are thrown out of gear before the reversing
switch breaks the circuit. This causes the whole of the starting resistance to
be inserted before the circuit is broken, thereby ensuring a gentle stoppage,
and saving said reversing switch from destructive arcing.
The force necessary to return the switch to the starting position when

page_text: released, as aforesaid, may be provided by a coiled or other spring, or a weight
acting by gravity on a lever or on a cord or chain H passed under a friction
roller and over a suitable pulley J on the switch spindle.
In cases where a limit is fixed for the amount of current to be taken from
the mains at starting, an additional device is provided in all cases where the
motor starting at full load requires current beyond the aforesaid limit for start-
ing at full load. In such cases the resistance in the circuit is made sufficiently
high to keep the initial current within the prescribed limit, and the cutting
out of the first sections of resistance is accomplished by means of a multiple
contact switch controlled by a dash pot.
A modification of this arrangement is shewn by Sheets 4, 5 and 6 of the
drawings, in which a vertical combination is shewn, with a compensatory. dash
pot. The contacts a are arranged in a straight line vertically, and a contact
bar b having a spring held between the sides 61 and under a cap slides over
these in succession. Attached to one side of the bar, but insulated from it
by material c¹ is the piston rod c of the dash pot d. On the other side of the
contact bar is attached a flexible cord or chain e passing over a floating pulley f
and so to a counterweight 9 which is sufficiently heavy to overbalance the
weight and frictional resistance of the contact bar upon the studs. The frame h
of the floating pulley f is attached by a rod j and flexible wire or chain through
a connection shown in Figures 12 and 13 to a stud on a wheel on the spindle
of the reversing switch. In the condition of rest the reversing switch is in
the OFF position, and the contact bar on the first stud, and the counterweight
rests on the base of the apparatus. When the reversing switch is turned "ON"
in either direction the floating pulley is pulled by means of rod j thus raising
the counterweight 9, the contact bar being meanwhile held almost stationary
by the action of the dash pot. After the movement of the reversing switch is
completed the dash pot d will gradually allow the counterweight to fall and
draw the contact bar 6 over the studs, cutting out the sections of resistance
connected between them.
The dash pot piston k is fitted with a cup leather 7 so as to form an air-tight
fit when being drawn out of its cylinder but to pass freely back. To regulate
the speed of yielding of the dash pot a leak is provided in the base of the
cylinder, by means of a screw threaded hole into which a special screw m_is
fitted. This screw has part of the thread on one side filed away so that at the
point all thread is removed but near the head full thread remains.
The piston
and its adjuncts are made sufficiently heavy by weight n to return promptly
to the starting position as soon as the reversing switch is turned to the OFF
position. The dash pot is provided with a dust cover p which also contributes
to the action of the weight n.
For motors of small power the dash pot device may perform the entire con-
trolling functions without the intervention of the ratchet and pawl device
before described.
Haying now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
First. In the construction of a ratchet operated rheostat the use of a recipro-
cating arm, adapted to be worked from the driven machinery, in combination
with a ratchet having teeth only over the range corresponding to the movement
of the contact brush, as and for the purposes herein before described.
Second. The combination with a ratchet operated rheostat of a releasing
device having a smooth edge corresponding to the outer surface of the
ratchet teeth and controlled by the circuit breaking switch, either electrically
or mechanically substantially as described.
Third. In the construction of a rheostat the combination of a dash pot, float-
ing pulley and a weight, whereby motion of the contact maker continues after

page_text: all communicated motion has ceased, as and for the purposes substantially as
herein before described.
Dated this 10th day of November 1900
BENJ. T. KING, A.Inst. Mech. E.
Registered Patent Agent,
165, Queen Victoria Street, London, E.C.,
Agent for Applicants.