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Jan. 20, 1948.
w. T. WHITE ErAL
2,4349680
LIMIT STOP APPARATUS
Filgd Aug; 2, 1944
2 Sheets-Sheet l
)
FIG-2
MHz-m
CONTROL
vSIGNAL.
IN VEN TOR.
WALTER T WHITE
DONALD H. COURTER
ATTORNEY
Jan. 20, 1948.
T, wHlTE HAL
7
2,434,680
LIMIT STOP APPARATUS
Filed Aug. 2, 1944
2 Sheets-Sheet 2
FIG.3
237
as
223
2131'
0.211;
2'
ma?
‘2'
021-2}-
22
224
INVENTOR.
"WALTER T. WHITE
By DONALD H. COURTER
ATTORNEY
Patented Jan. 20, 1948
2,434,680
uNirEo STATES PATENT OFFICE.‘
2,434,680
LIMIT STOP APPARATUS
Walter Thomas White and Donald Henschell
Courter, Hempstead, N. Y., assignors to Sperry
Gyroscope Company, Inc., a corporation of New
York
1
Application August 2, 1944, Serial No. 547,787
26 Claims. (Cl. 318-468)
2
This invention relates generally to motor con
trol systems in which the direction and speed of
currents in opposing ?eld windings of a motor or
a generator. A limit switch is operated in re
a motor is determined by an electronic control
circuit in response to the direction and magni
tude of a control signal, and particularly con
cerns limit stop apparatus for arresting the rota
tion of the motor irrespective of the control signal
sponse to a limit condition for removing the driv
ing power from the motor by applying a cut-oil‘
potential to the electron discharge device in the
balanced amplifier which is controlling the cur
rent in the driving ?eld winding. In order to
when a limit condition is reached.
I
quickly stop the motor, a reverse torque impulse
The major object of the invention is to provide
may be produced therein by causing a pulse of
an electronic cut-01f control responsive to a limit 10 current in the non-driving electron discharge de
condition to remove controlling signals from the
vice of the balanced ampli?er to produce a flux
motor during the existence of a limit condition.
pulse in the ?eld of the motor or generator which
Another object of the invention is to provide
opposes the direction of rotation of the motor.
electrical limit stop apparatus for‘ rapidly arrest
Accurate stopping control may be obtained by
ing rotation of a motor.
generating the pulse signal according to the con~
A further object of the invention is to provide
trol signal to produce a reverse torque impulse
electrical limit stop apparatus for rapidly arrest
which depends upon a control signal. In a motor
ing rotation of the motor independently of its
control system where the speed of the motor is
speed.
substantially proportional to the control signal,
A further object of the invention is to provide
the reverse torque impulse will then be substan
apparatus responsive to a limit condition of the
tially proportional to the speed of the motor. By
motor for applying a reverse torque impulse
appropriate selection of circuit values, it is pos
thereto,
sible to obtain quick and complete stoppage of the
A still further object of the invention is to
motor when a limit condition is reached.
provide limit stop apparatus in which a reverse
The motor control system shown in Fig. 1, is
torque impulse is produced in the motor of a
arranged to be connected to a control signal
magnitude, determined by the signal controlling
source as by leads H and [2 which are supplied .
the speed of the motor.
to an ampli?er l3 that may include a suitable
A still further object of the invention is to pro 30 demodulator circuit to convert the control signal
vide a limit stop apparatus for arresting a motor
to a balanced unidirectional voltage in the event
by modifying its control circuit in a manner
the control signal is an alternating voltage. The
which permits the motor to drive itself out of
balanced unidirectional voltage from the ampli
a limit condition.
Other objects and speci?c advantages of the
invention will become apparent from the follow
ing description taken in connection with the ac
companying drawings, wherein:
Fig. 1 is a schematic wiring diagram of a motor
control system in which the limit stop apparatus
is connected to a control circuit directly con
nected to the motor;
?er I3 is supplied as by leads l4 and I5 to control
35 grids l6 and I‘! of ampli?er tubes I8 and I9 that
are arranged in a conventional balanced circuit
with their plates 2| and 22 connected through
‘ load resistors 23 and 24 to a suitable source of
positive potential 25.
The ampli?ed control
signal, appearing across resistors 23 and 24, is
supplied through coupling resistors 26 and 2‘! and
coupling resistors 26’ and 21’ across grid leak
resistors 28 and 29 to control grids 3| and 32 of
Fig. 2 is a schematic wiring diagram of a motor
control system- in which the invention is con
power ampli?er tubes 33 and 34. The power am
nected to limit stop apparatus connected to a 45 plifier tubes are shown as pentodes connected in
control circuit for a generator, the output of
a conventional balanced ampli?er circuit direct
which controls a motor; and
ly coupled to the output of the ampli?er tubes l8
Fig. 3 is a schematic wiring diagram of a motor
and I9 and having their control grids 3| and 32
control system of the speed lag type which is
connected through resistors 28 and 29 to a source
provided with velocity damping and includes - 35 of negative potential. The positive and nega
limit stop apparatus embodying the invention to
produce a reverse torque in the motor dependent
upon its speed.
According to the invention, a control circuit
tive potentials, from terminals 25 and 35, have
substantially constant values measured with re
v spect to the ground.
Plates 36 and 31 of the power ampli?er tubes
includes a balanced ampli?er for controlling the 55 33 and 34 are connected through opposing ?eld
2,430,680
windings 36 and 39 of motor 40 to a source or
positive potential 4|. With this arrangement the
currents in the windings 36 and 39 depend upon
the space currents of tubes 33 and 34, which in
turn are controlled by the potentials of control
grids 3| and 32.
4
thereby momentarily increasing the conductivity
oi’ the non-driving tube 34 to increase its space
current as well as the current through winding
33. This pulse of current drawn through winding
39 produces a reverse torque impulse in the motor
40 which tends to reverse the motor and is, pref
erably, of just su?lcient magnitude to stop the
The motor 40 has its armature 42 connected to
motor, its driving torque having been already re
a suitable constant current source 43. so the speed
moved by cutting off tube 33.
or acceleration of the motor 40 and its output
It has been found advantageous to cause the
shaft 44 are dependent upon the effective ?eld 10 reverse
torque impulse to be dependent upon the
as determined by the difference between the cur
magnitude
of the control signal. Since the out
rents in the ?eld windings 38 and 39. The motor
put voltage of tube I6 is dependent upon the con—
40 may, of course, drive any suitable load, as rep
trol signal, the voltage pulse applied through con
resented by a rack 45, that is driven by a pinion
denser 62 is likewise dependent upon the control
46 from the shaft 44.
signal. Whether or not the reverse torque im
A pair of limit switches 5| and 52 are arranged
to be closed by limit conditions of the load to en
ergize coils 53 and 54 of relays 55 and 56 which
operate switch contacts 51 and 58 respectively.
The contact 51 is normally closed to complete the
coupling circuit, including resistors 26 and 23, be~
tween tubes I3 and 33 of the two balanced am
pli?er circuits. When the relay 55 is energized.
contact 51 breaks the connection between the re
sistors 26 and 26' thereby causing the full nega
tive potential of source 35 to be applied through
grid leak 28 to the control grid 3|. At the same
time, the contact 51 closes to its other position to
connect the output of tube I8 through resistor 26
across resistor 6| that is connected to ground. A
pulse corresponds to the speed of the motor, de
pends upon the dynamic characteristics of the
motor control system. If the system is designed
so that the motor is driven at a speed proportional
to the magnitude of the control signal, the reverse
torque impulse, which is also substantially pro
portional to the control signal, will also correspond
to the speed of the motor and, by appropriate se
:25 lection of proportionality factors, may be made
equal and opposite to the momentum of the arma
ture and the load driven thereby.
Fig. 2 shows a modi?ed motor control system in
which an error signal from leads III and H2 is
supplied to an ampli?er I I3, the output of which
is coupled to grids H6 and H1 of ampli?er tubes
II 8 and H9, arranged in a balanced circuit. rI‘he
control grid 32 of the tube 34 so the surge of cur
output of this balanced ampli?er circuit, appear
rent through resistor 6|, when the relay 55 is
ing across load resistors I23 and I24, is supplied
operated, causes a positive pulse to be applied
through coupling resistors I25 and I26 and cou
through condenser 52 to the control grid 32 of
pling resistors I25’ and I25’ to control grids I3I
the tube 34 thereby momentarily increasing the
and I32 of pentodes I33 and I34 which are also
conductivity of the tube 34, to increase the space
arranged in a balanced circuit, having their space
current and the current drawn through winding
paths respectively connected in series with op
39 of the motor 42.
posing ?eld windings I36 and I39 of a generator
40
Relay 56 may be energized by limit switch 52
I1I.
upon movement of the load in the opposite direc
The generator I1I has its armature I12 driven
tion to disconnect the control grid 32 from the
at a constant speed as by a motor I13 and con
ampli?er tube I9 thereby cutting of! the tube 34
nected to armature I42 of motor I40. Field wind
by the negative potential of source 35. At the
ing I50 of the motor I40 is energized from a suit
condenser 62 is connected from resistor 6| to the
same time, positive voltage, from the output of
the tube I9, is applied through resistor 21 and
able source I43 and the armature I42 drives
through shaft I44 and pinion I46 to move a rack
I45 representing a suitable load.
The tubes I33 and I34 have their cathodes I15
contact 58 across resistor 64 to ground. A con
denser 65 is connected between resistor 64 and
control grid 3| of the tube 33. When the relay 50 and I16 normally connected through a cathode
56 is energized, the surge of current through re
bias resistor I11 to ground. When the rack I45
sistor 64 charging the condenser 65 supplies a
reaches its upper limit, it closes limit switch I5I
positive pulse to grid 3| momentarily increasing
thereby energizing the coil I53 of relay I55 to op
the conductivity of the tube 33 to produce a pulse
erate switch contacts I51 and I51’. Actuation of
of current through winding 38 which causes the
contact I51, by energization of relay I55, removes
motor 40 to produce a reverse torque impulse.
the connection of cathode I15 to bias resistor I11
In operation a control signal applied to the am
and connects the cathode I15 directly to the
pli?er I3 controls the potentials of grids 3| and
source I4 I of positive potential thereby raising the
32 to regulate the space currents in tubes 33 and
potential of the cathode I15 to cut-off the tube
34 for controlling the currents in opposing ?eld
I33.
windingsg 38 and 39 so the effective ?eld of the
The grid I3I of the tube I33 is normally con
motor 40 depends upon the control signal and
nected through grid leak resistor I23 to a negative
causes the motor to drive shaft 44 and its rack
potential source I30 and grid I32 01 the tube I34
load 45. Assuming that the tube 33 is more ccn
is also normally connected through grid leak re
ductlve, the current in winding 33 will exceed that 05 sistor I29 to the negative source I30. When the
in winding 39, causing the motor 40 to move the
relay I55 is energized, contact I51’ removes a
rack 45 upwardly until it actuates limit switch 5|. '
short-circuit from parallel connected resistance
The actuation of the limit switch 5| energizes
condenser network I62 arranged between the re
relay 55 to remove the coupling between ampli?er
sistor I23 and the source I30. This removal of
tubes I8 and 33 thereby cutting 01! the tube 33
and removing the ?eld current from the winding 70 the short-circuit across the network I62 causes
a charging current to ?ow in the condenser which
36, to reduce the driving torque of the motor 40.
applies a positive voltage pulse to the grid I32,
At the same time, switch contact 51 is closed to
momentarilyincreasing the conductivity of the
apply the output voltage from tube I8 across the
tube I34 and the space current drawn thereby as
resistor 6| and condenser 62.
This‘ applies a positive pulse to the grid 33, 15 welLas the current in ?eld winding I39. This
'5
2,484,880
pulse of current in the ?eld winding I39 produces
a pulse voltage which is applied to armature I42
that produces a reverse torque impulse in the
motor I40. Since the driving power from motor
6
With this arrangement, the potential of grids
221 and 228, which in the quiescent state. are
biased through grid leak resistors 240 and 238 to
a source 239 of negative potential, is controlled
I40 has been removed by biasing the tube I33 to
reduce the output of the generator IN, the re
verse torque impulse produced by the pulse volt
according to the di?ference between the control
signal and velocity signal of the motor. This is
terposed between the grid leak resistor I28 and
the negatlvesource I30. Charging current in the
network I 65 applies a positive voltage pulse to the
grid I3I momentarily increasing the conductivity
?eld windings 251 and 258 to a source 259 of posi
tive potential.
During normal operation, the effective ?eld of
of the tube I 33 to cause a reverse voltage pulse
from the generator I1I to produce a reverse
the motor 233 will depend upon the diiference
between the currents in ?eld windings 251 and
a well known arrangement in that the velocity
age applied to the grid I32 will stop rotation of
signal is used in a degenerative sense to provide
the motor I42.
velocity damping for stabilizing the operation of
When the tube I34 is more conductive than the 10 the motor 233.
tube I33, it becomes the driving tube and pro
The combination of signals supplied to the grids
duces a current in the winding I39 so generator
221 and 228 is ampli?ed by the tubes 229 and 23I
I1I applies an output voltage to the motor I40
and is coupled through resistors 24I and 242 that
tending to drive the rack I45 downwardly. When
are normally connected to resistors 243 and 244
the rack I45 reaches its lower limit it closes limit 15 which are in turn connected to control grids 245
switch I52 to energize coil I54 of relay I56vwhich
and 246 of ampli?er tubes 241 and 248, shown in
operates contact I58 to connect cathode I16 of the
this case as pentodes having their cathodes 249.
tube I34 directly to the source I4I thereby raising
and 25I connected in a balanced circuit to ground.
the potential of the cathode I16 to cuto? the
During the quiescent state, control grids 245 and
tube. At the same time, relay I56 actuates con 20 246 are connected through grid leak resistors 252
tact I58’ to remove the short-circuit of parallel
and 253 to a source 254 of negative potential.
connected resistance condenser network I65 in
Plates 255 and 256, of the power tubes 241 and
torque impulse in the motor I40. Since the driv
ing power for the motor I40 is removed by cutting
oif the tube I34, ‘the reverse torque impulse will
tend to stop rotation of the motor and its load.
As in the case of the motor control system de
scribed in connection with Fig. 1, a voltage im
pulse is produced that is dependent upon the con
trol signal so a reverse torque impulse is obtained
in the motor that is related to its speed or
acceleration.
The motor control system, shown in Fig. 3, is
similar to that in Fig. 1, but is a more re?ned sys
tem in that velocity damping is provided for sta
bilizing the operation of the motor and the system
248, are respectively connected through opposing
258 as determined by the space currents of power
tubes 241 and 248 which in turn depend upon the
potentials of control grids 245 and 246 as deter- .
mined by the di?’erence between the control and
velocity damping signals.
The motor 233 has its armature 26I connected
to a suitable constant-current source 262 and
arranged to drive through shaft 263 and pinion
264 to operate a load in the form of a rack 265.
In order to stop the motor when the load reaches
a limit condition, limit switches 266 and 261 are
arranged to be actuated by the rack 265 when the
motor drives it to a limit condition. Actuation
of the limit switch 266 energizes coil 268 of a relay
268 that operates ganged contacts 21I and 212.
is of the type known as a speed lag control wherein
the speed of the motor is substantially propor
Similarly, actuation of the limit switch 261 ener- '
tional to the control signal. The control signal 45 gizes coil 213 of relay 214 which operates ganged
may be derived from any source and is frequently
switch contacts 215 and 216.
>
taken as the output of a remote control trans
When the load rack 265 is driven by the'motor
mission system or as the error signal in a follow
233 to its upper limit, it causes limit switch'266
up system.
Such an error or control signal may
be connected as by leads 2| I and 2 I2 to an ampli
?er 2I3, the output of which as represented by
leads ‘M4 and 2|5 is supplied to grids 2I6 and 2I1
to energize relay 269 thereby operating switch
contact 21I and switch contact 212. When the
motor is driving in this direction, tube 248 is sup
plying the driving current to ?eld winding 258.
of tubes 2I8 and 2| 9 that are arranged in a bal
Operation of the switch contact 212 removes the
anced ampli?er circuit to produce a differential
positive signal from the input grid of tube 248,
voltage across load resistors 22I and 222 of a 55 thereby cutting off the space current in the power
polarity and magnitude dependent upon the con
trol signal. In the case of a unidirectional error
or control signal, the differential voltage will be
of a polarity and magnitude corresponding to the
tube 248 due to the negative bias potential from
source 254.
This‘removes the driving power from the motor,
but in order to stop the motor, it is necessary to
polarity and magnitude of the control signal.
60 produce a reverse torque impulse. For this pur
This differential voltage is directly coupled as
pose, a condenser 28I is charged from the output
by resistors 223 and 224 and resistors 225 and 226
of tube 2| 8 through switch contact 2H and re
to grids 221 and 228 of summing ampli?er tubes
229 and 23I respectively. An additional signal,
corresponding to the speed of motor 233, is gen
sistor 282. The-potential of the condenser 28I,
when it is charged, depends upon the control
signal. Since the ampli?ers are all balanced cir
erated as by a permanent magnet generator 234
cuits and the stage including tubes 229 and 23I
driven from the motor, and is applied across re
inverts the signal from tubes 2 I8 and 2I9, a posi
sistor 235 having its center point grounded to
tivecharge will appear on the condenser 28I when
provide a balanced unidirectional signal which
the nature of the control signal is such that tube
may be applied through coupling resistors 236 70 248 provides the power current to the motor 233.
. and 231 to grids 221 and 228 respectively. The
When the switch contact 21I is operated by
polarity of the generator is selected so it produces
the relay 269, the charge on the condenser MI
a degenerative e?ect by opposing the differential
is applied directly to the control grid 245 of tube
voltage from tubes 2I8 and 2I9 which depends
241 and the discharge of the condenser 28I applies
upon the control signal.
a positive voltage pulse to this control grid. This
2,484,680
7
8
.
ing a control circuit including a pair of electro
application of a positive voltage pulse to the con
discharge devices arranged in a balanced circuit
trol grid 245 produces a momentary increase in
responsive to a control signal for controlling the
the space current of the power tube 241 thereby
direction and speed of the motor by the di?erence
momentarily increasing the current in ?eld wind
between the space currents of said devices, a limit
ing 25‘! to produce a reverse torque impulse in
switch arranged to be operated by a limit condi
the motor 233. Since the velocity of the motor
tion of said motor, and means controlled by oper
233, as previously explained, is substantially pro
ation of said limit switch for reducing the space
portional to the magnitude of the control signal,
current of the electron discharge device driving
the charge on the condenser 28l will also be sub
stantially proportional to the velocity or the ll) said motor into said limit condition and for in-:
creasing the space current of the other electron‘
motor. By appropriate selection of circuit con
discharge device a proportional amount.
stants, this charge may be made just su?icient
3. Limit stop apparatus for a motor comprising
to produce a reverse torque in the motor 233 that
a
control
circuit including a pair of electron dis
will oppose the momentum of the load, thereby
rapidly stopping rotation of the motor 25i when 15 charge devices arranged in ' a balanced circuit
responsive to a control signal for controlling the
the limit condition is reached.
direction and speed of the motor by the di?erence
By a similar arrangement, when the rack 255
between the space currents of said devices, a limit
reaches its lower limit condition, limit switch 251
switch arranged to be operated by a limit condi
energizes relay 214 to operate switch contacts 215
and 216. When the motor 233 is driving in this 20 tion of said motor, and means controlled by oper
ation of said limit switch for applying a negative
direction, the power tube 241 is supplying driving
potential to the control electrode of the electron
current and operation of the switch contact 215
discharge device driving said motor into said con
removes the positive control voltage from the
dition
for cutting o? the space current of said
control grid 245 so the tube 241 is cut-off by the
driving device.
application of the negative potential from the
4. Limit stop apparatus for a motor comprising
source 254. A condenser 285 is charged from the
a
control
circuit including a pair of electron dis
output of tube 2!!! through switch contact 215
charge devices arranged in a balanced circuit re
and resistor 286. When the relay 214 is operated,
sponsive to a control signal for controlling the
the charge on the condenser 285 causes a positive
pulse to be applied to the control grid 246 of the 30 direction and speed of the motor by the differ
ence between the space currents of said devices,
power tube 248 thereby causing a momentary
a limit switch arranged to be operated by a limit
increase in the space current of the tube 248
condition of said motor, and means controlled
which produces a reverse torque impulse in the
by operation of said limit switch for applying a
motor 233 to arrest motion of the load 265.
positive potential to the cathode of the electron
In the apparatus shown in Fig. 3, it will be
discharge device driving said motor into said limit
apparent that when a limit is reached, the driving
condition for cutting off space current of said
power is removed from the motor by cutting off
driving device.
the driving tube and at the same time the oppo
5. Limit stop apparatus for a motor compris
site tube of the balanced power ampli?er is pro
vided with a positive voltage pulse which pro 40 ing a’ control circuit including a pair of electron
discharge devices arranged in a balanced'circuit
duces a momentary increase in the current of the
having their space currents controlled by a con
motor ?eld, thereby producing a reverse torque
trol signal, means connected to said devices for
impulse in the motor which stops the motor and
controlling the speed of the motor by the differ
its load. The positive voltage pulse is made sub
ence between the space currents of said device,
stantially proportional to the error signal. Since
and a limit switch arranged to be operated by a
the velocity of the motor is also proportional to
limit condition of said motor for reducing the
the error signal, the reverse torque impulse is
control signal applied to one of said devices and
made substantially proportional to the velocity
adding said signal to that supplied to the other
of the motor. With this arrangement and by
proper selection of proportionality factors for the
device.
6. Limit stop apparatus for a motor compris
circuits, the reverse torque impulse becomes
ing a control circuit including a pair of electron
equivalent to. the momentum of the load and
discharge devices controlled by a control signal
rapidly stops rotation of the motor without re
and arranged in a balanced circuit with opposing
versing the direction of rotation.
Since many changes could be made in the above U. Ga ?eld windings of the motor connected in the space
circuit or said devices to control the speed of said
construction and many apparently widely di?er
motor by the di?'erence between the space cur
ent embodiments of this invention could be made
rents of said devices and in accordance with the
without departing from the scope thereof, it is
magnitude of said signal, and a limitswitch ar
intended that all matter contained in the above
description or shown in the acoompanying'idraw 60 ranged to be operated by a limit condition of said
motor for applying a potential for reducing the
ings shall be interpreted as illustrative and not
in a limiting sense.
space current of the more conductive device to
stop said motor and reduce the current in the
What is claimed is:
1. Limit stop apparatus for a motor comprising
?eld winding thereof and to increase the space
a control circuit including two control means
current in the other device from that when the
motor is out of a iimit~stop condition by an
responsive to opposing signals and having their
amount proportional to the magnitude or said
outputs differentially supplied to control the
signal.
speed and direction of operation of said motor,
a limit switch adapted to be operated by said
7. Limit stop apparatus for a motor comprising
a control. circuit including a pair of electron dis
motor when a limit condition thereof is reached,
charge devices controlled by a control signal and
and means controlled by operation of said limit
switch for adding a component of the one signal
arranged in a balanced circuit with their space
circuits connected to opposing ?eld windings of
to the other to reduce the driving power of said
a‘ generator, the output of which controls the
motor.
2. Limit stop apparatus for a motor compris 75 speed or a motor, to differentially vary the e?ec
2,434,680
tive ?eld of said generator according to the dif
ference between the space currents of said de
vices in response to a control signal and in ac
cordance with the magnitude of said signal, and
a limit switch arranged to be operated by a limit
condition of said motor for applying a potential
10
limit switch arranged to be actuated by a limit
condition of said motor, and means connected to
be controlled by actuation of said limit switch
for adding a component of the one signal to the
other whereby to reduce the driving torque there
of and simultaneously to produce a reverse torque
to the more conductive of said devices thereby re
impulse in said motor.
ducing the space current thereof to stop the mo
14. Limit stop apparatus for a ‘motor compris~
tor and decrease the current in the ?eld winding
ing
a control circuit including a pair of electron
of said generator and to increase the space cur 10
discharge devices arranged in a balanced circuit
rent in the other device from that when the mo~
responsive to a control signal for producing an
tor is out of a limit-stop condition by an amount
unbalance of the space currents of said devices,
proportional to the magnitude of said signal.
means connected to said devices for controlling
8. Limit stop apparatus for a motor compris~
a motor by the difference between said space cur
ing a control circuit including a pair of electron
rents, and a limit switch arranged to be actuated
discharge devices arranged in a balanced circuit
by a limit condition of said motor for reversing
with their control electrodes responsive to an
the unbalance of said currents for an interval to
error signal for controlling the direction and
stop said motor and adding a component of said
speed of the motor by the di?erence between the
control signal to the signal supplied to one of '
space currents of said devices, and a limit switch 20 said devices.
arranged to be operated by a limit condition of
15. Limit stop apparatus for a motor compris~
said motor for applying a cut-off voltage to one
ing
a control circuit including a pair of electron
of said devices.
discharge devices arranged in a balanced circuit
9. Limit stop apparatus for a motor compris
responsive to a control signal for producing an
ing a control circuit including a pair of electron 25 unbalance of the spaceccurrents of said devices,
discharge devices arranged in a balanced circuit
means connected to said devices for controlling
with their control electrodes responsive to an
a motor by the diii‘erence between said space cur
error signal for controlling the speed of a motor
rents, and a, limit switch arranged to be actuated
by the difference between the space currents of
by a limit condition of said motor for applying an
said devices, the direction of said motor being 30 added positive potential to the lesser conductive
determined by the more conductive discharge
device dependent upon said control signal for
device, and a limit switch arranged to be actu
momentarily reversing the unbalance of said cur
ated by a limit condition of said motor for ap
rents to apply a reverse torque to said motor de
plying a cut-off voltage to said more conductive
pendent upon said control signal.
device.
35
16. Limit stop apparatus for a motor compris
10. Limit stop apparatus for a motor compris
ing a control circuit including a pair of electron
ing a control circuit responsive to a control signal
discharge devices arranged in a balanced circuit
for controlling the motor and including two con
responsive to a control signal for producing an
trol means responsive to opposing signals and
unbalance of the space currents of said devices,
having their outputs di?erentially supplied to 40 means
connected to said devices for controlling
control the speed and direction of operation of
a motor by the difference between said space cur
said motor, a limit switch arranged to be actu
rents, and a limit switch arranged to be actuated
ated by a limit condition of said motor, and means
by a limit condition of said motor for applying
connected to be controlled by actuation of said
an added voltage to the lesser conductive of said
limit switch for adding a component of the one Y devices to momentarily reverse the unbalance of
signal to the other to apply a reverse torque im
said currents to produce a reverse torque impulse
pulse to said motor.
11. Limit stop apparatus for a motor compris
ing a control circuit including two control means
in said motor.
7
17. Limit stop apparatus for-a motor compris
a control circuit including a pair of electron
responsive to opposing signals and having their 50 ing
discharge devices arranged in a balanced circuit
outputs differentially supplied to control the
responsive to a control signal for producing an
speed and direction of operation of the motor, a
limit switch arranged to be actuated by a limit
condition of said motor, and means connected to
be controlled by actuation of said limit switch
and responsive to said control signal for adding
a component of the one signal to the other where
by to apply a reverse torque impulse to said motor
dependent upon said control signal.
12. Limit stop apparatus for a motor compris
unbalance of the space currents of said devices,
means connected to said devices for controlling
a motor by the difference between said space cur
rents, and a limit switch arranged to be actuated
by a ‘limit condition of said motor for applying
a cut-off potential to the more conductive of said
devices and momentarily reversing the unbalance
of said currents to produce a reverse torque in
said motor.
‘
,
ing a control circuit including two control means
18. Limit stop apparatus for a motor compris
responsive to opposing signals and having their
a control circuit including a pair of electron dis
outputs differentially supplied to control the
charge devices arranged in a balancedcircuit re
speed and direction of operation of the motor, a
sponsive to a control signal for unbalancing the
limit switch arranged to be actuated by a limit 65 relative conductivity of said devices, means con
condition of said motor, and means controlled
nected to said devices for controlling the speed of
by actuation of said limit switch for adding a
the motor by the difference between the space
component of the one signal to the other whereby
currents of said devices, a limit switch arranged
to apply a reverse torque impulse to said motor
to be actuated by a limit condition of the motor.
corresponding to the velocity of said motor.
‘
and means connected to be controlled by actua
13. Limit stop apparatus for a motor compris
tion of saidlimit switch for providing an added
ing a control circuit including two control means
pulse‘ voltage to cause momentary increase in the
responsive to opposing signals and having their
conductivity of the lesser conductive device there
outputs differentially supplied to control the
speed and direction of operation of the motor, a
by producing a reverse torque impulse to stop said
motor.
0,484,080
11
12
cuit comprising an input circuit for a control sig
i9. Limit stop apparatus for a motor compris
ing a control circuit including a pair of electron
discharge devices arranged in a balanced circuit
responsive to a control signal for unbalancing the
relative conductivity of said devices, means con
nected to said devices for controlling the speed of
the motor by the difference between the space
nal, a pair of electron discharge devices arranged
in a balanced circuit connected to said input cir
cuit and responsive to a control signal for ren
dering one or said devices more conductive than
the other, a limit switch, means responsive to
actuation of said switch tor applying a potential
to reduce conductivity of the more conductive de
currents of said devices, a limit switch arranged
vice, and means responsive to actuation of said
to be actuated by a limit condition of the motor,
switch for applying a pulse potential to the lesser
10
and means connected to be controlled by actua
conductive or said devices to momentarily in
tion of said limit switch for providing an added
crease its conductivity.
pulse voltage dependent upon said control signal
24. In a motor control system, a control circuit
to cause a momentary increase in the conductivity
comprising an input circuit for a control signal,
of the lesser conductive device thereby producing
a pair of electron discharge devices arranged in
a reverse torque impulse dependent upon said 15 a balanced circuit connected to said input circuit
control signal to stop said motor.
.
and responsive to a control signal for rendering
20. Limit stop apparatus for a motor compris
one oi! said devices more conductive than the
ing a control circuit including a pair of electron
other, a limit switch, and means responsive to
discharge devices arranged in a balanced circuit
responsive to a control signal for unbalancing the 20 actuation of said switch for applying a negative
potential to the control electrode of the more
relative conductivity 01 said devices, means con
conductive device to cuto? the conductivity
nected to said devices for controlling the speed
thereof.
of the motor by the difference between the space
25. In a motor control system, a control circuit
currents of said devices, a limit switch arranged
an input circuit for a control signal,
to be actuated by a limit condition of the motor, 25 comprising
a
pair
or
electron
discharge devices arranged in
means connected to be controlled by actuation of
a
balanced
circuit
connected
to said input circuit
said limit switch for reducing the conductivity
and responsive to a control signal for rendering
of the more conductive device, and means con
one of said devices more conductive than the
nected to be controlled by actuation of said limit
switch for providing an added pulse voltage to 80 other, a limit switch, and means responsive to
actuation of said switch for applying a positive
cause a momentary increase in the conductivity
potential to the cathode of the more conductive
of the lesser conductive device thereby producing
device to reduce conductivity thereof.
a reverse torque impulse to stop said motor.
26. In a motor control system, a control circuit
21. In a motor control system, a control circuit
comprising an input circuit for a control signal,
a pair of electron discharge devices arranged in a
balanced circuit connected to said input circuit
and responsive to a control signal for rendering
one of said devices more conductive than the
other, a limit switch, and means responsive to
actuation of said switch for simultaneously ap
plying a cut-oi! potential to the more conductive
comprising an input circuit for a control signal,
' a pair of electron discharge devices arranged in
a balanced circuit connected to said input circuit
and responsive to a control signal for rendering
one of said devices more conductive than the
other, a limit switch, and means responsive to
actuation of said switch for applying an added
pulse potential to the lesser conductive of said
devices to momentarily increase the conductivity
thereof.
/'
'
device to reduce the conductivity thereof, and a
pulse potential to the lesser conductive device to
45 momentarily increase the conductivity thereof.
22. In a motor control system, a control cir
WALTER THOMAS WHITE.
cuit comprising an input circuit for. a control sig
DONALD HENSCHELL COURTER.
nal, a pair of electron discharge devices arranged
in a balanced circuit connected to said input cir
REFERENCES CITED
cuit and responsive to a control signal for ren
dering one of said devices more conductive than 50 The following references are of record in the
the other, a limit switch, and means responsive
file of this patent:
to actuation of said switch for applying a poten
FOREIGN PATENTS
' tial to cuto? the conductivity of the more con
ductive device.
23. In a motor control system, a control cir 55
Number
102,887
- Country
Date
Sweden __________ __ Oct. 28, 1941
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