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Патент USA US3088070

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April 30, ‘1963
D. w. RICKE
3,088,060
CONTROL APPARATUS
Filed May 22, 1961
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FIG.
DONALD
INVENTOR.
W.' RICKE
BWPWW-M
ATTORNEY
United States Patent
1
3,088,060
CONTROL APPARATUS
Donald W. Ricke, East Bethel, Minu., assignor to Minne
apolis-Honeywell Regulator Company, Minneapolis,
Minn, a corporation of Delaware
Filed May 22, 1961, Ser. No. 111,753
12 Claims. (Cl. 318-19)
This invention relates to apparatus operable at varying
rates and more speci?cally to a dual speed motor servo
having a speci?c build-up of speed and a smooth change
from one speed to the other.
The use of dual speed motor servos in many ?elds
necessitates a predetermined build-up of speed and a
3,088,060‘
,.
IC€
Patented Apr. 30, 1963
2
ampli?er.
That is, until the motor reaches a certain
predetermined speed the impedance of the windings looks
relatively small to the output of the ampli?er, and the
voltage developed across these windings is relatively
small. A switching means connects the input of the sec
ond amplifying means to the output of the ?rst amplify
ing means and is so chosen that it will not operate until
the voltage across the windings is at a certain predeter
mined value. Thus, when the motor reaches the de
sired speed the impedance of the windings, which has
slowly increased as the back
of the motor has
increased, will reach a high enough value to develop a
predetermined amplitude of voltage across the switching
means. This predetermined amplitude of voltage will
cause the switching means to operate and send a signal
smooth shift of speed. That is, in many applications 15 to the second ampli?er which will in turn start the sec
the manner in which the speed of the output shaft of
ond motor rotating. The loading effect which the ?rst
the motor increases is very important. This increase
motor has on the ?rst amplifying means will keep the
or build-up of output shaft speed is generally spoken of
switching means from operating and, thus, keep the
as following a speci?c curve, which curve is actually
input voltage versus output speed. As already explained, 20 second motor from rotating until the ?rst motor has
attained the desired speed.
in many applications it is very important that the in
It is a primary object of this invention to provide an
crease in speed of the output shaft follow this speci?c
improved
control apparatus.
curve to reach the desired point on the curve rather than
It is a further object of this invention to provide an
following a different curve. Also, when the speed of
improved dual speed motor servo.
the output shaft changes from a ?rst rate of increase to 25
a second rate of increase the change must be smooth
and without any unwanted variations in the speed.
In some prior art arrangements the speed of the motor
servo was changed by means of a clutch and change of
gear arrangement. However, this was found to be very
jerky and extremely unsatisfactory.
It is a further object of this invention to provide a
dual speed motor servo with a smooth switching charac
teristic.
Still a further object of this invention is to provide
a dual speed motor servo with a predetermined output
shaft rate of turn with a given input signal.
These and other objects of this invention will become
In another prior arrangement two motors driving a
apparent from the following description of a preferred
summing differential are utilized. In this method a
embodiment form thereof and the accompanying speci
switching means is connected from an interstage point
?cation,
claims and drawings of which:
35
of a first multistage ampli?er for driving a motor to the
FIGURE 1 is a block diagram of the present appara
input of a second ampli?er for driving a second motor,
tus;
and the input signal is applied to the ?rst ampli?er.
FIGURE 2 is a curve of the output characteristics; and
When the input signal reaches a certain predetermined
FIGURE 3 is a block diagram showing a portion of
amplitude the switch operates and a signal is applied to
apparatus.
the second ampli?er thereby starting the second motor. 40 theInpresent
FIGURE 1 numeral 10 designates a condition re
However, if a sharp step function of voltage of a high
sponsive means. This condition responsive means may
enough amplitude to cause the switch to operate is ap
be any means responsive to a condition such as tempera
plied to the input, both motors will start at the same
ture, pressure or speed. In this preferred embodiment
time. When both motors begin to rotate at the same
condition responsive means 10 has a mechanical input
45
time the build-up speed of the output shaft will not fol
designated by a dotted line numeral 11 and an electrical
low the desired curve, but, rather, will take some short
output denoted by number 13. An electrical summing
cut to reach the point on the curve determined by the
point 12 is connected to the condition responsive means
amplitude of the input signal. Once this point is reached
10 by the output means 13. The electrical summing point
there may be a tendency to oscillate since there is no way
of controlling the amount of the speed of the output shaft 50 12 is also connected to a signal producing means, which
in FIGURE 1 is shown as an amplifying means ‘14, by
which each of the motors is contributing. Since both
a lead 15. A motor-generator means ‘16 is comprised of
motors are operating independently they may both at
a velocity generator G1 and a motor M1. This motor
tempt to increase enough in speed to contribute the total
output speed separately. Thus, the desired speed will
generator means 16 can be any standard electric servo
be surpassed, and then both motors will tend to slow 55 motor, such as the servomotor manufactured by Minne
apolis Honeywell as part Number 469139-5. This in
down simultaneously and independently. It can be seen
cludes a two phase motor and an A.C. velocity generator
that some considerable oscillation can occur before the
but it should be understood that the scope of the invention
desired point is ?nally reached. Thus, the prior art ar
includes DC. motors and DC. velocity generators as
rangements were inadequate for many applications.
The present device, in its preferred embodiment, is
comprised of a ?rst and second motor means which may
mechanically drive a summing differential means, a ?rst
and second ampli?er means to drive the motor means,
and a switching means connecting the output of the ?rst
well. Velocity generator G1 of motor-generator means
16 is electrically connected to electrical summing point 12
by a lead 17. Motor M1 of motor-generator means 16
is electrically connected to the output of amplifying means
14 ‘by a lead 18. Motor M1 of motor-generator means
amplifying means to the input of the second amplifying 65 16 is mechanically connected to a mechanical summing
di?’erential 20, said connection being depicted in FIG
means. A condition responsive means may be connected
URE 1 by dotted line 19.
V
to the input of a ?rst ampli?er and may in turn be con
A second amplifying means 24 is connected to an elec
trolled by the output of the summing differential means,
trical summing point 22 by means of a lead 25. A second
but this is not elaborated on since it is not a principal
70 motor-generator means 26, which is similar to motor
portion of the invention.
generator means 16, is comprised of a velocity generator
The present device utilizes the loading effect which
G2 and a motor M2. Also connected to the electrical
the ?rst motor windings have on the output of the ?rst
3
3,088,060
summing point 22 is the velocity generator G2 of motor
gencrator means 26 by a lead 27. The motor-generator
means 26 is connected to the output of amplifying means
24 by a lead 28. The motor M2 of motor-generator
means 26 is mechanically coupled to the mechanical sum
ming differential 20. This is shown in FIGURE 1 by
dotted line 29. The output of the mechanical summing
4
to rotate until motor M1 reaches this predetermined
speed. Thus, the curve shown in FIGURE 2 of the build
up of the output shaft rotation of differential means 20
will always follow the same curve. That is, motor M1
will increase rotation with the increase in output signal
from condition responsive means 10, designated E1, until
point 41 is reached at which time motor M2 will begin
differential means 20 is mechanically coupled to a load
to rotate also and the sum will increase the rate of rota
30. The load 30 may consist of a shaft which is to be
turned at varying speeds or may simply consist of a gear 10 tion of the output shaft of differential 20_as shown in
FIGURE 2 by the portion 42 'of the curve. This is true
train. Load 30 may be mechanically coupled to condi
tion responsive means 10, as shown in FIGURE 1 by
even if E, instantaneously reaches some amplitude higher
doted line 11, or may vary a condition, thereby, causing
speed designated by point 41 before the voltage at point
37 reaches an amplitude suf?cient to operate switching
condition responsive means 10‘ to react.
than point 41. ‘In this case motor M1 still must reach the
A switching means, which in ‘FIGURE 1 is designated 15
means 35. Thus, motor M1 of motor-generator means
by numeral 35, in this preferred embodiment consists of
16 acts like a ?lter for any sharp spikes of input voltage
two Zener diodes connected back-to-back. One side of
or any step functions of voltage input. The ?ltering
these Zener diodes is connected to a point 37 on lead
action of motor M1 insures that motor M2 will always
18 by a lead 36. The other side of Zener diode 35 is
connected to the electrical summing point 22 by a lead
23. The Zener ‘diodes connected back-to-back and desig
nated 35 are so chosen that a predetermined voltage at
point 37 will cause one of the diodes to break down and
the other diode to conduct a forward current, thus,
making the entire switching means 35 appear as an elec
trical short circuit. As long as the voltage at point 37
is below the predetermined amplitude the Zener diode
connected backwards in the circuit will not break down
react in the desired manner and, thus, give the desired
output at differential means 20.
Velocity generator G1 of motor-generator means 16
feeds a negative signal back to amplifying means 14
through lead 17, electrical summing point 12 and lead 15.
The negative feedback signal from velocity generator G1
acts as a rate damping signal to improve the system re—
sponse. Practically, system response means, how closely
the output follows the input. For example, if a step func
tion is applied to the amplifying means 14 motor M1 will
attempt to instantaneously reach the maximum speed
diodes are connected back-to-back to insure that current 30
corresponding to the amplitude of the step function.v Be
will not ?ow either way in the circuit until the proper
cause of inertia the motor will lag behind the input func
voltage is reached.
tion
and once the peak is reached will tend to overshoot
The voltage appearing on point 37 is a function of
causing oscillations. However, these oscillations are
the signal applied to ampli?er 14 by condition responsive
damped out by the negative feedback from the velocity
means 10 and the loading effect which motor M1 of motor 35 generator G1. At some point in the system response the
~generator means 16 has upon the output of ampli?er 14.
amount of negative feedback introduced by the velocity
The loading effect ‘which motor M1 of motor-generator
generator G1 to ampli?er 14 will be just suf?cient to
means 16 has upon ampli?er 14 is a function of the
damp the signal of the input step function so that motor
speed of motor M1. That is, when motor M1 is not rotat
M1 will overshoot, or oscillate, a minimum number of
ing the windings appear as nearly a short circuit. As 40 times
and will reach its maximum stable velocity in a
motor M1 begins to rotate a ‘back
is built up in
minimum of time.
the windings, as is well known to one skilled in the art,
Velocity generator G2 of motor-generator means 26
"causing the impedance to increase. As the impedance of
is connected to the electrical summing point 22 by lead
and switching means 35 appears as an open circuit. Two
the windings increases the voltage dropped across the
27. Velocity generator G2 has the same function, that
windings increases and, thus, the voltage at point 37 in 45 is to improve system response, as velocity generator G1.
creases in amplitude. When the voltage at point 37 has
In addition, however, it also serves as an electrical braking
increased to the predetermined amplitude to cause switch
means. When motor M1 is driving one input of differen
ing means 35 to operate a portion of the signal from
condition responsive means 10 is fed to the ampli?er 24.
tial means 20, because of friction within the differential
means 20, the movement of motor M1 may be trans
This causes motor M2 of motor-generator 26 to begin to 50 ‘mited through differential means 20 to motor M2 causing
rotate.
111 FIGURE 2 a curve is shown of vthe rotation rate
‘of the output shaft of the mechanical summing differen
it to rotate slightly. However, this rotation will be
counteracted by the fact that velocity generator G2 will
apply a negative signal to the input of ampli?er 24 which
tial means 20 as plotted against the [output voltage from
will in turn attempt to cause motor M2 to rotate the other
the condition responsive means 10 designated E1. The 55 way.
‘portion of the curve ‘40 designates the rate of rotation
Also connected to the output shaft 29‘ of motor M2 of
'of the output shaft of the mechanical summing differen
motor-generator means 26 is a friction braking means
tial means 20 when motor M1 of the motor-generator
45. This friction braking means consists of a drum 46
means 16 is running alone. The knee of the curve desig
which rotates with the shaft of motor M2 and a shoe or
nated numeral 41 is the point at which motor M2 of motor 60 other friction applying device 47. Shoe v47 is applied to
generator means 26 begins to rotate. It can be seen that
drum 46 to create a friction to stop any unwanted move
after point 41 the portion of the curve designated 42
ment of motor M2. Amplifying means 24 may have some
indicates a larger increase in the rate of rotation of the
small output voltage without having an input voltage.
output shaft of differential means 20 with a smaller in
This could be due to residual voltages, noise, or some
crease of the output voltage of condition responsive means 65 other disruption within the ampli?er. This small output
10. This increase of rate is because of the fact that motor
voltage will tend to cause motor M2 to creep. This slight
M2 of motor-generator means 26 has begun to rotate and
creep is highly undesirable in the closed system in FIG
the rotation is added to the rotation of motor M1 by
mechanical summing differential means 20. The voltage
URE 1 for the following reasons. As motor M2 creeps
differential 20 has a slight output which is transmitted to
at point 37 cannot reach a high enough amplitude to 70 load 30. Load 30 in turn causes condition responsive
means 10 to produce a signal. This signal is fed to ampli
operate switching means 35 until motor M1 of motor
?er 14 which causes motor M1 to turn in a direction oppo
generator means 16 reaches a predetermined speed, which
site to that of motor M2 thereby nulling each other in
is shown as point 41 in FIGURE 2, and, thus, motor
M2 of motor-generator means 26 will not be able to begin 75 differential 20. It can be seen that if motor M2 is allowed
to creep both motors will be turning constantly. Thus,
6
5
ampli?er means; switching means, said switching means
being characterized by acting (as a substantially open cir
a braking means such as the friction break 45 is used to
retard the undesirable movement of motor M2.
An electrical braking means which may be substituted
for friction braking means 45 is depicted in FIGURE 3.
The output of ampli?er 24' in FIGURE 3 is applied to
cuit until a predetermined amplitude of voltage is applied
thereto; and means ‘connecting said switching means be
tween said output of said ?rst ampli?er means and said
input of said second ampli?er means, said switching
motor M2’ through Zener diodes 45' and by means of a
means being characterized by being operable in response
lead 28’. The output rotation of motor M2’ is coupled to
the differential and this is shown in FIGURE 3 by dotted
to said output of said ?rst ampli?er means.
2. Apparatus of the class described comprising: a me
line 29. Diode means 45' consists of two Zener diodes
back-to-back acting as a switching means. That is, un 10 chanical summing differential means, said summing dif
less the voltage on one of the diodes is of large enough
amplitude to break it down and cause it to conduct back
ward while the other diode conducts forward no current
will be passed through them. Thus, diode means 45’ cf
fectively block any small voltages in the output of ampli
fying means 24" from being applied to motor M2’. How
ever, when a signal of large enough amplitude is applied
to ampli?er 24-’ the output is large enough to break down
ferential means having a ?rst and second input and an
output; a ?rs-t and second motor-generator means; means
connecting the motor of said ?rst motor-generator means
to the ?rst input of said summing di?erential means;
15 means connecting the motor of said second motor
generator means to the second input of said summing
diiterential means; ?rst ampli?er means having an input
and an output, said input being adapted to have a signal
applied
thereto, said output having a voltage thereon
one of the Zeners in diode means 45’ thereby allowing a
conduction path to motor M2’. Thus diode means 4-5’ 20 which is a function of the signal applied to said input
and the loading eitect of a load applied thereto; means
could effectively be used in place of friction break 45’.
connecting
said output of said ?rst ampli?er means to
It is believed that many innovations of this breaking means
can be found by one skilled in the art and these two‘
examples are not intended to limit this invention in any
way.
It should be noted that this device is not limited to dual
speed, but could be three speed, four speed or as many
different speeds as desired. vEach additional speed may be
obtained by simply ‘adding another unit.
That is, a
switching means connected at the output of the second
ampli?er to the input of a third ampli?er which powers
a motor, which in turn operates a differential, would give
a third speed. The differential which the third motor
operates could be another input of the same differential
2d the ?rst two operate or another differential having
two inputs, one of which is the output of di?erential 20
and the other of which is the output of the third motor.
This innovation is not shown since the invention may be
depicted completely in a two-speed device. However,
the three and four speed devices are mentioned to show
one of the advantages in this system.
Thus, a new and novel device ‘has been invented for
attaining a plurality of exact speeds. This invention has
the advantages of always following the same rate of rota
the motor-generator means, said motor etfectively load
ing said output of said ampli?er means to keep the volt
age thereon below a predetermined amplitude when oper
ating below a predetermined speed; means connecting the
generator of said ?rst motor-‘generator means to said input
of said ?rst ampli?er means; a second ampli?er means
having ‘an input and an output; means connecting said
output of said second ampli?er means to the motor of
said second motor-generator means; means connecting
the generator of said second motor-generator means to
said input of said second ampli?er means; and switching
means controllable to a conducting and a non-conducting
condition, said switching means being connected between
said output of said ?rst ampli?er means and said input
of said second ampli?er means, and said switching means
[being normally in the non-conducting condition and con
trolled to the conducting condition when the voltage on
said output of said ?rst ampli?er means is above said
predetermined amplitude.
3. Apparatus of the class described comprising: a ?rst
and second motor-generator means; ?rst ampli?er means
having an input and an output, said input being adapted
to have a signal applied thereto; means connecting said
output of said ?rst ampli?er means ‘to the motor of said
?rst
motor-generator means; means connecting the gen
when changing from one rate of rotation to another rate
erator of said ?rst motor-generator means to said input
of rotation. Also, this invention has the advantage of
of said ?rst ampli?er means; a second ampli?er means
insuring that there will be no ‘oscillations in the output
rotation regardless of the sharpness of the input voltage. 50 having an input and an output; means connecting said
output of said second ampli?er means to the motor of
What has been described is considered to be the pre
said second motor-generator means; means connecting
ferred embodiment of this invention, but it should be
the generator of said second motor~generator means to
understood that various changes and modi?cations there
said
input of said second ampli?er means; switching
of may be made without departing from the spirit or
means, said switching means being characterized by act
scope of the invention as de?ned in the appended claims.
ing as a substantially open circuit until a predetermined
What I claim is:
amplitude of voltage is applied thereto; ‘and means con
1. Apparatus of the class described comprising: a me
meeting said switching means between said output of said
chanical summing differential means, said summing dif
?rst ampli?er means and said input of said second ampli
ferential means having a ?rst and second input and an
output; a ?rst and second motor-generator means; means 60 ?er means, said switching means being characterized by
being operable in response to said output of said ?rst
connecting the motor of said ?rst motor-generator means
vampli?er means.
to the ?rst intput of said summing differential means;
4. Apparatus of the class described comprising: ?rst
means connecting the motor of said second motor
ampli?er
means having an input and an output, said input
generator means to the second input 0t said summing
di?'ierential means; ?rst ampli?er means having an input 65 being adapted to have a signal applied thereto; ?rst and
second motor means; means connecting said output of
and an output, said input being adapted to have a signal
tion to input voltage curve, as shown in FIGURE 2, dur
ing build-up speed and having a smooth switching process
applied thereto; means connecting said output of said ?rst
said ?rst ampli?er means to said ?rst motor means; a
second ampli?er means having an input and an output;
ampli?er means to the motor of said ?rst motor-generator
means connecting said output of said second ampli?er
means; means connecting the generator of said ?rst motor—
generator means to said input of said ?rst ampli?er 70 means to said second motor means; switching means, said
switching means being characterized by acting as a sub
means; a second ampli?er means having an input and
stantially open circuit until a predetermined amplitude
an output; means connecting said output of said second
of voltage is applied thereto; and means connecting said
ampli?er means to the motor of said second motor
switching means between said output of said ?rst ampli
generator means; means connecting the generator of said
?er means and said input of said second ampli?er means,
second motor-generator means to said input of said second
F5’
7
a,
.
.
said switching means ‘being characterized by being oper
able in response to said output of said ‘first ampli?er
means.
~
5. Apparatus of the class described comprising: a
mechanical summing di?’erential means, said summing
differential means having a ?rst and second input and an
output; a ?rst and second motor means; means connect
ing said ?rst motor means to the ?rst input of said sum
ming differential means; means connecting said second
motor means to the second input of said summing differ
ential means; ?rst ampli?er means havinv an input and
an output, said input being adapted to have a signal ap
plied thereto, said output having a voltage thereon which
dition responsive means; a ?rst and second motor means;
signal producing means having an input and an output;
means connecting said input to said condition respon
sive means, and said output having a voltage thereon
which is a function of the signal applied to said input and
the loading effect of a load applied thereto; means con
necting said output of said signal producing means to
said ?rst motor means, said ?rst motor means eliectively
loading said output of said signal producing means to
keep the voltage thereon below a predetermined ampli~
tude when operating below a predetermined speed;
switching means controllable to a conducting condition
and a non-conducting condition, said switching means
is a function of the signal applied to said input and the
being connected between said output of said signal pro
loading effect of the load applied thereto; means connect 15 ducing means and said second motor means being nor
ing said output of said ?rst ampli?er means to said ?rst
mally in the non-conducting condition and controlled to
motor means, said ?rst motor means effectively loading
said output of said ?rst ampli?er means to keep the volt
age thereon below a predetermined amplitude; a second
ampli?er means having an input and an output; means
connecting said output of said second ampli?er means to
said second motor means; and switching means control
lable to a conducting condition and a non-conducting
the conducting condition when the voltage on said out
put of said signal producing means is above said pre
determined amplitude; and means connecting said ?rst
motor means to said ?rst input of said differential means
and said second motor means to said second input of
said differential means.
9. Apparatus of the class described comprising: a me
condition, said switching means being connected between
chanical summing differential means, said summing dif
said output of said ?rst ampli?er means and said input 25 ferential means having a ?rst and second input and an
of said second ampli?er means, and said switching mews
being normally in the nonconducting condition and con
trolled to the conducting condition when the voltage on
said output of said ?rst ampli?er means is above said
predetermined amplitude.
6. Apparatus of the class described comprising: ?rst
ampli?er means having an input and an output, said in
put being adapted to have a signal applied thereto, said
output; a ?rst and second motor-generator means; means
connecting the motor of said ?rst motor-generator means
to the ?rst input of said summing diiierential means;
means connecting the motor of said second motor-gen
30 erator means to the second input of said summing dif
ferential means; braking means, said braking means sub
stantially arresting any creep of the motor of said sec
ond motor-generator means; ?rst ampli?er means having
an input and an output, said input being adapted to have
output having a voltage thereon which is a function of
the signal applied to said input and the loading effect of 35 a signal applied thereto, said output having a voltage
a load applied thereto; ?rst and second motor means;
means connecting said output of said ?rst ampli?er means
to said ?rst motor means, said ?rst motor means effec
tively loading said output of said ampli?er means to keep
the voltage thereon below a predetermined amplitude
when operating below a predetermined speed; a second
ampli?er means having an input and an output; means
connecting said output of said second ampli?er means to
thereon which is a function of the signal applied to said
input and the loading eiiect of a load applied thereto;
means connecting said output of said ?rst ampli?er
means to the motor-generator means, said motor effec
tively loading said output of said ampli?er means to keep
the voltage thereon below a predetermined amplitude
when operating below a predetermined speed; means
connecting the generator of said ?rst motor-generator
said second motor means; and switching means control
means to said input of said ?rst ampli?er means; a sec
lable to a conducting condition and a non-conducting 45 ond ampli?er means having an input and an output;
condition, said switching means being connected between
said output of said ?rst ampli?er means and said input
of said second ampli?er means, and said switching means
being normally in the non-conducting condition and con
trolled to the conducting condition when the voltage on
said output of said ?rst ampli?er means is above said
means connecting said output of said second ampli?er
means to the motor of said second motor-generator
means; means connecting the generator of said second
motor-generator means to said input of said second am
pli?er means; and switching means controllable to a con
predetermined amplitude.
ducting and' a non-conducting condition, said switching
input and the loading effect of a load applied thereto;
means connecting said output of said signal producing
amplitude.
means being connected between said output of said ?rst
7. Apparatus of the class described comprising: a ?rst
ampli?er means and said input of said second ampli?er
and second motor means; signal producing means having
means, and said switching means being normally in the
an input and an output, said input being adapted to have 55 non-conducting condition and controlled to the conduct~
a signal applied thereto, and said output having a voltage
ing condition when the voltage on said output of said
thereon which is a function of the signal applied to said
?rst ampli?er means is above said predetermined
means to said ?rst motor means, said ?rst motor means
effectively loading said output of said signal producing
means to keep the voltage thereon below a predetermined
amplitude when operating below a predetermined speed;
and switching means controllable to a conducting condi
tion and a non-conducting condition, said switching
means being connected between said output of said signal
producing means and said second motor means, and said
switching means being normally in the non-conducting
10. Apparatus of the class described comprising: a
summing ‘differential means having a ?rst and second in
put and an output; condition responsive means; means
connecting said output of said di?’erential means to said
condition responsive means; a ?rst and second motor
means; signal producing means having an input and an
output, means connecting said input to said condition re
sponsive means, and said output having a voltage there
on which is a function of the signal applied to said input
and the loading eiiect of a load applied thereto; means
connecting said output of said signal producing means to
condition and controlled to the conducting condition
when the voltage on said output of said signal producing 70 said ?rst motor means, said ?rst motor means effective
means is above said predetermined amplitude.
ly loading said output of said signal producing means to
8. Apparatus of the class described comprising: a sum~
keep the voltage thereon below a predetermined ampli
ming differential means having a ?rst and second input
tude when operating below a predetermined speed;
and an output; condition responsive means; means con
switching means controllable to a conducting condition
necting said output of said di?erential means to said con
and a n0n~conducting condition, said switching means
3,088,060
being connected between said output of said signal pro
ducing means and said second motor means, said switch
ing means being normally in the non-conducting condi
tion and controlled to the conducting condition when the
voltage on said output of said signal producing means is
above said predetermined amplitude; means connecting
connecting said output of said differential means to said
condition responsive means; a ?rst and second motor
generator means; signal producing means having an in
put and an output, means connecting said input to said
condition responsive means, and said output having a
voltage thereon which is a function of the signal applied
to said input and the loading effect of a load applied
said ?rst motor means to said ?rst input of said differen
thereto; means connecting said output of said signal pro
tial means and said second motor means to said second
ducing means to the motor of said ?rst motor-generator
input of said differential means; and braking means, said
braking means substantially arresting any creep of said 10 means, said motor of said ?rst motor-generator means
second motor means.
11. Apparatus of the class described comprising: a
?rst and second motor-generator means; signal producing
effectively loading said output of said signal producing
means to keep the voltage thereon below a predetermined
amplitude when operating below a predetermined speed;
means connecting said generator of said ?rst motor-gen
means having an input and an output, said input being
erator means to said input of said signal producing
15
adapted to have a signal applied thereto, said output
means; means electrically connecting said generator of
having a voltage thereon which is a function of the signal
said second motor-generator means to the motor of said
applied to said input and the loading effect of a load ap
second motor-generator means; switching means control
plied thereto; means connecting said output of said sig
lable to a conducting and a non-conducting condition,
nal producing means to the motor of said ?rst motor
generator means, said motor of said ?rst motor-generator 20 said switching means being connected between said out
put of said signal producing means and the motor of said
second motor-generator means, said switching means be
ing normally in the non-conducting condition and con
determined amplitude when operating below a predeter
trolled to the conducting condition when the voltage on
mined speed; switching means controllable to a conduct
ing condition and a non-conducting condition, said 25 said output of said signal producing means is above said
predetermined amplitude; means connecting the motor
switching means being connected between said output of
of said ?rst motor-generator means to said ?rst input of
said signal producing means and the motor of said second
said di?erential means and the motor of said second
motor-generator means, said switching means being nor
motor-generator means to said second input of said dif
mally in the non-conducting condition and controlled to
the conducting condition when the voltage on said out 30 ferential means; and means connecting said output of
said differential means to said input of said condition
put of said signal producing means is above said pre
responsive means.
determined amplitude; means connecting said generator
of said ?rst motor-generator means to said input of said
References Cited in the ?le of this patent
signal producing means; and means electrically connect
ing said generator of said second motor-generator means
UNITED STATES PATENTS
to said motor of said second motor-generator means.
2,751,535
Kuhnel _____________ __ June 19, 1957
12. Apparatus of the class described comprising: a
2,798,992
Adler ________________ __ July 9, 1957
summing di?’erential means having a ?rst and second
2,802,160
Engeler ______________ __ Aug. 6, 1957
input and an output; condition responsive means; means
means effectively loading said output of said signal pro
ducing means to keep the voltage thereon below a pre—
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