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Патент USA US2404571

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July 23, 1946.-
w. G. H. FlNCH
2,404,511
SYNCHRONI Z ING MECHANI SM
Filed gan. 19,v 1944
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MLIETORNEY
July 23, 1946.
-.w. G. H. FINCH
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2,404,571
SYNGHRONIZING MECHANISM
Filed Jan. 19, 1944
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Filed Jan. 19, 1944
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A“; ATTORNEY
Patented July 23, 194-6
2,404,571
UNITED STATES PATENT OFFICE
2,404,571
SYNCHRONIZING MECHANISM
William G. H. Finch, Newtown, Conn.
Application January 19, 1944, Serial No. 518,837
8 Claims.
(Cl. 178-695)
1
2
My invention relates in general to the ?eld
of picture transmission and reception and more
speci?cally to a novel continuous synchronizing
chronization between transmitting and recording
apparatus which utilizes a continuously trans
mitted alternating current synchronizing signal,
mechanism,
but which does not require the excessive ampli
In facsimile transmission, a signal is gener U! ?cation thereof mentioned above. In accordance
ated at the transmitter which represents the light
with my novel synchronizing mechanism, the
shades of a single line of a picture. This signal
recording apparatus is driven from any local
is then ampli?ed to a suitable energy level and
power supply, which may take the form of alter
transmitted by wire or radio to a remote receiver.
nating current mains, or a portable battery as
employed in an airplane or other vehicle.
As is well known in the art of facsimile, it is
essential that both transmitting and receiving
apparatus operate in synchronism. In the past,
If a battery supply is available at the receiver
then the drive mechanism may consist of an
ordinary direct current shunt motor of the re
quired horse power. The speed of this shunt
synchronizing systems have primarily been stop
start mechanical systems wherein the receiver
recording mechanism was operated at a some
15
what higher speed than the transmitting mech
anism. The scanning of a single line of the
picture at the receiver was thus accomplished in
less time than a corresponding cycle at the trans
mitter,
and the
motor is controlled directly by comparatively
simple and light apparatus which in turn is
governed by a small pilot synchronous motor
operated from a low level continuous synchro
nizing signal ampli?er. Thus the transmitting
recording
mechanism was 20 apparatus has associated with it means for gen
erating a continuous synchronizing signal and
chronizing signal from the transmitter. This
combining it with the picture signal to be trans
synchronizing signal representing the start of a
mitted. This multiple signal when received at
new scanning cycle at the transmitter would
the recording apparatus is separated electroni
release the receiving mechanism to record the
cally and the picture signal is passed through a
following line. The mechanical disadvantages
recording channel while the synchronizing signal
of such a start-stop mechanism are well known
is impressed upon an ampli?er having a signal
in the facsimile art.
output sufficient to drive the aforementioned
It is possible to obtain continuous synchro
small synchronous motor.
nizing of transmitting and recording mechanism
Immediately upon the receipt of a transmitted
brought to a halt to await the receipt of a syn
if both are operated from the same alternating
signal, the pilot synchronous motor operates to
current power supply. In this ideal instance,
matched alternating current synchronous motors
are utilized to provide absolute continuous syn
chronization between the rotational elements at
each station. Obviously, such a transmission
adjust the speed of the direct current motor to
that of the corresponding scanning apparatus at
the transmitter. Any ?uctuation in speed of
the direct current motor will thereafter be im
mediately compensated for by the small pilot
system would be limited to the area served by
the one central power station and would be of
no use whatsoever for facsimile systems operat
ing between separated points such as ship-to
shore or airplane-to-ground, or the like.
Continuous synchronization of transmitting
and recording equipment may also be obtained by
the continuous generation at the transmitter of
an alternating current synchronizing signal
which is transmitted to the receiving station and
ampli?ed thereat to a level sur?cient to drive all
the required recording apparatus. With modern
high speed telepicture apparatus, this particular
synchronizing system becomes impractical, since
the power requirements of the recording mech
anism are comparatively high and require ex
cessive ampli?cation of the synchronizing signal
by massive, ine?icient electronic apparatus.
My present invention proposes continuous syn
motor and result in a change of electrical or
mechanical circuit constants that will restore
the speed of the direct current motor to the
40
required synchronous speed.
It is therefore an object of my invention to
provide a facsimile transmitting and receiving
system wherein the recorder is continuously gov
erned to operate at the speed of the transmitter.
It is another object of my invention to pro
vide a continuous telepicture synchronizing sys
tem utilizing a small pilot synchronous motor
at the receiver.
Still another object of my present invention
is to provide facsimile recording apparatus which
may be operated from any power source whatso
ever and which is maintained in synchronism by
a continuously transmitted governing signa1 gen
erated at the transmitter.
A further object of my invention is to provide
2,404,571
75
picture signals a translated band of higher fre
quencies, the ?lters ill and it may be conven
a novel, differential speed adjusting means for
maintaining a direct current motor in synchro
nism with a synchronous alternating current
motor.
A still further object of my invention is to
tional high-pass and low-pass ?lters respectively.
The audio-frequency picture signals are ampli
?ed by ampli?er l5 and impressed in the well
provide a novel electrical circuit for controlling
the speed of a direct current motor within cer
known manner across an electrosensitive record
tain narrow pre-determined limits.
These and other object of my invention will
neous facsimile recording paper of the conductive
ing sheet H, which may be a sheet of instanta
type.
As is schematically illustrated in Figure 1, the
recording sheet El is mounted upon a rotating
drum 2i by a mounting bar
The drum 2! is
supported by suitablev bearings 23 and is driven
now become apparent from the following speci
?cation taken in connection with the accom
panying drawings in which:
Figure 1 is a schematic representation of one
modi?cation of my novel continuous synchro
by a motor “24 of the required horse power. Scan
ning the surface of the recording sheet I‘! is an
electrically conductive stylus 25, supported on a
suitable bracket 23, which in turn is driven by a
conventional feed screw mechanism.
nizing mechanism.
Figure 2 is a fragmentary View of the diifer
ential mechanism for governing the speed of a
direct current motor.
Figure 3 is a fragmentary view of one form
of speed control means; and
Figure 4 is another modi?cation of a motor
The picture signal output of ampli?er i5 is
impressed between the stylus 25 and the rotatable
drum 25 whereby the incoming picture signal will
?ow through the recording sheet ll’ and in the
speed control mechanism.
well known manner produce an instantaneous re
Referring now to Figure 1, there is shown a
schematic representation of a facsimile system
operable from radio signals received by antenna
ii and coupled to the radio frequency receiving
circuit E2.
cording.
‘
It will become evident that the present inven
tion is not particularly limited to the recording
drum 2! as illustrated in Figure 1, and that any
other well known facsimile recording mechanism,
such as the multiple stylus arrangement, or the
reciprocating arm arrangement, may be directly
substituted for the particular recorder described.
The facsimile signal received in circuit i2 con
sists of a carrier signal modulated by audio-fre
quency currents representing the variations of
light along individual lines of an image. These
signals are generated at the transmitter as is well
known in the art by an electro-optical scanning
The power source comprises a battery or other
direct current supply 3!. The source of motive
power for the drum 2i, as shown, is a direct cur
mechanism driven from a suitable source of
rent shunt motor 215, the armature terminals 32
power.
of which are directly connected to the battery
If an alternating source of power supply is
through a switch 33. The ?eld of the direct
available at the transmitter, then the transmit
cur rent shunt motor 215 is also energized from the
ting scanning mechanism is driven by an alter
battery 5! through the ?eld rheostat 34 and
nating current synchronous motor, To obtain
a signal at the transmittenwhich is representa ell) through a circuit contained in the speed control
apparatus 35, to be described later.
tive of he speed of the synchronous motor, it is
The alternating current synchronizing signal
then merely necessary to modulate the carrier
flowing from the signal ?lter i6 is impressed upon
with this alternating current,
a synchronizing signal ampli?er 36 having a
If it is necessary to drive the transmittingscan
power output su?icient to drive the small pilot
ning mechanism from a battery or other D. C.
synchronous motor 3?~ It is important to note
supply, it is then preferable to attach a small
synchronous alternator to the scanning drive
this point that the direct shunt motor 24 is
motor so that an alternating current signal hav
considerably larger than the pilot synchronous
ing a frequency proportional to the speed of the
canning apparatus is generated at all times. -;=:
As in the previous example, the output of this
synchronous alternator is used to modulate the
carrier to provide a transmitted synchronizing
motor 3? and that the energy required to drive
the recording drum 25 is supplied primarily by the
direct current motor 211 operating from the local
direct current source 35.
signal.
?er is an alternating current synchronous with
the alternating current utilized to drive the trans
.
When wired transmission is employed, the pic
ture signal and the continuous synchronizing sig
nal may be directly app-lied to the lines and mod
The output of the synchronizing signal ampli
mitting scanning mechanism, and is impressed
directly upon the armature terminals M of the
pilot synchronous motor 31.
ulation of a carrier and the receiving radio fre
quency circuits may be dispensed with.
described, the two signals are separated and the
translated current restored to its original fre
The direct current ?eld terminals 42 of the pilot
synchronous motor 37 are energized from the
local power supply 3! through the four-pole relay
contacts
The relay M is picture signal oper
ate-d and of the latching type. That is, upon the
receipt of a picture signal through picture am
pli?er i5 the coil 45 of the relay M will be ener
gized across the lines 48. The relay contact car
rying arm ii? is normally biased as indicated sche_
quency.
matically by springs 53 to the open circuit posi
Again referring to Figure 1, the received signal
is demodulated by the detector l3 and impressed
upon the two-channel electronic circuit compris
ing the picture signal ?lter l4 and the synchro
nizing signal ?lter H5. If the synchronizing sig
nal is, for example, an alternating current signal
of approximately 60 cycles‘ per second and the 75
tion illustrated.
Upon receipt of a picture signal over lines 46,
the relay coil £55 will be energized and cause the
movement of contact carrying arm 47 to the right
as viewed in Figure 1, and accordingly close the
four circuits illustrated.
Eince relay at is of the latching type, any sub
Since the picture currents and the synchroniz
ing signal may be in the same frequency band,
multiple transmission may be accomplished by
31)
translating either one of these two into another
frequency band by the addition of a constant fre,
quency signal thereto. At the receiver, as will be "
2,404,571
sequent temporary cessation of the picture signal,
6
synchronous motor shaft ‘H between the hub of
bevel gear of 12 and a pinned bushing 95.
t will now become evident that with the linkv
6| positioning bevel gear 75, as illustrated in
Figure 2, rotation of shafts ‘H and 14 at identical
speeds but in opposite directions will cause the
rotation of bevel gear 8| about shaft 82 but will
nal applied to the armature terminal 41, will
not result in rotation of bevel gear 9'3.
cause the synchronous motor 3'1 to look into syn
Bevel gear 96 is continuously engaged with
chronous speed, as is well understood in the art.
The speed of this synchronous motor 3i‘ is accord 10 bevel gear 9?: and hence under the last mentioned
condition of identical speeds, the bevel gear 96
ingly the speed at which it is desired to operate
and its attached shaft 9“! will remain stationary.
the direct current shunt motor 24. And as will
If the speed of the direct current shunt motor
be described later, the differential speed control
driving shaft ‘l4 deviates at any time from the
mechanism 35 will in connection with the syn
speed of the synchronous motor driving shaft ll,
chronous motor 3'1 provide means for continu
it is evident that bevel gear M will continue to
ously adjusting the speed of the shunt motor
rotate about shaft 82 but will, in addition, exert.
‘25 to maintain the desired scanning speed.
a force upon the ?xed link 93 which will tend to
The mechanism 35 is a mechanical coupling
drive the bevel gear 94 about shaft 1 I.
between the pilot synchronous motor 31 and the
The angular speed of bevel gear 94 is directly
direct current shunt motor 24. Since it may be
dependent
upon the different speed between the
desirable to operate the shunt motor 24 when no
D. C. motor and the synchronous motor, and the
picture signal is being transmitted, it is necessary
direction of rotation thereof is dependent upon
to uncouple the mechanical linkage between the
whether !the speed of the D. C. motor is greater
motor 24 and the synchronous motor 3'5. This
will not cause the contacts 43 to open. The clo
sure of contacts 52 and 53 of the relay 44 will, as
illustrated, energize the direct current ?eld at
terminals 42 from the local D. 0, supply 3|, and
in combination with the alternating current sig
is accomplished by a clutch mechanism operated .
by arm Bl pivoted at pin e2.
The normal position'of the pivoted link ill is
determined by the spring-‘53 applying tension in
the direction illustrated in Figure 1. However,
upon the energization of relay 45 and the closure
of contacts 64 and 65 by the contact carrying arm
41, the solenoid 86 will be energized and cause
counterclockwise rotation of pivoted link 6i
against the normal bias of spring 63. This, as
will be illustrated later, will cause the mechanical l
coupling between the synchronous motor 3'! and
shunt motor 24 to maintain the desired synchro
or less than that of the synchronous motor.
correspondingly, the rotation of shaft 91 and
the direction thereof is directly a measure of the
non-synchronous condition of the D. C. motor
and the direction of this deviation. As is evident
from Figure 2, the angular movement of bevel
gear fit will be considerably greater than that of
engaged bevel gear 234 and hence, is an extremely
sensitive detector of this aforementioned non
synchronous condition.
y
In accordance with my invention, I propose to
utilize the rotation of shaft 9? to maintain a
facsimile recorder at the speed of a correspond
ing unit at the transmitter.
The speed of the shunt motor 24, as is well
Referring now to Figure 2, there is illustrated
one possible mechanical structure of the synchro 40 known in the art, is determined by the magnitude
of its shunt ?eld current which in turn is deter
nizing linkage between the pilot motor 31 and
mined
by the variable resistor 34, and additional
the shunt motor 24.
electrical means in the differential mechanism 35.
As illustrated, the synchronous motor 3? drives
The means of accomplishing the speed control of
shaft ‘H to which is secured bevel gear 72. rI‘lhe
direct current shunt motor 26 is illustrated in
45
attachment is accomplished, as illustrated by pin
Figure 3.
13 passing through the hub of gear 12 and
The variable resistor I0! is connected in series
through shaft 1 l.
with the shunt ?eld circuit at the terminals we,
The direct current shunt motor 24 drives shaft
as illustrated, and hence the complete shunt ?eld
14 to which bevel gear ‘i5 is slidably but non
circuit comprises resistors 34 and lill, and the
rotatably keyed. Thus, keyways milled in shaft
?eld itself.
74 and bevel gear 15 engage a key 16 which is
The bevel gear 96 and the attached shaft 91,
secured to the shaft 14. The keyway in bevel
which is preferably of an insulating material,
gear 15 is somewhat larger than the key 16 and
control the magnitude of the resistance ml in
nous condition.
hence the bevel gear 15 may move to the right
or to the left as viewed in Figure 2.
The movement of bevel gear 15, is determined
by the movement of coupling link 6i illustrated
in Figures 1 and 2. The link 6| slidably engages
the hub of the bevel gear 15 in a cylindrical de
pression T! wherea't friction has been reduced to
a minimum by proper polishing.
The position of bevel gear '15 as illustrated in
serted into» the shunt ?eld circuit. Thus, con
ductive arm M23 is rigidly attached to shaft 91
by means of a pin “34, and completes the circuit
from the rheostat it! through the lines Hi2.
When the D. C. motor begins to run below the
synchronous speed, arm I23 will tend to rotate in
the direction of the arrow S, as illustrated in Fig
ure 3. Such rotation will increase the resistance
in the shunt ?eld circuit, thereby decreasing the
Figure 2, corresponds to the energization of sole
current and causing an immediate increase in
noid 66 shown in Figure 1. Upon de-energization 65 the armature speed thereof.
of this solenoid 6B, the spring 63 will act to move
bevel gear 75 to the right, as viewed in Figure 2,
It is important to note that it is desirable to
have the resistor it! of such magnitude that ex
and cause the disengagement of the gear ‘(5 with
tremely small rotation of the arm Hi3 will cause a
another bevel gear 81. The bevel gear BI is ro
considerable variation of resistance in the shunt
tatably positioned upon a shaft 82 by bushings 70 ?eld circuit, thus resulting in an immediate tend
ency to restore the speed. Conversely, any tend
83 and 84 pinned to the shaft by pins 85 and 86.
ency of the direct current motor to run at above
The shaft 82 is rotatably positioned by ?xed
the synchronous speed of the motor 31 will cause
bushings SI and 92 upon a link 93 which is an
the arm N13 to rotate in the direction F, as illus
integral extension of a large bevel gear 94. The
bevel gear 94 is rotatably positioned upon the 76 trated. in Figure 3, and result in an increase. of.
2,404,671
7
8
?eld current which ‘will tend to restore the speed
to that which corresponds to no rotation of the
bevel gear 96.
It is therefore evident that by utilization of an
extremely small synchronous motor governed by
signals transmitted from the scanning apparatus
at the transmitting station, I have been able to
immediately result in an increase in ?eld current
which correspondingly causes a decrease in the
speed of the motor 24. This decrease in speed
will through the diiferential mechanism illus
trated in Figure 2, immediately re-act to cause
the rotation of bevel gear 96 in the direction
marked S in Figure 4. Continued rotation in this
synchronize a comparatively large direct current
motor thereby and insure proper operation of the
recording apparatus 2|.
The power requirement of the synchronous mo
direction will ?rst cause contacts II 4 to disen
gage from the contact bridge II3. However, this
10
tor 37 is extremely small, and as may be seen
from Figure 2, is only that required to overcome
friction of the gears, and the rheostat mechanism.
The synchronous motor 37 does not to any extent
contribute directly to the driving force required
by the rotatable drum and scanning mechanism
2|.
Another modi?cation of my novel speed con
disengagement of contact II4 which accordingly
results in an open circuit between contacts H4
and H5 will not cause the de-energization of
contact relay coil I34, since this relay, when ?rst
energized, caused the engagement of armature
I23 with contact I25, which through wires I35
and I 36 serves to supply an alternate path for en
ergization of the coil I34.
Accordingly, the short-circuiting of resistor I I 6
which tends to slow down the shunt motor 24 will
continue even though I I4 has been disengaged by
trol mechanism is illustrated in Figure 4, and uti~
lizes the differential gear mechanism illustrated
the arm H3.
in Figure 2. Thus, di?erences in speed between
As the shunt motor continues to run below the
the D. C. motor and the synchronous motor re
speed of the synchronous motor, the arm I I I will
sults in rotation of bevel gear Q6 and attached
continue to rotate in the direction F of Figure 4
shaft 91, the direction being dependent upon the 25 until the contact bridge II3 leaves the contact
relative speeds thereof.
IIE, under which circumstances both paths
As illustrated in Figure 4, a link III of insulat
through which relay coil I34 could be energized
ing material is attached at one end to shaft 97
are open. This will immediately cause springs I24
by means of a pin H2, and carries at the oppo
and I25 to open circuit contacts H7, H8 and I26
site end thereof a conducting contact bridge H3. 30 resulting in the re-insertion of resistor II6 into
The length of contact bridge H3 is suf?cient to
the ?eld current circuit of the shunt motor 24.
interconnect contacts I I4 and I I 5 which are ?xed
Accordingly, as previously mentioned, this will
to the frame of the facsimile apparatus. As illus—
again, due to the predetermined value of resistor
trated in Figure 4, the circuit between contacts
I I 6, result in an increase of speed in the motor 24.
I I4 and I I5 is not completed by the bridge I I3.
35
Consequently, it may be seen that the electro
For this modi?cation, a ?xed resistor lid is
mechanical circuit illustrated in Figure 4, will
connected in series with the variable resistor 34
serve to maintain the shunt motor 24 in a non
and the shunt ?eld of motor 24 at the terminals
synchronous condition by maintaining the speed
I62, as is illustrated in Figure 1. Contacts Ill
either above or below the synchronous speed of
and H8 disposed at the ends of resistor II? are 40 motor 3?. However, it is important to note that
engageable by the armature I2I of a relay I22.
the angle of rotation of arm I II is comparatively
The armature I2I and an additional contactor
great for even extremely small differences in
I23 of the relay I22 are normally biased by the
speed between the pilot motor 31 and the shunt
spring I24 and I25 respectively, into position
motor 24. Evidently, therefore, the departure
wherein they are normally disengaged from the
from synchronous speed can be made to be ex
contacts II‘I, II8 and I26.
tremely small by the continuous and rapid open
Energization of the relay I22 will cause the
ing and closing of the contact arm I2I of the re
displacement of armatures IZI and I23 against
lay I22. That is to say, that the shunt motor 24
the normal spring bias illustrated, and cause the
when operated by the control mechanism illus
engagement of the armatures with their respec- 1. trated in Figure 4, will be continuously hunting,
tive contacts. With the contact bridge I I3 in the
that is, fluctuating about the synchronous speed
position illustrated in Figure 4, the resistor III}
of the motor 37, and Will on the average run at
is part of the shunt ?eld circuit. This resistor
I I6 has been adjusted in connection with the var
synchronous speed.
iable resistor 34 so as to provide a speed of the I
D. C. motor 24 which is above that of the syn—
chronous motor 3i when in circuit and a speed
lower than that of motor 3? when shorted out of
the circuit.
The maximum departure from synchronous
speed as determined by the angular displacement
of contacts H4, and H5, will be so small as to
make the effect upon a straight line in a picture
ure 2, such a condition of relative speed will cause
transmitted indiscernable.
Summarizing, therefore, the circuits of Figure
3 and Figure 4 when utilized with the mechanical
linkage between the synchronous motor and the
the rotation of bevel gear 96 and hence, of link
I I I in the direction marked F in Figure 4.
The continued rotation of the link III and its
shunt motor illustrated in Figure 2, comprise a
governor of the speed of motor 24. However, it
is evident that the governor thus formed is at all
As previously described in connection with Fig
associated contact bridge I I3 will ultimately
cause the closure of contacts I I4 and I I5. Closure
co
times responsive to changes in synchronous speed
which may be encountered at the transmitter,
particularly if the transmitter as previously de
scribed is operated by a battery which in turn
serves to generate an alternating current signal
of the contacts II4 and H5 will, through wires
I3I and I32 and the battery supply I33, cause the
energization of the coil I34 of relay I22 which in
turn will cause the displacement of armatures I2I 70 for synchronizing signal transmission.
and I23 against their normal spring bias.
If, as previously mentioned, between picture
The engagement of contacts I I ‘I and M8 by the
transmission it is desirable to operate the direct
armature I 2] will short-circuit the resistor IIS
current motor 24, the latching relay 44 may be
and hence reduce the total resistance in the shunt
released to the open circuit position illustrated
?eld circuit of the motor 24. This reduction will '
in Figure 1. This will immediately de-energlze
2,404,571
10
the solenoid 66 and cause the rotation of link
6i under the in?uence of spring 63 as illustrated
in Figures 1 and 2. This will cause slidably posi
tioned bevel gear 15 to move to the right and
result in disengagement thereof from bevel
gear 8|.
Accordingly, the mechanical linkage through
the synchronizing mechanism as illustrated in
Figure 2, will not be complete between the shafts
‘II and 74.
mitter, a di?erential coupling gear between said
direct current motor and said synchronous‘ motor
having an element responsive to speed differ
ences between said motors, said speed responsive
element being continuously operative to adjust
the ?eld of said direct current motor to maintain
said direct current motor at tho speed'of said
synchronous motor.
'
4. In a picture transmission system, a trans
mitter for generating signals in, accordance with
the lights and shades of ‘a picture, means for
The synchronous control mechanism described
generating a continuous alternating current sig
in the above paragraph obviously may be ex
nal of a frequency representative of the speed of
tended to the speed control of various other
said transmitter, means for transmitting said
types of motors. Thus, the shaft 91 controlled by
rotation of the bevel gear 96 may be used to 15 signals, a receiver for receiving said signals,
means for impressing said picture signals upon
actuate mechanism to control the speed of var
a picture recording mechanism, means for driv
ious other forms of motive power including the
ing said recording mechanism, comprising a mo~
Well known alternating current speed control
motors.
'
tor, means for impressing said alternating cur
Accordingly, I do not wish the scope of the
present invention to be limited to the particular
modi?cations described above, but to be bound
rent signal upon a synchronous pilot motor, said
driving motor and said synchronous motor being
by the appended claims.
means to cause said recording motor to fluctuate
mechanically coupled, said coupling comprising
signal upon a synchronous pilot motor, said driv
ing motor and said synchronous motor being me
in speed, said ?uctuations being rapid and con
tinuous and within narrow predetermined limits
above and below the speed of said synchronous
motor.
5. In a picture transmission system, a transmit
ter for generating signals in accordance with the
lights and shades of a picture, means for gen
erating a continuous alternating current signal
of a frequency representative of the speed of said
transmitter, means for transmitting said signals,
a receiver for receiving said signals, means for
impressing said picture signals upon a picture re
cording mechanism, means for driving said re
cording mechanism, comprising a motor, means
chanically coupled, said coupling comprising
for impressing said alternating current signal
I claim:
1. In a picture transmission system, a trans- =
mitter for generating signals in accordance with
the lights and shades of a picture, means for
generating a continuous alternating current sig
nal of a frequency representative of the speed of
said transmitter, means for transmitting said
signals, a receiver for receiving said signals,
means for impressing said picture signals upon a
picture recording mechanism, means for driving
said recording mechanism, comprising a' motor,
means for impressing said alternating current -
upon a synchronous pilot motor, said driving mo
ence between said motors to adjust the speed of in tor and said synchronous motor being mechan
ically coupled, said coupling comprising means
said drive motor to the speed of said synchronous
to cause the speed of said recording motor to ?rst
motor.
rise above the speed of said synchronous motor
2. In a picture transmission system, a trans
and operative when said recording motor has
mitter for generating signals in accordance with
reached a predetermined upper speed limit to
the lights and shades of a picture, means for gen
cause said speed to fall below the speed of said
erating a continuous alternating current signal
synchronous motor, whereby the average speed
of a frequency representative of the speed of said
is equal to the speed of the synchronous motor.
transmitter, means for transmitting said signals,
6. In a picture transmission system, a trans
a receiver for receiving said signals, means for
impressing said picture signals upon a picture 50 mitter for generating signals in accordance with
the lights and shades of a picture, means for
recording mechanism, means for driving said re
generating a continuous alternating current sig
cording mechanism, comprising a motor, means
nal of a frequency representative of the speed of
for impressing said alternating current signal
said transmitter, means for transmitting said sig
upon a synchronous pilot motor, said driving mo
nals, a receiver for receiving said signals, means
tor and said synchronous motor being mechani
for impressing said picture signals upon a picture
cally coupled, through a differential mechanism
recording mechanism, means for dI'iVll’lg said re
having an element responsive to the di?erence
cording mechanism comprising a direct current
in speed between said motors, said element being
motor, means for impressing said alternating cur
continuously operative to maintain the speed of
rent signal upon a synchronous pilot motor
said driving motor at the speed of said syn
whereby said synchronous motor is continuously
chronous motor.
operative at the speed of said transmitter, a, dif
3. In a picture transmission system, a trans
ferential coupling gear between said direct cur
mitter for generating signals in accordance with
rent motor and said synchronous motor having
the lights and shades of a picture, means for
an element responsive to speed differences be
generating a continuous alternating current sig~
tween said motors, said element being operative
nal of a frequency representative of the speed of
continuously to insert or remove resistance from
said transmitter, means for transmitting said
the ?eld circuit of said direct current motor
signals, a receiver for receiving said signals,
whereby the speed of said direct current motor
means for impressing said picture signals upon
is caused to rise above and fall below the speed
a picture recording mechanism, means for driv
of said synchronous motor.
ing said recording mechanism comprising a direct
'7. In a picture transmission system, a trans
current motor, means for impressing said alter
mitter for generating signals in accordance with
nating current signal upon a synchronous pilot
the lights and shades of a picture, means for
motor whereby said synchronous motor is con
generating a continuous alternating current sig
tinuously operative at the speed of said trans
comprising means operative upon a speed differ
A
2,404,571
11
nal of a frequency representative of the speed of
said transmitter, means for transmitting said sig
nals, a receiver for receiving said signals, means
for impressing said picture signals upon a picture
recording mechanism, means for driving said re
cording mechanism comprising a direct current
12
of a frequency representative of the speed of said
transmitter, means for transmitting said signals,
a receiver for receiving said signals, means for
impressing said picture signals upon a picture
recording mechanism, means for driving said re
cording mechanism comprising a direct current
motor, means for impressing said alternating cur
motor, means for impressing said alternating cur
rent signal upon a synchronous pilot motor
rent signal upon a synchronous pilot motor
whereby said synchronous motor is continuously
whereby said synchronous motor is continuously
operative at the speed of said transmitter, a dif
operative at the speed of said transmitter, a dif
ferential coupling gear between said direct cur
ferential coupling gear between said direct cur
rent motor and said synchronous motor having
rent motor and said synchronous motor having
an element responsive to speed differences be
an element responsive to speed differences be
tween said motors, said element cooperating with‘
tween said motors, said element cooperating with
an electrical time delay circuit to insert resistance 15 an electrical time delay circuit to insert resistance
into the field circuit of said direct current motor
into the ?eld circuit of said direct current motor
until the speed of said direct current motor rises
until the speed of said direct current motor rises
to a predetermined speed above the speed of said
to a predetermined speed above the speed of said
synchronous motor and then to remove resistance
synchronous motor and then to remove resistance
from the ?eld circuit of said recording motor un
from the ?eld circuit of said recording motor un
til the speed of said recording motor falls to a
til the speed of said recording motor falls to
predetermined speed below the speed of said
a predetermined speed below the speed of said
synchronous motor.
synchronous motor, said resistance variations be
8. In a picture transmission system, a trans
ing continuous and rapid whereby the average
mitter for generating signals in accordance with 25 speed of said recording motor is equal to the
the lights and shades of a picture, means for gen
speed of said synchronous motor.
erating a continuous alternating current signal
WILLIAM G. H. F'INCH.
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