US2108983A

US2108983A - Telepicture synchronizing system

Info

Publication number: US2108983A
Application number: US78993A
Authority: US
Inventors: William G H Finch
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-05-11
Filing date: 1936-05-11
Publication date: 1938-02-22
Anticipated expiration: 1955-02-22
Also published as: GB496485A

Description

Feb. 22, 193s.

w. c;A H. FlNcH 2,108,983

TELEPICTURE SAYNCHRONI Z ING SYSTEM Filed May ll, 1936 4 Sheets-Sheet 1 SYNCHRONIZIN SIGNAL.

GENERATOR TRANSMITER* n--a RECEIVER AUDIO AND AMPLIF'lER RECTIFIER o Feb. 22, 1938. W, G, HAF-,NCH 2,108,983

TELEPICTURE SYNCHRONIZING SYSTEM 4 Sheets-Sheet 3 Filed May ll, 1936 R. m N W W.

william ATTORNEY.

Feb; 22, 193s. w, G. Hf FINCH' 2,108,983

TELEPICTURE SYNCHRONIZING SYSTEM Filed May 1l, 1936 4 Sheets-Sheet 4 INVENTOR. wallzamrgbnclz,

Inf/wdr ATTORNEY.

Patented Feb. 22, 1938 UNITED STATES PATENT OFFICE 6 Claims.

This invention relates to synchronizing systems, and more particularly relates to novel methods of and apparatus for maintaining a telepicture receiver in phase synchronism with the transmitter.

Prior synchronizing systems comprised a friction clutch interposed'between the driving motor and the telepicture drum. synchronizing signals were used to disengage the friction clutch 10 until the receiver drum was in phase synchronism with the corresponding transmitter drum and then re-engage the clutch so that the receiver drum would continue to rotate in proper phase synchronism. However, a friction clutch could l5 not maintain accurate phasing of the apparatus since slight slippage inherent in the friction clutch, and intensified by wearing thereof, could not positively predetermine phase synchronous positions.

In my Reissue Patent No. 19,575, I disclose a positive driving connection between the scanner and the motor. The positive driving connection includes a pawl and ratchet wheel which are normally engaged to maintain'the scanner in 2, operation. When the scanner is out of phase, the positive driving connection is disconnected at the pawl and ratchet wheel until the scanner is in proper position. A cyclic synchronizing signal reengages the pawl and ratchet to continue the synchronous operation of the scanner.

In my co-pending application Serial No. 65,869,

filed'Feb. 26, 1936, I disclose a positive or over-.

running clutch in the positive driving connection between the motor and the telepicture drum. l) The receiver drum is rotated at a slighly faster rate thanthe corresponding transmitter drum. The overrunning clutch is disengaged at a predetermined angular position of the drum until the synchronizing signal reengages it. The synchronizing signal is transmitted during the cor- 40 responding angular position of the transmitter drum so that both drums are maintained in accurate phase synchronous relation.

In accordance with my present invention, I

tween the motor and telepicture drum with means for changing the relative phase relation between the motor and the drum without interrupting contemplate a positive driving connection be-v of the worm changes the phase relation between the motor and the drum without interrupting ythe positive driving connection therebetween.

The worm is turned when the drum is out of phase synchronism 'with respect to the trans- 5 mitter drum under the control of cyclic synchronizing signals. Normal interlocking of the Worm Wheel with the. worm gear permits normal rotation of the telepicture drum. However, when the'worm wheel is turned, a phase co-r- 10 recting motion is superimposed upon the normal rotation of the worm gear connected to the drum.

In a preferred arrangement, the worm wheel moves the worm gear in a direction opposite to the normal rotation thereof. The superposition 15 of the two oppositerotative effects produces a resultant rotation of the drum. Since the positive driving relation between the motor and the drum is' maintained during angular correction, my invention may be termed a controlled slip 20 driving mechanism. The slip, or relative angular change between the motor and the drum is directly controlled by rotation of the worm wheel normally interlocking with the wormv gear.

In a preferred embodiment of my invention, the worm wheel superimposes a speed of rotation upon the drum equal to its normal speed of rotation but in the opposite direction or sense thereto. 'Ihe resultant is an effective standstill or'interruption of rotation of the telepicture 3 drum without the use of a friction brake, clutch or the like. The drum is subjected to the controlled slip angular correction if it reaches a predetermined position in its rotation cycle beforeA the synchronizing signal is received. 'I'he effect 35 of the controlled s lip is to maintain the drum at this predetermined position until the synchronizing signal is received without interrupt.- ing the positive driving connection between the drum and the motor. The synchronizing signal .40 interrupts the controlled slip of the drum to co-ntinue its rotation in accurate phase synchronous relation with the transmitter drum.

Itis accordingly an object of my present invention to provide novel methods of and means for maintaining remote electro-mechanical systems in synchronous relation.

Another object of my invention is to provide novel methods of and apparatus for maintaining w a telepicture receiver in phase synchronism with its transmitter.

It is still another object of my invention to provide novel methods of and means for effecting stand-still of a driven member while maintaining u a positive driving connection with its source of motive power.

A further object of my invention is to provide novel methods of and means for changing the relative angular position of a rotating member without interrupting its positive drive connection to the driving member.

It is still a further object of my invention to j provide a novel synchronizing system whereby the translating member at a remote station is maintained in phase synchronous relation with the corresponding member at a transmitter station by controlling its angular position with cyclic synchronizing signals without the interruption of a positive driving connection to the source of nio= tive power for the translating member.

These and other objects of my invention will become evident in the following description taken in connection with the drawings, in which:

Figure 1 is a schematic illustration of a telepicture transmitter.

Figure 2 is a schematic illustration of a telepicture receiver.

Figure 3 is a pian view of a preferred embodiment of a telepicture receiver embodying the novel phasing mechanism.

Figure 4 is a longitudinal sectional View taken along 4 8 of Figure 3.

Figure 5 is the cross-sectional view taken along 5-5 of Figure 4, illustrating the operation of the phasing mechanism oi my present invention.

Figure 6-is a modification of my invention corresponding to Figure 5.

Figure 7 is a longitudinal cross-sectional view of a further modification of my present invention.

Figures 8 and 9 are sectional views taken along 8-8 and 9-9 of Figure 5 respectively showing details of the synchronizing apparatus.

Figure 10 is an end view of the embodiment corresponding to Figure 7 illustrating the synchronizing mechanism control.

The schematic diagrams Figures 1 and 2, of a telepicture transmitter and receiver respectively, are described to more clearly set forth the function and relation of the synchronizing mechanism of my present invention. It is to be understood that the telepicture system and circuits described are by example only and that the synchronizing mechanism to be hereinafter described in detail is applicable to other telepicture or facsimile systems.

Referring to Figure 1, a source of light I generates a beam I I focused to a point by a lens system I2 upon the picture I3 to be transmitted, which is mounted on the cylindrical drum I4. Ii the picture is scanned one hundred lines per inch, the diameterof the light spot focused upon the picture I3 vshould be .01 inch. The retracted beam I from the .picture is focused upon the photoelectric cell I6 by lens system I'I. The intensity of the refracted beam I5 is proportional to the shading of the picture elements which are successively moved past the light beam II.

The picture drum I3 is rotated by worm I8 and worm gear I9 which suitably reduce the speed of the motor 20. Motor 2U is preferably a synchronous motor connected to/a commercial electrical supply line 2I, for example a sixty cycle, 110 volt system. 'I'he drum may be driven at a normal speed of 100 revolutions per minute which, with one hundred lines scanned per inch, results in one inch of the picture traversed per minute.

The retracted picture light beam l5 impinging on photoelectric cell it produces corresponding electrical signals which are-amplied by amplifier 22. A light chopper or an audio frequency carrier wave may be employed with the amplifier 22 to facilitate transmission of the varying unidirectional picture signals as is well known in the art.

. The telepicture signals may be directly transmitted to a remote station overl wire lines or may be transmitted by radio transmission means. Figure 1 illustrates a transmitter 23 connected to the output of amplier 22 for converting the audio frequency telepicture signals into corresponding radio frequency signals which are radiated by antenna 2d. l

synchronizing signals are cyclically transmitted for effecting synchronization of the transmitter scanning apparatus in a manner to be described in detail. The synchronizing signals are preferably transmitted once per scanning operating. When a drum is used as in the preferred embodiment, the "underlap period of the rotation cycle is employed to transmit the synchronizing signal. The underlap period corresponds to the portion of the picture drum where the opposite ends of the picture i3 are gripped or otherwise fastened into position on the drum. In a continuous sheet system, the synchronizing signal is transmitted during the return oscillation movement, marking the beginning and end of each scanning line excursion. The transmission of a synchronizing signal for a continuous sheet system is described in my Reissue Patent No. 19,575.

A cam 25 is mounted upon the shaft 26 of the telepicture drum lll. A projection 2l of the cam 25 is positioned angularly corresponding to the underlap portion of the drum M. The edge 28 of the picture sheet i3 determines one side of the underlap zone and is gripped by clamping means internal to the drum I4 in a manner preferably as described in. my co-pending application Serial No. 72,990, filed April 6, 1936.

The synchronizing cam switch 30 is cyclically g closed by the cam projection 21 to impress suitable synchronizing impulses upon the ampliiier 22 from the synchronizing signal generator 3i. synchronizing switch 30 is connected in series with the synchronizing signal generator 3l output to a suitable portion of the telepicture amplifier 22 schematically indicated in Figure 1. 'Ihe synchronizing impulse effective during the underlap period is preferably of intensity somewhat greater than the maximum or white telepicture signal intensity in order to readily distinguish the synchronizing signals from the telepicture signals at the receiver.

The synchronizing signal generator 3 I may be a direct current source which produces a unidirectional impulse at each closure of cam switch 30 or may be an audio carrier frequency signal which is unmodulated during the synchronizing period and is suitably modulated by the picture signals during the remaining period of the cycle.

' A preferred embodiment of such a method for signal generation forms the basis of my co-pending application Ser. No. 74,419.

Figure 2 is a schematic diagram of a telepicture receiver used in conjunction with the transmitter of Figure l. and employing the synchronizing mechanism of my present invention. A radio receiver and rectifier 32 is connected to a receiving antenna 33 for receiving the radio transmitted signals from the radio transmitter 23. If a wire line is used, suitable amplifying and line arcanes equipment are instead employed. The output of the receiver and rectifier 32 are connectedto an audio amplifier 3d. The output of audio amplifier 34 is coupled to a class B push-pull output stage 35-36 by an inter-stage coupling transformer 31. The output of the push-pull stage 35-36 is connected tothe primary 38 of the output transformer 39. The output of the secondary 45 of transformer 3S is connected to a photolamp I containing a gas such as neon, for producing a light beam 62 output in accordance with the telepicture signals received. The light output 32 from lamp 5I is suitably focused upon the record sheet 49 on the receiving drum 55 by a lens system 42.

I prefer to use a neon crater photo-lamp di having a control electrode 43 which is connected to one terminal 45 of the transformer secondary LIU, and an auxiliary or striking electrode 45. The crater plate Q6 of lamp 5I is connected to the positive terminal of a suitable direct current source 51, the negative terminal of which is connected to ground. The other terminal i8 of the transformer secondary di) is connected to the crater plate 46 through a variable resistance 5I. The auxiliary or striking electrode 45 is connected to ground by lead 52. As is Well known in the art, the auxiliary electrode 45 maintains a striking or discharge condition at the photolamp crater plate 66, so that it will always be in readiness to respond to telepicture signals introduced between the plate 56 and the control grid 33. A by-pass condenser 53 is connected between the output terminal 48 and ground.

The receiver drum 55 is driven by a synchronous motor 56 connected to supply lines 2l'. The lines 2 I are preferably from the same alternating current supply lines 2| as those of the transmitter although such condition is not essential. The synchronous motor 5t drives drum 5@ through the schematically indicated synchronizing phase adjusting mechanism 55. The phase synchronizing or angular drum adjusting mechanism 55 is described in detail hereinafter. The drum phasing mechanism 55 maintains a positive driving connection between the shaft 55 which is driven positively from the motor shaft 51 through worm 58 and worm gear 59, and the shaft 6B directly attached to the receiver drum A control plate 5I cooperating with the phasing mechanism 55 is actuated by the synchronizing magnet 62 through its armature 63. Drum 50 is preferably driven at a slightly faster speed than the corresponding transmitter drum I6, for example in a ratio of 101:100.

The phasing mechanism 55 is under the control of the synchronizing magnet 62 to maintain the drum 50 in phase synchronism with the transmitter drum I as will be hereinafter set forth. Adirect current potential source 6d supplies the synchronizing magnet 52 through its relay contacts 65-65.

The anode potential source61 for the pushpull amplifier stage 35-36 is supplied to the center tap 68 of the primary 38 through the synchronizing cam switch 1li-1I. A cam 12 is connected to the shaft 60 adjacent the drum 50. The projection 'I3 of the cam 12 is in the same angular position on shaft 60 as the underlap or dead zone 14 of the drum 50. The cam switch 1li-1I is normally maintained closed during the ymajor-portion of the rotation of cam 12, and the anode current from source 61 normally directly ows to the push-pull amplifier stage 35-36 during the reception of the telepicture signals.

The cam switch l5- 1I is opened by the projection 13 of the cam 12 during the synchronizing or underlap period of the receiver. The anode current from source 61 is accordingly directed to the amplier 35-36 through the synchronizing relay 15, which relay is otherwise short-circuited by switch 1li-1I.

The synchronizing signal, as hereinabove described, occurs during the underlap period of the. picture transmitter, and is preferably of greater magnitude than the telepicture signals. Synchronizing relay 15 is preferably a marginal relay responding only to the increased magnitude signals so as to avoid the possibility of interference of the synchronizing action by any of the telepicture signals. The push-pull amplier 35-36 rectifles an alternating current synchronizing impulse in the anode lead if such is used, and the actuation of the relay 15 is by rectified or unidirectional current as will be understood by those skilled in the art.

Although I prefer to use synchronizing signals of increased intensity, and a marginal synchronizing relay, I have also successfully employed synchronizing signals of intensity equal to the maximum intensity picture signals to operate an ordinary relay. It is also to be understood that the synchronizing magnet 62 may be directly energized by the synchronizing signals, displacin the relay 15.

The receiver drum 5i) is prepared for the synchronizing signal during its underlap period by cam 12. 'Ihe synchronizing signal will flow through tol energizeV the synchronizing relay 15 which then closes the relay contacts 55-(56, locally energizing the synchronizing magnet 62. The synchronizing magnet 52, when energized, will attract the armature 63 away from control plate 6I to permit the phasing mechanism 55 to continue to normally drive the receiver drum 50; i. e., if the drum 50 were in phase synchronism and in proper phase, the release of armature 63 away from the plate 6I would avoid phasing or angular correction by the mechanism 55.

The control plate 5I of the phase correcting mechanism 55 has a notch 16 cn its periphery; the angular position of notch 16 corresponds to the angular position of the underlap zone 1d of drum 5G and that of the projection 13 of cam 12. The armature 63 is normally mechanically biased by spring 11 against the periphery of the control plate 6I. Armature 63 accordingly engages the notch 15 of control plate 6I and holds it against rotation. By preventing the rotation of control plate 5I, the angular or phase correcting mechanism 55 is actuated to effect the phase synchrovnism of drum 50 with transmitter drum I4 in a manner to be described in detail hereinafter.

By rotating drum 5G at a slightly faster rate than the transmitter drum I4, for example in the ratio of 101:100, the underlap period of the drum 5@ will reach the predetermined position corresponding to the engagement of armature 63 of notch 15 slightly before the normal reception of the synchronizing signal from the transmitter. The cam 12 will accordingdy open cam switch 1li-1I by the projection 13 and permit the energization of synchronizing relay 15 by lthe synchronizing impulse as it is received. The energization of synchronizing relay 15 by the synchronizing impulse will close relay 65-156 to correspondingly energize the synchronizing magnet 62 to attract the armature 63 away from engagement with notch 16 of control plate 6i. The positive driving connection between the motor 54 and the drum 56 is continuously maintained and the synchronizing signal in attracting the armature 63 from the control plate 6| permits the drum 99 to continue rotating with the positive driving connection intact and in accurate phase synchronous relation with the transmitter drum.

Figure 3 is a plan view of a preferred embodi-I ment of a telepicture receiver utilizing the phasing or angular correcting mechanism 55 hereinabove described. The apparatus is mounted upon a cast iron base 18. The motor 59 drives drum 59 through the mechanism 55 by worm 58. A pinion 99 connected to the end of shaft 69 drives a reduction gear train 8i to rotate, at a The focusing system 42 for the recording light' beam 42 corresponds to the optical recording system described in connection with Figure 2 to translate the receiving telepicture .signals upon the sensitive recording sheet 49 fastened on drum 50. The record sheet 49 is attached to the drum 50 by internal clamping mechanism such as disclosed in my application Serial No. 72,990, filed April 6, 1936, operated by levers 99. Roller 9| is pressed upon drum 59 to facilitate mounting of the record sheet 49 thereon by continuously smoothly pressing against the sheet.

Figure 4 is the cross sectional View taken along l--fl of Figure 3 through the phase correcting mechanism 55. The shaft 5t of motor 54 drives worm 58 which rotates worm gear 59 keyed to shaft 56 which is journalled in bracket 92. A sleeve 93 is keyed to the end of shaft 56. A bracket 99 extends from sleeve 93 to rotatably support shaft 95 of worm wheel 96. Worm 96 coacts with worm gear 91 which in turn is keyed to one end of shaft 60. Shaft 69 is journalled in bracket 98 and also in bracket 99 at the opposite end of drum 59. Drum 59 is also keyed to the sla;v 69. The synchronizing cam 12 is attached to the hub of drum 59. The synchronizing switch 't0-1i is attached to the top of bracket 99 to coact with the cam' 12.

The worm Wheel 96 and worm gear 91 normally I interlock to transmit the rotary motion of shaft 56 to shaft 69 inl a one-to-one or continuous manner. Figure 5 illustrates the interlocking of worm 96 and worm gear 91. The control plate 6| is loosely mounted upon shaft 60 between worm gear 91 and bracket 98. A skew bevel gear |99 is integral with control plate 6| and coacts with a skew bevel pinion I 0| attached to one end of the shaft 95 of worm 96.1 A housing 92 is attached to the outer edge of the control plate 6|.

The normal interlocking of worm 96 and worm gear 91 causes the control plate 6I torotate in correspondence with the normal rotation of

shafts

56 and 60, through the normal interlocking of skew bevel gear |00 and its co-acting pinion |0i. A positive driving connection is effected from motor shaft 51 through worm 58, worm gear 59,y

shaft 60, sleeve 93, worm 96 interlocking with worm gear 91 and shaft 60 to the drum 59. Worm 96 does not rotate during its normal interlocking with worm gear 91. The control plate 6|, free to rotate on shaft 60, is freely turned thereon due to the interlocking of the skew bevel gears and itil.

The armature 63 is normally biased by spring 11 against the periphery of control plate 6I. When armature 63 engages with notch 16 the normal rotation (indicated counterclockwise) ofcontrol plate 6| is arrested. A pawl |03 is normally biased against control plate 6| by spring G99 to co-act with a notch |95 on control plate 6l at the instant armature 63 engages notch 16 in order to prevent rebound of the control plate 6l to insure immediate stoppage thereof.

When control plate 6| is stopped from its free rotation on shaft 69, pinion |9| is moved relative to the stationary teeth of the skew bevel gear |60 since the interlocking action of worm 96 and worm gear 91 forces it to execute this relative motion. The relative movement of the pinion iti on skew gear H99 causes pinion Ill! to rotate. Since worm shaft is originally attached to pinion itil, the worm 96 will correspondingly rotate therewith. Rotation of 'pinion |9| as illustrated in Figure 5, will be clockwise as indicated by the arrow on the dotted position thereof. The dotted position of pinion lill and worm 96 corresponds to the continued rotation of the worm 96 and pinion |91! from the solid position.A

Clockwise rotation of worm 96 is designed to superimpose upon worm gear 91 a motion opposite to its normal rotation..

Accordingly, since the normal rotation of worm gear 9i and its shaft 69 is counterclockwise, the superimposed rotation by worm 96 is made clockwise. The phasing or angular correction of the synchronizing mechanism of my present invention superimposes upon the normal rotation of the driven member a counter-rotationv while maintaining a positive driving connection to the driven member. The ratio and proportions of the skew gears 99 and i0! and worm 96 and worm gear 91 are preferably chosen so that when the rotation of stop plate 6i isi arrested, the counter-rotation superimposed upon driven shaft @il is equal to the normal speed of rotation thereof but in the opposite direction. An effective stand-still of the shaft 60 is effected by the mechanism 55.

Although in my preferred embodiment a counter-rotation at a rate equal to the normal rotation is used to effect the phasing or angular correction of the drum 59 with respect to the transmitter drum in response to synchronizing signals, it is to be understood that it is by-way of example and not limitation. The principle of my present invention is also applicable to systems employing intermediate speeds of superimposed correction movement either in the counter-direction to the normal rotation or in the normal direction of rotation.J

When control plate 6| is stopped by the armature 63, normally mechanically biased toward it, the shaft 69 of the drum 50 is affected by the action of the phasing mechanism 55. Since the receiver drum is preferably normally rotated at a slightly faster rate than the transmitter drum,

control plate 6|to the bevel gear |20. A bevel is released, permitting the drum 50 to continue rotating in phase synchronous relation with the transmitter drum.

The synchronizing signal being transmitted during the underlap period as described in connection with Figure 1 marks the corresponding underlap position of the receiver drum which in turn corresponds to the position of notch 'i6 on control plate 6|.

Figure 6 is a modification of the embodiment as illustrated in Figure 5 by employing two opposed worm wheels 96 and 96' coacting with the worm gear 91 upon a common bracket 94'. The corresponding skew bevel pinions and |0| coact with the common skew bevel gear |00 integral with control plate 6|. The action, of the two opposed worm Wheels 96--96' together with their corresponding pinions |00 and |0| is additive in that they impose a common direction of motion upon worm gear 9`| when angular correction is eiected. The opposed worm and pinion arrangement is preferable from the standpoint of dynamic balancing about the axis of rotation. The control plate 6| and skew bevel gear- |00, integral therewith, is-preferably made of a light weight alloy to minimize the eiect' of residual inertia in the operation of the control mechanism for the phase adjusting device 55.

Figure 7 is a longitudinal cross-sectional view through another embodiment of the angular correcting me nism 55 corresponding to the mechanism 55 d scribed hereinabove. Shaft 5l' connected to a suitable motor, drives worm 58 which engages with worm gear 59'. The worm gear 59' is keyed to sleeve 56 concentric with control shaft H0. Sleeve 56 is journalled in bearing extending from the housing ||2 of mechanism 55' and integral with housing H3 enclosing worm gear 59 and worm 57?..

Bracket member Hd extends from sleeve 50' and rotatably supports shaft H5 of worm wheel i6. Worm I6 meshes with worm gear il which is keyed to shaft 60'. The telepicture drum 90 is keyed to shaft 60 to rotate therewith. Sleeve |8 is concentric with shaft 60' and is journalied in bearing |20 extending from housing i2. Sleeve Hi8 is integral with the bracket member and supports the right end thereof.

A positive 'driving connection is maintained from the shaft 5l' of the motor to the telepicture drum 50 as follows: Worm 58', worm gear 59', sleeve 60', bracket member ||l|, worm H6 supported by bracket I It and interlocking with worm. gear H1 which is keyed to shaft 60'. The interlocking of worm ||6 with worm gear H7 corresponds to the similar portion of the previous embodiment illustrated in Figures 4 to 6.

The phasing or angular adjusting means of drum 50 with respect to the motor shaft 5l' is eected by rotating worm ||6 to superimpose a counter-rotation upon gear lil. The control .plate 6|' is situated external to the mechanism 55 and is connected thereto by the shaft ||0 which is free to rotate relative to sleeve 5S'. The control plate 0| is affected by the synchronizing magnet 62 and the synchronizing signals in a manner similar to the hereinabove described control plate Si. However, in the embodiment described in connection with Figures '7 to 10, the control plate is external to the mechanism 55' and is connected to the phasing worm wheel H6 by a series of gearing connections in the following manner:

Referring to Figure 8, the rod 0 rotatably supported within sleeve 56 directly connects the gear |2| supported on rod |22 journalled in bracket member Hd meshes with the bevel gear |20. A spur gear |23 is external to the bracket member H0. Gear |23 meshes with gear |24 which is connected to the shaft l5 which supports the Worm H6. Figure 9 is the sectional view taken through Figure 7 along 9 9 and further illustrates the intermeshing gears connecting the control plate 0|' to the worm 6.

Worm H6 normally interlocking with Worm gear transmits the motive power directly imparted to bracket member iM to the worm gear to effect a link in the positive driving connection between the motor and the picture drum 50. Worm H6 does not normally rotate with its shaft H5 and is carried in a path concentric with the worm gear ||l with which it interlocks as bracket member ||Q rotates. The spur gears |23 and |20 accordingly do not normally rotate but are also carried in a circular path as is the worm HS. The bevel gears |20 and |2| normally mesh but do not move with respect to each other in a similar manner. Since bevel gears |20 and |2| do not normally rotate with respect to each other and since bevel gear |2| is moved in a path concentric to the axis of bevel gear |20, the gear |20 will be forced to rotate while intermeshing with gear |2|. Control plate 6|' being connected to bevel gear |20 byrod ||0 accordingly normally rotates during the rotation of the drum 50.

It is to be understood that during the normal operation of the drum 50 from the motor shaft 5l', a positive driving connection is maintained therebetween, that worm H6 does not rotate on its axis but is carried in a path concentric to the axis of the drum shaft 60 and that bevel gear |2| also does not rotate on its axis but forces bevel gear |20 to rotate to correspondingly re- Volve control plate 0|'. The normal rotation of rod i i0 by the intermeshing gearing system ofmechanism 55 is at the same speed and direction as the rotation of sleeve 56 encircling the rod H0. The rod H0 accordingly revolves together with the sleeve 56' with zero relative speed therebetween. fi

Figure l0 is an end view of the apparatus illustrated in Figure '7 showing the arrangement of the control plate 6|', the synchronizing magnet 62 and the armature t3 coacting with a notch 'I6' in the control plate periphery. Spring 'il' normally mechanically biases armature 69 toward the control disk 6|'. Pawl |03' coacts with plate 6| to prevent rebound of the plate when its notch 'i6' is arrested by armature 63.

A counter-weight |25 is preferably cast integral with bracket member i0 to dynamically balance the gearing mechanism connected to the opposite side of the bracket member Hd.

llhe operation of the phasing or angular correction mechanism 55' is similar to that described hereinabove in connection with the modiilcation illustrated in Figures 4 to 6. Ihe drum 50 is driven by the motor through the motor shaft 5l' by the-positive driving connection including the worm 58 and Worm gear 59' which motivates the synchronizing mechanism 55'. The drum 50 is preferably driven at a slightly faster rate""than the corresponding transmitter drum relation with the transmitter drum. If the drum gear 2| will be forced to rotate as it rolls around the stopped bevel gear |20. Rotation of bevel gear I2| correspondingly rotates spur gears |23 and |24 to turn the shaft ||5 of Worm wheel IE6. The rotation of worm wheel ||6 superimposes a counter-rotation upon worm gear ||1 to eifect the angular correction by the mechanism 55.

The ratio and proportions of the respective gearing in the phasing device 55' is designed so that by arresting the normal rotation of gear |20 the worm ||6 is turned lat a rate and in the direction to impose a counter-rotation upon gear at a rate which is equal to its normal rotation. The drum 50 will be effectively stopped from rotation and held in the stop position While rotation of control plate 6| is effected by the synchronizing armature 63.

The position of notch I6 corresponds to the underlap portion of the drum 50 in relation to the optical scanning system and also corresponds to the position of cam 12 connected to the drum opening the synchronizing switch l-1| by the cam projection 13. The synchronizing signal will cause synchronizing magnet 62 to be energized in a manner already described to attract armature 63 out of engagement from control disk 6|' and permit it to continue its normal rotation. The synchronizing signal accordingly starts the telepicture driun 50 rotating in proper phase syn chronous relation with respect to the transmitter drum as determined by the timing of the cyclic synchronizing signals.

' In the preferred embodiments of my invention, the telepicture drum is effectively maintained at a stand-still if the drum is not in proper phase is in the exact phase relation with the transmitter drum as determined by the timing of the synchronizing signals, a positive driving connection is maintained between the driving motor and the telepicture drum, so that no slippage can be had therebetween at any time, particularly during the phasing periods.

In accordance with my present invention, phase synchronism is effected in a definite and positive manner by superimposing the angular corrective motion upon the normal motivation of the drum while maintaining the positive driving connection to the drum. It willbe evident to those skilled in the art that modifications falling within the broader spirit and scope of my invention are feasible, and I do not intend to be limited except as set forth in the following claims.

Y I claim:

1. In a synchronizing system, a driven shaft; a l

driving shaft; gearing effecting a continuous mechanical interconnection between said driving and driven shafts; mechanism mechanically connected to and normally rotated with said gearing interconnection for independently controlling the rotation of said driven-shaft without interrupting said continuous mechanical interconnection; and a synchronizing magnet responsive to cyclic syn.- chronizing signals for cyclically arresting the rotation of said mechanism in the event said driven shaft is not in synchronism and until said driven shaft is in synchronous position.

2. In a synchronizing system, a driven shaft; a driving shaft; comprising gearing effecting a continuous mechanical interconnection between said driving and driven shafts; mechanism mechanically connected to and normally rotated with said gearing interconnection for independently aioaees controlling the rotation of said driven shaft without destroying said continuous mechanical interconnection whereby the angular position of said driven shaft is alterable with respect to said driving shaft; and a synchronizing magnet responsive to cyclic synchronizing signals for arresting the rotation of said mechanism in the event said driven shaft is not in synchronism until rsaid driven shaft is in synchronous position, once per revolution of said driven shaft.

3. In a synchronizing system, a driven shaft; a driving shaft; a driving connection including gearing from said driving shaft to said driven shaft; a stop-plate mechanically connected to and normally rotated with said driving connection for independently controlling the rotation of said driven shaft whereby the angular position of said driven shaft is alterable with respect to said driving shaft; and a synchronizing magnet responsive to cyclic synchronizing signals for arresting the rotation of said stop-plate in the event said driven shaft is not in synchronism until said driven shaft returns to synchonous position, one per revolution of said driven shaft.

4. In a synchronizing system, a driven shaft; a driving shaft; gearing effecting a continuous mechanical interconnection between said driving and driven shafts; mechanism mechanically connected to and normally rotated with said gearing interconnection for independently control g the rotation of said driven shaft without di onnecting said gearing whereby the angular position of said driven shaft is alterable with respect to said driving shaft; and a synchronizing magnet responsive to received cyclic synchronizing signals for cyclically arresting the rotation of said stop-plate until said vdriven shaft returns to synchronous position.

5. In va synchronizing system, a driven shaft; a driving shaft; a driving connection from said driving shaft to said driven shaft comprising gearing effecting a continuous mechanical interconnection between said driving and driven shafts; a stop-plate mechanically connected to and normally rotated with saidgearing interconnection for independently controlling the rotation of said driven shaft Without disconnecting said continuousymechanical interconnection whereby the anogular, position of said driven 'shaft is alterable with respect to said driving shaft; and a synchronizing magnet responsive to cyclic synchronizing signals for arresting the rotation of said stop-plate in the event said driven shaft is not in synchronism until said driven shaft returns to synchronous position, once per revolution of said driven shaft.

6. In a synchronizing system, a driven shaft; a

driving shaft; a driving connection including gearing from said driving shaft to said driven shaft; a stop-plate mechanically connected to and normally rotated with said gearing connection for independently controlling the rotationv of said driven shaft without disconnecting said gearing connection whereby the angular position of said driven shaft is alterable with respect to said driving shaft; and a synchronizing magnet responsive to cyclic synchronizing signals for arresting the rotation of said stop-plate in the event said driven shaft is not in synchronism, to effect a substantial stand-still of said driven shaft until said driven shaft returns to synchronous'r position, once per revolution of said driven shaft.

WILLIAM G. H. FINCH.