US2396705A

US2396705A - Facsimile system and apparatus

Info

Publication number: US2396705A
Application number: US473896A
Authority: US
Inventors: Khalil Seyed
Original assignee: Western Union Telegraph Co
Current assignee: Western Union Telegraph Co
Priority date: 1943-01-29
Filing date: 1943-01-29
Publication date: 1946-03-19
Anticipated expiration: 1963-03-19
Also published as: BE470594A; GB578416A; FR939103A; ES173330A1

Description

March 19, 1946. s. KHAUL FACSIMILE SYSTEM AND APPARATUS Filed Jan. 29. 19 6 Sheets-Sheet 1 S. KHAL".

AT TOR N EY March 19, 1946. s. KHALIL FACSIMILE SYSTEH AND APPARATUS 6 sheets-meet:

Fi1ed Jan. 29. 1943 FIG.

8. KHALIL ATTOR N EY March 19, 1946. '1 s. KHALIL" I 2,396,705

FACSIMILE SYSTEM AND APPARATUS Ema Jan. 29, 1945 v e Sheet Sheet s INVENTOR s. KHALIL ATTORNEY S. KHALlL FACSIMILE SYSTEM AND APPARATUS I arch 19, 1946.

Filed Jan. 29, 1945 s Sheets-Sheet 5 FE. m

' INVENTOR s. KHALH.

' ATTORNEY March 19, 1946. s. KHALIL 2,

FAcs1MILE sis'rEM AND APPARATUS r I a .6 Sheets-Sheet 6 FIG. I4

Filed Jan. 29, 1945 ATTORNEY .7 G) I INVENTOR 207 Patented STATE 2,396,105 FACSIMILE SYSTEM AND APPARATUS Application January 29, 1943, Serial No. 473,896

33 Claims. The present invention relates primarily to facsimile systems and apparatus therefor and more particularly to novel and improved transmitting and receiving facsimile machines and a novel synchronizing system employing the same for transmitting and receiving subject matter such as pictures and messages in facsimile.

There have been several types of facsimile machines proposed heretofore andv they may be classified in two general classes, the unilateral or unidirectional type wherein the direction of movement of the scanning element relative to the material scanned is always in-the'same direction, and the bilateral or back-and-forth type wherein the scanning element moves back-and-forth or in two directions relative to the material scanned.

The so-called cylinder machine is the most generalsof the first typewherein the subject matter sheet in the transmitter and the recording blank in the receiver are wrapped around cylinders and a scanning element in the transmitter and a recording element in the receiving machine move axially of the cylinders as the same rotate.

A lead screw is usually provided to produce relative movement between the rotating cylinders and the scanning or recording elements, and accordingly the movement of the scanning and re= producing elements relative to their respective cylinders is unidirectional and the elements trace a continuous helix on the cylinders. Inasmuch as no correction or synchronization is ordinarily applied to the rotating drums during the scan ning and reproducing of a subject matter sheet, any difierence in speeds of the drums will have an accumulative adverse efiect on the fidelity of the reproduction. In addition to the above, the cylinder type of facsimile machine has the disadvantage that considerable care must be exercised in placing the subject matter sheets and the recording blanks on the cylinders.

Another type of unidirectional facsimile machine sometimes employed, primarily as a receiving instrument, isthe type wherein the recording blank is maintained flat and a plurality of recording styli arranged on an endless belt to successively contact the recording blank one at" a time to reproduce .the subject matter. This type of machine has the disadvantage that it can only be used as a receiving instrument and like the cylinder type any speed difference between the driving means .for it and the transmitter will adversely affect the reproduction.

In this type or machine, as in the cylinder type. if the transmitter andreceiver aregoing at dittravel.

ferent speeds, the received copy will be skewed, that is, a vertical line for example or one substantially at right angles to the direction of the movement of the scanning element will be reproduced as a slanting line. If the transmitter is faster, the line will slope in one direction and if thereceiver is faster, the line will slope in the other direction. If the speed of either the transmitter or receiver varies with respect to one another during the scanning of a subject matter sheet, and the speeds are different, vertical lines will be reproducedas sloping lines with various degrees of curvature, the degree of curvature depending upon the variation of relative speeds.

In the bilateral type of machine, the scanning element moves back and forth and performs a scanning operation during each direction of its The scanning element is usually driven by a cam and insome types of machines the cam is released at the beginning of the scanning of a subject matter sheet while in others the cams for controlling the scanning elements are synchronized periodically or after each forward and back stroke of the elements. In this type of machine wherein the'driving means for the scanning elements are not synchronized after each forward and back stroke, any speed diilerence between the receiver and transmitter would have an accumulative adverse effect on the reproduction. If the speed of the transmitter and receiver are difierent and constant, a single vertical line for example on the subject matter in this type of machine will be recorded as two broken or dotted lines at an angle to each other, so that the two dotted lines will form a V. In a bilateral type of machine that is synchronized with the transmitter after each stroke or after each combined forward and back stroke of the scanning element, if there is a speed difierence between the transmitter and receiver, a single vertical line on the subject matter will be recorded either as a zig-zag line or as two brokenor dotted parallel lines on the reproduction. The varying of the speed of the driving means during a recording operation of either the transmitter or receiver in the above mentioned bilateral types of machines will also have an adverse effect on the reproduction, the distortion indicated above being modified by curvature of the two broken lines or by an increase in the amount of deviation of the zig-zag line.

From the above it is seen that any speed difierence or variation in the driving means for a transmitter and receiver in a facsimile system has anadverse effect on the fidelity of the reproduction and it is accordingly one of the primary objects of this invention to provide a facsimile system and apparatus wherein these adverse eifects are entirely eliminated or if not eliminated, reduced to a negligible minimum and as is the case with machines which are not periodically synchronized, to provide a machine wherein the speed difference and variation does not have an accumulative adverse effect on-the faithfulness or fidelity of the reproduction.

The present invention is illustrated in the accompanying drawings and hereinafter described as being applied to a facsimile transmitting machine wherein the subject matter is held flat and the scanning element moved back and forth relative thereto to perform a scanning operation during each direction of its travel. In a similar manner the recording stylus or element in the receiving instrument moves back and forth relative to a flat recording paper to perform a recording function during each direction of its travel. Although the invention is shown and de scribed in conjunction with one particular type of machine, it will be apparent that it is not so limited but that the principles thereof may be applied to various other types. In the described embodiment of the invention, the subject matter in the transmitting instrument and the recording paper in the receiving instrument pref erably move in a direction perpendicular to the direction of movement of the scanning and recordingelements intermittently at the end of each stroke of their respective elements.

- In the present invention synchronization between the transmitting andreceiving-mechanisms is maintained in a novel and improved manner, and as will be obvious hereinafter has man advantages over prior art devices.and systems. In the present arrangement the scanning elements or the scanning heads of the two machines, the transmitter and the receiver, are started in the same direction at the same instant. Some time during the first scanning stroke the direction of movement of the scanning heads is simultaneously reversed and, as the speed of the individual driving means of the scanning heads will not vary appreciably and can be assumed to remain substantially constant during a single oscillation of the scanning heads, they will reach their initial position at exactly the same time. However, should the speed of either one or both of the driving means vary during an oscillation of the scanning elements, there would not be an accumulative adverse effect on the reproduction, as will be apparent hereinafter. With the present arrangement the speed of movement of the two individual scanning heads may be substantially different from one another, but since they are started simultaneously and the direction of movement of the two heads is reversed at the same time they will reach'their initial positions at substantiall the same time even though one head may" travel a greater distance than the other. In other words, the scanning heads start together and move in one direction distances that are proportional to the speed of the individual driving means, and after a certain length of time the direction of movement of the two scanning heads is simultaneously reversed. Since the speed of the driving means of the two' heads may be assumed to remain constant, they will reach their initial pos tion simultaneously so as to start the scanning of the following line together. Any speed difference between the: driving means for ing element would be a difference in one dimension of the size of the reproduction relative to the subject matter.

With a facsimile machine wherein the line scanning isperformed as above and the line feed effected intermittently with the scanning operation, a vertical line, for example, on the subject matter will be reproduced on the recording blank as a vertical line with no distortion thereof or drift. Also, any horizontal line, for example, will be reproduced as a horizontal line on the record ing blank, and lines perpendicular to one another on the subject matter, as for example, vertical and horizontal lines, will be reproduced exactly perpendicular to one another on the recording blank. Such a system of facsimile reproduction has many obvious advantages and uses over the systems employed heretofore.

With a machine and system such as described above, enlargements or reductions of the subject matter may readily be made on the recording blank b changing the speed of the scanning head of the receiving mechanism relative to the speed of the scanning head of the transmitter together with an appropriate change in the line feeding mechanism.

.In view of the inherent limitations and disadvantages of prior art facsimile machines and systems, it is one of the objects of the present invention to provide facsimile transmitting and receiving equipment wherein exact synchronism between the driving means is not essential for the proper operation of the machines and the reproduction of a. reasonably exact facsimile of the subject matter.

Another object of the present invention is to;

provde transmitting and recording facsimile machines and control means therefor to operate and control the scanning and recording elements in the proper timerelation to one another whereby substantially exact reproduction of the subject matter is produced at the receiver.

Another object of the invention is to provide transmitting and receiving facsimile mechanism wherein the subject matter to be transmitted such as-pictures or messages ,may be maintained in a fiat condition during transmission and. in which the recording medium may also be maintained in a flat condition during reception.

Another object of the present invention is to provide facsimile mechanism wherein the subject matter scanned movesin a direction perpendicular to the scanning movement and preferably during non-scanning condition of the scanning element.

A still further object of the invention is to pro-- vide mechanism whereby the recording medium is moved perpendicularly relative to the direction of the recording movement of the recording element and preferably during. a non-recording condition thereof.

Another object of the present invention is to provide a facsimile system wherein the time consumed in performing a certain operation in the length of the lines scanned in both machines.

Another object of the invention is to provide facsimile transmitting and receiving mechanisms adapted to operate in accordance with a system as outlined above.

Another object of the invention is to provide facsimile machines adapted to operate on the above arrangement wherein the scanning elements have a bi-lateral or back and forth scanning movement relative to the subject matter and recording sheets.

Another object of the invention is to provide a correcting mechanism for a bi-lateral scanning facsimile machine whereby the time elapsingbetween the beginning of the scanning of successive lines is equalized.

Another object ofthe invention is to provide a correcting mechanism for a bi-lateral scanning facsimile sytem wherein correction is applied to a scanning'element of either a receiver or transmitting instrument at the end of one .stroke, for example, in proportion to the speed difference between the two scanning elements so that with I a correcting mechanism for a bi-lateral scanning facsimile machine wherein correction may be applied to both the transmitter and receiver scanning elements at the end of the first strokes thereof, for example, in proportion with the speed the speeds remaining constant the said scanning difference between the two elements and a given standard so that with the speeds remaining constant the scanning elements reach the ends of the next strokes in synchronism with the given standard.

Another object of the invention is to provide a rotating facsimile scanning element driving means arranged, for example, to* make one-half A revolution in one scanning stroke of the machine and correct the rotation of the driving element at the end of one-half revolution in'proportion to the speed difierence thereof and a given standard during the said one-half revolution to enable the rotating element with the speed thereof remaining constant to reach an initial position in synchronism with the given standard.

In accordance with the above, it is a still further object of the invention to provide means for rotating the facsimile scanning element driving means in a reverse direction after one-half revolution thereof an amount proportional to the speed difference between it.and a given standard during the said one-half revolution.

successively scanned. A lens system is employed in conjunction with the light beam in the usual manner and also a chopper disc which interrupts the light beam at a certain frequency to generate a carrier frequency. The tonal densities of the subject matter modulate the carrier frequency in proportion to the amount of light reflected from the scanned subject matter. In the preferred embodiment of the transmitting and receiving mechanisms, the scanning element and-the recording element move back and forth in a scanning and recording movement relative to the subject matter and the recording medium, while the so-called line feed of the subject matter and recording medium is in a direction perpendicular to the scanning and recording movements.

The recording element in the recording mechanism preferably consists of a stylus which duplicates the movement of the scanning element in the transmitting machine and reproduces a facsimile of the subject matter. The recording medium itself preferably is of the type which is adapted to change the color characteristic thereof on the passage of an electric current therethrough, the current passing through the paper being modulated in accordance with the subject 'matter scanned.

The preferred embodiment of the invention employs a reversing clutch for reversing the direction of movement of the scanning element in the transmitter and the recording element in the receiver. The reversing mechanisms may be controlled by any suitable means such as clock works which may be maintained in synchronism and A still further object of the invention is to provide a facsimile system and transmitting and receiving instruments to operate in conjunction therewith in such a manner that any speed difference, whether variable or constant. between the driving means for the said instruments does thereof.

The transmitting mechanism employed in the preferred embodiment of the invention employs a photocell in its scanning element, and a pencil or beam of light is directed on the subject matter so as to reflect on the photocell to excite the same in accordance with :the tonal densities of the subject matter as elemental areas thereof are corrected periodically from the transmitter or receiver or from a control point. A modified revers ing or correcting mechanism employs a so-called differential arrangement whereby difierences in speed of thedriving means-of the transmitter and receiver are corrected in amounts proportional to.

the diflerence in speed of'the two driving means, or in amounts proportional to their speed and a given standard. The correction. occurs periodically, and there is no accumulative effect on the reproduction of speed difference between the receiving and transmitting mechanisms or a given standard.

A more thorough understanding of the invention may be had from the following detailed description of the preferred and one modified embodiment thereof when taken in conjunction with the accompanying drawings, in which:

Fig. l is a diagrammatic view of a facsimile sytem'employing the mechanism of the present invention;

Fig. 2 is a perspective view of the principal elements of a facsimile machine constructed and controlled in accordance with the present invention;

Fig. 3 is a view showing the path of relative movement between the scanning element and the subject matter in the transmitting mechanism or the recording element and the recording medium in the receiving mechanism;

Fig. 4 is a detail view of some of the elements of the reversing clutch employed to reverse the direction of movement of the scanning element such as employed in Fig. 2;

Fig. 5 is a right hand view of the elements shown in Fig. 4; Fig. a is a detail view of the control mechanism employed to owrate the reversing mechanism;

Fig. 7 is a perspective view of the invention adapted to be controlled in accordance with the operation of the modified reversing mechanism employing the so-called differential correcting mechanism;

Fig. 8 is a diagrammatic representation of a modified control circuit for a facsimile system embodying mechanisms of the present invention;

Fig. 9 is a detail view partly in section of the differential correcting mechanism;

Fig. 10 is a detail view taken substantially on line |8|6 of Fig. 9;

Fig. 11 is a vertical sectional view taken substantially on line of Fig. 9;

Fig. 12 is a left hand end view of some of the mechanism shown in Fig. 9; and

Figs. 13 to 18 are diagrammatic views of the differential correcting mechanism shown in Figs.

. 9 to 11 illustrating the principles of operation thereof.

Referring first to Fig. 2 there are shown the elements included in the embodiment chosen to illustrate the invention. As will be pointed out hereinafter, and as will beapparent from the appended claims, the invention is not'limited to the particular arrangement shown in the drawings but may be incorporated in many other arrangements. In the arrangement shown in Fig. 2 a flat table 2| is supported on a base 22 and arranged to move longitudinally relative to the base being guided by means such as 23 in the base and projections 24 on the underside of the table.

The table 2| has thereon the subject matter sheet 26 to be scanned, and it may be a message, map or picture, etc. Clamping members 21 may be employed to hold the sheet 26 to the top of the table. As will be apparent, the mechanism disclosed in Fig. 2, while being described primarily as a transmitting machine, may be employed equally well as a recording machine, in which case the subject matter sheet 26 would be replaced by a recording blank. Attached to the table 2| is one end of a flexible band 28, the other end of which is arranged to wind up about a spring drum 29. The spring drum 29 may be of the type em ployed to advance the carriage in an ordinary typewriter and contains a spring (not shown) normally tending to rotate the drum in a clock wise. direction, as shown in Fig.. 2. The spring drum 29 through the flexible band 28 tends to move the table 2| in the direction indicated by the arrow 3| but is normally prevented from doing so by means hereinafter described. The spring drum 29 is provided with some means such as the knob 32 whereby the tension of the spring drum tending to advance the table may be varied.

Depending from the right hand side of the table 2| and extending the full length thereof is a rack 33 which is engaged by a pinion 34. The pinion 34 is mounted on a shaft 36 suitably supported in bearings (not shown) and has fixed to escapement wheel 41 the forward end thereof a gear 31. The gear 31 meshes with a smaller gear 38 on a shaft 39 which also has fixed thereto a toothed ratchet disc 4|. In axial alignment with the shaft 39 is a second shaft 42 which carries a multi-toothed camdisc 43. Extending axially from the back side of the cam disc 43 is a pin 44 which carries a pawl 46 held by a spring 45 in engagement-with the teeth of the ratchet wheel 4|. The spring drum 29 tends to advance the table 2| in a line spacing direction and at the same time tends to rotate the toothed ratchet wheel 4| through the described gear train including gears 38, 31, the pinion 34 and rack 33. Because of the pawl 46 and ratchet wheel 4|, the table 2| may be moved either manually or by suitable automatic means in a direction opposite to the arrow 3| for the purpose of resetting the table without effecting rotation of the shaft 42. This operation will, of course, be performed-prior to the beginning of the scanning of a subject matter sheet 26 and restores the tension to the spring in the spring drum 29.

Fixed to the forward end of the shaft 42 is a toothed escapement wheel 41 which has in operative relation therewith an escapement yoke, indicated generally by reference numeral 48, having

arms

49 and 5| positioned on the right and left hand sides, respectively, of the escapement wheel. The escapement yoke 48 is pivotally mounted on a pin 52, and a complete oscillation comprising movement in one direction and then in the opposite direction permits rotation of the escapement wheel 41 one tooth. A stroke or half oscillation of the yoke 48 permits rotation of the half the distance between adjacent teeth in the manner commonly employed in clock works.

The timing of the oscillations of the yoke 48 is controlled by a timing means including a flywheel 53 loosely mounted on a shaft 54. The flywheel 53 has one end of a hair spring 56 attached thereto, the opposite end of which is secured to the shaft 54. The flywheel 53 also carries a pin 51 extending axiall therefrom which engages the bifurcation 6| in the lower end of the escapement yoke 48. The escapement wheel 41, tending to rotate from power derived from the spring drum 29, causes the escapement yoke 41 to oscillate, and the timing of the oscillations is controlled by the flywheel 53 and attached spring 56. For each half oscillation of the escapement yoke 48 the table 2| is advanced a predetermined distance in the direction of the arrow 3|, and this advancement of the table is hereinafter referred to as the line feed advancement. The distance the table 2| advances for each half oscillation of the escapement yoke 48 is determined by the relative size of the gears 31 and 38 and the pinion 34. Preferably this advancement of the table is in steps of approximately one onehundredth of an inch so as to give scanning lines on one-hundredth of an inch apart. Obviously the distance the table advances for each half oscillation of the escapement yoke may readily be varied by changing the relative size of the gears 31 and 38 or by changing other elements of the advancing mechanism. It will also be obvious that the above-described mechanism effects advancement of the table 2| in intermittent steps.

and these preferably occur, as will'hereinafter be pointed out, during the non-scanning part of the movement of the scanning head or scanning elemerit. The timing period of the escapement yoke .48 is determined primarily by the tension of the supported on a pin 69 and has an armature 1| at its left hand end inoperative relation with electromagnets 12. A spring 13 normally pivo s an amount equal to one-- interrupting the light beam I Notion-8i to engage the flywheel 63, and if at this time the center of the notch 66 is anywhere else but directlyover the wedge-shaped projection 67, the flywheel will be rotated in either direction as the projection 61 enters the notch 88. Such operation of the electromagnets 12 co!- rects the position of the flywheel 53 in a'manner more fully described hereinafter and effects this correction to advance the flywheel if it is slow or to reset the same if it is fast. The amount the' flywheel 53 may be fast or slow is determined by the portion of the periphery of the flywheel that the notch 86 includes. While this portion is shown in the drawings to comprise only a small portion of the periphery of the flywheel 53, as it is expected only a small correction will be necessary, the design of the flywheel could be changed so that the correction could effect substantial parts of a revolution thereof. y

The actual scanning operation of the subject matter sheet in the transmitter and the recording blank in the receiver preferably occur alternately with a line feed operation, and in the embodiments shown herein the scanning elements are arranged to move relative to the table 2| to perform a scanningoperation. However, as will be apparent, the scanning element could be maintained stationary and the table moved back and forth in one direction for scanning movement and longitudinally in a different direction for line feeding. In Fig. 2 the scanning element is represented by the so-called scanning head 14 and it is adapted to move transversely of the subject matter sheet 26 on guide rods such as I6. The scanning head M of Fig. 2 would preferably include as shown in Fig. 1, a source of light 11, a chopper disc 19, and the photocell I9 together with the lens system which would include lenses such as 8!. As shown in Fig. 1, the light beam from the source TI is directed at the subject matter sheet 28 to successively illuminate elemental areas thereof and the light is reflected onto the photocell I9 in accordance with the tonal densities of the subject matter. The chopper disc I8 at a uniform rate generates a carrier frequency which is modulated in accordance with the tonal densities of the subject matter.

The output of the photocell which varies in accordance with the tonal densities of the elemental areas of the subject matter is applied to an amplifier represented by therectangle 82 of suitable design which controls the transmission of signals representing the subject matter over the line circuit such as 83. The line circu't 83 may be of any of the well known types and for the sake of simplicity only thesingle connection is shown.

At the receiving end of the line-circuit 83 is another amplifying means 84 which operates in the usual manner to apply modulated electrical potential over the conductor 88 to a recordin means such as a stylus 81-. The amplifier 84 applies the modulated potential to the stylus accordance with the modulated carrier frequency.

' The recording medium 88 has the elemental areas successively scanned by the stylus such as 81 and is supported on a conducting plate which in the arrangement shown in grounded. The recording medium 88 may be of the well known type such as disclosed in a patent to R. J. Wise et al. No. 2,294,147, issued August 25, 1942, that changes the stylus, there will be reproduced thereon an image similar to that on the subject matter sheet 28. Obviously, either of the amplifiers would contain a signal inverter if desired so that the reproduction would not be a negative of the subject matter. scanned. The diagrammatic showing in Fig. 1 also includes various control elements hereinafter described in detail which are employed to maintain the proper relation between the transmitting and receiving machines.

If the ing instrument, the scanning head I8 thereof would contain a recording stylus such as 81 of Fig. 1 instead of the light beam, photocell'and related elements. Preferably, of a machine would contain both the scanning light beam and photocell with its related equipment and a recording element or stylus such as 81 so that the machine could be used either as a transmitter or a receiver,-of course, only one of the elements, the scanning element or the recording element, being used at a time. p j

The mechanism for moving the scanning head 14 back and forth over the table will now be described. This mechanism includes two spring 2, normally tending to rodrums 89 and 9|, Fig. tate in the direction of the arrows adjacent thereto to wind-up about the circumferences thereof associated flexible bands 92 and'93. The flexible band 92 passes'over an idler pulley 94 and has the end thereof attached to the left hand side of the scanning head 14 while the flexible band 93 attached to the right hand side of the scanning head passes over an idler pulley 96 and then to its associated spring drum 9|. As shown'in more detail in Figs. 4 and 5, the spring drums 89 and 9| are pivotally mounted on independent'shafts such as 91 and rotatable with the spring drums 89 and 9| are associated

wheels

98 and 99 re- 99 one at a time is a drivewheel I9I. During the scanning of a. subject matter sheet the drive wheel |8| is arranged to be constantly rotated through elements hereinafter described and is brought into engagement first with one

wheel

98 or 99 and then the other to rotate the same independently and wind the

flexible bands

92 and 93 about the associated spring drums. The winding of the band 92 about the spring drum 89 causes the'scanning head I4 to move to the left and during such time the band 93 unwinds from its associated spring drum 9|. The subsequent engagement of the drive wheel IIlI with the wheel 99 causes the flexible band 93 to wind up about its spring drum 9| and move the scanning head in the opposite band 92 is unwinding from its drum. Themovement of the drive wheel |I|| from'engagement with one wheel such as 98 to the other such as 99 is controlled. by the escapement mechanism which also controls the line feed 'movement of the table.

The drive wheel I9| which also has thereon .a gear I03. The shaft I82 is supportedin the upper end of alever I98 pivotally mounted adjacent its center on a shaft I88. The shaft I86, as shown in Figs. 2, 4 and 5, is suitably journaled in a stationary part of the framework indicated generally by reference numeral I 91. Mounted on the shaft I95 is a gear I98 which machine shown in Fig. 2 were a receiv-- the scanning head 98 and.

direction to the right while the.

is mounted on a shaft I82 ence numeral III,

. shown in Fig. 4. In this position the meshes with the previously mentioned gear I03 and drives the same. The shaft I06 is driven from a motor drive shaft pinion I09 of a motor M and a gear IIO through anelectromagnetcontrolled clutch indicated in general by refer- The magnet 2 controls the clutch III in a manner hereinafter described.

The lower end of the lever I04 has a pin II 3 extending therefrom which engages a slot H4 in a jockey lever H5. The jockey lever H5 is pivotally mounted adjacent its center on a fixed pivot H6 and has attached to the upper end thereof the upper end of a jockey spring I II. The

lower end of the spring III is anchored on a pin H8 in vertical alignment with the shaft I06 and the fixed pivot H3. The jockey lever in conjunction with the spring- III biases the drive wheel- IOI into either one of its operative positions.

A pin II 9 located in the lever I 04 above the center pivot point engages a slot I2I in the left hand end of a link I 22. The link I22 is attached at its right hand end to the upwardly extending arm of a bell crank I23 which is pivotally mounted in a fixed pivot I24. The rightwardly extendingarm of the bell crank I23 is engaged by a bifurcated left hand end as shown in Fig. 6 of a lever I26. The lever I26 is pivoted at its right hand end on a fixed pivot I27 and has to the left of the pivot a cam follower I28 in operative relation with the periphery of the cam disc 43. A spring I29 holds the cam follower I28 in engagement with the disc 43.

The cam disc 43 is stepped in the manner hereinbefore described amounts equal to one-half the distance between successive teeth on the escapement disc 41. The cam disc 43 has projections such as I 3I equal in number to the teeth on the escapement disc and. after each step of the disc 43 either a projection I3I or a notch between two projections will be in engagement with the cam follower I28. Accordingly, the lever I26 will be oscillated up and down so as to make one movement for each step of the escapement disc 47. The movement of the lever I26 from its lower position as shown in Fig. 6'to its upper position as shown -by the dotdashed outline thereof will rock the bell crank I23, Fig. 4,.in a counterclockwise direction. This causes the link I22 to push on the pin II 9 and rock the lever I04 in a counter-clockwise direction. During this movement of the'jlever I04 the jockey lever H5 is also rocked in af'counter-clockwise direction to increase the tension in the jockey spring I I I and when the end of the jockey lever to which the spring is attached is just beyond dead center, the spring is effective to snap the jockey lever to its other position. Thus the movement of the lever I04 which is initiated by the link I 22 is d. by the jockey lever I I5 and attached spring II1, the slot I 2i in the left hand end of the lever I 22 permitting movement of the lever I I5 independently of the link'l22 In a similar manner the rocking of the bell crank I23 in a clockwise direction by the lever I26 pivots the lever I04 in a clockwise direction to the position drive wheel IOI carried in the upper end of the lever I04 is in engagement with the wheel 99 associated with the spring drum 9|, is pivoted in the opposite direction, the drive wheel IN is in its other position and engages the wheel 98 as shown by the fragmentary dotted portion thereof in Fig. 4.

whereas when the lever I04 the drive wheel ner engagement of the drive wheel with the wheel 98 moves the scanning head to the left. The springs such as I32, Fig. 4, in the spring drums 89 and 9!, preferably are arranged so that the tensions thereof may be varied by well known suitable means such as manually positionabw members I33. The tensions of the springs 1r, said drums are preferably adjusted so that they exert an equal tension on their associated flexible bands when the scanning head 14 is in substantiallythe center of its travel. When the flexible band winds up aboutone spring as controlled by the drive wheel II, the tension of the spring in the spring drum from which the band is unwinding is increased. This difference in tension of the springs in the spring drum which will occur when the scanning head I4 is near either end of its travel, assists in overcoming the inertia necessary to start the scanning head for the beginning of a scanning movement in an opposite direction to its last scanning stroke. However, IUI is arranged to move from one position. to the other extremely fast and during such movement the difierence in tensions of the springs in the spring drums 89 and SI preferably do not cause any independent movement of the scanning head I4, I

From the above arrangement it is obvious that reciprocating movement of the scanning head I4 is produced and that during its movement it will have, within the limitations of the driving motor, substantiallyuniform speed in each direction. Accordingly, a scanning function may be performed during each movement of the scanning head and time is not lost as is the case in some facsimile machines wherein the scanning element returns to a normal position at the beginning of a line'by a non-scanning return movement following each scanning movement. It will also be obvious that the above arrangement has the advantage that by changing the sizes of the wheels such as 93 and 99, the length of a line scanned in each scanning function may be varied while the time characteristics of the control mechanism are maintained constant. The length of the scanning line may also be varied by maintaining the proportions of the scanning head driving elements fixed and varying the time characteristics of the escapement control mechanism.

The advancement of the table 2I, Fig. 2, in a line spacing direction, preferably occurs during the operation of the reversing mechanism which includes the drive wheel I0 I, or while the scanning element in the scanning head is scanning the margin of the subject matter sheet and table, and is adapted to occur substantially instantaneously. This arrangement produces a scanning of the subject matter sheet 20as exemplified in Fig. 3 Where the dot-dashed line I34 represents the relative movement between the scanning head such as 74 and the subject-matter sheet 26. If the scanning head I4 is assumed to start at a point I 36 and then travel to the right across the subject matter sheet to the point I31, at which time the table 2I is advanced one scanning line, then the return scanning stroke of the scanning head will traverse the second dot-dashed line on the sheet 26, Fig. 3. This produces scanning lines which are exactly parallel with one another and in a direction perpendicular to the direction of movement of the subject matter sheet.- This arrangement has many obvious advantages over the method and mechanisms employed wherein the subject matter sheet is wrapped around a cylinder and scanned in one continuous helix or methods wherein the subject matter sheet is scanned by prior art arrangements..

The modified arrangement of the invention employs a so-called differential reversing mechanism, and this mechanism will now be described. The application of the differential mechanism to a machine such asdisclosed in Fig. 2 is shown in Fig. 1, and as will be apparent many of the elements of Fig. 7 are. identical with those of Fig. 2 and, accordingly, bear and are referred to by the same reference numerals. The differential mechanism itself may be enclosed within the box I46, Fig. '1, and the power therefor supplied from a constantly rotating motor M of suitable speed characteristics through an electromagnet controlled clut'ch I45 including a control magnet I44.

The control of the reversing mechanism is effected through a lever I48 which is operated from a cam disc 43' included in the escapement mechanism. The escapernent mechanism of the arrangement shown in Fig. 7 is somewhat the same as that of.

Fig. 2, with the exceptions hereinafter pointed out. The cam disc 43' in Fig. 7 has twice as many projections thereon as the teeth on its associated escapement wheel 41, and the escapement yoke '48 is pivotable on a pivot pin I42 at the lower end thereof under the control of separate electromagnets I43. With this arrangement the escapement yoke 48' is operated as the magnets I43 are alternately energized to escape the wheel 41 a half tooth for each movement of the yoke or one tooth for each complete back and forth oscillation thereof. The lever I48 is operated momentarily by the disc 43' once for each half tooth advancement of the escapement wheel 41.

The reversing mechanism will be described in detail hereinafter, but for the present it is be-,

lieved desirable to describe the connection thereof with the scanning head 14. As shown in Fig. 7, the reversing mechanism has a crank arm I49 at the forward end thereof to which is connected a link II. The link I5I is pivotally attached to a block I52 adjustable along-a slot I53 in a lever I54. The lever I54 is pivoted at its lower end on a pivot pin I 56, and the upper end has connected thereto a link I51. The other end of the link I51 is attached to a pin I58 extending from a spring drum I59. The spring drum I59, together with a second spring drum I6 I, is preferably of larger diameter than the spring drum 89 and 9| of Fig. 2,

and the reason for'this will be obvious hereinafter.

Bands

92 and 93 connect the scanning head 14 to preferred thereof efiects a complete scanning movement in one direction of the scanning head 14. As in the embodiment, the tension of the springs in thespring drums I59 and I6I, Fig. 7, is such that they exert substantially equal forces on the scanning head 14 when it is in the middle of its traveL. With such an arrangement the unequal tensions of the springs in the spring drums when the scanning head reaches the end of a stroke tends to overcome the inertia thereof in initiating a return stroke. By adjusting the position of the v block I52 along the slot I53 in the lever I54, the

amount of oscillation of the lever I54 may be varied, which in turn will vary the stroke of the scanning head 14. The pin I62 in the bl ck I52 is adapted to engage holes such as I63 in the lever I54 to lock the block in an adjusted position.

Referring now to Figs. 9 to 12, the details of the elements of the reversing mechanism will now be described. Included in this mechanism is a shaft I64 which is driven from the motor M through suitable reduction gearing, if desired, and through the electromagnet clutch I which includes the control magnet I44, Fig. 7. The shaft I 64 is suitably journaled in bearing supports such as I66 and has adjacent its right handend. as shown in Fig. 9, a threaded portion I61 preferably having-a multiple lead. Mounted on the threaded portion I61 of the shaft I64 is a sleeve I68 which has formed integrally therewith a socalled stop disc I69. A radial flange IN is formed in the lefthand end of the sleeve I68 and adapted to engage the right hand side of this flange are two diametrically opposite pins I12 The upper end of the yoke I13 is pivoted at I14 in a rightwardly extending arm of a member I16 attached by means of a screw I11 to the shaft I64 for rotation therewith. A spring I15 anchored in the member I16 and attached to the yoke I13 tends to pivot the yoke in a clockwise direction and keeps the pins I12 against the flange I1I. The lower end of the yoke I13, as shown in Fig. 9, is pivotally connected to theright hand .end of a link I18,.the left hand end of which is pivotally and adjustably connected adjacent the center of a lever I19. The lever I19 is pivotally mounted at its lower end on a leftwardly extending arm of the memthe spring drums I59 and I6I and tend towind up' about the spring drums due to the action of the springs contained therein.

As the crank arm I49 of the reversingmechanism rotates, the link I5I attached thereto causes the lever I54 to pivot back and forth, and it through the link I51 turns the spring drum I59 a predetermined amount in one direction and then an equal amount in the opposite direction.

. As the spring drum I59 is turned in one direction scanning head 14 will move to the right due to the as,' for example,.a counterclockwise direction, the

action-of the tension on the flexible band 93. The rotation of the spring drum I59 in the opposite direction causes its flexible band 92' to wind up about the circumference thereof to move the scanning head 14 to the left. The diameter of the spring drums, and especially the spring drum I59, such that approximately 120 ro ation her I16, which arm is diametrically opposite to the rightwardly extending arm thereof to which the upper end'of the yoke I13 is pivotally attached. The upper end of-thelever I19 is U- shaped and carries pins I8I which are located in a circular groove I82 in the right hand end of a cam member'I83. v

The cam member I83 is loosely mounted on the shaft I64 and is axially movable thereon in a manner hereinafter described. The cam member carries a. pin I84 which engages a helical groove I86 formed in the shaft I84 so that axial movement of the cam member along the shaft produces relative rotation between the two elements. The lead of the groove I86 is not the same as the lead of the threaded portion I61 of the shaft I64 for reasons that will be apparent. Formed integrally with the cam member I83 adjacent the left hand end is a disc I81 with diametrically opposite notches I88 in theperiphery thereof which-engage pins I89. The pins I89 ex-' tend axially from the right hand side of a disc I9I looselymounted on the left hand end of the shaft I64 and rotatable independently thereof. The pin shaped end of a screwl92 in the disc I9I engages a circular groove I 93 in the shaft I64 to prevent axial movement of thedisc I!" on the hand end thereof by screws such as I94 is the hereinbeforementioned crank arm I49, which has attached thereto the link I I.

As shown more clearly in Fig. 10, the stop disc I 69 has extending from the periphery thereof two diametrically opposite stop surfaces or projections I 95 and I96. In operative relation with the stop surfaces I95 and I96 is a T-shaped stop member I91 which is pivotally mounted on a pin I98 in the upper end of a lever, I99 pivotally mounted on a fixed pivot 20I. A spring 202 normally biases the stop member I91 to a stop disc stopping positionor in the path of the stop surfaces or projections I95 and I 96, as limited by a stop pin 203.

Extending from the lever I99 is a pin 204 which is engaged by the upper bifurcated end of a lever 206 secured at its lower end to a rock shaft 201 supported in brackets 208. Also secured to the rock shaft 201 is a. leftwardly extending arm 209 which, as best shown in Fig. 11, has a slot 2I2 in the left hand end thereof which engages a pin in the lower end of a rod 2I3. The rod 2I3 is guided for vertical movement in a portion 2M of the bracket member and has at its upper end a roller cam follower 2I6 engageable with the central surface of the cam member I83. roundingthe rod 2 I 3 tends to elevate the said rod to keep the cam follower 2 I6 in engagement with the periphery of the cam member I83. As shown in Fig. 11, the cam member I83 has two diametrically opposed notches or recesses 2I8 therein so that, as the same rotates, the rod 2 a downward direction twice for each complete revolution of the cam member I83.

In addition to the making of the stop member I91, Fig. 10, about the pivot I98 due to the operation of the lever I48, as hereinafter described.

the stop member moves back and forth in the direction of its length twice for each revolution of the cam member I83 through the instrumentalities of the above-described elements including the notches in the cam member I83, the rod 2I1, arm 209, lever 206 and lever I99. Thus, the stop projections I95 and I96 on the stop disc I 69 are engageable with the stop member I91 at a point variable distances ahead of the normal zero position shown in Fig. 10. In accordance with the proportions of the various elements, the stop projections I95 and I96 may engage the stop member I 91 at any point between the normal stop position shown by the full outline thereof in Fig. 10 and thedot-dashed position shown.

The correcting mechanism or the differential A sprin 2I1 sur-,

I3 is moved inreversing mechanism in the box I 66, Fig. 7, is so designed that when associated with a receiving instrument for example, and the shaft I 64 in exact synchronism with the driving shaft on a transmitting mechanism and/or the clock control elements, there is no functional or correcting operation of the elements comprising the differential reversing mechanism, as will be evident. The cam surfaces or notches 2I8 in the cam member I63 and the operating element for the stop member I91 are so arranged that the above-described lateral movement of the stop member from left to right and right to left is at the same speed as the peripheral speed of the stop projections I95 and I96 when rotating with the shaft I64. If the receiver is in exact synchronism with the transmitter or the synchronizing-mechanism, member I91 is pivot point pivoted by the lever I46 about the I98 just as the stop projection I95 rothe stop tates into its so-called zero position, as shown in Fig. 10. At the same time a notch 2I8 in the cam member I83 begins to move the stop member I91 laterally toward the left. The stop member I91 reaches the position shown by the dot-dashed outline thereof after approximately 30 rotation of the cam member I83 from its zero position and remains in this position for the time being. If it is assumed that it requires 30 rotation of the cam member to move the stop member to some such position as shown by the dot-dashed outline thereof in Fig. 10, then it will require 150 rotation of the stop disc I 69 from its zero position before the stop projection I96 rotates to a position where it is engageable with the end of the stop member I91.

Just as the stop projection I96 reaches the left hand end of the stop member I 91, the other notch 2I8 of the cam member I83 is operative to effect movement of the stop member to the right. As the notch 2 I8 is designed to produce lateral movement of the stop member toward the right at a speed substantially equal to the peripheral speed of the stop projections I 95 and I96, the stop memher will have no effect in reducing the speed of rotation of the stop disc I 69. Accordingly, the stop projection I96 and the stop member I91 will move to the right together with no functional engagement between the two. With the assumed condition of exact synchronism between the receiving and transmitting instrument, the lever I48-will pivot the stop member I91 about the pivot I96 just as the stop projection I96 reaches the position occupied by the stop member I95 in Fig. 10, and there will be no stopping or reduction-in speed of the stop disc I 69 during the first half revolution thereof. If the speed of the shaft I64 remains in synchronism with the transmitting mechanism, there will be no stopping or reduction in speed of the stop disc I69 during the .second half revolution thereof or at theend of first half revolution. Thus, as long as the shaft I64 remains in synchronism with the transmitting mechanism, there is no stopping or slowing down of the stop disc I69 once it is initiated into rotation until the completion of the scanning of a subject matter sheet.- For the above-described operation there is no functional operation of the correcting mechanism, and obviously the scanning heads of the transmitting and receiving mechanisms are in exact synchronism with each other and both scan respective elemental areas of the subject matter spectively. With such tical line, for instance, on the subject matter would be produced as a vertical line on the recording blank, and there will be no drift or sloping of the reproduced line on the recording blank. In addition, such a mechanism as described. wherein the line feedin -of the subject matter and recording blank is effected during non-scanning operation of the mechanism, all horizontal lines, for example, are reproduced strictly horizontal on the recording blank. Furthermore, it will be obvious that lines which are perpendicular to each other on the subject matter, such as vertical and horizontal lines, are produced exactly perpendicular to each other on the recording blank. If the scanning strokes of the transmitting and receiving machines are equal and the and recording blank, re-

line feeding mechanisms adapted to advance the an arrangement any ver- 4 before the stop member I91 same amount on each operation, the recording blank will be an exact reproduction in all dimensions of the subject matter.

The operation of the differential mechanism is considerably difierent from that described above when there is a speed difference between the transmitting and receiving mechanisms. The manner of operation of the reversing mechanism will now be described when, speed of rotation of the the speed of rotation of the shaft employed to operate the transmitting mechanism. It will be assumed for the following description that the shaft I64, which is rotating faster than the similar shaft On the transmitting mechanism where the synchronizing impulses originate, ,is at constant speed.

In Figs. 13 to 18 there is diagrammatically shown the operation of various elements of the correcting mechanism, and in these figures like reference numerals refer to like elements shown in Figs. 9 to 12. The stop disc I69 is shown in its zero position in Fig. 13, and the stop member I91 by the full outline thereof in the position it will assume after it has been pivoted by the escapement mechanism including the lever I48. After 150 rotation of the stop disc I69 from its zero position with the proportions of the elements as shown, the stop projection I96 reaches the position shown in Fig. 14 in operative relation with the end of the stop member I91 which has been moved to the left. Thereupon or during the next 30 rotation of the stop disc I69, the stop projection I96 rotates to the position shown in Fig. 15, while the left hand'end of the stop member I91 moves from its left hand position into the position shown in Fig. 15. As previously described, the notches 2I8 in the cam member I83 effect movement of the stop member I91 to the right at a speed substantially equal to the peripheral speed of a stop projection such as I96, and accordingly there is no operative engagement between the stop projection I96 and the end of the stop member I91 during the for example, theshaft I64 is faster than reach the position shown in Fig. 15 after 169 revolution thereof and for obvious reasons the correcting mechanism operates at that time in such a manner thatthe amount of correction applied to the disc is proportional to the amount that the stop disc was fast in the first half cycle. With this arrangement the stop disc will complete a revolution and reach its zero position in exact synchronism with the synchronizing mechanism, it being assumed that the speed of the shaft I64 remains substantially constant for one revolution or that the speed variation is such as to be of no consequence.

As the stop disc in Fig. 15, the stop projection I96 will engage the left hand end of the stop member I91 to be stopped thereat. As the shaft I64 continues to rotate, the collar I68, Fig. 9, immediately begins to thread along the threaded portion I61 of the shaft I64. Preferably the threaded portion I61 is multiple threaded and the movement of the collar I68 axially of the shaft I64 permits the spring I15 through the yoke I13, link I18 and lever I19 to slide the cam member I63 in a leftward direction along the axis of the shaft. The leftward movement of the cam member I83 produces rotation said rightward movement. If it is assumed that t the rotation of the stop disc I69 from the position shown in Fig. 13 to the position shown in Fig.

15 occurred while the corresponding element-on the transmitting mechanism rotated but 110, then the receiving stop disc I69 at this time would be 1 ahead of the transmitting stop disc. Accord-.

ingly, the stop disc I69 on the receiving mechanism should be corrected while the transmitting disc rotates 1 and, in addition, should be operated upon to effect a correction for the next or second half revolution of the stop disc of the transmitting mechanism. Correction is effected by retating the stop disc I69 on the receiving mechanism in a reverse direction an amount proportional'to the speed diifere'nce between the two rotating elements or in proportion to the amount the receiving stop disc was ahead of the stop disc on the transmitting mechanism in the first half revolution of the stop disc of the transmitting mechanism. Thus the stop disc I69 on the receiving mechanism will have to, in its second half cycle of operation, rotate 180 plus an amount pro-'- portional to the speed difference between the receiving and transmitting mechanisms.

With the-shaft I64, for example, on'the receiv-- ing mechanism rotating fast or at such a rate that it completes a revolution before the operation of v the synchronizing mechanism, the stop disc I69 will be in the position such as that shown in Fig.

has been pivoted about the pivot point I98. The stop disc I69 will 76 rotate the thereof relative to the in a direction ppposite to the direction of rotation of the shaft I64. As the cam member I83 rotates in the reverse direction, the mechanism comprising the rod 2I3, arms 269 and 266, and lever I99 moves the pivot point I98 for the stop member I91 to the left as shown in Figs. 10 and 13 to 18. The leftward movement of the stop member I91 rotates the stop disc I69 in a reverse direction relative to the direction of rotation of the shaft I64 so as to produce more axial movement thereof relative to the shaft which in turn through the described linkage produces further axial movement of the cam member I83. The various elements above mentioned are so designed and arranged that the leftward movement of the stop member begins substantially instantaneously with the stopping of the stop disc I69 in the position shown in Fig. 15 or its position after 180 rotation. The elements are also so arranged that the rate of rotation of the stop disc I69 in a reverse direction is exactly the same as the rate of rotation of the shaft I64 in the opposite direction.

The rotation of the stop disc I69 in a reverse direction will continue until the stop member I91 .is operated so as to pivot about the pivot point I96 in response to the synchronizing mechanism by some means such as the operating lever I48. When the stop member I91 is thus operated, the stop disc I69 and the cam member I83 will rotate with the shaft I 64,'and assuming the speed of the shaft I64 remains constant, the stop disc will reach its zero position in exact synchronism with the tripping mechanism or just as the stop mem ber I81 is operating the next time. The spring I15 tending to move the sleeve I68, Fig. 9, to the left insures thatthe sleeve will rotate with the shaft I64 when not stopped by the engagement of a stop projection I95 or I96 with the stop member I91.

Let it be ass'un'ed, for example, that'the movement of the stop member I91 to the left before being operated by the lever I48 was such as to stop disc I69 in a reverse direction,

I69 reaches the position shown shaft I64 by means of the j that asthe cam member 186 moves to the'le'ft, the same will be caused to rotate disc I69 is in its zero the stop disc is merely chosen to illustrate the principles of operation of the correcting mechanism and actually only a small fraction of such an amount would normally be required. However, the correcting mechanism could operate in such amounts or more if required. If the stop member I91 operates when the stop disc I69 is in some position such as shown in Figs. 16 and 17, then the cam follower 2 I 6 will be in some position other than in the bottom of the notch 2I8 in the cam member I83. Therefore, as the cam member I83 resumes its rotation with the shaft I64, the stop member I9! while still in a releasing position will move to the right the same distance it moved to the left to correct the rotation of the stop disc and then will move to the left to its extreme left hand position such as shown in Figz18. When the stop projection I95 reaches the stop member I91; then it will move to the right and as the stop projection I95 reaches its zero position, the stop member will be operated in the manner hereinbefore described without retarding the rotation of the stop disc at this time. The amount of correction applied to the stop disc I69 or the amount it is rotated in a reverse direction is such that it will complete a revolution and be in its'zero position at exactly the time of the operation of the synchronizing mechanism or at the time the member I48 is operated to pivot the stop Since the stop disc I69, the cam member I83 and the crank arm, I49 all rotate together, the amount of correction applied ried through to the crank arm I49. The elements operated by crank arm I 49 are so arranged that they are in one extreme position when the stop position and in their other extreme position when the stop disc has rotated the associated instrument will be in one extreme position when the stop disc I69 is in its zero poscanning or non-recording interval. In addition the correction to the'crank arm I49 is applied when it is in dead center position relative to the elements operated thereby and it may be moved or corrected a considerable amount before havon the scanning head.

recting mechanism it was assumed that the synchronizing impulses originated at the transmitting mechanism which was operating without correction being applied thereto or was operating at such-a speed that it'completed, a half revolution in exact synchronism with the operation 01' the synchronizing mechanism.- The correction applied to the receiving mechanism was such that it completed a complete revolution n exactly the length of time required for the transmitting mechmember IS! a second time.

to the stop disc I69 is car-' Thus, the scanning head ofasoaroa anism to complete a revolution. Thus, the two mechanisms start a cycle of operation or a cycle in which while the transmitting mechanism is scanning an elementary area on the subject matter, the respect to the speed cording mechanism is scanning a representative area on the recording blank, and this is true during both the forward and backward movement of the scanning heads.

Should both the transmitting and receiving mechanisms be going faster than the synchronizing mechanisms, they will both be corrected in amounts proportional to the amount they are faster than the synchronizing mechanism in the manner described above. Thus, regardless of the respective speeds, the scanning heads of both machines will start their forward strokes'and finish their backward strokes together.

In the above description the speed of the driving means for the receiver, while being faster than the speed of the driving means for the transmitter, was constant. For this condition the amount of correction applied after one-half revolution of the stop disc I69 in the receiving instrument, Fig. 9, was such that it completed the next half revolution in exact synchronism withthe transmitting instrument, it being assumed that the transmitting instru-- ment was in exactsynchronism with the synchronizing impulse transmitting means or that the synchronizing mechanism was operated in conjunction with the transmitting instrument. The diflerential mechanism will function, however, if the speed of th driving means varies with reof the synchronizing impulse transmitting means or with respect to the driving means for the instrument where the synchronizing signals originate. If, for example, the speed of the stop disc I69'during the second half of a revolution thereof is faster than the speed of ro- In the above described operation of the cor- 5 5 her tans operated,

the first and second th above condition tation during the first half revolution, the stop disc will reach its zero position, such as shown in Fig. 13, prior to the releasing operation of the stop member I91. The stop member I91, as hereinbefore described, will immediately begin to move to the left to correct the stop disc an amount proportional to the half revolutions thereof. For the amount of correction applied to the stop disc I69 after a complete revolution thereof, or with the disc I69 in its zero position, will not correct for the entire speed difference the driving means of the transmitting and receiving instruments, or the speed difierence between the shaft I64 and the synchronizing impulse transmitting means, but for the speed difference between the first and second half revolution of the stop disc I69. noted when the speed of the driving means is increasing relative to the synchronizing impulse transmitting means at its zero and one-half revolution positions. The correction to the disc I66 will continue to be applied in the same continues to increase in speed relative to the synchronizing impulses and in its 'one-hali' revolution position because of the speed difference between the synchronizing impulses and the driving means of the'disc I69. If th disc I69 is rotating faster than the synchronizing mechanism and b gins to lose speed relative thereto, the stop projection I will not quite reach its zero position when the stop memand accordingly the stop disc it was assumed that i,

difference in speed between Thus, the stop disc I 69 would be corits zero position as will reach its zeroposition a' little late or by an amount proportional to the decrease in speed between the first and second half revolutions thereof. Accordingly, it will take it a slightly longer interval for the disc I69 to reach its next half revolution position, and the correction ordinarily applied at this point, provided the speed of the disc is still faster than the synchronizing impulses, will not be so much as it would be if the speed had remained constant. This decrease in the amount of correction applied at the half revolution point accounts for the decrease in speed of the disc I69, and the decrease in speed will not have an accumulative effect on the position of the stop disc I69 relative to the time of transmission of the synchronizing impulse. Thus, as long as the speed of the stop disc I69 remains faster than the synchronizing impulses, it may vary in either direction, and th correcting mechanism will operate to effect a correction in the position of the stop disc relative to the synchronizing impulses.

The above correction prevails on the receiving instrument whether the synchronizing impulses originate with the transmitting instrument or from a separate control point. Where the synchronizing signals originate from a synchronizing impulse transmitting means separate from the transmitting and receiving instruments, they both will be corrected in the above-described manner when the speeds thereof are different from that of the synchronizing mechanism or when the speeds are varying relative to the synchronizing mechanism. When the synchronizing impulses originate independently of either the transmitting or receiving instruments, the speed of the driving means of one instrument may be increasing while the speed of the driving means of the other instrument is decreasing, and appropriate corrections will be applied to their respective stop discs such as I69.

Mention has been made hereinbefore in connection with the description of the various elements of the invention of synchronizing impulses which are employed to maintain proper synchronism between the transmitting and receivinginstruments of a facsimile system as disclosed herein. As will be apparent hereinafter, these synchronizing impulses may originate at the transmitter, the receiving, orat a point independent of both the transmitter and receiver. control circuits included in the present invention will now be given as they are arranged when the synchronizing impulses originate in conjunction with the operation of the transmitting mechanism. Referring to Fig. 1, there are shown the control elements of a transmitting instrument and those of a receiving instrument connected by the line The description of the r conductor 83. The escapement yoke 48 on the transmitting instrument, as shown, has associated therewith a set of contacts 22I which are adapted to be closed when the escapement yoke oscillates into its left hand position and to be open with the yoke in any other position. One of the terminals of the contacts 22I is connected to the movable arm'222 of a manually .operable switch 223, and the other terminal of the contacts is connected by a conductor 224 through the coil of a three-position polar relay 226 tothe amplifier 82. The relay 226 is of the type that on the passage of current of one polarity therethrough the associated tongue 22! is operated to contact one stop, and with the passage of current of opposite polarity therethrough, the tongue is operated to contact the other stop, and with thepassage of no current through the relay the tongue 221 assumes a central position in contact with neither of its associated stops. The left hand stop of the tongue 221 of relay 226, to which stop the tongue is moved on the passage of negative current through the relay, is connected through the coil of a relay 228 to ground. The relay 228 has two tongues connected to positive potential, and the make stop of the inner tongue is connected through the coil of the clutch control magnet II2 to ground, while the make stop of the outer tongue of relay 228 is connected through the coil of magnet 12 to ground. The movable arm 222 of the switch 223 has two associated stops, the left hand one of which is connected to negative potential and the right hand one to positive potential. With the movable arm 222 on its right hand stop a positive impulse will be transmitted therefrom through the contacts 22I over conductor 224 through the coil of relay 226, the amplifier 82, to the line circuit 83, each closed.

The grounded relay 229 connected to the amplifier 84 Y operation to the relay 226 at the transmitting station and responds to control impulses transmitted over the line circuit 83. The tongue 23I of relay 229 contacts its right hand stop on the passage of negative potential through the winding and its left hand stop onthe passage of positive potential through the winding. When there is no current through the winding of the relay 229, the tongue 23I assumes a central position in contact with neither of its stops. The tongue 23I of relay 229 is connected to positive potential, and its associated left hand stop is connected to the make stop of the outer tongue of a relay 232 in parallel with thewinding of the magnet I2 to ground; The right hand stop of the tongue 23I of relay 229 is connected through the coil of relay 232 to ground. The tongues of relay 232 are connected to positiv potential, and the-make stop of the inner tongue is connected through the coil of a I clutch control magnet II2 to ground.

Let it be assumed that the arm 222 of the switch 223 is on its left hand stop and that the contacts 22I are closed by the yoke 48 being in its left hand position. The yoke -48 is held in this position by means hereinafter described. Accordingly, negative potential from the left hand stop of switch 223 will be applied through the contacts 22I and through the

relays

226 and 229 to ground.

As hereinbefore described, negative potential'operates the tongues of

relays

226 and 229 to their left and right hand stops, respectively. With the tongue 22! of relay 226 on its left hand stop, relay 228 will b energized, causing its tongues to complete circuits through magnets H2 and 12 to energize the same. The energization of the clutch control magnet II2 operates the clutch III, Fig. 2, to disconnect the drive wheel IIlI from the motor M. Theenergization of magnet 12 operates the armature lever 68 to force th projection 61 into the notch in the flywheel 53. This holds the flywheel 53 and escapement yoke 48 at rest in a non-operating position, and in this position the contacts 22I are held closed. In addition to disconnecting the drive wheel IllI from the motor M,

' the operation of the magnetic clutch III preferably prevents further rotation of the drive wheel. With the tongue 23I of relay 229 at the receiving station on its right hand contact, relay 232.

time the contacts 22I are at the'receiving station is similar contacts its right hand periodic energization of the magnet 12 engages the flywheel doctor 83 the associated escapement yoke 48 to stop in its non-operating position, while the energization of the clutch control magnet H2 disengages the drive motor from the associated drive wheel at the receiving instrument in a similar manner, as the energization of magnet H2 at the transmitting station controls the clutch HI thereat. The instruments at both the transmitting and receiving stations are thus held in non-operating conditions with the respective elements thereof in the same relative positions. To initiate the operation of the two machines to scan a subject matter sheet.

and reproduce a facsimile thereof at the receiving instrument, thetables and scanning heads, if not already in a starting position, may be so placed and the switch 221i operated to place its movable arm in contact with its right hand stop. This operation impresses positive potential on the windings of

relays

226 and 229, whereupon the tongues thereof move to their right and left hand stops, respectively. As tongue 22'! of relay 226 stop, the circuit through relay 228 is interrupted, whereupon the tongues thereof open the circuit to the clutch control mag net H2 and the magnet 12. Th deenergization of the clutch control magnet H2 renders the associated clutch l l I, Fig. 2, operative to connect the motor M with the drive wheel ii, and the deenergization of magnet 72 releases the flywheel 53 to permit the escapement yoke 48 to oscillate. The escapement yoke 48 will continue to oscillate as timed by the flywheel 53, and at the end of each complete oscillation or as it moves into its left hand position, the contacts 22I will be closed momentarily to reapply positive potential over the line circuit 83, Fig. 1, to the relay 229 at the receiving station.

The movement of the tongue 23l of relay 229 from its right hand stop opens the circuit to relay 232, which in turn opens the circuits completed on the energization thereof to magnets H2 and 12'. Preferably, the relay 232 does not release until after the tongue of relay 229 has reached and left its left hand stop. Accordingly, magnets 12' and H2 The deenergization of the clutch control magnet H2 connects the drive wheel such as Hll at the receiver with the motor M and. initiates scanning movement of the associated scanning head containing the recording stylus 81. tion of magnet 12' releases the flywheel 53 at the receiving instrument and permits the escapement yoke to oscillate and shift the drive wheel illl from engagement with one wheel such as 38 to the other such as 99. The following positive impulses which are transmitted over the line circuit 83 each time the escapement yoke,48 at the transmitting station closes contacts 22l tariiy energize the relay 229 at the receiving station, causing its tongu 23! to periodically engage its left hand stop. As the tongue 23l engages the left hand stop, a circuit to the magnet 12 is completed to reenergize the same. The

the armature lever 88 so that the projection 61 thereof, as hereinbefore described, should it be in some other than the desired position. The positive synchronizing impulses will continue to be transmitted as long as the arm 222 of the switch 223 remains in its right hand stop. The movement of the arm 222 to its left hand stop causes transmission of negative potential of the line conthe next time the contacts 22! are remain energized until the contacts 7 22i open to transmit a no-current impulse.

The deenergizamomene operates for each complete back and a resistance 238 to a 53 to correct the position closed. This negative potential is eflected, as

hereinbefore described, to operat relays 226 and 223 to move the tongues to their left and right hand stops, respectively, and complete circuits to the clutch control magnets H2 and the magnets 12. This stops further operation of the transmitting and receiving instruments with their respective elements in the same relative position.

If desired, the

amplifiers

82 and 84 could be arranged to delete predetermined of the regular positive synchronizing impulses so that the mag net 12' at the receiving instrument would not be energized each time the contacts 22l were closed. In this manner a synchronizing impulse would be transmitted, for example, on each tenth oscillation of the escapement yoke 48 of the transmitting mechanism, or after any desired number as found necessary.

Another control circuit is shown in Fig. 8 which may be employed in conjunction with the differential correcting mechanism of Fig. 7. If it is assumed that the mechanism shown in Fig. 7 is a receiving instrument, that part of the circuit of Fig. 8 associated directly with the receiving amplifier 84 would be employed to control the same. However, as will be evident hereinafter, mechanisms such as disclosed in Fig. 7 may be employed as either a receiving or transmitting instrument. In Fig. 8 the circuits at the transmittingend are substantially similar to those at the transmitting station in Fig. l and like elements bear similar reference numerals. In Fig. 8 an additional set of contacts 233 is added which are arranged to be closed when the escapement yoke 48 is in its right hand position. One of the springs of the contact set 233 is connected to positive potential and the other in parallel with one of the springs of the contact set 224 is connected over the conductor 224 to the coil of the relay 226. With the arm .222 of switch 223 on its right hand stop, a. positive impulse will be transmitted over the line circuit 83 for each stroke or movement of the escapement yoke 48. Thus and forth oscillation of the escapement yoke two positive impulses are transmitted instead of the one impulse as in the system disclosed in Fig. 1. At the receiving station these positive impulses are eilective on the relay 229, Fig. 8, to cause the tongue 23l thereof to periodically moved from its center open line circuit position and engage its left hand stop. Such operation of relay 229 causes positive potential from its tongue to be periodically applied to the inner tongue of a relay 234. The break stop associated with the inner tongue of relay 234 is conneoted'by a conductor 236 through the left hand winding of a double coil relay 23'! point 239, and thence throu h another resistance 24! to negative potential at 242. The make stop of said inner tongue of relay 2341s connected through the winding of relay 234 and a resistance 243 to the point 239 and over a parallel circuit including a conductor 244, the right hand winding of relay 231 to a make stop thereof. The tongue associated with said make stop of relay 23! is connected through a rectifier 248 to ground. The outer tongue of relay 234 is connected to positive potential and the associated break and make stops are connected over individual circuits through the windings of the left and right hand magnets I43 assoelated with the yoke 48' to ground.

a The right hand stop 'of the tongue 23! of relay 228 in Fig. 8 is connected through the winding oi relay 232 to ground, the associated tongues of ,coil of relay 231 and which have positive potential applied thereto. On the energization of relay 232 a circuit is completed to the associated clutch control magnet. I44 to energize the same and also the left hand magnet I43 associated with the escapement yoke 48.

The energization of the clutch control magnet I44 operates the clutch I45, Fig. '7, to disengage the shaft I64 from the motor M and also prevents further rotation of the shaft. The energization of the left hand magnet I43 moves the escapement yoke 48 to its left hand position and holds the same there. With the magnets I43 and I44 energized, the associated instrument is held in an unoperating condition. This condition prevails when negative potential is applied over the line circuit 83 from theleft hand stop of the switch 223 at the transmitting station.

The positive impulses transmitted from the contacts 22I and 233 as the escapement yoke 48 at the transmitting station oscillates are effective to operate the escapement yoke 48 at the receiving station in a manner hereinafter pointed out. These positive impulses move the tongue 229 from its center open line circuit causing positive im-- of relay position to its left hand stop, pulses to be applied to the inner tongue of relay 234. If relays 234 and 231 are assumed to be in a deenergized condition on. the receipt of such a positive impulse as the first at the inner tongue of relay 234, a circuit will be completed from said tongue through the left hand coil of relay 231, the-resistances 238 and MI at 242. The completion of'the above circuitento negative potential yoke to move to the right.

ergize'sathe left hand coil'of relay 231, causing its tongue-which is connected through the rectifier 246 to" ground to engage its make stop and complete a' circuit from ground through the rectifier 243;- the tongue, make stop and right handcoil of relaylSl cOnduCtor ZM; the coil of relay 234, the resistance243 to-the point239 and thence through resistance 24I to negative-potential at 242. By choosingsuitable values/for thieres istances 238, 24I and 243 in connection with the resistances of the coil of. relay 234 and the left hand coil of relay 231, the potential at thepoint 239 when the above described circuit from negative potential at 242 to positive potential at the tongue 23! of relay 229 is completed will be zero or slightly positive with respect to ground. As

the above circuit includes the rectifier246, no current will flow through the coil of relay 234 so long as the above mentioned condition exists. However, when the tongue 23I of relay 229 leaves its left hand contact in response to the next open line condition, point 239 will become negative with respect to ground, causing current to pass through the rectifier 246, the tongue of relay 231, the right hand coil thereof and-coil of relay 234 to operate the relay 234 and to hold relay 231 operated. The above circuit through the right hand the coil of relay 234 is a locking circuit and maintains the said relay in an energized condition until conditions hereinafter described occur to deenergize the relays. Thus, the first positive impulse for example transmitted over the line circuit 83 causes the relays 234 and 231 to become energized and locked up.

Thus, in response to a positive relay 232 to the left hand magnet I43 of the escapement yoke. With relay 234 deenergized a parallel circuit to the left hand magnet I43 is completed from the inner tongue of relay 232 and make stop thereof. However, the operation of relay deenergization of relay 232 opens the two parallel circuits to the left hand magnet I43. The outer tongue of relay 234 contacting its make stop completes a circuit to the right hand coil I43, energizing the same and causing the escapement escapement yoke 4?) permits the associated ratchet wheel 41' to advance a half a tooth, whereupon operations hereinbefore described are performed.

impulse transmitted over the line circuit 83 following the transmission of negative potential, the escapement yoke 48' at the receiving instrument moves from its normal left hand position into its right, hand position. This movement of the escapement yoke 48 is in timed relation to the first movement of the escapement yoke 48 at the transmitting station, and hence the receiving and transmitting instruments are initiated into operation in phase with one another.

As long as the escapement yoke 48 at the transmitting station is free to oscillate, positive impulses will continue to be transmitted over the line circuit 83, and if it is assumed that the first positive impulse caused relays 234 and 23'! to operate and lock up the next positive impulse will these relays in a manner effect deenergization of hereinafter described. As relay 234 is deener- I43 of the escapement the lefthand magnet capement yoke to move tothe left and permits rotation of the associated ratchet .wheel 41 another half tooth.

With relays 234 and 231 locked up, as hereinbefore described, the next application of a posi- .tive impulse to-the inner tongue of relay 234 establishes a .circuit stop and coil of relay 234, resistance 243 to the point 239, through resistance 24I to negativepotential at 242. This circuit holds the relay 234 energized while at the same time the application of positive potential to the make stop of the inner-tongue of relay 234 is the locking current through the right handcoil of relay'23l, whereupon it releases and breaks the above mentioned locking circuit through the right handcoil of relay 231. The circuit through the coil of relay 234 is maintained until the tongue 23! of relay 229 leaves its left hand stop Whereupon the relay 234 is deenergized and the tongues thereof return to their break stops. means of the relays 234 and 231 connected in the manner described they are effective to causeenergization of first one of the relays I43 and then:

the other in definite timed relation to the receipt of the-positive impulses over the line circuit 83. The alternate energization of the magnets M3 in timed relation to the oscillation of the escapement yoke 43 at maintains the receiving instrument in synchrostruments, and although nism with the transmitting instrument.

Obviously, by arrangements .uch as described .above a single transmitting mechanism could be employed to control. a plurality of receiving inthe synchronizing impulses were described as originating at the transmitting instrument functions of the machines 234 practically simultaneously with the This operation of the through the associated make effective to neutralize Thus, by

the transmitting station which might originate under the above-described circuits could be reversed, or the receiving station could be employed for transmitting and the transmitting station for receiving. Furthermore, both transmitting and receiving stations could function as receiving stations with respect to the synchronizing impulses independently of either. From the preceding paragraphs it can be seen that the present invention provides a novel facsimile system and two modifications of apparatus that may be employed in conjunction with the novel system. The preferred embodiment of the apparatus includes a reversing mechanism or clutch for reversing the direction of movement of the scanning element at the desired time, while the modified embodiment of the apparatus provides a differential clutch r mechanism for correcting a scanning element driving means whenever necessary. Both embodiments of the apparatus function on a time basis whereby the operations of the transmitting and recording machines occcur. in a timed relationship. The differential clutch operates in such a manner as to retard the back stroke of the faster scanning element for an interval of time equal to twice the interval that the faster scanning element com- Dleted its forward stroke ahead of the corresponding stroke on the other machine. For instance, if, as explained, the seaming element of a recorder driven through'a differential mechanism reaches the end of its forward stroke before the scanning element on the transmitter reaches the end of its corresponding forward stroke, the differential mechanism of the recorder operates in a reverse direction until the transmitter seaming element reaches the end of its forward stroke. At the beginning-of the return stroke of theiransmitter scanning element the differential mechanism of the recorder resumes its forward direction, and the scanning element driven thereby its back stroke at the same ascavoe trol means, and means including said control means for reversing the direction of movement of said scanning member following the movement thereof in either direction in said path for predetermined lengths of time. I

3. In a facsimile system, a transmitting machine, a recording machine controlled thereby, scanning and recording elements respectively inof said'members back and forth through the same respective paths of movement, means for initiat- 'ingthe movement of said members in one direction in respective paths in'timed relation, and means for reversing the direction of movement of said membersin said paths in the same timed relation regardless of the length of travel of said time that the transmitter scanning element reaches the end of its eflect of stopping the driving means at dead recorder scanning element center for an interval equal to twice the length of time it completed its forward stroke ahead of the forward stroke of the transmitter, and in this manner each line scanning stroke of the transmitter scanning element is justifiedwith each corresponding line scanning stroke of the recorder scanning element. The justification of a scanning line in the transmittingapparatus included in the preferred embodiment of the invention with a corresponding line at the associated recording apparatus is accom- Plished as described by reversing the direction of the scamiing elements in a timed relation.

It will be obvious, of course, that various modifications other than those shown, described and sug ested herein may be made without departing from the spirit or essential attributes of the invention, and it is desired, therefore, that only such limitations be placed thereon as are imposed by the prior art or are specifically set forth in the appended claims.

What'is claimed is: 1. In a facsimile machine, a scanning element, means for moving said scanning element in opposite directions through a predetermined path,

and means for reversing the direction of movement of said scanning element at any point in said predetermined path.

2. In a facsimile machine, a scanning member, means for moving said scanning member in opposite directions through the same path, a conback stroke. This has the 1 members in said paths. I

5. In a facsimile system, a transmitting instrument and a receiving instrument controlled thereby, scanning elements included insaid instruments with associated rotatable driving means therefor, means for transmitting synchronizing signals concomitantly with each revolution of said transmitting scanning element driving means, means at said receiving instrument controlled by said synchronizinglmpulses and effective after a predetermined part of a revolution of said receiving instrument driving means to retard the same in amounts proportional to the amount it is faster than the driving means for said transmitting instrument whereby both or said rotatable driving means complete revolutions in the same length of time.

6. In a facsimile machine, a scanning member movable in opposite directions in the same path as the scanning progresses and a control means for reversing the direction of movement of said member at predetermined intervals.

7. In a facsimile machine, a scanning member movable to and fro in opposite directions in the same path as the scanning progresses, and means dependent upon the length of timeof movement of said member in one direction to terminate movement'thereof in said direction and initiate movement in the pposite direction.

8. In a facsimile system, a transmitting machine and 'g receiving machine controlled thereby, scanningelements included in said machines, driving means to move said elements in back and forth strokes along scanning lines, and synchronizing means associated with said machines to control the application of said driving means to said elements to move the same in said back and forth strokes in such a manner that the lengths of each corresponding scanning stroke of said machines is lustified.

9. In a facsimile system, a transmitting machine and a receiving machine controlled thereby, scanning elements included in said machines. a rotatable scanning element driving means in each of said machines for moving said elements in back and forth strokes along scanning lines during each revolution of said driving means, and means for neutralizing one of said driving means