US2125991A - Automatic television synchronizing apparatus - Google Patents

Description

A. J. CAWLEY AUTOMATIC TELEVISION'SYNCHRONIZING APPARATUS 3 Sheets-Sheet 1 Filed June 18, 1932 Aug. 9, 1938. A. J. CAWLEY AUTOMATIC TELEVISION SYNCHRONIZING APPARATUS Filed June 18, 1952 s Shgets-Sfieet 2 INVENTQR.

Aug. 9, 1938. A. J. CAWLEY ,9 v AUTOMATIC TELEVISION SYNCHRONIZING APPARATUS Fild June 18,- 1932' a Sheets-Sheet s The production of synchronism by means of the about acceleration of the speed and the other seg- 2o lighttraversing those segments into proper phoconstitutes an excellent synchronisrn indicator. 4O

56 electromagnetic, mechanical means for adjusting nism.

Patented Aug'.9,1938" 1 2,125,991

, AUTOMATIC TELEVISION SYNCHRONI ZING APPARATUS Aloysius J. Cawley, Pittston, Pa.

Application June 18; 1932, Serial No. 617,95'l 25 Claims. '(ci. 178-69.5)

This application is a. continuation in part apa friction drive, a rheostat or other electrical plication of my application for Television; Serial motor controlling means. No. 455,127, filed May 23, 1930, which is now U. S. Although the synchronizing .apparatus is shown Patent No. 2,026,610 of January 7, 1936 and of as being used with a television broadcasting sys 4 UNITED STATES] PATENT OFFICE 5 Serial No. 468,117, filed July 15, 1930 for .Teletern wherein the broadcast is periodically inter- 5 vision, both of which disclose synchronizing aprupted, thus rendering a separate wave channel paratus. unnecessary, the invention includes any of the The invention relates in general to the trans-, synch means in a S p W v cha ne mission of images by wire or wireless methods without any interruption of the television broadfrom one place to another. More particularly, cast. 10

it is concerned with the maintenance'of a rotat- A rotatable scanning element provided with a ing element at a receiving station in absolute pair of electrical contact strips or segments havsynchronism with a rotating element at a transing an insulated seg e betw the and a mitting station without any attention on the part ntact b us norma y n Co tact w t this inof the operator. Some of the objects of the invensulated segment it the disk isin sy chron s W th 15 tion are as follows, a similar disk at the transmitting station. The

The maintenance of synchronism without the c nt egments ctin to actuate an electrouse of a separate wave channelor separate conet app u for alte e Speed O the ducting circuit. rotatable element, one of the segments bringing regular television broadcast current by means of ment b g a u retardation of e Speed Of a periodic interruption in the latter. the rotatable element. The electromagnetic ap- A television scanning element provided with Daratus y also u eo y o s y p transparent segments bearing symbols or colors, ate a rheostat controlling the speed of the motor. or both, or other identification means, which in- A relay switch at the receiving station which 25 dicate the relative position of the rotating eleacts to maintain the synchronizing circuit open ment at the receiving station with relation to a fo t e e te P Of the Period of rotation of stationary light source which is illuminated at the scanning disk, the synchronizing circuit bethe time of interruption of the broadcast televins closed a brief int val r sp din o sion current at the transmitting station. the period of interruption of the television broad- 2.0

The maintenance of synchronism by means ofcast at the transmitting station. photoelectric cells and circuits in cooperation A stationary stroboscopic light source at the with transparent segments carried on a rotating receiving station which illuminates the rotating scanning element, the photoelectric cells being element for a very short period corresponding to in cooperation with means for controlling the 'the period of interruption of the broadcast at the 35 speed of the rotating element. transmitting station. This gives the illusion of A rotatable scanning element bearing transthe rotating element standing still in the posiparent segments and reflecting means in cooption it occupies relative to the disk at the transerative relation to said segments to reflect'the mitting station as regards synchronism; This toelectric cells. A contact strip placed onthe rotatable ele- An automatically controlled friction drive in m at h receiving station at a p n on th rocooperative relation with a rotatable scanning a ab e clement or'diS h h will be directly 9- element. consisting of a friction wheel in adjust- P051158 two Statlonary Contact brushes when the able Contact or engagement with the Scanning rotatable element is insynchronism, the brushes element, and electromagnetic mechanical means being if t if g g g jgzg ,gg z iffgg: for adjusting the position of this friction drive gage; gg g f synchronislh in d1 6 atbr with relation to the rotatable element, in order to vary the speed of the rotatable element and Also light sources or electromagnetic mdmat ing means in cooperative relation with the con- 56 thereby bring it into Synchronism- A mtata-ble tact segments carried upon the rotatable element fi m element pmvided with transparent whereby, as the latter are actuated, either a light merits controlling the operation of photoelectric is flashed or-else a pointer indicates whether the cells, and the latter controlling the operation or r t t b l t 1 ahead of 013 behindsyhchro- An adjustable friction drive provided with a lever controlled by electromagnetic means, the lever also acting to operate a motor controlling rheostat or other controller.

,A centrifugal speed controlling means acting in conjunction with a friction speed drive to further regulate the speed of the rotatable scanning element.

A switch operated by the centrifugal speed control means whereby the synchronizing current is not turned on until the speed of the rotatable element has reached a speed approximating synchronism.

An electrical switch operated by the centrifugal speed governor controls the speed of the motor either by means of a rheostat or other motor speed controlling means.

A rotatable scanning element consisting of a flat disk to which lenses or prisms, or the like are cemented, the disk being coated with opaque paint or the like. Such a disk is very easily and cheaply manufactured as compared to an ordinnary scanning disk employing lenses, or even those employing holes for scanning purposes.

A driving means consisting of a motor provided with a hollow shaft of irregular cross section, which accommodates a shaft of irregular cross section, the latter being attached to a, centrifugal governor. A variable speed friction drive wheel is carried on inner shaft. The variable speed friction drive and the centrifugal governor thus act jointly to maintain the apparatus in synchronism and at constant speed.

Other advantages and objects of the arrangements will be apparent from a consideraion of the following specification and claims when read in connection with the accompanying drawings wherein the various figures thereof represent in a conventional manner the principles covered by the invention.

Figure l is a front elevational view of a, scanning apparatus which is provided with means'for indicating synchronism consisting of a light mounted on said disk.

Figure 1a is a side elevational view of the ap paratus shown in Figure 1.

Figure-2 is a front elevational view of a scan ning apparatus provided with a photoelectric synchronizing apparatus.

Figure 3 is an elevational view of the interrupting apparatus at the transmitting station, shown in Fig. 2 in part. t

Figure 4 is a side elevational view partly in cross section of the scanning apparatus shown in Figure 2 in part.

Figure 5 is a front elevational view of a scanning apparatus provided with synchronizing means consisting of a variable speed friction drive controlled by photoelectric means. Fig. .50 is a view of the apparatus shown in FiBure 5 with a motor rheostat control added.

Figure 6 is a side elevational view of the apparatus illustrated in Figure 5.

Figure 7 is a front elevational view of a scanning apparatus provided with a variable speed drive in conjunction with electric contact elements carried on a rotatable disk.

Figure 7a is a modification of part of the iristion drive.

Figure 7b is a cross section of a special scanning disk. t

Figure 8 is a front elevational view of a scanning apparatus employing a variable speed friction drive and a centrifugal speed governor.

concentric shafts of the synchronizing apparatus.

Figure 9 is a front elevational view of a moditlcation of Figure 8.

An apparatus for indicating synchronism between a receiving station ands, transmitting station is illustrated in Figure 1. No separate wave channel is required for the attainment of synchronism. At the transmitting station the broadcasted television waves are interrupted during a short portion or period of each revolution of the scanning disk. As in most television systems, a revolution of the disk generally completes a single picture, it necessarily follows that after each image is televised, there is a very short interval during which no broadcast takes place. This does not introduce any more serious difficulty or defect than that already existing in ordinary motion pictures, as there, between images there is a short interval of darkness during which the film is shifted.

The standard Nipkow disk is mounted as shown at l upon shaft 4. The holes or lenses in this disk are shown at L. The neon, or other glow lamp 2 is shown in cooperation with the image area in the usual manner. Collector ring 3 is mounted upon shaft 4 but insulated very carefully from it. Brush b makes contact with this ring, while crush 0 makes contact directly with the shaft 4. The synchronizing lamp g is mounted upon the disk I and is in electrical connection by means of wires 11 and c with the shaft 4 and the collector ring 3. The broadcasted television current, after being amplified, is supplied to the neon lamp 2 by means of the wires A and B. Part of this current 'is shunted to the synchronizing indicating lamp 9 by means of wires 1:. and 0. As before stated, the television broadcast is interrupted for a short interval during. each revolution at the transmitting station.

i Assuming that this interruption is arbitrarily selected as at the extreme lower portion of the orbit of the lamp as indicated by i, then, if the receiving disk is in synchronism with the sending station disk, the scanning lamp y will describe a path of light p which is interrupted at i. If the receiving disk I should be in isochronism with the transmitting disk, thenthe point of interruption in the path of light 9 will be either to the right or to the left of the position shown in Figure i. For instance, if the receiving disk (shown in the figure) is in advanced isochronism, the point of interruption in the path 9 will be anywhere between a and the glow lamp different points during each revolution, no clear distinct interruption will be discernible, and there will be no gap f in the path of light described by the synchronizing lamp 0. The lamp 0, since it flashes only during a small portion of the revolution period 01' the disk I and since the disk makes about twenty revolutions per second, constltutes the equivalent of a stroboscope with the rotating disk I. If the disk I is in absolute synchronism, there will always be a dark area at i,

. and the path 9, consisting of a broken circle will appear stationary. The synchronizing lamp 0 takes a very small amount ofthe television broadcast current. as it is made very small. Figure 8a is a cross sectional view 0! the two Figure 1a is a side elevational view of the appsratus illustrated in Figure 1. The reference characters have the same meaning. The apparatus illustrated and described in connection with the above two figures. discloses merely a synchronism and is illustrated at d. An amplifying apparatus is shown at K, which intensifies the broadcast current as much as possible. Wires E and D conduct the amplified current to the glow lamp 2, which is shown in the usual cooperative relation with the scanning disk l provided with holesor lenses L. A portion of the amplified current is shunted by the wires F and G'to the relay R, which acts to open a circuit including a synchronizing lamp 1, shown in dotted'lines on the opposite side of the disk I. The current at. the

transmitting station is interrupted for a short interval during the revolution of the disk at the transmitting station. This inerruption will take place at a definite, prearranged point of the path of. rotation of the disk, and is indicated in the figures of this application at the extreme lower portion of the circle described by the disk. The relay R is so designed that it will respond readily to a vibration rate of twenty per second. The conventional representation of a relay is shown,

however, the armature of the relay together with its spring or other equivalent is such that it will readily vibrate at the frequency of television image change, which is from ten to twenty per second according to the degree of continuity of image that is desired. When the broadcast is being received, the armature of the relay R is' attracted towards the electromagnet and the circuit composed of the wires H and I, the source of power Pr and the lamp i is opened. However, during the short interval of a revolution that the broadcast is interrupted, the lever of the relay R is released and is attracted by its. spring (not shown) to the right and the above circuit is closed. The lamp i is then illuminated. Disk i is provided withtwo transparent segments and 6. Those transparent segments are separated by a relatively small portion of opaque disk. latter is shown as just covering the lamp 1!. Therefore, when the receiving disk is in synchronism with the sending disk, the lamp 1 is illuminated only when the short opaque space between the two transparent segments is just in front of the lamp, and its light cannot be seen. Synchronism is, therefore, indicated by absolute darkness. If the disks are rotating in admin-- nism and the receiving disk is behind the transmitting disk, then the transparent segment 5 will encroach upon the lamp 1 and be interposed between thelamp and the observer. The resuit is that the light of the lamp will be seen. i

The segment 5 may be colored red, or any other color, and the appearance of this color will indicate that the disk is behind the transmitting disk.

In addition, reference characters, such as numseveral different ways.

This.

. circle.

cylindrical type.

may desire. Transparent segment 6 may be I colored blue and suitable reference characters printed upon it.- The segments may be made much smaller, i. e., only a little larger than the diameter of the shaft 4, if desired. smallness is desirable, as the speed of the brushes in cont t with the collector rings in the modifications to be later described, will thereby be greatly re-- v duced. The segments are shown as increasing in width as the distance from the opaque portion increases. Theobject of this is to increase the amount of light that reaches the photo cells (to be described shortly) the farther the disk is out of synchronism, and therefore to correct the asynchronism as quickly as possible. The segments may increase uniformly in width, instead of in a stepped manner as illustrated. As the lamp I is only flashed on for a short interval of time, and as this interval is always in accordance with the time during which a certain portion of the disk is successively opposite the lamp I during each revolution, at virtually the same point, a strobescopic eifect is produced. Suppose that 45 is opposite the lamp 'l at each revolution, then it will be seen as stationary at that point. The same istrue of any other reference character at any other point on the disk if that particular point is opposite the lamp 1 during a series of successive revolutions. As synchronism is established by proper adjustment,the character 45 would move to the position shown in the illustration from that in front ofv lamp l. Thus the degree of advanced or retarded isochronism is readily determined by this apparatus. The segments b and t need not be of a size equal to approximately a semicircle, as shown, but may be much shorter. For instance, they may be only 45 or 90 degrees in extent.

, Automatic synchronism may be attained in By one method, photocells P and P are arranged to be excited, depending upon whether the disk is in advance or behind that at the transmitting station. A prism r. or a series of such prisms is placed over the windows or transparent segments 5 and 6. That over window 5 is illustrated by dotted lines in Figure 3, which illustrates the fact that the light is reflected downward into the photoelectric cell P. Segment 6 has a prism rb placed over it with its base turned inwards towards the center of the This is illustrated in Figure 4 and shows that the light is reflected upwards into photocell P. The photocells are shown as being of the It is to be noted that the width of the transparent segments 5 and 6 increases towards their opposite'ends. The result is that, the'greater the disk is out of synchronism, the

more light that will be admitted to the photocell and the greater the corrective response rought about by the circuits associated with the cells. Accordingly, the wire T leads to an accelerating means, while the wire S leads to aretarding means. If the disk is behind, cell P is actuated and the accelerating means brought into play, while if the disk is ahead, cell R is actuated and the retarding means brought into play. Wire C is a common return wire for both i circuits, i. e., acceleratingand retarding.

.ent sectlons 5 and 6. The cement used for attaching the disk and the prisms or other optical elements, such as lenses, may be Canada balsam. Lens making, prism making and plate glass makng have all reached the dignity of fine arts. They are almost perfect. The lenses, prisms and plate glass can therefore be made very cheaply and accurately. It is only necessary to cement the various optical elements to the disk. A very desirable' combination is that of a disk made of transparent Bakelite to which cylindrical lenses, or other optical elements are cemented. This gives a disk which is of itself very light, but the peripherally located lenses lend peripheral weight whichwill develop when in motion a desirable centrifugal force which will tend to maintain the disk in uniform motion. The portions of the disk which are unoccupied by lenses, prisms, etc., may be painted by means of dark, opaque paint. Thus the expense of drilling holes in a disk in order to mount the lenses is dispensed with. Another desirable quality of the Bakelite disk is that it is not nearly so fragile'as glass, consequently, a much thinner disk may be used.

Figure 5 illustrates another modification of the invention and also shows a means of correcting asynchronism by means of an electromagnetic arrangement. The amplified television current, whether received by wire or wireless means, is conducted by wires A and B to the neon or other glow lamp 2 and also to the relay R. The scanning disk I is here shown as being provided with transparent segments of different sizes, i. e., they are segments of circles of different diameters in order that each operates a diilerentphotocell without using prisms. Each transparent segment can only be opposite its own specific cell, and can never be opposite the other cell. The

television broadcast is interrupted periodicallycompanies, but it is here shown (according to the position of the disk. at the receiving station, which is illustrated) as taking place when the opaque portion located between the two transparent segments is at its extreme lower position. As before explained, the circuit containing the source of power Pr and the synchronizing glow (or other) lamp I, which are connected by the wires H and I, is broken during the period of interruption of the television broadcast from the central station. If the receiving disk I is in absolute synchronism with the transmitting station disk, then the lamp 1 will be illuminated'only while the opaque portion between the two transparent segments is directly opposite the lamp, and no light will be seen. Two cylindrical photoelectric cells P and P' are placed directly opposite the lamp 1. If the disk I is in synchronism with the disk at the transmitting station, neither cell will receive any light. If the disk I should lag behind the disk at the transmitting station, then transparent segment 5 will be found opposite the lamp I when itis illuminated and the light will enter photoelectric cell P. Depending upon the type of cell (the speed of response of selenium cells-has been greatly increased of late) either current will be permitted to flow, or in the vacuum tube type of cell a. small current of electricity will be generated in the cell and this will be ampli fled by the amplifying or power circuit Pr, and the solenoid I will receive this current and tug at the armature attached to lever l, with the result that the jaw J since the lever is pivoted at 1, will move to the right. The motor M is shown as provided with a square, or rectangular, or other irregular cross section shaft u. The wheel W is slidable laterally on this shaft but cannot rotate upon it. It will be seen that the jaw J moves the wheel W with which it engages, towards the center of the disk I. This means, obviously, that the speed of the disk will be increased. Pr represents any desirable source of power or amplifying means. If the disk I should gain over the speed at the transmitting station of the disk located there, then transparent segment 6 will be opposite the lamp 1 when it is illuminated and its light will reach the photoelectric cell P with the result that solenoid 9 will be actuated and a tug at its armature attached to the lever I will cause the jaw J and wheel W to move to the left towards the periphery of the disk I, resulting in a reduction of the speedof the disk. The flashes of the lamp i take place about twenty times per second or more if the best television reception is to be attained. However, a lower speed may be used. The wheel W is mounted upon shaft u in such manner that it must rotate with the shaft. It is slidable upon the shaft and can therefore be shifted to new positions. The friction wheel W engages with the disk I which is provided with a suitable surface to prevent slippage, such as leather, rubber, etc. The wheel W may be provided with a peripheral ring of adherent material such as leather or rubber as shown more clearly in' Figure 6. If desired, a special friction disk may be attached to disk I. As the transparent segments 5 and 6 are provided with reference characters, such as those described in connection with Fig. 2 above, and since the light is flashed on during a very, very small fraction of a second and repeated about twenty times per second; the particular reference character will be seen opposite the light and will be perfectly legible, as the light is extinguished during the time that this particular character moves around with the revolving disk. The reference character will apparently be standing still due to this stroboscopic effect. It is to be noted that there is a constant adjustment of the position of the wheel W relative to the shaft 11.. Just as soon as there is the slightest deviation from 'synchronism the corresponding photoelectric circuit is actuated and the friction wheel W is shifted to a position to correct this deviation. This operation is carried out in a purely automatic manner. The motor M may be a synchronous motor when the question of synchronism is mostly involved in a correction of isochfronism'or a conversion of isochronism into synchronism. The

motor may be a phonic motor. The motor M may be provided with an independent'speed governing apparatus so that its speed is constant, as

.illustrated in Fig. 5a. However the present disclosure is concerned with means for keeping the scanning disk in cooperative relation with any type of motor in absolute synchronism without any attention whatever on the part of the operato'r. This feature will be described in greater detail in connection with later figures.

Figure 6 is a side elevational view of Figure 5. The television broadcast is received by the wireless apparatus d and amplified by suitable circuits at K and the amplified current led to the neon or other lamp 2 by wires A and B and to the relay R. The relay breaks the circuit containing the amplification or power element P which is connected by the conductors H and I to the synchronizing lamp I. This lamp is therefore, only illuminated during a very small portion of the revolution of the disk I. Disk I is mounted upon the shaft 4; the latter is supported by two strong bearings. The friction wheel W with its peripheral ring of adherent material is shown mounted upon the shaft u of irregular cross section, which is here shown as square. However, a very desirable cross section of a shaft would be a rectangle. Another form would be that of a cross. The motor M rotates the shaft 1!. and the friction wheel W. The latter j engages'with the surface of the disk I, which also may be provided with an adherent surface. The

lever l with its fulcrum is clearly shown with its jaw J engagingthe wheel W. It is to be noted that the lever 2 should be designed to be perfectly balanced so that it will stay in any noeltion in which it is placed. The invention is not limited to this feature of the lever however. The synchronizing lamp I is shown opposite to-the two photocells, one of which is designated P. The accelerating solenoid is shown at 8. The

' photoelectric cells are shown as being of the cylindrical type.

The lever I may, in one modification be that of a rheostat governing the speed of the motor M. This may be used in an arrangement wherein the motor M is directly attached to the shaft 4 upon which the disk I is mounted. Or the arrangement shown in Figure 5a may be used and in which the lower half of the lever l constitutes virtually the arm or crank of a rheostat T or actuates such a rheostatlc'arm or crank. Or it may actuate any type, of motor speed control.

A modification "of the invention which dispenses with the use of photoelectric cells in the synchronizing circuits is illustrated in Figure l. .The television broadcast current is led into the amplifying apparatus K by means of the wires A and B; The amplified image varied current is then supplied to theneon lamp 2 and'the second amplifying apparatus K. The current is then supplied to the relay R. The conductors E and D connect the glow lamp 2 in circuit. The Nipkow disk or its equivalent is shown at l. The

, holes or lensesare shown at L and are arranged in a spiral line in the usual manner. Instead of r .the transparent segments described in connec tion with the previous figures, two contact strips 5a and 6a are attached to the disk I.'. Those strips are shown of varying width, which is shown as increasing progressively from the lower end of the strips to the upper in the figure. The object of this is to provide a greater contact area to the various brushes V and thus to furnish a greater current to the synchronizing circuits in proportion to the degree of asynchronism present. A single wide brush or a plurality of small--- er or narrower brushes may be provided at V. If brushes of highresistance are used, the varying area of contact of 5a and to will cause cprrespondingly varying amounts of electric cur: rent to pass. As described in connection with the previous figures, the broadcast current is periodically interrupted at the transmitting station at a predetermined point of the revolution of the transmitting disk. This isfor the present battery. However, since the disk I is in synchronlsm with that at the transmitting station, the brush V rests upon the nonconductinginterval between the two contact strips 5a and 6a and no current can pass from the battery Y or other source of power. The glow lamp U is connected to wire l which is in turn connected to the relay R so that when the latter closes, the synchronizing circuit, even though no current flows through the contactstrips, still the lamp U will be momentarily illuminated for its stroboscopic effect of illuminating the disk which may have various symbols located upon it indicating its position as regards synchronism. In fact, the position of the contact elements themselves thus serve. The lamp U may be a glow lamp of any desired type, but is not limited thereto. The disk i is supposed to be made of some insulating material, such as Bakelite. However, if it is made of metal it should be covered with a disk of insulating material upon which the contact strips a and 6a are mounted.

Suppose the disk I is lagging behind the transmitting disk, contact strip 5a comes in'contact with the brush V, and the battery or other current passes from Y to the relay switch R'to wire Ill, to brush V to contact strip 5a to wire 8 to collector ring 20, to brush X and by wire to the solenoid 8 which exerts a torque upon the armature of the lever I which is pivoted at f. The

current returns from the solenoid 8 to the battery or other source of power Y. The motor M- is provided with a shaft of irregular cross section, as already explained and has the slidable wheel W mounted upon it. The wheel W. makes frictional contact with the disk l and drives it. When the solenoid 8 attracts the armature attached to the lever I, it causes the clutch J to move the wheel W towards the center of the disk I, with the result that a greater speed is imparted to the latter. If the disk i is gaining on the transmitting disk, then contact strip Ba will engage with brush V and the current will pass from the battery Y to the relay R, to wire Ill, to brush V, to contact strip 6a, to wire t to collector ring. 12, to brush Z,-to solenoid 9 and back to Y. The solenoid causes the lever to be moved to the right with the result that the jaw separate synchronizing current is required with the disclosed apparatus, still the invention covers the use of the apparatus in a separate synchro nizing currentarrangement. The attainment of synchronization by the interruption of the broadcast of the television is an invention over the employment of a separate synchronizing wave channel or separate synchronizing circuit, if the apparatus is used with wires. The invention therefore, covers the use of the apparatus with a separate wave channel or circuit.

' The wheel W may be provided with means for being readily shiftable to a new position by the law or clutch .1. Figure '7a shows the wheel equipped with very delicate flexible strips of metal ,2! which make'contact with the shaft 14. The

holding it more securely in the position on the shaft in which'it is placed, and at the same time flat face of the shaft u may be roughened or pro- 15 vided with fine ridges as shown at 22, which are depressed below the surface of the shaft u in order not to interfere with the movement of the wheel W. The lever I should be well balanced with regard to its fulcrum ,1, just as the arm of a balance, so that it will have a tendency to remain at rest in any position in which it may be placed. A handle his shown for manual adjustment of the position of the wheel W inorder to manually attain synchronism, if desired.

The disk I may be made of plate glass or transparent Bakelite. The lenses La may be of glass and plane-convex and their fiat surfaces cemented to the disk I. The portions of the disk which are unoccupied by any lens or other optical element may be painted with an opaque paint or its equivalent. A transparent Bakelite disk I with glass prisms and lenses is a good construction. The expense of boring holes in the disk to accommodate the lenses or other optical elements is done away with. In manufacturing such a disk, a form is made which consists of a flat board, or the like, having spherical depressions located therein and the depressions arranged in a spiral. The lenses are simply placed in those depressions,

.which they fit snugly and their flat, upturned faces coated with a suitable cement, such as Canada balsam. The disk I is then laid upon this flat surface including the cement covered lens surfaces and left to harden, when it is removed together with the firmly adherent lenses. The cost of manufacture is thus greatly reduced. If such a disk were moulded of glass, for instance in one piece, the lenses (since they are molded) would be unsatisfactory from an optical standpoint. To grind the lenses which have been cast in one solid piece with the disk would be prohibitive and almost mechanically impossible. By the present method, the lenses have been manufactured in accordance with the best principles set down by optical manufacturers, the same is true of the plate glass or the Bakelite disk. The disk andthe optical lenses or other optical elements are then combined by the simple process of placing the lenses in the depressions in the form and simply coating their upturned faces with cement and the disk laid on. All of the expense of laying out the spiral, boring the holes in the disk and fitting the lenses into the holes is dispensed with. Oviously a disk made of Bakelite with cemented lenses could not be moulded in a single piece. This is a very desirable embodiment of the invention. After the disk is formed, the unoccupied portions are coated with opaque paint.

Another modification of the invention is illustrated in Figure 8. The motor is shown at M. It is provided with a hollow shaft ua of square, rectangular or other irregular cross-section. The square or other irregular cross-sectioned shaft u fits into this hollow shaft and is unrotatable relative to the shaft M. It may be readily slid in and out of the hollow shaft ua. The shaft it turns in the journal I! and it is here of a round cross section tolaccommodate the 'journal bearing surface. The shaft is further journalled at I'M. A centrifugal governor I6 of any desired well known type is shown in cooperative relation with the shaft u. As the speed increases, the balls fly out? ward from the shaft in the well known manner.

mg I! in order to permit it to shift or slide through the Journal bearing. The end of the shaft u will project farther and farther to the left beyond the journal I'Ia as the speed'is accelerated. All of the shaft that passes through the governor I6 is rounded. Thus a centrifugally operated speed governor is added to the previously described apparatus. If desired the governor I6 may have attached to it the contact brush 23 which makes contact with the contact point or strip 25 when the motor has been brought up to full standard synchronizing speed. The brush and contact strip are connected to the synchronizing circuits in such manner that contact is not made between Hand 25, and consequently the latter are not energized until full speed has been attained by the motor M and wheel W. The disk I is shown in synchronism with the transmitting disk and at the point it should occupy if it is in synchronism with the transmitting disk when the broadcast is interrupted. The relay R has closed the circuit and the current passes from the battery Y to relay switch R to brush V to contact strip 11, to brush a: to electromagnet I9 by means of wire ISa and back to Y. The armature-indicator I5 is attracted to its position indicating synchronism on its dial (not shown). It will be noted that the contact metal or other conducting strips 541 and 6a are made much smaller than those previously shown. If the disk I is lagging behind the transmitting disk, then the strip 5a is in contact with the brush V during the time thatthe relay R closes the circuit and the current passes through strip to to collector ring w to brush X to electromagnet I 9, which attracts the armature-indicator I5 to the position indicating retarded isochronism. If the disk I is running ahead of the transmitting disk, then contact strip Ila makes contact with brush V, and the current passes from Y to relay switch R, to brush V, to collector ring or contact strip 60, to brush Z, to electromagnet 20.

The latter attracts the armature-indicator I5 to the position indicating advanced isochronism or accelerated asynchronism. The current then passes from 20 to the solenoid 9, which attracts the armature attached to lever l and pulls the latter to the right with a resultant shifting of the wheel W by means of the clutch J towards the periphery of the disk I, and the latter is slowed down. In the former case, where the disk I was running behind the transmitting disk, the current returned from the electromagnet I9 to the solenoid 8 and from thence to the source of power Y. The solenoid 8 attracted the armature attached to lever l to the left, with a consequent shifting of'the wheel W to the right and towards the center of the disk I with a resultant speeding up of the latter. Thus a means is provided for indicating by means of a pointer and dial, the character of asynchronism, lsochronlsm or synchronism that may'exist at any time.

The jaws of the clutch J are turned down In the plane of the paper and two wheels Ja are rotatably supported on small shafts that are attached to the turned down ends. The wheels Ja may be coated with a ring of leather or rubber or other adherent surface. The purpose of those wheels is to eliminate the friction that would otherwise exist between the clutch J and the wheel W.

The synchronism indicator consisting of the elements I5, I0, I9 and 20 may be omitted if desired. It is a very convenient and useful part of the apparatus, however.

.The solenoids 8 and 9 in conjunction with the lever I operate the friction drive W for the pur- 75 pose of maintaining synchronism. However, in

one modification of the invention, the lever I may from a standpoint of momentum. A very important function performed by the governor I6 is to correct the irregularity of speed in an electric motor known as hunting, which is well known and understood to those skilled in the art.

Figure 8a illustrates a cross section of the two shafts tar and u. The hollow-shaft ua is shown as provided with roller bearings m, which fit closely to the inner shaft it. Thus the two shafts are absolutely unrotatable relative to each other, and yet shaft u may be slid in and out of the hollow shaft ua with very little resistance, due to theroller bearings.

In the operation of the apparatus, the solenoids and lever I act to maintain synchronism between the transmitting disk and the'receiving disk I. They are constantly at work correcting all irregularities of synchronism. They cannot, however, correct the speed irregularity known as hunting and it is principally for the correction of this irregularity that the centrifugal governor i6 is provided. It is to be noted that the lever Z shifts the wheel W on the shaft it, while the governor l6 shifts the shaft 11. and wheel W as a single unit.

There is therefore, 'no interference between the operation of those two speed controlling elements.

The brush 23 attached to the centrifugal speed a governor and the contact 25 may be connected in the synchronizing circuit between Y and R as illustrated in Fig. 9, and the latter will thus not be operative until the disk has been brought up to approximately synchronizing speed under control of the centrifugal governor It. The contact '25 is shown as a strip. but it may be a button,

thus making contact for ashorter interval of speed variation. The end of the governor i6 adjacent the bearing Illa is provided with a groove into which a tongue forming part of Ila projects and thus holds the ring of the governor always adjacent the hearing The shaft u is therefore, pulled to the left as the speed increases. However, the position of the motor M and the governor l6 might be reversed as shown in Figure 9, and in that case, the ring of the governor adjacent "a would not be attached thereto while it rotates. Instead, the ring oi the governor It adjacent the bearing i1 would always be in contact therewith, and the opposite end or ring of the governor would move with the variations in speed. An increase of speed would then push the shaft away from thegovernor, and the wheel W would be pushed peripherally with a decrease of speed, since the position of the motor M and the governor it would be reversed. Many other modiflcations readily suggest themselves to those skilled in the art, and they are all within the spirit of the invention. 1

Attention is called to the fact that although the impulses in the synchronizing circuit are of short duration, still they are repeated at the rate of twenty per second and are somewhat similar to a Farradic current and possess a cumulativeei'iect while they last. As previously mentioned, a separate wave channel might be used instead of ee- -contact with each other.)

may therefore be regarded as a position indi-- pending upon the interruption of the television broadcast to maintain s'ynchronism.

The arrangement of the transparent or conducting segments with the opaque or insulating segment located at the lower portion of the various figures of the drawings is such that it might be regarded as a means of determining the position of the disk during the stroboscopic illumination of the disk. (The upper portion or interval between the two segments may be much closer, in fact the contact segments are placed as nearly as possible to each other without actually making This arrangement eating arrangement, as it indicates the position in which the disk is located during the momentary illumination produced by-the intermittent synchronizing current.

Many modificationsfif the relationship of the centrifugal speed governor to the disk are pos-' sible. For'instance, Figure 8 may be regarded as turned on its right side, when the centrifugal governor would be found to be located at the top of the revolving disk. The operation would then be such that when the balls are centrifugally I'D-r tated outward, the shaft is permitted to drop downward through the journal H. The wheel W then, instead of being located in the upper half of the disk as illustrated in the figure, would be in contact with the lower half of the disk. Then, when the increased speed rotated the balls or other centrifugal elements outwards, the wheel W would be lowered to a point nearer the periphery of the disk and the speed slackened. Many other modifications readily suggest themselves without departing from the spirit of the invention.

In another modification, the Jaw J might be placed on guide rods, as described in my application Serial No. 468,117 or July 15, 1930, and an armature fastened to the jaw. The solenoids ll and 9 or their equivalents would be placed in cooperative relation with a pawl and ratchet, by

' means of which it would be moved to new positions.

The disks shown in the various figures might be regarded also as the disk portion of a cylinderdisk scanning element, the scanning holes or 'lensesbeing carried on the cylindrical surface,

while the synchronizing elements would be carried on the disk portion of theelement.

Although the synchronizing apparatus is shown in the .flgures as being arranged to operate duror more fulcruxned levers having one of their ends in firm contact by means of a spring or the like against the end of the shaft may be. used for the operation'ofspeed controlling means whether rheostats or other. Their free endsmay constitute part of a rheoatat arm, or may be in contact with various contact segments of speed controlling means. a e

The present disclosure is especially concerned with thdmaintenance of synchronism of television sets in isolated places where no synchronous mo tors operated by conventionally phased currents are available. In cases where a motor is operated by a dry or a storage battery, means are disclosed a point corresponding to the opaque or insulating segment in the various figures. It would be similar to the path :1 of Figure 1. A collector ring R2 of any type would also form part of the rotating element and be connected to the segment by conductor C3. The broadcasting current wou d be supplied to the contact segment by brush b2 and taken from the collector ring by brush bi. This would produce the desired interruption.

In Figure 8, contact strip 1 and associated brushes may cause a light to be illuminated instead of the indicator I5 and I9. Moreover, this light may have a specially significant color.

The relay R covers any known means of interrupting current.

Having described my invention, I claim as new and desire to secure by Letters Patent:

1. In combination: means including a rotatable element for reproducing a television image from an image varied current, a pair of transparent segments on said rotatable element the width of said transparent segments being progressively increased in order to increase their asynchronism correcting function, an opaque segment separating said transparent segments, a stationary light source in cooperative relation with said transparent segments and said opaque segment and means connected with said light source for illuminating said light source only during a portion of the revolutionary period of said rotatable element and when said opaque segment is opposite to and obscuring said light source when said rotatable element is in synchronism, said light source being when illuminated opposite to either of said transparent segments during asynchronism.

2. In combinationigeans including a rotatable element for reproduii'ing a television image from an image varied current, a pair of transparent segments on said rotatable element, an opaque segment separating said transparent segments, a stationary light source in cooperative relation with said transparent segments and said opaque segment and means connected with said light source for illuminating said light source only during a portion of the revolutionary period of said rotatable element and when said opaque segment is opposite to and obscuring said light source when said rotatable element is in synchronlsm, or when either of said transparent segments are opposite said light source when said rotatable element is in asynchronism and a pair of photoelectric cells, each of said cells being in cooperative relation with one only of said transparent segments to be influenced by the light of either of said transparent segments dur-' ing asynchronism' of said rotatable element said cells being connected to synchronizing apparatus.

3. A synchronism indicating apparatus consisting of means including a. rotatable element for cells on the side of said rotatable element oppo- I site said light source, each of said cells being adapted to be energized by the light of said source' when said transparent segments permit the light of said source to reach its specific cell and a speed adjusting means in cooperative relation with said cells and said rotatable element whereby synchronism is maintained.

4. In combinationf a rotatable element, means in cooperative relation with said rotatable element for reproducing an image from an image varied current, the diiferent portions of the surface of said rotatable element being rotatable at difierent uniform speeds, a variable position rotatabladriving means in cooperative relation with said rotatable element making driving contact with any of said portions of said surface to drive said element at any desired uniform speed and photoelectric means in cooperative relation with said rotatable element and said variable position rotatable driving means said photoelectric means including light influencing means borne on said rotatable element and a stationary photoelectric element in cooperation therewith by means of which the position of said driving means is varied in order that speed of said rotatable element is adjusted to attain synchronism and isochronism.

5. In combination: means including a rotatable element for reproducing an image from an image varied current, the different portions of the surface of said rotatable element being rotatable at different uniform speeds, a variable position rotatable driving means in cooperative relation with said rotatable element, making driving contact with any of said portions of said surface, mechanical means for varying the position of contact of said rotatable driving means, a pair of transparent segments on said rotatable element, an opaque segment separating said transparent segments on said rotatable element, a stationary light source in cooperative relation with said transparent segments, said light source being adapted to be illuminated only during a short period of each revolution of said rotatable element, a pair of photoelectric cells on the opposite side of said rotatable element to and in cooperative relation with said light source to be operated by the light from said source and elec- -tatable driving member for changing the position of said variable position rotatable driving member, and a centrifugal speed governing element in cooperative relation with said rotatable driving means in order to correct speed irregularities of said rotatable driving member.

7. :A synchronism indicatingmeans consisting of means including a rotatable element for reproducing animage from an image varied current, an electrical contact strip placed at a synchronisr'n indicating point on said disk, electrical means in cooperative relation with said strip for transmitting a periodic current received from a distant station through said contact strip when said rotatable'elen'ient is in synchronism' and a synchronism indicating means in cooperative relation with said electrical means which is actuated by said current when said contact strip is in contact with said electrical means said current is transmitted.

8. A television synchronizing apparatus conwhen sisting of means including a rotatable element for reproducing an image from an image varied current, the difierent portions of the surface of said element being rotatable at diflerent' uniform speeds, a variable position friction drive in cooperative relation with said rotatable element and matting driving contact With any of said portions of said surface to impart uniform speed thereto, a centrifugal speed governor in cooperative relation with said variable position friction drive to vary the position of said friction drive to correct speed irregularities therein, electro-- "Ill ' magnetic-mechanical means for'operating said variable position drive and electrical contact elements carried on said rotatable element in electrical cooperation with said electomagnctic-me- .chanicai means for operating said variable position drive, in order to maintain said rotatable element in synchronism by speed adjustment.

9. In combination: means including a retatable element for reproducing an image from an image varied current, the different portions of the surface of said element being rotatable at different uniform speeds, speed 'control'electrical contact elements carried onsaid rotatable element, electromagneticemechanical means in cooperative relation with and under control of said'speed control contact elements, a variable position friction drive in cooperative relation with said electromagnetic-mechanical means to vary the position of said variable position rotatable drive, said drive making driving contact with any of said portions of said surface, a motor controlling means in cooperative relation-with said eiectromagnetic-mechanical means for varying the speed of said motor and a centrifugal spccd governor in cooperative relation with said variable position drive to correct irregularities in the speed of said rotatable element.

iii, A television synchronizing system consisting of means including a rotatable element forduring a fraction of. each revolution of said rotatable element, means including a secondmtatable element for converting said image varied able element, a pair of current influencing s'egments borne on said rotatable element, a non'- influencing segment separating said segments and stationary synchronism controlling means in cooperative relation with said current influencing segments and said means for rotating saidrotatable element, said noninfiuencing segment being disposed opposite said stationary synchronismcontrolling means when a synchronizing current is received while said rotatable element rotates synchronously in order that said current influencing segments may be prevented from influencing said stationary synchronism 'controlling means when said rotatable element rotates in synchronism.

12. A television apparatus consisting of, means including a rotatable element for reproducing an image from an image-modulated electric current, the diflerent portionsfof the surface of said rotatable clement moving at diflerent uniform speeds, contact means borne on said rotatable element including a pair of arcuate contact segments, an insulating interval separating said arcuate contact segments, stationary contact means including a brush normally in position on said insulating interval when said rotatable elemerit rotates in synchronism, a pair of electromagnetic elements, means for furnishing a periodic synchronizing current operativeiy connected to said brush and to said pair of elec-' tromagnetic elements, a variable position Ero-. tatable driving means making driving contact with any one of said portions of said surface of said rotatable-element at a time and a clutch in cooperative relation with and operated by said pair of electromagnetic elements and connected with said variable position rotatable driving means in order to shift said driving means to engage any one of the said diflerent portions of said surface to cause said rotatable element to rotate in synchronism.

it. a television apparatus consisting of means including a rotatable elementfor reproducing an image from an image modulated current, the

surface at a time, electrical contact means borne on said rotatable element including two contact segments, an insulating interval disposed between said segments, a stationary contact brush normally making contact with said insulating interval when said rotatable element rotates in synchronism, shifting means for shifting the position of said rotatable driving means to attain and maintain said rotatable element in synchronism and 'means for operating said shifting means in cooperative relation therewith and electricaliy connected to said electrical contact means and said stationary contact brush in or-- der to cause said rotatable element to rotate synchronously.

14. A television apparatus consisting of means including a rotatable element for reproducing an image from an image-modulated current, the different portions of a surface of said rotatable element being rotatable at different uniform speeds, a rotatable driving means in cooperative relation with said rotatable element and making driving contact with any of said portions of said surface at a time, electrical contact means borne on said rotatable element including two contact segments, an insulating intervaldisposed between said segments, a stationary brush in cooperative relation with said segments and said insulating interval, said brush being situated on said insulating interval during synchronism, two electrical contact rings borne on said electrical rotatable element and connected to said contact segments,

a pair of stationary brushes making contact with .c

said contact rings, a clutch engaging said rotatabledriving means to bring said driving means in contact with said different portions of said surface, electromagnetic means in cooperative relation with and operating said clutch and connected by suitable circuits to and controlled by said contact segments said electrical contact brushes and said contact rings in order to maintain said rotatable element in synchronism.

15. A television apparatus consisting of means including a rotatable element for forming an image from an image modulated electric current,

means for uniformly rotating said rotatable element, synchronizing means including suitable electrical circuits and a controlling switch for operating said means for uniformly rotating said rotatable element at synchronous speed and a speed governing means operatively connected to said controlling switch to close said switch and circuits when said rotatable element is rotated at approximately synchronous speed.

16. An automatic television synchronizing apparatus consisting of a motor, a longitudinally shiftable shaft rotated by said motor, a rotatable driving element slidably mounted upon said shaft and being unrotatable relatively therewith, a rotatable scanning element, the different portions of a surface of said scanning element being mov able at different uniform speeds, said rotatable driving element making driving contact with any one of said different portions of said surface at a time, a centrifugal speed governor in cooperative relation with said shaft in order to longitudinally shift said shaft in accordance with speed variations to bring said rotatable drivin element into new driving positions, a clutch engaging with and acting to shift said rotatable driving element to different drivlng' positions, electromagnetic means operating said clutch and suitable electrical switching means in cooperative relation with said rotatable scanning element and connected by suitable circuits to said electromagnetic means to operate said clutch in 'accordance with speed variations occurring in said rotatable scanning element.

1'7. An automatic television synchronizing apparatus consisting of a motor a hollow shaft rotatable by said motor, a second shaft in cooperative relation with said hollow shaft and making slidable engagement in the hollow of said hollow shaft, said shafts being relatively unrotatable with each other, a rotatable driving element slidably mounted upon said second shaft and being unrotatable relatively thereto, a rotatable scanning element the different portions of 9.

surface of which move at different uniform speeds, said rotatable driving element making driving contact with any of said difl'erent portions of said surface at a time, a centrifugal speed governor in cooperative relation with said second shaft and acting to cause said shaft to enter more or less deeply in said hollow of said hollow shaft to move said rotatable driving element to contact with different portions of said surface to correct speed irregularities therein, a clutch for shifting said rotatable driving element into contact with any of said portions of said surface, electromagnetic means for operating said clutch and suitable electrical switching means 'in cooperative relation with said rotatable scanning element and connected by suitable circuits to said electromagnetic means to operate said clutch in accordance with speed variations in said rotatable scanning element.

18. An automatic television synchronizing apparatus consisting of means including a rotatable scanning element for forming an image from an image-modulated current, means for rotating said rotatable element at uniform speed, synchronizing means for maintaining said rotatable element in synchronism, a switch connected to and controlling said synchronizing means in order to out said synchronizing means in or out of circuit and a speed governing means in cooperative relation with said switch to bring said synchronizing means into action when said rotatable element rotates at approximately synchronous speed.

19. An automatic television synchronizing apparatus consisting of means including a rotatable scanning element for forming an image from an image-modulated current, a rotatable driving element slidably mounted upon a shaft and making driving contact with the surface of said rotatable scanning element, the different portions of the surface of said scanning element being rotatable at different uniform speeds and said driving element making driving contact with any of said portions of said surface at a time, a clutch for shifting the position of said driving element to bring it into contact with any of said portions,

electromagnetic means for operating said clutch,

suitable switching means in cooperative relation with said rotatable scanning element'and connected by suitable circuits to said electromagnetic means to operate said clutch in accordance with speed irregularities in the motion of said rotatable scanning element.

20. An automatic television synchronizing apparatus consisting of a uniformly rotatable driving means, a. centrifugal speed governor in cooperative relation with said driving means, to correct speed irregularities therein, a variable position rotatable contact element in cooperative relation with and driven by said driving means, means for shifting the position of said variable position rotatable contact element to impart different desired uniform speeds to said rotatable contact element, means including a rotatable scanning element for reproducing an image from an image modulated current, the different portions of a surface of said scanning element being rotatable at different uniform speeds and being in cooperative relation with said variable position contact element, electrical means including suitable contacts borne on said rotatable scanning element in cooperative relation with said means for shifting and a switch in cooperative relation with and controlling said electrical means and in cooperative relation with and to be operated by varied current, the different portions of the suraiaqaoi said centrifugal speed governor close said switch when said rotatable scannlngelement ro- 'tatable driving means in cooperative relation with said rotatable element making driving contact with any of said portions of said surface to drive said element at any uniform speed and means for producing corrective synchronizing adjustments in the position of said variable position rotatable driving means in cooperative relation with said rotatable element and said variable position rotatable driving means where said rotatable element is not rotating synchronously.

22. A claim in accordance with claim 21 but in which said means for producing corrective synchronizing adjustments includes transparent portions on said rotatable element. r

23. A claim in accordance with claim 21 but in which said means for'producing corrective synchronizing adjustments includes transparent portions borne on said rotatable element-in cooperative relation with a stationary light source and photoelectric cells.

24. A- claim in accordance with claim 21 but in which said means for producing corrective synchronizing adjustments includes transparent portions borne on said rotatable element and sta-- tionary photoelectric cells in cooperative rela-.

varied current, the diilerent portions or the surface of said rotatable element being rotatable at diflerent uniform speeds, a variable position rotatable driving means in cooperative relation with said rotatable element making driving contact with any of said portions of said surface to drive said element at any'uniiorm speed and means for producing corrective synchronizing currents when said rotatable element is not rotating synchronously, and means in cooperative relation with said means for producing corrective currents and with said variable position rotatable driving means to re-establish synchronism by changing the position of said variable position rotatable driving meana,

- iAI-OYSIUS J. CAWLEY.

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