US2810078A

US2810078A - Photo timer

Info

Publication number: US2810078A
Authority: US
Publication date: 1957-10-15
Anticipated expiration: 1974-10-15

Description

J. BALL ET AL Oct. 15, 1957 PHOTO TIMER 3 Sheets-Sheet 1 Filed Jan. 19, 1952 m OI INVENTORS JACK BALL & JOHN J. RUSSELL @471 MM mm ATTORNEYS Oct. 15, v1957 J. BALL ETAL 2,810,078

I PHOTO TIMER Filed Jan. 19, 1952 5 Sheets-Sheet 2 j FIG-3 IN V EN TORS JACK BALL 8. JOHN J. RUSSELL ATTORNEYS FIG-6 United States Patent It gsiaozs' PHOlI Q TIMER Jack Ball, Cleveland. Ohio, and John J. Russell, Greenv l a sners t0 Pi -R y Corpc a en,

Waite Manufacturing Division, Inc., Cleveland, ()lrio,

acorporationfof Ohio Application January 19, 1952, SeriaI No. 267,281 -7 Claims. (Cl. 2 5095) This invention relates to improved means sensitive to the luminosity of an image on a fluorescent screen and useful for controlling a timing period in a photographic process.

This application is a continuation in part of our copending' application serial No. 116,112, filed September 16, 1949, for Photo Timer, now abandoned.

One of the objects of the present invention is toprovide light sensitive means subject to the luminosity effect of an image on a fluorescent screen as observed from opposite sides of the same surface thereof so as to average the light effects over a large portion of the entire image whereby a light area of the image which is nearer to one of the luminosity responsive devices will be farther away from the luminosity responsive device on the opposite side of the image, thus averaging the total light effect and obtaining a more accurate value for photographic timing purposes.-

In one form of our invention, two photoelectric cells are positioned respectively on opposite sides of theimage -in position to receive light rays from alarge area of the image and the electrical output of the two photoelectric cells is totalized or averaged for timing purposes.

In another form of our invention, the luminosity effect from opposite sides of the image is focused by means of mirrors simultaneously from two mirrors on to a single photoelectric cell, thus averaging the-light effect from opposite sides of the image in a single cell, the output of which is utilized in a timing circuit.

Another object of the present invention is to do away with the errors which occur by timing an X-ray photograph where the timing value is determined from one side only of the image.

Still another object of the present invention is to do away with cumbersome movable light-sensitive devices which have to be moved over the image in the screen for operative purposes and thus are sensitive to the particular spot on which the light-sensitive device happens to'be focused and which is undesirable because of the wires connected to the device which have to be bent-back and-forth each time, together with the undesirability of'having the vision of the operator obstructed.

Another object of our invention is to provide a regular non-biological pattern of fluorescent luminosity on an area viewed by two photoelectric cell means located on opposite sides of the pattern area so that theslight rays from the area approach the cells at a very flat angle,

thus providing means for averaging the luminosity from the area as received at opposite sides thereof and at the same timeproviding a regular pattern diaphragmed upon saidarea. This gives a more accurate. source for timing aradiograph or a photograph than anyothcr method now known to us. I

In carrying out the purpose of the next preceding paragraph, this invention utilizes either a light-opaque mask interposed between the luminous fluorescent screen and the light sensitive cells so as to provide a pattern of the visible light between the luminescent screen and the cells; or we may provide fluorescent material arranged ina regular non-biological pattern and subject to the X-rays which pass through the film upon which a radiograph is being taken and this luminous pattern is then viewed by 'th'e photoelectric cell means.

of Eig. SandsoineWhat enlarged;'

2,810,078 Patented Oct. 15, 1957 "ice In another form of our invention, the regular light patsubjectto from both the original and the reflected sources;

Other objects and advantages of ourinvention will be apparent from the accompanying drawings and description and the essential features will besum'marizedin the appendedclaims'.

"In thed'rawings, Fig. 1 is a top plan view of a frame eq u'i'ppeld. with a fluorescent screen and a movable cas- .sette or film holder and equipped with thatfor'm of our device which'requires twov photoelectric cells;

Fig. 2 is a fragmental sectional view taken along the line 2-2 ofFig. I;

'Fig. 3 is a fragmental sectional view enlarged taken along the line 33 of Fig. 1 and partly brokenaway to more clearly show the construction; i

Fig.':4 is a diagrammaticview of a portion of an elec- ,t-rica'1'.tiniing.circuit for use with the device of'Figs. 1, 2 s fl H v c Fig. 5 is a top plan view of the left-hand portion of Fig; 1 to somewhat smaller scale and showing a modified form of ourdevice using mirrors;

,F1 g.6 is a fragmental sectional view enlarged taken modificatiolil'of our invention and including. a s'ectional (View a Bucky housing below an" examination .table, the sectional view being taken sa a' ls j 'Fig.,"8is a fragmental sectional view taken along the line f 8 8 of Fig; 7 but drawn to asornewhat smaller scale; 1 -Fig.,9 :i s a fragmental sectional view similar to 7 but showing another modificationof our'inverition'and takenalong the line 99 ofFig. 10; while w FigQIO is 'a fragmental sectional view taken along the larger than thescale of 10.

Qur invention is useful .for photo-timing an .X-ray photograph or for timing an ordinary photographof an 40 diliilQ-lt) of Fig. 9, the scale oflii g. 9 being somewhat 'TXi-ray imageon a fluorescent.screenL In either case, the

parts tobe photographed are viewed as an image on a g'flnores'cent screen and some measure'of the luminosity ofthe image must'be utilized for timing purposes. Une common'device for photo-timing a picture under these ,co ditions, consists in the use of a photo sensitiveitube is moved to a'central position of the pic ture when it is desired to time an exposure. One of the difl iculties of this device is that the phototube is in the way for viewing the. screen when it is moved to a position overthe screen, and furthermore the device. has high voltagejwires connected to it, which have to be bent back ahd forth each time the, phototube is placed in position or pushed out of the way. Another difficulty with thistype of timing is 'the great difference in the eifect depending upon whether the phototube isffocused over a dark shadow such as the -spine w uid makeor over a brighter spotisuch aslight tissuewould'make. This is particularly; noticeable where a patient-has been fed bismuth which, of course, provides .a verydark spot, and if the phototube were placed over Isucha sp ot, a very dark picture would result.

Anotherrnanner of photo-timing such pictures is the provision of a photo/ electric tube or cell along one side of the fluorescent screen and directed toward the. image on th Screen. This is a satisfactory arrangement except that of the light of the image on the phototube follows theiinverse square law and therefore the image areas nearer to the phototube give a much greater effect.

For instance, if it is desired to take a picture through one-half of the human body, if the phototube is toward the center of the body, then the dark portion of the body image will be nearer the phototube and the image farther away from the phototube may have a certain amount of splash where the view extends outside the confines of the body itself, giving a very bright spot on the screen. However, this bright spot on the screen is distant from the phototube and therefore the darker portion of the body nearer the phototube will control and one will obtain a dark picture. On the other hand, if the phototube is near one side of the body looking toward the center, then any splash will be close to the phototube and the darker portion of the body image will be further away from the phototube. In this case, the timer will cut off the exposure tube quickly and a light print will develop.

We have chosen to show our invention in combination with a frame which carries a fluorescent screen 11 in a binding frame 12 and mounted by means not shown for movement to various positions relative to the body of the patient to be observed. A cassette or film tray 13 is mounted by means of rollers 14 for movement along parallel tracks 15 either to a photographing position as shown in Fig. 1 or to a loading and unloading position in the area 16. For moving the tray 13 back and forth, a motor 17 is provided which through a slip clutch connection 18 drives a pinion 19 meshing with a rack 20 which in turn meshes with a mutilated gear 21 formed on one end of an arm 22 which is oscillatable about a fixed pivot 23 connected with the main frame 10. At the opposite end of lever 22 it has a pivotal engagement with a shoe 24 which is slidable in a slotted frame 25 which is rigidly carried and is a part of the tray 13. Movement of the rack 20 thus oscillates arm 22 to carry the tray 13 from loading to photographic position and back again. The particular device shown in the drawings is a spot film arrangement with

stop members

26 and 27 carried by arm 28 which is pivotally mounted at 29 on the main frame and is movable by means of a handle not shown. A Vshape stop 36 adjustably mounted on the tray 13 engages the stop 26 in the position shown in Fig. 1 so that the tray can move no farther toward the left. The slip clutch arrangement 18 provides a safe manner of stopping at any desired point, the motor 17 being arranged to overdrive until a stop member is reached. In this particular device, the tray 13 may be set to take a picture for each of its four quarters or for the left half or the right half or for the upper half or for the lower half or for the entire area of the screen. The particular arrangement of the main frame 19 and the movements of the tray 13 have no special bearing on the present invention and are only shown to illustrate one embodiment thereof.

In the form of our invention shown in Figs. 1 to 4 inclusive, a photoelectric cell 34 is mounted in fixed position on the frame 11 at the left-hand side of the fluorescent screen 11. A second photoelectric cell 34' is mounted in fixed position on the frame 10 at the righthand side of the fluorescent screen as shown in Figs. 1 and 2. As shown in Fig. 2, these photoelectric cells extend a very short distance above the level of the frame, approximately one and one-half inches, so that they are entirely out of the way and are not obstructing the view of the operator. As clearly shown in Fig. 2, the angle A between the beam of light coming from the image on the fluorescent screen toward each of the photoelectric cells is very flat, not over five to ten degrees. It results from this construction that a very shallow beam of depth B thus intercepts a wide area of width C on the fluorescent screen. In other words, the light beams com- -ing from the image toward each of the photoelectric cells is derived from a very large area of the fluorescent tering the cell openings. As shown in Fig. 3, this cornprises a pluraiity of parallel plates 33 and this insuresthat the beams of light directed to

cells

34 and 34 come from substantially the same exact area.

the two beams overlap for the width of the image indicated at C in Figs. 1 and 2. The rays from each cell converge along the broken lines as shown in Fig. 1.-

The rays toward the cell 34 converge along the dot-dob dash lines D and converge toward the cell 34 along the dot-dash lines E. Thus, except for the outer corners as shown in Fig. 1, the light beams moving toward cells 34 and 34' come from substantially the same area of the fluorescent screen and come from quite a large area thereof so that there is no specialized effect from a particularly light or dark spot of the image on the screen. It will be obvious that a light spot of the image nearer tube 34' will have a strong effect there but will have a weak effect on the tube 34. Thus the luminosity effects from opposite sides of the image are averaged.

An electrical connection between photo-

electric cells

34 and 34 so as to average out the results and to utilize this result in a timing circuit is illustrated in Fig. 4. The view of Fig. 4 is intended to be incorporated in the timing circuit shown and claimed in the copending patent application Serial No. 785,664 of lack Ball and Edward B. Graves for Photoelectric Timer for X-ray Apparatus, filed November 13, 1947, now Patent No. 2,541,187, granted February 13, 1951, to which reference may be had for a more complete description. It will be noted that the left-hand portion of Fig. 4 is exactly like a similar part of the drawing in the above mentioned copending application wherein a photoelectric cell 34 is shown in a broken line box indicated as 55. The right-handv portion of Fig. 4 is a complete duplication of the lefthand portion and any parts thereof may be referred to with reference characters having the sulfix prime. The

photoelectric tubes 34 and 34' are illustrated as being of the type shown in United States Patent No. 2,231,697, granted February 11, 1941, to V. K. Zworykin et al. The

cathodes

34b and 34b of the present application are intended to be the equivalent of the cathode 5 of the above mentioned Zworykin et a1. patent. It will be noted that whereas, in the above mentioned copending appli cation the termination of a photographic exposure depends upon the firing of the trigger tube 31 responsive to the output from a single photoelectric cell 34, the timer circuit when connected according to the teachings of Fig. 4 and the above mentioned copending application connects in parallel the

plates

34a and 34a of the two phototubes by means of the connector 57. It is well known to fire a trigger tube when a connected condenser .has collected sufficient electrons from an anode such as 34a of cell 34. The present invention supplies means for charging such a condenser responsive to the average luminosity of substantially the entire screen by connecting the

anodes

34a and 34a in parallel.

A trigger tube 31 is shown as of the cold cathode type. The plate 31a of this tube is connected through relay 32 having an armature 32a the purpose of which is to open a set of contacts and terminate the X-ray exposure responsive to the timing apparatus herein disclosed.

A phototube of the above mentioned Zworykin type is diagrammatically shown at 34. This tube has a plate 34a, a cathode 34b and a plurality of dynodes. Suitable taps on resistor 44 supply the dynodes with proper voltage all except the last one. This last dynode is connected to switch 52 which, in the full line position shown in the drawings, engages contact 52:: for radiography. The series resistor 46 is used as a calibrator. The phototube units are sent out fully assembled including the parts within the broken line 55. By adjusting the resistor .6,

In other words,

each phototube unit may be adjusted to the same sensitivity so as to give identical output.

selection of the capacity of the capacitor 56, the potential to which it is charged in order to fire the trigger tube, and the sensitivity of the phototube, an exposure may be terminated 'when a recording film has been properly exposed. The capacitor 56 and the trigger tube 31 are so selected and arranged as to take care of the output from the two photoelectric cells 34 and 34' so as to terminate the X-ray exposure after the film has been properly exposed.

Certain refinements will occur to those skilled in this art in order to make the above device operate properly. In the first place, each of the cells 34 and 34' will be separately focused on the same area, lighted in the same manner, and each of the phototube units will be adjusted to the same sensitivity so as to give identical output for identical input. This is done by adjusting the resistor 45 for cell 34 and by adjusting the equivalent resistor for the cell 34. i T he apparatus mentionedso far utilizestwo photoelectric cells and totalizes the output of the two cells electrically .in order to obtain an average result from the image on the fluorescent screen. The modification shown in Figs. and 6 averages the luminosity effect observe'd'from each side ofthe image by simply adding together the light rays as'they effect a single photoelectriccell. All ofthe parts of Fig. 5 are understood to be-the same as those described in connection with Fig. 1 except those now about to be described. Positioned in fixed relationship to thetrame 10 on opposite sides of the fluorescent screen 11,"I provide

housings

36 and 37. In eachof these housings there is a mirror "38 so positioned as to receive light rays 'from the image on the fluorescent screen and to reflect these rays parallel to thedot-dot-dash lines F of Fig. '5 to the cathode 39 of ,a photoelectric. cell 49 Which is mounted on the frame 10.

The cathode 39 is of -a similar character to that previous- 'ly described at 34b and 34b. Columnating device 41 exactly equivalent to-the devices 32 are positioned in "front of each of the mirrors 38 to provide parallel rays of light coming from the fluorescent screen towardgeach mirror and limiting the area covered-by therays of light going in opposite directions to the same width of image --as Zin'dicatedat C-in Figs. 1 and 2 in connection with the-first-form of our device, If necessary or desirable,

a lens-42 :maybe positioned-between each device 41 "The output equivalent to 34a of the photoelectric cell-40 isdirected ;to a trigger tube suchas shown at 31.in,-the cqpending application to produce a timing operation.

The necessary corrections can be made to take-careof .the light coming from two sources toward the cathode Z39Iinthe present instance, but it will be obviousto those skilled inthis arthow thismay be done so asto .utilize the. ,photo-timing circuit of .the above. mentioned copending application.

In amodification-shown in Figs. 7 to 10 inclusive, our

invention .is shown..in..connection -with adiaphragm or equivalent means for supplying a regular pattern of himinosity vi ewed by the phototubes so that the phototubes are not exposed to the entire area of the fluorescent screen but only "to a selected pattern thereof; We find that a much bett er timing job is performed when this pattern is used in connection with two phototubes' viewiugthe pattern from opposite sides thereof.

Fig. 7 is somewhat digrarnmatic andindicates anX-ray tube 'at 64 positioned above a table 65 so that its rays penetrate a subject indicated in dot-dash lines 6 6 lying upon the table. Beneath the table is the usual Bucky housing 67, in which is mounted a Bucky grid 68 and beneath that a filrn sensitive to X-rays indicated at 6 9. It: will be understood that this is diagrammatic as the fill-I1 is always in a holder. Beneath the film is provided our phototube unit 70 which consists essentially of a substantially square light tight casing having at its upper edge outwardlyextending flanges 70a which are slidable in ways 67a in the housing 67. Extending across theopento'p of the casing 70 and suitably supported there- :in'is a thin plate 71 of aluminum or the like. The'un- ,derside of this plate at its central portion is provided with .a .fluo rescentscreen 72 mounted on the plate 7.1 in a known manner. Beneath. the fluorescent screen is a mask 73 ofopaque material, black cardboard being suitable, and-mounted for sliding movement in ways 74 attached to theunderside of plate 71. 4 u l The mask 73 may be formed in various ways but I .have shown .in Fig. 8 how an elongated inask may be provided withthree different patterns any one of which .maybepositioned withinthe casing 70 by simply sliding thernask 73 in the ways 74. The regular patterns illustrated comprise a substantially square opening 73a located substantially .centrally' of the fluorescent screen area .-7 2.bnt' of less extent than the area 72. This is the regular pattern which is in position in Fig. 7. Another regular pattern is shown at 7312 in Fig. 8 and comprises four regularly spaced generally oblong holes, While athird regularpattern shown at 73c consists of sixteen regularly spaced round holes. Other patterns might be ,used .or a combination of screens might be superposed one upon the other to give the desired number of patterns. In the case of the pattern shown in Fig. 8, the pattern 73a might be used when a narrow part of the ody is being photographed such as an arm. The pattern of 73b might be utilized in taking a picture of the ribs of'the human body from a lateral position, whereas the pattern of 730 might .beused-for a full front or a full rear picture of. the human torso.

It vwill be notedin Figs. 7 and .8, that our invention has been aplied by placing two phototubes 75 on opposite sides of thefiuo'rescent .screen and positioned to receive the, rays therefrom at a very flat angle so that each photo- ;tube views a large area. These tubes are shown diagrammatically inFig. 8 but they are positioned in staggered relationship, the tubes coming intothe casing 76 suffiQl lfl l fa that the light sensitive. portion thereof is cen- ,tered on the area 72.

. The tubes in Fig. 7 might the .columnatedby providing devices like those shown at 32 in Fig. 3. However, much thesame efiectmay be obtainediby surrounding each phototube by a generally cylindrical shield 76, open to g nt rays only as indicated by the dot-dash lines 77 in The tubes 75 .of Fig. 7 areintended to he connected ,in atiming circuit exactly'like that shown in Fig. 4 so thatthe combined effect ofthe luminous'regular pattern upon the two tubes 75 positioned like the tubes 34 and :34 of Fig. 4. will eventually charge the condenser 56 and fire the-tube 31 so as to energize relay32 and terminate the X-rayexposure.

Themodification of Figs. 9 and 10 are quite similar tothose shown in Figs. 7 and;8 and intended to be used in the same combination. In Fig. 9, all partscfthe housing 67 above the parts shown inthedrawing are intended to be like those shown at 67 in Fig.7 and the device is intended to be mounted beneath the table 65 with the X-ray tube 64 above the table so that the X-rays pass through the subject 66 and through a sensitive film 69 after which they impinge upon the plate 78. This plate covers the open top of a casing 79 which is a square casing having flanges 79a slidably received in suitable ways in the housing 67 wholly analogous to the mounting of the casing 70 previously described.

In the modification of Figs. 9 and 10, the regular pattern forming means comprises the arrangement of fluorescent screen material at 80a in a regular pattern on the under side of a thin plate 80 of a luminum or the like which is slidable in ways 81 mounted on the under side of plate 7 8. Another portion of the plate 80 is provided with the pattern 80b of four regularly arranged oblongs like those shown at 73b, while a third pattern 800 is pro- .vided comprising sixteen regularly placed round holes similar to those shown at 730. In each case, the regular pattern is formed by fluorescent screen material arranged in this pattern on the plate 80. The X-rays coming through the film 69 and through the plate 80 impinge upon the fluorescent screen material so that only the

patterns

80a, 8012 or 800 have any luminosity.

The plate 80 bearing its

fluorescent patterns

80a, 80b and 88c might be utilized in connection with phototubes 75 of Fig. 7 with their cylindrical shields 76. However, in Fig. 9 I have shown another modification wherein a mirror 82 is mounted on the bottom of the casing 79 with its reflecting surface upward and parallel to the plate 80. The phototubes 83 are positioned on opposite sides of the pattern 80a and in position to receive the rays therefrom at a very flat angle. The luminous pattern at 80a is reflected in the mirror 82 and the tubes 83 are positioned so as to receive the luminosity both from the pattern 80a and from its reflected image in the mirror 82. The tubes 83 are intended to be connected in the timing circuit of Fig. 4 in place of the

tubes

34 and 34 with the proper balancing of the phototubes with the condenser 56 and trigger tube 31 to terminate the exposure at the proper time.

Another modification shown in Fig. 9 which is optional comprises light stops or barriers 84 positioned so as to shield the light sensitive element of phototubes 83 from rays coming from the portion of the fluorescent material closest to each phototube. Thus, each phototube will not View that portion of the fluorescent screen material which is closer to the tube in question, thus avoiding any intense eifect which close bright areas might have upon that phototube.

In order to make these devices absolutely light tight where the flanges 70a or 79a slide in their respective ways, the flanges are filled with silver solder and ground perfectly smooth and the ways are also formed exactly.

Where the mask 73 or the plate 80 slides horizontally in and out of the

casing

70 or 7 9 respectively, light seals may be provided similar to those provided in a film holder sealing against the film as it slides in and out of the holder.

In the claims relating to Figs. 7 and 9 we have defined the X-ray tube 64 as being over the subject 66 and have defined the film 69 as being under the table 65. These terms over and under have reference to the table 65 in a horizonal position. It is understood that the table might be tilted to other angles and the positioning of the parts is to be the same relative position as shown in Fig. 7.

Prior to our invention, it has been known to utilize a pattern of light in connection with the timing of X-ray photographs beneath a table such as that shown at 65 in Fig. 7. These prior devices utilize the large lead disc to provide a pattern by interrupting some of the X-rays. The lead disc was so bulky that is necessarily bad to be mounted below the equipment contained in the Bucky housing 67. With this prior known equipment, the

height of the table 65 had to be raised between one and three-quarters to two inches because of the bulky lead disc. Utilizing our invention, the regular pattern forming means may be incorporated into the Bucky housing itself and requires a raising of the table top height only a matter of one-half inch to three-quarter inch. Obviously, our improved device is much lighter because it does away with the heavy lead disc of the prior device.

What we claim is:

1. In combination, two photoelectric cells sensitive to fluorescent luminosity from a generally predetermined area of a plane for photographic timing purposes said cells being located respectively on opposite sides of said area and having their photosensitive elements positioned to receive luminosity from substantially the same area, said cells being located adjacent said plane, whereby the light rays from said area approach said cells at a very flat angle so as to average the luminosity from a substantial area, means providing a regular pattern of luminosity from said area, an electrical circuit connected with both cells to average the output therefrom, and a timer control member responsive to said circuit.

2. The combination of claim 1 wherein said last named means comprises a fluorescent screen covering substantially said entire area, and an X-ray pervious light-opaque mask interposed between said screen and said cells, said mask having through openings arrange-d in a regular pattern.

3. The combination of claim 1 wherein said last named means comprises fluorescent material arranged in a regular pattern area.

4. The combination of claim 1 and including a plane mirror parallel to said first named plane and positioned to reflect said pattern, and said cells lying between said planes and positioned to receive luminosity simultaneously from said area and from said mirror.

5. In combination a fluorescent screen having thereon an image of unevenly distributed luminosity, two devices positioned so as to be responsive to the luminosity of substantially the same area of said screen, means limiting said image to a regular pattern selected from a portion only of said area, said devices located on opposite sides of said area and adjacent the plane of said fluorescent screen, whereby the light rays from said pattern approach said devices at a very flat angle less than approximately ten degrees relative to the plane of said screen so as to average the luminosity from a substantial area of said screen, and photoelectric cell means operatively associated with both of said devices connected to average the luminosity eifects from said two devices.

6. Means as in claim 5 wherein said devices comprise two photoelectric cells positioned respectively on opposite sides of said image, and a timing circuit connecting the output of said cells in parallel, said timing circuit operatively connected with the source causing said image onsaid fluorescent screen.

7. The combination of claim 5 wherein said photoelectric cells are adjusted to approximately equal sensiivity.

References Cited in the file of this patent UNITED STATES PATENTS 2,060,957 Tarvin et al Nov. 17, 1936 2,124,404 Schroter July 19, 1938 2,182,987 Hopkins Dec. 12, 1939 2,183,717 Keall Dec. 19, 1939 2,246,501 Bradner et al June 24, 1941 2,441,324 Morgan et al. May 11, 1948 2,474,380 Simmon June 28, 1949 2,480,424 Simmon Aug. 30, 1949 2,486,866 Morgan et al. Nov. 1, 1949 FOREIGN PATENTS 593,764 Great Britain ..c Oct. 24, 1947 632,842 Great Britain Dec. 5, 1949