US1584098A

US1584098A - Projecting apparatus for moving-picture machines

Info

Publication number: US1584098A
Application number: US633925A
Authority: US
Inventors: Arthur J Holman
Original assignee: Individual
Current assignee: Individual
Priority date: 1923-04-23
Filing date: 1923-04-23
Publication date: 1926-05-11
Anticipated expiration: 1943-05-11

Description

May 11 1926. 1,584,098

I A. J. HOLMAN PROJECTING APPARATUS FOR MOVING PICTURE MACHINES Filed April 23, 1923 13 Sheets-Sh'et' 1 -May 11 1926. 1,584,098

v A. J. HOLMAN PROJECTING APPARATUS FOR MOVING PICTURE MACHINES Filed April 23, 1923 1s Sheets-Sheet 2 x illlllllllllllll u:

& u M

May 11 1926. 1,584,098

' A. J. HQLMAN PROJECTING APPARATUS FOR MOVING PICTURE MACHINES May 11 1926. 1,584,098

A. J. HOLMAN PROJECTING APPARATUS FOR MOVING PICTURE MACHINES Filed April 25, 1923 1s Sheets-Sheet 4 f7- roan/5y:

May 11 1926.

A. J HOLMAN PROJEC'IING APPARATUS FOR MOVING PICTURE MACHINES Filed April 23, 1923 13 Sheets-Shet' 5 May 11 1926.

A. J. HOLMAN PROJECTING APPARATUS FOR MOVING PICTURE MACHINES Filed April 23, 1923 13 Sheets-Sheet 6 May 11 1926; 1,584,098 A. .LHOLMAN PROJECTING APPARATUS FOR MOVING PICTURE MACHINES Filed April 23, 1923 13 Sheets-Sheet '7 A. J. HOLM AN PROJECTING APPARATUS FOR MOVING PICTURE MACHINES May 11 1926.

Filed April 23,

13 Sheets-Sheet 8 M'MW f 7' TERA/z May 11 1926. 1,584,098

' A. J. HOLMAN PROJEGTING APPARATUS FOR MOVING PICTURE MACHINES Filed April 23, 1923 15 Sheets-She'li 9 May 11 192s. 1,584,098

' A. J. HOLMAN PROJECTING APPARATUS FOR MOVING PICTURE MACHINES Filed April 23, 1923 13 SheetS-Sheet'lO May 11 1926.

1,584,098 A. J. HOLMAN PROJECTING APPARATUS FOR MOVING PICTURE MACHINES Filed April 25, 1923 13 Sheets-Sheet 11 /'g /Z- I e I WVENTUR:

13 Sheets-Sheet 12 May 11 1926.

A. J. HOLMAN PROJECTING APPARATUS FOR MOVING PICTURE MACHINES Filed April 23, 1923 A. J. HOLMAN PROJEGTING APPARATUS FOR MOVING PICTURE MACHINES May 11 1926. 1,584,098

Filed April 25, 1923 13 Sheets-Shei 13 Patented May 11, 192 6.

STATE ARTHUR 3'. HOLT/IAN, OF BOSTON, MASSACHUSETTS.

PROJECTING APPARATUS FOR MOVING-PICTURE MACHINES.

Application filed April 23 My invention relates to that type of projecting apparatus wherein the film strip is kept continously in motion and the effect of said motion is so compensated by means 5 of moving optical rectifying elements as to produce a steady image. jects of my invention have been to provide an improvedframing means whereby the operator may center the image position on the screen or frame while the apparatus is in,

operation. and subsequently focus without disturbance to framing adjustment and without the necessity for moving the optical sys tem along the optical axis; also, to provide means to accommodate the optical system to any degree of shrinkage of the film strip; also,-to provide a diaphragm system which will, while providing maximum illumination on the screen, limit the distortion of the image'resulting from the Variation of equivalent focal length inherent in revolving optical rectifying systems and, furthermore, cut off undesirable marginal rays and eliminate flicker; also, to provide means convene iently to adjust andmaintain in exact registration the optical rectifying elements. It has also been my object to provide a cer. tain improvement for such devices wherein the optical rectifying elements consist of oppositely rotating discs, the peripheries of which are composed of sectors of lenses, prisms, or other variable refracting elements, -which improvement consists in providing opaque areas to prevent the passage of light through parts of. the system which because of temporary angular position are not of correct refracting power. For devices of the character specified wherein the optical rectifying elements consist of oppositely rotating discs the peripheries of .which are composed of sectors of lenses I have sought to provide an improved means of mounting the several sectors and have also sought to provide an improved means for focusing and securing correct registration of images on the screen without the necessity of moving the revolving discs along the optical axis.

My invention may be best understoodby reference to the accompanying drawings in which v 1 Fig. 1 is a front view of my device.

Fig. 2 is a front view with the frontpb- 5 "jective mount and front housing removed.

Fig. 3 is a cross section on line 33 of .Fig. 1, viewed in the direction of the arrow.

The special ob- 1923. Serial No. 633,925.

Fig. 4- is a cross section on line H of Fig. 1, viewed in the direction of the arrow, with the right side door open.

Fig.5 is a cross section on line 5-5 of Fig. 6, viewed in the direction of the arrow, showing means for adjusting and maintaining in exact registration the optical rectifying elements.

Fig. 6 is a left side view with the left 6 side doors removed, showing the actuating gear train and automatic fire shutter control' mechanism.

Fig. 7 is a back view with the rear casing andside doors removed, the lower sprocket hearing and part of the idler bracket being cut away.

Fig. 8 is an enlarged View of the film actuating and framing mechanisms shownin Fig. 4: with the framing device set to advance the film and thereby raise-the image position on the screen.

Fig. 9 is a plan View of the aperture unit. Fig. 10 is a longitudinal cross section of the upper guide roller located above the aperture plate for guiding the film strip across the aperture.

Fig. 11 is a left side view of the aperture unit.

Fig.12 is a horizontal section of the aperture unit on line 1212 of Fig. 13. f

Fig. 13 is a vertical section of the aperture 'unit on line 1313 of Fig. 9.

Fig. 14 is a vertical section showing construction of the aperture unit sprocket support. I

Fig. 15 is a view of'the rear diaphragm.

Fig. 15v is a diagrammatic illustration of the method of arriving at the shape and size of the aperture in the rear diaphragm.

-Fig. 16 is a diagrammatic illustration of the optical influence of the optical system when the optical centers of complementary lens sectors in the revolving system coincide with the optical axis.

Fig. 17 "s a diagrammatic illustration of the optical influence of the optical system when radial edges of complementary lens sectors overlie on the optical axis.

Referring now more specifically to the drawings, in which like reference numerals indicate like parts, 1 is a metallic base late from which rises a web2 (see Fig. 7) w ich carries the main drive shaft bearing 3 in which rotates the drive shaft 4. Fast on my the drive shaft 4 is mounted gear 5 which has integral therewith the film take-up drive andis retained therein by set screw 12. The

shaft 4 is provided with a sleeve 13 fixed thereon. The sleeve 13 has a shoulder 14, which may engage a similar shoulder on a hand crank whenever manual operation is desired.

The actuating mechanism for they optical rectify ing system.

A counter-shaft 15 supported by bracket 1 16 on web 2 has fixed thereto a pinion 17 4), their front extremities being journale whichmeshes with gear 5. The countershaft 15 also bears fast thereto the gear 18 which meshes with gear 19' fast on crossshaft 20 (see Fig. 5). Cross-shaft 20 is mounted in the following manner: A transverse web 21, secured to base 1 and also to web 2 by means of screws 22 passing through lugs 23 on web 2, has cast integral therewith the lower portions of worm wheel cases/24 and 25. The upper portions 24 and 25* are cast integral with the bearing caps 26 and 27 respectively and are held in position by screws 28. (See Figs. 5 and 6.) The crossshaft 20 is mounted in bearings in the lower portions of worm wheel cases 24 and 25 in the following manner: In the lower portion of case 24 are fixed by pressed fitting bronze bushings 29 and 30 which support the left end/of the cross-shaft 20 and maintain the worm 31 which is fixed to cross-shaft 20 in operative contact with worm wheel 32. In the lower portion of the case 25 are press fitted internally threaded steel bushings 33 and 34 into which screw

bronze bearing bushings

35 and 36 which shoulder against opposite ends of worm 37 fixed to cross-shaft 20 and maintain worm 37in operative contact with worm wheel 38. Bronzebearing bushings '35 and 36 are provided with hexagonal ends 35 and 36 whereby these bushings may be screwed inwardly or outwardly so as to throw the cross-shaft 20 slightly to the right or left for a purpose to be hereinafter specified and to prevent end play of this shaft. When

bushings

35 and 36 are set in proper position they may be locked by lock nuts 39 and 40I Upon the left end of cross-shaft 20 is mounted a fly wheel 41.

The worm wheels 32 and 38 are mounted respectively by forced fit upon

shafts

42 and 43, the hubs of said'wheelsbeing journaled in the cases 24 and 25. The

shafts

42 and 43 extend forwardly (see Figs. 2,3, and

in bosses 44 and 45 on frame 46 which is secured to bosses 47 on the front of .web 21 by means of screws 48, after being positioned ma tose by dowel pins 49 on the ends of bosses 50, also on the front of web 21. 1n the center of frame 46 there is a circular aperture 51. The

shafts

42 and 43 protrude beyond their bearing bosses 44 and 45 and are provided with collars 52 and 53 which are set-screwed i in position so that these collars prevent end play of the

hafts

42 and 43.

Optical rectifying system.

her to the number of lens sectors 56 are attached to the'spiders 54 and 55..by screws 58 which may be tightly set up, thus clamping the lens sectors securely in position. These clamps 57 are seated against annular shoulders 59. It will be noted from examination of ljigs. 2 and 3 that the

spiders

54 and 55 and the elements carried thereon are oppositely faced so that the curved-faces of the lens sectors 56 adjacentwhere the lens sectors of the respective revolving elements overlap in the zone surrounding the optical aperture 51 in frame 46. The lens sectors 56 have their radial edges ground to such an angle that they will fit together to form a complete ring with a minimum space between the several sectors. Each of the sectors 56 has on its curved side an area over which the clam 57 fits, which is ground parallel to the p ane side, thus ensuring that the plane surfaces of all sectors in a ring or disc will lie in a common plane which is perpendicular to the shaft whereon the disc is mounted, and also ensurng that the pressure on the glass will 'be applied normally to the surface. Between the clamp 57 and the glass and between the spider and the glass I place on either side a piece of thin paper which forms a'yielding pad to distribute pressures due to slight irregularities in opposing surfaces. also useful as insulators to prevent excessive heat transfer from the glass to adjacent metal parts. Between the clamps 57 are placed.

dowel pins 60 for the purpose of preventing dislocation of the clamps by side shifting when screws 58 arebeing set up. It will be understood that the assembling and add justment of the lens sectors comprising the disc are performed previous to mounting the disc in the machine. When the discs are in position upon their respective shafts the com- These paper pads areaxis, which passes through the center of i axis. The relative angular positions of complei'nentary lens sectors on each disc are such that their optical centers coincide simuL taneously with the optical aXis. Located adjacent to the outer periphery of the discs and symmetrically placed across each pair of adjacent radial edges of the lens sectors 56 is a small patch 61 of opaque material such as black linen adhesive tape of substantially the relative size and shape shown in Fig. 2.

These patches 61 are shown as placed preferably on the curved side of each lens sector so that they may be as near as possible to the equivalent center of the revolving system. The function of these patches 61 will be later described.

Projecting forwardly from the'frame 46 is a pair of studs 62 and 63 which are paral lel to each other and to the

shafts

42 and 43 and located on either side of the aperture Directly above the aperture 51 is a rack 64 supported by a flanged base 65 which is attached by screws to the face of frame 46, A cylindrical front objective mount 66 is slidahly supported upon studs 62 and 63 which pass through bores in lugs 67 and 68 cast integral with said mount 66.. A boss 69 (see Figs. 1 and 4) on the top of mount 66 and parallel to the axis thereof is channeled to receive the rack 64 and is provided with a cover plate 70. At right angles to this boss 69 is a boss 71 bored to receive a retatable pinion shaft 72 provided with pinion 73 which meshes with rack 64. Aknurled handle 74 is mounted on the end of shaft 72. By'turning handle 74 the front objective mount 66 may be moved along the optical axis in either direction.

lVithin the front objective mount- 66 there is slidably fitted the lens tube 75, the inside of which is threaded at the rear end to receive the lens supporting ring 7 6 which carries the front objective 77. Fastened by .screws to the rear of the front objective mount is a rear diaphragm 78 (seeFig, 14) having an aperture 79 which is circular except for V-shaped projections 80 and 81 on the upper and lower parts of the diaphragm respectively. .The function of this diaphragm 78 will be later specified. In the front end of objective mount66 is slidably inserted a tube 82, the front end of which is threaded to receive diaphragm ring 83 in which is mounted'the front diaphragm 84 which is retained in place by a threaded collar 85 which is screwed into the interior of the ring 83. The diaphragm 84 has an aperture 85 the sides of which correspond in curvature and alignment with the outer peripheries of the revolving discs made up of lens sectors 56. The vertical dimension of the aperture 85' diminishes gradually toward its center, its shape being as shown in Fig. 1. The function of this aperture will be later described.

Means for actuating the film strip and adjusting its position relative to the optical system.

The web 2 (see Fig. 7) carries integral therewith the lower sprocket bearing 86 in which rotates shaft 87 driven by gear 88 which meshes with gear 5. ()n' the opposite end of shaft 87 is mounted the lower sprocket 89 of conventional form designed to engage the perforations in the standard film strip. The film strip is held in engagement with the sprocket teeth by idler roller 90, of conventional design, which is supported by a swinging bracket 91 (see Fig. 4) piv-- oted on screw 92 which enters web 2. The bracket 91 carries a pin 93 which bears upon a jack-knife spring 94 designed to retain the idler roller either in or out of' operative position, v

Fast upon shaft 87 is a helical gear 9.) which actuates vertical shaft 96 through helical gear 97 which is fast on shaft 96. The shaft 96 is supported by a bearing in boss 98 integral with web 2. The top of shaft 96 is supported at its upper end by a bearing in bracket 99 attached by screws'to a boss 100 on the top of web 2. The shaft 96 bears, near its top, a helical gear 101 which meshes with a helical gear 102 fast on the upper sprocket shaft 103 which has a bearing in boss 104 on web 2. This upper sprock et shaft. 103 bears the conventional sprocket 105 similar to the lower sprocket'89 and in align menttherewith. The sprocket 105 has an idler roller 106 which'is supported by a swinging bracket/107 pivoted on screw 108- which enters web 2. The bracket 107 car-- ries a pin 109 (,see Fig. 8) which bears upon a jack-knife spring 110 des gned to retain the idler roller 106 either in or out of operan tive position. The brackets 91 and 107 are each provided with a set' screw'lll and lock nut 112 which limit the movement of the idler rollers toward their respective sprockets, thus preventing undue pressurev on the film strip.

Integral with the transverse web 21 are bosses 113 and 114 (see Figs. 5 and 11) which have bores parallelto each other and t0 the optical axis in which are' slidably mounted

rods

115 and 116 which are fixed to the aperture mount 117. Mounted on the side of the aperture mount 117 is a rack 118 which meshes with a pinion 119.- This pinion 119 is fast on rod 120 (see Fig. 7) which .is provided with hearings in offsets in web 2 and extends vertically upward through top casing 121, terminating in hand Wheel 122. By turning the hand wheel 122 the aperture mount 117 and all parts carried thereby may be moved forward and back I 117. This plate 123 is provided with tracks &

along the optical axis. An aperture plate 123 (see Figs. 12 and 13) is attached by screws to the rear of the aperture mount 'or curved shoes 124 on either side of the aperture. The height of the aperture formed by the plate 123 is approximately two and three-quarters times the height of a film picture. Journaled in lugs 125 and 126 (see Figs. 9 and 10) in the top of aperture mount 117 is a shaft 127 which has fixed thereto the roller 128. This roller 128 has a side flange 129 integral therewith whereas the opposite flange 130 is integral with a detached portion 131 of roller 128. The detached portion 131 is free to slide on shaft 127 and is made to rotate with roller 128 by means of the pin 132 which is fixed in detached portion 131 and enters a clearance hole in roller 128. The detached portion 131 is forced toward the roller 128 by spring 133 which shoulders against the enlarged end 134 of shaft 127. The opposite end of shaft 127 is supported by threaded bearing bushing 135 which screws into lug 126. The bushing 135 contacts on its outer end with the collar 136 which is pinned to shaft 127 and on its inner end with roller 128, By turning bushing 135 by means of its knurled annular flange 137 the roller 128 may be shifted transversely to the optical axis and may be locked in a desired position of transverse adjustment by means of the lock-nut 138. o

Mounted in forked lug 139 (see Fig, 14) at the bottom of aperture mount 117 is shaft 140 which carries a sprocket 141 in

alignment Iwith sprockets

105 and 89. This shaft 140 is actuated by a gear 142 fast thereon. bushing 143 fitted closely in forked lug 139' forms a bearing for shaft 140 butting at one end against the gear 142 and at the other end against sprocket 141. thus preventing end play of shaft 140. The bushing 143 is secured by set screw 144. A swinging bracket'145 is pivoted on bushing 143 closely fitting'in the fork of lug 139. Mounted on screw stud 146 (see Figs. 11 and 13) which enters a boss 147 on swinging bracket 145 is a pinion 148 which meshes with gear 142 on the sprocket shaft 140. Press fitted on the extension hub of pinion 148 is gear 149, It will be readily apparent that since swinging bracket145 is pivoted on shaft 140 pinion 148 will remain. in operative contact with gear 142 regardless of the angular position of swinging bracket 145.

Mounted in a boss 150 on web 21 (see -Figs.'4 and 5), which boss has a bore concentricwith cross-shaft 20, is a bell-crank 151 V which may oscillate in said boss. A'stud 152 in the end of said bell-crank forms a bearing for gear 153 which meshes with gear 154, integral with gear 19 which is fast on cross-shaft 20 as previously described.

web 21 is a radius arm 159 which passes.

through a slot 160 in the web 21. The opposite end of radius arm 159 is connected by means of pivot screw 161 to

links

162 and 163, in such a manner that the relative angular positions of the arm 159 and

links

162 and 163 may be varied. The link 163 is connected by means of pivot screw 164 with swinging bracket 145. The lower end of link 162 is split to'straddle tongue 165 on the end of arm 166, being connected with said tongue 165 by pivot screw 167. The arm 166 is fixed in an annular hub 168 pivotally mounted 011 a boss 169 on web 2 by stud 170 (see Fig. 6) which is provided with nut 171 which sets against a spring washer 172, thereby providing the necessary friction between hub 168 and boss 169 to restrain the parts actuated through hub 168 from shifting except by manuipulation' of the handle 173 which enters hub 168. The relative distances between pivotal centers provided by stud 170 and pivot screws 161, 164, and 167 and the pivot in boss 158 are such that for any setting of the handle 17 3 the aperture mount 117 may be moved along the optical axis by operation of the hand wheel 122 without any rotative influence upon the sprocket'141.

It is to be noted that the lengths of link 163 and the radius arm 159 and the relative positions of their several points of pivoted support are all definitely interrelated and are dependent upon the following geometrical considerations; it is apparent that if aperture mount 117 is to be shifted longitudinally without affecting the speed of the sprocket 141 the movement of the pivot screw 164 must be limited to a path of travel which is substantially an are. This are is first determined experimentally by holding gear 154 stationary and restraining'sprocket 141 from rotating while shifting aperture mount 117 longitudinally. This will cause the center of pivot screw 164 to describe an :are

which may be observed and plotted, and from which can be obtained a radius and a fixed center. 163 is this radius andthe position of the pivot screw 161 is the center. It will also be apparent that if gear 154 is held stationary and the sprocket 141 is rotated slightly to a new position and restrained from rotating, and the aperture mount 117 is shifted The e fiective length of link longitudinally, as before, the center of pivot screw 1645 will describe a new arc requiring a relocation of the center at pivot'screw 161. Tn this way a series of center locations are obtained and plotted and from these are obtained the necessary length of the radius arm 159 and the position of the pivot 158.

Across the top of aperture mount 117 is a transverse boss 17 1 through which passes a shaft 175. A bell crank 176 (see Fig. 11) is fast on the end of shaft 17 5. The outer end of bell crank 17 6 is attached by pivot 177 to link 17 8 which is attached by pivot 179 to one end of rocker bar 180 which is" pivoted on screw 181 which enters aperture mount 117. The opposite end of rocker bar 180 is attached by pivot 182 to one end of link 183, the opposite end of which link is pivoted by screw 184 to gate block 185.

Fixed in the gate block 185 is a plunger 186 which enters with a close sliding fit a bore in the aperture mount 117 (see Fig. 12) passing into a cylindrical chamber 187 in a boss 188 on the side of the aperture mount 117. A plunger head 189 on the end of plunger 186 is formed to have a free sliding fit in the chamber 187. A coil spring 190 confined between the bottom of the chamber 187 and plunger head 189 normally holds the gate block 185 in extreme forward

positions Guide rods

191 and 192 which are fixed in gate block 185 enter bores in

pins

115 and 116 respectively and maintain the gate block 185 in vertical position. To move the gate block 185 rearward to the open position illustrated in Figs. 12 and 13 downward pressure is applied to arm 193 which is pinned to shaft 175. 'The arm 193 is pro vided with a knurled grip 194:. A pin 195 mounted in the side of aperture mount 117 is so positioned as to contact with the rocker arm 180 as its lower end comes into alignment with link 183 thereby automatically looking the gate block 185 in extreme rearward position. A slight upward pressure on grip 19 1 immediately releases the block 185 from the locked position thus permitting spring 190 to return the gate block to its forward position.

The gate block 185 is provided with'a vertical slot 196 through which pass the

guide rods

191 and 192 forming supports in the slot for the gate frame 197 which bears integral lugs 198 and 199 (see Fig.7) which are slotted to hook over said

guide rods

191 and 192 thus holding the gate frame 197 rigidly to the gate block 185. The gate frame 197 is thus removably mounted. Hinged on pin 200 which passes through

lugs

201 and 202 on the top of gate frame 197 is bracket 203 between the arms of which is mounted the roller 204. A leafspring 205 secured to the back of bracket 203 and bearing against the top of gate frame 197 actuates the bracket 203'forward'so that roller 204 will hold 2. Elm strip between the

flanges

129 and 130 onguide roller 128.- A

stop pin 206 mounted in the top of the gate frame 197 limits theforward movement of bracket 203 and prevents excessive pressure of roller 204-against the film strip.

Mounted on the bottom. of the gate slots in said plate 207 are mounted curved pressure fingers 208 which are designed to press upon the film strip on either side of each line of perforations thus retaining'the teeth on sprocket 111 in complete engagement with said perforated portions of said film strip. The fingers 208 are spaced and retained in position by pins 209 and 210 and are supported in plate 207 'by means of a;

spring clamp 211 mounted on the back of plate 207.

A rectangular frame 212 mounted within gate frame 197 is held in positionagainst frame 197 is a plate 207 which has a curved portion arranged to embrace sprocket 1&1, Within

lugs

213 and 214 on gate frame 197, which lugs bear upon its transverse portions by means of bow springs 215 and 216 which butt against pins 217 and 218 on the sides of gate frame 197 and also bear against the vertical portions of frame 212. The vertical portions of frame 212 are'curved to correspond to the curvature of shoes 124: of the aperture plate 123, and form spring pressure pads to hold the film strip in contact Slidably mounted on the shaft 96 is a sleeve 220 (see Figs. 6 and 7) which has integral therewith a flange 221 and a cross arm 222. Fixed to shaft 96 above sleeve 220 and spaced apart therefrom is a sleeve 223 provided with a cross arm 224. Two links 225 are hung from the ends of cross arm 224; being pivoted thereto. To each of said links 225 is pivotally attached atits opposite end one-half of a split annular governor weight 226. Links 227 connect vsaid governor weight 226 to the cross arm- 222 on sleeve 220, said links 227 being pivot-- ally mounted at each end. lUpon the rotation of shaft 96 centrifugal force will sep arate the split halves of weight 226 and cause the sleeve 220 to be elevated. An arm 228 pivoted at one end by screw 229 to web 2 carries a roller 230 which bears upon flange 221. The arm. 228 is pivoted at its I other end to link 231 which is pivotally connected with arm 232 which connects with 237 integral with the fire shutter 233. The

fire shutter 233 closes an aperture 238 in the back of casing 235 when the machine is at rest, but when the machine is in operation its normal speed will separate by centrifugal force the halves of governor weight 226 causing the flange 221 to lift arm 228,

thereby raising the fire shutter 233 and holding it in elevated position, so as to open completely aperture 238 through which passes illumination from a suitable light source, which illumination continues through the optical system.

The casing.

Hinged to the rear casing 235 is the right side door 239 in which is mounted a glass window 240. A knob 241 operates a snap catch 242 to hold the door 239-inclosed position. The top casing 121 has integral therewith a box 243 into the concave top of which 248. Above thisdoor is a casing door 249.

The worm wheel cases which are made up of lower portions 24 and 25 and upper portions 24 and 25 are covered by

plates

250 and 251 which are retained by screws. A casing 252 houses the back and sides of the revolving optical system. This casing 252 ,is flanged to partially embrace the right side of the device to the rearward of the revolving system. A housing 253 encloses the right hand gear box composed of parts 25 and 25 (see Fig. 3). The front opening of casing 252 is completely covered by housing 254 which is retained in position bythumb screws 255 and by knurled nuts 256 which screw upon studs 257 which are fixed in the casing 252 and pass through holes in the housing 254. In the rear of each side of housing 252 are hand hole covers 258 and 259 which are retained in place by screws 260. L Mode of operation.

To operate my device power is applied by motor to the friction disc 9 which through eeaoee valve roller 244 and

rollers

245 and 246, whence the film strip passes over the rear of sprocket 105 being held in engagement therewith by the idler roller 106. The conventional loop is then formed before the film strip is passed between the

flanges

129 and 130 of roller 128 where it is held in po sition by the roller 204. Next the film strip passes over the shoes 124 of the aperture plate 123, bridging the aperture and being pressed against said .shoes by the vertical sides of the rectangular frame 212. The film strip then passes over the rear of sprocket 141, being held in position by the curved pressure fingers 208. The conventi onal lower loop is then formed in the film strip which passes over and around the back of sprocket 89, being held in contact therewith by idler roller 90. To facilitate this operation of threading the film strip through the mechanism the idler rollers may be thrown back and the gate frame 197 may be thrown open by depressing knob 194. "ft will be observed that the anti-clockwise rotation' of the sprockets causes the down-- Ward movement of the film strip.

The starting of the machine at once causes lateral displacement of the two halves of the split weight 226 causing the flange 221 to lift arm 228 and elevate the fire shutter 233, thus opening the aperture 238 and allowing light rays from a condenser system to fall upon the film strip and thence pass .through the optical system.

The cross-shaft 20 through worm gear drivesconnectedtherewith rotates the lens discs in opposite directions so that overlying portions thereof are moving down wardly. It is to be noted that for positioning the discs with respect to the relative angular positions of their radial portions, so

that the radial edges of complementary lens sectors may register with each other on the optical axis as in Fig. 2, a very precise adjusting mechanism is provided through the means "described forshifting cross-shaft 20 slightly to the right or left, thus causing sufficient relative shifting of the overlying portions of revolving lens discs to secure the desired registrations. The gear ratios of the mechanism are such that one film picture is passed across the optical axis during the time occupied by the passage of a pair of complementary lens sectors across the optical axis. It will be readily understood that the revolving lens discs are a means of providing the variable refraction necessary for retaining upon a screen an image projected from a, continuously 'moving film strip according to an established principle. I feretofore'in the application of this principle the image has been successfully retained upon the screen but due to inherent character stics of optical rectifiers heretofore employed a periodic fluctuation of the imagev has appeared and this has been of suflicient magnitude to .be objectionable. tempt to overcome this objection has been made through the employment of an outer objective to which is imparted aperiodic movement in the vertical plane. This had been partially successful but has itself occasioned an objectionable periodic distortion of the image owingto the fact that the optical axis is thereby periodically shifted.

Instead of seeking to correct the inherent periodic fluctuation of the image common to optical rectifiers of this general description, and thereby producing a new disturbance as above stated, I have so constructed my device that I have reduced to a negligible amount the inevitable inherent fluctuation so that the image is practically steady and at the same time free from distortion. T have done this by reducing the angle A subtended at the center of the revolving discs by an individual lens sector, and also by reducing the angle B (see Fig. 15), the significance of which will be later described. Thus I limit the extent in variation of the rate of approach to and departure from the horizontal plane passing through theoptical axis by the optical centers of the lens sectors, so limiting the amplitude of fluctuation of the image resulting from this variation that when, for instance, the sum of angles A and B is 29 degreesthe amplitude of fluctuation of the image covering a screen twelve feet in height does not exceed onequarter of an inch and is, therefore, not visible to the observer.

Assuming, therefore, that the machine has been put in operation, the' image of the film pictures which now appears on the screen is centered on the screen by operating framing handle 173, the functioning of which will hereinafter be described. The image is now focused by operating handwheel' 122 and successive images are made to register on the screen by adjusting ;handwheel Should the latter require a considerable adjustment it will be necessary to slightly readjust the focus by turning handwheel 122. in order to illustrate the significance of these adjustments it will be assumed that the motor is stopped and the mechanism. is operated by slowly turning flywheel 41 until. a film picture is centered on the aperture plate 123. With this setting a straight line, which ll have called the optical axis, will pass through the center of the film picture, through the optical centers of the pair of complementary lens sectors 56' on the revolving discs, through the optical center of the front objective 77. and through the center of the image on the screen as illustrated diagrammatically in Fig. '16. For simplicity I have represented pairs of complementary lens sectors 'as well as the front objective by equivalent double convex An atlenses. ltw ill be apparent from Fig. 16 that for this particular setting the optical system is identical to that used in conventional projection lanterns, however, because of mechanical construction, focusing is accomplished by adjusting the film position with respect to the optical system instead of adjusting the lens system with respect to a fixed film position as is the case in conventional projection lanterns. v

Flywheel ll is now turned'tilla pair of film pictures are centered on the aperture plate 123., With this setting the optical axis will passv through the center of the space between the pair of film pictures, through radial edges of the lens sectors 56 on the revolving discs, through the optical center of the front objective 77, and through the center of the image on the screen as illustrated diagrammatically in Fig. 17. The solid lines represent the condition of proper adjustment for registration of successive images on the screen. For any positionof the front objective too close to the revolving system such as the dotted position shown in Fig. 17 it will be noted that the image will be larger and will no longer be centered on the screen. The film picture which is below the optical axis will have its image center below the center of the screen and the film picture which is above the optical axis will have its image center above the center of the screen. If the front objective is located too far from the revolving system the image will be smaller and againthe image centers will not fall on the center of the screen. It will be apparent from an inspection of the construction of the paths of the light rays in Fig. 17 that the axial adjustment of the; front objective will permit the registering of screen images no matter what the value of the distance between centers of pictures on the film strip. The picture spacing on 1 any given film strip at a given time will'be very uniform but itmay. differ by 1% or even more from the picturejspacing on another film strip due to film shrinkage which varies in amount depending on age of film,

chemical ingredients, and previous treatment. I have provided for this front objective axial adjustment to permit correct registration of images for any film strip regardless of amount of film shrinkage.

It will be apparent from an inspection of Fig. 2 that the radial edges of a pairv of complementary lens sectors 56 c'oincide only when they lie in the horizontal line-connecting the centers of shafts 42 and 43'. Forall other positions within the zone of light rays these radial edges intersect at a point, the acute angle between the said radial edges being proportional to the distance between this point of intersection and the optical axis, The areas included within