Patent GB-549934-A (GB)
Title: Improvements in or relating to optical projection apparatus
IPC: G03B23/10
Filed: 1941-07-11
Abstract: 549,934. Optical projection apparatus. KODAK, Ltd. July 11, 1941, No. 8798. Convention date, Aug. 2, 1940. [Class 97 (i)] .[Also in Group XVIII] Means for feeding image elements on a carrier successively into projection position includes a spring member serving to bring the carrier to rest as each element reaches correct position ; the spring may also bring each element into position and may be controlled by an escapement mechanism. The projector may be usable kinematographically or for a succession of " stills," may comprise two or more separate carriers, each provided with a separate optical system and with a shutter operable to produce a dissolve effect as projection is changed from one carrier to another, and may have optical compensation means which may be as described in Specification 549,935. As shown, the projector comprises four annular carriers 44, each supported by rollers 57, 74, 82 engaging its outer surface and by pairs of rollers 64, 67, 78, 79, and 83, engaging its sides, one of each pair being spring pressed. The carriers have lateral teeth 46 by which they are driven, and holders 48 for transparencies 55 cemented to glass plates 54 are secured to them, the holders being formed with gear teeth 50 for rotating an optical compensator. Projection is effected by lamps 26, condensers 27, 28, and projection lenses in mounts 29, the elements being adjustable by means described. The drive of a motor 101 is transmitted to the carriers.through a belt 102, reduction gearing 104, couplings 106, further reduction gearings 100 individual to the carriers, shafts 99, Fig. 13, springs 108, ratchet ,discs 92 and shafts 89 carrying pinions 88 meshing with the teeth 46. Each spring 108 is secured at one end to a disc 98 'fast on one of the shafts 99, and at the other end to a ratchet disc 92. The motor drive continuously rotates each shaft 99 and energizes the springs 108.until one of a number of rises on a cam plate 1.17, also continuously rotated by the shaft 99, turns an arm 115 pinned to a shaft 95 carrying a pawl arm 94, to release the ratchet disc 92; the spring then.first drives the pinion 88 to turn the carrier, and afterwards absorbs the energy due to the momentum of the carrier and brings it to rest just as the next ratchet tooth abuts the pawl arm 94. Each cam plate 117 is angularly adjustable on and secured to a disc 98. Each spring &c. is housed in an oil-retaining casing 86, and the pawl arms 94 have hoods 96 of U-section to trap oil and cushion the abutment. Spring-pressed rollers 123 in recesses form a one-way clutch preventing reverse movement of the shaft 89. Sliding shutters 144 . . . 147 are provided for the projection systems, and each is connected by cables passing from opposite sides round pulleys to one end of a lever 189 . . . 192 positioned by engagement of its other end with a cam disc 181 . . . 184 driven by a shaft 180 &c. from the reduction gearing 104. The cam discs have rises giving any desired projection effect, and preferably produce a cross-dissolve from each projection system to the other in turn. Errors of registration of successive projected images, produced as a consequence of the mass of each carrier, vibration, &c., are eliminated by the provision of an optical.compensator for each carrier The compensators may comprise plane-parallel glass plates 125 turned through 360 degrees during each feed movement by pinions 133 meshing with, and equal in number of teeth to, the teeth 50 on each holder 48 ; such compensators are described in Specification 549,935.