Patent GB-510692-A (GB)
Title: Improvements in and relating to projection devices
IPC: G03B21/10
Filed: 1937-10-30
Abstract: 510,692. Optical-projection apparatus. PRATT, V. E., and TAKATS, Z. Oct. 30, 1937, No. 29744. Void. Convention date, Nov. 6, 1936. [Class 97 (i)] A film in an optical-projection apparatus is carried; during projection, on a cylindrical, transparent, rotatable support having means extending within it for focusing the projection lens; auxiliary lenses may be provided to vary the image magnification, and also means for moving the film transversely relative to the support, means for feeding it slowly, two-speed means for driving the whole feed-mechanism, and a reflector system, between the projection lens and screen, which is adjustable to project an erect image from images which are erect or side uppermost on the film. Fig. 1 shows a casing for the apparatus having a hinged top 21 and a projection screen 23 on to which the image is reflected by a mirror 261. The mirror 261 may be replaced by a projection screen, the screen 23 being omitted. The lamp house 26 is carried on a panel 25 through which control-knobs 238, 316, and levers 30, 32 project; continuous feed of the film in either direction is normally effected by a crank 39 through a twospeed gear and a chain 59, Fig. 2. The film passes from a spool in one compartment 324 of a removable magazine, and under a roller 163, on to a glass cylinder 165 rotated by the film, and thence, under a roller 162, to the spool in a second compartment 323 of the magazine. Fig. 2 shows the parts in position for threading; rotation of a handle 153 away from the panel 25 secures the magazine in position, and moves a rack plate 125, Fig. 4, so that the rollers engage the film on the cylinder 165. Arms 144, 150 on a sleeve 300 raise the magazine when the knob 316 is rotated and shift the film in a direction perpendicular to the direction of feed to bring a different film track into the optical axis, the construction being such that the knob 316 must first be pushed inwards against the action of a spring 317 to operate through a rod 315 to rotate a shaft 305 within the sleeve 300 and cause an arm 306 upon it to move the rollers 162, 163 out of engagement with the film. The film may be slowly moved in the direction of feed or in the opposite direction by depressing one of the levers 30, 32, the levers being bell-crank levers operating through pins 274 on rods 266 to move the rods longitudinally and cause pawls 271 thereon to rotate ratchet wheels 84 on the spool spindles. The optical system comprises condenser lenses 260, 259, 161, a projection lens 208 within the cylinder, mirrors 214, 223, and 261, and auxiliary lenses 195, 197. Focusing of the lens 208 is effected by rotating the knob 238 to operate through a sector 230 and pinion 229 to turn a pinion in engagement with a rack on the lens cell. The auxiliary lenses are carried on arms 194, 196 which may be turned by a lever 201, Fig. 2, to bring them into or out of position as desired; a pointer 207 indicates the position of the lenses. The mirror 214 is rotatable about the axis of the lens 208, by turning a knob 219, so as to reflect to the mirror 223 and thence to the mirror 261 and screen 23, when the film images extend transversely across the film, as shown in Fig. 13, or to reflect directly to the mirror 261 when the images are longitudinally arranged on the film; the mirror 223 is adjustably carried on a lug 262. The driving mechanism between the shaft 61 of the chain sprocket 60 and the spool spindles 77, 78, comprises a bevel gear on the shaft 61 meshing with a bevel gear 101, Fig. 7, secured to a gear 102. Arms 105, 108, secured together, androtatable about the spindle of the gears 101, 102 by the effect of the drive, carry pinions 107, 110, alternatively meshing with pinions 93, 97, in accordance with the effect of the drive, to drive one or other of the spindles 77, 78 through a friction clutch; the spindles 77, 78 have fluted ends to engage fluted holes in the spools. Brushes 321, 322 engage and clean the surfaces of the glass cylinder 165.