Patent GB-1530041-A (GB)
Title: Film strip projector
IPC: G03B21/10
Filed: 1976-01-05
Abstract: 1530041 Film strip projectors; audio-visual apparatus BELL & HOWELL CO 5 Jan 1976 [9 Jan 1975] 00141/76 Heading G2J [Also in Division F2] The projector includes an intermittent rotary motion device, Figs. 11, 12, comprising gear 384 driven by e.g. an electric motor 380, and a gear with at least one segmental toothed portion 404 and a cylindrical surface 406 about its remaining periphery. Driven gear 340 has toothed portions 412 separated by cam locking means 414 which engage cylindrical surface 406 so that driven gear 340 cannot move during such engagement. Continued rotation of the gear causes teeth 404 to drive gear 340 by engagement with teeth 404, so that gear 340 is driven intermittently. General description. As shown in Fig. 1, the projector comprises a cabinet 34 with a base 38 and a top cover 36 with handle 39, the projection screen 40 being mounted at the front. Tape apparatus 42 is mounted in a drawer which can be pulled out for the insertion of a combined cartridge containing a film-strip and an audio tape. The tape has two tracks, one bearing a commentary related to the images on the film strip, and the other bearing signals which cause the film-strip to move to change the images. The first frame projected is framed exactly by operation of a framing knob 50; subsequent images may be framed automatically. The drawer for the tape reproducer is released for withdrawal by a button 68, which is interlocked so that it cannot be actuated if the film is still engaged with the film gate. Optical system. Light from the projection lens 222, Fig. 2, is reflected by mirrors 60, 62 to form an image on the screen 40. Film and tape cartridge. The cartridge, as shown in Fig. 6, consists of a base with depending flanges 82 and a cover 74 releasably hinged thereto. A standard audio cartridge (84) Fig. 5 (not shown) is held by a spring clip (86) between the flanges 82. The film-strip is held in a coil by springs 140 and passes over sprockets 170 towards the projection gate. The sprockets are carried by a spool journalled in the sides of the cover and driven to move the film through the projection gate. Projector system. A partition 182, Fig. 9, is mounted in the base 38. The partition carries the projection lamp 204 and a condenser system 206, which is mounted for easy removal for cleaning. Light from the condenser is brought to the film gate 46, and light from the gate is reflected by a 45 degrees mirror 220 to the projection lens 222 Fig. 2, for projection to the screen 40 as described above. As the film passes through the projection gate 46, it passes along a film guide 264 to a storage container 266. Film framing adjustment. As shown in Fig. 11, the framing knob 50 is carried by a shaft 280 which is slidable in a boss 296 formed on the bottom of a recess 284 formed in the partition 182. A toothed wheel 300, fast with a clutch element 294, is also journalled in the boss 296. When the knob 50 is pressed so that the shaft 280 moves longitudinally the clutch elements 292 thereon engage the clutch element 294. At the same time the end of the shaft 280 rocks a clutch lever 360. A film driveshaft 314 is journalled in a boss 318 on the partition 182, and carries at its end a driving piece 328 which engages the film sprocket drive 168, Fig. 6. A gear 310, fast with the shaft 314, engages the gear 300 through an idler gear 302. A gear 340 is slidable on the shaft 314 and is fast with a sliding sleeve 344 with a flange 346. Normally a spring 348 surrounding the shaft 314 presses against the flange 346 so that a clutch surface 354 on the gear 340 is pressed into engagement with a clutch surface 356 on gear 310, but this engagement is released when the clutch arm 360 is rocked about a pivot 361 by the shaft 240 to engage the flange 346. When, in this position, the knob 50 is rotated, the shaft 314 is rotated to move the film-strip through the gate until an image is framed. Film drive. A plate 320, which is mounted parallel to the partition 182, supports a journal for the shaft 314 and also supports the reversible D.C. electric motor 380. A pinion 384, fast on the shaft 382 of the motor 380, drives a pinion 386, which is fast with a smaller pinion 392 meshing with a gear-wheel assembly 394. This assembly consists of a plain gear whereon is mounted a partial gear having two sets of teeth 404 symmetrically positioned, with arcuate surfaces 406 therebetween, as shown in Fig. 12. The film drive gear 340 is driven intermittently by the assembly 394 in the following manner. As shown in Fig. 12, the teeth 404 are about to engage a projection 420 at the end of a cam surface 414. Teeth 404 then engage the teeth 412 between the cam surfaces, and gear 340 rotates. When the gear 340 has rotated through 90 degrees, the next cam surface 414 is in engagement with an arcuate surface 406, whereby, although the assembly 394 continues to rotate, the gear 340 is held stationary until the next set of teeth 404 engage the cam projection 416 as before. The assembly 394 carried two pins 408. These pins periodically rock a lever 424 (which has an arcuate recess 430 to allow passage of the pins) so that a micro-switch 428 is operated at each second revolution of the gear 340 opening the circuit to the driving motor 380 and energizing a brake. After projection of the film, the motor 380 is reversed to send the film-strip back into the cartridge 44.