Patent GB-518978-A (GB)
Title: Improvements in or relating to cinematograph apparatus
IPC: G03B19/18
Filed: 1938-09-09
Abstract: 518,978. Kinematograph apparatus. REDLER, A. Sept. 9, 1938, Nos. 26433/38, and 19480/39. [Class 97 (i)]. In kinematograph apparatus comprising a driving element continuously rotating at constant speed to stress a spring which is intermittently operative to actuate intermittent filmfeed mechanism, the driving element can be driven at a relatively low speed to cause successive picture frames to be exposed or projected for a relatively long time for virtual still pictures, and can be driven at a relatively high speed for rapid or kinematograph pictures, without affecting the time taken in feeding the film from one frame to the next the speed of the driving elements may lie. controlled manually or by a notched film through electrical or mechanical means. Figs. 2, 3 and 5 show a construction of projector wherein a ratchet disc 15 on a shaft 14, rotated through variable ratio gearing by a motor 1, winds up a spring 17, connected at its ends to the disc 15 and to drum 18, until the spring stress overcomes the resistance of an adjustable friction brake 25B operable on a pad 25 carried by the drum 18, the drum being then held by a pivoted catch 24A until the shutter has cut off the .projection beam-and being then released to actuate a claw feed mechanism and - feed the film. For one picture per second, the motor drives the disc 15 through a gear 11 secured to a hollow shaft 7, a gear secured to a timing wheel 13, and pawls 13B, Fig. 5, pivoted on the wheel 13 and engaging the disc 15. For sixteen, twelve, or eight pictures per second, the disc 15 is driven through one of three gears 26, 27, 28 all capable of being free on or selectively keyed to the shaft 7, and respectively meshing with gears 29, 30, 31 secured to' the shaft 14, the pawls 13B permitting the disc 15 to overrun the timing wheel 13 during such drive. The key 32A is carried by a rod 32 longitudinally movable in the shaft 7. The timing wheel is formed with sixteen spaced peripheral cams 13A each capable of raising the pivoted catch 24A from a position in which it holds the drum 18 by engagement in a slot 18B therein. The freed drum 18 is turned by the spring 17 until becoming braked, and operating, through a crank 19 on its shaft, and a crank 20 on a shaft carrying a gear 20A meshing with a gear 19A secured to the drum 18, claw feed mechanism C to feed the film one image. The brake pad 25 is secured to the gear 19A and is of spiral form, so. as to produce increasing brake action restraining the drum while the spring is increasingly stressed by rotation of the disc 15, and finally to release the drum so that the catch 24A and slot 18B may re-engage. A wedgeshaped shutter blade 22 is carried by a shaft 23 constantly driven at forty-eight revolutions per second, and is synchronized so that. every third cut-off occurs when a cam 13A raises the catch 24A, the shutter action being thus independent of the number of pictures fed per second. A modification is described in which the variableratio gearing is replaced by a second motor 41, Fig. 7, controlled by a manually-adjustable rheostat 42 and directly driving the shaft 14. The circuit of the motor 41, may be closed and opened under film control by notches in the opposite margins of the film, and by rollers 44, 45 contacting through them to complete circuits of solenoids 46A, 46B alternatively; a pivoted switch arm 46D is moved by the solenoids to make and break the motor circuit. In a further modification, two motors, one controlled by a rheostat, are alternatively coupled to a shaft which drives a claw feed mechanism and a shutter through an extensible spring and a lost motion device. Fig. 11 shows a shaft 55A which carries a cam operating the claw arm, a perforated L-shaped shutter blade 56, and also a crank 57 the pin of which engages a slot in a lever 58 connected to an extensible spring 59 anchored by an adjustable screw 59A. The shaft 55A is driven through half a revolution to extend the spring 59, and is then driven by the spring to feed the film and cut off the projection beam. A continuously-driven shaft 55, Fig. 10A, coaxial with the 'shaft 55A carries a crank 60 .having a driving pin 60A engaging in one-end of a slot 61A in a disc 61 on the shaft 55A. When the shaft 55A is driven by the spring 59, the disc 61 overruns the pin 60A until a spring 60B in the slot 61A contacts with the pin; the pin then moves round the slot to resume the drive. The shaft 55 is 'driven through gears from a shaft 50, Fig. 9, alternatively driven by chains and sprockets 51, 52 from one of the motors; a key 53A on an axially movable rod 53 determines the coupling between the sprockets and shaft, and may be moved manually in both directions or manually' in one direction and mechanically or electrically under film notch control in the other direction. As shown, the rod 53 is in two parts connected by a pin and slot enabling the part carrying the key to rotate while the other part carrying a knob 53B'and a shoulder 53C does not rotate. When the knob is pulled, against the action of a spring 53D, a catch 62 engages under the shoulder. Mechanical means for freeing the catch from the shoulder when a roller enters a film notch is described.