Patent GB-258612-A (GB)
IPC: G03B21/48
Abstract: 258,612. Foster, W. D. Sept. 19, 1925, [Convention date]. Kinematograph apparatus; optical-projection apparatus.-In a projector or other apparatus driven by a motor continuously operable in one direction, automatic means are provided to stop, rewind, and restart the film for kinematograph projection, and also to stop the film for still projection and restart it for kinematograph projection ; the film may remain stationary for an interval after being wound in each direction, and the automatic control may be exercised by the film itself. The Specification describes a projector embodying the constructional features described in Specification 258,264, the parts thereof being capable of being placed in position for film threading, kinematographic projection, still projection, or rewinding, by movement of a knob 101, Fig. 5, along a slot 102, Fig. 7, so that it occupies one of the positions S<1>, S<2>, S<3>, or S<4> respectively. The knob 101 is carried bv a pin 109 on a disc 160 which is thus rotated as the knob is moved along the slot, and the knob, when manually operated, is capable of being lowered on the rod so as to engage the slot in one of the positions S' &c. and lock the parts. As shown in Figs. 5 and 7, the disc 160 is secured to a pinion 162 engaging a rack bar 163 secured to the cores of solenoids 168, 169, and has a slot 163 engaging a fixed pin 166 so as to limit its movement, and a spring connection 167 to assist in moving the disc to one or other of its end positions, the parts of the projector being respectively arranged for kinematographic exhibition and rewinding when the disc is in such positions. The solenoids are connected in parallel circuits from a battery, and the circuits mav comprise respectively insulated portions of film guides near to the upper and lower film reels. The film may be secured to the reels by copper or like strips, and a length of asbestos &c. may cover part of each strip or extend between the strip and the film. Contact between the strip at either end of the film and the corresponding guide completes the circuit for one of the solenoids and causes the disc 160 to be rotated so as to occupy the other of its end positions and effect exhibition or rewinding. Modification of the means for making contact are described in the Specification, such modifications comprising separate roller contacts engaging the copper strips either at the position of the guides or at the reels, brushes engaging metal clips on the film, spring-pressed discs engaging opposite edges of the film one of which completes the circuit when it enters a recess in the film edge, and pivoted arms engaging the coils of film on the reels and operating a switch arm to complete one or other of the circuits when the coil of film on one of the reels reaches a predetermined diameter. The speed of the motor may be reduced during the time the solenoids are energized by means of a brake drum co-operating with brakes applied to it by means of additional solenoids simultaneously energized, or by means of variable resistances controlled by trips on the bar 163. The movement of the bar 163 may be slowed down, so that the film remains stationary for a time before each reversal, by the provision of a dashpot 184, containing pistons 185, 186 carried by an arm 187 secured to the bar 163. Controllable releases 188 permit the length of the stationary period to be varied, and a slot 189 renders the dashpot ineffective at the beginning and end of each movement so that the bar may then move quickly. The bar, in a modification, may operate the pinion 162 bv means of a pin-and-slot connection to a pivoted segmental rack meshing with the pinion. Fig. 19 shows means whereby a single title or other image may be exhibited for a prolonged period during the run of the film. The edge of the film f is provided with a notch 210 at a suitable point, so that when a spring-pressed finger 211, engaging the edge of the film, enters the notch, a contact 213 is tripped and the circuit of a time relay 215 is completed. The relay controls the energization of a solenoid 218. The core 219 of the solenoid is secured to the bar 163 and is so arranged that its movement causes the knob 101 to move to the position S<2> during the time the relay 215 is operative. The spring 167 returns the knob to the position S<1> after the operation of the relay. The shutter is stationary during still projection and to ensure that it then permits the passage of light, a cam 220, Fig. 21, is provided on its shaft, the cam being engaged by a spring- pressed roller 221 to retain the shutter in open position. Alternatively buttons of magnetic or magnetized material may be provided on the shutter blades, and permanent magnets or magnets energized when the solenoid 218 is energized may be provided to position the shutter. The film end secured to the take-up reel may be formed with an aperture such that intermittent sprocket is inoperative when the aperture lies over the sprocket. The initial movement of the film during exhibition is then produced solely by the take-up reel, and risk of film damage is avoided. Specifications 188,681 and 255,469 also are referred to.