Patent GB-1111765-A (GB)
Title: Film strip precision dynamic plotting projector
IPC: G03B21/00
Filed: 1966-10-14
Abstract: 1,111,765. Writing appliances. BELOCK INSTRUMENT CORPORATION. 14 Oct., 1966 [9 May, 1966], No. 46004/66. Heading B6P. [Also in Division G2] Apparatus for the projection of images scribed on a film strip 32 having an opaque metallic coating on a transparent base comprises a stylus 242 movable in a plane parallel to the film at the scribing station 70 (X and Y directions) and retractable normal to that plane (Z-direction) while the film is driven through trackway 68 to bring a selected frame to station 70 for scribing or re-scribing. Film drive.-Film 32 is intermittently wound between spools (50, 52), Fig. 3 (not shown), by the motor (76) acting through Geneva wheel (88), bevel gears (96, 98), and a belt drive to sprockets (64, 72). The spool shafts are driven through slip-clutches (103, 114). The selected frame is coarsely positioned by the above drive, with centre slightly below the final position and is brought into final register with station 70 by means of spring-loaded pins (122), Fig. 8 (not shown), whose tapered ends enter the film sprocket holes and cam the film slightly into position. Solenoids 134, Fig. 2, shift'the pins through bell-crank hammers 142 with dash-pot damping. Switches 150 sense the position of pins 122 and prevent lowering of the stylus until the film is in register. Frame selection.-Geneva wheel (88), Fig. 3, is connected by reduction gears (90) to a commutator, or counting switch (92), the reversible motor (76) being energized by a frame selection circuit including a set of push-buttons, one for each frame, a forward/reverse sensing means and a start/stop sensing means interlocking with the frame registration pin movement. The final motion of the film to coarsely position the selected frame, as above, is always from the same direction, the film overshooting the final position and returning if necessary. Gate.-Spring-loaded pressure pad 214 having a framing aperture holds film 32 against glass back-up plate 212. The pad is retracted by a solenoid during film movement and is guided by pins extending from the trackway 68. X and Z positioning at the film is controlled by slotted back-up plates 130. Film.-A transparent flexible polyester sheet is coated in two layers, one of pigmented organic resinous material, the other of vacuum deposited aluminium, gold, or silver. Scribing assembly.-Stylus 242 is designed to have a high Z-compliance and a low Z-inertia. An X-motion carriage 244 is slidably driven on shaft 246 and guided by pin 250 and slot 252, the Y-motion carriage 254 being slidably driven on a shaft 256 fixed to carriage 244, and being guided by pins 260 and slots 262. Carriage 254 is spring counter-balanced against gravity. Motors 270, 276 drive the two carriages through kinematic transmission devices comprising thin flexible metal belts 282, 310 each having a tuning fork shape with a connection between the tips of the legs. The output shaft of each motor is fixed to a rolling loop such as 294 formed in each belt. The motor inputs may be digital, analogue, or manual and may be taken from a memory bank or computer or a hand operated potentiometer. Stylus 242 is slidably set in a transparent plate 326, Fig. 2, mounted on the Y-carriage, by means of a flat spring 328 permitting rocking of the stylus in the Z direction by a solenoid for scribing. The stylus is lightly biased against the film by wire 348 stretched between spring arms 346. Shavings from the scribing action are removed by blower and suction means which also cool the film. Optical system.-Light from source 40 passes through condensers 42, scribing station 70, projection lens 44 and filter bank 46. Lens 44 is shiftable in X and Y directions to permit co-ordination with images on the screen from other projectors. The colour filters are counterbalanced and pivotable on a common shaft by separate solenoids, one for each filter.