Patent GB-774922-A (GB)
Title: Improvements in or relating to drum type photographic cameras
Inventor: TAYLOR HAROLD
IPC: G03B41/02
Filed: 1954-11-17
Abstract: 774,922. Photographic cameras. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Nov. 14, 1955 [Nov. 17, 1954], No. 33341/54. Class 98(1) A drum type photographic camera has at least two film paths extending end to end around the circumference of the drum, and for each path a film supply carrier and a film take-up carrier. As shown in Fig. 1. the camera drum 4 is mounted for rotation about a vertical axis within a casing 3 mounted on a central table 1. Tables 2 on either side of the table 1 support cabinets 8A, 8B, each enclosing a vertical bank of six cathode ray tubes 7. Lenses 5 on opposite sides of the drum 4 are connected by bellows 10 to light screening boxes 9 which are mounted in front of each cabinet. Each cabinet 9 has an inspection tube 11 by means of which the cathode ray tubes may be viewed for adjustment. Each screening box 9 also has a cylindrical shutter 13A or 13B, rotatable either by a manually operated knob 14 or by an electric motor 15A or 15B. As shown in Figs. 3 and 4, the drum 4 has a removable upper wall 19, below which are housed supply spools 17a, 17b and take-up spools 18a, 18b. One film a is led from the supply spool 17a over one side of a driving sprocket 28, over an idler roller, through a slit 32 in the drum periphery, and then passes half-way round the drum, being located by 'a channel 16. The film re-enters the drum through a second slot 33, passes over an idler roller and engages one side of a second driving sprocket 27 before being wound on the take-up spool 18a. A second film b is lead from the supply spool 17b, over the other side of the driving sprocket 27, through slot 33, then half-way round the drum, through slot 32 and over the other side of the driving sprocket 28 to the take-up spool 18b. The drum 4 is supported for rotation by a hollow shaft 35 which is embraced by a stationary sleeve 37 attached to the underside of the surface 36. An electric motor 39 mounted on a housing 38 at the base of the sleeve 37 drives a shaft 41 which extends through drum shaft 35 to drive the drum 4 through the wall 19 and a safety clutch, the members 42, 43 of which are pressed together by a compression spring 45. The shaft 41, in order to drive the take-up spools as well as the drum, carries a gear wheel 47 constituting the input of an epicyclic gear, also including planet gears 48 carried on a brake ring 50 which is freely rotatable about the shaft 41. Each planet gear 48 has an integral gear 51 which meshes with an epicyclic gear output wheel 52 freely rotatable on the shaft 41. The gear ratio between wheels 51, 52 is slightly less than the ratio between wheels 47, 48, so that if the brake ring 50 is arrested, the output wheel 52 will rotate in the same direction as, but slightly faster than, the driving shaft 41. If, however, the brake ring 50 is not arrested, then there is no relative rotation between the output wheel 52 and driving shaft 41. The epicyclic gear output wheel 52 is attached to a differential gear carrier 53 which is similarly freely rotatable on the shaft 41. The carrier 53 supports four shafts 54, two of which carry a pair of lower planet wheels 55 and the other two a pair of upper planet wheels 56 of similar size. Each upper planet wheel 56 is enmeshed with one of the lower planet wheels 55, and wheels 55 are also enmeshed with a gear 57 carried on an inner sleeve 58 freely rotatable on the shaft 41 and surrounded by a freely rotatable outer sleeve 60 carrying a gear 59, of similar size to gear 57, meshing with the upper planet wheels 56. The inner end and outer sleeves 58 and 60 are connected by axially disengageable dogs 62, 63, to inner and outer bushes '64, 65 extending through the lower drum wall 21 and carrying gear wheels 66, 67 of similar size which mesh through idler gears 68 (only one of which is shown in Fig. 3) with wheels 25 and 26 mounted on the spindles 24 of the receiving spools 18a, 18b. The differential gear enables the drive sprockets to be driven at different speeds if necessary to allow for variations in the film perforations, or in the diameters of the film rolls. The mechanism enables the drum to be driven at a chosen speed during the exposure of both the spools of film and also enables exposed portions of film to be replaced by unexposed portions without stopping the drum by arresting the brake ring 50. To this end, the brake ring 50 may be engaged by an armature 70 of the brake solenoid 69, which is energized by depressing a switch 72. This completes a circuit through normally closed contacts 71 and a holding relay 61. The winding of the film rotates a timing gear 74 on the drum which describes one revolution as the exposed film is entirely replaced. Gear 74 carries a striker 75, which, at the completion of the revolution, opens the contact 71 to de-energize solenoid 69 and holding relay 61. A permanent magnet 78 is attached to the underside of the drum so as to generate electric signals in two coils 77a, 77b fixed to the table 1 on opposite sides of the drum axis. Exposure is effected by brightening the traces of the cathode tubes 7, by a circuit which is so arranged that brightening can only occur between successive signals in the coils 77a, 77b, so that neither film is exposed more than once. A control box 79 (Fig. 1) on the table 1 has a rotary switch 80 which controls the camera so that both the films on the drum may be exposed simultaneously to the two banks of cathode ray tubes, or that the film on one side of the drum may be exposed to the first tube bank, or that the film on the opposite side of the drum is exposed to the second tube bank, or vice versa. Indicator lamps 90, 91 indicate which tube bank is being exposed to which film. Indicator lamps 88, 89 indicate the open and closed positions of the shutters 13A, 13B. An exposure is initiated by pressing a button 97, and a neon lamp N is lit after beam brightening has taken place and is extinguished only on operation of a manual control 96 which must be pressed before further beam brightening can take place. The cathode ray tube beams may be brightened by manual control 103A, 103B for monitoring purposes. A "recording brightness" button 104 operates when both shutters 'are closed to feed pulses simulating those of the drum coils 77a, 77b to the tube banks in order to check operation of the brightening pulses. Electric circuits associated with the controls for carrying out the functions referred to above are described in detail. An electrical drum revolution counter may be provided. In an alternative construction, two or more coaxial drums may be driven together, and each drum may be divided diametically or segmentally to provide a number of separate film paths.