Patent GB-516055-A (GB)
Title: Improvements in photographic cameras
IPC: G03B15/00
Filed: 1938-03-18
Abstract: 516,055. Photographic roll - film cameras. CHILD,. A. J., SMITH, W., HALL, J. C., and STOBART, J. W. March 18, 1938, No. 8331. [Class 98 (i)] In a camera for taking a series of photographs, a driving shaft drives the take-up spool of the sensitive strip step by step, for making successive exposures, through a ratchet clutch and an overload clutch, and also intermittently drives means in constant engagement with the strip; and means are provided also to interrupt the drive after a displacement of the strip corresponding to a predetermined number of exposures. The invention includes also provision for marking or severing the strip after each. predetermined series of exposures, provision for indicating the amount of strip in the supply spool and its exhaustion, means for attaching the end of the strip to the take-up spool spindle and for closing and detaching the take-up spool, a shutter mechanism comprising apertured blades oscillating in opposite directions, and provision for raising the shutter mechanism and replacing it by a reflex mirror to permit view-finding through the camera lens. The camera comprises a main casing housing the operating mechanism shown on the left of Fig. 1, and carrying a detachable spool casing (not shown) enclosing a spool 4 supplying film 1 to a detachable take-up spool casing 8 via a gate member 171 hinged to the front of the camera casing and provided with an exposure aperture 175 and film-locating channels. Hinged to the camera casing, in front of the gate, is a lens and shutter casing 127 held closed by a catch 128. Film driving means.-The film is driven by turning a handle 48, Fig. 1, connected through a clutch 46, 47 to a shaft 43 carrying a crank which has a resilient connection with a rod 36 pivoted between ' a pair of discs 34 mounted loosely on a shaft 26, said discs carrying a pawl 35 (Fig. 11, not shown) which engages a ratchet wheel secured to the shaft 26 between the discs 34, so that continuous rotation of the handle 48 produces intermittent rotation of shaft 26, and this drives intermittently an endless belt 29 having projections 30 which engage perforations in the film 1 and so feed it intermittently across the gate aperture 175. Also, on the shaft 26 is a gear 25 driving, through a ratchet clutch 23 a shaft 20 which is geared at its lower end through an overload clutch 17 to a pinion 15 on the take-up spool casing 8, so that the take-up spool 7 is also intermittently driven. The end of'the film is attached to the spool 7 by engaging it between the ends of a spring clip 13 (Fig. 26, not shown) gripping the spool spindle. Drive disconnecting means.-An eccentric 80 (Fig. 2, not shown) on the shaft 43 rocks a forked lever which is pivoted at its middle to the camera frame and at its end to a connecting, rod 73, Fig. 1, carrying a forked plate 76 embracing a shaft 71. Spring pawls on the plate 76 engage a ratchet wheel fixed on the shaft 71 so that, as shaft 43 is turned continuously, shaft 71 slowly turns intermittently. A crank on shaft 71 is pivoted to' a rod 68 whose hooked upper end is spring-pressed against an index wheel 64 rotatable against the action of a scroll spring 67, so that intermittent rotation of shaft 71 causes the hooked rod to turn the wheel 64 step by step, stressing the spring 67. A catch pawl 70 prevents reverse rotation. Pins 61, 62, 63 are set on wheel 64 at different points to correspond with different predetermined numbers of exposures of the film 1. After the number of exposures corresponding to, say, pin 63 has been made, pin 63 rocks a lever 65 which displaces a pin 56 mounted on a lever 51 forming one of a pair of toggle levers, the other lever 50 being pivoted to a yoke 49 whose consequential movement throws out the clutch 46, 47 and-so disconnects the driving shaft 43 from the handle 48. The lever 65 can be set, by a knob 59, for co-operation with any one of the index pins 61, 62, 63. Also mounted on shaft 71 is an eccentric driving a sheave 82 connected by a hooked rod 83, similar to rod 68, with a second index wheel 85 which is thereby rotated, at a slower rate than wheel 64, against the action of a scroll spring 86. A catch pawl 87 prevents reverse rotation of the wheel 85. This wheel makes approximately one turn during the time that the film is fed completely from the supply spool 4, and it carries a pin 206 which, at the end of said turn, engages a lever 205 mounted bn a spindle 208, which lever on the one hand trips the pawls 84, 87 to allow the wheel 85 to be returned by its spring 86 to its initial position, and on the other hand, through a catch 209 on the spindle 208, releases a spring-urged plate 211 which moves forward and covers the viewfinding aperture 134 and indicates thereby that the film supply is exhausted. In an alternative construction (Fig 54, not shown) this indicator plate is actuated from a brake arm 10, Fig. 1, on the spool 4, said arm also carrying a pointer which moves over an external scale to indicate the amount of film on the supply spool. Restoring means.-A control shaft 96, operated by a knob 95, is. axially movable against spring action into one or other of two positions. In one of these, rotation of the knob 95 operates (1) a punch to mark the film, (2) means for releasing the pawls 68, 70 from the wheel 64 to permit its spring to return it to initial position, and (3) means for re-setting the toggle 50, 51 to re-engage the driving clutch 46, 47. In' the other axial position of shaft 96, rotation of the knob 95 operates means for severing the exposed length of film, feeding the loose end thereof into the spool casing 8, moving a cover slide to close the entry-slot of the casing 8, and releasing catches to permit a spring buffer to displace the casing 8 from its mounting for removal. Shutter mechanism.-The main shaft 43, Fig. 1, carries bevel gearing driving a shaft 121 carrying pins at its forward end adapted to engage sockets in a driving disc 126 geared to a scroll cam 143, Fig. 33, operating a slidable member 145 to which are connected levers 147; 148 pivoted at their middle each to one of a pair of oppositely-movable apertured shutter blades 151, 152 mounted on the spindle 153. The other ends of levers 147, 148 are connected by springs 154, 155 to bell-crank levers 156, 157 linked to means 161 for adjusting the period of exposure. A rotating segmental safety shutter also turns on the pivot 153. View finding.-Rotation of a knob 168, Fig. 1, releases the shutter driving disc 126 from engagement with the drive shaft 121 to permit the shutter mechanism to be lifted as a whole in its casing 127, and this movement brings a reflex mirror 132, Fig. 33, into position behind the lens 3 to reflect an image of the object laterally through a viewing aperture 134 in the shutter casing.