Patent GB-1356279-A (GB)
Title: Double exposure prevention system and camera
IPC: G03B17/42
Filed: 1971-08-18
Abstract: 1356279 Cameras WHITE HOUSE PRODUCTS Inc 18 Aug 1971 [2 Oct 1970] 38797/71 Heading G2A A camera has a shutter release which can be pressed repeatedly when no film is in the camera, but which, when a film is present, can be pressed only in alternation with film advance. Fig. 1 shows the camera when no film is present. The shutter release member 42 is biased upwards by a spring 52. A tripping member 44 pivots on a pin 48, and is pivoted clockwise into the cocked position by a bottom portion 56 of the release 42, against the action of a spring 54' which biases it in the opposite sense. The shutter member 46 is pivoted on a pin 68' and biased anti-clockwise by a spring 70' to cover the exposure aperture 41. When release 42 is pressed, tripping member 44 is freed to pivot anti-clockwise until it strikes a finger 80' on shutter 46, so driving the latter clockwise to uncover the aperture 41. Member 44 continues to pivot so that a leg 76' mounts a ramp portion 84' of release 42. When release 42 is allowed to return to its original position, bottom portion 56 engages leg 88' of member 44 and pushes it back to its original position. A metering pawl 72 see also Fig. 6 (not shown) consists of an elongated strip with a sensing finger 76 at the rear end, a hooked portion 80 at the front end, and a notch 82 at its mid-point. One end of a spring 84 is attached to notch 82, its other end being attached to a fixed point 86 on the camera housing. A front wall 92 of the housing has an opening 90 which is surrounded on the rearward side by four walls 96, 98, 100, 102 forming a trapezoidal chamber 104 open at both ends. The front part of the pawl extends through this chamber 104. The back part extends through a slot 108 in the rear wall 110 of the camera housing, and is pulled across by spring 84 until the finger 76 abuts against the right-hand side of the slot. The spring also pulls the pawl back, until a nose 116 on the hooked front portion 80 enters a depression 114 on the front surface of release 42. In this position the release can be depressed and the shutter tripped, and this action can be carried out repeatedly, e.g. to amuse children, without needing to operate the film transport mechanism each time. If a film is inserted, a double-exposure prevention mechanism comes into operation. The camera shown is of the type in which a film cartridge 16 can be clipped on to the camera between arms 14. The rear end 120 of the sensing finger 76 abuts the film and the pawl 72 is pushed forward against spring 84. A projection 107 aligns with and enters a notch 118 in release 42, and so latches it against depression. As the film 26 is wound across from supply spool 22 to take-up spool 24 by rotating knob 62 in the direction A, a metering perforation 30 comes into alignment with finger 76, which then moves into the perforation because of spring 84. Projection 107, however, still remains in notch 118, so preventing the shutter from being actuated. As the film is advanced further, the end of pawl 72 is pulled over in the same direction, so that projection 107 now moves out of notch 118. The shutter can now be actuated by pressing release member 42. A curved rib 124 on the front of  release 42 engages in the hooked portion 80, drawing the pawl forward. As its rear end disengages from the metering perforation it is pulled over to the left by spring 84. Release 42 moves upwards again under spring 54 until projection 107 once more latches in notch 118. A locking pawl 70 is so mounted by a holding member 128 that it is held in a vertical position and can reciprocate backwards and forwards in the direction of film movement. Pawl 72 passes through a slot 126 in pawl 70, and when finger 76 has been drawn over into the extreme left position, pawl 70 has been drawn into engagement with toothing 68 on knob 62, so preventing any further film transport. When, after an exposure, finger 76 has been pulled over to the left again by spring 84, pawl 70 is drawn out of engagement with teeth 68, so allowing the film to be transported again.