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Shutter Mechanism to Prevent Double Exposures

IP.com Disclosure Number: IPCOM000081434D
Original Publication Date: 1974-Jun-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 57K

Publishing Venue

IBM

Related People

Yarrington, JC: AUTHOR

Abstract

In the operation of certain types of cameras, the photographic film is passed through twice, in opposite directions, exposing one-half of the emulsion surface on each pass. This shutter device for the film cassette prevents reuse of the first side once the second side has been exposed. It is a mechanical interlock to prevent a double exposure on side one.

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Shutter Mechanism to Prevent Double Exposures

In the operation of certain types of cameras, the photographic film is passed through twice, in opposite directions, exposing one-half of the emulsion surface on each pass. This shutter device for the film cassette prevents reuse of the first side once the second side has been exposed. It is a mechanical interlock to prevent a double exposure on side one.

In operation, to expose side one of the film, the cassette 1 is mounted on the camera 3 with side one of the cassette facing the operator, as seen in Fig. 1. The film 4 proceeds from left to right through the camera 3 passing from supply reel 5 to take-up reel 6. The shutter slide 2 is pulled open to the right to allow the film to emerge from the cassette.

When exposing side two, the cassette 1 is placed in the camera 3 with side two facing the operator. The side one take-up reel 6 becomes the side two supply reel 5, and the film 4 again moves from left to right through the camera.

The shutter 2 is once again opened to the right which is in the opposite direction (with respect to the cassette) to the way it was opened for side one. The same actuating device is used in both instances. This device and the shutter design provide the interlock to prevent reusing side one after side two has been exposed.

Referring to Fig. 2, the shutter slide mechanism 2 is shown open for side one exposure. The shutter slide 2 is moved to its open position by pin 7. The pin 7 is constrained by a suitable device, not shown, to enter and leave the elongated slot 8 of the slide 2 at point A only. The front half 10 of the film 4 is exposed in the camera 3.

The slide 2 may be found closed in one of three positions shown in Fig. 3. It is secured thus by a latching mechanism, not shown.

The position shown in Fig. 3a is the nominal position associated with an unexposed cassette 1. More specifically, it is associated with a cassette whose slide 2 has not been opened and closed by the actuating pin 7.

Fig. 3b illustrates the position where the slide 2 is left after exposing side one. It is displaced to the right a distance e from nominal.

Fig. 3c illustrates th...