US1944132A - Roll film for photographic cameras - Google Patents

Description

Jan. 16, 1934.

W. NAEWIGER ROLL FILM FOR PHOTOGRAPHIC CAMERAS Filed Aug. 5, 1953 J72 z/azfor:

VZJW

Patented Jan. 16, 1934 T T E S ROLL FILM FOR. PHOTOGRAPHIC CAMERAS Wilhelm Naewiger, Dresden, Germany Application August 5, 1933, Serial No. 683,825, and in Germany January 4, 1933 1 Claim.

This invention relates to roll films for photographic cameras.

In the case of the known roll films which are intended for use in photographic cameras, the light sensitive material (hereinafter termed the film) is rolled up on spools in strip form, together with another strip which protects it from the light and is usually made of paper which is black on its inner side and red on the other. The film is generally made in a length which is suitable for six, eight or more exposures. It is, therefore, necessary either to expose the entire film within a short time, which is often undesired for reasons of economy, or to wait until the whole film has been gradually exposed before developing it.

In order to obviate this disadvantage it has repeatedly been proposed to subdivide the film into two or more parts corresponding to the size of the exposures. In order to be able to remove these parts separately in daylight a sufficient length of the protective paper was provided between the parts of the film so that the separate parts of the film could be removed after being exposed without making use of a darkroom.

In order to facilitate the separation of the exposed portions, the protecting paper has previously been provided with cut out portions. These have the disadvantage, however, that the strips cannot be rolled up tightly because hollow spaces are formed at the cut out portions, at the edges of the spool.

A more advantageous method, which has also previously been proposed, was to provide the strip of protective paper with perforations. In this case the protective paper was firstly perforated on a line running across the strip at right angles to its edges and secondly on two further lines running at an acute angle from the two edges of the strip, which is to protect the unexposed film, to two points on the first line at a small distance on either side of the centre of the strip, so that, when the strip was torn along the perforation, the end forming the beginning of the second part of the roll was in the form of a tongue of the proper shape for insertion into an empty spool, while the other end of the strip forming the end of the exposed part of the roll was straight and at right angles to the edges of the strip. This method, however, has still considerable disadvantages. The perforation at right angles reduces considerably the tenacity of the protective paper. This becomes observable when manufacturing the spools. The spooling is effected under tension so that the paper is liable to be torn at this transverse perforation. Tearing is favored by the fact that the thickness of the paper for divisible spools must be reduced as far as possible in order to obtain a reasonable diameter of the spools. Thus the transverse perforation involves a higher waste of material in the manufacture of the roll films.

-A further important drawback is due to the fact that no regard was paid to the closure of the first exposed film. Gummed paper is not always readily available. If the back of the protective paper he gummed in the middle, a tight closure is not ensured. If however the paper be gummed over its whole width it is diificult to open the spool in the darkroom.

The object of the present invention is to avoid these disadvantages.

For this purpose the protective paper is prepared for being separated in the manner hereafter described and illustrated by the annexed drawing.

In the drawing a. is the protective paper seen from its inner or back side. b is the exposed photographic film, and b the unexposed photographic film. Now the protective paper in the middle between the twd photographic films is perforated on the lines 01, c2, c3, and c4 cutting out of the paper two triangular pieces d, d the points of which are connected by a further perforation on the line e. The triangular pieces d, d are gummed on their inner side (black side) as shown by dotted lines. After exposure of the first photographic film b the protective paper is separated on the lines 03, e, 04 thereby forming a tongue by which the protective paper of the second portion may be inserted in an empty spool. Then the end of the protective paper of the exposed portion is wound up and the two lateral tongues 12, d are stuck down. The spool which has been stuck down in this manner can be very easily opened by grasping the middle portion e, which has not been gummed and tearing it from the spool. The strip is thereby separated along the lines of perforation c1, 02.

I claim:-

A spool for photographic purposes, comprising a continuous opaque backing strip and a plurality of sensitized portions of film mounted successively thereon in spaced relation, said strip being provided in the middle between the adjacent ends of two successive films with perforations by which two triangular portions and two frustc-triangular tongues at the ends of the separated backing are formed, the triangular portions being gummed on their inner side.

WILHELM NAEWIGER.

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