Foil and Method for Protecting Film

The invention relates to a protected film strip as well as to a method for enveloping and at intervals severing such a protected film strip.

It is known that photographic film has to be protected for packaging after being developed so as to prevent damage of the sensitive surface of the film during dispatch to the laboratory and return to the customer. The protective sleeves are generally transparent to permit assessment of the film within the protective sleeve.

For the purpose of enclosing and at intervals severing a protected film strip, two methods have become usual in practice. According to one method, the developed film alone or while adhered to other rolls is fed to an apparatus in which the film is covered with protective foil on both sides. Both outer edges of the foil are then interconnected (welded, adhered, crimped) and form a protective tube which lies flat about the film strip. In this enclosed condition, the film strip can then be sent to the customer rolled together or it is dispatched in handier short sections of generally four to six pictures placed in an envelope.

According another known method, the developed film is immediately severed into shorter sections. These are then dispatched to the recipient either in protective envelopes or in interconnected protective pockets which each receive one film section.

Whereas the steps of enclosing have to a large extent been mechanized, severing of the films into individual sections which are easier to mail is undertaken by costlier manual work. Since the film is protected by the protective sleeve on all sides, film perforations or marginal notching cannot be utilized for precise mechanical advance.

Even if the film is severed without a protective sleeve, cutting and insertion into the dispatch pockets takes place manually.

Apparatus is also known in which the feeding of the unenveloped film, as well as the severing and introduction into the protective pockets, takes place mechanically. Since a comparatively long film section of four to six pictures possesses very little inherent stability because of its considerable flexibility, it is difficult and technically expensive readily to insert the film in the dispatch pockets. The equipment available on the market is therefore expensive and susceptible to faults.

The invention is based on the problem of providing protected film strips which permit mechanical severing into individual sections, particularly in a manner such that marking notches provided in the film to mark the position of the individual pictures can be utilized for mechanical feeding and for recognizing the suitable severing stations.

The solution of this problem is by means of the teaching according to the invention as herein recited.

The enveloping and severing at predetermined intervals of a protected film strip takes place in accordance with the invention by means of the teaching hereinafter provided.

A transparent protective foil strip of about twice the width of the film strip to be protected is coated in its central region with a pressure-sensitive adhesive. When folding the protective foil over onto itself, this adhesive coated region then lies in the fold of the foil. During the folding step, the film to be protected is inserted in the foil and is then enclosed by the foil at both sides. The pressure-sensitive adhesive touches the margin of the film and holds it securely within the protective foil but releasably and without having a residue on the film.

It is also possible to use adhesives which make a bond only when touching each other but do not adhere to the surface of the film. In this case, the two foils are joined through the film perforations and thereby anchor the film section.

For the further processing of the film thus protected, feeding grippers and sensing and regulating elements for a mechanical feeder can engage into the open side of the system. This makes it possible to mechanize the severing steps and also to automate the process when using marking notches to define the cutting position. Thereafter, the severed film sections need only be inserted in a suitable collecting envelope, a step which can be combined in a mechanized manner with the severing apparatus.

The invention will now be described by way of example with reference to the drawing, wherein:

FIG. 1 illustrates the principle of an apparatus with which the foil is folded, the film is inserted in the protective foil and the film is connected to the foil;

FIG. 2 shows the protective foil in the open unfolded condition;

FIG. 3 is a section through the film and foil;

FIG. 4 is an elevation of the complete system of foil and film with diagrammatically illustrated feeding elements which are part of a mechanical feeding and severing apparatus; and

FIG. 5 is a view similar to FIG. 1 of a combining unit for the film and foil but utilizing two separate protective foils.

The process of enclosing and severing at predetermined intervals of the protected film is conducted as follows.

A transparent plastics foil 1 has at its central region a layer 2 with the properties of a pressure-sensitive adhesive. By means of suitable guide tracks, the transparent foil 1 is folded together so that a fold line is created in the central strip 2. At the same time, the developed film 3 is fed as shown in FIG. 1 from a supply reel and then arrives in the operative zone of the pressure rollers 4, 5 which, by pressing on the region of the central strip 2, produce a releasable adhesive bond between the protective foil and the margin 6 of the film strip 3 or between the halves of the protective foil through the perforations in the film.

FIG. 3 clearly shows that the protective foil is connected only to a margin 6 of the film in the zone 2. The composite protective foil and film so created can now be fed directly to a severing station or wound into supply reels for temporary storage.

In a feeding track (not shown) for a severing apparatus, known gripping elements can now intermittently feed the film to a severing station because the margin 7 of the film extends beyond the edge the protective foil and is accessible. Suitable feeding means are either single-tooth grippers, serrated feed rollers which engage the perforations of the film, or friction rollers. Since the margin 7 of the film extends beyond the edge of the protective foil and is freely accessible, marking notches 21 at the edge of the film for controlling the feed can be employed so that optical-electronic or mechanical means 8 scan the position of the notch to determine the cutting position. This edge notching is generally used in developing laboratories for the proper positioning of negative film during automatic copying of paper prints (printer) and for the proper severing in framing apparatus in the case of diapositive reversal film.

As shown in FIG. 5, the process as described above can also be carried out with two separate protective foil strips 9, 10 because, with the aid of the pressure-sensitive adhesive coating 11, 12, it is possible to join the foils to the film 3 at the margin 6 of the film. The advantage of this method is that different foils can be employed, one foil preferably being matte and the other transparent. For the viewer, this provides the advantage that the back of the film adjacent to the matte foil gives him a diffused viewing light whereas the front permits unimpeded viewing through the adjacent clear foil.