INJECTION-MOULDED MICROFILM CONTAINER

Abstract: An integrally injection-moulded rectangular microfilm container with a box (11) and a hinged lid (12), which has co-operating snap-locking ridges (18 and 28) on lateral walls of the lid and of the box, that run in a direction generally parallel with the rear walls (22) and (31) of the lid and the box of the container, whereby easy unmoulding of the container from the mould is obtained.

Description: This invention relates to an injection-moulded generally rectanguloid light-tight container comprising box and lid portions which have meeting open ends which are connected together at rear walls of the box and lid by an integrally moulded hinge and which are provided with snap-locking means comprising co-operating formations on the lid and box for snap-locking the lid to the box against accidental opening. Containers of this type are commercially used on a very wide scale for spools of 16 mm × 30.5 m (100 ft) microfilm. The containers are usually injection moulded from a black-pigmented plastics material, often polypropylene. Such moulding is effected with the container in the completely open condition, the lid requiring to be turned through 180° with respect to the box for closure, to assist unmoulding, that is, separation of the moulded container from its mould. It is also known in the art to design the mould so that none of the opposed walls of an injection-moulded component run strictly parallel with one another. In practice, a wall divergence towards the open ends of the component portions of about 15 to 20 minutes of arc or more is adopted in order to facilitate unmoulding, and in particular, with containers of the kind referred to, a wall of the lid portion, for example the rear wall, may be angled by up to 10° or even more. A container with unexposed film is usually sealed against accidental opening by a label which is stuck on the lid, and/or by a wrapping foil which is heat shrunk onto the container, or by other means. It may happen that a user breaks the seal of one or several containers, and then decides either not yet to use all the unsealed films, or to use only a part of a film for carrying out microfilm recording. Also, the containers are commonly used as a convenient storage box in filing systems for exposed microfilms. Although light-tightness of the containers is relatively unimportant in this use, a reliable closure of the containers is still most desirable for handling during the developing and reviewing of the microfilms. Containers are known of which the lid is provided with small ridges or the like leading along close to the open edge of the lid front wall, those ridges being arranged to co-operate with corresponding ridges near the open end of the front wall of the box, thereby to constitute a snap-locking system for locking the container closed against accidental opening. After the container has been opened for the first time, the snap-­ locking system is the only means on which the user can conveniently rely for keeping the container closed. A satisfactory locking system for the container is therefore indispensible in practice. The cost of producing injection-moulded containers which are provided with locking ridges of that type to form a snap-locking system is increased because the moulds must be provided with movable parts which can be withdrawn from the main mould sections at the undercut locations behind the ridges in order to permit unmoulding of the containers. Moulds of this kind are expensive, and are subject to more maintenance than moulds without movable parts. There are also known injection-moulded containers which are provided with locking means, the effect of which is based on a springy co-operation of two corresponding members. This kind of locking causes a relaxation of the plastic material which results in a progressive reduction of the locking force. It is an object of the present invention to provide an injection-moulded light-tight plastics container which can be injection-moulded by means of moulds which do not require movable parts in addition to the main mould sections in order to allow unmoulding of the container. In this way, the containers can be moulded in a more economical way. According to the present invention, there is provided an injection moulded, generally rectanguloid light-tight container comprising box and lid portions which have meeting open ends which are connected together at rear walls of the box and lid by an integrally moulded hinge and which are provided with snap-locking means comprising co-operating formations on the lid and box for snap-locking the lid to the box against accidental opening, characterised in that at least one lateral wall of the lid and at least one lateral wall of the box are each provided with an elongate snap-locking formation which leads towards the open end face of the respective portion, and in that the direction in which each such elongate snap-locking formation and the directions in which the front and rear edges of the lateral wall on which it is formed are mutually non-convergent towards the open end face of the respective portion. By adopting the present invention, the direction in which the container is separated from a main mould section can be defined by the direction of the snap-locking formations, so that the previous requirement for complicated movable moulds is obviated. The term "snap-locking" as used in the present specification stands for the locking obtained by means of two co-operating members that hook behind each other, with no notable bias in the closed position of the container. In preferred embodiments of the invention, each snap-locking formation is formed on an interior surface of its respective lateral wall, at least one such formation being in the form of a ridge which extends to the closed end of its respective lateral wall. This gives a clean appearance to the exterior surface of the container, while at the same time permitting the avoidance of any undercut mould region behind the ridge. It would of course be possible for the snap-locking formations to be formed as a ridge on one portion of the container which co-operates with a groove on the other. However this entails that the lateral wall in which the groove is formed should be made rather thick in order that it shall have sufficient strength over the length of that groove. Also it can lead to excessive wear of the co-operating ridge. Preferably, therefore, each said snap-locking formation is constituted by a ridge which extends to the closed end of its respective lateral wall. In order to promote a more secure closure, it is preferred that a said snap-locking formation is provided on each lateral wall of the lid and the box. In preferred embodiments of the invention, the or each snap-locking formation on the box extends up to the open end face thereof, and the or each snap-locking formation on the lid is constituted by a ridge which projects beyond the open end face of the lid. This is found to facilitate the introduction of contents into the box portion as compared with embodiments in which a ridge projects from the open end of the box. Advantageously, the face of the or each snap-locking ridge on the lid which will first engage the corresponding snap-locking formation on the box is bevelled so that it is oriented obliquely in the closed end to open end direction of the lid and directly in the front to rear direction of the lid, and preferably also, the face of the or each snap-locking ridge on the lid which will next engage the corresponding snap-locking formation on the box is bevelled so that it is oriented directly in the closed end to open end direction of the lid and obliquely in the front to rear direction of the lid. The adoption of each of these features contributes to a smooth interengagement of the snap-locking formations. Preferably, the or each snap-locking formation on the lid is constituted by a ridge which projects a distance from its lateral wall which distance is greater than the thickness of the ridge measured in the front to rear direction of the container. This promotes a secure interengagement of the snap-locking formations while being economical of moulded material. Some preferred embodiments of the invention have the feature that the lid is provided with at least one rib on the interior surface of its closed end wall, the free edge of the or each such rib being sloped so that it decreases in height from the rear wall of the lid. Such a rib is useful for clamping contents, for example a microfilm spool into position in the container when the latter is closed, and the provision of such a rib which slopes is advantageous for trimming the rib to size should this be necessary to effect such clamping. It is also desirable that such rib should decrease in height from the rear wall of the lid so that clamping forces on a microfilm spool are exerted on the rear flange of that spool. It is to be noted here that some known microfilm containers are provided with an internal rib in their lids which slopes in the opposite direction so that such rib exerts clamping forces on the front flange of a spool. Arranging such a rib so as to exert clamping forces on the rear flange of a spool has the important advantage of relieving counteracting forces exerted between the snap-locking formations because they can easily be located more remotely from the hinge than the rear spool flange, thus leading to a more secure closure of the container against accidental opening. The invention will now be described in greater detail by way of example only with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side elevation of the upper part of an embodiment of container in accordance with the present invention, the lid being shown in its fully open position; Figure 2 is a cross sectional view from the front of the container of Figure 1, along the line 2-2 of Figure 3; Figure 3 is a cross sectional view from the side of the container of Figure 1, along the line 3-3 of Figure 2; Figure 4a is a plan view of the container shown in Figure 1; Figure 4b is a detail to an enlarged scale of part of Figure 4a; Figure 5 is a detail cross sectional view from the side of the container of Figure 1, showing the lid in a position where the snap-locking formations first come into contact; and Figure 6 is a detail cross sectional view from the side of the container of Figure 1, showing the lid in a position with the snap-locking formations in contact but prior to locking. Referring to Figure 1, a light-tight container 10 is illustrated which comprises a generally rectangular box 11 and a generally rectangular lid 12 which are interconnected by a hinge 13. The container has been manufactured by injection-moulding from suitable plastics, such as black-pigmented polypropylene and the hinge has been integrally moulded together with the box and the lid. The moulding of the container occurs with the lid in a position as illustrated in the figure, and the unmoulding of the container occurs by the vertical removal of the inner part of the mould from the outer part, and then the ejection of the moulded component from the outer part of the mould. The lid 12 is provided with an inner peripheral wall portion 14 which fits behind a peripheral wall portion 15 of the box, whereas said peripheral wall portion 15 fits into a peripheral groove 16 of the lid. The peripheral groove 16 extends as far as indicated by the broken line and is formed by a close spacing between the wall 14 and the outer lateral wall of the lid. In this way the container can form a light-tight receptacle for a spool with a roll of unexposed light-sensitive film. The box 11 has only partly been illustrated. The full height of the box amounts in practice to approximately 4 times the depth of the box. The container according to the present embodiment is now described in further detail, with reference to Figures 1 to 4. The lid 12 is provided with two ribs 17 and 18 on the interior surface of its lateral walls 19 and 20. As best seen in Figure 3, those ribs 17 and 18 and the front and rear walls 21,22 of the lid 12 (which define the edges of its lateral walls 19,20) are all slightly mutually divergent in the downward direction of Figure 3, towards the open end face of the lid. The ribs extend beyond the perimeter of the opening of the lid, as may be most clearly seen in Figure 1 for the rib 18, and the ribs are provided at their free ends which laterally facing bevelled faces 23 and 24. These faces are oriented obliquely in the closed end to open end direction of the lid and directly in the front to rear direction of the lid. Other faces 25,26 of the ribs that are comprised between the bevelled faces 23 and 24, and the edge of the lid, are also bevelled, see especially Figures 4a and 4b and are oriented directly in the closed end to open end direction of the lid and obliquely in the front to rear direction of the lid. Portions of the ribs bounded by these faces 25,26 form one half of the co-operating locking ridges of the container. The box 11 of the container is provided with two locking ridges 27 and 28 moulded on the interior surfaces of the lateral walls 39, 40 of the box, and they extend over the full height of the box, up to the open face of the box as illustrated by the broken line 35 in Figure 3. The ridges have slanting surfaces 29 and 30, and they form the other half of the co-­ operating locking ridges of the container. As best seen in Figure 3, those ribs 27,28 and the front and rear walls 45,31 of the box (which define the edges of its lateral walls 39,40) are all slightly mutually divergent in the upward direction of Figure 3, towards the open end of the box. The lid of the container is further provided with two ribs 33 and 34 on the inner surface of the front wall 21 of the lid. The ribs have slanting end faces such as the face 36 shown for the rib 34, see Figure 3. The purpose of these slanting end faces of the ribs is to cause a gentle pressure on the upper end of the front wall 45 of the box when the lid is closed. In this way the free end faces of the ribs have a redressing action on the front wall of the box which has an inherent tendency to curve inwardly of the box, and thus the closing of the container occurs smoothly. The lid 12 is finally provided with two laterally spaced locking ribs 37 and 38 the purpose of which is to engage the rear flange of a film spool in the container, as described already in the introduction of this specification. To that end, the free edges of said ribs are sloped as illustrated by the edge 39 of the rib 38 in Figure 3. The engagement of the rear flange of a spool by the wedge-like ribs is illustrated in Figure 3 for a spool 32, the contour of which has been illustrated in dash-and-dot lines. This rib configuration, which differs from ribs known in the art which have their greatest height near the front wall of the lid, has the advantage that the force for the clamping engagement of the spool acts now much closer to the hinge of the lid so that the counter-acting force at the snap-locking of the lid (which tends to open the lid), is much smaller than in the case when the contact of the rib with the spool flange occurs at the front of the container. The bottom wall of the box is provided with two laterally spaced ribs 41 and 42 which support the film spool in spaced contact from the said wall. The bottom wall of the box also has a small dome portion 43, at the under side of which is located the injection point for the injection-moulding of the container. The operation of the container will now be described with particular reference to Figures 1, 4, 5 and 6. The container being opened as illustrated in Figure 1, a film spool that comprises a roll of either exposed or unexposed film, is inserted into the box, whereupon the lid is closed. In a first part of the closing operation, the lid is swung until an angular position as illustrated in Figure 5 is obtained. In that position, the first bevelled faces 23 and 24 of the ribs 17 and 18 enter into contact with the upper edge of the slanting surfaces 29 and 30 of the ridges 27 and 28 in the box. Further lowering of the lid causes the contact of the box ridges with the lid ridges to move from the first bevelled faces 23, 24 towards the second bevelled faces 25 and 26 of the ribs 17 and 18. The contact between the surfaces of the co-operating ridges causes the ridges to smoothly slide over each other, thereby urging the lateral walls of the box slightly outwardly and the lateral walls of the lid slightly inwardly, under the increasing mutual pressure of the ridges. The angle # (Figure 5) between the co-operating ridges which amounted to approximately 30° at the moment of first contact, progressively decreases towards zero as the lid is further closed. As the lid is urged further towards the closed position, there comes a moment at which the free edges 36 of the ribs 33 and 34 just engage the upper edge of the front wall 45 of the box, see Figure 6. The end of the closing operation of the lid causes the edges 36 to slide behind the front wall 45 and they urge an occasionally inwardly deformed wall in an outward direction, so that such deformed wall becomes straightened, in accordance with the position of such rib edges. At the moment the angle # has become zero, the ridges of the lid have completely moved past each other, and the snap-locking of the ridges under the elastic recovery forces of the corresponding lateral walls of the container has been obtained. The mutual position of a pair of co-operating ridges in the closed position of the lid is illustrated in Figure 3 for the ridges 18 and 28. At the moment the ridges lock behind each other, the slanting end faces 36 of the ribs 33 and 34 have completely passed over the upper edge of the front wall of the box, and the end portions of said faces snap behind said front wall, thereby adding supplemental securing to the locking obtained already by the ridges 17, 18 and 27, 28. At the moment the lid was completely closed, the ribs 37 and 38 entered into contact with the rear flange of the microfilm spool in the container, thereby centering the spool in the container and also immobilising the spool in the container. A container loaded with a spool of unexposed light-sensitive film as described, may be sealed by means of an identification seal stuck on the front of the container over the lid and the box, it may be wrapped in a transparent or opaque foil that also may bear identification data for the photographic material, etc. The locking ridges of the container described hereinbefore, all run in a longitudinal direction which is parallel with the direction of unmoulding of the container, and they are free of undercuts or the like. In this way, these ridges do not interfere with the unmoulding of the container, and therefore the mould components may comprise an outer and an inner main mould section, without any displaceable elements being required in those main sections to allow the proper unmoulding. A container according to the present invention is not limited to the described embodiment. A co-operating groove-and-tongue engagement between lid and box may be omitted, and in such absence of an inner wall wall portion in the lid, the locking ridges of the lid may also be formed by ribs that are freely vertically projecting from the interior of the top wall of the lid, stiffened as the case may be by small side ribs that increase the rigidity of such ribs. The container according to the invention may optionally comprise more than one pair of co-operating locking ridges on each lateral wall. The container according to the invention may optionally be adapted for accepting two types of microfilm spools. As a matter of fact, in the case of 16 mm microfilm spools, the spools onto which the unexposed film is wound have a diameter of 91.7 mm (max. 91.95 mm), whereas spools onto which the exposed and processed film is wound and that are intended for use in a microfilm reader or printer or for storage of the film, have a diameter of 92 mm (max 94.0 mm). The latter spools are further usually transparent, and they have a radial slot which facilitates the threading up of a film. A container according to the present invention that is originally designed for receiving such recording-type spools, may be arranged for receiving also the reading-type spools, by the simple cutting away of a portion at the free edge of the locking ribs 37 and 38, as indicated by the broken line 44 in Figure 6, for example using ordinary scissors. This operation is much facilitated by the location of the highest point of the ribs close to the hinge of the container.

Claims: 1. An injection-moulded generally rectanguloid light-tight container (10) comprising box (11) and lid (12) portions which have meeting open ends which are connected together at rear walls (31,22) of the box and lid by an integrally moulded hinge (13) and which are provided with snap-locking means comprising co-operating formations (17,27; 18,28) on the lid and box for snap-locking the lid to the box against accidental opening, characterised in that at least one lateral wall (19,20) of the lid and at least one lateral wall (39,40) of the box (11) are each provided with an elongate snap-locking formation (17,27; 18,28) which leads towards the open end face of the respective portion, and in that the direction in which each such elongate snap-locking formation (17,27; 18,28) and the directions in which the front and rear edges of the lateral wall on which it is formed are mutually non-convergent towards the open end face of the respective portion. 2. An injection-moulded container according to claim 1, wherein each snap-­ locking formation is formed on an interior surface of its respective lateral wall, at least one such formation being in the form of a ridge (17, 18; 27,28) which extends to the closed end of its respective lateral wall (19,20; 39,40). 3. An injection-moulded container according to claim 2, wherein each said snap-locking formation is constituted by a ridge (17,18; 27,28) which extends to the closed end of its respective lateral wall (19,20; 39,40). 4. An injection-moulded container according to any preceding claim, wherein a said snap-locking formation (17,18; 27,28) is provided on each lateral wall (19,20; 39,40) of the lid (12) and the box (11). 5. An injection-moulded container according to any preceding claim, wherein the or each snap-locking formation (27,28) on the box (11) extends up to the open end face thereof, and the or each snap-locking formation (17, 18) on the lid (12) is constituted by a ridge which projects beyond the open end face of the lid. 6. An injection-moulded container according to claim 5, wherein the face (23, 24) of the or each snap-locking ridge (17,18) on the lid which will first engage the corresponding snap-locking formation on the box is bevelled so that it is oriented obliquely in the closed end to open end direction of the lid and directly in the front to rear direction of the lid. 7. An injection-moulded container according to claim 6, wherein the face (25,26) of the or each snap-locking ridge (17,18) on the lid which will next engage the corresponding snap-locking formation on the box is bevelled so that it is oriented directly in the closed end to open end direction of the lid and obliquely in the front to rear direction of the lid. 8. An injection-moulded container according to any preceding claim, wherein the or each snap-locking formation (17,18) on the lid (12) is constituted by a ridge which projects a distance from its lateral wall (19, 20) which distance is greater than the thickness of the ridge measured in the front to rear direction of the container (10). 9. An injection-moulded container according to any preceding claim, wherein the lid (12) is provided with at least one rib (37,38) on the interior surface of its closed end wall, the free edge (39) of the or each such rib being sloped so that it decreases in height from the rear wall (22) of the lid. 10. An injection-moulded container according to any preceding claim, wherein the open ends of the lid (12) and box (11) portions of the container are formed with an interengageable peripheral groove (16) and tongue (15). 11. An injection-moulded container according to any preceding claim, which is loaded with a microfilm spool.

Inventors: BUELENS, EDWARD, GOOSSENS, CAROLUS CONSTANTINUS
Applicants: AGFA-GEVAERT NAAMLOZE VENNOOTSCHAP
Application year: 1987
Main classification: B65D43
IPC codes: B65D45, B65D43