Light Box

The invention refers to a light box for photographic transparencies or the like.

In a known, single or double-sided light box there is provided for each group of supporting plates a special supporting frame, which can be frontally inserted respectively in the outer frame and can be secured in position therein by snap-closures or by screws. The supporting frame consists of many parts and has to be opened and closed again for a change of the photographic transparency. Such a configuration is relatively complicated, expensive to produce, inconvenient to handle when the photographic transparency is changed, and can only be utilized for light boxes of angular shapes.

The object of the invention is to provide a light box of the aforementioned kind which can be produced especially simply and economically and which, while providing a safe support of the supporting plates of the transparencies, permits a quick and simple frontal change of the photographic transparency.

The object of the invention is solved by a light box of the kind mentioned in the preamble of claim 1, firstly, by the features mentioned in the characteristic part of claim 1.

The light box according to the invention can be extremely simply and economically made of aluminium as well as plastic. The supporting plates receiving between each other a photographic transparency can respectively be directly inserted frontally in the outer frame and are simply and safely secured by the attachable sealing profile strips. For the purpose of changing the photographic transparency, the sealing profile strips can quickly be detached without tools. Simultaneously, they form a respective frontal decorative element, because the covering part, regardless of its function in the edge support of the supporting plates, can be configured in many ways in order to achieve a visual effect.

Preferably in the retaining pocket, there is an approximately U-shaped, resiliently deformable clamping profile part, which can be made of PVC, polyethylene or any other suitable, elastic material, for example also rubber. This clamping profile part forms a compensating element in case of deviations of tolerance and changes of shape of the light box due to mechanical or thermal influences and at the same time increases the grip with which the plug-in portion of the sealing profile strip is secured in the retaining pocket.

Further details and advantages of the invention result from the following description and the drawing, in which two exemplary embodiments of the object of the invention will be illustrated in greater detail.

FIG. 1 is a broken-away sectional view through a single-sided light box according to the invention;

FIG. 2 is an illustration similar to FIG. 1 of a light box according to the invention, of a double-sided configuration, and

FIG. 3 is a broken-away enlargement of a sectional view of an edge area of the cross-sectional profile of the outer frame.

The single-sided light box illustrated in FIG. 1 essentially comprises an outer frame 1, which usually consists of a number of frame supports which are joined together. The cross-sectional profile of the outer frame 1, or the frame supports thereof, comprises a thin wall part 2 and longitudinal molded projections 3, 4 extending along the inside thereof. As can be seen in FIG. 1, and in particular in FIG. 3, the frontal longitudinal edge area 5 of the wall part 2 and an angle flange 6 extending longitudinally on the inside thereof define a frontally open retaining pocket 7, in which there is disposed a clamping profile part 8 made of an elastic material, such as for example, PVC or polyethylene. This clamping profile part 8 can extend as a strip along the entire length of the retaining pocket 7. However, the clamping profile part 8 can also be configured in sections of various lengths, which can be distributed and arranged at a respective distance over the length of the retaining pocket 7.

The clamping profile part has an approximately U-shaped cross-section and has inwardly bent side legs 9, 10 and a floor leg 11. On the outside of the side legs 9, 10 and along the free edges thereof, the clamping profile part 8 is provided with longitudinally extending retention projections 12, 13 having approximately a semi-circular cross-section, the retaining projections 12, 13 engaging in their turn in the opposite walls of the retention pockets 7 in longitudinal grooves 14, 15 of approximately semi-circular cross-sections. Thus the clamping profile part 8 is thereby arrested in the retaining pocket 7 without thereby impairing the deformability of the side legs 9, 10. The side legs 9, 10 along with the floor leg 11 define a pocket 16, of which the inside diameter, due to the arched curvature of the side legs 9, 10, which begins at the entrance opening at the level of the retention projections 12, 13 at first becomes narrowed and then widened again towards the floor leg 11.

The leg of the angle flange 6 extending parallel to the wall part 2 or to the longitudinal wall area 5 thereof is provided with an inwardly protruding, longitudinal abutment flange 17 which forms the inner abutment for two supporting plates 18, 19, between which is arranged a photographic transparency which is not illustrated. Thus the supporting plate 19 usually consists of a ground-glass diffusion plate and the supporting plate 18 of a clear-glass plate.

The supporting plates 18, 19 are being held in their mounting position by a sealing profile strip 20 extending along the entire length of the retaining pocket 7, i.e., along the entire circumferential length of the outer frame 1. The sealing profile strip 20 is provided with a plug-in part 21 which engages in the pocket 16 in the clamping profile part 8, as can be seen especially clearly in FIG. 3. During the insertion of the clamping profile part 8 into the pocket 16, the plug-in part 21 expands the inwardly arched side legs 9, 10 which make contact with the plug-in part 21 due to the deformation from the pressure. The plug-in part 21 can have a thickness which increases from the covering part 22 towards its free end, as illustrated, which reinforces the fastening of the covering profile strip 20. The maximum thickness of the plug-in part 21 at its free end is somewhat less than the maximum width of the inner cross-section of the pocket 16 in the clamping profile part 8, as provided at the height of the floor leg 11. In connection with the dimension of the parts, to which it is expressly referred to in FIG. 3, it safeguards that upon the insertion of the plug-in part 21 of the sealing profile strip 20, the clamping profile part 8 can be freely deformed and leaves sufficient compensating play. It is preferable in this connection, that the clamping profile part 8 is engaged only in the area of the retention projections 12, 13 with the walls of the retaining pocket 7, i.e., that it is to some extent freely suspended.

The covering part 22 of the sealing profile strip 20 overlaps the retaining pocket 7, ends on the outside at the outer surface of the wall part 2 of the outer frame 1 and projects inwardly beyond the angle flange 6 so that together with the abutment flange 17 it forms a groove-shaped pocket for the edge support of the supporting plates 18, 19.

In the configuration according to FIG. 1 the backside of the light box is closed by a back wall 23 which can be fastened by screws which can be screwed into a longitudinal groove 24 in the molded projection 4. On the inside of the light box there are provided one or more fluorescent strip lamps which can be supported together with the respective control components on the back wall 23. However, for the support, there can also be used flanges 25, 26 extending parallel to the wall part 2 and which are tip-stretched on the angle flange 6 or molded projection 4.

In the double-sided configuration of the light box illustrated in FIG. 2, the rear longitudinal edge area 5' of the wall part 2 along with a respective angle flange 6' defines a holding pocket 7' which is open in the rear and which forms with a respective sealing profile strip 20 an edge support of the same kind for rear supporting plates 18', 19'. Preferably, the cross-sectional profile of the outer frame 1 is symmetrical to an imagined median plane parallel to the longitudinal edges of the wall part 2.

For the support of the fluorescent strip lamps, the wall part 2 is provided on the inside with additional longitudinal flanges 28.