Device preventing the simultaneous opening of a plurality of superposed drawers in a common piece of furniture
FIELD OF THE INVENTION 
     The invention relates to office furniture used for storing files, particularly furniture having superposed sliding drawers. 
     The problem posed by such furniture is due to the fact that for obvious reasons of space saving and accessibility of the files, the drawers have a length equal to three or four times their width. This results in considerable overhang when a drawer is pulled right out, and the cabinet will tip over if the weight lying on the lever formed by an open drawer gives rise to a pair of forces exceeding the cabinet&#39;s resistance to overturning. 
     PRIOR ART 
     The device described in French Pat. No. 1 568 229 (BRUNEAU) is characterized essentially in that means are provided for locking all the drawers except one by inclined side rails fastened to the drawers and each cooperating with a roller fastened to the locking rail,in such a manner that only one drawer can be opened at a time. 
     The drawer locking bar is controlled either by the lock or by the opening of the drawers: 
     by the lock: the eccentric of the lock raises the bar as it turns. 
     by the drawer: when one of the drawers is opened the ramp (10) raises the bar (4) by means of the roller (8). 
     The arrangement works well if only one drawer is opened at a time, but if a badly arranged file or any other cause entails the simultaneous opening of two or three drawers, the ramps (10) will raise the bar at the same time and two or three drawers will open simultaneously. 
     The problem to be solved is that of installing a device capable of preventing the simultaneous opening of a plurality of drawers. 
     SUMMARY OF THE INVENTION 
     To this end, the device according to the invention is characterized by the fact that it is composed of at least one safety bar preventing the simultaneous opening of a plurality of drawers (A, B, C) sliding freely between a bottom stop (D) and a top stop (E) in a slide guide (G) fixed against an internal side wall of the cabinet, parallel to a vertical edge bordering the face on which the drawers open, said bar carrying pivots provided with rotating rollers and judiciously distributed over that face of the bar which is directed towards the drawers, and said bar cooperating with rails fixed on at least one side face of each drawer, parallel to and near the bottom of the drawer; by the fact that the safety bar is displaced in the upward direction solely by the action of the rail of the drawers A or B, in the course of their opening, on the roller facing it, while the other rollers, which have been displaced with the bar carrying them by said drawer, lock the rails of the other drawers in order to prevent their simultaneous opening; and by the fact that on the closing of the previously opened drawer the safety bar will through the action of its own weight place a roller in front of the rail of each drawer A or B, with the exception of the bottom drawer (C), which can open without changing the position of the bar, but which locks the latter as soon as it is opened, thus preventing the opening of the drawers A and B. 
     The spacing of the rollers on the safety bar of the drawers is determined by the width of the rail of the center drawer passing between the two center rollers. 
     The top roller is disposed in such a manner as to correspond to the top of the rail of the top drawer. 
     The bottom roller is disposed in such a manner as to correspond to the bottom of the rail of the bottom drawer. 
     That end of the rails which is directed towards the outer face of the drawers and is situated near that face is dihedral in shape. 
     The principal advantage of the device according to the invention consists in that the opening of a drawer, after the key has been turned to release the independent locking means, raises or locks the safety bar, which, sliding freely in its guide between two reference positions, will place at least one roller in front of the rail of each of the drawers A and B, thus preventing their simultaneous opening. The closing of this drawer will return the rollers, through the sliding of the safety bar carrying them, to a position such that the rail of each drawer A and B will bear against a roller. An independent known device enables the cabinet to be locked with the key. 
     Other advantages will emerge from the description of one embodiment, given as a preferred but not limitative example, and from the drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a cabinet comprising three superposed drawers; 
     FIG. 2 is a diagram of the respective positions of the drawer rails and of the rollers when the three drawers are closed; 
     FIGS. 3, 4 and 5 are diagrams of the opening of each of the three drawers. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a schematic section of a cabinet comprising three superposed drawers A, B, C contained in the same cabinet 1 and movable on parallel guide rails (not shown). 
     In order to prevent the simultaneous opening of a plurality of drawers, which would entail the risk of overturning the cabinet 1, a rigid bar 2 is free to slide between a top stop E and a bottom stop D in a guide G fixed on one side face 100 inside the cabinet 1, parallel to a vertical edge 101 situated near that face of the cabinet on which the drawers open. 
     This bar 2 carries pivots provided with rotating rollers 1A, 1B, 1B&#39;, 1C serving to prevent the opening of the other drawers when one drawer has been opened. 
     The distance between the rollers 1A, 1B, 1B&#39; 1C on the bar 2 is determined by the width of the rail 20 of the drawer B passing between the two rollers 18 and 18&#39; when it is opened. The rollers 1A and 1C are disposed in such a manner as to correspond respectively to the top 10&#39; of the rail 10 of the drawer A and to the bottom 30&#34; of the rail 30 of the drawer C. 
     When the center drawer is opened, the other rails 10, 30 then each bear against a single roller 1A, 1C, which thus prevent the opening of the other drawers A and C. 
     Each drawer is provided on its side face directed towards the bar 2 with a rail 10, 20, 30 fixed parallel to its bottom. The end of each rail situated facing the outer face of the drawer has a dihedral shape in order to facilitate its passage above, below or between the rollers 1A, 1B, 1B&#39;, 1C judiciously distributed on the bar 2. 
     The function of the bar 2 can be explained as follows: 
     in the zero position (FIG. 2) the drawers A, B, C are closed; the bar carrying the rollers 1A, 1B, 1B&#39;, 1C is in the lower position against the bottom stop D; 
     the drawers A and B cannot be opened without entailing the lifting of the bar 2 with the aid of the rollers 1A or 1B; 
     the drawer C can be opened without changing the postion of the bar 2 (see position 1). 
     In position 1 (FIG. 3) the drawer C is open, and the drawers A and B are closed. The opening of the drawer C is possible without changing the position of bar 2 against the bottom stop D, but the latter is locked and the rollers 1A and 1B prevent the opening of the drawers A and B&#34; 
     In position 2 (FIG. 4) the drawer A is open and the drawers B and C are closed. The opening of the drawer A raises the bar 2 by means of the top 10&#39; of its rail acting on the roller 1A. This sliding of the bar 2 places the rollers 1B&#39; and 1C in front of the rails 20 and 30, thus preventing the simultaneous opening of the drawers B and C. 
     In position 3 (FIG. 5) the drawer B is open and the drawers A and C are closed. The opening of the drawer B raises the bar 2 by means of the top 20&#39; of its rail 20, acting on the roller 1B; the bottom 20&#34; of its rail 20 bears against the roller 1B&#39;, thus preventing any other displacement of the bar as long as the drawer B is open. In this position, in fact, the rail 10 of the drawer A bears against the roller 1A and the rail 30 of the drawer C bears against the roller 1C.