Abstract:
A slat from which door or window shutter may be composed is made of two identically profiled strips, defining between them a concavity.

Description:
BACKGROUND AND FIELD OF THE INVENTION 
     The invention relates to slats from which shutters for doors or windows can be assembled. More specifically, the invention concerns louvre shutters which comprise a rectangular frame in which the slats are rotatably journalled. The so composed shutter may be hingedly connected to the door, window-frame, or may be horizontally slidable in top and bottom rails. The shutters are intended to give protection from light, rain and wind in closed position, and variable light and air influx through adjustment of slat position, and also as protection against unauthorized entry. 
     The earliest shutters of such type had been made of wood. Such shutters could well serve as a protection against sunlight, and in order to be burglary proof had to be very thick, thus heavy and expensive. A further disadvantage of wooden shutters had been that they required much maintenance by frequent painting, but in spite of that, warping and deterioration due to climatic conditions, could not be prevented. 
     It has been suggested--and practised to a certain extent--to make slats out of aluminium. The aluminium slats were hollow bodies manufactured by means of an extrusion process which did withstand climatic influence, particularly when anodized, but aluminium slats are most expensive. 
     Finally, there are known plastic slats which are manufactured also by means of an extrusion process. These are not weatherproof, and are rather weak: they can be easily broken thus giving access to an unauthorized person into the room where shutters made of such slats had been installed. Moreover, these slats are easily bendable, and a person seeking entrance into a room through a door on which a shutter of plastic slats had been provided, needs only to exert pressure from the outside of the slat, bending it so that it bulges inwardly, and as a consequence is forced out of its frame. 
     Where this has been done to a number of slats, these are no longer held in position, and the shutter as a whole, no longer bars entrance into the room. 
     OBJECT OF THE INVENTION 
     It is the object of the invention to provide a slat which can be used in making louvre shutters, which is composed of horizontally extending slats assembled within a rectangular frame, the framed shutter being slidable in a vertical plane or hinged to the windows or door frame. 
     It is a further object of the invention to provide a slat which does not have the faults and disadvantages referred to above and which can be produced at a low cost. 
     SHORT SUMMARY OF DISCLOSURE 
     According to this invention, the new slat is composed of two identically profiled strips, defining between them a concavity, and made of cold rollformed galvanized steel; the two strips when positioned facing one another with their concavities complementing each other, each strip including a portion wherein the material of the strip constitutes a fold resulting in a rib extending along the whole length of the strip, each strip having along one longitudinal edge thereof a lip extending from said edge, while the opposite edge is bent double, two complementary strips being fixedly connected along their longitudinal edges so as to form a hollow slat within which the said rib forming folds extend from one strip toward the other one. 
    
    
     SHORT DESCRIPTION OF THE DRAWINGS 
     In the annexed drawing: 
     FIG. 1 schematically shows the profiles of two strips positioned for connection. 
     FIG. 2 is a fractional perspective view of a slat composed of the two strips of FIG. 1. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     The two strips 1 and 2 indicated by end views thereof, have identical profiles but are turned through 180° (in the plane of their major extension) relative to one another. The strips are made of sheet metal, preferably steel sheet, each strip being folded double in its longitudinal direction, as seen at a. One edge of the strip is bent over on itself at b resulting in a hook-like profile. The opposite edge of the strip marked c forms a lip extending from the plane of the strip. The strips define cavities at both sides of fold a. 
     As shown before, two such strips placed opposite each other their concavities facing one another but one turned through 180° relative to the other, can be assembled to form the slat shown in FIG. 2. To achieve this the lip c of one strip is introduced into the bent over fold b of the complementary strip. The desired permanent connection is achieved by submitting the two marginal portions of the assembly to lock-seaming pressure along the whole length of the two edges. 
     It will be seen that such a slat cannot be bent lengthwise, since the ribs a can withstand maximal bending stress. 
     The strips, before being assembled to form a slat, are galvanized and enamelled, and thus become weatherproof. 
     The shutters made with these slats are absolute weatherproof and almost burglarproof, since a shutter made therefrom would have to be fully demolished in order to gain access into a room closed with such shutter.