
{"publication_number": "US-4382460-A", "abstract": "a slat from which door or window shutter may be composed is made of two identically profiled strips , defining between them a concavity .", "application_number": "US-32386981-A", "description": "the two strips 1 and 2 indicated by end views thereof , have identical profiles but are turned through 180 \u00b0 ( 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 \u00b0 relative to the other , can be assembled to form the slat shown in fig2 . 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 ."