Composite window frame unit - has foam plastic-covered sectional hollow aluminium sections cut-back at mitre joints to allow differential contraction

摘要

The unit is intended for a window or door frame built up from frame sides (1,2) each having a length of aluminium, hollow section (5) with an outer plastic covering (6), partic. externally sealed foam plastic. The sides (1,2) are connected and secured (9c,d,10) at their mitred corners by angle pieces (9) inserted in the sections (5). After mitre-cutting the sides (1,2) the section (5) of at least one side (1) is cut back (11) from its mitre face (1a), pref. by milling, without affecting the remainder of that face. The recess (11) formed by the cut-back may extend into part of the plastic (6).