Method of fabricating hollow, foam-filled, metal structural members

The method of constructing a structural member for use in an architectural or building panel, comprising the steps of fabricating a pair of hollow frame members, each of said frame members being fabricated by shaping a pair of elongted thin sheet metal strips to desired cross-sectional profiles, assembling said profiled strips into a comparatively weak, hollow frame member by positioning the shaped strips in general alignment with one another with the profiled portions of said strips being in opposing spaced relation to one another and with each elongated edge of each strip being disposed adjacent to but spaced from an elongated edge of the other strip, said assembly step for each frame member further comprising bridging the space between the edges in each pair of adjacent edges of said two strips by means respectively of two elongated thermal insulating members which extend respectively along the two pairs of adjacent spaced edges to form two spaced longitudinal joints in said hollow frame member, each of said insulating members being in loose engagement with its associated pair of elongated strip edges at the time of said assembly step to define a gap which extends along each of said joints and through which air may escape from the interior to the exterior of said hollow frame member, positioning said pair of frame members in closely adjacent end-to-end relation to one another, interconnecting said pair of closely adjacent hollow frame members by inserting a hollow reinforcing member having two communicating hollow limbs into the adjacent hollow ends of said pair of hollow frame members respectively to conceal said reinforcing member completely within said frame members, said hollow reinforcing member being fit loosely into each of said frame members to provide a clearance between the exterior of said reinforcing member and the interior facing surfaces of said frame members, and thereafter strengthening said hollow frame members with a rigidifying plastic material by introducing plastic foam material in fluid form into the spaces between said pairs of profiled strips to completely fill each of said hollow frame members and to extend continuously between said two frame members via the communicating hollow limbs of said reinforcing member while displacing air from the interior of said reinforcing member and the interiors of said hollow frame members via said gaps in said joints, said plastic foam introducing step being continued to an extent sufficient to cause said plastic foam material to penetrate into each of said longitudinal joints and into said clearance to close each of said gaps and to form an adhesive bond connecting each of said thermal insulating elements to its associated pair of elongated strip edges thereby to fixedly connect the pair of metal strips in each frame member to one another along said joints and to fixedly connect said pair of frame members to one another at said reinforcing member, the portions of said introduced plastic foam material which penetrate into each of said joints and into said clearance changing in consistency at the time of penetration from a cellular foam to a solid homogeneous material to cause said plastic material to exhibit a higher density in said joints and clearance than in the main spaces within said hollow frame members.