Wooden I-beam with integrated insulating foam

Two elongated parallel rails have facing surfaces each with a longitudinally extending central groove opening toward the groove of the other rail. A rigid web sheet has its opposite longitudinal margins fitted in the grooves so as to form, in combination with the rails, a composite I-beam construction. Block units of a thickness approximately the same as the thickness of each rail are secured between the rails at opposite ends of the web sheet. Blocks of insulating foam fill the cavities at opposite sides of the web sheet.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to wooden structural members. More 
specifically, the present invention relates to a fabricated composite 
structural member including two parallel wooden rails having wood and foam 
spacing elements between them for use in building construction either as a 
beam or vertical wall stud. 
2. Prior Art 
Known building structural members include I-beams with metal webs, or with 
wood or laminated wooden webs. Various types of foam have been used for 
insulation. 
Patent Cooperation Treaty publication No. WO 81/00585 discloses a girder 
with two parallel wood beams joined by a spacing element of polyurethane 
foam. The foam binds the two beams together, but separated by a distance 
which is adapted to the desired depth for the web of the girder. 
Various wooden I-beam structures are also known in which a structural 
member has parallel wooden beams joined by a wooden web, such as those 
disclosed in U.S. Pat. Nos. 1,377,891; 4,336,678; 3,490,188; 4,195,462 and 
4,191,000. The advantage of such structures is that they provide the 
structural strength of solid lumber while utilizing smaller dimensions of 
wood, thus conserving valuable wood supplies. Such I-beam structures may 
be used, for example, in frame house construction. 
None of the known I-beam structures have contemplated the use of 
polyurethane foam to increase the structural strength of the structural 
member in addition to adding valuable insulating properties. 
SUMMARY OF THE INVENTION 
The present invention provides an I-beam structural member which 
incorporates expanded polyurethane foam fillers. Two parallel wood beams 
or rails are joined by a central wood web and are reinforced at spaced 
locations with wood spacers. The spaces or cavities thereby created in the 
I-beam skeleton on both sides of the central web are filled by one or more 
blocks of expanded polyurethane foam which are secured in position by 
adhesive.

DETAILED DESCRIPTION 
Referring to FIGS. 1 and 2, the structural member in accordance with the 
present invention has two elongated parallel beams or side rails 1, 
preferably wood, with spacing elements between them. The inside face of 
each rail has a longitudinally extending groove 2 opening toward the other 
rail. Wood spacing elements in the form of elongated rigid sheets 3 of 
plywood or particle-board, for example, have their opposite longitudinal 
margins snugly received in the rail grooves 2. A central or intermediate 
block unit 4 of approximately the same height as the rails 1 has 
oppositely projecting tongues 5 received in the rail grooves 2 and end 
grooves 6 registered with the rail grooves to receive the adjacent end 
margins of the spacing elements or sheets 3. 
At each end of the beam there is an end block or filler unit approximately 
the same height as the rails 1 with oppositely projecting tongues 9 snugly 
received in the rail grooves 2. Each end block or filler has a slot 8 only 
in one end, in each instance the inward-facing end, registered with the 
rail grooves 2 to receive the end margin of the corresponding spacer 
element or sheet 3 opposite its end received in the central or 
intermediate block unit 4. Preferably, all of the interlocking tongues and 
grooves are positioned approximately midway between the top and bottom 
longitudinal edges of the rails 1. The interlocking spacer elements or 
sheets 3 approximately bisect the rails to form the web of the composite 
I-beam skeleton. All interlocking joints can be secured with glue or 
adhesive. At each end of the structural member, staples 10 can be driven 
laterally through the rails into the end block or filler unit 7, 
preferably at a location registered with the rail grooves 2. For extra 
strength and to avoid problems with shrinking, the grain of each of the 
wooden end block unit and the intermediate block unit should run parallel 
to the grain of the side rails, preferably longitudinally of the 
structural member. 
When the structural member skeleton as thus far described has been 
assembled, there are four rectangular cavities 14, one toward each end of 
each side of the member. Each cavity is open at the outside, but is 
otherwise fully enclosed by the parallel rails 1, the intermediate block 
unit 4, an end block or filler unit 7 and the spacer sheet or web 3. Each 
cavity is filled with a block 16 of insulating expanded polyurethane foam 
which is secured and strengthened in position by glue or other adhesive 
substance on surfaces 17, as indicated in FIG. 2, so as to form completely 
integrated components of the structural member. The exposed faces of the 
foam blocks are flush with the opposite longitudinal edges of the rails 1. 
The wooden web sheets 3 can be predrilled to have holes 15 for the 
purposes of wiring, plumbing, etc. 
The composite structural member can be used as a building stud to replace 
solid 2".times.4", 2".times.6" or 2".times.8" lumber in frame house 
construction. The resultant stud has insulating properties which are 
superior to those of solid lumber or prior art I-beams by virtue of the 
integrated expanded polyurethane foam. Further, the construction causes 
the overall strength of the composite structural member to be superior to 
both prior art I-beams and solid lumber.