Title:
TRUSSED JOIST STRUCTURE
United States Patent 3748809


Abstract:
A special structure particularly applicable for a mobile home roof support including a joist frame braced with steel web members having flat connecting ends and an angled body portion.



Inventors:
JACKSON E
Application Number:
05/169998
Publication Date:
07/31/1973
Filing Date:
08/09/1971
Assignee:
STEEL WEB CORP,US
Primary Class:
Other Classes:
52/693
International Classes:
E04C3/292; (IPC1-7): E04C3/42
Field of Search:
52/693,692,690,643,644,639,695,694,45,143,DIG.6
View Patent Images:
US Patent References:
3570204N/A1971-03-16Birkemier
3531904REINFORCED CONSTRUCTION FOR WOOD STRESS MEMBERS1970-10-06Sanford
2732251N/A1956-01-24Meaker
2159589Roofing-truss structure1939-05-23Edison
2068052Joist1937-01-19Coddington
1899344Composite wood-metal structural member1933-02-28Macomber
1523711Builder's hardware1925-01-20Powell



Foreign References:
GB613947A
DE857139C
Primary Examiner:
Murtagh, John E.
Assistant Examiner:
Friedman, Carl D.
Claims:
I claim

1. A trussed joist frame structure comprising

Description:
BACKGROUND OF THE INVENTION

Prior to this invention difficulty was experienced in providing adequate support for mobile home roofs which was light in weight, durable, easy to use and not unreasonably expensive.

The existing conventional structures used for this purpose often were secured by glue and with gussets which tended to fail under stress. When such structures were made heavy enough to be durable, even further stress and consequent breakdowns of the structure were likely to occur. On the other hand, conventional lightweight roof supporting structures did not have sufficient rigidity and strength to be adequate for the heavy loads of large mobile homes.

Consequently, the primary purpose of this invention is to provide roof supporting structures adequate for large mobile homes which are light in weight and, at the same time, form a durable rigid support.

Other objects and advantages will be apparent from the following description.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial view, in perspective, of a mobile home utilizing trussed joist structure shown in ghost views in accordance with this invention.

FIG. 2 is an elevational view of a trussed joist taken through the vertical plane of support of 2--2 in FIG. 1 showing upper and lower chord members interconnected by short vertical compression web members and diagonal tension web members.

FIG. 3 is a fragmented perspective enlarged detail view of the diagonal tension web members interconnected to the upper and lower chords.

FIG. 4 cross-sectional view taken through 4--4 of FIG. 3 showing the angle formed section of the central body portion of a diagonal tension web member.

SUMMARY OF THE INVENTION

The special lightweight, rigid structures in accordance with this invention, which are particularly applicable for use as mobile home trussed joist roof supports include spaced upper and lower chord members connected by short, generally vertical compression web members and interconnected, diagonally mounted, steel web tension members.

DETAILED DESCRIPTION

Referring to the drawings, a preferred embodiment of this invention is illustrated which, in general, includes specially trussed joists 10 for support of a mobile home roof 12. Each of these joists 10 has a frame which includes an elongated upper chord member 14 and a matching, elongated lower chord member 16 spaced vertically below it. The joists 10 are interconnected parallel to each other and spaced laterally sufficient to provide the required roof support.

A plurality of horizontally spaced, short, vertical web members 18 interconnect the upper chord member 14 and the lower chord member 16. Toward the end of a joist 10 the chord member 14 and 16 approach closer to each other, so that they are interconnected by a vertical web member that functions as an end web member 20 which, as shown, takes the form of a short block shaped to conform to the adjacent abutting portion of the chord members.

In between at least some of the vertical web members 18 are diagonally mounted angled web numbers 22 which extend in a generally vertical plane interconnecting the upper chord member 14 and the lower chord member 16. These angled web members 22 are formed with an angled central body portion 24 terminating at a flat upper end 26 intended to be secured to the upper chord member 14 and a flat lower end 28 intended to be secured to the lower chord member 16.

Ordinarily, the angled web members 22 are made of steel strap which permits maximum strength with minimum weight. The legs which join to form the angled central body portion 24 extend approximately equally from their common juncture to their terminal edges.

In use, in the form shown in FIG. 3, the angled web members 22 are mounted between two vertical web members 18 (or end web member 20 when adjacent to an end) of a joist 10 by sliding the flat upper end 26 in between two separate wooden elements of the upper chord member 14 adjacent to one vertical web member 18. Similarly, the flat lower end 28 is slid in between two separate wooden elements of the lower chord member 16 adjacent to another vertical web member 18. The flat ends 26 and 28 are secured in place by suitable means. In the form shown in FIG. 2, the flat ends 26 and 28 are mounted between the respective upper and lower chord members 14 and 16, and the adjacent respective vertical web member 18 or end member 20.

Thus, as so mounted the angled web member 22 extends diagonally between upper chord member 14 and lower chord member 16 with the opposite ends 26 and 28 each adjacent to a vertical web member 18. A particularly strong, rigid, truss support for the joist 10 is provided by this structure since load bearing pressure on the chord member 14 and 16 causes tensioning of the angled web member 22. Such tension induced load is effectively carried by the angled web member 22 under compression of the vertical member 18, since the normal load bearing pressure is through the vertical plane of the upper and lower chord members 14 and 16, and the fastening of the ends 26 and 28 by staple or nail fasteners pass through the connected chords as in FIG. 3 or chord and vertical member 18 as in FIG. 2. This structural arrangement permits the maximum strength of the angled web member 22 to squarely meet the vertical load bearing force thereby allowing the weight and number of bracing supports for the joist 10 to be reduced to the minimum.

It is vital to the performance of this invention that the staple or nail fasteners 29, when used, extend through the connected wood members and ends 26 and 28,with sufficient penetration to, not only hold the members in position under the tension stress of a load, but also, bind the members and end of the fastener ruptured angle web member by friction pressure. In this regard, the fasteners are driven blindly through the confined metallic end terminals 26 and 28.

As an example, this truss joint structure may used chord members 14 and 16 which are one by two inch boards of sufficient length to provide the lateral span for support of a mobile home roof. The vertical web members 18 are 1 by 2 inch boards cut just long enough to extend between that portion of the upper and lower chords 14 and 16 where they are required to be placed in combination with the diagonally mounted angled web members 22 for the particular load which is to be supported. Since the distance between the upper and lower chords 14 and 16 varies, depending on the distance from their end connection, the length of the vertical web member will accordingly vary.

The spacing of the vertical web member 18 also varies in accordance with the load to be supported, and for minimum suitable support typically ranges from 20 to 40 inches apart. An angled web member 22 which has been found suitable for use in this invention is made of 1 to 2 inch width steel angle strap which has an angled central body portion 24 of a length that substantially extends the full distance between the ends 26 and 28. The length of each of the angled web members 22 varies according to the spacing of the upper and lower chords 14 and 16 and the vertical chords 18 adjacent to which the opposite ends 26 and 28 are mounted. These flat ends 26 and 28 are secured to chords 14 and 16 by fasteners such as 11/2 inch long staples.

Other forms of the diagonal load bearing member 22 which have ends 26 and 28 interconnected by staple-type fasteners 29, as previously discussed, may have body portion 24 which are tubular or corrugated, for instance, so long as they have similar rigidity to the angled body form described herein.

Though a preferred embodiment of this invention has been shown and described, this invention is not meant to be limited thereto, but is intended to embody all forms and modifications within the spirit of the following defined claims.