Floor Joist

Abstract

A truss-type floor joist formed of vertically aligned parallel chords connected together between their ends by alternating diagonal web members and at their ends by a pair of vertical end members arranged in face-to-face contact, with the chords, web members and end members all formed of 2.times.4 wood strips arranged with their narrow edges vertical. Each chord has an inner liner member in the form of a 2.times.4 wood strip member arranged in face-to-face contact therewith and extending from each end of the chord to a point just past its first, adjacent set of diagonal web members. Each of the joints formed by abutting web members and end members with the chords are overlapped on both vertical faces with metal connector plates having struck-out teeth embedded in the respective overlapped wood members.

Description

BACKGROUND OF INVENTION

Floor joists used to support the floor in a small building, and similarly used to support flat roof sections, have been typically made of large wood beams, such as 4.times.8 and 2.times.6 in cross section, or alternatively, out of metal I-beams. Suitable lumber for this purpose is relatively expensive and difficult to obtain and process. Likewise, metal I-beams are also relatively expensive and difficult to handle and assemble into the building construction.

Thus, the invention herein relates to floor joists formed in a truss-like shape out of conventional, readily available and inexpensive 2.times.4 wood strips which joists may then be used in small building construction such as in dwelling houses, for floor joists as well as ceiling joists where appropriate.

SUMMARY OF INVENTION

The invention herein contemplates forming floor joists in a truss-like configuration out of long, parallel chords made of conventional 2.times.4 lumber with the chords interconnected by alternating diagonally arranged 2.times.4 web members and vertically arranged end members with all joints connected together by means of conventional flat, sheet metal connector plates which include integral struck-out teeth for embedding into the wood. Such type connector plates are illustrated for example in the patent to Broder, U.S. Pat. No. 3,242,788 granted Mar. 29, 1966.

More specifically, the invention herein contemplates forming the opposite ends of the chords in double thickness by means of inner, short length 2.times.4 liners arranged in face-to-face contact with the opposite inner surfaces of the chords, and also forming the vertical end supports in double thickness 2.times.4 members and doubling the thickness of one of the two diagonal web members, whichever is the first tension loaded member, which are arranged between the doubled end portions of the chords. The 2.times.4's on all the members are arranged horizontally, that is, their thin or narrow edges are in the vertical plane and their wide edges are in the horizontal plane. Further, the doubled thickness members, being unconnected to each other except along the vertical plane by means of the vertical arranged connector plates, have some limited movement relative to each other to absorb stresses and strains and to avoid any tendency to crack or split lengthwise, thus forming a joist which may be of considerable length, yet of a high degree of stiffness and strength with minimal tendency to crack under varying loads.

Hence, an essential object of this invention is to form a truss-type joist of considerable strength and rigidity yet of low cost using readily available and low cost 2.times.4 lumber.

Other objects and advantages of this invention will become apparent upon reading the following description, of which the attached drawings form a part.

DESCRIPTION OF DRAWINGS

FIG. 1 is an elevational view of one end of the joist.

FIG. 2 is an enlarged, perspective view of the opposite end of the joist, and

FIG. 3 is an enlarged, fragmentary view of a section taken in the direction of arrows 3--3 of FIG. 2.

FIG. 4 is an elevational view of the end portion of a modified joist.

DETAILED DESCRIPTION

FIG. 1 illustrates a floor joist 10 which is of considerable length relative to its height. For example, typical sizes would run approximately 24 feet long by 16 inches high or 28 feet long by 20 inches high or 32 feet long by 24 inches high. Obviously, the length may be varied considerably whereas the height is relatively low compared to the length and varies only slightly despite increases of length.

The joist is formed of an upper chord 11, a lower chord 12, with the chords interconnected by sets of alternating diagonally arranged web members 13 and 14 and by opposite end vertical end members 15.

As illustrated in FIGS. 1 and 2, the upper chord 11 is formed of an outer, long 2.times.4 wood strip 17 having an inner, short 2.times.4 wood strip 18 arranged in face-to-face contact at its opposite ends. Likewise, the lower chord 12 is formed of a long 2.times.4, outer wood strip 19 having its opposite inner ends lined with a short 2.times.4 wood strip liner 20.

Each of the vertical end members 15 are formed of a pair of 2.times.4 wood strips 21, arranged face-to-face. Also, the diagonal web member 14a which is second from each of the opposite ends, and which is normally under tension, is formed of a pair of 2.times.4 wood strips 22 and 22a arranged face-to-face. In the event the joist is to be so loaded that the first web members 13a (the ones nearest to the joist ends) are to be in tension, then that first web member is formed of a pair of 2.times.4 wood strips, instead of the second web members 14a.

As is illustrated in FIG. 2, all of the 2.times.4's are arranged on their sides, that is, with their broad or wide faces in the horizontal plane and their narrow edges in the vertical plane.

The reference herein to 2.times.4 wood strips refers to conventional lumber, commonly called 2.times.4 meaning 2 inches by 4 inches in cross section, but actually of a slightly smaller size when the lumber is dressed. The size of the wood strips is not critical and may be varied somewhat but the size herein referred to indicates the use of the conventionally available inexpensive wood strips as contrasted with the previously used large size wood beams which are relatively expensive, tend to crack and are not readily available.

The opposite ends of the web members abut the interior surfaces of the chords as does the opposite ends of the end members 15 to form joints which are connected by means of conventional, flat sheet metal connector plates of the type illustrated, for example, in the above-mentioned Broder U.S. Pat. No. 3,242,788 of March 29, 1966. These plates consist of flat sheet metal having struck-out teeth of suitable configuration for embedding into the wood.

FIG. 3 illustrates a corner joint wherein the plates 25, arranged on each vertical face of the joint have their teeth 26 embedded into the chord strips 17 and 18 and into the vertical end members 21. The plates are typically secured into position by first arranging all the wood parts in their proper relationship, then placing the plates above and below the joints and squeezing them into the wood by means of a suitable press.

The size of the plates may vary, depending upon the size of the joints and thus, large plates 24 may be used on most of the joints with smaller plates 25 at the joints of less area.

As described above, the double thickness portions of the chords, web member 14a and end members 15 are so formed that the two strips making up the double thickness are relatively movable to the extent that they are not fastened face-to-face but are fastened together only on their vertical edges by means of the plates with the embedded teeth so that there is some degree of relative movement or relative buckling permitted between the double thickness members which functions to better absorb stresses and to yield thereunder and to avoid cracking or splitting which frequently occurs in heavier, prior types of wood beams. Thus, the double thickness members are for all practical purposes not secured together except at their ends and then only along their side or vertical edge faces so as to permit this relative movement or buckling.

However, for some constructions, it is desirable to anchor the double thickness portions of the chord further for suitable strength requirements. Thus, FIG. 4 illustrates a modification wherein the upper chord is provided with an additional connector plate 28 at the free end of its inner or liner wood strip 18 and the lower chord is provided with a similar connector plate 29 midway between its ends. The inner and outer members of each chord are still free to move slightly relative to each other particularly since they are secured together only along their vertical faces by the embedded connector plate teeth.

Claims

Having fully described an operative embodiment of this invention, I now claim:

1. A floor joist comprising:

a pair of long, vertically spaced apart, parallel chords, each formed of a long outer 2.times.4 wood strip and a pair of short inner 2.times.4 strips extending from the outer ends from the long outer wood strip a short distance towards the center thereof, the inner strips being in loose face-to-face contact with the respective outer strips to form double thickness short end portions on each chord, and with the 2.times.4 strips all laid on their sides so that their opposite narrow edges are vertical and coplanar;

a vertical end member spanning the space between and endwise abutting the inner chord strips at each opposite end thereof; each end member being formed of a pair of 2.times.4 wood strips arranged loosely together face-to-face with their narrow edges in the same planes as the corresponding chord strip narrow edges;

sets of alternating diagonally arranged web members extending along the length of the chord, with each web member diagonally spanning the space between the chords and endwise abutting the opposed inner surfaces of the chords, and with each formed of a 2.times.4 wood strip having its opposite narrow edges coplanar with the chord strip narrow edges;

a vertically arranged, flat sheet metal connector plate overlapping each of the vertical faces of each joint formed between the web members and the chord and the end members and the chord and secured to same by integral struck-out teeth embedded therein for securing the members and chord together;

with the plates overlapping the end member joints also overlapping and securing the outer and inner chord strips together and the plates overlapping the first set of web members closest to the end members also overlapping and securing the outer and inner chord strips together;

and the inner chord strips terminating only a short distance from said first set of web members;

the pairs of strips forming the double thickness chord end portions and the end members having their contacting faces free of securement to each other and being slightly relatively movable for absorbing stresses and avoiding longitudinal splitting.

2. A floor joist as defined in claim 1 and wherein the first tension loaded web member from each opposite end of the joist, that is, one of the two of the nearest set of web members to each opposite end which is to be loaded in tension, is formed of double thickness 2.times.4 wood strips, with the remaining web members being of single wood strips.