Improved Web Connection with Timber Flange

The present invention relates generally to structural members used in building construction. More particularly, the invention is directed to timber structural members having an I-beam configuration being formed from two timber flanges connected together by a web.

It is known in the art to provide a composite timber structural member having a general I-beam configuration. Typically, an elongate planar web (fabricated from materials as diverse as plywood, metal, and plastic) is used to join paired parallel timber flanges. Each flange has a slot running along its length, and the web inserts into the slots so as to provide the composite structure. An adhesive may be used at the interfaces of the flange slot and the web to provide for more secure connection between the components.

In use, the web resists shear forces while the flanges resist any bending moment occasioned on the beam. While the I-shaped section is a very efficient form for carrying both bending and shear loads in the plane of the web, the section has a reduced capacity in the transverse direction, and is also inefficient in carrying torsion.

It is noted in prior art I-beam composite timber structural members that splitting or cracking can occur in a flange and/or web when exposed to high loads. Furthermore, the planar web may at least partially dislodge from the flange into which it inserts. As will be readily appreciated splitting, cracking and web dislodgement may be addressed by increasing the cross-sectional area of web and/or the flanges. Whilst generally effective, that approach increases the cost of production given the need for large diameter timbers and more material overall. Larger diameter timbers are becoming increasing scarce, and there is a general preference to use more readily available smaller diameter timbers where possible without compromising safety.

Apart from any cost and supply issues, it is desirable to improve the load-carrying performance of an I-beam timber composite structural member without increasing the amount of material used whilst avoiding problems of cracking, splitting or web dislodgement.

It is an aspect of the present invention to provide an improvement to prior art composite timber structural members so as to improve load carrying performance and/or decrease the propensity of splitting, cracking and web dislodgement. It is a further aspect of the present invention to provide a useful alternative to prior art composite timber structural members.

The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

In a first aspect, but not necessarily the broadest aspect, the present invention provides a composite timber structural member comprising: a first timber flange having a first longitudinal slot formed therein, a second timber flange that is substantially parallel to the first timber flange and having a second longitudinal slot formed therein, and a web having a first long edge region and an opposing second long edge region, the first and second long edge regions being disposed in the first and second longitudinal slots respectively, wherein the first and/or second long edge region(s) comprise(s) a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than that of the shoulder portion from which it extends, the shoulder portion and the tongue portion together presenting only planar and curved external surfaces to the internal surfaces of its/their respective slots, and each slot is shaped and dimensioned so as to receive the long edge region disposed within it.

In a second aspect, the present invention comprises a composite timber structural member comprising: a first timber flange having a first longitudinal slot formed therein, a second timber flange that is substantially parallel to the first timber flange and having a second longitudinal slot formed therein, and a web having a first long edge region and an opposing second long edge region, the first and second long edge regions disposed in the first and second longitudinal slots respectively, wherein the first and/or second long edge region(s) comprise(s) a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than that of the shoulder portion from which it extends, the shoulder portion and the tongue portion together being devoid of any outwardly directed sharp corner, and each slot is shaped and dimensioned so as to receive the long edge region disposed within it.

In one embodiment of the first or second aspect, the long edge region(s) of the web is/are the region(s) that is/are disposed within the slot.

In one embodiment of the first or second aspect, the tongue region(s) has/have a planar terminal face.

In one embodiment of the first or second aspect, the tongue region(s) has/have opposing lateral planar faces.

In one embodiment of the first or second aspect, the tongue region(s) is/are of substantially even thickness.

In one embodiment of the first or second aspect, the tongue region(s) is/are at least about 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60% the thickness of the shoulder region(s) from it/they which extends.

In one embodiment of the first or second aspect, the web, when viewed end-on, has an axis of symmetry.

In one embodiment of the first or second aspect, the web extends to a depth of between about 20% to about 80% of the diameter of the flange into which it is disposed.

In one embodiment of the first or second aspect, the web extends the full length of the flanges, or extends beyond the length of the flanges, or the web is shorter than the length of the flanges.

In one embodiment of the first or second aspect, the web is formed of a relatively high strength planar material.

In one embodiment of the first or second aspect, the web is formed of a material selected from the group consisting of: timber, processed timber; chipboard, oriented strand board, plywood, metal sheet, metal plate, fibre reinforced cement sheet, plastic, and fibre reinforced plastic material.

In one embodiment of the first or second aspect, the first and/or second flange has a substantially circular cross-section.

In one embodiment of the first or second aspect, the first and/or second flange is a timber pole or a timber round.

In one embodiment of the first or second aspect, the first and/or second flange is/are a peeler core.

In one embodiment of the first or second aspect, the first and/or second flange has/have a planar surface distal to the planar web and at about 90 degrees to the flange slot.

In one embodiment of the first or second aspect, the first and/or second slot(s) is/are oversized so as to accommodate its respective long edge region with a layer of adhesive.

Unless otherwise indicated herein, features of the drawings labelled with the same numeral are taken to be the same features, or at least functionally similar features, when used across different drawings.

The drawings are not prepared to any particular scale or dimension and are not presented as being a completely accurate presentation of the various embodiments.

After considering this description it will be apparent to one skilled in the art how the invention is implemented in various alternative embodiments and alternative applications. However, although various embodiments of the present invention will be described herein, it is understood that these embodiments are presented by way of example only, and not limitation. As such, this description of various alternative embodiments should not be construed to limit the scope or breadth of the present invention. Furthermore, statements of advantages or other aspects apply to specific exemplary embodiments, and not necessarily to all embodiments, or indeed any embodiment covered by the claims.

Throughout the description and the claims of this specification the word “comprise” and variations of the word, such as “comprising” and “comprises” is not intended to exclude other additives, components, integers or steps.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may.

As used herein, positional terms such as “lateral”, “across”, “above”, “below”, “higher”, “lower”, “upward”, “downward”, “plan view” and the like are to be considered with reference to a composite timber structural member oriented as shown in. It will be appreciated that upon installation, a structural member of the present invention may be orientated in any way such that, for example, the upper edge of the web may face downwardly toward the ground, or laterally.

In a first aspect, but not necessarily the broadest aspect, the present invention provides a composite timber structural member comprising: a first timber flange having a first longitudinal slot formed therein, a second timber flange that is substantially parallel to the first timber flange and having a second longitudinal slot formed therein, and a web having a first long edge region and an opposing second long edge region, the first and second long edge regions being disposed in the first and second longitudinal slots respectively, wherein the first and/or second long edge region(s) comprise(s) a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than that of the shoulder portion from which it extends, the shoulder portion and the tongue portion together presenting only planar and curved external surfaces to the internal surfaces of its/their respective slots, and each slot is shaped and dimensioned so as to receive the long edge region disposed within it.

In a second aspect, but not necessarily the broadest aspect, the present invention provides a composite timber structural member comprising: a first timber flange having a first longitudinal slot formed therein, a second timber flange that is substantially parallel to the first timber flange and having a second longitudinal slot formed therein, and a web having a first long edge region and an opposing second long edge region, the first and second long edge regions disposed in the first and second longitudinal slots respectively, wherein the first and/or second long edge region(s) comprise(s) a shoulder portion from which a tongue portion extends, the tongue portion having a thickness less than that of the shoulder portion from which it extends, the shoulder portion and the tongue portion together being devoid of any outwardly directed sharp corner, and each slot is shaped and dimensioned so as to receive the long edge region disposed within it.

The present invention is predicated at least in part on the inventors' discovery that an improved or alternative composite timber structural member having an I-beam configuration is provided where the web long edge regions are devoid of sharp external corners. Such corners are found in external corners of 90 degrees, and also less than 90 degrees where a corner is bevelled, for example.

More particularly, the long edge region of the web may be formed into a shoulder region (the shoulders being curved or rounded, and not formed into sharp corners) and a tongue region (the distal end of the tongue also having curved or rounded corners rather than sharp corners).

Without wishing to be limited by theory in any way, it is proposed that prior art webs concentrate load forces at the sharp corners thereof, leading to cracking and splitting of the flange around the slots and/or the web itself, sometimes leading to dislodgement of the web from its position in the flange slot. Failure in prior art structural member disposed horizontally was often seen to occur from the bottom of the lower chord straight upwards (i.e. 90 degrees to the horizontal) and about one-third the way along the member. The use of rounded corners is proposed to distribute forces more evenly through the flange, thereby limiting the magnitude of a force along any vector.

A further advantage of rounding the web corners is that a greater surface area for the contact of adhesive is provided, thereby increasing level of bonding between the web and the flange.

Moreover, the formation of a shoulder portion at the edge region of a web, with a tongue portion extending therefrom is proposed to provide further advantage as load forces are distributed into two regions of the flange: into the region surrounding the shoulders and also deeper into the flange in the region surrounding the tongue terminus. Rounding the corners of the shoulder region has the same advantages as for the tongue, as discussed supra.

Furthermore, the formation of a relatively thin tongue portion requires less wood to be removed from the flange in order to form the flange slot. The tongue is thinner than the remainder of the web, and therefore the slot terminus deep in the flange can also be thinner. Leaving more wood in flange increases the ability of the flange (and therefore the structural member as a whole) to better resist load forces.

The invention will now be more fully described by reference to the non-limiting embodiments of the drawings.

Turning firstly toa composite structural member () is show in end-on view revealing the I-beam-like configuration. The composite structural member () comprises a first timber flange (), a second timber flange () and a web (). Each of the flanges (,) has a flattened region (,) to allow mounting of the member () on other planar building structures, or to allow other such structures to be mounted on the member ().

Considering now, greater detail of the web () insertion into the upper flange () is shown. A slot () is formed in the first flange (), and having a first relatively wide portion () which communicates with the outside, and a more narrow portion () at the blind end. In terms of fabrication, a tool could be used to rout a narrow slot for the full depth, and then a different tool used to rout the wider portion at more shallow depth to form the bipartite slot shown in.

The end region of the web () has a shape and dimensions that generally follow those of the slot () is so far as a relatively thick shoulder portion () is provided and a relatively thin tongue portion (). The shoulder portion () comprises paired opposed rounded shoulders (one marked). The tongue portion () comprises paired opposed rounded shoulders (one marked), and a planar terminal face ().

The slot () conforms very closely to the shape of the web portions (,) however is slightly oversized to allow for adhesive to retained in the slot () after insertion of the web portions (,). In embodiments where only frictional engagement is relied upon, there would be no need for oversizing the slot ().

As discussed supra, the use of rounded corners (,) better distribute load forces throughout the flanges (,) so as to avoid problems such as splitting, cracking and web dislodgement.

Reference is now made toandshowing respectively lateral and plan views of the composite structural member (). The structural member () will generally be very elongate so as to be useful in spanning supports in building construction.

The diameter of the flanges () and () and the dimensions of the web () are selected so that the structural strength of the composite member will meet predetermined design and load bearing requirements.

The flanges () and () are comprised of timber poles. In one embodiment, one or more of the round flanges has/have a diameter of less than about 125 mm, or about 100 mm, or about 75 mm, or about 70 mm, or about 65 mm, or about 60 mm, or about 55 mm, or about 50 mm, or about 45 mm, or about 40 mm. In another embodiment, the flange(s) has/have a diameter of less than about 60 mm.

In some embodiments, a flange is a “peeler core”. As is understood by the skilled person, a peeler core is a by-product of process of removing the outer layers of wood for plywood manufacturing (often by a milling process) to the point that substantially all the soft wood has been removed, leaving the heartwood core which is typically dense and inflexible. The milling process peels off the bark, cambium layer, sapwood, and even some of the heartwood to make veneer panels. This leaves no sapwood on the post.

The heartwood core of a peeler core does not absorb the pressure treatment and preservatives as well as the softwood resulting in an inferior post that will typically not last as long as a post with treated softwood on the exterior.

Applicant has discovered an economically and technically viable use for peeler cores in that the cores may be used in a structural member such as that disclosed herein. The use of multiple peeler cores (and even those with a diameter down to about 70, 60, 50 or 40 mm) can produce a member which is useful in construction and yet is highly cost-effective.