Patent Application
20110179729
This application relates to a stair tread assembly, such as may sometimes be referred to as a “false tread”, and to a method for renovating a stair tread.
It is well known that stair treads may wear out. Rather than replacing an entire staircase, or going to the significant trouble of removing the existing worn tread to permit complete replacement, it is also known to cover over the treads of a worn staircase with a new material, whether in the nature of a carpet, such as a stair runner, or a new surface. The new surface is often termed a “false tread”, namely a new tread that covers over an existing worn tread. An example of a false tread apparatus is shown in US patent publication US 2008/0271390 of Lopez, published Nov. 6, 2008.
In an aspect of the invention there is a stair tread assembly. It has a core member. The core member has a thickness, a step-wise depth, and a cross-wise width. The step-wise depth and the cross-wise width is greater than the thickness. The core member has a wood-based core matrix. The core matrix has a plurality of overlying layers. The matrix has substantially uniform properties of mechanical elasticity cross-wise, and having substantially uniform properties of mechanical elasticity stepwise. The matrix has an upper surface and an opposed lower surface. The core includes at least a first wood veneer portion mounted to the upper surface of the core matrix, and a second wood veneer portion mounted to the lower surface of the core matrix, the first and second wood veneer portions lying in parallel planes. The core member has a quadrilateral form when viewed looking in a direction perpendicular to the plane of the first wood veneer portion. The core member has a periphery and an array of edge members mounted thereto about the periphery such that the core matrix is concealed from view. The edge members are made of solid hardwood. The edge members include at least a first nosed edge member. The edge members include at least a first un-nosed edge member. The core has a first edge portion for mating engagement with the first un-nosed edge member. The first edge portion has a first profile machined along at least a first portion thereof. The first un-nosed edge member having a second profile machined therealong. The first and second profiles include out-of-plane features. The first and second profiles are mutually mating profiles. The first un-nosed edge member has a through thickness matching the core such that when the first and second profiles are mated the first un-nosed edge member mates flush with the first wood veneer portion of the core. The core has a second edge portion for mating engagement with the first nosed edge member. The second edge portion has a third profile. The first nosed edge member has a fourth profile machined therealong. The third and fourth profiles are mutually mating profiles such that when mated together the first nosing is flush with the first wood veneer portion of the core. The nosing has an overall height greater than the thickness of the core.
In another feature of that aspect of the invention the first nosed edge portion is oriented cross-wise to the first un-nosed edge portion. The first un-nosed edge portion has a first end. The third profile is cut across the first end of the first un-nosed portion. The first nosed edge portion has an end region mated to the first end of the first un-nosed edge portion. In still another feature, the first nosing edge member includes a bullnose, and the bullnose has a through thickness greater than the thickness of the core. In still another feature the first nosing edge member includes a depending edge located stepwise inwardly of the bullnose, and the depending edge has a rearward facing abutment surface for engaging an existing stair. In still another feature the stair tread includes four edge members in a set, the set including any one of: first, second and third nosed edge members and the first un-nosed edge member; first and second nosed edge members and first and second un-nosed edge members; and the first nosed edge member and first, second and third un-nosed edge members.
In still another feature, the core matrix is a plywood matrix. In a further feature (a) red oak; (b) white oak; (c) maple; (d) walnut; and (e) cherry. In still another feature the core has a through thickness of less than ¾ inches. In yet another feature the first nosed edge member includes a bullnose, and the bullnose has a through thickness of at least 1 inch. In still yet another feature the core is substantially rectangular and has a pair of long edges and a pair of short edges. The first un-nosed edge extends along one of the long edges. When assembled, the core and the first un-nosed edge, taken together, have an overall dimension step-wise of at least 7½″. In a still further feature the bullnose has a depending flange. The depending flange has a rearwardly facing abutment surface for engagement of an existing stair, the rearwardly facing abutment surface extending in a plane flush with a forward edge of the first wood veneer portion. In still yet another further feature the first profile is a tongue and the second profile is a mating groove. In still another feature the third profile is a tongue and the fourth profile is a mating groove. In another feature the first and third profiles are the same, and the second and fourth profiles are the same.
In another aspect of the invention, there is a replacement stair tread assembly for covering over an exiting stair tread. The replacement stair tread assembly has a core having a periphery including a stepwise leading edge, a stepwise trailing edge, and first and second cross-wise end edges. The core has matched hardwood upper and lower surface layers. There are edge members that extend fully about the periphery of the core. The edge members include at least a first nosed edge member mounted along the stepwise leading edge. The core and edge members have interlocking profiles that are mate together. The core has a neutral axis. The core has multiple layers with cross-wise variation of grain direction between successive layers. The core has a cross-section that is matched above and below the neutral axis. In a further feature the core has a cross-wise length and a stepwise tread distance, and a ratio of the length to tread distance that is greater than 36:9½.
In still another aspect of the invention there is a replacement stair tread assembly for covering over an exiting stair tread. The replacement stair tread assembly has a full width core having a periphery including a stepwise leading edge, a stepwise trailing edge, and first and second cross-wise end edges. The full width core has a cross-wise length of at least than 30 inches. There are edge members extending fully about the periphery of the core. The edge members include at least a first nosed edge member mounted along the stepwise leading edge. The core and edge members have interlocking profiles that are mate together. The core has a neutral axis. The core has multiple full width layers with cross-wise variation of grain direction between successive layers. The core has a cross-section that has substantially matched physical properties above and below the neutral axis.
In another feature of that aspect of the invention the substantially matched physical properties include moisture absorption. In still another feature the substantially matched physical properties include resistance to out of plane bending in both cross-wise and step-wise orientation.
The invention may be explained with the aid of the accompanying illustrations, in which:
a is a general arrangement isometric view taken from behind, above and to the right hand side of an embodiment of a stair tread assembly according to an aspect of the present invention;
b shows an isometric view of a sub-assembly the stair tread assembly of
c shows an isometric view of a core of the sub-assembly of
d shows an enlargement of a profile of an edge member of the stair tread assembly of
a is a general arrangement isometric view taken from behind, above and to the right hand side of an embodiment of a stair tread assembly according to an aspect of the present invention;
b shows an isometric view of a sub-assembly the stair tread assembly of
c shows an isometric view of a core of the sub-assembly of
The description that follows, and the embodiments described therein, are provided by way of illustration of an example, or examples, of particular embodiments of the principles of the present invention. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the invention. In the description, like parts are marked throughout the specification and the drawings with the same respective reference numerals. The drawings are not necessarily to scale and in some instances proportions may have been exaggerated, more clearly to depict certain features of the invention.
The inventor seeks a fair and reasonable interpretation of the claims, and of this specification. The terminology used in this specification is thought to be consistent with the customary and ordinary meanings of those terms as they would be understood by a person of ordinary skill in the art in North America. Following from the decision of the Court of Appeal for the Federal Circuit in Phillips v. AWH Corp., the Applicant expressly excludes all interpretations that are inconsistent with this specification, and, in particular, expressly excludes any interpretation of the claims or the language used in this specification such as may be made in the USPTO, or in any other Patent Office, unless in some way supported by the specification or by objective evidence of record in accordance with In re Lee, (for example, earlier publications by persons not employed by the USPTO or any other Patent Office), demonstrating how the terms are used and understood by persons of ordinary skill in the art, or by way of expert evidence of a person or persons of experience in the art.
The current invention pertains to stair treads. In that context it may help to define a frame of reference or co-ordinate system. While stairs may be built on curves, such as circular staircases, they are most commonly rectangular. In that context a Cartesian co-ordinate system may be used in which the x-direction is the step-wise direction from the back of the step at the riser to the front of the step at the nosing, in the direction in which a person climbs or descend the stair. The y-direction is the cross-wise direction of the stair, the x and y directions tending then to define a plane, that plane being, or being parallel to, the plane of the surface of the face of the tread on which a person may step. The z-direction is then the through thickness or vertical direction as installed. Although the description is made in a Cartesian context, it is intended to be generic such that it is also applicable to non-rectangular stair treads.
In a typical step the stepwise extent of the tread, x20, may most often be about 9½-11 inches, the cross-wise extent, L20 may commonly be 30, 32, 36, 42 or 48 inches, and the thickness may be less than 2 inches, typically about or slightly less than 1 inch. A common existing step tread size is about 10¼ to 10½″. That is, the stair is typically several times as large in the cross-wise direction as the step-wise direction, and is much smaller, typically an order of magnitude smaller, in the thickness direction.
a shows an embodiment of a false tread assembly, which may also be termed a replacement tread assembly, indicated generally as 20, falling within an aspect of the present invention. The assembly has a core 22. An array or set of edge members 24 is mounted about the periphery of core 22. That set may include an un-nosed edge member 26, and first, second and third nosed edge members 28, 30, 32. Core 22 is a substantially planar member having a breadth L22, a depth x22, and a thickness t22. By the co-ordinate system identified above, the breadth is in the cross-wise or y-direction, the depth is in the step-wise or x-direction, and the thickness is in the vertical or z-direction. Core 22 is a quadrilateral, which may be a rectangle having two long sides 34, 36, and two short sides, 38, 40. Un-nosed edge member 26 lies along a rearward or step-wise inward or long edge 36 of core 22, first nosed edge member 28 lies along the step-wise forward or opposite long edge 34, and the second and third nosed edge members 30, 32 lie along the short sides 38, 40 of core 22. Core 22 includes an internal matrix 42 that has an upper surface 44 and a lower surface 46. A first sheet of veneer 48 is mounted to upper surface 44, and a second sheet of veneer 50 is mounted to lower surface 46. Thus all sides of core 22 are covered, i.e., they are hidden from view, concealed, no longer externally visible, however expressed.
In the past, false treads have been known where the false tread came in two parts, those parts being installed in cross-wise spaced apart relationship, for covering the lateral edges of the step, with, for example, a carpet runner arranged to run between those end parts.
Replacement tread assembly 20 is a full width replacement tread. It is intended to span the full width of the underlying worn step, without the need for an intermediate carpet runner or similar device for covering the worn center section of the step. Of course, this does not preclude the possibility that someone might still wish to place a carpet runner over a full width tread, but that is an option, rather than a requirement. For the purposes of this specification, the term “full width”, L20 means a tread that is wider than 24″, most commonly expected to be 32″ or wider, and in other embodiments it is 42″ or 48″ wide, respectively. That is, it is not merely one half of a two part matched pair of end portions.
Core 22 has a profile 52 formed on each of its edges, in this case each of its four edges, for engagement with a mating profile 54 formed on the corresponding nosed or un-nosed edge member, as may be. These profiles are out-of-plane profiles. That is, rather than merely employing a planar abutment face, which would extend typically in a vertical horizontal plane, the profiles are in the nature of mating finger-groove or male-and-female tongue and groove profiles that depart from, for example, a purely planar surface. While each edge member 26, 28, 30, 32 may have its own particular, different profile, it is convenient that those profiles be the same.
Internal matrix 42 is a dimensionally stabilised member having mechanical stress field reaction properties that are substantially uniform in the step-wise or x-direction, and that are substantially uniform in the cross-wise or y-direction. In this specification, the term “dimensionally stabilised” means an element that has criss-crossed layers of wood fiber materials assembled or bonded together such that the end product is planar and of a substantially uniform moisture content, that has balanced wood layers above and below the neutral axis in both the x and y directions such that the core may tend to be less prone than solid wood to out-of plane deflection due to a change in humidity than it might otherwise be if it were made of, for example, a solid piece of wood. The multilayer construction is used in distinction to the multiple solid block construction, whether sandwiched between veneer or otherwise, as shown and described variously in U.S. Pat. No. 6,860,071 of Weaber et al.; US Publication 2006/0196129 of Lin; and US Publication 2008/0028699 of Mak.
Internal matrix 42 is assembled from an array of plies or wood, each ply having a predominant grain direction, the grain of each successive ply being oriented in a different direction from the next adjacent ply in the direction moving away from the neutral axis of the section. Most typically that difference in orientation approximates very nearly, or is, a right angle (i.e., 90 degree) difference in orientation. That is, matrix 42 is assumed to be substantially planar, and to have a neutral plane, referred to when viewed in cross-section as the “neutral axis”, in bending. The structure of the assembled layers of matrix 42 is substantially symmetrical about the neutral axis. In practice this may tend to mean that whatever the thickness of the various layers may be, the number of plies is uneven, with one ply 60, of whatever thickness, being a central ply bisected by the neutral axis. Central ply 60 is sandwiched by two matching adjacent plies 62, 64, commonly oriented at right angles to central ply 60. Those two plies may be sandwiched or bracketed by an additional two layers or plies 66, 68 having a predominant grain direction at right angles to the preceding layer, and so on. Five, seven, or nine layers may be typical. Some layers may be made of flake, such as poplar flake. Prior to assembly the various plies or layers may be cut from material of a known substantially uniform moisture content. The wood may be dried. That is, the moisture content of the wood layers may corresponding to the moisture content of kiln dried wood, being typically in the range of 8% to 12% by weight. This 8% to 12% range may also be the range of moisture content in the final core product as assembled. The overall matrix may also be dried and of substantially uniform moisture content prior to the addition of the veneer skins. The outermost layers of this sandwich may be of the same species to ensure that the layers have the same properties in terms of moisture absorption. To the extent that core 22 is sanded to a specified thickness, that sanding may be evenly matched from top and bottom surfaces to retain the balance of structural properties. It may be that all of the plywood layers are made of the same species.
The veneer skins may also be of matching properties in terms of moisture absorption and drying, which, in practical terms may tend to mean that it is of matching wood species or type. That is, whether the veneer is red oak, white oak, maple, cherry, walnut, or some other natural grain hardwood suitable for flooring, the type of wood of both layers is the same, and the predominant direction of the grain of the top and bottom veneer layers is also aligned to run in substantially the same direction, that direction being, typically, the cross-wise or y-direction. To the extent that these layers are subject to post-gluing processing or finishing, such as sanding or provision of a surface treatment, that post-processing may apply equally to both top and bottom surfaces. That is, the method of construction includes matching the structure above the neutral axis to the structure below the neutral axis, such that the physical properties of the structure above and below the neutral axis are balanced.
After construction of the core matrix, and the addition of the veneer surfaces, the core may be prepared for receiving the edge members. Considering the first edge member along the rear of the false tread, the tongue is formed on the non-showing edge, a groove is formed on the non-showing hardwood edge member, and the two are mated together. If there is more than one non-showing edge member, the edge member along the longest side is mounted first, as shown in
As may be appreciated, the un-nosed edges are of substantially identical through thickness to the overall thickness of the core, if overlain by veneer, or the core and veneer including top and bottom sheets if not overlain by veneer sheets. The nosed edges have a greater through thickness than the core-and-veneer sandwich. Considering the profile shown in
It need not be that one side of the false stair tread assembly have an un-nosed edge, while three other sides have nosed edge members. In
Similarly, it need not be that the upper and lower veneer surfaces, 48 and 50 are made of continuous monolithic sheets as if the main body of the tread were made from a single piece of hardwood. Rather, as suggested in
As shown in
Various embodiments of the invention have been described in detail. Since changes in and or additions to the above-described best mode may be made without departing from the nature, spirit or scope of the invention, the invention is not to be limited to those details but only by the appended claims.
