Patent Application
20080302055
The present invention relates to a reinforcement mesh to bend and conform to a profile of curved architectural features on an architectural moulding, and to an architectural moulding reinforced by the mesh.
Fiber glass mats are used as a facing material to reinforce flat insulation panels of polyurethane foam. However the glass mats or mesh have never been engineered to comply with the needs of the industry to reinforce curved profiles of architectural mouldings.
An architectural moulding comprises a decorative strip that has the appearance of being made of solid plaster or solid cement when installed on a building. The moulding comprises a light weight polymeric foam core having a surface topography shaped with decorative, curved architectural features to provide a decorative appearance, and a surface layer of cementitious material to provide an exterior finish coating over the curved architectural features. For example, the finish coating comprises plaster for indoor use or Portland cement for outdoor use.
Moreover, as new architectural profiles are designed and built, existing mesh products have been unable to adapt to a new profile, such that the mesh will tend to lift away from the surface of the profile, particularly at an abrupt radius of curvature or at a series of reversing radii of curvature. Manufacturers deal with this problem by delaying or interrupting the process of applying the cementitious coating and relying on hand work to press down the uplifted mesh, or by applying a localized amount of adhesive to re-attach the mesh against the profile and waiting for the adhesive to cure to a tenacious adherent state. What results is a delay in manufacturing, as well as, the increased probability of producing a defective part in which the mesh is insufficiently attached to the profile, or may even protrude out from the cementitious coating.
An architectural moulding has a light weight foam core, typically an expanded high density polystyrene, in the form of an elongated beam of substantial length, eight feet or two meters, for example, and of substantially large aspect ratio of length versus transverse dimensions. The cross sectional dimensions are thin relative to the length. Thus, the architectural moulding is vulnerable to sagging, by beam deflection, under the influence of its own weight and length when transported and handled prior to installation on a building. Sagging applies stress that tends to crack the ceinentitious coating when placed under tension. Sagging further applies stress that tends to separate the cementitious coating from the foam core. Ambient temperature changes further contribute to such cracking and/or separation due to a difference in thermal expansion rates of the foam core and the cementitious coating. Thus, to restrain sagging and undue thermal expansion and contraction of the foam core relative to the cementitious coating, a reinforcement mesh is applied to the foam core before the cementitious coating is applied. This requires bending of the mesh to conform to and against the decorative, curved profile of the architectural features on the foam core.
The mesh carries an adhesive on one side of the mesh to adhere the mesh to the profile. However, the mesh when bent tends to undergo elastic strain, which stores resilient spring energy in the bent yarns of the mesh. The stored spring energy thereby provides an impetus to the bent mesh to return to its former unbent orientation, a behavior referred to as undergoing shape memory recovery. The elastic strain and tendency for shape memory recovery lifts the mesh away from the profile of the polystyrene core, and spring biases the adhesive to give way under tension and release the mesh from adherence to the profile. Moreover, a mesh complying with an industry standard specification for minimum areal weight tended to undergo significant strain and shape memory recovery, which lifted the mesh from the surface of the architectural moulding core.
Over the mesh is applied a coating of a proprietary plaster, concrete, or other cementitious material to a thickness of about 0.13 inches, 3.3 mm., which bonds to the mesh and penetrates through openings through the mesh to bond with the foam core. Given the weight and brittle nature of the cementitious coating, the softness of the polystyrene core and the beam length and large aspect ratio of the moulding, it is easy to foresee that its own weight and length would induce a bending moment capable of cracking the coating. Moreover, given the length of the moulding and its construction of dissimilar materials, it is understandable that cracking of the cementitious material would occur due to differences in thermal expansion rates of the dissimilar materials. The reinforcement mesh serves to resist the beam deflection and bear the thermal expansion loads. However, prior to the invention, the reinforcement mesh was prone to lifting away from the polystyrene core due to a tendency for shape memory recovery.
What the moulding industry requires in terms of mesh behaviors are, for the mesh to bend and conform to and against a profile of curved architectural features on an architectural moulding, and for the mesh to remain substantially where it was placed and remain adhered to the profile over the passage of time, at least until the cementitious coating is applied and dried to a stable rigid state. Further, compliance of a mesh with an industry accepted standard for a minimum areal weight is desirable.
The invention pertains to a reinforcement mesh having weft yarns that bend and conform to and against a curved profile of curved architectural features on an architectural moulding. The weft yarns bend relative to the relatively straight warp yarns of the mesh. The weft yarns bend with limited elastic strain. The reinforcement mesh has relatively straight and substantially stiff warp yarns to extend longitudinally straight along the length, and against the architectural moulding. Advantageously, the substantially straight warp yarns resist beam deflection and restrain differential thermal expansion while the weft yarns bend and conform to and against the curved profile of the moulding with limited elastic strain.
Further, the invention relates to a method of making the reinforcement mesh. Further, the invention relates to an architectural moulding having the reinforcement mesh. Further the invention relates to a method of making the architectural moulding.
A mesh of engineering design is specifically aimed at solving the problem wherein the yarns of prior known mesh tend to lift away from a curved profile of architectural features on an architectural moulding. The invention complies with the requirements of end use, to resist beam deflection of the moulding, to restrain undue thermal expansion and contraction and to retain the mesh attached to a foam core of the moulding for an adequate time period during a manufacturing process until a cementitious coating is applied and cured to a stable solidified state. The usual time period comprises seven days for the cementitious coating to cure to a stable solidified state. The cementitious coating may continue to cure after attaining a stable solidified state.
Embodiments of the invention will now be described by way of example with reference to the drawings.
The weft yarns 304 bend relative to the straight warp yarns 302 in the mesh 300. Each of the weft yarns 304 comprise ribbons, low twist multifilaments or rovings. To manufacture a lower range of low yield sizes, the weft yarns preferably comprise multifilaments. To manufacture an upper range of low yield sizes, the weft yarns preferably comprise rovings. In an embodiment of the invention, the areal weight and thickness sizes of the weft yarns 304 are substantially less than that of the warp yarns 302, such that the weft yarns 304 are relatively more limp, and the warp yarns 302 are relatively more stiff. The weft yarns 304 are smaller in yield sizes than the warp yarns 302, such that the weft yarns 304 are thinner and weaker, and readily bend relative to the warp yarns 302. The weft yarns 304 conform to the curved profile 202 of the foam core 200 with limited amounts of elastic strain incurred, which limits the tendency for shape memory recovery. The elastic strain is substantially relieved when bending the thinner and weaker weft yarns 304. According to embodiments of the invention, the weft yarns 304 are of lower tensile strength material compared to the material of the warp yarns 302. For example, the warp yarns 302 comprise glass, and the weft yarns 304 comprise a more pliable material, such as a natural fiber material, polymer, plastic or other material described herein.
After being interlaced, the mesh 300 is coated with a polymeric binder, for example, Acrylic 292, that adheres the yarns together at crossovers in the mesh 300 where the warp yarns 302 cross over the weft yarns 304, and additionally where the pairs of warp yarns 302 cross over each other in the hurl leno weave. In
The 0033 mesh is commercially available from Saint-Gobain Technical Fabrics Canada, Ltd. and has the following construction.
(a.) A leno weave of ASTM D-3775 fiber glass yarns
(b.) 25 warp yarns per 10 cm., 20 weft yarns per 10 cm.
(c.) weight of 80 g/m2 by ASTM D-3776
(d.) thickmess of 0.31 mm. by ASTM D-1777, and
(e.) minimum tensile strength 350 Newtons per 2.54 cm. by ASTM D-5053.
The lengthwise direction of the moulding 100 is the direction along which bending and undue thermal expansion loads occur. The mesh 300 is always applied to the foam core 200 such that the warp yarns 302, further referred to as, the machine direction yarns, extend and run substantially parallel to the longitudinal axis, or lengthwise, of the moulding 100 and core 200, and are adhered in place by the adhesive. Thereby, the warp yarns 302 are always substantially linear and straight when they are positioned against the profile 202 of respective curved surfaces of the moulding 100. The warp yarns 302 resist the longitudinal beam bending loads and the longitudinal thermal expansion and contraction loads. Since the warp yarns 302 are always substantially straight and longitudinal of the core 200 when they are positioned against the profile 202, they are substantially free of bends. The warp yarns 302 are interlaced substantially straight in the mesh 300 to limit the strain that would result from having to straighten the warp yarns 302. Further, the substantially limited strain of the warp yarns 302 substantially limits the stress transferred to the weft yarns 304. Further, the warp yarns 302 must be substantially free of torque when interlaced in the mesh 300 to limit, and even avoid, undue undulation or bending. Accordingly, a hurl leno weave is selected for the mesh 300, which has a low internal torque component.
The architectural features of the moulding 100 and core 200 comprise one or more curved surfaces that provide the moulding 100 with a decorative appearance. The profile 202 of the curved surfaces is curved with respective radii of curvature transverse to a longitudinal axis, lengthwise, of the moulding 100. For example, the one or more curved surfaces comprise, reversely curved surfaces, outside corners and inside corners, respectively, which are difficult for the mesh 300 to bend and conform thereagainst. The weft yarns 304, extend in the weft direction, or cross-machine direction relative to the warp yarns 302. Moreover, the weft yarns 304 extend in directions transverse to the longitudinal axis of the moulding 100. In the transverse directions the bending loads of the moulding 100 and thermal dimensional loads are substantially less than such loads in the longitudinal direction. The weft yarns 304 are selected, less for resisting high loads, and more for their capability of bending and conforming to and against the curved surfaces of the core 200 of the moulding 100, with substantially limited or reduced elastic strain contributing to a tendency for shape memory recovery of the weft yarns 304. By relieving the elastic strain and relieving the tendency for shape memory recovery, the bent weft yarns 304 remain fixed in place after being bent to conform to and against the curved profile 202 of the curved architectural features.
An exemplary embodiment of a mesh 300 is disclosed by TABLE 1 compared with an existing 0033 fiber glass fabric available from Saint-Gobain Vetrotex.
The weft yarns 304 are moved to bend and conform along the curved profile 202. The greater the complexity of the curved profile 202 the more bends are required in the weft yarns 304, which increases the likelihood that bending produces elastic strain in the weft yarns 304. The weft yarns 304 are not required to exhibit high tensile strength, such that another embodiment of the weft yarns 304 comprises a reduced or limited yield or tex (grams/1000 meters of the yarn) or denier (grams/9000 meters) allowing them to bend with limited elastic strain tending to cause shape memory recovery. The yield of fibers, particularly, polyester, rayon, cotton, nylon or other polyamide yarns is usually expressed in units of denier rather than tex. According to an embodiment of the invention, the weft yarns 304 comprise one or more yarn materials, which are relatively limp or ductile, or both limp and ductile, when bent. Such weft yarns 304 are bent to conform to and against the curved profile 200 without incurring significant elastic strain contributing to a tendency for shape memory recovery of the weft yarns 304. For example, the weft yarns 304 comprise multifilaments, fiber rovings, ribbons or strands including, but not limited to, cellulose, cotton, kapok, sisal, flax, hemp, jute, kenaf, ramie, silk, wool, acetate, azlon, acrylic, nylon, saran, spandex, olefin, polyester, polyethylene, rayon, triacetate, vinal and combinations thereof.
According to another embodiment of the invention, the weft yarns 304 comprise a binder coating of a ductile, low elastic modulus binder material, for example, a polyacrylic, rather than a stiff, high elastic modulus material, such as, styrene butadiene rubber (SBR).
The warp yarns 302 in the woven mesh 300 tend to apply torque to the weft yarns 304. Such torque tends to induce a significant strain on the weft yarns 304 that would contribute to an undesired tendency for shape memory recovery. Accordingly, the mesh 300 comprises a hurl leno weave to minimize the torque applied by the warp yarns 302 to the mesh yarns, and particularly, when the mesh 300 is interlaced with warp yarns 302 of greater areal weight than the weft yarns 304.
The hurl leno weave 500 will now be described. A first warp yarn strand 502 is woven to cross over a first weft yarn 505 while a second warp yarn strand 504 is woven to cross under the first weft yarn 505 and then to cross over the first warp yarn strand 502 to produce a self crossover 508.
Then the first warp yarn strand 502 crosses under a successive or second weft yarn 506 while the second warp yarn strand 504 crosses over the second weft yarn 506, without producing another self crossover like the self crossover 508.
Then the first warp yarn strand 502 crosses over a successive third warp yarn 505a, while the second warp yarn strand 504 crosses under the third warp yarn 505a and under the first warp yarn strand 502 that has crossed over the third warp yarn 505a. Another self crossover 508 is produced wherein the warp yarn strands 502, 504 cross over each other
Then the first warp yarn strand 502 crossed under a successive fourth warp yarn 506a, while the second warp strand 504 crosses over the fourth warp yarn 506a without crossing over the first warp yarn strand 502 that has crossed under the fourth warp yarn 506a. No self crossover is produced like the self crossover 508. The weave is repeated to interlace the two warp yarn strands 502, 504 with successive weft yarns to produce self crossovers 508 that are less in number than the number of successive weft yarns, such as, the self crossover 508 and the successive weft yarns 505, 506, 505a, 506a. The number of self crossovers 508 is less than the number of successive weft yarns 304,
According to embodiments of the invention, the reinforcement mesh 300 or 500 includes successive weft yarns 505, 506, 505a, 506a, which are consecutive and adjacent or which include additional weft yarns, respectively, between successive weft yarns 505, 506, 505a, 506a. Although the exemplary hurl leno weave 500 is disclosed in
In
Further, according to TABLE 1, the mesh 300 is interlaced with warp yarns 302 of greater areal weight than the weft yarns 304 (134 tex, two warp yarns 302 of fiber glass versus 56 tex or 500 denier, one weft yarn of polyester). A greater mass and surface area of glass yarns in the warp direction means that a higher volume of adhesive is carried by the glass yarns, which increases the adhesion or adherence of the mesh 300 to the moulding, and counteracts a tendency for the weft yarns 304 for shape memory recovery. The glass yarns in the warp direction increases the strength of the mesh 300, such that the mesh 300 is rolled up on itself into a roll, and is unwound without tearing either the warp yarns 302 or the weft yarns 304. The breaking strength of the mesh 300 actually increased by 61% compared to the existing 0033 fabric, which corresponds to the 61% increase in the weight of warp yarns 302 in the warp direction. The areal weight of the mesh 300 is 87 g/m2. The industry has adopted a standard for a mesh areal weight at 2.5 ounces/yard2 (85 g/m2). However, the invention is not limited to a specific mesh areal weight. There is an opportunity to reduce or limit the areal weight and cost of the individual warp yarns 302, and of the mesh 300, to comply with a lower amount of resistance to bending by a specific architectural feature. The warp is in the direction in which reinforcement to resist bending is needed by the moulding. The strength gain or reduction in the warp direction can be adjusted by a corresponding adjustment in either the areal weight or the tex of the warp yarns 302 to correspond with an amount of resistance to bending required by a specific architectural feature of a moulding. Thus, an embodiment of the invention involves limiting or reducing the tex of the warp yarns 302 to comply with a lower amount of resistance to bending corresponding to specific architectural features of the moulding 200.
There is an opportunity to reduce or limit the areal weight and cost of the individual weft yarns 304, and of the mesh 300, by one or more of; using polyester or other polymeric warp yarns 302 in place of fiber glass or other stiff warp yarns 302, reducing or limiting the count of the weft yarns 304 (yarns/10 cm. unit length) and reducing or limiting the yield or tex or denier of the weft yarns 304. In TABLE 1, a mesh 300 has polyester weft yarns 304 compared to fiber glass in the existing 0033 fabric. Polyester has a tensile elastic modulus that is 30 times lower than that of glass. Thus, polyester is more ductile, more limp and bends easier with less resistance to bending than does glass. The present invention includes, but is not limited to polyester warp yarns 302. Further, the mesh 300 has a slightly lower count in the weft direction compared to an existing 0033 fabric (17.7/10 cm. versus 19.8/10 cm.). The weft yarn count can be reduced or limited further when the ariel weight of the completed mesh 300 is permitted to fall below the industry accepted standard at 2.5 oz/yd2 (85 g/m2).
This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical, ” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.
Although the invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.
