Patent Application
20070045897
The invention relates in general to apparatuses and methods for producing cast articles, and in particular to a plastic tray for constructing a mold to manufacture a simulated stone product, and to a method of manufacturing a simulated stone product using the tray.
Simulated stone products include simulated stone veneers and simulated stone architectural trim products. Simulated stone veneers are used as a lightweight veneer facing on masonry, metal framed, or wood framed construction for architectural aesthetics. The products can be used for exterior applications such as building walls or interior applications such as fireplaces. Simulated stone architectural trim products include capstones, hearthstones, keystones, trimstones and the like. The simulated stone products are usually lower in cost than the natural stones that they replace. CULTURED STONE® products are simulated stone products manufactured by Cultured Stone Corporation, a division of Owens Corning, Napa, Calif. The Cultured Stone product line includes hundreds of precast stone veneers and architectural trim products that replicate an extensive variety of textures, sizes, shapes and colors of natural stone. The products are manufactured by casting them in molds taken from natural stones. The molds include a latex layer having a mold cavity, a structural foam that supports the bottom of the latex layer, and a tray that holds the foam and the latex layer. The current trays include a metal frame and a plywood bottom.
Several patents or published applications disclose polymer molds used to manufacture stone or cement articles. For example, U.S. Patent Application Publication No. 2004/0070106 discloses a method and apparatus for molding articles such as stone panels. The molds are preferably formed from flexible polymer materials. Each of U.S. Pat. Nos. 3,995,086 and 4,036,839 discloses a shaped cement article cast in a polymer mold.
The invention relates to a mold for manufacturing a simulated stone product. The mold includes a flexible layer having a mold cavity in the shape of the simulated stone product. The flexible layer includes a first surface in which the mold cavity is formed and a second surface opposite the first surface. The mold also includes a structural foam that conforms to the shape of the second surface of the flexible layer and provides support to the second surface. The mold further includes a plastic tray holding the structural foam and the flexible layer.
Another embodiment of the invention relates to a plastic tray for constructing a mold to manufacture a simulated stone product. The plastic tray is structured to hold a flexible layer having a mold cavity in the shape of the simulated stone product. The flexible layer includes a first surface in which the mold cavity is formed and a second surface opposite the first surface. The tray is also structured to hold a structural foam that conforms to the shape of the second surface of the flexible layer and provides support to the second surface. The tray includes at least one opening for introducing the structural foam between the tray and the flexible layer. The tray also includes at least one stiffening structure that increases rigidity of the tray.
Another embodiment of the invention relates to a method of manufacturing a simulated stone product. A flexible layer is applied over a master mold that includes a natural stone protruding from a base, so that the flexible layer conforms to the shape of the protruding natural stone to form a mold cavity in a first surface of the flexible layer. The flexible layer also includes a second surface opposite the first surface. A plastic tray is positioned over the master mold to enclose the flexible layer. A structural foam is introduced between the plastic tray and the flexible layer, so that the foam conforms to the shape of the second surface of the flexible layer and provides support to the second surface. The plastic tray, the structural foam and the flexible layer are removed from the master mold. A production mold is formed by positioning the plastic tray, the structural foam and the flexible layer so that the plastic tray holds the structural foam and the flexible layer, and the structural foam provides support to the second surface of the flexible layer. A castable material is introduced into the mold cavity in the first surface of the flexible layer. The castable material is allowed to harden to form the simulated stone product. The simulated stone product is then removed from the mold cavity.
Various advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.
Referring to the drawings,
For the sake of simplification, in the illustrated method the natural stones 14 are flat pieces that are large and generally square-shaped. However, any desired type of natural stones can be simulated by the method. For example, the CULTURED STONE® products include the following. Cultured Stone® Textures: Blended Textures, Cobblefield®, Coral Stone, Country. Ledgestone, Dressed Fieldstone, Drystack Ledgestone, European Castle, Fieldstone, Limestone, Old Country Fieldstone, Pro-Fit Ledgestone®, River Rock, Southern Ledgestone, Split Face, Stream Stones and Weather Edge Ledgestone. Cultured Brick®: Used Brick. Architectural Trim: Capstones, Hearthstones, Keystones and Trim Stones, Quoins, Tuscan Lintels, Watertables and Sills. These products are illustrated on the web site www.culturedstone.com. The simulated stone products can be in the form of flat pieces, corner pieces, hearth pieces and architectural trim products.
The apparatuses 10 also include a flexible layer 18 covering the top of the master mold 12. The flexible layer 18 is applied such that it conforms to the shape of the natural stones 14 and the top of the base 16, closely following their contours.
As best shown in
Referring to
As shown in
The plastic tray 26 includes at least one opening for introducing the structural foam between the tray and the flexible layer 18. In the illustrated embodiment, the plastic tray 26 includes two such openings 34. The rigid fixture 30 is structured to provide access to the openings 34 from the exterior of the fixture. In the embodiment shown, the rigid fixture 30 includes two slots 36 that overlap the openings 34 and are sized to provide access to the openings.
As shown in
The cured structural foam 38 is a rigid, load supporting foam capable of adding structural strength. Any suitable type of structural foam can be used in the manufacturing method. Some examples include polyurethane, polystyrene and polyphenylene oxide; many other types of structural foams are well known.
After the structural foam 38 has cured, the rigid fixture 30 is removed from over the plastic tray 26. Then the plastic tray 26 and the structural foam 38 are removed from the master mold 12. The flexible layer 18 is also removed from the master mold 12. The flexible layer 18 may be removed along with the plastic tray 26 and the structural foam 38, or it may be removed separately. For example, the flexible layer 18 may tend to adhere to the master mold 12, so that it is removed separately by peeling it off the master mold after the plastic tray and the structural foam have been removed. The flexible layer retains its shape after removal from the master mold; in particular, the shapes of the mold cavities 20 are retained in the flexible layer.
As shown in
After the production mold 42 has been set in position, a castable material 46 is introduced into the mold cavities 20 formed in the flexible layer 18. The castable material 46 can be introduced by any suitable means, such as by pouring it into the mold cavities 20. The production mold 42 may be vibrated after introducing the castable material into the mold cavity to insure that the castable material flows into all the contours of the mold cavity. Also, the upper surface of the castable material in the mold cavity may be raked to level the surface and to provide a textured surface to assist in bonding the finished product to mortar during installation of the product.
After hardening, the castable material 46 in each of the mold cavities 20 becomes a simulated stone veneer 46a, as shown in
The simulated stone veneers 46a are then removed from the mold cavities 20. Any suitable means can be used for removing the simulated stone veneers 46a. One embodiment of a means for removing the simulated stone veneers 46a is partially illustrated in
The simulated stone veneers 46a are usually relatively thin compared to the natural stones that they replace. For example, the simulated stone veneers may have a thickness of up to about 3 inches, and an average thickness of about 1¾ inches, compared to natural stones that have more depth.
The simulated stone products are usually installed by cementing them in place with mortar. For example, the simulated stone veneers are usually applied with mortar to any suitable wall surface, resulting in a permanent and strong attachment of the veneer to the wall surface. Optionally, one or more layers of different material (e.g., insulation, sheathing and/or weather-resistant material) may be first applied to the wall surface, before applying the simulated stone veneers with mortar to the outermost of those layers.
The apparatuses 60 also include a flexible layer 68 covering the top of the master mold 62. The flexible layer 68 conforms to the shape of the protruding natural stone 64 to form a mold cavity 70 in a first surface 72 of the flexible layer. The mold cavity 70 is in the shape of the protruding portion of the natural stone 64, and the mold cavity is also in the shape of the simulated stone veneer as described below.
The apparatuses 60 also include a plastic tray 76 according to the invention. The plastic tray 76 is structured to be positioned over the master mold 62 to enclose the flexible layer 68. Like the master mold 62, the plastic tray 76 extends in a direction away from the viewer, so that the plastic tray 76 has an elongated shape with an L-shaped cross section. A space 78 remains between the plastic tray 76 and the flexible layer 68.
The apparatuses 60 may also include a rigid fixture 80. The rigid fixture 80 is structured to be positioned over the plastic tray 76 after the plastic tray has been positioned over the master mold 62, and then held in place by chains or other means.
The plastic tray 76 includes at least one opening 84 for introducing a structural foam between the tray and the flexible layer 68. The rigid fixture 80 includes a slot 86 that overlaps the opening 84 and is sized to provide access to the opening.
As shown in
After the structural foam 88 has cured, the rigid fixture 80 is removed from over the plastic tray 76. Then the plastic tray 76 and the structural foam 88 are removed from the master mold 62. The flexible layer 68 is also removed from the master mold 62.
As shown in
After the production mold 92 has been set in position, a castable material 96 is introduced into the mold cavity 70 formed in the flexible layer 68. After hardening, the castable material 96 in the mold cavity 70 becomes a simulated stone veneer 96a in the form of a corner piece, as shown in
The simulated stone veneer 96a is then removed from the mold cavity 70. Adjacent to the opening 84 in the plastic tray 76, a void 98 remains in the structural foam 88 at the location where the foam injection nozzle 40 (
In contrast to the previously used trays including a metal frame and a plywood bottom, the plastic tray 26 according to the invention is made from plastic. Preferably, the tray is made from a flexible plastic material. A flexible plastic tray is generally more resistant to damage than the metal/plywood tray, so that it can be reused in the manufacturing operation for a longer period of time. The flexibility allows the plastic tray to bend on the production line. Also, it can regain its original shape after being deformed. The plastic tray is also lighter than the metal/plywood tray. Any suitable plastic/polymeric material can be used to make the plastic tray. In one embodiment, the plastic tray is made from a thermoformable plastic. Two specific examples of thermoformable plastics that may be suitable include polyethylene and acrylonitrile-butadiene-styrene copolymer (ABS). Other examples of thermoformable plastics include polypropylene, polybutene, poly(4-methyl-pentene), ethylene/propylene copolymers, ethylene/butene copolymers, propylene/butene copolymers, ethylene/vinyl alkanoate copolymers, ethylene/alkylacrylate copolymers, and ethylene/alkylmethacrylate copolymers. Many other types of thermoformable plastics are well known.
The plastic tray 26 can be made from plastic having any suitable thickness for providing the tray with its functional properties. In one embodiment, the thickness of the plastic used to make the plastic tray 26 is between about 0.15 inch and about 0.25 inch.
The plastic tray 26 includes at least one opening 34 for introducing the structural foam between the tray and the flexible layer, as described above. Any suitable number of openings can be used. In the illustrated embodiment, the plastic tray 26 includes two openings 34 through one side 112a of the tray, and a third opening 54 through an opposite side 112c of the tray. As described above, the two openings 34 can be used for injecting the structural foam, and subsequently one of the openings 34 can be used for injecting air to separate the flexible layer from the tray and the flexible foam. The third opening 54 allows the air to pass through the opposite side of the tray.
The plastic tray 26 also includes at least one stiffening structure that increases rigidity of the tray. Any suitable stiffening structure(s) can be used, such as ribs, offsets, webs, or other such structures. In the illustrated embodiment, the bottom 110 of the plastic tray 26 includes a plurality of stiffening ribs 114. The sides 112a-d of the plastic tray include a plurality of offsets 116 or ribs that increase the rigidity of the sides.
The plastic tray 26 may also include at least one locking structure that locks the structural foam inside the tray. This retains the structural foam inside the plastic tray when the tray is removed from the top of the master mold. Any suitable locking structure(s) can be included. In the illustrated embodiment, opposite sides 112b and 112d of the plastic tray 26 include extended protrusions 118 that protrude a short distance into the interior of the tray. The structural foam locks around these protrusions to mechanically hold the foam in place during the stone manufacturing operation. In another embodiment, the locking structure(s) can be cavities instead of protrusions.
The plastic tray 26 may further include at least one stacking structure that facilitates stacking the tray with a second tray. For example, during the manufacturing operation it may be desirable to stack a plurality of trays on top of each other while the castable material hardens. Any suitable stacking feature(s) can be included. In the illustrated embodiment, the plastic tray 26 includes a lip 120 that extends around the perimeter of the tray on top of the sides 112a-d and corners 122 of the tray. The lip facilitates the stacking of a second plastic tray on top of the illustrated plastic tray. The lip also increases the stiffness of the plastic tray, such as by helping the sides to keep their shape. The lip also provides a place to clamp the flexible layer during foam injection and air injection.
The plastic tray 26 may also include radiused or rounded corners 122. The rounded corners 122 increase the strength of the plastic tray 26 compared to squared corners. The rounded corners also facilitate conveying the plastic tray through a conveyor system in a production line; squared corners may sometimes hang up or snag on the conveyor guides of a conveyor system. In the illustrated embodiment, the plastic tray 26 also includes rounded lower edges 124 between the sides 112a-d and the bottom 110.
In the illustrated embodiment of the plastic tray 26, the sides 112a-d of the tray are not perpendicular to the bottom 110, but rather extend outward at a small angle from the bottom to the top of the tray. For example, if the plastic tray is 48 inches×48 inches at the inside bottom, the tray may be 50 inches×50 inches at the inside top. The angled sides facilitate removing the plastic tray from its mold during a thermoforming process of manufacturing the tray, as described below. The plastic tray may further include at least one zero draft structure having a surface that is perpendicular to the bottom. In the embodiment shown, the plastic tray includes three zero draft pads 126. The zero draft pads have an exterior surface that is perpendicular to the bottom of the plastic tray. The zero draft pads may serve two purposes. One purpose is to provide a vertical surface for abutment cups or shields of the foam injection apparatus and the air injection apparatus during the manufacturing operation, making it easier to handle the apparatus and avoid leakage. Another purpose is to provide vertical exterior surfaces that engage the conveyor guides of a conveyor system to facilitate conveying the plastic tray during the manufacturing operation.
The plastic trays according to the invention can be produced by any suitable manufacturing process. In one embodiment, the plastic trays are produced by a thermoforming process such as vacuum thermoforming. Typical vacuum thermoforming equipment includes a mold that has a shape opposite that of the plastic tray (in other words, the mold is the “positive” of the plastic tray). The mold is heated, and a sheet of thermoformable plastic is heated to its softening point. Then the mold and the plastic sheet are brought together such that the plastic sheet deforms over the positive shape of the mold. The mold includes small holes that enable a vacuum to be pulled on the plastic sheet so that the sheet follows the contours of the mold. The mold and the now formed plastic tray are allowed to cool. Then the tray is removed from the mold and subjected to a trimming operation to remove any flashing. Openings are then cut through the sides of the tray.
In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.
