Patent Application
20110131921
Synthetic doors, those made of thermoset plastics with skins formed by using a sheet molded composition (SMC), a bulk molded composition (BMC) or fiber reinforced plastic composition (FRPC), have become very popular in the building trades. The popularity of these doors stems from the fact such doors are lightweight, often have wood graining on their outer surfaces for aesthetic purposes and come in a multitude of panel configurations, the latter being a feature of more expensive doors. Moreover they do not warp, are easy to paint and are impervious to rot and insect attack.
A synthetic door of one type described is disclosed in U.S. Pat. No. 4,864,789 issued to Thorn wherein skins are attached to opposite sides of a rectangular frame. Each of the skins is a compression molded sheet molding compound (SMC) panel which includes 15% to 40% fibrous glass reinforcement, by weight, and 10% to 40% inert material filler, by weight, dispersed in the molding resin. Unsaturated polyester polymers blended with vinyl monomers such as styrene are molding resins that may be cured under heat and pressure form the thermoset compression molded skins. The molding resins include unsaturated polyester resin compositions and modifications as disclosed in, for examples, U.S. Pat. Nos. 3,772,241 and 3,883,612.
Each of the skin of such doors has a thickness of between 0.050 inch and 0.120 inch and are mounted on the rectangular frame with the interior space between the skins filled with a foamed plastic material.
While the above type of synthetic door was the type first introduced, applicant later developed an improved novel door structure that did not employ the rectangular frame described in the Thorn patent, supra. In applicant's development of this novel door type, interlocking projections are formed adjacent to the lengthwise perimeter of the skins at the time they are compression molded. These projection are normal to the interior surface of the skins and extend upward from the interior surface of each skin about half the width of the assembled door. At the distal ends of these projections, an interlocking joint is formed, such as rib on one projection and a groove on the other, that mesh when the skins are assembled the ribs are fitted into the grooves and secured, such as by gluing. Typically these projections are used in place of the stiles. Rails are inserted between the skins at the top and bottom of the door to close the interior or core of the door and fastened in place. There after the core is filled with a foamed plastic. As a result there is no need for a rectangular frame used in conventional construction of doors of this type as taught by Thorn.
A drawback of many such synthetic doors either type described above is their comparative lack of fire resistance with conventional doors, such as those constructed of wood. Under fire conditions the thin skins are often consumed leading the collapse of the door. This lack of fire resistance has been addressed in the prior art by constructing such doors with panels of cementitious material positioned directly beneath the exterior skins of such a door as shown, for example in U.S. Pat. No. 5,816,017 to Hunt et al, that discloses a fire retardant door which includes a core of fire resistant-blocking material, being Tectonite™, having a fire rating of approximately 90 minutes. U.S. Pat. No. 6,115,976 to Gomez discloses an assembly for sealing a fire resistant door within a door frame during a fire event with a plurality intumescent strips within a slots in each door edge. The intumescent strips are designed to expand upon reaching a reaction temperature n a fire event or other extreme heat source.
U.S. Pat. No. 5,417,024 to San Paolo discloses a fire resistant panel door constructed from panels, stiles, intermediate rail and rails having a core of fire resistant material. The door components are joined together so that the fire resistant material extends substantially continuously from side to side and from top to bottom of the finished door. The fire resistant core of each door panel is recessed within the fire resistant core of the associated rails and stiles to reduce hot gas infiltration through the door which can compromise the door's fire resistance.
U.S. Pat. No. 4,930,276 to Bawa et al. discloses a fire door window construction. The fire door includes a trim strip having inner and outer members. The inner member is of a high density incombustible mineral material or ceramic and is nailed in position to securely and uniformly hold the pane of glass in the door opening. An intumescent caulking compound is applied between an inner portion of the outer trim member and the pane of glass. U.S. Pat. No. 4,441,296 to Grabendike et al. discloses a fire resistant wood door structure designed to pass code and testing laboratories' requirements. U.S. Pat. Nos. 4,529,742; 6,031,040; and 6,153,674 all disclose the use of intumescent compounds/fire barrier materials within door construction to reduce or eliminate the passage of smoke and fire gases between the door and door frame. In such doors inert fillers are used in the core such as calcium carbonate or aluminum trihydrate.
While improving fire resistance such interior panels in such prior art doors substantially increase the weight of the door and create difficulties in manufacturing, handling, and installing them.
One of the objects of the current invention is to improve the fire resistance of synthetic doors of the type described without substantially increasing their weight or costs, thereby obtaining the benefits of easier manufacturing, easier handling, and easier installation.
Another object is the provided a synthetic door with appealing exterior surfaces along with increased fire resistance.
A further object is the provision of a design for a synthetic door which allows cheaper materials to be employed in its construction without seriously comprising its fire resistance.
Other objects and advantages of the novel door structure will be apparent form the disclosures in this specification and the accompanying drawings.
An improved synthetic door having improved fire resistance includes a first door skin having interior, spaced apart raised projections adjacent to its lengthwise edges, with the first door skin having a reinforcing backing sheet secured to its interior surface, a second door skin having interior, spaced apart, raised projections adjacent to its lengthwise edges, with the second skin having a reinforcing backing sheet secured to the interior surface, with the distal ends of the raised projections operable to interlock and create a space between the reinforcing sheets when assembled, a top rail inserted between the reinforcing sheets at the top of the skins and a bottom rail inserted between the reinforcing sheets at the bottom of the skins, with the rails operable to close the interior between the sheets, and a fire resistance phenolic foam disposed in the hollow interior between the reinforcing sheets along with at least one slat of fire resistance material married to the exterior surfaces of the projections and exterior surfaces of the top and bottom rails plus an outer slat of a polyvinyl chloride material disposed on and attached to the exterior surfaces fire proof slats for aesthetic and trimming purposes.
The reinforcing sheets attached to the interior surfaces of the skins are selected from the group of fiberglass cloth or carbon fiber sheets which decompose at much higher temperatures than the skins to which they are attached and maintain a structural connection between door components even after decomposition of its skins.
An exploded perspective of novel synthetic door 20 is shown in
The connection of the skins is shown in
Referring to
The afore described skins 21 and 22 are constructed using conventional thermal set molding processes by employing sheet molded compositions (SMC), bulk molded compositions (BMC) or fiber reinforced plastic compositions (FRPC). In such processes the out surfaces of the skin can include wood graining and panels. Typically these skins will have a thickness from 0.050 inches to 0.120 inches when compression molded.
With the skins 21 and 22 joined by the integral projection 23 as described, and the location of these projections inboard of the outer edges 40 of these skins, there is an extension of these edges of the skins beyond the interlocking projections as can be seen in
It is desirable to add exterior polyvinyl slats 50 and 51 to the exterior edges of the top and bottom rails and fire proof slats for aesthetic reasons and provide a surfaces which can be worked (planed or cut) to fit the door into the door frame. Slats 50 are attached to the top and bottom rails 32 and slats 51 are attached to the slats 41, as can be seen in the exploded perspective in
A bead of an intumescent material can be placed in a groove (not shown) in outer most of the fireproof slats which will expand as polyvinyl slat is burned away so a large gap does not occur between the edges of the door and its door frame. Such intumescent materials are will known and typically comprise from 40 to 70% by weight of a copolymer of vinyl acetate and ethylene as a flexible polymeric binder, and from 15 to 60% by weight of expandable graphite, the percentages being based on the combined weight of said copolymer and the graphite.
Before the skins 21 and 22 are joined as described in reference to
Once skin and reinforcing sheet are married together, skins 21 and 22 are assembled as described. In all the embodiments, a phenolic foam 70, which itself has very little structural integrity, even though it has good fire resistance qualities, is employed in the core 31, typically by an in place foaming technique.
As can be seen in
As to the fire proof slats 32, 33 and 41 they are construction of sheet materials of calcium silicate plate, hard wood, and extruded foamed polyvinyl chloride having a thickness from 1 to 3 inches, and glued in place with a fire proof glue such as a phenolic glue or mechanically secured with fasteners. Using multiple slats in place of single wider slat is desirable limit heat transfer across the slats when hot gases engage the edges of the door where there can be some infiltration these gases in the cracks between the door's edges and the door frame.
In general the described invention allows fire proof materials to be disposed at the edges of the door thereby limiting the weight of the door while maintaining the overall integrity of the door by using sheets of carbon fiber and or glass fiber to hold the components together under adverse fire conditions when the skins are compromised by the heat. Moreover the fire proof materials are located at the door edges where the heat is more intense during a fire.
