HK1090601B - Hollow core door, and method of manufacturing a molded door skin - Google Patents

Description

Hollow core door and method of making a molded door skin

This application is a divisional application of PCT application No. 99810413.2, entitled "method of forming a molded door panel from a flat wood composite material and door panel and door made thereby", having international application date of 27/7/1999.

Technical Field

The present invention relates to a method of forming a molded door skin from a solid flat wood composite material and to the skin and hollow core doors formed thereby. More particularly, the present invention relates to a method of manufacturing a molded door skin, wherein a flat or planar solid blank of wood composite material is preheated, moistened and heated in a press to a temperature sufficient to soften the blank, the press platens are closed under pressure, and the closing pressure is continuously increased to a predetermined threshold to deform the blank into a molded shape conforming to the door skin, and ultimately to form a hollow core door.

Background

Hollow doors are used indoors and outdoors. Many hollow core doors are made with door skins made of wood composites. These wood composites include chipboard, hard high-pressure board, and medium density fiberboard ("MDF"). Wood composites typically employ a resin binder, typically a thermosetting resin, to maintain the wood fibers forming the composite in a solid state.

Hollow core doors may be "flush" (i.e., flat or planar on both major surfaces (i.e., the two door skins are flat and do not include panels molded thereon). Alternatively, the hollow core door may be of the "moulded" type having a series of three-dimensional panels or the like formed or moulded into the skin panel at the time of manufacture.

Standard molded door facings are made from thicker non-solid blocks (mat) or batts (bat) that are pressed in a press to a thinner thickness. The blocks may be made of dry or wet fibers. If the block has a high moisture content, the moisture is squeezed out during the pressing process. The press may be a multi-platen press having a set of skin panel forming cavities. Because the block is in a flexible state prior to pressing, the wood fibers are flowable to conform to the mold, and the finished solid panel is quickly formed into the consumer desired configuration. Because of the high capital investment required to build a factory to produce molded panels, manufacturers typically require a single order to produce a large number of panels for their maximum production efficiency. Small orders are not cost effective.

A flat door panel may be manufactured in a manner similar to a molded panel, except that the original wood fiber block or batt is flattened and not molded into a panel or the like in a three-dimensional manner. In addition, a continuous belt press may be used to make flat panels. Accordingly, flat door facings are produced from relatively thick non-solid wood fiber blocks or batts that are pressed into a flat or planar shape to form a flat solid facing. This means that standard medium density fiberboard or hard high pressure board can be used.

Standard molded door facings are relatively expensive due to the relatively high cost required of the molds, presses, etc. In addition, flat or planar panels for flat doors are less expensive, but do not have the aesthetic characteristics typically required by consumers.

Because of the different costs of wood composite "flush" or "flat" panels as compared to wood composite "molded" panels, attempts have been made to convert flush panels to molded panels to produce molded doors less expensively. This prior effort has not been commercially successful because of the unsatisfactory surface shape. Efforts to convert flush panels to molded panels have typically resulted in cracking, scratching, or other unsightly shapes and/or contours in the final molded panel.

Accordingly, there is a need for a method of forming a molded door skin from a flat wood composite blank that can use a standard flush or flat blank as a base material and produce a molded door skin having consumer acceptable characteristics and surface characteristics. Another need is to make a flat wood composite door panel into a molded door that is moisture resistant so that it can be used outdoors.

In us patent application 08/942976 (a family of co-pending patent applications of british patent application 9707318.3), owned 1997.10.2, the present applicant discloses a method of manufacturing a hollow core door by forming a flush or flat door skin into a molded skin using a press in which the pressure applied to the press platens is progressively increased. The method of the applicant's prior application may be further improved to allow more efficient formation of flat panels and to provide improved strength in the finished door, as will be described below.

The present invention addresses these needs and others. The present invention is directed to fulfilling the above needs.

Disclosure of Invention

It is a primary object of the present invention to provide a method of forming a flush wood composite blank into a molded door skin by continuously applying increased pressure to a moistened and softened flat blank such that the resulting skin has consumer acceptable molding characteristics and surface characteristics.

It is a further object of the present invention to provide a moisture resistant molded door panel which is not subject to deformation and is therefore suitable for outdoor use.

According to the present invention, there is provided a method of manufacturing a door panel, comprising the steps of: a solid flat blank of wood composite material (i.e., compressed from a thick, loose, aqueous state) is provided. The blanks are preheated, moistened, coated with a sealer, and placed between the platens of a heated press. The pressing plate is heated to a temperature sufficient to soften the resin contained in the blank plate and soften the blank plate, and a pressure sufficient to close the pressing plate is applied, and the pressure is continuously increased, thereby deforming the blank plate into a molded shape defined by the shape of the pressing plate. The closing rate of the press is determined by and a function of a number of characteristic parameters including hardness, density distribution, depth of the die, and percent binder or resin content in the flush panel to be shaped. The molded, shaped blank is then removed from between the press platens.

In accordance with the present invention, a door panel is provided that includes a molded three-dimensional blank of medium density fiberboard. The blank has a first portion having a first predetermined thickness. The blank has a second portion having a second predetermined thickness. The second thickness is less than the first thickness.

According to the present invention, there is provided a door panel which, after being reformed by a press, comprises a three-dimensional blank of molded medium density fiberboard having a density of about 550-³The density of which is substantially uniform throughout the thickness of the panel (i.e., about 75kg/m throughout the thickness of the panel³Preferably about + -25 kg/m³Within range).

In accordance with the present invention, a door is provided that includes a peripheral door frame having oppositely disposed sides. At least a first molded panel is provided. The panel has first and second sides. The first or exterior side of the panel has a moisture barrier attached over its entire surface. The second or interior side of the door panel is secured to one side of the door frame. The second door panel is fixed to an opposite side of the door frame.

It is a further object of the present invention to provide a door panel that, after being shaped into a molded panel, has greater strength than standard flush or flat skin blanks and molded panels. In one embodiment, the bond strength of the orthopedic molded panels is at least about 2.0N/mm²Preferably at least about 2.5N/mm². This can and usually doubles the internal bond after processing.

These and other objects and advantages of the present invention will be apparent from the following detailed description of the embodiments of the invention, which is to be read in connection with the accompanying drawings.

Drawings

FIG. 1 is a plan view of a hollow core door including a pair of opposed cosmetic panels (i.e., molded from flat panels) made in accordance with an embodiment of the present invention.

Fig. 2 is a partial cross-sectional view taken along 2-2 of fig. 1.

Figure 3 is a partial cross-sectional view of a flat or flush door skin in the compression molding apparatus of the present invention showing the flat or flush skin still in a flat condition.

Fig. 4 is a flow diagram of a method of manufacturing the hollow core door of fig. 1 and 2, according to an embodiment of the present invention.

FIG. 5 is a flow diagram of a solid flat plate entering the infrared preheating station, humidifying station, sealing station, pre-pressing station, and pressurizing station of FIG. 4.

Fig. 6 is a cross-sectional view of a facer panel according to the embodiment of fig. 1-5.

Fig. 7 is a graph of molding pressure versus time for the embodiment of the present invention shown in fig. 4 and 5, showing that pressure is continuously applied to the press plate during the pressing (reforming) of the flat panel, and then the press plate is maintained at a constant pressure, after which the downward sloping curve indicates that the press plate pressure is released to open the press mold.

FIG. 8 is a graph of an embodiment of the present invention, each shaping panel having a substantially constant density throughout its thickness.

FIG. 9 is a graph of an embodiment of the present invention showing the rate of die platen closure as a function of the hardness of the pressed solid flat door skin to be reformed.

Fig. 10 is a flow chart of a method and apparatus for manufacturing the door of fig. 1-9 in accordance with an embodiment of the present invention.

Detailed Description

In the drawings, like numbering represents like elements.

As shown in fig. 1 and 2, according to an embodiment of the present invention, hollow core door 1 can be efficiently manufactured to be aesthetically similar to standard molded hollow core doors made by methods similar to those commonly used to make solid fiber doors from stiles, rails, and panels. According to the invention, the panels 7, 9 of the door 1 are not moulded directly from non-solid blocks or batts to form a three-dimensional moulded panel 3 as in standard moulded doors. Instead, as shown in fig. 3, a flush (i.e., flat or planar) solid composite panel 10 is provided that has been pressed into a compacted rectangular flat shape, pre-heated, moistened, sealed, and then subjected to a reforming process on a platen press to obtain reformed molded panels 7, 9, each having panels 3. The form-moulded panels 7, 9 may be used to manufacture the hollow core door 1.

By shaping the flat pressed blank 10 in this manner, the aforementioned prior art door panel molding process (e.g., by dies, presses, and the like that can process and press non-solid batts into molded panels) can be eliminated. Thus, the molded door 1 can be manufactured more efficiently and at lower cost, and the resulting panel has twice as much strength as a standard molded panel, and twice as much strength as a standard flush or flat panel. Standard die of Masonite corporationThe bond strength of the finished panel is typically about 1.4N/mm²The bonding strength of the facer sheets 7, 9 of embodiments of the present invention is at least about 2.0N/mm²And preferably at least about 2.5N/mm²。

According to an embodiment of the invention, it is important to control the closing rate of the platens 17, 19 of the press 21, as shown in fig. 3, as a function of the hardness, density profile, depth of the die, and percent binder or resin content of the sheet 10 to be shaped, so that when the sheet 10 is shaped, increased pressure is continuously applied to the platens 17, 19 of the press 21 in a non-stepped or progressively smooth manner. As the rate of closure is controlled as a function of the material composition of the panel 10, the continued increase in pressure results in a more effective reformed panel 7, 9 with fewer surface cracks and allows the wood fibers of the flat panel 10 to more readily flow to new locations within the panel 7, 9 during the reforming process.

The addition of a conditioning resin (e.g., melamine or urea formaldehyde thermosetting resin) to the solid panel 10 prior to pressing results in panels 7, 9 that are stronger and more aesthetically pleasing. The stretching or broken internal bonds created when the added resin deforms the panel actually repair the fibers and ultimately make the bond stronger than it was originally. The amount of these resins can be varied to suit the final properties of the product as required by moisture resistance and internal bond strength.

As shown in fig. 1 and 2, the hollow core door 1 appears to be of the standard molded type, but is not actually. The door 1 is made using a pressed flush or flat panel 10 that is reshaped according to an embodiment of the present invention to form molded panels 7 and 9 having panels 3. The door 1 comprises on each main surface a plurality of three-dimensionally shaped panels 3 and corresponding raised planar portions 5. The door 1 comprises a pair of opposed, shaped panels 7 and 9 (aesthetically similar to a conventional moulded panel), the panels 7 and 9 defining a hollow region 11 therebetween. In doors used indoors (as shown in fig. 1), the panels 7 and 9 of the door 1 present the outer major surfaces of the door 1, whereas in doors used externally (as shown in fig. 2), a melamine impregnated crepe paper or phenolic resin crepe paper 13 may be provided on the entire or entire outer surface of each panel 7 and 9. The paper 13 provides a moisture barrier so that the moisture absorbed by the door 1 is reduced.

As shown in fig. 1 and 2, the trim panels 7 and 9 of the door 1 are adhesively secured to the door frame 15, for example by polyvinyl acetate ("PVA"). It will be apparent that the door frame 15 extends around the perimeter of the rectangular shaped trim panels 7 and 9 and the door 1 and typically includes two parallel wooden stiles extending along the longitudinal edges of the door and two parallel wooden rails at the bottom and top of the door. The panels 7 and 9 are spaced apart from each other by a door frame 15 to form a hollow area 11 into which foam or the like can be inserted.

Fig. 3 shows solid blank 10 being placed between platens 17 and 19 of die press 21, which will be described in detail below. Blank 10 is prefabricated into the illustrated flush or flat blank 10 by known techniques. Typically, the blank 10 is formed into a solid flat door skin 10 without a molded panel by pressing a relatively thick slab or batt of non-solid wood fibers. At press 21, flat blank (or flat skin blank) 10 is then reshaped to form molded panels 7 and 9, each of which includes panel 3 molded thereon. At the press 21, the bottom platen 19 may remain fixed in position and the upper platen 17 may move vertically relative to the platen 19 to facilitate opening and closing the press. In this manner, when platen 17 is moved downwardly to apply pressure to blank 10, projections 23 (each corresponding to a panel 3 to be formed) mate with corresponding recesses 25 with blank 10 therebetween, thereby reforming flat blank 10 into molded panels 7, 9 with panels 3. Figure 6 shows the reformed panel 7, 9 with the panel 3 after leaving the press 21. In summary, the press 21 can shape the flat blank 10 so as to mold a plurality of panels 3 thereon.

As shown in fig. 6, after reforming in the press 21, each panel 7, 9 has opposed surfaces 31 and 33 constituted by the surfaces of the reformed panel. Each panel has a flat first portion 35 and a flat second portion 37. The portion 37 constitutes, together with the inclined portions 39 and 41, the pane 3 of the plastic panel. The inclined portions 39 and 41 preferably have a shape that facilitates the extraction of the panels 7, 9 from the platens of the press 21 at the end of the reforming process. The portions 35, 37, 39 and 41 have different thicknesses due to the stretching, and the wood fiber flow shapes the blank 10 in the press. For example, for a blank 10 having a nominal thickness of 2.5-5mm, preferably 3.0-3.5mm, the first portion 35 and portion 37 of the shaping panel may be reduced by about 10% from an original thickness of slightly less than 4mm, while the inclined portions 39 and 41 have a thickness of about 2.5-3.5mm (preferably about 3.0 mm). In another embodiment, portions 35, 37, 39 and 41 have approximately the same thickness.

The manufacturing method described below allows the solid pressed flat blank 10 to be formed into a shaped panel 7, 9, the resulting panel 7, 9 being aesthetically pleasing, cost effective to manufacture, substantially crack free and damage free.

As shown in fig. 4, 5 and 10, a solid and flush/flat pressed door blank 10 is provided. The flat blank 10 is preferably a wood composite material such as Medium Density Fiber (MDF) board or a hard high-pressure board bonded together by a thermosetting resin. MDF typically have urea formaldehyde resins as binders that are moldable at temperatures ranging from 320 ° f to about 425 ° f. The MDF solid flat door blank 10 may have a variety of thicknesses and weights ranging from about 3 to about 7 mm. In a preferred embodiment, blank 10 is at an upper thickness range, thereby providing sufficient wood fibers to have sharp and good features and avoid surface cracking in the transition zone. However, any thickness in the range of about 3-7mm may suffice.

Solid flat blank 10 is received at loading station 45. The density of blank 10 is at least about 550kg/m³Preferably about 750-³And the thickness is about 3-7 mm. The initial weight of blank 10 is approximately 340-600 grams (gms). The initial moisture content of the blank 10 is about 7-9% by weight, preferably about 8%. Typically, all of the resin (e.g., melamine or urea formaldehyde) binder in the blank 10 is uncured, as excessive curing can cause embrittlement. Therefore, the temperature of the molten metal is controlled,the manufacturer cures the treated blank 10 sufficiently to provide it with sufficient hardness characteristics and leave some uncured resin. About 5-20% (and sometimes about 10-15%) of the resin in the flat blank 10 is uncured or undercured. 5-20% of the uncured resin in flat blank 10 is subsequently cured during the reforming process, so that reformed panels 7 and 9 have a higher hardness than other molded panels currently available.

Alternatively, blank 10 may be brushed clean at cleaning station 46 (see FIG. 10) to remove dirt, dust, and other potential surface contaminants.

As shown in FIGS. 4 and 5, blank 10 is then fed into an Infrared (IR) preheating station 47, which preheats panel 10 using infrared radiation or any effective means for raising the temperature of the sheet. The infrared preheater 47 preferably has a series of upper and lower infrared lamps with the blank 10 positioned between the upper and lower infrared lamps. The outputs of the infrared banks are individually controlled to accommodate different thicknesses, compositions, etc. of blank 10 so that blank 10 is not heated too high. Preheating to approximately 80-100 c begins the initial pre-treatment of blank 10 and enhances its ability to accept additional moisture (e.g., water vapor, water mist, or direct roller coating). Preheating station 47 removes about 3-15 grams of the weight of blank 10 when blank 10 is preheated for a period of about 25-125 seconds, preferably about 30-90 seconds. Blank 10 leaves pre-heat station 47 with a moisture content of about 5-7%. The preheating station 47 preheats at least one surface of the slab to at least about 80 ℃.

The preheated flat blank 10 is then fed to a direct roll coating station 49 where moisture is added. As shown in fig. 5, rollers 50 and/or 51 of table 49 rotatably contact the blank and apply moisture (e.g., water or the like) to at least one major surface (and possibly both major surfaces in some embodiments) of blank 10. The moisture content of the mat is increased to about 9-15%, preferably about 10-12%. During the addition of moisture, the temperature of blank 10 is maintained at approximately 80-100 ℃ to readily accept the added moisture. In one embodiment, roller 50 is a non-moisture-added press roller, and moisture is added to blank 10 by roller 51. A moisturizing agent (e.g., water) containing a surfactant to aid in moisture absorption is applied to one or both major surfaces of blank 10 in an amount of about 60 to about 290 grams per square meter, and preferably about 80 to about 120 grams per square meter. According to another embodiment of the invention, moisture may be added to flat, solid blank 10 by directing water vapor onto blank 10 at station 49.

In one embodiment, the major surface of blank 10 may be grit blasted prior to adding moisture so that moisture is more effectively absorbed into the surface, thereby effectively increasing the moisture content of the blank. The blasting removes material from the surface of blank 10, which typically has a cured resin content in excess of the internal cured resin content. The resin removed from the surface facilitates the entry of moisture into the blank 10.

The moisture-added slab 10 then enters the two-roll coating apparatus 55. Rollers 57 and 59 contact blank 10 and apply a conditioning resin and a tintable sealer to flat blank 10. The applied resin and sealant may increase the moisture content of the green sheet 10 to about 12-14% by weight. The conditioning resin may include water with about 5-20% by weight of a melamine or urea resin additive. At the stage 55, about 20-200g/m²Is applied to the raw plate 10. Thus, although the blank 10 already has some resin to keep the wood fibers in a solid state and uncured resin, additional resin is added at the work stage 55. The added resin increases the ability of the blank 10 to be efficiently shaped and also increases the stiffness of the finished molded panel. Surprisingly, melamine or urea resin may be added at table 55 even if the resin originally present in blank 10 is melamine-based, or urea or melamine resin may be added at table 55 even if the resin originally present in blank 10 is urea-based. The temperature of blank 10 at station 55 is such that the resin has not yet begun to react or cure. In one embodiment, roller 59 applies the conditioning resin to blank 10, while roller 57 applies the colored seal coat。

A colored sealer (e.g., with titanium dioxide pigment to provide white or other color) applied by a roller 57 at a station 55 forms a uniformly colored surface on the facer sheet. Preferably, the colored sealant is applied to an outer surface portion of the panel. The colored sealer coats the finished panel with primer. Doors constructed from existing molded panels require priming which adds to the cost. About 4-10g/m²May be applied to blank 10 at station 55 by upper roller 57.

After the station 55 has applied the colored sealer and additional resin, the flat blank 10 enters a pre-press station 61 for additional heating. In table 61, blank 10 is held at a temperature of about 110 ℃ and 130 ℃ (preferably about 120 ℃) for a period of about 20 to 60 seconds (preferably about 30 seconds). Since the capacity of the preliminary pressing table 61 is limited, the moisture in the slab 10 is not easily evaporated into the atmosphere. As its temperature increases, moisture remains in the blank. Table 61 is closed so that moisture in blank 10 is not easily removed from blank 10. The pre-pressing station 61 may be comprised of opposed oil-heated or electrically heated platens spaced apart from one another with the blank 10 therebetween.

For exterior doors, as shown in fig. 10, after the blank 10 exits the pre-compaction station 61, it enters the barrier application station 62. At station 62, a barrier layer such as melamine impregnated crepe paper or phenolic resin crepe paper 13 is applied to the major surface of blank 10 that will be the exterior door panel surface (i.e., the surface facing away from the interior of the door). Suitable papers are commercially available from Akzo Nobel under the name SWEDOTEC^TMTGPN and TXP. Alternatively, a cross-linked polymeric resin system that forms a moisture barrier may be applied at station 62 as a two-part liquid that is sprayed or otherwise applied onto the surface of blank 10. Moisture barriers such as creped paper or cross-linked resin can also increase the hardness of the finished skin and provide corrosion protection, which is beneficial for shipping and installation. After the moisture barrier 13 is applied, the blank 10 is fed into a press 21.

In the door used in the room, the flat blank 10 enters the press 21 after the blank 10 is preheated and optionally further added with moisture at the preliminary press table 61, and the press 21 has an upper platen 17 and a fixed lower platen 19.

Press 21 is preferably heated by recirculating oil or electrical resistance elements to heat platens 17 and 19 to a temperature sufficient to prepare the resin in blank 10 to produce the blank. As shown in fig. 3, the press 21 is vented, preferably through small vents v. The bottom platen is gas permeable to facilitate the venting of moisture, volatiles and similar gaseous species generated during the pressing process. Surprisingly, venting the press 21 results in a finished panel that is stronger than a finished panel made by intermittent venting of the press. The diameter of the holes v is small enough to avoid wood fibers to plug them and/or damage the underlying surface.

As shown in fig. 3, flat blank 10 is positioned between platens 17 and 19 in press 21. The platen 19 remains stationary or stationary and pressure is applied to the upper platen 17 to move the platen 17 downwardly toward the platen 19. When press 17 is pushed against press 19, blank 10 is reshaped to a shape defined by the active surfaces of presses 17 and 19 and their respective members 23 and 25 (e.g., the shape of panel 3).

In another embodiment, the two platens may be moved simultaneously toward each other, or the bottom platen 19 is moved upward toward the fixed upper platen 17.

As shown in fig. 7, the pressure acting on the platens (e.g., the pressure acting on the platens 17) to close the press 21 is increased (see the upwardly inclined portion 63) without interruption to a predetermined pressure limit and/or physical stops to control the thickness. The applied pressure 63 (which in some embodiments may be applied continuously and without variation and/or in a linear fashion) causes the platens 17 and 19 to close very slowly at a rate of 0.25mm per second. The blank 10 is correspondingly shaped at a slower speed until the shape shown in fig. 6 is obtained and the press 21 is closed. When the press 21 is closed, the platens 17 and 19 are held in the closed position for a period of about 10-60 seconds, preferably about 20-30 seconds, at a pressure 65 shown in FIG. 7. During the hold phase, the wood fibers in blank 10 continue to flow as blank 10 obtains its final shape. In addition, both the initially uncured resin and the resin with the added regulating agent begin to react and cure. Curing the resin to harden it; this hardens the reformed blank 10 into the panel 7. The smooth or substantially flat pressure portion 65 of the graph shown in fig. 7 indicates that the pressure acting on the platens of the press 21 remains substantially constant for the duration of the hold or cure. After the curing time has elapsed, the press 21 is then opened along the curve 67, for example by lifting the press plate 17 upwards, so that the shaped door skin 7, 9 can be removed therefrom. In fig. 7, the downward inclined pressing portion 67 indicates that the press 21 is in an open state. Preferably, the pressure section 67 of fig. 7 is inclined at a greater angle than the section 63, so that the pressure is released during opening faster than the pressure is applied during closing of the press.

In pressure section 65, when peak pressure is applied to blank 10 by the platens, the applied pressure is up to 1200 pounds per square inch, although such substantially constant pressure is preferably about 600-900 pounds per square inch, and more preferably about 750 pounds per square inch. The platens 17 and 19 are preferably a hard chrome plated steel mold, preferably having a Rockwell hardness of 60 to 70 or higher. The surface of the press plate has a hard chrome plating layer to avoid the build-up of xylose that might otherwise occur. Each platen preferably has a thickness of about 3 to 5 inches, and more preferably about 4 inches, and each platen is electrically heated, such as by Kalrod, although in some embodiments a circulating flow of oil or steam is used as the heating medium. The pressure plates 17 and 19 are preferably mirror images of each other, one being concave and the other being convex. Preferably, each platen 17, 19 is maintained at a temperature of about 320-. The temperature selected is a function of the resin and the thickness of the blank 10, and should be maintained throughout the pressing operation for shaping the flat blank 10, thereby ensuring that the binder resin in the blank is melted/remelted and remains flowable in the pressure-applied portion 63.

As shown in fig. 9, to optimize the shaping process, the closing rate of the press 21 should be controlled as a function of at least one of the hardness, density profile, depth of the die, and percent binder or resin content in the blank 10 to be shaped. The harder the blank 10, the slower the closing rate of the press 21. In some embodiments, the closing rate of the press 21 is kept substantially constant and varies from about 0.25mm/s to about 1.0mm/s depending on the hardness of the blank 10. If the press 21 is changed too quickly, the resin bonding in the blank 10 is broken. Thus, the harder the solid blank 10, the slower the heated platens should close, substantially avoiding disruption of the resin bond during the reforming process.

When the press 21 is opened, the reformed panels, i.e., the door panels 7, 9 shown in figure 6, each having a plurality of panels 3 formed or molded thereon, are removed. It is clear that structures other than the panels 3 can also be moulded onto the panels.

Fig. 8 shows that the shaping panels 7, 9 have a substantially constant density throughout their thickness. This is another effect of the unique manufacturing method described above. The density of the panels 7, 9 throughout their thickness is preferably about 800-³But is approximately 10% higher than the density of the original flat blank 10.

After exiting the press 21, the reshaped molded facesheets 7, 9 may enter an optional trim station 69, as shown in FIG. 4, where the facesheets are again humidified to add a moisture content of up to about 8% (if the moisture content is below this value after exiting the press). After re-humidification, external finishing may also be performed at the station 69. Re-humidification can be achieved at station 69 by water mist or the like or by passing the shaping panel through a water bath. If a colored sealer or colored pre-press sealer applied at station 55 is used, no primer is necessary. It is preferred to apply the primer in all other applications. When finishing again, which is also optional, the panels 7, 9 are passed to a door forming station 71 where each panel is adhesively secured to a door frame, preferably a wooden door frame, to produce the hollow door 1. If the door is an exterior door, a further layer of moisture barrier is attached to the exposed edge of the door frame at station 73 by edge binding or coating. Obviously, the door 1 need only have one moulded panel 7 or 9, with its opposite sides flat.

The finished door 1 described above is shown in fig. 1 and 2, with the crepe paper 13 used only on the outer door.

Figure 10 shows a production line for carrying out the method described above. It has two presses 21, each with a prepressing table 61. This is because the press 21 is operated slower than its corresponding pre-pressing station 61 throughout the operation. Also, for each of the loading table 45, the humidifying table 49, the sealing/adjusting table 55, and the like, there may be a plurality of pre-pressing tables 61 each having two presses 21. Thus, the production line shown in FIG. 10 is readily scalable; the initial cost required to produce the same number of door facings is reduced.

It is evident that the present invention has many other structural features, variations and improvements in addition to the embodiments described above. Such structural features, variations and modifications are intended to be part of this disclosure, and are intended to be within the scope of the invention as defined in the appended claims.

Claims (13)

1. A hollow core door, comprising:

a door frame;

first and second door panels secured to said door frame so as to define a hollow area therebetween, at least one of said panels being a molded door panel;

said one molded door panel having a plurality of panels molded thereon; and

wherein said one molded door panel has thermosetting conditioning resin applied to at least one major surface to form at least 2.0N/mm²The adhesive strength of (a).

2. The door of claim 1, wherein each of the first and second door skins is a molded door skin having a bond strength of at least 2.5N/mm²。

3. The door of claim 1, wherein each of the first and second door skins is formed by pressing loose batting or blocks to a density of at least 550kg/m³And then humidifying, heating, and shaping the flat door blank in a press into a molded door panel having panels molded thereon such that the bond strength of each panel is increased relative to the bond strength of the original flat blank from which they were formed.

4. A door as claimed in any one of claims 1 to 3, wherein said one molded door panel has an exterior side having a paper moisture barrier thereon.

5. The door of claim 4, wherein the paper moisture barrier is selected from the group consisting of melamine impregnated crepe paper or phenolic resin crepe paper.

6. A door according to any one of claims 1 to 3, wherein said one molded door panel has a substantially constant density.

7. A door as claimed in any one of claims 1 to 3, wherein said one molded door panel has a planar first portion and a planar second portion and an inclined portion located between and integral with said planar first portion and planar second portion, said planar first portion and inclined portion together defining said panel.

8. A door as claimed in any one of claims 1 to 3, wherein said one molded door panel has an exterior side having a colored sealant thereon.

9. The door of claim 8 wherein said colored sealant provides a uniformly colored surface.

10. A door as claimed in any one of claims 1 to 3, wherein the hollow region is filled with foam.

11. A door as claimed in any one of claims 1 to 3, wherein said one molded door panel has 550-1200kg/m³The density of (c).

12. Door according to any one of claims 1 to 3, characterized in that said one moulded door panel has 800-³The density of (c).

13. A method of manufacturing a molded door panel, comprising the steps of:

providing a flat solid wood composite blank having a density of at least 550kg/m³；

Applying a liquid heat activated resin to at least one major surface of the flat blank;

placing the flat blank into a press having first and second platens;

heating the first and second platens to a temperature of each of 320 DEG and 425 DEG F;

closing the press at a predetermined closure rate to shape the flat blank into a door panel comprising a plurality of panels molded thereon; and

curing the resin in the shaped door panel to form a door having a caliper of at least 2.0N/mm²The bond strength of (a).