U.S. patent number RE36,240 [Application Number 08/924,934] was granted by the patent office on 1999-06-29 for compression molded door assembly.
This patent grant is currently assigned to Therma-Tru Corporation. Invention is credited to Ronald C. Minke, Kenneth J. West.
United States Patent |
RE36,240 |
Minke , et al. |
June 29, 1999 |
Compression molded door assembly
Abstract
A door assembly having a core positioned within a frame. The
door assembly further includes a pair of opposed molded skins.
There are edge adjacent the skins. The skins a made of a polymer
material, a low profile additive and reinforcement fibers. Each of
the skins has an exterior surface and an interior surface. The
interior surface is adjacent the core. The exterior surface
includes a textured pattern consisting of level portions and
depressions. The depressions have a range in depth from a 0.025 mm
to about 1.0 mm from the level portions. The skins further include
undercuts adjacent the depressions. The undercuts have a range in
extent of undercutting from about 0.025 mm to about 0.10 mm from
the depressions.
Inventors: |
Minke; Ronald C. (Fort Wayne,
IN), West; Kenneth J. (Grabill, IN) |
Assignee: |
Therma-Tru Corporation (Maumee,
OH)
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Family
ID: |
23050381 |
Appl.
No.: |
08/924,934 |
Filed: |
September 8, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
274978 |
Jul 14, 1994 |
05537789 |
Jul 23, 1996 |
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Current U.S.
Class: |
52/313; 264/129;
52/309.9; 52/784.15; 52/479; 264/162 |
Current CPC
Class: |
E06B
3/78 (20130101); B44C 5/0453 (20130101); B44F
9/02 (20130101); B29L 2031/724 (20130101) |
Current International
Class: |
B44C
5/00 (20060101); B44C 5/04 (20060101); B44F
9/02 (20060101); B44F 9/00 (20060101); E06B
3/72 (20060101); E06B 3/78 (20060101); E04B
002/20 (); B44F 009/02 () |
Field of
Search: |
;52/309.9,309.11,313,316,479,784.1,784.15 ;264/129,162 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2258510 |
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Sep 1975 |
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FR |
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2304763 |
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Nov 1976 |
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FR |
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551432 |
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May 1977 |
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SU |
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604937 |
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Apr 1978 |
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SU |
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1420244 |
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Jan 1976 |
|
GB |
|
1487309 |
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Sep 1977 |
|
GB |
|
2044316 |
|
Oct 1980 |
|
GB |
|
2057037 |
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Mar 1981 |
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GB |
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Primary Examiner: Friedman; Carl D.
Assistant Examiner: Wilkens; Kevin D.
Attorney, Agent or Firm: Brooks & Kushman P.C.
Claims
We claim:
1. A door assembly comprising, in combination, a core positioned
within a frame, a pair of opposed molded skins attached to said
frame, edges adjacent said skins, said skins .[.consisting of.].
.Iadd.comprising .Iaddend.a polymer material, a low profile
additive and reinforcement means, each of said skins having an
exterior surface and an interior surface, said interior surface
being adjacent said core, said exterior surface including a
textured pattern consisting of level portions and depressions, said
depressions having a range in depth from about 0.025 mm to about
1.0 mm from said level portions, said skins further including
designed variable undercuts adjacent said depressions, said
undercuts having a predetermined range in extent of undercutting
from about 0.025 mm to about 0.10 mm from said depressions, whereby
said door assembly has a simulated wood grain.
2. The door assembly of claim 1, wherein said core consists of a
foamed material.
3. The door assembly of claim 1, wherein said frame includes two
parallel stiles and two parallel rails, said stiles being
positioned in perpendicular relationship to said stiles.
4. The door assembly of claim 3, wherein one of said stiles is
heavier than the other said stile.
5. The door assembly of claim 1, wherein said polymer material is
selected from the group consisting of sheet molding compound, bulk
molding compound, thick molding compound, kneading molding
compound, and injection molding compound.
6. The door assembly of claim 1, wherein said polymer material is
an acid-modified propylene glycol maleate.
7. The door assembly of claim 1, wherein said low profile additive
is selected from the group consisting of polymethylmethacrylate,
polymethylmethacrylate copolymers, polystyrene, polystyrene
copolymers, polyvinyl acetate, polyethylene and saturated
polyesters.
8. The door assembly of claim 7, wherein said low profile additive
is added directly to said polymer material.
9. The door assembly of claim 7, wherein said low profile additive
is added to said polymer material by combination with a carrier
material.
10. The door assembly of claim 7, wherein a shrinkage control agent
is added to said low profile additive.
11. The door assembly of claim 1, wherein said reinforcement means
is selected from the group consisting of fiberglass, aramid fibers,
carbon fibers, and mineral reinforcements.
12. The door assembly of claim 1, wherein said depressions have
nonuniform extents ranging from about 0.025 mm to about 1.0 mm.
13. The door assembly of claim 1, wherein said undercuts have
nonuniform extents of undercutting ranging from about 0.025 mm to
about 0.10 mm.
14. The door assembly of claim 1, wherein said depressions and
undercuts receive a topcoat.
15. The door assembly of claim 14, wherein said topcoat is a stain
having pigment contents of from about 4 to about 70 weight percent.
Description
BACKGROUND OF THE INVENTION
The present invention is directed to a door assembly. More
specifically, the invention is directed to a door assembly having
molded door skins that include a textured pattern that simulates
the grain of natural wood.
Wood as a building material has advantages and disadvantages. The
advantages of wood include an appealing appearance due to the
annual variations, color and width of bands resulting from the
growth of the wood. In addition, the cells in the wood provide
porosity that can absorb stain. The disadvantages of wood are many.
For example, wood can experience significant dimensional changes
with variations in temperature and humidity. This can result in
cracking and splitting. Further, the natural growth of wood can
result in aesthetic and mechanical flaws from such occurrences as
sap pockets and knots. Therefore, there is a need for a door
assembly that has the appearance and stainability of wood with
superior mechanical properties.
Door assemblies made of compression molded door skins are known in
the art. These door assemblies provide uniform and reproducible
products that can be aesthetically pleasing. An example of a prior
art door assembly is shown in U.S. Pat. No. 4,550,540. It has been
found that prior art doors contain imperfections that are
recognized by knowledgeable consumers and persons involved in the
door industry. For example, the surface of prior art door skins is
not sufficiently rough at a microscale, the range of depth of the
grain is too narrow, the grain pattern does not include undercuts
and angle changes, the door assemblies are substantially lighter
than wood doors, the prior art door assemblies flex more than wood
doors, and the prior art doors can warp from the differences in
skin surface temperature between the two opposed door skins.
Therefore, there is a need for a door assembly that overcomes these
problems.
SUMMARY OF THE INVENTION
The present invention is directed to a door assembly having an
inserted core or a core formed in-situ positioned within a frame. A
pair of opposed molded skins are attached to the frame. There are
edges adjacent the skins. The skins are made of a polymer material,
a low profile additive and reinforcement fibers. Each of the skins
has an exterior surface and an interior surface. The interior
surface is adjacent the core. The exterior surface includes a
textured pattern consisting of level portions and depressions. The
depressions have a range in depth from about 0.025 mm to about 1.0
mm from the level portions. The skins further include undercuts
adjacent the depressions. The undercuts have a range in extent of
undercutting from about 0.025 mm to about 0.10 mm from the
depressions.
It is the primary object of the present invention to provide a door
assembly that has the appearance of natural wood.
It is an important object of the invention to provide a door
assembly that has superior mechanical properties.
It is another important object of the invention to provide a door
assembly that is stainable,
Other objects and advantages of the invention shall become apparent
upon a review of description of the preferred embodiment and the
accompanying drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front elevational view of a door assembly according to
the present invention;
FIG. 2 is a side elevation view of the door assembly of the present
invention;
FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 2
showing the frame of the present invention with the core positioned
therein;
FIG. 4 is a partial cross-sectional view taken along line 4--4 of
FIG. 1 showing a door skin of the present invention having level
portions, depressions, and undercuts;
FIG. 5 is a view similar to FIG. 4 showing a topcoat applied to the
door skin; and,
FIG. 6 is a partial cross-sectional view showing the molding of a
door skin used in the door assembly of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention will now be described in detail with
reference being made to the accompanying drawings. The door
assembly of the present invention is indicated generally by the
reference number 10. Referring to FIGS. 1,2 and 3, the door
assembly 10 includes a core 12 positioned within a frame 14. The
core 12 can be an inserted core or a core formed in-situ. The core
12 can be made of a variety of materials depending on the
application. For example, inserted cores can include continuous or
discontinuous compressed mineral board, compressed inorganic
fillers with binders, compressed organic filler with binders,
compressed organic and inorganic blends with binders or in-situ
formed binder; molded or shaped thermoplastics such as expanded
polystryene, foamed polyvinyl chloride, or foamed or expanded
polyolefins; molded or shaped thermosets such as flexible or rigid,
solid or foamed polyurethanes, polyurea-urethanes, polyureas,
polyisocyanurates, and phenolics; blow molded shells; or honeycomb
inserts comprised of organic fibers, organic pulps, thermoplastics,
and thermosets; preforms derived from either air-laid or
vacuum-laid mats of cellulosic fiber, glass fiber, thermoplastic
fiber, or thermoset fiber or woven mats or veil of the same
materials where a binder or resin has been applied or injected to
shape a core; and blends or mixtures of these various types of
insertable cores. In-situ formed cores include cores developed from
reaction injection molding with or without reinforcement of
thermosets such as polyurethanes, polyurea-urethanes,
polyisocyanurates, and phenolics; gas injection of a thermoplastic,
ceramic, or thermoset; activation of in-situ blowing agents or
forming of material introduced into the shell; mechanical tension
applied to melted or softened thermoplastic or thermoset materials;
or blends and combinations of these in-situ cores. The choice of a
core material is constrained by .+-.10% dimensional change in the
range of -40.degree. C. to 95.degree. C. with .+-.5% preferred.
As shown in FIG. 3, the frame 14 includes a first stile 16 and
second stile 18. The stiles 16 and 18 are parallel to one another.
The stiles 16 and 18 are positioned in a perpendicular relationship
to a first rail 20 and a second rail 22. The frame in FIG. 3 has a
rectangular geometric configuration. However, it should be
understood that the frame can be arranged in a variety of geometric
configurations depending upon the application. The stiles and rails
can be made of wood or some other suitable material. In the present
embodiment, the first stile 16 is manufactured to add weight to the
stile. The stile 16 can be made of material strips attached or
independent from the core 12 that are formed from a plurality of
layers of sheet material. The sheet material can be cellulosic
veneers and plies or compressed slurry of cellulosic fibers. The
stile 16 when positioned at the outer edge of the pivot away from
the hinges provides the door assembly 10 with a closing momentum
which makes a person closing the door to believe the door to be
substantial or "solid". The stile 16 has a width in the range of
from about 2.5 cm to 16 cm. The stile 16 can also be a hollow
channel of pultruded or extruded reinforced plastic, a metal hollow
channel, a partially or totally metal reinforced channel made of a
material other than metal, or a compressed mineral stile depending
on the application.
As shown in FIGS. 1 and 2, the door assembly 10 includes a first
molded skin 24 and an opposed second molded skin 26. The texture of
sins 24 and 26 can be made by a variety of casting and deposition
processes. These casting processes include silicone molds, epoxy
molds, metal molds from sandcasting, metallic shell on a mandrel,
electroless metallic disposition on a mandrel and cold isostatic
pressing using any of the above texture transfer techniques to
create the textured surface for the mandrel. The skins 24 and 26
can be formed with the texture by many molding techniques including
resin transfer molding, vacuum assisted resin intrusion, rotational
molding, low and high pressure injection molding, as well as low
and high pressure compression molding.
In the preferred embodiment, the skins 24 and 26 are compression
molded door skins that are prepared from a Low Coefficient of
Linear Thermal Expansion (LCLTE) material such as a modified
unsaturated polyester sheet molding compound that is doped with
0.25-20 weight percent of an immiscible phase of a low profile
additive. The unsaturated polyester sheet molding compound is
formed by a condensation polymerization using polyols including
ethylene glycol, propylene glycol, neopentyl glycol, diethylene
glycol, dipropylene glycol, timethylpentanediol, cyclohexane diol,
propoxylated bisphenol A, hydrogenated bisphenol A,
dibromoneopentyl glycol and blends thereof. The adds or anhydrides
used in the polymerization may include the following as well as any
dimers and blends thereof: phthalic anhydride, maleic anhydride,
adipic acid, isophthalic acid, orthophthalic acid, terephthalic
acid, fumaric acid, glutaric acid, azelaic acids, chlorendic acid,
tetrabromophthalic anhydride, tetrachlorophthalic acid, and
endomethylenetetrahydrophthalic anhydride. The low profile additive
can be selected from any of the following blends thereof:
polymethylmethacrylate, polymethylmethacrylate co-polymers with
other acrylates, polystyrene, polystyrene copolymers, polyvinyl
acetate, polyethylene, saturated polyesters, and shrinkage control
agents. The saturated polyesters and shrinkage control agents
include vinyl chloride-vinyl acetate copolymers, polyurethanes,
styrene butadiene copolymers, polycaprolactone, and cellulose
acetate butyrate. The low profile additives can be added directly
to the formulation or they can be applied or incorporated onto a
carrier material such as a filler. The molding compound can be
reinforced with, for example, fiber glass, aramid fibers, carbon
fibers, or mineral reinforcements such as mica. Other polymer
materials that can be used include bulk (or dough) molding
compound, kneading molding compound, an injection molding compound
known as ZMC, and thick molding compound.
An example of a preferred formulation of the LCLTE sheet molding
compound that can be used to make the molded skins of the present
invention is as follows:
EXAMPLE
______________________________________ Parts Per Material Hundred
Resin ______________________________________ Unsaturated polyester:
80-50 Acid modified propylene glycol maleate Low Profile Additive
20-50 Polyvinyl acetate Condensation Reaction Catalyst 0.75-2.5
Filler 130-250 Pigment 3-15 Mold Release 4-9 Chemical Thickener
1.5-3.5 Chopped Fiberglass Reinforcement 15-35
______________________________________
As shown in FIGS. 1 and 2, the skins 24 and 26, each has an
exterior surface 28 and an interior surface 30. The interior
surface 30 is adjacent the core 12. The interior surface 30 can
show machining marks to the unaided eye (rough machined) or be
textured. The interior surface 30 can also include means, such as
projections, to assist in the adherence of the skins to the core
(not shown).
As shown in FIGS. 1, 4 and 5, the exterior surface 28 of a skin
includes a textured pattern 31 consisting of level portions 32 and
depressions 34. The textured portion simulates a natural woodgrain
pattern. As used herein, the term "level portion" means the
outermost planar surface of the door skin. The term "depression"
means any deviation from the level portions. In the present
embodiment, the depressions 34 can have a depth from about 0.025 mm
to about 1.0 mm from said level portions 32, with the preferred
range being from about 0.025 mm to about 0.40 mm. As shown in FIG.
4, the exterior surface 28 includes numerous depressions. The
depressions 34 can be defined in the skins by various obtuse and
acute angles to simulate how grain is defined in natural wood. The
exterior surface 28 further includes undercuts 36. The extent of
the undercuts 36 varies with the rigidity of the skins at the same
time of demolding. The rigidity of the skins are dependent on the
molding process and materials used and other variables such as
time, temperature, and depth of the undercut from the surface. It
has been found that LCLTE material provides sufficient
partially-cured, hot, green strength of the skins during the
molding process to allow relatively deep undercuts. The combination
of material shrinkage and the proportional limit of the material
while hot and partially cured determine the extent to which
undercuts are feasible. The best production method to assess the
compatibility of the material composition with the mold undercut
design is a use test. To achieve this in the preferred embodiment,
the material must be designed to have about the first 2.5% of
elongation governed by resin properties, with stiffness after that
governed by the reinforcements. The preferred Coefficients of
Linear Thermal Expansions (CLTE) are listed in the following
table:
TABLE ______________________________________ 90 Degrees C. 23
Degrees C. mm/mm/C mm/mm/C ______________________________________
CLTE 0-8.3 .times. 10.sup.-6 0-7.2 .times. 10.sup.-6 preferred 4-7
.times. 10.sup.-6 3-6 .times. 10.sup.-6
______________________________________
In the preferred embodiment, the undercuts 36 range from about
0.025 mm to about 0.10 mm as measured from the depressions 34. As
shown in FIG. 6, a skin 24 can be compression molded using a mold
form 38 and first and second mold backing plates 40 and 42,
respectively. The mold form 38 includes a textured pattern 31 that
is mirrored by the exterior surface 28 of the skin 24. As shown in
FIG. 4, the upraised features 33 of the textured pattern 31 can
have a height to base ratio of as much a 4 and survive intact over
3000 reproductions in pressure ranges from 21 to 315 kg/cm.sup.2
with few changes noticeable to the unaided eye. The number of
reproductions will vary significantly depending on many variables
including reinforcement content of the reproduction formula, the
pressures of the molding, and the materials used in the molding
process. In the preferred embodiment, the skins 24 and 26 are
compression molded at compression pressures ranging between 21 to
315 kg/cm.sup.2. The skins 24 and 26 can be molded to a thickness
in the range of from about 0.125 cm to about 3.0 cm.
As shown in FIG. 5, the textured pattern 31 created by the level
portions 32, depressions 34 and undercuts 36 allow for the
application of a topcoat 45, such as stains and paints, to be
applied to the skin. The textured pattern 31 provides a rough
surface that resists the movement of the topcoat 45 like a wood
door as it is brushed or otherwise applied to the skin 24. The
increased depth of the depressions 34 also allows for the
wipe-on/wipe-off application of stains having low pigment contents.
The product can be used with stains having a pigment loading of
4-70 weight percent, with the preferred range being 15-25 weight
percent. It has been found in prior art compression molded door
assemblies that stains with pigment loadings less than about 15
weight percent did not trap sufficient pigment in the texturing to
highlight the texture in most applications. In addition, in the
prior art assemblies the preferred stain application was by
hand-rubbing accompanied by brushing. These are not the traditional
methods of professional painters and stainers.
Referring to FIG. 2, the door assembly 10 includes vertical edges
46 and horizontal edges 48. The edges are adjacent and
substantially perpendicular to the skins 24 and 26.
Referring to FIGS. 1 and 3, the door skins 24 and 26 can be larger
than the frame 14. This allows for the door to be cut squarely,
rebated or beveled as required by the user of the door assembly 10.
The edges 46 and 48 can also include weatherstrip members (not
shown).
The above detailed description of the present invention is given
for explanatory purposes. It will be apparent to those skilled in
the art that numerous changes and modifications can be made to the
invention described above without departing from the scope of the
invention. Accordingly, the whole of the foregoing description is
to be construed in an illustrative and not a limitative sense, the
scope of the invention being defined solely by the appended
claims.
* * * * *