U.S. patent number 3,815,657 [Application Number 05/197,213] was granted by the patent office on 1974-06-11 for overhead garage door sections.
This patent grant is currently assigned to Architectural Molded Products Ltd.. Invention is credited to Walter K. Malek, Henry Substelny.
United States Patent |
3,815,657 |
Malek , et al. |
June 11, 1974 |
OVERHEAD GARAGE DOOR SECTIONS
Abstract
An articulated closure comprising a plurality of hingedly
connected sections adapted to be positioned adjacent a structural
opening is provided. The sections cooperate to define reversible
closure surfaces facing opposite sides of the structural opening.
Each of the sections is integrally formed of a closed-cell, rigid
polyurethane foam which provides a central core substantially
enclosed within an integrally connected, substantially continuous
skin of increased density. According to one aspect of the
invention, the section further includes a case structure which is
integrally molded with the low density core and has a relatively
higher density. The case is chemically and mechanically bonded to
the core at an interface zone having a higher average density than
the core and the case so that the interface zone serves as an inner
reinforcement for the section. According to another aspect of the
invention, the case is provided with reinforcing means
substantially embedded therein and comprising a net-type structure
or randomly oriented glass fibers. In addition, methods of forming
such sections are provided.
Inventors: |
Malek; Walter K. (Hinckley,
OH), Substelny; Henry (Cleveland, OH) |
Assignee: |
Architectural Molded Products
Ltd. (Richfield, OH)
|
Family
ID: |
26751543 |
Appl.
No.: |
05/197,213 |
Filed: |
November 10, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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70839 |
Sep 9, 1970 |
|
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Current U.S.
Class: |
160/229.1;
52/309.7; 264/45.3; 428/310.5; 428/318.8; 52/309.2; 160/201;
428/212; 428/314.4 |
Current CPC
Class: |
E06B
3/485 (20130101); E06B 3/7001 (20130101); Y10T
428/24942 (20150115); Y10T 428/249976 (20150401); Y10T
428/249961 (20150401); Y10T 428/249989 (20150401) |
Current International
Class: |
E06B
3/32 (20060101); E06B 3/70 (20060101); E06B
3/48 (20060101); E04b 002/10 () |
Field of
Search: |
;160/201,229,232,236
;264/46,DIG.14,48,54 ;52/309 ;161/159,166 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Taylor; Dennis L.
Attorney, Agent or Firm: McNenny, Farrington, Pearne &
Gordon
Parent Case Text
This application is a continuation-in-part of our copending
application, Ser. No. 70,839, filed Sept. 9, 1970 now abandoned.
Claims
What is claimed is:
1. An articulated closure adapted to be guided into a position
adjacent a structural opening, including closure surfaces disposed
adjacent opposite sides of said opening, comprising a plurality of
hingedly connected sections, each of said sections having a
thickness substantially less than its width or length and including
first and second section surfaces cooperating to define said
closure surfaces, each of said sections being a single molded
plastic material comprising a closed-cell rigid polyurethane foam
of varying densities, having a relatively low density core, an
integrally formed external case of increased density, and a
cellular reinforcing interface zone between the core and case
having an average density higher than the average core density and
the average case density, portions of said interface zone being
substantially coextensive with each of said section surfaces and
spaced apart by the thickness of said core.
2. An articulated closure adapted to be guided into a position
adjacent a structural opening, including closure surfaces disposed
adjacent opposite sides of said opening, comprising a plurality of
hingedly connected rectangular sections, each of said sections
including first and second section surfaces cooperating to define
said closure surfaces, each of said sections being a single molded
plastic material comprising a closed-cell rigid polyurethane foam
of varying densities, having a relatively low density core, an
integrally formed external case of increased density substantially
surrounding and enclosing said core, and a cellular reinforcing
interface zone between the core and case having an average density
higher than the average core density and the average case
density.
3. An articulated closure as set forth in claim 1 wherein said case
substantially, entirely surrounds and encloses said core.
4. An articulated closure as set forth in claim 3 wherein the
density of said interface zone progressively increases through its
thickness from opposed regions thereof located adjacent said core
and said case to a maximum value at an intermediate location within
said interface zone.
5. An articulated closure as set forth in claim 4 wherein said
interface zone provides both mechanical interengagement and
chemical bonding between said core and said case.
6. An articulated closure as set forth in claim 1 wherein said case
includes reinforcing means substantially, completely embedded
therein, and said reinforcing means is substantially coextensive
with the planar extent of each of said sections.
7. An articulated closure as set forth in claim 1 wherein said case
includes local reinforcing means substantially, completely embedded
therein, said reinforcing means comprising substantially disjuncted
members which are more rigid than said case and core.
8. A closure as set forth in claim 6 wherein said reinforcing means
comprise a net-type reinforcing member having openings therein, and
said case substantially, entirely fills said openings to provide
said case with a substantially continuous structure having said
net-type member embedded therein.
9. A closure as set forth in claim 6 wherein said reinforcing means
comprise randomly oriented, glass fibers, and said fibers are
embedded substantially, completely within the regions of said case
adjacent to said core, said regions being spaced from the exterior
surfaces of said sections.
10. An articulated closure as set forth in claim 2 wherein said
closure surfaces are reversible and said first and second section
surfaces cooperate to define said reversible closure surfaces, each
of said sections forming an interlocking joint with adjacent
sections.
Description
FIELD OF INVENTION
This invention generally relates to articulated closures such as
overhead garage doors, having a plurality of hingedly connected
sections, and, more particularly, to a novel and improved closure
wherein the sections are formed of a rigid polyurethane foam having
an integral exterior skin of increased density and provide
interchangeable closure surfaces.
PRIOR ART
Overhead garage doors of the general type with which this invention
is concerned are formed of flexibly articulated sections which are
adapted to be guided from an overhead storage position to a
vertical closed position adjacent a door opening. Such doors may be
spring-tensioned or power-driven to facilitate the opening and
closing thereof, and are employed in both residential and
commercial structures. The door sections are desirably formed of
sturdy but lightweight materials which have good insulating and
weather-resisting properties.
In the past, garage doors have been typically made of materials
such as wood, wood laminates, hardboard, solid plastic materials
reinforced with woven glass fiber cloth, or metal, as well as
combinations of these materials. In addition, the use of cellular
plastic materials to form an inner lamina or core which is bonded
to oppositely disposed, wood reinforcing laminae is known in the
prior art. Although such materials are generally adequate for some
structural purposes, they are not entirely satisfactory when used
to form garage doors.
The wood compositions are highly susceptible to weathering, and
particularly, moisture absorption. In order to avoid rapid and
excessive moisture damage, it is necessary to periodically paint
the wood surfaces with various types of weather-resistant paints
and varnishes. Even though these wood surfaces may be regularly
treated with paints and varnishes, the wood compositions are
frequently subject to moisture damage.
The moisture damage to wood compositions includes warpage and
distortion of the door, which may result in misalignment of the
door with the door opening and with a track and roller system in
which the door sections are mounted. Consequently, it may be
necessary to realign the door and/or replace the door sections when
severe warpage or distortion occurs.
When a hardboard material supported by a wood frame is employed,
moisture absorption tends to cause the unsupported or exposed
hardboard sections to flex in a convex or concave fashion with
respect to the wood frame. This permanent deflection is
aesthetically displeasing and structurally undesirable, since the
rigidity of the door is diminished.
The wood composition laminates frequently tend to delaminate as a
result of moisture absorption. In this case, the outermost lamina
tends to separate from the body of the laminate. This separation is
exceptionally harmful, since the weather-resistant paint or varnish
is only applied on the outermost lamina. Consequently, the exposed
interior laminae may deteriorate at an even greater rate due to the
moisture absorption. Accordingly, it is frequently necessary to
replace entire door sections because of delamination.
Similar delamination and distortion problems have been found to
occur when laminates of different types of materials are employed.
Such problems are encountered when a foamed resin core is
adhesively bonded to exterior laminae. Since the different
materials may have wide variations in their coefficients of thermal
expansion, the delamination and distortion problems are
accentuated. In this case, changes in temperature may result in the
stressing of the bonds between the laminae and rupture thereof. In
addition, the variations in thermal expansion may cause separations
and gaps to occur between the different materials of the door
sections. Such separations permit the relatively unimpeded
penetration of moisture, which accelerates the rate and increases
the severity of the resulting moisture damage.
It should be appreciated that all such laminate structures involve
costly step-wise production techniques necessitated by the layered
structure which may involve intermediate curing steps. Further, it
is often necessary to include multiple adhesive applying steps
wherein the uniform application of the adhesive must be maintained
to assure uniform bonding so as to avoid the formation of stress
concentration points at unbonded sites. Even though uniform
adhesive application and bonding may be achieved, it should be
appreciated that such an adhesive bonding layer frequently
constitutes a plane of weakness in the overall structure.
Since wood composition materials are subject to a relatively high
degree of moisture absorption, variations in weather conditions and
moisture exposure also tend to cause the weight of door sections to
fluctuate. In some cases, the door sections tend to absorb moisture
in a random manner so as to result in an uneven weight
distribution. Consequently, it is difficult to maintain the proper
spring balance in a spring-tensioned door system. In the case of a
power-driven door system, an uneven weight distribution tends to
cause irregular movement of the door by the power drive and
excessive wear of the drive as well as the door supporting
structure.
In order to eliminate the problem described above, a variety of
metal materials have been employed for such door structures.
Although metal doors eliminate some of those problems, they are
more expensive than most of the non-metal materials. Since metal
doors are generally heavier than comparable wooden structures, it
is necessary to provide a stronger, more expensive door mounting
structure for metal doors. Since metal doors are subject to
corrosion and/or rust due to continuous moisture exposure, it is
also necessary to periodically paint metal doors with protective
paints. In addition, the relatively high coefficient of thermal
conductivity of metal, as compared to wood, has resulted in
additional insulation problems in some instances. Thus, the use of
metal doors has been limited by their cost and they still have
serious disadvantages.
SUMMARY OF THE INVENTION
The present invention provides an articulated closure comprising a
plurality of hingedly connected sections adapted to be guided to a
position adjacent a structural opening. The sections cooperate to
define reversible closure surfaces which face opposite sides of the
opening. The sections are molded plastic bodies comprising a
closed-cell, rigid polyurethane foam core and integral outer skin
of increased density which completely surrounds the lower density
core and imparts additional toughness to the exterior surfaces of
the closure.
In one of the illustrated embodiments, each door section is
provided with a high density foam case which substantially,
completely encases a foam core. The case is integrally connected to
the core at an interface zone having a cellular structure
characterized by the chemical bonding and mechanical
interengagement or interlocking so as to contigously unite the case
and core without the use of additional adhesive materials. The
interface zone has a higher average density than the case and the
core so that it serves as an internal reinforcing means for the
molded section.
When it is desirable to provide additional strength and rigidity,
additional reinforcing means may be completely encased within the
section. The encasement of the reinforcing means within the section
results in the achievement of reinforcing strength and rigidity
without the prior art disadvantages of a laminate structure as
described more fully hereinafter.
The integral skin, the closed-cell structure, and the inherent
tendency of polyurethanes to repel water cooperate to substantially
eliminate moisture absorption and the associated problems
encountered in the prior art. For example, the polyurethane foam
door section is not subject to warpage, deterioration, such as
rotting or corrosion, delamination, or weight variation due to
moisture absorption.
As indicated above, the integral structure of each of the door
sections also eliminates delamination problems as well as the
problems associated with the different degrees of thermal expansion
and contraction displayed by the various laminae of laminated prior
art structures. In particular, since the door section of the
present invention is primarily formed of an integrally joined,
single material having varying densities, there is no tendency for
delamination or distortion to occur.
The primary structural material of the closure, polyurethane foam,
displays a very low coefficient of thermal expansion over a broad
range of temperatures. For example, such foams undergo no
dimensional changes at temperatures as low as -20.degree.F., and
only slight dimensional changes at temperatures as high as
160.degree.F. Consequently, the foam door sections of the closure
substantially eliminate the prior art problems associated with
thermal dimensional changes.
Since the sections cooperate to provide reversible or
interchangeable closure surfaces, the sections can be structured to
provide two visually different closure surfaces. For example, in
one of the illustrated embodiments, one closure surface is
essentially planar and the other surface is nonplanar,
geometrically configured pattern. In this manner, the same set of
door sections is adaptable for use with either of two different
styles of architecture.
The present invention also provides methods of forming such
sections, with or without additional reinforcing materials, which
is semi-continuous and eliminates the prior art step-wise, laminate
assembly techniques which require intermediate curing steps in some
cases. The method of the present invention utilizes the chemical
and mechanical bonding of a contigously disposed, compressively
retained foam forming solution and a partially cured foam layer to
provide an integrally formed section of exceptional strength. Thus,
the method eliminates the prior art use of adhesives to bond
indivdual laminae and the possible formation of undesirable planes
of weakness as well as stress concentration points between
laminae.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a prespective, front view of an overhead garage door
according to one aspect of the present invention;
FIG. 2 is a plan view on an enlarged scale of a portion of the back
of the door shown in FIG. 1;
FIG. 3 is a side elevational view of a portion of the door shown in
FIGS. 1 and 2;
FIG. 4 is a sectional view on an enlarged scale, taken along the
line 4--4 of FIG. 2;
FIG. 5 is a fragmentary, perspective, front view, on an enlarged
scale, of the door shown in FIG. 1, with the sections reversed;
FIG. 6 is a sectional edge view of another aspect of the present
invention, having integrally molded hinges connecting adjacent
sections;
FIG. 7 is a sectional edge view of yet another aspect of the
present invention, having an inner core surrounded by an outer case
with reinforcing means comprising a net-type structure embedded
therein;
FIG. 8 is an enlarged, fragmentary, sectional view illustrating the
interface zone between the inner core and outer case portions of
the door section shown in FIG. 7;
FIG. 9 is a sectional edge view of still another aspect of the
present invention using randomly oriented fibrous reinforcing
material; and
FIG. 10 is a schematic illustration of a split mold useful in
forming a door section according to the teachings of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, there is illustrated an overhead garage door
10 comprised of hingedly connected door sections 12. The door
sections 12 cooperate to define a front door surface 14 and a back
door surface 16. The door 10 includes track rollers 18 which are
adapted to travel in spaced trackways (not shown) so as to guide
the door from an overhead storage position to a substantially
vertical closed position adjacent a doorway opening (not
shown).
A conventional handle 20 may be secured adjacent the front door
surface 14 for purposes of opening and closing the door 10. A
similar handle (not shown) may be provided adjacent the back
surface 16 of the door 10. In addition, the door 10 may be provided
with a lock 22 of conventional construction.
Referring to FIGS. 2 and 3, a portion of the back surface 16 of the
door 10 is illustrated. As there shown, the upper track roller 18
is supported by a conventional residential hinge 24. The hinge 24
is secured to each of the adjacent door sections 12 by bolt and nut
fasteners 26. Thus, the hinge 24 pivotally connects the adjacent
door sections 12 and secures the track roller 18 to the door.
The roller 18, located adjacent the lower extremities of the door
10, is secured thereto by a conventional bottom bracket 28. The
bottom bracket 28 may also be secured to the door by bolt and nut
fasteners 26. A bottom expander 30 is provided adjacent the closing
or abutting edge of the door 10 and secured thereto by bolt and nut
fasteners 26. The bottom expander 30 is formed of metal and it is
designed to protect the door when it is inadvertently closed upon
objects lying within the opening of the doorway.
The bottom expander 30 is adapted to retain a seal 32 which is
formed of a rubberlike material. The seal 32 extends across the
entire width of the door 10, and it is adapted to form a
weatherseal with the abutting doorway opening surface. Since the
seal 32 is formed of a rubberlike material, it also serves as a
bumper or cushion for the closing impact of the door 10.
As best shown in FIG. 4, the adjacent door sections 12 form a ship
lap joint 34 having a step-shaped cross section. The ship lap joint
34 is formed of a first portion 36 extending to a second portion
38. The two portions 36 and 38 are connected by an intermediate
portion 40 which is upwardly inclined when the door is in a closed
position. Thus, the second portion 38 adjacent the back surface of
the door 16 is elevated with respect to the first portion 36, which
is adjacent the front surface 14 of the door. Consequently, the
step-shaped cross section of the ship lap joint 34 substantially
eliminates the flow of water or moisture therethrough to the
interior of the garage.
Referring to FIG. 5, a portion of the door 10 is shown with the
door sections 12 reversed in the sense that each of them is rotated
180 degrees about a horizontal axis so as to interchange the front
door surface 14 and the back door surface 16 from the arrangement
shown in FIGS. 1 through 4 so that the surface 16 is now the front
or exposed outside surface of the door 10. Thus, the door sections
may be initially assembled so as to expose either of their panel
surfaces to the outside. As may be noted by a comparison of FIGS. 4
and 5, the ship lap joint 34 has the same inwardly and upwardly
stepped cross section in both cases so as to impede the penetration
of water therethrough.
The door sections 12 are structured to provide two visually
different closure surfaces 14 and 16. As illustrated, the surface
14 is substantially planar and provides an appearance suitable for
a contemporary style home. By contrast, the surface 16 is provided
with geometrically configured recessed panels 48 formed by
horizontally extending rails 42, vertical stiles 44, and vertical
muntins 46. The closure surface 16 is designed for use with a
colonial style home. Thus, a single set of sections 12 may be
assembled to provide either of two different architectural styles.
Accordingly, the manufacturer and the distributor are able to
reduce their inventories of such closure units without limiting the
variety of architectural effects obtainable.
As indicated above, the door sections 12 are formed of a molded
closed-cell, rigid polyurethane foam and each of the sections
includes an integrally formed, thin outer skin 12a which has an
increased density. The types of polyurethanes which are useful in
the present invention are formed by the exothermic reaction of a
isocyanate with a polyhydroxy material or polyol. Although both
polyether and polyester polyols are useful, polyether polyols are
preferable from a cost standpoint. The rigidity and degree of
closed cells present are influenced by the polyol selected. For
example, low molecular weight polyols which display a high degree
of branching are useful in forming closed-cell rigid foams of the
type employed in the present invention.
During the course of the urethane-forming isocyanate-polyol
reaction, a foam structure is imparted to the polyurethane by the
production of a gaseous compound within the reaction mixture. For
example, a foam structure may be provided by generating carbon
dioxide by the reaction of water with isocyanate during the
urethane forming reaction. Another known method of providing at
least part or all of the foam structure involves the addition of
volatile liquid which is subsequently vaporized by the heat of
reaction developed during the course of the exothermic urethane
forming reaction.
In the latter method, the preferred class of volatile materials are
the alkanes and the fluoro-substituted alkanes. Specific examples
of such materials include tri-chlorofluoromethane,
dichlorofluoromethane, dichlorotetrafluoroethane,
trichlorotrifluoroethane, ethyl chloride, methane and ethane. When
a closed-cell foam structure is produced and such blowing agents
are employed, the closed cells retain the blowing agents in the
gaseous state (where the blowing agent is a gas at room
temperature) for at least a considerable period of time. This
retention is especially useful where the blowing agent is a
fluoroalkane or a chlorofluoroalkane, since it tends to enhance the
insulation value and the fire-resistant properties of the foam.
The structure and physical properties of the urethane foam are also
influenced by a variety of other factors, including the
incorporation of surfactants, catalysts, and fire-retardancy
agents. The incorporation of fire-retardancy agents renders the
foam nonburnable or self-extinguishing. This is highly desirable
for safety reasons, and a clear advantage over prior art wooden
composition door materials.
Although rigid polyurethane foams can be produced with a wide range
of densities, the door sections are preferably provided with an
average core density of from about 2 to about 10 pounds per cubic
foot. Rigid foams within this density range have provided
satisfactory insulation, sound deadening, and strength properties.
In addition, the door produced of such a rigid foam is
approximately one-third the weight of a conventional wood door.
Accordingly, the door supporting structure and other hardware
necessary for installation are relatively less expensive.
Referring to FIG. 6, another aspect of the present invention is
illustrated. As there shown, the door sections 50, which are
similar to the door sections 12 and include an integrally molded
thin external skin 50a, are connected by an integrally molded hinge
52. The hinge 52 is securely retained within the sections, since
urethanes adhere tightly to metal as well as a wide variety of
other structural materials. Although any type of hinge may be
employed, the hinge 52 is a double-leaf piano hinge having its
associated leaves 54 and 56 integrally molded in the adjacent
sections. The piano hinge 52 may extend along the entire horizontal
length of the door sections 50, or suitable portions thereof. The
associated leaves 54 and 56 are retained in an interlocked
condition by a pivot bar 58.
Although the embodiment illustrated in FIG. 6 does not provide
reversible closure surfaces, it should be noted that multiple
hinges may be provided on opposite sides of the door sections so as
to permit reversibility. In this instance, a decorative appearing
hinge would be employed. The oppositely disposed hinges which are
not being employed to connect the sections would be operatively
disconnected. For example, the pivot bar 58 would be removed from
the hinge 52 so as to permit independent movement of the leaves 54
and 56.
Referring to FIGS. 7 and 8, there is shown another aspect of the
present invention. According to this aspect of the invention, a
door section 60 is provided with an outer case portion 62 and an
integrally connected inner core portion 64. The case and core are
both formed of a rigid polyurethane foam and they are integrally
connected at an interface zone 66 disposed between hypothetical
zone boundary lines 66a and 66b. These boundary lines are not
subject to precise location based upon visual observations and they
are depicted herein as shown for convenience and clarification in
describing the interface zone. It should be understood that the
zone 66 is continuous and it exists at all locations intermediate
the adjacent regions of the inner core and outer case.
The outer case 62 is formed of a high density rigid polyurethane
foam and it provides a covering structure for the section. A
relatively thin face skin 60a of significantly higher density and
substantially less thickness is provided adjacent the exterior
surface of the case. The average density of the case excluding the
skin 60a and the interface zone 66 is in the range of from about 15
pounds per cubic foot to about 60 pounds per cubic foot.
Satisfactory results have been obtained when the case is provided
with an average density ranging from about 20 pounds per cubic foot
to about 30 pounds per cubic foot.
In a typical garage door installation, the outer case 62 is
provided with a thickness ranging from about one-sixteenth inch to
about three-sixteenths inch. Generally, it has been found that a
case thickness of about one-eighth inch provides the door section
with adequate rigidity and strength.
The core 64 is formed of a relatively lower density rigid
polyurethane foam and average density valves within the range of
from about 1.2 pounds per cubic foot to about 12.0 pounds per cubic
foot have been found to provide suitable door section structures.
The optimum thickness and density of the core is a function of the
overall dimensions of the door section and the thickness of the
case.
The physical characteristics of the interface zone 66 are primarily
determined by the method by which it is formed, as will become more
apparent hereinafter. The density of the interface zone has a
maximum value adjacent an intermediate planar location therein,
which is indicated by hypothetical line 66c for convenience, and
decreasing values at planar locations spaced therefrom which
ultimately correspond with the average densities of the adjacent
outer case and inner core. Accordingly, the density of the zone
increasingly varies from the opposite, outer regions thereof to a
maximum value adjacent the intermediate planar location 66c.
The region adjacent the hypothetical intermediate plane 66c is
characterized by a cellular structure which is not susceptible to
planar delamination in destructive testing, thus indicating the
strength of the interface zone adjacent the intermediate plane 66c
to be greater than that of the opposed inner core and outer case.
Generally, the failure occurred in the low density core portion
during the destructive tests.
A uniting of the case and core portions occurs within the interface
zone and is characterized by mechanical interengagement of the
portions and chemical bonding therebetween. The mechanical
interengagement and chemical bonding phenomena, which are defined
and discussed more fully below, cooperate to unite the portions
without the formation of an adhesion plane between disjuncted
laminae as known in the prior art, since the uniting of the
portions occurs throughout the interface zone which provides a
continuity of structure not clearly susceptible to physical
location by precise boundaries.
The mechanical interengagement of the inner core and outer case
portions relates to the mechanical adhesion or bonding resulting
from the physical interlocking developed by contacting an irregular
surface with a flowable material which is subsequently cured. In
this instance, the mechanical interengagement is further enhanced
by the positive pressures developed during the molding process
which assure the contiguous relationship of the ultimate portions
formed and tend to promote the physical interlocking thereof.
With regard to the chemical bonding between the portions, this
phenomenon includes both the intermolecular forces of adhesion
and/or cohesion and chemical reaction bonding. With regard to the
latter, such bonding may include both polymer chain extension and
cross linking which assure a continuous structure.
The interface zone 66, therefore, is a zone of relatively high
density material which constitutes an inner reinforcement means
which is not subject to chipping or spalling as would a purely
external reinforcement means.
The door section 60 may be provided with reinforcing means of a
net-type structure having openings therethrough, such as metal
netting 68, embedded within the outer case 62 of the door section
when additional strength and rigidity are desired. The metal
netting may be treated to enhance the adhesion between it and the
rigid foam. However, it should be appreciated that the ultimately
cured foam structure is essentially continuous through the openings
of the net structure, and the metal netting is substantially
embedded and enclosed within the case 62.
A suitable metal netting has been provided by the use of one inch
mesh, poultry netting of 20 gage galvanized steel wire. This metal
netting material is particularly suitable for commercial uses where
security is an important consideration.
Although the net-type structure may be disposed throughout the case
so as to surround the inner core, satisfactory results have been
obtained with the net structure disposed in the outer case adjacent
only one of the closure surfaces. Consequently, it has been found
convenient to limit the disposition of the net structure to the
outer case adjacent a planar exterior surface of the section.
Although metal netting has been found particularly useful in
commercial applications, it should be appreciated that other
net-type materials have been found to provide satisfactory results.
For example, a known, continuous filament, glass fiber, woven
netting has also provided suitable rigidity and impact strength for
such door sections. For this purpose, a relatively open, square
woven, glass fiber netting having a fiber or strand count per inch
of 10 by 20 is suitable. Of course, a broad range of such nettings
having various types of weaves and strand counts may be employed.
However, it is preferable to utilize a relatively open weave
pattern so as to insure complete "wetting" of the
reinforcement.
Referring to FIG. 9, there is shown another embodiment of the
present invention comprising a door section 70 including a case 72
and a core 74 similar in structure to that of the door section 60.
In this embodiment, the reinforcing means comprise randomly
oriented, chopped glass fibers 76. The chopped fibers are embedded
within an interior region of the case 72 adjacent the core 74
throughout the entire extent of such region so as to completely
surround the inner core of the section. The fibers may be of any
suitable length and satisfactory results have been obtained with
fibers having lengths in the range of from about one-half inch to
about 2 inches.
It should be appreciated that the chopped fibers are preferably but
not necessarily limited to disposition in the interior region of
the case. This disposition of the chopped fibers is preferable for
a number of reasons.
Initially, the chopped fibers are spaced from the exterior surfaces
of the door section for asthetic purposes. Specifically, their
presence adjacent the exterior surfaces may detract from the
provision of a simulated wood grain exterior appearance and
otherwise provide a somewhat non-uniform finished surface. In
addition, the substantial encasement of the chopped fibers within
the interior regions of the case 72 eliminates the possibility of
moisture transfer to the interior portion of the door section by
way of capillary action.
The embodiment shown in FIG. 9, also illustrates the use of
additional, substantially disjuncted, local reinforcing means such
as the elongated wood slat member 78. Such reinforcing means are
disposed to provide local reinforcement adjacent hinge sites and,
therefore, they typically coincide with the stiles or muntins in a
patterned door section.
Although the reinforcing member 78 comprises a wood slat, it should
be understood that any material providing a sufficiently rigid
structure could be utilized. For example, the reinforcing member
may be formed of metal, a compatible solid plastic material, or an
integral layer of high density foam. It should be appreciated that
such reinforcing means could also be employed in the previously
discussed embodiments of the present invention with or without the
use of reinforcing net-type structures or chopped glass fibers.
As shown in FIG. 9, the wood slat 78 is disposed adjacent a hinge
80 which is secured to the door section by means of a bolt 82 and a
threadedly engaged nut 84. During the installation of the door, an
appropriate bore for the bolt 82 may be provided by means of
drilling a hole through the section and the reinforcing slat.
The door sections 12, 50, 60 and 70 are molded within a closed,
split half mold 86 including halves 86a and 86b, as schematically
shown in FIG. 10. Each of the mold halves includes interior
surfaces which cooperate to define the section to be formed when
the mold halves are closed.
The mold is formed of a metal or like material having a relatively
high coefficient of thermal conductivity and conventional release
agents are employed. The exothermic heat of the urethane reaction,
which promotes the generation and/or volatilization of cell-forming
gases, is rapidly dissipated by walls of the mold.
In practice, the mold is generally preheated to retard the heat
dissipation and assure flowability and/or wetting-out of the
interior surfaces of the mold by the liquid foam resin. However,
the temperature of the polyurethane reaction is reduced in the
regions adjacent to the interior walls of the mold. Consequently,
thin integral skins 12a, 60a, 50a and 70a are formed at the
external surfaces of the door sections. The skin is a less
cellular, higher density layer of polyurethane which provides a
tough surface for the door section, as well as a barrier against
moisture penetration.
A conventional barrier coat for urethanes may be applied over the
release agent previously applied to the mold surfaces. The barrier
coat is retained on the surface of the molded product or door
section to protect the polyurethane against ultraviolet
degradation.
The door sections can be provided with uniquely inlaid designs
which are either not available or are economically impractical in
prior art structures, since each section is integrally molded as a
single unit. As illustrated by the closure surface 16, multiplanar
designs can be provided without combining separate pieces.
Furthermore, such intricate designs can be formed without a
significant increase in the manufacturing costs.
In the case of the door sections illustrated in FIGS. 1 through 6,
there is provided a single deposition of foam within the mold
halves. The mold halves are then closed and secured to one another
by clamp means or the like (not shown) locking the mating flanges
88 of the mold halves together. The section is then cured and
removed from the mold.
When it is desirable to provide a case such as outer case portions
62 and 72, the split half mold 86 is utilized in a somewhat
different manner. In this instance, it is of course necessary to
utilize foam forming solutions formulated to provide cured foams
having two different, predetermined average densities. The
variation in density may be achieved by conventional means such as
utilizing polyols of different molecular weights as well as
adjusting the amount of blowing agent.
A high density foam forming solution A which ultimately forms the
case of the door section is initially applied to the inner mold
surfaces of the mold halves 86a and 86b. The deposition of the foam
forming solution may be achieved in any manner, although the use of
conventional urethane spray apparatus has been found satisfactory.
The deposited foam solution forming the case of the section is
permitted to freely expand or blow until its rise is completed. As
previously indicated, the blowing of the foam is an exothermic
reaction and the heat generated results in temperatures ranging
upwards from room temperature initially to about 190.degree.F. as
measured at the surface of the foam portion being formed.
Subsequent to the completion of the rise of the solution A, which
ultimately forms the case, but prior to any significant degree of
curing of the foam and while the surface temperature thereof is
still above room temperature, a low density foam forming solution
which ultimately forms the core portion of the section is deposited
over the solution A or the semi-cured outer portion in at least one
of the mold halves. The deposition of the low density foam solution
may also be achieved by means of conventional apparatus. The mold
halves are immediately closed and secured following the deposition
of the low density foam forming solution.
It should be appreciated that the low density foam forming solution
is deposited while the semi-cured outer portion is still at an
elevated temperature, as a result of the exothermic reaction, in
order to achieve the desired flow of the low density solution as
well as a maximum surface wetting-out thereby so as to provide a
uniform density. Thus, the exothermic heat of reaction of the case
is somewhat analogous to the preheating of the mold 86 with regard
to the wetting-out of the low density, core forming foam
solution.
The low density core forming solution is deposited at about 25
percent excess or overpour based upon the calculated amount of foam
solution required to form the inner portion of the section with the
predetermined average density. The deposition of excess foam
results in packing and the development of positive molding
pressures upon the closing of the mold halves. It should be
understood that the precentage excess or overpour may range from
about 10 to about 30 percent in order to achieve a good fill and
provide the positive pressures necessary for the mechanical and
chemical interengagement and bonding of the case and the core as
previously discussed.
The time lapse between the completion of the rise of the case and
deposition of the foam solution forming the core is a primary
factor in the achievement of an interface zone having the
mechanical interengagement and chemical bonding characteristics
previously described. This time relationship is illustrated by the
three test samples discussed below. In each of the test samples,
the same rigid, polyurethane foam forming solutions were used,
namely; a high density, 20 pound per cubic foot, case foam solution
and a low density, 2 pound per cubic foot, core foam solution.
Further, equal volumes of foam forming solutions were employed in
identically sized molds.
In the first test sample, the time lapse following completion of
rise was about 20 seconds and the surface temperature of the case
was about 140.degree.F. when the low density, core foam solution
was deposited. In the second test sample, the time lapse was about
31/2 minutes and the surface temperature of the case was about
110.degree.F. In the third test example, the time lapse was about
191/2 minutes and the surface temperature of the case was about
72.degree.F. Each of the test samples was thereafter cured for a
period of 24 hours.
Each of the cured samples was tested for delamination between the
core and the case. The first and second test samples did not show a
plane of delamination upon destructive testing but rather resulted
in fracture substantially limited to the low density core
indicating achievement of the interface zone described above.
The third test sample did result in actual delamination at a plane
which formed between the case and the core. In addition, the core
did not provide a sufficient fill although the same volumes of foam
solution were employed in each of the test samples. The latter is
believed to be related to the relatively low temperature
(72.degree.F.) of the outer portion at the time of the deposition
of the core and an insufficient wetting-out by the foam core
forming solution.
With regard to the wetting-out of the core foam forming solution,
the surface temperature of the case at the time of the core
deposition should be in the range of from about 100.degree.F. to
about 140.degree.F. However, in practice, it may be desirable to
maintain a lower temperature limit of about 120.degree.F. to
provide an interface zone of optimum strength.
When it is desirable to provide the door section with additional
strength and rigidity through the use of reinforcing means of a
net-type structure, such as metal netting 68, the above described
method is slightly modified to permit the incorporation of the
net-type structure in the section. Specifically, the deposition of
the foam solution forming the case of the section is interrupted
and performed in two steps.
In the first step, about one half of the foam solution A is
initially deposited on the inner surfaces of the split mold half
86b. The foam deposition is then interrupted and the netting is
disposed on the solution already disposed within the mold. If the
netting does not assume a satisfactory planar configuration, it may
be provided with such by means of mechanical tensioning thereof or
magnetic forces provided by disposing appropriate magnetic means
below the mold half. Of course, when a glass fiber net-type
structure is employed for reinforcing means, it generally assumes a
planar configuration or it may be mechanically tensioned to provide
the same.
Subsequent to the positioning of the net-type structure, the
remaining portion of the foam solution A is deposited over the net
and the initial portion of the foam solution previously deposited.
This step is performed as soon as possible to assure the formation
of a substantially continuous case having the net-type structure
embedded therein. The remaining steps of the method are essentially
identical to those described above.
When it is desirable to employ reinforcing means comprising
randomly oriented fibers, such as glass fibers 76, the case is
similarly deposited within the mold in two steps. In this instance,
the fibers may be simultaneously introduced in the second step of
the case foam deposition by incorporation of the fibers within the
foam forming solution being deposited. In practice, this method has
been satisfactorily achieved by means of conventional urethane
spray apparatus including means to introduce the chopped fibers at
the spray mixing head.
The provision of local reinforcing means such as the member 78 is
also achieved by means of a two step deposition of the foam
solution A which forms the case of the section. In this instance,
the reinforcing members are disposed upon the initial coating of
the solution A and the remaining steps of the method are the same
as those described above. Of course, additional reinforcing means
such as net-type structures or chopped fibers may also be utilized
with the local reinforcing members.
The specific details of the preferred form and method of the
invention as described and shown herein are merely illustrative and
may be modified in various ways within the scope of the invention
as defined in the appended claims.
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