Note: Descriptions are shown in the official language in which they were submitted.
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DOOR PANEL
The present invention relates to a door panel for example
particularly, but not exclusively, a door panel with
reinforcement features that offers improvement on the
bending stiffness and tensile strength.
BACKGROUND OF THE INVENTION
Conventional door panels usually includes two door skins
adhesively bonded to a core that is made of material that
serves the specific purpose of the door panel. Stiles and
rails are provided to seal off any free end of the door
panel to provide a clean and tidy finishing. The stiles
and rails are nailed and/or adhesively glued to the rest
of the door panel.
Such doors, especially when used outdoor are exposed to
the ever-changing external environment. The humidity and
temperature adjustment would force the various parts of
the door panel to expand and contract. Overtime, this
results in cracks and splits. When there is a fire, door
with high heat tolerance, tensile strength and bending
stiffness may help reduce the loss of life and property
by slowing or preventing the spread of fire and smoke.
This provide additional time for people to escape.
Taking fiberglass door members comprising fiberglass
reinforced sheet compression molded skins as an example,
it has relatively recently acquired consumer acceptance.
Fiberglass door members typically comprise a door-shaped
wooden frame member, a polymeric foam-type core
positioned within the frame member, a first fiberglass
reinforced compression molded door skin secured to a
first side of the frame member, and a second fiberglass
reinforced compression molded door skin secured to a
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second side, opposite the first side, of the frame member.
The fiberglass reinforced compression molded door skins
are prepared from a molding compound.
The fiberglass door members compare favorably to wood
material doors in that they are less expensive than wood
material doors. Moreover, fiberglass door members
overcome the cracking, splitting, delaminating veneers
and poor insulating efficiency associated with wood doors.
Furthermore, these fiberglass door members compare
favorably to steel doors in that they resist the denting,
rusting and do not have the cold feel associated with
steel doors.
A conventional door with fiberglass reinforced sheet
compression molded skins is formed by adhesively joining
the skins to the door frame. When it is under the attack
of fire, the skin closest to the fire is the first to
burn and carbonize. The heat from the fire then
penetrates the door causing the adhesive to disintegrate
and the skin to detach from the frame, followed by
dehydration of the frame resulting in cracks formation,
disintegration, burning and cabonization. This brings
about contraction and thinning. The time required to
bring about the bending of the door in a fire is a good
indicator of the bending strength of the door. When heat
continues to penetrate the door, the cracks expand and
the door becomes fragmented and fragile. The resulting
door is sustained by the remaining adhesive material. The
contraction and thinning of the various materials in the
door causes the door to bend and deform.
The invention seeks to eliminate or at least to mitigate
such shortcomings for better performance without a
substantial increase in costs by providing a new or
otherwise improved door panel.
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SUMMARY OF THE INVENTION
According to the invention, in a first aspect of the
invention there is provided a door panel comprising a
body having front and rear door skins delimiting an
interior for sandwiching filling material, an
interlock
provided with the body and configured to lock the front
and rear skins thereby prevent displacement of the front
and rear skins along at least two transverse directions,
and a reinforcement member provided between the front and
rear door skins and extend transversely to the interlock
for providing reinforcement to the body.
Preferably, the reinforcement member intersects the
interlock to form a reinforcement intersection.
More preferably, the reinforcement member extends
perpendicular to the interlock.
Yet more preferably, the reinforcement member is inserted
into an aperture preformed in the body and is retained
therein by way of friction.
It is preferable that the reinforcement member has
friction enhancement means on its outer periphery for
enhancing the friction between the outer periphery and
the aperture.
Advantageously, the reinforcement intersections are
provided at respective apertures preformed at respective
corners of the body.
More advantageously, the interlock compartmentalized the
interior of the body and the reinforcement member extends
across two compartments via the reinforcement
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intersection.
Yet more advantageously, the four corners are each being
reinforced by a pair of reinforcement intersections with
the reinforcement members running parallel to one
another.
More preferably, the reinforcement member is formed from
a material comprises metal.
More preferably, the interlock is formed from the
interlocking of first and second locking members one from
each of the front and rear door skin.
It is preferable that the first and second locking
members are configured complementarily for complementary
engagement thereby interlocks the first and second door
skin.
Preferably, the first and second locking members project
from respective front and rear door skin into the
interior such that the interlock is located between the
front and rear door skin.
More preferably, the first and second locking members are
integrally formed on the respective front and rear door
skins as a one-piece structure.
It is preferable that the first locking member includes a
guide for guiding movement of the second locking member
towards the first locking member.
Advantageously, thickness of the interior is defined by
overall length of the interlock.
More advantageously, the first locking member includes a
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free end shaped to engage with a complementarily shaped
free end of the second locking member.
It is advantageous that the free end of the first locking
member includes a male engagement member for engaging a
female engagement member on the free end of the second
locking member.
Preferably, the body includes two specially separated
interlocks which are each configured to prevent
displacement of the front and rear skins along at least
two transverse directions.
More preferably, each of the interlocks includes first
and second locking members, the front door skin is
provided with two locking members, one from each pair of
locking members.
It is preferable that the front door skin is provided
with first and second locking members which are
structurally distinct and spatially separated.
BRIEF DESCRIPTION OF DRAWINGS
The invention will now be more particularly described, by
way of example only, with reference to the accompanying
drawings, in which:
Figure 1 is a cross-sectional view of a door skin in
accordance with the invention and the mould used during
sheet compression molding for the production of the door
skin;
Figure 2A and 2B are perspective views of door skins in
Figure 1 being assembled to define an interior and show
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an interlock formed between the door skins;
Figure 2C is an enlarged view of the interlock in Figures
2A and 2B;
Figure 3 is an illustrative view of a part of the door
panel in Figure 2A and 2B with a pair of reinforcement
members being inserted into the interior via the
interlock;
Figure 4A and Figure 4B are enlarged cross-sectional
views of part of the door panel with respective
interlocks;
Figure 5 is a perspective view of the door panel in
accordance with the invention having interlocks and eight
reinforcement members arranged to intersect with the
respective interlocks;
Figure 6 is a table showing fire test results of a
conventional door;
Figure 7 is a table showing fire test results of a door
with the invention which includes interlocks and
reinforcement members; and
Figure 8 shows the direction of deformation or bending of
a door subject to the fire test.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
Referring to Figures 1 to 5, there is shown an embodiment
of the invention in the form of a door panel 100 with
front and rear door skins 200 and 300, rails and stiles
101 delimiting an interior 400 to be filled with filling
material.
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In the specific embodiment, the door skins 200 and 300
are fiberglass reinforced sheet compression molded skins.
However, there is no intention to limit the universal
application of the invention to doors formed from
different methods with different materials in different
constructions. As an example, a door with door skin
formed from extrusion will not prevent the implementation
of the invention therein.
Referring to Figures 2A and 2B, the door skins 200 and
300 are rectangular plates of material that form the
outside of the door panel 100. Usually, the external
surfaces of the front and rear door skins 200 and 300 are
decorated for aesthetic purposes. At least one interlock
500 is provided between the front and rear door skins 200
and 300 to maintain separation between them as well as
preventing relative movements of the front and rear door
skins 200 and 300 in at least two transverse directions X
and Y. In other words, the interior 400 is maintained by
the interlocks 500.
In more detail and with reference to Figure 2C, the
interlock 500 comprises two locking members, the first
and second locking members 501 and 502. The first locking
member 501 extends or protrudes from an internal surface
of the front door skin 200 while the second locking
member 502 extends or protrudes from an internal surface
of the rear door skin 300. In the embodiment as shown in
Figure 2C with reference to Figure 1, the first locking
member 501 is integrally formed with the front door skin
200. The first locking member 501 and the front door skin
200 are formed as a one-piece structure simultaneously by
way of compression moulding. The second locking member
502 is also integrally formed with the rear door skin
300. The second locking member 502 and the rear door skin
300 are also formed as a one-piece structure
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simultaneously by way of compression moulding.
The first and second locking members 501 and 502 each has
a free end. The free ends are each provided with an
engagement surface 501A. The engagement surface 501A of
the first locking member 501 is shaped complementarily to
the engagement surface 502A of the second locking member
502. With reference to Figure 2C, the engagement surface
501A defines a groove or void for accommodating a
corresponding protrusion on the engagement surface 502A.
The groove or void also act as a guide to guide movement
of the protrusion into it thereby guiding movement of the
first and second door skins 200 and 300 towards one
another in the direction of X as the door skins are
assembled to form the door panel 100. Upon engagement,
the locking members 501 and 502 form an interlock 500
between the door skins 200 and 300. More specifically,
side walls of the groove or void abut side walls of the
protrusion to prevent movement of the locking members 501
and 502, hence the door skins 200 and 300 from moving
relative to one another in the direction of Y. Once the
protrusion is fully inserted into the groove or void,
further movement of the locking members 501 and 502
towards each other, hence movement of the door skins 200
and 300 in the direction of X is prevented. As a result,
the interlock 500 once in place would serve to prevent
relative movement between the door skins 200 and 300 in
both the directions X and Y which are transverse to one
another.
Each of the locking members 501 and 502 extend along
substantially entire height of the respective door skin
200 and 300. The resulting interlock 500
compartmentalizes the interior and are functionable as
tensile or mechanical reinforcement ribs to offer
additional strength to the door panel 100, particularly
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in the direction along the height of the door panel 100.
In an embodiment of the invention, length of the locking
members 501 and 502 is shorter than that of the door
skins 200 and 300 at top and bottom ends to define a
space for accommodating the top and bottom rails.
In the embodiment as shown in Figures 1 to 2C, there are
two pairs of interlocks 500 between the door skins 200
and 300 of a door panel 100. On the front door skin 200,
there are two locking members, first and second locking
members 501 and 502 on the same inner side of the front
door skin 200. The first and second locking members 501
and 502 are arranged in spatial separation from one
another. On the rear door skin 300, again two locking
members, second and first locking members 502 and 501 are
provided on the same inner side. These locking members
are arranged at positions on the rear door skin 300 that
correspond to those on the front door skin 200.
To facilitate the formation of the door skins 200 and
300, it is possible that the front and rear door skins
200 and 300 are identical and formed from a same mould
701 and 702 except that when in use, they are oriented
differently.
As an alternative, it may be possible for the front door
skin 200 to be provided with two first locking members
501 while the rear door skin 300 being provided with two
second locking members 502.
Furthermore, in an alternative embodiment, the second
locking member 502 may be an indentation with an
engagement surface 502A being shaped complementarily to
that of the first locking member 501.
The door panel 100 as detailed above benefits from the
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improved mechanical support offered by the interlocks
500. In addition to the maintaining of the interior 400
and preventing the relative movement between the door
skins 200 and 300. To enhance the bending stiffness of
the door panel 100 along substantially the entire height
thereof, in particular under severe condition such as
when the door panel 100 is subject to high heat,
reinforcement members 600 are tactfully installed in the
door panel 100. The material from which the reinforcement
member 600 is made is carefully selected. It must be able
to ensure heat without deformation at reasonable cost and
be easy to install without overburdening the
manufacturing process.
In the embodiment of the invention as shown in Figures 4A
to 5, the reinforcement members 600 is in the form of a
metal rod or are made from a material with tensile
strength greater than that of the rest of the door panel
100. The reinforcement members 600 are provided in the
interior 500 of the door panel 100 to enhance the tensile
strength and the bending stiffness of the overall door
panel 100 in a direction transverse to the height of the
door panel 100. As shown in Figure 3, insertion of the
reinforcement member 600 is guided by a guide preformed
on the door panel 100. In the specific embodiment, the
reinforcement member 600 is inserted in a pre-drilled
aperture 601 to intersect with the interlock 500. The
reinforcement member 600 runs transverse to and in the
specific embodiment, perpendicular to the interlock 500.
As shown in Figures 4A and 4B, the reinforcement member
600 runs through the engagement surfaces 501A and 502A
from one side of the interlock 500 to the other side
thereof. As explained above, the interlock 500 partitions
or compartmentalizes the interior 400 such that the
reinforcement member 600 extends from one compartment to
another via the interlock 500.
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In more detail, as shown in Figure 5, a pair of
interlocks 500 runs along the height of the door panel
100 in the interior 400. The interlocks 500 are shorter
than the height of the door skins 200 and 300 leaving
respective clearance at the top and bottom sides of the
door skins 200 and 300 to define top and bottom spaces
for accommodating top and bottom rails therein
respectively. These interlocks 500 are separated
spatially and are positioned adjacent to the left and
right extremities of the door panel 100. These interlocks
500 partition the interior 400 into three compartments,
the left, right and center compartments. The door panel
100 takes the shape of a rectangle with four corners. At
each corner, a pair of reinforcement members 600 are
arranged parallel to each other and perpendicular to the
relevant interlock 500. The pair of reinforcement members
600 are provided on a same plane yet being vertically
displaced. As a result, there are eight reinforcement
members 600 two at each corner of the door panel 100.
With reference to Figures 3 and 5, the apertures 601 are
formed through the stiles 101 and into the interior 400.
After the insertion of the reinforcement members 600, the
apertures 601 for accommodating them may be sealed off by
any conventional means. The reinforcement member 600 is
dimensioned to form a tight fit with an interior wall of
the aperture 601 such that the reinforcement member 600
is retained in the aperture 601 by friction. Adhesive may
not be required to fix the positions of the reinforcement
members 600 in the door panel 200. Corrugations are
provided on an outer surface of the reinforcement members
600 to function as friction enhancer thereby enhance th3
friction between the reinforcement members 600 with the
interior walls of the respective apertures 601.
Eight reinforcement intersections 700 are formed where
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the respective reinforcement members 600 intersect the
respective interlocks 500. These
intersections
substantially improves the mechanical and tensile
strength as well as the bending stiffness of the overall
door panel 100. Force applied on the door skins 200 and
300 are evenly spread to the entire door panel via the
reinforcement members 600 and the interlocks 500 thereby
improving the bending stiffness of the overall door panel
100. In an alternative embodiment, the reinforcement
members 600 may extend across entire width of the door
panel 100 and as such only four are required.
The door skins 200 and 300 are held in place relative to
one another by the interlocks 500 and the reinforcement
members 600 in addition to adhesive. These parts of the
door panel 100 are held together without the use of
adhesive. Heat endurance of the interlocks 500 and the
reinforcement members 600 is comparatively much better
than that of adhesive. The door skins 200 and 300 are
less likely to detach from one another and heat is less
likely to penetrate as quickly as with conventional doors
in which the door skin is secure by adhesive. The
resulting door panel 100 is less likely to disintegrate
or fall apart.
The reinforcement members 600 integrate or join various
parts of the door panel 100 together such that when the
door panel 100 is subject to fire and heat, even though
any wood components contract, the reinforcement members
600 serve to resist the bending of the door panel 100 and
its disintegration. The adhesive that binds the door
skins 200 and 300 to door frame will disintegrate but are
maintained in position and in attachment to the rest of
the door panel 100 by the reinforcement member 600 and
the interlock 500. Disintegration of the overall door
panel 100 is postponed or slowed down. The resulting door
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panel 100 is able to resist deformation for a longer
period of time in a fire.
In an embodiment of the invention, the door skins 200 and
300 are made of sheet moulding composite (SMC), a ready
to mould glass-fiber reinforced polyester material. The
rails and stiles 101 have wooden cores covered by plastic
outer skin. The filling material that fills the interior
500 comprises PU foam or phenolic foam (fire resisting).
Interlocks 500 runs along height of the door panel 100
and reinforcement members 600 are provided at the corners
of the door panel 100 as detailed above.
In a conventional door panel 100, the door skins are
adhesively attached to the core. There is no interlock or
reinforcement member.
When subject to heating, various parts of the door panel
100 will separate from one another thereby progressively
lowers the tensile and mechanical strength as well as the
bending stiffness of the door panel 100. This is
illustrated by the following fire tests.
Fire tests
With reference to Figures 5 and 6, fire tests were
performed on a conventional door panel and the door panel
100 with the invention respectively. After prolonged
heating at a temperature of about 1000 degree C in an
oven that simulates the conditions when the doors are
subject to the burning of fire, the deformation of the
conventional door is more substantial than that of the
door with the invention.
In more detail, as an example, for the conventional door,
when it is heated for 30 minutes and the oven is at 1043
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degree C, the deformation at position A' is +30.1 while
that at position B' is +14.1. When the door with the
invention is heated for 70 minutes and the oven is at
1022 degree C, the deformation of the door with the
invention at position A is +17.9 and at position B' is -
2.9. With reference to Figure 7, the sign + indicates a
bending direction towards the fire source and the sign -
indicates a bending direction away from the fire source.
The number indicates the magnitude of deformation. The
magnitude of deformation at position A' in the door with
the invention is about half of that in a convention door.
The magnitude of deformation at position B' in a
convention door is 7 times higher than the door with the
invention. The sign +/- indicate the direction of bending
in the deformation. The test clearly demonstrate the
durability of the door with the invention, in particular
its ability to resist deformation as a result of
relatively higher mechanical and tensile strength as well
as higher bending stiffness.
In another example, for the conventional door, when it is
heated for 16 minutes and the oven is at 888 degree C,
the deformation at position A' is +17.9 while that at
position B' is +9.9 and at position C' is +6.6. When the
door with the invention is heated for 30 minutes and the
oven is at 888 degree C, the deformation of the door with
the invention at position A is +15.0 and at position B'
is +0.54. Again, the figures show that the deformation in
the door panel in accordance with the invention is
smaller at various locations of the door when compared to
that of a conventional door.
The conventional door has a 1110mm x 2388mm door panel in
a 1200mm x 2400mm door frame with sheet compression
moulded fiberglass skins sandwiching a phenolic foam core
without reinforcement member 600 or interlock 500. The
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door with the invention has a 1110mm x 2440mm door panel
in a 1200mm x 2500mm door frame with sheet compression
moulded fiberglass skins sandwiching a phenolic foam core
with reinforcement member 600 and interlock 500. The
position A' is a upper corner of the door being tested on
the side where the door handle is provided while position
B' is a lower corner of the door being tested on the same
side of the door as position A'.
The invention has been given by way of example only, and
various other modifications of and/or alterations to the
described embodiment may be made by persons skilled in
the art without departing from the scope of the invention
as specified in the appended claims.
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