U.S. patent application number 10/581438 was filed with the patent office on 2007-07-26 for panel structure.
Invention is credited to Iain Norman Bridge.
Application Number | 20070169432 10/581438 |
Document ID | / |
Family ID | 29764456 |
Filed Date | 2007-07-26 |
United States Patent
Application |
20070169432 |
Kind Code |
A1 |
Bridge; Iain Norman |
July 26, 2007 |
Panel structure
Abstract
A panel structure (10) is formed from two sheets (12). The
sheets (12) are spaced apart to provide avoid (13) between them.
The sheets (12) are tied together at various positions (14). The
ties (14) are formed of substantially the same material as the
sheets (12), in such a way that the sheets (12) and the tie means
(14) form an uninterrupted body of material. The ties (14) leave
unobstructed voids (13) within the plane of the panel. An elongate
reinforcing member (15) is located within one of the voids.
Inventors: |
Bridge; Iain Norman;
(Staffordshire, GB) |
Correspondence
Address: |
PATENT DOCKET CLERK;COWAN, LIEBOWITZ & LATMAN, P.C.
1133 AVENUE OF THE AMERICAS
NEW YORK
NY
10036
US
|
Family ID: |
29764456 |
Appl. No.: |
10/581438 |
Filed: |
November 16, 2004 |
PCT Filed: |
November 16, 2004 |
PCT NO: |
PCT/GB04/04825 |
371 Date: |
January 29, 2007 |
Current U.S.
Class: |
52/783.1 |
Current CPC
Class: |
B32B 7/04 20130101; B32B
5/18 20130101; B32B 3/20 20130101; B32B 3/28 20130101 |
Class at
Publication: |
052/783.1 |
International
Class: |
E04C 2/54 20060101
E04C002/54 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2003 |
GB |
0327961.9 |
Claims
1. A panel structure comprising two sheets which are spaced apart
to provide a void between, and are tied together by a plurality of
tie means extending from one of the sheets to the other, the tie
means being formed of substantially the same material as the
sheets, and the sheets and the tie means forming an uninterrupted
body of the material, the ties being arranged to leave unobstructed
voids within the plane of the panel, and there being an elongate
reinforcing member located within at least one of the voids.
2. A panel structure according to claim 1, wherein the ties are
arranged across the sheets in a geometric lattice.
3. A panel structure according to claim 1, wherein the void between
the sheets contains a material different to the sheets.
4. A panel structure according to claim 3, wherein the different
material is an expanded material.
5. A panel structure according to claim 1, wherein the material of
the sheets and tie means is a thermosetting or thermoplastic
plastics material, polymer material, metal or board material.
6. A panel structure according to claim 1, wherein the material of
the sheets incorporates reinforcing fibers.
7. A panel structure according to claim 1, wherein the sheets are
generally planar.
8. A panel structure according to claim 7, wherein the sheets are
generally parallel.
9. A panel structure according to claim 1, wherein the tie means
each consist of material of one or more sheets, deformed out of the
plane of the corresponding sheet and fused to material of the other
sheet.
10. A panel structure according to claim 9, wherein material of
both sheets is deformed from the respective plane to be fused with
material of the other sheet at a position between the sheets.
11. A panel structure according to claim 10, wherein the material
of the sheets is fused midway between the sheets.
12. A panel structure according to claim 9, wherein the material is
deformed by a process which includes the application of heat.
13. A panel structure according to claim 9, wherein the material is
deformed by a process which includes the application of
pressure.
14. A panel structure according to claim 9, wherein the material is
deformed to form hollow projections toward the other sheet.
15. A panel structure according to claim 9, wherein the material is
deformed to form solid projections toward the other sheet.
16. A panel structure according to claim 9, wherein the projections
are formed with pointed, rounded or flat peaks for fusion with
corresponding peaks formed from the other sheet.
17. A panel structure according to claim 9, wherein no more than
one half of the area of the sheets is deformed to form tie
means.
18. A panel structure according to claim 17, wherein the sheets are
substantially planar between areas of deformation.
19. A panel structure according to claim 17, wherein the sheets are
deformed only at points, being substantially undeformed
therebetween.
20. (canceled)
21. (canceled)
22. A panel, comprising: first and second generally planar sheets
spaced apart from one another; the first sheet having a plurality
of projections extending toward the second sheet, the projections
of the first sheet and the first sheet being formed of
substantially the same material; the second sheet having a
plurality of projections extending toward the first sheet, the
projections of the second sheet and the second sheet being formed
of substantially the same material; each of the projections of the
first sheet coupled to a corresponding one of the projections of
the second sheet in a manner that forms an uninterrupted body
between corresponding pairs of projections of the first and second
sheets; the projections of the first and second sheets being
arranged to provide a plurality of voids between the first and
second sheets at positions at which there are no projections; and
an elongate reinforcing member disposed within at least one of the
voids.
23. The panel of claim 22, wherein each of the projections of the
first sheet meets the corresponding one of the projections of the
second sheet along the same plane.
24. The panel of claim 22, wherein each of the first and second
sheets is formed of one of thermoset plastic material,
thermoplastic material, polymer material, metal alloy and paper
board.
25. The panel of claim 22, wherein each of the first and second
sheets includes reinforcing fibers.
26. The panel of claim 22, wherein each of the projections of the
first and second sheets includes a flat peak so that each of the
projections of the first sheet meets the corresponding one of the
projections of the second sheet along the entire flat peaks of the
projections.
27. The panel of claim 22, comprising foam material disposed within
a plurality of the voids between the first and second sheets.
28. The panel of claim 27, wherein the foam material disposed
within the plurality of the voids is adapted to provide at least
one of thermal and sound insulation.
29. The panel of claim 22, wherein the elongate reinforcing member
is substantially rigid.
30. The panel of claim 29, wherein the elongate reinforcing member
is of sufficient size to bear against both the first and second
sheets at positions of the first and second sheets at which there
is no projection.
31. The panel of claim 30, wherein the elongate reinforcing member
is disposed within one of the voids having a hexagonal shape, the
elongate reinforcing member bearing against opposite sides of the
hexagonal shape representing positions of the first and second
sheets at which there is no projection.
32. The panel of claim 22, wherein the elongate reinforcing member
is hollow and adapted to be used as a service duct.
33. The panel of claim 22, wherein the elongate reinforcing member
is straight and extends along an entire length of the first and
second sheets.
34. The panel of claim 22, comprising a plurality of elongate
reinforcing members disposed within the voids; a first of the
elongate reinforcing members being coupled to a second of the
elongate reinforcing members to form a joint.
35. The panel of claim 34, wherein the first and second elongate
reinforcing members extend perpendicular to one another.
36. The panel of claim 22, wherein the elongate reinforcing member
is bent.
37. The panel of claim 22, wherein each of the projections of the
first and second sheets is conical in shape and includes a pointed
peak so that each of the projections of the first sheet meets the
corresponding one of the projections of the second sheet at the
pointed peaks of the projections.
38. The panel of claim 37, wherein the elongate reinforcing member
is substantially rigid and of sufficient size to bear against both
the first and second sheets at positions of the first and second
sheets at which there is no projection.
39. The panel of claim 22, wherein each of the projections of the
first and second sheets is solid.
40. The panel of claim 39, wherein a surface of the first sheet not
facing the second sheet reveals no depressions towards the second
sheet, and a surface of the second sheet not facing the first sheet
reveals no depressions towards the first sheet.
41. The panel of claim 22, wherein each of the projections of the
first and second sheets is hollow.
42. The panel of claim 41, wherein a surface of the first sheet not
facing the second sheet reveals visible concavities at positions at
which there exist projections, and a surface of the second sheet
not facing the first sheet reveals visible concavities towards the
first sheet at which there exist projections.
43. The panel of claim 42, wherein each of the projections of the
first and second sheets is arranged at an interstice of a square
lattice, and a size of the square lattice is sufficiently wide to
provide unobstructed straight voids in which to receive elongate
reinforcing members.
44. The panel of claim 42, wherein an area of each of the first and
second sheets disposed between the visible concavities is
substantially greater than one half a total area of the respective
one of the first and second sheets.
45. The panel of claim 22, wherein each of the corresponding pairs
of projections of the first and second sheets forms a column
extending between the first and second sheets.
46. The panel of claim 45, wherein each of the projections of the
first and second sheets is substantially solid.
47. A method of forming a panel, comprising the steps of: providing
a first generally planar sheet having a pre-formed plurality of
projections; providing a second generally planar sheet having a
pre-formed plurality of projections; bringing peaks of the
plurality of projections of the first sheet together with peaks of
the plurality of projections of the second sheet; applying heat to
the peaks of the projections to soften material in a region of each
of the peaks; and fusing the peaks of the projections of the first
and second sheets in contact with one another to provide a fused,
solid material at positions of contact of the peaks of the
projections of the first and second sheets.
48. The method of claim 47, wherein the step of bringing the peaks
of the projections of the first and second sheets together is
carried out by bringing the peaks together around an elongate
reinforcing member, the elongate reinforcing member being disposed
within a void between the first and second sheets.
49. The method of claim 47, comprising the step of introducing an
elongate reinforcing member axially into a void between the first
and second sheets after peaks of the projections of the first and
second sheets are brought together.
50. The method of claim 47, comprising continuously feeding the
first and second sheets toward first and second rollers each having
a plurality of heating elements; wherein the step of applying heat
is carried out by the heating elements of the first and second
rollers.
51. A method of forming a panel, comprising the steps of: providing
a first generally planar sheet; providing a second generally planar
sheet; bringing the first and second sheets together in contact
with one another; applying localized heat to each of the locations
on the first and second sheets at which a projection is to be
provided to fuse together corresponding heated locations on the
first and second sheets; moving, after fusion has begun but before
the first and second sheets have fully cooled, the first and second
sheets apart from one another to form projections between the
sheets at fused locations of the first and second sheets; and
maintaining the first and second sheets in a position apart from
one another until the first and second sheets have cooled.
52. The method of claim 51, comprising introducing an elongate
reinforcing member within a void formed between the first and
second sheets.
53. The method of claim 51, wherein the step of moving the first
and second sheets apart from one another is carried out by
employing suction from outside the panel.
54. The method of claim 51, wherein the step of moving the first
and second sheets apart from one another is carried out by blowing
a substance between the first and second sheets to force the first
and second sheets apart.
55. The method of claim 51, comprising applying a secondary region
of heat around said each of the locations on the first and second
sheets at which a projection is to be provided.
56. The method of claim 55, wherein the step of applying a
secondary region of heat is carried out in a manner that does not
fuse the first and second sheets of material at positions at which
the secondary region of heat is applied.
57. The method of claim 56, wherein positions of the first and
second sheets of material at which the secondary region of heat is
applied form side walls of the projections when the first and
second sheets are moved apart from one another.
58. The method of claim 55, wherein the step of applying a
secondary region of heat is carried out at a lower temperature than
a temperature at which the localized heat is applied.
59. The method of claim 55, wherein the step of applying a
secondary region of heat is carried out for a shorter period of
time than a period of time for which the localized heat is
applied.
60. The method of claim 51, comprising continuously feeding the
first and second sheets toward first and second rollers each having
a plurality of heating elements and a plurality of suction
elements; wherein the step of applying localized heat is carried
out by the heating elements of the first and second rollers, and
the step of moving the first and second sheets apart is carried out
by the suction elements of the first and second rollers.
61. The method of claim 60, comprising feeding an elongate
reinforcing member within a void formed between the first and
second sheets while the first and second sheets are continuously
fed toward the first and second rollers.
Description
[0001] The present invention relates to panel structures and their
formation.
[0002] In accordance with the present invention, there is provided
a panel structure comprising two sheets which are spaced apart to
provide a void between, and are tied together by a plurality of tie
means extending from one of the sheets to the other, the tie means
being formed of substantially the same material as the sheets, and
the sheets and the tie means forming an uninterrupted body of the
material, the tie means being arranged to leave unobstructed voids
within the plane of the panel, and there being an elongate
reinforcing member located within at least one of the voids.
[0003] The ties are preferably arranged across the sheets in a
geometric lattice. The void between the sheets may contain material
different to the sheets, such as an expanded material.
[0004] The said material of the sheets and tie means may be a
thermosetting or thermoplastic plastics material, other polymer
material, metal, or board. The material of the sheet may
incorporate reinforcing fibres.
[0005] The sheets are preferably generally planar and preferably
generally parallel.
[0006] The tie means may each consist of material of one or more
sheets, deformed out of the plane of the corresponding sheet and
fused to material of the other sheet. Preferably material of both
sheets is deformed from the respective plane to be fused with
material of the other sheet at a position between the sheets.
Preferably, the material of the sheets is fused midway between the
sheets.
[0007] The material may be deformed by a process which includes the
application of heat and/or pressure. The material may be deformed
to form hollow projections toward the other sheet. Alternatively,
the material may be deformed to form solid projections toward the
other sheet. The projections may be formed with pointed, rounded or
flat peaks for fusion with corresponding peaks formed from the
other sheet.
[0008] Preferably no more than one half of the area of the sheets
is deformed to form tie means. The sheets are preferably
substantially planar between areas of deformation. The sheets may
be deformed only at points, being substantially undeformed
therebetween.
[0009] Various embodiments of the present invention will now be
described in more detail, by way of example only, and with
reference to the accompanying drawings in which:
[0010] FIG. 1a is a perspective view of a panel structure in
accordance with a first embodiment of the invention, shown partly
cut away;
[0011] FIG. 1b is a section along the line B-B of FIG. 1a and FIG.
1c is an enlarged view of part of FIG. 1b;
[0012] FIGS. 2a, 2b and 2c correspond with FIGS. 1a, 1b and 1c
respectively, illustrating a second embodiment;
[0013] FIGS. 3a, 3b and 3c correspond with FIGS. 1a, 1b and 1c
respectively, illustrating a third embodiment;
[0014] FIG. 4 is a section through a fourth embodiment of panel
structure;
[0015] FIGS. 5a and 5b illustrate the panel faces of the first and
fourth embodiments;
[0016] FIG. 6, FIGS. 7a and 7b illustrate various methods and
arrangements for forming panel structures in accordance with the
invention; and
[0017] FIGS. 8a and 8b illustrate further methods and arrangements
for forming panel structures in accordance with the invention.
[0018] FIG. 1 shows a panel structure 10 formed from two sheets 12.
The sheets 12 are spaced apart to provide a void 13 between them.
The sheets 12 are tied together at various positions by tie means
indicated generally by the numeral 14. The ties 14 extend from one
of the sheets 12 to the other.
[0019] As will be described, the ties 14 are formed of
substantially the same material as the sheets 12 and in such a way
that the sheets 12 and the tie means 14 form an uninterrupted body
of material. The tie means 14 are arranged to leave unobstructed
voids within the plane of the panel. An elongate reinforcing member
15 is located within at least one of the voids.
[0020] Each sheet 12 is generally planar except in the region of
each tie 14. At these positions, the material of the sheet 12 is
deformed from the plane of the sheet 12, in a manner to be
described, to form a projection 16 toward the other sheet 12. The
projections 16 are hollow. The projections 16 meet corresponding
projections from the other sheet 12 at a plane indicated in FIGS.
1b and 1c by a broken line 17. A solid line is not used because the
material of the projections 16 is fused at this location, as part
of the forming process, in order to form a single uninterrupted
body of material across the sheets 12 and through the ties 14.
[0021] The sheets 12 may be formed of a thermosetting or
thermoplastic plastics material, a polymer material, a metal alloy,
or a paper board etc. for example. The material may optionally
incorporate reinforcing fibres indicated at 18.
[0022] It can be seen from FIGS. 1a to 1c that in this embodiment,
the projections 16 have generally flat peaks prior to fusion, so
that fusion takes place across the whole of the area of the
peak.
[0023] The void 15, which is defined between the sheets 12,
contains reinforcing members 15, and may otherwise be left
unfilled, as an open void (as shown toward the left of FIG. 1b) or
may contain a foam material 22 (as shown toward the right of FIG.
1b). The foam material is not necessarily required for the
structural performance of the panel 10, but may be incorporated for
other reasons, such as thermal or sound insulation. The reinforcing
members 15 are preferably substantially rigid and of sufficient
size to bear against the sheets 12, to provide strength against
distortion of the panel. Thus, the panel is strengthened by the
presence of the reinforcing members. The reinforcing members may be
of metal or other material, and may be solid or hollow, the latter
allowing the reinforcing member to be used as a service duct.
[0024] The reinforcing members may be straight, extending across
the whole of the panel, or joints may be formed within the panel,
such as is illustrated at 19. In a further alternative, the
reinforcing members may be bent, rather than straight.
[0025] A second embodiment is shown in FIGS. 2a to 2c. Features
corresponding with those of FIG. 1 are given corresponding
reference numerals, suffixed a.
[0026] In the second embodiment, the panel 10a again comprises two
sheets 12a connected by tie means 14a formed by projections 16a.
Reinforcing members 15a are provided in the voids 13a left between
the projections 16a. The difference between the first and second
embodiments relates to the shape of the projections 16a. In the
second embodiment, the projections 16a are conical, with pointed
peaks, so that the area of intimate contact and fusion between the
projections 16a is relatively small in the second embodiment, in
comparison with the area provided by the flat peaks of the
projections 16.
[0027] Fusion of the peaks results in a single uninterrupted body
of material across the sheets 12a and through the ties 14a.
[0028] Again, the sheets 12a are preferably a thermosetting or
thermoplastic plastics material, other polymer material, a metal or
a board etc., and may incorporate reinforcing fibres (not shown in
FIG. 2). The space 20a may be left as an open void, or filled with
foam (not shown in FIG. 2).
[0029] FIGS. 3a to 3c show a third embodiment of panel structure
10b. Again, like reference numerals are used for corresponding
features, with the suffix b.
[0030] In this third embodiment, the sheets 12b are tied by tie
means 14b in the form of conical, pointed and solid projections
16b. Thus, the main difference between the third embodiment and the
first two embodiments is that the projections 16b are solid rather
than hollow. Thermosetting or thermoplastic plastics material,
another polymer material, a metal or a board etc. is again
preferably used, and may optionally incorporate reinforcing fibres.
The void 13b contains reinforcing members 15b in the unobstructed
voids between tie means 14b, and may otherwise be an open void or
foam-filled.
[0031] Fusion of the peaks results in a single uninterrupted body
of material across the sheets 12b and through the ties 14b.
[0032] A fourth embodiment of panel structure 10c is illustrated in
section in FIG. 4, again using like numerals and the suffix c.
[0033] In the panel 10c, the sheets 12c are planar across almost
their entire area. The ties 14c are in the form of thin spindles
16c of material, forming spaced columns extending substantially
perpendicular to the sheets 12c. Again, the sheets 12c and ties 14c
are preferably formed of thermosetting or thermoplastic plastics
material, a polymer material, a metal alloy, or a paper board etc.
with optional reinforcing fibres. The sheets 12c and spindles 16c
together form a single uninterrupted body of material. The void 13c
is in the form of a series of parallel, straight unobstructed voids
running across the entire width of the panel. At least some of the
voids 13c contain reinforcing members 15c.
[0034] FIGS. 5a and 5b show the outer faces of the first and fourth
embodiments. In FIG. 5a, the hollow nature of the projections 16
results in visible concavities 26 at each projection location 28.
The projection locations are arranged at the interstices of a
geometric lattice, illustrated in this example as a square lattice
30, indicated by broken lines. The square size of the lattice 30,
in comparison with the size of the concavities 26, results in the
projections 16 being sufficiently widely spaced to leave
unobstructed straight voids 13 to receive the reinforcing members
15, which extend within the plane of the panel 10, between the
projections 16.
[0035] In the fourth embodiment, illustrated in FIG. 5b, the
projections 16c are again arranged on a square lattice 30. However,
the narrow and solid nature of the spindles 16c results in the
exposed face of the panel 10c being wholly or virtually unaltered
from a planar surface, even at the projection locations 28. For
clarity, the locations of the spindles 16c are illustrated in FIG.
5b by means of small circles. It can again be seen, in common with
the first embodiment, that the spacing of the spindles 16c leaves
the voids 13c unobstructed and straight, allowing the reinforcing
members 15c to extend in various directions through the plane of
the panel 10c.
[0036] It can readily be seen from both FIGS. 5a and 5b that the
area between the projection locations 28 represents significantly
more than one half of the total area of the sheets 12. That is to
say, no more than one half of the area of the sheets 12 is deformed
to form ties 14. In FIG. 5a, there is deformation to form the
concavities 26, but these are sufficiently small to leave half, or
more than one half of the area of the sheets undeformed, between
projection locations 28. In the arrangement of FIG. 5b, as has been
described, the columns 24 are sufficiently small that the outer
face of the panel 10c is virtually undeformed by the formation of
the spindles 16c.
[0037] FIG. 6 illustrates a first method for forming a panel
structure in accordance with the invention. This first method is
particularly appropriate for use with the first embodiment, but may
also be used with the second embodiment. The method will be
described in relation to the first embodiment.
[0038] The sheets 12 are first provided, preformed to have the
projections 16. The sheets 12 are oriented so that the respective
projections 16 each project towards the other sheet, and the sheets
12 are then brought together, around the reinforcing members 15.
Thus, the peaks of the projections 16 come together in intimate
contact and the reinforcing members 15 are placed in the voids 13,
as they are formed. Alternatively, the reinforcing members may be
introduced axially into the voids 13, from the edge of the panel.
Heat is then applied to the peaks, for example by introducing
sources of heat into the concavities 26, at the positions indicated
by the arrows 34, resulting in the material in the region of the
projection peaks being heated and softened. This allows the
material of the two sheets to be fused by melting, so that the
material of the two sheets blends into a single whole. The result
is illustrated particularly in FIG. 1c. It is this process of
creating fusion between the sheets which makes it appropriate to
use a broken line to indicate the two projections 16 in FIG. 1c,
rather than a solid line. In practice, after the fusion has
occurred, it ceases to be possible to identify the precise location
of the boundary between the two projections which have fused. A
single body of material has been formed from the fusion of the two
bodies which were initially separate and distinct.
[0039] FIGS. 7a and 7b illustrate a second method which may be used
to form a panel structure.
[0040] In this method, two planar sheets of material 12 are brought
together in intimate contact, both being planar at this stage.
Heating is then applied at the projection locations, as indicated
by arrows 36. This causes localised heating of the thermoplastic
material of the sheets 12, so that the material of the two sheets
fuses together at these locations.
[0041] After fusion has begun, but before the material has fully
cooled, and thus while the material remains plastic, the sheets 12
are moved apart (FIG. 7b), causing ties 14 to begin to form by
material being stretched between the sheets 12. The sheets 12 may
be moved apart either by suction from outside the panel or by
blowing air or other fluid between the sheets 12, forcing them
apart.
[0042] As the separation continues, the ties 14 continue to form
until their final form is reached. The sheets 12 are then
maintained in this position until the material fully cools.
[0043] The process just described is particularly appropriate for
forming the fourth embodiment, using localised heating to form
columns connecting the sheets. The process can be modified when
used to form the first and second embodiments, in two principal
respects. First, secondary regions of heating, indicated by arrows
38, are applied as rings of heating around each projection
location. The secondary heating at 38 is less than at the
projection location, either being at a lower temperature, or for a
shorter duration, so that the material around the ring is not
softened sufficiently to fuse with the other sheet 12.
Consequently, whereas the material at the projection location 28
fuses, material in the surrounding ring is merely softened.
Consequently, as the sheets 12 are moved apart, the softened
material of the rings 38 can stretch to form side walls 40 of the
projections 16, 16A, but without fusing to material of the other
sheet 12. This helps form projections of the type shown in the
first and second embodiments, and may be further assisted by
forcing the sheets 12 against a shaped mould tool or other former,
as they move apart.
[0044] In this method, reinforcing members are introduced after the
ties and voids have been formed.
[0045] FIG. 8 illustrates a technique in which the methods of FIGS.
6 or 7 may be implemented as a continuous process. Sheets 12 are
fed continuously from the left hand side of FIG. 8a toward the nip
of rollers 42. The surface of one of the rollers 42 is illustrated
on an enlarged scale in FIG. 8b. The roller 42 has lines of suction
apertures 44 and lines of heating elements 46. Consequently, as the
sheets 12 pass through the nip of the rollers 42, regions
corresponding with the projection locations 28 are heated by the
heating elements 46. As the sheets 12 leave the nip, suction though
the apertures 44 tends to hold the sheets 12 against the rollers,
so that the sheets 12 are held or pulled apart. Consequently, the
locations 28 which have been heated and fused are then stretched to
form ties, in the manner described in relation to FIG. 7b.
Alternatively, the rollers 42 may have more complex surface form,
to allow reinforcing members to be fed between the sheets 12 as
they pass through the nip of the rollers. Alternatively, the
reinforcing members can be introduced from the panel edges, after
the tie means have been fully formed. The roller 42 may be formed
to accommodate sheets 12 which are preformed with projections 16
(for example by means of a previous step involving heated forming
rollers), so that heat is applied at the peaks of the projections
16 (as illustrated in FIG. 6a) but without suction thereafter being
required.
[0046] In all of the methods described above, the use of fusion
between two panels of thermoplastic material allows a single,
uninterrupted body of material to be formed, effectively without
boundaries and thus, without structural weaknesses which boundaries
create. They are further strengthened by the presence of the
reinforcing members. The result is a panel structure in which two
spaced apart panels are tied together and reinforced, so that their
flexural or shear movement is restricted. (Shear movement is
movement within their plane, relative to the other sheet). Shear
movement would be required for any bending of the panel structure
and thus, resistance to bending is provided by this resistance to
shear movement and is further enhanced by the presence of the
reinforcing members. The result is a structure in which the
strength, for example strength against impact, is provided
primarily by the sheets (which may be formed as thickly as is
appropriate), but in which bending resistance is provided primarily
by the manner of tying them together and reinforcing them. The
presence of a void within the structure allows a rigid but
lightweight structure to be created.
[0047] A rigid, lightweight panel structure of the type described
can be used advantageously in the formation of motor homes, boats,
buildings (especially temporary or portable buildings), formwork,
decking, transportation packaging and platforms, vehicle bodies,
window shutters and other applications. In many of these, it is
advantageous that the undeformed outer surface of the sheets 12
forms at least 50% of the total surface area, so that additional
panels or sheet material, particularly covering applied for
cosmetic reasons, can be applied with a good visual finish. Thus,
the panel structure may be used as the wall of a transportable
building or mobile home, and covered with a conventional wallpaper,
without the form of the panel structure becoming apparent,
particularly if the fourth embodiment is used.
[0048] Many variations and modifications may be made to the
structures described above, without departing from the scope of the
invention. In particular, a range of different materials could be
used. Also, different means of achieving continuity in the ties may
be used, such as exothermic fusion for thermosetting polymers or
resin impregnated board. Dimensions and relative dimensions could
be changed from those described.
[0049] The description has referred to two parallel sheets, tied
together, but could be implemented with a greater number of sheets,
or with sheets which are not precisely parallel. Also, curvatures
and compound shapes may be created by modified layout of the ties
and disposition of reinforcing members.
[0050] Whilst endeavouring in the foregoing specification to draw
attention to those features of the invention believed to be of
particular importance it should be understood that the Applicant
claims protection in respect of any patentable feature or
combination of features hereinbefore referred to and/or shown in
the drawings whether or not particular emphasis has been placed
thereon.
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