US20060213140A1

US20060213140A1 - Extruded permanent form-work for concrete

Info

Publication number: US20060213140A1
Application number: US11/351,301
Authority: US
Inventors: Cecil Morin; Clifford Rondin; Brian Reimer; Stanley Lachmansingh
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-02-09
Filing date: 2006-02-10
Publication date: 2006-09-28
Also published as: US7444788B2; US7818936B2; US20090139171A1; US20050016083A1

Abstract

A set of extruded panels is provided which can be assembled on site to create a permanent form-work for concrete. The set includes inside and outside extruded side wall panels which are arranged to be connected edge to edge to form inside and outside walls. Longitudinally spaced connecting wall panels span between the inside and outside walls at spaced positions across the width of the walls to hold the walls apart and define a hollow interior therebetween including a plurality of interconnected cells with a plurality of holes for communication of concrete and reinforcing bars between each cell and the next. Each connecting wall panel has T-shaped connectors at each edge for attachment to corresponding C-shaped receptacles on the side wall panels. Rigid foam insulation is inserted at the outside wall. The inside wall panels are arranged to support without bowing cast concrete poured into the interior within each cell and three different arrangements are shown to support the inside wall each including a wall portion at right angles to the inside wall and between the connecting walls. In one, an integral double wall is provided. In a second, a short support wall extends to a supplementary wall parallel to the inside wall and in the third, a support wall identical to the connector walls spans between the inside and outside walls.

Description

This application is a Divisional application from application Ser. No. 10/097,644 filed Mar. 15^th2002 and now issued as U.S. Pat. No. INSERT.
This invention relates to a set of extruded form-work panels which are interconnected in use to define a form-work for casting of concrete and which are intended to remain in place after the concrete is cured to define inner and outer surfaces of the finished concrete structure.

BACKGROUND OF THE INVENTION

There have been many attempts over the years to generate an alternative form of building construction which utilizes permanent forms into which concrete is poured and cured to provide the structural strength for the exterior form work. The use of plastic extruded panels for the formwork has previously been proposed and these can be readily assembled on sight to provide a structure into which reinforcing bars can be inserted and into which the concrete can be inserted and into which the concrete can be poured. The plastic panels then remain in place forming inside and outside surfaces for the concrete structure thus avoiding the necessity for additional cladding and providing in one step a finished attractive appearance.
One example and arrangement of this type is shown in Canadian Patent No: 957,816 (Rodighiero et al) issued Nov. 19, 1974 which discloses inside wall panels and outside wall panels which are connected edge to edge so as to form inside and outside walls respectively. The panels are connected edge to edge and supported in their spaced position by transverse connecting walls. Embodiments are disclosed in which an insulation material can be applied between the concrete and one of the side walls. The side wall which supports the concrete is prevented from bowing primarily by transversely extending stiffening ribs. However additional wall portions can be provided connected to the side wall and extending generally at right angles thereto so as to hold the side wall against bowing outwardly under the weight of the concrete.
A further arrangement which has achieved some commercial success is shown in U.S. Pat. No. 5,216,863 (Nessa et al) issued Jun. 8, 1993. This discloses a generally cylindrical structure with one open face where the cylindrical elements slide each into the next using male and female couplings to form a similar permanent form work structure to develop the above patent but in which the structure takes the form of a series of interconnected columns.
Canadian Patents No: 2,215,939, 2,218,600 and 2,226,497 of Piccone disclose various constructions of form work of a similar nature to that shown in the above patent of Rodighiero but many shaped to form the column structure similar to that of Nessa.
It has been determined recently that the most commercial structure for arrangements of this type is one in which the inside and outside walls are generally flat and of course the materials are kept substantially to a minimum so as to reduce the construction cost of the initial formwork. It is of course important also to minimize the labour involved in assembly of the structures on site.
One problem which arises in meeting the above criteria is to ensure that the structure is stable and prevents the bowing of the side wall which is contact with the concrete.

SUMMARY OF THE INVENTION

It is one object of the present invention, therefore, to provide an improved set of extruded form-work panels for use in defining a form-work for casting of concrete structures.
According to one aspect of the invention there is provided a set of extruded panels for use in constructing a form-work for concrete comprising:
a plurality of first side wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to be connected edge to edge to form a first side wall with a height of the first side wall defined by the length of the panels and a width of each panel defining a part of a width of the first side wall;
a plurality of second side wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to be connected edge to edge to form a second side wall with a height of the second side wall defined by the length of the panels and a width of each panel defining a part of a width of the first second wall;
a plurality of connecting wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to span between the first and second side walls at spaced positions across the width of the side walls to hold the first and second walls apart and define a hollow interior therebetween including a plurality of cells formed between each connecting wall panel and the next;
each connecting wall panel having a plurality of holes for communication of concrete and reinforcing bars between each cell and the next;
each connecting wall panel having a first pair of connector element at one edge for attachment to respective ones of the first wall panels and a second pair of connector element at an opposed edge for attachment to respective ones of the second wall panels;
the first side wall panels being arranged to support without bowing cast concrete poured into the interior within each cell;
the first side wall panels being supported against bowing by a wall portion between the connecting wall panels and extending generally parallel thereto and thus at right angles to the first side wall panel.
Preferably the connecting walls each include a pair of projecting tongues extending therefrom generally at right angles thereto at a position adjacent to and spaced from the second wall panels for locating between the tongues and the second wall panels pieces of rigid foam insulation.
Preferably the second wall panels include a plurality of longitudinally extending ribs, each rib including a pair of sides and a panel portion.
Preferably the connector elements on the connector walls comprise T-shaped members for engagement into co-operating C-shaped members on an inner surface of the first and second panels.
According to a second aspect of the invention there is provided a set of extruded panels for use in constructing a form-work for concrete comprising:
a plurality of first side wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to be connected edge to edge to form a first side wall with a height of the first side wall defined by the length of the panels and a width of each panel defining a part of a width of the first side wall;
a plurality of second side wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to be connected edge to edge to form a second side wall with a height of the second side wall defined by the length of the panels and a width of each panel defining a part of a width of the first second wall;
a plurality of connecting wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to span between the first and second side walls at spaced positions across the width of the side walls to hold the first and second walls apart and define a hollow interior therebetween including a plurality of cells formed between each connecting wall panel and the next;
each connecting wall panel having a plurality of holes for communication of concrete and reinforcing bars between each cell and the next;
each connecting wall panel having a first pair of connector element at one edge for attachment to respective ones of the first wall panels and a second pair of connector element at an opposed edge for attachment to respective ones of the second wall panels;
the first side wall panels being arranged to support without bowing cast concrete poured into the interior within each cell;
the first side wall panels including an outer wall facing outwardly of the interior and an inner wall generally parallel to the outer wall and spaced inwardly therefrom, the outer wall being supported against bowing by a wall portion between the connecting wall panels and extending generally parallel thereto and thus at right angles to the first side wall panel, the wall portion being formed integrally with the inner and outer walls.
Preferably there is provided a plurality of parallel wall portions interconnecting the inner and outer walls.
Preferably the inner wall is closed to prevent entry of concrete between the inner and outer walls.
According to a third aspect of the invention there is provided a set of extruded panels for use in constructing a form-work for concrete comprising:
a plurality of first side wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to be connected edge to edge to form a first side wall with a height of the first side wall defined by the length of the panels and a width of each panel defining a part of a width of the first side wall;
a plurality of second side wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to be connected edge to edge to form a second side wall with a height of the second side wall defined by the length of the panels and a width of each panel defining a part of a width of the first second wall;
a plurality of connecting wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to span between the first and second side walls at spaced positions across the width of the side walls to hold the first and second walls apart and define a hollow interior therebetween including a plurality of cells formed between each connecting wall panel and the next;
each connecting wall panel having a plurality of holes for communication of concrete and reinforcing bars between each cell and the next;
each connecting wall panel having a first pair of connector element at one edge for attachment to respective ones of the first wall panels and a second pair of connector element at an opposed edge for attachment to respective ones of the second wall panels;
the first side wall panels being arranged to support without bowing cast concrete poured into the interior within each cell;
each first side wall panel being associated with a respective one of a plurality of inner walls generally parallel to the side wall panel and spaced inwardly therefrom, the first side wall panel being supported against bowing by a wall portion located between the connecting wall panels and extending generally parallel thereto and thus at right angles to the first side wall panel, the wall portion being connected between the first side panel and the inner wall so as to communicate forces therebetween.
Preferably the inner wall and the wall portion have holes for penetration of concrete.
Preferably the inner wall and the first wall panel each have a female connector thereon for receiving a male connector at the end of the wall portion.
Preferably the female connector comprises a pair of C-shaped receptacles facing each other and the male connectors comprise a pair of T-shaped members back to back.
Preferably the connector elements on the connector walls comprise T-shaped members for engagement into co-operating C-shaped members on an inner surface of the first and second panels.
Preferably the inner wall and the first wall panel are identical.
According to a fourth aspect of the invention there is provided a set of extruded panels for use in constructing a form-work for concrete comprising:
a plurality of first side wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to be connected edge to edge to form a first side wall with a height of the first side wall defined by the length of the panels and a width of each panel defining a part of a width of the first side wall;
a plurality of second side wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to be connected edge to edge to form a second side wall with a height of the second side wall defined by the length of the panels and a width of each panel defining a part of a width of the first second wall;
a plurality of connecting wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to span between the first and second side walls at spaced positions across the width of the side walls to hold the first and second walls apart and define a hollow interior therebetween including a plurality of cells formed between each connecting wall panel and the next;
each connecting wall panel having a plurality of holes for communication of concrete and reinforcing bars between each cell and the next;
each connecting wall panel having a first pair of connector element at one edge for attachment to respective ones of the first wall panels and a second pair of connector element at an opposed edge for attachment to respective ones of the second wall panels;
the first side wall panels being arranged to support without bowing cast concrete poured into the interior within each cell;
each of the first side wall panels being supported against bowing by a wall portion located between the connecting wall panels and extending generally parallel thereto and thus at right angles to the first side wall panel, the wall portion being connected at one end to the first side wall panel and at its other end to the second side wall panel.
Preferably the wall portion and the connecting walls are identical.
Preferably the connector elements on the connector walls comprise T-shaped members for engagement into co-operating C-shaped members on an inner surface of the first and second panels and wherein the wall portion includes T-shaped members identical to those of the connector walls and wherein the first and second wall panels include two C-shaped receptacles facing each other at a mid point on an inside surface thereof for receiving the T-shaped members of the wall portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Three alternative embodiments of the invention will now be described in conjunction with the accompanying drawings in which:
FIG. 1 is an isometric view showing in general a form-work for casting of concrete.
FIG. 2 is a horizontal cross sectional view of a first embodiment of the panels according to the present invention to provide a form-work of the general construction shown in FIG. 1.
FIG. 3 is a horizontal cross sectional view of a second embodiment of the panels according to the present invention to provide a form-work of the general construction shown in FIG. 1.
FIG. 4 is a horizontal cross sectional view of a third embodiment of the panels according to the present invention to provide a form-work of the general construction shown in FIG. 1.

DETAILED DESCRIPTION

In FIG. 1 is shown a formwork of the general type shown in the above Canadian patent of Rodighiero. Thus the construction includes a plurality of inside wall panels 10 which stand vertically upwardly and are connected at side edges 11 and 12 to form an inside wall structure 13. A similar outside wall structure 14 includes outside wall panels 15 and 16 connected together at edges 17 and 18.
The inside wall structure 13 and the outside wall structure 14 are interconnected by connecting wall panels 19 which bridge the space between the inside and outside wall and also act to connect together the panels at their edges 11, 12 and 17, 18. The connecting wall panels 19 include holes 20 which allow concrete poured into the individual cells defined between the connecting members to pass between the cells and thus form an integral concrete structure throughout the formwork defined between the side walls. Prior to pouring the concrete, suitable reinforcing bars 21 can be inserted through the aligned holes in the connecting members 20.
All of the panels are formed by extrusion so that they have a constant cross section and details of the panels are shown and described in FIGS. 2, 3 and 4 as set out hereinafter.
The connecting walls 19 have a pair of right angles tongues 22 and 23 projecting outwardly from the sides thereof parallel to the side wall 14 and closer to the side wall 14. The tongues thus define a channel for receiving a portion 24 of rigid foamed insulation material which is cut to the required shape and inserted into the cell adjacent the side wall 14 and outside the tongues 22 and 23. The concrete is thus restricted to the area between the foam insulation material 24 and the inside wall 13.
The connector walls 19 include at each edge a pair of male connectors 25 for insertion into female receptacles 26 at the edges 11 and 12 of the panels 10 and at the edges 17 and 18 of the panels 15.
In between the edges, it is necessary to provide support for the panels 10 to prevent their bowing inwardly into the building under the weight of the concrete prior to its curing. Thus the panels are supported by support walls 30 shown schematically in FIG. 1 and shown in further detail and in different alternatives in FIGS. 2, 3 and 4.
Turning firstly to FIG. 2, it will be noted that the male connectors 5 on the interconnecting walls 19 are generally T-shaped with a leg of the T connected to the connecting wall 19 at its edge and the top of the T generally parallel to the connecting wall.
It will be further noted that the female receptacles 26 are generally C-shaped so as to wrap around the top of the T-shaped connector 25. Thus the C-shape includes a base 26A parallel to the top of the T bar and two legs which wrap around the T bar and extend toward the leg of the T bar. Thus the ends of the legs on the inside surface of the T bar lies adjacent or in contact with the respective side surface of the connecting wall 19. The other leg of the C-shape as indicated at 26B is provided on the exposed surface of the side wall panel 10 and forms a portion or edge 26C which abuts with the corresponding edge of the next adjacent panel so that the connecting wall panel 19 is not itself visible from the outside of the structure. Thus the interconnections between the panels are in the form of a single vertical line providing an attractive appearance.
The interconnection with the outer wall 14 is identical and is again formed by the T-shaped male members on the connecting wall 19 and a female C shaped receptacles on the outer wall panels 15, 16.
The right angles tongs 22 and 23 are visible in FIG. 2 spaced from the outer wall 14 by a distance D which is substantially equal to the thickness of the foam insert of insulation material.
An additional T-shaped male member 31 is provided on the connecting wall at a position adjacent to the inner wall 10. This is not used in the construction of FIG. 2 but is provided as an alternative mounting arrangement to allow flexibility in the construction to accommodate different structural arrangements and particularly the arrangement shown in FIG. 3 which may be adopted in some circumstances.
The outer wall panels 15 are shaped so as to define a generally flat plane 32 forming a flat wall structure. However in order to provide an attractive appearance and in order to accommodate expansion and contraction which will occur due to significant temperature changes at the outside surface, the outer wall panels 15 include ribs 33 and 34 each of which is defined by an inclined side wall 35, an outer panel portion 36 parallel to the plane 32 and a second inclined side wall 35. This arrangement allows the expansion which will occur to be taken up in slight changes in angle in the inclined walls 35. A projecting flange 37 is provided on the inside of the rib. From the aesthetics point of view, therefore, the ribs break up the appearance of the flat surface so that any imperfections in what would otherwise be a totally flat surface are not immediately apparent to the eye. Slight changes in angle or surface shape are therefore not visible due to the presence of the ribs and the changes of shading which occur due to light patterns formed by those ribs. However the centre section between the ribs lies in a common plane 32 and therefore the side wall is basically flat.
In the embodiment of FIG. 2, the inside wall 10 supports the concrete within the cell and is prevented from bowing by the construction generally indicated at 30. In the embodiment of FIG. 2 the arrangement which prevents the bowing is defined by an additional inside wall 40 and three transverse support walls 41, 42 and 43. The inside wall 40 is equal in width to the panel and forms a contiguous extension of the inside leg of the C-shaped receptacle 26.
The outer wall 10A of the panel is integrally extruded with the C-shaped receptacles 26, with the inner wall 40 and with the transverse connecting walls 41, 42 and 43 to form an integral closed structure defining four hollow interior cells between the transverse walls. The inner wall 40 is fully closed so that concrete is prevented from entering into the hollow interior cells. The width of the wall 42 is slightly greater than that of the walls 41 and 43 and also slightly greater than the cross bar 26A of the C-shape receptacle 26 so that the wall 40 is slightly V-shaped reaching an apex at the wall 42.
The double wall integral structure thus formed as a simple single extrusion of the embodiment of FIG. 2 thus supports the concrete and prevents bowing of the inside wall panel 10. The hollow cells can also provide a space for receiving utilities such as wiring and the like.
Turning now to FIG. 3, there is shown an alternative construction which uses the same connector walls 19 and the same outer wall panels 15 as that of FIG. 2.
In this embodiment the inner wall panel 10 includes the same C-shaped receptacles 26 but is formed only from a single sheet of plastics material as indicated at 50. In this embodiment the single wall 50 includes two female receptacles 51 and 52 on the inside surface of the panel 50 with the C-shaped receptacles facing each other and spaced so as to receive the T-shaped male members 53 of a supporting wall portion 54. Thus the C-shaped receptacles 51 and 52 include as one side of the C-shape the panel 50 itself and extend from the panel at right angles to the panel a leg which wraps around the T bar top of the T-shape members 53.
The wall portion 54 thus is supported by the female receptacles 51 and 52 and projects generally at right angles to the wall 50 to an opposed end 55 spaced from the panel 50.
An additional wall panel 56 which is identical in cross section to the inner wall panel 10 is attached to the end 55 and to the T-shaped members 31 on the connector walls 19. The additional wall 56 is thus parallel to the wall 50 and spaced therefrom across the hollow interior of the cell. Both the support wall 54 and the additional wall 56 have holes which allow the concrete to pass through those holes from the interior of the cell to enter and fill the rectangular areas between the walls 50 and 56. Thus the whole of the structure is filled with concrete up to the wall 50 and the additional wall 56 and the support wall 54 are present merely to provide support for the wall 50 during installation.
Turning now to FIG. 4, there is shown a further alternative arrangement which uses the same inside wall panel 50 and connecting walls 19 as that shown in FIG. 3. Thus the inside wall panel 50 is connected using the receptacles 26 to the male connectors at the edge of the connecting wall 19.
In this embodiment, the support 30 is provided by an additional support wall 60 which is identical in cross section to the connecting walls 19 and extends thus across the full width of the cell from the side wall 50 to the outside wall panel 15A. Thus the outside panel 15A is modified relative to that of the previous embodiment by the addition of C-shaped receptacles 51A and 52A identical in construction to the receptacles 51 and 52 on the panel 50. Thus the T-shaped male connectors on the edge of the support wall are engaged into the receptacle defined by the receptacle portions 51A and 52A and at the same time the male connectors on the other edge of the wall 60 are engaged into the receptacles 51 and 52. Thus the support wall bridges the whole width of the cell and communicates bowing forces on the panel across the width of the structure to the outer wall panel 15A.
In this embodiment, the construction is simplified by the fact that the support wall 60 is identical in cross section to the connecting walls 19 thus reducing manufacturing cost and inventory problems.
The arrangements described above therefore provide an effective support for the inside wall panel to prevent its bowing while allowing use of simple forms and reducing manufacturing costs by use of the same cross sectional elements at different locations in the structure.
Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Claims

1. A set of extruded panels for use in constructing a form-work for concrete comprising:

a plurality of first side wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to be connected edge to edge to form a first side wall with a height of the first side wall defined by the length of the panels and a width of each panel defining a part of a width of the first side wall;

a plurality of second side wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to be connected edge to edge to form a second side wall with a height of the second side wall defined by the length of the panels and a width of each panel defining a part of a width of the first second wall;

a plurality of connecting wall panels which are extruded longitudinally to define a constant cross section along a length of the panel including two opposed side edges and an intermediate panel wall portion and which are arranged to span between the first and second side walls at spaced positions across the width of the side walls to hold the first and second walls apart and define a hollow interior therebetween including a plurality of cells formed between each connecting wall panel and the next;

each connecting wall panel having a plurality of holes for communication of concrete and reinforcing bars between each cell and the next;

each connecting wall panel having a first pair of connector element at one edge for attachment to respective ones of the first wall panels and a second pair of connector element at an opposed edge for attachment to respective ones of the second wall panels;

the first side wall panels being arranged to support without bowing cast concrete poured into the interior within each cell;

the first side wall panels including an outer wall facing outwardly of the interior and an inner wall generally parallel to the outer wall and spaced inwardly therefrom, the outer wall being supported against bowing by a wall portion between the connecting wall panels and extending generally parallel thereto and thus at right angles to the first side wall panel, the wall portion being formed integrally with the inner and outer walls.

2. The set of extruded panels according to claim 1 wherein there is provided a plurality of parallel wall portions interconnecting the inner and outer walls.

3. The set of extruded panels according to claim 1 wherein the inner wall is closed to prevent entry of concrete between the inner and outer walls.

4. The set of extruded panels according to claim 1 wherein the connecting walls each include a pair of projecting tongues extending therefrom generally at right angles thereto at a position adjacent to and spaced from the second wall panels for locating between the tongues and the second wall panels pieces of rigid foam insulation.

5. The set of extruded panels according to claim 1 wherein the second wall panels include a plurality of longitudinally extending ribs, each rib including a pair of sides and a panel portion.

6. The set of extruded panels according to claim 1 wherein the connector elements on the connector walls at the first wall panels comprise T-shaped members each for engagement into a co-operating C-shaped member on a respective one of the first wall panels, the C-shaped member being formed by the edges of the inner and outer walls.

7. A set of extruded panels for use in constructing a form-work for concrete comprising:

each first side wall panel being associated with a respective one of a plurality of inner walls generally parallel to the side wall panel and spaced inwardly therefrom, the first side wall panel being supported against bowing by a wall portion located between the connecting wall panels and extending generally parallel thereto and thus at right angles to the first side wall panel, the wall portion being connected between the first side panel and the inner wall so as to communicate forces therebetween.

8. The set of extruded panels according to claim 7 wherein the inner wall and the wall portion have holes for penetration of concrete.

9. The set of extruded panels according to claim 7 wherein the inner wall and the first wall panel each have a female connector thereon for receiving a male connector at the end of the wall portion.

10. The set of extruded panels according to claim 9 wherein the female connector comprises a pair of C-shaped receptacles facing each other and the male connectors comprise a pair of T-shaped members back to back.

11. The set of extruded panels according to claim 7 wherein the connecting walls each include a pair of projecting tongues extending therefrom generally at right angles thereto at a position adjacent to and spaced from the second wall panels for locating between the tongues and the second wall panels pieces of rigid foam insulation.

12. The set of extruded panels according to claim 7 wherein the second wall panels include a plurality of longitudinally extending ribs, each rib including a pair of sides and a panel portion.

13. The set of extruded panels according to claim 7 wherein the connector elements on the connector walls comprise T-shaped members for engagement into co-operating C-shaped members on an inner surface of the first and second panels.

14. The set of extruded panels according to claim 7 wherein the inner wall and the first wall panel are identical.