WO2008135636A1

WO2008135636A1 - Method and apparatus for constructing a footing mould

Info

Publication number: WO2008135636A1
Application number: PCT/FI2008/050240
Authority: WO
Inventors: Sami Pelto-Lampola
Original assignee: PELTI KIINNI Oy
Current assignee: PELTI KIINNI Oy
Priority date: 2007-05-04
Filing date: 2008-04-30
Publication date: 2008-11-13
Anticipated expiration: 2009-11-04
Also published as: FI123045B; FI20070351A0; FI20070351L

Abstract

The invention relates to a method for constructing a footing mould, which method comprises placing lower coupling members (3) on the ground and placing first side wall members (1) on the ground in engagement with the lower coupling members (3). Most of the first side wall members (1) are nested telescopically for extensions of each other. Second side wall members (2) are placed on the ground in engagement with the lower coupling members (3), at a distance from the first side wall members (1) and in a parallel relationship therewith. Most of the second side wall members (2) are nested telescopically for extensions of each other. The first side wall members (1 ) are fitted in a first support formation (13a) present in the lower coupling members (3) and the second side wall members (2) are fitted in a second support formation (13b) present in the coupling members (3), such that the first (1) and the second (2) side wall members are detachably connected by way of the lower coupling members (3) in a parallel relationship with each other and spaced from each other by a distance between the support formations (13a, 13b) of a lower coupling member (3). The invention relates also to an apparatus for constructing a footing mould, comprising at least first side wall members (1), second side wall members (2) and lower coupling members (3).

Description

METHOD AND APPARATUS FOR CONSTRUCTING A FOOTING MOULD

TECHNICAL FIELD OF THE INVENTION

The invention relates to a method and an apparatus according to the preambles of the appended independent claims for constructing a footing mould.

PRIOR ART

The footing in a building is generally a top element of the foundation, distributing the building's weight over an extensive area on the ground.

Footings are commonly made from reinforced concrete. Footing moulds are constructed e.g. from timber, especially boards. Constructing a mould from boards is a tedious process and the recycling of boards is inconvenient, being difficult to clean after use. Dismantling a mould without breaking the boards, as well as the sawing and sizing of used boards for reuse, is also an awkward process.

Finnish utility model publication U20060265 discloses a casting mould, having its wall made of sheet metal. The wall panel comprises apertures for fixing bracing members. According to figures and a second principal concept of the invention, presented in the publication, it seems that the intention is to leave the wall panels in engagement with the casting as part of a structure to be built, which is why new casting moulds are required for each casting process.

Patent publication US 2,661 ,517 discloses a concrete form, comprising telescopically arranged inner and outer members for constructing a wall for the form. Each member includes a wall intended for vertical orientation, as well as upper and lower flanges projecting orthogonally therefrom. The upper and lower flanges are provided with apertures and slots, through which are extended vertical rods for securing and anchoring the elements to each other and to the ground, respectively. The form has its two separate walls connected to each other by means of wire ropes or rod-like crosspieces secured to the vertical rods. The solution may prove inconvenient to use in the event that the ground is hard or fixing a vertical rod therein is difficult for some other reason. The ability to determine a proper distance between vertical rods, and hence between the walls, is necessary prior to fixing the rod to the ground. This calls for said crosspiece or some other means assisting in distance-setting. In the solution disclosed in US 4,121 ,804, the members of a casting form are also arranged telescopically and fixed to the ground by means of vertical rods. The solution resembles that of US 2,661 ,517, but there is no description in US 4,121 ,804 about fastening two mutually parallel form walls in engagement with each other.

Publications JP 11148137, DE 20201604 and Fl 2110 U disclose methods for constructing a footing mould. All these methods make use of side wall members, such that most of the side wall members are nested telescopically within one another as extensions of each other. In addition, these methods involve the use of lower coupling members for interconnecting the side wall members in a detachable manner by way of the lower coupling members.

One problem in the cited solutions is the fact that the preformed apertures or slots used therein may easily become blocked, and shafts, rods, and the like fastening members intended therefor may become distorted or lost and may easily pick up concrete, after which such members are difficult to remove from the apertures or to reinsert therein. Distances between the apertures are prefixed, as a result of which the length adjustment options for the wall of a mould under construction are stepwise.

OBJECT AND DESCRIPTION OF THE INVENTION

It is an object of this invention to mitigate or even totally eliminate the above- described prior art problems.

A particular object of this invention is to provide a solution, wherein the installation of side walls for a footing mould is more straightforward than in the prior known solutions.

It is an object of this invention to provide a solution, wherein the side walls can be placed firmly in position without having to fasten the same to the ground by means of a rod or the like fastening means.

An object of this invention is to provide a solution, wherein two side wall members, intended for use as the side walls of a footing mould, can be set at a correct distance from each other without having to measure or determine the distance therebetween during assembly work.

Another object of this invention is to provide a solution, wherein the length of a footing mould wall can be adjusted in a stepless manner.

In order to accomplish, among other things, the foregoing objects, a method and an apparatus according to the invention for constructing a footing mould are characterized by what is presented in the characterizing clauses of the appended independent claims.

The working examples presented in this specification apply, as appropriate, both to a method and to an apparatus of the invention, even if this is not always specifically pointed out.

A typical method for constructing a footing mould comprises the steps of

- placing lower coupling members on the ground,

- placing first side wall members on the ground in engagement with the lower coupling members, such that an internal surface of the first side wall members sets in a position which is substantially vertical and defines a first side of the footing to be cast, and nesting most of the first side wall members telescopically for extensions of each other and thereby adjusting the first wall length of a constructed footing mould as desired,

- placing second side wall members on the ground in engagement with the lower coupling members, at a distance from the first side wall members and in a parallel relationship therewith, such that an internal surface of the second side wall members sets in a position which is substantially vertical and defines a second side of the footing to be cast, and nesting most of the second side wall members telescopically for extensions of each other and thereby adjusting the second wall length of a constructed footing mould as desired.

The method comprises fitting the first side wall members in a first support formation present in the lower coupling members and fitting the second side wall members in a second support formation present in the coupling members at a distance from the first support form, such that the first and second side wall members are detachably connected by way of the lower coupling members in a parallel relationship with each other and spaced from each other by a distance between the support formations of a lower coupling member. Preferably, the method also involves the use of side wall members which are substantially C-shaped sections, comprising

-a vertical wall part, having its internal surface adapted to set against the footing to be cast,

-as extensions of the vertical wall part, horizontal top and bottom parts, which are folded to a substantially 90-degree angle with respect to the vertical wall part and which are adapted to extend perpendicularly from the footing to be cast, and -as extensions of the top and bottom parts, vertical leg parts folded towards each other by substantially 90 degrees relative thereto.

A typical apparatus of the invention for constructing a footing mould comprises at least

- first side wall members, having an internal surface capable of being set in a position which is substantially vertical and defines a first side of the footing to be cast, and which first side wall members are capable of being nested for extensions of each other, such that the first wall length of a constructed footing mould is adjustable,

- second side wall members, having an internal surface capable of being set in a position which is substantially vertical and defines a second side of the footing to be cast, and which second side wall members are capable of being nested for extensions of each other, such that the second wall length of a constructed footing mould is adjustable, and

- lower coupling members for arranging the side wall members in engagement with each other.

The lower coupling members comprise

-a first support formation for fitting the first side wall member therein, and -a second support formation at a distance from the first support formation for fitting the second side wall member therein in such a way that the side wall members are detachably connected by way of the lower coupling members in a parallel relationship with each other and spaced from each other by a distance between the support formations of a lower coupling member.

Furthermore, the side wall members are substantially C-shaped sections, comprising

-a vertical wall part, having its internal surface adapted to set against the footing to be cast, -as extensions of the vertical wall part, horizontal top and bottom parts, which are folded to a substantially 90-degree angle with respect to the vertical wall part and which are adapted to extend perpendicularly from the footing to be cast, and -as extensions of the top and bottom parts, vertical leg parts folded towards each other by substantially 90 degrees relative thereto.

The apparatus according to the invention can also be referred to as means for constructing a footing mould.

An advantage offered by the invention is the convenience of setting side walls firmly in place in engagement with a support formation present in lower coupling members without having to secure the side walls by means of some fastening element for example to the ground or to other components of the footing mould. Without the need for other bracing or fastening elements, the support formations are adapted to hold the wall members firmly upright.

The method and apparatus disclosed in the above-cited publications JP 11148137, DE 20201604 and Fl 2110 U differ from the present invention in that the side wall members are substantially C-shaped sections and are provided, among other features, with vertical leg parts, which establish extensions to the top and bottom parts and which are folded relative thereto by substantially 90 degrees towards each other. The technical impact of this feature, and especially the sub-feature according to which the leg parts are folded towards each other, is that the apparatus lends itself also to the use of upper coupling members, which fit firmly and solidly in the support formations of the side wall members. This results in a solid and robust structure, which has bracing elements in all four parts, at the bottom, on both sides, as well as at the top.

Yet another advantage gained by the invention is that the two side wall members, intended for establishing the side walls of a footing mould, can be placed readily and quickly at a correct distance from each other without having to measure or determine the distance therebetween during assembly work. It is the lower coupling member, and the distance between support formations therein, which determines the distance of side wall members from each other.

The footing to be cast refers to a footing which is intended to be cast, for example from concrete, after the footing mould has been assembled. The C-shaped sections of side wall members are intended to open in lateral directions and away from the footing to be cast.

According to one embodiment of the invention, the support formations in coupling members are substantially U-shaped sections, comprising two vertical leg parts, as well as a horizontal bottom part interconnecting the same.

According to one embodiment of the invention, the top part of side wall members has upper coupling members engaged therewith, such that the first side wall member's top part fits in a first support formation present in the upper coupling member and the second side wall member's top part fits in a second support formation present in the upper coupling member at a distance from the first support formation.

According to one embodiment of the invention, the upper and lower coupling members are identical to each other. One and the same coupling member can thus be used either as a lower coupling member, whereby the U-section shaped support formations are oriented to open upward, or as an upper coupling member, whereby the U-section shaped support formations are oriented to open downward. Accordingly, the identical upper and lower coupling members are arranged upside down relative to each other in the process of constructing a footing mould.

Nesting the side wall members telescopically for extensions of each other is understood to mean that such members are assembled partially within each other for a longitudinal extension to themselves and to a wall constructed therefrom. In one preferred embodiment, the side wall members come in two different sizes, such that every other member is arranged telescopically outside the preceding one and every other inside the preceding one.

According to one embodiment of the invention, there are pieces removed from the end of an outer or larger-size C-sectiori shaped side wall member, and especially from the corners thereof, in order to facilitate the placing of an inner side wall member with its end part against a vertical wall part of the outer side wall member and then telescopically pushing it partially inside the outer side wall member. For the same effect, the ends of a side wall member can be cut diagonally, e.g. at an angle of about 45 degrees, relative to the vertical wall part. In one embodiment, the same purpose is served by removing the horizontal top and bottom parts, as well as the vertical leg parts bent as extensions thereof towards each other, from the ends of a side wall member over a distance of e.g. 1-5 cm.

The first and second side wall members can be identical to each other. The side wall members can be e.g. 200-500 mm in height.

In the method, the side wall members' internal surfaces are generally arranged at a distance of about 200-600 mm from each other. This distance matches the width of a footing to be cast. The distance can also be about 200-1000 mm or 200-3000 mm.

According to one embodiment of the invention, the method further comprises arranging middle coupling members between the internal surfaces of side wall members. Generally, the middle coupling members are set at a height somewhere between the lower and upper coupling members. The middle coupling member is preferably similar to the upper and/or lower coupling member, but there are no support formations, e.g. shaped as U-sections, at its ends.

According to one embodiment of the invention, the side wall members and the coupling members are made from thin sheet, having a thickness of not more than 4 mm, preferably 0,4-3 mm, most preferably 1-1 ,5 mm. In this application, the term thin sheet is used in reference to sheet metal, having a thickness of not more than 4 mm.

The material for thin sheet can be for example zinc-plated steel or aluminum. Other metals or materials can be used as well. The side wall members and the coupling members can also consist of e.g. plastic, carbon fiber or fiberglass.

The upper and lower coupling member are commonly referred to as a coupling member, when not wishing to specifically point out which one is presently discussed.

Preferably, the method employs coupling members as a base for reinforcement. The coupling members can be provided with recesses for holding the reinforcement stationary. The coupling members can have a body section thereof between the support formations provided with apertures. The apertures can be used in the reinforcement tying process. Some apertures are also preferably left vacant for the casting concrete to fill the aperture, the coupling member becoming firmly embedded in concrete and the casting becoming considerably stronger. This makes it even possible to omit some of the steel reinforcements.

A body section of the coupling members, extending between the support formations, can be provided with a bend-pressed formation, making the coupling member more rigid. The coupling member's body section can have on its first side an edging upward and on its second side an edging downward. Thus, one and the same coupling member is well suitable for use either an upper or a lower coupling member.

According to one embodiment, the coupling members are adjustable in length. This can be enabled e.g. with the coupling member consisting of a two-component telescopic or other equivalent sliding assembly.

One simple upper coupling member is shaped like a U-section, such that its first leg is disposed in the footing mould outside a first side wall member and its second leg is disposed outside a second side wall member. The U-section's base, interconnecting the first and second legs, extends from the first side wall member to the second one, thus coupling the same together.

According to one embodiment of the invention, the length of a footing mould's walls is adjustable in a stepless manner. In this embodiment, as opposed to prior known solutions, the side wall members, capable of being assembled telescopically in engagement with each other, do not require preformed apertures set at fixed intervals, which should be arranged in alignment with each other and through which should be extended a shaft or rod element for fixing the wall length. Preferably, the apparatus is thus devoid of means for a stepwise adjustment of wall lengths.

The footing can be cast e.g. on top of a compacted bed of sand, gravel or aggregate or other equivalent soil material. In this application, these are referred to as the ground.

The vertical wall part of a side wall member, on the side facing the casting, can be provided with a patterned siding other than a smooth surface, e.g. a patterned or profiled metal sheet, such as a corrugated metal sheet. The footing mould according to the invention is not only easy to assemble but also very convenient to dismantle and clean, and accordingly its components, particularly side wall members, can be re-employed dozens, even hundreds of times. Preferably, it is the intention that the side walls of a footing mould according to the invention be removed from the engagement with the finished casting, but can also be left in engagement with the casting. It is a general practice to leave the coupling members embedded in the casting.

Preferably, the edges and comers of coupling members and side wall members are rounded for eliminating sharpness, in view of not inflicting cuts in hands or gloves during the course of handling.

According to one preferred embodiment of the invention, the coupling members can be fastened to the side wall members by means of drill screws. If necessary, the first side wall members among themselves, and respectively the second ones among themselves, can be fastened to each other with drill screws. Other useful options include e.g. pop rivets, welding, clamping.

The foregoing embodiments are applicable both to a method of the invention and to an apparatus of the invention.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described more closely with reference to the accompanying schematic drawing, in which

Fig. 1 shows in cross-section a part of the apparatus according to a first embodiment of the invention for constructing a footing mould,

Fig. 2 shows an example, in which the side wall members are fitted in support formations present in the lower coupling member,

Fig. 3 is a perspective view, showing a lower coupling member according to a second embodiment of the invention,

Fig. 4 shows in cross-section the lower coupling member of fig. 3, and the side wall members and ribbed reinforcement bars in engagement therewith, Fig. 5 is a perspective view, showing a coupling member according to a third embodiment of the invention,

Fig. 6 shows in cross-section a footing mould constructed from an apparatus according to one embodiment of the invention, and

Fig. 7 shows the footing mould of fig. 6 in a perspective view.

DETAILED DESCRIPTION OF THE ILLUSTRATED EXAMPLES

Referring to fig. 1 , there is shown in cross-section a part of the apparatus according to a first embodiment of the invention for constructing a footing mould. The figure visualizes first 1 and second 2 side wall members in the shape of C- sections, which are intended to be fitted, in the direction of arrows 50, in U-section shaped support formations 13a, 13b present in a lower coupling member 3. The side wall members 1 , 2 comprise a vertical wall part 4. Internal surfaces 5a, 5b of the side wall members 1 , 2 are intended to lie against a footing to be cast until the casting is set, after which the side wall members 1 , 2 can be removed. As extensions of the vertical wall part 4 there are horizontal top 6 and bottom 7 parts, which form a substantially 90-degree angle relative to the vertical wall part 4 and which extend perpendicularly from a space between the vertical walls 4, i.e. from a footing to be cast. As extensions of the top 6 and bottom 7 parts there are vertical leg parts 8, arranged at a substantially 90-degree angle relative to the top and bottom parts and towards each other. The lower coupling member 3 has both of its U-section shaped support formations 13a, 13b configured to open upward and to comprise two vertical leg parts 11 as well as a horizontal base part 12 interconnecting the same.

In the example of fig. 2, the side wall members 1 , 2 are fitted in the support formations 13a, 13b of the lower coupling member 3. Diagonal lines 9 represent concrete, which has been cast inside the footing mould between the side wall members 1 , 2. The lower coupling member 3 is left embedded in the casting, but the side wall members 1, 2 are lifted off the support formations 13a, 13b and thereby removed from engagement with the cast footing as the concrete has set sufficiently. As can be seen in the figure, the U-section shaped support formation

13a, 13b of the lower coupling member is adapted accommodate the bottom part of the side wall member 1 , 2. In this embodiment, the bottom part of the side wall members' 1 , 2 vertical wall parts 4, as well as the vertical leg parts 8, abut against the leg parts 11 of the lower coupling member's 3 support formations.

Fig. 3 shows in a perspective view a lower coupling member 3 according to a second embodiment of the invention, having its body section between the support formations 13a, 13b provided with an edging 14a upward from a plane 19 of the body section. The coupling member is also provided with apertures 18 for fixing reinforcement.

Fig. 4 shows in cross-section the lower coupling member 3 of fig. 3, having side wall members 1 , 2 and ribbed reinforcement bars 16, 17 placed in engagement therewith. It can be seen in the figures that the edging 14a present in the coupling member's 3 body section is provided with two recesses 15 for fitting the ribbed reinforcement bars 16 therein.

Fig. 5 shows in a perspective view a coupling member according to a third embodiment of the invention, having its body section between the support formations 13a, 13b provided with two edgings 14a, 14b, the first edging 14a of which is arranged to extend upward from a plane 19 of the body section and the second edging 14b of which is adapted to extend downward from the plane 19 of the body section. One and the same coupling member can be used both as a lower coupling member, whereby the U-section shaped support formations 13a, 13b are oriented to open upward, and as an upper coupling member, whereby the U-section shaped support formations 13a, 13b are oriented to open downward. The coupling member is also provided with apertures 18 for fixing reinforcement.

Fig. 6 shows in cross-section a footing mould constructed from an apparatus according to one embodiment of the invention. In engagement with the top part of side wall members 1 , 2 is fitted an upper coupling member 23, such that the top part of the first side wall member 1 is fitted in a first support formation 13a present in the upper coupling member 23 and the top part of the second side wall member 2 is fitted in a second support formation 13b present in the upper coupling member 23 at a distance from the first support formation 13a. Between the upper 23 and lower 3 coupling members, which are mutually identical but arranged upside down relative to each other, is further a middle coupling member 33. In engagement with the coupling members' 3, 23, 33 recesses 15 are fitted ribbed steel bars 16 for bracing reinforcements. Fig. 7 shows in a perspective view the footing mould of fig. 6. The ends, and especially corners 20, of the C-section shaped side wall members 1 , 2 are cut diagonally, such that subsequent side wall members (not shown in the figure), to be partially nested within the illustrated side wall members 1 , 2, are convenient to place with their end parts against a vertical wall part 4 of the illustrated side wall members 1 , 2 and thereafter to push the same telescopically inside the side wall member 1 , 2 in a longitudinal direction 40 of the side wall members.

In some of the figures, the folded component corners are depicted to be sharp, although, in reality, such corners are generally somewhat more rounded. Some of the figures illustrate a small gap between the side wall members and the coupling members' support formations for the sake of visualization, although, in reality, the contact between various members is at least partially very tight indeed, such that the side wall members are capable of being fitted in the support formation in a way to hold said members firmly upright without other fastening means.

There is no intention to limit the invention to the foregoing embodiments described by way of example, but it is intended for an extensive interpretation within the scope of protection as defined in the appended claims.

Claims

1. A method for constructing a footing mould, said method comprising the steps of

- placing lower coupling members (3) on the ground, - placing first side wall members (1) on the ground in engagement with the lower coupling members (3), such that an internal surface (5a) of the first side wall members (1) sets in a position which is substantially vertical and defines a first side of the footing to be cast, and nesting most of the first side wall members (1) telescopically for extensions of each other and thereby adjusting the first wall length of a constructed footing mould as desired,

- placing second side wall members (2) on the ground in engagement with the lower coupling members (3), at a distance from the first side wall members (1) and in a parallel relationship therewith, such that an internal surface (5b) of the second side wall members (2) sets in a position which is substantially vertical and defines a second side of the footing to be cast, and nesting most of the second side wall members (2) telescopically for extensions of each other and thereby adjusting the second wall length of a constructed footing mould as desired, and the step of -fitting the first side wall members (1) in a first support formation (13a) present in the lower coupling members (3), and fitting the second side wall members (2) in a second support formation (13b) present in the coupling members (3) at a distance from the first support formation (13a), such that the first (1) and second (2) side wall members are detachably connected by way of the lower coupling members (3) in a parallel relationship with each other and spaced from each other by a distance between the support formations (13a, 13b) of a lower coupling member

(3), characterized in that the side wall members (1 , 2) are substantially C-shaped sections, comprising

-a vertical wall part (4), having its internal surface (5a, 5b) adapted to set against the footing to be cast,

-as extensions of the vertical wall part (4), horizontal top (6) and bottom (7) parts, which are folded to a substantially 90-degree angle with respect to the vertical wall part (4) and which are adapted to extend perpendicularly from the footing to be cast, and -as extensions of the top (6) and bottom (7) parts, vertical leg parts (8) folded towards each other by substantially 90 degrees relative thereto.

2. A method according to claim 1 , characterized in that in engagement with a top part of the side wall members (1 , 2) are provided upper coupling members (23), such that the top part of the first side wall member (1) is fitted in a first support formation (13a) present in the upper coupling member (23), and the top part of the second side wall member (2) is fitted in a second support formation (13b) present in the upper coupling member (23) at a distance from the first support formation (13a).

3. A method according to claim 1 or 2, characterized in that there are further provided middle coupling members (33) between the side wall members' (1 , 2) internal surfaces (5a, 5b).

4. An apparatus for constructing a footing mould, comprising at least

- first side wall members (1), having an internal surface (5a) capable of being set in a position which is substantially vertical and defines a first side of the footing to be cast, and which first side wall members (1) are capable of being nested for extensions of each other, such that the first wall length of a constructed footing mould is adjustable,

- second side wall members (2), having an internal surface (5b) capable of being set in a position which is substantially vertical and defines a second side of the footing to be cast, and which second side wall members (2) are capable of being nested for extensions of each other, such that the second wall length of a constructed footing mould is adjustable, and

- lower coupling members (3) for arranging the side wall members (1 , 2) in engagement with each other, and said lower coupling members (3) comprising

-a first support formation (13a) for fitting the first side wall member (1) therein, and

-a second support formation (13b) at a distance from the first support formation

(13a) for fitting the second side wall member (2) therein in such a way that the side wall members (1 , 2) are detachably connected by way of the lower coupling members (3) in a parallel relationship with each other and spaced from each other by a distance between the support formations (13a, 13b) of a lower coupling member (3), characterized in that the side wall members (1 , 2) are substantially C-shaped sections, comprising

-a vertical wall part (4), having its internal surface (5a, 5b) adapted to set against the footing to be cast, -as extensions of the vertical wall part (4), horizontal top (6) and bottom (7) parts, which are folded to a substantially 90-degree angle with respect to the vertical wall part (4) and which are adapted to extend perpendicularly from the footing to be cast, and -as extensions of the top (6) and bottom (7) parts, vertical leg parts (8) folded towards each other by substantially 90 degrees relative thereto.

5. An apparatus according to claim 4, characterized in that the length of the footing mould walls is adjustable in a stepless manner.

6. An apparatus according to claim 4 or 5, characterized in that it further comprises upper coupling members (23), comprising

- a first support formation (13a) for fitting the first side wall member's (1) top part therein, and - a second support formation (13b) at a distance from the first support formation (13a) for fitting the second side wall member's (2) top part therein.

7. An apparatus according to claim 6, characterized in that the upper (23) and lower (3) coupling members are identical to each other.

8. An apparatus according to any of claims 4-7, characterized in that the side wall members (1 , 2) and the coupling members (3, 23, 33) are made from thin sheet, having a thickness of not more than 4 mm, preferably 0,4-3 mm, most preferably 1-1 ,5 mm.

9. An apparatus according to any of claims 4-8, characterized in that the support formations (13a, 13b) are preferably U-shaped sections, comprising two vertical leg parts (11), as well as a horizontal bottom part (12) interconnecting the same.