This invention relates to self-supporting interconnectable formwork elements for the casting of especially wall constructions, and otherwise of the kind closer defined in the preamble of the following claim 1. The invention also involves a method for the use of said framwork elements, as set forth in the preamble of claim 9.

Casting of e.g. foundations, sustaining walls, walls, pavement or roof in concrete or similar hardenable filling materials by means of formwork elements in the form of wooden doors is laborious and time-consuming. Such formwork doors are heavy and unhandy; they have to be transported on crane vehicle and require binders, the necessary working operations comprising carrying, erecting, removal, oiling (lubrication) and storage of the doors.

Likewise, finished brick blocks and elements require much treatment in factory, costly transport, laborious erecting and comprehensive after-treatment.

Prior art comprises also Norwegian patent specification No. 46,428, DE-OS 2,213,358, DE-AS 1,684,357 and U.S. patent specification No. 2,184,714.

NO-PS 46,428 relates to a pile blanking consisting of hollow

interconnectable sections. Substantially as a result of the design of the connecting means of this known pile blanking, the pile blanking will - used as a formwork - only be usable for the casting of spaced columns; on the other hand it will not enable casting of a continuous wall, or permit reinforcing using horizontal and/or diagonally extending reinforcing rods. However, between adjacent sections or elements it is from this patent specification known per se to use mutually cooperating coupling means adapted to be brought into firmly maintaining engagement with each other.

DE-OS 2,213,358 relates to a flexible, reinforced formwork cloth which is not self-supporting, but has to be used in combination with suitable walls of timber placed endwise and, thus, exhibiting substantially the same disadvantages as door formworks.

DE-AS 1,684,357 relates also to a flexible, reinforced, not self-supporting formwork cloth divided into interconnectable sections, which can be connected mutually by means of connecting means adapted to be brought into firmly maintaining engagement with each other. This prior art formwork system does not permit casting of continuous walls and, moreover, prohibits the arrangement of crossing reinforcing rods.

US-PS 2,184,714 does not relate to formwork, but concerns casted pre-reinforced concrete elements. When such concrete elements or blocks are being used for building purposes, locking rods are used for keeping adjacent concrete blocks in place in the finished construction.

According to the present inventioon one has aimed at providing a formwork system consisting of self-supporting interconnectable disposable formwork elements capable of

being connected mutually in order to form especially a wall formwork, wherein the concrete or another hardenable filling material during the filling operation may flow freely between the interconnected formwork elements, so that the result becomes a continuous construction which - when the formwork is kept (not removed) - becomes coated with its material, e.g.. plastic.

Likewise, one has aimed at eliminating or substantially restricting disadvantages and drawbacks in prior art formwork systems.

This object is achieved through designing the formwork elements as defined in the characterizing part of claim 1. The method for the use of said formwork elements comprises the features appearing from the characterizing part of claim 9.

In an advantageous embodiment, the conditions are arranged for accomodating cross reinforcement of the resulting casted construction.

The substantially cylinder-shaped formwork element according to the invention are interconnected so that they form e.g. a wall formwork which upon filling of concrete permits the concrete to flow freely between the formwork cylinders, so that - upon hardening of the concrete - a number of fused concrete columns constituting the resulting wall are formed.

Using a formwork in accordance with the invention, one may use less concrete around the reinforcing rods than conventional formwork allow, because the water-tight formwork cylinders protect against penetrating water, etc. When casting a foundation, one does not have to use the so- called foundation plastic along the foundation; one also

saves plastering, mudding and closing of holes after the binders.

A preferred material for the cylinder-formed formwork elements according to the invention is polyvinylchloride plastic having a high impact strength and a thickness of some 1 mm, because such a material, when the formwork is kept, will give the concrete construction an attractive surface coating, but in principle there is nothing to prevent the use of carboard or a similar material having corresponding properties and/or wall thickness, respectively.

Because of the cylinder shape, the formwork elements become strong and particularly resistant to bending. The cross- sectional form may be circular, oval or polygonal (e.g. octagonal, 16-edged and so forth); when edged the corner edges are preferably rounded. A square cross-sectional shape is also possible.

The formwork elements according to the invention may be kept after casting or their external portions removed after use. In case the formwork is to remain after casting, an advantageous formwork material may be obtained from surface-treated plastics, the casted foundation, etc., thereby becoming maintenance-free.

The formwork elements according to the invention are of very light weight and so resilient that they possibly may be stacked one within the other, whereby the transport volume and weight are substantially reduced - up to 98% - as compared with door formwork.

When casting a foundation, the cylinder-formed formwork elements are put together on a finished casted base, or

Disposable formwork elements in accordance with the invention are well suited for casting operations above and under water, such as in wharfs and the like. When casting under water all reinforcement can be mounted in the formwork from the surface, so that the use of divers for this kind of work becomes superfluous.

Embodiments of the invention are closer explained in the following, reference being made to the drawings, wherein:

Figures 1 element and a corner ele with a first embodiment

Figure 3 in plan view shows five interconnected formwork el th

Fi el

Fi fo Fi

Figure 6 shows a side wall of a formwork element (Figures 4 and 5) which in interconnected position engages a neigbour element; ^-- _

interconnection;

Figure 9 in top plan view shows three interconnected formwork elements according to the third embodiment, at a formwork corner;

Figure 10 in perspective view shows a formwork element of the embodiment shown in Figures 1 - 3; and

Figure 11 in top plan view indicates different modes of assemblage for formwork elements of the type, shown in Figures 1 - 3 and 10.

In the three embodiments according to Figures 1 - 3, 10 and 11; Figures 4 - 6 and Figures 7 - 9, respectively, the same or similar reference numerals are used for the same or corresponding parts.

In the first embodiment, Figures 1 - 3, 10 and 11, the reference numeral 1 indicates an enlongated cylindrical standard formwork element, while 1' denotes a corner element having the same general design. The elements 1, 1' have open ends.

The cylinder-shaped formwork elements 1, 1' have substantially octagonal cross-section with rounded corner edges.

At two opposite sides, the standard element 1 is provided with connecting means for the interconnection with adjacent elements. The connecting means have the form of T-shaped ledges 2 and corresponding T-shaped grooves 3. The corner element, Figures 2 and 11, is provided with corresponding connecting means 2' and 3', respectively, on e.g. four, in pairs opposite sides. The interconnection which is ensured

through the engagement of the connoting ledges 2, 2' within the grooves 3, 3', is illustrated in Figure 3 and 11. It appears therefrom that the corner elements 1' in another embodiment may have connecting means only at two or three sides, angularly displaced 90 degrees in relation to each other.

In this embodiment. Figures 1 - 3, 10 and 11, each formwork element has at one side portion thereof an aperture 4, 4', which possibly may extend over the entire height of the formwork element, and in another side portion which (as seen in cross-section) is angularly displaced (in standard elements 180 degrees, in corner elements e.g. 90 degrees) in relation to the former side portion as well as the aperture 4, 4', equidistantly spaced apertures 6 are provided, Figure 10, for the flowing-through of concrete between interconnected formwork elements 1, 1' .

The formwork elements 1, 1* are made of PVC-plastic, cardboard or similar material having corresponding properties. The wall thickness may be of the order 1 mm. The cylindrical shape gives the formwork elements a high strength, especially to bending, at the same time as they are resilient.

The preferably through-going apertures 4, 4' contribute strongly to this resilience and permit i.a. stacking of two or more formwork elements, one within the other, during transport.

Figure 11 indicates some modes of assemblage for formwork elements 1, 1 ^! according to the embodiment shown in Figures 1 - 3 and 10. Uppermost in this figure, three interconnected standard elements 1 are shown. Because of their elasticity, they have been capable of being placed along an arch-shaped

or angular path. The lower portion of Figure 11 shows the interconnection of "corner elements", both in the longitudinal and lateral direction, for the establishment of a broader formwork, without having to increase the cross- sectional dimensions of the individual formwork elements.

In the embodiment shown in Figure 4 - 6, the formwork elements 1" are circular-cylindrical and being at one side thereof provided with a through-going aperture 4" corresponding to the apertures 4, 4', so that each separate formwork element 1" attains an approximately C-shaped cross- section.

The formwork elements 1" are externally provided with connecting means in the form of ledges 5 having claw-shaped cross-sectional form. The claw-shaped connecting ledges 5 are located and designed such that adjacent ledges of neighbour elements 1" may be brought into engagement when one element 1" is partially inserted into the longitudinal aperture 4" of the adjacent element 1", so that an unshakable wall formwork is achieved.

The wall portion of each formwork element 1" located opposite the aperture 4" is provided with equidistantly spaced apertures 6, Figure 6, and therebetween placed holes for horizontal (and/or diagonal) reinforcing rods 7, Figure 5. The apertures 4", 6 permit free flow of concrete between the elements 1" .

In the embodiment according to Figures 7 - 9, the formwork elements l' ¹ ' have varying cross-sectional form over the length thereof; this being due to the design of the connecting means.

In Figure 7, two formwork elements 1' ' ' are shown prior to

being interconnected. Each of these formwork elements l''* is at two opposite sides thereof formed with spaced apertures 8, which for each element 1' ' ' are axially displaced in relation to the apertures 8 at the opposite side, so that portions 9 between the apertures 8 of one element may be brought into engagement with the apertures 8 of a neighbour element. The interconnection is secured by means of vertical locking rods 10.

In Figure 9 a formwork corner is shown, wherein the corner element 1"" is somewhat differently designed than the standard elements l ¹ ' ¹ ; i.e. the corner element 1"" having interconnecting portions 8, 9 at two sides angularly displaced 90 degrees in relation to each other.

Through designing the connecting means e.g. as shown in Figure 4 and 5, the mutual engagement between the connecting means 5 is strengthened whenever the formwork elements are loaded from the concrete.

Practical experiments with disposable formwork elements according to the invention have shown that they in spite of minor wall thickness and low weight are capable of accomodating the forces present during casting. Formwork elements in accordance with the invention may substitute the common door formwork in the great majority of applications of use. Thus, foundations and sustaining walls are only to be considered as examples of the invention's applicableness in practice, the formwork elements also being usable for e.g. the casting of pavement and roof. When casting a pavement and a roof, the upper wall portion of the formwork elements must be provided with cavities for the filling of concrete.

One has also conceived the use of pre-connected sets of

formwork elements, wherein several sets form a formwork when interconnected.

As previously mentioned, the present invention also provides a method for the casting of walls and other constructions through the use of formwork using formwork elements of the kind described in the foregoing specification.