The present invention concerns a formwork column for making concrete columns with cylindrical or square cross-section.

Background

It is a challenge to produce formworks for concrete columns of varying heights and thickness in a quick and effective manner, especially in places in which the space is limited. The challenge is related to quickly, inexpensively and effectively setting up tailor made formworks for such columns.

From DE 9 200 496 Ul is known a framework column with longitudinal flanges which is closed by means of bolts or the like as well as reinforcing "list" covering the flanges. The formwork is preferably made of a flexible fibre plate. There is no solution for length adaptation or cross- sectional adaptation for this formwork and there is neither described formation of columns of other cross-sections than circularly.

In US patent No. 4 255 071 is described a formwork column which in some embodiments is longitudinally extendable. In one variant this is foreseen by means of a bellow (Fig. 3) while the formwork column in another variant is comprised by two cylindrical formwork parts with marginally different cross-section, arranged to overlap one another to a varying extent in the vertical direction. The thickness is also adjustable by that each formwork part, being comprised by a plate formed to a cylinder shape, can be arranged with a varying (horizontal) overlap; see e.g. Fig. 1-2 and Fig. 12. This overlap will however, give rise to a longitudinal (vertical) edge in the column casted, and in the area where the two formwork parts overlap each other vertically, there will be a void between the inner and outer formwork part, close to the inner end of outer formwork part. This will require subsequent sanding to obtain a nice and smooth column. It is not indicated how the two formwork parts are mutually locked in the longitudinal direction when the desired length has been found.

US patent No. 4 277 204 also describes a formwork column which is telescopically adjustable and where each part, a lower and an upper part, is made by bending a flexible plate to a circular shape with a certain longitudinal overlap of the edges that meet in a longitudinal joint along the cylinder wall. Large fittings or bands are tightened around the cylinder wall at certain intervals to ensure that the cylinder shape is maintained before and during use. This formwork also comprises a flexible bag large enough to cover the inner walls of the formwork; some kind of lining. This is a relatively complex structure to handle and devices for holding the bag in position before and while it is being filled, to prevent it from being torn loose and ending up under the casting mass, thereby loosing its function, are shown.

There is thus still a need for a reusable formwork column which is easily adaptable to different heights (lengths) and which is easy to lock at a desired, adjusted height. There is also a need for a formwork column that renders it possible to produce columns with a cross-section other than circularly, particularly with square cross-sections.

Objectives

It is thus an object with the present invention to provide a formwork column for casting which is easily reusable and which is simple to adapt to different column heights, which is inexpensive and which provides a nice end result with a minimum of follow-up. It is furthermore desired that it is reusable and environmentally friendly in general.

It is also an object that the formwork column is simple to use so that one person alone is able to set it up.

The present invention

The above mentioned objects are achieved with the formwork according to the present invention as defined by the appended independent claims.

Preferred embodiments of the invention are disclosed by the dependent claims.

Use of thin-plate elements according to the invention ensures that there are hardly visible edges from the formwork in the casted column, which means less follow-up to obtain a desired result. Absence of overlapping joints in the length direction completely eliminated longitudinal edges (vertical edge) in the columns casted with the formwork. The formwork according to the present invention is furthermore easy to manage, even for one person, it is easy to adjust its length and it is closed and locked to desired length in one and the same operation. It should be understood that with circularly profiles is meant profiles with a circularly cross-section and with square profiles is meant profiles having square cross-section, all profiles naturally being three-dimensional.

The invention in detail with reference to the drawings

Below the invention is described in further detail in the form of preferred embodiments illustrated by drawings, where:

Fig. 1 is a perspectival view of a section of an embodiment of a formwork column according to the present invention.

Fig. 2 is a cross-sectional view of an area of the formwork column shown in Fig. 1.

Figs. 3a and 3b show a wedge-shaped tightening member for use with the formwork column according to the present invention, in a front view and a side view.

Fig. 4 is a cross-sectional view of the formwork column of Fig. 1 with an expansion element.

Fig. 5 is a cross-sectional view of the formwork column of Fig. 1 with additional elements for square columns.

Fig. 6 is an alternative variant of the embodiment shown in Fig. 5.

Figure 1 shows a perspectival view of part of a formwork column 1 according to the present invention comprising two mainly cylindrical thin-plate elements 2, 3 partly overlapping one another. Thin-plate element 2 has a longitudinal opening in its periphery flanked by flanges 4 and thin-plate element 3 has a longitudinal opening in its periphery flanked by flanges 5. In the flanges 4 holes 6 are arranged at certain intervals and adjacent to each other so that locking plugs can be inserted through "pair" of holes 6 in the flanges 4 at each side of the longitudinal opening, and by tightening also closing the longitudinal opening in thin-plate element 2. In a corresponding manner the flanges 5 have holes 7 at a common interval and adjacent to each other so that locking plugs can be inserted through "pair" of holes 7 in the flanges 5 at each side of the longitudinal opening, and by tightening also closing the longitudinal opening in thin-plate element 3. In the area in which thin-plate element 2 and 3 overlap one another, one and the same locking plug can be inserted through holes 6 as well as holes 7 and thereby, in addition to close a longitudinal opening in the periphery, also lock the length of the formwork column 1. Thin-plate elements are typically made of steel and with a thickness less than 1.5 mm, preferably about 0.9 mm.

The holes 6 and 7 in respective elements 2 and 3 are shown as oblong in the longitudinal direction. It is preferred that at least one set of holes 6 or 7 is oblong to allow a stepless fine-tuning of the length of the formwork column.

Figure 2 shows a section of a part of thin-plate elements 2 and 3 in the region in which they overlap one another subsequent to attachment means in the form of a locking plug 8 has been inserted into double pair of holes 6, 7 at each side of the longitudinal opening in the cylinder periphery and tightened by a wedge-shaped tightening member (tightening wedge) 10. The locking plug 8can be of any suitable type of which so-called cassette locks, with a head, included a disc, which is too large to pass through the holes 6 and 7, and with a head in the opposite end small enough to pass through the holes 6 and 7 for thereafter to be tightened by a particular device. The tightening wedge 10 can as an example be that particular device. It is also possible, but bore labour demanding to use bolts with threads and corresponding nuts. Outside each of the outer flanges, rails 9 or plates of metal with holes corresponding to the holes 6 and 7 are placed to distribute the tension from a locking plug and tightening wedge so that no point of the thin flanges 6 and 7 shall be overloaded. The rails 9 can have different length and typically extend for a number of holes between 2 and 8 along the flanges of the formwork column. The rails 9 having holes

"corresponding" to the flanges 4 and 5 means that their mutual interval is the same. The holes in the rails 9 need not have the exact same shape and they can be circularly even if the holes in the flanges are oblong. Fig. 3a shows a tightening wedge 10 in a front view while Fig. 3b shows the same tightening wedge in a side view. It has a through hole 31a in the thin end 32 of the tightening wedge and a track 31b that extends from the hole 31 and into the thicker part 33 of the tightening wedge 10 which gradually increases in thickness towards the end away from the hole 31a. The diameter of the hole 31a is larger than the (small) head of the locking plug 8 or the cassette lock, while the width of the track 31b is less than the diameter of the head of the locking plug or the cassette lock. The tightening wedge is quick in use and is attached with a light knock to its thick end 34 by hand or by a club or hammer, and is loosened again with a light knock to its thin end 35.

Fig. 4 shows a cross-section principally equal to the one shown in Figure 2 but with two differences. One difference is that the cross-section is positioned outside (vertically above) the area in which the two parts 2, 3 of the formwork column overlap each other. The other difference is of technical character and is comprised by an expansion element 41 being positioned adjacent to the flanges 4 with a double flange 42 having holes corresponding to the holes 6 in the flanges 4, so that it is possible to pull the flanges 4 apart and to place spacing laths 43, also these provided with holes for locking plugs, between the flanges 4 and the flange 42. In this way the thickness of a column can be finely adjusted without changing the formwork column when desired. This typically requires locking plugs with greater length. The expansion element 41 is however, not telescopic, and must be cut to relevant length when it is required to use such an element. In the area where upper and lower element 2, 3 overlap each other, there will be a total of six flanges (or four single 4, 5 and a double 42) that the locking plug 8 must penetrate. It is therefore important that the plates are of limited thickness and typically do not constitute more than about 6 mm in total.

Figure 5 shows a variant of formwork column according to the present invention intended for casting of columns with a substantially square cross-section. The outer thin-plate element 2 with circularly cross-section as described above is used also for this embodiment, but inside this is arranged a thin-plate formwork element 52 of mainly square cross-section, supported externally by formwork element 2. Correspondingly, though not shown in Fig. 5, a telescopically arranged cylindrical element as shown in Fig. 1, is used above or below the cylindrical element 2 and a telescopically arranged formwork element above or below formwork element 52, with same cross- sectional shape as the latter. All formwork elements used have external flanges with holes as already described. AT the corners the substantially square formwork element 52 is supported directly by the externally arranged formwork element 2 with circularly cross-section. As shown in Fig. 5, a cross-section that slightly deviates from a square may be used, in that each corner is slightly bevelled 53.

For further support of the formwork element 52 there is in the region between the corners, external of the square formwork element 52, provided support profiles 54 which continuously or in sections run mainly through the entire height of the column. The support profile 54 can be made in any suitable material but is preferably made of steel.

With the construction according to the present invention an even pressure resistance is obtainable for column elements of circularly cross-sections as well as for square cross-section. Figure 6 shows principally the same as Figure 5 but here the support profile 54 is replaced by a mould body ("formlegeme") 64 that to a larger extent fills the volume between the outer formwork element 2 of circularly cross-section and the inner formwork element 52 having a square cross-section. Such a mould body 64 may typically be made in a material substantially lighter than steel, such as e.g. polyurethane which is sufficiently rigid when a substantial part of its surface is externally supported.

Where the telescopic formwork elements overlap each other in this embodiment, there are a total of four overlapping elements, two cylindrical and two square ones. If all elements are provided with flanges in the entire length of the elements, there will be a total of eight flanges to be penetrated by each locking plug in the overlap area. It can, however, be convenient to omit the flanges on the mainly square profiles near both ends of these profiles. Thereby is prevented that the number of flanges to be penetrated by the locking plugs exceeds six. With a tightening wedge having a thickness variation for more than one cm, this is not a problem to manage and assemble, even though it is clearly simpler for one person alone to handle solely elements with circularly cross-section than the same elements in combination with areas having square cross-section. It is generally important that the production of the elements is made with small tolerances so that undesired forces and friction between the elements is avoided in their unloaded condition, i.e. when it is relevant to perform length adjustments of the formwork.

The present invention provides a number of advantages over the priory known technology in the field. It provides a telescopic formwork column where the length can be adjusted stepless and where there are practically no visible edges in the casted column requiring subsequent treatment. In addition it provides a very quick closure of the formwork and a correspondingly quick and precise locking, in principle not depending upon tool use. It provides possibilities for casting columns having circularly cross-section as well as square cross-section, optionally with cut-off corners. With respect to columns of circularly cross-sections, there is the possibility by means of an expansion element, to make thickness adaptations (diameter adjustments) without changing formwork column. In other words, the thickness may be changes in steps - or almost stepless - as the need may be, by means of standard elements in addition to the expansion element.