Formwork Column
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 crosssectional
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 t o 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 t o 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 t o 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 t o 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 t o the present invention is furthermore easy to manage, even for one
person, it is easy t o adjust its length and it is closed and locked t o 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 t o 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 t o 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 t o 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 t o
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" t o 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 t o 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 t o 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 t o 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 t o 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 crosssectional
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 t o 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.
Claims
1. Formwork column (1) comprising at least two flexible, thin-plate elements (2, 3) of mainly
cylindrical shape, arranged mutually telescopically extendable with an outer element (2) and an
inner element (3), characterized in that each element is provided with a longitudinal extending
flange (4, 5) provided with holes (6, 7) arranged in a row in the longitudinal direction for closing of
the formwork column (1) by means of locking plugs (8), while insertion of locking plug (8) in
adjacent holes (6, 7) of both thin-plate elements (2, 3) also arrests the formwork length.
2. Formwork column as claimed in claim 1, characterized in that the flanges (4) are arranged to be
covered by reinforcing rails (9) with holes corresponding t o the ones of the flanges (4, 5) before
the formwork is closed by locking plugs (8).
3. Formwork column as claimed in claim 1, characterized in that the locking plugs (8) are arranged
to be tightened by wedge-shaped tightening members (10).
4. Formwork column as claimed in claim 1, characterized in that at least one of the elements (2
resp. 3) is provided with holes (6 or 7 resp.) which are oblong in the longitudinal direction for
thereby allowing a stepless fine-tuning of the formwork's (1) length.
5. Formwork column as claimed in claim 1, characterized in that the formwork, for manufacture
of square columns, comprises inner square thin-plate profiles (52) adapted to be supported by the
thin-plate elements (2) at their corners and having flanges () which mainly correspond to the
flanges (4, 5) of the thin-plate profiles (2, 3) for closing of the square profiles by means of same
locking plugs (8) which close the thin-plate profiles (2, 3).
6. Formwork column as claimed in claim 1, characterized in that the square profiles (52) in
addition is externally supported by longitudinal support profiles (54) arranged inside the cylindrical
profile, in the area between the corners of the square profile (52).
7. Formwork column as claimed in claim 6, characterized in that the square profiles (52) in
addition is supported by longitudinal , lightweight ...bodies (64) arranged inside the cylindrical
profile, in the area between the corners of the square profile (52).
8. Formwork column as claimed in claim 1, characterized in that the locking plugs (8) have the
form of so-called cassette lock.
9. Formwork column as claimed in claim 1, characterized in that the thin-plates are made of steel
with a thickness not exceeding l . mm and preferably about 0.9 mm.
10. Formwork column as claimed in claim 1, characterized in that it in an area along the flanges
(4, 5) at the inside of the thin-plate profiles (2, 3) is provided with an expansion profile (41)
allowing a fine-tuning of the diameter of the profile cross-section.