Note: Descriptions are shown in the official language in which they were submitted.
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Column Formwork
Field of the Invention
The present invention is directed to a column formwork for use in concrete
construction.
Background of the Invention
Column formworks are used in concrete construction to build columns, supports,
or
similar concrete elements. Recently, in addition to conventional steel and
wood
formworks, wound formworks of sheet metal, cardboard, or synthetic material
have
increasingly been employed. In the case of wound cardboard formworks, the
outer
formwork tube, which primarily serves to hold the formwork together, is
constructed of
paperboard or cardboard. After the column has been concreted and the concrete
has set,
the outer formwork element is removed by tearing it open by means of an
integrated tear
strip.
A column formwork comprising a multilayered wound flat material is known from
DE 295 18 077. The flat material is a polyethylene-coated paper sheet. Due to
the
multilayered winding, paper layers and polyethylene layers alternate in the
wall of the
formwork tube in this column formwork.
DE 296 09 259 discloses a column formwork comprising a tube segment divided
along its
longitudinal axis. Connecting means are provided in the area of the dividing
line to hold
the formwork together. To construct this column formwork, a tube segment is
slit open
once along its longitudinal axis. To ensure simple removal, it is recommended
that the
column formwork be constructed of a synthetic material that can be bent apart
when
removing the formwork. To the inside of the column formwork is applied an
auxiliary
formwork material, which avoids form marks resulting from the dividing line.
These known column formworks have various disadvantages in common. For one
thing,
the formworks exhibit an extremely large volume, thus causing problems,
particularly
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during transportation, that are reflected in high costs. The column formwork
interior,
provided for filling up with concrete, is nothing other than dead volume
during
transportation, and thus only a very small quantity can be transported in each
load. The
column formwork according to DE 296 09 259 also exhibits this problem, as it
involves
shape-retentive synthetic material tubing that can be bent apart briefly with
sufficient
expenditure of force only during removal.
Moreover, the above-described column formworks are single-use products, as the
outer
formwork element is removed from the cured concrete by tearing it open. Reuse
of the
column formwork is thus excluded. In the case of the column formwork according
to
DE 296 09 259, this problem is solved only partially. Although the outer part
of the
formwork can be reused, the necessary interior lining having e.g. a tube of
thin
paperboard is a single-use product.
Description of the Invention
This is where the present invention begins. It is intended to provide a column
formwork
that can be reused and easily transported. According to the present invention,
this object
is solved by the column formwork according to independent claim 1. Other
advantageous
aspects, details, and embodiments of the present invention are evident from
the
dependent claims, the description, and the drawings.
The present invention is based on the idea of using, not, as previously
typical,
prefabricated tubes as column formworks in concrete construction, but rather
planar
members equipped with connecting sections, through which a form-fit connection
of two
opposing edges of the planar member is possible. The material comprising the
planar
member must satisfy two conflicting conditions: on one hand, it must exhibit
sufficient
strength to withstand the pressure of the poured concrete, and on the other
hand, it must
exhibit sufficient elasticity to be able to be bent into a tube with no
difficulty. In particular,
this tube must remain dimensionally stable, that is, circular in diameter,
under the
pressure of concrete, that is, after the concrete is poured.
The column formwork according to the present invention for use in concrete
construction
comprises a planar member constituting the formwork, and at least one
connecting
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section, provided for form-fit connecting two opposing edges of the planar
member and
thus for forming a tube segment, wherein at least the connecting-section
surface facing
the planar member exhibits a substantially constant curvature that
substantially
corresponds to the curvature of the tube segment. In this way, it is achieved
that the
column formwork takes on a round shape. If connecting sections having no
curvature are
used, the bent planar member would take on a slightly tear-shaped form and
thus cause
unsatisfactory results in the concrete parts. Slight differences between the
curvature of
the connecting section and the curvature of the tube segment are tolerated
within the
context of the present invention, since acceptable results can be obtained
nonetheless.
The column formwork according to the present invention can be transported with
no
difficulty in large quantities in a flat state before bending it into a tube.
The use of the term "substantially constant curvature" is intended to make
clear that
manufacturing-dependent deviations from a constant curvature are, of course,
tolerated,
as long as they are not so marked that the column formwork exhibits a diameter
that
deviates substantially from a circular diameter.
According to a preferred embodiment of the present invention, the planar
member
comprises an elastic synthetic material. Such a material fulfills the two
above-mentioned
conditions especially well, namely sufficient shape-retentiveness after the
concrete is
poured and, at the same time, sufficient elasticity that allows bending into a
tube with no
difficulty. Such a column formwork exhibits the great advantage that no single-
use
materials are provided, such as the typically used cardboard, thus
facilitating multiple
reusage of the formwork.
The two opposing edges of the planar member must be form-fit connected
together. To
do this, at least two connecting sections are generally used. Advantageously,
each of
these connecting sections is attached to the planar member flush with one edge
of the
planar member. However, in the context of the present invention, the
connecting sections
can, in principle, also be attached to the planar member at a short or even a
somewhat
long distance from the edges to be connected. In such a case, the tongues
described
below for connecting the connecting sections must be adjusted accordingly in
their
dimensions or e.g. replaced by flexible bands.
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However, an embodiment having just one connecting section attached near an
edge of
the planar member and protruding over this edge is also conceivable. The part
of the
connecting section protruding out over the edge is then connected with the
planar
member near the opposing edge after the planar member is bent into a tube
segment.
This connection can, in principle, take place in any manner, for example
through glueing.
However, the planar member can also exhibit e.g. projections that engage in
corresponding recesses of the connecting section and thus facilitate a secure
form-fit
connection of the opposing edges.
Although the two above-mentioned conditions "stability of dimension" and
"elasticity" are
naturally fulfilled to a sufficient extent by a number of materials that can,
in principle, be
used in any thickness, certain materials used in certain thicknesses yield
particularly good
results for the purpose of very easy handling. For these reasons, both the use
of fiber
reinforced materials, of fiber reinforced synthetic materials, or of
polyester, especially
synthetic fiber reinforced materials, glass fiber reinforced materials, and
carbon reinforced
materials, especially glass fiber reinforced materials or carbon reinforced
synthetic
materials, especially fiber reinforced polyester, as the elastic synthetic
material, and a
planar member having a thickness of 0.5 to 5 mm, especially having a thickness
of 1 to
4 mm, particularly preferably having a thickness of 1.2 to 3 mm, are preferred
embodiments of the present invention. Planar members having a thickness of 1.4
to
2.5 mm are particularly well suited, and those having a thickness of 1.5 to 2
mm are most
particularly preferred.
For reasons of reduced variety of form of the connecting sections, the
connecting-section
surface facing away from the planar member can additionally be provided with a
substantially constant curvature, this curvature then differing from the
curvature of the
tube segment. In this way, a connecting section can be used for column
formworks of
varying diameters.
Although the column formworks according to the present invention can be used
for
concreting columns of greatly varying diameters, and in principle even for
concreting
columns of any diameter, column formworks having a typical concrete
construction
diameter of 100 to 2000 mm, especially of 200 to 1000 mm, are preferred.
Diameters of
200 to 450 mm, of 250 to 500 mm, of 500 to 900 mm, and of 600 to 1000 mm are
particularly preferred.
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The connecting sections can be affixed to the planar member in various ways,
namely
e.g. through glueing, riveting, nailing, or welding. Clueing the connecting
section and the
planar member is particularly preferred because doing so causes no visible
traces in the
finished concrete parts.
5 Column formworks having connecting sections that exhibit, in the direction
of the tube-
segment tangent perpendicular to the tube-segment axis, an extension of 1 to
50%,
especially 3 to 25% of the tube-segment diameter, are particularly preferred
embodiments
of the present invention. This ensures that, after the concrete is poured into
the formwork,
the connecting sections do not detach from the planar member. Pouring the
concrete
creates strong forces perpendicular to the formwork wall, and there is thus a
risk of the
formwork breaking apart along the planar member edge held together by the
connecting
sections. To prevent such breaking apart, the connecting sections must be
appropriately
tightly connected together, and an appropriately strong connection between
connecting
section and planar member must be ensured. For this reason, connecting
sections that
exhibit, in the direction of the tube-segment tangent perpendicular to the
tube-segment
axis, an extension of 5 to 15%, especially of about 10% of the tube-segment
diameter,
are most particularly preferred.
In view of the above-mentioned column diameters typical in concrete
construction,
connecting sections that exhibit, in the direction of the tube-segment tangent
perpendicular to the tube-segment axis, an extension of 10 to 100 mm,
especially from 20
to 75 mm, are preferred. Connecting sections that exhibit, in the direction of
the tube-
segment tangent perpendicular to the longitudinal axis of the tube segment, an
extension
of 30 to 50 mm, especially of 35 to 45 mm, are particularly preferred.
In principle, the connecting sections can be constructed of any kind of
sufficiently
dimensionally stable material. The connecting sections are preferably
constructed of
synthetic material, and the connecting sections are particularly preferably
constructed of
polyester, of a fiber reinforced synthetic material, especially of glass fiber
reinforced
synthetic material or carbon reinforced synthetic material, particularly
preferably of glass
fiber reinforced polyester or carbon reinforced polyester.
Most particularly advantageous characteristics result when the connecting
sections and
the planar member comprise the same material. In this way, an especially
simple and
tight connection between the parts is possible through glueing.
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To ensure a secure, form-fit connection of the opposing edges of the planar
member, in
the context of the present invention, it is particularly preferred that the
connecting sections
extend in the direction of the tube segment axis over the entire length of the
tube
segment. In this way, the edges of the planar member can be form-fit connected
over the
entire length of the column formwork with particularly great strength and
precision.
The connecting sections can, in principle, be mechanically connected with one
another in
any manner known in formwork engineering, thus for example using clamps,
wedges,
locks, or bolts. In the context of the present invention, connecting sections
that exhibit
grooves and tongues are preferred. To connect the edges of the planar member,
one
tongue of one connecting section engages in a groove of the other connecting
section
with a precise fit. The stable cohesion of the edges of the planar member is
ensured e.g.
through a bolt that is guided through bores in the connecting sections and
then screwed
down.
Another important condition for achieving good results in the form of an
excellent surface
finish of the concrete columns is preventing water and cement paste from
penetrating the
formwork. At the junction of the edges of the planar member, there is a risk
that, in the
case of an insufficiently form-fit junction, water penetration and thus
bleeding of fine
concrete components could occur at the seam. This can cause visible unevenness
on the
surface of the concrete column. For this reason, a planar member and
connecting
sections are preferably used whose edges are especially smooth due to an
appropriate
subsequent treatment such as grinding or polishing, and that facilitate a very
good,
precisely fitting connection. Furthermore, according to a particularly
preferred
embodiment of the present invention, the tongues of the connecting sections
are
equipped with seals, thus preventing penetration of water through the
connecting
sections.
Brief Description of the Drawings
The invention is intended to be explained in greater detail below by reference
to an
exemplary embodiment in association with the drawings, wherein
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Fig. 1 shows a cutaway of a cross-section through a column formwork according
to
the present invention;
Fig. 2 shows a part of a cross-section through a column formwork according to
the
present invention, having a larger diameter compared with the column formwork
of Figure 1.
Detailed Description of the Invention
Figure 1 shows a cutaway of a cross-section through a column formwork. The
planar
member 1 is equipped with the connecting sections 2 and 2', which are each
attached
adjacent to the edges 3, 3' of the planar member. The connecting-section
surface 4, 4'
facing the planar member 1 exhibits a constant curvature, the curvature
substantially
corresponding to the curvature of the tube segment. In this way, it is
achieved that the
column formwork takes on a precisely round shape. The connecting-section
surface 5, 5'
facing away from the planar member likewise exhibits a constant curvature, the
surface 5,
5' of the connecting section shown being more sharply curved than the surface
4, 4'. The
edges 3, 3' of the planar member 1 exhibit a highly precise fit. The
connecting section 5 is
equipped with two tongues 6, while the connecting section 5' exhibits two
corresponding
grooves. However, each of the two connecting sections can also be equipped
with one
tongue and one groove. The connection between the two connecting sections and
thus
the positive connection of the two edges of the planar member results through
an
engagement of the tongues 6 in the corresponding grooves. The penetration of
water
through the connecting sections 2, 2' is prevented by the longitudinally
running seals 7.
The required securing of the connection through a clamp that covers the two
connecting
sections 2, 2', or a bolt that is guided through the two connecting sections
2, 2' and then
screwed down, is not shown.
Figure 2 likewise shows a cutaway of a cross-section through a column
formwork. In
Figure 2, the extension t of connecting section 2 in the direction of the tube-
segment
tangent perpendicular to the axis of the tube segment is emphasized.
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List of Reference Numbers
1 Planar member
2, 2' Connecting section
3, 3' Edges of the planar member
4, 4' Connecting section surface facing the planar member
5, 5' Connecting section surface facing away from the planar member
6 Tongues
t Extension of a connecting section in the direction of the tube-segment
tangent
perpendicular to the tube segment axis
