Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02299193 2000-02-23
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TITLE
FORMWORK FOR CREATING COLUMNS AND CURVED WALLS
s FIELD OF THE INVENTION
This invention relates to modular formwork for forming concrete columns and
curved concrete structures.
to BACKGROUND OF THE INVENTION
It is known to provide formwork for pouring concrete columns comprising
semi-circular sections of steel pipe which are joined to form a tube and into
which
concrete is poured. Once the concrete has set, the steel pipe sections are
removed.
is
It is also known to provide modular PVC formwork for the purpose of creating
straight and flat concrete walls, and in which the formwork stays in place
after the
concrete has set. Canadian Patent No. 2,215,939 discloses such formwork which
comprises flat elongated wall elements connected to one another by engaging
means
2o along their respective edges, and connecting members extending across the
width of
the formwork to retain opposed wall surfaces in spaced relationship. The
result is
modular stay in place formwork for creating straight walls.
However, there remains a need to provide modular stay in place formwork that
2s is capable of producing concrete columns and curved walls and which avoids
the
difficulty of dealing with bulky semi-circular sections of steel pipe.
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It is accordingly an object of this invention to provide stay-in-place modular
formwork elements for pouring concrete into columns or curved surfaces, and a
method of assembling them. It is a further object of this invention to provide
such
elements which are capable of being used to connect to stay-in-place modular
straight
s wall formwork of the kind described in Canadian Patent No. 2,215,939.
As noted above, prior art modular PVC formwork elements for forming
straight walls are known to provide cross members between opposing surfaces of
the
formwork for the purpose of providing rigidity against the outward pressure of
io concrete. However, when forming a column or a curved wall, the provision of
a cross
member between opposing faces presents problems. For example, the use of such
a
cross member may impede the ability to install rebar. It is therefore an
object of this
invention to provide modular formwork for creating curved concrete walls or
services
which provides inherent structural rigidity to the formwork and which resists
outward
is bulging due to pressure from the concrete.
SU1~IMARY OF THE INVENTION
2o According to the invention there is provided a curved elongated modular
wall
element comprising a curved portion and connector means at each longitudinal
edge
of the curved portion. The arc angle defined by the outer surface preferably
comprises an even fraction of 360°. A connector element according to
the invention
comprises an elongated, straight planar surface, one longitudinal edge of
which
2s includes two opposed connecting means for engaging the connecting means of
the
wall elements.
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In another aspect of the invention, a curved wall is formed by a plurality of
individual elongated formwork elements connected end to end by means of a
connector element extending radially inward from the point where two edge
adjacent
wall elements meet, one end of such connector being attached to the ends of
s respective adjacent wall elements, and said connector having a planar
surface
extending in said radial direction.
In another aspect, the invention comprises a curved wall element as described
above and further including inwardly extending projections spaced inwardly
from
~o each opposed end of each element.
Bracing elements are described which comprise a planar central portion
terminating at each longitudinal edge in angled connecting means extending at
45°
and 135° with respect to the plane of the central portion. The
connecting means of the
~s bracing elements are adapted to engage the inwardly spaced projections of
the wall
elements.
Other aspects of the invention will be appreciated by reference to the
detailed
description of the embodiments of the invention and to the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The preferred and alternative embodiments of the invention will be appreciated
2s by reference to the following description and to the drawings thereof in
which:
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Fig. 1 is a cross-sectional view of a segment of a column of formwork made
using the formwork elements according to the invention;
Fig. 1 (a) is an enlarged view of a portion of Fig. 1 comprising two wall
s elements according to the invention;
Fig. 2 is a cross-sectional view of a wall element according to the invention;
Fig. 3 is a cross-sectional view of a connector element according to the
io invention;
Fig. 4 is a cross-sectional view of an alternative embodiment of the wall
element of the invention;
~s Fig. 5 is a cross-sectional view of a segment of a column of formwork made
from the wall elements of Fig. 4;
Fig. 5(a) is an enlarged view of a portion of Fig. 5 comprising a single wall
element;
Fig. 6 is a cross-sectional view of a 45° element according to the
invention;
Fig. 7 is an enlarged view of two 45° elements connected to a
connector
element and two curved wall elements;
2s
Fig. 8 is a cross-sectional view of a section of curved formwork according to
the invention joining two straight formwork sections; and,
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Fig. 9 is a cross-sectional view of two connected curved wall elements,
bracing
elements and 45 degree elements according to an alternative embodiment.
s DETAILED DESCRIPTION OF THE PREFERRED AND
ALTERNATIVE EMBODIMENTS
A formwork structure forming a segment of a column according to the
invention is shown in Fig. 1. All of the drawings show cross sectional views
of the
~o elements. The elements are elongated through the plane of the drawings.
Referring to Fig. 1 and Fig. 1 (a), the formwork comprises a plurality of
curved
wall elements 10 connected in edge to edge relationship as at 11. Connector
elements
12 extend radially from connection points 11 between adjacent elements 10.
~s
Referring to Fig. 2, each curved wall element 10 comprises a curved surface
14, and a C-shaped termination 16 at each longitudinal edge 18, 20 of element
10. T-
shaped key projections 36 are spaced inwardly from the longitudinal edges of
element
10.
As best seen in Fig. 3, each connector element 12 comprises an elongated
planar surface 22, and opposed T-shaped projections 24, 26 and 23, 25
extending
outwardly from longitudinal edges 28, 30 respectively of the connector element
12.
L-shaped extensions 27, 29 serve to bracket projections 24, 26.
2s
A column of formwork formed with the connector and wall elements according
to the invention will provide rigidity against bending out of the vertical
plane. The
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rigidity is provided by the curved wall elements themselves, but is thought to
be
significantly enhanced by the presence of radially disposed connector
elements, which
will tend to resist bending of the column along the plane of the connector
elements. It
will be appreciated that the more connectors are provided along the inside
periphery
s of the formwork, the greater the overall resistance to bending of the
formwork will be.
The curved wall element 10 is preferably chosen to be an integral fraction of
360°. Thus, a real number of elements 10 may be used without truncation
to complete
a circle. In the preferred embodiment, the arc length of element 10 is chosen
to be
io 3.14 inches or centimeters or a multiple thereof.
Referring to Fig. 4, in an alternative embodiment of the invention, wall
elements 34 comprise a plurality of wall segments 31, 33 and 35, each segment
having the characteristics of element 10, but the segments are integrally
formed as a
is single element 34. A column of formwork made using elements 34 is
illustrated in
Fig. 5.
Referring to Figs. 1, 1(a), 5 and 5(a), the wall elements 10 and 34 preferably
include key projections 36 extending inwardly from the inner surface of the
wall
2o element and being spaced inwardly in relation to the longitudinal edges of
the wall
element. Key projections 36 enable the use of a 45° element 38, such
use being
illustrated in Fig 5.
As is best appreciated by reference to Fig. 6, 45° element 38 comprises
a flat
2s planar surface 40. Each longitudinal edge terminates in a C-shaped portion
42, 44.
One of the C-shaped portions defines an angle of 45° to the planar
surface 40 while
the other defines an angle of 135° to the planar surface 40. As is best
illustrated in
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Fig. 7, elements 38 may be disposed on key projections 36 so as to extend from
the
key projection 36 to the T-shaped projections 23, 25 of a connector element
12. The
45° elements 38 provide additional rigidity to resist outward pressure
from the
concrete.
s
The curved wall elements 10 and the connector elements 12 may also be used
to interpose a curved wall section between straight wall sections of formwork,
as
illustrated in Fig. 8. The curved wall elements 10 are adapted to integrate
into straight
formwork wall elements 50 and straight formwork connector elements 52 of the
types
o described in Canadian Patent No. 2,215,939, straight formwork elements 50
being
provided with C-shaped portions 54 corresponding to the C-shaped terminations
16 of
curved wall elements 10, and straight formwork elements 12 being provided with
key
projections 56 corresponding to key projections 36 of connector elements 12.
~s It may also be desirable to further enhance structural rigidity of a column
of
formwork by cross-bracing opposing walls. This may be accomplished by
extending
diametrically opposed connector elements inward so as to connect them
together.
Appropriately wide connector elements may be made to extend inward from
connection points between curved wall elements at diametrically opposed sides
of the
2o column. The wide connector elements may be adapted to connect to one
another end
to end at the epicenter of the column.
It will be appreciated that the connection means between the wall elements 10
and the connector elements 12 have been illustrated in the preferred
embodiment as
2s C-shaped portions on the curved wall elements 10 and cooperating opposed T-
shaped
portions on the connector elements 12 to form a tongue and groove type of
connection. The arrangement can of course be substituted for T shaped portions
at the
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end of the wall elements and C shaped portions on the connector elements, or
indeed
any other type of connection system, provided the connector elements act to
secure
edge to edge adjacent curved wall elements to one another.
s Similarly, the connection means between the 45° elements 38 and the
key
projections 36 have been illustrated in the preferred embodiment as C-shaped
portions on the 45° elements and cooperating opposed T-shaped key
projections on
the connector elements (23, 25) and the curved wall elements (36) to form a
tongue
and groove type of connection. The arrangement can of course be reversed, or
to indeed any other type of connection system, provided the 45°
elements act to brace
the connector elements 12 to the curved wall elements 10.
In an alternative approach, the connector means between adjacent curved wall
elements is as shown in Fig. 9. According to this approach, each curved wall
element 70 includes a male connector 72 along one longitudinal edge and a
female
connector 74 along the other longitudinal edge. The element 70 includes
connectors
76 spaced inwardly from the longitudinal edges of the element. Connectors 76
are
adapted to connect to bracing elements 12 to provide resistance to bending of
the
formwork in the vertical plane. Elements 70 otherwise have projections 36
spaced
2o inwardly from each longitudinal edge of the element, as in the case of the
curved
wall elements 10 described above. Forty five degree elements 38 are used to
brace
the curved wall portion of elements 70 against outward bulging due to the
pressure of
the concrete.
2s It will be appreciated that the preferred and alternate embodiments have
been
specifically described, but that variations therein may be practiced without
departing
from the scope of the invention, which is properly defined by the claims.
