A METHOD FOR PRODUCTION OF REINFORCEMENT CHAIRS AND A MOULD FOR USE IN THE PRODUCTION

PROCEDE DE PRODUCTION DE CHAISES A BETON ET MOULE UTILISE POUR LEUR PRODUCTION

English Abstract

The invention concerns a method for production of reinforcement chairs in
concrete for use in steel-armoured concrete structures, wherein the
reinforcement chairs are cast in a mould (9) of a material which is elastic,
preferably a two-component rubber mass, and that after hardening the
reinforcement chairs are removed by elastically bending the mould's wall parts
(11). The invention also concerns a mould for use in production of
reinforcement chairs wherein the mould has walls adapted to the shape of the
reinforcement chairs, which are made of an elastic material, especially a two-
component rubber mass, and that a releasable metal rod (10) is provided
perpendicularly through the mould's wall parts, for production of through-
going mounting holes in the reinforcement chair.

French Abstract

L'invention concerne un procédé pour la production de chaises à béton prévues pour être utilisées dans des structures en béton, à armatures d'acier. Les chaises à béton sont coulées dans un moule (9) d'un matériau élastique, de préférence, une matière à base de caoutchouc à deux composants. Après durcissement, on retire les chaises en fléchissant, de manière élastique, les parois (11) du moule. L'invention concerne également un moule utilisé pour la production de chaises à béton. Ce moule comprend des parois adaptées à la forme des chaises à béton, constituées en une matériau élastique, en particulier, une matière à base de caoutchouc à deux composants. En outre, une tige métallique amovible (10) est introduite de manière perpendiculaire, à travers les parois du moule, pour former des trous de montage traversants dans la chaise à béton.

Claims

CLAIMS
1. A method for production of reinforcement chairs in concrete for use in
steel-armoured concrete structures,
characterized in that the reinforcement chairs are cast in a mould of a
material which is elastic, preferably a two-component rubber mass, and that
after hardening the reinforcement chairs are removed by elastically bending
the mould's wall parts.
2. A method according to claim 1,
characterized in that the reinforcement chairs are cast in a mould which is
formed by casting the mould walls in a box, in which there are provided one
or more models, e.g. plaster models of the reinforcement chairs.
3. A mould for use in production of reinforcement chairs according to
claim 1, wherein the mould has walls adapted to the shape of the
reinforcement chairs,
characterized in that it is made of an elastic material, especially a
two-component rubber mass.
4. A mould according to claim 3,
characterized in that there is provided a releasable-metal rod perpendicularly
through the mould's wall parts, for the production of through-going mounting
holes in the reinforcement chair.
5. A mould according to claim 3,
characterized in that it is designed for casting several reinforcement chairs ata time.

Description

CA 0221982~ 1997-11-21
W O96137351 pCTANO95/00082
.A method for production of reinforcement chairs
and a mould for use in the production
The present invention concerns a method for production of reinforcement
chairs in concrete for use in steel-armoured concrete structures, together with
s a mould for use in production of the reinforcement chairs.
Reinforcement chairs are used in order to position reinforcement steel which
is provided in casting moulds, both before and during filling of the casting
moulds with concrete. The reinforcement chairs can be made of various
materials, such as, e.g., plastic, extruded concrete. The problems involved in
10 using known reinforcement chairs can be divided into the following two
categories:
1. Reinforcement chairs made of materials which have different physical
properties from concrete. In the event of temperature changes, due to
different expansion coefficients, these will lead to the occurrence of
5 openings/cracks between concrete and reinforcement chair, thus causing water
to penetrate into the concrete, which in turn can cause corrosion damage in
the reinforcement steel. This drawback is further reinforced if there is not
adequate adhesion between the concrete and the reinforcement chair.
2. Reinforcement chairs made of concrete which do not have the strength
20 necessary in order to withstand the loads to which they are exposed in the
casting moulds. Production processes currently in use restrict the possibilitiesof giving the reinforcement chairs the design necessary in order to satisfy
requirements for securing them in the casting moulds, and requirements that
the reinforcement chairs should not fall out of the completed structure,
25 thereby permitting water to penetrate into the concrete, even without adhesion
between reinforcement chair and concrete.
The object of the present invention is to provide a method for production of
reinforcement chairs which avoids the above-mentioned disadvantages, and a
~' mould for use in connection with the method.
30 These objects are achieved with a method for production of reinforcement
chairs and a mould for use in connection with the method according to the

CA 022l982~ l997-ll-2l
W O96/37351 PCTANO~5/0~7
type mentioned in the introduction, which is characterized by the features
indicated in the attached claims.
By means of the invention a method is obtained by simple means for the
production of reinforcement chairs which substantially increases the strength
5 and reduces the production time for reinforcement chairs.
The design according to the invention increases the contact surface between
concrete and reinforcement chair, and by means of cut-outs and through-
going holes the reinforcement chair is secured against sliding out of the
completed concrete structure.
10 In short the principle of the invention consists in the fact that the method for
production of reinforcement chairs for use in steel-armoured concrete
structures and the casting mould for use in the production of the
reinforcement chairs is designed in such a manner that completed
reinforcement chairs both with cut-outs and holes can be removed without
15 having to deskoy the casting mould.
The invention will now be described in more detail by means of an
embodiment which is illustrated in the drawing, in which:
fig. 1 is a perspective view of a reinforcement chair,
fig. 2 is a perspective view of a plaster model of a reinforcement chair
20 provided in a simple wooden casting mould for the production of prototypes,
preferably of plaster, and
fig. 3 is a perspective view of a partial section of an elastic casting mould
according to the invention.
Fig. 1 illustrates a reinforcement chair 1 which consists of a base part 2 to
25 abut against the foundation and which in a first upper surface 3, opposite the
base part 2, is provided with a cut-out or recess to abut against a
reinforcement steel (not shown), and where in a second upper surface,
opposite the base part 2, there is provided a through-going hole 4 for
mounting it on to the foundation, e.g. by means of nails. In the largest side
30 surfaces there is further provided a through-going hole 5 in the area of the

CA 0221982~ 1997-11-21
W O96/37351 PCTAN095/CA~Y2
cut-out 3, for mounting the reinforcement chair 1 by means of binding wire to
the reinforcement bar. The reinforcement chair 1 is also provided with further
cut-outs or grooves 6 and recesses 7 in order to increase the contact surface
~ between reinforcement chair and concrete and thereby provide maximum
binding power to the surrounding concrete. In order to simplify the
production of the reinforcement chairs, one of the largest side surfaces is
completely flat.
As illustrated in fig. 2, the base part 2 is designed with least possible contact
with the formwork in order to reduce the surface of the part of the
reinforcement chair which will be aligned with the completed concrete, and
thereby reduce the penetration of moisture between reinforcement chair and
the surrounding concrete.
Fig. 3 is a partial section of a casting mould 9 for the production of
reinforcement chairs in concrete.
1S The method for production of reinforcement chairs in concrete for use in
steel-armoured concrete structures is implemented in the following manner:
1. A plaster model in the desired shape, e.g. according to the design in fig.
1, is produced manually.
2. The plaster model is then arranged in a simple wooden mould 8, see fig.
2, and a mixture of two-component rubber mass is then poured down into the
mould.
3. The negative impression of the reinforcement chair thus constitutes a
casting mould for the production of further plaster models/prototypes, which
are then moulded in the desired number corresponding to the size of the
actual main mould.
4. The plaster models are then glued to the bottom of the main mould,
~' which is also made of wood, according to an optimum pattern, e.g. according
to fig. 3, thus providing room for as many plaster models as possible. The
main mould is thus intended for production of several chairs at a time, e.g.
50-150. The wooden mould is then filled with a two-component rubber mass
9.

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CA 0221982~ 1997-11-21
W O96/373~1 PCTnN095/00082
5. The moulding mass is then hardened for approximately 12 hours,
whereupon the plaster models are easily released from the elastic mould.
6. For the production of the through-going hole 4 for nails, holes are drilled
in the rubber mould 9, thus enabling, e.g., a teflon-coated metal rod/-shaft
5 10, which is coated with a thin layer of oil, to be arranged horizontally in the
mould, cf. fig. 3. With regard to the through-going holes 5 for binding wire,
these are provided by the design of the rubber mould in the form of bosses
which extend perpendicularly upwards from the bottom of the mould.
7. The main form is then filled with concrete, which is vibrated and
hardened for approximately 8 hours at 40~C . The metal rods 10 are then
removed from the rubber mould and completed reinforcement chairs can be
easily loosened from the mould 9 by elastically bending the mould's wall
parts 11. Since the rubber mould 9 consists of an elastic material, and the
completed reinforcement chairs are removed after hardening by elastically
15 bending the mould's wall parts 11, and without the mould being destroyed,
the rubber mould can be used repeatedly and is thereby particularly suited to
mass production of reinforcement chairs.
With respect to steps 1 to 6, these apply to production of the actual rubber
mould 9, while step 7 concerns the actual production of reinforcement chairs
20 in concrete for use in steel-armoured concrete structures.
Since the reinforcement chairs are cast in moulds made of two-component
rubber mass, which makes the casting moulds very flexible, it is thereby
possible to produce reinforcement chairs supplied with cut-outs 6, recesses 7
and through-going holes 4,5, while at the same time the nature of the rubber
25 moulds as opposed to known designs permits the moulds to be re-used.
The strength of the reinforcement chairs is particularly due to the fact that
they are cast in moulds of heat-insulating materials, and thus maintain a
stable temperature during the hardening process.

Representative Drawing