EP0651691B1

EP0651691B1 - An arrangement and method for vibrating concrete by means of a vibrating pole

Info

Publication number: EP0651691B1
Application number: EP93915070A
Authority: EP
Inventors: Stefan Rickne
Original assignee: SKANSKA STOCKHOLM AB
Current assignee: Skanska AB
Priority date: 1992-06-25
Filing date: 1993-06-23
Publication date: 1997-09-17
Anticipated expiration: 2013-06-23
Also published as: WO1994000281A1; JPH07508231A; DE69314036T2; DE69314036D1; SE9201965L; SE9201965D0; CA2138545A1; ATE158221T1; DK0651691T3; EP0651691A1; SE500828C2

Abstract

The present invention relates to an arrangement for vibrating concrete using at least one internal vibrator (1). According to the invention, the arrangement includes a horizontally displaceable carrier (4) for the internal vibrator, which carrier comprises means (3, 4) to displace the internal vibrator in a vertical direction. The invention also relates to a method for automatically controlling the displacement pattern of the internal vibrator (1).

Description

The present invention relates to an arrangement for vibrating concrete, comprising an internal vibrator and a method for vibrating concrete using an internal vibrator (see e.g. CH-A-328693).
In order to obtain homogeneous and non-porous concrete, concrete which has been poured into a mould is often subjected to vibration using an internal vibrator. An internal vibrator consists of a vibrating tube, the high frequency vibrations of which are often achieved by means of an internal rotating eccentric within the tube. When the vibrating tube is lowered into concrete, the concrete is subjected to very rapid vibration. In this manner, the internal friction of the concrete is to all intents and purposes eliminated, which implies that the concrete becomes less viscous, settles and compacts. The majority of the air which is trapped within the concrete and which for normal concrete consistencies can make up some 5-20 % of the total volume, is forced out of the concrete and thus a non-porous and homogeneous concrete is obtained. The low viscosity consistency of the concrete which is imparted by the vibrations further implies that the concrete will flow into any parts of the mould which are relatively inaccessible and surround any reinforcement which may be present.
Since each percent of remaining air-filled cavities which occur due to insufficient settling of the concrete reduces the strength of the structure by approximately 5 %, it is immediately apparent that good vibration of the concrete is of utmost importance in order to ensure high quality of the concrete casting.
Presently, vibration work is carried out using an internal vibrator which is manually inserted into the concrete in the mould to a certain depth following a predetermined pattern. Thereafter, the internal vibrator is very slowly pulled out of the concrete so that air-pockets will not be formed during the removal. Such work is clearly very time consuming and places high demands on accuracy and precision during its performance. In addition, the work is very heavy. Furthermore, once the work has been carried out, it is virtually impossible to check, and the consequences of insufficient vibration will not be apparent until the casting mould is removed or perhaps not before the cast concrete construction is loaded.
It is therefore an object of the present invention to provide an arrangement and a method for vibrating concrete using an internal vibrator which overcome the disadvantages of manual methods and which increase the uniformity of quality of cast concrete products.
According to the invention, this object is achieved by means of an arrangement according to claim 1.
According to the invention, automatic control is achieved using a control unit which is arranged to displace the internal vibrator and its carrier in a predetermined displacement sequence. The control unit advantageously comprises a computer, and the carrier is in the form of a trolley which runs along a track arranged on a support member which, in turn, is connected to a casting mould for concrete.
The invention also relates to a method for vibrating concrete in a casting mould using the arrangement of claim 1, characterized in that the displacement sequence of the internal vibrator and its trolley is automatically controlled by means of a control unit which operates means to displace the internal vibrator horizontally and vertically according to a predetermined pattern.
An embodiment of the invention will now be described with reference to the attached drawings in which

Fig. 1: shows a schematic perspective view of an arrangement according to an embodiment of the invention connected to a casting mould, and
Fig. 2: shows the arrangement and the casting mould of Fig. 1 in a partially sectioned side view.

The arrangement shown in Fig. 1 comprises an internal vibrator 1 which is attached to one end of a flexible tube 2 which houses cables for the supply of current to the internal vibrator. The other end of the tube 2 is connected to a device 3 for winding up and winding out the tube. In Fig. 1 the device 3 is symbolized by a circle and can, for example, be in the form of a motor-driven drum or similar. The wind-up device 3 is carried by a trolley 4 which, in turn, is supported by a frame 5. The frame is rigidly connected to a wall of a casting mould 6. At its upper region, the frame comprises a horizontal platform 7 to which the trolley 4 is attached and displaceable along an edge thereof. The attachment between the trolley 4 and the platform 7 can, for example, be in the form a guide groove 8 on the underside of the platform 7 and in which a shaped edge 9 of the trolley 4 runs. In addition, a similar guide groove or a rail 10 is attached to the frame 5 and a co-operating shaped edge of the trolley 4 runs therealong. The arrangement further includes drive means to displace the trolley along the edge of the platform, which means can be in the form of a toothed rack/gear-pinion mechanism or similar. So that personnel are able to walk along the platform 7, the tube 2 is guided in a guide tube 11 which extends in an arch above the platform and terminates in a vertical section 12. The arrangement further includes a not-shown control unit to control the displacement of the trolley and the raising and lowering of the internal vibrator. Preferably, the control unit is connected to a control panel 13 which is placed at an easily accessible location for an operator.
A displacement sequence of an internal vibrator for vibrating concrete in a casting mould for wall elements will now be described with reference to Fig. 2.
In said figure, a casting mould 6 for a wall element is schematically illustrated in which two casting layers C1 and C2 have been introduced. The arrows P1-P6 symbolize the various phases in a vibration cycle for the casting layer C2, and reference numerals 4₁, 4₂ and 1₁, 1₂ denotes two different positions of the trolley 4 and the internal vibrator 1 respectively. Reference numerals 101₁, 102₂ denote the lowest positions of the internal vibrator 1 in two successive vibration cycles in the casting layer C1.
A vibration cycle for the casing layer C2 will now be described starting from the moment when the trolley 4 with the raised internal vibrator 1 reaches the position 4₁.
The first phase P1 of a vibration cycle consists of lowering a switched-off internal vibrator through the air. During this phase the lowering speed is relatively high.
In the second phase P2, a switched-on internal vibrator is lowered through the casting layer C2 with a speed of approximately 0.1 m/s until the upper end of the internal vibrator reaches the bottom of the casting layer C2.
In phase P3, vibration takes place with a stationary internal vibrator 1₁ for a time interval which is typically 5-15 seconds. The position of the internal vibrator 1₁ is chosen so that good shaking down of the casting layers C1, C2 is achieved.
Thereafter, the internal vibrator is slowly raised during phase P4 through the casting layer C2 with a speed of approximately 0.05 m/s until the vibrator has left the casting layer.
During phase P5, the internal vibrator is raised in a switched-off condition through the air and thereafter the trolley 4 is moved, and therewith it the internal vibrator, during phase P6 from the position 4₁ to the position 4₂. The vibration cycle is thereby terminated and a new vibration cycle begins. The distance L by which the trolley 4 is displaced is dependent on the effective radius of the internal vibrator (typically 40 cm), the reinforcement density and the demands on non-porosity of the completed wall element. Normally, the distance L is between 0.3-0.5 m. The length of the wall element in the X-direction is often a multiple of 2.4 m, thereby implying that a plurality of vibration cycles must be effected in each casting layer. The height in the Z-direction is typically 2.5 m, which normally requires three casting layers. The width of the wall element is normally 16-18 cm, maximum 30 cm. With the widest walls, a double submersion of the internal vibrator is required. In order to permit submersion of the internal vibrator at various widths, the connection between the guide tube 11 and the rest of the trolley 4 is advantageously flexible so that the vertical extension of the guide tube can be placed at any location across the width of the mould 6.
In order to reduce the time for a vibration cycle, the lifting movement of the internal vibrator can be terminated once it has exited the uppermost casting layer and the trolley 4 can thereafter immediately be displaced to the next position, provided that no obstructions to the horizontal movement of the internal vibrator are present in the casting mould.
The vibration of the casting layer C1 is performed in the same way as described above for the casting layer C2, with the exception that in its lowest position 101₁, 101₂ the internal vibrator is located just above the bottom of the mould 6, since the layers C1 is the first casting layer.
From the above, it will be apparent that the further casting layers which may be added to the mould on top of the layer C2 to thereby fill the mould can be vibrated in the same manner as for the casting layer C2.
A vibration program to control the internal vibrator accordingly includes a great many parameters even for one wall element of the simple type shown in the drawings. With more complicated elements, such as wall elements with windows and/or door-openings and openings for pipes, the displacement sequence for the internal vibrator is made more complicated. It is therefore suitable that the control unit for controlling the internal vibrator includes a computer which is programmed to generate a displacement path for the internal vibrator dependent on inputted parameters, such as the concrete quality, the effective radius of the internal vibrator, the reinforcement density, the geometry of the casting mould, any obstructions to displacement, the depth of the casting layers, etc.
The displacement path for the internal vibrator which is theoretically calculated by the computer is suitably tested in an empty casting mould in order to establish that the internal vibrator during actual casting will not contact the mould or any obstructions therein. The test is performed with a switched-off internal vibrator and with higher lowering and lifting speeds than with the casting.
In a preferred variation of the invention, during the actual moulding and once the vibration has finished in one casting layer, the internal vibrator is placed at a height above the already-vibrated casting layer which corresponds to the height of the subsequent casting layer in order to provide an indication as to when the pouring of the subsequent layer shall cease.
A plurality of modifications to the shown embodiment is of course possible within the scope of the claims. For example, the carrier trolley for the internal vibrator can be supported on the top surface of the casting mould and can run in tracks formed on the upper surfaces of the corresponding mould halves. It is also conceivable that the control unit control several trolleys provided with internal vibrators so as to accelerate the vibration of each casting layer. In addition, the arrangement according to the invention can also be adapted to casting of objects other than wall elements.

Claims

Arrangement for vibrating concrete using at least one internal vibrator, comprising a horizontally displaceable trolley (4) for the internal vibrator, which trolley has means (2,3,12) for displacing the internal vibrator in a vertical direction, and guide means (9) for guiding the horizontal displacement, characterized in that said guide means (9) for the trolley run in cooperating guides (8, 10) on the underside of a platform (7) which is attached to a casting mould (6) for the concrete and that an automatic control unit is arranged to displace the internal vibrator (1) and its trolley (4) in a predetermined displacement sequence.
Arrangement according to claim 1, characterized in that the control unit includes a computer.
Method for vibrating concrete in a casting mould (6) using the vibrating arrangement of claim 1, characterized in that the displacement sequence of the internal vibrator and its trolley is automatically controlled by means of a control unit which actuates means (2, 3, 4) to displace the internal vibrator horizontally and vertically in a predetermined pattern.
Method according to claim 3, characterized in that the displacement pattern of the internal vibrator (19) is calculated by a computer.