Patent Application
20090295031
The present invention relates to casting of a concrete product with a substantially horizontal slipform casting process, wherein concrete mix is fed through a limited cross-section for manufacturing a concrete product of a desired form. More precisely, the invention is related to the motion of feeding elements of an apparatus to be used in slipform casting.
In traditional casting machines of extruder type, concrete mix is fed from a concrete tank by means of hydrostatic pressure to feed screws, said feed screws extruding the concrete mix by means of rotating and reciprocating motion through a limited cross-section for providing a concrete product of a desired form. When casting hollow-core slabs, the feed screw is followed by a hollow-core mandrel forming a hollow core to the product to be cast. In addition, the aggregate formed by the feed screw and the hollow-core mandrel perform reciprocal motion for compacting the concrete mix. A mass chute is provided under and partly around the feed screw for guiding concrete mix around the hollow-core mandrel. Above the hollow-core mandrel and partly also above the feed screw there is located a compacting beam of the upper surface for defining the upper surface of the product to be cast, said compacting beam comprising a reciprocating throweling beam compacting and smoothing the upper surface of the product to be cast. The sides of the product to be cast are defined by sidewalls moving back and forth in the longitudinal direction, the movement compacting and smoothing the side surfaces of the product to be cast.
The feed screw performs compacting of the concrete mix by means of rotating motion causing the pressurized feed of the concrete mix to the limited cross section, and by means of reciprocal compacting motion.
In the solution disclosed in the Patent publication FI 118175, arched or in several phases eccentric feed screws are used, which when performing the rotating motion and the longitudinal reciprocal motion, compact the concrete mix by pressing it against each other and the mass chute and the side walls of the mold. Thereby, due to the eccentricity of the feed screws, the space between the screws and the space between the screw and the mass chute alternately increases and decreases, when the feed screws rotate, whereby the spaces, when they are at the largest, are filled with the concrete mix flowing from the concrete mix tank effected by the hydrostatic pressure. When the feed screws continue to rotate, the concrete mix in these spaces is compressed and compacted due to this compression.
In the solution in accordance with the publication FI 118175, the eccentricity of the eccentric feed screws is relatively big and the rotating motion is slow. Thus, in this solution, the eccentric motion is slow and has long movements. The compacting effect of the solution is limited to the area of the feed screw, where the concrete mix is not compacted or partly compacted.
In the solution according to the present invention, a feed screw acting as feeding means and an eventual hollow core forming means (a hollow-core mandrel) following the same, are brought to a rotational motion, which means substantially a circular motion on the plane transversal to the longitudinal direction of the aggregate formed by the feed screw and the hollow-core mandrel. This circular motion of the aggregate formed by the feed screw and the hollow-core mandrel intensifies the compacting of the concrete mix in addition to the rotating motion and the reciprocal longitudinal motion of the traditional feed screw.
The circular motion of the feed screw, and if necessary, of the hollow-core mandrel, according to the invention intensifies the compacting of the concrete mix over the total length of the feed screw and the hollow-core mandrel, and by means of the rotating direction of the circular motion, the intensifying of the compacting can be targeted to the desired direction and location of the limited cross section.
In the solution according to the invention, the ratio of the speed of the circular motion of the feed screw to the rotating speed of the feed screw is preferably ca. 10:1, and the radius of the circular motion is relatively small, which means that the eccentricity of the circular motion is small. This provides quick, short-motion compacting effect for the whole length of the feed screw and the eventual hollow-core mandrel following the same. This compacting caused by the circular motion effects in the area of the tail end portion of the feed screw and the forward end portion of the eventual hollow-core mandrel, where the pressure of the concrete mix is the strongest and the concrete mix still in a plasticized state.
More precisely, the solution according to the present invention is characterized by what is stated in the characterizing part of Claim 1, and the apparatus according to the present invention by what is stated in the characterizing part of Claim 5.
The invention will be described by way of example in more detail in the following, with reference to the enclosed drawings, wherein
Essential parts of the traditional solution shown in
The rotating motion of the feed screw 1 is provided by the drive motor 4, from which the rotating motion is transmitted to the drive shaft 3 of the feed screw with the drive chain 5. In addition to the rotating motion, the feed screw 1 performs reciprocal compacting motion provided by the drive motor 6 and transmitted by a drive lever system to the drive shaft 3 of the feed screw.
In the solution according to the invention, shown in
Slide bearings 7 enable the usual rotating motion of the feed screw, and the reciprocal compacting motion of the feed screw. The circular motion of the feed screw 1 is provided by rotating the eccentric bushing 8 supported by the bearings 9 to the frame of the slipform casting machine by means of a drive motor for separate circulating motion (not shown) and a drive chain 10.
As shown in
In the solution according to the invention, the circular motion of the feed screw and the eventually following hollow-core mandrel can be parallel with the rotating motion of the feed screw, or opposite thereto. The circular motion parallel with the rotating motion of the feed screw intensifies the feed of the concrete mix, whereas the opposite circular motion intensifies the compacting of the concrete mix.
In the solution according to the invention, the rotating speed of the circular motion of the feed screw and the eventually following hollow-core mandrel is preferably ca. from 400 to 800 rotations per minute, and the radius of the circular motion, that is the eccentricity, is preferably about from 1 to 3 mm.
The solution according to the invention is not limited to the slipform casting machine moving on a casting bed, but it can also be implemented as a fixed casting station, whereby the cast concrete product is moved out from the casting station with casting beds movable with respect to the fixed casting station.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20085541 | Jun 2008 | FI | national |
