Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B3/00—Producing shaped articles from the material by using presses; Presses specially adapted therefor
  • B28B3/20—Producing shaped articles from the material by using presses; Presses specially adapted therefor wherein the material is extruded
  • B28B3/22—Producing shaped articles from the material by using presses; Presses specially adapted therefor wherein the material is extruded by screw or worm
  • B28B3/228—Slipform casting extruder, e.g. self-propelled extruder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B1/00—Producing shaped prefabricated articles from the material
  • B28B1/08—Producing shaped prefabricated articles from the material by vibrating or jolting
  • B28B1/084—Producing shaped prefabricated articles from the material by vibrating or jolting the vibrating moulds or cores being moved horizontally for making strands of moulded articles

Definitions

• the invention relates to a method according to the preamble of claim 1 for manufacturing hollow-core slabs of different heights by means of an extrusion continuous- casting machine.
• the invention also relates to an assembly suited for implementing the method and further relates to a hollow- core concrete slab series that can be manufactured by virtue of the method.
• the concrete mix is extruded through a mold or nozzle section generally with the help of feeder augers.
• the casting machine moves propelled by the reaction force of the feeder augers over a casting bed and the finished product remains resting on the bed, whereon it is allowed to harden at least partially.
• long castings are made that are then trimmed to a length required at the final erection site.
• the product has a relatively large hollow-core portion that serves to reduce the product weight and amount of mix needed for casting without substantially compromising the product strength.
• the hollow cores are molded into the product with the help of core-forming members adapted to the auger rear ends.
• the feeder augers and core-forming members are aligned parallel to the longitudinal axis of the casting bed and the product, whereby the core-troweling or other core-forming member generally is nonrotatable, but may in some machine con- structions rotate with the auger.
• the function of the feeder augers is to propel the concrete mix past the molding member and the nozzle section and to simultaneously exert a compacting pressure on the mix as it is forced through the molding cross section delimited by the nozzle section and the core-forming members.
• the core- forming member is generally located so that at least a portion thereof extends into the delimited molding cross section.
• the hollow cores had a circular cross section, whereby the diameter of the auger and the diameter of the core were determined by the slab thickness, and the number of cores adapted laterally over the slab width was made as large as permitted by the minimum possible thickness of the isthmuses between the cores.
• the shape of the cores and the proportional area thereof in the overall cross-sectional area of the slab was limited, and the number of cores had to be selected according to the slab thickness.
• the most commonly used slab width is 1200 mm and the respective slab heights are standardized as 150, 200, 265, (250), 320, 400 and 500 mm.
• the envelope generated by the tips of the rotating auger flights is obviously circular, it is possible in the concurrent technology to combine such an auger with core-forming members having a noncircular cross section so that a desired shape of the core can be troweled. In fact, it is possible to use hollow cores of different cross-sectional shapes in one and the same slab.
• the feeder auger and the core-forming member are mounted on the same shaft thus acting as the core-forming assembly.
• the forming member is advantageously mounted in a pivotal manner to the core-forming assembly so as to prevent the forming member from rotating about its longitudinal axis, but instead allowing it to move in some other manner, e.g., so that a compacting motion is attained.
• Some constructions utilize a mounting technique that allows the core-forming member to perform a limited reciprocating rotation even when the shape of the core- forming member is made noncircular.
• Prior-art technology is handicapped by needing the feeder auger, the core-forming assembly and the cross section of the nozzle section that define the external dimensions of the cast article to be matched with each other so that the feeder augers will provide a suitable compacting pressure during casting without unduly obstructing the flow of the concrete mix through the cross section of the forming assembly.
• conventional continuous casting machines are generally designed for the manufacture of a single hollow-core slab type and size.
• the goal of the invention is achieved by way of shaping the top side of the core-forming member so that the shape of the initial end of the core-forming member jointed to the auger rear end is made equal to the circular envelope of the auger rear end, wherefrom it gradually changes toward the other end of the member toward a shape corresponding to the desired core dimensions of the hollow core to be manufactured, whereby also the underside shape of the nozzle section upper wall is made conforming to the varying shape of the core-forming member top surface.
• Respective gradual shaping may also be made on the underside surface of the core-forming member, whereby also the underside shape of the core-forming member can be made to change from the auger rear end dimension toward the core dimension and the shape of the concrete mix feed trough 5 is then made conforming to the varying shape of the core- forming member underside surface.
• the slab series according to the invention is characterized by what is stated in the characterizing part of claim 12.
• the invention provides significant benefits
• a single continuous-casting machine can be advantageously used for the manufacture of slabs of different heights and widths.
• the isthmus thicknesses of the slabs can be optimized irrespective of a change in the hollow core size, since the variations in the core dimensions are accomplished by way of changing the core height without changing the spacing/number of the cores in the slab lateral direction.
• To change the slab/core height only the core-forming member assembly and the top part of the mold nozzle section must be re- placed, which is a relatively uncomplicated operation. Hence, there is no need to realign the locations of the feeder augers when the core dimensions are changed.
• the aggressive shaping of the compacting beam assembly mem- bers over the nozzle section gives a novel type of means to control the degree of filling over the entire cross section and to achieve a balanced casting process.
• the top portion of the cast cross section can be subjected to a compacting pressure, whereby the compaction in this region is not solely determined by the compacting effect of mere vibration.
• the flow channels of concrete mix in the cross section of the product being cast can be kept constant, whereby the feed power exerted by the auger is at all times sufficient for the casting operation.
• the invention also makes it possible to produce slabs of different widths by way of mounting in the lateral direction a required number of core-forming members and feeder augers.
• the nozzle section is readily subdividable by means of a mold partition to a desired lateral width, as well as the concrete mix feed hopper, too.
• FIG. 1 shows a partially sectioned side view of an embodiment of an apparatus according to the invention
• FIG. 2 shows a partially sectioned side view of another embodiment of an apparatus according to the invention
• FIG. 3 shows a cross section of a slab manufactured using the apparatus illustrated in FIG. 1;
• FIG. 4 shows a partially sectioned side view of a still another embodiment of an apparatus according to the invention.
• FIG. 5 shows a cross section of a slab manufactured using the apparatus illustrated in FIG. 4;
• FIG. 6 shows a partially sectioned side view of a still another embodiment of an apparatus according to the invention.
• FIG. 7 shows a cross section of a slab manufactured using the apparatus illustrated in FIG. 6.
• FIG. 8 shows different kinds of slab cross sections that can be manufactured by virtue of the invention.
• the concrete casting assembly has a construction similar to conventional continuous-casting machines.
• a hollow-core slab is cast onto a casting bed 1 or mold that is adapted to support the travel of the casting machine on wheels 9.
• the operating controls of the machine are mounted in an enclosure 2 at the rear of the machine.
• This enclosure houses, e.g., the controls of the feeder augers and reinforcement steel inserters and the operating controls of vibrators possibly adapted to the augers.
• the concrete mix is poured into a feed hopper 3 located above feeder augers 4.
• Plural augers 4 are used in parallel, whereby the number of the augers is equal to the number of hollow cores in the product.
• a concrete mix flow guide or feed trough 5 that delimits the concrete mix flow channel formed under the auger 4.
• the shape of the feed trough 5 may be kept unchanged from run to run, or, advantageously, the shape of the trough is always arranged conforming to the shape of the core-forming member.
• the nozzle section At the rear end of the auger 4 begins the delimited cross section of the flow channel later called the nozzle section. This nozzle section is delimited by the casting bed 1, the sidewalls of the machine and a compacting beam assembly 7 located above the feeder auger 4.
• the compacting beam assembly 7 is adapted to be movable in the vertical and horizontal directions by means of an electric-motor-driven actuator 8.
• This actuator device may be adapted to make the trowel beam assembly perform either a slow compacting movement or a vibratory motion at a higher frequency.
• the appro- priate compaction technique is selected according to the product being manufactured and the properties of the concrete mix being used.
• a characterizing feature of the present invention is related to the conforming shaping of the combination formed by core-forming member 6 and the trowel beam assembly 7.
• the height of the core-forming member 6 is made larger than the largest diametral dimension of the feeder auger 4. Accordingly, the largest outer dimension of the core-forming member 5 must be adapted to mate with the rear end of the auger at their mutual interface.
• the shape of the trowel beam assembly 7 is contoured conforming to the shape of the core-forming member 6, which means that the assembly has an upward flaring portion 10 that conforms in the downstream direction of the concrete flow to the increasing cross section of the nozzle section in a manner allowing the core-forming member to flare in the portion of the nozzle section to the desired dimension of the hollow cores being cast.
• the trowel beam assembly may be mounted in an adjustable or replaceable manner.
• FIG. 3 is shown the cross section of a slab manufactured using the above-described embodiment of the continuous-casting machine.
• the diameter of the core-forming member 6 is substantially equal to the diameter of the feeder auger 4, whereby the trowel beam assembly 7 is made straight in the same manner as the perimeter of the core-forming member.
• the construction shown in FIG. 6 has the vertical dimension of the core-forming member 6 made smaller than the diameter of the auger 4, whereby the trowel beam assembly must be provided with a slanted portion 12 that conforms to the tapering height of the core-forming member 6.
• FIGS. 5 and 7 illustrate hollow- core slabs manufactured using these embodiments of the casting machine.
• the core widths as well as the thicknesses of the intercore isthmuses are kept constant, but the height of the cores are varied according to the slab height in order to optimize the slab dimensions.
• the shape of the hollow cores can be varied by changing the core-forming members. Obviously, such a change necessitates a simultaneous replacement of the overlying trowel beam assembly into one conforming to the shape of the new core-forming member.
• the above-described diagrams illustrate a method through which modular core-forming member sets for larger and smaller heights of hollow cores may be obtained by modulating the basic shape of the core-forming member. In this fashion, it is possible to manufacture slabs with standardized size of, e.g., 200/4, 265/4, 320/4, 400/4 and 500/4 on one and the same continuous-casting machine.
• the spacing between the core-forming members and the lateral locations of the feeder augers are kept constant, while the thicknesses of the intercore isthmuses as well as of the top and bottom shell portions of the hollow-core slab may be varied and adjusted to desired values in the fashion determined by the shaping of the overlying trowel beam assembly and/or the underlying concrete mix flow guide trough.
• the intermediate slab size of FIG. 4 may be defined to represent the basic shape of the core-forming member adapted to mate with the diameter of the feeder auger and suited for the manufacture of a 320/4-size slab, for instance. Then, the other modular heights of the hollow cross section shown in FIG. 2 and FIG.
• the nozzle section extrudes a slab 265 mm thick, and yet the compaction space of the concrete mix behaves in a con- trolled manner by virtue of the proper shaping.
• this kind of aggressive shaping of the trowel beam assembly offers a novel method of casting process control.
• trowel beam assembly not only as a concrete mix flow guide and retarder, but also as a backing surface in ramming compaction for the concrete mix to be compacted irrespective of the frequencies and amplitudes used in the compacting movement .
• the trowel beam assembly can be implemented either using a beam assembly of the kind described above or as a combination of beams or trowel plates that comprises at least a compacting beam set typically followed by a trowel member.
• the set of compacting and trowel beams is arranged to be tiltable into different angles and positions so that the inclination of the assembly can be adjusted conforming to the shape of the core-forming member, whereby the height difference between the ingoing and outgoing edges of the assembly in the flow direction of the concrete mix is from 10 to 400 mm, typically in the order of a few centimeters.
• the ingoing end of the trowel beam assembly can be adjusted even above auger, while the outgoing end is simultaneously located below the top level of the rotational envelope perimeter of the auger.
• the shape of the trowel beam assembly and the core-forming member may be contoured different from a simple slanted plane, e.g., as an appropriately curved plane.
• the shape of the surface formed by the trowel beam assembly or other part of the nozzle section that delimits the flow channel must be adapted to conform to the shape of the core-forming member so that the height difference between the ingoing end and the outgoing end of the trowel beam assembly is within a 50 % tolerance equal to the height difference between the top level of the rotational envelope perimeter of the auger and the top level of the core- forming member that trowels the hollow core of the slab.
• the term core-forming member is used when reference is made to that part of the member over which the concrete is shaped to make a desired core into the slab. In practice, this part is located there where the core-forming member has its largest or smallest outer diameter.
• nozzle section is used when reference is made to the confined cross section that determines the shape of the outer surfaces of the produced article. While the apparatus embodiment according to the invention described above has no means for shifting the position of the feeder augers in the lateral direction, a provision must be arranged for shifting the augers in the vertical direction if the difference between the selected sizes of the core-forming members is substantial. Normally, the lateral dimension of the core-forming members is kept constant even if the height of the members is varied. In FIG. 8 is shown a series of slab cross sections in which the slab manufactured in the basic shape and width has six hollow cores, while the narrower one has only three cores.
• the narrower slab in this kind of modular series of slabs could be manufactured by way of, e.g., using a partition to delineate the nozzle section during the casting process.
• the diameter of the auger may vary over its length, whereby diametral dimensions of the core- forming member must be evaluated relative to the largest diameter of the auger, that is, the rotational envelope perimeter of the maximum diameter of the auger.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Mechanical Engineering (AREA)
• On-Site Construction Work That Accompanies The Preparation And Application Of Concrete (AREA)
• Devices For Post-Treatments, Processing, Supply, Discharge, And Other Processes (AREA)
• Holo Graphy (AREA)
• Press-Shaping Or Shaping Using Conveyers (AREA)

Applications Claiming Priority (3)

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• 1999
  • 1999-08-23 FI FI991792A patent/FI19991792A/fi unknown
• 2000
  • 2000-08-22 AU AU67056/00A patent/AU6705600A/en not_active Abandoned
  • 2000-08-22 AT AT00954695T patent/ATE275466T1/de not_active IP Right Cessation
  • 2000-08-22 EP EP00954695A patent/EP1212180B1/fr not_active Expired - Lifetime
  • 2000-08-22 WO PCT/FI2000/000712 patent/WO2001014114A1/fr active IP Right Grant
  • 2000-08-22 DE DE60013615T patent/DE60013615T2/de not_active Expired - Lifetime

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