NZ626355B - Method, apparatus and hollow core forming member for casting concrete products by slipform casting - Google Patents

Abstract

Disclosed is a method, apparatus (1) and core forming member (4) for casting concrete hollow core products. The disclosure notes that hollow core concrete slabs have webs of uniform thickness. End areas of the slab usually provide support and are subject to maximum shear stresses. The present apparatus (1) allows the core forming member (4) to be adjusted during the casting process to produce thicker end areas and relatively thinner webs distal to the end areas. The apparatus (1) includes a slipform mould (5, 6, 7) defining a limited cross-section for the product to be cast. A feed screw (3) feeds concrete mix through the slipform mould in at least one feeding stage. The apparatus (1) further comprises the core forming member (4) which includes a linear motion device to change the width of the core forming member (4) during the slipform casting process. tus (1) allows the core forming member (4) to be adjusted during the casting process to produce thicker end areas and relatively thinner webs distal to the end areas. The apparatus (1) includes a slipform mould (5, 6, 7) defining a limited cross-section for the product to be cast. A feed screw (3) feeds concrete mix through the slipform mould in at least one feeding stage. The apparatus (1) further comprises the core forming member (4) which includes a linear motion device to change the width of the core forming member (4) during the slipform casting process.

Description

METHOD, APPARATUS AND HOLLOW CORE FORMING MEMBER FOR CASTING CONCRETE PRODUCTS BY SLIPFORM CASTING Technical Field The present invention relates to casting of prefabricated concrete products with a substantially horizontal slipform casting process, where the concrete mix is fed at least in one step though a limited cross-section moving progressively along with the cast.

Background Art Any discussion of the prior art throughout the specification is not an admission that such prior art is widely known or forms part of the common general knowledge in the field.

Several different slipform casting methods and devices are known in the art. The two main slipform casting methods for casting concrete products are extruder and slipformer methods. In the extruder method concrete mix is fed in a single feeding stage from a concrete mass container to feed screws which extrude the concrete mix to a slipform casting mould defined by the upper surface of a casting bed and side and top plates of a casting machine. When casting hollow core slabs, the feed screws are followed by core forming mandrels forming the cores in the form of longitudinal voids in the casted concrete product. The compacting of the concrete product to be cast is achieved by vibrating and/or levelling motion of the side and top plates, and the forming of the cores is secured by the back-and-forth compacting motion of an entity formed of the feed screw and the attached core mandrel. The casting machine moves along the casting bed driven by the reaction force from the feed screws extruding the concrete mass and optionally with an additional drive motor. The ready cast product remains on the casting bed as the casting progresses.

In the slipformer casting method concrete mix is fed in at least two feeding stages from a concrete mass container to a slipform casting mould. In the first feeding stage concrete mass is fed to a lower portion of the casting mould formed by a top surface of a casting bed and side plates of a casting machine. The first feed stage of concrete mix is followed by vibrating shoes and core-forming mandrels that, by vibrating the concrete mix, compacts the cast concrete mix and forms the final shape of the lower part of the concrete product to be cast. In the second feeding stage concrete mix is fed onto the end portions of the core-forming mandrels and on the previously cast concrete mix for casting the upper portion of the product to be cast, after which the concrete mix is compacted with a vibrating plate defining the upper surface of the slipform casting mould and located at the rear part of the casting machine. The ready cast product remains on the casting bed as the casting progresses.

Slipform casting is generally used for casting long products with uniform cross-section, such as massive or hollow core slabs, which are cut to predefined lengths after the concrete is cured.

Patent publication EP 1 843 882 B1 discloses a slipform casting method and apparatus for casting concrete products with cores, where the thickness of the cast concrete product can be changed by changing the height of the core forming mandrel and the location of the top plate of the slipform casting mould during the casting process. The disclosed apparatus may also be used to cast products with different thicknesses.

In hollow core concrete slabs thickness of the webs between the cores is one of the main features defining a shear stress capacity for the slab, especially in the end areas of the slab, where the end areas are generally used for providing support for the slab in buildings.

The thickness of the webs between the cores is thus dimensioned based on the maximum shear stresses affecting the end areas of the slab. These maximum shear stresses do not affect the central area of the slab, but since the core forming members forming the hollow cores and the webs in the slab cannot be changed in slipform casting machines during the casting process, the webs have uniform thickness throughout the cast slab. This causes increased weight and decreased load capacity, for example, for the slabs.

One known solution for increasing the strength of the end areas of a hollow core slab is to fill the ends of the cores with concrete mass after the slipform casting process and thus add concrete in the critical areas of the slab. This however increases the use of concrete mass and slows down the manufacturing process.

Disclosure of Invention In the present invention the width of cores, and thus also thickness of the webs between the cores, is changed in a slipform casting process by changing the width of core forming member(s) during casting. This allows casting thicker webs in the end areas of hollow core slabs, which increases durability against shear stresses of these areas, and the middle area or portion of the slab may be cast with thinner webs, which decreases the weight of the slab and use of concrete mass in the casting process.

In the present invention the height of the core forming member may advantageously also be changed during the slipform casting process. This allows the whole cross- section of the cores to be changed during the casting process to optimize the best cross-sectional area of the cores for each section of the slab to be cast.

Advantageously the width and/or height of the core forming member are changed only on part or portion of the length of the core forming member. This allows the upstream end of the core forming member to substantially maintain its height and width during the casting process and only the width and/or height of the downstream end of the core forming member is changed with suitable gradual increase or decrease of these dimensions along the length of the hollow core forming member, for example.

Alternatively a section or portion of the length of the core forming member is provided at the upstream end of the core forming member, wherein the section has fixed unchangeable cross-section. This section advantageously provides a fixing point for fixing the width and/or height changeable section or portion of the core forming member to the casting machine.

The present invention is advantageously used in extruder-type casting methods and apparatuses, where the concrete mass is fed through a slipform casting mould in the form of a restricted cross-section progressing along the cast with at least one feed screw, and the core forming member is connected at the down-stream end of the feed screw. In this extruder-type casting process concrete mass is advantageously fed through the slipform casting mould in only one feeding stage.

In the present invention the casting distance the slipform casting process and apparatus has proceeded may be measured, and this measurement data may be used to control the changing of the width and/or height of the core forming member so that correct cross-section of the core may be cast in correct portions and sections along the hollow core slab. This may be done with an automatic control system of the slipform casting machine following and measuring the distance cast with the machine, and based on this measurement data and design data of the slab to be cast input in the automatic control system, the automatic control system changes the width and/or height of the core forming member(s) at determined points of the slipform casting process.

The changing of the width and height of the core forming member of the invention may be implemented with suitable electrical, pneumatic or hydraulic means, with suitable cylinders or other linear movement devices for example, located advantageously inside the core forming member. These means are advantageously used to move surface parts forming the outer surface of the core forming member, of which surface parts there are at least two, preferably at least four, for changing the outer dimensions of the core forming member on at least part of the length of the core forming member.

The present invention also relates to a core forming member of a slipform casting machine for casting concrete hollow core products, the core forming member including at least two surface parts forming the outer surface on the length of the core forming member, and means for changing the distance between the at least two surface parts for changing the width of the core forming member.

Therefore, the present invention provides a method for casting a hollow core concrete product with a substantially horizontal slipform casting process, wherein concrete mass is fed in at least one feeding stage through a limited cross-section, moving progressively along with the cast, and at least one core is formed in the concrete product to be cast with a core forming member, characterized in that the thickness of at least one web between or adjacent to the or each core of the concrete product is changed during the slipform casting process by changing the width of the at least one core forming member.

Preferably the height of the core forming member is also changed during the slipform casting process.

Preferably the width and/or height of only part of the length of the core forming member is changed.

Preferably the concrete mass is fed through the limited cross-section with at least one feed screw, and one core forming member is connected at the downstream end of the or each feed screw.

Preferably a measurement is obtained by measuring casting distance and the changing of the width and/or height of the core forming member is controlled based on the measurement.

The present invention also provides an apparatus for casting a hollow core concrete product with a substantially horizontal slipform casting process, the apparatus including a slipform mould defining a limited cross-section for the product to be cast, means for feeding concrete mix through the slipform mould in at least one feeding stage, and at least one core forming member, characterized in that the apparatus includes means for changing the width of the at least one core forming member during the slipform casting process.

Preferably the apparatus includes means for changing the height of the core forming member during the slipform casting process.

Preferably the apparatus includes means for changing the width and/or height of only part of the length of the core forming member.

Preferably the apparatus includes at least one feed screw for feeding concrete mass through the slipform casting mould, one core forming member being connected at the downstream end of the or each feed screw.

Preferably the apparatus includes means for measuring casting distance travelled by the apparatus.

The present invention further provides a core forming member of a slipform casting machine for casting concrete hollow core products, said core forming member including at least two surface parts forming an outer surface along the length of the core forming member, characterized in that the core forming member includes means for changing the distance between the at least two surface parts for changing the width of the core forming member.

Preferably upstream ends of the at least two surface parts are connected to each other and the means for changing the width of the core forming member are adapted to move only downstream ends of the surface parts.

Preferably the core forming member includes at least four surface parts forming the outer surface along the length of the core forming member, and the core forming member further includes means for changing the height of the core forming member.

Brief Description of Drawings By way of example only, embodiments of the invention and their advantages are explained in greater detail below with reference to accompanying drawings, where: Figure 1 shows schematically an extruder-type slipform casting apparatus of the invention, Figures 2A-2C show schematically a top view of a core forming member of the invention in different adjustment positions, Figures 3A-3C show schematically a top view of an alternative core forming member of the invention in different adjustment positions, and Figures 4A and 4B show schematically a back view of different core forming members of the invention.

Best Mode for Carrying Out the Invention Figure 1 shows schematically an extruder-type slipform casting apparatus 1, which is operated during a slipform casting process by feeding concrete mass from a concrete mass container 2 to feed screws 3. The feed screws extrude the concrete mass in a slipform casting mould formed by a casting bed 5, side plates 6, and a top plate 7.

Connected at the downstream end of the feed screws 3 are core forming members or mandrels 4, which also restrict the slipfom casting mould and form cores as longitudinal voids in the slab to be cast. The concrete mass is compacted during the slipform casting process by the rotating motion of the feed screws 3 extruding the concrete mass achieved with a drive motor 8, and by the back-and-forth movement in the casting direction of the feed screws and the core forming members 4 achieved with a drive motor 9. The outer surfaces of the product to be cast are compacted by the back-and-forth movement of the side plates 6, and vibrating and/or throwelling motion of the top plate achieved with a drive motor 10.

Figures 2A-2C schematically show the core forming member 4 of the invention attached to the feed screw 3 in different adjustment positions. In the embodiment of figures 2A-2C the core forming member 4 includes two surface sections 4a and 4b forming the outer surface of the core forming member, where the surface section 4a is located partially inside the surface section 4b. Further, the surface sections 4a and 4b are connected to each other so that the upstream ends of the surface sections define a substantially constant cross-section, but the connection between the surface sections allows the downstream ends of the surface sections to be moved towards and away from each other. This can be achieved with a swivelling connection between the surface sections 4a and 4b at their upstream ends, for example, and allows the core forming member to be fixed securely to the end of the feed screw 3.

In the position of figure 2A the hollow core forming member 4 has uniform width along its length; this configuration corresponds to the known core forming members.

In the position of figure 2B the downstream ends of the surface sections 4a and 4b of the core forming member 4 are moved in a direction away from each other to provide a core forming member that has a gradually widening cross-section along its length.

Since the downstream end of the core forming member 4 defines the cross-section of the core formed in the product to be cast, the adjustment position of figure 2B creates a wider core in the slab to be cast and thus also thinner webs between the cores in the slab.

In the position of figure 2C the downstream ends of the surface sections 4a and 4b of the core forming member 4 are moved in a direction towards each other to provide a core forming member that has a gradually thinning cross-section along its length. This adjustment position creates a thinner core in the slab to be cast and thus also thicker webs between the cores in the slab.

Figures 3A-3C schematically show a top view of an alternative core forming member 4 of the invention in different adjustment positions. The core forming member 4 and the positions shown in figures 3A-3C correspond to figures 2A-2C with the exception that the core forming member includes section 4x at the upstream end of the core forming member. This section 4x of the core forming member has a substantially uniform unadjustable cross-section along its length, and thus section 4x can be used to fix the core forming member 4 at the downstream end of the feed screw 3 easily, that is similarly to the connection between the feed screw and any prior art unadjustable core forming member. Further, the section 4x also makes the connection between the section 4x and the adjustable surface sections 4a and 4b much easier since the section 4x provides a non-rotating part for fixation and thus facilitates a better starting point for creating an adjustable connection that withstands the pressure of concrete mass inside the slipform casting mould.

Figures 4A and 4B schematically show a back view of different hollow core forming members of the invention.

In the embodiment of figure 4A, the core forming part 4 includes two surface sections 4a and 4b, where the surface section 4a is partially inside the surface section 4b. The surface sections 4a and 4b are connected to each other with a suitable swivel connection (not shown) at their upstream ends, and near their downstream ends the surface sections are connected to each other with a suitable linear motion device 11, such as a hydraulic or pneumatic cylinder or an electric linear motor, for proving means and power to adjust the position of the downstream ends of the surface sections with respect to each other. The embodiment of figure 4A allows adjustment of the width of the downstream end of the core forming member 4.

In the embodiment of figure 4B, the core forming part 4 includes four surface sections 4a, 4b, 4c and 4d. In this embodiment the upstream ends of the surface sections 4a, 4b, 4c and 4d are connected at the overlapping area to the other overlapping surface section with a suitable swivel connection (not shown). The surface sections 4a and 4b are connected to each other near their downstream ends with suitable linear motion device 11, which allows the width of the downstream end of the core forming member 4 to be changed. The surface sections 4c and 4d are connected to each other near their downstream ends with another suitable linear motion device 12, which allows the height of the downstream end of the core forming member to be changed.

The specific exemplifying embodiments of the invention shown in figures and discussed above should not be construed as limiting. A person skilled in the art can amend and modify the embodiments of the core forming member of the invention described above, for example, in many evident ways within scope of attached claims.

Thus the invention is not limited merely to the embodiments described above.

Claims (13)

Claims 1.

1. A method for casting a hollow core concrete product with a substantially horizontal slipform casting process, wherein concrete mass is fed in at least one feeding stage through a limited cross-section, moving progressively along 5 with the cast, and at least one core is formed in the concrete product to be cast with a core forming member, characterized in that the thickness of at least one web between or adjacent to the or each core of the concrete product is changed during the slipform casting process by changing the width of the at least one core forming member.

2. The method according to claim 1, wherein the height of the core forming member is also changed during the slipform casting process.

3. The method according to claim 2, wherein width and/or height of only part of 15 the length of the core forming member is changed.

4. The method according to any one of claims 1 to 3, wherein the concrete mass is fed through the limited cross-section with at least one feed screw, and one core forming member is connected at the downstream end of the or each feed 20 screw.

5. The method according to any one of claims 1 to 4, wherein a measurement is obtained by measuring casting distance and the changing of the width and/or height of the core forming member is controlled based on the measurement.

6. An apparatus for casting a hollow core concrete product with a substantially horizontal slipform casting process, the apparatus including a slipform mould defining a limited cross-section for the product to be cast, means for feeding concrete mix through the slipform mould in at least one feeding stage, and at 30 least one core forming member, characterized in that the apparatus includes means for changing the width of the at least one core forming member during the slipform casting process.

7. The apparatus according to claim 6, wherein the apparatus includes means for 35 changing the height of the core forming member during the slipform casting process.

8. The apparatus according to claim 7, wherein the apparatus includes means for changing the width and/or height of only part of the length of the core forming member.

9. The apparatus according to any one of claims 6 to 8, wherein the apparatus includes at least one feed screw for feeding concrete mass through the slipform casting mould, one core forming member being connected at the downstream end of the or each feed screw.

10. The apparatus according to any one of claims 6 to 9, wherein the apparatus includes means for measuring casting distance travelled by the apparatus.

11. A core forming member of a slipform casting machine for casting concrete 15 hollow core products, said core forming member including at least two surface parts forming an outer surface along the length of the core forming member, characterized in that the core forming member includes means for changing the distance between the at least two surface parts for changing the width of the core forming member.

12. The core forming member according to claim 11, wherein upstream ends of the at least two surface parts are connected to each other and the means for changing the width of the core forming member are adapted to move only downstream ends of the surface parts.

13. The core forming member according to claim 11 or 12, wherein the core forming member includes at least four surface parts forming the outer surface along the length of the core forming member, and the core forming member further includes means for changing the height of the core forming member. 3 4 5 3 3 3 4 4 4 4b 4b 4x 4x 4x 4 4 4 4b 4a