METHOD AND APPARATUS FOR FORMING FROGS IN THE SIDES OF A CONCRETE ELEMENT

Abstract: This publication discloses a method and apparatus for forming frogs (7) in the sides of a slipformed concrete element (5), especially a hollow-core slab. In accordance with the inven­ tion, the frogs (7) are formed in the sides of the element (5) by removing cast material from the sides by a reciprocative scraping action. The reciprocative movement parallel to the side of the element (5) is effected with a drive motor (8) and a lever assembly (l7). By means of the method, it is possible to obtain a desired frog shape and depth without damaging the side surfaces.

Description: The present invention relates to a method for forming frogs in the sides of a concrete element in accordance with the preamble of claim 1. The invention also provides an apparatus for the implementation of the method. From DE-C-862 420 it is known to cut recesses into a clay strand by means of a tensioned wire. This wire is maintained undisplaceable in the advance direction of the clay strand and is moved upwardly and downwardly only, whereby the recess is cut into the clay strand. US-A-2 075 038 relates to the provision of holes in a ceramics block, the recesses being made in that a cutter proper is pressed into the block. To reinforce the joints of hollow-core concrete elements in the horizontal direction, the sides of the slabs are provided with a sufficient number of frogs, suitably deep, which are filled with concrete during the construction for jointing the adjacent slabs to each other. In practice, the requirement of frogs varies greatly with the magnitudes of horizontal forces imposed on the joints between the slabs. In prior art methods the frogs are formed during the slipform­ ing process by pressing indentations with a toothed wheel or a toothed belt mat into the sides of the formed element. A disadvantage of the prior art technique is the difficulty with which the desired frog shape is achieved by pressing because the additional compression of the concrete is counter­ acted by the binding forces of the compacted and sheared con­ crete, which tend to retain the original form of the element, consequently inhibiting the forming of frogs with a desired depth of indentations. Also, the surroundings of the frog indentations tends to raise from the imposed pressure, leading to a deformed shape of the element sides. Additionally, the prior art technique makes it difficult to change the depth or mutual distance of frogs, which requires changing the pressing roller or belt mat. Achieving a desired frog depth may be impossible with the conventional technique because a deeper frog depth presumes a high compressing force, and excessive compression will break the hollow-core construction. The present invention aims to overcome the disadvantages of the aforementioned technique, and to achieve a completely novel method for the fabrication of frogs in hollow-core elements. The invention is based on forming the frogs in the element by removing cast concrete from the elements by a reciprocative scraping action. More specifically, the method in accordance with the invention is characterized by what is stated in the characterizing part of claim 1. Furthermore, the apparatus in accordance with the invention is characterized by what is stated in the characterizing part of claim 5. The invention provides appreciable benefits. The frog-forming apparatus in accordance with the invention can be visibly mounted to allow the continuous monitoring of its operation. The shape, depth and mutual distance of the frogs is freely adjustable, in addition to the possibility of discontinuing the frog-forming process when required. In the following, the invention is exemplified in detail with the help of the exemplifying embodiment shown in the attached drawings. Figure 1 shows in side view, parallel to the cores, an embodi­ ment of the frog-forming apparatus, in which scraping is per­ formed in the direction of the hollow cores. Figure 2 shows a frog-forming apparatus in accordance with Figure 1 viewed perpendicular to the hollow cores of the hollow-­ core element. Figure 3 shows in side view another embodiment of the frog-­ forming apparatus, in which the reciprocative scraping movement is parallel in respect to the hollow cores of the hollow-core element. Figure 4 shows in top view a frog-forming apparatus in accord­ ance with Figure 3. Figure 5 shows in side view a frog-forming apparatus, in which the reciprocative scraping movement is perpendicular in respect to the hollow cores of the hollow-core element. Figure 6 shows in top view a frog-forming apparatus in accord­ ance with Figure 5. Figure 7 shows in top view an adaptation for transferring the scraper to and away from the element. Figure 1 shows a possible embodiment for the implementation of the frog-forming apparatus. The integrated equipment is attached to a slipforming machine. A shaft 20 of a gear box 19 of a motor 1 is attached eccentrically to a crankshaft 2, reciprocatingly movable, which generates for a scraper 3 a perpendicular movement in relation to the side of a hollow-core element 5, with which movement the scraper 3 can be connected or disconnected to operate. The actual scraping action paral­ lel to hollow cores 6 of the element is achieved with a moving side mold 4, driven by, for instance, an electric motor (not shown). A frog 7 is formed when the crankshaft 2, driven by the motor 1, draws the scraper 3 against the side of the element 5 so that the scraper 3 removes cast concrete from the element 5 when moving in a reciprocative manner paral­ lel to the hollow cores 6. The desired frog depth is adjusted by the stroke length of the crankshaft 2, determined by the eccentricity of the attachment of the crankshaft 2 to the motor. The length and mutual distance of the frogs 7 is deter­ mined by both the rotation speed of the motor 1 and the operat­ ing speed of the slipforming machine. Figure 3 illustrates a mechanism for the implementation of the reciprocative movement. The shaft of a motor 8 is attached to a lever assembly 17, which converts the rotation movement into a reciprocative movement parallel to the hollow-cores 6 of the element. The lever assembly is connected to a case 10, which glides reciprocatingly on a rail 11, connected to the slipforming machine. A second motor 9 operates as a drive for a lever assembly 18, which transfers reciprocatingly the scraper 3, connected with joints to the case 10, to and from the side of the element. Figure 5 illustrates a mechanism, with which the reciprocative scraping movement is adapted perpendicular to the longitudinal axis of the hollow cores 6. In this case, the rail 11 is mounted in a vertical position to achieve the desired direction of movement. Principally, the direction of the scraping movement is not limited to those directions mentioned in the foregoing but all directions essentially parallel to the plane of the element side are technically feasible and possible to implement. The rate of the scraping movement can be 1...100 Hz. Figure 7 shows an embodiment in which a wedge-shaped member 13, attached to a wheel 12 of the slipforming machine, implements the reciprocative movement of the scraper approximately perpen­ dicular to the side of the element 5. An auxiliary lever 14 is connected to the shaft of the scraper 3. A peg 15 of the auxiliary lever remains in contact with the wedge member 13 during the rotation of the slipforming machine wheel 12, and when the peg 15 is at the thickest part of the wedge 13, also the scraper 3 is deepest in the element 5. The return movement of the scraper 3 is effected with a spring 16, connected to the scraper shaft and with its other end connected to the chassis of the slipforming machine.

Claims: 1. A method for forming frogs (7) in the sides of a slipformed concrete element (5), especially a hollow-core slab, characterized in that - the frogs (7) are formed by removing cast concrete from the sides of the element (5) by a reciprocative scraping action in a plane at least approximately parallel to the side of the element (5). 2. A method in accordance with claim 1, characterized in that support members (8, 17, 10, 11) attached to the slipforming machine, are used for generating a reciprocative movement in a plane approximately parallel to the side of the element (5), a scraper (3) connect­ ed to the support members (8, 17, 10, 11) is transferred repe­ tetively to contact approximately perpendicularly the side of the element (5) by means of transfer members (9, 18 or 13, 14, 15) so that the reciprocatingly moving scraper (3) forms a frog in the side of the element, with a depth deter­ mined by the transfer members (9, 18 or 13, 14, 15), and the scraper is detached from the side of the element (5) by means of return members (9, 18 or 16). 3. A method in accordance with claim 1 or 2, characterized in that the reciprocative movement parallel to the side of the element (5) is generated by means of a rotary motor (8) and a lever assembly (17). 4. A method in accordance with claim 1, 2 or 3 characterized in that the perpendicular movement of the scraper (3) in relation to the side of the element (5) is generated by the rotary motor (9) and a lever assembly (18). 5. A method in accordance with the claim 1, 2 or 3, characterized in that the perpendicular movement of the scraper (3) in relation to the side of the element (5) is implemented by means of a wedge-shaped member (13) adapted to a wheel (12) of the slipforming machine, an auxiliary lever (14), a peg (15) on the auxiliary lever, and a spring (16). 6. An apparatus for forming frogs (7) in the sides of a slip­ formed concrete element (5), especially a hollow-core slab, characterized by - support members (8, 10, 11, 17), which are capable of being moved reciprocatingly parallel to the side of the element (5), - a scraper (3), which is connected to the support members (8, 10, 11, 17) and by means of which the frogs (7) are capable of being fabricated in the side of the element (5), and - transfer members (9, 18, or 13, 14, 15, 16) by means of which the perpendicular movement of the scraper (3) is capable of being implemented in relation to the side of the element (5). 7. An apparatus in accordance with claim 6, characterized in that the support members com­ prise a drive motor (9), a lever assembly (17), a case (10), and a rail (11). 8. An apparatus in accordance with claim 6 or 7, characterized in that the transfer members com­ prise a drive motor (9) and a lever assembly (18). 9. An apparatus in accordance with claim 6 or 7, characterized in that the transfer members com­ prise a wedge-shaped member (13) attached to a wheel (12) of the slipforming machine, by means of which the perpendicular movement can be implemented, an auxiliary lever (14), and a peg (15), with which the perpendicular movement can be con­ nected to the scraper (3), and a spring (16), with which the return movement of the scraper (3) can be effected. 10. An apparatus in accordance with claim 6, characterized in that the scraping rate of the scraper (3) is 1...100 Hz, preferably about 50 Hz.

Inventors: SEPPAENEN, AIMO, Seppänen, Aimo
Applicants: KT-SUUNNITTELU OY
Application year: 1987
Main classification: B28B11
IPC codes: B28B11, B28B1, B28B5