SLIP-FORM CASTING MACHINE FOR FABRICATION OF ELONGATED CONCRETE PRODUCTS

Abstract: A slip-form casting machine for the fabrication of elongated concrete products comprises a feed hopper (1), an auger (6) for exerting pressure onto a concrete mix to be cast, and a casting mould (10,11). The casting mould (10,11) is of tubular construction plugged at one end, and the auger (6) is connected to a casting machine body (18) which substantially conforms with the cross-section of the casting mould (10) and is movable with respect to the mould (10) in order to facilitate slip-form casting of a product (7) with an elongated shape in the axial direction of the casting mould.

Description: The present invention relates to a slip-form casting machine for the fabrication of elongated concrete products such as pillars, beams, pylons, fence poles and the like. The conventional technology applied in the fabrication of elongated concrete products is based on casting fluid concrete mix into prefabricated moulds. The actual casting process involves the feeding of the fluid mix into a mould and then vibrating the mould either by manual means or mechanical vibrators so as to compact the concrete. The disadvantages of the prior art production technology are the high proportion of manual work required and the difficulties involved in compacting the concrete sufficiently, necessitating the use of a highly fluid concrete mix and resulting in a significantly increased hardening time and a significantly higher consumption of cement in order to achieve a comparable final strength. The resulting concrete product also exhibits inferior fire- and low-temperature-resistance properties as well as reduced corrosion resistance in comparison with products produced from a stiff concrete mix. Alternatively DE-C-203 244 discloses a slipform casting machine for the fabrication of elongated concrete products comprising a feed hopper, a casting mould and body portion which supports an auger to compact a concrete mix fed into the mould. The aim of the present invention however is to overcome the disadvantages associated with the aforedescribed prior art technology and to achieve an entirely new kind of slip-form casting machine for producing elongated concrete products. The invention is based on fabricating the elongated products by using ground-wet, extremely stiff concrete mix extruded into a closed, elongated, tubular mould, and provides a slip-form casting machine for the fabrication of elongated concrete products including a feed hopper or like means for a concrete mix to be cast, a casting mould which is of tubular construction plugged at one end and is capable of receiving the concrete mix from the feed hopper, and a casting machine body which substantially conforms with the cross section of the casting mould and which carries an auger for exerting pressure on the concrete mix fed into the mould, the casting machine body being movable with respect to the casting mould in order to facilitate the slip-form casting of a product with an elongated shape in the direction of the casting mould characterised in that the auger is provided with its free end part tapered into a wedge shape in order to facilitate the fabrication of solid elongated products. The invention allows moulded concrete elements to be made with smooth surfaces of high quality, and improves the final strength of the concrete significantly in comparison with conventional grades. A specific embodiment of the invention will now be described, by way of example, with reference to the attached drawings, in which: Figure 1 shows a cross-sectional side view of a slip-form casting machine in accordance with the invention; Figure 2 shows a fence with posts manufactured using concrete elements fabricated in a slip-form casting machine in accordance with the invention; Figure 3 shows telegraph poles manufactured using concrete elements fabricated in a slip-form casting machine in accordance with the invention; and, Figure 4 shows railway sleepers manufactured using concrete elements fabricated in a slip-form casting machine in accordance with the invention. The slip-form casting machine shown in Figure 1 moves in a tubular mould 10, which is closed at one end by a mould bottom element 11, and is used to fabricate elongated cast concrete products. The casting machine is hoistable from above the mould 10 by a hoisting eyelet 12. Prior to the casting process a concrete storage container 1, which also functions as a concrete feeding hopper, is filled with stiff, ground-wet concrete. A motor 3 actuating a feeder screw 2 is then started to transfer concrete mix by means of the feeder screw 2 into an extruding space 4 within the mould. Simultaneously, a motorized drive mechanism 5 is started which actuates the casting machine and delivers power to rotate an auger 6 for operating on the mix fed into the mould. The auger 6 is rotatably mounted on bearings on the machine body 18, which is in turn, essentially compliant with the cross-section of the mould 10 and is movable axially with respect to the casting mould 10. The auger 6 is appropriately shaped to develop, from its rotational movement, a simul- taneously feeding and compacting effect on the mix, thereby obviating the use of any auxiliary vibrating equipment. However, if necessary, vibrating equipment may easily be incorporated within the body of the auger 6. At the start of the casting process, the auger 6 typically rests against the mould bottom 11. During the process while rotating, feeding, and compacting the mix, the auger 6 experiences a reactive counterpressure from the already compacted concrete 7, which forces the casting machine to move longitudinally within the tubular mould 10. Consequently, the casting operation is performed in a continuous slip-form process until the desired concrete element is cast. The feed of concrete mix into the mould 10 is based on an extrusion method. The auger 6 feeds the mix into the mould and simultaneously compacts the concrete to the desired extent. The machine uses extremely stiff concrete mix allowing the cast concrete to retain its desired shape in the mould 10. The cross-sectional dimension and the thickness of the element wall 7 can be altered by adjusting either the size of the mould 10 or the shape of the auger 6. In order to produce a solid elongated concrete product the free end part of the auger 6 is tapered into a wedge shape denoted by dashed lines 9 allowing the space left by auger 6 to be filled as the slip-form casting machine moves. The casting operation is most advantageously performed in vertical moulds, but the system can also be applied to the manufacture of horizontal elongated structures of tubular shape. In the latter case, the concrete mix hopper 1 is obviously orientated in a different manner allowing the hopper 1 to be filled from above. The mould construction may also be arranged to open at the side so that the stiff, undeformable concrete product may be stripped from the mould immediately after casting and transferred to a curing oven thus factilitating the reuse of the mould. Consequently, a slip-form casting machine in accordance with the invention may be used to optimize the production of elongated cast structures that may later be trimmed as appropriate for different applications. Practical applications for products fabricated using a slip-form casting machine in accordance with the invention are numerous. Illustrated in Figure 2 is a fence construction in which rotting wooden posts and rusting steel poles are replaced by concrete posts 15 fabricated by a casting machine in accordance with the invention. Telegraph poles 16 such as those illustrated in Figure 3 can also be manufactured using a slip-form casting machine of the aforedescribed construction. As illustrated in Figure 4, a slip-form casting machine is also adaptable to produce concrete railway sleepers 17.

Claims: 1. A slip-form casting machine for the fabrication of elongated concrete products (7) including a feed hopper (1) or like means for a concrete mix to be cast, a casting mould (10, 11) which is of tubular construction plugged at one end and is capable of receiving the concrete mix from the feed hopper, and a casting machine body (18) which substantially conforms with the cross section of the casting mould (10) and which carries an auger (6) for exerting pressure on the concrete mix fed into the mould, the casting machine body (18) being movable with respect to the casting mould (10) in order to facilitate the slip-form casting of a product (7) with an elongated shape in the direction of the casting mould characterised in that the auger (6) is provided with its free end part (9) tapered into a wedge shape in order to facilitate the fabrication of solid elongated products. 2. A machine according to claim 1, characterised in that the casting mould (10) is orientated in a vertical position.

Inventors: TOMMINEN, HANNU
Applicants: LOHJA PARMA ENGINEERING LPE OY
Application year: 1988
Main classification: B28B21
IPC codes: B28B21, B28B1