US3534450A - Apparatus for moulding hollow concrete elements - Google Patents

Description

H. .J. G. IPSEN ,450

APPARATUS FOR MOULDING HOLLOW CONCRETE ELEMENTS Get. 20, 1970 Filed May 13, 1968 United States Patent 3,534,450 APPARATUS FOR MOULDING HOLLOW CONCRETE ELEMENTS Harald Jannik Gerald Ipsen, Vedbaek, Denmark, assignor to Aktieselskabet Dansk Spaendbeton Filed May 13, 1968, Ser. No. 728,509

Int. Cl. B2811 7/28 U.S. Cl. 25-41 3 Claims ABSTRACT OF THE DISCLOSURE Apparatus for casting concrete slabs with passages therethrough in which cores to form the passages are laid in the mould and are advanced one or some at a time by applying a force to one or some cores and the reaction force to the remainder.

In the manufacture of concrete elements in the form of plates it is known to cast a considerable number of elements in series in a mould having parallel cores which are moved in the longitudinal direction of the mould in rhythm with the pouring of the concrete.

In practice, in order to move the cores, a trolley or carriage can be utilized which is moved in the longitudinal direction of the mould, either with the aid of friction-wheels engaging the edges of the mould, or with the aid of a winch, the carriage being connected to the set of cores in such a manner that these are moved in the mould together, be it in a continuous manner or by steps. However, in order to achieve this object, it is necessary to utilize a considerable traction effort on the trolley, moreover, it is difficult to avoid damaging to a greater or lesser degree the freshly-cast elements which have not yet set.

While taking these drawbacks into consideration, it has been proposed to advance the cores in succession, more precisely, in such a fashion, that each time only one core is advanced towards a new casting position, while the other cores remain stationary. By doing this, one can certainly obtain a reduction in the drawing effort or the carriage, but the method is difiicult to put into effect and, moreover, it has been proved in practice that an appreciable risk of damage to the freshly-cast elements always exists when the cores are freed in their exit position, by overcoming adhesion. In this respect it is unfortunate that the transmission between the cores and the traction fittings to the carriage, particularly in the case where the traction is effected by cable, operates with a considerable degree of elasticity, for this brings about a rather significant jerky movement of the cores and of the carriage at the moment, when the adhesion of the cast mass is being overcome.

It is an object of the invention to provide an improved method of advancing a set of cores by which the risks of such damage being caused to the elements, can be reduced and which is easy to put into effect by employing simple, mechanical means and a minimum of manual operations, and there is provided according to the invention a method of successively moving a set of parallel cores, at least one by one, in a mould for the manufacture of concrete elements, e.g. ceiling elements for the division of storeys in buildings, characterized in that a force is applied to at least one core in a direction to advance that core, the reaction to said force being applied to and withstood jointly by the other cores immobilised in the mass.

In this case too, a carriage can be utilized which is movable in the longitudnnal direction of the mould, but the role of this carriage is reduced to merely control or guide the front end of each core and to support the source "ice of energy necessary for advancing of the cores. Its own movement can be created through the advancing of the cores, so that no further exterior advance fittings are required, such as a winch or a set of friction wheels. Thus, in the method according to the invention it is, so to speak, a question of a direct transfer of force between the immobilized cores and the core or cores moved at any given moment, and since consequently the length of the path of the force as well as the elasticity of the transmission means can be reduced to a minimum, one thus has the possibility of ensuring a regular and controlled movement of the cores, even at the moment when the maximum adhesion is being overcome, a requisite condition for making it possible to avoid damaging the cast elements.

The transfer of force between the cores can be effected by mechanical means, e.g. with the aid of a horizontal shaft extending transversely to the longitudinal direction of the cores and provided with a set of angularly offset cams situated each in front of its cores. During a fraction of the rotation of the shaft, each cam will pull or push its core in the mould, while the other cams simultaneously advance the carriage, since the immobilized or stationary cores, during this time, serve as a fixed support.

However, in a preferred embodiment of the invention, the reaction is uniformly distributed by hydraulic means among the several immobilized cores. By doing this, one achieves that each of the immobilized cores supports the same portion of the total force of reaction, and the hydraulic fluid, e.g. oil, permits the obtention of exactly the desired traction effort on the core or cores which are being moved. Furthermore, the hydraulic transmission of force easily permits the modification of the length of core travel in their forward movement.

Moreover, the invention relates to an apparatus for carrying out the method explained, this apparatus comprising in a manner known per se, a mould and a number of parallel cores, as well as a hydraulic control device for the moving of the cores. According to the invention, the apparatus is characterised in that the control device comprises a plurality of hydraulic cylinders fixed to one another and each comprising its own piston, which is coupled to the front end of a corresponding core, the cylinder cavities on the rear sides of the pistons being in communication with each other, while the cylinder cavities on the opposite side of the pistons are connected to a common pump and a corresponding tank through valve means controlling the admission and discharge of the hydraulic fluid.

In such an apparatus, the cylinder unit is moved forward in relation to the mould, and the starting of the movement of the various cores merely requires a corresponding control of the valve means, which can be achieved in an entirely automatic manner with the aid of well-known control elements. Thus, if oil under pressure is being admitted to the front end of one of the cylinders, the movement of the piston in this cylinder on the one hand creates a movement of the associated core, and on the other a transfer of oil from the cavity behind this piston towards the cavities behind the pistons of the other cylinders. The cavities in front of the pistons, in these cylinders are connected with the tank, and as these pistons are kept stationary as a consequence of their connection with the immobilized cores, the result of this will be that the whole of the cylinder unit moves forward in the same direction as that of the movement of the first piston in its cylinder. When the number of cylinders 'is n, the cylinder unit is moved by a length l/n -l, where L is the movement of the first piston in relation to the cylinder unit. Consequently, the absolute length of the stroke of this piston and thereby also the absolute travel of the corresponding core will be When the travel has been completed, the same process is resumed by the following core. It therefore appears that the working of the apparatus is extremely simple and that the movement of the set of cores can be carried out very rapidly.

In the apparatus according to the invention, it may be advantageous to place between the outlet of the pump and the tank a by-pass or shunt provided with an adjustable valve. In this way, the extent of travel of each piston can be individually adjusted, so that the starting and arrival point of movement of each core can be determined at will.

In order that the invention may be well understood there will now be described an embodiment of the apparatus according to the invention, given by way of example only, reference being had to the accompanying drawing which is a diagrammatic plan view of a mould shown in chain-dot lines with a core advancing mechanism.

The mould intended to be utilized in conjunction with the apparatus comprises a bottom 1 and two edge rims 2; this mould can be of a very great length, e.g. 100 m. or more. Such a mould can for instance be used in the manufacture of concrete ceiling elements having longitudinal passages, and for this purpose the apparatus comprises a plurality of cores 3, which in the example shown are seven in number and of which only the extreme front part is shown. These cores 3 have to be moved over the length of the mould 1, 2 in rhythm with the pouring operation. In the embodiment shown in the drawing, this movement is being effected hydraulically, each core 3 being associated with a cylinder A, B, C, D, E, F, or G, which together form a unit or a block movable over the length of mould. The block of cylinders may for instance be carried by a frame, which by means of wheels rests on the edge rims 2. For the sake of clarity, this has not been shown in the figure. Each cylinder has a piston 4 coupled to the corresponding core 3 by means of a rod 5. The spaces or cavities behind the pistons 4 of the cylinders A to G communicate through a pipe 6, and at the opposite or front end each cylinder is connected to a common distribution valve 8 by means of a pipe 7. This valve, together with a hydraulic pump 9 that is driven by an electric motor 10 and is placed in a tank 11 containing the hydraulic fluid, may be mounted on the same frame as the block of cylinders. A feed pipe 12 connects the pump 9 with the inlet of the distribution valve 8, while a return pipe 13 permits the return of the fluid from the distribution valve to the tank 11. The feed pipe 12 comprises a by-pass valve 14 from which a by-pass conduit or shunt leads to the return pipe 13.

As can be seen from the drawing, the cores 3, as Well as the pistons 4 are, in the position shown, staggered in relation to each other in the longitudinal direction of the mould. Thus, the core 3 associated with cylinder G is the one furthest in front while the core 3 associated with cylinder D is the hindmost one, the other cores occupyirrg intermediate positions.

In the position shown, the distribution valve 8 which may be of any type known per se, shall conduct fluid under pressure via the pipe 7 towards the front cavity of cylinder D, while for the other cylinders an unobstructed passage exists through the pipes 7 and the distribution valve 8 towards the tank 11 via the return pipe 13. The result of this is, that the piston 4 in cylinder D is moved in this cylinder, which on the one hand causes a forward traction on the corresponding core in the mould, and on the other hand a transfer of the quantity of fluid behind the piston towards the other cylinders via pipe 6. Thus, a backward pressure is being exerted on each of the cores 3 associated with the other cylinders, but this pressure is insufficient for creating a movement of the cores, and instead the entire block of cylinders and thereby also the distribution valve 8 and of the pump 9 will be advanced in the opposite direction, i.e. towards the top of the drawing.

When the piston in cylinder D has reached its extreme position, i.e. the top position in the drawing, the block of cylinders will have been moved forward to such an extent that the piston 4 of cylinder B will be in its lowest position in this cylinder. Then the adjustment of the distribution valve 8 is changed so as to conduct the fluid under pressure to cylinder B and to receive fluid returning from the other cylinders. This changing of the adjustment of the distribution valve 8 may, e.g. be obtained by means of a camshaft driven by a motor, not shown.

In the process described, the different cores 3 may be alternately advanced in the mould 1, 2 over a length corresponding to the stroke of the pistons, and during these movements the pistons retain their mutual staggering. In certain cases it may, however, be desirable to place the cores on the same line, that is to say, in such a manner that they are placed exactly side by side in the mould, and this is the reason why the by-pass or shunt valve 14 is inserted in the feed pipe 12 from the pump 9. It is then possible to control the quantity of fluid under pressure admitted to each cylinder in such a Way that the corresponding piston does only travel a certain pre-deterrnined fraction of its complete stroke, the set of pistons, and thereby also the set of cores 3, being thus brought into exact lateral relationship.

I claim:

1. In an apparatus for manufacture of concrete elements having cavities therein, said apparatus comprising a mould, a number of parallel cores, and a hydraulic control device for moving the cores, the improvement according to which said control device comprises a plurality of hydraulic cylinders fixed relative to each other and each comprising a piston which is coupled rearwardly to the front end of a corresponding core, the cylinder cavities in front of the pistons being in communication with each other, while the cylinder cavities on the opposite side of the pistons are connected to a common pump and a corresponding tank through distribution valve means adapted to selectively control the admission of hydraulic fluid to said opposite side of at least one cylinder to advance its associated piston and core, and cause the discharge of hydraulic fluid from the cylinder cavity in the front of said at least one cylinder into the cylinder cavities in front of the remaining cylinders.

2. Apparatus as claimed in claim 1 in which said cylinders are mounted to move as a unit lengthwise of said mould.

3. Apparatus as claimed in claim 1 comprising an adjustable valve between the pump outlet and the tank.

References Cited UNITED STATES PATENTS 3 047,928 8/1962 Carl 25-41 3,095,628 7/1963 Norton et a1. 25-34 X 3,181,222 5/1965 Palmer 2541 FOREIGN PATENTS 654,982 1/ 1938 Germany. 43 5,962 10/1926 Germany.

ROBERT D. BALDWIN, Primary Examiner US. Cl. X.R.

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