Machine for vertical casting of pipes of concrete or a similar m

Details Machine for vertical casting of pipes of concrete or a similar m Machine for vertical casting of pipes of concrete or a similar m

1994-01-28

1995-09-12

Mackey, James P.

Plastic article or earthenware shaping or treating: apparatus

Means withdrawing trowel type shaping member from within...

425427, B28B 2126, B28B 2128

Patent

active

054492831

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention concerns a machine for substantially vertical casting of pipes of concrete or a similar material, comprising inner and outer mould parts, respectively, which are displaced axially with respect to each other during the casting process, at least one vibrator being preferably arranged upwardly in the inner mould part, an axially journalled distributor wheel being rotatably mounted on the top of said mould part, said distributor wheel having a plurality of blades for distributing the material in the space between the two mould parts.


BACKGROUND

Casting of e.g. concrete pipes generally takes place in mould systems of the above-mentioned type by filling fresh concrete from above down into the ring gap between the vertically positioned mould parts, the concrete being then vibration compressed, while the two mould parts are displaced with respect to each other. The simultaneously rotating distributor wheel on the top of the inner mould part is to serve to distribute the concrete uniformly and evenly in the ring gap, but since the relatively dry concrete, which is normally used for such purposes, is stiff and difficult to deform in a fresh non-vibrated state, it has not been possible to distribute the concrete fully satisfactorily in the ring gap with the known distributor wheels. This problem is particularly pronounced at the upper termination of the pipe and has significantly contributed to the impossibility of casting pipes with the desired narrow length tolerances and with spigot ends which satisfy the requirements made of the quality of the concrete in any respect.


SUMMARY OF THE INVENTION

In a very widely used method the spigot end is shaped by pressing a profile ring with a specific pressure down against the upper side of the concrete in the filled mould, whereby the uppermost layer of concrete is compressed and compacted in a proportion corresponding to the applied pressure. However, the resulting compression, which finally determines the overall length of the finished pipe, may vary greatly from pipe to pipe within the same series depending upon possible differences in the composition of the concrete, the charging accuracy, and the duration of the pressure, and also because of the failure of the above-mentioned conventional distributor wheels to distribute the concrete evenly and uniformly in the uppermost concrete layer of the ring gap.
It is attempted to control these factors, all of which have a generally adverse impact on the longitudinal tolerance of the pipe, in specially developed casting machines with such a great accuracy as is feasible, and in this manner it has been possible to narrow the longitudinal tolerance of the cast pipes to a certain degree with generally the same basic method. However, the achieved tolerances are still not completely satisfactory, and to this should be added that the casting machines in question have an extremely complicated structure, and that it is therefore difficult permanently to keep control over the casting process.
In another method the pipe is cast in one operation with a firm profile ring ensuring that the longitudinal tolerances are carefully observed. However, the relatively inaccessible area below this firm profile ring cannot readily be filled completely with concrete by means of the conventional distributor wheels, just as the concrete is not always compressed sufficiently with certainty, and these factors can lead to casting of pipes with spigot ends having a deficient shape and/or a too poor conrete quality.
The object of the invention is to provide a machine of the type mentioned in the opening paragraph, which, with much narrower longitudinal tolerances than known before, can repeatedly cast concrete pipes with spigot ends which have the desired full shape and a concrete quality which satisfies the made requirements with certainty.
This is achieved according to the invention by constructing the distributor wheel and its mount so stiffly that the vibrations generated by the vibrator can be transmitted to the

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patent: 5040968 (1991-08-01), Kraiss
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