Pumps – Slurry pumps
Patent
1998-01-06
1999-11-30
Kashnikow, Andres
Pumps
Slurry pumps
417519, 417532, F04B 1502
Patent
active
059931817
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for feeding concrete or other thick materials from a container into a feeding pipe by means of two feeding cylinders which are alternately connectable by a switching device to the container or the feeding pipe, with the feeding pistons of the feeding cylinders alternately performing a suction stroke and a pressure stroke, and the average piston speed during the suction stroke being at least temporarily greater than during the pressure stroke, and to an apparatus for performing the method.
2. Description of the Related Art
A corresponding method and a corresponding apparatus are known from German patent specification 3525003. The gist of the known method consists in the feature that the first feeding cylinder has not yet finished its pressure stroke, while the second feeding cylinder already starts with its pressure stroke at a lower feeding speed. After the first feeding cylinder has finished its pressure stroke, the switching operation of the switching device is started, while the second feeding cylinder continues its feeding operation at a lower feeding speed. Such a procedure has the effect that the concrete in the second feeding cylinder is already advanced, so that after the switching operation of the switching device the concrete column in the feeding pipe has no chance to perform an excessive rebound movement. This method, and the apparatus used therefor, have proved to be successful in general. However, in the present technical field, demands for more and more efficient methods for concrete feeding machines have been made recently. For instance, serious attempts have been made to increase the length of the feeding pipe and thus, in particular, the feeding height. Since in the known method the pumping operation is carried out at a reduced feeding speed during the switching period, a small pulsation is created in the feeding flow. Such a pulsation could be disregarded under the feeding conditions which have so far prevailed, but will lead at the feeding heights that are now demanded, and thus at the great lengths, for instance in the case of an arm of a concrete conveying vehicle, to vibrations at the feeding pipe end.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore the object of the present invention to provide a method and an apparatus for feeding concrete from a container into a feeding pipe, whereby irregularities in the feeding flow are further reduced.
According to the present invention such an object is achieved by a generic method in which during the switching period t.sub.u of the switching device the two feeding cylinders are substantially separated from the container at least temporarily and are short-circuited together to form a joint connection with the feeding pipe, and in this state the one feeding piston is still finishing its pressure stroke and the other feeding piston already starts its pressure stroke at the same time, with the corresponding feeding piston performing its suction stroke not before the short circuit has substantially been cancelled again and the associated feeding cylinder has been connected to the container.
A mere feeding at a reduced feeding rate is avoided by the inventive method during the switching period t.sub.u. This is accomplished by short-circuiting the two feeding cylinders which in the short-circuited state can alternate during the feeding operation at a full feeding speed without any losses in the switching period. As a result of the short-circuiting operation, the concrete column is automatically compressed in the feeding cylinder which starts the pressure stroke. Pulsation impacts are avoided in this method by the continuous feeding flow provided for. The method of the invention is suited in a particularly advantageous manner for concrete pumps having a single switching device (for instance a single pivot pipe) which cooperates with the two feeding cylinders at the same time.
In an advantageous variant of the method, even more attention is paid to
REFERENCES:
patent: 3663129 (1972-05-01), Antosh
patent: 4533300 (1985-08-01), Westerlund et al.
patent: 5458470 (1995-10-01), Mannhart et al.
Hudelmaier Gerhard
Hudelmaier Gotz
Hudelmaier Jorg
Hudelmaier Ulrike
Kashnikow Andres
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