Liquid purification or separation – With repair or assembling means
Patent
1993-01-19
1994-05-03
Sever, Frank
Liquid purification or separation
With repair or assembling means
21033301, 210340, 210411, B01D 2901, B01D 3912
Patent
active
053084845
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a filtration apparatus for synthetic thermoplastics material, with a housing, in which at least one supply channel for the material to be filtered and at least one discharge channel for the filtered material are provided, and with at least one carrier body displaceably guided in the housing between a filtration position and a back wash position for a screen arrangement having at least two nests of screens, whereby in the filtration position, distribution spaces, arranged at the inflow sides of the nests of screens are joined by means of inflow flow channels to the supply channel or the supply channels and collection spaces arranged at the outflow side of the nests of screens are joined by way of outflow channels to the discharge channel or the discharge channels and, in the back wash position, filtrated material is fed from the collection space of a nest of screens via a back flow channel into the collection space of another nest of screens to be cleaned and the distribution space of this other nest of screen discharges the contaminations from the apparatus, whereas in this back wash position the outflow channel of this other nest of screens is closed off.
Such a filtration apparatus is known (EP-B 250 695). It has the advantage that, during the cleaning of the screen arrangements, the supply of melt to the machine, which follows on the filtration apparatus, mostly an extruder with a mould, connected thereto, is not interrupted, but--even if with reduced throughflow--further runs continuously so that also a considerable pressure increase in the flow channel ahead of the filtration apparatus is avoided. However, it is disadvantageous that a relatively long back flow channel is used, through which also no continuous flow takes place so that thereby a thermic damage of the synthetic plastics material (cracking) present therein is possible.
In a further known filtration arrangement of somewhat deviating construction (EP-A 314 024) four nests of screens are located in a carrier body, which is displaceable in longitudinal direction, which nests of screens are located in pairs in series in longitudinal direction of the carrier body. Also in this design it is disadvantageous that parts of the channel used for backwashing and disposed in the housing are filled in each production position with synthetic plastics melt but no flow takes place so that the danger of cracking exists.
The present invention has as object to further improve the known arrangement, in particular regarding the simplicity of the construction and regarding the increase of the quantity of the melt volume supplied to the screen to be cleaned, which is equivalent to an improvement of the intensity of backwashing and therewith a screen cleaning, however, in particular regarding shortening the back washing channel and avoiding synthetic plastics melt standing in it. The invention solves this task by the features that the back flow channel which is disposed fully in the carrier body, passes through a separation wall of the carrier body between the two nests of screens and directly joins the collection spaces of the nests of screens of that carrier body together.
In such a manner the melt used for the back flow, which is branched off from the melt flowing from the discharge channel in the collection space of the one nest of screens, merely is led in the carrier body to the collection space of the other nest of screens to be cleaned because the back flow channel, which can be formed by an aperture of the separation wall does not leave the carrier body, that is, this back flow channel does not lead also through the housing or via the outflow channel, as is the case in the design described initially. The avoidance of redirections of the melt flow used for back flow also causes better pressure relationships at the inflow side of the nest of screen subject to the back flow so that a better cleaning results, inasmuch the overall back flow current concentrates only on one screen surface, which, in comparison to the know designs, resul
REFERENCES:
patent: 4332541 (1982-06-01), Anders
Bacher Helmut
Schulz Helmuth
Wendelin Georg
Wendelin Gerhard
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