Liquid purification or separation – Filter – With movable means to compress medium
Patent
1995-08-02
1997-07-01
Walker, W. L.
Liquid purification or separation
Filter
With movable means to compress medium
210407, 210408, 210413, B01D 2964
Patent
active
056434502
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/AT94/00012, filed Feb. 2, 1994.
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a filter apparatus for fluids, in particular for thermoplastic synthetic plastics material fluid, with continuous cleaning of the surface of the filter, comprising a housing for a stationary, metallic, substantially planar filter to which the fluid to be filter is supplied through at least one upstream channel and from which the cleaned fluid is conducted off the housing through at least one downstream channel, at least one scraper provided with some scraping edges lying in a common plan and following curved lines, at least one drive means for rotation of the scraper so that the scraper strokes over the upstream surface of the filter and thereby strips off the impurities adhering thereon and carries them towards the center of the filter, wherefrom the impurities are conveyed off by at least one worm through at least one outlet channel extending from the center of the filter and leading out of the housing.
Filter apparatus for thermoplastic synthetic plastics fluid operating continuously in the most cases show as a filter a cylindric sleeve fixed in the housing (EP-A-411,163), which sleeve on its outside is surrounded by the scraper in form of a spiral band. This, inter alia, has the disadvantage the problems arise during assembly or disassembly, for example for service purposes, due to the length of the filter cylinder, in particular for bigger units. The filter sleeve consists of thin sheet metal and, therefore, is comparatively weak. When axially assembling or disassembling such a filter sleeve, deformations cannot be avoided, in particular due to the scraper that frictionally engages the filter sleeve. In order to ensure the necessary penetrability of the filter openings, these openings must show a greater diameter on the outside of the filter shell that at the inner side. Economically, such openings can only be produced by lasers, and this has a consequence that these bores are produced at the planar filter element which after production of the bores is rolled round and is welded at the location of the joint. This makes it difficult to obtain the necessary exactness. It is not possible to product the filter openings after rolling round the sleeve because the laser operators cannot be introduced into the sleeve. A further disadvantage consists in a lack of operation reliability. This results from that the spiral band, in dependency of its direction of rotation, tends either to jam at the filter sleeve or to surround it only loosely. In the first case there is at least the disadvantage of an increased power requirement in order to overcome the arising friction forces, and what is more, there is a breakdown of operation or a tearing of the filter element. In the second case, the scraper does no more sufficiently engage the filter and, therefore, cannot more reliably convey off the impurities that collect at the outside of the filter.
For this reason, it has been already proposed to provide a continuously operating filter apparatus with a planar sieve (DE-A-3,335,949, DE-A 2,324,581) and to construct it in the initially described or in a similar manner. However, it is of disadvantage within this construction, that it is suitable only for relative small throughputs. The reason for this is that the planar sieve plate used within this know construction tends to deformations under the pressure of the supplied fluid containing impurities, which pressure may amount to about 350 bar, so that the scraping edges of the scraper do not more exactly contact the surface of the sieve plate to be cleaned. Therefore, there is soon a soiling of the sieve plates and therefore a breakdown of operation. Similar disadvantages occur within further know apparatus in which stripper elements are disposed a small distance apart from the filter (GB-A 640,276) or in which instead of scrapers impellers are provided (U.S. Pat. No. 4,657,636). Restrained textile filters (FR-A 1,356,496) cannot be used for
REFERENCES:
patent: 3361263 (1968-01-01), Street
patent: 4657636 (1987-04-01), Satomi
Bacher Helmut
Schulz Helmuth
Wendelin Georg
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