Liquid purification or separation – Filter – With residue removing means or agitation of liquid
Reexamination Certificate
1999-06-07
2001-05-08
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Filter
With residue removing means or agitation of liquid
C210S413000
Reexamination Certificate
active
06227380
ABSTRACT:
TECHNICAL FIELD
The invention relates to a filter apparatus for liquids containing impurities, in particular solid particles, and more particularly to a filter apparatus for filtering plasticised thermoplastic synthetic plastic material, comprising a housing in which there is disposed at least one stationary, substantially flat filter to which the liquid to be cleaned is supplied in the region of its periphery by means of at least one supply channel, and from which the cleaned fluid is conducted off and out of the housing through at least one downstream channel, and further comprising at least one scraper element which has a scraping edge that is pressed against the upstream side surface of the filter and is movably connected to a scraper carrier which can be rotated by a drive means around an axis disposed substantially perpendicular to the upstream-side surface of the filter, whereby the scraper element strips off the impurities adhering to this surface and conveys them towards the center of filter, wherefrom the impurities are conveyed off the housing by means of at least one screw through at least one discharge channel starting from the center of the filter and extending out of the housing.
BACKGROUND OF RELATED ART
Such a filter apparatus is known (WO 94/17981). Within this known apparatus, each one of the scraping edges is constituted by a plurality of scraper elements separated from each other and pressed against the filter either by means of springs or by means of the pressure of the supplied liquid to be filtered. In the latter case, the scraper elements are movably connected to the scraper carrier by means of pins directed perpendicular to the filter surface so that each element can move along the pins, and each scraper element is so designed that the pressure exerted on it by the supplied liquid in direction towards the filter is greater than the pressure acting in the opposite direction. Both embodiments, however, suffer from the disadvantage that a solid particle can adhere between the filter and the scraper element, so that it is not engaged by the scraping edge of the scraper element. Then, this solid particle keeps the scraper element spaced apart from the filter surface to be cleaned so that the respective scraper element becomes inactive. This leads not only to a decrease of the cleaning effect on the upstream-side filter surface, but frequently causes also an additional wear on this surface by solid particles conveyed always along a circle and having frequently sharp edges.
SUMMARY
The invention has at its object to avoid this disadvantage of the known apparatus in a simple manner. The invention solves this task by the fact that at least one scraper element is mounted on the scraper carrier swivellable around an axis and protudes from this axis towards the filter obliquely and in direction of motion of the scraper carrier, the scraping edge of the scraper element being pressed towards the filter during revolution of the scraper element by the counter-pressure of the liquid to be cleaned. Therefore, the respective scraper element is so mounted on the scraper carrier that it can freely oscillate or swing, however, it protudes from the scraper carrier in direction of its rotation. As soon as the revolution of the scraper carrier around its axis of revolution is started, the counter-pressure exerted onto the scraper element by the fluid to be cleaned presses this scraper element against the filter surface to be cleaned so that there an effective scraping action occurs. There are no dead spaces in which solid particles can rest, so that there are no particles hindering this function of the scraper element, so that always a reliable function of the scraper element is ensured, if the construction is suitably made.
According to a preferred embodiment of the invention, the scraper element has a straight-lined scraping edge extending parallel to the swivel axis, the outer end of the scraping edge advances or leads relative to a radial line starting from the axis of rotation of the scraper carrier and extending to the inner end of the scraping edge, when seen in direction of revolution of the scraper carrier. By this disposition of the swivel axis of the scraper element and its scraping edge a conveyance of the impurities scraped off the filter surface to be cleaned towards the center of the filter is automatically obtained, when the scraper carrier rotates, and these impuritites are taken up by at least one screw and are conveyed off the housing through the discharge channel.
As a rule, a plurality of scraper elements are swivelably connected to the scraper carrier in the described manner, and these scraper elements are arranged star-shaped with respect to the axis of revolution of the scraper carrier. However, always two or more scraper elements can be disposed along an arm of such a star so that their scraping edges constitute extensions with respect to each other, e.g. along curved paths, as this is the case within scraper elements of the initially described known apparatus. As a rule, however, one single scraper element per said arm of the star is sufficient. In order to ensure that the impurities scraped off by the scraper element are reliably conveyed towards the center of the filter element, according to a further embodiment of the invention a protrusion on the scraper carrier may be provided adjacent to the inner end of the scraping edge of the scraper element which protrusion is directed towards the center region of the scraper carrier and conveys the impurities towards the center of the filter and to the discharge channel. Preferably, within the spirit of the invention, this protrusion is formed as a ledge extending with its longitudinal extension in direction of the scraping edge of the scraper element.
According to a suitable further embodiment of the invention, the scraper element carries a wearing member which constitutes the scraping edge and preferably is exchangeable. As soon as a wear occurs at this wearing member, this wearing member is exchanged so that an effective function is obtained again.
A particular favourable embodiment of the inventions consists in that the supply channel is conducted into a space between two adjacent filters which preferably are disposed in parallel to each other, the scraper carrier being common for both filters and carries on its both sides scraper elements cooperating with the filters, which scraper elements preferably are disposed in pairs, each of which scraper elements carries on its end facing the filter a member constituting the scraping edge, preferably a wearing member, which member has two scraping edges and the scraper elements of the one side of the scraper carrier are exchangeable against the scraper elements of the other side of the scraper carrier. Thereby, the working life time of each scraper element or, respectively, of its wearing member can be doubled.
A further improvement of the filter action can be obtained according to a further embodiment of the invention by the fact that at least one supply channel leads to a distribution space which surrounds the filter or the filters along at least of a major part of its periphery or their periphery, respectively, which distribution space is in connection via a plurality of openings provided in an intermediate wall with the upstream-side of the filter or, respectively, with the space disposed between the two filters. The distribution space ensures that the filter surface over at least the major part of its periphery, if desired even over the entire periphery, is supplied with the liquid to be cleaned. The openings in the intermediate wall constitute a preliminary filter which retains coarse impurities, e.g. metal clips, stones and the like. Thereby, the real filter is relieved and treated with care.
REFERENCES:
patent: 600928 (1978-06-01), None
patent: 3937930 (1991-05-01), None
Bacher Helmut
Schulz Helmuth
Wendelin Georg
Barry Chester T.
Salter & Michaelson
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