Liquid purification or separation – Casing divided by membrane into sections having inlet – Each section having inlet
Patent
1992-11-05
1994-03-29
Sever, Frank
Liquid purification or separation
Casing divided by membrane into sections having inlet
Each section having inlet
21032187, 210356, 210388, 210411, 210427, B01D 6306
Patent
active
052981614
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase of PCT/CH 91/00275 filed 20 Dec. 1991 and based, in turn, upon Swiss national application 31/91 of 7 Jan. 1991 under the International Convention.
The invention relates to an apparatus for cleaning a working liquid of an EDM or ECM machine. More particularly, the invention relates to an apparatus for the cleaning of a machining liquid of an electroerosive or electrochemical machining apparatus having a device for sedimenting contaminants from the liquid coming from a machining zone, a membrane filter for filtering the liquid, and a device for backwashing the filter.
The working liquid for electroerosive machining of workpieces (EDM) is, as is known, a dielectric with very low electrical conductivity, which in ram erosion by means of a shaped electrode [Die Sinking]is composed of hydrocarbons and in erosive cutting by means of wire electrodes is composed of deionized water. As the working liquid for electrchemical machining of workpieces (ECM) an electrolyte with higher electrolyte conductivity is provided which contacts the workpiece. The machining liquid used in both processes for the machining of the workpiece is passed in a continuous circulation. During the machining period, the purity and electrical conductivity of the machining liquid varies continuously with the increasing contamination which has an undesirable and disadvantageous influence on the machining process. Consequently, filters, either as cup filters or. membrane filters are introduced to always remove the contaminants arising as a consequence of the machining in the machining liquid. The cup filters formed as filter mats or filter cartridges have the disadvantage that during their operation, the filter characteristics vary in an uncontrolled manner. The contaminant particles filtered from the machining liquid block the pores so that the throughput of the filtered liquid is reduced. A backwashing of the cup filter to clean it is not possible so that contaminant particles penetrating into the pores cannot be removed. Consequently, in more recent times, membrane filters have been employed which can be freed from the contaminant particles by means of backwashing. The cleaning effect can be improved, therefore, because the contaminant particles can accumulate a number of times upon the membrane surface.
In printed Japanese application 62-24917, there is shown a membrane filter for an electroerosive machining apparatus which is arranged in a partial region of an ion and only filters a part the total machining liquid. The greater part of the machining liquid is filtered through a cup filter.
Printed European patent application 0321751 shows a filtering device for the precleaning of a contaminated machining liquid of an erosion machine by sedementation through treatment with a flockulating agent and then feeding to a tube-shaped membrane filter, wherein the greater part of the machining liquid flows past the filter wall unfiltered and only is employed to flush or clean the filter wall. The smaller proportion of the machining liquid passes perpendicularly through the membrane and is filtered. Over relatively short time intervals, the membrane filter is backwashed by means of the cleaned machining liquid to which compressed air is supplied and is cleaned. The newly contaminated liquid is fed again to the total filter process including precleaning and filtering. The cleaning effect is unsatisfactory because many parts of the membrane surface are backwashed nonuniformly which leads to a nonuniform distribution and penetration depth of contamination particles over the entire membrane surface. As a result an elevated backwashing pressure and a greater volume of the cleaned machining liquid is required for the backwashing. The increased backwashing pressure can be detrimental to the filter membrane. The greater volume of liquid required for the cleaning operation reduces the efficiency of filtering since this liquid, although already filtered once, must be returned to transver
REFERENCES:
patent: 5039347 (1991-08-01), Hindstrom et al.
Patent Abstracts, vol. 13, No. 211, May 17, 1989.
Patent Abstracts, vol. 10, No. 355, Nov. 29, 1986.
Patent Abstracts, vol. 15, No. 96, Mar. 7, 1991.
Patent Abstracts, vol. 3, No. 114, Sep. 21, 1979.
Dubno Herbert
Erosonic AG
Sever Frank
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