Title of Invention: Liquid filtering system in machine tools
Abstract: A liquid filtering system in machine tools which uses, in a recycling circuit, a work tank, a dirty liquid tank, a filter and a clean liquid tank in which water of a very low conductivity is used and adding at least one ferric oxide flocculent based on a polyelectrolyte polymer to the low conductivity water.
Detailed Description: Part PAR: The following is an example of non-limiting practical performance example of this invention.
Part PAR_2: A work tank (1), in which the work of the machine tool is carried out on the component, serves as a container for the water (a) used for this work which is contaminated by particles produced by the job, such as milling, roughing-down, eroding, polishing, etc.
Part PAR_3: The components to be worked on are usually iron (Fe) compounds in the majority of cases, such as steel, and therefore one of the main polluting agents of the water or dirty liquid that exits through the duct (2) towards the dirty liquid container (3) is iron.
Part PAR_4: After reaching the dirty liquid container (3), it is then passed through a filter (4) from which a clean liquid tank (5) and also the work tank (1) are supplied (all this is explained in a simplified way).
Part PAR_5: In many work processes it is convenient to carry out this process with water that has a conductivity (.gamma.) lower than normal, for example .gamma..ltoreq.60 .mu.S/cm, such as in the electroerosion processes.
Part PAR_6: In order to obtain this low conductivity, the applicant has a mixed bed ionic exchange resin tank (6) in closed circuit as regards the clean liquid tank (5), with very cationic and anionic resins in approximately the same proportion.
Part PAR_7: At times it is convenient to deionize the water until conductivity (.gamma.) values close to a: .gamma..congruent.10 .mu.S/cm, as for example in electroerosion processes using submerged wire. It can be seen in these processes with very low conductivity water that the introduction of the resin tank (6) in the filtering system achieves the objective of obtaining low conductivity but the liquid that is recycled from the work tank (1).fwdarw.dirty liquid tank (3).fwdarw.filter (4).fwdarw.clean liquid tank (5) remains continuously contaminated by a new product that gives the liquid a reddish color and that has properties which are harmful for the work.
Part PAR_8: The applicant, on studying the problem, has reached the conclusion that the cause of the new contamination is the iron in a ferric state.
Part PAR_9: When working with water that does not have a very low conductivity (.gamma.), for example .gamma.&gt;40 .mu.S/cm, the residual concentrations of other ions of Ca.sup.++, Na.sup.+, Mg.sup.++, etc., allow dissolution of the iron of the shavings coming from the part to be worked on, transforming it into a ferrous ion Fe.sup.++, but prevent it from dissolving at saturation levels and, therefore, the water that goes through the filter (4) becomes completely transparent.
Part PAR_10: If the water used in the work process is, as has been stated previously, of a very low conductivity (.gamma.) of: .gamma..ltoreq.30 .mu.S/cm, it is seen that the iron dissolves up to saturation levels, passing from ferrous ion to ferric ion: Fe.sup.++ .fwdarw.Fe.sup.+++ which oxidizes and becomes ferric oxide: Fe.sub.2 O.sub.3, that has a reddish color and that the filter (4) used is not even able to filter the system in general. However, it does settle the ferric oxide although this remains in the circuit
Part PAR_11: In these circumstances, it seems that the Fe.sub.2 O.sub.3 has colloid properties.
Part PAR_12: Once the cause of the polluting agent (Fe.sub.2 O.sub.3) has been verified, a flocculent polyelectrolyte polymer (7) (or a mixture of them) is introduced into the circuit at the level of the dirty water outlet duct (2) towards the dirty water tank (3) which electrically unstabilizes the surface of the contaminating particles. This results in colloidal ferric oxide (Fe.sub.2 O.sub.3) particles forming floccules which can be filtered and settled.
Part PAR_13: The polyelectrolyte can be an organic flocculent based on a granule or solution polyacrylamide, which causes the electrical unstabilization and the chaining of numerous individual particles resulting in floccules.
Part PAR_14: In a specific case, with conductivity water .gamma.=12 .mu.S/cm, a molecular mass polyacrylamide of nine million in a solution of 0.08% weight has been used with good results.


{'bibliographic_information': "{'Patent Number': '059936630', 'Series Code': '9', 'Application Number': '1120980', 'Application Type': '1', 'Art unit': '174', 'Application Filing Date': '19980709', 'Title of Invention': 'Liquid filtering system in machine tools', 'Issue Date': '19991130', 'Number of Claims': '11', 'Exemplary Claim Number(s)': '6', 'Primary Examiner': 'Cintins; Ivars', 'Number of Drawing Sheets': '1', 'Number of figures': '1'}", 'source_file': './grant/1999/pftaps19991130_wk48.txt', 'source_data': 'USPTO-Grant'}