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.
Machine tools claims
I claim:
1. In a liquid filtering system for machine tools having a recycling
circuit employing water in a work tank, a dirty liquid tank, a filter
and a clean liquid tank, the improvement comprising a flocculent
tank connected to said recycling circuit and containing at least
one ferric oxide flocculent wherein said water in said recycling
circuit has a conductivity of less than or equal to 30 .mu.S/cm.
2. The liquid filtering system of claim 1 wherein the ferric oxide
flocculent is a polyelectrolyte polymer.
3. The liquid filtering system of claim 2 wherein the flocculent
tank is connected to the dirty liquid tank.
4. The liquid filtering system of claim 1 further comprising a
mixed bed ionic exchange resin tank connected in a closed circuit
with the clean liquid tank.
5. The system of claim 1 wherein said water has a conductivity
of 12 .mu.S/cm.
6. A method for filtering, cooling and cleaning liquid used for
machine tools comprising the steps of:
recycling said cooling and cleaning liquid in a recycling circuit
which comprises a work tank, a dirty liquid tank, a filter and a
clean liquid tank;
using water having a conductivity of less than or equal to 30 .mu.S/cm
as the cooling and cleaning liquid in said recycling circuit;
adding to said water at least one ferric oxide flocculent so as
to flocculate ferric oxide contained in said water; and
filtering said flocculated ferric oxide from said water with said
filter.
7. The method of claim 6 further comprising the step of treating
said water with a mixed bed ionic exchange resin.
8. The method of claim 6 wherein said water has a conductivity
of 12 .mu.S/cm.
9. The method of claim 6 wherein said ferric oxide flocculent is
a polyelectrolyte polymer.
10. The method of claim 9 wherein said polyelectrolyte polymer
is a polyacrylamide.
11. The method of claim 10 wherein said polyacrylamide has a molecular
mass of nine million and is used in an amount of about 0.08% by
weight.
Machine tools description
In the machine tools where material is removed, the liquid used
to cool and clean the work area, for example normal distribution
network water, becomes contaminated by the shavings of the actual
material being worked on.
A filtering system, in which the polluting agent is retained, is
provided so that the liquid/water used is not consumed or wasted,
for example in electroerosion jobs the spherical type shavings that
are produced when the electrical current is applied on the part
to be worked on are retained.
The polluting agent in the liquid/water, usually the shavings of
the worked on material, partially dissolves without causing problems
in the filtering system.
When the work methods recommend using low conductivity water, (.gamma.):
.gamma..ltoreq.20 .mu.S/cm, it has been confirmed that the water
becomes cloudy in the work/water filter area. This water is of a
reddish color, which could mean the presence of a new polluting
agent and which causes work problems, but it cannot be filtered
or settled by conventional systems used in the machine tools.
The applicant has verified that the new polluting agent is ferric
oxide of colloidal behavior and has solved the problem by adding
a flocculent compound to the filtering circuit for the ferric oxide,
such as a flocculent polyelectrolyte polymer.
In order to better understand the purpose of this invention, the
drawings represent a preferential way for its practical performance,
subject to accessory changes that do not impair its basis.
FIG. 1 is a schematic representation of a practical performance
of the system described in this invention.
The following is an example of non-limiting practical performance
example of this invention.
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.
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.
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).
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.
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.
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.
The applicant, on studying the problem, has reached the conclusion
that the cause of the new contamination is the iron in a ferric
state.
When working with water that does not have a very low conductivity
(.gamma.), for example .gamma.>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.
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
In these circumstances, it seems that the Fe.sub.2 O.sub.3 has
colloid properties.
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.
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.
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. |