GB2251194A

GB2251194A - Filter for machine tool

Info

Publication number: GB2251194A
Application number: GB9028114A
Authority: GB
Inventors: Fernando Martinez Mugica
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-12-28
Filing date: 1990-12-28
Publication date: 1992-07-01
Anticipated expiration: 2010-12-28
Also published as: FR2670396B1; GB2251194B; DE4101701A1; CH683751A5; GB9028114D0; DE4101701C2; FR2670396A1

Abstract

Machine tool coolant, particularly used in electro-erosion, is filtered downwards through a bed 4 of ilmenite, of density about 6g./cm<3>, particle size 0.2 to 1 mm and crushed to produce sharp edges. The bed may comprise a fine layer (0.3 to 0.6 mm) on top of a coarser layer (0.6 to 1 mm). The bed is cleaned by backwashing with air and liquid to flush filtered particles out through inlet 2, but the bed particles are too heavy to be flushed out with them. <IMAGE>

Description

i FILTER FOR MACHINE TOOL ?- 2 511 ')4 In machine tools with chip removal

or electrical discharge work is carried out in a cooling, lubricating, dielectric or petrochemical liquid agent, that is to say, there is an intervention of the steel, brass, copper, petroleum, graphite which through beat or on producing the relevant dicharges originate a series of particles of complex chemical products causing contamination of the agent and the need for their elimination.

In a standard type filter a container is provided with an inlet for the liquid to be filtered, a filter element inside and an outlet for filtered liquid (filtration phase). When the filtering element becomes saturated liquid is introduced through the inlet and regenerates the filtering element the resultant liquid discharging through the inlet (washing phase).

In normal technique two problems have been noted:

In the filtration phase the filtering element is contaminated and the duration of this phase Is extremely short owing to the rapid saturation of the filtering element.

In the regeneration of the filtering element, part of the filtering element is lost, so that it has to be replaced leading to obvious expense and inconvenience; The purpose of this patent is a new filter design which avoids the problems as cited.

The various contan.inating particles have been examined in the laboratory, and they are metallic or of complex formulat4 on, with various shapes, many of them being spherical.

Various materials have also been investigated to research their filtering properties and the characteristics or basic variables which govern the process during the various phases of the filter operation.

Among other products those derived from silica have been examined, but did not give good results where the filtered liquid carry complex particles, for instance, petro-chemical or organic particles, which also appear frequently in the case of usual cooling and lubricating fluids. Even more so where the medium is petroleum In an electro-erosion machine.

The various iron minerals also fail to give good results and progress has been made to solve problems with crushed bronze.

From the various tests it has been concluded that a good filtering element must be governed by three basic properties:

a) The density (d) must be high, in excess of 3 g/cn? and preferably above 5 g/cff?; b) crushed materials of a mesh size (t) no smaller than 012 mm and no greater than 1 mm should be used; c) the crushing should produce grains with sharp edged f aces.

Ilmenite has been used for many hours as a filtering agent with optimum results.

Ilmenite is a high weight mineral, its density being of the order of 6 g/cO easily broken and of prevailing rhombohedric and hexahedric shapes. After the material is obtained in the raw form it is crushed and screened, obtaining grains with many sharp edges and irregular faces of dimensions from 013 to 1 mm between the most widely separated points. Its highest percentage measurement varies around 014 mm, filling the middle volume of the filter and 0175 mm at the bottom of the filter.

Quite apart from the advantages obtained and derived from its geometric configuration as outlined, attention is also drawn to its high density, which is translated into a given compression and consequently greater stability of the grain. This ensures the absence of extensive modifications within the cavities they form (excepting on the surface).

In experiments with other known filter grits derived from quartz, silica and others of a specific gravity below 3 glcffP, pump stoppage presupposes a sudden grit decompression, all -3 the higher as the differential pressure is high, The same can be said for edge impact produced during operation, so that movement of the grit causes the cavities to undergo modifications of such a nature that particles lodged therein escape from the filter causing deterioration in the quality.of the filtered liquid and allowing the formation of connecting paths between the upper and lower diffuser which impede the filter liquid.

With regard to the filtering element the filter has also been developed as a component part.

Fig. 1 is a schematic view of the filter object of the invention.

Fig. 2 is a schematic view of a lower diffuser tube.

Fig, 3 is a schematic view of another practical version of the filter object of the invention.

The filter consists of a cylindrical container (1) comprised of two outlets connected on the inside to two upper (2) and lower (5) tubes with diffusers. The vertical position is preferred although it will also operate in other positions.

The upper diffuser (14) is located in the highest part of the filter container (1) (close to the plug (16)) and in the central zone consists of a hemispherical shaped component which the curved surface has he perforations (15) required for equal distribution of th e fluid (3). Its purpose is to provide liquid to be filtered (3) preventing the generation of turbulence, vortices, etc. which disturb the surface of the filter grain (5) located at a distance of at least 1/6th of the total height (h2). Through it also the filtered particles are dislodged when the liquid flow is reversed. The expansion undergone in this cycle of the filter elements is absorbed by the distance at which these are located in relation to the diffuser (14), from which It is deducted that the rising force of the liquid at the time of washing removes the filtered, not the filtering particles as a result of their size and their weight.

The contaminating particles are retained in the filter element (4) but it will be gradually obstructed by those particles. At the bottom of the filter (1) a diffuser is located consisting of a series of tubes (6) with a grid component in star formation.

is The tube (6) may have a closed end (7) and a number of reinforcement rings (14).

The tubes (6) have serrations (9) or grooving allowing the passage of the fluid from the filter zone (4) to the Inside (8) of the tube (6), the said inside (8) opening out Into the lower feed duct (5) of filter (1).

The width (a) of the serration striations (9) is smaller than the size of the filtering particles.

Serrations (9) are of minimal length (3) with parallel walls from which they spread towards the inside (8) of the tube.

In order to avoid air under pressure remaining in the upper part of the filter, an air purge (10) is provided.

The operatIon of the filter comprises three completely different actions: filtering, washing and rinsing, as described below.

Filtering phase: In this phase the foul liquid (3) coming for instance from electro erosion is pumped towards the filter container (1) through the upper diffuser (14). This distributes upwards and equally the liquid thus received creating a downwards uniform movement of the volume between the upper diffuser (14) and the Ilmenite surface (S), passing through it and leaving particles contained therein so that once filtered, they may be received by the collectors of the lower diffuser and through it go to the outside.

When the process is repeated without interruption, the cavities ^5 or porosity formed in the ilmenite is saturated with partieles as Indicated by a pressure gauge (17) interposed in the circuit and showing the differential pressure between the upper inlet and the lower outlet (5) giving rise to the washing cycle.

-5 is Filter washing. During this process the liquid from the pump enters the container through the lower diffuser creating a rising current which removes the particles deriving from external erosion through the upper diffuser (14), at the same time as the grit filtering expands and selects according to its filtering mesh size, so that the coarser grit remains in the deepest zone of the filtering end and the finest is found on the surface.

Rinsing of the filter: In this process the liquid enters through the upper diffuser (14) and goes out through the outlet (5) stabilising and compressing the filtering elements (4) and generating a new arrangement of its cavities once more arranged to receive the particles deriving for instance from electro erosion.

In fig. 3 it will be seen that instead of tubes (6) a number of grooved hemispheres (11) are arranged as diffuser, the inside (81) of which opens out into a lower chamber (12) than the one from which the lower duct (5) proceeds.

Both in the washing and rinsing phases, it may be useful to to ensure counterflow not only of the liquid, but also of air, for which reason fig. 3 has a split air inlet line (13) facilitating removal of contaminating particles from the filtering element (4) right up to the upper duct (2). The air duct may open out into other points allowing the proposed purpose, for instance directly into the lower chamber (12).

The lower chamber (12) may be separated from the filtering element (4) by a grid or other, of which the grooves fulfil the purpose described for the tubes (6) or hemispheres (11).

It has been established experimentally that the filter operates satisfactorily under a head of filtered liquid with a surface of filtered liquid (S) in the filter (1) retaining an approximate ratio of: 25 < Q/S < 40 0/h-mt and preferably of 30 < Q/5 < 35 e/h-m,, using a filter having the specified properties.

The height (h,) of the filter bed is approximately equal to the diameter of the filter h, -- 0, using an impulse pump only.

These properties will vary according to the type of pump during the various processing phases, but since the filter operates satisfactorily with a single pump, it is considered that the use of several pumps is a disadvantage.

As already indicated, the upper collector (14) is located in the vicinity of the plug (16), so that in practice there is an approximate overall total height of h2 j- P2 h,.

To facilitate correct metering to each filter, two types of grain in separate bags are available, being W6 to 1 mm which is first introduced to a depth of some 10 cin above the lower diffuser then adding the smaller grit which varies between 013 and W6 mm, leaving without cover at least 1/6th of the total height of the container as already previously mentioned, It is considered in view of the small differences, that the distance between diffusers Is the same as between the inlet/outlet (2)/(5) duct.

1 C 1 A 1 M 5 Filter for machine-ttool, of the type consisting of an upper duct. a lower duct and a filtering element, characterised in that, the filtering element is a crushed product of which the particles have a density (d): d > 3 qicm3 of which the size (7) is W2 < t < 1 mm and of which the fracture faces have sharp edges.

2. Filter for machine-tool, according to the previous claim, characterised in that, a head (Q) of filtered medium is provided in a fitter with a filter area (S) complying with the equation 25 < 10QIS < 40 M3/h.M2.

3. Filter for machine tool, according to claim 2, characterised in that, the ratio of head (Q) to filtered medium is 30 < Q/5 < 40 m31h-M2.

4. Filter for machine tool, according to claim 1, characterised in that, at the bottom of the filter element a diffuser is placed consisting of grooved elements, the width of the groove being sm.aller than the smallest size of filtering material particles and the inside of the diffuser communicating with the lower duct, 5. Filter for machine tool, according to claim 4, characterised in 20 that, the grooves expand towards the inside of V1,e grooved elements.

6. Filter for machine tool, according to claim 5, characterised in that, the grooved elements are tubes forming a star shape.

7. Filter for machine tool, according to claim 1, characterised in.ering medium have a crystalline that, the particles of filt fracture.

8. Filter for machine tool, according to clafin 1, characterised in that, the filtering element is ilmenite.

9. Filter for machine tool., according to claim 1, characterised in 30 that, the density (d) of the particles is 6 < d < 8 g/CM3 10. Filter for machine tool, according to previous claims, characterised in that, the length (h) of filtering material in the filter has approximately the same dimension as the filter: 0 -- hl 11. Filter for machine tool ' according lt 0 previous claims, 3 5 characterised in that, the ratio of distance between diffusers (h2) and the length k'hl) of the filtering mass is approximately h2-1.2bl. 1,2hl.

12. Filter for machine tool, according to claim 5, characterised in that, the grooved elements- are hemispheres communicating with a compartment below that from which the duct starts.

13. Filter for machine tool, according to previous claims, characterised in that, an air duct is provided to operate as a counterflow in the filtering element.

14. Filter for machine tool, according to claim 1, characterised in that, a lower compartinent is provided which may be separated from the filtering element by a grid or grating, of which the grooves comply with the description relating to the tubes or hemispheres.

15. Filter for machine tool, according to previous claims, characterised in that, the upper duct has a diffuser of hemispherical shape of which the outlet holes lead in the reverse direction to the filtered material direction.

16. Fi l ter for machine tool., according to previous claims, characterised in that, the coarser mesh-size filtering alement is located in the lower part of the filter.

001, according to previous claims, 17. Filter for machine 111 characterised in that, a differential pressure- gauge is located between upper- and lower ducts whose signals indicate the filter operating phases.

Claims

1. A filter for a machine tool comprising an upper duct, a lower duct and a filtering element wherein the filtering element comprises a crushed medium of which the particles have a density (d) greater than 3 gms per cubic centimetre, of which the size (t) is between 0.2 and lmm and of which the fracture faces have sharp edges, and wherein the middle volume of the filter is filled with particles having a size approximately equal to 0.4mm and the bottom of the filter is filled with particles having a size of approximately 0.75mm.

2. A f ilter according to claim 1 wherein a head (Q) of filtered medium is provided in a filter with a filter area (S) complying with the equation 25 < Q/S < 40 m3/h-iri.

3. A f ilter for a machine tool, according to claim 2, wherein the ratio of head (Q) to filtered medium is 30 < Q/S < 40 M3 /h-m.

4. A filter for a machine tool, according to claim 1, wherein at the bottom of the filter element a diffuser is placed consisting of grooved elements, the width of the groove being smaller than the smallest size of filtering material particles and the inside of the diffuser communicating with the lower duct.

5. A filter for a machine tool, according to claim 4, wherein the grooves expand towards the inside of the grooved elements.

6. A filter for a machine tool, according to claim 5, wherein the grooved elements are tubes forming a star shape.

7. A filter for a machine tool, according to claim 1, wherein the particles of filtering medium have a crystalline fracture.

8. A filter for a machine tool. according to claim 1, wherein \_ 10- the filtering element is ilmenite.

9. A filter for a machine tool, according to claim 1, wherein the density (d) of the particles is 6 < d < 8 g/cml.

10. A f ilter f or a machine tool, according to previous claims, wherein the length (h) of filtering material in the filter has approximately the same dimension as the filter: 0--- h,.

11. A f ilter for a machine tool, according to previous claims, wherein the ratio of distance between diffusers (h2) and the length (h,) of the filtering mass is approximately h2-1. 2 h,. 1. 2 h,.

12. A f ilter f or a machine tool, according to claim 5, wherein the grooved elements are hemispheres communicating with a compartment below that from which the duct starts.

13. A f ilter f or a machine tool, according to previous claims, wherein an air duct is provided to operate as a counterflow in the filtering element.

14. A filter f or a machine tool, according to claim 1, wherein a lower compartment is provided which may be separated from the filtering element by a grid or grating, of which the grooves comply with the description relating to the tubes or hemispheres.

15. A f ilter f or a machine tool, according to previous claims, wherein the upper duct has a diffuser of hemispherical shape of which the outlet holes lead in the reverse direction to the filtered material direction.

16. A filter f or a machine tool, according to previous claims, wherein the coarser mesh-size filtering element is located in the lower part of the filter.

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17. A f ilter f or a machine tool, according to previous claims, wherein a differential pressure-gauge is located between upper and lower ducts whose signals indicate the filter operating phases.

18. A f ilter f or a machine tool substantially as hereinbef ore described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.

19. A filter for a machine tcLo-1 subs tantially as hereinbefore described with reference to and as illustrated in Figure 3 of the drawings.