This invention relates to a device and method for filtering an auxiliary liquid, more particularly a liquid which is applied in performing grinding, sawing and milling processes as a liquid for cooling and/or lubricating and/or removal of the ground product.

In particular, the invention is intended for the removal of wheel swarf and similar of stone and glass from an auxiliary liquid.

When grinding stone, more particularly natural stone, it is known that the auxiliary liquid, together with the wheel swarf present therein, is collected in a receptacle in the shape of a container.

Hereby, the wheel swarf consists of a heavy powder which sinks down very fast in the receptacle. At the bottom of the container, thus, a heavy layer of wheel swarf is created which has to be removed regularly.

The removal of the wheel swarf layer takes place by shovelling the wheel swarf out of the container. This technique has the disadvantage that it is complicated.

Another disadvantage thereof consists in that the complete installation has to be shut down as, during shovelling, too much wheel swarf is brought back into suspension for permanently sucking liquid off the receptacle at that moment and re-using it for cooling or similar.

The present invention aims at a device for filtering an auxiliary liquid which allows for a very efficient filtration, mainly in the case that heavy powdery wheel

swarf and similar must be filtered out of the liquid, with which moreover the aforementioned disadvantages of the known device described heretofore can be excluded.

To this aim, the invention relates to a device for filtering an auxiliary liquid, characterized in that it substantially consists of a conduit system; means for circulating the liquid to be filtered through this conduit system; at least one filter, included in this conduit system, provided with a filter element; and a collecting chamber cooperating with the filter for collecting the products kept back at the filter element, and, either directly or not, removing them from the conduit system.

By the combination of a filter and a collecting chamber, the possibility is created to free the filter, which, with heavy powdery wheel swarf, usually clogs rapidly, regularly from the product which is kept back, whereby this product then is collected in the collecting chamber.

The invention also relates to a method for filtering an auxiliary liquid, whereby use is made of the aforemen- tioned device which is described further on, with as a characteristic that it consists in circulating the auxiliary liquid to be filtered through the conduit system; in regularly removing the products kept back on the filter element from this filter element; and thereby collecting the removed products in the collecting chamber.

With the intention of better showing the characteristics of the intention, hereafter, as an example without any limitative character, several preferred forms of embodi- ment are described, with reference to the accompanying drawings, wherein:

figure 1 schematically represents a device according to the invention; figure 2 represents the filter element which is applied in figure 1; figure 3, at a larger scale, represents the part which is indicated by F3 in figure 1; figure 4 represents a variant of the part which is indicated by F4 in figure 1; figure 5 schematically represents another form of embodiment of a device according to the invention.

As represented in figure 1, the device 1 according to the invention is intended in the first place for application in or with a device 2 for sawing and/or grinding of stone 3, more particularly natural stone, or similar.

In this case, the device 2 comprises a processing machine 4, for example, with a grinding disc 5, and a liquid circuit cooperating therewith, hereafter called main circuit 6, for circulating an auxiliary liquid 7, usually water.

By means of the main circuit 6, the auxiliary liquid 7 is sucked up from a receptacle 8, by means of a pump 9, and supplied through a conduit 10 to the processing machine 4, where this auxiliary liquid 7 is suitably conducted over the grinding disc 5 and/or the stone 3, or similar, to be treated. The drained-off auxiliary liquid 7, in which then also wheel swarf or similar is present, is supplied back into the receptacle 8 through a collecting means 11 and possibly a conduit 12.

According to the invention, for cleaning this auxiliary liquid 7, use is now made of a device 1 showing the characteristic that it substantially consists of a con- duit system 13, in this case in the shape of a secondary

circuit forming a closed circuit which cooperates with the receptacle 8; means, in this case a pump 14, for circulating the auxiliary liquid 7 to be filtered through this conduit system 13; at least one filter 15 included in this conduit system 13, provided with a filter element 16; and a collecting chamber 17 cooperating with the filter 15 for collecting the product 18, in other words, the aforementioned wheel swarf, kept back at the filter element 16, and removing it from the conduit system 13.

Preferably, the collecting chamber 17 is situated under the filter element 16, such that the product 18 kept back at the filter element 16, as further described hereafter, can easily brought into the collecting chamber 17 by means of the gravitation.

As represented, the filter element 16 comprises a wall 19 which extends in height in an oblique manner, whereby this wall 19 is bent towards the inside according to the general flow direction V. More particularly, it is preferred that the filter element 16 has a layout as shown in figure 2, in other words, has a conically shaped wall 19, with a conicity which is such that a tapering towards the top is created. Still more particularly, it is preferred that this filter element 16 is realized in the shape of a conical hat with a flange-shaped part 20 which, as further described hereafter, allows for a clamping at the edge.

Hereby, the filter element 16 consists of a membrane. In order to be able to resist to the high pressures which are present, this membrane according to the invention is supported by a permeable support structure 21 which, as is represented in greater detail in figure 3, preferably consists of a perforated plate. Depending on the application, this support structure 21 shall further be

supported by additional support elements 22.

The support structure 21 and the filter element 16 have a corresponding design, in other words, the filter element 16 fits precisely against the inside of the support structure 21.

The filter element 16 preferably consists of a web, fabric or similar which is manufactured of monofilaments.

The use of such monofilaments offers the advantage that a very smooth surface is obtained to which the wheel swarf or similar cannot adhere. Furthermore, by means of these monofilaments, it is possible to create a filter fabric the filter openings of which are very small and can be realized with very precise dimensions.

The filter element 16 and the collecting chamber 17 are arranged in, limited by, respectively, a housing 23 extending upward, consisting of a base part 24 in which the collecting chamber 17 is situated, and a cylindrical cap 25 extending around the filter element 16 and the support structure 21.

In the housing 23, more particularly in the base part 24, one or more inlets 26 are provided. Preferably, several inlets 26 are provided along the circumference, as a result of which a uniform flowing in of the auxiliary liquid 7 to be filtered is obtained. These inlets 26 give out in the housing 23 on places located between the collecting chamber 17 and the filter element 16, in other words, the collecting chamber 17 is situated lower than the inlets 26.

The filtered auxiliary liquid 7 is supplied back to the receptacle 8 through a conduit 27. This conduit 27 connects to an outlet 28 provided at the housing 23. This

outlet 28, as represented, preferably is situated at the upper side of the housing. It is noted that the chamber 29 behind the support structure 21 preferably widens in the direction of the outlet 28.

The device 2 is provided with means which allow to empty the collecting chamber 17. In the example of figure 1, these means consists in that the collecting chamber 17 comprises one or more detachable parts 30-31, in such a manner that, by the detachment thereof, the product 18 collected in the collecting chamber 17 can be removed.

Further, the device preferably is also provided with auxiliary means for removing the kept back products 18 from the filter element 16. In the embodiment of figure 1, to this end means are applied for creating a counterflow through the filter element 16 by means of compressed air. To this aim, the device 2 is provided with a connection 32 for compressed air which gives out in the aforementioned space 29. Furthermore, correspon- ding valves 33 and 34 are provided, respectively in the conduit 27 and at the location of the connection 32.

For these auxiliary means, other means can be applied, too, as further described hereafter.

In the aforementioned receptacle 8, means, such as a stirring element or pump 35, are provided in order to keep the auxiliary liquid 7 in motion, in such a manner that all of the product 18, in other words, all of the wheel swarf, is suctioned up into the conduit 10.

The working of the whole which is shown in figure 1 is as follows.

Through the main circuit 6, the processing machine 4 is

permanently provided with auxiliary liquid 7 from the receptacle 8.

Through the main circuit 13, the polluted auxiliary liquid 7 is led through the filter 15. Thereby, the product 18 settles against the inner wall of the filter element 16. After a certain period of time, the flow in the conduit system 13 is stopped by switching off the pump 14. As a result of this, the product 18 drops downward into the collecting chamber 17. The loosening of product 18 which possibly still is present at the inner side ofothe filter element 16 can take place by blowing compressed air in counterflow through the filter element 16, whereby to this end, during a well-defined period of time, the valve 33 is opened and the valve 34 is closed.

Subsequently, the conduit system 13 can again be taken into usage. The product 18 present in the collecting chamber 17 remains there, due to its weight.

The aforementioned operation can be repeated several times until the collecting chamber 17, which then also functions as a storage chamber, is full. Hereafter, it has to be emptied by, in this case, detaching the parts 30 and possibly 31, by removing the product 18, and by re-assembling these parts 30 and 31.

The aforementioned auxiliary means for loosening the product 18 at the filter element 16 may also be designed in another way. In figure 4, for example, a variant is represented, whereby means are applied to this end with which the filter element 16 can be deformed, which, in this case, consist of a pressure cylinder 36 with a piston rod 37 with which the filter element 16 can be pushed downward. As represented, this may possibly be

combined with the compressed air connection 32, too.

Other embodiments are also possible, such as means for supplying the auxiliary liquid 7 for a short time in counterflow through the filter element 16, or a combination of one or more of these means.

Figure 4 also shows that the means which allow to empty the collecting chamber 17 can also be realized in another manner. In this case, the collecting chamber 17 is provided with a shut-off element 38, more particularly a shut-off slide. This shut-off element 38 may either be operated manually, or, as represented in figure 4, be equipped with an operating element, in this case, a pressure clinder 39 for automatically shifting the shut- off element 38.

It is obvious that all aforementioned operations can also be completely automatized.

According to a variant, the device 1 may also form a part of the main circuit 6. In this case, the pump 9 is not present, and the auxiliary liquid 7 originating from the outlet 28 is supplied to the processing machine 4.

According to a not represented variant, several filters 15 can be provided around a collecting chamber 17, for example, one filter 15 arranged centrally, such as represented in figure 1, and various other similar filters 15 which are arranged around it in an oblique manner.

The conduit system 13 may have very small dimensions.

Possibly, the filter can be mounted in or at the receptacle.

Instead of applying stirring means, the receptacle may also be provided with a funnel-shaped bottom, whereby the conduit system 13 starts below in the bottom.

The term collecting chamber has to be interpreted broadly and may also include a discharge opening which is opened each time product 18 is removed from the filter element 16, such that the product 18 is discharged directly outward.

The filter element 16 preferably has a height of several dozens of centimeters.

The form of embodiment represented in figure 5 differs from the forms of embodiment described heretofore substantially by having another supply for the auxiliary liquid 7 in the filter 15, other means for loosening the kept back products 18 from the filter element 16, other means which allow to empty the collecting chamber 17 and because a same filter 15 is applied for filtering the auxiliary liquid 7 with several devices 2 or processing machines 4 and therefore is connected to several receptacles 8.

In figure 5, the parts which are also present in the above-described forms of embodiment, are indicated with the same reference number and are not described again in detail.

As far as the supply of the auxiliary liquid 7 to be filtered into the filter 15 is concerned, the inlets 26 do not give out radially, but upwards.

To this end, these inlets 26 are formed by a number of, for example, four, pipes 41 bent about 90 which, with one extremity, connect to a distribution chamber 42

which, in the shape of a hollow ring, is provided between the base part 24 and the cap 25 of the housing.

With their other extremity, these pipes 41 are practically directed vertically upward. They are distributed equally over the inner side of the ring- shaped distribution chamber 42. The conduit 43 which connects the pump 14 to the inlets 26, connects to the outer side of this distribution chamber 42.

To this distribution chamber 42, a conduit 45 giving out to the atmosphere is connected at the top which can be closed off by a valve 44.

On the outlet 28 or in the conduit 27, a flow rate meter 46 is provided which connects to a control device 47 controlling the pump 14.

This control device 47 also controls means for vibrating the filter element 16, namely a vibrator 48 which is attached on the cap 25 of the housing 23.

In this form of embodiment, the collecting chamber 17 and, thus, also the base part 24 of the housing 23 are funnel-shaped. At a distance above the shut-off element 38 formed by a valve which normally closes off the underside of the collecting chamber, a second shut-off element 49, also formed by a valve, is provided which can divide the collecting chamber 17 into two parts.

Both shut-off elements 38 and 49 are connected to the control device 47.

To that part of the collecting chamber 17 which is situated between the two shut-off elements 38 and 49, a compressed air conduit 50 is connected which is in

connection with a source 51 of compressed air and can be closed off by a valve 52 which is controlled by the control device 47.

At a small distance above the topmost shut-off element 49, a level detector 53, for example, a vibrating fork, is provided in the collecting chamber 17. This level detector 53 is also in connection with the control device 47.

The device 1 comprises various receptacles 8 which are situated at almost the same level, three receptacles 8A, 8B and 8C in the represented form of embodiment, into which auxiliary liquid 7 from the processing machines flows through a conduit 12 not represented in figure 5, and in which, thus, a pump 9, not represented in figure 5, is provided.

Only one receptacle 8A, namely the receptacle which, in figure 5, is situated furthest to the left, is directly connected to the filter 15, through the conduit system 13.

In this receptacle 8A, a pump 14 is situated with which auxiliary liquid can be pumped through the conduit 43 to the filter 15, whereas filtered liquid flows back into it through the conduit 27.

In this receptacle 8A, also a submergible pump 35 is provided for keeping the auxiliary liquid 7 in motion, and a water conduit 54 is giving out therein which can be closed off by a valve 55 which is controlled by a float 56 in the receptacle 8A.

The outmost receptacle 8C also comprises a similar submergible pump 35, but the exiting water is divided in

two, namely one part flowing back through a conduit 57 into the receptacle 8C to keep the auxiliary liquid in motion, and one part flowing through a flexible conduit 58 towards the receptacle 8B.

This conduit 58 extends through a flexible conduit 49 which connects the two receptacles 8B and 8C to each other.

In an analogous manner, the receptacle 8B also comprises a similar submergible pump 35 to which conduits 57 and 58 are connected, whereby the flexible conduit 58 extends through a flexible conduit 59 which also connects the receptacles 8A and 8B to each other.

The working of this form of embodiment of the device 1 is as follows: During filtering, the shut-off element 38 is closed and the shut-off element 49 is open, and the filter 15 as well as the collecting chamber 17 are filled with liquid.

Auxiliary liquid 7 to be filtered is pumped by means of the pump 14 off the receptacle 8A and through the conduit 43 to the distribution chamber 42, from where this auxiliary liquid 7 flows through the inlets 26 into the space beneath the filter element 16.

The product 18 is kept back by the fabric, woven from monofilaments, of the filter element 16, and the filtered liquid flows out of the space 29, through outlet 28, over the flow rate meter 46 and the conduit 27, back to the receptacle 8A.

This circuit is represented in figure 5 by arrows in full lines.

As the layer of product 18 on the filter element 16 becomes thicker, the flow rate of liquid flowing back will diminish.

When the flow rate meter 46 measures a flow rate which is below a set limit, the control device 47 coupled thereto will induce the pump 14 to stop and, immediately afterwards, induce the valve 44 to open.

Consequently, the auxiliary liquid 7 still to be filtered which is beneath or at the inner side of the filter element 16, will flow back through the inlets 26, the distribution chamber 42, the conduit 43 and the pump 14 into the receptacle 8A.

As the distribution chamber 42 is brought into connection with the environment, by opening the valve 44, this reverse flow takes place very fast.

The product 18, more particularly wheel swarf, remains upon the filter element 16.

After a well-defined period of time, when this flowing back is finished, the control device 42 sets the vibrator 48 to work.

Hereby, the product 18, so to say, becomes liquid and is detached from the filter element 16, whereafter it drops into the collecting chamber 17, as is represented in figure 5 by arrows in dash-dot-line.

From the moment that the product 18 no longer closes off the filter element 16, already filtered water from the space 29 flows through the filter element 16, as represented by arrows in dashed line in figure 5, as a result of which it is washed.

Subsequently, the control device 47 commands the vibrator 48 to stop, the valve 44 to close, and the pump 14 to work again, after which the cycle described heretofore starts again.

The product 18 in the collecting chamber 17 is stacked above the shut-off element 38. By the shape of the inlets 26, it is guaranteed that the auxiliary liquid flows upward into the filter 15 and is prevented that a part thereof stirs up the product 18 present in the collecting chamber 17.

When the product 18 reaches a well-defined level, the level detector 53 sends a signal to the control device 47, as a result of which this latter commands the shut- off element 49 to close and subsequently the valve 52 to open and the vibrator 48 to start working again.

By opening the valve 52, compressed air from the compressed air source 51 flows into the space between the shut-off elements 38 and 49, as a result of which the slug of product 18 is pressed outward between these latter and is collected in a receptacle 60. By the vibration of the housing 1, caused by the vibrator 48, the last remainders of product 18 which adhere to the walls in the aforementioned space, will become loosened and drop out of the collecting chamber 17.

After a period of time, the control device 47 stops the vibrator 48 and commands the valve 52 and the shut-off element 38 to close and subsequently the shut-off element 49 to re-open.

This cycle of removal of product 18 is completely independent from the heretofore described cycle for loosening product 18 from the filter 15, as a result of

which an immobilization of the device 1 is reduced to a minimum.

In the manner described heretofore, not only the auxiliary liquid 7 is filtered out of the receptacle 8A, but indirectly also the one from the receptacles 8B and 8C, in consideration of the fact that auxiliary liquid 7 from the receptacle 8C is pumped to the receptacle 8B by means of a pump 35 and through a conduit 58, and auxiliary liquid 7 from the receptacle 8B is pumped in an analogous manner to the receptacle 8A by means of a pump 35 through a conduit 58.

Due to pumping by means of the pumps 35, auxiliary liquid 7 is removed from the receptacles 8B and 8C which is compensated by auxiliary liquid 7 which is filtered to a large extent and flows through the conduit 59 of the receptacle 8A to the receptacle 8B and from the receptacle 8B to the receptacle 8C.

In fact, the water level has to be regulated only in the receptacle 8A, which takes place by means of the float 56 with which the valve 55 in a fresh water supply conduit is controlled.

As only one filter 15 is necessary for several receptac- les 8 and, thus, several processing machines 4, a large saving in space is obtained.

Moreover, in this manner the total liquid contents may be kept smaller, whereas the filter 15 can work with a higher efficiency.

As a result of all this, cost savings are achieved.

The present invention is in no way limited to the forms

of embodiment described as an example and represented in the figures, on the contrary may such method and device for filtering an auxiliary liquid be realized according to various variants without leaving the scope of the invention.