"SELF-CLEANING FILTERING SYSTEM FOR PRESSURIZED

FLUIDS".

Technical field

The present invention relates to a self-cleaning filtering system for pressurized fluids particularly suitable for use in equipment featuring a system for cooling tools with high pressure liquid such as, for example, work centres, numerical control adjustments.

Background Art

As it is known, the liquids used in mechanical processing for removal, deformation, or for non-conventional processes, are contaminated with solid particles or contaminants of various origins, e.g. products resulting from the deterioration of fluids and residues from machining. To ensure a reliable performance from the machines that carry out the processing, the liquids must be cleaned to remove impurities resulting from such processing.

At present, for example, filter cartridges are used to filter liquids in work centres or in numerically controlled machines, and such cartridges must be replaced frequently as they clog quickly or break as a result of the wear caused by impacts with the swarf, which causes tears in the material of which such filters are made, in addition to the wear caused by operating pressure levels. One such type of filter cartridge is illustrated in American patent US 2,988,227. The filtering element is composed of a bellows composed of a multitude of pleats that are held in position by a toothed profile made of a plastic material which allows the pleats to be kept reciprocally spaced in order to allow the passage of the liquid to be filtered.

The cartridges described in the American patent, and likewise those mentioned earlier, need to be replaced frequently and constantly in order to ensure adequate filtration of the liquids used in the work centres or in the numerically controlled machines. These maintenance operations involve machine downtime which slows down production, with consequent increases in costs resulting from both the replacement of the cartridges and the slow production, in addition to the constant presence of workers for maintenance work. Furthermore, a constant monitoring of the machines is required to prevent sudden stoppage of processing due to incorrect machine operation caused by cartridges which are not always perfectly efficient. In particular, when the fluid filtering is not optimal, there is a risk of significant damage to equipment, which becomes worn or even unusable due to breakages without, sometimes, it being possible to take prompt action because of the presence of harmful impurities in the fluids. Numerically controlled machines currently feature equipment which is extremely sophisticated, delicate, and very expensive and nowadays, all of them feature cooling systems which run to the end of the line, and therefore there is considerable need to be able to filter the cooling liquid effectively and without drawbacks.

In addition, without proper and adequate filtering, contaminated lubricating coolants must be replaced more frequently, resulting in highly polluting materials being wasted and leading to high costs for both maintenance and waste disposal, since such materials are considered special waste.

The machines mentioned above require very effective filtration systems since they use a liquid which has to be extremely clean and since the pumps that circulate the liquid work at high pressure need microfiltered liquids which have no particles with a diameter over 10 microns in order to ensure proper functioning of the said pump and many other of the machine's moving parts.

As mentioned earlier, these machines wear out quickly, causing great damage if the liquid has impurities and dirt with ensuing considerable maintenance and reconditioning costs that have repercussions on the of management and production costs as a result of processing carried out poorly and/or downtime. Furthermore, there are also other plants which need to filter liquids in order to remove particles in, for example, the food industry or other areas. In particular, in these areas, there is a strong need to be able to filter out and retain particles with diameters measuring approximately 5 microns and less.

The applicant is familiar with French patent n.2989283, which illustrates a system for filtering water by means of a diatomaceous filter.

The device comprises a chamber within which there is a series of cage-like modules held in position by spacers. The modules are covered with a polypropylene fabric which is coated with a diatomaceous layer. The water to be filtered flows through the diatomaceous layer and the fabric and enters the module, where such water then flows up towards a manifold for the filtered water, which is then reused.

The water enters in the lower section, flows through the diatomaceous layer and the fabric, and then flows out through the holes in the cage, ending up in a delivery manifold. The water to be filtered is pumped into the filter, entering from the lower section and exiting from the upper section. During the filtration, the fossil meal composing the diatomaceous layer is compacted around the fabric, thereby retaining the dirt. When the filter mantle starts to clog, increasing the load loss and thereby reducing the filter's flow rate, the device illustrated in the patent envisages a cleaning cycle which consists in allowing the air to enter the cage-like module, which then makes the polypropylene fabric vibrate and this vibration breaks up the diatomaceous layer and the accumulated dirt ends up on the base of the filter. After a number of cycles, the spent diatomaceous layer must be replaced.

The French patent cited illustrates a low-pressure filtering system for fluids which is designed to eliminate the particles which cloud the water, for example, in a swimming pool and which consist of organic compounds, inorganic compounds, micro- organisms, bacteria, algae, metals such as iron and manganese, and as such are very different from the particles present in lubricating coolants for machine tools.

Disclosure of Invention

The object of the present invention is substantially to solve the problems of the currently known technique by overcoming the aforesaid drawbacks by means of a self-cleaning filtering system for pressurized fluids which can offer high efficiency for all applications needing a fine system for filtering processing liquids.

A second object of the present invention is to produce a self-cleaning filtering system for pressurized fluids which is structurally simple, very functional, and - above all - automatic.

A third object of the present invention is to produce a self-cleaning filtering system for pressurized fluids which is integrated into the lubricating coolant circuit of machine tools used for processing in which impurities in the fluid must be controlled as such impurities could block orifices in and/or nozzles on the tools.

A further object of the present invention is to have a self-cleaning filtering system for pressurized fluids which can be used to filter liquids in plants in various areas such as, for example, the food industry or other area.

A still further object of the present invention is to have a self-cleaning filtering system for pressurized fluids which does not require particular maintenance, does not use disposable filtering materials, has lower operating costs, and offers a drastic reduction in polluting materials to be disposed of.

A still further object of the present invention is to have a self-cleaning filtering system for pressurized fluids which can curb the management and maintenance costs therefor, thereby allowing greater productivity.

A further but not final object of the present invention is to produce a self-cleaning filtering system for pressurized fluids which is structurally simple and works well. These objects and others besides, which will better emerge over the course of the present description, are essentially achieved by means of a self-cleaning filtering system for pressurized fluids, as outlined in the claims below.

Brief Description of Drawings

Further characteristics and advantages will better emerge from the detailed description of a self-cleaning filtering system for pressurized fluids according to the present invention, provided in the form of a non-limiting example, with reference to the accompanying drawings, in which:

Figure 1 shows, schematically and in a three-dimensional front view, a self- cleaning filtering system for pressurized fluids according to the present invention,

Figure 2 shows, schematically and in a three-dimensional rear view, the self- cleaning filtering system for pressurized fluids in Figure 1,

Figure 3 shows, schematically, a rear view of the system in Figure 1,

- Figure 4 shows, schematically, a front view of the system in Figure 1 ;

- Figure 5 shows, schematically, a section view of the system in Figure 1 in operational mode;

Figure 6 shows, summarily, the cleaning scheme of the filtering system in Figure 1 ;

- Figure 7 shows, summarily, the impurity discharge scheme of the filtering system in Figure 1 ;

- Figure 8 shows, schematically and in a three-dimensional view, a variant of the self-cleaning filtering system for pressurized fluids according to the present invention,

- Figure 9 shows, schematically, a section view of the system in Figure 8; - Figure 10 shows, schematically and in a three-dimensional view, the filtering component of the system for pressurized fluids in Figure 8,

- Figure 11 shows, schematically and in a three-dimensional view, a second component of the system in Figure 8;

- Figure 12 shows, schematically and in a three-dimensional view, a detail of the system in Figure 8;

- Figure 13 shows, schematically, a section view of the detail in Figure 12;

- Figure 14 shows, schematically, a section view of the system in Figure 8 in operational mode;

- Figure 15 shows, summarily, the cleaning and impurity discharge scheme for the filtering system in question.

Best Mode for Carrying Out the Invention

At present, all machines which use high-pressure liquid coolants (for example, work centres) have, as standard, an emulsion tank with various macrofiltration stages and, during the last stage thereof, the cleanest emulsion is obtained, which is pumped up by a low-pressure impeller pump operating with a pressure ranging from a few bars to a maximum of 16 bar and with a flow rate ranging from 15 to 80 litres per minute and higher, depending on the type of machine and/or requirements.

In particular, the machines which work with high-pressure liquids, which require a particularly clean liquid, need a microfiltration stage for the liquid in order to reduce the diameter of the particles present in the liquid to just a few microns.

When installed on work centres, the filtering system according to the present invention is fitted between the collection tank and a supplementary tank with a high-pressure pump, in which case the tank receives the liquid from the filtering system in question and a pump draws the liquid from the tank and sends it, under high pressure, to the machine. As mentioned earlier, users need a filtered liquid with particles whose a diameter is less than 10 microns, in order to protect the high-pressure pump and all the spindles which turn on ceramic materials.

Now, with reference to the figures, in particular to Figure 1, 1 is used to denote a filter system for pressurized fluids according to the present invention as a whole.

The filtering system according to the invention is envisaged to be installed downstream of the impeller pump so as to receive liquid to be filtered from the pump in order to send the filtered liquid to the tank and from there to the machine, said liquid having been drawn up by a high-pressure pump.

The filtering system 1 is essentially constituted of an essentially cylindrical body 2 which is sealed at one end by a closing cover 3. The body 2 features fixing brackets 4 which allow the system to be secured at any point of the machine downstream of the impeller pump.

As shown in Figure 1, at the other end of the body 2 there is a closing element 5, which has an inlet conduit 6 for the liquid to be filtered, which is equipped with an inlet valve 60, actuated by an actuator 600, and an outlet conduit 7 for the filtered liquid, which is equipped with a valve 70 actuated by an actuator 700.

In accordance with the present embodiment, branching out from the body 2 there is a discharge conduit 9 for the dirty fluid, which is equipped with a discharge valve 90 which is actuated by an actuator 900, as shown in figure 2. In particular, the concentrated dirty liquid comes out via the discharge conduit 9.

One variant envisages that the inlet conduit 6 features a pair of valves, each of which is driven by an actuator, in which an inlet valve is envisaged to allow the liquid to be filtered to enter and a discharge valve is envisaged to allow the concentrated liquid loaded with dirt and impurities to exit and be discharged. Inside the body 2, there is a filtering element 20 envisaged, which is made of a metallic material such as, for example, steel and features a surface which allows the passage of liquid and particles with a diameter of less than 10 microns, while for applications in other areas, the diameter must even be less than 5 microns. In greater detail, the filtering element is substantially composed of a stainless steel cylinder consisting of a "sandwich", made up of a first internal metal mesh frame 20a, preferably made of stainless steel, a second external metal mesh frame 20b, also made of steel, and a microtextile layer 20c, made of stainless steel, placed between the two frames, as shown in Figure 9.

To better clarify, the microtextile layer 20c is essentially composed of a mesh in which the weave of the fabric consists of the alternation of a thicker thread and a thinner thread, and thus also for the warp. This structure of the microtextile lends the fabric good wear resistance and, at the same time, a reduction in the space useful for the passage of the particles, thereby obtaining a filtering capacity which is able to stop particles with a diameter which is even less than a few microns. In particular, the structure of the microtextile is only dampened by the liquid when in static conditions, since the liquid is able to pass only when pressurized.

In addition to the explanations so far, on the external surface the second mesh frame 20b there is a plurality of deflecting elements 20d uniformly distributed along the surface as shown in Figure 10. The deflecting elements 20d are envisaged to protect the filtering element and the microtextile, preventing the breaking thereof due to direct impact with the particles to be filtered. In this way, it is possible to allow a high flow speed for the liquid to be filtered.

In the embodiment shown in Figure 8, the body 2 features a distribution conduit 2a connected to the inlet conduit 6 for the liquid to be filtered, which extends along the length of the said body so as to ensure the liquid is filtered simultaneously along the entire length of the filtering element 20. In particular, the distribution conduit 2a has a flow diverter 2b, shown in Figure 14, which is envisaged to create a vortex in the liquid and make the liquid circulate along the walls of the body and along the external surface of the deflecting elements 20d. The liquid to be filtered moves tangentially to the filtering element and the particles contained therein do not collide with the microtextile, which remains protected and preserved, thereby permitting better filtering quality and greater long-term durability. Furthermore, the flow diverter 2b is suitably tilted and positioned to favour the discharge of the liquid after washing the filtering element, as will be better explained hereinafter.

In addition to the explanations so far, the self-cleaning filtering system 1 has an air inlet conduit 12 with a valve 120 which is driven by an actuator 121 which allows air or compressed air to enter the filtering element 20, as shown in Figure 6, so that the particles of dirt and impurities deposited on the external surface of the filtering element 20 are detached from this surface, depositing instead in the space 21 present between the external surface of the filtering element 20 and the internal surface of the body 2. In the variant of the embodiment, inside the filtering element 20 there is a diffuser 2c envisaged, which is constituted of a cylindrical body which is microslotted along the entire length thereof, as shown in Figure 1 1. The diffuser is envisaged to release air from the inside outwards uniformly along the entire length thereof so that the dirt particles deposited on the external surface of the second mesh frame 20b are detached and are collected by the counter-washing liquid, which circulates in the reverse direction to the liquid to be filtered, but also exiting via conduit 2a.

In addition to this case, the air inlet conduit 12 delivers air or compressed air into the diffuser 2c of the filtering element 20, as shown in Figure 15.

Furthermore, the system comprises a timer envisaged to close the valve on the inlet conduit 6 and the valve on the outlet conduit 7 and open the valve on the air inlet conduit 12 and the discharge valve on the conduit 6 for a period of approximately 5 seconds, as will be explained later.

In the version of the system shown in Figures 1 to 7, the timer is envisaged to close the valve 60 and the valve 70 and to open the valve 120 and the valve 90, always for the same period of time.

In addition to the explanations so far, the actuators are driven by pneumatic actuators controlled by a control panel.

The filtering system according to the present invention comprises a device which reduces the noise level when the liquid loaded with dirt and impurities is expelled from the space 21 in the body 2. The liquid loaded with impurities, together with the air which is used to clean the filtering element when it exits the body 2, is also very noisy because of the pressure at which it exits, which can reach up to 6 bar.

The device 50 is constituted of a body 51 inside which there is a drilled screen 52 envisaged which is positioned diagonally as shown in figure 5 with respect to the section of the body. The space in the body to the rear of the screen is filled with a multitude of plastic filaments and, in the present embodiment, such filaments are made of nylon, the task of which is to cushion the flow of air and liquid by distributing the flow over the entire surface to prevent the formation of shock waves which would be particularly noisy and annoying for the working environment. The screen and the nylon filaments act as a diffuser. The device 50 is located downstream of a conduit for discharging the dirt, which is located after the discharge valve on the conduit 6 and before the collection tank for the concentrated dirty liquid.

The filtering system 1 envisages an operational working stage, as shown in Figure 6, in which the liquid is filtered through the following operating steps:

- liquid is drawn from a storage tank by action of an impeller pump,

- liquid enters an inlet conduit 6 through a valve 60 in the body 2, liquid flows through the surface of the filtering element 20, with the impurities retained by the external surface thereof,

clean liquid exits via an outlet conduit 7 through the corresponding valve.

In this variant, the passage of liquid takes place by means of the distribution conduit 2a, which is arranged within the space 21· between the external surface of the filtering element 20 and the internal surface of the body 2, by action of the flow diverter 2b, which creates a vortex in the liquid, making the liquid circulate along the walls of the body and along the external surface of the deflecting element s 20d and resulting in the filtration of the liquid by means of the passage thereof through the surface of the filtering element 20, with the impurities retained on the external surface thereof.

In accordance with the present invention, the filtering system comprises a cleaning stage for the filtering element, involving the following operating steps:

closure of the valve on the liquid outlet conduit 7,

- closure of the valve on the liquid inlet conduit 6,

- opening of the discharge valve on the discharge conduit 9 or - in this variant - on the inlet conduit 6,

- opening of the valve on the conduit 12 with intake of air within the filtering element 20 before or inside the diffuser 2c and then within the filtering element,

- passage of air through the "sandwich" of the filtering element with detachment and removal of dirt and impurities from the external surface of the filtering element 20 and accumulation thereof in the space 21 between the external surface of the filtering element 20 and the internal surface of the body 2,

- closure of the valve on the conduit 12 and interruption of the flow of air within the filtering element 20. At this point, the filtering system comprises a washing stage, involving the following operating steps:

- liquid is drawn from the storage tank by action of an impeller pump,

- liquid enters an inlet conduit 6 through the valve and the body 2,

- liquid passes through the space 21 between the external surface of the filtering element 20 and the internal surface of the body 2, with removal of the impurities present in the space 21,

the dirty liquid loaded with impurities exits via a discharge conduit 9 through the valve 90 or via the distribution conduit 2a,

- concentrated dirty liquid is discharged into the storage tank through the discharge valve.

The filtering system envisages that the filtering element cleaning and washing stage takes place automatically, when commanded by a timer present in the filtering system at preset intervals, e.g. every hour, or even at shorter intervals, depending on operating requirements.

After the predominantly structural description, the invention in question will now be outlined.

Through the inlet valve and the conduit 6, the filtering system according to the present invention allows the liquid to be filtered to enter the body, as shown in Figure 5 or Figure 14. In greater detail, the liquid is drawn from the collection tank by the pump on the machine's circuit and then sent to the inlet conduit 6.

The liquid enters the body and flows through the filtering element 20, leaving the dirt and impurities on the external walls thereof, so as to exit, clean, through the conduit 7 and the relative valve. The filtering system according to the present invention is arranged so as to carry out a cleaning cycle for the filtering element automatically, controlled by pulses sent by a timer according to the setting thereof.

When the timer commands the washing stage, the system cleans off the impurities present on the external surface of the filtering element.

During the filtering element washing operations, the inlet valve - which is operational during the filtering of the liquid - is closed and the discharge valve is opened.

A jet of air coming from the system is forced into the filtering element 20 through the air inlet conduit 12, which pushes the particles deposited on the external surface of the filtering element, detaching them therefrom, said particles then depositing in the space 21 between the internal surface of the body 2 and the external surface of the filtering element 20.

At this point, the flow of air is interrupted and liquid taken from the storage tank is delivered, which enters through the valve and the conduit 6 to remove the dirt present in the space 21 by discharging such dirt into the conduit 9 through the discharge valve, from where it is conveyed to the emulsion storage tank.

In greater detail, when the timer comes into operation, a pulse is sent which closes the valve on the conduit 7 so that no filtered liquid seeps out of the conduit 7, closing - at the same time - the inlet valve on the conduit 6 so that the liquid to be filtered does not enter and the discharge valve connected to a discharge conduit is opened.

With this set-up, the valve on the conduit 12 is opened for a period of approximately 5/10 seconds, allowing air to enter, which will detach the dirt particles from the external surface of the filtering element and lead to them depositing in the space 21. The flow of air is automatically interrupted and the discharge is opened and the liquid taken in so as to remove the dirt present in the space 21 which is conveyed to the storage tank. At this point, the filtering system returns to the working stage.

During this time, the filtering element cleaning stage and the washing stage for the space 21 are performed and the concentrated dirty liquid is sent to the storage tank containing the emulsion.

Thus the present invention achieves the objects set.

The filtering system according to the present invention proves to offer high efficiency for all applications needing a fine system for filtering processing liquids.

Advantageously, the filtering system in question allows frequent automatic cleaning of the filtering element without machine or plant downtime, resulting in better operation of the said filtering element and of the machine to which it is applied, since the liquid is kept cleaner.

In particular, the filtering system is integrated into the lubricating coolant circuit of machines which use high-pressure liquid in which impurities in the fluid must be controlled greatly as such impurities could block important and delicate parts of the machine.

Furthermore, the filtering system in question can be used to filter fluids of any type with variable flow rates ranging from a few litres per minute to very high rates in other areas of application and/or use, and in different plants, such as those used in the food industry or other area.

In addition, the filtering system does not require particular maintenance, does not employ disposable filtering materials (such as the cartridges according to the commonly known technique), has lower operating costs, and offers a drastic reduction in polluting materials to be disposed of.

The filtering system according to the present invention operates extremely efficiently as it has quite remarkable durability, unlike all existing filters, which offer gradually lower filtering capacities over time and become less effective and operational until they finally collapse, while the filter in question always maintains the same characteristics and the filtering capacity, since they return to the equivalent of a new filter after each wash cycle.

A still further advantage of the filtering system in question stems from the fact that such system allows management and maintenance costs therefor to be curbed, thereby allowing greater productivity.

A further advantage of the filtering system is that it offers an improvement in the processing conditions of machinery such as work centres etc or filtering equipment used in the food industry and an improvement in maintainability, with consequent reduction in the servicing times and an extension of the maintenance intervals, thereby allowing the machine greater productivity.

Furthermore, since the filtering system cleans the filtering element automatically, the presence of personnel is no longer required to monitor the machine in order to prevent breakages or problems with the components of the said machine.

A further but not final advantage of the present invention is that the said system proves to be remarkably easy to use and structurally simple, and works well.

Naturally, further modifications or variants may be applied to the present invention while remaining within the scope of the invention that characterises it.