EP0000004B1 - Continuous filtration centrifuge for separation, washing or draining, and application to an automatic coffee machine - Google Patents

Description

The invention relates to filtration in general, and more particularly to the preparation of coffee.

It is known that the filtration operation in general consists in passing a liquid through a porous wall which retains solid particles, these solid particles possibly being previously contained in suspension in the liquid, in the case of filtration for separation. , or on the contrary be placed in advance in the filter and then watered by the liquid when it is desired to carry out a washing or exhausting operation using an appropriate solvent of soluble active substances contained in the solid particles . This is particularly the case for the preparation of coffee which consists of passing hot water through ground coffee.

In the simplest case, the passage of the liquid takes place by simple gravity. However, the filtration efficiency can be improved by passing the liquid under the effect of centrifugal force by using a porous cylindrical wall driven in rotation at high speed around its axis. In both cases the filtration operation is necessarily intermittent, that is to say that filtration phases are followed by cleaning phases for the evacuation of the solid substances accumulated against the porous wall.

However, continuous filters are known in which an endless porous wall is used, either in the form of an endless band, or in the form of a rotary cylinder, and in this case there is a filtration zone or sector followed by another zone. or cleaning sector, this cleaning generally being obtained by scraping using a fixed squeegee then unclogging the porous wall by rinsing in the opposite direction. In the case of such continuous filters, the passage of the liquid is necessarily by gravity or by suction, but it is excluded to operate by centrifugal means, the displacement or rotation of the porous wall being necessarily slow since it is he who presides the sequence of filtering and washing operations.

To overcome the above drawbacks, it is finally known, from German patent No. 691,923, to produce a filter which is both continuous and centrifugal, the cylindrical filtering wall of which is rotatable and constituted by a helical winding with contiguous turns of a long strap mounted in a rotary cage constituted by cylindrical rollers arranged according to external generators of this cylindrical wall, the strap being looped on itself in an endless assembly and driven so that the porous cylindrical wall advances slowly in the direction of the axis constantly renewing itself. However, the drive of the strip is ensured by a central capstan which takes up the strip radially at the base of the cylinder and recycles it at the top, which has the disadvantage of malfunctioning given the difficulty in providing suitable tension. to the endless belt which is simply supported inside the cage formed by the rollers. On the other hand this capstan placed in the center as well as the radial strands which terminate therein and leave it constitute an obstacle which does not allow the central region of the filter to be used and also does not allow the cylindrical filtering wall to be connected with a wall. background. Finally, the endless strip is itself perforated, which does not completely eliminate the problems of unclogging.

The object of the invention is to produce a continuous centrifugal filter of the above type but which eliminates the aforementioned drawbacks by providing a safe and effective drive while freeing the central part of the cylindrical wall.

The invention consists, in an endless centrifugal filter of the preceding type, in ensuring the drive of the strap by the rotational drive on themselves of the rollers of the support cage by an appropriate mechanism, and in carrying out the endless looping by a return channel which extends from one end to the other of the helical winding passing through the outside of the winding and of the roller cage. In addition, the strap is advantageously devoid of perforations and constituted by a solid part provided only with suitable notches on the surface.

• la fig. 1 est une coupe verticale axiale d'un dispositif de filtrage selon l'invention appliqué à une machine à café;
• la fig. 2 est une coupe horizontale selon II-II de la fig. 1;
• la fig. 3 est une vue extérieure en élévation de la partie essentielle du filtre dans sa cage;
• la fig. 4 est une vue de dessous en coupe selon IV-IV de la fig. 3 montrant la disposition du train d'engrenages;
• la fig. 5 est une vue en perspective à grande échelle d'un fragment de la lanière flexible constituant la paroi de filtration.

Other ^p articularities of the invention will appear in the following description of an embodiment taken as an example and represented in the appended drawing, in which:

• fig. 1 is an axial vertical section of a filtering device according to the invention applied to a coffee machine;
• fig. 2 is a horizontal section on II-II of FIG. 1;
• fig. 3 is an external elevation view of the essential part of the filter in its cage;
• fig. 4 is a bottom view in section on IV-IV of FIG. 3 showing the arrangement of the gear train;
• fig. 5 is a perspective view on a large scale of a fragment of the flexible strap constituting the filtration wall.

According to the invention, the porous filtration wall is constituted by a long flexible strap 1 of small section arranged in a helical winding with contiguous turns to form a cylindrical sleeve 2, the two ends of the strap being connected to each other by a strap back 3 to form an endless set. This flexible strap 1 can be made of metal or plastic, preferably of square or rectangular section, and it can advantageously include in its upper or lower face notches 4, preferably inclined so as to widen towards the exterior, starting from a very shallow depth on the side intended to constitute the interior, this depth corresponding to the desired filtration fineness, for example 0.1 mm.

The cylindrical sleeve 2 thus formed is mounted in a cage constituted by a number of cylindrical rollers 5, four in number in the figures, each arranged along a generatrix of the cylinder. Each of these rollers journals by its base in a lower flange 6 and by a part close to its upper end in an upper flange 7 by means of a notch 8 opening towards the center in a bore 9 of a diameter just sufficient to allow the passage of the sleeve 2. The upper flange 7 is rigidly fixed to the lower flange 6 by spacers 10, and the lower flange 6 is itself rigidly fixed by its hub 11 to an axis 12 journalled in fixed bearings 13 while being driven by a drive motor not shown.

The entire cage assembly, including the two flanges and the four vertical rollers, therefore rotates as a block around the axis 12 at a suitable speed to obtain centrifugal filtration, for example 1500 revolutions / min. In addition, the four rollers 5 are driven at a low speed of rotation on themselves, all in the same direction, thanks to an appropriate mechanism located below the flange 6.

This mechanism, visible in particular in FIGS. 1 and 4. has a gear 14 integral with each of the lower ends of the rollers 5, below the flange 6, the four gears 14 meshing simultaneously on a single central gear 15 idling around the axis 12, this central gear being itself -Even driven in rotation by a pinion 16 secured to a gear 17 which rotates around an axis 18 carried by the flange 6 and meshes with a central pinion 19 idly mounted on the axis 12 and whose base 20 can be immobilized in rotation by means of a suitable device not shown. The directions of rotation are those represented by the arrows in FIG. 4, remembering that this is a bottom view, and the ratios of the gears are such that the rollers rotate slowly on themselves at a very low speed while the whole of the cage rotates at high speed .

Under these conditions, the sleeve 2 formed by all of the contiguous turns is applied by centrifugal force against the guide and drive rollers 5 and consequently begins to turn slowly on itself in the direction of the arrow 21 (see fig. 2) in a relative movement of rotation at low speed of the order of 12 revolutions / min in the example chosen. Of course, if we refer to the frame 22 of the device and no longer to the rotating cage, the sleeve 2 actually turns in the same direction as the cage, that is to say in the direction of the needles of a watch in fig. 2, and at a speed barely lower, for example 1500 rpm for the cage and 1448 rpm for the sleeve. As a variant, it would naturally be possible to rotate the sleeve in a direction such that its slow differential speed is added to that of the cage instead of being entrenched.

On the other hand, the direction of winding of the contiguous turns of the sleeve 2 is chosen in such a way that, in the aforementioned relative movement of the sleeve relative to the cage, the strap takes place at the top, just after passing under one of the axial retaining cheeks 23 of one of the rollers 5, then performs the return turn 3 passing outside the following rollers 5, but preferably inside the spacers 10 to wind continuously 'lower end on the cylindrical outer surface of a bottom wall 24 visible in FIG. 1 and turning madly around the hub 11 in order to be able to take with respect thereto the slow rotational movement of the entire filter. This movement is communicated to the bottom 24 by meshing or by friction on its periphery of a drive zone 25 situated at the base of the rollers 5 below the axial retaining cheeks 26.

In this way the winding by force of a new continuous winding under the previous ones obliges the whole of the sleeve to progress slowly upwards, that is to say towards its open end, the number of turns being constant this which allows the cheeks 23 and 26 to maintain the actually contiguous turns with a slight tightening or a calculated clearance. In the embodiment, a coil in the lower position takes approximately 2 minutes 36 seconds to reach the top and complete a complete cycle.

It is therefore understood that with such a filter, it suffices to introduce the product or products to be filtered axially, and to deposit them for example on the bottom 24, so that these products are projected onto the inner face of the sleeve 2 where filtration takes place, the filtrate being projected tangentially against the wall 22 which surrounds the cage to then flow through a peripheral channel 27 towards a discharge chute 28, while the solid residues progress slowly upwards while being systematically wrung until exhausted and end up being ejected by centrifugal force beyond the last turn, that is to say above the upper flange 7. To prevent the return of solid residues to the lower compartment, the primer upper of the back turn 3 passes through this flange 7 through an adjusted light surrounded by a cover 29 also adjusted.

Since the strap 1 once unrolled no longer has any perforation, but simply slight notches, no unclogging, no rinsing is necessary. At most, provision can be made for scraping the three smooth faces of the strap and possibly brushing the face comprising the notches 4, using a fixed or rotary brush integral for example from one of the rollers 5, this in the case where the centrifugal force is not sufficient to eject the solid residues. To facilitate the evacuation of solid residues, it is also possible to have two shovels 30 located in a fixed position and inclined downwardly towards the inside of the last upper turns of the sleeve in order to evacuate solid residues before the beginning of the unwinding of the strap. These solid residues are therefore all cases projected by centrifugal force against the wall 22 but in the upper compartment where they are discharged by a tangential chute 31. Two flexible blades 32, fixed vertically on the top of the flange 7 to lick the interior surface of the wall 22, facilitate the collection and evacuation of solid residues.

With such a filter, it is therefore possible to permanently supply the heterogeneous mixture to be separated in the axis, or the pulverulent product and the liquid separately in the event of washing or exhaustion, and continuously discharge the solid residues at the top and the filtrate at the bottom, and this in continuous operation without requiring any cleaning stop. This continuity of mechanical operation and this automaticity of cleaning is however not necessarily linked to continuity over time of operations. Indeed, if desired, the filter according to the invention can be operated by successive loads by simply providing for this a braking device controlled from the base 20 of the central pinion 19 relative to the frame 22. It is then sufficient in a first time to feed the products while braking this device, which allows by the ascent of the spiral to distribute the products, then in a second time to remove the braking which thereby eliminates the differential movement of the spiral which ceases consequently its upward movement while continuing to rotate at high speed, which makes it possible to continue the filtering and spinning operation for as long as desired. Finally in a third step, it suffices to put the brake of part 20 back into action to produce again the ascent of the spiral and the evacuation of the products, this phase being able to be combined with the first of a following cycle.

For the application to the manufacture of coffee, the filtering device according to the invention also has the advantage that it is possible to extend the axis 12 by an upper part 33, separable or not from the previous one and placed in the axis of the cylindrical sleeve 2, to drive at the upper part a screw grinder of the type known for grinding coffee. For this, the grinding screw 34 is cut directly in the upper end of the axis 33 and rotates in an outer part 35 with a conical interior located at the base of a hopper not shown feeding the coffee beans using 'An adjustable flow distributor 36 which can also be driven by the same axis. The fineness of the grinding is adjusted, for example, by moving the base 35 in a helical movement with a vertical axis using a control rod 37 sliding in an inclined lumen 38 integral with the frame 22, the screw 33 being axially fixed.

When the filter according to the invention is used for washing or depleting a pulverulent solid substance with a liquid substance, it is advantageous to first have the solid substance near the bottom 24 in a uniform cylindrical layer, then to distribute the liquid above the place where the distribution of the solid takes place. This can be done very easily according to the invention by arranging a coaxial rotary distributor 39 comprising a central passage for the solid product and an at least partially conical external surface 40 onto which the liquid is poured which is thus projected by centrifugal force, the distributor 39 being for this purpose driven in rotation, for example at the speed of the axis 12 or 33 by being secured to it by means of a through pin 41. As a variant, this distributor could be secured to the bottom 24 by pins parallel to the axis, the bottom speed being, as we saw above, very little different from that of the axis.

The conical outer surface 40 of the distributor 39 can be extended by a cylindrical part which preferably has asperities to distribute the spraying of the liquid over a certain height. By way of example, these asperities can be constituted by a rib 42 in the form of a helical spiral developing on the cylindrical outer surface 43 of the dispenser. In addition, a circular rib 44 forming a deflector can be placed at the base of the dispenser to evacuate the droplets of liquid which could possibly fall outside the exterior surface of the dispenser.

For application to a coffee machine, the ground coffee can be fed into the axial passage of the rotary distributor 39 by any suitable means. In particular, if there is an axis 33 and a coaxial grinder 34 as explained above, it is perfectly possible to place this distributor coaxially and outside this axis by extending it axially by a tubular part 45 of which the upper end journals at the base of the grinding cone 35. If the latter moves axially to allow adjustment as indicated above, an oblong hole 46 is provided in the base of the axis 33 for the passage of the pin 41 and allow this movement to occur.

In this case the ground coffee which escapes directly between the screw 33 and the tubular part 45 may be pressed against the latter by centrifugal force and accumulate there. This is avoided according to the invention by having a fixed spiral 47 of helical steel wire freely mounted in the interval between the axis 33 and the bore of the tube 45 and the rotary distributor. 39, being only immobilized axially and in rotation by fixing its upper end 48 in the base of the cone 35. In this way the ground coffee is routed regularly and without the possibility of blocking to the lower end of the distributor 39 where it is thus distributed by centrifugal force in the interval between the bottom 24 and the rib 44 to come to accumulate on an area of the same height on the inner surface of the sleeve 2.

Still in the case of the coffee machine, the liquid substance, which is obviously hot water in this case, can be continuously supplied and heated and distributed on the conical part 40 of the distributor 39. It is however preferable according to the invention to produce a water supply intermittently by supplying a continuous flow to a device well known in physics under the name of intermittent fountain and constituted by a self-priming siphon placed in a container (not shown) which gradually fills and empties under the effect of the siphon. In this case, the capacity of this container between the high level and the low level is preferably chosen equal to a cup of coffee.

The cold or preferably preheated water is therefore distributed by a continuous distributor, such as a pump, to the intermittent fountain, which distributes it by a pipe 49 at a small capacity 50 in the form of an annular sleeve arranged coaxially with outside the tube 45 and stationary in rotation, this capacity 50 comprising an internal heating resistor 51 supplied by wires 52, while flow spouts 53 are formed all around its bottom and vertically above the surface conical 40 of the dispenser 39. In this way the water is heated or reheated by this resistance before flowing over the dispenser and, from there, is projected onto the cylindrical layer of coffee before passing through it and to be wrung against the wall 22.

The periods of intermittent fountain shutdown have two advantages, the first being that there is a cessation of the flow of coffee through the chute 28 thus allowing to remove a full cup and replace it with an empty cup without losing of coffee, and the second being that, on the next arrival of the distribution of water on the hot resistance 51, there occurs a partial vaporization of this water which thus causes the ground coffee beans which have been dispensed to swell. the interval near the bottom 24.

We can thus distinguish on the inner surface of the sleeve 2 and from bottom to top three successive distinct zones of progressively increasing width, the first that is to say the lowest corresponding to the distribution of the coffee and then to its inflation with steam. , the second located at the height of the rib 42 corresponding to the watering of the coffee which produces the maximum amount of liquid coffee by centrifugal passage, and the third which overcomes the previous one corresponding to the advanced wringing of the marc crown to recover the last drops of coffee and evacuate almost dry grounds at the top using the general means indicated above. Of course, the grounds evacuation chute 31 is directed towards a grounds tank forming part of the apparatus and which is emptied periodically. The device also includes a water tank if you want to avoid a connection on the pipeline.

It can thus be seen that the apparatus according to the invention, with relatively simple means and all mounted coaxially on the same axis, except for the various tanks, makes it possible to quickly and automatically carry out all the operations of grinding, distribution, vaporization, pouring, passage and spinning as well as cleaning of the filter and evacuation of the grounds, the apparatus being able thus to function in an absolutely uninterrupted manner and to produce as many cups of coffee as desired if simply to supply it and empty its grounds container without it being necessary to stop it. Conversely, it is perfectly possible to stop its production when desired by stopping the distribution of water, then the engine after a determined time, production can resume immediately as soon as desired, provided that the water has been kept at temperature.

Although the above embodiment is with a vertical axis of rotation, this axis could also be arranged according to any other angle of orientation, for example horizontally, the rotary distributor 39 then being in this case replaced by simple fixed conduits, and the bottom 24 also being optional.

Claims (11)

1. A continuous centrifugal filtering device for separation, washing or draining by passing a liquid substance through a porous cylinder wall rotating at high speed which holds back the solid particles contained in the liquid or deposited beforehand on the filter, the cylinder wall being formed by a helical winding with touching turns of a long band mounted inside a rotary cage formed by cylindrical rollers around the outer generatrices of the cylindrical wall, with the band forming a continuous loop on itself in an endless system and so driven that the porous cylinder wall advances slowly along the centre line and constantly gets renewed, which device is characterized by the fact that the band drive is formed by the rotary drive of the said rollers on their axis through a suitable mechanism and that the endless loop is achieved by means of a return turn which stretches from one end of the said helical winding to the other passing outside the winding.

2. The device according to claim 1, characterized by the fact that the band has a square or rectangular cross-section with three smooth faces and one surface containing notches or slots flared towards the outer side.

3. The filtering device according to either claim 1 or claim 2, characterized by the fact that the cage is formed by two end plates connected by spacers, one end plate being solid and rigidly connected to a drive shaft and one end plate being annular with a centre hole bored through it through which passes the helical winding forming the cylindrical filter wall, with the guide rollers being extended through the annular end plate through notches acting as half (sleeve) bearings which open onto the said centre hole on the inside, whilst a suitably shaped window permits the said return turn also to pass through the annular end plate, the directions of rotation of the shaft, of the rollers and of the band winding in the touching turns section being such that the whole of the porous wall moves slowly round its axis in the same direction as the annular end plate.

4. The filtering device according to claim 3, characterized by the fact that on the solid end plate side the band coming from the return turn is wound continuously onto the cylindrical outer surface of an end wall fitted loose on the shaft and driven with respect to the solid end plate with a low speed rotary motion corresponding to the rotary motion of the filter wall.

5. The filtering device according to any of the previous claims, characterized by the fact that the various cylindrical rollers of the cage are driven in rotation round their axis simultaneously with the rotation of the cage by means of a gear train from a centre pinion mounted on the shaft and capable of being fixed in rotation.

6. The filtering device according to claim 5, characterized by the fact that the said centre pinion is fixed by a controlled brake device which enables the axial motion to be interrupted without interrupting the rotary motion of the filter.

7. The filtering device according to any of the previous claims, characterized by the fact that the cage is surrounded by a casing of which the section located on the same side of the annular end plate collects the filtrate and the part located on the other side of this end plate collects the solid residues, detached from the inside of the cylindrical wall, or from the outside of the band by suitable scraper devices, and sent to an outlet port by devices for scraping the inside wall of the casing.

8. The filtering device according to any of the previous claims, characterized by the fact that its axis is vertical and that it contains inside a rotary distributor with an axial duct for the powder product and an outer surface which is tapered, at least in part, for distribution of the liquid product.

9. The filtering device according to claim 8, more especially designed for producing coffee, characterized by the fact that its centre shaft is extended through the rotary distributor to a screw mill of known type mounted coaxially with the filter, the rotary distributor being extended by a tubular part as far as the base of the screw mill.

10. The device according to claim 9, characterized by the fact that, in the space located between the extension of the rotary shaft and axial duct of the rotary distributor and its tubular extension, a helical wire with a large coil pitch is placed and fixed axially and in rotation at the top.

11. The device according to claim 10, characterized by the fact that the distribution of the liquid which consists of water, preheated or not, occurs at a constant flow rate but through an intermittent fountain or feed system holding the contents of one cup of coffee and feeding a heating or superheating and steam generation device arranged coaxially outside the tubular extension to the rotary distributor and discharging onto the tapered part of this rotary distributor.

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