EP0000004A1 - Continuous filtration centrifuge for separation, washing or draining, and application to an automatic coffee machine - Google Patents

Abstract

Continuous centrifugal filtration device for separation, washing or exhaustion, characterized in that the rotary cylindrical wall is constituted by a helical winding with contiguous turns of a long strap (1) mounted in a rotary cage constituted by cylindrical rollers (5 ) arranged according to external generators of the cylindrical wall and driven in rotation at low speed all in the same direction by an appropriate mechanism, the strap being looped into an endless assembly by means of a return coil (3) which extends from from one end to the other of said helical winding, whereby the porous cylindrical wall advances slowly in the direction of the axis, constantly renewing itself. Application: automatic coffee machine.

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, it is possible to improve the filtration efficiency 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 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 reverse. 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.

It is therefore absolutely not possible with the state of the art to benefit from both the automaticity of continuous filtration and the efficiency of centrifugal filtration. The object of the invention is to overcome the above drawbacks by producing a filter which is both centrifugal and continuous, while being of a relatively simple embodiment, and which furthermore does not require any unclogging rinsing.

The invention consists in constituting the porous filtering wall by a helical cylindrical winding with contiguous turns of a flexible strap of small section, this wall being mounted between several guide and drive rollers of elongated shape arranged according to generatrices of the cylinder. and mounted in a cage rotating at high speed around the axis of the cylinder, while the rollers rotate on themselves at a low speed relative to the cage to give the entire cylindrical wall a relative rotational movement differential, the strap being looped into an endless assembly so that in this relative movement it takes place constantly at one open end of the cylinder and is constantly wound at the other end, preferably around a closed bottom, the movement slow differential rotation is therefore accompanied by a continuous axial movement towards the open end, the product or products to be filtered being conveyed s by one or more suitable conduits in the vicinity of said bottom, while the centrifuged filtrate is collected by a casing outside the cage and the spun solid residues are continuously ejected at the open end of the cylinder.

• 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 features of the invention will appear in the following description of an embodiment taken as an example and shown in the attached 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 along 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 together by a turn 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 outwards in 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, by means of an appropriate mechanism located below the flange 6.

This mechanism, visible in particular in FIGS. l and 4, comprises 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 it -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 turn 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 slightly lower speed, 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 movement above mentioned relative of the sleeve relative to the cage, the strap takes place at the upper part, just after the passage under one of the axial retaining cheeks 23 of one of the rollers 5, then carries out the return coil 3 passing to the outside the following rollers 5, but preferably inside the spacers 10 to wind continuously at the 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 with 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 part of the back turn 3 passes through this flange 7 through an adjusted light surrounded by a cover 29 also adjusted,

Since the strip 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 secured for example to 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 downwards towards the inside of the last upper turns of the sleeve in order to evacuate the solid residues before the start of unwinding of the strap. These solid residues are therefore in 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 surface inside 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 not however necessarily linked to the 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 allows 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 distribute the liquid above the place where the distribution of the solid takes place. This can be achieved 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 on 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 spindle 41. As a variant, this distributor could be secured to the bottom 24 by pins parallel to the axis, the speed of the bottom 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 of 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 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 fed and heated continuously 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 by a continuous flow a device well known in physics under the name intermittent fountain and consisting of 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 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 practically dry marc at the top thanks to 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. Continuous centrifugal filtration device for separation, washing or exhaustion by passage of a liquid substance through a porous cylindrical wall rotating at high speed which retains solid particles contained in the liquid or previously deposited on the filter, the cylindrical wall rotary being 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 generatrices of the cylindrical wall, the strap being looped on itself in an endless and driven assembly so that the cylindrical porous wall advances slowly in the direction of the axis, constantly renewing itself, device characterized in that the drive of the strip is carried out by the rotary drive on themselves of said rollers by a mechanism appropriate, and that endless looping is achieved using a return coil which extends from one extrem ity to the other of said helical winding passing through the outside of the winding. 2. Device according to claim 1, characterized in that the strap is of square or rectangular section with three smooth faces and a surface comprising notches flared outwards. 3. Filtration device according to either of Claims 1 and 2, characterized in that the cage consists of two flanges joined by spacers, including a full flange secured to the end of a drive shaft and an annular flange pierced with a central bore through which passes the helical winding constituting the cylindrical filtration wall, the guide rollers extending through the annular flange passing through notches forming half-bearing and opening towards the inside in said bore, while a window of suitable shape allows said return coil to also pass through the annular flange, the directions of rotation of the axis, rotation of the rollers and winding of the strap in the part to contiguous turns being such that the slow axial movement of the entire porous wall takes place in the direction of the annular flange. 4. A filtration device according to claim 3, characterized in that on the side of the full flange, the strap from the return coil is wound continuously on the cylindrical outer surface of a back wall mounted madly around the 'axis and driven relative to the full flange of a relative movement of rotation at low speed corresponding to the rotational movement of the filtration wall. 5. A filtration device according to any one of the preceding claims, characterized in that the various cylindrical rollers of the cage are rotated on themselves simultaneously with the rotation of the cage using a train of 'gears from a central pinion mounted on the axis and can be immobilized in rotation. 6. A filtration device according to claim 5, characterized in that said central pinion is immobilized by a controlled brake device making it possible to interrupt the axial movement without interrupting the rotational movement of the filter. 7. Filtration device according to any one of the preceding claims, characterized in that the cage is surrounded by a casing, the part located below the annular flange collects the filtrate and the part located beyond this flange collects the solid residues, peeled from the inside of the cylindrical wall, or from the outside of the strap by suitable scraping devices, and conveyed to an outlet orifice by scraping devices from the inside wall of the casing. 8. A filtration device according to any one of the preceding claims, characterized in that its axis is vertical and that it internally comprises a rotary distributor with an axial passage for the pulverulent product and an outer surface at least partially conical for the distribution of the liquid product. 9. A filtration device according to claim 8, more particularly intended for the manufacture of coffee, characterized in that its axis extends through the rotary distributor to a screw grinder of known type mounted coaxially with the filter, the distributor rotary extending by a tubular part to the base of the screw mill. 10. Device according to claim 9, characterized in that, in the space located between the extension of the rotary axis and the axial passage of the rotary distributor and its tubular extension, there is disposed a helical wire with large pitch immobilized axially and in rotation by its upper part. 11. Device according to claim 10, characterized in that the distribution of the liquid consisting of water, preheated or not, takes place at a continuous rate but by means of an intermittent fountain of the capacity of a cup of coffee and which feeds a heating or superheating and vaporization device arranged coaxially outside the tubular extension of the rotary distributor and pouring onto the conical part of this rotary distributor.

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