Abstract:
A brewing unit comprises a body containing a brewing chamber with vertical axis capable of receiving a pressing plunger mounted mobile along the vertical axis, and a hydraulic jack whereof the piston rod is connected to the pressing plunger and can pass from an inoperative position to a working position, by the effect of a liquid under pressure. The hydraulic jack is a single-acting actuator, the piston rod being returned in inoperative position by compressible and extensible elements. The invention is applicable to espresso coffee brewing machines.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is the 35 USC 371 national stage of international application PCT/FR98/01906 filed on Sep. 4, 1998, which designated the United States of America. 
     FIELD OF THE INVENTION 
     The present invention relates to an infusion assembly for automatically dispensing beverages made from powdered coffee or the like and comprising a body enclosing an infusion chamber with a vertical axis having a bottom and an outlet, comprising a filter plate movably mounted in said chamber by means of an ejection mechanism, and adapted to receive a presser piston mounted movably along said vertical axis, as well as a hydraulic jack whose piston is connected to said presser piston and can pass from a rest position to a working position, under the influence of a liquid under pressure; the presser piston being in compression in the chamber in the working position. 
     BACKGROUND OF THE INVENTION 
     In automatic beverage dispensers, there already exist different types with various infusion assemblies. These assemblies have complicated mechanical movements performed by electric motors and reducers, of high cost, as well as lever transmissions which must be very precise. These assemblies also require a very precise volumetric dosage of the coffee powder so as to avoid interfering with the movements and transmissions. It will be understood that the operation of such assemblies is delicate and require careful production and assembly of multiple mechanical pieces. 
     To overcome these delicate and difficult constructions, it has already been proposed to replace these motorized movements and lever transmissions with movements performed by double-acting hydraulic jacks. Unfortunately, this type of hydraulic jack is difficult to control, not only as to the movement of its piston, but also as to the equilibrium of the opposing pressures, and gives rise to prohibitive costs for automatic beverage dispensers, such as espresso coffee-making machines which must be mass-produced. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to simplify the mechanisms and hence to render them more reliable and less costly on an industrial scale, whilst providing flexible and practical operation to guarantee the maximum results in the preparation of the infusion. 
     These objects are achieved by providing a single-acting hydraulic jack, the piston being returned to its rest position by compressible and extensible means. 
     Thus, the piston ensures, in a first step, the descent and compression of the presser piston into the infusion chamber under the force of the liquid under pressure, and in a second step the rising and automatic withdrawal of said presser piston from the chamber under the influence of the compressible and extensible means. Moreover, to produce real espresso coffee, it is necessary to ensure certain essential parameters which are the temperature of the water and the compaction of the coffee powder within the infusion chamber. This compaction, depending either on the degree of grinding of the ground coffee, or its hygrometry, can be guaranteed by this single-acting jack which adjusts automatically to the mass of ground coffee during its compression, and which is returned automatically by the compressible and extensible means at the end of an infusion cycle. Thus, said jack and the presser piston operate without an end of path microswitch at either end of the path and cannot become blocked in an intermediate position because there is no supplemental linkage with adjusted movement. 
     In a first embodiment, the compressible and extensible means is a coil spring and the single-acting jack has corresponding structure. 
     In a second embodiment, the compressible and extensible means is a gas and the single-acting jack has a slightly different structure from that of the spring jack. 
     According to a preferred characteristic of the invention, the body of the infusion assembly is arranged laterally of the cylinder and the upper rod of the hydraulic jack carries the arm forming a beam whose free end is connected to the presser piston, the paths of the pistons thus extending in practically parallel directions. 
     Thanks to such an arrangement, there is obtained a compact height of the assembly and a reliable operation despite the drawbacks or precision inherent in fabrication of pieces of mass production. Moreover, the space saving is connected directly to the reduction in sales price of the automatic beverage dispensing machine. 
     According to another characteristic of the invention, there is provided a means to dry the cakes of coffee grounds at the end of the infusion cycle, and for this, the presser piston comprises an internal conduit for passage of the infusion which has three openings, a first inlet opening for the infusion opening into the lower surface of the piston, a second outlet opening forming a small fountain for the outlet of the infusion and a third opening forming an air intake and arranged in the upper portion of the piston, said presser piston being mounted moreover movably axially on the pivot and said third opening comprising a joint adapted to close this opening when the piston comes into contact with the lower portion of the arm. 
     According to still another aspect of the invention, there is provided an ejection mechanism for the cake of grounds formed in the infusion chamber and which comprises, on the one hand, a rod secured to the filter plate, mounted along a vertical axis, sliding in the body and having at its external end a small plate, said filter plate being returned resiliently downwardly of the infusion chamber by a spring arranged between the body and the small plate, and, on the other hand, an arm transversely connected to the lower rod of the jack, movably mounted rotatably on said rod, and which one end comes into engagement with a track of a cam carried by a wing extending in a vertical plane below the jack, whilst the other end is adapted either to come into engagement with the small plate when the piston head passes from its lower position to its upper position, or to escape from this plate when the head passes from its upper position to its lower position. 
     According to still another important characteristic of the invention, the infusion assembly comprises an expulsion device for the grounds comprising a guide console projecting upwardly, secured to the jack and having a lever pivotably mounted about an axis transverse to the vertical axis and carrying at its free end a scraper adapted to be moved transversely for pendular sweeping in the outlet region by means of a finger secured to the arm which comes into engagement with a notch on the lever at the level of the axis, when the piston head occupies its rest position. 
     This device is of extremely simple construction, requiring only a single movable member thus not requiring any precise adjustment after production and hence increasing the reliability of operation and concomitantly reducing the cost of production. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The characteristics and advantages of the invention will become apparent from the description which follows, given by way of non-limiting example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a front elevational view of an infusion assembly according to the invention; 
     FIG. 2 is a left side view of the infusion assembly of FIG. 1; 
     FIG. 3 is a fragmentary vertical cross-sectional view of the assembly according to FIG. 1, showing an infusion chamber, a hydraulic jack, and an ejection mechanism; 
     FIG. 4 is a fragmentary vertical cross-sectional view of the assembly of FIG. 2 with an instantaneous heater shown exploded and without the ejection mechanism; 
     FIG. 5 is an elevational view on an enlarged scale of a presser piston according to the invention; 
     FIG. 6 is a vertical cross-section of the presser piston of FIG. 5; 
     FIG. 7 is a bottom view of the presser piston of FIG. 5; 
     FIG. 8 is a top view on the line  8 — 8  of FIG. 5; 
     FIG. 9 shows schematically in elevation a device for expelling grounds with a lever, incorporated in the infusion assembly according to the invention; 
     FIG. 10 is a fragmentary cross-sectional view of a plug of the hydraulic jack shown particularly in FIG. 3; 
     FIG. 11 is a plan view of a detail of the ejection mechanism shown particularly in FIGS. 3 and 4; 
     FIG. 12 is a bottom view of FIG. 10, with a joint eliminated; 
     FIGS. 13,  14 ,  15 ,  16 ,  17  and  18  are different views in fragmentary cross-section of the infusion assembly according to the invention showing the various steps of operation during the cycle of preparing an infusion; 
     FIG. 19 is a modified embodiment of the infusion assembly and shows in fragmentary cross-section a new hydraulic jack according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The infusion assembly shown particularly in FIGS. 1 to  4  is adapted to equip a coffee machine of the automatic type comprising a cold water supply, a powdered coffee dispenser from either a store of powdered coffee, or a coffee grinder integrated in the dispenser, a heater to heat the cold water, an electric circulation pump for water connected to the cold water supply and to the heater to prepare the infusion and to operate a hydraulic jack, as well as an electronic command and control device for the cycles of preparing infusions. 
     This infusion assembly comprises a body  10  enclosing an infusion chamber  31  with a vertical axis V having a bottom  11  and an outlet  15 , comprising a filter plate  36  movably mounted in said chamber by means of an ejection mechanism  16 , and adapted to receive a presser piston  62  mounted movably along the vertical axis V, as well as a hydraulic jack  61  whose piston  35  is connected to said presser piston and can pass, under the influence of a liquid under pressure such as the water propelled by the electric pump, from a rest position to a working position, in which working position the presser piston  62  is in compression in the infusion chamber  31  (see FIGS.  15  and  16 ). 
     As is seen particularly in FIGS. 3 and 4, the heater  60  of the instantaneous type is formed from a single piece with the body  10  enclosing the infusion chamber  31  and comprises an electric heating resistance  36  inserted in the body  10 . This resistance is of the shielded type for example and is shaped as a pin of U-shape which is inserted in a groove  29  of the sidewall of the body  10  and which extends over practically all the height of this body so as to heat integrally the infusion chamber  31  and the channels  30  that are rectilinear and parallel to the axis V and serve as passages for the cold water which enters these channels by an inlet  32  arranged at the base of the body  10 . 
     In order to impart to this type of coffeemaking machine described above a “steam outlet” function, the infusion assembly according to the invention also comprises a secondary heater  83  secured to the sidewall  44  of the body  10  and providing a flattened chamber  45  heated by the resistance  26  and having a water inlet  81  and a steam outlet  82 . 
     According to the invention, the hydraulic jack  61  is a single-acting jack, the piston  35  being returned to its rest position by a compressible and extensible means. According to a first characteristic of the invention, said compressible and extensible means is a coil compression spring  34 . This spring is either of the cylindrical type with non-touching turns, or of the conical type with non-touching turns permitting a greater axial compression and hence a saving of height of the jack. 
     According to a modified embodiment of the invention shown in FIG. 19, the compressible and extensible means is a gas  34 . This gas is preferably a neutral gas. This gas is introduced for example through a loading valve  17  arranged in the bottom  19  of the jack  61 . 
     In the first embodiment shown in FIGS. 1 to  18 , the hydraulic jack comprises a cylinder  18  closed at its ends by an upper plug  28  and a bottom  19  and through which slide respectively an upper rod  65  connected by an arm  101  to the presser piston  62  and a lower rod  68  connected to the ejection mechanism  16 , said rods  65  and  38  being secured to the head of the piston  35  slidably mounted in the cylinder  18  and movable between a high position in which the head  35  is pressed by the pressure of the liquid from the pump (7 to 10 bars) and introduced by an inlet-outlet conduit  71  (FIG. 10) provided in the plug  28  and supplied by a three-way electrovalve (not shown), and a low position in which the head  35  is pressed toward the upper position by the spring  34  arranged below the head  35 . 
     To ensure good sealing of the jack, the plug  28  has (FIGS. 10 and 12) a seat  74  which receives the force of the edge of the cylinder  18 , as well as a seat  75  for a sealing joint  75 ′ for the rod  65  which passes through a bore  76   5  provided in said plug. On the other hand, the piston head  35  carries a sealing means  35 ′. 
     In the modified embodiment shown in FIG. 19, in which the same reference numerals are used for similar parts, the hydraulic jack  61  comprises a cylinder  18  closed at its ends by an upper plug  28  and a bottom  19 . The bottom  19  receives the valve  17  for loading gas  134 , whilst the plug  28  is traversed by the rod  65 . The head  35  of the piston carries a sealing means comprising two peripheral joints  111  and  113 . 
     Thanks to this hybrid hydraulic jack of the single-acting type, there is obtained a simple, reliable and less costly construction. Thus, there are eliminated the problems of controlling the piston by a supplemental electrovalve as well as path detectors associated with the head and the electric pump is provided because the spring or the gas alone maintains said head in the upper position without exerting abnormal pressure on the plug  28 . 
     According to another preferred characteristic of the invention, the body  10  of the infusion assembly is arranged laterally of the cylinder  18  and the rod  65  of the hydraulic jack  61  carries the arm  101  forming a beam whose free end  19  is connected to the presser piston  62 , the paths of the pistons  35  and  62  thus being arranged in practically parallel directions. Moreover, the presser piston  62  is floatingly mounted on a pivot  99  connected to the arm  101 , thereby providing a slight play between the upper portion  62   a  of the presser piston and the lower portion  101   a  of the arm (see FIGS.  5  and  6 ). 
     Thanks to such a construction, the height-wise size of the infusion assembly is greatly reduced relative to an arrangement with a jack aligned along the vertical axis V of let the infusion chamber. On the other hand, the beam connection between the jack  61  and the presser piston  62  permits the floating mounting of said piston without a complicated mechanism and hence ensures a good coincidence and/or concentricity between the presser piston  62  and the chamber  31  during its introduction and its sliding within said chamber. To facilitate this introduction of the presser piston, the edge of the outlet  15  can be slightly hollowed. Another advantage of this beam construction is the distribution of the forces between the jack  61  and the presser piston  62  during incorrect loading of the ground coffee into the infusion chamber  61 , which distribution of forces arises from the assembly of rod  65 , arm  101  and pivot  99 . 
     According to another particular characteristic illustrated in FIGS. 5 and 6, the presser piston  62  comprises an internal conduit  42  for passage of the infusion which has three openings, a first inlet opening for the infusion  42   c  opening in the lower surface  43  of the presser piston, a second outlet opening  42   b  forming a small fountain  64  for outlet of infusion, and a third opening  42   a  forming an air intake and arranged in the upper portion  62   a  of the piston. The small fountain  64  is connected directly to a trough (not shown) for filling cups. The presser piston  62  has at its end a head  63  comprising a peripheral sealing joint  46  as well as a filter  52  for the infusion retained on said head by a screw  48  screwed into a hole  51 . As will be seen in FIG. 6, the presser piston  62  is moreover movably axially mounted on the pivot  99  thanks to the axial play of securement of this pivot in the hole  98  provided in the arm  101 , and said third opening  42   a  comprises a joint  13  adapted to close this opening when the piston comes into contact with the lower portion  101   a  of the arm  101  during compression of the presser piston  62  against the ground coffee contained in the chamber  31 . 
     The interest of this mounting of the presser piston axially movable in combination with the third opening  42   a , resides in the creation of an external air inlet which, during rising movement of said presser piston from its compression position to its extraction position, creates a vacuum in the chamber  31  and hence a sufficiently great fresh air intake into the conduit  42  to drive the cake of coffee grounds resting on the filter plate  36 . 
     According to still another characteristic of the invention, the ejection mechanism  16  comprises, on the one hand, a rod  20  secured to the filter plate  36 , rising along the vertical axis V, sliding in the body  10 , and having at its external end a small plate  22 , the filter plate  36  being returned resiliently toward the bottom  11  of the infusion chamber  31  by a spring  21  arranged between the body  10  and the small plate  22 , and on the other hand, an arm  67  transversely connected to the lower rod  38  of the jack  61 , movably mounted in rotation on said rod by means of a holding plate assembly  66  connected to the rod and friction spring  68 , and whose one end  70  comes into engagement with a track  69   a  of a cam  69  (see FIGS. 3 and 11) carried by a wing  72  extending in a vertical plane below the jack  61 , whilst the other end  73  is adapted either to come into engagement with the small plate  22  when the piston head  35  passes from its working position to its rest position, or to escape from this plate when the head  35  passes from its rest position to its working position. This cam  69  has a slope  69   b  for returning to a lateral position of the arm  67  relative to the small plate  22 . 
     This ejection mechanism  16  is of a simple and economical construction because it comprises no adjustment mechanism or adjusted connection, the arm  67  positioning itself below the small plate  22  as a function of the movement of its end  70  in the single cam  69 . This ejection mechanism, by its simplicity, guarantees the automatic rising of the filter plate  36  at each end of an infusion cycle and at the right time, which is to say at the end of the path of the head  35  of the hydraulic jack  61  toward its rest position. 
     In order to improve the ejection of the cake of grounds dried by the air current from the conduit  42 , the infusion assembly comprises a device for expelling infusion grounds from the filter plate  36 . This device, better seen in FIGS. 2,  4 ,  9 ,  14  and  18 , comprises a guide console  42  projecting upwardly, secured to the jack  61  and bearing a lever  24  pivotally mounted about an axis  102  transverse to the vertical axis V and carrying at its free end  103  a scraper  23  adapted to be given a transverse pendular sweeping movement in the region of the outlet  15  by means of a finger  40  secured to the arm  101 , projecting transversely, and which comes into engagement with a notch  41  carried by the lever  25  at the level of the axis  102  when the piston head  35  comes to occupy its rest position. This expulsion device of the grounds is also of a very simplified construction and acts directly, in eliminating any adjustment after construction. The single lever  25  is directly actuated at the end of the path of the jack and is briskly swung into the expulsion position because of the connected implantation of the notch  41  of the axis  102 . It is to be noted that the expulsion device and ejection mechanism shown in FIG. 19 are different in their embodiment from those described above and do not form a portion of this patent application. 
     Referring now only to FIGS. 13 to  18 , the operation of the infusion assembly will be summarized hereafter for the automatic beverage dispenser from powdered coffee poured (arrow F) from a hopper schematically shown at T (FIG.  13 ). 
     In the first phase of an infusion cycle (FIGS.  13  and  14 ), the single-acting hydraulic jack  61  is in the rest position under the influence of spring  34  and the presser piston  62  is maintained above the infusion chamber  31 , thereby permitting filling this chamber with a measured quantity of powdered coffee  90 ; the scraper  23  being maintained spaced from the outlet  15  of the chamber by means of the finger  40  in engagement with the notch  41 , and the ejection mechanism  16  being neutralized because the arm  67  is maintained by the cam  69 , namely the upper portion of the slope  69   b , beside and above the small plate  22 . 
     In a second phase of said cycle (FIGS. 15,  16 ), there is introduced by the electric pump liquid under pressure  92  into the chamber  18  above the head  35  of the piston to bring it into engagement with the spring  34  in its working position, in which position the spring is totally compressed and thereby determines the corresponding path of the presser piston  62  and hence the compression, of the powdered coffee  90  in the chamber  31 . During this compression, the arm  101  has closed the air inlet opening  42   a  and the arm  67  of the ejection mechanism is positioned by the cam  69 , namely the narrow guide  69   c , in alignment with and below a small plate  22 . By means of the single electropump and by the three-way electrovalve, cold water is introduced through the inlet  32  which is instantaneously heated in the channels  30  forming a heat exchanger, and which passes through the powder  90  during a predetermined pressure time, then the infusion thus made passes through the conduit  42  to flow through the fountain  64 , via a flexible tube (not shown), toward the distribution means into coffee cups positioned on a base of the coffee-making machine. It will be noted that in this phase, the lever  25  (FIG. 16) and the scraper  23  are in the ready position, the finger  40  extending toward the bottom of the notch  41 . 
     In the third phase, the so-called end of the infusion cycle (FIGS.  16  and  17 ), the three-way electrovalve controlled by the electronic control device cuts the supply of cold water of the heater  60  and permits escape of the liquid from the jack  61  which is done by means of the spring  34  which automatically extends and pushes the head  35  to its rest position. In the course of this movement of the piston  35 , on the one hand, the arm  67  is positioned thanks to the path  69   a  of the cam  69  below the small plate  22  and presses upwardly under the influence of the spring  21  a filter plate  36  to bring it to the end of expansion of the spring  34  at the level of the outlet  15  of the infusion chamber  31 , and on the other hand, simultaneously with the rising movement of the piston  35  and thanks to the beam  65 - 101 , the presser piston  62  is disengaged from the chamber  31 . During the movement of said presser piston, the arm  101  pulls on this presser piston by means of the pivot  99  and permits the escape of air at the level of the third opening  42   a  to cause this air to enter into the conduit  42  up to the opening  42   c  so as to permit drying and better compacting the body of coffee grounds  90  to be ejected. Then, practically at the end of the path of the head  35  of the piston of the jack  61 , the finger  40  carried by the arm  101  engages in the notch  41  of the lever  25 , thereby giving rise to the abrupt pendular sweeping movement of the scraper  23  which thus abruptly ejects the cake of grounds  90  from the filter plate  36  and hence from the outlet  15  of the chamber  31 . Immediately the cycle is terminated, the cam  69 , by its slope  69   b , has again positioned laterally the arm  67 , giving rise to the fall of the filter plate  36  to the bottom of the chamber  31  under the strength of the return spring  21 ; the scraper  23  will be returned to its standby position when a new infusion cycle will be started. 
     The invention is particularly applicable to machines for the preparation of espresso type coffee.