Abstract:
A machine for preparing an infusion includes: an infusion chamber ( 14 ) delimited by a lower vessel ( 3 ) and an upper packing head ( 6 ) that can move relative to one another; a supply of hot pressurized water to the infusion chamber, the packing head ( 6 ) having an inner conduit ( 26 ) having an inlet ( 27 ) that communicates with the infusion chamber and enabling the infusion to pass through the packing head ( 6 ) in an upward direction toward the distribution outlet, and; elements ( 30 ) located inside the conduit ( 26 ) in the vicinity of its inlet and configured for forming the foam in the infusion when passing through the packing head ( 6 ) and for preventing the infusion from returning into the infusion chamber. These elements are formed by a deformable flexible piece ( 30 ) passed through by at least one hole ( 35 ) calibrated for forming the foam and for preventing the infusion from returning.

Description:
BACKGROUND OF THE INVENTION 
     1. Field Of The Invention 
     This invention relates to a machine for preparing an infusion and, in particular but not exclusively, for preparing coffee. 
     More particularly, the invention relates to an infusion preparation machine that comprises an infusion chamber that is designed to receive a product to be infused and that is delimited by a lower vat and a so-called upper tamping head that move relative to one another, and a supply of pressurized hot water to the infusion chamber, whereby said tamping head comprises an internal tube that has an inlet that communicates with the infusion chamber and that makes possible the passage of the infusion through the tamping head in an upward direction toward a distribution outlet, and means that are located in said tube close to its inlet and suitable for forming foam in the infusion during its passage through the tamping head and for preventing the infusion from returning into said infusion chamber. 
     2. Description Of The Related Art 
     Such a machine is known from the document DE-U-20 2004 018 776, which relates to an espresso-type coffeemaker that comprises foam-forming means arranged in a vertical internal tube of the tamping head. These means consist of a valve that comprises a seat that is formed in the wall of the internal tube, a ball with a diameter that is suitable for resting in a sealed manner on the seat, and an open coil spring that is combined with a stop and pushes the ball against the seat. As indicated in this document, these means that form a valve make possible the formation of foam in the coffee. They also keep the coffee that is located above the ball from returning into the chamber after the percolation operation because of the spring pushing the ball against the seat. 
     These means that form a valve, however, use several parts that are expensive and difficult to install and that require a precise machining in the internal tube of the tamping head to form the seat against which the ball can rest in a sealed manner. This increases, of course, the production cost of the coffeemaker, primarily when it is desired to produce the latter on a large scale by reducing the production stages as much as possible. The effectiveness of these means that form a valve can also decrease after a large number of operating cycles if coffee deposits are formed at the level of the moving parts, in particular between the ball and its seat. 
     SUMMARY OF THE INVENTION 
     This invention has as its object to remedy the above-mentioned drawbacks by proposing means that both allow the foam to form in the infusion and keep the infusion contained in the internal tube from returning to the infusion chamber, which are simple, inexpensive and reliable. 
     For this purpose, this invention has as its object a machine of the above-mentioned type, characterized in that said means are formed by a deformable flexible part that is pierced by at least one calibrated orifice to form the foam and to keep the infusion from returning. 
     The foam-forming and nonreturn means of the infusion are thus formed by a single part that can be produced on a large scale at low cost. The space occupied by this part is reduced in particular relative to a valve system with a ball and a spring, and it has high reliability because of the absence of any moving element in its structure. In addition, this part is placed close to the inlet of the internal tube, and even at the very inlet of the latter, and consequently, the infusion residue that is able to return to the infusion chamber is almost non-existent. 
     In preferred embodiments of the invention, there is also recourse to one and/or the other of the following arrangements:
         The flexible part has the shape of a plate that has lower and upper faces into each of which the orifice empties, and the opening of the orifice in said lower face has a section that is higher than that of the opening of said orifice in said upper face;   The orifice has the shape of a slightly elongated slot, whereby the openings of said orifice in the lower and upper faces of the plate have an approximately rectangular section;   The opening of the orifice in the lower face of the plate has a width of between 0.5 and 1 mm and preferably 0.8 mm, and a length of between 1 and 2 mm, and preferably 1.4 mm, and the opening of the orifice in the upper face of the plate has a width of between 0.1 and 0.4 mm, and preferably 0.3 mm, and a length of between 0.6 and 1.5 mm, and preferably 0.9 mm;   The calibrated orifice has, from the lower face of the plate up to its upper face, a first continually decreasing section portion followed by a second constant section portion;   The orifice has, from the lower face to the upper face of the plate, a total height of between 1.5 and 2.5 mm, and preferably 2 mm, whereby the first portion of the orifice has a height of between 1 and 1.5 mm, and preferably 1.3 mm, and the second portion of the orifice has a height of between 0.4 and 1 mm, and preferably 0.7 mm;   The orifice consists of an approximately circular basin that extends from the lower face of the plate and is lengthened by a cylindrical hole that is approximately coaxial to said basin and that extends up to the upper face of the plate;   The cylindrical hole has a height of between 0.6 and 1.2 mm, and preferably 0.9 mm, and a diameter of between 0.5 and 0.7 mm, and preferably 0.6 mm;   The flexible part is made of a silicone that has a Shore hardness of between 60 and 70, and preferably 65;   The flexible part has at least one keying element that is suitable for working with a corresponding relief of the tamping head.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       Other characteristics and advantages of the invention will emerge during the following description, provided by way of nonlimiting example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a simplified cutaway view of an infusion group of a coffeemaker that comprises a flexible foam-forming and nonreturn part according to a first embodiment of the invention; 
         FIG. 2  is a view on a larger scale of the detail A of  FIG. 1 ; 
         FIG. 3  is a perspective view of the flexible part that is produced according to the first embodiment; 
         FIG. 4  is a bottom view of the flexible part along arrow IV of  FIG. 3 ; 
         FIG. 5  is a top view of the flexible part along arrow V of  FIG. 3 ; 
         FIG. 6  is a cutaway view along line VI-VI of  FIG. 4 ; and 
         FIG. 7  is a view that is analogous to  FIG. 6  of a second embodiment of the flexible part. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the different figures, identical references to designate identical or similar elements are preserved. 
     An infusion group  1  that is installed inside a housing, not shown, of a machine for preparing an infusion is shown in  FIG. 1 . The group  1  is designed in particular to prepare a coffee infusion, but it may also be suitable for preparing tea, warm milk, a mixture of these drinks, or any other type of infusion that is prepared by passing hot water though a powdered product to be infused. 
     The infusion group  1  comprises a lower vat  3  with a vertical axis that has a bottom  4  and an inside cylindrical wall  5  along which an upper tamping head  6  slides vertically and in a sealed manner using an O-ring seal  7  that is provided between the periphery of the tamping head  6  and the inside wall  5  of the vat  3 . 
     The infusion group  1  also comprises a heating block  8 , with a vertical axis, that can house the vat  3  in its upper part and that contains an electric heating element  9  and a water pipe  10 . The pipe  10  is connected to a water circuit by means of a pump, not shown, which makes it possible to put the water under a pressure on the order of 15 bar. The pipe  10  has an opening  11  that is located in the bottom  4  of the lower vat  3 , which forms a supply of pressurized hot water. 
     The tamping head  6  has a lower end face  6   a , a better view of which is given in  FIG. 2 , which delimits an infusion chamber  14  with a vertical axis with a portion of the cylindrical wall  5  and the bottom  4  of the vat  3 . The infusion chamber  14  comprises a lower perforated grid  15  that is located on the side of the bottom  4  of the vat  3  and an upper perforated grid  16  that is fastened by a screw against the end face  6   a  of the tamping head  6 . 
     Against its upper face, the lower perforated grid  15  supports the product to be infused, namely the loose coffee grounds in this embodiment, and hot water coming from the heating block  8  passes through it. The lower grid  15  is fastened on a rod  19  that is mounted to slide through the heating block  8 , so that the lower grid  15  can be moved vertically. 
     The upper grid  16  is analogous at all points to the lower grid  15  and defines with the latter the infusion chamber  14 . 
     As shown in  FIG. 1 , the tamping head  6  is carried by an arm  20  that is fastened to an internal piston  21  of a hydraulic jack  22  that makes it possible to slide the upper tamping head  6  vertically into the infusion chamber  14  to tamp the grounds contained in the latter. 
     A pin  23  is mounted to move around the lower end of the piston  21  of the jack  22  and is designed to work with the lower end of the rod  19  during the lifting of the jack to lift the latter simultaneously and to compress a spring (not shown) that is connected to the rod  19  so as to move the lower grid  15  upward. 
     As can be better seen in  FIG. 2 , a collecting chamber  25  is formed between the end face  6   a  of the tamping head  6  and the upper face of the upper perforated grid  16 . In contrast, an internal tube  26  at the tamping head  6  extends vertically through the tamping head from an inlet  27  that is located in the collecting chamber  25 . This inlet  27  consists of the opening of the internal tube  26  in the portion of the end face  6   a  of the tamping head that delimits the collecting chamber  25 . The internal tube  26  is connected at its outlet to outlet pipes (not shown) that orient the coffee toward the outside where it is collected in one or more cups. 
     The operation of the infusion group is briefly described below, but for more detail, it is possible to refer to the document WO-A-99/12457. An automatic coffee preparation sequence begins starting from a position in which the tamping head  6  is raised so as to release the infusion chamber  14 , and in which the lower perforated grid  14  is arranged close to the bottom  4  of the vat  3  in a lowered position as shown in  FIG. 1 . The coffee grounds are then poured out through a discharge spout, not shown, into the infusion chamber  14 . Then, the tamping head  6  is lowered using the hydraulic jack  22  until taking the position shown in  FIG. 1 . During this lowering movement, the coffee grounds are tamped between the lower and upper grids ( 15 ,  16 ). Pressurized hot water is then supplied to the infusion chamber  14  by the heating block  8  and passes through the grounds in an upward movement. The drink that is obtained is collected beyond the upper grid  16  in the collecting chamber  25 , then it passes into the vertical internal tube  26  of the tamping head  6  and flows through the outlet pipes into a cup outside of the machine. Once the infusion operation has ended, the tamping head  6  is lifted to its initial position using the hydraulic jack  22 . During the lifting of the jack, the moving pin  23  works with the lower end of the rod  19  to lift the latter by compressing the spring that is combined with it. The lower grid  15  that supports the used coffee grounds is moved upward by the rod  19  to occupy a position in which it is flush with the opening of the lower vat  3 . The used coffee grounds are then ejected into a grounds dump box, for example by means of a scraper, not shown. Once the used coffee grounds are evacuated, the pin  23  pivots and releases the lower end of the rod  19  so that the lower grid  15  is returned to its lowered position under the action of the spring combined with the rod. 
     As can be better seen in  FIG. 2 , a part  30  is arranged in the immediate proximity of the inlet  27  of the internal tube  26  of the tamping head  6 . 
     The part  30  is made of a flexible material and is deformable under the action of the increase of pressure in the infusion chamber  14  when the latter is supplied with hot water. Preferably, the material that constitutes this part is an elastomer. More particularly, in a preferred embodiment, the part  30  is an alimentary silicone that has a Shore hardness of between 60 and 70, and preferably 65, to impart to the latter a certain deformation taking into account operating pressures. The part  30  that is made of silicone is produced by molding, which makes it possible to produce it on a large scale with precise dimensions and at low cost. 
     The deformable flexible part  30 ,  FIGS. 2 and 3 , consists of a plate that has here the shape of a disk that has a lower face  30   a  that is located on the side of the infusion chamber  14 , an upper face  30   b  and a lateral face  30   c  with a height that is clearly less than the dimensions of said lower and upper faces. 
     In  FIG. 2 , the periphery of the upper face  30   b  of the flexible part  30  rests against a radial shoulder  28  that is formed in the tube  26 , close to the inlet  27  of the latter. The lower face  30   a  of the part  30  comprises projecting studs  31 , a better view of which is given in  FIG. 3 ; in the embodiment shown, the studs  31  are three in number and are arranged in a circle that is concentric to the lower face  30   a  by being distributed equiangularly. 
     When the upper grid  16  is fastened to the tamping head  6 , the latter rests against the top of at least a portion of the studs  31 , which holds the periphery of the upper face  30   b  of the part  30  against the shoulder  28  of the tube  26 . Thus, the deformable flexible part  30  is installed in the tamping head  6  without having to resort to additional fastening elements. 
     The upper face  30   b  of the part  30  in the shape of a disk comprises a cylindrical annular projection  32 , a better view of which is given in  FIG. 2 , which is also concentric to the upper face  30   b . The projection  32  forms a sealing means between the internal tube  26  and the part  30  by resting against an inside flange  29  that is located above the shoulder  28  and/or by being fitted together in the cylindrical portion of the pipe that is located between the shoulder  28  and the flange  29 . 
     The annular projection  32  also forms, with the studs  31 , keying means that prevent a reverse installation of the flexible part  30 , i.e., an installation with the upper face  30   b  oriented downward in the direction of the infusion chamber  14 . For this purpose, the diameter of the annular projection  32  and the diameter of the portion of the internal tube  26  that is located between the shoulder  28  and the flange  29  are less than the diameter D 1  ( FIG. 6 ) of the circle on which the studs  31  are arranged. 
     The flexible part  30  is pierced by an orifice  35  that constitutes a passage for the infusion from the collecting chamber  25  toward the internal tube  26  in which the infusion passes in an upward direction toward a distribution output. 
     The orifice  35  of the part  30  is calibrated, on the one hand, to form foam in the infusion during its passage into the vertical internal tube  26  from the tamping head  6 , and, on the other hand, to prevent the return of the infusion that is contained in the internal tube  26 , above the part  30 , toward the infusion chamber  14  after the infusion operation. For this purpose, the orifice  35  should have particular dimensions and a particular profile and the flexible part  30  should have a given deformation. Actually, the pressurized infusion that is coming from the chamber  14  should undergo an acceleration and a significant loss of pressure during its passage through the orifice  35  so as to obtain foam in the infusion jet that exits via the opening  35   b  of the orifice  35  in the upper face  30   b . However, it is not necessary that the orifice  35  forms too large an obstacle to the flow of the infusion toward the distribution outlet, which would unacceptably lengthen the time for preparing a coffee, and would even disturb the operation of the machine. On the other hand, the characteristics of the orifice  35  and the flexible part  30  should prevent the return of the infusion into the collecting chamber  25  under the action of the weight of the infusion column that is contained in the tube  26 , preferably even if a slight partial vacuum prevails in the infusion chamber  14  or a slight overpressure prevails in the internal tube  26 . For this purpose, it is natural to reduce the passage section of the orifice  35 . 
     The nonreturn function of the part  30  keeps the infusion from falling back, after the ejection of the used coffee grounds, into the empty infusion chamber  14 . Actually, such a return would create vapor, since the heating block  8  remains at an elevated temperature. The vapor produced would then condense on other parts of the machine, and in particular on the grounds discharge spout. The presence of water in this discharge spout, however, would create sticking of a portion of the poured-out grounds, and even a clogging of the discharge spout after several cycles. It will be noted that the infusion that remains in the collecting chamber  25  after the infusion operation is eliminated with the used coffee grounds. 
     The foam-forming and nonreturn operations should therefore satisfy various constraints that require a precise calibration of the orifice  35  that can be determined using numerous tests that lead in particular to adopting the dimensional characteristics that are indicated below. 
     The applicant noted, however, that it was preferable to adopt an orifice  35  whose opening  35   a  in the lower face  30   a  of the part  30  has a section that is higher than that of its opening  35   b  in the upper face  30   b . Thus, under the action of the pressure of the infusion in the collecting chamber  25 , the upper face  30   b  of the part  30  adopts a bent profile that has the tendency to widen the upper opening  35   b  because of the flexibility of the material, while the lower opening  35   a  always forms an opening because of its larger section, even if its section has a tendency to decrease because of the deformation of the part  30 . In contrast, when the pressure that is exerted on the lower face  30   a  of the part  30  is equal to the pressure on the upper face  30   b , the section of the upper opening  35   b  is small enough to retain the liquid that is located above the part  30 , in particular because of the capillary action phenomena. In addition, if the upper face  30   b  of the part  30  has a recessed profile because of a pressure difference exerted between the lower faces  30   a  and upper faces  30   b , this deformation has a tendency to reduce the section of the upper opening  35   b , optionally until the walls of the orifice  35  come into contact, which also increases the difficulty of the return of the infusion to the infusion chamber  14 . 
     It is preferable that the orifice  35  be located at the center of the deformed zone of the part  30  during the passage of the infusion and in particular at the geometric center of the disk shape of the part  30  of the embodiments shown, so that the effect of variation of the sections of the openings ( 35   a ,  35   b ) is fully manifested. However, it is not absolutely necessary that the part  30  has the shape of a disk, since the deformed zone also depends on the installation of this part in the tube  26 . 
     In the first embodiment shown in  FIGS. 1 to 6 , the orifice  35  has the shape of a slightly elongated slot, i.e., whose length does not significantly exceed the width. As can be seen in  FIG. 5 , the opening  35   b  of the orifice  35  in the upper face  30   b  of the part  30  has a rectangular shape, while the opening  35   a  of said orifice  35  in the lower face  30   a , visible in  FIG. 4 , has an overall rectangular shape with rounded corners because of the presence of a connecting shelf between the lower face  30   a  and the inside walls of the orifice  35 . It turns out that the orifice that is thus produced in the form of a slot makes it possible to correctly perform the foam-forming and nonreturn functions. 
     It seems that the following dimensional characteristics of the orifice  35  make it possible to meet the operational requirements of the flexible part  30 . 
     The opening  35   a  of the orifice  35  in the lower face  30   a  of the part  30  in the shape of a disk, visible in  FIG. 4 , has a width  1   a  of between 0.5 and 1 mm, and preferably 0.8 mm, and a length La of between 1 and 2 mm, and preferably 1.4 mm. Furthermore, the opening  35   b  of the orifice  35  in the upper face  30   b  of the part  30 , visible in  FIG. 5 , has a width  1   b  of between 0.1 and 0.4 mm, and preferably 0.3 mm, and a length Lb of between 0.6 and 1.5 mm, and preferably 0.9 mm. 
     As can be better seen in  FIG. 6 , the calibrated orifice  35  has, from the lower face  30   a  up to the upper face  30   b , a first continually decreasing section portion, followed by a second constant section portion. More particularly, the first portion of the orifice  35  has a height ha of between 1 and 1.5 mm, and preferably 1.3 mm, and the second portion of the orifice has a height hb of between 0.4 and 1 mm, and preferably 0.7 mm. The part  30  in the shape of a disk has a total height H of between 1.5 and 2.5 mm, and preferably 2 mm. 
     It is also possible to perform correctly the foam-forming and nonreturn functions despite a certain dispersion of the production sides of the flexible part  30  by adopting, for example, the second embodiment that is shown in  FIG. 7 . In this embodiment, the orifice  35  of the part  30  consists of a basin  40 , preferably approximately circular, which forms a wide opening  35 ′ a  with a diameter Da in the lower face  30   a  of the part  30 . The basin  40  is lengthened by a cylindrical hole  41 , preferably arranged coaxially to said basin, which extends up to the upper face  30   b  of the part  30  so as to form an opening  35 ′ b  in the latter. 
     In this second embodiment, whereby the part  30  has, as above, the same height H, the cylindrical hole  41  has a height hb of between 0.6 and 1.2 mm, and preferably 0.9 mm, and a diameter Db of between 0.5 and 0.7 mm, and preferably 0.6 mm. The presence of the basin  40  imparts more flexibility to the portion of the upper face  30   b  into which the hole  41  empties. 
     Of course, the embodiments that are described are in no way limiting, and it will be noted that the deformable flexible part  30 , object of the invention, can comprise one or more orifices  35  of a shape that is essentially different from those described. However, it turns out that the geometric indications given above make it possible to perform the foam-forming and nonreturn functions correctly in an efficient manner, despite the possible variations of operating conditions from one machine to the next and while adhering to the constraints linked to a large-scale industrial production.