Abstract:
An apparatus for the production of espresso coffee and the like is disclosed. The apparatus includes a lower vessel having an inlet opening, a substantially funnel-shaped intermediate vessel placed axially at the inlet opening to the lower vessel, and an electric heater in the lower vessel for heating water contained therein. The intermediate vessel comprises at least a perforated plate that defines a chamber for containing coffee in a finely ground or powder form. An upper vessel is mounted axially to the lower vessel in a desirable fashion and in communication with the lower vessel through the intermediate vessel. The intermediate vessel is reversibly connected to the lower vessel in a relatively tight fashion relative to the outside. The lower vessel is hydraulically connected to a water reservoir through a pump. The water reservoir is positioned alongside the lower vessel and on the same support. Water is fed into the lower vessel in close proximity to the heater. Further provided are valves for controlling the pressure of the heated water and/or coffee produced, whereby dispensing coffee in the upper vessel occurs only when the water and/or coffee pressure reaches a predetermined value.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an electric coffee maker for the production of espresso coffee.  
       DESCRIPTION OF THE PRIOR ART  
       [0002]     The traditional coffee maker for domestic use, of the type commonly known as moka or mocha, is formed by a lower vessel and an upper vessel generally screwed axially and tightly one to the other and communicating via an intermediate, substantially funnel-shaped vessel having a tubular portion. An axial duct, open at the upper end and if necessary provided with a dispensing member, extends from the base of the upper vessel. The coffee powder is placed in the intermediate vessel, while the lower vessel, which acts as a boiler, is filled with water as far as a preset level. The formation of steam in the boiler following the administering of heat causes an increase in pressure therein, sufficient for causing the hot water to rise up along the tubular portion of the intermediate vessel, forcing it to diffuse in the layer of coffee powder, traversing it and rising up along the axial duct of the upper vessel so as to pour into it, flowing from its free end.  
         [0003]     In this type of domestic coffee maker the working pressure of the hot water that traverses the layer of coffee powder is generally very low and, since it is limited by a safety valve, the pressure drop through the layer of coffee powder cannot go beyond certain values. The low pressure of the hot water is responsible for the incomplete process of infusion whose effect influences the properties of the coffee produced.  
         [0004]     Conventional domestic coffee makers generally use an external source of heat, for example a gas or other fuel cooker or an electric plate, although small coffee makers for domestic use with electrical heating are becoming increasingly widespread, that is to say coffee-makers provided with their own dedicated electric heater, in some cases integral with the boiler and in others separable therefrom. The success of electric coffee makers is due above all to their greater versatility of use, as they allow coffee to be prepared anywhere, even where a cooker is not available, for example in a bedroom or an office and, in the portable version, also in a car.  
         [0005]     From the standpoint of the properties of the coffee produced, both traditional domestic coffee makers and those associated with dedicated electrical heating means, have the limitation, as referred previously, of not allowing preparation of real espresso coffee such as that which can be produced with professional machines for use in bars or also with espresso coffee makers for domestic use. The production of espresso coffee requires, as is known, in addition to a very fine grain size of the coffee powder used, also careful control of the temperature and pressure inside the boiler. In order to obtain the correct density of the infusion, it is important that diffusion of the water in the layer of coffee powder is as complete as possible and takes place at a constant temperature and for a preset time. These conditions cannot be observed in conventional domestic machines of the moka type wherein the contact time and the diffusion within the layer of coffee powder are controlled solely by the pressure of the steam which is formed in the boiler and which is responsible for the flow of hot water intended to traverse the layer of coffee powder.  
         [0006]     In known machines for the production of espresso coffee, both domestic and professional, the pressure of the hot water inside the boiler is provided by a pump which feeds it over a filter filled with coffee powder and enclosed in a filter holder. The pressure of the water, associated with the finer grain size of the powder and a smaller section of the holes of the filtering plate, allows a more intense infusion process whereby the substances contained in the coffee powder, which confer to the infusion the typical properties of espresso coffee, are almost completely extracted.  
         [0007]     On the other hand, for a number of reasons, including their simplicity of use and their established customary use, domestic moka coffee makers continue to be preferred over domestic machines for espresso coffee, despite the fact that the former do not succeed in achieving the typical quality features of espresso coffee. Their bulk in particular is considered to be one disadvantage of domestic machines for espresso coffee, which means they must be kept always on view on some furniture unit, and the fact that they traditionally do not allow preparation of more than two servings of coffee simultaneously, and therefore force replacement of the powder for each cup, or at most two cups, of coffee produced, whereas in moka coffee makers, according to their size, a much larger number of cups of coffee can be made.  
       OBJECTS AND SUMMARY OF THE INVENTION  
       [0008]     Therefore, the main object of the present invention is to provide a coffee maker for domestic use which has the structure of a moka coffee maker yet which enables coffee infusions to be made with the typical properties of espresso coffee.  
         [0009]     A particular object of the present invention is to provide a coffee maker of the type mentioned above which is small in size and, in any case, only slightly larger in size than a traditional moka coffee maker.  
         [0010]     Another object of the present invention is to provide a coffee maker of the type mentioned above which allows the production of several servings of espresso coffee.  
         [0011]     A further object of the present invention is to provide a coffee maker of the type mentioned above wherein the ordinary maintenance operations (washing of the boiler and coffee collecting vessel, and emptying the used coffee powder) are simple and fast and the risks of soiling for the user and worktops are minimised.  
         [0012]     The basic features of the coffee maker for domestic use according to the present invention are claimed in claim  1 . Further important features are claimed in the dependent claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     These and other features, and advantages, of the coffee maker for domestic use according to the present invention will be made clearer by the following description of some embodiments thereof, given by way of a non-limiting example with reference to the accompanying drawings, wherein:  
         [0014]      FIG. 1  is an elevational sectional view of a first embodiment of the coffee maker according to the invention;  
         [0015]      FIG. 2  is a partially sectioned top plan view from above of the coffee maker of  FIG. 1 ;  
         [0016]      FIG. 3  is a sectioned view of the coffee maker of  FIG. 1  along line III-III of  FIG. 2 ;  
         [0017]      FIG. 4  is a partial elevational sectional view of a variation of the coffee maker of  FIG. 1 ;  
         [0018]      FIG. 5  is an enlarged section of detail A of  FIG. 4 ;  
         [0019]      FIG. 6  is a detail view of a releasable coupling for connection of the water supply line to the boiler of the coffee maker of  FIG. 1 ;  
         [0020]      FIG. 7  is an elevational sectional view of a second embodiment of the coffee maker according to the invention;  
         [0021]      FIG. 8  is a partial cross sectional view along line VIII-VIII of  FIG. 7 ;  
         [0022]      FIG. 9  is an axial sectional view along line IX-IX of  FIG. 7 ;  
         [0023]      FIG. 10  is an elevational sectional view of a third embodiment of the coffee maker according to the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     Referring to  FIGS. 1, 2  and  3 , the domestic coffee maker for producing espresso coffee according to the invention comprises a lower vessel  1  or boiler, an intermediate, substantially funnel shaped vessel  2  suitable for holding the coffee powder and tightly connected to the boiler  1  at its inlet, and an upper vessel  3  for collecting the coffee infusion, arranged coaxially to the boiler  1  and to the intermediate vessel  2 . More specifically the intermediate vessel  2  has a cylindrical portion  2   a  and a tubular portion  2   b  joined one to the other by a truncated cone portion  2   c , the tubular portion  2   b  extending axially towards the bottom wall of the boiler  1 . The inlet of the boiler  1  is defined by a tubular wall  1   a  whereto the cylindrical portion  2   a  is connected tightly by means of an O ring  60 . A small perimetric edge  2   d  projecting from the cylindrical portion rests on the edge of the tubular wall  1   a.    
         [0025]     A disk-shaped body  4  extends above the intermediate vessel  2  and is bordered around its perimeter by a sleeve edge  5  which is screwed externally to the tubular wall  1   a . The disk  4  has a substantially conical shape slanting towards the upper vessel  3  above, and on the side of the intermediate vessel  2  holds a filtering plate  6  attached by means of an annular seal  7  engaged in a groove  8  formed on the internal face of the sleeve  5  immediately below the disk  4 . The seal  7 , in an elastic material, creates the hermetic tightness of the boiler  1  once the tubular sleeve  5  is screwed fully to the tubular wall  1   a  of the boiler  1 .  
         [0026]     Inside the cylindrical portion  2   a  of the intermediate vessel  2  a container  9  is placed, with a finely perforated base  9   a  which, together with the filtering plate  6 , defines a chamber  10  for containing the coffee powder. The container for the coffee powder  9  has a small projecting perimeter edge  9   b  which is placed between the seal  7  and the corresponding small edge  2   d  of the intermediate vessel  2  when the sleeve  5  is completely screwed to the tubular wall  1   a  of the boiler  1 , in this way securing the container  9  inside the intermediate vessel  2 .  
         [0027]     An elastic element  11  is provided inside the truncated cone portion  2   c  of the intermediate vessel  2 . The elastic element  11  is placed between the truncated cone walls of portion  2   c  and the bottom wall  9   a  of the coffee powder container  9 . The elastic element  11  is compressed by the base  9   a  when the sleeve  5  is fully screwed to the tubular wall  1   a , so that, when said sleeve is unscrewed and removed, the elastic reaction of the elastic element  11  pushes the container  9  axially, making it project partially from the intermediate vessel  2  and thus facilitating its grip for subsequent extraction and removal of the used coffee powder. Moreover raising of the container  9  creates a vacuum in the part below it which draws the water located between the disk  4  and the surface of the coffee powder. This water, mixed with coffee powder, would otherwise inevitably flow to the outside, when the disk-shaped body  4  is unscrewed from the lower vessel  1 .  
         [0028]     A first tubular element  12  extends axially from the centre of the disk  4  inside the upper vessel  3  and a second tubular element  13 , extending coaxially from the bottom wall  3   a  of the upper vessel  3 , engages slidingly on the first tubular element  12 . The base  3   a  rests on the disk  4 , with the same configuration and slant, and along its perimeter a groove  14  is formed, wherein the tubular sleeve  5  engages, in this way removably securing the upper vessel  3  to the boiler  1 .  
         [0029]     The tubular element  12 , which extends from the disk  4 , defines a duct  15  ending with a flared portion in which a truncated cone bush  16  is engaged, with the same slant, ending with a radially perforated head  16   a  through which the coffee produced can flow. A skirt  17  extends radially from the bush  16 , immediately below its perforated head  16   a , and around the tubular element  13  at its free end. The bush  16 , forming a watertight connection with the tubular element  12  due to the conicity of the respective reciprocal contact walls, prevents infiltration of the coffee infusion between the upper vessel  3  and the disk  4 , assisted for this purpose also by the skirt  17  which covers the free ends of the two tubular elements  12  and  13 .  
         [0030]     The upper vessel  3  is provided, as is customary, with a lid  18 , with a central knob  19  for its raising, and a side handle  20 .  
         [0031]     The lower vessel  1  is mounted on a box-shaped body  21  provided with a removable base  22 . More specifically the box-shaped body  21  has a raised portion  23  which engages in a corresponding cavity  24  formed on the base of the lower vessel  1 . A water reservoir  25 , with a removable lid  26 , is also positioned on the box-shaped body  21 , alongside the lower vessel  1 . Inside the box-shaped body  21  a pump  27  is placed, supported by elastic vibration-preventing supports  28  and connected to the reservoir  25  via a suction duct  29  and to the boiler  1  via a discharge duct  30 . The connection between the duct  29  and the base of the reservoir  25  is formed by means of a valve  61  suitable for preventing the release of water from the reservoir when the latter is disengaged from the duct  29  so as to be removed from the box-shaped body  21 , for example for cleaning. The discharge duct  30 , in the present embodiment of the invention, is instead connected to the boiler  1  via a fixed coupling joint  31 , so that the boiler  1  is integral with the box-shaped body  21  and can be separated therefrom only by accessing its interior and adjusting a connection ring nut. The joint  31  is connected to a release nozzle  32  situated on the bottom wall of the boiler  1 , wherefrom the cold water flows out, preferably tangentially to the base of the boiler so as to eliminate, or at least limit, turbulence phenomena. In the present embodiment of the invention the water is heated by means of an electrical resistor  33  embedded in the metal of the boiler  1  on the bottom wall thereof and the temperature is controlled by means of a thermostat  52 .  
         [0032]     The coffee maker according to the invention is also provided with a control panel, not shown, formed for example frontally on the box-shaped body  21  and provided with all the pushbuttons and the operation indicators required for operative control of the coffee maker.  
         [0033]     When using the coffee maker according to the invention, after having filled with water the reservoir  25  and the boiler up to the level indicated therein, and after having placed the coffee powder in the container  9 , the chamber  10  is closed by screwing the disk  4  to the boiler  1  and positioning the upper reservoir  3  above it. The heating device is then switched on and remains in operation until the temperature of the water has reached the preset value (generally around 95° C.). At this point the user, by pressing the pushbutton for starting the pump  27 , causes water to flow into the boiler  1  which forces the hot water into the tubular portion  2   b , making it pass through the layer of coffee powder and from there rise up through the duct  15  until it flows out into the upper vessel  3 . The user will keep the pump  27  in operation until the level in the upper vessel  2  has risen to the level corresponding to the servings required. Preferably, for a direct check of the level in the upper vessel  3 , the latter will be made of a transparent material and a scale indicating the servings which correspond to the level reached by the coffee infusion will be provided on the vessel wall.  
         [0034]     In order to ensure that the hot water traverses the layer of coffee powder at an optimal pressure (generally around 2-4 bars, according to the degree of compression of the powder and its grain size), a valve  34  is placed inside the tubular portion  2   b  of the intermediate vessel  2 , illustrated by way of an example in the form of a rubber ball forced elastically against the aperture for access to the tubular portion  2   b . This valve avoids the pulsed feed of hot water at low pressure through the layer of coffee powder before the start of the pump. A further valve  35 , also illustrated by way of an example in the same way as the valve  34 , is provided at the inlet of the duct  15  with the triple function of ensuring discharge of the coffee infusion only after the pressure in the chamber  10  has reached a preset value sufficient for providing an optimal water-powder contact time, of forming in the duct  15  an orifice with restricted section for causing turbulence in the flow of liquid and with formation of the typical cream of espresso coffee, and finally of preventing the residual coffee remaining in the duct  15  from flowing out therefrom when the coffee maker is disassembled for cleaning.  
         [0035]     Whereas the valve  35  is considered essential for the multiple functions it is called on to perform, the valve  34  is not strictly necessary for controlling the pressure inside the boiler. Although with a limited loss of working flexibility, this control too can be assigned to the valve  35 . In this case the hot water gradually fills the intermediate vessel as the pump feeds cold water into the lower vessel and dispensing of the coffee infusion only starts when the pressure of the infusion above the coffee powder exceeds the calibration pressure of the valve  35 .  
         [0036]      FIGS. 4 and 5  show a variation of the coffee maker according to the invention. In these figures, the components identical to those of the embodiment previously described and illustrated will be denoted by the same reference numerals and will not be described again. The variation illustrated in  FIGS. 4 and 5  relates to the intermediate vessel  2  which, in this case, is housed removably in a freely sliding manner in the inlet opening of the boiler  1  and is not provided with the container  9  for the coffee powder, but has an evenly perforated plate  36  on which the coffee powder is placed directly. The seal  7  has an axial edge  37  extending inside the cylindrical portion  2   a  of the second vessel  2  and ending with an enlargement  37   a  which engages in a groove  38  formed on the wall of the cylindrical portion  2   a . In this way engaging of the enlarged portion  37   a  in the groove  38  makes the cylindrical portion  2   a  integral with the seal  7  and therefore, by removing the disk  4 , the intermediate vessel  2  is also extracted simultaneously from the boiler  1  with its content of used coffee powder. Once extracted from the boiler  2 , it is easy to separate the intermediate vessel  2  from the seal  7  by a slight traction, in order to proceed subsequently with its emptying and washing. In addition to allowing easy removal of the intermediate vessel, with this solution too the leakage of liquid mixed with coffee powder is avoided when unscrewing the disk-shaped body  4  due to the vacuum created by raising of the intermediate vessel  2 .  
         [0037]      FIG. 6  illustrates an example of coupling connection joint which allows the boiler  1  to be separated from the body  21  whenever required, for example for cleaning of the boiler, and which can be used as an alternative to a fixed coupling. In this case on the bottom wall  39  of the boiler a valve  40  is provided which intercepts the exit of a tubular element  41 , at the entrance whereof the discharge duct  30  of the pump is connected and which is fixed thereon by means of a tightening screw nut  42  screwed to the body of the tubular element  41 . The latter is attached, for example screwed, to the raised portion  23  of the base  21  in a special housing  23   a  formed thereon. The tubular element  41  is tightly coupled in a housing  43  formed on the base  39  at the valve  40 .  
         [0038]      FIGS. 7, 8  and  9  illustrate a second embodiment of the coffee maker according to the invention wherein components identical to those present in the first embodiment previously described and illustrated have the same reference numerals. In this embodiment of the invention the pump  27  is housed in a box-shaped body  46  integral with the lower vessel  1  and rests on a base  48  on which the reservoir  25  also rests. The pump  27  is mounted on vibration-preventing supports  28  and is connected to the reservoir  25  via a suction duct  29  and to the boiler  1  via a discharge duct  30 . The discharge duct  30 , in the present embodiment of the invention, flows into a spiral path  49  formed on the base of the boiler  1 , which can be seen in particular in  FIG. 8 , and forming part of a known and so-called “Thermoblock” device, denoted by  50 , formed by armoured and co-moulded resistors  51  embedded in the metal of the boiler  1  and extending above the spiral path  49 . A pair of thermostats  52  are provided on the base of the boiler  1  to control the temperature of the water which in this case reaches almost instantaneously its optimal value while passing in the spiral duct  49  and then the production of coffee can begin automatically once the boiler  1  is filled.  
         [0039]     A rapid electrical connection, generally indicated at  53  in  FIG. 7 , known commercially by the name STRIX, which, since it is well known in the sector of small electric household appliances, is not illustrated in further detail.  
         [0040]     Compared to the embodiment shown in  FIGS. 2-3 , in this case the actual coffee maker with associated box-shaped body  46  can be separated from the reservoir  25  and from the base  48  whenever necessary, for example in order to remove the used coffee powder, allowing performance of the operation for example over the sink in order not to soil the worktop with sprays of water which inevitably come out of the boiler when it is separated from the disk  4 .  
         [0041]     In the embodiment illustrated in  FIG. 10 , the pump  27  for feeding water to the boiler  1  is housed in a cavity  55  formed in the lower part of the water reservoir  25  and its suction and discharge ducts  29  and  30  are connected in a fixed manner to the reservoir  25  and to the boiler  1  respectively. The base  48  contains only the electrical part of the appliance and the electrical connector  53 , of the STRIX type, and can be separated from the rest of the appliance. In this solution the reservoir  25  surrounds the boiler  1 , in this way recovering the volume lost due to the cavity  55 .  
         [0042]     The heating device provided in one of the embodiments described and illustrated above can alternatively be used also in the other embodiments, and different heating devices and means from those illustrated can be used, provided they are functionally equivalent. The same applies for the valves illustrated only by way of an example.  
         [0043]     Variants and/or modifications may be made to the coffee maker for domestic use for making espresso coffee according to the present invention without thereby departing from the scope and spirit of the invention as set forth in the following claims.