Espresso machine

The invention relates to an espresso machine, wherein water in the boiler (1) is superheated and kept at a temperature above 100.degree. C. for producing steam to be supplied to a dispenser nozzle (10), which superheated water is mixed with cold water at a mixing station (12), to obtain hot water having a temperature below 100.degree. C., supplied to the coffee brewing unit (13) and to the dispenser nozzle (10). According to the invention, the coffee brewing unit (13) is attached to the lower side of the boiler (1) and is connected to the mixing station (12) by means of a feed pipe (14), which is at least partly housed in the boiler (1). In the pipe (4) for feeding cold water to the boiler (1), a non return valve (16) is provided, which opens in the direction of flow into the boiler and is situated downstream from the branch point of the pipe (11) for feeding cold water to the mixing station (12).

BACKGROUND OF THE INVENTION 
The invention relates to espresso machines having a boiler and at least one 
coffee brewing unit, as well as at least one hot water and/or steam 
dispenser nozzle, in which machines boiler water is superheated and kept 
at a temperature (above 100.degree. C.) for producing steam to be supplied 
to the dispenser nozzle, and which superheated water is mixed with cold 
water at a mixing station preferably provided in the upper part of the 
boiler, to obtain hot water having a lower temperature (below 100.degree. 
C.), to be supplied to the coffee brewing unit and to the dispenser 
nozzle, a pump being provided to draw cold water from a tank and to 
transfer it to the boiler through a first feed pipe, branching from the 
pump delivery pipe, and--through a second feed pipe branching from the 
pump delivery pipe--to said mixing station, which communicates with the 
upper part of the boiler through a steam or superheated water drawing 
pipe, with the dispenser nozzle through a delivery pipe, and with the at 
least one coffee brewing unit. 
In such espresso machines, both the steam supplied to the dispenser nozzle 
and the hot water supplied to the dispenser nozzle and to the coffee 
brewing unit are immediately available, with no idle time, and the 
espresso machine is always ready for any operating condition. 
SUMMARY OF THE INVENTION 
The present invention relates to some improvements to espresso machines as 
described hereinbefore and aims at making these machines simpler as 
regards construction and functionally safer and versatile, by reducing 
their size and widening their application range. 
According to a first improvement, the invention provides an espresso 
machine as described hereinbefore, particularly intended for home use, 
wherein the at least one coffee brewing unit is disposed under the boiler 
and is preferably attached to the lower side thereof, whereas the mixing 
station is connected to the coffee brewing unit through a feed pipe which 
extends at least partly inside the boiler. 
According to an embodiment of this improved espresso machine, the mixing 
station is outside the boiler, and over it, and the pipe for drawing 
superheated water and steam from the boiler branches upwards from the 
upper part of the boiler, while the upper open end of the feed pipe, 
extending inside the boiler, and connected to the coffee brewing unit fits 
therein from below. 
According to a further embodiment of the above improved espresso machine, 
the mixing station is provided inside the boiler, in the upper part 
thereof, and consists of the pipe fitting connecting the cold water feed 
pipe and the pipe for delivery to the dispenser nozzle, as well as the 
feed pipe accommodated inside the boiler and connected to the coffee 
brewing unit, which pipe fitting communicates with the upper part of the 
boiler through at least one opening or at least one pipe, for drawing 
steam and superheated water therefrom. This embodiment has the advantage 
to further reduce the number of external pipes, and so the machine size. 
A further reduction of the external pipes, resulting in a smaller size of 
the machine, may be obtained thanks to the invention by providing that at 
least one part of the pipe for feeding cold water to the boiler and/or at 
least one part of the pipe for feeding cold water to the mixing station 
are housed in the boiler, preferably with calibrated throats, or the like, 
inserted in said pipes. Further improvements of the invention relate to 
all above espresso machines, i.e. both to general machines, as described 
hereinbefore and to the above improved machines, particularly both to 
machines in which the at least one coffee brewing unit is substantially 
separated from the boiler and is connected to the mixing station by means 
of a delivery pipe which is parallel to or branching from the delivery 
pipe connected to the dispenser nozzle, and to machines in which the at 
least one coffee brewing unit is disposed under the boiler and is 
preferably attached to the lower side thereof, and the mixing station is 
connected to the coffee brewing unit by means of a feed pipe at least 
partly extending inside the boiler. In both espresso machine types, it may 
happen that when steam is drawn by the pipe for delivery to the dispenser 
nozzle, a small pressure drop is determined between the inner part of the 
boiler and the mixing station. Due to this pressure drop, water contained 
in the boiler may flow through the pipe for feeding cold water to the 
boiler and through the attached pipe for feeding cold water to the mixing 
station and may get to the mixing station, where it is carried by the 
outcoming steam flow in the form of small drops. These water drops affect 
the quality of steam dispensed by the dispenser nozzle and cause the 
beverage heated by said steam to be undesirably watered. 
This drawback is obviated thanks to the invention in a simple and effective 
manner, by providing, in the pipe for feeding cold water to the boiler, a 
non return valve, downstream from the branch point of the pipe for feeding 
cold water to the mixing station, which opens in the direction of flow 
into the boiler. 
Another drawback shared by both espresso machine types consists in that, 
when an excessive amount of steam is drawn from the boiler, i.e. for a 
long time, the level of superheated water lowers to such an extent that, 
on further hot water demand, e.g. for a coffee brewing operation, water is 
dispensed at a lower temperature than desired, due to the fact that the 
cold water quickly and abundantly supplied to the boiler to restore the 
fill-up level, temporarily lowers the average water temperature of boiler 
water. A solution to this drawback is known, which consists in operating 
the pump for supplying cold water to the boiler intermittently and for 
short periods, upon steam dispensing, so that cold water can be supplied 
to the boiler in a constant and gradual manner, to compensate for 
consumption. Yet, this intermittent supply of cold water to the boiler 
automatically causes a corresponding simultaneous cold water supply to the 
mixing station, whereby steam coming out of the mixing station carries 
small drops of the simultaneously supplied cold water with it, thereby 
getting colder and watered. 
This drawback is obviated thanks to the invention by providing--in 
combination with an intermittent supply of cold water to the boiler upon 
steam dispensing--the mixing station inside a mixing chamber, which forms 
an upper extension of the boiler and wherein the cold water feed pipe an 
the delivery pipe connected to the dispenser nozzle open from above, at 
separate and suitably spaced locations, so that, when coffee has to be 
brewed or hot water has to be dispensed, the superheated water drawn from 
the boiler carries the cold water coming out of its respective feed pipe 
with it, mixing with it and thereby reducing its temperature, whereas, 
when steam has to be dispensed, with the cold water feed pump operating 
intermittently, the steam coming out of the pipe for delivery to the 
dispenser nozzle has not a sufficient speed to carry the cold water 
entering trough its respective feed duct in the pump operation periods. 
These and other improvements, characteristics and advantages of the present 
invention will appear in greater detail from the following description of 
a few embodiments, shown very schematically and by way of non-limiting 
examples in the accompanying drawings, in which:

DETAILED DESCRIPTION 
In FIG. 1, numeral 1 denotes the boiler of an espresso machine. The boiler 
1 is supplied with cold water from a tank 2 by means of a pump 3 and of a 
feed pipe 4. A nonreturn valve 5 (typically integrated in the pump 3) and, 
at a certain distance downstream from the valve, a calibrated throat S4 
are provided in the cold water feed pipe 4, downstream from the pump 3. 
Water in the boiler 1 is heated by means of an electrical resistor 6, with 
the help of a thermostatic switch. A pipe 8 for drawing steam and 
superheated water from the boiler 1 branches upwards and preferably at the 
center of the boiler 1. This drawing pipe 8 is connected to at least one 
steam and hot water dispensing nozzle 10, through a delivery pipe 9 and an 
on-off valve V9. A calibrated throat S9 may be provided in the delivery 
pipe 9. 
A feed pipe 11, having a calibrated throat S11 branches from a point of the 
pipe 4 for supplying hot water to the boiler 1, situated between the 
nonreturn valve 5 and the throat S4, and opens into a mixing station 12 in 
the delivery pipe 9 connected to the dispenser nozzle 10. The mixing 
station 12 is situated over the drawing pipe 8 communicating with the 
inner part of the boiler 1, and is directly connected to said pipe 8. 
The coffee brewing unit 13, which is shown schematically, is provided under 
the boiler 1 and is attached to the lower side thereof. This coffee 
brewing unit 13 is connected to the mixing station 12 through a hot water 
feed pipe 14, which is housed in the boiler 1 and opens, by its open upper 
end, into the drawing duct 8 next to the mixing station 12. In the 
illustrated embodiment, the feed pipe 14 consists of a central riser pipe, 
coaxial to the drawing pipe 8, whose upper end, which fits and terminates 
into the drawing pipe 8, has an outside diameter which is smaller than the 
inside diameter of the drawing pipe 8, so that an annular opening for 
communication between the drawing pipe 8 and the boiler 1 is provided. 
The feed pipe 14 is connected to the coffee brewing unit 13 by means of a 
calibrated valve 15 which automatically opens in the flow direction 
towards the coffee brewing unit 13. 
A nonreturn valve 16 which opens in the direction of cold water supplied to 
the boiler 1 is provided in the pipe 4 for supplying cold water to the 
boiler 1, at an area upstream or downstream from the calibrated throat S4, 
but always downstream from the branch point of the feed pipe 11 connected 
to the mixing station 12. 
Water in the boiler 1 is superheated and kept--thanks to the resistor 6 and 
to the thermostatic switch--at a steam producing temperature, i.e. at a 
temperature above 100.degree. C., and for instance at a temperature of 
120.degree. C. So, the valve V9 shall simply be opened to have steam 
dispensed through the dispenser nozzle 10, while the pump 3 is kept idle 
or is intermittently operated for short periods. Water in the boiler 1 
starts boiling immediately due to the pressure being lowered after opening 
the valve V9 and immediately supplies steam to the dispenser nozzle 10 
through the drawing pipe 8, the mixing station 12 and the delivery pipe 9. 
Yet, the throat S9 in the delivery pipe 9 limits steam emission so that 
pressure in the boiler 1 is kept above atmospheric pressure. As a result, 
water in the boiler 1 boils at a temperature above 100.degree. C., 
preferably at a temperature as close as possible to 120.degree. C., 
whereby superheated steam is dispensed, which is perfectly dry. The 
nonreturn valve 5 prevents water from returning towards the tank 2 when 
the pump 3 stops. 
Said steam dispensing causes a small pressure reduction at the mixing 
station 12 as compared with the pressure in the boiler 1. However, the 
nonreturn valve prevents superheated water from flowing out of the boiler 
1 through the feed pipe 4 and from getting to the mixing station 12 
through the pipe 11 branching therefrom. So the problem of water drops 
being carried by steam coming out of the mixing station 12 through the 
delivery pipe 9 is obviated. 
Hot water supplied to the coffee brewing unit 13, or dispensed through the 
dispenser nozzle 10, must anyway have a temperature below 100.degree. C., 
e.g. a temperature of the order of 90.degree. C. In order to brew coffee 
or dispense hot water through the dispenser nozzle 10, the pump 3 is 
operated, for delivering a cold water flow F to pipes 4 and 11. The two 
calibrated throats S4 and S11 are so dimensioned as to divide the incoming 
cold water flow F into a partial flow F1, corresponding to a greater 
fraction, e.g. to about 70% of the incoming flow F, which is fed to the 
boiler 1 through the throat S4, the feed pipe 4 and the nonreturn valve 
16, and a partial flow F2, corresponding to a smaller fraction, e.g. to 
about 30% of the incoming flow F, which is fed to the branch feed pipe 11, 
passing through the throat S11. Superheated water in the boiler 1 gets to 
the mixing station 12 through the drawing pipe 8, in which mixing station 
12 a flow of this superheated water, corresponding to the flow F1 fed to 
the boiler 1, mixes with the partial flow F2 of cold water fed to said 
mixing station 12, through the feed pipe 11 and through the calibrated 
throat S11. This mixture of a part of cold water (e.g. corresponding to 
30%) coming from the pump 3 and having, for instance, a temperature of 
20.degree. C., and of a part of superheated water (e.g. corresponding to 
70%) coming from the boiler 1 and having, for instance, a temperature of 
about 120.degree. C., creates hot water having a temperature which is 
substantially lower than that of superheated water contained in the boiler 
1, e.g. a temperature of about 90.degree. C., and this hot water is fed 
from the mixing station 12, through the feed pipe 14 inside the boiler 1 
and its automatic valve 15, to the coffee brewing unit 13 and/or to the 
dispenser nozzle 10, through the delivery pipe 9, and through the open 
valve V9. 
The throat S9 downstream from the mixing station 12 of the delivery pipe 9 
is so dimensioned that hot water dispensed through the dispenser nozzle 10 
is limited to such an amount as to allow the pump 3 to keep a pressure in 
the boiler 1, which is higher than the boiling pressure of water at the 
desired temperature. Hence, for instance, if water in the boiler 1 has a 
temperature of about 120.degree. C., said overpressure in the boiler 1 
must be at least 1 kg/cm2 higher than the outside atmospheric pressure. 
Without said overpressure, steam bubbles would be formed, which would 
alter the desired mixture ratio, and hence the final temperature of the 
dispensed hot water. 
The embodiment of the home espresso machine as shown in FIG. 2 is 
substantially identical to the one described above and shown in FIG. 1, 
equal parts being denoted by the same reference numerals. Yet, unlike the 
embodiment as shown in FIG. 1, in the machine as shown in FIG. 2 the 
mixing station 12 is inside the boiler, preferably in the upper part 
thereof. To this end, the cold water feed pipe 11 penetrates the boiler 1 
in a water-tight manner, e.g. upstream from its calibrated throat S11 (so 
the latter is also housed in the boiler 1) and is connected to the mixing 
station 12, wherefrom the riser pipe 14 for feeding hot water to the 
coffee brewing unit 13 and the pipe 9 for delivering steam and hot water 
to its dispenser nozzle 10 branch. The mixing station 12, consisting of 
the pipe fitting, e.g. a tee, between the two pipes 9, 11 and the pipe 14, 
also communicates with the upper inner part of the boiler 1 through at 
least one opening (not shown) or through a steam and superheated water 
drawing pipe 108. This drawing pipe 108 is preferably directed from the 
mixing station 12 upwards. 
In the embodiment as shown in FIG. 2, an end portion of the pipe 4 for 
supplying cold water to the boiler 1 is also housed in the boiler 1, e.g. 
from a location upstream from the branch point of the feed pipe 11 
connected to the mixing station 12, including therein its calibrated 
throat S4 and the nonreturn valve 16. 
The embodiment as shown in FIG. 3 relates both to home espresso machines as 
shown in FIGS. 1 and 2 and to espresso machines, wherein coffee brewing 
units are not situated on the lower side of the boiler 1, but are 
separated and possibly disposed at a certain distance therefrom. In 
accordance with this embodiment of the invention, the station 12 for 
mixing the cold water supplied by the pump and the superheated water 
coming from the boiler 1 is provided inside a mixing chamber 208, which 
may form an upper extension of the boiler and replace the steam and 
superheated water drawing pipes 8 or 108, provided in the embodiments as 
shown in FIGS. 1 and 2. The duct 11 for feeding cold water to the mixing 
station 12, and the duct 9 for delivering steam or hot water to the 
dispenser nozzle (not shown), open into the mixing chamber 208 preferably 
from above and at spaced locations. When the coffee brewing unit (not 
shown) is attached to the lower side of the boiler 1, as in the 
embodiments of FIGS. 1 and 2, then said unit can be connected to the 
mixing chamber 208 through the feed pipe 14 inside the boiler and made, 
for example, in the form of a riser pipe, as previously described with 
reference to FIGS. 1 and 2 and outlined by dashed and dotted lines in FIG. 
3, which feed pipe 14 fits into the mixing chamber 208 from below and 
opens therein. However, when the coffee brewing unit/s are separated from 
the boiler 1 and possibly disposed at a certain distance therefrom, then 
they are connected to the mixing chamber 208 through a feed pipe (not 
shown) branching from the pipe 9 for delivery to the dispenser nozzle. 
In the embodiment as shown in FIG. 3, the mixing chamber 208 and the 
openings of pipes 11 and 9 therein are conformed and dimensioned in such a 
way as to obtain the following operation: 
When hot water is to be dispensed to the coffee brewing unit/s or to the 
dispenser nozzle, the superheated water flow coming from the boiler 1 and 
entering the mixing chamber 208, mixes with the cold water flow F2 which, 
though coming down from the feed duct 11, is carried by said superheated 
water flow, mixing therewith, towards the upper inlet end of the feed pipe 
14 or towards the entrance of the delivery pipe 9. However, if steam is to 
be dispensed, the cold water feed pump 3 is operated preferably 
intermittently, i.e. by pulses, and the steam which is formed and 
collected in the mixing chamber 208 and flows towards the entrance of the 
delivery pipe 9, has a speed which is insufficient to carry with it the 
cold water coming down from its feed duct 11, whereby this water falls 
into the boiler 1 by gravity. Hence, cold water supplied by the pump 3 in 
the periods of intermittent operation thereof, both directly to the boiler 
1 through the feed pipe 4 and unavoidably also to the mixing chamber 208, 
through the feed pipe 11, is completely fed to the boiler 1, and is thus 
prevented from being partly carried by the outcoming steam, and from 
cooling and watering it. 
By using the embodiment as shown in FIG. 3, the nonreturn valve 16, 
provided in the embodiments of FIGS. 1 and 2 in the pipe 4 for feeding 
cold water to the boiler 1 may be omitted. 
Espresso machines, and particularly machines wherein coffee brewing units 
are not in heat conducting contact with the boiler, whereby they are not 
kept at a certain temperature by the boiler, have the drawback that the 
coffee brewing unit and the coffee blend contained therein are cold when 
the machine is started, and absorb a certain amount of heat from hot water 
supplied thereto, which considerably lowers the temperature of the first 
coffee to be dispensed. Therefore, coffee, particularly strong coffee has 
an undesirably low temperature at the beginning. The same drawback is 
noted after long inactivity periods of the espresso machine, during which 
coffee brewing units are even considerably cooled. 
Said drawback is obviated thanks to the invention by the embodiment as 
shown in FIG. 4, wherein the delivery pipe 9, branching from the mixing 
station 12 is connected to the steam and hot water dispensing nozzle, 
downstream from any calibrated throat S9, through a branch pipe 109 and 
through the on-off valve V9, and to one or more coffee brewing units (not 
shown), more or less distant from the boiler 1 or anyway unable to receive 
heat directly from the boiler, through another branch pipe 209 and another 
on-off valve V19. The delivery pipe 104 of the pump is connected to a 
pre-heating chamber 17 which is housed in the boiler 1 and is provided 
with a thermal insulator 18. This pre-heating chamber 17 is connected to 
the mixing chamber 12 through the feed pipe 11 and its calibrated throat 
S11. Also, the preheating chamber 17 is connected to the inner part of the 
boiler 1 through the feed pipe 4 with its calibrated throat S4 and 
nonreturn valve 16. In the illustrated embodiment, the feed pipe 4 (with 
its throat S4 and nonreturn valve 16), as well as the mixing station 12, 
and the feed pipe 11 (with its throat S11) are housed in the boiler 1. The 
mixing station 12 communicates with the upper inner part of the boiler 
through the riser pipe 108 for drawing steam and superheated water, as 
described for the embodiment of FIG. 2. Yet, the mixing station 12 may be 
also obviously provided outside the boiler 1, e.g. over it, as in the 
embodiment of FIG. 1, or the mixing chamber 208 of the embodiment of FIG. 
3 may be also used. The preheating chamber 17 may be housed only partly in 
the boiler 1 or may be connected thereto in another heat conducting 
manner. The chamber 17 inside the boiler 1 might even supply the pipe 11 
only (upstream or downstream from the throat S11), branching the pipe 4 
upstream from it, directly from the pipe 104. 
In this embodiment, the capacity of the preheating chamber 17 and its 
ability to absorb heat from water contained in the boiler 1 are selected 
in such a manner, e.g. by properly dimensioning the insulator 18 of the 
preheating chamber 17, as to obtain the following operation: During the 
idle period preceding any new start of the espresso machine, for instance 
in the morning, when coffee brewing unit/s are still cold, as well as 
during longer inactivity periods, in which no coffee is brewed, and the 
coffee brewing unit/s get notably colder, the water contained in the 
preheating chamber 17 is heated by the water in the boiler 1 to a 
temperature which is higher than that of the cold water supplied by the 
pump. Hence, when coffee is first brewed, hot water supplied to the coffee 
brewing unit, has a higher temperature than normal, since it results from 
mixture, at station 12, of superheated water from the boiler and cold 
water preheated in the chamber 17 to a temperature higher than normal cold 
water. This higher temperature of hot water used for the first brewing 
operation/s compensates for the loss of heat required to heat the coffee 
brewing unit/s at the beginning. When the espresso machine is further 
used, cold water fed to the mixing station 12 through the preheating 
chamber 17 remains in this chamber for a period of a certain length, 
substantially corresponding to the idle periods between the individual 
coffee brewing operations, and hence corresponding to the different 
cooling levels of the coffee brewing unit/s, whereby said cold water is 
automatically preheated to a temperature which substantially corresponds 
to the cooling level of the coffee brewing unit/s and hence capable to 
exactly compensate for this cooling effect. In this manner, the coffee 
brewing unit/s are automatically kept at a substantially constant 
operating temperature, and the coffee brewed always has substantially the 
same temperature, regardless of the amount of brewed coffee and of the 
idle interval between two successive brewing operations. 
Obviously, the invention is not limited to the embodiments described and 
illustrated herein, but may be greatly varied, especially as regards 
construction, and in the range of construction and function equivalents. 
So, for example, the calibrated throats S4, S9, S11 may be provided in 
such a manner as to allow variation and adjustment of their section and 
may be replaced by adjustable flow control valves. The valves V9, V19 may 
be operated manually or consist of solenoids. All the characteristics 
described, illustrated and claimed according to the invention are intended 
to be protected both individually and in any combination of two or more of 
them, as well as in their application to espresso machines whose remaining 
parts are made in any manner. All this without departure from the guiding 
principle disclosed above and claimed below.