Apparatus for mixing water with CO.sub.2 gas to produce carbonated water

Apparatus including a circulating pump inside a carbonator tank which blends CO.sub.2 with still water and which is started and stopped for predetermined time periods in repetitive cycles having an on/off ratio ranging between 1:10 and 1:20. A timing circuit controls the operating and non operating times of the circulating pump so that sufficient carbonation of the water with CO.sub.2 gas is achieved along with the formation of an ice bank on the cooled wall of the storage tank. During intervening periods when the circulating pump is not operating, the carbonated water arranges itself in layers according to its density so that the relatively warmer water sinks while the colder water together with any ice particles or small pieces of ice floating therein join together, becoming fixed to the ice bank in the upper portion of the carbonator. During the next operating cycle of the circulating pump, these particles are frozen together and become relatively harmless to the extent that the shutoff valve and output carbonated water line remains unobstructed. Whenever carbonated water is removed from the storage tank or fresh water is supplied to the storage tank, the circulating pump is again started for an additional on-period time interval which is greater than the normal on-period.

This is a continuation of International Application PCT/EP93/02282, with an 
international filing date of Aug. 25, 1993. 
BACKGROUND OF THE INVENTION 
This invention relates to apparatus for mixing water with CO.sub.2 gas to 
produce carbonated water in a storage tank and operates to cool its 
contents and to form an ice bank on the cooling pipes of a cooling circuit 
in the wall area of the storage tank, whose interior also includes the 
placement of a circulating pump, whereby CO.sub.2 gas from the head area 
of the storage tank is mixed by rotation and/or circulation with the water 
inside the storage tank. Both fresh water and CO.sub.2 gas are fed into 
the head area of the storage tank while carbonated water is removed from 
the base or bottom of the tank. 
Apparatus which mixes water with CO.sub.2 gas to produce carbonated water 
is well known and is used, for example, in post-mix beverage dispensing 
machines so that carbonated beverages can be prepared and dispensed on 
demand by mixing carbonated water with a suitable drink concentrate. The 
carbonated water mixed with the drink concentrate is produced directly in 
the storage tank by mixing water CO.sub.2 gas which is fed thereto and 
thereafter cooled for better carbonation, this being a requirement for a 
cool refreshing drink which is prepared for consumption as the need 
arises. The storage tank, commonly referred to as a carbonator, is fed 
fresh water of drinking quality either from the line of a water supply 
system or a pressurized storage tank. The fresh water, moreover, can be 
fed from the water supply system under pressure and can be enhanced, when 
desired, by the use of a pressure pump. Further, CO.sub.2 gas is fed to 
the carbonator from a CO.sub.2 gas storage tank by a pressure-reducing 
regulating valve so that a pressure of, for example, about 4 bars is built 
up in the carbonator. 
In order to ensure sufficient carbonation of the fresh water, the 
carbonation process can be accomplished by or assisted by the use of a 
CO.sub.2 circulating pump located in the carbonator. This type of pump 
draws CO.sub.2 gas from the upper or head-space region of the carbonator 
filled with CO.sub.2 gas and blends it with circulating water which is set 
in circular motion, such as by spinning. 
As already noted, cooling of the carbonator is used, not only to improve 
the carbonation, but also as a requirement so that the finally prepared 
and dispensed drink exhibits a desired low and basically constant 
temperature. The cooling of the carbonator is achieved by a cooling 
system, which is adapted to form an ice bank of generally uniform 
thickness along the inner side walls of the carbonator as a result of the 
circulating water. Consequently, a cooling capacitor is produced, thus 
enhancing its "refrigerating capacity", thereby removing the need for a 
relatively powerful cooling system which would be necessary in a 
once-through cooling system. 
Arrangements having a corresponding design as described above are well 
known, a typical example being shown and described in U.S. Pat. No. 
5,184,942, Deininger et al, Feb. 9, 1993. 
In the dispensing of a freshly prepared carbonated drink, a shutoff valve 
is typically opened in a line connected to the bottom of the carbonator, 
whereupon cooled carbonated water is fed therefrom to a concentrate mixing 
station. As a result of forming the ice bank in the area of the cooling 
coils, the carbonated water is cooled to near the freezing point. As such, 
an inherent danger exists due to the fact that the ice particles or pieces 
of ice floating in the carbonated water can get into the area of the 
outlet which can become clogged. Ice formation in this area is 
substantially impossible due to the fact that relatively warmer water 
tends to sink because of the special behavior of water relative to its 
specific density near the freezing point, and because the discharge 
opening is normally placed in the immediate vicinity of the circulating 
pump which also radiates a certain amount of heat. However, the 
circulating movement of the water, which is necessary or at least helpful 
for carbonation and for uniform formation of the ice bank on the walls of 
the carbonator, causes detached floating or otherwise suspended ice in the 
upper areas, particularly those with open dispensing channels, to 
accumulate in and clog the outlet region. 
SUMMARY OF THE INVENTION 
The object of this invention, therefore, is to provide a means which 
guarantees highly reliable, trouble-free operation of a carbonator for a 
post-mix dispenser. 
Apparatus which meets this requirement includes a circulating pump inside a 
carbonator tank which blends CO.sub.2 with still water and is started and 
stopped for predetermined time periods in repetitive cycles while being 
controlled by a timing circuit. 
Apparatus which accomplishes the desired objectives of this invention 
controls the operating and nonoperating times of the circulating pump so 
that sufficient carbonation of the water with CO.sub.2 gas is achieved 
along with the formation of an ice bank on the cooled wall of the storage 
tank. During intervening periods when the circulating pump is stopped, the 
carbonated water arranges itself in layers according to its density so 
that the relatively warmer water sinks while the colder water together 
with any ice particles or small pieces of ice floating therein join 
together, becoming fixed to the ice bank in the upper portion of the 
carbonator. During the next operating cycle of the circulating pump, these 
particles are frozen together and become relatively harmless to the extent 
that the shutoff valve and output carbonated water line remains 
unobstructed. The on and off control of the circulating pump is 
accomplished by a timing circuit which produces a relatively simple mode 
of operation. 
According to a preferred embodiment of the invention, the circulating pump 
is controlled so that an on-period of about 1 to 2 minutes is produced and 
a ratio of on-period to off-period of about 1:10 to 1:20 is provided. It 
turns out that an on-period of 1 to 2 minutes within an on/off cycle ratio 
of 1:10 to 1:20 achieves sufficient carbonation of the still water while 
maintaining a uniform ice bank of a desired thickness. 
According to another embodiment of the invention, when carbonated water is 
removed from the storage tank or fresh water is supplied to the storage 
tank, the circulating pump is again started for an additional on-period 
time interval. In this instance, a supplemental on-period of about 2 to 4 
minutes has been determined to be suitable. Following this additional 
on-period, the normal constantly repeating control cycle is again resumed, 
i.e. the circulating pump is turned on for 1 to 2 minutes while the 
off-period between the on-phases in each case is made to be 10 to 20 times 
larger.

DETAILED DESCRIPTION OF THE INVENTION 
A storage tank 1, as it is represented in the figures, is particularly 
adapted for use in devices for preparing post-mix beverages where a 
suitable amount of concentrate is added to carbonated water or optionally 
simply to fresh or still water without carbonation. 
Fresh water is fed into the tank 1 by a feed pipe 2, and CO.sub.2 gas fed 
thereto by a feed pipe 3. In order to prepare a post-mix beverage, a 
predetermined amount of cooled sufficiently carbonated water is removed 
from the tank 1 by an output line 4. Carbonation takes place and is at 
least assisted by a circulating pump 5, which draws the CO.sub.2 gas from 
head region 6 of the storage tank 1 by a suction pipe 7 and mixes it with 
stored fresh water 8 at the level of circulating pump 5. As a result, the 
CO.sub.2 gas fed into the pipe 7 is dissolved to its fullest in the fresh 
water 8. The circulating pump 5 is driven by an electric motor 9. 
The cooling of the carbonated supply 8 takes place in the vicinity of a set 
of externally located evaporator coils 10 of a cooling system, not shown. 
A shell of ice 11 is formed on the interior wall surface of the storage 
tank 1 in the area adjacent the evaporator coils 10. The thickness of this 
ice bank 11 is monitored by an ice sensor 12 which controls the 
refrigeration cycle and thus the refrigerating capacity of the system. 
The effect of the shape of the ice bank 11 is that the water 8 can be 
cooled to a very constant temperature in the immediate range of its 
freezing point without very sensitive detections, when a water change 
occurs, i.e., when carbonated water is removed from the carbonator tank 1 
via by output line 4 or is replenished by warmer water, controlled by a 
water level sensor 13, fed by feed pipe 3. In this case, the ice pack 
partially breaks down relatively quickly in certain areas, however, it is 
again built up by the cooling effect of the evaporator coils 10. 
The fact that not only does the stored water 8 but also the ice bank 11 in 
the boundary area of the water attain a freezing temperature, ice 
particles or small floating or suspended pieces of ice are formed in the 
water 8 which are also circulated by the activity of the circulating pump 
5 during carbonation of the water 8. When the output line 4 is opened, 
some of this ice can get into the discharge opening of the output line due 
to the pressure of the CO.sub.2 gas in head area 6 on the water 8. As a 
result, the dispensing process of the water by output line 4 can adversely 
be affected and even blocked. The preparation of a normal beverage is thus 
prevented. 
To prevent this condition from occurring, the subject invention provides a 
scheme for keeping the outlet ice-free. Previous measures attempting to 
prevent the icing of the output line 4 was to locate the opening in the 
immediate vicinity of and/or below a randomly operated circulating pump 5, 
whereupon the heat generated by the pump drive motor 9 provided some 
de-icing effect. However, this approach has been found to be insufficient 
when suspended particles of ice are present in the carbonated water For 
this reason, the electric circulating motor 9, in accordance with this 
invention, is now controlled so as to be periodically actuated in a 
predetermined repetitive sequence which will now be explained. An "ON" 
operating time period of about 1 to 2 minutes is immediately followed by 
an "OFF" time having a period of 10 times to 20 times the ON time period. 
During the OFF time period, the heretofore agitated circulated water 8 
becomes calm, and ice particles and small pieces of ice parts suspended in 
the water rise to the surface because of their lower density. There they 
are combined and/or attach themselves to the outer surface of the ice bank 
10. These icy elements are thus neutralized when the following ON period 
occurs. 
To bring the water supply as quickly as possible to the necessary degree of 
carbonation in the case of water change, i.e., when carbonated water is 
removed and/or fresh water is added, the electric motor 9 is also actuated 
each time carbonated water is removed or fresh water is added 
notwithstanding the cyclic operation described above. Thus the circulating 
pump 5 is again started for a predetermined supplementary ON time period 
for each water removal or addition, after which the respective on/off 
cycle described above starts again. 
The circuit for controlling the on/off periods of the circulating pump 5 
uses a start signal derived from the water level sensor 13. This signal is 
initially fed to a counter circuit 14 following initial water feed 
delivery to the tank and which closes a power switch 15 coupled to the 
electric motor 9 driving the circulating pump 5, and which begins to 
operate. When the water level sensor 13 detects a predetermined amount of 
water during a filling or refilling operation, the water in the feed line 
2 is cut off and the power switch 15 opens. At this time the counter 
circuit 14 also begins to count and generate the desired ON and OFF time 
period control signals for the pump drive motor 9. Thus for a time ranging 
between 1 to 2 minutes, depending on the design of the counting chain, the 
power switch 15 remains closed and the circulating pump 5 is driven. The 
switch 15 then opens until the counting circuit 14 has reached a preset 
upper value or count, after which it is reset back to an initial starting 
value where the cycle starts all over unless interrupted by a water 
delivery and/or replenishment operation. 
FIG. 2 shows a modification of the storage tank illustrated in FIG. 1. 
There the outer evaporator coils 10' on storage tank 1' are still located 
on the upper wall portion of the tank, with the ice bank 11' also being 
formed thereat on the inside wall surface. Now a set of inner coils 16 are 
located in the tank 1' around the circulating pump 5' and its drive motor 
9'. The coils 16 carry and transport other water which is cooled by the 
carbonated water 8'. As before, however, during the rest or OFF period of 
the circulating pump 9', relatively warmer water 8' collects in the lower 
zones of storage tank 1', because of its greater density, so that the 
danger of icing of water in the pipe coils 16 is also prevented. 
The invention being thus described, it will be obvious that the same may be 
varied in many ways. Such variations are not to be regarded as a departure 
from the spirit and scope of the invention, and all such modifications as 
would be obvious to one skilled in the art are intended to be included 
within the scope of the following claims.