GB2363343A

GB2363343A - Beverage dispenser with frothing of milk using jet of air

Info

Publication number: GB2363343A
Application number: GB0014366A
Authority: GB
Inventors: John Nicholas Reid
Original assignee: INVEND TECHNOLOGIES Ltd
Current assignee: INVEND TECHNOLOGIES Ltd
Priority date: 2000-06-13
Filing date: 2000-06-13
Publication date: 2001-12-19
Anticipated expiration: 2020-06-13
Also published as: GB0014366D0; GB2363343B

Abstract

Beverages such as cappuccino coffee, are prepared by frothing milk using a jet of air rather than steam. Air is supplied under pressure from pipe 22 to a venturi nozzle 60 in a milk reservoir 10. Milk froth is forced through pipe 48 into a settling tank 12 where the froth sinks to the bottom and air is discharged through vent pipe 54. Froth is dispensed from tank 12 by a plunger 52. The air may be supplied by a compressor 20 from a source of sterilised air derived from an air pump 38, an ozoniser 36 and carbon filter 26.

Description

2363343 FROTHING APPARATUS The present invention relates to a method and

an apparatus for use in a drinks dispensing machine for 5 frothing a liquid such as milk.

When serving certain beverages, such as cappuccino coffee, it is necessary to be able to produce a stable froth. Hitherto, machines specifically designed to make 10 cappuccino coffee have used steam to froth milk but such machines have several disadvantages. First, they are not always effective and cannot operate satisfactorily with all varieties of milk. They tend to require milk with a high protein content and at certain times of the year, because of is the diet of the dairy herds, the milk will not froth readily, if at all. Other disadvantages are the danger of working with steam under pressure and the difficulty of maintaining the steam nozzle sterile at all times.

20 With a view to mitigating the foregoing disadvantages, there is provided in accordance with a first aspect of the invention a method of producing a froth from a liquid such as milk, which comprises introducing air at high speed into a quantity of the liquid in a reservoir and storing in a 25 settling tank for subsequent dispensing froth that is generated in the reservoir in this manner and that is transported by the air at speed out of the reservoir.

In a second aspect, the invention provides an apparatus 30 for use in a drinks dispensing machine for frothing a liquid such as milk, comprising a reservoir for retaining the liquid to be frothed, a nozzle for introducing a high velocity jet of air into the liquid in the reservoir to cause the liquid to froth and to be ejected from the 35 reservoir, a settling tank for separating the ejected froth from the air transporting the froth, and means for dispensing the froth that settles in the settling tank.

It has been discovered by the present inventor that milk and other comestible liquids will produce a stable froth if air is blown through them at very high speed. To achieve a stable froth with small air bubbles, it has been 5 found necessary to introduced air into the liquid through a nozzle having an orif ice of less than 1 mm in diameter, the air being supplied to the nozzle at a pressure of around 6 bar (90 psi). Such a flow of air cannot however be used in the same way as steam to froth milk in an open cup because 10 the milk would simply be expelled from the cup at high speed. Instead, the invention proposes the use of a reservoir that communicates with a settling tank. When air is blown into the milk, froth is expelled at high speed from the reservoir but is captured within the settling tank where 15 the air transporting the froth separates from the froth. A stable froth that may subsequently he dispensed at low pressure settles in the bottom of the tank while the surplus air is vented from the top of the tank.

20 Preferably, the settling tank is cylindrical and the means for dispensing the froth from the settling tank comprises a plunger mounted for axial displacement in the tank. Such a construction has the advantage that the plunger wipes down the sides of the settling tank and 25 maintain the tank clean.

The settling tank and the reservoir will still need to be cleaned on a regular basis arid it is advantageous for means to be provided for filling the reservoir and the 30 settling tank with water to rinse off any froth adhering their surfaces.

Preferably, means are also provided for sterilising the reservoir and the settling tank, for example by filling the 35 reservoir and settling tank with a fluid containing ozone. The ozone may readily be generated within the apparatus by means of a spark discharge or a source of ultraviolet light.

To prevent ozone from escaping from the apparatus, it is possible to pass exhaust air through a carbon filter.

While it would be possible to use a canister as a 5 source of pressurised air, it is more convenient for the pressurised air to be supplied to the nozzle by means of a compressor. In this case, a supply of sterilised air may be obtained from the downstream side of the carbon filter used to remove ozone from air vented from the apparatus back into 10 the ambient atmosphere.

The invention will now be described further, by way of example, with reference to the accompanying drawing, in which the single figure is a schematic representation of an is apparatus of the invention.

The drawing shows a reservoir 10 connected by a pipe 48 to a settling tank 12. The reservoir is a small sealed cylinder similar in size and shape to the carbon dioxide 20 bulbs used in soda siphons to carbonate drinks while the settling tank 12 has a larger volume and is vented at its upper end through a pipe 54 which can be closed of f by a valve 56.

25 The reservoir 10 is connected to a milk bag 14 by means of a pipe 16 containing a shut-off valve 18. When the valve 18 is opened, milk flows from the bag 14 into the reservoir 10. When the level of the milk in the reservoir 10 reaches a sensor switch 50, the valve 18 is closed.

A second connection pipe 22 controlled by a shut-off valve 24 connects a compressor 20 to the reservoir 10. The pipe 22 extends deep into the reservoir 10 below the level of the sensor switch 50 and terminates in a venturi nozzle 35 60. Typically, the pipe 22 has a diameter of 6 mm, the nozzle 60 has a diameter of less than 1 mm and the compressor is run at a pressure of 6 bar. When cold air is blown into the small quantity of milk held in the reservoir 10 at this rate, the milk froths and is forced by the fast air flow through the pipe 48 into the settling tank 12, where the froth sinks to the bottom of the tank 12 while the 5 air is discharged through the vent pipe 54. The thick froth produced in this way is stable and remains in the settling tank 12 until it is needed.

When it is desired to dispense froth from the tank to 10 make a cappuccino coffee, a plunger 52 is pushed down and forces the froth out of a spout at the bottom of the tank 12 into the coffee containing cup. The plunger wipes down the sides of the tank so that tank 12 is kept clean.

is The remaining connection to the reservoir 10 is provided for the purpose of periodic cleaning and sterilisation of the reservoir 10 and the tank 12. To this end, the reservoir is connected by way of a pipe 44 containing a shut-off valve 46 to a water supply and by way 20 of a pipe 34 containing a shut-off valve 32 to a source of ozonised air. The latter source consists of an air pump 38 connected by a pipe 40 to an ozoniser which produces ozone using either a spark discharge of ultraviolet light.

25 To clean the apparatus, shut-off valves 30, 32, 24, 18 and 56 are all closed and the valve 46 is opened. Water from the supply 42 then enters into the reservoir 10 and flows out through the pipe 48 to fill the tank 12. The water is kept running to rinse all the parts of the 30 apparatus that have come into contact with the froth.

Once the tank 12 and the reservoir 10 have been thoroughly rinsed, and the plunger 52 has been actuated a few times to wipe the surface of the tank 12, the valve 46 35 is closed and the rinsing water is drained from the tank 12 and the reservoir 10. The reservoir 10 is provided with a drainage tube (not shown) for this purpose at its lower end.

After the water has been rinsed, the valve 32 is opened to allow ozonised air into the reservoir 10 and the tank 12 to maintain the apparatus sterile when not in use.

Before being used again, the ozonised air is flushed from the apparatus by blowing air from the compressor through the apparatus. Ozone in the exhaust air is converted back to oxygen by the carbon filter.

10 The air that is blown into the milk to make froth needs to be sterile and to this end the intake air of the compressor is drawn from a carbon filter 26 that is used to neutralise ozone generated by the ozoniser. Such air will be sterile in that any air-borne viruses or bacteria will is have been killed off by the ozone and the ozone, which can itself be harmful, is converted back to oxygen by the carbon filter 26. The act of converting ozone to oxygen cleans the carbon filter 26 so that it in use it requires little or no maintenance for extended periods.

It has been found in practice that using cold air, it is possible to produce a stable froth with any type of milk. No seasonal problems are encountered. Furthermore, the protein and fat levels of the milk can vary widely without 25 affecting the production of froth nor the stability of the froth.

Though the invention has been described by reference to the frothing of milk, it can be applied to other liquids, 30 such as cream. It is further possible to make various alterations to the apparatus, for example one may incorporate a heater to warm the milk being frothed.

Claims

1 Apparatus for use in a drinks dispensing machine for frothing a liquid such as milk, comprising a reservoir 5 for retaining the liquid to be frothed, a nozzle for introducing a high velocity jet of air into the liquid in the reservoir to cause the liquid to froth and to be ejected from the reservoir, a settling tank for separating the ejected froth from the air transporting the froth, and means 10 for dispensing the froth that settles in the settling tank.

2. Apparatus as claimed in claim 1, wherein the air is introduced into the liquid through a nozzle having an orif ice of less than 1 mm in diameter, the air being 15 supplied to the nozzle at a pressure of around 6 bar (90 psi).

3. Apparatus as claimed in claim 2, wherein the nozzle orifice is a venturi connected to an air supply pipe 20 of around 6 mm in diameter.

4. Apparatus as claimed in any preceding claim, wherein settling tank is cylindrical and the means for dispensing the froth from the settling tank comprises a 25 plunger mounted for axial displacement in the tank.

5. Apparatus as claimed in any preceding claim, wherein pressurised air is supplied to the nozzle by means of a compressor.

6. Apparatus as claimed in any preceding claim, wherein means are provided for filling the reservoir and the settling tank water to rinse off any froth adhering thereto.

35

7. Apparatus as claimed in any preceding claim, wherein means are provided for sterilising the reservoir and the settling tank.

8. Apparatus as claimed in claim 7, wherein the sterilising means are operative to fill the reservoir and settling tank with a fluid containing ozone.

5

9. Apparatus as claimed in claim 8, wherein the ozone is generated within the apparatus by means of a spark discharge or a source of ultraviolet light.

10. Apparatus as claimed in claim 9 when appended to 10 claim 5, wherein a carbon filter is provided to convert ozone produced within the apparatus back to oxygen and wherein the output of the carbon filter is connected to the compressor to ensure the sterility of the air compressed by the compressor and introduced into the liquid.

is

11. Apparatus for use in a drinks dispensing machine for frothing a liquid constructed and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

12. A method of producing a froth from a liquid such as milk, which comprises introducing air at high speed into a quantity of the liquid stored in a reservoir and storing in a settling tank for subsequent dispensing froth that is 25 generated in the reservoir in this manner and that is transported by the air at speed out of the reservoir.

13. A method of producing a froth from a liquid such as milk substantially as hereinbefore described with 30 reference to and as illustrated in the accompanying drawings.