Automatic device for heating and frothing a liquid, in particular milk
An automatic device for heating and frothing a liquid, in particular milk, comprises a container for the liquid, inside which a first tube for introducing pressurised steam into the liquid is removably mounted. The first tube has an inlet in correspondence of the bottom of the container, for receiving steam from a duct located within a support base of the container, and is secured, for at least part of its length, to a second tube for introducing air into the liquid.
This application is a divisional application of U.S. patent application Ser. No. 10/312,367, filed Jul. 9, 2003, which is the U.S. National Phase of international application No. PCT/EP01/06966, filed Jun. 19, 201, and claims priority of Italian application No. T02000A000616, filed Jun. 23, 2000.
FIELD OF THE INVENTIONThe present invention concerns an automatic device for heating and frothing a liquid, in particular milk.
BACKGROUND OF THE INVENTIONPreferably, the invention is applied in espresso coffee machines for bars, for producing frothy hot milk to be used e. g. in preparing cappuccinos, and the following description will refer to such a preferred application.
It is known that, in order to produce milk froth by means of espresso coffee machines, the operator utilises a container into which he pours a certain quantity of milk; then he introduces steam into the milk by a nozzle while stirring the container, so as to create a certain turbulence in the milk and incorporate the ambient air necessary to form the froth.
The characteristics and the quantity of the froth produced depend on the modalities of milk stirring and steam introduction, and therefore on the sensitivity and the skill of each operator.
Thus, such characteristics, and therefore the characteristics of the cappuccino in which the frothy milk is used, change from one operator to another and may be wholly unsatisfactory for the client, even if the operator judges them optimal.
Moreover, with the present technique problems may arise also from the hygienic standpoint, due in particular to the presence of milk crusts on the nozzle tip that are produced by successive frothing operations and that can remain exposed to air for a certain time.
SUMMARY OF THE INVENTIONA solution of the problems related to the dependency of the product quality on the individual operator is the subject matter of French patent application No. 2,604,077. That application discloses a device in which the steam nozzle is secured to an air feed duct, which has a bottom axial opening for air outlet arranged in front of the steam outlet opening of the nozzle, so that the steam licks the air jet and generates the required turbulence. Such a solution requires, for a proper operation, the presence of a chamber for mixing air and steam before introducing them into the liquid, and this makes the structure rather complex. Moreover, it leaves the problems of hygienic nature unsolved.
GB 382 972 discloses an apparatus for making what is known in the culinary art as whipped cream. This apparatus comprises a tank having close to its bottom a block of material porous to air. Between the block and the bottom of the tank a pressure chamber is defined where compressed air is admitted. Whipped cream is produced by forcing air in an ascending direction into the tank through the bottom block which is preferably made of porous stone.
EP 0287906 refers to an apparatus for heating and emulsifying liquids, in particular milk, contained in a tank, comprising a tube to be immersed in the liquid in the container, said tube being opened at its upper end for coupling the tube to a source of steam and at its lower end for expelling the steam into the liquid. According to this invention the tube comprises a radial calibrated orifice close to its upper end so as to obtain a level inside the tube equal to the external level.
FR 0775618 and FR 0769848 disclose an apparatus for mixing air into a liquid for the purpose of preparing cream through a separating porous plate provided close to the bottom of a tank and defining a chamber for pressurized air between said plate and the bottom of the tank.
U.S. Pat. No. 5,335,588 refers to an apparatus for milk frothing comprising a first pipe for admitting steam into the milk through its bottom open end and a second pipe for creating a venturi effect and improving the quantity of air mixed with the milk.
DE 29721055U refers to an arrangement for holding a pail on a stove during cooking having a pair of vertical arms which hold the pail firmly in position.
The aim of the invention is to provide an automatic heating and frothing device, which allows producing a froth with substantially constant characteristics, is of simple structure and does not give rise to the above mentioned hygienic problems.
The characteristics of the invention will become apparent from the appended claims.
A device comprising a container for the liquid having a bottom to which there are connected means for introducing pressurised steam into the liquid, according to the non-characterising clause of claim 1, is disclosed in Utility Model Application No. TO 2000 U 000076.
For a better understanding, reference is made to the accompanying drawings, which show a preferred embodiment of the invention, given by way of non limiting example, and in which:
BRIEF DESCRIPTION OF THE DRAWINGS
As shown in
For sake of simplicity, the drawing shows neither the means for electric power supply of the device, nor the connections, if any, with the espresso coffee machine, nor the water feed/discharge ducts for the internal steam source, if any.
Referring to
Tube 6 is secured onto the internal side of the bottom of container 1 by means of a threaded member 8, e. g. welded onto the bottom of container 1, which is engaged by a complementary member 9 arranged on tube 6 near the lower end thereof. Member 8 has an axial through-hole 10 (
Moreover, for securing container 1 to base 3, the bottom of container 1 is externally equipped with a set of tongues 14 arranged to engage corresponding openings 15 in the upper face of base 3 and to be retained, upon a rotation of container 1 about its axis, by plates 16 separating openings 15. Openings 15 and plates 16 adjacent thereto are preferably arranged on an annulus concentric with cavity 12.
Turning again to
When pouring the frothy milk, such a shape prevents small quantities of the milk entering tube 6 through opening 65 from flowing out through opening 10 in the container bottom.
Air tube 7 is open at both ends and includes two sections 70, 71 arranged substantially parallel with the intermediate and end portions 62,63, respectively, of steam tube 6. The open end of section 70 is to lie above the milk level within the container. End portion 72 of section 71, as better shown in
The operation of the described device is as follows. Once the container 1 has been filled with the required milk amount (in any case, up to a level below the upper opening of tube 7), it is placed on base 3 so that the outward projecting portion of member 8 engages cavity 12 and tongues 14 enter cavities 15. By rotating container 1, the engagement of tongues 14 beneath plates 16 is obtained. Thereafter, the desired heating time is set through timer 5, which opens the electric valve in the duct ending at the bottom of cavity 12. Thus the steam can pass from the source (inside or outside the base) to tube 6 and flow out through opening 65 thereof. Given the relative position of steam and air outlets 65,73, steam flowing out of opening 65 originates a vacuum, which in turn causes air intake through tube 7. The steam outflow speed thus creates a turbulence on the milk bottom, making the milk become heated and mix with air supplied through tube 7. Thus a milk-air-steam mixture is created directly within the milk. When the time set is over, the electric valve is closed thereby stopping steam supply and, after rotating container 1 to release tongues 14, container 1 can be removed from base 3 to pour the frothy milk.
Referring now to FIGS. 7 to 10, a second embodiment is shown employing different and more robust means for securing container 1 to base 3. In such Figures, the elements already discussed in connection with FIGS. 1 to 6 are denoted by the same reference numerals. The arrangement of tubes 6,7 introducing steam and air into the milk is the same as in the first embodiment.
Container 1 has on its external wall a pair of diametrically opposed projections 20 (of which only one can be seen in the drawings), arranged to co-operate with a pair of upright retaining members 21 projecting from the upper surface of base 3. Retaining members 21 are each made by a bar, with rounded cross-sectional shape, bent to an inverted U shape. Each projection 20 engages, in operating conditions of the device, the underside of a horizontal upper section 21a of a respective retaining member 21, as shown in
A vertical stem 22 projecting from base 3 carries a control panel 23 on which on/off switch 4 and control knob 5 for the timer are mounted. Stem 22 will house the necessary electric wiring for the switch and the knob.
As shown in
Base 3 has a central projection 26 housing end portion 27 of the steam feed duct located internally of base 3. Projection 26 is intended to sealingly engage, through a seal ring 28, a cavity 29 (visible in
The operation of that second embodiment is quite similar to that of the embodiment shown in FIGS. 1 to 6. Once container 1 has been filled with milk, it will be put on base 3 between retaining members 21, so that projections 20 lie externally of such members, as shown in
One can immediately appreciate that the invention allows solving the problems mentioned in the introduction. Actually, on the one side the device is automatic, and hence gives a product of which the quality no longer depends on the skill and/or the sensitivity of the individual operator; on the other side, the portions contacting the milk (in particular, steam and air tubes 6 and 7) can be removed from the container and washed immediately after use, thus avoiding possible pollution.
It is clear that the above description has been given only by way of non-limiting example and that changes and modifications can be made without departing from the scope of the invention. For instance, the arrangement of switch 4 and control knob 5 shown in
Moreover, even if reference has been made to the preparation of milk froth and warm milk in espresso coffee machines, the device can be used to froth and/or heat other liquids, in particularly for preparing infusions.
Claims
1. A device for heating and frothing a liquid comprising a container and a steam tube in a container, one end of said steam tube being connected to a source of steam, the other end of said steam tube being located near the bottom of said container and having an outlet opening by which steam exits the steam tube in a direction parallel to the bottom of the container, wherein said container is removably mounted on a base and said base and said steam source comprise an opening in said base through which steam is provided to said steam tube.
2. A device, as in claim 1, wherein the tube outlet is located near the side of the container and the outlet opening causes the steam to exit the tube in a direction toward the center of the container.
3. A device, as in claim 1, wherein the container includes a second tube, the second tube having an inlet open to the atmosphere and located high enough in the container to be above a preselected level, said preselected level being above the intended highest liquid level in the container, the second tube having an opening located adjacent the exit opening of the steam tube.
4. A device, as in claim 2, wherein the container includes a second tube, the second tube having an inlet open to the atmosphere and located high enough in the container to be above a preselected level, said preselected level being above the intended highest liquid level in the container, the second tube having an opening located adjacent the exit opening of the steam tube.
Type: Application
Filed: Nov 5, 2004
Publication Date: Jun 2, 2005
Inventors: Renzo Oldani (Villastanza di Parabiago), Eliano Bottelli (Villastanza di Parabiago)
Application Number: 10/981,978