Field

[0001 ] The present invention relates to apparatus and methods for steaming liquids, in particular beverages.

Background

[0002] Creating specialty beverages such as lattes, cappuccinos and hot chocolates requires milk to be frothed to produce a stable and creamy texture. One method of frothing milk involves mixing it with a whisk or other mixing device to aerate the milk. The motor-driven whisk needs to be powered separately from the home coffee machine. Some conventional milk frothers include a heater to simultaneously heat the milk while it is being whisked, otherwise the milk has to be heated in a separate step. This method of frothing milk without steam is more accessible to the average home user but creates a lower quality texture compared to milk frothed using a conventional steam wand

[0003] Milk steamed using a steam wand (as typically found on professional espresso machines) has a more uniform, silky texture known as "microfoam" and sweeter, creamier flavour, since pressurised steam more evenly heats sugars and breaks down fat in the milk. However, this method of steaming milk requires skill and experience. For example, the steam wand needs to be held at a particular angle relative to the container of milk and at a particular depth relative to the surface of the milk, in order to create and maintain a vortex in the milk, to thoroughly and continuously mix steam into the milk. Inexperienced users will typically create bubbles that are too large and unstable.

[0004] In this context, there is a need for improved apparatus and methods for steaming liquids, in particular for frothing milk.

Summary

[0005] According to the present invention, there is provided apparatus for mixing a liquid comprising:

a hollow tube configured to allow passage of fluid from an inlet end to an outlet end;

a rotatable head in fluid connection with the outlet end of the hollow tube; and at least one nozzle in fluid connection with the rotatable head and positioned such that fluid exiting an outlet of the nozzle drives the rotatable head to rotate about a longitudinal axis of the hollow tube.

[0006] The apparatus may comprise three nozzles spaced in radial symmetry about the longitudinal axis of the hollow tube.

[0007] The rotatable head may further comprise a stirring element.

[0008] The stirring element may comprise an annular spring, one or more paddles, one or more whisks, or a combination thereof.

[0009] The fluid may be pressurised steam.

[0010] The inlet end of the hollow tube may be sized and configured to be connected to a steam wand of a coffee machine.

[001 1 ] The rotatable head may further comprises one or more blades.

[0012] According to a second aspect of the present invention, there is provided a method of heating a liquid using the apparatus described.

[0013] According to a third aspect of the present invention, there is provided a method of steaming and/or frothing milk using the apparatus described.

[0014] According to a fourth aspect of the present invention, there is provided a method of blending a soft food substance while mixing the blended liquid, using the apparatus described.

[0015] According to a fifth aspect of the present invention, there is provided a coffee machine comprising:

a steam generator;

a hollow tube attached to the steam generator and configured to allow passage of steam to an outlet end of the tube;

a rotatable head in fluid connection with the outlet end of the hollow tube; and at least one nozzle in fluid connection with the rotatable head and positioned such that steam exiting an outlet of the nozzle drives the rotatable head to rotate about a longitudinal axis of the hollow tube. [0016] According to a sixth aspect of the present invention, there is provided a milk frother comprising:

a pressurisable vessel configured for generating steam;

a hollow tube attached to the pressurisable vessel and configured to allow passage of steam from the vessel to an outlet end of the tube;

a rotatable head in fluid connection with the outlet end of the hollow tube; and at least one nozzle in fluid connection with the rotatable head and positioned such that steam exiting an outlet of the nozzle drives the rotatable head to rotate about a longitudinal axis of the hollow tube.

Brief Description of Drawings

[0017] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of an apparatus for mixing a liquid according to one embodiment;

Figure 2 is a bottom view of an apparatus for mixing a liquid according to another embodiment;

Figure 3 is a cross-sectional view of the apparatus of Figure 2, taken from line A-

A; and

Figure 4 is a perspective view of the apparatus of Figure 2. Description of Embodiments

[0018] Referring to the drawings, apparatus 100 for mixing a liquid according to preferred embodiments comprises a hollow tube 2 configured to allow passage of fluid from an inlet end 4 to an outlet end 6 of the tube, a rotatable head 8 in fluid connection with the outlet end 6 of the tube 2, and at least one nozzle 10 in fluid connection with the rotatable head 8. The nozzle 10 is positioned such that fluid exiting the nozzle outlet 12 drives the rotatable head 8 to rotate about a longitudinal axis 13 of the hollow tube. In preferred embodiments, the fluid exiting the nozzle outlet 12 follows a flow path that is radially spaced from the rotatable head and substantially orthogonal to the longitudinal axis 13, in order to spin the nozzle 10 around the longitudinal axis 13.

[0019] The apparatus 100 is therefore powered by steam or other pressurised fluid, eliminating the need for a motor for drive the rotatable head 8. When used to steam milk for a beverage, steam flowing through apparatus 100 rotates the rotatable head 8 to create and maintain a vortex within the milk, resulting in uniform, fine-textured "microfoam", similar in effect to professionally steamed milk produced with a steam wand. In this way, the untrained user may easily create cafe-quality specialty beverages at home.

[0020] In some embodiments, rotatable head 8 may be held between hollow tube 2 and a non-rotatable end cap 16. The end cap 16 may function to space the nozzles 10 a predetermined distance away from the bottom of the container of milk, so that the vortex is formed at the ideal depth below the surface of the milk. In other embodiments, the end cap 16 is integral with rotatable head 8.

[0021 ] In one embodiment, the apparatus 100 comprises three nozzles 10, preferably spaced in radial symmetry about the longitudinal axis 13 of the hollow tube. Fewer or more nozzles may be provided. Apparatus 100 is preferably constructed of a heat- resistant and food-grade material, such as stainless steel or heat-resistant plastics.

[0022] The rotatable head 8 may further comprise a stirring element, such as an annular spring 14, one or more paddles, one or more whisks, or a combination thereof. As shown in Figure 1 , the spring 14 may comprise a coiled spring in an annular arrangement between the nozzles 10. The spring 14 may further improve or speed up mixing/frothing of the liquid. However, as shown in the embodiment of Figures 2 to 4, the rotatable head 8 need not comprise a stirring element in cases where the rotating nozzles 10 themselves can provide sufficient mixing ability.

[0023] In preferred embodiments, the fluid that is input into apparatus 100 is pressurised steam. Apparatus 100 may be attached to a steam generator which outputs steam at a sufficient pressure to rotate the rotatable head 8 at a sufficient speed for mixing and/or frothing the liquid. For example, the inlet end 4 of the hollow tube 2 may be sized and configured to be connected to a steam wand of a coffee machine (not shown). In preferred embodiments, apparatus 100 may be installed or retrofitted to a steam wand or other steam-generating device on the coffee machine, via for example, threaded connector 18. Since apparatus 100 is steam-powered, there is no need to drive a separate motor. Further, since the liquid is simultaneously heated by the steam, there is no need for a separate heating element. Apparatus 100 therefore provides a compact and energy-efficient frothing device that may be easily integrated with existing coffee machine designs.

[0024] Fluid preferably exits through nozzles 10 at sufficient pressure such that the liquid to be mixed does not enter into the nozzles. Further, steam passing through hollow tube 2, rotatable head 8 and nozzles 10 clears and sterilises the internal cavities of these components. Accordingly, apparatus 100 provides a hygienic and easy-to-clean mixing and/or frothing device.

[0025] In other embodiments, the rotatable head 8 may alternatively or additionally comprise one or more blades, so that apparatus 100 may be used to heat and blend soft foods (eg solid chocolate for a hot chocolate drink, soft foods to make baby food, protein shakes, soups, etc). In some embodiments, rotatable head 8 may be detachable from hollow tube 2, for swapping between different rotatable heads.

[0026] In some embodiments, other types of pressurised fluid such as compressed air, unheated water, pressurised carbon dioxide, etc may be input into apparatus 100 to drive the rotating head 8.

[0027] The present invention may alternatively be embodied in a standalone milk steamer (not shown). The milk frother may comprise a pressurisable vessel configured for generating steam eg by heating water on a stove, a hollow tube attached to the pressurisable vessel and configured to allow passage of steam from the vessel to an outlet end of the tube, a rotatable head in fluid connection with the outlet end of the hollow tube and at least one nozzle in fluid connection with the rotatable head and positioned such that steam exiting an outlet of the nozzle drives the rotatable head to rotate about a longitudinal axis of the hollow tube. Alternatively, apparatus 100 may be installed or retrofitted to a standalone steamer such as a stovetop milk frothing device.

[0028] In some embodiments, the apparatus 100 or the standalone milk steamer (not shown) may comprise a thermometer to allow the user to easily monitor the temperature of the milk being steamed.

[0029] Embodiments of the present invention provide apparatus and methods for steaming liquids, which are useful for enabling the untrained user to froth milk and create specialty beverages at home. Embodiments of the present invention additionally or alternatively provide apparatus for steaming liquids that may be integrated with and powered by steam generators on coffee machines, resulting in a compact, energy- efficient design.

[0030] For the purpose of this specification, the word "comprising" means "including but not limited to", and the word "comprises" has a corresponding meaning.

[0031 ] The above embodiments have been described by way of example only and modifications are possible within the scope of the claims that follow.