EP4694742A1

EP4694742A1 - Frother for milk based beverages

Info

Publication number: EP4694742A1
Application number: EP24726211.6A
Authority: EP
Inventors: Alex Gort-Barten; Leslie Alexander Gort-Barten
Original assignee: Individual
Current assignee: Individual
Priority date: 2023-05-12
Filing date: 2024-05-13
Publication date: 2026-02-18
Also published as: WO2024235923A1; GB2629867A; GB202307126D0

Abstract

A whisk means (3) for a frother for producing a hot chocolate beverage, which whisk means (3) is adapted to rotate in the liquid to mix the heating liquid. The whisk means (3) comprises a whisk comprising a plurality of coils, which whisk is mounted on a support, the whisk means further comprising a hood (80) to restrict flow of milk to the frother coils.

Description

Frother for milk based beverages

The invention relates to a frother for milk based beverages and to a whisk for a frother.

Espresso based coffee drinks such as caffe latte and cappuccino have become increasingly popular and consumers want to be able to easily and reliably produce these drinks. Traditionally, baristas have been trained to use the steam generated by an espresso machine to heat and froth milk in a jug to produce the hot milk and froth required for these drinks. Producing the appropriate amount of hot milk and froth without burning the milk or damaging the jug requires some training or experience. Smaller espresso machines are also much harder to use to treat the milk.

A number of separate milk frothers have been produced which are suitable for home or small scale commercial use. EP1656866 discloses a frother with a tank to receive a milk-based liquid food with a magnetic beater. A magnetic beater driving system produces a magnetic field which drives the beater in rotation in the tank. The system, beater and a beater positioning unit break or prevent symmetrical circulation of the liquid around a median of vertical axis of the tank. Heating units are disposed in association with the tank for heating the liquid. This is used for preparing foam from a milk-based liquid food product.

GB2454421 discloses a device for frothing milk that is provided with a rotating heating element to be inserted in the milk. The device is provided with a whisk attachment for producing froth and a paddle attachment for producing a more creamy finish.

A further problem with the known frothers is that the milk tends to burn on the element as when the frother has frothed the milk, the user immediately pours the milk out and a small residue remains behind, which burns on the element. If this is not cleaned quickly, the burnt on residue becomes difficult to remove and also affects future performance. The standard approach to this has been to reduce the temperature to which the milk is heated to around 60 C but at this temperature, the frothed milk is not suitable for use in other beverages such as hot chocolate, which would require a higher temperature to be palatable.

Known milk frothers and hot chocolate makers use small DC motors to rotate the whisk. The motor drive shaft can be connected directly to the whisk via a mechanical coupling, or remotely by means of a magnetic coupling. These motors do not have much torque and so stall easily> The magnetic couplings in the motor can also slip and become unphased.

GB2486872 represented a significant advance in the art of domestic milk frothers but is limited to use with milk. It is also a single cup design which is the standard capacity in the industry. Designing a milk frother with a higher capacity and suitable for making hot chocolate than the known milk frother designs requires that more power will need to be sent to the motor as the motor may stall or the magnetic drive may disengage. Known whisk designs may not remain stable and/or may wear out too quickly with this increased power.

A further design is shown in CN208725556 and sold under the Gastroback® brand. This design has a fixed cover that fully encloses the spring whisk but which is unable to texturise the milk. It is also difficult to clean.

The most difficult drink to produce for a home user is a flat white coffee. A flat white is a coffee drink consisting of espresso with microfoam (steamed milk with small, fine bubbles and a glossy or velvety consistency). Making microfoam is generally regarded as a skilled job by a barista as it requires the correct use of a steam wand at the surface of the milk whilst spinning the milk. Although comparable to a latte, but smaller in volume and with less microfoam, therefore having a higher proportion of coffee to milk, and milk that is more velvety in consistency - allowing the espresso to dominate the flavour, while being supported by the milk. As steam is regarded as essential in the formation of the microfoam, domestic frothers have been reproduce this effect.

The present invention therefore seeks to provide a frother that can be used for producing a wider range and volumes of in particular milk based beverages.

According to the invention there is provided whisk means for a frother for producing a beverage, the frother comprising a tank for receiving a liquid, magnetic drive means adapted to drive whisk means, which whisk means is adapted to rotate in the liquid to mix the liquid, the frother further comprising heating means adapted to heat the liquid, the magnetic drive means being located outside of the tank, wherein the whisk means comprise a whisk comprising a plurality of coils mounted on a support, which coils are exposed to the liquid in use, wherein a cover is provided which restricts flow of the liquid to the coils. Preferred aspects of the invention can be found in the subclaims. In a preferred embodiment the ratio of the area of openings in the hood to the free volume of the hood is in the range of 300 to 420 per 30 ml of free volume. Preferably, the openings in the hood wall each have an area of between 100 and 140 mm². Preferably, the ratio of the area of the slots to the surface area of the hood is in the range of 6 to 12%.

The whisk design of the invention advantageously restricts flow to the coils of the whisk, which surprisingly facilitates the formation of a microfoam which is needed to make a flat white coffee. The milk spends more time in the vicinity of the coils and so can be texturized or velvetised to form the microfoam rather than the looser foam produced by known frothers The attachment or hood restricts the flow of milk to and from the coils of the whisk so that the whisk coils can break up the bubbles that form in the milk to create the smaller bubbles of a microfoam.

Exemplary embodiments of the invention will now be described in greater detail with reference to the drawings in which:

Fig. 1 shows a perspective view of a frother;

Fig. 2 shows a perspective view of a whisk;

Fig. 3 shows a further whisk design;

Fig. 4 shows a detail of a basket;

Fig. 5 shows a further whisk design;

Fig. 6 shows a further whisk design with an upstand;

Fig. 7 shows a whisk with a flat white attachment and

Fig. 8 shows an inverted perspective view of the flat white attachment.

Figure 1 shows a perspective view of a milk frother having a tank 1 having a generally circular outer and inner circumference for receiving milk to be frothed and a handle 5. A magnetic drive means 2 is provided below the lower surface of the tank 1 , which drive means 2 is adapted to impart a drive to a removeable stirrer or whisk means 3 located in the tank without a mechanical connection member intruding through the wall of the tank 1 . The removeable stirrer or whisk means 3 is supported on the base of the tank 1 to ensure that it remains centred and that the drive mechanism can impart drive to the stirrer.

A heating plate 4 is located beneath the base of the tank 1 , which heating plate is adapted to heat the milk in use. The frother is provided with control means adapted to control the actuation of the heating plate and also, independently, the actuation of the magnetic drive means. The control means can be either a single ECU or independent PCBs. The magnetic drive means can also have more than one speed so that the liquid is not frothed depending on the beverage to be made. For example follow on baby milk would not be frothed.

In use, the control means are adapted to turn off the heating plate a predetermined time before the stirrer stops stirring so that the residual heat of the plate can be removed by the action of the stirrer passing the milk over it for the predetermined period of time. The length of time will depend on both the dimensions of the tank, the speed of the stirrer and the desired temperature of the milk. An exemplary predetermined length of time is around 10s. A possible range of times is 6 to 20s.

This particular arrangement has the attraction of permitting the milk to be heated to a higher temperature than would otherwise be possible but by the time the milk is poured from the frother the base of the tank will have cooled sufficiently that any residual milk that is left in contact with the tank will not burn. For example, in a frother of the invention it is possible to heat the milk to 75 C, which is suitable for making hot chocolate, whereas in most prior art devices, the milk is only heated to around 60 C as any higher temperature would result in unacceptable levels of milk burning on the surface of the frother.

Figure 2 shows a perspective cross-sectional view of whisk from above in accordance with a first embodiment of the invention, which whisk is suitable for using with for example large chocolate flakes. The whisk means 3 comprises an upstanding wall 7, which wall is joined by two radial arms 8 to an axial spindle 9. Each of the arms is provided with a cut out in the region of the wall, which cut out receives a clip of a cover to retain the cover in position. The spindle 9 extends above and below the radial arms 8. A whisk 10 is rotatably mounted on a rotatable drive shaft at the lower end of the spindle 9, which drive shaft is housed within the spindle 9. The wall shown is an annular wall but need not be a continuous annular wall.

The whisk is provided with a basket 20. The basket can clip onto the spindle 9 or alternatively be formed integrally with it. In use, the basket needs to stay attached to the whisk means/spindle so that it spins in use and also so that it does not fall off when the drink is poured. The spinning of the basket helps move the flakes outwards and into the milk vortex, aiding mixing., Allowing the basket to rotates helps the vortex form, thus introducing more air into the mixture, creating the froth. The basket is provided with a plurality of slots, which enable fluid to pass into the basket but which around 2- 2.5mm wide. The spinning also reduces the load on the motor / drive couple. The clump of chocolate can spin with the rotating milk, rather than being stationary and acting like a brake

In use the whisk and basket are fitted in the tank and preferably the milk is followed by the chocolate or other beverage precursor if required. The basket that receives the chocolate flakes in the milk frother prevents the motor from stalling and / or the magnetic or similar drive coupling from disengaging by keeping the chocolate above and away for the rotating whisk. The milk is initially frothed with a slow start below the chocolate. When the milk reaches chocolate melt temperature, the speed can be increased so the height of the milk in the frother increases and then the chocolate begins to melt and mixes into the milk. The basket additionally keeps the chocolate away from the heating plate of the frother, which makes it easier to clean.

The wall of the basket can be optional. Removal of the wall would allow the basket to be slimmer and give more design freedom to adjust the height of the whisk. The height of the basket also effects the amount of froth and chocolate residue left on the whisk. The required height may need to change based on the hot chocolate recipe.

The basket design may be angled up or down as well as the flat version shown in Figure 2. This adjusts the how the chocolate sits during the frothing cycle, which affects the amount of froth and chocolate residue left on the whisk. Alternatively, the basket can be substantially flat and have no wall. This way it can be reversible to adjust the height.

The spacing of the concentric rings forming the gaps in the basket can be even or uneven, this can be used to control the amount of froth and also to reduce undissolved chocolate residue, that may remain at end of the cycle.

The basket could have 2 or more radial arms that attach the concentric rings to the central shaft, the radial arms could be straight or curved. The cross section of the concentric rings can be circular, diamond, teardrop, to reduce the chance of the undissolved chocolate settling on the basket. Figure 3 shows a further whisk design. The whisk 30 of Figure 4 also comprises an upstanding wall 7, which wall is joined by three radial arms 38 to an axial spindle 9. Each of the arms is provided with a cut out in the region of the wall, which cut out receives a clip of a cover to retain the cover in position. The spindle 9 extends above and below the radial arms 38. A whisk comprising coils, not shown, is rotatably mounted on a rotatable drive shaft at the lower end of the spindle 9, which drive shaft is housed within the spindle 9. The wall shown is an annular wall but again need not be a continuous annular wall.

The use of three arms allows each arm to be made thinner for the same overall strength as with two arms. Each arm may be given an aerofoil style section as shown in Figure 5 so that drag on the flow of liquid, initially milk but later with cocoa mass, can be reduced. The reduction in drag advantageously leads to the formation of smaller bubbles in the mix improving the organoleptic properties of the drink.

The load on the motor and coupling can become more significant depending on the recipe to be used in the hot chocolate maker, such as increasing the % of chocolate to milk used. In a typical hot chocolate drink around 35 grams of chocolate is used with 220ml of milk. This would make one serving of hot chocolate. Other recipes might want to use are 35 gram of chocolate and 120ml of milk to make cold frothed milk or 70 grams of chocolate and 120 ml milk to make a chocolate dipping sauce / pudding.

The embodiment of Figure 4 and 5 enables the production of drinks using larger flakes, which have a comparatively reduced surface area. With a reduced surface area, it is harder to get chocolate to melt / dissolve into a set volume of milk in the given time, (with simple controls the time is fixed by volume of milk and how long it takes to heat to 67-70 degrees).

The lower the resistance on the whisk / drive motor the faster it spins. Therefore if the resistance of the whisk support part is reduced it should spin faster, mixing the milk and chocolate quicker. The extra speed enables the device to act like a blender, breaking down the larger pieces of chocolate so they dissolve more quickly.

As the pieces fall though the basket they get exposed to the sharper leading edge of the support arms (as well as the extra arm compared to the first embodiment) and this helps with the breaking down of the pieces in a controlled way as to not stall the whisk It has been found that the optimum height for basket, relative to the bottom of the jar should be the minimum level of milk required in the recipe. The measurement is taken from the top of the basket.

Figure 5 shows a further embodiment of the basket. As with the previous embodiment, the basket can clip onto the spindle 9 or alternatively be formed integrally with it. The basket therefore spins in use. The spinning helps move the chocolate pieces outwards and into the milk vortex, aiding mixing. In this embodiment the concentric rings 63 are spaced out more closer to the centre of the whisk. The radial arms are also reduced in length in three of the arms 62, which reduced length arms alternate with the full length arms 61 The change in spacing out of the concentric rings closer to the centre of the whisk can reduce the amount of residual chocolate.

The spacing between the rings should be less than the smallest piece of chocolate flakes, so as the diameter of the device increases, more concentric rings may be required and vice versa. More radial arms may be required to be added purely for strength of the basket to support the additional weight of cholate. An exemplary gap between rings is between 4 and 6mm.

Figure 6 shows a further embodiment of the invention in which the innermost ring of the basket has been removed. In its place is an upstand 70 that disrupts the flow of the milk in use when the whisk and basket are rotating in unison. The upstand 70 can be formed on the whisk means or on the basket and extends above the height of the basket. The upstand stops the chocolate from collecting or sitting on the basket where, depending on the precursor ingredients, it can start to form clumps after the precursor has started to melt.

Figure 7 shows a whisk with a flat white attachment and Figure 8 shows an inverted perspective view of the flat white attachment. The flat white attachment 80 comprises a bell shaped or frustoconical shaped cover or hood for the whisk coils with a central opening to fit over the spindle and three slots 81 configured to fit over the arms of the whisk so that the attachment sits on the arms and is clear of the base of the frother. Each slot has an area of around 120 mm². The width of the slot may be between 7.8mm and 12.9mm. The hood has an approximate overall volume of 30.8 ml which can be taken up by the liquid, i.e the free volume. The bottom of the cover can be approx 3-4 mm off the base so milk moves from there and through the slots 81 . The coils of the whisk are spaced approximately 4.6mm from the interior surface of the hood 80. The hood has an edge 82 with an approximate length of 500 mm. The edge is defined by the lower surface of the hood and comprises the edges forming the slots 81. The edge of the hood apart from the slots is approximately 146 mm, that is the part of the edge adjacent to the heating plate. The surface area of the hood is around 4600 mm².

With the flat white attachment the milk will be texturized and micro bubbles but no froth. The flat white hood or attachment leads to the breaking down of the larger bubbles by containing the froth within the hood. The whisk is constantly reducing the size of the bubbles as they have restricted path into the main body of the milk. The flat white attachment or hood should preferably be dimensioned so that there is substantially reduced or even little to no cavitation in the liquid in the interior space of the attachment. The flat white attachment enables a higher pressure to be generated within the cap compared to the prior art solutions. The higher pressure limits the forming size of the vapour pocket. The increased pressure is due to the only exit point for the milk (and any vapour pockets) is out through the small gap between the hood and heating plate.

The location of the exit / entry gap of the hood for the milk, forces the milk over the heating plate; which may also help with the micro bubble creation analogously to when milk is frothed with a stem wand, in which the nozzle is held close to the bottom of the jug initially, to generate the vapour pockets, and then drawn out into the milk by lowering the jug.

The restriction may also enable texturizing of the milk at the end of frothing analogously to a tap of the jug to reduce the vapour pocket sizes. This may force the milk and vapour pockets through a restriction between the cap and the heating plate help physically squash down, disperse and standardise the vapour pockets size.

The inception of the vapour pocket may be on the edge of the hood, as the turbulent milk flows out under it. The edge of the cap 80 is significantly shorter than the combined edge of the known designs such as CN208725556 due to all of the slots cut in the known design of cap.

Perhaps a ratio between the length of edge, and the width of the slot, relates to the size of froth (vapour pockets) formed. Apart from chocolate, other milk based beverage precursors are possible such as honey. Milk can include non dairy milks. A standard hot chocolate recipe comprises 220ml milk and 35g chocolate

Claims

1 . A whisk means for a frother for producing a beverage, the frother comprising a tank for receiving a liquid, magnetic drive means adapted to drive whisk means, which whisk means is adapted to rotate in the liquid to mix the liquid, the frother further comprising heating means adapted to heat the liquid, the magnetic drive means being located outside of the tank, wherein the whisk means comprise a whisk comprising a plurality of coils mounted on a support, which coils are exposed to the liquid in use, wherein a hood is provided which restricts flow of the liquid to and from the coils, wherein the hood leads to the breaking down of bubbles by containing froth within the hood.

2. A whisk according to Claim 1 , wherein the whisk is constantly reducing the size of bubbles in the liquid as the liquid has a restricted path into the main body of the liquid.

3. A whisk according to Claim 1 or Claim 2, wherein the hood is dimensioned so that there is substantially reduced or little to no cavitation in the liquid in the interior space of the hood.

4. A whisk means according to any one of Claims 1 to 3, wherein the hood has the form of a bell shaped or frustoconical hood.

5. A whisk means according to any one Claims 1 to 4, wherein the whisk means is provided with a spindle and the cover means has an opening so that the spindle passes through the opening.

6. A whisk means according to any one of Claims 1 to 5, wherein the whisk means is provided with radial arms to the axial spindle, which radial arms have a curved surface to reduce drag on liquid in the frother.

7. A whisk means according to any Claim 6, wherein the hood is provided with an opening in a side wall so that the hood sits on the arms.

8. A whisk means according to any one of Claims 1 to 7, wherein hood is supported on the whisk means so that it is clear of the bottom of the tank, preferably by approximately 3-4mm.

9. A whisk means according to any one of Claims 1 to 8, wherein the cover means can clip onto the spindle or alternatively be formed integrally with it so that the cover means can spin in use.

10. A whisk means according to any one of Claims 1 to 9, the ratio of the area of openings in the hood to the free volume of the hood is in the range of 300 to 420 per 30 ml of free volume.

11. A whisk means according to any one of Claims 1 to 10, wherein the openings in the hood wall each have an area of between 100 and 140 mm²

12. A whisk means according to any one of Claims 1 to 11 , wherein the ratio of the area of the slots to the surface area of the hood is in the range of 6 to 12%.