The invention concerns a process for dissolving a portion of rapidly soluble powder, e.g. coffee powder, in a volume of liquid having a relatively large surface in a mixing chamber. The mixing chamber is typically in- corporated as a component of a machine for automatic mixing of the mentioned media, e.g. in a coffee vending machine.

For example the US Patent Specification 3 300 094 dis¬ closes a coffee vending machine designed to mix a pre- determined amount of hot water and a predetermined amount of coffee powder to make a cup of coffee upon insertion of a coin in the apparatus. This and other known devices are vitiated by the drawback that effective solution of the powder in the water takes a relatively long time (typically 5 seconds for a cup of coffee) because of the methods employed for introduction of the two media into the mixing chamber. Typically, the powder is advanced by means of a worm and drops down into the mixing chamber, while the water is introduced as a jet into the chamber.

The object of the invention is to provide a process of the present type, which significantly reduces the time necessary to dissolve the powder in the water, in par¬ ticular in respect of dissolution of individual portions (e.g. 1 cup of coffee). This object is achieved by carry¬ ing out the process as stated in the characterizing portion of claim 1, it having been found that by this technique a single cup of coffee can be mixed within about 1 second. This technique is based on an improve- ment of the process disclosed by the Norwegian Patent

Specification 62 000, from which it is known to dis¬ solve powder in water by imparting a large surface to the water and distributing the powder over this surface.

It will be appreciated that in case of a hot beverage the.water will be almost boiling so that a relatively large amount of vapour will be released because of the large water surface in the mixing chamber. It is well- known that vapour is a drawback since moisture may settle in particular around the means for discharging the coffee powder so that these means will be clogged. The previously mentioned US patent specification discloses a method for venting the mixing chamber so that the moist air is sucked out through the bottom of the mixing chamber and does not get near the moisture- sensitive parts of the apparatus.

The invention is thus based partly on the finding that venting can be made so effective that the necessary large water surface in connection with the process does not involve any drawbacks, but solely the advantage known per se from the Norwegian patent specification, and partly that the dispensing technique disclosed by the Norwegian patent specification cannot be made to operate in practice when small powder portions are to be dissolved individually. More particularly, it is not possible in the prior art to spread a small portion of powder both rapidly and uniformly because normally spreading has a non-reproducible initial course. It has been found that a small powder amount can be distributed rapidly and uniformly precisely when the air flow through the mixing chamber, which is known in principle

from the said US patent specification, is utilized in contributing to guide and spread the powder, so that a surprisingly good result is obtained by combination of the mentioned techniques and by utilization of the guiding effect of the injected air on the distribution of the powder.

Claim 2 defines preferred" details in- the provision of the extended liquid layer known per se. If several cups of coffee are to be mixed in a row, the water may optionally flow evenly through the mixing chamber, but in any event it is a prerequisite for the invention that the powder is discharged intermittently. Precise¬ ly this operational condition, which is essential to the mixing of a single cup of coffee, provides for a significant reduction in the mixing time, and the reduction in the mixing time with respect to the prior art is so great that an apparently continuous mixing (when many cups of coffee are to be made) can be pro¬ vided by a rapid series of intermittent discharges according to the invention.

The invention also relates to an apparatus for perform¬ ing the process and of the type stated in the intro¬ ductory portion of claim 4.

The apparatus is characterized by the features defined i _n the characterizing portion of claim 4, which combined bring about the surprising effect explained in the fore¬ going. Typically, the mixing chamber is in the form of a flat-bottomed vessel, which will be described later, but may also be shaped as a trough so that the bottom of the mixing chamber is cylindrical or spherical. The configuration of the mixing chamber bottom is in prin¬ ciple limited only by the possibilities of feeding liquid such that a relatively thin liquid layer is

provided for a moment covering the bottom of the mixing chamber, and is limited by the possibility of spreading the powder evenly over the liquid surface by means of the distributing effect of the air flow on the powder.

The means for introducing the liquid are preferably arranged as stated in claim 5, while claim 6 defines preferred details in the mixing chamber of the in¬ vention. It has been found in practice that the even downgrade mentioned in claim 6 can be configured so that a relatively thin, coherent liquid layer is achieved over the entire bottom of the mixing chamber. Claim 7 defines a preferred embodiment of the means for discharging the powder. These means are a further development of a metering device known per se and stated in the introduc¬ tory portion of claim 7. The advantage is that the powder is discharged effectively in a very short time, it being possible to make the discharge particularly effec¬ tive by configuring the cavity of the dispensing means as stated in claim 8, because precisely this structure cooperates well with the guiding effect of the air flow on the spreading of the powder. It will be appreciated that one or more cavities may be present in a single cylinder, and that even two or more cylinders may be used at the same time when the area of the mixing bowl bottom is increased correspondingly and when the inlet openings for the ^' air flow through the mixing chamber are widened to ensure the uniform, instantaneous distribution of the powder.

The mixing bowl may advantageously be provided with the intermediate chambers mentioned in claim 9, which have an opening facing upwardly in the position of use. In operation the latter opening will be disposed below a branch through which. the above-mentioned amount of

liquid is discharged, e.g. from a reservoir, which involves the advantage that the mixing chamber can be removed as a unit from the apparatus with a view to cleaning or possible replacement. The mixing-chamber can be introduced into the apparatus again by a single operation, so that in the preferred embodiment it is not necessary to connect it with hoses for water supply, exhaustion or the coffee outlet.

Claim 10 defines an expedient embodiment of the appara- tus for performing the- process, which also provides for an effective "blanket" of dry air around the dis¬ pensing cylinder itself.

In a preferred embodiment of the position of the inlet openings, these are disposed as a pair of rows of holes located outside the slots mentioned in claim 10, cf. the following description.

The invention will be explained more fully by the following description of a preferred embodiment with reference to the drawing, in which

fig. 1 is a schematic view of a coffee vending machine provided with a mixing assembly according to the > invention,

figs. 2 and 3 are sections through a preferred embodi¬ ment of a mixing assembly, while

figs. 4 and 5 are corresponding sections to facilitate the understanding of the mode of operation of ^' the apparatus.

In the following the invention will be explained in connection with a coffee vending machine of the type shown in fig. 1. The coffee vending machine comprises a cabinet 1 having on the exterior a coin insert 2 and an opening 3 for a mug 4 to receive hot coffee from the machine. At 5 there is indicated a door allowing the mixing chamber of the machine to be withdrawn from the machine; this mixing chamber will be described later.

Pig. 1 moreover shows the fundamentally important components inside the cabinet 1. These components com¬ prise a water container 6 and a container 7 for coffee powder. The water and the coffee powder are mixed in an assembly 8 which can be withdrawn from the door 5 and which rearwardly communicates with an exhaust manifold 9 connected with a fan 11 through a hose 10. The purpose of the fan is to draw water vapour out of the assembly 8, air being drawn in through the grid 12 shown in- fig. 1. This air is utilized according to the invention to affect the spreading of powder from a powder magazine and is drawn through the assembly 8, where the air is mixed with water vapour, and then the mixture is blown out through a hose 13. Finally, at 14 there is indicated a box containing the electric con- trol circuitry for the machine.

More particularly, the invention concerns the mixing assembly 8, and the invention is thus not dependent upon the example of a coffee vending machine shown in fig. 1. For use in restaurant kitchens, for example, the coin insert 2 will be replaced by a button i.a. for selection of the desired number of cups of coffee, the opening ^' 3 being sufficiently large to receive a coffeepot. In large kitchens, certain parts, e.g. the water container, the fan and the electric control cir-

cui ry may be shared by several mixing assemblies 8, which will be understood from the following explanation of a preferred embodiment of the mixing assembly 8 with associated coffee container 7.

The constructive arrangement will be explained first in connection with figs. 2 and 3, and then the mode of operation of the apparatus will be explained by means of the following figures. Figures 2, 4 and 3, 5 show sections along the shown lines II-II and III-III, respectively.

As appears from the figures the mixing assembly 8 com¬ prises a housing 15, which contains a collection funnel 16 and a mixing chamber 17, said parts being preferab¬ ly of injection moulded plastics. The collection funnel

_* 16 rests on some supporting legs 18 in the housing 15, and the mixing chamber 17 is in the form of a vessel having at the top an annular flange 19, which is horizontal in the position of use and whose outer edge- rests on a bent edge of the upper rim of the housing 15. The mentioned edges fit in a passageway in a pair of rails 20, 21 which are secured to the underside of the container 7 so that the mixing assembly 8 can be with¬ drawn as a drawer, e.g. when the mixing assembly is to be cleaned. The mixing chamber 17 is contiguous with an intermediate chamber 22, which has an upwardly directed _. opening 23 and communicates with the mixing chamber 17 through a narrow slit 23. In the position of use the opening 23 is flush with a branch 25 com¬ municating with the water container 6 through a hose 26 and a magnet valve 27.

The container 7 comprises a coffee powder magazine, whose bottom comprises a pair of opposite, inclined walls 28, 29 hermetically sealed to the surface of

a rotable dispensing cylinder 30 by means of gaskets (not shown). Below each of the inclined walls 28, 29 is provided a substantially closed cavity by means of a screen plate 31. This cavity serves as an inlet mani- fold for air drawn through the mixing assembly and out through the exhaust manifold 9 through a filter 32. ^• The air is sucked in through holes 33, 34 and down into the mixing chamber 17 through some holes 35A and 35B and a pair of narrow slits 36A and 36B, which are defined between the screen plate 31 and the dispensing cylinder 30. Then the air flows through a slot 37 in the bottom of the mixing chamber 17 and out through the filter 32, there being an air gap between the mixing chamber 17 and the collection funnel 16. The air can advantageously be sucked in through hoses 42, which are connected with a jacket 43 in direct heat- conductive contact with the water container 6, allowing the inlet air to be preheated by the passage through the chamber 43 so that the air flow through the slit 36, in addition to having the powder guiding effect described later, provides a safeguard against deposit of condensation on the dispensing cylinder 30.

The dispensing cylinder 30 has a shaft which is journalled in a pair of opposite walls of the con- tainer 7, and which is provided with a gear wheel 38 ^• 'at one side, said gear wheel being in mesh with a gear wheel 39 in an activation mechanism 40. The mechanism 40 is arranged to rotate the cylinder 30 half a revolu¬ tion, so that the coffee powder contained in a longitu- dinal slit 41 in the dispensing cylinder is discharged to the mixing chamber 17. The powder can thus be dis¬ charged rapidly in small portions (corresponding to e.g. one cup of coffee), which could not be combined with a quite even distribution of the powder portion over the liquid surface. When, in accordance with the

invention, the air flow through the mixing chamber is utilized for affecting the powder distribution, it is now possible to distribute small powder portions inter¬ mittently and very evenly over the liquid surface.

The mode of operation will now be described more fully, assuming that a single cup of coffee is to be made. Initially, the magnet valve 27 opens for a predetermined period of time so that the intermediate chamber 22 is rapidly filled with hot water at e.g. 95°C. The water will flow from the intermediate chamber 22 through the slit 24 and into the bottom of the mixing chamber 17 so inclined as to have a downgrade away from the slit 24 and a downgrade toward the slot 37. The slit 24 is defined by means of a height-adjustable angle bar 44, so that the entire bottom of the mixing chamber is filled with a thin layer of water for a moment. Figs. 4 and 5 show the situation where all the water still has not left the intermediate chamber 22. When all the water has left the intermediate chamber and, as previously mentioned, covers the entire bottom of the mixing chamber for a moment, the drive mechanism 40 is activated so that the dispensing cylinder 30 is rapidly rotated half a revolution to the position shown in fig. 4, thus dis¬ charging a predetermined amount of coffee powder which is indicated at 47 and is distributed uniformly under the action of the air flow through the mixing chamber in •the form of a thin layer across the water surface which covers the entire bottom of the mixing chamber. In this method the powder is dissolved almost instantaneously and before the water flows out through the slot 37 and down into the collection funnel 16 because of the in¬ clined bottom of the mixing chamber, from where it is passed to a discharge opening 45, which, in the position of use, is disposed vertically above the mug 4 shown in fig. 1.

JLO

The air flow is guided by the screen plate 31 so that the air flow contributes to the desired, uniform dis¬ tribution of the coffee powder across the bottom of the mixing chamber, partly because of the slots 36A and 36B, where the air flow through these provides a safe¬ guard against condensation on the dispensing cylinder 30, and partly through the two rows of holes 35A and 35B extending in parallel with the dispensing cylinder 30. It will be appreciated that some water vapour is re- leased in the mixing chamber 17 owing to the large surface area of the water, which however does not cause any problems because of the described effective air flow which is shown by arrows in figs. 4 and 5.

It should moreover be observed that the plane of the slot 37 is inclined with respect to the bottom of the mixing chamber 17, which thus exhibits a lip 46. The air flow will thus be deflected through the slot 37 to the side (to the left in figs. 2 and 4), which has the effect that the water leaving the lower edge of the lip 46 is initially relatively unaffected by the air flow and drops as a "water curtain" at any rate so far as -to effectively prevent coffee powder from being discharged from the dispensing cylinder 30 directly through the slot 37, without this coffee powder having been in contact with the water.

The embodiment described in the foregoing has an addi¬ tional advantage, viz. that the mixing chamber is very easy to remove from the apparatus in case of cleaning or replacement. With reference to fig. 4, the housing 15, the collection funnel 16 and the mixing bowl 17 are removably disposed in the rails 20, 21, and it is therefore essential that the intermediate chamber 22 (fig. 3) is disposed below the water branch 25, which, in the position of use, is disposed vertically above

the opening 23 in the intermediate chamber. Likewise, it is important that the exhaust manifold 9 is arranged to receive the rear open end of the housing 15, which, in the position of use, is hermetically enclosed by an annular collar 48 on the exhaust manifold 9. As appears from the figures, the filter 32 may be mounted in the mentioned open end of the housing 15, which involves the advantage that also the filter can be cleaned or replaced when the housing 15 is removed from the appara- tus.