Patent Description:
Electric coffee grinders are known which are provided with a substantially cylindrical grinding chamber, in which a fixed grinder is placed, connected to the chamber itself, and a mobile grinder, coupled to an electric motor for its rotation with respect to the fixed grinder within the grinding chamber. The coffee beans are dropped between the two grinders to be broken and progressively transformed into powder of the desired grain size, essentially linked to the type of the two grinders and their distance from each other.

The coffee dust that comes out of the grinders collects on the bottom and on the side wall of the grinding chamber and is evacuated from it by an impeller integral with the mobile grinder and dragged into rotation with it. The impeller, which is generally made of metallic material and preferably aluminium, includes several substantially vertical arms, which slide at a minimum distance from the side wall of the grinding chamber and collect the coffee powder, which adheres to the side wall itself during grinding.

These substantially vertical arms are configured in such a way as to also impart a centrifugal force to the coffee powder with their movement and to convey it towards an opening made in the side wall of the grinding chamber to then make it exit from this towards an external chute.

Given the position of this opening, the exit of the coffee powder through it occurs partly due to the dragging effect due to the arms of the impeller, and partly due to the centrifugal effect imparted by these to the powder itself.

Since the coffee powder is present throughout the grinding chamber while the opening for its exit from this has a well-defined position on its side wall, when the impeller and the mobile grinder are stopped at the end of the grinding, a certain quantity of dust remains inside the grinding chamber and is not used. For example, if <NUM>/<NUM> grams of coffee powder are used to produce a cup of espresso, a substantially similar quantity of coffee powder generally remains inside the coffee grinder and can only be removed at the next grinding cycle.

This constitutes a limitation of current coffee grinders of this type, given that the current trend is to grind coffee on demand, i.e. only at the moment of its use to prepare the infusion, in order to maintain its aroma intact, which as is known it tends to alter as time passes between obtaining and using the coffee powder.

It is clear that this trend requires reducing the so-called retention time to a minimum, i.e. the time between grinding the coffee and using the powder obtained.

If the coffee grinder is used in an environment in which there is a continuous demand for coffee infusions, in particular in a bar, the substantially continuous demand for coffee powder makes the time spent in the grinding chamber of the coffee grinder practically insignificant , while if the coffee grinder is used in a domestic environment or in any case in an environment with low demand for coffee, the residence time of coffee powder in the coffee grinder before its use can be long, and since the quantity of coffee powder that remains for a long time inside the grinding chamber is substantially equal to the quantity of coffee needed to prepare an infusion, in practice a large number of infusions are prepared with coffee powder retained for a long time in the coffee grinder.

<CIT> already describes a coffee grinder which addresses the technical problem of differentiating the rotation speed of the mobile grinder, which must be low so as not to excessively heat the coffee powder obtained, from the rotation speed of the impeller, which must be higher to give the coffee powder sufficient centrifugal force to exit completely or almost completely from the grinding chamber, avoiding its permanence in the coffee grinder for periods of time which may even be long. According to this previous document, the technical problem just stated is solved with a coffee grinder equipped provided with two chambers for collecting the coffee powder and more particularly with a first collection chamber, which is located in a position below the mobile grinder and houses a rotating blade integrally with said mobile grinder and configured to collect the coffee powder and to convey it into a second collection chamber through an opening provided therein. A second paddle is housed in this second collection chamber, which can be rotated at a different speed, in particular a higher one, to impart a greater centrifugal force to the coffee powder and thus facilitate its exit from this second collection chamber.

This solution proved to be more advantageous than the previous technique, and in particular it allowed the coffee beans to be ground at low speed, and therefore without excessively heating the coffee powder obtained, and at the same time it allowed it to come out in an almost total quantity. from this second collection chamber, but at the same time it did not prove to be completely satisfactory both due to the manufacturing complexity of the coffee grinder, which must have two coffee powder collection chambers and two rotating blades mounted on two distinct parallel shafts, and because it did not eliminate the permanence of coffee powder in the first collection chamber when the coffee grinder stops working. This is because the greater speed with which the second paddle may be rotated to allow the coffee powder to come out more completely from the second collection chamber cannot have any effect on the coffee powder that is still in the first chamber. collection.

The aim of the invention is to eliminate all these drawbacks and to create an electric coffee grinder in which the quantity of coffee powder retained inside the grinding chamber and not immediately used is practically eliminated.

Another aim of the invention is to create a coffee grinder that can use mobile grinders of any type, and in particular conical or flat mobile grinders.

Another aim of the invention is to create a coffee grinder whose performance can be easily adapted to different types of coffee and/or to different user needs.

Another aim of the invention is to create a coffee grinder which, compared to coffee grinders with similar performance, is simpler to manufacture and more reliable in operation.

Another aim of the invention is to create a coffee grinder capable of offering performances that cannot be obtained with traditional coffee grinders.

All these aims and others that will result from the following description can be jointly or separately achieved according to the invention with an electric coffee grinder, as defined in claim <NUM>.

The present invention is further clarified below in some of its preferred practical embodiments described for purely illustrative and non-limiting purposes with reference to the attached drawings in which:.

As can be seen from the figures, the coffee grinder according to the invention is externally similar to a traditional coffee grinder and comprises a base <NUM> which houses the motorization of the grinding apparatus inside it and which supports a container <NUM> of the coffee beans to be ground and a conveyor of the coffee powder obtained.

Furthermore, the illustrated coffee grinder uses a pair of so-called conical grinders, comprising in particular a mobile grinder <NUM> with the active part significantly conical, cooperating with a fixed grinder <NUM> with an essentially complementary shape, however, the present invention is also applicable to pairs of so-called "flat" millstones, i.e. comprising a mobile millstone provided with an active band in the shape of a flat or almost flat circular crown, cooperating with a fixed millstone, also provided with an active band at flat or almost flat circular crown shape.

With reference to <FIG> and <FIG>, the coffee grinder according to the invention comprises a grinding chamber <NUM> having an essentially cylindrical shape, open at the top and i.e. comprising a bottom <NUM> and a cylindrical side wall <NUM>, on which there is obtained, near the bottom, a through opening <NUM>, having an axis slightly inclined downwards and designed to connect the grinding chamber <NUM> with an external chute <NUM> for the evacuation of the coffee powder as it is produced.

Inside the grinding chamber <NUM> are housed the mobile grinder <NUM>, a fixed grinder <NUM> and an impeller <NUM>.

The mobile grinder <NUM> has a traditional overall conical shape, although the invention could also find application in coffee grinders with fixed flat-type grinders, as defined above.

The fixed grinder <NUM> has a shape which in the lower part is substantially complementary to the lower part of the mobile grinder <NUM> and with the latter delimits the grinding slot in a traditional manner.

In the upper part, the mobile grinder <NUM> and the fixed grinder <NUM> delimit between them a circumferential groove <NUM> with a flared profile for collecting the coffee beans to be ground coming by gravity from an overlying feeding container, not shown as it is traditional in itself.

The fixed grinder <NUM> is connected with its non-active part to the grinding chamber <NUM> in a traditional way, which does not require further explanation.

The impeller <NUM> can advantageously include an annular element <NUM>, which in operation is positioned between the mobile grinder <NUM> and the bottom <NUM> of the grinding chamber <NUM>, and can also include a plurality of arms <NUM>, which extend from said annular element <NUM> and they develop vertically upwards in close proximity to the side wall <NUM> of the grinding chamber <NUM>.

The mobile grinder <NUM> is fixed, for example by means of a screw <NUM>, to the upper end of a vertical shaft <NUM>, which constitutes the extension of the shaft of a first electric motor <NUM> housed inside the base <NUM> of the coffee grinder.

The impeller <NUM> is fixed, for example, by means of screws <NUM>, to the upper end of a tubular shaft <NUM>, which is externally coaxial to the shaft <NUM> and constitutes the extension of the shaft of a second electric motor <NUM>, also housed inside the base of the coffee grinder in a position above the first electric motor <NUM>.

Therefore, the shaft <NUM> of the first electric motor <NUM> runs for its entire extension inside the tubular shaft <NUM> of the second electric motor <NUM> and is kept axially centered with respect to this by a rolling bearing <NUM> placed between their upper ends, as well as naturally by traditional bearings <NUM> placed between the rotor and stator of each motor <NUM>,<NUM>.

The two motors <NUM>,<NUM> can be powered and controlled independently of each other and therefore can rotate the mobile mill <NUM> and the impeller <NUM> at the appropriate speeds.

This allows the mobile grinder <NUM> to be rotated at the most suitable speed for optimal grinding of the coffee beans, a speed which advantageously is between <NUM> and <NUM>,<NUM> revolutions per minute and is preferably equal to <NUM> - <NUM> revolutions per minute, as the more suitable for obtaining effective grinding without overheating the coffee powder and therefore without causing an unwanted dispersion of its aromas. At the same time, the independent control of the two electric motors <NUM>,<NUM> not only allows the impeller to rotate at the most suitable speed to give the coffee powder the centrifugal force necessary to make it come out of the opening <NUM> (speed generally between <NUM> and <NUM>,<NUM> revolutions per minute) but also to continue to rotate the impeller <NUM> even after the mobile grinder <NUM> has finished grinding the coffee beans, and to thus ensure the complete evacuation of the coffee powder from the grinding chamber <NUM>.

Advantageously, both electric motors <NUM>,<NUM> can be made up of torque motors.

The embodiment illustrated in <FIG> and <FIG> differs from the previous embodiment in that, although it provides a differentiation between the rotation speeds of the mobile grinder <NUM> and the rotation speed of the impeller <NUM>, it achieves this differentiation by using a single electric motor <NUM>, which also in this case can advantageously consist of a torque motor.

The shaft <NUM> of the electric motor <NUM> is hollow and has the impeller <NUM> applied to the upper end, while a kinematic mechanism <NUM>, preferably with toothed belts, is applied to the lower end, through which actuates in rotation at a lower speed, linked to the ratio of predefined reduction, a shaft <NUM>, running coaxially inside the shaft <NUM> and having the mobile grinder <NUM> applied to the upper end.

More particularly, a first toothed wheel <NUM>, of small diameter, is integral with the shaft <NUM> of the electric motor <NUM>, to which a second toothed wheel <NUM> of larger diameter is coupled, via a first toothed belt <NUM>. This second toothed wheel <NUM> is integral with a small shaft <NUM>, which is supported by the base of the coffee grinder so that it can rotate around its own axis and which carries integrally a third toothed wheel <NUM>, of small diameter, to which it is coupled, via a second toothed belt <NUM>, a fourth toothed wheel <NUM> of larger diameter, in turn integral with the shaft <NUM>.

In this way, with a single electric motor <NUM> it is possible to obtain differentiated speeds of the mobile grinder <NUM> and of the impeller <NUM>, so that each of these can rotate at the most suitable speed for the function to be performed.

This second embodiment is more advantageous than the previous one in terms of simplicity and cost-effectiveness of production, since it uses only one electric motor <NUM>, but at the same time it is more disadvantageous from a performance point of view, both because it does not allow to control independently the rotation speeds of the mobile grinder <NUM> and of the impeller <NUM>, both because it does not allow the impeller <NUM> to be kept rotating after the grinding of the coffee beans has ceased and therefore does not ensure the complete evacuation of the coffee powder produced. The invention also envisages a variant of this second embodiment (not shown in the drawings), with the electric motor <NUM> coupled directly to the mobile grinder <NUM> and indirectly coupled, via a speed amplifier kinematic mechanism, to the impeller <NUM>.

Claim 1:
Electric coffee grinder with a fixed grinder (<NUM>) and a mobile grinder (<NUM>) arranged inside a grinding chamber (<NUM>), which has an essentially cylindrical shape and is provided with at least one inlet opening for the intended coffee beans to be ground between the two grinders (<NUM>,<NUM>) and with an impeller (<NUM>) arranged inside said grinding chamber (<NUM>) in a position underneath said mobile grinder (<NUM>) and provided with arms (<NUM>) configured to cause the leakage of coffee powder, which is obtained by grinding said beans, through at least one outlet opening (<NUM>) foreseen in the side wall (<NUM>) of said grinding chamber (<NUM>), characterized in that said mobile grinder (<NUM>) and said impeller (<NUM>) are coaxial and are connected to means (<NUM>,<NUM>,<NUM>) for their rotation at different speeds.