GRINDER AND COFFEE MACHINE HAVING SUCH A GRINDER

A grinder for grinding coffee beans having a first grinding tool and a second grinding tool forming a grinding nip, and the second grinding tool being rotatable relative to the first grinding tool. The grinder has at least one force generation device for applying a selectable force F to a first grinding tool or a second grinding tool, which force can be transmitted to the coffee beans. A coffee machine having such a grinder and a method for preparing coffee using said type of coffee machine and said type of grinder.

The invention relates to a grinder for grinding coffee beans according to the preamble of claim1and to a coffee machine, in particular a fully automatic coffee machine, having such a grinder.

The right fineness of the coffee powder is a prerequisite for successful coffee preparation. It determines the speed with which the water can flow through the coffee powder and the period of time in which aromas and flavors can be extracted from the coffee powder. This time is called extraction time and is a quality criterion for the appropriate extraction of the flavors and aromas of the respective coffee beverage.

In addition to contact pressure, water temperature, water quality and bean properties, the extraction intensity of a coffee beverage is significantly influenced by the degree of grinding of the coffee grounds. The degree of grinding describes the fineness with which the bean is ground. The grinding process of coffee beans produces a fineness distribution, i.e. not all coffee particles have the identical size, but are subject to a grain size distribution typical for coffee.

The finer the grind, the greater the total particle surface area and consequently the contact time of the water with the coffee powder.

The degree of grinding of the coffee powder can usually be adjusted in coffee machines with grinders. High-quality machines even allow infinitely variable adjustment of the grinder and compensate for undesirable boundary conditions (e.g. thermal expansion, grinding disc wear, etc.) by readjusting the grinder components. Some systems use the extraction time of the coffee beverage as an indirect characteristic to check the appropriate grinder setting.

For the preparation of a high-quality coffee beverage, the appropriate and product-related setting of the grinding degree plays an overriding role.

In the prior art, there are essentially two proven types of coffee grinders that are used in coffee machines. One is a disc grinder and the other is a cone grinder. Both types of grinders have in common that they consist of two grinding tools, wherein one of these tools is fixed and the other is driven. The rotational movement of one of the grinding tools draws the beans into a grinding gap and grinds them finer and finer as the grinding gap narrows. The smallest distance between the two grinding tools is decisive for the degree of grinding produced in the coffee powder. To change the degree of grinding, the fixed tool can be adjusted relative to the rotating tool so that the distance is varied. These systems are geometry-based methods for changing the degree of grinding.

Thus, according to the technical teaching of EP 2 286 699 B1, it is provided that the grinder for a coffee machine comprises a first grinding disc which can be driven about an axis of rotation by a drive means and comprises a second grinding disc. The second grinding disc is fixed in a screw-in part which can be screwed into a housing and can be rotated with respect to the housing by adjusting means. This allows a grinding gap between the two grinding discs to be adjusted. The adjusting means are formed by a drive wheel arranged coaxially with respect to the screw-in part, which drive wheel cooperates with an adjusting wheel rotatable via adjusting means. The grinder further comprises a feed opening for feeding the coffee beans to be ground and a discharge opening for discharging the coffee ground between the two grinding discs. The grinder has a central adjustment facility for adjusting the grinding gap, which operates in an infinitely variable manner.

An existing problem of these grinding systems is the determination of a zero point at which a minimum fineness can be defined. Only if this is successful can a grinding degree suitable for the product be set directly and precisely in relation to this zero point. The prerequisite for this is particularly high manufacturing accuracy in the overall design of the grinder (e.g. high axial run-out accuracy in the disc grinder).

Furthermore, in conventional coffee grinders, disturbing influences such as thermal expansion of the grinder components, grinding disc wear, bean changes, etc. can only be compensated for indirectly (e.g. by evaluating the extraction time). Heat influences in particular lead to varying degrees of grinding and different swelling behavior of the coffee powder in the brewing unit and are thus the main cause of fluctuating extraction times.

As a result, long adjustment cycles are often required in order to adjust the grinder of a coffee machine ideally to the desired product and taste profile. Furthermore, the degree of grinding can usually only be set for and regulated to a specific product.

In the patent specification EP1493368B1 a further possibility of the admission is described. The grinding discs are screwed into the respective carrier by means of a bayonet catch. For this purpose, there are elongated interrupted projections on the circumference of the discs, which are inserted into the carrier slot by means of a plug-in rotary movement. Since the grinder is only ever operated in one direction of rotation, the disc and carrier are locked against rotation and the discs are also locked in the axial degree of freedom.

The invention has the object of further developing a generic grinder in a functionally advantageous manner.

The invention solves this problem by a grinder having the features of claim1, a coffee machine of claim26and the method having the feature of claim27.

A grinder according to the invention is used for grinding coffee beans. It can be used as a stand-alone device or integrated in a coffee machine, for example a fully automatic coffee machine.

The grinder has two grinding disc carriers, each with a grinding tool, a drive unit and at least one force-generating device. The at least one force-generating device for applying an adjustable force F to a first grinding tool or a second grinding tool, which is transmitted to the coffee beans, wherein the force F is directed in such a way that it presses the respective grinding tool to which the force F is applied in the direction of the respective other grinding tool, is designed with an adjusting device for the force F.

The grinder includes a first grinding tool and a second grinding tool.

The grinding tools form a grinding gap or delimit such a grinding gap from opposite sides. This gap can be flat or can increase towards the center.

The second grinding tool is thereby rotatable relative to the first grinding tool, in particular rotatably driven by a drive unit such as a drive motor.

The force-generating device adds a further adjustable force to the dead weight of the grinding tools, which is applied by the force-generating device. The force F is directed in such a way that it presses the respective grinding tool to which the force F is applied, in particular axially in the direction of the respective other grinding tool. The force-generating device thus presses the two grinding tools together and not—as known from the prior art—away from each other.

The application of force virtually replaces the support of the grinding tool on an abutment—with an adjustable force, a product-specific optimum degree of grinding can be achieved which remains largely constant even under changed process conditions.

Advantageously, it may be provided that by applying force with a process force of the force-generating device adjustable by means of the adjusting device, a product-specific degree of grinding can be repeatedly adjusted. In this respect, it can also be provided that when the type of coffee or the product type (e.g. from espresso to cafe cream) is changed when the product is drawn from a fully automatic coffee machine in which the grinder is integrated, a product-specific setting or adjustment of the degree of grinding is automatically carried out. This setting of the degree of grinding can be carried out extraordinarily quickly with the invention, for example in order to change from a setting of the degree of grinding for an espresso to a setting of the degree of grinding for a cafe creme. Since the setting or changeover is very fast, it may even be possible to dispense with a second grinder in a fully automatic coffee machine.

Accordingly, the invention according to claim26creates an advantageous method for preparing a coffee with a coffee machine, in particular with a fully automatic coffee machine, and with a grinder according to one of the preceding claims relating thereto, in which coffee beans are ground with the grinder and in which a coffee of a certain type is prepared from the coffee beans and water in a brewing unit. Depending on the type of coffee, a setting or adjustment of the degree of grinding is automatically carried out by means of the adjusting device prior to grinding when the type of coffee is changed (depending on the amount of water and the amount of ground coffee and possibly depending on additives such as milk), e.g. when changing from an espresso to a cafe creme.

During operation of the grinder, one of the two grinding tools can be stationary and the second of the two grinding tools can be rotated by a drive unit, for example a drive motor. However, both grinding tools can also rotate, in particular in opposite directions to each other.

The force-generating device can act on both the first and the second grinding tool, so that a more even distribution of force occurs. However, it is constructively simpler if the force-generating device only acts on one grinding tool, in particular the stationary one of the two grinding tools.

Further, a respective force-generating device may also act on the first grinding tool and the second grinding tool.

In one embodiment, the adjusting device comprises an adjusting ring having a ramp and an adjusting element, wherein the ramp is in engagement with the first grinding disc carrier. This results in an advantageously simple and compact structure.

In this respect, it is of space-saving advantage if the first grinding disc carrier comprises the first grinding tool, a filling hopper, and a carrier, wherein the carrier is in engagement with the ramp of the adjusting ring, and wherein the first grinding tool is arranged with an axial degree of freedom and is connected to the filling hopper via at least one spring, in particular a compression spring.

In a further embodiment, the at least one spring exerts an axial force on the first grinding tool, wherein a pretensioning force of the at least one spring is adjustable by means of the adjusting ring of the adjusting device. The spring is a low cost, high quality component and may be formed in many different embodiments.

It should be noted that it is not primarily important which of the grinding tools (also referred to as “cutting tools” in the following)—driven or stationary grinding tool—has a degree of freedom in the direction of the process force and is actively subjected to a force in this direction. The force adjustment can be automatic (e.g. drive motor) or manual (e.g. adjusting wheel). In the case of drive-motor adjustment, a control loop is conceivable, wherein the degree of grinding is changed if the last extraction times deviate from the set run-out time.

The constructive implementation of a force control can be realized in different ways. One possibility is to compress the mechanical spring by a certain distance x with a known force-distance characteristic.

For an advantageously simple adjustment, the adjusting ring is rotatably mounted on a grinding housing of the grinder.

A further embodiment provides that the adjusting ring surrounds a receiving section of the grinding housing and is rotatably guided on a circumferential collar of the grinding housing, wherein the first grinding disc carrier is arranged in the receiving section of the grinding housing. In this way, an advantageously space-saving structure can be made possible.

In a still further embodiment, the adjusting ring is provided with an external toothing with which the adjusting element engages.

It is also advantageous if the force-generating device comprises at least the one spring and the adjusting device for adjusting a pretensioning force of the spring, in particular in the form of a servomotor. This variant is structurally particularly easy to implement and it is readily controllable and/or adjustable.

However, there are also other solutions for applying a defined force to one of the cutting tools. First of all, a pneumatic approach is conceivable here, wherein one grinding disc carrier can be actively pressed against the other with variable air pressure. A passive variant would be a gas pressure spring with a fixed force-displacement characteristic, in which case only a specific degree of grinding would be adjustable in the grinder. However, springs are also available with variable gas pressure. Alternatively, however, it can also be provided that the force-generating direction is based on a fluid operating principle. Since the distance between the grinding tools or cutting tools in the disc grinder only has to change slightly by up to 0.2 mm as a function of the process force during grinding, hydraulic solutions with fluids of higher compression modules are also possible for controlling the force. Even then, a damping effect would be present in the system during grinding. For example, a rubber diaphragm can be used to apply force, which is filled with water via an adjustable pressure reducer. A hydraulic water system is already present in coffee machines and could be used to regulate the degree of grinding.

Furthermore, the force-generating device can also advantageously be based on an electromagnetic principle. In this solution, the movable cutting tool carrier is pressed against the fixed one due to a variable magnetic force. Since the magnetic force changes with increasing distance between the armature and the yoke, a balance of forces can also be established in an electromagnetic system during the grinding process between the cutting tools.

Thus, in another embodiment, the force-generating device can be based on a pneumatic operating principle, on a fluid operating principle or/and on an electromagnetic operating principle.

In another embodiment, the adjusting device is independent of an operating or resting state of the grinder. In this way, the adjusting device can be actuated both in the operating state of the grinder, i.e. when it is being driven to grind coffee beans, and in the idle state of the grinder, i.e. when it is stationary.

The grinder can be designed as a disc or roller or cone grinder. The adjusting device thus has an advantageously wide range of application.

In one embodiment, during operation of the grinder, one of the two grinding tools is stationary and the second of the two grinding tools is rotatably operated by the drive unit, in particular by a drive motor. This results in an advantageous structure.

The force-generating device may comprise a device for adjusting a pretensioning force of the spring, in particular the compression spring, in particular in the form of a servomotor. This servomotor is preferably an actuator which is controlled and/or regulated by a control and/or evaluation unit.

The setting of the servomotor can be adjusted depending ona) the coffee beans, in particular the type of bean and its degree of roasting,b) the temperature of the grinder and/orc) a degree of wear of the grinder.

For example, the type of coffee beans can be specified by manual setting or determined on the basis of the power of the drive motor for driving the grinding tool or tools. In this case, the determined power is compared within the scope of an actual/setpoint value comparison with a data record stored on the control and/or evaluation unit with regard to the power as a function of the force to be applied to achieve a specific degree of grinding or with regard to a bean type as a function of the force to be applied to achieve a specific degree of grinding.

It is advantageous if the first grinding tool and the second grinding tool are coupled to a respective grinding tool carrier via latching lugs on a circumference of the respective grinding tool, since in this way a simple assembly and also a quick change are possible. At the same time, the latching lugs enable a torque transmission to the respective grinding tool.

In a still further embodiment, it is provided that the drive unit comprises a drive shaft, a gear housing and a drive motor, wherein the drive shaft is coupled to the second grinding disc carrier for driving the second grinding tool, is in engagement with the drive motor indirectly via a gear or directly, and is rotatably mounted in the gear housing. This results in an advantageously compact structure.

The drive shaft may be engaged with the drive motor via a worm gear, wherein the drive shaft is connected to a worm wheel of the worm gear, and wherein the drive shaft is engaged with the second grinding tool via a carrier section.

Such a multifunctional design of the drive shaft with the carrier section results in several advantages: Firstly, fewer joining operations are required for the assembly of the grinder. The reduced number of components also results in a particularly cost-effective and compact design. Finally, in addition to the very good axial run-out properties of the carrier section, a large upper bearing automatically provides a seal between the greased gear area and the grinding housing, which is mounted above the upper bearing on a flange of the gear housing.

In one embodiment, the drive shaft is integrally formed with the worm wheel and the carrier section.

In an alternative embodiment, the drive shaft may be formed in two parts, wherein a first part of the drive shaft comprises the carrier section, and wherein a second part of the drive shaft comprises a worm wheel. This allows for a very compact and space-saving structure.

Another embodiment provides that the gear housing is connected to a grinding housing of the grinder, wherein different positions of an ejection section of the grinding housing are fixed relative to a position of the drive motor of the gear housing. An advantage of this is that it is easy to adapt the grinder to different coffee machines.

In order to nest several grinders as compactly as possible in coffee machines, it is advantageous that the ejection position on the circumference can be varied in several positions. For this purpose, in one embodiment the different positions of the ejection section of the grinding housing are defined as different angular positions relative to a grinder axis by depressions or recesses formed in a flange of the gear housing, which are in engagement with respective cams or pins of the grinding housing.

A still further embodiment provides that the grinder comprises a grinding degree indicator with an indicator. An advantage of this is that a specific grinding degree can always be set in a repeatable manner.

In this regard, it is advantageous if the grinding degree indicator interacts with the adjusting device and indicates a grinding degree of the grinder by means of an indicator.

In one embodiment, the grinding degree indicator may interact with an external toothing of an adjusting ring of the adjusting device to advantageously indicate the direct position of the adjusting ring corresponding to a particular degree of grinding.

In another advantageous embodiment, the grinding degree indicator may comprise an adjusting drive and may adjust the adjusting ring of the adjusting device to adjust a degree of grinding and simultaneously indicate the adjusted degree of grinding.

During the grinding process, a force is generated by the cutting of the beans, with which the cutting tools (grinding discs) are pressed apart. The stronger the force applied by the process force or counteracting force-generating device, the finer the degree of grinding. If there are no more beans, the disc-like grinding tools are braced against each other with the contact force. Since the grinding tools are usually designed in such a way that they cannot get caught in each other, consequently the grinder cannot fail.

However, in the event of a malfunction of an empty bean hopper, grinding noises and damage to the face surface of the grinding discs could occur. In addition, there may be undesirable heat effects that can have a negative impact on the quality of the coffee grinding. In the case of cone grinders, this could even lead to blockage of the cutting tools. To solve this problem, it can be advantageously provided that the grinder comprises a stop, in particular an adjustable stop, for setting a minimum degree of grinding.

In this respect, it can be provided in particular that the axially movable tool part or the corresponding grinding tool is pressed against a stop. This end stop can be set before the grinder is put into operation and at the same time defines the minimum degree of grinding to be produced. When force is applied, ideally there should only be a minimum gap between the cutting tools. If a greater contact force is later specified than the process force during the grinding process, a ground product with the fineness of this grinding disc gap is produced.

For this purpose, it is provided in a further embodiment that the grinding degree indicator comprises at least one stop which defines a minimum or/and maximum degree of grinding to be produced.

In practice, the touching point (beginning of audible grinding noises) of grinding disc grinders is an indicator for the zero point of the grinder. However, this is strongly dependent on the axial run-out of the grinding discs and the individual hearing sensation of the fitter of the grinder.

Further advantageous designs are disclosed in the remaining subclaims.

InFIG. 1, a schematic front view in section of a first exemplary embodiment of a grinder1according to the invention for grinding coffee beans5is shown. The grinder1has a grinder axis1a, a first grinding disc carrier M1with a first grinding tool2, a second grinding disc carrier M2with a second grinding tool8and a drive unit AE. The grinding tools1,2are formed here as so-called grinding discs. The first grinding tool2is mounted in a rotationally fixed manner in a housing not shown inFIG. 1, which will be described further below. In this respect, the first grinding tool2is stationary during operation of the grinding unit1.

The first grinding tool2has a cylindrical envelope geometry and a centric aperture3. The grinding tool2can also be designed differently, for example as a grinding cone. The aperture3is penetrated here by a feed hopper4. Coffee beans5to be ground are fed to the grinder1through the feed hopper4and the aperture3. The grinder1may also be provided for grinding other luxury foods or foodstuffs, but preferably it is provided for grinding coffee beans5. The feed hopper4is advantageously designed in such a way that undesirable bridging of the coffee beans5in the feed hopper4is prevented.

The first grinding tool2has a conical depression6on its side facing away from the feed hopper4. The depression6has at least one grinding edge7.

The second grinding tool8of the second grinding disc carrier M2is arranged coaxially to the grinding axis1aand to the first grinding tool2, and below the first grinding tool2. The term “below” refers to the drawing plane ofFIG. 1. The second grinding tool8is rotatably mounted in a housing not shown here, which will be described in more detail below. In this respect, the second grinding tool8rotates during operation of the grinder1.

The second grinding tool8also has a cylindrical envelope geometry. The second grinding tool8can also be designed differently, for example as a grinding cone. The second grinding tool is rotatable relative to the first grinding tool2about the grinding axis1a. Here, the second grinding tool8is connected to a drive shaft9of a drive motor10of the drive unit AE in a rotationally fixed manner, so that the second grinding tool8is set into a rotational movement during operation of the grinder1while the first grinding tool2is stationary.

This is advantageous, but not mandatory. Alternatively, the first grinding tool2can be rotatable while the second grinding tool8is stationary. It is also possible that both grinding tools2,8are rotatable—for example in opposite directions of rotation and/or at different speeds, so that there is always a relative movement between both grinding tools2,8.

The drive shaft9is shown here only symbolically and will be described in detail later.

Alternatively, a shaftless direct drive is also possible, in which one of the grinding tools2,8is the rotor of the drive motor10, or an indirect drive, in which the drive motor10acts on one of the grinding tools2,8via a gear.

The second grinding tool8has a conical depression11on its side facing away from the drive motor10. The depression11has at least one grinding edge12.

The conical depression6of the first grinding tool2and the conical depression11of the second grinding tool8thus form a kind of double conical grinding chamber13, which opens at its outer circumference into a grinding gap14. A collecting device (not shown here) can be connected to the grinding gap14, which collects the coffee beans—preferably coffee powder—emerging from the grinding gap14and feeds them to an extraction process.

The grinding tools2,8form the grinding gap14or delimit this grinding gap14from opposite sides. This grinding gap14may be flat or may increase towards the center. It preferably defines a plane E, preferably a symmetry plane. The grinding gap14extends over the plane E.

The grinder1further comprises at least one force-generating device15. The force-generating device15acts here on the first grinding tool2, thereby causing a respective force F to act continuously on coffee beans located between the first grinding tool2and the second grinding tool8. This is advantageous, but not mandatory. The force-generating device15can also act on the second rotatable grinding tool8or on both grinding tools2,8.

Here, the force-generating device15comprises two compression springs16which can be pretensioned by a corresponding device17, for example by a servomotor, by a variable pretensioning distance X, so that the respective force F acting on the first grinding disc2and thus on the coffee beans is variable or adjustable in its amount.

The compression springs16exert an axial force perpendicular to the plane E on the first and/or second grinding tools2,8which can be adjusted or varied in this way.

The force-generating device15can also be designed differently than shown inFIG. 1. The force effect is essential here, wherein the amount of the force F is preferably variable or adjustable. In this case, the force-generating device15can also be designed in such a way that the amount of the force F is regulated automatically and/or continuously as a function of higher-level operating parameters of a coffee machine. The force-generating device15is explained in detail below by means of an exemplary embodiment.

This makes it advantageously possible to carry out a defined presetting of a specific degree of grinding, since the force F correlates with the respective degree of grinding—i.e. the size distribution of the ground coffee particles, characterized by the particle size of a 50% median—of the ground coffee, which, however, will not be further discussed here.

Furthermore, the force acting on the coffee beans by the grinder1can advantageously be adjusted by the force-generating device15depending on the coffee beans5to be ground and the respective desired degree of grinding. Preferably, for this purpose, data records relating to the respective degree of grinding, the type of bean and the force to be generated by the force-generating device15are stored on a data memory of a control and/or evaluation unit18for controlling a coffee machine and, in particular, the grinder1. The aforementioned control and/or evaluation unit18can be associated with the grinder1or be part of a coffee machine, for example a fully automatic coffee machine.

An adjustment of the degree of grinding C can therefore be regulated in a bean-specific manner (e.g. hard/strongly roasted beans vs. less strongly roasted café crème beans). Alternatively, it is possible to adjust the degree of grinding to a specific type of bean by determining the difference in grinding performance at constant force and then using this difference as a factor for the force adjustment.

Furthermore, the force-controlled adjustment of the respective degree of grinding enables a permanent reproducibility of the degree of grinding even in case of grinding tool wear. For this purpose, a characteristic curve for wear over time can be stored depending on the type of bean. The number of grinding processes can be weighted differently depending on the type of bean used. Thus, after, for example, 100 grinding operations of a “hard” bean type, a readjustment can be carried out by the device17.

Likewise, the force-controlled adjustment of the respective degree of grinding can advantageously compensate for thermal expansion effects, in particular of the grinding tools2,8. For this purpose, a temperature sensor (not shown) can detect the heat of the coffee beans as they leave the grinder1and, taking into account the coefficients of thermal expansion of the material of the grinding tools2,8, adjust the force of the force-generating device15, in particular the pretensioning force of the compression springs16, accordingly.

FIG. 2shows a schematic exploded view of a second exemplary embodiment of a grinder1according to the invention.

The first grinding disc carrier M1includes the first grinding tool2, the feed hopper4, and a carrier23having lugs23adistributed on its outer periphery. The first grinding disc carrier M1is also called the upper grinding disc carrier M1and is described in further detail below.

The force-generating device15has three compression springs16(seeFIG. 5) arranged in the first grinding disc carrier M1, which will be explained below.

The adjusting device17comprises an adjusting ring26and an adjusting element27. The adjusting device17is attached to a grinding housing25and interacts with the first grinding disc carrier M1. This will be explained in more detail below.

The grinding housing25comprises a bottom section25aand a receiving section25b, which are arranged one above the other and connected to each other. Surrounding this connection is a circumferential, radially outwardly projecting collar25c.

The grinding housing25is arranged coaxially to the grinder axis1aand receives the first grinding disc carrier M1in the receiving section25b. Here, the lugs23aof the carrier23engage with axially extending openings25din the wall of the receiving section25bof the grinding housing25.

The adjusting ring26of the adjusting device17is provided with an external toothing26b, surrounds the receiving section25bof the grinding housing25and is rotatably guided with its lower side on the circumferential collar25cof the grinding housing25.

The adjusting element27has an annular section27ato which tooth sections27bare integrally formed in a regularly distributed manner on its inner diameter. The tooth sections27bare formed as internal teeth corresponding to the external toothing26b.

The adjusting element27is arranged around the external toothing26bof the adjusting ring26in such a way that the tooth sections27bare in engagement with the external toothing26b, and that the underside of the adjusting element27rests rotatably on the collar25cof the grinding housing25. Fastening elements19with washers19aare arranged in a regularly distributed manner around the circumference of the collar25cand form an axial fixing of the adjusting element27(see alsoFIG. 7).

By means of a radially outwardly projecting actuating section27c, for example in the form of a lever, the adjusting element27and thus the adjusting ring26in engagement therewith can be rotated about the grinder axis1a. With this rotation, the adjusting device17adjusts the force-generating device15to adjust the force F. This will be further discussed below.

The bottom section25aof the grinding housing25includes an ejection section25ewhich is open radially outwardly. The bottom section25afurther accommodates the second grinding tool8.

The second grinding disc carrier M2is also referred to as the lower grinding disc carrier M2, and thus comprises the second grinding tool8and the bottom section25aof the grinding housing25.

The second grinding tool8is mounted on a carrier section9aof the drive shaft9, and is in a rotationally fixed connection therewith via projections8a. This will be described in more detail below.

The drive shaft9is disposed in an interior20bof a gear housing20of the drive unit AE. In this example, the drive motor10having a drive motor shaft10ais attached to the gear housing20via a screw-on flange20aof the gear housing20.

The grinding housing25is mounted on a flange20eof the gear housing20, here facing upwards towards the grinding disc carriers M2, M1, by means of fastening elements29, for example screws. In this case, the bottom section25asurrounds the second grinding tool8. The grinding housing25can be mounted on the flange20eof the gear housing20in different angular positions relative to the grinding tool axis1a. These angular positions are defined by recesses20fformed in the flange20e, which are in engagement with respective cams28(seeFIG. 17). This will be further explained in connection withFIGS. 17 to 19.

FIG. 3shows a schematic exploded view of the drive unit AE of the grinder1. In addition,FIG. 4shows a schematic sectional view of drive unit AE of the exemplary embodiment according toFIGS. 2-3.

In this exemplary embodiment, the drive unit AE comprises a worm gear between the drive shaft9and the drive motor10.

The drive shaft9comprises the carrier section9a, a body9b, a toothing9cand a bearing journal9d.

The drive shaft9is a hollow cylinder of circular cross-section forming the body9b, which is here closed at its upper end by the carrier section9a.

The carrier section9ais of plate-shaped design and is provided on its upper surface, which faces the grinding housing25, with a driver and ejector geometry of the grinder1. On the outer periphery of the carrier section9a, tab-like projections are arranged in a regularly distributed manner and protrude from the carrier section9a.

Thereunder, the carrier section9ais provided with a circumferential wall in which a bearing seat9eis formed. An outer diameter of this bearing seat9eis larger than the outer diameter of the body9b.

A toothing9cis formed on the lower free end of the body9bof the drive shaft9, which forms a worm wheel of the worm gear and engages with a toothing10bof the drive motor10formed as a worm.

A bearing journal9dis centrally disposed within the hollow-cylindrical body9band has one end integrally formed on the inner surface of the grinding carrier section9a. The other, free end of the bearing journal9dprotrudes beyond the lower edge of the body9b.

In this way, the drive shaft9with the lower carrier section9ais formed so as to simultaneously perform the function of the worm wheel of the worm gear.

For optimal accommodation of the drive shaft9in the gear housing20, the drive shaft9is rotatably supported about the grinder axis1aby an upper bearing21and a lower bearing22in the gear housing20. The bearings21,22are, for example, sealed or covered bearings.

The inner ring of the upper bearing21shown inFIG. 4is used up on the bearing seat9eof the drive shaft9, and is of such a size that the worm wheel with the toothing9con the body9bof the drive shaft9can be inserted through this upper bearing21for assembly. The outer ring of the upper bearing21is inserted into a bearing seat20cof the gear housing20. This bearing position with the upper bearing21substantially takes over the axial process forces during the grinding operation.

For radial guidance of the drive shaft9and the worm wheel with the toothing9cat the lower end of the body9b, the free end of the bearing journal9dforms a bearing seat for the inner ring of the lower bearing22, for example a radial deep groove ball bearing. The outer ring of the lower bearing22is accommodated in a bearing seat20dof the gear housing20.

It is also conceivable to design the gear between the drive shaft, which is designed as a multi-functional part, as a belt gear or spur gear, if a belt or spur gear is desired in the grinder1.

The multifunctional design of the drive shaft9with the carrier section9aresults in several advantages: Firstly, fewer joining operations are required for the assembly of the grinder1. Furthermore, the reduced number of components results in a particularly cost-effective and compact structure. Finally, in addition to the very good axial run-out properties of the carrier section9a, the large upper bearing21automatically provides a seal between the greased gear area (in the interior20bof the gear housing20) and the grinding housing25, which is fixed above the upper bearing21on the flange20eof the gear housing20as described above.

FIG. 5shows a schematic exploded view of the first grinding disc carrier M1of the second exemplary embodiment according toFIGS. 2-3.FIG. 6shows a schematic sectional view of the first grinding disc carrier M1.FIG. 7shows a schematic exploded view of the adjusting device17.FIG. 8shows a schematic top view of the grinding housing25.FIG. 9shows a schematic sectional view of the grinding housing25, adjusting ring26and adjusting element27.FIG. 10shows a schematic sectional view of the adjusting ring26.

The upper or first grinding disc carrier M1comprises the first grinding tool2, which is spring-loaded with compression springs16, is guided in the carrier23and is braced with three fastening elements24, for example screws, and the feed hopper4.

The first grinding tool2has one axial degree of freedom.

Here, the compression springs16form the force-generating device15and are guided on the feed hopper4at projections4bfacing the first grinding tool2with one end in each case and are each accommodated with their other end in receptacles2bof the first grinding tool2.

The compression springs16are arranged symmetrically about the grinder axis1ain order to achieve an optimally distributed application of force. More than the three compression springs16shown can also be provided.

A helical spring is preferred as the compression spring16for the present application. However, springs or spring assemblies of other types can also be used.

The pretension of the compression springs16advantageously corresponds to the value which leads to a desired maximum degree of grinding (for example for filter coffee). The further pretension of the compression springs16is generated by rotating the adjusting ring26of the adjusting device17about the grinder axis1a.

The adjusting ring26has a hollow-cylindrical wall26a, which is provided on the outside with the external toothing26b. A ramp26cis formed on the inner side of the wall26a. This adjusting ring26is axially fixed to the grinding housing25and can be rotated about the grinder axis1aby means of the adjusting element27. The rotational movement of the adjusting ring26moves the entire first or upper grinding disc carrier M1axially in the direction of the grinder axis1ain such a way that the compression springs16are further braced and the first grinding tool2is even more strongly sprung, depending on the angle of rotation, because the upper grinding disc carrier M1is guided via three screw heads of the fastening elements24in three grooves of the ramp26cin the adjusting ring26, each groove extending uniformly along the circumference of the inner wall of the adjusting ring26. The screw heads of the fastening elements24extend through the openings25dthrough the wall of the receiving section25bof the grinding housing25into the ramp26cof the surrounding adjusting ring26.

The system can be flexibly adapted to a wide variety of gradations of the degree of grinding via the spring rate of the compression springs16and the ramp gradient of the ramp26c.

Moreover, the adjusting ring26can be positioned in such a way that the entire upper grinding disc carrier M1can be removed from the grinder1. This is particularly advantageous with regard to cleaning and maintenance of the grinder1.

In particular, the upper grinding disc carrier M1can also be made in one piece. In this case, the two parts are pressed together directly via latching lugs2aattached to the first grinding tool2. The lugs prevent the first grinding tool2from falling out of the carrier23. Further joining processes, such as screw connections, can be omitted.

As a rule, grinding discs as grinding tools in disc-type grinders are fixed to the respective carriers by means of screw-on holes with screws. On the one hand, these holes reduce the cutting performance of the grinding disc. On the other hand, coffee grounds can deposit in these areas and are therefore not completely discharged from the grinder.

FIG. 11shows a schematic top view of a grinding disc as the second grinding tool8of the second exemplary embodiment according toFIGS. 2-3.FIG. 12shows a side view.FIG. 13shows a schematic top view of the drive shaft9of the second exemplary embodiment according toFIGS. 2-3, whereinFIG. 14shows a schematic sectional view of the drive shaft9.

A further possibility will be indicated in which the grinding tools2,8can be connected to the respective grinding disc carrier M1, M2without screw holes or threaded blind holes. InFIGS. 11 and 12, the second grinding tool8is shown as an example with three latching lugs8aas radial projections on the periphery of the second grinding tool8.

These latching lugs8aengage grooves9gin the lower grinding disc carrier M2in the carrier section9ain such a way that the necessary torques can be transmitted. The grooves9gare each formed here in a foot region of a lug-like projection9f, wherein each groove9gis fixed by lateral stops.

Since the grinding tools2,8push apart in the direction of the grinding axis1aduring the grinding process, no further axial securing of the second grinding tool8is required. Thus, the second grinding tool8is merely inserted into the carrier section9aof the drive shaft9, which is a very assembly- and maintenance-friendly solution.

FIG. 15shows a schematic plan view of a variation of the first grinding disc carrier M1according toFIGS. 5-6.FIG. 16shows a sectional view ofFIG. 15.

At the upper, first grinding disc carrier M1, it is suitable for a force-controlled grinding degree adjustment to guide the latching lugs2aof the first grinding tool2in grooves which, on the one hand, transmit the torque and, on the other hand, effect an axial degree of freedom against the adjustable spring pressure of the compression springs16.

In a system having a grinder1without force control, a second component is required that prevents the axial movement of the first grinding tool2. Here, the contour of the latching lugs2ain a steel grinding disc can either be milled or bores located on the periphery can be provided with pins. On a ceramic grinding disc, the latching lugs2aare advantageously taken into account directly in the tool.

FIG. 17shows a schematic top view of the underside of the grinding housing25of the second exemplary embodiment according toFIGS. 2-3.FIG. 18shows a schematic top view of the gear housing20, withFIG. 19showing a section through the gear housing20.

The grinding housing25has an ejection position with the ejection section25e. This ejection position is always arranged at a certain angle to the drive motor10in the case of an angular gear unit (seeFIG. 2). The position of the drive motor10is fixed to the gear housing20by the screw-on flange20a. In order to nest several grinders as compactly as possible in coffee machines, it is advantageous that the ejection position can be varied in several positions on the circumference.

In the exemplary construction shown, there is an interface between the grinding housing25and the gear housing20. The grinding housing25has three cams28(FIG. 17) on its underside, which engage in recesses20fon the flange20eof the gear housing20so as to transmit the necessary torques during the grinding process. These two parts, namely grinding housing25and gear housing20are bolted together with a flange solution. Via three elongated holes25fin the grinding housing (FIG. 17) and through-holes20g(FIGS. 18, 19) in the gear housing20, the gear housing20and the grinding housing25can be screwed together by means of fastening elements29(FIG. 2).

Fifteen recesses20fare provided on the circumference of the flange20eof the gear housing20, so that the ejection position of the ejection section25eof the grinding housing25to the drive motor can be mounted in fifteen different positions. Five positions each can be changed in a simple manner by loosening the flange screws (fastening elements29) and inserting the grinding housing25into the adjacent recesses. In order to mount the other ten positions, the fastening elements29must be completely unscrewed so that the two housing parts (gear housing20and grinding housing25) can be placed one elongated hole25ffurther.

If several positions of the grinder1are required in one machine or machine generation, there are great advantages with regard to maintenance and assembly because identical parts can be used. In many similar designs, the ejection position can only be changed to a limited extent or with increased effort.

FIG. 20shows a schematic perspective view of a variant of the gear of the second exemplary embodiment according toFIGS. 2-3.FIG. 21shows a schematic perspective exploded view of the variant of the gear according toFIG. 20.FIG. 22shows a schematic sectional view of the variant of the gear according toFIGS. 20-21.

The variant of the gear has a gear housing20which is substantially reduced in size relative to the gear of the second exemplary embodiment.

The interface between the grinding housing25and the gear housing20described above is not shown, but is readily imaginable.

The gear housing20of the variant has the screw-on flange20afor the drive motor10. In contrast to the gear of the second exemplary embodiment, the interior20band the bearing seats20cand20dare modified.

The interior20bhas a circumferential inner wall20hin which an opening for the worm10bof the drive motor10is formed. The interior20bis provided with a circular cross-section, the upper region of which is provided as the bearing seat20cfor the upper bearing21. The inner diameter of the inner wall20hcorresponds to the outer diameter of the outer ring of the upper bearing21.

The lower bearing22is seated with its inner ring on the other bearing seat20d. This bearing seat20dprotrudes from the bottom of the interior20binto the interior20bas a kind of cylindrical column. The outer diameter of the bearing seat20dcorresponds to the inner diameter of the inner ring of the lower bearing22.

In order to be able to use a larger worm wheel (toothing9c) with greater tooth strength (modulus) for the same grinding disc diameter, in this variant the drive shaft9with the carrier section9aand the toothing9cnow formed as the toothing30aof a worm wheel30from the second exemplary embodiment are designed in two parts.

The first part of the drive shaft9comprises the carrier section9ahaving the bearing seat9eand the body9b, wherein the second part of the drive shaft9comprises the worm wheel30having the toothing30aand a hub section30b.

The upper bearing21is pushed with its inner ring onto a partial section of the bearing seat9eof the carrier section9abelow the carrier section9a. In this case, the upper bearing21is completely covered by the carrier section9aarranged above it, wherein a circumferential collar of the carrier section9aprojects and engages with a circumferential web section of the bearing seat20cof the gear housing20projecting upwards in the axial direction in such a way that a kind of labyrinth seal31is formed. Sealing between the gear and the coffee dispensing area is effected via this labyrinth seal31.

The carrier section9ais rotationally fixedly connected to the worm wheel30by means of the body9b, which is here of bolt-shaped design (FIG. 22). For this purpose, the bolt-shaped body9bis in a rotationally fixed engagement with the hub section30bof the worm wheel30, for example, by means of a shaft-hub connection such as a positive connection in form of a serrated connection or splined shaft/splined hub connection or the like, whereby the assembly can be made compact and simple.

The maximum diameter of the tip circle diameter of the toothing30aof the worm wheel30is then limited by the outer diameter and no longer by the inner diameter of the upper bearing21. Advantageously, the carrier section9a, the worm wheel30with the toothing30aand the two rolling bearings21,22are then pre-assembled and assembled as an assembly with the gear housing20.

In the assembled state of the two parts of the drive shaft9, an upper section of the hub section30bof the worm wheel30forms another section of the bearing seat for the inner ring of the upper bearing21.

In this particular embodiment, the worm wheel30with the toothing30ais pressed onto the lower bearing22and rests with the upper bearing surface (not designated, but clearly visible inFIG. 22) on the inner ring of the upper bearing21. The upper bearing21can also be, for example, a needle roller and cage assembly. In this case, no further axial securing of the drive shaft9with the carrier section9aand worm wheel30is necessary, since the process force during the grinding process presses the carrier section9ain the direction of the axial upper rolling bearing21anyway. This enables simple assembly by means of a pressing process without the use of further standard parts.

FIG. 23shows a schematic exploded view of the second exemplary embodiment with the variant of the gear shown inFIGS. 20-22and with a grinding degree indicator32.FIG. 24shows an enlarged schematic perspective view of the grinding degree indicator32according toFIG. 23.

It is common to change the degree of grinding of a coffee grinder (here grinder1) by rotating the upper, i.e. the first grinding disc carrier M1, around the grinder axis1a. This is realized in a thread or a ramp. Often, a worm gear is located between an adjusting rim (adjusting ring26) of the first grinding tool2and an adjusting worm (not shown, but easily imaginable). The adjusting worm allows the adjusting ring26to be adjusted continuously, but without any indication as to the current position of the first grinding tool2in a vertical position with respect to the grinding axis1a, since the adjusting worm is rotated by more than 360°.

For this purpose, a grinding degree indicator32is provided in this exemplary embodiment. This grinding degree indicator32is given here only by way of example; it can of course also be designed in a different embodiment.

The grinding degree indicator32interacts here with the adjusting device15, in particular with the adjusting ring26of the adjusting device15, in such a way that an adjusting rotary movement of the adjusting ring26is transmitted to the grinding degree indicator32by means of a transmission element. The grinding degree indicator32converts this input variable of the transmission element into a linear displacement variable or/and an angular variable, which in each case corresponds to the set degree of grinding and is indicated in a suitable manner by an indicator36of the grinding degree indicator32.

Here, the grinding degree indicator32includes a holder33, a shaft element34, an indicator element35, and an indicator36.

The shaft element34is formed as the transmission element with a toothing34cas input and with a movement thread34das output.

The holder33has a holding plate33a, on the underside of which a respective fastening dome33band a respective downwardly projecting bearing wall33c,33dare attached at both ends. By means of the fastening domes33band associated fastening elements33e, for example screws, the holder33with the grinding degree indicator34is fastened to a holder section25g. The holder section25gis here a widening of the collar25cof the grinding housing25. For fastening the holder33, corresponding bores (e.g. with threads) for the fastening elements33eare formed in the holder section25g.

The bearing walls33cand33dare arranged parallel to each other and form a bearing for the shaft element34, which is thus rotatable about a shaft axis34aand is arranged axially secured in the holder33in a manner which is not shown but can be easily imagined.

The shaft element34has a shaft body34bprovided with the toothing34cbetween the bearing walls33c,33d. One end of the shaft body34bis supported in the bearing wall33c, which is arranged on the right here. The other end of the shaft has an end face34eand is connected to the shaft body34bvia the movement thread34d.

The movement thread34dinteracts with the indicator element35.

The indicator element35comprises a drive section35a, a scale carrier35bhaving an indicator scale36and a guide lug35c. The drive section35ais angled upwardly by 90° at one end of the scale carrier35bfacing the holder33, and carries on its lower surface the guide lug35cwhich projects downwardly by 90° with respect to the scale carrier35b. The movement thread34dof the shaft element34is screwed through the thread of the drive section35aand extends longitudinally of the shaft axis34aover the indicator scale36of the scale carrier35b. Here, the indicator scale36is applied to the scale carrier35bin an upwardly facing manner.

In the installed state, the grinding degree indicator32is fixed to the holder section25gby means of its holder33. In this regard, on the one hand, the shaft element34extends tangentially to the adjusting ring26in such a manner that the toothing34cof the shaft element34is in engagement with the external toothing26bof the adjusting ring26. The external toothing26bof the adjusting ring26and the toothing34cof the shaft element thus correspond to each other. And on the other hand, the guide lug35cis accommodated in a slidably guided manner in a groove25hof the holder section25gof the grinding housing25. The groove25hextends parallel to the shaft axis34aof the shaft element34and, like the latter, tangentially to the adjusting ring26.

Here, for identifying the grinding degree position, in this exemplary embodiment according toFIGS. 23 and 24, a rotational movement of the shaft element34about its shaft axis34ais generated by the adjusting rotational movement of the adjusting ring26via its external toothing26b, which are engaged with the toothing34cof the shaft element34. In this case, the rotational movement of the shaft element34produces a linear movement of the indicator element35by means of the movement thread34dwhich engages with the drive section35aof the indicator element35, which in turn is also rotationally fixed by means of the guide lug35cwhich is rotationally fixed in the groove25h. In this way, the scale carrier35bis axially displaced with respect to the shaft axis34a. The end face34eof the shaft element34, in conjunction with the indicator scale36, serves as a means for reading the degree of grinding on the indicator scale36.

At the respective end of the groove25h, the guide lug35cof the indicator element35comes to a respective stop. These stops limit the adjustment travel of the indicator element35and thus the rotational adjustment movement of the adjusting ring26. In other words, these stops simultaneously represent the stop for the minimum and maximum degree of grinding of the grinder1.

Another embodiment (not shown, but easily imaginable) of the grinding degree indicator32is conceivable, wherein instead of the shaft element34, a gearwheel, for example with spur toothing, meshing with the external toothing26bof the adjusting ring26, is rotated during an adjusting rotational movement of the adjusting ring26. This gearwheel can then rotate, for example about an axis which is parallel to the grinder axis1a, and the degree of grinding can be uniquely assigned depending on the angular position of the gearwheel, for example on the basis of an angular scale on the gearwheel. The gearwheel may also be in engagement with further gearwheels of a gear to effect a gear reduction or gear transmission ratio for the indication. To implement the stops, the gearwheel or the output gearwheel of the gear with the angular scale may be rotatable, for example by means of a pin, between two stops.

Moreover, in an embodiment not shown, the grinding degree indicator32can be used simultaneously to adjust the adjusting ring26. In this case, the external toothing26bof the adjusting ring26are in the form of a worm gear toothing, wherein the toothing34cof the shaft element34is the associated worm and is driven by an adjusting drive.

In the case of the gearwheel in place of the toothing34c, this gearwheel may of course be driven to adjust the adjusting ring26.

A drive of the shaft element34or the gearwheel for adjusting the adjusting ring26can be realized in many ways, for example by means of a stepper motor.

The above described change of the degree of grinding, i.e. the adjustment or rotation of the first grinding disc carrier M1around the grinder axis1acan be performed in all operating and rest positions of the grinder1.

The invention is not limited by the above exemplary embodiment, but is modifiable within the scope of the claims.

For example, it is conceivable that the receiving geometries of the grinding tools2,8are injection-molded with plastic.

Several springs16, in particular compression springs, may also be provided. These can be arranged symmetrically about the grinder axis1a, about which the grinding tool2,8rotates, in order to achieve an optimally distributed application of force.

It is also conceivable to use tension springs instead of or together with compression springs.

It is also conceivable that instead of the worm gear between the drive motor10and the drive shaft9, other types of gear with spur gears, bevel gears, helical gears can be used. To achieve a high reduction ratio with a spur gear, it is also possible to use a pinion with a minimum number of teeth.

LIST OF REFERENCE SIGNS