Patent Grant
7273005
The present invention relates to a coffee grinder assembly comprising a housing, a first, lower grinding wheel support member and a first, lower grinding wheel, and a second, upper grinding wheel support member and a second, upper grinding wheel. At least one of the first and second grinding wheels is rotatably received in the housing.
The first, lower grinding wheel support member and the first, lower grinding wheel both comprise first cooperating connecting means for fixing the first, lower grinding wheel in the first, lower grinding wheel support member, and the second, upper grinding wheel support member and the second, upper grinding wheel both comprise second cooperating connecting means for fixing the second, upper grinding wheel in the second, upper grinding wheel support member.
Grinder assemblies of the kind referred to herein above consist mainly of plastic material, whereby the grinding wheels thereof are manufactured of a hard, non-abrasive material, for example of hardened steel. The quality of the coffee powder prepared with such grinder assemblies particularly depends on the wear resistance of the grinding wheels used in the grinder assembly, since, with progressive wear of the grinding wheels, the particle size of the coffee powder varies, resulting in decreasing quality both of the ground coffee powder and the coffee beverage prepared therewith.
In order to fix the grinding wheels in the associated grinding wheel support members, usually the wheels are provided with a plurality of bores, running through the grinding wheels and adapted to receive connecting means like screws, rivets or similar means. A disadvantage of providing connecting bores may be seen in the fact that they claim a substantial amount of the theoretically available grinding surface of the grinding wheel, because the toothing of the grinding wheel is interrupted by these bores. Moreover, the harder the grinding wheel is,—which is desirable per se—, the more difficult it is to machine these connecting bores in the grinding wheels. Finally, the provision of connection bores has the further disadvantage that coffee powder is collected both in the bores an in the connecting means; of course, this is not desired at all due to hygienic reasons.
The patent document EP 1,065,962 discloses a coffee grinder having a grinder assembly of the kind referred to herein above. The grinder assembly comprises a conical gear wheel as well as two coaxially arranged grinding wheels having a spiral-like toothing. One of the grinding wheels is stationary and the other one rotatable. Both grinding wheels are provided with connecting bores adapted to receive connecting screws by means of which the grinding wheels are fixed to the associated grinding wheel support members. In particular,
U.S. Pat. No. 6,164,574 discloses a mill for grinding material such as salt grains or pepper corns whose coarseness can be adjusted and whose grinding gear can be disassembled for cleaning. The mill has a middle part which serves as a reservoir for the material to be ground and an upper part which is attachable to the middle part by means of an attachment and adjustment element. In addition, the mill has a lower part which is designed to unscrew from the middle part for the purpose of cleaning the grinding gear. The grinding gear includes both an upper grinding wheel which is disposed underneath on the middle part and a lower grinding wheel which is screwed together with the attachment and adjustment element through a pivot pin. The pivot pin is connected in a non-rotatable way to the upper part. Turning the upper part actuates the grinding gear.
For fixing the grinding wheels in its associated support member, the grinding wheels are provided with four recesses located along their periphery, which are engaged by correspondingly arranged cam members provided in the associated support member. Such a design shows the disadvantage that the grinding wheels cannot be positioned exactly neither in axial direction nor in radial direction, with the result that they can move within their support member under the influence of the torque forces occurring during the grinding operation.
It is an object of the present invention to provide a coffee grinder assembly for a coffee machine in which the grinding wheels do not have any connecting bores extending through the grinding wheel, whereby the grinding wheels are nevertheless exactly positioned and fixed both in axial and radial directions.
To meet these and other objects, the present invention provides a coffee grinder assembly comprising a housing, a first, lower grinding wheel support member and a first, lower grinding wheel, and a second, upper grinding wheel support member and a second, upper grinding wheel. At least one of the first and second grinding wheels is rotatably received in the housing.
The first, lower grinding wheel support member and the first, lower grinding wheel both comprise first cooperating connecting means for fixing the first, lower grinding wheel in the first, lower grinding wheel support member, and the second, upper grinding wheel support member and the second, upper grinding wheel both comprise second cooperating connecting means for fixing the second, upper grinding wheel in the second, upper grinding wheel support member.
Each of the first and second cooperating connecting means is designed as a rotational closure in which a mutual rotation of the first, lower grinding wheel support and the first, lower grinding wheel as well as of the second, upper grinding wheel support and the second, upper grinding wheel in each case provides for an interlocking closure that is driven in its locked position under the influence of the torque force occurring during the grinding operation.
By the provision of the above-mentioned rotational closure to fix each of the grinding wheels in its associated support member, the effective grinding surface of the grinding wheels is enlarged because space consuming connecting bores in the grinding wheels are avoided. Moreover, the difficult, time consuming drilling of the connecting bores can be avoided, which is a particular advantage in the case of very hard grinding wheels. Furthermore, it is ensured that the grinding wheels cannot become loose under the influence of the torque forces occurring during the grinding operation, but are even more firmly seated and positioned in the associated grinding wheel support. Finally, by the design according to the invention, the requirements of hygiene in the grinding and cutting area are also considered.
In a preferred embodiment of the invention, the grinding wheels comprise radially extending protrusions, cooperating with corresponding recesses provided in the associated support members in the kind of a bayonet closure. Such grinding wheels can be fixed in the associated supports quickly and easily.
In the following, an embodiment of the grinder assembly according to the invention will be further described, with reference to the accompanying drawings, in which:
The coffee grinder assembly according to
Since the design and the operation of such coffee grinding assemblies are well known to any person skilled in the art, in the following, only the characteristics essential to the present invention are further discussed.
The lower and upper grinding wheel supports 4, 8 preferably are made of plastic material and serve for receiving and fixedly supporting the lower and upper grinding wheels 5, 7, respectively. Instead of bores for fixing the respective grinding wheel to its associated grinding wheel support, as it is provided for in the coffee grinder assemblies according to the prior art, both grinding wheels 5, 7 are provided with radially projecting elements 10, 11 for fixing the grinding wheel to its associated grinding wheel support 4,8.
Both the lower and upper grinding wheel supports 4, 8 are provided with recesses 12, 13 corresponding in size and position to the radially projecting elements 10, 11 provided on the grinding wheels 5, 7. The radially projecting elements 10, 11 engage the recesses 12, 13 and establish therewith a bayonet interlocking. In the exploded view of
The lower grinding wheel support 4 is provided with six vertically extending protrusions 15. Three of them comprise the previously mentioned slot-shaped recesses 12, serving to receive and fix the lower grinding wheel 5 by means of the radially extending protrusions 10 thereof. The upper grinding wheel support 8 is provided with three slot-shaped recesses 13 as well, serving to receive and fix the upper grinding wheel 7 by means of the radially extending protrusions 11 thereof. The slot-shaped recesses 12 both provided in the lower grinding wheel support 4 and the upper grinding wheel support 8, however, are only partially visible in the illustration of
Both the lower grinding wheel 5 and the upper grinding wheel 7 are provided with a toothing 25 in each case provided on that surface of the grinding wheel 5, 7 that faces the opposite grinding wheel 7,5. In the exploded view of
In order to provide for a positive interconnection between the lower grinding wheel support 4 and the rotating disc 2 driven by the electric motor 1, the lower grinding wheel support 4 comprises a protrusion 16 provided with an peripheral toothing, the protrusion 16 being adapted to engage a bore 17 provided in the rotating disc 2 and having a corresponding inner toothing. The rotating disc 2 is driven by the electric motor 1 having a worm gear wheel 19 engaging a peripheral toothing 18 provided on the rotating disc 2.
In contrast to the lower grinding wheel support 4, the upper grinding wheel support 8 is non rotatable, but fixed to the housing 3. To prevent a rotation of the upper grinding wheel support 8, it comprises cams 22 engaging correspondingly located recesses 23 provided in the housing 3. The upper feed screw 9, finally, is screwed onto the threaded upper end of the shaft 6, while the lower threaded end of the shaft 6 is fixed to the rotating disc 2 by means of a (not shown) nut.
Preferably, the bottom side of the rotating disc 2 can be provided with permanent magnets (not shown), cooperating with a sensor (not shown) fixed to the housing to measure the number of the revolutions when the coffee grinder is operated. Thus, the number of the revolutions performed by the lower grinding wheel 5 during a coffee grinding cycle establishes a measure for determining the amount of coffee ground during one operating cycle.
Due to the torque force acting on the grinding wheel 7 during the grinding operation, the wheel 7 is loaded in locking direction; in other words, by choosing a proper sense of rotation of the grinding wheel and due to the design of the rotational locking mechanism, the grinding wheel 7 is loaded in locking direction. Thereby, the grinding wheel 7 is firmly fixed in the grinding wheel support 8 and it is ensured that the grinding wheel 7 does not become loose unintentionally. Moreover, due to this load, it is also ensured that the rear side of the grinding wheel 7 is moved against the supporting surface 24 of the grinding wheel support 8 and rests there against without play. The result is that no coffee dust can accumulate between the grinding wheel 7 and the grinding wheel support 8. It is understood that all of the above is also true in connection with grinding wheel 5 and its associated support 4.
In
Instead of the bayonet locking mechanism with radially projecting locking members discussed herein above, other types of rotational locking mechanisms can be used for locking the grinding wheel with regard to its associated support member. For example, a threaded locking mechanism could be used for fixing the grinding wheel to the associated support member. On the other side, the locking means could be arranged in axial direction on the grinding wheel, particularly on its rear surface facing the associated support member. Also, a central location of a protrusion or several protrusions would be possible. Finally, it is understood that the locking mechanism could be designed in a kinematically opposite manner: The grinding wheels could be provided with a recess or with several recesses, and the associated support member could comprise one or several corresponding protrusions engaging these recesses in the grinding wheel.
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| Number | Date | Country |
|---|---|---|
| 945 410 | Jul 1956 | DE |
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| 1 065 962 | Jan 2001 | EP |
| Number | Date | Country | |
|---|---|---|---|
| 20050279219 A1 | Dec 2005 | US |
