Patent Description:
As shown in the Chinese utility model <CIT>, electric driven kitchen machines such as cooking machines often has a fan in order to cool a motor-drive unit. Mostly, the fan is positioned on a drive shaft of a rotor of the electric motor.

In <CIT> a rotary coupling for a drive motor shaft is shown. The coupling integrates a clutch for connecting an appliance of a kitchen machine and a fan and is fixedly connected to the shaft via a press fit. <CIT> discloses another rotary coupling for a kitchen machine.

In known kitchen machines of the applicant, a motor-drive unit has two interfaces at opposite ends in order to attach an appliance. One interface is created by a fan-clutch arrangement which is provided on the rotor shaft, wherein the fan is used for cooling purposes and the clutch is configured to be connected with a respective appliance of the kitchen machine such as a blender. The fan is attached to the clutch via press fit and the clutch is attached to an adapter such as a sleeve or bushing via press fit as well. The adapter is attached to an end section of the rotor shaft via thread engagement.

It is an object of the present invention to provide an alternative technique allowing a tight fit of a fan and of a clutch on a drive shaft, a fan-clutch arrangement enabling a tight fit of the fan and of the clutch on a drive shaft, an electric motor-drive unit and a kitchen machine that fan and clutch is tightened to a drive shaft.

The object is solved by a method according to claim <NUM>, a fan-clutch arrangement according to claim <NUM>, an electric motor-drive unit according to claim <NUM> and a kitchen machine according to claim <NUM>. Preferred embodiments are disclosed in the dependent claims, the description and the figures.

According to the invention, a method for assembling a fan on a drive shaft of an electric motor-drive-unit of a kitchen machine, wherein the fan is positioned on a clutch provided to connect an appliance to the drive shaft, comprising the following steps:.

As the fan is held in place via form fit and not via press fit, a replacement of the fan is simplified. Thereby, a tight fit is guaranteed. By means of this, different fans can be engaged thus enabling individual fan designs which are adapted to separate motor performances. A modification of the clutch can be omitted, thus reducing technical complexity. Disassembling the clutch is not necessary. "Directly or indirectly" means that either the clutch is pressed directly on the end section or, alternatively, the clutch is positioned on the end section via at least one adapter whereas the clutch is attached to the at least one adapter via press fit.

Preferably, the adapter is a sleeve and held on the end section of the drive shaft via press fit. Due to this, thread engagement can be omitted, thus simplifying the manufacturing and the assembly.

According to the invention, a fan-clutch arrangement of an electric motor-drive unit of a kitchen machine, comprises a fan in order to cool the motor-drive unit and a clutch in order to connect an appliance to the drive unit. The clutch is held via press fit on an end section of a drive shaft, and the fan is held via form fit on the clutch. By means of this, a tight fit of a fan and of a clutch on a drive shaft is provided whereas changing the fan is simplified. An example for a form fit is a so-called "snap and click connection".

In a preferred embodiment, the clutch is mounted to the drive shaft via at least one adapter, for instance a sleeve which is in press fit with both, the end section of the drive shaft and the clutch. Due to this, thread engagement can be omitted, thus simplifying the manufacturing and the assembly. In order to prevent a slippage in the unlikely event that the press fit might become loose, the adapter might have an adequate outer contour such as longitudinal projections extending in mounting direction of the clutch. Alternatively, and/or in addition, the clutch can be provided with an adequate inner contour.

Preferably, the clutch has a first part acting together with the fan and a second part acting together with the appliance. As the fan and the appliance are not acting on the same parts, both parts can be optimised for their individual function. For instance, the first part is a radial outer collar and the second part is a radial inner hub for the appliance. If the parts are positioned on different diameters, they can project in the same direction, thus enabling a compact axial extension of the clutch.

Preferably, the fan can have a radial outer wheel with a plurality of air wings and a radial inner hub for acting together with one part of the clutch By means of this, an effective colling and a tight positioning is enabled.

In order to prevent a rotational slippage between the clutch and the fan, first elements of the first part of the clutch and first counter elements of the fan hub are provided. In order to prevent an axial slippage between the first part of the clutch and the fan hub, second elements of the clutch and second counter elements of the fan are provided. As a rotational slippage and an axial slippage is prevented by different parts and elements, respectively, the respective parts and elements can be optimised for their individual function.

Preferably, the first elements are longitudinal recesses and the first counter elements corresponding longitudinal projections or vice versa.

The second elements are preferably elastic tongues each having a hooked end and the second counter elements corresponding recesses, thus enabling a so-called "snap and click connection" which enables a tight fit and which can easily be disengaged.

A preferred electric motor-drive unit for a kitchen machine has a fan-clutch arrangement according to the invention. The fan-clutch arrangement enables a tight fit to a drive shaft and an easy replacement of the fan.

A preferred kitchen machine has an electric motor-drive unit with a fan-clutch arrangement according to the invention. The fan-clutch arrangement enables a tight fit to a drive shaft and an easy replacement of the fan.

In the following, preferred embodiments of the present invention are explained with respect to the accompanying drawings. As is to be understood, the various elements and components are depicted as examples only, may be facultative and/or combined in a manner different than that depicted. Reference signs for related elements are used comprehensively and not defined again for each figure. Shown is schematically in.

In <FIG>, a perspective view of an electric motor-drive unit <NUM> of a kitchen machine such as a cooking machine is shown. The motor-drive unit comprises a motor casing <NUM> having a stator <NUM> and a rotatable rotor <NUM> included, a gear box <NUM> and an electric control unit <NUM>.

The rotor <NUM> has a drive shaft <NUM> that on its first end section is in connection with a rotatable gear shaft of the gear box <NUM> in order to form a first interface <NUM> for engaging an appliance. On its opposite second end section, the drive shaft <NUM> has a second interface <NUM> configured to be engaged with a second appliance such as a blender. The first and second interface <NUM>, <NUM> are couplings or clutches, respectively, enabling an interlocking or form fit, that means mechanically and by geometry, with counter parts of the appliances. In order to prevent the motor-drive unit <NUM> from overheating, a fan <NUM> for cooling purposes is provided. The fan <NUM> is positioned at the second end section of the drive shaft <NUM> and such engaged to the drive shaft <NUM> that both the drive shaft <NUM> and the fan <NUM> has the same rotational speed.

As can been seen in <FIG>, the fan <NUM> is positioned on the second interface, respectively on the clutch <NUM>, and the clutch <NUM> is positioned on the second end section of the drive shaft <NUM> via an adapter <NUM> such as a sleeve. The fan <NUM> and the clutch <NUM> are forming a kind of fan-clutch arrangement wherein the fan <NUM> is releasable attached to the clutch <NUM> via form fit and the clutch <NUM> is attached to the sleeve <NUM> via press fit. The sleeve <NUM> is then again attached to the second end section of the drive shaft <NUM> via press fit.

As can be seen in more detail in <FIG>, the sleeve <NUM> is inserted into an axial cylindrical recess <NUM> of the clutch <NUM>. In order to support the press fit arrangement between the sleeve <NUM> and the clutch <NUM>, at its outer surface the sleeve <NUM> has a plurality of longitudinal projections <NUM> extending in axial direction, respectively mounting direction, of the sleeve <NUM> and the clutch <NUM>, respectively. Preferably, the longitudinal projections <NUM> do not extend over the whole axial length of the sleeve <NUM>, but an outer surface area <NUM> at the front-end side of the sleeve <NUM> has a blank outer surface. An inner surface <NUM> of a through hole of the sleeve <NUM> is preferably smooth and prepared adequately for the press fit arrangement.

In order to align the sleeve <NUM> and the clutch <NUM> axially, the second end section of the drive shaft <NUM> has a radial outer shoulder <NUM> forming a stop for the front-end side of the sleeve <NUM>, and the axial cylindrical recess <NUM> of the clutch <NUM> has a radial inner shoulder <NUM> near its bottom <NUM> forming a stop when acting together with an opposite back-end side of the sleeve <NUM>.

According to <FIG>, the clutch <NUM> has a first part <NUM> and a second part <NUM>. The first part <NUM> is a radial outer collar and the second part <NUM> is a radial inner hub of the clutch <NUM>. The collar <NUM> surrounds the hub <NUM>, whereas both the collar <NUM> and the hub <NUM> are extending in the same axial direction and have different functions. Whereas the collar <NUM> is configured to hold the fan <NUM> via releasable form fit, the hub <NUM> is configured to receive the sleeve <NUM> via press-fit and to engage the second appliance. In order to receive the sleeve <NUM>, the cylindrical recess <NUM> is positioned in the hub <NUM>. In order to engage the second appliance, the outer surface of the hub <NUM> is provided with longitudinal projections <NUM> extending in axial direction.

The collar <NUM> comprises first elements <NUM> which are configured to act together with corresponding first counter elements <NUM> of the fan <NUM>. In the shown embodiment, the first elements are longitudinal recesses <NUM> which extends over the entire axial length of the collar <NUM> and which are evenly distributed over the circumference of the collar <NUM>. Here, three longitudinal recesses <NUM> are provided.

The collar <NUM> also comprises second elements <NUM> which are configured to act together with second counter elements <NUM> of the fan <NUM>. In the shown embodiment, the second elements are elastic tongues <NUM> extending over the entire axial length of the collar <NUM> and which are evenly distributed over the circumference of the collar <NUM>. Here, three elastic tongues <NUM> are provided. At their free ends, each tongue <NUM> has a hooked end <NUM> which is directed radially outwards.

Between the first and second elements <NUM>, <NUM> of the collar <NUM>, rigid wall <NUM> sections are provided.

Both the first and the second elements <NUM>, <NUM> has different functions. The first elements <NUM> in cooperation with the rigid wall elements <NUM> are provided in order to prevent rotational slippage between the clutch <NUM> and the fan <NUM>, the second elements <NUM> comprising the hooked ends <NUM> are provided in order to prevent axial slippage between the clutch <NUM> and the fan <NUM>.

In <FIG> an embodiment of a fan <NUM> according to the invention is shown. The fan <NUM> has a radial outer wheel <NUM> with a plurality of air wings <NUM> and a radial inner hub <NUM>. The wheel <NUM> and the hub <NUM> aligned axially to each other and arranged one after the other, whereby the wheel <NUM> is connected with a front side of the hub <NUM> via its back side. The wheel <NUM> is used for cooling purposes and the hub <NUM> is used for engaging the fan <NUM> via form fit to the collar <NUM> of the clutch <NUM>. The hub <NUM> comprises the aforementioned first counter elements <NUM> and the second counter elements <NUM>.

The first counter elements are longitudinal projections <NUM> corresponding to the longitudinal recesses <NUM> of the clutch <NUM>. They extend over the entire axial length of the hub <NUM> and are evenly distributed over its circumference. Here, three longitudinal recesses <NUM> are provided.

The second counter elements are radial recesses <NUM> in a bottom ring <NUM> of the hub <NUM>. The bottom ring <NUM> extends radially inwardly and forms an axial stop when the fan18 is in form fit engagement with the clutch <NUM>. The radial recesses <NUM> extend over the entire radial extension of the bottom ring <NUM> an correspond the hooked ends <NUM> of the elastic tongues <NUM> of the clutch <NUM>. They are evenly distributed over the circumference of the hub <NUM>. Here, three radial recesses <NUM> are provided.

With reference to <FIG>, when the fan <NUM> and the clutch <NUM> are in form fit engagement and forming the fan-clutch arrangement, the longitudinal projections <NUM> of the fan <NUM> are introduced into the longitudinal recesses <NUM> of the collar <NUM>, thus preventing rotational slippage between the fan <NUM> and the clutch <NUM>. The hooked ends <NUM> of the elastic tongues <NUM> are introduced into the radial recesses <NUM> of the fan <NUM> and the collar <NUM> abuts with its back side of its collar <NUM> against the bottom ring <NUM> of the fan hub <NUM>, thus preventing axial slippage and enabling a releasable disassembling of the fan <NUM>.

In <FIG>, a further embodiment of a fan <NUM> according to the invention is shown. Although this embodiment shows a different wheel design and a different hub design, the fan <NUM> is configured to be engaged with the same collar <NUM> of the clutch <NUM> via releasable form fit.

In this embodiment, the hub <NUM> of the fan <NUM> has an front inner surface <NUM> with a conical shape that passes over in an inner back cylindrical surface <NUM>. Longitudinal projections <NUM> acting as first counter elements extend over the entire length of the front inner surface <NUM> and end at the cylindrical surface <NUM>. Preferably, they end stepless at the cylindrical surface <NUM> and do not extend radially over it. The front inner surface <NUM> is configured to form an axial assembling stop for the fan <NUM> on the collar <NUM> of the clutch <NUM>.

Longitudinal recesses <NUM> acting as second counter elements extend over the entire length of the hub <NUM> and thus over both the conical surface <NUM> and the cylindrical surface <NUM>.

In <FIG>, a further embodiment of a fan <NUM> according to the invention is shown. Again, although this embodiment shows a different wheel design and a different hub design, the fan <NUM> is configured to be engaged with the same collar <NUM> of the clutch <NUM> via releasable form fit.

In main difference to the embodiment of <FIG>, the fan <NUM> according to this embodiment has not only a back inner cylindrical surface <NUM>, but also a front inner surface <NUM> with a cylindrical shape. The front inner surface <NUM> carries longitudinal projections <NUM> acting as first counter elements extend over the entire length of the front inner surface <NUM>.

The front inner surface <NUM> has a larger radial diameter as the back cylindrical surface <NUM> such that a shoulder <NUM> is formed in their transition region providing an axial assembling stop for the fan <NUM> on the collar <NUM> of the clutch <NUM>. Preferably, the longitudinal projections <NUM> are ending stepless at the back cylindrical surface <NUM> and do not extend radially over it.

Longitudinal recesses <NUM> acting as second counter elements extend over the entire length of the hub <NUM> and thus over both the front inner surface <NUM> and the back cylindrical surface <NUM>.

In a preferred assembly method according of the invention, the clutch <NUM> is pressed on the sleeve <NUM> and the sleeve <NUM> equipped with the clutch <NUM> is then pressed on the end section of the rotor shaft <NUM> as a part of the rotor assembly. The fan <NUM> is mounted via form fit on the clutch <NUM> at an end station of the assembly.

Preferably, the clutch <NUM> and the fan <NUM> are plastic parts made by plastic injection moulding, for instance, and the sleeve <NUM> is a metal part.

Claim 1:
A method for assembling a fan (<NUM>) on a drive shaft (<NUM>) of an electric motor-drive-unit (<NUM>) of a kitchen machine, wherein the fan (<NUM>) is positioned on a clutch (<NUM>) provided to connect an appliance to the drive shaft (<NUM>), comprising the steps:
- holding the clutch (<NUM>) on an end section of the drive shaft (<NUM>) via press fit directly or indirectly, and
- holding the fan (<NUM>) on the clutch (<NUM>) via form fit.