0001 This invention relates to a coupling device for a kitchen machine in accordance with the prior-art portion of patent claim 1. 0002 Coupling devices of this type for kitchen machines are known from the art. For example, FR 1467108 describes a device in which a socket arranged on a tool shank hooks elastically into the lower region of the drive part. For this to happen the drive part has at its lower end a latch which, under the action of a helical spring, engages radially in a groove provided on the outer circumference of the socket. In this arrangement the latch can be released by an actuating button which in the latched position projects sideways out of the drive part. 0003 From FR 1467108 there is also known an ejecting device which is integrated in the drive part. According to this prior art, a helical spring is biased when the tool shank is pushed in and used as an ejector when released. 0004 Furthermore, from EP 0692215 A1 there is known a handheld blender with a drive part and an interchangeable tool shank in which a tool shaft is rotatably mounted. To fasten the tool shank to the drive part an expansion clamp of the drive part engages in a mounting groove of the tool shank. To release the tool shank the expansion clamp, which is constructed as a metal spring, is pushed by means of a pushbutton, which is constructed as a separate component, in the direction of an opposite lying pushbutton. 0005 It is an object of the present invention to provide a simple and low-cost solution for connecting a tool shank to the drive part of an appliance for domestic use, particularly a handheld blender or immersion blender. 0006 This object is accomplished by a coupling device with the features of patent claim 1. A particularly simple coupling device affording low-cost manufacture is provided by the construction of the invention. The device of the present invention may find application not only on handheld blenders such as immersion blenders but also on stand-alone kitchen machines or other electrical appliances for domestic use. The coupling section of the drive part may be constructed, for example, essentially as a cylindrical end portion having arranged in its interior the locking device. The upper part of the tool shank is likewise of an essentially cylindrical configuration at its inner circumference enabling it to slide over the coupling section of the drive part quasi like a sleeve to be centered and axially fixed in place on the cylindrical end portion. Furthermore, rotatably mounted in the tool shank is a tool shaft whose one end is adapted to be coupled with the drive shaft of the drive part and whose other end projects into the blending space of a bell-shaped shield and is securely connected to a processing blade, such as was initially referred to in the prior art. 0007 It will be understood, of course, that other annular configurations of the spring element, e.g., circular, prismatic, elliptical or other forms of ring, are also possible. With these configurations the upper part of the tool shank, which is constructed essentially as a sleeve, is shaped to conform to the shape of the coupling section of the drive part in order to be able to plug these parts together. The detent element, which here is constructed preferably as a depression provided on the inner circumference of the tool shank, may be constructed as a circumferential groove, for example, or as a single elongated slot. In the event of the locking device being constructed as an ellipse, the points furthest apart from each other lie on the long diameter of the ellipse. If the spring element is shaped as a rhombus, the points furthest apart from each other lie on the long diagonal. 0008 The locking element may be formed by a projecting lug or a bead or a depression, for example, which is integrally connected as a one-piece construction with the spring element and then engages in a corresponding depression or lug or other projection on the tool shank. The actuating device involved may be a bead which is formed on the spring element and has the function of a pushbutton. A multiple function results from the fact that both the actuating device and the locking element are integrally connected as one piece with the spring element, thereby reducing the number of additional components and having the actuating and locking function performed by a single component. 0009 Through the superimposed arrangement of the actuating device and the locking element the locking element is displaced radially inwardly when the spring element on the actuating device is pressed, as the result of which it slides out of the detent element, thus releasing the tool shank for removal. According to the invention the actuating element may simultaneously form the locking element as well. According to the invention the spring element is deformed by the actuating element being pressed on the one side while the spring element takes support upon the housing of the drive part on the other side. 0010 An advantageous embodiment of the coupling device of the present invention is described by the features of patent claim 2. By virtue of the diametric arrangement of the locking and actuating elements it is possible to press together the spring element in simple manner and with little force using the thumb and index finger of one hand, as the result of which the locking elements move likewise in inward direction. When released, the spring element and the locking elements return to their initial position. 0011 According to the features of patent claim 3 the openings for the actuating elements may be elongated or oval slots or, alternatively, openings shaped in a rectangular, circular or some other configuration. In the locked state the actuating elements project out through these openings and are therefore freely accessible from the outside for actuation. When actuated by hand the actuating elements partly disappear in the openings of the outer wall of the coupling section of the outer part, as the result of which the locking elements also move inwardly and slide out of their detent elements, as the result of which the tool shank is in turn released and allowed to slide downward from the coupling section and drive part. 0012 Through the features of patent claim 4 it is possible for the spring element to be actuated particularly effectively and easily from the outside because the spring element is essentially symmetric in construction and pressed together uniformly from both sides when force is applied. 0013 According to the features of patent claim 5 the superimposed arrangement of the locking element and the actuating device results in the path traveled on the actuating device being equal to the path traveled on the locking element, i.e., a direct transmission of travel results with minimum actuating forces and displacement travels, leading ultimately to a simple and direct unlocking operation of the coupling device. 0014 A particularly advantageous further aspect of the present invention is provided by the features of patent claim 6. Suitable materials to be considered include, for example, elastic polypropylene, polyethylene or polyamide. These materials can be used for injection-molded parts in a simple and low-cost manner. The inherent elasticity of these plastics guarantees that the spring element recovers its original form after being accordingly deformed as required. Furthermore, a multiplicity of functions can be performed by a single component through its construction as a one-piece plastic part. 0015 An advantageous embodiment with the features of patent claim 7 displays in particular the multiple function of the ejector constructed in one piece with the spring element. Components can be saved as the result and the costs reduced accordingly. Furthermore, the functions of the ejector and the locking elements are skillfully interconnected because the ejector is arranged at an angle of 90 degrees to the locking elements in the case of a spring element of cylindrical configuration, on the short diameter in the case of a spring element of elliptical configuration, and on the short diagonal in the case of a spring element of rhombic configuration. When the locking device is accordingly actuated by means of the actuating elements the spring element is deformed for the releasing operation, thus enlarging the regions of the spring ring around the ejectors or the lengths of the short diagonals or short diameters whilst compressing the actuating region of the spring element. The ejectors are thereby pressed against the obliquely extending inner circumference of the tool shank, as the result of which the locking elements are unlocked and the tool shank simultaneously decoupled from the drive part, pushed away and thereby ejected axially in the longitudinal direction of the drive part. 0016 A further advantageous multiple function is described by the features of patent claim 8 in which the ejectors have ramp surfaces which, when actuated radially, effect an axial ejecting movement in the longitudinal direction of the drive part. A flat ramp pitch is selected so that the actuating forces are not too high for the operator but the travel is still sufficient for the tool shank to be visibly disengaged from the drive part. 0017 Finally, a further advantageous embodiment of the present coupling device is provided by the features of patent claim 9. Suitable guide devices, which may be formed, for example, by grooves provided on the spring element and guide ribs on the drive part, are used to prevent the spring element from skewing, for example, thus ensuring a reliable function. 0018 It is also particularly advantageous for the locking device of the present invention to exhibit the features of patent claim 10. A captivating device of this type may be provided, for example, by having either the ejectors or the locking elementspreferably the ejectors in the embodimentalways engaged with the passages formed on the drive part. Fixing the spring element in the drive part in this manner facilitates the assembly operation significantly because, once installed, the spring element is fixed in its position. Slipping out of the predefined position and jamming with other components is thereby prevented. The ejectors penetrate the drive part and project out of it far enough in radial direction as to latchingly engage in depressions formed on the tool shank in order to act as detent elements when the tool shank is inserted. 0019 A further advantageous embodiment of the present invention is provided by the features of patent claim 11. It is thereby possible for the locking elements to snap in place during the coupling operation, without the actuating devices being in the way. This is achieved by spatial separation of the locking elements relative to the actuating devices. When mounting the tool shank it is thus possible for the locking elements to be pressed, without actuating the actuating device, back into the corresponding opening in the outer wall of the coupling section until they are aligned with the depressions on the inner circumference of the tool shank. At this moment the locking elements snap back on account of the spring action of the vertical connecting bar. The coupling connection is now engaged and locked. Unlocking is now only possible by actuating the actuating devices. 0020 To improve the snap-action effect of the locking elements they are constructed in accordance with patent claim 12. On the one hand the locking elements thus act as a barb, on the other hand the centering surfaces on the tool shank cooperate with the sliding surfaces on the spring element, resulting in the spring element invariably urging the tool shank into the drive part without play, as the result of which the walls are biased against the abutment surfaces because the spring element in the drive part always maintains a small bias. 0021 According to the features of patent claim 13 the tool shank slides on the wedge-shaped ejector as on a ramp during the decoupling operation. The additional spring action through the second connecting bars helps to control the ejection pressure. It also prevents skewing.

0022 Further aspects and advantages of the present invention will be explained by the following description of embodiments with reference to the accompanying drawings. In the drawings, 0023 FIG. 1 is a schematic representation showing in a partial longitudinal sectional view an invention embodiment of a coupling device for an immersion blender; 0024 FIG. 2 is a sectional view of the invention embodiment of FIG. 1 turned through 90 degrees, but without motor, drive spindle, coupling sleeve and drive shaft; 0025 FIG. 3 is a perspective view of the invention spring element of the coupling device of FIG. 1; 0026 FIG. 4 and FIG. 4a are schematic representations of the function of the invention embodiment of FIG. 1 in locked condition; and 0027 FIG. 5 and FIG. 5a are schematic representations of the function of the invention embodiment of FIG. 1 in unlocked condition.

0028 FIGS. 1 and 2 show a schematic sectional view of an advantageous embodiment of the coupling device 1 of the invention. They show the tool shank 6 with its upper portion which embraces the lower frusto-conical coupling section 24 of the drive part 7 quasi like a sleeve. In the present embodiment the drive part 7 and the tool shank 6 are manufactured mainly of plastic. As shown in FIG. 1 the tool shank 6 has at its upper inner circumference locking recesses or detent elements 10 which are constructed as elongated grooves for accommodating locking elements 3. Fastened in a bore 15 of the drive part 7 is a bearing sleeve 16 having a bore 20 in which a further bearing sleeve 22 is fastened, which again has a bore 23 in which a plain bearing 25 is inserted, in which is rotatably mounted the drive spindle 26 of the electric motor 27 non-rotatably mounted in the drive part 7. The free end of the drive spindle 26 is non-rotatably fastened to a coupling sleeve 28 which has an accommodating bore 29 in which the drive shaft 30, which is non-rotatably and releasably mounted in the tool shank 6, is non-rotatably and releasably coupled. Fastened to the other end, not shown in the drawings, of the tool shaft is a blade or processing tool (not shown) for processing food, which is surrounded by a shield, preferably a bell, of the type known from FR-B-1467108, for example. 0029 The drive shaft 30 has driving elements, not shown in the drawings, which engage in corresponding driving elements (not shown) in the accommodating bore 29 in a non-rotatable but releasable relationship. According to FIG. 1 the bearing sleeve 16 has an annular collar 17 with 90 offset, which takes support upon and centers itself on the bore 15 of the housing 18 at the drive end. 0030 FIG. 1 also shows in section the spring element 2 made of elastic plastic. The spring element 2 is shaped in a rhombic configuration having radiused corners. FIG. 1 shows the corner points on the long diagonal. The plane formed by the rhombic spring element 2 is referred to in the following as the spring element plane. 0031 Also shown in FIG. 1 are two opposing locking elements 3 connected in one integral piece with connecting bars 12. In this arrangement the locking elements 3 are of a wedge-shaped configuration abutting with their abutment surface 34 against the horizontally extending wall 37 of the detent elements 10 constructed as blind-end bores or depressions, after they were pushed by the radial bias exerted by the spring element 2 upward as far as the stop via cooperating sliding and centering surfaces 40, 39. In this position, as in the decoupled position, the locking elements 3 penetrate the passages 35 and engage in the undercut detent elements 10. 0032 According to FIGS. 1 and 3 the connecting bars 12 are integrally formed on the spring element 2 perpendicular to the spring element plane. At their lower ends the connecting bars 12 have perpendicularly extending guide grooves 5, as is particularly well visible in FIG. 3. 0033 Furthermore, in FIGS. 1 and 3 provision is made at the fastening point of the connecting bars 12 above the locking elements 3 for diametrically opposed actuating devices 4 which are equally integrally formed on the spring element 2 as a one-piece construction. In this arrangement the actuating devices 4 are configured as bead-type pushbuttons which, according to FIG. 1, project out of the coupling section of the drive part 7 through an opening 13. To prevent soiling of the drive part 7, provision is made for flexible rubber seals 14 which cover the openings 13 and the actuating devices 4. The spring element 2 is held in its position by guide ribs 8 and the annular collar 17 on the housing 18 of the drive part 7. The guide grooves 5 shown in FIG. 3 slide on the guide ribs 8 when the locking device is actuated. 0034 FIG. 2 shows the same embodiment as FIG. 1, but the section extends in a 90-degree offset relation and some parts are omitted for the sake of simplicity. Shown in FIG. 2 are the ejectors 9 arranged in a 90-degree offset relation to the locking elements 3. The ejectors are connected equally in a one-piece construction to the spring element 2 by way of connecting bars 11 (see FIG. 3) and are slightly wedge-shaped, forming on their bottom sides ramp surfaces 32 which engage abutment surfaces 33 of the tool shank 6 and which, when pressure is applied from both sides radially from without to within against the actuating devices 4 (see the direction of the arrow X in FIG. 1) cause the ejectors 9 to move radially outwardly precisely in the reverse direction, pushing the tool shank of FIG. 2 downward via the abutment surfaces 33, which however is not shown in the drawings because only the assembled position of the tool shank 6 and the drive part 2 is shown. As this occurs, the locking elements 3 have already moved radially inwardly out of the depressions 38 and released the tool shank 3 for axial movement. At their lower ends the connecting bars 11 also have guide grooves 5 which are guided in radial direction by guide ribs 8 in that they embrace said ribs from above and the side. The ejectors 9 are shown in a perspective view in FIG. 3. 0035 The spring element 2 shown in FIG. 3 as an individual part is injection molded as an integral piece manufactured from an elastic thermoplastic material. The spring element 2 of an annular shape, and the actuating devices 4 and the locking elements 3 fitted underneath to a connecting bar 12 are arranged at an angle of 90 degrees to the connecting bars 11 on which the ejectors 9 and the downwardly open guide grooves 5 are formed. The locking elements 3 are arranged on a connecting bar 12 which has the guide grooves 5 further below. 0036 FIG. 4 and FIG. 4a show a schematic functional view of the coupling device of the invention, in which the spring element 2 accommodated in the drive part 7 is shown as a broken line. In FIG. 4 the tool shank 6 is shown in the locked state. In this state the actuating devices 4 are at their furthest apart. By contrast, the ejectors 9 are arranged opposite each other at a shorter relative distance. This becomes also apparent from the greatly simplified sketch in FIG. 4a, which shows a schematic plan view of a rhombic spring element 2. 0037

FIGS. 5 and 5

a show a second schematic functional view in which the actuating devices 4 of FIGS. 4 and 4a have been actuated in the direction of the arrow A. As the result, the rhombic spring element 2 deforms such that the locking elements 3 are unlocked and the ejectors 9 separate the tool shank 6 from the drive part 7. This can be seen particularly well in the schematic plan view of the rhombic spring element 2 in FIG. 5a. In the actuated position the ejectors 9 are situated on the long diagonal of the rhombus, while the actuating devices 4 are to be found on the short diagonal. The locking devices 3 fully disappear in the drive part, as becomes apparent from FIG. 5.