Fixing device for a shaft seal and gearbox assembly with such a

Description

[0001] The invention relates to a gear unit comprising a first gear part rotatable about an axis of rotation, a sealing seat formed in the first gear part, a shaft seal fitted in the sealing seat, and a second gear part extending through the first gear part and the shaft seal and rotatable about the axis of rotation, wherein a sealing lip is formed on the shaft seal which engages with an outer surface of the second gear part and is pre-tensioned by a spring element arranged on the shaft seal, wherein a fixing device for the shaft seal is provided.

[0002] Shaft penetrations in gearbox housings with shaft seals are known, whereby the shaft seals are used to prevent the leakage of oils, lubricants, or greases and simultaneously to prevent the ingress of dust, dirt, and the like from the outside into the interior of the gearbox. The inlet and outlet openings of rotating shafts located on a gearbox housing are particularly vulnerable. For example, radial shaft seals are used on rotating shafts, whereby the shaft seals are inserted, fitted, or pressed into a housing component, and the rotating shaft is sealed by a sealing lip formed on the shaft seal.To ensure a tight seal between the sealing lip and the rotating shaft, a spring washer in the form of a worm spring or coil spring is provided. This washer is fitted into the shaft seal and exerts a radial clamping force on the sealing lip in the direction of the rotating shaft. This increases the service life of the shaft seal and / or extends the sealing effect of the sealing lip, which decreases with wear.

[0003] Radial shaft seals are installed with a fixed fit in the housing or housing cover, or in a sealing bearing seat of a gearbox. Their sealing lip runs on the surface of the rotating shaft and is usually pressed radially against the shaft surface by a coil spring or worm spring. The radial shaft seal consists of an elastomer part, a stiffening ring, and the aforementioned coil spring or worm spring. The outer surface of the elastomer part of the shaft seal creates a reliable static seal against the housing or housing cover, thus fixing the radial shaft seal to the housing or housing cover. The stiffening ring provides the radial shaft seal or the elastomer part with the necessary stability. The coil spring or worm spring additionally pre-tensions the sealing lip, ensuring radial contact of the sealing lip with the rotating shaft.In addition to the actual sealing lip, which is pressed against the rotating shaft by the aforementioned springs, a protective lip may also be provided to keep out dirt and dust. Due to its simple design, the shaft seal can usually be easily installed and removed.

[0004] Radial shaft seals of the type described above are disclosed, for example, in the following documents.

[0005] German patent DE 102012218099 A1 describes a sealing arrangement for sealing a shaft against a medium. The sealing arrangement comprises a spring element and a shaft seal with a first sealing lip and a second sealing lip. The spring element is designed to press the shaft seal against the shaft. The second sealing lip is radially smaller than the first sealing lip. This means the shaft seal is stepped.

[0006] Another embodiment of a shaft seal is disclosed in US 20120104701 A1, wherein a seal comprises an annular portion with a static sealing surface in contact with a first element and made of an elastomeric material. An annular lip provides a dynamic seal against a second element. A worm spring and a leaf spring work together to hold the annular lip in an operating configuration on a sliding surface of the second element.

[0007] Furthermore, DE 3606994 A1 also shows a shaft seal with a radially outer static sealing element that can be fitted into a housing opening. The radially outer sealing element is reinforced by a metal ring. The shaft seal also has an inner sealing element with a radially inwardly directed sealing lip that can engage with a rotating shaft to seal it. The inner sealing element is surrounded by a worm spring that exerts a radially inwardly directed preload force, pressing the inner sealing element and the sealing lip formed thereon against the surface of the rotating shaft.

[0008] Further state of the art is shown in DE 21 45 783 A1, which discloses a centrifugal clutch with shaft seal arrangements, or in DE 10 2012 107382 A1, which shows a radial shaft seal for installation in a rapidly rotating hollow shaft.

[0009] This is also the case in DE 102015 103921 A1, which shows a transmission device in the form of a belt drive system for driving a drive shaft of a switchable and switchable unit that can be driven with two different transmission ratios, preferably for use in a harvesting machine. The unit shown has a pair of drive belts driven via drive pulleys, which drive two output pulleys of different diameters associated with the drive shaft.

[0010] The radial shaft seal designs known in the prior art are primarily suitable for gearboxes with static, i.e., stationary, housings. This means gearboxes have housing components into which the shaft seal is fitted and which are not set in motion. In other words, the shaft seal itself is not subject to rotation. However, with gearbox housings that themselves rotate, the problem arises that the shaft seal rotates along with it and is subjected to centrifugal forces. Due to the rotational movement of the shaft seal and the associated centrifugal forces, the preload effect of the coil spring can be partially compensated, causing the coil spring to loosen or detach.pop out, so that the sealing lip can detach from the component to be sealed and the sealing function of the sealing lip is severely impaired or even completely eliminated, since no contact force is exerted on the surface of the rotating shaft by the coil spring.

[0011] The object underlying the invention is seen as being to provide a device of the type mentioned above which can be used in a transmission device with rotatable housing parts, so that the aforementioned problems are overcome.

[0012] The problem is solved according to the invention by the teaching of claim 1. Further advantageous embodiments and developments of the invention are set forth in the dependent claims.

[0013] According to the invention, a gear assembly with a fixing device for a shaft seal of the type mentioned above is designed such that the gear assembly comprises a first gear part rotatable about an axis of rotation, a sealing seat formed in the first gear part, a shaft seal fitted in the sealing seat, and a second gear part extending through the first gear part and the shaft seal and rotatable about the axis of rotation. The first and second gear parts can furthermore be arranged to rotate relative to each other or rotate at the same speed. A sealing lip is formed on the shaft seal, which engages with an outer surface of the second gear part. The sealing lip is pre-tensioned by a spring element arranged on the shaft seal, so that an additional contact pressure of the sealing lip is exerted on the outer surface of the second gear part.The fixing device is arranged in the gear unit such that a retaining ring rotatable about an axis of rotation is provided, which has several pivotably arranged pivot bodies, each pivot body having a pivot bearing through which the retaining ring extends as a pivot axis, each pivot body comprising a first and second pivot arm, each extending from the pivot bearing in directions opposite to the axis of rotation, so that the retaining ring is arranged between the respective pivot arms and a deflection of the respective first pivot arms in a first direction radial to the axis of rotation causes a deflection of the respective second pivot arms in a direction opposite to the first direction radial to the axis of rotation. The second pivot arm of each pivot body pivots towards the second gear part by rotation of the retaining ring.Rotation of the retaining ring exerts a clamping force in the direction of the second gearbox part.

[0014] The pivoting suspension of the swivel bodies on the retaining ring, with opposing axial extensions of the respective swivel arms, ensures that a deflection of one swivel arm in one direction results in a deflection of the opposite swivel arm in the opposite direction. An annular groove is formed in the sealing seat of the first gear component, in which the retaining ring of the fixing device is mounted. The second swivel arm of each swivel body projects into the shaft seal and can be engaged with the spring element by rotating the retaining ring. The mounting in an annular groove axially fixes the retaining ring in the area of ​​the sealing seat. The length of the respective second swivel arms is preferably dimensioned such that they act on the spring element from above in the direction of the axis of rotation, fixing or holding it down by a clamping force.The more pivoting elements are arranged around the circumference of the retaining ring, the more evenly the spring element is loaded around its circumference and the more evenly the sealing lip is pressed against the outer surface of the second gearbox part around its circumference.

[0015] The swivel arms are designed and dimensioned such that the product of the mass of the first swivel arm and the distance of its center of mass from the pivot axis is greater than the product of the mass of the second swivel arm and the distance of its center of mass from the pivot axis. This ensures that a centrifugal force generated by the rotation of the retaining ring around an axis of rotation causes the first swivel arm to deflect radially outward from the axis of rotation. The greater the rotational speed of the retaining ring, the greater the resulting centrifugal force and the associated radial outward deflection of the first swivel arm and radial inward deflection of the second swivel arm, relative to the axis of rotation of the retaining ring.Thus, an increase in the rotational speed of the retaining ring is directly linked to an increase in the force moving the second pivot arm radially inwards towards the axis of rotation. This force presses the second pivot arm onto the spring element, securing it in place. To generate a sufficiently high centrifugal force to produce a resulting contact force on the sealing lip or the coil spring, the pivot elements are preferably made of metal or another castable material with a comparably high density. Alternatively, other manufacturing processes besides casting may be suitable for the pivot elements. For example, they can also be produced by stamping or forging.

[0016] The spring element arranged on the shaft seal can be designed as a coil spring, worm spring, or ring spring, although other types of spring elements can also be used that exert a radially inward contact force on the sealing lip towards the second gear component. A coil spring, worm spring, or ring spring is a circular ring formed from a wound compression spring that is bent into a circle and connected at both ends. A coil spring generates a radial force directed towards its center as the radius of the coil spring increases. In other words, a coil spring, worm spring, or ring spring is closed around its circumference and acts similarly to a rubber band.

[0017] The sealing seat of the first gear component features recesses distributed around its circumference, designed to allow the first pivot arm of each pivoting element to move into them. These recesses enable the respective first pivot arms to pivot radially outwards. The greater the centrifugal force pushing the pivot arms outwards, the further they protrude into the recesses. In other words, as the rotational speed of the retaining ring or the first gear component increases, so does the extent to which the first pivot arms protrude into the recesses. Simultaneously, this also increases the degree to which the respective second pivot arms press against the spring element, thereby exerting a clamping force and securing it in place.

[0018] The transmission assembly can be designed as a toothed belt drive, and the first transmission component can be non-rotatably connected to a first pulley of the toothed belt drive. Other transmission assemblies that utilize shaft seals can also be equipped with the aforementioned fixing device. This is advantageous when the sealing function of the sealing lip is compromised by rotation of the shaft seal. In this way, when the shaft seal rotates, the rotating retaining ring or the pivoting elements of the fixing device attached to it can secure the spring element and ensure a contact force on the sealing lip, thus guaranteeing its reliable sealing function.

[0019] The second transmission component can be axially displaceable and rotationally fixed to an output shaft of the toothed belt drive. This allows for a rotationally fixed connection between the second transmission component and the output shaft, while the axial displacement of the second transmission component enables its connection to various other rotating transmission components, such as different gear stages or differently driven rotating bodies. This allows for different output shaft speeds to be achieved.

[0020] The second transmission component can preferably be connected to either the first pulley or a second pulley of the toothed belt drive in a rotationally fixed manner by axial displacement. The pulleys can, for example, have different diameters and both be connected to the same output shaft in rotation. This allows for the creation of different gear ratios and thus different speeds and torques at the output shaft.

[0021] With reference to the drawing, which shows an embodiment of the invention, the invention as well as further advantages and advantageous developments and embodiments of the invention are described and explained in more detail below.

[0022] It shows: Fig. 1a a schematic perspective view of a fixing device according to the invention, Fig. 1b a schematic perspective view of a retaining ring of the fixing device made of Fig. 1a, Fig. 1 a schematic perspective view of a top side of a swivel body of the fixing device made of Fig. 1a , Fig. 1 your schematic perspective view of a bottom side of the swivel body made of Fig. 1c Fig. 2a a schematic perspective partial cross-sectional view of a shaft seal, Fig. 2b a schematic perspective view of an assembly of the shaft seal made of Fig. 2a with the fixing device from Fig. 1a , Fig. 2 a schematic perspective view of an assembly consisting of a shaft seal and a fixing device made of Fig. 2b In an exemplary gearbox part, Fig. 3 shows a schematic perspective cross-sectional view of a segment of an assembly consisting of a shaft seal and a fixing device. Fig. 2b in a first and a second gear section, Fig. 4 a schematic cross-sectional view of a gear assembly with shaft seal and fixing device made of Fig. 2b, Fig. 5 an enlarged part of the cross-sectional view from Fig. 4 and Fig. 6 a schematic perspective view of the gear assembly from Fig. 4 .

[0023] One in the Figures 1a to 1d The illustrated fixing device 10 for a shaft seal 12 comprises a retaining ring 14 and several pivoting bodies 16 arranged on the circumference of the retaining ring 14. The retaining ring 14 is shown separately in Figure 1b The device is depicted and consists of a round or circular profile (or wire) whose ends are joined around a rotational axis 18 to form a ring. The retaining ring 14, with its longitudinal central axis, forms a pivot axis 20 for the several pivoting bodies 16, which pass through an opening 22 formed between the ends of the ring ( Figure 1b ) inserted into the retaining ring 14 and pivotably suspended or mounted on it, as in particular Figure 1aThe retaining ring is rotationally symmetrical about the axis of rotation 18.

[0024] At the in Figure 1a In the illustrated embodiment, eight pivoting bodies 16 are arranged pivotably distributed around the circumference of the retaining ring 14, the number of which is variable and the number of pivoting bodies 16 distributed around the circumference can also be varied. Further details are described in the Figures 1c and 1dAs shown, each pivot body 16 comprises a pivot bearing 24, a first pivot arm 26, and a second pivot arm 28. The pivot bearing 24 includes a through-opening 30 with a circular cross-section and a diameter dimensioned according to the diameter of the retaining ring 14, and an arc-shaped longitudinal profile, such that a center line 32 extending through the pivot bearing 24 forms a circular arc of the retaining ring 14. Extending from the pivot bearing 24 in a first direction towards the axis of rotation 18 is the first pivot arm 26, and in an opposite second direction towards the axis of rotation 18 is the second pivot arm 28. The first pivot arm 26 is designed as a cylindrical extension. The second pivot arm 28 is designed as a T-shaped extension.The first and second pivot arms 26, 28 are designed such that the product of the distance of the center of mass of the first pivot arm 26 to the pivot axis 20 on the retaining ring 14 and the mass of the first pivot arm 26 is greater than the product of the distance of the center of mass of the second pivot arm 28 to the pivot axis 20 on the retaining ring 14 and the mass of the second pivot arm 28. This ensures that when the retaining ring 14 rotates about the axis of rotation 18, the torque about the pivot axis 20 generated by the centrifugal force of the first pivot arm 26 is greater than the torque generated by the centrifugal force of the second pivot arm 28, so that the first pivot arm 26 is moved radially outwards about the axis of rotation 18 and the second pivot arm 28 is moved radially inwards about the axis of rotation. The second pivot arm 28 has a [missing information - likely a specific feature or characteristic] parallel to the pivot axis 20 or...swivel arm part 34 formed towards the center line 32, with an arc-shaped course, wherein a retaining groove 36 is further formed on the side of the swivel arm part 34 facing the axis of rotation 18, as shown in . Figure 1d can be seen.

[0025] The swivel bodies 16 are preferably made of metal, in particular of a cast iron material. The higher the density of the material, the stronger the leverage effect of the swivel bodies 16 can be, and thus also the fixing effect of the fixing device.

[0026] In the Figure 2aFigure 12 shows a conventional shaft seal 12, as used in the embodiment described here. Such a shaft seal 12 comprises an annular elastomeric part 38, which is designed as a U-profile and formed into a ring around an axis of rotation 18. An open side 40 of the U-profile points in one axial direction and a closed side 42 of the U-profile points in the opposite axial direction of the axis of rotation 18, resulting in an outer leg 44 and an inner leg 46 of the U-profile relative to the axis of rotation 18. In the region of the outer leg 44 and the closed side 42 of the U-profile, the elastomeric part 38 is formed with an annular stiffening element 48, which is embedded in the elastomeric part 38 and provides the shaft seal 12 with the necessary stability and rigidity.On the side of the inner leg 46 facing the axis of rotation 18, an annular sealing lip 50 is formed in the form of a ring-shaped protrusion directed radially towards the axis of rotation 18. On the side of the inner leg 46 facing away from the axis of rotation 18, at the same location axially to the axis of rotation 18, an annular groove is formed in which a spring element 52 in the form of a coil spring (also called a ring or worm spring) is embedded. The spring element 52 causes the sealing lip 50 to be pre-tensioned radially in the direction of the axis of rotation 18. At a transition area between the closed side 42 and the inner leg 46 of the U-profile, a protective lip 54 is also formed, which extends obliquely in an annular shape both axially towards the closed side 42 of the U-profile and radially towards the axis of rotation 18.

[0027] In the Figures 2b and 2cis shown how the fixing device 10 described above is used with a commercially available and conventional shaft seal 12 according to Figure 2a interacts. For this purpose, the fixing device 10 and the shaft seal 12 are inserted or fitted into a first gear part 56 of a gear assembly 58, which is described in more detail below, and which is to be sealed. How particularly well in Figure 3As can be seen, a sealing seat 60 is formed in the first gear part 56, in which the sealing shaft seal 12 is fitted and received. Adjoining the sealing seat 60, a retaining ring groove 62 is formed in the first gear part 56, into which the retaining ring 14 of the fixing device 10 is inserted or fixed. Corresponding to the number and position of the pivoting elements 16 provided on the fixing device 10, recesses 64 are formed on the first gear part 56 at the same axial position relative to the axis of rotation 18. These recesses extend radially outwards towards the axis of rotation 18 and axially into the interior of the gear unit. The recesses 64 are dimensioned such that space and pivoting room are created for the pivoting elements 16 of the fixing device 10, allowing them to pivot freely and enabling the retaining ring 14 to be fixed in the retaining ring groove 62. For sealing the gear unit 58, or rather...a rotatable first gear part 56 and a second rotatable gear part 66 of the gear unit 58 mounted therein, see also . Figures 3 to 6First, the fixing device 10 with the first pivot arms 26 is inserted (pointing into the inner area of ​​the gear assembly) so that the retaining ring 14 is embedded in the retaining ring groove 62. This fixes the fixing device 10 and thus the pivoting elements 16 in the first gear part 56, and the pivoting elements 16 are pivotably received in the recesses 64 formed in the first gear part 56. The shaft seal 12 can then be inserted or fitted into the seal seat 60, with the second pivot arms 28 of the fixing device 10 projecting into the interior of the shaft seal 12 at the open side 40 of the shaft seal 12. The second pivot arms 28, with their pivot arm sections 34 and the retaining grooves 36 formed thereon, engage the spring element 52, pressing and fixing it in place, which is particularly evident in Figure 2b and Figure 3This can be seen. The protective lip 54 is dimensioned in such a way that it seals an annular gap between the elastomer part 38 and the second gear part 66 against penetrating dirt particles from the outside.

[0028] In the Figures 4 to 6 The gear assembly 58, including the shaft seal 12 and the locking device 10 for sealing the rotatable first gear part 56 against the also rotatable second gear part 66, is shown in detail. The locking device 10 and the shaft seal 12 are arranged in the first gear part 56 as described above. In this example, the gear assembly 58 is designed as part of a toothed belt drive (not shown) and comprises a first pulley 68 and a second pulley 70 as drive elements, wherein the first and second pulleys 68 and 70 are each driven or set in rotation by a belt of the toothed belt drive (not shown).

[0029] The first gear unit 56 is rotationally fixed to the first pulley 68. The first pulley 68 is rotatably mounted on a bearing flange 74 formed on the second pulley 70 via a ball bearing set 72 and is axially fixed. The second gear unit 70 is rotatably mounted on an output shaft 78 via another ball bearing set 76 and is axially fixed. The second gear unit 66 is axially displaceable on an external toothing 80 formed on the output shaft 78, the second gear unit 66 being provided as a shift hub or shift sleeve with internal teeth 82 and external teeth 84. The internal teeth 82 of the second gear unit 66 are complementary to the external teeth 80 on the output shaft 78, thus ensuring a rotationally fixed connection and axial displaceability.Both the first gear part 56 and the second pulley 70 each have internal teeth 86, 88, wherein the internal teeth 86 on the first gear part 56 and the internal teeth 88 on the second pulley 70 can be selectively brought into rotational contact with the external teeth 84 formed on the second gear part 66 by axially displacing the second gear part 56, and thereby a drive connection can be selectively established between the first pulley 68 and the output shaft 78 or between the second pulley 70 and the output shaft 78.Furthermore, the axial distance between the internal toothing 86 on the first gear part 56 and the internal toothing 88 on the pulley is chosen such that the second gear part 66 can be moved axially into an intermediate position in which the external toothing 84 on the first gear part 56 can be positioned between the two internal toothings 86 and 88, so that an idle position can be achieved in which neither the first gear part 56 nor the second pulley 70 is in rotational connection with the drive shaft 78.At one end of the second gear part 56, which protrudes from the gear assembly 58, an adjusting knob 90 is formed, by means of which a manual axial displacement of the second gear part 66 can be initiated, whereby by axial displacement of the second gear part it is possible to select between a switching position for connection with the first pulley 68, for connection with the second pulley 70 or for idle.

[0030] The output shaft 78 is designed as a hollow shaft with further internal teeth 92 and engages with further external teeth 94, which are formed on a drive shaft 96 of a device or assembly (not shown) to be driven by the transmission unit 58, for example, a shredder, cutter, blower, or conveying device, which can be driven at different speeds. The latter is achieved by the pulleys 68, 70 having different diameters, thus achieving different gear ratios. Furthermore, the transmission unit 58 is provided with a dirt-repellent sealing sleeve 98, which is placed on the second transmission part 66 at the transmission opening and additionally covers the shaft seal 12 and protects it against external contamination (see in particular...). Figures 5 and 6 ).

[0031] The fixing device 10 for the shaft seal 12 comes into play particularly when the first gear part 56, and thus also the shaft seal 12, is set into rotation by driving the first pulley 68. Due to rotation, the shaft seal 12 is subjected to centrifugal forces, and there is a risk that the spring element 52 arranged in the shaft seal 12, which exerts a contact force on the sealing lip 50 and ensures a certain degree of tightness between the sealing lip and the second gear part 66, will detach or that the contact force of the spring element 52 will be reduced by the effect of the centrifugal forces. The pivoting elements 16 formed on the fixing device 10 ensure that the contact force or fixing force on the spring element 10 increases with increasing centrifugal force, whereby the first pivoting arms 26, which are pivoted outwards into the recesses 64 by the centrifugal force, prevent the second pivoting arms 28 from pivoting.The pivot arm parts 34 formed on the second pivot arms 28 cause the spring element to be pressed against and fixed in place. This prevents the spring element from loosening or the contact force on the sealing lip 50 from decreasing, even at high speeds.

Claims

1. Transmission device (58) having a first transmission part (56) which is rotatable about an axis of rotation (18), a sealing seat (60) formed in the first transmission part (56), a shaft sealing ring (12) fitted in the sealing seat (60) and a second transmission part (66) which extends through the first transmission part (56) and the shaft sealing ring (12) and is rotatable about the axis of rotation (18), a sealing lip (50) being formed on the shaft sealing ring (12), said sealing lip engaging with an outer surface of the second transmission part (66) and being pretensioned by a spring element (52) arranged on the shaft sealing ring (12), furthermore, a fixing device (10) for the shaft sealing ring (12) being provided, having a retaining ring (14) which is rotatable about an axis of rotation (18) and a plurality of pivot bodies (16) arranged pivotably on the retaining ring (14), wherein each pivot body (16) has a pivot bearing (24) through which the retaining ring (14) extends as a pivot axis (32), wherein each of the pivot bodies (16) comprises a first and second pivot arm (26, 28) which each extend from the pivot bearing (24) in opposite directions axially with respect to the axis of rotation (18) such that the retaining ring (14) is arranged between the pivot arms (26, 28) and a deflection of the first pivot arm (26) in a first direction radially with respect to the axis of rotation (18) causes a deflection of the second pivot arm (28) in a direction opposite to the first direction radially with respect to the axis of rotation (18), wherein, by rotation of the retaining ring (14), the second pivot arm (28) of each pivot body (16) exerts a contact force in the direction of the second transmission part (66), characterized in that an annular groove (62) is formed in the sealing seat (60) of the first transmission part (56), in which annular groove the retaining ring (14) of the fixing device (10) is mounted in such a manner that the second pivot arm of each pivot body (16) protrudes into the shaft sealing ring (12) and can be brought into engagement with the spring element (52) by rotation of the retaining ring (14) in such a manner that the respective second pivot arm (28) presses against the spring element (52) and acts upon and fixes the latter with a contact pressure force.

2. Transmission device (58) according to Claim 1, wherein the product of the mass of the first pivot arm (26) and the distance of the mass centre of gravity of the first pivot arm (26) from the pivot axis (32) is greater than the product of the mass of the second pivot arm (28) and the distance of the mass centre of gravity of the second pivot arm (28) from the pivot axis (32), and therefore a centrifugal force arising by rotation of the retaining ring (14) about an axis of rotation (18) causes the first pivot arm (26) to be deflected radially outwards with respect to the axis of rotation (18).

3. Transmission device (58) according to Claim 1 or 2, wherein the spring element (52) arranged on the shaft sealing ring (12) is designed as a tube spring or worm spring.

4. Transmission device (58) according to any one of Claims 1 to 3, wherein recesses (64) distributed over the circumference of the sealing seat (60) are formed in the sealing seat (60) of the first transmission part (56) in such a manner that the first pivot arm (26) of each pivot body (16) is movable into the recesses (64).

5. Transmission device (58) according to any one of Claims 1 to 4, wherein the transmission device (58) is designed as a toothed belt transmission and the first transmission part (56) is connected to a first belt pulley (68) of the toothed belt transmission for rotation therewith.

6. Transmission device (58) according to Claim 5, wherein the second transmission part (66) is connected to an output shaft (78) of the toothed belt transmission in an axially displaceable manner and for rotation therewith.

7. Transmission device (58) according to Claim 6, wherein the second transmission part (66) is connectable by axial displacement either to the first belt pulley (68) or to a second belt pulley (70) of the toothed belt transmission for rotation therewith.