Dry drive device with variable transmission

Abstract

Variable speed drive device (10) comprising the following: a rotatable drive shaft (14); a fixed drive disc (16) which is fixed relative to the drive shaft (14) and is attached for rotation with the drive shaft (14); a movable drive disc (20) which is mounted for axial movement relative to the drive shaft (14); a plurality of drive fingers (28) extending axially from one of the drive disks (16), each drive finger (28) defining a finger contact (56) and each drive finger (28) with its finger contact (56) being formed integrally with the drive disk (16) from a single piece of material; and a plurality of recesses (38) in the other drive disk (20), wherein each drive finger (28) is movably received by a corresponding recess (38), and wherein each recess (38) defines a recess contact (88) which slidably engages in the corresponding finger contact (56), wherein the recess contact (88) is a surface of the recess (38) at which the drive finger (28) comes into contact with the recess (38) when a torque is transmitted from the fixed drive disk (16) to the movable drive disk (20), wherein a torque can be transmitted from the fixed drive disk (16) to the movable drive disk (20) by the engagement of the finger contact (56) of the drive finger (28) in the recess contact (88).

Description

Territory of Revelation

[0001] The present disclosure relates to a drive device with variable transmission and thus a variable speed. Background of the Revelation

[0002] Current variable-speed drive systems typically include a fixed drive pulley and a movable drive pulley coupled to a drive shaft via splined connections. This splined connection must be regularly lubricated with a lubricant, such as oil or grease. Seals are required for the translational movement of the parts to retain the lubricant along the splined interface. If the lubricant leaks through the seals, the resulting lubricant loss leads to premature splined wear. Furthermore, leaking lubricant often comes into contact with one or more V-belts, causing premature V-belt wear.

[0003] Other variable fan drives utilize drive fingers in one of the drive pulleys and corresponding recesses in the other drive pulley to rotatably couple the fixed drive pulley to the movable drive pulley. The drive fingers incorporate a wear element positioned between the drive finger and the recess.

[0004] Variable fan drives, in which either the lubricated wedge connections or the wear elements are implemented, must be maintained and monitored to ensure that the fixed drive pulley and the movable drive pulley mesh cleanly with each other or with the drive shaft.

[0005] A variable-speed drive mechanism is known from DE 10 2015 201 860 A1 and US 3 375 738 A. AT 517594 A4 further describes a drive device with a variable transmission. US 2002 / 0 155 909 A1 discloses a continuously variable, belt-driven transmission comprising a drive pulley assembly, a driven pulley assembly, and a V-shaped belt that engages between these components to transmit the torque. US 4 504 022 A discloses an extendable feed roller having two separate, adjacent discs mounted on a rotatable drive shaft. Each disc has circumferentially spaced ribs that extend inward toward the other disc and are inclined toward the shaft. The ribs of the two discs are interlocked to form a threaded recess between them.One of the discs is fixed to the shaft, while the other can be moved axially along the shaft toward and away from the other disc to change the effective circumference of the base of the line-receiving groove between the discs. A spring pushes the two discs apart against an adjusting mechanism that can be actuated to change the relative axial positions of the discs as the drive shaft rotates. US Patent 4,398,899 A discloses a variable-speed, wide-range pulley or belt pulley specifically designed for self-propelled lawn mowers. The variable-speed pulley is mounted on a drive shaft of a transmission in the form of a transaxle or power transmission unit on the lawn mower and is driven by a belt connected to the drive shaft of the lawn mower engine. Summary

[0006] One embodiment of the present disclosure is a variable-speed drive device comprising a rotatable drive shaft, a drive disk fixed relative to the drive shaft and for rotation with it, a movable drive disk mounted for axial movement relative to the drive shaft, a plurality of drive fingers extending axially from one of the drive disks, each of the drive fingers defining a finger contact, and a plurality of recesses in the other drive disk, each of the drive fingers being movably received by a corresponding recess, and each recess defining a recess contact that slidably engages in the corresponding finger contact.

[0007] Another embodiment is a variable drive comprising a rotatable drive shaft, a fixed drive disk which is axially fixed relative to the drive shaft and mounted for rotation with the drive shaft, a movable drive disk which is mounted for axial movement relative to the drive shaft, a plurality of drive fingers extending from one of the drive disks, each drive finger defining a finger contact, and a plurality of recesses in the other drive disk, each recess defining a recess contact. Each drive finger is movably received by a corresponding recess, and the finger contact slidably engages in the corresponding finger contact. Furthermore, at least one of the finger contact or the recess contact has been hardened by a surface treatment.

[0008] Another embodiment is a method for manufacturing a fixed drive pulley and a movable drive pulley for a variable-speed drive device, comprising forming a first drive pulley by shaping a first material to define a first flange engaging with the belt and at least one drive finger defining a finger contact; forming a second drive pulley by shaping a second material to define a second flange engaging with the belt and at least one recess defining a recess contact; curing the first or second material of the respective finger contact or recess contact by a surface treatment; fixing one of the drive pulleys to a drive shaft; and positioning at least one section of the drive finger in the recess.where the finger contact is slidably engaged in the recess contact. Brief description of the drawings

[0009] The above-mentioned aspects of the present disclosure and the manner of its implementation become clearer, and the disclosure becomes more understandable, when one refers to the following description of the embodiments of the disclosure in connection with the accompanying drawings, wherein: Fig. 1 is an elevated perspective view of a variable belt drive arrangement; Fig. 2 a cross-sectional view of the variable belt drive arrangement Fig. 1 is; Fig. 3 an extended view of the variable belt drive arrangement from Fig. 1 is; Fig. 4 is an isolated perspective view of a fixed drive pulley; Fig. 5 a top view of the fixed drive pulley Fig. 4 is; Fig. 6 an isolated top view of a finger from the fixed drive pulley Fig. 4 is; Fig. 7 an isolated side view of the finger from Fig. 6 is; Fig. 8 is an isolated perspective view of a moving drive pulley; Fig. 9 a top view of the movable drive pulley Fig. 8 is; Fig. 10 a sectional view through a recess of the movable drive pulley Fig. 8 is; Fig. 11 a sectional view of the variable belt drive arrangement from Fig. 1 is; and Fig. Figure 12 shows an extended sectional view of a shaft and the movable drive pulley.

[0010] The same reference numbers are used in the different views to identify the corresponding parts. Detailed description

[0011] With reference to Fig. 1 and Fig. Figure 2 shows an embodiment of a variable-speed belt drive 10 as a drive device. The variable-speed belt drive 10 can include a housing 12 which supports a rotating drive shaft 14. A fixed drive pulley 16 can be attached to one end of the drive shaft 14, for example by bolts 18, and a drive wheel 54 can be coupled to another end of the drive shaft 14 opposite the fixed drive pulley 16. The fixed drive pulley 16 is thus mounted for rotation with the drive wheel 54 and the drive shaft 14 about an axis 62 defined by the drive shaft 14. A movable drive pulley 20 can be mounted for axial movement relative to the drive shaft 14.The movable drive disc 20 can be fixed to the drive shaft 14 by means of one or more drive fingers 28, as described in more detail below, by means of the fixed drive disc 16.

[0012] With reference to now Fig. Figure 3 includes the fixed drive pulley 16, a central hub 22 which has bolt-receiving bores 23 extending through it, and a flange 24 engaging a belt, which surrounds the hub 22. The drive fingers 28 project axially from the fixed drive pulley 16 and in the direction of the movable drive pulley 20.

[0013] The movable drive pulley 20 includes an axially extending central hollow hub 30 and a flange 32 that engages the belt and surrounds the hub 30. The hub 30 forms a first and a second bearing element 34 and 36, which receive the shaft or drive shaft 14. The hub 30 also includes a plurality of spaced-apart recesses 38. The recesses 38 are open in one direction towards the fixed drive pulley 16 and extend axially into the hub 30 and away from the fixed drive pulley 16.

[0014] Each drive finger 28 is movably received by a corresponding recess 38. More precisely, the fixed drive disc 16 can be rigidly coupled to the drive shaft 14 by one or more bolts 18. In this configuration, when the drive shaft 14 rotates, the fixed drive disc 16 can also rotate, since it is rigidly coupled to it.

[0015] In one embodiment, a primary drive can exert a torque on the drive wheel 54. The drive wheel 54 can be coupled to the drive shaft 14 via splines or otherwise, and transmit the exerted torque from the primary drive through the drive shaft 14 and into the fixed drive disc 16. The fixed drive disc 16 can transmit the torque to the movable drive disc 20 through contact between the drive fingers 28 and the recesses 38.

[0016] One aspect of the present disclosure is the ability of the movable drive disk 20 to slide axially along the drive shaft 14 relative to the fixed drive disk 16 while rotating with it. In other words, the movable drive disk 20 can be axially spaced from the fixed drive disk 16 at various distances along the drive shaft 14 while still transmitting sufficient torque through the drive fingers 28 and the recesses 38 to rotate the movable drive disk 20 with the fixed drive disk 16. In this embodiment, the drive fingers 28 can be inserted into the recesses 38 on a finger contact 56 (see Figure 1). Fig. 4) The central hub 30 can engage the drive shaft 14 at the corresponding bearing elements 34, 36. The finger contact 56 can be located at the top of the drive finger 28, which engages in a corresponding section of the recess 38 when a torque is applied to the fixed drive disc 16. Accordingly, the movable drive disc 20 can come into contact with the drive shaft 14 at the corresponding bearing elements 34, 36, and the fixed drive disc 16 at the corresponding finger contacts 56, when the movable drive disc 20 moves axially along the drive shaft 14.

[0017] The central hub 30 can also have a first seal 58 and a second seal 60 positioned at each end of the central hub 30. The first and second seals 58, 60 essentially prevent foreign matter from entering the space between the drive shaft 14 and the central hub 30. More precisely, the respective seal 58, 60 can extend from the central hub 30 or another section of the movable drive disc 20 and be in contact with the outer surface of the drive shaft 14. In this configuration, as the movable drive disc 20 moves along the drive shaft 14, the respective seals 58, 60 slide along the outer surface of the drive shaft 14, removing any foreign matter that may be present on it.In one aspect of the present embodiment, the seals 58, 60 can essentially prevent foreign bodies from entering between the corresponding bearing elements 36, 40.

[0018] While the embodiment shown here depicts the first and second seals 58, 60 coupled to the central hub 30, this disclosure is not limited to the inclusion of seals at all. More precisely, the movable hub or drive disc 20 may not have any first and second bearing elements 34, 36. Rather, the central hub 30 may have an inner diameter larger than the outer diameter of the drive shaft 14. In this configuration, a gap may exist between the outer surface of the drive shaft 14 and the inner surface of the central hub 30. The gap between the drive shaft 14 and the central hub 30 may be large enough to accommodate foreign bodies without substantially impairing the axial movement of the movable drive disc 20 relative to the fixed drive disc 16.

[0019] With reference to Fig. Figure 4 now shows a non-exclusive arrangement of the drive fingers 28. In the Fig. In the embodiment shown in Figure 4, four drive fingers 28 can be shown, arranged radially spaced about the axis 62. Each of the drive fingers 28 can extend axially from the fixed drive disk 16 and define a leading edge 64 and a trailing edge 66. The leading edge 64 can be the leading edge of the corresponding drive finger 28 as the fixed drive disk 16 rotates with the drive shaft 14. In a non-limiting example, the drive finger 28 shown in Figure 4 can be arranged in a different configuration. Fig. The fixed drive pulley 16 shown in section 4 is designed to be positioned relative to the drive pulley shown in the diagram. Fig. The perspective shown in Figure 4 shows the drive fingers 28 rotating counterclockwise in a 68-degree direction. Accordingly, when the drive fingers 28 are positioned in the corresponding recesses 38 and a torque is applied to the fixed drive disk 16, said torque can be transmitted to the movable drive disk 20 essentially through the finger contact 56 of the corresponding drive fingers 28. In this configuration, the finger contact 56 can be the only section of the fixed drive disk 16 and the drive shaft 14 that essentially transmits the torque to the movable drive disk 20.

[0020] With reference to Fig. Figure 5 now shows the radial positioning of each drive finger 28 more clearly. More precisely, each drive finger 28 can be positioned along a first radius 70 from the axis 62. Furthermore, each drive finger 28 can have an essentially arc-shaped profile between the corresponding front and rear edges 64, 66. The essentially arc-shaped profile of the drive fingers 28 can have a radius that is exactly or approximately equal to the first radius 70. The arc-shaped profile of the drive fingers 28 allows the drive fingers 28 to move freely in the corresponding recesses 38 until the finger contact 56 engages in the corresponding section of the recess 38. In other words, the arc-shaped profile of the drive fingers 28 can define an arc axis that is coaxial with the axis 62 about which the drive disks 16, 20 rotate.Accordingly, the drive fingers 28 of the fixed drive disc 16 do not connect to the movable drive disc 20 or otherwise engage with it until the finger contact 56 of the front edge 64 engages the corresponding surface of the recess 38 during a counterclockwise movement 68.

[0021] With reference to Fig. Figure 6 now shows an enlarged isolated view of one of the drive fingers 28. More precisely, a profile of the front edge 72 at the finger contact 56 is shown. In the Fig. In the embodiment shown in Figure 6, the profile of the front edge 72 is substantially arcuate. The arcuate shape of the profile of the front edge 72 can be defined about a leading edge axis 74. Furthermore, the leading edge axis 74 can be defined on or in close proximity to the first radius 70. In this embodiment, the profile of the front edge 72 can increase the surface area of ​​the finger contact 56 compared to a substantially straight profile of the front edge 72. In a non-limiting example of the present disclosure, an increase in the surface area of ​​the finger contact 56 can enable a more favorable wear rate of the finger contact 56. Furthermore, by positioning the leading edge axis 74 close to the first radius 70, the arcuate profile of the front edge 72 can be oriented such that it exerts a counterclockwise rotational torque 68.

[0022] While an arcuate profile of the front edge 72 has been shown and described above, this disclosure is not limited to such an embodiment. While the arcuate profile of the front edge 72 has been further compared with a straight profile of the front edge 72, an embodiment of the present disclosure can be described instead of the one described in Fig. In addition to the arcuate profile of the front edge 72 shown in Figure 6, a straight profile of the front edge 72 can be used. Furthermore, any other profile of the front edge 72 is also considered herein. In other embodiments, the profile of the front edge 72 can have a triangular, oval, octagonal, or similar shape. Those skilled in the art in this field will further understand that, with regard to this disclosure, other profiles of the front edge can also be used.

[0023] The trailing edge 66 of the drive finger 28 can be inclined relative to a base section 76 of the fixed drive disk 16. In one embodiment, the drive finger 28 can have an upper width 78 that is less than its lower width 80. The leading edge 64 can be substantially perpendicular to the base section 76, while the inclined trailing edge 66 extends to a height 82 of the drive finger 28 between the lower width 80 and the upper width 78. The inclined trailing edge 66 and the overall dimensions of the drive finger 28 can be large enough to transmit a torque from the fixed drive disk 16 to the movable drive disk 20 without shearing or otherwise deforming the drive finger 28. Accordingly, while the trailing edge 66 has been shown and described as inclined, such a configuration is not limiting.In other embodiments, the trailing edge 66 can be perpendicular to the base section 76. Accordingly, many different orientations for the trailing edge 66 are possible, and no particular orientation is restrictive.

[0024] With reference to Fig. Figure 8 shows a perspective view of the movable drive disc 16. In particular, the recesses 38 are shown spaced radially apart around the axis 62. In the non-restrictive embodiment from Fig. Figure 8 shows four recesses 38 which are connected to the four drive fingers 28. Fig. 4. However, this disclosure is not limited to a specific number of recesses 38 or drive fingers 28. In other embodiments, there may be only one recess 38, which corresponds to only one drive finger 28. In another embodiment, there may be more than ten recesses 38, which correspond to more than ten drive fingers 28. Accordingly, the exact number of drive fingers 28 and recesses 38 is not limiting.

[0025] The radial space between the recesses 38 can essentially resemble the radial space between the drive fingers 28, as shown in Fig. Figure 9 illustrates this. More precisely, each recess 38 can have an arc-shaped profile defined along an arc of the first radius 70. Furthermore, each of the recesses 38 can define a leading edge 84 and a trailing edge 86. The leading edge 84 and the trailing edge 86 of the recess 38 can coincide with the leading edge 64 and the trailing edge 66 of the corresponding drive finger 28 if the drive finger 28 is at least partially positioned in the recess 38.

[0026] Fig. Figure 10 shows a side profile cross-sectional view of recess 38. More precisely, in Fig. Figure 10 shows the leading edge 84 and the trailing edge 86 of the recess 38 more clearly. The leading edge 84 of the recess 38 is of a suitable size to accommodate the leading edge 64 of the corresponding drive finger 28. Furthermore, the leading edge 84 of the recess 38 can define a recess contact 88, which can engage with the finger contact 56 of the drive finger 28. The recess contact 88 can be a surface of the recess 38 where the drive finger 28 comes into contact with the recess 38 when a torque is transmitted from the fixed drive disk 16 to the movable drive disk 20. Accordingly, by the engagement of the finger contact 56 with the recess contact 88, a torque can be transmitted from the fixed drive disk 16 to the movable drive disk 20.

[0027] With reference to Fig. 11 and Fig. Figure 12 shows a first and a second shaft contact 90, 92. The first and the second shaft contact 90, 92 can be areas along the outer surface of the drive shaft 14 that can come into contact with the first and second bearing elements 34, 36 of the movable drive pulley 20. In the embodiment shown and described herein, the movable drive pulley 20 can move axially along the drive shaft 14 to adapt the variable-speed belt drive 100. During axial movement, the movable drive pulley 20 can slide axially along or near the drive shaft 14 towards or away from the fixed drive pulley 16. Furthermore, the movable drive pulley 20 can move between a minimum axial distance from the fixed drive pulley 16 (the minimum axial distance is not shown) and a maximum axial distance from the fixed drive pulley 16, as shown in Fig.11 shown.

[0028] The section of the outer surface of the drive shaft 14 adjacent to the respective first and second bearing elements 34, 36 can vary depending on the axial position of the movable drive disk 20 relative to the fixed drive disk 16. Accordingly, the first and second shaft contacts 90, 92 can have an axial width greater than the width of the first and second bearing elements 34, 36, to ensure that the first and second bearing elements 34, 36 are positioned close to the respective first and second shaft contacts 90, 92, regardless of the axial position of the movable drive disk 20 relative to the fixed drive disk 16.

[0029] In one embodiment, the first and second bearing elements 34, 36 and the corresponding first and second shaft contacts 90, 92 can be essentially in contact with each other. In this configuration, when the movable drive disk 20 slides axially along the drive shaft 14, the first and second bearing elements 34, 36 slide along the outer surface of the drive shaft 14 along the first and second shaft contacts 90, 92.

[0030] However, in another embodiment, the bearing elements 34, 36 may essentially not come into contact with the drive shaft 14, regardless of the axial position of the movable drive disc 20 relative to the fixed drive disc 16. In this embodiment, the bearing elements 34, 36 may be spaced from the outer surface of the drive shaft 14 and therefore may not come into direct contact with the drive shaft 14. In this configuration, no bearing elements 34, 36 may be defined in the movable drive disc 20 at all. Furthermore, the first and second shaft contacts 90, 92 may not be positioned on the drive shaft 14. In other words, in an embodiment in which the movable drive disc 20 is essentially not in direct contact with the drive shaft 14, the bearing elements 34, 36 and shaft contacts 90, 92 may not be required.

[0031] In one aspect of the present disclosure, the material positioned along the finger contact 56 and the recess contact 88 can be configured to interlock and transmit a torque from the fixed drive disc 16 to the movable drive disc 20 without the need for additional lubricants or other materials. More specifically, in one embodiment, the fixed drive disc 16 and the movable drive disc 20 can be made of a material that can be hardened. In another embodiment, a surface treatment can be applied at least to the finger contact 56 and the recess contact 88 to harden the respective surfaces. Any type of surface treatment, such as heat treatment or case hardening, can be applied to the finger contact 56 and the recess contact 88 to extend the service life of the respective surfaces during use.In one embodiment, the finger contact 56 and the recess contact 88 can be made of ADI (bainitic spheroidal graphite cast iron). In this embodiment, the bainitic treatment of the finger contact 56 and the recess contact 88 can form a surface with increased wear resistance. Hardening the finger contact 56 and the recess contact 88 can improve the service life of the corresponding finger and recess contacts 56, 88 without requiring additional maintenance steps such as applying grease or other lubricants to the finger and recess contacts 56, 88.

[0032] While ADI has been described as a surface treatment method for hardening the finger contact 56 and the recess contact 88, this disclosure is not limited to such a method. Any form of heat treatment, case or surface hardening, laser hardening, or the like can be applied to the finger contact 56 and the recess contact 88.

[0033] Similarly, in an embodiment where the first and second bearing elements 34, 36 are arranged in contact with or near the corresponding first and second shaft contacts 90, 92, a hardening surface treatment can be applied to the bearing elements 34, 36 and the shaft contacts 90, 92. By hardening the surface of the bearing elements 34, 36 and the shaft contacts 90, 92, the application of grease or other lubricants to these surfaces may be unnecessary while maintaining the same wear resistance.

[0034] In one embodiment, the fixed drive disc 16 and the movable drive disc 20 can be cast parts. In this embodiment, after casting the fixed drive disc 16 and the movable drive disc 20, a machining process can perform additional forming steps on the fixed drive disc 16 and the movable drive disc 20. If the fixed drive disc 16 and the movable drive disc 20 have the appropriate shape, a hardening process can be performed on the finger contact 56 and the recess contact 88. Alternatively, in another embodiment, the hardening process can be performed on the entire fixed drive disc 16 and the movable drive disc 20. The hardening process can be at least one of the hardening processes described above, but it is not limited to these hardening processes.Any process known to a person skilled in the art for producing a harder surface of the finger contact 56 and the recess contact 88 is suitable, and this disclosure is not limited to any particular hardening process. While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the scope of this disclosure as claimed in the claims.

Claims

[1] Variable speed drive device (10) comprising: a rotatable drive shaft (14); a fixed drive disc (16) which is fixed relative to the drive shaft (14) and is attached for rotation with the drive shaft (14); a movable drive disc (20) which is mounted for axial movement relative to the drive shaft (14); a plurality of drive fingers (28) extending axially from one of the drive disks (16), each drive finger (28) defining a finger contact (56) and each drive finger (28) with its finger contact (56) being formed integrally with the drive disk (16) from a single piece of material; and a plurality of recesses (38) in the other drive disk (20), wherein each drive finger (28) is movably received by a corresponding recess (38), and wherein each recess (38) defines a recess contact (88) which slidably engages in the corresponding finger contact (56), wherein the recess contact (88) is a surface of the recess (38) at which the drive finger (28) comes into contact with the recess (38) when a torque is transmitted from the fixed drive disk (16) to the movable drive disk (20), wherein a torque can be transmitted from the fixed drive disk (16) to the movable drive disk (20) by the engagement of the finger contact (56) of the drive finger (28) in the recess contact (88). [2] Variable speed drive device according to claim 1, wherein the finger contact (56) is formed from a material that has been hardened by a surface treatment. [3] Variable speed drive device according to claim 1, wherein the recess contact (88) is formed from a material that has been hardened by a surface treatment. [4] Variable speed drive device according to claim 1, wherein both the finger contact (56) and the recess contact (88) are formed from a material that has been hardened by a surface treatment. [5] Variable speed drive device according to claim 4, wherein the surface treatment is a heat treatment, the heat treatment being quenching, tempering, case hardening or laser hardening. [6] Variable speed drive device according to claim 1, wherein the finger contact (56) includes an arc-shaped profile of the front edge (72) which engages in a corresponding surface of the corresponding recess (38), wherein the recess contact (88) is the surface of the recess (38). [7] Drive device comprising the following: a rotatable drive shaft (14); a fixed drive disc (16) which is fixed relative to the drive shaft (14) and is attached for rotation with the drive shaft (14); a movable drive disc (20) which is mounted for axial movement relative to the drive shaft (14); a plurality of drive fingers (28) extending from one of the drive disks, each drive finger (28) defining a finger contact (56) and each drive finger (28) with its finger contact (56) being formed integrally with the drive disk (16) from a single piece of material; and a plurality of recesses (38) in the other drive disk (20), wherein each recess (38) defines a recess contact (88); wherein each drive finger (28) is movably received by a corresponding recess (38), and the finger contact (56) engages slidably in the corresponding recess contact (88); wherein the recess contact (88) is a surface of the recess (38) at which the drive finger (28) comes into contact with the recess (38) when a torque is transmitted from the fixed drive disk (16) to the movable drive disk (20), wherein a torque can be transmitted from the fixed drive disk (16) to the movable drive disk (20) by the engagement of the finger contact (56) of the drive finger (28) in the recess contact (88). [8] Variable speed drive device according to claim 7, wherein at least the finger contact (56) or the recess contact (88) is hardened by a surface treatment and / or wherein the drive finger (28) and the recesses (38) have an arc-shaped profile defined around the drive shaft (14). [9] Variable speed drive device according to claim 7, which further comprises: at least one bearing element (34, 36) defined by the movable drive disc (20); and at least one shaft contact (90, 92) defined along an outer surface of the drive shaft (14); wherein the bearing element (34, 36) is defined by the movable drive disc (20) at a location adjacent to the shaft contact (90, 92). [10] Variable speed drive device according to claim 9, wherein the bearing element (34, 36) has a first axial length defined along the drive shaft (14), and the shaft contact (90, 92) has a second axial length defined along the drive shaft (14), and wherein the second axial length is greater than the first axial length. [11] Variable speed drive device according to claim 9, which further comprises at least one seal (58, 60) positioned between the movable drive disk (20) and the drive shaft (14). [12] Variable speed drive device according to claim 9, wherein the finger contact (56) includes an arc-shaped profile of the front edge (72) which engages in a corresponding surface of the corresponding recess (38), wherein the recess contact (88) is the surface of the recess (38). [13] A method for manufacturing a fixed drive disc and a movable drive disc for a variable-speed drive device, comprising the following: Forming a first drive pulley (16) by forming a first material to define a first flange engaging in a belt, and at least one drive finger (28) defining a finger contact (56), wherein the at least one drive finger with its finger contact is formed integrally with the first drive pulley from a single piece of material; Forming a second drive pulley (20) by forming a second material to define a second flange engaging in a belt, and at least one recess (38) defining a recess contact (88); Fixing one of the drive discs (20) to a drive shaft (14) and positioning the other of the drive discs (16) around the drive shaft (14); and Positioning at least one section of the drive finger (28) in the recess (38), wherein the finger contact (56) slidably engages in the recess contact (88), wherein the recess contact (88) is a surface of the recess (38) at which the drive finger (28) comes into contact with the recess (38) when a torque is transmitted from the fixed drive disk (16) to the movable drive disk (20), wherein a torque can be transmitted from the fixed drive disk (16) to the movable drive disk (20) by the engagement of the finger contact (56) of the drive finger (28) in the recess contact (88). [14] Method according to claim 13, comprising hardening the first or second material of the corresponding finger contact (56) or recess contact (88) by a surface treatment and wherein preferably the hardening of the first or second material comprises only hardening the section of the first or second material that corresponds to the finger contact (56) or the recess contact (88). [15] Method according to claim 13, which further comprises forming a bearing element (34, 36) in a first drive disk (16) or second drive disk (20) and hardening the bearing element (34, 36).

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