Drive train assembly for an electric toothbrush and method of manufacture

Abstract

This invention relates to a drivetrain assembly for an electric toothbrush, the drivetrain assembly including a shaft having a rear side and a front side, wherein the front side of the shaft is configured to receive a brush head. The drivetrain assembly further includes: a drive mechanism including a shaft interface configured to receive the shaft, wherein the shaft interface includes a rear surface and a front surface, wherein the rear side of the shaft connects to the shaft interface from the direction of the front surface of the shaft interface for connection to the drivetrain; and a connecting element configured to connect the shaft to the shaft interface, wherein the connecting element extends at least partially along an outer surface at the rear side of the shaft for connecting the shaft interface and the shaft at the rear side of the shaft. The invention also relates to a toothbrush including the drivetrain assembly and a method of manufacturing the shaft and shaft interface assembly.

Description

Technical Field

[0001] This invention relates to the field of oral care devices. In particular, this invention relates to the field of electric toothbrushes and their transmission components, and to a method for manufacturing such transmission components. Background Technology

[0002] Electric toothbrushes consist of various parts, some of which must move. For example, within the housing (to which the brush head can be assembled via a shaft), an actuator moves components, enabling the toothbrush head to move. These moving parts are subjected to various forces and fatigue. In particular, the connections between mechanical parts are prone to joint failure. The toothbrush must be robust under extreme conditions. Moving parts, especially the shaft connecting the toothbrush head to the body, must remain connected to the body during use.

[0003] US2018228584A1 discloses a toothbrush with a fluid-guided drive assembly. The toothbrush includes: a handle having an end surface; a brush shaft extending from the end surface of the handle; a drive assembly positioned within the handle and causing the brush shaft to oscillate when a motor is actuated; a brush tip removably coupled to the brush shaft and positioned adjacent to the end surface of the handle; and a fluid channel defined within the drive assembly within the handle. Summary of the Invention

[0004] Therefore, an improved toothbrush drive system assembly may be needed, wherein the components of the drive system assembly remain connected to provide the toothbrush function.

[0005] One object of the present invention is to provide an improved transmission system assembly, particularly an improved connection between the shaft and the transmission system, for maintaining a robust connection, thereby preventing disconnection due to fatigue. Problems that can be overcome include loss of primary function and the inability of the user to use the device.

[0006] The object of the invention is addressed by the subject matter of the independent claims, wherein further embodiments are included in the dependent claims.

[0007] According to a first aspect of the invention, a drivetrain assembly is described. The drivetrain assembly includes a shaft comprising a rear side and a front side, wherein the front side of the shaft is configured to receive a brush head. The assembly also includes a drivetrain comprising a shaft interface configured to receive the shaft, wherein the shaft interface includes a rear surface and a front surface. The rear side of the shaft is connected to the shaft interface from the direction of the front surface of the shaft interface for connection to the drivetrain. Furthermore, the assembly includes a connecting element configured to connect the shaft to the shaft interface, wherein the connecting element extends at least partially along an outer surface at the rear side of the shaft for connecting the shaft interface and the shaft at the rear side of the shaft.

[0008] The drivetrain assembly may additionally include an actuator configured to move the shaft. For example, an electric motor can be used as the actuator to generate power and / or transmit power to the shaft. The drivetrain actuator may also be connected to a brush head, which can be coupled to the shaft via a shaft interface. The actuator may be configured to apply torque to the shaft to generate movement of the shaft.

[0009] A shaft can include any shape, such as circular, rectangular, and hexagonal shapes, but the shape of the shaft is not limited to these. For example, at least the rear side of the shaft can include a shape different from the rest of the shaft.

[0010] In this invention, the term "shaft interface" should be understood to describe an interface for a shaft configured to receive the shaft. Specifically, a shaft interface can be configured and can be used to connect a shaft to a drivetrain assembly. For example, a shaft interface can be a so-called "front bracket" configured to receive the shaft and connect it to drivetrain components. The shaft interface allows for a secure connection between the shaft and other components of the drivetrain.

[0011] In this invention, the term "connecting element" should be understood to describe any element capable of connecting two mechanical components (such as a shaft and a shaft interface) to form a robust connection that can withstand forces / torques applied to the shaft and is not easily broken. The connecting element can be a material-bonded connecting element, which connects the shaft and shaft interface by adding material or by a corresponding manufacturing process. For example, the material of the connecting element can be adapted to the material of the shaft and shaft interface to provide a good connection. Alternatively, the connecting element can be formed during a manufacturing process, i.e., welding, where, for example, a laser can liquefy the material at the region of the connecting element to form a connection, and after cooling, these parts become integral and connected to each other. The connecting element extends partially along the outer surface of the shaft. For example, if the shaft comprises a circular shape at its rear side, the connecting element can follow the shape of the shaft. Thus, the connecting element extends along the circumference of the shaft. It should be noted that the connecting element is not merely a simple point or point connection. In particular, the connecting element extends along a portion of the outer surface of the shaft, for example, at least along half of the outer surface of the shaft, wherein the extension length is not limited to this example.

[0012] According to an exemplary embodiment of the invention, the connecting element may extend along the entire outer surface of the shaft at the rear side of the shaft and may connect the outer surface of the shaft to the shaft interface. Therefore, the connecting element is arranged such that it surrounds the entire outer surface of the shaft in the region where the shaft is connected to the shaft interface. For example, when the rear side of the shaft comprises a circular shape, the connecting element extends along the entire circumferential outer surface of the shaft. This allows for a full connection between the shaft and the shaft interface, thereby preventing fatigue fracture and being able to withstand the forces / torques applied to the shaft when it is driven via the drivetrain. Therefore, the improved drivetrain assembly can maintain the primary function of the connection between drivetrain components, and thus maintain the primary function of the connection between toothbrush components. Extending along the entire outer surface of the shaft allows the connection between components to last longer and is less prone to breakage compared to a one or two-point connection (between the shaft and the shaft interface).

[0013] According to an exemplary embodiment of the invention, a connecting element can be configured to connect a first portion of the rear side of a shaft and the rear surface of a shaft interface. The rear side of the shaft extends through the shaft interface, wherein the first portion of the rear side can be arranged near the end of the shaft, particularly near or at the end surface of the rear side of the shaft. For example, the first portion is the area where the rear end side of the shaft and the outer surface of the shaft are adjacent to each other. In particular, the first portion is arranged at the edge where the rear end surface of the shaft and the outer surface of the shaft meet. Furthermore, depending on the extent to which the shaft extends outward from the shaft interface, the first portion can be arranged to be spaced apart from the rear side and the surface of the shaft. In other words, the position of the first portion of the rear side of the shaft can be located in the area where a plane parallel to the rear surface of the shaft interface intersects with the outer surface of the shaft. Accordingly, the position of the connecting element can be adapted to the insertion length of the shaft, wherein when arranged at the first portion, the connecting element can provide a connection between the rear surface of the shaft interface and the rear side of the shaft.

[0014] According to an exemplary embodiment of the invention, the transmission assembly may further include an additional connecting element configured to connect a second portion of the rear side of the shaft and the front surface of the shaft interface. By providing this additional, second connecting element, the connection between the shaft and the shaft interface can be further improved and made less prone to fatigue. The first and second portions of the shaft may be spaced apart from each other. In particular, the first and second portions of the shaft may be separated by the shaft interface. The second portion of the rear side of the shaft and the first portion of the rear side of the shaft may be spaced apart by a distance approximately equal to the thickness of the shaft interface when viewed from the shaft's extension direction. In particular, the second portion at the rear side of the shaft may be a region / location where a plane parallel to the front surface of the shaft interface intersects the outer surface of the shaft.

[0015] According to an exemplary embodiment of the invention, the shaft may further include a collar extending in a direction away from the shaft's central axis and along the outer surface of the shaft's rear side. Furthermore, the collar may contact the front surface of the shaft interface. The shaft's central axis may be an axis extending between the shaft's rear and front sides. Specifically, the collar may be disposed on the outer surface of the shaft, spaced a distance from the rear end surface of the shaft to the front surface of the shaft interface. Alternatively, the collar may be a protrusion of the shaft projecting away from the shaft's central axis in a direction perpendicular to it.

[0016] The collar can be configured to form a stop for the shaft to stop at the shaft interface, such that the collar can be positioned on the front side of the shaft interface, abutting the front surface of the shaft interface. The collar allows the shaft to be prevented from being inserted too deeply into the shaft interface.

[0017] According to exemplary embodiments of the present invention, particularly as an additional / alternative to the embodiments describing the connecting element and other connecting elements, an additional connecting element may be arranged between the collar of the shaft and the front surface of the shaft interface. Therefore, the additional connecting element can be used to form a connection between the collar of the shaft and the front surface of the shaft interface. This additional connecting element can allow for improved connection via the shaft and shaft interface by connecting the collar of the shaft to the shaft interface.

[0018] According to an exemplary embodiment of the present invention, a shaft interface may include a through-hole, into which the rear side of a shaft is inserted to form a connection between the shaft and the shaft interface. The through-hole may be a through-hole or a cutout through which the shaft may extend. In particular, the shape of the through-hole may be adapted to the shape of the shaft, allowing the shaft to be easily inserted into the through-hole. The through-hole may extend from the front surface of the shaft interface to the rear surface of the shaft interface. For example, when the shaft includes a collar, the shaft may be inserted into the through-hole until the collar of the shaft is positioned at the front side of the shaft interface.

[0019] According to an exemplary embodiment of the invention, when the shaft can be connected to a shaft interface, the rear end surface of the shaft extending in a plane perpendicular to the shaft's extension direction and the rear surface of the shaft interface are arranged in the same plane. For example, when a collar is additionally arranged at the shaft, the collar can function as a stop element when the shaft is inserted through a through hole.

[0020] Additionally / optionally, the connecting element can be disposed at the rear end surface of the shaft and the rear surface of the shaft interface. The connecting element provides a material bond between the two surfaces (i.e., the rear surface of the shaft interface and the rear end surface of the shaft). This allows for a good connection via the connecting element. Depending on the material and manufacturing method of the connecting element, the connecting element can extend into or be disposed in a through-hole, such that a connection can be formed between the rear surface of the shaft interface, the rear end surface of the shaft, and the outer surface of the shaft.

[0021] On the other hand, the rear end surface of the shaft can extend above the rear surface of the shaft interface and also above the front surface of the shaft. Furthermore, the rear end surface of the shaft can be positioned between the rear surface and the front surface of the shaft interface. Therefore, the rear end surface and the rear surface of the shaft are spaced apart from each other along the shaft's extension direction.

[0022] According to an exemplary embodiment of the invention, the shaft may include a shaft chamfer extending along the rear end surface of the shaft, wherein a connecting element may be arranged at the shaft chamfer and connect the rear surface of the shaft interface and the rear end side of the shaft. The shaft chamfer allows for easier insertion of the shaft into the shaft interface. Furthermore, the shaft chamfer provides a larger area where the connecting element may be arranged and attached to the shaft.

[0023] According to an exemplary embodiment of the present invention, the inner wall of the through hole of the shaft interface may include a straight shape, or alternatively, the inner wall of the through hole of the shaft interface may taper from the rear surface of the shaft interface to the front surface of the shaft interface, thereby forming an undercut inside the through hole.

[0024] For example, when the inner wall of the through-hole is straight, this means that the through-hole extends straight through the shaft interface without any protrusions or recesses. For example, the straight shape can be a cylinder, so the through-hole can be formed as a straight cylinder. The shaft can be easily inserted through the straight-shaped through-hole. According to an exemplary embodiment, the straight through-hole can be combined with a (first) connecting element and an additional (second) connecting element.

[0025] On the other hand, when the through-hole tapers from the front surface to the rear surface of the shaft interface, the initial opening of the through-hole at the front surface of the shaft interface can be smaller than the end opening of the through-hole at the rear surface of the shaft interface. For example, when the through-hole comprises a circular shape, the diameter of the through-hole at the front surface of the shaft interface can be smaller than the diameter of the through-hole at the rear surface of the shaft interface. This allows for a form-fit connection between the shaft and the shaft interface, making only one connecting element required. In other words, the tapered through-hole provides one or more forces along the shaft interface connecting the two parts according to a press-fit standard. This forced connection establishes an additional connection besides the connection via a connecting element.

[0026] According to an exemplary embodiment of the present invention, the shaft interface may include an interface chamfer extending along one side of a through-hole disposed on the front surface of the shaft interface. The interface chamfer allows for easier insertion of the shaft at the front side of the shaft interface. Furthermore, space for additional connecting elements may be formed by the shaft interface chamfer.

[0027] According to exemplary embodiments of the present invention, the connecting element and / or additional connecting elements may be welds applied by laser welding. In particular, when only connecting elements are used, there may be only one weld. Alternatively, two connecting elements may be welds. Or only the additional connecting elements may be welds.

[0028] According to a second aspect of the invention, an electric toothbrush is described, comprising a drivetrain assembly according to any one of the preceding claims, and at least one brush head connected to the drivetrain via a shaft of the drivetrain assembly. The components and embodiments described herein with respect to the drivetrain assembly can be incorporated into the electric toothbrush. The shaft of the drivetrain assembly can be connected to the brush head at its front side. Due to this connection, the shaft is able to transmit movement generated by an actuator to the brush head, enabling the user to clean their teeth. In the toothbrush, the drivetrain assembly can be a component that generates the required force and / or torque for moving the brush head and initiating the user's cleaning process. When using the drivetrain assembly described herein according to embodiments, an improved toothbrush is provided, wherein the shaft of the drivetrain is securely assembled to the drivetrain, making the shaft less prone to fatigue and less likely to break off from the shaft interface.

[0029] According to a third aspect of the invention, a method for manufacturing a transmission assembly for an electric toothbrush is described. The method includes the steps of: providing a shaft interface; providing a shaft; providing a through hole to the shaft interface; inserting the shaft into the through hole of the shaft interface; and connecting the shaft to the shaft interface on its rear side via a connecting element, wherein the connecting element extends at least partially along the outer surface of the rear side of the shaft for connecting the shaft interface and the rear side of the shaft. The above steps do not need to be performed in the stated order, therefore the order may be different, or additional steps or sub-steps may be added.

[0030] The insertion step may further include applying an insertion force to the shaft from the front side to press the shaft into the through hole. Additionally, the step of providing a through hole to the shaft interface may include punching the through hole into the shaft interface, through which the shaft can be inserted.

[0031] For example, the method may include additional or different steps that allow the formation of the drivetrain assembly described according to different embodiments herein.

[0032] According to another embodiment of the invention, the connection step may include welding connecting elements for connecting the rear side of the shaft to the shaft interface. Specifically, the connecting elements may be welded using laser welding. Furthermore, the connecting elements may be welded partially along the outer surface of the shaft element. In particular, the connecting elements may be welded along the entire outer surface of the shaft element.

[0033] According to another embodiment, the method may further include the step of connecting an additional connecting element to the shaft and shaft interface, wherein the additional connecting element may be welded by laser welding. The additional connecting element may also be welded partially or completely along the outer surface of the shaft. Specifically, the connecting element and the additional connecting element may include all the features and may be formed and welded to the shaft as described in the embodiments relating to the transmission system.

[0034] It should be noted that embodiments of the invention have been described with reference to various subjects. In particular, some embodiments are described with reference to claims of the method type, while others are described with reference to claims of the device type. However, those skilled in the art will understand from the above and below description that, unless otherwise stated, any combination of features related to different subjects, in addition to any combination of features belonging to one type of subject matter, is also considered to be disclosed with this application. However, all features can be combined to provide synergies that exceed the simple sum of these features. Attached Figure Description

[0035] The aspects of the invention as defined above, and other aspects of the invention, will become apparent from the exemplary embodiments described below, and will be explained with reference to these examples. The invention will be described in more detail below with reference to examples of embodiments, but the invention is not limited to these examples.

[0036] Figure 1 A toothbrush component including a transmission system assembly according to an exemplary embodiment of the present invention is schematically illustrated.

[0037] Figure 2 A cross-sectional view illustrating details of a transmission system assembly according to an exemplary embodiment of the present invention is shown.

[0038] Figure 3 The illustration shows a view from the rear surface of the shaft interface according to an exemplary embodiment of the present invention.

[0039] Figure 4 The illustration shows a side view of a shaft connected to a shaft interface according to an exemplary embodiment of the present invention. Detailed Implementation

[0040] Figure 1 A toothbrush component 100 including a drivetrain assembly 101 according to an exemplary embodiment of the present invention is schematically illustrated. The toothbrush 100 is only partially illustrated and does not include all components of a complete toothbrush. Figure 1 The toothbrush component 100 includes a drivetrain assembly 101, which includes a shaft 103 having a rear side and a front side, wherein the front side of the shaft 103 is configured to receive a brush head 102. The drivetrain assembly 101 includes a shaft interface (not shown) configured to receive the shaft 103, wherein the shaft interface includes a rear surface and a front surface. The rear side of the shaft 103 connects to the shaft interface from the front surface of the shaft interface for connection with the drivetrain 101. The toothbrush 100 also includes an actuator 109 configured to move the shaft 103 when inserted into the toothbrush 100. For example, an electric motor can be used as the actuator 109, which can generate power and / or transmit power to the shaft 103 to move the brush head 102. Figure 1 The actuator in the diagram is shown with different parts; this is merely a schematic illustration to indicate an actuator using a magnet and to show the connection of different components of the toothbrush assembly 100, such as using a magnet and several springs 105, 106, and 107. The actuator 109 of the drivetrain 101 can also be connected to the brush head 102 via a shaft 103. The brush head 102 can be coupled to the shaft 103 via a shaft interface. The actuator 109 can be configured to apply torque 104 and / or 110 to the drivetrain components, the torque being... Figure 1 The image is illustrated by arrows 104 and 110. Furthermore, the toothbrush may include corresponding springs: a first spring 105 connecting the drivetrain assembly to the frame 108; a second spring 106 connecting the drivetrain assembly and the load inertia member to the balancing inertia member 109; and a third spring 107 connecting the balancing inertia member 109 to the frame 108. Therefore, the actuator may be a magnetically driven actuator, but is not limited to this. It is possible to replace these components with another actuator (not shown), such as a rotatable electric motor.

[0041] Figure 2 A cross-sectional view detailing a drivetrain assembly 101 according to an exemplary embodiment of the present invention is illustrated. The drivetrain assembly 101 includes a shaft interface 211 configured to receive a shaft 203, wherein the shaft interface 211 includes a rear surface 213 and a front surface 212, wherein a rear side 218 of the shaft 203 connects to the shaft interface 211 from the direction of the front surface 212 of the shaft interface 211 for connection to a drivetrain. A connecting element 221 (in...) Figure 2 (Not clearly visible in the illustration) is configured for connecting shaft 203 and shaft interface 211. Connecting element 221 extends at least partially along the outer surface of the shaft 203 at its rear side 218 for connecting shaft interface 211 and the shaft at the rear side 218 of the shaft 203. Connecting element 221 extends along the entire outer surface of the shaft 203 at its rear side and connects the outer surface of the shaft 203 to shaft interface 211. Figure 2In this embodiment, shaft 203 has a circular shape, and therefore connecting element 221 extends along the outer circumferential surface of shaft 203. Connecting element 221 is configured to connect a first portion of the rear side 218 of shaft 203 and the rear surface 213 of shaft interface 211. Specifically, in this embodiment, connecting element 221 is arranged in a region of the rear surface 213 of shaft interface 211 adjacent to the outer surface of shaft 203. Furthermore, another connecting element 222 is arranged and configured to connect a second portion of the rear side 218 of shaft 203 and the front surface 212 of shaft interface 211. The first portion of the rear side 218 of shaft 203 may be located at a region where a plane parallel to the rear surface 213 of shaft interface 211 intersects the outer surface of shaft 203. Specifically, the second portion of the rear side 218 of shaft 203 may be a region / location where a plane parallel to the front surface 212 of shaft interface 211 intersects the outer surface of shaft 203. Shaft 203 also includes a collar 217 that extends in a direction away from the shaft's central axis A and along the outer surface of the rear side 218 of shaft 203, wherein collar 217 contacts the front surface 212 of shaft interface 211. Additional connecting elements 222 are arranged between collar 217 of shaft 203 and the front surface 212 of shaft interface 211.

[0042] In addition, according to Figure 2 In the illustrated embodiment, the shaft interface 211 includes a through-hole 216, into which the rear side 218 of the shaft 203 is inserted to form a connection between the shaft 203 and the shaft interface 211. The inner wall of the through-hole 216 of the shaft interface 211 tapers from the rear surface 213 to the front surface 212 of the shaft interface 211, such that an undercut 214 is formed inside the through-hole 216. Specifically, as... Figure 2 As shown in the figure, the through hole is a through hole 216 with a circular tapering shape. The diameter of the through hole (hole) 216 on the rear side 213 of the shaft interface 211 is larger than the diameter of the through hole (hole) 216 on the front side 212 of the shaft interface 211.

[0043] Shaft 203 includes a chamfer 219 that extends along the rear end surface 220 of shaft 203, which facilitates insertion of shaft 203 into shaft interface 211. Connecting element 221 is arranged at the chamfer 219 and connects the rear surface 213 of shaft interface 211 and the rear end side 220 of shaft 203.

[0044] The shaft interface 211 includes an interface chamfer 215 that extends along one side of a through-hole 216 disposed on the front surface 212 of the shaft interface 211. The chamfer 211 extends in particular along the circumference of the through-hole. This chamfer 211 facilitates the insertion of the shaft 203 into the shaft interface 211.

[0045] In addition, such as Figure 2As can be seen, the rear side 218 of the shaft 203 inserted into the shaft interface 211 has a smaller diameter than the rest of the shaft 203 that is not inserted into the shaft interface 211.

[0046] In addition, the connecting element 221 and / or the other connecting element 222 are welds applied by laser welding.

[0047] Figure 3 The illustration shows a view of the rear surface 213 of the shaft interface 211 as described in an exemplary embodiment of the present invention. Figure 3 The diagram illustrates region 331 of the connecting element, which indicates the area where the connecting element 221 is attached to the shaft 203 and the shaft interface 211. Furthermore, the outer surface 330 of the shaft is illustrated. The connecting element 221 extends along a portion of the outer surface 330 of the shaft 203. It can be seen that the shaft interface 211 is a so-called "front support" that receives the shaft 203. The shaft 203 has a circular shape. Similarly, the through-hole 216 has a circular shape. When the shaft 203 is connected to the shaft interface 211, the rear end surface 220 of the shaft 203 extending in a plane perpendicular to the shaft's extension direction and the rear surface 213 of the shaft interface 211 are arranged in the same plane. The connecting element 221 is arranged at the rear end surface 220 of the shaft 203 and the rear surface 213 of the shaft interface 211.

[0048] Figure 4 The illustration shows a side view of a shaft 203 connected to a shaft interface 211 according to an exemplary embodiment of the present invention. The shaft 203, including a collar 217, is arranged in the shaft interface 211, wherein the rear end surface 220 of the shaft 203 and the rear surface 213 of the shaft interface 211 extend in the same plane. A connecting element 221 is arranged at the rear surface 213 of the shaft interface 211 and connects it to the rear end surface 220 of the shaft 203. An additional connecting element 222 is arranged at the front surface 212 of the shaft interface and connects it to the shaft 203 at the surface of the collar 217 facing the shaft interface 211.

[0049] While the invention has been detailed and described in the accompanying drawings and the foregoing description, such description and illustration should be considered illustrative or exemplary rather than restrictive. The invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and implemented by those skilled in the art in practicing the claimed invention through study of the drawings, the disclosure, and the dependent claims.

[0050] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. A single processor or other unit can perform the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously. No reference numerals in the claims should be construed as limiting the scope. List of reference numerals in the attached diagram: 100 toothbrushes 101 Transmission System 102 brush heads Shafts 103 and 203 104 Torque 105 First Spring 106 Second Spring 107 Third Spring 108 Frame 109 Actuator 110 Nm of torque 211 axis interface 212 axis interface front surface Rear surface of 213 axis interface 214 Tapered section 215 Interface Chamfer 216 Through Hole 217 rings Rear side of 218 shaft 219 axis chamfer 220 axis rear end surface 221 Connecting element 222 Other connecting elements 330 shaft outer surface 331 Area of ​​connecting elements The central axis of axis A

Claims

1. A transmission system assembly for an electric toothbrush, comprising: The shaft includes a rear side and a front side, wherein the front side of the shaft is configured to receive a brush head. A drivetrain including a shaft interface configured to receive a shaft, wherein the shaft interface includes a rear surface and a front surface, and wherein the rear side of the shaft connects to the shaft interface from the direction of the front surface of the shaft interface for connection with the drivetrain. A connecting element configured to connect the shaft to the shaft interface. The connecting element extends at least partially along the outer surface at the rear side of the shaft for connecting the shaft interface and the shaft at the rear side of the shaft. The connecting element is a weld applied by laser welding and extends along the entire outer surface of the shaft at the rear side of the shaft, connecting the outer surface of the shaft to the shaft interface.

2. The transmission system assembly according to claim 1, The connecting element is configured to connect the first portion of the rear side of the shaft and the rear surface of the shaft interface.

3. The drivetrain assembly according to any one of the preceding claims, It also includes additional connecting elements configured to connect the second portion of the rear side of the shaft to the front surface of the shaft interface.

4. The transmission system assembly according to any one of the preceding claims, The shaft further includes a collar extending away from the central axis of the shaft and along the outer surface of the shaft at its rear side. The collar contacts the front surface of the shaft interface.

5. The drivetrain assembly according to claims 3 and 4, The additional connecting element is arranged between the collar of the shaft and the front surface of the shaft interface.

6. The drivetrain assembly according to any one of the preceding claims, The shaft interface includes a through hole, into which the rear side of the shaft is inserted to form a connection between the shaft and the shaft interface.

7. The drivetrain assembly according to any one of the preceding claims, When the shaft is connected to the shaft interface, the rear end surface of the shaft extending in a plane perpendicular to the shaft extension direction and the rear surface of the shaft interface are arranged in the same plane. The connecting element is arranged on the rear end surface of the shaft and the rear end surface of the shaft interface.

8. The drivetrain assembly according to any one of the preceding claims, The shaft includes a chamfer extending along the rear end surface of the shaft. The connecting element is arranged at the chamfer of the shaft and connects the rear surface of the shaft interface to the rear end side of the shaft.

9. The drivetrain assembly according to any one of the preceding claims, The inner wall of the through hole in the shaft interface has a straight shape, or The inner wall of the through hole of the shaft interface tapers from the rear surface of the shaft interface to the front surface of the shaft interface, such that an undercut is formed inside the through hole.

10. The drivetrain assembly according to claim 9, The shaft interface includes an interface chamfer that extends along one side of the through hole disposed on the front surface of the shaft interface.

11. An electric toothbrush, comprising: The drivetrain assembly according to any one of the preceding claims A brush head, which is connected to the drivetrain via the shaft of the drivetrain assembly.

12. A method for manufacturing a drivetrain assembly for an electric toothbrush, the method comprising the steps of: Provides shaft interface, Provide shafts, Provide a through hole to the shaft interface, Insert the shaft into the through hole of the shaft interface. The shaft is connected to the shaft interface on its rear side by a connecting element, wherein the connecting element extends at least partially along the outer surface of the rear side of the shaft for connecting the shaft interface and the rear side of the shaft. The connection step includes welding the connecting element to connect the rear side of the shaft to the shaft interface.

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