The present invention relates to a sprocket assembly with an adapter.
A sprocket assembly is known, for example, from document EP 1688345 B1. In this instance, the adapter is constructed as a sprocket carrier or “spider” with an inner ring and securing arms which extend radially outwards therefrom for securing one or more sprockets. The inner profile of the adapter formed by the drive elements ensures in this instance both transmission of torque from the sprocket to the driver which is provided with a corresponding outer profile and radial centering of the sprocket assembly on the driver.
This places high demands on the production precision for the adapter, especially since this is preferably constructed to be substantially wider in the axial direction than the sprocket in order to produce a surface-area which transfers the greatest possible force, which in turn makes the correct radial centering more difficult.
On the other hand, there is known, for example, from EP 2319752 A2, a sprocket assembly in which no separate adapter at all is provided, but instead the drive elements are constructed for interaction with the outer profile of the driver directly on the inner periphery of the sprocket itself.
Although it is thereby possible to achieve relatively precise centering, the width of the drive elements is limited to the width of the sprocket so that the face which transmits force is relatively small.
In particular with the material pairing of a sprocket of steel and a driver of aluminium, this leads to embedding of the sprocket in the driver, which can destroy the driver and can make the assembly or disassembly of the sprocket assembly and the driver more difficult.
In sprocket cassettes, which are used on a specific type of driver (for instance, an XD driver), the forces and the resultant torques of all of the sprockets are further introduced via only a single end sprocket and consequently only at a single location in the driver, which further increases the problems explained above.
As a result of the manufacture process, many drivers additionally have an undercut on the axial stop. This leads to in particular the last (largest) sprocket, that is to say, the end sprocket, additionally losing coverage surface with the driver.
Both the sprocket assemblies mentioned above and known from the prior art have the common feature that the drive elements are each used both for radial centering of the sprocket assembly on the driver and for transmission of torque from the sprocket assembly to the driver.
Against this background, an object of the present invention is to further develop the sprocket assembly known from the prior art in such a manner that the radial centering is improved, without notably impairing the torque transmission in this case.