US Patent 7850604 Flexible shaft for an endoscope and such an endoscope

A flexible shaft for an endoscope comprises a shaft body which, in the longitudinal direction of the shaft, has a first portion with a first degree of flexibility, and, proximally from the first portion, has at least a second portion with a second degree of flexibility which is less than the first degree of flexibility, the shaft body having, in the first portion, at least a first spring element, and, in the second portion, at least a second spring element. A spring hardness of the second spring element is increased by a permanent pretensioning of the second spring element, as a result of which the flexibility of the shaft body is reduced in the second portion.