Patent ID: 8646583

Claim:
A dust boot covering at least a part of a piston rod projecting from a cylinder or a cylinder fixed member, comprising: a cylindrical bellows comprising crest parts and groove parts which are disposed alternately; wherein, an end of the bellows is supported by a support fixed to an outer surface of the cylinder; the cylinder or the cylinder fixed member comprises a projecting portion as a part which is fixed to the cylinder or the cylinder fixed member and projects into the bellows; the bellows is divided into several sections in the direction of projection of the piston rod, the several sections including a first section which comprises a plurality of some of the crest parts and the groove parts and passes a projecting end of the projecting portion without contacting when the piston rod elongates and contracts with respect to the cylinder, and a second section located between the first section and the support and comprising a plurality of other ones of the crest parts and the groove parts; the inner diameter of all the groove parts in the second section is set to be smaller than the inner diameter of a groove part located at a boundary between the first section and the second section; and the inner diameter of the groove parts in the first section gradually increases as a distance from the second section along the piston rod increases.