Patent ID: 7775891

Claim:
A joint boot comprising a large diameter cylindrical portion that is tightly fastened onto an outer peripheral wall of an outer member of a constant velocity universal joint, a small diameter cylindrical portion that is tightly fastened onto a side peripheral wall of a shaft member, and a bellows that intervenes between said large diameter cylindrical portion and said small diameter cylindrical portion, the bellows becoming reduced in diameter from said large diameter cylindrical portion toward said small diameter cylindrical portion, wherein said large diameter cylindrical portion has a thin-walled part with a smaller inner diameter as compared with an opening, wherein a first tapered part is provided between said opening and said thin-walled part, whereby an inner diameter of said large diameter cylindrical portion becomes reduced in diameter toward said small diameter cylindrical portion, wherein a thick-walled part, which is inserted into an axially extending recess disposed on an outer peripheral wall of said outer member, is disposed on an inner peripheral wall of said large diameter cylindrical portion, wherein said thick-walled part has a second tapered part starting from an end of said opening, whereby the internal diameter of said large diameter cylindrical portion becomes reduced in diameter toward said small diameter cylindrical portion, said second tapered part extending circumferentially over said first tapered part and having the same reduced diameter ending point as that of the first tapered part; and a constant diameter part that extends from the opening and continues to said first tapered part in a direction perpendicular to the circumferential direction in said large diameter cylindrical portion.