Patent ID: 7229356

Claim:
A boot for a universal joint for coupling an input-side shaft to an output-side shaft of the type in which one end of the boot is fitted on one shaft of both the shafts via a one-end fitting portion of the boot and the other end of the boot is fitted on the other shaft of both the shafts via an other-end fitting portion of the boot to cover the universal joint comprising: one-end fitting portion of the boot contiguous with an annular lip portion extending from an end portion, in a shape which facilitates outward expansion of the annular lip portion under centrifugal forces, the one-end fitting portion and the annular lip portion each having a partial passage for allowing an inside region of the boot to communicate with an outside region of the boot, a tip of the annular lip portion being expanded in diameter outward by centrifugal force generated by rotation of the annular lip portion, wherein the partial passages for allowing the inside of the boot to communicate with the outside of the boot are closed when the tip is expanded outward to a predetermined diameter to seal against a surface.