Patent attributes
A first bush is attached to each of the opposite end parts of a first cylindrical part of a first hinge member. Second bushes are attached respectively to the inner end parts of second cylindrical parts which are disposed at the opposite end parts of a second hinge member and to the opposite end parts of a second cylindrical part which is disposed at the central part of the second hinge member. The first bush is provided with a protection cylindrical part. This protection cylindrical part is fitted to the outer periphery of the first cylindrical part. The second bush is provided with a second protection cylindrical part. This second protection cylindrical part is fitted to the outer periphery of the second cylindrical part.