Patent ID: 7926370

Claim:
A rotation and extension/retraction link mechanism with a first link therein and a second link therein coupled through a rotation and extension/retraction joint mechanism, said first link having a first virtual center line and said second link having a second virtual center line, wherein said rotation and extension/retraction joint mechanism is constructed so that it couples said first link and said second link in such a manner that as the second virtual center line rotates relative to the first virtual center line from a state where the first virtual center line entirely overlaps with the second virtual center line, while crossing the first virtual center line, an intersection between the first virtual center line and the second virtual center line moves on the first virtual center line by a predetermined distance corresponding to an angle of the rotation; wherein said first link includes first and second opposing wall portions facing each other at a predetermined spacing; and said second link includes a first opposed wall portion facing said first opposing wall portion and a second opposed wall portion facing said second opposing wall portion; and wherein said rotation and extension/retraction join mechanism includes; a first rack gear provided at said first opposed wall portion and extending along the second virtual center line; a first sector gear including a plurality of cogs to be engaged with said first rack gear, said first sector gear being slidably supported by said first opposing wall portion so that said first sector gear rolls on said first rack gear and slides along the first virtual center line; a second rack gear provided at said second opposing wall portion and extending along the first virtual center line; and a second sector gear including a plurality of cogs to be engaged with said second rack gear, said second sector gear being slidably supported by said second opposed wall portion so that said second sector gear rolls on said second rack gear and slides along the second virtual center line.