Patent attributes
A stable extension and retraction motion is realized in a robot arm mechanism including a linear extension and retraction joint. In the robot arm mechanism including the linear extension and retraction joint, the linear a extension and retraction joint includes an arm section, and an ejection section for supporting the arm section. The arm section includes a first connection piece string and a second connection piece string. The first connection piece string includes a plurality of first connection pieces. The second connection piece string includes a plurality of second connection pieces each having a substantially flat plate shape. The first connection piece string is joined to the second connection piece string to thereby constitute a columnar body. The columnar body is sent out forward from the ejection section. A guide roller for guiding the second connection piece string to the ejection section and keeping an engaged state of a linear gear provided on the second connection piece and a drive gear is provided behind the ejection section.