Patent ID: 7751555

Claim:
An angle variable mechanism comprising: a fixed unit that has a pair of guide surfaces recessed in a circular arc shape and a pair of coaxial shaft portions located between the guide surfaces; a movable unit that includes an outer peripheral surface being curved in a circular arc shape and being in slidable contact with the pair of guide surfaces, a concave portion being opened in the outer peripheral surface and having a pair of side surfaces which face each other, a pair of guide grooves formed on the pair of side surfaces respectively and curved along the outer peripheral surfaces, to slidably receive the pair of shaft portions, and a pair of notches formed at respective edges between the pair of outer peripheral surfaces and the pair of side surfaces to guide the pair of shaft portions into the pair of guide grooves; and a lock member that is swingably supported with the fixed unit and interposed between the pair of side surfaces to regulate a swing angle of the movable unit with respect to the fixed unit, wherein the lock member has a pair of convex portions located on a swing center axis of the lock member, wherein the pair of convex portions are slidably fitted to the pair of guide grooves through the pair of notches respectively, wherein each of the convex portions has a first end portion and a second end portion separated from each other in a lengthwise direction of the guide grooves in a state where the pair of convex portions are received in the pair of guide grooves respectively, wherein a length of the convex portion between the first end portion and the second end portion is larger than an opening width of each of the notches in the lengthwise direction, wherein the second end portion is formed thinner than the first end portion, so that a gap is formed between the second end portion and an inner surface of the guide groove to allow the lock member to swing.