Angle variable joint for foldable chair

Claim 1

A joint comprising a movable rod attached to a back rest frame member and having at its lower end a pair of flat discs spaced apart in facing relation to each other and including peripheral gear portions respectively, free cam means in the form of two free cam discs of approximately the same size as the flat discs disposed in the space between the flat discs and including outer peripheral gear portions having a pitch equal to that of the gear portions, a pin member for pivotably supporting the discs and cam means at the junction of a stationary support member attached to a seat frame member, and a latch member accommodated in the stationary support member and having a support pawl urged into resilient contact with the outer peripheries of the discs and cam means, the movable rod being thus supported by and connected to the stationary support member in a forward and backward inclinable manner at progressively decreaSing and increasing variable angles for the change of angle of inclination, one of the pair of opposing flat discs being formed with a projection positioned at an upper portion of the space, the free cam means being composed of two discs including in their toothless circular arc portions recesses to be engaged by the projection and permitting the projection to move freely predetermined amounts with different amounts of play, whereby when the movable rod is pivotally moved a predetermined amount for changing the angle the flat discs alone are moved to displace their gear portions the predetermined amount with the two free cam discs retained in a stationary position by the resilient contact with the latch member and when the movable rod is subsequently moved the same amount as above in the same direction the free cam disc with a recess of a smaller width and the flat discs are moved together to displace their gear portions the same amount as the predetermined amount through the engagement of the projection with the recess while the aforementioned displaced relationship being retained therebetween, the modes of relative displacement thus effected permitting the respective tooth grooves to be partially overlapped with the tooth profiles whose tooth tip faces are in partially overlapped relation to each other so as to cause the tip faces of the respective teeth to form a smooth face for the paul of the latch member to slide on.