Chairs with foldable backs

Claim 1

A chair, comprising: a chair seat and a chair back, said chair back connected to and generally upstanding from an edge of said chair seat; said chair back including an upper back frame having two downwardly directed spaced-apart upper legs, and a lower back frame having two upwardly directed spaced apart lower legs, said lower legs connected to said upper legs by individual pivot means; each of said pivot means including an upper connector secured to said upper leg, a lower connector secured to said lower leg, a pivot pin interconnecting said upper and lower connectors, and a lock mechanism for releasably interlocking said upper and lower connectors to prevent relative rotation therebetween, one of said upper and lower connectors including two spaced-apart generally parallel first projections extending from an end thereof, the other of said upper and lower connectors including a second projection extending from an end thereof, said second projection disposed between said two spaced-apart first projections; each of said first and second projections including transversely extending parallel lugs through which coaxial pivot holes are formed for receiving said pivot pin, thereby allowing rotational relative movement between said upper and lower connectors; said lock mechanism including at least one positioning hole formed in an inner surface of one of said first projections, and a spring and at least one spring biased ball retained in said second projection, said ball having a portion extendable from a surface of said second projection and urged by said spring to engage the positioning hole when said locking mechanism is in the locked position; whereby, when said upper back frame is rotated relative to said lower back frame about said pivot pin, said ball moves away from the positioning hole thereby releasing said lock mechanism, and said upper back frame is folded so as to situate adjacent said lower back frame.