Image Number 4 for United States Patent #5725278.
Disclosed is a device for positionally adjusting and releasably locking a chair backrest in any of a plurality of positions on a seat support member between two extreme positions. The device includes a first bracket adapted to be rigidly secured to the backrest and a second bracket adapted to be rigidly secured to the seat support member and slidably receiving the first bracket for sliding movement between two extreme, longitudinally spaced, first and second positions. A locking mechanism is provided for releasably locking the second bracket to the first bracket, the locking mechanism comprising a longitudinal array of lock stop members on the second bracket confronting a lock element secured to the first bracket, the lock stop members each having a locking surface. At least one longitudinal guide track is on the first bracket and defines a first longitudinal path and a second longitudinal path, the guide track having respective ends defining the first and second extreme positions and providing access points at such position between the paths to permit movement of the path tracking elements from one path to the other path. The lock element has a lock tongue for locking association with a locking surface of a selected one of the lock stop members. The lock element further has a path tracking element for sequential engagement with the first and second paths, wherein, when the path tracking element is in engagement with the first path, the lock element is forced into engagement with a selected one of the lock stop members and when the path tracking element is in engagement with the second path, the lock element is held out of engagement from all lock stop members.