Patent ID: 7766426

Claim:
A tilt mechanism for a chair comprising: upper and lower housing parts adapted to be coupled respectively to a chair seat/back assembly and to a chair base, said parts being pivoted together for movement with respect to one another about a pivot axis to permit tilting of the seat/back assembly with respect to the base in use; a compression spring extending between respective spring seats carried by said upper and lower housing parts so as to normally maintain said parts in a rest position, while being compressed when the upper housing part tilts with respect to the lower housing part in use; and, a spring tension control including wedge means between one of said spring seats and the associated housing part, said wedge means including a first wedge component coupled to one of said spring seats and said associated housing part and a pair of second wedge components co-operating with said first wedge component, said second wedge components being supported for lateral displacement towards and away from one another, the respective wedge components having co-operating sliding surfaces angled so that displacement of the second wedge components towards one another compresses the spring, increasing spring tension, while displacement of said moveable components away from one another allows the spring to relax, reducing spring tension, said second wedge components having a position of maximum spacing from one another in which the spring is fully relaxed and the overall length of the spring is less than the spacing between said spring seats for facilitating installation or removal of the spring; and an operator controlled actuator for effecting said displacement of the second wedge components towards and away from one another.