Patent ID: 6540296
Filing Date: 2003-04-01
Classification: A47C

Abstract:
A mechanism for adjusting the height of a chair back relative to a seat, comprising:first and second structural members adapted to be connected to the seat and back respectively and coupled to one another for relative sliding movement along a defined axis along which the back is to be adjusted with respect to the seat; a rack on said first said structural member extending in the direction of said defined axis; a pinion carried by the second said structural member and engaged with the rack; a pawl pivotally mounted on the second structural member for movement between (a) an engaged position in which the pawl engages the pinion and permits rotation of the pinion in one direction only corresponding to relative movement between the first and second structural members for height-wise adjustment of chair back in a first direction along said axis, while preventing relative movement between the first and second structural members in a second, opposite direction along said axis, and (b) a disengaged position in which the pawl is clear of the pinion and the first and second structural members are free for movement in either said direction; and actuator means carried by said second structural member for moving the pawl between said engaged position and said disengaged position at respective limits of travel of the first and second structural members with respect to one another along said axis; wherein said actuator means includes a spring that co-operates with the pawl for selectively biassing the pawl towards said engaged position or said disengaged position, and respective end-stop means on said first structural member co operating with the spring, the spring being longitudinally displaceable by contact with said end stop means at said limits of travel to move the pawl between its engaged position and its disengaged position; and wherein said pawl includes a first limb for engagement with said pinion and a second limb that is angularly disposed with respect to said first limb, and wherein said spring acts on said second limb to withdraw the first limb of the pawl from the pinion as a consequence of said longitudinal displacement of the spring in one direction, and wherein said second limb of the pawl is arranged to co-operate with the relevant said end stop means to cause longitudinal displacement of the spring in the opposite direction to move the first limb of the pawl into engagement with the pinion.