Chair with a back or forward adjustable backrest with one central chair leg.

摘要

When the back rest is turned down rearward, a seat portion moves forward so that one can assume a recumbant posture. This chair solves simultaneously the two problems that when the back rest is turned down backward, the center of gravity moves backward and a user is apt to fall down backward and that when the back rest is moved backward, the motion of one's back is not synchronized with that of the back rest and one receives an offensive feel. Therefore, in the chair of the present invention, the front end of the seat portion is supported by a support base portion in such a manner as to be movable back and forth, a balance member is disposed below this seat portion, a support point portion set between the front and rear points of application of the balance member is supported by the support base portion, the back rest is disposed at the back of this balance member, the rear end side of the seat portion is supported movably back and forth at the rear point of application of the balance member through a seat receiving means and vertical motion of the front point of application of the balance member is converted to the advance motion of the seat portion by a motion conversion means. When the seat moves forward, its rear end side sinks so that the user is not given the feel of sliding forward. Resilient urging means is also disposed in order to urge rearward the seat portion and to provide the back rest with the self returning force in the forward direction. Furthermore, the seat receiving means has the function of generating the seat traction force in the rear direction in accordance with the weight of the user so as to increase or decrease automatically the initial repulsive force of the back rest in accordance with the weight of the user. Lock means is disposed to lock the motion of the seat portion and that of the back rest.