Patent ID: 7364229

Claim:
An automatic ventilation device arranged under a chair cushion comprising a lower frame, an upper frame, upper and a lower stretchable air bags, a moveable plate capable of moving upwards and downwards with respect to the lower frame, and reset springs, wherein the lower frame is box-shaped and the upper and lower air bags with the moveable plate in the middle thereof are arranged inside an inner space of the lower frame while a top surface and bottom surface of the upper air bag are connected with an inner top surface of the lower frame and an upper surface of the moveable plate respectively; the moveable plate is capable of moving upwards and downwards inside the inner space of the lower frame by vertical guiding rails; the upper frame is a shielding frame arranged above the lower frame and connected with the moveable plate inside the lower frame and the cushion of the chair so that the upper frame and moveable plate move upwards and downwards together, with respect to the lower frame; the moveable plate arranged between the upper and the lower air bags and connected with the upper frame as well as the cushion to form a connecting body that moves upwards and downwards synchronously within a certain range of height; the upper and lower stretchable air bags having respective one-way air intakes and air outlets are disposed on an upper side and a lower side of the moveable plate respectively; when the moveable plate moves upwards and downwards, one of the upper and the lower air bags is extended for intake of air while the other is compressed for exhausting air; the one-way air outlets of the upper and the lower air bags are connected to the chair cushion or a seat back by a connecting duct so as to exhaust air through a ventilation structure on the cushion or the seat back; the reset springs are set between the upper frame and the lower frame for providing a restoring force to make the connecting body return to an original position with respect to the lower frame; when the cushion moves upwards and downwards, the moveable plate moves upwards and downwards synchronously so as to compress one of the lower and upper air bags to exhaust air while the other air bag extends to intake air for blowing to the cushion or the seat back.