Angle adjusting device of infusion chair back plate

The invention discloses an angle adjusting device of an infusion chair back plate in a very simple and convenient adjusting manner. The device comprises a back plate, wherein the both sides at the lower end of the back plate are respectively hinged with a chair bracket. The chair bracket is provided with a handrail, the tail of a controllable air spring is hinged with the lower end of the back plate, the front end of a piston rod of the controllable air spring is fixedly connected with a wrench bracket which is fixedly installed at the bottom of the chair bracket, and a wrench is moveably arranged on the wrench bracket. The wrench is connected with a driving device which can pull the wrench so that the wrench moves toward one side of the controllable air spring and pushes a valve ejecting rod at the end of the piston rod to move into the piston rod, therefore, an inner vale of the controllable air spring can be opened to unlock the piston rod and loosen the free end of a pressure rod. The valve ejecting rod m