Patent ID: 8317161

Claim:
An air balancer comprising: a rotary drum on which a rope member is to be wound, the rotary drum being rotatably supported by a stationary shaft in a casing; a conversion system that converts pressure of first air supplied into said casing into rotational force of said rotary drum for winding the rope member on said rotary drum; a cylindrical rotary member that is rotatably supported by said stationary shaft and linked with said rotary drum to integrally rotate therewith; a rotation restriction mechanism that comprises a pair of substantially semi-circular brake shoes that are pressed radially inwardly from radially opposite sides of the rotary member into contact with an outer circumferential surface of said rotary member, thereby restricting rotation of said rotary member; a disengagement mechanism that causes said brake shoes to retract radially outwardly by pressure of second air supplied into said casing to thereby disengage the contact between said rotary member and said brake shoes; and a control module having an air circuit that supplies said second air into said casing only when said first air is supplied into or discharged from said casing.