US Patent 7424846 Pneumatically static balancer for machine tool

A pneumatically static balancer for a machine tool counterbalances or lightens a gravitational load generated by an own weight of a vertically moving driven member. The pneumatically static balancer includes a pneumatic cylinder supporting the driven member and allowed to move vertically, a pneumatically static bearing having a piston inserted into the pneumatic cylinder, the pneumatic static bearing being formed by feeding compressed air, which is in an interior of the pneumatic cylinder, into a small clearance formed between the pneumatic cylinder and the piston, a cylinder rod connected to an upper end of the piston and a saddle supporting a leading end portion of the cylinder rod.