Air cushion cylinder apparatus with a lock

An air cushion cylinder apparatus with a lock, the apparatus comprising a cylinder and a pneumatic circuit for supplying compressed air to the cylinder, wherein

• the cylinder includes a piston, a piston rod, first and second pressure chambers on opposite sides of the piston, first and second ports for supplying compressed air to the pressure chambers, an air cushion mechanism for restricting a flow rate of exhaust discharged from the respective pressure chambers to thereby stop the piston at stroke ends in a cushioned manner, and a lock mechanism for locking the piston rod at a stop position,
• the lock mechanism has a ring-shaped lock member fitted over the piston rod to be displaced between an inclined position for locking the piston rod and a non-inclined position for unlocking the piston rod, a lock spring for pressing the lock member in an inclined direction, a third pressure chamber for causing air pressure to act on the lock member to displace the lock member to the non-inclined position, and a third port for supplying compressed air to the third pressure chamber,
• the pneumatic circuit includes a solenoid valve for opening and closing a flow path connecting the cylinder and a compressed air source, speed controllers each formed by connecting a check valve and a throttle valve in parallel are respectively connected in first and second pipes connecting the solenoid valve and the first and second ports, a speed controller formed by connecting a check valve and a throttle valve in parallel is connected in a third pipe connecting the third port and the first pipe or the second pipe, and a buffer tank for adjusting a pressure variation in the third pressure chamber is connected at a position between the speed controller and the third port in the third pipe.