end face of the piston 4 of the first actuator 1 the second actuator 7 includes a rod chamber 7a and a bottom chamber 7b having ports 10 and 11 formed therein respectively in the arrangement of the above mentioned actuators 1 and 7 the stroke s 1 of the first actuator 1 is longer than the stroke s 2 of the second actuator 7 reference numeral 12 denotes a slide valve which comprises a valve body 13 formed as an integral part of the second actuator 7 and a spool 14 slidably inserted within the valve body 13 the valve body 13 has formed therein a first inlet port 15 which communicate with the port 6 of the bottom chamber 1b of the first actuator 1 a second inlet port 16 which communicates with the bottom chamber 7b of the second actuator 7 and a drain port 17 which communicates with the port 10 of the rod chamber 7a of the second actuator 7 the spool 14 is biased by a spring 18 and under such condition its small diameter portion 14a allows the communication between the second inlet port 16 and the drain port 17 on the side of the spool 14 oposite to the spring 18 the end face of a load piston 20 having a smaller diameter than that of the spool 14 and located within a pressure chamber 19 abuts against the right hand end of the spool 14 the pressure chamber 19 communicates through a port 19a with the first inlet port 15 when the above mentioned spool 14 is moved to the left in the drawing against the resilient force of the spring 18 by the action.