Pneumatic System 167Introducing the Packer Air SystemThe hydraulic valve, which controls some of the hydraulic functions, is equipped with air actuators.The packer air actuator pushes back and forth on the hydraulic spool of the valve, resulting in amovement of the packer (extension or retraction).Figure 7-6 Packer air actuatorAs the packer reaches the end of a stroke, the proximity switch, located behind the packer, sends asignal to the electronic module to indicate that the packer has reached the end of its stroke. Themultiplex module then operates the air solenoid valve, inside the air control box, with a 12volt signal(one signal for packer extend, one signal for packer retract).When receiving the 12-volt signal (extend or retract) from the module, the air solenoid valve enablesthe air pressure to reach the actuator on the main control valve. The spool moves according to thesignal received.Two quick exhaust valves, located close to the body main valve (see Figure 7-6), are designed torelease air pressure from the packer air actuator installed on the main control valve. They release airwhen the packer reaches the end of a stroke, allowing the spool to move in the opposite direction andaccelerate air release in the actuator.Quick exhaust valves
