Series 39 Pneumatic Actuator

Twin piston double rack and pinion pneumatic actuator offers long cycles life for rotary applications. 



Design Features
COMPACT DOUBLE-PISTON DESIGN develops extremely high torque output from a short stroke. Plant air from a single connection is valved through ports in sliding piston guide rods to inner and outer air chambers alternately. Both pistons thus provide power for both opening and closing actions. Each piston is affixed to, centered, and guided by a moving stainless steel guide rod, operating in new, lower friction acetal resin bearings, eliminating side loading of piston.

STAINLESS STEEL GUIDE RODS make the Series 39 actuator unique. It is the only double piston rack and pinion actuator designed with piston guide rods. This feature results in: 

  • Reduced friction between the pistons and the cylinders, thereby increasing "O" ring life and eliminating the need for piston bearings.
  • Positioning of the pistons away from the cylinder. This means even if the piston seals are totally worn out, the pistons will never contact the cylinder.
  • Prevention of the pistons tilting as the linear motion of the pistons cause the pinion rotation. This allows for even transfer of force from the racks to the pinion, extending the life of the gears.
  • The weight of the pistons being kept off the piston seal, therefore preventing them from flattening. 

Guide rods also allow for transfer of air as well as activating the probes of the end mounted limit switches.


RACK AND PINION transfers power from pistons to shaft with gear racks cast into each piston. Gear teeth cut across the full face of piston and pinion provides maximum engagement with minimum tooth loading. Internal piston bearings eliminate side loads on "O" rings, extending life.

RUGGED CONSTRUCTION - CORROSION .RESISTANT body of the Series 39 actuator is aluminum, Coro-lube coated, both inside and outside, for strength and corrosion resistance. Increased metal thickness of body improves life of shaft bearing. Pistons are aluminum for strength and corrosion resistance. End caps are aluminum, Coro-lube coated. Integral pinion and shaft is steel, electroless nickel plated for corrosive resistance. Stainless steel end cap screws are used. 

Coro-lube is a nickel-acetate filled coating. It provides greater resistance to wear and corrosion and also provides increased lubricity on internal surfaces. 

EXTENDED TOP SHAFT provides visual indication of valve position and permits the use of optional accessories, such as top-mounted limit switches, a pneumatic positioner or means for manually overriding the actuator. It also allows the operation of two valves with a single actuator. The extended shaft simplifies mounting to virtually any rotary valve.

LOWER INTERNAL FRICTION results from Coro- lube coatings, low coefficient-of-friction acetal resin bearings, and polished piston guide rods. Operating speed and torque output are improved as a result of requiring a very small pressure differential to produce motion. 

MULTIPLE SPRINGS spring return models are available for applications requiring the valve to move to either a closed or opened position on failure of electrical or air supplies. Depending on air supply pressure, the multi-spring design provides sufficient torque to cycle the valve in the event of such failures. The failure mode can be changed simply by inverting the actuator, and/or changing the valve position and remounting the actuator. 

In corrosive or contaminating environments, the spring chamber port can be piped to a cleaner environment to reduce corrosion inside the actuator. Optional Stainless Steel springs are available.

BLOCK MOUNTED SOLENOID provides extremely fine independently adjustable speed control for both opening and closing strokes of double acting units. Only the spring stroke is adjustable on spring return units. Available with General Purpose TYPE 1, Watertight TYPE 4, Hazardous Environment TYPE 7 (UL & GSA listed for Class 1, Group C, D) and TYPE 9 (Class 11, Groups E, F & G) solenoids for 24, 15 and 230 VAC and 6, 12 and 24 VDC operation, TYPE 4 and 7 solenoid in one enclosure is also available. In the event of electrical failure or when local operation is desired, the double-acting solenoid may be overridden by manual operation of the control block, which is a standard option.


Pneumatic Control, Inc. 1999/2000