Air Torque GmbH | PNEUMATIC PART TURN ACTUATORS

Pneumatic Actuators

Applications: Part turn actuators are used for the automation of valves, which are controlling the flow of different medias (fluid, gas) or granulated material.
All actuators of the Edition 2010 line (4th Generation Upgrade) are service friendly by external travel stops for open and close position adjustable from -5° to +15° and from +75° to +95°. This special feature eliminates alignment problems due to a clearance of connections between the stem of the valve adaptor and the shaft of the actuator.

Due to a triple bearing of the piston all actuators have a constant torque, even under high load. Beside the guides on the outside of the piston there is an additional guide inside which absorbs the cross load through the integrated support at the drive shaft.The drive shaft is held in position by two bearings, one at the top of the pinion, one at the bottom. This assures less friction and abrasion-free operation.
Due to the special design of the bearings at the shoulders of the piston, the drive shaft is blowout proof and fulfills the hard US-standards for product liability.

The drive shaft has a 25-30 µm electroless nickel coating (Protection E -> Stainless steel).The bearings are temperature resistant to 155 °C. Due to an internal retaining shoulder the bearings are blowout safe.

The maintainance free spring cartridges allow a safe and simple assembly and disassembly. Therefore the adaptation of the AT actuators to your working conditions with the recommended pneumatic pressure can be arranged easily. The modification of a double acting to a spring return actuator can be easily managed. Only the necessary springs have to be mounted. This advantage of AT actuators reduces stocking costs significantly.

Silicon free:
All actuators are silicon free.

Serial inspection:
Each actuator has to pass a comprehensive serial inspection with e.g. a tightness / density check and a torque check.
After passing the inspection the actuator is given a serial number according to ISO 9001.

Quality Assurance:

The company received the highest international ISO 9001 certification by Lloyd’s Register of Shipment.

The Principle

The Double Acting Actuators - Type DR

When port ‘2’ is pressurized and port ‘4’ is vented, the both pistons are moving into its end positions and a rotation of the drive shaft is achieved (a rotation of the drive shaft in its opposite is possible by a mirrored mounting of the pistons).

When port ‘4’ is pressurized and port ‘2’ is vented, the pistons are moving into the middle position. The result is a
rotation of the drive shaft (a rotation of the drive shaft in its opposite is possible by a mirrored mounting of the
pistons).

For rack and pinion construction the output torque of an actuator is calculated by multiplying the piston force (given by air supply pressure) with the pitch shaft radius (lever arm) less the force lost for friction (efficiency).

By reason of this concept, the output torque is linear in both clockwise and counterclockwise rotation.

The Single Acting Actuators - Type SC

When port ‘2’ is pressurized and port ‘4’ is vented both pistons are moving into the endpositions and will compress the springs – the result is a rotation of the drive shaft (a rotation of the drive shaft in its opposite is possible through a mirrored mounting of the pistons).

Due to the spring force a fail-save position by air or electricity loss is guaranteed.

For spring return applications the output torque is obtained by two different operations. Each operation produces two different values in relation to the stroke position (0° or 90°).

For spring return actuators the output torque is calculated by multiplying the force (air or springs acting on the pistons) with the lever arm.

First case:
The output torque is generated by air supply pressure at port ‘2’ after compressing the springs, called ‘output torque air stroke’. In this case air forces the pistons to move from the 0° to the 90° position and consequently the torque starts from a high value and during the stroke it constantly decreases until 90° due to the natural force that springs generate (oppose) when they are compressed.

Second case:
The output torque is generated by the force of the springs released onto the pistons when air fails, called ‘output torque spring stroke’. In this case the torque, starting from the 90° position, constantly decreases until 0° because of springs extending.
AT spring return actuators are designed to produce a balanced output torque like the two cases explained above, when the number of springs per side is equal to the air pressure supply (4 bar – 4 springs each side).

For certain applications it is possible to achieve (where desired), the unbalanced torque, by changing the relation between the number of springs per side and air pressure supply in bar (for example 6 springs and 5,5 bar or vice versa).

For spring return applications two executions can be offered: air fail to close or fail to open.