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Rack & Pinion Actuators

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Single Acting Spring Return Actuator

Principle of Operation

In single acting spring return actuators, compressed and processed air is supplied to one side of rack piston. This is responsible for unidirectional movement of rack piston. Movement in opposite direction is attained by means of mechanical springs. Energy generated by dry compressed air, is stored in the form of spring compression while unidirectional stroke of rack piston. Stored energy in compressed springs is used to attain opposite direction stroke of rack piston.

Operation

• CCW : CCW is standard at M-torQ Controls India
  • Air to port A apply pressure on piston rack, generates force on face of piston rack. This applied force cause pinion to rotate counter clockwise, piston rack outward and springs compression. while exhaust air passes through port B.
  • Energy stored in mechanical springs during compression, is used and springs forces piston rack inward, while exhaust air passes through port A


• CW :
  • Air to port A apply pressure on piston rack, generates force on face of piston rack. This applied force cause pinion to rotate clockwise and rack outward while exhaust air pass through port B
  • Energy stored in mechanical springs during compression, is used and springs forces piston rack inward, while exhaust air passes through port A.

• Output Torque of Single Acting Actuators
• Output torque table of Single Acting Spring Return Actuators

• Sizing of Single Acting Spring Return Actuators

Under normal working conditions, recommended factor of safety is 30% to 50%

    Example:

  • Torque required by valve to open/close = 95 Nm.
  • Torque considering recommended factor of safety (1+30%) = 124 Nm.
  • Air Supply = 6 bar.
    • Referring output torque table of single acting spring return actuators, we find output torque to be:

  • Air Stroke 0° = 199 Nm
  • Air Stroke 90° = 136 Nm
  • Spring Stroke 90° = 193 Nm
  • Spring Stroke 0° = 130 Nm
    • All the output torques are higher than torque values required by valve.

  • Spring Mounting Pattern of Single Acting Spring Return Actuators