How It Works: Air/Spring Stop and Start the Shaft Clutch-Brake

Mach III stop and start the shaft clutch-brakes transmit rotary motion from a constantly rotating machine component that is connected to the unit’s pilot by a chain, belt or other means to the shaft on which it is mounted. When motion is not required, the clutch-brake stops and holds the shaft stationary.  This model requires only one air signal to energize the clutch when motion is required.  The brake is energized by spring pressure and therefore automatically engaged when the clutch is released.


  • The DRIVE HUB slides over the SHAFT. The drive hub includes a keyway which corresponds to the keyseat in the SHAFT. When a KEY is in place, the two members are connected. The clutch-brake is locked onto the SHAFT with SET SCREWS.
  • The clutch-brake must be connected to an ANTI-ROTATION RESTRAINT such as a bracket or the machine frame to react the brake torque.
  • Lugs (tabs) on the outside diameter of the CLUTCH and BRAKE FRICTION DISCS fit into corresponding slots in the SLEEVE and CYLINDER. The inside diameter of the CLUTCH DRIVE DISCS and BRAKE DISC are connected to the DRIVE HUB via gear teeth or other drive geometries.
  • The SLEEVE includes a precision machined pilot onto which a sprocket, pulley, sheave, coupling or adapter can be attached.
  • The clutch-brake is capable of rotation in both clockwise and counterclockwise directions.


  • Compressed air supplied to the AIR INLET moves the PISTON forward which forces the CLUTCH FRICTION DISCS and DRIVE DISCS to squeeze together.
  • Once adequate pressure is achieved to collapse the RELEASE/BRAKE ENGAGEMENT SPRINGS located between the CLUTCH FRICTION DISCS and DRIVE DISCS, the brake is de-energized and the discs come into contact and create the friction that transmits torque to the SHAFT.
  • The amount of clutch torque transmitted is linear in proportion to the air pressure (PSI, BAR) supplied. More air pressure = higher torque output.
  • The maximum recommended air pressure for most Mach III products is 80 PSI.


  • The CLUTCH FRICTION DISCS and DRIVE DISCS remain in contact rotating with one another until compressed air is no longer supplied to the unit.
  • In the absence of air pressure, RELEASE/BRAKE ENGAGEMENT SPRINGS located between the CLUTCH FRICTION DISCS and DRIVE DISCS force them apart.  Neutral air is pushed out of the PISTON fully disengaging the clutch.
  • Simultaneously, the spring pressure forces the BRAKE DISC against the BRAKE FRICTION DISC, creating the torque which stops the shaft and holds it in place.
  • The amount of brake torque transmitted is fixed due to the force applied by the RELEASE/BRAKE ENGAGEMENT SPRINGS.
  • Timing for full disengagement of the clutch and engagement of the brake is short but, depending upon the cycle rate of the application, it is sometimes advisable to install a quick exhaust port to allow the air to exit the unit more quickly.