Electric Clutches

Electric clutches are equipment drive assemblies that contain electrically actuated components for connecting two shafts so that they can either be locked together and spin at the same speed, or decoupled and spin at different speeds. Engaging the clutch transfers power from an engine to devices such as a transmission and drive wheels. Disengaging the clutch stops the power transfer, but allows the engine to continue turning. Electric clutches permit faster cycling times than pneumatic or hydraulic clutches, but do not provide the same range of torque. They are best suited for automatic machinery that transmits control commands as electric signals rather than as pedal or lever motions. Electric clutches are also useful in applications where the clutch is so far removed from the control point that mechanical connections or pneumatic or hydraulic piping would be difficult to maintain or prohibitively expensive.

Specifications for electric clutches include torque rating, power, rotational speed, and operating voltage. Spring-return clutches require power to engage. Spring-actuated clutches require power to disengage. A variety of engagement methods are available. Non-contact clutches uses methods such as magnetic fields and eddy currents. Friction clutches generate friction between contact surfaces. Wrap spring clutches transmit torque from the input to the output through a wrapped spring that uncoils to disengage the clutch. Oil shear clutches achieve drive engagement through the viscous shear of transmission fluid between the clutch plates. Sprags, steel wheels that tip in one direction to wedge between inner and outer races, are clutches that can often transmit more torque than other slip or overrunning devices. Ball detent clutches feature a slip mechanism in which, upon overload, seated balls are dislodged and overcome springs or air pressure engagement. Similarly, pawl clutches overcome spring or air pressure engagement and rotate out of their detent. With roller detent clutches, rollers that are held in place by springs wedge between the inner and outer races to engage the clutch. 

Selecting electric clutches requires an analysis of measurements, shaft configurations, drive and load connections, and special features. Measurements include diameter, the cross-sectional width of the assembly; length, the dimension along the axis of rotation; and weight. Shaft configurations can be in-line along the axis of the load, parallel but offset from the axis, or perpendicular (right angle) to the axis. Drive and load connections for electric clutches use shafts that attach to bores or flanges. With some drive shafts that attach to bores, the output is a drive component such as a pulley, gear, or sprocket. Often, these types of electric clutches are designed to accept several different drive components. Special features for electric clutches include feedback, zero backlash, and washdown capability.

Industrial or general-purpose electric clutches are designed for a wide variety of power transmission applications. Specialized devices are available for aerospace, automotive, heavy transport, marine, military, and off-road applications. Some electric clutches are designed for use with web tension control, automation, or robotics systems. Other devices are designed for use with conveyor drives and pump motor drives. Power take off clutches (PTO) are typically used with heavy equipment such as dump trucks, snowplows, and tractors.

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Part Numbers for Electric Clutches