Mechanical Brake and Clutch Assemblies Information
In the world of power transmission, mechanical brake and clutch assemblies play an import role when space minimization is important. Mechanical brake and clutch assemblies consist of a mechanical clutch for engaging power from the power source to the assembly and a mechanical brake used to slow or stop rotating equipment. Mechanical brake and clutch assemblies are distinguished from hydraulic brake and clutch assemblies in the way the braking and clutching components are actuated. Most mechanical brakes and clutches use mechanical actuators to engage/disengage clutches and brakes. Some mechanical brakes are regenerative and convert kinetic rotating energy to electricity. Engaging the clutch transfers power from an engine or motor to driven devices such as a transmission or drive sprockets for a conveyor. Disengaging the clutch stops the power transfer, but allows the engine to continue turning. Braking slows or stops the movement of coupled shafts.
Mechanical brake and clutch assemblies are used in production equipment such as conveyors, bottle capping machines, box makers, fill and sealers, and textile processing equipment. They can also be found in transportation and off-road vehicles. Any application requiring regular disengaging and engaging gears, pulleys, belts, chains, and other rotating devices are good candidates for a mechanical brake and clutch assembly.
When specifying mechanical brake and clutch assemblies, these application specific variables are important:
- Torque Rating
- Rotational Speed
- Mounting Geometry—Inline, Parallel, Right Angle
- Connection Interface
Clutch engagement is the major differentiator between clutch types:
- Noncontact—Use a noncontact technology such as a magnetic field or eddy currents to provide engagement and drive.
- Friction—Between contact surfaces transmits power. This is the most common configuration.
- Toothed—Toothed contact surfaces transmit power without slipping. No heat is generated. Devices are engaged only when stopped or running at a slow speed (< 20 rpm).
- Wrap Spring—Torque is transmitted from input to output by a coiled spring that wraps around the output element. The device is disengaged when the spring is uncoiled via a control tang at its end.
- Oil Shear—Drive engagement is achieved by the viscous shear of transmission fluid between the device's plates.
- Plate/Disc—The torque level is controlled by compression springs that force plates together.
- Ball Detent—Ball detent is a slip mechanism in which, upon overload, balls ride up out of seats to overcome springs or air pressure engagement.
- Roller Detent—Rollers, held in place by springs, wedge between the inner and outer races to engage the clutch.
- Pawl Detent—Pawl detent is a slip clutch mechanism in which, upon overload, the pawl overcomes spring or air pressure engagement and rotates out of its detent.
Brakes operate using a broad range of methods. Different types of operation available include:
- Noncontact—Braking action is achieved through a non-contact technology such as a magnetic field, eddy currents, etc.
- Friction—Friction between contact surfaces transmits power. This is the most common type of brake.
- Toothed—Toothed contact surfaces transmit power without slipping or heat generation. Teeth are engaged only when stopped or running at a slow speed (< 20 rpm).
- Wrap Spring—A coiled spring wraps downward onto the rotating element. The brake is disengaged when the spring is uncoiled via a control tang at its end.
- Oil Shear—Braking action is engaged via the viscous action of the shearing of transmission fluid.
Brakes have several construction styles to achieve adequate braking force:
- Band—Band brakes are the simplest type of brake. They have a metal band lined with heat- and wear-resistant friction material.
- Drum—Drum brakes press shoes against a spinning surface. They are often used on automobile rear wheels.
- Disc—Disc brakes have brake pads, a caliper, and a rotor. During operation, the brake pads are squeezed against the rotor. Disc brakes have good heat dissipation properties.
- Cone—Cone brakes consist of a cup and a cone that is lined with a heat- and wear-resistant friction material. During actuation, the cone is pressed against the mating cup surface. Cone brakes are not commonly used.
Additional capacities can be added to a mechanical brake and clutch assembly. These features help customize the unit to meet special or unique requirements. Typical features and options include:
- Adjustable Torque—Adjustable torque is used primarily for slip clutches and torque limiters. Users can adjust the torque at which the clutch disengages or slips.
- Zero Backlash—There is no play or backlash during the engagement of the load and no load disengagement during a direction reversal.
- Washdown Capable—The housing is rated for washdown cleaning.
- Bi-directional—Devices can be set-up to rotate in either direction.
- Automatic Re-engagement—The clutch re-engages the load when the torque drops to an acceptable level.
- Slip Indication—Slip indication can move a pin radially when an overload occurs, or send an electrical signal to the drive motor.
- Feedback—Feedback provides an electrical or electronic signal for monitoring parameters such as position, speed, torque, lockup, or slip status.
Brakes and clutches have been used over the centuries to both impart rotational energy to a rotating device using a clutch and to remove kinetic energy from a rotating system using a brake. While nearly all rotating systems will require a clutch to disconnect and connect the power source and a brake to slow or stop the system, clutch/brake assemblies allow for robust design without sacrificing space. Mechanical brake/clutch assemblies are suitable when a mechanical actuation source is available.