Pneumatic Brakes Information

Pneumatic Brakes Information

Pneumatic brakes are equipment drive assemblies that use air-actuated components to slow or stop shafts. There are several basic types of pneumatic brakes. Band brakes, the simplest pneumatic brake configuration, feature a metal band lined with heat and wear resistant friction material. Drum brakes, which are commonly used on automobile rear wheels, actuate when shoes press against a spinning surface called a drum. Disc breaks consist of a caliper that squeezes brake pads against a rotor. Cone brakes include a cone that is lined with heat and wear resistant material that presses against a mating cup surface. Typically, pneumatic brakes are used in large motorized vehicles such as buses because they provide reduced braking distances.

Specifications

Specifications for pneumatic brakes include torque rating, speed, power, maximum pressure, linear force, and linear speed. Spring-return brakes require power to engage. Spring-actuated brakes require power to disengage. A variety of engagement methods are available. Non-contact brakes use methods such as magnetic fields and eddy currents. Friction brakes generate friction between contact surfaces. Wrap spring brakes transmit torque from the input to the output through a wrapped spring that uncoils to disengage the brake. Pneumatic brakes with teeth engage only during stops or at slow speeds. Oil shear brakes achieve engagement through the viscous shear of transmission fluid between the brake plates. 

Selection

Selecting pneumatic brakes requires an analysis of measurements and mounting configurations. Important 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 pneumatic brakes often 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 pneumatic brakes are designed to accept several different drive components.  

Special Features

Pneumatic brakes are available with a variety of special features. Some devices use electrical or electronic signals to monitor parameters such as position, speed, torque, lockup, or slip status. Others prevent play or backlash during load engagement and prevent direction reversal during load disengagement. Adjustable torque, the torque at which the brake disengages or can be manually adjusted, is used primarily for torque limiters. Washdown-capable pneumatic brakes use housing materials that are rated for washdown cleaning. Bidirectional pneumatic brakes can be set up to rotate in either direction.