Brakes
Brake
Brake is a device used for device for slowing or or to control its speed to a certain value under varying conditions or stopping a vehicle or other moving mechanism by the absorption or transfer of the energy of momentum, usually by means of friction.
Where brakes are used?
The usual answer is in a car or a vehicle where safe, fast and smooth stopping when required or simply when there is a need to stop at a stop sign or in a driveway. And not always brakes are used to bring the vehicle to a full stop. For slowing down in traffic or to turn round a curve requires braking to decrease the speed from a higher to a lower speed.
Brake are also used in elevators, escalators, hoists, and winches, which must stop and hold a load after lifting it. Also in machine tools, conveyors, and other manufacturing equipment must often be brought to a safe, quick stop employs brakes.
Classification of Brakes
Drum brakes
Band brake
Cone brake
Disk or axial brake
Drum Brakes
Drum brakes apply friction to the external or internal circumference of a cylinder.A drum brake consists of the brake shoe, which has the friction material bonded to it, and the brake drum. For braking, the shoe is forced against the drum developing the friction torque. Drum brakes can be divided into two groups depending on whether the brake shoe is external or internal to the drum.
Internally expanding shoes
Externally contracting shoes
Internal expanding shoe brake
Most drum brakes use internal shoes that expand against the inner radius of the drum with brake lining . Internal drum brakes are used in automotive applications. A drum brake consist of two brake shoes and linings supported on a back plate bolted to the axle casing of drum. The shoes are pivoted at one end on anchor pins fixed on to the back plate . The brake can be actuated by a double hydraulic piston expander or cams, which forces the free ends of the brake so that the shoes come into frictional contact with the rotating brake drum. The leading shoe is identified as the shoe whose expander piston moves in the direction of rotation of the drum.The trailing shoe is the one whose expander piston moves in the direction opposite to the rotation of the drum.
Internal Expanding shoe brake
Band Brake
One of the simplest types of braking device is the band brake.This consists of a flexible metal band lined with a frictional material wrapped partly around a drum.The brake is actuated by pulling the band against the drum as illustrated in figure.
Bank brake
Disk Brakes
Disc brakes are familiar and common from in automotive applications. They are used extensively in cars and bikes.Disk Brakes consist of a cast iron disc, bolted to the wheel hub. This is sandwiched between two pads actuated by pistons supported in a calliper mounted on the stub shaft . When the brake pedal is pressed, hydraulically pressurized fluid is forced into the cylinders pushing the opposing pistons and brake pads into frictional contact with the disc. The advantages of this form of braking are steady braking, easy ventilation, balancing thrust loads and design simplicity.The use of a discrete pad allows the disc to cool as it rotates, enabling heat transfer between the cooler disc and the hot brake pad.
Disk brake operation