Abstract: A system for starting an air compressor in a low-temperature state includes a motor configured to generate rotation force according to a control signal of a controller, a piston configured to compress air through reciprocating motion using rotation force of the motor, an oil pump configured to provide oil stored in an oil pan to a rotation axis of the motor, an oil supply line configured to connect the oil pan to the oil pump, a recovery line configured to connect a discharge port of the oil pump to the oil supply line, and a valve connected to the recovery line and controlled by the controller, where the controller controls an on/off state of the valve based on a temperature of the motor, revolutions per minute (RPM) of the motor, or a pressure of the oil pump.

Abstract: An S-cam brake includes an S-cam unit for braking a drum, where the S-cam unit includes an S-cam of an “S” shape having an involute tooth profile at left and right sides thereof, and horizontal tangential members forming contacting surfaces engaged with the involute tooth profile symmetrically around a center point of a circle at the left and right sides of the S-cam, and being spread at the left and right sides with normal lines of the contacting surfaces as a horizontal direction when the S-cam rotates.

Abstract: An S-cam brake includes an S-cam unit for braking a drum, where the S-cam unit includes an S-cam of an “S” shape having an involute tooth profile at left and right sides thereof, and horizontal tangential members forming contacting surfaces engaged with the involute tooth profile symmetrically around a center point of a circle at the left and right sides of the S-cam, and being spread at the left and right sides with normal lines of the contacting surfaces as a horizontal direction when the S-cam rotates.