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The term pressure angle refers to the angle at which the drive force between two gears is at its greatest. It is the angle that puts the most pressure on the teeth or cogs of the two gears being driven into each other. As the teeth of a gear mesh with each other, there is an amount of energy created through pressure and torque. When the teeth of the gear reach a certain point in their respective radiuses, especially in the instance of drive gears, there is a transfer of energy between the two that is at its greatest when the teeth of the gear have reached the pressure angle.
The pressure angle is generally the point of the radius after the teeth of the gear have meshed fully. The teeth have begun to apex their radius. This occurs when the drive gear uses its teeth to push the driven gear in the direction determined by the design of the machine utilizing the gears.
When the pressure angle is reached, the energy created by the application of the pressure from the drive gear to the driven gear is usually enough to turn the driven gear and force it to perform the task it is designed to. This application can also cause another pressure angle within the gear system. This occurs especially when the driven gear is utilized to operate a drive belt or chain, and the teeth of the gear are instrumental parts of the belt or chain’s movement.
As the teeth of the gear engage the belt, regardless of the direction the belt is being driven in, pressure angles are created when the gear has turned far enough to create force. That force exists behind the gear teeth and is transferred then into the belt. The angle here is the same point at which the drive gear is pushing the driven gear. Both gears are being used to exert force into another medium.
The way a gear works on its axis is what creates the generation of the pressure angle, in a physical sense. The gear itself is used to drive something, whether it is a belt or chain or even another gear. Any time the gear is used to engage another mechanism, there is a pressure angle at some point within the system. It’s most typically found at the point after full contact between the gear and the medium being driven, or just after the apex of the radius. Usually, because most mechanisms relate vertically, the pressure angle is shortly after the tooth of a gear passes the centermost point of the top of the gear’s rotation.