A: The framework oil seal is generally composed of three parts: oil seal body, strengthen the skeleton from the tight spring. Oil seals, usually in the free state of the skeleton and its inner diameter is smaller than the shaft diameter, with a certain amount of interference, when the oil seal is a sealed chamber and the shaft lip pressure and spring contractility. axis radial clamping force over a period of time, the pressure decreases rapidly disappeared. Thus, coupled with the spring at any time to compensate for the tightening force of the oil seal.