Synthesis of the Pipeline Valve Drive with Automatic Switching of Speeds

Abstract

In the drives of the shut-off valves, planetary gears are widely used. However, their existing designs with manual speed switching are difficult to manufacture and inconvenient to operate. The drive, made on the basis of an eccentric planetary gear with flexible elements, is devoid of these disadvantages and provides automatic switching speeds depending on the load on the operating body of the valve. The most important details of this drive are flexible elements made in the form of rods rigidly embedded in the driven member. Their dimensions should provide the required strength and rigidity and correspond to the parameters of the planetary gear. The diameter of flexible elements and their length for a given number were determined based on the condition that when the mechanism is operating in the mode of direct transfer of movement from the pulley to the driven link, the radial displacement of the movable gearwheel as a result of deformation of the flexible elements does not exceed the gap between the surfaces of the tops of teeth of gearwheels in the absence of load; and when operating in the gearbox mode, it is equal to the interaxial distance of the gear. In this case, the methods of structural mechanics were used. Parameters of the planetary gear (the number of gearwheel teeth, pressure angle, gearing module, and facewidth) were determined from calculation of teeth for bending strength and with account of the eccentricity of the gearwheel with external teeth when operating in the gearbox mode. Thus, it was found that with the torque at the input shaft of the drive under 240 Nm and rational values of gearwheel tooth numbers, the length of flexible elements does not exceed 150 mm and their diameter is 13 mm. The presented structure of the shut-off pipeline valve drive with automatic switching of speeds and methods of its analysis allow for performing the rational design of the described mechanism.