Development and research of hydraulic drive of sheet shears

The paper describes the pump gear-multiplier drive of sheet shears with a two-cylinder power unit. The description of the developed drive scheme with the use of dual dispensers (reducer and multiplier) of periodic action is given. The gear is engaged at idle, the multiplier – at work. Their charging comes up at the reverse course of the power unit. Each dispenser has an input cylinder connected to the pump and two dosing (output) cylinders connected separately with the power cylinders of the power unit. In this case, the cylinder bodies form a fixed block, and the plungers (pistons) – a movable block. It solves the main task: synchronization of movement of the pistons (plungers) of the power cylinders during all operation periods. Due to different ratio of the area of pistons (plungers) of inlet (Fв ) and dosing cylinders (2Fд ), a direct stroke mode with two stages of pump speed and pressure is provided. For the reducer, ratio (Fв /(2Fд )) determines reduction coefficient (Kp 1). As a result, the idling speed of the pistons of the power cylinders and pressure developed by the pumps increase, and  during the working stroke – these values decrease. Working pressure of the pumps is equalized at a direct flow at a reduced level, which determines reduction of their installation power (up to 30 %). The analysis of graphs of power loading and speed was made. The condition of constant load at each of three main periods of the drive operation was accepted as: idle, working and reverse. Determinant parameters of the considered drive are the coefficients Kр (reduction), Kм (animation) and Kс – the gain of the power unit. The paper presents a comparative analysis of the considered and simple pump drive in order to establish the received combination and range of these values.