Development and Research of Multi-Stage Hydraulic Gear-Multiplier Drive for Metallurgical Presses

The paper presents a solution to reduce the generated power and to increase the efficiency of a hydraulic pump drive of the high-capacity press equipment applied at the metallurgical plants. We developed a multi-stage gear-multiplier pump hydraulic drive on the base of the blocked gear-multiplier. Plungers of all cylinders form a movable block, the cylinders—a fixed block. A combination of the output cylinders supplying fluid into the power cylinder provides the operating mode (reduction, multiplication) by switching a part of them to drain. We compare the four-stage drive with the three-stage gear-multiplier to a simple single-pump drive. The four-stage drive with two output cylinders provides the gear stage and two multiplier stages, the stage of supplying liquid to the power cylinder directly from the pumps (the pumping stage) being combined with them. The force loading during the working stroke and the speed mode during the working cycle—forward (idle and working) and reverse – govern the power and the kinematic drive parameters. Application of the multi-stage drive is appropriate under the smoothly increasing load over the entire working stroke (upsetting and draw-forming operations). We analyze the basic and additional stage combinations for the linearly increasing power load governed by the pressure at the beginning, P 0 , and the maximum pressure at the end of the working stroke, P max . In the basic version, a gear stage (idling), a pump stage, and two multiplier stages are sequentially combined (work stroke). At the additional combination, the gear stage covers the idling and the initial part of the working stroke. Under the conditions of the pressure and the pump power equality in each stage and equality of the forward stroke duration for the compared drives, we performed the analysis and estimated the ratio of the pump capacities. We obtain the dependences of the main parameters of the drive developed, as well as the reduction and the multiplication coefficients. At the initial data considered, it is possible to reduce the pressure and the power of the developed drive pumps (as compared to a simple one) by 28–37% (increasing with the idling stroke increase) by means of additional step combinations. For the basic combination—by 5–9% lower (more reduction at lower idling values). Application of the additional combination is limited by the ratio P 0 / P max ≤ 0/4.