Hoist drum drive control

摘要

A hoist drum drive control is provided with both variable displacement and fixed displacement motors geared to the drum and connected in parallel to a variable displacement pump. During high speed hoisting the variable displacement motor is shifted to zero displacement until the back pressure reaches a certain level at which time the displacement is automatically increased until a balanced condition is achieved. When lowering heavy loads a feedback to the variable pump decreases its displacement to prevent over speeding the engine.