| 摘要 |
<p>An hydraulic control system is disclosed for energizing a load, such as the lift cylinder (56) of an electric lift truck, with a minimum of power loss during the transition from zero to full energization, i.e. during the feathering range. An electric motor (44) drives a positive displacement pump (42) which supplies the flow requirements of different load circuits, one having a greater flow requirement than the other and requiring higher pump speed. A proportioning valve (86) of the open centre type provides full flow to the tank (54) when the valve (86) is closed and full flow to the load circuit having the greater flow requirement when the valve (86) is open. A manually actuable lever (16) actuates the valve (86) through the feathering range with the pump motor in a low speed range and actuates a speed control switch (218) to operate the motor (44) in the high speed range when the valve (86) is fully open.</p> |
