| 摘要 |
A jack pump, such as the type capable of use in pumping crude oil from an oil well, the jack pump including a double acting piston and cylinder motor with the piston rod of the motor being adapted to be connected to the polished rod projecting upwardly from a well head. A variable displacement hydraulic pump, which is driven by a motor or engine, is included in a closed hydraulic loop wherein conduits are connected to a pair of output ports of the pump. A pump control means controls the direction and volume of flow in the loop so as to establish a total velocity profile during the complete pumping cycle and to determine the length and position of the stroke of the piston rod. |
