The most common lift tables are hydraulically operated and use what is referred to as an Electro/Hydraulic power unit. The 5 main power unit components are electrical controls, electric motor, a hydraulic gear pump; a solenoid operated lowering valve, and a reservoir.
The electrical controls take an input voltage and allocate electrical power to the different components as required to facilitate the operation of the equipment. The electrical controls also include a user interface which is typically a hand held push button /control station with up and down push buttons. The controls can also include limit switches to stop the lifts travel at predetermined positions. Other customization can be provided to the electrical controls to accommodate specific applications requirements.
The electric motor is typically connected to the gear pump. To raise the lift table the operator depresses the Up button on the control station. The electric motor starts to operate and pumps hydraulic oil from the reservoir to hydraulic cylinder(s) causing the lift table to rise. When the Up button is released a check valve in the pump prevents the oil from running back to the reservoir holding the lift table in the raised position.
To lower the lift table the operator depresses the Down button on the control station. The solenoid operated lowering valve opens, the hydraulic oil exits the hydraulic cylinder(s) and returns to the reservoir as the lift table lowers.
For any lift table, the hydraulic gear pump output rate (gallons per minute) determines the lift speed. To achieve a faster lift speed a larger volume pump is required, to drive a larger volume pump a higher horsepower rated electric motor is required.
The lowering speed varies depending on the configuration of the lift table, The size & weight, number of cylinders, hydraulic power unit size, hydraulic hose size, the viscosity of the hydraulic fluid and the amount of load on the platform during lowering all can affect the lowering speed of a lift table.) The power units are equipped with a pressure compensated fixed flow control valve in the hydraulic return line restricting the maximum lowering speed as determined by the manufacturer. The pressure compensation somewhat offsets the effects of the lift table load on the lowering speed.
For additional information on power units or any Pentalift product please contact the Pentalift Sales Department.