Lifting device

A lifting device for motor vehicles, comprising:

• at least two main lifting units,
• at least two additional lifting units,
• one of the at least two additional lifting units being disposed on one of the at least two main lifting units in such a way that by using one of the at least two additional lifting units a main lifting height of the lifting platform may be extended to a total lifting height,
• a control unit, and
• at least two measuring units for determining lifting heights,
• wherein both one of the at least two main lifting units and one of the at least two additional lifting units can be driven by the control unit,
• wherein at least one main control element and at least one additional control element is provided, the main control element and the additional control element being switchable in dependence upon each other in such a manner that alternatively only the main control element or the additional control element may respectively be transferred into an active state,
• wherein the control unit has a flow divider and a plurality of by-pass valves,
• wherein if a lifting difference is determined, one of the plurality of by-pass valves is opened by the control unit to discharge a part of an oil volume directly into an oil reservoir from a side having a greater height, and
• wherein the control unit comprises a synchronization control of the at least two main lifting units and of the at least two additional lifting units, and synchronization control of the at least two main lifting units or of the at least two additional lifting units may alternatively be performed by means of the control unit.