Patent ID: 6935111

Claim:
A drive device, in particular for a closing unit, an injection unit or ejectors of an injection molding machine for plastics, having a drive element ( 25 , 234 , 253 ) which is movable axially by an electric motor ( 11 , 170 ), and having a hydraulic unit ( 12 ) which is movable in same direction as the drive element ( 25 , 234 , 253 ) by a movement of the drive element, wherein the hydraulic unit ( 12 ) is a power transmission means having two pistons ( 28 , 228 , 256 , 334 ; 36 , 290 , 318 ), which include a small piston and a large piston that are movable relative to one another and differ from one another in the sizes of their effective areas, and having an intermediate part ( 37 , 287 , 317 , 437 ) which together with the two pistons encloses a pressure space ( 35 ) filled with a pressure fluid, wherein the small piston ( 28 , 228 , 256 , 334 ) having the smaller effective area is mechanically connected to the drive element ( 25 , 234 , 253 ), wherein the hydraulic unit ( 12 ) is movable as an entity for a regulating movement, and wherein for exerting a high force by the large piston ( 36 , 290 , 318 ) having the larger effective area, the intermediate part is locked against displacement relative to a fixed frame ( 10 , 240 , 433 ).