Patent ID: 7003953
Filing Date: 2006-02-28
Classification: B29C

Abstract:
1. A drive device, in particular for a closing unit, injection unit or ejectors of a plastics injection molding machine, the drive device comprising a drive element ( 10 ) which is axially moveable, and a hydraulic unit ( 12 ) which, by movement of the drive element ( 10 ), is moveable in same direction as the drive element, wherein the hydraulic unit ( 12 ) is a force multiplier comprising an intermediate part ( 15 ), and a large piston ( 13 ) and a first small piston ( 14 ) which are moveable within the intermediate part and which pistons are movable in relation to one another and differ from one another in size of their effective surface areas, wherein the intermediate part ( 15 ) together with the pistons enclose a pressure chamber ( 16 ) filled with a pressure fluid, the first small piston ( 14 ) has a smaller effective surface area than the large piston, and is mechanically connected to the drive element ( 10 ), wherein the hydraulic unit ( 12 ) as a whole is moveable for a positioning movement, and wherein, for exertion of a great force by the large piston ( 13 ), the intermediate part ( 15 ) can be blocked against displacement in relation to a fixed frame ( 11 ) by a blocking device during a force build-up movement of the drive element ( 10 ), and wherein the hydraulic unit ( 12 ) further comprises a second small piston ( 19 ) moveable within the intermediate part ( 15 ) and a fluid chamber ( 21 ) which is disposed in the intermediate part ( 15 ) and is adjoined by the second small piston; and wherein, arranged between the fluid chamber ( 21 ) and the pressure chamber ( 16 ) is a valve ( 28 , 40 ), via which valve pressure fluid is forceable out of the fluid chamber ( 21 ) into the pressure chamber ( 16 ), and by which valve the fluid chamber ( 21 ) is shutable off with respect to the pressure chamber ( 16 ).