Plastic article or earthenware shaping or treating: apparatus – With apparatus assembly or dismantling means or with idle part – For extrusion or injection type shaping means
Patent
1995-09-28
1997-10-07
Mackey, James P.
Plastic article or earthenware shaping or treating: apparatus
With apparatus assembly or dismantling means or with idle part
For extrusion or injection type shaping means
425589, 425590, 4254501, B29C 4567
Patent
active
056745419
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a mold closing unit for an injection molding apparatus, having a moving mold platen and a fixed mold platen that are connected by four guide rods positioned at the platen corners, with the symmetric platen being attached to hydraulic cylinders in prolongation of the rod axes and moveable along the guide rods.
The objective of such a mold closing unit is, on the one hand, to allow a displacement of a moving mold platen toward and away from a fixed mold platen at a high velocity, and, on the other hand, to effect at already closed mold a high clamping pressure that compensates the counterforce generated by the injected compound and prevents an opening of the mold and therefore an escape of the molding compound from the mold.
A number of proposals are known to meet these objectives.
Typically, between two fixed plates, that are connected together by four rods, a slideably supported plate is moved by a drive mechanism along these rods.
In general, this mechanism includes one or several hydraulic cylinders for effecting the high-speed traverse, and one or more pressure pad cylinders for generating the clamping force.
Furthermore, distinction is being made between direct clamping machines, in which the pressure pad cylinders are supported by an aspirated oil column, and hydromechanical machines that effect the support by means of a mechanical clamping action.
Systems are also known which use a toggle lever device for displacement of the plate.
In general, such a toggle lever device is driven via a centrally acting hydraulic cylinder. However, the second fixed platen used in this configuration must be movable in order to permit adjustment of the respective zero point during a tool change (for varying workpiece heights). This is especially required as the toggle lever device allows only a maximum position. The displacement of this platen is generally effected by a gear motor and a planet wheel, thereby further complicating the structure.
It is known from the above-mentioned configurations to operate the closing unit by a centrally acting piston cylinder which during displacement of the mold platen replaces its oil volume via a tank positioned directly below the unit. A second cylinder, which may also be arranged within the piston cylinder, effects a rapid motion of the unit, with oil being aspirated via the second cylinder, and with a pump building up pressure for generating the clamping force after closing the piston space.
Further, a mold closing unit is known in which the clamping force is generated by rods serving simultaneously as piston rods This unit uses a symmetrical 4-point force introduction, with oil being displaced through separate high-speed cylinders from one piston side to the other. Oil is thereby moved through external oil conduits that are arranged about the unit, with the rods being secured on a plate-shaped stand. The use of the high-speed cylinder again reduces the space required for ejection.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a mold closing unit of the afore-mentioned type, obviating the drawbacks of the prior art.
It is thus an object of the invention to provide a mold closing unit of simple configuration without a support plate, of shorter structure, smaller weight, better accessibility and therefore creation of more space for the ejection unit.
It is a further object of the invention to provide a rapidly reacting motion cycle of the mold closing unit without particular additional measures, especially without high-speed cylinders as well as to provide a higher mold opening force.
It is also an object of the invention to avoid a feeder tank and to enable a simple and quick withdrawal of the rods for installation of bulky molds.
These objects are attained in accordance with the invention by providing two piston rods of a diameter which is smaller and two piston rods of a diameter which is greater than the diameters of the identical rods so that the contact surfaces of the pistons of each hydraulic cyl
REFERENCES:
patent: 3663140 (1972-05-01), Hehl
patent: 4105385 (1978-08-01), Hehl
patent: 4111629 (1978-09-01), Nussbaumer
patent: 4128380 (1978-12-01), Jamann
patent: 4249880 (1981-02-01), Wohlrab
patent: 5336462 (1994-08-01), Wohlrab
patent: 5422060 (1995-06-01), Nakamura
Feiereisen Henry M.
Mackey James P.
Stutius Wolfgang
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