"DIE-CASTING MACHINE"

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Field of Invention

This invention concerns horizontal die-casting machines and refers in particular to a die-casting machine with an improved closing and clamping device. State of the technique

More often, the machines for die-casting metal parts comprise a bedplate and on said bedplate a fixed vertical platen, and a moving vertical platen, where said two platens are parallel and the moving platen is guided above the bedplate and movable horizontally towards and away from said fixed platen.

The moving vertical platen, besides being guided along the bedplate, is guided along the horizontal columns, usually four, that extend from the fixed platen. The facing sides of the fixed and moving platens support the two complementary parts of a mould forming together the shape of the item to be die-cast. One part of the mould is stationary, fastened to the fixed vertical platen; the other part of the mould is fixed and moves with the moving platen to close and open the mould.

On the bedplate, in association with the external face of the fixed platen an injection unit is provided and supported to deliver the molten metal into the cavity of the mould when the latter is closed.

The fast movements of the moving platen with the relative part of the mould, between the open and closed positions, can be achieved by means of at least one hydraulic cylinder. However, when it is then in the closed position, the moving platen must also be blocked to ensure that the mould remains closed in opposition to the thrust of the molten material that is injected into it.

Blocking can be carried out either by using clamps positioned and operated to radially engage the horizontal guide columns, just behind the moving platen, or by using a toggle system. In the first case, the machine will have only two vertical planes, one fixed and the other mobile, and the horizontal guide columns are substantially overhanging starting from their proximal ends connected to the fixed vertical platen, as their distal ends have no support. Even if they extend through the moving platen, the columns remain susceptible to flexure/deflections, conditions that can be adverse for a correct and precise guide of the moving platen along the bedplate during its opening and closing movements of the mould. In the second case, which is a widely used application in plastic injection machines, the toggle blocking system is connected to the rear face of the moving paten and can be supported by a third vertical platen, a so-called reaction platen, that extends upwards from the bedplate, at the back and at a distance from the moving platen.

However, the reaction platen is not properly fixed or rigid in that it is assembled on the bedplate with the possibility of traverse for its positioning and movements, even though limited, in response to the blocking thrusts of the toggle system when this is activated. Consequently, it can still be seen

that the guide columns are not rigidly supported at their distal ends and that the guide of the moving platen in its opening and closing movements does not always seem correct and precise. Objective and Summary of the Invention

The objective of this invention is to eliminate the above inconveniences and drawbacks in a die-casting machine and at the same time create the conditions so that such a machine has a structure which is really rigid so as to improve its performance by having a moving platen with maximum movement precision and subsequent closure of the mould. The objective is achieved with a die-casting machine according to the preamble in claim 1 and characterised by a third rigid vertical platen, fixed stably on the bedplate in parallel at a distance and at the back of the moving platen so that said third platen forms a positive support for the distal ends of the horizontal guide columns. With this embodiment the die-casting machine has the following advantages:

- the ends of the horizontal guide columns are both supported, a fact that ensures permanent linearity and parallelism even under stress;

- the moving platen is guided and slides correctly along the horizontal columns, with the possibility in this way of being able to simplify the centring and sliding means of the moving platen on and relatively towards the bedplate;

- given its rigidity and stability, the third fixed platen can also be used to carry the actuator or actuators or the hydraulic cylinders designed for the

movements of the moving platen when closing or opening the mould. Brief description of the Drawings

Greater details will however become evident from the following description made in reference to the enclosed indicative and not limiting drawings, in which:

Fig. 1 is a schematic side view of an example of a die casting machine according to the invention,

Fig. 2 is a view from above of the machine in Fig. 1 , and

Fig. 3 is an end on view of the machine from the third fixed platen. Detailed Description of the Invention

As shown in the example given, the die-casting machine comprises a bedplate 21 from which extend upwards, vertically and in parallel, a first fixed platen 22, a second moving platen 23 and a third fixed platen 24 and where the moving platen 22 is positioned between the fixed platens and is movable horizontally towards and away from the first fixed platen.

Both the first platen 22 and the third platen 24 are firmly fixed to the bedplate 21 and form means of support, respectively for the proximal and distal ends, of four horizontal columns 25 placed according to the sides of a quadrilateral. The moving platen 23 is guided on the bedplate 21 and along the columns 25 that cross it.

The first fixed platen 22 and the moving platen 24 hold to two matching parts of a forming mould-not shown- which is opened and closed in response to the movements of the moving platen away from and towards the first fixed platen, respectively.

The bedplate also supports an injection unit 26 placed external to the first fixed platen 12 and designed to inject the molten metal into the mould when the latter is closed. At least one hydraulic actuator 27 can be associated with the moving platen 23 for its movements from one position to the other. More specifically in the example illustrated in the drawings two hydraulic cylinders are provided, assembled advantageously in a symmetric position on the third fixed platen 24 and with relative rods facing towards and connected to the moving platen.

Lastly, the face of the moving platen 24 opposite the one holding its respective part of the mould and related to each guide column 25, is associated a stopping device 28, which is in itself well known, provided to radially engage the relative column and to block the moving platen in the forward closed position of the mould during the die-casting steps.