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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 Some machines for die-casting metal parts usually comprise a bed and on said bed a first vertical fixed plate, a second vertical fixed plate at a distance from the first and a moving vertical plate between the fixed plates which moves horizontally.

Horizontal columns rigidly join the two vertical fixed plates, whereas the intermediate moving plate is guided on the b_ecLaαd_slides-alQn§-the-horizoπtah columns to move towards and away from the first fixed plate.

The facing sides of the first fixed plate and the moving plate hold a mould made up of two complementary parts forming the cavity of the item to be die cast. One part of the mould is stationary, fixed to the first fixed vertical plate; the other part of the mould is fixed and moves with the moving plate to close and open the mould.

The bed, working in association with the external face of the first fixed plate, supports an injection unit to deliver the melted metal into the mould when the latter is closed.

The movements of the intermediate plate with the relative part of the mould can be achieved by at least one hydraulic cylinder. However, when it is in the forward, mould closed position, the moving plate must also be clamped to ensure that the mould remains closed in opposition to the thrust of the melted material that is injected into it.

In die-casting machines this clamping operation is usually achieved using a toggle system positioned between the moving plate and either the second fixed vertical plate or another stationary reaction element. However, such a toggle system, even if functional, is relatively complex and cumbersome, also influencing the complexity and overall dimensions of the machine. Furthermore its closing and clamping force is exercised principally in an intermediate zone of the moving plate and consequently of the mould, but not uniformly also around the peripheral zone of the mould, thus allowing the possibility of leaks at the highest injection pressure of the melted metal.

In truth, in another field of_^p^lic^tjojτJhatJs _^ inJnjeGtion-mauldirtg-τ)f- plastic materials, horizontal presses have been proposed with a structure similar to that of die-casting machines, that is with fixed plates connected by horizontal columns and a moving plate holding the forming mould with one of the fixed plates, but where clamping in the closing position of the moving plate and consequently the mould is achieved by jaws gripping the horizontal columns externally just to the rear of the moving plate.

As far as is known, a technological solution of this kind has never been proposed neither applied to die-casting machines. Objective and Summary of the Invention

It is therefore the objective of this invention to propose and manufacture a horizontal die-casting machine in which the more usual toggle closing system is eliminated and replaced by thrust and clamping means directly associated with the horizontal guide columns and moving plate supporting one part of the closable mould which can close against another matching part of the mould supported by a fixed plate. In this configuration the die-casting machine has the advantages of being simpler and open and where there is the possibility even of eliminating the second fixed plate, leaving the fixed plate and the mobile plate holding the half moulds. Furthermore the machine is easier to access for maintenance and, powers being equal, it can be less cumbersome due to the elimination of the toggle closing mechanism and, if required, the second fixed plate. Above all, the system allows a more efficient closing of the mould, uniform in all its parts, even along its periphery where closing and sealing always seem problematic.

In agreement with the invention, such an objective and the aforementioned advantages are achieved in a machine for die casting according to the characterising part of claim 1 of the appendix. Brief description of the Drawings

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

which:

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

Fig. 2 shows a view from above of the machine in Fig. 1 ; Fig. 3 shows an end on view;

Fig. 4 shows, in an enlarged cross section, the clamping means associated with a guide column of the moving plate; and

Fig. 5 shows a cross section according to arrows V-V in Fig. 4 Detailed Description of the Invention In the example given, the die casting machine comprises a base 11 from which a first fixed plate 12, and a second fixed plate 13 extend upwards, the latter at a distance from the first, and a moving plate 14 positioned and moving horizontally between the fixed plates.

These two fixed plates 12, 13 are connected rigidly to each other by horizontal columns 15 positioned according to the sides of a four-sided figure, and the moving plate 14 is guided on the bed 11 and along the columns 15 which cross it. The first fixed plate 12 and the moving plate 14 hold the two matching parts of a forming mould - not sJnfflΛ∞- _^ -whiGh-aFe-θpened-and- closed in response to the movements of the moving plate either away from or towards the first fixed plate, respectively.

The bed also supports an injection unit 16 placed external to the first fixed plate 12 and used to inject the melted metal into the mould when the latter is closed.

At least one hydraulic actuator 17 can be associated with the moving

plate 14 for its fast movements finalised at opening and closing the mould.

Now, according to the invention, in the face of the moving plate 14 opposite the one holding the respective part of the mould, there is, around each column 15, a chamber 18, which is fed by a fluid under pressure like a hydraulic cylinder and which houses a piston 19 positioned around the column itself.

Furthermore, on a length of each column 15, such length corresponding to at least the stroke of the moving plate 14 required to open and close the mould, are machined a number of parallel annular teeth 20 protruding radially, defined by a series of grooves 21. The bottoms of these grooves are preferably sloping towards the axis of the same column in the direction of the movement of the moving plate to open the mould, so that each tooth 20 defines a radial shoulder 22 facing towards the moving plate, that is to say, on the contrary, in the opposite direction to the one for opening the mould. A pair of opposed clamping jaws 23 is fixed behind piston 19,which follow the axial movements of the piston and which move radially, towards and away from the respective column 15, in a clamping and releasing position, i.e. by means of a hydraulic control cyljnder 24.

These jaws each have internal teeth 25 to engage with the annular teeth 20 around column 15 when they mate. The internal teeth 25 of the jaws are shaped so as to present a radial side 26 made to rest against the radial shoulder 22 of the annular teeth of said column.

Basically, when the moving plate is moved forward and backwards the jaws 23 remain in the clamped position and the piston 19 is inactive.

When the moving plate is moved forward in the closed position of the mould so that the machine can be used, the pair of clamping jaws 23 associated with the moving plate are driven and moved towards their respective column to engage their teeth 20. Then the pistons 18, also associated with the moving plate and positioned around the columns, are activated so as to close tightly and hold the mould in the closed position, finding opposition from the teeth of the jaws engaged with those of the columns against the thrust from the injection of the melted metal into the mould. For the successive opening of the mould, simply deactivate the pistons

19, then retract the jaws 23 in the clamped position and move the moving plate backwards using the relative hydraulic actuator.

Lastly it should be noted that the same mould clamping system when closing it is also applicable for die casting machines with only two vertical plates: one fixed plate and one moving plate joined by means of guide columns and holding the two matching parts of a mould.