IMPROVED MOLDING CHAMBER FOR GREEN SAND MOLDS

PURPOSE OF THE INVENTION

The present invention relates to a moulding chamber for green sand cakes, which has been improved in order to permit a reduction in the consumption of sand participating in the cake, when so permitted by the dimensions of the mould to be obtained, through the infra-dimensioning of the respective cake, based on obtaining a moulding chamber of variable volume.

BACKGROUND OF THE INVENTION

In cake moulding machines for casting, a tubular chamber is formed, generally rectangular in cross section, which is closed at one of its extremities by means of a movable wall, hinged in order to permit the egress of the cake once moulded, whilst at its other end it is closed with the wall associated with the actual piston for compacting and subsequent expulsion of the cake, that is, in said chamber participate four fixed walls, those constituting the tubular body, the upper one with the pertinent mouth or orifice through which the sand enters, and two movable ones, in correspondence with the six general faces of the cake to be obtained, see e.g. US-A-5 332 025.

More specifically and as is illustrated in the different sequences of figure 1, the sand cavity is produced with the two movable walls duly separated (first sequence), next the movable walls are moved towards each other in order to produce the compacting action and rapid expulsion (second sequence), after this one of the movable walls is displaced outwards longitudinally and then tilted upwards, in order to leave a free passage for the cake (third sequence), following this the other movable wall, that associated with the compacting and expulsion piston, is displaced by the action of its own piston displacing the cake until it comes into contact with that immediately preceding (fourth sequence), then the piston is again retracted returning to its initial position and the filling of the mould takes place (fifth sequence), and finally the hinged other wall descends and is displaced longitudinally until facing the first (sixth sequence), in the same position as in the first sequence in order to commence the work cycle once more.

As may be deduced from the foregoing explanation, the actual characteristics of the moulding chamber define some invariable parameters there for, given that both its upper and lower walls, and its side walls, are fixed, in such a manner that when the casting to be obtained, by being smaller in size, would theoretically permit the use of smaller cakes, that is having less quantity of sand, this is not possible as it is necessary to fill with sand the entire chamber defined in the machine.

This unnecessary over-dimensioning of the cakes implies the following drawbacks:

• As the sand available in the factory is fixed (a determined number of tons), the case can arise wherein the amount of sand available is insufficient to meet the cake production rate of the machine. That is, the machine is capable of producing more cakes than the quantity which the sand available in the casting shop can provide for.
• The sand, after the casting process and destruction of the mould, has to be treated in order to remove impurities, which involves the moving and handling of said sand and the ensuing processing, which assumes costs and times in terms of the amount of sand to be processed.

DESCRIPTION OF THE INVENTION

The improvements in green sand cake moulding chambers which are proposed through the invention overcome the aforementioned problems in an entirely satisfactory manner.

To this end said improvements consist in making the moulding chamber be of variable volume, permitting its adaptation to the specific requirements of each type of cake to be obtained, particularly reducing the theoretical and maximum dimensions of said chamber.

For this and in a more specific manner, the walls of the chamber, previously fixed, are now made to be movable, specifically formed on a basis of respective plates, each of which in turn is mounted on a plate-holder frame, accompanied by hydraulic cylinders for the movement thereof, as well as by guides conveniently mounted on a support, which ensure perfect displacement of the plates in their closing and opening movements.

Clearly this entails the need to also alter the traditional two movable walls, whereby on each of these is defined a pattern plate, of appropriate width for the cake to be obtained, width variable between a maximum measurement and a minimum measurement, the maximum measurement corresponding to the greatest width foreseen in the mould-making chamber and a minimum measurement defined by the width of a plate-holder frame to which is secured, preferably by screwing, the pertinent pattern plate, said plate-holder frame being in turn fastened, preferably by means of pneumatic clamps, to the plate which in one case shall be fixed to the pneumatic compacting cylinder and in the other to the hinged and displaceable arm which permits the opening of the mould-making chamber.

DESCRIPTION OF THE DRAWINGS

To complete this descriptive specification and in order to assist in a better understanding of the characteristics of the invention, in accordance with an exemplary practical embodiment thereof, as an integral part of said descriptive specification, a set of drawings is attached in which by way of illustration and not restrictively, the following is shown:

• Figure 1.- Shows, in accordance with a diagram comprising six sequences, the complete cycle of a green sand cake moulding chamber of conventional type, such as has been described under the heading of background of the invention.
• Figure 2.- Shows a transversal cross section of the mould-making chamber, implemented according to the improvements of the invention.
• Figure 3.- Shows a detail in plan view of the same chamber as the previous figure, positioned appropriately for obtaining cakes of maximum size.
• Figure 4.- Shows a similar drawing to that of the previous figure, but corresponding to the position of the chamber for obtaining cakes of minimum size.
• Figure 5.- Shows, finally, a freehand perspective drawing of an alignment of cakes, all of them for obtaining identical castings, half of them obtained with a conventional machine and the other half obtained with a machine equipped with a moulding chamber implemented in accordance with the improvements of the invention.

PREFERRED EMBODIMENT OF THE INVENTION

Starting with a basic conventional chamber like that shown in the different sequences of figure 1, in which said mould-making chamber has been given the reference (1), and in which participate an upper wall (2) in which the mouth (3) has been formed for discharging sand from the pertinent hopper (4), a lower wall (5), two fixed side walls not visible in said figure and two other movable walls, one wall (6) associated with the relative compacting and expulsion piston, and one wall (8) associated in turn with a hinged arm (9), being at the same time longitudinally displaceable, in such a manner that said wall (8) is capable of being separated from wall (6) and subsequently swivelling upwards, as can be seen in the third sequence, in order to permit the expulsion of the cake (10), the improvements of the invention consisting in making the two side walls mentioned, those not shown in figure 1, also movable, in order to vary the volume of the chamber (1), in accordance with the requirements of each type of cake (10).

In more specific terms, each of these side walls has a structure based on a plate (11), which constitutes the wall in itself, mounted on a plate-holder frame (12) to which are joined guides (13) which permit its transversal displacement on a fixed support (14) when they are operated by a hydraulic cylinder (15), in such a manner that said plates (11) can take up the position of maximum separation shown by continuous line in figure 2 or any intermediate spacing up to a limiting separation of maximum proximity, that shown by dashed lines in the same figure. These two limiting positions are those which have in turn been shown in plan view in figures 3 and 4.

Additionally, between these plates or side walls (11), the plate-holder frame (16) is slid, to which is fastened by screws, as is normal practice, the plate (17) provided with the relative pattern (18 - 18'), and this assembly is fastened, in turn, preferably by means of hydraulic clamps (19) to a plate (20) joined in turn to the rod of the hydraulic cylinder (7), in such a manner that depending on the type of pattern (18- 18') to be employed in each case and on a same plate (20), different frames (16) shall be mounted with their corresponding pattern plate (17 - 17' - 18 - 18'), as is illustrated for example in figures 3 and 4.

Clearly a similar structure is repeated for the other movable wall of the chamber, that associated with the hinged arm (9).

One achieves, in this manner, as is shown in figure 5, that in order to obtain a determined casting, the dimensions of which so permit, use to be made of cakes (10) of considerably smaller dimensions, that is, with the participation of a much smaller quantity of sand, than those which would be necessary with a conventional moulding chamber and which appear referenced with (10') in the upper left-hand part of said figure 5.

From the construction described it can be deduced that the improvements of the invention not only permit a dramatic reduction in the consumption of sand in order to obtain the cakes, but also offer the possibility of employing tools of different patterns of machines of smaller size, flexibility in designing new tools, by having available distinct options for the superficial distribution of the patterns, and an optimisation of process efficiency in the event of a limited sand storage capacity.