ITPD20120094A1 - PERFECT PRESS FOR INJECTION MOLDING OF ARTICLES WITH MORE COLORS IN PLASTIC MATERIALS, PARTICULARLY IN ETHYLVINYL ACETATE - Google Patents

Description

PRESS PERFECTED FOR INJECTION MOLDING OF MULTI-COLORED ARTICLES IN PLASTIC MATERIAL, ESPECIALLY IN ETHYLVINYL ACETATE

DESCRIPTION

The present invention relates to an improved press for the injection molding of multi-colored articles in plastic material, particularly in ethylvinylacetate.

Although the invention has been conceived for the production of articles in EVA, it can be used in general with expanded cross-linked polymeric materials with behavior similar to that of EVA.

To date, various types of molding presses are known for the production of multi-colored articles in ethyl vinyl acetate (which from here on will often be referred to in the text with the acronym EVA), such as soles, midsoles, clogs or in general technical articles.

For example, some presses with vertical closing movement are provided with an upper and a lower half-mold between which an intermediate plate is interposed.

This, suitably shaped in correspondence with its opposite faces, constitutes with the two half-molds an upper imprint and a lower imprint in which are respectively injected, substantially horizontally by injectors positioned on one side of the press, EVA of a first color for the molding of a first portion of a multi-colored article and EVA of a second color for molding a second portion of the article.

Subsequently the intermediate plate is extracted, the lower and upper half-molds are closed to make the two injected portions adhere, they are heated up to the cross-linking temperature and finally opened. During the extraction of the intermediate plate this is made to translate substantially horizontally towards the injector to leave the operator, who works on the side of the press opposite to the injection side, the free space necessary to take the finished product from the mold .

Although the use of EVA is now very widespread, as it is known, its injection releases small particles of dirt on the walls of the mold that produce waste material, consequently raising production costs and reducing productivity.

During the production of EVA items it is therefore essential to properly clean the walls of the mold.

But if on the one hand these structures allow the operator to easily extract the product, on the other hand they are impractical when he has to access the intermediate plate for maintenance operations, such as cleaning and silicone coating. In fact, when the plate is moved towards the injector, it is positioned on a side of the press that is inaccessible to the operator and therefore cannot be adequately cleaned and siliconed.

The object of the present invention is to improve a press for molding multi-colored EVA articles by solving the problems generated during production.

Within this aim, an object of the invention is to provide a press which allows to reduce the waste, and therefore the production costs, allowing the operator to adequately clean the mold from any residues of dirt and to perform the silicone coating easily. This task, as well as these and other purposes which will appear better below, are achieved by an improved press for the injection molding of multi-colored articles made of plastic, particularly ethylvinyl acetate, of the type comprising, in a support structure, a composite mold consisting of:

- a first half-mold and a second half-mold, at least one of which movable according to an opening and closing direction of said press;

- an intermediate plate, to be interposed between said first half-mold and said second half-mold and extracted therefrom, which constitutes on its two opposite faces a first intermediate half-mold and a second intermediate half-mold which, with the mold closed, define respectively with said first half-mold and with said second half-mold two series of impressions into which are respectively injected, by means of injectors positioned on one side of said press with respect to said opening and closing direction, EVA of a first color for molding a first portion of the article and EVA of a second color for molding a second portion of the article, said press being characterized by the fact that said intermediate plate can be translated according to a translation direction substantially perpendicular to said opening and closing direction by means of suitable translation means to pass from a position of injection, in which it is placed between said first and second s half-mold, to a first access position for cleaning said first intermediate mold half, in said first access position said intermediate plate being extracted from said mold from one side of said press opposite to the injection side,

and said intermediate plate is hinged to said support structure in proximity to an external side thereof oriented according to said translation direction, around a relative hinging axis to pass, by means of suitable rotation means, from said first access position to a second access position for cleaning said second intermediate mold, in said second access position said intermediate plate being rotated substantially by at least one right angle with respect to said first access position.

Further characteristics and advantages of the invention will become clearer from the description of a preferred but not exclusive embodiment of the equipment according to the invention, illustrated, by way of non-limiting example, in the accompanying drawings, in which:

Figure 1 is a perspective view of the molding press according to the invention, provided with injectors approaching the mold and with the intermediate plate in the injection position;

Figure 2 is a perspective view of the press according to the invention with the intermediate plate in the first access position;

Figure 3 is a perspective view of the press according to the invention with the mold closed;

Figure 4 is a perspective view of the press according to the invention with the intermediate plate in the second access position;

Figure 5 is a perspective view of the press according to the invention with the intermediate plate in a further position;

Figure 6 is a perspective view of the press according to the invention with an open mold for extracting the finished product.

With reference to the aforementioned figures, the press according to the invention, indicated as a whole by the reference number 10, is of the type with a vertical closing movement and has been developed for the production of two-colored EVA soles. The press 10 comprises, in a support structure 11, a composite mold 12 consisting of a first half-mold 13a and a second half-mold 13b, of which at least one of the two movable according to the opening and closing direction A of the press 10. In the illustrated example the first half of the mold 13a, upper, is movable, while the second half of the mold 13b is fixed.

The press 10 also comprises an intermediate plate 14, to be interposed between the first half-mold 13a and the second half-mold 13b and to be extracted therefrom, which constitutes on its two opposite faces a first intermediate half-mold 15a (upper) and a second intermediate half-mold 15b ( lower), which, with the mold 12 closed, define respectively with the first mold half 13a and with the second mold half 13b two series of impressions into which they are respectively injected, by means of injectors 16 positioned on one side of the press 10 with respect to the opening direction and closure A, EVA of a first color for molding a first portion of the article and EVA of a second color for molding a second portion of the article.

Advantageously, the intermediate plate 14 can be moved according to a translation direction B substantially perpendicular to the opening and closing direction A of the press 10 by means of suitable translation means 17, to pass from an EVA injection position C (illustrated in figure 1) inside the cavities to a first access position D (illustrated in Figure 2) for cleaning the first intermediate half-mold 15a.

Still advantageously, the intermediate plate 14 is hinged to the support structure 11 in proximity to its external side 18 oriented according to the translation direction B, around a relative hinging axis 19, to pass, by means of suitable rotation means 20, from the first access position D to a second access position E for cleaning the second intermediate mold 15b. In this second access position E, the intermediate plate 14 is rotated substantially by a right angle with respect to the previous position and is turned with the second intermediate half-mold 15b towards the operator.

From the second access position E, the intermediate plate 14 is also conveniently translatable, again by means of the same translation means 17, to a side-by-side position F according to which it flanks the press at a side of the press 10 different from the side of injection 21, i.e. a side of the press 10 consecutive to the injection side.

In particular, the intermediate plate 14 consists of two half-plates 22 side by side and the press 10 is suitably provided with translation means 17 and with rotation means 20 for each half-plate 22. The two half-plates 22 can therefore be moved according to the direction of translation B and are hinged to the support structure 11 respectively in proximity to two opposite outer sides 18 of the overall intermediate plate 14, so as to pass, by means of the rotation means 20, from the first access position D to the second access position E, indicated in Figures 2 and 4 respectively.

As clearly visible in Figure 4, following rotation in this latter position they face each other with the faces defining the second intermediate mold half 15b.

By means of the translation means 17, the half-plates 22 can be moved from the second access position E to a side-by-side position F in which they flank the press at two opposite sides 23 and 24 of the press 10 consecutive to the injection side 21.

Conveniently, for each half-plate 22 the translation means 17 consist of a shaft 25, to which the half-plate 22 is integral, sliding along the hinging axis 19 inside a translation guide 26 fixed to the support structure 11. The shaft 25 is also rotatable around the same hinging axis 19 inside the translation guide 26.

Again for each half-plate 22, the rotation means 20 comprise a lever 27 moved by an oleodynamic cylinder 28 transversal to the shaft 25 (according to the example shown of a press 10, which has a vertical closure, the shaft 25 and the translation 26 are positioned horizontally, while the oleodynamic cylinder 28 is positioned vertically). In particular, the lever 27 is connected to the shaft 25 by means of at least one bush 29 whose internal surface is counter-shaped to the surface grooves of the shaft 25. In this way the shaft 25 is free to move inside the guide. of translation 26 and the translational movement of the oleodynamic cylinder 28 is transformed, by means of the lever 27, into rotational movement of the shaft 25.

Conveniently, the first half-mold 13a, which is mobile, is linked to a half-mold-carrying slide 30 which in the opening and closing movement of the press 10, and therefore of the mold 12, is controlled by suitable lifting and lowering means 31, which they consist of a toggle device, and is guided by special guides 32.

The second half-mold 13b, which is instead fixed, is constrained to a half-mold holder plate 33 mounted in correspondence with the lower part of the support structure 11.

The use of the press according to the invention is as follows.

Initially with the mold closed, EVA is injected simultaneously with its two colors respectively in the two series of impressions by means of the injectors 16.

Then, as can be seen from Figure 2, the mold 12 is opened by lifting the first mold half 13a according to the opening direction A and at the same time extracting the intermediate plate 14 according to the translation direction B.

The extraction of the intermediate plate 14 takes place by translation on a substantially horizontal lying plane of the intermediate plate 14, in the direction of the operator and from the side of the press 10 opposite to the injection side 21. The half-plates 22 move integrally with the shafts 25 which slide out of the translation guide 26. In this way the two half-plates 22 are arranged in the first access position D which allows the operator to clean the first intermediate half-mold 15a of EVA residues.

During the cleaning of the first intermediate half-mold 15a, the press 10 is closed (Figure 3) closing the first half-mold 13a on the second half-mold 13b, so as to bring the two sole portions in the two colors closer together to allow cross-linking, bringing the first half-mold 13a and the second 13b at the crosslinking temperature. During crosslinking, as illustrated in figure 4, for each half-plate 22 the oleodynamic cylinder 28 moves the lever 27, which rotates the shaft 25 around the hinging axis 19 until the two half-plates 22 are brought into the second access position E, which allows the operator to clean the second intermediate half-mold 15b and to approach the support structure 11 of the press 10.

By controlling the sliding of the shafts 25 inside the translation guides 26, the half-plates 22 are made to translate according to the hinging axes 19 until they are placed side by side with the press 10 in correspondence with the opposite sides 23 and 24, arranging themselves in the side-by-side position F indicated in the figure 5. In this way, with the subsequent opening of the mold 12, the operator has the free space necessary to remove the soles produced and also clean the two half-molds 13a and 13b.

It should be noted that the three positions defined for the half-plates allow the operator to adequately perform not only the cleaning operations of the half-molds, but also any silicone-coating operations, which can be performed with the application of a release agent rather than with Teflon coating. .

In practice it has been found that the invention achieves the intended aim and objects by improving a press which solves production problems by allowing the operator to easily access the mold to pick up the finished product and the half-molds of the intermediate plate for maintenance operations. .

In particular, the present invention provides a press which allows the operator, thanks to the positions assumed by the half-plates during the various molding stages, to easily access all the half-molds of the press without hindering the injectors.

Another advantage of the press according to the invention is that of reducing production costs and increasing productivity thanks to the possibility of adequately carrying out the cleaning and maintenance operations, which are fundamental in molding EVA articles.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; moreover, all the details can be replaced by other technically equivalent elements.

In practice, the materials employed, so long as compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to the requirements and the state of the art.

Where the features and techniques mentioned in any claim are followed by reference marks, such marks have been affixed for the sole purpose of increasing the intelligibility of the claims and consequently such reference marks have no limiting effect on the interpretation of each element. identified by way of example by these reference signs.

Claims (8)

CLAIMS 1) Improved press (10) for the injection molding of multi-colored articles in plastic material, particularly in ethyl vinyl acetate, of the type comprising, in a support structure (11), a composite mold (12) consisting of: - a first half-mold (13a) and a second half-mold (13b), at least one of which movable according to an opening and closing direction (A) of said press (10); - an intermediate plate (14), to be interposed between said first half-mold (13a) and said second half-mold (13b) and to be extracted therefrom, which constitutes on its two opposite faces a first intermediate half-mold (15a) and a second intermediate half-mold ( 15b) which, with the mold (12) closed, define respectively with said first mold half (13a) and with said second mold half (13b) two series of impressions into which they are respectively injected, by means of injectors (16) positioned on one side of said press (10) with respect to said opening and closing direction (A), EVA of a first color for molding a first portion of the article and EVA of a second color for molding a second portion of article, called press (10) being characterized by the fact that said intermediate plate (14) can be translated according to a translation direction (B) substantially perpendicular to said opening and closing direction (A) by means of suitable translation means (17) to pass from an injection position (C), in which it is placed between said first and second mold halves (13a, 13b), to a first access position (D) for cleaning said first intermediate mold halves (15a), in said first access position (D) said intermediate plate (14) being extracted from said mold (12) from one side of said press (10) opposite to the injection side (21), and said intermediate plate (14) is hinged to said support structure (11) near its external side (18) oriented according to said translation direction (B), around a relative hinging axis (19) to pass, by means of suitable rotation means (20), from said first access position (D) to a second access position (E) for cleaning said second intermediate half-mold (15b), in said second access position (E) said intermediate plate (14) being rotated substantially by at least a right angle with respect to said first access position (D). 2) Press, according to claim 1, characterized in that said intermediate plate (14) can be translated by means of said translation means (17) from said second access position (E) to a side-by-side position (F), in which it flanks said press (10) at a side (23) of said press (10) different from the injection side (21). 3) Press, according to claim 1, characterized in that said intermediate plate (14) consists of two side-by-side half-plates (22), which are translatable, by means of said translation means (17), according to said translation direction (B ) and which are hinged to said support structure (11) in proximity to two opposite external sides (18) of said intermediate plate (14) to pass, by means of said rotation means (20), to said second access position (E ) in which said half-plates (22) face each other with the faces defining said second intermediate half-mold (15b). 4) Press, according to claims 2 and 3, characterized in that in said side-by-side position (F) said half-plates (22) flank said press (10) at two opposite sides (23, 24) of said press (10 ) different from the injection side (21). 5) Press, according to claim 3, characterized in that said translation means (17) consist, for each of said half-plates (22), of a shaft (25) sliding along said hinging axis (19) inside of a translation guide (26) and rotatable around said hinge axis (19) inside said translation guide (26), said half-plate (22) being integral with said shaft (25) and said translation guide ( 26) being fixed to said support structure (11). 6) Press, according to claims 1 and 5, characterized in that said rotation means (20) comprise a lever (27), moved by an oleodynamic cylinder (28) transversal to said shaft (25), said lever (27) being connected to said shaft (25) by means of at least one bush (29) whose internal surface is counter-shaped to surface grooves of said shaft (25). 7) Press, according to claim 1, characterized in that said first half-mold (13a) is connected to a half-mold-holder slide (30) which is controlled and guided, in the opening and closing movement of said mold (12), respectively by designated lifting and lowering means (31) and by appropriate guides (32). 8) Press, according to claim 1, characterized in that said second half-mold (13b) is constrained to a half-mold holder plate (33) mounted in correspondence with the lower part of said support structure (11).