Description

Mould for shoe bottom provided with monolithic structure with differentiated rigidity and bottom obtained with said mould.

The present patent application for industrial invention relates to a mould for shoe bottom made of plastic materials, provided with monolithic structure with differentiated rigidity and to the bottom obtained with said mould. As it is known, plastic moulded bottoms are obtained by casting with open mould or by injection with closed mould.

Within the said technology it has been noted that the various areas of the shoe bottom, especially if provided with considerable thickness, should not have the same rigidity level. In particular, the heel area should have considerable rigidity to ensure stable support for the user's foot, while the area of the front half plant should have lower rigidity, because it needs to be bent following the normal tendency of the user's foot during walking.

The manufacturers who have taken this issue into consideration have so far adopted a single technology, realising similar bottoms in two successive moulding operations, each of them inside a specific die.

The first operation is designed to obtain by moulding a first section of the bottom (either the front or rear section), with a specific rigidity level by using an especially suitable moulding material. During the second operation, the section that has been previously obtained is inserted into a second mould, in which a second material is injected or cast to originate the remaining section of the bottom with different rigidity characteristics.

During the second moulding operation, the two interfaced surfaces of the two sections are permanently joined, thus creating a complete bottom.

A close consideration of the traditional technology has identified at least one critical aspect, which is intended to be overcome by the present

invention.

The said criticality refers to the need to use two different successive moulding operations in two different moulds to obtain a bottom with differentiated rigidity. Evidently, the costs of such a procedure are quite high, in view of the need to have two different moulds, and also in view of the rather long time needed to perform the two aforementioned moulding operations in sequence.

The purpose of the present invention is to devise a mould that allows for obtaining a shoe bottom with areas with differentiated rigidity with one single moulding operation.

The mould of the invention is internally provided, approximately half way its length, with a transversal vertical partition that forms two separate compartments inside the mould, of which the first one is basically designed to mould the heel area of the bottom and the second one is basically designed to mould the front half plant of the same bottom.

Moreover, the two compartments of such a mould are filled with two plastic materials that settle with different rigidity and flexibility levels; it being provided, in particular, that the rear compartment (that corresponds to the heel area) is filled with a material having higher rigidity and lower flexibility and the front compartment (that corresponds to the half plant area) is filled with a material having lower rigidity and higher flexibility.

During the said selective filling operation, the function of the transversal partition is to avoid the total uncontrolled mixing of the two moulding materials in fluid state, although leaving the possibility for both materials to permeate partially to ensure structural continuity of the bottom obtained from this mould.

As mentioned above, the bottom of the invention can be obtained by injection moulding (that is to say: with closed mould), using expanded materials, such as for example: expanded TR, expanded PVC, expanded EVA and similar materials.

In such a case, the vertical partition may be indifferently mounted on the bottom of the mould or on the internal side of the lid.

Alternatively, the bottom of the invention can be obtained by cast- moulding (that is to say: with open mould), using suitable expanded polyurethane materials.

In such second case, the vertical partition necessary to separate the two cast materials must be necessarily mounted on the bottom of the mould.

Moreover, a third solution exists for the application of the said vertical partition inside the mould.

The vertical partition can be simply laid on the bottom of the mould and supported in vertical position by means of suitable fixing pins attached onto the walls of the bottom of the mould.

The partition is designed to be incorporated between the two different moulding materials and completely drawn ("concealed") inside the structure of the bottom that is being moulded.

In such a case the partition is made of sufficiently rigid plastic materials that are suitable to be joined and incorporated between the two castings of plastic materials made from opposite sides with respect to it.

The use of the said fixing pins permits the easy extraction of the partition from the mould together with the bottom that incorporates it.

Finally, it must be noted that, once it has settled and it has been extracted from the mould, the bottom of the invention can be used for different purposes within the traditional footwear manufacturing technique.

In fact, it can be used as bottom for shoes; in such a case, it will be simply necessary to finish the surface of the lateral sides, possibly by painting, and associate it with a corresponding upper. Alternatively, it may be used as a sort of "supporting core" for a perimeter coating (either a partial or total one), made of fabric or leather and designed to characterise the general aspect of the bottom obtained with the present invention.

For purposes of clarity, the description of the invention continues with reference to the enclosed drawings, which are intended for purposes of illustration only and not in a limiting sense, wherein: - figure 1 is a cross-sectional view with a vertical longitudinal plane of the

mould of the invention, which is filled with the two moulding materials;

- figure 1 A is the longitudinal cross-sectional view of the bottom extracted from the mould of figure 1 ;

- figure 2 is the same as the figure above, except in that it refers to a second embodiment of the said mould;

- figure 3 is a cross-sectional view with a transversal plane of the mould of figure 1 ;

- figure 4 is a cross-sectional view with a transversal plane of the mould of figure 2; - figure 5 is the same as figure 3, except in that it refers to a third embodiment of the said mould;

- figure 6 is a partial top view of the mould of figure 5, without lid;

- figure 7 is a cross-sectional view with a transversal plane of an additional embodiment of the mould of the invention; - figure 8 is the same as figure 4, except in that it refers to an embodiment of the said mould provided with a mobile partition designed to descend from up down inside the impression;

- figure 9 is the same as the figure above, except in that it refers to an embodiment of the said mould provided with a mobile partition without passage sections;

- figure 10 is the same as figure 3, except in that it refers to an embodiment of the said mould provided with a mobile partition designed to ascend from down up inside the impression;

- figure 1 1 is the same as the figure above, except in that it refers to an embodiment of the said mould provided with a mobile partition without passage sections.

With reference to figure 1 , the mould of the invention (1 ), normally with lid (2), is internally provided with a transversal vertical partition (3) situated approximately half way the internal cavity. The presence of the partition (3) forms two separate compartments

(V1 , V2) inside the impression (4) of the mould (1 ), respectively designed to mould the heel area and the front half plant area of the bottom (10) that is

being moulded, and designed to be filled with different plastic materials having different rigidity and flexibility characteristics, once they have settled.

In particular, the moulding material poured in the rear compartment

(V1 ) is designed to obtain the basically rigid rear section (1 Oa) of the bottom (10), while the moulding material poured in the front compartment (V2) is designed to obtain the basically flexible front section (10b) of the same bottom (10); reference is made to figure 1 A.

Nevertheless, as mentioned above, the two different moulding materials must penetrate mutually inside the mould (1 ) partially, in such a way that the rear and front sections (10a, 10b) of the bottom (10) obtained with them can be joined irreversibly.

Such a result has been achieved with a careful design of the said vertical partition (3) provided inside the mould (1 ) of the invention.

The partition (3) must not originate the hermetic separation between the two compartments (V1 , V2) provided inside the mould (1 ), and must leave some passage sections between them.

The passage sections make the two compartments (V1 , V2) partially intercommunicating and permit limited seeping of the moulding materials in fluid state from one compartment to the other. In particular, the said seeping and consequent mutual penetration of the two moulding materials are obtained on the interfaced surfaces of the two sections (10a, 10b) of the bottom (10), that is to say in the areas immediately upstream and downstream the partition (3).

According to a first embodiment illustrated in figures 1 and 3, the transversal partition (3) protrudes vertically from the bottom of the mould (1 ).

In particular, it has a slightly lower height than the impression (4) obtained in the mould (1 ), and a slightly lower width than the impression.

In view of the above, when the lid (2) of the mould (1 ) is applied, a passage section (SP1 ) is created between the top of the partition (3) and the internal side of the lid, in favour of the moulding materials in fluid state.

Two additional passages sections (SP2) are created on the two sides of the partition (3), in intermediate position between each lateral side of the

partition and the adjacent lateral wall of the impression (4) of the mould (1 ).

The seeping of plastic materials through the upper passage section (SP1 ) and the two lateral passage sections (SP2) gives structural continuity to the upper side and to the lateral sides of the bottom that is being moulded. Additional passage sections (SP3) are also provided in the central area of the partition (3), in order to permit the mutual penetration of the two moulding materials also for the entire thickness of the bottom that is being moulded.

With reference to figure 3, the central passage sections (SP3) are obtained by providing the partition (3) with a series of basically vertical notches (5) with up-down direction starting from the upper border of the partition (3).

In particular, the said notches (5) have a basically V-shaped profile in order to favour the extraction of the settled bottom (10) from the mould (1 ). It must be noted that the partition (3) provided with a similar structure can be applied both in a mould for injection moulding and in a mould for casting moulding.

With reference to figures 2 and 4, a second embodiment of the partition (30) is applied on the internal side of the lid (2) of the mould used for injection moulding, in such a way that the partition (30) adopts its operational position inside the impression (4), only when the lid is brought in closed position.

Also in this case, the partition (30) has a lower height than the impression (4) that contains it, in such a way that the passage section (SP1 ) for the moulding materials is arranged between the lower horizontal border of the partition (30) and the horizontal bottom wall of the impression (4).

In this case the notches (50) obtained on the partition (30) must have a basically overturned V-shaped profile.

It must be noted that the partitions (3, 30) can be also obtained in sliding gate-like version, suitably associated with corresponding actuators, in such a way to free the impression (4) of the mould (1 ) from their presence; reference is made to figure 10 and figure 8, respectively.

With reference to fig. 10, the partition (3) that protrudes from the bottom of the mould (1 ) is designed to be removed in up-down direction when necessary; with reference to fig. 8, the partition (30) that protrudes from the inside of the lid (2) is designed to be removed in down-up direction when necessary.

According to this specific solution, the partitions are not provided with passage sections, as shown in figure 1 1 and figure 9.

In this case they must be removed within a predefined time period from the end of the casting or injection process of the two moulding materials inside the compartments (V1 , V2) and in any case before the said materials have lost fluidity.

In such a way, the space freed by the partitions (3, 30) can be immediately filled by the moulding materials that tend to penetrate mutually in this central area. It must be noted that the said gate-like removable partitions have been provided in order to avoid that the impression of the partitions remains on the bottom (10) that has settled inside the mould (1 ), with a sort of vertical cavity between the rear section (10a) and the front section (10b) of the bottom (10). Finally, rather than being alternative, as illustrated above, the two partitions (3, 30) can be complementary, meaning that the mould (1 ) can d be simultaneously provided with a partition (3) that protrudes from the bottom of the impression (4) and a partition (30) that is perfectly aligned with the first partition, which protrudes from the lid (2); reference is made to fig. 7.

In such a case, the two partitions (3, 30) in vertical aligned position must have a total height basically equal to the impression (4).

Figures 5 and 6 refer to an additional embodiment of the partition (300), which is expressly designed to be incorporated inside the bottom (10) that is being moulded.

To that end, the partition (300) is made of rigid plastic materials, in such a way to be irreversibly joined and enclosed between the plastic materials poured in the said compartments (V1 , V2) when they tend to penetrate partially.

In particular, the partition (300) must be positioned on the bottom of the impression (4) using a series of suitable metal pins (S) provided hereby.

The partition (300) has a slightly lower height and width than the impression (4) in which it is inserted, thus creating corresponding upper and lateral passage sections (SP1 , SP2).

At the same time, it is also provided with a series of circular openings (6) that originate the said central passage sections (SP3).

Because of the presence of the openings (6), the partition (300) can be completely incorporated and held between the two moulding materials, thus becoming a permanent integral part of the bottom (10) extracted from the mould (1 ).

It must be noted that the pins (S) used to hold in vertical position the partition (300) inside the impression of the mould (1 ) are provided on the lateral sides of the partition (300) with an inclination that makes them converge towards the top of the mould (1 ).

This special position of the lateral pins (S) has been provided in order to allow the partition (300), which is incorporated in the structure of the bottom (10), to be easily removed from the pins, when the entire bottom (10) has been removed from the mould (1 ).