Method for producing metal accessories for clothing and handles

Technical Field

This invention relates to a method for producing metal accessories for clothing and handles, in particular metal accessories for clothing and handles having particularly complex shapes with a large number of undercuts.

Background Art

Generally speaking and in this text in particular, the term "undercut" refers to an inner or outer protrusion which would prevent removal of the accessory from a conventional mould without breaking the mould or the accessory itself.

In other words, the term "undercut" means that part of the accessory which would prevent the opening of a conventional mould (in particular one without carriages) if the accessory were produced with conventional moulding methods using matching male and female mould parts.

The undercuts are otherwise formed by steps (positive or negative) which prevent the extraction of the manufactured article from a mould. It should be noticed that in the case of modern moulds of traditional type, made of steel in two halves, the problem cannot be solved: if a mould has an undercut, the part cast simply does not come out of the mould (unless there are complex and expensive carriages, which in any case could not be used to produce relatively small objects, such as those referred to in this text, with very complex shapes).

Even more particularly, the present invention relates to the production of accessories having at least one cage-shaped part, for example buckles, eyewear frames, shoe heels and the like.

By way of example, the present invention is applied in the production of metal accessories with mechanical and structural properties such that they can withstand even significant loads, for example heels or wedge heels for footwear.

Metal accessories for clothing are usually produced with vast-scale industrial processes.

At present, however, some accessories for clothing, and handles, in particular those having at least one undercut, are handcrafted and therefore have very high production costs which means that such accessories are not widely used or are only used in the haute couture sector. In particular, handles and accessories for clothing are handcrafted when they have at least one cage-shaped part.

Cage-shaped parts are those portions of the clothing accessory consisting of a structure which completely surrounds a cavity, completely or partly preventing access to the cavity from the outside environment.

An example of such cage-shaped parts is given by a structure comprising an upper wall, a lower wall and lateral walls extending around the perimeter of the upper wall and which are connected to the lower wall. Therefore, said structure delimits an inner cavity, that is to say, an empty inner space. The walls constituting the structure briefly described are reticular, that is to say, they are substantially net-shaped, thus forming a cage-shaped structure.

A metal accessory for clothing or a handle comprising one or more undercuts or a cage-shaped portion (in the sense described above) or completely cage-shaped, is, as is known in the prior art, handcrafted, that is to say, made entirely by hand.

Similarly, any product or clothing accessory having a complex shape which cannot be produced by moulding with matching male and female mould parts, or which has a shape which, once produced, prevents opening of the matching male and female mould parts is usually handcrafted.

Aim of the Invention

In this context, the technical purpose which forms the basis of the present invention is to propose a method for producing metal accessories for clothing and the like, or handles, which overcomes the above mentioned disadvantages of the prior art.

In particular, the present invention has for an aim to provide a method for producing metal accessories which have a complex shape which is able to significantly reduce production costs in particular in the case of large-scale productions. Another aim is to propose a method for producing clothing accessories or handles which allows the production of a plurality of different models, significantly containing industrialization costs.

The technical purpose indicated and the aims specified are substantially achieved by a method for producing metal accessories for clothing, or handles, with the technical features described in one or more of the appended claims. Brief Description of the Drawings

Further features and advantages of the present invention are more apparent from the non-limiting description which follows of a preferred, non-limiting embodiment of a method for producing metal accessories for clothing and handles, as illustrated in the accompanying drawings, in which:

- Figure Ia schematically illustrates a step of a method for producing metal accessories for clothing according to the present invention;

- Figure Ib schematically illustrates the step of Figure Ia for a second embodiment of a clothing accessory; - Figure 2 schematically illustrates another step of the method of Figure 1 ;

- Figure 3 schematically illustrates yet another step of the method of Figure 1;

- Figure 4 schematically illustrates an alternative embodiment of the method of Figure 1; - Figure 5a shows a metal accessory for clothing obtained using the method according to this invention;

- Figure 5b shows a second embodiment of a metal accessory for clothing obtained using the method according to this invention; and

- Figure 6 shows a metal handle obtained using the method according to this invention.

Detailed Description of the Preferred Embodiments of the Invention

The method for producing metal accessories for clothing according to the present invention is intended in particular for producing metal accessories for clothing designed to withstand significant loads.

Advantageously, said method is suitable for producing a variety of products, such as sidepieces for eyewear, handles (Figure 6), heels and wedge heels for shoes, buckles for belts and other items. For simplicity, hereinafter explicit reference is made to the production of clothing accessories, without thereby limiting the scope of the invention.

The invention described is intended, for example, for producing metal accessories for clothing having one or more undercuts in the sense described above.

More specifically, the invention is intended, for example, for producing metal accessories for clothing which have at least one cage-shaped portion.

In the context of this invention, the term cage-shaped refers to a structure having walls surrounding and delimiting an empty space, that is to say, an inner cavity.

Said walls, or at least one of said walls, are not solid, but comprise a plurality of holes which put the above-mentioned inner cavity in communication with the outside environment. An example of a cage-shaped metal accessory for clothing is illustrated in

Figure 5a, while an example of a handle 200 is illustrated in Figure 6.

Figure 5b shows a second example of an accessory, which can preferably be obtained with the method according to the present invention and having a complex shape. In particular, Figure 5a shows a steel heel 100 for footwear, having a plurality of walls 101 which delimit an inner cavity. The walls 101 have a plurality of holes 102 which put the inner cavity in communication with the surrounding environment.

The walls 101 extend in such a way that they form undercuts and recesses and have a substantially reticular shape.

The accessory 100 comprises solid parts 103, that is to say, parts which are not cage-shaped (in the sense indicated above), for example the bottom wall which will rest on the ground.

The accessory 100 comprises a fixing wall 103 a having an opening 104 whose purpose is described below.

In the example heel illustrated in Figure 5a, the fixing wall 103a used to fix the accessory 100 to the rest of a shoe, not illustrated, has three openings 104.

As illustrated in Figure 5b, the accessory 100, again a heel, comprises a body 111 extending from the fixing wall 103a. It should be noticed that the fixing wall 103a is solid, not having any openings 104.

As illustrated, the body 111 has two significant undercuts and is particularly suitable for being produced using the method according to this invention. The accessories 100 also comprise pins 112 for positioning and/or fixing the accessory 100 relative, in the example illustrated, to the rest of a shoe, not illustrated, making its assembly easier.

For clarity, this description of the method according to the present invention will refer explicitly to the heel 100 of Figure 5a or 5b. However, the same method may be applied to produce any metal accessory for clothing having one or more undercuts.

For example, the method may be applied for producing cage-shaped accessories, in particular of the type intended to withstand loads.

It should be noticed that the production of such particular types of products, having undercuts and/or being cage-shaped, would be impossible with conventional moulding methods, using matching male and female mould parts, which would be impossible to open once the product has been moulded.

Moreover, preferably relating to accessories whose designs are continuously modified and updated, the method proposed, given its simplicity, allows the development of new shapes and products without the high system costs of conventional methods and without meticulous handcrafted work. Figure 6 shows a handle 200 having a plurality of walls 201 which delimit an inner cavity. The walls 201 have a plurality of holes 202 which put the inner cavity in communication with the surrounding environment.

The walls 201 extend in such a way that they form undercuts and recesses and have a substantially reticular shape. It should be noticed that the handle preferably comprises a plurality of reticular (cage-shaped) structures also inside the cavity.

The method comprises the step of making a plastic copy 1 of the metal accessory to be produced.

The copy 1 (see Figures Ia and Ib) exactly reproduces the shape and dimensions of the accessory to be made. In the specific example, the copy 1 exactly reproduces the shape and dimensions of the heel 100, including the solid parts 2, that is to say, the parts which are not cage-shaped or do not have undercuts.

The copy 1 is made of plastic material. The plastic material is preferably polystyrene.

Advantageously, in this way the copy 1 is easily and rapidly produced using numeric control prototyping machines.

These machines use plastic material in the form of pellets or powder, on which a laser beam acts, striking the material in the form of pellets or powder in such a way as to sinter the plastic material and thus making the copy 1 of the accessory 100 to be produced.

One example of such machines involves using energy from a CO ₂ laser beam directed into a construction chamber filled with powdered plastic material. The laser beam, guided by a control unit in which data was entered relating to the copy 1 to be made, heats the layer of powder to the melting point. The process for construction of the copy 1 takes place in layers, that is to say, producing a first layer of the copy 1 and moving a work platform vertically to produce one layer after another.

The use of polystyrene is particularly advantageous.

Said material has a very low cost and is ideal for large-scale production of accessories 100. Moreover, polystyrene has good recycling properties.

In general, during production of the copy 1, a significant amount of material is consumed, because the laser beam also affects, by heating it, the plastic material extraneous to the copy 1. This material is usually disposed of. However, thanks to the use of polystyrene, even the heated material does not lose its distinctive features and may be re-used in the production of a subsequent copy 1. This avoids wasting material and represents a saving in economic terms.

Advantageously, said plastic material may contain, as well as polystyrene, additives which improve its mechanical and sliding properties.

The additive may be metallic. For example, the additive is aluminium. The presence of aluminium or the like facilitates the work of the prototyping machine used to make the copy 1.

As illustrated in Figure Ia, during the step of making the copy 1 of the accessory 100, at least one projection 3 is made, extending from a wall of the copy

1 corresponding to the wall 101 of the accessory 100 and extending away from it. In the embodiment illustrated in Figure Ia, two projections 3, positioned close to opposite ends of the copy 1, are made.

As illustrated in Figure Ib, the copy 1 has a body 11 corresponding to the body 111 of the accessory 100 of Figure 5b.

A first projection 3 extends from a wall 3a corresponding to the fixing wall 103a of the accessory 100 of Figure 5b.

A second projection 3 extends from a body 11 extending from the wall 3a and corresponding to the body 111 of the accessory 100 of Figure 5b.

The projection 3 is also made of plastic material, in particular made of the same material as is used to make the copy 1, that is to say, preferably polystyrene. The projection 3 is substantially prismatic in shape.

The function of the projections 3 is described in more detail below.

In the examples illustrated, the copies 1 comprise pins 12 corresponding to the pins 112 of the corresponding accessories 100.

Once the copy 1 has been made, it is covered with a die made of ceramic material 4, as is schematically illustrated in Figure 2.

In other words, once the copy 1 has been made, it is substantially inserted in a die made of ceramic material 4, as is schematically illustrated in Figure 2. During covering of the copy 1 inside the ceramic die 4, the projections 3 are only partly covered by the die 4. In that way, it is possible to form channels which can be accessed from the outside of the ceramic die 4.

Insertion of the copy 1 in the ceramic die 4 is carried out, for example, by immersing the copy 1 in a liquid solution which, after a predetermined time, hardens, producing the above-mentioned ceramic die 4.

Preferably, said insertion step is carried out by immersing the copy 1 in the liquid solution several times one after another, so as to create a succession of ceramic layers around the copy 1. After said plurality of immersions, the ceramic die 4 covering the copy 1 is between 3 mm and 12 mm thick, preferably between

5 mm and 10 mm thick.

As illustrated in Figure Ia, the plastic copy 1 of the accessory 100 has openings 8 corresponding to the openings 104 of the accessory 100 which allow simple entry of the ceramic liquid solution which can therefore completely fill the copy 1.

It should be noted that after the step of covering the copy 1 with the ceramic die 4, the ceramic material is distributed all around the copy 1 and fills the inner cavity or cavities and the holes of the copy 1 corresponding to the holes 102 in the lateral walls 101 of the accessory to be made. The copy 1 is therefore "confined" within the ceramic die 4.

At this point, the plastic copy 1 is substituted with molten metal material.

More precisely, the copy 1 is removed from the die 4 in such a way as to leave inside the die 4 a plurality of cavities connected to each other which reproduce the shape of the accessory 100 to be made. In other words, removal of the copy 1 from the ceramic die 4 creates a mould, that is to say, a negative of the copy 1 inside the die 4.

Removal of the copy 1 from the ceramic die 4 is accomplished by making the copy 1 evaporate, by heating the ceramic die 4, and discharging the vaporized plastic material from the die 4. For that purpose, the method comprises a step of heating the ceramic die 4 in which the ceramic die 4 is substantially brought to the melting point of the metal material. That way, the die 4 is at the same temperature as the molten metal material, allowing the material to be poured easily into the die 4. During the heating step, the plastic material used to make the copy 1 of the accessory 100 turns to liquid then evaporates, and flows out of the ceramic die 4.

Only when the copy 1 has been removed from the ceramic die 4 are the cavities inside the die 4 filled with molten metal material. As already indicated, this step is carried out by casting the molten metal material into a channel formed by the projections 3 of the copy 1.

Since, as already indicated, the ceramic material is distributed all around the copy 1 and fills the inner cavity or cavities and the holes in the lateral walls of the copy 1, the inner cavities of the die 4 filled with molten metal material perfectly coincide with the shape and dimensions of the copy 1 made of plastic material.

In other words, as indicated above, the ceramic die 4 acts as a mould for the molten metal material. When the molten metal material fills all of the cavities left free by the plastic material, the molten metal comes out of the die 4.

The fact that molten metal comes out of the ceramic die 4 indicates that all of the cavities left free inside the die 4 by the copy 1 have been filled with molten metal material. Preferably, said metal material is of the high melting point type. In other words, said metal material has a high melting point, at least above 1200°C. Preferably, the metal material has a melting point of between 1200°C and 1700 ⁰ C, even more preferably between 1300°C and 1600°C.

This type of metal material allows the accessory 100 to be given the mechanical properties needed to withstand significant loads, for example as is required in the case of heels and wedge heels for footwear.

For example, this metal material may be steel, titanium or other metal. When the metal has solidified, the semi-finished product 6 obtained in this way is freed from the ceramic die 4 (as is schematically illustrated in Figure 3). The metal material is freed from the ceramic die 4 by breaking and removing the ceramic material surrounding the metal semi-finished product 6 and breaking and removing the ceramic material present in the inner cavity or cavities of the semi-finished accessory 6.

For example, this operation is carried out by working with a pointed tool through the holes in the lateral walls of the semi-finished product 6 so as to break up the ceramic material present in the cavity or cavities then remove it through the holes.

The semi-finished product 6 obtained in this way is a metal object whose shape and dimensions are identical to those of the accessory to be produced and which also has metal projections 7 corresponding to the plastic projections 3 which were connected to the plastic copy 1 (Figure 3).

The projections 7 are then removed from the semi-finished product 6, obtaining a manufactured article (Figures 5a, 5b) constituting the metal accessory for clothing 100.

Preferably, the accessory 100 is subjected to surface finishing and/or polishing machining or even painting. The method described herein also comprises the step of making a plurality of plastic copies 1 of the accessory 100 to be produced.

The plurality of copies 1 is made in a similar way to what is described above.

As illustrated in Figure 4, a rod 5 made of the same material used to make the copies 1 is provided. In other words, the rod 5 is preferably made of polystyrene.

At this point, all of the plastic copies 1 are attached to the rod 5 to form a casting tree. hi the example illustrated, a plurality of copies 1 like that of Figure Ia are attached to the rod 5. hi more detail, each plastic copy 1 is connected to the rod 5 by means of the respective projections 3. The connection is preferably made by heating the ends of the projections 3 and/or the rod 5.

The rod 5 preferably has a longitudinal hole 5a. The hole 5a extends substantially along the entire length of the rod 5.

According to the present invention, a threaded bar 10 engages in the hole 5a to support, as is explained in more detail below, the assembly consisting of the rod 5 and copies 1.

Once all of the above-mentioned connections have been made, the plastic copies 1 and the rod 5 are inserted hi the ceramic die 4. Said operation, similarly to what was said above, is accomplished by successive immersions of the copies 1 and the rod 5 hi liquid solutions and allowing them to dry each time.

Advantageously and preferably, the copies 1 and the rod 5 are retained by the bar 10 engaged in the rod 5 and fed in successive ceramic baths in the substantially known way.

The method preferably comprises a step of connecting a bell 9 made of plastic material to the rod 5 before inserting the rod 5 and the copies 1 attached to it hi the ceramic die 4.

According to the preferred embodiment described, the bell 9 is kept joined to the rod 5 by the threaded bar 10.

In particular, the bell 9 is made of polystyrene, like the rod 5 and the copies 1, or of another plastic material such as polyethylene or the like. During covering of the rod 5 and the copies 1 with the ceramic die 4, the bell 9 is partly inserted in the ceramic die 4. hi other words, during the successive immersions, the bell 9 is only partly immersed in the solutions.

Once the ceramic die has been formed, before proceeding with heating of the assembly, the threaded bar 10 is extracted from the rod 10.

When the die 4 formed in this way is subjected to the heating described above and the rod 5 as well as the copies 1 and the bell 9 evaporate, in the ceramic die 4 a kind of funnel is created at a channel - inside the die 4 - formed by the rod 5. During the step of casting the molten metal material, the latter is poured into the funnel. As well as making casting easier, this allows a predetermined amount of molten metal material to be kept in the funnel which, thanks to its weight, facilitates entry of the molten material into the cavities in the ceramic die 4, thus avoiding the formation of hollow zones in the metal casting. The invention achieves the preset aim.

Thanks to the method described, and in particular making the copies using plastic material and their insertion in the ceramic die, the subsequent steps of casting molten metal material and freeing the solidified metal material from the ceramic die, industrial production is possible for metal accessories for clothing or handles which are cage-shaped or have one or more undercuts.

In particular, the accessories produced have mechanical properties suitable for withstanding a load and production times and costs are significantly lower than those for handcrafted items.