The invention relates to a number of improvements to processes for obtaining soles used in steam irons, and in particular to soles of the kind made by superimposing and assembling two parts to each other, one being a rolled aluminium and the other an injected aluminium part, such parts being provided with respective steam outlet holes, the necks obtained from punching the rolled aluminium or bottom part to make the holes being precisely the means interconnecting both parts to make up the sole.

The object of the invention is to achieve a more reasonable, advantageous and practical process for obtaining steam iron soles, considerably reducing the rejection of parts.

Systems and/or processes used for obtaining steam iron soles differ, noteworthy among these being processes in which the sole is obtained by means of mainly pressure injection moulded aluminium alloys, although alloys of such kind afford relatively little strength and the iron sole surface may as a result be easily scratched, causing the iron sole to be worn and naturally increasing its friction coefficient, making ironing increasingly difficult.

Another system which attempts to resolve the above-mentioned drawback relies on enamelling the outer iron sole surface with ceramic materials, the main drawback of which operation is the fact that upon applying the high enamelling temperatures required to the injected aluminium sole, bubbles frequently appear in the enamel, and the parts are consequently rejected.

British Patent number 1,380,415 discloses a process for obtaining an iron sole which attempts to resolve the above-mentioned drawbacks, the process being based on obtaining a first part or member made of a moulded aluminium alloy, in which the tubular heating resistors are embedded, and a second part or member comprising a preferably steel metal plate onto which the enamel layer is applied, wherein this second part or plate is coupled to the first one, thereby for the sole to be obtained.

Although this system obviously resolves the drawbacks referred to hereinbefore, the fact that the sole must be obtained from two parts made of different materials will result in problems arising due to the differing expansions of the materials and moreover the fact that heat transfers between both parts are not uniform.

European Patent number 0 220 647 attempts to provide another solution, relying upon a system or process for obtaining an iron sole, similarly from two parts, one being a moulded aluminium and another one a rolled aluminium part, wherein the moulded aluminium part is provided with the tubular heating resistors, whilst the rolled aluminium part is fixed to the first part and has the enamel layer applied onto its outer face.

The essential drawback of this technique lies in that enamelling takes place on both aluminium parts together, and therefore if there are any rejections due to a faulty enamelling, both parts must be rejected together, the manufacturing process hence become costlier.

Furthermore, the silicone that is normally used as an intermediate component to transmit the temperature must be capable of withstanding the temperature required for firing the ceramic, i.e. the enamel, and the same goes for the resistor caps, which must be capable of withstanding the required temperatures.

The object of the improvements disclosed herein is none other than using a new process for obtaining enamelled iron soles starting from two parts, namely a moulded aluminium and a rolled aluminium part, in a manner that is both simple and cheap, fully eliminating the above-mentioned drawbacks.

Specifically, the process according to the improvements of the invention relies upon the sole being manufactured by obtaining the two basic parts independently, the rolled aluminium part being provided with the respective enamelling, i.e. the ceramic that is to become the enamel layer is applied at the required firing temperature and said enamelled rolled aluminium part is later assembled with the moulded aluminium part, rejections being thereby reduced and each process being thus simplified.

Furthermore, the insertion of silicone between both parts, which allows temperature transmission to be enhanced, will not undergo the firing process for the enamel layer to be applied.

The different stages of the process for obtaining the iron sole are the following:

• The rolled aluminium part or plate is first obtained and the moulded aluminium part is obtained separately by injection, the tubular heating resistors being thus embedded in the second part;
• The rolled aluminium plate is then provided with holes for the passage of steam when the sole is part of the respective iron, which holes are obtained by punching at a predetermined angle in order for the punched material projections to form a sort of almost perfect cylinders,
• The rolled aluminium plate with the holes already made is then enamelled with ceramic;
• The enamelled face of the rolled aluminium plate is then covered with a sheet of protective paper affixed with special glues;
• The rolled aluminium plate then undergoes a positive deformation that tends to avoid or offset potential deformations of both parts, namely the rolled aluminium plate and the moulded aluminium part, when the latter are interconnected, which might result in then not being perfectly adhered throughout their surface upon being coupled;
• The inner rolled aluminium plate surface is then applied a fine layer of silicone, spread in such a way as to allow the filling of potential gaps remaining and which may remain between both parts, namely the moulded aluminium part and the rolled aluminium plate, when they are connected, thereby enhancing heat transmission between the two;
• Both aluminium parts are then interconnected by superimposing and applying pressure between the two, the flanges or necks of the holes of the first plate being subsequently flared, both parts being connected through such flanges, as if they were rivets;
• Finally, the respective lid closing the steam chamber is also coupled by pressure.

In order to provide a fuller description and contribute to the complete understanding of the characteristics of this invention, in accordance with a preferred embodiment thereof, a set of drawings is attached to the specification as an integral part thereof which, while purely illustrative and not fully comprehensive, shows the following:

Figure 1. - Is a representation of a longitudinal sectional view of the rolled aluminium plate obtained in accordance with the object of the invention.

Figure 2.- Is a view identical to that of the preceding figure, albeit with the plate already provided with the enamel, although the latter is not to be seen, with the enamelled layer about to be protected with the respective sheet of protective paper.

Figure 3.-Is a longitudinal sectional view of the two aluminium parts about to be coupled to each other, the bottom one of which parts already has the sheet of protective paper affixed, whereas the top part is provided with the respective heating resistor.

Figure 4.- Shows the two parts shown in the preceding figure fixed to one another, and at the top the lid that is to close the chamber defined in the top part.

Figure 5.- Is a longitudinal sectional view of the steam iron sole made in accordance with the object of the invention, i.e. with the two aluminium parts interconnected, the connection having been made with the cylindrical necks resulting after punching the bottom plate to obtain its holes, and with the lid closing the steam chamber mounted.

Figure 6.- Is a sectional close-view of the shape of the holes obtained upon punching the rolled aluminium plate.

Figure 7.- Is finally a close-view showing how the two aluminium parts are fixed to each other, which connection takes place by flaring the cylindrical necks defined by the steam outlet holes.

With reference to the aforesaid figures, the steam iron sole made according to the improvements of the invention is based upon the two constituent parts of the actual sole being independently obtained, and thus figure 1 shows a rolled aluminium plate (1) with respective holes (2) that are to define the steam outlets in constructing the respective iron sole, which holes (2) are obtained by punching, resulting in largely cylindrical inwardly projecting necks (3), as may be clearly observed in figure 1. Having obtained this rolled aluminium plate (1) and punched the holes (2), the plate surface is enamelled with ceramic, namely its outer face, the enamelled face then being covered with a sheet of protective paper (4) that is affixed to it using special glues.

After protecting the enamelled rolled aluminium plate (1) surface the plate undergoes a positive deformation in order that when the plate is coupled to a moulded aluminium part (5) it is slightly convex in the coupling direction, i.e. its central area is dished, the edges of the plate (1) being more separated than its central part. This deformation tends to avoid or offset potential deformations of both parts (1) and (5) which may result in their being imperfectly adhered throughout their surface upon being coupled.

For its part, the protective sheet (4) allows the plate (1) to be positively deformed without the enamel cracking or snapping, and further acts as a protection for the plate, allowing risk-free handling throughout the sole assembling and mounting process.

The moulded aluminium part (5) includes respective walls and holes (6) for the necks (3) of the respective holes (2) of the plate (1) to pass when the plate and part are assembled, which part (5) moreover has the appropriate heating resistors (7) embedded in its constituent material.

Before proceeding to couple parts (1) and (5) to each other, a fine layer of silicone is applied onto the inner rolled aluminium plate (1) surface, which silicone is not designed to provide an adherent effect but is rather useful to fill the gaps that may remain between parts (1) and (5) to improve heat transmission between the two.

The parts (1) and (5) are coupled to each other by superimposing and applying pressure between the two, then flaring (8) the cylindrical necks (3) of the holes (2), both parts being connected to one another through such flarings (8), as shown in figure 7, the above in order that when both parts (1) and (5) are perfectly joined to one another, as noted above, the respective lid (9) is mounted to delimit the steam chamber, which lid (9) is also coupled by pressure onto positioning spigots (10), as shown in figure 5.

The aforesaid process for obtaining an iron sole based upon two aluminium parts, one being a rolled aluminium and another a moulded aluminium part, is obviously successful in interconnecting or fixing these parts (1) and (5) to each other simply and efficiently, for such connection is based upon flaring (8) the cylindrical necks (3) resulting from punching the holes (2) in the rolled aluminium plate (1), the role played by the sheet of protective paper (4) being also noteworthy, for it allows the rolled aluminium plate (1) to be positively deformed and thereby ensure a tight contact between such plate and the moulded aluminium part (5) and, consequently, a good heat transmission to be achieved, being particular in that such tight connection is achieved due to the peripheral connection obtained by means of the riveted (8) cylindrical necks, whereas the positive deformation of the plate (1) provides an assurance that the latter will not tend to become detached from part (5) due to constructive deformations.