DESCRIPTION Field of the Invention

The present invention is generally related to the filed of the plastic materials processing and more precisely it relates to a process for the partially coating of articles with a layer of plastic material. In particular, the articles to be coated are backs of the brooms. Description of the prior art

In the production of articles made either of plastic or other material much attention is paid to both mechanical features, such as lightness and strength, and aesthetical features, such as the degree of surface finishing, brightness, colour and presence of drawings and/or decorations on the article surface. Very often, however, materials with excellent mechanical features do not exhibit so good aesthetical features. In these cases the articles are coated with films or layers of material of a different type and more satisfactory from the aesthetical point of view.

Among the articles for which mechanical and aesthetical qualities are an essential requirement, there are in particular the backs of the brooms. A broom back substantially consists of an elongated body made of wood or plastic to a face of which cleaning bristles are set, while to the other face a threaded support is formed for engagement with the end of a long handle. In order to save the production costs and to make easier the application of the cleaning bristles, the back is generally made of plastic material such as polypropylene both of the compact

and the foam type. In the first case the back is heavier, but exhibits a satisfactory surface finishing, while in the second case, which is the less expensive one, the back is lighter but the surface finishing is very poor. In both cases, the backs made of these materials and of similar materials are covered by applying plastic masks produced separately and snap fitted to them. The mask covering system is expensive because two moulds are necessary one for the back and one for the mask. The backs made of foam polypropylene may also be painted; however, to allow the painting to adhere to the surface, a preliminary treatment with a solvent must be carried out, thereby the production cost is further increased.

It is an object of the present invention to provide a process for the partially coating of articles, in particular broom backs, with a layer of plastic material which is unexpensive and easy to exploit, and capable of produce a high surface finishing and brightness coating with the possibility of obtaining decorations and fancy drawings on it even in different colours.

Another object of the invention is to provide backs for brooms having the above mentioned features. Summary of the Invention

The above objects are reached with the process according to the invention for the partially coating of articles such as broom backs with a layer of plastic material, characterized in that said articles are placed on a supporting plane and at least a plate of plastic material is put on them. Under the action of radiant heat and vacuum conditions the plastic plate evenly melts and wraps the upper face and the side faces of the articles. The plastic material therefore forms a single sheathing covering the articles and holding them secured together. The articles

are then separated by cutting and plastic scraps removed.

Further characteristics and advantages of the process according to the invention will be clearer with the following description of a non limiting, exemplifying embodiment, with reference to the attached drawings.

Brief description of the drawings

In the drawings:

Figures 1 and 2 show respectively a longitudinal and a transverse sectional view of an article such as a back of a broom to be coated according to the process of the invention;

Figure 3 shows the coating steps according to the process of the invention;

Figures 4 and 5 show respectively a longitudinal and a transverse sectional view of an article such as a back of a broom as coated according to the process of the invention.

Description of the preferred embodiment

With reference to Figures 1 and 2, an article 1, in the present case a back of a broom, has a base 2 and a support 3 in which a threaded seat 4 is formed for accomodating the end of a long handle, not shown. The back 1 does not exhibit a satisfactory surface finishing because it is made with materials having excellent mechanical features, such as compact or semifoam polypropylene, but having poor aesthetical qualities.

With reference to Figure 3, a thermoforming machine of conventional type, diagrammatically shown and indicated at

5, comprises an internal chamber 6 suitable of being placed under vacuum by known means, a supporting plane 7 and a heat radiating panel 8.

According to the invention, in order to carry out the coating of the backs 1 it is necessary to arrange them on the supporting plane 7 of the machine 5 and put on them a

plate 9 of plastic material; afterwards, it is necessary to place the chamber 6 under vacuum condition and make the panel 8 to radiate heat. The plate 9 of plastic material, for example polystyrene or PVC, has the characteristic of being thermoformable and due to the heating operated by panel 8 and the vacuum condition in the chamber 6, passes from a plane configuration indicated at A and shown with a dashed line, to a deformed configuration, indicated at B, forming a layer wrapping the base 2, the support 3 and the internal walls of the seat 4 of the backs 1 with the exception of the lower face 2a of said backs. The layer 9 has almost completely coated the backs 1 and, after it has been cooled or, alternatively, after panel 8 has discontinued the heat radiation and chamber 6 has been opened, holds the backs 1 secured together through layer portions 10. Portions 10 can be removed by cutting with known means. It has to be noted that on the plane 7 there can be arranged backs or even other objects of different shape from one another, in this way remedying to the problem of the manufacture of a different mould for each shape of back or other article to be coated.

With reference to Figures 4 and 5, the back as produced is completely coated except face 2a, to which a plurality of cleaning brushes 11 is applied according to known processes such as hot injection. The layer 9 coating back 1 is of a material such that an excellent surface quality and brightness is preserved even after thermoforming has been carried out as described above.

The layer 9 can be of any colour and inscriptions and/or fancy drawings of any type can be preprinted on it obtaining articles particularly desirable by the customers as well as fully satisfactory from the point of view of the functions for which they have been created, as in the case

of the backs of brooms that, up to now, have been produced in only one colour and with a surface finishing less acceptable from an aesthetical point of view.

Besides polystyrene and PVC the layer 9 can be made of any other thermoformable plastic material capable of maintaining excellent brightness and surface finishing after heating and under vacuum deformation.

Vacuum thermoforming machines, though well known, never have been used to coat articles according to the above described process, but to form plastic articles such as, for example, protective helmets for workmen, masks and toy moulds and other articles starting from stelle models of the same shape.

Variations and/or modifications may be brought to the process according to the invention and to the articles obtained with it without departing from the scope of the invention as defined in the appended claims.