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Sector of the invention

The invention relates to the sector of polishing and/or sanding of products, and in particular of polishing of metal substrates, for example made of steel or brass, or else of painted products.

More in particular, the invention regards the sector of polishing of painted substrates using pads, whether with rotary or orbital motion, for example of the type used in vehicle-body repair or in the motor-vehicle industry in general or again in the industry of wood and plastic.

State of the art

There have been known and marketed for some time polishing devices, rotary and random-orbital polishers actuated by electric motors or pneumatic turbines, which use a pad that is set in rotation by a tool and that is passed over the product possibly in combination with abrasive polishing pastes or creams.

However, known systems are not satisfactory since their use entails progressive and/or violent rise in temperature, which is dangerous for the surface being treated, on account of the operating friction between the polishing pad chosen and the surface of the product to be polished.

Moreover, in the case of polishing of wooden surfaces, the air tends to cause clogging with the moisture present therein, whereas nitrogen is anhydrous and dries the surface during polishing, thus preventing this drawback.

A further drawback is represented by the considerable interference that is caused by the relative humidity present in the operating environment and by the high temperatures of the environment, for example in summer periods or in given localities, in addition to the dust in suspension in the polishing environments.

In the case of painted products, the rise in temperature of the materials (plastic material, aluminium, ferrous materials, products made of glossy lacquered wood, etc.) inevitably leads, in fact, to serious problems of loss of elasticity of the underlying film of paint causing pattern formation, lesions and cracking, but also phenomena of halos and so-called holograms, i.e., marks left by traditional random-orbital polishers on the polished products.

Purpose of the invention

A first purpose of the present invention is hence to propose a polishing device and a polishing method that will be free from the drawbacks referred to above and will enable improvement of the polishing quality, at the time same reducing power consumption and the processing time necessary.

Summary of the invention

The above and further purposes have been achieved with a device and a method according to one or more of the annexed claims, which envisage the use of treated air, preferably cold dry air obtained, for example, with a dryer with cooling cycle or by absorption (indicatively with dew point comprised between -20°C and +10°C), or even more preferably nitrogen or else modified air rich in nitrogen, heat-conditioned at a temperature indicatively comprised between -5°C and +20°C.

A first advantage is represented by the fact that the treated air is heat- conditioned at various temperatures that can be selected according to the environment of use and/or to the type of the substrates to be polished, and is injected between the fibres of wool or other materials (for example, sponge) commonly used in polishing pads. In this way, in fact, the surface of contact between the pad and the product remains cold even at high speeds, and the risk of damage to the polished surface, and in particular to the film of paint, is extremely reduced.

A further advantage is represented by the fact that a considerable saving of time is obtained, owing to a higher rate of execution of the polishing process, and hence marked reduction above all for long jobs that involve several hours of application and expenditure of a great amount of physical energy.

Yet a further advantage is represented by the fact that nitrogen is an inert gas, free from humidity and any type of impurity, which sensibly reduces the risk of damage to the polished surface, and in particular to the film of paint.

Yet a further advantage is represented by the fact that use of nitrogen enables a saving in energy, roughly up to 40% less, as compared to the use of traditional systems. A further advantage is represented by the fact that it is possible to respect safety values as regards the temperature of the surface treated, since the random-orbital movements with cooling obtained with treated air prevent said values from being exceeded, without the risk of "burning" the transparency and jeopardizing the brilliancy defined in the quality specifications of the paints. A further advantage is represented by the fact that the use of heat-conditioned treated air enables complete exploitation of the surface of contact of the pad, whereas in traditional systems, on account of the high temperatures that are dangerous for the surface being treated, it is necessary to keep the pad inclined with respect to the working surface, and the operator necessarily uses on average just 40% of the potential useful surface of contact.

A further advantage is represented by the fact that there is obtained a painted surface without holograms, i.e., without the marks left by traditional random- orbital polishers. The use of heat-conditioned treated air in a random-orbital polisher does not, in fact, create holograms and guarantees a high quality of the finished surface, even in a single pass, removing completely scratches, halos, streaks, and oxidation.

List of the drawings

The above and further advantages will be better understood by any person skilled in the branch from the ensuing description and from the annexed drawings, which are provided by way of non-limiting example and in which:

Figure 1 shows a manual polishing device according to the invention; Figure 1 a shows a front view of the disk of the device of Figure 1 ;

Figure 2 shows a polishing apparatus according to the invention; and - Figure 3 is a schematic representation of a device and an apparatus according to the invention.

Detailed description

With reference to the attached drawings, there now follows a description of a device for polishing and/or sanding products M, in particular but in a non-limiting way, painted products.

The device comprises a disk 1 provided with an operating surface 4, which, in use, assumes a circular or orbital movement obtained with appropriate means 13, for example an electric or pneumatic motor, capable of impressing the polishing motion on the operating surface 4.

Preferably, removably applied on the surface 4 of the disk is a polishing pad 12 permeable to a flow of gas.

According to the invention, the device comprises a source 7 of a flow of treated air, for example cooled dry air, or nitrogen, or nitrogen-rich modified air, and one or more air ducts 3 extending from an inlet opening 5, which communicates with the source 7 by means of ducts 22, to one or more outlets 6 for the flow of treated air, located on the operating polishing surface 4, for example in areas corresponding to holes and/or a gap created between the pad and a suction hood 20.

Advantageously, the invention envisages means 8 for regulating the temperature and/or pressure of said flow of treated air.

Preferably, the regulation means are provided for regulating the temperature at a value comprised between -5°C and +20°C and the pressure of the flow of treated air at a value comprised between 1 bar and 5 bar.

In the embodiment illustrated, the source 7 and the regulation means 8 are integrated in a unit 9 for delivering a flow of treated air, for example nitrogen- rich modified air produced by means of hollow-fibre separation membranes or by means of a system with PSA (Pressure-Swing Absorption) molecular sieves. Advantageously, the unit 9 comprises a second outlet 17 for a flow of a pressurized carrier fluid suitable for painting, for example a flow of treated air as described above, which is in turn possibly regulated in pressure and/or temperature, said outlet communicating via ducts 23 with an air-painting device 10. With this solution, one and the same supply unit 9 can be used both for polishing and for painting the product M.

In order to improve the efficiency of the polishing and/or painting operation, there may moreover be provided an ionization unit 1 provided for charging said flow of treated air with an overall positive, negative, or neutral charge, which is for example integrated in the unit 9.

Preferably, the means 13 for impressing the motion on the disk 1 comprise an electric motor 13 housed within a casing 14 provided with manual grip 16, extending inside which are the air ducts 3 that communicate with the source of treated air.

In a different embodiment, the means 13 comprise a pneumatic motor 21 , the movement of which is supplied by a pressurized airflow.

Advantageously, the pressurized flow that supplies the pneumatic motor 21 may be formed by a part of a flow of treated air used for the polishing operation. In use, to carry out polishing of a painted product M, the operator simply has to start the motor drive of the polishing element 1 , enable delivery of a flow of treated air to the outlet holes 7, and bring the operating surface 4 up to the product M possibly after application of a layer of abrasive cream or paste of the type commonly used for polishing.

Thanks to the invention, the flow of treated air that exits from the holes 6 carries out a continuous cleaning of the surface being polished with a gas free from humidity and impurities and at the time same improves the treatment of the paint and prevents the heat generated by contact between the operating surface 4 and the product M from inducing deformation.

The effect of compensation of the heat generated by the friction is further improved by the use of heat-conditioning of the flow of treated air, which may be regulated both on the basis of the type of polished material and on the basis of the ambient conditions.

The present invention has been described according to preferred embodiments, but equivalent variants may be conceived, without thereby departing from the sphere of protection of the invention.