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PLANT AND RELEVANT PROCESS TO ENAMEL SANITARY FIXTURES

TECHNICAL FIELD

The invention relates to a plant and a relevant process to enamel sanitary fixtures, such as a washbasin, a bidet, a toilet, etc.

BACKGROUND ART

One of the crucial phases in the manufacturing of sanitary fixtures is the so-called "enamelling", namely the process that allows the fixture to be shining, colourful and resistant to wear and avoids the occurrence of ugly and dangerous moulds on the surface of the sanitary fixture itself .

Furthermore, enamelling is carried out by means of airbrushes that spray - onto the surface of the sanitary fixture - a product that (after a firing process) allows manufacturers to obtain a vitrified enamel layer.

The thickness of the enamelling product that can be commonly found on sanitary fixtures before the firing ranges from a minimum of 0.5 mm to a maximum of 1 mm.

Obviously, the ideal situation is achieved when the sanitary fixture is entirely covered with an enamel layer whose thickness ranges from a minimum to a maximum that are as close as possible.

The homogeneous distribution of the enamel on the sanitary fixture plays a crucial role.

As a matter of fact, a non-homogeneous distribution of the enamel on the sanitary fixture is responsible for the occurrence of cracks, imperfections and other surface defects that usually arise only during the fixture firing step .

This surface defects can cause the fixture to be ultimately rejected with a consequent remarkable economic loss for the manufacturer.

This hints at the importance of obtaining a repeatable enamelling process to ensure a high productive efficiency.

In the past, the airbrush used to be handled by an enamelling operator, who, using his/her experience and skills, manually enamelled the sanitary fixture with a spraying nozzle, making sure that the enamelling product was homogeneously distributed on the surface of the sanitary fixture .

Therefore, in the past, the homogeneity of the enamel layer actually deposited on the surface of the sanitary fixture was merely visually controlled by the operator.

In more recent years, almost everywhere, enamelling operators were replaced by robots, which are designed to handle one or more airbrushes with the aim of obtaining high quality standards.

Therefore, enamelling experts were progressively moved from the production department to the one dealing with the programming of the robot itself.

Generally speaking, the robot is programmed by means of software that allows the robot to be programmed off-line and uses a hypothetical morphology of the spray as input in the process of simulation of the thickness of the enamelling product .

The aforesaid recent improvements were dictated by the need to minimize enamel wastes, with evident advantages both in economic terms and in environmental terms.

To this regard, a drawback that manufacturers tried to minimize, but is still very present, is that of overspray; wherein "overspray" means the quantity of enamelling product that is sprayed by the airbrush but does not hit the surface of the fixture to be enamelled.

Due to overspray, manufacturers suffer a remarkable loss of product with a consequent economic loss.

For example, experiments have shown that, with the manual application of the enamelling spray, more than 50% of dry product got lost as overspray.

Obviously, in all modern plants, manufacturers always tend to reduce the loss of enamel through overspray.

Should the application of the enamelling product on the fixture not be satisfying at the first try, the following operations will have to be repeated:

- programming the robot off-line so as to obtain a "second-try spray", which is aimed at uniformly applying the enamel on the fixture;

- enamelling the fixture;

- firing the fixture;

- controlling the quality of the finished fixture. The aforesaid operations will have to be repeated until a qualitatively acceptable product is obtained.

Obviously, if - at the end of the process - the fixture has unacceptable defects, it will have to be rejected by the quality control system.

This all leads to an expensive adjustment of the sanitary fixture production process.

Furthermore, there are many parameters that lead to a lack of homogeneity in the distribution of the enamelling product, among these parameters there are the features of the enamel (i.e. viscosity and/or grain size of the suspended particles), which can change over time.

Another factor that could contribute to the change of the operating conditions of the enamel spray is, for example, a possible accumulation of material in the airbrush, an accumulation that would deflect the spray or even, if it is especially large, would prevent it from flowing out towards the fixture.

Furthermore, enamels used in the field of sanitary fixtures contain ground abrasive particles, such as, for example, silicon dioxide and alumina.

These abrasive particles, due to their hardness, can abrade the inner surface of the nozzle during their passage through the nozzle; these abrasions can turn into defects and lack of homogeneity of the enamel layer deposited on the surface of the fixture.

DISCLOSURE OF INVENTION

Therefore, the object of the invention is to provide a plant to enamel sanitary fixtures, which is at least partially not affected by the aforementioned drawbacks and, at the same time, can be manufactured in a simple and low- cost manner.

Hence, according to the invention, there is provided a plant to enamel sanitary fixtures according to Claim 1 or to anyone of the Claims that directly or indirectly depend on Claim 1.

A further object of the invention is to provide a process to enamel sanitary fixtures, which is at least partially not affected by the aforementioned drawbacks and, at the same time, can be implemented in a simple and low- cost manner.

Hence, according to the invention, there is provided a process to enamel sanitary fixtures according to Claim 11 or _r

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to any one of the Claims that directly or indirectly depend on Claim 11.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be best understood upon perusal of the following detailed description of a preferred embodiment, which is provided by way of example and is not limiting, with reference to the accompanying drawings, in which :

- figure 1 schematically shows a perspective view of a generic plant to enamel sanitary fixtures;

- figure 2 schematically shows some enlarged details of the plant of figure 1 in a first configuration of an airbrush moving arm for the application of enamel on the sanitary fixtures ;

- figure 3 schematically shows some enlarged details of the plant of figure 1 in a second configuration of an airbrush moving arm for the application of enamel on the sanitary fixtures;

- figure 4 schematically shows a front view of a detection apparatus to detect the morphology of the sprays used in the plant of figure 1; and

- figure 5 schematically shows a view from the top of the detection apparatus of figure 4.

BEST MODE FOR CARRYING OUT THE INVENTION

In figure 1, number 100 indicates, as a whole, a generic plant to enamel a sanitary fixture (AIS) comprising, first of all, an application device 10 to apply an enamelling spray (JT) onto the sanitary fixture (AIS) .

The plant 100 also comprises a support device 20 to support the sanitary fixture (AIS) .

As explained more in detail hereinafter, the application device 10 used to apply the spray (JT) and the support device 20 used to support the sanitary fixture (AIS) can move relative to one another.

Furthermore, the plant 100 according to the invention is provided with a detection device 30 to detect at least one feature of the morphology of the spray (JT) .

To this regard, among the features defining the morphology of the spray (JT) there can be, for example, the shape and the density of the spray (JT) in each point of any cross section of the spray (JT) .

The composition and the operation of the detection device 30 will be better explained hereinafter, with special reference to figures 4 and 5.

In the embodiment shown in figures 1, 2, 3, the application device 10 for the application of the spray (JT) comprises, in turn, a robotic arm 11, which moves - in the space - an airbrush 12 ending with an emission nozzle 13 letting out an enamelling spray (JT) (namely, a spray (JT) of an enamelling product) . In particular, the application device 10 comprises moving means, which, in turn, comprise the robotic arm 11. The enamelling product typically is a water suspension containing particles, usually finely ground particles with high percentages of silicon dioxide and alumina.

The robotic arm 11, which is provided with a suitable motor (not shown), can rotate around a vertical axis (Yl) according to a double-headed arrow (Rl) (figure 1) .

The robotic arm 11, with known systems, can cause the nozzle 13, which lets out the enamel, to perform any translation and rotation movement in the space.

The enamel is sprayed onto the sanitary fixture (AIS)

(in this case, a toilet), which is fitted on the support device 20.

As you can see in figure 1, the support device 20 comprises, in turn, a piece-carrier table 21, to which the sanitary fixture (AIS) is fixed with known systems. The piece-carrier table 21 is fitted on a rotary base 22, which can rotate around a vertical axis (Y2) according to a double- headed arrow (R2) (figure 1) .

Advantageously, though not necessarily, the two vertical axes (Yl) and (Y2) are parallel to one another.

In the embodiment of figure 1, the support device 20 is provided with an evacuation device 40 for the enamel that does not hit the sanitary fixture (AIS) (overspray) .

In particular, the enamel evacuation device 40 comprises a collection tank 41, which is arranged under the rotary base 22, the piece-carrier table 21 and the sanitary fixture (AIS) being processed.

The evacuation device 40 can also comprise further overspray suction elements, which will be described hereinafter (see below) .

In order to comply with specific sanitary rules, wastewater, which is removed from the collection tank 41 through a duct 41 by means of a pump (P) , is treated in a suitable treatment plant (not shown) , which fulfils the double function of, on the one hand, avoiding the dispersion of wastewater in the environment and, on the other hand, ensuring the maximum recovery of the solid part (solid enamel) present in the water solution.

As already mentioned above, the application device 10 and the support device 20 can move relatively to one another, so that the enamelling spray (JT) hits, in a programmed and controlled manner, the entire surface (net of the base) of the sanitary fixture (AIS) to be enamelled.

When spraying the enamelling product, particular attention must be paid to the corners (both convex and concave) of the fixture. As a matter of fact, in "convex corners", the enamelling product will hardly stick on the surface and, therefore, there will be areas with an insufficient enamel covering, whereas, on the contrary, in "concave corners", there will be, in general, an accumulation of enamel with a consequent increase in the thickness of the enamelled layer.

In the embodiment shown in figure 1, the entire enamelling plant 100 is contained in a booth (CB) , where both the enamelling of the sanitary fixture (AIS) and the control of the properties of the enamel spray (JT) take place .

In another embodiment, which is not shown herein, the room where the control of the morphology of the spray (JT) is carried out is physically separate from the room where the enamelling of the sanitary fixture (AIS) takes place. In the latter case, the application device 10 will be moved, with known means that are not shown herein, to a room that is separate from the booth (CB) , where the aforesaid morphology controls can be carried out by means of the detection device 30. Therefore, in this event, the sole enamelling of the sanitary fixture (AIS) takes place in the booth (CB) .

Obviously, in the case, the detection device 30 will not be located in the booth (CB) , but in the other room (not shown) , which is properly arranged for the controls to be carried out on the spray (JT) .

Once the nozzle 13, if necessary, has been reset or replaced and, if necessary, other operating parameters of the nozzle 13 have been changed, the application device 10 is brought back to the booth (CB) , where it can keep on painting the other sanitary fixtures (AIS) supplied to the booth (CB) .

The supply and the post-enamelling removal of the sanitary fixture (AIS) from the booth (CB) are operated by means of suitable apparatuses (not shown) and according to specific programs implemented by means of a first electronic control unit (CC1), which, in any case, was configured to control all the enamelling steps to be undergone by the sanitary fixture (AIS) .

Figure 2 shows a first enamelling configuration (C0NF1) of the application device 10 when the nozzle 13 is enamelling a sanitary fixture (AIS) .

When the application device 10 assumes said first enamelling configuration (CONF1), the application device 10, the support device 20 and the sanitary fixture (AIS) are in a first working environment (AMB1), where the sanitary fixture (AIS) is subjected to the enamelling step.

The first working environment (AMB1) is in the booth (CB) .

Figure 2 basically shows, more in detail, the situation shown in figure 1.

In the first enamelling configuration (CONF1) (figure 2), the detection device 30 is entirely contained in a compartment 50 obtained in a first wall (WL1) of the booth (CB) .

The compartment 50 is closed with a sliding door 51, which, in the first enamelling configuration (CONF1) (figures 1, 2) protects the electronic equipment comprised in the detection device 30 against possible undesired enamel sprays .

In order to complete the information, and with reference to figures 2 and 3, a second wall (WL2) , which is in front of the application device 10, is provided with a suction device 60, which, when needed, sucks a given amount of enamel generated by the overspray or the entire spray, when, as discussed more in detail hereinafter, the controls are carried out on the spray (see below) .

Anyway, the suction device 60 is part of the aforesaid evacuation device 40.

Figure 3, on the other hand, shows a second control configuration (CONF2) of the spray produced by the nozzle 13.

When the application device 10 assumes the second spray control configuration (CONF2), the nozzle 13 and the detection device 30 are in a second control environment (AMB2), where the spray (JT) undergoes the control step as explained more in detail below.

In the embodiment shown in the accompanying drawings, the second control environment (AMB2) is contained in the booth (CB) , as well.

In the second control configuration (C0NF2) (figure 3), the sliding door 51 was opened through a translation of the sliding door 51 itself in a direction identified by an arrow (Fl).

The opening of the sliding door 51 produces the effect of being capable of using the electronic equipment comprised in the detection device 30.

In order to protect again the electronic equipment belonging to the detection device 30, you simply need to move the door 51 in an opposite direction identified by an arrow (F2), thus closing the compartment 50.

At regular time intervals, or when needed, the robotic arm 11, which is controlled by the first electronic control unit (CC1), brings the airbrush 12 (ending with the nozzle 13 having axis (Y3) - figures 4, 5) in the second control environment (AMB2) , as it is shown in figure 3

For example, the control of a spray (JT) of the nozzle 13 in the detection apparatus 30 can be carried out after a given number of hours of use of the nozzle 13 or after a given number of pieces painted in the booth (CB) . According to some non-limiting embodiments, the control of the spray (JT) takes place before starting with the treatment of each sanitary fixture (AIS) .

The control of the spray (JT) can also take place when an operator visually realizes that the sanitary fixtures (AIS) coming out of the booth (CB) have surface faults.

As you can see more in detail in figures 4 and 5, the detection apparatus 30 comprises at least one laser generator 31, which is designed to generate laser beams 32 having a direction that is substantially orthogonal to the axis (Y2) of the nozzle 13.

The laser beam 31 operates a sort of cross sectioning of the spray (JT) , so as to define a cross section 33, which can be detected by a video camera 34 with axis (Y4) , which is at an angle (a) relative to the axis (Y3) of the nozzle 13.

In order to prevent the surrounding light from disturbing the reading of the images by the video camera 34, said video camera 34 is preferably provided with a specific filter for the wavelengths of the beams emitted by the laser 31.

The cross section 33 usually has a denser part at the centre (substantially in the area of the axis (Y3) ) and the density of the enamelling product decreases from the centre towards the edge 35 (figure 5) .

The laser generator 31, the video camera 34 and their mutual positioning are chosen by the manufacturer in such a way that, by means of these devices controlled by a second electronic control unit (CC2) (figure 4), a process can be implemented to capture and process the images of the cross sections 33 of the spray (JT) .

The recording of the images carried out by the video camera 34 can produce a precise mapping of the distribution of the enamelling product sprayed by the nozzle (JT) onto the cross section 33.

Both the laser generator 31 and the video camera 34 are provided with moving and pivoting means (not shown) , which, upon request, vertically, horizontally and angularly move the two devices 31, 34 according to programs set by the operator in order to detect different cross sections 33 of the spray (JT) .

This technology leads to further advantages. As a matter of fact, if you analyse the section of the enamelling spray (JT) at different distances from the nozzle 13, you can decide which is the best enamelling distance, namely the one that ensure the most uniform covering of the sanitary fixture (AIS) and the smallest overspray.

Therefore, by managing to measure the space distribution of the enamelling product inside the spray (JT) , you can identify the ideal technological set-up determined by the operating parameters of the airbrush 12.

During the acquisition of data by the detection apparatus 30, the nozzle 13 could be caused to rotate (by 360°) around its axis (Y3) (double-headed arrow (R3) - figure 4) so as to have a more precise mapping of the edge 35 (figure 5) of the cross section 33.

As a matter of fact, through the 360° rotation of the nozzle 13 around the axis (Y3) , you can obviate the shielding effect (during the reading by the video camera 34) of enamel particles located in a portion of the spray above the section 33 being read.

The second electronic control unit (CC2) reprocesses the data detected by the detection apparatus 30 and can order some actions, for example:

1) visually and/or acoustically signalling faults found in the spray (JT) and suggesting the operator to change the nozzle 13 because it is unsuited for the use;

2) comparing one or more features of the morphology of the spray (JT) acquired in real time instant by instant with one or more features of the morphology of the spray (JT) stored in a memory and, then, if the data acquired do not match, signalling to the operator the actual state of the system; or causing a change in the system in order to adjust it for the purpose of improving its performances based on the defect detected in the morphology of the spray (JT) ; periodic comparisons of the actual distribution of enamel in the spray (JT) with reference data allow you to identify faults, due - for example - to a clogging of the nozzle 13, and/or undesired changes of the nozzle 13 and of its operating parameters;

3) acquiring data in real time, so that the system can change - in real time - the setting of the actual spraying modes with which the enamelling product is applied onto the sanitary fixture (AIS) present in the booth (CB) .

For example, in the latter case, if the detection apparatus 30 realizes that the best distribution of enamelling product on the sanitary fixture takes place in a section 33 that is located at a distance (D) from the nozzle 13 (figure 4), when the application device 10 resumes the first working configuration (CONF1), thus moving back to the first working environment (AMB1), the system will make sure that the mean distance of the three-dimensional surface of the sanitary fixture (AIS) is always (D) , by moving the nozzle 13 through the robotic arm 11 or by moving the support device 20 (figure 1) or by adopting both systems.

For example, corrections of an ideal distance (D) could be made during the actual spraying of the enamelling product on the fixtures in the area of "convex corners", by placing the nozzle at a distance (D1)<(D) in order to increase the thickness of the layer of enamelling product, or in the area of "concave corners", by placing the nozzle at a distance (D2)>(D) in order to decrease the thickness of the layer of enamelling product.

Alternatively or in addition, if the features of the morphology of the spray (JT) are not compatible with the current parameters (comprising, in particular, the actual path of the nozzle 13 and/or the actual pressure of application of the enamelling spray onto the fixtures) of the emission of the spray (JT) onto the sanitary fixture (AIS) , these parameters are changed (adjusted) by the system in real time.

Especially relevant enamelling parameters are the pressure of atomization of the enamel and/or the pressure of deformation of the edge 35 and/or the mass flow rate of the dry substance emitted by the nozzle 13.

According to some non-limiting embodiments, features of the morphology of the spray (JT) to be taken into account are the shape of the spray (JT) and/or the point-by-point density of each cross section of the spray (JT) , etc.

In some applications, the two electronic control units (CC1), (CC2) could be integrated in one another, or some functions of one of them could be fulfilled by the other one .

As already mentioned above, the invention further relates to a process to enamel sanitary fixtures.

The process to enamel sanitary fixtures according to some non-limiting embodiments of the invention comprises:

(fl) at least one emission step, during which an enamelling spray is emitted onto the surface of the fixtures by means of the use of a spraying nozzle;

the process being characterized in that it comprises: (f2) at least one second step, during which at least one morphology feature and/or at least one operating parameter of the enamelling spray are controlled; and

(f3) at least one third step, during which, depending on the control carried out during the previous step (f2), at least one signal is generated, which is designed to retrospectively change said at least one morphology feature and/or said at least one operating parameter of the enamelling spray.

More in detail the process comprises an (the) emission step to emit an enamelling spray (JT) onto the surface of the fixtures by means of the use of a spraying nozzle 13, and provides that the morphology of the enamelling spray (JT) is controlled, so as to retrospectively cause the performance of maintenance operations to be carried out on the nozzle 13 and/or so as to generate retrospective orders on the actual spraying modes with which to spray the enamel onto the fixtures.

In this process, the control of the morphology of the spray (JT) is carried out by means of a methodology that uses image capturing through video cameras.

Furthermore, depending on the result of the control of the morphology of the enamelling spray (JT) , visual and/or acoustic signals are generated, which are such as to retrospectively cause the performance of maintenance operations to be carried out on said spraying nozzle 13.

According to other non-limiting embodiments, depending on a comparison carried out between the actual morphology of the enamelling spray (JT) and at least one reference morphology, at least one parameter is changed, with which the enamelling spray (JT) is emitted. In particular, the actual path of the spraying nozzle and/or the actual pressure of application of the enamelling spray (JT) onto the sanitary fixtures and/or the pressure of deformation of the edge 35 and/or the mass flow rate of dry substance emitted by the nozzle 13 are changed.

In a first solution, the actual path of the spraying nozzle and/or the actual pressure of application of the enamelling spray onto the sanitary fixture is/are extracted from a library containing a plurality of reference models.

In a second solution, the actual path of the spraying nozzle and/or the actual pressure of application of the enamelling spray onto the sanitary fixture is/are calculated by the system in real time.

In other words, depending on the result of the control of the morphology of the enamelling spray (JT) , the system changes, in real time, the setting of the actual spraying modes with which to spray the enamel onto the sanitary fixtures present in a given working booth (CB) .

The main advantages of the plant to enamel sanitary fixtures according to the invention are the following:

- immediate detection of the physical-chemical causes that jeopardize an optimal application of the enamelling product onto the surface of the fixture, with consequent reduction of production waste;

- significant reduction of enamelling times;

- remarkable improvement of the finishing of the enamelled surfaces;

- greater homogeneity of the thickness of the enamel layer, even in concave and convex corners;

- minimization of the quantity of enamelling product lost due to overspray.