"PLANT FOR SPRAYING LAMINATES PARTICULARLY LEATHER IN THE TAN INDUSTRY"

Description

The present invention concerns a plant for spraying varnishing products on flexible and non-flexible laminates .

In particular, the plant in obj ect is used to varnish the surface of leather in the tan industry .

However, this plant can advantageously be used in the furniture industry and the. like .

The rest of the present description considers , without limitations , a spraying plant to be used in the tan industry .

It is known that in modern leather varnishing plants special spray compartments are used inside which the leather to be varnished is brought transported by a wire-type conveyor .

The spray compartments in question comprise a suitable spraying apparatus inside them suitable for laying the desired layer of varnish on the surface of the leather that passes at a controlled speed under the same spraying apparatus .

The most recent spray compartments use suitable spray guns arranged on rotating carousels or else pulled by elliptical chains according to a predetermined path . In recent years spray compartments have been researched and made at prototype level comprising a rod along which many spray guns are arranged, or else a succession of air brushes .

Such a rod can be kept fixed in the direction transversal to the movement of the laminates to be sprayed, or else made so

that it can oscillate according to the same transversal direction or even equipped with more complex movement .

The main drawbacks of the known plants quoted above consist of the constructive complexity, particularly of the spraying apparatus , and of the need to periodically clean the same apparatus .

Such an operation should be carried out frequently and in any case each time the colour of the product to be sprayed is changed and requires long maintenance times and substantial consumption of solvents , which may even be harmful .

If the same operation is not accurate the result of the spray can be of inferior quality, if not actually harmful in the leather finishing process . It . is totally clear that the first purpose to be sought after lies in the varnishing quality obtained, which depends firstly upon the uniformity and regularity of the film of varnish deposited by the aforementioned spraying apparatus on the leather to be varnished. Another purpose sought after is the efficiency of deposition, measured by the ratio between the amount of product actually deposited on the obj ects to be varnished and that emitted by the spraying apparatus .

A further purpose of the present finding is to make a spray compartment that can easily be mounted in its components , as well as easy and quick to dismount for periodic cleaning and/or maintenance .

Yet another purpose sought after by the same finding is that the dimensions of the plant are such as to allow it to be completely mounted in the production factory and subsequently transported by container .

Another purpose of the finding is that the vapour suction

system associated with known plants and the relative scrubber of the coloured particles in suspension be directly- integrated in the new plant in question .

The aforementioned purposes are accomplished by the plant of the present finding which, in accordance with the content of the first claim, comprises a spray compartment in which the manufactured articles to be sprayed travel on a wire-type conveyor, a bridge casing supporting at least one cross member, also transversally equipped with possibly controlled oscillating motion, the same cross member being associated with a corresponding feeding and spraying rod comprising one or more modular portions that can be assembled through joining means .

Again in accordance with the first claim, along said rod a plurality of air brushes are regularly distributed associated with corresponding actuator members controlled by control devices , the aforementioned air brushes being suitable for emitting finely pulverised varnishing products , upon command . The plant of the finding is characterised in that the two ends of said feeding and spraying rod are respectively associated with a group for adj usting the pressure of the liquid product to be sprayed and a group for discharging the colour and the washing liquids . The same plant is further characterised in that said air brushes each have a spray nozzle of the type able to be quickly and advantageously replaced, being able to insert- remove it into/from the base of said feeding and spraying rod through rapid manoeuvring means . Further characterising features of the same plant lie in the fact that said air brushes are associated with said corresponding actuator members through a sliding block coupling system between the aforementioned feeding and. spraying rod and a linear structure above comprising the

aforementioned actuator members and also carried by the cross member of the bridge casing .

The last characteristic of the plant in question consists of the fact that the suction system of the aforementioned vapours also has the function of purifying the vapours themselves and us integrated in the same plant .

The aforementioned purposes shall become clearer in the rest of the present description that refers to an example embodiment of the finding specifically aimed at the field of leather spraying in the tan industry .

Such an example should be considered to have been given just for descriptive purposes and should not be considered to be limiting for other embodiments and/or applications ; it is illustrated in the attached tables of drawings, where : - figure 1 shows an overall perspective view of the central operative part of the spraying plant ;

- figure 2 shows the detail of the j oining means between two contiguous portions of the feeding and spraying rod;

- figure 3 illustrates the system for slidably coupling a portion of the same rod with the linear guide belonging to the aforementioned cross-member;

- figure 4 shows a front view of the feeding and spraying rod associated at its ends _, with the pressure adjustment group and with the discharge group; - figure 5 shows a section view of the aforementioned adj ustment group;

- figure 6 shows a section view of the aforementioned discharge group;

- figure 7 shows a cross section of the cross-member that supports the various components of the spraying apparatus;

- figure 8 shows three views of the outer shape of the spray nozzle ;

- figure 9 shows an exploded view of the components of the same nozzle;

- figure 10 is an axial section of the same nozzle, entirely assembled;

- figure 11 illustrates the way of inserting one of the nozzles into the body of the rod, represented in inverted position; - figure 12 shows how the anchoring of the nozzles in the body of the same rod takes place;

- figures 13 , 14 and 15 are section views of the same rod of figure 7 , but highlighting the three different positions that the actuator members can take up; - figure 16 shows a side view of the cross-member, complete with the airtight box comprising the devices and the control boards and connected to the electrovalves through BUS transmission lines ;

- figure 17 illustrates the possibility of orientating the spray direction of a spraying rod with respect to the vertical; figure 18 schematically shows the components of the suction system of the vapours integrated with the plant .

The spraying plant in question is shown, in its main components , in the partial perspective view of figure 1. It refers to a schematic example embodiment particularly suitable . for spraying leather in the tan industry .

The same plant essentially comprises the spray compartment 1 in which the leather P to be sprayed pass on the wire-type conveyor 2.

The same plant, inside the spray compartment 1, comprises a bridge casing supporting at least one cross-member 3 , also transversally equipped with possibly controlled oscillating motion .

Such a cross-member 3 supports a corresponding feeding and spraying rod 4 comprising one or more modular components that can be assembled through j oining means .

Along the aforementioned rod 4 a plurality of ^v air brushes are regularly distributed associated with corresponding actuator members controlled by control devices , assembled inside a linear structure 5 above the aforementioned rod 4 and also supported by the cross-member 3.

The aforementioned air brushes that shall be illustrated later on in the description, are suitable for emitting the finely pulverised varnishing products upon command according to j ets G substantially in accordance with those shown in figure 1.

As stated above , the feeding and spraying rod 4 can be made in a single portion or else in many contiguous portions , which can be assembled according to the dimensions of the plant, space limitations and/or for ease of assembly-

, disassembly, as well as to make the periodic cleaning operations of the same rod as easy as possible .

Figure 2 shows an example embodiment of j oining means between two contiguous portions 4 ' and 4 ' ' Of the rod 4 , an example that foresees the use of a pair of side harpoons 41 suitable for allowing said contiguous portions 4 ' and 4 ' ' to be quickly attached-detached .

Figure 3 shows how the feeding and spraying rod 4 has a plate 42 on its back suitable for slidably coupling with a linear guide 43 belonging to said cross-member 3.

The adopted solution allows the rod 4 to be quickly

assembled and disassembled, by respectively inserting and withdrawing the various component portions , by sliding in the same guide .

Figure 4 shows the cross-member 3 interrupted at the middle and supporting the rod 4 and the linear structure 5 quoted above .

The same rod 4 has , at its base, the plurality of air brushes 6 and is associated at its ends, respectively, with the pressure adjustment group 7 of the liquid product to be sprayed entered into the feeding and spraying rod, and with the discharge group 8 of the colour and of the washing liquids .

The aforementioned adjustment group 7 , shown in section in figure 5, comprises a counteracted membrane adjustment device 71, suitable for keeping a preset pressure value practically constant .

The discharge group 8 , shown in section in figure 6 , comprises a superimposed back pressure device 81, associated with an electrovalve 82 , normally open in work position and that is excited to provide the washing operation.

Figure 7 represents a cross section of the cross-member 3 , in the body of which a plurality of channels are formed, some for making the body itself lighter, others , like those indicated with 31 , for supplying air to actuate the actuator members of the spraying apparatus .

Such actuator members are inserted inside the linear structure 5 above the rod 4.

Each actuator member, visible in the section of figure 7 , comprises a first actuator piston 51 which is provided with the thrusting stem 52, suitable for acting on the manoeuvring head 44 belonging to the corresponding air brush below inserted in the feeding and spraying rod 4 , as shall

be specified more clearly hereafter .

The same actuator member also comprises a second actuator piston 53 that is axially perforated and able to slide on the thrusting stem 52 and provided at the bottom with a traction means 54 acting on the manoeuvring head 44.

The aforementioned first actuator piston. 51 and second actuator piston 53 are controlled by suitable control devices to take up three different positions, as shall be illustrated hereafter . The same figure 7 shows , again in section, the composition of each air brush that substantially comprises the spray nozzle 9, the alternative axial manoeuvring stem 45 , associated at the bottom with the pin 46 for opening-closing the same spray nozzle and at the terminating at the top with the aforementioned manoeuvring head 44.

Figure 7 also highlights the presence in the body of the rod 4 of a first channel 47 for supplying air and of a second channel 48 for supplying colour towards each spray nozzle 9.

The outer shape of the latter can be seen in the three views of figure 8.

The same nozzle is made in many pieces (shown in figure 9 ) assembled together and guite small in size, such pieces being produced even using low-cost materials, in such a way making the frequent replacement of the nozzles themselves advantageous, rather than the periodic cleaning required by the air brushes currently in use .

Indeed, they are complex to make and expensive for which reason they cannot be replaced frequently .

On the other hand, their frequent cleaning requires long periods of time and unproductive stops during processing .

The nozzle 9 of the finding is shown in an exploded view in

figure 9 and is then shown assembled and axially sectioned in the subsequent figure 10. It comprises the base element 91 , the coaxial intermediate element 92 and the top element 93 , also coaxial . The exploded view of figure 9 is completed with the two circular gaskets 94 and 95.

The base element 91 has the central star-shaped recess 911 equipped with a plurality of peripheral vertical channels 912 for supplying the air for pulverising the product, such a star-shaped recess 911 being clamped onto a central air outlet hole 913.

The same central hole 913 is countersunk in outlet , as shown by figure 10 , in order to create the ideal spraying cone in outlet from the nozzle 9 and in order to eliminate the danger of creation of an undesired deposit halo of the varnishing product around the hole itself .

The same base element 91 has a flat collar 96 (visible in all of figures 8 to 10 ) provided with a pair of diametric clamping holes 961, these being suitable for being engaged by the quick manoeuvring means , which shall be discussed hereafter .

The aforementioned intermediate element 92 is suitable for coupling axially with the aforementioned top element 93.

The same intermediate element 92 has the central chamber 921 ( fig . 10 ) for collection of the product to be sprayed, said chamber terminating at the bottom with the axial hole 922 for the outlet of the product itself and for the sliding of the aforementioned pin 46 for opening-closing the central hole 913. The aforementioned top element 93 is suitable for coupling at the bottom with the star-shaped recess 911 , provided prior coupling with the intermediate element 92.

The same top element 93 has, at the top, an accumulation chamber 931 ( figs . 9 and 10 ) of the product to be sprayed. Such an accumulation chamber 931 communicates with the aforementioned central collection chamber 921 through a plurality of peripheral vertical holes 932 suitable for filtering the product on its way through, and has an axial hole 933 for the sliding of the aforementioned pin 46.

The manoeuvring for insertion-withdrawal of each nozzle 9 in the seats 49 formed in the base of the rod 4 can be easily understood by observing figures 11 and 12.

What we shall call "quick manoeuvring means" is indicated with 10 in figure lla . It is j ust a non-limiting example embodiment and has the manoeuvring handle 101 and the two pegs 102 for insertion into the corresponding holes 961 of the flat collar 96, holes which are suitably shaped in order to be easily and quickly engaged by the same pegs through a small rotation .

Having achieved engagement, according to the situation of fig . lib, the insertion of each nozzle 9 in a corresponding seat 49 of the base of the rod 4 takes place by pressing and subsequently rotating, which can be understood from the examination of the sequence of the two situations illustrated, going from the right, in figure 12. The third situation represented here is identical to the second and is only given to indicate, through the section view, the "bayonet" engagement of the flat collar 96 below the base of the rod 4.

It is absolutely clear that the withdrawal manoeuvring of any nozzle 9 from the rod itself takes place with a manoeuvring sequence that is inverted with respect to the one j ust described.

Figures 13, 14 and 15 all repeat the composition of figure 17 , but highlighting the three positions that each of the actuators members inserted in the linear structure 5 can

take up with respect to the corresponding air brush below .

The position of figure 13 concerns the situation of thrusting exerted by the thrusting stem 52 of the first actuator piston 51 on the manoeuvring head 44 of the corresponding air brush to close the central hole 922 of the nozzle 9.

The position of figure 14 concerns the situation of traction exerted under the same manoeuvring head 44 by the traction means 54 , under the action of the second actuator piston 53. Finally, the position of figure 15 concerns the intermediate situation of detachment of the same manoeuvring head 44 , a position that allows the portions of rod 4 to be inserted and withdrawn with respect to the linear guide 43 , without interference with the aforementioned actuator members . The control devices of all of the movements of the plant, in particular of the components carried by each cross-member 3, comprise, as indicated in figure 16, electronic boards 11 contained inside airtight boxes 12 arranged on the cross- member 3 j ust above the electrovalves , like the one indicated with 13 in the same figure .

The electrical connections necessary for the dialogue between the aforementioned control devices and the actuator members are represented by the transmission lines 14 , of the serial BUS type . Such lines are intended in particular to control the electrovalves associated with the air brushes .

That which has just been stated illustrates the declared purpose of compacting the assembly of the control devices and actuator members as much as possible, arranging everything on the same cross-member with substantial advantages in terms of bulk, the protection of the more delicate electronic components and the transmission speed of

the information and of the commands .

It has been stated above that the plant of the finding comprises at least one cross-member supported by the bridge casing over the spray compartment .

In figure 17 such a bridge casing is wholly indicated with 15. It supports the cross-member 3 through positioning means 16 suitable for adj usting the position of the same cross- member in height , according to the arrow X .

A particular embodiment of the finding foresees the use of three parallel units of the cross-member 3 , fully described above .

Such units , substantially identical and corresponding to that of figure 17 , can also be arranged adj ustably spaced apart, both horizontally and vertically, and this by means of manual or automatic adj ustment devices , of the type of those 16 represented in the same figure .

This figure also shown how at least one of the three parallel units of the same cross-member 3 can be equipped with further movement that allows them to be tilted by a certain angle , according to arrow Y, with respect to the vertical spraying direction .

This allows the j et of spraying product to be aimed in the direction most favourable for the best finish of the leather . The plant in question also comprises an innovative vapour suction system, schematically represented in figure 18.

It comprises a plurality of horizontal linear suction elements 17-18 , each of which is substantially tubular- shaped. Such a shape is suitable for containing a suitable amount of water on the bottom, circulating to encapsulate particles of

colour .

The same suction elements 17-18 are arranged inside the spray compartment at the four perimetric sides , respectively two (both indicated with 17 ) in the longitudinal sense above the wire-type conveyor 2 and two (both indicated with 18 ) in the transversal sense below and/or above the same conveyor .

All of the suction elements comprise a plurality of water spraying nozzles inside them (not represented in the figure) suitable for promoting the aforementioned encapsulation of the particles of colour sucked in .

The perimetric arrangement of the suction elements outlined above, and illustrated in figure 18 , allows an optimal confinement of the spray vapours to be obtained and prevents the dripping of the product on the leather passing through on the conveyor 2.

A further advantage due to the presence of the aforementioned spray nozzles is given by the fact that the same vapour suction system also has the function of purifying them, a function that, on the other hand, is carried out by a complex separate apparatus in existing plants .

Moreover, the suction system of the finding comprises the decanting reservoir 19 , which is provided on the inside with the pump for continuously circulating the water .

The whole thing is arranged inside, or partially close to the spray compartment, for which reason it can be stated that the vapour suction and purification system is integrated in the conceived plant .

It is also absolutely clear that the aforementioned reservoir 19 shall be connected, through suitable piping 20 , to the suction mouth of a fan outside the plant .

What has been described and illustrated above allows it to

be highlighted how the plant of the finding achieves all of the predetermined purposes .

At the embodiment stage some constructive details of the various components described above can be modified to adapt them to particular requirements or to applications in different production fields from the tan industry, considered here as a preferred example .

Any variant embodiment that derives from the concepts outlined above should be considered to be covered by the scope of protection of the present finding .