Head for paint gun

Abstract

The present invention relates to a spray head (10) for paint guns, comprising a substantially cylindrical body with a front spray surface (SF) substantially flat for its whole extension and without projections protruding from said front spray surface (SF), wherein said front spray surface (SF) carries a plurality of calibrated holes (13), in communication with corresponding feeding ducts obtained in the body of the spray head (10).

Description

[0001] The present invention relates to a head for paint gun.Background

[0002] Automatic paint guns consist of a main body thereon a spray head is screwed. The spray head is equipped with a series of calibrated holes which can have different angular tilts. Said holes are useful to atomize and to open the nebulized jet to form the spray fan.

[0003] However, the shape of the currently used spray heads involves some difficulties, especially in terms of cleaning and maintenance.

[0004] In particular, the shape of the head, which provides a pair of protrusions whereon some of the calibrated holes are implemented, causes, especially upon use, an important accumulation of painting product. Of course, this product accumulated on the head has to be removed, to avoid that it could disturb the correct scattering and the correct atomization of the product itself during painting.

[0005] Consequently, it is necessary to interrupt frequently the painting procedure to cleanse the spray head.

[0006] Moreover, considering the head shape, even such cleaning procedure turns out to be particularly hard-working.

[0007] EP 2 468 413 relates to a spray gun comprising a gun body, on which a replaceable air cap 18 is arranged on the outlet side. The disk-shaped air cap has an outlet opening, centrally positioned in the front surface of the outlet side of the air cap, which is surrounded by a truncated cone-shaped recess and from which a medium intended for coating can emerge.

[0008] WO 2007 / 024381 relates to an external mix air atomizing spray nozzle assembly comprising a nozzle body and an air cap 12 mounted at the downstream into the nozzle body. The air cap is formed with a central cylindrical opening which receives the forwardly extending nose of a liquid spray tip. The air cap is formed with a central hub defined by an annular air plenum and is formed with a plurality of air discharge passages defined by respective conical indentations or dimples disposed at a 45° angle to a plane normal to the longitudinal air cap axis.

[0009] DE 10 2011 079982 relates to a spray head consisting of a main body with a bore extending through the main body. The spray head further comprises a spray device with a spray channel through which components mixed in a mixing chamber are ejected out. The spray device has a deflection section in which the channel undergoes a curvature so that the component mixture is deflected. An atomizer channel can be provided on the deflection section so that gas such as air can be introduced into the spray channel to accelerates the component mixture in the direction of the outlet of the spray device.Technical problem solved by the invention

[0010] The object of the present invention is to solve the problems left unsolved by the known art, by providing a spray head as defined in claim 1.

[0011] The present invention further relates to a paint gun as defined in claim 3.

[0012] Additional features of the present invention are defined in the corresponding depending claims.

[0013] The advantages, together with the features and the use modes of the present invention will result evident from the following detailed description of preferred embodiments thereof, shown by way of example and not for limitative purposes.Brief description of the drawings

[0014] Hereinafter in this description the drawings shown in the enclosed figures will be referred to, wherein: figure 1 is a perspective view of a gun with traditional head; figures 2A and 2B are a front view and a side view of the gun of figure 1, respectively; figure 3 is a section view taken along the line A-A of figure 2A; figure 4 is a section view taken along the line B-B of figure 2A; figure 5 is a side view of a spray head of known type; figure a 6 is a side view of a spray head according to the present invention; figures 7A and 7B are a front view and a section view (taken along the line A-A of figure 7A) of a spray head according to the present invention, respectively; figures 8A, 8B, 8C are front views of possible embodiments of a head according to the present invention; and figure 9 is a partial view of a paint gun, in section, with a spray head according to the present invention. Detailed description of preferred embodiments

[0015] The present invention will be described hereinafter by making reference to the above-mentioned figures.

[0016] The indication of some of the references existing in the figures will be reported hereinafter: R3: Piston actuation air inlet; C1: Atomization air duct; C2: Fan opening air duct; SC: Contact and centering surfaces.

[0017] With reference to figures 1 to 5, they show an automatic paint gun, equipped with a spray head of known type.

[0018] An automatic paint gun includes a main body 1 thereon a calibrated nozzle 2 is screwed which has to act as mechanical seal on the resting conus A to avoid the leakage of the pigment coming from the connection R1.

[0019] Inside the nozzle 2 a closing rod 3 slides, which allows the passage and the adjustment of the pigment from the orifice of the nozzle 2.

[0020] A spray head 4, resting and centering on the nozzle 2, is provided with a series of holes, calibrated too, having different diameter, both on the plane and on the projections 14, which can have different angular tilts. Said holes are useful to atomize and open the nebulized jet to form the spray fan.

[0021] The head 4 is kept in centered and axial position with respect to the closing rod 3 and to the nozzle 2 by a threaded ferrule 9 screwed on the body itself.

[0022] The feeding of the ducts C1 and C2 takes place by inletting air from the connection R2, which feeds the distribution valve 5, by putting in pressure its chamber B2.

[0023] When, through command with electro-valve, air is inlet through the connection R3 in the chamber B3, an axial pushing force is exerted on the piston 7 which, by lifting, puts into communication the chamber B2 with the chamber B1 of the distribution valve 5.

[0024] By making this, the air crosses the ducts C1 and C2 until outgoing from the calibrated holes of the head. The piston, by continuing its stroke, hooks and lifts the rod 3 which by freeing the orifice of the nozzle 2 allows the passage of the paint which is hit by the air previously released by the distribution valve 5.

[0025] The air of the duct C1 is useful to atomize the paint whereas the air of the duct C2 is useful to originate the fan.

[0026] Generally, these ducts are interrupted by a regulating valve 8 which is useful to dose the air quantity to be assigned to the single addresses, that is atomization and fan.

[0027] In the herein represented gun, as it is visible in figure 3, one single regulating valve 8 is present which in this case intervenes on the fan width. The hand wheel 6 rotates and rubs by means of the position snaps allowing the rod 3 to have a travel going from zero to the maximum opening of some millimetre, by determining the product capacity required for painting.

[0028] Among the various types of known guns those working with only pressure of the paint pump and without the help of air are distinguished, called AIRLESS. Among those using air, there are the high-pressure guns, called HT or conventional, those working with lower pressure by using greater air volume called HVLP and those of last generation working by exploiting a low air volume thereto a still lower pressure value corresponds, called LVLP. With the latter it is possible to apply the same amount of paint by reducing up to 40% of the dispersed one in booth by the rebound effect of the paint on the material to be painted.

[0029] The subsequent figures 6 to 9 instead relate to a spray head according to the present invention.

[0030] In general terms, a spray head 10 according to the present invention is characterized by a substantially flat front spray surface SF and by the absence of the typical projections.

[0031] According to the present invention, the calibrated holes are implemented on the front spray surface SF of the head according to various diameters and tilts, depending upon the use that the head itself has to carry out.

[0032] In the section view of figure 7B with number 12 the central hole is designated which is useful to nebulize the liquid outgoing from the nozzle and with number 13 the holes are designated (preferably implemented in symmetric position with respect to the central hole 12) which by hitting the flow of the nebulized fluid, create the fan effect by further helping the jet atomization.

[0033] The interference calibrated holes 13 are arranged symmetrically with respect to the nebulization central calibrated hole 12 and angled with respect to the latter by an angle β. Of course, the holes 13 on a head could be implemented, singularly or in groups, with angulations different therebetween, even in the same head, to implement the wished effect.

[0034] Advantageously, an embodiment according to the present invention allows to arrange the holes so as to obtain more effective configurations of the fan and to be able to decrease the turbulences appearing during the rotation of the painting system.

[0035] Moreover, as already said, it allows less deposit of residue of nebulized paint existing in booth, thanks to the absence of projections or tilted surfaces arranged to collect the exceeding paint fumes.

[0036] Consequently, a greater ease of cleaning results, even thanks to the absence of projections, and then even a decrease in the chemical products used for the same cleaning.

[0037] At last, since a substantially flat front spray surface is available, substantially as wide as the whole head, it will be possible to select suitably the number and arrangement of the calibrated holes, with the purpose of obtaining the wished fan shape, for example by arranging the holes along a diametral axis D of the head, according to an arc of circle AC, or combined, as exemplified in figures 8A, 8B and 8C.

[0038] According to the invention and as shown in figure 8B, the front spray surface SF comprises a nebulization central calibrated hole 12, and a plurality of interference calibrated holes 13, tilted with respect to the central hole 12, arranged along two arcs of circle AC symmetrically arranged therebetween with respect to the nebulization central calibrated hole 12.

[0039] According to the invention and as shown in figure 8C, the spray head comprises a second plurality of interference calibrated holes 13', tilted with respect to the central hole 12 too, and having smaller diameter than the interference calibrated holes 13, and arranged along two additional arcs of circle AC' symmetrically arranged therebetween with respect to the nebulization central calibrated hole 12, at a smaller distance from said central calibrated hole 12 with respect to the arcs of circle AC.

[0040] With reference to figure 9, which represents a section of a head 10 according to the invention, mounted on a paint gun, it is possible to appreciate that, under working conditions, the head 10 houses its spherical surface inside a conical surface SC obtained on the nozzle. In this way a perfect centering is obtained which the locking ferrule, once tightened, keeps aligned according to the axis of the nozzle itself. The expansion chamber 20 obtained in the head itself fosters the expansion chamber 21 existing in the gun body in favour of the low-pressure use of the paint gun, allowing to atomize the pigment at lower pressures, thus favouring the paint transfer on the finished product and the possibility to work on light leather.

[0041] A head according to the present invention results to be particularly suitable and advantageous for guns working at ultra-low pressure, preferably at pressure comprised between 0.2 and 0.9 bar.

[0042] The present invention has been sofar described with reference to the preferred embodiments thereof. It is to be meant that each one of the technical solutions implemented in the preferred embodiments, herein described by way of example, can advantageously be combined, differently from what described, with the other ones, to create additional embodiments, as long as the resulting embodiments fall within the protective scope of the herebelow reported claims.

Claims

1. A spray head (10) for paint guns, comprising a substantiallly cylindrical body with a front spray surface (SF) substantiallly flat for its whole extension and wiithout projectiions protruding from said front spray surface (SF), wherein said front spray surface (SF) comprises a nebulization central calibrated hole (112), and first interference calibrated holes (13), tilted with respect to the nebulization central calibrated hole (12), so that air outgoing from the first interference calibrated holes (13) hits the flow of the nebulized paint outgoing from the nebulization central calibrated hole (12), creating a fan effect by further helping the atomization of the nebulized paint, said first interference calibrated holes (13) being arranged along a diametrical axis (D) of the spray head and / or along two arcs of circle (AC) symmetrically arranged therebetween with respect to the nebulization central callibrated hole (12), in communication with corresponding air feeding ducts obtained in the body of the head (10), characterized in that the spray head (10) comprises second interference calibrated holes (13'), tilted with respect to the nebulization central calibrated hole (12), in communication with corresponding air feeding ducts obtained in the body of the head (10), having smaller diameter than the first interference calibrated holles (13), and arranged along the diametrical axis of the spray head and / or along two additional arcs of circle (AC') symmetrically arranged therebetween with respect to the nebulization central calibrated hole (12), at a smalller distance from said nebulization central calibrated hole (12) than the first interference calibrated holes (13).

2. The spray head (10) according to claim 1, made of stainless steel AISI 303.

3. A paint gun comprising a spray head (10) according to any one of the preceding claims.

4. The paint gun according to claim 3, characterized by an ultra-low-pressure operability, preferably at a pressure comprised between 0.2 and 0.9 bar.

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