TW200821042A - Air cap for a paint gun - Google Patents

Abstract

An air cap for a paint spray gun includes a centrally positioned, axially extending aperture 21, wherein the aperture 21 (through which, in use, atomising air is passed) has a rotationally symmetrical shape which includes a plurality of radially extending protrusions 22.

Description

200821042 IX. DESCRIPTION OF THE INVENTION: TECHNICAL FIELD OF THE INVENTION The present invention relates to a gas cap for pigment spray, and more particularly to reducing noise when used in a cap spray. [Prior Art]

The nozzles of the paint spray gun can be broadly classified into two types: a round spray and a fan spray. In both sprays, the gas cap has a centrally located, generally circular, axially extending bore; in use, the atomizing gas from the pigment to which the gas cap is attached is guided through the orifice. The fan spray cover differs from a circular spray cover in that the fan spray includes a plurality of side holes that generally appear in the form of "horns" and extend from the outer surface of the gas cover. Out. The center hole may taper toward the direction of the mist gas outlet. These designs are well suited to provide a uniformly distributed and controllable spray pattern; however, it has been found that considerable noise is generated when the atomizing gas flows through the gas cap in such a design. SUMMARY OF THE INVENTION One object of the present invention is to provide an improved gas cap design that produces less noise when compared to conventional gas cap designs when the gas cap is used on a paint spray gun. According to the present invention, there is provided a gas cap for a paint spray gun, the gas cap comprising a centrally disposed axially extending bore through which atomizing gas passes when used, wherein the bore has a rotational symmetry The shape includes a plurality of protrusions of 5, 2010, 214, 42 extending radially. The protrusions can take a variety of different forms, for example, they can be pointed, square end shaped, truncated, rounded or otherwise curved. The hole may taper toward the direction of the gas mist atomizing gas outlet. Alternatively, but not necessarily, in an axial direction, the projections may extend parallel to the longitudinal axis of the aperture or at an angle different from the remainder of the aperture.

Preferably, at least 3 projections are provided. In fact, up to 24 protrusions can be provided. Preferably, the hole is designed to pass between about 20% (including 20%) to 80% (including 80%) of the atomizing gas passing through the hole through the hole. Stretching. In a preferred embodiment, the atomizing gas passing through the projections is between 40% (containing 40%) and 60% (containing 60%). EXAMPLES For a given gas cap and nozzle that can be captured with a gas cap, the geometry of the hole can be defined as follows:

6 200821042 Number: Di = = outer diameter of the fluid tip element d2 : = inner diameter of the hole D 3 = = outer diameter of the hole d4 : diameter of the root of a large extension Θ = $ half angle of the angle of the inner surface Φ = sudden Interval angle of the extension

Suppose there are a plurality of substantially V-shaped projections: Number of projections N = 2 7Γ /Φ Exit area of each projection Ag = ((D4 - D2)2 - (D4 - D3)2) tan0 /4 annular outlet area Aa = 7Γ (D22 - area ratio R = N · Ag / Aa total outlet area At = N · Ag + Aa As mentioned above, R is preferably between 20% (inclusive) and 80% (including Between the better, the system is between 40% (including 40%) and 60% (including 60%). Under considerable atomization, it is preferable to make At equal to the central hole area of the conventional gas cap. At, the At will be in the range of 1.0 to 20 square millimeters (mm2). The inventors have found that adjusting the gas cap in accordance with the present invention can reduce the noise generated by the running paint spray to 3 dB. It is equivalent to a 50% reduction in sound intensity. It is believed that this novel design can reduce the velocity gradient when the gas leaves the hole, thereby reducing noise. No adverse effects are found in gas atomization. 7 200821042 [ Implementation method

As shown in Fig. 1, the nozzle assembly of a pigment gun comprises a nozzle body 36, a cylindrical sealing member 38 and a gas cap 40. The nozzle body 36 is fixed to the body of the pigment grab by means of a screw connection 42. The nozzle body 36 has a cylindrical hollow interior 44 that opens into a nozzle opening in the nozzle tip 46 at the forward end of the nozzle tip 46 through which the fluid can be dispersed. The nozzle body 36 has a radially extending flange or weir 48 having an opening 50 through which compressed gas can pass. The radially extending weir 48 and the facing surface 51 of the body together form a gas distribution chamber 53 and direct gas from the gas chamber 20 and its column region 26 to the gas distribution chamber 53. The gas cap 40 is disposed at the front end of the nozzle body 36. The gas cap 40 has a central hole 52 which can form an annular passage in the nozzle body 36. The atomizing gas can be ejected from the hole 52 and can exit the nozzle. The fluid of the tip 46 is atomized. The pair of corners 5 4 each have a pair of apertures 5 6 through which the compressed gas can be directed to create a pigment that is ejected when the pigment from the nozzle tip 46 is combined with the gas from the aperture 52. Spray mode. Each side of the central aperture 5 2 is provided with a plurality of small openings 5 9, and the gas flowing through these openings prevents the pigment from clogging the equal angles 54. The retaining ring 58 is screwed to the end of the body 2 to secure and position the gas cap 40 on the nozzle body 36. The gas system entering the gas distribution chamber region 57 through the hole 51 is turned around the radially extending flange or the edge of the crucible 48 and flows through the plurality of flow passages (not shown) to the equiangular angle The openings 5 in 5 2 are 6 . The gas flowing from the equiangular angle can be used to shape the spray of the atomized pigment flowing out of the central nozzle 8 200821042 pattern. Figure 2 illustrates an embodiment of a gas cap made in accordance with the present invention. The construction of this gas cap is substantially similar to that of the gas cap 40 of Figure 1, but the shape of the central bore is different.

Referring to the central aperture 21 shown in the figures, the central aperture 21 is substantially hexagonal when viewed from the surface of the atomizing gas outlet and has a truncated protrusion 22 at each corner. An enlarged view of a detail of a protruding portion is shown at the upper left of Fig. 2. As shown by the three cross-sectional views of the gas cap, the projections are a plurality of grooves 23 extending substantially in the axial direction, and the grooves 23 are cut to a conventional circular shape similar to the conventional gas cap shown in FIG. Inside the wall of the central hole 2 1. Thus, the resulting projection 22 has a groove wall substantially parallel to the central axis of the hole, however the inner wall of the original hole (before the groove is cut) forms an angle with the central axis. Figure 3 illustrates a perspective view of a circular spray gas cap and a fan-shaped spray gas cap made in accordance with the present invention. It will be appreciated that the use of a fan angle or other shaped corners will not shake the effectiveness of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The embodiments of the present invention are described in more detail with reference to the following drawings, wherein the drawings are as follows: FIGS. 1a and 1b illustrate a conventional fan spray type gas cap design; FIG. 2 illustrates in detail the gas according to the present invention. Various views of the cover embodiment, and Figure 3 illustrates a perspective view of a circular spray and fan spray gas cover, both constructed in accordance with the present invention. 9 200821042

[Key element symbol description] 2 Pigment gun 20 Gas chamber 21, 52 Center hole 22 Projection 23 Groove 26 Pillar field 36 Nozzle body 38 Cylindrical sealing member 40 Gas cap 44 Cylindrical hollow interior 46 Nozzle tip 48 Convex Edge or 堰50 opening 51 facing surface 53 gas distribution chamber 54 angle 56 small hole 57 gas distribution chamber I^r 58 retaining ring 59 small opening π

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Claims (1)

200821042 X. Patent application scope: 1. A gas cover for pigment spray blasting, comprising a hole disposed at the center and extending axially, and in use, atomizing gas passes through the hole, wherein the hole has a rotational symmetry The shape and the shape comprises a plurality of radially extending projections. 2. The gas cap of claim 1, wherein the orifice tapers in a direction toward the atomizing gas outlet of the gas cap. 3. The gas cap of claim 1 or 2, wherein in an axial direction, the projections extend parallel to the longitudinal axis of the bore. 4. The gas cap of any of the preceding claims, having at least 3 projections. 5. The gas cap of claim 4, having no more than 24 protrusions. 6. The gas cap of any of the preceding claims, wherein the orifice is designed to provide between 20% (including 20%) to 80% of the atomizing gas passing through the orifice during use. The atomizing gas (including 80%) passes through the projections. 7. The gas cap of claim 6, wherein the atomizing gas passing through the hole will have between 40% (including 40%) and 60% (including 60%) of the 11 200821042 atomizing gas. Pass through the projections. 8. The gas cap of any of the preceding claims, wherein the geometry of the hole is defined as follows for a given gas cap and nozzle of a paint gun to which the gas cap will be used: D ! = outer diameter of the fluid tip element D2 = inner diameter of the hole D3 = outer diameter of the hole D4 = diameter of the root of the protrusion Θ = half angle of the angle of the inner surface of the protrusion Φ = the angle of the projection of the protrusion is assumed to be large a substantially V-shaped projection: the number of projections Ν = 2; τ / Φ the exit area of each projection Ag = ((D4 - D2) 2 - (D4 - D3) 2) tan0 / 4 ring Shape of the exit area Aa = 7Γ (D22 - D!2) / 4 ratio of area R = N · Ag / Aa total exit area At = N · Ag + Aa where R is between 20% (including 20%) to 80% (including Between 80%), and choose to make At equal to the central aperture area of the conventional gas cap that can be used for the same pigment, and At between 1 and 0 (including 1.0) to 20 (including 20) square mm. 9. The gas cap of any of the preceding claims, wherein the aperture comprises a substantially hexagonal shape and has a head 12 200821042 projection at each corner of the hexagon. 10. The gas cap of claim 9, wherein at the atomizing gas outlet surface of the hole, each of the protrusions has two sides, and the two sides form about 20 with respect to the radius of the hole, respectively. Degree of angle. 11. A gas cap as described in the present invention and illustrated in Figures 2 and 3 of the accompanying drawings.