Airless fan-type spray nozzle and nozzle molding core

Abstract

To provide an airless fan-type spray nozzle that does not cause a tail phenomenon even under low spray liquid pressure, and a core for molding the nozzle. [Solution] A throttle wall is formed at the tip of the supply path before reaching the nozzle of the nozzle body, gradually reducing the cross-sectional area of ​​the liquid flow path toward the nozzle. The throttle wall narrows the flow path by drawing an arch-shaped concave surface toward the nozzle from the left and right, while drawing a curved roof-shaped convex surface toward the nozzle from the top and bottom. The shapes of the arch-shaped concave surface and the curved roof-shaped convex surface are formed so that the liquid pressure reaches 3.0 MPa (30.6 kgf / cm). 2 ) below to avoid tail phenomenon.

Description

[Technical Field]

[0001] The present invention relates to a nozzle for a spray (airless spray) that sprays paint or other liquid in a fan shape using only hydraulic pressure without using compressed air, and to a core for molding a nozzle blank. In particular, the present invention relates to a nozzle suitable for spraying paint or other liquid in a fan shape under low hydraulic pressure without causing a tail phenomenon, and to a core for molding a nozzle blank. [Background technology]

[0002] The key to airless spray painting is to keep the spray pressure low. Achieving low pressure has the following advantages: 1. Improved coating efficiency due to reduced overspray and rebound paint scattering. Improved coating efficiency also reduces the amount of paint and thinner used, resulting in reduced VOC (volatile organic substance) emissions. 2. In electrostatic airless spraying, where electrostatic voltage is applied to an airless sprayer, not only is the coating efficiency further improved, but the atomization performance of the airless sprayer is also improved, as the effect of applied voltage on paint atomization is particularly noticeable in the low-pressure range of the sprayer. 3. It is now possible to design the nozzle outlet to be larger, eliminating the problem of nozzle clogging caused by paint lumps or foreign matter. This is particularly advantageous for managing automatic painting lines. 4. Wear and damage to equipment parts, including nozzles, is reduced, enabling equipment to be used for a longer period of time. It also prevents paint from being discharged, which is advantageous for controlling paint thickness in automatic coating. The nozzle is made of a wear-resistant cemented carbide alloy, an alloy of the rare metals tungsten and cobalt. Tungsten is a strategic material, making it particularly difficult to obtain, so reducing the number of nozzles is important.

[0003] As such, there are significant advantages to lowering the paint spray pressure, but conventional nozzles of this type have a serious drawback in that low pressure causes large particles known as heavy edges or tails to form on both sides of the fan-shaped spray.

[0004] "Tails" are groups of coarse particles that form on the outside of both sides of the flat, fan-shaped spray produced by airless spraying, and the occurrence of tails leads to poor coating quality, such as uneven film thickness, and a poor appearance. The causes of tails include a lack of boundary layer velocity near the inner wall of the nozzle due to the high viscosity of the paint, and the overall flow pattern of the flow inside the tip. Tails can be reduced by increasing the paint pressure and decreasing the paint viscosity. Therefore, a high liquid pressure of 6.9 to 20.6 MPa (70 to 210 kgf / cm) is recommended. 2 Currently, spraying is carried out using a spraying method such as

[0005] There are several airless spray nozzles that have been improved to have a unique shape at the nozzle tip or the inside near the tip, allowing for a spray pattern that does not produce tailing even at relatively low fluid pressure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 41-13033 [Patent Document 2] Special Publication No. 54-34170 [Patent Document 3] Special Publication No. 61-50655 [Patent Document 4] Special Publication No. 53-413 [Patent Document 5] Special Publication No. 47-4799 [Patent Document 6] Special Publication No. 6-7937 [Patent Document 7] Special Publication No. 7-90186

[0007] Patent Document 1 is an invention by Gustav S. Levy and Stanton F. Harvey concerning an airless fluid spray method, which discloses a nozzle equipped with a restrictor (narrow orifice) that accelerates the velocity of the fluid jet introduced into the spray nozzle to a velocity nearly equal to the velocity of the liquid passing through the nozzle itself.

[0008] Patent Document 2 is a spray nozzle invention by Eric T. Nord, Alvin A. Ladd, and Frederick M. Bosworth, which discloses a spray nozzle equipped with a turbulence plate that causes the fluid to collide with the nozzle before it enters, creating turbulence and reducing the scattering of spray particles to the sides.

[0009] Patent Document 3 is an invention of an airless spray nozzle by Alvin A. Rood, which discloses a cross-cut nozzle in which a wedge-shaped groove on the inlet side and a trapezoid-shaped groove on the outlet side interpenetrate to form an orifice opening.

[0010] Patent Document 4 discloses an airless painting nozzle tip invented by Kihachi Chimura, in which both ends of the nozzle hole edge and the arc-shaped cut-out portion of the pilot hole are aligned, eliminating overlap between both ends of the nozzle hole edge and the arc-shaped cut-out portion. This increases the paint spray speed and paint spray energy, sufficiently atomizes the paint, and reduces the causes of tailing.

[0011] Patent Document 5 is an invention by Shiro Ito regarding a nozzle for an airless paint sprayer, and discloses a nozzle for an airless paint sprayer in which the depth of the V-shaped groove is made to match the boundary between the concave surface and the cylindrical surface in order to form a corner at the boundary.

[0012] Patent Document 6 is an invention by the inventor of the present invention regarding an airless coating spray nozzle. The invention discloses a nozzle having a dome-shaped recessed cavity that opens toward the rear of the nozzle, a groove that intersects with this recessed cavity to form a lip-shaped orifice-type spray nozzle, and a through-hole that is located behind this recessed cavity and is connected to a paint supply source. The nozzle has multiple pairs of inclined surfaces on the inner diameter of the nozzle through which the paint fluid passes, and the mutual shapes and angles of the inclined surfaces are precisely defined.

[0013] Patent Document 7 is an invention of a fan-shaped spray nozzle by the inventor of the present invention, and discloses a fan-shaped spray nozzle in which the flow cross-sectional area upstream leading to the dome-shaped concave surface where the lip-shaped orifice nozzle is formed is increased, and the front end portion of the flow path that contacts the rear end of the dome-shaped concave surface is a straight guide portion with no step formed in the direction of the V-shaped groove, and a shoulder-shaped step is formed in the direction perpendicular to the V-shaped groove, and the V-shaped groove is formed so as not to intersect with the step.

[0014] Although these prior arts claim to spray low liquid pressure, the paint liquid pressure is 3.0 MPa (30.6 kgf / cm 2 It was difficult to obtain a fan-shaped spray pattern without tail phenomenon under low liquid pressure spray conditions below 1000 mbar. Summary of the Invention [Problem to be solved by the invention]

[0015] The object of the present invention is to provide a coating material having a pressure of 3.0 MPa (30.6 kgf / cm 2 The present invention aims to provide a nozzle capable of generating a fan-shaped spray that does not cause a tail phenomenon even under low liquid pressures of 1000 kJ / min or less, and to provide a molding core that enables the production of such a nozzle. [Means for solving the problem]

[0016] In describing the configuration of the airless fan atomizing spray nozzle according to the present invention, the directions of the various parts of the nozzle will be defined as follows in this specification. Assuming that the fan-shaped spray is sprayed out vertically in front of the spray, (1) The direction of the eruption is called the forward direction, and the opposite direction is called the backward direction. (2) When viewed from behind, the two sides of the fan-shaped spray are called the left side and the right side, respectively. (3) When viewed from behind, the two edges of the fan-shaped spray are referred to as the upward and downward directions, respectively.

[0017] The configuration of the airless fan spray nozzle of the present invention is no different from a conventional spray nozzle in that it has a supply passage for the liquid to be sprayed provided behind the central axis of the nozzle body, an injection port opened in front of the central axis of the supply passage, a throttle wall formed at the tip of the supply passage just before reaching the injection port that gradually reduces the cross-sectional area of ​​the liquid flow path toward the injection port, and the injection port opening at the bottom surface and a groove extending in the vertical direction are formed on the front end face of the nozzle body.

[0018] In the airless fan spray nozzle of the present invention, the throttle wall is formed so as to draw arch-shaped concave surfaces from the left and right toward the injection port to throttle the flow path, and also draw curved-roof-shaped convex surfaces from the top and bottom toward the injection port to throttle the flow path, and the shapes of the arch-shaped concave surfaces and the curved-roof-shaped convex surfaces are adjusted so as to reduce the liquid pressure of the liquid to 3.0 MPa (30.6 kgf / cm 2 ) below in a range that does not cause tail phenomenon.

[0019] The airless fan-spray nozzle of the present invention may be formed so that the radius of curvature of the curve of the arched concave surface gradually increases toward the injection port.

[0020] In the airless fan spray nozzle of the present invention, the radius of curvature of the curve of the curved roof-shaped convex surface may be formed so as to gradually increase toward the injection port.

[0021] In the airless fan atomizing spray nozzle of the present invention, the curve of the arched concave surface may be a cycloid curve.

[0022] In the airless fan spray nozzle of the present invention, the curve of the curved roof-shaped convex surface may be an elliptical ogive curve.

[0023] In the airless fan spray nozzle of the present invention, the length La on the central axis from the starting end of the arched concave surface that constitutes the throttling wall to the front end of the nozzle body, and the length Lb on the central axis from the starting end of the curved-roof-shaped convex surface to the front end of the nozzle body may satisfy La≦Lb.

[0024] In the airless fan spray nozzle of the present invention, the groove may be formed so that the cross section of a plane intersecting the longitudinal direction of the groove is trapezoidal.

[0025] The core used to mold the airless fan-type spray nozzle of the present invention has a cylindrical mold surface for forming a supply passage that protrudes forward from the base, and the front end of the cylindrical mold surface is provided with an arched convex surface corresponding to the arched concave surface and a curved-roof concave surface corresponding to the curved-roof convex surface.

[0026] The airless fan atomizing spray nozzle of the present invention may be used for painting. [Effects of the Invention]

[0027] The airless fan spray nozzle of the present invention has a constriction wall that forms an arch-shaped concave surface from the left and right toward the nozzle to narrow the flow path, and also forms a curved-roof-shaped convex surface from the top and bottom toward the nozzle to narrow the flow path. By appropriately combining the shapes of the arch-shaped concave surface and the curved-roof-shaped convex surface, it is possible to achieve a pressure of 3.0 MPa (30.6 kgf / cm 2 Even under low liquid pressures of 1.0 MPa (10.2 kgf / cm) or less, a spray that does not cause tail phenomenon can be obtained. Furthermore, by combining the pumps appropriately, 2 This allows for a spray that does not cause a tail phenomenon even under low hydraulic pressures. This will be described in detail in the "Embodiments of the Invention" section.

[0028] The airless fan spray nozzle of the present invention is designed so that the radius of curvature of the arch-shaped concave curve gradually increases as it approaches the nozzle, thereby creating a curve that allows pressure from above and below to act efficiently on the flow of paint or other liquid that is narrowed from above and below by the curved-roof-shaped convex surfaces toward the nozzle, making it possible to suppress the tail phenomenon even at lower liquid pressures.

[0029] In the airless fan spray nozzle of the present invention, the radius of curvature of the curved roof-shaped convex surface is formed so that it gradually increases toward the nozzle. This allows the flow of liquid such as paint to be smoothly narrowed toward the nozzle, and the narrowed liquid to flow in an expanding manner when released from the nozzle, thereby further suppressing the tail phenomenon.

[0030] The airless fan spray nozzle of the present invention has a cycloidal curve (branch of descent) for the concave arch surface, which can further suppress the tail phenomenon even under lower liquid pressure.

[0031] The airless fan spray nozzle of the present invention can further suppress the tail phenomenon by forming the curve of the curved roof-shaped convex surface into an elliptical ogive curve.

[0032] In the airless fan spray nozzle of the present invention, by making the length La on the central axis from the starting point of the arched concave surface that constitutes the throttling wall to the front end of the nozzle body and the length Lb on the central axis from the starting point of the curved-roof convex surface to the front end of the nozzle body such that La≦Lb, it is possible to obtain a combination of the shapes of the arched concave surface and the curved-roof convex surface that further suppresses the tail phenomenon.

[0033] The airless fan spray nozzle of the present invention can prevent nozzle clogging due to lumps of paint, etc., by forming the groove so that the cross-sectional shape of the surface intersecting the longitudinal direction of the groove is trapezoidal. [Brief explanation of the drawings]

[0034] [Figure 1]1A and 1B are (1) and (2) cross-sectional views of a nozzle according to an embodiment of the present invention; [Figure 2] FIG. 2 is a front view of a nozzle according to an embodiment of the present invention. [Figure 3] FIG. 2 is a perspective view of a nozzle according to an embodiment of the present invention. [Figure 4] 1 is an image of a spray pattern obtained using a nozzle according to an embodiment of the present invention. [Figure 5] FIG. 4 is an illustration of an arcuate concave curve in a nozzle according to an embodiment of the present invention. [Figure 6] 1 is an illustration of a convex roof curve in a nozzle according to an embodiment of the present invention. FIG. [Figure 7] FIG. 2 is a perspective view of a molding core for a nozzle according to an embodiment of the present invention. [Figure 8] 1 is an illustration of a preferred combination of an arched concave surface and a curved roof convex surface of the nozzle of the present invention. [Figure 9] Photographs of spray patterns obtained using prior art nozzles, including U.S. Patent Nos. 5,629,092; 5,629,093; 5,629,094; and the nozzle of the present invention. [Figure 10] Photographs of spray patterns obtained using a nozzle of the present invention at varying fluid pressures. DETAILED DESCRIPTION OF THE INVENTION

[0035] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0036] The configuration of the airless fan-spray spray nozzle of the present invention will be described with reference to Figure 1. The configuration of the nozzle of the present invention is no different from that of a conventional spray nozzle in that it has a supply passage 2 for the liquid to be sprayed provided behind the central axis A of the nozzle body 1, an injection port 3 opened in front of the central axis A of the supply passage 2, a throttle wall formed at the tip of the supply passage 2 just before reaching the injection port 3 that gradually reduces the cross-sectional area of ​​the liquid flow path toward the injection port 3, and a groove 8 opening at the bottom of the front end face 7 of the nozzle body 1 and extending in the vertical direction.

[0037] To open the nozzle outlet 3, the throttling wall forms arch-shaped concave surfaces 5 from the left and right toward the outlet 3, narrowing the flow path (Fig. 1(1)), and forms curved-roof convex surfaces 6 from the top and bottom toward the outlet 3, narrowing the flow path relatively early from the front (Fig. 1(2)). The front end surface 7 of the nozzle body 1 is formed with a linear groove 8 that opens the outlet 3 at the bottom and extends vertically, open at the front and both the top and bottom ends. In this way, a recessed portion 4 consisting of the arch-shaped concave surface 5 and the curved-roof convex surface 6 is formed. As will be described later, the shape of the recessed portion 4 is the key to the present invention.

[0038] The present invention has been explained above using a longitudinal and transverse cross-sectional view (FIG. 1) of the nozzle configuration, but understanding of the present invention will be facilitated by also referring to FIGS.

[0039] The shape of the supply channel 2 is not limited to a square as shown in Fig. 2, but may be rectangular, circular, elliptical, etc. The groove 8 does not necessarily need to be open to both ends, as long as it is open enough to sufficiently prevent accumulation of liquid such as paint. Furthermore, the cross-sectional shape of the groove 8 is not limited to a trapezoid as shown in Fig. 1(1), but may be U-shaped, V-shaped, rectangular, etc.

[0040] Figure 5 shows an example of an arched concave surface 5. As shown in the figure, the arch curve can be formed so that the radius of curvature gradually increases toward the front. Furthermore, it can be a cycloid curve (brachystochrone curve) or an involute curve.

[0041] Here, the term "arched concave surface" refers to a surface in which, when the nozzle of the present invention is viewed in cross section including an arch curve, the length of a perpendicular line drawn from a point on the arched surface to the central axis A monotonically decreases toward the nozzle. In that sense, the arched concave surface 5 may have shapes other than those mentioned above, such as a semicircular arch, a parabolic arch, a pointed arch, a pointed Saracen arch, a four-core arch, a lancet arch, a three-core arch, a pseudo three-core arch, or a shouldered arch.

[0042] FIG. 6 shows an example of a curved roof-shaped convex surface 6. As shown in the figure, the curve can be formed so that the radius of curvature gradually increases as it moves forward (FIG. 6(1)). It can also be an elliptical ogive curve. The area near the front end may be nearly horizontal (FIG. 6(2)), or conversely, it may remain at an acute angle (FIG. 6(3)).

[0043] Here, the term "convex arched roof surface" refers to a surface in which, when the nozzle of the present invention is viewed in cross section including a curved arched roof, the length of a perpendicular line drawn from a point on the curved arched roof surface to the central axis A monotonically decreases in the direction of the nozzle outlet.

[0044] The nozzle body 1 is manufactured from cemented carbide such as WC-Co or ceramics, and is generally formed by molding a blank before cutting the grooves 8. The grooves 8 are generally formed by grinding (with a diamond grinding wheel) after sintering the cemented carbide or ceramic. A molding core 9 for this blank is shown in Figure 7.

[0045] The molding core 9 has a cylindrical mold surface 11 that protrudes forward from a base 10 to form the supply channel 2, and the front end of the cylindrical mold surface 11 is provided with an arched convex surface 12 that corresponds to the arched concave surface 5 and a curved roof concave surface 13 that corresponds to the curved roof convex surface 6.

[0046] The effectiveness of the tail suppression is determined by the combination of the arched concave surface 5 and the curved-roof convex surface 6, i.e., the shape of the recess 4. Figure 8 is an explanatory diagram, with (1) and (3) showing cross-sectional views and (2) showing a longitudinal section. La indicates the length along the central axis A from the beginning of the arched concave surface 5 to the front end of the nozzle body, and Lb indicates the length along the central axis A from the beginning of the curved-roof convex surface 6 to the front end of the nozzle body. One side of the supply channel 2 is common to Lc, meaning that the cross section of the supply channel 2 perpendicular to the central axis A is square.

[0047] Without wishing to be bound by any particular theory, it is believed that for the arched concave surface 5, a greater force widening the spray pattern is beneficial in preventing tailing, and the shorter La is, the greater the force widening the spray pattern (Figure 8(1)). On the other hand, for the curved-roof convex surface 6, a smaller force narrowing the spray pattern is beneficial in preventing tailing, and the longer Lb is, the smaller the force narrowing the spray pattern (Figure 8(2)). If we were to manufacture a nozzle body 1 that satisfies La = Lb while maintaining the advantageous shapes of the arched concave surface 5 and curved-roof convex surface 6, Ld > Lc would result, as shown in Figure 8(3). This means that the cross section of the supply passage 2 perpendicular to the central axis A would be rectangular, far from being square. As mentioned above, the cross-sectional shape of the supply passage 2 can be rectangular, but due to the nature of the product, it is desirable to have a shape that is closer to square. Therefore, it is clear that the relationship between La and Lb is necessarily La ≦ Lb. In other words, it is desirable that the length on the central axis A from the starting point of the arch-shaped concave surface 5 that constitutes the throttling wall to the front end of the nozzle body be shorter than the length on the central axis A from the starting point of the curved-roof-shaped convex surface 6 to the front end of the nozzle body.

[0048] The above describes an embodiment of the present invention, but it goes without saying that the present invention is not limited to the configuration of the above embodiment, and can be modified in any way within the scope of the idea of ​​the invention defined in claim 1 to the extent that a person skilled in the art can understand it. [Example]

[0049] In order to confirm the effect of the nozzle of the present invention, a paint spray test was carried out under the following conditions. The nozzles used in the test are as follows: (A) Graco standard nozzle (B) Nozzle described in Patent Document 1 (C) Nozzle described in Patent Document 2 (D) Nozzle described in Patent Document 3 (E) Nozzle described in Patent Document 4 (F) Nozzle described in Patent Document 5 (G) Nozzle described in Patent Document 6 (H) Nozzle described in Patent Document 7 (I) Nozzle of the Present Invention The main spraying conditions are as follows: Paint used: Melamine resin paint Amirac ZERO White (Kansai Paint Co., Ltd. product) Paint viscosity: 0.03Pa·s (20 seconds / Zahn2) Spray distance: 250mm

[0050] Using nozzles (A) to (I), under the main spray conditions, the spray pressure was 1.0 MPa (10.2 kgf / cm 2 ) The spray pattern when the paint is sprayed is shown in Figure 9. In the spray pattern (A), tails occurred above and below the spray pattern. In the spray patterns (B) to (H), tails also occurred, just like in (A). Therefore, nozzles (A) to (H) were insufficient to prevent tails from occurring under low fluid pressure. On the other hand, the spray pattern in (I) did not produce the tail that occurred in (A) to (H). For this reason, the fan-type spray nozzle in (I) was designed to produce a spray pressure of 1.0 MPa (10.2 kgf / cm). 2 ) even under low hydraulic pressure, the occurrence of tailing was prevented.

[0051] Using the nozzle (I), under the main spray conditions, the spray pressure was 1.0 MPa (10.2 kgf / cm 2 ), 0.7MPa (7.1kgf / cm 2 ), 0.4MPa (4.1kgf / cm 2 ) The spray pattern when paint is sprayed is shown in Figure 10. Spray pressure 1.0 MPa (10.2 kgf / cm 2 ) and 0.7 MPa (7.1 kgf / cm 2 Therefore, no tail occurred even under the condition of a spray pressure of 0.7 MPa (7.1 kgf / cm 2 ) the occurrence of tails was prevented even under these conditions. [Industrial Applicability]

[0052] The airless fan atomizing spray nozzle of this embodiment is useful in the field of painting, and can also be used in a wide range of fields other than painting, such as applying liquids to electronic devices, coating chemicals, and in agriculture and horticulture. [Explanation of symbols]

[0053] A center axis 1 Nozzle body 2 Supply route 3 injection port 4. Recess 5 Arched concave surface 6 Convex arched roof 7 Front end surface 8 grooves 9 Molding core 10 base 11 Cylindrical surface 12 Arched Convex Surface 13 Concave roof

Claims

1. a supply passage for the liquid to be sprayed is provided behind the central axis of the nozzle body, and an injection port is opened in front of the central axis of the supply passage; a throttle wall is formed at a tip of the supply path before reaching the injection port, the throttle wall gradually reducing the cross-sectional area of ​​the flow path of the liquid toward the injection port; In the airless fan-type spray nozzle, a groove extending in the vertical direction is formed on the front end surface of the nozzle body, with the injection port opening on the bottom surface, the throttle wall is formed so as to draw an arch-shaped concave surface from the left and right toward the injection port to throttle the flow path, and also draw a curved-roof-shaped convex surface from the top and bottom toward the injection port to throttle the flow path, The shapes of the arch-shaped concave surface and the curved roof-shaped convex surface are determined by the liquid pressure of the liquid being 3.0 MPa (30.6 kgf / cm ２ ) or less in combination within a range that does not cause tail phenomenon.

2. 2. An airless fan atomizing spray nozzle according to claim 1, wherein the radius of curvature of the curve of said arched concave surface is gradually increased toward said nozzle.

3. 3. An airless fan atomizing spray nozzle according to claim 1, wherein the radius of curvature of the curve of said curved roof-shaped convex surface is gradually increased toward said nozzle.

4. 2. An airless fan atomizing spray nozzle as defined in claim 1, wherein the curve of said arcuate concave surface is a cycloidal curve.

5. 5. An airless spray nozzle for fan atomization according to claim 1 or 4, wherein the curve of said curved roof-shaped convex surface is an elliptical ogive curve.

6. 2. The airless fan spray nozzle according to claim 1, wherein a length La on the central axis from the starting end of the arch-shaped concave surface constituting the throttle wall to the front end of the nozzle body and a length Lb on the central axis from the starting end of the curved-roof-shaped convex surface to the front end of the nozzle body satisfy La≦Lb.

7. 2. The airless fan atomizing spray nozzle according to claim 1, wherein said groove is formed so that a cross section of a plane intersecting the longitudinal direction of said groove is trapezoidal.

8. 2. A core for molding an airless fan-type spray nozzle according to claim 1, wherein a cylindrical mold surface for forming a supply passage is provided in a protruding state forward from a base, and the front end of the cylindrical mold surface is provided with an arched convex surface corresponding to the arched concave surface and a curved roof concave surface corresponding to the curved roof convex surface.

9. 2. The airless fan-type spray nozzle according to claim 1, which is used for painting.

Images