WO2011151728A2

WO2011151728A2 - Airless spray gun

Info

Publication number: WO2011151728A2
Application number: PCT/IB2011/001577
Authority: WO
Inventors: Isamu Yamasaki; Xiao Jing Zhang; Michio Mitsui; Yoshiharu Yokomizo; Toshio Hosoda; Takao Ueno; Yoshimi Hamada
Original assignee: Toyota Motor Corp; Ransburg Industrial Finishing KK
Current assignee: Carlisle Fluid Technologies Ransburg Japan KK; Toyota Motor Corp
Priority date: 2010-06-04
Filing date: 2011-06-02
Publication date: 2011-12-08
Anticipated expiration: 2012-12-04
Also published as: WO2011151728A3; JP5060594B2; JP2011251278A

Abstract

An airless spray gun includes: an ultrasonic device that has a vibrating element (11) that generates ultrasonic vibrations, and a horn (12), connected to the vibrating element (11), that transmits the ultrasonic vibrations generated by the vibrating element (11); a cap (13), in which a jet orifice (16) is formed, that is fitted to a distal end portion of the horn (12); and a coating material chamber (17) that stores a coating material and that is located between the distal end portion of the horn (12) and the cap (13). Acoustic streaming is produced at the distal end portion of the horn (12) by the ultrasonic vibrations generated by the vibrating element (11). The acoustic streaming discharges the coating material from the coating material chamber (I7) through the jet orifice (16).

Description

AIRLESS SPRAY GUN

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to an airless spray gun that discharges a coating material without using high-pressure air.

2. Description of Related Art

[0002] A conventional airless spray gun is described in, for example, Japanese Patent Application Publication No. 2009-248020 (JP-A-2009-248020).

[0003] The airless spray gun described in Japanese Patent Application

Publication No. 2009-248020 (JP-A-2009-248020) includes a coating material chamber provided with a nozzle for discharging a coating material; a coating material tank that stores the coating material; and a pump that pumps the coating material from the coating material tank into the coating material chamber. The airless spray gun, using the pressure generated by the pump, sends the coating material from the coating material tank into the coating material chamber, and then discharges the coating material from the coating material chamber through the nozzle.

[0004] In order to finely atomize the coating material discharged through the nozzle, it is necessary to decrease the nozzle orifice diameter. However, if the nozzle orifice diameter is descreased (e.g., to about 50 micrometers (μιη)), the pressure loss in the nozzle increases. In particular, if the viscosity of the coating material is high, the pressure loss increases even more. In addition, if a pump of a common pressure region (e.g., of 2 MPa to 3 MPa), pressure insufficiency sometimes occurs so that the coating material may sometimes be fixed to a portion (wall surface) near the opening of the nozzle, the coating material thus fixed may dry and clog the nozzle. Accordingly, it may become difficult to stably discharge the coating material through the nozzle.

[0005] Therefore, a method in which the discharging pressure for the coating material is increased by using a pump that is capable of supplying high pressure (e.g., of several ten MPa) is conceivable. However, if the discharge pressure of the coating material is increased, the component parts of the apparatus, such as pipes, threaded component parts for use for connecting the coating material tank and the coating material chamber, etc., must have sufficient strength to withstand the increased pressure. Hence, the size, weight, and production cost of the apparatus are sharply increased.

SUMMARY OF THE INVENTION

[0006] The invention provides an airless spray gun that stably discharges a coating material from a coating material chamber through a jet orifice while adopting a simple construction and not requiring much cost.

[0007] A first aspect of the invention relates to airless spray gun that includes: an ultrasonic device that has a vibrating element that generates ultrasonic vibrations, and a horn that is connected to the vibrating element and that transmits the ultrasonic vibration generated by the vibrating element; a cap that has a jet orifice, through which a coating material is discharged, and that is fitted to a distal end portion of the horn; and a coating material chamber that stores the coating material and that is formed between the distal end portion of the horn and the cap. Acoustic streaming is produced at the distal end portion of the horn by the ultrasonic vibrations generated by the vibrating element. The acoustic streaming produced at the distal end portion discharges the coating material from the coating material chamber through the jet orifice.

[0008] In the foregoing aspect of the invention, the jet orifice may be formed in a direction in which the acoustic streaming is produced, and the jet orifice may be tapered, and a diameter of an opening of the jet orifice on an inner surface side of the cap may be larger than the diameter of an opening of the jet orifice on an outer surface side of the cap.

[0009] In the foregoing aspect, the direction in which the acoustic streaming is produced coincides with an axial direction of the horn.

[0010] In the foregoing aspect, the airless spray gun may further include: a coating material tank in which the coating material is stored; and a pump that pumps the coating material from the coating material tank into the coating material chamber. The coating material in the coating material tank may be pumped into the coating material chamber by the pump when the coating material is discharged through the jet orifice by the acoustic streaming.

[0011] In the foregoing aspect, the cap may be provided with a passageway through which the coating material is pumped, and the passageway may be connected to the coating material chamber.

[0012] In the foregoing aspect, the passageway may be formed on the outer surface of the cap.

[0013] In the foregoing aspect, a passageway, through which the coating material is pumped, may be formed in the horn, and an end of the passageway may open to a non-resonance region on an outer surface of the horn, and another end of the passageway may open to the distal end portion of the horn.

[0014] In the foregoing aspect, the passageway may provide communication between the pump and the distal end portion of the horn.

[0015] According to the foregoing aspect, it is possible to stably discharge a coating material from the coating material chamber through the jet orifice while adopting a simple construction and not requiring much cost.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Features, advantages, and technical and industrial significance of example embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a general construction diagram of an airless spray gun according to a first embodiment of the invention;

FIG. 2 is an enlarged partial view of the airless spray gun shown in FIG. 1 ; and

FIG. 3 is a general construction diagram of an airless spray gun according to a second embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS 7

4

[0017] An airless spray gun 10 according to an embodiment of the invention will be described below with reference to the accompanying drawings. It should be noted that arrows A in FIG. 1 to FIG. 3 show the directions of an axis of a horn 12 described later.

[0018] The airless spray gun 10 discharges a coating material without using high-pressure air. As shown in FIG. 1, the airless spray gun 10 includes an ultrasonic device (a vibrating element 11 and the horn 12) a cap 13, a coating material tank 14, and a pump (hydraulic pump) 15.

[0019] The ultrasonic device includes the vibrating element 11 and the horn 12. The vibrating element 11 may be a conventional ultrasonic vibrating element, and may include a piezoelectric element (hereinafter "piezo element") that expands and contracts in response to an applied voltage, and a metallic member that clamps the piezoelectric element. When alternating-current voltage is applied, the vibrating element 11 generates ultrasonic vibrations. The vibrating element 11 is connected to a proximal end of the horn 12 by, for example, fastening it with a screw, or the like. The horn 12 transmits the ultrasonic vibrations generated by the vibrating element 11 to the cap 13 while amplifying the amplitude of the ultrasonic vibrations.

[0020] The horn 12 is substantially cylindrical, and the diameter thereof decreases from an intermediate position in the axial direction so that the diameter of a distal end of the horn 12 (i.e., the cap-side end) is smaller than the proximal end portion (i.e., the vibrating-element-side end). An intermediate portion of the horn 12 is provided with a flange porting 12a that protrudes radially outward. The flange portion 12a is provided on the proximal end side of the diameter-decreasing portion of the horn 12.

[0021] The cap 13 is fitted onto a distal end 12b of the horn 12 in the axial direction, and the cap 13 covers the distal end 12b of the horn 12 in the axial direction.

[0022] The cap 13 is a cylinder that is closed at one end, and is supported by the horn 12. The closed end of the cap 13 is formed by a bottom wall portion 13a that is disc-shaped, and a peripheral wall 13b that is formed in a shape of circular tube. The 1 001577

5

bottom wall portion 13a covers an end of the peripheral wall 13b (a lower end thereof in FIG. 1). The bottom wall 13a seals the end of the peripheral wall 13b by fixing an edge portion of an inner surface (an upper surface in FIG. 1) of the bottom wall portion 13a to the end of the peripheral wall 13b by screws or the like. A seal member 13c is interposed between the bottom wall 13a and the peripheral wall 13b.

[0023] A protrusion 13d that protrudes radially outward from the peripheral wall 13b is formed in the opposite or second end portion (the upper end portion in FIG. 1 ) of the peripheral wall 13b . At the second end side of the protrusion 13d of the peripheral wall 13b, a flat lid 13e is disposed facing the protrusion 13d.

[0024] The flange 12a formed on the intermediate portion of the horn 12 is positioned between the protrusion 13d and the lid 13e. The flange 12a is clamped by the protrusion 13d and the lid 13e with a seal member 13f or the like interposed between the protrusion 13d and lid 13e, and thus the cap 13 is supported on the horn 12. Because the cap 13 is supported by the horn 12, the distal end portion 12b of the horn 12 is disposed within the cap 13 (i.e., within a space surrounded by the inner surface of the bottom wall 13a and the inner peripheral surface of the peripheral wall 13b). That is, the distal end portion 12b of the horn 12 is covered by the inner surfaces of the cap 13 (the inner surface of the bottom wall 13a and the inner peripheral surface of the peripheral wall 13b).

[0025] A space (coating material chamber 17) that stores a coating material is formed between the inner surfaces of the cap 13 and outer peripheral surfaces of a portion of the distal end portion 12b of the horn 12 covered by the cap 13. That is, the coating material chamber 17 is formed between a side surface (outer peripheral surface) of the horn 12 and the inner peripheral surface of the peripheral wall 13b, and between a distal end surface of the horn 12 (a lower surface thereof in FIG. 1) and the inner surface of the bottom wall portion 13a. The coating material chamber 17 is tightly closed by the seal members 13c and 13b, and the like. As shown in FIG. 1 , the peripheral wall 13b is provided with a coating material passageway 13g that extends therethrough between the outer peripheral surface and the inner peripheral surface thereof. The coating material passageway 13g communicates with the coating material chamber 17, and the coating material may be supplied into the coating material chamber 17 through the coating material passageway 13g.

[0026] A plurality of jet orifices 16 (two jet orifices 16 are shown in FIG. 1) are formed in the bottom wall portion 13a. The jet orifices 16 extend through the bottom wall portion 13a through which the coating material stored in the coating material chamber 17 is discharged. The surface of the bottom wall portion 13a that is in contact with or exposed to the coating material chamber 17 will be referred to as the inner surface, and the surface of the opposite side of the bottom wall portion 13a will be referred to as the outer surface.

[0027] As shown in FIG. 2, each jet orifice 16 has a tapered portion 16a, and a small-diameter portion 16b.

[0028] The tapered portion 16a of each jet orifice 16 is located on the inner surface side of the bottom wall portion 13 a. The diameter of the tapered portion 16a gradually decreases in a taper fashion toward the outer surface side of the bottom wall portion 13b. The smaller-diameter-side end portion of the tapered portion 16a is provided with a small-diameter portion 16b that continuously formed from the tapered portion 16a. The small-diameter portion 16b of each jet orifice 16 is located in the outer surface side of the bottom wall portion 13 a, and the diameter of the small-diameter portion 16b is the same as the diameter of the smaller-diameter-side end portion of the tapered portion 16a. At each jet orifice 16, the larger-diameter-side end portion of the tapered portion 16a opens to the inner surface of the bottom wall portion 13 a, and the small-diameter portion 16b opens to the outer surface of the bottom wall portion 13 a. That is, the jet orifices 16 are shaped so that the orifice diameter decreases toward the outer surface side of the bottom wall portion 13a (the tapered portion 16a), and in which the diameter of the opening in the inner surface side of the bottom wall portion 13a (the diameter of the larger-diameter-side end portion of the tapered portion 16a) is larger than the diameter of the opening in the outer surface side of the bottom wall portion 13a (the diameter of the small-diameter portion 16b). [0029] In each jet orifice 16, the coating material from the coating material chamber 17 enters the jet orifice 16 through the tapered portion 16a, and moves through the small-diameter portion 16b, and is discharged from the opening in the outer surface side of the bottom wall portion 13a (see dotted-line arrows in FIG. 2).

[0030] When the coating material is discharged from the small-diameter portions 16b, the coating material discharged therefrom forms a liquid thread shape. Then, the liquid threads break, so that the coating takes a spherical shape by surface tension, and is thus made into fine particles. The diameter of the small-diameter portion 16b is set so as to be substantially equal to, or slightly larger than, the desired particle diameter of the coating material. Therefore, the liquid threads discharged from the small-diameter portions 16b have a thickness that is substantially equal to or slightly larger than the desired particle diameter. In this embodiment, the diameter of the small-diameter portions 16b is , for example, about 50 micrometers.

[0031] The horn 12 has such a shape and dimensions so that the distal end portion 12b thereof in the axial direction is disposed at an antinode of the ultrasonic vibration emitted by the horn 12. Therefore, when the ultrasonic vibration generated by the vibrating element 11 is transmitted to the horn 12, the distal end portion 12b of the horn 12 vibrates in the axial direction of the horn 12 at the frequency of the ultrasonic vibration. For example, the distal end portion 12b vibrates with a stroke of about 30 to 40 micrometers at a frequency of about 20 kHz (see a blank arrow in FIG. 2).

[0032] As shown in FIG. 2, the distal end portion 12b of the horn 12 faces the jet orifices 16 of the bottom wall 13a, across the coating material chamber 17. Therefore, when vibrated in the axial direction by the vibrating element 11 , the distal end portion 12b of the horn 12 vibrates in such a direction as to move toward and away from the jet orifices 16.

[0033] The jet orifices 16 are formed in the axial direction of the horn 12 (the vibration direction thereof) at positions that face the distal end portion 12b of the horn 12 (the distal end surface of the horn 12). Therefore, the vibration direction of the distal end portion 12b of the horn 12 coincides with the direction in which the jet orifices 16 extend (the direction of discharge of the coating material through the jet orifices 16).

[0034] The flange 12a formed on the intermediate portion of the horn 12 is disposed at the position of a node of vibration that does not vibrate in the axis direction (disposed in a non-resonance region) as shown in FIG. 1.

[0035] The coating material is stored in the coating material tank 14. The coating material tank 14 communicates with the coating material chamber 17 (the coating material passageway 13g) through a pipe 18. The passageway 13g is formed on the outer surface of the cap 13 (the peripheral wall 13b). One end of the pipe 18 is connected to the coating material tank 14, and another end of the pipe 18 is connected to the coating material passageway 13g, via a nipple 19.

[0036] The pump 15 is provided at an intermediate portion of the pipe 18. When the pump 15 is driven, the coating material in the coating material tank 14 is pumped through the pipe 18 and the coating material passageway 13g, and is therefore supplied into the coating material chamber 17.

[0037] As show in FIG. 2, the airless spray gun 10 discharges the coating material through the jet orifices 16 by vibrating the distal end portion 12b of the horn 12 in the axial direction via the vibrating element 11 , while the coating material chamber 17 is supplied with the coating material. Simultaneously, at the distal end portion 12b of the horn 12, the acoustic streaming is produced outward in the axis direction of the horn 12 (see solid arrows in FIG. 2). Due to the effect of the acoustic streaming, the coating material is discharged through the jet orifices 16. The acoustic streaming serves as a force that thrusts the coating material in the coating material chamber 17 to the outside in the axis direction of the horn 12 when the distal end portion 12b (vibration surface) of the horn 12 is vibrated to the outside in the axis direction (to such a side as to move toward the jet orifices 16 by the ultrasonic vibration generated by the vibrating element 11.

[0038] With the above-described configuration, the airless spray gun 10 stably discharges the coating material from the coating material chamber 17 through the jet orifices 16 by the acoustic streaming produced from the distal end portion 12b of the horn 12. Because the airless spray gun 10 discharges the coating material through the jet ^■ orifices 16 by the acoustic streaming produced from the distal end portion 12b of the horn 12, the components of the apparatus, such as the pipe 18, the nipple 19, etc., do not need to be strengthened to withstand high pressure. Therefore, neither the size nor the structural complexity of the apparatus increases, which minimizes the production cost of the apparatus.

[0039] In addition, the jet orifices 16 are formed in the axial direction of the horn 12 (the direction in which the acoustic stream is produced), at positions that face the distal end portion 12b of the horn 12, and are shaped so that the diameter of the jet orifices decrease toward the outer surface side of the cap 13. Accordingly, the diameter of the openings of the jet orifices 16 in the inner surface side of the cap 13 is larger than the diameter of the openings thereof in the outer surface side of the cap 13 (see FIG. 2). Therefore, the jet orifices 16 efficiently concentrate the acoustic streaming.

[0040] The airless spray gun 10 is able to continuously discharge the coating material by pumping the coating material from the coating material tank 14 into the coating material chamber 17 using the pump 15 as the coating material is discharged through the jet orifices 16 by the acoustic streaming.

[0041] In the airless spray gun 10, the coating material passageway 13g is formed in the cap 13, and is not formed at a location where vibration occurs, for example, the distal end portion 12b of the horn 12. Therefore, damage to the nipple 19 or the pipe 18 due to vibration may be avoided in the apparatus 10, and therefore is able to stably supply the coating material from the coating material tank 14 into the coating material chamber 17.

[0042] Hereinafter, the air spray coating apparatus 20 is a second example embodiment of the invention, and will be described with reference to FIG. 3. In the airless spray gun 20, those members that are substantially the same as those in the airless spray gun 10 are denoted by the same reference characters, and will not be described in detail below.

[0043] As shown in FIG 3, a horn 12 is provided with a coating material passageway 12c. A first end of the coating material passageway 12c opens to a non-resonance region (at the position of a node of ultrasonic vibration) in a side surface (outer peripheral surface) of the horn 12, and the second end thereof has an opening in a surface of a distal end portion 12b of the horn 12 (a distal end surface thereof). The first end of the coating material passageway 12c, that is, the opening thereof formed in the non-resonance region in the side surface of the horn 12, is connected to a second end of a pipe 18 via a nipple 19.

[0044] When a pump 15 is driven, the coating material in a coating material tank 14 is pumped into the coating material passageway 12c through the pipe 18. The coating material pumped into the coating material passageway 12c is discharged through the distal end portion 12b of the horn 12, and is thus supplied into a coating material chamber 17.

[0045] As described above, in the airless spray gun 20, the first end-side opening of the coating material passageway 12c connected to the pipe 18 via the nipple 19 is formed in the non-resonance region of the horn 12, and is not formed at a location where vibration occurs, for example, the distal end portion 12b of the horn 12. Therefore, the air spray coating apparatus 20 avoids the damage to the nipple 19 or the pipe 18 connected to the first end of the coating material passageway 12c the airless spray gun 20 is avoided, so that it is possible to stably supply the coating material from the coating material tank 14 into the coating material chamber 17.

[0046] While the invention has been described with reference to example embodiments thereof, it is to be understood that the invention is not limited to the described embodiments or constructions. To the contrary, the invention is intended to cover various modifications and equivalent arrangements. In addition, while the various elements of the disclosed invention are shown in various example combinations and configurations, other combinations and configurations, including more, less or only a single element, are also within the scope of the appended claims.

Claims

1. An airless spray gun comprising:

an ultrasonic device that has a vibrating element that generates ultrasonic vibrations, and a horn that is connected to the vibrating element and that transmits the ultrasonic vibration generated by the vibrating element;

a cap that has a jet orifice, through which a coating material is discharged, and that is fitted to a distal end portion of the horn; and

a coating material chamber that stores the coating material and that is formed between the distal end portion of the horn and the cap,

the airless spray gun being characterized in that:

acoustic streaming is produced at the distal end portion of the horn by the ultrasonic vibrations generated by the vibrating element; and

the acoustic streaming produced at the distal end portion discharges the coating material from the coating material chamber through the jet orifice.

2. The airless spray gun according to claim 1, wherein:

the jet orifice is formed in a direction in which the acoustic streaming is produced; and

the jet orifice is tapered, and a diameter of an opening of the jet orifice on an inner surface side of the cap is larger than the diameter of an opening of the jet orifice on an outer surface side of the cap.

3. The airless spray gun according to claim 2, wherein the direction in which the acoustic streaming is produced coincides with an axial direction of the horn.

4. The airless spray gun according to any one of claims 1 to 3, further comprising: a coating material tank in which the coating material is stored; and

a pump that pumps the coating material from the coating material tank into the coating material chamber, wherein the coating material in the coating material tank is pumped into the coating material chamber by the pump when the coating material is discharged through the jet orifice by the acoustic streaming.

5. The airless spray gun according to claim 4, wherein

the cap is provided with a passageway through which the coating material is pumped, and

the passageway is connected to the coating material chamber.

6. The airless spray gun according to claim 5, wherein the passageway is formed on the peripheral wall of the cap.

7. The airless spray gun according to claim 4, wherein

a passageway, through which the coating material is pumped, is formed in the horn, and

an end of the passageway opens to a non-resonance region on an outer surface of the horn, and

another end of the passageway opens to the distal end portion of the horn.

8. The airless spray gun according to claim 7, wherein the passageway provides communication between the pump and the distal end portion of the horn.