JPH09155253A - Spit occurrence preventive device in liquid spray gun - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of spit in a liquid spray gun with a simple structure. SOLUTION: An ejector 9 is interposed in a flow passage halfway between a stop valve 6 and a nozzle 3, and a suction chamber 12 thereof is made to communicate with a pressure receiving surface 7a of a pressure sensor 7 to keep the pressure of a space except a flow passage from the stop valve 6 to the nozzle 3 in a spraying state lower than that of the flow passage. And the pressure of the liquid accumulated in the space except the flow passage during the spray stoppage which is the factor behind the spit occurrence is reduced, and a circulating flow by differential pressure is formed in the space except the flow passage from the stop valve 6 to the nozzle 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION When a liquid jet gun such as a spray gun for painting is used, large-sized droplets are generated due to incomplete atomization at the start and end of jetting to contaminate the coating film in spots. The so-called "spit phenomenon" tends to occur, but the present invention relates to a device for preventing such a spit phenomenon, and in particular, a spit in a liquid jet gun of the type in which a pressure sensor is attached upstream of the jet nozzle. The present invention relates to an occurrence prevention device.

[0002]

2. Description of the Related Art When a liquid jet gun such as a spray gun for painting is applied to a painting robot and used for automatic painting, it is detected that the nozzle is clogged during use and the automatic painting line is stopped. At the same time, it is necessary to restore the troubled part, and as a means for detecting nozzle clogging, a pressure sensor is provided in the middle of the flow passage between the on-off valve and the nozzle, and a technique for detecting nozzle clogging by changing the pressure in the flow passage (special feature Fair 2-
39311) has been developed.

[0003]

In the above-mentioned prior art, no measure is taken to prevent the spit phenomenon, and a pressure sensor is provided in the middle of the flow passage between the on-off valve and the nozzle. The volume of the flow passage between the on-off valve and the nozzle inevitably increases, and bubbles tend to remain, which is one of the causes of the spit phenomenon.

Therefore, an object of the present invention is to provide a device for preventing spit generation in a liquid jet gun with a simple structure.

[0005]

[Means for Solving the Problems] The causes of the spit phenomenon are
It is considered that the pressurized liquid stored in the flow path between the on-off valve and the nozzle slowly flows out when the valve is closed, and the liquid in the flow path flows out due to the expansion of the air remaining in the flow path. Based on these findings, the present invention provides an ejector in the middle of the flow path between the on-off valve and the nozzle so that its suction portion communicates with the pressure receiving surface of the pressure sensor, and the flow from the on-off valve to the nozzle in the injection state. The pressure of the space other than the passage is kept lower than that of the passage so as to reduce the cause of spit generation due to the hydraulic pressure stored in the space other than the passage when the injection is stopped, and the on-off valve. A circulation path was formed by the differential pressure so as to generate a liquid flow in a space other than the flow path from the nozzle to the nozzle.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the embodiments of the drawings. As a liquid jet gun to which the spit generation preventing apparatus of the present invention is applied, for example, FIG.
As described above, the mounting member 2 is fixed to the tip of the gun body 1, and the airless fan-shaped jet nozzle 3 is fixed to the tip of the mounting member 2 with the retaining nut 5 while being fitted in the holder 4 and mounted. A valve seat 6a is fixed to the inside of the member 2, and a needle valve 6b that comes in contact with and separates from the valve seat 6a can be moved forward and backward on the gun body 1 by a rear drive mechanism (not shown). Is provided on the mounting member 2 and a pressure sensor 7 is provided on the mounting member 2 close to the opening / closing valve 6 to expose a pressure receiving surface 7a of the pressure receiving chamber 8 in the flow path between the opening / closing valve 6 and the nozzle 3. Adopt a spray gun for painting of the type installed so as to communicate in the middle.

As a special configuration of the present invention for the above liquid jet gun, in the embodiment shown in FIGS. 1 to 3, an ejector 9 is provided in the intermediate flow passage between the on-off valve 6 and the nozzle 3 and the suction side thereof is provided. The ejector 9 communicates with the pressure receiving surface 7a. For example, the ejector 9 has a first member 11 having an orifice 10 as a constituent member of the ejector 9 in front of the valve seat 6a and an orifice as shown in FIG. An annular suction chamber 12 and an orifice 1 which surround the opening of 10
The second member 13 having 0 and the third member 14 having the annular suction chamber 12 surrounding the opening of the orifice 10 in the second member 13 are liquid-tightly fitted in order from the upstream under the common axis. The pressure receiving chamber 8 and the suction chamber 1 of the second member 13
A through hole 15 is provided between the pressure receiving chamber 8 and the suction chamber 12 of the third member 14 so as to communicate therewith.

It is preferable that the pressure receiving chamber 8 and the suction chamber 12 have their volumes as small as possible, and therefore, the tip end portion of the first member 11 and the tip end portion of the second member 13 are placed in the suction chamber 12 respectively. The suction chamber 12 may be made to enter so that a slight cap-shaped gap is formed, and the suction chamber 12 may be formed in a taper shape in which the diameter gradually decreases toward the front.

With the above construction, the pressurized paint is supplied from the rear of the gun body 1, and the paint passes through the on-off valve 6 by opening the on-off valve 6, and then the first member 11, the second member 13, Third
While sequentially passing through the member 14, it is supplied to the nozzle 3 at the tip and is ejected as a fan-shaped jet flow to form a fan-shaped spray.

When the paint passes between the orifices 10 of the first member 11 and the second member 13, the suction chamber 12 has a pressure lower than that of the flow-through paint due to the ejector effect, and the through hole 15 is formed. Also, the pressure inside the pressure receiving chamber 8 decreases, and similarly when the paint passes between the orifices 10 of the second member 13 and the third member 14, the suction chamber 12 becomes more than the pressure of the overflow paint due to the ejector effect. Is also low pressure, through hole 1
6, the pressure inside the pressure receiving chamber 8 also decreases, and therefore the pressure inside the pressure receiving chamber 8 is maintained at a lower pressure than the flow path between the opening / closing valve 6 and the nozzle 3, whereby the opening / closing valve 6 is stopped when the injection is stopped. The cause of spit generation due to the hydraulic pressure stored in the space between the nozzle 3 and the nozzle 3 is reduced.

The meaning of providing the through holes 15 and 16 is as follows.
When a circuit including the pressure receiving chamber 8 is configured and a difference in pressure is generated between the suction chambers 12, it is possible to promote the transfer of the pressure change. Further, when cleaning the inside of the gun, the pressure receiving chamber 8 However, since the inside of the pressure receiving chamber 8 is cleaned by circulating the cleaning liquid, it is important to design both suction chambers 12 so that an appropriate pressure difference is generated. In the illustrated embodiment, the ejectors 9 are provided in two stages in the front-rear relationship, and the opening areas of both orifices 10 are made different.

In order to discharge the air in the pressure receiving chamber 8 and to discharge the residual liquid in the pressure receiving chamber 8 at the time of cleaning the gun, as shown in FIG. It is preferable that the drain valve 18 is provided and a drain valve 18 associated with the drain hole 17 is provided so that the drain valve 18 can be advanced and retracted and opened and closed by an operation on a threaded handle (not shown) as necessary.

In order to make the through holes 15 correspond to each other and the through holes 16 correspond to each other, a cutout groove 19 is formed on the outer periphery of the second member 13 of the ejector 9, and the mounting member 2 is also provided. Is provided with a projection 20 corresponding to the cutout groove 19, and the projection 20 is engaged with the cutout groove 19.

The embodiment of FIG. 4 is a simplification of the structure of the ejector 9 portion in the above embodiment, in which both suction chambers 12 are formed at the rear end and the front end of the second member 13, and Since the members are omitted, the operation is almost the same as in the above embodiment.

In the embodiment of FIG. 5, in addition to forming the first member 11 and the second member 13 constituting the ejector 9 in the same body,
The suction chamber 12 and the pressure receiving chamber 8 are formed adjacent to each other, and the cylindrical second member 1 is provided in front of the first member 11.
3, the liquid passage 21 is provided at the base of the second member 13, and the second member 13 is inserted into the suction chamber 12 of the third member 14 so that a slight cap-shaped gap is formed. Further, the pressure receiving chamber 8 is formed so as to be continuous with the suction chamber 12 of the third member 14, and the pressure sensor 7 is attached to the pressure receiving surface 7.
It is attached so that a is exposed in the pressure receiving chamber 8.

In the embodiment shown in FIG. 5, when the on-off valve 6 is opened, the liquid flow straight from the orifice 10 of the first member 11 flows from the inside of the suction chamber 12 of the third member 14 through the liquid passage 21 in the direction of the arrow. While inducing the circulation flow of the gas, the gas is sprayed from the nozzle 3 by going straight in the axial direction, and the pressure in the pressure receiving chamber 8 and the suction chamber 12 is kept at a low pressure.

[0017]

As described above, according to the present invention,
It has the following effects.

A. Since the ejector 9 is provided in the middle of the flow path between the on-off valve 6 and the nozzle 3 and the suction chamber 12 communicates with the pressure receiving surface 8 of the pressure sensor 7, the flow path from the on-off valve to the nozzle in the injection state is thereby achieved. It is possible to keep the pressure of the space other than the pressure lower than that of the flow path, and reduce the cause of spit generation due to the stored liquid pressure when the injection is stopped.

B. Since the ejector 9 is provided in front and rear in two stages and each suction chamber 12 is communicated with the pressure receiving chamber 8 through the separate through holes 15 and 16, the pressure of the space other than the flow passage from the on-off valve to the nozzle flows in the injection state. It is possible to reliably keep the pressure lower than that of the passage and to promote the flow of the pressure receiving chamber 8 or the like where residual air is likely to occur, thereby preventing the occurrence of spits.

C. Since the pressure receiving chamber 8 is formed so as to be continuous with the suction chamber 12 itself of the ejector 9, and the pressure receiving surface 7a of the pressure sensor 7 is attached so as to be exposed to the pressure receiving chamber 8, this allows air to remain in the pressure receiving chamber 8. Can be reliably prevented, and the structure can be simplified.

D. Since the drain valve 18 is attached to the pressure receiving chamber 8, it is possible to easily and reliably discharge the air in the pressure receiving chamber 8 at the start of use and the residual liquid in the pressure receiving chamber 8 at the time of cleaning the gun.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing a main part of a liquid jet gun to which a spit generation preventing device of the present invention is applied.

2 is a rear view of a second member of the apparatus of FIG.

3 is a cross-sectional view taken along the line III-III in FIG.

FIG. 4 is a vertical cross-sectional side view showing a main part of a liquid jet gun to which a spit generation preventing device of another embodiment is applied.

FIG. 5 is a vertical cross-sectional side view showing a main part of a liquid jet gun to which a spit generation preventing device of still another embodiment is applied.

[Explanation of symbols]

 1 Gun Main Body 2 Paint Nozzle 3 Nozzle 6 Opening / Closing Valve 7 Pressure Sensor 7a Pressure Receiving Surface 8 Pressure Receiving Chamber 9 Ejector 10 Orifice 12 Suction Chamber 15 Through Hole 16 Through Hole 18 Drain Valve

Claims (4)

[Claims] 1. An airless fan-shaped jet nozzle (3) is fixed to the tip of a gun body (1), and the nozzle (3) is also attached.
Is provided with an on-off valve (6) near the upstream side, and a pressure sensor (7) is provided near the on-off valve (6), and a pressure receiving chamber (8) whose pressure receiving surface (7a) is exposed is referred to as the on-off valve (6). Nozzle (3)
In a liquid injection gun of the type provided so as to communicate with the middle of the flow path of the suction chamber, the ejector (9) is provided in the middle of the flow path of the opening / closing valve (6) and the nozzle (3). (1
2. A device for preventing spit generation in a liquid jet gun, characterized in that 2) is communicated with a pressure receiving surface (7a) of a pressure sensor (7). 2. The ejector (9) is provided in front and rear in two stages, and each suction chamber (12) is connected to the pressure receiving chamber (8) by a separate through hole (15), (16). Spit generation prevention device for liquid injection gun. 3. The pressure receiving chamber (8) is formed so as to be continuous with the suction chamber (12) of the ejector (9), and the pressure receiving surface (7a) of the pressure sensor (7) serves as the pressure receiving chamber (8). The device for preventing spit generation in a liquid jet gun according to claim 1, which is mounted so as to be exposed. 4. A device for preventing spit generation in a liquid jet gun according to claim 1, further comprising a drain valve (18) attached to the pressure receiving chamber (8).