JPH06246203A - Method for coating spherical body and air ejecting nozzle used for it - Google Patents

Abstract

PURPOSE:To solve a problem wherein it is difficult to coat the whole surface of a spherical body to be coated at one time and it is also a problem to hold an undried spherical body to be coated as a damage is given to the coating face by holding the spherical body to be coated under floating condition and applying a coating on it. CONSTITUTION:An air ejecting nozzle 2 consisting of an air path 2a and an apex part 2d where a recessed face muffle 2c covering a part of a spherical body 1 to be coated is formed at an air ejecting hole 2b as a center, is used. Coating is performed by holding the spherical body 1 to be coated under floating condition with air ejecting flow ejected from the air ejecting hole 2b while the recessed face muffle 2c faces downward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating small and light spherical objects and an air jet nozzle used for the method.

[0002]

2. Description of the Related Art There are several methods for coating small and light spherical objects, but when the spherical objects are placed on a tray and painted, it is not possible to paint the entire surface of the spherical objects at one time. Painting while replacing spherical objects is an extremely everyday scene. Dip coating
Is a coating method used for small and light spherical objects. In this coating method, the spherical object is immersed in the paint tank and then pulled up,
Remove excess paint and dry. The selection of paint, the control of paint in the tank, the pulling method and pulling speed are important. If the pulling-up method and pulling-up speed are not proper, coating unevenness may occur on the coated surface (the surface of the coating film). In addition, if the paint selection and the paint management in the tank are not proper, the paint film may be defective due to the sedimentation of the pigment or the viscosity of the paint, and as a countermeasure, replace all the paint in the tank in a timely manner. I do.

Rolling coating, in which an object to be coated is placed in a polygonal container and rotated and coated, is also a coating method applicable to small and light spherical objects. In this painting method, in addition to the choice of paint, consideration must be given to the number of revolutions, the number of spherical objects to be placed in the container, and the quantity of paint, and there are many empirical factors. As belonging to the above-mentioned dip coating, after putting the article to be coated in a basket and dipping it,
There is a method of rotating the basket to shake off the paint and drying it, but in this case as well, the number of rotations and the number of spherical objects to be put in the basket are important.

[0004]

What is difficult when a spherical object is entirely coated is that it is difficult to prevent the coated surface from coming into contact with other objects. In the coating method described above, when determining the number of spherical objects to be put in a container or basket, it may be considered that the coating surface does not come into contact with other objects excessively. On the other hand, as in other technical fields, even in coating technology, "safer" is a constant goal, and "resource conservation" and "environmental conservation" have become more important. From the above viewpoint, there is still room for improvement in the above-mentioned coating methods such as dip coating and rolling coating, which use small and light spherical objects as the object to be coated.
"Replacement of all paint in tank at appropriate time" in dip coating
Is a typical example.

In view of the above circumstances, the present invention levitates a small and light spherical object in the air in a coating chamber, the spherical object is coated in a levitated state, and the coated spherical object is levitated. It is designed to be moved to a predetermined place. In addition, the solvent and paint floating in the coating chamber due to overspray, etc. are captured by using the jet air used to realize the levitation, and resources are collected and the environment is protected.

[0006]

The coating method of the present invention is characterized in that a spherical object is held in a floating state by an air jet and the spherical object is coated in this floating state. Further, the air jet nozzle used in the coating method of the present invention for holding the spherical object in a floating state is an air passage, an air jet nozzle, and a concave muffle that covers a part of the spherical object centered on the air jet nozzle. Is formed, and an air jet is formed from the air outlet.

[0007]

1 is an explanatory view of the operation of the present invention. Reference numeral 1 denotes a spherical object to be coated (hereinafter referred to as a spherical object to be coated), 2 denotes an air passage 2a, and a concave muffle 2c for covering a part of the spherical object 1 around the air ejection port 2b. The air ejecting nozzle 3 including the nozzle tip 2d is a tray having a bottom made of a net having a predetermined mesh and through which air can pass. Now, the air jet nozzle 2 is brought close to the spherical article 1 placed on the tray 3 so that the concave muffle 2c of the nozzle tip 2d covers a part of the spherical article 1. The distance L between the spherical object 1 and the concave muffle 2c (see FIG. 2).
If the size, weight, air ejection speed, etc. of the spherical object 1 are in predetermined conditions, the air is ejected from the air ejection port 2b, the spherical object 1 floats up from the tray 3,
The spherical object 1 can also be floated away from the nozzle tip 2d.

A phenomenon similar to that described above can be viewed at a soap bubble game or a soap bubble show. However, it is not easy at the level of soap bubble play. In the case of soap bubble shows, the performers use trade secret soap bubble liquids, as well as magic tricks. Then, a thin tube corresponding to the above-mentioned air ejection nozzle 2 and having a curved disk (corresponding to the concave muffle 2c) at one port is used.
A bubble of soap liquid is applied to the mouth of a thin tube with a disk, and a single bubble (soap bubble) of an appropriate size generated by blowing from the other mouth is vibrated to separate it from the thin tube and float. To In a simple performance, the fan is used to move the soap bubbles, but the performance level is increased, and the soap bubbles are stopped at a position just below the narrow tube, and the performance is shown to move with the thin tube. Although the spherical article 1 in the present invention is a solid, the soap bubbles are liquid, and there is a big difference in the density, the levitating of the spherical article 1 and the staying of the soap bubbles cannot be considered the same. , I can understand the phenomenon visually. In addition to the soap bubble game, there are also toys that float a light plastic hollow body with an upward air flow.

The levitating phenomenon of the spherical article 1 in the present invention can be roughly explained as follows. FIG. 3 shows a flow structure when the spherical object 1 is placed in the laminar air flow, and a vortex train is generated behind the spherical object 1. The curve a in FIG. 4 shows the pressure distribution at each position on the surface of the spherical article 1 in this case.

FIG. 5 analytically shows the force acting on the spherical article 1. In the spherical object 1, when the pressure P acts on an annular band formed by dividing the inclination φ and the inclination (φ + Δφ) with respect to the air flow direction, the x
The directional component force is PΔS _x obtained by multiplying the projected area ΔS _x in the x direction of the annular band by the pressure P. If PΔS _x is integrated with respect to φ = 0 ° to 90 ° and φ = 90 ° to 180 °, and the definite integrals thereof are F _x1 and F _x2 , respectively, the air to the spherical object 1 in FIG. The total of all the forces acting from the upstream side of the laminar flow is F _x1 , and the total of all the forces acting from the downstream side of the laminar flow is F _x2 . Then, from the curve a in FIG. 4, F _x1 >
It is F _x2 , and it can be seen that the spherical article 1 is pushed in the downstream direction. Regarding F _Y1 and F _Y2 obtained in the same manner, F _Y2 = F _Y1 and it is not necessary to consider it.

On the other hand, FIG. 6 shows a flow structure when the spherical object 1 is placed in the air jet from the air jet nozzle 2 shown in FIG. 1 and in the vicinity of the air jet nozzle 2. . In this case, the concave baffle 2c of the air ejection nozzle 2
The force received by the spherical object 1 changes depending on the distance L between the spherical object 1 and the spherical object 1. FIG. 7 is a diagram showing the relationship between the distance L and the force received by the spherical article 1. In the range of the interval L = L _{1 to} L ₂ , the adsorption force is positive, the force acts on the spherical article 1 from the downstream direction, and in the range of the interval L <L ₁ and the interval L = L _{2 to} L ₃ , The adsorption force is negative, which means that the spherical object 1 is subjected to a force from the upstream direction.

When the spherical object 1 approaches the concave baffle 2c and the interval L becomes small (L <L ₁ ), the passage of the air jet narrows and the pressure increases, so that the spherical object 1 has the concave baffle 2c. Receives a force that keeps it away from, that is, a negative adsorption force. However, spherical object to be coated 1 is some distance from the concave baffle 2c and _{(L = L 1 ~L 2)} , than the effect of the pressure near the concave baffle 2c, the flow rate of a little away from the air ejection port 2b is increased As a result, the influence of the pressure drop becomes larger, and a force to bring the spherical object 1 closer to the concave baffle 2c, that is, a positive suction force is generated.

The pressure distribution at each position on the surface of the spherical article 1 in FIG. 6 is shown by the curve b in FIG. The difference between the curve b and the curve b is related to the distance L between the concave baffle 2c and the spherical object 1 and the central angle of the concave baffle 2c. For example, the larger the distance L exceeds the value corresponding to L ₃ , the closer the curve b is to the curve a and the better the degree of overlap. Now, let us say that the interval L is a value corresponding to the middle of L ₁ and L ₂ , and the angle φ at the intersection of the curve b and the atmospheric pressure axis line at that time is φ _b . The above PΔS _x is φ = 0 ° to φ
_{If b} ° and φ = φ _b ° to 180 ° are integrated, and their definite integrals are F _x1b and F _x2b , respectively, (F _x2b −F
_x1b )> 0 is maximum and curve b is significantly different from curve a. On the other hand, the central angle of the concave surface baffle 2c is related to the intersection point between the atmospheric pressure axis and the curve b and the gradient φ corresponding to the minimum value of the curve b.

As described above, when the spherical object 1 is placed near the air jet nozzle 2 which forms the air jet, the spherical object 1 is placed in correspondence with the distance L between the concave baffle 2c and the spherical object 1. The coating material 1 receives a force in a direction away from the air ejection nozzle 2 or a suction force. Therefore, if the spherical coating object 1 is located in a range where the suction force from the air ejection nozzle 2 exceeds the weight of the spherical coating object 1, even if the nozzle tip 2d is oriented in the direction of gravity, Below, the spherical article 1 can be held in a floating state.

Next, unlike the case shown in FIG. 6, when the central axis of the air ejection nozzle 2 and the central axis of the spherical object 1 are not aligned, that is, at right angles to the central axis of the air ejection nozzle 2. The case where the central axis of the spherical article 1 is displaced in the direction is referred to. What corresponds to the curve b of FIG. 4 showing the pressure distribution is FIG. 8 (φ = 0 ° to 180 °) and FIG. 9 in this case.
(Φ = 0 ° to −180 °). If the central axis of the air jet nozzle 2 and the central axis of the spherical object 1 are on a straight line, the pressure distribution at each position on the surface of the spherical object 1 is φ = 0 °.
It is symmetrical with respect to the central axis of the spherical article 1 about 180 ° and φ = 0 ° to −180 °. If the central axis of the spherical object 1 is displaced in the downward direction at right angles to the central axis of the fluid ejection nozzle 2, then the results are shown in FIG. 8 (φ = 0 ° to + 180 °) and FIG. 9 (φ = 0).
(° to −180 °), the pressure distributions have different shapes and are asymmetric with respect to the central axis of the spherical article 1.

From FIGS. 8 and 9, when the spherical article 1 approaches the concave muffle 2c of the tip 2d of the air jet nozzle 2, the position on the surface of the spherical article 1 where the pressure becomes maximum is − Move to φ side. At the same time, at the location where the spherical object 1 approaches the concave muffle 2c, the flow rate becomes extremely narrow due to the narrowing of the flow path, so that the flow rate becomes slower than the other parts and the pressure drop becomes small. For these reasons,
The spherical object to be coated 1 receives a force to be returned in the central axis direction of the air ejection nozzle 2.

As described in detail above, the air ejection nozzle 2
When the tip portion 2d of the concave portion faces the gravity direction and the distance L between the concave muffle 2c and the spherical object 1 is in a specific range, if the air is continuously ejected from the air ejection port 2b at a proper flow velocity, the concave muffle 2c Underneath, the spherical article 1 is held in a levitated state. Further, when the air jet nozzle 2 is lifted up in this state, the spherical object 1 is also moved up together. In this way, while holding the spherical object to be coated 1 under the concave muffle 2c in a floating state, the air jet nozzle 2 is moved to a coating booth (not shown), and the coating material is in a floating state by a spray coating method or the like. Spray on the spherical object 1.

In addition to uneven surface roughness and sphericity of the spherical object 1, the turbulence of the air flow and the distortion of the air jet nozzle 2 affect the spherical object 1 to rotate at irregular high speed. Therefore, the paint is sprayed all over the surface of the spherical object 1 in a short time. As paint, natural (normal temperature) dry type, heat dry type,
It can be selected and used from any of the ultraviolet drying types. It is then dried in a manner suitable for the paint used. The coating method of the present invention has a remarkable feature that it is self-contained in the drying process. That is, since fresh air is constantly supplied to the coating surface formed on the surface of the spherical article 1 by the air jet, drying is promoted. The spherical object 1 to which the paint has been sprayed is moved to a drying chamber, a drying oven or an ultraviolet irradiation (fluorescent lamp irradiation or high pressure mercury lamp irradiation) device while being held in a floating state by an air jet nozzle 2, and the spherical object is coated. The paint sprayed on the surface of the article 1 is dried in a short time, and good adhesion of the paint is obtained. The spherical object to be coated 1 on which the paint sprayed on the surface is dried is returned to the tray 3 which has a bottom made of a net having a predetermined mesh and through which air can pass.

The spherical object to be coated according to the present invention is limited in size and weight due to the principle of the present coating method, and the material of the spherical object is mainly plastic or metal. Prior to the painting, it is necessary to pretreat the spherical coated object.
Similar to other coating methods, appropriate pretreatment is performed according to the material of the spherical coating object. A reciprocating or rotating air compressor is used as an air source, and an air tank, an air purifier and a pressure regulator are attached. Compared with the compressed air for spray coating, the compressed air that has been cleaned more severely is supplied to the air ejection nozzle 2.

[0020]

First Embodiment FIG. 10 is a diagram showing the construction of a first embodiment according to the coating method of the present invention. In the figure, 1 is a spherical object to be coated, 2 is an air jet nozzle, and 3a and 3b are trays whose bottoms are composed of a net.
The spherical article 1 is placed on the tray 3a. Reference numeral 4 denotes a conveyor circulation route for moving the air ejection nozzle 2 in the horizontal direction. Although illustration of the conveyor and the conveyor drive device is omitted, it is used for a known one, such as a typical mass production coating or an automatic electrostatic coating system that is an automated coating, for suspending and moving an object to be coated. It has the same structure as the conveyor device. The conveyor is erected from the floor to an appropriate height and, if necessary, with a change in height. In addition, an electric power line for supplying a servo mechanism for vertically moving an air jet nozzle described below is provided near the conveyor. The traveling speed, traveling stop, traveling start, etc. of the conveyor are controlled by a controller (not shown).

The air ejection nozzle 2 is held by a vertical movement arm which is a part of a control device including a servo mechanism for vertically moving the air ejection nozzle. The control device other than the vertical movement arm is housed in a case, and the case is hung on a conveyor. Then, for example, the air ejection nozzle 2 is moved along the circulation route 4 of the conveyor, and air is ejected onto the spherical object 1 placed on the tray 3a in order to hold the spherical object 1 in a floating state. When the nozzle 2 is brought closer, the control device including the servo mechanism for vertically moving the air ejection nozzle lowers the air ejection nozzle 2 via the vertically moving arm. In the circulation route 4, the position where the air ejection nozzle 2 should move up and down is generally determined. Therefore, if the conveyor is erected by changing the height from the floor to correspond to that position, the air ejection nozzle 2 can be moved up and down. The servo mechanism and its related components are unnecessary, and in this case, the air ejection nozzle 2 is structured to be directly hung on the conveyor.

Next, 5 is a coating booth, 6 is an air cleaner (not shown), an air compressor equipped with a pressure regulator, and 7 is connected to the air compressor 6 by an air piping pipe 6a. A certain air tank, 7 a, is an air take-out portion provided on the upper portion of the air tank 7. The air take-out portion 7a is rotatable with respect to the air tank 7, and the amount of air leakage is suppressed by using a high-pressure rotary mechanical seal and a motion O-ring. Air ejection nozzle 2 and air extraction portion 7a
Has a hose coupling part for coupling the air hose 8 with a designated joint. When a plurality of air ejection nozzles 2 are used as shown in the figure, the air extraction part 7a has a plurality of hose coupling parts. The air hose 8 has a structure in which the air ejection nozzle 2 can move along the circulation route 4.
In consideration of the pressure drop up to the air ejection port 2b (see FIG. 1), the selection is made. Air supply to the air jet nozzle 2 is
A control device (not shown) controls pressure, flow rate, opening and closing, and the like.

Reference numeral 9 is a paint supply device, 10 is a coating machine, 11 is a paint recovery device including appropriate devices such as an exhaust fan, a cyclone, and a filter, 12 is a purified air passage, and 13 is a recovered / separated paint or solvent. It is a collection passage. Coating machine 1
0 is a control device (not shown) that controls the pressure, the amount of jetting, the operating time, etc., for example, when the spherical object 1 comes in front of the coating machine 10, it operates for a predetermined time. There is. Valves are provided in the purified air passage 12 and the recovered material passage 13 as needed. As a result, for example, these valves can be operated to return the recovered paint to the paint supply device 9. In the wall surface that constitutes the coating booth 5, a portion having a corresponding shape is provided in a portion where the air ejection nozzle 2 and the air hose 8 move in and out and penetrate.
A goodwill mist curtain made of oil-resistant rubber having appropriate softness is suspended in this opening to prevent the paint mist in the coating booth 5 from diffusing from the opening to the outside. .

In the present embodiment configured as described above, the spherical object 1 is sent to the tray 3a by an object supplying device (not shown) and placed on the tray 3a at a predetermined position. . When the air jet nozzle 2 that horizontally moves along the circulation route 4 by the conveyor reaches the upper surface of the spherical article 1 at the predetermined position of the tray 3a, the horizontal movement is stopped by the traveling stop of the conveyor, and the downward movement is performed. Meanwhile, air ejection is gradually started. When the condition of the jetted air and the above-described interval L (see FIG. 2) fall within a predetermined range, the air jet from the air jet nozzle 2 keeps the spherical object 1 in a levitated state, and at the same time the air is blown. The ejection nozzle 2 moves upward by a predetermined distance together with the spherical object 1 to be coated.
Then, the conveyor resumes traveling at a predetermined speed, the air jet nozzle 2 moves horizontally along with the spherical object 1 to be coated, and enters the coating booth 5.

In the coating booth 5, when the spherical object 1 to be coated, which is held in a floating state below the air jet nozzle 2, reaches the front of the coating machine 10, the coating machine 10 operates for a predetermined time and moves horizontally. Meanwhile, the spherical object 1 is painted. At this time, since the spherical coated object 1 in the levitating state rotates irregularly at a high speed, the paint is sprayed all over the surface of the spherical coated object 1 in a short time, suppressing the degree of overspray. it can. The coated spherical object 1 held in a floating state below the air ejection nozzle 2 leaves the coating booth 5 and then
It is dried at room temperature while moving horizontally along the circulation route 4. If necessary, a drying device may be provided on the circulation route 4 after passing through the coating booth 5. Air jet nozzle 2
When the coated spherical object 1 which is held in a levitating state below and has the coating film dried reaches the top of the tray 3b, the traveling of the conveyor is stopped, while the air ejection nozzle 2 is moved downward by a predetermined distance. Just move. While moving downward, the air jet nozzle 2 gradually reduces the air jet and places the dried and coated spherical object 1 on the tray 3b to complete the painting process. In consideration of the fact that the paint mist floating in the coating booth 5 is forcibly settled downward by the downward air jet of the air ejection nozzle 2, the position of the connection port to the exhaust fan 11 in the coating booth 5 and the exhaust fan 11 are considered. Select a capacity.

In the first embodiment, the air jet nozzle 2 is shown in FIG.
Although the coating machine 10 having the structure shown in 1 has been described as a mechanical spray coating machine, other embodiments will be described below. Second Embodiment FIG. 11 shows the structure of the air ejection nozzle used in the second embodiment. This air jet nozzle 2'is a spherical object 1 with an air passage 2'a and an air jet 2'b as the center.
In addition to a nozzle tip 2'd having a concave muffle 2'c covering a part thereof, a paint passage 2'e and a paint outlet 2'f opening in the concave muffle 2'c are provided. In the first embodiment, when the air jet nozzle 2'is used instead of the air jet nozzle 2, the paint supply device 9 and the coating machine 10 are unnecessary, and instead, for example, the paint take-out portion having the same structure as the air take-out portion 7a is taken out. A paint tank having a portion will be arranged above the air tank 7. The paint outlet and the air jet nozzle 2'are connected by a paint hose.
In the case of the present embodiment, for example, paint is dripped from the paint outlet 2'f to the spherical object 1 which is kept in a floating state and is rotating at high speed irregularly, and coating is performed by flow coating. It is also possible to apply electrostatic coating without using spray paint.

Third Embodiment The defective product selection function of the air ejection nozzle 2 is utilized. That is, when the spherical object 1 has a sphericity of a certain degree or more,
Alternatively, if the structure is not uniform and the center of gravity deviates from the center of gravity by a certain degree or more, the levitated state cannot be maintained. Therefore, such a spherical object 1 can be selected as a defective product,
If FIG. 10 showing the configuration of the first embodiment is considered as one coating system, this coating system has not only the transfer of coated objects, coating and removal of contaminants, but also a defective product selection function.

[0028]

As described above, the coating method of the present invention and the air jet nozzle used for the same allow a small and light spherical object to be held in a floating state by an air jet, and the spherical object to be coated in the floating state. Since the spherical coating object is not in contact during the coating process, the entire surface can be coated at once. Further, there is a possibility that the self-contained characteristic of the drying process can be utilized. Moreover, since the spherical object to be floated rotates irregularly at high speed, it is possible to perform coating without uneven coating. In addition, the solvent and paint floating in the coating chamber due to overspray, etc. are designed not to be discharged to the outside of the coating chamber by using the airflow that keeps the floating state, and thus the composition of the coating system suitable for small and light spherical coating objects. Is possible. Further, as an additional effect, it is possible to select a spherical object having an abnormal sphericity or density distribution.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an operation of the present invention.

FIG. 2 is an explanatory diagram of an operation of the present invention.

FIG. 3 is a diagram showing a flow structure when a spherical coating object is present in a laminar air flow.

FIG. 4 is a pressure distribution diagram of the surface of a spherical object to be coated during laminar air flow and air jet flow.

FIG. 5 is an analysis diagram of a force acting on a spherical article to be coated in a laminar air flow.

FIG. 6 is a diagram showing a flow structure in the case where a spherical coating object is present near an air ejection nozzle.

FIG. 7 is a diagram of the distance between a concave muffle and a spherical object to be coated versus the force received by the spherical object to be coated.

FIG. 8 is a pressure distribution diagram when the fluid ejection nozzle and the spherical object to be coated are misaligned.

FIG. 9 is a pressure distribution diagram when the fluid ejection nozzle and the spherical object to be coated are misaligned.

FIG. 10 is a diagram showing the configuration of a first embodiment of the coating method of the present invention.

FIG. 11 is a diagram showing a configuration of an air ejection nozzle according to a second embodiment of the coating method of the present invention.

[Explanation of symbols]

 1 spherical object 2 air jet nozzle 2a air jet nozzle air passage 2b air jet nozzle air jet 2c air jet nozzle concave muffle 2d air jet nozzle tip 3 tray

Claims (2)

[Claims] 1. A method of coating a spherical object, which comprises holding the spherical object in a floating state by an air jet and coating the spherical object in the floating state. 2. An air passage, an air jet, and a tip having a concave muffle that covers a part of a spherical object centered on the air jet, and is formed by an air jet from the air jet. An air jet nozzle for holding the spherical object in a floating state.