JP3355062B2 - Resin powder coating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for coating a welding seam of a can body with a molten film of a resin powder in order to mainly prevent corrosion. The present invention relates to an apparatus for electrostatically applying a liquid.

[0002]

2. Description of the Related Art An inner surface and an outer surface of a can body of a three-piece can used as a container for food or drink are subjected to a surface treatment for corrosion prevention and a surface treatment for decoration. In this type of surface treatment, painting, offset printing, lamination, or the like is performed collectively while leaving the end of the flat can-making material. Then, the can-forming material is roll-formed into a cylindrical shape, and after joining both side edges of the can-forming material by means such as resistance mash seam welding, a film mainly for preventing corrosion is formed on the welded joint. Have been.

[0003] This film is generally composed of a cured film obtained by drying and baking a thermosetting resin solution or a molten film of a resin powder. Japanese Patent Publication No. 5-32210 discloses an example of an apparatus for applying a resin powder to a weld seam portion of a can body in order to form a molten film of the resin powder. This is shown in FIG. 6 and will be described briefly.

In this resin powder coating apparatus, a can body 1 welded by an electric resistance welding means is moved so that a joint portion 1a thereof is on a lower side, and a can body 1 is fed through a powder inlet 2 provided inside the can body. The resin powder 3 is supplied to the inner surface of the welding seam portion 1a. In addition, the resin powder 3 is charged and electrically attached, and the excess resin powder 3 is sucked and removed. In order to limit the adhesion range of the resin powder 3, a pair of inner and outer masking brushes 4 and 5 are provided.
The welding seam portion 1a is disposed at both sides of the welding seam portion 1a with a predetermined space therebetween and in contact with the inner surface of the can body 1. On the other hand, the outer masking brush 5 is arranged outside the inner masking brush 4 side by side.

[0005]

The above-mentioned resin powder is
Eventually, the film is heated and melted to form a film. However, in the above-described conventional apparatus, the can body whose temperature has been increased by welding is directly supplied to the resin powder coating step. The temperature of the welding seam portion of the can body in this coating step is not high enough to immediately melt the resin powder, but since the masking brush is constantly in contact with the can body, the temperature gradually increases. As a result, the resin powder adhering to the masking brush may melt and gradually accumulate. In such a state, the fibers of the masking brush are bundled, so there is a gap, from which the resin powder leaks out of a range limited by the masking brush, and the masking brush loses its original shape. Stop functioning.

Therefore, in the above-mentioned conventional apparatus, a pair of masking brushes is provided inside and outside, and when a gap occurs in the inside masking brush, leakage of the resin powder is prevented by the outside masking brush. If the resin powder leaks to the outer masking brush, the resin application area will be wider than if the area was limited by the inner masking brush. is there.

Even if the resin mask can be prevented from leaking by the outer masking brush, the outer masking brush is in sliding contact with the can body and also contacts the resin powder. Similar to the inner masking brush, resin powder adheres and agglomerates.
It loses its original masking function. In other words, the above-described conventional apparatus merely disposes the masking brushes whose functions are impaired with the passage of time without dissolving the fundamental cause of the welding of the resin powder to the masking brushes. It is difficult to continue the resin application work stably for a long time, and there is much room for improvement in terms of quality stability and ease of maintenance.

The present invention has been made in view of the above circumstances, and has as its object to provide an apparatus capable of stably applying a resin powder to a welded joint.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a can body formed by welding both side edges of a cylindrical can forming material by a welding device. The body is fed to a powder diffusion section in which the resin powder is charged and maintained in a floating turbid state, and the resin powder is electrostatically applied to a weld seam portion on the inner surface thereof. In the apparatus, between the welding device and the powder diffusion unit, a plurality of nozzles for blowing cold air to a weld seam portion on the outer surface side of the can body are arranged along the axial direction of the can body, and At least the opening shape of the nozzle at a position close to the powder diffusion portion of the nozzle is formed in a shape that is long in the axial direction of the can body, and the cross-sectional area of the nozzle gradually decreases toward the opening. Is what you do.

[0010]

The present invention is directed to an apparatus configured to electrostatically apply a resin powder held in a suspended and turbid state to a weld seam portion on an inner surface side of a can body formed into a cylindrical shape by welding. Means for cooling the weld seam are provided between the welding device and the powder diffusion section. The means for cooling is mainly composed of a plurality of nozzles for jetting cool air, and these nozzles are arranged on the outer surface side of the can body along the axial direction thereof. Further, the opening shape of the nozzle on the side of the powder diffusion portion for applying the resin powder at least is a long shape in the axial direction of the can body, such as an oval or an ellipse.

That is, since the opening is long in the axial direction, it is possible to reliably blow the cool air intensively on the hottest welded seam portion of the can body, and furthermore, to reduce the cross-sectional area of the nozzle to the opening. By making it gradually smaller,
Compared to a straight circular nozzle in which the nozzle cross-sectional area does not change up to the tip of the opening, the flow velocity of the cool air is increased, and the can body that passes at high speed under the cool air can be efficiently cooled.

Then, the cool air blown toward the outer surface of the welding seam portion removes heat from the welding seam portion and flows along the outer peripheral surface of the can body. In this case, the ratio of the cool air flowing in the axial direction of the can body decreases based on the arrangement of the nozzles and the shape of the openings.

In other words, as described above, the flow rate of the cool air can be reduced without lowering the cooling capacity, and the width of the opening is narrow in the axial direction. (In a direction perpendicular to the direction), the gas is ejected by changing the flow, and the influence of the cold air on the powder diffusion portion disposed in front of the cooling means is reduced.

Therefore, the floating and turbid state of the resin powder in the powder diffusion section is not disturbed, and the electrostatic application of the resin powder in the powder diffusion section is performed well.

A plurality of nozzles arranged between the welding device and the powder diffusion section along the axial direction of the can body are preferably formed such that most or all of the nozzles therebetween have an oval or elliptical opening shape. This is preferable for reducing the amount of cold air used.

Further, the temperature of the welding seam portion of the can body which has reached the powder diffusion portion is sufficiently lowered by blowing the cold air, so that the applied resin powder is immediately melt-softened or the application range is limited. This prevents the resin powder from adhering and depositing on the masking member due to an increase in the temperature of the masking member. As a result, it is possible to stably apply the resin powder to the welding seam for a long period of time.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in FIGS. The resin powder coating apparatus of this embodiment mainly includes an epoxy resin or a nylon at a welded seam and a vicinity thereof (hereinafter, referred to as a welded seam portion 10a) in a cylindrical can body 10 for corrosion prevention. Resin powder 1 made of resin or polyester resin
1 (hereinafter referred to as powder).

As shown in FIG. 1, the resin powder coating apparatus includes a welding means 12 for performing resistance mash seam welding on both side edges of a can-forming material formed into a cylindrical shape and stacked.
Conveying means 13 for continuously conveying the can body 10 formed by the welding means 12, cooling means 14 for cooling at least the welding seam portion 10a of the can body 10, and can body 10 cooled by the cooling means 14. Coating means 15 for electrostatically applying powder 11 to the welded seam portion 10a on the inner surface side of
Suction means 16 disposed so as to substantially face coating means 15 across welding seam portion 10a of can body 10 to be conveyed.
And a heating means 17 for heating the welded seam portion 10a of the can body 10 so as to form a molten film of the powder 11 applied to the welded seam portion 10a on the inner surface side of the can body 10.

Hereinafter, each means will be specifically described. The welding means 12 includes a pair of electrode rollers 18a and 18b arranged so that the outer peripheral surfaces thereof are opposed to each other, and the both side edges overlapped by roll-forming a plate-shaped can material cut into a predetermined size. The part is connected to the electrode roller 18 disposed oppositely.
a, 18b, and resistance mass seam welding is performed to obtain the can body 10. Then, an injection nozzle of an inert gas (for example, N ₂ gas) not shown
The welding means 12 is provided appropriately toward a welding location by the electrode rollers 18a and 18b, and welding by the welding means 12 is performed in an inert gas atmosphere. Therefore, oxidation of the welding seam portion 10a of the can body 10 is prevented, and the powder 1
1 is formed favorably.

The conveying means 13 conveys the can body 10 obtained by the welding means 12 with the welding seam portion 10a positioned above, and rotates with a driving roller 19a connected to a driving shaft (not shown). Followed roller 1 freely held
9b, two belts 20 made of a suitable rubber material are disposed so as to be in contact with both sides of the can body 10 drawn out from the welding means 12. Then, the can body 10 sent from the welding means 12 is spaced at a predetermined interval,
The driving roller 19a is driven so as to continuously convey at a speed of about 100 m (1.7 m / s) per minute.

The cooling means 14 includes a main body 14a serving as a reservoir disposed between the welding means 12 and the coating means 15.
And an air nozzle 14 provided on the lower surface side of the main body 14a.
b. That is, the main body 14
a is a cylindrical hollow container, the longitudinal direction of which is arranged above the can body 10 conveyed by the belt 20 along the conveying direction, that is, the axial direction of the can body 10. A chiller (not shown) for cooling the introduced air is connected to the main body 14a via a duct 14c.

Each of the air nozzles 14b is formed of a thin pipe having an inner diameter of, for example, about 2 mm (a cross-sectional area of about 3.1 mm ² ). That is, they are arranged at a pitch of, for example, about 10 mm along the axial direction of the can body 10, and the leading end opening thereof is directed to the welded joint portion 10 a on the outer surface side of the can body 10. The open ends of these air nozzles 14b are
As shown in FIG. 5, the major axis is an oval or elliptical shape along the axial direction of the can body 10 (approximately 2.7 mm in major axis direction, approximately 0.7 mm in minor axis direction, and approximately 1.8 mm ² in cross-sectional area). Has been crushed. Therefore, these air nozzles 14b spread the cold air in a film shape in the axial direction of the can body 10 and blow it to the outer surface of the can body 10. The flow rate of the cold air varies depending on the intended cooling temperature. For example, when the welding seam portion 10a is cooled to a temperature (for example, 55 ° C.) lower than the softening start temperature of the powder 11 (about 60 ° C.), the flow rate is 100 °
m / s.

It should be noted that all the air nozzles 14b are
The air nozzle 14b may be arranged obliquely with respect to the welding seam portion 10a so that the cool air flows along the outer peripheral surface of the can body 10.

The coating means 15 is for applying the powder 11 to the welding seam portion 10a of the can body 10 so that a coating film of the powder 11 is formed to a thickness of about 50 μm. As shown in FIGS. 3 and 4, a powder nozzle body 21a disposed on the inner surface side of the can body 10 to be conveyed, and an earth brush which is in contact with the outer surface of the can body 10 passing through the application means 15 and is grounded 22.

The powder nozzle body 21a is a rectangular parallelepiped block-shaped member formed of an insulating material such as a synthetic resin, and is formed in a size that can be inserted into the can body 10. It is arranged along the running direction of the can body 10 so as to be located inside the can body 10 continuously conveyed by the conveying means 13.

A powder nozzle portion 21b is formed on the upper surface of the powder nozzle body 21a along its longitudinal direction. The powder nozzle portion 21b is formed into a rectangular shape.
In the center of the bottom of the device, a static electricity generator (multiplier) 23
Are arranged along the longitudinal direction thereof. The electrode pins 24 can be replaced with electrodes made of a conductive metal plate having a large number of sharp portions formed on one side at regular intervals.

In the upper part of the powder nozzle body 21a, on both left and right sides of the powder nozzle part 21b,
A pair of masking members 25 whose tips are in sliding contact with the inner surface of the can body 10 are attached so that their heights can be adjusted. The masking member 25 is a brush member made of glass fiber having excellent heat resistance and abrasion resistance, or a sheet member made of fluororesin woven with glass fiber, and is provided over substantially the entire length of the powder nozzle body 21a. These masking members 25 are arranged so as to be inclined such that their upper ends are close to each other, and the interval between the tips is slightly wider than the width of the welded seam portion 10a of the can body 10.

In the powder nozzle portion 21b, the can body 1
A powder supply path 26 that supplies the powder 11 to the powder nozzle portion 21b is connected to a portion on the rear side (so-called upstream side) in the transport direction 0. A powder recovery path 27 is connected to a portion of the powder nozzle portion 21b on the front side (so-called downstream side) in the transport direction of the can body 10. The powder supply path 26 and the powder recovery path 27 are formed of small-diameter tubes, and are configured to transport the powder 11 by a carrier gas (for example, air). That is, the powder supply path 26 is connected to a powder storage unit (not shown) that stores the powder 11 in a flowing state by the carrier air, and transfers the powder 11 from the powder reservoir to the powder nozzle unit 21b by the carrier air. To be supplied. The powder recovery path 27 is folded back at the tip end of the powder nozzle main body 21a and is disposed so as to extend on the inner peripheral side of the can body 10 to the rear side in the transport direction. The powder recovery path 27 has a predetermined negative pressure. It is connected to a power source, and is configured to suck and transport the powder 11 together with air from the powder nozzle 21b.

That is, the powder nozzle body 21a
In the upper part of the powder nozzle portion 21b opening on the upper surface, a closed space in the left-right direction with respect to the longitudinal direction is formed by the masking members 25, 25 and the inner surface of the can body 10 slidably contacting the distal end thereof. The powder 11 supplied from the powder supply path 26 to the powder nozzle 21b together with the carrier air is configured to be in a floating turbid state in this closed space. That is, the powder nozzle portion 21b and the masking member 25 form a powder diffusion portion.

The powder 11 in the powder supply path 26
The pressure of the conveying air and the suction force in the powder recovery path 27 are set to a pressure that keeps the floating turbid state of the powder 11 in the powder nozzle part 21b, that is, the powder diffusion part, in a good state.

The powder 11 is charged by the electrode pins 24 in the powder diffusion portion, and the powder 11 adheres and deposits on the inner surface of the can body 10 by an electric attraction force generated between the powder pin and the inner surface of the can body 10. It has become.
Further, it is configured that excess powder 11 that cannot be attached to the inner surface of the can body 10 is recovered from the powder recovery path 27.

Next, the suction means 16 will be described.
The suction means 16 is for collecting the powder 11 leaked to the outside without being attached to the inner surface of the can body 10,
A suction hood 16a having a width of about 20 mm and substantially the same length as the powder nozzle main body 21a is disposed so as to face the powder nozzle main body 21a with the can body 10 to be conveyed therebetween. The suction hood 16a is connected to a predetermined suction source (not shown) such as a suction port of a blower via a duct 16b. The suction pressure of the suction means 16 is applied to the powder 1 in the powder nozzle 21b.
The pressure is set so as not to disturb the suspended turbid state.

Further, the heating means 17 is for melting the powder 11 applied to the welding seam portion 10a of the can body 10 to form a film, and is provided on the downstream side of the applying means 15, that is, the can body 10 Are arranged on the front side in the transport direction. Since the heating means 17 needs to accurately heat the predetermined area to which the powder 11 is applied, that is, the welding seam portion 10a of the can body 10 partitioned by the masking member 25, for example, a high-frequency induction heating device is employed. .

Next, the operation of the above powder coating apparatus will be described. The can-making material cut into a rectangular flat plate is rolled and formed into a cylindrical shape. In this state, both side edges overlapped with each other pass between the electrode rollers 18a and 18b in the welding means 12. Resistance mash seam welded. In this case, since the non-oxidizing atmosphere is maintained by injection of N ₂ gas or the like, the welding seam 1
Oxidation at and near 0a is prevented.

The can body 10a thus formed is
It is sandwiched between the pair of rubber belts 20 in the transporting means 13 and is transported at a high speed in the axial direction thereof. During passing through the cooling means 14, cooling air is blown toward the welding seam portion 10a. That is, the air nozzle 14b
The cold air whose temperature has been lowered by the chiller is constantly jetted at a predetermined flow rate, and when the can body 10 running at a high speed by the conveying means 13 passes below, the welding seam portion is formed. Cold air is blown toward 10a, so that welding seam portion 10a is cooled to a predetermined temperature, specifically, a temperature at which softening or melting of powder 11 does not occur.

In this case, since the air nozzles 14b are arranged along the axial direction of the can body 10 and the open end thereof is an oval or elliptical shape long in the axial direction of the can body 10, the welding seam portion is formed. 10a is efficiently cooled.
In addition, the cold air becomes a film spread in the axial direction of the can body 10,
After being sprayed on the can body 10, it flows to the side of the can body 10 along the outer peripheral surface thereof. Therefore, the flow of the cool air to the coating means 15 disposed in front of the cooling means 14 is suppressed, and the influence of the cool air on the powder diffusion portion in which the powder 11 is kept in the floating and turbid state by the powder nozzle portion 21b is extremely reduced. . As a result, the floating and turbid state of the powder 11 is favorably maintained, so that the powder 11 is preferably applied.

On the other hand, inside the powder nozzle portion 21b of the coating means 15, a powder 11
Is supplied together with the carrier air, and as a result, the powder 11 is dispersed in a floating turbid state inside the powder nozzle portion 21b. The electrode pins 24 are negatively charged by the multiplier 23,
In contrast, since the can body 10 is grounded, charges concentrate on the electrode pins 24. Therefore, the powder 11 in the floating turbid state receives the electric charge from the electrode pin 24 and becomes negatively charged.

The can body 10 having passed the cooling means 14 to cool the welded seam portion 10a to a predetermined temperature passes through the coating means 15 with the welded seam portion 10a on the inner surface thereof facing the powder nozzle portion 21b. I do. In that case, the ground portion is grounded via the ground brush 22, and a predetermined width portion of the inner surface sandwiching the welded seam portion 10 a is defined by the masking member 25. The state is exposed to the floating powder diffusion part. Therefore, the negatively charged and floating powder 11 is attracted toward the inner surface of the can body 10 exposed to the powder nozzle portion 21b by an electric attraction force, and the predetermined powder sandwiching the welded seam portion 10a is provided. Attaches to the width.

In this case, since the welding seam portion 10a is sufficiently cooled by blowing the cool air in the cooling means 14 in the previous step, the applied powder 11 does not melt, and therefore, the localized powder 11 Deposition can be prevented and a uniform coating film of the powder 11 can be formed. In addition, the temperature of the masking member 25 that is constantly in contact with the can body 10 that is continuously running is maintained at a relatively low temperature because the can body 10 is cooled in advance, so that the masking member 25 The powder 11 is prevented from being melted and deposited. Therefore, in the above-described apparatus, the application width of the powder 11 can be maintained constant for a long period of time, and the product quality can be stabilized, and troublesome maintenance such as frequent replacement of the masking member 25 can be eliminated. .

The powder 1 leaked to the outside of the can body 10
1 is sucked and collected by the suction hood 16a of the suction means 16 to prevent extra powder 11 from adhering to the can body 10 and peripheral devices. Further, although not specifically shown,
A resin solution (a paint obtained by dissolving a resin in a solvent) is applied to the welded seam portion 10a on the outer surface side.

The can body 10 having the resin applied to the welded seam portions 10a on the inner and outer surfaces of the can body 10 is conveyed to the heating means 17, where the welded seam portion 10a is heated and applied to that portion. The powder 11 and the resin solution thus melted or dried and hardened to form a film.

In the above embodiment, all the air nozzles 14b have an oval or elliptical opening shape. However, the present invention is not limited to the above embodiment. It is only necessary that the opening shape of the nozzle located on the side of the diffusion portion be long in the axial direction of the can body, and that the cross-sectional area of the nozzle gradually decrease toward the opening portion.

[0043]

As described above, according to the resin powder coating apparatus of the present invention, a nozzle for blowing cold air to a welding seam portion immediately after welding of a can body to cool the same and to spray the cold air therefrom. Are arranged in the axial direction of the can body, and the opening shape of the nozzle on the powder diffusion part side is formed in a long shape such as an elliptical shape or an elliptical shape. As a result, the temperature of the can body can be lowered, and the floating turbid state of the resin powder can be favorably maintained. Therefore, according to the present invention, when the resin powder is applied, the resin powder is melted and local aggregation occurs, or the resin powder is welded to the masking member and the masking function is hindered early. This can be prevented beforehand, and the resin powder can be stably and uniformly applied to the welding seam. Furthermore, since the welding of the resin powder to the masking member can be prevented, the durability of the device can be improved, and troublesome operations such as frequent maintenance can be prevented, and the operation rate of the device can be improved.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a side view showing an overall configuration of the cooling means and a view showing an opening shape of an air nozzle.

FIG. 3 is a cross-sectional view illustrating an overall configuration of a coating unit.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a sectional view showing another example of the masking member.

FIG. 6 is a schematic sectional view showing an example of a conventional resin powder coating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Can body 10a Weld seam part 11 Powder (resin powder) 12 Welding means 14 Cooling means 14b Air nozzle 15 Coating means 25 Masking member

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B05B 5/00-5/16 B05B 12/00-13/06 B05D 7/14

Claims (1)

(57) [Claims] 1. A can body is formed by welding both side edges of a cylindrical can forming material by a welding device, and the can body is maintained in a floating turbid state by charging a resin powder. In a resin powder application device for feeding to a certain powder diffusion portion and electrostatically applying the resin powder to a weld seam portion on the inner surface side thereof, between the welding device and the powder diffusion portion, A plurality of nozzles for blowing cold air to the welding seam portion on the outer surface side of the can body are arranged along the axial direction of the can body, and the opening shape of the nozzle at a position of at least a position near the powder diffusion part among the nozzles Is formed in a shape elongated in the axial direction of the can body, and the cross-sectional area of the nozzle gradually decreases toward the opening.