Rotary Bell Cup Coating Machine

Abstract

To realize micronization and uniformization of coating particle sizes in a rotary bell cup coater.SOLUTION: A rotary bell cup coater 1 includes: a feed tube 22 for ejecting a coating material; a bell cup 3; and a bell hub 5 which receives the coating material ejected from the feed tube 22. The bell cup 3 has a first inner peripheral surface 33a extending along a central axis C direction and surrounding the bell hub 5, and a second inner peripheral surface 33b which is provided on a tip side relative to the first inner peripheral surface 33a, and whose diameter expands toward the tip side. The bell hub 5 has an end surface 53 discharging the coating material ejected from the feed tube 22 toward the bell cup 3, when rotating about the central axis C together with the bell cup 3, and an extension line Le extended outward from this end surface 53 intersects with a base end side portion 33R at the time the first inner peripheral surface 33a along the central axis C direction is divided into the base end side portion 33R and a tip side portion 33T.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The technology disclosed herein relates to a rotary bell cup painting machine.

Background Art

[0002] In Patent Document 1, as an example of a rotary bell cup painting machine, there is disclosed a rotary atomizing head type painting apparatus including a rotary shaft into which a feed tube is inserted, a bell cup (rotary atomizing head) attached to the tip of the rotary shaft, and a bell hub (hub member) attached to the center of the base end of the bell cup. The bell hub according to this document is formed in a disc shape with a conical protrusion provided at its central portion, and is oriented with the protrusion facing the feed tube side.

[0003] The bell hub disclosed in Patent Document 1 has, on its outer peripheral portion, a plurality of leg portions and a plurality of notch grooves. Each notch groove is formed alternately with each leg portion, and when it is fitted into a concave groove (hub fitting concave groove) provided in the bell cup, a plurality of hole-shaped paint passages are formed between the concave groove and the bell hub. The paint discharged onto the inner bottom surface of the bell hub is guided to the inner peripheral surface of the bell cup through these hole-shaped paint passages, and the paint particles atomized on the inner peripheral surface of the bell cup are configured to be discharged.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When using a bell hub as disclosed in Patent Document 1, in the process of the paint discharged from the feed tube flowing on the inner surface of the bell hub, the collision of the paint with the inner surface, the eccentricity of the collided paint with respect to the rotation axis, the inhibition of the flow by obstacles such as the legs disclosed in Patent Document 1, and the collision when transferring from the bell hub to the bell cup, etc., may cause the liquid film of the paint to ripple. The rippling of the paint is not desirable for miniaturizing and equalizing the paint particle size.

[0006] The technology disclosed herein is made in view of such points, and its object is to realize miniaturization and equalization of the paint particle size in a rotary bell cup painting machine.

Means for Solving the Problems

[0007] The technology disclosed herein relates to a rotary bell cup painting machine that discharges centrifugally atomized paint particles. This rotary bell cup painting machine includes a paint supply pipe that discharges paint from its tip, a bell cup provided so as to surround the tip of the paint supply pipe and rotates around the central axis of the paint supply pipe, A rotating shaft into which the paint supply pipe is inserted and which rotates integrally with the bell cup, opposite to the tip of the paint supply pipe and receiving the paint discharged from the tip and a bottomed cylindrical shape formed at the tip of the paint supply pipe with an opening facing the tip a paint receiving member, A support member disposed on the tip side of the paint supply pipe, inserted into the inner peripheral side of the bell cup, and positioned with respect to the bell cup; and a connecting member that connects the paint receiving member and the support member so that the bell cup and the paint receiving member rotate integrally via the support member. The bell cup A contact portion that protrudes inward in the radial direction orthogonal to the central axis and positions the support member by contacting the support member, extends along the central axis direction from the contact portion to the boundary between a portion that overlaps and a portion that does not overlap the inner peripheral surface of the paint receiving member when viewed along a direction orthogonal to the central axis and has a first inner peripheral surface that surrounds the paint receiving member, and a second inner peripheral surface provided on the tip side compared to the first inner peripheral surface and having a diameter that expands toward the tip side. The paint receiving member has an end surface that discharges the paint discharged from the paint supply pipe toward the bell cup when the paint receiving member rotates around the central axis together with the bell cup. extending continuously from the first inner peripheral surface so as to And the extension line extending outward from the end surface

[0008] is intersecting the first inner peripheral surface, the connecting member connecting the inner peripheral surface of the paint receiving member and the outer peripheral surface of the support member .

[0009] Here, the term "extends along the central axis direction" also includes a configuration that extends slightly inclined with respect to the central axis direction.

[0010] As a result of intensive studies, the inventors of the present application have found that when a conventional bell hub is used, the liquid film flow on the inner surface of the bell hub becomes non-uniform due to the eccentricity of the paint that has collided with the inner surface of the paint receiving member with respect to the rotation axis, which causes the liquid film on the inner surface of the bell cup to ripple, and that the rippling of the liquid film is caused by the connection structure of the bell hub by legs or the like.

[0011] On the other hand, according to the above configuration, the paint that has flown from the end face of the paint receiving member will flow sequentially along the first inner peripheral surface and the second inner peripheral surface. According to the findings obtained by the inventors of the present application, by flowing the paint along the first inner peripheral surface extending in the central axis direction, the influence of eccentricity as described above can be reduced and the liquid film of the paint can be made uniform in thickness. Thereby, the rippling of the liquid film of the paint can be suppressed.

[0012] Furthermore, according to the above configuration, the paint that has flown from the end face of the paint receiving member will reach the base end side portion on the first inner peripheral surface. By doing so, the paint that has reached the first inner peripheral surface will flow not only through the tip side portion but also through the base end side portion. Thereby, the flow distance when flowing through the first inner peripheral surface can be made longer, and the rippling of the paint liquid film can be more reliably suppressed.

[0013] Thus, according to the above configuration, it becomes possible to suppress the rippling of the paint liquid film, and as a result, to realize the refinement and uniformization of the paint particle diameter.

[0014] Also, if the inclination angle formed by the first inner peripheral surface with respect to the central axis direction is θc, 0°≦θc≦20° it may be satisfied.

[0015] According to this configuration, by configuring the first inner peripheral surface so that the above relationship is satisfied, the rippling of the paint liquid film can be more reliably suppressed.

[0016] Also the The paint receiving member has an inner bottom surface facing the paint supply pipe and an inner peripheral surface extending from the inner bottom surface toward the end surface. having, the inner peripheral surface of the paint receiving member Extending from the inner bottom surface toward the end surface 、 The paint receiving member rotates around the central axis together with the bell cup, so that the paint discharged from the paint supply pipe toward the inner bottom surface the paint receiving member's May be configured to reach the inner peripheral surface of the bell cup through the inner peripheral surface and the end surface.

[0017] According to this configuration, the paint discharged onto the paint receiving member flows along its inner bottom surface and inner peripheral surface before reaching the bell cup. According to the findings obtained by the inventors of the present application, in addition to receiving the paint on the inner bottom surface of the member formed in a concave cross-section, by flowing the paint along its inner peripheral surface, the influence of eccentricity as described above can be reduced, and the paint liquid film can be made uniform in thickness. Thereby, the undulation of the paint liquid film can be suppressed.

[0018] In addition, by suppressing the undulation of the paint in advance before the paint transfers from the paint receiving member to the bell cup, even considering the influence of the collision when the paint transfers from the paint receiving member to the bell cup, the thickness of the paint liquid film can be kept as uniform as possible. This is advantageous in realizing the refinement and homogenization of the paint particle size.

[0019] Also the The connecting member may be provided on a part of the inner peripheral surface in the circumferential direction around the central axis. the paint receiving member's May be provided on a part of the inner peripheral surface 。

[0020] this According to the configuration, the paint flowing along the inner bottom surface becomes a diffused flow due to the centrifugal force caused by the rotation of the paint receiving member. On the other hand, the paint flowing along the inner peripheral surface becomes a so-called parallel flow because it flows substantially parallel to the central axis. According to the findings obtained by the inventors of the present application, the parallel flow is less affected by obstacles compared to the diffused flow. Therefore, by providing the connector on the inner peripheral surface instead of the inner bottom surface, the influence of the connector as an obstacle on the flow can be suppressed, and thus it is advantageous for realizing the refinement and uniformization of the paint particle size.

[0021] Further, it may be that the outer peripheral portion on the end face side of the paint receiving member is formed to taper toward the radially outer side.

[0022] Here, the "radial direction" refers to the direction perpendicular to and radially extending from the central axis.

[0023] According to this configuration, when the paint attempts to transfer from the paint receiving member to the bell cup, the paint flies from the outer peripheral portion on the end face side of the paint receiving member to the bell cup. By tapering the outer peripheral portion, the paint flies from the tip of the tapered portion. As a result, the paint flies from a specific portion on the outer peripheral portion. This keeps the flow distance of the paint substantially constant, and thus is advantageous for realizing the refinement and uniformization of the paint particle size. Further, by forming the outer peripheral portion on the end face side to be tapered, it is possible to suppress the paint from flowing around the paint receiving member due to surface tension. This also effectively acts for realizing the refinement and uniformization of the paint particle size.

[0024] Also, the paint receiving member's It may be that the inner peripheral surface extends away from the central axis as it goes from the inner bottom surface side toward the end face.

[0025] According to this configuration, the paint on the inner peripheral surface can be made to flow from the inner bottom surface side to the end surface side by the centrifugal force caused by the rotation of the paint receiving member. By doing so, for example, it is possible to prevent the paint from remaining in the vicinity of the corner where the inner bottom surface and the inner peripheral surface intersect, and thus improve the usability of the rotary bell cup coater. This is particularly effective when painting while exchanging multiple types of paint. 。

Advantages of the Invention

[0026] As described above, according to the rotary bell cup coater, it is possible to achieve refinement and uniformization of the paint particle size.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Modes for Carrying Out the Invention

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description is illustrative.

[0029] (Configuration of Rotating Bell Cup Coating Machine) FIG. 1 is a longitudinal sectional view illustrating the tip of the rotating bell cup coating machine 1, and FIG. 2 is a longitudinal sectional view illustrating the configuration of the bell cup 3. Further, FIG. 3 is a cross-sectional view illustrating the tip of the rotating bell cup coating machine 1. Further, FIG. 4 is a perspective view illustrating the configuration of the bell hub 5. Note that FIG. 1 is a cross-section along the central axis C of the rotating bell cup coating machine 1, and FIG. 3 corresponds to the A-A cross-section in FIG. 1.

[0030] In the following description, the "base end side" refers to the side of the feed tube 22 (opposite side of the object to be coated) in the direction of the central axis C, and the "tip end side" refers to the opposite side of the feed tube 22 (object to be coated side) in the same direction. Also, in the following description, the "radial direction" refers to the direction orthogonal to the central axis C and extending radially from the central axis C, and the "circumferential direction" refers to the direction orthogonal to the radial direction and circulating around the central axis C.

[0031] The rotating bell cup coating machine 1 shown in FIG. 1 etc. is a rotary atomizing type coating device for electrostatic coating, and is configured to discharge centrifugally atomized paint particles. That is, the rotating bell cup coating machine 1 sprays and atomizes the paint from the bell cup 3 attached to the high-speed rotating rotating shaft 21 by centrifugal force, and performs coating using the gravitational force acting between the paint particles with a negative charge and the object to be coated such as an automobile body charged positively.

[0032] Specifically, the rotary bell cup coater 1 includes a cylindrical housing 10, a tubular member 2 inserted into the housing 10 and discharging paint from its tip, a bell cup 3 provided so as to surround the tip 22a of a feed tube 22 in the tubular member 2 and rotating around the central axis C of the feed tube 22, a bell hub 5 facing the tip 22a of the feed tube 22 and receiving the paint discharged from the tip 22a, and a support 4 for attaching the bell hub 5 to the bell cup 3.

[0033] Among these, the housing 10 is formed in a cylindrical shape. The housing 10 houses the tubular member 2 and a high-voltage power source (not shown) for charging the paint. Further, the base end portion of the bell cup 3 is inserted into an opening 10a provided at the tip portion of the housing 10. Although not shown in the figure, air for deflecting paint particles can be discharged from the tip portion of the housing 10.

[0034] Also, the tubular member 2 has a rotating shaft 21 that rotates integrally with the bell cup 3 and a feed tube 22 inserted into the rotating shaft 21 and discharging paint from its tip. The feed tube 22 is an example of the "paint supply tube" in the present embodiment.

[0035] Among these, the rotating shaft 21 is configured as a hollow shaft member and is inserted into a cylindrical portion 31 on the base end side of the bell cup 3. The rotating shaft 21 is configured to receive power from the outside and rotate around the central axis C, and rotates integrally with the bell cup 3 via the cylindrical portion 31.

[0036] The feed tube 22 is configured as a tube-shaped member for circulating paint and is inserted into the rotating shaft 21. The tip 22a of the feed tube 22 is configured as an open end capable of discharging paint and is exposed from the rotating shaft 21. The feed tube 22 according to the present embodiment circulates paint from one side in the direction of the central axis C (the side opposite to the object to be painted) to the other side (the side of the object to be painted S) and discharges the paint from the tip 22a. The paint discharged from this tip 22a will collide with the inner bottom surface 51 of the bell hub 5.

[0037] As shown in FIG. 2, the bell cup 3 has a substantially cup shape. The bell cup 3 has a cylindrical portion 31 on the base end side and a tapered portion 32 on the tip end side.

[0038] Among these, the cylindrical portion 31 is formed in a short cylindrical shape extending along the central axis C direction. The rotating shaft 21 is inserted from the base end side, and at the same time, the support tool 4 is inserted from the tip end side. On the inner peripheral surface of the cylindrical portion 31, a contact portion 31a protruding inward in the radial direction is provided. This contact portion 31a is configured to position the support tool 4 by coming into contact with the support tool 4 inserted into the cylindrical portion 31.

[0039] Among the inner peripheral surface of the cylindrical portion 31, the first inner peripheral surface 33a on the tip end side of the contact portion 31a is configured so that the paint scattered from the bell hub 5 by centrifugal force can flow. This first inner peripheral surface 33a, together with the second inner peripheral surface 33b described later, constitutes a paint diffusion surface 33 for diffusing the paint.

[0040] Specifically, the first inner peripheral surface 33a of the bell cup 3 is configured to extend along the central axis C direction and at least surround the bell hub 5. Specifically, the first inner peripheral surface 33a is slightly inclined with respect to the central axis C direction and gradually increases in diameter toward the tip side. The first inner peripheral surface 33a surrounds the tip of the tubular member 2 (specifically, the tip 22a of the feed tube 22), the support 4, and the bell hub 5 (specifically, the inner peripheral surface 52 and the end surface 53 described later). That is, when viewed along the direction orthogonal to the central axis C (radial direction), the first inner peripheral surface 33a overlaps with the inner peripheral surfaces 52 and the end surface 53 of the feed tube 22, the support 4, and the bell hub 5.

[0041] More specifically, if the inclination angle formed by the first inner peripheral surface 33a with respect to the central axis C direction is θc, preferably, the relationship of 0° ≤ θc ≤ 20° is satisfied, and more preferably, the relationship of 0° ≤ θc ≤ 5° is satisfied.

[0042] The tapered portion 32 expands in diameter in a tapered shape toward the tip side. The inner peripheral surface of the tapered portion 32 forms a second inner peripheral surface 33b through which the paint that has passed through the first inner peripheral surface 33a flows. This second inner peripheral surface 33b, together with the first inner peripheral surface 33a, constitutes the paint diffusion surface 33.

[0043] Specifically, the second inner peripheral surface 33b of the bell cup 3 is provided on the tip side compared to the first inner peripheral surface 33a and expands in diameter toward the tip side. When viewed along the radial direction, this second inner peripheral surface 33b does not overlap with the inner peripheral surfaces 52 and the end surface 53 of the feed tube 22, the support 4, and the bell hub 5.

[0044] Also, the support 4 is arranged on the tip 22a side of the feed tube 22 and is inserted into the inner peripheral side of the bell cup 3. Specifically, the support 4 according to the present embodiment is formed in a cylindrical shape extending in the central axis C direction, and is inserted into the cylindrical portion 31 of the bell cup 3 with the tip 22a of the feed tube 22 inserted therethrough. That is, the inner diameter of the support 4 is larger than the tip 22a of the feed tube 22, and the outer diameter of the support 4 is smaller than the cylindrical portion 31.

[0045] Furthermore, on the outer surface of the support 4, a flange-like protruding collar portion 4a is provided. When the support 4 is inserted into and pushed into the cylindrical portion 31, the collar portion 4a of the support 4 abuts against the portion 31a to be abutted in the cylindrical portion 31. Thereby, the support 4 is positioned with respect to the bell cup 3, particularly the cylindrical portion 31.

[0046] The bell hub 5 is provided on the inner peripheral side of the bell cup 3 and is arranged with the recess facing the feed tube 22. The bell hub 5 has a concave cross-section. Specifically, the bell hub 5 has an inner bottom surface 51 facing the feed tube 22, an end surface 53 facing the feed tube 22 side, and an inner peripheral surface 52 extending from the inner bottom surface 51 toward the end surface 53. The bell hub 5 is an example of the "paint receiving member" in the present embodiment.

[0047] Specifically, the bell hub 5 according to the present embodiment is formed in a bottomed cylindrical shape with an opening and the inner bottom surface 51 facing the tip 22a of the feed tube 22, and has a circular inner bottom surface 51, a substantially cylindrical inner peripheral surface 52, and an end surface 53 corresponding to the opening edge of the bell hub 5. The bell hub 5 is connected to the support 4 via a connecting tool 6 to be described later, and rotates integrally with the bell cup 3 via this support 4.

[0048] Among these, the inner bottom surface 51 is formed as a circular plane, is perpendicular to the central axis C, and is arranged such that the central portion of the inner bottom surface 51 (the portion corresponding to the center when the inner bottom surface 51 is regarded as a circle) faces the tip 22a of the feed tube 22. By arranging it in this way, the paint discharged from the feed tube 22 collides with the central portion of the inner bottom surface 51.

[0049] Subsequently, the inner peripheral surface 52 is formed as a substantially cylindrical curved surface and extends substantially perpendicularly from the peripheral edge of the inner bottom surface 51 toward the proximal end side. Here, the inclination angle θh formed by the inner peripheral surface 52 with respect to the inner bottom surface 51 is slightly obtuse, i.e., slightly less than 90 degrees. That is, the inner peripheral surface 52 according to the present embodiment extends away from the central axis C (i.e., toward the outer side in the radial direction) as it goes from the inner bottom surface 51 side toward the end surface 53. Further, as shown enlarged in FIG. 1, a rounded portion is provided at the corner where the inner bottom surface 51 and the inner peripheral surface 52 intersect, and the inner bottom surface 51 and the inner peripheral surface 52 are smoothly connected.

[0050] Here, a feed tube 22 and a connector 6 for connecting the bell hub 5 as a paint receiving member are provided on the inner peripheral surface 52. As shown in FIG. 3, the connector 6 is provided at a part of the inner peripheral surface 52 in the circumferential direction. Specifically, the connector 6 according to the present embodiment is composed of a bolt-shaped fastening member and is provided at equal intervals (in the example shown in FIG. 3, at three locations at 120-degree intervals) at a plurality of locations along the circumferential direction around the central axis C. Each connector 6 extends in a direction substantially orthogonal to the inner peripheral surface 52.

[0051] When the inner peripheral surface 52 is in a state of being connected to the support 4 by the connector 6, as illustrated in FIG. 1, it faces the outer peripheral surface of the support 4 (particularly, the outer peripheral surface on the tip side of the flange portion 4a) with a gap therebetween. By doing so, paint can be made to flow through the gap between the inner peripheral surface 52 of the bell hub 5 and the outer peripheral surface of the support 4.

[0052] Further, when the bell hub 5 as a paint receiving member rotates around the central axis C together with the bell cup 3, the end surface 53 discharges the paint discharged from the feed tube 22 toward the bell cup 3.

[0053] Here, the end face 53 according to the present embodiment is configured such that, instead of the second inner peripheral surface 33b of the bell cup 3, the paint is discharged toward the first inner peripheral surface 33a thereof, and an extension line Le extending outward (radially outward) from the end face 53 intersects with the first inner peripheral surface 33a. Specifically, as shown in FIG. 2, the extension line Le extending outward from the end face 53 of the bell hub 5 intersects with the proximal end side portion 33R when the first inner peripheral surface 33a is divided into a proximal end side portion 33R and a distal end side portion 33T along the central axis C direction.

[0054] Specifically, the end face 53 of the bell hub 5 is formed as a substantially annular plane. This end face 53 extends along a plane perpendicular to the central axis C from the proximal end side end portion of the inner peripheral surface 52 of the bell hub 5. When the end face 53 is connected to the support 4 by the connector 6, as illustrated in FIG. 1, it faces the flange portion 4a of the support 4 with a space therebetween. By doing so, paint can be circulated between the end face 53 of the bell hub 5 and the flange portion 4a of the support 4.

[0055] The bell hub 5 according to the present embodiment is arranged on the inner peripheral side of the bell cup 3 in the radial direction and is inserted into the cylindrical portion 31 on the proximal end side of the tapered portion 32 in the central axis C direction. That is, the inner peripheral surface 52 and the end face 53 of the bell hub 5 overlap with the first inner peripheral surface 33a when viewed along a direction orthogonal to the central axis C direction.

[0056] In addition, the outer peripheral portion 54 on the end face 53 side of the bell hub 5 is formed to taper toward the outer side in the radial direction. Specifically, the outer peripheral portion 54 on the end face 53 side in the present embodiment refers to the outer peripheral portion of the bell hub 5 on the proximal end side and around the opening. As shown in FIG. 4, this outer peripheral portion 54 tapers over the entire circumference in the circumferential direction. The tip of the outer peripheral portion 54 forms an acute angle of less than 90°.

[0057] (Operation of the Rotary Bell Cup Painting Machine) FIG. 5 is a diagram illustrating the flow of paint in the rotary bell cup coater 1. FIG. 6 is an explanatory diagram showing a comparison of the influence of the connector 6 on the flow.

[0058] The bell hub 5 as a paint receiving member, together with the bell cup 3, rotates around the central axis C, so that the paint discharged from the feed tube 22 toward the inner bottom surface 51 of the bell hub 5 reaches the inner peripheral surface (paint diffusion surface 33) of the bell cup 3 via the inner peripheral surface 52 and the end surface 53 of the bell hub 5.

[0059] Hereinafter, the above-described configuration will be specifically described. First, when the rotating shaft 21 rotates around the central axis C, the bell cup 3 rotates integrally with the rotating shaft 21. Along with the rotation of the bell cup 3, the support 4, and thus the bell hub 5, also rotate integrally.

[0060] When paint is discharged toward the rotating bell hub 5, the discharged paint reaches the central portion of the inner bottom surface 51 of the bell hub 5 as shown by the arrow A1 in FIG. 5. The paint that has reached the central portion of the inner bottom surface 51 forms a diffusion flow according to the centrifugal force caused by the rotation of the bell hub 5 and flows radially outward along the inner bottom surface 51 as shown by the arrow A2.

[0061] The paint flowing along the inner bottom surface 51 passes through the inner bottom surface 51 and reaches the inner peripheral surface 52. The paint that has reached the inner peripheral surface 52 forms a parallel flow flowing along the substantially central axis C direction and flows toward the proximal end side along the inner peripheral surface 52 as shown by the arrow A3.

[0062] The paint flowing along the inner peripheral surface 52 reaches the end surface 53 through the inner peripheral surface 52 while its flow is obstructed by the connector 6. The paint that has reached the end surface 53 forms a diffusion flow again and flows radially outward along the end surface 53 as shown by the arrow A4.

[0063] The paint flowing along the end face 53 scatters from the tapered outer peripheral portion 54 and reaches the first inner peripheral surface 33a of the paint diffusion surface 33, particularly the base end side portion 33R of the first inner peripheral surface 33a. The paint that has reached the base end side portion 33R flows toward the tip side in the direction of the central axis C as shown by the arrows A5 and A6, passing in order through the first inner peripheral surface 33a (specifically, the base end side portion 33R and the tip side portion 33T of the first inner peripheral surface 33a) and the second inner peripheral surface 33b. At the tip of the second inner peripheral surface 33b of the paint diffusion surface 33, the paint becomes filamentous, and the filamentous paint is atomized and discharged.

[0064] (Regarding the refinement and uniformization of the paint particle size) As a result of intensive studies, the inventors of the present application have found that due to the eccentricity of the paint colliding with the inner surface of the bell hub 5 as a paint receiving member with respect to the rotation axis 21, the liquid film flow on the inner surface of the bell hub 5 becomes non-uniform, which causes the liquid film to ripple on the inner surface, and that the connection structure of the bell hub 5 by legs or the like causes the liquid film to ripple.

[0065] On the other hand, according to the present embodiment, the paint flying from the end face 53 of the bell hub 5 flows through the first inner peripheral surface 33a and the second inner peripheral surface 33b in order as shown by the arrow A5 in FIG. 5. According to the findings obtained by the inventors of the present application, by flowing the paint along the first inner peripheral surface 33a extending in the direction of the central axis C, the influence of eccentricity with respect to the rotation axis 21 can be reduced, and the liquid film of the paint can be made uniform in thickness. Thereby, the rippling of the liquid film of the paint can be suppressed.

[0066] Furthermore, according to the present embodiment, the paint flying from the end face 53 of the bell hub 5 reaches the base end side portion 33R of the first inner peripheral surface 33a. By doing so, the paint that has reached the first inner peripheral surface 33a flows not only through the tip side portion 33T but also through the base end side portion 33R. Thereby, the flow distance when flowing through the first inner peripheral surface 33a can be made longer, and the rippling of the paint liquid film can be more reliably suppressed.

[0067] Thus, according to the above configuration, it is possible to suppress the undulation of the paint liquid film, and as a result, it is possible to achieve the refinement and uniformity of the paint particle size.

[0068] Also, as illustrated in FIG. 2, when the inclination angle of the first inner peripheral surface 33a with respect to the central axis C direction is θc, by configuring the first inner peripheral surface 33a so as to satisfy the relationship of 0° ≤ θc ≤ 20°, it becomes possible to more reliably suppress the undulation of the paint liquid film.

[0069] Also, as illustrated in FIG. 5, the paint discharged onto the inner bottom surface 51 of the bell hub 5 flows along its inner peripheral surface 52 once before reaching the bell cup 3 through its end surface 53 (see arrow A3 in FIG. 5). According to the findings obtained by the inventors of the present application, by flowing the paint along the inner peripheral surface of a member formed in a concave cross-section, the influence of eccentricity with respect to the rotation axis 21 can be reduced, and the liquid film of the paint can be made uniform in thickness. Thereby, it is possible to suppress the undulation of the paint liquid film caused by the inhibition of the flow due to the eccentricity of the collided paint with respect to the central axis C.

[0070] Also, by suppressing the undulation of the paint in advance before it transfers from the bell hub 5 to the bell cup 3, even considering the influence of the collision when transferring from the bell hub 5 to the bell cup 3, the thickness of the paint liquid film can be kept as uniform as possible. By doing so, it becomes possible to achieve the refinement and uniformity of the paint particle size.

[0071] Also, as described with reference to FIG. 5, the paint flowing along the inner bottom surface 51 of the bell hub 5 becomes a diffusive flow due to the centrifugal force caused by the rotation of the bell hub 5. On the other hand, the paint flowing along the inner peripheral surface 52 of the bell hub 5 flows substantially parallel to the central axis C, so that it becomes a so-called parallel flow. According to the findings obtained by the inventors of the present application, the parallel flow is less affected by obstacles compared to the diffusive flow. That is, as shown in FIG. 6, in the case of the diffusive flow, since the flow of the paint colliding with the connector 6 as an obstacle diffuses around the connector 6, it becomes relatively difficult to merge. On the other hand, in the case of the parallel flow, since the flow of the paint colliding with the connector 6 is substantially parallel around the connector 6, it becomes relatively easier to merge compared to the case of the diffusive flow.

[0072] Therefore, as illustrated in FIGS. 1 and 3, by providing the connector 6 on the inner peripheral surface 52 of the bell hub 5 instead of the inner bottom surface 51, the influence of the connector 6 as an obstacle on the flow is suppressed, and thus it is advantageous in realizing the refinement and uniformization of the paint particle size.

[0073] Also, as described with reference to FIG. 5, the paint transferred from the end surface 53 of the bell hub 5 to the bell cup 3 flows not only on the second inner peripheral surface 33b on the tip side but also on the first inner peripheral surface 33a on the base end side of the inner peripheral surface of the bell cup 3. This first inner peripheral surface 33a exhibits the same function as the inner peripheral surface 52 of the bell hub 5. As a result, it becomes even more advantageous in realizing the refinement and uniformization of the paint particle size.

[0074] Also, as described with reference to FIG. 5, when the paint attempts to transfer from the bell hub 5 to the bell cup 3, as it flies from the outer peripheral portion 54 on the end surface 53 side of the bell hub 5 to the bell cup 3, as shown in FIG. 4, by tapering the outer peripheral portion 54, the paint flies from the tip of the tapered portion.

[0075] If the outer peripheral portion 54 has a rounded shape, the paint adhering to the outer peripheral portion 54 due to surface tension will fly from various rounded locations. In this case, since the flow distance of the paint becomes non-uniform, it is disadvantageous for realizing the refinement and uniformization of the paint particle size.

[0076] On the other hand, according to the present embodiment, as shown in FIG. 5, the paint will fly from a specific site (the tip of the tapered portion) in the outer peripheral portion 54. By this, the flow distance of the paint can be kept substantially constant, and thus it is advantageous for realizing the refinement and uniformization of the paint particle size.

[0077] Also, as shown in FIG. 1, the inner peripheral surface 52 of the bell hub 5 extends away from the central axis C as it goes from the inner bottom surface 51 side of the bell hub 5 toward the end surface 53. According to this, the paint on the inner peripheral surface 52 can be made to flow from the inner bottom surface 51 side to the end surface 53 side by the centrifugal force caused by the rotation of the bell hub 5. By this, for example, it is possible to prevent the paint from remaining in the vicinity of the corner where the inner bottom surface 51 and the inner peripheral surface 52 intersect, and thus the usability of the rotary bell cup coater 1 can be improved. This is particularly effective when performing coating while exchanging a plurality of types of paint.

[0078] (Modification of the Rotary Bell Cup Coater) FIG. 7 is a view corresponding to FIG. 1 showing a conventional example of the rotary bell cup coater, and is a view exemplifying the flow of paint in the conventional example. Also, FIG. 9 is a view corresponding to FIG. 1 showing a modification of the rotary bell cup coater 1, and FIG. 10 is a view exemplifying the flow of paint in the modification.

[0079] In the above embodiment, in order to realize the refinement and uniformization of the paint particle size, the configuration utilizing the synergistic effect of the bell hub 5 having a concave cross section and the bell cup 3 having the first inner peripheral surface 33a extending in the central axis C direction has been described, but the present disclosure is not limited to that configuration.

[0080] For example, a configuration may be adopted in which a bell cup 103 configured in the same manner as in the above-described embodiment and a bell hub 305 configured in the same manner as in the conventional example are combined, such as in the rotary bell cup painting machine 101 according to the modification example.

[0081] Specifically, the bell hub 305 of the rotary bell cup painting machine 301 according to the conventional example has a cross-sectional shape with a raised central portion. Further, the bell cup 303 according to the conventional example is formed such that the dimension of the cylindrical first inner peripheral surface 333a (particularly, the dimension in the central axis direction) is shorter as compared with the first inner peripheral surface 33a in the above-described embodiment.

[0082] Therefore, the extension line extending from the end face of the bell hub 305 according to the conventional example does not intersect the cylindrical first inner peripheral surface 333a, and extends so as to be substantially flush with the second inner peripheral surface 333b that has a tapered diameter expansion.

[0083] Therefore, as indicated by the arrow in FIG. 8, the flow of the paint in the conventional example does not flow through the first inner peripheral surface 333a, but only through the second inner peripheral surface 333b. In this case, it is not possible to achieve refinement and uniformization of the paint particle diameter.

[0084] On the other hand, although the shape of the bell hub 305 of the rotary bell cup painting machine 101 according to the modification example is substantially the same as that of the conventional example, it is configured to use the same bell cup 103 as in the above-described embodiment.

[0085] In this case, the extension line Le' extending outward from the end face of the bell hub 305 in the modification example intersects the base end side portion 133R when the first inner peripheral surface 133a is divided into a base end side portion 133R and a tip end side portion 133T along the central axis C direction, in the same manner as in the above-described embodiment (see FIG. 10).

[0086] Therefore, as indicated by the arrows in Fig. 10, the flow of the paint in the modified example is configured to flow in sequence through the proximal end side portion 133R, the distal end side portion 133T, and the second inner peripheral surface 133b of the first inner peripheral surface 333a. By flowing the paint over the entire area of the first inner peripheral surface 133a, it is possible to achieve miniaturization and uniformization of the paint particle size, similar to the above-described embodiment.

Explanation of Reference Numerals

[0087] 1 Rotating bell cup coater 2 Tubular member 21 Rotating shaft 22 Feed tube (paint supply tube) 3 Bell cup 33 Paint diffusion surface 33a First inner peripheral surface 33b Second inner peripheral surface 33R Proximal end side portion of the first inner peripheral surface 33T Distal end side portion of the first inner peripheral surface 4 Support 5 Bell hub (paint receiving member) 51 Inner bottom surface 52 Inner peripheral surface 53 End face 54 Outer peripheral portion 6 Connector C Central axis

Claims

1. A rotary bell cup painting machine that discharges centrifugally atomized paint particles, comprising: a paint supply pipe that discharges paint from its tip; a bell cup provided so as to surround the tip of the paint supply pipe and rotating about the central axis of the paint supply pipe; a rotating shaft into which the paint supply pipe is inserted and rotating integrally with the bell cup; a paint receiving member that faces the tip of the paint supply pipe, receives the paint discharged from the tip, and is formed in a bottomed cylindrical shape with an opening facing the tip of the paint supply pipe; a support member that is disposed on the tip side of the paint supply pipe, inserted into the inner peripheral side of the bell cup, and positioned with respect to the bell cup; a connecting member that connects the paint receiving member and the support member so that the bell cup and the paint receiving member rotate integrally via the support member; The bell cup has: a contact portion that protrudes inward in the radial direction perpendicular to the central axis and positions the support member by contacting the support member; along the central axis direction, from the contact portion, to the boundary between a portion that overlaps and a portion that does not overlap the inner peripheral surface of the paint receiving member when viewed in a direction perpendicular to the central axis, and a first inner peripheral surface that surrounds the paint receiving member; a second inner peripheral surface that is provided on the tip side compared to the first inner peripheral surface, extends continuously from the first inner peripheral surface, and has a diameter that increases toward the tip side; The paint receiving member has an end surface that discharges the paint discharged from the paint supply pipe toward the bell cup when the paint receiving member rotates about the central axis together with the bell cup; an extension line extending outward from the end surface intersects the first inner peripheral surface; The connecting member connects the inner peripheral surface of the paint receiving member and the outer peripheral surface of the support member. A rotary bell cup painting machine characterized by the above.

2. In the rotary bell cup painting machine according to Claim 1, when the inclination angle formed by the first inner peripheral surface with respect to the central axis direction is θc, 0° ≤ θc ≤ 20° is satisfied. A rotary bell cup painting machine characterized by the above.

3. In the rotary bell cup painting machine according to Claim 1 or 2, the paint receiving member has an inner bottom surface facing the paint supply pipe; the inner peripheral surface of the paint receiving member extends from the inner bottom surface toward the end surface. The paint receiving member is configured such that, by rotating together with the bell cup around the central axis, the paint discharged from the paint supply pipe toward the inner bottom surface reaches the inner peripheral surface of the bell cup through the inner peripheral surface and the end surface of the paint receiving member. A rotary bell cup painting machine characterized by the above.

4. In the rotary bell cup painting machine according to Claim 3, the connector is provided on a part of the inner peripheral surface of the paint receiving member in the circumferential direction around the central axis. A rotary bell cup painting machine characterized by the above.

5. In the rotary bell cup painting machine according to Claim 3 or 4, the outer peripheral portion on the end surface side of the paint receiving member is formed to taper toward the radially outer side. A rotary bell cup painting machine characterized by the above.

6. In the rotary bell cup painting machine according to any one of Claims 3 to 5, the inner peripheral surface of the paint receiving member extends away from the central axis from the inner bottom surface side toward the end surface. A rotary bell cup painting machine characterized by the above.

Images