Patent Application
20130026258
The present invention relates to an electrostatic paint applicator and, more particularly, to a rotary atomizer head to be attached to the electrostatic paint applicator.
Nowadays where electrostatic paint applicators are in widespread use, such machines having a rotary atomizer head are widely used in the field of car body coating, for example. These paint applicators are called rotary-atomization-type paint applicators. As disclosed in Patent Documents 1 to 8, the rotary atomizer head is an assembly of an atomizer head body and a functional member disposed in a central portion of the atomizer head body. Paint is supplied to the rotary atomizer head through a feed tube, and atomized by the rotary atomizer head that rotates at a high speed. For this intended role of the rotary atomizer head, it is required to have a highly precise rotational balance.
For internal cleaning of the rotary atomizer head, there have been developed techniques for easier disassembling and reassembling of the rotary atomizer head. Patent Document 1 discloses a rotary atomizer head that is configured to attach the functional member to the atomizer head body by access from behind it. It is proposed in Patent Document 1 to form a paint outlet in the atomizer head body and to make a paint chamber of the rotary atomizer head, which is a chamber for receiving paint supplied from a feed tube, by cooperation of the atomizer head body and the functional member attached to the atomizer head body from behind it.
Patent Documents 2 et sec. disclose rotary atomizer heads configured to attach a functional member called “hub member” to the atomizer head body by access from its front face. Patent Document 2 proposes to fix the hub member in a central recess of the atomizer head body via an elastic ring. More specifically, the rotary atomizer head disclosed in Patent Document 2 has a circumferential groove (first circumferential groove) formed in a circumferential wall surface of the central recess of the atomizer head body and another circumferential groove (second circumferential groove) formed in a circumferential surface of the hub member. By laying the elastic ring in the first and second circumferential grooves to be commonly grasped by these grooves, the hub member is removably fixed to the atomizer head body. With the rotary atomizer head disclosed in Patent Document 2, the hub member can be easily removed from the atomizer head body for the purpose of cleaning, and attached again to the atomizer head body after completion of the cleaning.
Patent Document 3 discloses another existing rotary atomizer head that can be disassembled and reassembled. The rotary atomizer head disclosed in Patent Document 3 has a step formed at the front end of the peripheral wall of the central recess of the atomizer head body, and a disc-shaped hub member fittingly engages with this step. More particularly, the disc-shaped hub member has elasticity and flexibility owing to natures of its shape and material, and it can get in fitting engagement with the step of the atomizer head body with the elasticity and flexibility. Further, a retaining circumferential ridge is formed on the circumferential surface of the step of the atomizer head, or the circumferential surface of the step is tapered to decrease its diameter forward, as a measure for preventing the hub member from being disengaged forward of the atomizer head body. Further, Patent Document 3 discloses a rotary atomizer head having a spoon-cut groove formed in the bottom of the central recess of the atomizer head body and having an inclined wall surface extending continuously from the spoon-cut groove and enlarging its diameter gradually forward. The above-mentioned disc-shaped hub member has a plurality of paint outlets formed to align concentrically in the outer circumference thereof. The paint outlets extend tangentially to the inclined wall surface.
Patent Document 4 proposes to attach permanent magnets on a disc-shaped hub member and an atomizer head body for receiving the hub member, such that the disc-shaped hub member can be fixed to the atomizer head body with the attraction of the permanent magnets.
Patent Document 5 proposes to use a disc-shaped hub member having a number of legs, which can be removably fixed to the atomizer head body by engagement of free ends of the legs with a circumferential groove in the central recess of the atomizer head body in order to removably secure the hub member to the atomizer head body. In addition to this, Patent Document 5 proposes to provide a clearance between the outer circumference of the disc-shaped hub member and the atomizer head body to use it as a paint passageway.
One problem of the rotary atomizer head disclosed in Patent Document 2, which relies solely upon a resistance force produced by the elasticity of the elastic ring for fixing the hub member to the atomizer head body. Another problem of this rotary atomizer head, which relies on the elasticity of the elastic member for fixing the hub member in position, is a difficulty for a user to be sure that the hub member has taken its proper position when he should attach it to the atomizer head body. Still another problem of this atomizer head is that the elastic ring deforms, when the rotary atomizer head rotates at a high speed, and thereby degrades in its sealing performance.
To interpose the elastic ring between the atomizer head body and hub member means that a relatively large clearance exists between the atomizer head body and hub member. Therefore, the technique proposed by Patent Document 2 can be considered to admit inrush of paint through the clearance. When paint should be changed one in another color, the rotary atomizer head needs internal cleaning without being disassembled. However, it is difficult to remove paint having entered the clearance between the atomizer head body and the hub member by the internal cleaning. Because of this and other reasons, the invention disclosed in Patent Document 2 has not yet been put into practice.
Patent Document 3 proposes to put the disc-shaped hub member in fitting engagement with the step portion of the atomizer head body and to form the retaining circumferential ridge on the circumferential surface of the step portion of the atomizer head, or to taper the circumferential surface of the step to decrease its diameter forward, as a measure for preventing the hub member from being disengaged forward of the atomizer head body. This invention of Patent Document 3 has not yet been put into practice as well.
Patent Document 4 proposes to secure the disc-shaped hub member and atomizer head body to each other by the attraction force of permanent magnets. Because of this structure, this technology is disadvantageous in that the materials of the disc-shaped hub member and the atomizer head body are limited to nonmagnetic ones (aluminum).
In Patent Document 5, it is disclosed that the disc-shaped hub member is fixed by engagement of the legs of the hub member with the circumferential groove formed in the peripheral wall of the central recess of the atomizer head body and that paint outlets are formed in each interval between every adjacent legs in the clearance between the outer circumference of the disc-shaped hub member and the peripheral wall of the central recess. Therefore, when the rotary atomizer head is cleaned with a cleaning liquid supplied to the rotary atomizer head, paint having adhered to the circumferential groove and legs will remain unremoved. Because of this problem among others, Patent Document 5 explains in detail how to remove the hub member from the atomizer head body when the atomizer head should be disassembled for cleaning.
An object of the present invention is to provide a rotary atomizer head for an electrostatic paint applicator, which not only can be cleaned by disassembly but also can be cleaned by internal cleaning without disassembly for changing paint of a color to one of another color.
Another object of the invention is to provide a rotary atomizer head that enables a user to ascertain positioning of a functional member and can alleviate the problem of residual paint upon internal cleaning.
Still another object of the invention is to provide a rotary atomizer head improved in efficiency of internal cleaning.
Yet another object of the invention is to provide a rotary atomizer head for an electrostatic paint applicator, which can suppress bubbles from taken into the paint applied for coating an object.
These objects of the invention are attained by providing a rotary atomizer head (1) for an electrostatic paint applicator, having a paint space (S) for receiving paint supplied from a paint feed tube and a spoon-cut groove (30) formed in the bottom surface of the paint space (S), comprising:
Since the outer circumferential surface (14a) of the functional member (4) is substantially in contact with the peripheral wall (8) of the central recess (6) over the entire longitudinal area thereof, paint cannot easily flow onto the outer circumferential surface (14a) of the functional member (4). Further, since the outer circumferential surface (14a) of the functional member (4) and peripheral wall (8) of the central recess (6) are gradually expanded forward in diameter, even if paint enters into between the functional member (4) and peripheral wall (8) of the central recess (6), it is centrifugally ejected to outside. Therefore, since it is thus possible to prevent paint from going around to between the outer circumferential surface (14a) of the functional member (4) and peripheral wall (8) of the central recess (6), the elastic ring disclosed in Patent Document 2 is not required for the present invention.
The spoon-cut groove (30) may be formed in the synthetic resin-made functional member or may be formed in the atomizer head body (2). In case the spoon-cut groove (30) is to be formed in the atomizer head body (2), it is preferable to employ the following specific configuration. That is, a circumferential projection (20) projecting rearward is formed radially inside the plurality of legs (16) of the functional member (4), while the atomizer head body (2) has a circumferential seat (22) formed around a through-hole (10) through which the atomizer head body (2) receives a paint feed tube formed in the central portion of the atomizer head body (2). Thus, the spoon-cut groove (30) is formed in the circumferential seat (22) to extend in the circumferential direction coaxially with the through-hole (10). It is recommended to configure the circumferential projection (20) of the functional member (4) to sit on the outer circumferential portion of the circumferential seat (22) of the atomizer head body (2), and at the same time, to abut against the outer circumferential surface of the circumferential seat (22).
According to the above-mentioned embodiment, the functional member (4) can be removably fixed to the atomizer head body (2) with the claws (16a) formed at the distal ends of the legs (16) of the functional member (4). In addition, by configuring the circumferential projection (20) positioned inside the legs (16) of the functional member (4) not only to sit on the circumference of the circumferential seat (22) of the atomizer head body (2) but also to be in abutment with the circumference of the circumferential seat (22) of the atomizer head body (2), it is possible to improve the supporting rigidity of the fixing structure by the legs of the functional member (4) removably attached to the atomizer head body (2). Further to the above, seating the circumferential projection (20) of the functional member (4) onto the circumferential seat (22) of the atomizer head body (2) leads to easier positioning of the functional member (4) relative to the atomizer head body (2) and enhances reliability of the positioning.
The other objects and advantages of the present invention will become apparent from the detailed description of preferred embodiments that follows.
Preferred embodiments of the present invention are explained below in detail with reference to the accompanying drawings.
As disclosed in Patent Documents 1 and 2 for example, the rear end portion of the atomizer head body 2 is threaded in its inner surface to form a female an internal thread (as indicated with a numeral 2a) into which a rotating shaft of an air motor (not shown) is to be screwed. The internal thread 2a has a central axis common to the rotary atomizer head 1. The rotary atomizer head 1 is driven to rotate by the air motor similarly to the conventional rotary atomizer heads.
As described in detail in Patent Document 2, the rotating shaft of the air motor is hollow, and a paint feed tube is inserted in the rotating shaft. That is, paint is supplied to the central portion of the rotary atomizer head 1 through the paint feed tube. Further, the space between the outer circumferential surface of the paint feed tube and inner circumferential surface of the rotating shaft serves as a path for a cleaning liquid (typically a thinner). The rotary atomizer head 1 is washed with the cleaning liquid supplied through the cleaning liquid path. Since Patent Document 3 provides detailed explanation about supply of paint and cleaning liquid, the present specification omits its explanation by invoking the description of the same document.
In the central portion of the inner circumferential surface 2b of the atomizer head body 2, a central recess 6 opening forward is formed (
The functional member 4 has a disc-shaped front wall 12 in its front elevation (
The functional member 4 has a plurality of legs 16 extending rearward from the outer circumferential portion of the rear end and disposed circumferentially at regular intervals as seen from
At the bottom, which is the rear end of the functional member 4, a circumferential projection 20 is formed to project circumferentially inward of the legs 16 adjacently thereto to extend continuously in the circumferential direction. In association with the circumferential projection 20, a circumferential seat 22 is formed to rise continuously in the circumferential direction around the circular through-hole 10 in cross section on the bottom of the central recess 6 of the atomizer head body 2. When the circumferential projection 20 of the functional member 4 is seated on the outer circumferential portion of the circumferential seat 22, it abuts the outer circumferential surface of the circumferential seat 22 (
As such, by employing the structure at the rear end of the functional member 4, in which the circumferential projection 20 located inside the legs 16 is seated onto the circumferential seat 22 of the atomizer head body 2 and brought into abutment with the outer circumferential surface of the circumferential seat 22, it is possible to hold the functional member 4 with an enhanced rigidity to the fixing structure of the functional member 4, which is the combination of the legs (16) and circumferential groove 18.
In the outer circumferential portion of the front wall 12, the functional member 4 has a plurality of paint outlets 24 formed at regular intervals on a common circle as seen from
Regarding the sidewall 14 of the functional member 4, the inner circumferential surface 14b opening rearward is an inclined wall gradually increasing its diameter forward. The paint outlets 24 are formed contiguous to the front end of the inner circumferential surface 14b. That is, the paint outlets 24 are contiguous to the inner circumferential surface 14b of the sidewall of the functional member 4. Most preferably, the axes of the paint outlets 24 incline in the same direction as the inner circumferential surface 14b of the sidewall 14 inclines in (
The circumferential seat 22 of the atomizer head body 2 preferably has a spoon-cut groove 30 formed in a forward-oriented surface, namely, in a surface opposite from the front wall 12 of the functional member 4 to extend circumferentially continuous, coaxially with the circular through-hole 10. The spoon-cut groove 30 has an outer circumferential wall surface 30a (
Most preferably, the end face at the outer circumferential side, namely, a top face 32, of the circumferential seat 22 having the spoon-cut groove 30 formed therein has a ridge-and-furrow configuration defined by a step 34 resulted from cutting a part facing to the spoon-cut groove 30 (
Furthermore, when the outer circumferential-side top face 32 of the circumferential seat 22 is fitted in the ridge-and-furrow portion 36 in the free end of the circumferential projection 20 of the functional member 4, the inner circumferential surface 14b of the sidewall 14 of the functional member 4 is flush with the outer circumferential wall surface 30a of the spoon-cut groove 30 in the circumferential seat 22. This flush engagement can prevent paint from entering between the sidewall 14 of the functional member 4 and the circumferential seat 22 of the atomizer head body 2.
As understood from
It will be needless to say that, owing to the above-mentioned structure, paint having flown out from the paint outlets 24 is centrifugally driven to flow out radially along the outer circumferential edge of the front wall 12 of the functional member 4 and then it is ejected from the outer circumferential edge 2c along the inner circumferential surface 2b of the atomizer head body 2. However, since the outer circumferential surface 14a of the functional member 4 is substantially in contact, throughout the entire length thereof, with the peripheral wall 8 of the central recess 6, paint is not likely to enter between the functional member 4 and central recess 6. More specifically, even if paint enters there, it tends to be centrifugally ejected forward because the peripheral wall 8 of the central recess 6 is an inclined wall expanded forward in diameter. Therefore, it is possible to prevent paint from flowing around to between the hub body and central recess 6 in the atomizer head body 2 in which the hub body is received.
When the rotary atomizer head 1 needs to be cleaned by washing for using paint in another color, a cleaning liquid (typically a thinner) is supplied to the rotary atomizer head 1 as previously described. As indicated with dash lines in
In the first embodiment, the paint space S in the rotary atomizer head 1, in which paint supplied from the paint feed tube is received, is defined by the functional member 4 and atomizer head body 2. In the paint space S surrounded by the functional member 4 (see
With reference to
The step 40 is called as a dam hereunder. Paint supplied from the feed tube (not shown) flows out of the paint outlets 24 formed in the outer circumferential portion of the front wall 12 and spreads in the radially outward direction. However, this paint is once banked up by the dam (step 40) before moving further. That is, it has been proved by the Inventors' experiments that the step 40 could surely function as a dam and air bubbles in the paint be removed due to the dam function of the step 40. In other words, the object coated using the rotary atomizer head 1 having the above-mentioned step 40 exhibited a paintwork that was free from bubbles and had excellent smoothness. Other embodiments of the present invention will be explained hereunder with reference to
The first embodiment has been explained as providing the spoon-cut groove 30 in the atomizer head body 2. In the second embodiment, a rotary atomizer head 200 additionally includes a synthetic resin-made bottom member 202, and the spoon-cut groove 30 is formed in this bottom member 202. According to the second embodiment, the paint space S in the rotary atomizer head 200 is defined by two functional members 208 and 202.
The second embodiment is explained here in greater detail with reference to
As seen from
The first functional member 208 is designed substantially equal to the functional member 4 in the first embodiment. Therefore, the same elements as those of the functional member 4 in the first embodiment are labeled with the same reference numerals as those used in the explanation of the first embodiment to omit their explanation.
As seen in
As shown in
That is, in the rotary atomizer head 200 according to the second embodiment, the paint space S to receive paint supplied from the paint feed tube is defined by the first functional member 208 and additional functional member 202 both formed by molding a synthetic resin material. The first functional member 208 and the additional functional member 202 are removable from the atomizer head body 204.
As best shown in
In the rotary atomizer head 200 according to the second embodiment, since the bottom of the central recess 6 in the atomizer head body 204 is designed simpler than in the rotary atomizer head according to the first embodiment, the atomizer head body 20 can be produced with less costs. Of course, also in the rotary atomizer head 200 according to the second embodiment, the paint space S can be cleaned while keeping the first functional member 208 and the bottom member 202 in assemblage in the atomizer head body 204. Further, the atomizer head body 204, first functional member 208 and bottom member 202 can be individually washed and reused by removing the first functional member 208 and the bottom member 202 from the atomizer head body 204. Further, since the first functional member 208 and the bottom member 202, which is the additional functional member, are separate elements, they may be made of different synthetic resin materials. For example, the first functional member 208 may be made of PEEK (polyether ether ketone) resin, whereas the bottom member 202 may be made of a fluoroethylene resin (typically Teflon (registered trademark)), which is excellent in washability.
The third embodiment is a rotary atomizer head 300 that is a variant of the second embodiment (
The fourth embodiment is a variant of the first embodiment (
More specifically, in the rotary atomizer head 400 according to the fourth embodiment, the paint space S to receive paint supplied from the paint feed tube is defined by the first functional member 4, spoon-cut member 404 and atomizer head body 402. Also in this fourth embodiment, the paint space S has an inner wall free from clearance and step.
Also in the fourth embodiment, of course, since the first functional member 4 and the spoon-cut member 404, which is an additional functional member, are separate elements from the first functional member 4, they may be made of the same synthetic resin or different resin materials, respectively.
The fifth embodiment is a rotary atomizer head 500 having a functional member 502 consisting of a first functional member 504 and an additional functional member 506. It is common to the fifth embodiment and previously explained first to fourth embodiments that the first functional member 504 and additional functional member 506 are formed independently of each other. However, the first functional member 504 and additional functional member 506 in the fifth embodiment are united with each other by screwing unlike those in the first to fourth embodiments.
Basically, the first functional member 504 is equivalent to the first functional member 208 of the rotary atomizer head 200 according to the second embodiment, but it is different from the rotary atomizer head 200 (first functional member 208) in that a rearward extending cylindrical portion 508 is provided at the inner circumferential side of the legs 16. The cylindrical portion 508 is threaded in the inner circumferential surface thereof to make a first threaded portion 510.
The additional functional member 506 included in the fifth embodiment includes has basically the same configuration as those of the additional functional members, i.e. bottom members 202, of the second and third embodiments. However, the additional functional member 506 used in the fifth embodiment is different from the additional functional member (bottom member 202) used in the second and third embodiments in that the additional functional member included in the fifth embodiment, i.e., the bottom member 506, is threaded in the outer circumference thereof to make a second threaded portion 512. By screwing the second threaded portion 512 into the first threaded portion 510, the first functional member 504 and additional functional member 506 are separably coupled with each other.
The cylindrical portion 508 of the first functional member 504 included in the fifth embodiment has a step 514 on the inner circumferential portion thereof, and the distance L from the step 514 to the rear end of the cylindrical portion 508 is equal to the thickness of the outer circumferential portion of the additional functional member, that is, bottom member 506. When the additional functional member (bottom member 506) is screwed to the first functional member 504, the outer circumferential portion of the bottom member 506 is engaged at the front end face thereof on the step 514 of the first functional member 504 (
The rotary atomizer head 500 according to the fifth embodiment includes an atomizer head body 520. The atomizer head body 520 has an additional cylindrical indentation 522, which is open forward (
In the rotary atomizer head 500 according to the fifth embodiment, the paint space S to receive paint supplied from the paint feed tube is defined by the first and additional functional members 502 and 506 both made of a synthetic resin. The paint space S has a smooth inner wall that has no gap and no unevenness. When a user wants to clean the rotary atomizer head 500 by disassembling it, the user may remove the functional member 502 from the atomizer head body 520 and next disassemble the functional member 502 to separate the first functional member 504 and the additional functional member 506. In this state, he can perform the intended cleaning The first functional member 504 and the additional functional member 506 and 506 may be made of the same synthetic resin or different resin materials, respectively.
Heretofore, the first to fifth embodiments of the present invention have been explained. It should be noted however that the step 40 included in these embodiments and having the dam function may of course be formed by a functional member. For example, in the functional member 4 included in the rotary atomizer head 1 according to the first embodiment (
The present invention is suitable for application to rotary atomization type electrostatic paint applicators.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-001542 | Jan 2010 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2011/050136 | Jan 2011 | US |
| Child | 13541858 | US |
