JP2527437B2 - Electrostatic spray coating device for rotary atomizing liquid - Google Patents

Description

The present invention relates to electrostatic spray coating, and more particularly to an electrostatic spray coating apparatus for atomized liquids utilizing rotary atomization.

In the past, electrostatic spray applicators with rotary atomizers have long been used. In that case, a conductive static cup or disc, which is usually kept at a high voltage, is rotated at an ultra-high speed, which guides the liquid coating material to the central part of the cup or disc and, under centrifugal force, the surface of the cup or disc. It is adapted to move outwardly, leaving these cups or discs from its outer edge and being sprayed. Since the atomization edge of the cup or disk is sharp,
The application of a high voltage to the conductive cup or disk ionizes the air in the atomizing edge region and imparts an electrostatic charge to the atomized liquid coated particles as is well known in the electrostatic spray coating art. As described above, when a conductive spray cup and a disk kept at a high voltage are used, particularly when a flammable paint is used, it is known that there is a risk of giving an impact to a worker or causing a fire. . Such a danger is simply that a significant amount of electrical energy is capacitively stored in a conductive cup or disk kept at a high voltage,
This is caused by the fact that the stored energy is rapidly discharged when the cup or disk is inadvertently brought to the ground or near the grounded body. Many methods have been proposed to minimize such risks. For example, the atomization cup or disk is formed of an insulating material except for the conductive skin or layer, and these skins or layers are provided on the surface of the spray member, and a high voltage is applied to the atomization edge to ionize it. It has been proposed that it is configured as follows. Further, a spraying cup or a disc using a resistance material has been proposed. These and other conventional methods are U.S. Pat. Nos. 2,926,106 to Gauthier, 2,989,241 to Gautier, and Schotland's second, respectively.
No. 955,565, No. 3,009,441 of Juvinall,
No. 3,010,478 of Sedlacsik, No. 3,021,077 of Gaucha, No. 3,048,498 of Jubinar, etc., No. 3,063,642 of Point (Point) 3,072,
No. 341, Gaucha No. 3,083,121, Gaucha No. 3,128,
No. 045, Point No. 3,178,114, Felici
No. 3,279,429, Scharfenberga (Scharfenber
ger) etc. 3,826,425, point 3,075,706,
And PCT International Publication No. WO85 / 0 by Robisch
It is described in No. 1455.

However, the above method is not completely satisfactory for various reasons. For example, the transfer efficiency of the spray device could not be as high as 90% or higher. The paint transfer efficiency means the percentage or ratio of the coating material actually sprayed from the coating device.

In view of the drawbacks of the conventional methods, it is an object of the present invention to provide a rotary atomization type safe electrostatic spraying device having high paint transfer efficiency.

To achieve the above object, the present invention provides an electrostatic spray coating device comprising a rotary atomizer made of an insulating material, the atomizer being a liquid paint when it is rotated about its axis of rotation. Can flow outwards towards its atomizing edge
A surface and a second separated from the first surface by an atomizing edge
And a surface. Further, a circular ring-shaped charging electrode is mounted on the first surface, and a current conducting element is mounted on a second surface electrically connected to the circular charging electrode. A plurality of static conductors are provided, each having a free end closely spaced to the circular current conducting element. The stationary electrode facilitates the transfer of electrostatic energy to the cup electrode when the stationary conductor is energized by a high voltage source, causing the paint to abut the fill electrode under the centrifugal force toward the atomizing edge. It enables contact charging of the liquid paint applied to the first surface as it flows outwardly over the first surface. By minimizing the amount of conductive material used in the rotary atomizer, the electrical energy stored capacitively by the atomizer is kept within a safety limit, and one stationary electrode configuration and a rotary atomizer. A circular moving current conducting element associated with the stationary electrode above, and a conductive electrode embedded in the surface of the atomizer through which the paint flows under the action of centrifugal force as it further moves toward the atomization edge. A high transfer efficiency is provided by the provided contact charging.

According to a preferred mode of the invention, the safety of the spraying device is further improved by forming the circular contact charging electrode, its associated circular current conducting element and the connecting means between these members with a semiconductor material. Can be enhanced and improved.

Further in accordance with the present invention, and to further improve the safety of the spray device, the free end of the electrode for transferring electrical energy to the contact electrode arranged inside the cup and the outer ring electrode and the outside of the cup are It is protected from damage and undesired contact by being placed in the rotating fitting. According to another feature of the invention designed to increase the compactness of the spray applicator, the atomizer bearing housing containing the drive means for the rotary atomizer has a midsection diameter of front and rear bearings. An annular cavity is provided between the above sections that has a generally cylindrical outer shape that is significantly smaller than that of the sections, thereby placing the liquid paint and wash solvent valves that control the flow of liquid paint and solvent to the rotary atomizer. ing. This allows the liquid paint and solvent valves to be located not only in close proximity to the rotary atomizer but also within the entire envelope of the bearing housing the rotary drive assembly for the atomizer. .

In order to make it easy to attach the spray device to the post,
A mounting bracket of desired design is provided from which a number of spaced side-by-side struts project forward, the struts at their front ends carrying various valves and rotary atomization drive assemblies. The support of the spraying device to be stored is attached. According to a preferred mode of the invention, one of the struts is hollow and houses an electrostatic energy transfer core, which is a remote high voltage source and a circular on a rotary atomizer connected to the circular charging electrode. High-voltage electrostatic energy is transmitted between the static electrode and a stationary electrode arranged in the vicinity of the conductive element. According to a preferred embodiment, the hollow post contains a Gun resistor in series with the static conductor.

According to another principle of the invention, an annular air ring with a circular array of ports defining a forward-directed air jet is removably mounted on the entire surface of the bearing. The air ring has an annular fitting in its rear wall that distributes air into a circular array of air passages to form an air jet and acts as a circular air manifold to shape the spray liquid paint. The rear wall of the air ring further comprises an annular fitting that encloses a single circular conductor to which a high voltage is applied from a remote electrostatic power source. The circular conductor has connected thereto a plurality of stationary conductors that transfer electrostatic energy to the charging electrodes of the cup. According to one preferred method, the static conductors are arranged in an outer sheath which is detachably screwed into a suitable threaded bore in the front face of the air ring. The sheath may further house a charging resistor in series with the fixed conductor. It has been found that the above construction is relatively easy to manufacture, assemble and maintain.

According to another embodiment of the invention, the annular air ring has an aerodynamically shaped outer surface to eliminate eddy currents generated by the air flow along the outer surface of the rotary atomizer cup. It has a cap shape. This improves the energy transfer efficiency and further reduces the clogging of the spray device with the coating material by preventing the spray pattern from being pulled back towards the spray device. The base of the cap has a groove that encloses a first circular conductor to which a high voltage is applied from a remote static power source, and the other side of the one-way cap has a repulsion ring located in a recess around it. The repulsion ring improves the energy transfer efficiency and prevents the coating material from depositing on the spraying device, so that the first circular conductor is electrically conductive so that it is biased with the same polarity as the charge imparted to the sprayed particles of coating material. Connected.

Instead of using an outer shell screwed to the air ring, another embodiment of the invention embeds a plurality of fixed conductors and their associated charging resistors within the cap. This has the effect of protecting and stabilizing the leads associated with the charging resistor and reducing the overall length of the spray device. Further in accordance with the present invention, the cap preferably includes a slightly oversized fitment in which a spray cap is disposed, thereby defining a gearup between a wall of the fitment and an outer surface of the cap. In order to prevent inadvertent contact of the charging electrodes, their free ends and the outer circular conductors of the spray cup are respectively arranged in said gear.

EXAMPLE As shown in FIGS. 1 and 2, the rotary atomizing liquid spray applicator of the present invention has a front or front section 12
And a bearing 10 with a rear section 14 and
An intermediate section 16 is arranged between the above sections. The bearing sections 12, 14, and 16 are generally cylindrical in shape. The diameters of the front and rear bearing sections 12 and 14 are approximately the same. The diameter of the intermediate bearing section 16 is much smaller than that of the bearing sections 12 and 14 and defines an annular cavity 18 between said sections, in which cavity the liquid application material, as will be described in more detail below. And various valves that control the flow of the solvent and the flow of solvent that cleans the interior and exterior of the rotary atomizing cup can be located and installed.

The rotary atomizing cup 20 extends forward from the front surface 22 of the front bearing section 12. An annular ring 24 is appropriately detachably fixed to the front surface 22 of the front section 12 of the support body 10 by bolts, screwing means or the like. This ring 24
Has a circular airway or manifold 26 formed in its rear surface, with a spray cup in front of this ring.
Extending are a plurality of circular air ports 28 that form a circular array of air jets that shape the spray liquid paint spray pattern 29 formed on the front edge or rim 42 of 20.

Extending from the front section 12 of the bearing 10 forward is a rotary atomizing cup 20. The cup 20 is drivably mounted on the shaft 23 so as to be rotatable about its axis. The cup drive shaft 23 is located in the bore 12 of the front bearing section 12.
An air bearing or ball bearing 25, which extends through b and is commercially available in the prior art, is disposed in a suitably configured bearing cavity or bore 27 in the intermediate bearing section 16. The shaft 23 is driven at the rear (left in FIG. 2) by a rotary actuator 31, such as a conventional air-driven turbine, which is a bore in the rear bearing section 14.
31a or behind the bearing 25 of the turbine cavity. A liquid application control valve 33 mounted on the rear surface of the flange-defining portion of the front section 12 of the support 10 provides a flow of liquid application material to the application nozzle 30 via a passage 32 formed in the front section 12 of the support 10. To control. The slightly pressurized liquid paint exiting the nozzle 30 flows into an annular cavity 34 formed in the rear section of the cup 20. Under centrifugal force due to the rotation of the cup 20 by the drive shaft 23, the liquid coating material in the annular cavity 34 passes through a series of paint passages 36 in the radial cup wall 20c, radially outward and forward, forward. It flows out toward the cup cavity 38.
In the front cup cavity 38, the fluid paint moves radially forward toward the front spray edge 42 of the cup 20 along the first surface defined by the inner cup wall 40, where the paint atomizes under centrifugal force. To form a spray pattern 29.
The flat circular ring-shaped charging electrode 46 embedded in the inner wall 40, which is connected to a conventional electrostatic high voltage source (not shown) as described below, has a liquid coating material from the passage 36 of the wall 20c. Contact causes the liquid coating material to become charged as the liquid passes through the electrode toward the forward spraying edge 42 of the cup that is centrifugally sprayed to form the spray pattern 29.

A mounting bracket 50 is arranged behind the support body 10 and spaced apart therefrom. The bracket 50 has a circular plate 52 and a collar 54 extending rearward. These circular plates
52 and collar 54 are provided with through holes into which circular posts 56 can be positioned that are properly supported by a spray reciprocating device, a fixed pedestal, or the like. A set screw 58 screwed in a radial direction is provided on the wall portion of the collar 54, and thereby the bracket 50 is fixed to the post 56.

The rear surface of the circular plate 52 and the rear section 14 of the support 10
Between 60 are several mounting posts or struts 62, 64 and
66 has been extended. The columns 64 and 66 are the circular plate 52 and the support
It can be suitably secured to the rear face 60 of the rear section 14 of the 10. For example, these stanchions 64 and 66 may be threaded at their forward ends to provide a rear surface of the rear section 14 of the bearing 10.
It can be screwed into a screwing inner hole that is properly provided in the 60. The struts 64 and 66 have reduced diameter portions at their rear ends which are behind the rear surface 55 of the plate 52 (to the left in FIG. 1). Extending through a suitably provided bore in plate 52 to project. A nut is used to thread the rear end of the strut 62, as described below, by threading the reduced diameter portion of the rear end of the strut 64 and 66 projecting rearward of the plate surface 55. Similarly, the rear ends of struts 64 and 66 can be secured to plate 52.

Post 62 has a reduced diameter portion 62c at the rear or left hand end
This portion extends behind its surface 55 through a suitable bore in the plate 52. The nut 62d is the end 6
The support column 62 is fixed to the plate 52 by being screwed into 2c. Support post 62
Extends forward at its forward end towards the rear wall 12a of the front bearing section 12 through a suitably provided bore 70 in the rear section 14 of the bearing 10. Front part 62a of the pillar 62
Has a reduced diameter, which is the front bearing section
An appropriate screwing inner hole 72 formed on the rear surface of 12 is screwably engaged.

The column 62 is provided with an axial inner hole 62b, inside which is provided a high-voltage insulated cable 74 whose rear end is connected to an electrostatic high-voltage power supply (not shown). This cable 74 has its front end
74a is connected to gun resistor 76. A conductor 78 extends between the forward ends of the gun resistor to energize electrode 46 as described in more detail below.

As shown in FIG. 1, the dump valve 80 mounted on the front wall 57 of the plate 52 is a liquid application valve via a flexible duct 82.
33 and also to waste receptacle 86 via duct 88. The dump valve 80 acts in a manner known in the art to change the flow path of the cleaning solvent from the applicator valve 33 during a color change operation.

In addition to the application control valve 33, solvent valves 90 and 92 are mounted on the rear surface 12a of the flange-defining portion of the front bearing section 12, which valves are respectively third, fourth, as described below. , 7 and 8 control the solvent flow to the exterior and interior of the rotary atomization cup 20. Valve 90 above
And 92 are located in the annular cavity 18.

The rotary atomizing cup 20 best shown in FIG. 2 comprises a frustoconical tubular section 20a and a hub 20b which are connected by a radial wall 20c, both of which are associated with the rear annular cavity 34 and the front. A cavity 38 is defined. The non-uniform cross section of this tubular section 20 increases along its axis in the direction of the atomization edge 42. The hub 20b is provided with a tapered bore 20f which is slidably fitted in a similarly tapered portion 23a of the drive shaft 23. The front end portion 23b of the drive shaft 23 is screwed to the drive shaft 2
Lock nut 100 to properly secure hub 20b of cup 20 to 3
It can be screwed freely. Embedded in the outer surface 20d of the frustoconical section 20a of the cup 20 is a circular current-conducting flat ring element 102, preferably made of a semiconductor material. This ring element 102 is electrically connected to a flat electrode 46, preferably made of semiconductor material, through a series of conducting means in the form of pins 104 arranged in bores provided at appropriate locations in the cup section 20a. It The pins 104 are preferably made of a semiconductor material and their opposite ends are in electrical contact with the opposing surfaces of the ring 102 and the electrode 46. Cup 20 and nut 10
0, shaft 23, bearing 25, annular ring 24, bearing 10, rotary actuator 31, valves 33, 80, 90, and 92, and associated fluid ducts, mounting brackets 50, and device posts 62,
As with 64 and 66, it is preferably made of an insulating material to minimize the electrical energy stored capacitively in the spray applicator. The insulating material used for the cup 20 is preferably American ICI PEEK (polyether ether ketone), and the other insulating elements are Erta Incorp of Malvern, Bens.
orated) is commercially available from ERTALYTE
(Polyester) is preferred.

Around the bracket 50, bearing 10, and various valves,
As best shown in FIG. 1, a tubular housing is provided and encloses the various operating components of the spray device. The housing is preferably made of an insulating material.

The liquid application valve 33, which can be a conventional one, preferably has a valve body 120 having an inner hole 122 having a step portion in the diametrical direction.
A valve seat insert mount 124 with an inner bore 126 is located at the front end of the inner bore 122, and a valve seat insert 128 with an axial passage 128a is located in the inner bore. The passage is always blocked by a ball valve element 130 formed at the front end of the reciprocable lot 132, and the rod is valved by a spring-loaded pneumatic piston 134 fixed at the rear end 132a of the shaft 132. Always close,
It is biased forward. Spring 135 always biases piston 134 forward (to the right in FIG. 2). The air chamber 136 is connected to a source of pressurized air via a passage 138 provided in the rear wall of the valve body 120. When pressurized air is supplied to the air chamber 136 via the passage 138 under the control of means not shown, the piston 134 is driven rearward (to the left) and the valve seat insert 128.
The ball valve element 130 is released with respect to the valve seat and the passage 128a is connected to the liquid application chamber 142. This coating chamber 142 has a paint supply conduit 14
A pressurized liquid paint source (not shown) is communicated via a passage 144 formed in the wall of the valve pair 120 which contacts the valve 5.

In this way, when pressurized air is introduced into the cavity 136 via the air passage 138, driving the piston 134 backwards and disengaging the valve ball element 130, the pressurized liquid paint in the application chamber 142 will pass through. Passage 128a through passageway 32 in front bearing section 12
Where it flows under pressure from the nozzle 30 into the rear cavity 34 of the rotating cup 20. As explained above, the liquid coating material in the rear cavity 34 flows over the flat ring electrode 46 and along the inner wall 40 of the front cavity 38 through the passage 36 where it is electrostatically charged. Finally, the charged electrostatic paint is atomized or atomized at the front edge 42 of the cup 20 to form a spray pattern 29.

Air cavity 136 and application cavity 142 are rod 132
Are separated by a suitable seal 150 that allows axial reciprocation of the. The cavity 142 of the valve 33 is connected to the conduit 82 via a passage 152 formed in the wall of the valve body 120 and is finally guided to the waste receptacle 86 via the dump valve 80 and the conduit 88. The dump valve 80 is configured substantially the same as the valve 33 except that it has only one outlet passage for the liquid coating material in addition to a single inlet passage. The dump valve 80, like the valve 80 above, is pneumatic and therefore comprises a controlled source of pressurized air (not shown) connected to this valve via an air hose 80a.

As mentioned earlier, the front edge of the rotary atomizer cup 20
The atomized liquid paint spray pattern 29 ejected from 42 is shaped by circular air formed in an annular ring 24 which guides a plurality of axially extending ports 28 of circular shape forming a forward projecting air jet. Done by road 26. In order to provide pressurized air to the circular air passage 26 formed in this annular ring 24, the front bearing section 12 comprises a passage 160, which at its front end communicates with the circular air passage 26. And is connected at its rear end via a hose 162 to a suitable source of pressurized air (not shown). The air flow in the hose 162 is adjusted in the same manner as the conventional one by a control means (not shown). When pressurized air is applied to the hose 162, the air is expelled under pressure from the circular port 28, shaping the electrostatically charged atomized liquid paint particle spray pattern 29 as desired.

If it is desired to change the color of the liquid application material sprayed from the device of the present invention, solvent is introduced into port 144 of valve 33 and valve 80 is opened in a manner known in the art. This solvent flows through valve 33, passage 32, and nozzle 30, cleaning them and also through passage 152 and hose 82 to dump valve 80, further through the dump valve, and into hose 88 into waste receptacle 86. To do. Solvent cleaning of the outer surface 20d of the liquid coating material associated with the color change is accomplished by a solvent nozzle 170 screwed into a suitably provided lumen 172 in the front surface 22 of the front bearing section 12. A rear end of the passage 172 is connected to the output port 90a of the solvent valve 90. A solvent hose 174 led from a suitable pressurized solvent source (not shown) is connected to the input port 90b of the solvent valve 90. The solvent valve 90 is constructed almost the same as the dump valve 80, and like the dump valve 80, the spring-operated air-operated piston 90e.
A pneumatic ball valve element 90c is provided at the front end of the rod 90d controlled by A controlled pressurized air source is connected to the valve 90 via a suitable air hose 176 to operate the valve as desired.

Along with the color change is the rear cup cavity
34, passage 36, and front cup cavity 38 of coating material
Nozzle for solvent as shown in FIG.
A valve 94 and a valve 92 are provided which are substantially equivalent to those shown in FIG. 4 for cleaning the outer surface of the atomizing cup 20. A solvent cleaning nozzle 94 for cleaning the inside of the cup 20 described above.
And a nozzle to clean the valve assembly 92 and the outside of the cup
The only difference between 170 and valve 90 is that a nozzle 94 for cleaning the interior of the cup projects from the front surface section 22a of the front bearing section 12 into the rear cavity 34 of the cup 20. Since adjustment of various valves for performing color change, cleaning of these valves, nozzles, associated passages, hoses, etc., and cleaning of the inside and outside of the atomizing cup are performed by a method known in the art, It will not be detailed here.

Pressurized solvent valve 180 leads to hose 182, which
A hose 174 that feeds the solvent leads to a valve 90 that controls the flow of the solvent that cleans the outside of the cup 20 and also that supplies the solvent.
It is branched so as to lead 175 to the internal cavity 34 of the atomizing cup 20.

A source of pressurized air 185 is connected to hoses 186 and 188 which drive the turbine rotor and brake, then shaft 23 and finally atomizer cup 20 to the braking air turbine. Is entered. Hose 190 is turbine 31
Exhaust the waste gas from. An air turbine by selectively controlling the pressure and flow of air in hoses 186 and 188.
31, thus output shaft 23, therefore rotating atomization cup
The 20 speed can be controlled as known to those skilled in the art.

An air hose 192 connected to a selectively operable source of pressurized air controls a solvent valve 92 for cleaning the interior of the rotary atomizing cup 20. The air hose 192 functions similarly to the solvent valve 92 as the air hose 176 connected to the solvent valve 90 to control its operation and the air hose 138 connected to the paint valve 33 to control its operation.

In order to minimize the buildup of coating material on the surface of the shaft 23, air purging means are provided to provide a rotary atomizing cup.
Supply a positive air flow along the shaft towards 20.
This air purging means, as shown in FIG. 2, is preferably provided with a port 300 provided in the rear wall 12a of the front bearing section 12 and used for connection to an air supply line (not shown). This air supply line supplies air from the passage 302 to the discharge port 304 into the space between the front bearing section 12 and the shaft 23. This air travels along the shaft 23 in the cup 20
To provide a positive air purge to the paint to prevent the paint from flowing back along the shaft into the bearing 25. .

High voltage electrostatic energy is delivered from the electrode 78 at the output of the gun resistor 76 to the semiconductor ring 102 via the path described below (and finally via the semiconductor pin 104 to the semiconductor electrode 46).
To be combined). Here, the above-mentioned path is defined by the conductive spring contact 200 arranged at the front end portion of the inner hole 72 formed in the front bearing section 12 and the electric conductor slidingly fitted in the inner hole formed in the front bearing section. 202, an electrode ring 204 embedded in an annular fitting portion formed on a rear wall 206 of the annular ring 24, the ring conductor 204, and the semiconductor ring 102.
And several parallel circuit paths connected between the two. The series circuit path between the rings 204 and 102 comprises: a) a conductor 212 connected between the resistor 210 and the ring 204;
b) Resistor 2 facing and close to semiconductor ring 102
It includes a resistor 210 disposed between a conductor 214 extending from the front end of 10. An insulative sheath 216 threaded at the interior or rear end into the appropriately threaded bore of the annular ring 24 encloses the resistor 210, the conductor 212 and the conductor 214 projecting from the front end of the sheath. Covered. This exterior 216
Insulating sheaths 218 and 22 equivalent to sheath 216 mounted circumferentially spaced around annular ring 24 on either side of
Zero has resistors 218a (FIG. 3) and 220a equivalent to resistor 210. The resistor 218a includes: a) an outer conductor 218b extending from the front end of its associated armouring toward and proximate to the semiconductor ring 102;
b) Static voltage connected to conductive ring 204 to resistor 218a
Is connected between the conductors 218c that transfer to. Above resistor 22
0a is a) a conductor 220b, which extends from the front end of its associated armor towards and close to the semiconductor ring 102, and b) a resistor and a conductive ring.
It is connected between the conductor 220c and the conductor 220c.
The forward protruding ends of the conductors 214, 218b, and 220b are spaced slightly from the outer surface of the semiconductor ring 102, which allows high voltages to be applied to the insulated cable 74, the gun resistor 76, and the conductor 7.
8, through the spring 200, the conductor 202, the ring conductor 204, and the conductor / resistor pairs 210/212, 218a / 218c, and 220a / 220c, electrostatic energy, when applied to the protruding end,
Ring electrode 46 across the gap to semiconductor ring 102 and finally via pin 104 to contact-charge the liquid coating material flowing radially outward and forward along inner wall 40 over the surface of semiconductor electrode 46. Be transmitted to.

It has been found that paint transfer efficiency is enhanced with three circumferentially-spaced conductors 212, 218c, and 220c, as compared to using only a single conductor. The use of multiple conductors in this way improves transfer efficiency and is clearly necessary when high transfer efficiency is desired.

The gun resistor 76 can have a resistance that varies according to the operating range of the electrostatic power source energizing the cable 74. If the operating range of the electrostatic power source is in the range of 50kv to 125kv, the gun resistor preferably has a resistance of 75 megohms.
The resistors 210, 218a, and 220a can also have variable resistances, but each such resistance preferably has a resistance value of about 12 megohms.

Although the insulated cable 74 can take many forms, it is assigned to the applicant of the present application and is disclosed and claimed in Hastings et al., US Pat. No. 4,576,827, dated March 18, 1986. A cable in which the conductive core 74b is manufactured from silicon carbide according to the above range is preferably used. Semiconductor ring 102, pin 104, and electrode
46 may be made of RYTON (polyphenylene sulfide (PPS)), commercially available from Phillips, although other semiconductor materials may be used. In addition, and while not preferred, the ring 102, the pin 104, and / or the electrode 46 can be made from a conductive material. However, when made of a conductive material, the ability of the rotary atomizing cup 20 to capacitively store electrical energy is limited to the ring 10.
2, more than when the pins 104 and the electrodes 46 were made of a semiconductor material. If necessary, conductive elements 78, 200, 202,
204, 212, 214, 218b and 218c, and also 220b and 220c can be made of semiconductor material rather than conductive material. Therefore, and in order to minimize the electrical energy that is capacitively stored in the spray device of the present invention, all elements of the spray device are statically charged to the paint charging electrode 46 of the rotary spray cup 20 from a remote power source (not shown). It is preferably formed of an insulating material, except for those made of semiconductor and / or conductive materials for carrying electrical energy at high voltages.

In a preferred embodiment of the invention, a rotary atomizing cup
Although 20 has been described as having a frustoconical shape, other shapes can be utilized without departing from the spirit and scope of the invention, as will be apparent to those skilled in the art.

Valves 33, 80, 90 and 92 are generally Hastings, assigned to the applicant of the present application, cited herein.
s) et al., U.S. Pat. No. 3,870,233.

Other Embodiments Another aspect of the present invention is illustrated by the other embodiments shown in FIGS. 10 and 11 cited herein. Except for the differences noted below, this other embodiment is substantially the same as the first embodiment described above, and therefore like parts will be assigned like reference numerals.

As shown, another embodiment of the rotary liquid spray paint system of the present invention comprises a bearing 10 having a front or front section 12. As in the first embodiment, an annular cavity 18 is arranged behind the front section 12. Inside the cavity 18, as will be described in detail later, various valves for controlling the flow of the solvent for cleaning the liquid coating material and the inside of the rotary spray cup 20 and the outside are arranged.

The rotary atomizing cup 20 is located on the front side 22 of the front bearing section 12.
It extends from the front. A cup that can be detachably attached to the front surface 22 of the front section 12 of the bearing 10 by bolts or screws.
400 is secured, this cup 400 is generally a convex outer surface
402, and an inwardly tapered fitting portion 404 arranged in the center where at least a part of the atomizing cup 20 is arranged. The cap 400 is a base having a generally circular air passage or manhold 26 formed therein.
406 is provided. Gasket 408 comprises a suitably sized, properly positioned opening and is interposed between front surface 22 of anterior section 12 of bearing 10 and cap 400, as will be described below. Provide a proper seal for the air and solvent passages between the front section 12 and the cap 400. Similar to the annular ring 24 of the first embodiment, the cap 400 includes a plurality of circularly arranged air ports 28 forming a circular array of air jets surrounding the rotating atomizing cup 20.
It acts to shape the atomized liquid coating spray pattern 29 formed on the front edge or rim 42 of 20 and to jet it towards the workpiece to be coated as previously described.

As already noted, a rotary atomizing cup 20 extends forward from the forward section 12 of the bearing 10. The cup 20 is mounted so as to be rotatable around a shaft 23 of a rotary actuator (not shown). The cup drive shaft 23 extends through the bore 12b in the front bearing section 12. Similar to the case of the first embodiment, the liquid application control valve
A 33 is mounted on the rear surface of the front section 12 to control the flow of liquid coating material to the coating nozzle 30. The liquid paint, which has been ejected from the nozzle 30 and is slightly pressurized, enters the cup 20 and passes through this cup as already described in the first embodiment.

Inside the cavity 18 and on the rear face of the front bearing section 12, in addition to the application control valve 33, a single solvent valve 412 is installed instead of the inner and outer dual solvent valves 90, 92 of the first embodiment. is there. This valve 412 controls the flow of solvent into and out of the rotary atomizing cup 20, as described below.

The diameter of the frustoconical rotary atomizing cup 20 increases along the axis of the cup in the direction of the spray edge 42. Embedded in the outer surface 20d of this frustoconical cup 20 is a circular current-conducting flat ring element 102, which is preferably made of a semiconductor material. In accordance with one aspect of the present invention, the ring element 102 is housed substantially completely within the fit 404, and the cup 20 is located in the ring element so that an employee or object is at risk of impact. We try to reduce the possibility of contact with 102.
As in the first embodiment, the ring element 102 is electrically connected to the charging flat electrode located on the inner surface of the cup 20 as previously described. A housing 416 is used to enclose all operating elements and various conduits for coating material solvent and waste, and the high voltage electrical cable is suitable for rear mounting brackets rather than through sidewalls as shown in FIG. It is preferably disposed rearward through a large opening (not shown). This is to keep the conduits and cables as far as possible from the spray pattern 29 emanating from the edge of the atomization cup 20 so that coating material does not accumulate on them. It is more glossy and gives a uniform and clean appearance.

If it is desired to change the color of the liquid coating material sprayed from the device of the present invention, the coating valve 33 is solvent washed using a dump valve as previously described. According to another embodiment of the invention, cleaning the interior and exterior of the atomizing cup 20 of the liquid coating material with the solvent associated with the color change is a single solvent valve 41.
Done using 3. To this end, the valve 412 communicates with the bore 420 of the bearing section 12. The bore 420 includes a pair of branch lumens 422,424. One branch inner hole 422
The cup connected to the nozzle 32, as described above.
Clean the inside of 20. The other branch inner hole 424 is the gasket 4
It then extends through a suitable opening in 08 and abuts bore 426 of cup 400. This inner hole 426 is outside the cup 20
An outlet port 428 is provided on the wall of the inwardly tapering fitting 404 arranged to wash 20d.
The valve 413, as described above, is constructed approximately the same as the dump valve 30 and is actuated by a controlled pressurized air source to simultaneously clean the interior and exterior of the cup 20 with solvent prior to color change or regular cleaning.

According to the first embodiment, purging air is provided which minimizes the buildup of coating material on the surface of shaft 23. According to another embodiment, the bearing 25 was an air bearing. This is due to the normal air leakage of the air bearing (not shown) in the space 306.
Since the air flows along the shaft 23 like the above air purging means, the separate purging air passage such as the passage 302 already described in the first embodiment is unnecessary. This leaking airflow provides a positive air purge along the shaft 23 towards the cup 20, thereby preventing the paint from moving back along the shaft into the bearing (not shown).

Here, the inner wall 20d of the atomizing cup 20 according to another embodiment.
The path for high voltage electrostatic energy flowing from the gun resistor 76 to the charging electrode 102 embedded in the will be described in more detail. An annular conductor 430 that substantially encloses the cap 400 is disposed in an annular stepped groove 432 carved in the base or rear surface 434 of the cap 400. The conductor 430 is secured within the groove 432 by an insulating ring 436 that is sealed in the larger step groove with a suitable adhesive sealant such as epoxy. This conductor 430
Is connected to the conductive disk 438, preferably made of brass or other conductive corrosion resistant material, by soldering, brazing, or any other suitable means. The disk 438 fits into a mating portion 440 of an electrically insulative bushing 442, which in turn fits partially into the front end of the bearing post 62 that houses the gun resistor 76. The opposite ends of the bushing 442 fit into the pockets of the ring 436. The bushing 442 includes an axial bore 444 that receives the cylindrical protrusion 446 of the strut 62. Strut end 62a and protrusion
446 includes an inner bore 448 that communicates with the gun resistor 76. The bore 448 receives the hollow tubular bearing portion 450 of the conductive spring contact assembly 452. The bearing portion 448 is compressed and biased by a plunger 456 with a head 458 which abuts the disk 438 when the base of the bearing portion 450 abuts the gun resistor 76, thereby causing the gun resistor to move. Providing good electrical contact between the 76 and the disc 438, the disc 438 is connected to the next annular conductor 430.

Electrostatic energy is transferred from the conductor 430 to the charging electrode 102 by three charging resistors 210 of equivalent nominal resistance electrically connected in parallel between the charging electrode 102 and the conductor 430. According to another embodiment, the charging resistors 210 are physically mounted in the cap 400 at regular intervals in the circumferential direction. All of the resistors 210 are in sliding contact with the conductors 430 and in bores 460 located in the fittings 404 of the cap 400 in which the atomizing cup 20 is located. Each of these bores 460 is a ring element 102 of the atomizing cup 20.
At a location opposite to that of the mating portion 404 so that the free end 462 of the charging resistor acts as an electrode that terminates in close proximity to the semiconductor ring element 102. cap
By embedding charging resistors 210 within 400, the present invention serves to provide significant protection against the damage or misalignment of these resistors from accidental shock. Further, since the electrode leads 462 are located within the mating portion 404, the likelihood of these leads coming into contact with employees or objects is reduced, thus reducing electrical shock or mechanical damage. The opposite lead 464 of the charging resistor 210 has a groove 432
Lead 464 is connected to conductor 430 by soldering or any other suitable means through the reduced diameter portion of lumen 460 that intersects at the intersection.

In this way, the high voltage electrostatic energy is delivered to the gun resistor 76 by the high voltage cable 74 as previously described. This is then sent to conductor 430 by spring contact 452 and disk 438. From this conductor 430, electrostatic energy is carried by three charging resistors 210 to the charging electrode 102 of the atomizing cup, where the resistor 210 atomizes with the electrodes or the free end 462 of the resistor. It is electrically connected in parallel between the gap between the outer side of the cup 20 and the ring element 102 and the conductor 430. This electrostatic energy is then delivered across the gap between each of the electrodes 462 and the semiconductor ring element 102. This electrostatic energy is used to apply an electric charge to the coating material as in the case of the first embodiment.

The resistance values of the gun resistor 76 and charging resistor 210 are selected as previously described. As with the previously described embodiments, and in order to minimize the electrical energy stored capacitively in the atomizer of the present invention, all components of the atomizer are rotated from a remote source (not shown). It is preferably made of an insulating material, except for those made of a semiconductor material and / or a conductive material to convey electrostatic energy at high voltage to the paint charging electrode 102 of the oxidization cup 20.

The above-described other embodiment of the rotary atomization liquid spraying system of the present invention has a spray pattern forward toward the workpiece to be coated.
It has several features to assist in spraying 29 and to prevent build-up of coating material on the spray device itself, thereby increasing energy transfer efficiency and reducing spray device fouling. One such feature, namely, the plurality of air ports 28 that form an array of forward-directed air jets that surrounds the spray cup 20 to eject and shape the spray pattern 29 toward the object to be coated, has already been described. It has been explained. Furthermore, according to the invention, it is preferred that the spraying device of this embodiment further comprises at least one of the additional features described below.

The atomizing cup 20 is surrounded by electrostatic repulsion means, which is in the form of a substantially continuous, electrically conductive or, more preferably, semiconductive ring 470. The ring 470 is
For reasons which will become apparent later, it is buried in a groove 472 cut into the outer surface 402 of the cup 400 so as to be substantially flush with the groove 472 and not to interfere much with its outer shape. The ring 470 is electrically connected directly to the conductor 430 by a current-carrying pin 474, which energizes the ring 470 with a high voltage charge of the same polarity as the charge carried by the paint particles. This facilitates movement of the spray pattern away from the spray device and towards the workpiece to be coated.

It has been found to be useful in increasing transfer efficiency and avoiding buildup of paint material on the spray device by avoiding air vortices which tend to impede the forward movement of spray pattern 29. Another important aspect of the present invention is provided by having a curved aerodynamic profile on the outer surface 402 of the cap 400 as shown. The front portion of cap 400 defines a circular dome, which has a dome-shaped outer surface 40.
2 and a central fitting 404 in which the frustoconical atomization cup 20 is placed. It is not believed that the extent to which the cup 20 fits inside the cap 400 is critical to avoid reverse air vortices. In fact, the recess 404 only needs to have the outer surface 402 almost completely behind the cup 20 and thus may be eliminated. However, as previously described, the cup 20 is within the cap 400 about 1/2 to 2/3 of its entire length so that the conductive ring 102 and the electrode 462 are protected. It is preferable. The fitting part
The 404 tapers inwardly slightly larger than the wall of the cup 20, and thus the cup 20 and the fitting 404.
The gap between them is slightly narrower at the base than at the mouth. The above-mentioned tapered fitting portion 404 and the outer curved surface 4
The transition edge between 02 is not sharp, but rather has a large radius as shown. This aspect of the invention will be further clarified by the theory of operation provided below.

The atomizing cup 20 rotates at an angular velocity sufficient to atomize the paint material, typically between 10,000 and 40,00 RPM, so that the atomizing edge 42 with a larger diameter than the base 480 has a greater surface velocity than the base. Rotate. The air surrounding the cup 20 tends to move with the surface of the cup 20 due to frictional resistance, thus creating a pressure gradient along the outer wall 20d of the cup 20, which is generally parallel to the wall 20d. Along with, causing an air flow from the base 480 to the edge 42. It is believed that this airflow partially depressurizes the region near the base of the cup, so that the constituent airflow flows inwardly toward the base 480 of the cup 20 along the wall of the fitting 404. The shape of the cap 400, and in particular the shape of its outer surface 402, is selected so that under normal operating conditions the constituent air flow along its surface is in a generally laminar state. This is considered to prevent the generation of swirl in the vicinity of the cup 20, and if this is not the case, swirl will occur and the coating material will be sent back to the spraying device rather than being directed to the desired object.

[Brief description of drawings]

FIG. 1 is a side view of the rotary atomizing liquid spray coating apparatus of the present invention, particularly in section, and FIG. 2 is a cross section of the front section of the rotary atomizing liquid spray coating apparatus shown in FIG. It is a side view, showing the general relationship of the atomization cup and its drive, the air jet that shapes the atomization paint spray pattern, the high voltage circuit path, and the valve associated with the liquid paint flow path, FIG. 3 is a cross-sectional view taken along the line 3-3 in FIG. 2, showing a main part of the flow paths of the liquid paint and the solvent to the rotary atomizing cup, and the general arrangement of the respective valves. FIG. 4 shows a main part of an air path for shaping the liquid paint spray pattern and a conductor for applying a high voltage to the ring-shaped liquid paint charging electrode mounted in the atomizing cup, and FIG. A rotary atomization in a sectional view along line 4-4 in the figure FIG. 5 is a diagram showing a flow path of a solvent for cleaning the outside of the cup and a valve arrangement. FIG. 5 is a sectional view taken along line 5-5 in FIG. 3, showing an air flow for shaping the atomized liquid spray coating pattern. FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 1 showing the main portion of the tract, showing the struts between the front and rear bearing sections of the atomizer, the housing and the dump valve. FIG. 7 shows a general relationship, and FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 1, which is used for a solvent for cleaning the inside and outside of the liquid coating material and the rotary liquid atomizing cup. FIG. 8 is a view showing a general relation of the valve, and FIG. 8 is a sectional view taken along line 8-8 in FIG. 3, showing a solvent flow path and a valve for cleaning the inside of the rotary atomizing cup. FIG. 9 is a sectional view taken along line 9-9 of FIG. FIG. 10 illustrates a rear bearing section, stanchions, and various air and solvent nozzles, FIG. 10 is a front view of another embodiment of a discharge nozzle of a rotary atomizing spray applicator, and FIG. 11 is a partial sectional view taken along the line 11-11 in FIG. [Explanation of symbols for main parts] 10 ... Support 12 ... Front section 14 ... Rear section 16 ... Intermediate section 18, 34 ... Annular cavity 20 ... Rotating atomizing cup 22 ... Front section of front section 12 24 …… Annular ring 25 …… Turbine cavity bearing 26 …… Circular air passage or manhold 28 …… Air port 29 …… Spray pattern 30 …… Application nozzle 31 …… Rotating actuator 31a …… Inside rear section 14 Cavity 32,36,138,144,152,160,302 …… Passage 33 …… Liquid application control valve 38 …… Front cup cavity 40 …… Inner cup wall 42 …… Front spray edge 46 …… Charging electrode 50 …… Mounting bracket 52 …… Circular plate 54… … Color 56 …… Post 58 …… Set screw 60 …… Rear surface of rear section 14 62,64,66 …… Mounting post or support 62c …… Reduced diameter portion 62d, 100 …… Nut 70 …… With thread Lumen 74 ... High voltage insulation Cable 76 …… gun resistor 78,202,212,218b, 218c, 220b, 430 …… conductor 80 …… dump valve 82 …… flexible duct 86 …… disposable receptacle 102 …… ring element 104 …… pin 120 …… valve 122… … Stepped diameter bore 124 …… Valve seat insert mount 128 …… Valve seat insert 130 …… Ball valve element 132 …… Reciprocating rod 134 …… Piston 136 …… Air chamber 142 …… Liquid paint chamber 150 …… Seal 162,174,176,192 …… Hose 185 …… Pressurized air source 204 …… Electrode ring 216,218,220 …… Exterior 300,304 …… Port 400 …… Cap 404,440 …… Fitting part 412 …… Solvent valve 416 …… Housing 438 …… Conductive disc 442 ... Bushing

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Jiyoung Shear Press United States. 44074 Ohio, Oberlin, Vermilion Road 11643 (72) Inventor Arangie. Nobu United States. 44053 Ohio, Lorain, Apple Seed Drive 675 (72) Inventor James C. Murphy United States. 44147 Ohio, Broadevue Heights, Elmbruck Drive 3409 (56) References JP 61-61659 (JP, A) JP 34-19765 (JP, Y1)

Claims (10)

(57) [Claims] 1. A rotary atomizing liquid electrostatic spray applicator, comprising a support of insulating material with front, middle and rear sections, and a rotary atomizer of insulating material having a rotation axis. A first surface through which liquid paint can flow outward with respect to the atomization edge of the atomizer when the atomizer is rotated about the axis of rotation; and the first surface due to the atomization edge. A rotary atomizer having a second surface separated from the rotary atomizer, a circular ring-shaped charging electrode mounted on the first surface surrounding the rotation axis, and a second ring surface surrounding the rotation axis. A circular current-carrying element, means for electrically connecting the circular electrode and the current-carrying element, mounted on the rotary atomizer, driving the rotary atomizer to the front section of the support. The rotary atomizer incorporated in the bearing body to be freely mounted. Drive means for rotating about the axis of rotation, means comprising an insulating material for supplying liquid paint to the first surface of the atomizer when the atomizer is rotating about its axis, Further, a plurality of circumferentially-spaced electrical conductors secured to the front section of the support, the free-end portion closely spaced to the circular current-carrying element, wherein the secured conductors are Transfers electrostatic energy to the circular current-carrying element when energized by high voltage reduction, and the paint is directed outwardly toward the atomizing edge over the first surface abutting the charging electrode. An electrostatic spray coating device for a rotary atomizing liquid, comprising an electric conductor that facilitates contact charging of the liquid coating material supplied to the first surface when flowing out. 2. First and second solvent spray nozzles secured to the front section of the bearing proximate to the first and second surfaces, respectively, for cleaning the surfaces. A nozzle for injecting a solvent, a solvent valve means mounted in close proximity to the front section of the support, further connecting the solvent valve means and the solvent nozzle, and the solvent under the control of the solvent valve means. Apparatus as claimed in claim 1 further comprising solvent conduit means for supplying solvent to the nozzle to clean the first and second surfaces. 3. A rotary atomizing liquid electrostatic spray applicator, comprising a support of insulating material, comprising front, middle and rear sections, said front section comprising a front surface. And a rotary atomizer made of an insulating material having a rotation axis, the liquid paint being able to flow outward with respect to the atomization edge when the atomizer is rotated around the rotation axis. A rotary atomizer having a surface and means for charging a liquid coating material; and a rotary atomizer incorporated into the support body drivably mounted to the front section of the support body, Drive means for rotating the rotary atomizer about the rotation axis, and means for supplying liquid paint to the rotary atomizer when the atomizer is rotating about the rotation axis and is made of an insulating material. Detachable to the front section of the bearing A currently mounted annular ring comprising a rear surface abutting the front surface of the front section of the bearing and a front surface with a circular array of airways, the rear surface comprising: First
An annular insert that communicates with and supplies air to the circular array of air passages, thereby forming a circular array of air jets to shape a pattern of sprayed liquid paint; Furthermore, the rear surface of the annular ring includes an annular ring having a second annular fitting portion, a circular conductor mounted in the second annular fitting portion, and a plurality of stationary conductors mounted on the annular air ring. A peripherally spaced conductor, each comprising a rear end connected to the circular conductor and a front free end spaced adjacent to the rotary atomizer charging means, The front free end transfers electrostatic energy to the rotary atomizer when the static conductor is energized by a high voltage source connected to the circular conductor, and the paint is the rotary atomizer. The charging unit has a charging relationship with the charging unit. Electrostatic atomization of a rotary atomizing liquid composed of a conductor that facilitates charging of the liquid paint supplied to the surface of the atomizer when flowing outward toward the atomizing edge. Coating device. 4. A rotary atomizing liquid electrostatic spray applicator, comprising a generally cylindrical bearing with front and rear sections located on opposite sides of the intermediate section, said intermediate section being A bearing having a diameter substantially smaller than those of the front and rear sections and defining an annular cavity between these sections; and a rotary atomizer made of an insulating material having a rotation axis. A rotary atomizer having a surface through which liquid paint can flow outwardly toward the atomizing edge of the atomizer when the atomizer is rotated about the axis and with means for charging the liquid coating material. Drive means for rotating the rotary atomizer about its axis of rotation, a) an air turbine arranged in the cavity of the rear section bearing section, and b) the turbine and the rotation. A drive shaft connected between the atomizers and extending through an inner bore of the front bearing support section, and c) arranged in a cavity of the intermediate bearing support section to allow the shaft to rotate. A drive means comprising a bearing for supporting, and supplying liquid coating to the surface of the rotary atomizer when the atomizer is rotating about its axis of rotation, and a) the front of the bearing body. A liquid paint valve located in the annular cavity proximate to the section; b) a liquid application nozzle mounted in the front bearing support section proximate to the surface of the rotary atomizer; and c) the liquid. A liquid coating material supply means including a liquid coating conduit that connects the liquid coating nozzle to the liquid coating nozzle and supplies the liquid coating nozzle to the liquid coating nozzle under the control of the liquid coating valve; A pedestal is a conductor resting on a bearing section, comprising a free end closely spaced to the circular conducting element, the quiescent conductor being static when energized by a high voltage source. Electrical energy is transferred to the electrically conductive element such that the paint is in charge relationship with the charging means toward the atomizing edge under centrifugal force generated by the rotation of the rotary atomizer. An electrostatic spray coating device for a rotary atomized liquid, comprising a conductor for facilitating charging of the liquid coating material supplied to the surface when flowing outwards over the surface. 5. A solvent application nozzle statically mounted on the front section of the front bearing proximate to the surface of the rotary atomizer for spraying its solvent to clean the surface, and the bearing. A solvent valve mounted in the annular cavity proximate the front section of the vehicle, further connecting the solvent valve to the solvent nozzle to supply solvent to the solvent nozzle under the control of the solvent valve to rotate the solvent. The apparatus of claim 4 further comprising solvent conduit means for cleaning the surface of the atomizer. 6. The apparatus of claim 5 wherein said solvent and liquid application valve is formed substantially of an insulating material. 7. A rotary atomizing liquid electrostatic spray coating device, comprising a support and a tubular rotary atomizer having a frnsto-cone shape, which is composed of an insulating material supported by the support. The atomizer cup has an inner surface and an outer surface extending between a rear edge and a front atomization edge, the diameter of the front edge being larger than the diameter of the rear edge and having an axis of rotation. And a means for supplying a liquid coating material to the atomizer cup to form a spray coating pattern of the coating material, an electrostatic charging means for imparting an electrostatic charge to the coating material, and a front section of the support. A cap included, having a generally convex outer surface along at least a portion thereof, the outer surface of the atomizer when the rotary atomizer rotates about the axis of rotation during normal operation. Providing an almost laminar flow of air across A cap made, an air flow means arranged behind the atomization edge to form an air flow generally flowing forward, and further biased to the same polarity of the electrostatic charge applied to the coating material. And a repulsion ring configured so that the outer surface of the cap, the air flow means,
And an electrostatic spray coating device for a rotary atomizing liquid, in which the repulsion ring cooperates to form the coating pattern generally in front of the rotary atomizer. 8. The apparatus according to claim 7, wherein said cap further comprises a recess and said rotary atomizer is at least partially disposed within said recess. 9. The air flow means comprises at least one air passage arranged behind the atomizing edge, and further means for supplying pressurized air to the air passage. The apparatus according to item 7. 10. The air passages are arranged in an array surrounding the rotary atomizer to form a corresponding array of air jets to shape the spray pattern and generally inject forward. The apparatus according to item 9.