JPH0685896B2 - A device for spraying cooled electrostatically charged particles onto the surface of a large object. - Google Patents

Description

FIELD OF THE INVENTION The present invention relates to an apparatus for spraying cooled, fine particles onto the surface of large metal objects having cracks and pores. In particular, the invention relates to a device for cooling electrostatically charged particles and spraying them onto large metal objects. In particular, the invention relates to a device for maintaining this desired high temperature while rotating this large object while spraying the cooled particles.

Prior Art Clarence W. Patented October 18, 1966. Clarence W. Forestek, U.S. Pat. No. 3,279,936, is directed to treating metal surfaces with cracks or pores with perfluorocarbon polymer particles to deposit and plug the particles into the pores. There is.
While raising the temperature of the metal to thermally expand the pores, when the cooled particles are brought into contact with this, the particles and the metal enter an equilibrium temperature state, the particles expand and the pores contract, The particles are embedded in the pores.

United States Patent No. 4,051,275, issued September 27, 1977
The issue is also Clarence Table. Granted to Forestec, this patent applies the cooling particles described above in the form of a fluid stream carrying the particles at a pressure of 30 psi (2.1 kg / cm ² ) to 120 psi (8.4 Kg / cm ² ). The first particles are struck to make them dense, and the additional particles are allowed to adhere to the gaps or spaces created by this compression solidification, the temperature of the additional particles being at least 100 ° F (55 ° F).
C.) below the temperature of the metal surface, these additional particles are also intended to be retained in the crack when they reach the equilibrium temperature.

OBJECT OF THE INVENTION It is an object of the present invention to aid in the deposition of fine particles in the cracks and pores of the surface of metal objects, especially large metal objects, by electrostatically charging these particles.

It is also an object of the present invention to arrange the object so as to be charged with diametrically opposite static electricity so as to be filled with particles.

Also, put electrostatically charged particles in the blast of the fluid medium,
It is also one of the objects of the present invention to direct the particles charged with static electricity to the metal surface by this wind and introduce them into the cracks and pores.

It is also possible to increase the space where additional particles adhere by compressing and solidifying the electrostatically charged particles on this blast that already exist in cracks and pores so that the free space increases. This is one of the purposes of the present invention.

It is also possible to rotate an object, especially a large object, on an axis to repeatedly expose the adherent particles to compression solidification, creating an additional free space for additional adhesion of the cooled particles. It is one of the purposes.

Another object of the present invention is to provide a device for rotating a large object while spraying the electrostatically cooled particles onto the large object.

DISCLOSURE OF THE INVENTION According to the present invention, cooled fluoroparticulates of perfluorocarbon polymers or graphite, molybdenum sulphate, boron nitride or other suitable electrostatically charged particles, metal objects having cracks or pores on their surface, in particular Application to large objects involves rotating the metal object on its axis and maintaining the metal object at a high temperature while cooling and charging electrostatically charged particles such as perfluorocarbon polymer to the surface of the metal object. It has been found that by applying it can be achieved easily and properly. Preferably, the metal object is substantially enclosed within the hood or shield to reduce radiant heat loss from the object. While maintaining the object at the desired high temperature, a stream of cooled, electrostatically charged particles suspended in dry air or an inert gas such as helium, nitrogen, argon, etc. is applied to the surface of this metal object. These particles are made to collide with and adhere to the cracks and pores, and in this way, the particles previously attached to the cracks and pores are densely compressed and solidified.

The electrostatic charge applied to particles is 50 kilovolts (kv) to 15
A range of 0 kilovolts (kv) is convenient, but the official one is about 100 kv. Suitably these particles are given a positive charge and the object is given a negative potential. This is preferable, but the positive and negative signs may be reversed. Such charging may be accomplished by any suitable means, but a particularly advantageous device is a spray gun such as is used in electrostatic spray coating. This spray gun has an internal passage through which the injection medium passes,
In this case, particles suspended in dry air or an inert gas are mixed with the cooled gas. Keep a cooling medium such as liquid nitrogen or solid carbon dioxide in the adjacent container,
The cooling gas, which is preferably the same gas used as the suspending medium, is now cooled with the cooling medium, and this cooled gas is passed through by the medium in which the electrostatically-charged particles are suspended through the cooling device. This is cooled by introducing it in between. Before cooling this gaseous suspension, the particles are charged with static electricity. This is done by passing a floating body of particles through the electrolysis formed by electrodes located in the charging chamber of the spray gun. An appropriate charge for this electrode is maintained by the high voltage transformer and the high voltage capacitor.

The cooling gas introduced into the suspension is -20 ° C (-4 ° F) to -130 ° C (-202 ° F), preferably -50 ° C (-58 ° F) to -120 ° C (-184 ° F). Is. The method of cooling the suspended gas and suspended particles may include any suitable means of providing this cooling condition, but one particularly effective means is to attach an attachment to the front of the spray gun. It is a cooling device described later.

The spray gun could be any one of the many commercially available spray guns suitable for spraying electrostatically charged particles. A particularly suitable spray gun is
Commercially available under the trademark "GEMA", it has four electrodes and a high voltage power grid containing a high voltage transformer and a set of high voltage capacitors. A cooling attachment is attached to the front or spray end of the spray gun. A spray gun sprays electrostatically charged airborne particles through a cooling device passage,
And it goes out beyond the collision diffusion conical plate.

The polymer suspended stream is preferably injected from a spray gun at a pressure of 15 psi (1 atm) to 150 psi (10 atm). Suspended particles in the suspending medium are preferably maintained in a storage tank. In this reservoir, the particles are vigorously agitated by supplying nitrogen or other gas. When attempting to apply this stream of airborne particles, a suitable valve is opened to allow the gas to flow out with the airborne particles and bring them to the electrostatic charging chamber of the spray gun before mixing with the cooling gas medium. As means for supplying and suspending polymer particles in gas, a venturi, a screw feed,
Various other means such as blowers, pumps, etc. can be used.

Also, large objects of various shapes can be treated by the method according to the invention, cylindrical objects being particularly suitable for this. For example, there is a large roll with a diameter of 1,800 mm (70.86 inch) or more and a length of 2,500 mm (98.4 inch) or more. If the object does not have an end wall, or a cylindrical or other shaped double-ended support, such a support is attached to allow the cylindrical or other shaped object to rotate about its axis. The support shaft end is mounted concentrically with the axis and is preferably supported by roller bearings and is preferably motor driven at a controlled speed of about 0.1 rpm to 10 rpm.

As mentioned above, hoods or other partial covers have been used to reduce heat loss to objects. During the spraying operation, suction by exhaust air is exerted under the hood to remove the gas that suspends the particles and the particles that remain suspended here. Particles that fall under the object can be collected and reused if desired.

The desired temperature of the object to be treated is obtained by directing a stream of hot air at this object rotating under the hood. Infrared or other suitable heating means can be used if desired. The hood has slots or openings along the length of the object and parallel to its axis, through which the electrostatic spray is applied. If desired, sliding or hinged doors may be provided to cover this opening when spraying is not performed. Object temperature is 38 ° C (100.4 ° F)
Temperatures as low as possible, but preferably around 150 ° C
It is best to maintain a temperature of (302 ° F) to 180 ° C (356 ° F). The heated air or other heating means is closed during the blowing operation, and the hood is also moved after the blowing operation to cool the object. The temperature of the cooled particles during the spraying operation is at least 55 ° C (130.
5 ° F.), preferably at least 165 ° C. (329 ° F.).

A roller or cylinder having a thickness of 25.4 mm (1 inch), an outer diameter of 1,800 mm (70.86 inch), and a length of 2,500 mm (98.4 inch) generally requires about 12 hours for the temperature to drop from 150 ° C to 60 ° C. When three workers manually spray such rolls using a hand-held spray gun in the spraying operation, it takes about 30 minutes to complete the spraying.
If desired, multiple spray guns may be fixedly used on the rack. The rack is moved manually or by mechanical means in a path parallel to the axis of the object. The rate of such translation is adjusted according to the number of revolutions of the object so that the sprayed particles completely cover the surface of the object.

The mottled appearance of the surface of the object indicates that the particles are not fully in the cracks and pores. The spraying is continued until such mottle is no longer visible. In some cases, satisfactory results were obtained by spraying while the object was rotated 5 times. Preferably 20 revolutions or more will produce the desired result. In general, 120 revolutions or more will produce no additional benefit.

Felt strips, brushes or soft rollers extend down the entire length of the object from the hood down to the surface of the object beyond the spray area, which injects particles into cracks and pores, cracks and cracks. Wipe off the particles on the surface of the object where there are no pores. This wiping can be carried out continuously or periodically after the spraying operation. Generally, it is sufficient to carry out this wiping operation at least 4 to 5 times or more.

During the spraying operation, it is advantageous to maintain the spray gun about 300 mm (12 inch) to 500 mm (20 inch) away from the object to be sprayed. It is generally sufficient to carry out the spraying while the object makes 20 to 100 revolutions. As mentioned above, the spraying is carried out continuously or intermittently until the mottle is no longer visible.

The velocity of particles toward an object is determined by the pressure of the floating gas and the voltage of the electrostatic field. It is desirable to supply the particles to the gas either before the gas enters the spray gun or while it is passing through the spray gun, but to supply the particles into this gas stream after the gas is released from the spray gun. Would also be possible. In this case, the particles are charged with static electricity on their way to the surface of the object. However,
More preferably, the particles are charged with static electricity before cooling, or the cooled gas is mixed with a floating body of electrostatic particles to cool the particles.

4.7 ^-10 when grams or 5 micron sized particles was exposed to approximately 80kv to voltage 100kv between the spray gun and the object, the initial velocity of the particles becomes about 11 meters / sec, 0.09 in the object near To 0.10 meters / second. Smaller particles, such as 1 micron or less, are more convenient because the final velocity due to the electric field will be faster than for larger particles.

In electrostatic charging, it is advantageous to provide a pair of spaced-apart electrodes along the path of airborne particles and to apply a voltage of about 20 kv across the gas flow direction between each pair of electrodes. is there.

Embodiment In FIG. 1, a roll 1 is supported by a shaft 2. This shaft 2 rests on bearings 3, 3. The bearing 3 includes a leg 7 ', a crossbar 6 and a base plate 7
It rotates on the support pin 4 fixed to the support base 5 having the. The shaft 2 is rotated by a belt or chain 8 driven by a power source (not shown) to give the roll 1 the desired number of rotations. The hood 9 is located above the roll 1 and has an exhaust hole 10.
If desired, this hood may extend further down to enclose most of the roll 1. A catch basin 12 is provided in the lower region of the roll and surrounds the lower part of the roll 1. Like the hood 9, the catch basin 12 reduces heat loss from the roll 1 and at the same time catches particles falling from the surface of the roll 1.

FIG. 2 is a side view of the device shown in FIG. The heating device 11 is shown as being located on one side (or rear) of the roll 1 with the support means 11 '. The spray gun is located on the opposite side (or front) of the roll 1 (only the tip of its attachment is shown in dashed outline). Felt or soft brush 13 roll 1
Is arranged next to the upper part of the spraying area and has a supporting means.
Held by 14.

FIG. 3 is a side view of the spray gun 18 and its attachment 19. The attachment 19 is designed to cool the gas flow after the particles suspended in the gas flow are charged with static electricity. The cooling nozzle 15 is preferably made of polytetrafluoroethylene (PTFE). Attach metal ring or band 16 19
The gas inlet duct 20
Is held in place. A cooling gas such as nitrogen is supplied from the cooling tank 21 to the attachment 19. The cooling tank 21 is made of rigid polyurethane foam, and the heat exchange coil 22 is arranged inside the cooling chamber 23 inside. The heat exchange coil 22 is preferably made of a copper tube having a diameter of about 10 mm. The cover 24 covers the cooling chamber 23 to reduce heat input. Desirably, the refrigerant contained in the cooling chamber 23 is dry ice (solid carbon dioxide) or liquid nitrogen. When the gas inlet line 25 is opened, nitrogen gas or other suitable gas is used as a heat exchange coil for cooling.
Flowing through 22, the cooled gas (preferably at a temperature of -70 ° C to -140 ° C) flows through hose connector 26 to gas inlet duct 20. This gas inlet duct 20
Is connected to and communicates with a recess 20 ′ that extends along the entire circumference of the attachment 19, and supplies the cooling gas to the inside of the mixing chamber 15 ′ of the attachment 19 via the passage 27.

FIG. 4 is a plan view of the spray gun 18 and its attachment 19 shown in FIG.

FIG. 5 is a sectional view taken along the line 5-5 in FIG. The attachment 19 has a gas inlet duct 20 fixed in place on the cooling nozzle 15 and sealed by a band 16. The hose connector 26 shown in FIG. 3 supplies cooled gas to this gas inlet duct 20. The cooled gas passes from the gas inlet duct 20 through the passage 27 to the mixing chamber 15 '.
to go into. The electrostatically charged particles in this mixing chamber 15 'are cooled by the gas to a desired low temperature, preferably about -120 ° C (-184 ° C).
Cooled to ° F) and sprayed on a rotating roll or other large object in front of the spray gun. This object is
Grounded to attract and attach electrostatically charged particles. The conical collision plate 29 is the exit end of the cooling nozzle 15.
The particle cloud can be adjusted to a desired size by moving the rod 31 in the longitudinal direction and setting the conical collision plate 29 at an appropriate position. 70kv to 12
A high voltage, which is preferably in the range of 0 kv, is generated in the generator 32, is sent via the wire 33 into the interior of the spray gun and is applied via the switch 34 to the high voltage series capacitor 35. This high voltage is applied to the electrode 37 via the high voltage transformer 36. On the other hand, particles of desired size and desired type are stored in the storage tank 38 in a suspended state by the gas introduced from the line 39 at the bottom of the storage tank 38. This gas flow passes between the electrodes 37 of the charging chamber 17 of the spray gun 18 from the storage tank 38 through the hose 40, and the floating particles are charged with static electricity. The charged suspended particles are mixed in the mixing chamber 15 'of the cooling nozzle 15 of the attachment 19 by the inlet duct.
It is mixed with cold gas introduced from 20 and cooled to a suitable low temperature.

FIG. 6 is a side view of the device shown in FIG. 2 with the addition of a hood extension 9'extending around the roll. Instead of the heating device shown in FIG. 2, the heating device 11 and its supporting means 11 ′ support the wheel 41 via the supporting part 42.
It is portable using the means to keep it at 1 '. The heating source is not shown, but could be an electrical method, such as a hot wire or heating lamp, or hot air supplied to the heating device 11 in a flexible duct. When the rolls are properly positioned, a portable spray gun, not shown in this figure, is moved to the position where the heating device has withdrawn and the soft brush 13 is positioned on top of the spray gun. In this case, it is desirable to rotate the roll in the opposite direction to that shown in FIG. Although the embodiments of the present invention have been described in detail above, it is obvious that modifications can be made thereto without departing from the spirit and scope of the present invention. Also, the invention is not intended to be limited to the particular embodiments, except as limited by the claims of the invention.

[Brief description of drawings]

1 is a front view showing an embodiment of the present invention, FIG. 2 is a side view of FIG. 1, FIG. 3 is a side view of a spray gun and its attachment, and FIG. 4 is a plan view of FIG. FIG. 5 is a sectional view taken along line 5-5 of FIG. 4, and FIG. 6 is a side view showing another embodiment of the present invention. 1 ... Roll, 2 ... Axis, 3 ... Bearing, 4 ... Support pin, 5 ... Support base, 6 ... Crossbar, 7 ... Base plate, 7 '... Leg, 8 ... Chain, 9 ...... Hood, 9 '... Extension, 10 ... Exhaust hole, 11 ... Heating device,
11 '... Supporting means, 12 ... Catch basin, 13 ... Felt or soft brush, 14 ... Supporting means, 15 ... Cooling nozzle, 15' ... Mixing chamber, 16 ... Metal ring or band, 17 ... … Charging chamber, 18 …… Spray gun, 19 …… Attachment, 20 …… Gas inlet duct, 20 ′ …… Concave, 21
…… Cooling tank, 22 …… Heat exchange coil, 23 …… Cooling chamber,
24 …… cover, 25 …… gas inlet line, 26 …… hose connector, 27 …… passage, 29 …… conical collision plate, 30 …… outlet end, 31 …… rod, 32 …… generator, 33 ...... Electric wire, 34
...... Switch, 35 …… Series capacitor, 36 …… High voltage transformer, 37 …… Electrode, 38 …… Storage tank, 39 …… Line, 40
...... Hose, 41 ...... Wheels, 42 ...... Support section.

Claims (9)

[Claims] 1. An apparatus for spraying cooled fine particles to pores or cracks on a metal surface of a large object to compress and solidify it, wherein (a) the large object is supported and controlled about its axis. Means for rotating at a number of revolutions; (b) heating for heating the large body until the temperature of the metal surface is sufficient to give the desired increments in the size of the pores and cracks for receiving the particles. An apparatus, (c) means for charging particles floating in a gaseous medium with static electricity, and (d) second charging means for charging the large object to a potential opposite to the potential charged on the particles. (E) cooling means for cooling the electrostatically charged particles, and (f) spraying the cooled and electrostatically charged gas suspended particles onto the heated metal surface of the large object. The rotatable large object is configured to combine a particle with pores or cracks on a metal surface of the large object to adhere to pores and cracks, and the rotatable large object is a substantial part of the upper region of the object from the object. By a catch basin surrounded by a hood which reduces heat loss, and which substantially shields a substantial part of the lower region of the body from particles falling from the surface of the body and further shields the body from heat loss. Enclosed, the heating device and the spraying means are both portable, allowing each of these devices and means to be moved to a position adjacent to the object, and after moving away from the object, It is subsequently characterized in that the other device or means can likewise be moved to an adjacent position so as to fulfill its role. And the device. 2. A device according to claim 1, characterized in that the heating device comprises means for directing heated gas to the metal surface of the object. 3. The device according to claim 2, wherein the hood has an exhaust duct connected to it, through which the heating gas flows after flowing over a portion of the large object. The device characterized in that 4. The device according to claim 3, wherein the adjacent positions are the same position with respect to both the spraying means and the heating device. 5. A device according to claim 4, wherein the sprayed particles are arranged to come into contact with the object after they have been located on the metal surface of the object, where they come into contact by contact with the object. An apparatus, further comprising brush means for dispensing particles into the cracks and pores and for wiping the particles from the surface of the object between the cracks and pores. 6. A device according to claim 1, characterized in that said adjacent position is the same position for both said spraying means and said heating device. 7. A device according to claim 6, wherein the sprayed particles are arranged on the metal surface of the object, where the contact with the object causes the particles to be dispensed into the cracks or pores. And further comprising brush means for wiping the particles from the surface of the object between the cracks and pores. 8. The apparatus of claim 6 wherein said heating device includes means for directing heated gas to the metal surface of said object. 9. An apparatus according to claim 6 wherein said heating device includes means for directing heated gas to the metal surface of said object, and said hood being connected thereto. And heating the heated gas over a portion of the larger object before exiting the exhaust duct.