Paint spray housing for reducing paint buildup

Details Paint spray housing for reducing paint buildup Paint spray housing for reducing paint buildup

2000-02-03

2001-10-09

Scherbel, David A. (Department: 3752)

Fluid sprinkling, spraying, and diffusing

Processes

Including electrostatic charging

C239S690000, C239S693000, C239S695000, C239S700000, C239S703000, C239S706000, C427S421100, C427S480000

Reexamination Certificate

active

06299073

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to electrostatic spray coating, and more specifically, to an improved spray head for spray coating.
BACKGROUND
Various products including automotive vehicle are typically painted using an electrostatic spray process. An electrostatic spray process uses a conductor that applies a potential difference between paint spray particles and the device to be painted. A modification of electrostatic spraying is a bell-atomizer spray process. For large products such as automotive vehicles, these systems are typically automated.
In the bell-atomizer process, electrostatic forces are combined with shaping air to direct paint toward the component to be painted. An application head has a bell cup that rotates at speeds in excess of about 30,000 rpms. The rotation of the bell cup acts to atomize the paint which is directed through the cup. Once atomized, the paint interacts with the shaping air through drag forces that divert the paint toward the target. An electric potential is applied to increase the axial momentum of the particles to increase the paint transfer efficiency.
One problem with known bell-atomizer automated spray processes is that due to side drafts, downdrafts, shaping air turbulence and interaction with the target, some air recirculates about the support housing and bell housing. As a result, paint may drip from the support housing and bell housing onto the component being painted. If this occurs, the component typically must be repainted and thus the cost of the component is increased.
To prevent drips from accumulating on the support housing and the bell housing, the automated process is typically stopped at frequent intervals so the support housing and bell housing can be cleaned. This also increases the cost of the product, particularly in assembly plants operating at full capacity. One known device for electrostatic spraying has a planar electrostatic shield surrounding the paint application head. The planar shield is spaced apart from the application head. Therefore, it is believed that the movement of the application head will result in air currents that cause paint to bypass the shield and buildup on the paint application head. Particularly, it is believed that paint will buildup on the sides of the application head resulting in the aforementioned drips. The buildup may be increased by spray from adjacent heads.
It would therefore be desirable to provide an improved paint application process that reduces the amount of maintenance as well as reduces the amount of repair costs for paint drip from the application head to the components to be painted.
SUMMARY OF THE INVENTION
It is therefore one object of the invention to improve bell-atomizer type electrostatic spray process that reduces the aforementioned problems by providing a bell atomizer having a bell housing extends from the front surface of the support housing and has a paint channel therethrough. The paint channel is fluidically coupled to the paint source. The bell-atomizer produces charged paint particles. An electrically conducted film is applied to the surface of the bell housing. The film is coupled to the power source and generates an electric field that in turn produces a force on the paint particles away from the bell housing.
In another aspect of the invention, conductive tape may be applied to the surfaces of a support housing to prevent paint buildup thereon.
In another aspect of the invention, a method of painting a part comprises the steps of: applying an electrically conductive tape to a bell housing of an atomizer head; generating charged paint particles through a bell atomizer; electrically coupling the tape to a power source; and, generating an electrical field and thereby an electrical force on said particles away from the bell housing.
One advantage of the invention is that the adhesive tape is easily replaced resulting in reduced clean up time and consequently in a less expensive paint process. Another advantage of the invention is that the paint transfer efficiency to the part has been increased. This is a particularly advantageous aspect with respect to a high volume mass production facility where incremental changes can result in significant cost savings.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.


REFERENCES:
patent: 4748043 (1988-05-01), Seaver et al.
patent: 4811906 (1989-03-01), Prus
patent: 4977000 (1990-12-01), Murayama et al.
patent: 5169673 (1992-12-01), Demeny et al.
patent: 5346139 (1994-09-01), Davis et al.
patent: 5527564 (1996-06-01), Napadow et al.
patent: 5738727 (1998-04-01), Cebola et al.

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