Electrostatic Coating Apparatus Cover Member Deposition
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Solution Overview
Problem
Conventional electrostatic coating apparatuses face issues with paint deposition on the cover member due to induced positive charge on paint particles, leading to reduced insulation and frequent interruptions for cleaning, and spark discharges between external electrode members and the rotary atomizing head.
Innovation Solution
The electrostatic coating apparatus features a conductive rotary atomizing head and shaping air ring connected to earth, with an electric field concentrating portion on the shaping air ring to generate a secondary corona discharge around air outlet holes, ensuring corona ions are supplied to paint particles to maintain negative charging and prevent deposition on the cover member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electrically insulating cover member is used to enshroud the motor, then high voltage electrostatic charges are prevented from leaking to earth potential, but paint particles with induced positive charge deposit on the cover member surface, reducing insulation and requiring frequent cleaning interruptions
Solution Approach 1:
The invention applies preliminary anti-action by introducing negative corona ions to neutralize the induced positive charge on paint particles before they reach the cover member. The external electrode assembly generates negative corona discharge that charges paint particles negatively, preventing their attraction to the negatively polarized cover member surface, thus preventing deposition before it occurs
Solution Approach 2:
The invention converts the harmful induced positive charge on paint particles into a beneficial negative charge through corona discharge. The external electrode assembly uses high voltage to generate corona ions that electrify the paint particles, transforming the original harmful electrostatic attraction to the cover member into beneficial electrostatic repulsion, while also enabling controlled deposition on the workpiece
2Productivity
If a high voltage is applied to the external electrode assembly to electrify paint particles, then deposition efficiency on the work piece is improved, but spark discharges occur between the external electrode members and the rotary atomizing head
Solution Approach 1:
The invention introduces an intermediary mechanism by using corona discharge as a intermediate step between the high voltage external electrode and the paint particles. Instead of direct contact or proximity discharge, the external electrode generates corona ions that serve as intermediaries to transfer charge to paint particles, enabling high voltage application without direct spark discharge to the atomizing head
Solution Approach 2:
The invention applies parameter changes by controlling the voltage application mode - using corona discharge regime instead of direct breakdown discharge. By maintaining the external electrode voltage in the corona discharge range rather than allowing it to reach spark breakdown levels, the system achieves effective paint particle electrification while preventing harmful spark discharges
3Productivity
If the shaping air ring is provided with air outlet holes to atomize paint, then spray pattern is improved, but electric field concentration at the holes causes secondary corona discharge and unstable electrical conditions
Solution Approach 1:
The invention converts the harmful electric field concentration at air outlet holes into a beneficial effect by utilizing the resulting secondary corona discharge. The sharp edges of the air outlet holes naturally concentrate the electric field, and instead of viewing this as a problem causing instability, the invention harnesses this concentration to generate additional negative corona ions that enhance paint particle charging and are carried by the shaping air flow to the spray zone
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively prevents paint deposition on the cover member by maintaining negative charging of paint particles, enhancing deposition efficiency on the work piece while stabilizing the corona discharge and reducing electrical discharges on the shaping air ring.
Implementation Method 1
corona ions are generated by a corona discharge, and a negative ionization zone is formed by these corona ions
Implementation Method 2
paint particles which are electrified to opposite polarity are also formed by induction charging
Implementation Method 3
the charged paint particles are urged to fly toward the work piece and deposit on surfaces of the work piece which is connected to the earth
Data Source
AI summary
A rotary atomizing head is mounted on a fore end side of a motor. A shaping air ring having a plurality of air outlet holes at fixed intervals is provided on a rear side of the rotary atomizing head. Outer surfaces of the air motor and outer surfaces of the shaping air ring are enshrouded over the entire circumference by a cover member formed of an electrically insulating material. An external electrode assembly is provided radially outwardly of the cover member. An annular projecting portion which projects forward is provided on the shaping air ring over the entire circumference. The air outlet holes are open in a fore distal end of this annular projecting portion. As a result, a corona discharge can be generated by allowing an electric field to be concentrated at the fore distal end of the annular protecting portion.