Tribo-electric powder spray gun

A tribo-electric powder spray gun which comprises:

• means for mixing powder with a conveying gas;
• a charging section downstream of the mixing means, the charging section including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core positioned within a hollow outer cylinder, an annular gap being formed between the outer cylinder and inner core providing a friction charging flowpath for the powder, at least one of the inner core and outer cylinder being electrically connected to ground through an annular ground ring positioned externally to the flowpath of the powder, the ground ring located at the inlet of the charging section and extending along substantially less than half of the charging section, whereby the powder is frictionally charged by repeated contact with the cylinder and the core during flow through the annular gap;
• and
• a sprayhead downstream of the charging section for dispensing the charged powder.

A tribo-electric powder spray gun which comprises:

• means for mixing powder with a conveying gas;
• a charging section downstream of the mixing means, the charging section including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core positioned within a hollow outer cylinder, the inner core and the outer cylinder each having inner charging surfaces, an annular gap being formed between the outer cylinder and inner core providing a friction charging flowpath for the powder, at least one of the inner core and outer cylinder being electrically connected to ground through a ground electrode located externally to the flowpath of the powder, the ground electrode being positioned at the inlet to the charging section, a second gap being present between elements forming part of the powder flowpath, the second gap being positioned adjacent to the ground electrode, there being at least one ring made of electrically insulating material located between the inner core and the outer cylinder, the ring being in contact with the charging surfaces, whereby the powder is frictionally charged by repeated contact with the cylinder and the core during flow through the annular gap;
• and
• a sprayhead at the outlet of the charging section for dispensing the charged powder.

A tribo-electric powder spray gun which comprises:

• means for mixing powder with a conveying gas;
• a charging section downstream of the mixing means, the charging section including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core having at least one inner core member positioned within a hollow outer cylinder having at least one outer cylinder member, the outer cylinder member having an external inner dimension and the inner core member having an external outer dimension, the outer dimension of the inner core member and the inner dimension of the outer cylinder member each having a plurality of increases and decrease providing undulating inner charging surfaces, the outer dimension of the inner core member increasing at generally the same longitudinal position that the inner dimension of the outer cylinder member increases, the outer dimension of the inner core member decreasing at generally the same longitudinal position that the inner dimension of the outer cylinder member decreases, an annular gap being formed between the outer cylinder member and inner core member providing a friction charging flowpath for the powder, at least one of the inner core member and outer cylinder member being electrically connected to ground through a ground electrode located externally to the flowpath of the powder, whereby the powder is frictionally charged by repeated contact with the cylinder member and the core member during flow through the annular gap;
• and
• a sprayhead downstream of the charging section for dispensing the charged powder.

A tribo-electric powder spray gun which comprises:

• means for mixing powder with a conveying gas;
• a charging section downstream of the mixing means, the charging section including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core positioned within a hollow outer cylinder, the outer cylinder including an outer wear cylinder formed of a stiffening element with a contact layer forming an outer charging surface, the inner core including an inner wear cylinder formed of a stiffening element with a contact layer forming an inner charging surface, the stiffening elements being made from a NEMA Grade G-10 material, an annular gap being formed between the outer charging surface and the inner charging surface providing a friction charging flowpath for the powder, whereby the powder is frictionally charged by repeated contact with the charging surfaces during flow through the annular gap;
• and
• a sprayhead at the outlet of the charging section for dispensing the charged powder.

A tribo-electric powder spray gun, which comprises:

• a body;
• means mounted on the body for mixing powder with a conveying gas;
• a charging section removably attached to the body downstream of the mixing means, the charging section including means for electrically charging the powder as it flows therethrough, the charging means comprising an inner core positioned within a hollow outer cylinder, the inner core being positioned relative to the outer cylinder by at least one ring located between the inner core and the outer cylinder, an annular gap being formed between the outer cylinder and inner core providing a friction charging flowpath for the powder, whereby the powder is frictionally charged by repeated contact with the cylinder and the core during flow through the annular gap, a tubular extension fitting over the outer cylinder and removably attached to the body to releasably secure the inner core and the outer cylinder to the body;
• and
• a sprayhead at the outlet of the charging section for dispensing the charged powder.