Improvements in and relating to spray guns

摘要

A tribo-electric powder spray gun includes a diffuser for mixing powder with a conveying gas, a charging portion downstream of the diffuser, and a sprayhead at the outlet of the charging portion for dispensing the charged powder. The charging portion has an inner core removably positioned within a hollow outer cylinder with an annular gap formed therebetween providing a charging flowpath for the powder. The inner core and the outer cylinder have undulating or wavy charging surfaces made of an electrically insulating material, so that the annular gap provides a tortuous path for the powder, enhancing powder contact and the charged imparted to the powder. Grounding is provided by surface conduction of the electrically insulating contact material through a ground ring located outside the powder path at the inlet to the charging portion where the greatest amount of charging occurs. Locating the ground ring outside the powder path keeps the ground ring clean and minimises the amount of charging surface. The inner core and the outer cylinder are longitudinally symmetrical to facilitate re-assembly.