Spray applicator

A spray applicator for receiving intermittent delivery of distributable product, receiving a stream of propellant gas, and applying said received propellant gas to spray said received distributable product during periods when the distributable product is being delivered, and cleanly terminating delivery of the distributable product during pauses in delivery of the distributable product, comprising:

• a nozzle piece having a substantially uniform longitudinal nozzle bore between a front outlet end and a rear inlet end thereof;
• a primary air chamber at said rear inlet end of said nozzle piece, communicating with said nozzle bore at a front side of said primary air chamber;
• a pausible source of distributable product carried by said spray applicator;
• a material transfer tube connected, in use, to receive distributable product from said source of distributable product and to deliver the received distributable product to the primary air chamber to be sprayed through the nozzle bore, a front end of said material transfer tube being aligned with the nozzle bore and delivering distributable product into a rear side of the primary air chamber;
• a propellant gas reservoir adapted to receive therein pressurized propellant gas;
• a plurality of primary gas delivery passages connected at a rear end to said reservoir to receive said pressurized propellant gas from the reservoir and connected at a front end to the primary air chamber in a substantially equally spaced pattern at the periphery of said front end of the transfer tube to deliver the propellant gas into the primary air chamber, across the front end of the transfer tube, and into the rear inlet end of the nozzle bore;
• a plurality of secondary gas delivery passages communicating at a rear end to the primary air chamber to receive the propellant gas from the primary air chamber and connected at a front end to the side of the nozzle bore between front and rear ends of the nozzle bore, said secondary gas delivery passages being spaced equally around the nozzle bore, the front end of the secondary gas delivery passages being angled forwardly and centrally with respect to the nozzle bore to deliver the propellant into the nozzle bore in a converging and forward angled pattern;
• wherein, in use, propellant gas being delivered through the primary gas delivery passages and the secondary gas delivery passages establishes a backpressure at the front end of the material transfer tube sufficient, during pauses in delivery of the distributable product from the source, to terminate delivery of the coating from the front end of the material transfer tube and substantially clear residual coating from the nozzle bore.