Pressure compensated HVLP spray gun

An improved high volume, low pressure air atomization spray gun capable of operating from a source of high pressure air, having a pressure of at lest 2.8 Kg/cm.sup.2 and including an air hose for delivering said high pressure air to said spray gun, and for receiving liquid to be atomized from a liquid source, comprising:

• a housing comprising a horizontally disposed, radially extending barrel portion, and a vertically disposed, axially extending handle portion having air inlet means for attachment to said air hose for receiving said high pressure air delivered by said air hose;
• first axially extending passage means defined within said handle portion of said housing and fluidically connected to said air inlet means for conducting said high pressure air into said handle portion of said housing;
• a high pressure air chamber defined within said handle portion of said housing and fluidically connected to said first passage means at a location remote from said air inlet means for receiving high pressure air from said first passage means;
• air and fluid nozzle means attached to a distal, free end of said horizontally disposed, radially extending barrel portion of said housing for atomizing said liquid;
• second radially extending passage means defined within said barrel portion of said housing and fluidically connected to said air and fluid nozzle means for delivering low pressure air to said air and fluid nozzle means;
• a low pressure air chamber defined within said housing at a junction defined between said handle and barrel portions of said housing so as to be fluidically connected to said second radially extending passage means at a location remote from said air and fluid nozzle means for delivering low pressure air to said second radially extending passage means;
• and
• variable control valve means for lowering said pressure of said high pressure air to a predetermined low pressure valve of not greater than 0.7 Kg/cm.sup.2 and for maintaining said predetermined low pressure during changes in said pressure of said high pressure air and during changes in the flow rate of said air through said air and fluid nozzle means,
• said variable control valve means comprising a tapered valve seat interposed between and separating said high pressure air chamber and said low pressure air chamber;
• a tapered valve needle disposed within said high pressure air chamber and having an end portion thereof extending through said tapered valve seat and into said low pressure air chamber so as to define with said tapered valve seat an annular valve orifice;
• a valve needle biasing spring disposed within said high pressure air chamber for biasing, along with said high pressure air disposed within said high pressure air chamber, said valve needle toward said tapered valve seat;
• diaphragm means for separating said low pressure air chamber from an ambient air chamber and for engaging said end portion of said tapered valve needle disposed within said low pressure air chamber;
• and a pressure control spring disposed within said ambient air chamber and engaged with said diaphragm means for biasing said tapered valve needle away from said tapered valve seat so as to allow air to flow from said high pressure air chamber, through said annular valve orifice, and into said low pressure air chamber and said second radially extending passage means, and to said air and fluid nozzle means, said pressure of said high pressure air dropping to said predetermined low pressure as said air flows through said annular valve orifice whereby said predetermined low pressure acts upon said diaphragm means so as to vary said air flow through said variable control valve means so as to maintain said predetermined low pressure at said air and fluid nozzle means.