SPECIFICATIONAir spray gunThe present invention relates to air spray guns.
Fluid passages through the head of an air spray gun are often made of corrosion-resistant material for protection against corrosion by various types of coating materials. Prior approaches to corrosion protection contemplated, generally, either use with the gun of a separate and removable corrosionresistant head casting, or screwing a stainless steel insert and a stainless steel fluid inlet fitting into the gun head at right angles to each other, machining the inserts while they are in the gun to form fluid passages and then securing the inserts in place with epoxy resin. A problem encountered in the former approach is that a compromise occurs in the weight and balance considerations that are important to the "feel" of a spray gun, and in the latter approach loosening of the epoxy resin often occurs when a gun is soaked in solvent for an extended period of time.In addition, in prior spray guns, the screw threads for receiving an air cap for mounting an air nozzle on the head of the gun are usually formed on the gun body. This arrangement presents difficulties in that the threads are susceptibie to damage, and, if damaged, then the entire gun body, which is essentally the entire gun, is ruined.
The present invention resides in an air spray gun having a gun body and a spray head assembly carried at a forward end of said body for discharging therefrom an atomized spray of fluid, said spray head assembly comprising a fluid inlet fitting which has a passage therethrough connectable at one end with a supply of fluid; a fluid nozzle which has a passage therethrough terminating at one end in a fluid outlet orifice; a fluid nozzle retainer which is detachably connected to said fluid inlet fitting and which supports said fluid nozzle with adjoining other ends of said passages in communication with one another, whereby fluid introduced into said one end of said inlet fitting passage flows through said passages for being discharged from said fluid outlet orifice; and atomizing air discharge means at said one end of said fluid nozzle for discharging air to atomize into a spray fluid discharged from said fluid outlet orifice.
Because the spray head assembly is comprised of separate but interconnectable elements including the fluid nozzle, the fluid inlet fitting and the fluid nozzle retainer, are separate from the gun body, the fluid inlet fitting and fluid nozzle may be manufactured conveniently from corrosion-resistant material, and the arrangement of the elements offers significant improvements in weight, feel, maintenance and reliability of the gun.The components may readily be assembled on the forward end of the gun to provide corrosion-resistant fluid passages without need for any machining or compromises in the "feel" of the gun, and the fluid nozzle retainer itself, not the gun body, has means, such as screw threads for mounting the air nozzle means on the gun, so that, should the threads be damaged, only the nozzle retainer, and not the substantial entirety of the spray gun, needs to be replaced.
The invention is further described by way of example, with reference to the accompanying drawings, in which :Figure I is a side elevation view, partly in section, illustrating an air spray gun having a spray head assembly, in accordance with the present invention;Figure 2 is an exploded cross sectional view of the spray head assembly illustrated in Figure 1, andFigure 3 is a cross sectional exploded view of the spray head assembly.
Referring to Figure 1, an air spray gun assembly includes a paint spray gun 22 having a handle 24 adapted for connection at a lower end thereof with a source of compressed air (not shown) through a fitting 26. The gun has an air nozzle 28 and fluid nozzle means 30, through which fluid supplied to the gun through an inlet fitting 32 connected with a source (not shown) of such fluid is dispensed for being atomized into a spray and formed into a fan-shaped pattern by jets of air emitted from the air nozzle. To control the spraying operation, an air valve means 34 is movable between open and closed positions to control a flow of pressurized air through the gun, a fluid valve stem 36 is movable between open and closed positions to control a flow of fluid through the fluid nozzle means and a manually manipulatable trigger 38 is operably connected with the valve means and stem.The trigger 38 is mounted at an upper end by a pivot pin 40, and is manually movable between a gun off position away from the handle, whereat the air valve means and fluid valve are closed, to a gun on position towards the handle, whereat the air valve means and fluid valve are open and a spray of material is emitted. Adjustment of an air control knob 42 determines the amount of atomizing air emitted when the gun is on and adjustment of a fluid control knob 44 determines the dispensing rate of material.
The spray gun assembly thus far described is known in the art and, if conventional and having corrosion-resistant fluid passageways, would ordinarily be provided either with a corrosion resistant spray head casting or with a stainless steel fluid inlet insert and a stainless steel fluid outlet insert screwthreaded into the head of the gun at right angles to each other, machined while in the gun to form the fluid passage and secured in place by epoxy resin.
However, since the gun body is usually aluminium so that it might have a light weight, a problem encountered in the former approach is that a compromise occurs in the weight and balance considerations that are important to the "feel" of a gun, and in the latter approach loosening of the epoxy resin often occurs when a gun is soaked in solvent for an extended period of time. Also, with conventional guns, screw threads for receiving an air cap for mounting an air nozzle are usually formed on the aluminium gun body, which presents difficulties in that aluminium threads are relatively susceptible to damage, and if they are damaged then the entire gun body is ruined.
In improving upon prior art spray guns, in the gun of the present invention, the spray head assembly comprises separate but connectible elements includ ing a fluid nozzle, a fluid inlet fitting and a fluid noule retainer, which, because they are separate, enable the fluid nozzle and fluid inlet fitting to be manufactured conveniently out of a corrosionresistant material. The elements may readily be mounted on the forward end of the gun body without threaded attachment to the body, and provided corrosion-resistant and leak-proof fluid passages without need for any machining or compromises in the "feel" of the gun. At the same time, the fluid nozzle retainer itself, not the gun body, has threads for mounting an air cap, so that, should the threads be damaged, only the nozzle retainer needs to be replaced, and not the substantial entirety of the spray gun.
Referring also to Figures 2 and 3, a spray head assembly 46 is mounted on a downwardly depending extension 48 of a forward body portion 50 of the gun. The spray head assembly, which includes the fluid nozzle means 30, comprises the air nozzle 28 and the fluid inlet fitting 32, together with a fluid nozzle 52, a fluid nozzle retainer 54 and an air cap 56.
The inlet fitting 32 and the fluid nozzle 52 have respective fluid passages 58 and 60 therethrough, and are made of a material which is corrosionresistant to fluids conveyed through the passages, for example, of stainless steel or hardened steel.
The inlet fitting 32 is L-shaped and the extension 48 of the body 50 has a passage 62 therethrough which has a relatively small diameter at an inner end, increases in diameter towards an outer end and defines two conical shoulders 64 and 66. One leg of the inlet fitting has screw threads 68 and is received through the passage 62 for connection with the fluid nozzle retainer 54 by means of corresponding screw threads 70 therein, thereby to mount the inlet fitting 32 and fluid nozzle retainer 54 on the forward end portion 50 of the gun body. When these two elements are securely tightened together, conical shoulders 72 and 74 on the fluid nozzle retainer abut and seal with the shoulders 64 and 66, respectively.
To connect the fluid nozzle 52 with the fluid nozzle retainer 54, the nozzle is inserted into the retainer and threadably engaged therewith by means of respective screw threads 76 and 78 on the nozzle 52 and in the retainer until a conical seat 80 at an inner end of the nozzle moves against and seals with a conical seat 82 at the outer end of the passage 58 through the inlet fitting 32. This connects the inlet fitting, the fluid nozzle retainer and the fluid nozzle together and establishes a leakproof path through the fluid passages 58 and 60 in the inlet fitting and the nozzle.
To complete the spray head assembly 46, the air nozzle 28 is moved over the outer end of the fluid nozzle 52 so that an outer end 84 of the fluid nozzle extends into a passage 86 formed centrally through a front wall of the air nozzle and until a tapered shoulder 88 of the air nozzle engages and seats against a tapered shoulder 90 of the fluid nozzle. The air cap 56 is then placed around the air nozzle and screwed onto the fluid nozzle retainer 54 by means of internal threads 92 in the air cap and external threads 94 on the retainer, until a radially inwardly extending annular flange 96 at the outer end of the air cap engages a radially outwardly extending annular flange 98 of the air nozzle and moves the air nozzle against the fluid nozzle to form a seal between the shoulders 88 and 90.
It is to be appreciated that the entirety of the spray head assembly 46, which includes the air nozzle 28, the inlet fitting 32, the fluid nozzle 52, the fluid nozzle retainer 54 and the air cap 56, is mounted on the forward end portion 50 of the spray gun body without any screw-threaded attachment to the body.
It is also to be appreciated that, since all of the elements of the spray head assembly are separate and distinct, they may be manufactured very conveniently of any selected material and, if necessary, readily disassembled for repair or replacement without need to repair or replace the entirety of the spray head assembly.
Referring in particular to Figure 2, to supply atomizing air to the spray head assembly 46, the gun body 50 has an air passage 100 which receives air under pressure upon opening of the air valve means 34, and an air valve stem 102 extends through the passage to engage a seat 104 at a forward end thereof. The air valve stem 102 is coupled to the trigger 38 for being retracted when the gun is turned on, with the amount of retraction being determined by the setting on the air control knob 42, and, when retracted, establishes communication between the passage 100 and an annular passage 106 in the body extension 48, leading both to pattern-forming air outlet orifices 108 in opposed ears or wings of the air nozzle 28 and to an annular atomizing air outlet orifice 110 define between the outer extension 84 of the fluid nozzle 52 and the wall of the air nozzle passage 86.To establish a path between the passage 106 and the orifices 108, passages 112 are formed through the fluid nozzle retainer and passages 114 through the ears of the air nozzle 28, and to enable air to reach the orifice 110, passages 116 are formed through the fluid nozzle 52. Thus, triggering the gun discharges air for atomizing dispensed material into a spray and forming the spray into a fan-shaped pattern.
To control dispensing of fluid or coating material, the fluid valve stem 36 extends through an opening 118 formed in the rearward end of the fluid inlet fitting 32 and thence through the fluid passage 58 and 60 to a forward tapered valve seat 120 in the fluid nozzle passage. The valve stem 36 is sealed to the opening 118 by means of a packing gland 122 and a compression fitting 124, and a forward end of the stem is provided with a taper 126 for movement against the valve seat 120. The rearward end of the valve stem 36 is coupled to the trigger 38, whereby operation of the trigger to turn on the gun retracts the stem 36 from the valve seat 120 for dispensing coating material from an outlet orifice 128 at the end of the fluid nozzle 52. Consequently, upon retracting the gun trigger, fluid is discharged from the spray head assembly and is atomized and formed into a fan-shaped spray.
There is thus disclosed, an improved air spray gun having a spray head assembly formed of discrete components for ease in manufacture, assembly and replacement or repair of the same. The entirety of the spray head assembly, including the air cap for the air nozzle, is connected to the forward end of the gun body without need for any screw-threaded connections with the body itself, whereby there are no threads on the gun body which may be damaged by the assembly.
While one embodiment of the invention has been described in detail, various modifications and other embodiments thereof may be devised without departing from the scope of the invention, as defined in