Spray nozzle

A spray nozzle has a nozzle body defining therein a tubular chamber with an outer wall of generally circular cross-section. A generally coaxial discharge orifice at an end of this chamber has a bounding surface externally of the chamber which forms an included angle toward the chamber of less than 110.degree. with the axis of the chamber. Passage means are provided in the nozzle body to receive a flow of liquid to be sprayed and having an outlet arranged to discharge the liquid into the chamber as an annulus about the axis of the chamber. Means is provided for directing gas under pressure into the chamber in a flow path past the outlet and out the orifice, with any chamber wall portions defining the flow path between the outlet and the orifice being convergent toward the orifice in the direction of flow.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a spray nozzle which, although of more general 
utility, is particularly suited for spraying liquids at low pressure from 
a hand-held spray device with contained propulsion power source, such as a 
battery operated paint sprayer. 
2. Description of the Prior Art 
Hand-held spray devices of the prior art with self-contained propellant 
power sources have in general required large propellant power, such as gas 
pressure of the order of 70 p.s.i. provided by fluorocarbons, hydrocarbons 
or like propellants of the so-called aerosol type of such device in most 
general use. Devices using as the propellant air compressed by 
electrically operated compressors have generally also been designed to 
utilize high propellant gas pressure, with electric power requirements 
beyond the capacity of batteries suitable for inclusion in a hand-held 
spray device. Accordingly, such electrically-operated devices have had to 
suffer the disability of requiring connection to an external electric 
power source and/or compressor. 
It has been ascertained that a reason for the use of such high pressure 
propulsion power has been the lack of a spray nozzle structure which would 
produce a satisfactory spray without it. In particular, the nozzles 
utilized have required such high propulsion gas pressures to effectively 
break up the liquid into a suitable droplet spray. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide a spray nozzle structure suitable 
for forming even viscous liquids, such as paint, into a spray of high 
droplet uniformity and confined regular pattern with the aid of only low 
gas propellant pressures, of the order of 4 p.s.i. or less, such as can 
readily by supplied by an electric compressor and operating batteries of 
size and weight suitable for containment in a hand-held spray device. 
Another object is to provide such a nozzle structure which, at the low 
propellant gas pressures mentioned, produces a spray at least as suitable 
for like purposes as the sprays of conventional aerosol spray devices. 
Additional objects are to provide such a nozzle which operates 
satisfactorily at low volume flow of compressed air at the low pressures 
mentioned, which does not externally foul with the sprayed material and is 
internally sealable when not in operation, which may be made in small size 
and at low cost suitable for integral throw-away attachment to containers 
in which liquids to be sprayed are sold, and which, while having the 
foregoing advantages, is also of more general utility, for example, to 
replace with advantage existing nozzle structures in uses where higher 
propellant gas pressures are available. 
A spray nozzle in accordance with the invention has a nozzle body defining 
therein a tubular chamber with an outer wall of generally circular 
cross-section. A generally coaxial discharge orifice at an end of this 
chamber has a bounding surface externally of the chamber which forms an 
included angle toward the chamber of less than 110.degree. with the axis 
of the chamber. Passage means are provided in the nozzle body to receive a 
flow of liquid to be sprayed and having an outlet arranged to discharge 
the liquid into the chamber as an annulus about the axis of the chamber. 
Means is provided for directing gas under pressure into the chamber in a 
flow path past the outlet and out the orifice, with any chamber wall 
portions defining the flow path between the outlet and the orifice being 
convergent toward the orifice in the direction of flow. 
In preferred embodiments, the chamber outer wall is frusto-conical with the 
discharge orifice at the smaller end, an open-faced annular groove in this 
wall forms the annulus of liquid to be sprayed spaced from the orifice 1/2 
to 3 times the diameter of the orifice, and the chamber is provided with 
an inner wall forming member of like shape and smaller included angle 
which is movable axially of the chamber to close or open the outlet, and 
the bounding surface of the discharge orifice forms an included angle 
toward the chamber with the chamber axis of less than 90.degree., such as 
75.degree.. 
A chamber with a cylindrical outer wall produces an acceptable spray only 
if the annulus of liquid to be sprayed is located directly at the outlet 
orifice, so that there is essentially no wall area between the annulus and 
the orifice. Otherwise, the drop size is too irregular and there is too 
much overspray (e.g. an excessively fine fog which drifts away). The 
preferred frusto-conical shape of this wall produces a better, more 
uniform spray with less overspray and less air power required, 
particularly when the annulus forming groove is in the preferred location 
and the inner wall forming member is provided. The annulus may be formed 
on the inner wall provided by this member, but the spray is less 
satisfactory. If the outlet orifice has a cylindrical throat of any 
appreciable length between the orifice exit plane and the annulus, the 
spray is not satisfactory. The included angle toward the chamber between 
the outlet orifice external bounding surface and the chamber axis should 
be below 110.degree. and the nozzle produces a better spray if that angle 
is less than 90.degree.. 
The size of the discharge orifice is not critical, its optimum size being 
determined by such factors as viscosity of the liquid to be sprayed, spray 
area desired at a given distance therefrom, volume of pressurized gas 
available, and volume of spray liquid flow desired, the chosen diameter 
being as small as consistent with such factors. For paint spraying with 
air pressurized to 3 to 4 p.s.i. and flow rates of 12 to 30 cubic feet per 
hour (0.35-0.85 m.sup.3 /hr.), a discharge orifice diameter of 0.055 inch 
(0.138 cm) has been found suitable. The presence of the preferred movable 
inner wall forming member has the additional advantage that its axial 
position can be adjusted to vary the construction of the gas flow passage 
between it and the outer chamber wall, thus increasing or decreasing the 
gas flow rate at a given pressure, and also changing the amount of liquid 
sprayed per unit time. 
In contrast to many prior art nozzles which utilizes a swirling gas stream 
to atomize the liquid before ejection, the nozzle according to the 
invention does not need swirling gas, and preferably the compressed gas, 
normally air, is directed in a generally linear flow directly toward the 
discharge orifice with substantially no angularity about the chamber axis. 
With the preferred construction mentioned, observation indicates that such 
flow forms a continuous, thin film flow of the liquid to be sprayed from 
the annulus to the discharge orifice along the converging outer wall of 
the chamber. Due to the included angle mentioned between the chamber axis 
and the external bounding surface of the discharge orifice, the film 
encounters a sharp corner as it reaches the orifice. As it passes this 
corner, the film breaks into substantially uniform droplets that are 
dispersed in the stream as a homogeneous spray that forms a frusto-conical 
pattern as it progresses away from the nozzle orifice. Larger included 
angles than the maximum specified above are not suitable because they are 
large enough to support film flow around the intersection, thus impairing 
the spray forming action described, tending to form intermittent large 
drops. The angular relation of orifice bounding surface and chamber axis 
has another advantage in that the surface is out of the path of any 
overdivergent spray drops near the orifice. The exterior of the nozzle is 
thus antifouling, which is important when the nozzle is used for spraying 
viscous materials such as paint. 
The preferred embodiment for hand operated sprayers disclosed herein is 
also disclosed in application of Roger Demler and myself filed 
contemporaneously herewith and assigned to the assignee of the present 
application, which is directed to certain features thereof. In that 
embodiment, the inner wall forming member is a valve head which is 
spring-urged to a position in which its smaller end seats against the rim 
of the discharge orifice to seal the interior of the nozzle when not in 
use. Means is provided for sealing the liquid supply passages from the gas 
supply passages when the valve head is in this position. Handle leverage 
is provided for retracting the valve for spray operation. A valve is 
provided to seal the liquid flow passages to the annulus forming outlet 
when the device is not in use. The nozzle may have its inlet for liquid to 
be sprayed integral with a cover for a container of such liquid and may be 
provided with passages for discharging air under pressure through the 
cover into the container. 
A typical nozzle of preferred construction suitable for spraying paint at a 
propellant gas pressure of 3 to 4 p.s.i. may have a discharge orifice 
diameter of 0.050 to 0.055 inch (about 1/8 cm), a frusto-conical chamber 
outer wall with an included angle of 60.degree., an annulus-forming groove 
in that wall 0.015 inch (about 0.4 mm) wide and about the same depth, 
spaced 0.065 to 0.110 inch (about 0.16 to 0.28 cm) from the nozzle outlet, 
and a valve head with an included angle of 50.degree.. Liquid flow through 
the nozzle may be produced in a variety of ways. The nozzle may be 
self-aspirating if the pressure head due to speed of the gas at the 
annulus reduces the pressure sufficiently below the pressure on the 
liquid. Gravity flow may be utilized if the nozzle is located below the 
spray liquid source level. Pressure may be supplied to the source to cause 
or assist in the flow. A liquid flow rate of about 45 c.c. per minute at 4 
p.s.i. air flow of about 30 cubic feet per hour (0.85 m.sup.3 /hr.) has 
been found well suited for paint spray.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, the nozzle body shown, designated generally 10, 
is a hollow cylinder provided in its side with a pair of radially directed 
ports 12 and 14 to which are press-fitted respectively the ends of tubes 
16 and 18. Tube 16 connects port 12 to a source of air under pressure (not 
shown) while tube 18 connected port 14 to a source of liquid to be sprayed 
(not shown). Between ports 12 and 14 an annular ledge 20 projects inwardly 
toward the axis of the body. Ledge 20 has a frusto-conical inner surface 
22, a flat end surface 24 and an annular groove 26. Groove 26 forms one 
side of an annular reservoir 30 for liquid to be sprayed communicating 
with port 14. End surface 24 forms one side of an annular slot passage 32 
opening from reservoir 30 into the interior of body 10 at the forward 
extremity of surface 22. 
The forward end of nozzle body 10 has press-fitted thereto a disc member 
designated generally 34 which closes the forward end of the body except 
for a central orifice therein, which forms the outlet orifice 36 for the 
spray. Orifice 36 is bounded interiorly of member 34 by a frusto-conical 
surface 38 having the same cone angle C as surface 22, as shown about 
60.degree.. A flat surface 40 at the inner end of surface 38 is spaced 
from surface 24 to form the opposite side of annular slot passage 32. The 
outer end of surface 40 joins inclined annular surface 42 which defines 
with groove 26 the annular reservoir 30. Surface 22 and its continuation 
by surface 38 beyond passage 32 define the outer wall of a frusto-conical 
inner chamber 44 of nozzle body 10. The exterior surface 46 of member 34 
bounding orifice 36 defines an included angle A toward chamber 44 with the 
axis of the chamber which is less than 110.degree., and as shown is formed 
as a frusto-conical surface with such included angle being about 
75.degree.. 
Although the use of an inner wall forming member is preferable as in FIG. 
2, the nozzle of FIG. 1 functions effectively without such a member, in 
which case its open rearward end is closed by a plug 48. Desirably, such a 
plug has a reduced portion 50 opposite port 12 to distribute the 
pressurized gas from the port evenly about the axis of chamber 44. Valves 
(not shown) in tubes 16 and 18 control the flow of gas and liquid 
respectively. The liquid to be sprayed passes from tube 18 through port 14 
to reservoir 30 and is discharged therefrom as an annulus about the axis 
of chamber 44 through slot passage 32. The pressurized gas, sweeping past 
the outlet of passage 32, removes liquid from the annulus and causes it to 
flow as a thin film along convergent outer wall 38 and as an annular 
continuous thin film at the sharp corner of discharge orifice 36 between 
surfaces 38 and 46. The liquid and the parallel flow of gas accelerate 
smoothly as they progress towards discharge orifice 36 across the bounding 
surface 38 of decreasing area. As the liquid film passes the sharp corner 
of discharge orifice 36, the pressurized gas flowing parallel with the 
liquid abruptly expands through the liquid film and breaks up that film 
into a spray of generally conical pattern and uniform drop size. 
As shown, the annulus forming outlet of passage 32 is spaced from orifice 
36 about 11/4 times the orifice diameter. As earlier stated herein, this 
outlet is preferably spaced from the orifice from 1/2 to 3 times the 
orifice diameter, although it may be located directly at the orifice with 
only a plate of negligible thickness forming its outer surface. In any 
event, any wall surfaces within the nozzle contacting the gas flow between 
the annulus outlet and the orifice are convergent toward the axis of the 
nozzle chamber. 
FIG. 2 shows the nozzle of FIG. 1 with the same reference numerals applied 
thereto, provided with an inner wall forming member in the chamber 44. The 
use of such a member is preferred, both for its functional effect on the 
gas flow and because of its ability to act as a seal for the spray 
discharge orifice when the nozzle is not in operation. A piston of 
circular cross-section designated generally 60, which replaces the plug 48 
in FIG. 1, has a reduced portion 62 which slidably fits within the 
cylindrical opening at the rearward end of nozzle body 10, with sufficient 
closeness to prevent the flow of pressurized gas out the rearward end of 
the body. A further reduced portion 64 of piston 62 has a conically shaped 
forward end portion 66 coaxial with chamber 44 but of smaller cone angle 
which extends from its larger end at the rear of passage 32 to its tip 68. 
At the fully inserted position of piston 60 shown in dash lines, circular 
orifice 36 tightly engages about conical portion 66 with tip 68 projecting 
through it to seal chamber 44 from ambient air. When piston 60 is 
retracted from this position to a position such as shown by full lines in 
FIG. 2, orifice 36 is opened except for so much of tip portion 68 as may 
project through it. The conical end portion of piston 60, forming an inner 
wall for chamber 44, opposite and spaced from surfaces 22 and 38, defines 
with those surfaces a conical sleeve flow path 70 of diminishing thickness 
toward orifice 36 for the pressurized gas, past the outlet of passage 32 
and out the orifice. 
An aperture 72 in the external rearward end of piston 60 serves as a 
coupling means, via a pin inserted therein, for trigger linkage (not 
shown) for reciprocating the piston between open and closed positions. 
Where, as in FIG. 2, a spring is not provided in the nozzle itself, such 
trigger linkage may be biased to normally maintain the piston in 
nozzle-closing position. For uses in which sealing of the nozzle is not 
desired, as where the nozzle operates in a combustion system, the piston 
60 may be fixed in an open position. 
Portion 64 of piston 60 has an annular surrounding channel 74 formed 
therein, having one end open toward orifice 36. A port 76 in the outer 
wall of channel 74 communicates with compressed gas inlet 12 to provide 
equalized distribution of the gas about the nozzle axis and substantially 
uniform flow thereof toward orifice 36. In FIG. 2, as in FIG. 1, the gas 
flow is past the annulus formed by passage 32 and out the orifice 36 and 
is essentially non-angular. However, swirling flow may be utilized, formed 
for example by one or more tangential gas inlet ports. 
Shown in FIGS. 3 and 4 is a paint dispensing unit 100 of the throw-away 
type that includes a cylindrical container 102 and integral dispensing 
head unit 104. This replaceable unit is designed for releasable attachment 
to the hand-held operating unit 106 shown in FIG. 5. Container 102 
includes a rigid outer can that has cylindrical side wall 108, bottom wall 
110 secured to side wall 108 by bead 112, and upper wall 114 secured to 
side wall 108 by bead 116. Within the rigid can is a compressible bag 120 
of flexible material that contains the liquid paint to be sprayed. Bag 120 
has a neck portion 122 that is secured over depending stem 124 and extends 
through opening 126 in upper can wall 114. Dip tube 128 extends from stem 
124 towards the bottom of bag 120. Formed integrally with, and 
surrounding, stem 124 is container cover 130 that has an annular flange 
132 that is sealed to the annular bead 116 of container 102. A helical rib 
134 is on the outer periphery of flange 132. 
Integral with cover 130 and connected to stem 124 is dispensing head 104 
which includes a housing member 140 with a gas inlet passage 142 and 
coupling flange 144 on its upper side. Formed in housing 140 is an axially 
extending gas flow passage 146 connected to gas inlet passage 142, and 
axially extending liquid flow passage 148 connected to the passage 150 
through stem 124. A rotary valve disc 152 is seated on the front surface 
of the dispenser housing 140 and secured in position by nozzle cap 154 
that includes a cylindrical sleeve 156, a protective skirt 158, and a 
front wall 160 in which is disposed discharge orifice 162. 
Formed within housing 140 is a cylindrical chamber having a wall 164 in 
which is disposed a reciprocable member 166 (shown in greater detail in 
FIGS. 8 and 9) that has a cylindrical valve head 168 with an annular valve 
bead 170 on its front face and a rearwardly extending bar portion 172 
which passes through aperture 174 in rear chamber wall 176. A coupling 
aperture 178 is provided in the rear end of bar portion 172. Spring 180 
acts between rear chamber wall 176 and cylindrical head 168 to urge the 
valve head 170 forward into sealing engagement with the rear surface of 
valve disc 152. Bar portion 172 has an aperture 182 and valve head 168 has 
a bore in which is disposed orifice valve member 184. That valve member 
has a cylindrical body 186, a conical nose 188 and a hub flange 190. 
Spring 192 acts between the rear wall of aperture 182 and hub flange 190 
to urge valve member 184 forward so that its conical nose 188 extends 
through and closes discharge orifice 162. 
The cooperating hand-held operating unit 106 shown in FIG. 5 includes a 
coupling ring 200 that extends forward from support frame 202. Formed in 
the inner surface of ring 200 is a helical rib 204. Above support ring 200 
is cantilever arm 206 that carries a resilient coupling 208. A central 
bore 209 in coupling 208 is connected by tube line 210 to a battery 
powered compressor (not shown) that supplies compressed air at a pressure 
of about 4 p.s.i. Also formed in frame 202 is boss 212 that slidingly 
carries reciprocable link 214 which has a connecting pin 216 at its 
forward end and a pivot connection 218 to trigger 220 at its rear end. 
Trigger 220 and link 214 are biased forwardly by spring 222. Adjustment 
member 224 controllably limits the rearward movement of the trigger and 
link assembly. 
The container-dispensing head unit 100 is attached to hand-held operating 
unit 106 by inserting the dispensing head 104 upwardly through ring 200 so 
that flange 144 is in alignment with resilient coupling 208 and angularly 
aligning helical ribs 134 and 204 to be in cooperating relation. The 
dispensing unit 100 is then rotated until link pin 216 enters and is 
latched in bar aperture 178. In this position, flange 144 is seated 
against resilient coupling 208, providing a seal between air supply line 
210 and passage 142. The axially movable valve assembly of members 166 and 
184 is coupled to trigger 220 by link 214 so that operation of the trigger 
moves orifice valve member 184 and cylindrical valve head 168 rearwardly 
to open the chamber valve and the discharge orifice valve. 
The dispenser housing member shown in FIGS. 6 and 7 is of molded plastic. 
That housing member includes container cover 130 and the cylindrical 
housing body 140 connected by webs 230. Stem passage 150 passes through 
one web and a second passage 232 passes through a second web. The housing 
body 140 has a planar front face 234 with a central axially extending 
cylindrical chamber 236 defined by wall 164. Three axially extending 
passages 146, 148 and 238 extend rearwardly from front face 234. Also 
formed in front face 234 is an arcuate groove 240 that has an angular 
length of about 90.degree.. One end of groove 240 is in communication with 
passage 238, the other end 242 of the groove has a width equal to the 
passage width, and the intermediate section of the groove 240 is of 
reduced width. Passage 146 is at the top of the cylindrical housing and in 
communication with air inlet passage 142; passage 148 is offset 
120.degree. from passage 146 and in communication with liquid supply 
passage 150; and passage 238, offset 120.degree. from passage 148, is in 
communication with passage 232 that extends through cover 130. An annular 
groove 244 is formed in the outer surface of housing 140, and a stop 
projection 246 with a detent 248 is at the base of the housing between the 
webs 230. 
Valve member 166 is of molded plastic and has a length of about six 
centimeters or less and its head 168 has a diameter of about one 
centimeter or less. As shown in FIGS. 8 and 9, that valve member includes 
cylindrical head 168 with annular valve rib 170 formed on its front 
surface and a cylindrical through passage 250. Extending rearwardly from 
head 168 is elongated bar portion 172 of rectangular cross-section. Formed 
in bar portion 172 adjacent cylindrical head 168 is an elongated aperture 
182 with a post 252 at its rear edge which defines a spring guide. 
The orifice valve member 184 shown in FIG. 10 is also a molded plastic 
member and is about two centimeters or less in length with a cylindrical 
body portion 186 about 1/2 centimeter or less in diameter. Its conical 
nose 188 has an included angle of 50.degree.. The hub 190 at the rear of 
body 186 has a front stop surface 254 and a rear spring seat surface 256. 
The valve disc 152, shown in FIGS. 11-13, is a molded plastic member of 
about 41/2 centimeters or less in diameter and about 1/3 centimeter in 
thickness. Its rear surface 260 seats on front surface 234 of housing 140. 
The disc has a central through passage that has a cylindrical section 
defined by surface 262 and a convergent section defined by frusto-conical 
surface 264 at an angle of 30.degree. to the axis of disc 152. Formed in 
rear surface 260 at the upper side as shown in FIG. 11 is a recess that 
includes a central portion 266 that has a radial length of about 3/4 
centimeter, a first arcuate portion 268 that extends from the outer edge 
of central portion 266 and has an angular length of 45.degree. and a 
second arcuate portion 270 that extends from the inner edge of central 
portion 266 in the opposite direction and has an angular extend of 
60.degree.. Through passage 272 is angularly offset by 120.degree. from 
the central portion 266, and vent notch 274 that extends to the periphery 
of disc 152 is angularly offset from passage 272 by 75.degree.. The front 
surface 276 of disc 152 is defined by rim 278. Projecting forwardly from 
rim 278 is tooth 280. Extending inwardly from rim 278 is a recessed planar 
surface 282 that terminates in annular groove 284. The inner wall 286 of 
groove 284 slopes inwardly and terminates at a planar rim surface 288 that 
is about 0.2 millimeter below surface 276. 
The nozzle cap 154, also of molded plastic, is shown in FIGS. 14 and 15. 
That cap includes a cylindrical body section 156 that has an annular rib 
300 formed on its inner surface that is adapted to be seated in annular 
groove 244 of housing 140 (FIG. 7), a skirt 158 of octagonal shape as 
indicated in FIGS. 3 and 15, and a front wall 160 in which discharge 
orifice 162 is provided. Orifice 162 is defined by the intersection of 
annular surfaces 302 and 304, surface 302 being disposed at an angle of 
75.degree. to the axis of cap 154 and surface 304 being disposed at an 
angle of 30.degree. to that axis. Also formed in the rear surface of front 
wall 160 is an annular groove defined by cylindrical surface 306 and 
inclined surface 308 that terminates in annular rim surface 310 that 
extends to conical surface 304. Rim surface 310 is about 0.2 millimeter 
below the rear surface 312 of wall 160. At the upper edge of the surface 
312 is a recess 314 which receives tooth 280 of valve disc 152. A 
forwardly projecting lip 316 is disposed above and on either side of 
discharge orifice 162 as an extension of skirt 158; a vent port 317 
extends through body 156; and a limit slot 318 (about 90.degree. in 
angular extent) is at the rear edge of body 156. 
In assembly, valve disc 152 is inserted into the nozzle cap with tooth 280 
in recess 314 and surface 278 seated on surface 312 as a first 
subassembly. Orifice valve 184 is inserted through bore 250 of valve 
member 166 and spring 192 is positioned between seats 252 and 256 so that 
the orifice valve 184 is urged forward and its hub surface 254 is seated 
against the rear surface of valve head 168. That valve subassembly, 
together with biasing spring 180 is inserted into the cylindrical cavity 
236 of the housing body 140 with the rear end of bar 172 extending through 
aperture 174. The cap-valve disc subassembly is then inserted over the 
outer surface of housing 140 with rib 300 seated in groove 244. Indexing 
stop 246 is received in slot 318. In this position, the nozzle cap-valve 
disc subassembly may be rotated through 90.degree. as limited by the 
engagement of projection 246 and slot 318. 
An enlarged cross-section view of the dispensing nozzle is shown in FIG. 16 
with the axially movable valves in closed position and the rotary valve in 
open position. Frusto-conical surfaces 264 and 304 are aligned and form 
the outer wall of a convergent discharge passage 320 that terminates at 
discharge orifice 162. Surfaces 288 and 310 define an annular opening 322 
in the outer wall of the discharge passage which is in communication with 
an annular reservoir 324 defined by surfaces 284, 286, 306 and 308. An 
annular passage extends radially outward from reservoir 324 to port 272 in 
disc 152. In the open position of the rotary valve disc, as indicated in 
FIG. 17, port 272 is in alignment with passage 148. In that valve 
position, the central portion 266 of the groove is in alignment with air 
supply passage 146, groove arm 268 bridges the end 242 of groove 240 in 
housing face 234, and the inner portion of groove arm 270 bridges 
cylindrical surface 164. Thus low pressure air supplied through passage 
146 is applied to the annular chamber surrounding valve bead 170 and, 
through groove 240 and passage 238 and 232 is applied through container 
cover 130 to pressurize the compressible bag 120 of paint. The pressurized 
paint flows upwardly through dip tube 128, stem passage 150 and axial 
passage 148 towards the annular reservoir 324 surrounding the discharge 
passage 320. No dispensing occurs as valves 170 and 188 are closed. 
When trigger 220 is operated, valve member 166 is pulled rearwardly, 
separating valve bead 170 from disc surface 260, and allowing air to flow 
into the dispensing passage 320. The rear surface of valve cylinder 168 
engages hub 190 of orifice valve 184 and moves that valve rearwardly, 
opening orifice 162. The dispensing nozzle with both axially movable 
valves in open position is shown in FIG. 18. In this position pressurized 
air flows through the convergent discharge passage 320 across the liquid 
paint at the annular outlet 322. The parallel flows of liquid paint and 
air accelerate smoothly as they move through the discharge passage towards 
the discharge orifice 162 with an annularly continuous thin film of paint 
at the sharp orifice edge defined by surfaces 302 and 304. As the film of 
paint exits orifice 162, the flowing gas expands abruptly through that 
film and forms a conical spray of paint droplets 326 of small and uniform 
size. 
This dispensing action continues until trigger 220 is released. Springs 
180, 192 and 222 move the valve members 166 and 184 forward, the discharge 
orifice 162 being closed when nose 188 seats against it and the air supply 
passage to the discharge passage 320 being closed when valve rib 170 seats 
against disc surface 260. In this condition, the paint in bag 120 is 
sealed from the atmosphere. 
The nozzle cap 154 may be rotated 90.degree. (counterclockwise as viewed in 
FIG. 3) to close the rotary valve. In that position, as indicated in FIG. 
19, all three housing passages 146, 148 and 238 are closed by the valve 
disc 152. The nozzle cap may be located in an intermediate position 
(45.degree. from the open position) as shown in FIG. 20. In that position, 
the end of groove arm 268 overlies air supply passage 146 so that 
pressurized air is supplied to the chamber surrounding valve rib 170; and 
the vent passage (notch 274 and port 317) is in communication with passage 
238. The paint supply passage 148 is closed. In this intermediate 
position, the upper portion of container 102 is vented to atmosphere, 
relieving the pressure on bag 120. If trigger 220 is depressed, the ports 
closed by axially movable valve members 166 and 184 are opened and air 
flows through the dispensing passage 320 without flow of additional paint 
from bag 120, thereby permitting the nozzle passage to be cleared of any 
residual paint. 
Other embodiments are within the scope of the invention and claims.