Note: Descriptions are shown in the official language in which they were submitted.
103~22
BACKGROUND OF THE INVENTION
This invention relates to spray guns for liquids
such as paint or the like and, more particulariy, to a spray
gun for hydraulically atomizing the liquid to be sprayed.
In a hydraulically atomizing spray system or "airless
spray", the liquid is ~orced through a spray tip or nozzle open-
ing ha~ing sharp edges ~t sufficiently high Yelocities to provide
ato~ization of the liquid. The nozzle opening has an elliptically
shaped cross-section with sharp vertices to produce an elliptical
O~ oval sh~ped spray pattern. In airless spraying techniques,
the hydraulic pressures are rel~tively high and typically range
~rom ~bout 1500 psig to a~out 3000 psig.
The adyant~ges of airless spraying are discussed in
U. $. Patent No. 3,000,576 to Levey et al. In accordance with
: this ~rior patent, the non-uniform spray pattern having thick-
ened portions or "p~g-t~ils?' which had thereto~ore characterized
airless spray techniques was eliminated by the use of a restricted
pre-orifice having a circular cross-sec~ion disposed upstream
~rom the spray tip nozzle opening.
The occurrence of such non-uniform spray patterns
was a~s~ciated wlth the ~ormation of a vena contraçta upon
accelcration of the liquid ~ith a large pressure drop through
the nozzle openin~ which prevents full atomization of the
li~uid at the vertices of the spray pattern. The fo~mation of
a ~rm~ul yena contracta was eliminated by accelerating the
l~uid ~ith a large pressure drop through the restricted pre- ~`
orifice to proyide ~ submerged jet moving through the nozzle
opening by its own kinetic energy at substantially the same
29 yelocity. By controlling the liquid in this manner, a s
c~' - 1 - ~
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10386Z2
stantially uniform pressure and velocity was obtained across
the a~ea of the nozzle opening, so that the liquid was uniformly
atomized and distributed across the spray pattern with a unifoxm
reduction in density or feathering at the margins of the pattern.
For purposes of obtaining optimum atomization quality,
the cross-sectional area of the pre-orifice opening should be
substantially equal to the cross-sectional area of the nozzle
opening of the spray tip. Satisfactory results are obtained so
long as the area of the pre-orifice is not less than about one-
fourth or more than about twice the area of the nozzle opening.A number of variously sized, circular pre-orifices are presently
required to accommodate the full commercial range of spray tips
in accordance with the teachings of the said Patent No. 3,000,576.
For use with seven different sized spray tips having nozzle areas
ranging from the equivalent of a round opening with a diameter of
0.011 of an inch to a~round opening of 0.031 of an inch, eight
different circular pre-orifices are currently marketed having
diameters ranging from 0.012 of an inch to 0.039 of an inch,
so that each spray tip may be provided with a pre-orifice with an
area substantially equal to or not exceedlng twice the area of
the nozzle open~n~. The changing of a pre-orifice may involve
the ~isassembly of a significant portion of the spray gun and,
- at least, results ~n a considerable loss of production time~
In some p~int spraying applications, particularly in
construction or ~aintenance work, speed o~ application is para-
~ount and ~ual~ty of atom~zat~on may be sacrificed for the maximum
~an w~dth appl~ed as ~u~ckly as possible. To that end, the
oFerator may ~orego the use of a pre-orifice in order to obtain
2~ as wide a spray f~n width as possible since it has been observed
,
cb/ - 2 -
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~Q3~622
that the use of a pre~orifice will reduce the fan width and the
volume delivered by as much as 10% to 15% in an 80 designated
spray tip. After the faster "rough" applications have been
applied, the operator will necessarily expend valuable production
time inserting an appropriate pre-orifice to obtain the quality
atomization required for the areas or applications in which
quality is critical, and airless spraying without a pre-orifice
is unsatisfactory.
SUMM~RY OF THE INVENTION . .
In accordance with the present invention, a pre-
orifice adjustable in cross-sectional area by operation of con-
trol means externally mounted on the spray gun is provided.
Upon operation of the control means, the cross-sectional area
of the pre-orifice opening is varied to provide corresponding
variations in the spray fan and spray pattern of the spray gun.
In a first illustrated embodiment, the pre-orifice
opening is defined by relatively movable members which are
movable by operation of the control means. In accordance with
afurther discovery of the present invention, the pre-orifice
opening defined by the relatively movable members has a non-
circular configuration when adjusted to minimum area sizes
without ad~erse effects to the pre-orifice function. Accordingly,
quality atomization as well as controlled variation of the spray
fan and spray pattern are obtained uponoperation of the control
means.
In a second illustrated embodimentl the pre-orifice is
defined by an aperture through an elastomeric or resilient member
or disc. The cross-sectional a~ea of the pre-orifice opening is
29 adjustable upon elastic deformation of the elastomeric disc by
'
c~ - 3 -
1038~i22
operation of the control means. Accordingly, quality atomization `~
as well as controlled variation of the spray fan and spray pattern
are again obtained upon operation of the control means.
In the first illustrated embodiment, the pre-orifice
means include a pre-orifice assembly or capsule which supports
the relatively movable members. The pre-orifice opening is
defined by cooperating surfaces of the relatively movable members.
The pre-or;fice opening has a non-circular, generally elongated
configuration upon adjustment to a reduced cross-sectional area
size. The major cross-sectional dimension of the pre-orifice
opening is maintained in substantially parallalrelationship
with the major cross-sectional dimension of the elliptically
shaped spray tip opening by means of interfitting orientation
surfaces.
In the second illustrated embodiment, the pre-orifice
means includes relatively movable rigid wall means for engaging
and confining the opposite sides of the elastomeric member or
disc. The rigid wall means include bores aligned with and of
substantially no greater diameter than the pre-orifice opening.
Upon closing relative movement of the movable rigid wall means,
the cross,sectional area of the pre-orifice opening is corres-
pondingl~ decreased to a value less than that of the adjacent
bores. In a preferred form, the pre-orifice means also include
rigid wall means for confining the elastomeric disc against
xad~ally outward flow.
The range of cross-sectional pre-orifice areas of
the adjustable pre-orifice is selected to accommodate the con-
ventional spray tip or nozzle opening sizes which vary from an
29 area equal to that of a circle of 0.011 of an inch in diameter
"~
' :
1~3B62Z
to an area equal to that of a circle of 0.035 of an inch in
diameter. ~For purposes of convenience, the nozzle opening
and pre-orifice opening cross-sectional areas are hereinafter
simply designated by the diameter in inches of a circle having
an equal area.) Accordingly, a single pre-orifice unit in accord-
ance with the present invention may be adjusted to provide an
optimum 1:1 area ratio between the pre-orifice opening and the
nozzle opening for the entirè rangè of commèrcially availablè
spray tip sizes.
In addition to providing the optimum 1:1 area ratio,
t~e adjustable pre-orifice of the present inventian also pro-
vides area ratios substantially in excess of 2:1 for most of the -
spray tips commonly employed to enable an operator to achieve
iull spr~y fan angle width potential in high speed rough work
~y simply adjustIng the pre-orifice to its maximum size. Sim-
ilarly, the spray fan an~le may be narrowed or decreased for
spectf~c tr~m and finishing applications by reducing the size
of the pre-orifice. In bot~ of these cases, it is apparent
that the ~olume delivery and the spray pattern are adjusted
without a significant loss of production time.
Thus, the advantages of using a pre-orifice in an
airless spray system are obtained in accordance with the present
invention while simultaneously eliminating the aforementioned
prior art disadvantages. The pre-orifice cross-sectional area
is readily adjustable by hand operation of the control knob
without disassembly of the spray gun and the attendant loss of
product1on time. ;
In one particular aspect the present invention pro-
29 vides an airless paint spray gun comprising a body portion -
. , .
cb/ - 5 -
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~03~6~Z
havins a conduit adapted to be connected at its inlet end to a
source of liquid paint under pressure and adapted to have a spray
tip connected to the discharge end thereof, pre-orifice means
adjacent the discharge end of said conduit including an axially
ex.ending pre-orifice opening adjustable in cross-sectional area,
and manually operable means carried by said body portion operably
associated with said pre-orifice means and movable to vary the
area of said pre-orifice opening.
In another aspect the present invention provides an
airless paint spray gun comprising a body portion having a conduit
adapted to be connected at its inlet end to a source of liquid
paint under pressure and adapted to have a spray tip having an
elongated spray opening connected to the discharge end thereof,
prerorifice means adjacent the discharge end of said conduit
; including relatively movable members de~ining therebetween a
pre-orifice opening adjustable in cross-sectional area, and
~anually oper~ble means carried by said body porti~n operably
connected to said relatively movable members and ~ovable to vary
the axea of said pre-orifice-opening.
In a further aspect the present invention provides an
airles~ paint spray gun comprising a body portion having a conduit
adapted to be connected at its inlet end to a source of liquid
paint under pressure and adapted to have a spray tip having an
elongated spray opening connected to the discharge end thereof,
pre-orifice means adjacent the discharge end of said conduit
including an elastomeric disc having a central aperture forming
an axially extending pre-orifice opening adjustable in cross-
sectional area, said pre-orifice means including relatively
29 movable rigid wall means engaging and confining the opposite
cb~ - 6 -
: : . i . .. ~ , - . : : .
:. , " , . '
''.' . ~' , ' ' . .
' - ' : . :, ,,- . ' .. ': '... ~' . .- ' ' ,.' , .
10386ZZ
sides of said disc radially outward from the central pperture
thereof, said relatively movable wall means having axial open-
ings aligned wit~ and of substantially no greater diameter than
said central aperture, and manually operable means associated
witn said pre-orifice means operable to move said relatively
movable wall means toward each other to elastically deform
said disc and to reduce th~ diameter of said pre-orifice open-
ing to a diameter less than those of said axial openings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an elevational view of an airless spray :
gun provided with adjustable pre-orifice means in accordance
with the present invention;
Figure 2 is a fragmentary, vertical section on an :~
enlarged scale through the valve port and nozzle area portion ~ . .
: of the spray gun shown in Figure 1 depicting the pre-orifice
capsule and having parts broken away for purposes of clarity;
F~gure 3 is a sectional view on an enlarged scale
taken along the line 3-3 of Figure 2 showing the relatively
moyable j~w ~embers in a ~ull open position;
Figure 3a is a fragmentary elevational view on an
enlarged scale showing a portion of the jaw members in a full
closed position;
Figure 4 is an exploded perspective view of the pre- - :.
orifice capsule viewed from the forward end of the spray gun;
~igure 5 is a sectional view of the spray tip and pre-
orifice caps~le similar to Figure 2 but on a greatly enlarged -
scale; ::
Figure 6 is a sectional view through a pre-orifice .-.
29 capsule 5~0wing a modified sealing arrangement for the jaw -
.
cl~/ -- 7 ~ -
103B6Z;~
members adjacent the pre-orifice opening;
Figure 7 is a fragmentary, vertical section similar
to Figure 2 showing another embodiment of the present invention
wherein the adjustable pre-orifice means include a pre-orifice
capsule having an elastomeric member or disc mounted therein;
Figure 8 is a sectional view on an enlarged scale
showing the pre-orifice opening through the elastomeric member
in an uncompressed condition;
Figure 8a is a sectional view similar to Figure 8
10 showing the elastomeric member in a compressed condition with .
the pre-orifice opening having a reduced cross-sectional area
substantially equal to the cross-sectional area of the spray
tip opening;
Figure 9 is an exploded perspective view of the pre-
- orifice capsule and elastomeric member, and
Figure 10 is a sectional view through a portion of a
pre-orifice capsule showing a modified elastomeric disc and pre-
orifice capsule in accordance with the present invention. .
DETAILED DESCRIPTION OF THE DRAWINGS
Referring to Figure 1, an airless spray gun 10 is
shown. The spray gun body includes a handle portion 12, a
forwardly extending stock portion 14 and a spray portion 16 which
is secured to the stock portion 14 by means of a bolt 18. In
accordance with the present invention, an adjustable pre-orifice
spray assembly 20 is fixed to the forward end of the spray
portion -16,
The liquid to ~e sprayed is introduced into the spray
gun through a cDmbined swivel fitting and strainer holder 22
2~ which is threadedly connected to the spray portion 16 of the gun.
cb,' - 8 -
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- `
~03~36Z2
The fitting 22 is adapted to be connected to a source of liquid
under pressure (not shown~ and the liquid is delivered to the
internal portions of the gun through a passageway 22a extending
through the fitting. The liquid to be sprayed may be pressurized
in any conventional manner and a supply hose ~not shown~ leading
to the fittin~ 22 may ~e branched if it is desired to use a
heater in the supply line.
The spray gun 10 has a pivoted trigger 24 which is
~ixed to ~he stem of a needle valve 26 for purposes of operating
10 t~e spray gun. The needle valve 26 and trigger 24 are biased ;~
to a forward, non-spraying position by conventional means.
The spray gun is actuated upon movement of the trigger 24 towards
the handle 12 and the corresponding, following movement of the
needle valye 26 tn a rearward direction.
- Referring to Figure 2, the details of the forward por- -
tion of the spray gun 10 are shown. The adjustable pre-orifice
spray assembly 20 includes an axially fixed, cylindrical mounting
slee~e 28 having an internally threaded rearward bore 30 which
threadedly engages the external threads provided on a cylindrical
boss 16a extending from the spray portion 16 of the spray gun.
The sleeve 28 has a radially, inwardly extending shoulder 32
: ~hich abuts against the forward end of the boss 16a when the
sleeve 28 is tightly connected. Alternatively, the spray portion
16 and the sleeve 28 may be integrally formed.
The forward end of the sleeve 28 has an internally ~;
threaded bore 34 which engages an externally threaded nut 36.
The nut 36 secures a spray tip or nozzle assembly 38 to the
forward end of the spray gun 10. A sealing gasket 36a formed of
2~ a suitable seal material such as nylon or Teflon is provided at
.. . .. .
cb/ _ g _ .
103~62Z
the forward face of the spray tip holder. The spray tip or
nozzle assembly includes a spray tip holder 39 having a "flat fan"
spray tip 40 mounted therein.
The liquid to be sprayed is introduced into the gun
by means of the fitting 22 and, more particularly, a passageway
22a extending therethrough and communicating with a central
bore 42 in the spray portion 16 of the spray gun. The needle
valve 26 is axially movable within the bore 42, and its movement
is guided by a counterbore 44 (Figure 1). The stem of the
needle valve extends through the counterbore 44 and a gland nut
46 which seals the free, rearward end of the counterbore.
The forward end of the bore 42 is internally threaded
for engagement with the rearward portion of a cylindrical nut
member 48. The forward portion of tne member 48 is threadedly
- engaged with a valve body holder 50. The cylindrical nut member
48 and the valve body holder 50 are respectively provided with
communicating, coaxial internal bores 48a and 50a which in turn
communicate wit~ t~e central bore 42 to provide a conduit or
passageway through the spray gun for delivery of liquid to the
spray t~p 40.
The forward end of the bore 50a has a valve body 52
press-fitted therein so that it is secured in place and sealed
against fluid leaXagP. The valve body 52 is preferably made of
a hard erosion resistant material such as tungsten carbide.
The valve body 52 has a valve port 54 which provides a flared,
rear~ard seating surface 56 for sealing, valving engagement
with the rounded end of t~e needle valve 26.
The forward end of the valve port 54 opens into a
29 pre-orifice assembly or capsule 58 having a coaxially extending
cb~ - 10 -
62~:
passageway therethrough including an adjustable pre-orifice 60.
The passageway t~rough the pre-orifice capsule 58 communicates
with the spray tip 40 for delivery thereto of the liquid to be
sprayed.
Referring to Figures 3 through 5, the pre-orifice
capsule 58 includes as its principal parts a forward capsule
half member 62, a pair of relatively movable jaw members 64 and 66,
a pair of biasing springs 68 and 70, and a rearward capsule half
member 72. When the pre-orifice capsule is assembled, the capsule
half members 62, 72 are interlocked together in an interference
fit and t~e~ cooperate to contain the springs and jaw members in
a fixed axial position. The springs are compressed in the
assembled capsule and they resiliently urge the jaw members in
opposite directions along the diameter of the pre-orifice capsule.
The member 72 has a generally cylindrical configuration
including a central wall 73, a forwardly, axially extending skirt
portion 74, and a rearwardly, axially extending skirt portion 75.
The skirt portion 74 is divided into four arcuate sections by
radially opposed slots 76a, 76h and relatively larger, radially
2Q off-set slots 78a, 78b.
Each of the arcuate sections o~ the skirt portion 74
includes an internal shoulder 80 which cooperates to define an
internal recess for purposes of engaging the member 62. Each of
the arcuate sections also includes a reduced diameter or wall
portion 82 extending to the forward surface of the wall 73.
The portions 82 cooperate to define a chamber for receiving the
jaw members 64, 66 and spring members 68, 70.
The jaw members 64, 66 respectively include radially
24 extending cam following arms 84, 86 and guide legs 85, 87.
cb/ - 11 -
1038~ZZ
When the pre-orifice capsule is assembled, the guide legs of each
of the jaw members engage adjacent portions of the other of the
jaw members in sliding relationship as indicated below in greater
detail. As best shown in Figure 3, the slots 76a and 76b are
dimensioned to receive the cam following arms 84, 86 and conti-
guously disposed portions of the legs 85, 87 to rotationally fix
and stabilize the mounting of the jaw members within the pre-
orilice capsule.
The jaw members 64, 66 are also respectively provided
with guide arms 88 and 90. The guide arms are dimensioned to
engage the reduced diameter portion 82 of an adjacent arcuate
section of the skirt portion 74 when the jaw members are in a
full open position as shown in Figure 3.
The jaw members 64, 66 are biased apart to their full
open position by the springs 68 and 70 whic~ comprise double
layer leaf springs. The springs are mounted within the pre-
orifice capsule adjacent the recesses 78a, 78b which provide
clearance for accommodating the deflection of thesprings upon
relative movement of the jaw members toward one another. The
springs 68, 70 have an axial dimension corresponding to that of
the reduced diameter portion 82 and they are entrapped witllin
the assembled pre-orifice capsule. As shown in Figure 3, the
springs 68, ~0 work between the adjacent radially inward surfaces
of the guide arms 88, 9~ and the adjacent, planar wall portions
82 of the slots 78a, 78b to bias the jaw members apart.
The forward capsule half member 62 includes an axially
extending alignment boss 94, a disc portion 96 and a sealing
boss 98 projecting from the rearward surface of the disc portion
29 96 (Figure 51. The disc portion 96 is dimensioned to be received
cv/ - 12 -
10:~:Z2
against the shoulders 80 to provide an interference fit with
the overlying skirt portion 74 of the member 72 in order to
lock the capsule halves together when they are assembled. In
the assembled condition, the d~sc portion 96 cooperates with
the reduced diameter portion 82 and the forward face of the -~
central wall 73 to define a chamber having the jaw members and
spring members axially contained therein. The rearwardly extend-
ing skirt portion 75 of the m~mber 72 defines a recess 102
dimensioned to receive a forward shoulder of the valve body
lO holder 50 ~igure 2~. -
A pair of threaded bores 103 extend through the central -
wall 73 at spaced locations clear of the springs 68, 70 and
the jaws 64, 66. The bores 103 are employed in a screw-jacking ~-
operation to separate the assembled capsule half members 62, 72 ;
after the pre-orifice assembly 58 has been removed from the `~
spray gun. `~
The forward face of the wall 73 includes a sealing
boss 104 w~ich cooperates with the sealing boss 98 to facilitate
the proyision of a fluid seal with the jaw members 64, 66.
2Q The boss 104 surrounds the forward end of a passageway 106 which
extends through the wall 73 and communicates between the valve
port 54 and the ~djusta~le pre-orifice 60. ;
Upon emerging from the passageway 106, the liquid
enters the adjustable pre-orifice 60 which is defined by the
overlying central portions of the jaw members 64, 66. The jaw
mem~ers are formed of a hard erosion resistant material such as - :
tungsten carbide.
The central portions of the jaw mem~ers 64, 66 res-
2~ pectively, include a curved surface portion 108 and llO and a
.
- 13 -
.. =. . . .. . ., . .. ~, ., .. , ,.. . ... , . , ., . ,. ,. . . - ... ~ . - . . .
1038622
transversely disposed planar surface portion 112 and 114. The
planar surface portions 112, 114 are provided along the guide
legs 85, 87 as best shown in Figure 3. Thus, the central
portions of the jaw mem~ers have a generally J-shaped configura-
tion with the curved bottom portions of the ~ configurations
oppositely disposed from one another.
The planar surface portions 112, 114 engage associated
planar surfaces provided by the adjacent iaw member for purposes
of guiding the relative movement of the jaw members toward and
away from one another. The segments of the planar sur~ace por-
tions which are not engaged for purposes of guiding the jaw
members cooperate with the curved surface portions 108, 110 to
define the adjustable pre-orifice 60 when the jaw members are
positioned to define a relatively larger pre-orifice cross-
sectional area.
Referring to Figure 3a, the ~aw members 64, 66 are
sho~n in a fully closed or minimum pre-orifice area position
wherein t~e curved surface portions 1~8, 110 completely define
the pre-orifice 60. In this position, the pre-orifice cross-
section has a generally elliptical configuration. The curvedsurjface~ 1~8, 110 may be provided with flats adjacent the engag-
ing edges thereof at the extremities of the long dimension or
~ajor a~is o$ the pre-orifice for wear purposes.
In the full open or maximum pre-orifice area position
shown in Figure 3, the pre-orifice cross-section assumes a some-
what circular configuration with substantially equal major and
minor axes. In the full open position, the cross-sectional area
of the passageway 1~6 is slightly greater than that of the pre-
29 orifice. In the intermediate positions of the jaw members
cb~ - 14 -
., . . . , .: ; .. ... " .. , : . .. :.. ... . . . . . . .................. ... .. .
. : .: . ......................... . : . - : . . . ................ . . . ..
. . ~ . ~.. : . . . ,. - . . .: . . ~- - - . : . . . .
103~6ZZ
between full open and full closed, the pre-orifice is provided
with a generally elongated, oval shaped configuration with
blunted ends adjacent its major dimension. This variation in
cross-sectional configuration of the pre-orifice is not detri-
mental to the pre-orlfice function and its ef~ectiveness in pro-
Yiding uniform atomization of the sprayed liquid.
The pre-orifice 60 is coaxial with the passageway 106
and it remains in a coaxial relationship as its cross-sectional
area is Yaried since the jaw members are arranged for correspond-
ing radial movement in opposite directions toward and away fromone qnother, The relative movement of the jaw members 64, 66
is controlled by the axial positioning of a cylindrical cam
member 116 ~igure 21 provided by the adjustable pre-orifice
spray assembly 20.
The cam member 116 includes a beveled cam surface 118
adjacent its forward end which is arranged to engage camming
surfaces 84a and 86a provided by the cam following arms 84,
86 of the jaw members. The cam member 116 is shown in a fully
retrac~ed position in Figure 2 with the cam surface 118 thereof
in non-closing engagement with the cam surfaces 84a, 8Ça of the
jaw members.
m e cam member 116 is driven by a plurality of
angularly spaced, T-shaped drive keys 120 extending through
associated slots 122 in the cylindrical mounting sleeve 28
~only one drive key and slot is shown~. The outer radial
portion 120a of the drive key 120 is received within a groove
124 in an adjustment nut or control knob 126 and contained by
retainer plate 154 secured to the nut 126. The adjustment
2g nut 126 ha~ an internallY threaded bore 127 which is threadedly
cb~` - 15 -
~3862Z
engaged with the axially fixed mounting sleeve 28. Upon
rotation of t~e nu~ 126, it threadedly moves relative to the
sleeve 28 and correspondingly moves the cam member 116 by means
of the drive key 120.
The actual amount of relative movement of the jaw
members 64, 66 upon rotation of the adjustment nut 126 is a
function of the angle between the cam surfaces 118 and 84a,
86a together with the pitch of the threads 127. In the illustra~-
ed embodiment, each of the jaw mem~ers moves a radial distance
of about 0,018 inch for each full revolution of the adjustment
nut.
As best shown in Figure 5, the adjustable pre-orifice
60 opens into a passageway 128 provided in the forward capsule
half member 62. The cross-sectional area of the passageway
; 128 is dimensioned so as to not interfere with the fluid jet
emerging from the pre-orifice 60. The passageway 128 includes
an enlarged portion 130 which opens into a similarly dimensioned
bore 132 in the spray tip 40. The bore 132 preferably has a : :
su~stantially perpendicular forward end wall 133 and opens into ::
a relatively s~all diameter bore 134 which leads to the spray
tip nozzle opentng 136.
. As the liquid to be sprayed passes through the pre-
orifice 60, it is accelerated with a consequent drop in pressure
and emitted as a high velocity stream or jet of fluid. The
passage~ay 128 and the bore 132 are filled with liquid, and
liquid passes through the bore 134 and nozzle opening 136.
The high velocity stream or jet of liquid moves coaxially out
of the pre-orifice 60 and travels through the center of the
29 passageway 128 and bore 132 as a submerged jet. The submerged
cb' - 16 -
103~362;i~
jet enters and fills the bore 134 and upon passing through the
nozzle opening 136 it is uniformly atomized to provide the
desired oval spray pattern. '-'
W~en the area of the pre-orifice 60 is equal to the '
area of the nozzle opening 136,the pressure of the liquid through ~-~
the ~re-orifice drops ~rom the relatively high values in the val~e '~
port 54 and passageway 106. The liquid is carried through the
bore 134 and the nozzle opening 136 by the Yelocity of the su~- -
merge~ fluxd jet or kinetic energy thereof, with a relatively
small pressure drop, rather than being driven through the nozzle
~pening b~ a hi~h ~ressure-head on the upstream side of the
nozzle opening. The liquid in the chamber defined by the
passageway 128 and bore 132 is at a relatively low static
pressure~ and the su~merged fluid jet travels through the center
.. . . .
of this cha,m~er with a relatively minimum amount of frictional
reslstance. The quality of atomization is optimized in this ,
1:1 area relation between the pre-orifice and nozzle opening. ',,
The pre-orifice 60 has a sufficient axial length to ~,'
stabilize the fluid jet as it is formed therein and cause it '
to persist as a submerged jet until it reaches and fills the
bore 134 leading to the nozzle opening. It has been found
that these objectives are achie~ed when t,he pre-orifice is
provided with a mlnimum axial length equal to from about 1/2 '
to ~bout 1 times it~ maximum cross-sectional dimension. The
pre-ox~~ce may be provided with a greater relative axial length , ,
without ~ign~ft~cantl~ inter~ering with the volume of liquid
or necessitating excessively high pressures. ;~
The nozzle opening 136 has a conventional "flat
29 ~an" or "cat eye" configuration comprising a generally '',
'',.
cb/ - 17 -
103~62Z
elliptical cross-section with sharp vertices adjacent the ends
of its major axis. The cat eye configuration is provided by
initially forming the bore 134 as a blind bore terminating in
a spherically-s~aped end 138. A transversely disposed V-shaped
slot 140 is then cut into the spray tip so as to intersect
the spherical end 138 of the bore 134.
As depicted in Figure 5, the long dimension of the
nozzle openlng 136 is perpendicular to the plane of the section.
Accordin~ly, the major dimensions of the spray fan emitted
from the nozzle opening and the resulting oval shaped spray
pattern are also perpendicular to the plane of the section and
the sFray tip holder 39 is provided with a recess 142 to accommo-
date the ~ull width of the spray fan.
When the pre-orifice 60 is adjusted to a less than
- full open cross-sectIonal area, it is necessary to maintain
the elongated dimension or major axis thereof in substantially ,','
parallel relationship with the elongated dimension or major
axis o~ the nozzle opening 136. Accordingly, the alignment
boss 94 extending from the forward capsule half member 62 is ~
20 proyided with a non-circular cross-section by means of flats ~ ,
144 extend~ng along its peripheral surface. ''
The boss 94 is received wi,thin a correspondingly
shaped recess 146 in an insert 148. The insert 148 is pre-
fitted tnto ~ bore 150 in the spray tip holder 39 to prevent ' '
relati~e rotation there~etween. The spray tip 40 is similarly ',
press-fitted into the holder 39 so that the major dimension
o~ the nozzle openin~ 136 extends in a predetermined direction
~ith respect to the recess-146, and in parallel rel~tionship
29 with respect to the major dimension of t~e closed position
c~/ - 18 - - '
pre-orifice when the boss 94 is received within the recess 146.
The boss 94 also has an axially extending slot 152 which
bisects a portion of the axial extent thereof. The bore 146
is dimensioned to slightly compress the bisected portion of the
boss upon insertion therein to resiliently lock the pre-orifice
capsule 58 to the spr~y nozzle assemhly 38. A plastic washer
seal 153 is disposed about the boss 94 between the spray tip
holder 39 and the central disc portion 96 of the member 62 to
prevent li~uid from escaping between the pre-orifice capsule
10 and holder. :
If an operator desires to rotate the major dimensions
o~ the spray fan and the oval shaped spray pattern relative to
the spray gun 10, it is simply necessary to loosen the nut 36
and rotate the spray nozzle assembly 38 by grasping it adjacent
its forward end. Upon rotation of the spray nozzle assem~ly 38, -
the pre-orifice capsule 58 is correspondingly rotated about the
forward shoulder of the valve body holder 50 and the parallel
relationship between the major dimensions of the pre-orifice
60 and nozzle opening 136 is maintained. Accordingly, a con-
-20 ventional ~pray tip and nozzle assembly may be modified to pro-
yide a unitized assem~ly with the pre-orifice capsule and to
assure the maintenance o~ the desired parallel relationship.
The range of cross-sectional pre-orifice areas
through which the pre-orifice is adjustable may be selected on -
the basis of particular spray ~pplications. The pre-orifice
60 is proYided with a minor dimension of 0.009 inch and a
major dimenston of 0.035 inch ~hen the jaw mem~ers 64, 66 are
moved to the minimum area or full closed position as shown
~9 in Figure 3a~ and the pre-orifice has an equi~alent area ~alue
.
cb/ - 19 -
~103B62Z
equal to about that of a circle of 0.011 of an inch in diameter.
~hen the jaw members are moved to t~e maximum area or full open
position as shown in Figure 2, the minor and major dimensions
of the pre-orifice 60 are each equal to about 0.035 inch, and
the pre-orifice has an e~uivalent area value approximately equal
to that of a circle of 0.035 of an inch in diameter.
Thus, the ratio of the cross-sectional area o~ the -~
pre-orifice to the cross-sectional area of the nozzle opening
may be varied from one-fourth to two for fine finishing spray
tips and a restricted volume and modified spray pattern is
obtainable for most commercially available spray tips by reduc-
ing the ratio value to about 1.0 or less. When the area of the
pre-orifice is less than that of the nozzle opening, uniform
~tomization and di~tribution is still obtained but a lesser
volume of liquid is delivered through the nozzle than would
otherwise be obtained at a given liquid pressure. Although
th~ deliyered liquid volume is reduced in this instance, the ~-
li~uid ~elocity remains the same, and the resulting spray
pattern applied to work surface can be narrowed without loss
of quality or film thickne~s by manually bringing the spray
gun closer to the work surface.
If the area of the pre-orifice is reduced too much,
the jet of liquid delivered to the bore 134 is insufficient
to fill the same and the desired atomization is not o~tainable.
The critical limit is believed to be reached when the area of
the pre-orifice is about 1/4 the area of the nozzle opening.
Ratios in excess of 2.0 are available to provide
full spray angle potential for most spray tips commonly employed.
29 It should be appreciated that uniform atomization is obtained at
cb/ - 20 -
1038~iZ2
ratios of about 2.0 or when the pre-orifice area is twice that
of the nozzle opening but that a compromise in atomization quality
is made when the ratio exceeds 2.0 in order to obtain high volume
and high speed spraying. '
Referring to Figure 6, a modified embodiment of the '
pre-orifice capsule is shown. For purposes of convenience, the ,
parts of the modtfied e~bodiment have been designated with the
sa~e numbers as the corresponding parts of the embodiment shown '
in Figures 1 through 5 but for the addition of prime designations.
In Figure 6, the pre-orifice capsule 58' includes as
its ma~or elements a forward capsule half member 62', relatively
moyable jaw members 64', 66' and a rearward capsule half member ,
72'.' The jaw members 64', 66' cooperate to define an adjustable
pre-orifi,ce 6Q' and the adjustment thereof is controlled in the
- same manner as previously described.
The central wall 73' of the capsule half member 72'
has a centrally disposed, circular recess 170 which is sized
to receive a compression disc insert 172 in sliding relationship.
The disc insert 172 includes a bore 173 which is coaxial with
,20 the pasSageway 106'. '
The disc insert 172 projects beyond the forward sur-
face of the wall 73' and into sealing engagement with the jaw
members 64', 66'. The insert 172 is axially biased in a forward
direction into engagement with the jaw members by means of a
Belleville spring 174 disposed between the insert and the bottom
of the recess 170. The Bellevllle spring has a generally circular
configuration, and it includes a central bore 176 extending
therethrough.
29 The disc portion 96' of the forward capsule half
c~ 21 - '
1038622
member 62' has a centrally disposed recess 178 in the rearward
face thereof which communicates with a passageway 128'. A
circular insert 180 is bonded and axially fixed within the
recess 178. The insert 180 has a central bore 182 which
communicates between the adjustable pre-orifice 60' and the -
passageway 128'.
The insert 180 projects axially beyond the rearward
surface of the disc portion 96' of the member 62' and in~o
sea~lng engagement with t~e jaw members 64', 66'. Accordingly,
the compression disc insert 172 and the insert 180 cooperate
to engage t~e jaw members in a fluid sealing arrangement similar
to that provided by the sealing bosses 96 and 104. However,
t~e proyision of the fluid seal is facilitated by the use of
the Belleville spring 174 to bias the disc insert 172, jaw
-- members 64', 66' and the insert 180 into sealing relationship.
Referring to Figures 7 through 9, a second embodi-
ment of the present invention is shown. An adiustable pre-
orifice spray assembly 200 is shown mounted to the spray portion
16 of the spray gun 10. The spray assembly 200 is threadedly
secured to the cylindrical boss 16a of the spray gun 10. Accord
ingly, each of the illustrated adjustable pre-orifice spray
- assemblies 10 and 200 can be readily used with conventional
airless spray guns to provide an adjustable pre-orifice having
a cross-~ect;onal area variable in size to accommodate the full
range of commercial spray tips.
Referring to Figure 7, the details of the forward
portion of the spray gun 10 and adjustable pre-orifice spray
assembly 200 are shown. The adjustable pre-orifice spray
29 assembly 200 includes an adaptor 202 for mounting the assembly
~ .
F~ - z2 -
1~386Z2 ~ `
to the cylindrical boss 16a extending from the spray portion
16 of the spray gun. The internal threads of the adaptor 202
may be modified to accommodate the particular type of spray gun,
and it is axially fixed relative to the spray gun once it has
been threadedly engaged therewith.
The adjustable pre-orifice spray assembly 200 also
includes a control knob 204 and a knob closure member 206
which cooperate to secure a spray nozzle assembly 208 and a
pre-ori~ice capsule or assembly 210 adjacent the discharge end
of the spray portion 16 of the spray gun in fluid tight sealing
engagement. An elastomeric pre-orifice member or disc 212
haYing a central pre-orifice opening or aperture 214 there-
through is mounted within the capsule 210. The control knob
204 is ~rranged to axially bias the spray no~zle assembly 208
and pre-orifice assembly 210 in order to elastically deform
and vary the cross-sectional area of the pre-orifice opening
214.
The control knob 204 is formed of a low friction
plastic material such as Delrin or nylon in order to minimize
friction upon the axial loading of the elastomeric member 212.
The use of a plastic material is also advantageous in that it
adds relatiYely little weight to the assembly and tends to reduce
the overall total weight of the spray gun. The external surface
of the knob 204 may be provided with serrations to facilitate
the rotational adjustment thereof by the operator.
As previously indicated with respect to the embodiment
of Figures 1 to 6, the liquid to be sprayed is intr~duced into
the spray gun 10 by means of the fitting 22, and more particularly,
29 a passageway 22a extending therethrough and communicating with
c~/ - 23 -
. - - - . - . ~ .. . . .. . ~ .
: .: .. . .. , .. ~ .
; ~ . : :
: . :~ . .. .. . . . i .. .
103~6Z2
a central passageway or bore 42 in the spray portion16 of the
spray gun. The needle valve 26 is axially movable within the
bore 42 for purposes of actuating the spray gun upon operation
of the trigger 24.
~he forward end of the bore 42 is internally threaded
for engagement with the rear~ard portion of a valve body holder
216. The valve body holder 216 includes a rearwardly opening
recess 218~ A valve body 220 is press-fitted within the recess
218 and provides a val~e port 222 which communicates with the
passageway 42. The val~è port 222 includes a flared seating
surface 224 for yalving engagement with the rounded end of the
needle val~e 26,
The forward end of the valve body holder 216 has a
hexagon configuration~ and it is disposed in sealing engagement
- with a crushable gasket 226. The gasket 2~6 is formed of rigid
polyeth~lene or a similar plastic material. The valve body
holder 216 includes an opening 216a extending through the for-
ward end thereof and communicating between the valve port 222
and an opening 226a extending through the gasket 226.
2Q The adaptor 202 has a forward wall 202a having a rèar-
w~rdly opening recess 202b formed therein for receiving the ~
crushable gasket 226. Accordingly, when the pre-orifice spray ~ -
assembly 20~ is secured to the spray portion 16 of the spray
gun, the crusha~le gasket 226 ~s compressed between the adaptor
2n2 and the hexagon portion of the valve body holder 216 by
the spray assembly 200 to provide a fluid tight seal.
The forward wall 202a of the adaptor includes an
axially projecting cylindrical shoulder or boss 202c which is -
29 arranged for sliding engagement with the pre-orifice capsule 210. ~j -
c~/ - 24 - ~
- . ~ ' . . ~ ` ` -. ' . ; . ! . . ` ; . . ~ ` ` ' ` `: . - ' : :
103~:
The adaptor 202 is also provided with an axially extending
opening 202d which communicates with the opening 226a through
the gasket 226.
The pre-orifice capsule 210 comprises a cylindrical
shaped capsule member 228 having a rearwardly extending cylindri-
cal recess 232 therein ~ig. 9~. The pre-orifice disc 212 ~ -
is mounted witnin the base of the recess 232 in a radially
confining interference fit. The pre-orifice capsule 210 is
disposed in sliding engagement with the shoulder 202c of the
adaptor 202. To that end, the recess 232 is dimensioned for
sliding engagement with the shoulder 202c of the adaptor 202,
and the thickness of the disc 212 i5 less than the depth of
the recess 232. Thus, the capsule member cooperates with a
fixed portion of the pre-orifice spray assembly and the spray
gun to provide a relati~ely movable rigid wall for purposes
of elastically deform~ng the disc.
The capsule member 228 is formed of stainless steel,
and an erosion resistant insert 233 is provided about the
in~et of the bore 228a which extends through the capsule member
228. The insert 233 is formed of an aluminum oxide, "synthetic
sapphire" material. The capsule member-228 may be formed of
any suitable corrosion resistant metal or a rigid plastic material.
$he capsule member 228 has an axially projecting
member 234 which is detachably connected to the spray nozzle ~ -
assembly 208. To that end, the spray nozzle assembly 208 -
includes an annular shaped insert 236 which is press fitted into -~ -
a recess 238. The insert 236 includes a shouldered recess 240
having a reduced diameter portion sized to receive the forward
29 most, enlarged portion of the projecting member 234 of the -~
.
cb~ - 25 - ~
,, ., .. , ., , . ., . ,.. , , . , , . . , ,.. - - - , - , .
~O;~i22
capsule member 228. The axially projecting member 234 is
provided with a reduced diame~er portion which is axially
aligned with the enlarged portion of the recess 240 when the
co~ponents are assembled to define an annular chamber 242.
An elastomeric sealing ring 244 is disposed within the chamber
242 to detachably secure the pre-orifice capsule 210 and the
spray nozzle assembly 208 together. -
The spray nozzle assem~ly 208 includes a spray tip
holder 246 and a spray tip 248 having a spray tip or nozzle
opening 250 therein. The spray tip 248 is press fitted within
the holder 246 and it includes a first bore 252 which communi-
cates with the central bore 228a extending through the capsule
member 228, A reduced diameter second bore 254 communicates
between the first bore 252 and the spray tip opening 250.
-~ The spray tlp opening 25Q ~as a conventional "flat fan" or "cat
eyel' confi~uration which is identical with the spray tip open-
ing 140 of the first em~odiment.
As indicated above, the spray nozzle assembly 208 is
secured within the pre-orifice spray assembly 200 by means of
the knob closure member 206. The member 206 has a cylindrical
configuration including a radially inwardly projecting wall or
:
skirt 206a adjacent the forward end thereof. The member 206 is
initially t~readedly engaged with the control knob 204 using a
spanner wrench to engage the spanner holes 2~6b,and it is then ~ I ;
~ixed to the control knob 204 for axial movement therewith.
As shown in Figure 7, the member 206 cooperates with ~ -
a cantilever mounted, plastic thrust washer 256 to define an
annular chamber 258 extending around the forward portion of the
2~ spray tip holder 246. A pair of double leaf Belleville springs
c~/ - 26 -
103~622
or washers 260, 262 are disposed within the chamber 258 for
purposes of transmitting axial loading to the elastomeric
pre-orifice disc 212 upon adjustment of the control knob 204.
To that end, the thrust washer 2~6 is arranged to transmit
the spring loading to the spray tip holder 246. The thrust
washer is formed of a plastic material such as Delrin or nylon
haying a low-coefficient of friction.
The Belleville springs 260, 262 assure the uniform
transmission of deformation loads to the capsule member 228
and elastomeric member 212 upon operation of the control knob
2a4 since the springs bias the thrust washer 256 around its
entire, adjacent working surface. Further, the sensitivity
of the adjustment or t~e adjustment range of the control knob
2~4 or the deformation of the elastomeric member 212 in response
to a giVen rotational adjustment of the knob 204 may be varied
by selection of appropriate spring rates.
The elastomeric disc 212 is formed of a suitable
abrasion resistant and paint base resistant plastic material
which is capable of elastic deformation within the range required
to ~ccommodate the commercially available spray tips. The disc
212 is formed of a polyurethane elastomer having an 80 to 85
Shore A durometer, and it has been found to provide satisfactory
performance in water and oil base paint spraying applications
at presSures in excess of 3000 psig.
As shown in Figure 7, the elastomeric disc 212 is in
a full open position wherein the cross sectional area of the pre-
orifice`opening 214 is greater than the cross-sectional area of
the adjacent portion of the opening 228a. In this condition,
29 the pre-orifice is effectively removed from the spraying operation
cb~ - 2 7 -
. .. , . , ... ... ,,., .. , .. , ~ ,,.. ,, , , . , . .. , .. , .. . ,; .. ~ .
~L03~622
and the maximumi fan width is obtained for high speed rough work.In the full open position, the cross-sectional area of the pre-
orifice opening 214 has been slightly reduced ~y virtue of the
control knob 204 being s~fficiently tightened to retain the
spray nozzle assembly 208 and pre-orifice capsule 210 in fluid
tight sealing engagement.
Referring to Figure 8, the elastomeric disc 212 is
shown in a nonaxially deformed or uncompressed condition free
of the a~;al loads applied thereto by sufficiently tightening
t~e control knob 204 to retain the chain of parts in`fluid
ti~ht engagement. In this condition, the cross-sectional area
of the pre-orifice openin~ 214 is further increased as compared
with the cross-sectional area of the adjacent portion of the
opening 228a as shown in Figure 7.
The elastomeric disc 212 is provided with an outside
diameter of approximately one-half inch and the recess 232 is
sized to provide an interference fit therewith. The outside
dimenslon of the elastomeric disc is rèlated to the quality
and effectiveness of the pre-orifice opening which results.
Eor example, if the outside diameter is reduced to about three-
eig~ths of an inch, there is a tendency for irregular distortion
or deformation to occur, and it does not result in a desirably
uniform walled pre-orifice.
The uncompressed diameter of the pre-orifice opening
214 has also been found to be related to the quality of atomiza-
tion obtained and the ability to control the same throughout
the full range of commercial spray t~p sizes. Satisfactory
results have been o~tained w~en the pre-orifice opening in an
29 uncompressed condition has a diameter in the range of from 0.060
--
cb/ - 28 -
- . , . .. , . . . .. . . , . . . - . . . . , .. .: - .
, ~L03~6zz
inch to 0.125 inch. As shown in Figure 8, the unrestrained
diameter of the pre-orifice openlng 214 is about 0.105 inch.
The pre-orifice opening 214 has a sufficient axial
length to stabilize the fluid jet as it is formed therein and
cause it to persist as a submerged jet until it reaches and
fills the bore 254 leading to the spray tip opening 250. These
objectives are achieved when the pre-orifice opening has a
minimum axial length equal to from about one-half to about five
times its maximum diameter. Accordingly, the elastomeric disc
212 is about one-sixteenth of an inch thic~. The pre-orifice
opening may be provided with a greater relative axial length
without slgnificantly interrering with the volume of liquid
or necessitating excessively ~igh hydraulic pressures.
As shown in Figure 8a, the elastomeric disc 212 has
been elastically deformed to provide the pre-orifice opening 214
with a reduced cross-sectional area. In this instance, the
diameter of the pre-orifice opening has been reduced to about
0.011 inch which approximately provides a 1:1 area ratio bet-
ween the pre-orifice opening and the smallest commercially avail-
able spray tip opening.
The pre-orifice opening 214 is substantially cylindri-
cal with the wall thereof remaining substantially parallel to
axis of the passageway andliquid flow at a reduced, minimum
cross-sectianal area siZe, as well as intermediate sizes
encountered as it is moved to a full open position. As a
practical matter, the pre-orifice opening can be completely
closed by further ti~hténing the control knob 204 or rotatin~
it in a clockwlse direction as shown in Figure 7, in order
29 to ~oye it in an axially rearward direction relati~e to the
cb,~ - 29 -
spray gun. 10~22
As depicted in Figure 7, the long dimension of the spray
tip opening 250 is perpendicular to the plane of the section
and the spray gun, The spray nozzle assembly 208 is maintained
in this position and rotationally fixed by means of pins 264
extending between the spray tip holder 246 and the adaptor 202,
and passing through associated bores 266 in the capsule membPr
228 with an interference fit. One end of each of the pins 264
is receiyed within a recess or hole 264a in the holder 246 and
the other end is received within an aligned recess or hole 264b
in the adaptor 202. Accordingly, the pins and associated recesses
proyide interfitting orientation surfaces for rotationally and
angularly fixing the spray tip relative to the spray gun.
The adaptor 202 is provided with six angularly,
- equally spaced holes 264b ~only two being shown) to provide
three diametrically aligned pairs of holes in its forward face.
The ada,ptor 202 is initially threadedly engaged with the boss
16a so that a pair of the aligned holès 264b is disposed along
a line wh~ch is preferably within the plane of the spray gun
~as sho~n in Fig. 7) or perpendicular thereto. It is convenient
to use six holes 264b ~or 3 aligned pairs of holes) in order to
reduce the amount of additional deformation of the crushable
gasket 226 beyond that amount necessary to obtain a fluid tight
seal ~hen the adaptor 202 is further tightened and rotated so
as to dispose one of the aligned pairs of holes 264b in a pre-
ferred plane.
The spray tip holder 246 is provided with four angularly,
equally spaced holes 264a (only two being shown) to provide two
29 dia~etrically ~ligned pairs of holes in its rearward face. -''-
c~`/ - 30 -
10386Z2
Accordingly, either pair of aligned holes 264a may be engaged
with the pins 264 in order to rotationally ~ix the spray nozzle
assembly 208 and major dimension of the oval shaped spray pattern
Felative to the spray gun. For example, t~e appropriate pairs
of holes 264a and 264b may be aligned upon initial assembly of
the spray gun so as to rotationally fix the spray nozzle assembly
208 as shown in ~igure 7 and provide an oval shaped spray pattern
having its major dimension perpendicular to the plane of the
$pray gun.
If it is desired, in a particular spraying application
to rotate the major dimensions of t~e spray fan and oval shaped
spray pattern 90 relative to the plane of the spray gun, the
contrOl knob 204 and ~nob closure member 206 together with the
t~ust washer 256 and entrapped Belleville springs 260, 262 are
initially removed as a unit in order to permit the removal of
the spray nozzle assembly 208 from the pre-orifice capsule
asse~bly 210 which remains on the gun. The assembly 208 is then
~ot~te~ to the desired position and the pi~s 264 engaged in
the other pair of aligned holes 264a in the spray tip holder 246
to provide a 90 rotation of the spray pattern. Of course,
the c~psule member 228 having the pins 264 fitted therein may
itself be removed, rotated to a desired position and the pins
264 engaged with~n a d~fferent pair of aligned holes 264b to
proyide addition~1 angular orientations.
When the pre-orifice assembly 200 is initially secured
to the spray ~ortion 16 of the gun, the adaptor 202 is suffi-
cientl~ tightened down to provide a fluid-tight seal with the
yalve bod~ holder 216 by means of the crushable gasket 226.
2~ The pre-orifice capsule 210 and the spray nozzle assembly 208
.
cb/~ - 31 -
~03~62~
are retained in fluid-tight sealing engagement by means of the
axial loading applied thereto by the control knob 204. The
low coefficient of friction of the plastic material used to
form the control knob 204 and the thrust washer 256 minimizes
~rictional resistance enco~ntered in applying axial loads to
the chain of parts and enables the ready de~elopment of suffi-
cient axial loads to maintain them in fluid tight sealing
relationship without the use of à wrench as is required in
prior art systems.
The pre-orifice opening 214 has an uncompressed
diameter sufficientl~y greater than that of the adjacent portion
of the bore 228a to maintain this relative size relationship
even when a fluid-tight sealing load is applied to the elastomeric
disc 212 and the cross-sectional area of the pre-orifice open-
- ing 214 is correspondingly decreased. Thus, the elastomeric
disc 212 functio~s as a sealing gasket in its full open condition
~erein unrestricted flow is permitted. Of course, it also
functions as a sealing gasket when the cross-sectional area
of the pre-orifice opening 214 is reduced to flow restrictive
~izes.
As the cross-sectional area of the pre-orifice opening
~i~ being increased from a flow restrictive size, the knob 204
in the illustrated embodiment is provided with an additional 270
....... .. .
~f ro~ation after the area of t~e pre-orifice opening matches
that ~f the opening 228a during which time a fluid-tight seal
is maintained. In other words, wnen an operator desires to
~unctionally remove the pre-orifice from the spray gun for pur-
poses of high speed, rough work, tne knob 204 may be rotated
29 ~n additional 270 after he has achieved his objective without
cb,' - 32 -
.. , .. ,. .. , . ., , , . , .. .-. ~., . ... .~. . :
62Z
encountering fluid leaks or reducing t~e axial loading below
the minimum load necessary to maintain the spray nozzle assembly
and ~re-orifice capsule in fluid-tight, sealing engagement.
If any 1uid does leak into the pre-orifice spray
~ssembly, it is vented througn relief channels 206c and the
spanner holes 206b. The relief chan~els 206c are formed by
the intersection of the spanner holes 206b with the axially
extending base wall of the annular chamber 258. The upper
Spanner hole 206b and relief channel 206c in Figure 7 have been - -
shs~n ~n dotted outline for purposes of clarifying the mounting
Of the Belleville springs 260, 262 and thrust washer 256 within
the spray assembly 200.
The ratational adjustment range of the control knob 204
in providing deformation of the elastomeric member 212 and, more
important1y, the pre-oriice functioning of the pre-orifice
opening 214 at flow restrictive sizes is a function of the
~itch o the threads between the knob 204 and the adaptor 202
as well as t~e effective spring rate of the Belleville springs
260, 262. In addition, the adjustment sensitivity has also
2Q been found to be related to the hydraulic spraying pressure.
For example, when the fluid pressure is relatively high ~e.g.
3QOQ psig or greater~, the rotational adjustment of control
~nob 2Q4 ~rom a full open condition to a condition of substantial
~re-or~fice restriction may be as small as 45 or 1/8 of a turn.
Howeyer, at a rel~tively low hydraulic pressure ~e.g. 1500 psig.),
t~e rotation~l adjustment will be as much as 1/4 to 1/2 turn for
full o~en to substantial restrictive conditions. ~ccordingly,
the pre-orifice ef~ects in an average spray application at about
29 2250 psig are controlled by about a 90 rotational adjustment
'
c~/ - 33 -
~0386~2
with an additional 270 of leakage free rotation to provide a
conyenient adjustment range.
Referring to Figure 10, a modified embodiment of the
~re-orifice capsule 228 is shown. For purposes of convenience,
the p~rts of the modified embodiment have been designated with
t~e same numbers ~s t~e corresponding parts of the embodiment
s~own in Figures 7 through 9, but for the addition of prime
designations.
In Figure 10, a pre-orifice capsule member 228'
lncludes a rearwardly extending cylindrical recess 232' having
a modified elastomeric pre-orifice disc or member 212` disposed
therein. The member 212' has a generally conical configuration
~herein the forward surface 212'a thereof is substantially
planar and the rearward surface 212'b is sloped to provide a
uniforml~ decreasing thickness in a direction radially outward
from the pre-orifice opening 214'. The elastomeric member 212'
is sElo~n in an uncompressed or fully open position, and the
cylindrical shoulder or boss 202'c is provided with a concave
forward face 202'e which corresponds to the configuration of -~
2Q the surface 212'~. Upon the axial loading of the elastomeric
disc 212'~ the mating surfaces 212'b and 202'e cooperate to
proyide a radially inward component of loading upon the member
212' to facilitate its radial deformation.
cb,
.~ . .. ,, , . . , . ~.. . . . ... .. ..... .. . . .. .. . . . . . .
