U.S. patent number 3,659,787 [Application Number 05/022,492] was granted by the patent office on 1972-05-02 for nozzle.
This patent grant is currently assigned to Ransburg Electro-Coating Corp.. Invention is credited to Siro Ito.
United States Patent |
3,659,787 |
Ito |
May 2, 1972 |
NOZZLE
Abstract
A spray nozzle for an apparatus which hydraulically atomizes and
sprays coating material. The spray nozzle includes a body and a
passageway in the body. A forward portion of the passageway has
converging side walls. An opening, formed in the body, communicates
with the passageway to provide an orifice for the coating material.
A step is provided in the passageway. The passageway, the opening
and the step in the passageway of the nozzle cooperate to provide a
pattern of deposited coating material having feathered edges.
Inventors: |
Ito; Siro (Kawasaki,
JA) |
Assignee: |
Ransburg Electro-Coating Corp.
(Indianapolis, IN)
|
Family
ID: |
12279892 |
Appl.
No.: |
05/022,492 |
Filed: |
March 25, 1970 |
Foreign Application Priority Data
|
|
|
|
|
Apr 16, 1969 [JA] |
|
|
44/29575 |
|
Current U.S.
Class: |
239/708; 239/601;
239/599 |
Current CPC
Class: |
B05B
1/02 (20130101) |
Current International
Class: |
B05B
1/02 (20060101); B05b 005/00 () |
Field of
Search: |
;239/568,597,599,601,412 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wood, Jr.; M. Henson
Assistant Examiner: Love; John J.
Claims
I claim:
1. A nozzle for an airless coating apparatus for hydraulically
atomizing and spraying coating material, the nozzle comprising
a unitary, one-piece body,
a passageway in the body,
a converging wall portion at one end of the passageway, the other
end of the passageway adapted to be connected to a source of
coating material,
an opening in the body, the opening communicating with the
converging wall portion of the passageway to provide a coating
material discharge orifice, and,
a step in the passageway at about the junction between the
converging wall portion of the passageway and a main portion of the
passageway, the step and the passageway and the opening cooperating
to provide a spray pattern of deposited coating material having
feathered opposite extremities.
2. A nozzle for an airless coating apparatus as claimed in claim 1,
wherein the opening is a substantially V-shaped groove.
3. A nozzle for an airless coating apparatus as claimed in claim 1,
wherein the step in the passageway is at the junction between the
converging wall portion of the passageway and the main portion of
the passageway.
4. A nozzle for an airless coating apparatus as claimed in claim 3,
wherein the opening is a groove having a base extending to a
location adjacent the junction between the converging wall portion
of the passageway and the main portion of the passageway.
5. A nozzle for an airless coating apparatus as claimed in claim 3,
wherein the converging wall portion of the passageway is a
concavity.
6. A nozzle for an airless coating apparatus comprising
a body,
a passageway in the body,
a converging wall portion at one end of the passageway, another end
of the passageway adapted to be connected to a source of coating
material,
a substantially V-shaped groove in the body, the groove
communicating with the converging wall portion of the passageway
and adapted to provide a coating material discharge orifice,
and
a step displaced from the other end of the passageway and in the
passageway at about the junction between the converging wall
portion of the passageway and the main portion of the passageway,
the base of the "V" of the V-shaped groove being at about the
junction between the converging wall portion and the main portion
of the passageway, the step and the passageway and the groove
cooperating to provide a spray pattern of deposited coating
material having feathered opposite extremities.
7. A nozzle for an airless coating apparatus as claimed in claim 6
wherein the converging wall portion of the passageway is a
concavity.
8. A nozzle for an airless coating apparatus as claimed in claim 6,
wherein the step in the passageway is an annular step.
9. A nozzle for an airless coating apparatus as claimed in claim 8,
wherein the step is at about a right angle with the main portion of
the passageway.
10. In combination an electrostatic airless spray gun and a nozzle
for the electrostatic spray gun comprising
a body,
a passageway in the body,
a converging wall portion provided at one end of the passageway,
another end of the passageway adapted to be connected to a source
of coating material
a substantially V-shaped groove in the body, the groove
communicating with the converging wall portion of the passageway
adapted to provide a coating material discharge orifice, and
an annular step displaced from the other end of the passageway and
in the passageway at about the junction between the converging wall
portion of the passageway and the main portion of the passageway,
the base of the "V" of the V-shaped groove being adjacent the
junction between the converging wall portion and the main portion
of the passageway, the step and the passageway and the groove
cooperating to provide a spray pattern of deposited coating
material having feathered opposite extremities.
11. In combination, an electrostatic airless spray gun and a nozzle
for the gun as claimed in claim 10, wherein the converging wall
portion of the passageway is a concavity.
12. A nozzle for airless coating apparatus characterized in that
the nozzle body has formed therein a dome-shaped cavity which is
opened to the outside at its rear end, said nozzle body also having
formed at its front a V-shaped groove arranged to cross the
foremost end portion of said cavity, said dome-shaped cavity being
defined by a saucer-shaped or deep cut-shaped concavity and a
cylinder having a diameter equal to or slightly larger than the
diameter of said concavity, and an annular corner section is formed
at the boundary between said concavity and cylinder, said V-shaped
groove being formed such that its root is adjacent said boundary,
the corner section and the cavity and the groove cooperating to
provide a spray pattern of deposited coating material having
feathered opposite extremities.
13. A nozzle comprising a unitary, one-piece body, a passageway in
the body, a concavity at one end of the passageway, a substantially
V-shaped groove in the body, the groove communicating with the
concavity providing a discharge orifice for material, and a step in
the passageway at the junction between the concavity of the
passageway and a main portion of the passageway, the step being
annular and at about a right angle with the main portion of the
passageway, the base of the "V" of the V-shaped groove projecting
to or beyond the junction between the concavity and the main
portion of the passageway, the step and the passageway and the
groove cooperating to provide a spray pattern of deposited material
having feathered opposite extremities.
14. The nozzle of claim 13 wherein the main portion of the
passageway is cylindrical in shape and has a diameter slightly
larger than the largest dimension of the concavity.
15. A nozzle providing a spray pattern of deposited material having
feathered opposite extremities, the nozzle comprising a unitary,
one-piece body, a passageway including a rear end in the body, a
concavity at an end of the passageway opposite the rear end, an
opening in the body, the opening communicating with the concavity
providing a discharge orifice for material, and a substantially
annular step in the passageway at about the junction between the
concavity of the passageway and a main portion of the passageway
and displaced from the rear end of the passageway, the step and the
passageway and the opening cooperating to provide the spray pattern
of deposited material having feathered opposite extremities.
Description
The present invention relates to an apparatus which atomizes and
sprays coating material. More particularly, the present invention
relates to a nozzle for either a non-electrostatic or electrostatic
hydraulic or airless spraying apparatus. The nozzle of the
apparatus assists in hydraulically atomizing coating material and
provides a deposited pattern of coating material particles having a
relatively wide central portion within which the distribution of
coating material particles is reasonably uniform. The opposite
extremities or margins of the pattern have a progressively
decreasing number of particles per unit of width.
A hydraulic or airless spraying apparatus causes the coating
material to emerge from the orifice of its nozzle under high
pressure. When the coating material emerges from the orifice of the
nozzle, it is atomized into a fine spray. The airless apparatus has
advantages over several other techniques of depositing the coating
material such as reducing the amount of coating material sprayed in
order to obtain a suitable film thickness of coating material upon
the article thereby resulting in a coating material savings.
Another advantage of the airless apparatus is that it is capable of
projecting the coating material into the recesses of articles.
A problem generally associated with several known spray nozzles
used with an airless spraying apparatus is the apparent inability
of such nozzles to atomize the coating material in a manner as to
provide a pattern having a relatively wide central portion within
which the distribution of coating material particles is reasonably
uniform and opposite extremities or margins thereof having a
progressively decreasing number of particles per unit of width. The
relatively heavy number of paint particles at the opposite
extremities of the pattern are sometime referred to as "pig-tails"
or simply "tails". The apparent inability of such nozzles to reduce
the number of coating material particles at the margins or
extremities of the pattern in relation to the number of particles
in the central portion of the pattern, that is to feather the
pattern, renders it difficult to properly blend together adjacent
patterns in such a manner as to provide a suitably uniform film of
coating material upon the article.
Therefore, it would be desideratum to provide a means and/or a
method whereby a deposited pattern of coating material has a wide
central portion having a substantially uniform distribution of
material particles with opposite extremities feathered by a
decreased number of material particles in relation to the number of
particles in the wide central portion of the pattern. The apparent
inability of several of the known nozzles to provide a pattern of
coating material which substantially eliminates "tails" may be due,
in part, to either the physical properties of the coating material
such as viscosity, surface tension, density and the like or to the
construction of the nozzle or both. Attempts have been made to
improve the atomization properties of the coating material by
improving properties of material such as viscosity, surface
tension, density and the like and by altering the construction of
the nozzle.
An attempt to improve the atomization properties of coating
material includes heating the material prior to atomization. While
heating of the material tends to improve properties such as
viscosity, surface tension and the like, other properties of the
material remain substantially uneffected resulting in a pattern
which does not appear to be particularly advantageous for high
quality finishes.
Another attempt to improve the atomization properties of coating
material includes thinning of material such as paint so as to
reduce its viscosity and subjecting the thinned paint to high
pumping pressure so as to provide the paint with a high velocity as
it emerges from the nozzle. The thinning of the paint and pumping
the thinned paint at a high pressure of about 80 to 100 Kg/cm.sup.2
or higher, which when converted to pounds per square inch is
approximately 1,100 to 1,450 p.s.i., may result in excessive paint
flow through the orifice of the nozzle thereby resulting in an
undesirable finish on the article. Furthermore, subjecting the
apparatus to high internal pressures may result in undesirable wear
of components such as paint seals and the like of the
apparatus.
It is, therefore, an object of the present invention to provide a
spray nozzle with means for substantially reducing the number of
coating material particles at the opposite extremities of a
deposited pattern in relation to the number of material particles
found in the wide central portion of the pattern. A further object
of the present invention is to provide a spray nozzle having an
annular step at about the junction between the cylindrical and the
converging wall portions of a passageway in the body of the spray
nozzle. The annular step assists in substantially eliminating the
"tails" from the pattern of coating material deposited upon the
article. Yet another object of the present invention is to provide
a spray nozzle structure including a substantially V-shaped orifice
opening or groove in the body of the nozzle. The base or root of
the "V" of the opening projects to about or beyond the annular step
at the junction between the cylindrical and the converging wall
portions of the passageway.
Generally speaking, the present invention relates to a spray nozzle
which significantly reduces the number of coating material
particles at opposite extremities of a deposited coating material
pattern when compared to number of material particles found in the
wide central portion of the pattern. The spray nozzle includes a
body and a passageway in the body. The passageway formed in the
body includes a converging wall portion formed at one end thereof.
An opening, formed in the body, communicates with the passageway to
provide an orifice through which the pressurized coating material
emerges. The other end of the passageway is adapted to be connected
to a source of coating material. A step is provided in the
passageway at about the junction between the converging wall and
the cylindrical portions of the passageway. The passageway, the
opening and the step in the passageway cooperate so as to
substantially eliminate "tails" from the pattern of coating
material deposited upon the article.
In the drawing:
FIG. 1 is a perspective view of a spray apparatus incorporating the
nozzle of the present invention in operation and the surface of an
article being coated by coating material emerging from the nozzle
of the spray apparatus;
FIG. 2a is a diagrammatic illustration of a spray pattern obtained
employing the nozzle of the present invention with the spray
apparatus shown in FIG. 1;
FIG. 2b is a diagrammatic illustration of a spray pattern generally
obtained using a conventional nozzle with the spray apparatus shown
in FIG. 1;
FIG. 3 is a cross sectional view of a conventional nozzle which
provides the spray pattern illustrated in FIG. 2b;
FIG. 4 is a cross sectional view of the conventional nozzle taken
across the line 4--4 of FIG. 3;
FIG. 5 is a cross sectional view of an embodiment of the nozzle
according to the present invention;
FIG. 6 is a cross sectional view of the nozzle illustrated in FIG.
5;
FIG. 7 is a cross sectional view taken along line 7--7 of FIG.
6;
FIG. 8 is a cross sectional side view of another embodiment of the
nozzle of the present invention;
FIG. 9 is a cross sectional plane view taken along line 9--9 of
FIG. 8;
FIG. 10 is a cross sectional side view of yet another embodiment of
the nozzle of the present invention;
FIG. 11 is a cross sectional plane view taken along line 11--11 of
FIG. 10;
FIG. 12 is a cross sectional side view of yet still another
embodiment of the nozzle of the present invention;
FIG. 13 is a cross sectional plane view taken along line 13--13 of
FIG. 12; and
FIG. 14 is a schematic of an airless electrostatic apparatus using
a nozzle of the present invention.
Referring now to FIG. 1 of the drawing, an apparatus including an
airless non-electrostatic spray gun 10, coupled to a suitable
source (not shown) of coating material under pressure, is
predeterminately spaced from the surface article 11. Maintaining
the spray gun 10 spaced from the surface of article 11 by about 20
to 30 cm (approximately 8 to 12 inches) results in an instantaneous
spray pattern 12 being deposited upon the surface of article 11.
Moving the spray gun 10 across the article 11 or displacing the
article 11 in relation to the spray gun 10 results in a continuous
spray pattern 13 being deposited upon the surface of article.
As shown in FIGS. 1 and 2a, an advantageous instantaneous pattern
of an airless spray gun is the oval-like or barshaped pattern 12.
The strip-shaped pattern 13, illustrated in FIG. 2a, results from a
substantially continuous application of coating material from the
gun 10 across the article 11. The absence of "tails" at the
opposite extremities of each of the deposited patterns should be
noted.
A conventional nozzle 20, as exemplified in FIGS. 3 and 4, includes
a nozzle body 21 in which is formed a passageway 22 opened at its
rear end 23 so as to communicate with a source of coating material
(not shown) under pressure. The passageway 22 includes a
substantially hemispherical concavity or dome-shaped portion 24 at
the front thereof. The radius of the cylinder portion of the
passageway 22 is substantially equal to the radius of the concavity
portion 24 of the passage way. An elongated, substantially V-shaped
notch 25 is in the front of the nozzle body 21. The notch 25 opens
forwardly and the base or root portion thereof projects rather
shallowly into the concavity portion 24 of the passageway 22. The
interface between the notch 25 and the concavity portion 24 of the
passageway 22 provides a relatively small orifice through which the
coating material under pressure emerges.
Generally, coating material is fed into the passageway 22 under
pressure of about 100 Kg/cm.sup.2 or higher, (about 1,450 p.s.i.)
and emerges forwardly from the orifice formed by the concavity
portion 24 of the passageway and the V-shaped notch 25. The
pressurized coating material emerging from the orifice of nozzle 20
breaks into a very fine spray of coating material particles.
However, when employing conventional nozzle 20 with airless spray
gun 10, its instantaneous spray coating pattern 14 tends to include
at its margins or extremities "tail-like" deposits 15 and 16 as
shown in FIG. 2b. The "tail-like" deposits 15 and 16 of coating
material at the extremities of the pattern make feathering of
adjacent patterns difficult at best. The continuous pattern 17
provided by conventional nozzle 20 is shown in FIG. 2b. Note that
the continuous pattern 17 is accompanied by strip-like marks 18 and
19 at the opposite extremities thereof.
A conventional nozzle 20, which provides either an instantaneous
pattern 14 or a continuous pattern 17 with "tail-like" extremities
15 and 16 or 18 and 19, respectively, is suitable for non-finish
coating but is not entirely satisfactory for high quality finish
coating. Further, since some coating material used for high quality
finish coating has more of a tendency to produce such "tail-like"
marks than other types of coating material, airless coating methods
have not been as widely accepted for finish work as is desired.
A nozzle 27 embodying concepts of the present invention is
illustrated in FIGS. 5-9. It has been found that if the base or
root of a coating material opening or groove 26 in body 34 of
nozzle 27, such as an elongated V-shaped notch, projects into
passageway 28 to such an extent so as to substantially adjacent
with or project beyond the boundary or junction 29 between the
converging wall or concavity portion 30 and the cylindrical portion
31 of the passageway, as shown in FIGS. 5-9, the "tail-like" marks
in the deposited pattern are not as pronounced as are found when
using a conventional nozzle 20. The base or root of the "V" of the
V-shaped notch 25 of the conventional nozzle 20, shown in FIGS. 3
and 4, does not project to about the boundary or junction between
the converging wall portion and the cylindrical portion of the
passageway.
Also, it was found that it is possible to further reduce
pronouncedness of such tail-like marks in the deposited pattern of
coating material by forming an annular corner section or step 32 in
body 34 of nozzle 27' as shown in FIGS. 10-13, at about the
boundary or junction 29 between the converging wall portion 30 and
the cylindrical portion 31 of the passageway 28. The "tail-like"
marks of the deposited spray pattern are substantially completely
eliminated by the combination of a V-shaped groove 26 formed in the
body 34 of the nozzle 27' such that the base or the root of the "V"
of the notch is substantially adjacent with or projects beyond the
annular corner section 32 at the boundary or junction 29 between
the converging wall portion 30 and the cylindrical portion 31.
The substantially complete elimination of the tails from the
deposited pattern may be realized by selecting the diameter of the
cylinder portion 31 of the passageway 28 so as to be slightly
larger than the diameter of the converging wall portion 30 of the
passageway thereby forming the annular corner section or step 32 at
the boundary or junction 29 between the converging wall portion 30
and the cylindrical portion 31. It is preferred that step 32 be
formed in such a manner as minimize the possibility of a formation
of step having a "rounded" or fillet area at junction 29. A nozzle
27' including step 32 at junction 29 is shown in FIGS. 10-13.
A theoretical explanation of the factors acting to inhibit or
substantially eliminate the appearance of such tails in the pattern
by using nozzles 27 or 27' of the present invention is not
presently clearly understood.
Nozzle 27' including an annular corner section or step 32 of
substantially a right angle at the boundary or junction 29 between
the converging wall portion 30 and the cylindrical portion 31 of
the passageway 22 and a V-shaped groove 26 projecting into the
passageway in such a manner that the base of the "V" of the groove
is substantially adjacent with or projects beyond the boundary or
junction 29 is the preferred embodiment of the present
invention.
In the foregoing embodiments of the nozzles 27 and 27' illustrated
in FIGS. 5-13, inclusive, the converging wall portion 30 may be
shaped in the form of a hemisphere, or shaped in a shallow
saucer-like form having a depth less than that of a hemisphere or
shaped in a cup-like form having a depth greater than that of a
hemisphere. The embodiments illustrated in FIGS. 5-13 show the
converging wall portion 30 having either a saucer-like form having
a depth less than that of a hemisphere or a cup-like form having a
depth greater than that of a hemisphere. It is to be understood
that the converging wall portion 30 may be in the form of a
hemisphere.
The passageway 28 of the nozzles 27 and 27' is open at its rear end
33 so as to communicate with a source of suitable coating material
(not shown) under pressure. The interface between groove 26 and the
converging wall portion 30 provides a relatively small orifice
through which coating material emerges.
As disclosed above, the present invention substantially prevents
the appearance of the "tail-like" marks in the deposited pattern
which have been associated with several of the coating patterns
provided by conventional nozzles. Also, it was found that a
melamine resin coating material, which tends to produce the
"tail-like" marks when sprayed from an airless spray device using a
conventional nozzle of the type shown in FIGS. 3 and 4, can be
effectively used with the nozzles of the present invention without
producing such marks in the deposited pattern.
Furthermore, the spraying distance, which has conventionally been
set at more than 30 cm (about 12 inches) for fear of producing a
non-uniform coating film can be reduced to 20 cm (about 8 inches)
or less without the undesirable "tail-like" marks appearing in the
deposited pattern. The airless device may be effectively used with
coating material pressures of about 70 Kg/cm.sup.2 (about 980
p.s.i.) or less as compared with the conventional devices which
pressurize the coating material to about 1,450 p.s.i. or
higher.
The nozzles of the present invention as illustrated in the drawing
and described above may have the following dimensions:
The diameter of the cylindrical portion 31 of the passageway 28 may
be about 0.25 to 1.3 of a millimeter (approximately 0.010 to 0.051
of an inch) or more with the preferred diameter of the cylindrical
portion being about 0.45 to 0.8 of a millimeter (approximately
0.017 to 0.032 of an inch).
A suitable thickness for the annular corner section or step 32 may
be about 0.01 of a millimeter (approximately 0.0004 of an inch) to
about 0.03 of a millimeter (approximately 0.0012 of an inch) or
more. It is to be understood that the dimensions of the annular
corner section or step 32 are merely illustrative and are not to be
construed as limiting with regard to the step dimensions which
cooperate to assist in substantially eliminating "tail-like" marks
from the spray pattern.
A suitable radius for the converging wall portion 30 of the
passageway at the junction 29 only may be about 0.115 to 0.64 of a
millimeter (approximately 0.0045 to 0.025 of an inch). It is to be
understood that the axial radius of the converging wall portion 30
may either be equal to, greater than or less than that of a
hemisphere.
A suitable location of the root of the V-shaped groove is to extend
to a location adjacent the junction or boundary 29. For example,
the root of the V-shaped groove may extend to within about 0.01 of
a millimeter (approximately 0.0004 of an inch) of the junction or
boundary, coincide with the junction or boundary or extend beyond
the junction or boundary by about 0.01 of a millimeter or more.
The angle of groove 26 depends on the desired pattern size. A
suitable angle for the groove 26 is about 30.degree.-90.degree.
with the preferred angle being about 55.degree..
The ratio of the length of the cylindrical portion 31 of the nozzle
to the diameter of the cylindrical portion of the nozzle may be
from about 2 to 1 to 6 to 1 or greater.
Coating material, as used herein, includes but is not limited to a
fluid or semi-fluid material which may be applied to the surface of
an article in relatively thin layers and which changes to a solid
coating with the passage of time. The change of the material to a
solid may or may not be reversible and may occur by evaporation of
solvent, by chemical reaction, or by the combination of the two. A
suitable coating material is paint.
The nozzles 27 and 27' of the present invention may be used with
any suitable non-electrostatic airless spray apparatus 10 or
electrostatic airless spray apparatus 40. Referring to FIG. 14 of
the drawing, an airless electrostatic spray gun is designated by
the reference numeral 40. The airless electrostatic spray gun 40
includes a barrel 41 and a handle 42. Conduit 43 connects the gun,
and hence the nozzle 27', to a source 44 of coating material under
pressure to be sprayed. A voltage lead 45 extends into the handle
42 from an ungrounded terminal of a voltage source 46, the other
terminal of which is grounded as indicated at 47. A trigger 48
carried by the gun controls the supply of coating material under
pressure and voltage in any convenient manner to the gun. Exterior
portions of the gun 40, including the handle 42 and trigger 48 may
be grounded as through a conductive sheave surrounding, but
insulated from, the voltage lead 45. FIG. 14 also shows a grounded
article 49 in position to receive the spray from the gun. An
electrostatic spray gun is described in detail in U.S. Pat. No.
3,169,883.
The nozzle 27 or 27' should be fabricated from any suitable wear
resistant material such as tungsten carbide, ceramic, sapphire,
stainless steel, titanium carbide and the like. A preferred
material from which either nozzle 27 or nozzle 27' may be
fabricated is tungsten carbide.
* * * * *