U.S. patent number 3,667,675 [Application Number 05/115,685] was granted by the patent office on 1972-06-06 for electrostatic powder coating apparatus.
This patent grant is currently assigned to Graco Inc.. Invention is credited to Richard M. Sherman, Robert M. Webb.
United States Patent |
3,667,675 |
Sherman , et al. |
June 6, 1972 |
ELECTROSTATIC POWDER COATING APPARATUS
Abstract
An electrostatic powder coating apparatus for coating the
surfaces of articles with pulverulent materials having an
ionization member which serves as both an improved charging means
and a pattern forming deflecting means including a probe portion
positioned immediately to the rear of a deflecting member and a
probe portion extending past a forward-most surface of the
deflecting member, with said portions of the probe being maintained
at an electrical potential substantially different than that of the
article to be coated.
Inventors: |
Sherman; Richard M.
(Northville, MI), Webb; Robert M. (Chicago, IL) |
Assignee: |
Graco Inc. (Minneapolis,
MN)
|
Family
ID: |
22362847 |
Appl.
No.: |
05/115,685 |
Filed: |
February 16, 1971 |
Current U.S.
Class: |
239/698;
361/227 |
Current CPC
Class: |
B05B
5/032 (20130101) |
Current International
Class: |
B05B
5/025 (20060101); B05B 5/03 (20060101); B05b
005/00 () |
Field of
Search: |
;239/15,3 ;317/3 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Wood, Jr.; M. Henson
Assistant Examiner: Culp, Jr.; Thomas C.
Claims
We claim:
1. An electrostatic powder coating apparatus for electrostatically
coating the surfaces of articles with pulverulent materials
comprising:
a gun body having a longitudinal passage therethrough, said
longitudinal passage having an inlet for receiving pulverulent
materials and a discharge for discharging said pulverulent
materials from the gun body toward an article to be coated;
an elongated ionization member having a first end disposed within
said longitudinal passage and a second end spaced forward from the
discharge of said gun, said ionization member further including
a probe extending from said first end to said second end of said
ionization member, said probe being constructed of an electrically
conductive material,
a body member constructed of an electrically non-conductive
material surrounding said probe and extending from said first end
to a point along said probe such that substantially all of said
probe disposed within said passage is surrounded by said body
member,
a deflecting member for deflecting pulverulent materials being
discharged from said discharge, said deflecting member being
constructed of an electrically non-conductive material and disposed
near said second end such that said deflecting member is spaced
from said body member so that a portion of the probe immediately to
the rear of said deflecting member is exposed to pulverulent
materials passing through said passage and such that a portion of
said probe passes through said deflecting member and extends past
an exterior surface of said deflecting member; and means for
connecting a high voltage energy source with said probe so as to
maintain a high voltage difference between said probe and the
article to be coated.
2. The electrostatic powder coating apparatus of claim 1 having a
sleeve member constructed of electrically non-conductive material
which is slidably mounted to said gun body adjacent to the
discharge of said longitudinal passage for axial movement
therealong, said sleeve member being movable from a retracted
position to a plurality of extended positions in which the front
end of said sleeve member is forwardly spaced from the discharge of
said passage.
3. The electrostatic powder coating apparatus of claim 2 having
means for axially moving said sleeve member and means for retaining
said sleeve member in any desired axial position and limiting the
axial movement of said sleeve member.
4. The electrostatic powder coating apparatus of claim 3 wherein
said means for retaining said sleeve member in a desired axial
position includes a threaded member extending through a portion of
said sleeve member and engaging a longitudinal channel on the
surface of said gun body.
5. The electrostatic powder coating apparatus of claim 1 having a
contact member constructed of an electrically conductive material,
said contact member being secured to said body member and
electrically connected to said probe.
6. The electrostatic powder coating apparatus of claim 5 wherein
said means for connecting a high voltage energy source with said
probe includes an electrically conducting member projecting into
said passage and engaging said contact member for electrically
connecting the high voltage source with said contact member and for
limiting the movement of said ionization member into said
passage.
7. The electrostatic powder coating apparatus of claim 1 having a
plurality of fins integrally formed with said body member, said
fins being circumferentially spaced about the periphery of said
body member and extending radially outwardly therefrom for
retaining said ionization member within said passage.
8. The electrostatic powder coating apparatus of claim 7 having a
contact member constructed of an electrically conductive material,
said contact member being mounted to a portion of said fins and
electrically connected to said probe, such that a portion of said
contact member is radially spaced from said body member.
9. The electrostatic powder coating apparatus of claim 8 wherein
there are four fins constructed of a relatively flexible material
for resiliently retaining said ionization member within said
passage and wherein said means for connecting a high voltage energy
source with said probe includes an electrically conducting member
projecting into said passage between an adjacent pair of said fins
and engaging said contact member for electrically connecting the
high voltage source with said contact member and for limiting the
movement of said ionization member into said passage.
10. The electrostatic powder coating apparatus of claim 9 wherein
said contact member is a relatively circular ring having an
external diameter conforming substantially to the internal diameter
of said passage and having an internal diameter substantially
greater than the external diameter of said body member such that
pulverulent material passage through said passage must pass between
said body member and said ring.
11. The electrostatic powder coating apparatus of claim 1 wherein
said deflecting member includes a concave surface which is
perpendicular to the longitudinal axis of said probe and which is
the surface of said deflecting member past which a portion of said
probe extends.
12. The electrostatic powder coating apparatus of claim 11 wherein
said concave surface joins with a second surface of said deflecting
member to form an edge such that all portions of said edge are
spaced forwardly from the discharge of said passage at least as far
as the portion of said probe extending past said concave
surface.
13. The electrostatic powder coating apparatus of claim 2 having a
contact member constructed of an electrically conductive material,
said contact member being connected with said body member and
electrically connected to said probe.
14. The electrostatic powder coating apparatus of claim 2 having a
plurality of fins integrally formed with said body member, said
fins being circumferentially spaced about the periphery of said
body member and extending radially outwardly therefrom for
retaining said ionization member within said longitudinal
passage.
15. The electrostatic powder coating apparatus of claim 2 wherein
said deflecting member includes a concave surface which is
perpendicular to the longitudinal axis of said probe and which is
the surface of said deflecting member past which a portion of said
probe extends.
16. The electrostatic powder coating apparatus of claim 13 having a
plurality of fins integrally formed with said body member, said
fins being circumferentially spaced about the periphery of said
body member and extending radially outwardly therefrom for
retaining said ionization member within said longitudinal
passage.
17. The electrostatic powder coating apparatus of claim 13 wherein
said deflecting member includes a concave surface which is
perpendicular to the longitudinal axis of said probe and which is
the surface of said deflecting member past which a portion of said
probe extends.
18. The electrostatic powder coating apparatus of claim 16 wherein
said deflecting member includes a concave surface which is
perpendicular to the longitudinal axis of said probe and which is
the surface of said deflecting member past which a portion of said
probe extends.
19. The electrostatic powder coating apparatus of claim 18 wherein
said contact member is mounted to a portion of said fins and is
adapted for engaging a conducting member projecting into said
passage for electrically connecting the high voltage source with
said probe and for limiting the movement of said ionization member
into said passage, and wherein said concave surface joins with a
second surface of said deflecting member to form an edge such that
all portions of said edge are spaced forwardly from the discharge
of said passage at least as far as the portion of said probe
extending past said concave surface.
20. A charging and deflecting unit for use in an electrostatic
powder coating apparatus for electrostatically coating the surfaces
of articles with pulverulent materials, said apparatus having a
passage through which dispersed pulverulent materials are conveyed
and a discharge end of said passage through which said pulverulent
materials are discharged, said charging and deflecting unit
comprising:
an electrically non-conductive deflecting member around which
pulverulent material must be deflected upon leaving the discharge
end of said gun, said deflecting member being spaced forwardly from
the discharge end of said passage and oriented centrally along the
extended longitudinal axis of said passage;
a central charging electrode portion positioned immediately to the
rear of said deflecting member and exposed to the pulverulent
materials being discharged from said passage;
a forward charging electrode portion positioned immediately forward
of said deflecting member;
means connecting said charging electrode portion and said forward
charging electrode portion with a high voltage power source for
maintaining both of said electrode portions at an electrical
potential substantially different from that of said article to be
coated; and
a sleeve member constructed of electrically non-conductive material
which is slidably mounted to said gun body adjacent to the
discharge end of said passage for axial movement therealong, said
sleeve member being movable from a retracted position to a
plurality of extended positions in which the front end of said
member is forwardly spaced from the discharge end of said passage
for thereby varying the pattern of said pulverulent materials being
discharged from said passage.
21. The charging and deflecting unit of claim 20 wherein said
central charging electrode portion is spaced forward of the
discharge end of said passage.
22. The charging and deflecting unit of claim 20 wherein said
deflecting member includes a concave surface substantially
perpendicular to the extended longitudinal axis of said passage and
wherein said concave surface joins with a second surface of said
deflecting member to form an edge such that all portions of said
edge are spaced forwardly from the discharge end of said passage at
least as far as said forward charging electrode portion.
23. The charging and deflecting unit of claim 20 having a body
member rigidly connected with said central charging electrode
portion and said deflecting member, said body member extending into
said passage and being resiliently retained therein for supporting
said deflecting member.
24. The charging and deflecting unit of claim 23 wherein a portion
of said central charging electrode portion extends through said
body member.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to an electrostatic powder
coating apparatus for electrostatically coating pulverulent
materials onto an article to be coated. More specifically, the
present invention relates to an improved electrostatic powder
coating apparatus having an improved nozzle portion for charging
the pulverulent materials as they pass through and exit from a
material passage of the spray gun and for forming the pulverulent
materials into a desired spray pattern for maximum deposition and
wrap-around of the particles onto the article to be coated. With
the present invention, the desired deposition and wrap-around is
attained with a voltage substantially less than that necessary in
the past.
Although the concept of electrostatic coating is generally fairly
well understood, especially the electrostatic coating of liquid
materials, the details of the concept of electrostatic deposition
of pulverulent materials requires further refinement. In other
words, the general problems and difficulties dealing with the
electrostatic deposition of pulverulent materials are known, but
their solutions in terms of designing a spray gun to operate at
optimum conditions is unknown. For example, it is well known in the
field of electrostatic powder coating that an operable
electrostatic powder coating apparatus must include a means for
dispersing the pulverulent materials by a compressed air current or
other means so that the particles can be deposited onto the article
to be coated as individual particles, a means for imparting a
charge to the individual particles either by causing the particles
to directly contact an electrically conductive element containing
such charges or by causing the particles to pass through an
electrostatic field set up between electrodes maintained at two
different potentials, and a means for deflecting and forming the
pulverulent materials into a desired spray pattern. One of the
specific shortcomings of the prior spray guns was the inefficient
use of the high voltage supplied to the ionizing member. Often the
high voltage potential of the prior art ionizing members was not
efficiently used because of the stray or unintentional capacitance
between the ionizing electrode and grounded objects other than the
article to be coated.
SUMMARY OF THE INVENTION
In contrast to the electrostatic powder coating apparatus of the
past, the present invention provides an improved spray gun having
an improved nozzle assembly including an ionization member adapted
to be quickly and easily removed from the forward portion of the
spray gun for cleaning and then reinserted and which serves both as
an improved charging means and a pattern forming deflector. The
specific structure on the improved ionization member includes a
probe extending from one end of the ionization member to the other,
a body member having a plurality of fins equally spaced and
radially extending from the rearward end of the probe for retaining
the ionization member within the spray gun, a contact ring member
mounted on the fins for electrically connecting a high voltage
source with the probe, and a deflecting member positioned at the
forward end of the probe in a position such that a portion of the
probe extends past an exterior surface of the deflecting member
such that the deflecting member is spaced forwardly from the body
member. When the high voltage source is actuated, the probe is
elevated to a potential substantially greater than the potential of
the article to be coated and an electrostatic field is set up
between the article to be coated and each of the portion of the
probe extending through the deflecting member and the portion of
the probe located between the deflecting member and the cone body.
It has been found that a structure of this sort affords the desired
deposition and wrap-around of the pulverulent materials onto the
article to be coated with a significant reduction in stray or
unintentional capacitance between these probe portions and grounded
objects other than the article to be coated and thereby requiring a
much smaller voltage than spray guns of the past.
Accordingly, it is an object of the present invention to provide an
electrostatic powder coating apparatus having an ionization member
which serves both to charge the pulverulent materials to be coated
and as a deflector to form the pulverulent materials into a desired
spray pattern.
Another object of the present invention is to provide an
electrostatic powder coating apparatus having an electrically
non-conductive cylindrical sleeve telescopically mounted for axial
movement along the end of the gun barrel so that one end of the
sleeve extends to a plurality of positions past the end of the gun
barrel for varying the spray pattern of the pulverulent materials
being discharged from the gun.
Another object of the present invention is to provide an
electrostatic powder coating apparatus in which the ionization
member which serves as both a charging means and a deflecting means
is easily removable from the spray gun to facilitate easy cleaning
of the member when it is desired to use the apparatus to coat a
material having a different characteristic.
A further object of the present invention is to provide an
electrostatic powder coating apparatus having an ionization member
with which the same deposition of pulverulent materials and the
same wrap-around of pulverulent materials can be attained with a
substantially lower voltage than electrostatic guns of the
past.
These and other objects of the present invention will become
apparent by referring to the preferred embodiment, the drawings,
and the appended claims.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevated view partially in section showing the
improved spray gun of the present invention.
FIG. 2 is a detailed exploded perspective view partially in section
of the nozzle portion of the spray gun.
FIG. 3 is a sectional view of FIG. 1 as viewed from line 3--3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in FIG. 1 of the preferred embodiment, the electrostatic
powder coating gun 10 of the present invention includes generally a
barrel portion 11, a nozzle portion 15 located near the front of
the barrel portion 11, a handle 12, a trigger 14 and a means
located near the rear portion of the gun 10 for supplying high
voltage and pulverulent materials to the gun 10.
More specifically, the barrel portion 11 of the gun 10 encloses a
generally cylindrical material passage 18 extending longitudinally
through the spray gun 10 and through the entire barrel portion 11,
and a generally cylindrical high voltage chamber 19 extending
longitudinally through part of the barrel portion 11. In the
preferred embodiment, substantially all of the barrel portion 11,
and especially those portions of the barrel 11 which enclose the
material passage 18 and high voltage chamber 19, are constructed
from a molded polyethylene which is electrically
non-conductive.
The high voltage chamber 19 is separated from the material passage
18 by a molded polyethylene wall 20 and is disposed within the
barrel 11 in a position which is substantially parallel to the
passage 18. The chamber 19 extends forwardly through the barrel 11
to a forward barrel portion 21 and rearwardly through the barrel 11
to and through a metal rear portion of the gun 22. At its front
end, the chamber 19 houses a 150-megohm resistor 24, the rear end
of which is electrically connected to a high voltage cable 25
housed in the rearward portion of the chamber 19. The resistor 24
and the cable 25 are electrically connected by a stress relief cap
26 which includes a compression spring 28 biasing the resistor 24
toward the forward end of the chamber 19. The rearward portion of
the high voltage cable 25 is electrically connected by an
appropriate fitting to the ungrounded terminal of a high voltage
source indicated schematically by the reference numeral 30. The
other terminal of the high voltage source 30 is electrically
grounded.
Located in the forward portion of the chamber 19 is an electrically
conductive set screw 31 threadedly extending through the wall 20 to
thereby electrically connect the resistor 24 with a contact or ring
member 32 disposed within the material passage 18 and which will be
more fully described below. Directly above the set screw 31 is a
plug 34 which is threadedly received by a portion of the barrel and
which can readily be removed for adjustment or removal of the set
screw 31.
The nozzle portion 15 located near the forward end of the barrel 11
generally includes a pattern control sleeve or cylindrical member
36 telescopically mounted over a portion of the forward end of the
barrel 11 and adapted for axially sliding movement along the
forward portion of the barrel 11. The sleeve 36, constructed of an
electrically non-conductive material such as a linear synthetic
polyamide, commonly sold under the trademark Nylon, includes a
relatively cylindrical interior surface 38 substantially conforming
in diameter to the exterior surface of the forward end of the
barrel 11, a forward end portion 39 which, when the sleeve 36 is
moved to an extended position, is disposed at a position spaced
forwardly from the forward end of the passage 18, a rearward end
portion 40, and a set screw 41 extending through the body of the
sleeve 36 for a limited distance to engage the longitudinal channel
42 which is formed in a portion of the exterior surface of the
barrel 11. As shown by the broken line 33, the sleeve 36 can be
moved to a plurality of extended positions in which the forward end
39 is forwardly spaced from the forward end of the passage 18. When
in a retracted position, the forward end 39 does not extend forward
of the forward end of said passage 18. When the screw 41 engages
the channel 42, the axial movement of the sleeve 36 is limited as a
result of the screw 41 engaging the shoulder portions of the
channel 42. In this manner, the sleeve 36 cannot inadvertently be
moved to an extent that the sleeve is removed from the barrel 11.
Also, the screw 41 can be tightened against the inner surface of
the channel 42 when the sleeve 36 is in a desired position to
thereby retain the sleeve 36 in that position.
As also shown in FIG. 1, the forwardmost interior surface of the
passage 18 is curved or flared outwardly. This flaring, in
combination with the axially movable sleeve 36 and the deflecting
member 44, which will be described in more detail below, causes the
pulverulent materials passing through the passage 18 to be formed
into a desired spray pattern.
Referring now to FIG. 2, an elongated ionization member 37 disposed
within the passage 18 includes a probe or electrode 45, a
deflecting member 44, a body member 46 and a ring member 32. The
probe 45 extends the entire length of the ionization member 37. At
its rearward end 48, the probe 45 is electrically connected to the
ring member 32 by a conducting wire 49. At its forwardmost end, the
probe 45 passes through the deflecting member 44 and extends past
the concave surface 59 of the deflector 44. The portion of the
probe 45 extending past the surface 59 serves an an ionization
point or needle 50 causing an electrostatic field to be set up
between the point 50 and the article to be coated 13 when the point
50 and the article 13 are maintained at substantially different
electrical potentials.
The generally cylindrical body member 46 surrounds a substantial
portion of the probe 45 and extends from the rearward end 48 of the
probe 45 to a point 51 near the forward end of the probe 45. In the
preferred embodiment, the location of the point 51 is substantially
even with the forward end of the passage 18 when the member 37 is
operatively disposed within the passage 18.
A plurality of fins 52 integrally formed with the rearward portion
of the body member 46 are spaced about the circumference of the
member 46 and extend upwardly therefrom such that the diameter of
the exterior fin surfaces is slightly larger than the interior
diameter of the material passage 18 so that the ionization member
37 may be retained within the passage 18. As better seen in FIG. 3,
the plurality of fins 52 are equally spaced about the circumference
of the body member 46 and extend radially outwardly therefrom.
Referring now to both FIGS. 2 and 3, a ring member 32 is mounted to
a portion of the fins 52 at a position which is spaced forwardly
from the rearward end 48 of the probe. Referring specifically to
FIG. 3, the mounting of the ring in this manner provides a
plurality of passages 54 through which the pulverulent materials
may pass as they are conveyed through the passage 18.
The ring member 32 is constructed of an electrically conductive
material and is electrically connected to the resistor 24 (FIG. 1)
by the set screw 31. When the ionization member 37 is inserted into
the forward end of the passage 18, the ring 32 engages the set
screw 31, thereby electrically connecting the ring 32 with the
screw 31, and also preventing further inward movement of the
ionization member 37. The member 37 is then retained in this
position by the plurality of fins 52 which are force fitted against
the interior surface of the passage 18. Because the member 37 is
secured within the passage 18 due to the flexible and somewhat
resilient nature of the fins 52, the member 37 can easily be
removed, cleaned and replaced when such cleaning is desired. This
is often the case when the gun or the system is changed from
spraying a pulverulent material having one characteristic to a
pulverulent material having another.
The deflecting member 44 through which the forward portion of the
probe 45 passes is generally conical in shape and includes a
cylindrical surface 56, a tapered or conical surface 55 extending
from the surface 56 and tapered inwardly toward the body member 46,
a tapered surface 58 extending from a cylindrical portion 57 of the
member 44 inwardly away from the body member 46, a shoulder portion
60 connecting the surface 56 with the surface 58, and a concave
surface 59 which is perpendicular to the longitudinal axis of the
probe 45 and which is the forwardmost surface of the deflector 44.
The body member 46, the fins 52 and the deflecting member 44 are
all constructed of non-conductive material such as a linear
synthetic polyamide commonly sold under the trademark Nylon.
As best shown in FIG. 2, the tapered surface 55 tapers inwardly
toward the body member 46 and terminates at a point which is spaced
from the forwardmost point 51 of the body 46. This provides for a
portion 61 of the electrically conductive probe 45 to be directly
exposed to the pulverulent materials being discharged from the end
of the material passage 18. It is believed that an electrostatic
field is set up between the portion 61 and the grounded article 13
to thereby supercharge or precharge the pulverulent materials being
emitted from the passage 18, thereby causing greater wrap-around
and better deposition of the particles onto the article 13 with a
substantially lower voltage.
As shown in FIG. 2, the forwardmost portion of the probe 45, the
ionization point 50, extends for a distance past the concave
surface 59. A difference in electrical potential between the point
50 and the article 13 causes an electrostatic field to be formed
between the point 50 and the grounded article 13 to thereby
additionally charge the pulverulent materials emitted from the
material passage 18 and direct those charged particles toward and
onto the article 13. It should be noted that in the preferred
embodiment the forwardmost point of the needle 50 does not extend
past the edge formed between the tapered surface 58 and the concave
surface 59, but rather is shielded within the concave portion
formed by the surface 59. This shielding prevents pulverulent
materials which have been precharged by the portion 61 from being
repelled by the needle 50 which contains charges of identical
polarity to the charges then carried by the pulverulent particles
and also limits undesired contact with the point 50. It is believed
that this shielding results in a more efficient system which can
provide the same wrap-around and same deposition with a much lower
voltage.
Referring again to FIG. 1, the rearward portion of the gun 10 of
the present invention can be seen as including a metal portion 22,
a handle 12 extending downwardly from the rear portion 22, a
trigger 14 pivotally connected to the gun at the pivot 62, and a
hook 64 by which the gun 10 can be hung when it is not in use.
Extending through the material passage 18 is a relatively rigid,
electrically non-conductive tube 65 for conveying pulverulent
materials through the passage 18. As shown in the preferred
embodiment, the tube 65 extends through a substantial portion of
the passage 18 with its forward end 66 terminating at a point which
is spaced rearwardly of the set screw 31. The rearward end 68 of
the tube 65 includes a portion containing a plurality of
circumferential ribs 69 which are adapted for attachment of the end
68 to a flexible tube 70 of the type normally used for transporting
pulverulent materials in an electrostatic spraying system.
The tube 65, although relatively rigid when compared to the hose
70, is not so rigid that it cannot be bent slightly, and is
generally cylindrical having an external diameter slightly smaller
than the internal diameter of the material passage 18. With this
construction, the tube 65, with the flexible hose 70 attached to
its rearward end, can be easily inserted into and removed from the
material passage 18 when such insertion or removal is desired. When
the tube 65 has been inserted into the passage 18, it is held
tightly in place by the fitting 71 which contains internal threads
for engagement with a corresponding externally threaded member 72
integrally formed with the gun body 10. A set screw 67 may also be
contained in the gun wall and adapted to aid in retaining the tube
65 within the passage 18.
The specific structure of the embodiment shown in FIG. 1, due to
the fact that the tube 65 and hose 70 are easily and quickly
removable from the gun, allows several such tubes and hoses, each
associated with a pulverulent material with a different
characteristic, to be selectively used with the gun. This permits
the spray gun of the present invention to be changed from the
spraying of a pulverulent material having one characteristic to the
spraying of a pulverulent material having another with little
inconvenience to the operator. This feature will be discussed in
more detail below.
Also shown in FIG. 1 is the means 74 for selectively actuating both
the powder supply 75, which includes a plurality of powder supply
units, and the high voltage source 30. This means includes an
"on-off" control switch 76 which, when in the "on" position,
electrically connects a ground terminal with a male jack 80. This
ground terminal (not shown) enters the gun together with the high
voltage cable. When the switch is in the "off" position, the
aforementioned ground terminal and the male jack 80 are not
electrically connected. The control switch 76, in turn, is
controlled by movement of the trigger 14 toward or away from the
handle 12 respectively. When the trigger 14 is moved toward the
handle 12, a spring-loaded shaft 78 is moved inwardly, thereby
turning the control switch 76 to an "on" position and connecting
the male jack 80 with the grounded terminal. When the trigger 14 is
released, the spring-loaded shaft 78 moves away from the handle 12,
thereby turning the control switch to an "off" position and
disconnecting the male jack 80 from the grounded terminal. The
shaft 78 is centered and retained in the gun handle 12 by the
fitting 79.
The switch 76 is secured to the gun handle 12 by the jam nut 82. A
cylindrical sleeve member 81, which is integrally formed with the
gun handle 12 surrounds the jack 80 and a portion of the switch 76
to shield the jack 80 from any sudden jar which could be caused,
for example, by dropping the gun. Also shown in FIG. 1 is a cord 84
containing a single conducting wire and having one end which
includes a female jack 85 adapted to engage and connect with the
male jack 80. When the female jack 85 and the male jack 80 are
engaged, the wire within the cord 84 and the grounded terminal (not
shown) are electrically connected. The female jack 85 is retained
in engagement with the male jack 80 by the resilient nature of the
female jack 85. Although it is specifically shown in FIG. 1, the
cord 84 extends from the male jack 80 to a relay switch contained
in the powder supply 75, which, when energized, actuates both the
powder supply 75 and the high voltage source 30.
The preferred embodiment further includes a supply unit having a
plurality of flexible hoses 70 (a-c) and a plurality of cords 84
(a-c) associated respectively with each of the hoses 70 (a-c). All
of the hoses 70 (a-c) and the cords 84 (a-c) have one end connected
with a powder supply means 75 and the other end adapted for
selective engagement with the material passage 18 and the male jack
80 respectively by appropriate connections. In this respect, each
of hoses 70 (a-c) includes a fitting 71 (a-c) respectively
corresponding to the fitting 71 for engagement with the threaded
member 72, and a relatively rigid tube 65 (a-c) respectively
corresponding to the tube 65 for insertion into the chamber 18.
Also, each of the cords 84 a-c) includes a female jack
corresponding to the female jack 85 adapted to engage the male jack
80. Each of the tubes 70 (a-c) are held to the corresponding cord
84 (a-c) respectively by a clamp 88 so that corresponding pairs of
hoses 70 (a-c) and cords 84 (a-c) will be connected with the gun 10
together.
Each of the pairs of hoses 70 (a-c) and cords 84 (a-c) is
associated with a pulverulent material having a different
characteristic which can be selectively engaged with the gun 10
when a material with a particular characteristic is desired. For
example, the hose 70a, the tube 65 a and the cord 84a are all
associated with a material having a certain characteristic and when
it is desired to coat this particular material onto the article 13,
the tube 65a with the hose 70a attached is inserted into the
material passage 18 and the fitting 71a is tightened over the
fitting 72. Likewise, the cord 84a is connected with the male jack
80. When a material having a different characteristic is desired to
be coated onto the article, the tube 65a, the hose 70a and cord 84a
are removed, and the hose, tube and cord associated with that
different material are connected with the material passage 18 and
the male jack 80 in a similar manner. Although the pulverulent
materials with different characteristics commonly would be
materials having different colors, the different characteristics
could be differences in materials also such as vinyl, polyester, or
cellulose-acetate-butyrate.
Each of the cords 84 (a-c) shown in FIG. 1 like the cord 84, is
electrically connected to a relay switch which, when energized,
actuates the high voltage source 30 and that portion of the powder
supply 75 with which the cord 84 (a-c) is associated. For example,
if the hose 70a and the cord 84a are each associated with certain
pulverulent material and each are connected to the gun 10 as above
described, depression of the trigger 14 will cause the circuit to
be completed between the grounded terminal and the conducting wire
within the cord 84a to energize a relay switch. When this relay
switch is energized, the high voltage source 30 and that portion of
the powder supply 75 associated with the cord 84a and hose 70a is
actuated. When the trigger 14 is released, the circuit between the
grounded terminal and the wire within the cord 84a is open and the
relay switch is deenergized, thereby turning off the power source
30 and the powder supply 75.
When a material having a different characteristic is desired to be
coated onto the article 13, the hose 70a and the cord 84a are
disengaged from the gun 10, the ionization member 37 taken out and
cleaned by compressed air and then replaced, and one of the other
hoses 70 (b, c) and cords 84 (b, c) associated with a material
having the desired characteristic are connected to the gun 10.
Although the description of the present invention has been quite
specific, it is understood by the application that there may be
many alternative embodiments of the present invention which can be
constructed without deviating from the spirit of the invention.
Consequently, the scope of the present invention should be dictated
by the appended claims rather than by the description of the
preferred embodiment.
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