U.S. patent number 3,691,991 [Application Number 05/195,270] was granted by the patent office on 1972-09-19 for apparatus for spray-coating components.
This patent grant is currently assigned to Atlas Copco Aktiebolog. Invention is credited to Anton Ettenhofer, Manfred H. Luderer.
United States Patent |
3,691,991 |
Luderer , et al. |
September 19, 1972 |
APPARATUS FOR SPRAY-COATING COMPONENTS
Abstract
An apparatus for spray-coating components or workpieces with a
dry material, such as powder, or with a wet material, such as
paint, includes a removable and replaceable supply container for
the coating material. When the container is mounted in the
apparatus, an agitator therein is connected to an air supply to
agitate the material in the container. The material is supplied
from the container to a feeding trough through a regulatable
discharge opening, the trough being vibrated parallel to the
direction ofmovement of the material therealong and the support for
the container being vibrated vertically. The trough delivers the
material to an injector connected to asource of compressed air with
the mixture of compressed air and material being directed through a
closed conduit or the like to a spray-gun havinghigh voltage
electrodes at its outlet or discharge end. A control panel is
provided with controls for selecting the voltage and the polarity
of the electrodes at the spray-gun outlet, and for regulating the
vibration effect and the supply of air to the apparatus. The
electrical operation iseffected underthe control of air pressure
operated switches to which air is supplied responsive to operation
of air supply control members.
Inventors: |
Luderer; Manfred H. (Weiller
Zum Stein, DT), Ettenhofer; Anton (Winnenden,
DT) |
Assignee: |
Atlas Copco Aktiebolog (Nacka,
SW)
|
Family
ID: |
27430719 |
Appl.
No.: |
05/195,270 |
Filed: |
November 3, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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819216 |
Apr 25, 1969 |
3637135 |
Jan 25, 1972 |
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Foreign Application Priority Data
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Apr 26, 1968 [DT] |
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P 17 71 263.9 |
Jan 14, 1969 [DT] |
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G 69 01 158.1 |
Mar 27, 1969 [DT] |
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P 19 15 651.1 |
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Current U.S.
Class: |
118/629; 239/706;
427/483; 118/621; 118/627; 427/475; 427/600 |
Current CPC
Class: |
B05B
5/032 (20130101); B05B 5/1683 (20130101); B05B
7/144 (20130101); B05B 7/1445 (20130101) |
Current International
Class: |
B05B
5/025 (20060101); B05B 5/03 (20060101); B05B
5/00 (20060101); B05B 5/16 (20060101); B05B
7/14 (20060101); B05c 005/02 () |
Field of
Search: |
;118/621,627,629,640
;117/17.5 ;239/3,15 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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517,728 |
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Mar 1953 |
|
BE |
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514,988 |
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Nov 1952 |
|
BE |
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473,159 |
|
Dec 1950 |
|
IT |
|
Primary Examiner: Stein; Mervin
Assistant Examiner: Millstein; Leo
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a division of application Ser. No. 819,216,
filed Apr. 25, 1969, and now U.S. Pat. No. 3,637,135, issued in
Jan. 25, 1972.
Claims
What is claimed is:
1. Apparatus for spray coating material in powdered or liquid form
onto workpieces comprising, in combination, a supply station; a
support means at said supply station; a materials supply container,
containing material to be spray coated and having a discharge
opening, removably insertable into said supply station for mounting
on said support means; valve means normally closing said discharge
opening; means operable, responsive to insertion of said container
into said supply station, to open said discharge opening; a source
of air under pressure; means operable responsive to insertion of
said container into said supply station to couple said source of
air under pressure to said container to supply air into said
container for agitating the material therein; an injector means
mounted on said support means and connected to a source of air
under pressure; means connecting said discharge opening to said
injector means for delivery of material to said injector means for
directing compressed air into the material; a spray-gun; means
connecting said injector means to said spray-gun to deliver the
powder-air mixture to said spray-gun; electrodes positioned at the
discharge outlet of said spray-gun; a high voltage generator; and
means operable to selectively connect said high voltage generator
to said electrodes.
2. Apparatus, as set forth in claim 1, in which said means
connecting said discharge opening to said injector means comprises
an elongated feed trough mounted on said support means in a
generally horizontal position, with one end spaced beneath said
discharge opening and the other end in operative relation with said
injector means.
3. Apparatus, as set forth in claim 2, including a first vibrator
operatively associated with said support means for vibrating said
container and said feeding trough in one direction, and a second
vibrator operatively associated with said feeding trough for
supplying vibration thereto in another direction.
4. Apparatus, as set forth in claim 3, including an air-injection
member connected to a source of air under pressure and arranged
centrally within and spaced inwardly from the inner surfaces of
said container for producing an air current directed upwardly in
such a manner that an approximately revolving motion of the
material from the bottom to the top of the container is
produced.
5. Apparatus, as set forth in claim 4, wherein said air-injection
member has a ring-shaped configuration.
6. Apparatus, as set forth in claim 3, wherein said support means
comprises a chassis; a plurality of first cushions of a rubber-like
material supported in spaced relationship on said chassis; a
support member supported on said first cushions; second cushions
formed of a rubber-like material mounted on said support member;
support elements secured to and extending upwardly from said second
cushions and supporting said feeding trough at the upper ends
thereof; and a support bracket secured to and extending upwardly
from said support member for supporting said container
independently of said second cushions.
7. Apparatus, as set forth in claim 6, in which said supply
container is funnel-shaped and has its discharge opening directed
downwardly and located at the lower end thereof.
8. Apparatus, as set forth in claim 7, including a carrier mounted
on said support bracket; said supply container being removably
secured to said carrier.
9. Apparatus, as set forth in claim 6, including a first vibrator
attached to said support member and arranged to vibrate in the
vertical direction; and means for regulating the vibration of said
first vibrator.
10. Apparatus, as set forth in claim 9, including a second vibrator
secured to said feeding trough and arranged for vibrating said
feeding trough in the horizontal direction; and means for
regulating the vibration of said second vibrator.
11. Apparatus, as set forth in claim 1, in which said valve means
is a butterfly valve; said means operable to open said butterfly
valve comprising a lever connected to said butterfly valve and
operating means engageable with said lever responsive to insertion
of said container into said supply station.
12. Apparatus, as set forth in claim 11, wherein said operating
means comprises a cam engageable with said lever.
13. Apparatus, as set forth in claim 1, including a vent valve
positioned between said injection means and said spray-gun and
arranged to be actuated when the air supplied to said injector
means is cut off.
14. Apparatus, as set forth in claim 3, including a control panel
associated with said container, said first and second vibrators,
said high voltage generator and said spray-gun; an indicator; and a
test key arranged on said control panel for switching off the high
voltage from said spray-gun and for switching-on said indicator,
calibrated in KV, for adjusting the high voltage value in such a
way that after releasing said test key the high voltage value set
is applied to said electrodes on said spray-gun.
15. Apparatus, as set forth in claim 1, wherein said ejector is
disposed directly beneath the discharge opening of said
container.
16. Apparatus, as set forth in claim 1, wherein said valve means
comprises a cellular wheel lock containing several chambers; said
cellular wheel lock being positioned at the lower end of said
container so that the chambers face the interior of said container,
for delivering of the material through the discharge opening as
said lock is rotated.
17. Apparatus, as set forth in claim 1, wherein at least a part of
the walls within said container in contact with the material
therein are equipped with fluidizing bodies; the air supply into
said container being separately adjustable for regulating the air
supply to said fluidizing bodies.
18. Apparatus, as set forth in claim 1, wherein at least part of
the walls within said container contacting the material comprise
plastic materials of one of the group consisting of
polytetrafluoroethylenes, copolymers of tetrafluoro-ethylene and
hexafluoropropylene.
19. Apparatus, as set forth in claim 1, wherein said spray-gun
includes a trigger; a first switch and a second switch arranged to
be actuated by said trigger; means cooperating with said first
switch for supplying a smaller quantity of material and compressed
air from said spray-gun; and second means associated with said
second switch for supplying a full quantity of material and
compressed air from said spray-gun.
Description
FIELD OF THE INVENTION
This invention is directed to the spray-coating of workpieces and,
more particularly, to a novel, improved, simplified and versatile
apparatus for coating workpieces with either powdered or liquid
material.
SUMMARY OF THE INVENTION
The apparatus of the invention primarily is adapted to apply powder
to components but, by quick conversion, it can be used equally well
for applying paint by the wet process, in which airless
paint-spraying or air-operated paint-spraying may be used. As
compared to known prior art apparatus for coating components, the
invention apparatus utilizes novel features and combinations of
these novel features, and includes novel means for feeding the
coating material, novel setting and switching-in means, and novel
change-over and cleaning means. The individual components differ
from known apparatus in that they provide for much faster
change-over from one color to another, and also for better cleaning
of the apparatus.
In accordance with the invention, the apparatus includes a novel
mount for a powder funnel and associated parts, the mount for the
powder funnel, that for the feeding trough, and that for the air
injector being combined to form a single compact unit. This unit is
so designed that a support chassis, acted upon by a vertical
vibrator, has directly coupled thereto a supporting carrier for the
powder funnel and the injector, while the feeding trough, which is
acted upon along its longitudinal center line by a horizontal
vibrator, is coupled to the support chassis through rubber
cushions, with the compact unit being connected to the appliance
chassis also through rubber cushions. The mounting arrangement of
the invention has the great advantage that, on the one hand, a
horizontal action on the powder occurs in the feeding trough and,
on the other hand, a vertical motion in the powder funnel and in
the direction of feeding the material or powder toward the feeding
trough, and in the injector in the direction toward the hose
connection to the gun, is provided. The compact mounting is one of
the most important features of the apparatus.
In addition, the apparatus embodying the invention is so designed
that the powder funnel is exchangeable, and that it is provided
with means which automatically open and close the powder outlet
responsive to mounting and removal of the powder funnel,
respectively, thus eliminating loss of powder. At the same time,
this means provides for easy removal of the powder funnel from the
apparatus. The funnel can be filled, outside the apparatus, or a
different powder funnel, with a different powder, can be mounted in
the apparatus.
Individual catches are provided for cooperation with the powder
funnel, and permit adjustment of the vertical distance between the
funnel outlet and the feeding trough, so that a preselection of the
outlet opening with respect to the feeding trough can be easily
effected. This exchangeability of the powder funnel is an essential
feature of the apparatus, as it is possible, with one manipulation,
to remove the powder funnel, for example, for refilling, so that
contamination of the entire plant or apparatus by powder is
prevented.
When the powder funnel is being mounted in the apparatus, the
powder outlet is automatically opened, this being effected, for
example, by dogs or rollers running against cams. It is preferable
to shut off the powder in the funnel by means of a butterfly valve
or other valve elements, such as slide valve elements. Furthermore,
when attachment of the funnel has been effected, at the same time
an air connection is completed for supplying air to air injection
bodies in the powder funnel.
Adjustment of the powder quantity fed to the gun is further
possible by adjusting the supply voltage to the horizontal vibrator
of the feeding trough. By so doing, two adjusting means are
provided regulating the quantity of powder fed to the gun. The
adjusting means for the supply voltage of the horizontal vibrator
and for the air valve for the injector can be directly coupled or
can be coupled through gear members.
Thus, a further simplification of the adjustment of the apparatus
is obtained. Coupling can be effected by means of a through shaft
or, alternatively, machine elements, such as cams, dogs,
differentials, or the like can be arranged between the operating
shafts. In this way, functionally different operating relations
between the shafts can be realized.
The apparatus according to the invention permits switching over of
the high voltage supply by a control switch at a control desk,
switching to positive-zero-negative being possible, so that the
high voltage potential at the electrode of the gun can have a
selected polarity. The change-over switch for the polarity is
arranged at the high voltage supply, and proceeds through various
cascade stages, the polarity of the respective switching elements
being changed in each stage. In the mid-position "zero" of the
change-over switch, the capacitors are discharged.
A further improvement of the invention apparatus over the prior art
is that, when switching off the air supply for the injector, at
least one vent valve is actuated at the same time to reduce the
pressure in the direction toward the gun. This has the great
advantage that, immediately after switching off, discharge of a
powder gas mixture at the front of the gun is eliminated and there
is no afterflow.
The vent valve can be installed between the shut-off valve and the
injector. However, it is also possible to install a further vent
valve between the injector and the gun, and also to install two
vent valves, one at each of the above-mentioned locations. The
apparatus of the invention is switched on by actuating a compressed
air switch seated in the gun and actuating, in the apparatus, a
compressed air operated switch which controls the cascade, the
vibrators and the compressed air valve for the injector. By virtue
of this, it is possible to use a gun which needs no lines or
conductors other than the high voltage cable.
A special advantage of the invention apparatus is that the injector
is arranged in a quick-action clamping holder on the support
chassis, this holder, for example, permitting removal of the
injector after unlocking a lever. This provides for quick cleaning
of the injector and also for quick change-over of the apparatus,
for example, from one color to another.
A special test key in the control panel permits, on the one hand,
switching off the high voltage from the gun and discharge of the
electrode at the gun. On the other hand, however, regulation of the
high voltage for the electrostatic field can be obtained at a
KV-calibrated indicating instrument in the primary circuit.
Adjustment is effected by an adjusting regulator, for example, a
regulating transformer in the primary circuit. After releasing the
test key, the high voltage value set is applied to the electrodes
of the gun.
The apparatus is further so designed that, on the one hand, the
powder current, which is adjustable at the control desk, is acted
upon by air in the injector and, on the other hand, an additional
air line supplies accelerating air to the gun, with the
accelerating air being also adjustable at the control desk. By this
arrangement, easy and reliable breaking up of the powder in the
injector can be obtained and, at the same time, there can be
obtained also sufficient acceleration of the broken up powder
current at the gun, so that the powder current impinges on the
component or workpiece with sufficient acceleration energy.
In a modification of the apparatus of the invention, connections
and valves are arranged on the apparatus permitting, alternatively,
connection of wet spraying devices, airless devices, or
air-operated devices, in such a way that, in the case of airless
operation, a respective compressed air tank pressure converter,
with a respective airless gun, can be applied, or a compressed air
operated gun can be applied, in such a way that also the high
voltage connection for additional electrostatic spraying can be
used fully in the apparatus. This universal applicability provides
the apparatus embodying the invention with a further field of
service and, for smaller enterprises, the possibility of operating
according to different processes. This has the advantage that the
apparatus attains a much greater performance and has a longer
operating time as the various possibilities eliminate down
times.
Basically, the apparatus embodying the invention provides, with the
influence on the power current in the various active components,
further very important combinations results which are important in
using the plant. These include influencing the powder quantity by
adjustment of the distance between the powder funnel and the
feeding trough, and by adjusting the voltage at the horizontal
vibrator of the feeding trough. Also, premixing and feeding to the
gun is effected by adjusting the air current at the injector. The
degree of atomization and acceleration at the gun outlet is
adjustable by the accelerating air current supplied directly to the
gun, and by adjustment of a high voltage field to a voltage of a
selected polarity between the electrodes and the workpieces being
coated. A cloud shape of the powder discharged from the gun is
provided by a baffle and guide bodies in front of the gun discharge
outlet. The combination of various features for influencing the
powder current in the various active components of the apparatus is
a very important characteristic of the apparatus, and involves a
combination of features not found in any prior art apparatus for
coating workpieces.
The provision for reduction of pressure when switching off the
powder current of the gun, in the line between the control valve of
the compressed air and the injector and the gun, provides the great
advantage that, when switching off, afterflow of powder does not
occur.
As a further feature of the apparatus, at least part of those walls
or surfaces coming in contact with the powder are provided with
fluidizing bodies. By the term "fluidizing bodies", as used herein,
is to be understood sintered bodies which are porous and within the
powder containers or passages. Air is supplied from the exterior
into the sintering bodies and directed, through the sintering
bodies, on a larger surface into the powder. For example, a
ball-shaped fluidizing body may be provided in the powder funnel
for effecting circulation of the powder in the funnel. The air
supply for groups of fluidizing bodies associated with each other
may be separately adjustable.
In a further modification of the invention, a cellular wheel lock,
with several chambers, is arranged directly beneath the powder
funnel in such a way that those chambers facing the funnel collect
the powder from the funnel and the delivery air acts upon at least
one lower chamber in an axial direction, subject to the condition
that, in the wall side, an injector is arranged in the outgoing
direction and to which the feed hose to the powder gun is
connected. This has the advantage of providing apparatus of a
relatively simple design.
In accordance with the invention, the apparatus can be so designed
that all vibrating equipment, which can be switched off, as well as
the injector, can be mounted directly underneath the power funnel
and, in this way, an apparatus is provided which is suitable for
spraying relatively specifically light and specifically heavy
powders, such as frit or ceramic powder.
At least part of those walls contacted by the powder are coated
with plastic materials of the group of the
polytetrafluoroethylenes, or plastic materials of the group of the
copolymers from tetrafluoroethylene, hexafluoropropylene, or the
like. Furthermore, these walls can be made solely of these plastic
materials. It is also possible to use, generally, fluorinated or
siliconated plastic materials, or both, for this purpose.
As a further feature of the invention, the trigger of the gun for
the discharge of the powder-air mixture, in the range of the first
portion of a path of movement, is designed so that it actuates a
valve for a smaller quantity and, in the latter part of the range
of movement, a valve for full quantity. In this way, the powder-air
current can be regulated and thus, with the smaller quantity, for
example, grooves, pipe sections, protuberances, etc., requiring a
smaller quantity can be treated and, on the other hand, when fully
depressing the trigger, large surfaces are immediately coated with
powder.
It is, however, also possible that the trigger actuates a valve for
continuously, functionally, or both, increasing powder-air
delivery, providing the advantage that a powder quantity
continuously increasing in quantity, or increasing according to a
certain function, can be controlled by the operator.
Separate lines may lead from the apparatus to the valves in the
gun, these lines being separately adjustable in the apparatus, so
that the gun can be adapted easily to various situations without
unnecessary spraying of powder.
For an understanding of the principles of the invention, reference
is made to the following description of typical embodiments thereof
as illustrated in the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
In the drawing:
FIG. 1 is a generally diagrammatic view illustrating the overall
apparatus, for explaining the principle of operation;
FIG. 2 is a perspective view of a practical embodiment of the
apparatus;
FIG. 3 is a view, similar to FIG. 2, of a part of the apparatus and
with a front section open to illustrate the injector;
FIG. 4 is a diagrammatic illustration of the circuit
interconnecting the valves of the venting appliance;
FIG. 5 is a partial side elevation view of an embodiment of the
apparatus in which the injector is arranged directly beneath the
powder funnel;
FIG. 6 is a vertical sectional view illustrating an embodiment of
the apparatus with a cellular-wheel lock arranged beneath the
powder funnel;
FIG. 7 is a partial and somewhat diagrammatic sectional view taken
along the line II--II of FIG. 6;
FIG. 8 is a diagrammatic view, in line representation, of an
embodiment of the invention and illustrating an arrangement of
fluidizing bodies; and
FIG. 9 is a schematic air and electric circuit diagram illustrating
the regulation of the powder-air mixture at the apparatus and at
the gun.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to FIG. 1, rubber cushions 2 mounting a support
chassis 3 are mounted on an appliance chassis 1. Rubber cushions 4
on support chassis 3 carry, through supports 5, a feeding trough 6.
An injector 15 and a funnel 11, containing powder 48, are mounted
on support chassis 3. Funnel 11 is seated on chassis 3 and, through
catches 14, only two of which are shown, by way of example, can be
adjusted in height, as desired, relative to feeding trough 6.
In powder funnel 11, there is arranged an air-injection body 12
designed as an annular body, for example, and which is
automatically coupled to an air supply line at the connection 13
when funnel 11 is being mounted on chassis 3. The arrows in powder
funnel 11 indicate the direction of circulation of powder 48 in a
manner such that the powder is broken up in funnel 11.
A butterfly valve 9 is provided in powder funnel 11 and, through
coupling members, is connected to a roller 10 and a dog, for
example, which open valve 9 when funnel 11 is mounted from above,
and close valve 9 automatically, when funnel 11 is pulled upwardly
for removal from the apparatus, so that no powder will then flow
out of funnel 11.
Powder 48 flows from funnel 11 onto feeding trough 6, which is
slightly inclined toward injector 15. A vertical vibrator 8, of
known design, is arranged on support chassis 3 and supplied with
current through a connection 20. Vibrator 8 vibrates support
chassis 3, together with funnel 11, in a vertical direction. At the
same time, trough 6 is also vibrated in a vertical direction due to
the fact that vibrator 8 is coupled to trough 6 through chassis 3
and rubber cushions 4. A horizontal vibrator 7 is arranged at
feeding trough 8 and supplied with current through a connection 19.
An adjusting device 16 is provided in the supply line for adjusting
or setting the voltage for vibrator 7.
Injector 15 is supplied with compressed air through a line 18, with
the quantity of compressed air being regulated by an adjusting
device 17. In injector 15, the compressed air accelerates the
powder received in the injector from trough 6 and carries it
through holes or conduit 26 to spray-gun 32. Spray-gun 32 is
additionally supplied with accelerating air from a line 25, and the
supply of accelerating air can be set by an adjusting device 52.
From adjusting device 52, the accelerating air flows to spray-gun
32 through a line or conduit 27.
A handle 30 is arranged on spray-gun 32, and includes an air valve
31 by means of which all electrical switching operations can be
controlled by compressed air. For this purpose, a compressed air
operated electrical switch 23 is connected to handle 30 and to air
valve 31 through a line 28. The electrical contacts of switch 23
are connected to the supply means as indicated at 24, and
electrical connector 53 of switch 23 is connected to the electrical
connectors 19, 20 and 21 of the electrically operated components.
This arrangement has the advantage that no further control lines
need be connected to the spray-gun 32.
The high voltage for the electrodes 33 of spray-gun 32 is generated
in a high voltage generator 36, for example, in a cascade, and
supplied by high voltage cable 29 to the electrodes 33. The high
voltage leaves the cascade, forming part of or connected to high
voltage generator 36, through suitable means, such as an insulator
37. FIG. 1 also illustrates how the powder current or spray 35 is
directed on workpiece 34.
A switch 40 is provided at the cascade of generator 36, for
changing the polarity, and makes it possible to draw high voltage
of either positive polarity or negative polarity. In the primary
circuit, the voltage can be regulated by means of an adjusting
device 39, and a test key 38 serves to regulate the high voltage,
whose magnitude can be indicated at the indicator 41 in FIG. 2. The
function of the test key and the adjustment of the high voltage is
described in more detail hereinafter.
FIG. 2 illustrates the entire apparatus, with powder spray-gun 32
suspended from a stand 51'. From FIG. 2, it will be noted that
powder funnel 11 is inserted into the housing from the top, while
the control knobs are arranged on a front surface of the
housing.
The voltage for horizontal vibrator 7 can be set by adjusting
device 16, and the quantity of compressed air for injector 15 can
be set at the adjusting regulator 17. The two adjusting devices 16
and 17 can be coupled, as shown by the dotted line 54 in FIG. 1,
for conjoint operation. With respect to the schematically
illustrated connection 54, it is possible to provide gear members
or the like between devices 16 and 17 to effect such conjoint
regulation. The accelerating air can be adjusted at the adjusting
device 52, and pressure gauges, for pressure indication, are
arranged behind adjusting devices 17 and 52, as will be apparent
from FIG. 2.
The solenoid valve for the accelerating air can be switched on and
off by a switch 42, shown in FIG. 2, while the air supply to
injector 15 can be switched on and off by a switch 43. The high
voltage is switched on and off by switch 51, and the test key is
indicated at 38 in FIG. 2.
After powder funnel 11 has been inserted from the top into the
housing shown in FIG. 2, and turned into the proper position with
simultaneous opening of butterfly valve 19 and the locking in
adjusted vertical position at 14, funnel 11 can be locked in
position by a lever 55. After lever 55 is disengaged, funnel 11 can
be lifted upwardly out of the housing.
FIG. 3 illustrates the apparatus with front door 45 of the housing
being opened so that injector 15 is visible. This injector is
arranged on support chassis 3, and can be easily removed and
cleaned after unlocking a lever 44. Discharge hose 26, illustrated
in FIG. 3, connects injector 15 to spray-gun 32, this hose also
being illustrated in FIG. 1.
A water-trap 46 is incorporated in the air supply line to injector
15, as explained more in detail with respect to FIG. 4. In FIG. 3,
feeding trough 6 can be seen behind injector 15. After depressing
test key 38, the high voltage can be adjusted to the desired value
by adjusting regulator 39, and the reading can be taken from the
indicating instrument 41. The remaining controls and parts are
denoted by the same reference characters in FIG. 2 as used in FIG.
1.
Referring to the schematic circuit diagram of FIG. 4, compressed
air from line 18 is supplied to solenoid valve 42 which switches
the air current to injector 15 on and off. Water-trap 46 is
connected between valve 42 and injector 15. FIG. 4 also illustrates
how powder 48 flows from feeding trough 6 into injector 15 and, by
the compressed air supplied to injector 15, is supplied to line 26
which carries the powder-air mixture to powder spraying gun 32.
When solenoid valve 42 is closed, it opens a by-pass valve 47, by
means of which pressure build-up in the direction of hose 26 to the
injector 15 is abruptly reduced, so that spraying of the powder-air
mixture at the powder spraying gun 32 is abruptly interrupted. A
valve 49 also can be arranged in line 26, to provide the
possibility of coupling valves 47 and 49 to reduce the pressure
simultaneously in both pipe sections.
An advantage of the invention apparatus is that the high voltage
supply, the proportioning means and the powder storage container
are accommodated in a desk-like sheet-steel casing so that the
apparatus forms a compact unit. In prior art apparatus, the control
disk and the powder container, with its chassis, are separately
arranged.
A further advantage is that the high voltage supply is designed for
either negative polarity, positive polarity, or reconnectable for
both polarities. There is no need for replugging the high voltage
cable when changing the polarity. In a known prior art apparatus,
two different and separate high voltage cascades are installed for
changing the polarity, and these are coupled in alternation to
change the polarity. On the other hand, in the apparatus of the
invention, only a single high voltage cascade is necessary.
Moreover, a very useful feature of the invention apparatus is that
charging the large opening of the powder funnel is relatively easy,
in addition to which the powder funnel as a whole can be exchanged.
A further advantage is that the powder funnel is kept free of
pressure, so that it is always easy to check, from above, whether
there is still sufficient powder in the funnel. The ball catch for
the powder funnel provides for easy adjustment of the spacing of
the powder funnel above the feeding trough, so that continuous
powder quantity adjustment can be maintained. Also, the completely
filled powder funnel can be easily exchanged, which is very useful
for cleaning or for changing the color.
The preproportioning means is also accommodated in the casing, and
permits extremely fine regulation of the throughput quantities over
a relatively wide range of regulation. Afterspraying of the
material being charged, which is encountered in practice with prior
art apparatus, when completeing the working process, and delay of
the material flow when beginning work, is largely eliminated by the
design of the feeding trough with both horizontal and vertical
vibration. Additionally, vent valves assure afterspraying being
interrupted immediately upon switching off at the spray-gun.
The apparatus can be used selectively for either powder spraying or
wet coating, which is a special advantage for smaller enterprises.
The regulation of the powder quantity and of the air pressure can
furthermore be of such a design that the switching devices 42 and
43 are provided as step switches, and that the adjusting devices 17
and 52 are provided as fine pressure regulators. Furthermore, with
the invention apparatus and air blow-out gun, for cleaning the
containers and the like, can be connected to the air line.
FIG. 5 illustrates a modification of the apparatus in which
injector 61 is arranged directly beneath feed hopper or funnel 55.
As described for the embodiment of the invention shown in FIGS. 1
through 4, and as can be seen from FIG. 8, the powder-air current
is delivered from injector 61 to the spray-gun, the injector being
fastened to the chassis by means of a thumbscrew 63. In the
modification shown in FIG. 5, powder funnel 55 and injector 61 do
not require vibration energy.
As a further development, the apparatus described with reference to
FIGS. 1 through 4, and which is provided with a vibration drive,
can be designed in such a way as to permit removal of the vibration
drive with a few manipulations, and placing of the injector 61
directly underneath the powder funnel 55, so that the plant can be
operated without a vibration drive. This is applicable especially
in the case of specifically relatively light types of powder. When
using relatively heavy types of powder, however, the vibration
drive and the feeding trough are provided.
From FIG. 5, it will be seen how butterfly valve shaft 57, which
controls the butterfly valve for closing the bottom opening of the
powder funnel, is automatically movable through a lever 58,
carrying a roller, and a cam track 59, when powder funnel 55 is
removed from its bayonet catch by turning of the funnel.
The advantage of the present invention is that an alternatively
individually adaptable apparatus for spraying all types of powder
is provided, and can be used fully in practice for various fields
of service without requiring different models of the apparatus.
A further modification of the apparatus is illustrated in FIG. 6,
in which a cellular wheel lock 65 is arranged beneath powder funnel
54 for receiving powder from funnel 64 into cellular wheel 66
through an opening 43' and, upon rotation of wheel 66, delivering
the powder toward a lower section and to an opening 70, the
rotation being indicated by the curved arrow. The blade ends of
cellular wheel 66 are provided with brushing devices 67 to close
the individual cellular chambers.
As shown in FIG. 7, cellular wheel 66 is driven by a motor 68 in
the direction of the arrow. In the lower section, an air inlet 72
is provided which, for example, feeds air into the chamber 73 and,
by means of injector 70, blows the powder into the line 74
connected with powder gun 101 which is substantially identical to
the powder gun 32. With this arrangement, a predetermined quantity
of powder is supplied to the powder gun through line 74, in
dependence on the speed of motor 68 and the size of slot 43'.
In order to provide a pressure balance in the direction toward
filling slot 43', a pressure balance opening 71, illustrated at the
left in FIG. 6, is provided, and this pressure balance opening may
be connected, for example, to fluidizing bodies 69. FIG. 7
illustrates how the powder, flowing in the direction of the arrow
75', arrives from powder funnel 64 through opening 43' into the
upper section of cellular wheel lock 65, and the figure also
illustrates how lock 65 is combined with injector 70.
FIG. 8 diagrammatically illustrates an embodiment of the invention
apparatus wherein fluidizing bodies 69 can be arranged in powder
funnel 64. In addition, fluidizing bodies 76 are arranged in
discharge passage 75, and fluidizing bodies 78 are arranged in
injector 77. From FIG. 8, it will be noted that fluidizing bodies
69 can be supplied with air by an adjusting valve 79, fluidizing
bodies 76 can be supplied with air by adjusting valve 80, and
fluidizing bodies 78 can be supplied with air through an adjusting
valve 81, so that optionally a selected fluidizing effect can be
set by selection of the respective air pressures. The mixing
chamber 61 can be seen at the lower section of injector 77, and
compressed air is supplied to mixing chamber 76 in the direction of
the arrow 98, with the powder-air mixture flowing out through
opening 62 in the direction of the arrow adjacent thereto, the
powder-air mixture being supplied through a hose or conduit to the
powder spraying gun. With this embodiment of the invention, there
is realized the effect that, in its passage from the funnel to the
spray gun, the powder is broken up at the various locations and an
agglomeration of powder at the points of deflection is avoided.
FIG. 9 schematically illustrates the circuits for regulation of the
powder-air mixture at the apparatus and at the gun. When moving
trigger 82, which is arranged on the gun, a short distance in the
direction of arrow 83, valve 84 is actuated and, through line 86, a
compressed air operated switch 87 is actuated to open solenoid
valve 89. Thus, a smaller quantity of compressed air, supplied from
line 86 through a pressure reducing valve 92 and proportioned
through a checkvalve 93, is supplied to injector 95 receiving
powder from funnel 64 and feeding a powder-air mixture to line 96
connected to the powder gun. With the illustrated arrangement, in
the first stage only relatively little compressed air, and thus
also relatively little powder, is supplied to the powder gun so
that smaller projections or lugs on the workpieces can be coated
easily with powder without loss of larger powder quantities.
If trigger 82 is further depressed in the direction of arrow 83,
valve 85 is opened to actuate compressed-air operated switch 88 to
energize solenoid valve 90, so that a larger quantity of compressed
air is fed from pressure reducing valve 91 through checkvalve 94 to
injector 95, so that maximum performance, with respect to the
powder weight of the spraygun, is obtainable. It will be
appreciated that the arrangement illustrated in FIG. 9 provides, in
a relatively uncomplicated manner, for a quick adaptation of the
powder quantity fed to the requirements of the design of the
workpiece to be coated.
In further accordance with the invention, at least part of those
walls or surfaces coming into contact with powder are coated with
fluorinated or celluconated plastic materials, or both, of the
mentioned groups, or these walls can be formed from such plastic
materials. The walls or surfaces in question are the walls of the
powder funnel, or of the discharge passage of the powder funnel, or
the walls of the injector, or the walls of the cellular wheel lock.
Preferably, the powder conduit extending between the injector and
the powder gun is treated in the same manner. With this procedure,
there is assured that the powder does not, due to its adhesion,
stick to the walls with which it comes in contact, and does not
form agglomerations.
Referring again to FIG. 7, this figure illustrates a spray gun 100
with an extended gun tube 101 and a baffle body 102 having high
voltage electrodes 103.
While specific embodiments of the invention have been shown and
described in detail to illustrate the application of the principles
of the invention, it will be understood that the invention may be
embodied otherwise without departing from such principles.
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