U.S. patent number 3,918,641 [Application Number 05/534,675] was granted by the patent office on 1975-11-11 for electrostatic powder coating installation.
This patent grant is currently assigned to Gema AG Apparatebau. Invention is credited to Ernst Lehmann, Robert Prinzing.
United States Patent |
3,918,641 |
Lehmann , et al. |
November 11, 1975 |
Electrostatic powder coating installation
Abstract
An electrostatic powder coating installation incorporating a
cabin in which there are arranged means connected with a supply
container for the delivery of electrostatically charged powder. A
part of the internal compartment of the cabin is limited by one
side or face of a filter moving through the cabin, the other face
of which confronts the suction side of a suction device effective
through the filter at the aforementioned internal compartment. A
cleaning device is operatively associated with the filter in order
to remove therefrom excess powder deposited thereon. The cleaning
device embodies a suction nozzle directed towards the one face of
the filter and which while interposing a separator is operatively
connected with the suction side of a suction blower. The outlet of
the separator is connected with a supply container. The method of
operating the installation entails depositing fresh powder upon a
section of the filter located in front of the suction nozzle for
the purpose of replacing the powder consumed during the coating
operation.
Inventors: |
Lehmann; Ernst (St. Gall,
CH), Prinzing; Robert (St. Gall, CH) |
Assignee: |
Gema AG Apparatebau (St. Gall,
CH)
|
Family
ID: |
4407012 |
Appl.
No.: |
05/534,675 |
Filed: |
December 20, 1974 |
Foreign Application Priority Data
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|
|
|
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Nov 14, 1974 [CH] |
|
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15177/74 |
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Current U.S.
Class: |
118/620; 118/50;
118/621; 239/708; 118/634; 361/227 |
Current CPC
Class: |
B05B
14/20 (20180201); B05B 5/1683 (20130101); B05B
14/43 (20180201); B05B 7/144 (20130101); B05B
5/087 (20130101); B05B 14/45 (20180201); Y02P
70/10 (20151101) |
Current International
Class: |
B05B
15/12 (20060101); B05B 5/08 (20060101); B05B
5/00 (20060101); B05B 5/16 (20060101); B05B
7/14 (20060101); B05B 15/04 (20060101); B05B
005/02 () |
Field of
Search: |
;239/3,15 ;317/3 ;117/17
;118/621 |
References Cited
[Referenced By]
U.S. Patent Documents
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|
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3691991 |
September 1972 |
Luderer et al. |
3724755 |
April 1973 |
Diamond et al. |
|
Primary Examiner: Wood, Jr.; M. Henson
Assistant Examiner: Mar; Michael
Attorney, Agent or Firm: Kleeman; Werner W.
Claims
Accordingly, what is claimed is:
1. An electrostatic powder coating installation comprising a cabin,
a supply container, means operatively coupled with the supply
container for delivering electrostatically charged powder into the
interior of the cabin, said cabin being provided with an internal
compartment, a filter movable in a predetermined direction of
travel through the cabin, said filter having opposed faces, one
face of said filter bounding a part of the internal compartment of
the cabin, a suction device having a suction side and effective
through the filter at said internal compartment, the other face of
said filter confronting the suction side of the suction device, a
cleaning device operatively associated with the filter for removing
excess powder which has deposited on the filter, said cleaning
device possessing a suction nozzle directed towards the one face of
the filter, a suction blower having a suction side, a separator,
the suction nozzle being connected by means of the separator with
the suction side of the suction blower, said separator having an
outlet flow communicating with the supply container.
2. The installation as defined in claim 1, wherein said filter
comprises a filter band which moves along said predetermined
direction of travel and extends out of said cabin in the direction
of travel of said filter band, said suction nozzle being arranged
at the region of a section of the filter band located externally of
the cabin.
3. The installation as defined in claim 1, further including a
delivery mechanism having an outlet for fresh powder, said outlet
of the delivery mechanism being directed towards the one face of
the filter, and wherein the delivery mechanism is arranged ahead of
the suction nozzle with respect to the direction of travel of the
filter.
4. The installation as defined in claim 2, further including means
acting upon the filter for the removal of electrostatic charges and
arranged between the cabin and the suction nozzle.
5. The installation as defined in claim 4, wherein said means for
the removal of electrostatic charges comprises a corona
electrode.
6. The installation as defined in claim 4, further including a
delivery mechanism having an outlet for fresh powder, said outlet
being directed towards the one face of the filter, said delivery
mechanism being arranged ahead of the suction nozzle with respect
to the direction of travel of the filter, and wherein the means for
the removal of the electrostatic charges is arranged between the
cabin and the outlet of the delivery mechanism.
7. The installation as defined in claim 1, further including means
for generating current surges in the suction nozzle, said
generating means being arranged between the suction nozzle and the
separator.
8. The installation as defined in claim 7, further including a
connection conduit disposed between the suction nozzle and the
separator, said connection conduit having a throughpassage and
being provided with an oscillating floating body for periodically
throttling said throughpassage.
9. The installation as defined in claim 7, further including a
connection conduit arranged between the suction nozzle and the
separator, means defining a false air opening provided in the
connection conduit and controlled by a to-and-fro movable closure
element.
10. The installation as defined in claim 1, wherein a sieve
mechanism is arranged between the outlet of the separator and the
supply container, said sieve mechanism due to its sieving action
improving the friability of the powder arriving out of said outlet
of the separator prior to its entry into the supply container.
11. The installation as defined in claim 10, wherein a sluice
impeller is positioned to cooperate with said sieve mechanism.
12. The installation as defined in claim 11, wherein said sluice
impeller is selectively arranged upstream or downstream of the
sieve mechanism.
13. The installation as defined in claim 3, wherein the delivery
mechanism possesses a regulatable dosing mechanism.
14. The installation as defined in claim 1, wherein said suction
blower has a pressure side, and means for connecting the pressure
side with the internal compartment of the cabin.
15. The installation as defined in claim 14, further including a
distributor conduit having a number of outlet openings arranged in
the internal compartment of the cabin at the region of the exit of
the filter band out of the cabin, the pressure side of said suction
blower being connected with said distributor conduit.
16. The installation as defined in claim 14, wherein the conveying
capacity of the suction device is a multiple of the conveying
capacity of the suction blower.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a new and improved construction of
electrostatic powder coating installation.
The coating of articles or the like by means of electrostatically
charged powder -- briefly hereinafter referred to as electrostatic
powder coating-- at the present time cannot hardly be dispensed
with in fabrication or manufacturing operations in consideration of
the presently available advantages in contrast to wet spraying (for
example, greater layer thickness per working operation, no solvent
vapors, just to mention a few). Hence it is particularly incumbent
to especially take into account two aspects during electrostatic
powder coating in order to maintain such coating technique
economically competitive with wet spraying.
Both aspects are entwined with the circumstance that a relatively
great proportion of the released electrostatically charged powder
in fact does not even impinge upon the article or object to be
coated or does not sufficiently adhere thereto, for instance
because the desired layer thickness has already been attained. This
proportion can be designated as excess powder. A part of this
excess powder deposits like dust at the parts or components of the
installation and upon changing the quality of the powder -- for
instance changing the powder color-- must be removed by performing
an extremely time consuming work. On the other hand, a further part
of this excess powder is removed by a suction device belonging to
the installation out of the installation itself in order to
possibly again be delivered for reuse.
Hence, there is applicable on the one hand the aspect of the time
needed for cleaning the installation, since this time constitutes
downtime or deadtime for the installation and, on the other hand,
there is also to be considered the aspect of reclaiming and reusing
the excess powder since such constitutes a considerable cost
factor.
A state-of-the-art installation by means of which it has been
attempted to satisfy both of the above-mentioned aspects possesses
a cabin in which there are arranged means coupled with a supply
container for the purpose of delivering electrostatically charged
powder. A part of the internal space of the cabin is bounded by one
face of a filter moving through the cabin, the other face of which
is in confronting relationship with the suction side of a suction
device which is effective through the filter at the aforementioned
internal space. A cleaning device is associated in operative
coaction with the filter for removing therefrom excess powder which
has deposited thereon.
With this already proposed prior art installation the greatest
portion of the excess powder falls onto the filter under the action
of the suction device, so that the remaining parts of the
installation are considerably less contaminated by depositions. By
means of the cleaning device the excess powder is removed from the
filter and delivered to a collecting container. In this way while
the excess powder is not lost, still it is incapable of being
re-employed in the then existing state since it has lost a
considerable proportion of its trickling or friable properties.
Also the proposed equipment does not permit of a continuous working
operation since, firstly, the collecting container from
time-to-time must be exchanged for an empty container, and the
reclaimed powder after having been re-processed, if desired
together with fresh powder, must be deposited into the supply
container.
SUMMARY OF THE INVENTION
Hence it is a primary object of the present invention to provide an
improved electrostatic powder coating installation which is not
associated with the aforementioned drawbacks and limitations of the
prior art proposals.
Another and more specific object of the invention is directed to
constructing an installation of the previously mentioned type in
such a manner that re-processing of the powder removed from the
filter is practically superfluous, so that it can be delivered in a
truly closed circulation system directly and continuously to the
supply container with a minimum danger of contamination.
Now in order to implement these and still further objects of the
invention which will become more readily apparent as the
description proceeds the installation of this development is
manifested by the features that the cleaning device is equipped
with a suction nozzle directed towards the one face of the filter,
this suction nozzle, while interposing a separator, is connected
with the suction side of a suction blower, the outlet of the
separator being operatively coupled with the supply container.
The removal of the powder from the filter by means of the
installation of this invention occurs therefore by carrying out a
suction operation, i.e., pneumatically, which automatically
provides the result that the removal in the suction line takes
place to a certain extent in suspension, whereby the thus occurring
turbulence maintains the friability or trickling properties of the
powder or again establishes such properties in the event such is
even necessary. Additionally due to the connection between the
outlet of the separator and the supply container there is
established a truly closed circulation system for the excess powder
which permits of a continuous working operation.
The filter advantageously constructed as a filter band can extend
out of the cabin in its direction of movement, the suction nozzle
then advantageously being arranged at the region of the section of
the filter band located externally of the cabin. With this
construction it is especially beneficial that the replenishment of
fresh powder and its admixing with the excess powder circulating
throughout the closed circulation system is extremely simple. In
the direction of movement of the filter there can be arranged an
outlet of an infeed device for fresh powder which is disposed ahead
of the suction nozzle, i.e. upstream thereof when considered with
respect to the direction of movement of the filter band.
Furthermore, the outlet of the infeed device just mentioned above
is arranged to be directed towards the one face or side of the
filter. Consequently, there is not only sucked through the suction
nozzle the excess powder, rather also the fresh powder deposited
upon the same side or face of the filter, so that during the course
of this operation both of the powder components are automatically
intimately admixed with one another.
Between the cabin and the suction nozzle there can be arranged a
device acting at the filter for removal of the electrostatic
charge. In this way it is possible to remove any existing
electrostatic residual charge from the excess powder deposited upon
the filter. In order to be also able to protect the connection
prevailing between the suction nozzle and the suction blower
against deposition of the excess powder which flows through in
suspension, it is possible to provide means for generating flow or
current surges. In this way the suction action of the suction
nozzle takes on a pulsating characteristic and in the connection
line or conduit there is favored the formation of turbulence or
vortexes.
Between the outlet of the separator and the supply container there
can be provided a sieve mechanism, especially for the purpose of
removing possibly entrained contaminants by sieving the powder
prior to entry into the supply container and, if necessary, to
again re-establish the trickling or friable properties of the
powder.
In the separator such friable or pulverulent properties of the
powder will be obtained to a better degree the less intense the
separator separates the powder out of the air current. In other
words, this means that the friable behavior will hardly be impaired
when the degree of separation of the separator is not 100 percent.
On the other hand this leads to the result that the air conveyed by
the suction blower is associated with a residual proportion of
powder. It is therefore advantageous to couple the pressure side of
the suction blower with the internal compartment or space of the
cabin. Consequently, there is formed to a certain extent a second
closed circulation system, wherein the powder which possibly was
not separated out during the first passage through the separator
again arrives at the filter, removed therefrom by the suction
nozzle and again delivered to the separator.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be better understood and objects other than
those set forth above, will become apparent when consideration is
given to the following detailed description thereof. Such
description makes reference to the annexed drawing wherein:
FIG. 1 is a schematic side view, partly in section, of an
electrostatic powder coating installation; and
FIGS. 2 and 3 respectively show exemplary embodiments of a
component of the installation portrayed in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Describing now the drawing, the exemplary illustrated embodiment of
installation shown therein will be understood to comprise a cabin
10 which is delimited or bounded by a ceiling or cover 11, end
walls 12 and 13 and side walls which have been conveniently omitted
from the drawing to preserve clarity in illustration and to reveal
internal structure. The internal space or compartment which is
enclosed by the cabin 10 has been conveniently designated by
reference character 14. As indicated by means of the double broken
lines 15 there can be provided a conveyor mechanism which extends
through the cabin 10 and by means of which there are delivered in
the direction of the arrow 16 through a gantry-like opening (not
shown) the articles or the like to be coated into the internal
space or compartment 14, the gantry-like opening being conveniently
provided for instance in the end wall 12. Further the articles can
again be removed out of the cabin 10 by means of a similar opening
which in this case is provided at the end wall 13.
Within the internal compartment or space 14 of the cabin 10 there
is arranged at least one spray nozzle, for instance, in the form of
a spray gun or pistol 17, the outlet end of which obviously is
directed towards the articles to be coated. The spray pistol 17 is
connected via a connection line, for instance a hose 18 or
equivalent, with a supply container 19 and by means of an infeed or
delivery line 20 with a voltage source 21. By means of the infeed
or delivery line 18 there is delivered to the spray pistol 17
through the agency of conveying air the powder which is to be
electrostatically charged. By means of the infeed line 20 there is
furnished the electrical energy needed for electrostatic charging.
In this connection it is mentioned that the infeed line 20 can be
arranged in or at the hose 18.
Continuing it is to be observed that the floor of the cabin 10 is
formed by the upper face of the upper run 22 of an endless filter
band 23 or equivalent structure, which is guided about deflecting
rollers 24, 25 in the manner of a conveyor band. As regards the
deflecting rollers 24, 25 it is possible for one, such as the
deflecting roller 25 to be driven through the agency of a chain
drive or a shaft 26 by means of a gear or transmission motor 27 or
the like in the direction of the arrow 28.
The lower face or side of the run 22 of the filter band 23 bears on
the one hand upon a flange 29 which laterally protrudes and
surrounds the open side of a suction vat or trough 30 and, on the
other hand, bears upon a grate 31 formed for instance of a fine
wire mesh, and which grate spans the open side of the vat or trough
30 and is substantially coplanar to the flange or flange means 29.
Internal compartment 32 of the vat 30 is connected by means of a
connection line 33 with the suction side of a blower 34. From what
has been discussed above it will be apparent that during operation
of the blower 34 such acts through the part of the upper run of the
filter band which spans the vat or trough 30 at the internal
compartment 14 in the sense that within such internal compartment
there always prevails a lower negative pressure and a slight air
flow in the direction of the arrows 35. By means of this air flow
excess powder, delivered by the spray pistol 17, yet not adhering
at the article to be coated, will be caused to deposit primarily at
the upper face of the upper run 22 of the filter. By suitably
selecting the permeability of the filter band 23 it is possible to
prevent penetration of the powder through the same.
During the course of its movement the upper run 22 of the filter
band 23 leaves the internal compartment 14 of the cabin 10 at the
location 36 and carries along therewith the powder which has
collected thereon during the course of the throughpassage of such
filter band. The outlet 36 is provided with a corona electrode 37
which radiates the upper face of the filter band run 22. This
electrode 37 is powered by a high-voltage source 39 through the
agency of a connection line or conductor 38. The corona electrode
37 serves the purpose of removing the residual charge adhering to
the powder possibly present at the upper face of the run 22. This
corona electrode 37, of course, could be equally replaced by
another device which produces an ionized surrounding region, i.e.,
electrically conductive surrounding region, for instance by using a
weak beta radiating device.
In the direction of travel 23' of the upper run 22, and following
the corona electrode 37, there is arranged a delivery or infeed
device which has been designated in its entirety by reference
character 40. This infeed device 40 possesses a filling funnel 41
or the like which supplies a dosing worm 43 driven by a motor 42.
The dosing worm 43 in turn extends practically over the entire
width of the filter band 23. This dosing device or dosing mechanism
40 serves the purpose of delivering to the installation new powder,
whether such be of the same or a different quality, as shall still
be more fully described hereinafter.
The delivery mechanism or device 40 has arranged thereafter a
suction nozzle 44 possessing a suction slot 45 which likewise
extends practically over the entire width of the filter band 23.
This suction nozzle 44 is connected via a device 46 for producing
air surges or pulses with a connection conduit or line 47 leading
to a separator 48 in the form of a cyclone, by way of example. The
separator 48 is coupled through the agency of a suction conduit 50
with the suction side of a blower 49, so that upon operation of the
suction blower 49 there prevails a pronounced suction action in the
connection conduit 47. The device 46 for generating the air surges
serves the purpose of insuring that the suction action emanating
from the blower 49 is not continuous rather pulsating, whereby
there is rendered more difficult in any case, if not completely
avoided, a deposition of the powder removed by the suction nozzle
44 from the filter band at the inner wall of the connection conduit
47.
This separator 48 possesses an outlet or discharge 51 by means of
which there is continuously delivered the powder separated out at
the separator 48 by means of the suction air, for instance through
the agency of a bucket wheel or sluice impeller 52 driven by a
motor 53, to an oscillating or rotary sieve 54. Both the bucket
wheel or impeller 52 as well as also the oscillating or rotary
sieve 54 are arranged in a closed housing, which among other
things, serves the purpose of protecting against contamination the
powder located upon the sieve 54, and, in the event there is
omitted the impeller wheel 52, serves as sluice, in order to
maintain the negative pressure prevailing in the separator 48 and
preventing the generation of any false air currents. The powder
which has been prepared by the sieve or filter 54, that is to say,
to the extent necessary freed of possible contaminants and again
rendered friable, arrives through the agency of a sieved material
outlet or discharge 55 directly and continuously in the supply
container 19. Possibly existing coarser fractions of the powder
removed by the suction nozzle 44 from the upper run 22, and which
are not again comminuted by the action of the sieve 54, arrive via
a waste conduit 56 in a waste or refuse container 57.
The pressure side of the blower 49 is connected with a pressure
conduit 58 which, in turn, leads to the internal compartment 14 of
the cabin 10 and there opens into a distributor conduit or pipe 59
having a multiplicity of openings 60. The reason for this
arrangement, among other things, resides in the fact that the
separator 48 as a general rule cannot be designed such that it
completely separates out the powder from the powder-air current
existing in the connection conduit 47, because the danger thereby
exists that the separated out powder particles will cake together
or conglomerate in the separator 48, which prohibits the direct
reuse, i.e., the delivery into the supply container. Since the
separator 48 as will be recognized cannot separate out all of the
powder out of the flow emanating from the connection conduit 47, a
part of this powder arrives via the suction conduit 50 in the
pressure conduit 58 and thus at the distributor conduit 59, where
such powder again arrives in the internal compartment 14 of the
cabin 10 and thus is subjected to the suction action emanating from
the blower 34. Consequently, this powder again is deposited at the
upper face of the upper run 22 of the filter band 23. It is to be
observed that the conveying capacity of the blower 34 amounts to a
multiple of the conveying capacity of the suction blower 49, so
that even when the pressure line or conduit 58 opens into the
internal compartment 14, the negative pressure in this internal
compartment thus will be only slightly affected.
From the above discussion it will be recognized that the upper run
22 of the filter band 23 passes approximately the following
sections between the deflecting roller 24 and the driven deflecting
roller 25. In a first section a there is deposited upon such upper
run to an increasing degree excess powder coming out of the spray
pistol or gun 17. In the next following section b this deposition
of excess powder emanating from the spray pistol 17 continues,
whereby however there is added a residual amount of excess powder
which was not previously separated out in the separator 48. In the
sections a and b this powder is fixedly held in the filter material
of the filter band 23 due to the suction action which prevails upon
the travel of the filter band over the open side of the vat or
trough 30. Hence upon exit out of the cabin 10, i.e., upon the
transition to the section c this powder cannot be whirled about. In
the section c there is additionally effective the corona electrode
37 which insures that any possibly present residual charges are
removed. If the delivery or infeed mechanism 40 is in operation the
powder layer appearing at the upper run is supplemented by fresh
powder, so that at the section d of the upper run there is present
powder from the total of three regions. In the section e the upper
run is thus freed of all present powder by the suction nozzle 44,
and the three fractions are forcefully brought to turbulence or
whirled about prior to reaching the separator 48. Following the
section e is a last section f, the significance of which will be
explained more fully hereinafter.
In FIG. 2 there is schematically illustrated a possible device or
mechanism 46 for producing air surges or pulses. There will be
recognized a part of the upper run 22, the suction nozzle 44 with
its suction slot 45, as well as the starting portion of the
connection conduit or line 47. In a substantially pot-shaped
widened portion 62 which directly merges with the suction nozzle 44
there is formed a type of conical valve seat 63 which coacts with a
closure element or floating body 65 prebiased by a weak pressure
spring 64 or the like. When the installation is switched off the
floating body 65 normally almost closes the through-passage formed
by the valve seat 63. As soon as the nagative pressure in the
connection conduit 47 is sufficient, then the floating body 65
raises off of the valve seat 63, so that a powerful air current is
formed. As a result the pressure differential between both sides of
the valve seat 63 drops and the spring 64 is capable of overcoming
such pressure differential and again forcing the floating body 65
in the direction of the valve seat 63. Hence with time the floating
body 65 is brought into a state of oscillation, so that the flow in
the connection conduit 47 and together therewith -- even if to a
lesser extent-- the flow in the suction conduit 50 and in the
pressure conduit 58 as well as in the separator 48 will be
pulsating. Consequently, the deposit, especially the fine fractions
of the powder taken up by the suction nozzle 44, at the inner wall
of such conduits at least will be rendered more difficult.
Approximately the same action can be realized with the equipment
shown in FIG. 3. With this device a false air opening 66 is
provided in the connection conduit 47 directly at the connection
with the suction nozzle 44, this false air opening normally being
closed by a flap member 67 or equivalent structure. If this flap 67
is periodically and briefly opened in the direction of the arrow
68, then, since the through flow cross-section of the false air
opening 66 is considerably greater than the through flow
cross-section between the upper run 22 and the slot 45, there
prevails a powerful air surge. Of course, the opening time of the
flap or flap member 67 is calculated such that in this time the
upper run only passes through a path of travel which is
considerably smaller than the width of the slot 45.
The mode of operation of the described apparatus can be considered
as follows: The articles to be coated are moved through the cabin
10 in the direction of the arrow 16. The spray gun or pistol 17
generates in the internal compartment 14 a cloud of
electrostatically charged powder particles, and which cloud, owing
to the fact that a slight negative pressure prevails in the
internal compartment 14, is limited to such internal compartment
14. A large proportion of the electrostatically charged particles
thus deposit upon the articles to be coated and while adhering to
such articles leave the cabin. The proportion of the powder which
has not found its way to the articles deposits upon the upper run
of the filter band and thus arrives beneath the suction nozzel 44
where it is reclaimed and via the separator 48 again delivered to
the supply container 19. With the exception of that part of the
powder which remains adherent to the articles, the powder
accordingly moves through a first closed cycle or circulation
system, starting from the supply container 19 through the hose 18
to the spray gun 17, from that location into the internal
compartment or space 14 and after depositing on the run 22 arrives
at the suction nozzle 44, then through the connection conduit 47 to
the separator 48 and through the outlet 51 and the sieve 54 again
arrives back at the supply container 19. It is to be observed that
this circulation system is closed and practically only accessible
in the sections c to e at the upper run. A further powder
circulation system is passed through by that part of the powder
which is not separated out by the separator 48. This circulation
system begins at the suction conduit 50, thereafter leads through
the suction blower 49, through the pressure conduit 58, the
distributor conduit 59 into the internal compartment 14, and after
depositing on the run 22 continues up to the suction nozzle 44 and
via the connection conduit 47 leads back to the separator 48. Also
this closed cycle or circulation system is practically only
accessible at the sections c to e of the upper run. In order to
replace the powder consumed by the actually occurred coating of the
articles or objects, fresh powder is likewise deposited upon the
upper run 22 by means of the delivery device 40. Hence, the supply
container 19 is not directly refilled, rather the fresh powder
initially is deposited upon the excess powder and then taken up
through the suction nozzle 44 whereby there occurs a powerful or
forceful admixing. If there is compared the quantity of powder
delivered to the installation with the quantity actually consumed
by the coating operation, then it has been found that the loss in
powder with the described installation is considerably below 1%, so
that it can be justifiably stated that the reclaiming and direct
reuse is complete, whereby it is to be observed that these
operations take place continuously.
Also upon changing the quality of the powder the installation
affords notable advantages. With such change initially no articles
are delivered for instance any longer to the cabin. Then the hose
conduit 18 is separated from the supply container and compressed
air blown therethrough. The remaining parts of the installation
operate as previously described. The powder still located in the
installation passes through one of the two previously described
circulation systems until it finally arrives at the supply
container which is no longer coupled with the hose 18. At the same
time it is possible for instance with the aid of a powerful
industrial vacuum cleaner to subject the filter band 23 at the
section f of the upper run to a cleaning action which deeply
penetrates such upper run of the filter band. Of course at this
point in time the delivery mechanism 40 is not in operation.
Consequently, the supply container 19 can be replaced by an empty
one, whereafter the delivery mechanism 40 can be charged with the
new powder and the hose conduit 18 can be connected to the new
supply container 19. After a brief start-up time the installation
is faultlessly charged with the new color without there being
discernible with the naked eye at the formed coatings a
contamination by powder particles of the preceding color. Apart
from the short conversion time and the cleaning of the filter band
23 there are practically no deadtimes.
While there is shown and described present preferred embodiments of
the application, it is to be distinctly understood that the
invention is not limited thereto but may be otherwise variously
embodied and practiced within the scope of the following
claims.
* * * * *