Note: Descriptions are shown in the official language in which they were submitted.
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1-5 1 78
TITLE OF THE INVENTION
POWDER SPRAY COATING DEVICE
- CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable.
5STATEMENT REGARDING FEDERALLY SPONSORED
RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
The invention relates to apparatus for coating articles with a coating powder.
10 It is well known in the art that articles being manufactured may be coated with a
powder which, for example, may be a therrnoplastic material. After the coating is
applied, it is heated to fuse the coating to the article. It is also well know, for
example, from United States patent 4,196,465, that the coating apparatus preferably
imparts an electrostatic charge to the coating powder during spraying to cause the
15 powder to be attracted to and to adhere to the article being coated.
The feeding of powder between a powder supply and the spray coating
apparatus may be effected by gravity, suction air or compressed air. When the
powder is fed through a hose, it must be assured that the hose connections to the
spray coating apparatus are air tight and powder tight. However, the hose should be
20 easily and quickly disconnected from the spray coating apparatus. The quick
exchange of hoses or of spray apparatus units is very important, particularly when
changing the coating powder. Extreme care must be taken to prevent mixing of
powder particles of one powder with another powder to prevent cont~min~tion of
the applied coating. The powder hose and/or spray apparatus units are replaced by
25 clean ones during a powder change, while those used before are either cleaned or
stored for later reuse with the same coating powder.
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Hose connectors as taught, for example, from German patents DE-A-28 40
648, DE-A-35 13 188 and DE-A-34 46 568 have proven to be unsuited for coupling
hoses for powder coating material either because the connector leaks or because
powder deposits frequently build up in the hose connector. Tests have shown that5 leaks also may occur between connectors and hoses due to variations in the cross-
sectional dimensions in the hose from the design or nominal dimensions. This maybe due either to measuring inaccuracies in the hose manufacture and/or to changing
cross-sectional dimensions due to ambient temperature and aging.
It would be desirable to have a quick disconnect hose connector suitable for
10 use with powder hoses for powder coating apparatus which is pneumatically tight
and powder tight, irrespective of fluctuating cross-sectional dimensions of the hose.
BRIEF SUMMARY OF THE INVENTION
The invention is directed to a hose connector suitable for connection either
directly to a powder feed hose in a powder spray coating system or to an adapter15 secured to an end of a powder feed hose. The hose connector has a tubular section
into which the hose end slips and forms a powder and air tight seal. A clamping
sleeve is then moved on the adapter to a locking position to tighten a collet against
the hose and to cause projections on the collet to engage the hose. The optionaladapter has a barbed end for securing to the hose end and has a tubular end section
20 which slides into and seals to the tubular connector section. The tubular end section
of the adapter has the same outside diameter as the nominal diameter of the hose.
Preferably, the hose, the adapter and the hose connector have the same inside
diameters to prevent powder buildup during use. Recesses are provided on the
tubular end section of the adapter for receiving the collet projections when the25 clamping sleeve is in the locked position. When the clamping sleeve is in an
unlocked position, the projections are moved radially clear of the hose or adapter to
permit easy withdrawal from the hose connector.
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Objects and advantages of the invention will become apparent from the
following detailed description of the invention and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic diagram of powder spray coating apparatus in which the
5 invention is used;
Fig. 2 is a side elevational view, in partial section, of a powder spray gun
with an attached hose connector according to the invention;
Fig. 3 is a longitudinal cross sectional view of a hose connector according to
the invention shown in an unlocked position; and
Fig. 4 is a longitudinal cross sectional view of the hose connector of Fig. 3,
only shown in the locked position.
DETAILED DESCRIPTION OF THE INVENTION
Fig. 1 is a schematic diagram of exemplary powder spray coating apparatus.
The apparatus includes a coating spray booth 1 in which spray apparatus 6 directs a
15 spray of coating powder at an article 8 being coated. The booth 1 has a bottom
formed by an endless revolving filter belt 2. The filter belt 2 carries surplus coating
powder which drops on it out of the spray booth 1. Outside the booth 1, the powder
is sucked off the filter belt 2 by a suction nozzle 7 and is fed by means of a suction
air flow through a hose 7.1 to a cyclone separator 12. Powder separated from the20 suction air flow drops out of a bottom end of the cyclone separator 12 through a
valve 9 and passes through a screening m~chine 10 to a powder container 5 where it
is reclaimed. In addition to the reclaimed powder, fresh powder also is added to the
powder container 5 to replace the powder which has been applied to the article 8.
Both the reclaimed powder and the fresh powder are fluidized in the powder
25 container 5 by means of compressed air. The suction airflow in the suction nozzle 7
is generated by a fan or blower 13. The suction side of the blower 13 is fluidically
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connected through a filter 14 to the top end of the cyclone separator 12. Powder in
the suction air which is not removed by the cyclone separator 12 is removed by the
filter 14. The filtered air discharged by the blower 13 either is returned to the spray
booth 1, or is discharged to the atmosphere or, according to the embodiment of Fig.
S 1, is delivered to a suction line 15. A downstream end of the suction line 15
connects to the suction side of a further fan or blower 3. At an upstream end, the
suction line 15 is connected to suck air from the spray booth 1 through the filter 2.
Air discharged from the blower 3 passes through a heavy duty filter 4 to the
atmosphere.
The fluidized powder present in the powder container 5 is pneumatically fed
by a feed pump acting as an injector 16 through a powder hose 28 to the spray
apparatus 6. A compressed air source 18, such as a compressed air line commonly
available in a company, is fed to the injector 16. The air flow through the injector
16 sucks the powder out of the powder container 5 and carries the powder to the
15 spray apparatus 6. The various powder carrying components of the powder spraycoating apparatus are mostly interconnected by hoses which are connected to suchcomponents with hose connectors as hereafter described. The apparatus
components to which a powder hose can be connected in this way include the
suction nozzle 7, the cyclone separator 12, the filter apparatus 14, the blowers 3 and
20 13, the injector 16 and the spray apparatus 6.
As shown in Fig. 2, a hose connector 22 according to the invention is
mounted on a rear end of the spray apparatus 6 for attaching the powder hose 28.The end of the powder hose 28 may be detachably secured directly to the hose
connector 22. Or, as illustrated in Figs.3 and 4, an adapter 32 may be mounted on
25 the end of the powder hose 28 for detachably securing to the hose connector 22.
The hose cormector 22 is either detachably or permanently connected to the rear
end of a powder tube 24. The powder tube 24 fluidically connects the hose
connector 22 to a spray discharge device 26, such as a spray nozzle or a rotary
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atomizer head on a front end of the spray apparatus 6. As is known in the art, ahigh voltage electrode for imparting an electrostatic charge to the coating powder
may be located at the front end of the apparatus 6. A high voltage generator forgeneration of a high voltage for the electrode may be located either inside of or
5 external to the spray apparatus 6.
Referring to Figs.3 and 4, the hose connector 22 includes a tubular element
34 having a collet section 48 at one end and a coupler 38 on an opposite end, and an
axially movable clamping sleeve 36. The coupler 38 is in the form of a tubular
bushing having an externally threaded end portion and/or an internally threaded end
10 portion for attachment to a unit on which the connector 22 is mounted. The powder
tube 24 in the spray apparatus 6 is shown as being inserted into the coupler 38 and
the connector 22 is secured to the powder tube 24 by means of glue or adhesive
applied to the internal threads 42. Alternately, a conventional threaded connection
may be used for mounting the connector 22. The tubular element 34 is configured
15 as a hose fitting 44 which features an axial mounting section 46 into which an end
of the powder hose 28 may be slipped. The mounting section 46 is disposed insideof the collect section 48. The collet section 48 is provided with a plurality ofresilient collet jaws 50 which may elastically bend in a direction transverse to a
center axis 52 of a duct 54 which extends stralght through the connector 22. The20 clamping sleeve 35 surrounds the tubular element 34 and is axially adjustable on
the tubular element 34 between a decoupling or unlocked position as illustrated in
Fig.3 wherein the collet jaws 50 are released, and a coupling or locked position as
illustrated in Fig. 4 wherein the collet jaws are radially positioned inwardly towards
the center axis 52.
Preferably, the tubular mounting section 46 and the collet jaws 50 are
integrally formed from metal or from a plastic such as polyamide or polyacetal.
When the clamping sleeve 36 is in the unlocked position, the resilient collet jaws 50
form an axially outwardly flaring funnel having an axially outer end of a diameter
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greater than the outside diameter of the hose 28. The inner end of the collet jaws 50
match the diameter of the mounting section 46 of the tubular element 34.
Preferably, the tubular mounting section 46 has a diameter of equal size or only a
few tenths of a mm larger than the outside diameter of the hose 28 in order to allow
5 easy axial shifting when inserting the hose 28 into and when removing the hose 28
from the mounting section 46 while providing a very close fit.
While the inside diameter of the mounting section 46 can be manufactured
accurately with very accurate tolerances, the manufacture of the hose 28 produces
variations in the outside diameter of the hose 28 from hose to hose. This gives rise
10 to the risk that while one hose 28 may form a air tight fit in the slip on mounting
section 46, another hose 28 may not fit as well and may allow compressed air andpowder to escape into the atmosphere between the hose 28 and the connector 22. In
addition to manufacturing tolerance variations, changes in temperature and agingalso may change the outside diameter of the hose 28.
Different types of powder, specifically different powder colors, are often
used alternately in a spray coating system. In such powder or powder color change,
no mixing of the various types of powder must take place, since mixing would
result in defects in the coating applied to an article. In order to not lose too much
time cleaning components in a powder change, different hoses 28 and different
20 spray apparatus 6 are used for each powder type. At least two hoses 28 and at least
two spray apparatus 6 are used so that the coating operation may be continued with
one hose and spray apparatus 6 while the other is being cleaned.
In order to avoid a risk of leakage due to variations in hose diameters, an
adapter 32 may be used with the connector 22. The adapter 32 is tubular and, in
25 axially successive arrangement, has a slip-in section 60 and a hose fitting 62. A
duct 64 extends axially through the section 60 and the hose fitting 62. The slip-in
section 60 is inserted through the collet section 48 into the mounting section 46.
When the section 60 of the adapter 32 is slipped into the mounting section 46 of the
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connector 22, the duct 64 is coaxial to the duct 54 through the tubular element 34.
The slip-in section 60 complements and has an external diameter of essentially the
same size as the internal diameter of the mounting section 46. At a maximum, theslip-in section 60 had a diameter of a few tenths of a mm smaller than the mounting
5 section 46 in order for these tow parts to form together a pneumatically tight fit on
their abutting surfaces.
The duct 64 is formed with essentially the same diameter as the internal
diameter of the hose 28. Further, the duct 54 in the connector 22 and, preferably,
the powder tube 24 have the same internal diameter. As a consequence of
10 providing a uniform duct diameter, powder flowing from the hose 28 to the powder
tube 24 does not build up at the connector 22.
An annular groove 70 is formed on an outer circumference of the slip-in
section 60. An o-ring seal 72 is placed in the groove 70 to engage the inner surface
of the mounting section 46 on the hose connector 22. The o-ring seal 72 improves15 the air and powder seal between the hose connector 22 and the adapter 32.
According to a modified embodiment of the invention, several o-ring seals 72 or
other known seal types, such as a labyrinth seal, may be employed.
The hose fitting 62 on the adapter 32 is designed to be connected
permanently to an end of the hose 28, or, at best, to be poorly detachable from the
20 hose 28. Preferably, the hose 28 is secured to the adapter 32 by welding,
vulc~ni7ing, gluing and/or by means of barbed projections 68. The barbed
projections 68 are designed to allow the end of the hose 28 to be slipped onto the
hose fitting 62 by hand. The barbed projections 68 are shaped to dig into the
interior surface of the hose 28 when the hose 28 is pulled away from the adapter 32.
25 In forcing the hose 28 off of the adapter fitting 62, the barbed projections 68 cause
damage to at least the inside surface of the hose 28. In the illustrated preferred
embodiment, the projections 68 are formed integrally with the adapter 32. The
projections 68 are barbs directed obliquely from the adapter center axis 52
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outwardly and in the direction on the hose fitting 62 towards the slip-in section 60.
At its free outer end, the hose fitting 62 is tapered up to about the inside diameter of
the unexpanded powder hose 28. The taper facilitates slipping the end of the hose
28 onto the hose fitting 62.
S The adapter 32 is formed from a considerably harder and less flexible
material than the powder hose 28 and, consequently, can be manufactured to a
considerably higher tolerance without significant dimensional fluctuations between
individual adapters 32. Preferably, the adapter 32 is made of the same material as
the tubular element 34 of the hose connector 22. When the materials are the same,
temperature changes have no negative effect on the sealing between the slip-in
section 60 on the adapter 32 and the mounting section 46 of the hose connector 22.
In order to more efficiently retain the hose 28 or the adapter 32 in the hose
connector 22 and to prevent against unintended separation, a plurality of locking
projections 74 are formed on the collet jaws 50. The locking projections 74 are
annular, extending around the portion of the passage formed by the collet jaws 50,
or they may be of another suitable shape. The locking projections are integrallyformed on a surfaces of the collet jaws 50 and are directed towards the center axis
52. When the clamping sleeve 36 is in the released or unlocked position as shownin Fig.3, the locking projections 74 are disposed radially outside of the path of the
hose 28, or of the slip-in section 60 of the adapter 32, when inserted through the
collet jaws 50 into the tubular mounting section 46. Thus, the projections 74 do not
interfere with the insertion and withdrawal of the powder hose 28 or of the adapter
32 into the hose cormector 22.
When the clamping sleeve 36 is moved axially over an outer cam surface 78
of the collet jaws 50 to the locked position, as shown in Fig.4, the spring free ends
of the collet jaws 50 are forced radially inwardly until they are arranged at
essentially the same diameter as the exterior nominal diameter of the hose 28 and of
the slip-in section 60 of the adapter 32. The projections 74 project radially
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inwardly from this diameter towards the axis 52. When an end of the powder hose
28 is inserted into the tubular clamping sleeve 36 and the clamping sleeve 36 is then
moved to the locked position, the projections 74 deform and engage the outer
surface of the hose 28 to securely retain the hose 28 in the hose connector 22.
5 Preferably, the locking projections 74 have the form illustrated in Figs. 3 and 4 or a
similar barbed or wedge shaped form.
The slip-in section 60 of the adapter 32 is provided with a plurality of
annular grooves or recesses 76. A groove 76 is provided for each projection 74 on
the collet jaws 50. The grooves 76 are arranged to receive the projections 74 when
10 the slip-in section 60 is seated in the tubular mounting section 46 and the clamping
sleeve 36 is moved to the locked position. By providing a wedge shape to the
projections 74, the projections 74 will align the adapter 32, if necessary, as the
projections 74 enter the grooves 76. The projections 74 tightly engage the adapter
32 to prevent pulling the adapter 32 from the hose connector 22. The locking
15 recesses or grooves 76 may be annular or of other configurations and that thelocking projections 74 may be circular ribs complementing the grooves 76 or may
have other forms.
It will be appreciated that various modifications and changes may be made to
the above described preferred embodiment of without departing from the scope of
20 the following claims. Although the hose connector 22 and the adapter 32 have been
described as being made of metal or, preferably, of a plastic such as polyamide or
polyacetal, other plastics may be used as well, such that allow easy manufacturing,
are durable and are compatible with the coating powder.
