Note: Descriptions are shown in the official language in which they were submitted.
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A wall member of a cabin for electrostatic powder coating.
The instant invention relates to a wall member of a cabin for
electrostatic powder coating, comprising inner and outer
cover layers of electrically non-conductive material, as well
as a core layer.
Such wall members may be used to build modular cabins of dif-
ferent dimensions for purposes of powder coating, as described
in EP 0 588 003 Bl, for example. The wall members specified in
that publication have a core layer made of polyurethane foam
covered by outer and inner cover layers of polyvinyl chloride
(PVC). Additionally, an electrically conductive separating
layer may be provided between the core layer and one of the
two cover layers. The continuous or integral core layer may be
substituted by individual spacers arranged at regular spac-
ings.
From U.S. Patent 5,259,879, granted to Khattab et al. on No-
vember 9, 1993 a wall member of a powder coating cabin is
known which consists of inner and outer thermoplastic layers
and a core layer made of thermoformed circular or bubble-like
spacers which are arranged with a distance from each other so
that air can freely circulate within the core layer.
It is an object of the invention to provide for a wall member
for modular construction of a cabin for electrostatic powder
coating which will minimize the depositing of powder within
the cabin and permit reducing the wall thickness as compared
to that of a cabin according to the state of the art.
This object is met by claim 1.
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Advantageous modifications of the invention are recited in the
dependent claims.
A cabin made of wall members according to the invention has a
core layer which consists of an integral honeycomb structure,
whereby maximum stability is warranted at much lower overall
thickness than is the case with the known wall member. The in-
terconnected honeycombs of the honeycomb structure, preferably
have their primary axes oriented at right angles to the cover
layers, and are characterized by a very thin wall thickness.
And yet they offer sufficient supporting strength for the
cover layers of which the wall thickness is very thin.
A particular advantage of the invention is obtained due to the
fact that the honeycomb structure according to the invention
prevents the exchange of air within the core layer and thus
minimizes the resulting local static charging of the wall mem-
ber.
In comparison with the air volume trapped between the cover
layers, only a minor proportion of honeycomb material is dis-
posed between the cover layers. Tests have shown that, as a
consequence thereof, much less excess powder accumulates on
the interior walls of a cabin made of wall members according
to the invention than is the case with conventional wall mem-
bers. This is true, in particular, in comparison with an em-
bodiment of known wall members which include spacers. With
such wall members it was observed that the spacers, given
their large cross sectional surface area for reasons of sta-
bility, lead to especially great accumulations of powder be-
cause air can freely circulate within the core layer and the
lines of flux of the electric field are concentrated in the
area of the spacers, thereby provoking undesirably great de-
posits of electrically charged powder particles.
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Another reason why the use of wall members according to the
invention causes only minor accumulations of powder is to be
seen in the fact that the density of the lines of flux is
greater with a greater wall thickness of the cabin, in other
words with long spacers,y.than it is when short spacers are
provided. However, a certain minimum length of spacersyor a
minimum thickness of a core layer consisting of polyurethane
foam is unavoidable in order to achieve sufficient stability.
Providing an integral honeycomb structure as the core layer
can cut this minimum thickness by almost one half.
Both the cover layers and the core layer with its honeycomb
structure preferably are made of plastics, especially of PVC.
A wall member according to the invention has the following ad-
vantages:
- small wall thickness
- small total thickness
- high stability
- low weight
- minimized powder accumulation.
These advantages are derived from the use of an integral hon-
eycomb structure as the core layer which affords the consid-
erably reduced overall thickness of the wall member while re-
taining its stability. As a consequence of the small wall
thickness, reduced amounts of powder will deposit, as already
mentioned. Furthermore, the honeycomb structure affords the
weight reduction mentioned and thus also contributes to saving
building material.
The invention will be described further, by way of example,
with reference to the accompanying drawings, in which:
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Fig. 1 is a cross sectional elevation of a conventional wall
member for a powder coating cabin, including spacers
between two cover layers;
Fig. 2 is a perspective view of a wall member according to
the invention, comprising an integral honeycomb
structure as the core layer in a first embodiment.
The conventional wall member shown in fig. 1 has an outer
cover layer 2, an inner cover layer 4, and a core layer 6 con-
sisting of individually disposed spacers 8 which are arranged
at regular spacings between the cover layers.
The two cover layers 2, 4 as well as the spacers 8 of the core
layer 6 are made of a kind of plastics which is not electric-
ally conductive, such as PVC.
Reference numeral 10 in fig. 1 indicates lines of flux of an
electrostatic field building up across the wall member il-
lustrated, particularly so in the area of the spacers 8. De-
posits of electrically charged powder particles of excess pow-
der accumulate accordingly at the inner side of the cover
layer 4.
Fig. 2 illustrates the structure of a wall member according to
the invention. Again, an outer cover layer 22 and an inner
cover layer 24 are provided spaced from each other. The spac-
ing is bridged by a continuous core layer 26 consisting of an
integral honeycomb structure comprising honeycombs 28. For
reasons of clarity, only a few honeycombs 28 are illustrated;
they are interconnected and fill the entire space between the
two cover layers 22 and 24.
The honeycombs 28 of the honeycomb structure according to fig.
2 are oriented with their principal axes at right angles to
the cover layers 22, 24. This orientation of the honeycomb
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structure is advantageous as it should provide maximum sta-
bility at minimum wall thickness of the material of the honey-
combs.
As with the known wall member, also the wall element according
to the invention, shown in fig. 2, has the cover layers 22, 24
and the honeycomb structure 26 of the core layer made of elec-
trically non-conductive plastics, for example PVC. Of course,
some other non-conductive material is conceivable as well,
particularly for the honeycomb structure.
Cabins for powder coating of any desired dimensions may be
built of wall members such as shown in the drawing. Also the
doors of such cabin may be made of this type of wall members.
Doors may be located, for instance, at the ends of an elon-
gated cabin to permit passage of workpieces in longitudinal
direction through the cabin; or they may be provided in the
lateral walls for an outside manual coating station.
Other than known cabins, cabins composed of wall members ac-
cording to the invention are angular in external shape.
The total thickness of wall members according to the invention
may be made smaller than the wall thickness of known cabins.
The features disclosed in the specification above, in the
claims, and drawing may be significant for implementing the
invention in its various embodiments, bath individually and in
any combination.
