METHODE DE POUDRAGE

METHOD OF POWDER COATING

Abrégé français

Un procédé de revêtement à poudre d'au moins une surface d'un objet non conducteur, qui comporte une pluralité d'étapes séquentielles, est proposé. La première étape est le prétraitement de la surface de l'objet non conducteur pour garantir que la surface est nettoyée de façon appropriée. La deuxième étape est l'application d'une quantité suffisante d'humidité sur la surface de l'objet non conducteur pour faciliter l'adhérence d'un revêtement à poudre sur la surface. L'étape suivante est la pulvérisation d'une poudre de revêtement polymère sur la surface humidifiée de l'objet non conducteur. Cette étape de pulvérisation est réalisée immédiatement après l'application d'humidité, mais avant une évaporation complète de l'humidité appliquée. La cinquième étape est l'évaporation de toute humidité appliquée restante à partir de l'objet non conducteur avant le traitement thermique. La dernière étape est le traitement thermique du revêtement sur la surface de l'objet non conducteur sans décomposer la poudre et puis le refroidissement ou le refroidissement naturel de l'objet non conducteur.

Abrégé anglais

A method of powder coating at least one surface of a non-conductive object having a plurality of sequential steps. The first step is pretreating the surface of the non-conductive object to ensure that the surface is suitably cleaned. The second step is to apply a sufficient quantity of moisture on the surface of the non-conductive object to facilitate adhesion of a powder coating to the surface. The next step is to spray a polymer coating powder on the moistened surface of the non-conductive object. This spraying step is done immediately following the application of moisture but prior to a complete evaporation of the applied moisture. The fifth step is to evaporate any remaining applied moisture from the non-conductive object prior to curing. The last step is to cure the coating on the surface of the non-conductive object without decomposing the powder and then either cool or allow the non-conductive object to cool naturally.

Revendications

11
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of coating an exterior surface of a non-
conductive object with a heat curable powder, the method
comprising the steps of:
cleaning the exterior surface of the non-
conductive object;
pretreating the exterior surface of the non-
conductive object by spraying a sufficient quantity of
moisture, at a relative humidity of not less than 100%, to
the cleaned exterior surface of the non-conductive object,
without formation of any water droplets on the cleaned
exterior surface, to facilitate adhesion of powder thereto;
spraying a polymer coating powder onto the
exterior surface of the non-conductive object following
completion of applying the sufficient quantity of moisture
to the exterior surface of the non-conductive object but
prior to complete evaporation of the applied moisture from
the exterior surface of the non-conductive object;
evaporating remaining moisture on the exterior
surface of the non-conductive object prior to commencing
curing of the non-conductive object; and
curing the polymer coating powder to the
exterior surface of the non-conductive object, once all
remaining moisture on the non-conductive object is
evaporated, without decomposing the polymer coating powder.

12
2. The method of powder coating according to claim 1,
further comprising the steps of placing the non-conductive
object on a moving surface to sequentially subject the
exterior surface of the non-conductive object to the
cleaning step, the pretreating step, the spraying step, the
evaporating step and the curing step.
3. The method of powder coating according to claim 1,
wherein the moisture is supersaturated steam.
4. The method of powder coating according to claim 1,
further comprising the step of spraying the powder onto the
exterior surface of the non-conductive object in a spray
chamber having a plurality of powder spray nozzles.
5. The method of powder coating according to claim 1,
further comprising the step of curing the powder on the
exterior surface of the non-conductive object in a curing
chamber at a temperature which is sufficient to melt and
cure the polymer powder but is insufficient for the heat to
penetrate into the exterior surface of the non-conductive
object and result in thermal expansion thereof.
6. The method of powder coating according to claim 1,
wherein polymer coating power is electrostatically sprayed
after electrically grounding the exterior surface of the
non-conductive object.
7. The method of powder coating according to claim 1,
further comprising the steps of:

13
cooling the cured exterior surface of the non-
conductive object following the curing step;
sequentially placing a steam chamber, a
spraying chamber, an evaporation chamber and a curing
chamber in order,
separating the steam chamber from the spraying
chamber by a first air curtain,
separating the spraying chamber from the
evaporation chamber by a second air curtain, and
separating the evaporation chamber from the
curing chamber by a third air curtain.
8. The method of powder coating according to claim 1,
further comprising the steps of:
using a thermoplastic material as the polymer
coating powder and performing the pretreating step, the
spraying step, the evaporating step and the curing step
within a time period determined by a line speed of a
moving surface supporting the non-conductive object;
spraying a second thermoplastic polymer coating
powder onto a previously coated and heated exterior
surface of the non-conductive object, prior to
solidification of the first thermoplastic polymer coating
powder, with the second spraying step being performed in
a spray chamber having a plurality of powder spray

14
nozzles which spray a powder mist that adheres to the
previously coated and heated exterior surface of the non-
conductive object;
passing the previously coated and heated
exterior surface of the non-conductive object through a
second curing chamber to heat the second thermoplastic
polymer coating powder to the previously coated and heated
exterior surface of the non-conductive object without
decomposing the thermoplastic polymer coating powder;
spraying a third thermoplastic polymer coating
powder onto the previously coated and heated exterior
surface of the non-conductive object, prior to
solidification of the second thermoplastic polymer coating
powder, with the third spraying step being performed in a
third spray chamber having a plurality of powder spray
nozzles which spray a powder mist that adheres to the
previously coated and heated exterior surface of the non-
conductive object; and
passing the previously coated and heated
exterior surface of the non-conductive object through a
third curing chamber to heat and cure the third
thermoplastic polymer coating powder to the previously
coated and heated exterior surface of the non-conductive
without decomposing the thermoplastic polymer coating
powder.
9. A method of coating an exterior surface of a non-
conductive object with a heat curable powder, the method
comprising the steps of:
cleaning the exterior surface of the non-
conductive object;
pretreating the exterior surface of the non-

15
conductive object in a first spray chamber by spraying a
sufficient quantity of moisture, at a relative humidity of
not less than 100%, to the cleaned exterior surface of the
non-conductive object, without formation of any water
droplets on the cleaned exterior surface, to facilitate
adhesion of powder thereto;
spraying a polymer coating powder onto the
exterior surface of the non-conductive object following
completion of applying the sufficient quantity of moisture
to the exterior surface of the non-conductive object but
prior to complete evaporation of the applied moisture from
the exterior surface of the non-conductive object;
evaporating remaining moisture on the exterior
surface of the non-conductive object prior to commencing
curing of the non-conductive object; and
curing the polymer coating powder in a first
curing chamber to the exterior surface of the non-
conductive object, once all remaining moisture on the non-
conductive object is evaporated, without decomposing the
polymer coating powder;
using a thermosetting plastic material as the polymer
coating powder and performing the pretreating step, the
spraying step, the evaporating step and the curing step
within a time period determined by a line speed of a moving
surface supporting the non-conducive object;
pretreating the exterior surface of the non-conductive
object by spraying a further sufficient quantity of
moisture onto the exterior surface of the non-conductive
object;
spraying a second thermosetting polymer coating powder
onto the previously coated and cured exterior surface of
the non-conductive object with the second spraying step

16
being performed in a second spray chamber having a
plurality of powder spray nozzles which spray a powder mist
that adheres to the previously coated and cured exterior
surface of the non-conductive object;
passing the previously coated and cured exterior
surface of the non-conductive object through a second
curing chamber to heat and cure the second thermosetting
polymer coating powder to the previously coated and cured
exterior surface of the non-conductive object without
decomposing the thermosetting polymer coating powder;
pretreating the exterior surface of the non-conductive
object by spraying a still further sufficient quantity of
moisture onto the exterior surface of the non-conductive
object;
spraying a third thermosetting polymer coating powder
onto the previously coated and cured exterior surface of
the non-conductive object with the third spraying step
being performed in a third spray chamber having a plurality
of powder spray nozzles which spray a powder mist that
adheres to the previously coated and cured exterior surface
of the non-conductive object; and
passing the previously coated and cured exterior
surface of the non-conductive object through a third curing
chamber to heat and cure the third thermosetting polymer
coating powder to the previously coated and cured exterior
surface of the non-conductive without decomposing the
thermosetting polymer coating powder.
10. A method coating an exterior surface of a non-
conductive wood object with a heat curable powder, the
method comprising the steps of:
cleaning an exterior surface of the non-

17
conductive wood object;
pretreating the exterior surface the non-
conductive wood object by spraying a sufficient quantity of
moisture, at a relative humidity of not less than 100%, to
the exterior cleaned surface of the non-conductive wood
object to darken the appearance of the exterior cleaned
surface of the non-conductive wood object, without
formation of any water droplets on the cleaned exterior
surface, and to facilitate adhesion of powder thereto;
spraying a polymer coating powder onto the
exterior surface of the non-conductive wood object
following completion of applying the sufficient quantity of
moisture to the exterior surface of the non-conductive wood
object but prior to complete evaporation of the applied
moisture from the exterior surface of the non-conductive
wood object;
evaporating remaining moisture on the exterior
surface of the non-conductive wood object prior to
commencing curing of the non-conductive wood object; and
curing the polymer coating powder to the
exterior surface of the non-conductive wood object, once
all remaining moisture on the non-conductive wood object is
evaporated, without decomposing the polymer coating powder.
11. The method of powder coating according to claim 10,
further comprising the steps of placing the non-conductive
wood object on a moving surface to sequentially subject the
exterior surface of the non-conductive wood object to the
cleaning step, the pretreating step, the spraying step, the
evaporating step and the curing step.
12. The method of powder coating according to claim 10,

18
wherein the moisture is supersaturated steam.
13. The method of powder coating according to claim 10,
further comprising the step of spraying the powder onto the
exterior surface of the non-conductive wood object in a
spray chamber having a plurality of powder spray nozzles.
14. The method of powder coating according to claim 10,
further comprising the step of curing the powder on the
exterior surface of the non-conductive wood object in a
curing chamber at a temperature which is sufficient to melt
and cure the polymer powder but is insufficient for the
heat to penetrate into the exterior surface of the non-
conductive wood object and result in thermal expansion
thereof.
15. The method of powder coating according to claim 10,
further comprising the step of electrostatically spraying
the powder after electrically grounding the exterior
surface of the non-conductive wood object.
16. A method coating an exterior surface of a non-
conductive plastic object with a heat curable powder, the
method comprising the steps of:
cleaning the exterior surface of the non-
conductive plastic object;
pretreating the exterior surface of the non-
conductive plastic object by spraying a sufficient quantity
of moisture, at a relative humidity of not less than 100%,
to the exterior cleaned surface of the non-conductive
plastic object to absorb onto the exterior cleaned surface
of the non-conductive plastic object, without formation of

19
any water droplets on the cleaned exterior surface, and to
facilitate adhesion of powder thereto;
spraying a polymer coating powder onto the
exterior surface of the non-conductive plastic object
following completion of applying the sufficient quantity of
moisture to the exterior surface of the non-conductive
plastic object but prior to complete evaporation of the
applied moisture from the exterior surface of the non-
conductive plastic object;
evaporating remaining moisture on the exterior
surface of the non-conductive plastic object prior to
commencing curing of the non-conductive plastic object; and
curing the polymer coating powder to the
exterior surface of the non-conductive plastic object, once
all remaining moisture on the non-conductive plastic object
is evaporated, without decomposing the polymer coating
powder.
17. The method of powder coating according to claim 16,
further comprising the steps of placing the non-conductive
plastic object on a moving exterior surface and moving the
moving exterior surface to sequentially subject the
exterior surface of the non-conductive plastic object to
the cleaning step, the pretreating step, the spraying step,
the evaporating step and the curing step.
18. The method of powder coating according to claim 16,
further comprising the step of moisturizing the exterior
surface of the non-conductive plastic object with
supersaturated steam.
19. The method of powder coating according to claim 16,

20
wherein the spraying the powder onto the exterior surface
of the non-conductive plastic object is in a spray chamber
having a plurality of powder spray nozzles.
20. The method of powder coating according to claim 16,
further comprising the step of curing the powder on the
exterior surface of the non-conductive plastic object in a
curing chamber at a temperature which is sufficient to melt
and cure the polymer powder but is insufficient for the
heat to penetrate into the exterior surface of the non-
conductive plastic object and result in thermal expansion
thereof.
21. The method of powder coating according to claim 16,
wherein the powder is electrostatically sprayed after
electrically grounding the exterior surface of the non-
conductive plastic object.

Description

'" CA 02365030 2001-12-10
1
method of powder coating
FIELD OF TH8 INVENTION
The present invention relates to a method of powder
coating, applicable to powder coating any type of material
and, in particular, wood and other non-metallic surfaces.
io
Conventional powder coating processes involve
spraying a coating of polymer plastic powder onto an
is object, and then applying heat to the coating. The heat
applied must be sufficient to cure the powder and, if
applicable, to enable it to chemically react, but not so
extreme in either time or duration as to cause the polymer
to start to decompose. When heat is removed, the powder
2o hardens onto the object.
In theory, powder coating will work effectively with
any object that can withstand the application of the heat
necessary to melt the powder. In practice, however,
2s problems are often encountered in getting the powder to
adhere to the object. In an effort to improve adherence
of powder, the object being coated is commonly heated or
electrostatically charged.
A particularly difficult material to get a polymer
3o plastic powder to adhere to is wood. Notwithstanding the
heating of the wood and the use of electrostatic
application methods, the quality of powder coating
finishes on wood have generally been unsatisfactory.

. ' CA 02365030 2001-12-10
2
What is required is a method of powder coating that
s will improve the adherence of the powder to the object
being coated, particularly when that object is made of
wood or other non-metallic materials.
According to the present invention there is provided
to a method of powder coating. A first step involves
moisturizing a surface of an object which is to be coated
with supersaturated steam to provide moisture on the
surface just sufficient to cause powder to adhere to the
surface. A second step involves spraying polymer coating
15 powder onto the surface before the moisture evaporates,
whereby moisture on the surface aids in the adhesion of
the powder to the object. A third step involves curing
the powder adhering to the surface after the moisture has
evaporated from the surface, without decomposing the
zo powder.
The method, as described above, has resulted in a
greatly improved quality of coating. Having moisture on
the application surface greatly enhances the ability of
2s the powder to adhere to the surface, much as the licking
one's finger enhances one's ability to pick up sugar. The
teaching in the prior art of heating the object and
immersing it in a fluidized bed of powder, is believed to
be counter-productive, especially when coating objects
3o made of wood which have limitations on the temperature to
which they can be heated. When working with metal, care
must be taken to avoid excessive moisture, as excessive
moisture will adversely effect the quality of the coating.

" ' - CA 02365030 2001-12-10
3
Wood and other non-metallic materials are believed to be
best suited for the application of this method.
Although beneficial results may be obtained through
s the use of the method, as described above, even more
beneficial results may be obtained when a plurality of
spray nozzles are used to apply, the powder which generate
a low velocity powder mist. In the prior art, the spray
nozzles utilized were generally high volume/high velocity
io jets which bombarded the object with powder. It is
believed that such high volume/high velocity sprays are
counter-productive. When the object is dry such sprays
tend to polish the application surface. This is
especially the case with wood. This polishing effect
15 actually clears powder from the application surface. It
is, therefore, preferred that the spray nozzles generate a
low velocity powder mist onto the moist application
surf ace .
20 BRTEF DESCRIPTION OF THE DRAWING
These and other features of the invention will become
more apparent from the following description in which
reference is made to the appended drawing, wherein:
25 THE FIGURE is a schematic representation of a method
of powder coating in accordance with the teaching of the
present invention.
The preferred method of powder coating will now be
described with reference to THE FIGURE.

CA 02365030 2001-12-10
4
The preferred manner of performing the method steps,
which will hereinafter be described, is to position an
obj ect 12 on a conveyor 14 and then subj ect obj ect 12 to
the method steps sequentially as conveyor 14 advances.
s Prior to being subjected to the method steps, object 12
must be suitably cleaned. The~preferred manner of doing
this is by means of vacuums 16 with vacuum heads 18
disposed about conveyor 14. It may also be desirable to
subject object 12 to other pretreatment, depending upon
io the materials out of which object 12 is made. It is
preferred that wood products be sanded and vacuumed.
The preferred method of powder coating, with
presently contemplated enhancements, includes the
i5 following steps. The first step involves moisturizing
object 12, prior to it being sprayed, by passing object 12
through a steam chamber 20. When object 12 has completed
passing through steam chamber 20 it has a moist
application surface 22. Steam chamber 20 is connected by
2o conduit 24 to a source of steam 26. Although this method
can be used with any material, wood is believed to be best
suited for the application of this method, as it tends to
temporarily hold moisture on its surface. Moisture can be
detrimental to the coating process if excess moisture is
as released during heating.
The second step involves spraying polymer coating
powder 28 onto the moist application surface 22 by passing
object 12 through a spray chamber 30a. Spray chamber 30a
3o has a plurality of spray nozzles 32 which generate a low
velocity powder mist. The moisture on application surface
22 has been found to facilitate the adhesion of powder 28
to object 12. The powder is delivered to spray chamber

CA 02365030 2001-12-10
30a by conduit 31. A spray unit 33 is used to draw powder
from a powder reservoir 34 and deliver the powder through
conduit 31 to spray nozzles 32. Although not essential,
it is preferred that the powder be applied using a spray
s application process. Having a moist application surface
22 has been found to enhance the spray application
process, with better adherence of powder along edges and
in recesses. The spray application can be, but need not
be, performed in combination with conventional
io electrostatic processes.
The third step involves curing powder 28 adhering to
application surface 22. The preferred manner of curing
powder 28 is by heating. There are alternative curing
i5 processes such as through the use of radiation. Powder 28
is brought to a temperature sufficient to melt and react,
without decomposing, by passing object 12 through at least
a first curing 34a in which is disposed a heat source. A
heat source is preferred that is capable of heating powder
20 28, with the least penetration possible with respect to
object 12. A penetrating heat source is to be avoided, as
it is unnecessary and undesirable to heat object 12.
Heating of object 12 results in thermal expansion, with
inevitable thermal contraction when object 12 cools.
2s Thermal contraction during cooling can adversely effect
the adherence of the coating.
It is viewed as being desirable to have flexibility
to apply a plurality of thin coats of powder or one thick
3o coat. When a plurality of thin coats are desired,
additional steps may be added relating to placing of
second, third and perhaps subsequent coats on object 12.
Spraying a second coat of polymer coating powder 28 onto

' CA 02365030 2001-12-10
6
object 12 by passing object 12 through a second spray
chamber 30b. Heating the second coat of powder 28
adhering to object 12 to a temperature sufficient to melt,
without decomposing, powder 28 by passing object 12
s through a second curing chamber 34b. Spraying a third
coat of polymer coating powder 28 onto object 12 by
passing object 12 through a third spray chamber 30c.
Heating powder 28 adhering to object 12 to a temperature
sufficient to melt, without decomposing, the powder 28 by
io passing object 12 through a third curing chamber 34c.
It is preferred that a further and final step be
taken of passing object 12 through a cooling chamber 36.
Cooling chamber 36 is kept cool by means of a
i5 refrigeration unit, generally indicated by reference
numeral 38.
It is preferred that spray chambers 30a, 30b, 30c
have powder recovery and recirculation means. The powder
2o recovery and recirculation means include a plurality of
powder recovery sumps 40 connected to recovery tanks 42
and to recirculation conduit 44.
Each chamber described above, must be isolated from
2s the other chambers. It is preferred that this be
accomplished by means of by air generated curtains 46. A
source of inert air 48 is connected by means of air
conduit 50 to each air curtain 46. Each chamber is
isolated from outside air and from the other chambers.
As the application of moisture to an object surface
during a powder coating process runs contrary to current
practises, the moisture application will now be further

CA 02365030 2001-12-10
7
described. The process has particular utility for
obtaining adhesion of powder to non-conductive substrates,
where there would otherwise be no adhesion, poor adhesion
of irregular adhesion of the powder; such as wood,
s plastic, and cardboard. When wood is being coated, the
wooden object is prepared by standard procedures for wood
working. The wood is cut to the desired design, sanded,
and vacuumed to produce a uniform clean surface free of
oils and dirt.
Zo
The steam chamber consists of a cabinet into which
wood panels or other types of non-conductive objects can
be rapidly introduced and retrieved. An example of a way
in which this can be done is a chamber with a roller
15 conveyor system, in which wood parts are carried rapidly,
tunnel style, through the chamber on rollers. The chamber
is equipped with an array of nozzles through which
saturated steam is directed onto the object. The
arrangement of nozzles can be adjusted for uniform
2o application of steam to the object. The nozzles direct
steam at the part, but also ensure that the steam chamber
is completely filled with saturated steam. Care must be
taken to ensure that drops of condensed water cannot fall
on the workpiece as it passes through the chamber, as this
2s is highly detrimental to resulting coating quality.
Steam is preferably generated by heating water to
boiling and directing the resulting saturated vapour
through steam lines into the steam chamber. The steam
30 lines are, preferably, well insulated so that the
temperature of the steam does not drop significantly. A
small amount of moisture that does condense, should be
drawn off separately so that it is not introduced into the

CA 02365030 2001-12-10
8
steam chamber. The steam is supersaturated, and is
visible as a "cloud of steam". The process works best
when hot steam (near the boiling point of water) is used.
It would be possible to carry out the process at low
s temperatures, including room temperatures. At room
temperature "supersaturated steam" can be created with an
atomizer by passing liquid water through a nozzle to
produce a cloud of droplets and vapour. The atomized
water is projected onto the wood surface, resulting in a
io moisturized surface which can be powder sprayed. The
process will not be as effective at lower temperatures as
it is when hot steam is used. The reason for this is that
the moisture must be evaporated before cure. With hot
steam this evaporation occurs very rapidly. At room
is temperature additional time or a heating step may be
required after spraying, but before curing. Humidity, that
is moisture at a relative humidity of less than 100, (not
visible as a cloud) would not be as effective in this
process and possibly would not be effective at all.
The process works best when moisture application,
powder spraying, and evaporation occur rapidly in
succession. Timing and co-ordination of these processes
is essential to successful operation of the process. This
2s co-ordination will now be described with reference to a
pilot plant that was developed to prove this process . In
the pilot plant, the moisturizing process takes about 15
to 20 seconds, which is the time required for the object
to pass through the steam chamber. The steam temperature
3o is slightly below the boiling temperature of water. The
moisturized wood immediately passes into the powder spray
chamber, for powder application. It takes about 25
seconds for the panel to pass through the spray chamber,

CA 02365030 2001-12-10
9
at which time much of the moisture has evaporated.
Another 25 to 30 seconds pass before the coated panel
enters the cure chamber, the additional seconds help
ensure complete evaporation of moisture prior to curing.
s Moisture application and evaporation must occur rapidly.
It is highly undesirable for the moisture to penetrate
into the wood, as release of water vapour from the wood
would create problems during curing. It is very important
that the moisturized wood be transferred immediately from
io the humidity cabinet to the spray booth, as moisture
rapidly evaporates and the benefits to powder adhesion are
lost. It should be noted that the rapid nature of the
process will provide a commercial advantage.
15 The following guidelines are provided to assist in
determining an appropriate amount of moisture. An
appropriate amount of moisture has been applied to the
wood surface when the powder coating uniformly adheres to
the surface, and the moisture fully evaporates prior to
2o cure.
C''nrrPntllr moisturized pieces When the wood object emerges
from the steam chamber, the wood has darkened
considerably, due to moisture on the surface. The surface
of such pieces will feel moist to the touch. If passed
2s immediately through the spray chamber, without spraying,
the pieces lose the dark colour (ie. their moisture) by
the time they leave the spray chamber.
Inadec,~~ moisturized pieces The pieces are not
adequately moisturized if the powder coating will not
3o stick to the surface.
ntrPr moisturized nieces The pieces are over moisturized if
free water (droplets or films) can be observed on the
surface. Excessive moisture interferes with the uniform

' CA 02365030 2001-12-10
1~
application of powder to the surface, causing it to clump
or flow.
In summary, the correct amount of moisture is that
s amount which rapidly absorbs onto the surface of the wood
without deep penetration or without leaving a thin film of
moisture on the surface. The correct amount of moisture
can be applied to the wood surface by varying the
following parameters to optimize the process; steam
io temperature, steam delivery rate, residence time of the
object in the steam chamber, residence time of the object
in the spray chamber. The correct amount of moisture will
vary with the type of substrate being coated. For
example, some woods absorb little water, and with such
i5 woods a small amount of moisture must be applied very
rapidly followed rapidly by spraying. Other woods are
highly absorbent and with such woods larger amounts of
moisture must be applied to ensure wetness. Consequently,
additional time is required for evaporation of the
2o moisture prior to cure.
It will be apparent to one skilled in the art that
modifications may be made to the illustrated embodiment
without departing from the spirit and scope of the
2s invention as hereinafter defined in the Claims.

Dessin représentatif