Coating processes – Vacuum utilized prior to or during coating
Reexamination Certificate
1999-07-19
2001-03-06
Bareford, Katherine A. (Department: 1762)
Coating processes
Vacuum utilized prior to or during coating
C427S345000, C427S421100, C118S050000, C118S326000, C118S603000, C239S104000, C239S120000, C239S124000, C239S424000
Reexamination Certificate
active
06197376
ABSTRACT:
The present invention relates to the covering of a surface of a substrate with a layer of a fluid material, or the depositing on the said surface of a continuous layer of the said fluid material.
BACKGROUND OF THE INVENTION
Various solutions have already been proposed in the prior art, for covering a surface of a substrate, in relative motion or otherwise, with a fluid material (liquid or powder for example).
All the proposed solutions have in common on the one hand the prior formation, by overpressure or under vacuum, of a turbulent mixed flow obtained by mixing, with entrainment if necessary, of a controlled fluid stream comprising the fluid covering material, and of a gas stream, and on the other hand various arrangements making it possible to recover the unused or unconsumed turbulent mixed flow so as to avoid its diffusion into the ambient air.
In accordance with document WO-92/12803, and in particular according to the embodiment described with reference to
FIGS. 22
to
24
, and from line
11
of page
27
to line
33
of page
29
, there is described an installation for covering the surface of a substrate
643
with a fluid material.
This installation comprises a means of treatment comprising a confining wall
657
, with an edge defining the area to be treated. A means
666
makes it possible to establish a controlled vacuum inside the area to be treated, by admitting several incoming gas streams
684
and
680
, through the aforesaid void. A means of controlled introduction, or head
642
, into the area to be treated of the fluid material
644
, associates a controlled flow void with a pressurized air inlet
645
/
446
, so that a turbulent mixed flow
682
/
683
, circulating in contact with the substrate
643
, is produced directly at the head outlet; cf. page
27
, lines
14
to
21
.
The incoming air streams
684
and
680
are all formed only so as to contain the turbulent mixed flow in the area to be treated; cf. for example page
29
, lines
1
to
4
, and lines
25
to
30
.
In accordance with document WO-79/00469, a turbulent mixed flow is obtained by previously mixing a controlled fluid stream (
3
) comprising the fluid covering material, and a gas stream, these two streams being under overpressure so as to eject the mixed flow through a distribution vessel (
5
). Two successive confining walls of cylindrical shape form two concentric peripheral volumes
6
and
7
, under vacuum, so as to discharge the turbulent mixed flow after its contact with the surface to be covered.
In accordance with document GB-1 134 069, a turbulent mixed flow is obtained, under vacuum, by mixing a fluid stream (powder) and a gas stream. The turbulent mixed flow resulting from this circulates as a co-current, still under vacuum, in contact with the surface of an elongate substrate moving translationally.
In accordance with document WO-96/09122, a nozzle for spraying a powder is described, making it possible to eject under pressure a turbulent mixed flow obtained previously by mixing a fluid stream (powder) and a gas stream. The unused mixed flow is reaspirated around the nozzle by appropriate means.
At the conclusion of this examination, all the prior solutions have the common characteristic of pushing as it were the fluid material onto the surface of the substrate to be covered. This characteristic may prove to be inefficient for covering substrates with an irregular surface, for example a porous surface.
SUMMARY OF THE INVENTION
In accordance with the present invention, consideration is therefore given to any substrate or support, whose apparent surface area is smaller in value than the actual or developed surface area of the same substrate, by reason of the presence of asperities, bumps, or surface pores, generating a larger developed surface area than the apparent area, that is to say that visible to the naked eye.
The subject of the present invention is a process and an installation for covering a surface such as defined above, and doing so by attracting as it were the fluid covering material towards and into the entire surface of the substrate.
The process in accordance with the present invention associates in cooperation the following steps:
(a) with a confining wall closed up on itself, arranged some distance from and above the surface to be covered, and whose lower edge forms together with the latter a peripheral void, a treatment chamber delimiting on the surface to be covered an area to be treated is defined or made available
(b) a controlled vacuum is established inside the treatment chamber by admitting an incoming gas stream via the peripheral void, and by extracting an outgoing gas stream from the treatment chamber, so as to obtain in the said chamber an internal pressure which is lower than the external pressure, that is to say outside the same chamber
(c) a controlled fluid stream is introduced into the treatment chamber under vacuum, this stream comprising the fluid covering material, which forms at the level of the peripheral void, together with the incoming gas stream, a turbulent mixed flow, which is aspirated into contact with the developed surface in the area to be treated, depositing the fluid material in the latter; then this mixed flow is discharged with the outgoing gas stream.
An installation for implementing the process described above comprises, in a general manner:
a means of treatment, comprising a confining wall closed up on itself, designed so as to be arranged some distance from and above the surface to be covered, with a lower edge adapted or designed so as to form together with the said surface to be covered a peripheral void; this confining wall defines a treatment chamber delimiting an area to be treated on the said surface to be covered
means for establishing a controlled vacuum inside the treatment chamber by admitting an incoming gas stream through the peripheral void, and by extracting an outgoing gas stream from the treatment chamber, so as to obtain an internal pressure in the said chamber which is lower than the external pressure, that is to say outside the said chamber
a means of controlled introduction into the treatment chamber, under vacuum, of a fluid stream comprising the fluid covering material, so as to form, at the level of the peripheral void, with the incoming gas stream a turbulent mixed flow, which is aspirated into contact with the entire developed surface in the area to be treated, depositing the fluid material thereat; this mixed flow is then discharged with the outgoing gas stream.
The term “fluid material” should be understood to mean any product, substance or material, in the liquid, fluid or viscous state, which can be dispersed by the incoming gas stream in the treatment chamber, so as to form with the latter a turbulent, mixed flow, that is to say one composed of particles of the said fluid material in suspension in this incoming gas stream, doing so under the predetermined conditions, especially of temperature, adopted for treating the surface to be covered with the said fluid material. As an example of a fluid material of this kind may be cited any paint, comprising pigments or dyes in suspension or solution in an appropriate liquid medium, or else any material in the substantially solid or solid state under the normal or ambient conditions of temperature, but liquid or liquefied at the temperature for treating the surface, the covering obtained subsequently solidifying on the surface of the substrate; in this latter case may be cited for example any heavy hydrocarbon, for example a paraffin.
The term “fluid stream” should be understood to mean any liquid, fluid, viscous or pasty flow or stream which can be dispersed by the incoming gas stream in the treatment chamber, under the conditions, especially of temperature, adopted or predetermined for the operation of the treatment chamber.
By virtue of the process and the installation according to the present invention, the treatment or covering of the surface of the treated substrate is performed as close as possible to the latter, without spraying the fluid material a
Bareford Katherine A.
Bio Merieux
Oliff & Berridg,e PLC
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