Note: Descriptions are shown in the official language in which they were submitted.
~04934Z
This invention relates generally to coating of surfaces
of articles with coating materials. More particularly, the
invention relates to a process and apparatus for simultaneous
and continuous coating of both surfaces of a long sheet mate-
rial, which process comprises causing a coating material (e.g.,
a paint) to adhere simultaneously to the two surfaces of a
long sheet material of metal or a synthetic resin or a metal
foil (hereinafter referred to as a "sheet"), adjusting the
coating film thicknesses on the two surfaces to specific
thicknesses, and causing the sheet to travel in its longitu-
dinal direction as a span thereof is supported on supports,
in which span the coating films are caused to set.
Heretofore, the common procedure for coating the two
surfaces of a sheet with a coating material has been to first
apply the coating material on one of the surfaces and set the
same and then to apply the coating material on the other
surface and set the same. This conventional procedure is
inefficient.
In accordance with this invention in one aspect
thereof, briefly summarized, there is provided a process for
. coating a long sheet material which comprises passing the
sheet material continuously through a body of a coating liquid
thereby to cause the coating liquid to adhere to and form
coating films simultaneously on the two surfaces of the sheet,
regulating the thicknesses of the coating films at specific
values by allowing passage of said sheet through a means
provided with one or more helical grooves or with one or more
helically wrapped steel wires, all of which make an oblique
angle with the travelling direction of the sheet, causing
the sheet thus coated to travel in its longitudinal and
horizontal direction as it is supported in a manner providing
an unsupported span thereof over a specific length, and
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setting the coating films on the sheet in this span.
According to this invention in another aspect thereof,
there is provided an apparatus for carrying out the process
of the invention, the apparatus comprising: a vessel contain-
ing a coating liquid with a constantly maintained liquid
surface level and having opposed upstream and downstream end
walls provided therethrough respectively with an inlet and an
outlet both of horizontal slit shape disposed at a height level
below the liquid surface level; means for causing the long
sheet material to travel in a longitudinal direction longitu-
dinally and continuously through the coating liquid, entering
the vessel through the $nlet and exiting through the outlet,
thereby to coat simultaneously and continuously the two
surfaces of the sheet material with respective films of the
coating liquid; means for regulating the thicknesses of the
coating liquid films on the sheet material exiting from the
vessel at specific values, said means being provided there-
around with one or more helical grooves or with one or more
helically wrapped steel wires, all of which grooves and wires
, 20 making an oblique angle with the travelling direction of the
:' sheet; and means for supporting the sheet material thus
coated in a manner to provide an unsupported span thereof
of a length sufficient for setting of the coating liquid films
thereon.
The nature, utility, and further features of the
invention will be apparent from the following detailed
description when read in conjunction with the accompanying
drawing.
. In the drawing, the single figure is a side elevation,
in vertical section, showing one example of apparatus suitable
for practice of the process of this invention.
In the example illustrated in the drawing of apparatus,
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there is provided a coating vessel 2 containing a coating
liquid (e.g., paint) I and having a horizontal inlet 5 of slit
shape in its upstream end wall 3 and a horizontal outlet 6 of
slit shape in its downstream end wall 4. A pair of adjustment
plates 7 capable of moving in the up-and-down directions are
provided at the outer wall surface of the end wall 4 at the
outlet 6.
Jackets or troughs 8 and 9 for recovery of coating
liquid are provided respectively at the lower outer sides of
the end walls 3 and 4 of the coating vessel 2, whereby any
coating liquid flowing or dropping into these jackets 8 and 9
is recirculated into the coating vessel 2. Furthermore,
coating liquid is appropriately replenished thereby to main-
tain the surface of the coating liquid 1 in the coating vessel
2 at a constant level.
In the jacket 8, there are provided a pair of rolls
11, the upper roll of which is contacted by a reverse-rotation
roll 10, while in the jacket 9, there are provided a pair of
regulating rolls 12 capable of being moved in the up-and-down
directions. Each of the regulating rolls 12 is provided
therearound with one or more helical grooves (not shown) or
with
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one or more helically wrapped steel wires (not shown), whereby the rolls 12
function as means for regulating the thicknesses of the coating films at
specific values. The axes of rotation of the rolls 11 lie in a substant-
ially vertical plane, and the midpoint of the gap between these rolls is
substantially at the same height level as the inlet 5. The axes of rotation
of the regulating rolls 12 also lie in a substantially vertical plane, and
the midpoint of the gap therebetween is substantially at the same height
level as the outlet 6.
When a continuous sheet 13 is to be coated with the coating liquid,
the sheet 13 is passed between a pair of back tension rolls 14 and the rolls
11, introduced through the inlet 5 into the coating vessel 2, led out through
the outlet 6, and passed between the adjusting plates 7 and the regulating
rolls 12. By suitably adjusting the slit gap between the adjusting plates
; 7, the coating liquid can be caused to assume an appropriate flow rate an
the surfaces of the sheet 13. Furthermore, by suitably adjusting the squeez-
ing pressure of the regulating rolls 12 on the sheet 13 and suitably select-
ing the shape of the helical groove or grooves or the thickness of the steel
wire or wires on these rolls, a desired thickness of the coating liquid can
be caused to be deposited on the two surfaces of the sheet or foil.
Thereafter, the sheet or foil 13 is supported on a roller 15
installed downstream from the regulating rolls 12 at a distance therefrom
which is sufficient for the coating liquid adhering to the sheet 13 in the
span therebetween to set, whereby the sheet 13 is caused to travel between
the regulating rolls 12 and the roller 15 without any object contacting the
coating liquid adhering thereto. During its travel through the span between
the regulating rolls 12 and the roller 15, the coating liquid on the sheet
is dried or baked, and then the sheet 13 is taken up on a recoiler (not
shown).
In one example of practice of this invention, aluminum sheets (a
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basic sheet, a sheet with anodic oxidation film formed on the surfaces there-
of by an ordinary method, and a sheet which had been subjected to coloring
treatment) were passed at a traveling speed of 3 to 4 meters/minute through
a coating vessel containing a transparent, water-soluble, acrylic resin paint.
This coating vessel constituted the principal component of an apparatus as
illustrated in the drawing, in which the distance between the rolls 12 and
the support roller 15 was 40 meters. In this span, the sheet thus coated
with a paint film of a thickness of approximately 20 microns on its upper
surface and a paint film of a thickness of approximately 5 microns on its
lower surface was passed through a furnace of 30-meter length at~l210C there-
by to bake and set the paint. As a result, excellent coating films were
obtained on the aluminum sheets.
By the practice of this invention, a coating liquid can be caused
to adhere with desired thicknesses simultaneously on the two surfaces of a
sheet and be set by drying or baking. For this reason, the process accord-
ing to this invention is extremely efficient, requiring a process time which
is approximately one half of that of the conventional process which comprises
applying the paint on one surface of the sheet, setting it by drying or
baking, then applying the paint on the other surface, and setting the same
by drying or baking.
