Note: Descriptions are shown in the official language in which they were submitted.
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RACR~,~OUND OF THE lNV~ ~lON
1. Field of the Invention
The present invention relates to a method of providing an
inscription or logo, with or out of a lacquer, on articles of
synthetic material, particularly articles manufactured by a foaming
process in a mold which is composed of two mold halves and whose
interior has been sprayed with a parting agent, wherein the outer
layer of the articles is composed of a polyurethane material.
2. Description of the Related Art
The manufacture of hollow bodies, for example, barrels or
other containers for liquids, which have an inner high-grade steel
bubble and an outer casing of polyurethane, is known in the art.
In order to provide such articles of synthetic material with an
inscription, such as, directions for use, description of contents,
references to intellectual property rights, trademarks, etc., or
with a logo of any type, the inner surfaces of the two mold halves
of the open foaming mold are sprayed, prior to the foaming process,
with a parting agent which ensures that the finished article can be
removed from the mold. Subsequently, at least one stencil
containing the logo or the inscription is placed in the mold halves
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and the ink is sprayed onto the area of the inner wall of the mold
which is covered by the stencil. If multiple colors are desired,
a separate stencil is required for each color, wherein the stencils
are placed on top of each other. Because this procedure is very
cumbersome, the multiple colors are restricted to two colors.
After the at least one stencil has been removed from the
foaming mold, for example, a bubble of high-grade steel, is fixed
and clamped in the mold, and the mold which is still open until
this time can be closed. The components of the polyurethane foam,
i.e., polyol and isocyanate, can then be introduced into the closed
mold and the components react with each other over a period of a
few minutes. At the end of the foaming process, the finished
article can be removed from the mold after opening the mold. The
ink which had previously been sprayed onto the interior wall of the
mold now adheres to the polyurethane casing of the finished
article.
Aside from the fact that the application of multicolor
inscriptions or logos is very cumbersome, this type of applying the
inscriptions or logos has the disadvantage that shadings cannot be
avoided and, moreover, the lines formed by the inscription or the
logo in the stencil are visible.
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It is also known in the art to manufacture single-layer or
multiple-layer articles of synthetic material by injection molding.
For example, DE 23 42 794 C3 discloses multiple-layer molded
articles of thermoplastic material which have a foamed core and an
outer skin which is not foamed. In that case, initially a portion
of the non-foamed synthetic material and subsequently a synthetic
material containing a propellant are simultaneously injected with
an additional non-foamed synthetic material through a central
nozzle and an annular nozzle surrounding the central nozzle into a
mold or a two-part molding tool, wherein the non-foamed synthetic
material is injected through the central nozzle and the synthetic
material containing the propellant is injected through the annular
nozzle.
As compared to molded articles of compact synthetic material,
molded articles of synthetic material containing a propellant have
the advantage that they can be manufactured independently of the
wall thickness, on the one hand, and that they are substantially
lighter, on the other hand, which results in a material saving
without negatively effecting the strength. A separate work step is
required for applying inscriptions or decorative effects of a
lacquer on these injection-molded articles of synthetic material.
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For placing a printed label or material blank, for example, a
label, onto at least the side walls of a container of synthetic
material manufactured in accordance with a deep-drawing process in
a thermoforming machine, it has become known from DE 41 24 994 A1
to place a label of a synthetic material into the mold, wherein the
label covers at least the side walls of the container of synthetic
material and the label is intimately connected to the outer side of
the container. The synthetic material required for forming the
container is used in the form of a foil; the foil is pulled from
a roll and is supplied to a preheating station. Subsequently, the
foil of synthetic material enters the actual deep-drawing unit.
The deep-drawing unit has several deep-drawing troughs into which
the labels or material blanks are placed by means of an insertion
device prior to the deep-drawing step of the foil of synthetic
material. The insertion device consists essentially of a turnstile
and several arms extending in a vertical plane, wherein the
turnstile is arranged so as to be displacable in longitudinal
direction. Several such arms are arranged in transverse direction
of the turnstile in accordance with the number of molding nests of
the tool of the thermoforming machine. A transverse support member
having one or two vertically adjustable suction members cooperates
with the turnstile, wherein the suction members remove the labels
from two parallel magazines which are arranged one above the other
and transfer the labels to the arms of the turnstile.
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SUMMARY OF THE lNv~ lON
Therefore, it is the primary object of the present invention
to provide a method of the above-described type, particularly for
applying an inscription or a logo on the polyurethane casing of an
article of synthetic material manufactured by a foaming process, in
which the above-mentioned disadvantages are avoided and separate
steps of operation during the manufacture of the articles are
unnecessary.
In accordance with the present invention, a carrier foil
forming the visible side of a label is provided with an inscription
or a logo of lacquer. Prior to the molding procedure, the carrier
foil is placed with its side opposite the inscription or logo
against the surface of at least one of the mold halves. After the
molding procedure, the carrier foil is pulled off from the article
of synthetic material.
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DETATT-~n DESCRIPTION OF THE lNV~. l-lON
Thus, in accordance with the present invention, it is merely
necessary to place and fix in the mold half or mold halves the
carrier foil which previously has been provided with the
inscription or the logo, preferably by means of a screen printing
method, in order to ensure that in mass production the inscription
or the logo always appear at the same location in the finished
articles of synthetic material. In addition, a fixing agent can be
printed onto the side of the carrier foil opposite the inscription
or logo.
The present invention is based on the finding, obtained
through many experiments, that a residue-free removal of the
carrier foil with the fixing agent is primarily possible if the
article of synthetic material, or at least the outer layer of the
article in the case of a multiple-layer article, is composed of a
material whose adhesive force is greater than that of the carrier
foil. This is particularly the case in articles which are composed
of a polyurethane material or have a casing of a polyurethane
material. The carrier foil or the label can be placed into the
mold either manually, or by means of suction members or an
electrostatic device.
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An advantageous embodiment of the present invention provides
that the lacquer is printed onto a carrier foil composed of
polypropelene. It has been found that a carrier foil of
polypropelene produces the best results with respect to
electrostatic behavior which, together with the adhesion, is a
decisive factor for the secure adhesion of the label in the mold.
The transfer of the inscription or logo onto the article of
synthetic material during the foaming or injection procedure does
not require an adhesive because the lacquer imprint adheres
permanently to the outer surface of the article of synthetic
material after the foaming or injection procedure. Accordingly, it
is not required to glue or intimately connect labels to the article
of synthetic material in order to provide the desired inscriptions
on the finished article. Moreover, it does not pose a problem to
apply multiple-color inscriptions or logos because the lacquer is
ini~ially applied onto the carrier foil by a screen printing
method. It is easily possible in this manner to achieve four-color
printing quality.
While specific embodiments of the invention have been shown
and described in detail to illustrate the inventive principles, it
will be understood that the invention may be embodied otherwise
without departing from such principles.
