U.S. patent application number 10/939601 was filed with the patent office on 2005-05-05 for cooking appliance door with an inner borosilicate glass window pane and cooking appliance with said door.
Invention is credited to Haustein, Holger, Lebacher, Rainer, Roch, Klemens, Schnell, Wolfgang, Schwarz, Erhard, Wagner, Michael.
Application Number | 20050092318 10/939601 |
Document ID | / |
Family ID | 33039364 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050092318 |
Kind Code |
A1 |
Haustein, Holger ; et
al. |
May 5, 2005 |
Cooking appliance door with an inner borosilicate glass window pane
and cooking appliance with said door
Abstract
The cooking appliance door has a borosilicate glass inner window
pane, on which a paint layer and an infrared-reflecting layer are
applied. The paint layer is high-temperature-resistant non-enamel
paint with an organic or inorganic binder. In order to provide
especially good adherence and high scratch resistance for the paint
layer, the paint layer is applied directly on one side of the inner
window pane and the infrared-reflecting layer is applied on and
over this paint layer. A cooking appliance with this cooking
appliance door is also part of this invention.
Inventors: |
Haustein, Holger;
(Orlamuende, DE) ; Schwarz, Erhard; (Jena, DE)
; Lebacher, Rainer; (Palling/Freutsmoos, DE) ;
Wagner, Michael; (Grabenstaett, DE) ; Roch,
Klemens; (Trostberg, DE) ; Schnell, Wolfgang;
(Trostberg, DE) |
Correspondence
Address: |
STRIKER, STRIKER & STENBY
103 EAST NECK ROAD
HUNTINGTON
NY
11743
US
|
Family ID: |
33039364 |
Appl. No.: |
10/939601 |
Filed: |
September 13, 2004 |
Current U.S.
Class: |
126/200 |
Current CPC
Class: |
C03C 17/42 20130101;
C03C 17/3411 20130101; F24C 15/04 20130101 |
Class at
Publication: |
126/200 |
International
Class: |
F24C 015/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 25, 2003 |
DE |
103 44 442.4 |
Claims
We claim:
1. A cooking appliance door comprising an inner window pane (1),
said inner window pane comprising borosilicate glass; at least one
paint layer (2) applied directly to a surface on one side of said
inner window pane, wherein said at least one paint layer (2)
comprises a high-temperature-resistant non-enamel paint with an
organic or inorganic binder; and at least one infrared-reflecting
layer (3) applied on said at least one paint layer (2) on said one
side of the inner window pane.
2. The cooking appliance as defined in claim 1, wherein said at
least one paint layer (2) has a thickness of from 10 to 15
.mu.m.
3. The cooking appliance as defined in claim 1 or 2, wherein said
at least one paint layer (2) is printed on the inner window pane
(1).
4. The cooking appliance as defined in claim 1, wherein said at
least one infrared-reflecting layer (3) contains tin oxide.
5. The cooking appliance as defined in claim 1 or 4, wherein said
at least one infrared-reflecting layer (3) is applied to the at
least one paint layer (2) by a hot spraying process.
6. A cooking appliance (10) comprising a cooking compartment (30)
with an opening for placing cooking materials in the cooking
compartment (30) and a cooking appliance door (20) for closing said
opening; wherein said cooking appliance door (20) comprises an
inner window pane (1) made of a borosilicate glass, at least one
paint layer (2) applied directly to a surface on one side of said
inner window pane, said at least one paint layer (2) comprising a
high-temperature-resistant non-enamel paint with an organic or
inorganic binder and at least one infrared-reflecting layer (3)
applied on said at least one paint layer (2) on said one side of
the inner window pane.
7. The cooking appliance as defined in claim 6, wherein said at
least one paint layer (2) has a thickness of from 10 to 15
.mu.m.
8. The cooking appliance as defined in claim 6, wherein said at
least one infrared-reflecting layer (3) contains tin oxide.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a cooking appliance door with an
inner window pane comprising a borosilicate glass, on which a paint
layer made from a high-temperature-resistant non-enamel paint with
an organic or inorganic binder and an infrared-reflecting layer are
applied. The invention also relates to a cooking appliance with
this sort of door.
[0003] 2. Description of the Related Art
[0004] A household cooking appliance, especially an oven, has a
cooking chamber or compartment with an opening, which is closable
by a cooking appliance door with an observation or viewing window.
Cooking appliances with a door that is completely glass are known.
A baking oven with an oven muffle acting as cooking compartment is
a typical currently known household appliance. This sort of baking
oven has been equipped to a large extent with a pyrolytic
self-cleaning means, by which cooking residues are decomposed to
ash at pyrolysis temperatures above 500.degree. C.
[0005] The typical household cooking appliance door and thus its
viewing window is of course heated during operation due to the
comparatively high temperatures in the cooking appliance. An
entirely glass appliance door, which typically comprises a glass
pane packet, is also heated during operation. The same is true to a
special extent during the pyrolysis occurring at extremely high
temperatures in pyrolyzing baking ovens. High-quality glass is used
for door panels of cooking appliances because of this high heat
load. This is particularly true for the viewing windows or full
glass doors for cooking appliances and baking ovens with pyrolytic
self-cleaning means. A pre-stressed borosilicate glass is thus used
for the inner window pane that is closest to the oven muffle. This
sort of glass is characterized by a special resistance to high
temperatures.
[0006] In order to keep the temperature on the outer side of the
viewing window or full glass door of the cooking appliance as small
as possible to reduce the danger of burns and other injuries due to
contact with the outer surface of the viewing window, the viewing
window is provided with a coating that reflects heat into the
interior of the cooking compartment, i.e. an infrared-reflecting
coating. An observation window described in U.S. Pat. No. 4,898,147
has an inner window pane made from borosilicate glass with an
infrared-reflecting multilayer coating and noble gas layer between
the inner and outer window panes, in order to reduce the heat
transferred. A so-called "cold door" for a pyrolysis-baking oven is
thus provided by means of these features. This "cold door" is
defined by GIFAM DOC 266/01 by stating an upper limiting
temperature, which the contacting surface of the door can have,
when the outside temperature is 23.degree. C. and the temperature
in the cooking compartment is about 500.degree. C. (with glass,
less than 70.degree. C.).
[0007] Furthermore it is known to provide the borosilicate glass
inner window pane with printing made from enamel paint, comprising
special writing (letters, words) and symbols, especially usage
hints for the operators, particularly which indicate different
cooking programs. This printed information can be located on the
side of the inner window pane facing the door interior and also on
the side facing the cooking compartment, as described in DE 100 07
923 C1. DE 101 43 925 A1 discloses a suitable borosilicate inner
window pane for a cooking appliance door printed with enamel
paint.
[0008] Conventional enamel paints melt or fuse with the glass
surface during burning on the borosilicate inner window pane.
Stresses are developed in the glass window pane due to the
differing thermal expansion properties of the glass window pane and
the printing with the enamel paint. These stresses occur in
connection with interactions (ion exchange) between the enamel
paint, a glass flux-based print ink and the borosilicate glass.
Because of that the impact resistance of the glass window pane is
degraded for impacts on the side facing away from the printed
information. For that reason the above-mentioned DE 100 07 923 C1
suggests that the color printing printed with the enamel paint
should be applied to the outside of the inner window pane facing or
turned toward the interior of the cooking compartment. Since the
current enamel paints are not heavy-metal-free, especially not
lead-free, there is a danger the heavy metals, especially lead,
could be volatilized in the cooking compartment at higher operating
temperatures because of the color printing on the exposed side in
direct contact with the cooking compartment. Furthermore the enamel
paint coating has a rough, unpleasing surface.
[0009] There is no enamel print or enamel for printing currently
known for borosilicate glass, which (1) is heavy-metal-free, (2)
has a smooth aesthetically pleasing surface and (3) maintains the
impact resistance of the borosilicate glass pane, when the impacts
occur on the side facing away or opposite from the printing. As a
result, non-enamel paint with organic (e.g. silicones or
fluoropolymers) or inorganic (e.g. water glass; sol-gel binders)
binders was develop, which in contrast to the conventional enamel
paint is not bonded with the glass surface by melting. These
non-ceramic paints are described in the old Patent application DE
103 13 630, whose subject matter is incorporated herein by explicit
reference thereto.
[0010] This paint is only a SiO.sub.2-based paint with carbon
particles, which are coated or enveloped by SiO.sub.2, as pigment,
as is described in DE 195 25 658 C1.
[0011] Up to now the color printing on inner window panes of
borosilicate viewing windows with infrared-reflecting coatings
provided by the above-described non-enamel paints has been applied
directly to the infrared-reflecting coating. This leads to certain
process uncertainties and unreliabilities, since the adherence of
the paint developed for direct application to borosilicate glass is
not guaranteed on an infrared-reflecting coating. The
infrared-reflecting coating usually comprises a tin oxide material,
which differs significantly from a borosilicate glass. Furthermore
the above-described paint coating is not very resistant to
scratching.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide a
cooking appliance door of the above-described type with an inner
window pane comprising borosilicate glass, which has an
infrared-reflecting coating and printing, such that the printing
reliably adheres to the window pane and resists scratching.
[0013] This object and others, which will be made more apparent
hereinafter, are attained in a cooking appliance door with an inner
window pane comprising a borosilicate glass, on which a paint
layer, which comprises a high-temperature-resistant non-enamel
paint with an organic or inorganic binder, and an
infrared-reflecting layer are applied.
[0014] According to the invention surprisingly the paint layer is
applied directly on one side of the inner window pane and the
infrared-reflecting layer is applied on and/or over this paint
layer.
[0015] The present invention also includes a cooking appliance with
the above-described cooking appliance door according to the
invention.
[0016] Because of the critical feature of the invention, i.e. the
application of infrared-reflecting layer after applying the color
printing or paint layer to the inner window pane, one very
advantageously obtains a resistant color printing on the inner
window pane of borosilicate glass. Besides greater adherence of the
paint layer on the glass substrate the color printing is also
scratch-resistant, since the infrared-reflecting layer is very hard
and thus mechanically protects the printed information provided by
the non-enamel paint. Furthermore use of the non-enamel paint in
this manner also maintains the impact strength for impacts
occurring on the side of the inner window pane opposite from the
side bearing the printing. The printing also can be provided on the
side of the inner window pane facing away from or opposite from the
cooking compartment. In that case there are no interactions between
the coating and the cooking compartment.
[0017] Of course the color printing can also be provided on the
side of the inner window pane closest to or facing the cooking
compartment, especially with the infrared-reflecting coating
covering the color printing. Thus the occurrence of printing with
paint portions in the cooking compartment is at least reduced.
[0018] DE 101 62 220 A1 discloses a two-layer coating on a glass
pane for a cooking appliance door. This two-layer coating comprises
a first dark, especially black colored, heat-radiating layer and
above it a second white colored heat reflecting layer. The second
layer should reflect a substantial part of the radiated heat back
into the oven. In contrast heat, which reaches the glass pane,
should be radiated away by the first dark layer.
[0019] DE 101 62 220 A1 does not provide any hint or suggestion of
a paint coating made from non-enamel paint or a solution of the
associated adherence problems due to the foregoing problems.
BRIEF DESCRIPTION OF THE DRAWING
[0020] The objects, features and advantages of the invention will
now be illustrated in more detail with the aid of the following
description of the preferred embodiment, with reference to the
following figures, in which
[0021] FIG. 1 is a diagrammatic cutaway cross-sectional view
through an inner window pane of an observation window of a cooking
appliance door or a completely glass door, especially a cooking
oven door; and
[0022] FIG. 2 is a schematic cross-sectional view through one
embodiment of a cooking appliance including a cooking appliance
door according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] This inner window pane 1 is exposed to the highest
temperatures because it is immediately adjacent to the hot oven
muffle or cooking compartment 30 (FIG. 2) during operation of the
cooking appliance 10. This is especially true during pyrolytic
self-cleaning, in which temperatures of over 500.degree. C. are
present in the cooking compartment 30. Because of this reason the
inner window pane 1 of the cooking appliance door 20 is made from
borosilicate glass, preferably from a pre-stressed borosilicate
glass, which has a high resistance to these high temperatures and a
small thermal expansion coefficient. The color printing or paint
layer 2 is printed on one side of the inner window pane, which is
an interior side as shown in this embodiment. The color printing or
paint layer 2 can form a colored surface or also letters or
symbols, which provide a hint or suggestion for the operator,
especially of different cooking programs that the cooking appliance
can perform. The color printing or paint layer 2 is made from the
above-described non-enamel paint, which is applied directly to the
inner surface of the borosilicate glass of the inner window pane by
a printing process, especially a screen printing process and burned
in after that. The layer thickness is preferably in a range of 10
to 15 .mu.m. The printing preferably occurs in a dot matrix or
pattern.
[0024] Subsequently an infrared-reflecting coating 3 is applied to
the color printing or paint layer 2, for example by a hot spraying
process. This coating 3 typically contains tin oxide as "effective
ingredient" and is usually formed in a know way, e.g. in regard to
coating thickness, etc. These IR-reflecting coatings are especially
known for heat-resistant glazing (e.g. K-GLAS.RTM. or
OPTIFLOAT.RTM. mirror glass), and for example are described in DE
198 25 437 A1. Since the infrared-reflecting layer 3 is very hard,
the scratch-resistance of the color printing 2 is high, and the
adherence of the color printing directly on the glass surface is
very high.
[0025] The preferred embodiment shown in the sole Figure has only a
single IR-reflecting coating and a single color printing or paint
layer. It is understandable however that another embodiment could
have more than one of each of these layers.
[0026] FIG. 2 shows a cooking appliance 10 including a simplified
representation of a cooking appliance door 20 according to the
invention. The cooking appliance door 20 includes an inner window
pane 1 made of borosilicate glass. As explained above, the inner
window pane 1 is first provided with color printing or a paint
layer 2 on its surface closest to or facing the cooking compartment
30. Then an infrared-reflecting coating 3 is provided on the inner
surface of the inner window pane 1 by a hot spraying method, so
that the coating 3 completely covers the color printing or paint
layer 2.
[0027] The disclosure in German Patent Application 103 44 442.4-16
of Sep. 25, 2003 is incorporated here by reference. This German
Patent Application describes the invention described hereinabove
and claimed in the claims appended hereinbelow and provides the
basis for a claim of priority for the instant invention under 35
U.S.C. 119.
[0028] While the invention has been illustrated and described as
embodied in a cooking appliance door with an inner window pane made
of borosilicate glass and a cooking appliance containing that door,
it is not intended to be limited to the details shown, since
various modifications and changes may be made without departing in
any way from the spirit of the present invention.
[0029] Without further analysis, the foregoing will so fully reveal
the gist of the present invention that others can, by applying
current knowledge, readily adapt it for various applications
without omitting features that, from the standpoint of prior this
invention.
* * * * *