U.S. patent application number 10/812945 was filed with the patent office on 2005-09-01 for glass-ceramic plate and its manufacturing process.
This patent application is currently assigned to EUROKERA S.N.C.. Invention is credited to Grandpierre, Gilles.
Application Number | 20050188983 10/812945 |
Document ID | / |
Family ID | 34834064 |
Filed Date | 2005-09-01 |
United States Patent
Application |
20050188983 |
Kind Code |
A1 |
Grandpierre, Gilles |
September 1, 2005 |
Glass-ceramic plate and its manufacturing process
Abstract
The present invention relates to a glass-ceramic plate, intended
notably to cover heating elements, and having at least one opening
located within a local deformation of the plate, this opening being
at a location other than a heating area and/or having at least one
dimension greater than 10 cm and/or an angular and/or complex
shape. The invention also relates to the process for manufacturing
the plate and to the cooking appliance comprising said plate.
Inventors: |
Grandpierre, Gilles; (Mont
St-Pere, FR) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
EUROKERA S.N.C.
Chateau-Thierry
FR
|
Family ID: |
34834064 |
Appl. No.: |
10/812945 |
Filed: |
March 31, 2004 |
Current U.S.
Class: |
126/299R ;
126/211 |
Current CPC
Class: |
F24C 15/2042 20130101;
C03B 23/0252 20130101; F24C 15/102 20130101; H05B 3/74
20130101 |
Class at
Publication: |
126/299.00R ;
126/211 |
International
Class: |
F24C 015/10; F24C
015/20 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 2004 |
FR |
04/01947 |
Claims
1. A glass-ceramic plate intended, for example, to cover or receive
heating elements, and comprising at least one opening located
within a local deformation of the plate, this opening being at a
location other than a heating area and/or having at least one
dimension greater than 10 cm and/or an angular and/or complex
shape.
2. The plate as claimed in claim 1, wherein it is provided or
combined or intended to be used with a suction hood allowing in
particular the extraction of cooking gases.
3. The plate as claimed in either of claims 1 and 2, wherein the
opening is at least 35 mm from the edge and/or from each heating
area of the plate.
4. The plate as claimed in one of claims 1 to 3, wherein the
opening occupies a position mid-way between the cooking areas,
generally it is in a central area of the plate.
5. The plate as claimed in one of claims 1 to 4, wherein the
opening has a polygonal or angular shape.
6. The plate as claimed in one of claims 1 to 5, wherein the hood
is located beneath the plate in its operating position.
7. The plate as claimed in one of claims 1 to 6, wherein the
opening is covered with a protective element preventing objects
from dropping through it while still allowing the cooking gases to
be sucked out, such as a mesh.
8. A process for manufacturing a plate as claimed in one of claims
1 to 7, comprising the forming of the plate, preferably consisting
in a sinking, molding or pressing operation, with, where
appropriate, the use of one or more supports or one or more
surfaces having the desired geometry.
9. The process as claimed in claim 8, wherein a forming operation
is carried out by a sinking operation, in order to raise the edge
of the opening relative to the plane of the plate during the glass
plate ceramification cycle, the raising being preferably produced
by means of an element or bearing piece of shape corresponding to
that of the opening that it is desired to obtain.
10. A cooking and/or high-temperature-maintaining device comprising
a glass-ceramic plate as claimed in one of claims 1 to 7.
11. An apparatus for manufacturing a glass-ceramic plate as claimed
in one of claims 1 to 7, comprising at least one element or bearing
piece for producing the raised feature.
Description
[0001] The present invention relates to a glass-ceramic plate
intended notably to cover or receive heating elements, in
particular intended to be used as a cooking plate (or hob), the
heating elements associated to this plate being, for example,
halogen or radiant heat sources or induction heaters or atmospheric
gas burners.
[0002] The sales of glass-ceramic plates have been constantly
increasing in recent years. This success is explained in particular
by the attractive appearance of these plates and by the ease with
which they are cleaned.
[0003] It will be recalled that a glass-ceramic is initially a
glass, called precursor glass, the specific chemical composition of
which makes it possible to induce controlled crystallization by
suitable heat treatments, called ceramification treatments. This
specific partly crystallized structure gives the glass-ceramic
unique properties.
[0004] At the present time there are various types of glass-ceramic
plates, the appearance of which may vary according to the type of
heating employed or the application: white or black plates,
exhibiting local deformations (support pads), curved or straight
shapes, inclined edges, etc. Each variation is the result of
extensive studies and many trials, given that it is very difficult
to make modifications to these plates (for example to their shape
or to their composition) and/or to the process for obtaining them
(change of temperature for example) without running the risk of an
unfavorable effect on the desired properties (solid structure, heat
shock resistance, smooth appearance, high transmission for
wavelengths in the infrared range and low transmission for
wavelengths in the visible range, without thereby masking the
heating elements in the operating state for safety reasons,
etc.).
[0005] In particular, it is very difficult to conceive plates with
surface variations or interruptions for fear of mechanical strength
problems and/or heat shock resistance problems and/or flatness
problems, etc., it being possible that any dimensional, positional
or shape changes in these variations or discontinuities compared
with already approved plates will mean that these plates do not
comply with the requirements associated with their use.
[0006] In particular as regards openings, the openings most
frequently produced consist of small openings of rounded shape,
which are necessary for the operation of certain functional areas
of the plate, namely openings for atmospheric gas burners or for
knobs or levers. Patent Application EP 0 879 797 also discloses a
process for obtaining openings for atmospheric gas burners at the
top of a local deformation of the plate. This combination of a
local deformation of the plate and an opening has, however, never
been envisaged for openings of different sizes or different shapes
because of the abovementioned fears and risks.
[0007] The aim of the present invention is to develop a novel type
of glass-ceramic plate allowing the range of existing products to
be enlarged and providing novel functions, without the
modifications made having deleterious effects on the desired
properties of the plates, this plate remaining practical in use and
easy to clean, and posing no manufacturing or processing
problems.
[0008] The novel plate according to the invention is a
glass-ceramic plate intended, for example, to cover or receive
heating elements, and is characterized by the presence of at least
one opening located within a local deformation of the plate, this
opening being at a location other than a heating area and/or having
at least one dimension greater than 10 cm and/or an angular and/or
complex shape. According to a preferred embodiment of the
invention, the plate is advantageously provided or combined, or
intended to be used, with a suction hood allowing in particular the
extraction of cooking gases.
[0009] The term "glass-ceramic plate" is understood hereafter to
mean not only plates made of glass-ceramic itself, but also plates
made of any other similar material that is resistant to high
temperature and has a zero or almost zero expansion coefficient
(for example less than 15.times.10.sup.-7 K.sup.-1). Preferably
however, this is an actual glass-ceramic plate. The invention is
also not limited to the manufacture of plates for cookers or
cooktops, but may also relate to other plates that have to be very
insensitive to temperature variations.
[0010] In accordance with the definition of the invention, the
plate is distinguished from existing plates by an opening (or
cut-out) combined with local deformation of the plate, it being
differentiated, in terms of location and/or size and/or shape, from
existing plates.
[0011] The opening according to the invention is therefore an
opening made within a local deformation of the plate. In other
words, the opening is in a plane other than the main plane of the
plate, and generally above said main plane. Also in general, the
opening is at the top of the local deformation, and in a plane
parallel to the main plane of the plate. The wall or walls defining
the deformation (and likewise defining in general the opening) may
be vertical or inclined, plane or curved, depending on the process
used, as will be explained later. The combination of the opening
and the deformation affords many advantages in terms in particular
of sealing or spill-proof, ease of operation and ease of cleaning.
It allows, among other things, a defined orientation of the flow,
where appropriate, of liquids (reduced risk of leaking of liquids
into the opening especially owing to the raising of the opening),
as well as good mechanical protection of the opening, and without
this being to the detriment of the ease of cleaning the device, it
being possible to clean it right to the edge of the opening
(especially owing to the fact that there is a continuous variation
of the plate). Furthermore, if a protection element is associated
with the opening, such as a grid, in order to prevent objects from
falling into it, as will be indicated later, it is unnecessary to
seal between it and the plate, for example by suitable gluing or
bonding, thereby especially simplifying the operations of fitting
these various elements together.
[0012] Preferably, the height of the opening relative to the main
plane of the plate is at least 2 mm, in particular around 4 mm.
[0013] According to a first embodiment of the invention, the
opening coupled with the deformation differs from what exists as
regards position, and in particular is at a position other than a
heating area. The term "heating area" is understood to mean the
area covering a heating element (the term cooking area may also be
used). It is also advantageously at a position other than a control
area (that is to say outside the position of a control element) of
a heating area. It is also preferably located other than at the
edge of the plate. In particular, the opening is preferably at
least 35 mm, advantageously at least 40 mm, from the edge and/or
from each heating area and/or each aforementioned control area of
the plate. In a particularly preferred embodiment of the invention,
the opening according to the invention occupies a position mid-way
between the cooking areas, generally it is in a central area of the
plate.
[0014] In a second embodiment of the invention, at least one
dimension of the opening (width, length, diameter, etc.) is greater
than 10 cm, or even at least one dimension is greater than 20 cm
or, where appropriate, the width and the length of the opening are
greater than 10 cm. There was a negative a priori to make an
opening in combination with a deformation as large as this for the
abovementioned reasons, in particular through fear of
ceramification problems or problems having repercussions as regards
the flatness of the plate or its strength characteristics. The
present invention, in conjunction with the processes described
later, demonstrates that none of this is so, the departure from
flatness obtained (apart from the desired deformations) notably not
exceeding 0.2 mm on plates according to the invention.
[0015] In the same way, with regard to the third embodiment of the
invention, there was a negative a priori about obtaining an
opening, in combination with a deformation, having a polygonal or
angular shape, or complex (non-geometrical) shape, with a regular
and satisfactory appearance, in particular at the corners. Now, the
openings according to the present invention, in conjunction with
the processes described later, may very well have reproducible
angular shapes (in particular a rectangular shape), of clearly
defined and well designed appearance, with generally rounded,
clearly defined and reproducible angles, these angles possibly
being further refined, for example by an additional shaping
operation. The opening according to the first two embodiments may
also have other shapes, particularly oval or circular shapes.
[0016] In general, at least one part of the edge of the opening
according to the invention is shaped (preferably so as to have a
rounded profile without sharp angles) so as, in particular, to
eliminate if necessary any risk of mechanical weakening.
[0017] The plate may also be equipped with at least one seal,
especially at the opening, such as a fibrous annular seal, for
example providing additional impermeability to liquids and/or
providing where necessary the mechanical interface between the
glass-ceramic plate and the associated through-element, while
avoiding direct contact and preventing any risk of scratches or
shocks.
[0018] According to the invention, the plate is preferably provided
or combined, or intended to be used, with at least one suction
hood, this hood cooperating with the defined opening according to
the invention, generally in a middle or central position relative
to the cooking areas and/or relative to the plate. In a preferred
embodiment, the opening is in the form of a rectangular cut-out,
having for example a width of the order of several centimeters,
notably around ten centimeters, and a length of about ten to
several tens of centimeters, for example around thirty
centimeters.
[0019] The hood is preferably added beneath the plate (or the plate
is positioned above the hood) in its operating position so as,
where appropriate, to be masked by the cooking appliance on which
the plate has to be mounted. Advantageously, the opening or cut-out
is covered with a protective element preventing objects from
falling through it, such as saucepans, while allowing the passage
of cooking gases and their suction by the hood, for example the
opening is covered with a grid or with a mesh cover, as illustrated
in particular later, it being possible for this element to be
simply positioned and not needing to be fastened by bonding, as
explained above.
[0020] The plate according to the invention may have several
openings, including at least one as defined according to the
invention and, optionally, one or more other openings, for example
for burners and/or knobs or levers. However, the degree of coverage
of the plate (solid parts in the plane of the plate) preferably
represents at least 60%, generally at least 75%, of the surface
area of the plate. The plate may have various shapes (generally
rectangular shapes), local deformations (hollows and/or reliefs,
such as studs, a separating line or "wave", for example for the
control strip, etc.) and may also have a lower face provided with
prongs or teeth for mechanical reasons, etc. The plate according to
the invention may be provided with functional or decorative
elements, generally added elements, such as one or more connectors
and/or cables, one or more cooking or temperature-maintaining means
and one or more associated control means. Apart from the advantages
explained above, the plate according to the invention is
particularly simple and inexpensive.
[0021] The invention also relates to appliances or devices for
cooking and/or for maintaining a high temperature (cookers, set-in
hobs, etc.) comprising at least one plate according to the
invention and having, where appropriate, one or more heating
elements such as one or more radiant or halogen elements and/or one
or more atmospheric gas burners and/or one or more induction
heating means. The invention covers cooking appliances having a
single plate and appliances having several plates, each of these
plates having a single heater (cooking spot) or multiple heaters.
The invention also relates to mixed cooking appliances whose plate
or plates have several types of heater (such as gas heaters,
radiant heaters, halogen heaters or induction heaters). The plate
according to the invention may, in a known manner, be mounted on or
set in a support or work surface, such as the work surface of the
cooker (or cooktop) or the casing of a cooker. The plate may be
surrounded by a frame and/or may have free edges that are generally
shaped (rounded, beveled, etc.).
[0022] The subject of the invention is also a process for
manufacturing a plate according to the invention. The reader is
reminded that the manufacture of glass-ceramic plates generally
takes place as follows: the glass of composition chosen to form the
glass-ceramic is melted in a melting furnace, the molten glass is
then rolled into a standard sheet or strip, by making the molten
glass pass between rolling rolls, and the glass strip is cut to the
desired dimensions. The plates thus cut are then ceramified in a
manner known per se, the ceramification consisting in baking the
plates according to the chosen thermal profile for converting the
glass into what is called the "glass-ceramic" polycrystalline
material which has a zero or almost zero expansion coefficient and
is able to withstand a heat shock possibly up to 700.degree. C. The
ceramification operation generally comprises a step of
progressively raising the temperature up to the nucleation range,
generally lying near the glass transformation range, a step of
passing through the nucleation range for several minutes, a new
progressive increase in the temperature up to the temperature of
the ceramification stage, holding the temperature of the
ceramification stage for several minutes, and then rapid cooling
down to room temperature.
[0023] In the present invention, the process for obtaining the
plate defined above advantageously comprises an operation of
shaping the plate (which may be carried out at various moments
during the abovementioned operating method, provided that the
constituent material of the plate is at a high enough temperature
for it to undergo plastic deformation) consisting, for example, of
a sinking, molding or pressing operation (by rolling or by any
other operation), with the use of one or more supports or one or
more surfaces having the desired geometry, the ceramification of
the plate generally taking place after or following the forming
operation.
[0024] Preferably, a sinking-type forming operation (similar to
that of document EP 0 879 797) is carried out in order to raise the
edge of the opening (cutting of the opening generally taking place
before the forming operation), during the ceramification cycle
(generally before crystalline growth) of the glass plate.
Particularly preferably, the raising is carried out by means of an
element or bearing piece whose shape corresponds to that of the
opening that is desired to obtain, this element being positioned on
a forming support (for forming the other parts of the plate) and
generally having a size slightly greater than that of the opening.
Thus, during the ceramification cycle, the plate collapses under
its own weight except at the point where it is held by the element,
without it being necessary to use a specific tool.
[0025] The element for producing the raised feature may be hollow
or solid and is advantageously chosen to be made of a ceramic
material or a refractory steel. Preferably, the height of this
element is equal to at least 2 mm, generally around 4 mm. Also
preferably, each dimension (width, length and/or diameter) of the
element is greater than the corresponding dimension of the opening
by at least 5 mm. This element or bearing piece may also be
replaced with several elements or bearing pieces designed to occupy
the same perimeter and fulfill the same role.
[0026] It is also possible to use other forming means, for example
a molding or pressing means of forming, preceded and/or followed,
where appropriate, by a cutting operation, for example using a
water jet, optionally followed by a shaping operation.
[0027] The plate may also undergo other operations during its
manufacture (for example deformations in order to produce
protuberances, drilled holes for the subsequent incorporation of
control elements, screen printing for indicating or esthetic
purposes, the screen printing preferably taking place before
ceramification so as to allow, where appropriate, the enamel to be
baked during said ceramification, etc.) and it may be provided with
added elements such as control elements or the hood as explained
above. After the plates have been cut out, they may also be shaped
(machined, beveled, etc.), before and/or after ceramification, for
example by a buff wheel cooled at its center, in particular on at
least part of their edges and/or of their openings, so as to avoid,
for example, the presence of sharp edges that might injure
users.
[0028] The subject of the present invention is also an apparatus
(or device) for manufacturing a glass-ceramic plate as defined
above, comprising at least one element or bearing piece for
producing the raised feature as mentioned above.
[0029] Other details and advantageous features will become apparent
below from the description of non-limiting embodiments of the
invention with reference to the appended drawings in which:
[0030] FIG. 1 shows diagrammatically, in plan view, a plate
according to the invention; and
[0031] FIG. 2 shows diagrammatically a cross section on the line
A-A of the plate of FIG. 1, incorporated into a cooking appliance
and in operation.
[0032] For the sake of clarity, the various parts have not
necessarily been drawn to scale. The same references are used for
similar parts.
[0033] The plate 1 is a glass-ceramic plate comprising at least
four areas 2 defined, for example, by screen printing and
indicating the heating areas intended to be above the heating means
(not shown) incorporated into the cooking appliance 3 on which the
plate is mounted, these heating means being, for example, in the
present illustration, radiant or induction elements. The plate also
includes at least one opening 4, such as defined according to the
present invention, this opening being of rectangular shape and
having, for example, a width of around 11 cm for a length of around
30 cm and being in an approximately mid-way or central area of the
plate. The opening is at the top of a local deformation of the
plate, that is to say the edges 5 of the plate around the periphery
of the opening are raised. Control elements 6 can allow the various
members of the cooking appliance, such as the heating means, to
operate.
[0034] In combination with the opening 4, a hood (shown
schematically at 7) is provided beneath the plate 1 facing the
opening. A metal support 8 with a mesh 9 closes off the opening in
order to prevent objects falling through it, while allowing passage
of the gases sucked out by the hood. When cooking food in a cooking
vessel as shown schematically at 10, the cooking gases 11 are
extracted by activating the hood as shown schematically by the
arrows under the action in particular of a fan 12 and extracted via
a duct (not shown). Advantageously, the hood is masked by the
casing of the cooking appliance 3.
[0035] The plate is also equipped with one or more suitable seals
13, for example for sealing and/or providing the mechanical
interface between the glass-ceramic plate and the associated
elements.
[0036] The plates according to the invention may notably be used
advantageously for producing a new range of plates for cookers or
cooktops.
* * * * *