EP1032792B1 - Prefabricated set for making a cooking surface - Google Patents

Description

The invention relates to a prefabricated assembly, intended for the production of hobs, including a hob ceramic.

Such hobs may include, among other things, heating elements such as radiant or halogen fireplaces and regulating means for varying the power thereof.

These various elements are usually arranged in a usually metallic structure called "box" and covered by a ceramic hob fitted with a metal frame which closes the structure.

The assembly of these hobs ends with the installation glass ceramic plate on the metal structure. Beforehand, the assembly of the ceramic hob and the frame is carried out by bonding using a silicone adhesive, which is suitable for such use. Indeed the silicone glue fulfills functions of natures different and complementary.

First of all, it keeps the ceramic hob on the frame in a defined position; a hob thus produced can be easily transported, all the elements constituting it fixed to each other, after mounting on the box.

Another function of the silicone glue is to seal between the metal frame and the ceramic hob.

The sub-assembly formed by the plate and the frame must, on the one hand, have a good seal so that water, for example used to clean the visible surface of the ceramic hob, do not not enter inside and may create a short circuit. On the other hand, from a hygienic point of view, such a plate used for preparation food, avoid any risk of fouling in areas difficult to access and impossible to clean so as not to see the appearance of germ development.

Another function still fulfilled by silicone glue is to cushion mechanical shock. It thus avoids direct contact between the frame metal and the ceramic hob and also can compensate the expansions of the metal frame, the ceramic hob having practically zero expansion. An advantageous feature silicone glue is to have good temperature resistance. Although silicone glue is only used in the peripheral part of the ceramic hob and therefore at a certain distance from the areas of heating, this resistance to temperature must be high.

So the periphery of the plate is still elevated by temperature when one or more fireplaces are in working order. Of more, a heated container, such as a pan, can be placed on the edge of the plate and therefore subjects the frame to a high temperature.

A final function of the silicone glue is aesthetic: at minus part of the glue being deposited from above, it is important to be able to smooth it so as to give it a beautiful appearance because the less a part can remain visible.

On the other hand, the assembly consisting in sticking the ceramic hob on the metal frame using an adhesive of the type mentioned above has several drawbacks.

First, the amount of glue required is relatively important, the cost of this product is also important. Another downside is related to the polymerization time which increases with the amount of material, which leads to increased manufacturing costs.

Finally, a last drawback lies in the proper mounting said. In fact, the ceramic hobs are usually delivered as such to the cooktop manufacturers who are responsible for assembly. A priori, such assembly in the factory does not present any insurmountable problems insofar as the workers have the necessary tools. By cons, it appears much more difficult for a craftsman who must reassemble a ceramic hob on a frame metallic after performing an electrical repair or to change this plate that may have suffered damage. Indeed, it seems delicate for the craftsman to fix the ceramic hob because he must, at the same time place the silicone adhesive on the periphery of the plate on the inside and around the edges, smooth the glue in the visible area and hold the plate well centered while pressing it during the previous operations and during the curing time of the glue which is relatively long, as previously mentioned.

The removal of such a ceramic hob is also not Easy. The craftsman must cut the silicone glue using the below, that is to say on the underside of the ceramic hob, and a cut from above, that is to say on the edge of the plate. These two operations that must be performed on the entire periphery are not simple because the two cutting lines must meet for good separate the two elements: ceramic hob and frame metallic. In addition, and more particularly when cutting on the face side internal of the ceramic hob, it is not easy to perform this cut without risking scratching the underside of the plate which is the face the most fragile of the plate.

This risk of scratching can lead to a risk of cracking during constraints and therefore a breakage of the plate. A disassembly of a glass-ceramic plate, with a view to reassembling it later, therefore appears almost impossible to achieve without damaging the plate.

In addition, to reattach it to the frame, it is necessary to eliminate maximum traces of silicone glue from the previous assembly, which risks also cause scratches with the same consequences as previously.

To remedy these drawbacks, it has already been proposed according to the FR 2 744 201 patent to provide the ceramic hob with a profile thermosetting overmolded in the lower peripheral part, profiled by means of suitable fixing means allows the fixing of the plate to a metal frame without direct contact between the two.

It has also been proposed, in particular in patent EP 0 449 347, to directly overmold, by a double injection technique, a plastic frame on the periphery of the ceramic hob, the plastic frame then being fixed to a metal base, support various heating elements.

This solution is not fully satisfactory. The frame in plastic being directly in contact with the upper part of the plan working, the interface between these two parts is not clear, in particular from a sealing point of view. Therefore, the risk of fouling are important.

An assembly according to the preamble of claim 1 and a method according to the preamble of claim 1 are known from EP-A-748 676.

The inventors then set themselves the goal of providing a set prefabricated of the type mentioned above, that is to say comprising a plate ceramic hob and a frame that allows, once assembled in cooktop, the latter to have a clear interface with the work plan for which it is intended.

To do this, the invention relates to a prefabricated assembly, intended for the production of a hob, comprising a plate of glass ceramic cooking and a frame consisting of a part extending to the periphery of the plate and of another part extending in a plane substantially vertical to the plate, characterized in that at least one of the two parts of the frame has an elastomer overmolding, this topping comprising legs to immobilize the frame in the workplan.

The prefabricated assembly thus proposed by the invention satisfies the problem.

Indeed, the overmolding in the outer peripheral part of the frame ensures a clear interface with the upper part of the work plan, in particular from a sealing point of view. Nature elastic of the elastomer allows the profile to marry the form of the work plan, which can be particularly effective when it is not plumb and / or when its surface condition is not regular.

The frame according to the invention is preferably made of plastic. he is advantageously molded. Preferably again, it is made of resin polymer resistant to temperatures of at least 180 ° C.

Regarding the connection between the hob glass ceramic and the frame, it can be chosen to overmold the frame directly on the plate instead of bonding them together by a joint in elastomer, silicone type.

Such a choice could be made in particular according to the geometry of the manufacturing technique inherent in the frame.

In order to integrate the heating element controls, other heating means such as gas burners and / or others functional elements of the ceramic hob, such as a clock, the frame advantageously has holes opening through which are molded elastomer buttons.

According to a very advantageous characteristic of the invention, the overmolding is a profile.

According to this same characteristic, each of the two parts of the above-mentioned frame, advantageously comprises an elastomer profile.

Very advantageously, the elastomer profile of the part of the frame extending in the substantially vertical plane of the plate consists of legs, preferably having indentations. The Flexible “legs” of the overmolded profile allow, according to this variant, to immobilize the hob perfectly in the worktop, even if it has not been cut within the tolerances desired. This way, we avoid leaving an important game between the vertical walls of the frame and the worktop, play that cannot be compensated in this case only by the presence of parts of setting tricky to set up.

Another advantage provided by this variant of the invention is the guarantee not to damage the worktop when setting the table of cooking assembled in the latter.

The elastomer profile of the part of the frame extending to the periphery of the plate preferably has a lip, which allows further avoid the risk of fouling.

By its elasticity, this lip participates, with the elements of flexible supports mentioned above, in support of the frame on the worktop.

The molding elastomer according to the invention is advantageously silicone.

The invention also relates to a hob incorporating a prefabricated assembly previously defined in claims 1 to 12, the frame of which is fixed to a base supporting heating elements, such as radiant elements or halogen and / or at least one burner with atmospheric gas and / or minus a means of induction heating.

a) on introduit un cadre moulé dans un poinçon de forme telle qu'on puisse injecter un élastomère à la surface d'au moins une des deux parties du cadre ;

b) on place une plaque de cuisson vitrocéramique dans le poinçon en légère surélévation par rapport au cadre moulé ;

c) on ferme l'ensemble ainsi constitué au moyen d'une matrice de forme au moins en partie complémentaire au poinçon ;

d) on injecte un élastomère dans les canaux formés par l'espace libre entre le poinçon et la matrice ;

e) on polymérisé l'élastomère ;

f) puis, on éjecte l'ensemble ainsi constitué.

Finally, the invention relates to a method for manufacturing a prefabricated assembly according to at least one of claims 1 to 12. According to this method, the following steps are carried out:

a) a molded frame is introduced into a punch of such shape that an elastomer can be injected onto the surface of at least one of the two parts of the frame;

b) a ceramic hob is placed in the punch slightly raised relative to the molded frame;

c) the assembly thus closed is closed by means of a matrix of shape at least partially complementary to the punch;

d) an elastomer is injected into the channels formed by the free space between the punch and the die;

e) the elastomer is polymerized;

f) then the assembly thus ejected.

The advantages provided by the invention are numerous. First of all the fact that the elastomer is injected and then polymerized, it no longer has to be smoothed by hand as could be the case according to the prior art, its state of surface is no longer penalizing for the decorative aspect. Similarly, in injecting the elastomer onto an already shaped frame, it is possible to from frames of various shapes and / or colors. Such varieties help to give an aesthetic appearance to the hob.

The various shapes also allow the integration of equipment usually integrated into the plate such as the controls heating elements which most of the time require careful drilling of the plate.

For reasons of manufacturing cost, the frame used according to the process of the invention is preferably made of plastic.

The elastomer used is advantageously silicone.

According to a very advantageous characteristic of the process, one realizes step e) of high frequency polymerization.

The milk to polymerize the elastomer according to the invention by high frequency also saves considerable time during manufacturing. Of more, in such a process, the tool used is usually a elastomer. Therefore, the flexible contact between the tool, in particular the mold, and the different parts making up the prefabricated assembly according to the invention does not risk altering the materials, in particular the glass ceramic constituting the hob.

Thus, in industrial production, the risk of scrap is reduced.

□ figure 1 : une table de cuisson incorporant un premier ensemble préfabriqué conforme à l'invention et placée dans un plan de travail ;

□ figures 2a à 2e : les différentes étapes du procédé de fabrication d'un deuxième ensemble préfabriqué conforme à l'invention.

Other details and advantageous characteristics will emerge below on reading detailed examples according to the invention made with reference to FIGS. 1 to 2e which represent respectively:

□ Figure 1 : a hob incorporating a first prefabricated assembly according to the invention and placed in a work surface;

□ Figures 2a to 2e : the different stages of the manufacturing process for a second prefabricated assembly according to the invention.

Figure 1 is a sectional view showing a table of cooking 1, carried out in accordance with the invention, integrated into a plan of work 2 of a kitchen.

This hob 1 essentially consists of a plate of vitroceramic cooking 3 and a prefabricated assembly according to the invention 4 fixed to a metal base 5, of rectangular section, by means of screws not represented.

On this base 5 are fixed, in a manner known per se, elements heaters not shown.

The association of a prefabricated assembly according to the invention with the base metallic therefore substitutes, at least from the point of view of function enclosure, to a metal frame used according to the state of the art. A frame in plastic loaded in particular with glass fibers 6, as possibly the plastics listed below, constitute the framework for the prefabricated assembly according to the invention.

This frame 6 essentially comprises three parts, namely the sides vertical 61, 62, the outer peripheral portion 63 which surrounds the vitroceramic cooking plate 3 by being directly in contact with it and a flat part 64 which extends substantially in the main plane of the ceramic glass hob 3.

This flat part 64 has openings whose function will be explained below.

A silicone profile 7 extends over the entire periphery of the frame 6. This has the shape of a lip 71 for the part directly in contact with the upper part of the worktop. This lip 71 has the function ensure a clear interface between frame 6 and the upper part of the work surface, i.e., among other things, a liquid tightness and foods likely to come nearby.

What is more, the curved shape of the lip 71 gives it an appearance aesthetic.

The silicone profile 7 has, in its vertical part, tabs 72, 73 in contact, on the one hand, with the entire height of the vertical flanks 61, 62 of the frame 6 and, on the other hand, with the entire height of the plane of job. The elastic nature of the silicone allows these tabs 72, 73 to be deformed when the hob is inserted into the hob work and therefore ensure perfect immobilization without play between these two elements.

Removing the hob is also very easy, without risk damage frame 6 and / or work surface 2.

The flat part 64 of the frame, meanwhile, has two openings circular 65 and a rectangular opening 66.

Through the two circular openings 65 are clipped or, preferably overmolded on the frame, control buttons in silicone 67 which allow, once pressed, to trigger the operation of the heating members not shown.

Below the rectangular opening 66 is arranged a display digital type which allows viewing the programmed time and / or duration a heating cycle of at least one of the heating members. he can also indicate which heater is in operation if the plate is under electric voltage, the temperature of the organ (s) of heated...

Finally, under this flat part, opposite the openings described, is encapsulated, using silicone, a support 68 on which are engraved conductive tracks through which the electrical supply of the different organs is established.

Figures 2a and 2e represent the different successive stages the manufacturing process of a second prefabricated assembly according to the invention.

According to this second variant, the prefabricated assembly 4 and the plate glass ceramic cooking plates 3 are linked together by means of a silicone seal 8.

Figure 2a relates to the initial stage of setting up a frame molded 6 in a punch 9. This molded frame 6 is of a chemical nature and similar in shape to that of FIG. 1.

Figure 2b shows the glass ceramic plate 3 placed in the punch 9, so as to be slightly raised relative to the frame 6 and leaves an empty space 10.

Once the two aforementioned parts are in place in punch 9, a die 11 is applied against the punch 9 and, in certain places, against the plate 3 and the frame 6 so that injection channels 12 closed are created, as shown in Figure 2c.

Silicone is then injected inside these channels 12 at by means of an appropriate device.

Once the channels 12 are completely filled with material silicone (as shown in Figure 2d), the injection is stopped and proceeds to a polymerization of this same material using a high frequency technique for a time of 0.5 to 2 min, in depending on the mass of silicone to be transformed.

The die 11 is then unlocked from the punch 9 and the ejection of the prefabricated assembly is produced, as shown in Figure 2e.

Such a method has the advantage of being simple to implement and fast. It is also advantageous since the production of new series with new molded frame shapes can be easily carried out at no additional production cost, the creation of new die and / or punch tools being easy.

It goes without saying that many modifications can be made without departing from the scope of the invention. So brand new plastic of the molded frame may be suitable as long as it withstands high temperatures, typically above 250 ° C.

So, for example, the plastic of the frame conforms to the invention may be chosen from polybutyleneterephthalate (PBT), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyacrylate (PAR), polyethersulfone (PES), polyetherimide (PEI), polyamideimlide (PAI), liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE), polyetherethersulfone (PEES), polyepoxides (EP) and, optionally, polysulfone (PSF), fluoropolymer resins (FEP such as for example PTEFE, PFA, ETFE, etc.), polythioethersulfone (PTES), thermoplastic poyimide (TPI), cross linked polyimide (CLPI), polyetherketone (PEK), polyethermitrile (PEN), polycyclohexyleneterephthalate (PCT), polyphthalamide (PPA).

For reasons of material cost, the frame may be chosen advantageously among polyester resins (UP).

Similarly, any other equivalent profile that can be injected in accordance with the invention, is included within the scope of the invention in the provided that silicone-like features such as elasticity and high temperature resistance are fulfilled.

The elastomers, respectively marketed under the denomination VITON and KALREZ by the company DUPONT DE NEMOURS, thus fit perfectly.

Similarly, the elastomers marketed under the names FLUOREL and CHEMRAZ, respectively by 3M companies and GREEN TWIN, are perfectly suited.

Claims (17)

1. Prefabricated assembly (4), intended for producing a hob, comprising a glass-ceramic hotplate (3) and a frame (6) comprising a part extending at the periphery of the plate (63) and another part extending in a plane substantially vertical to the plate (61, 62), characterised in that at least one of the two parts (61, 62) of the frame comprises an elastomer overmoulding (7, 8), this overmoulding comprising lugs (72, 73) able to immobilise the frame in the work surface.
2. Assembly according to Claim 1, characterised in that the frame is made from plastics material.
3. Assembly according to Claim 1 or 2, characterised in that the frame is moulded.
4. Assembly according to one of Claims 2 or 3, characterised in that the frame is made from polymer resin resistant to temperatures of at least 180°C.
5. Assembly according to one of Claims 1 to 4, characterised in that the plastic frame is directly moulded onto the glass-ceramic hotplate.
6. Assembly according to one of Claims 1 to 4, characterised in that the frame and glass-ceramic hotplate are connected together by an elastomer seal, of the silicone type (8).
7. Assembly according to one of the preceding claims, characterised in that the frame comprises through holes, through which elastomer knobs (67, 68) are moulded on.
8. Assembly according to any one of the preceding claims, characterised in that the overmoulding is a profiled member (72, 73).
9. Assembly according to Claim 8, characterised in that each of the two parts of the frame comprises an elastomer profiled member.
10. Assembly according to Claim 8 or Claim 9, characterised in that the lugs on the elastomer profiled member have indentations.
11. Assembly according to Claim 8 or Claim 9, characterised in that the elastomer profiled member of the part of the frame extending at the periphery of the plate comprises a lip (71).
12. Assembly according to any one of the preceding claims, characterised in that the elastomer of the overmoulding is made from silicone.
13. Hob incorporating a prefabricated assembly according to one of Claims 1 to 12, the frame of which is fixed to a base supporting heating elements, such as radiant or halogen elements and/or at least one atmospheric gas burner and/or at least one means of heating by induction.
14. Method of manufacturing a prefabricated assembly (4), intended for producing a hob according to at least one of Claims 1 to 12, comprising a glass-ceramic hotplate (3) and a frame (6) formed from a part extending at the periphery of the plate and another part extending in a plane substantially vertical to the plate (61, 62), characterised in that the following steps are performed:

    a) a moulded frame (6) is introduced into a punch (9) with a shape such that it is possible to inject an elastomer on the surface of at least one of the two parts of the frame and so that the elastomer injected forms lugs (72, 73) able to immobilise the frame in the work surface;

    b) a glass-ceramic hotplate is placed in the punch slightly raised with respect to the moulded frame;

    c) the assembly thus formed is closed by means of a die (11) with a shape at least partly complementary to the punch;

    d) an elastomer is injected into the channels (12) formed by the free space between the punch and the die;

    e) the elastomer is polymerised;

    f) then the assembly thus formed is ejected.
15. Method according to Claim 14, characterised in that the frame is made from plastics material.
16. Method according to Claim 14 or Claim 15, characterised in that the elastomer is silicone.
17. Method according to Claim 15 or Claim 16, characterised in that the polymerisation step e) is carried out at high frequency.

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