Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
  • F24C15/00—Details
  • F24C15/10—Tops, e.g. hot plates; Rings
  • F24C15/108—Mounting of hot plate on worktop

Definitions

• the present invention is directed to the manufacture of stoves, cooktops, and ranges (hereinafter, collectively, “stoves”) which carry a ceramic cooktop surface within a metal frame.
• a glass-ceramic (“ceramic " ) cooking surface. Below the surface may be mounted ceramic hobs which are heated with resistance wire such as nickel-chromium wire, or quartz halogen lamps.
• the cooktop surface is often colored and/or textured, and is in general considered an aesthetic improvement over conventional electric cooktops with exposed heating coils.
• the cooktops are commonly termed “ceramic” although they are sometimes also termed “glass ceramic " as well.
• the "stove" 1 ( Figure 1) has a top surface 5 which is a steel stamping, and contains an opening into which the ceramic cooktop 2 is positioned, the opening further characterized by edges or side walls 8 ( Figure 3) and ceramic cooktop support surface 5a.
• a sealing compound 6 generally a silicone, fills the gap between the metal frame and the ceramic cooktop.
• sealant is a hand operation, and the sealant must be difficultly flowable and preferably thixotropic, since otherwise it will flow past the adhesive pads 7 and drip into the space below the cooktop, as shown at 6c in Figure 3. Applying too much sealant can independently cause exuding of sealant as well. Due to the stiff nature of the sealant, the sealant must be forced into the space between the cooktop and frame with some difficulty, and hand tooling must be used immediately following its application in order to provide a smooth, uniform surface. Often, several "passes" must be made in order to provide the desired aesthetics, with final cleaning up often involving removal of cured sealant with a razor blade.
• Ceramic cooktops are mounted within metal frames having a support surface by supplying a dam around the inner periphery of the support surface, positioning a ceramic cooktop onto the dam, and injecting a measured quantity of low viscosity, self- leveling, curable silicone between the cooktop and the metal frame, the curable silicone being prevented from leaving the inner periphery of the support surface by the dam, and extending upwards to uniformly fill the gap between the ceramic cooktop edge and the metal frame.
• the subject of the invention is a process for mounting a ceramic cooktop in a stove, comprising :
• FIGURE 1 illustrates a free standing range having a ceramic cooktop.
• FIGURE 2 illustrates a close-up of the top of a range, showing the sealant between the cooktop and the frame.
• FIGURES 3 and 4 illustrate prior art processes of mounting ceramic cooktops.
• FIGURES 5, 6, and 7 illustrate embodiments of the present invention process of mounting ceramic cooktops.
• FIGURE 8 illustrates a further embodiment of a support surface and dam in accordance with the present invention .
• the metal frame per se of the range may be made in any conventional marnner.
• the range has an opening to receive the ceramic cooktop, a depressed ledge or "support surface" 5a of a depth such that the thickness of the ceramic cooktop and a dam (as later described) may be accommodated, while presenting a substantially flush surface with respect to the top 5 of the metal frame and the top of the ceramic cooktop 2. In some designs, it may be desirable that the surfaces not be flush.
• the key to the present invention is the ability to use a low viscosity silicone sealant with self leveling capability, in particular, at a known volume. In the prior art process, such a silicone could not be used, since it would merely flow past the adhesive pads and trickle down into the space below the cooktop .
• volume of sealant used would vary with the depth of penetration into the space between the cooktop 2 and the support surface 5a, and would vary also with the shape, size, and positioning of the adhesive pads.
• a dam which is preferably proximate the inner edge or “periphery” of the support surface, or alternatively, spaced apart from and preferably parallel to the periphery of the ceramic cooktop, liquid silicone is prevented from flowing into the range interior.
• a dam is shown at 10 in Figures 5, 6, and 7.
• the required volume of silicone may be measured or calculated with reasonable accuracy, such that robotic dispensing tools may be employed.
• the cooktop may simply be left alone following injection, and the silicone will form a smooth, uniform, and aesthetic seal between the frame and the ceramic cooktop. In most cases, no hand tooling or clean-up will be required.
• the dam may be supplied by three distinct methods, each of which are embodiments of the present invention.
• the dam is supplied as a rapidly solidifying bead of elastomer and/or adhesive, preferably applied by robotic means in order to provide uniform application.
• the rapidly solidifying adhesive may be a hot melt adhesive of any chemical type, preferably one which is heat and oxidation resistant, such as a silicone hot melt adhesive.
• the dam is composed of a very viscous and/or thixotropic, curable adhesive which rapidly cures to a rubbery state. In either case, the bead thus produced should preferably have the characteristics of a tacky, rubbery elastomer .
• the bead is preferably tacky in order that the cooktop, once positioned, will not move, even if the stove is jostled or inadvertently (or purposefully) tilted during manufacture, or during the cure period of the later applied self-leveling silicone.
• the bead may have characteristics known in the elastomer industry as "froggy hand", which provides the elastomer with a tendency to grip smooth surfaces without itself being tacky.
• the bead must only provide a modest locating capability together with the ability to prevent flow of liquid silicone past the bead (its "dam" function) . In such cases, a non-tacky and only modestly deformable elastomer or polymer may be used.
• the rapidly solidifying adhesive is preferably a silicone adhesive, since organopolysiloxanes (silicones) have very advantageous characteristics.
• silicones are thermally resistant to relatively high temperatures, and can thus readily survive the temperatures expected near the cooktop periphery, even under conditions where all burners are used for extended periods.
• silicones are oxidatively stable, and thus long life and continued elasticity can be expected, even after long periods of use.
• a silicone bead is used for the dam, it may be of any rapidly curing type, if not a hot-melt type. Suitable silicones are, for example, peroxide curing, condensation curing, and addition curing. Addition curing silicones are preferable.
• the organopolysiloxanes employed may contain any organic groups in addition to the reactive groups, for example but not by limitation, methyl, ethyl, propyl, phenyl, chlorophenyl, etc. Halogenated and in particular, fluorinated alkyl groups such as hexafluoropropyl and heptafluoropropyl groups may be present as well. For reasons of economy, in particular, methyl and phenyl groups are preferred, most preferably methyl groups.
• the preferred elastomers are substantially polydimethylsiloxanes .
• the reactive groups in addition-curable silicone elastomers which cure by hydrosilylation are Si-bonded hydrogen and Si-C bonded ethylenic or ethylynic unsaturation . Both, ⁇ -, ⁇ - terminated silicones as well as silicones containing pendent reactive groups may be used.
• the cured hardness is generally influenced by the crosslink density, with higher crosslink densities providing harder elastomers.
• the uncured viscosity is largely determined, in the absence of fillers and thixotropes, by the chain length and hence molecular weight of the individual organopolysiloxanes. Addition of fillers, in particular fine particle size fillers, increases the viscosity and may render the composition thixotropic, as may also viscosity and/or flow regulators.
• materials which may be used for a rapidly setting dam are epoxy resin-based elastomers, particularly those which incorporate fluorinated compounds for heat resistance, and polyurethanes .
• Other curable polymer systems such as cyanate resins, bismaleimide resins, and the like can also be used, often at higher cost.
• Hot melt adhesives based on polyesters, polyamides, polyimides, mixtures thereof, and the like may also be used.
• the raised polymer bead or dam be constructed of a silicone elastomer.
• thermoset polymer When hot melt adhesives are employed, it is preferable that these be the type which crosslink to a thermoset polymer following application, or be thermally stable at elevated temperatures, for example the aliphatic polyamides such as polyamide 6, polyamide 6,6, polyamide 6,12, and the like.
• silicone or other dam material For minimum usage of silicone or other dam material, and hence the highest economy, it is desirable that the bead of material laid down assume a roughly half-circular shape in cross-section following application, with the flattened side of the half- circle abutting the surface of the frame. In practice, however, a somewhat vertically flattened or elliptical shape is obtained, and in principle, a quite broad (quite flattened) cross-section may be used, so long as the height is satisfactory for maintaining the ceramic cooktop at the design height.
• a suitable silicone elastomer formulation is ELASTOSIL ® RT 722, a two component, RTV-2 elastomer available from Wacker Chemical Corporation, Adrian, Michigan, and Wacker Chemie AG, Muenchen, Germany.
• This elastomer composition exhibits a curing time of about 10 minutes at 150 0 C.
• the curing time is only critical to the extent that longer curing compositions may slow down the production cycle, or may, in some compositions allow for such flow that only a broad bead can be created.
• An initial cure which provides a dimensionally stable bead followed by a more complete cure is perfectly acceptable also.
• the curing time is preferably between 5 and 20 minutes, short curing times being limited by the application speed, i.e. the elastomer should not cure while still in the "gun".
• the rapidly solidifying polymer bead may be laid down by hand, particularly if pneumatic guns are employed to exude a constant amount of material.
• a conventional robot be employed.
• Such robots generally contain an articulated arm which directs the nozzle or "gun” through which rapidly settable polymer flows.
• the robotic application has the distinct advantage of far greater consistency.
• the bead should be applied so as to produce at least one substantially continuous dam which will prevent the flow of later applied flowable silicone past the dam. Small "vacancies" in the continuous dam can be tolerated so long as these do not allow for substantial leakage past the dam.
• the end of the continuous bead may abut the beginning of the bead, may overlap its flanks, or have any other termination such that substantial leakage of low viscosity silicone past the dam and into the stovetop interior is prevented.
• a continuous dam of already solid elastomer is applied, either by hand or by machine (i.e. a robot) .
• a continuous roll of double sided adhesive tape of suitable thickness is hand applied, or preferably applied by robotic means.
• continuous linear strips which abut at their corners to provide a continuous dam may be used, or a lengthy strip which is bent around the corners may be used.
• it is preferable that the width of the strip not be excessive, in order that bending around corners may be facilitated.
• the same modes of applications may be made robotically, which is to be preferred over manual methods.
• the support surface from which the ceramic cooktop will be spaced apart may be manufactured with a groove, step, or other locating device to assist with proper location and positioning of the dam.
• any "vacancies" in the continuous dam should be small enough so as to avoid leakage of low viscosity silicone past the dam.
• the support surface itself is provided with a raised dam as shown in Figure 8 at 5b, for example by stamping the dam at the same time as the stamping of the frame.
• the dam will have no positioning restraining ability an its own.
• the ceramic cooktop once positioned, may slide if the stove is tilted, or may be easily jostled out of position,
• manual application of spray adhesive or tacky substance may be used, since the dam is already positioned, and application of the adhesive spray can be done very quickly.
• dam is broadly meant a raised area above the level of the support surface located between the inner periphery of the support surface and tbe sidewalls of the opening in the frame, which is capable of eliminating or substantially eliminating the flow of flowable silicone past the dam after the ceramic cooktop has been positioned in the opening, resting on the dam.
• substantially eliminating is meant preventing the flow of flowable silicone into the interior of the stovetop to the extent that the commercial viability of the process is not defeated.
• dam is also meant a continuous structure, i.e. in the form of a loop, such that such leakage is prevented.
• a discontinuous structure with discontinuities of sufficient size such that considerable flowable silicone can flow through or past the discontinuities is not a dam within the scope of the invention.
• a dam is not necessarily a single, unitary, closed structure.
• a raised spiral where the pathway between the entrance, through which flowable silicone can flow, to the exit is so long that either the viscosity and surface tension of the flowable silicone or its cure rate prevent flow out of the spiral into the stove interior is within the scope of the invention, as are a plurality of concentric rings having openings in adjoining rings, such that a labyrinthal path is presented to the flowable silicone.
• the principle consideration is the function of the dam, prevention of substantial leakage of flowable silicone, and maintenance of proper spacing between the support surface and the ceramic cooktop, and not its exact configuration.
• the cooktop is then placed atop the support surface in the proper spatial relationships with the edges 8 of the frame. This operation is also preferably robotically performed.
• a low viscosity, curable silicone (11) is applied between the edge 9 of the ceramic cooktop and the edge 8 of the frame.
• hand application is possible, and is far less time consuming than the application of conventional, high viscosity silicone, robotic application is far to be preferred.
• Hand application while saving some time, still in general would require hand tooling for finishing, since even the most skilled worker will be unable to attain the precision required such that the silicone self levels to a uniform, aesthetic seal between edges 8 and 9.
• the volumetric output of adhesive, lineal speed, etc., of a robot is easily adjusted within fine limits, such that hand tooling should not be required. Robotic application is thus preferred.
• the amount of silicone dispersed can be calculated from the volume encased between the dam and the surface height of the silicone between edges 8 and 9.
• the delivery rate can be adjusted to supply more silicone at corners if the "dam" does not follow the cooktop periphery at these locations.
• the silicone composition is preferably an addition-curable composition with a relatively low viscosity and a moderate gel time.
• the gel time and viscosity have, essentially, an inverse relationship, since it is desired that the silicone be self leveling, i.e. that it flows to fill any voids, and also forms a smooth and level seal between the ceramic cooktop edge and the stovetop frame.
• the more viscous the composition the more flow time prior to gelation will be required.
• the amount of particulates in the silicone will, in general, be much less than in a caulk or traditional sealant.
• the composition will offen be pigmented, i.e.
• compositions white, gray, or black, by incorporation of pigments such as ground chalk, titania, black transparent iron oxide, or carbon black. As with most pigments, a relatively small amount is generally all that is required. It may be desirable to leave the composition colorless and translucent or transparent. For such compositions, either no filler of any kind is used, or fillers such as very small particle size silica or titania, preferably the former, i.e. fumed silica, are used.
• the cure time is preferably between 5 and 30 minutes, more preferably between 5 and 20 minutes. The cure time may also be much longer, and as indicated earlier, full cure may even occur only upon use of the stove, although this is not desired.
• the addition-curable silicone composition like that of the polymer dam previously described, contains both Si-bound ethylenic or ethylynic unsaturation, and Si-bound hydrogen, and a hydrosilylation catalyst.
• the amount of catalyst is generally lower than that of the rapid-curing bead silicone, since a slower curing composition is desired.
• the amount can be easily adjusted by one skilled in the art to vary the gel time and cure rate, or even to adjust these rates for changing climatic conditions, i.e. the temperature in the manufacturing facility.
• curable liquid silicones for example those whose cure is facilitated with peroxides, or condensation curing systems, for example those employing silanol-functional organopolysiloxanes and alkoxysilanes or alkoxysiloxanes as crosslinking agents, or those employing silanol-functional organopolysiloxanes and silanes or siloxanes (including polysiloxanes) bearing Si- bonded hydrogen.
• curable RTV-2 and LTV-2 silicone elastomers are well known, and are available from numerous sources.
• RTV-I compositions may in principle be used, although they are not preferred, and RTV-I compositions containing catalysts or initiators which are activated at only modestly elevated temperature may be used, if the stove can be heated, for example in a heat tunnel, etc. However, elastomers which require elevated temperature cure are not desirable .
• the viscosity of the curable, liquid, self leveling silicone composition, as applied, is preferably between 10 mPa-s and 100,000 mPa-s, more preferably between 5,000 and 15,000 and most preferably between 8,000 mPa-s and 10,000 mPa-s. A composition with a viscosity (25°C) of 9,000 mPa-s has been found very advantageous.
• viscosity which is suitable is dependent an many factors, including the distance of separation between the ceramic cooktop edge and the metal frame, and between the ceramic cooktop bottom surface and the support surface, higher or lower viscosity silicones may also be useful for certain applications.
• the viscosity should increase at a moderate pace following application, to give the composition time enough to flow and level. Cure should reach a degree of completion after, for example, but not by limitation, 10 - 15 minutes, whereby the stove or stovetop can be manipulated without damage to the sealant, but complete cure may be prolonged, even over days or weeks, or may be effectuated during use of the appliance, when the temperature of the appliance is elevated.
• the self-leveling silicone may cure at ambient temperature, generally in the range of 15°C to 30 0 C, or at higher temperatures, for example but not by limitation, up to 150 0 C.
• Preferred flowable, low viscosity is silicones are two component addition curable silicones with viscosities in the range of 6,000 to 9,000 mPa-s, most preferred is ELASTOSIL ® RT749, available from Wacker Chemical Corporation and from Wacker Chemie AG. These silicones have a cure time of 10 minutes at 150 0 C.
• a stovetop having a frame 5 dimensioned to receive a ceramic cooktop 2 is positioned within reach of a robot which dispenses a rapidly curing, very viscous and/or thixotropic RTV-2 silicone through nozzle or "gun" 12.
• the robot supplies the RTV-2 silicone 11 through a nozzle to form a raised, substantially semi-circular bead or "dam" 10 of tacky silicone elastomer onto the support surface and at a pre-defined location, such as a bead parallel to the edge of the support surface or parallel to the edge position of the later-applied ceramic cooktop, the positioning of the frame and placement of the dam preferably being such that the bead always occupies the same position with respect to the frame for each stove of the same type.
• the dam is substantially continuous so as to prevent leakage of later applied flowable silicone past the dam.
• a second robot then positions a ceramic cooktop within the opening in the frame, the lower surface of the ceramic cooktop resting on the raised bead (dam) of silicone, defining a "seal" volume extending outwards from the outer periphery of the dam towards the side or edge of the frame, and upwards to the level of the top of the cooktop and frame or the lower of these, should they not be at the same height.
• dam raised bead
• a further robot (or the same robot with a further silicone supply and/or nozzle) dispenses a flowable silicone 11 around the periphery of the cooktop, between the frame and cooktop, in an amount which is substantially the same as the defined seal volume.
• the flowable silicone is allowed to fill the defined seal volume and to level itself, forming, as it hardens (cures) , a non-tooled seal 13 between the edge of the frame and the edge of the cooktop.
• the preferred embodiment is substantially followed, but with certain deviations.
• the dam is applied robotically as is also application of the flowable silicone.
• the cooktop is manually positioned.
• the application of a polymer dam is not practiced; rather, a support surface with a raised section which provides the function of a dam is used instead, as illustrated at 5b in Figure 8.
• a dam is present, regardless of whether it is supplied as a raised portion of metal produced while stamping the frame from sheet metal, or applied as a continuous strip of solid adhesive or a continuous bead of rapidly solidifying adhesive.
• support surface is meant an inward extension and usually horizontal extension of the frame onto which the ceramic cooktop rests, through the intermediary of the dam.
• the support surface is preferably integral with the frame, but may also be separately manufactured and attached to the frame. Due to the heightened positioning accuracy inherent in the inventive process, the width of the support surface may be made narrower than in prior support shelves, onto which adhesive pads were placed.
• “stove” is inclusive of stoves, ranges, drop-in cooktops, etc.
• flowable when not defined by a viscosity limitation, is meant a composition which flows by itself under the influence of gravity.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Cookers (AREA)

Priority Applications (4)

Applications Claiming Priority (4)

Publications (1)

Family

ID=37487541

Family Applications (1)

Country Status (6)

Cited By (4)

Families Citing this family (9)

Citations (5)

Family Cites Families (42)

• 2005
  • 2005-09-30 US US11/240,127 patent/US20070044788A1/en not_active Abandoned
• 2006
  • 2006-08-25 CA CA002619525A patent/CA2619525A1/en not_active Abandoned
  • 2006-08-25 MX MX2008002643A patent/MX2008002643A/es unknown
  • 2006-08-25 EP EP06793001A patent/EP1917477A1/en not_active Withdrawn
  • 2006-08-25 WO PCT/EP2006/065664 patent/WO2007023183A1/en active Application Filing
  • 2006-08-25 JP JP2008527471A patent/JP2009506288A/ja active Pending

Patent Citations (5)

Also Published As

Similar Documents

Legal Events