FR2554913A1 - ELECTRICAL HEATING APPARATUS FOR LIQUIDS, FOR HOUSEHOLD USE IN PARTICULAR - Google Patents

Abstract

ELECTRIC HEATING APPLIANCE FOR LIQUIDS, FOR HOUSEHOLD USE IN PARTICULAR. THE INVENTION CONCERNS AN ELECTRIC HEATING APPARATUS FOR LIQUIDS, AND IN PARTICULAR A WATER HEATER FOR HOUSEHOLD USE, PROVIDED WITH A PIPING CONDUCTING THE LIQUID GATHERED IN CONTACT OF THERMAL CONDUCTION TO AN ELECTRIC HEATING CONDUCTOR. IT IS CHARACTERIZED IN THAT THE PIPING 36 IS MADE OF A MATERIAL HAVING HIGH HEAT RESISTANCE AND PROVIDING ELECTRICAL INSULATION, SUCH AS A GLASS OR A CERAMIC MATERIAL. THE HEATING APPARATUS ACCORDING TO THE INVENTION IS MORE PARTICULARLY MADE IN THE FORM OF AN ELECTRIC COFFEE MAKER.

Description

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  Electric heaters for liquids for hazardous use

  In particular, the present invention relates to an electric heater

  for liquids, and in particular a water heater for household use.

  manages, provided with a pipe of liquid gathered in contact with

  thermal insulation to an electric heating conductor.

  A heating appliance of this type is for example known from patent application DE 26 38 380. This is a coffee maker

  equipped with an instantaneous water heater in the form of a metal container

  in which the liquid passes vertically, and in the wall of which is melted an electric tubular heating element. Another electric heater of this type is known from patent application DE 25 45 483, in the form of a coffee maker. This well-known electric coffee maker has an instant water heater

  in a horizontal position under a hot plate used to

  heat; this water heater is provided with a metal water pipe along which is brought a heating element

  tubular electric. In both cases, the metallic water pipe

  the disadvantage that the chemicals used to

  trage may react with the metal of the pipe, thereby forming toxic products. If rinsing after descaling is insufficient, these products may enter the prepared liquid during the next use of the coffee machine. Aluminum water pipes are likely to experience

  "pitting", which can at worst lead to premature failure.

  the device. These devices therefore know, for one

  problems of hygiene, and on the other hand problems of resistance

this to wear.

  The object of the present invention is to provide a heating apparatus

  An electric fog of the type described at the beginning of the present patent application, which eliminates to a large extent (or totally), and with a relatively low manufacturing cost, the problems of hygiene and

  the problems of resistance to wear.

  For this purpose, the electric heater complies with the

  vention is remarkable in that the pipeline is made in one

  high heat resistance and electrically insulating

  such as glass or ceramic material.

  A preferred embodiment of the heating apparatus according to the invention is remarkable in that the material providing the electrical insulation which is between the electric heating conductor and the inner face of the wall of the pipe (face which

  is in contact with the liquid) has a thickness of at least 2 mm.

  According to another embodiment of the heater

  according to the invention, the pipe is connected in contact with

  heat to a hot plate (hot plate),

and heat the latter.

  With this latter embodiment, an additional feature

  it provides that the heating plate is made of a heat-resistant material and providing electrical insulation, such as a glass, a ceramic material or a high-plastic material

resistance to heat.

  The pipe and the hot plate may then be made of a similar material, and melted or sintered together.

  Another possibility is to stick to each other the canali-

and the hotplate.

  Another additional feature is that the electric heating conductor is disposed at least partially

  between the pipe and the heating plate.

  An additional possibility then consists in arranging between the heating plate and the pipe an intermediate piece leading to

  heat, ceramic material or aluminum for example.

  A further new possibility is then to dispose the electric heating conductor next to the pipe on the

  hot plate or the intermediate piece.

  An advantageous embodiment of the heating apparatus according to the invention is remarkable in that the heating plate has, on its side channel side and vis-à-vis a section

  end of the pipeline, a recess that allows for a flexible

  connecting cable above the final section of the pipe. A particularly advantageous additional feature then provides that the heating plate has in the area of contact with the pipe a thicker portion protruding from the face of the channel side plate, on which rests the pipe

  by its heated longitudinal part, which ends before the

  end of the pipeline, so that the latter are cleared. Another advantageous additional possibility then provides, in case of use of an intermediate piece, that this intermediate piece

  It develops essentially on the heated length of the canalization.

  and. that the final sections of the pipeline, basically

  right protrude above this room, - or that the room-inter-

  The median has recesses at the ends of the canal.

  lisation. According to another preferred embodiment of the apparatus of

  heating according to the invention, the pipeline presents for the essen-

  a round section, and at the level of its final parts, a section

  the long axis extends parallel to the plane of the plane.

as hot.

  Another derivative embodiment is remarkable in that the

  channel in its contact zone with the hotplate

  flattening in the form of a right circumferential section. An embodiment derived from the heating apparatus according to

  to the invention and provided with a regulator forming part of the electrical circuit.

  of the heating conductor is remarkable in that the regulator

  placed next to the pipe is connected in conductive contact with

  to the hotplate or an intermediate part.

  According to another embodiment derived from the heating apparatus

  In accordance with the invention and provided with a regulator forming part of the electric circuit of the heating conductor, the regulator is connected in thermal conduction contact with the pipe, preferably on an unheated portion thereof, and by means of by

  example of a thermoconductive glue.

  An advantageous additional feature then provides that the pipe has a rounded section, with a flattening at the location of the regulator, in the form for example of a subsidence or

enlargement.

  According to another embodiment derived from the heating apparatus

  In accordance with the invention, the heating plate and the pipe are made in one piece, the pipe then being a conduit.

  formed in the material of the heating plate.

  An advantageous additional feature then provides that the heating conductor is disposed on a portion of the heating plate

  contiguous to this conduit, and preferably of increased thickness.

  A new embodiment derived from the heating apparatus

  of the invention is remarkable in that the pipeline

  almost horizontally, and that an upper and / or

  the circumference of the pipe is heated, thanks to a

  heating conductor preferably placed on this partial area.

  Another embodiment derived from the heater

  according to the invention is remarkable in that the apparatus is

  in the form of a machine for making coffee and tea, where the

  pipeline serving as an instantaneous water heater is connected by a

  rising to a filter to which boiling water is fed, and is also

  connected by a contact ensuring a good thermal conduction to

  a hotplate for keeping the prepa-

  to heat this plate.

  An additional characteristic then provides that the pipeline

  constitutes, in sectional view, a circular surface to which it lacks

  a segment of a circle, so that the pipe has a flat surface along its entire length by which it rests against the heating plate, the heating element then having the shape

  of a helix wound around the pipe, so that the

  flat face also carries the heating element, which is also -5-

covered with an insulating layer.

  Another possibility is remarkable in that the pipe is, seen in section, a circular surface which would lack a segment of a circle, so that the pipe has a flat surface along its entire length by which it rests against the heating plate, the heating element being meander around the pipe so that the flat surface does not carry a heating element. An additional feature is that only

  the meandering heating element is coated with an insulating layer

  te, so that the flat surface does not have an insulating layer.

  A new additional feature of the above-mentioned derived embodiment of the heater

  according to the invention consists in that part of the column

  aunt is produced in the form of a glass or

  ceramic material provided with a heating element affixed to its outer surface. The solution proposed by the invention, namely the realization of the heated pipe leading the liquid into a material providing thermal insulation and high heat resistance, has the advantage of obtaining a remarkable resistance of this pipe to corrosion against substances that usually come in contact with it, and thus prevent the appearance on the material of

  its wall of toxic reaction products or decompositions of

  res degrading the resistance of the device.

  The material providing electrical insulation between the electrical heating conductor and the inner face of the wall of the

  channel (face which is in contact with the liquid) having preferably

  thickness of at least 2 mm, an insulation

  sufficient electrical power of the liquid (with which the user risks

  contact with the heating conductor. The land of protection

  necessary on known appliances with metal water

  here is deleted. This allows a reduction in the cost of manufacturing

  By eliminating assembly steps and parts: one can thus use for connection to the network a single wire to two

  strands, as well as a single hold. This requires that the other elements

  also be provided with adequate insulation.

  The pipeline can develop almost horizontally; then an upper part and / or a lateral part of the circumference of the pipe is preferably heated by means of a heating conductor preferably arranged on this partial zone. The horizontal arrangement of the pipeline, for example under the heating plate

  used to keep the prepared liquid warm in an electric coffee machine

  This causes too great a formation of vapor bubbles, and consequently an irregular flow of water. Added to this is scaling, usually unavoidable. Heating only a lateral part and / or

  upper circumference of the pipe brings here an

  considerable improvement, which can partly be explained by the phenomenon

  following name: the unilateral heating produces an asymmetry which

  leads to a circulation of water in the pipeline, or even movements

  spiraling of the water particles in the pipe, resulting in a more homogeneous mixing of the water, which reduces the formation of

  vapor bubbles, which is partly due to occasional overheating of

  the. Top heating brings -the fact that steam bubbles, in the part of the pipe carrying the hottest water,

  accumulate preferably in the upper zone of the pipe-

  a stronger neutralization between heating and water, and consequently a softer heating of the water. Compared to thinner pipes, the thickness prescribed above for the wall of the pipe (two mm or more) provides a more even distribution of heat, even during the process of water heating, allowing to prevent the material from being subjected to high stresses; this last point is particularly important to avoid breaks in

  ducting when using a ceramic material.

  When the pipe is placed under a plate that it heats

  fe (hot plate of a coffee maker for example),

  the warming plate may be coated or fully

  killed from a heat-resistant material and providing insulation

  electric, such as a glass, a ceramic material or a

  -7 plastic material with high thermal resistance. This has the advantage that when the materials of the pipe and the hot plate are the same or the same, they can be assembled by melting or sintering, or by an effective bonding thus facilitated. The heating plate and the pipe are thus made as a single piece, and the heat transfer from one to the other is excellent. This also allows, for example, to have the

  heating conductor under the heating plate, next to the

  tion. This has the advantage of being able to print to the driver

  For example, a flat shape, for example meanders developing along the pipeline, or arranging it in the form of another type of coating, which reduces the cost of manufacture. We can also

  place on a flat side of the hotplate and beside the

  The temperature regulator is part of the electrical circuit of the heating conductor. The regulator can be glued to the heating plate by means of a glue with good heat conduction, for example a glue loaded with ceramic powder. elastically against the heating plate, for example by means of a

  elastic-anchored loop on the pipe.

  The electric heating conductor may be arranged at least

  tially between the water pipe and the hotplate,

  for example, they are melted or sintered together, so that it is on the one hand entirely incorporated and isolated, and on the other hand it heats simultaneously in a manner. ideal pipe and plate

heating.

  For manufacturing reasons, it may be advantageous to use straight pipes; however, in order to create flexible connection possibilities, it would be desirable for the sections to

  The end of the pipe runs in the elbow of the hotplate.

  Nevertheless, it is possible to realize a straight pipe while allowing the connection of hoses if the hot plate has at its final section recesses creating in this place a

  spacing between the outer face of the pipe and the hotplate

  which is approximately equal to the thickness of the wall of the hose, or

slightly higher.

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  In order to allow the formation of such recesses without too much

  blir the heating plate, we can strengthen the heating plate in

  the installation area of the pipeline.-If this reinforcement is

  so, that is to say if the thickness of the heating plate on the installation area of the pipe is important, one can also just stop this extra thickness before the ends of the pipeline, so that these ends protrude from the normal thickness areas of the hotplate, and remain

  enough space between the hotplate and the canalisa-

  to pull the end of a hose over the end of the line. Instead of this thicker part, you can also

  use an additional intermediate piece between the hotplate

  itself and the pipeline (Figures 4 and 8). The intermediate piece

  diary can be made of the same material as the pipe, but also (for example) metal, and the heating plate itself, contiguous with the intermediate part, can also be constituted by

  metal, or any of the materials proposed for the pipe; we say-

  thus provides a range of combinations offering various advantages in terms of manufacture or operation. As shown in the figure

  8, a metal intermediate piece offers easier possibilities.

  It is also possible to connect fastening and / or

  latters and fuses. The metal intermediate piece, as well as a metal hot plate, has a particularly good thermal conductivity. The intermediate parts and / or the heating plates themselves made of one of the materials proposed for the pipe offer the advantage of providing good insulation

  electric, as well as to allow to create, thanks to identical materials

  ticks or the like, bonds providing good thermal conduction

  nomic. The intermediate part may be considered as a heat-mounting and conduction plate having the task of distributing the heat well, whereas the heating plate itself must have before

all a decorative aspect.

  According to another preferred embodiment, the end portions of the pipe are, in order to form hose connections disengaged from the heating plate, deformed relative to. the essentially round section of the heated portion of the pipe, so that they have an oval or approximately elliptical section

(Figure 5).

  The pipe may furthermore have at its point of installation against the heating plate or against an intermediate part a flattening, that is to say a circumferential cross-section essentially

  on the right, in order to increase the contact area and as a result

  to improve heat transmission, and also - where appropriate - to increase

  put the reserved area between the two elements to house the driver

  heating. The pipe may also have a face of installation

  It can be used for a regulator forming part of the electric circuit of the heating conductor or for a fuse, and can for this purpose have a small section of wall recessed or bulged (Figures 6 and 7). According to another derived embodiment, the pipe can, according to a characteristic in itself known instantaneous water heaters of aluminum, have a zone with a greater wall thickness developing over its entire length and over part of its circumference, zone which allows, by grinding a small portion of surface at any desired location along the length of the pipe, to create a flat surface for coupling the regulator. A thermistorCTP can also be used as a regulator inasmuch as the heating conductor

  itself does not have sufficient PTC regulation characteristics

  for the desired control operations. In particular, a PTC regulation can, once the passage of the water has been completed, lower the power to that necessary for heating the heating plate, and eliminate or even completely eliminate the overheating, and consequently

the risk of fire.

  In the manufacture of a combination of a heating plate and a water pipe, where the two elements are firmly connected to each other, the heating conductor may be affixed, for example by a heating technique. molding or other coating technique, on a flat area of the face of the hotplate; the pipe is then placed on this zone, above the heating conductor, and the

  bonding of parts is achieved by melting, sintering or gluing. The ad-

  this way of proceeding is that we are more at hand with

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  the hot plate with the pipe to affix the driver

  heating, thus reducing the manufacturing cost.

  The following description presents in more detail examples of

  embodiment of the invention with the aid of the accompanying drawing, in which: Figure 1 is a vertical sectional view of a water heater in the form of a coffee machine; Figure 2 is a view in the same section as Figure 1 of an embodiment derived from electric coffee maker, with instantaneous water heater disposed under a hotplate; Figure 3 is a sectional view substantially along the axis III-III of Figure 2; Figures 4 to 6 are sectional views corresponding to that of Figure 3 other derivative embodiments; Figure 7 is a sectional view, substantially along the axis VII-VII of Figure 6; Figures 8 and 9 are sectional views corresponding to that of Figure 3 other derivative embodiments, presented with

  the carcass of the coffee machine, which had been removed for simplicity

  in Figures 2 to 7; Fig. 10 is a sectional view through the hot holding plate and the instantaneous water heater of another embodiment;

  FIG. 11 is a perspective view of the instantaneous water heater

tane according to Figure 10;

  Fig. 12 is a perspective view of another embodiment of

  derived from the instantaneous water heater.

  The electric coffee machine shown in FIG. 1 is provided with a carcass 2, closed downwards by a bottom 4, and which has, at the top of a small height upright 6, an upward opening 8, which is closed. by a hotplate (hotplate) 10 ceramic material placed from below. This plate is heated by a heating element 12 disposed below it, whose wires

  electrical connection were not shown, for the sake of simplicity

  cation. A coffee pot 14 is placed on the hot holding plate 10, and a coffee filter 16 is placed on this pot. An upwardly open fresh water reservoir 20 is disposed on an upright 18 of the carcass 2,

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  higher than the amount 6; this tank is provided with a bottom 22 provided with a discharge connection 24 projecting downwards, and is traversed by

  a riser 26 formed in one piece with it. A channel

  overflow 28 is placed on the upper end of the riser 26; it is provided with an outlet orifice coming above the coffee filter 16. The lower end of the riser 26 is connected, by means of a flexible connection 34 widening downwards, to a heater instantaneous water disposed under the bottom 22 in the raised portion of the carcass 2. The water heater 32 comprises a ceramic pipe 36, with a wall thickness of 2.2 mm, and on the outer periphery of which is wound a heated conductor

  in the form of wire 38, which is preferably fixed by hot enameling.

  The final sections of Line 36 are not coated with

  heating conductor; they are covered from the outside under

  elastic connection, respectively by the flexible hose 34 and the descending column hose 40. Above the heated zone, and at a distance from the upper edge, a regulator 42 forming part of the electrical circuit

  heating conductor 38 is fixed on the outer wall of the channeling

  36 by means of an adhesive ensuring good thermal conduction,

  ceramic paste filled with ceramic glue for example.

  Figures 2 and 3 show a hot plate (hot plate) 202 of a coffee maker of another embodiment, with an instant water heater 204 fixed on the underside of the plate and

  developing substantially horizontally. In this case, the heater

  Instant water also heats the hot plate. The hot-keeping plate is provided over most of its surface with a wall thickness of about 3 mm, and is provided at the attachment zone of the instantaneous water heater 204 with a further portion.

  thick 206 which protrudes downwards and has a lower face

  plate 208, into which is buried the ceramic pipe

  210 circular section of the instantaneous water heater 204. The hot plate 202 made of ceramic material and the pipe

  210 are sintered together by common cooking, however, before

  appearance of these two parts, the pipe 210 is coated with

  heating conductor 212 surrounding it in spirals. For the sake of simplicity

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  nication, neither the supply lines nor the connection points of these pipes were mentioned. The coating ends at a certain distance from the ends of the pipe, so that there remain unheated final sections 214 and 216, which make it possible to connect a down pipe 218 and a riser 220, in the form of silicone hoses. . The thicker part 206 ends a little

  before each end of the pipe seen in the longitudinal direction

  tudinal, and the hot plate 202 is provided on its underside, above the final sections of the pipe 214 and 216, recesses 222 and 224, which allow to introduce the walls of the hoses between the final sections of the pipe 214 and 216 and the hot plate 202. By means of an adhesive ensuring good thermal conduction, a regulator 230 forming part of the circuit

  electric heating conductor 212 is stuck next to the channeling

  tion 210 on the flat surface 208 which is on the underside of the

thicker part 206.

  In an embodiment derived from that shown in FIGS.

  2 and 3, the ceramic duct 210 may be surrounded,

  above the heating conductor 212, a ceramic insulating layer, which also develops between the pipe 210 and the plate of

  maintaining the heat 202 then being sintered to form with the latter a single piece, or which develops only around the part

  bottom of the pipe 210, going from both sides to the hot plate 202, and then can continue a little by

  its final sections on the underside of the thicker part 206.

  The derived embodiment shown in FIG. 4 has a stainless steel heating or holding plate 402 on the underside of which is pressed an intermediate piece 404 made of ceramic material, serving as a mounting and heat transfer member; a ceramic pipe of circular section 408 is pressed into the substantially flat lower face 406 of this intermediate piece. The ceramic pipe does not carry a heating conductor and is sintered with the intermediate piece 404 by common cooking. By a printing technique, a heating conductor 410 is disposed on the flat underside of the intermediate piece

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  404, next to the ceramic pipe 408; this hot conductor

  The heating plate 404 and the pipe 408 are heated by means of the part 404. In addition, a regulator forming part of the electrical circuit of the heating conductor 410 is adhesively bonded to the flat underside 406 of the heater. intermediate piece 404, next to the pipe 408. The intermediate piece 404 ends at a distance from each of the ends of the pipe 408, so that the latter, as well as for the embodiment

  shown in Figures 2 and 3, protrude, thus allow the connection

  hoses. The ability to pull hoses above

  final sections clear of the water heater piping.

  tane is an important advantage; indeed, the need to

  to kill the connection by means of a flexible plug embedded in the

  This entails a noticeable narrowing of the section and requires

  to form in a special way the ends of the connecting hoses.

  hence an increase in the manufacturing cost. With the embodiments shown in FIGS. 2 to 4, it is possible to use

  straight ceramic pipes of simple realization, and ef-

  make the connection by means of a single section of hose fixed by external voltage on the pipe, which allows to obtain a cost of

overall low manufacturing.

  The embodiment shown in FIG. 5 has a ceramic material holding plate which has, over its whole extent (only a section of which is shown in the figure), an identical thickness of about 3 mm. A 506 ceramic pipe

  is attached to the bottom of the warming plate 502 by collar.

  using a ceramic glue 504 ensuring good thermal conduction. The ceramic pipe 506 is provided with a final section 510 for connecting a hose 512 (suggested by the dashed lines); the end portion 510 is formed to have an oval section whose longitudinal axis develops parallel to the plane of the hot-holding plate 502 and whose shortest axis develops perpendicularly to the plate 502. Since the oval final section 510 is arranged symmetrically with respect to

  the axis of the circular section of Line 506, there is a

* - 14 -

  between the oval section and the bottom of the hot-holding plate 502, which allows the wall of the hose 512 to be inserted. The figure does not show the other end section of the pipe 506, which is

  configured in the same way as the final section 510, and also allows

  the connection of a hose. In order to ensure in all respects

  tension of the wall of the hoses against the wall of the connection

  the final sections must have on all their edges a

concave bulge.

  The embodiment shown in FIGS. 6 and 7 has a planar hot-plate 602 of thick ceramic material

  uniform, on the underside of which is sintered an instant water heater

  604. The instantaneous water heater is provided with a 606 ceramic pipe, the section of which has the shape of a pipe

  initially circular which would be depressed flat on one side. The sec-

  608 of the wall of Line 606 rests against the

  602, and a heating conductor meandering along the central zone of the ceramic pipe 606, which meanders, is printed before being laid against the plate 602.

  cross the flat section 608 and go down on the side wall.

  on the right side of the 606 ceramic pipe. This asymmetry of the heating must allow a circulation of water in the

  ceramic channel 606, or at least a spiral movement of water.

  At one point of its length, the ceramic channel 606 has a flattening in the form of a depression 612, to which is bonded

  a regulator 614 by means of a ceramic glue conducting the heat.

  The end portions of the conduit 606 extend beyond the side edge 602 of the warming plate, and terminate in circular sections (not shown) on which are drawn

connecting hoses.

  According to the embodiment shown in FIG. 8, the casing 802 of a coffee maker has an opening 804 at the top, on the underside of which is placed a hot plate 806 made of stainless steel sheet. On the underside of the hot plate 806 rests an intermediate piece 808 whose shape of the section resembles that of the

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  letter W. In its middle part, the intermediate piece 808 has a cutout in the shape of a circular arc 810 whose rounding follows the shape of a ceramic pipe 812, in order to remove heat from this

  circular ceramic pipe. The canalisation of ceramics

  812 is coated with a heating conductor which surrounds it in spirals (not shown), a heating conductor which is itself coated with a

  insulating layer which provides electrical insulation for the heat conductor

  gh vis-à-vis the intermediate piece 808 which is aluminum. The middle section 810 of the intermediate piece 808, which section is contiguous with the ceramic pipe 812 and which is spaced from the underside of the heat-holding plate 806, continues on both sides by side portions 814 and 816 which develop approximately radially to the axis of the pipe and go obliquely to the hot-holding plate 806, where they terminate in clamping sections 818 and 820 joined to the hot-holding plate 806. In the position of the clamping sections 818 and 820, it is possible, in order to improve the heat transfer, to intercalate between the intermediate piece 808 and the hot-holding plate 806, a paste or a conductive glue.

  heat. It is also possible to insert a paste or a conductive adhesive

  the side portion 816 of the intermediate piece 808 which is closest to the side wall 830 of the frame 802 may be provided with an orifice of heat between the ceramic pipe 812 and the middle portion 810 of the intermediate piece 808. allowing to

  screw a regulator 832. The lateral part 814 of the intermediate part

  diaire, which is the farthest from the wall 830, has a longitudinal hole 834 in which is embedded the hook-shaped end 836 of a steel elastic flange 838. The elastic flange

  passes under the ceramic pipe 812 and develops longitudinally

  nally approximately parallel to the warming plate to close, near the wall 830 of the carcass 802, by a forked end 840 which is introduced into a sliding element 842. The sliding element 842 is fixed on the underside of a fixing eye 844 extending from the carcass, projecting downwardly from the hot-keeping plate 806. During assembly, the elastic stirrup 838 is suspended by its hook end 836 in the orifice 834 of S4913

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  the intermediate element 808, and bent below the ceramic pipe 812, fixing its end 840 to the fixing eye via the sliding element 842. While holding together the intermediate piece 808 and the ceramic channel 812, the resilient yoke 838 also presses through the ceramic channel 812 the intermediate piece 808 against the hot plate 806, and the hot plate 806 against

  the underside of the opening 804 of the carcass.

  According to the embodiment shown in FIG. 9, the carcass 902 of a coffee maker has on its top an opening 904,

  on the underside of which is placed a hotplate 906. The

  The heating element 906 is held in place by an elastic clip 908 which is supported on one side on the hot plate and the other in an orifice 910 of a fixing rib 912 projecting downwardly. inside the carcass 902, next to the hot-keeping plate; this resilient clip presses the hot holding plate 906 against the lower edge of the opening 904, and against a circular seal 914 surrounding this opening. The hot holding plate 906 is made of a ceramic material, and has over most of its extent a uniform thickness of about 4 mm. From the hot plate part extends an enlarged portion 916 which forms a ceramic pipe, in that a conduit 918 of circular section, whose axis develops parallel to the surface of the

  906 holding plate is formed within this part.

  enlarged section. On one side of the conduit 918, the enlarged portion 916 itself has an extension 920, which has a flat surface 921 parallel to the surface of the hot-holding plate, and on which is printed a heat-conducting strip of conductor meandering, developing

  parallel to the duct 918, that is to say whose circuits, with the excep-

  Connection of the connecting circuitry extends perpendicularly to the conduit 918. The surface 921 carrying the heating conductor 922 is at a height approximately intermediate between the central axis and the upper end of the conduit 918; on the extension side 920, the outer wall of the enlarged portion 916 of the heat holding plate 906 does not follow the inner wall of the conduit 918, but, from

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  approximately a height located in the middle between the median axis and the lower end of the duct 918, develops tangentially to the duct 918 to go obliquely upwards to the surface 921 provided with the heating conductor 922. Because of the size plus important heat conducting section, as well as the proximity of the heating conductor 922, the heat is thus brought priority to the left side of the duct 918. This asymmetric heating of the duct 918 causes a spiral circulation of water in the water. leads 918 and causes a decrease in heat production, or at least allows to obtain a high temperature of the hot water prepared without too much steam being produced. According to an embodiment derived from that presented, the left outer face of the wall of the duct 918 may have an extension 950 (shown in dashed lines) to a location 960 o the wall of the retaining plate 906 a a

  normal thickness, the increased thickness part 920 then being

  winning. In this case, as the dashed line 964 suggests, the heating conductor is affixed to the tangential left outer wall 950, or its lower extension. As this wall develops obliquely with respect to the vertical, it can be easily reached by the tools used to affix the heating conductor 964

(pressure tool for example).

  In FIG. 10, the number 301 designates the heating pipe, and the number 302 the hot plate. The sectional view shows

  that the heating pipe is united in thermal conduction contact

  to the hotplate 302 by a channeling surface

  relatively important. Of course, an even more efficient heating of the hotplate can be achieved by using

  several heating pipes which will be fixed most uniformly

  possible on the underside of the warming plate 302.

  Figure 11 shows the embodiment where the heating element

  The heating element 304 is screen printed in the form of a paste made of, for example, tungsten and aluminum oxide. Both ends of the pipe 301 are provided with contact surfaces 306 which make it possible to feed the element

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  heating 304 electric current. The heating element 304 is, with the exception of the contact surfaces 306, isolated by a layer 305 which

  is for example also made of aluminum oxide. The channeling

  Then, by means of staples, for example, is fastened to the heating plate 302 so that the flat face 303 is in direct contact with the plate 302. Connection contacts are fixed on

  contact surfaces 306, and suitable hoses are drawn

  above the ends of the pipe 301, in order to pass the water through this pipe. Once heated, the water rises in a manner known in itself in the riser, to be finally brought

  in a filter on the coffee powder.

  Fig. 12 shows an embodiment which, from a security point of view, is even better; indeed, the heating element can not in any case come into contact with the metal hot plate. In this embodiment, the heating element 704, in the form of meanders, is printed only on the cambered surface of the channel 701, while the flat surface 703, which will subsequently come into contact with the hot plate 702. , is completely devoid of any metallic conductor. The number 706 designates the contact surfaces on which the electrical contacts are fixed, which make it possible to feed the heating element

  in electric current. Fixing and feeding the hoses takes place

  kill as described above for Figure 11.

  In order to keep the liquid on the hotplate at a constant temperature constant, a possibility

  consists of attaching to the warming plate or the channeling

  a regulator which cuts off the power supply when the

  has reached the allocated temperature and supplies power again when the temperature has fallen below a given minimum value. Another possibility is not to fabricate the heating element into a metal having a characteristic curve PTp weakly CTP

  inclined, but in a characteristic material / whose characteristic curve

  the resistance increases with temperature so that the temperature

  liquid is maintained even in the absence of a regulator.

- 19 -

  It is also possible that a portion of the riser is also constituted by a heating pipe of the type presented,

  which will bring a further reduction of the dead time (which is

  their already brief with this type of heating), as well as what is often desirable - an increase in the temperature of the hot water. This additional heating part makes it possible to obtain a more favorable heat transfer to the liquid. If such a device is used, care should be taken that this part of the heating system is

  stopped once the water has completely passed through the riser.

  The heating devices described above have the advantage of improving

  improve the heat transfer from the pipe to the hot plate

  in such a way that a relatively small amount of energy is required to maintain the liquid on the hotplate at the constant temperature allocated. The form of

  embodiment proposing to wind the heating element in the form of

  around the pipe so that the flat surface of the pipe does not receive a heating element is particularly

  advantageous. This safely eliminates any risk of

  conque conduction between the heating element and the metal hot plate. In addition, we can then remove the insulating layer

  on the flat surface, or even on the entire heating element.

- 20 -

Claims (25)

claims   1. Electric heaters for liquids, and in particular   water heater for household use, provided with a duct   the liquid connected in thermal conduction contact with an electric heating conductor, characterized in that the pipe (36;   210; 301; 408; 506; 606; 701; 812; 916) consists of a material   high heat resistance and providing electrical insulation,   such as a glass or a ceramic material.   2. Heating apparatus according to claim 1, characterized in that the electrically insulating material between the electrical heating conductor (38; 212; 304; 610; 704) and the inner face of the pipe wall. (face who is in contact with   the liquid) has a thickness of at least 2 mm.   3. Heating apparatus according to claim 1 or 2, characterized in that the pipe (210; 301; 408; 506; 606; 701; 812) is   together in a contact providing good thermal conduction to a   heater (or hot plate 202; 302; 402; 502;   602; 806; 906), and heat the latter.   4. Heating apparatus according to claim 3, characterized in that the heating plate or hot plate (202; 502;   602; 906) is made of heat-resistant material and ensures   electrical insulation, such as glass, ceramic material,   or a plastic material with high heat resistance.   5. Heating apparatus according to claim 4, characterized in that the pipe (210; 606; 916) and the heating plate (202; 602; 906) are made of a similar material and melted or sintered together.   6. Heating apparatus according to claim 3 or 4, characterized in that the pipe (506) and the heating plate (502) are glued to each other.   Heating apparatus according to one of the claims   3, 4, 5, 6, characterized in that the electric heating conductor   (212; 304; 610) is disposed at least partially between the channeling   (210; 301; 606) and the heating plate (202; 302; 602). - 21 -   Heating apparatus according to one of the claims   3, 4, 5, 6, 7, characterized in that an intermediate piece leading   heat (404; 808) made of ceramic material or aluminum, for example   plenum is disposed between the heating plate (402; 806) and the channel tion (408; 812).   Heating apparatus according to one of the claims   3, 4, 5, 6, 7, 8, characterized in that the electric heating conductor (410) is arranged adjacent the pipe (408) on the plate   heater or the intermediate piece (404).   Heating apparatus according to one of the claims   preceding, characterized in that the heating plate (202) has, on its side pipe side (210) and vis-à-vis a final section (214, 216) of the pipe (210), a recess (222). , 224) which makes it possible to pull a connecting hose over the final section of the pipeline.   Heating apparatus according to one of the claims   3, 4, 5, 6, 7, 8, 9, 10, characterized in that the heating plate (202) has in the area of contact with the pipe (210) a thicker portion (206) projecting from the face the channel side plate, on which rests the pipe (210) by its heated longitudinal portion, and which ends before the final sections (214, 216) of the pipe (210), so that the latter are released.   Heating apparatus according to one of the claims   8, 9, 10, 11, characterized in that the intermediate piece (404; 808)   essentially develops over the heated length of   tion (408; 812), and the final sections of the mainline-   Straight line protrude above this piece, or the intermediate piece has recesses at the ends of the pipeline.   Heating apparatus according to one of the claims   3, 4, 5, 6, 7, 8, 9, 10, 11, 12, characterized in that the pipe (506) essentially has a round section (506), and at its end portions (510) ) an oval section whose major axis extends   parallel to the plane of the heating plate (502). - 22 -   Heating apparatus according to one of the claims   3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, characterized in that the channeling   (301; 606; 701) present in its contact zone with the   heating plate (302; 602) a flattening in the form of a   right circumferential circumference (303; 608; 703).   Heating apparatus according to one of the claims   3 to 13 and provided with a regulator forming part of the electric circuit of the heating conductor, characterized in that the regulator (230; 832) located adjacent the pipe is connected in thermal conduction contact to the heating plate (202) or to an intermediate piece (808).   Heating apparatus according to one of the claims   1 to 14 and provided with a regulator forming part of the electrical circuit of the heating conductor, characterized in that the regulator (42; 614) is connected in thermal conduction contact with the pipe (36; 606), preferably on a portion unheated of the latter, and   for example by means of a thermoconductive glue.   Heating appliance according to claim 16, characterized in that the duct (606) has a rounded section, with a flattening (612) at the location of the regulator, in the form for example   subsidence or enlargement.   Heating apparatus according to one of the claims   1 to 17, characterized in that the heating plate (906) and the channel   (duct 918) are made in one piece, the ducting   being then a duct (918) formed in the material of the heating plate   Fante. Heating apparatus according to Claim 18, characterized in that the heating conductor (922) is arranged on a part (920)   of the heating plate adjacent to this duct, and preferably thick increased.   Heating apparatus according to one of the claims   1 to 19, characterized in that the pipe (408; 606) develops almost horizontally, and a portion (608) upper and / or lateral   the circumference of the pipe is heated, thanks to a conduc-   heater (610) preferably placed on this partial zone. - 23 -   21. The heater according to any of the claims   1 to 20, characterized in that the apparatus is configured as a coffee and tea making machine, wherein the pipe serving as an instantaneous water heater (210; 301; 408; 506; 606; 701; 812; 916) is connected by a riser to a filter to which the boiling water is supplied, and is also connected by a contact providing good thermal conduction to a heating plate for maintaining   in the heat of the prepared drink, in order to heat this plate.   Heating apparatus according to claim 21, characterized in that   the pipe (301) constitutes, in sectional view, a circular surface   a segment of a circle, so that the pipe (301) has a flat surface (303) along its entire length by which it rests against the heating plate (302), the heating element (304) ) then having the shape of a helix wound around the pipe (301), so that the flat surface (303) also carries the heating element (304), which is further covered   an insulating layer (305) (Figure 11).   Heating apparatus according to claim 21, characterized in that   the pipe (701) constitutes, in sectional view, a circular surface   the pipe (701) has a flat surface (703) along its entire length that rests against the heating plate, the heating element (704) being meandered around it. of the pipe (701) so that the flat surface (703) does not carry any element heating (704) (Figure 12).   Heating apparatus according to claim 23, characterized in that only the meandering heating element (704) is coated with an insulating layer (705), so that the flat surface (703)   has no insulating layer (705).   Heating apparatus according to one of the claims   21, 22, 23, 24, characterized in that a portion of the riser is in the form of a pipe of glass or material   provided with a heating element affixed to its outer surface. dull.