EP0814302A1 - Self-regulating fuel oil heater - Google Patents

Abstract

The heater includes a tubular square sectioned heating body (4) of thermo-conducting material, longitudinally traversed by a circular sectioned conduit (5) having members (2,3,7) for sealingly coupling one side of the inlet under pressure of oil to be heated and the other, at the jet nozzle of the burner. The heating element is in form of a plate (8,9) of positive coefficient of Temperature which adjusts itself against a plane face (4a,4b) of the tubular heating body. There is a feed circuit (26), and a circuit of temperature detection (15) controlling the functioning of the burner. The heating plate (8,9) is pressed (F) onto a plane face (4a,4b) of the heating body (4) by a rectangularly shaped wing (10,11) of thermo-conducting material of width equal to that of the body (4). At the end of the zone of intersection between this plane face of the body (4a,4b) and the face immediately adjacent (4d), this wing (10,11) extends practically the length of the heating body and is spaced adequately to be turned down in cooperation with the folding zones (20,24), against the external face opposite to the heating plate (8,9) to recover the heat diffusing to its exterior.

Description

The invention relates to an improvement made to devices intended for heating fuel oil before it is sprayed into an oil burner.

In the field of oil burners, it is quite known to heat the oil before it is admitted to the nozzle to be sprayed there. This reheating is necessary to decrease the viscosity of the fuel oil on the one hand, and increase the fineness of spraying on the other hand.

Many solutions already exist, essentially consisting of heating a heating body interposed between the oil pump and the nozzle. Generally, it is known to have around this heating body, with high thermal conductive characteristics, a more or less conventional heating device, the operation of which will of course be sought to regulate; indeed, if it is essential to heat the fuel oil before spraying, as we have seen, it is also important not to exceed a maximum heating temperature from which coking phenomena would begin to appear, and we knows the particularly harmful effects on the sprinklers.

Heating systems have therefore been imagined for a long time coupled with temperature regulation devices which, apart from their often very high cost, find it difficult to accommodate the lack of accessibility offered by the vast majority of oil burners in boilers. The oil heaters must indeed be as close as possible to the sprinklers, that is to say in often very congested areas, thus leaving only little room to develop thermal regulations.

Given these often severe space requirements, many manufacturers have already suggested in the past, to use self-regulating systems in the reheating oil burners.

Among all the systems proposed, the use of heating elements with a positive temperature coefficient (PTC thermistor) provides a relatively decisive solution.

As an example, one can read in patent DE-29 12 000 filed March 27, 1979 by MEKU METALL the description of a device intended for the heating of fuel oil upstream of the nozzle of a burner whose heating system was produced from thermistors with a positive temperature coefficient maintained around a heating body inside which the fuel oil to be heated circulates by coating the assembly mounted in an insulating resin.

The operation of such a device is simple: energizing the heating elements provides the primary desired effect, namely the increase in temperature of the heating body but also of the thermistors, thereby causing the internal resistance which then comes to limit the electrical power absorbed and consequently reduce the production of calories. It is therefore understandable that such an arrangement provides thermal self-regulation since the theoretical increase in temperature is automatically limited by the thermal power of the heating element which decreases when the temperature increases.

Such a self-regulating device has the advantage of a very small footprint and above all a great hardiness of use; however, such a device is particularly difficult to adjust because its effectiveness is closely linked to the often random mechanical problems of contact between the heating elements and the heat transfer means. It is well understood indeed that if such contact was not particularly careful, it could lead to a rapid rise in temperature of the thermistor, resulting from a low thermal transfer to the product to be heated, with the consequence that the internal resistance of the thermistor, increasing proportionally, would immediately limit the heating power, which would further amplify the heat transfer fault; conversely, a particularly careful contact between the thermistors and the heating body allows the latter to recover a maximum of calories, that is to say to limit the temperature rise of the thermistor which can thus provide a power sufficient and constant to heat the fuel oil.

In addition, such heaters necessarily having to be in a small footprint as already mentioned, it is mandatory that these devices are particularly effective, since the available heat exchange surfaces are necessarily small.

• réaliser un contact aussi intime que possible entre les éléments chauffants du type CTP et le corps de chauffe,
• aménager les éléments chauffants pour que les déperditions thermiques soient les plus faibles possible afin d'assurer un transfert de puissance optimale vers le corps de chauffe, et donc vers le mazout que l'on veut réchauffer avant pulvérisation.

In this regard, it has already been suggested in German application DE-42 16 008 of May 15, 1992 in the name of RAPA RAUSCH to replace the coating techniques for holding the thermistors around the heating body, as described in the patent MEKU already mentioned, by two lateral flanges coming by means of upper and lower clips enclose the thermistors around the heating body. If it undoubtedly results in an improvement in the thermal contact between the heating elements and the heating body, the fact remains that such a solution only very incidentally takes into account the heat losses corresponding to the external faces of the thermistors, which leads to the elevation of their temperature and therefore the decrease in their power; moreover, it can be observed that the mechanical fastenings by clips necessarily have reliefs which will nevertheless have to fit into an often limited space; in this sense, and due to the current standardization of oil burners, the envelopes intended to receive the heaters, have internal and external dimensions fixed by the manufacturers of burners; the most common models of heater casings have an outside diameter of 18.4 mm for a useful length of 92 mm; we understand while we are looking for an optimal exchange surface for this material, since in any case its external dimensions are fixed. It is therefore essential to use the maximum of the interior volume of the envelope, while respecting the conditions developed previously, namely:

• make contact as intimate as possible between the heating elements of the PTC type and the heating body,
• arrange the heating elements so that the heat losses are as low as possible in order to ensure an optimal transfer of power to the heating body, and therefore to the fuel oil that is to be heated before spraying.

• un corps de chauffe tubulaire en matériau fortement thermo-conducteur, de section transversale avantageusement carrée, traversé longitudinalement par au moins un conduit de section circulaire présentant des moyens pour le couplage étanche, d'un côté à une arrivée sous pression du mazout à réchauffer et de l'autre au porte-gicleur du brûleur,
• au moins un élément chauffant en forme de plaquette du type à coefficient positif de température (CTP) venant s'ajuster contre au moins une face plane du corps de chauffe tubulaire, et avantageusement deux faces planes opposées.
• un circuit d'alimentation du ou des CTP,
• un circuit de détection de température commandant la mise en route du brûleur,

   caractérisé en ce que au moins une plaquette CTP est maintenue en appui sur au moins une face plane du corps de chauffe par une aile avantageusement rectangulaire en matériau fortement thermo-conducteur, de largeur sensiblement égale à celle du corps et issue de la zone d'intersection entre ladite face plane du corps et la face immédiatement adjacente, ladite aile s'étendant sur pratiquement toute la longueur du corps de chauffe et présentant une épaisseur adéquate pour pouvoir être convenablement rabattue en coopération avec des zones de pliages adéquates, contre la face opposée de ladite plaquette CTP et récupérer ainsi les calories diffusant à l'extérieur de celle-ci .For this purpose, it is proposed in accordance with the invention, a heater for an oil burner, comprising inside a cylindrical envelope called a heater carrier:

• a tubular heating body made of a highly thermally conductive material, of advantageously square cross section, traversed longitudinally by at least one duct of circular section having means for tight coupling, on one side to a pressurized arrival of the fuel oil to be heated and on the other side to the burner nozzle holder,
• at least one heating element in the form of a wafer of the positive temperature coefficient (PTC) type which adjusts against at least one flat face of the tubular heating body, and advantageously two opposite flat faces.
• a supply circuit for the CTP (s),
• a temperature detection circuit controlling the start-up of the burner,

characterized in that at least one PTC plate is held in abutment on at least one flat face of the heating body by an advantageously rectangular wing made of highly thermally conductive material, of width substantially equal to that of the body and coming from the zone of intersection between said flat face of the body and the immediately adjacent face, said wing extending over practically the entire length of the heating body and having an adequate thickness so as to be able to be folded down properly in cooperation with adequate folding zones, against the opposite side of said PTC plate and thus recover the calories diffusing outside thereof.

According to the solution of the invention, such a heater has the advantage of recovering the inevitable heat losses on the external faces of the PTC plates by pumping and thermo-injection into the heater body thus contributing to a very marked improvement in the thermal efficiency of all.

Another object of the invention which contributes to strengthening the mechanical contact between the various elements participating in the heating, is to provide the heater with arrangements characterized in that the folding zones of each wing consist of a double preforming of their base from of their connection line with the heating body, such as during assembly by lateral pressure on a wing, the latter, -articulated first around its connection line, then around a second line parallel to said line connection to escape the thickness of the PTC plate, comes in position parallel to the contact face of the heating body while remaining in positive support over the entire external surface of the PTC plate.

According to this first general variant of the invention, it is clear that it is possible both to obtain intimate contact between the heating body and the wing which results therefrom, with the two active faces of the PTC plates.

According to a preferred variant of the invention, the heating body can be differently equipped to achieve the same end result and, in this sense, it is characterized in that a reserve of several plies is provided at the base of each wing which extends from its line of connection, first towards the outside and substantially in the plane of the contact face of the heating body with the plates, then performs a complete reversal in substantially a semicircle of diameter approximately equal to the thickness of the PTC plate to bring the contact face of the wing against the said plate by lateral pressure so as to hold it against the heating body in such a way that the wing remains well parallel to the contact face of the body and is, moreover, in positive support over the entire external surface of the same PTC plate.

• la figure 1 représente une vue en coupe longitudinale et en élévation du réchauffeur montrant l'ensemble monté ;
• la figure 2 représente en vue de gauche le réchauffeur de la figure 1 suivant le plan de coupe II-II ;
• la figure 3 est une vue de dessus du réchauffeur montrant dans un arrachement partiel en coupe la cale de contre-blocage du corps à l'intérieur de son enveloppe dans sa forme préférée de lame ressort ondulée ;
• la figure 4 est une vue en perspective du corps de chauffe seul muni de ses deux ailes latérales, l'une à gauche en position de fonctionnement, l'autre à droite en position inclinée avant montage des plaquettes CTP par pliage suivant la flèche F ;
• la figure 5 est une vue en perspective montrant par des arrachements successifs et juste avant leur insertion entre les ailes et le corps de chauffe de la figure 4, tous les éléments intermédiaires comprenant les éléments chauffants latéraux, la cale plastique et le circuit souple d'alimentation des plaquettes CTP, comprenant les électrodes et le raccordement au thermostat de régulation.

Other characteristics and advantages will emerge more clearly from the description which will be given below of a preferred example, although not limiting, of the heater for an oil burner in accordance with the invention with reference to the appended drawings in which:

• FIG. 1 represents a view in longitudinal section and in elevation of the heater showing the assembled assembly;
• Figure 2 shows in left view the heater of Figure 1 along the section plane II-II;
• Figure 3 is a top view of the heater showing in partial cutaway in section the blocking blocking of the body inside its envelope in its preferred form of wavy spring blade;
• Figure 4 is a perspective view of the only heating body with its two lateral wings, one on the left in the operating position, the other on the right in the inclined position before mounting the PTC plates by folding according to arrow F;
• Figure 5 is a perspective view showing by successive cutaway and just before their insertion between the wings and the heater body of Figure 4, all the intermediate elements comprising the lateral heating elements, the plastic shim and the flexible circuit supply of PTC plates, including electrodes and connection to thermostat of regulation.

Referring to Figures 1 to 3, the heater, according to its preferred embodiment, internally comprises a cylindrical casing 1 normally made of steel, having a diameter of 18.4 mm in its useful part and a total length of approximately 92 mm; these dimensions correspond to the dimensions widely used in other heaters; at one end of the casing 1 is fitted a connection assembly 2 to the burner pump and at the other, a device 3 allowing the heater to be connected to the spray nozzle of the burner (such connections are shown in thin phantom in Figures 1 and 3).

Inside the casing 1, is the heating body 4, the tubular shape of square cross section determines four rectangular outer faces, namely: two right and left side faces 4 a , 4 b , an upper face 4 c and a lower face 4 d ; the tubular heating body 4 is made of a highly thermally conductive material such as brass, copper or bronze and according to the most advantageous version of the invention, it is provided in the axis of the heating body 4, a longitudinal duct 5 opening out, of circular section, inside which the fuel oil to be heated can freely circulate to be heated there, or better still, flow through stuffing elements 6 such as, for example, sintered bronze balls or the like, thereby increasing the heat exchange surfaces between the heating body 4 and the fuel oil.

As an accessory to mounting, the inner duct 5 of the heating body 4 having, at each of its two ends, an O-ring 7 is mounted in a circular counterbore intended to receive, in a sealed manner, the connectors 2, 3 of the pipes coming respectively from the pump and the nozzle.

Coming to rest by one of their active faces, on the lateral faces 4 a and 4 b of the heating body 4, heating elements 8, 9 are arranged over the entire length of said body 4, over a height substantially identical to the width of the side faces 4 a , 4 b of the same body, in order to provide as large an exchange surface as possible between said heating elements 8,9 and the heating element 4.

According to an important characteristic of the invention, the heating elements 8, 9 are ceramic plates with a positive temperature coefficient (PTC); it is recalled here that such ceramics subjected to an electric current between their two active faces heat up and their internal resistance, unlike the conventional material, increases with temperature; at constant voltage, it follows that the current decreases and consequently, the absorbed power decreases: there results a self-limitation in temperature of these heating elements and consequently, a self-limitation of the production of heat energy.

We understand, therefore, that it is necessary to precisely calculate the power of such heating elements 8,9, and from this calculation that can be done by those skilled in the art, it will emerge an optimal thickness of the pads 8,9; Of course, the self-limiting phenomenon characteristic of PTC ceramics should also be taken into account and therefore, particular care should be taken of all thermal contact surfaces.

In addition to their positioning in support as intimate as possible on the side faces 4 a and 4 b of the body 4 by mechanical means incorporating the electrical supply circuit of the PTCs which will be detailed later, it is planned to recover the calories that can escape on the external faces of the two CTP plates 8.9. Indeed, if the calories emitted by the external faces of the CTP 8.9 were allowed to radiate naturally and taking into account the very poor coefficient of thermal conduction of the air, we would contribute to a very high rise in temperature of the ceramics 8.9, so that these would be very quickly limited in power and it would become difficult to obtain an acceptable thermal power.

In the context of the invention and according to its main characteristic, the external face of the CTPs 8.9 is coupled with lateral wings 10.11 arranged, as will be said later, in positive support over the entire external surface of each CTP , in order to pump the calories from these same external faces and bring them back to the heating body 4 where they can be thermally reinjected.

Finally, the entire heating body 4, plates 8.9, pumping wings 10.11 and supply circuit are slid into the casing 1 of the heater and interlocked between its inner wall and each side wing 10.11 by means two springs 12,13 mounted longitudinally by force, at the same time as the other parts.

Advantageously, the two springs 12, 13 are made up of blades preferably made of spring steel, wavy along their edge, providing an elastic effect well distributed over the entire length of the wings 10, 11, thanks to the tops of the corrugation which come alternately in support on the wings 10,11, then on the internal face of the envelope 1; it is clear that such a setting, in addition to centering the assembly mounted in the cylindrical casing 1 and blocking it in the suitable position, maintains a relatively high transverse pressure coming to clamp each lateral wing 10,11 on the external face of the 8,9 platelets and help to strengthen the support between the inner face of each of the wafers 8,9 with the sides 4 a and 4 b of the heating body 4.

This is an exceptionally advantageous arrangement since it contributes both to the mechanical stiffening of the device and to the maintenance of optimum thermal power, which in the same space imposed by the manufacturers will lead to heating of the fuel oil. optimum under conditions ideal thermal.

According to a particular and unexpected advantage of the invention, it is observed that the thermal short-circuit inevitably operated by the springs between the wings 10, 11 and the casing 1 creating incontestable heat losses is, in principle, largely compensated in that such a short circuit actually contributes to lowering the temperature of the PTC wafers, i.e. to a slight increase in their intrinsic power and it has been calculated that the final heat balance is clearly positive.

Finally and according to a particular variant, the shims with wavy spring 11,12 can be replaced by shims obtained from a strip, for example made of brass copper or the like, folded back on itself longitudinally, the two faces being brought together. 'from each other without contact to form a half moon in cross section; these shims can then be forced in, the flat side coming against the wings 10,11 and the semi-circular part against the casing 1.

According to a last characteristic of the invention, provision is made, at the end of at least one lateral wing 10, to extend it upwards in order to create an appendage 14 capable of being folded down on the upper face 4 c of the heating element 4 and to capture the temperature which advantageously comes to combine with that of the lateral wing from which the appendix 14 comes; of course, the appendix 14 has a width not exceeding the width of the upper face 4 c of the heating body 4 and has at least one surface capable of receiving the active face of a thermostat 15, the closing contact putting in operation the oil burner is established as soon as the temperature in appendix 14 corresponds to the ideal reheating temperature for spraying the oil with the nozzle.

Thus at the start, the heater is energized by pins 16.17 supplying the PCT plates 8.9, the burner not yet being supplied; fuel oil parked at this time in the heater just before the nozzle, therefore begins to heat up inside the duct 5 of the heating body 4, until reaching a correct spraying temperature which will then be detected by the thermostat 15, which can then switch, that is to say start the burner supplied by the two pins 17,18.

In accordance with FIGS. 4 and 5, the construction of the heating body 4 provided with its lateral recovery wings 10, 11 will be described more particularly below, as well as the system for connecting and mounting the pads 8, 9 around the same body. heating 4.

In accordance with FIG. 4, the heating body 4 of the heater, according to the preferred variant of the invention, is of tubular shape with square section whose width and length of the four faces 4 a , 4 b , 4 c , 4 d will be readily determined by those skilled in the art, depending on the type of oil burner and if necessary, taking into account the space available around said burner. The heating body 4 is, for example, obtained by spinning from a block of copper, brass or the like, traversed along its longitudinal axis by an advantageously circular duct 5 ensuring the passage of the fuel oil to be heated between the pump and the nozzle (not shown) of the oil burner. Incidentally and advantageously, the duct 5 is filled with packing elements 6 formed, for example, by small bronze balls held by any means such as sintering inside the duct 5 to increase the heat exchange surfaces between the fuel oil and the heating body 4, without too much hindering the flow of the fuel oil to be heated, which would cause a phenomenon of coking and would naturally lead to malfunction of the nozzle.

From the lower face 4 d of the body 4, the two lateral wings 10, 11 intended for pumping calories from the external faces of the CTP plates 8, 9 emerge, as was said above.

The wings 10, 11 are formed from copper, bronze or brass plates whose length and width are substantially equal to the length and width of the faces of the tubular heating body 4; the thickness of the side wings 10,11 depends on the PTC plates used and their thermal power delivered; those skilled in the art can perfectly adapt the thickness of these wings to achieve optimal pumping of the heat losses from the plates 8,9.

Each lateral wing 10, 11 must come into intimate contact with the external face of the plates 8, 9 which themselves must come into intimate contact with the lateral faces 4 a and 4 b of the heating body 4; this implies that the wings 10,11 are parallel to the lateral faces 4a and 4b of said body, after mounting of the pads 8,9.

According to the invention, this result is obtained by thermally bonding the two wings 10, 11 joined together by a common base 19, the central and horizontal part of which exactly matches the lower face 4 d of the heating body 4 to which said base 19 is secured by brazing or equivalent. On either side of this base 19, the lateral wings 10, 11 are connected, which by adequate folding can be folded vertically to bear against the external faces of the plates 8, 9; this simple assembly makes it possible in theory to carry out the pumping of heat losses as has been said; however, to ensure proper final positioning, that is to say vertical on the drawings of the wings 10, 11, there is provided, according to the invention, a bead 4 e extending along the midline of the face lower 4 d of the heating body 4, obtained directly by spinning, making it possible to precisely position the base 19 which is provided with a hollow rib along its median line that upon assembly it marries said bead 4 e , after having inserted a thin layer of solder for welding the two parts; in the same way, it is planned to preform the base of each wing ; the purpose of this preforming is to reserve material to take account of the thickness of the PTC plates 8.9 when, for example, by folding according to arrow F in FIG. 4, the wing 11 against the face external of said CTP plates 8.9. According to a first variant, the base of each wing is preformed by a first downward folding, from the connection line 20 to the heating body 4, then by a complete reversal according to an arc of circle of diameter equal to the thickness of the pads 8,9, the vertical portion is folded and flat 10a, 11a of the side flanges 10,11 for supplying and vertically parallel to the faces 4a, 4b of the heating body 4 (this first embodiment is not shown in Figure 4).

According to another variant of the invention, the vertical and flat part 10 a , 11 has lateral wings 10,11 will simply be connected to the heating body 4 by preforming the connection zone consisting of two successive folds from the connection line 20 to the heating body 4; the base of each wing then extends along a first surface 21 towards the outside and in the extension of the lateral contact faces 4 a , 4 b of the heating body 4; according to a first folding carried out along a line 22 parallel to the connection line 20, the flaps 10.11 are folded outwards and upwards, at an angle a; then a second folding along a new line 24 parallel to the previous two 20,22 is carried out in the same direction at an angle β making it possible to bring the vertical part 10 a , 11 a of each wing in position parallel to the lateral surfaces 4 a , 4 b of body 4; it will be noted that advantageously, the angle of folding α is equal to 45 ° and the angle β equal to approximately 135 °; indeed, it is important that the heating body 4 is centered on the axis of the casing 1 of the heater, which leads to choosing an angle of 45 ° so that the part 23 of the basic preforming comes to register enough precisely on the inner wall of the envelope 1. Under these conditions, a simple calculation shows that the vertical part of the preforming coming from the body 4 from the connection line 20 must be of a length practically equal to the thickness of the CTP plates 8, 9 and likewise, the distance between the two parallel fold lines 22.24 must be equal to the thickness of the CTP plates multiplied by √2; it also follows that the fold line 24 must then be substantially at the same level as the connection line 20 (see cross section of the assembly mounted in Figure 2).

According to a particular characteristic of the invention, provision is also made to extend one of the two lateral wings 10,11 upwards, at least over part of its length to form an appendage 14 capable of being folded down on the face. upper 4 c of the heating body 4, after complete assembly of said body and its heating and supply system, as said; this involves capturing the temperature of said body as accurately as possible by means of a thermostat 15 disposed on the upper surface of appendix 14, in order to trigger the start-up of the burner as soon as the desired heating oil temperature is reached. Of course, the shape of the appendage 14 depends on the shape of the bearing face of the thermostat 15.

In accordance with FIG. 5, there will now be described the mounting of the CTPs 8.9 on the heating body 4 as well as their supply system.

The plates are mounted on either side of the body thanks to a plastic wedge 25 having the general shape of a stirrup whose length is equal to the length of said body, its width and its height being substantially equal to the widths of the lateral faces. of the same body 4; the stirrup wedge 25 is intended to come over the heating body 4 from above. The thickness of the wedge 25 is slightly less than the thickness of the PTC plates 8.9 so that they can be embedded therein. lateral cuts 25 a , 25 b made exactly at the level of the lateral support faces 4 a , 4 b of the heating body 4, without the wedge 25 preventing the wings 10,11 from coming to be applied as intimately as possible on the active faces of the PTCs.

The mounting and above all the correct and final positioning of the PTC 8.9 plates are thus considerably facilitated by the bracket 25.

According to particular variants of the invention, it may be advantageous to replace one of the plates CTP 8,9 or both moreover, by a succession, a combination, a juxtaposition or a stack of two or more plates whose dimensions and the thermal characteristics may vary and even be significantly different, while remaining within the dimensional space or the cutouts 25 a and / or 25 b of the spacer 25.

One can, for example, use on a cut 25 a of the wedge 25 two or more plates side by side having different temperatures to obtain a desired final temperature, while not modifying anything on the other cut 25 b or, on the contrary , by juxtaposing other elements of different characteristics or not. This makes it easier to use standardized, less expensive elements to achieve various reheating temperatures that meet user requirements.

The electrical supply of the CTP 8,9 plates is advantageously, but not necessarily, via a flexible circuit 26 which envelops the wings of the plastic stirrup 25 equipped in its lateral cutouts 25 a , 25 b of the plates CTP 8,9, so that electrodes 27,28 made for example of thin conductive strips of tinned copper or aluminum printed in the flexible circuit 26 come exactly into contact with the two lateral faces of the CTP plates 8,9, as illustrated in FIG. 5. The flexible circuit 26 (not shown in the drawings) comprising printed connections supplies the electrodes 27, 28 placed in parallel, and connected to the heater power source.

• montage des plaquettes CTP à l'intérieur des découpes latérales prévues dans l'étrier de calage 25 réalisé préférentiellement dans un matériau plastique ;
• mise en place du circuit souple 26 venant envelopper les deux ailes verticales de l'étrier plastique ; l'ensemble est ensuite monté sur le corps de chauffe 4, les ailes latérales de l'étrier plastique 25 venant guider les plaquettes CTP et le circuit souple 26 dans l'espace compris entre les ailes de pompage 10,11 et les faces latérales 4a,4b du corps de chauffe 4. Lorsque l'étrier 25 est au contact de la surface supérieure 4c du corps 4, on rabat les deux ailes latérales planes 10a,11a sur les ailes de l'étrier 25 ; l'appendice 14 est ensuite rabattu contre la face supérieure 4c du corps de chauffe 4 pour venir contre la partie supérieure de l'étrier 25 ;
• on monte les ressorts ondulés 12,13 contre les faces externes des ailes latérales 10a et 11a qui sont munies à cet effet d'encoches 30 à leurs extrémités verticales permettant de recevoir les extrémités courbées 29 des ressorts 12,13 et ainsi les maintenir en place, notamment longitudinalement ;
• on introduit à force l'ensemble ainsi constitué à l'intérieur de l'enveloppe 1 du réchauffeur : compte tenu de la géométrie des éléments en présence, on comprend qu'il y ait centrage automatique du corps de chauffe 4 dans l'enveloppe 1 en même temps ;
• enfin, on dispose, grâce à une lumière prévue à cet effet sur l'enveloppe 1 (non représentée sur les dessins), le thermostat 15 correctement relié au circuit souple 26.

The steps for mounting the heater according to the preferred variant of the invention are now clearly understood:

• mounting of the PTC plates inside the lateral cutouts provided in the wedging stirrup 25 preferably made of a plastic material;
• fitting of the flexible circuit 26 which envelops the two vertical wings of the plastic stirrup; the assembly is then mounted on the heating body 4, the lateral wings of the plastic stirrup 25 coming to guide the PTC plates and the flexible circuit 26 in the space between the pumping wings 10,11 and the lateral faces 4 a , 4 b of the heating body 4. When the stirrup 25 is in contact with the upper surface 4 c of the body 4, the two flat lateral wings 10 a , 11 a are folded over the wings of the stirrup 25; the appendix 14 is then folded against the upper face 4 c of the heating body 4 to come against the upper part of the stirrup 25;
• the wavy springs 12, 13 are mounted against the external faces of the lateral wings 10 a and 11 a which are provided for this purpose with notches 30 at their vertical ends making it possible to receive the curved ends 29 of the springs 12, 13 and thus to maintain them in place, especially longitudinally;
• the assembly thus formed is forced into the interior of the casing 1 of the heater: taking into account the geometry of the elements present, it is understood that there is automatic centering of the heating body 4 in the casing 1 at the same time ;
• finally, by means of a light provided for this purpose on the casing 1 (not shown in the drawings), the thermostat 15 is correctly connected to the flexible circuit 26.

Claims (17)

Oil burner heater comprising, inside a cylindrical casing (1): a tubular heating body (4) made of highly thermally conductive material, of advantageously square cross section, traversed longitudinally by at least one duct (5) of circular section provided with means (2,3,7) for tight coupling, on one side to a pressure supply of the fuel oil to be heated and on the other to the burner nozzle holder, - at least one heating element in the form of a plate (8, 9) of the positive temperature coefficient (PTC) type which adjusts against at least one flat face (4 a , 4 b ) of the tubular heating body (4) , and advantageously two opposite flat faces. - a supply circuit (26) of the PTC (s), - a temperature detection circuit (15) controlling the start-up of the burner, characterized in that at least one PTC plate (8, 9) is held in abutment on at least one flat face (4 a , 4 b ) of the heating body (4) by a wing (10, 11) advantageously rectangular in material strongly thermally conductive, of width substantially equal to that of the body (4) and coming from the area of intersection between said flat face of the body (4 a , 4 b ) and the immediately adjacent face (4 d ), said wing ( 10,11) extending over practically the entire length of the heating body (4) and having an adequate thickness so that it can be folded down properly in external cooperation with suitable folding zones (20 to 24), against the opposite external face of said PTC plate (8,9) and thus recover the calories diffusing outside of it. Heater according to the preceding claim, characterized in that the folding zones of each wing (10,11) consist of a double preforming of their base from their connection line (20) with the heating body (4), such that during pressure mounting lateral (F) on a wing (10,11), the latter, articulated first around its connection line (20) then around a second line parallel to said connection line to escape the thickness of the PTC plate (8,9), comes in position parallel to the contact face (4 a , 4 b ) of the heating body (4) while remaining in positive support over the entire external surface of said PTC plate. Heater according to claim 1 characterized in that a reserve is provided at the base of each wing (10,11) which extends from its connection line (20), first outwards and substantially in the plane of the contact face (4 a , 4 b ) of the heating body (4) with the plates (8, 9), then performs a complete inversion following substantially a semicircle of diameter normally equal to the thickness of the PTC plate (8,9) to bring by side pressure (F) the contact face of the wing (10,11) against said plate to thus hold it against the heating body (4) so that the wing remains well parallel to the contact face (4 a , 4 b ) of the body and is, moreover, in positive support over the entire external surface of the same PTC plate (8, 9). Heater according to claim 3 characterized in that the reserve is obtained by successive folding (22,24) of the wing (10,11) from its connection line (20), to form: - a first surface (21) in the extension and outside of the contact face (4 a , 4 b ) of the PTC plates (8, 9) on the body, - a second surface (23) connected to the first (21) by a fold line (22) parallel to the connection line (20) and forming therewith an angle a of approximately 45 ° towards the outside, - A third surface (11a) connected to the second (23) by a fold line (24) parallel to the previous one and forming with the second surface (23) an angle β of about 135 ° so as to bring it towards the body (4) in position substantially parallel to the contact face (4 a , 4 b ), the width of each surface corresponding successively to the width of the PTC plates (8,9) for the third (11 a ), at the thickness of the wafer multiplied by √2 approximately for the second (23) and approximately the thickness of the wafer for the first surface (21). Heater according to any one of the preceding claims, characterized in that the lateral wings (10,11) are joined by a common base (19) which closely follows the lower face (4 d ) of the heating body (4) to which it is soldered or equivalent. Heater according to the preceding claim characterized in that a bead (4 e ), extending along the midline of the lower face (4 d ) of the body (4) comes to cooperate with a hollow rib, corresponding to it, on the base (19) connecting the two lateral wings (10,11), a brazing layer being advantageously interposed between the face (4 d ) and the base (19) for welding the parts. Heater according to any one of the preceding claims, characterized in that the electrical supply of the PTC plates (8,9) is obtained by inserting a first electrode (27) between said plate (8,9) and the contact face (4 a , 4 b ) on the body (4), the second electrode (27) being interposed between the wing (10,11) and the opposite face of the plate (8,9). Heater according to claim 7 characterized in that the electrodes (27,28) are constituted by thin conductive strips for example of tinned copper or aluminum, coming to cover approximately all of the opposite active faces of the PTC plates (8,9). Heater according to claim 7 characterized in that the electrical connections putting the PTC plates under tension are effected by a flexible circuit (26). A heater according to any one of previous claims characterized in that the CTP plates (8,9) are embedded according to their thickness inside cutouts (25 a , 25 b ) of a plastic wedge (25) keeping them on the one hand away from isolation and on the other hand in an adequate position with respect to the electrodes 27,28 between the wings (10,11) and the heating body (4), the shim (25) advantageously taking the form of a stirrup when having PTC plates (8,9) on two opposite flat faces (4 a , 4 b ) of the heating body (4). Heater according to any one of the preceding claims, characterized in that a wing (10,11) of the heating body (4) is extended in height and over at least part of its length to form an appendage (14) capable of receive a thermostatic sensor (15), the appendage (14) being folded against the upper face (4 c ) of the heating body (4), after mounting the PTC plates (8,9) on the side face (s) (4 a , 4 b ) of the body (4). Heater according to any one of the preceding claims, characterized in that the internal duct (s) (5) of the heating body (4) are provided with stuffing elements (16) such as balls or the like to increase the exchange surface without obstructing the duct (s) (5). Heater according to any one of the preceding claims, provided with heating elements (8, 9) on two opposite flat faces (4 a , 4 b ) of the heater body (4) characterized in that a shim ( 12,13) between the inner face of the casing (1) and the outer lateral face of the wings (10,11) in the folded position on the PTC plates (8,9) in contact with the heating body (4) in the purpose of locking the assembly in the envelope (1) and creating a thermal short circuit between it and the wings (10,11). Heater according to the preceding claim characterized in that the shims (12,13) are blades, of preferably in spring steel, longitudinal and wavy along their edges to provide a spring effect well distributed over the entire length of the wings (10,11) to guarantee positive and permanent contact with the PTC plates (8,9). Heater according to claim 13 characterized in that the longitudinal wedges (12,13) are produced from a strip folded longitudinally on itself, the two faces being brought close to each other without contact, of cross section generally in the shape of a half-moon of length normally equal to the length of the wings (10,11), the spring effect resulting from the compression between the semi-circular part on the internal wall of the envelope (1) and the face plane resting on the wings (10,11) ensuring positive and permanent contact with the CTP. Heater according to the preceding claim characterized in that the shims (12,13) are made of copper, brass or the like. Heater according to any one of the preceding claims, characterized in that each CTP (8,9) can result from a combination, a juxtaposition or a stacking of two or more elementary plates whose total size is identical to that of CTP (8,9), but whose thermal characteristics can be different from one elementary plate to another.

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