Electric fluid preheating unit in a pipe or container

Abstract

Fluid preheating unit designed to be attached to a pipe or container of a fluid to be heated, characterized in that it comprises: - at least two heating elements (120), each consisting of a metal tube (121) closed at one end and containing a heating element for immersion in the fluid, wherein this tube terminates at its end (123) (head part) in an output terminal (124) connected to the power supply, the tube itself being connected to one end of the element (122) for grounding, - an electrically conductive connecting plate (110) provided with receptacles (112) for receiving the head part (123) of each tube and with fastening devices (113) for connecting to the pipe / container, - an electrically insulating plate (130),which covers the receptacles (112) of the head parts (123) of the tubes (121) and is traversed by the connecting pins (124) of the heating elements (120), - a terminal strip (140) above the electrically insulating plate (130) to which the connecting pins (124) are attached, this strip (140) having a single mains plug (142), and - a projection (150) that covers the strip (140) and the electrically insulating plate (130) in order to be attached to the connecting plate (110) by leaving the mains plug (142) protruding.

Description

Field of the InventionThe present invention relates to an electric fluid preheating unit intended to be mounted in a conduit or container of a fluid to be heated. The fluid may be air, for example feed air of an engine, or a liquid or a gas contained in a container or flowing in a conduit or in a container.Prior ArtHeating elements such as glow plugs are already available which are intended to preheat the combustion chamber of a diesel engine and to assist / allow the start of the engine.Such a glow plug is shown in Fig. 4, and its installation for preheating a fluid is shown in Fig. 5.As shown in Fig. 4, the heater element 1 in the form of a glow plug is constituted by a glow plug which is a tubular member 11 in which a heating resistor is accommodated to heat the metallic shell which radiates and heats the environment.The heating element 1 terminates in the upper portion by a terminal pin 12 entering a plug connector 13, the unit also being provided with a plug body 14 which is screwed into the housing of the motor. In the case of an automobile manufacturer, the plug connector 13 receives the dedicated connector 15 of the customer (FIG. 5 ).The plug body 14 has a seal 16 and is separated from the plug connector 13 by an insulating washer 17.FIG. 5 is a very schematic sectional view of a housing 20 delimiting a chamber of a fluid 21 to be heated. This housing (container, conduit) is provided with a plurality, for example two, of glow pins 1 or glow elements, which partly open into the chamber of the fluid 21.These heating elements are similar to those described above; they must be individually connected to the power supply at the source and screwed through their body 14 into the housing 20.DE 600 16 700 T2 discloses a mounting structure for a glow plug, DE 40 01 538 A1 discloses a pre-glow device for diesel engines, and DE 32 29 648 A1 discloses an automatic device for the rapid heating of liquids.Object of the inventionThe present invention aims to provide a simple means for incorporating glow plug type heating elements into a conduit or container for heating a fluid.PRESENTATION AND ADVANTAGES OF THE INVENTIONTo this end, the invention relates to a fluid preheating unit intended to be attached to a conduit or a container of a fluid to be heated, characterized in that it comprises:at least two heating elements each consisting of a metal tube closed at one end and housing a heating resistor for being immersed in the fluid, said tube terminating at its mouth end (head portion) in an output connecting pin connected to the power supply, said tube itself being connected to one end of the resistor for being grounded,an electrically conductive connecting plate,* which is provided with receptacles for receiving each the head part of a pipe and with fastening means for being connected to the pipe / container,an electrically insulating plate covering the seats of the heads of the tubes and crossed by the terminals of the heating elements,a connector bar over the electrically insulating plate to which the connector pins are attached, said bar having a power plug; andan overmould covering the strip and the electrically insulating plate to be fixed to the connection plate by leaving the mains plug protruding.The preheating unit according to the invention has the advantage of facilitating the assembly of glow elements in a pipe or a container by simplifying the connection, since there is a single distributor for the preheating unit, irrespective of the number of heating elements that this unit is to be fitted, i.e. the number depending on the power that this preheating unit is to deliver. Their installation in the conduit or fluid container is also very simple, since there is only one device to be inserted and fastened.The same simple application is found in maintenance in case of failure for the replacement of a heating element or the entire preheating unit.Unit space requirements are also greatly reduced and the uniformity of the pre-heating unit instead of many heater elements to be incorporated also simplifies the design of the infrastructure incorporating this pre-heating unit.According to a further advantageous feature, the connecting plate has shafts which form the receptacles for the head parts of the various heating elements.This connecting plate with slots, and in particular if these slots are made with an overthickness of the plate, which also has fixing lugs and an over-forming groove in the periphery of the overthickness, facilitates the insertion of the head part of the heating elements and in particular the firm fixing of these heating elements by a welded connection or by a press-fit, which simultaneously ensures the tightness and the compressive strength and the grounding by means of the electrically conductive connecting plate.According to a further advantageous feature, the connecting pins are welded to the terminal strip.According to a further advantageous feature, the heating elements are distributed in series or according to a two-dimensional arrangement on or in the connecting plate.According to a further advantageous feature, the electrically conductive plate is made of metal.The invention also relates to a production method of such a preheating unit, which is characterized in thatan electrically conductive plate having receptacles for receiving the heating elements is produced, each of which consists of a metal tube, one end of which is closed and the other end of which forms the head part from which a connecting pin insulated with respect to the tube emerges,the head part of the heating elements is fastened in the receptacles of the connecting plate in such a way that the connecting pins project beyond the plate,covering the plate and the heating elements with an electrically insulating plate by passing only the connecting pins through,then covering the electrically insulating plate with a terminal strip which is welded to the terminal pins and installing a single power plug on the terminal strip,the terminal strip, the electrically insulating plate and the connecting plate are covered around their part receiving the head parts of the heating elements with an electrically insulating overmoulding by leaving the single mains plug projecting.This manufacturing process is extremely simple, both in the manufacture of the components forming the preheating unit and in their assembly.DRAWINGSThe present invention will be described in greater detail below with the aid of an embodiment of a fluid preheating unit and its manufacturing method illustrated in the accompanying drawings, in which:FIG. 1 is a sectional view of an embodiment of a preheating unit,FIG. 2 is an example of installation of the preheating unit of FIG. 1 in a fluid line,FIGS. 3A-3F show the various steps of the method of manufacturing a fluid preheating unit according to the invention,FIG. 4 is a schematic view of a glow plug according to the prior art,FIG. 5 shows the installation of two glow plugs into a fluid housing according to the current prior art.DESCRIPTION OF EMBODIMENTS OF THE INVENTIONAccording to FIG. 1, the invention relates to a fluid preheating unit 100 intended to be attached to a conduit or a container of a fluid to be heated. The preheating unit 100 consists of an electrically conductive connecting plate 110 in which heating elements 120 are held.Referring to Figs. 1 and 3A, a heating element 120 is comprised of a metal tube 121 which is closed at one end 122 (lower end) and the other orifice end or head portion 123 of which has a positive supply pin 124 projecting therefrom. The heating element 120 accommodates a heating resistor, one end of which is fixed to the metal tube 121, 122, and the other is connected to the positive supply pin 124. The energization of this heater element 120 is provided by the supply pin 124 and return is provided through the grounded metallic heater tube.The connecting plate 110 forms receptacles or slots 112 consisting of through-holes having a diameter substantially equal to that of the head portion of the heating elements 120 to receive and transversely hold them.In fact, the connecting plate 110 has an overthickness 111 in which the slots 112 are inserted, thus having a good length for supporting the heating elements 120. Beyond the overthickness 111, the connecting plate has fastening tabs 113 traversed by screw holes 116. The periphery of the connecting plate 110 has an overmoulding groove 114 and the bottom of the plate has a groove 115 surrounding the surface of the installation site of the wells 112 to receive a seal when it is connected to the pipe or container to ensure tightness.The plate 110 is covered by an electrically insulating plate 130 crossed by the supply pins 124 of the heating elements 120. The insulating plate 130 is itself covered by an electrical terminal block 140 which is connected to the terminal pins 124. These pins 124 are welded in particular to the terminal strip 140.The side of the terminal block 140 opposite to that of the terminal pins 124 has a power plug 142 protruding therefrom.The unit is covered by an overmould 150 which allows the mains plug 142 to protrude but covers the electrical connector 140 and the insulating plate 130 to be clipped in the groove 114 under the edge of the connection plate 110.The above-described fluid preheating unit 100 may be installed on or against the wall of a container or on or against the wall of a liquid pipe 200, as shown in FIG. 2. The attachment of the pre-heating unit 100 is by means of its connecting plate 110 and bolts 116 carried by the pipe or container, which pass through the screw holes 117 and receive the connecting lugs 113 of the pre-heating unit 100, with the insertion of a seal in the groove 115.The heating elements 120 are distributed in the connection plate 110 according to a linear or offset arrangement or, more generally, in the two directions of the plane of the connection plate 110 so as to as effectively enter as possible the medium to be preheated contained in or flowing in the conduit or the container.In this unit 100, the tubular heating elements 120 are oriented substantially perpendicular to the plane of the connecting plate 110.FIGS. 3A-3F show the various manufacturing steps of the fluid preheat unit 100 described above.Thus, Figure 3A shows the fabrication of the connecting plate 110 with the through holes forming wells 112 in the plate overthickness 111 to receive the head portion 123 of the separately fabricated tubular members 120. These tubular members 120 are preferably manufactured to have uniform electrical power to obtain the desired power for the preheat unit 100 by the combination of an appropriate number of heating elements 120. The heating elements 120 are inserted through their head part 123 into the shafts 112 of the connecting plate 110 by being firmly connected to the connecting plate 110 by adhesive bonding or press-fitting or also by welding or overmolding. The assembly must ensure a tightness at a certain pressure, for example 10 bar, between the heating elements 120 and the connection plate 110 and at the same time ensure good electric current conductivity between the tubes 121 of the heating elements 120 and the connection plate 110 for the electrical ground return.The number of heating elements depends on the power desired for the preheat unit 100.After the insertion of the heating elements 120 into the connection plate 110, the unit shown in FIG. 3B is obtained.The following step (FIG. 3C ) is to insert the electrically insulating plate 130 to cover the top of the tops 123 of the heating elements 120 and to let only the electrical connection pins 124 of each of the heating elements 120 pass through this electrically insulating plate, the ground return being effected by the contact between the metallic shell 121 of each heating element 120 and the electrically conductive connection plate 110, in particular a metal plate. The insulation plate 130 provides electrical insulation between the terminal block 140 and the heating element tubes 121 that provide ground return through the connector plate 110. The insulating plate 130 must withstand constant operating temperatures over time, on the order of 150 to 180°C.Referring to Fig. 3D, the following step is to install the terminal block 140 on the tip ends of the terminal pins 124 of each of the heating elements. These pins 124 are inserted into and fixed to the terminal block 140, for example, by welded joints 141. After welding the pins 124 to the ledge 140 by welded joints 141, the common power connector 142 is installed by welding it to the ledge 140. The welded joints can be laser welded joints, TIG welded joints, or else spot welded joints. The welded connections must not damage the surrounding components.The unit thus produced (Fig. 3E) is ready to receive the insulation overmolding 150, which, according to Fig. 3F, is snapped onto the perimeter of the connecting plate 110 at the overmolding groove 114, which forms an undercut portion, in order to ensure a permanent coupling between the assemblage of the overmolding and the connecting plate 110.The insulation hood 150 formed by the overmolding is preferably made of an electrically insulating composite material in order to create a tight enclosure that ensures, in time, the power supply function of the terminals by means of the power plug 142 and the electrical connector 140 while avoiding short circuits with elements outside the preheating unit 100, cleaning fluids of the engine, brake fluid or engine oil. The overmolding 150 comprises the entirety of the components and seals the system in the area of the overmolding groove 114 and the power plug 142. Thus constructed, the preheating unit 100 can be installed at any position without fear of malfunction.The fluid preheat unit 100 is then ready and ready to be attached to a conduit or container.This preheating unit 100 makes it possible to have different preheating powers depending on the number and individual power of each heating element 120 integrated into the preheating unit 100. By standardization of the manufacture, it is thus possible to cover a very large range of heating powers with standard heating elements.In practice, the heating elements are provided for the usual DC voltages of 6, 12, 18, 24 and 48 volts. The 12 volt supply is the most common. In the case of a supply of below 12 volts, the preheat unit 100 is provided to supply powers of 1,000 to 1,200 W for four preheat elements when these elements are designed to supply a single power on the order of 250 to 300 W. The starting current of a preheating unit of four elements of 300 W is about 130 A for a few tenths of a second, then this current drops to 40 A, which rapidly stabilizes after a few operating seconds.This preheating unit can be controlled by its power supply, for example by means of additional equipment such as a thermostat in front of and / or behind the fluid to be heated with respect to the position of the preheating unit.The fluid preheating unit 100 according to the invention is advantageously used in tubular lines or containers, i.e. planar or curved surfaces, for many applications such as preheating the hydraulic fluid of underground construction machines such as excavators or the like, in order to quickly reach the temperature of use of the hydraulic fluid before the start of the main engine, or also for preheating the hydraulic fluid of the high-pressure units of industrial machines, or also for keeping a central heating circuit warm or frost-free when the heating boiler is deactivated, or also in the food sector for preheating edible oil or water.The invention also relates to the automotive sector for preheating a cooling liquid, for accelerating the temperature rise of the exhaust gases for optimum operation of the particulate filter, or also for additional heating with air circulation of the truck cabins and of small transporters, without these examples being in any way restrictive.LIST OF REFERENCE CHARACTERS1 Conventional glow plug 11 tubular element 12 terminal pin 13 plug connector 14 plug body 15 customer connector 16 seal 17 insulating disk 20 housing 21 enclosure for fluid to be heated 22 fastening screw 100 fluid preheating unit 110 connecting plate 111 shaft-shaped overthickness 112 shaft 113 fastening tab 114 overmoulding groove 115 seal-receiving groove 116 bolt / screw 120 heating element 121 metal tube 122 lower end (welding zone resistance / tube) 123 head part / tube 124 positive terminal pin 130 electrically insulating plate 140 terminal strip 141 welded connection pin / strip 142 common mains plug 150 overmoulding 200 line / liquid container

Claims

Fluid preheating unit intended to be fixed to a pipe or a container of a fluid to be heated, characterized in that it comprises: - at least two heating elements (120) each consisting of a metal tube (121) closed at one end and in which a heating resistor is housed in order to be immersed in the fluid, this tube terminating at its mouth end (123) (head part) in an output connecting pin (124) connected to the power supply, the tube itself being connected to one end of the resistor (122) in order to be grounded, - an electrically conductive connection plate (110) provided with seats (112) in order to receive each head part (123) of a tube and with fixing means (113) in order to be connected to the pipe / container, an electrically insulating plate (130) covering the seats (112) of the headers (123) of the tubes (121) and crossed by the terminal pins (124) of the heating elements (120), a terminal strip (140) above the electrically insulating plate (130) to which the terminal pins (124) are attached, this strip (140) having a single power plug (142), and an overmoulding (150) covering the strip (140) and the electrically insulating plate (130) to be attached to the connection plate (110) by leaving the power plug (142) protruding.Preheating unit according to Claim 1, characterized in that the connecting plate (110) has shafts (112) which form the receptacles for the head parts (123) of the various heating elements (120).Preheating unit according to claim 2, characterised in that the slots (112) are made in an overthickness (111) of the plate (110) having fixing lugs (113), the periphery of the plate (110) being provided with an overmoulding groove (114).Preheating unit according to Claim 1, characterized in that the connecting pins (124) are welded to the connecting strip (140).Preheating unit according to claim 1, characterised in that the heating elements (120) are distributed in series or according to a two-dimensional arrangement on the connecting plate (110).Preheating unit according to claim 1, characterised in that the electrically conductive plate (110) is made of metal.Method for manufacturing a preheating unit according to any one of claims 1 to 6, characterised in that - an electrically conductive plate is produced with seats (112) for receiving the heating elements (120), which consist of a metal tube (121), one end (122) of which is closed and the other end (123) forms the head part from which a terminal pin (124), which is insulated with respect to the tube (121), emerges, - the head part (123) of the heating elements (120) is fastened in the seats (112) of the connecting plate (110) in such a way that the terminal pins (124) project beyond the plate, - the plate and the heating elements of an electrically insulating plate (130) are covered by only passing through the terminal pins (124), - then the electrically insulating plate (130) is covered with a terminal strip (140), which is welded to the terminal pins (124) and a power plug (142) is installed on the terminal strip (140), the terminal strip (140), the electrically insulating plate (130) and the connecting plate (110) are covered around their part accommodating the head parts (123) of the heating elements (120) with an electrically insulating overmould by allowing the power plug (142) to protrude.

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