DK159359B

DK159359B - Apparatus for heating up a liquid in a closed plastic container

Info

Publication number: DK159359B
Application number: DK141086A
Authority: DK
Inventors: Amilcare Dogliotti
Original assignee: Ferrero Spa
Priority date: 1977-10-14
Filing date: 1986-03-26
Publication date: 1990-10-01
Also published as: DK159359C; DK141086D0; DK141086A

Description

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Opfindelsen angår et apparat til opvarmning af en væske i en beholder af termoplast, der er lukket tæt ved hjælp af et metallåg, omfattende en kombination af bæreorganer for beholderen indrettet til at gribe be-5 holderen i omvendt stilling, et modstandsopvarmningsorgan anbragt således i forhold til bæreorganerne, at det under hele opvarmningsprocessen er i termisk berøring med praktisk taget hele metallåget af den på hovedet vendende beholder, og en elektronisk styreenhed 10 for opvarmningsorganet forbundet til en strømforsyningskilde gennem en hovedafbryder , hvilken styreenhed omfatter en Wheatstone-bro fødet ved hjælp af strømtilførselsledninger, som er forbundet til indgangsklemmer for den elektroniske styreenhed, hvor modstandsopvarm-15 ningorganet indgår i en af Wheatstone-broens grene, hvilken bro på en målediagonal frembringer et signal til indikering af den af opvarmningsorganets modstand opnåede temperatur.BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an apparatus for heating a liquid in a thermoplastic container closed tightly by means of a metal lid, comprising a combination of carrier means for the container arranged to engage the container in the reverse position, a resistance heating means thus disposed in relation to to the support means that during the entire heating process it is in thermal contact with practically the entire metal lid of the head-facing container and an electronic control unit 10 for the heating means connected to a power supply source through a main switch, which control unit comprises a Wheatstone bridge fed by means of a power supply lines connected to input terminals of the electronic control unit, wherein the resistance heating means is included in one of the branches of the Wheatstone bridge, which bridge on a measuring diagonal generates a signal to indicate the temperature obtained by the heating element resistance.

Fra beskrivelsen til US patent nr. 3.789.190 20 kender man en kobling til regulering af et elektrisk varmelegemes temperatur, hvilken kobling bl.a. indbefatter en Wheatstone-bro, hvis ene målediagonal afgiver et styresignal til en reguleringskreds, og hvor broens anden diagonal er koblet over varmelegemet, hvis tempe-25 ratur skal reguleres.From the specification of US Patent No. 3,789,190 there is known a coupling for controlling the temperature of an electric heater. includes a Wheatstone bridge whose one measurement diagonal outputs a control signal to a control circuit and the second diagonal of the bridge is coupled over the heater whose temperature is to be controlled.

Denne kendte kobling har primært til formål at regulere temperaturen på en given værdi og udnytter derfor selve varmelegemet både som varmeelement og varme-føler.This known coupling is primarily intended to regulate the temperature at a given value and therefore utilizes the heater itself as both a heating element and a heat sensor.

30 Hvis man imidlertid, denne kendte teknik taget i betragtning, står over for det problem at skulle opvarme en væske i en beholder af termoplast, må der tages særlige forholdsregler, idet det f.eks. er vigtigt, at opvarmningen sker uden beskadigelse af beholderen.30 However, if this prior art is considered, one has to face the problem of heating a liquid in a thermoplastic container, special precautions must be taken. It is important that the heating is done without damaging the container.

35 Apparater af den indledningsvis angivne art finder især anvendelse, hvor man til anvendelse for travle folk, f.eks. på jernbanestationer, i forlystelsesetablissementer eller på arbejdspladser, har behov 235 Apparatus of the kind mentioned above are particularly applicable where one is used for busy people, e.g. in railway stations, in entertainment establishments or in workplaces, needs 2

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for på meget kort tid at kunne opvarme en drikkevare til den, for den pågældende drikkevares indtagelse, optimale temperatur, typisk af størrelsesorden 50°C.to be able to heat a beverage to the optimum temperature for the drink in question in a very short time, typically of the order of 50 ° C.

Det er følgelig opfindelsens formål at tilveje-5 bringe en styreenhed til styring af apparatet således, at drikkevaren hurtigt bringes op på den ønskede temperatur, at opvarmningen ophører, når den nødvendige varme er tilført, og at opvarmningen, der sker ved hjælp af et elektrisk modstandsopvarmningsorgan, sker 10 uden at beholderens plastmateriale beskadiges.Accordingly, it is the object of the invention to provide a control unit for controlling the apparatus such that the beverage is rapidly brought up to the desired temperature, that heating ceases when the necessary heat is supplied and that the heating occurs by means of an electric resistance heating means, 10 occurs without damaging the plastic material of the container.

Disse formål opfyldes ved et apparat af den indledningsvis nævnte art, hvilket apparat ifølge opfindelsen er ejendommeligt ved a) en reguleringskreds til regulering af strøm-15 tilførslen til Wheatstone-broen i afhængighed af signalet på broens målediagonal, så at opvarmningsorganets temperatur efter en indledende transient fase i hovedsagen forbliver inden for et bestemt interval under hele væskens opvarmningsperiode, og 20 b) en tidsstyreenhed indrettet til efter en bestemt tid, regnet fra det øjeblik opvarmningen begynder, at afbryde for strømtilførslen til Wheatstone-broen ved -hjælp af reguleringskredsen og at åbne hovedafbryderen til frakobling af styreenheden fra strømforsyningskilden, 25 og ved at reguleringskredsen omfatter et første styret kobleorgan indskudt mellem Wheatstone-broen og en af strømtilførselsledningerne og indrettet til at bryde eller slutte strømmen til brokredsløbet, 30 en første manøvrekreds til frembringelse af styresignaler til lukning af det første styrede kobleorgan, og et styrekredsløb med en indgang forbundet til Wheatstone-broens målediagonal og indrettet til at styre den første manøvrekreds til skiftevis åbningstyring eller 35 blokering af sidstnævnte kreds i en følge af faser, hvis varighed afhænger af værdien af det signal, som optræder på Wheatstone-broens målediagonal, i overensstemmelse med en formel af den proportional/integrale type, hvilken 3These objects are met by an apparatus of the kind mentioned in the preamble, which apparatus according to the invention is characterized by a) a control circuit for regulating the current supply to the Wheatstone bridge, depending on the signal on the measurement diagonal of the bridge, so that the temperature of the heating means after an initial transient phase substantially remains within a specified range throughout the heating period of the liquid, and b) a time control unit adapted to after a specified time, starting from the time the heating begins, to disconnect the power supply to the Wheatstone Bridge by means of the control circuit and to open the main switch for disconnecting the control unit from the power supply source, and the control circuit comprising a first controlled switching means interposed between the Wheatstone bridge and one of the power supply lines and arranged to interrupt or connect the current to the bridge circuit, a first control circuit for generating control signals and a control circuit having an input connected to the measuring diagonal of the Wheatstone bridge and arranged to control the first maneuvering circuit for alternating orifice control or blocking of the latter circuit in phases, the duration of which depends on the value of that signal which appears on the Wheatstone Bridge's diagonal, in accordance with a proportional / integral type formula, which 3

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første manøvrekreds i blokeringsfaserne styrer den periodiske kortvarige lukning af det første styrede koblingsorgan til muliggørelse af en periodisk tilførsel, selv under de nævnte blokeringsfaser, af forsyningsstrømmen 5 til Wheatstone-broen med henblik på at holde opvarmningsorganet delvis i gang.first maneuvering circuit in the blocking phases controls the periodic short-term closure of the first controlled coupling means to enable a periodic supply, even during said blocking phases, of the supply current 5 to the Wheatstone bridge to keep the heating means partially running.

Idet selve modstandsopvarmningsorganet ved på i og for sig kendt måde at indgå i en Wheatstone-bro anvendes som temperaturføleorgan, sikres det, at den 10 målte temperatur er den højeste, der forekommer i opvarmningssystemet. Herved er det muligt at sikre, at den højest forekommende temperatur holdes på et niveau, hvor beholderens plastmateriale ikke skades, medens en konventionel anvendelse af et varmelegeme og en termo-15 føler indebærer, at varmelegemet opvarmes til en højere temperatur end den, der registreres af termoføleren.By using the resistance heating element itself in a manner known per se in a Wheatstone bridge as a temperature sensing means, it is ensured that the measured temperature is the highest occurring in the heating system. Hereby it is possible to ensure that the highest temperature is kept at a level where the plastic material of the container is not damaged, while a conventional use of a heater and a thermocouple means that the heater is heated to a higher temperature than that recorded. of the thermocouple sensor.

Efter en indledende opvarmningsfase holdes opvarmningsorganet på en konstant forud valgt temperatur, og idet varmeoverføringsegenskaberne for varmeoverføring 20 fra opvarmningsorganet til beholderens metallag antages at være ens fra beholder til beholder, lader den tilførte varmemængde sig enkelt styre ved en styring-af den tid, modstandsopvarmningsorganet holdes på den fastlagte temperatur, d.v.s. den tid, hvori der føres 25 strøm til styreenheden.After an initial heating phase, the heater is maintained at a constant preselected temperature, and since the heat transfer properties of heat transfer 20 from the heater to the metal layer of the container are assumed to be the same from container to container, the amount of heat supplied is simply controlled by a control of the time, the heating element at the set temperature, ie the time during which 25 power is supplied to the control unit.

Hensigtsmæssige udformninger af reguleringskredsen, dennes kobleorgan og første manøvrekreds, styrekredsløbet samt tidsstyreenheden og den i denne indgående anden manøvrekreds fremgår af underkravene.Appropriate designs of the control circuit, its coupling means and first maneuvering circuit, the control circuit as well as the time control unit and the second maneuvering circuit included in this are set out in the subclaims.

30 Opfindelsen forklares nærmere nedenfor under hen visning til tegningen, hvor fig. 1 viser i perspektiv en udførelsesform for et apparat ifølge opfindelsen til opvarmning af drikkevarer, fig. 2 et aksialt snit gennem en beholder inde-35 holdende en drikkevare til opvarmning med det i fig. 1 viste apparat, fig. 3 et longitudinalt snit taget langs linien 4The invention is explained in more detail below with reference to the drawing, in which fig. 1 is a perspective view of one embodiment of an apparatus for heating beverages; FIG. 2 is an axial section through a container containing a beverage for heating with that of FIG. 1; FIG. 3 is a longitudinal section taken along line 4

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III-III i fig. 1, idet apparatet er vist i en hviletilstand, fig. 4 et lignende snit som vist i fig. 3 i en opvarmningstilstand, 5 fig. 5 et snit i større målestok gennem en de talje af det i figurerne 3 og 4 viste, og fig. 6 et diagram delvis i blokdiagramform over det elektriske kredsløb for det i fig. 1 viste apparat. Apparatet ifølge opfindelsen har et hus 1, jf.III-III of FIG. 1, the apparatus being shown in a resting state; FIG. 4 is a sectional view similar to FIG. 3 in a heating state; FIG. 5 is an enlarged sectional view through one of the waists of the one shown in FIGS. 3 and 4; and FIG. 6 is a partial block diagram diagram of the electrical circuit of FIG. 1. The apparatus according to the invention has a housing 1, cf.

10 fig. 1. En plan overflade 2 af huset 1 er forsynet med en åbning 3, som er indrettet til at rumme en kopformet beholder 5 for en væske, i dette tilfælde en drikkevare 7, i et C-formet eller gaffelformet bæreorgan 4. Beholderen 5, der er vist i fig. 2, er 15 fremstillet af en termoplast og er lukket hermetisk tæt ved hjælp af et metallåg 6. Beholderen 5 skal, når den er vendt på hovedet, være i indgreb med bæreorganet 4, således at drikkevaren 7 forbliver i berøring med metallåget 6 under hele opvarmningsperioden.10 FIG. A flat surface 2 of the housing 1 is provided with an opening 3 arranged to accommodate a cup-shaped container 5 for a liquid, in this case a beverage 7, in a C-shaped or fork-shaped carrier 4. The container 5, shown in FIG. 2, 15 is made of a thermoplastic and is hermetically sealed tightly by means of a metal lid 6. The container 5, when turned upside down, must engage the carrier 4 so that the beverage 7 remains in contact with the metal lid 6 throughout. heating period.

20 Bæreorganet 4 udgør den ene ende af en arm 8, hvis anden ende er fastgjort til et beslag 9, som er i stiv forbindelse med en bæreplade 10, der er fremstillet af et plastmateriale, som går under handelsnavnet "vetronite". Beslaget 9 holder det C-formede bæ-25 reorgan 4 i en i det væsentlige horisontal stilling, når apparatet befinder sig i hvile.The support member 4 constitutes one end of an arm 8, the other end of which is attached to a bracket 9 which is rigidly connected with a support plate 10 made of a plastic material which goes by the trade name "vetronite". The bracket 9 holds the C-shaped support member 4 in a substantially horizontal position when the apparatus is at rest.

Bærepladen 10 basrer et trykt kredsløb og er fastgjort til huset 1. Pladen 10 understøtter en bægerformet beholder 11 af metal, hvori der findes 30 tre fjedre 12, der bærer et elektrisk modstandsopvarmningsorgan 13. Opvarmningsorganet 13 er anbragt neden under det C-formede bæreorgan 4, og strømforsynes gennem et par ledninger 14.The support plate 10 bases a printed circuit and is attached to the housing 1. The plate 10 supports a cup-shaped container 11 of metal, in which there are 30 three springs 12 carrying an electric resistance heating means 13. The heating means 13 is arranged below the C-shaped support means 4 , and powered by a pair of wires 14.

På pladen 10 er der ligeledes anbragt en elek-35 tromagnet 15, der er indrettet således, at dens polstykker 16 kan virke på to arme 8a, som går på tværs af armen 8. En hovedafbryder 17, i form af en mikro-kobler, som normalt er åben, er indskudt mellem netled-Also mounted on the plate 10 is an electromagnet 15 arranged so that its pole pieces 16 can act on two arms 8a extending across the arm 8. A main switch 17, in the form of a micro-coupler, which is normally open is inserted between the mains

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5 ninger, som ikke er vist, og en elektrisk styreenhed 18, der er indrettet til at regulere strømforsyningen til modstandsopvarmningsorganet 13 og magnetiseringen af elektromagneten 15.5, not shown, and an electrical control unit 18 adapted to control the power supply to the resistor heating means 13 and the magnetization of the electromagnet 15.

5 Under apparatets brug holdes armen 8 i en ho risontal hvilestilling ved hjælp af beslaget eller bøjlen 9.5 During use of the apparatus, the arm 8 is held in a high horizontal rest position by the bracket or bracket 9.

Når der på en beholder, der er vendt på hovedet, og som er anbragt i det C-formede bæreorgan 4, jf. fig.When on a container turned upside down and housed in the C-shaped carrier 4, cf.

Ί0 4, udøves et nedadrettet tryk til overvindelse af beslaget 9's elastiske modstand, forskydes bæreorganet 4 en smule nedefter, hvilket bringer beholderen 5's låg 6 i berøring med opvarmningsorganet 13.40 4, a downward pressure is exerted to overcome the elastic resistance of the bracket 9, the support member 4 is slightly displaced downwards, bringing the lid 6 of the container 5 into contact with the heating means 13.

Opvarmningsorganet 13, der er af den helt luk-Ί5 kede type, er formet som en plankonveks linse med sin konyekse side 19 vendende opad. Fjedrene 12 trykker opvarxnningsorganet 13 i tæt berøring med hele låget 6's overflade, idet der sker en tilpasning til eventuelle vridninger af låget hidrørende fra dets opvarm-20 ning.The heater 13, of the fully closed type, is shaped like a flat convex lens with its conical side 19 facing up. The springs 12 press the heating member 13 into close contact with the entire surface of the lid 6, adapting to any twisting of the lid resulting from its heating.

Opvarmningsorganet 13's opadvendende konvekse overflade 19 er af metal, jf. fig. 5, og virker som en varmeflade, idet den er anbragt i termisk berøring med et varmelegeme 191 af nikkeltråd, jf. fig. 5.The upwardly convex surface 19 of the heater 13 is of metal, cf. 5, and acts as a heating surface in thermal contact with a nickel wire heater 191, cf. 5th

25 Det nævnte varmelegeme 191 er viklet i spiral form ovenpå en isolerende bærer 192, og er indstøbt i et glasagtigt formstof. Strømtilførslen sker gennem ledninger 14, som går ud igennem opvarmningsorganet 13's nederste plane flade 193.Said heater 191 is wound in a spiral form on top of an insulating support 192 and is embedded in a glassy resin. The power is supplied through conduits 14 which extend through the lower plane face 193 of the heater 13.

30 Når beholderen 5 trykkes ned i den i fig. 4 viste opvarmningsstilling, lukker armen 8 mikrokoble-ren 17, hvilket forbinder strømforsyningen med den elektroniske styreenhed 18, som strømforsyner modstandsopvarmningsorganet 13 og leverer magnetiserings-35 strøm til elektromagneten 15.When the container 5 is depressed in the embodiment of FIG. 4, the arm 8 closes the micro coupler 17, which connects the power supply to the electronic control unit 18, which supplies the resistance heating means 13 and supplies magnetizing 35 to the electromagnet 15.

Efter at være blevet magnetiseret virker elektromagneten 15 på armen 8's tværgående arme 8a og holder derved armen 8 i en nedtrykket tilstand indtil 6After being magnetized, the electromagnet 15 acts on the transverse arms 8a of the arm 8, thereby holding the arm 8 in a depressed state until 6

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elektromagneten afaktiveres ved hjælp af styreenheden 18 ved afslutningen af opvarmningsperioden. Når elektromagneten er afaktiveret vender armen 8 tilbage til sin oprindelige hvilestilling, hvilket giver mikrokob-5 leren 17 mulighed for at åbne igen og afbryde for strømforsyningen til styreenheden 18, hvilket igen afbryder for strømforsyningen til opvarmningsorganet 13.the electromagnet is deactivated by the control unit 18 at the end of the heating period. When the electromagnet is deactivated, the arm 8 returns to its original resting position, allowing the micro coupler 17 to open again and disconnect the power supply to the control unit 18, which in turn cuts off the power supply to the heater 13.

Fig. 6 viser skematisk et kredsløb for styreenheden 18. Denne enhed 18 omfatter en Wheatstone-bro 10 20, hvis ene gren omfatter modstandopvarmningsorganet 13, der er balanceret mod en anden gren indeholdende en shuntmodstand 21 forbundet i serie med opvarmningsorganet 13, hvorhos broen har to forholdsgrene indeholdende henholdsvis en fast modstand 22 og en regu-15 lerbar modstand 23.FIG. 6 schematically shows a circuit for the control unit 18. This unit 18 comprises a Wheatstone bridge 10 20, one branch of which comprises the resistor heating means 13 balanced against another branch containing a shunt resistor 21 connected in series with the heating means 13, the bridge having two ratios. containing a fixed resistor 22 and a controllable resistor 23, respectively.

Et par strømforsyningeledninger 24 og 25, der er forbundet til indgangsklemmer henholdsvis 26 og 27 for styreenheden 18, er sluttet til Wheatstone-broen 20 gennem en tyristor (eller SCR) 28, der udgør en 20 del af et strømregulerende kredsløb 30, der er vist med stiplet streg. Reguleringskredsen indeholder en første manøvrekreds 29 bestående af en unijunctiontran-sistor (UJT), der fungerer som impulsgenerator.A pair of power supply lines 24 and 25 connected to input terminals 26 and 27 of controller 18, respectively, are connected to Wheatstone Bridge 20 through a thyristor (or SCR) 28 which forms a 20 portion of a current regulating circuit 30 shown. with dashed dash. The control circuit contains a first maneuvering circuit 29 consisting of a uniunction transistor (UJT) acting as a pulse generator.

Wheatstone-broen 20's målediagonal omfatter et 25 styrekredsløb 31, der ligeledes udgør en del af strømreguleringskredsen 30. Styrekredsløbet 31 består af en differensforstærker 32, hvis udgangssignal ledes videre til et integrationskredsløb 33, der er forbundet til en første tærskelkomparator 34. Udgangen 30 af denne første tærskelkomparator 34 er forbundet til den første manøvrekreds 29, som styrer tændingen af tyristoren 28.The measurement diagonal of the Wheatstone Bridge 20 comprises a control circuit 31 which also forms part of the current control circuit 30. The control circuit 31 consists of a differential amplifier 32 whose output signal is passed to an integration circuit 33 connected to a first threshold comparator 34. The output 30 of this first threshold comparator 34 is connected to first maneuvering circuit 29 which controls the ignition of thyristor 28.

Den normalt åbne mikrokobler 27 afskærer strømforsyningen fra styreenheden 18 under apparatets hvi-35 lestilling.The normally open microcoupler 27 cuts off the power supply from the control unit 18 during the rest position of the apparatus.

En brokoblet ensretter 35 er forbundet via en triac 36 til strømtilførselsledningerne 24 og 25 og har sin ensrettende diagonal forbundet til elektromag- 7A bridge-connected rectifier 35 is connected via a triac 36 to the power supply lines 24 and 25 and has its unidirectional diagonal connected to electromagnetic

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neten 15, som er koblet i parallel med en stabiliserende diode 37. Triac'en 36's styreelektroder 38 er forbundet til en timer 39, som er vist med stiplede linier, og som omfatter en savtand-generator 40, der 5 kan indstilles ved hjælp af en regulerbar modstand 41. Savtand-generatoren 40's udgang er forbundet til en anden tærskelkomparator 42, hvis udgang er forbundet til en anden manøvrekreds 43, der styrer trigningen af triac'en 36.the network 15, which is connected in parallel with a stabilizing diode 37. The control electrodes 38 of the triac 36 are connected to a timer 39, shown in broken lines, which comprises a sawtooth generator 40 which can be adjusted by means of an adjustable resistor 41. The output of the sawtooth generator 40 is connected to another threshold comparator 42, the output of which is connected to a second operating circuit 43 which controls the triggering of the triac 36.

10 En vekselstrøm/jævnstrøm-omsætter 44 er for bundet til strømtilførselsledningerne 24 og 25, og frembringer et par stabiliserede og balancerede spændinger +V og -V og en ikke-stabiliseret spænding V , der påtrykkes de foroven nævnte kredsløb 29, 32, C w 15 34, 40, 42 og 43 således som vist skematisk på tegnin gen.An AC / DC converter 44 is too connected to the power supply lines 24 and 25 and produces a pair of stabilized and balanced voltages + V and -V and a non-stabilized voltage V applied to the circuits 29, 32, C w 15, 34, 40, 42 and 43 as shown schematically in the drawing.

I det følgende beskrives styreenheden 18's virkemåde .The operation of the control unit 18 is described below.

Når mikrokobleren 17 lukkes .ved nedtrykning af 20 armen 8 aktiverer manøvrekredsen 43, som er trigget ved hjælp af den af omsætteren 44 tilvejebragte spænding V , triac'en 36, som følgelig tillader magne-When the microcoupler 17 is closed by depressing the arm 8, the maneuvering circuit 43, which is triggered by the voltage V provided by the converter 44, activates the triac 36, which consequently allows the

OOISLAND ISLAND

tisering af elektromagneten 15 med én af den brokoblede ensretter 35 frembragt ensrettet strøm. Når elek-25 tromagneten 15 er blevet magnetiseret holder den armen 8 nede, idet den således holder mikrokobleren 17 lukket.tapping the electromagnet 15 with one of the bridged rectifiers 35 produced unidirectional current. When the electromagnet 15 has been magnetized, it holds the arm 8 down, thus holding the microcoupler 17 closed.

Samtidig hermed startes savtand-generatoren 40, der påtrykker den anden tærskelkomparator 42 en spæn-30 ding, som stiger lineært med tiden. Efter et bestemt tidsinterval, regnet fra det øjeblik mikrokobleren 17 lukkes, når det af savtand-generatoren 40 frembragte signal et sådant spændingsniveau, at den anden tærskelkomparator 42 udløses og forårsager, at den anden ma-35 nøvrekreds 43 blokerer for triac'en 36. Triac'en er således afaktiveret, og enretterkredsen 35 ophører med at levere strøm til elektromagneten 15, der efter afaktiveringen giver armen 8 mulighed for at vendeAt the same time, the sawtooth generator 40 is started, which applies to the second threshold comparator 42 a voltage which increases linearly with time. After a certain time interval, calculated from the moment the microcoupler 17 is closed, when the signal generated by the sawtooth generator 40 reaches a voltage level such that the second threshold comparator 42 is triggered and causes the second motor circuit 43 to block the triac 36. Thus, the triac is deactivated and the rectifier circuit 35 ceases to supply power to the electromagnet 15 which, after deactivation, allows arm 8 to reverse.

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8 tilbage til sin hvilestilling med en deraf følgende genåbning af mikrokobleren 17 og frakobling af den elektroniske styreenhed 18 og af opvarmningsorganet 13 fra energikilden.8 returns to its resting position with a subsequent reopening of the micro coupler 17 and disconnection of the electronic control unit 18 and of the heater 13 from the energy source.

5 Idet der vendes tilbage til det tidspunkt, hvor mikrokobleren 17 lukkes, beskrives virkemåden af den resterende del af den elektroniske styreenhed 18 i det følgende under henvisning til fig. 6.Turning back to the time when the microcoupler 17 is closed, the operation of the remaining portion of the electronic control unit 18 is described below with reference to FIG. 6th

Styret af manøvrekredsen 29 lukker tyristoren 10 28, således at strømforsyningen forbindes til Wheat- stone-broen 20, hvorved opvarmningsorganet 13 får tilført strøm.Controlled by the maneuvering circuit 29, the thyristor 10 28 closes so that the power supply is connected to the Wheatstone bridge 20, whereby the heater 13 is supplied with power.

Opvarmningsorganet 13 for det illustrerede eksempel har i kold tilstand en nominel effekt på ca. 2 kW, 15 og modstanden i varmelegemet har en positiv temperaturkoefficient, således at værdien af denne modstand stiger mærkbart med temperaturen (5% pr. °C).The heater 13 for the illustrated example has a nominal power of approx. 2 kW, 15 and the resistance of the heater have a positive temperature coefficient, so that the value of this resistance increases noticeably with the temperature (5% per ° C).

Målespændingen over Wheatstone-broen 20's målediagonal, som aftastes af reguleringskredsen 30, er 20 derfor et mål for den af opvarmningsorganet 13's modstand opnåede temperatur. Denne målespænding føres, efter at være blevet forstærket i differensforstærkeren 32 og integreret i integrationskredsløbet 33, til den første tærskelkomparator 34, der ophører med at strøm-25 forsyne manøvrekredsen 29, når spændingen på indgangen overskrider et bestemt tærskelniveau, hvilket blokerer tyristoren 28 og dermed afbryder strømforsyningen til opvarmningsorganet 13.The measuring voltage across the measuring diagonal of the Wheatstone bridge 20, sensed by the control circuit 30, is therefore a measure of the temperature obtained by the resistance of the heater 13. This measurement voltage, after being amplified in the differential amplifier 32 and integrated into the integration circuit 33, is applied to the first threshold comparator 34, which ceases to supply the maneuver circuit 29 when the voltage at the input exceeds a certain threshold level, thus blocking the thyristor 28 and thus switches off the power supply to the heater 13.

Strømforsyningen til modstandsopvarmningsorganet 30 13 genoprettes automatisk for hver femte cyklus ved hjælp af cyklusstyreorganer, således at den foroven nævnte målespænding påtrykkes reguleringskredsen 30's indgang til periodisk indikering af modstandsopvarmningsorganet 13's temperatur.The power supply to the resistor heater 30 13 is automatically restored for every five cycles by means of cycle controllers such that the above measured voltage is applied to the input of the control circuit 30 to periodically indicate the temperature of the resistor heater 13.

35 Styrekredsløbet 31 frembringer på denne måde en proportional/integral-regulering af det målesignal, der tilvejebringes ved hjælp af Wheatstone-broen 20's målediagonal, således at strømforsyningen til opvarmnings-The control circuit 31 thus provides a proportional / integral control of the measurement signal provided by the measurement diagonal of the Wheatstone Bridge 20 so that the power supply for the heating circuit

Claims

20 PATENT REQUIREMENTS

An apparatus for heating a liquid in a thermoplastic container sealed tightly by a metal lid, comprising a combination of carrier means (4, 8) for the container (5) arranged to engage the container (5) in reverse position, a resistance heating means (13) arranged relative to the supporting means so that during the entire heating process it is in thermal contact with practically the entire metal lid (6) of the upside-down container 30 (5), and an electronic control unit (18) for the heating means connected to a power supply source through a main switch (17), comprising a Wheatstone bridge (20) fed by power supply OC wires (24, 25) connected to input terminals (26, 27) of the electronic control unit (18), wherein the resistance heating means (13) is included in one of the branches of the Wheat-stone bridge (20), which bridge on a measuring diagonal DK 159359 B produces a signal to indicate that of the heating means etch (13) resistance obtained temperature, characterized in: a) a control circuit (30) for controlling the power supply to the Wheatstone bridge (20) depending on the signal on the measurement diagonal of the bridge so that the temperature of the heater after an initial transient phase remains substantially within a specified interval during the entire heating period of the liquid (7), and (b) a timing controller (39) arranged to after a certain time, starting from the time the heating begins, cut off the power supply to the Wheatstone bridge (20). the control circuit (30) and opening the main switch (17) to disconnect the control unit (18) from the power supply source, and in that the control circuit (30) comprises a first controlled coupling means (28) interposed between the Wheatstone bridge (20) and one of the power supply lines ( 24) and arranged to interrupt or connect current 20 to the bridge circuit (20), a first maneuvering circuit (29) for generating control signals for closing the first controlled coupling means (28), and a control circuit (31) having an input connected to the measuring diagonal of the wheatstone bridge (20) and arranged to control the first maneuvering circuit (29) for alternately opening or blocking the latter circuit in consequence of phases whose duration depends on the value of the signal appearing on the measurement diagonal of the Wheatstone bridge in accordance with a proportional / integral type formula, which first maneuvering circuit (29) in the blocking phases controls the periodic short-term closure of the first controlled coupling means (28) to enable a periodic supply, even during said blocking phases, of the sewing flow to the Wheatstone bridge (20) to keep the heating means (13) partially running.

Apparatus according to claim 1, characterized in that the first controlled switching means (28) comprises a thyristor (SCR) and that the first operating circuit (29) comprises a pulse generator containing a uniunction transistor (UJT).

Apparatus according to claim 1, characterized in that the control circuit (31) consists of a differential amplifier (32) for amplifying the signal appearing on the measuring diagonal of the Wheatstone bridge (20), an integration circuit (33) connected to the output of the differential amplifier. ) and a first threshold comparator (34) connected to the output of the integration circuit and arranged to block said first maneuvering circuit (29) when the voltage at the input of the first comparator exceeds a pre-established threshold value. 15 4. Apparatus according to one or more of the preceding claims, characterized in that the timing control unit (39) comprises a sawtooth generator (40) for feeding a second threshold comparator (42), a second operating circuit (43) connected to the output of this comparator. -20 to keep the main switch (17) closed in said predetermined interval by activating an electromagnet (15) cooperating with said switch (17).

Apparatus according to claim 4, characterized in that the second actuating circuit (43), after the elapsed period of 25, deactivates the electromagnet (15) by opening another controlled coupling means (36), such as a triac, which is inserted into the the power supply to the electromagnet (15). 30 35