WO2012168906A1 - Résistance blindée d'un appareil électroménager et procédé de fabrication de ladite résistance - Google Patents

Résistance blindée d'un appareil électroménager et procédé de fabrication de ladite résistance Download PDF

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Publication number
WO2012168906A1
WO2012168906A1 PCT/IB2012/052894 IB2012052894W WO2012168906A1 WO 2012168906 A1 WO2012168906 A1 WO 2012168906A1 IB 2012052894 W IB2012052894 W IB 2012052894W WO 2012168906 A1 WO2012168906 A1 WO 2012168906A1
Authority
WO
WIPO (PCT)
Prior art keywords
tube
shaped casing
tip
resistor
narrowing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/IB2012/052894
Other languages
English (en)
Inventor
Roberto Colombo
Maurizio Biasi
Carlo Sonego
Gino Sonego
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
IRCA SpA Industria Resistenze Corazzate e Affini
Original Assignee
IRCA SpA Industria Resistenze Corazzate e Affini
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by IRCA SpA Industria Resistenze Corazzate e Affini filed Critical IRCA SpA Industria Resistenze Corazzate e Affini
Publication of WO2012168906A1 publication Critical patent/WO2012168906A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/40—Heating elements having the shape of rods or tubes
    • H05B3/42—Heating elements having the shape of rods or tubes non-flexible
    • H05B3/48—Heating elements having the shape of rods or tubes non-flexible heating conductor embedded in insulating material
    • H05B3/52—Apparatus or processes for filling or compressing insulating material in tubes
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
    • H05B2203/021—Heaters specially adapted for heating liquids

Definitions

  • the present invention relates to an armoured resistor of an electric household appliance and a method for the manufacture thereof.
  • Armoured electric resistors are used in electric household appliances which come into contact with water, such as washing machines, dishwashers, etc.
  • Such armoured resistors incorporate within themselves security systems which, in the event of malfunction of the apparatus or of any component thereof, eliminate the risk of fires started by said resistor.
  • Thermal fuses that are capable of interrupting the resistor's power supply when said resistor exceeds a predetermined temperature in particular are incorporated.
  • a resistive wire is inserted into the substantially tube-shaped casing and isolated therefrom by means of powdered magnesium oxide.
  • a metal tip partially projects at each end of tube-shaped casing, which tip is duly electrically insulated from the tube-shaped casing by means of suitable insulating sheaths, both tips are intended to be connected to a source of electricity.
  • a thermal fuse is present in at least one of said ends.
  • the magnesium oxide electrically insulates the resistive wire from the metal casing, but is responsible for transporting the heat generated by the resistive wire towards the outside, for heating water.
  • thermodynamic system there is a requirement both for the thermodynamic system to be rapid for large reductions in the dispersion of heat, on account of the absence of water, and also for the thermal fuse not to intervene prematurely on account of slight variations in dispersion, for example due to accumulation of sediments.
  • the known art teaches the subjection of resistors filled with magnesium oxide to what is known as a rolling process, which leads to a 2%-20% reduction in the diameter of the casing.
  • rolling is a procedure according to which the tube-shaped casing undergoes a process of narrowing by passing between rollers which, little by little, reduce its diameter in accordance with a cross-section, uniformly along the entire longitudinal development of the casing. This process is rendered necessary by the fact that when the magnesium oxide is inserted into the casing, it tends not to compact, incorporating air which, as is known, is a good thermal insulator.
  • the magnesium oxide is therefore compacted by rolling, improving the thermal conductivity of the layer of magnesium oxide which envelops the resistive wire.
  • US2846537 is localised at the bead, in order to ensure that the bead fits perfectly, preventing the insulating material from being able to escape from the armouring.
  • uniform reductions of the casing cross-section are within the range from 2% to 20% of the original cross-section.
  • About aim of the present invention is to provide an armoured resistor for an electric household appliance, having improved thermal fuse behaviour in respect of the accumulation of sediments on the resistor without prejudicing the security thereof.
  • the aim of the present invention is an armoured resistor for an electric household appliance according to claim 1.
  • Such narrowing, localised at the inner tip is limited to a portion of the longitudinal development of the casing and not to the entire length, as in the rolling process.
  • an increase in the thermal conductivity of the magnesium oxide at the level of a proximal zone of the thermal fuse which increase is obtained due to narrowing at least at one portion of the inner tip, enormously improves fuse behaviour, by determining a synergistic effect between the behaviour of the fuse and the presence of the localised narrowing. This effect has been demonstrated by numerous different laboratory tests.
  • a further aim of the invention is to provide a method for a manufacturing an armoured resistor of an electric household appliance which enables an armoured resistor to be obtained having improved thermal fuse behaviour in respect of the accumulation of sediments on the resistor, without prejudicing the security thereof.
  • Such narrowing locally modifies the thermal conductivity of the magnesium oxide. This translates into improved local heat dispersion during normal operation of the resistor, that is, when it is submerged in water.
  • the conduction of heat produced by the resistive wire towards the thermal fuse is not reduced in the disadvantageous case of dry operation of the armoured resistor; in brief, the narrowing does not modify the speed of intervention of the thermal fuse, as a result of which the resistor security in the event of operation under conditions of abnormal overheating (for example in the absence of water) is not prejudiced.
  • the mechanical characteristics of the resistor are not prejudiced during the process of bending thereof.
  • Another subject of the invention is a method of manufacturing an armoured resistor of an electric household appliance.
  • the method of manufacturing the present invention may also be applied to pre-existing armoured resistors or those anyhow manufactured according to alternative methods.
  • Fig. 1 represents a portion of one end of an armoured resistor, prior to rolling
  • Fig. 2 represents the same part as in Fig. 1 , after the rolling process
  • Fig.3 shows the same portion of the preceding figures according to the present invention.
  • figure 1 shows a portion of one end of any armoured resistor prior to rolling.
  • Numeral 1 indicates the outer casing, 2 the tip, 3 box, as well as 31 the space between the box 3 and the casing 1 and a so-called inner tip 4 the purpose of which tip is to connect the thermal fuse 6 to the resistive wire, not represented here since it may be of any type.
  • the point of connection between the inner tip 4 and the resistive wire may also be of any kind.
  • Use of the attribute tube-shaped here does not imply that any cross-section should be circular. It may be of any shape, but preferably circular.
  • Fig. 2 shows the same portion of Fig. 1 following the process of reducing the cross-section of the casing, for example by rolling. It can be seen that the space 31 , also called "air”, has disappeared. In other words, the box adheres perfectly to the casing and vice versa.
  • box 3 is made so as to deform and adhere perfectly to the casing during any process of reduction of the cross-section of the casing.
  • cross is meant perpendicularly relative to the axial development X of the casing.
  • the inner tip 4 is of a shape which tends to taper at the inner end 41 directed towards the inside of the casing, that is, to the right with reference to the drawings.
  • the armoured resistor comprises a localised narrowing of the casing 1 along a length corresponding to the inner tip. For example, astride the inner end 41 of the inner tip 4
  • the heat is no longer adequately dissipated in the environment and establishes alternative routes. That is, as well as propagating through the inner tip 4 which is in direct contact with the resistive wire, the heat also dissipates via the magnesium oxide or an equivalent insulating powder which exhibits improved thermal conductivity within the zone of narrowing, precisely because it is narrower, until it reaches the thermal fuse, which intervenes more promptly.
  • the thermal fuse may be dimensioned in such a way that slight increases in temperature due to possible accumulation of sediments on the casing may be overlooked.
  • the narrowing has limited axial extension, that is, along the X-development of the armoured resistor, which preferably does not exceed the length of the inner tip. Furthermore, this narrowing preferably does not involve the part of the casing in contact with the box 3.
  • the longitudinal development of the narrowing may vary.
  • a preferred length of this development may be within the range from at least 0.5 to 4 times the average outer diameter of the casing.
  • average outer diameter is meant a average diameter calculated within a zone different from that affected by the narrowing.
  • the zone of narrowing 11 may extend axially for 5 to 40 mm and beyond.
  • the narrowing is such as to present a diameter within the range from 70% and 98% of the average outer diameter, that is, calculated within a zone outside the narrowing.
  • This narrowing 11 may be given to the casing 1 at any point in the manufacture of the resistor or after manufacture thereof.
  • This narrowing may be provided in many ways. For example, by means of planar or radially circular pressing, also called sectoral pressing, or by coining.
  • the radially circular pressing/re-pressing reduces the diameter of the zone involved via a plurality of sectors which radially compress the zone in question, maintaining a substantially circular geometry of the portion affected by the narrowing.
  • the total extent of narrowing may be obtained by means of further operations, successively repeated.
  • the above-mentioned narrowing ratios refer to a preferably uniform narrowing both along the X axis of development of the casing, and along a cross-section of the zone affected by the narrowing. However, this does not detract from the fact that the narrowing may not be relative to these two directions, for example giving rise to another cross-section, or to two or more consecutive narrowings, etc.
  • the process of manufacturing the armoured resistor may provide for a prior or subsequent step of reducing the average outer diameter of the tube-shaped casing 1 , that is, of the portions of the tube-shaped casing 1 remaining relative to said zone(s) of narrowing 11.
  • Preferred reductions in percentage are of the order of 0% to 20%.
  • the narrowing may be located at one or both inner tips 4.

Landscapes

  • Thermistors And Varistors (AREA)

Abstract

L'invention concerne une résistance blindée d'un appareil électroménager comprenant un boîtier tubulaire (1) définissant une étendue longitudinale (x) et au moins une extrémité, une pointe extérieure (2) sortant au moins partiellement de l'intérieur de ladite extrémité, une pointe intérieure (4) sur le boîtier tubulaire, un fusible thermique connectant électriquement la pointe extérieure (2) à la pointe intérieure (4) ; la pointe intérieure (4) est configurée pour être connectée à un fil résistif ; l'intérieur du boîtier tubulaire (1) est rempli d'une poudre isolante qui isole le boîtier tubulaire (1) des composants électriques internes ; le boîtier tubulaire (1) comprend une partie plus étroite (11) au niveau de la pointe intérieure (4).
PCT/IB2012/052894 2011-06-09 2012-06-08 Résistance blindée d'un appareil électroménager et procédé de fabrication de ladite résistance Ceased WO2012168906A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITRM2011A000286 2011-06-09
IT000286A ITRM20110286A1 (it) 2011-06-09 2011-06-09 Resistenza corazzata di elettrodomestico e relativo metodo di fabbricazione

Publications (1)

Publication Number Publication Date
WO2012168906A1 true WO2012168906A1 (fr) 2012-12-13

Family

ID=44554993

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2012/052894 Ceased WO2012168906A1 (fr) 2011-06-09 2012-06-08 Résistance blindée d'un appareil électroménager et procédé de fabrication de ladite résistance

Country Status (2)

Country Link
IT (1) ITRM20110286A1 (fr)
WO (1) WO2012168906A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1960221A (en) * 1929-11-30 1934-05-22 Edison General Elec Appliance Electric heating unit
US2846537A (en) 1954-03-03 1958-08-05 Wiegand Co Edwin L Electric heaters
EP0086465A1 (fr) * 1982-02-12 1983-08-24 Elpag Ag Chur Corps de chauffe tubulaire muni d'un coupe-circuit de surcharge

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1960221A (en) * 1929-11-30 1934-05-22 Edison General Elec Appliance Electric heating unit
US2846537A (en) 1954-03-03 1958-08-05 Wiegand Co Edwin L Electric heaters
EP0086465A1 (fr) * 1982-02-12 1983-08-24 Elpag Ag Chur Corps de chauffe tubulaire muni d'un coupe-circuit de surcharge

Also Published As

Publication number Publication date
ITRM20110286A1 (it) 2012-12-10

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