EP0910267A1 - Recipients servant a rechauffer des liquides a l'electricite - Google Patents

Recipients servant a rechauffer des liquides a l'electricite

Info

Publication number
EP0910267A1
EP0910267A1 EP97926114A EP97926114A EP0910267A1 EP 0910267 A1 EP0910267 A1 EP 0910267A1 EP 97926114 A EP97926114 A EP 97926114A EP 97926114 A EP97926114 A EP 97926114A EP 0910267 A1 EP0910267 A1 EP 0910267A1
Authority
EP
European Patent Office
Prior art keywords
base part
grit
vessel
glass
layer
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.)
Withdrawn
Application number
EP97926114A
Other languages
German (de)
English (en)
Inventor
Keith Barrie Doyle
John Crawshaw Taylor
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.)
Strix Ltd
Original Assignee
Strix Ltd
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
Priority claimed from GBGB9612357.5A external-priority patent/GB9612357D0/en
Priority claimed from GBGB9613028.1A external-priority patent/GB9613028D0/en
Application filed by Strix Ltd filed Critical Strix Ltd
Publication of EP0910267A1 publication Critical patent/EP0910267A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
    • A47J27/00—Cooking-vessels
    • A47J27/21—Water-boiling vessels, e.g. kettles
    • A47J27/21008—Water-boiling vessels, e.g. kettles electrically heated
    • A47J27/21041—Water-boiling vessels, e.g. kettles electrically heated with heating elements arranged outside the water vessel
    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
    • A47J27/00—Cooking-vessels
    • A47J27/21—Water-boiling vessels, e.g. kettles
    • A47J27/21166—Constructional details or accessories
    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
    • A47J36/00—Parts, details or accessories of cooking-vessels
    • A47J36/02—Selection of specific materials, e.g. heavy bottoms with copper inlay or with insulating inlay
    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
    • A47J36/00—Parts, details or accessories of cooking-vessels
    • A47J36/42—Devices to prevent deposition of scale, i.e. fur, or the like
    • 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
    • H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
    • H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
    • H05B3/26—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base
    • H05B3/262—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base the insulating base being an insulated metal plate

Definitions

  • the present invention relates to electric liquid heating vessels and in particular to such vessels having a base part with a stainless steel liquid-contacting surface.
  • Liquid heating vessels with stainless steel base parts are well known and may be of a construction such that the entire vessel, the base or only a portion of the base is made of stainless steel, the rest of the vessel being of another material such as plastics.
  • Stainless steel is used in such vessels as it has a relatively low coefficient of thermal conductivity and can therefore be utilised to effectively enclose the heat from a heating element, for example to prevent damage to plastics components of vessels, such as the side walls, due to excessive temperature in the event of the element overheating.
  • the internal surfaces of such vessels are in contact with the liquid to be heated and in particular the base of the vessel will always be covered to some extent by the liquid to be heated.
  • the stainless steel inner surfaces of the vessel are subjected to the corrosive effects of the liquid in the vessel, which effects are exacerbated by the temperatures at which the vessel operates and the consequent heating and cooling of the stainless steel.
  • Such corrosion is particularly problematic in the case of the stainless steel surfaces of electric water heating vessels, as chloride ions in the water can enter pits or imperfections in the stainless steel surface and facilitate a galvanic reaction between the constituent elements of the stainless steel, known as pitting corrosion.
  • chloride ions also accelerate the stress corrosion to which the steel is susceptible.
  • deposits of limescale from boiled water may lead to crevice corrosion of some stainless steels.
  • the base In the case of electric liquid heating vessels in which the heating element is below the stainless steel base of the vessel, the base is constantly heated by the element in order to heat the liquid in the vessel. The consequent high temperature at the base further exacerbates the above-described corrosion problems.
  • a method of preventing corrosion of a liquid- contacting stainless surface of a base part of an electric liquid heating vessel wherein the stainless steel surface is provided with a layer of glass, glass ceramic or ceramic (hereinafter collectively termed 'glass' ) .
  • the glass layer By providing a layer of glass over the surface of the base part of the vessel, contact between the liquid in the vessel and the stainless steel is entirely prevented and thus corrosion cannot occur.
  • the glass layer also provides a hard, abrasion resistant coating that resists limescale formation, but which allows any scale deposits to be removed by chemical or mechanically abrasive means.
  • the glass layer will also prevent the deposition of metal ions from the base part into the liquid in the container.
  • the base part may be integrally formed with the liquid heating vessel, in which case the other internal stainless steel surfaces of the vessel may also be provided with a layer of glass to prevent corrosion.
  • the base part may also be a discrete stainless steel component, for example a plate, forming the bottom internal surface of the vessel, or only a part thereof.
  • the rest of the vessel may be constructed of non-metallic material such as plastics.
  • the base part may be positioned below the heating element in the assembled liquid heating vessel, but the method of the invention is of particular advantage when the base part is provided with a heating element on its underside.
  • a heating element on its underside.
  • Such an underfloor heating element may be, for example, a sheathed heating element, preferably provided with a heat diffuser, or a thick film printed heating element.
  • An example of this kind of plate heater is disclosed in WO 96/18331 which describes a heated metallic plate forming at least a part of the base of a liquid heating vessel having a peripheral channel grippingly receiving a depending portion of the vessel wall.
  • thick film printed heating elements on the underside of such a base part are provided on a glass (as herein defined) layer between the heating element and the lower stainless steel surface of the base part, such that the stainless steel base part is electrically insulated from the heating element.
  • the present invention has the additional advantage that the glass layer on the upper side of the base part acts to balance out stresses in the base part due to the different rates of thermal expansion of the stainless steel compared to the glass layer which can cause distortion of the base part.
  • the balancing effect of the layers of glass on both sides of the base part strengthens the structure of the base part sufficiently that peripheral strengthening grooves such as are described in WO 96/18331 are not required and the base part may be substantially flat.
  • a thick film printed heater comprising a substantially flat steel substrate provided on both opposed surfaces with a layer of glass as herein defined.
  • the glasses used on each face of the substrate may be the same.
  • the layer of glass that will receive the resistive heating track will have a thickness of the order of 100-150 ⁇ m.
  • the two layers of glass may be applied to the base part at the same point in the manufacturing process, and then may be fired simultaneously.
  • a suitable thickness generally would be not greater than 15 ⁇ m and preferably less than 10 ⁇ m. It is believed that the minimum achievable thickness of a continuous pinhole-free glass layer will be between 5 and 7 ⁇ m, and this is therefore the most preferable thickness. Of course, the necessary thickness of the layer will depend on the glass used and a layer greater than 15 ⁇ m may be necessary. However, such a layer will generally be less than 1 mm in thickness.
  • the glass layer may be opaque or transparent. Such opaque material may be coloured or even patterned to increase the aesthetic appeal of the base. Equally, in the case of transparent material, the stainless steel of the base part may be polished or provided with a pattern, again to increase aesthetic appeal.
  • the glass layer may be of any suitable material, for example soda lime glass such as EPSOM GLASS INDUSTRIES 23169/150 glass powder. The glass will generally be applied in powder form by, for example screen printing, transfer printing, electrophoretic deposition, decal transfer, tape lamination or electrostatic spraying, before being fired.
  • the invention also extends to a stainless steel base part for an electric liquid heating vessel provided with a layer of glass on its upper surface.
  • the invention further extends to an electric liquid heating vessel incorporating such a base part.
  • Such elements and resistors typically comprise a metallic substrate, typically of polished stainless steel, onto which is deposited a glass (as herein defined) insulating layer. A thick film resistive track is provided on the insulating layer.
  • the metallic substrate is usually pre-oxidised, either through heat treatment or chemically.
  • Such processes are expensive, particularly where stainless steels are being used since it is then normal to use pre-polished steel, which is expensive, particularly since the polish is then removed by the oxidation process.
  • stainless steel surfaces are typically supplied with a protective plastic film (itself an additional cost) . This film is removed manually from each individual element, prior to further processing. This is an expensive and critical process.
  • the present invention seeks to provide a less expensive and more reliable method by which a surface may be pre-treated to receive an insulating layer.
  • the invention provides a method of pre-treating a steel surface for receiving an electrically insulating glass layer for an electrically resistive track wherein said surface is grit blasted using dry and clean grit.
  • a steel surface preferably a stainless steel surface
  • grit blasted prior to receiving the insulating layer.
  • This is substantially less expensive than heat or chemical treatment but will provide a surface which is chemically clean and which will provide a suitable key for the insulating layer.
  • an unpolished stainless steel may be used as a starting material, which is considerably less expensive than a polished one. The method provides a consistent surface for deposition of the glass layer leading to a more consistent bond.
  • the grit used is clean and dry. If it is not, impurities such as oil may be deposited on the surface which may, when the insulating layer is being fired, carbonize to cause incomplete bonding of the layer to the substrate locally. Furthermore, if the grit is not dry, moisture may be deposited on the surface leading to the formation of corrosion products which, again, will lead to an unsatisfactory bond being formed between the insulating layer and the substrate. The blasting process effectively removes the natural protective surface of the steel, which means that corrosion products will form on the surface of the steel within seconds, even in stainless steels, if impurities or moisture are present. The grit may be cleaned and dried using known and commercially available apparatus.
  • the grit may be cleaned inertially to remove dust and other particles therefrom.
  • the air or gas supply to the blaster may be dried and de-oiled in known manner, for example using commercially available equipment. This is important, since any oil deposited on the surface will lead to an unsatisfactory bond.
  • the invention provides a method of pre- treating a steel surface for receiving an electrically insulating glass layer for an electrically resistive track, wherein said surface is abraded by alumina particles.
  • the steel substrate on which the glass insulating layer is deposited is preferably stainless steel, and is preferably in the form of a plate.
  • WO 96/18331 it has been proposed in WO 96/18331 to reduce the thickness of such a plate to around .5 mm.
  • the grit impinging on a surface expands the surface by cratering. In a thin plate, this may cause deformation of the plate, leading to difficulties in successfully depositing the glass insulating layer. It has been found, however, that this distortion can be minimised by limiting the maximum size of the grit particles used.
  • the resultant surface may also be too rough to allow easy deposition of the glass layer. It has been found that a satisfactory result can be obtained by limiting the maximum nominal particle size to 100 mesh size (152 ⁇ m diameter) .
  • the invention provides a method of pre-treating a steel surface, preferably a steel plate surface for receiving an electrically insulating glass layer for an electrically resistive heating track, wherein said surface is grit blasted with a grit having a nominal maximum particle size of about 100 mesh.
  • a grit having a nominal size of 120-150 mesh having a nominal maximum particle size of 100 mesh
  • more preferably 180-220 mesh having a maximum nominal particle size of 150 mesh (104 ⁇ m)
  • the smaller the grit size the better is the finish.
  • the invention provides a method of treating both sides of a steel plate to receive respective glass layers, by grit blasting.
  • the grit blasting technique may be used to prepare that surface only. Once the surface has been blasted, it may be cleared of excess grit and dust by any suitable, clean method, for example using a so-called 'air knife' which provides a clean, dry stream of air. It may also be cleaned with a solvent to ensure that no oil deposits are left on the surface.
  • the glass insulating layer may be applied to the treated surface in a desired manner.
  • the glass may be screen printed in a conventional manner, or alternatively it may be applied electrostatically as described in GB 2306873, or more preferably in the form of a pre-formed green ceramic member, as described in WO 97/01259.
  • the invention also extends to a steel surface treated in accordance with the invention, to a heater comprising a surface treated in accordance with the invention, and to a liquid heating vessel having such a heater mounted or provided in a base thereof.
  • this aspect of the invention resides in grit blasting a metal surface prior to applying an electrically insulating glass layer thereto.
  • the method of the invention provides a less expensive, but equally effective, method of treating a substrate than previously proposed methods. It also provides a more consistent method than the prior art methods discussed above as it creates, rather than tries to maintain and treat an existing surface.

Landscapes

  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Resistance Heating (AREA)
  • Surface Heating Bodies (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Cookers (AREA)
  • Prevention Of Electric Corrosion (AREA)

Abstract

L'invention concerne un procédé servant à empêcher la corrosion de la surface en contact avec le liquide d'une partie base en acier inoxydable d'un récipient servant à réchauffer un liquide à l'électricité. Ce procédé consiste à revêtir la surface d'une couche de verre, de vitrocéramique ou de céramique. On soumet la surface, de préférence, à un traitement préalable de sablage à la grenaille d'alumine possédant une dimension nominale de 180-220 mesh. On peut utiliser cette technique de sablage afin de traiter d'autres surfaces en acier destinées à recevoir une couche de verre.
EP97926114A 1996-06-13 1997-06-13 Recipients servant a rechauffer des liquides a l'electricite Withdrawn EP0910267A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
GB9612357 1996-06-13
GBGB9612357.5A GB9612357D0 (en) 1996-06-13 1996-06-13 Electric liquid heating vessels
GBGB9613028.1A GB9613028D0 (en) 1996-06-21 1996-06-21 Heating elements
GB9613028 1996-06-21
PCT/GB1997/001598 WO1997047223A1 (fr) 1996-06-13 1997-06-13 Recipients servant a rechauffer des liquides a l'electricite

Publications (1)

Publication Number Publication Date
EP0910267A1 true EP0910267A1 (fr) 1999-04-28

Family

ID=26309503

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97926114A Withdrawn EP0910267A1 (fr) 1996-06-13 1997-06-13 Recipients servant a rechauffer des liquides a l'electricite

Country Status (4)

Country Link
EP (1) EP0910267A1 (fr)
CN (1) CN1195272A (fr)
GB (1) GB2331219B (fr)
WO (1) WO1997047223A1 (fr)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2775576B1 (fr) * 1998-03-04 2000-05-05 Seb Sa Procede pour eviter l'adherence du tartre sur un fond chauffant en acier inoxydable d'une bouilloire
WO2000028866A1 (fr) * 1998-11-16 2000-05-25 Schreitmueller Bernd Bouilloire electrique
JP3858811B2 (ja) * 2002-11-22 2006-12-20 松下電器産業株式会社 炊飯器
DE10302594A1 (de) * 2003-01-22 2004-07-29 Oellerich, Jörn Verfahren zur Vorbereitung von Oberflächen kohlenstofffaserverstärkter Kunststoffe für die Weiterverarbeitung zu tragenden Strukturteilen
CN101461282A (zh) * 2007-07-27 2009-06-17 林一峰 电热容器及电热方法
GB2470368A (en) * 2009-05-19 2010-11-24 Sagentia Ltd A glass kettle with a heating element comprising a film coating of semiconducting material
IT1396769B1 (it) * 2009-10-23 2012-12-14 Cmt Costr Mecc & Tec Metodo di trattamento di superfici d'acciaio in macchine casearie
CN102076126A (zh) * 2010-01-07 2011-05-25 张鸿鸣 金属基板玻璃陶瓷电加热器和电加热器具
CN110274097A (zh) * 2018-03-17 2019-09-24 深圳市艺水科技有限公司 一种用于腐蚀性液体的加热装置及其加工方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2692426B1 (fr) * 1992-06-11 1994-08-26 Seb Sa Plaque chauffante pour récipient chauffant, notamment pour bouilloire.
GB2283155B (en) * 1993-10-21 1997-08-06 Otter Controls Ltd Improvements relating to electrically heated water boiling vessels
GB9512559D0 (en) * 1995-06-21 1995-08-23 Strix Ltd Printed heating elements
DE29513126U1 (de) * 1995-08-16 1995-10-19 AKO-ISMET Elektrogeräte GmbH & Co. KG, 88353 Kißlegg Kochtopf

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9747223A1 *

Also Published As

Publication number Publication date
GB2331219A (en) 1999-05-12
GB9827497D0 (en) 1999-02-10
WO1997047223A1 (fr) 1997-12-18
GB2331219B (en) 2000-11-22
CN1195272A (zh) 1998-10-07

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