EP0079730A1 - Ofenmuffel - Google Patents

Ofenmuffel Download PDF

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Publication number
EP0079730A1
EP0079730A1 EP82305883A EP82305883A EP0079730A1 EP 0079730 A1 EP0079730 A1 EP 0079730A1 EP 82305883 A EP82305883 A EP 82305883A EP 82305883 A EP82305883 A EP 82305883A EP 0079730 A1 EP0079730 A1 EP 0079730A1
Authority
EP
European Patent Office
Prior art keywords
furnace
muffle
closure member
opening
support
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Withdrawn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
EP82305883A
Other languages
English (en)
French (fr)
Inventor
Albert George Docx
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.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Publication of EP0079730A1 publication Critical patent/EP0079730A1/de
Withdrawn legal-status Critical Current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
    • H05B3/62—Heating elements specially adapted for furnaces
    • H05B3/66—Supports or mountings for heaters on or in the wall or roof
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B17/00—Furnaces of a kind not covered by any preceding group
    • F27B17/02—Furnaces of a kind not covered by any preceding group specially designed for laboratory use
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B5/00—Muffle furnaces; Retort furnaces; Other furnaces in which the charge is held completely isolated
    • F27B5/06—Details, accessories, or equipment peculiar to furnaces of these types
    • F27B5/14—Arrangements of heating devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D11/00—Arrangement of elements for electric heating in or on furnaces
    • F27D11/02—Ohmic resistance heating

Definitions

  • the present invention relates to furnace muffles and to furnaces comprising such muffles.
  • furnace muffles are available which are designed for the firing of ceramic work-pieces such as are required, for example, for dental applications.
  • these furnace muffles it is known to provide a furnace muffle comprising a coiled electric heating element held in place within the muffle in a channel by means of a plurality of strips of ceramic fibrous material cemented across the opening of the channel.
  • This arrangement does not provide an even distribution of heat within the furnace muffle because the strips cemented across the top of the coiled electric heating element impede the radiation of heat therefrom.
  • closure member of the furnace is located at the top of the furnace it means that a user of the furnace must usually stand to see into thr furnace and that access to objects within the furnace is awkward due to heat rising from the interior of the furnace.
  • a furnace muffle comprising a hollow ceramic fibrous support member, an open channel defined in the inside surface of said support member, and a heating element loosely disposed in said channel, characterised in that the said heating element is prevented from moving out of the said channel by means of a member of low thermal impedance material located in a facing relationship to the said inside surface of the support.
  • the said member is tubular and is formed from glazed quartz crystal, and the support member is tubular with the open channel being helical.
  • a support on which a work-piece can be mounted in the furnace muffle is provided, the said support being comprised of glazed quartz crystal.
  • a furnace comprising a furnace muffle of the above type, the furnace further comprising a closure member adapted to close an opening in the furnace through which opening a work-piece may be directly introduced into the muffle, and means for energising the heating element to heat the muffle, wherein the closure member and the opening to the muffle are arranged in the front of the furnace, the closure member being adapted to pivot about a horizontal axis to close the opening and being adapted to be normally open unless held closed.
  • the closure member comprises a thermally insulating body adapted to close the opening of the muffle.
  • the closure member is adapted to seal the muffle so as to enable evacuation of the muffle, by for example a vacuum pump.
  • the closure member pivot may be located beneath the opening to the muffle so as to extend parallel to the front face of the furnace, the centre of gravity of the closure member being located such that it falls open unless held closed.
  • the pivot may extend perpendicular to the front face of the furnace.
  • closure member is held closed by the pressure difference across it when it is closed and the vacuum pump is on.
  • the illustrated furnace comprises a casing 1, within which are mounted on the left hand side a furnace container 2 and on the right hand side of the casing control devices and indicators which it is considered are unnecessary to describe in detail.
  • the furnace container 2 is opened and closed by a door 3, which is pivotable about a horizontal axis provided by pivot 4.
  • a shelf 25 is provided in the bottom of the interior of the furnace container 2 upon which work-pieces to be fired can be mounted. As can be seen from Figs. 1 and 2 access to the interior of the furnace container 2 is from the front of the furnace itself.
  • the furnace container 2 comprises a cup shaped vessel 5 which receives a cylindrical muffle 6.
  • the muffle 6 comprises an outer cylinder 7 of ceramic fibrous material and an inner cylinder 8 of ceramic fibrous material, in the inner surface of which is defined a helically shaped channel 9.
  • a coiled heating element 10 Located within the channel 9 is a coiled heating element 10 the ends of which are connected to conductors (not shown) which extend through the muffle wall and the cup shaped vessel 5.
  • the heating element 10 is held in place in the helical channel 9 by means of a glazed quartz crystal tube 11, the outer diameter of which is slightly less than the inner diameter of the inner cylinder 8, enabling the tube 11 to be push fitted into the furnace container.
  • the crystal quartz tube 11 ensures an even distribution of heat from the heating element 10 into the interior of the furnace container 2 where a work-piece is placed.
  • a crystal quartz plate 25 is mounted in the bottom of the crystal quartz cylinder 11 on which to mount a work-piece. The plate .25 holds the work- piece centrally within the interior of the furnace container 2 and because it is crystal quartz ensures that there is no uneven heat distribution between the top and bottom of it.
  • a pad 13 of ceramic fibrous material is located at the inside end of the vessel 5 to close the muffle 6 at its inside end and the door 3 supports a thermally insulating body 14 of ceramic fibrous material which engages in the opening to the interior of the furnace.
  • An 0-ring 15 of ceramic fibrous material is located against the outside end of the muffle 6 so that when the door 3 is closed a thermal seal is formed between the 0-ring 15 and the body 14 of the door 3.
  • a silicon rubber 0-ring (not shown) is also provided in the door 3 so that when it is closed an air-tight seal of the interior of the furnace is formed.
  • a temperature sensing device 16 extends through the pad 13.
  • a door 3 is pivotably connected to the casing 1 below the entrance to the furnace interior.
  • the door is pivotable about a horizontal axis provided by pivot 4 and its centre of gravity is such that the door 3 always opens unless held in its closed position.
  • the pivot 4 is connected to an arm 17 which operates a switch (not shown) through a slot 18 in the casing 1.
  • arm 17 moves in slot 18 and actuates the switch which turns on a vacuum pump (not shown) which is connected to the interior of the furnace container 2, through outlet 19, and energises the heating element 10.
  • Air is bled into the furnace interior through a solenoid controlled bleed valve (not shown) via inlet 20. The resulting pressure differential across the door 3 is sufficient to maintain the door 3 closed.
  • the air bled in via inlet 20 passes diametrically across the container, scavenging gassed off vapours in the process.
  • the solenoid controlled bleed valve is shut to give a full vacuum.
  • the bleed valve is reopened to release the vacuum and the pump is stopped.
  • air is bled into the container via inlet 17.
  • the pressure differential across the door 3 falls and because of the weight of the door 3 it drops open.
  • furnace muffle and the furnace of the present invention provides a number of advantages over the prior art.
  • the crystal quartz tube provided in the interior of the furnace muffle ensures a clean firing chamber by keeping metallic oxides from the heating coil away from the workpiece.
  • the outer skin of the workpiece remains at the same temperature as the body of the workpiece thus ensuring no thermal stress between the two which could result in crazing of the surface.
  • the door 3 swings open about a horizontal pivot running parallel to the front face of the furnace. After use, the inner surface of the door is hot and this can cause discomfort to a person using the furnace.
  • This problem can be overcome by providing an alternative door support mechanism which results in the door swinging away from the entrance to the furnace interior about a horizontal pivot perpendicular to the front face of the furnace.
  • the door could be supported on a short arm pivoted on a shaft extending from the front to the back of the furnace casing, the shaft being positioned above and to one side of the centre of the furnace entrace.
  • the door can be spring loaded so that when released it moves forwards parallel to the shaft axis and then swings away from the furnace entrace as a result of pivoting about the shaft under the influence of gravity.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Clinical Laboratory Science (AREA)
  • Furnace Details (AREA)
  • Muffle Furnaces And Rotary Kilns (AREA)
EP82305883A 1981-11-10 1982-11-04 Ofenmuffel Withdrawn EP0079730A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8133948 1981-11-10
GB8133948 1981-11-10

Publications (1)

Publication Number Publication Date
EP0079730A1 true EP0079730A1 (de) 1983-05-25

Family

ID=10525783

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82305883A Withdrawn EP0079730A1 (de) 1981-11-10 1982-11-04 Ofenmuffel

Country Status (1)

Country Link
EP (1) EP0079730A1 (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1985000964A1 (fr) * 1983-09-07 1985-03-14 Rudolf Barget Appareil de coulee en particulier pour des travaux de technique dentaire
EP0194727A1 (de) * 1985-03-11 1986-09-17 European Atomic Energy Community (Euratom) Hochtemperaturapparat für die Untersuchung der Wirkung eines gasförmigen Mittels auf einem Stoff
DE19746872A1 (de) * 1997-10-23 1999-05-12 Heraeus Quarzglas Heizelement und unter seiner Verwendung hergestellter Ofen
DE19813251A1 (de) * 1998-03-25 1999-10-07 Daimlerchrysler Aerospace Ag Widerstandsheizvorrichtung
WO2004001311A1 (en) * 2002-06-20 2003-12-31 Dentsply International Inc. Device for firing ceramic for dental prostheses
EP2639537A3 (de) * 2012-03-16 2014-11-19 MWT Mikrowellen Labor Technik AG Ofen mit feuerfestem Einsatz
FR3035396A1 (fr) * 2015-04-23 2016-10-28 Adam Pyrometrie Four electrique portatif de recuisson de perles de verre

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1390876A (fr) * 1964-04-17 1965-02-26 Four à corps cylindrique portatif particulièrement pour la cuisson de céramiques et emplois similaires
US3406242A (en) * 1967-05-04 1968-10-15 Karl A. Lang Diffusion furnace hearth plate
DE1294600B (de) * 1963-07-19 1969-05-08 Inst Ziegelforschung Essen E V Laboratoriums- oder Kleinofen
GB1441577A (en) * 1972-09-02 1976-07-07 Docx A G Muffle furnaces
US3972682A (en) * 1975-10-06 1976-08-03 Envirotech Corporation Pyrolysis furnace
US4272670A (en) * 1976-05-01 1981-06-09 Docx Albert G Furnace muffles and furnaces

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1294600B (de) * 1963-07-19 1969-05-08 Inst Ziegelforschung Essen E V Laboratoriums- oder Kleinofen
FR1390876A (fr) * 1964-04-17 1965-02-26 Four à corps cylindrique portatif particulièrement pour la cuisson de céramiques et emplois similaires
US3406242A (en) * 1967-05-04 1968-10-15 Karl A. Lang Diffusion furnace hearth plate
GB1441577A (en) * 1972-09-02 1976-07-07 Docx A G Muffle furnaces
US3972682A (en) * 1975-10-06 1976-08-03 Envirotech Corporation Pyrolysis furnace
US4272670A (en) * 1976-05-01 1981-06-09 Docx Albert G Furnace muffles and furnaces

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1985000964A1 (fr) * 1983-09-07 1985-03-14 Rudolf Barget Appareil de coulee en particulier pour des travaux de technique dentaire
EP0194727A1 (de) * 1985-03-11 1986-09-17 European Atomic Energy Community (Euratom) Hochtemperaturapparat für die Untersuchung der Wirkung eines gasförmigen Mittels auf einem Stoff
DE19746872A1 (de) * 1997-10-23 1999-05-12 Heraeus Quarzglas Heizelement und unter seiner Verwendung hergestellter Ofen
DE19746872C2 (de) * 1997-10-23 2001-09-27 Heraeus Quarzglas Heizelement und unter seiner Verwendung hergestellter Ofen
DE19813251A1 (de) * 1998-03-25 1999-10-07 Daimlerchrysler Aerospace Ag Widerstandsheizvorrichtung
DE19813251C2 (de) * 1998-03-25 2000-03-16 Daimlerchrysler Aerospace Ag Widerstandsheizvorrichtung
WO2004001311A1 (en) * 2002-06-20 2003-12-31 Dentsply International Inc. Device for firing ceramic for dental prostheses
US7202448B2 (en) 2002-06-20 2007-04-10 Dentsply International Inc. Device for firing ceramic for dental prostheses
EP2639537A3 (de) * 2012-03-16 2014-11-19 MWT Mikrowellen Labor Technik AG Ofen mit feuerfestem Einsatz
FR3035396A1 (fr) * 2015-04-23 2016-10-28 Adam Pyrometrie Four electrique portatif de recuisson de perles de verre

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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AK Designated contracting states

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STAA Information on the status of an ep patent application or granted ep patent

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Effective date: 19840427