GB1559438A - Conveyor rollers for continous furnaces - Google Patents

Conveyor rollers for continous furnaces Download PDF

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Publication number
GB1559438A
GB1559438A GB2126977A GB2126977A GB1559438A GB 1559438 A GB1559438 A GB 1559438A GB 2126977 A GB2126977 A GB 2126977A GB 2126977 A GB2126977 A GB 2126977A GB 1559438 A GB1559438 A GB 1559438A
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GB
United Kingdom
Prior art keywords
roller
conveyor roller
steel
plasma jet
continuous furnace
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.)
Expired
Application number
GB2126977A
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.)
Siemens AG
Original Assignee
Siemens AG
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 Siemens AG filed Critical Siemens AG
Publication of GB1559438A publication Critical patent/GB1559438A/en
Expired legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B35/00Transporting of glass products during their manufacture, e.g. hot glass lenses, prisms
    • C03B35/14Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands
    • C03B35/16Transporting hot glass sheets or ribbons, e.g. by heat-resistant conveyor belts or bands by roller conveyors
    • C03B35/18Construction of the conveyor rollers ; Materials, coatings or coverings thereof
    • C03B35/181Materials, coatings, loose coverings or sleeves thereof
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/38Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for roll bodies
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27FURNACES; KILNS; OVENS; RETORTS
    • F27DDETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D3/00Charging; Discharging; Manipulation of charge
    • F27D3/02Skids or tracks for heavy objects
    • F27D3/026Skids or tracks for heavy objects transport or conveyor rolls for furnaces; roller rails

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • General Engineering & Computer Science (AREA)
  • Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
  • Rollers For Roller Conveyors For Transfer (AREA)
  • Tunnel Furnaces (AREA)

Description

(54) IMPROVEMENTS IN OR RELATING TO CONVEYOR ROLLERS FOR CONTINUOUS FURNACES (71) We, SIEMENS AKTIENGESELLSCHAFT, a German Company of Berlin and Munich, German Federal Republic, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to conveyor rollers for continuous furnaces, in particular continuous furnaces used in the production of window or plate glass.
In the production of glass, it has long been known to use powered conveyor rollers having at least possible adverse effect on the surface of the glass carried by them, for conveying material in plate form in the heated part of the furnace. It has been found that operating conditions exist, however, particularly in the production of special glass, e. g. prestressed glass of high mechanical strength, which impose demands on the kinds of roller already known which latter are not capable of meeting. As a result of an excessively high surface temperature during the processing operation (the need for which cannot, however, be avoided), it may happen that surface roughness, impurities (such as dust falling from the furnace roof), or tiny surface defects originating from earlier damage in the roller zone, produce deep flaws that cannot be repaired in the mirror-smooth surface of plate or window glass which is naturally especially sensitive from this point of view.
Various efforts have consequently been made in the past to provide conveying methods which do not have the abovedescribed disadvantages, and as a result of these efforts, there have. for example, been used steel conveyor rollers with woven ceramic coverings, and rollers made of ceramic materials, and precision-ground high-grade steel.
The use of conveyor rollers covered with woven ceramic material seems to be highly advantageous provided the coating material has a sufficiently high melting point.
However, it must be remembre that frequent changing of these coverings (often several time a day) is necessary because of the embrittlement that occurs as a result of the repeated thermal loading. For its part, the use of rollers made exclusively of ceramic material brings all the problems which are known when ceramic materials are used with highly heated glass, and in addition, it must be expected that high internal stresses will arise and will lead to cracks in the peripheral direction. The strength of the roller can certain be fully maintained during production by appropriate design, for example, by incorporating load-bearing steel rods, but the peripheral cracks lead to longitudinal markings on the glass surface which become clearly visible, even when the cracks are only fine hairline cracks in the initial stages.
The use of conveyor rollers made from special steel with a precision-ground surface seems perfectly reasonable so far as steel technology is concerned, even in the temperature ranges required in the production of normal glass, and would also be feasible from the standpoint of design. However, in this connection, it must be remembered that the conveying operation will bring a high) y heated silicate glass into contact with an iron alloy. In the course of time, therefore, mutual interaction must develop between the silicon of the material being conveyed and the material carrying it and reactions corresponding to siliconisation of the steel are very difficult to prevent with such an arrangement. Together with this goes a change in the specific grain size at the surface of the roller, which again leads in the long term to the appearance of cracks like those formed in the ceramic rollers. The embrittlement of the surface zone can be avoided for a certain time by choosing certain grades of steel, but the cost of such alloys, even when they are only applied as surface coatings on lower-grade steels, is so high that the relationship between the improvement of the product and the depreciation costs appears doubtful from the viewpoint of economic operation.
Consequently, other ways of overcoming the above-described disadvantages have been sought, and as one solution, the theoretically elegant and simple solution of conveying the material within the surface of an air-cushion has been proposed. In this process, the glass sheet or plate, either heated or to be heated, is kept floating on jets of air blown vertically upwards from corresponding openings in the floor of the conveyor channel, transportation along the length of the furnace being effected by other auxiliary means which need not be ex plained here but are described in German Patent Specifications Nos. 1,531,878 and 1,756,070 as open to inspection.
It is clear that the use of the process referred to in the preceding paragraph could form the basis for a considerable technological advance, but the question must first be posed whether the strong air or gas flows required would not, in furnaces of the size encountered in practical glass manufacture, also raise or blow about at least small amounts of dust which is inevitably present from movement of the furnace lining during temperature changes and could hardly be avoided even when operating with the greatest care. This dust would settle on the surface of the glass and form an undissolvable bond therewith at that processing stage.
According to the present invention, there is provided a conveyor roller for use in a continuous furnace, in particular in a continuous furnace for the production of window or plate glass, said roller being made of steel and having a martensitic surface coating on its curved surface which in use comes into contact with the material to be conveyed, said coating having been produced by a two-stage hardening of the steel body of said roller in which said surface is first rapidly heated and thereafter allowed to cool rapidly.
The properties of such martensitic surface coatings have already been described in detail, for example, in a paper by Dr.
Swoboda and Dr. Pater at the Leoben Iron and Steel Congress 1965, and are essentially such that give an insoluble structure which is extremely hard and resilient. The siliconisation and diffusion processes which are likely to occur with the steel conveyor rollers previously described, are thus suppressed because of the insoluble structure of the martensitic coating, which acts as a diffusion inhibitor preventing silicon transfer even at fairly high temperatures. Because of the high resistance to distortion of this coating, the required resistance to temperature changes is also ensured, so that no cracks due to scaling or hardening are likely to be found on the surface.
To produce such surface coatings, it is advantageous to use a two-stage hardening process which entails rapidly supplying a large amount of energy to a small surface area, and thereafter allowing the surface to cool equally rapidly.
The invention will now be described with reference to the drawing, which is a schematic side view of one form of apparatus for producing a roller in accord- : ance with the invention.
Referring to the drawing, a highfrequency generator 1 is provided with a pin-shaped electrode 2 to serve as a generator for an electric field, the electrode 2 being disposed in a tube 3 through which an ionisable gaseous medium flows, so that-this medium is converted into the ionised state by stimulation by the field and emerges as à~ high frequency plasma jet in the form of a thin linear glow discharge up to several metres in length, through a shaping nozzte 4 disposed at the end of the tube 3 forming the primary discharge chamber towards the steel roller 5 to be treated. The interaction of this discharge with the surface of the metal roller causes very intense superheating followed by equally rapid cooling of the surface as soon as the plasma jet is removed, owing to the high heat capacity of the steel roller, thus producing the desired, change in the structure of the metal. Such an arrangement is described in Austrian Patent No. 294, 266.
It should be pointed out that, in principle, any kind of energy supply can be used for the formation of the coating, provided that it allows the necessary localise concentration of energy of suitable intensity.

Claims (4)

  1. WHAT WE CLAIM IS: 1. A conveyor roller for use in a continuous furnace, in particular in a continuous furnace for the production of window or plate glass, said roller being made of steel and having a martensitic surface coating on its curved surface which in use comes into contact with the material to be con veyed, said coating having been produced by a two-stage hardening of the stem body of said roller in which said surface is first rapidly heated and thereafter allowed to cool rapidly.
  2. 2. A conveyor roller as claimed in Claim 1, wherein the heating stage of said twostage hardening is effected by means of a high-frequency plasma jet.
  3. 3. A conveyor roller as claimed in Claim 2, wherein said high-frequency plasma jet is produced by the passage of an ionisable gas through a high-frequency electric field in a discharge chamber and passage of the highfrequency plasma jet so formed through a shaping nozzle.
  4. 4. A conveyor roller for a continuous furnace substantially as hereinbefore described with reference to the drawing.
GB2126977A 1976-06-04 1977-05-20 Conveyor rollers for continous furnaces Expired GB1559438A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT410976A ATA410976A (en) 1976-06-04 1976-06-04 CONVEYOR ROLL FOR CONTINUOUS

Publications (1)

Publication Number Publication Date
GB1559438A true GB1559438A (en) 1980-01-16

Family

ID=3559771

Family Applications (1)

Application Number Title Priority Date Filing Date
GB2126977A Expired GB1559438A (en) 1976-06-04 1977-05-20 Conveyor rollers for continous furnaces

Country Status (6)

Country Link
AT (1) ATA410976A (en)
BE (1) BE855398A (en)
DE (2) DE2711465A1 (en)
DK (1) DK218377A (en)
FR (1) FR2353820A1 (en)
GB (1) GB1559438A (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4006497A1 (en) * 1990-01-18 1991-07-25 Nassheuer Loi Industrieofenanl Transporting roller for heated products in ovens - has cylindrical body and screw form transporting surface with larger pitch in centre than at ends

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2619439A (en) * 1950-06-09 1952-11-25 United States Steel Corp Method of hardening rolls
AT262357B (en) * 1964-09-23 1968-06-10 Boehler & Co Ag Geb Process for surface hardening of hardenable steels
DE2111183B2 (en) * 1970-09-21 1978-03-23 Vereinigte Edelstahlwerke Ag (Vew), Wien Niederlassung Vereinigte Edelstahlwerke Ag (Vew) Verkaufsniederlassung Buederich, 4005 Meerbusch Process and arrangement for the two-stage surface hardening of workpieces made of hardenable iron and steel alloys
US3723083A (en) * 1970-12-23 1973-03-27 Libbey Owens Ford Co Textured conveyor roll and method of finishing the same

Also Published As

Publication number Publication date
ATA410976A (en) 1981-06-15
DE2711465A1 (en) 1977-12-15
DK218377A (en) 1977-12-05
FR2353820A1 (en) 1977-12-30
DE7708119U1 (en) 1978-11-16
BE855398A (en) 1977-10-03

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PCNP Patent ceased through non-payment of renewal fee