US3636229A - Electrically resistive crucible - Google Patents

Electrically resistive crucible Download PDF

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Publication number
US3636229A
US3636229A US83786A US3636229DA US3636229A US 3636229 A US3636229 A US 3636229A US 83786 A US83786 A US 83786A US 3636229D A US3636229D A US 3636229DA US 3636229 A US3636229 A US 3636229A
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United States
Prior art keywords
crucible
electrode
heating
stud
electrically resistive
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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 - Lifetime
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US83786A
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English (en)
Inventor
George J Sitek
Robert N Revesz
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Laboratory Equipment Corp
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Laboratory Equipment Corp
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Publication date
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Publication of US3636229A publication Critical patent/US3636229A/en
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    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
    • B01L3/04—Crucibles
    • 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

Definitions

  • the crucible not only constitutes the resistance element in such a usage; it also provides the reactive material in the event that oxygen is the subject of the analysis. Upon heating of the sample, the oxygen will react with the carbon of the crucible to fonn carbon monoxide which may be swept from the furnace by a nitrogen stream for subsequent analysis.
  • the crucible hitherto employed for this purpose has been a simple cylinder having an axial bore extending partially therethrough from one end so as to leave a relatively heavy base.
  • the heating in a resistance device will, of course, be greatest where the section is smallest. Therefore, with the conventional crucible, the maximum heating will occur in the wall portion-of the crucible above the base. Since, however, there is heat loss to the cooled electrodes, the areas of highest temperature will be about midway along the length of the crucible.
  • such a crucible To withstand the clamping of the crucible between the electrodes for satisfactory conductivity and to withstand handling generally, such a crucible must obviously have a certain minimum wall thickness. With an increase in the diameter of the crucible, therefore, such as might be desired for the analysis of larger samples or solid samples of appreciable length, the area of the minimum section will increase and the heating effect be diminished for any given current. Thus, with a given power supply, there is a highly restrictive limit to the diameter of the crucible employed. The time for heating could, of course, be extended, but this is undesirable in such analytical apparatus, and by virtue of the heat-sinking effect of the electrodes, even the extension of heating time will run into a limit.
  • the floor of the crucible must receive its heat by thermal conduction from the walls. At the same time there is the heat loss to the electrodes. The latter effect can be minimized by making the crucible bottom thick, but as the diameter of the crucible increases, the loss to the electrode becomes proportionately greater to a point where, again, the temperature achieved at the floor is inadequate.
  • This invention teaches a carbon crucible having an integral stud on the exterior of the bottom thereof through which the crucible is connected into the electrode circuit whereby the size limitations of the conventional crucible discussed above are avoided and whereby the point of maximum heating occurs on the bottom of the crucible rather than a distance up the sides thereof.
  • FIG. 1 is a vertical, somewhat diagrammatic, section through an impulse furnace adapted to use the graphite crucible of the invention, shown with a crucible mounted therein;
  • FIG. 2 is a vertical section through the crucible of FIG. 1 taken along the line 2-2 of FIG. 1;
  • FIG. 3 is a somewhat diagrammatic representation of the section of FIG. 2 illustrating the zone of maximum heat.
  • FIG. 1 there is shown a portion of combustion apparatus to be used in conjunction with analytical equipment, the portion illustrating an impulse furnace particularly.
  • the furnace includes a stationary top electrode 12 and a lower support electrode 14 movable toward and away from the top.
  • the support electrode is cup-shaped with an annular rim 16 and a post 18 extending upward from the center of the bottom of the cup, defining an annular groove 20 between the rim and the post.
  • the post is hollow as at 22 to provide for a flow of liquid coolant therethrough.
  • the upper end of the post has a cuplike socket 24 in the center thereof, and from the socket, the upper end slopes broadly conically downward as at 26.
  • a crucible 28, the subject of this invention, will be mounted to the lower electrode post 18 with the stud 30 thereof received in the socket 24.
  • the top stationary electrode 12 is likewise cup-shaped, but downwardly facing. It includes a rim or skirt 32 fitting closely telescopically within the rim 16 of the lower electrode, and 0- rings 34 embedded in the outer periphery of the skirt make a gastight seal with the rim 16.
  • the top electrode has a large diameter passage 36 extending upward from the cup floor 38 for sample introduction and carrier gas admission.
  • the passage 36 while large, is smaller than the mouth of the crucible 28.
  • Radial grooves 40 are formed in the floor of the electrode extending from the passage 36 to the upper end of the skirt 32.
  • Liquid passages 42 are provided within the body of the electrode for the flow of coolant.
  • a gas exhaust duct 44 extends from the bottom face of the skirt 32 upwardly through the electrode to be connected to analysis apparatus.
  • the crucible 28 is formed of a short length of cylindrical graphite rod which is machined to provide an interior cavity 46 defined by upstanding walls 48, a base 50 somewhat heavier than the walls, and the cylindrical stud 30 projecting centrally from the bottom 50 of the crucible.
  • the stud will be received in the socket 24 of the support electrode as stated above.
  • the electrodes are connected across a source of low voltage high current power 52 and desirably are made of copper.
  • the relation of parts in the furnace is such that, when the support electrode 14 is raised to its uppermost position with the crucible attached for sample heating, the top edge of the crucible walls 48 engages the floor 38 of the top electrode 12 concentrically with the gas passage 36. The crucible is thus clamped under pressure between the support electrode 14 and the top electrode 12. In such position, the sleeve 32 slides telescopically into the groove 20 but stops short of the bottom of the groove 16.
  • the O-rings 34 effect a gas seal between these telescoping surfaces and likewise serve to space the sleeve from the rim 16 in electrically insulating relationship under the low voltage of heating.
  • the sleeve 32 is also thin enough such that it stands well clear of the center post 18 of the support electrode. Since, as illustrated, the crucible has a smaller diameter than the center post, it will be appreciated that raising the crucible into heating position will define an annular chamber about the outside of the crucible.
  • the bottom edge of the skirt 32 stands well above the bottom of the groove 20, and the outlet passage 44 is thus in communication with the above-defined annular chamber.
  • the radial grooves 40 in the top electrode open the interior of the crucible to the outside, annular chamber.
  • a sample will be placed in a conventional loading device above the passage 36, not shown, and there purged by a flow of carrier gas.
  • the crucible will be heated in the same gas stream to eliminate occluded and absorbed gases.
  • the sample will be dropped by the loading device into the crucible and the crucible heated to fuse the sample.
  • Evolved gases from the sample will be swept by the carrier gas stream, entering through passage 36, through radial grooves 40 and out the gas outlet 44 to analyti' cal apparatus.
  • a representative crucible made in accordance with the teachings of this invention will have an outside diameter of 0.56 inch and a wall thickness of 0.04 inch.
  • the floor of the crucible has a thickness of 0.12 inch, and the stud has a diameter of 0. l 87 inch and a projection of about 0.13 inch.
  • the stud is filleted at its juncture of the bottom of the crucible 50 for reasons of strength.
  • the socket 24 is 0.08 inch deep, thus leaving a separation of 0.05 inch between the bottom of the crucible and the upper end 26 of the post 18.
  • the areas of pressure contact, as well as providing conductive contact, are also the principal areas of heat loss to the electrodes.
  • the increment of stud nearest the bottom of the crucible will therefore be the hottest portion of the system. This is in notable contrast to the previously employed studless crucible, where the outer periphery of the base of the crucible is in contact with the lower electrode (through a tripodal electrode configuration), current flow is primarily through the annular portion of the base aligned with the walls, and wherein the point of maximum heating occurs about halfway up the walls of the crucible.
  • the diameter of the crucible can be made substantially larger and thus be receptive to larger samples including pin samples which can lie flat on the floor of the crucible rather than be held in an inclined position therewithin as would be the case with the smaller diameter crucible.
  • the stud not only provides a small section conductor whereby the heating effect is augmented; it also serves as a stand-off insulator whereby contact of the base of the crucible with the water cooled electrode is avoided thus preventing loss of heat from the base to the electrode. Also, since the floor alone is the matter of primary interest in the crucible heating, there is less bulk of crucible to be outgassed, and accordingly, the outgassing time may be substantially reduced.
  • An electrically resistive graphite crucible for fusion apparatus having cylindrical sidewalls, a bottom, and a stud projecting downwardly from said bottom, said stud having a cross-sectional area less than the cross-sectional area of said wall.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Clinical Laboratory Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Devices For Use In Laboratory Experiments (AREA)
  • Sampling And Sample Adjustment (AREA)
  • Crucibles And Fluidized-Bed Furnaces (AREA)
  • Investigating And Analyzing Materials By Characteristic Methods (AREA)
US83786A 1970-10-26 1970-10-26 Electrically resistive crucible Expired - Lifetime US3636229A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US8378670A 1970-10-26 1970-10-26

Publications (1)

Publication Number Publication Date
US3636229A true US3636229A (en) 1972-01-18

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ID=22180695

Family Applications (1)

Application Number Title Priority Date Filing Date
US83786A Expired - Lifetime US3636229A (en) 1970-10-26 1970-10-26 Electrically resistive crucible

Country Status (6)

Country Link
US (1) US3636229A (enrdf_load_stackoverflow)
JP (1) JPS5438043B1 (enrdf_load_stackoverflow)
CA (1) CA929998A (enrdf_load_stackoverflow)
DE (1) DE2130532C3 (enrdf_load_stackoverflow)
FR (1) FR2109728A5 (enrdf_load_stackoverflow)
GB (1) GB1302479A (enrdf_load_stackoverflow)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3899627A (en) * 1974-06-28 1975-08-12 Leco Corp Crucible
US3936587A (en) * 1974-06-28 1976-02-03 Leco Corporation Electrode construction for resistance heating furnace
US4056677A (en) * 1976-04-19 1977-11-01 Leco Corporation Electrode system for resistance furnace
US4072814A (en) * 1976-05-10 1978-02-07 Institut De Recherches De La Siderurgie Francaise Irsid Furnace for melting metal by the Joule effect
DE3001239A1 (de) * 1980-01-15 1981-07-30 Moskovskij institut stali i splavov, Moskva Verfahren zur bestimmung der wasserstoffmenge in anorganischen materialien
US20130337396A1 (en) * 2012-06-19 2013-12-19 Leco Corporation Crucible
USD712446S1 (en) 2012-06-19 2014-09-02 Leco Corporation Crucible
US9808797B2 (en) 2012-06-19 2017-11-07 Leco Corporation Resistance analytical furnace
CN109012777A (zh) * 2018-08-20 2018-12-18 北海飞九天电子科技有限公司 一种坩埚
CN109046488A (zh) * 2018-08-20 2018-12-21 北海飞九天电子科技有限公司 一种坩埚
CN109046489A (zh) * 2018-08-20 2018-12-21 北海飞九天电子科技有限公司 一种坩埚

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2225421C2 (de) * 1972-05-25 1982-05-06 Bodenseewerk Gerätetechnik GmbH, 7770 Überlingen Vorrichtung zum Atomisieren von Proben durch elektrische Beheizung für die flammenlose Atomabsorptions-Spektrometrie
US4328386A (en) * 1980-09-24 1982-05-04 Leco Corporation Crucible assembly
FR3127036B1 (fr) 2021-09-16 2023-08-04 Psa Automobiles Sa Dispositif d’éclairage et/ou de signalisation de véhicule automobile.

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1015091A (en) * 1911-05-05 1912-01-16 William Speirs Simpson Apparatus for melting and mixing metals in vacuums.
US1430858A (en) * 1920-10-05 1922-10-03 Morgan Crucible Co Electrically-heated furnace
US1551839A (en) * 1923-10-08 1925-09-01 Nash Engineering Co Electric furnace
US2930602A (en) * 1957-11-25 1960-03-29 Lab Equipment Corp Gas analysis crucible

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS451096Y1 (enrdf_load_stackoverflow) * 1964-10-05 1970-01-19

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1015091A (en) * 1911-05-05 1912-01-16 William Speirs Simpson Apparatus for melting and mixing metals in vacuums.
US1430858A (en) * 1920-10-05 1922-10-03 Morgan Crucible Co Electrically-heated furnace
US1551839A (en) * 1923-10-08 1925-09-01 Nash Engineering Co Electric furnace
US2930602A (en) * 1957-11-25 1960-03-29 Lab Equipment Corp Gas analysis crucible

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3899627A (en) * 1974-06-28 1975-08-12 Leco Corp Crucible
US3936587A (en) * 1974-06-28 1976-02-03 Leco Corporation Electrode construction for resistance heating furnace
US4056677A (en) * 1976-04-19 1977-11-01 Leco Corporation Electrode system for resistance furnace
US4072814A (en) * 1976-05-10 1978-02-07 Institut De Recherches De La Siderurgie Francaise Irsid Furnace for melting metal by the Joule effect
DE3001239A1 (de) * 1980-01-15 1981-07-30 Moskovskij institut stali i splavov, Moskva Verfahren zur bestimmung der wasserstoffmenge in anorganischen materialien
US20130337396A1 (en) * 2012-06-19 2013-12-19 Leco Corporation Crucible
USD712446S1 (en) 2012-06-19 2014-09-02 Leco Corporation Crucible
US9527076B2 (en) * 2012-06-19 2016-12-27 Leco Corporation Crucible
US9808797B2 (en) 2012-06-19 2017-11-07 Leco Corporation Resistance analytical furnace
CN109012777A (zh) * 2018-08-20 2018-12-18 北海飞九天电子科技有限公司 一种坩埚
CN109046488A (zh) * 2018-08-20 2018-12-21 北海飞九天电子科技有限公司 一种坩埚
CN109046489A (zh) * 2018-08-20 2018-12-21 北海飞九天电子科技有限公司 一种坩埚

Also Published As

Publication number Publication date
DE2130532C3 (de) 1973-10-18
CA929998A (en) 1973-07-10
GB1302479A (enrdf_load_stackoverflow) 1973-01-10
JPS5438043B1 (enrdf_load_stackoverflow) 1979-11-19
DE2130532A1 (de) 1972-04-27
FR2109728A5 (enrdf_load_stackoverflow) 1972-05-26
DE2130532B2 (de) 1973-04-05

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