Browse Prior Art Database

PREFERENTIALLY HEATED STRUCTURE CRUCIBLE

IP.com Disclosure Number: IPCOM000023011D
Original Publication Date: 1976-Jun-30
Included in the Prior Art Database: 2004-Mar-27
Document File: 2 page(s) / 242K

Publishing Venue

Xerox Disclosure Journal

Abstract

A method is disclosed for providing preferential heating to a crucible, e~g,, a tube crucible, without the need for radiation shields, Presently1 a tube crucible is heated by passing a high current through the structure, thereby heating the metal (resistance heated) which in turn melts the photoconductive material and causes it to evaporateS The instant invention comprises a method whereby the crucible is constructed in such a way that the areas not in contact with the evaporant can be heated to a different temperature than the areas which are in contact with the evaporant. Principles of heat radiation are used. It is desirable to have the areas in contact with the evaporant material operate at a cooler temperature than the areas of the crucible not in contact with the evaporant. Therefore, the latter areas should be treated to provide highly reflective surface (bright or reflection) and the former areas treated to provide a highly emissive surface (black) Therefore, with the same current density, the reflective areas will be relatively hotter than the black areas, Therefore, the inside area of the tube crucible can be treated in a similar way. For efficient heat transfer to the evaporant~ the inside area should be dark, The pre~ ferred embodiment comprises a tube crucible having an upper portion having a bright surface and a lower portion having a dark surface. The temperature of the upper half will allow a higher heat flux to strike the surface of the evaporant giving the effect of heating the evaporant from above. Also, it would provide a heat zone through which the evaporant must pass on its way to the exit port.

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XEROX DISCLOSURE JOURNAL

PREFERENTIALLY HEATED Proposed Classification

    ~~CRUCIB~j U.S, CL 96
Frank Erhart Into Cl, G03c

A method is disclosed for providing preferential heating to
a crucible, e~g,, a tube crucible, without the need for
radiation shields, Presently

                   1 a tube crucible is heated by
passing a high current through the structure, thereby
heating the metal (resistance heated) which in turn melts
the photoconductive material and causes it to evaporateS
The instant invention comprises a method whereby the
crucible is constructed in such a way that the areas not in
contact with the evaporant can be heated to a different
temperature than the areas which are in contact with the
evaporant. Principles of heat radiation are used. It is
desirable to have the areas in contact with the evaporant
material operate at a cooler temperature than the areas of
the crucible not in contact with the evaporant. Therefore,
the latter areas should be treated to provide highly
reflective surface (bright or reflection) and the former
areas treated to provide a highly emissive surface (black)
Therefore, with the same current density, the reflective
areas will be relatively hotter than the black areas,
Therefore, the inside area of the tube crucible can be
treated in a similar way. For efficient heat transfer to
the evaporant~ the inside area should be dark, The pre~
ferred embodiment comprises a tube crucible having an
upper portion having a bright surface and a lower portion
having a dark surface. The te...