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US 4,058,699 AGranted
Radiant zone heating apparatus and method
AssigneeArthur D. Little, Inc.
InventorCurtis P. van Vloten
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AssigneeArthur D. Little, Inc.
InventorCurtis P. van Vloten
Estimating the term…
A heating zone of accurately controlled length and predetermined energy profile throughout its length is formed within a focusing apparatus. An elliptical cavity is provided having a conically-configured reflector positioned such that its longitudinal axis coincides with one of the focal axes of the elliptical cavity. An elongate body is placed within the cavity such that its longitudinal axis coincides with the other focal axis. When a beam of radiant energy within a wavelength range which couples with the body to heat it, e.g., a laser beam, is directed onto the conically-configured reflector it is concentrated uniformly around the body throughout a predetermined length. The energy profile along the zone length may be varied either by adjusting the energy distribution in the energy beam prior to being reflected, by modifying the surface contour of the reflector, by modifying the contour of the walls defining the elliptical cavity or by a combination of two or more of these techniques. A plurality of overlapping elliptical cavities may be arranged to have one common axes along which the reflector is positioned and a plurality of axes along which a plurality of elongate bodies are positioned. The apparatus of this invention is particularly suited for heating rods and tubes and, if desired, for use within a controlled atmosphere.
An apparatus for focusing a radiation beam around the surface of at least one body within a relatively narrow band height, comprising in combination
An apparatus for focusing a radiation beam around the surface of a body within a relatively narrow band length, comprising in combination
An apparatus for providing a heating zone of controlled length and predetermined energy profile throughout said length, comprising in combination
An apparatus for providing a heating zone of controlled length and predetermined energy profile throughout said length, comprising in combination
An apparatus for processing an elongate body which includes forming a molten zone within said body, comprising in combination
An apparatus for processing an elongate body which includes forming a molten zone within said body, comprising in combination
A method for forming around the surface of a body a heating zone of radiant energy having a relatively narrow, controllable height, comprising the steps of
A method for forming around the surface of each of a plurality of bodies a heating zone of radiant energy having a relatively narrow, controllable height, comprising the steps of
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
No related US applications are recorded in the indexed filing history.
In a special environment or atmosphere, e.g. in an enclosure: in an enclosure
By means of optical elements, e.g. lenses, mirrors or prisms: comprising mirrors
Shaping the laser spot: into an annular shape
From reheated softened tubes, rods, fibres or filaments , e.g. drawing fibres from preforms: furnaces therefor
Term ended 15 Nov 1994 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
This invention relates to apparatus for focusing a beam of radiant energy around the surface of a body and within a relatively narrow band length to concentrate the energy in a heating zone with controlled energy distribution. The radiation is derived from that portion of the electromagnetic spectrum which will couple with the body to be heated in the zone. Exemplary of such energy is a beam from a laser.
The use of radiant energy, and particularly laser energy, to provide a concentrated heating zone for such processes as zone refining and forming refractory fibers and tubings by the processes described in U.S. Pat. application Ser. Nos. 369,884, now U.S. Pat. No. 3,944,640 and 318,911, now U.S. Pat. No. 3,943,324 assigned to the same assignee as this application, has certain distinct advantages. Thus, for example, laser energy has no characteristic temperature of its own and therefore there are virtually no upper limitations on the temperatures which can be attained in a heating zone. Laser energy can be employed in a manner to eliminate or minimize problems of heat transfer to the body within the heating zone. Moreover, the use of laser energy imposes few, if any, restrictions on the atmosphere in which the heating is performed and it thereby provides a wide latitude in the choice of such atmospheres. Finally, the use of laser energy permits visual observation of a process employing it.
All of these important advantages associated with laser energy make its use highly desirable. There is, however, the problem of optically focusing such radiant energy, generally originating as a single beam, around the entire surface of a rod, fiber or tube to attain uniform peripheral heating. In zone melting, such uniform heating is desirable, while in forming fibers or tubes by the methods of U.S. Pat. Nos. 3,944,640 and 3,943,324, such uniform peripheral heating is essential.
For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings in which
FIG. 1 is a longitudinal cross section of the focusing apparatus of this invention showing one embodiment of the conically-configured reflector;
FIG. 2 is a cross section of the focusing apparatus of FIG. 1 taken through plane 2--2 of FIG. 1;
For convenience in describing the method and apparatus of this invention it will be assumed that the radiant energy is derived from a laser. However, this method and apparatus are equally suitable for the focusing of other forms of radiation beams such as those derived from incandescent, arc and discharge lamp sources, and the like.
FIGS. 1 and 2 illustrate the focusing apparatus of this invention in cross sectional detail. This apparatus comprises a block 10, formed of such materials as a plastic, aluminum, brass, bronze or the like, having an elliptical cavity 11 cut therethrough. The wall 12 of cavity 11 may be coated such as by plating with gold to render it highly reflective to radiant energy. Elliptical cavity 11 has two focii which, since they have height, may be referred to as focal axes, designated by the reference numerals 13 and 14.
Positioned within elliptical cavity 11 is a conically-configured reflector 15 which is so located that its axis coincides with the first optical axis 13. In FIG. 1, conically-configured reflector 15 is shown to comprise a true cone reflecting surface 16 and a cylindrical base 17, the latter being held firmly by any suitable means such as a chuck 18 supported by a load bearing rod member 19. As will be described below in connection with FIG. 4, the position of the conically-configured reflector within the elliptical cavity determines the location of the heating zone 20 within the cavity. The height of the cavity, h.sub.c, must be greater than the length of the heating zone, l.sub.z, so that the heating zone is defined entirely within the elliptical cavity.