Communications: radio wave antennas – Antennas – Antenna components
Reexamination Certificate
1999-04-23
2001-03-13
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Antenna components
C029S600000
Reexamination Certificate
active
06201515
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to reflectors such as used for antennas and particularly to a method and apparatus for producing such reflectors.
The invention also relates to the construction of such reflectors and particularly to individual reflector segments formed by a hardened thread net wound on a contour segment.
BACKGROUND AND PRIOR ART
Reflectors or antenna reflectors are used in outer space for communication purposes. They have a surface which follows the contour of a hyperbola or parabola. Accordingly, they have a double-curved surface. Effective and accurate operation requires that the surface have a substantially exact curvature.
Conventional reflectors have a netting or a network structure of composite fiber material as the reflector surface. In a conventional procedure, the reflector surface is fabricated by laying a thread in such a way as to produce a network structure. The laying of the thread is effected on a flat support, for example, by a thread laying robot. Next, the preliminary structure is transferred to the desired contour surface, for example, a parabolic surface which has a double curvature.
The known manufacturing method, however, has the drawback that a deformation of the structure occurs when the preliminary structure is transferred from a planar support or from a single-curved support, such as a winding spindle, to the double-curved contour surface. Furthermore, stresses are induced in the structure and the network surface becomes distorted. The network structure is also distorted or deformed when the network structure is first fabricated on a winding spindle and then transferred to the contour surface. Therefore, the reflector surfaces produced by the conventional manufacturing processes have an imprecise contour, which deviates from the ideal shape. In addition, surface imperfections such as dents or the like may arise from stresses in the reflector surface.
Furthermore, especially in the case of reflectors which are folded for purpose of transport into orbit and deployed upon reaching their station in outer space, the problem arises that additional stresses are induced by virtue of differing degrees of curvature in different regions of the deployed reflector surface. This contributes to further distortion of the network surface, especially when in use over a long time.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a method and apparatus for making a reflector, by which the accuracy of the reflector surface is enhanced and stresses or deformations of the reflector surface are avoided. Furthermore, a network structure is produced that serves as a reflector surface and is substantially free from stresses.
The method according to the invention for making a reflector comprises the steps of:
winding a thread on a winding spindle to obtain a thread network structure on the spindle, the winding spindle having contour segments on its surface, whose contour corresponds to the contour of a segment of a surface of the reflector being produced;
hardening the thread network structure on the winding spindle;
dividing the network structure into individual segments; and
assembling the individual segments to form the reflector.
By virtue of the method of the invention, a reflector is produced with a reflector surface that is substantially free of stress in the operating condition and has a highly accurate contour.
In advantageous manner, after the dividing of the thread network structure the contour segments are separated from the winding spindle, each carrying a single segment of the thread network structure. Preferably, the single segments of the thread network structure are in contact with the contour segments of the winding spindle or are supported by the latter when being assembled to form the reflector. The means that the individual elements of the reflector remain in their original shape from fabrication until final assembly.
Preferably, the laying angle of the thread is varied when winding the thread on the spindle. In this way, the stiffness of the individual segments can be adapted to local requirements. Preferably, the thread tension is regulated during the winding, so that a tension in network can be obtained to satisfy particular requirements.
A stiffening structure, especially one in the form of ribs, can be arranged on the network structure while said structure is located on the winding spindle. In this way, an additional stabilization of the reflector surface is achieved. Preferably, the thread is made of carbon fibers and/or HT fiber. This ensures that little or no contour change occurs during temperature fluctuations and, due to its low E-modules, easier curvature is accomplished. The fiber can be impregnated and soaked in synthetic resin prior to the winding operation.
Several winding spindles can be placed in a row in the lengthwise direction. In this way, the reflectors can be fabricated in an especially efficient manner, since there is minimization of the reversal mechanism.
The device according to the invention for making the reflector comprises a winding spindle including a central body, a detachable contour segment on said central body onto which a thread can be wound to form a sector of a reflector, said contour segment having a double-curvature surface whose contour corresponds to the sector of the reflector such that a plurality of said sectors can be assembled to obtain the reflector.
Preferably, a plurality of contour segments are advantageously arranged to extend radially outwards from a center of the reflector adjacent to one another circumferentially around the reflector. Positioning elements, in the form of pins, can be arranged on the segments to assure a precise positioning of the segments to form the reflector surface.
According to yet another aspect of the invention, a network structure for reflectors is provided, especially for antennas in outer space, in which an angle of winding the thread of the thread network is varied so that the network structure has a different, selectable rigidity in individual areas. In this way, it is possible to equalize stresses and prevent buckling of the reflectors due to the different radii of curvature in different areas of the reflector.
In advantageous manner, the network structure of the invention constitutes a segment of a reflector surface Thus, it is e specially suitable for the fabrication of a high-precision deployable reflector.
REFERENCES:
patent: 4092453 (1978-05-01), Jonda
patent: 5488383 (1996-01-01), Friedman et al.
Dupier Jürgen
Roth Martin
Sperber Franz
Daimler Chrysler Ag.
Dinh Trinh Vo
Ladas & Parry
Wong Don
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