Flexible joint for waveguides

May 6, 1947.

2,420,007

R. G. OLDEN

FLEXIBLE JOINT FOR WAVEGUIDES

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INVENTOR.

Patented May 6, 1947

2,420,007

UNITED STATES PATENT OFFICE

2,420,007

FLEXIBLE JOINT FOR WAVEGUIDES

Roger G. Olden, Princeton Township, Mercer : County, N· J·, assignor to Radio Corporation of America, a corporation of Delaware

Application September 3

Claims.

This invention relates generally to electric wave transmission systems and more particularly to an improved flexible joint for use in waveguides.

Heretofore, various types of flexible waveguide structures and joints have been employed. One type of flexible waveguide in common use comprises a spirally-wound conductor in which successive convolutions overlap in a manner similar to that employed in conventional BX power cable 1 shields. The principal disadvantage of flexible waveguide construction of the spiral type Is that relatively poor electrical contact is made between successive conductor convolutions. It is well known in the art that, due to relatively high 1 circulating currents on the inner surface of a waveguide, poor contact between adjacent portions thereof provides undesired resistive losses.

Another type: of flexible joint employed between adjacent rigid portions of conventional 2 waveguide transmission systems comprises curved telescoping rigid or flexible conductive elements which also have the same disadvantage with respect to losses due to erratic electrical contact between adjacent parts. Flexible rubber cou- . plings between adjacent rigid waveguide sections introduce serious wave discontinuities and, in addition, usually involve objectionable wave absorption from the waveguide system.

The. instant invention comprises a novel flex- 3 ible joint for a waveguide transmission system which permits adjustment of the waveguide direction over an angle of the order of 60° with a minimum of sliding contacts between· adjacent conductive elements. Since all contacts are of 3 the wiping variety, and since special preparation of the wiping surfaces is not required, erratic contact effects are reduced to a minimum with an extremely economical and practical construction. 4

Briefly, the invention comprises a frame which supports two cylindraceous journal members having flat inner surfaces which form an opening for the waveguide path and which provide limiting means, for controlling the movement of 4 the adjustable portions of the joint. A pair of complementary bearing members are journaled on the. outer surfaces of the journal members and. arranged to rotate thereabout throughout the desired adjustment angle, A pair of flat 5 flexible. conductive elements, supported at adjacent, ends of the bearing members, extend into the .opening formed between the inner surfaces of the journal members. End plates, flxed+to the . frame, close the adjacent ends of the flat flexible 5

0,1944, Serial No. 556,520

CI. 250—11) members to form therebetween a rectangular wave path, the direction of which may be adjusted by rotation of the rotatable bearing members. The only points at which electrical con5 tact between conductive elements are critical are the two points at which the flexible conductive elements wipe against the fixed journal members.

By suitably proportioning the joint elements, 0 the wave path through the flexible joint may be changed gradually to minimize objectionable wave discontinuities with resultant wave reflections. The frame member may be proportioned to engage a terminating flange of a conventional 5 wave guide, while the adjustable bearing member may include a wave horn or other wave terminating means.

Among the objects of the invention are to provide an improved flexible joint for a wave;0 guide: transmission system. Another object of the: invention is to provide an improved flexible waveguide joint including means for coupling said joint to a conventional waveguide transmission system; An additional object of the invention !5 is to provide an improved waveguide flexible joint which is angularly adjustable to a predetermined degree. A further object of the invention is to provide an improved Waveguide joint which is angularly adjustable to a predetermined 1. degree, wherein all sliding mechanical parts may be readily lubricated and wherein contacting electrical elements are of the wiping variety. Another object of the invention is to provide an improved flexible joint for coupling a rectangular waveguide to a conventional microwave horn.

The: invention will be described in further detail by reference to the accompanying drawing of which Figure 1 is a right elevational view of a preferred embodiment of the invention, . Figure 2 is a cross-sectional view of the device taken along the section line II—-II of Figure 1 and Figure 3 is a cross-sectional view similar to the view of Figure .2 but showing the angular adjustment: of the device.: Similar reference characters are applied to similar elements throughout the drawing.

Referring to the drawing,-an embodiment of the invention is disclosed which is particularly advantageous for . use with a wave image transmission system of the general type· described, in..; the copending application of Harley A. lams et al., Serial No. 531,628, filed April 18, 1944. In the device described? in said copending application, a relatively.wide, thin beam of microwave energy is radiated for scanning a scene in ac2,420,007 cordance with a novel modification of the radar principle. The invention may be utilized with any other type of waveguide system requiring directional scanning in a plane.

A pair of fiat frame members I, 3, having a length determined by the width of the desired microwave beam, are supported adjacent their ends by end plates 5, 7, 9 and 11, 13, 15 to provide a relatively long rectangular opening 17. A pair of cylindraceous journal members 19, 21 are secured to the supporting frame members I, 3 by means of screws 23, 25, respectively. The journal members 19, 2 ί are shaped to provide a circular external journal surface 27 with coacting substantially flat inner surfaces 29, adjacent ends of which coincide with the aperture i7 between the frame supporting members I, 3.

A pair of complementary bearing members 31, 33, supported by a frame 34, engage the journal surface 27 in a manner wherely the bearing may be· rotated about the journal. A pair of substantially flat, flexible, conductive elements 35, 37, comprising for example, beryllium copper or phosphor bronze, are secured to adjacent ends of the rotatable bearing elements 31, 33. The ends of the conductive elements 35, 37 wipe against, or closely mesh with, the inner surfaces of auxiliary high-conductive end plates 39, 41, and the ends of the flexible elements remote from the bearing members 31, 33 wipe against the flat inner surfaces of the journal members 19, 21. Thus the aperture formed between the supporting frame members I, 3 coincides with the aperture formed between the flexible conductive elements 35, 37 and the auxiliary end plates 39, 41 to provide an adjustable wave path which passes through a suitable aperture 43 in the bearing support plate 34 to provide wave access to a wave matching device such, for example, as a wave horn 45; A conventional waveguide 47 connected to a source of microwave energy, not shown, may be connected to the waveguide joint in any manner known in the art.

Figure 3 illustrates the slight deformation of the flexible conductive elements 35, 37 when the bearing elements 31, 33 are rotated through an angle of the order of 30° from the axis of the waveguide 47. By means of suitable mechanical coupling, not shown, the flexible waveguide joint thus provided may be motor-driven to provide continuous angular adjustment at any desired rate and throughout a substantial angle.

Suitable lubrication may be provided for the journal surface 27 without affecting the electrical contact between the flexible elements 35, 37 and the corresponding inner surfaces 29 of the journal members. Due to the positive wiping contact of the journal inner surfaces 29 by means of the flexible elements 35, 37, erratic electrical contact therebetween is minimized.

Thus the invention described and claimed hereinafter comprises an improved waveguide flexible joint mechanism providing economical and efficient means for adjusting the direction of waves propagated through a waveguide transmission system.