US2514160A - Rotary joint - Google Patents

Description

July 4, 1950 c. w. KLosTERMANN 2,514,160

v ROTARY JOINT Filed Oct. 21, 1944 2 Sheets-Sheet 1 Filed Oct. 21, 1944 2 Sheets-Sheec 2 APatented July 4, 1950 UNITED STATE OFFICE ROTARY JOINT Curt W. Klostermann, Chicago, Ill.

Application October 21, 1944, Serial No. 559,820

4 Claims. 1

This invention relates to rotary joints and is more particularly concerned with rotary joints employed for connecting the ends of radio frequency transmission lines of the type embodying conductors held in coaxial relation by means of a solid dielectric.

More particularly, this invention relates to rotary joints adapted for use with radio installations in which it is desirable to rotate the receiving or transmitting antenna in order to receive or transmit signals in various directions. It is now common practice to supply radio frequency energy through coaxial conductors in which a center conductor is coaxially positioned within an outer conductor or shield. It has heretofore been common practice to construct coaxial transmission lines having a central conductor mechanically and electrically isolated from and held in coaxial position with the outside conductor or shield by means of insulating spacers or discs located at spaced intervals. In this type of construction, the dielectric between the center conductor and the shield is largely air and, in order to prevent moist air from condensing and causing moisture to form within this space with consequent deterioration of the electrical characteristics of the transmission line, it was necessary to ll such lines with dried air or other gas under pressure. Due to the possibility of air leakage from the transmission line, it was also necessary to provide pressure indicating means.

While rotary joints and connectors have been widely employed for use in transmission lines employing air or gas as a dielectric, such joints and connectors are similar in construction to the transmission lines in that the coaxial conductors are maintained in position by means of insulating spacers and the dielectric is predominantly air or gas. This type of joint and connector, therefore, is objectionable for the same reasons presented in consideration of the air lled transmission line and, in addition thereto, considerable diiiiculty is encountered in maintaining the transmission line and connecting rotary joints tight and free from leaks, particularly when same are subjected to vibration and shock.

Due to these objectionable features, such transmission lines are now being replaced with cables having coaxial conductors mechanically and electrically isolated and held in coaxial position by means of solid, semiflexible dielectric such as polyethylene. In the use of the solid dielectric in cable construction, there is no air space between the center conducto-r and the outside shield and a better coaxial alignment may be maintained.

Other advantages to be derived from the use of a coaxial cable employing a solid dielectric are:

1. Freedom from corona diiiiculties.

2. Much higher voltage breakdown characteristics because oi the use of a solid dielectric in place of air as an insulating medium.

3. Freedom from moisture condensation.

4. Constancy of electrical and mechanical characteristics when installed in locations where vibration and shock are present.

It is an object of the present invention to provide a rotary joint or connector adapted for use with coaxial transmission lines embodying a solid dielectric, and further contemplates the provision of a device of this kind which possesses all the inherent advantages of the cable construction in order that the electrical or mechanical properties of the transmission line system will not be prejudiced in any way due to the introduction of the rotatable joint cr connector therein. A rotary joint or connector constructed in accordance with the present invention ernbodies the following novel features:

1. Is as free from corona as the cable to which it is attached.

2. Has as high a voltage breakdown characteristic as the cable.

3. Is free from air spaces in which moisture could condense. K

4.. Has continuity of impedance throughout its length.

5. Is capable of trouble-free mechanical and electrical operation through many thousands of revolutions.

6. Has constancy of electrical and mechanical characteristics when subjected to vibration and shock.

This invention embodies other novel features, details of construction and arrangement of parts which are hereinafter set forth in the specication and claims and illustrated in the drawings, wherein:

Fig. 1 is a view partly in section and partly in elevation showing a rotary joint embodying features of this invention.

Fig. 2 is an end view of same with the cable omitted.

Fig. 3 is a view partly in section and partly in elevation showing a modified form of this invention.

Fig. 4 is an end view of same, partly in section.

Fig. 5 is a detailed view showing a stator ground sleeve.

Referring now to the drawings for a better understanding of this invention and more particularly to Figs. 1 and 2 therein, the rotary joint connector is shown as comprising a stator shell I I which is bored at I2 to receive a standard type of solid dielectric coaxial cable I3. The

cable I3 is of well known construction and of theV type now commonly employed for feeding radio frequency energy to antennas. As shown in the drawings, the cable comprises an Vinner con-M ductor I4 and an outer conductor I6 which are held in coaxial relation by means of a solid dielectric Il. The outer conductor I is formed of woven wire covered by a vinyl jacket I8.

Prior to coupling engagement of the ends of the cable I3 withinthe rotary joint or connector, the ends of the cables are pre-formed by stripping the vinyl jacket and braided conductor back from the respective ends of the cable, then forming a tapered shoulder I9 on the solid dielectric, and counter-boring the center conductors I4 at 2| to receive male and female contact members 22 and 23, respectively, for soldered engagement to the conductors I4. The end of the contact member 22 is formed with one or more longitudinal slotsv 24 to provide a spring contact engagement with the contact member 23. The contacts 22 and 23 are of the same diameter as the conductors I4 to provide a perfect continuity of impedance therethrough.

A dielectric sleeve 26 is mounted within the bore I2 of the stator shell II and has its ends formed with frustro-conical recesses 21, one of which receives the tapered shoulder I9 formed on the solid dielectric Il of the cable. The dielectric sleeve is provided with an annular rib 28 for engagement against an annular shoulder 29 formed within the bore I2 of the stator shell II. The stator shell is internally threaded at 3| to receive an externally threaded stator ground sleeve 32 which acts to secure the annular ring 28 against the shoulder 29. The ground sleeve 32 is secured in position on the stator shell by means of a set screw 33.

The stator shell II is formed with a tapered shoulder 34 for engagement under the braided outer conductor I6 and the vinyl jacket I8. The vinyl jacket I8 and the braided outer conductor I6 are engaged against the shoulder 34 of the stator shell II by means of a seal and ground ring 36 and a seal and ground nut 31. The seal and ground nut 31 is internally threaded at 38 for engagement on the threaded end of the stator shell II and is externally threaded at 39 to receive an internally threaded clamp nut 4I. A clamp ring 42 is mounted Within the clamp nut 4I for tapered wedging engagement against a slotted clamping collet 43. Contraction of the clamping collet 43 against the outer periphery of the vinyl jacket I3 acts to firmly secure the cable to the stator shell I I. A neoprene sealing ring gasket 44 is mounted on the inner endof the seal and ground ring 3Sto seal this portion 0f the joint against the entrance of moisture.

A rotor shell 5I is journaled for rotational movement in a bearing 52 which is secured to a ange portion 53 of the stator shell II by means of screws 54. The rotor shell is bored at 5i) to receive a dielectric sleeve 59 which is formed with an annular ring 6I for locked engagement against a shoulder 62 by means of a threaded rotor ground sleeve 63. The rotor ground sleeve 63 is held against displacement by means of a set screw 64. The inner end of the dielectric sleeve 59 is formed with a tapered shoulder 5B for engagement within the tapered recess 21 formed in the dielectric sleeve 25. The other end of the dielectric sleeve 59 is formed with a frustreconical recess 57 to receive the tapered shoulder I9 provided on the end of the cable dielectric I'I. The stator ground sleeve 32 is slotted at 65 to provide a plurality of resilient fingers 66 which bear against the outer peripheral contact surface 31 formed on the rotor ground sleeve 63.

The rotor shell 5I is connected to the other end of the cable I3 in the manner heretofore described in connecting the cable to the stator shell I I, and as similar parts are employed for making the connection, these parts are indicated by similar members. The means employed for turning the rotor shell with respect to the stator shell comprises a tube 'II which is connected to the rotor shell 5I by means of a split coupling 12. The split coupling is formed in two parts joined together by means of screws 73. To insure against relative movement between the tube II Y and the rotor shell 5I, key pins 'I4 and 'I6 are employed for keying the coupling to the rotor shell and tubing, respectively.

The bearing surfaces provided for the rotor shell are lubricated through a threaded opening Il by removing a screw 'I8 therefrom. The lubricating fluid is retained against leakage from the bearing surfaces by means of packing rings 'I9 held in engagement against the outer surface of the stator ground sleeve by means of a packing nut 8| threaded onto the inner end of the rotor shell. Packing rings 82 are employed to engage the outer surface of the rotor shell and held in position by means of a packing nut 83 which is threaded onto the rotor shell bearing 52. During assembly of the rotary joint, the threaded openings provided for the locking screws 33 and 64 are sealed at their outer ends by a suitable rubber cement such as the type manufactured by the Goodyear Rubber Co. and known as AF 12C rubber cement.

In order to eliminate air spaces within the rotary joint, the ends of the cable dielectric I'F and the ends of the dielectric sleeves 26 and 59 arecoated prior to assembly with a suitable paste or grease-like substance, such as Dow-Corning Sealing Compound No. 4 which insures that no air will be present when the joint is assembled. Such a sealing compound must necessarily have good electrical characteristics and must not interfere with the electrical contact of the metal parts. Use of the sealing compound upon tapered dielectric junctions of the type shown and described insures that there will be no corona or voltage breakdown difficulties in the completed assembly, and further that there will be no air Spaces in which moisture can condense.

It will be observed that perfect continuity of impedance is preserved by continuing the center conductor at its original diameter through the rotary joint and doing likewise with the outer conductor. By preserving the continuity of the center conductor and outer conductor diameters,

the characteristic impedance of the transmission line through the rotary joint will be uniform and the same as that of the cable, providing the dielectric used in the sleeves 26 and 59 has the same dielectric constant as that of the Cable insulation itself. Actual tests have shown this type of rotary joint to be free from objectionable reiiection losses caused by impedance discontinuities for frequencies up as high as 3000 megacycles.

Referring now to lFigs. 3 and 4 in the drawings, a modified form of the rotary joint construction is provided by which transmission line cables may be attached at right angles to the longitudinal axis of the rotary joint. Since it is impossible to bend large cables around a small radius without damaging the dielectric, it is desirable to make the right angle connection within the joint itself. In this form of the invention a rotor shell 86 is journaled within a bearing member 81 secured to a stator shell 8S by means of screws 8S. A pair of dielectric sleeves 9i and 92 are secured within the rotor shell B and stator shell 83, respectively, by means of the rotor ground sleeve E3 and stator ground sleeve 32, respectively. The dielectric sleeves are formed with frustro-conical engaging surfaces at 93 and have their outer ends abutting against dielectric plugs 9i!- and 9K5, respectively, disposed within elbow ttings 91 and 98, respectively. Fittings 9'! and S3 are in threaded engagement with the outer ends of the rotor shell 85 and stator shell 231i, respectively, and are secured against relative movement therewith by means of set screws S39. Ring gaskets lili, formed of neoprene or the like, are provided in the threaded connections between the elbow fittings and their respective shells.

The ends of the transmission cable are connected to the outer ends o the elbow fittings 91 and 98 by the method heretofore set forth in the description of the preferred form of this invention and by the use of similar parts which have accordingly been assigned similar numbers. The inner conductors lll are counter-bored to receive contact members il?? which are soldered to the outer ends of conductors 183 and lcd, respectively. The inner ends of the conductors W3 and iill are formed for electrical rotational contact by counter-boring the conductor 1&3 to receive the spring lingers liliof the conductor i524.

In this form or" the invention, a coupling sleeve lill' is threaded onto the seal and ground nut 3l in place of the clamping nut All. The tubing 'il is inserted within the coupling sleeve lill and held against displacement therefrom by means of set screws M38. Packing material lili) is employed to prevent leakage between the tubing 'il and the coupling sleeve, and is held in position by means of a packing nut lll which is threaded onto the end oi the coupling sleeve. This form of the invention is otherwise similar to the construction shown in Figs. l and 2.

Another form of a rotary joint may consist of a straight connection between the cable i3 and the stator shell l i as illustrated in Fig. 1, and a right angle connection. for the cable connection with the rotor shell BS as illustrated in Fig. 3.

While this invention has ybeen shown in but two forms, it is obvious to those skilled in the art that it is not so limited, but is susceptible ci various changes and modifications without departing from the spirit and scope of the claimed invention.

I claim as my invention:

l. In a rotary joint for use with a radio frequency transmission line cable having coaxial conductors held in spaced relation by a solid dielectric, a stator shell for detachable mechanical and electrical engagement with one end of the transmission line cable, a rotor shell for detachable mechanical and electrical engagement with another end of the transmission line cable and rotatably adjustable with respect to said stator shell, a pair of dielectric sleeves mounted within said stator and rotor sleeves and having coaxial inner and outer diameters to correspond to the diameters of the solid dielectric of the transmission line cable, a rotor ground sleeve for securing one dielectric sleeve to the rotor shell, a sta-tor ground sleeve for securing the other dielectric sleeve to said stator shell, said stator ground sleeve eing in electrical contact with said rotor ground sleeve.

2. In a rotary joint for use with a radio frequency transmission line cable having coaxial conductors held in spaced relation by a solid dielectric, a stator shell for detachable mechanical and electrical engagement with one end of the transmission line cable, a rotor shell for detachable mechanical and electrical engagement with another end of the transmission line cable and rotatably adjustable with respect to said stator shell, a pair of dielectric sleeves mounted within said stator and rotor sleeves and having coaxial inner and outer diameters to correspond to the diameters of the solid dielectric of the transmission line cable, a rotor ground sleeve for securing one dielectric sleeve to the rotor shell, a stator ground sleeve for securing the other dielectric sleeve to said stator shell, said stator ground sleeve being in electrical contact with said rotor ground sleeve, and a bearing sleeve provided on the stator shell to receive said rotor shell.

3. In a rotary joint for use with a radio frequency transmission line cable having coaxial conductors held in spaced relation by a solid dielectric, a stator shell for detachable mechanical and electrical engagement with one end of the transmission line cable, a rotor shell for detachable mechanical and electrical engagement with another end of the transmission line cable and rotatably adjustable with respect to said stator shell, a pair of dielectric sleeves mounted within said stator and rotor sleeves and having coaxial inner and outer diameters to correspond to the diameters of the solid dielectric of the transmission line cable, a rotor ground sleeve for securing one dielectric sleeve to the rotor shell, a stator ground sleeve for securing the other dielectric sleeve to said stator shell, said stator ground sleeve being in electrical contact with said rotor ground sleeve, said rotor and stator ground sleeves having inner diameters corresponding to the diameter of the outer conductor of the cable and the outer diameters of the dielectric sleeves.

4. In a rotary joint for use with a radio frequency transmission line cable having coaxial conductors held in spaced relation by a solid dielectric, a stator shell for detachable mechanical and electrical engagement with one end of the transmission line cable, a rotor shell for detachable mechanical and electrical engagement with another end of the transmission. line cable and rotatably adjustable with respect to said stator shell, a pair of dielectric sleeves mounted within said stator and rotor sleeves and having coaxial inner and outer diameters to correspond to the diameters of the solid dielectric of the transmission line cable, a rotor ground sleeve for securing one dielectric Sleeve to the rotor shell, a stator 7 ground sleeve for securing the other dielectric sleeve to vs ajlnstator shell, said stator ground sleeve; beingelectrical Contact with said rotor ground, sleeve, a bearing sleeve provided on the stator shell to receive said rotor shell, a packing chamber provided between the inner end of the rotor shell and said stator ground sleeve, and a packing chamber provided between the outer end of said sleeve bearing and said rotor shell.

CURT W. KLOSTERMANN.

REFERENCES CITED The following references are of record in the le of this patent:

Number Number 8 UNITED STATES PATENTS Name Date Oakes May 26, 1914 Morrison Aug. 9, 1932 Walter Mar. 31, 1936 Bruno July 28, 1942 Reppert Oct. 26, 1943 Fraser Mar. 5, 1946 Hallstrand June 24, 1947 Bard July ,'29, 1947 FOREIGN PATENTS Country Date Germany Sept. 22, 1891 Germany Dec. 29, 1939

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