US 3870978 A
Electrical contact means for use in connecting a pair of aligned conductors, especially in microwave applications where thermal expansion and contraction is a problem. The contact means comprises at least one block of electrically conductive resilient material engaging the end of an elongated conductor and held in abutting relation with an adjacent conductor, both conductors being within tubular dielectric means which also confines the compressed conductive block. In one form of the invention, a D.C. block in the form of a ceramic capacitor is connected in series with aligned central conductors within a flange mounted connector for a microwave source by means of conductive resilient contact blocks on opposite sides of the capacitor and squeezed between the capacitor and the central conductors. In another form, a pair of aligned central conductors in a two-part hermaphroditic coaxial connector assembly have conductive resilient contacts mounted at their outer ends which are brought into compressed abutting relation when the outer conductors of the two connector parts are drawn into abutment. Various shapes and mounting techniques for the contact blocks are shown, some of which are useful for internal fixed constructions which have a step up or a step down in diameter.
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Description (OCR text may contain errors)
United States Patent [191 Dreyer 1 Mar. 11,1975
1 1 ABUTTING ELECTRICAL CONTACT MEANS USING RESILIENT CONDUCTIVE MATERIAL  Inventor: Charles W. Dreyer, Plymouth,
 Assignee: Omni Spectra, Inc., Farmington,
[221 Filed: Sept. 13, 1973 ] Appl. No.: 397,022
 US. Cl 333/97 R, 333/24 C, 339/48, 339/147 R, 339/177 E, 339/278 T, 339/DIG. 3
 Int. Cl I-I0lp 1/04, HOlr 3/00, I-IOlr 13/24  Field of Search..... 333/24 C, 97 R; 339/147 R, 339/177 E, 48, 49 B, 9 E, 278 T, DIG. 3
OTHER PUBLICATIONS Rice, D. W., Extender-Type Pluggable Electrical lnterconnector, IBM Tech. Disclosure Bull, Vol. 13, No. 6, 11-1970, PP- 1625.
Primary Examiner-Alfred E. Smith Assistant Examiner-Wm. H. Punter Attorney, Agent, or Firm-Harness, Dickey & Pierce  ABSTRACT Electrical contact means for use in connecting a pair of aligned conductors, especially in microwave applications where thermal expansion and contraction is a problem. The contact means comprises at least one block of electrically conductive resilient material engaging the end of an elongated conductor and held in abutting relation with an adjacent conductor, both conductors being within tubular dielectric means which also confines the compressed conductive block. In one form of the invention, a DC. block in the form of a ceramic capacitor is connected in series with aligned central conductors within a flange mounted connector for a microwave source by means of conductive resilient contact blocks on opposite sides of the capacitor and squeezed between the capacitor and the central conductors. In another form, a pair of aligned central conductors in a two-part hermaphroditic coaxial connector assembly have conductive resilient contacts mounted at their outer ends which are brought into compressed abutting relation when the outer conductors of the two connector parts are drawn into abutment. Various shapes and mounting techniques for the contact blocks are shown, some of which are useful for internal fixed constructions which have a step up or a step down in diameter.
20 Claims, 18 Drawing Figures PATENTEDHARI 11975 q 870 978 SHEETlUFZ /Z 7 f i ABUTTING ELECTRICAL CONTACT MEANS USING RESILIENT CONDUCTIVE MATERIAL BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to electrical connectors and conductors, and particularly connectors in which a pair of aligned conductors are present which must be mated. In some aspects, the invention pertains particularly to microwave and other high frequency applications, to coaxial connectors and to D.C. blocks on connectors to microwave sources.
2. Description of the Prior Art The broad concept of abutting contacts for electrical connectors is not new, although the specific constructions described and claimed herein are believed novel. The advantages of abutting contact means are well known; they eliminate the need for matching male and female contacts, thus reducing the number of different parts needed to complete an assembly. Among the difficulties associated with abutting contact means, especially in microwave or high frequency applications, is the deleterious effect of severe environmental conditions which cause thermal expansion and contraction, shock and vibration of the contacts or their associated parts. For example, a connector for a microwave source to a cable or the like should be associated with a D.C. block capacitor. It is known to provide a D.C. block externally of the connector but this is expensive and occupies substantial space. It has heretofore been difficult to incorporate a DC. block within the connector because the ceramic capacitors involved are subject to significant thermal shock from external sources, subjecting the ceramic to possible cracking or other breakage.
The present invention makes use of what are termed conductive resilient contact blocks. The materials from which such blocks are fabricated are well known by themselves, but not for the applications herein described and claimed. One manufacturer of such materials is Chomerics, lnc., a subsidiary of Deering Milliken, lnc., Arlington, Massachusetts, which manufactures this material under the brand name Cho-Seal. The material is described by the manufacturer as a metalfilled form-stable (heat and pressure molded) electrically conductive silicone as described in US. Pat. No. 3,140,342. The metal filler is a heat-stable silver-plated granular copper particle as described in US. Pat. No. 3,202,488. In sheet form for shielding purposes, the material is described by the manufacturer as being a highly conductive elastomer which provides electrical continuity in a compressible, resilient structure.
Another manufacturer of such materials is Technical Wire Products, lnc., Cranford, New Jersey, manufacturing the material under the brand name -Consil."
Although the manufacturers list broadly various possible applications of the materials, including environmental gaskets, resilient electrical contacts, resilient ground planes, compressible sensing elements and impact-absorbing piezoelectric crystal contacts, it is believed that the abutting electrical contact means and other features of the present invention as described and claimed herein are neither shown nor suggested by the prior art.
It is also known to use conductive resilient contacts in a coaxial microwave attenuator assembly in which the central conductors carry conductive resilient blocks at their ends abutting opposite ends of a fiat attenuator element which extends radially to the outer conductor.
Various assemblies incorporating D.C. blocks are available having electrical contact made by soldering, conductive epoxy, or metallic spring members, but they are generally of a much more complex and expensive construction than the present invention. Soldering sometimes damages the capacitor and special methods must be used to assure that extensive heat and incorrect flow of solder do not damage the components.
BRIEF SUMMARY OF THE INVENTION It is an object of the present invention to provide a novel and improved construction for abutting electrical contact means which permits the elements with which the contact means are associated to undergo thermal expansion and contraction caused by external sources, without deleterious effects.
It is a further object to provide improved contact means having shock absorbing qualities beneficial in environments where shock and vibration are present as well as with normal mating and unmating of connectors.
It is another object to provide novel and improved abutting electrical contact means as above described which greatly reduces the cost of manufacturing of abutting contacts, especially for microwave and high frequency applications.
It is a further object to provide an improved contact means of this character especially useful for incorporating a D.C. block in a connector for a microwave source.
It is also an object to provide an improved contact means of this nature which facilitates the manufacture of coaxial hermaphroditic connector assemblies.
It is another object to provide improved contact means which permits various configurations to be adapted for the resilient conductive contact blocks, thus offering versatility in mounting the contact blocks on their conductors and adapting the conductors for internal fixed constructions as well as separable connectors, and for steps up or steps down in conductor diameter.
It is a further object to provide a D.C. block which is much simpler, less expensive and generally superior mechanically and electrically than those of the prior art.
It is another object to provide an improved D.C. block of this character in which the connection between the capacitor and the central conductor is resilient and does not require soldering, spring members, or special tooling.
It is another object to provide electrical contact means that has the advantages of less wear and a less expensive construction than the typical pin-and-socket (male to female) or metallic spring types, this advantage being especially useful in smaller contact assemblies required at higher microwave frequencies.
Briefly, the invention comprises first and second aligned conductors of electrically conductive relatively rigid material, said conductors being disposed within tubular dielectric means and having end surfaces in facing relation, and at least one contact block disposed between said facing surfaces, said contact block being fabricated of resilient conductive material whereby thermal expansion and contraction of said conductors in an axial direction will be absorbed by said block, the block being compressed in its operative position and confined by said tubular dielectric means.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view in elevation of a flange mounted connector for a microwave source incorporating an internal D.C. block and utilizing the principles of this invention.
FIG. 2 is an enlarged fragmentary cross-sectional view in elevation of the portion of FIG. 1 marked 2.
FIG. 2A is a view similar to FIG. 2 but showing a modified form of the D.C. block assembly using only one resilient contact block.
FIG. 3 is a side elevational view in cross section of one of a pair of identical mateable hermaphroditic microwave connectors utilizing the principles of this invention.
FIG. 4 is a side elevational view in cross section showing the mated connectors.
FIGS. 5 through show various configurations for the conductive resilient contact blocks and means for mounting them on their respective conductors.
FIGS. 11 through 14 show frustoconically shaped contact blocks for use in internal fixed constructions where steps up or steps down in diameter are desired; and
FIGS. through 17 show two different shapes of contact blocks which are not secured to conductors.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to the embodiment of FIGS. 1 and 2, a flange mounted connector is generally indicated at 10 for a microwave source indicated partially in dot-dash lines at 11. Flange mounted connector 10 has a body generally indicated at 12 which acts as an outer conductor and has a flange 13 securable to microwave source 11, and an elongated cylindrical portion 14 having an external thread 15 at its outer end for connection to a cable or the like. A tubular dielectric bushing 16 is mounted within a bore 17 of housing 12 and secured therein by an epoxy locking pin 18 extending into a groove 19 or other appropriate means. Dielectric bushing 16 may be fabricated of a low hygroscopic material such as Teflon or TF E Fluorocarbon.
A pair of aligned conductors 21 and 22 are pressed into a bore 23 of dielectric bushing 16, being held in position by flared shoulders 24 and 25 respectively which are embedded in the bushing. Conductors 21 and 22 may be fabricated of a suitable material such as beryllium copper, stainless steel or brass, having the desired resilient and wear-resistant qualities. The outer ends of conductors 21 and 22 have slits 26 and 27 respectively for the reception of pins shown partially at 28 and 29.
A D.C. block in the form of a ceramic capacitor generally indicated at 31 is disposed between the facing flat surfaces of shoulders 24 and 25. This capacitor comprises a ceramic plate 32 with opposite faces 33 and 34 of gold, silver or the like. The combination of the ceramic plate and metallic coatings enables the ca.- pacitor to transmit high frequencies but block low frequencies or D.C. The external diameter of capacitor 31 is such that it will fit within bore 23 in a manner permitting slight radial play and thus also permitting axial movement except as explained below.
A pair of contact blocks 35 and 36 of conductive resilient material are disposed on opposite sides of capacitor 31, between the capacitor and the facing end surfaces of shoulders 24 and 25 respectively. The material of which these blocks are made is that described previously under the heading Description of the Prior Art. Basically, the resilient contacts are a rubber or synthetic rubber base filled with a known amount of electrically conductive particles. Insulative bushing 16 is used to house the capacitor-contact assembly and to insulate the inner conductors and contact means from outer conductor 12.
Although blocks 35 and 36 may be of any appropriate shape in their unstressed condition, those shown in FIGS. 1 and 2 are originally spherical as indicated by the contact block 37 in FIG. 17. When placed between capacitor 31 and conductors 21 and 22, and tapered shoulders 24 and 25 of the conductors are forced into bushing 16, members 35 and 36 will be compressed into the flattened spheroidal shape shown in FIGS. 1 and 2, pressing outwardly against bore 23 of bushing 16. An advantage of the originally spherical shape of the blocks is that when compressed there will be slight annular spaces 38 between the outer portions of the blocks and the capacitor. The contact blocks will thus be in non-interfering relation with the electrical properties of the capacitor.
In use, connector 10 will be attached by flange 13 to microwave source 11. Because capacitor 31 is internal, the assembly will be quite compact as compared with previous arrangements. Axial thermal expansion and contraction of conductors 21 and 22 during operation of the microwave source, and vibration of the unit during use, will not place any stresses on the ceramic capacitor 31 because conductive resilient contact blocks 35 and 36, as well as the play allowed capacitor 31, will absorb this movement. The result is a low cost, compact and relatively trouble-free unit.
FIG. 2A shows a modified form of the invention which differs from that of FIGS. 1 and 2 in that only a single resilient conductive block 51 is utilized. This block is disposed between central conductor 52 and capacitor face 53 of the ceramic capacitor generally indicated at 54. The other central conductor 55 has an end face 56 directly engaging face 57 of the capacitor. Advantages described above with respect to FIGS. 1 and 2, especially with respect to thermal expansion, contraction and vibration, will be present in this embodiment.
FIGS. 3 and 4 show a modified form of the invention, FIG. 3 showing one of the two identical mateable microwave connectors, the connector shown being generally indicated at 100, and the second connector being indicated generally at 101 in FIG. 4. Each connector comprises a rod-like central or inner conductor 102 which may be made of beryllium copper or the like, an annular outer conductor 103 and a dielectric insulating bushing 104 therebetween. A sleeve 105 having external threads 106 is slidably mounted in a recessed portion 107 on the exterior of conductor 103. An internallythreaded nut 108 is mounted on member 103 outwardly of member 106.
Outer conductor 103 has an annular radial face 109 for engaging the corresponding face on the other connector as seen in FIG. 4. The face 111 of bushing 104 adjacent face 109 is slightly recessed, and the face 112 of inner conductor 102 is further recessed. Conductor 102 carries a contact block 113 such as that indicated in FIG. 15. This block is of cylindrical shape and of conductive resilient material, having a narrow portion 114 held in counterbore 115 in the end of conductor 102. The means for holding block 113 in place may be a compression fit between portion 114 and counterbore 115, and in addition a bonding material could be used between surface 112 and the contacting surface of block 113. The block, when unstressed, extends beyond the plane of surface 109 on conductor 103. Other forms of contact blocks, such as those shown in FIGS. 7 through 10, could be used in appropriate circumstances.
In use, connectors 100 and 101 will be placed in facing relation and one of the nuts 108 will be threaded onto the sleeve 105 of the other connector. In FIG. 4, the nut 108 of left-hand connector 101 has been threaded onto the sleeve 105 of the right-hand connector 100. The nut 108 of connector 100 may be removed. Tightening of nut 108 on connector 101 will draw a shoulder 116 of sleeve 105 on connector 100 into engagement with shoulder 117 of recess 107, and further tightening will squeeze contact blocks 113 of the two connectors together. At the same time, surfaces 109 of the two outer conductors 103 will be pressed together. Sleeve 105 of connector 101 will not interfere with this tightening.
An advantage of the construction shown in FIGS. 3 and 4 is that a hermaphroditic connector assembly may be made with two identical connectors and it is unnecessary to stock and locate male and female connectors to be matched. Moreover, the contact blocks 113 will absorb any thermal expansion and contraction of conductors 102.
FIGS. 6 through show various ways in which the resilient conductive contact blocks may be fixed to their respective conductors. In FIGS. 5 and 6, the contact block 301 is flat sided and tapered, being narrower at its outer end, and is held by crimping conductor 302 on opposite sides of a slot 303. In FIGS. 7 and 8, contact block 401 is of frustoconical shape with its base being secured to conductor 402 by an epoxy or similar conductive bond 403. FIGS. 9 and 10 illustrate a frustoconical contact block 501 having a flat sided extension 502 disposed within a slot 503 in the outer end of conductor 504. This block may be held in place by a compression fit within slot 503 plus a conductive epoxy bond 505 between the face of conductor 504.
FIGS. 11 through 14 show contact block constructions usable for internal fixed assemblies where there is a step up or a step down in the diameter of a conductor. FIGS. 11 and 12 show a frustoconical block 601 having its base 602 secured to a conductor 603, the base being somewhat wider than the diameter of the conductor and the outer surface 604 being somewhat narrower. This block would be useful where there is a step down in diameter from conductor 603 to the next conductor. The manner of securing block 601 to conductor 603 may be by a counterbore and/or a conductive bond as described above.
FIGS. 13 and 14 show a contact block 701 of frustoconical shape but in which the narrower end 702 is adjacent conductor 703 and the wider end 704 will engage the adjacent conductor. This construction would be used rather as a step up in diameter from conductor 703.
FIGS. 15 and 16 show a cylindrical contact block 801 which could be used between aligned conductors without being bonded or otherwise secured thereto. This method of assembly would be similar to that shown in FIG. 1 with respect to blocks 37 (FIG. 17).
1. Abutting electrical contact means comprising first and second aligned elongated conductors of electrically conductive relatively rigid material, tubular dielectric member means within which said conductors are disposed, said conductors having end surfaces in facing relation, the diameters of said conductors being substantially equal to the bore within said dielectric member means, and at least one contact block disposed between said facing surfaces, said contact block being fabricated of resilient conductive material whereby thermal expansion and contraction, shock and vibration of said conductors in an axial direction will be absorbed by said block, said contact block being compressed when in its operative position so that at least a substantial portion thereof is spread outwardly against the inner wall of said dielectric member means.
2. The combination according to claim 1, there being two contact blocks between said facing surfaces.
3. The combination according to claim 2, said contact blocks being compressed against each other and engaging said facing surfaces.
4. The combination according to claim 2, further provided with a D.C. block in the form of a ceramic capacitor disposed between said two electrically conductive blocks, said capacitor having conductive outer surfaces against which the contact blocks are compressed.
5. The combination according to claim 4, said ceramic capacitor having slight radial play within said tubular dielectric member means.
6. The combination according to claim 2, said 'contact blocks being mounted on the ends of said conductors.
7. The combination according to claim 2, further provided with an annular outer conductor surrounding said two aligned conductors, said dielectric member means comprising an insulative bushing between the central conductors and outer conductor.
8. The combination according to claim 2, said two contact blocks being carried by the ends of said aligned conductors, each conductor being part of a connector, said two connectors being identical, each connector further comprising an outer conductor, said dielectric means comprising a dielectric insulative sleeve between the inner and outer conductors, the outer conductors having facing radial surfaces, the outer ends of said contact blocks in their unstressed condition being axially outwardly of said radial surfaces, and means for drawing together said two connectors whereby the contact blocks will be compressed against each other and the outer conductors brought into conductive relation to form a hermaphroditic connector assembly.
9. The combination according to claim 8, each contact block comprising an outer cylindrical portion and an inner portion of lesser diameter disposed within a counterbore in its conductor with a compressive fit.
11. The combination according to claim 1, there being a single contact block between said facing surfaces. 7
12. The combination according to claim 11, further provided with a D.C. block in the form of a ceramic capacitor disposed between said two conductors, said capacitor having conductive outer surfaces against one of which said contact block is compressed and against the other of which the end of an elongated conductor is compressed.
13. The combination according to claim 12, said ceramic capacitor having slight radial play within said dielectric member means.
14. A connector for a microwave source comprising an outer conductive housing attachable to the microwave source, a bore within said housing, a dielectric insulative bushing within said bore, a pair of aligned central conductors of relatively rigid material secured within said bushing in spaced relation, a DC. block in the form of a ceramic capacitor disposed between the facing surfaces of said central conductors, and at least one contact block of resilient conductive material compressed between an end surface of one central conductor and a facing outer surface of said capacitor.
15. The combination according to claim 14, said contact blocks being of spherical shape in their unstressed condition whereby they will assume flattened spheroidal shapes when compressed.
16. The combination according to claim 15, said central conductors being provided with tapered shoulders whereby they may be pressed into said bushing from opposite sides and held thereby.
17. The combination according to claim 14, said ceramic capacitor having slight radial play in said bushmg.
18. The combination according to claim 17, there being two contact blocks between said conductors and capacitor.
19. A connector for use in a herrnaphroditic connector assembly comprising a central conductor of elongated cylindrical shape, an outer conductor of annular shape surrounding said central conductor, a dielectric insulative bushing therebetween, said outer conductor having a radial end surface, said bushing having an end surface spaced axially inwardly from said outer conductor end surface, said central conductor having an end surface spaced axially inwardly from said bushing end surface, a contact block of conductive resilient material secured to the outer end of said central conductor and having an outer surface spaced axially outwardly from the plane of said outer conductor end surface, and means for drawing two identical such connectors together so that their outer conductor end surfaces are in electrically conductive relation and their resilient conductive contact blocks are compressed together.
20. The combination according to claim 19, the end surface of said central conductor having a counterbore, said contact block having a portion with a compression fit within said counter bore.