US 3321732 A
Abstract available in
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Description (OCR text may contain errors)
May 23, 1967 E, w. FORNEY, JR
CRIMP TYPE COAXIAL CONNECTOR ASSEMBLY 5 Sheets-Sheet 1 Filed May 14, 1965 May 23, 1967 E. w. FORNEY, JR
CRIMP TYPE COAXIAL CONNECTOR ASSEMBLY Filed May 14, 1965 3 Sheets-Sheet 2 INVENTOR. EDGAR wumr FoaneyAm. BY (M/u,
May 23, 1967 Filed May 14, 1965 E. W. FORNEY, JR
CRIMP TYPE COAXIAL CONNECTOR ASSEMBLY 3 Sheets-Sheet 3 INVENTOR.
I EDGAR WILMOT Fokunst- BYcu/Jw, mm,
United States Patent 3,321,732 CRHVIP TYPE COAXIAL CONNECTOR ASSEMBLY Edgar Wilmot Forney, Jr., Harrisburg, Pa., assignor to AMP Incorporated, Harrisburg, Pa. Filed May 14, 1965, Ser. No. 455,819 4 Claims. (Cl. 339-89) This invention relates to crimp type coaxial connector assemblies of the type adapted to serve cable utilized to transmit television signal frequencies and the like. The Community Antenna Television (CATV) Industry has developed a variety of equipment adapted to supply consumers with improved television signal reception. In practive a CATV service company constructs a rather elaborate antenna tower in a location which is optimum for signal reception with respect to various television station complexes, usually large cities. From this central tower antenna the company installs a network 'of transmission lines routed into the'various communities nearby. For a fee and service charge the company then provides tap-offs or drop lines from the transmission line network to individual consumers. In this way an indi vidual consumer may receive a variety of high quality channels from a high quality antenna and network far beyond his means as an individual to support.
The most expensive part of a CATV system is the network of lines and cables connecting'a central antennato the various consumers with a good part of the expense going to cable connectors and installation labor. One reason for this is that the cable utilized must be high quality coaxial cable capable of, in certain instances, transmitting television signals without signal degradation over substantial distances to several hundred or thousand consumers. For what might be termed trunk transmission the cable employed takes the form of a semi-rigid construction employing a solid or tubular copper center conductor supported by a dielectric material within a relatively heavy aluminum outer sheathing which forms the cable outer conductor. For branch lines a smaller flexible cable is frequently employed which has a solid copper center conductor surrounded by foam dielectric material and a corrugated shield surrounded by a relatively heavy, tough, protective outer sheathing of flexible and insulating material. The usual consumer drop line cable consists of a solid copper inner conductor surrounded by foamed dielectric material and a heavy copper braid surrounded by a tough and flexible insulating outer sheath. For reasons of economy, the cable network is worked out to the individual consumer with these various cables being reduced in diameter in accordance with power requirements, and it has been the practice to manufacture connectors in various sizes to accommodate the different sizes of cable. One of the problems has been that connectors designed in accordance with the prior art are of a configuration wherein few, if any, of the same parts of a connector for one size cable may be employed with a connector for a different size cable. For example, in one of the most frequently used connector designs of the prior art the mechanical connection to the cable is accomplished through a split wedge ring axially driven by threaded nut having surfaces therein to engage the ring and compress such to clamp the cable and including a forward connector portion mating with a nut. The ring,
nut and forward portion of the connector are generally suitable for only one size of cable. This same problem is also encountered in the connector devices used to terminate cable, such as for inputs and outputs for various amplifiers, couplers and taps distributed along the transmission line network.
Still another problem affecting the connection and termination of CATV type cables is one of labor. While television signals are only on the order of 215 megacycles, the frequency involved is still sufliciently high to make it necessary to maintain the conductive portions of the connector device employed in careful alignment to prevent discontinuities and large losses in the transmitted signal. This means that skilled labor must be employed with great care being taken in the assembly of the connector to the cable. The relative complexity and large number of parts of connectors and terminals utilized with CATV installations adds to this problem and to the amount of time necessary for each connection or termination.
Accordingly, it is one object of the present invention to provide a coaxial connector and terminal assembly adapted to accommodate a range of cable sizes and constructions with the same structure. It is another object to provide a connector and terminal assembly for coaxial cable having few parts and requiring little skill in assembly. It is a further object of the invention to provide a connector and terminal assembly for use with coaxial cable which itself becomes a part of the assembly tooling and to provide a method of connection and termination for coaxial cable utilizing the connector parts as tooling. It is a general object of the invention to provide a universal connector and terminal assembly for coaxial cables of a design and construction reducing the average cost per installation on coaxial cable.
The foregoing objectives are obtained in the present invention through the use of a receptacle adapted to receive the center conductor of a range of coaxial cable sizes which may be simply inserted therein. To mechanically and electrically connect to the cable and its outer conductor, a mating plug member is provided which is crimped to the cable outer conductor and which supports the center conductor and dielectric core in a manner continuous with the cable. The receptacle of the invention includes a double-ended contact sleeve carrying a spring capable of receiving a range of conductor diameters with the sleeve being coaxially mounted in the receptacle in a manner matching the receptacle impedance to that of the line. The plug of the invention is arranged so that it may be used in conjunction with the stripping preparation of the cable through a method adapted to facilitate cable termination. In the practice of this method the cable is partially stripped, inserted into the plug member of the invention, crimped and then further stripped to the final form for use in the receptacle of the invention.
In the drawings:
FIGURE 1 is a perspective view showing the connector receptacle of the invention and two plug members positioned for insertion therein to terminate different sizes of cable;
FIGURE 2 is a perspective of the receptacle of the invention in a terminal embodiment;
FIGURE 3 is a longitudinal section of the receptacle of the invention having one plug member carrying one cable size fitted therein and another plug member termi- 3 mated to a cable shown in section, positioned for insertion within the receptacle;
FIGURE 4 is an enlarged longitudinal section view of the center conductor sleeve of the receptacle of FIG- URE 3;
FIGURE 5 is an enlarged perspective of one of the contact springs utilized in the sleeve assembly of FIG- URE 4 and the connector receptacle of FIGURE 3;
FIGURE 6 is a longitudinal section of the terminal receptacle of the invention shown in FIGURE 2; and
FIGURES 7-11 are views showing the assembly pro cedure and method of the invention utilizing the plug member to facilitate a termination of the cable.
Referring now to FIGURE 1 there is shown a connector assembly 30 adapted to interconnect cables 10 and 10' of different power capacities and geometrics. These cables have essentially the same construction with differently sized inner and outer conductors to adjust the cable impedance to some standard impedance such as seventy-five ohms. Viewing the two cables 10 and 10', the center conductors 12-12' are of solid copper rod coaxially supported and surrounded by a dielectric filling 14-14, typically of foamed dielectric material; an outer conductor shown with respect to cable 10' as 16', typically a braid of flat copper strips and an outer protective and insulating sheathing 18'. The cable 10 may be considered as a secondary trunk or distribution cable and the cable 10 may be considered as a drop line to a single consumer of CATV service. As can be seen the center conductor 12' is substantially larger than the center conductor 12. The outer conductors and spacing between the conductors of the cables are also different. It is this difference which represents a problem in termination and which has caused prior art devices to turn to assemblies which can only be employed to terminate one set or pair of differently sized cables.
The invention assembly for performing a connection of the cables 10 and 10' is, as shown in FIGURE 1, comprised of a receptacle 30 adapted to receive and mechanically and electrically connect to plug members 20 and 20' individually terminated to the respective cables. To accomplish a termination of one of the cables to equipment such as to an amplifier or to the consumer receiver or to accomplish a connection through a bulkhead, the receptacle assembly may take the form shown in FIGURE 2, as assembly 50, which is similar to with the addition of structure to accommodate a bulkhead or box fitting. The assembly thus includes a receptacle on one end and a plug andreceptacle structure on the other end. A plug like that of 20 is utilized with 50 with the addition of a threaded nut fitted over the end thereof generally in the manner to be described with respect to the nut structure of the assembly 30.
Referring now to FIGURE 3, a more detailed description of the assembly of the invention will now be given. The plug member shown as 20 as terminated to the cable 10 is comprised of but three parts; a metallic plug body 22 having an integral extension to fit beneath the cable outer conductor 16, a gasket 24 and an outer ferrule 26 adapted to be crimped in two spaced regions as shown by the numerals C1 and C2 from a generally cylindrical configuration as shown in FIGURE 7. The plug body 22 has a forward relatively heavy portion havinga series of threads 22a along the outer surface thereof and having a bore of constant diameter 22b extending therethrough. The bore 22b also extends through an integral sleeve extension 22c and is of a diameter adapted to receive and support the dielectric sheath 14 of the cable. The outer surface of the extension 220 includes annular projecting rings shown as 22d which serve to lock the surface to the outer conductor of the cable upon crimping and to break up oxides further improving the connection of the outer conductor to the body of the plug. The outer end of the extension 22c is terminated in a beveled end portion 22:; which serves to facilitate insertion of the extension within braid or outer conductor of the cable. The extension 220 is made sufficiently rigid and deformation resistant to permit the crimping operation to be described hereinafter without constriction of bore 22b. The gasket 24 is positioned overlying extension 220 at the point of junction with the body of 22. This gasket is made sufiiciently resilient to be compressed by the forward portion of crimp C-l during the crimping operation to seal the connection at this point. The ferrule of 26 is of relatively thin malleable material slightly larger in its undeformed shape than the outer sheathing of the cable so as to fit thereover and to be crimped inwardly by the deformations C-1 and 0-2 to mechanically and electrically join the cable to the plug. The spaced crimps of C-1 thus seal and join the cable outer conductor to the sleeve extension 220 and the crimps of C2 grip and mechanically support the cable through compression of the outer sheath at a point displaced from the end of the extension. The deformations represented by C-1 and C2 are preferably 0 shaped in cross section to grip the cable fully around its circumference and the deformation of 0-2 is limited radially so as not to displace the outer conductor 16 to present a discontinuity in the cable at this point. It has been found useful to make the crimps as shown with a space between the points of deformation in each crimp to permit the bulging that is apparent from FIG- URE 3. This reduces the force necessary to complete the crimp and at the same time permits some axial flow of materials within the budged portion to both serve as a seal and preclude undue inward deformation.
The opposing plug 20' is substantially identical to the plug 20 with the exception of dimensions increased to accommodate the large cable 10. These changes in dimension do not include the forward outer diameter of the plug body and the outer threading of the plug which are the same in all plugs to fit within the same receptacle 30. The dielectric of the cable is caused to extend fully through the bore of the plug to a point flush with the front face of the plug and the center conductor of the cable 12' is permitted to extend outwardly from this forward face as shown in FIGURE 3. The assembly and installation of cable in a plug member will be described in greater detail hereinafter relative to FIGURES 7-11.
Again, referring to FIGURE 3, the connector receptacle of the invention is shown to be comprised of an outer sleeve 30a having a constant diameter bore 30b. The wall thickness of 30a is made sufficiently rigid to avoid bending in use and is typically made of a conductive material such as brass tubing. On each end of the sleeve 30a is a ring 300 welded, braized or otherwise affixed, which serves to secure a nut 32 having internal threading 32a adapted to cooperate with threading 22a of a plug. The nut assembly is the same on each end of the connector receptacle 30 as shown. Carried within each nut 32 is an O ring 34 of resilient material adapted to be driven in compression upon full insertion of a plug within the connector receptacle.
In the center of the receptacle sleeve 30a is a dielectric insert and support structure 36 which includes an internal bore 36a adapted to receive and hold coaxially of the sleeve bore a further sleeve carrying contact springs for engagement with the center conductors of cable. The insert 36 is preferably made in two halves or split so as to be fitted over the relieved center portion of 38 to captivate 38 upon being positioned within the sleeve 30a. After fitting, the insert is staked as indicated at 39 to trap the assembly and hold it against axial displacement. The insert is made sufliciently long to provide an adequate bearing area for holding the sleeve 30a and is made of a material sufficiently strong to prevent movement of 38 due to plastic flow. The insert 36 is further made of a dielectric material having. dielectric constant and shape to match the portion in the center of 38 to the..characteristic impedance of the lines; e.g., to seventy-five ohms.
The shaping shown at 36b is for the purpose of reducing or minimizing effective losses due to the change in conductor spacing at this point and is in accordance with the compensation technique disclosed in U.S. application S.N. 395,150 by John Fan, filed Sept. 9, 1964.
Sleeve 38 is duplicated on the opposite side of the connector receptacle by sleeve 38' and the two sleeves are joined together in the center. Each sleeve includes as shown with respect to 38 an outer conductive sleeve portion 38a of considerable length, open at one end and reduced at the other end a at 3812 to a smaller diameter portion welded as at 38c to the opposing sleeve. A copper plug 40 substantially filling the smaller sleeve portions and extending into each sleeve is provided to add rigidity to the joint of the sleeves and to increase the conductive material at the point of juncture of the sleeves. The reduction in diameter of the sleeves and the resulting faces 38b define surfaces permitting the insert to lock the sleeves against axial displacement. The inner bore of 38 as shown 38d is terminated at the end opposite to the joint of the sleeves by a recessed portion with end 382 of the sleeve turned inwardly to entrap portions of a spring member carried within the sleeve. This spring member is shown at 42 to include at one end outwardly displaced tabs 42a, a barrel portion 42b and spaced therefrom a barrel portion 420 with the barrel portions being joined by integral spring arms 42d, which are relatively fiat in cross sectional configuration, but are bowed and twisted along the lengths thereof. The type of spring represented in FIGURE 5 is disclosed in greater detail in US. application, S.N. 286,725, filed in the name of Glenwood A. Fuller on June 10, 1963, now Patent No. 3,286,671. As mounted with the sleeve, the spring 42 is capable of being expanded radially in the center portions and axially at one end; namely, the free end or the barrel 420. This expansion is depicted on the right side of FIG- URE 4 where the conductor 12 is shown as inserted within the sleeve and spring member. The basket type of spring is preferred since it permits a connection to be made with different diameter conductors inserted therein. In an actual embodiment having a configuration generally depicted in FIGURES 4 and 5, the spring member and sleeve quite adequately accommodated conductors ranging from No. 9 AWG through No. 14 AWG, or six sizes of center conductors. If it is desired to extend utility of the spring to even smaller sizes a conductive pin may be secured to the conductor 12 or 12' having a forward diameter to fit within the basket spring. For most uses, however, it is preferred to utilize the structure shown in the drawings with an incidental saving in parts and in assembly time.
As an important point the amount of material utilized for the sleeve 38 and 38' and their conductivity should be made such as to carry the currents involved in CATV systems. Additionally, the contact spring employed should provide an adequate contact area with the conductor outer surface to avoid excessive heat being developed through losses under the higher loads found in CATV transmission. The helical spring 42 maximizes this contact area and for that reason is preferred.
FIGURE 6 shows a terminal bushing 50 which is substantially like the connector receptacle 30 with the addition of a flange 52 and threaded portion at one end 54, which replaces the nut utilized in the assembly 30. It is contemplated that a sleeve structure may be employed on one end with other terminal configurations on the other end.
As part of the invention, the plug structure heretofore described is utilized to aid in preparing the cable for its final termination in a connector or terminal structure. This is depicted in FIGURES 7-11. The assembly procedure begins with a first preparation of the cable which includes a removal of the portion of the outer sheath 18 for a length as generally shown in FIGURE 7 to expose a section of the outer conductor or braid 16 approximately as long as the extension 22c and a portion of the dielectric sheath 14 and center conductor 12 considerably longer than, the assembly 20. With the cable so prepared the ferrule 26 is slipped back on to the cable over sheath 18 and the plug is inserted as indicated in FIGURE 8, with the braid being pulled up over 22c to a point where its end is near the gasket 24. This leaves the portion of the dielectric 14 and center conductor 12 protruding continuously through the plug body as indicated in FIGURE 9. With the cable and plug structure so arranged the crimp heretofore described is accomplished as indicated in FIGURE 10. After this the cable and plug structure will be tightly locked together against any relative displacement; principally through the two spaced deformations C-1 and C2 and the dielectric can be removed to a point flush with the outer face of 22, as indicated in FIGURE 11. The plug then becomes a tool for holding the cable during the final preparation for use. If a center pin member need be added to the center conductor it may then be positioned on a portion thereof and crimped or soldered thereto. In the present invention the principal use of the assembly is contemplated to be without center pin members and the cable will be terminated in its finished form after the step depicted by FIGURE 11. This method has substantial advantages over and above merely serving as a holding means to permit the final stripping of the cable. First of all, any accidental or forced displacement of the dielectric sheathing or center conductor arising during the crimping operation can be accommodated in the final cable preparation step. Secondly, since the cable is tightly gripped during the final preparation step so no further relative movement can take place. As can be appreciated, in high frequency devices small discrepancies in conductor spacing are significant. The invention method minimizes these discrepancies.
While the present invention has been described particularly relative to CATV cable and application, it is fully contemplated that the advantages attendant thereto may be utilized in other fields for other purposes wherein there is a need to connect or terminate coaxial cable.
Having described the invention in terms of its preferred mode of practice, the invention is now defined by the appended claims.
What is claimed is:
1. In an assembly for connecting coaxial cables of the type having an inner conductor surrounded by dielectric material and an outer conductor, the combination comprising a conductive receptacle including a first tubular sleeve having a bore of substantially constant diameter extending therethrough with means at either end of said first sleeve to electrical-1y and mechanically connect to plug members terminated to coaxial cable for insertion at either end of said receptacle, a dielectric bead adapted to be fitted within said first sleeve toward the center thereof, said bead having an axial length small in comparison to the axial length of said sleeve and having a central bore extending therethrough, a second condctive sleeve having a center section of reduced diameter to define spaced shoulders adapted to engage the outside end surfaces of said bead, said bead being split along its length so as to be fitted over the center section of said second sleeve with said second sleeve in the said bore of said bead and axially aligned within said first sleeve whereby to be closed against the said center section of said second sleeve to position and axially lock said second sleeve within said first sleeve, said second conductive sleeve being of a diameter substantial-ly less than the interior diameter of said first sleeve and being held by said bead to extend coaxially along portions of said first sleeve, said second sleeve carrying therein spring contact members having a plurality of spirally formed fingers extending along the second sleeve length with a substantial spring action transverse to the length of said second sleeve whereby to be capable of substantial radial deflection to accommodate differently sized center conductors of coaxial cable inserted therewithin.
2. The assembly of claim 1 wherein said second conductive sleeve has an exterior surface configuration which is smooth whereby to maintain the spacing between the outer surface of the second sleeve and the inner surface of the first sleeve substantially constant along said assembly except in said center section whereby to maintain the characteristic impedance of said asesmbly substantially constant, notwithstanding the insertion of differently sized center conductors inserted therewithin.
3. The assembly of claim 1 wherein said spring contact members are afiixed at the outside ends of said second sleeve and free for axial displacement at the inside ends of the spring members within said second sleeve.
4. The assembly of claim 1 wherein said second sleeve References Cited by the Examiner UNITED STATES PATENTS 3,040,288 6/1962 Edlen et a1 339-177 X 3,120,418 2/1964 Deakin 399-221 X FOREIGN PATENTS 695,439 8/1953 Great Britain. 993,316 5/ 1965 Great Britain. 183,270 4/1963 Sweden. 154,312 8/ 1932 Switzerland.
MARVIN A. CHAMPION, Primary Examiner.
is comprised of a pair of conductive sleeve members se- 15 DONALD MILLER, Examine"- cured together at the inner ends thereof.