US 3171707 A
Description (OCR text may contain errors)
March 2, 1965 POWELL 3,171,707
SUBMINIATURE CONNECTOR FOR COAXIAL CABLE Filed July 31, 1961 III gri l x 42 /1111? s INVENTOR F 4 ALBERT E. POWELL BY Malta- ATTORNEY United States Patent 3,171,707 SUEMINKATURE COPXNECTOR FOR COAXIAL C BLE Albert E. Powell, Old Greenwich, Conn, assignor to Micon Electronics, Ind, Garden City, N.Y. Filed July 31, 1961, Ser. No. 127,939 4 Claims. (Cl. 339-177) The present invention relates to electrical connectors and more particularly to an improved coupling means adapted for use with flexible coaxial cable.
Coaxial transmission lines are widely used to propagate wave-signal energy along a restricted path between two spaced points; for example, between an antenna and a radio receiver. It frequently is desirable to provide an electrical connector between two sections of such transmission line or between the end of the line and a utilization apparatus.
Relatively little difiiculty is experienced in the design and construction of such connectors where they are to be used with a coaxial transmission line of relatively large physical size since the inner and outer conductors of the line are then sufficiently large that the inner and outer conductors of the connector may readily be constructed of approximately the same diameters while yet possessing adequate rigidity and mechanical strength.
However, the present-day trend is toward coaxial trans mission lines of relatively small physical size often of external diameter of the order of an eighth inch or less. Electrical connectors for use with such small transmission lines cannot readily be constructed to have their inner and outer conductors of approximately the same diameters as corrseponding conductors of the line since the inner conductor of the connector then becomes so small that it not only does not possess the required rigidity and mechanical strength but can be connected to the inner conductor of the transmission line only with great diificulty.
It is an object of the present invention, therefore, to provide a new and improved electrical connector for an end of a coaxial transmission line which avoids one or more of the disadvantages and limitations of prior connectors of the type described.
It is a further object of the invention to provide an electrical connector, for an end of a flexible coaxial cable adapted to be constructed of small physical size yet one which is not only capable of withstanding without failure relatively high electrical potentials but additionally possesses impedance characteristics matching that ofthe coaxial line.
It is an additional object of the invention to provide a new and improved electrical connector for an end of a coaxial transmission line and one which while of sturdy mechanical construction may have a physical size appreciably smaller than that heretofore readily obtainable.
It is a further object of the invention to providea new and improved electrical connector, for an end of a coaxial transmission line, of relatively simple and inexpensive construction which permits close mechanical tolerances to be maintained during manufacture and assembly thereof.
It is a particular feature of the invention to provide a subminiature connector having greater cable pullout re sistance than heretofore attainable in subminiature connectors.
Another object of this invention is to provide a connector meeting the requirements of US. Government specification MIL C 22557 but which is of smaller size and lesser weight than prior devices meeting the requirements of the said specification.
Still another object of the invention is to provide a subminiature coaxial connector with means to clamp the.
outer insulator sheath of a coaxial cable.
3,1713%? Patented Mar. 2, 1965 A feature of this invention is the provision of subminiature connector for coaxial cable which is operable over a broad temperature range.
A particular object of the present invention is to provide in a coaxial connector having the structural advantages mentioned, a construction wherein the structural advantages are achieved without the introduction of any significant electrical discontinuity.
Still other objects and advantages of the present invention will in part be obvious and will in part be pointed out with particularity as the following description proceeds, taken in conjunction with the accompanying drawmg.
In the drawing:
FIG. 1 is a full size side elevation of the male and female portions of the connector shown separated.
FIG. 2 is a full size side elevation of the male and female portions secured together.
FIG. 3 is a vertical section, greatly enlarged, of the male portion shown clamped to a coaxial cable.
FIG. 4 is a vertical section, greatly enlarged, of the female portion shown clamped to a coaxial cable.
Referring now more particularly to FIG. 1 of the drawing, there are shown a female cable connector 10 and a male cable connector 11. The two connectors may be coupled together as shown in FIG. 2 or may be used to connect coaxial cable 12 to fixed coaxial terminals conventionally provided on electronic devices.
In the cross-sectional views of FIGS. 3 and 4 the internal construction of the male and female connectors are shown in greater detail.
The construction will be brought out more fully in the following description of the method of installing an RG 188/ U coaxial cable in the male connector. The installation procedure is similar for the female connector. For other cable sizes, the dimensions stated will, of course, vary.
Referring to FIG. 3, the coaxial cable 12 comprises a solid, or stranded, inner conductor 15, a cylindrical layer of insulation 18, commonly formed from polyethylene, Teflon, or other low-loss flexible plastic, a cylindrical outer conductor 19 made of metal braid, and an outer jacket 2t) made of Teflon or other suitable insulating plastic.
The end of the coaxial cable 12 is cut at a angle with A of the outer jacket removed. Compression nut 22, Wedge 24 and cup-like recessed Washer 26 are slipped over the cable. The inner diameter of the wedge, which is tapered about 4 is slightly smaller than the inner diameter of the bore of the recessed washer for RG l88/U cable; for example the diameters are 0.105" and 0.125 respectively. It will be noted that the inner radial face 27 seats against the edge of the insulation layer 20. The braid is then combed out and bent radially against the outer face 28 of the recessed Washer 26. A ferrule 30 having an outer wall tapered about 4 and a radially extending flange 31 is forced between insulator l8 and braid 1? until flange 31 seats against the braid. The braid extending beyond the flange 31 is trimmed oil.
The cable insulation is then triinrned to within 0.040" of the flange 31 and the center conductor is cut so that 0.120" extends beyond the insulator l8. Insulator 32 is slipped over the cable end and male contact member 34 is slipped onto the center conductor and soldered thereto. An access hole as in member 37 permits a visual check to be made of the solder joint.
Insulator 4i) is slipped over the contact 34 and the entire assembly inserted into shell 42. The shell is provided with a crimped end to make captive insulator 4% The insulators 32 and 40 seize radially extending portion 37 of the contact member and captivate it against movement. Rapid changes in environmental conditions impose mechanical strains and the relief of inherent cable stresses cause cable dielectrics (particularly in extruded Teflon) and/or center conductors to recede. Ordinary connector contacts, as a result, are pulled away from each other; often producing actual disconnects. The captivated contact avoids these problems.
Compression nut 22 is then tightened. As nut 22 is tightened it forces wedge 24 along the outer insulator 2t) driving ahead of it a wave of insulator material (through cold flow) against recessed washer 2.6 to form an annular lip 43 which prevents the insulator 2% from slipping out when under tension. This is an important advantage of the invention. The leading edge of the wedge is preferably chamfered.
The shell 42 is provided with a male thread 44- adapted to receive internally threaded captive coupling nut 46 of female connector it} (FIG. 4). The assembly of the female connector is identical. It will be noted that insulator 40a is adapted to slip into its counterpart 4% when female connector 3451 seizes male connector 3 The forward end of the female connector 34a is slotted and squeezed together to provide a resilient electrical contact designed to overlie and grip the central male contact 34.
When mated, connectors it) and 11 form in cooperation, a coaxial line having throughout a characteristic impedance substantially equal to that of the cable 12.
The overlap between insulators 32 and 40 provides a relatively long leakage path between the outer and inner conductors.
The connector shown incorporates means for captivating the coupling nut 46 without tools, which means is disclosed and claimed in the application of Martin Turkel for Captive Coupling Nut Arrangement for Subminiature Coaxial Connectors, SN. 128,219, filed July 31, 1961, now abandoned, and assigned to the same assignee as this application.
Considering the captivating means in greater detail, coupling nut did is essentially a cylinder of soft, malleable material such as brass. One end l? is provided with internal threads while the other end terminates in thin wall section 4%, the inner and outer diameters of which cooperate with constructional features of body 42a to be described subsequently.
Body 42a, like nut 46, is basically cylindrical, comprising three distinct and separate sections along its longitudinal axis. The first section 48 of body 42a is slightly smaller than the diameter of the internal thread of nut 46 so that it is free to rotate thereon. The central section 49 of body 42a comprises a necked down portion forming a shoulder 51 at its junction with first end section 43. At its junction with enlarged diameter portion 52, central section 49 terminates in a concave undercut 53 recessed in the radial face 54.
To perform the assembly of the nut 46 and body 42a, portion 48 is inserted into open thin-walled end 47a. Since the periphery of undercut 53 is somewhat larger than the outer diameter of end 47a, application of a longitudinal in-line force on nut 46, as by the blow of a hammer or by means of an arbor press, will cause thinwalled end 47a to enter concave undercut 53 and be inwardly deformed, forming a lip Mb.
It is to be noted that in the connector of this invention reliance is not being placed on the strength of the relatively thin center conductor of the coaxial cable.
The center conductors of the connector are held captive by the insulators to insure against their being pulled out.
Merely compressing the outer jacket, as is done in many prior devices of this type, is not a satisfactory solution to the clamping problem as the plastic tends to age harden and/ or cold deform, releasing pressure against the clamping means. Clearly, the present invention overcomes this problem.
The metal parts of the connector are preferably formed of brass which is then gold plated.
Teflon is suitable, and is indeed presently preferred for the plastic parts.
It is to be understood that either the male or female connectors may be used independently of each other, with other mating connectors.
The connector of this invention despite its small size will operate over a temperature range of -l0il F. to +200 F. The female connector is but long (not including the clamping nut) and the male connector but (not including the clamping nut).
Having thus disclosed the best embodiment of the inven tion presently contemplated, what is claimed is:
1. An improved, subminiature coaxial connector for coupling to a small diameter flexible coaxial cable of the type having an inner conductor, an inner insulator coaxially surrounding the inner conductor, a conductive braid co axially surrounding the inner insulator and an outer insulator having an outer diameter not in excess of /s" coaxially surrounding the conductive braid, said improvement comprising:
(a) flaring means including a radial face portion said flaring means being disposed coaxially between the inner insulator and the conductive braid whereby the conductive braid and the outer insulator are flared outwardly along the axis of the connector and the end of the conductive braid is positioned against said radial face in a plane transverse to the axis of the conneotor;
(b) coaxially disposed cup means having first and second ends, the first end defining a radial face abuttingly disposed against the transverse end of the conductive braid the second end defining the periphery of said cup means dimensioned to snugly receive the outer insulation of the cable; and I (c) an annular, outer insulator deforming wedge disposed coaxilly about the outer insulator and in abutting engagement with the second end of said cup means whereby the outer insulator is forced into said cup means to lock the conductive braid against the flaring means.
2. The device of claim 1 wherein said flaring means is comprised of an elongated portion having a cylindrical bore, a tapered outside diameter and a transverse radial face proximate the enlarged end of the tapered outside diameter said tapered outside diameter extending from the end of said flaring means opposite said radial face up to the radial face, the radial f-ace abutting the conductive b-r-aid in opposition to the radial face of said cup means.
3. A subminiature connector for a small diameter coaxial cable of the type having an inner conductor, an inher plastic insulator, a braided outer conductor and an outer plastic insulator having an outer diameter not in excess of A3" in coaxial relationship comprising:
a metal shell having an internally threaded portion;
insulator means positioned in said shell, said insulator means having an axial bore therethrough;
a metal contact member positioned in the bore of said insulator means, said insulator means having a hollow portion for receiving the inner conductor;
a hollow ferrule having a tapered outer wall coaxially disposed beneath the outer conductor and the outer insulator to expand the end thereof, said ferrule having a bore adapted to receive said inner insulator in a closefitting relationship, said ferrule being further provided with a radially extending flange whereby the end of the conductive braid is radially positioned against the flange;
a cup member having an enlarged radial face adapted to clamp the braid against said flange and a recessed portion adapted to receive the end portion of the outer insulator expanded by the tapered Wall of said ferrule;
an annular wedge adapted to force the end of the outer insulator into the recess of said cup member, said Qua T wedge having an inner diameter smaller than the interior side wall diameter of said cup member; and
a lock nut, having a bore adapted to receive the cable, said nut being engaged by the internally threaded portion of said metal shell and forcing said annular wedge against said cup member.
4. A connector for a coaxial cable of the type having an inner conductor, an inner plastic insulator, a braided outer conductor and an outer plastic insulator having an outer diameter not in excess of /s" in coaxial relationship comprising:
a metal shell having a front bore of a first diameter contiguous With a rear bore of a larger diameter, the rear bore having an internally threaded portion and an internal shoulder;
a first insulator positioned in said front bore and having an axially located bore;
a second insulator having a portion coaxially mated with a portion of said first insulator and an axially located bore;
a metal contact member, positioned in the bores of said first and second insulators, said contact member having a hollow portion extending rearwardly for receiving the inner conductor, said contact member being further provided with an enlarged, radially extending portion securedly disposed between said first and second insulators;
a ferrule provided with a tapered outer wall, a bore adapted to receive the inner insulator in a closefitting relationship, and a radially extending flange, said flange having a first radial face seated against the shoulder of said shell and said second insulator and a second radial face, said ferrule being coaxially disposed beneath the conductive braid and the outer insulator to outwardly flare the aforementioned com- 6 ponents, the end of the conductive braid being radially disposed against the second radial face of the ferrule flange;
a recessed washer having a radial face adapted to clamp said braid against said second radial face of the ferrule flange, a stepped bore having a first diameter adapted to engage a portion of the braid and a second diameter portion adapted to receive an expanded portion of said outer insulator when the radial end face of the outer insulator is seated against the step of the bore;
an annular nondeformable wedge for deforming the cable outer insulator, said Wedge having an inner diameter smaller than the larger diameter of said recessed Washer bore; and
a lock nut having a bore adapted to receive the cable,
said nut being engaged in the internally threaded portion of said metal shell and forcing said annular wedge against said cup member.
References Cited by the Examiner UNITED STATES PATENTS 2,425,834 8/47 Salisbury 339-89 2,443,635 6/48 Morris et al 339-177 2,540,012 1/51 Salati 339-94 X 2,581,655 1/52 Harden 339-94 X 2,870,420 1/59 Malek 339-177 2,937,360 5/60 True 339-89 3,107,135 10/63 Keil 33994 X FOREIGN PATENTS 810,556 3/59 Great Britain.
JOSEPH D. SEERS, Primary Examiner.
ALBERT H. KAMPE, Examiner.