GB2145578A - Connector for semirigid coaxial cable - Google Patents

Abstract

An electrical connector for receiving a semirigid coaxial cable includes, at the proximal end of the connector body, an annular sleeve 32 inwardly tapered to a diameter smaller than the minimum manufactured diameter of the cable 12, and a plurality of relatively narrow slots 34 axially defined in the sleeve so that, as the cable is inserted into the connector body towards its proximal end, it enters and contacts the sleeve which diametrically expands at the slots to accommodate and firmly grasp the cable at the mating interface end of the connector to eliminate RF choking. <IMAGE>

Description

SPECIFICATION Improved connector for semirigid coaxial cable The present invention relates to an improved electrical connectorforsemirigid coaxial cable and, more particularly, to a connector constructed to eliminate an RF choking phenomenon associated with connectors crimped to semirigid coaxial cable.

Atypical semirigid coaxial cable includes an inner electrical conductor, a surrounding dielectric and a semirigid outer conductor peripherally enveloping the dielectric. Although such cables are generally provided in standard diametric sizes, commonly practiced manufacturing techniques result in diamet ricvariations along the cable length such that, for purposes of standardization, this cable parameter is often specified in terms of nominal size-the magnitude of acceptable variations from nominal size being known.

Terminating electrical connectors for semirigid coaxial cable must be correspondingly provided with inside diameters dimensioned to accommodate the manufacturing variations permissibleforcableofa given nominal size. The combination of required connector and cable tolerances yields a small but variable annular gap between the outer diameter of the cable and the interior diameter ofthe connector. In utilizing known connectors that are soldered to the cable, the solder flows into and fills the radial gap to create an electrically and mechanically stable structure.However, in solderless connectors-- i.e. those that are crimped or similarly mechanically secured to the semirigid outer conductor of the cable-the annular gap is notfilled and its presence, particularly atthe interface with a mating connector or jack, produces a so-called choke effect. In essence, the gap acts as a microwave cavity which resonates at frequencies dependent upon its dimensions; the result is a sharp increase in the voltage standing wave ratio (VSWR) at some particularfrequency.

Referring, byway of example, to Fig. 1, a prior art crimp-type connector generally designated 10is illustrated in secured relation about a semirigid coaxial cable 12. Cable 12 comprises an inner conductor 14surrounded by a dielectric 16 and, in turn, by a semirigid outer conductor 18 of a minimum manufactured diameter. The elongated connector body 20 is crimped about cable 12 at the rear or distal end ofthe body. Athreaded coupling nut 22 disposed forfree axial rotation aboutthe proximal end of body 20 (is coupled to the body bya C-ring 24orthe like.An annulargasket24providesa cushioned seal when connector 10 is coupled or secured to a mating connector (not shown) in conventional fashion to electrically connect cable 12 to another cable orto a terminal device orthe like.

Clearly visible in Fig. 1 is the aforementioned annular gap 28 lying between the outer periphery of semirigid outer cable conductor 18 and the interior peripheral wall 30 at the proximal end of connector body 20 Clearly, even with careful machining ofthe proximal bore in body 20 the dimensions of gaps 28 willvaryfrom cabletocable in accordancewith corresponding variations in the cable outer diameter.

In addition, a the dimensions of gap 28 are altered when the cable is stressed orflexed in the vicinity of connector 10, causing the VSWR peaks to be evanescent in nature. The points of contact between connector body surface 30 and the periphery of semirigid outer cable conductor 19 shift back and forth with stress on orflexing ofthe cable causing transitory impedance disturbances and reflective losses at the interface between mated connectors.

It is accordingly the desideratum ofthe present invention to provide an improved connectorthat, when conventionally crimped or otherwise attached about semirigid coaxial cable, provides a secure mechanical connection to the cable in the area of the mated connection interface.

It is a further object of the invention to provide an improved connector for semirigid coaxial cable that prevents the formation of a gap between the outer periphery ofthe cable and the interior surface ofthe connector bodyatthe proximal end or mated connection interface ofthe connector.

It is another object of the invention to provide an improved connector for semirigid coaxial cable that eliminates the so-called choke effect produce when conventional crimping-type connectors are attached to semirigid cable.

It is a still further object of the invention to provide an improved connector for semirigid coaxial cable that satisfies the foregoing objects while remaining electrically and mechanically compatible with existing conventional mating connectors.

Other objects and features ofthe present invention will become apparentfrom the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition ofthe limits of the inventionforwhich reference should be made to the appended claims.

In the accompanying drawing, wherein similar reference characters denote similar elements throughoutthe several views: Figure lisa side view, in section, of a known prior art connector crimped about a semirigid coaxial cable; Figure 2 is a side view, in section, of an improved connector body in accordance with the invention as initially manufactured; and Figure 3 is a side view, in section, of an improved connector in accordance with the present invention and crimped about a semirigid coaxial cable.

Referring now to Fig. 2, there is shown an improved connector body 32 constructed in accordance with the present invention. More particularly, in the manufacture of body 32 a plurality of relatively narrow slots 34 are axially defined in the sleeve forming the proximal end of the body. Slots 34 are circumferentially spaced aboutthe sleeve and adjacent slots may be equally spaced one from the other. Fig. 2 illustrates the initially manufactured appearance of connector body 32 wherein slots 34 are substantially rectangularlyconfi- gured.Priorto engagement of body 32 with threaded coupling nut 32, however-and correspondingly before a coaxial cable 12 is inserted into the inventive connector-the proximal end of the body 32 is crimped or similarly radially compressed ta diametri cally constrict its mating interface end to a diameter smallerthan the minimum manufactured diameter of the semirigid outer conductor 18 of cable 12. Slots 34, as a consequence of this operation, thereby generally take on thefrusto conical shape seen in the centrally disposed slot of Fig. 3.

It should in any event be understood that the tapering, by radial compression or otherwise, ofthe proximal end of body 32 is intended to be performed as part ofthe connector manufacturing process and not by its end user. Although such tapering could be done by the end user, it is contemplated thatthis step be completed priorto shipmentto or receipt by the end userofthe inventive connector.

The inventive connector body 32 in Fig. 2 is additionally illustrated at its distal end with crimp able shell 36 which comprises a series of axial or longitudinal flutes 38 and substantially transverse cross threads 40. Flutes 38 and cross th reads40 are formed as projections which extend radially inward from shell 36 to immediately surround a semirigid outer cable conductor 18 inserted into body 32 sothat, when deformable shell 36 is crimped the projections bite into the outer surface of semirigid outer conductor 18 (see Fig. 3) to secure the same to the body distal end against rotational and longitudinal movement.In any event, the particular crimpable or alternative attaching structures provided at the body distal end and their precise manner of operative securementto the semirigid outer conductor of the cable are purely matters of design choice and no limitation on the present invention is intended by the illustrated construction.

In use, semirigid coaxial cable 12 is inserted into the inventive connector 42 through the distal end of body 32 until the cable end as defined by the end of outer conductor 18-is substantially aligned with the proximal end face or mating connection interface of connector body 32 (Fig. 3). Asthe cable is inserted into body 32 toward its proximal end the semirigid outer conductor 18 enters and contacts the proximal end sleeve which, having been previously crimped to less than the minimum manufactured diameter ofthe cable outer conductor, diametrically expands at slots 34to accommodate and firmly grasp the cable at the connector body proximal end.In this manner, the connector body makes firm and secure electrical and mechanical contact with semirigid outer cable conductor 18 along the entire periphery ofthe cable along a plane perpendicularto the cable axis atthe connector body mating interface or proximal end. The connector may then be crimped to semirigid outer cable conductor 18 atthe distal end of body 32 in conventional fashion.

The disclosed construction for an improved connector body has been demonstrated to yield notably superior performance with respectto prior artconnec- tors over a wide frequency range. With the elimination of possibleformation of an annular gap atthe connector mating interface end has come a corres ponding elimination ofthe so-called choke effect.

Moreover, the mechanical and electrical attachment of improved connector 42 to a semirigid coaxial cable 12 is unaffected byflexing or stressing of the cable, thereby eliminating a heretofore common source of signal distortion or perturbations.

While there has been shown and described and pointed outfundamental novel features of the inven tion asappliedto a preferred embodimentthereof, it should be understood that various omissions and substitetions and changes in the form and detailsof the deviillustrated and in its operation may be rnade bythoseskilteri in the artwithout departing from the spirit of theinvention, It is the intention, therefore, to be limitedonlyas indicated by the scope of the claims appended I reretaw

Claims (8)

1. In an elEctrical connector for receiving a coaxial cable having gn innerconductor surrounded by a dielectric andin turn byasemirigid outer conductor of a minimum nianufacturect diameter, and including an axially elongal ed body having attaching means proxi- mate its distal endfor achieving positive mechanical secu rement of tlieattaching means to the semirigid outer conductor Cf acable inserted into the body at its distal end and extendingto a position proximate its proximal end, the improvement comprising cable coupling means attheproximal endofthe body for assuring firm electricaland mechanical contact with the cable outer conductor, said coupling means comprising: an annular sleeve inwardlytapered in the direction ofthe body proximal end to a diameter smaller than the minimummanufactured diameter of the cable outer conductor;-a nd a plurality of relatively narrow slots axially defined in said sleeve so that as the cable is inserted into the connector body toward its proximal end the semirigid outer conductor enters and contacts said sleeve which diametrically expands at said slots to accommodate and firmly grasp the cable atthe connector body proximal end.

2. In a connector in accordance with Claim 1, each of said slots being inwardlytapered in the direction of said body proximal end.

3. In a connector in accordance with Claim 1,said plural slots being circumferentially spaced about said sleeve.

4. In a connector in accordance with Claim 1, said attaching means comprising a radially deformable annular shell to surroundthe semirigid outer conductor of the cable at the conrrector body distal end, and means forming projections extending radially inward within said shell to immediately surround the outer conductorsothatwh.ensaiddeformableshell is crimped said projections bite into the outer surface of the semirigid outer conductor to secure the sameto the attaching means against rotational and longitudinal movement.

5. In a connector in accordance with Claim 4, said projection forming means being aligned axially along the connector body.

6. In a connector in accordance with Claim 4, said projection forming means extending substantiallls- transverseto the elongation ofthe connector body.

7. Inaconnectorin accordancewith Claim 4said projection forming means extending both axially along and substantially transverse to the elongation of the connector body.

8. In a connector in accordance with Claim 1, said attaching means comprising crimpable means.