CA1145430A - Method of and electrical termination for coaxial cable - Google Patents

Method of and electrical termination for coaxial cable

Info

Publication number
CA1145430A
CA1145430A CA000368878A CA368878A CA1145430A CA 1145430 A CA1145430 A CA 1145430A CA 000368878 A CA000368878 A CA 000368878A CA 368878 A CA368878 A CA 368878A CA 1145430 A CA1145430 A CA 1145430A
Authority
CA
Canada
Prior art keywords
dielectric core
cable
clamp member
braid
portion
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000368878A
Other languages
French (fr)
Inventor
James J. Karol
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Bendix Corp
Original Assignee
Bendix Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US15536880A priority Critical
Application filed by Bendix Corp filed Critical Bendix Corp
Application granted granted Critical
Publication of CA1145430A publication Critical patent/CA1145430A/en
Priority to US155,368 priority
Application status is Expired legal-status Critical

Links

Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01RELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
    • H01R9/00Structural associations of a plurality of mutually-insulated electrical connecting elements, e.g. terminal strips or terminal blocks; Terminals or binding posts mounted upon a base or in a case; Bases therefor
    • H01R9/03Connectors arranged to contact a plurality of the conductors of a multiconductor cable, e.g. tapping connections
    • H01R9/05Connectors arranged to contact a plurality of the conductors of a multiconductor cable, e.g. tapping connections for coaxial cables
    • H01R9/0521Connection to outer conductor by action of a nut

Abstract

Abstract:

METHOD OF AND ELECTRICAL TERMINATION FOR COAXIAL CABLE

An electrical connector assembly (100) including a rotatable clamp member (300) terminating a "square cut"
end of a coaxial cable (10) of the type having a dielectric core (14) surrounded by conductive braid (16), the clamp member (300) comprising a tapered frusto-conical body (310) having a central passage (311) sized to receive the dielectric core extending therethrough.
Thread-like portions (500, 600) having an advancing helical groove of like sense and pitch are disposed on both the outer-surface of the tapered body and on the passage wall and simultaneously coact to improve the quality of the electrical termination and a high frequency impedance match.

Description

5~
-METHOD OF AND ELECTRICAL TERMINATION FOR COAXIAL CABLE

This invention relates to an electrical termination for a coaxial cable having a square-cut end portion and more particularly to a terminating clamp member which interconnects with the cable to improve axial securement and reduce undesirable impedance mismatch.

BA~KGROUND OF THE INVENTION

Many approaches have been suggested for electrically terminating and or securing an electrical connector to a coaxial-type electrical cable.
Some approaches have required that the cable be prepared by removing forward portions of the outer jacket, the braid, the dielectric core insulator layer, and the central conductor in progressively longer lengths (i.e., describing a "stepped" arrangement) prior to insertion thereof into an electrical connector. Such a "stepped'l arrangement of the conductor is undesirable in that it requires additional time and effort by the user and provides a chance that the preparation would not be properly done. Such an arrangement is shown in U.S.
Patents 3,054,981; 3,107,135; 3,209,287; 3,264,602 and 3,634,815.
Another approach provides a clamp member with a frusto-conical shape that is pushed axially inward over the central conductor and within the jacket and braid.
When the cable jacket is thick or made of a heavy, non-yielding material, inward movement of the clamp member can be resisted and the clamp pushed axially outward.
Such an approach suggested in U.S. Patent No. 3,373,243.
~hen the clamp member is not fully enqaged with the braid and/or the central conductor, a poor electrical connection is made. Undesirable resistance can develop `'`'`' ' , ~ ~

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between the braid and the clamp. High frequency impedance mismatch can develop if an air ~ap is formed between the clamp member and the central-conductor. Provision of ribbed grooves have not been entirely satisfactory in that a crimping process usually is required to form a tight fitment between the clamp and the cable.
Other solutions to poor electrical termination problems have been suggested respectively in Canadian Patent Application serial number 343,890, filed on January 17, 1980 and in U.S. Patent 3,110,756. While variously providing mechanical securement and electrical terminations, each separate connection approach did not coact to provide both a reliable electrical termination having a secure positional fitment between a connector member and the cable, as well as a termination having high frequency impedance matching.
The present invention is a connector assembly having a clamp member for terminating a coaxial cable which is easy and quick to assemble to the cable, which overcomes the limitations and undesirable features of the prior art, which resists rearward axial movement of the clamp member from the ~;
cable prior to complete assembly and which provides improved high frequency impedance match between the cable and the connector.
According to the present invention there is provided an electrical termination between an electrical connector and an end of a coaxial cable characterized by a dielectric core, a braided outer conductor and an outer external jacket square-cut, and by a central conductor extending forward of ... , ~, ~

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5~30 the square-cut. The electrical connector includes a rotatable clamp member for engaging the cable end, the clamp member having a forward face and a rear face with a generally frusto-conical body portion having tapered sides and a central passage extending between the faces for receiving the dielectric core and central conductor. The central passage includes a first helical thread having raised edge portions for progressively engaging the dielectric core and the tapering portion including a second helical thread having a raised edge portion for progressively engaging the braid. The first and second threads are of like sense such that after the dielectric core is received in the central passage and the clamp member is rotated about the cable, the raised edge portions coact to progressively engage the dielectric core and the braid to secure and to electrically connect the cable to the clamp member. The first threads substantially eliminate any separation between dielectric core and clamp passage to improve high frequency impedance mismatch.
In a specific embodiment of the invention the passage wall includes an axial groove portion that is disposed within the helical thread to receive insulative material scraps as a result of biting engagement by the first threads.
According to another aspect of the present invention there is provided a method of terminating a coaxial cable of the type having a square-cut end and including a conductive braid circumposing a dielectric core surrounding a central conductor having an exposed end portion extending from the square-cut. The method includes the step of assembling '~:~n 1~ ~ 3 -~5~30 a frusto-conical member having a central passage over the dielectric core such that the frusto-conical portion faces the conductive braid and the central passage faces the dielectric core, the central passa~e conical portion being provided with progressively spiralling thread of the same sense and having raised edge portions. The frusto-c~nical member is rotated to progressively engage the raised edge portions of a helical threads with the dielectric core and the braid to prevent removal of the member from the cable and to reduce high frequency impedance mismatch caused by separation between the dielectric core and the clamp member.
A rear nut and a forward contact element are assembled over the frusto-conical member to complete the contact for the coaxial termination and captivate the member therebetween.
The assembly of the present invention is advantageous in that it uses a "square cut" cable termination in which the jacket, braid conductor and insulation layer are cut to a uniform length (i.e., in a single cut for ca~le preparation).
The central conductor has an exposed portion that extends forwardly of the single cut. Such a square cut termination is an easy and quick one to accomplish in preparation of the cable and economizes on labor costs.
The connector and clamp of the present invention is compatible with any type of jacket and does not require the slitting of the jacket maintaining the cable's integrity is advantageous in that it increases the life of the cable and the termination.

~- 3a -. ` ~, .~ 5 , , ' ~ 1~ ' , ', ' ; ' , ' :.
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~.'. "' ' ' ~"' ; ' ~ ~ ~s4343 The connector of the present invention has an advantage in that the el~ectrical termination between the insulation and the connector is improved in its reliability and uniformity.
Yet another advantage is the improved high frequency impedance matching achieved by the electrical termination provided by a clamp member of the present invention.

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As a further advantage of the present invention, the connector of the present invention involves the use of only three separate assemblies of relatively large size to be handled conveniently. The use of a minimum number of pieces reduces the chance of inadvertent loss of a part durinq packaging or assembly. With only three dis-similar parts, assembly instructions can be quite simple.
The connector of the present invention has an advan-tage in that the clamp member is merely rotated to draw it into progressive engagement with the cable. Such an engagement minimizes possible damage to the cable.
Other ob;ects and advantages of the present inven-tion will be apparent to one skilled in the art in view of the following detailed description and claims in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a cross sectional view of an electrical connector assembly terminated to a square-cut coaxial cable.
FIGURE 2 is an enlarged side view of a clamp member used in the connector assembly of FIGURB l showing external helical thread portion.
FIGURE 3 is a cross sectional view of the clamp member looking along the lines III-III of FIGURE 2 and showing a central passage having an internal wall provided with helical~thread and an axial slot.
FIGURE 4 is an end view of the clamp member looking along lines IV-IV of FIGURE 3.
FIGURE 5 shows the clamp member of the present invention partially inserted over the coaxial cable with and both helical threads coacting and respectively in engagement with the cable braid and the dielectric core insulation.

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FIGURE 6 is a cross sectional view of the coaxial cable and clamp member of FIGURE 4 when the clamp member is in complete engagement within the coaxial cable and held in place therewith by the coacting helical threads.

DETAILED DESCRIPTION OF THE INVENTION

FIGURE 1 shows a cross sectional view of an electrical termination between a coaxial cable 10 and an electrical connector assembly 100 according to the present invention.
The coaxial cable 10 includes a core of dielectric material 14 disposed between a central conductor 12 and an outer braid conductor 16. A protective outer jacket 18 surrounds the conductors and the dielectric core. The outer jacket 18 and the dielectric material 14 are both made of electrically insulating materials to electrically isolate the conductors 12 and 16 from each other and from the environment.
The electrical connector assembly 100, in the ~ embodiment shown, includes three components which are supplied and handled as separate pieces: a forward body 200, an internal clamp member 300 and a rear nut 400.
The forward body 200 includes electrically insulating material 220 and an internal thread at the rear end thereof for coupling to the nut 400. An outer electrical contact 230 is disposed outside the insulating material 220 and is electrically isolated from the central contact 210 upon assembly. When the connector 100 is attached to the cable 10, the central contact 210 is electrically coupled to the central conductor 12 of the cable 10 and the outer contact 230 is electrically coupled to the braid conductor 16 o the cable 10.

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54~30 The nut 400 may be of the type described in U.S.
Patent 3,373,243 and include a rear portion 410 adapted to be grasped during installation and an external screw thread portion located forward of the rear portion 410 for engaging the internal thread of the body to secure the connector assembly 100 together. The nut 400 further includes a central aperture 430 through which the cable 10 extends and steps 440 whic:h provide the central aperture 430 in the forward region with increasingly larger diameters. When used in conjunction with the frusto-conical shaped clamp of the present design and as described later the steps 440 enable the assembled connector 100, to captivate the jacket 18 and the braid 16 and thereby to retain the cable 10 therein to provide increased resistance to axial decoupling forces applied on the cable. Captivation of the cable jacket 18 and the braid 18 occurs between the steps 440 and a frusto-conical surface of the clamp member 300.
The clamp member 300 includes an electrically con-ductive body 310 and an insulator body 320 and central mating contact 210. Preferably and in accord with the present invention the insulator body 320 includes a central bore 321 which is large enough to receive only the central conductor 12 therein. The insulator body 320 fits within an undercut portion 312 extending rearwardly from the front end of the conductive body 310. The insulator body 320 electrically isolates the exposed portion of the central conductor 12 of the cable and the contact 210 from the body 310. The insulator body 320 is -retained within the undercut by one of many known expedients (e.g., adhesively bonded or interference fit).
- ~ portion of solder 700 would be provided between the central conductor 12 and the rearward end of the conductive body 210 to complete an electrical intercon-nection between cable and connector.

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FIGURE 2 is an enlarged view of the clamp member 300 of the present invention showing the external surface of the clamp body 310. The clamp body 310 has a constant diameter forward portion 313 and a tapered frusto-conical portion rear portion 314, rear portion 314 extending from the forward portion 313 rearwardly and having forward end 314b of greater diameter than a rear end 314a.
A helical groove 500 or threaded portion having raised edge portions and undercuts spirals progressively rearward around the frusto-conical portion 314 making several revolutions between the ends 314a and 314b.
FIGURE 3 is a cross sectional view of the clamp body 310 without the insulator body 320 and shows the forward undercut portion 312 for receiving the insulator body.
Preferably and in accord with the present invention, the bod~ 310 of the clamp includes a central passage 311 sized large enough to receive the layer of insulation 16 of the cable 10. The internal wall 315 of the central passage 311 is provided with a helical groove 600 or threaded portion having raised edge portions and adjacent undercuts that spiral progressively rearward around the passage, making several revolutions. The sense of each respective thread or helical groove 500 and 600 would be identical. That is, both grooves would be left-handed or both would be right-handed. It has been found that for the external thread 50û a continuous spir al of right-handed buttre~es-type thread of 40 pitch having a depth of 0.005 inches works to advantage. Although left-handed threads could be substituted and used to advantage in the present design, these threads would be unconventional and more difficult to install manually inasmuch as an operator is accustomed to install a screw member with right handed threads. The threads 600 on the ': - : . , ~ ~' -.
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passage wall 311 could be of the same type (i.e., buttress) as on the clamp or, more advantageously, V-shaped. Each V-shaped groove would act to bite sharply into the core of dielectric material.
Further, a pair of axially extended grooves 318 disposed at substantially diametrically opposite portions of the central passage wall could be provided if desired to receive any scraps of insulative material as a result of the sharp teeth 600 biting into the cable insulation.

OPERATION

In FIGURE 5 The cable 10 has been prepared in a manner which is referred to in the industry as a "square-cut" end wherein the central conductor 12 is exposed to - extend forwardly of the rest of the cable (outer layer 18, braid conductor 16 and dielectric core 14), these other portions being cut-off square and at a position rearwardly of the exposed end of conductor 12.
The tapered outer frusto-conical surface of the clamp 300 is pressed between the dielectric core 14 and the conductive braid layer 16, urging the braid 16 and the outer jacket 18 slightly radially outward.
At the stage shown in FIGURE 5, the helical grooves 500 and 600 begin to coact to threadably engage with the braid and the dielectric core. Because the braid 16 is also being urged radially inward by the surrounding jacket 18, the braid 16 is partially urged into the groove 50n.
As the clamp 300 is rotated in the direction of helical grooves 500, 600, the raised edge portions of grooves 500 coact with the braid 16 to draw the body 310 inwardly in t:he nature of a screw being drawn into wood as it rotates. Continued rotation of the body 310 causes additional grooves to engage the braid 16 and secures the .. .

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clamp and cable 10 together by the grooves against unwanted axial movement out of the cable 10 because the braid 16 is engaged by the grooves 500.
Further, and in coaction with the external grooves 500, rotation of the clamp member 300 causes the raised edge portions of the interior V-shaped teeth 600 to bite into the dielectric core 14, thereby eliminating the slight air gap circumposing the dielectric core 14 that otherwise would exist if the dielectric core 14 were to be slidably slipped within passage 311 in a clearance fit. At extremely high frequencies (e.g. 18 gigahertz) an air gap defined by the passage 315 can develop an impedance mismatch from the typically desired 50 ohms.
Since 10 gigahertz corresponds to approximately 1 wave length with respect to passage 315 and inasmuch as any impedance mismatch of length 1/20 wavelength (i.e. at 0.5 gigahertz) begins to adversely effect performance of the transmission line as measured by VSWR, this mismatch must be reduced to tolerable limits. Accordingly, the length of V-shaped teeth 600 in the passage 311 serves to eliminate both this air gap as well as to provide increased resistance to unwanted axial withdrawal.
FIGURE 6 shows the clamp 300 when the body 310 is fully engaged with cable 10. The braid 16 and the outer jacket 18 extend forwardly on the clamp body 310 over the enlarged portion 313 thereof, fully cove`ring the tapering frusto-conical portion 314, with the helical groove 500 being embedded along its length within the braid 16. The dielectric core 14 is well forward within the clamp body and in the central passage 315 thereof with the helical thread 600 bitingly engaged along its length within the core to eliminate any air layer thereabout.
While other types of grooves and threads could be used - either exposed external threads, discontinuous grooves, or varying shapes of grooves, the threads of the .:

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type shown in FIGURE 6 are believed the preferred embodi-ment as they can be formed quite easily on automatic screw machines. Of course, the threads could be formed using other techniques.
While a preferred embodiment of the invention has been disclosed, it will be apparent to those skilled in the art that changes may be made to the invention as set forth in the appended claims and, in some instances~ cer-tain features of the invention may be used to advantage without corresponding use of other features. For exam-ple, additional members could be used in the present assembly. The clamp of the present invention could also be used for tri-axial cables with appropriate modifica-tions. Accordingly, it is intended that the illustrative and descriptive materials herein be used to illustrate the principles of the invention and not to limit the scope thereof.

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Claims (4)

Claims:
1. An electrical termination between an electrical connector and an end of a coaxial cable characterized by a dielectric core, a braided outer conductor and an external jacket square-cut and by a central conductor extending forward of the square-cut, the improvement wherein the electrical connector includes a rotatable clamp member for engaging the cable end, the clamp member having a forward face and a rear face, a generally frusto-conical body portion with tapering sides and a central passage extending between the faces for receiving the dielectric core and central conductor, the central passage including a first helical thread having raised edge portions for progressively engaging the dielectric core and the tapering portion including a second helical thread having raised edge portions for progressively engaging the braid, the first and second threads being of like sense such that after the dielectric core is received in the central passage and the clamp member is rotated about the cable, the raised edge portions coact to progressively engage the dielectric core and the braid to secure and to electrically connect the cable to the clamp member, said first threads substantially eliminating any separation between dielectric core and the clamp passage to improve high frequency impedance matching.
2. An electrical connection of the type described in Claim 1 wherein the passage wall includes an axial groove portion that is disposed within the helical thread to receive insulative material scraps as a result of biting engagement by the first threads.
3. A method of terminating a coaxial cable of the type having a square cut end and including a conductive braid circumposing a dielectric core surrounding a central conductor having an exposed end portion extending from the square cut, the method comprising the steps of:
assembling a frusto-conical member having a central passage over the dielectric core such that the frusto-conical portion faces the conductive braid and the central passage faces the dielectric core, said central passage and conical portion being provided with progressively spiralling thread of the same sense and having raised edge portions;
rotating the frusto-conical member to progressively engage the raised edge portions of the helical threads with the dielectric core and the braid to prevent removal of the member from the cable and to reduce high frequency impedance mismatch caused by separation between the dielectric core and the clamp member; and assembling a rear nut and a forward contact element over the frusto-conical member to complete the contact for the coaxial termination and captivate the member therebetween.
4. A coaxial cable having an electrical connector termination comprising:
said coaxial cable including a central conductor, a dielectric core surrounding the conductor, a braid conductor surrounding the dielectric core and a protective sheath surrounding the braid conductor and characterized by a free end of the cable having a portion cut-square and the central conductor having an exposed end portion that extends axially from the portion cut-square;

said electrical connector including a body of conductive material, a clamp member disposed within the body and a nut assembling the clamp member to the body, the clamp member comprising a frusto-conical shaped body having a central passage having a passage wall provided with a continuous spiral groove described by a series of sharp biting portions having undercuts for and adapted to threadably receive and engage the dielecric core;
said clamp further including a second continuous spiral groove defining a series of raised edge portions for engaging the braid to resist unwanted axial withdrawal of the cable, both spiral grooves being of the same sense; and said clamp member being mounted proximate the free square cut end of the cable with the central conductor and the insulating layer extending through the central passage with the insulation layer including portions progressively engaged within the undercuts defined by the sharp biting portions and said clamp member secured to the contact.
CA000368878A 1980-06-02 1981-01-20 Method of and electrical termination for coaxial cable Expired CA1145430A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US15536880A true 1980-06-02 1980-06-02
US155,368 1993-11-22

Publications (1)

Publication Number Publication Date
CA1145430A true CA1145430A (en) 1983-04-26

Family

ID=22555163

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000368878A Expired CA1145430A (en) 1980-06-02 1981-01-20 Method of and electrical termination for coaxial cable

Country Status (2)

Country Link
EP (1) EP0041419A1 (en)
CA (1) CA1145430A (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4613199A (en) * 1984-08-20 1986-09-23 Solitron Devices, Inc. Direct-crimp coaxial cable connector
GB8629638D0 (en) * 1986-12-11 1987-01-21 Ici Plc Cable connectors
US5389012A (en) * 1994-03-02 1995-02-14 Huang; George Y. Coaxial conductor and a coax connector thereof
US7179121B1 (en) * 2005-09-23 2007-02-20 Corning Gilbert Inc. Coaxial cable connector

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1075699B (en) *
US3110756A (en) * 1960-11-22 1963-11-12 Thompson Ramo Wooldridge Inc Coaxial cable connector
US3255795A (en) * 1964-01-10 1966-06-14 Ginsburg Yale Self-locking nut
GB1186138A (en) * 1968-11-05 1970-04-02 Kings Electronics Co Inc Cable Grip Device.
DE2159867A1 (en) * 1971-12-02 1973-06-07 Spinner Georg Coaxial connector for coaxial cable with tightly packed dielectric
DE2628490C3 (en) * 1976-06-25 1981-02-26 Siemens Ag, 1000 Berlin Und 8000 Muenchen
CA1141834A (en) * 1979-05-23 1983-02-22 Donald H. Gould Electrical connector for coaxial cable

Also Published As

Publication number Publication date
CA1145430A1 (en)
EP0041419A1 (en) 1981-12-09

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