Low cost, high performance cable-connector system and assembly method

[00002] This application is a continuation-in-part of application Ser. No. 10/248,741, filed Feb. 13, 2003, owned by the assignee of the present application, Andrew Corporation of Orland Park, Ill.

[00003] 1. Field of the Invention

[00004] The invention relates to an improved cable-connector system, and more particularly to a system comprising: 1) a low cost, high performance, water blocking aluminum cable as described in U.S. utility patent application Ser. No. 10/131,747 filed Apr. 24, 2002 also assigned to Andrew Corporation and hereby incorporated by reference in its entirety, and 2) a low cost, high performance water-blocking connector uniquely configured to mate with such low cost aluminum cable.

[00005] As described in detail in the '747 application, no known cable product exists which met all four of the desired foam coaxial cable attributes: 1) low cost comparable to braided cable cost; 2) electrical properties including shielding effectiveness and intermodulation suppression comparable to that of solid tubular shielded cable; 3) mechanical properties, primarily flexibility, comparable to braided cable; and 4) water blockage comparable to annular corrugated cable.

[00006] The unique capabilities of the aforesaid cable were achieved by a novel combination of cable materials, manufacturing methods and cable structural configurations. The very low cost of the cable was achieved in part by the use of an outer conductor composed of aluminum or aluminum alloy. The use of aluminum provides enhanced water blockage by permitting the helical outer conductor during formation to be permanently deformed into the foam insulator material, thus eliminating air gaps at the corrugation crests of the cable and providing a moisture seal.

[00007] The manufacturing cost of the cable was dramatically reduced in part by using a dual lead helix on the corrugation, permitting the cable line speed to be doubled. One aspect of the present invention is to provide a connector for such a cable which complements the cable by offering low cost of manufacture, excellent electrical performance and moisture blockage, secure cable retention, and superior ease and speed of field installation.

[00008] The unique dual lead helical corrugations and aluminum construction of the cable outer conductor presents first-ever challenges to the connector designer. The dual helical corrugation creates two separate and independent helical grooves which must each be sealed to prevent moisture migration. The use of aluminum as the material for the outer conductor, being much softer and more ductile than conventional copper and copper alloys, has to be treated differently in designing a crimp type connector to prevent over deformation of the outer conductor which could degrade electrical performance of the cable.

[00009] To better understand the construction of a dual lead helical cable corrugation, reference may be had to FIGS. 12 and 13. A single lead coaxial cable 175 is depicted in FIG. 12. The single lead coaxial cable 175 of FIG. 12 has an inner conductor 220, a dielectric foam insulator 210 that surrounds the inner conductor 220, and an outer conductor 200 surrounding the foam insulator dielectric 210. The outer conductor 200 has single lead corrugations 195 which compress the foam insulator dielectric 210. The single lead coaxial cable 175 may also have a jacket 190 that surrounds the outer conductor 200. The angle 196 is the pitch angle of the outer conductor 200 corrugations.

[00010] A dual lead coaxial cable 180 of the type preferred for use in the system of the present invention is depicted in FIG. 13. The dual lead coaxial cable 180 of FIG. 13 also has an inner conductor 220, a foam insulator dielectric 210 that surrounds the inner conductor 220, and an outer conductor 200 surrounding the dielectric 210. The outer conductor 200 may be a thin strip of ductile material with a longitudinal high frequency weld seam. The outer conductor 200 has dual lead corrugations 197 which tightly compress the dielectric 210. The compression of the dielectric 210 substantially eliminates the formation of fluid propagating air gaps and passageways between the outer conductor 200 and the dielectric 210. The dual lead coaxial cable 180 may also have a jacket 190 that surrounds the outer conductor 200. The angle 198 is the pitch angle of the outer conductor dual lead corrugations 197 which is twice the pitch angle of a single lead helical corrugation 196.

[00011] It will be understood from FIGS. 12 and 13 that dual lead helical corrugations are in essence two interposed single lead corrugations. As suggested, this creates two separate helical grooves along the cable which must be closed to block invasion and migration of moisture into the connector.

[00012] The chief competition for the novel cable-connector system of the present invention is the various braided cable systems. Braided cable suffers from electrical and water blockage performance which is inferior to the low cost corrugated cable described. Further, as will become evident from the ensuing description of the connector of the present invention, braided cable connectors are much more difficult to attach to the cable, requiring elaborate cable preparation in some cases. They are more expensive to manufacture than the present connector as they all require that the connector body provide an inner ferrule against the electrically conductive braid or foil is compressed to retain the connector on the cable. Means for moisture-blocking the connector may be integrated into or separate from the means for compressively securing the connector on the cable.

[00013] The connector of the present system, in contrast offers a relatively simple and low cost approach to securely installing the connector on the cable and preventing moisture invasion into the connector and attached cable. As will be described at length below, the connector of the present invention does not require an inner ferrule against which a braid or foil is compressed to hold the connector on the cable. In one embodiment, internal helical grooves formed in the hollow inner connector body of the connector enable the connector to be simply screwed onto mating corrugations of the cable outer conductor until the connector reaches a stop. To prevent the cable from inadvertently unscrewing or backing out, the connector body is crimped down on the corrugated outer conductor. This prevents the cable from rotating while in use or during assembly, solidly locking the connector permanently onto the cable.

[00014] In other embodiments, the internal bore of the connector body which receives the corrugated cable body may be ribbed longitudinally or circumferentially, roughened or otherwise perturbed in other ways such that when the connector body is crimped down on the outer conductor of the cable, it cannot unscrew or otherwise back out.

[00015] In preferred embodiments, as will be explained, the connector body is provided with radial external ribs which reduce and control the amount of force required to deform the connector body. The crimping of the connector body is accomplished with a conventional crimping tool having a hexagonal clamp opening.

[00016] In accordance with a feature of the present invention, because of the use of the connector with a cable having a an outer conductor composed of soft, ductile aluminum or aluminum alloy, the ribs may be varied in length and/or width to define a deformation profile on the connected cable which permanently secures the cable in the connector, but also optimizes electrical performance and moisture blockage.

[00017] The connector component of the system will now be described in detail. It should be understood that while the connector is most advantageously used with the described low-cost cable having a dual lead helically corrugated aluminum outer conductor, the connector may be employed also with other corrugated cables.

[00018] 2. Description of Related Connector Prior Art

[00019] Connectors for corrugated outer conductor cable are used throughout the semi-flexible corrugated coaxial cable industry.

[00020] Competition within the cable and connector industry has increased the importance of minimizing installation time, required installation tools, and connector manufacturing/materials costs.

[00021] Previously, connectors have been designed to attach to coaxial cable using solder, and or mechanical compression. The quality of a solder connection may vary with the training and motivation of the installation personnel. Solder connections are time consuming and require specialized tools, especially during connector installation under field conditions. Mechanical compression connections may require compressive force levels that are excessive for field installation, and or special tooling that may not be portable or commercially practical for field installation use. Mechanical compression designs using wedging members compressed by tightening threads formed on the connector may be prohibitively expensive to manufacture.

[00022] The corrugation grooves of helically corrugated coaxial cable may provide a moisture infiltration path(s) into the internal areas of the connector and cable interconnection. The infiltration path(s) may increase the chances for moisture degradation and or damage to the connector, cable, and or the connector and cable interconnection. Previously, O-rings or lip seals between the connector and the cable outer conductor and or jacket have been used to minimize moisture infiltration. O-rings may not fully seat/seal into the bottom of the corrugations and lip seals or O-rings sealing against the jacket may fail over time if the jacket material deforms.

[00023] Heat shrink tubing has been used to protect the connector and cable interface area and or increase the rigidity of the connector/cable interconnection. However, the heat shrink tubing may not fully seal against the connector body, increasing the moisture infiltration problems by allowing moisture to infiltrate and then pool under the heat shrink tubing against the outer conductor seal(s), if any.

[00024] Therefore, it is an object of the invention to provide a coaxial connector that overcomes deficiencies in the prior art.

[00047] One embodiment of a crimp connector, for example a type N connector, is shown in FIG. 1a. The crimp connector 1 has a connector end 10 (FIG. 2) and a cable end 20 (FIG. 3). The specific form or connector interface of connector end 10 may depend on the coaxial cable diameter and or the application the crimp connector and selected coaxial cable is intended for. The connector end 10 of the crimp connector may be configured with a connector interface selected to mate with any type of connector mounted on a device or other cable using, for example, standard type F, BNC, SMA, DIN, UHF, CATV, EIA, or a proprietary connector interface configuration. Dimensions and or configuration of the crimp connector 1 at the connector end 10 that form the desired standardized connector type are known in the art. A connector end 10 in a type N connector interface configuration is shown in FIGS. 1a-1e, 2 and 3. A type F and or CATV connector interface configuration is shown in FIG. 11.

[00048] As shown in FIGS. 4a and 4b, a body 30 forms the outer shell of the cable end 20. The body 30 may have a connector end annular shoulder 40 for receiving and retaining via, for example an interference fit, the connector end 10. In the case of smaller dimensioned connectors, for example a type F or CATV connector as shown in FIG. 11, the annular shoulder 40 may be formed as a radial groove into which the connector end 10 may be rotatably attached by, for example, metal stamping or swaging.

[00049] As previewed above, a helical groove section 50 of the embodiments shown in FIGS. 1a, 1b, 4a and 11 preferably mates with exterior configurations and dimensions of a dual lead helical corrugated outer conductor 200 of a dual lead coaxial cable 180 as described in U.S. utility patent application Ser. No. 10/131,747 filed Apr. 24, 2002. The helical grooves may be formed from continuous, threadlike, grooves or helical shaped rows of axially spaced bumps or other form of appropriately sized and spaced internal perturbations (FIG. 1f). Any form of internal perturbation which keys with the single or dual lead corrugations of the applicable single lead coaxial cable 175 or preferably dual lead coaxial cable 180 to enable threading of the cables into the helical groove section 50 and which then prevents axial removal without a corresponding unthreading may be used.

[00050] The dual lead coaxial cable 180, as shown for example in FIG. 13, as generally described, above, may be dimensioned for various applications with, for example, 50 or 75 ohm impedance. The dual lead helical corrugation provides the dual lead coaxial cable 180 with advantageous strength, flexibility and weight characteristics. However, dual grooves that form the dual lead helical corrugation also increase the opportunity for moisture infiltration due to the presence of an additional groove, compared to a traditional single lead helical corrugation, as shown in FIG. 12.

[00051] The helical groove section 50 increases the contact surface area between the cable outer conductor 200 and the body 30 in the crimp area 100, thereby improving the electrical characteristics of the connection between the body 30 and the outer conductor 200. Also, during installation, the connector 1 is initially threadably retained upon the dual lead coaxial cable 180.

[00052] Although the helical groove section 50 is preferred for optimizing electrical interconnection, accurately forming the helical groove profile of the helical groove section 50 may require advanced machining equipment and or casting methods that may make the body 30 comparatively expensive for some applications and or connector types. Examples of simplified alternative mating section structures are shown in FIGS. 1c-1e. In FIG. 1c, a plurality of axial grooves 52 may be dimensioned to create an interference fit with the outer conductor 200 of the dual lead coaxial cable 180. Alternatively, as shown in FIG. 1d, radial grooves 54 may be used. FIG. 1e demonstrates an embodiment using a plurality of radial ridge(s) 56 where the dual lead coaxial cable 180 may be easily inserted against sloping faces of the radial ridge(s) 56 in the insertion direction towards the connector end 10 but backfaces generally tangential to the axial length of the connector 1 inhibit easy removal. Also, upon compression and or deformation (crimping) of the compression area 100, each of the alternative structures may be expected to securely grasp the outer conductor 200, increasing the reliability of the electrical connection between the dual lead coaxial cable 180 and the connector 1 and also inhibiting separation.

[00053] The body 30 may be formed from, for example brass or other metal alloy. To minimize corrosion and or dissimilar metal reactions with the connector end 10 and or the outer conductor 200 of the dual lead coaxial cable 180, the body 30 may have a corrosion resistant plating, for example, tin or chromium plating.

[00054] A cable end shoulder 80 may be added to the body 30 for seating a gasket 90 or an application of sealant, described herein below.

[00055] Compared with braided cable systems, the present invention facilitates rapid and foolproof field installation. A dual lead coaxial cable 180 may be prepared for attaching the crimp connector 1 by exposing an appropriate length of the cable's inner conductor 220 and by removing any outer jacket 190 from a section of the outer conductor 200. A gasket 90 may be screwed upon the outer conductor 200 and the crimp connector 1 may then be hand threaded onto the dual lead coaxial cable 180 until the cable's outer conductor 200 impacts upon a stop 60 that extends radially inward across the radial depth of the body 30. When the leading edge of the cable outer conductor 200 contacts the stop 60, further threading may partially collapse/compress the cable outer conductor corrugations into a deformation groove 70. The connector 1 is then electrically interconnected and physically secured upon the dual lead cable 180, without requiring field application of solder or conductive adhesive, by applying a crimp in the crimp area 100 sufficient to deform the internal helically grooved section 50 to a point where the dual lead cable 180 may not be unthreaded.

[00056] If alternatives to the helical grooved section 50, as shown for example in FIGS. 1c-1e are used, the connector 1 may be pressed and or screwed upon the similarly prepared dual lead coaxial cable 180, in an interference fit into the mating section, until the outer conductor 200 impacts the stop 60. However, unless a higher level of crimping force is applied, the alternatives may not produce the same resistance to separation once the connector 1 is crimped upon the dual lead coaxial cable 180, because the interlocking effect of the mating between the internal surface of the crimp area 100 and the, for example, dual lead corrugations 197 in the outer conductor 200 is reduced. Further, if too high a crimp force is applied, the spacing between the outer conductor 200 and the inner conductor 220 may be decreased to a point where the electrical characteristics of the dual lead coaxial cable 180 are degraded.

[00057] The outer diameter of the crimp area 100 may be adjusted to mate with, for example, industry standard hexagonal crimp hand tools by adjusting the radius and or width of the crimp area 100.

[00058] A plurality of ridges 105 may be formed in the crimp area 100. The depth and width of grooves between the ridges 105 may be selected to adjust the compressive force required to compress and or deform the, for example, internal helical groove section 50 and outer conductor 200 of the dual lead coaxial cable 180 during the crimp operation and also to create a corresponding retentive strength of the compressed material once crimped.

[00059] In alternative embodiments, the ridges 105 may be formed with varied heights for example to form a barrel shaped profile with a middle peak. As shown in FIG. 1b, ridges 105 having a lower depth at either end of the crimp area 100 and an increased height generally in the middle of the crimp area 100 may be formed to both tune the necessary compressive force and or to create a compression/deformation pattern of varied width and depth, once compression is applied over the crimp area 100.

[00060] During the threading of the connector 1 onto the helical corrugations in the outer conductor 200 of the dual lead coaxial cable 180, the inner conductor 220 is inserted into an inner contact 110 (FIGS. 5a-7). The inner contact 110 extends between the connector end 10 (FIG. 6) and the cable end 20 (FIG. 7). An insulator 115 may be mounted in the connector end 10 to locate the inner contact 110 coaxially spaced away from the body 30. A radial barb 117 or other structure on the inner contact 110 may be used to retain the inner contact 110 within the insulator 115.

[00061] A socket contact section 120 on the cable end 20 of the inner contact 110 may be formed with a cable end 20 diameter smaller than an outer diameter of the inner conductor 220. A plurality of slits 130 may be formed in the socket contact section 120 to allow the socket contact section 120 to easily flex and accommodate the inner conductor 220 upon insertion, creating a secure electrical connection without requiring, for example, soldering or conductive adhesive.

[00062] The inner contact 110 may be formed from a spring temper material, for example beryllium copper, phosphor bronze or other metal or metal alloy with suitable spring/flex characteristics. The inner contact 110 may be given a low contact resistance surface treatment, for example, gold or silver plating to increase conductive characteristics and negate dissimilar metal reactions with the center conductor of the dual lead coaxial cable and or other connectors. The appropriate length of exposed inner conductor 220, mentioned above, may be a length that results in the inner conductor 220 being inserted into the socket contact section 120 short of contacting a depression 140 when the outer conductor 200 of the dual lead coaxial cable 180 has fully seated against the stop 60 and any compression of the outer conductor 200 into the deformation groove 70 is completed.

[00063] As shown in FIG. 11, when the connector 1 is configured for use with some connector types, for example, a type F or CATV connector end 10, the inner contact 110 is not required. The dual lead coaxial cable 180 is prepared with a portion of the inner conductor 220 exposed so that it will extend through the body 30 to the connector end 10 when the dual lead coaxial cable 180 is mated with the connector 1.

[00064] As shown in FIG. 10, heat shrink tubing 170 may be applied over the body 30 and dual lead coaxial cable 180 interface as an additional environmental seal and to improve rigidity of the connection between the crimp connector 1 and the dual lead coaxial cable 180. The extended section of heat shrink tubing 170 covering the dual lead coaxial cable 180 creates an extended path through which moisture must pass to infiltrate the interconnection between the body 30 and the dual lead coaxial cable 180. However, the section of heat shrink tubing 170 over the body 30 is relatively short, creating an increased opportunity for moisture infiltration. To reduce this opportunity, an outward facing radial body barb 160 may be formed on the body 30. When the heat shrink tubing 170 is shrunk into place upon the body 30, the body barb 160 presents an acute contact surface that the heat shrink tubing 170 will tightly seal against and or around thereby reducing the opportunity for moisture infiltration and increasing the overall rigidity of the assembly.

[00065] As described, the crimp connector 1 provides the following advantages. The crimp connector 1 has a limited number of components and may be cost effectively assembled with only a few manufacturing operations. Further, the crimp connector 1 may be installed in the field, without requiring soldering or conductive adhesives, using only industry standard hand tools. Also, the crimp connector 1 may be used with dual lead coaxial cable 180 to form a cable/connector interconnection with a high level of moisture infiltration resistance. When heat shrink tubing 170 is applied to the crimp connector 1, an improved seal is created and the cable/connector interconnection has increased rigidity.

[00066] The cable-connector system of the present invention in its preferred execution offers a unique combination of features: 1) low manufacturing cost due to the low-cost dual lead helically corrugated aluminum cable and low-cost connector; 2) excellent moisture blockage attributable to the inherent superior moisture resistance of the cable, the dual lead helical groove compression gasket and unique high-surface-area, crimp-on-threads feature of the joint between the connector and cable; 3) permanent attachment of the connector and cable by the crimping of the connector onto a helically corrugated cable; 4) simplified and foolproof field installation enabled by the dry, secure, and unmistakable connection made with very few steps, minimal cable or connector preparation, lack of easy-to-lose extra parts and standard hand tools; and 5) excellent electrical performance.

[00002]

Table of Parts
1	crimp connector
10	connector end
20	cable end
30	body
40	connector end shoulder
50	helical groove section
52	axial grooves
54	radial grooves
56	raidal ridges
58	internal protrusions
60	stop
70	deformation groove
80	cable end shoulder
90	gasket
100	crimp area
105	ridge
110	inner contact
115	insulator
117	inner contact barb
120	socket contact section
130	slits
140	depression
150	thread
160	body barb
170	heat shrink tubing
175	single lead coaxial cable
180	dual lead coaxial cable
190	jacket
195	single lead corrugations
196	angle (single lead pitch)
197	dual lead corrugations
198	angle (dual lead pitch)
200	outer conductor
210	dielectric
220	inner conductor

[00067] Where in the foregoing description reference has been made to ratios, integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth.

[00068] While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant's general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims.