Patent Publication Number: US-2003236020-A1

Title: Field installable, field adjustable angled boot for multi-conductor cables and process for installing the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
     [0001] The present application claims the benefit under Title 35, United States Code §119(e), to U.S. Provisional Patent Application Serial No. 60/389,969 filed Jun. 19, 2002. The contents of the foregoing provisional application are incorporated herein by reference. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present invention relates to connector assemblies for use with multi-conductor connection cables. More specifically, the present invention relates to an angled boot assembly for use with a multi-conductor cable where the angled boot defines an area for receiving the multi-conductor cable for positioning the cable at a known orientation with respect to the angled boot at least one location, and where the angled boot may be coupled to the connector in one or a plurality of alternate orientations. The present invention also relates to a process for installing such an angled boot assembly.  
       BACKGROUND OF THE INVENTION  
       [0003] Modern information systems such as telecommunication systems, computing systems and the like typically rely upon one or more connection cables to couple the various components of the system together for purposes of communication. The connection cables typically include one or more conductive elements (such as, for example, wires and/or optical fibers) that are used to communicate information through the connection cable in the form of electrical and/or optical signals.  
       [0004] To promote high bandwidth communications and to reduce the number of connection cables needed for a system, many connection cables include a plurality of conductive elements and may include, for example, several wires or optical fibers within a single connection cable. Such multi-conductor connection cables may include, for example and without limitation, four, eight or twelve optical fibers or wires. The multiple conductors in a multi-conductor connection cable may be arranged in various ways including a side-by-side relationship or an arrangement where the conductors form a generally cylindrical cable. In many multi-conductor connection cables that include a number of optical fibers, the optical fibers comprising the connection cable are arranged in a side-by-side relationship to form a cable commonly known as a “ribbon cable.” 
       [0005]FIG. 1 generally illustrates the components that form a traditional twelve optical fiber ribbon cable  10 . For purposes of illustration, the ribbon cable  10  of FIG. 1 is illustrated as being a “jacketed” cable, meaning that it includes an outer protective jacket although many ribbon cables are “unjacketed” and do not include the protective jacket.  
       [0006] Referring to FIG. 1, the exemplary illustrated ribbon cable  10  includes twelve optical fibers  12 , although it will be appreciated that a ribbon cable can have anywhere from two optical fibers to a number substantially greater than twelve (e.g., seventy-two). To prevent light traveling down one of the optical fibers, from creating interference or noise with adjacent optical fibers, and to protect each fiber, each of the optical fibers is surrounded by a buffer material  14  that may be in the form of a plastic jacket or the like. While the thickness of the buffer material  14  will vary from application to application, it is not uncommon for the buffer material to have a thickness of at least 250 micrometers. To hold the fibers forming the ribbon cable  10  together and to provide strength and stretch resistance, an outer binding material  16  typically surrounds the individually buffered cables. In the example of FIG. 1, the outer binding material takes the form of an outer layer of Aramid yarn. A protective jacket  18 , which may be formed of a rubber or flexible plastic material, surrounds the binding material  16 .  
       [0007] In an effort to ensure that the appropriate communications links are established when a connection cable is coupled to a system component, most connection cables include at least one connector element positioned at an end of the connection cable. The connector typically includes a housing structure that receives an end of the connection cable. The connector is typically formed so as to be received in a mating engagement fashion with a terminal positioned on the system component to which the connection cable is to be attached. The conductive elements that form the connection cable (e.g., the wires or optical fibers) are either coupled to further connection elements, such as for example, an optical ferrule assembly or an electrical terminal pin or exposed in such a way that when the connector is coupled to the terminal on the system component, the appropriate conductive elements on the cable are coupled to appropriate corresponding elements with the system components such that information in the form of, for example, electrical or optical signals may be transmitted through the connection cable to the system component.  
       [0008] For multi-conductor fiber optical connection cables, especially multi-optical fiber connector cables utilizing ribbon cables as described in connection with FIG. 1, connectors that include a housing defining a generally rectangular opening that provided access to an optical ferrule within which the optical fibers forming the cable are embedded. One such connector that is commonly used in connection with such ribbon cables in the connector style known in the art as the MPO (multipath push on) connector, a form of which is known as the MTP©) connector. The MPO connector is a multi-fiber connector that can be used with connection cables having 4, 8, 10, 12 or higher fiber counts.  
       [0009]FIG. 2 generally illustrates a connection cable  20  that includes a multi-conductor ribbon cable  22  having the construction, for example, of the twelve-fiber cable of FIG. 1. An MPO connector  24  is coupled to a terminal end of the ribbon cable  22  such that the individually optical fibers that form the cable  22  are accessible through the housing to allow for a ready connection between one element of a system and another element of the system through the connector  24  and the connection cable.  
       [0010] One difficulty with many multi-fiber connection cables and connector systems is that because of the many elements that form the multi-fiber cable, the cable portion of the connection cable is very stiff and difficult to bend in confined or tight areas. For example, it may require significant force to bend the twelve-fiber cable of FIG. 1 (including the fibers, the buffer material, the binding material and the jacket), and once bent, the cable will have a tendency to re-straighten itself. This difficulty in bending and tendency to straighten can cause significant difficulties in applications where a large number of connection cables are to be coupled to a system component or number of system components. In such applications, the stiffness of the ribbon cable can render system installations difficult, time consuming and confusing, and the tendency of the cables to straighten out after installation can, among other things, render the system unsightly and difficult to readily troubleshot and repair.  
       [0011] In addition to the problems described above, the construction of conventional multi-conductor connection cables often subjects the cables to undue stresses which could, in certain extreme instances, result in cable failure. For example, a ribbon cable such as that illustrated in FIGS. 1 and 2, because of its flat geometry, exhibits various stiffness characteristics at various points along the cable. Depending on the precise way in which the connector portion of the connection cable is coupled to the relevant system component, the cable may be forced to bend at an extreme angle or twist and bend. Such extreme bending and/or twisting and bending can expose the conductive elements (e.g., the optical fibers) to breakage as the bends and twists are often uncontrollable and difficult to manage. For example, referring to the cable of FIG. 2, a twist and/or extreme bend in cable  22  may result in breakage of one or more of the optical fibers forming the cable and, therefore, cable failure.  
       [0012] A further limitation of conventional multi-element cable systems is that the multi-conductor cable is often exposed to orientations which render the cable susceptible to failure. For example, in many applications, the orientation at which the connector of a cable is coupled to a system component will require a cable, for example a ribbon cable, to twist from one orientation to another orientation. Because the elements (e.g., optical fibers or wires) within the cable over the twisting portion of the cable will already be subject to some stress from the twisting forces, the application of additional forces to that portion of the cable (e.g., an uncontrolled bending force) may result in failure of the conductive element. For example, undue stresses can cause a fiber optical cable to break —rendering the fiber incapable of transmitting data in the form of an optical signal—or can cause a wire to bend or kink in such a way that a discontinuity in the wire is established that will cause interference or reflections of the transmitted electrical signals causing the wire to fail as a proper conductor of information. The problem with improper bends and kinks in wire-based cables is of particular significance where the cable is intended to support very high bandwidth communications.  
       [0013] Conventional approaches to solve the problems described above have fallen short. In certain applications, factory installed right angle boots have been permanently affixed to cable systems during manufacture. While providing support to protect the conductive elements within the cable, the permanently affixed boot is limited in that it establishes a fixed orientation of the cable with respect to the portion of the connection cable within the boot. As such, depending on the orientation of the connector to the system to which the connector is to be attached, the cable may be required to twist. Because the permanently attached angled boot prohibits twisting within the boot, any twisting of the cable will occur outside the confines of the permanently attached boot, thus exposing the cable to damage or breakage. A further limitation of conventional cables with permanently attached boots is that the permanently attached boot provides for only a single orientation of the cable with respect to the connector and that preselected and fixed orientation may not be the most convenient orientation.  
       [0014] To avoid some of the limitations of conventional permanently installed boots, some have used “boot clips” to control the bend radius of round, non-ribbon cables. The boot clip is typically a clip that attaches to the connector and to a round cable so as to control the bend of the cable. Unlike the permanently installed boots, boot clips can be installed in the field. Boot clips are limited, however, in that they do not prevent or control twisting of the cable to which the boot clip is attached. Moreover, boot clips typically are not readily adapted for use with ribbon cables.  
       [0015] The connector assembly and method of assembling the same described herein overcomes the above-described and other problems and limitations of conventional connectors.  
       SUMMARY OF THE INVENTION  
       [0016] In accordance with one exemplary embodiment of the present invention, an angled boot assembly for use with a multi-conductor cable that includes a connector is provided where the angled boot assembly includes an angled boot that defines an area for receiving the multi-conductor cable, a structure for positioning the cable at a known orientation with respect to the angled boot in at least one location and a structure for coupling the angled boot to the connector in one or a plurality of alternate orientations.  
       [0017] In accordance with a further exemplary embodiment of the present invention, a process for installing an angled boot assembly on a connection cable that includes a multi-conductor cable and a connector is provided where the process includes the steps of coupling a clip defining an outer mounting structure to the connection cable at a location where the multi-conductor cable is received by the connector, positioning the multi-conductor cable within the angled boot so as to define the orientation of the multi-element cable with respect the angled boot at least one location on the angled boot and coupling the angled boot to the outer mounting structure at a desired orientation. 
     
    
    
     DESCRIPTION OF THE FIGURES  
     [0018] The following figures form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these figures in combination with the detailed description of specific embodiments presented herein.  
     [0019]FIG. 1 generally illustrates the components that form a traditional twelve optical fiber ribbon cable  10 .  
     [0020]FIG. 2 generally illustrates a connection cable  20  that includes a multi-conductor ribbon cable  22  and an MPO connector  24 .  
     [0021]FIG. 3A generally illustrates an exemplary embodiment of an improved field installable, field adjustable angled boot for multi-conductor cables and a process for installing the same. Specifically, the process of installing the cable clips is shown.  
     [0022]FIG. 3B generally illustrates the process of connecting the cable clips to the cable connector.  
     [0023]FIG. 3C generally illustrates the attachment of the angled boot attachment to a cable.  
     [0024]FIG. 3D generally illustrates the engagement of the angled boot with the outer portion of the clips to form a connector assembly.  
     [0025]FIG. 4A generally illustrates an exemplary embodiment of the angled boot and cable clip of the invention.  
     [0026]FIG. 4B illustrates an orientation of the angle boot of 0° with respect to the cable clips.  
     [0027]FIG. 4C illustrates an orientation of the angle boot of 45° with respect to the cable clips.  
     [0028]FIG. 4D illustrates an orientation of the angle boot of 90° with respect to the cable clips.  
     [0029]FIG. 5A illustrates a protective embodiment of the angled boot, wherein no twisting of the cable is required.  
     [0030]FIG. 5B illustrates a protective embodiment of the angled boot, wherein twisting of the cable in order to align the cable with a system component is required.  
     [0031]FIG. 6A illustrates an alternative embodiment of the present invention involving a double angled boot.  
     [0032]FIG. 6B illustrates a protective embodiment of an alternative embodiment of the present invention, wherein a double angled boot protects a cable which must be twisted in order to align the cable with a system component.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0033] Referring to the drawings, in particular to FIGS.  3 A- 3 D, a connection cable assembly  30  is illustrated for use in applications where a connection cable is to be bent at or after initial installation. In general, the cable assembly  30  includes a multi-conductor cable component  31  that may be, for example, a multi-optical fiber ribbon cable as described above in connection with FIG. 1. The cable assembly further includes a connector  32  that, in the illustrated exemplary embodiment, is an MPO-type connector having a rectangular opening as described above in connection with FIG. 2. Coupled to the connector  32  are cable clips  33   a  and  33   b  and coupled to the cable clips  33   a - 33   b  is an angled boot  34 . The outer exterior surface of the cable clips  33   a  and  33   b  is received in the interior of the angled boot  34  such that the angled boot  34  maintains a controlled and protective bend of the ribbon cable  31  as it exits the connector  32 . The angle of the bend defined by the angled boot  34  is such that no undue stresses are placed on the cable  31 .  
     [0034] By providing a controlled bend in the cable  31 , the connection assembly of FIGS.  3 A- 3 D maintains and controls the bend radius of the cable (ensuring an appropriate minimum bend radius). It also inhibits undesirable, unprotected twists and bends of the cable  31 . Moreover, because the bend of the cable  31  is controlled, the connection assembly  30  directs the cable  31  in a defined and known manner and helps maintain and promote neat cable management enabling faster, less costly system installation and simplifying system maintenance and repair.  
     [0035]FIG. 3A- 3 D further illustrate an exemplary method by which the assembly  30  may be assembled. Focusing first on FIG. 3A, a conventional connection cable having a ribbon cable  31  and a connector, such as an MPO connector  32 , is illustrated. This is the type of cable that may be obtained as an “off the shelf” item. As illustrated in FIG. 3A, the cable clips  33   a  and  33   b  include a thin portion  35  and an outer housing portion  36 . The clips also include an interior recess  37  sized to receive the cable  31 .  
     [0036] The thin portions of the cable clips  33   a  and  33   b  are sized to be able to slip into the space defined by connector  32  where the cable  31  mates with the connector  32  so as to couple the clips  33   a  and  33   b  to the connector  32  through a slip-fit connection. To connect the clips  33   a  and  33   b  to the connector, one—either in manufacturing or in the field during system installation or maintenance—slips the thin portions  35  of the cable clips under and between the existing MPO connector  32  and the cable  31  to produce the cable  30 /connector clip assembly of FIG. 3B.  
     [0037] Referring to FIG. 3C, the angled boot  34  may then be placed about the ribbon cable  31 . In the illustrated example of FIG. 3C, the angled boot  34  defines a generally rectangular slot  38  into which the ribbon cable  31  is received. The angled boot  34  further defines a proximal outer housing portion  39  that is sized to mate with the outer housing portion  36  of clips  33   a  and  33   b . During installation, after the clips  33   a  and  33   b  are coupled to the cable  31  and the connector  32 , the cable  31  is positioned within the angled boot  34 , and the angled boot  34  is slid until the outer housing  39  of the angled boot  34  engages with the outer housing  36  of the clips  33   a  and  33   b  to form the connector assembly  30  of FIG. 3D.  
     [0038] Because the precise orientation of the connector  32  and the orientation of the desired bend of a cable  31  with respect to the connector  32  may not be known, it is desirable that the connector assembly be able to allow the angled boot  34  to extend from varying orientations from the connector  32 . In one exemplary embodiment, the outer housing  36  of the cable clips  33   a  and  33   b  and the outer housing  39  of the angled boot  34  are formed such that the angled boot  34  an be coupled to the clips  33   a - 33   b  and, thus, to the connector  32  in a variety of orientations. This embodiment allows for “field selection” of the angle of the boot  34  to the connector  32 .  
     [0039] FIGS.  4 A- 4 D generally illustrate an embodiment of the connector assembly  30  of FIG. 3A that provides for field selectable orientation of the angled boot  34  with respect to the connector  32 .  
     [0040] Referring to FIG. 4A, details of an exemplary cable clip  33  and an angled boot  34  are provided. Only one cable clip  33  is illustrated as the other clip  33  will have the same construction.  
     [0041] Referring to FIG. 4A, the cable clip includes the thin portion  35  and an outer housing  36 , as described above. The thin portion  35  is provided with sloped edges to enable easier insertion into the space between the cable  31  and the connector  32 .  
     [0042] In the example of FIG. 4A, the outer surface of the outer housing  36  defines the interior recess  37  that is sized to receive the ribbon cable  31 , and the outer surface  36  defines a “half-octagon.” The cable clip  33  is configured such that when the two cable clips  33  are coupled to the connector  32  as illustrated in FIGS.  4 B- 4 D, the interior recesses  40  of the cable clips  33  surround the ribbon cable  31  and the outer surfaces  36  of the outer housings of the clips form an outer octagonal surface  42 . This is generally illustrated in FIGS.  4 B- 4 D which illustrates a view of connector clips  33  surrounding a ribbon cable  31 . Note: In FIGS.  4 B- 4 D, the connector  32  to which the cable clips  33  would be connected is not illustrated.  
     [0043] Referring to FIGS.  4 A- 4 D, the angled boot  34  includes a bent portion  43  that, in the illustrated embodiment, defines a generally rectangular slot  38  that is sized to receive the ribbon cable  31 . The degree of the bend of the angled boot  34  should be selected so as to ensure that no undue bending forces or stresses are placed on the cable  31 . Because the ability of a cable to handle bending stresses will vary from cable to cable, the precise degree of the bend of the angled boot  34  may vary from application to application. In general, however, the bend of the angled boot  34  should be such that the radius of the bend of the boot is greater than or equal to ten times the dimension of the shortest cross-section of the cable  31 . Thus, for a ribbon cable that has a major axis (the width of the ribbon) and a minor axis (the height of the ribbon), the radius of curvature of the angled boot  34  should be at least ten times the minor axis. Embodiments of multiple versions of the angled boot  34  are provided having differing degrees of bend to accommodate different applications.  
     [0044] The dimensions of the slot  37  should be such that the ribbon cable can “twist” within the slot  37  if the orientation of the connector and the cable are such that a twisting of the cable is desired. Accordingly, the slot should be sized such that both of the dimensions of the slot (i.e., the width and height of the slot  37 ) are greater than the largest cross-section of the cable  31 .  
     [0045] One or more capture elements  44  are provided near the distal end of the bent portion of the angled boot  34  to capture the cable  31  within the slot  38 . This capturing of the cable within the slot ensures that the orientation of the cable  31  within the slot  38  at the distal end of the boot  34  is known and defined. In the illustrated example, the capture element  44  consists of a raised nib that may be biased away from the slot by pressure to insert the cable  31  into the slot and that, when released, presses against the cable  31  to retain the cable with the slot in a defined orientation. In the illustrated example, the capture element  42  and the slot  38  are configured such that when the cable  31  is positioned within the slot, the orientation of the cable  31  at the point where the capture element  44  engages the cable  31  will be such that the flat side of the cable will be resting on the lower flat portion of the slot  38 . Other known orientations are possible.  
     [0046] The presence of the capture element  44  ensures that any twisting of the cable  31  necessary to accommodate a particular orientation of the cable with respect to the connector  32  will occur within the protective confines of the angled boot  34 . As such, the portion of the cable  31  that would be most vulnerable to uncontrolled bending forces (i.e., the portions over which the twist is occurring) are protected from potentially damaging forces by the substantially rigid angled boot  34 .  
     [0047] In the illustrated example, the outer housing  39  of the angled boot  34  defines a sleeve member  45  that defines—throughout at least part of its interior surface—an inner octagon surface  46  that is sized to fit in a press fit relationship about the outer octagon surface  42  defined by the outer surface of the cable clips  33 . Because the inner octagon surface  46  defined by the angle boot  34  is sized to mate with the outer octagon surface  42  of the cable clips  33 , in the illustrated example, the angled boot  34  may be coupled to the cable clips  33 —and thus the connector  32 —in one of eight possible orientations. Each orientation is offset from an adjacent orientation by 45°. Examples of the various orientations of the angled boot  34  with respect to the clips  33 —and thus with respect to the connector  32 —are illustrated in FIGS.  4 B- 4 D.  
     [0048] In the illustrated example, all of the components of the connection assembly including the cable clips  33  and the angled boot  34  are formed of molded plastic using known molding techniques and processes.  
     [0049] FIGS.  5 A- 5 B illustrate protective advantage provided by the angled boot  34  described above in applications where a twisting of the cable must occur. Referring to FIG. 5A, an arrangement is illustrated where the orientation of the connector  32 , when coupled to a system component (not illustrated), is such that no twisting of the cable  31  is required. Specifically, in the example of FIG. 5A, the flat portion of the rectangular opening of the connector  32  (through which connection is made with the cable) is aligned with the flat portion of the cable  31 . As such, in this example, the angled boot  34  controls the degree of the bend of the cable  31 , but the cable  31  does not “twist” within the angled boot  34 .  
     [0050]FIG. 5B illustrates an arrangement similar to that described above in connection with FIG. 5A. In the arrangement of FIG. 5B, however, when the connector  32  is coupled to a system component (not illustrated) the rectangular opening through which connection with the conductive elements of the cable  31  is made is not in alignment with the flat portion of he majority of cable  31 . Accordingly, in this illustrated example, the cable  31  must “twist” at some point near the connector  32 . In the illustrated example, the capture element  44  holds the cable  31  in a known position at the end portion of the angled boot  34  such that the flat portion of the cable as it exits the angled boot  34  is aligned with the flat portion of the majority of the length of the cable. Accordingly, the capture element  44  defined by the angled boot  34  ensures that the twisting of the cable  31  occurs within the protection of the angled boot  34 .  
     [0051] While the apparatus and methods of this disclosure have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the process described herein without departing from the concept and scope of the invention. For example, the apparatus and methods described herein are not limited to use with the MPO connectors used in the exemplary embodiments. The apparatus and process of the present disclosure is also applicable to other forms of MPO connectors and other forms of connectors. FIGS. 6A and 6B illustrate an alternate embodiment of the apparatus and process of the present invention wherein angled boots  34  of the present disclosure are used with a “double” MPO connector  60 . The apparatus and process of the present disclosure may be applied to many other types of connectors including, for example and without limitation, MMC (multi-media card) and SMT (sub-miniature C) style connectors and LC type connectors.  
     [0052] As a further example, the use of the cable clips, such as clips  33   a  and  33   b , are not necessarily required to provide a base for attachment of the angled boot to the connector housing. Any mechanism capable of providing a secure adjustable attachment of the angled boot to a connector will be within the scope of the present disclosure. Alternate embodiments are envisioned wherein an outer mating surface—like the octagonal surface  42  of clips  33 —is integrally formed with and defined by a connector  32 . Further alternate embodiments are envisioned wherein surfaces other than octagonal surfaces—such as triangular, square, hexagonal, decahedral, dodecahedral, and icosahedral surfaces —are utilized to provide an adjustable mating between the angled boot and the connector or an element attached to the connector. Still further alternate embodiments are envisioned wherein the angled boot snaps around or under the connector housing or wherein a screw-type connection is provided to allow the angled boot to be coupled to the housing in a variety of orientations.  
     [0053] Further embodiments are envisioned wherein some sort of locking structure, such as a cotter pin passing through mating elements or a C-clip is provided to lock the angled boot in place once it is positioned at the desired orientation.  
     [0054] As yet a further example of variations that would be within the scope of this disclosure, the angled boot  34  need not have the precise construction illustrated herein. Alternate designs that do not utilize a slot, such as slot  38 , are envisioned. In such embodiments, the angled boot  34  may have a two-piece construction and may be such that it can be snapped around a multi-conductor cable. Still further alternate embodiments are envisioned where the capture element of the angled boot is something other than a raised nib, such as some form of a gripping device.  
     [0055] In summary, while the apparatus and processes of this invention have been described in terms of preferred illustrative embodiments, it will be apparent to those of skill in the art that variations may be applied without departing from the content and scope of the invention. Additionally, the apparatus and processes described in this disclosure are not intended to be limited to any particular art. All such similar substitutes and modifications apparent to those skilled in any relevant art where these apparatus and processes may find use are deemed to be within the scope and concept of the invention.