Abstract:
A connector for attachment to a coaxial cable having an annular corrugated outer cable conductor, includes a connector head having a threaded portion and defining a ring surface for establishing a contact from inside with an end zone of an outer cable conductor. The outer cable conductor is enclosed by a contact sleeve which has a plurality of radially resilient segments. Surrounding the contact sleeve is a clamping bush which is so threadably engageable with the connector head along a predetermined clamping path, until an end zone of the outer cable conductor, which projects beyond an end face of the contact sleeve, is urged against the contact surface of the connector head. The clamping path of the clamping bush is subdivided in two sections to define an indexing mechanism, with the first section corresponding to a preassembled state of the connector, and with the second section commensurate with a fully assembled connector onto the connecting end of the cable. The indexing mechanism is formed by the interaction between a smooth portion of the clamping bush and by a threaded portion of the connector head, with the threaded portion having a length which is equal or smaller than a length of the smooth portion of the clamping bush.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the priority of German Patent Application, Serial No. 198 46 440.1, filed Oct. 8, 1998, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates, in general, to a connector for coaxial cables, and more particularly to a connector for coaxial cables of a type having annularly corrugated outer cable conductor. 
     U.S. Pat. No. 4,046,451, issued on Sep. 6, 1977, describes a connector assembly for a coaxial cable of a type having an annularly corrugated outer cable conductor, with a connector head which is formed with a beveled clamping surface to engage the inner surface of the end zone of the outer cable conductor. Cooperating with the clamping surface of the connector head is a further clamping surface formed on one end of a contact sleeve for engaging the outer surface of the end zone of the outer cable conductor. The contact sleeve is formed at the same time as a hollow screw and has a plurality of slits extending from the connector head proximal end to form a plurality of resilient segments. Each of the segments terminates in a bead for meshing in the first valley of the outer cable conductor and clamping the outer cable conductor against the clamping surface of the connector head along the end zone extending over the contact sleeve, when the connector assembly is mounted to the coaxial cable. 
     The necessity to dismantle the connector before attachment to the coaxial cable is disadvantageous for several reasons. For one, components may fall out, get lost or mixed up. Moreover, manipulation of several components is time-consuming and annoying, in particular when carrying out the assembly at exposed sites. There is also a risk that errors occur during assembly. A further drawback is the inevitable friction encountered between the beads at the free ends of the segments of the contact sleeve and the outer cable conductor along the outer surface to be contacted and clamped during threaded engagement of the contact sleeve in the connector head. As the outer cable conductor is normally made of a relatively soft copper alloy, the friction frequently results in a squeezing of material in the circumferential direction, leading to respective bending of the segments of the contact sleeve, or as a result of an increase of the torque to be applied for tightening the components in a false indication that a secure clamping and contacting has been attained when in fact that is not the case. 
     SUMMARY OF THE INVENTION 
     It is thus an object of the present invention to provide an improved connector, obviating the afore-stated drawbacks. 
     In particular, it is an object of the present invention to provide an improved connector for coaxial cables having annularly corrugated outer cable conductor, which is easy to make and quick to mount onto the coaxial cable while yet being reliable in operation. 
     These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a connector head having a threaded portion and defining a ring surface for establishing a contact from inside with an end zone of an outer cable conductor, a contact sleeve adapted to fit over the outer cable conductor and having a plurality of radially resilient segments, a clamping bush formed with a thread which is interrupted by a smooth portion and adapted to fit over the contact sleeve for threaded engagement with the connector head such as to load, after moving a clamping path, the segments of the contact sleeve in a direction of a clamping action so that the segments clamp the outer cable conductor along the end zone, which projects beyond an end face of the contact sleeve, against the ring surface of the connector head, and an indexing mechanism for subdividing the clamping path of the threaded clamping bush into first and second sections, with the first section corresponding to a preassembled state of the connector, and with the second segment corresponding to a complete assembly of the connector onto the cable end, wherein the indexing mechanism is formed by the smooth portion of the clamping bush and by the threaded portion of the connector head, interacting with one another, with the threaded portion having a length which is equal or smaller than a length of the smooth portion of the clamping bush. 
     A connector according to the present invention can be installed to one end of the coaxial cable, without preceding dismantling thereof because the novel and inventive design of the pre-assembled connector allows the installer to simply slip the connector over the prepared cable end and to screw the clamping bush to a sufficient extent into the connector head until the threaded portion of the connector head is in engagement with the smooth portion of the clamping bush. This represents a first phase of the clamping path and is commensurate with the correct pre-assembly stage of the clamping bush with respect to the connector head. 
     The incorporation of the smooth portion of the clamping bush can easily be made in a same work cycle as the cutting of the thread, using a conventional N/C machine. 
     The connector can be designed of comparably short size when the clamping bush is formed as hollow screw, and the threaded portion of the connector head is an inner thread in a recess of the connector head. 
     According to another feature of the present invention, the connector head has an axial end for receiving the hollow screw, whereby the connector head may be formed with a ring collar, positioned between the threaded portion and the axial end, for providing a guide when the hollow screw is threaded into the connector head. 
     Alternatively, the clamping bush may also be designed as a clamping ring which has an inner thread, whereby the threaded portion of the connector head is provided externally. 
     According to another aspect of the present invention, the connector head may have a smooth portion which complements the smooth portion of the clamping bush. In this case, the thread of the clamping bush includes a first threaded portion, with the smooth portion of the connector head being positioned axially inwardly of the threaded portion of the connector head and defined by a length which at least corresponds to the length of the first threaded portion of the clamping bush. A further threaded portion of the connector head is then positioned axially inwardly of the smooth portion. 
     In order to ensure a sufficiently stable guidance of the clamping bush in the connector head in the pre-assembly stage of the connector, the smooth portion of the clamping bush, and, if provided, the smooth portion of the connector head may each be formed by a recess in the thread, which recess only slight exceeds the depth of the thread. 
     The number of revolutions of the clamping bush until clamping the outer cable conductor can be decreased by configuring the engaging threads of connector head and clamping bush as multiple threads. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The above and other objects, features and advantages of the present invention will now be described in more detail with reference to the accompanying drawing, in which: 
     FIG. 1 is a partially exploded sectional view of a first embodiment of a connector according to the present invention, showing individual components of the connector before pre-assembly; 
     FIG. 2 is a sectional view of the connector of FIG. 1 in the pre-assembled stage; 
     FIG. 3 is a sectional view of the connector of FIG. 1 during a first phase of attachment onto a cable end; 
     FIG. 4 is a sectional view of the connector of FIG. 1, illustrating the fully assembled connector; 
     FIG. 5 is a partially exploded sectional view of a second embodiment of a connector according to the present invention, showing individual components of the connector before pre-assembly; 
     FIG. 6 is a sectional view of the connector of FIG. 5 in the pre-assembled stage; 
     FIG. 7 is a sectional view of the connector of FIG. 5 during a first phase of attachment onto a cable end; 
     FIG. 8 is a sectional view of the connector of FIG. 5, illustrating the fully assembled connector; 
     FIG. 9 is a partially exploded sectional view of a third embodiment of a connector according to the present invention, illustrating the connector in a pre-assembly stage; 
     FIG. 10 is a sectional view of the connector of FIG. 9, illustrating the fully assembled connector; and 
     FIG. 11 is a partially exploded sectional view of a fourth embodiment of a connector according to the present invention, illustrating the fully assembled connector. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Throughout all the Figures, same or corresponding elements are generally indicated by same reference numerals. 
     Turning now to the drawing, and in particular to FIG. 1, there is shown a partially exploded sectional view of a first embodiment of a connector according to the present invention for attachment to a connecting end of a coaxial cable. In this context, reference is made to commonly assigned copending patent application, appl. Ser. No.: 09/145,677, entitled “Connector for a Coaxial Cable with Annularly Corrugated Outer Cable Conductor”, the disclosure of which is incorporated herein by reference to show one type of connector involved here. 
     The connector includes a connector head  5  which is shown here only by way of its cable-proximal end that is of relevance as far as the present invention is concerned. The connector head  5  accommodates an inner conductor  4  held centrally in and spaced from the connector head  5  by an insulating plastic disk (not shown). On its cable-proximal end, the connector head  5  is formed with a recess  51  which is flanked by a beveled ring surface  52  and destined to accommodate a contact sleeve  6  which is configured in the form of a collet. The contact sleeve  6  has a plurality of axial slits  61  extending from the connector head proximal end to form a plurality of resilient segments  62 . Each segment  62  has a free end terminating in a bead  63 . On its opposite connector head distal end  64 , the contact sleeve  6  has a slightly greater outer diameter than in the area of its resilient segments  62 . 
     The contact sleeve  6  is inserted in a clamping bush in the form of a hollow screw  7  by pushing the resilient segments  62  together. In the assembly stage, shown in FIG. 1, the contact sleeve  6  is freely movable within the hollow screw  7  but held captive in the hollow screw  7 , e.g. through provision of an inwardly projecting inner collar  71 , located near the cable-proximal axial end of the hollow screw  7 , which collar  71  interacts with a shoulder  6   a  of the beads  63  and an enlarged and substantially rigid bead-distant end  6   b  of the contact sleeve  6 , so that the axial movement of the contact sleeve  6  in both directions is restricted. The resiliency of the segments  62  allows the contact sleeve  6  to glide under the inner collar  71  and thus a detachment thereof. The hollow screw  7  has an external thread which includes a first short threaded portion  72 , positioned slightly inwardly of the axial end of the hollow screw  7  and comprised of only few threads, and a second long threaded portion  73 , spaced inwardly of the first threaded portion  72 , thereby demarcating therebetween a smooth portion  74  that is free from any threads. The long threaded portion  73  terminates in an annular circumferential groove for receiving an O-ring  75  which provides a seal between the connector head  5  and the hollow screw  7  and a seal of the recess  51  when the hollow screw  7  is rotated into the connector head  5 . 
     The inside of the axial end zone of the connector head  5  for receiving the hollow screw  7  is designed to complement the outer configuration of the hollow screw  7  and includes a smooth portion  53  extending inwardly of the axial end face and continued by an inner threaded portion  55  which has a length which is equal or smaller than the length of the smooth portion  74  of the hollow screw  7 . The complementary configuration between the outside of the hollow screw  7  and the inside of the connector head  5  in the attachment area forms an indexing mechanism by which the attachment and thus the clamping path of the hollow screw  7  in the connector head  5  is subdivided into two sections, as will now be described. 
     Turning now to FIG. 2, there is shown a sectional view of the connector of FIG. 1 in a pre-assembled stage, with the hollow screw  7  rotated into the connector head  5  to such an extent that the inner threaded portion  55  of the connector head  5  lies fairly loosely in the smooth portion  74  of the hollow screw  7 . This position of the hollow screw  7  relative to the connector head  5  marks the end of a first phase of the clamping path of the hollow screw  7  in the connector head  5  and thus the beginning of a second phase of the clamping path. This first phase of the clamping path of the hollow screw  7  in the connector head  5  represents the preassembled state of the connector, as supplied by a manufacturer, for attachment to a conventional coaxial cable with annularly corrugated outer cable conductor  3 , shown in FIG.  3 . 
     FIG. 3 shows a partial longitudinal section of the preassembled connector for attachment onto a suitably prepared connecting end of the coaxial cable, with the connector not yet occupying its fully assembled disposition. The coaxial cable includes an inner tubular cable conductor  1  which is centered inside the cable and spaced and insulated from the outer cable conductor  3  by a dielectric  2 , with the outer surface of the outer cable conductor  3  being covered by a sheath  4 . Persons skilled in the art will appreciate that the connection of the inner conductor does not form part of the present invention and thus has been omitted from the drawings for the sake of simplicity. The connector is placed over the connecting end of the coaxial cable whereby the end of the outer cable conductor  3  pushes the contact sleeve  6  into the illustrated position in which either the end faces of the beads  63  of the outwardly deflected resilient segments  62  of the contact sleeve  6  contact the bottom of the recess  51  of the connector head  5 , as shown in FIG. 3, or the inner surfaces of the beads  63  at the end of the outwardly deflected resilient segments  62  contact the beveled ring surface  52  of the connector head  5 . 
     As the connector is further advanced from the position shown in FIG. 3 over the cable end, the end zone  32  of the outer cable conductor  3  migrates between the ring surface  52  and the complementary confronting surface of the beads  63  of the resilient segments  62 . While the connector head  5  is now held in place, the hollow screw  7  is further threaded into the connector head  5  to cover the second section of its clamping path until the end zone  32  of the outer cable conductor  3  is firmly clamped between the ring surface  52  and the beads  63  of the contact sleeve  6  to thereby effect a secure contacting, as shown in FIG.  4 . This now represents the fully assembled stage of the connector. The axial end  76  of the hollow screw  7  prevents a radial deflection of the segments  62  of the contact sleeve  6  and the contact sleeve  6  is secured in axial direction as the inwardly projecting inner collar  71  of the hollow screw  7  bears upon the annular shoulders  6   a  of the beads  63 . 
     Prior to attachment of the connector onto the coaxial cable, it may be suitable to install a separate sealing ring in a first valley on the exposed portion of the outer cable conductor  3 , immediately following the sheath  4 . Persons skilled in the art will understand, however, that sealing of the gap between the inner surface of the hollow screw  7  and the outer surface of the outer cable conductor  3  may also be effected by other means, e.g. through injection of an elastic sealant into the annular gap. 
     Turning now to FIG. 5, there is shown a partially exploded sectional view of a second embodiment of a connector according to the present invention. Parts corresponding with those in FIG. 1 are denoted by identical reference numerals and not explained again. In contrast to the embodiment of FIG. 1, the smooth portion  74  of the hollow screw  7  is of shorter configuration than the complementary threaded portion  55  of the connector head  5 , whereby the axial length of the threaded portion  55  is equal or smaller than the length of the smooth portion  74  of the hollow screw  7 . Provided inwardly of the threaded portion  55  is a smooth portion  56  defined by an axial length which is at least equal to the axial length of the first threaded portion  72  of the hollow screw  7 . Following inwardly of the smooth portion  56 , the connector head  5  has a second threaded portion  57 . 
     FIG. 6 shows a sectional view of the connector of FIG. 5 in a pre-assembled stage, and it can be seen that the smooth portion  56  of the connector head  5  is in engagement with the first threaded portion  72  of the hollow screw  7 , and the smooth portion  74  of the hollow screw  7  is in engagement with the first threaded portion of the connector head  5 , thereby marking the first phase of the clamping path to effect attachment of the hollow screw  7  in the connector head  5 . 
     FIGS. 7 and 8 show partial longitudinal sections of the connector for attachment onto the suitably prepared connecting end of the coaxial cable. The attachment is realized in a same manner as described with respect to FIGS. 3 and 4. The connector is placed over the prepared end of the coaxial cable such that the end of the outer cable conductor  3  pushes the contact sleeve  6  into the illustrated position in which either the end faces of the beads  63  of the outwardly deflected resilient segments  62  of the contact sleeve  6  contact the bottom of the recess  51  of the connector head  5 , as shown in FIG. 7, or the inner surfaces of the beads  63  at the end of the outwardly deflected resilient segments  62  contact the beveled ring surface  52  of the connector head  5 . As the connector is further advanced from the position shown in FIG. 7 over the cable end, the end zone  32  of the outer cable conductor  3  moves between the ring surface  52  and the complementary confronting surface of the beads  63  of the resilient segments  62 . While the connector head  5  is now held in place, the hollow screw  7  is further rotated into the connector head  5  to cover the second section of its clamping path until the end zone  32  of the outer cable conductor  3  is firmly clamped between the ring surface  52  and the beads  63  of the contact sleeve  6  to thereby effect a secure contacting, as shown in FIG.  8 . This now represents the fully assembled stage of the connector. 
     Turning now to FIG. 9, there is shown a partially exploded sectional view of a third embodiment of a connector according to the present invention. The connector includes a connector head  95  which accommodates therein an inner conductor  94  and is formed with an outer threaded portion  955 . Projecting out from one axial end of the connector head  95  is a beveled ring surface  952 . While the contact sleeve  6  is identical with the configuration shown in FIG. 1, the clamping bush is now designed—instead as a hollow screw—in the form of a clamping ring  97  with inner thread. The contact sleeve  6  is captivated in the clamping ring  97  by means of an inwardly projecting collar  971  so as to limit the axial displacement of the contact sleeve  6 . The inner thread of the clamping ring  97  is comprised of a first threaded portion  972  and a second threaded portion  973  which is inwardly spaced from the first threaded portion  972  so as to define therebetween a smooth portion  974 . As shown in FIG. 9, the outer threaded portion  955  of the connector head  95  is shorter than the smooth portion  974  of the clamping ring  97 . The illustration of FIG. 9 represents the preassembly stage of the connector in which the outer threaded portion  955  of the connector head  95  engages the smooth portion  974  of the clamping ring  97 , thereby marking the first phase of the clamping path of the clamping ring  97  in the connector head  95 . 
     FIG. 10 shows the fully assembled connector, with the second inner threaded portion  973  of the clamping ring  97  in mesh with the outer threaded portion  955  of the connector head  95 . The end zone  32  of the outer cable conductor  3  is clamped between the ring surface  952  and the beads  63  at the end of the segments  62  of the contact sleeve  6  to thereby realize a secure contacting. 
     The embodiments described in FIGS. 1 to  10  embody the invention in connectors that are so designed that the end zone  32  of the outer cable conductor  3  is preferably cut in the area of a corrugation crest and is mechanically clamped and electrically contacted between the beveled ring surface of the connector head and the essentially complementary confronting surfaces of the beads  63  at the ends of the resilient segments  62  of the contact sleeve  6 . Persons skilled in the art will understand, however, that the present invention should not be limited to such connectors because the concept of the present invention is equally applicable to connectors which realize the mechanical clamping and electric contacting of the cable and outer cable conductor in a different manner. An example is shown in FIG. 11 which depicts a partially exploded sectional view of a fourth embodiment of a fully assembled connector according to the present invention. This embodiment of the connector corresponds substantially to the embodiment of FIGS. 1 to  4 , with the difference residing primarily in the type of clamping mechanism and type of contact-making mechanism. In this context, reference is made to German Pat. No. DE 43 44 328, published Jan. 12, 1995, which illustrates the type of clamping mechanism and type of contact-making mechanism, involved in the embodiment of FIG.  11 . Parts corresponding with those in FIG. 1 are denoted by identical reference numerals and not explained again. 
     The end zone  32  of the outer cable conductor  3  is in contact in the recess  51  with the confronting end face of the connector head  5 . In contrast to the embodiments shown in FIGS. 1 to  10 , the recess  51  is not flanked by a beveled ring surface but is bounded by a bottom area  58  which extends substantially in a radial plane, with the flanged end zone  32  of the outer cable conductor  3  being clamped against the bottom area  58 . The flanged end zone  33  is formed automatically during insertion of the hollow screw  7  along the second section of its clamping path in the recess  51  of the connector head  5  as a consequence of the configuration of the beads  63  at the ends of the resilient segment  62  of the contact sleeve, which beads  63  have end faces also oriented in a radial plane, so that in the preassembly stage of the connector, the beads  63  enter the first corrugation valley of the outer cable conductor  3 . In the event, the initial end face of the outer cable conductor  3  is located in the area of a corrugation crest, as described in the previous embodiments, the end zone of the outer cable conductor is outwardly deflected in one layer in the form of a flange. If, however, the initial end face of the outer cable conductor is located in the area of a corrugation valley, a double-layer, flanged deformation of the end zone  32  of the outer cable conductor  3  is realized, as shown in FIG. 11 when turning the hollow screw  7  along the second section of the clamping path. 
     While the invention has been illustrated and described as embodied in a connector for a coaxial cable with annularly corrugated outer cable conductor, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.