Abstract:
The present disclosure relates to an optical plug connector ( 1 ) having an improved unlocking mechanism. A locking arm ( 4 ), which protrudes toward the back in a slanted manner, is operatively connected to a collar ( 7 ) by way of a bracket ( 9 ). By displacing the collar ( 7 ) in an unlocking direction (−x), the connector ( 1 ) can be unlocked and removed from a sleeve.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a 35 U.S.C. §371 National Phase conversion of PCT/EP2009/055161, filed Apr. 28, 2009, which claims benefit of Swiss Application No. 00707/08, filed May 7, 2008, the disclosures of which are incorporated herein by reference. The PCT International Application was published in the German language. 
     BACKGROUND 
     1. Field of the Disclosure 
     The invention relates to the field of plug connectors, in particular plug connectors for optical cables. 
     2. Related Art 
     Plug connectors for optical cables are known from the prior art. So-called LC connectors are likewise known. In a further sense, these are push-pull connectors which have a high packing density. Corresponding connectors are manufactured by the applicant but are also available from a wide variety of other manufacturers. 
     European patents EP 0 762 558 B1 and EP 0 768 547 B1 describe an optical plug connector. The plug connector has a base body for accommodating the optical conductor. A structural extension member (also designated latching member or locking member) which is designed in an elastically resilient manner and has locking shoulders is integrally formed on the outside of the plug connector, the free end of said structural extension member being directed toward the rear end of the plug connector. A flange or trigger is also integrally formed on the outside of the plug connector, the free end of said flange or trigger pointing toward the front end of the plug connector in a manner protruding obliquely upward and interacting with the free end of the locking member. When the free end of the trigger, which is arranged in a fixed position, is depressed in an elastically resilient manner, the free end of the locking member is pressed toward the central axis and the plug connector can be pulled out of the socket by pulling the base body toward the rear if, or as long as, the trigger is simultaneously depressed in the process. One disadvantage is the unfavorable conduction of the forces: since a force which is directed forward is required for depressing the trigger, but a force which is directed toward the rear is required for removing the connector from a socket, the connector can be unlocked only with comparative difficulty. 
     European patent EP 1 091 227 B1 discloses a further design variant of a plug connector with a trigger which is fixed in position. A locking member is integrally formed on the base body. The plug connector also comprises a collar-like reinforcement element (designated yoke) with a square cross section which completely surrounds a subregion of the base body perpendicular to the central axis of the plug connector. A trigger, which is of elastically resilient design, is also integrally formed on the reinforcement element, the free end of said trigger—analogously to EP 0 762 558 B1 and EP 0 768 547 B1—interacting with the free end of the locking member which is integrally formed on the base body. During manufacture or assembly of the plug connector, the reinforcement element is pushed onto the base body along the central axis and fixed in a defined position. As in EP 0 762 558 B1 and EP 0 768 547 B1, the plug connector can be pulled out of the socket when the trigger is depressed onto the locking member and, at the same time, the plug connector or base body is pulled toward the rear. 
     U.S. Pat. No. 6,565,262 B2 discloses a further design variant of a plug connector with a trigger which is fixed in position. As in EP 1 091 227 B1, a locking member, which protrudes toward the rear in an oblique manner, is integrally formed on a base body of the plug connector, it being possible for said locking member to likewise be operated by a trigger. The trigger is integrally formed on a protective collar which is arranged in a fixed manner in the axial direction and has a substantially C-shaped cross section. The protective collar can be snapped onto the base body or the conductor both in a direction which is diverted away from the central axis, and also pushed toward and onto the base body in the direction of the central axis. In the functional position which meets requirements, the protective collar is mounted or positioned on the base body in a fixed manner; projections from the protective collar engage in corresponding cutouts in the base body. The plug connector can be removed from the collar when—as in the case of the preceding prior art—the trigger is pressed downward and the plug connector is pulled toward the rear at the same time. In this case, the protective collar is not displaced toward or in relation to the base body. 
     US patent application US 2004/0247252 A1 discloses a plug connector which consists of a base body and an unlocking element. The base body and the unlocking element are coupled to one another in an interlocking manner and are designed in such a way that an optical conductor can be received in the direction of the central axis. A locking member which protrudes obliquely toward the rear is fitted on the outside of the base body by means of a hinge. The base body also has, on the side, a continuous recess which interacts with a tongue of the unlocking element and determines the travel of the displacement between the base body and the unlocking element along the central axis. The unlocking element comprises a dimensionally stable structure which protrudes from the central axis and has a shaft which accommodates the free end of the locking member. When the unlocking element is pulled toward the rear along the central axis, the locking member is pressed against the base body and, in the process, unlocks the plug connector, and therefore the plug connector can be pulled out of the socket. In comparison to the prior art which is acknowledged above, the trigger does not have to be held in a depressed position as the plug connector is being pulled toward the rear, while the unlocking element—and not the basic housing—is pulled toward the rear. One disadvantage is that the unlocking element has a very complicated structure. 
     U.S. Pat. No. 6,752,538 B1, U.S. Pat. No. 6,821,024 B2 and U.S. Pat. No. 7,052,186 B1 each disclose a plug connector or a pair of coupled plug connectors having an apparatus which is intended to prevent unintentional unlocking. In order to prevent unintentional unlocking of the locking member, a securing collar, which can be displaced in the direction of the central axis, is mounted on the base body. The securing collar can firstly be pushed forward by way of the rear end of the operating element, so that the front end of the operating element engages beneath the locking member, therefore presses said locking member upward and additionally locks said locking member, that is to say protects it against being unintentionally released. If the securing collar is pushed toward the rear, the front end of the operating element is no longer positioned beneath the locking element, and this locking element can therefore be pressed downward in order to unlock the connector in the usual manner. 
     U.S. Pat. No. 5,984,531 discloses an optical connector which has an integrated cover which opens automatically when the connector is inserted and closes again when it is removed. An arm, which is mounted on the rear end of the housing and protrudes obliquely forward, serves as a locking member. A sleeve which is pressed into the housing from the rear as far as a stop and has an integrally formed crimping neck closes off the connector at the rear. At the same time, the sleeve serves as an abutment for supporting a spring which is arranged in the interior and is clamped between the sleeve and a ferrule holder and actively presses said sleeve forward. 
     U.S. Pat. No. 6,206,581 is directed at an optical connector with an integrally formed housing. A locking member is integrally formed on a side wall in the front region of the housing and protrudes upward and obliquely toward the rear. Said locking member is of resilient design and, in its rear region, can be pressed elastically against the side wall of the housing for unlocking purposes. In order to close the housing, a sleeve which is provided with laterally protruding locking elements is inserted into a longitudinal opening in the housing from the rear until the locking elements of the sleeve latch into correspondingly provided lateral openings in the housing. The cross section of the longitudinal opening is of rectangular or polygonal design at least at the rear end. In the rear region, the housing has slots which run in the longitudinal direction and allow the housing sides to be bent outward when the locking elements latch in. The cross section of the sleeve is designed such that the sleeve cannot rotate about its longitudinal axis in the latched-in state on account of its interlocking design. An unlocking element which is fitted onto the connector housing from the rear has an unlocking lug which protrudes obliquely forward and upward and can be pressed forward and downward onto the rear end of the locking element, so that said locking element is unlocked. Therefore, depending on the configuration, more than one connector can be unlocked at the same time. Further connectors of a similar nature are also known from U.S. Pat. No. 5,481,634 and, respectively, U.S. Pat. No. 5,579,425. The housings of these connectors are closed at the rear end by a correspondingly configured cover which is produced by injection molding. 
     One disadvantage of the solutions known from the prior art is the unfavorable conduction of forces during unlocking, and also the complicated structure. Many of the known connectors require two movements—the trigger being pressed downward and the plug connector being pulled toward the rear—to be performed approximately synchronously in order for said connectors to be released from the socket. Other plug connectors are distinguished by a complicated structure which has a disadvantageous effect on the manufacturing costs. 
     SUMMARY 
     One object of the invention is to overcome the disadvantages of the connectors known from the prior art. A further object of the invention is to specify an optical connector which is distinguished by simplified operability. 
     The object is achieved by the connectors defined in the independent patent claims. 
     In contrast to the connectors known from the prior art, a connector according to the invention has a structure which is simple to manufacture. In addition, the forces required for unlocking and removal are matched to one another such that operation is markedly simplified. 
     Further advantages include a higher packing density in comparison to that of the connectors known from the prior art, this having an advantageous effect on the arrangement. A plurality of connectors, or connector pairs, can be arranged one above the other and/or next to one another in a narrow space. The connectors have a lower overall height. Secondly, unlocking with higher packing densities is not problematic since it is not necessary to press the unlocking lever downward from above as is customary. Put simply, the fingers are outside the region of the locking arms during the unlocking operation. 
     Connectors of this generic type generally have a largely standardized structure with a single- or multi-part base body and a locking arm which is mounted on said base body and protrudes obliquely toward the rear. The connectors are designed in such a way that they can latch into sockets provided for them. Locking shoulders which project laterally from the locking arm are snapped into a rear-engagement means in the socket and thus prevent the connector from unintentionally slipping out of the socket. For unlocking purposes, the locking arm can be pressed against the base body in such a way that the locking shoulders are moved out of the rear-engagement means and thus release the connector so that it can be removed from the socket. The base body has a continuous opening in which an optical fiber is arranged. At the front end, the optical fiber issues into a ferrule which is mounted in a resilient manner in the longitudinal direction and is usually composed of ceramic. At the rear end, the connectors generally have a crimping neck which serves for connection of a cable jacket of the optical cable. A spring, which presses against a block which is mounted in the region of the rear end of the ferrule, is generally arranged in the interior of the connector. The housings of the connectors are typically manufactured from injection-molded plastic. 
     In the connectors known from the prior art, a clip generally has to be pressed forward and downward for unlocking purposes, before the connector can be removed from a socket in the opposite direction toward the rear. These force conditions are unfavorable since while one force is exerted forward and downward, a greater opposing force has to be superimposed toward the rear in order to unlock and to remove the connector. 
     In one embodiment of the invention, this disadvantage is avoided by a force toward the rear—that is to say in the removal direction—primarily being required for unlocking purposes. Operator control is markedly simplified by virtue of this vectorial coordination of the forces. In terms of design, this is achieved by an unlocking element being arranged on a base body of the connector, it being possible for said unlocking element to be displaced in relation to said base body and said unlocking element being operatively connected to a locking arm. 
     The unlocking element generally has a displacement element which can be displaced in relation to the base body. A clip which is integrally formed on the displacement element or is operatively connected to said displacement element serves to transform the movement of the displacement element into a force which serves to unlock the locking clip. In this case, the clip is designed, or operatively connected to the locking arm, in such a way that the connector can be snapped into a socket without problems, that is to say the locking arm can execute the movement required for locking purposes in the direction of the base body without a high degree of complexity and obstruction. 
     One embodiment of the invention relates to a plug connector having a base body and an articulated locking arm which is integrally formed in the region of the front end of the base body and protrudes toward the rear in an oblique manner. A collar-like displacement element surrounds the rear region of the base body at least in regions and can be displaced in relation to said base body in the longitudinal direction. The unlocking element is operatively connected to the locking arm by means of a clip. The operatively connected locking arm is unlocked by the unlocking element being displaced in an unlocking direction. Depending on the design and the field of use, the clip and the locking arm and/or the clip and the displacement element can be of integral design. Thin areas, for example in the form of film hinges, guarantee the requisite mobility in this case. Depending on the design, the displacement element can be operatively connected to the base body in a permanent or detachable manner. In the case of a detachable design, the displacement element can have a C- or U-shaped cross section which partially surrounds the base body. The displacement element can be designed in such a way that it can be snapped onto one or more connectors at the same time. In the case of a non-detachable design, the displacement element can have an annularly closed cross section which surrounds the base body. 
     The unlocking forces, and the removal forces which are required to remove the plug connector from the socket, are normally transmitted from the displacement element, by means of the clip, to the locking arm, and from there to the base body. The locking arm is first unlocked by pulling the displacement element, and then the base body of the connector is pulled out of the socket. If required, the displacement element and/or the base body can have means for limiting displacement, for example in the form of mechanical stops. 
     If required, the plug connector has coupling means which serve for lateral operative connection to a further plug connector. Depending on the field of use, the coupling means can be arranged on the base body and/or the displacement element. In one embodiment, the coupling means are projecting pins and recesses which are formed so as to correspond to said pins and which prevent the plug connectors from twisting in relation to one another. 
     The coupling means can be designed such that two connectors can be permanently connected to another by said coupling means. As an alternative or in addition, a retaining clamp (connector clamp) which is suitable for holding two or more connectors can be provided. The retaining clamp may be suitable for jointly unlocking the connectors. 
     As already mentioned above, US 2004/0247252 discloses a connector with a very complicated structure. Although this connector has a displaceable part, it cannot be compared, in respect of the structure and the manner of operation, with a connector according to the invention disclosed in this document, which, amongst other things, can be produced in a substantially simpler manner. The connector known from US 2004/0247252 has a displaceable rear part which forms the entire rear region of the connector. Depending on the embodiment, the displaceable part interacts with the locking arm by means of one or more short, steep ramps which are arranged in the interior of the housing. The ramps are arranged on a rigid, non-deformable structure. By displacing the rear part in relation to a front part of the connector, the locking arm is pressed downward by sliding along the ramp and the locking arm is thus unlocked. Disadvantages of this design are, in addition to the construction-related sliding friction which occurs, the complicated structure which has a negative effect on the manufacturing costs of the connector. A further disadvantage is that the ramp produces unfavorable force conditions on account of its design and arrangement and gradient. A further disadvantage is that, on account of the design, it is not clearly defined when the connector is unlocked. In addition, it is not clear whether the connector can actually be both unlocked and also removed by pulling the rear part. These disadvantages are avoided by the connectors according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in greater detail with reference to the exemplary embodiments which are shown in the following figures in which 
         FIG. 1  shows a perspective illustration of two examples of a first embodiment of a plug connector obliquely from the front and above; 
         FIG. 2  shows a perspective view of two plug connectors according to  FIG. 1  which are arranged next to one another and a connecting clamp obliquely from the front and above; 
         FIG. 3  shows a perspective view of the plug connectors according to  FIG. 2  with an operatively connected connecting clamp obliquely from the front and above; 
         FIG. 4  shows a side view of the plug connectors according to  FIG. 3 ; 
         FIG. 5  shows a perspective view of a second embodiment of a plug connector obliquely from the rear; 
         FIG. 6  shows the plug connector according to  FIG. 5  from the side; 
         FIG. 7  shows the plug connector according to  FIG. 5  from the rear; 
         FIG. 8  shows two further plug connectors obliquely from above and operatively connected to one another; 
         FIG. 9  shows an illustration of the two plug connectors according to  FIG. 8  in the separated state and partially in section; 
         FIG. 10  shows a plug connector according to  FIG. 8  without an unlocking element; 
         FIG. 11  shows an exploded illustration of a plug connector according to  FIG. 8 ; 
         FIG. 12  shows an unlocking element for a connector and an unlocking element for two connectors; 
         FIG. 13  shows a plan view of the two connectors according to  FIG. 8 ; and 
         FIG. 14  shows a sectional illustration along section line AA according to  FIG. 13 . 
     
    
    
     Corresponding elements are provided with identical reference symbols in the figures. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  shows two connectors  1  in a first embodiment side by side.  FIG. 2  shows the connectors  1  according to  FIG. 1  joined laterally, together with a connector clamp  3  which is not yet operatively connected.  FIG. 3  shows a perspective illustration of the two connectors  1  according to  FIG. 1  obliquely from the front and above. The connectors  1  are situated side-by-side and operatively connected by means of the connector clamp  3 .  FIG. 4  shows the connectors according to  FIG. 3  from the side. 
     The connectors  1  have a base body  2  and a blocking arm  4  which protrudes in an elastically resilient manner obliquely toward the rear from the front end of the base body  1 . Laterally projecting locking shoulders  5  are arranged on the locking arm  4  and serve to snap into corresponding recesses in a correspondingly designed socket (not illustrated). A ferrule  8  for accommodating and for connecting an optical conductor (not illustrated in any detail) can be seen at the front end of the base body  2 . 
     An unlocking element  6  is arranged on the base body  2 . Said unlocking element has a collar (displacement element)  7  which at least partially surrounds the base body  2  and can be displaced in relation to said base body in the longitudinal direction (x direction). The unlocking element  6  is arranged in front of an anti-kink sheath  19  in the axial direction. 
     A clip  9  is arranged on the collar  7  so as to project, said clip being operatively connected to the locking arm  4  in an articulated manner. In the embodiment shown, the articulated operative connection is provided by one or more thin areas  10 . Depending on the embodiment, the clip  9  can be of elastically resilient or rigid design. The thin areas  10  can be designed as film hinges. 
     By virtue of the collar  7  being displaced in the direction of the rear end (x direction) of the connector  1 , the clip  9  exerts a force on the locking arm  4  and pulls said locking arm downward in the direction of the base body  2 . The locking shoulders  5  are likewise displaced downward, and therefore they are unlocked and release the connector  1 . The forces exerted on the collar  1  simultaneously serve for removal of the connector  1  from a socket. 
     The two connectors  1  have, in the region of the collars  7 , coupling means in the form of projecting elements  12  which—as illustrated in FIG.  2 —can engage in correspondingly designed recesses  13  in an adjacent connector  1 . The projecting elements  12  and the recesses  13  serve to operatively connect two connectors to one another. At the same time, they prevent unintentional twisting or displacement of the connectors  1  relative to one another. In the embodiment shown, the connector clamp  3  has a substantially C-shaped cross section which surrounds the connectors  1  on three sides. Other single- or multi-part designs are possible. In the embodiment shown, the connector clamp  3  can—as illustrated in FIG.  3 —be snapped over the collars  7  of the two connectors  1  from the rear, so that said connectors are firmly connected to one another and to the connector clamp  3 . In the embodiment shown, the operative connection is established by corresponding snap-action connection means in the form of projecting elements  12  and correspondingly designed recesses  14 . 
     On account of the connector clamp  3 , as schematically indicated in  FIG. 4  (arrow p 1 ), being pulled in the direction of the rear end of the connector  1  (cf.  FIG. 4 ), the clips  9  are stretched and therefore the locking arms  4  which are operatively connected to said clips are pulled in the direction of the base body  2  together with the locking shoulders  5  (arrow p 2 ). 
       FIG. 5  shows a view of a plug connector  1  according to the invention obliquely from the rear and above.  FIG. 6  shows a side view of the connector  1  according to  FIG. 4 .  FIG. 7  shows a view of the connector from the rear. 
     The plug connector  1  has a base body  2 , a locking arm  4  and an unlocking element  6 . A crimping neck  16  can be seen at the rear end, said crimping neck serving for connection of an optical cable (not illustrated in any detail). 
     The locking arm  4  is arranged so as protrude obliquely toward the rear and upward from the front end of the base body  2  and is of elastically resilient design. The locking arm  4  has a locking shoulder  5  on either side, said locking shoulders serving to lock the plug connector  1  in a correspondingly designed socket in a known manner. 
     In the embodiment shown, the unlocking element  6  has a collar-like displacement element  15  which can be displaced on the base body  2  and has integrally formed on it a clip  17  which projects obliquely forward in the direction of the locking arm  4  and surrounds the locking arm  4  in the region of the rear end. On account of the interaction with the locking arm  4  which runs obliquely upward in a ramp-like manner (ramp  11 ) in the rear region, said locking arm is pressed downward to a defined extent by the clip  17  when the collar  15  of the unlocking element  5  is pulled back (arrow p 1 ). Since the locking shoulders are moved downward as a result (arrow p 2 ), the connector is unlocked. In the embodiment shown, a mechanical stop  18  prevents the clip  17  from slipping off the locking arm  4 . At the same time, the stop  18  can serve to transmit to the locking arm  4  the forces which are required for removing the connector. 
     In the embodiment shown, the clip  17  is designed in such a way that the rear end  18  of the clip  4  can still be operated from the outside and, if required, can be depressed manually. 
     As can be seen in  FIG. 7 , the unlocking element  6  is designed as a snap-action element in the embodiment shown, it being possible for said snap-action element to be snapped onto the connector  1  subsequently. 
     To this end, the collar (displacement element)  15  is designed to be open in the lower region. The cross section is of substantially C-shaped design. Other designs are possible. However, the collar can also be of closed design, for example by a flap which is integrally formed by means of a hinge, or a mating element. The clip  17  can be designed such that it actively presses the locking arm  4  upward in a front position and therefore prevents unintentional unlocking. If required, the clip  17  can be designed in such a way that it latches in a rear position and therefore securely holds the locking arm  4  in an unlocked position. 
     If required, the unlocking element  6  can be designed such that it is suitable for accommodating and coordinating more than one connector. In this case, the displacement element  15  is designed such that more than one base body  1  can be operatively connected to it. In one embodiment, the cross section has a double-C-shaped design in which the two substantially C-shaped cross sections are situated back-to-back or side-by-side. Other designs are possible. In this case, the unlocking element serves to hold and to coordinate the movements of the two connectors. In this case, the unlocking element assumes the function of the connector clamp  3  of the exemplary embodiment from  FIGS. 1 to 4 . 
       FIG. 8  shows a perspective illustration of two connectors  1  of a third embodiment obliquely from above.  FIG. 13  shows a plan view of the connectors  1  according to  FIG. 8 .  FIG. 14  shows a section through the arrangement of  FIG. 13  along section line AA. The two connectors  1  illustrated in  FIGS. 8 and 13  are operatively connected to one another by means of a connector clamp  20  which simultaneously serves as an unlocking element  6 . 
       FIG. 9  shows two connectors  1  according to  FIG. 8  side-by-side. The connector  1  which is at the front as seen by the viewer is illustrated partially in section so that the internal structure can be seen more clearly. In contrast to the arrangement according to  FIG. 8 , each connector  1  has its own unlocking element  6 . If required, the unlocking elements may have operative connection means (not illustrated further) by means of which two unlocking elements can additionally be operatively connected to one another. 
     The plug connectors  1  each have a base body  2 , a locking arm  4  and an unlocking element  6 . The locking arm  4  is arranged so as to protrude obliquely toward the rear and upward from the front end of the base body and is of elastically resilient design in the embodiment shown (other designs are possible). The locking arm  4  has a locking shoulder  5  on either side, said locking shoulder serving to lock the plug connector  1  in a correspondingly designed socket in a known manner. The unlocking element  6  has a collar-like displacement element  15  which can be displaced in relation to the base body  2  and has integrally formed on it a clip  17  which projects obliquely forward in the direction of the locking arm  4  in this case. At the rear end, the locking arm  4  has a thick area  21  which, in this case, forms a ramp  22  on each side of the locking arm  4  and is surrounded by the clip  17 . To this end, the clip has an inwardly projecting pin  35  on each side. For unlocking purposes, the unlocking element  6  is pulled toward the rear (x direction) on the base body  2 , for example using the thumb and forefinger. As a result, the clip  17 , or the pins  35 , forms/form an operative connection with the ramps  22  and thus press the rear part of the locking arm  4  downward toward the base body  2  on account of the gradient of the ramp  22 . As a result, the locking shoulders  5  are likewise pulled downward, and this leads to the connector  1  being unlocked. A low configuration with precise conduction is possible by virtue of the selected arrangement and design. 
       FIG. 9  (front connector) and  FIG. 14  (sectional illustration along section line AA according to  FIG. 13 ) and the exploded illustration according to  FIG. 11  show the internal workings of the connector.  FIG. 10  illustrates the connector according to  FIG. 11  in the assembled state. The connector according to  FIG. 10  can, if required, also be used without the unlocking element  6 . In this case, the thick area  21  at the end of the locking arm  4  is not necessarily required either. 
     As can be seen in  FIGS. 9 and 14 , the base body  2  has a continuous opening  23  in the longitudinal direction. A ferrule holder  24  with a ferrule  25 , which serves to accommodate an optical fiber (not illustrated further), is inserted into said opening from the rear end. The ferrule holder  24  is pressed against a shoulder  27 , which is formed in the interior of the opening  23 , by a prestressed spring  26 . The ferrule holder has a polygonal cross section which interacts with a correspondingly designed indentation in the shoulder  27  in an interlocking manner. By virtue of this design, the ferrule holder can be positioned about its axis for fine adjustment purposes. The spring  26  is supported at the rear on a press-in sleeve  28  which is pressed into the base body  2  and, in the embodiment shown, projects beyond the base body  2  and at the same time serves as a crimping neck. Similar connector designs are known from other connectors from the prior art (cf., for example, U.S. Pat. No. 5,984,531) but these connectors form part of another generic type and are significantly larger, and therefore they have a significantly greater wall thickness in the region of the sleeve. The packing density is accordingly poorer in comparison to the connectors according to the invention disclosed in this document. Comparable designs have, to date, been regarded as being impossible to achieve in the connector class of LC connectors under discussion here and were therefore not known either. The requisite pull-out values when pulling the cable in the longitudinal direction of the connector and transverse thereto are achieved by virtue of the special design and matching of the press-in sleeve  28 . 
     As can be seen particularly clearly in  FIGS. 11 and 13 , the press-in sleeve  28  has a stop edge  29  which determines the press-in depth of the press-in sleeve  28  into the opening  23  in the base body  2 . In the rear region, the press-in sleeve has a crimping neck  16 . When fitting the connector  1  to a cable (not illustrated further), the cable jacket is pushed onto the crimping neck  16  and fixed by a compressed crimping sleeve  30 . An anti-kink means  19 , which is not necessarily required for the actual functioning of the connector  1 , can be pushed onto the crimping sleeve  30  as a termination. 
     The sectional illustration according to  FIG. 13  shows the structure and the internal workings of the connector  1  in the assembled state. The locking arm  4  has, in the region of its connection to the base body  2 , a thin area  31  which improves the elastic spring behavior during unlocking operations. 
     At the rear end, the ferrule holder  24  merges with a flexible tube  32  which projects through the spring  26  and into the press-in sleeve  28  in the assembled state. By virtue of this design, the requisite lateral mobility of the ferrule holder  24  in the interior of the base body  2  is not impeded. Nevertheless, the cable is protected against the spring  26 . Furthermore, the flexible tube  29  serves, if required, as an assembly aid. A further advantage is that, when the connector is adhesively bonded, the adhesive is prevented from unintentionally establishing a connection with the spring  26  and the press-in sleeve  28 . 
     As can be seen in  FIG. 11 , the ferrule holder  24  has, at the rear end, a connection region  33  onto which the tube  32  can be pushed and adhesively bonded. Other attachment methods are possible. In the embodiment shown, the press-in sleeve  28  has two radially projecting teeth  34  which are spaced apart from one another and engage in the manner of teeth in the opening  23  in the material of the base body  2  during the press-in operation. The teeth  34  can have different diameters, and this can improve the effect. The length of the active region (region which is pressed in) of the press-in sleeve  28  corresponds to twice or three times the diameter. In contrast to the prior art, no longitudinally running strain-relief slots are required in the base body  2  in the connector disclosed in this document. As a result of the relaxation of the material, the teeth are embedded in the material of the base body such that they are protected against being pulled out. 
       FIG. 14  shows perspective illustrations of a single (a) and the double (b) unlocking element  6  obliquely from below. The two unlocking elements  6  are designed as snap-action elements which can be snapped onto one (a) or two (b) connectors  1  according to  FIG. 10 . To this end, the collar (displacement element)  15  is designed to be open in the lower region. The cross section is substantially C-shaped, or double-C-shaped. Other designs are possible. However, the collar can also be designed to be closed, for example by a flap which is integrally formed by means of a hinge, or a mating element. The clip  17  can be designed such that it actively presses the locking arm  4  upward in a front position and therefore prevents unintentional unlocking. If required, the clip  17  can be designed in such a way that it latches in a rear position and therefore securely holds the locking arm  4  in an unlocked position. 
     In  FIG. 12(   b ), the unlocking element  6  is designed such that it is suitable for accommodating and coordinating more than one connector. In this case, the displacement element  15  is designed such that more than one base body  1  can be operatively connected to it. In one embodiment, the cross section has a double-C-shaped design, in which the two substantially C-shaped cross sections are situated back-to-back or side-by-side. Other designs are possible. In this case, the unlocking element serves to hold and to coordinate the movements of the two connectors. 
     The connectors  1  according to  FIGS. 8 to 14  allow a particularly low structure. In addition, the open (not continuous) design of the clip  17  enables the locking clip  4  to be operated manually or using a tool. 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  Connector 
           2  Base body 
           3  Connector clamp 
           4  Locking arm 
           5  Locking shoulder 
           6  Unlocking element 
           7  Displacement element (collar) 
           8  Ferrule 
           9  Clip 
           10  Articulated joint 
           11  Ramp 
           12  Projecting element 
           13  Indentation 
           14  Recess 
           15  Displacement element 
           16  Crimping neck 
           17  Clip 
           18  Mechanical stop 
           19  Anti-kink means 
           20  Connector clamp 
           21  Thick area 
           22  Ramp 
           23  Continuous opening 
           24  Ferrule holder 
           25  Ferrule 
           26  Spring 
           27  Shoulder 
           28  Press-in sleeve 
           29  Stop edge 
           30  Crimping sleeve 
           31  Thin area 
           32  Tube 
           33  Connection region 
           34  Tooth 
           35  Pin