Abstract:
A contact unit for a card-shaped carrier element of electronic components is provided. The contact unit includes an insertable card-shaped housing that has a base plate and a cover plate that is congruent to the base plate at least in the transverse direction. Formed between the base plate and the cover plate is a slot-like insertion channel that opens on one side of the housing for accommodating a chip-card. At the opposite side is provided a plug-in strip. Disposed parallel to the insertion channel, in the housing, is a printed circuit board that is electrically connected to the plug-in strip and that is provided on its surface with a contact field for contact with the chip-card. The insertion channel is continuously open on both sides over its entire length in the direction in which the chip-card is inserted. The base plate and the cover plate are securely attached to one another solely in the region adjacent to the insertion channel in the direction of insertion.

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns a contact unit for a card-shaped carrier element of electronic components, especially in accordance with PCMCIA standards, comprising a plug-in or insertable card-shaped housing that comprises a base plate and a cover plate that is congruent thereto at least in the transverse direction, between which is formed a slot-like insertion channel that opens on one side of the housing for accommodating a chip-card, and that at the opposing side is provided a plug-in strip, and furthermore comprising arranged parallel to the insertion channel in the housing a printed circuit board that is connected electrically to the plug-in strip and that is provided on its surface with a contact field for contact with the chip-card. 
     Given the increasing miniaturization in the field of computer technology, electronic components are more and more frequently arranged on or in card-shaped carrier elements with a view toward variability and transportability. Frequently encountered are carrier elements in accordance with PCMCIA standards that are cards that comprise a standard-compliant matrix-like connector strip and can accommodate a great variety of electronic components, depending on application. For instance, such cards are employed as memory expansion cards, drive cards, modem cards, etc. The interface to a data processing system (e.g., a notebook computer) is created by means of the plug-in strip, which effects a mechanical and electrical contact with a PCMCIA slot in the data processing system. 
     Widely used are chip-cards that have integrated circuits and comprise flush contact fields arranged for contact with, e.g., correspondingly designed reading units. Known areas of application for this type of chip-cards are currently telephone cards, authorization cards, or what are known as “SmartCards”. 
     Known in the current art are contact units that make it possible to connect a chip-card to a PCMCIA standard interface in a data processing system. The combination of a PCMCIA card and a chip-card contact unit that can be inserted into a corresponding modular insertion slot in a computer and then read is useful in a wide variety of applications (e.g., electronic banking, pay TV, authenticating access authorization to data networks, etc.). The disadvantage is that known chip-card readers of this type comprise an extension in the housing in the form of an enlarged insertion guide for the chip-card that extends beyond the insertion area of the modular insertion slot in the computer and that simultaneously provides a grip for the user. This means the readers are substantially longer than standard PCMCIA cards so that when in the operating position this extension projects out of the insertion slot, e.g., in a notebook computer, so that during mobile operation there is a risk that the contact unit will jam in the slot or might even be bent or damaged. This extension has thus far been considered necessary for safely guiding the chip-card into and out of the slot-type insertion channel without the risk of inserting the card improperly—that is, for introducing, retaining, and removing a chip-card. 
     As the usage of transportable computers (e.g., laptop and notebook computers) continues to increase, there is a technical requirement that a chip-card reader situated in the operating position be completely insertable into the slot in the computer without projecting parts interfering with usage. This becomes important, e.g., when a chip-card must be inserted for personal authorization to use the computer. Although contact elements are known that do not comprise an extension and thus correspond to the PCMCIA standard, these are provided at least partially with closed sides in order to achieve lateral guidance for the chip-card. However, a significant market requirement is that the width of a contact unit also comply exactly with the PCMCIA standard so that even the wall thickness, {fraction (1/10)}mm, for the sides does not deviate substantially from the PCMCIA standard. An additional disadvantage of very thin-walled sides is that the slightest misplacement of the chip-card when it is inserted into the contact unit can damage the card. An additional disadvantage results when the thin sides are deformed and it is then no longer possible to insert the chip-card. 
     The object of the invention is to further develop a contact unit for a card-shaped carrier element in electronic components such that the contact unit can be completely inserted into a PCMCIA slot in a computer without parts projecting therefrom and the object is furthermore also to ensure that proper insertion is still possible and that there is sufficient mechanical stability and simple manufacture. 
     This object is achieved in a contact unit of the type cited in the foregoing in that the insertion channel is continuously open over its entire length in the direction the chip-card is inserted and in that the base plate and cover plate are securely attached to each other solely in the region adjacent to the insertion channel in the direction of insertion. 
     The features in accordance with the invention make it possible to provide a contact unit the length and width of which comply precisely with the PCMCIA standard, e.g., Type II, and which can be inserted in its entirety into the PCMCIA slot of a computer (e.g., a notebook computer) without parts projecting therefrom. The complete insertability precludes any risk of damage, especially during transport, wherein a protective flap can also be provided that closes the PCMCIA slot when the contact unit is inserted. Of course, in this case it is not possible to leave a chip-card in the contact unit since, corresponding to the length of the region adjacent to the insertion channel, it projects from the contact unit when in its inserted position. 
     In a preferred embodiment of the invention, the connection of base plate and cover plate in the region adjacent to the insertion channel in the direction of insertion is also a swivelling axis relative to which the base plate and cover plate can swivel slightly such that the height of the insertion channel can be changed against the effect of a restoring force. The advantage of this is that when inserted into the insertion channel the chip-cards can be retained clamp-like in the channel. It is particularly advantageous when the height of the insertion channel declines as the distance from the connection increases when there is no chip-card inserted therein. When the chip-card is inserted into the insertion channel, the latter expands and the chip-card is held securely in the channel by means of inherent elastic return deformation. At the same time a high degree of form stability in the contact unit and compensation of production tolerances can be achieved in this manner. 
     Furthermore, a particular advantage is that the printed circuit board is connected at its end opposing the plug-in strip to a metal strip that is affixed to the printed circuit board in the housing and that comprises flexibly extending tabs that electrically conductively adjoin the metal cover plate. The metal strip in this manner keeps the printed circuit board level in the housing and also provides a grounded transition to the printed circuit board. With regard to this latter, it is necessary that the metal strip is connected to grounded contact surfaces in the printed circuit board. In order to facilitate simple assembly, in accordance with an additional feature of the invention the metal strip is arranged on a plastic profile that is connected to the cover and that constitutes an upper insertion guide for the chip-card. The plastic profile can be provided on its side facing the insertion channel guides for a chip-card and can be joined to the metal strip, e.g., by clamping, adhesive, or locking means. 
     In accordance with a further advantageous development of the invention, provided in the insertion channel is at least one spring element, the one end of which is securely joined to the cover plate and the other, free end of which can be detachably attached to the base plate. The spring element fulfills a plurality of roles. When no chip-card is inserted, the spring element ensures that the height of the insertion channel remains the same against the action of the restoring force so that the chip-card can be easily introduced. Since the free end of the spring element is detachably attachable to the base plate, the insertion channel is simultaneously protected against outward expansion. This provides the contact unit additional form stability. Introducing the chip-card releases the free end and the spring element is bent in the insertion channel in the direction of the cover plate so that due to this spring-effect the chip-card is subjected to increased pressure which also ensures the contact. Advantageously the spring element is produced integral to the metal strip and when a chip-card is inserted extends to the cover plate through cut-outs in the printed circuit board so that chip-card and metal cover plate are conductively connected to each other, whereby static charging of the chip-card can be prevented. Securing the free end of the spring element on the base plate also makes it possible to achieve a bonding point between cover plate, printed circuit board, and base plate when there is no chip-card inserted. The metal strip and the spring element are cost-effective to produce by means of stamping and bending as strip-type goods and can be joined to the cover plate or to the plastic profile constituting the upper insertion guide in a single step by means of caulking, adhesive, welding, or ultrasound welding. 
     In order to obtain the compression/tension effect with the spring element, it is useful to embody the spring element in an approximate S-shape and to provide at its free end a claw-shaped extension that engages a mating lock element for securing the spring element. In accordance with an additional feature of the invention, it is advantageous to provide the lock element an undercut in which the claw-shaped extension of the spring element is releasably held. In an advantageous embodiment of the invention it is furthermore suggested that the lock element is embodied in a reinforcing plate made of plastic or metal that is joined to the base plate. While a reinforcing plate made of plastic can be joined to the metal base plate by means of injection molding, a metal reinforcing plate can be joined to the base plate by means of welding or adhesive. Advantageously the lock element is employed as a separate component in the reinforcing plate or as a cut-out in the reinforcing plate that is at least single-layer. In the latter case the undercut in the lock element can be produced by punching or stamping a single-layer reinforcing plate or by the offset arrangement of two reinforcing plates, one above the other and provided with openings. If, however, the lock element comprises a separate component, it is useful to prefabricate this component and press it into an opening in the reinforcing plate. 
     In accordance with an additional feature of the invention, the base plate at its end opposing the plug-in strip is provided with a plastic profile that functions as a lower insertion guide in order to ensure that the chip-card can be easily inserted. The plastic profile can be provided guides analogous to those for the upper insertion guide. 
     In an advantageous embodiment of the invention it is furthermore suggested that the base plate and cover plate are each provided at said plug-in strip with plastic holders arranged on the edge for fastening thereto that can be securely joined by means of a plastic bond like adhesive, ultrasound welding, or heat pressing. Base plate and cover plate can be securely joined in this manner. Alternatively, or in addition thereto, in accordance with an additional feature of the invention the base plate and cover plate are congruent and are welded to each other at lateral welded brackets. In this case it is particularly advantageous when the length of the secure joining of base plate and cover plate is approximately 30% of the overall length of the contact unit because this results in high form stability in the contact unit. Finally, it is suggested that an end stop comprising a stop angle is provided for limiting the insertion of the chip-card. Depending on requirements, insertion of the chip-card can also be limited by the lateral welding brackets or by the plastic holders, which are then provided with appropriate rounded stop surfaces. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional details, features, and advantages of the subject of the invention can be appreciated from the following description of two exemplary embodiments, with reference to the associated drawings, in which: 
     FIG. 1 is a perspective view of a contact unit that does not have a chip-card inserted therein; 
     FIG. 1 a  is a perspective view of the contact unit in accordance with FIG. 1 into which a chip-card has been inserted; 
     FIG. 1 b  is a perspective view of the contact unit in accordance with FIG. 1 showing swiveling of the base plate and the cover plate relative to one another. 
     FIG. 2 illustrates the individual parts of the contact unit in accordance with FIG. 1 in a perspective view of housing members that have been flipped open and taken apart and their internal composition; 
     FIG. 3 illustrates the individual parts of the contact unit in accordance with FIG. 2 in an intermediate stage of assembly; 
     FIG. 3 a  is a perspective exploded view of the attachment of a metal strip to a plastic profile; 
     FIG. 3 b  is a perspective view of the attachment of the metal strip in accordance with FIG. 3 a  to a printed circuit board; 
     FIG. 4 illustrates a side view of the contact unit in accordance with FIG. 1; 
     FIG. 4 a  illustrates a side view of the contact unit in accordance with FIG. 1 a;    
     FIG. 5 illustrates the individual parts of an alternative embodiment of a contact unit in a perspective view of the housing members that have been flipped open and taken apart and their internal composition; 
     FIG. 6 illustrates the individual parts of the contact unit in accordance with FIG. 5 in an intermediate stage of assembly; 
     FIG. 7 shows a side view of the contact unit in accordance with FIG. 5 that does not have a chip-card inserted therein; and 
     FIG. 7 a  illustrates a side view in accordance with FIG. 6 into which a chip-card has been inserted. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The exemplary embodiment of the invention illustrated in FIG. 1 shows a contact unit  1  designed as a chip-card reader that is provided for contact with a notebook computer by means of a standard PCMCIA interface. The contact unit  1  comprises a two-member external housing  2  having a base plate  3 , a PCMCIA interface field in the form of a plug-in strip  4  with 68 poles at the front end (relative to the direction in which it is inserted into the notebook computer, as indicated by the arrow), an upper and lower insertion guide  5 ,  5   a  on the opposing end for introducing a chip-card  9 , e.g., in accordance with ISO 78 16, and a cover plate  6  that extends parallel to and at a distance from the base plate  3  and that is rigidly joined to the base plate  3  in the region of the plug-in strip  4 . The parts of the contact unit cited are carried by the interior plastic profile elements made of PCB and illustrated in FIGS. 2 and 3, which furthermore hold a PCMCIA printed circuit board  7  spaced parallel to the base plate  3  in such a manner that formed therebetween is an insertion channel  8  for the ISO 78 16 chip-card  9  that is insertable into the contact unit via an insertion slot  10  between the insertion guides  5 ,  5   a . The chip-card  9  can be inserted into and withdrawn from the contact unit  1  in the direction of the double arrow shown in FIG. 1, wherein contact can be created by means of the chip field  11  arranged on the surface of the chip-card  9  and a contact field  11 ′ on the underside of the PCMCIA printed circuit board  7 , which contact makes it possible to process the chip-card via the PCMCIA card when the contact unit  1  is inserted into the notebook and is connected to its PCMCIA interface via the plug-in strip  4 . 
     FIG. 2 illustrates the two individual members of the external housing  1 , i.e., the base plate  3  in a perspective view of the interior and the cover plate  6 , flipped 180°, also in a perspective view of the interior. Base plate  3  and cover plate  6  are separate pieces of sheet that are not joined to each other and that have clips  12  bent inward on the longitudinal sides  13 ,  14  and in the back side  15  (relative to direction of insertion), while the front side (relative to direction of insertion) remains free so that the plug-in strip  4  can be arranged there later. In the exemplary embodiment illustrated in FIG. 2, the base plate  3  is provided with a welded reinforcing plate  16  that makes it possible to employ an extraordinarily thin housing sheet of approximately {fraction (2/10)}mm thickness. It should be appreciated that instead of metal, a reinforcing plate  16  made of plastic can be used that can be manufactured, along with other plastic parts described below, in a single process step by means of injection molding. 
     The clips  12  comprise an L shape and it is provided that these be punched from the sheet of the base plate  3  and cover plate  6 , bent upward 90° out of the plane toward the interior and then be bent again 90° inward so that there is a free leg that projects into the subsequent interior of the contact unit  1  parallel to the base plate  3  and cover plate  6  at the clips  12 , which represents a particularly advantageous fastening device for coating the clips  12 , also described below. The number and arrangement of the clips  12  on the base and cover plates  3 ,  6  are coordinated to provide a housing that is as torsion-proof as possible, wherein it has proved useful to provide a plurality of clips  12  on the cover plate  6 , while on the base plate  3 , the plastic profile  18  that constitutes the lower insertion guide  5   a  is held in place with clips  12  on the side  15  and with hooks  17 . The hooks  17  are likewise punched from the sheet for the base plate  3  and bent upward and inward in an L shape. In principle, instead of using clips  12  and hooks  17  punched out of the material of the base and cover plates, it is also possible to use separate fastening elements that then must be mechanically joined to the housing members. 
     FIG. 2 furthermore illustrates the plastic profiles employed in the interior of the contact unit  1 , which profiles in the preferred embodiment are not however manufactured separately and introduced into the housing but rather are manufactured in connection with the corresponding metal parts of the housing in a single process step in the injection molding process. Provided in the front region of the base plate  3  (relative to the direction of insertion) for holding the plug-in strip  4  are plastic holders  19 ,  20  that simultaneously constitute axial stops for limiting the insertion of the chip-card  9  and that comprise corresponding rounded stop surfaces  24 . 
     The plastic holders  19  correspond to correctly shaped holders  25 ,  26  on the free ends of a U-shaped plastic frame  27  that belongs to the cover plate  6  and that at its closed side comprises a strip  28  constituting the upper insertion guide  5  and provided with a platform-type tier  21  for attaching a metal strip  22 . The longitudinal legs of the plastic frame  27  comprise a guide that is open toward the interior and that is in the form of a step  29  for engaging and holding the printed circuit board  7 , which when assembled is fixed by the plastic frame  27 , wherein the holders  25 ,  26  together with the plastic holders  19 ,  20  fix the plug-in strip  4  connected to the printed circuit board  7 . The plastic elements illustrated in FIGS. 2 and 3 are furthermore provided various positioning projections and recesses  30  for positioning purposes. 
     The printed circuit board  7  shown adjacent thereto is arranged on the cover plate  6 , flipped 180°, such that at the front the knobs  31  on the side of the plug-in strip  4  engage in the corresponding recesses on the plastic holders  25 ,  26  and opposing grounded contact surfaces  23  in the printed circuit board  7  are pushed flush under the clamp contacts  32  in the metal strip  22 . The base plate  3  is arranged flipped 180° on the cover plate  6 . This means that formed between the base plate  3  and the cover plate  6  with the printed circuit board  7  is the insertion channel  8  that remains free for introducing the chip-card  9  and that makes it possible for the chip field  11  to contact the PCMCIA card through the contact field  11 ′. 
     The base plate  3  and the printed circuit board  7  in FIGS. 2 and 3 are not shown in their assembled positions, but flipped 180° in order to make it possible to see the interior. It shall be appreciated that allocated to the cover plate  6  is the U-shaped plastic frame  27 , which is held to the cover plate  6  by the corresponding clips  12  and upon which the prepared base plate  3  is placed after assembly with the printed circuit board  7  in the manner described. 
     In addition, in contrast to FIG. 2, FIG. 3 illustrates the correct arrangement of the plastic elements on the base plate  3  and cover plate  6 , wherein it can be seen that the clips  12  are no longer visible. This is due to the preferred manufacturing process used during the manufacture of the contact unit  1  in which the exterior housing members in the form of base plate  3  and cover plate  6  are punched as separate pieces of sheet that are not connected to each other, the clips  12  and hooks  17  being punched and bent inward at the same time; in a second process step the base plate  3  is provided with the plastic holders  19 ,  20  and the plastic profile  18  and the cover plate  6  is provided with the plastic frame  27 , this being done separately using an injection molding process in the form of a unit. The printed circuit board  7  and its plug-in strip  4  are then flipped 180° and placed onto the cover plate  6 , positioned on the metal strip  22  and the plastic holders  25 ,  26 , and in a final process step the housing members pre-assembled in this manner with interior plastic elements are arranged upon each other and joined to each other by means of a plastic joining technique, particularly adhesive or ultrasound welding. 
     FIG. 3 a  illustrates the assembly of the metal strip  22  with the upper insertion guide  5  and FIG. 3 b  illustrates its [the metal strip&#39;s] assembly with the printed circuit board  7 . The clamping contacts  32  in the metal strip  22  are arrested on the grounded contact surfaces  23  on the printed circuit board  7 . Spring elements  33  that are integral to the metal strip  22  engage in the cut-outs  34  of the printed circuit board  7 , as can be seen especially in FIG. 3 b . The metal strip  22  is also provided with bores  35  and grounded contact springs  36 . The bores  35  cooperate with corresponding pins  37  on the tier  21  in the strip  28 , the metal strip  22  and the printed circuit board  7  connected to the metal strip  22  via the clamp contacts  32  being centered on the cover plate  6 . The metal strip  22  is fixed by subsequent ultrasound welding. 
     The functionality of the spring elements  33  integral to the metal strip  22  can be seen in FIGS. 4 and 4 a . FIG. 4 illustrates the contact unit  1  with no chip-card  9  inserted, while as can be seen in FIG. 4 a , the chip-card  9  has been inserted into the insertion channel  8  up to the rounded stop surfaces  24 , the chip field  11  of the chip-card  9  coming to rest at the contact field  11 ′ in the printed circuit board  7 . The spring element  33  is essentially S-shaped and is provided at its free end with a claw-shaped extension  39  that engages under prestress when there is no inserted chip-card  9  a lock element  40  embodied as a recess in the reinforcing plate  16 . As can be seen in FIG. 4 a , the lock element  40  comprises an undercut that ensures that the spring element  33  is arrested. The cover plate  6  and the base plate  3  are connected to each other by the plastic holders  19 ,  20 ,  25 ,  26  such that they are subject to a clamping force. The spring element  33  ensures that the height of the insertion channel  8  does not change, which facilitates simple insertion of the chip-card  9 . When the chip-card  9  is inserted into the insertion channel  8 , the front of the chip-card  9  (relative to direction of insertion) presses the spring element  33  in the direction of the cover plate, the spring element  33  being pressed through the cut-out  34  in the printed circuit board  7  against the metal cover plate  6 . Thus the chip-card  9  can be inserted into the insertion channel  8  up to the rounded stop surfaces  24  and is clamped therein by the internal stress inherent in the base and cover plates  3 ,  6 . In addition, the spring element  33  presses on the chip-card  9  so that contact is assured between chip-card  11  and contact field  11 ′. When the chip-card  9  is removed from the insertion channel  8 , the spring element  33  returns to the lock element  40 , this also creating a connection between metal strip  22  respectively to cover plate  6  and base plate  3 . 
     The alternative embodiment of the contact unit  1  illustrated in FIGS.  5  through  7   a  comprises on the base plate  3  and cover plate  6  in the region adjoining the insertion channel  8  in the direction of insertion additional welded brackets  41  by means of which the base plate  3  and cover plate  6  are joined together and the clamping internal stress in the contact unit  1  is obtained. In contrast to the embodiment in accordance with FIGS. 2 through 4 a , the metal strip  22  does not comprise the spring element  33  so that when no chip-card  9  is inserted the insertion channel  8  in the contact unit  1  tapers from the welded brackets (which are also the swivelling axis) in the direction of the upper and lower insertion guides  5 ,  5   a . When a chip-card  9  is inserted, the insertion channel  8  expands while generating a restoring force, this holding the chip-card  9  in the insertion channel  8  in a clamping manner. The welded brackets  41  on the cover plate  6  are offset for enabling the brackets  41  to be welded without infringing on the width dimensions in the PCMCIA standard. In addition, the plastic holders  19 ,  20 ,  25 , and  26  can be welded together in a known manner. 
     From FIGS. 2 and 5 it can be seen that the reinforcing plate  16  can be provided with an insulating film or element  42  that is used particularly when the reinforcing plate  16  is made of metal so that short-circuits can be prevented between the contact field  11 ′ on the printed circuit board  7  and the reinforcing plate  16  arranged opposed thereto. In addition, a wear-resistant insulating film can be applied to the underside of the printed circuit board  7  to prevent wear on the chip-card  9  and to simultaneously insulate the conductors and through-contacts on the printed circuit board  7  on the side facing the insertion channel  8 . It can also be seen from FIG. 2 that the lock element  40  can also embody a separate component that is pressed into recesses in the reinforcing plate  16 . This is particularly simple and cost-effective. In order to make it simple to introduce a chip-card  9  into the insertion channel  8 , the lower insertion guide  5   a  can in addition be embodied in the form of a lower lip (relative to the upper insertion guide  5  in the direction in which the chip-card  9  is inserted). 
     With the contact unit  1  described in the foregoing a chip-card reader is created that precisely corresponds to PCMCIA dimensions when a chip-card is not inserted and that provides assured contact and sufficient mechanical stability. In addition, security is increased in that the cover plate  6  and base plate  3  are congruent so that when inserted into the PCMCIA slot in a computer the base plate  3  and cover plate  6  are conducted into the lateral guides in the PCMCIA slot. This prevents the cover plate  6  from being forcibly bent upward or downward relative to the base plate  3  in an adjacent PCMCIA slot in the computer. Furthermore, the metal embodiment of the base plate  3  and cover plate  6  provides shielding and a high degree of functional stability and stability in the contact unit  1 , even at high stagnation and ambient temperatures above 100° C. Finally, the contact unit  1  is also distinguished by simple and cost-effective manufacture. 
     The specification incorporates by reference the disclosure of German priority document 298 11 425.9 of Jun. 29, 1998 and European Patent Application priority document PCT/EP99/03560 of May 25, 1999. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims. 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                  1 
                 Contact unit 
               
               
                  2 
                 Exterior housing 
               
               
                  3 
                 Base plate 
               
               
                  4 
                 Plug-in strip 
               
               
                  5 
                 Upper insertion guide 
               
               
                  5a 
                 Lower insertion guide 
               
               
                  6 
                 Cover plate 
               
               
                  7 
                 PCMCIA printed circuit 
               
               
                   
                 board 
               
               
                  8 
                 Insertion channel 
               
               
                  9 
                 Chip-card 
               
               
                 10 
                 Insertion slot 
               
               
                 11 
                 Chip field 
               
               
                     11′ 
                 Contact field 
               
               
                 12 
                 Clips 
               
               
                 13 
                 Longitudinal side 
               
               
                 14 
                 Longitudinal side 
               
               
                 15 
                 Side 
               
               
                 16 
                 Reinforcing plate 
               
               
                 17 
                 Hook 
               
               
                 18 
                 Plastic profile 
               
               
                 19 
                 Plastic holder 
               
               
                 20 
                 Plastic holder 
               
               
                 21 
                 Platform or tier 
               
               
                 22 
                 Metal strip 
               
               
                 23 
                 Ground contact surface 
               
               
                 24 
                 Stop surfaces 
               
               
                 25 
                 Plastic holder 
               
               
                 26 
                 Plastic holder 
               
               
                 27 
                 Plastic holder 
               
               
                 28 
                 Strip 
               
               
                 29 
                 Step 
               
               
                 30 
                 Positioning 
               
               
                   
                 projection/recess 
               
               
                 31 
                 Knobs 
               
               
                 32 
                 Clamp contact 
               
               
                 33 
                 Spring element 
               
               
                 34 
                 Cut-out 
               
               
                 35 
                 Bore 
               
               
                 36 
                 Grounded contact spring 
               
               
                 37 
                 Pin 
               
               
                 38 
                 End stop 
               
               
                 39 
                 Extension 
               
               
                 40 
                 Lock element 
               
               
                 41 
                 Welded bracket 
               
               
                 42 
                 Insulating element