Abstract:
In a connector unit having primary and secondary connectors ( 11  and  12 ) which have a plurality of primary contact leads ( 111 ) and a plurality of secondary contact leads ( 121 ) which correspond to the respective primary contact leads ( 111 ), the primary contact leads ( 111 ) have primary contact ends displaced from one another in a predetermined direction. The secondary contact leads ( 121 ) have secondary contact ends which are extended in an opposite direction to be contacted with the corresponding primary contact ends and which are displaced stepwise to compensate for the displacement of the primary contact ends and to thereby reduce a variation of sums of the primary and the secondary contact leads ( 111  and  121 ).

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. Ser. No. 09/335,681, filed Jun. 18, 1999, which claims priority under 35 USC §119 from Japanese application JP 10-172587, filed Jun. 19, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a connector unit for electrical and removable connection of primary and secondary electric devices and, in particular, to the connector unit which comprises primary and secondary connectors connected to the primary and the secondary electric devices. 
     In a conventional connector unit of the type described above, the primary and the secondary connectors generally comprise a plurality of primary and secondary contact leads, respectively. Furthermore, at least one of the primary and the secondary connectors (for example, the primary connector) is generally a right-angle type so that one (primary) contact lead is arranged over top of another in turn. Namely, one primary contact lead is arranged over top of another in a height direction of the primary connector. 
     When the primary and the secondary connectors are connected to each other, the primary contact leads and the secondary contact leads are connected to each other, respectively, to thereby form a plurality of signal paths for transmitting signals, respectively. The signal paths have different lengths from one another. This is because one primary contact lead is longer than another as mentioned above. Therefore, signals transmitted through the signal paths are different from one another in delay or passage time. The delay-time difference among transmission of signal is often called “skew”. 
     Recently, the connector unit is requested to transmit high frequency signal at a high speed when applied to such electric devices as a circuit board provided with a large scale integrated semiconductor chip, a data storage device, and so on. However, the electric devices can not perform their functions at a desired high speed by signal transmission through the conventional connector unit because the signals transmitted through the signal paths have different delay times as described above. 
     Furthermore, the connector unit is also required to increase a number of signal paths because the electric devices recently tend to because large in the number of input/output signals. In the conventional connector unit, when the number of signal paths is increased, the numbers of the primary contact leads and the secondary contact leads must be also increased. This results in an increase of a difference between the shortest length and the longest one of the primary contact leads. As the difference in length among the signal paths becomes large, a difference among the time delays are also increased. 
     Also, the connector unit is required to reduce a size thereof because electric devices having a compact size suitable for a mobile and/or a small place use are recently required. Particularly, the connector unit is required to reduce a height thereof when mounted on the electric device such as the circuit board. When heights of the connectors are reduced while the number of signal paths is increased as mentioned above, the primary and the secondary contact leads arranged in the connectors must be arranged at a very short pitch. Such a very short pitch of arrangement increases a cross talk between adjacent ones of the contacts. 
     In order to transmit a high frequency signal, two conventional connectors are disclosed for example in Japanese Patent Unexamined Publications (JP-A) Nos. 315916/1996 and 122335/1995, respectively. The connectors have the contact leads arranged at a slant in order to shorten lengths thereof. Furthermore, the signal contact leads are arranged alternately with the ground contact leads and/or the signal contact leads are surrounded by the ground contact leads. Thus, this structure enables improvement of the cross talk mentioned above. However, the skew is not much improved by both the connectors maintained in both of the publications. In addition, the height and/or the size can not be small with both the connectors. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a connector unit which can transmit signals at a substantially equal delay time. 
     It is another object of the present invention to provide a connector unit which can make signal paths substantially equal to one another in delay time. 
     It is still another object of the present invention to provide a connector unit which can be reduced in height thereof. 
     The other objects, features, and advantages of the present invention will become clear as the following description proceeds. 
     The present invention is directed to a connector unit comprising a primary connector which has a plurality of primary contact leads extended in a predetermined direction and a secondary connector having a plurality of secondary contact leads extended in a direction opposite to the predetermined direction. The primary contact leads have a plurality of primary contact ends, respectively. On the other hand, the secondary contact leads have a plurality of secondary contact ends brought into contact with the corresponding primary contact ends. The primary contact ends are displaced stepwise in the predetermined direction while the secondary contact ends are displaced stepwise to compensate for the displacement of the primary contact ends and to thereby shorten a variation of sums of the primary and the secondary contact leads. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing a conventional connector unit; 
     FIG. 2 is a cross sectional view of the connector unit with the two connectors thereof connected to each other shown in FIG. 1 along a line A 1 -A 2  in FIG. 1; 
     FIG. 3 is a perspective view showing a connector unit according to a first embodiment of the present invention; 
     FIG. 4 is a cross sectional view of the connector unit with the two connectors thereof connected to each other shown in FIG. 3 along a line B 1 -B 2  in FIG. 3; 
     FIG. 5 is a perspective view showing a connector unit according to a second embodiment of the present invention; 
     FIG. 6 is a cross sectional view of the connector unit with the two connectors thereof connected to each other shown in FIG. 5 along a line C 1 -C 2  in FIG. 5; and 
     FIG. 7 is a cross sectional view showing a connector unit according to a third embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In order to facilitate an understanding of the present invention, description will at first be made with reference to the drawing about a conventional connector unit which is substantially equivalent to that described in the preamble of the present specification. 
     Referring to FIGS. 1 and 2, the conventional connector unit is used for electrical and removable connection between primary and secondary printed circuit boards  700  and  800  as primary and secondary electric devices. The connector unit comprises primary and secondary connectors  21  and  22  respectively mounted on one main surfaces of the printed circuit boards  700  and  800 . 
     The primary connector  21  comprises a primary insulator  212  and a plurality of primary contact-sets respectively provided with six primary contact leads  211  and supported in the primary insulator  212 . The primary contact-sets are arrayed horizontally in parallel with one another so that the primary contact leads are superposed on one another with a space left in the primary insulator  212 . The primary contact leads  211  are arranged in parallel to one another. The primary contact leads  211  have different lengths from one another. This is because that the primary connector is the right-angle type so that one primary contact lead  211  is arranged over top of another primary contact lead  211  in turn. In other words, one primary contact lead  211  is arranged over top of another primary contact lead  211  in a height direction of the primary connector  21 . One ends of each of the primary contact leads  211  are soldered in the primary printed circuit board  700 . Furthermore, the primary insulator  212  is fixed on the primary printed circuit board  700  by the use of screws  21   d.    
     Likewise, the secondary connector  22  comprises a secondary insulator  222  and a plurality of secondary contact-sets respectively provided with six secondary contact leads  221  and supported in the secondary insulator  222 . The secondary contact-sets are arrayed horizontally in parallel with one another so that the secondary contact leads are superposed on one another with a space left in a direction of the secondary insulator  222 . The secondary contact leads  221  of each set are horizontally extended and arranged in parallel to one another. However, it is to be noted that the secondary contact leads  221  have the same length as one another. Namely, the secondary connector  22  has no bent portion and is not the right-angle type connector. In any event, the secondary contact leads  221  have ends soldered to the secondary printed circuit board  800 . 
     As is apparent from FIG. 2, a plurality of signal paths for transmitting signals are formed or established between the primary and the secondary printed circuit boards  700  and  800 . The signal paths have different lengths from one another because the primary contact leads  211  have different lengths from one another as mentioned above. 
     The conventional connector unit has disadvantages, as described in the preamble of the instant specification. 
     Now, preferred embodiments of the present invention will be described with reference to FIGS. 3 to  7 . 
     First Embodiment 
     Referring to FIGS. 3 and 4, a connector unit according to a first embodiment of the present invention is used for electrical and removable connection between primary and secondary printed circuit boards  100  and  200  which will be called as primary and secondary electric devices, respectively. The primary printed circuit board  100  is horizontally extended and is provided with first and second main surfaces on which wiring patterns (not shown) are printed. The connector unit comprises primary and secondary connectors  11  and  12  both of which are electrically connected to each other. The illustrated primary connector  11  is divided into first and second primary connectors  11   a  and  11   b  which are mounted on and attached to first and second main surfaces of the primary printed circuit board  100 , respectively. 
     On the other hand, the secondary connector  12  is mounted on and attached to a main surface of the secondary printed circuit board  200  perpendicular to the primary printed circuit board  100 . 
     In the primary connector  11 , each of the first and the second primary connectors  11   a  and  11   b  comprises a primary insulator  112  and a plurality of primary contact-sets arranged in adjacent rows. As showing FIG. 4, each of the primary contact-sets is provided with three primary contact leads (collectively shown by  111 ) and which are supported in the primary insulator  112 . Although not explicitly shown in FIGS. 3 and 4, a pair of primary contact-sets is horizontally arrayed in parallel to one another so that the primary contact leads  111  in each pair of the primary contact-sets are identical with or superposed on one another in the primary insulator  112 . The primary contact leads  111  of each primary contact-sets are arranged in parallel to one another and have different lengths from one another, like in FIGS. 1 and 2 are. More specifically, each primary contact-set comprises first through third primary contact leads  111 - 1 ,  111 - 2 , and  111 - 3 . The number of the primary contact leads may not be restricted to three but increased or decreased. In this connection, the number of the primary contact leads may be generalized by n, where n is an integer not smaller than 2. As shown in FIG. 4, the primary contact lead  111 - 2  is arranged or stacked over the primary contact lead  111 - 1  with a spacing left to the primary contact lead  111 - 1  and the primary contact lead  111 - 3  is arranged or stacked over the primary contact lead  111 - 2  with a spacing left to the primary contact lead  111 - 2  in turn. From this fact, it is readily understood that an n-th one of the primary contact lead is arranged over an (n−1)-th primary contact lead  111 -(n−1) in a height direction of the primary connector  11 . As shown in FIG. 4, the primary contact lead  111 - 2  is longer than the primary contact lead  111 - 1  and the primary contact lead  111 - 3  is longer than the primary contact lead  111 - 2  in turn. 
     The first and the second primary connectors  11   a  and  11   b  are mechanically coupled to each other by screws  11   d  to support the primary printed circuit board  100 . In addition, the primary contact leads  111  of the first and the second primary connectors  11   a  and  11   b  are press-fitted to the first and the second main surfaces of the primary printed circuit board  100  to be electrically connected to the printed circuit, respectively. Namely, the primary contact leads  111  have one ends connected mechanically and electrically to the primary printed circuit board  100  without soldering. 
     The primary contact leads  111  of the first and the second primary connectors  11   a  and  11   b  are provided with first portions which are contiguous to and extended from the first and the second primary main surfaces of the primary printed circuit board  100  in a direction remote from the main surfaces and second portions which are extended from the first portions in parallel to the first and the second primary main surfaces, respectively. The primary contact leads  111  except for both ends thereof are embedded in the primary insulator  112 . One and the other ends of the primary contact leads  111  have elasticity. 
     On the other hand, the secondary connector  12  comprises a secondary insulator  122  and first and second contact lead-groups of secondary contact leads arranged in adjacent rows corresponding to the rows of the primary contact. The first and the second contact lead-groups are provided with a plurality of secondary contact-sets, respectively. The secondary contact-sets are arrayed horizontally in parallel with one another so that the secondary contact leads  121  are identical with those of the other sets and can be superposed on one another. The secondary contact-sets are provided with three secondary contact leads (collectively shown by  121 ) in each of the first and the second contact-groups. 
     The secondary contact leads  121  of each contact-groups are arranged in parallel to one another as shown in FIG.  4 . The secondary contact leads  121  have different lengths from one another. More particularly, the illustrated secondary contact leads  121  are composed of first through third secondary contact leads  121 - 1 ,  121 - 2 , and  121 - 3  but the number of the secondary contact leads may be represented by n, like in the primary contact leads. Therefore, the secondary contact leads may be generally expressed as first thorough n-th contact leads. As shown in FIG. 4, the secondary contact lead  121 - 2  is arranged or stacked over the secondary contact lead  121 - 1  with a spacing left to the secondary contact lead  121 - 1  and the secondary contact lead  121 - 3  is arranged or stacked over/under the secondary contact lead  121 - 2  with a spacing left to the secondary contact lead  121 - 2  in turn. Thus, an n-th one of the secondary contact lead is arranged over/under an (n−1)-th secondary contact lead  121  -(n−1) in a height direction of the secondary connector  12 . As shown in FIG. 4, the secondary contact lead  121 - 2  is shorter than the secondary contact lead  121 - 1  and the secondary contact lead  121 - 3  is shorter than the secondary contact lead  121 - 2  in turn. One ends of each of the secondary contact leads  121  are connected mechanically and electrically to the secondary printed circuit board  200  by soldering. 
     The secondary contact leads  121  are extended in straight from the secondary main surface of the secondary printed circuit board  200  in perpendicular to the main surface, respectively. The secondary contact leads  121  are supported by or embedded in the secondary insulator  122  approximately all over one to the other ends thereof. 
     When the secondary connector  12  is positioned so that the secondary contact leads  121  are directed in parallel to the second portions of the primary contact leads  111 , the secondary contact leads  121  are connected to the second portion of the primary contact leads  111  as shown in FIG.  4 . Herein, the second portions of the primary contact leads  111  and the secondary contact leads  121  are respectively connected to each other where each end of the second portions and each end of the secondary contact leads  121  are offset to one another in a depth direction of the connector unit extending in parallel to the first and the second primary main surfaces of the primary printed circuit board  100 . 
     As is apparent from FIG. 4, a plurality of signal paths for transmitting signals are formed or established between the primary and the secondary printed circuit boards  100  and  200 . The signal paths are substantially equal to one another in length because the secondary contact leads  121  have different lengths from one another so that respective sums of the primary and the secondary contact leads  111  and  121  are substantially equal to one another in length. 
     More specifically, a signal path established by the primary and the secondary contact leads  111 - 1  and  121 - 1 , a signal path established by the primary and the secondary contact leads  111 - 2  and  121 - 2 , a signal path established by the primary and the secondary contact leads  111 - 3  and  121 - 3  are approximately equal to one another. Therefore, signals transmitted through the signal paths are delayed by approximately equal delay times. 
     Furthermore, the connector unit can be reduced in height thereof even if the connector unit has many contact leads because the connector unit is mounted on the primary electric device so as to be located over both sides of the electric while not only one side of that. The reason is also why the primary and the secondary contact leads  111  and  121  are respectively connected to each other where each end of the second portions and each end of the secondary contact leads  121  are offset to one another in a depth direction of the connector unit extending in parallel to the first and the second primary main surfaces of the primary printed circuit board  100 . In other words, the connector unit can be provided with a wide arrangement pitch of contact leads if the connector unit has the same number of the contact leads as the conventional unit. Thus, the connector unit has an advantage about the matter of the cross talk. 
     Second embodiment 
     A connector unit according to a second embodiment of the present invention has the secondary connector designated by the same reference numerals that are described in the first embodiment with illustrating by FIGS. 3 and 4. The secondary connector  12  is omitted in detailed description. 
     Referring to FIGS. 5 and 6, the connector unit according to the second embodiment of the present invention is used for electrical and removable connection between a flat ribbon cable  400  as a primary electric device and the secondary printed circuit board  200  as a secondary electric device. 
     The flat ribbon cable  400  has a bifurcated or forked end which is divided into first and second end portions of the upper and the lower sides shown in FIG.  6 . The first and the second end portions have printed wiring patterns (not shown) thereon, respectively. 
     The illustrated connector unit, it is to be noted that a primary connector  31  is different in structure from the primary connector  11  shown in FIG. 4 but the secondary connectors  1   2  are same as those of FIG.  4 . The primary connector  31  is divided into first and second primary connectors  31   a  and  31   b  respectively connected to first and second end portions of the flat ribbon cable  400  and a spacer  31   c  held between the first and the second primary connectors  31   a  and  31   b  through the first and the second end portions of the flat ribbon cable  400 . 
     The first and the second primary connectors  31   a  and  31   b  comprise a primary insulator  312  and a plurality of primary contact-sets, respectively. The primary contact-sets are provided with three primary contact leads (collectively shown by  311 ) and which are supported in the primary insulator  312 , respectively. The primary contact-sets are arrayed horizontally in parallel with one another so that the primary contact leads  311  are superposed on one another with a space left in the primary insulator  312 . The primary contact leads  311  are arranged in parallel to one another. The primary contact leads  311  have different lengths from one another like that of the first embodiment illustrated by FIGS. 3 and 4. More specifically, the primary contact lead  311  comprises primary contact leads  311 - 1 ,  311 - 2 , and  311 - 3  as first through n-th primary contact leads. Herein, “n” is an integer not smaller than 2. The primary contact lead  311 - 2  is arranged over top of the primary contact lead  311 - 1  and the primary contact lead  311 - 3  is arranged over top of the primary contact lead  311 - 2  in turn. In other words, an n-th primary contact lead is arranged over top of an (n−1)-th primary contact lead in a height direction of the primary connector  31 . Thus, the primary contact lead  311 - 2  is longer than the primary contact lead  311 - 1  and the primary contact lead  311 - 3  is longer than the primary contact lead  311 - 2  in turn. 
     The first and the second primary connectors  31   a  and  31   b  and the spacer  31   c  hold in cooperation with one another the first and the end portions of the flat ribbon cable  400  therebetween by using screws  31   d.  Thus, the primary contact leads  311  of the first and the second primary connectors  31   a  and  31   b  are press-fitted to the first and the second end portions of the flat ribbon cable  400 , respectively. Namely, One ends of each of the primary contact leads  311  are capable of being connected mechanically and electrically to the flat ribbon cable  400  without soldering. 
     The primary contact leads  311  of the first and the second primary connectors  31   a  and  31   b  are provided with first portions which are extended from the flat ribbon cable  400  and second portions which are extended from the first portions in parallel to the flat ribbon cable  400 , respectively. The primary contact leads  311  without one and the other ends thereof are supported by the primary insulator  312 . One and the other ends of the primary contact leads  311  has elasticity, respectively. 
     When the secondary connector  12  is positioned so that the secondary contact leads  121  are directed in parallel to the second portions of the primary contact leads  311 , the secondary contact leads  121  are connected to the primary contact leads  311  as shown in FIG.  6 . Herein, the second portions of the primary contact leads  311  and the secondary contact leads  121  are respectively connected to each other where each end of the second portions and each end of the secondary contact leads  121  are offset to one another in a depth direction of the connector unit extending in parallel to the first and the second end portions of the flat ribbon cable  400 . 
     As is apparent from FIG. 6, a plurality of signal paths for transmitting signals are formed or established between the flat ribbon cable  400  and the secondary printed circuit board  200 . The signal paths are substantially equal to one another in length because the secondary contact leads  121  have different lengths from one another so that respective sums of the primary and the secondary contact leads  311  and  121  are substantially equal to one another in length. 
     More specifically, a signal path established by the primary and the secondary contact leads  311 - 1  and  121 - 1 , a signal path established by the primary and the secondary contact leads  311 - 2  and  121 - 2 , a signal path established by the primary and the secondary contact leads  311 - 3  and  121 - 3  are approximately equal to one another. Therefore, signals transmitted through the signal paths are also equal to one another in delay time. 
     Furthermore, the connector unit can be reduced in height thereof even if the connector unit has many contact leads because the connector unit is mounted on the flat ribbon cable  400  so as to be located on both sides of the flat ribbon cable  400  without being mounted on only one side of that. The reason is also why the primary and the secondary contact leads  311  and  121  are respectively connected to each other where each end of the second portions and each end of the secondary contact leads  121  are offset to one another in a depth direction of the connector unit extending in parallel to the first and the second end portions of the flat ribbon cable  400 . In other words, the connector unit can be provided with a wide arrangement pitch of contact leads if the connector unit has contact leads equal number of the conventional unit. Thus, the connector unit has an advantage about the matter of the cross talk. 
     Third embodiment 
     A connector unit according to a second embodiment has the secondary connector designated by the same reference numerals that are described in the first and the second embodiments with illustrating by FIGS. 3 to  6 , respectively. The secondary connector  12  is omitted in detailed description. 
     Referring to FIG. 7, a connector unit according to a third embodiment of the present invention is used for electrical and removable connection between a primary printed circuit boards  600  as a primary electric device and the secondary printed circuit board  200  as the secondary electric device. The primary printed circuit board  600  is provided with a primary main surface. 
     The connector unit comprises a primary connector  51  and the secondary connector  12 . The primary connector  51  comprises a primary insulator  512  and first and second contact lead-groups of primary contact leads. The first and the second contact lead-groups of the primary contact leads are provided with a plurality of primary contact-sets, respectively. The primary contact-sets are arrayed horizontally in parallel with one another so that the primary contact leads  511  are superposed on one another with a space left in the primary insulator  512 . The primary contact-sets are provided with three primary contact leads (collectively shown by  511 ), respectively. 
     The primary contact leads  511  are arranged in parallel to one another. The primary contact leads  511  have different lengths from one another. More specifically, the primary contact lead  511  comprises primary contact leads  511 - 1 ,  511 - 2 , and  511 - 3  as first through n-th primary contact leads. The primary contact lead  511 - 2  is arranged over top of the primary contact lead  511 - 1  and the primary contact lead  511 - 3  is arranged over top of the primary contact lead  511 - 2  in turn. In other words, an n-th primary contact lead is arranged over top of an (n−1)-th primary contact lead in a height direction of the primary connector  51 . Thus, the primary contact lead  511 - 2  is longer than the primary contact lead  511 - 1  and the primary contact lead  511 - 3  is longer than the primary contact lead  511 - 2  in turn. One ends of each of the primary contact leads  511  are connected mechanically and electrically to the primary printed circuit board  600  by soldering. 
     The primary contact leads  511  are extended in straight from the primary main surface of the primary printed circuit board  600  in perpendicular to the main surface, respectively. The primary contact leads  511  are supported by the primary insulator  512  over one to the other ends thereof. 
     When the secondary connector  12  is positioned so that the secondary contact leads  121  are directed in parallel to the primary contact leads  511 , the secondary contact leads  121  are connected to the primary contact leads  511  with the primary and the secondary printed circuit boards  600  and  200  parallel to each other. Herein, the primary contact leads  511  and the secondary contact leads  121  are respectively connected to each other where each end of the primary contact leads  511  and each end of the secondary contact leads  121  are offset to one another in a depth direction of the connector unit extending in parallel to the primary main surface of the primary printed circuit board  600 . 
     As is apparent from FIG. 7, a plurality of signal paths for transmitting signals are formed or established between the primary and the secondary printed circuit boards  600  and  200 . The signal paths are substantially equal to one another in length because the secondary contact leads  121  have different lengths from one another so that respective sums of the primary and the secondary contact leads  511  and  121  are substantially equal to one another in length. 
     More specifically, a signal path established by the primary and the secondary contact leads  511 - 1  and  121 - 1 , a signal path established by the primary and the secondary contact leads  511 - 2  and  121 - 2 , a signal path established by the primary and the secondary contact leads  511 - 3  and  121 - 3  are approximately equal to one another. Therefore, signals transmitted through the signal paths are also equal to one another in delay time. 
     Furthermore, the connector unit can be reduced in height thereof even if the connector unit has many contact leads because the primary and the secondary contact leads  511  and  121  are respectively connected to each other where each end of the primary contact leads  511  and each end of the secondary contact leads  121  are offset to one another in a depth direction of the connector unit extending in a direction remote from the primary main surface of the primary printed circuit board  600 . In other words, the connector unit can be provided with a wide arrangement pitch of contact leads if the connector unit has contact leads equal number of the conventional unit. Thus, the connector unit has an advantage about the matter of the cross talk. 
     In the embodiments described above, one part connected to another part may be practically and concretely connected by the use of press-fitting or soldering. On the other hand, one part removably connected to another part may be practically and concretely connected by the use of press-fitting or the removable insertion of the ZIF—(Zero Insertion Force)—type known already. 
     While the present invention has thus far been described in conjunction with embodiments thereof, it will readily be possible for those skilled in the art to put the present invention into practice in various other manners.