Patent Publication Number: US-5839917-A

Title: Connector for flat cable

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a connector for a flat cable, and more particularly to a compact connector for a flat cable, which is suitable for a high density packaging on a printed circuit board. 
     High density packaging and scaling down of electronic elements on a printed circuit board have been required, whereby the connector for a flat cable has also been required to be adjusted for the high density packaging and its substantial scaling down. Typical connectors for the flat cable are disclosed in the Japanese laid-open patent publications Nos. 6-77186 and 5-84071. 
     FIG. 1 is a cross sectional elevation view illustrative of a conventional connector for a flat cable, which is disclosed in the Japanese laid-open patent publication No. 6-77186. A connector 1 comprises a housing 2 which is box-shaped but opened at opposite sides, and a contact member 6 mechanically engaged with the housing 2 as well as a lever also engaged with the housing 2 for holding a flat cable 4 in cooperation with the lever 5. The contact member 6 is inserted via a first opening side of the housing 2 into the interior of the housing 2. The contact member 6 comprises a body 6d vertically extending, a supporting head 6a laterally extending from an upper portion of the body 6d toward the interior of the housing 2, a U-shaped spring portion 6b largely and laterally extending from a lower portion of the body 6d toward the interior of the housing 2 and a lead terminal portion 6c provided at the lower portion of the body 6d but in the opposite side to the U-shaped spring portion. The supporting head 6a extends under an inner surface of the top wall of the housing 2. The supporting head 6a has a top which is cyrindrically shaped and fitted with a cyrindrically shaped recess formed at a lower portion of the lever so as to allow a pivotal motion of the lever around the cyrindrically shaped top of the supporting head 6a for securing the flat cable 4 in cooperation with the U-shaped spring portion 6b of the contact member 6. The U-shaped spring portion 6b comprises lower portion extending over an inner surface of the bottom wall of the box-shaped housing 2 and an upper portion connected via a curved portion to the lower portion and positioned over the lower portion thereof. The top of the upper portion of the U-shaped spring portion 6b has a convex portion which may be in contact with the bottom surface of the flat cable 4. The lever 5 has a holding head portion 5a. When the lever 5 stands vertically, the holding head portion 5a of the lever 5 fits the top surface of the flat cable 4 so that the flat cable 4 is sandwiched between the holding head portion 5a of the lever 5 and the convex provided on the top of the upper portion of the U-shaped spring portion 6b. 
     In order to realize the high density packaging and the substantial scaling down of the connector, it is required to make the pitch between the adjacent contact members 6 narrow, whilst the adjacent contact members 6 are required to be spaced for isolation between them. This limitation to the pitch between the contact members 6 prevents the scaling down of the connector. 
     Further, in order to realize the high density packaging and the substantial scaling down of the connector, it is required to limit the height of the connector 1. This requires a limitation in thickness of the supporting head 6a even the supporting head 6a receives a stress by pivotal motion of the lever 5. Namely, if the substantial scaling down of the connector takes place, this makes it difficult for the supporting head 6a of the contact member 6 to have a sufficient thickness for supporting the pivotal motion of the lever 5. For this reason, the supporting head 6a of the contact member 6 is required to support the levers in cooperation with a part of the top wall of the housing 2. The walls of the housing 2 are made of a plastic material for electrical isolation. In the light of a possible reduction in height of the connector 1, it is difficult to have the top wall of the housing 2 with a sufficient thickness for supporting the pivotal motion of the lever 5 in cooperation with the supporting head 6a of the contact member 6. The frequent pivotal motions of the lever 5 may cause creeps which lead to permanent deformations of the plastic housing 2 and the supporting head 6a of the contact member 6. As a result, a stress appears on the lead terminal portion 6c of the contact member 6 thereby causing cracking the lead terminal portion 6c which has to be soldered with pads of the printed circuit board. This makes it difficult to ensure a stable connection between the connector and the printed circuit board. 
     Another conventional connector is disclosed in the Japanese laid-open patent publication No. 5-84071. FIG. 2 is a decomposed cross sectional view illustrative of the conventional connector. FIG. 3 is a plane view illustrative of the conventional connector. FIG. 4 is a cross sectional view illustrative of the conventional connector. The connector 8 comprises a box-shaped mold 11, and first and second contact members 9 and 12. The box-shaped mold 11 has opposite open sides through which the first and second contact members 9 and 12 are inserted into the interior of the box-shaped mold 11. A flat cable 10 is inserted into the box-shaped mold 11 from the same side as the second contact member 12 is inserted thereinto. The first contact member 9 comprises a base portion laterally extending over an inner surface of the bottom wall of the box-shaped mold 11 and a head portion 9b laterally extending under an inner surface of the top wall of the box-shaped mold 11. The base portion and the head portion 9b are connected via a vertically extending portion and both extend in parallel to each other. The head portion 9b has a top portion which has a convex portion 9a extending downwardly for holding the flat cable 10. The first contact 9 also has a lead terminal portion 9c which is provided at an opposite side to the base portion. The first contact 9 is electrically connected via the lead terminal portion 9c to pads of the printed circuit board. The second contact 12 also has a base portion laterally extending over the bottom wall of the mold 1 and a head portion 12b laterally extending under an inner surface of the top wall of the mold 11. The base portion and the head portion 12b are connected via a vertically extending portion. The head portion 12b has a top which is provided with an convex 12a extending downwardly for securing the flat cable 10. As can be understood from FIG. 3 that the first contacts 9 arc aligned at the first side of the mold 11 at a predetermined constant pitch and the second contacts 12 are also aligned at the second side of the mold 11 at a predetermined constant pitch but the first and second contacts 9 and 12 aligned to alternate with each other so as to be isolated from each other. 
     It is required to isolate the first and second contacts 9 and 12 from each other. This limits the scaling down of the connector 8 and bars for improvement in he high density packaging on the printed circuit board. 
     In the above circumstances, it had been required to develop a novel connector for a flat cable, which is substantially scaled down and suitable for high density packaging on printed circuit broads. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a novel connector for a flat cable, which is free from any problems or disadvantages as described above. 
     It is a further object of the present invention to provide a novel connector for a flat cable, which is substantially scaled down. 
     It is a still further object of the present invention to provide a novel connector for a flat cable, which is suitable for a high density packaging on printed circuit broads. 
     The above and other objects, features and advantages of the present invention will be apparent from the following descriptions. 
     The present invention provides a connector for a flat cable comprising the following elements. A housing is provided, which comprises a rectangular-shaped base portion defined by first and second sides opposite to each other and parallel to a first lateral direction and third and fourth sides opposite to each other and parallel to a second lateral direction which is vertical to the first lateral direction, and first and second side walls provided on the third and fourth sides. A plurality of first contacts are provided, each of which has a first contact convex and a first lead terminal. The first contacts laterally extend from the first side toward the second side in the second direction. The first lead terminals project from the first side outwardly in the second direction. The first contact convex portions are provided at inner and top end portions of the first contacts. The first contact convex portions face upwardly. The first contacts are discontinuously aligned at a first pitch to form a first line in parallel to the first direction. A plurality of second contacts are provided, each of which has a second contact convex and a second lead terminal. The second contacts laterally extend from the second side toward the first side in the second direction. The second lead terminals project from the second side outwardly in the second direction. The second contact convex portions are provided at inner and top end portions of the second contacts. The second contact convex portions face upwardly. The second contacts are discontinuously aligned at a second pitch to form a second line in parallel to the first line. The second line is distanced from the first line in the second direction. Each of the second contact convex portions are positioned to correspond to an intermediate position between adjacent two of the first contact convex portions in the first direction so that the first and second contact convex portions are positioned to alternate to each other in the first direction. A lever is further pivotally provided to the side walls of the housing. The lever has an engaging portion which is spaced over the first and second contact convex portions for sandwiching a flat cable between the engaging portion and the first and second contact convex portions. 
     The above arrangement of the first and second contact convex portions of the first and second contacts substantially shortens the pitch of the contact points of the flat cable into a half in the first direction even the adjacent two of said first and second contact convex portions are distanced from each other by at least a minimum distance necessary for isolation between them. This provides a reduction in size of nearly one half along the first direction of the connector while the necessary isolation is ensured for the adjacent first and second contacts, resulting in a substantial reduction in size of the connector. 
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
     Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     FIG. 1 is a cross sectional elevation view illustrative of a conventional connector for a flat cable. 
     FIG. 2 is a decomposed cross sectional view illustrative of the conventional connector. 
     FIG. 3 is a plane view illustrative of the conventional connector. 
     FIG. 4 is a cross sectional view illustrative of the conventional connector. 
     FIG. 5 is a schematic view illustrative of a novel connector for a flat cable in a preferred embodiment according to the present invention. 
     FIG. 6A is a partially enlarged view illustrative of one of first contacts of a novel connector for a flat cable in a preferred embodiment according to the present invention. 
     FIG. 6B is a partially enlarged view illustrative of one of second contacts of a novel connector for a flat cable in a preferred embodiment according to the present invention. 
     FIG. 7A is a cross sectional elevation view illustrative of a first contact engaged in a novel connector for a flat cable when a lever is opened in a preferred embodiment according to the present invention. 
     FIG. 7B is a cross sectional elevation view illustrative of a second contact engaged in a novel connector for a flat cable when a lever is opened in a preferred embodiment according to the present invention. 
     FIG. 7C is a cross sectional elevation view illustrative of a second contact engaged in a novel connector for a flat cable when a lever is closed in a preferred embodiment according to the present invention. 
     FIG. 8 is a bottom plane view illustrative of a bottom surface of a flat cable for which a novel connector is designed in a preferred embodiment according to the present invention. 
     FIGS. 9A-9C are view illustrative of variations contact force of a connector to a flat cable versus various angles of lever. 
    
    
     DISCLOSURE OF THE INVENTION 
     The present invention provides a connector for a flat cable comprising the following elements. A housing is provided, which comprises a rectangular-shaped base portion defined by first and second sides opposite to each other and parallel to a first lateral direction and third and fourth sides opposite to each other and parallel to a second lateral direction which is vertical to the first lateral direction, and first and second side walls provided on the third and fourth sides. A plurality of first contacts are provided, each of which has a first contact convex and a first lead terminal. The first contacts laterally extend from the first side toward the second side in the second direction. The first lead terminals project from the first side outwardly in the second direction. The first contact convex portions are provided at inner and top end portions of the first contacts. The first contact convex portions face upwardly. The first contacts are discontinuously aligned at a first pitch to form a first line in parallel to the first direction. A plurality of second contacts are provided, each of which has a second contact convex and a second lead terminal. The second contacts laterally extend from the second side toward the first side in the second direction. The second lead terminals project from the second side outwardly in the second direction. The second contact convex portions are provided at inner and top end portions of the second contacts. The second contact convex portions face upwardly. The second contacts are discontinuously aligned at a second pitch to form a second line in parallel to the first line. The second line is distanced from the first line in the second direction. Each of the second contact convex portions are positioned to correspond to an intermediate position between adjacent two of the first contact convex portions in the first direction so that the first and second contact convex portions are positioned to alternate to each other in the first direction. A lever is further pivotally provided to the side walls of the housing. The lever has an engaging portion which is spaced over the first and second contact convex portions for sandwiching a flat cable between the engaging portion and the first and second contact convex portions. 
     The above arrangement of the first and second contact convex portions of the first and second contacts substantially shortens the pitch of the contact points of the flat cable into a half in the first direction while the adjacent two of said first and second contact convex portions are distanced from each other by at least a minimum distance necessary for isolation between them. This provides a reduction in size of newly one half along the first direction of the connector even the necessary isolation is ensured for the adjacent first and second contacts, resulting in a substantial reduction in size of the connector. 
     It is preferable that the engaging portion of the lever comprises a curved engaging end portion and a flat engaging portion adjacent to the curved engaging end portion so that if the lever stands vertically or is oblique, then the curved engaging end portion is made into contact with the flat cable, and if the lever lies down, then the flat engaging portion is made into contact with the flat cable. 
     In the above case, it is more preferable that the curved engaging end portion has variations in thickness to have a maximum value at a critical position relatively near a boundary between the curved engaging end portion and the flat engaging portion so that if the lever is made into contact with the flat cable at the critical position, then a contact force between the lever and the flat cable becomes maximum. 
     It is advantageous to further provide a plurality of first slits laterally extending from the first side toward the second side in the second direction and a plurality of second slits laterally extend from the second side toward the first side in the second direction. The first slits have a width slightly larger than a width of the first contacts for receiving the first contacts except for the first lead terminals. The first contact convex portions project over the first slits. The first slits are discontinuously aligned at the first pitch in parallel to the first direction. The second slits have a width slightly larger than a width of the second contacts for receiving the second contacts except for the second lead terminals. The second contact convex portions project over the second slits. The second slits are discontinuously aligned at the second pitch in parallel to the first direction. The second slits are distanced from the first slits in the second direction. Each of the second slits is positioned to correspond to an intermediate position between adjacent two of the first slits in the first direction so that the first and second slits are positioned to alternate to each other in the first direction. 
     In the above case, it is more advantageous that a body of the first contact comprises a head portion laterally extending toward an inside of the first slit, and a base portion laterally extending toward the inside of the first slit but being shorter than the head portion. The head and base portions are formed from a single piece. 
     In the above case, also it is more advantageous that a body of the second contact comprises a contact arm portion laterally extending toward an inside of the second slit, a base portion laterally extending toward the inside of the second slit but being longer than the contact arm portion, the contact arm and base portions being unitary formed, and a spring supporting portion laterally extending in the same direction as the contact arm portion and the base portion. The spring supporting portion is positioned over the contact arm portion and extends to beyond an end of the contact arm portion. The end portion of the spring supporting portion is generally cylinder-shaped. The spring supporting portion further has a recessed portion positioned on a bottom side thereof and just inside the generally cylinder-shaped end portion thereof. The spring supporting portion is formed via a vertically extending portion to the contact arm portion and the base portion, so that the spring supporting portion is positioned over the flat cable whilst the contact arm portion is positioned under the flat cable if the flat cable is inserted into the connector. 
     In the above case, it is more preferable that the base portion of the second contact has the same bottom level as the rectangular-shaped base portion of the housing so that if the connector is mounted on a printed circuit board, then the base portion of the second contact is securely in contact with and supported by the printed circuit board so that when the lever rotates around the generally cylinder-shaped end portion of the spring supporting portion of the second contact, a rotation stress appears on the spring supporting portion of the second contact. This rotation stress is, however, absorbed by the base portion of the second contact having the same bottom level as the housing since the base portion is securely supported by the printed circuit board on which this connector is mounted. On the other hand, the first contact is free from any rotation stress caused by the operation of the lever. The above structure allows an absorption of the rotation stress via the base portion of the second contact and further allows the first contact to be free from any stress, for which reason no stress appears on the first and second lead terminal portions of the first and second contacts. This causes no clucking on the first and second lead terminal portions which are connected to the pads on the printed circuit board. This allows a stable connection of the connector to the printed circuit board. 
     In the above case, it is further preferable that the generally cylinder-shaped end portion of the spring supporting portion of the second contact is positioned over an intermediate point between the first and second contact convex portions of the first and second contacts so that the generally cylinder-shaped end portion and the contact convex portions form a generally isosceles triangle. 
     It is also preferable that opposite side walls of the lever are provided with convex portions, whilst inside faces of the side walls of the housing are provided with concave portions which are to be engaged with the convex portions when the lever becomes lie down. 
     PREFERRED EMBODIMENT 
     A preferred embodiment according to the present invention will be described, wherein a novel connector for a flat cable is provided, which is scaled down and suitable for a high density packaging. 
     FIG. 5 is a schematic view illustrative of a novel connector for a flat cable in a preferred embodiment according to the present invention. A connector 14 is designed for a flat cable 19. The connector 14 comprises a housing 15 having first and second sides, a set of first contacts 16 engaged into the first side of the housing 15, a set of second contacts 17 engaged into the second side of the housing 15, and a lever 18 provided on the housing 15 for holding the flat cable 19. The housing 15 has opposite side walls 21 vertically extending to define a flat cable receiving area which correspond to a width of the flat cable 19. The lever 18 has substantially the same width as that of the flat cable receiving area. In FIG. 5, the lever 18 is opened. The housing 15 has the first side through which the flat cable 19 is inserted into the flat cable receiving area of the housing 15. 
     The first side of the housing 15 is formed with a set of first slits 20a aligned at a predetermined constant interval, wherein the first slits 20a extend from the first side thereof toward inside thereof in parallel to each other. The first contacts 16 are provided to fit into the first slits 20a except for lead terminal portions thereof which project from the first side of the housing 15 for providing electrical contacts with pads on a printed circuit board. FIG. 6A is a partially enlarged view illustrative of one of the first contacts 16 and the first slits 20a. The each slit 20a has a width just wider than a width of the first contact 16. The each first contact 16 comprises a head portion 16a laterally extending toward an inside of the first slit 20a and a base portion 16b laterally extending toward the inside of the first slit 20a but being shorter than the head portion 16a. The head and base portions are unitary formed. The each first contact 16 further has a lead terminal portion 16c which laterally extends but in an opposite direction to the base and head portions 16b and 16a so that the head and base portions 16a and 16b fit into the first slit 20a whilst the lead terminal portion 16c projects from the first slit 20a. The each first contact 16 further has a contact point 16d which is provided on an end portion of the head portion 16a so that the first contact is in contact via the contact point 16d to the bottom plane of the flat cable when the flat cable is inserted into the connector 14. The bottom level of the first contact 16 is the same as the bottom level of the first slit 20a or the bottom level of the housing 15. 
     The second side of the housing 15 is formed with a set of second slits 20b aligned at a predetermined constant interval, wherein the second slits 20b extend from the second side thereof toward inside thereof in parallel to each other. The second contacts 17 are provided to fit into the second slits 20b except for lead terminal portions thereof which project from the second side of the housing 15 for providing electrical contacts with pads on the printed circuit board. FIG. 6B is a partially enlarged view illustrative of one of the second contacts 17 and the second slits 20b. The each slit 20b has a width just wider than a width of the second contact 17. The each second contact 17 comprises a contact arm portion 17a laterally extending toward an inside of the second slit 20b and a base portion 17b laterally extending toward the inside of the second slit 20b but being longer than the contact arm portion 17a. The contact arm and base portions are formed from a single piece. The each second contact 17 further has a lead terminal portion 17c which laterally extends but in an opposite direction to the base and contact arm portions 17b and 17a so that the contact arm and base portions 17a and 17b fit into the second slit 20b whilst the lead terminal portion 17c projects from the second slit 20b. The each second contact 17 further has a contact point 17d which is provided on an end portion of the contact arm portion 17a so that the second contact is in contact via the contact point 17d to the bottom plane of the flat cable when the flat cable is inserted into the connector 14. The each second contact 17 further more has a spring supporting portion 17e laterally extending in the same direction as the contact arm portion 17a and the base portion 17b. The spring supporting portion 17e is positioned over the contact arm portion 17a and extends to beyond the end portion of the contact arm portion 17a. The end portion of the spring supporting portion 17e is generally cylinder-shaped. The spring supporting portion 17e has a recessed portion positioned on a bottom side thereof and just inside the generally cylinder-shaped end portion thereof The spring supporting portion 17e is formed via a vertically extending portion to the contact arm portion 17a and the base portion 17b. The spring supporting portion 17e is positioned over the flat cable 19 whilst the contact arm portion 17a is positioned under the flat cable 19 if the flat cable 19 is inserted into the connector 14. The second side of the housing 15 is thicker than the first side thereof so that if the second contact 17 fits into the second slit 20b, then not only the contact arm portion 17a and the base portion 17b but also the spring supporting portion 17e fit into the second slit 20b, even the lead terminal portion 17c is positioned outside the second slit 20b as described above. The bottom level of the second contact 17 is the same as the bottom level of the second slit 20b or the bottom level of the housing 15. 
     With reference back to FIG. 5, even the first and second slits 20a and 20b extend from the first and second sides of the housing 15 toward the inside thereof, both the contact points 16d and 17d of the first and second slits 20a and 20b do not cross to each other and are spaced from each other in the direction along which the first and second slits 20a and 20b extend as well illustrated in FIG. 5. Further, in the direction parallel to the first and second sides of the housing 15 and vertical to the direction along which the first and second slits 20a and 20b extend, the first and second slits 20a and 20b are provided to alternate to each other. The distance between the adjacent first slits 20a is almost the same as the width of the second slit 20b. The distance between the adjacent second slits 20b is almost the same as the width of the first slit 20a. As a result, the contact points 16d of the first contacts 16 are aligned on a first straight line in parallel to the first and second sides of the housing 15, whilst the contact points 17d of the second contacts 17 are aligned on a second straight line in parallel to the first straight line but separated therefrom by a distance which is nearly equal to the size of the contact points 16d and 17d of the first and second contacts 16 and 17. The contact points 16d and 17d of the first and second contacts 16 and 17 are arranged on the first and second lines but to alternate to each other in the direction along the first and second lines as well illustrated in FIG. 5. The above arrangement of the contact points 16d and 17d of the first and second contacts 16 and 17 shortens the pitch of the contact points 16d and 17d by half in the direction along the first and second sides of the housing 15 even the adjacent contact points 16d and 17d are distanced from each other by a minimum distance necessary for isolation between them in the oblique direction to the first and second sides of the housing 15. This provides a nearly half reduction of the width of the connector 14 even the necessary isolation is ensured for the adjacent contact points 16d and 17d whereby resulting in a substantial reduction in size of the connector 14. 
     As illustrated in FIGS. 7B and 7C, the generally cylinder-shaped end portion of the spring supporting portion 17e of the second contact 17 is positioned over an intermediate point between the contact points 16d and 17d of the first and second contacts so that the generally cylinder-shaped end portion and the contact points 16d and 17d form an isosceles triangle. 
     The lever 18 is pivotally provided on the housing 15. The lever 18 has a curved engaging portion 18a which is engaged with the generally cylinder-shaped end portion of the spring supporting portion 17e of the second contact 17 as illustrated in FIG. 7B so that the lever 18 may pivot around the generally cylinder-shaped end portion of the spring supporting portion 17e. The lever 18 stands vertically as illustrated in FIGS. 5, 6A and 6B before the flat cable 19 is inserted into the flat cable receiving area of the connector 14. Thereafter, the lever 18 is made down by pivotal motion of the lever 18 around the generally cylinder-shaped end portion of the spring supporting portion 17e of the second contact 17 whereby the flat cable 19 is securely sandwiched between the lever 18 and the contact points 16d and 17d of the first and second contacts 16 and 17. 
     FIG. 8 is illustrative of a bottom surface of the flat cable 19. First contact pads 22a and second contact pads 22b are provided on a head region in the bottom surface of the flat cable. The first contact pads 22a and second contact pads 22b are arranged to form first and second parallel lines respectively in parallel to the first and second sides of the housing 15. The first contact pads 22a and second contact pads 22b are aligned to alternate to each other in the direction along a head edge of the flat cable 19. The first contact pads 22a and second contact pads 22b are thus positioned to correspond to the contact points 17d and 16d of the second and first contacts 17 and 16 respectively. Accordingly, when the flat cable 19 is inserted into the connector 14 and the lever 18 is made down to hold the flat cable 19, then the contact points 17d and 16d of the second and first contacts 17 and 16 are electrically and physically made into contact with the first and second contact pads 22a and 22b of the flat cable 19 respectively. When the lever 18 is made down and closed, the lever 18 may act as a cap of the housing 15 for covering the flat cable 19. When the lever 18 is opened, which vertically stands, the end of the curved engaging portion 18a of the lever 18 is made into contact with the flat cable 19. When the lever 18 is half-opened and becomes oblique, an intermediate point of the curved engaging portion 18a of the lever 18 is made into contact with the flat cable 19. When the lever 18 is closed and becomes lie down, a flat engaging portion adjacent to the curved engaging portion 18a of the lever 18 is made into contact with the flat cable 19. The above structure shortens the effective pitch of the contact pads 22a and 22b into half. This further reduces the width of the flat cable 19. 
     Further, as illustrated in FIG. 5, the opposite side walls of the lever 18 are provided with convex portions 18b, whilst inside faces of the side walls of the housing 15 are provided with concave portions 21a which are to be engaged with the convex portions 18b when the lever 18 is closed and becomes lie down to hold the lever 18 in closing state. 
     The above arrangement of the contact points 16d and 17d of the first and second contacts 16 and 17 shortens the pitch of the contact points 16d and 17d into a half in the direction along the first and second sides of the housing 15 even the adjacent contact points 16d and 17d are distanced from each other by a minimum distance necessary for isolation between them in the oblique direction to the first and second sides of the housing 15. This provides a nearly half reduction of the width of the connector 14 even the necessary isolation is ensured for the adjacent contact points 16d and 17d whereby resulting in a substantial reduction in size of the connector 14. The above structure also shortens the effective pitch of the contact pads 22a and 22b into half. This further reduces the width of the flat cable 19. Those allow a high density packaging of the connector for the flat cable. 
     Further, when the lever 18 rotates around the generally cylinder-shaped end portion of the spring supporting portion 17e of the second contact 17, a rotation stress appears on the spring supporting portion 17e of the second contact 17. This rotation stress is absorbed by the base portion 17b of the second contact 17 having the same bottom level as the bottom level of the housing 15 since the base portion 17b is securely supported by the printed circuit board on which this connector 14 is mounted. On the other hand, the first contact 16 is free from any rotation stress caused by the operation of the lever 18. The above structure allows an absorption of the rotation stress via the base portion 17b of the second contact 17 and further allows the first contact 16 free from any stress, for which reason no stress appears on the lead terminal portions 16c and 17c of the first and second contacts 16 and 17. This causes no clucking on the lead terminal portions 16c and 17c which are connected to the pads on the printed circuit board. This allows a stable connection of the connector 14 to the printed circuit board. 
     Furthermore, the curved engaging portion 18a of the lever 18 allows a smooth rotary motion of the lever 18 around the generally cylinder-shaped end portion of the spring supporting portion 17e of the second contact 17 and further provides a secure holding of the flat cable 19. 
     FIG. 9A is illustrative of variations in contact force of the lever 18 with the flat cable 19 versus the rotation angle of the lever 18. When the lever 18 stands vertically, the contact force of the lever 18 with the flat cable is almost zero. As the lever 18 is made oblique, then the curved engaging portion 18a of the lever 18 is made into contact with and pushes the flat cable 19 whereby the contact force of the lever 18 with the flat cable is rapidly increased from zero so that when the curved engaging portion 18a in the vicinity of the flat engaging portion is in contact with the flat cable 19 (FIG. 9B), the contact force has a maximum value. As the lever 18 is made lie down and the flat engaging portion of the lever 18 is in contact with the flat cable 19, then the contact force is reduced from the maximum value as well illustrated in FIG. 9C. When the lever 18 is closed and the flat engaging portion of the lever 18 is in contact with the flat cable 19, the contact force is lower than the maximum value by a self lock force which locks the lever once made lie down. If the lever 18 once made lie down is risen up, it is required to apply the lever 18 with a force larger than the self lock force. In addition, the lever 18 has the opposite sides which are provided with the convex portions 18b to be engaged with the concave portions 21a formed on the inner sides of the side walls of the housing 15 only when the lever 18 is made lie down. This structure provides a further self lock of the lever 18. 
     The following structural modification to the above embodiment may be possible. Even in the above embodiment, the first and second contacts 16 and 17 are inserted into the first and second slits 20a and 20b, in the modification it is possible that no slit is provided but the first and second contacts 16 and 17 are shaped to sandwich the base of the housing 15 between the head portions 16a or the contact arm portion 17a and the base portion 16b or 17b. 
     Even in the above embodiment the lever 18 is supported only by the second contacts 17, it is further possible as a modification that the lever 18 is supported by not only the second contact but also the first contact modified to be engaged with the lever 18. 
     Whereas modifications of the present invention will be apparent o a person having ordinary skill in the art, to which the invention pertains, it is to be understood that embodiments as shown and described by way of illustrations are by no means intended to be considered in a limiting sense. Accordingly, it is to be intended to cover by claims any modifications of the present invention which fall within the spirit and scope of the present invention.