Patent Publication Number: US-7901232-B2

Title: Electrical connector for a flexible flat cable

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT International Application No. PCT/JP2008/060450, filed Jun. 6, 2008, which claims priority under 35 U.S.C. §119 to Japanese Patent Application No. JP 2007-153299, filed Jun. 8, 2007. 
    
    
     FIELD OF INVENTION 
     The invention relates to an electrical connector, in particular, to an electrical connector to which a flexible flat cable is connected. 
     BACKGROUND 
     An electrical connector (hereinafter referred simply to as a connector) for a flexible flat cable such as a flexible printed circuit (FPC) or a flexible flat cable (FFC) is mounted on a printed wiring board. In a housing of the connector, a plurality of contacts that are electrically connected to the printed wiring board are provided. By electrically connecting these contacts to the conductors of the flat cable, the flat cable is connected to the printed wiring board. 
     In the connector, in order to keep an electrically connected state between the flat cable conductors and the contacts, typically, the flat cable is clamped by the contacts, and each of the contacts is made in a state of being pressed against the flat cable conductor by utilizing the elasticity of the contact itself. When the flat cable is inserted into the connector, the insertion of the flat cable should be prevented from being hindered by the resistance of contacts. For this purpose, a ZIF (Zero Insertion Force) type connector that keeps the contacts in an opened state is available. 
     In such a ZIF type connector, the contact having been in an opened state is deformed and operated by an actuator, whereby the contact is pressed against the flat cable conductor. A known ZIF type connector, for example, is disclosed in Japanese Patent Laid-Open No. 2002-270290. As shown in  FIG. 5 , a known contact  1  is a flat and having a substantially H-shape. The contact  1  includes contact arms  2  and  3 , a pivot  4 , a lever  5 , and a base  6 . When an actuator  7  is turned clockwise, the lever  5  is displaced upward by a cam  8 , and the pivot  4  of the contact  1  is elastically deformed. Thereby, a flat cable  9  is clamped between the contact arms  2  and  3 , and is electrically connected to the contact  1 . 
     However, conventional contacts, as described above, have certain problems. 
     In the contact  1 , the contact arm  2  and the lever  5  form one beam, and the contact arm  3  and the lever  6  also form one beam. Therefore, in order to reliably clamp the flat cable  9  between the contact arms  2  and  3 , the displacement of the lever  5  caused by the elastic deformation of the pivot  4 , produced by the operation of the actuator  7 , must be transmitted efficiently to the contact arm  2 . However, when the lever  5  is displaced upward by the operation of the actuator  7 , the displacement of the contact arm  2  is restricted by the contact of the contact arm  2  with the flat cable  9 . Thereby, the contact arm  2  is subjected to a reaction force from the flat cable  9 , so that the lower portion of the pivot  4  is raised, and lifts from a printed wiring board  100 . Therefore, the displacement of the contact arm  2  becomes smaller than the displacement inherently produced in the contact arm  2  by the operation of the actuator  7 , along with the elastic deformation produced in the contact arm  2  and the lever  5 . As a result, depending on the thickness of the flat cable  9 , the force for pressing the contact arm  2  against the flat cable  9  (referred to as a contact pressure) may be insufficient To solve this problem, it is thought that the distance from the pivot  4  to the point of application of the force in the actuator  7  is increased by lengthening the lever  5  to increase the clamping force for the flat cable  9  between the contact arms  2  and  3 , or the rigidity of the lever  5  is enhanced. However, in such a design, the size of the contact  1  is increased, or the length in the front-back direction thereof is increased. As the sizes of various pieces of electrical and electronic equipment decrease, the connector especially requiring a large mounting area on the printed wiring board  100  is also required to be made small in size. The increased size and rigidity of the contact  1  are unfavorable because they hinder the decrease in size of connector. Also, in the case where the rigidity of the lever  5  is enhanced, the force required for the operation of the actuator  7  increases, so that the operability of the actuator  7  may be degraded. 
     The connector is required to be formed so that the height, thereof in the state of being mounted on the printed wiring board  100 , is decreased as far as possible (this is called low-profile). The conventional flat and substantially H-shaped contacts are also formed so as to meet this requirement. However, if the lever  5  is lengthened, the displacement on the rear end side of the lever  5  at the time when the lever  5  is operated by the actuator  7  increases, which hinders the contact from being low-profile. 
     Also, the contact  1 , the cam  8  of the actuator  7 , and the flat cable  9  vary in dimensions. By the variations in the gap between the lever  5  and the base  6  of the contact  1 , and the variations in dimension in the major axis direction of the cam  8 , the upward displacement of the lever  5  at the time when the actuator  7  is operated varies. Also, by the variations in the gap between the contact arms  2  and  3  of the contact  1 , the displacement of the contact arm  2  caused by the displacement of the lever  5  varies. Further, the variations in thickness of the flat cable  9  also lead to the variations in the relative displacement of the contact arm  2  with respect to the flat cable  9 . The variations in these dimensions are amplified according to the lengths (lever ratio) of the contact arms  2  and  3  and the lever  5 . As a result, the variations in these dimensions lead to the variations in contact pressure of the contact arm  2  against the flat cable  9  for each contact  1  or each connector. If the contact pressure is insufficient, the flat cable  9  may not be clamped reliably by the contact  1 . Also, if the contact pressure is excessive, the surface of the contact point of the contact  1  may roughen and electrical conductivity may become impaired. In the case where the contact pressure is excessive, the contact arm  2  and the lever  5  may be deformed plastically, exceeding the elastic deformation zone. In this case, when the flat cable  9 , having been clamed by the contact  1 , is unclamped by the operation of the actuator  7 , for example, at the time of maintenance, the gap between the contact arms  2  and  3  does not widen sufficiently. As a result, even if an attempt is made to insert the flat cable  9  again, the flat cable  9  may interfere with the contact arms  2  and  3 . Also, if the lever  5  has been deformed plastically, when the flat cable  9  is inserted between the contact arms  2  and  3  again after being unclamped, and is clamped by operating the actuator  7 , the contact arms  2  and  3  may not exert a sufficient clamping force on the flat cable  9 . 
     SUMMARY 
     An object of the present invention is to provide an electrical connector capable of exerting a necessary and sufficient clamping force on a flat cable to reliably provide electrical conductivity while the connector is low-profile 
     The electrical connector to electrically connect a flexible flat cable to a printed wiring board, includes a housing made of an insulating material and having a cavity into which an end portion of the flat cable is inserted, an actuator having a cam, and a contact. The contact accommodated in the housing, includes a base of the contact fixed to the housing and electrically connected to the printed wiring board, a lever extending from the base of the contact, a contact beam provided with a support arm that is supported by the lever, and a pressing arm projecting from the base toward the cam of the actuator. The cam of the actuator presses one end of the contact beam in a direction away from the printed wiring board while pressing the pressing arm and another end of the contact beam in a direction toward to the printed wiring board when a change-over operation of the contact to the clamping state is performed, the clamping state where the contact clamps end portion of the flat cable and thereby electrically connects to the printed wiring board. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are described in greater detail in the following description and are shown in a simplified manner in the drawings, in which: 
         FIG. 1A  is a plan view a connector according to the present invention; 
         FIG. 1B  is a front view of the connector of  FIG. 1  according to the present invention; 
         FIG. 1C  is a side view of the connector of  FIG. 1  according to the present invention; 
         FIG. 2A  is a cross-sectional view taken along the line  2 - 2  of  FIG. 1A ; 
         FIG. 2B  is a cross-sectional view of the connector showing a state in which the deformation of a contact produced by an actuator is completed, and a flat cable is clamped; 
         FIG. 3A  is a cross-sectional of the connector view showing a case where a part to be pressed is deformed less than in the case shown in  FIG. 2B ; 
         FIG. 3B  is a cross-sectional view of the connector showing a case where the part to be pressed is deformed more than in the case shown in  FIG. 2B ; 
         FIG. 4  is a cross-sectional view of the connector showing another example of the shape of a part to be pressed; and 
         FIG. 5  is a cross-sectional view of a known conventional electrical connector. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     For an improved understanding of the invention, it will now be described in more detail with the aid of the drawings. 
     As shown in  FIGS. 1A to 1C , a connector (electrical connector)  10  is mounted on a printed wiring board  100  to electrically connect a flat cable  200  to the printed wiring board  100  by inserting an end portion of the flat cable  200 . Hereinafter, for ease of explanation, in the connector  10 , the side on which the connector  10  is mounted on the printed wiring board  100  (the lower side in  FIG. 1C ) is referred to as the lower side, and the side on which the flat cable  200  is inserted (the left side in  FIG. 1C ) is referred to as the front side. 
     As shown in  FIGS. 1A to 1C , the connector  10  includes a housing  11 , a plurality of contacts  20  accommodated in the housing  11 , and an actuator  12  for operating these contacts  20 . 
     In the embodiment shown, the housing  11  and the actuator  12  are each made of an insulating material, such as a resin. The contact  20  is formed by stamping a thin plate made of a conductive material such as a copper alloy. 
     On the front surface of the housing  11 , a cavity  30  is formed so that the end portion of the flat cable  200  may be inserted into this cavity  30 . The cavity  30  is open in a slit form. 
     In the cavity  30 , the plurality of contacts  20  for making electrical connection with conductors in the end portion of the flat cable  200  are arranged in one row. The contacts  20  are arranged in the direction in which the slit-form cavity  30  is continuous (the longitudinal direction of the housing  11 ). The contacts  20  are press fitted into the housing  11 . 
     The actuator  12  is made of an insulating material, such as a resin, like the housing  11 , and is provided on the rear end side on the upper surface of the housing  11 . The actuator  12  extends in the longitudinal direction (the width direction) of the housing  11 , and pins  12   a  provided in both end portions thereof are pivotally mounted on the housing  11 , so that the actuator  12  can rotate in a plane that is perpendicular to the surface of the printed wiring board  100  and includes the front-back direction of the housing  11 . 
     As shown in  FIGS. 2A and 2B , the actuator  12  has a camshaft  12   b  extending along the rotating shaft thereof, and the camshaft  12   b  is formed with cams  40  at positions corresponding to each of the contacts  20 . The cam  40  is eccentrically provided with respect to the rotating center C (that is, the pin  12   a ) of the actuator  12 . As shown in  FIG. 2A , the cam  40  has a substantially rectangular cross section that is slightly long in the front-back direction in a state in which a lever  41  of the actuator  12  is erected with respect to the housing  11 . In this state, the contacts  20  are opened so that when the flat cable  200  is inserted into the housing  11 , the insertion resistance caused by friction against the flat cable  200  is restrained. As shown in  FIG. 2B , when the actuator  12  is rotated, the cam  40  rotates to press the contact  20 , whereby the actuator  12  can change over the contact  20  from the opened state to a clamping state in which the contact  20  clamps the flat cable  200 . 
     As shown in  FIGS. 2A and 2B , the cavity  30  is formed so as to be continuous to an intermediate portion in the front-back direction of the housing  11  so that the flat cable  200  is inserted into the cavity  30 . The rear portion of the cavity  30  is opened upward to form a space  31  for accommodating the contacts  20  and the actuator  12 . In the lower portion of the rear end portion of the cavity  30 , a recess  32  that engages with the contacts  20  to fix them is formed. In the inner peripheral surface of the recess  32 , an engaging recess  32   a  for engaging the contacts  20  is formed. 
     The contact  20  has a base  61  extending from the front of the housing  11  toward the rear thereof in a state in which the contact  20  is mounted in the housing  11 , a contact beam  62  for being electrically connected to the flat cable  200 , and a lever (deformed part)  63  formed between the base  61  and the contact beam  62 . And the contact  20  is of a tuning fork type, such that the flat cable  200  is held and clamped between the contact beam  62  and the base  61 . 
     A rear end section  61   a  of the base  61  is inserted into the recess  32  of the housing  11 . The rear end section  61   a  is provided with a protrusion  61   b  corresponding to the engaging recess  32   a  formed in the recess  32 . By the engagement of the protrusion  61   b  with the engaging recess  32   a , the contact  20  is prevented from dropping off to the front. 
     In the bottom surface side of a front end section  61   c  of the base  61 , a stopper claw  61   d  engaging with the front end portion on the bottom surface  11   b  side of the housing  11  is formed to restrict the rearward movement of the contact  20 , in a state in which the rear end section  61   a  of the base  61  is inserted into the recess  32 . The bottom surface of the front end section  61   c  in the base  61  that is located forward of the stopper claw  61   d , serves as a tine  65 , electrically connected to the conducive part of the printed wiring board  100 . That is to say, in this embodiment, the stopper claw  61   d  and the tine  65  are continuously formed. Therefore, in a state in which the rear end section  61   a  of the base  61  is inserted into the recess  32 , and the stopper claw  61   d  is engaged with the front end portion on the bottom surface  11   b  side of the housing  11 , the tine  65  is approximately flush with the bottom surface  11   b  of the housing  11 , or slightly projects downward from the bottom surface  11   b  of the housing  11 . 
     The lever  63  is formed at a position closer to the rear end section  61   a  than a middle point between the rear end section  61   a  and the front end section  61   c  of the base  61 , so as to extend upward from the base  61 . 
     The contact beam  62  includes a support arm  62   a  supported by the lever  63 , a lever arm  62   b  extending from the support arm  62   a  to the rear of the housing  11 , and a contact arm  62   c  extending from the support arm  62   a  to the front of the housing  11  for being electrically connected to the flat cable  200 . 
     The support arm  62   a  is a part in which the lever  63  joins with the contact beam  62 . 
     The lever arm  62   b  is arranged above the cam  40  of the actuator  12 . The lever arm  62   b  is shorter than the contact arm  62   c , and is formed so as not to project rearward from the rear end section  61   a  of the base  61 . 
     The contact arm  62   c  is formed so as to extend obliquely downward from the support arm  62   a.    
     When the lever  41  of the actuator  12  is operated to rotate the actuator  12  in the clockwise direction, the cam  40  comes into contact with the lower surface of the lever arm  62   b  of the contact beam  62 , and presses the lever arm  62   b  upward. At this time, the lever  63  is elastically deformed so as to fall down forward, because it has a cross-sectional area smaller than that of the contact beam  62 , whereby the contact arm  62   c  of the contact beam  62  is displaced downward. When the contact arm  62   c , being displaced downward, is pushed against the flat cable  200 , after being inserted into the cavity  30 , the contact arm  62   c  is electrically connected to the flat cable  200 . 
     When the contact arm  62   c  is pushed against the flat cable  200  inserted into the cavity  30 , the downward displacement of the contact arm  62   c  is restricted. When the actuator  12  is further rotated from this state, the contact beam  62  is elastically deformed. By a force such that this elastic deformation tends to be restored, the contact arm  62   c  of the contact beam  62  is pressed against the flat cable  200 . Thereby, the flat cable  200  is clamped between the contact arm  62   c  of the contact beam  62  and the base  61 . When the lever  41  of the actuator  12  is rotated to a state, being approximately parallel with the surface of the printed wiring board  100 , the actuator  12  is locked by the cam  40 . 
     The contact  20  further includes a pressing arm  64 , which is subjected to a downward pressing force from the cam  40  of the actuator  12 , under the cam  40  of the actuator  12 . The pressing arm  64  is provided in the vicinity of the joint portion of the base  61  and the lever  63 . The pressing arm  64  can have a substantially inverse L shape consisting of, for example, a columnar section  64   a  extending upward from a position at the rear of the joint portion of the base  61  and the lever  63 , and a beam section  64   b  extending from the tip end of the columnar section  64   a  toward the rear. 
     The housing  11  includes a stopper  52 , which restricts the downward displacement exceeding a fixed value of the beam section  64   b , under the beam section  64   b  of the pressing arm  64 . An upper surface  52   a  of the stopper  52  is formed so that a gap between the upper surface  52   a  and the beam section  64   b  has a predetermined dimension. When being pressed downward by the cam  40  of the actuator  12 , the beam section  64   b  of the pressing arm  64  is elastically deformed downward. If the displacement caused by the elastic deformation exceeds a predetermined value, the beam section  64   b  of the pressing arm  64  comes into contact with the stopper  52 , so that further displacement is restricted. In the state in which the beam section  64   b  of the pressing arm  64  comes into contact with the stopper  52 , the pressing force of the cam  40  of the actuator  12  is distributed and applied to not only the beam section  64   b , but also the stopper  52 . Thereby, the force acting on the beam section  64   b  is reduced. In the case where the stopper  52  is not provided, the beam section  64   b  may be plastically deformed if the displacement of the beam section  64   b  becomes excessive. However, this plastic deformation can be prevented by providing the stopper  52 . 
     At the same time that the cam  40  of the actuator  12  presses the lever arm  62   b  of the contact beam  62  upward, as described above, some of the pressing force generated by the cam  40  is transmitted to the pressing arm  64 , and presses the beam section  64   b  of the pressing arm  64  downward. When the lever arm  62   b  of the contact beam  62  is pressed upward, the lever  63  is elastically deformed as described above. At this time, on the base  61 , a force such as to raise the base  61  upward acts in the joint portion of the base  61  and the lever  63 . On the other hand, the base  61  of the contact  20  is pressed downward by the cam  40  of the actuator  12  through the pressing arm  64 , so that the base  61  is prevented from lifting. As a result, the displacement of the contact  20  becomes the displacement to be produced inherently by the operation amount of the actuator  12 , so that the flat cable  200  can be pressed reliably. Moreover, by pressing the base  61  through the pressing arm  64 , the base  61  can be prevented from lifting without lengthening the contact beam  62 , and the connector  10  is not hindered from being low-profile. 
     At this time, the deformation state of the beam section  64   b  of the pressing arm  64  differs depending on the thickness S 1  of the flat cable  200 , the gap S 2  between the lever arm  62   b  of the contact beam  62  and the beam section  64   b  of the pressing arm  64  in the contact  20 , and the dimension S 3  in the major axis direction of the cam  40  of the actuator  12 . 
     As shown in  FIG. 3A , in the case where the thickness S 1  is smaller, the gap S 2  is wider, or the dimension S 3  is smaller than those in the case shown in  FIG. 2B , the cam  40  of the actuator  12  may not come into contact with the beam section  64   b  of the pressing arm  64 . In such a case, the displacement of the beam section  64   b  is also not produced. In this case, all of the pressing force generated by the cam  40  can be transmitted to the lever arm  62   b  of the contact beam  62 , so that the flat cable  200  can be clamped reliably. 
     When the contact arm  62   c  is pushed against the flat cable  200  by operating the contact beam  62  using the actuator  12 , the cam  40  is pressed downward by the reaction force from the contact beam  62 . As shown in  FIG. 3B , in the case where the thickness S 1  is larger, the gap S 2  is narrower, or the dimension S 3  is larger than those in the case where each part is as designed as shown in  FIG. 2B , when the cam  40  is pressed by the contact beam  62 , the camshaft  12   b  itself of the actuator  12  is elastically deformed in the direction perpendicular to the camshaft  12   b , so that the cam  40  is displaced. Thereby, the displacement of the lever arm  62   b  produced by the cam  40  is reduced, and therefore the contact pressure applied to the flat cable  200  in the contact arm  62   c  of the contact beam  62  can be reduced. In this case, if the beam section  64   b  is displaced until coming into contact with the stopper  52 , the force applied to the beam section  64   b  can also be distributed to the housing  11 . 
     Also, in the case where the dimension S 4  on the pressing arm  64  side from the rotation center of the cam  40  or the gap S 5  between the rotation center of the cam  40  and the beam section  64   b  of the pressing arm  64  is smaller than those in the case where each part is as designed as shown in  FIG. 2B , the pressing force generated by the cam  40  of the actuator  12  tends to become excessive. In these cases, the beam section  64   b  of the pressing arm  64  is deformed downward by the pressing force generated by the cam  40  of the actuator  12 , whereby the pressing force transmitted to the lever arm  62   b  of the contact beam  62  can be reduced, and the contact pressure in the contact arm  62   c  can be lowered. In this case as well, if the beam section  64   b  is displaced until coming into contact with the stopper  52 , the force applied to the beam section  64   b  can also be distributed to the housing  11 . 
     Thus, by providing the pressing arm  64  in the contact  20 , the pressing force of the cam  40  of the actuator  12  can be transmitted to the base  61  through the pressing arm  64 . As a result, the deformation of the base  61 , such that the base  61  lifts up from a bottom surface  30   a  of the cavity  30 , can be restrained. Therefore, the flat cable  200  is clamped reliably by the contact  20 , and the electrical conduction between the contact  20  and the flat cable  200  can be achieved reliably. 
     Also, by the elastic deformation of the pressing arm  64 , the range of variations in the contact pressure of the contact arm  62   c  of the contact beam  62  caused by the variations in the thickness S 1 , the gap S 2 , the dimension S 3 , and the like can be made narrow. That is to say, the variations in the thickness S 1 , the gap S 2 , the dimension S 3 , and the like are permitted. In particular, even in the case where the thickness S 1  of the flat cable  200  is excessive, the contact pressure of the contact arm  62   c  can be effectively prevented from becoming excessive. Therefore, the plastic deformation of the contact  20  that may be produced as the result of excessive contact pressure can be prevented. Accordingly, the durability of the contact  20  can be enhanced, while the contact  20  clamps the flat cable  200  reliably. 
     Moreover, the contact  20  is of a tuning fork type shape, such that the connector  10  can be low-profile. The length of the lever arm  62   b  is set so as to be shorter than the contact arm  62   c  and such that the lever arm  62   b  does not project rearward from the rear end section  61   a  of the base  61 . Since the contact  20  can clamp the flat cable  200  reliably without lengthening the lever arm  62   b , the displacement of the lever arm  62   b  at the time when the lever arm  62   b  is operated by the actuator  12  is also small, so that the connector  10  is not hindered from being low-profile. Also, it is unnecessary to increase the rigidity of the lever arm  62   b  to prevent the lift of the base  61 , and the operability of the actuator  12  is not degraded as the result of the increase in force necessary for the operation of the actuator  12 . 
     In the above-described embodiment, an example of the specific shape of the pressing arm  64  has been described. However, there is no intention of denying the adoption of other shapes. By the elastic deformation of the part to be pressed, variations in manufacture dimensions of the housing, contact, and cam can be allowed. 
     For example, if the purpose is only to prevent the lift of the base  61 , the pressing arm  64  can be made a block-shaped convex part that is not elastically deformed by the operation of the actuator  12 . 
     Also, as shown in  FIG. 4 , a beam section  64   b ′ may be formed into a shape extending toward the front of the housing  11  with respect to a columnar section  64   a ′ of a pressing arm  64 ′. Further, the columnar section  64   a ′ of the pressing arm  64 ′ may have a shape extending obliquely rearward from the base  61 . With the pressing arm  64 ′ having such a shape, the moment produced by the pressing force of the cam  40 , as applied to the base  61  through the pressing arm  64 ′, acts in the direction such that the joint portion of the base  61  and the lever  63  is pushed downward. Therefore, it can be anticipated that the lift of the base  61  will be effectively restrained. 
     Although the actuator  12  is of a so-called back flip type in the embodiment shown, such that the actuator  12  rotates on the rear side with respect to the insertion direction of the flat cable  200 , the actuator  12  can also be of a front flip type, such that the actuator  12  rotates on the front side with respect to the insertion direction of the flat cable  200 . Also, the position of the actuator  12  is not limited to the rear end side of the housing  11 , and the actuator  12  may be provided on the front end side or the like of the housing  11 . 
     Also, the detailed configurations of the housing  11 , the contact  20 , and the like can be changed appropriately without departing from the spirit and scope of the present invention. 
     Besides these, the configurations described in the above-described embodiment can be selected optionally or can be changed appropriately to other configurations without departing from the spirit and scope of the present invention.