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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a window blind and, more specifically, to a cord member safety connector used in a window blind, which will be self-unconnected from the window blind when the cord member receives an exceeding load. 
     2. Description of the Related Art 
     A variety of window coverings including Venetian blinds, roller blinds, etc. are known. These window coverings commonly comprise a headrail, a bottom rail, a blind body coupled between the headrail and the bottom rail, a lifting mechanism controlled to lift the bottom rail to the desired elevation to further change the shading status of the window covering. The lifting mechanism comprises a plurality of pull cords for operation by the user to adjust the elevation or shading status of the window covering. 
     In the aforesaid window coverings, the pull cords are exposed to the outside and accessible to children. An accident may happen when a child playing with the cord members for fun.  FIG. 1  shows a conventional roller blind, which comprises a headrail  1 , a bottom rail  2 , a blind body  3  coupled between the headrail  1  and the bottom rail  2 , and a lifting mechanism  4  adapted to control the lifting and positioning of the bottom rail  2  to change the shading status of the blind body  3 . The lifting mechanism  4  comprises two lift cord sets  5 , two lift cord brackets  6  at the back side of the headrail  2 , and a lift lock  7 . The lift cord sets  5  each have a respective rear cord section  5   a  respectively fastened to the lift cord brackets  6  and then extended downwards over the bottom side of the bottom rail  2 , a respective front section  5   b  extended upwards to the inside of the headrail  1  and then inserted through the lift lock  7 , and a respective operation section  5   c  extended out of the headrail  1  for operation by the user. The rear section  5   a  and front section  5   b  of each cord member of the lift cord set  5  form an enclosed loop  5   d . This enclosed loop  5   d  may be tangled and hung on the retaining portion of the child who plays with the lift cord sets  5  for fun. 
     Therefore, it is desirable to provide a cord member safety connector that eliminates the aforesaid problem. 
     SUMMARY OF THE INVENTION 
     It is the main object of the present invention to provide a cord member safety connector, which automatically disconnects the cord member from the window blind when the cord member received a stretching force surpassed a predetermined level. 
     To achieve this object of the present invention, the connector for connecting a cord member of a window blind includes a supporting member and a coupling member detachably coupled to the supporting member. The supporting member has a receiving space and an escape opening that is communicated with the receiving space and has a diameter smaller than that of the receiving space. The coupling member has a retaining portion received in the receiving space and stopped above the escape opening, and a cord member tie portion for connection of the cord member. When the cord member is pulled by an external force over a predetermined level, the retaining portion is allowed to pass through the escape opening such that the coupling member is detached from the supporting member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a window blind according to the prior art. 
         FIG. 2  is an exploded view of a cord member safety connector according to a first preferred embodiment of the present invention. 
         FIG. 3  is a schematic sectional view of the cord member safety connector according to the first preferred embodiment of the present invention. 
         FIG. 4  is a perspective view showing the cord member safety connector of the first preferred embodiment of the present invention installed in a headrail of a window blind. 
         FIG. 5  is an exploded view of a cord member safety connector according to a second preferred embodiment of the present invention. 
         FIG. 6  is a perspective assembly view of the cord member safety connector according to the second preferred embodiment of the present invention. 
         FIG. 7  is an exploded view of a cord member safety connector according to a third preferred embodiment of the present invention. 
         FIG. 8  is a sectional assembly view of the cord member safety connector according to the third preferred embodiment of the present invention. 
         FIG. 9  is a perspective view showing the cord member safety connector of the third preferred embodiment of the present invention installed in the headrail of a window blind. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 2 , a cord member safety connector  10  in accordance with the first preferred embodiment of the present invention is shown comprised of a supporting member  20  and a coupling member  30 . The supporting member  20  is molded from plastics or elastic material, comprising a solid base  21  and a flat mounting portion, i.e. mounting flange  22 , perpendicularly extended from the periphery of the top side of the solid base  21 . The solid base  21  has a coupling portion  23  having a receiving space, e.g. a cylindrical through hole  24 , which extends through the top and bottom sides of the solid base  21 . The cylindrical through hole  24  has a reduced bottom end  25  of relatively smaller diameter, forming an escape opening of the coupling portion. The flat mounting flange  22  has an elongated slot  26 . The coupling member  30  is a cylindrical rod member having a body portion  32 , a radially compressible retaining portion, namely, the expanded top split head  31  at one end of the body portion  32  (the top split head  31  is a round head having a plurality of radial splits), and a cord member tie portion formed of a tie hole  33  at the other end of the body portion  32  for the connection of a cord member. The body portion  32  has a diameter slightly smaller than the reduced bottom end  25  of the cylindrical through hole  24 . The top split head  31  is radially compressible, having a diameter slightly smaller than the cylindrical through hole  24  of the coupling portion  23  but slightly greater than the reduced bottom end  25  of the cylindrical through hole  23 . 
     The connection between the supporting member  20  and the coupling member  30  is outlined hereinafter with reference to FIG.  3 . The coupling member  30  is downwardly inserted into the coupling portion  23  of the supporting member  20  from the top side, keeping the expanded top split head  31  of the coupling member  30  stopped at the reduced bottom end  25  of the cylindrical through hole  24  of the coupling portion  23  of the supporting member  20 . At this time, the coupling member  30  can be rotated in the coupling portion  23  of the supporting member  20 . When the tie hole  33  of the coupling member  30  is receiving an external force that pulls the coupling member  30  outwards from the coupling portion  23  of the supporting member  20 , the expanded top split head  31  is forced against the peripheral wall of the reduced bottom end  25  of the cylindrical through hole  24  of the coupling portion  23  of the supporting member  20  and radially inwardly compressed to reduce its outer diameter and the reduced bottom end  25  is pressed to slightly expend its diameter. If the external force is continuously increased, the expanded top split head  31  will be compressed to such an extent that the diameter of the compressed top split head  31  becomes smaller than the diameter of the reduced bottom end  25  of the cylindrical through hole  24 , for enabling the coupling member  30  to be disconnected from the supporting member  20 . 
     Referring to  FIG. 4 , the elongated slot  26  of the flat mounting flange  22  of the supporting member  20  is fastened to the headrail A of a window blind (not shown) with a hanger B, and a cord member C is fastened to the tie hole  33  at the bottom end of the body portion  32  of the coupling member  30  after insertion of the coupling member  30  into the cylindrical through hole  24  of the coupling portion  23  of the supporting member  20 . On design, the friction force F between the top split head  31  of the coupling member  30  and the reduced bottom end  25  of the cylindrical through hole  24  of the coupling portion  23  of the supporting member  20  must surpass the load of window blind W so that the coupling member  30  is normally maintained connected to the supporting member  20 . When the coupling member  30  received an external force P over a predetermined value (for example, a stretching force from a child), the top split head  31  of the coupling member  30  is forced to pass through the reduced bottom end  25  of the cylindrical through hole  24  of the supporting member  20 , and therefore the coupling member  30  and the cord member C are disconnected from the headrail A of the window blind; i.e., the friction force F is designed as the following formula.
 
load of window blind W&lt;friction force F&lt;external force P 
 
     In short, the main feature of the present invention is to set a safety range for the load at the cord member of the window blind so that the cord member is automatically disconnected from the window blind when received a pressure surpassed the set safety range, preventing a hanging accident of the cord member on a child playing the cord member. 
       FIG. 5  shows a cord member safety connector  40  according to the second preferred embodiment of the present invention, which is comprised of a supporting member  50  and a coupling member  60 . The supporting member  50  has a downwardly extended flat base  51 , and a coupling portion  53  at the base  51  for receiving the coupling member  60 . The coupling portion  53  comprises a receiving space, i.e. a circular through hole  54 , cut through the front and back sides of the base  51 , and an escape opening, i.e. a curved crevice  55  extended from the circular through hole  54  to the periphery of the base  51 . The coupling member  60  is a cylindrical member having a round head  61   a  at one end, a tie hole  63  at the other end, a collar  61   b  on the middle around the periphery, and a retaining portion  62  between the round head  61   a  and the collar  61   b . The diameters of the round head  61   a  and the collar  61   b  are slightly greater than the diameter of the circular through hole  54 . The diameter of the retaining portion  62  is smaller than the diameter of the circular through hole  54  but greater than the width of the crevice  55 . 
     The connection between the supporting member  50  and the coupling member  60  is outlined hereinafter with reference to FIG.  6 . The coupling member  60  is inserted into the circular through hole  54  of the coupling portion  53  of the supporting member  50  by force, keeping the retaining portion  62  suspended in the circular through hole  54  and the round head  61   a  and collar  61   b  respectively stopped at the back and front sides of the base  51 . When the cord member  63  at the tie hole  63  of the coupling member  60  excessively stretched by an external force, the crevice  55  is forced to expand, allowing the retaining portion  62  to pass through the crevice  55  to the outside of the coupling portion  53 , and therefore the coupling member  60  is disconnected from the supporting member  50 . 
       FIG. 7  shows a cord member safety connector  70  according to the third embodiment of the present invention, which is comprised of a supporting member  80  and a coupling member  90 . The supporting member  80  comprises a hollow base  81 , a mounting portion  82  at the top side of the hollow base  81 , a wire hole  86  in the mounting portion  82  for connection to the window blind, and a coupling portion  83  in the hollow base  81  below the wire hole  86  for receiving the coupling member  90 . The coupling portion  83  comprises a receiving space, i.e. a chamber  84 , and an escape opening, i.e. a through hole  85  downwardly extended from the chamber  84  to the bottom side of the hollow base  81 . The diameter of the through hole  85  is smaller than the diameter of the chamber  84 . The coupling member  90  is a substantially U-shaped springy member having a tie hole  91  at the bottom side, two upwardly extended parallel springy arms  92 , and two rounded retaining portions  93  respectively formed integral with the distal ends of the springy arms  92 . 
     The installation of the third embodiment of the present invention is outlined hereinafter with reference to  FIGS. 8 and 9 . After connection of the wire hole  86  to the hanger B at the headrail A of the window blind and connection of a cord member C to the tie hole  91  of the coupling member  90 , the springy arms  92  of the coupling member  90  are squeezed inwards to force the retaining portions  93  toward each other for enabling the coupling member  90  to be inserted through the through bole  85  of the coupling portion  83  into the inside of the chamber  84 . When released the hand from the coupling member  90  after its insertion through the through hole  85  into the chamber  84 , the springy arms  92  automatically return to their former shape due to the effect of their springy material property, and therefore the separated retaining portions  93  are stopped inside the chamber  84  and prohibited from passing through the through hole  85 . When the cord member C received an excessively high stretching force, the springy arms  92  are forced toward each other by the peripheral wall of the through hole  85  to force the retaining portions  93  against each other, for enabling the retaining portions  93  to pass through the through hole  85 , and therefore the cord member C with the coupling member  90  are disconnected from the supporting member  80  at the window blind. 
     The aforesaid three embodiments are commonly designed for use in roller blinds. Actually, the invention can be designed to connect the load-carrying cord member or exposed cord member of any of a variety of window blinds. When the load surpassed the set safety range, the cord member is disconnected in time, preventing the occurrence of an accident. 
     Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.

Summary:
A connector for connecting a cord member of a window blind includes a supporting member and a coupling member detachably coupled to the supporting member. The supporting member has a receiving space and an escape opening that is communicated with the receiving space and has a diameter smaller than that of the receiving space. The coupling member has a compressible retaining portion received in the receiving space and stopped above the escape opening, and a cord member tie portion for connection of the cord member. When the cord member is pulled by an external force over a predetermined level, the retaining portion is allowed to pass through the escape opening.