Abstract:
A nut-fixing part  20  formed in a housing  10  has a nut-holding room  26 , where a nut  30  is insertable and detachable by a movement in a direction perpendicular to the thickness direction of the nut  30 . At the entrance of the nut-holding room  26 , a projection  27  is provided to prevent the inserted nut  30  from sliding out. By this construction, this type of connector can be miniaturized further. In addition, when this connector mounted on a circuit board is heated in a furnace for soldering electrical connections, even if the housing experiences a stress relief, there is no possibility of any nut falling off from the housing.

Description:
RELATED APPLICATIONS 
     This application claims the priority of Japanese Patent Application No.11-281363 filed on Oct. 1, 1999 filed which is incorporated here in by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a nut-prefixed connector whose housing has pre-installed nuts, to which bolts are applied to fix the connector on a circuit board in a later assembly process. 
     BACKGROUND OF THE INVENTION 
     There is a conventional electrical connector whose housing incorporates a plurality of contacts and which is to be fixed tightly on a circuit board with bolts and nuts. For such a connector, it is a customary design practice that nuts are press-fit into and fixed at predetermined positions of the housing during the assembly of the connector before the connector is actually installed on a circuit board. This type of connector simplifies the process of assembling the connector on a circuit board. Because the nuts are already provided at predetermined positions of the connector, the connector placed on a circuit board can be fixed simply by putting bolts through pre-arranged through-holes of the circuit board. 
     Because this connector needs a strength to withstand the press-fitting of the nuts at the predetermined positions of the housing, the housing must be designed to have a sufficient thickness. As a result, the external dimensions of the housing are relatively large, so it is difficult to miniaturize the connector. Furthermore, in an assembly process where this type of connector is mounted on a circuit board, the contacts of the connector are placed directly on solder-coated connection terminals of electrical pathways of a circuit, which is printed on the circuit board, and then the connector and the circuit board in this condition are heated together in a furnace to fuse the solder and thereby to connect the contacts of the connector to the corresponding pathways of the circuit on the circuit board ( surface-mounting process ). If the above mentioned connector with nuts press-fit in the housing is heated in a furnace, then the resin forming the housing is somewhat relieved of the stress that resulted from the press-fitting of the nuts, so, accordingly, the force holding the nuts in the housing of the connector is reduced. This condition may result in one or all of the nuts to fall off from the housing. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to miniaturize a nut-prefixed connector. 
     It is another object of the present invention to provide a nut-prefixed connector whose nuts will not fall off even if the connector is heated in a furnace when it is installed (surface-mounted) on a circuit board. 
     In order to achieve these objectives, the present invention provides a nut-prefixed connector with a nut-fixing part which is provided in a housing. This nut-fixing part includes a nut-holding room, and a nut is insertable into and detachable from the nut-holding room by a movement in a direction perpendicular to the thickness direction of the nut. In addition, a projection is provided at the entrance of the nut-holding room to prevent the nut inserted in the nut-holding room from coming out. 
     In a prior-art connector of this type, the nut inserted in the nut-holding room is retained therein by the pressure exerted by the elastic deformation of the housing as a result of the press-fitting of the nut. However, in the nut-prefixed connector according to the present invention, the nut inserted in the nut-holding room of the housing is held therein by the projection, which is provided at the entrance thereof, so the housing of the connector according to the present invention does not need as great a strength as required for the prior-art connector, which must withstand the press-fitting of the nut. Therefore, the housing of the connector according to the present invention can be formed thinner with reduced external dimensions than that of the prior-art connector. Thus, the present invention enables a further miniaturization of the connector. In addition, when this connector is mounted on a circuit board and passed through a furnace during an assembly process, even if the housing experiences a stress relief because of the heating, there is no possibility of the nut falling off from the housing. In a case of the prior-art connector whose nut is press-fit and retained therein by the elastic deformation of the housing, the nut may fall off as the housing experiences a stress relief. Because there is no such problem with the connector according to the present invention, the assembly process can be operated at an improved efficiency. Furthermore, in the connector according to the present invention, the nut inserted is kept therein by a simple structure, not by the pressure that is generated from the deformation of the housing, which is the case with the prior-art connector. As a result, the nut-fixing part of the connector according to the present invention does not require the same level of precision for the dimensions of the nut-holding room as the prior-art connector. Therefore, the cost-effectiveness of the connector can be improved further. In addition, because the design of the nut-holding room does not require a high level of precision, a few types of nuts with a relatively wide range of dimensions (especially for the thickness) can be used in the connector without any design change of the housing. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only and thus are not limitative of the present invention. 
     FIG. 1 is a perspective view of a nut-prefixed connector according to the present invention, looked at slantingly from a front side. 
     FIG. 2 is a perspective view of the connector, looked at slantingly from a rear side. 
     FIG. 3 is a plan view of the connector. 
     FIGS. 4A and 4B are perspective views of a nut-fixing part of another nut-prefixed connector according to the present invention. FIG. 4A is a view being looked at slantingly from a front side while FIG. 4B is a view being looked at slantingly from a rear side. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG.  1  and FIG. 2 show a nut-prefixed connector (hereinafter referred to simply as “connector”)  1  according to the present invention with a matable connector  81 , which engages with this connector  1 . FIG. 1 shows a view of the connector  1  slantingly from a front side while FIG. 2 shows a view of the same connector slantingly from a rear side ( the direction in which the connector  1  faces the matable connector  81  is herein defined as “forward”). 
     As shown in these figures, the connector  1  comprises a housing  10 , which has a laterally extending rectangular box figure, and a plurality of contacts  12 , which are mounted in the housing  10 , each contact extending in the front and rear direction. As shown in FIG. 1, the housing  10  opens forward, and it has a protrusion  11  which protrudes forward in the opening. The contacts  12  are mounted through the protrusion  11  in two rows, each row extending laterally. As shown in FIG. 2, the lead portions  12   a  of the contacts  12  which extend outward from the rear of the connector  1  are surface-mounted and connected onto connection terminals of electrical pathways of a circuit printed on a circuit board  60  (not shown in FIGS.  1  and  2 ). 
     The housing  10  is provided with nut-fixing parts  20  at the right and left ends thereof, and nuts ( hexagon nuts )  30  are attached in the nut-fixing parts  20 , respectively. The housing  10  includes through-holes  13  (refer to FIG. 3 ) which extend downward from the nut-fixing parts  20 , respectively. The nuts  30  are engageable with bolts  40 . At first, the connector is placed and positioned on the circuit board to align the lead portions  12   a  of the contacts  12  with the corresponding connection terminals of the electrical pathways of the circuit on the circuit board  60 , and then the bolts  40  are inserted from the lower surface of the circuit board  60  upward through the circuit board  60  and the through-holes  13  of the connector. By fixing the bolts  40  to the nuts  30 , the connector  1  is fixed firmly on the circuit board  60 . 
     With the connector  1 , which is fixed on the circuit board  60 , a matable connector  81  is engaged by moving the matable connector  81  relatively in the direction shown by arrow A in FIG.  1 . The housing of the matable connector  81  has an opening (not shown), where a concave part is provided to receive the protrusion  11  of the connector  1 . In this concave part of the matable connector  81 , a plurality of contacts are provided and arranged to meet and engage with the corresponding contacts  12  in the protrusion  11  of the connector  1 . As a result, when the connector  1  is engaged with the matable connector  81 , a signal transmission is possible through the connector assembly. 
     FIG. 3 is a plan view of the connector  1  (the lower side of the figure is the front of the connector  1 . Bolts  40  are not shown). The nut-fixing parts  20 , which are to hold the nuts  30 , are provided at the right and left ends of the housing  10  as shown in this figure. Each nut-fixing part  20  in the body of the housing  10  includes a lower wall  21  which is formed lower than the upper surface of the housing  10 , four lateral walls  22  which are to meet four lateral surfaces of the six lateral faces of the nut  30 , and three nut-holding arms (upper wall)  23  which extend horizontally inward from the lateral walls  22 . The lower wall  21 , the lateral walls  22 , and the nut-holding arms  23  together define a nut-holding room  26 , where a nut  30  is insertable by a shift in a direction perpendicular to the thickness direction of the nut  30 . The nut-holding room  26  has a storing space just enough to accommodate the nut, so the inserted nut  30  cannot wobble. Furthermore, a projection  27  is formed with the housing  10  at the entrance of the nut-holding room  26  to prevent the nut  30  inserted in the nut-holding room  26  from escaping. 
     For installing the nuts  30  in the nut-fixing parts  20 , the nuts  30  are inserted through the entrance of the nut-holding room  26 . As shown in FIG. 3, the entrance of the nut-holding room  26  are provided in the diagonal directions of the housing  10 , so the right and left nuts  30  are inserted in the diagonal cross directions of the housing  10 . Four lateral surfaces of each nut  30  installed in a corresponding nut-holding room  26  are in contact with the four lateral walls  22  of the nut-fixing part  20  of the housing  10  while one of the remaining lateral surfaces of the nut  30  is in contact with the inner face  27   a  of the projection  27 . In this condition, the nuts  30  are fixed firmly in the nut-fixing parts  20 , respectively. As shown in FIG.  1  and FIG. 2, preferably, each projection  27  is formed with a gentle slope (tapered like a triangular column as shown in the figure) in the direction of the insertion of the nut  30 . With this arrangement, the nuts  30  are inserted relatively easily, but they will not come out so easily from the nut-holding rooms  26 . If the housing  10  is made of a resin, then the insertion of the nuts  30  will be easier because the whole nut-fixing parts  20  can undergo an elastic deformation. 
     In this connector  1 , the nuts  30  inserted in the nut-holding rooms  26  of the housing  10  are held therein by the projections  27  provided at the entrances thereof. As the nuts  30  are not installed and fixed by a method of press-fitting, the housing  10  does not need to be formed with a thickness which is required to withstand the impact of the press-fitting in a conventional connector. Therefore, the external dimensions of this connector can be reduced to miniaturize the connector  1 . Furthermore, when this connector  1  is surface-mounted on the circuit board  60  by placing the lead portions  12   a  of the contacts  12  of the connector  1  on the connection terminals of the electrical pathways of the circuit printed on the circuit board and then by passing the connector and the circuit board together through a furnace to heat and fuse the solder provided between the lead portions  12   a  of the contacts  12  and the corresponding terminals of the circuit, there is no possibility of any of the nuts  30  to fall off from the housing. As mentioned previously, in the case of a prior-art connector whose nuts are press-fit therein, the housing may lose one or two of the nuts during this heating process because the housing holding the nuts loosens to release the stress that is created from the press-fitting of the nuts. In comparison, the connector  1  according to the present invention is advantageous on this point because of the above described construction of the connector  1 , so the assembly process can be carried out more efficiently. 
     Furthermore, the entrances of the nut-holding rooms  26  of the connector  1  are arranged diagonally, so the projections  27  can be provided easily on the lateral lower walls  21  at corners of the housing  10  without sparing special spaces for the positioning of the projections  27 . In other words, if the entrances of the nut-holding rooms  26  were arranged in the front and rear direction or in the right and left direction, the housing  10  would need extra spaces in the front and rear direction or in the right and left direction for the provision of the projections  27 . However, the connector  1  constructed as described above is compact without any such extra space. Moreover, the nuts of the connector  1  are kept therein not by the pressure generated by the deformation of the housing, which is the case when the nuts are press-fit in a prior-art connector, but they are maintained there by a simple structure which is designed to hold the nuts. This structural feature does not require the same degree of precision for the dimensions of the nut-holding rooms  26  as the prior-art connector. Therefore, the production cost of the connector  1  can be comparatively low. In addition, because the design of the nut-holding rooms  26  does not require a high degree of precision, a few types of nuts with a relatively wide range of dimensions (especially with various dimensions for the thickness) can be used in the connector  1  without any design change of the housing  10 . 
     In the connector  1 , each of the upper walls of the nut-holding rooms  26  is constituted of a plurality of nut-holding arms  23 , which project inward from the upper end of the nut-holding room  26  to hold the respective nut  30 , so the nut-holding rooms  26  are not totally closed but are somewhat open upward. This construction is advantageous for fabricating metal molds to mass-produce the housing  10 , so the connector  1  can be manufactured cost-effectively. 
     Another embodiment of nut-prefixed connector according to the present invention is shown in FIG.  4 A and FIG.  4 B. The design of this connector is based on a conventional connector whose nuts are press-fit in the housing, but the housing of this connector includes projections, each of which is provided at the entrance of a corresponding nut-holding room ( where a nut is press-fit) to prevent the respective nuts from coming out. The side of the housing which has openings for receiving nuts  130  is defined here as the front of the connector. In this housing, each of the openings leads to a nut-fixing part  120 , respectively, and each nut-fixing part  120  comprises an upper wall  121 , a lower wall  122 , right and left lateral walls  123  and  124  and a rear wall  125 . These walls together define a nut-holding room  126  which can receive a nut  130  inserted by a relative movement in a direction perpendicular to the thickness of the nut. The centers of the upper wall  121  and the lower wall  122  are U-shaped, opening forward to make the press-fitting of the nuts  130  easier, and a projection  127  is provided at the entrance of the nut-holding room  126  on the right lateral wall  124  of the housing to prevent the nut  130  from escaping. 
     For the installation of the nut  130  in the nut-fixing part  120 , the nut  130  is inserted through the entrance of the nut-holding room from the front of the connector. Upon insertion, the nut  130  received in the nut-holding room  126  is held and fixed by the projection  127  in the nut-fixing part  120  in the same way as in the case of the above-mentioned embodiment. It means that if the housing of a prior-art connector having press-fit nuts is provided with a projection at the entrance of the nut-holding room, the nuts are prevented from escaping. In this way, the same effect is achieved as the previously mentioned embodiment. In the embodiment shown in FIG. 4, the projection  127  is provided on the lateral wall  124  of the nut-fixing part  120 . However, the projection  127  may be provided on the upper wall  121  or on the lower wall  122 , instead. 
     The present invention is not limited to the above described embodiments of nut-prefixed connector. For example, other embodiments are also possible as long as the nut-holding room is formed to receive a nut which is inserted therein by a relative movement in a direction perpendicular to the thickness direction of the nut. Also, the upper or lower wall does not need to be open as in the above described embodiments. However, if the connector is designed to have an opening in the upper or lower wall, then the molding of the housing can be simpler, and also the rigidity of the nut-fixing part becomes smaller, making the insertion of the nut into the nut-holding room easier. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.