Abstract:
An electrical contact for attachment to an insulated wire includes an insulator crimp section ( 11 ) having a pair of insulation engaging arms ( 12   a   , 12   b ) which are offset from each in an axial direction of the wire. The insulation engaging arms include facing edges ( 38   a   , 38   b ) which are arranged to contact each other along a spiral track when the insulation engaging arms are press-bonded to the insulation of the wire. Inside beveled surfaces ( 18   a   , 18   b ) and outside beveled surfaces ( 28   a   , 28   b ) serve to guide the insulation engaging arms into position and to facilitate sliding contact between the facing edges ( 38   a   , 38   b ) during the press-bonding. The inside beveled surfaces ( 18   a   , 18   b ) also provide a gap ( 4 B) which serves as a relief area for compressed insulation. As a result of the press-bonding, the insulation engaging arms ( 12   a   , 12   b ) are formed into an integral unit and are strongly fastened to the insulation of the electrical wire.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an electrical contact and a method for press-bonding [this] electrical contact to an electrical wire. 
     DESCRIPTION OF THE PRIOR ART 
     Electrical contacts having wire retaining barrels engage and maintain an electrical wire therein are generally known in the art. One example of such an electrical contact, which is disclosed in Japanese Utility Model Application Kokoku No. S45-33001, is shown in FIG.  7 . This electrical contact  100  has a contact part  102  that electrically contacts a mating electrical contact (not shown in the figures), and a wire retention part  104  that is connected by bending the barrel around the outer circumference of an electrical wire (not shown in the figures). The wire retention part  104  is constructed from a pair of conductor barrels  104   a ,  104   a  which are bent about the core of the wire and frictionally engage the core wire, i.e., the conductor of the electrical wire. A pair of insulator barrels  104   b ,  104   b  are also provided and are bent about the outer covering of the wire and frictionally engage the outer covering, i.e., the insulation of the electrical wire. The conductor barrels  104   a ,  104   a  are formed so that their positions are offset relative to each other in the axial direction of the electrical contact  100 . The insulator barrels  104   b ,  104   b  are also formed so that their positions are offset relative to each other in the axial direction of the electrical contact  100 . The barrels are bent or press-bonded so that they envelop and frictionally engage the electrical wire from both sides of the electrical wire, thus pressing and fastening the outer covering of the electrical wire in place with the broadest possible area. 
     Furthermore, an electrical contact in which beveled surfaces are formed on the tip ends of the insulator barrels that are press-bonded or frictionally engaged to the outer covering of the electrical wire is disclosed in Japanese Utility Model Application Kokai No. S56-119264. 
     The barrel parts  104   b ,  104   b  of the electrical contact  100  disclosed in the above-mentioned Japanese Utility Model Application Kokoku No. S45-33001 are separated from each other in the axial direction of the electrical contact  100  after the barrels have been bent; accordingly, these barrel parts  104   b ,  104   b  are wrapped around the circumference of the outer covering of the electrical wire without contacting each other. As a result, the electrical contact  100  can be used on wires of various diameters, and the total length of the electrical contact  100  can be made relatively short. However, the pair of barrel parts  104   b ,  104   b  have no structural integrity following bending or press-bonding; consequently, the barrel parts  104   b ,  104   b  tend to open, so that the frictional engagement with the wire is weak, thereby allowing the wire to be inadvertently removed causing electrical failure. 
     Furthermore, in the latter prior art example, there are limits on the diameter of the electrical wires that can be used. Moreover, there is a danger that the tip ends of the insulator barrel will strike each other and bite into the outer covering of the electrical wire creating the possibility of damage to the outer covering of the electrical wire. 
     SUMMARY OF THE INVENTION 
     The present invention was devised to solve the above referenced problems. Consequently, the invention provides a compact electrical contact which has a high press-bonding strength while facilitating a broad range of applicable electrical wire diameters. 
     The electrical contact of the present invention has an electrical contact part, a conductor barrel that is press-bonded to or in frictional engagement with the core wire of an electrical wire, and an insulator barrel that is press-bonded to or in frictional engagement with the insulating covering of the electrical wire. The insulator barrel is constructed from a pair of left and right press-bonding parts disposed in positions that are offset relative to each other in the axial direction of the electrical wire. The electrical contact is constructed so that when the press-bonding parts are press-bonded to the electrical wire, the facing edges of the press-bonding parts, which face each other in the axial direction, contact each other on the electrical wire. 
     Both surfaces of the facing edges of the press-bonding parts may be subjected to swage working. Alternatively, the entire circumferences of only the inside surfaces of the press-bonding parts may be subjected to swage working. Or the entire circumferences of the outside surfaces may be subjected to swage working in addition to the entire circumferences of the inside surfaces. 
     The term “both surfaces of the facing edges” refers to both the inside surfaces of the facing edge parts of the plate members that form the press-bonding parts, i.e., the surfaces that contact the outer covering of the electrical wire when press-bonding is performed, and the outside surfaces of the facing edge parts, i.e., the surfaces that can be seen from the outside following press-bonding. 
     The term “entire circumference” does not necessarily refer strictly to the entire circumference of each press-bonding part; this term also refers to cases in which the area in the vicinity of the fixed end of each press-bonding part is not included in this circumference. 
     The shapes of the tip end portions of the press-bonding parts and the shapes of the corresponding portions that face these tip end portions during the press-bonding of the press-bonding parts may be complementary shapes. In addition to cases in which the shapes of the entire tip end portions of the press-bonding parts and the shapes of the corresponding portions of the electrical contact are shapes that are complementary to each other, the term “complementary” also includes cases in which the shapes of only portions of the tip end portions and the shapes of the corresponding portions are shapes that are complementary to each other. 
     The electrical wire press-bonding method using the electrical contact of the present invention is also described. When the electrical contact is press-bonded to the electrical wire, the pair of press-bonding parts make sliding contact with each other at the facing edges of said press-bonding parts, so that the respective tip ends of the press-bonding parts move while describing portions of a spiral track along the outer circumference of the aforementioned electrical wire. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of an electrical contact of the present invention. 
     FIG. 2 is a front view of the electrical contact shown in FIG.  1 . 
     FIG. 3 is a side view of the electrical contact shown in FIG.  1 . 
     FIG. 4 are partial enlarged views showing the electrical contact press-bonded to a large-diameter electrical wire. FIG.  4 (A) is a side view of the press-bonded parts, FIG.  4 (B) is a front view, and FIG.  4 (C) is a side view of the opposite side. 
     FIG. 5 are partial enlarged views similar to those of FIG. 4 showing the electrical contact press-bonded to a small-diameter electrical wire. FIG.  5 (A) is a side view of the press-bonded parts, FIG.  5 (B) is a front view, and FIG.  5 (C) is a side view of the opposite side. 
     FIG. 6 are partial enlarged sectional views of the press-bonding parts along line  6 — 6  in FIG.  4 (B). FIG.  6 (A) shows a state in which the press-bonding parts are overlapped, and FIG.  6 (B) shows a state in which the press-bonding parts are properly press-bonded. 
     FIG. 7 is a perspective view which shows one example of a conventional electrical contact according to the prior art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The contact  1  is formed by stamping and bending a single metal plate. The contact main body  4  is substantially box-shaped, and has a pin receiving section  6  in front, and a wire termination section  8  in the rear. The wire termination section  8  has a conductor crimp section  10  and an insulator crimp section  11 . The main body  4  has a set of side walls  13  that extend parallel to each other. The side walls  13  extend from the main body  4  to the pin receiving section  6 . A bridge or partial top wall  16  is formed on the front end portion of a first respective side wall  13 . The bridge extends from the respective side wall to the other side wall, such that the side walls  13  are bridged by this bridge  16 . In the rear portion of the main body  4 , a connecting member  20  extends from the upper edge of the other side wall  13 , and forms a bridge to the first respective side wall  13 . A cut-out  24  is formed in the connecting member  20 . A tongue  26 , which has a shape that is complementary to the shape of the cut-out  24 , protrudes from the first respective side wall  13 . The side walls  13  are connected as a result of the engagement of the tongue  26  with the cut-out  24 . 
     A resilient contact section  30  extends from the connecting member  20  toward the interior of the pin receiving section  6  along the longitudinal axis of the contact  1 . A lance  36 , pushed out by means of a press mold (not shown in the figures), is formed as an integral part of a bottom wall  34  of the pin receiving section  6  opposite the resilient contact section  30 . 
     The conductor crimp section  10 , which is formed as an integral part of the main body  4  at the rear of the main body  4 , is fastened to a core wire or conductor  52  (FIG. 4) of wire  50  or to a core wire or conductor  62  (FIG. 5) of wire  60  by crimping or any other known means of terminating a conductor to a terminal. The insulator crimp section  11  is formed to the rear of the conductor crimp section  10 . The insulator crimp section  11  has a pair of insulator engaging arms  12   a  and  12   b  whose positions are offset relative to each other in the axial direction of the contact  1 . These insulator engaging arms  12   a  and  12   b  are fastened by crimping or press-bonding to the outer insulation covering  54  (FIG. 4) of the wire  50  or the insulation covering  64  (FIG. 5) of the wire  60 . 
     As best shown in FIG. 6, the inner circumferential edges of the insulation engaging arms  12   a  and  12   b  are swaged or work hardened to create inside beveled surfaces  18   a  and  18   b  on the interior surface  15   a  and  15   b  thereof. The surfaces  15   a  and  15   b  engage the insulation covering  54  or  64 . Furthermore, the outer circumferential edges of the insulation engaging arms  12   a  and  12   b  are swaged or work hardened to create outside beveled surfaces  28   a  and  28   b  on the outside surfaces  22   a  and  22   b  of the insulation engaging arms  12   a  and  12   b.    
     As is shown in FIG. 4, the outer covering  54  of the electrical wire  50  is press-bonded or crimped by the insulation engaging arms such that the outer covering  54  is captured from both sides by the insulation engaging arms  12   a  and  12   b . The core wire  52  is crimped and electrically connected by the conductor crimp section  10 . When pressure from a crimping force is applied to the insulation engaging arms  12   a  and  12   b , the respective facing edges  38   a  and  38   b , that are positioned facing each other in the axial direction, contact each other as shown in FIG.  4 (B). As crimping is performed, the facing edges  38   a  and  38   b  move in opposite directions as indicated by the arrows M and M′ while making sliding contact with each other. Since the insulation engaging arms  12   a  and  12   b  are tapered from the tip end portions  40   a  and  40   b  to the fixed ends of the insulation engaging arms, the insulation engaging arms  12   a  and  12   b  move in opposite directions in the axial direction of the electrical wire  50  while making sliding contact with each other. In this case, the tip end portions  40   a  and  40   b  describe portions of a spiral track along the outer circumference of the electrical wire  50 . As a result, the insulator engaging arms  12   a  and  12   b  are formed into an integral unit, and are fastened by crimping or press-bonding to the electrical wire  50 . Since the electrical wire  50  has a large diameter, the tip end portions  40   a  and  40   b  of the respective press-bonding parts  12   a  and  12   b  do not reach the edges of corresponding portions (described later) of the contact  1 , as is shown in FIGS.  4 (A) and  4 (C). 
     In the case of a small-diameter wire  60 , as is shown in FIG. 5, the insulator engaging arms  12   a  and  12   b  are completely wrapped around the circumference of the electrical wire  60 . As is shown in FIG. 5, the insulator engaging arms  12   a  and  12   b  are wrapped further around the outer circumference of the electrical wire  60  than the arms are in the case of the electrical wire  50 . Accordingly, the range in which the facing edges  38   a  and  38   b  make sliding contact is greatly increased. Furthermore, the respective insulator engaging arms  12   a  and  12   b  are further displaced in opposite directions along the axial line of the electrical wire  60 , so that the electrical wire  60  is firmly held in position, In this embodiment, the tip end portion  40   a  of the insulator engaging arm  12   a  is positioned in the first corresponding portion  42  of the contact  1 . This first corresponding portion  42  is located in a transition area between the insulator engaging arm  12   b  and the conductor crimp section  10 , and has a curved shape that is complementary to the shape of the tip end portion  40   a . The tip end portion  40   a  fits precisely into the first corresponding portion  42 , so that movement of the tip end portion  40   a  into and away from the outer insulation covering  64  is prevented. As a result, damage to the outer covering  64  of the electrical wire  60  that might be caused by the tip end portion  40   a  of the insulator engaging arm  12   a  moving inward and biting into the outer covering  64 , as well as an increase in the external dimensions of the contact  1  that might be caused by the tip end portion  40   a  moving outward, can be prevented. Furthermore, the tip end portion  40   a  and first corresponding portion  42  make surface contact with the electrical wire  60  as an integral unit, so that strong press-bonding or crimping is accomplished. 
     As is shown in FIG.  5 (A), a second corresponding portion  44  that corresponds to the tip end portion  40   b  of the insulator engaging arm  12   b  is at the rear end of the contact  1 . A part of the second corresponding portion  44  has a complementary shape to the conductor engaging arm  12   b.    
     In a case where the facing edge  38   b  of the insulator engaging arm  12   b  rides over the facing edge  38   a  of the insulation engaging arm  12   a  as shown in FIG.  6 (A), if a pressing force used for the purpose of press-bonding or crimping is applied from above in the direction indicated by the arrow F, the inside beveled surface  18   b  slips over the outside beveled surface  28   a , so that the insulator engaging arm  12   b  moves diagonally downward in the direction indicated by the arrow D. As a result, the insulator engaging arm  12   b  is moved to the position shown in FIG.  6 (B). Since the inside beveled surfaces  18   a  and  18   b  facing the insulation covering  54  of the wire  50  are both tapered with respect to the insulation covering  54  in a direction away from the insulation covering  54 , the insulator engaging arms  12   a  and  12   b  are prevented from biting into the insulation covering  54  during the crimping process. Furthermore, in the engaged state, as in shown in FIG.  6 (B), a portion of the insulation covering  54  that is displaced due to the compression caused by the press-bonding enters a gap  48  formed between the inside beveled surface  18   a  and the inside beveled surface  18   b  . As a result, the insulator engaging arm  12   a  and  12   b  and the insulation covering  54  engage with each other in an interlocking state, thus preventing relative movement of the electrical wire  50  and contact  1 . The same is true in the case of the small-diameter wire  60 . 
     The present invention is described in detail with reference to the embodiments shown in the drawings. However, these embodiments are illustrative and the invention is not limited to such embodiments. For example, it would also be possible to swage only the inside surface of each of the insulation engaging arms  12   a  and  12   b , and to omit swaging on the outside surfaces. The corrective effect such as that shown in FIG.  6 (A) can be obtained in this case as well. 
     Furthermore, in regard to the electrical contact of the present invention, a female-type contact is described in the embodiment; however, invention can also be used in a male-type contact. 
     Advantageously, when the pair of insulator engaging arms are disposed in positions that are offset relative to each other in the axial direction of the electrical wire and are crimped or press-bonded to the electrical wire, the facing edges of the insulator engaging arms contact each other and contact the electrical wire. Accordingly, the press-bonding strength can be increased by forming the pair of insulator engaging arms into a unit that has structural integrity while maintaining a broad range of applicable electrical wire diameters. Furthermore, since the facing insulator engaging arms are not separated by a gap in the axial direction of the electrical wire, the dimension of the electrical contact in the axial direction can be shortened, so that a compact connector can be obtained. 
     Furthermore, in a case where both surfaces of the facing edges of the insulator engaging arms are subjected to swage working, even if the insulator engaging arms should overlap each other in the swage-worked areas, the insulator engaging arms will be caused to move laterally in the mutual swage-worked areas by the pressing force during press-bonding, so that the insulator engaging arms are corrected to the proper position. Accordingly, overlapping of the insulator engaging arms is prevented, so that an increase in the external dimensions of the electrical contact can be avoided. 
     Furthermore, if the entire circumference of the inside surface of each insulator engaging arm is subjected to swage working, the gaps formed in the swage-worked areas act as relief areas for the compressed insulation covering. This prevents the insulator engaging arms from biting into or damaging the insulation covering. This is especially effective in the case of electrical wires that are superior in terms of flexibility but easily damaged, e.g., electrical wires with an outer covering made of silicone, etc., that extend to the back side of the display screen in notebook-type personal computers. 
     Furthermore, if the entire circumference of the outside surface of each insulator engaging arm is subjected to swage working, flash generated on the outside surface is eliminated. Accordingly, when the electrical contact is inserted into the cavity of a connector housing, there is no interference between the inside walls of the cavity and such flash, so that the insertion of the electrical contact can be smoothly accomplished. 
     Furthermore, if the shape of the tip end portions of the insulator engaging arms and the shape of the corresponding portions that are contacted by these tip end portions during the crimping or press-bonding of the insulation engaging arms are complementary in shape, then sliding contact between the insulation engaging arms can be smoothly accomplished. The tip end portions are prevented from movement toward or away from the wire. Specifically, since there is no protrusion of the tip end portions of the insulation engaging arms, an increase in the external dimensions of the contact can be prevented. 
     In the electrical wire crimping or press-bonding method using the electrical contact of the present invention, the pair of insulation engaging arms, that are press-bonded when the electrical contact is press-bonded to the electrical wire, make sliding contact with each other at the facing edges of the insulation engaging arms. In so doing, the respective tip ends of the insulation engaging arms move while describing portions of a spiral track along the outer circumference of the electrical wire. Accordingly, an increase in the contact area with the electrical wire is smoothly accomplished along with the formation of the insulation engaging arms into an integral unit, so that a contact that has a large press-bonding strength and a small dimension in the axial direction is obtained.