Terminal and crimping method

Abstract: To provide a terminal capable of securing an electrical connection. A folded portion 55 is placed on a bottom portion 48 while a bottom projection 61 provided at the bottom portion 48 of an outer terminal 40 is biting thereinto. After a crimping piece 46 is brought into close contact with the outer surface of the folded portion 55 and an upper projection 62 is caused to bite into a sheath 54 of the folded portion 55, a crimping piece 47 is brought into close contact with the outer surface of the folded portion 55 and the end thereof is placed on that of the crimping piece 46. In this way, crimping is performed. Then, an outer crimping portion 45 squeezes the sheath 54 and is crimped while being held in close contact with the sheath 54 of the folded portion 55, and the two projections 61, 62 bite into the sheath 54. Since the folded portion 55 and the outer crimping portion 45 are electrically connected to a sufficient degree and a sufficient fastening force can be obtained, a stable electrical connection can be established.

Description: The present invention relates to a terminal and to a method for crimping a terminal on a shielded cable, and particularly relates to a terminal to be connected with a shielded cable by crimping. One of known terminals of this type is disclosed in Japanese Unexamined Utility Model Publication No. 5-27983. This terminal 1 is provided with an inner conductor crimping portion 1a, an outer conductor crimping portion 1b and a sheath crimping portion 1c as shown in FIG. 11. The above known terminal 1 is obliged to have a long length since it has the inner conductor crimping portion 1a, the outer conductor crimping portion 1b and the sheath crimping portion 1c for the connection with a shielded cable 2. This stands as a hindrance to making the entire terminal smaller. As a countermeasure, it may be considered to use one crimping portion which serves both as the outer conductor crimping portion 1b and as a sheath crimping portion 1c. In such a case, the outer conductor is folded back over the sheath in the cable and crimping is applied to this folded portion, and the terminal is designed not to damage the outer conductor. Alternatively, it is desirable to apply so-called "overlap crimping" in order to deal with a variation in cable diameter or for other purposes. Even with the above arrangements, it is necessary to increase a fastening force in the crimped portion in order to compensate for a reduction in the number of the crimped portions. This is also essential to ensure an electrical conduction with the outer conductor. GB1007053 describes a terminal having a crimping portion which comprises two crimping pieces. The crimping pieces are connected by a bottom section of the crimping portion. The bottom section and the crimping pieces are provided with indents forming inward protuberances for biting into the outer braid conductor of a coaxial conductor. The indents formed in the crimping pieces are equally spaced from the bottom section and from the leading ends of the crimping pieces. It is an object of the present invention to provide a terminal which ensures a satisfactory fastening within a range of outer diameters of the cable. This object is solved according to the invention by a terminal according to claim 1 and by a method according to claim 8. Preferred embodiments are subject of the dependent claims. According to the invention, there is provided a terminal, comprising a crimping portion to be fastened to an end of a shielded cable in which an insulating element is provided between inner and outer conductors and the outer surface is covered by a sheath, wherein the crimping portion can be fastened to the outer conductor, the crimping portion comprising one or more crimping pieces which are to be so crimped as to at least partly wind on or around the outer conductor being preferably folded back over the sheath, wherein one or more projections are provided in such positions of the inner surface of the crimping portion as to hold the outer conductor preferably folded back over the sheath while biting thereinto, and wherein at least one projection is provided in a specified position of a bottom surface of the crimping portion and at least one projection is provided in a position at the leading end of the crimping piece, preferably the second crimping piece placeable below after crimping. According to a preferred embodiment, the crimping portion can be fastened both to the sheath and to the outer conductor being preferably folded back over the sheath. Accordingly, a higher mechanical strength is provided for and particularly the connection is less sensitive to mechanical forces (such as pulling) on the shielded cable. Preferably, the crimping pieces are to be or can be so crimped as to at least partly wind on or around the outer conductor with the end of a first crimping piece substantially placed or placeable on that of a second crimping piece. Accordingly, an "overlap crimping" is advantageously possible. Accordingly, crimping is applied to a portion where the outer conductor is folded back over the sheath so that the terminal can be simultaneously fastened to the outer conductor and to the sheath. Accordingly, the entire length of the terminal is allowed to be shorter. In this case, the projections provided at the crimping portion hold the shielded cable by biting into the outer conductor folded back over the sheath. Thus, the terminal can be fastened to the shielded cable with a sufficient force. Further, the terminal can be stably fastened to the shielded cable since the projections are so arranged as to firmly hold the shielded cables. Preferably, the at least two crimping pieces extend from the bottom surface of the crimping portion while being spaced apart wider from each other toward the leading ends thereof. According to a further preferred embodiment, the crimping pieces extend from the bottom surface of the crimping portion while being spaced apart wider from each other toward the leading ends thereof, and at least one projection is provided in a specified position of the bottom surface of the crimping portion and at least one projection is provided in a position at the leading end of the other crimping piece placed below. Accordingly, since the projections are arranged at the bottom surface and at the leading end of one of the crimping pieces spaced apart wider toward the leading ends thereof, i.e. since they are arranged in such positions that the projections and the shielded cable are unlikely to interfere with each other when the shielded cable is inserted into the terminal for crimping, the shielded cable can be smoothly inserted. Preferably, the projection provided at the leading end of the second or other crimping piece placed below after crimping is provided in a position spaced apart from the leading edge of the other crimping piece by a specified distance such that this projection can be located substantially right above the projection at the bottom surface when the outer diameter of the outer conductor, preferably of the folded portion of the outer conductor is a reference value of its range of variation. The outer diameter of the outer conductor at the folded portion may vary. In such a case, the position of the projection located at the leading end of the crimping piece after crimping is circumferentially displaced. As a result, the biting forces of this projection and the one at the bottom surface may not be balanced along vertical direction. However, according to the above embodiment, if the terminal is fastened to the folded portion whose outer diameter is a reference value (about a middle value between the maximum and minimum diameters) of a range of predictable variation, the projection at the crimping piece can be located substantially right above the one at the bottom surface. When the folded portion whose outer diameter is the maximum or minimum value of the predictable variation range is fastened, the projection at the crimping piece is only circumferentially displaced from the right above position by an equal angle, which does not hinder the fastening in either case. Most preferably, each projection has such a wedge-shape that its front surface extends at an angle different from 0° or 180°, preferably substantially normal to an insertion direction of the cable and its height is lowered toward the back. Accordingly, since each projection is wedge-shaped, the shielded cable can be smoothly inserted without the projection getting caught by the shielded cable, especially by the outer conductor folded back over the sheath. Therefore, the cable can be inserted with an improved efficiency. According to the invention, there is further provided a method for crimping a terminal according to the invention having a crimping portion on a shielded cable, in which an insulating element is provided between inner and outer conductors and the outer surface is covered by a sheath, comprising the following steps: stripping the sheath to substantially expose the outer conductor; and fastening the crimping portion to the outer conductor by at least partly winding one or more crimping pieces of the crimping portion on or around the outer conductor thereby biting one or more projections provided on the crimping portion into the outer sheath. According to a preferred embodiment, in the fastening step the crimping portion is fastened to both the sheath and the outer conductor being preferably folded back over the sheath. Preferably, in the fastening step the crimping pieces are so crimped as to at least partly wind on or around the outer conductor with the end of a first crimping piece substantially placed or placeable on that of a second crimping piece. These and other objects, features and advantages of the present invention will become more apparent upon a reading of the following detailed description and accompanying drawings in which: FIG. 1 is an exploded side view showing parts constructing a terminal according to a first embodiment, FIG. 2 is a perspective view of an outer terminal of the terminal, FIG. 3 is an enlarged view of a projection, FIG. 4 is a perspective view of the terminal before being fastened to a folded portion, FIG. 5 is a perspective view of the terminal after crimping, FIG. 6 is a vertical section of the terminal after crimping, FIG. 7 is a horizontal section of an outer conductor crimping portion and the folded portion after crimping, FIGS. 8(a) and 8(b) are horizontal sections of the outer conductor crimping portions when shielded cables of different diameters are fastened, FIG. 9 is a perspective view of an outer terminal of a terminal according to a second embodiment, FIG. 10 is an enlarged view of a projection of a terminal according to an other embodiment (2), and FIG. 11 is a perspective view of a prior art terminal. Hereinafter, embodiments of the invention are described with reference to the accompanying drawings. < First Embodiment> A shielded connector 10 according to the first embodiment has such an integral construction that an inner terminal 20 is at least partly accommodated substantially in an outer terminal 40 via a dielectric element 30, and a shielded cable 50 is connected or connectable therewith. In the description below, a side (right side in FIG. 1) of the connector 10 to be connected with an unillustrated mating connector is referred to as a front side and an opening direction (an upward direction in FIG. 1) of an outer crimping portion 45 before being assembled is referred to as an upward direction. The shielded cable 50 is constructed such that an insulating element 53 is provided between an inner conductor 51 formed e.g. by bundling a plurality of strands and an outer conductor 52 made e.g. of a braided wire and the outer surface of the outer conductor 52 is surrounded by a sheath 54 made of, e.g. vinyl (see FIG. 1). The inner conductor 51 is connected or connectable with the inner terminal 20, whereas the outer conductor 52 is connected or connectable with the outer terminal 40. The inner terminal 20 is preferably a female terminal as shown in FIG. 1 and is electrically conductive. A front part of the inner terminal 20 is a tab portion 21 engageable with an unillustrated female terminal and a tapered surface 22 is formed at the leading end thereof. At a rear part of the inner terminal 20 is provided a biting or engaging projection 23 for securing the inner terminal 20 by biting into or engaging the upper wall of an accommodating hole 31 when being inserted into the dielectric element 30 to be described later. Behind the biting projection 23 is provided an inner crimping portion 24 to be fastened to the inner conductor 51. The dielectric element-30 is made of an insulating material such as resin, and is electrically insulated from the inner and outer terminals 20, 40. Inside the dielectric element 30 is defined the accommodating hole 31 for fixing the inner terminal 20 accommodated therein. In order to be fixed in the outer terminal 40, the upper wall of the dielectric element 30 is formed with a locking recess 32 and the bottom wall thereof is formed with a contact portion 33 (see FIG. 1). The outer terminal 40 is formed e.g. by bending an electrically conductive plate, and a front part thereof is an accommodating portion 41 preferably in the form of a rectangular tube. In order to lock the aforementioned dielectric element 30 in a specified position in the accommodating portion 41, a substantially elastically deformable locking portion 42 and a contact piece 49 are provided on the upper and bottom walls of the accommodating portion 41, respectively. Contact pieces 43 for substantially elastically contacting an unillustrated shielded connector and locking it are provided on the left and right side walls. Behind the accommodating portion 41, stabilizers 44 projecting outward along the transverse direction of the accommodating portion 41 are provided to substantially position the shielded connector 10 while it is inserted into an unillustrated connector housing and substantially stably fix the shielded connector 10 in the connector housing after insertion. Behind the stabilizers 44 is provided an outer crimping portion 45 to be fastened to a folded portion 55 of the shielded cable 50. The outer crimping portion 45 is provided with a pair of preferably substantially strip-shaped crimping pieces 46, 47 extending from a bottom portion 48. The crimping pieces 46, 47 are spaced gradually wider and slanted surfaces are preferably formed at the leading ends thereof. The crimping pieces 46, 47 preferably have a length sufficient to at least partially surround shielded cables of various diameters, preferably to surround them while partly overlapping on each other (FIGS. 7 and 8). In the outer crimping portion 45, slits 60 are formed in specified positions of the crimping portions 46, 47 and/or the bottom portion 48 beforehand, and portions of the crimping portions 46, 47 and/or the bottom portion 48 behind the slits 60 are embossed inward to form such projections 61, 62 that preferably have their leading ends substantially located at the slits 60 and are substantially in the form of a triangular prism (see FIG. 2) or other protruding polygonal shape. As shown in FIG. 3, the front ends of the projections 61, 62 serve as raised portions 63 which are substantially open forward, and left and right side surfaces 64 thereof facing backward are closed and are so wedge-shaped that it is moderately lowered toward the back. In this embodiment, the bottom projection 61 and the upper projection 62 are formed in the bottom portion 48 and at the end of the crimping piece 46. Next, how the shielded connector 10 is assembled is described. First, the sheath 54 is stripped at the end of the shielded cable 50 to expose the outer conductor 52, which is preferably folded back over the sheath 54, thereby forming the folded portion 55 (see FIG. 1). Subsequently, the insulating element 53 of the shielded cable 50 is stripped to substantially expose the inner conductor 51, to which the inner crimping portion 24 of the inner terminal 20 is then fastened. Next, the dielectric element 30 is inserted into the accommodating portion 41 of the outer terminal 40 from front. Then, the contact portion 33 comes into contact with the contact piece 49 and the locking portion 42 slips substantially into the locking recess 32, thereby substantially locking the dielectric element 30 in a specified position in the accommodating portion 41. When the inner terminal 20 connected with the inner conductor 51 is then inserted into the accommodating hole 31 of the dielectric element 30, the biting projection 23 bites or presses into or engages the upper wall of the accommodating hole 31 to stably fix the inner terminal 20 (see FIG. 6). Then, the folded portion 55 is placed on the bottom portion 48 of the outer terminal 40 while the bottom projection 61 formed at the bottom portion 48 is biting thereinto. At this time, since the crimping pieces 46, 47 are most narrowly spaced at their bases near the bottom portion 48 as shown in FIG. 4, the folded portion 55 will not be displaced in widthwise direction since being held between the bases of the crimping pieces 46, 47 and hooked by the bottom projection 61. Thereafter, the shielded connector 10 in the state of FIG. 4 is placed in an unillustrated crimper. The crimping piece 46 is at least partly brought into substantially close contact with the outer surface of the outer conductor 52 or its the folded portion 55 and the bottom and upper projections 61, 62 are caused to sufficiently bite into or press against or engage the folded portion 55, and the crimping piece 47 is at least partly brought into substantially close contact with the outer surface of the outer conductor 52 or its the folded portion 55. At this time, crimping is preferably performed such that the end of the crimping piece 47 is placed on that of the crimping piece 46 (see FIG. 7). FIG. 5 shows the shielded connector 10 after crimping. Here, the outer crimping portion 45 is so crimped as to substantially squeeze the sheath 54 and be in close contact with the folded portion 55. Further, the projections 61, 62 tightly hold the folded portion 55 while strongly biting into or engaging the sheath 54 of the folded portion 55 (see FIGS. 6 and 7). As a result, electrically connection is secured since the folded portion 55 and the outer crimping portion 45 are sufficiently electrically connected and a sufficient fastening force is obtained. According to the terminal of this embodiment, the projections 61, 62 secure an electrically connection with the outer conductor 52 by biting into or pressing against or engaging the outer conductor 52 preferably of the folded portion 55 of the shielded cable 50, and securely hold the shielded cable 50 by further biting into or engaging the sheath 54. This increases a fastening force and stabilizes the connection. Even if the crimping pieces 46, 47 come to have a weaker fastening force due to the elastic restoration after crimping and vibrations produced while the connector 10 is being used, the projections 61, 62 biting into the folded portion 55 effectively stabilize the connection of the shielded connector 10 with the shielded cable 50 after crimping, therefore considerably improving the fastening force of the shielded connector 10 and securing the electrical connection. Further, with the shape of the projections 61, 62 according to this embodiment, the raised portions 63 bite more into the sheath 54 as shown in FIG. 6 if a stretching load acts on the shielded cable 50 in backward direction after crimping. This prevents the shielded cable 50 from coming out and enables the connection to be maintained. Further, since the crimping is preferably formed at the crimping piece 46 located below the ends of the crimping pieces 46, 47 placed one over the other and the upper projection 62 are doubly pressed, the fastening force can be further increased. The upper projection 62 is provided at the leading end of the crimping piece 46 and the crimping piece 46 is so formed as to be spaced substantially wider apart from the crimping piece 47 toward its leading end before crimping. Since this prevents an occurrence of an undesirable event where the shielded cable 50 gets caught by the upper projection 62, crimping can be smoothly performed. Particularly, the folded portion 55 is likely to get caught by an other member since having its outer surface surrounded by the braided wire. However, since the projections 61, 62 of the shielded connector 10 of this embodiment do not have any surface extending in such a direction as to face the shielded cable 50 being inserted in an insertion direction I, they do not catch the folded portion 55 during the insertion of the shielded cable 50. This enables the shielded cable 50 to be smoothly inserted, therefore improving operation efficiency. As already described, this embodiment is designed to increase the fastening force by providing the projections 61, 62 in two vertically displaced positions and causing them to bite into the shielded cable 50 from above and below. However, the outer diameter of the folded portion 55 formed by folding back the outer conductor 52 may vary. This is thought to cause a problem depending on the situation. Accordingly in this embodiment, the position of the upper projection 62 is set to ensure satisfactory fastening in any case within a range between the minimum and maximum values of predictable variation (see FIG. 8). Specifically, the position of the upper projection 62 is set in a position spaced from the leading edge of the crimping piece 62 by a specified distance in this embodiment. A middle value between the maximum and minimum diameters of the predictable variation is set as a reference value, and the position of the upper projection 62 is set such that the upper projection 62 is located right above the bottom projection 61 when the folded portion having an outer diameter of the reference value is fastened. Thus, depending upon whether the outer diameter of the folded portion is larger or smaller than the reference value, the upper projection 62 is circumferentially displaced to the right or clockwise or left or anticlockwise from the position right above the bottom projection 61. In other words, the upper projection 62 is displaced to the left or anticlockwise as shown in FIG. 8(a) if the outer diameter of the folded portion 55 is larger than the reference value while displaced to the right or clockwise as shown in FIG. 8(b) if it is smaller than the reference value. The displacement from the reference value is small in any case and, therefore, the folded portion can be satisfactorily fastened over the entire range of the variation. <Second Embodiment> FIG. 9 shows a second embodiment of the invention. The second embodiment differs from the first embodiment in that two bottom projections 61 a, 62b are provided at the bottom portion 48 of the outer crimping terminal 45. Since the other construction is same or similar as the first embodiment, no repetitive description is given thereon by identifying it by the same reference numerals. By providing the two projections at the bottom of the terminal according to this embodiment, the shielded cable 50 can be more stably and firmly held since the three projections bite thereinto after crimping. Further, since the two projections provided at the bottom bite into or engage the outer conductor 52, preferably its the folded portion 55 when the shielded cable 50 is placed on the outer crimping portion 45, the crimping operation can be more easily performed with the shielded cable 50 more stably held, thereby improving an operation efficiency. <Other Embodiments> The present invention is not limited to the foregoing embodiments. For example, embodiments as described below are also embraced by the technical scope of the present invention as defined in the claims. Besides the following embodiments, a variety of changes can be made without departing from the scope of the present invention as defined in the claims. (1) Although one or two projections are provided at the bottom surface and one projection is provided at the side surface(s) in the foregoing embodiments, one or a plurality of projections may be provided at each or either of the bottom surface and the side surface(s) such as in a case where two projections are provided both at the bottom surface and at the side surface. (2) Although the projections 61, 62 are substantially in the form of a triangular prism and the side surfaces 64 there are planar in the foregoing embodiments, the side surfaces 64 may be curved surfaces. Alternatively, the projections 61, 62 may have a continuously or partly curved surface as shown in FIG. 10. LIST OF REFERENCE NUMERALS 40 Outer Terminal (Terminal) 45 Outer Crimping Portion (Crimping Portion) 46 Crimping Piece 47 Crimping Piece 50 Shielded Cable 51 Inner Conductor 52 Outer Conductor 53 Insulating Element 54 Sheath 61 Bottom Projection (Projection) 62 Upper Projection (Projection) 63 Standing Portion (Standing Surface)

Claims: A terminal, comprising a crimping portion (45) to be fastened to an end of a shielded cable (50) in which an insulating element (53) is provided between inner and outer conductors (51, 52) and the outer surface is covered by a sheath (54), wherein the crimping portion (45) can be fastened to the outer conductor (52), the crimping portion (45) comprising one or more crimping pieces (46, 47) which are to be so crimped as to at least partly wind on or around the outer conductor (52) being preferably folded back over the sheath (54), wherein one or more projections (61; 61 a; 61 b) are provided in such positions of the inner surface of the crimping portion (45) as to hold the outer conductor (52) preferably folded back over the sheath (54) while biting thereinto, wherein at least one projection (61; 61 a; 61 b) ) is provided in a specified position of a bottom surface (48) of the crimping portion (45), characterized in that least one projection (62) is provided in a position at the leading end of the crimping piece (46), preferably the second crimping piece (46) placeable below after crimping. A terminal according to claim 1, wherein the crimping portion (45) can be fastened both to the sheath (54) and to the outer conductor (52) being preferably folded back over the sheath (54). A terminal according to one or more of the preceding claims, wherein the crimping pieces (46, 47) are to be or can be so crimped as to at least partly wind on or around the outer conductor (52) with the end of a first crimping piece (47) substantially placed or placeable (FIG. 7; FIG. 8) on that of a second crimping piece (46). A terminal according to one or more of the preceding claims, wherein the at least two crimping pieces (46, 47) extend from the bottom surface of the crimping portion (45) while being spaced apart wider from each other toward the leading ends thereof. A terminal according to one or more of the preceding claims, wherein the projection (61) provided at the leading end of the second crimping piece (46) placed below after crimping is provided in a position spaced apart from the leading edge of the first crimping piece by a specified distance such that this projection (61) can be located substantially right above the projection (61) at the bottom surface (48) when the outer diameter of the outer conductor (52), preferably its folded portion (55) is a reference value of its range of variation. A terminal according to one or more of the preceding claims, wherein each projection (61; 61a; 61b) has such a wedge-shape (FIG. 6; FIG. 10) that its front surface extends at an angle different from 0° or 180°, preferably substantially normal to an insertion direction (I) of the cable (50) and its height is lowered toward the back. A method for crimping a terminal according to one or more of the preceding claims having a crimping portion (45) on a shielded cable (50), in which an insulating element (53) is provided between inner and outer conductors (51, 52) and the outer surface is covered by a sheath (54), comprising the following steps: stripping the sheath (54) to substantially expose the outer conductor (52); and fastening the crimping portion (45) to the outer conductor (52) by at least partly winding one or more crimping pieces (46; 47) of the crimping portion (45) on or around the outer conductor (52) thereby biting one or more projections (61; 61 a; 61 b) provided on the crimping portion (45) into the outer sheath (52). A method according to claim 7, wherein in the fastening step the crimping portion (45) is fastened to both the sheath (54) and the outer conductor (52) being preferably folded back over the sheath (54). A method according to claim 7 or 8, wherein in the fastening step the crimping pieces (46, 47) are so crimped as to at least partly wind on or around the outer conductor (52) with the end of a first crimping piece (47) substantially placed or placeable (FIG. 7; FIG. 8) on that of a second crimping piece (46).

Inventors: AOYAMA MASAHIKO, KOIDE TAKASHI, SAITO MASASHI, TANAKA MASAHIRO, AOYAMA, MASAHIKO, KOIDE, TAKASHI, SAITO, MASASHI, TANAKA, MASAHIRO, Aoyama, Masahiko c/o Sumitomo Wiring Systems Ltd., Koide, Takashi c/o Sumitomo Wiring Systems Ltd., SAITO, MASASHI C/O SUMITOMO WIRING SYSTEMS LTD., Tanaka, Masahiro c/o Toyota Jidosha K.K.
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1999
Main classification: H01R4
IPC codes: H01R43, H01R4, H01R9