An insulation-displacement terminal fitting and production method therefor

Abstract: [Object] To prevent an occurrence of a crack and/or split in blade portions when the blade portions are formed by bending side walls of an insulation-displacement terminal fitting in V-shape. [Solution] Slits 15 having an area corresponding at least to a forming range of blade portions 11B are formed along boundaries between a bottom wall 13 and side walls 11A, and a bent portion 16 is formed in a forming area of the slits in the bottom wall 13. When the blade portions 11B are formed by bending the side walls 11A, the bent portion 16 is simultaneously formed in the bottom wall 13. At this time, neither the blade portions 11B nor the side walls 11A undergo an extensional deformation since base ends 11Ba of the blade portions 11B are brought closer to each other in the side walls 11a and base ends 16a of the bent portion 16 are brought closer to each other in the bottom wall 13.

Description: The present invention relates to an insulation-displacement terminal fitting and to a production method therefor. A known insulation-displacement terminal fitting is disclosed in Japanese Unexamined Patent Publication No. 8-241740. This terminal fitting is such that inward facing blade portions are formed on a pair of side walls. When a wire is pushed in between the two blade portions, the blade portions cut a resin coating of the wire to come into contact with a core of the wire. Each blade portion is V-shaped when viewed in a direction in which the wire is pushed, and is formed by bending a portion of the flat side wall into V-shape. When the blade portions of the prior art insulation-displacement terminal fitting are formed by embossing the side walls in V-shape, the side walls are extended by placing a pressing jig at positions which become apices of the V-shaped blade portions. Thus, the thickness of the blade portions becomes gradually thinner toward the apices thereof. As a result, the apices of the blade portions may crack or split. In order to avoid a crack or split, it may be considered to emboss the side walls to a smaller degree to widen a spacing between the blade portions or to make the insulation-displacement terminal fitting of a relatively soft material. The former means cannot cope with thin wires, while the latter means may cause a deformation and/or an insufficient contact pressure during insulation displacement. Neither means can solve the above problem. US - A - 4 057 314 which is considered as the closest prior art discloses an electrical connector provided with a plurality of contacts, each of the contacts having an insulation-opening terminal element of sheet metal construction to electrically contact an insulated conductor. The terminal element portion of each contact preferably includes an elongate open channel of U-shaped cross-sectional configuration having side and bottom walls, the side walls including opposite portions dimpled in to provide inner detents forming, and separated by, a conductor-receiving notch for opening the insulation of the conductor and electrically engaging the underlying exposed conductor. An aperture is provided at the junction of the side wall and the bottom wall to facilitate forming of the detent by a pressing process so that lancing or an upward swedging is not necessary at that point. EP - A - 251 556 discloses a contact terminal having a termination section including a spaced pair of axially extending slots, within each of which a respective one of a pair of conductor wires is held in an interference fit for weld termination such as laser welding. The terminal is stamped from a metal blank in its termination section has a raised central portion surfaces of a height about equal to a wire diameter, said central portion having a planar top surface and parallel vertical side defining the inner slot walls. Furthermore, parallel vertical side walls are bent upward from side portions of the termination section. The side walls are spaced from the side surfaces of the raised central portion and define the outer slot walls, so that the slot width at least at one location is just less than the wire diameter. An object of the present invention is to prevent an occurrence of a crack or split in blade portions when side walls of an insulation-displacement terminal fitting are deformed to form blade portions. This object is solved according to the invention by an insulation displacement terminal fitting according to claim 1 and by a production method according to claim 6. Preferred embodiments of the invention are the subject of the dependent claims. According to the invention, there is provided an insulation-displacement terminal fitting in which portions of a pair of side walls extending from a bottom wall are bent to form at least one pair of blade portions, and a wire is at least partly pressable or can be at least partly pressed in between the blade portions to be connected therewith, wherein: two or more slits including an area corresponding at least to an entire forming area of the blade portions are formed along boundaries between the bottom wall and the side walls. Furthermore, a bent portion is formed in the bottom wall for coming into contact with a front end face of the wire. According to a preferred embodiment of the invention, the blade portions are substantially V-shaped. Further preferably, the bent portion is formed within a forming area of the slits. According to a further preferred embodiment, there is provided an insulation-displacement terminal fitting in which portions of a pair of side walls extending upward from the opposite lateral ends of a bottom wall are bent inwardly to form V-shaped blade portions, and a wire is pressed in between the blade portions in a direction normal to the longitudinal axis of the wire, wherein: slits including an area corresponding at least to an entire forming area of the blade portions are formed along boundaries between the bottom wall and the side walls, and a bent portion is formed within a forming area of the slits in the bottom wall. When the blade portions are formed by bending the side walls, the bent portion is simultaneously formed in the bottom wall. At this time, since the slits are formed along the boundaries between the bottom wall and the side walls, an operation of bringing base ends of the blade portions closer to each other in the side walls and an operation of bringing base ends of the bent portion closer to each other in the bottom wall are independently performed. Thus, the blade portions do not undergo an extensional deformation. Therefore, the blade portions do not become thinner and an occurrence of a crack and/or split in the blade portions can be avoided. Preferably, the bent portion is located in such a position of the bottom wall as to come into contact with an end portion of the wire such that when the wire is positioned in a proper position an end face of the wire comes into contact with the bent portion without substantially bending the wire while when the wire is positioned in an improper position the wire is bent upward by the bent portion. Preferably, the insulation-displacement terminal fitting is to be locked by a retainer when being inserted into a connector housing and in which an end face of the wire mounted in a proper contact position is in proximity to the retainer, wherein the bent portion is located in such a position as to be interfered by an end of the wire and deformed when the wire is mounted in an improper contact position displaced toward the end of the wire from the proper contact position. In the case that the wire is mounted in an improper contact position displaced toward the end of the wire from the proper contact position, the retainer may interfere the end of the wire to thereby cause an assembling error if the insulation-displacement terminal fitting is mounted while being left displaced. However, in the present invention, the end of the wire mounted in the improper contact position is interfered by the bent portion and deformed, which enables detection of the wire in the improper contact position due to the deformation of the wire, and prevents the wire and the retainer from interfering each other. Most preferably, after bending a shortened length of the bottom wall and that of the side walls between front and rear ends of the slits are substantially the same. According to the invention, there is further provided a production method for forming an insulation-displacement terminal fitting, in particular according to the invention or an embodiment thereof, comprising the following steps: bending portions of a pair of side walls extending from a bottom wall to form at least one pair of blade portions, wherein a wire is at least partly pressable in between the blade portions to be connected therewith, and forming two or more slits including an area corresponding at least to an entire forming area of the blade portions along boundaries between the bottom wall and the side walls. The production method further comprises the step of forming a bent portion in the bottom wall for coming into contact with a front end face of the wire. According to a preferred embodiment of the invention, the blade portions are formed to have substantially a V-shape. Preferably, the bent portion is formed within a forming area of the slits. Most preferably, during the bending step of the blade portions, front and rear base ends of the respective blade portion are brought closer to each other in the side walls and simultaneously front and rear ends (16a) of the bent portion are brought closer to each other in the bottom wall, wherein a sum of the shortened distances of the spacings between the base ends of the front and rear blade portions is preferably substantially equal to a shortened distance of a spacing between the base ends (16a) of the bent portion. These and other objects, features and advantages of the present invention will become apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings in which: FIG. 1 is a perspective view partly cut away of an insulation-displacement terminal fitting according to one embodiment of the invention, FIG. 2 is a plan view of the insulation-displacement terminal fitting, FIG. 3 is a section along X-X of FIG. 2, FIG. 4 is a section showing a state where a wire is mounted in a proper contact position, FIG. 5 is a section showing a state where the wire is mounted in an improper contact position, and FIG. 6 is a development of the insulation-displacement terminal fitting. Hereinafter, one preferred embodiment of the invention is described with reference to FIGS. 1 to 6. Insulation-displacement terminal fittings T of this embodiment are preferably produced from chained terminals A in which a multitude of substantially plate-shaped terminal materials S stamped or cut out in a specified shape are connected by a carrier C, and are formed by bending or deforming or embossing or configuring the terminal materials S detached from the carrier C into a specified (predetermined or predeterminable) configuration. It should be noted that left side in FIGS. 2 to 5 is referred to as front and vertical direction is based on FIGS. 3 to 5 in this embodiment. The formed insulation-displacement terminal fitting T is first described. The insulation-displacement terminal fitting T is substantially narrow along forward and backward or longitudinal directions as a whole. A substantially front half thereof is a connection portion 10 as a connection means with a mating male terminal fitting (not shown), a substantially rear half thereof is an insulation-displacement portion 11 to be connected with a wire W, and a coupling portion 12 is provided between the connection portion 10 and the insulation-displacement portion 11. The connection portion 10, the insulation-displacement portion 11 and the coupling portion 12 are connected one after another in this order preferably by a bottom wall 13. The connection portion 10 has, as a whole, a substantially rectangular box-shape having open front and rear end faces, and is comprised of the bottom wall 13, a pair of side walls 10A standing from the opposite lateral ends of the bottom wall 13, and a pair of upper walls 10B, 10C extending inwardly from preferably the upper edges of the side walls 10A and placed substantially one over the other. A substantially triangularly bent elastic contact piece 10D formed e.g. by folding back a portion of the bottom wall 13 extending from the front end of the connection portion 10 is at least partly accommodated in the connection portion 10. The rear edges of the upper walls 10B, 10C serve as a locking portion 10E. When the insulation-displacement terminal fitting T is inserted into a respective cavity Ha of a connector housing H preferably from behind, it is locked there by engaging a retainer R with the locking portion 10E preferably from behind. The insulation-displacement portion 11 includes blade portions 11B formed by bending or embossing or deforming portions of a pair of side walls 11A extending at an angle different from 0° or 180°, preferably substantially normal or upward preferably from the opposite lateral ends of the bottom wall 13 e.g. into substantially V-shape. The left and right blade portions 11B make a pair, and preferably two pairs of the blade portions 11B are provided one after the other or spaced along a longitudinal direction of the terminal fitting T in this embodiment. The wire W is or can be at least partly pushed in between the pairs of blade portions 11B. A resin coating of the wire W is cut by the upper edges of the blade portions B during insulation-displacement, and the leading ends of the V-shaped blade portions 11B enter the thus made cuts to come into contact with a core of the wire W. Behind the blade portions 11B, a pair of crimping pieces 11C extend upward from the bottom wall 13. The crimping pieces 11C are crimped or bent or deformed into connection with the wire W held in contact with the blade portions 11B. It should be noted that the side walls 11A of the insulation-displacement portion 11 are substantially continuous with those of the coupling portion 12. A continuos slit 15 is formed along a boundary between the bottom wall 13 and each side wall 11A over a range or length at least where the front and rear blade portions 11B are formed. A rear end 15R of the slit 15 is located slightly behind a rear base end 11Ba (continuous with the side wall 11A) of the rear blade portion 11B as seen along the longitudinal direction of the terminal fitting T. A front end 15F of the slit 15 is located in a position (slightly behind the locking portion 10E) substantially corresponding to a portion of connecting the coupling portion 12 and the connection portion 10 beyond the range where the blade portions 11B are formed. In the coupling portion 12, a portion of the bottom wall 13 is bent into a bent portion 16. This bent portion 16 is substantially formed along forward and backward directions in a range where the slits 15 are formed. The position of the bent portion 16 is set such that a front end face Wa of the wire W is or can be located at a base end 16a (connecting portion with the bottom wall 13) of the bent portion 16 when the wire W is brought into contact with the blade portions 11B in a proper contact position along forward and backward directions (see FIG. 4). While being held in contact with the blade portions 11B in the proper contact position, the wire W extends preferably substantially straight so as to bring its bottom end into contact with the bottom wall 13 up to the front end face Wa. In this proper state, the front end face Wa of the wire W is located below the retainer R and substantially opposed to a slanted surface Ra of a bottom portion of the retainer R at a short distance although not interfering (see FIG. 4). In the case that the wire W is brought into contact with the blade portions 11B in an improper contact position displaced forward (toward the end of the wire W) than the proper contact position, a front end portion of the wire W is placed on the bent portion 16 while being curved upward (see FIG. 5). In this case, the front end of the wire W is located at a higher level than in the case where the wire W is properly brought into contact, and may interfere the retainer R. In other words, the front end of the wire W project upward from the side wall in the improper contact state although the lower surface of the retainer R is located higher than the upper edge of the side walls of the insulation-displacement portion 11. Thus, the retainer R and the wire W interfere each other. Next, a production process of the insulation-displacement terminal fitting T is described. First, the respective terminal materials S are preferably separated from the carrier C in the chained terminals A and then bent along specified folds (no reference numerals are given, but shown in broken line in FIG. 6). At this time, while the side walls 11A of the insulation-displacement portion 11 are still substantially in flush with the bottom wall, the blade portions 11B are formed by bending portions of the side walls 11A in V-shape and simultaneously the bottom wall 13 is preferably bent in substantially V-shape to form the bent portion 16. Alternatively, the bent portion 16 may be formed by cutting out a portion of the bottom wall 13 and bending such cut out portion upward or toward a wire arrangement space. During this bending or forming step, the front and rear base ends 11Ba of the respective blade portion 11B are preferably brought closer to each other in the side walls 11A and simultaneously front and rear ends 16a of the bent portion 16 are brought closer to each other in the bottom wall 13. A sum of the shortened distances of the spacings between the base ends 11Ba of the front and rear blade portions 11B is substantially equal to a shortened distance of a spacing between the base ends 16a of the bent portion 16. In other words, a shortened length of the bottom wall 13 and that of the side walls 11A between the front and rear ends 15F, 15R of the slits 15 during bending are substantially same. Thus, neither the bottom wall 13 including the bent portion 16 nor the side walls 11A including the blade portions 11B undergo an extensional deformation during bending. Thereafter, the side walls 10A, 11A are bent substantially at an angle different from 0° or 180°, preferably at a substantially right angle to the bottom wall 13, and the elastic contact piece 10D and the connection portion 10 are formed. In this way, the insulation-displacement terminal fitting T is completely formed. As described above, in this embodiment, the slits 15 are formed along the boundaries between the bottom wall 13 and the side walls 11A, and the bent portion 16 is formed in the bottom wall 13 during formation of the blade portions 11B. Accordingly, an operation of bringing the base ends 11Ba of the blade portions 11B closer to each other in the side walls 11A and an operation of bringing the base ends 16a of the bent portion 16 closer to each other in the bottom wall 13 are independently performed. Thus, distortions of the side walls 11A are taken up and neither the side walls 11A nor the blade portions 11B undergo an extensional deformation. Therefore, the blade portions 11B do not become thinner and an occurrence of a crack and/or split in the blade portions 11B can be avoided. When the insulation-displacement terminal fitting T in which the wire W is mounted in a proper contact position is inserted into the cavity Ha, the front end face Wa (end face as a feature of the invention) of the wire W faces the slanted surface Ra at the bottom portion of the retainer R at a short distance. Accordingly, if the insulation-displacement terminal fitting T is inserted into the cavity Ha with the wire mounted in an improper contact position displaced forward from the proper contact position, the slanted surface Ra of the retainer R may interfere the front end of the wire W, thereby causing an assembling error. However, in this embodiment, the front end of the wire W is deformed by moving onto the bent portion 16 if the wire W is mounted in the improper contact position. This enables detection of the wire W in the improper contact position due to the deformation of the wire W, and prevents the wire W and the retainer R from interfering each other, when the wire is incorrectly inserted. The present invention is not limited to the above described illustrated embodiment. For example, following embodiments are also embraced by the technical scope of the present invention as defined in the claims. Besides them, various changes can be made without departing from the scope of the present invention as defined in the claims. (1) Although the bent portion projects upward from the bottom wall in the foregoing embodiment, it may project downward (outward) from the bottom wall. (2) Although the bent portion has a triangular shape pointing upward in the foregoing embodiment, it may have a wavy, trapezoidal, arcuate or other shape according to the present invention. LIST OF REFERENCE NUMERALS T insulation-displacement terminal fitting 11A side wall 11B blade portion 13 bottom wall 15 slit 16 bent portion H connector housing R retainer W wire Wa front end face of the wire (end face)

Claims: An insulation-displacement terminal fitting (T) in which portions of a pair of side walls (11A) extending from a bottom wall (13) are bent to form at least one pair of blade portions (11B), and a wire (W) is at least partly pressable in between the blade portions (11B) to be connected therewith, wherein: two or more slits (15) including an area corresponding at least to an entire forming area of the blade portions (11B) are formed along boundaries between the bottom wall (13) and the side walls (11A), characterized in that a bent portion (16) is formed in the bottom wall (13), for coming into contact with a front end face (Wa) of the wire. An insulation-displacement terminal fitting according to claim 1, wherein the blade portions (11B) are substantially V-shaped. An insulation-displacement terminal fitting according to claims 1 or 2, wherein the bent portion (16) is formed within a forming area of the slits (15). An insulation-displacement terminal fitting according to claim 1, 2 or 3 wherein the bent portion (16) is located in such a position of the bottom wall (13) as to come into contact with an end portion of the wire (W) such that when the wire (W) is positioned in a proper position (FIG. 4) an end face (Wa) of the wire (W) comes into contact with the bent portion (16) without substantially bending the wire (W) while when the wire (W) is positioned in an improper position (FIG. 5) the wire (W) is bent upward by the bent portion (16). An insulation-displacement terminal fitting according to one or more of the preceding claims 1 to 4, wherein after bending a shortened length of the bottom wall (13) and that of the side walls (11A) between front and rear ends (15F, 15R) of the slits (15) are substantially the same. A production method for forming an insulation-displacement terminal fitting (T) according to claim 1, comprising the following steps: bending portions of a pair of side walls (11A) extending from a bottom wall (13) to form at least one pair of blade portions (11B), wherein a wire (W) is at least partly pressable in between the blade portions (11B) to be connected therewith, and forming two or more slits (15) including an area corresponding at least to an entire forming area of the blade portions (11B) along boundaries between the bottom wall (13) and the side walls (11A), forming a bent portion (16) in the bottom wall (13) ) for coming into contact with a front end face (Wa) of the wire. A production method according to claim 6, wherein the blade portions (11B) are formed to have substantially a V-shape. A production method according to claim 6, wherein the bent portion (16) is formed within a forming area of the slits (15). A production method according to claim 6, 7 or 8 wherein during the bending step of the blade portions (11B), front and rear base ends (11Ba) of the respective blade portion (11B) are brought closer to each other in the side walls (11A) and simultaneously front and rear ends (16a) of the bent portion (16) are brought closer to each other in the bottom wall (13), wherein a sum of the shortened distances of the spacings between the base ends (11Ba) of the front and rear blade portions (11B) is preferably substantially equal to a shortened distance of a spacing between the base ends (16a) of the bent portion (16).

Inventors: KOJIMA EIJI, KOJIMA, EIJI, Kojima, Eiji, c/o Sumitomo Wiring Systems, Ltd.
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 2001
Main classification: H01R4
IPC codes: H01R4, H01R13, H01R43