An insulation-displacement terminal fitting

Abstract: [Object] To securely cut an insulation coating open to prevent it from projecting beyond side walls. [Solution] While a wire W is being pushed in, an insulation coating Wb is cut open by V-shaped contact portions 23 after having cuts C made by blades 27 in the form of a single plate. Since a cut-open piece Wc of the insulation coating Wb caught by the contact portions 23 is not forcibly stretched, a core Wa is not pulled in such a direction to be withdrawn from a clearance between the contact portions 23 due to the cut-open piece Wc having got caught. Since an accommodation space 30 in which the cut-open piece Wc of the insulation coating Wb caught by the contact portions 23 is accommodated is located within a height range of side walls 21, the cut-open piece Wc of the insulation coating Wb does not project above the side walls 21.

Description: The present invention relates to an insulation-displacement terminal fitting having preferably substantially V-shaped insulation-displacement portions. An insulation-displacement terminal fitting, according to the preamble of claim 1, having V-shaped insulation-displacement portions is disclosed in Japanese Examined Patent Publication No. 57-10550 which corresponds to US 3 867 005 A. This terminal fitting is as follows. The insulation-displacement portions are formed by deforming portions of a pair of left and right side walls extending upward from a bottom wall to project in V-shape so that contact edges at the projecting ends of the insulation-displacement portions. While a wire is being pushed in between the insulation-displacement portions, an insulation coating of the wire is caught by the upper ends of the contact edges to be cut open, and the contact edges are caused to bite in the cut-open sections to be brought into contact with a core of the wire. In an insulation-displacement terminal fitting of the type which cuts an insulation coating by catching it by V-shaped insulation-displacement portions when viewed in a wire pushing direction as described above, an insulation coating 1 may remain caught by the upper ends of contact edges 3 of insulation-displacement portions 2 without being cut as shown in FIG. 8, and may be stretched and torn as a core 4 is pushed. In such a case, the core 4 is lifted up in a direction to disengage from the insulation-displacement portions 2 due to a force of the stretched insulation coating 1 to return in a contracting direction. As a result, a contact reliability between the core 4 and the insulation-displacement portions 2 may be reduced. Further, since the upper ends of the V-shaped insulation-displacement portions 2 are not located considerably lower than side walls 5, the insulation coating 1 caught by the upper ends of the contact edges 3 of the insulation-displacement portions 2 projects more upward than the side walls 5. Thus, the insulation coating 1 projecting from the side walls 5 may be caught by a terminal insertion opening when the insulation-displacement terminal fitting is inserted into a housing (not shown), thereby hindering an inserting operation. In view of the above problems, it is an object of the invention to provide an insulation-displacement terminal fitting which provides for an improved operability and contact reliability. This object is solved according to the invention by an insulation-displacement terminal fitting according to claim 1. Preferred embodiments of the invention are the subject of the dependent claims. According to a preferred embodiment of the invention, the blades are shaped substantially in the form of a single plate. Preferably, the cutting edges are located more toward the corresponding side walls than toward the contact edges when viewed in the wire pushing direction. Further preferably, the insulation-displacement portions are provided on opposite side walls in a direction substantially normal to the longitudinal direction of the wire. Still further preferably, the contact portions project inwardly in substantially V-shape. Most preferably, the contact edges extend substantially along the wire pushing direction at their projecting ends. According to a further preferred embodiment of the invention, there is provided an insulation-displacement terminal fitting in which a wire is pushed in between a pair of insulation-displacement portions provided on opposite side walls in a direction normal to the longitudinal direction of the wire to cut an insulation coating of the wire open and bring a core of the wire into contact with the insulation-displacement portions, wherein the contact portions comprises: contact portions projecting inwardly in V-shape from the corresponding side walls when viewed in a wire pushing direction and having contact edges which extend along the wire pushing direction at their projecting ends and with which the core is brought into contact, blades in the form of a single plate projecting from the corresponding side walls so as to be located before the contact portions with respect to the wire pushing direction and having cutting edges at their projecting ends, the cutting edges being located more toward the corresponding side walls than toward the contact edges when viewed in the wire pushing direction, and an accommodation space defined between one pair of blades and having a width larger than a spacing between one pair of contact edges. Since the blades in the form of a single plate make cuts in the insulation coating while the wire is being pushed in, the insulation coating is more securely cut open by the V-shaped contact portions thereafter, and the core is pushed in between the contact portions with a cut-open piece of the insulation coating caught by the contact portions. Since the cut-open piece of the insulation coating caught by the contact portions is securely separated from a portion of the insulation coating surrounding the core without being forcibly stretched, the core is not pulled in such a direction as to be withdrawn from a clearance between the contact portions due to the caught cut-open piece. Therefore, a high contact reliability can be secured between the core and the contact portions. The cut-open piece of the insulation coating caught by the contact portions is located in the accommodation space, which is located between the blades projecting from the side walls, i.e. within a height range of the side walls. Thus, the cut-open piece of the insulation coating accommodated therein also remains within the height range of the side walls. Preferably, substantially slanted guide surfaces capable of substantially guiding the core to between the contact edges are formed at the rear ends of the contact edges with respect to the wire pushing direction or formed at end portions of the contact edges (24) first coming into contact with the wire (W) being inserted into contact with the insulation displacement portions (20). The core can be securely pushed in between the contact edges by the guide surfaces without getting caught by the contact portions. Further preferably, each contact portion comprises a shelf portion before the contact edges with respect to the wire pushing direction, preferably extending substantially normal to the wire pushing direction, for substantially preventing an entrance of insulation coating into the clearance between the contact edges by being caught by the shelf portion. Still further preferably, an edge of each contact portion facing the accommodating space serves as a shelf portion extending substantially normal to the wire pushing direction. Since the shelf portions preferably extending in the direction substantially normal to the wire pushing direction are formed before the contact edges with respect to the wire pushing direction, the insulation coating does not enter the clearance between the contact edges by being caught by the shelf portions while the wire is being pushed in. Therefore, a contact failure resulting from the insulation coating caught between the core and the contact edges can be prevented. Still further preferably, the accommodation space communicates with an outer space via a clearance between the cutting blades. The accommodation space has such an extension along the wire pushing direction that a cut-open portion of the wire insulation coating (w b ) is substantially fully accommodated therein. 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 of one preferred embodiment of the invention, FIG. 2 is a partial perspective view showing an insulation-displacement portion, FIG. 3 is a horizontal section showing an intermediate state of insulation displacement of a wire, FIG. 4 is a horizontal section showing a state where the insulation displacement of the wire is completed, FIG. 5 is a partial plan view showing the intermediate state of the insulation displacement of the wire, FIG. 6 is a partial plan view showing the state where the insulation displacement of the wire is completed, FIG. 7 is a partial development of chained terminals, and FIG. 8 is a horizontal section of a prior art insulation-displacement terminal fitting. Hereinafter, one preferred embodiment of the present invention is described with reference to FIGS. 1 to 7. An insulation-displacement terminal fitting 10 according to this embodiment is made e.g. of a metallic plate material preferably stamped out into a specified shape by a press, and formed by separating a terminal material 12 from a corresponding carrier 13 of chained terminals 11 shown in FIG. 7 and applying, e.g. bending and/or embossing or deforming to the separated terminal material 12. The shape of the formed insulation-displacement terminal fitting 10 is described. A substantially front or first half of the insulation-displacement terminal fitting 10 is formed into an engaging portion 15 preferably in the form of a substantially rectangular tube hollow in forward and backward directions, and an elastic contact piece 17 (only part thereof is shown in FIG. 1) is formed in the engaging portion 15 preferably by folding back a portion of a bottom wall 16 extending from the front end of the engaging portion 15. A tab of an unillustrated male terminal fitting is or can be at least partly inserted into the engaging portion 15 from front to be elastically brought into contact with the elastic contact piece 17. Further, an open barrel portion 18 is formed at the rear or second end of the insulation-displacement terminal fitting 10 by forming a pair of crimping pieces 18A standing from the left and right or lateral side edges of a bottom wall 16. In the open barrel portion 18, the crimping pieces 18A are or can be crimped or bent substantially into connection with a wire W to be brought into contact with insulation-displacement portions 20 to be described later by insulation displacement. The wire W may be, however, first inserted into the insulation-displacement portions 20 and only then the crimping pieces 18A may be crimped or bent into connection with the wire W. Next, the insulation-displacement portions 20 for connecting the wire W by insulation displacement are described. One or more, preferably two pairs of transversely arranged insulation-displacement portions 20 are provided one after the other between the engaging portion 15 and the open barrel portion 18 in such a manner as to project inwardly from a pair of side walls 21 standing at an angle different from 0° or 180°, preferably at substantially right angles from the left and right side edges of the bottom wall 16. Slits 22 are substantially formed along folds at the boundaries between the bottom wall 16 and the side walls 21 in ranges including areas corresponding at least to the insulation-displacement portions 20. The insulation-displacement portions 20 are formed by pushingly deforming or embossing portions of the side walls 21 corresponding to the slits 22 inwardly or in a direction intersecting a wire pushing direction D (FIG. 3). Each insulation-displacement portion 20 is provided with one contact portion 23 and a pair of front and rear blades 27, and an accommodation space 30 is defined substantially between the pair of insulation-displacement portions 20. The contact portion 23 is so formed (see FIGS. 5 and 6) as to project inwardly in V-shape or substantially pointed shape from the side wall 21 when viewed in a wire pushing or insertion direction D (when viewed from above in FIGS. 3 and 4), and its projecting end serves as a substantially vertically extending contact edge 24 substantially along the wire pushing direction D. A core Wa of the wire W comes into contact with the contact edge 24. A dimension of a forming area of the contact edge 23 in height direction (wire pushing direction D) is substantially lower half of the side wall 21 (substantially front half of the side wall 21 in the wire pushing direction D). Accordingly, the height of the upper edge of the contact portion 23 from the bottom wall 16 is substantially half the height of the upper edge of the side wall 21 from the bottom wall 16. It should be noted that a small clearance is formed between the bottom edge of the contact portion 23 and the upper surface of the bottom wall 16. The contact portion 23 and the contact edge 24 have heights sufficient to secure a contact with the core Wa. At the upper end (rear ends with respect to the wire pushing direction D) of each contact edge 24 is formed a substantially slanted guide surface 25 which is inclined at an angle between 0° and 90°, preferably at about 45° to the wire pushing direction D when viewed in the longitudinal direction of the wire W (forward and backward directions) as shown in FIGS. 3 and 4. The guide surfaces 25 are so inclined as to guide the core Wa to between the contact edges 24 during insulation displacement. Further, the upper edge (edge facing the accommodation space 30 to be described later) of each contact portion 23 serves as a shelf portion 26 extending in a direction substantially normal to the wire pushing direction D. The inner end of the shelf portion 26 is substantially continuous with the upper end of the corresponding guide surface 25 preferably at about 45° when viewed in the longitudinal direction of the wire W. Each blade 27 preferably in the form of a single plate projects from the side wall 21 at a height preferably immediately above the contact portion 23 (before the contact portion 23 in the wire pushing direction D). The blade 27 is in the form of a substantially flat plate and is substantially continuous and in flush with the contact portion 23. The inner leading edge of the blade 27 is adapted to make a cut C in an insulation coating Wb of the wire W, and serves as a cutting edge 28 substantially extending in a direction along the wire pushing direction D. Although the leading end surface of the blade 27 is substantially normal to a projecting direction of the blade 27 from the side wall 21 when viewed from above (when viewed in the wire pushing direction D), it is oblique to the longitudinal direction of the wire W (forward/backward directions). The substantially vertically extending side edge or side edge substantially parallel to the wire insertion direction D of the leading end surface of the blade 27 facing the wire W functions as the cutting edge 28. The cutting edge 28 of the blade 27 is located in a position retracted toward the side wall 21 from the contact edge 24 at the leading end of the contact portion 23. In other words, the projecting distance of the cutting edge 28 from the side wall 21 is smaller than that of the leading end of the contact portion 23. The guide surface 25 at the upper end of the contact portion 23 and the shelf portion 26 at the upper edge of the contact portion 23 can be ensured by the positional relationship of the contact edge 24 and the cutting edge 28. Further, an upper edge of each blade 27 serves as a guiding edge 29 whose inner side (toward the cutting edge 28) is inclined down when viewed in the longitudinal direction of the wire W. The accommodation space 30 is so provided as to be shared between the pair of left and right insulation-displacement portions 20. This space 20 is preferably an area substantially defined between the pair of blades 27 with respect to widthwise direction and defined between horizontal virtual straight lines (not shown) connecting the shelf portions 26 at the upper ends of the contact portions 23 and the upper edges of the side walls 21 with respect to vertical direction. A transverse (widthwise) dimension or width WI of the accommodation space 30 is longer or greater than a spacing between the pair of contact edges 24. Further, when viewed in the wire pushing direction D, a substantially triangular area substantially enclosed by the V-shaped contact portion 23 and a virtual straight line connecting the front and rear cutting edges 28 and extending along forward and backward directions serves as the accommodation area 30. A volume of the accommodation space 30 is so set as to be sufficient to accommodate a cut-open piece Wc which is a piece of the insulation coating Wb of the wire W separated from a portion of the insulation coating Wb surrounding the core Wa by cutting the insulation coating Wb open by the blades 27 and the contact portions 23. Further, the accommodation space 30 communicates with an outer space S, i.e. a substantially triangular space S enclosed by the V-shaped contact portion 23 and a virtual straight line (straight line extending along the outer surface of the side wall 21) connecting the base ends of the contact portion 23 at the side wall 21 and extending in forward and backward directions when viewed from above, via a clearance between the front and rear cutting edges 28. Next, the action of this embodiment is described. In the insulation-displacement terminal fitting 10 according to this embodiment, the insulation coating Wb of the wire W is or can cut and the core Wa thereof is brought into contact with the insulation-displacement portions 20 by pushing the wire W in between one or more pairs of insulation-displacement portions 20 in a direction at an angle different from 0° or 180°, preferably substantially normal to the longitudinal direction of the wire W (downward). The cuts C are made in the outer surface of the insulation coating Wb by the blades 27 while the wire W is moving in or at least partly inserted into the accommodation space 30 between the blades 27 in the operation of pushing the wire W. Since the blades 27 are in the form of a single plate and the wedge-shaped cutting edges 28 thereof bite in the insulation coating Wb, the cuts C can be securely made in the insulation coating Wb (see FIG. 5). Thereafter, when the wire W starts being pushed in between the contact portions 23, the insulation coating Wb is cut open by having its outer surface caught by the upper ends (upper ends of the contact edges 24) of the leading ends of the V-shaped contact portions 23. At this time, since two cuts C preferably extending substantially symmetrically oblique to each other are made in the insulation coating Wb, the insulation coating Wb is securely cut from its outer surface to its inner surface along the cuts C, and a piece between the oblique cuts C become a cut-open piece Wc. The cut-open piece Wc is connected with a portion of the insulation coating Wb surrounding the core Wa only at its upper end (rear end with respect to the wire pushing direction D). Accordingly, the cut-open piece Wc is easily deformable into such a wing-shape as to extend to the left and right sides (see FIG. 4). The insulation Wb is substantially not forcibly stretched during this deformation, with the result that a force which tries to return the cut-open piece Wc in a closing direction toward the core Wa hardly acts. As the wire W is further pushed, the cut-open piece Wc is caught by the upper edges of the contact portions 23, thereby remaining in the accommodation space 30, and substantially only the core Wa enters the clearance between the contact edges 24 to be electrically connected with the contact edges 24. In this way, the wire W is connected with the insulation-displacement terminal fitting 10 by insulation displacement (see FIG. 4). The operation of connecting the insulation-displacement terminal fitting 10 and the wire W is completed when the open barrel portion 18 is crimped into connection with the wire W thereafter. As described above, since the insulation coating Wb can be securely cut open by making the cuts C in the insulation coating Wb beforehand in this embodiment, the cut-open piece Wc can remain before the contact edges 24 with respect to the wire pushing direction D while being only deformed without being stretched. Thus, substantially no force acts in such a direction as to return the remaining cut-open piece Wc to the core Wa (direction to withdraw the core Wa from the clearance between the contact edges 24). As a result, a contact reliability between the core Wa and the contact edges 24 can be maintained. The cut-open piece Wc of the insulation coating Wb caught by the contact portions 23 before the contact edges 24 with respect to the wire pushing direction D is located in the accommodation space 30. Since the accommodation space 30 is located between the blades 27 projecting from the side walls 21, i.e. within the height range of the side walls 21, the cut-open piece Wc can be accommodated therein within a height range of the side walls 21. Accordingly, the insulation coating Wb neither projects above the side walls 21 nor gets caught by the opening edge of a terminal insertion opening when the insulation-displacement terminal fitting 10 according to this embodiment is inserted into a housing (not shown), enabling a smooth insertion. Further, since the guide surfaces 25 inclined with respect to the wire pushing direction D are formed at the entrance of the contact edges 24 for the core Wa, the core Wa can be smoothly and securely pushed in between the contact edges 24 without getting caught by the upper edges of the contact portions 23, and strands forming the core Wa do not become loose. Furthermore, since the shelf portions 26 substantially extending in a direction substantially normal to the wire pushing direction D are formed before the contact edges 24 with respect to the wire pushing direction D, the cut-open piece Wc of the insulation coating Wb securely remains in the accommodation space 30 by getting caught by the shelf portions 26 while the wire W is being pushed, and does not enter the clearance between the contact edges 24. Therefore, a contact failure resulting from the insulation coating Wb caught between the core Wa and the contact edges 24 can be prevented. The present invention is not limited to the above described and illustrated embodiment. For example, following embodiments are also embraced by the technical scope of the present invention as defined in the claims. (1) Although the V-shaped contact portion and the blades in the form of a single plate are substantially continuous and in flush with each other in the foregoing embodiment, they may be discontinuous according to the present invention. In such a case, clearances are formed between the upper edge of the contact portion and the lower edges of the blades. Alternatively, the base ends of the contact portion at the side wall may be located in different positions from the base ends of the blades when viewed in the wire pushing direction D. (2) Although two blades are provided in one insulation-displacement portion in the foregoing embodiment, only one blade may be provided in one insulation-displacement portion according to the present invention. (3) In the foregoing embodiment, an angle of the blades with respect to the side wall is substantially same as an angle of the contact portion with respect to the side wall when viewed in the wire pushing direction D. However, these angles may be different according to the present invention. (4) Although the upper edge of the contact portion is at a right angle to the wire pushing direction D in the foregoing embodiment, the angle of this upper edge to the wire pushing direction may be an angle close to the right angle. In such a case, the upper edge of the contact portion may be inclined downward toward the inner side or upward toward the inner side when viewed in the longitudinal direction of the wire being pushed in. LIST OF REFERENCE NUMERALS 20 insulation-displacement portion 21 side wall 23 contact portion 24 contact edge 25 guide surface 26 shelf portion 27 blade 30 accommodation space W wire Wa core Wb insulation coating D pushing or inserting direction

Claims: An insulation-displacement terminal fitting (10) in which a wire (W) is to be pushed in between at least one pair of insulation-displacement portions (20) to cut an insulation coating (Wb) of the wire (W) open and bring a core (Wa) of the wire (W) into contact with the insulation-displacement portions (20), wherein the insulation-displacement portions (20) comprise: contact portions (23) projecting inwardly from corresponding side walls (21) of the terminal fitting (10) when viewed in a wire pushing direction (D) and having contact edges (24) with which the core (Wa) can be brought into contact, one or more blades (27) projecting from the corresponding side walls (21) so as to be located before the contact portions (23) with respect to the wire pushing direction (D) and having cutting edges (28) at their projecting ends, and an accommodation space (30) to accommodate a cut-open piece (Wc) of the insulation coating (Wb) of the wire (W) defined between one pair of blades (27) characterized in that said accommodation space (30) it arranged between said cutting edges (28) and a width (WI) of said accommodation space (30) is larger than a spacing between one corresponding pair of contact edges (24). An insulation-displacement terminal fitting according to claim 1, wherein the blades (27) are shaped substantially in the form of a single plate. An insulation-displacement terminal fitting according to one or more of the preceding claims, wherein the cutting edges (28) are located more toward the corresponding side walls (21) than toward the contact edges (24) when viewed in the wire pushing direction (D). An insulation-displacement terminal fitting according to one or more of the preceding claims, wherein the insulation-displacement portions (20) are provided on opposite side walls (20) in a direction substantially normal to the longitudinal direction of the wire (W). An insulation-displacement terminal fitting according to one or more of the preceding claims, wherein the contact portions (23) project inwardly in substantially V-shape. An insulation-displacement terminal fitting according to one or more of the preceding claims, wherein the contact edges (24) extend substantially along the wire pushing direction (D) at their projecting ends. An insulation-displacement terminal fitting according to one or more of the preceding claims, wherein substantially slanted guide surfaces (25) capable of substantially guiding the core (Wa) to between the contact edges (24) are formed at end portions of the contact edges (24) first coming into contact with the wire (W) being inserted into contact with the insulation displacement portions (20) An insulation-displacement terminal fitting according to one or more of the preceding claims, wherein each contact portion (23) comprises a shelf portion (26) before the contact edges (24) with respect to the wire pushing direction (D), preferably extending substantially normal to the wire pushing direction (D), for substantially preventing an entrance of insulation coating (Wb) into the clearance between the contact edges (24) by being caught by the shelf portion (26). An insulation-displacement terminal fitting according to one or more of the preceding claims, wherein the accommodation space (30) communicates with an outer space (S) via a clearance between the cutting blades (28).

Inventors: HIO MASAHIDE, KOJIMA EIJI, HIO, MASAHIDE, KOJIMA, EIJI, Hio, Masahide. c/o Sumitomo Wiring System,LTD, 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