An insulation displacement terminal fitting and production method therefor

Abstract: To prevent an occurrence of a crack when V-shaped blade portions are formed by embossing. A deformation facilitating portion (17) for increasing a stretching degree of a portion of a side wall (15) which becomes an edge (16A) (pointed edge at the leading end of a V-shaped portion) by forming weakened portions (17A) is provided at a portion of the blade portion (16) continuous with the side wall (15). Since connecting portions (17B) of the deformation facilitating portion (17) are stretched to a large degree during embossing, a stretching degree of a portion near the edge (16A) can be small, thereby preventing an occurrence of a crack in the edge (16A).

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. 50(SHO)-114592. This terminal fitting is such that inward-facing blade portions are formed on a pair of side walls. When a wire is inserted between the blade portions, the blade portions cut a resin coating of the wire to be brought into contact with a core of the wire. Each blade portion is V-shape when viewed in an inserting direction of the wire, and is formed by embossing the flat side wall by means of a press such that a part of the side wall is bent in V-shape. In the case that the blade portions are formed by embossing the side walls into V-shaped portions, the side walls become gradually thinner toward the pointed edges at the leading ends of V-shaped portions since dies are placed where the pointed edges are to be formed to stretch the side walls. As a result, the pointed edges at the leading ends of V-shaped portion blade portions, i.e. contacting edges with the wire may crack. In order to avoid such a crack, it may be considered to widen a spacing between the blade portions by embossing the side walls to project to a smaller degree or to form the insulation-displacement terminal fitting of a relatively soft material. The former means cannot cope with thin wires, and the latter means may cause a deformation during insulation-displacement connection and an insufficient contact pressure. Either means cannot solve the above problem. From EP-A-0722197 (D1) an insulation displacement contact connector for multiple wire sizes is known, which is provided with slots in its side walls in order to improve the deflection characteristics of an insulation displacement contact. Furthermore, a slot parallel to a bottom wall of the connector is provided in blade portions of the side walls which separates an upper and a lower area of each blade portion. In the upper area of the blade portions the respective blades are divided while in the lower area the blades are connected. From US-A-4057314 (D2) an electrical connector including an insulation-opening contact is known, at which an aperture is provided at the junction of the sidewall and the bottom wall of the connector to facilitate forming a detent by a pressing process so that lancing or an abrupt swedging is not necessary at that point. It is the object of the invention to prevent an occurrence of a crack when V-shaped blade portions for insulation-displacement connection are formed by embossing. This object is fulfilled by an insulation-displacement terminal having the features disclosed in claim 1 and by a production method according to claim 7. Preferred embodiments are defined in the dependent subclaims. According to the invention, there is provided an insulation-displacement terminal fitting in which one or more side walls are embossed inwardly to form one or more substantially V-shaped blade portions projecting from the side walls for cutting into an insulation coating of wire to be connected with a core of the wire, wherein one or more weakened portions are formed at or near the portions continuous with the blade portions and the side walls. Since the portions where the weakened portions are formed are stretched to a large degree during embossing, a stretching degree of the blade portions, preferably pointed edges at the leading ends of the V-shaped blade portions, can be small, thereby preventing an occurrence of a crack in the blade portions, preferably in the pointed edges thereof. According to a preferred embodiment of the invention, pointed edges provided at the leading ends of the substantially V-shaped blade portions cut the insulation coating of the wire to be connected with the core of the wire, when the wire is pressed in between the blade portions. Preferably, there is provided an insulation-displacement terminal fitting in which a pair of side walls are embossed inwardly to form V-shaped blade portions projecting from the side walls and, when a wire is pressed in between the blade portions, pointed edges at the leading ends of the V-shaped blade portions cut a resin coating of the wire to be connected with a core of the wire, wherein weakened portions are formed at and/or near portions continuous with the blade portions and the side walls. Further preferably, the weakened portions are at least partly in the form of through holes. Still further preferably, the weakened portions are at least partly in the form of recesses formed by partial thinning. According to a further preferred embodiment, the weakened portions are so formed as to substantially continuously extend over the blade portions and/or the side walls in particular in embossing directions, i.e. along the longitudinal extension of the blade and side wall portions. Since the forming areas of the weakened portions in stretching directions are larger as compared with a case where the weakened portions are formed either in the blade portions or in the side walls, the portions where the weakened portions are formed is distorted only to a small degree, with the result that these portions can remain relatively thick. Preferably, the insulation-displacement terminal fitting further comprises a bottom wall, wherein at least one slit is formed at least partly between the blade portions and the bottom wall. According to the invention, there is further provided a production method for producing an insulation-displacement terminal fitting, in particular according to the invention or an embodiment thereof, comprising the steps of: providing an electrically conductive plate member; embossing one or more portions of the plate member corresponding to one or more side walls to form one or more substantially V-shaped blade portions projecting from the side walls for cutting into an insulation coating of wire to be connected with a core of the wire, characterized by the steps of: forming one or more weakened portions at and/or near portions of the blade portions and/or the side walls; and such that the weakened portions being stretched larger than the rest of the blade portions during embossing of the blade-portions. According to a preferred embodiment of the invention, the plate member is provided such that the portions to be embossed have a substantially constant thickness. Most preferably, the one or more weakened portions are provided at least partly in the form of through holes and/or of recesses formed by partial thinning. 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. It should be understood that even though embodiments are separately described, single features thereof may be combined to additional embodiments. FIG. 1 is a perspective view of a first embodiment connected with a wire, FIG. 2 is a perspective view of the first embodiment before connection with a wire, FIG. 3 is a plan view partly in section showing press-formed blade portions, FIG. 4 is a partial side view of the press-formed blade portion, FIG. 5 is a partial section showing through holes before press-forming, FIG. 6 is a plan view partly in section showing press-formed blade portions of a second embodiment, FIG. 7 is a partial side view showing the press-formed blade portion, FIG. 8 is a partial section showing through holes before press-forming, FIG. 9 is a plan view partly in section showing press-formed blade portions of a third embodiment, FIG. 10 is a plan view of through holes in a development of the third embodiment, and FIG. 11 is a partial section showing recessed portions before press-forming. [First Embodiment] Hereinafter, a first preferred embodiment of the present invention is described with reference to FIGS. 1 to 5. An insulation-displacement terminal fitting is formed by bending and embossing a metal plate member preferably having a substantially constant thickness and stamped out or cut in a specified shape, and comprised of an engaging portion 11, an insulation-displacement portion 12 and a crimping portion 13 which are integrally or unitarily connected with each other by a common bottom wall 14 in this order from front (upper right side in FIGS. 1 and 2). The engaging portion 11 is in the form of a substantially rectangular tube having open front and rear end surfaces, and is formed therein with an elastic contact piece (not shown) to be brought into contact with a tab (not shown) of a mating terminal fitting. The elastic contact piece is formed e.g. by being folded at the front edge of the bottom wall 14. The crimping portion 13 is comprised of a pair of barrel portions 13A, 13B which extend at an angle different from 0° or 180°, preferably substantially normal or upward from the left and right edges of the bottom wall 14 and are preferably displaced from each other in forward and backward directions, and a wire 21 is or can be fastened by crimping or bending or deforming the barrel portions 13A, 13B into connection with the outer surface of the wire 21. The insulation-displacement portion 12 is such that e.g. two pairs of front and rear blade portions 16, each pair preferably substantially facing each other at the side walls 15, are formed by embossing portions of side walls 15 inward to have a substantially V-shape when viewed from above (in a direction D in which the wire 21 is pushed into connection). Pointed edges 16A (ridges of blades 16B) at the leading ends of the substantially V-shaped blade portions 16 when viewed from above act as substantially vertically (direction D in which the wire 21 is pushed into connection) extending edges. When the wire 21 is pushed in between the side walls 15 from above, the upper edges of the blades 16B of the blade portions 16 cut or can cut an insulation coating, preferably a resin coating of the wire 21, so that the contacting edges 16A come or can come into contact with a core of the wire 21. Next, how the blade portions 16 are formed is described. In a development of the terminal fitting before bending in which the bottom wall 14 and the side walls 15 are substantially continuous in flush with each other, two deformation facilitating portions 17 are formed for each blade portion 16. In each deformation facilitating portion 17, a weakened portion 17A preferably in the form of a substantially rectangular through hole is formed to be open in the inner and outer surfaces of the plate member, and the side wall 15 and the blade portion 16 are connected via connecting portions 17B above and below the weakened portion 17A. Further, a fold 18 which is a boundary or boundary or transitional portion between the side wall 15 and the blade 16B of the blade portion 16 extend through the weakened portion 17A, which is so formed as to continuously extend over the side wall 15 and the blade portion 16 in a stretching direction of the plate member during embossing. The weakened portion 17A is formed in an area at and/or near a portion continuous with the blade portion 16 and the side wall 15 excluding the contacting edge 16A (pointed edge at the leading end of the substantially V-shaped blade portion 16). A slit 19 is formed at a boundary between the side wall 15 and the bottom wall 14 in order to prevent a deformation of the side wall 15 from influencing the bottom wall 14 when the blade portion 16 is formed by embossing. Embossing is applied to the flat plate member by an unillustrated press. During embossing, a die (not shown) is placed along folds 20 which become the contacting edges 16A of the blade portions 16 from outside, and a mating die (not shown) is placed along the folds 18 at the boundaries of the blades 16B and the side walls 15 from inside. In this state, the press dies are caused to advance inwardly, thereby gradually forming the blade portions 16. At this time, portions of the side walls 15 are stretched in embossing directions. If the portions to be embossed simply have a constant thickness, the side walls 15 become gradually thinner toward the leading ends (portions which become the edges at the leading ends of the substantially V-shaped blade portions 16). However, in this embodiment, the deformation facilitating portions 17 are provided by forming the weakened portions 17A at the boundaries 18 between the portions of the side walls left intact and portions thereof to be embossed, so that a degree of stretching deformation (distortion) in vicinity of the weakened portions 17A during embossing is set larger than that of the portions which become the contacting edges 16A (pointed edges at the leading ends of the substantially V-shaped blade portions 16). Accordingly, the connecting portions 17B of the deformation facilitating portions 17 are stretched to a large degree during embossing, with the result that the portions which become the contacting edges 16A (portions in vicinity of the pointed edges at the leading ends of the substantially V-shaped blade portions 16) are stretched to a small degree. Thus, the thickness of the formed blade portions 16 is substantially constant over the entire area from the boundaries 18 with the side walls 15 to the contacting edges 16A. This obviates a likelihood that portions of the blade portions 16 at and near the contacting edges 16A become thinner or crack. Further, a range where the weakened portions 17A are formed in embossing direction (stretching direction) is larger as compared to a case where they are formed only in a narrow area where the blade portion 16 is formed. Accordingly, the degree of stretching deformation (degree of distortion) of the connecting portions 17B of the deformation facilitating portions 17 can be small. Thus, the connecting portions 17B of the deformation facilitating portions 17 remain relatively thick, deformation of the blade portions 16 resulting from a resistance created when the wire is pressed into connection can be prevented, and a specified contact pressure can be secured between the blade portions 16 and the core. [Second Embodiment] Next, a second embodiment of the invention is described with reference to FIGS. 6 to 8. The second embodiment differs from the first embodiment in the forming range of deformation facilitating portions 22. Since the second embodiment is similar or identical to the first embodiment in the other construction, no description is given to the structure, action and effects of the same construction by identifying it by the same reference numerals. The deformation facilitating portion 22 of the second embodiment includes a weakened portion 22A as the deformation facilitating portion 17 of the first embodiment does. A degree of stretching deformation (distortion) of connecting portions 22B above and below the weakened portion 22A during embossing is set larger than that of the portions which become the contacting edges 16A of the blade portion 16. The weakened portions 22A are not formed in portions of the side walls 15 which remain as part of the side walls 15 even after embossing, but formed substantially within a range of the blades 16B of the blade portion 16. Specifically, the forming area of the weakened portions 22A in embossing direction is smaller as compared to the first embodiment. It should be noted that the vertical dimension of the forming area of the weakened portions 22A is same as in the first embodiment. [Third Embodiment] Next, a third embodiment of the invention is described with reference to FIGS. 9 to 11. Unlike the deformation facilitating portions 17, 22 of the first and second embodiments which include the weakened portions 17A, 22A in the form of through holes open in the inner and outer surfaces of the plate member, deformation facilitating portions 23 of the third embodiment include weakened portions 23A formed by stepwise thinning or recessing the inner surface of the side walls (the inner sides of the side walls 15 are thinned). A stretching degree of thick portions 23B above and below the weakened portion 23A resulting from embossing is set larger than that of the portions which become the contacting edges 16A of the blade portion 16. The forming area of the weakened portions 23A is the same as in the first embodiment. It should be noted that no description is given to the structure, action and effects of the similar or same construction by identifying it by the same reference numerals since the third embodiment is identical to the first embodiment in the other construction. [Other Embodiments] The present invention is not limited to the above embodiments. For example, following embodiments are also embraced by the technical scope of the invention as defined in the claims. Besides these embodiments, various changes can be made without departing from the scope and spirit of the invention as defined in the claims. (1) Although the weakened portions are holed or thinned in the foregoing embodiments, they may be a combination of holed and thinned portions according to the present invention. (2) Although one pair of weakened portions are provided for each blade portion in the foregoing embodiments, more weakened portions may be provided and the positions thereof may be arbitrarily set according to the present invention. (3) Although the weakened portions are formed on the inner surfaces of the side walls in the third embodiment, they may be formed on the outer surfaces of the side walls or may be formed on both the inner and outer surfaces of the side walls. (4) Although the weakened portions are made stepwise thinner than the other portions before embossing in the third embodiment, they may be gradually thinned. (5) Although the weakened portions are formed at the blade portions or over the blade portions and the side walls in the foregoing embodiments, they may be formed only at the side walls or independent weakened portions may be separately formed in the blade portions and the side walls according to the present invention. (6) Although the terminal fitting was described as having two pairs of blade portions 16, only one pair or three or more pairs of blade portions 16 may be provided. LIST OF REFERENCE NUMERALS 15 side wall 16 blade portion 16A contacting edge (pointed edge at the leading end of a V-shaped blade portion) 17A weakened portion 22A, 23A weakened portion

Claims: An insulation-displacement terminal fitting in which one or more side walls (15) are embossed inwardly to form one or more substantially V-shaped blade portions (16) projecting from the side walls (15) for cutting into an insulation coating of wire (21) to be connected with a core of the wire (21), characterized in that one or more weakened portions (17A; 22A; 23A) are provided at or near the portions continuous with the blade portions (16) and the side walls (15) such that the weakened portions (17A; 22A; 23 A) being stretched larger than the rest of the blade portions (16) during embossing of the blade portions (16). An insulation-displacement terminal fitting according to claim 1, wherein pointed edges provided at the leading ends of the substantially V-shaped blade portions (16) cut the insulation coating of the wire (21) to be connected with the core of the wire (21), when the wire is pressed in between the blade portions (16). An insulation-displacement terminal fitting according to one or more of the preceding claims, wherein the weakened portions (17A; 22A) are at least partly in the form of through holes. An insulation-displacement terminal fitting according to one or more of the preceding claims, wherein the weakened portions (23A) are at least partly in the form of recesses formed by partial thinning. An insulation-displacement terminal fitting according to one or more of the preceding claims, wherein the weakened portions (17A; 23A) are so formed as to substantially continuously extend over the blade portions (16) and/or the side walls (15). An insulation-displacement terminal fitting according to one or more of the preceding claims, further comprising a bottom wall (14), wherein at least one slit (19) is formed at least partly between the blade portions (16) and the bottom wall (14). A production method for producing an insulation-displacement terminal fitting, comprising the steps of: providing an electrically conductive plate member; and embossing one or more portions of the plate member corresponding to one or more side walls (15) to form one or more substantially V-shaped blade portions (16) projecting from the side walls (15) for cutting into an insulation coating of wire (21) to be connected with a core of the wire (21), characterized by the step of: forming one or more weakened portions (17A; 22A; 23A) at or near the portions continuous with the blade portions (16) and the side walls (15) such that the weakened portions (17A; 22A; 23 A) being stretched larger than the rest of the blade portions (16) during embossing of the blade portions (16). A production method according to claim 7, wherein the plate member is provided such that the portions to be embossed have a substantially constant thickness. A production method according to claim 7 or 8, wherein the one or more weakened portions (17A; 22A; 23A) are provided at least partly in the form of through holes and/or of recesses formed by partial thinning.

Inventors: AOYAMA MASAHIKO, AOYAMA, MASAHIKO, Aoyama, Masahiko, Sumitomo Wiring Systems, Ltd.
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 2000
Main classification: H01R4
IPC codes: H01R4, H01R11