An insulation-displacement terminal fitting and a production method therefor

Abstract: Since cutting edges (21) of two blades (19) forming a V-shape have different angles of inclination α, β when viewed in the longitudinal direction of a wire (16), they come into contact with a resin coating (16A) at different timings while the wire (16) is being pushed in. When the resin coating (16A) is to be cut, the two blades (19) do not simultaneously come into contact with the resin coating (16A), but one blade first coming into contact therewith cuts it. Thus, a resistance during cutting can be small.

Description: The present invention relates to an insulation displacement terminal fitting and to a production method therefor. Some insulation displacement terminal fittings are formed by making cuts in a pair of side walls, bending cut portions inwardly substantially at right angles as blades, so that inwardly facing edges of a pair of blades act as cutting edges. Such insulation displacement terminal fittings are produced by applying plating to the outer surface of a planar conductive metal plate having a specified thickness, stamping out the metal plate in a specified shape having U-shaped slits in a part of wall portions, portions surrounded by the U-shaped slits becoming blades, bending the planar metal plate piece such that the wall portions stand and the blades extend inwardly to oppose cutting edges to each other. At this time, the opposed end surfaces of the cutting edges which are to be brought into contact with a core of a wire are fractured surfaces formed at the time of stamping-out, they are not protected by plating. Thus, if these surfaces are brought into contact with the core as they are, there is a problem in terms of contact reliability. Accordingly, plating has been generally applied to the fractured surfaces (opposed end surfaces). Such plating at a later stage means an increased number of operation steps, which results in higher production costs. In view of the above, insulation displacement terminal fittings which do not require plating at a later stage were developed. One example of such terminal fittings is disclosed in Japanese Unexamined Patent Publication No. 50(SHO)-114592. In this terminal fitting, blade portions are formed by striking a pair of side walls to project inwardly by a press. Each blade portion is such that a V-shaped blade project from the corresponding side wall and an projecting edge of the blade serves as a contacting edge. When a wire is pushed in between the blade portions, the cutting edges of the V-shaped blades cut a resin coating of the wire and a thus exposed core comes into contact with the contacting edges. The projecting edges of the V-shaped blades which serve as contacting edges are left plated since they are formed by pushing the side walls plated before stamping-out inwardly. Thus, plating at a later stage is unnecessary. In the case of the blades formed by cutting portions of the side walls and bending the cut portions, the blades are "I-shaped" when viewed in a direction in which the wire is pushed in. Thus, an insulation displacement resistance (resistance created during insulation displacement) is relatively small because the planar blades come into contact with the resin coating of the wire while the wire is being pushed in. However, in the case of the blades formed by embossing, the blades are "V-shaped" when viewed in the direction in which the wire is pushed in. Accordingly, an insulation displacement resistance is disadvantageously large. For example, EP-A-722 197 relates to an electrical tap connector comprising an insulation displacement contact having multiple aligned insulation displacement contact sections for receiving a multitude of throughwire diameters along the length thereof and a conductor engaging section for electrical engagement with a mating wire end. It is the object of the invention to provide an insulation displacement terminal fitting and a production method therefor allowing to reduce an insulation displacement resistance of V-shaped blade portions. This object is fulfilled by an insulation displacement fitting according to claim 1 and by a production method therefor according to claim 9. Preferred embodiments are defined in the dependent subclaims. According to the invention, there is provided an insulation displacement terminal fitting in which: a wire can be pushed in between at least one pair of blade portions in a direction at an angle different from 0° or 180°, preferably substantially normal to its longitudinal axis; each blade portion comprises two blades and contacting edges being arranged in a wire pushing direction from the projecting end of the two blades; an insulation coating of the wire pushed in between the two blade portions can be cut by cutting edges of the blades so that a core of the wire can be brought into contact with the contacting edges, wherein the cutting edges of the two blades are so arranged as to come into contact with the insulation coating at different timings while the wire is being pushed in. Further, the contacting timings of the cutting edges of the two blades with the insulation coating are differed by differing angles of inclination of the cutting edges, and/or the cutting edges of the two blades forming a V-shape are so arranged at both of the one pair of blade portions as to come into contact with the resin coating at different timings while the wire is being pushed in. According to a preferred embodiment of the invention, the blades are formed by bending portions of side walls of the insulation displacement terminal fitting inwardly. Preferably, the blades are projecting substantially in V-shape when viewed in a wire pushing or insertion direction in which the wire is to be pushed. Most preferably, the contacting edges are continuously extending in the wire pushing direction from the projecting end of the two blades. According to a further preferred embodiment, there is provided an insulation displacement terminal fitting in which a wire is pushed in between one pair of blade portions in a direction normal to its longitudinal axis; each blade portion comprises two blades formed by bending portions of side walls of the insulation displacement terminal fitting inwardly and projecting in V-shape when viewed in a wire pushing direction in which the wire is pushed, and contacting edges extending in the wire pushing direction at the projecting end of the two blades; a resin coating of the wire pushed in between the two blade portions is cut by cutting edges of the blades so that a core of the wire is brought into contact with the contacting edges, wherein the cutting edges of the two blades forming a V-shape are so arranged as to come into contact with the resin coating at different timings while the wire is being pushed in. When the resin coating is to be cut, the two blades forming a V-shape do not simultaneously come into contact with the resin coating, but one blade first coming into contact therewith cuts it. Thus, a resistance during cutting can be small. Preferably, the cutting edges of the two blades preferably forming substantially a V-shape are inclined from a corresponding side wall of the insulation displacement terminal fitting toward the corresponding contacting edge in such directions as to laterally guide the wire. In other words, the cutting edges of the two blades forming a V-shape are inclined from the corresponding side wall toward the corresponding contacting edge in such directions as to guide the wire when viewed in the longitudinal direction of the wire, and the contacting timings of the cutting edges of the two blades with the resin coating are differed by differing angles of inclination of the cutting edges. Since the cutting edges of the blades are inclined, the position of the wire can be corrected even if the wire is displaced with respect to widthwise direction. Further preferably, contacting timings of the cutting edges of the two blades with the insulation coating are differed by differing the position or height from the bottom at which the blades are positioned along the wire pushing direction. Since a cutting operation performed by bringing one blade first into contact with the resin coating is performed at both of the one pair of blade portions, an insulation displacement resistance is smaller as compared to a case where such a cutting operation is performed only at either one of the blade portions. Still further preferably, the preferably parallel cutting edges of the one pair of blade portions opposed to each other when viewed in the wire pushing direction come into contact with the resin coating at the same timing. Most preferably, the cutting edges of the one pair of blade portions substantially opposed to each are substantially parallel to each other. In the case that the cutting edge of one blade portion first coming into contact with the wire and the one of the other blade portion first coming into contact with the wire are so positioned as to form a V-shape together when viewed in the wire pushing direction (e.g. in the case that the front cutting edge of the left blade portion and the front cutting edge of the right blade portion first come into contact with the wire), the wire is pressed in oblique directions by the respective cutting edges due to an elastic restoring force of the resin coating while the resin coating is being cut, and pushed along the longitudinal direction (e.g. forward) of the wire by additional pushing forces from the two cutting edges which act in oblique directions toward the longitudinal axis (e.g. a force acting in an obliquely forward direction to the right is given from the front cutting edge of the left blade portion and a force acting in an obliquely forward direction to the left is given from the front cutting edge of the right blade portion. However, since the cutting edge of the one blade portion first coming into contact with the wire and the cutting edge of the other blade portion first coming into contact with the wire are positioned parallel to each other when viewed in the wire pushing direction according to the invention, these two cutting edges cut the resin coating as a single blade would do. As a result, the wire pushing forces from the cutting edges cancel each other. Therefore, there is no chance of displacing the wire along the longitudinal direction. According to the invention, there is further provided production method for producing an insulation displacement terminal fitting according to the invention or an embodiment thereof having blade portions being formed with blades having cutting edges for cutting an insulation coating of a wire, comprising the following steps: forming side walls by bending a flat metal piece; forming slits at folds extending in the side walls preferably up to a bottom wall in an area where the blade portions are to be formed; setting a set of three transversely extending folds in an area where each slit is formed, preferably at regular intervals in forward and backward directions, wherein two sections between the first or front and second or rear folds and the second or middle fold correspond to the blades of the blade portions, and the second or middle folds correspond to the contacting edges of the blade portions; and embossing portions of the side walls for forming the blade portions. According to a preferred embodiment of the invention, substantially triangular notches are formed in portions of the plate piece, which correspond to upper ends of the side walls after bending and where the blade portions are to be formed, wherein two inclined edges of each of the substantially triangular notches correspond to the cutting edges of the blades. 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 side view of one embodiment of the invention, FIG. 2 is a partial enlarged side view showing blade portions, FIG. 3 is a partial enlarged plan view showing the blade portions, FIG. 4 is a section along X-X of FIG. 2 showing a state where a wire is in contact with cutting edges of the blades, FIG. 5 is a section along X-X of FIG. 2 showing a state where the wire is pushed into connection, and FIG. 6 is a development of a portion of a stamped-out metal plate piece which becomes blade portions. Hereinafter, one preferred embodiment of the invention is described with reference to FIGS. 1 to 6. In the following description, left sides of FIGS. 1 to 3 are referred to as front; vertical direction is based on FIGS. 1 and 2; transverse direction is based on FIGS. 4 and 5; and right side of FIG. 3 is referred to as upper side. An insulation displacement terminal fitting according to this embodiment is produced preferably by stamping out or cutting a flat conductive metal plate 10 preferably having plating applied to its outer surface in a specified shape e.g. by a press, and applying embossing and bending to the stamped-out metal piece. A front end portion of the insulation displacement terminal fitting is an engaging portion 11 preferably in the form of a substantially rectangular tube, into which an unillustrated mating terminal fitting is insertable, and a rear end portion thereof is a wire connecting portion 12, which has an insulation displacement portion 13 preferably substantially at its front half and a crimping portion 14 preferably substantially at its rear half (rear end of the insulation displacement terminal fitting). The crimping portion 14 is comprised of a pair of crimping pieces 14A standing from a bottom wall 15 and crimped or bent or deformed or deformable into connection with a wire 16. The insulation displacement portion 13 is comprised of preferably two pairs of right and left blade portions 17R, 17L (collectively referred to as blade portions 17 in the following description unless either one of the blade portions is specified) which pairs are displaced in forward and backward directions. However, one or three or more blade portions 17 may be provided. The respective blade portions 17R, 17L are formed by embossing or bending or deforming side walls 18R, 18L (collectively referred to as side walls 18 in the following description unless either one of the side walls is specified), and are comprised of two blades 19RF, 19RR and two blades 19LF, 19LR (collectively referred to as blades 19 in the following description unless either one of the blades is specified) preferably projecting substantially in V-shape from the side walls 18 when viewed from above (in a direction in which the wire 16 is pushed in between the blade portions 17), and contacting edges 20R, 20L (collectively referred to as contacting edges 20 in the following description unless either one of the contacting edges is specified) vertically (wire pushing or inserting direction D) extending at a projecting end of the blades 19RF, 19RR and a projecting end of the 19LF, 19LR, respectively. Each pair of such blade portions 17R, 17L are preferably substantially opposed to each other while providing a specified spacing between the contacting edges 20R, 20L. The wire 16 is pushed in between the pair of the blade portions 17R, 17L in a direction arranged at an angle different from 0° or 180°, preferably substantially normal to a longitudinal axis from above. The pushed-in wire 16 has its insulation coating 16A, preferably its resin coating 16A cut or notched by cutting or notching edges 21RF, 21RR, 21LF, 21LR (collectively referred to as cutting edges 21 in the following description unless either one of the cutting edges is specified) of the blades 19, and the contacting edges 20R, 20L enter the cuts made in the resin coating 16A to come into contact with a core 16B at the substantially opposite sides. Next, a production process of the blade portions 17 and the form of the cutting edges 21 of the blades 19 for cutting the resin coating 16A are described in detail. The blade portions 17 are formed by embossing portions of the flat metal plate piece (see FIG. 6), which become the side walls after bending, by means e.g. of a press. The side walls 18 are described here. Slits 22 are formed at folds 23F, 23C, 23R extending in the side walls 18 up to the bottom wall 15 in an area where the blade portions 17 are to be formed. The presence of the slits 22 prevents the bottom wall 15 from being distorted when the side walls 18 are embossed. In an area where each slit 22 is formed, a set of three transversely extending folds 23F, 23C, 23R (i.e. at an angle different from 0° or 180°, preferably substantially normal) are set at substantially regular intervals in forward and backward directions. These two sets of folds 23F, 23C, 23R are preferably symmetrically formed in the left and right side walls 18R, 18L with respect to a center longitudinal axis. Two sections between the front and rear folds 23F, 23R and the middle fold 23C become the blades 19 of the blade portions 17, and the middle folds 23C become the contacting edges 20 of the blade portions 17. Further, triangular notches 24R, 24L are formed in portions of the plate piece, which become the upper ends of the side walls 18 after bending and where the blade portions 17 are to be formed. Two inclined edges of each of the notches 24R, 24L become the cutting edges 21 of the blades 19. The respective notches 24R, 24L are asymmetrical with respect to forward and backward directions as well as transverse direction. More specifically, at the right (lower in FIG. 6) notch 24R, the front end of the front cutting edge 21 RF is located at the intersection of the side edge of the side wall 18R and the front fold 23F, and the rear end thereof is located at the middle fold 23C. On the other hand, the front end of the rear cutting edge 21 RR is located at the middle fold 23C (at the rear end of the front cutting edge 21RF), but the rear end thereof is located further backward from the intersection of the rear fold 23R with the side edge of the side wall 18R. Accordingly, an angle of inclination α of the front cutting edge 21RF of the right notch 24R with respect to forward and backward directions is larger than an angle of inclination β of the rear cutting edge 21RR with respect thereto. The front cutting edge 21RF having a larger angle of inclination α comes into contact with the resin coating 16A of the wire before the rear cutting edge 21RR does. On the other hand, at the left (upper in FIG. 6) notch 24L, the front end of the front cutting edge 21LF is located more forward than the intersection of the side edge of the side wall 18L and the front fold 23F, and the rear end thereof is located at the middle fold 23C. Further, the front end of the rear cutting edge 21LR is located at the middle fold 23C (at the rear end of the front cutting edge 21LF), and the rear end thereof is located at the intersection of the rear fold 23R with the side edge of the side wall 18L. Accordingly, an angle of inclination of the front cutting edge 21 LF with respect to forward and backward directions is smaller than an angle of inclination a of the rear cutting edge 21LR with respect thereto. The rear cutting edge 21LF having a larger angle of inclination α comes into contact with the resin coating 16A of the wire before the rear cutting edge 21 RR does. The right and left notches 24R, 24L are preferably symmetrical with respect to an intersection P (FIG. 6) of a widthwise center line of the bottom wall 15 and a line connecting the two middle folds 23. Thus, the angles of inclination of the front cutting edge 21RF at the right side and of the rear cutting edge 21 LR at the left side are substantially the same, i.e. α, and the angles of inclination of the rear cutting edge 21 RR at the right side and of the front cutting edge 21LF at the left side are substantially the same, i.e. β. Jigs (not shown) are or can be placed along the respective folds 23F, 23C, 23R of the side walls 18R, 18L in the development of the metal plate piece, and the blade portions 17R, 17L are formed by embossing e.g. by means of a press. Thereafter, the side walls 18R, 18L are bent at an angle different from 0° or 180°, preferably at a substantially right angle to the bottom wall 15 to form the insulation displacement portion 13. When the formed insulation displacement portion 13 is viewed from above, the cutting edges 21RF, 21LR having the larger angle of inclination α and the cutting edges 21RR, 21 LF having the smaller angle of inclination β are located substantially on diagonal lines, respectively, as shown in FIG. 3. It should be noted that embossing is applied such that the angles of inclinations α, β of the respective cutting edges 21 with respect to a horizontal line when viewed from front are the same as those in the development of the plate piece. When being pushed into the insulation displacement portion 13, the wire 16 first comes into contact with the cutting edges 21RF, 21LR having the larger angle of inclination α as shown in FIG. 4. These two cutting edges 21RF, 21LR preferably are substantially parallel to each other when viewed from above (when viewed in the pushing direction of the wire 16) as shown in FIG. 3 as if they would form portions of one blade. When the wire 16 is pushed in between the blade portions 17R and 17L in this state, the resin coating 16A is first cut by the cutting edges 21RF, 21LR having the larger angle of inclination α and then cut by the cutting edges 21RR, 21LF having the smaller angle of inclination β. The contacting edges 20R, 20L forcibly enter the cut portions of the resin coating 16A to contact the core 16B at the opposite sides. As described above, in this embodiment, when the resin coating 16A is to be cut, the two blades 19 having a V-shape do not simultaneously cut it, but one of them first coming into contact with the resin coating 16A cuts it substantially as a single blade would do. Accordingly, a resistance (insulation displacement resistance) during cutting can be reduced. Further, since a cutting operation performed by bringing one blade 19 first into contact with the resin coating 16A is performed at both the left and right blade portions 17R, 17L, an insulation displacement resistance is smaller as compared to a case where such a cutting operation is performed only at either one of the blade portions 17R, 17L. Since the respective cutting edges 21 of the blades 19 are inclined from the side walls 18 toward the contacting edges 20 in such directions as to guide the wire 16 when viewed in the longitudinal direction of the wire 16, the position of the wire 16 can be corrected (to a widthwise center position) even if the wire 16 is displaced with respect to widthwise direction, avoiding an erroneous cutting operation and a contact failure between the blade portions 17 and the core 16B. In the case that the cutting edge of the right blade portion 17R first coming into contact with the wire 16 and the one of the left blade portion 17L first coming into contact with the wire 16 are so positioned as to form a V-shape together when viewed in the wire pushing direction (e.g. in the case that the front cutting edge 21 RF of the right blade portion 17R and the front cutting edge 21LF of the left blade portion 17L first come into contact with the wire 16) during insulation displacement, the wire 16 is pressed in oblique directions by the respective cutting edges due to an elastic restoring force of the resin coating 16A while the resin coating 16A is being cut, and pushed along the longitudinal direction (e.g. forward) of the wire 16 by additional pushing forces from the two cutting edges which act in oblique directions toward the longitudinal axis (e.g. a force acting in an obliquely forward direction to the left is given from the front cutting edge 21RF of the right blade portion 17R and a force acting in an obliquely forward direction to the right is given from the front cutting edge 21LF of the left blade portion 17L. However, since the cutting edge 21RF of the right blade portion 17R first coming into contact with the wire 16 and the cutting edge 21LR of the left blade portion 17L first coming into contact with the wire 16 are positioned substantially parallel to each other when viewed in the wire pushing direction in this embodiment, these two cutting edges 21RF, 21LR cut the resin coating substantially as a single blade would do. As a result, the wire pushing forces from the cutting edges 21RF, 21LF cancel each other. Therefore, there is no chance of displacing the wire 16 along the longitudinal direction. The present invention is not limited to the above embodiment. 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 cutting edges of the two blades forming a V-shape are inclined with respect to the wire pushing direction in the foregoing embodiment, the heights of these cutting edges from the bottom wall may be differed by causing either one or both of the cutting edges to extend substantially normal to the wire pushing direction. (2) Although the cutting edges of the two blades have the substantially same height at the contacting edge while having different heights at the side wall when viewed in the longitudinal direction of the wire in the foregoing embodiment, they may have the same height at the side wall while having different heights at the contacting edge or may have different heights both at the side wall and at the contacting edge. In the case that the cutting edges have different heights both at the side wall and at the contacting edge, the two cutting edges may intersect with each other in their intermediate positions when viewed in the longitudinal direction of the wire. (3) Although the contacting timings of the two blades with the resin coating are differed by differing the angles of inclination of these blades in the foregoing embodiment, the heights thereof may be differed while forming them to have the same angle of inclination. LIST OF REFERENCE NUMERALS 16 wire 16A resin coating 16B core 17R blade portion 17L blade portion 18R side wall 18L side wall 19RF blade 19RR blade 19LF blade 19LR blade 20R contacting edge 20L contacting edge 21RF cutting edge 21RR cutting edge 21LF cutting edge 21LR cutting edge

Claims: An insulation displacement terminal fitting comprising at least one pair of blade portions (17), whereby a wire (16) can be pushed in between the at least one pair of blade portions (17) in a direction at an angle different from 0° or 180°, preferably substantially normal to its longitudinal axis; each blade portion (17) comprising two blades (19) and contacting edges (20) being arranged in a wire pushing direction (D) from the projecting end of the two blades (19); cutting edges (20) being provided on the blades (19) so that an insulation coating (16A) of the wire (16) pushed in between the two blade portions (17) can be cut by the cutting edges (21) of the blades (19) so that a core (16B) of the wire (16) can be brought into contact with the contacting edges (20), characterized in that the contacting timings of the cutting edges (21) of the two blades (19) with the insulation coating (16A) are differed by differing angles of inclination (α, β) of the cutting edges (21) and/or the cutting edges (21) of the two blades (19) preferably forming substantially a V-shape are so arranged at both of the blade portions (17) of the at least one pair of blade portions (17) as to come into contact with the insulation coating (16A) at different timings while the wire (16) is being pushed in. An insulation displacement terminal fitting according to claim 1, wherein the blades (19) are formed by bending portions of side walls (18) of the insulation displacement terminal fitting inwardly. An insulation displacement terminal fitting according to one or more of the preceding claims, wherein the blades (19) are projecting substantially in V-shape when viewed in a wire pushing direction (D) in which the wire is to be pushed. An insulation displacement terminal fitting according to one or more of the preceding claims, wherein the contacting edges (20) are continuously extending in the wire pushing direction from the projecting end of the two blades (19). An insulation displacement terminal fitting according to one or more of the preceding claims, wherein the cutting edges (21) of the two blades (19) preferably forming substantially a V-shape are inclined from a corresponding side wall (18) of the insulation displacement terminal fitting toward the corresponding contacting edge (20) in such directions as to laterally guide the wire (16). An insulation displacement terminal fitting according to one or more of the preceding claims, wherein contacting timings of the cutting edges (21) of the two blades (19) with the insulation coating (16A) are differed by differing the position at which the blades (19) are positioned along the wire pushing direction (D). An insulation displacement terminal fitting according to one or more of the preceding claims, wherein the cutting edges (21) of the one pair of blade portions (17) substantially opposed to each other when viewed in the wire pushing direction (D) come into contact with the insulation coating (16A) at the substantially same timing. An insulation displacement terminal fitting according to one or more of the preceding claims, wherein the cutting edges (21) of the one pair of blade portions (17) substantially opposed to each are substantially parallel to each other. A method of producing an insulation displacement terminal fitting according to one or more of the preceding claims having blade portions (17) being formed with blades (19) having cutting edges (21) for cutting an insulation coating (16A) of a wire (16), comprising the following steps: forming side walls (18) by bending a flat metal piece; forming slits (22) at folds (23F; 23C; 23R) extending in the side walls (18) preferably up to a bottom wall (15) in an area where the blade portions (17) are to be formed; setting a set of three transversely extending folds (23F, 23C, 23R) in an area where each slit (22) is formed, preferably at regular intervals in forward and backward directions, wherein two sections between the first or front and second or rear folds (23F, 23R) and the second or middle fold (23C) correspond to the blades (19) of the blade portions (17), and the second or middle folds (23C) correspond to the contacting edges (20) of the blade portions (17); and embossing portions of the side walls (18) for forming the blade portions (17), and wherein substantially triangular notches (24R, 24L) are formed in portions of the plate piece, which correspond to upper ends of the side walls (18) after bending and where the blade portions (17) are to be formed, wherein two inclined edges of each of the substantially triangular notches (24R, 24L) correspond to the cutting edges (21) of the blades (19).

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