Cramping terminal

Abstract: To provide a cramping terminal having a strong groove portion and an electrical connection with an improved reliability. A side cramping blade 29 provided in a groove portion 25 of a cramping terminal 20 is formed by bending projections 40 constructing the side cramping blade 29 in different directions. Accordingly, by forming the projections 40, holes 42 are left in one side wall 27 more toward one end of the groove portion 25 than the side cramping blade 29 and in the other side wall more toward the other end of the groove portion 25 than the side cramping blade 29. Therefore, the side walls 27 remain opposite to the hole 42, enhancing the strength of the groove portion 25.

Description: The present invention relates to a cramping terminal. In general, a cramping terminal has a cramping blade inside a groove portion having a substantially U-shaped cross section which is formed e.g. by bending a metal plate. When a wire is pushed into a slit formed in this cramping blade, an insulation coating of the wire is cut, thereby bringing a core of the wire into contact with the inner surface of the slit to establish an electrical connection. There are two types of cramping blades: a U-slot cramping blade 5 made by forming a slit 4 in an upright piece 3 formed by cutting and bending a portion of a bottom wall 2 of a groove portion 1 having a U-shaped cross section as shown in FIG. 7, and a side cramping blade 8 formed by cutting and bending portions of opposite side walls 6 of a groove portion 1 in such a manner as to face each other as shown in FIG. 8. With the side cramping blade 8, a pair of holes 7A are formed in the opposite side walls 6 in the same position along the longitudinal direction of the groove portion 1, causing a reduction in the strength. Further, there is a demand for additionally providing a side press blade to a known cramping terminal 9 (see FIG. 9) provided with a pair of U-slot cramping blades 5 in order to improve the reliability of an electrical connection with a wire. In such a case, if a side cramping blade 8 is merely additionally formed in the cramping terminal 9 to have a construction shown in FIG. 10, a hole 9B left in the bottom wall 2 by forming the U-slot cramping blade 8 and the holes 7A of the opposite side walls 6 concentrate in the same position with respect to the longitudinal direction of the groove portion 1, leaving only a small area of walls (see hatched portions in FIG. 11 ) as shown in FIG. 11. This presents a problem in view of strength. In view of the above problems, an object of the present invention is to provide a cramping terminal which has a groove portion of a higher strength and ensures a more reliable electrical connection. This object is solved according to the invention by a cramping terminal according to claim 1. Preferred embodiments of the invention are subject of the dependent claims. According to the invention, there is provided a cramping terminal, comprising: at least one cramping portion provided in or at a groove portion, the cramping portion cutting an insulation coating to be electrically connected with a core of a wire when the wire is at least partially pushed into the groove portion, wherein the cramping portion comprises at least one side cramping blade formed by causing the leading ends of a pair of portions or projections formed by cutting and bending portions of substantially opposite side walls of the groove portion to face substantially opposite to each other, a substantially C-shaped notch made in one side wall to form one projection of the side cramping blade and a substantially C-shaped notch made in the other side wall to form the other projection, the projections being bent from the respective side walls inwardly so that the projections are oriented in substantially opposite projection directions. Furthermore, holes formed in the side walls by bending the projections are displaced with respect to each other in a longitudinal direction of the cramping connector and the groove portion is formed by bending a metal plate to have a substantially U-shaped cross section. Accordingly, the strength of the cramping terminal can be enhanced, since the material thereof is not weakened in longitudinally same or similar positions of the holes. Preferably, engaging corners of the projections are rounded. Accordingly, holes are left in the side walls when the projections are bent from the opposite side walls of the groove portion to form the side cramping blade. Since the projections of the side cramping blade are bent in different directions in the cramping terminal according to this invention, the holes left by forming the projections are or may be located in the one side wall more toward the one end of the groove portion than the side cramping blade and in the other side wall more toward the other end of the groove portion than the side cramping blade i.e. the holes are longitudinally displaced with respect to each other. Thus, the side walls remain substantially opposite to the holes, enhancing the strength of the groove portion. Preferably, the cramping portion comprises at least one pair of substantially U-slot cramping blades each formed by making a slit in the substantially middle of an upright piece formed by cutting and bending a portion of the bottom wall of the groove portion, and the side cramping blade. Accordingly, since the pair of U-slot cramping blades and the side cramping blade are provided in the groove portion, thereby increasing contact portions with the wire, the reliability of the connection can be improved. Most preferably, the upright piece is arranged at an angle different from 0° or 180°, preferably substantially normal to the bottom wall. These and other objects, features and advantages of the present invention will become more apparent upon a reading of the following detailed description and accompanying drawings in which: FIG. 1(A) is a section of a usual wire, and FIG. 1(B) is a section of a flexible wire, FIG. 2 is a perspective view of a cramping terminal according to one embodiment of the invention, FIG. 3 is a front view of the cramping terminal, FIG. 4 is a development of a groove portion, FIG. 5 is an enlarged perspective view of the groove portion, FIG. 6 is a section along A-A of FIG. 3, FIG. 7 is a perspective view of U-slot cramping terminals, FIG. 8 is a perspective view of a side cramping terminal, FIG. 9 is an enlarged partial perspective view of a groove portion of a prior art cramping terminal, FIG. 10 is a section of the prior art cramping terminal additionally provided with a side cramping blade, and FIG. 11 is a section along B-B of FIG. 10. Hereafter, one embodiment of the invention is described with reference to FIGS. 1 to 6. A cramping terminal 20 (see FIG. 2) according to this embodiment is modified such that a conventional cramping terminal designed for a usual wire 10 (see FIG. 1(A)) can also be used for a so-called flexible wire 15 (see FIG. 1(B)). The usual wire 10 has a core 13 made of a plurality of strands 12 inside an insulation coating 11. The flexible wire 15 has an insulation coating 16 and a core 18 having the same outer diameters 1, 2 as those of the usual wire 10, but has more strands 17 because the strands 17 are thinner than those of the usual wire 10. In other words, the outer diameter 4 of the strands 17 of the flexible wire 15 is smaller than the outer diameter 3 of the strands 12 of the usual wire 10. By using the thinner strands, the flexible wire 15 has an advantage that bendability is better than the usual wire 15 and a disadvantage that no large force cannot be exerted on the strands 17 while the flexible wire 15 is being connected. The cramping terminal 20 described below has a construction for compensating for this disadvantage. The cramping terminal 20 is so formed as to substantially have e.g. an L-shape as a whole as shown in FIG. 2 e.g. by successively cutting and bending a conductive metal plate. A portion vertically extending in FIG. 2 acts as a tab connection portion 21 with an unillustrated mating terminal. The tab connection portion 21 is substantially in the form of a rectangular tube, and four walls of this rectangular tube extend from an intermediate position to the bottom end in the form of strips. A pair of opposite strip portions 23 are bent substantially closer (or to be convergent) to each other (see FIG. 3) so as to tightly hold a tab of the unillustrated mating terminal being at least partially insertable therebetween. The cramping terminal 20 is also provided with a groove portion 25 having preferably a substantially U-shaped cross section at the leading end of a flat portion 24 extending from one side at the upper end of the rectangular tube of the tab connection portion 21. A cramping portion 22 comprised of substantially U-shaped slot cramping blades 28 and a side cramping blade 29 is provided in or at the groove portion 25. The groove portion 25 is constructed such that a pair of side walls 27 are bent at an angle different from 0° or 180°, preferably at substantially right angles at the opposite sides of a bottom wall 26 which extends substantially in flush with or adjacent to the flat portion 24. The pair of U-slot cramping blades 28 are preferably provided at a side of the groove portion 25 substantially away from the flat portion 24. These blades 28 are formed as follows. A pair of substantially upright pieces 30 extending in substantially opposite directions along the longitudinal direction L of the groove portion 25 are formed by punching portions of a metal plate of the groove portion 25 in its developed state shown in FIG. 4, and the upright pieces 30 are bent at an angle different from 0° or 180°, preferably substantially at right angles so as to face each other. Locking portions 31 project from the substantially opposite side edges of each upright piece 30. The respective locking portions 31 are engaged or engageable with lock holes 32 formed in the opposite side walls 27 so as to hold the cramping blade 28 standing or in a position or orientation at an angle different from 0° or 180°, preferably substantially normal with respect to the bottom wall 26 (see FIG. 5). In the substantially middle of each upright portion 30 with respect to its widthwise direction is formed a slit 33 which is open at a free end. The flexible wire 15 is guided into the slit 33 by tapered portions 33A formed at the open side of the slit 33. The width of the slit 33 is slightly narrower than the diameter 2 (see FIG. 1 (B)) of the core 18 of the flexible wire 15. The core 18 of the flexible wire 15 is or can be at least partially pushed into the slit 33 to be electrically connected. The slit 33 preferably is slightly wider than a slit of a cramping blade used to cramp the usual wire 10, so that no large force acts on the strands 17 when the flexible wire 15 is pushed into the slit 33. As shown in FIG. 6, the side cramping blade 29 is formed at a portion of the groove portion 25 in vicinity of or adjacent to the flat portion 24. The blade 29 is formed by causing the leading ends of a pair of portions or projections 40, 40' cut and bent or folded or twisted from the opposite side walls 27 of the groove portion 25 to substantially face each other via a slit 41. The first or upper one 40 of the projections 40, 40' in FIG. 6 is formed by making a substantially C-shaped notch C1 (see FIG. 4) in one side wall 27 and bending a portion inside the notch C1 in a direction D1 substantially away from the portion of the groove portion 25 near the flat portion 24, and the second or lower projection 40' in FIG. 6 is formed by forming a substantially inverted C-shaped notch C2 (see FIG. 4) in the other side wall 27 and bending a portion inside the notch C2 in a direction D2 substantially toward the portion of the groove portion 25 near the flat portion 24. Accordingly, the projections 40, 40' cannot be easily bent in one same direction by a force acting on the wire 15 inserted therebetween, since the different or opposed bending directions D1, D2 cause different bending properties of the projections 40, 40' when subjected to a force in a substantially same direction. Holes 42, 42' (see FIG. 6) left in the side walls 27 by forming the projections 40, 40' are displaced from each other with respect to the longitudinal direction L of the groove portion 25 or of the lateral side walls 27 (transverse direction in FIG. 6). Further, the slit 41 of the side cramping blades 29 has the same width as the slits 33 of the U-slot cramping blades 28. The upper or engaging corners (or corners first coming into contact with the wire 15) of the projections 40, 40' are rounded or slanted or tapered as shown in FIG. 5 in order to guide the flexible wire 15 into the slit 41. Next, the action of this embodiment is described. In order to connect the flexible wire 15 with the cramping terminal 20 according to this embodiment, the flexible wire 15 is at least partially inserted in or pushed substantially to the bottom of the groove portion 25 through an opening in the lateral or upper surface (or insertion side) of the groove portion 25 of the cramping terminal 20, for example, with the cramping terminal 20 accommodated in an unillustrated housing. Then, the flexible wire 15 is substantially pressed into the slits 33, 41 in the cramping blades 28, 29 with the insulation coating 16 thereof cut in by the edges of the slits 33, 41, and the core 18 is brought substantially into contact with the inner surfaces of the slits 33, 41. The flexible wire 15 and the cramping terminal 20 are electrically connected in at least three positions where the cramping blades 28, 29 are provided. In the cramping terminal 20 of this embodiment, there are more contact portions than in the cramping terminal (see FIG. 9) provided with two cramping terminals for the usual wire 10. Thus, the reliability of the electrical connection can be improved. There are some cases where a force acts on the cramping terminal 20 during the assembling of the cramping terminal 20 into the housing, the cramping operation, etc. Since the projections 40, 40' of the side cramping blade 29 are bent in different or opposed directions D1, D2 in the cramping terminal 20 of this embodiment, the hole 42 left in the one side wall 27 by forming the projection 40 is located more toward one end of the groove portion 25 than the cramping blade 29 and the hole 42' left in the other side wall 27 by forming the projection 40' is located more toward the other end of the groove portion 25 than the cramping blade 29. Thus, as shown in FIG. 6, the holes 42, 42' are not substantially opposed and the side walls 27 remain substantially opposite to the respective holes 42, 42', which enhances the strength of the groove portion 25. In other words, the holes 42, 42' are substantially displaced or positioned at a distance in or along a longitudinal direction L (FIG. 6) of the side walls 27 or of the cramping terminal 20. According to the cramping terminal 20 of this embodiment, the strength of the groove portion 25 can be enhanced while the reliability of the electrical connection with the flexible wire 15 can be improved. < Other Embodiments > The present invention is not limited to the described and illustrated embodiment, but the following embodiments are also embraced by the technical scope of the present invention as defined in the claims. Besides the following embodiments, a variety of other changes can be made without departing from the scope of the invention as defined in the claims. (1) Although the side cramping blade 29 is provided more toward one end of the groove portion 25 than the U-slot cramping blades 28 in the foregoing embodiment, it may be provided between the U-slot cramping blades 28. (2) Although the flexible wire 15 is connected with the cramping terminal 20 in the foregoing embodiment, the latter may be connected with the usual wire 10. (3) Even though only two U-shaped slot cramping blades 28 are provided in the above embodiment, only one or three or more may be provided as needed. LIST OF REFERENCE NUMERALS 15 Flexible Wire (Wire) 16 Insulation Coating 18 Core 20 Cramping Terminal 22 Cramping Portion 25 Groove Portion 26 Bottom Wall 27 Side Wall 28 U-Slot Cramping Blade 29 Side Cramping Blade 30 Upright Piece 33 Slit 40, 40' Projection 41 Slit 42, 42' Hole C1, C2 C-shaped Notch

Claims: A cramping terminal (20), comprising: at least one cramping portion (22) provided in or at a groove portion (25) formed by bending a metal plate to have a substantially U-shaped cross section, the cramping portion (22) cutting an insulation coating (16) to be electrically connected with a core (18) of a wire (15) when the wire (15) is at least partially pushed into the groove portion (25), wherein the cramping portion (22) comprises at least one side cramping blade (29) formed by causing the leading ends of a pair of portions or projections (40, 40') formed by cutting and bending portions of substantially opposite side walls (27) of the groove portion (25) to face substantially opposite to each other, a substantially C-shaped notch (C1) made in one side wall (27) to form one projection (40) of the side cramping blade (29) and a substantially C-shaped notch (C2) made in the other side wall (27) to form the other projection (40'), characterized in that the projections (40, 40') are bent from the respective side walls (27) inwardly, so that the projections (40, 40') are oriented in substantially opposite projection directions (PD1, PD2) , and that holes (42, 42') formed in the opposite side walls (27) by bending the projections (40, 40') are displaced with respect to each other in a longitudinal direction (L) of the cramping connector (20). A cramping connector according to claim 1, wherein engaging comers of the projections (40, 40') are provided with tapered comers, preferably rounded, the engaging corners being the corners of the projections (40, 40') first coming into contact with the wire (15). A cramping terminal according to one or more of the preceding claims, wherein the cramping portion (22) comprises at least one pair of U-slot cramping blades (28) each formed by making a slit in the substantially middle of an upright piece (30) formed by cutting and bending a portion of a bottom wall (26) of the groove portion (25), and the side cramping blade (29). A cramping terminal according to claim 3, wherein the upright piece (30) is arranged at an angle different from 0° or 180°, preferably substantially normal to the bottom wall (26).

Inventors: CHISHIMA MASAMITSU, SAKA YUKINORI, SEKO SATOMI, CHISHIMA, MASAMITSU, SAKA, YUKINORI, SEKO, SATOMI, Chishima, Masamitsu, c/o Sumitomo Wiring Systems,, Saka, Yukinori, c/o Sumitomo Wiring Systems, Ltd., Seko, Satomi, c/o Sumitomo Wiring Systems,
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1999
Main classification: H01R4
IPC codes: H01R4