Electrical connection element of connector for electric ribbon wire

Abstract: An electrical connection element is formed by stamping a plate having a thickness. A contact surface is formed at an edge surface of an end portion of the electrical connection element. The end edge portion is bent toward both lateral sides of the plate to form the contact surface. The lateral edge portions are offset towards opposite sides of the plate, so that the width between the opposite lateral edges is about twice the thickness of the plate. This edge surface is flat and smooth. Therefore, if the round conductor of a ribbon tape contacts any portion of the contact surface, a good electrical contact is obtained. Thus, the electrical connection element for contacting the side surface of the round conductor of the ribbon wire can be produced from a thin plate material.

Description: This invention relates generally to a connector for connecting an electric ribbon wire comprising conductors having a round cross-section. Particularly, this invention is drawn to a connector having a smooth, flat, plate-like end portion, an edge of the end portion forming a contact surface, the end portion being bent toward both lateral sides of the connector. Electric tape or ribbon wires, in which conductors are often made very thin and are often arranged at a very small pitch, have been used as the internal wiring in household appliances such as VCRs, video cameras, office automation devices, and the like. This ribbon wire comprises electrical conductors, each comprising twisted wire elements, flat conductors, or single wire conductors having a round cross-section (thereinafter referred to as "round conductors"). A suitable ribbon wire is selected and used in accordance with an intended application. For example, in the electric ribbon wire 4 shown in Fig. 7, a plurality of round conductors 41 each have a diameter d of 0.12 mm. The conductors 41 are arranged in a parallel relation at a pitch D of 0.8 mm. The conductors 41 are covered at their opposite sides by a flexible insulating sheath 42 to provide a ribbon-like, one-piece construction. The insulating sheath 42 is removed from one side of one end of the ribbon wire to expose a portion 43 of the conductors 41. This exposes the side surfaces of the conductors 41. The exposed portion 43 is inserted into a connector which collectively connects the plurality of conductors arranged at the narrow pitch D to a plurality of electrical connection elements arranged within the housing 1. One conventional electrical connection element (not shown) is disclosed in Japanese Utility Model Unexamined Publication No. 3-46976, in which one end portion of the plate-like element, which has a width corresponding to the pitch of conductors, is bent at an acute angle. The end portion is resilient and acts as a leaf spring. This end portion is urged into contact with the conductor inserted into the housing. Fig. 8 shows an electrical connection element 51 disclosed in Japanese Patent Unexamined Publication No. 61-131382. The connection element 51 is formed by stamping a plate material, and has an end edge surface (i.e., the surface in the direction of the thickness of the plate) which acts as a contact surface 56. This electrical connection element 51 includes a pair of generally parallel opposed arms 52 and 53, which are formed into a U-shape. The exposed front end portion of the ribbon wire 4 is inserted into the space between the two arms 52 and 53. A prong 55 of a retainer 54 is used to force the contact surface 56 of the arm 53 into contact with the exposed portion 43 of the conductor 41. However, with respect to the first above-mentioned conventional electrical connection elements, the pitch D of the conductors is approximately 0.8 mm. Therefore, it is very difficult to produce the leaf spring corresponding to this narrow pitch. Additionally, this electrical connection element is normally not used with a single round conductor. It is possible that the round conductor may be severed by a distal edge of the electrical connection element. Thus, this first conventional electrical connection element has been limited to twisted wire element applications, and has not been suitable for a ribbon wire having round conductors. The second above-mentioned electrical connection element can be used with a ribbon wire having round conductors. However, since the narrow contact surface 56 must be brought into contact with the thin conductor along its length, the contact surface 56 must be accurately aligned with the exposed conductor. Therefore, if there is a slight manufacturing or assembling error, or if the exposed conductor is bent to the right or to the left, even slightly, the conductor 41 is offset from the electrical connection element 51, as shown in Fig. 9. As a result, a stable contact cannot be obtained. In the worst case, a contact failure occurs. This can be avoided by making the electrical connection element from a plate having a greater thickness, as shown in Fig. 9, so that the contact surface 56 has a larger width. With this arrangement, however, each connection element-receiving slot of the housing for receiving the electrical connection element 51 must be increased in width. In other words, partition walls of the housing must be reduced in thickness. This makes molding the housing difficult. This also makes it difficult to manufacture the housing having sufficient strength. EP-A-0 145 315 shows - especially in Fig. 8 thereof - a cross-sectionally view of an electrical connection element, the electrical connection element having upper and lower arms lying juxtaposed to each other for gripping the conductors of a flat ribbon wire therebetween and for making electrical contact therewith. The arms are provided with offset portions each having a plurality of projections or teeth for holding the indvidual conductors. However, the sawtooth-like offset portions of EP-A-0 145 315 are liable to simply cut through the round conductors of the flat ribbon wire, as the sharp edges act like knifes, the more as both arms have the offset portions with the sawtooth-like surface facing to each other, thus resulting to a scissors-effect which is liable to cut partially or even totally through the round conductors. There is also the disadvantage in case of EP-A-0 145 315 that the offset contact portions with there inclined surfaces tend to squeeze the round conductor wires to the left or to the right, if there is a certain misalignment between the contact portions and the round conductor wires. This invention therefore has as an object to provide for an electrical connection element which enables a connector to stably contact the round conductor of an electric ribbon wire without damages to it. To solve these problems, in this invention and according to claim 1 thereof, there os provided an electrical connection element of a ribbon wire connector providing electrical connections to a ribbon wire, the ribbon wire having a plurality of cross-sectionally round conductor wires arranged in a parallel relationship at a predetermined pitch, the electrical connection element comprising: a first arm; a second arm; a connecting portion connecting a first end of the first arm to a first end of the second arm; a terminal portion, a first end of the terminal portion being connected to the connecting portion; and a projecting portion extending from one of the first and second arms; wherein the projection portion comprises: at least one first electrical contact portion offset towards a first side of the projecting portion and having a first surface formed on a free end of the first electrical contact portion; and at least one second electrical portion offset towards a second side of the projecting portion and having a second surface formed on a free end of the second electrical contact portion; wherein the electrical connection element has a first thickness, and the first and second surfaces form a planar flat and smooth contact surface having a second thickness greater than said first thickness, said contact surface being pressed against the conductor wires to be connected to the electrical connection element along the length of said conductor wires in a parallel relation thereto. With this arrangement, the edge surface of the generally plate-like end portion of the electrical connection element serves as the contact surface. Therefore, the thickness of this plate is the width of the contact surface. The end edge portion is bent toward both sides and the lateral edges of the bent portions are offset, so that the laterally offset edge portions provide a contact surface having a greater width than the general thickness of the electrical connection element. Therefore, even if the pitch of the conductors is irregular, the widened contact surface is able to contact the conductors. The contact surface is flat and smooth. Therefore, even if any portion of the contact surface is brought into contact with the conductor, the contact surface securely contacts the conductor, however without severing or cutting it. Thus, only the width of the end portion serving as the contact surface is increased, so that the thickness of the electrical connection element does not need to be increased. As described above, in this invention, the contact surface for contacting the conductor is formed at the edge surface of the generally plate-like end portion. The end edge portion is bent toward both lateral sides of the end portion to provide the contact surface which is flat, planar and smooth. With this construction, the contact surface can be widened without increasing the thickness of the plate, and the electrical connection element can positively achieve an electrical connection to the ribbon wire having the round conductors. A preferred embodiment of the invention will now be described in detail with reference to the following figures, wherein: Fig. 1 is an exploded, perspective view of a connector; Fig. 2 is a cross-sectional view showing the connector in a completely-retained condition; Fig. 3 is a perspective view of an electrical connection element; Fig. 4 is a bottom view of a portion of an upper arm of the electrical connection element; Fig. 5 is a cross-sectional view taken along the line A-A of Fig. 4, showing a conductor contacting a round conductor; Fig. 6 is a cross-sectional view showing the connector in a provisionally-retained condition; Fig. 7 is a plane view of the ribbon wire; Fig. 8 is a cross-sectional view of a conventional connector; and Fig. 9 is an end view of the conventional electrical connection element. One preferred embodiment of the present invention will now be described with reference to Figs. 1 to 6. As shown in Fig. 1, a connector in this embodiment comprises a housing 1 having a generally rectangular prism shape, a plurality of electrical connection elements 2 (only one of which is shown in the drawings) inserted into the housing 1 from a rear side of the housing, and a retainer 3 inserted into the housing 1 from a front side of the housing. An electric ribbon wire (not shown) is to be inserted into the housing 1 from its front side, and is fixedly held in the housing 1 by the retainer 3. The housing 1 has a number of receiving slots 11, each receiving one of the connection elements 2. The receiving slots are positioned at a pitch corresponding to the pitch of the conductors of the ribbon wire. The receiving slots 11 are separated from one another by partition walls 12. A pair of retaining projections 14 are formed on opposite side ends of the housing 1, respectively, and serve to hold the retainer 3 in a provisionally-retained condition relative to the housing 1. The retainer 3 can also be completely retained by a second pair of retaining projections (not shown). As shown in Fig. 2, each receiving slot 11 has a rectangular shape in a directior extending between the front and rear sides. The opening of the slots 11 at the rear side of the housing 1 has a lower narrow portion 11b and an upper wide portion 11a. Each receiving slot 11 opens to both the front and rear sides of the housing. Additionally, a lateral plate 15 is positioned at a central portion of each receiving slot 11 to divide the receiving slots 11 into upper and lower portions. The electrical connection element 2 is formed by stamping a plate of a copper alloy (or the like) having a thickness W1. As shown in Fig. 3, the connection element 2 has upper and lower arms 22 and 23 extending generally parallel to each other from an interconnecting portion 21. The arms 22 and 23 and the interconnecting portion 21 cooperate to form the generally U-shape connection element 2. A projection 22a is formed on and projects downwardly from a distal end portion of the upper arm 22. A lower portion of the projection 22a is bent towards both lateral sides of the upper arm 22. That is, as shown in Fig. 4, a first portion 22b of the projection 22a extends to the right side of the upper arm 22, while a second portion 22c extends to the left side of the upper arm 22. A lower surface of the projection 22a is formed into a flat, smooth contact surface 25 (as shown in Figs. 4 and 5). Therefore, the width W2 of the contact surface 25 is generally twice the thickness W1 of the plate. A pair of engagement projections 26 is formed on the upper surface of the lower arm 23. A terminal portion 24 extends rearwardly from the lower end of the interconnecting portion 21. As shown in Fig. 2, the electrical connection element 2 is inserted into a receiving slot 11 from the rear side of the housing, with the lower arm 23 inserted into the narrow lower portion 11b of the slot 11 and the upper arm 22 having the laterally bent projection 22a inserted into the wide upper portion 11a of the slot 11. The upper and lower arms 22 and 23 extend over and below the lateral plate 15, respectively. The engagement projections 26 can thus engage the lateral plate 15, so that the electrical connection element 2 is securely held in the housing 1. The lateral plate 15 also acts to hold the distal end portions of the upper and lower arms 22 and 23 apart from each other at the front portion of the connection element-receiving hole 11. The ribbon wire 4 can thus be inserted between the upper and lower arms 22 and 23. The retainer 3 has a wedge portion 31 which fits into the front portion of receiving slots 11. A pair of engagement arms 32 is formed on the opposite ends of the retainer 3, respectively. An engagement portion 33 which engages with the one of the pair of retaining projections 14 is formed on each engagement arm 32 (as shown in Fig. 1). The retainer 3 is inserted into the front side of the housing so that the wedge portion 31 slides over the upper surface of the lower arm 23. At this time, the wedge arm 31 forces the ribbon wire 4 upwardly by contacting the lower side of the ribbon wire 4. The ribbon wire 4 is thus wedged between the wedge portion 31 and the upper arm 23 and is firmly pressed against the contact surface 25 of the upper arm 22. Next, the operation of this embodiment will be described. First, each electrical connection element 2 is inserted into one of the receiving slots 11. The engagement projections 26 engage with the lateral plate 15 to hold the connection elements in the slots 11. The retainer 3 is then inserted into the front end of the housing, with the pair of engagement arms extending outside of the sides of the housing 1. The retainer 3 is inserted only to the point at which the engagement portions 33 of the retainer 3 engage the retaining projections 14, so that the retainer 3 is held in a provisionally-retained condition relative to the housing 1, as shown in Fig. 6. In this provisionally-retained condition, an opening is formed above the engagement portion 31, as shown in Fig. 6. The front end portion of the ribbon wire 4 is inserted into this opening. The ribbon wire 4 has been previously prepared, as shown in Fig. 7, to expose an end portion 43 of the conductors 41. When the ribbon is inserted, the exposed portion 43 is face-up. The ribbon wire 4 is inserted to a predetermined depth, with the front end of the tape wire 4 abutting against the lateral plate 15. In this condition, the retainer 3 is pushed from the provisionally-retained position deeper into the housing 1 to the completely-retained position, so that the retainer 3 is completely retained relative to the housing 1, as shown in Fig. 2. In this completely-retained position, the wedge portion 31 is positioned between the upper and lower arms 22 and 23, and the ribbon wire 4 is wedged by the wedge portion 31 into firm contact with the contact surface 25 formed on the lower side of the projection 22a of upper arm 22 to achieve an electrical contact. The projection 22a on the distal end portion of the upper arm 22 is bent toward both lateral sides of the upper arm 22. The lower surface of the projection 22a is formed into the flat and smooth contact surface 25. The width W2 of the contact surface 25 is about twice the thickness W1 of the connection element 2, as shown in Fig. 5. Therefore, even if the pitch of the conductors 41 is slightly irregular, the contact surface 25 can be firmly pressed against the conductor 41. In addition, since the contact surface 25 is flat and smooth, a good electrical contact is obtained. Furthermore, since the narrow contact surface 25 is pressed against the conductor 41 along the length of the conductor 41 in a parallel relation to the conductor 41, the contact surface 25 will not cut the conductor 41, and can maintain a good electrical contact. In this embodiment, the electrical connection element 22 has a generally U-shape form, having the upper and lower arms 22 and 23. The contact surface 25 is formed on the distal end portion of the upper arm 22 and the wedge portion 31 of the retainer 3 is inserted in between the upper and lower arms 22 and 23 to retain the ribbon wire 4. Therefore, the connector can be of a simple construction. In this embodiment, the electrical connection element 2 is formed by stamping the plate having the thickness W1, and therefore can be easily produced. In the above embodiment, although the projection 22a is formed on the upper arm 22, it is not always necessary to do so, and the projection 22a may be formed on the lower arm 23 so that the ribbon wire 4 can be connected to the lower arm 23. In the above embodiment, although each portion 22b and 22c of the projection 22a is bent only once to each lateral side of the upper arm 22, the number of projection portions 22b and 22c of projection 22a bent to each lateral side is not limited to one. Further, although only the distal end portion of the upper arm 22 is bent, this is not imperative. Thus, the projection 22a may be formed anywhere along the entire length of the upper arm 22 as long as the contact surface is able to contact the exposed portion 43 of the ribbon wire 4. Thus, the projection 22a may extend as far as a central point of the upper arm 22. While the invention has been described with reference to the structure disclosed, it is not confined to the details set forth, but is intended to cover such modifications or changes as may come within the scope of the following claims.

Claims: An electrical connection element of a ribbon wire connector (1) providing electrical connections to a ribbon wire (4), the ribbon wire (4) having a plurality of cross-sectionally round conductor wires (41) arranged in a parallel relationship at a predetermined pitch, the electrical connection element (2) comprising: a first arm (22); a second arm (23); a connecting portion (21) connecting a first end of the first arm (22) to a first end of the second arm (23); a terminal portion (24), a first end of the terminal portion being connected to the connecting portion (21); and a projecting portion (22a) extending from one of the first and second arms (22, 23); wherein the projection portion (22a) comprises: at least one first electrical contact portion (22b) offset towards a first side of the projecting portion (22a) and having a first surface formed on a free end of the first electrical contact portion (22b); and at least one second electrical portion (22c) offset towards a second side of the projecting portion (22a) and having a second surface formed on a free end of the second electrical contact portion (22c); wherein the electrical connection element (2) has a first thickness (W1), and the first and second surfaces form a planar flat and smooth contact surface (25) having a second thickness (W2) greater than said first thickness (W1), said contact surface (25) being pressed against the conductor wires (4) to be connected to the electrical connection element (2) along the length of said conductor wires (4) in a parallel relation thereto. The electrical connection element of claim 1, wherein said second thickness (W2) of said contact surface (25) is twice said first thickness (W1). The electrical connection element of claim 1 or 2, wherein said projecting portion (22a) is formed on a free end portion of said first arm (22). The electrical connection element of claim 3, wherein said projecting portion (22a) extends from said free end portion to a central point of the first arm (22). The electrical connection element of anyone of claims 1 to 4, wherein said first arm (22) is an upper arm. A ribbon wire connector, comprising: a plurality of receiving slots (11); a plurality of partition walls (12) separating first end portions of the plurality of receiving slots (11) receiving a ribbon wire (4); a retainer (3); and a second end portion of each receiving slot (11) receiving an electrical connection element (2), the second end portion having a first section (11b) having a first width and an second section (11a) having a second width greater than the first width; wherein: said electrical connection element (2) being as defined in anyone of claims 1 to 5, and said second arm (23) corresponding in its thickness (W1) to the first width and said first arm (22) having said contact portion (25) corresponding in its thickness (W2) to the second width.

Inventors: CHISHIMA MASAMITSU, NOZAKI TAKAO, CHISHIMA, MASAMITSU, NOZAKI, TAKAO, CHISHIMA, MASAMITSU, C/O SUMITOMO WIRING, NOZAKI, TAKAO, C/O SUMITOMO WIRING
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1993
Main classification: H01R9
IPC codes: H01R13, H01R12