Contact strip

Abstract: Contact strip for the electrical connection of at least one flat conductor of a flexible conductor film, which contact strip com­ prises a strip-type base part of electrically conducting material and at least one group of teeth projecting outwards from a surface of the base part, for cutting through the flexible conductor film and contacting the conductor while the teeth can be deformed in the direction of the base part to press the base part. According to the present invention the base part comprises at least a second group of teeth projecting outwards from the surface of the base part, in which the first and second group of teeth are positioned within the periphery of the strip-type base part. All teeth of a group are arranged in a closed peripheral line such as circle, ellipse, triangle, square or other geometrical polygon and the distance between these teeth is smaller than the smallest dimension of the flat conductor to be contacted. Each group of teeth preferably con­ sists of four pointed, triangular teeth.

Description: The present invention relates to a contact strip terminal for electrically interconnecting at least one flat conductor of a flexible conductor film with at least a conductor lead wire, said contact strip terminal comprising a strip-type base part of electrically conducting material and at least one group of teeth projecting outwards relative to a first surface of said base part for contacting at least one flexible conductor of said flexible conductor film, in which each group of teeth consists of four pointed triangular teeth, the base of each triangle mainly coinciding with the first surface of said base part, each group of teeth being placed within the periphery of the strip-type base part, so that the base line of the teeth of each group lies on a simple closed contour, wherein each tooth has a sharp pointed end and projects over its total length mainly at a right angle away from said first surface of said base part, the contact strip terminal further comprising at least one lip-like member projecting from a longitudinal edge of the base part and being deformable in the direction of the base part for clamping said conductor lead wire between said lip-like member and said base part. A contact strip terminal of this type is known from US Patent Specification 3,197,729. Flat electrical cables such as ribbon cable or flexible conductor film are generally known and have been in use for several years now, principally for connection purposes. The term "flexible conductor film" is generally used for a polyester film serving as a carrier, with a copper layer applied thereto, which is etched to form a combination of several parallel conducting strips or a printed circuit board. Over the etched copper it is also possible to apply one or more electrically insulating flexible protection layers, with the object of protecting the conducting strips against undesired contacting, damage, oxidation through the effects of damp, etc. The use of flexible conductor film as wiring for electrical circuits, particularly in automobile technology, is reaching ever - increasing proportions. Flexible conductor film permits, on the one hand, a saving of space and weight compared with other wiring techniques and, on the other, a considerable simplification of the generally complex wiring to electrical instruments, lighting and electronic components. In practice, it is therefore necessary to be able to produce interconnections in a simple manner at any desired points on the film for the purpose of accommodating electrical components (resistors, capacitors, diodes, etc.) on the flexible conductor film, but also in order to connect the conductors of one flexible conductor film in a simple manner to conductors of other flexible conductor film, signal wires, bridging wires, etc. However, in order to provide good electrical contact between the known contact strip terminal and a conductor of conductor lead wires part of the insulation has to be removed from the conductor lead wires, which is a relatively labour-intensive, time-consuming and therefore quite expensive operation, which is also less suitable for the connection of the conductors by automatic means. Another disadvantage is that the places where the insulation is removed are readily accessible to the effects of damp, which can cause oxidation and in the long run does not benefit the reliability of the connections. In automobile technology such connections are therefore highly undesirable. The connection of the conductors by means of soldered connections also adversely affects the flexibility of the film. US Patent 3.197.729 discloses a semi-rivet connector for a flexible ribbon conductor, formed of a connector strip of substantially malleable conductive metal and having a plurality of spread apart pointed tangs or lances, extending from the strip surface. These tangs or lances are formed by a puncturing operation, such that their pointed ends curl outwardly, away from the puncturing axis. When compressed against the flexible ribbon conductor to be connected with, having a relative puncture resistant surface, the pointed ends first penetrate the dielectric layer of the ribbon conductor, but then fold back and spread apart against the metal conductor surface and not cutting this conductor. The metal of these tangs or lances is such malleable, as the strip material, that upon separation of the contact element from the ribbon conductor, the curled pointed ends of the tangs or lances fold back to their original position. US Patent 4,082,402 discloses a contact strip terminal comprising a strip-type base part of electrically conducting material and a group of teeth projecting outwards relative to a surface of the base part, for cutting through a flexible conductor film and possibly contacting the conductor - which may be covered with insulation material - of the flexible conductor film, while the teeth are deformable in the direction of the base part in such a way that the conductor can hereby be pressed against the base part. In the terminal of the US Patent Specification 4,082,402 no insulation material need be removed from the strip conductor. The pointed projecting teeth of the terminal, which are situated opposite each other, can penetrate first on either side of the conductor through the insulation and then, if necessary, through the conductor, following which they are bent over backwards in such a way that mainly the pointed ends of these teeth produce an electrical connection with the conductor. Since the distance between opposite teeth is slightly smaller than the width of the conductor, the conductor will in general undergo a considerable deformation on its edges. Because the teeth in this terminal lie along the edges of the contact strip on either side of the elongated conductor, this configuration is not suitable for use as a contact strip for connecting two conductors forming arbitrary angles with each other. For, a separate contact strip will always be needed for each angular position, in such a way that the teeth always lie on either side of the conductor. Due to the fact that the conductor is enclosed between the teeth, the same terminal is also less suitable for contact conductors of various widths. For, in the case of a narrower conductor and relatively long teeth, the pointed ends of the teeth can be bent past the edge of this conductor, as a result of which no contact is made with the conductor. In the case of broad conductors it can, on the other hand, happen that the teeth are not strong enough to penetrate through the copper layer of the conductor film, which offers relatively more mechanical resistance. The object of the present invention is to provide a contact strip terminal by which a better electrical contact to a conductor of conductor lead wires is possible than may be obtained by the contact strip terminal known from the US Patent Specification 3,197,729. To this end, the contact strip according to the invention is characterized in that said at least one lip-like member projects from a second surface of said base part opposite to said first surface and in that a second group of teeth projects from said second surface of said base part and is situated next to said at least one lip-like member in order to receive said conductor lead wire when clamped by said at least one lip-like member. The at least one lip-like member when clamping a conductor lead wire presses the conductor lead wire into the teeth of the second group of teeth that is situated next to said at least one lip-like member. Thereby the connection of connecting wires of differing thicknesses are permitted. Furthermore, tolerances in the thickness of identical connecting wires are prevented from affecting the quality of the connections. Moreover, any insulation around a conductor of a conductor lead wire need not be removed because it will be cut through by sharp edges of the teeth. By these measures a reliable, good-quality connection between the contact strip terminal and a conductor lead wire is guaranteed. At the opposite side of the base part at least one other group of teeth projects in order to provide for good and reliable electrical connections to strip conductors. Therefore, any electrical component or any electrical wire can be arranged on any place on a flexible conductor film. In a first embodiment of the present invention the contact strip terminal is characterized in that two groups of teeth project from the base part in a direction opposite to the second group of teeth and that said second group of teeth is situated between said two groups of teeth. Preferably two opposite edges of the base part comprise lips which are deformable in a direction towards the second surface of said base part and projecting in the same direction for clamping a connecting wire between the base part and the lips, with one lip being disposed on one edge and two lips being disposed on the opposite edge, said lips having such dimensions that after bending the lips join one another. The clamping action is further enhanced by providing the lips with several pointed sharp projections, in such a way that after bending the lips said projections are directed towards a surface of the base part for contacting and clamping the connecting wire. The contact strip according to the invention can advantageously be stamped out of a strip of electrically conducting material. Precisely because no particular preworking or finishing operations are needed for applying or finishing off the contact strip according to the invention, this strip provides excellent possibilities for mechanical positioning at any desired angles relative to the conductors and over the entire surface of a flexible conductor film. For this purpose, it is an advantage to stamp a continuous series of contact strips from a strip of electrically conducting material, and these can then be fixed individually to the film. In addition to mechanical processing, the contact strips can, of course, also be placed on the film by hand, preferably using suitable equipment for the purpose. The invention will now be explained in greater detail with reference to the examples of embodiments shown in the drawings. Fig. 1 is a perspective drawing of a contact strip for the connection of conductors of a flexible conductor film; Fig. 2 is a perspective drawing of a different embodiment of a contact strip for the connection of conductors of flexible conductor films; Fig. 3 is a perspective drawing of a further embodiment of a contact strip for the connection of conductors of two flexible conductor films placed one above the other; Fig. 4 shows on an enlarged scale a side view of the contact strip of Fig. 3; Fig. 5 shows on an enlarged scale the bottom view of the contact strip of Fig. 3; Fig. 6 shows by dashed lines the lines of intersection along which the pointed teeth of the contact strip according to Fig. 3 are punched from the strip of electrically conducting material forming the base part; Fig. 7 shows a partially cutaway connection between the conductors of two flexible conductor films for which a contact strip according to Fig. 3 is used; Fig. 8 is a perspective drawing of an embodiment of a contact strip for the connection of components or connecting wires to a conductor of a flexible conductor film; Fig. 9 is a perspective drawing of a flexible conductor film to which a resistor is connected between two conductors by means of the contact strip of Fig. 8; Fig. 10 shows a different embodiment of the contact strip according to Fig. 8, in which the upright lips are provided with sharp, pointed projections; Fig. 11 shows a preferred embodiment of a contact strip according to the invention for the connection of electronic components or connecting wires to the conductors of a flexible conductor film; Fig. 12 shows on an enlarged scale a front view of a contact strip according to Fig. 11 connected to a conductor of a flexible conductor film, with the successive positions to be taken up by the lips for connecting wires of various thicknesses being shown in dashed lines; In the embodiment shown in Fig. 1 of a contact strip 1 the electrically conducting strip-type base part 2 of the electrically conducting sheet material comprises a first group 3 and a second group 4 of triangular teeth 5 which are virtually at right angles to a surface of the base part and are outward projecting in the same direction, said groups being displaced relative to each other over a distance in the longitudinal direction of the base part. The teeth are all grouped within the periphery of the strip-type base part. The corners 6 of the base part are bevelled in order to prevent undesired contacts on bending of the flexible conductor film, through the sharp corner points penetrating through the insulation layer of the film. This contact strip is particularly suitable for the interconnection of conductors of the same film. In the embodiment of the contact strip shown in Fig. 2, the teeth of the second group 4 project outwards in the opposite direction to that of the teeth of the first group 3. The contact strip according to this embodiment is particularly suitable, for example, for the interconnection of conductors on opposite sides of a flexible conductor film which is wired on both sides. In the contact strip shown in Fig. 3, provision is made between the first and second group of teeth projecting outwards in the same direction for a third group of teeth 7 projecting outwards in the opposite direction. This side view of the contact strip of Fig. 3 shown on an enlarged scale in Fig. 4 shows clearly the sharp edges 8 and the pointed ends 9 of the individual teeth which can penetrate through the carrier, the conductor and any further insulation layers of the flexible conductor film surrounding the conductor. In the bottom view of the contact strip of Fig. 3 shown on an enlarged scale in Fig. 5, it can be seen that each group of theeth 3, 4, 7 comprises four individual circular sector-shaped teeth 5, which can be stamped in a simple manner from the contact strip and bent over in a circular sector form if necessary. Fig. 6 shows by dashed lines the lines of intersection 11, 12, 13, 14, 15, 16 of the circle sectors along which the teeth can be stamped. The structural strength of the strip can be increased considerably by selecting the lines of intersection of two adjacent groups of teeth, for example 11, 13 and 12, 14, in such a way that the angle between them is less than 90 degrees. In Fig. 6 this angle is approximately 45 degrees. The recesses 10 (Fig. 5) are for the purpose of preventing tearing of the base part 2 at the ends of the lines of intersection 11, 12, 13, 14, 15, 16 during bending over of the teeth. When the teeth are formed in this way the radius of the circle bounding the teeth of a group is the determining factor for the height of the teeth, which is connected with the thickness of the flexible conductor film and the number of films possibly lying on top of each other and for which the contact strip can be used with sufficient holding power of the teeth which are bent backwards towards the base part. It will be clear that, instead of a circle, the teeth of a group can be bounded by an ellipse, triangle, square or other geometrical polygon. The manner in which, for example, conductors of conductor films lying on top of one another can be interconnected by means of the contact strip according to Fig.'s 3 and 4 is shown in Fig. 7. By means of the contact strip of Fig. 3, conductor 19 of film 17 is here connected to conductor 20 of film 18. Once the teeth 5 have penetrated through the film and the conductor, they are bent backwards in the direction of the base part 2 with the pointed ends 9 facing away from each other, as a result of which the film is pressed against the base part of the contact strip. Contacting of the conductor takes place by means of the sharp edges 8 of the teeth 5. Depending on the force with which the film is pressed by means of the bent-over teeth against the contact strip, contacting of the conductor can also take place by means of the pointed ends 9 of said teeth. However, this is not necessary, so that it will be clear that the contact strip can be fitted both from the conductor side and from the carrier side of the conductor film. The films 17 and 18 are shown perpendicular to each other, but this is not necessary. The width of the contact strip is preferably chosen equal to or smaller than the width of the conductor to be contacted. The closed peripheral line which bounds the teeth 5 along their ends fixed to the base part must, however, be selected in such a way that the distance btween the teeth of a group is smaller than the smallest dimension of the conductor to be contacted, in order to ensure that the teeth are sufficiently enclosed by conductor material to give a reliable contact. This means that it is possible with the single contact strip according to the invention to interconnect any desired conductors which form any desired angles with each other. The distance between the groups of teeth 3, 4 and 7 can advantageously be selected as full multiple of the common insertion width or distances between the conductors of a flexible conductor film. The thickness of the contact strip and the choice of the type of material from which the strip is made determine the strength of the teeth. A condition is that the teeth should have sufficient strength to penetrate through the film and the conductor, but that they should not be so strong that disproportionately great force is required to bend them backwards. Out of a contact strip of a copper alloy, and with a thickness of the order of 0.2 millimetre, it is possible to stamp strong enough teeth which can penetrate through practically all commercially available conductor films, and the teeth can also be deformed by hand. In addition to the interconnection of conductors of flexible conductor film, a contact strip may be produced with which electronic components or signal wires can be connected to conductors of a conductor film. As shown in Fig. 8, the contact strip of Fig. 1 is to this end provided on its long sides with lips 21, 22 and 23. These lips project outwards virtually at right angles to the base part 2 and here in the opposite direction relative to the teeth 5. The lips can be bent in such a way towards the base part 2 that the wire to be connected is clamped between the lips and the base part, as shown in Fig. 9. By means of the contact strip shown in Fig. 8, a resistor 24 with connecting wires 25 is clamped herein between two conductors 27, 28 of the flexible conductor film 26. After bending over, the single lip 21 in the centre of one long side of the contact strip and the lips 22, 23 provided in a U-shape on the other long side of the contact strip form a closed face between which the base part 2 of the conductor is held firmly clamped. It will be clear that the electronic components can also be connected at any desired angles to the conductors of a flexible conductor film. In order to make it possible to accommodate various diameters or tolerances in connecting wires of electronic components without the reliability of the connection being reduced by a poorer clamping action, Fig. 10 shows an embodiment of the contact strip of Fig. 8 in which the lips are provided with sharp, pointed projections or elevations 29 which, after bending over of the lips, point towards the base part 2. These projections or elevations 29 can bite into the connecting wire 25, which means that for various wire cross sections a good, sturdy clamping action is achieved, without any insulation layer round the connecting wire having to be removed. A preferred embodiment of a contact strip according to the invention for the connection of wires of differing diameters is shown in Fig. 11. This is essentially the contact strip of Fig. 3, in which the lips 21, 22 and 23 now project outwards in the same direction as the third group of teeth 7. Through the bending over of the lips, the connecting wire 30, 31 is pressed between the teeth 5, and the sharp edges 8 can bite into the conductor, thereby achieving a firm clamping action, also without insulation having to to be removed. Fig. 12 shows the position between the teeth for wires with varying diameters 30, 31. The lips 32, 33 in this embodiment are bent inwards on the top side, as a result of which they make a better connection with the round shape of the connecting wires 30, 31 to be connected. It can also be seen how the teeth 5 on the underside of the contact strip are pressed through the conductor 28 and the film 26 and backwards in the direction of the base part 2, when the pointed ends 7 are pressed into the carrier of the film 26. It will be clear that one or more lips in the embodiment shown in Fig. 11 can also be provided with sharp, pointed projections 29. It will be clear that further modifications and additions, for example in the shape, the quantity and the placing of the teeth per contact strip, the shape of the base part and the quantity and position of the lips for clamping a connecting wire, are possible without going beyond the scope of the invention.

Claims: Contact strip terminal for electrically interconnecting at least one flat conductor of a flexible conductor film with at least a conductor lead wire, said contact strip terminal comprising a strip-type base part (2) of electrically conducting material and at least one group (3; 4) of teeth (5) projecting outwards relative to a first surface of said base part (2) for contacting at least one flexible conductor of said flexible conductor film, in which each group (3; 4) of teeth (5) consists of four pointed triangular teeth, the base of each triangle mainly coinciding with the first surface of said base part (2), each group (3; 4) of teeth (5) being placed within the periphery of the strip-type base part (2), so that the base line of the teeth (5) of each group lies on a simple closed contour, wherein each tooth (5) has a sharp pointed end (9) and projects over its total length mainly at a right angle away from said first surface of said base part (2), the contact strip terminal further comprising at least one lip-like member (21, 22, 23; 32, 33) projecting from a longitudinal edge of the base part (2) and being deformable in the direction of the base part for clamping said conductor lead wire (25; 30, 31) between said lip-like member (21, 22, 23; 32, 33) and said base part (2), characterized in that said at least one lip-like member (21, 22, 23; 32, 33) projects from a second surface of said base part (2) opposite to said first surface and in that a second group (7) of teeth (5) projects from said second surface of said base part (2) and is situated next to said at least one lip-like member (21, 22, 23; 32, 33) in order to receive said conductor lead wire (25; 30, 31) when clamped by said at least one lip-like member (21, 22, 23; 32, 33). Contact strip terminal according to claim 1, characterized in that two groups (3, 4) of teeth (5) project from the base part (2) in a direction opposite to the second group (7) of teeth and that said second group (7) of teeth is situated between said two groups (3, 4) of teeth (5). Contact strip terminal according to claim 1 or 2, characterized in that two opposite edges of the base part comprise lips (21, 22, 23) which are deformable in a direction towards the second surface of said base part (2) and projecting in the same direction for clamping a connecting wire (25; 30, 31) between the base part (2) and the lips (21, 22, 23), with one lip (21) being disposed on one edge and two lips (22, 23) being disposed on the opposite edge, said lips (21, 22, 23) having such dimensions that after bending the lips join one another. Contact strip terminal according to one of the preceding claims, characterized in that the lips are provided with several pointed sharp projections (29), in such a way that, after bending the lips (21, 22, 23) said projections (29) are directed towards a surface of the base part (2) for contacting and clamping the connecting wire (25; 30, 31). Contact strip terminal according to any of the preceding claims, characterized in that the teeth (5) have such dimensions that after bending backwards in the direction of the base part (2) they do not extend beyond the periphery of said base part (2).

Inventors: MOUISSIE BOB, MOUISSIE, BOB
Applicants: BERG ELECTRONICS MFG, CONNECTOR SYSTEMS TECH NV, DU PONT, DU PONT NEDERLAND, BERG ELECTRONICS MANUFACTURING B.V., CONNECTOR SYSTEMS TECHNOLOGY N.V., DU PONT DE NEMOURS (NEDERLAND) B.V., E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1987
Main classification: H01R4
IPC codes: H01R12, H05K3, H01R4