Contact strip with edge clip connector

Abstract: 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 two groups of teeth (5) projecting outwards relative to a surface of said base part (2) for contacting at least one flexible conductor of said flexible conductor film, wherein each tooth (5) has a sharp pointed end (9) and projects over its total length mainly at a right angle away from said surface of said base part (2), the contact strip terminal further comprising an edge clip connector for connecting the terminal with contact faces of one or both surfaces near an edge of a substrate, the edge clip connector comprising a stem strip (34) and a clip contact (35) in the form of a closed flat longitudinal loop strip which at one end passes into the stem strip (34) and which is bent at the other end backwards about a transverse axis (38) of said flat loop, so that the legs (36, 37) formed by the two halves of said loop come to rest adjacent to each other and together define an approximately U-shaped clip opening.

Description: This is a divisional patent application of European Patent Application 87200611.9 (EP-A-243 998). 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 two groups of teeth projecting outwards relative to a 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 surface of said base part, said groups 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 surface of 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. For this purpose, various devices are known, but they are mainly designed for the connection of conductors of a flexible conductor film which is provided with a specific wiring pattern. Part of the insulation also generally has to be removed from the conductors to be contacted, 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 which is suitable for the connection of at least one conductor of a flexible conductor film to contact faces at edges of substrates. In general known edge clip connectors used for connection with the contact faces of a substrate, such as a LCD substrate, are held in place by means of plastic holders. Most of these known edge clip connectors have to be fixed to the printed circuits of the substrate by means of a soldered joint. These constructions in terms of dimensions are such that there can be no question of a compact design. The construction is also such that only a single contact point rests with a contact force on the contact faces of the substrate, while there is a spring action which is largely determined by the geometric dimensions of this type of contact. As a result of this construction, the known edge clip connectors have to be placed in a plastic carrier to ensure that they do not flip over before they are plugged onto the substrate and possibly soldered. Therefore it is a further object of the present invention to eliminate the above-mentioned problems and to provide a contact strip terminal which comprises an edge clip connector, the base part of the terminal comprising several groups of teeth, placed within the periphery of the strip-type base part, and in which each group comprise four pointed triangular teeth with sharp edges for contacting the conductors; in which both the spring action and the connector opening of the edge clip connector contacts are reproducible. To achieve these objects the contact strip terminal according to the invention further comprises an edge clip connector for connecting the terminal with contact faces of one or both surfaces near an edge of a substrate, the edge clip connector comprising a stem strip and a clip contact in the form of a closed flat longitudinal loop strip which at one end passes into the stem strip and which is bent at the other end backwards about a transverse axis of said flat loop, so that the legs formed by the two halves of said loop come to rest adjacent to each other and together define an approximately U-shaped clip opening. Preferably, the teeth have such dimensions that, after bending backwards in the direction of the base part, they do not extend beyond the periphery of the base part. This prevents the bent teeth from producing an undesired connection between adjacent conductors. The contact strip terminal 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 terminal 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. In an advantageous embodiment of the terminal one edge clip leg of each half of the loop is a meander shape with at least two supporting bracket contact points directed to the other leg, the other leg is a slight V-shape, whose top is directed to said one leg and opposite the bend lying between the two supporting bracket contact points of the one leg, so that the substrate in question can be inserted parallel to the end leg part of the other leg at an angle to the longitudinal direction of the clip contact mainly perpendicular to said transverse axis until its edge lies in the said bend of the one leg and subsequently can be introduced with lever action on the V-shape of the other leg along the longitudinal direction up to the closed end of the two halves of the loop. Preferably the surface of the base part strip is bent perpendicularly with respect to the plane of the edge clip connector for interconnection with a separate flexible conductor. The invention also relates to a process for the production of a row of contact strip terminals or a single contact strip terminal as defined above. Here the contact strip terminals are stamped out of a flat sheet of resilient metal and by means of a stem strip are held firmly on a carrier strip made from the sheet, while after the stamping operation the closed flat loop strip thus obtained is bent about the symmetrical transverse axis, and the stem strip with its related clip contact is bent over at right angles relative to the base part. In this embodiment according to the process the reproducibility both of the spring action and of the clip opening of the edge clip connectors is amply ensured, since production of this row of above-mentioned contacts is determined by the stamping precision and not, as in the case of the hitherto known edge clip connectors, by the folding precision thereof. The edge clip connectors can be separated from the carrier strip in the known way. The shape of the above-mentioned closed loop strip is selected in such a way that if this flat loop strip is bent about its central transverse axis from its original plane, an approximately U-shaped or jaw-shaped clip opening of the connector is obtained. Since the ends of each half of the loop, which have now come to rest adjacent to each other, form an approximately obtuse angle, a self-centering action of the edge clip connector is obtained when it is fitted on the edge of a substrate. This row of edge clip connectors has great dimensional stability, which is largely determined by the precision of the stamping. The U-shaped connector opening is very stable and cannot flip over, essentially due to the double design of the U-shaped jaw. Since one leg of the connector has two supporting bracket contact points and the other V-shaped leg has one contact point, on gripping if the substrate a definite contacting will be obtained, with resulting greater reliability. Since the connection edges of substrates, which are currently often of glass, are very sharp, the embodiment according to the invention results in a shape which will prevent damage of the contact point through these sharp edges. This is obtained because the substrate is inserted parallel to the projecting leg part of the V-shaped leg at a particular angle to the longitudinal direction and then is subsequently tilted with lever action on the V-shaped leg, so that this leg is held under tension of the contact face of the substrate. Only a slight force is then needed for sliding on, which is determined only by the friction between contact points of the connector and contact faces on the substrate. The invention will now be explained in greater detail with reference to the examples of embodiments shown in the drawings. Figure 1 is a perspective drawing of a contact strip for the connection of conductors of a flexible conductor film; Figure 2 is a perspective drawing of a different embodiment of a contact strip for the connection of conductors of flexible conductor films; Figure 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; Figure 4 shows on an enlarged scale a side view of the contact strip of figure 3; Figure 5 shows on an enlarged scale the bottom view of the contact strip of figure 3; Figure 6 shows by dashed lines the lines of intersection along which the pointed teeth of the contact strip according to figure 3 are punched from the strip of electrically conducting material forming the base part; Figure 7 shows a partially cutaway connection between the conductors of two flexible conductor films for which a contact strip according to figure 3 is used; Figure 8 is a top view of an edge clip connected with the contact strip in an embodiment of the present invention; Figures 9a and 9b respectively show a top view and a side vies of the edge clip connector of figure 8; Figure 10 is a perspective view of a row of edge clip connectors separated from a carrier strip; and Figure 11 is a perspective view of a row of edge clip connectors plugged on the one end onto a substrate and on the other end to a flexible conductor by means of the contact strip of the present invention. In the embodiment shown in figure 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 group 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 being 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 figure 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 figure 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 figure 3 shown on an enlarged scale in figure 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 figure 3 shown on an enlarged scale in figure 5, it can be seen that each group of teeth 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. Figure 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 figure 6 this angle is approximately 45 degrees. The recesses 10 (figure 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 figures 3 and 4 is shown in figure 7. By means of the contact strip of figure 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 between 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 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. Figures 8-11 show a contact strip of the present invention. having as a further connecting means a particular loop strip contact for connecting a flat flexible conductor with a substrate or printed circuit board. In figure 8 the reference number 34 indicates the stem strip and 2 the base part having prestamped teeth 5 as in figure 1 for instance. The closed flat loop strip is generally indicated by 35, whilst 36 and 37 indicate the respective legs thereof. After bending of this flat loop about the centre transverse axis 38 (figure 9B) an approximately U-shaped clip contact is obtained. Figure 9a shows a top view of figure 9b a side view of two clip contacts with contact strip. It can be seen clearly from figure 9a how the edge clip connector projects crosswise from a carrier strip 39. From the carrier 39 runs a base part 2, which passes into the stem strip 34, as shown in figure 8. The stem strip comprises at the end the closed flat loop strip 35, which is bent about the centre axis 38 as shown in figure 9b. It is also indicated that in the process for producing this edge clip connector the stem strip 34 with the edge clip contact 35 is bent perpendicularly with respect to the contact strip 1. Figure 9b shows that the leg 37 of each half of the loop through the stamping operation has a slight V-shape with leg parts 37.1 and 37.2, the top of which V-shape is directed inwards, and that the leg 36 of each half of the loop has a meander shape with at least two inward-directed supporting bracket points 36.1 and 36.2. This shape of the two halves of the loop is selected in such a way that substrates which currently are made of glass and are consequently very sharp can be pushed easily at an angle into the clip connector opening, in such a way that it is inserted parallel to the leg part 37.2 until the edge of the substrate comes to rest in the bend between the contact points 36.1 and 36.2. If the substrate is then tilted so that the contact leg 37 is under tension on the contact face of the substrate, this substrate can be pushed in. The edge clip connector 35 comprises at its extension base part 2 projecting teeth 5 for connection of the clip connector 35 to a flexible foil or flexible conductor. Figure 10 gives a perspective view of a row of edge clip connectors which are already separated from the carrier strip 39. Figure 11 shows how such a row of edge clip connectors is plugged to a substrate 26 contacting the contact faces 40 thereof. The base parts 2 are connected to a flexible circuit or a flexible conductor, as described above by beating the teeth 5 through the contact strip 18 of the flexible circuit. Figure 11 is a perspective view of a row edge clip connectors plugged onto a substrate. For the production of edge clip connectors initially fixed to a carrier strip one starts from a flat sheet or strip of resilient metal, from which with the aid of stamping equipment a carrier strip is stamped with stem strips which project crosswise therefrom and each pass into a closed flat loop strip. The thus stamped-out projecting parts constitute a preform from which the final edge clip connectors are formed. It will be clear that modifications and additions in the shape, the quantity and the placing of the teeth per contact strip, and the shape of the base part are possible without going beyond the scope of the invention as defined in the appended claims.

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 two groups of teeth (5) projecting outwards relative to a surface of said base part (2) for contacting at least one flexible conductor of said flexible conductor film, in which each group of teeth (5) consists of four pointed triangular teeth, the base of each triangle mainly coinciding with the surface of said base part (2), said groups 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 surface of said base part (2), characterized in that the contact strip terminal further comprises an edge clip connector for connecting the terminal with contact faces of one or both surfaces near an edge of a substrate, the edge clip connector comprising a stem strip (34) and a clip contact (35) in the form of a closed flat longitudinal loop strip which at one end passes into the stem strip (34) and which is bent at the other end backwards about a transverse axis (38) of said flat loop, so that the legs (36, 37) formed by the two halves of said loop come to rest adjacent to each other and together define an approximately U-shaped clip opening. Contact strip terminal according to claim 1, 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). Contact strip terminal according to any of the preceding claims, characterized in that one leg (36) of each half of said loop is a meander-shape with at least two supporting bracket contact points (36.1, 36.2) directed to the other leg (37), said other leg (37) is a slight V-shape, whose top (37.3) is directed to said one leg (36) and opposite the bend lying between the two supporting bracket contact points (36.1, 36.2) of the one leg (36), so that the substrate in question can be inserted parallel to the end leg part (37.2) of the other leg (37) at an angle to the longitudinal direction of the clip contact mainly perpendicular to said transverse axis (38) until its edge lies in the said bend of the one leg (36) and subsequently can be introduced with lever action on the V-shape of the other leg (37) along the longitudinal direction up to the closed end of the two halves of the loop. Contact strip terminal according to any of the preceding claims, characterized in that the surface of the base part (2) is perpendicularly bent with respect to the plane of the edge clip connector for interconnection with a separate flexible conductor. Process for the production of a row of contact strip terminals or a single contact strip terminal according to any of the preceding claims, in which the contact strip terminals are stamped out of a flat sheet of resilient metal and by means of a stem strip (34) are held firmly on a carrier strip (39) made from the sheet, while after the stamping operation the closed flat loop strip thus obtained is bent about said symmetrical transverse axis (38) and the stem strip (34) with its related clip contact (35) is bent over at right angles relative to the 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: H01R9
IPC codes: H01R4, H05K3