ELECTRICAL JUNCTION SYSTEM

Abstract: An electrical junction system having a wiring board (1) provided with branching conductors formed by bus bars (3) on an insulation plate, the bus bars (3) being connectable to printed conductors (23) carried on a printed circuit board (5) and to wires (18) in a wiring harness to form branching electric circuits, the board (5) being detachably mounted on said wiring board (1) and carrying functional parts (22), the printed conductors (23) being provided with terminals (14) arranged on one side edge of the board (5), and the bus bars (3) being provided with tab-like contactors (7) by which they are connected to the terminals (14), the connection between the terminals (14) and the tab-like contactors (7) being effected through intermediate terminals (12).

Description: The present invention relates to an improvement in an electrical junction system which has a multiplicity of branching lines constituted by laying BUS bars and adapted for use in connecting electric lines in a wiring harness to constitute a branching circuit arrangement. In general, a wiring harness used for internal electric wiring in automobiles require a large number of branching circuits at an intermediate portion thereof. To cope with this demand, a known electrical junction system has been used in which the branching lines corresponding to the branching circuits of the wiring harness are concentrated to a wiring board by means of a BUS bar so that the desired electric circuit arrangement is built up in a concentrating manner by connecting the lines of the wiring harness to the branching line on the wiring board. For instance, in an electrical junction system proposed hitherto, electronic circuits incorporating various relays having different functions such as intermittent wiper relay, fuel cut relay and so forth are formed in respective branching circuits. More specifically, control elements constituting each branching circuit, e.g. relays capacitors, diodes and so forth are contained by an independent casing which is connected to suitable portion of the conductive part of bus bar through tab-like terminals provided on the casing. In recent years, there has been a tendency to upgrade automobiles which in turn increases the electric equipment provided on the automobile, as well as higher quality and diversification of function of each unit of electric equipment. On the other hand, there is an increasing demand for the improvement in the safety, driveability and comfort of automobiles. These demands naturally increase the number of the branching circuits in the wiring harness, as well as remarkably increasing diversifying the electronic parts incorporated in each branching circuit. A general description of the prior art and specific prior art junction systems are, inter alia, described and illustrated in parent application 83302124.9 (EP-A-91835). DE-A-2454508 discloses an electrical junction system which has a wiring board provided with a plurality of bus bars on an insulating plate, and in which a printed circuit board is detachably mounted on the wiring board, the printed circuit board carrying a plurality of circuits incorporating a plurality of functional parts. According to the present invention, there is provided an electrical junction system having a wiring board provided with branching conductors formed by a plurality of bus bars on an insulation plate, said plurality of bus bars being connectable to a plurality of printed conductors carried on a printed circuit board and to electric wires in a wiring harness to form branching electric circuits, said printed circuit board being detachably mounted on said wiring board and carrying a multiplicity of functional parts, said printed conductors being provided with terminals arrayed on one side edge of said printed circuit board, and said bus bars being provided at one end with contactors by which they are connected to said terminals thereby to attain the electrical connection between said bus bars and said printed conductors provided for said functional parts such that the electrical connection between said terminals on said printed circuit board and said contactors of said bus bars is achieved by moving said printed circuit board parallel to said wiring board, characterized in that the contactors are tab-like contactors extending upwardly from the wiring board and are provided with intermediate terminals which are L-shaped female terminals having a central portion curved through 90° and having receptacle-like contactors on respective sides of the central portion. Some embodiments of the invention will now be described, by way of examples, with reference to the accompanying drawings, in which:- Fig. 1 is an exploded perspective view of the whole of an embodiment of the invention; Fig. 2 is a perspective view of the printed circuit board incorporated in the system shown in Fig. 1 as viewed from the rear side thereof; Fig. 3 is an enlarged perspective view showing the connection between the printed circuit board incorporated in the system shown in Fig. 1 and the connecting portion of a bus bar; Figs. 4 and 5 are vertical sectional views showing the mounting of the printed circuit board in the system shown in Fig. 1; Fig. 6 is a sectional view taken along the line XVIII-XVIII of Fig. 5; Fig. 7 is a sectional view explanatory of essential parts of a second embodiment of the invention; Fig. 8 is a view similar to that in Fig. 3, showing the connection between a connecting portion of a bus bar and a printed circuit board which constitutes an essential part of a third embodiment of the invention; Fig. 9A is an illustration similar to that in Fig. 4, showing how a printed circuit board and a cover member are attached to each other in the third embodiment of the invention; Fig. 9B is a sectional view taken along the line XXIVB-XXIVB of Fig. 9A; Fig. 10 is an illustration similar to that in Fig. 5, showing how a printed circuit board and a cover member are attached to each other; Fig. 11 is a sectional view taken along the line XXVI-XXVI of Fig. 10; Figs. 12A to 12E are a front elevational view, a right side elevational view, left side elevational view, plan view and a bottom plan view, respectively, of an intermediate terminal used in the third embodiment of the invention; Fig. 12F is an end view as viewed in the direction of the line XXVIIF-XXVIIF; Fig. 12G is a sectional view taken along the line XXVIIG-XXVIIG of Fig. 12A; Fig. 12H is a sectional view taken along the line XXVIIH-XXVIIH of Fig. 12B; Figs. 13A to 13E are a front elevational view, right side elevational view, left side elevational view, plan view and a bottom plan view, respectively, of a terminal used in the third embodiment; Fig. 14 is an exploded perspective view showing the whole of a fourth embodiment of the electrical junction system of the invention; Fig. 15 is a perspective view of the reverse side of a printed circuit board shown in Fig. 14; Fig. 16 is a vertical sectional view of the fourth embodiment showing how the printed circuit board is accommodated and showing how the housing member is mounted in a recess; Fig. 17 is a cross-sectional view of the portion of the fourth embodiment shown in Fig. 16; and Fig. 18 is a vertical sectional view showing how the housing member engages the recess. Fig. 1 shows an embodiment of the invention having a wiring board 1 having a laminated structure constituted by a plurality of insulation plates 1' in the form of thin sheets. Each insulation plate 1, carries known bus bars 3 which constitute a group of branching conductors corresponding to the branching circuits assembled in the wiring harness. This system further has a casing member 2 which covers the wiring board 1 from the upper side thereof, a printed circuit board 5 mounting various functional parts 22 in a concentrated manner and a cover member 6 for the printed circuit board 5. The casing member 2 is provided with a rectangular recess 4 adapted to receive the printed circuit board 5 to which the cover member 6 is secured. In assembly, the casing member 2 is attached to cover the wiring board 1 as indicated by arrow A, while the cover member 6 is secured to the printed circuit board 5 as shown by an arrow. Then, the printed circuit board 5 with the cover member 6 is mounted in the recess 4 to achieve electrical connection between the conductors of the printed circuit board 5 and the ends of the bus bars 3. More specifically, the ends of the bus bars 3 to which the functional parts are to be connected are arranged in a concentrated manner and have upright tab-like contactors 7 arrayed along a straight line. Slit-like through holes 8 are formed in the bottom of the recess 4 in the casing member 2 at positions corresponding to the positions of the tab-like contactors 7. Intermediate terminal receiving seats 9, which are defined by walls 10, are formed above the through holes 8. Each receiving seat 9 receives an intermediate terminal 12 which is an L-shaped female terminal formed, as shown in Fig. 3, by bending the central portion of a substrate 12' at 90° with a small curvature and forming receptacle-like contactors 13A and 13B at both outer sides of the bent substrate 12'. The lower contactor 13B is able to be connected to the tab-like contactor 7 projecting through the through hole 8 while the upper contactor 13A rests in the receiving seat 9 defined by the walls 10. The printed circuit board 5, which will be described in greater detail later, is inserted in the direction of arrow C so that a connection is achieved between the tab-like contactor 14' of the terminal 14 on the front edge 5' of the printed circuit board 5 and the contactor 13A of the intermediate terminal 12. In Fig. 1, a reference numeral 15 denotes tab-like contactors on the end of the bus bars 3 which are to be connected to wires 18 of the wiring harness. The arrangement is such that, as the casing member 2 is mounted, the tab-like contactors 15 are positioned beneath connection ports 16 which are formed in a concentrated manner at a corner of the casing member 2 so that they are electrically connected to the wires 18 as connectors 17 connected to the ends of the wires 18 are received by the connecting parts 16. In Fig. 1, the reference numeral 19 designates a fuse support of the branching conductors which are arrayed in the vicinity of side edge of the wiring plate 1. The fuse support 19 is mounted in a fuse receiving recess 20 formed in the casing member 2. Bifurcated fuse 21 is inserted into each fuse support 19 from the upper side of the latter. On the other hand, the printed circuit board 5 carries all of the functional parts 22 necessitated by the branching circuits of the wiring harness, e.g. relays, diodes, capacitors and so forth. As will be seen from Fig. 2, conductors 23 for respective functional parts 22 are printed on the lower side of the printed circuit board 5. The ends of the conductors 23 are arranged along one side edge 5' of the printed circuit board 5 at a suitable pitch. The arrangement is such that the positions of the ends of the conductors 23 precisely correspond to the positions of the tab-like contactors 7 of the wiring board 1 when the printed circuit board 5 is attached to the latter. As will be seen from Fig. 3, terminals 14 having tab-like contactors 14' for connection to the intermediate terminals 12 are formed on the portions of the upper side of the printed circuit board 5 corresponding to the conductors 23. The terminals 14 have tabular bodies with legs 14" at base portions thereof and are electrically connected to the conductors 23 on the lower side of the board 5 by being soldered at these legs 14". The cover member 6 is a hollow protective member for accomodating the functional parts 22 , and is detachably secured to the wiring board 1 as it is secured to the printed circuit board 5 in such a manner as to cover the functional parts 22. More specifically, referring to Figs. 2 and 14 to 16, attaching holes 24 are formed in the rear portions of both side edges 5" of the printed circuit board 5, while engaging grooves 26 are formed at the inner central portion of the lower edges of both side walls of the cover member 6. In assembly, the cover member 6 is pressed with small force from the upper side thereof so that the engaging grooves 26 are brought into engagement with the side edges 5". Then, locking pins 27 are inserted into the attaching holes 24 so as to fix the base portion to the boss portion 28 of the cover member 6 so that the cover member 6 is secured to the printed circuit board 5. A resilient tab 29 for making pressure contact with the lower side of the printed circuit board 5 is provided on the head of the locking pin 27 so as to absorb and eliminate the vertical play of the printed circuit board 5 due to vibration during use. Holder tabs 30A and 30B spaced vertically from each other and constituting a pair are formed on the front portion of the inner side of each side wall of the recess 4 in the casing member 2. A holding tab 31 is formed on the rear portion of the same side wall. On the other hand, engaging protrusions 32 which are to be received by the gap between the holding tabs 30A, 30B are formed on the outer surfaces of the side walls of the cover member 6. Also, openings 25 for receiving the holding tabs 31 is are formed at the rear side of the engaging protrusions 32. Slits 25' for clamping the holding tabs 31 are formed at the upper portions of the openings 25 so as to extend rearwardly therefrom along the engaging protrusions 32. In assembly, the printed circuit board 5 with the cover member 6 is fitted in the rearmost position in the recess 4 as shown by broken lines in Figs. 4 and 5 such that the holding tabs 31 are received by the openings 25 and is then slid forwardly as indicated by an arrow so that the engaging protrusions 32 are brought into the gaps between the holding tabs 30A and the holding tabs 30B on both sides, while the holding tabs 31 are received by respective slits 25'. In this state, the cover member 6 makes a stable engagement with the recess 4 without substantial play in lateral directions. The reference numeral 33 appearing in Fig. 4 designates a guide portion provided on the inner side of the recess 4 to auxiliarily support and guide the lower edge of the printed circuit board 5 received by the recess 4. By mounting the printed circuit board 5 on the wiring board 1 together with the cover member 6 in the manner described, the circuits formed on the printed circuit board 5 are connected to corresponding branching circuits constituted by the bus bars 3. It will be seen that the printed circuit board 5 can easily be detached from the wiring board 1 for inspection or maintenance work, by taking the reverse procedure. In this electrical connection system, the functional parts necessitated by the branching circuits of the wiring harness are arranged densely on the printed circuit board 5 so as to take up the minimum of installation space, so that the size of the electrical connection system as a whole is much decreased as compared with the conventional relay-unit type system which employs casings of large sizes and volumes. This well meets requirements such as an increase in the number of the functional parts, upgrading and complication of the branching circuits and so forth to cope with the demand for upgrading of automobiles, while satisfying the requirements imposed by the restricted installation space. Furthermore, this electrical junction system offers various other advantages. For instance, the construction of the wiring harness as a whole is simplified to facilitate the division and automation of the production process to remarkably improve productivity. In addition, the function parts are safely protected by the cover member 6. It is also to be noted that the printed circuit board 5 carrying the cover member 6 can easily be attached to and detached from the wiring board without encountering substantial resistance in connecting and disconnecting the mating terminals. In the system heretofore described, the conductors 23 of the printed circuit board 5 may be connected to other portions of the bus bars 3 than the intermediate portions of the latter. Specifically, in some cases, the occasion may demand to connect one end of the functional part circuit of the printed circuit board 5 to the bus bar 3 and the other end of the same to the terminal of the connector. Fig. 7 shows an essential part of a second embodiment of the electrical junction system in accordance with the invention. The second embodiment is characterized by having, in addition to the described construction, a resistance bearing mechanism which bears the resistance produced when the terminals 14 and the intermediate terminals 12 are connected and disconnected to and from each other during mounting and demounting of the printed circuit board 5 to and from the wiring board 1, thereby to protect the terminals 14 and the printed circuit board 5 which are soft and fragile. More specifically, referring to Fig. 7, a bearing hole 34 is formed in the longitudinal intermediate portion of the terminal 14 while a bearing rod 35 is suspended from the top wall of the cover member 6. The arrangement is such that, in attaching the cover member 6, the bearing rod 35 is inserted into the bearing hole 34. In addition, the printed circuit board 5 is allowed to move slightly only in the left and right directions as viewed in Fig. 7. According to this arrangement, the force generated to overcome resistance during connecting and disconnecting the terminals 14 and the intermediate terminals 12 is borne by the bearing rod 35, so that no force is applied to the soldered portions and the printed circuit board 5 which are generally weak and fragile. Specifically, when the cover body 6 and the printed circuit board 5 as a unit are moved in the direction of the arrow C to bring the terminals 14 into engagement with the receptacle-like contactors 13A, the force applied to the portion of each terminal 14 at the left side of the bearing rod 35 is received and borne by the latter, so that no substantial force is applied to the printed circuit board 5 nor to the connection between the printed circuit board 5 and the terminals 14. The functional part circuits on the printed circuit board 5 are connected to corresponding branching conductors constituted by the bus bars 3, as the printed circuit board 5 is mounted on the wiring board 1 while making the resistance bearing mechanism bear the resistance encountered during the mounting. Other portions of the second embodiment are materially identical to those previously described. As will be understood from the foregoing description, in the second embodiment of the invention explained in connection with Fig. 7, the force required to overcome the resistance generated during the mounting and demounting of the printed circuit board is effectively borne by the resistance bearing mechanism, so that the printed circuit board 5 and the terminals 14 on the latter are protected from damage and deformation and the repetitional mounting and demounting of the printed circuit board can be made in quite a smooth manner to ensure a stable long-lasting electrical function of the electrical equipments. In Fig. 7, the same reference numerals are used to denote the same parts or members as those used in Figs. 1 to 6. Figs. 8 to 13 in combination show a third embodiment of the invention which is similar to the system explained before in connection with Figs. 1 to 5. Figs. 8, 9A, 10 and 11, therefore, correspond to Figs. 3, 4, 5 and 6, respectively. In the third embodiment of the invention, terminals 14 having tab-like contactors 14' are attached to the upper side of the printed circuit board 5, as in the case of the first embodiment. As will be clearly understood from a comparison between Figs. 8 and 13A to 13E with Fig. 3, the terminal 14 in the third embodiment differs from the terminal 14, in that the terminal 14 of the third embodiment is provided at its intermediate portion with a sufficiently strong engaging tab 66 extending upright therefrom. A resistance bearing portion 64 is formed on the inner front portion of the cover member 6 immediately above the terminal 14. A resistance bearing hole 65 formed in the lower end of the bearing portion 64 receives and holds the engaging tab 66 standing upright from the upper side of the intermediate portion of the terminal 14. As shown in Fig. 9B, the breadth of B₁ of the engaging tab 66 in the front and rear directions (left and right directions as viewed in Fig. 9B) is slightly smaller than the breadth B₂ of the bearing hole 65, so as to absorb any dimensional or positional error which may be incurred during machining thereby to ensure the safe fitting of the engaging tab 66 in the bearing hole 65. At the same time, the gap or play between the aforementioned attaching hole 24 and the locking pin 27 is selected to be greater than the difference between the breadths B₁ and B₂. The engaging tab 66 and the bearing hole 65 in combination constitute a resistance bearing mechanism which bears the force required to overcome the resistance produced by the friction on the terminal 14 during mounting and demounting of the printed circuit board 5. A guide tab 67 formed on the front inner side of the cover member 6 contacts the upper edge of the intermediate terminal 12 when the printed circuit board 5 with the cover member 6 is correctly secured to the wiring board 1. The guide tab 67 has a curved guide edge 68 at the front lower side thereof for correctly positioning and guiding the intermediate terminal 12 during the mounting and demounting of the printed circuit board 5. A retaining tab 69 formed on the frontmost portion of the cover member 6 is a locking tab which engages with the wall of the casing member 2 to stabilize the printed circuit board 5 after the mounting thereof. The portions of the third embodiment other than those described above are materially identical to those previously described. Therefore, in Figs. 8 to 13, the same reference numerals are used to denote the same parts or members as those in Figs. 1 to 6. It will be understood that the mounting of the printed circuit board 5 with the cover member 6 can be carried out in the same manner as that in the previously described system. Specifically, the printed circuit board 5 with the cover member 6 attached thereto is placed parallel with the wiring board 1 and is engaged with the recess 4 closely to the rear end of the latter as shown by broken lines in Fig. 10. Then, after inserting the holding tab 31 in the opening 25, the printed circuit board is slid forwardly as indicated by the arrow. In consequence, the engaging protrusions 32 is received by the gap between the holding tabs 30A and 30B, while the holding tab 31 is received by the slit 25'. In this state, the cover member 6 makes contact with the inner surface of the recess 4 without any play in the lateral directions. Needless to say, the printed circuit board 5 can easily be demounted from the wiring board 1 by carrying out the reverse procedure, for the purpose of protective maintenance and inspection of the function parts 22. During the mounting and demounting of the printed circuit board, the resistance bearing portion 64, guide tab 67 and other members function in a manner explained hereinunder. Namely, the tab-like contactor 14' of the terminal 14 is guided by the curved surface of the intermediate terminal 12. If the intermediate terminal 12 is floated above the receiving seat 9 due to incorrect shape thereof or inferior mounting, it is forcibly corrected by the curved edge 68 of the guide tab 67 of the cover member 6 which slides forwardly from the rear side, so that the intermediate terminal 12 is smoothly and safely connected to the terminal 14. If the resistance is increased in the beginning period of the connection between the intermediate terminals 12 and the terminals 14, the printed circuit board 5 is moved rearwardly in the cover member 6 only by a distance equal to the gap or play between the engaging tab 66 and the resistance bearing hole 65. Then, as the bearing hole 65 is brought into engagement with the engaging tab 66, the resistance is borne by the bearing portion 64 so that no substantial force is applied to the legs 14" of the terminals 14 contacting the printed circuit board 5 nor to the solder by which the legs are fixed to the printed circuit board 5. Clearly, the force required to overcome resistance produced when the printed circuit board 5 is withdrawn also is borne by the bearing portion 64. As has been described, in the third embodiment of the invention, the printed circuit board 5 and the terminals 14 attached on the same are protected from any damaging or deforming force, partly because the intermediate terminal 12 is guided and corrected by the guide tab 67 and partly because the resistance generated during the mounting and demounting of the printed circuit board is borne by the resistance bearing mechanism, so as to permit a smooth repetitional mounting and demounting while ensuring long-lasting and stable functioning of the electric equipments. Figs. 12A to 12H show the detail of the intermediate terminal 12 incorporated in the third embodiment. As will be clearly seen from these Figures, the intermediate terminal 12 is a substantially L-shaped terminal having a substrate 12' which is bent at its mid portion at 90° with a small curvature and a pair of receptacle-like contactors 13A and 13B at both sides of the bent portion for receiving the tab-like contactors. In the illustrated embodiment, both side edges of the substrate 12' are bent substantially through 180° to form curved portions, the lower edges of which constitute curved edges 13' at both longitudinal ends thereof. As in the case of the arrangement shown in Fig. 8, the lower contactor 13B is fitted to the tab-like contactor 7 of the end of the bus bar 3 projecting upwardly through the through hole 8, while the upper contactor 13A rests in the receiving seat 9 defined by the walls 10. Then, the printed circuit board 5 is inserted in the direction of the arrow C so that the tab-like contactors 14' of the terminals 14 on the front edge 5' of the printed circuit board 5 are connected to the contactors 13A of the intermediate terminals 12. The intermediate terminals 12 shown in Figs. 12A to 12H are materially identical to that incorporated in the previously described system. Figs. 14 to 18 show a fourth embodiment of the electrical junction system of the invention. As shown in Fig. 14, this embodiment has a wiring board 1 having a laminated structure consisting of a plurality of insulation plates 1' each carrying known bus bars 3 arranged to form branching circuits corresponding to the branching circuits of the wiring harness, a casing member 2 covering the wiring board 1, a printed circuit board 5 attached to the wiring board 1 and carrying circuits having functional elements, the terminals of the circuits being arrayed at one side of the printed circuit board 5, and a housing member 6 housing the printed circuit board 5, the housing member 6 having a cover member 6A covering the upper and lateral sides of the printed circuit board 5 and a bottom plate 6B. The printed circuit board 5 is received by the housing member 6 as indicated by arrows A and B to form an independent body. Then, the casing member 2 is attached to the wiring board 1 as indicated by arrows C and D. Subsequently, the housing member 6 accomodating the printed circuit board 5 is mounted in the rectangular recess 4 formed in the casing member 2, thereby to achieve electrical connection between the conductors 14 on the printed circuit board 5 and the ends of the bus bars 3. More specifically, the ends of the bus bars 3 which are to be connected to the required functional parts are shaped into the form of upright tab-like contactors 7 which are arrayed in a concentrating manner along a straight line on an intermediate portion of the wiring board 1. These tab-like contactors 7 project upwardly through slit-like through holes 8 formed at in the bottom of the recess 4 in the casing member 2 at positions corresponding to the tab-like contactors 7, when the latter is fitted to the wiring board 1. In addition, intermediate receiving seats 9 are defined above the through holes 8 by walls 10. Each receiving seat 9 receives an intermediate terminal 12. As shown in Fig. 16, the intermediate terminal 12 is an L-shaped female terminal which is bent at its mid portion at 90° and provided with receptacle-like contactors 13A, 13B formed at both sides of the central bend so as to receive the tab-like contactors 14. The lower contactor 13B fits around the tab-like contactor 7 projected through the through hole 8 while the upper contactor 13A is received by the receiving seat 9 defined by the walls 10. The arrangement is such that the printed circuit board 5 is slid rearwardly to bring the tab-like contactors 14′ of the terminals 14 arrayed on the front edge 5′ of the printed circuit board 5 into electrical contact with the contactors 13A. The reference numeral 15 appearing in Fig. 14 denotes tab-like contactors on the ends of the bus bars 3 which are to be connected to the wires 18 of the wiring harness. These tab-like contactors 15 are housed, when the casing member 2 is attached, by connection ports 16 which are formed in a concentrated manner at a corner of the casing body 2. Then, connectors 17 connected to the end of the wires 18 are inserted into the connecting ports 16 so as to attain electric connection between the wires 18 and the bus bars 3. A reference numeral 19 designate fuse holders for holding fuses 21 which are used in the protection of respective branching circuits. These fuse holders 19 are received by recesses 20 formed in the casing member 2. Bifurcated fuses 21 are inserted into respective fuse holders 19 from the upper side thereof. On the other hand, the printed circuit board 5 densely carries all of the functional parts such as relays, diodes, capacitors and so forth required by the branching circuits of the wiring harness. As will be seen from Fig. 15, conductors 23 for respective functional parts are printed on the reverse side of the printed circuit board 5. The ends of the conductors 23 are arrayed along one side edge 5' of the printed circuit board 5 at suitable intervals to take positions precisely correspond to the tab-like contactors 7 on the wiring board when the printed circuit board 5 is mounted on the wiring board 1. As in the case of the arrangement shown in Fig. 16, terminals 14 having tab-like contactors 14' for connection to the intermediate terminals 12 are mounted on the upper side of the printed circuit board 5. Each terminal 14 has legs 14" at its base portion at which it is electrically connected and fixed by soldering to corresponding conductor 23 on the reverse side of the printed circuit board 5. The tab-like contactors 14' project from the front edge 5'. As stated before, the printed circuit board 5 is housed by a housing member 6 consisting of a cover member 6A which covers the upper and lateral sides of the printed circuit board 5 including the ends of the terminals 14 and a bottom plate 6B which closes the lower side of the cover member 6A. The printed circuit board 5 is housed by the housing member 6 leaving only the slit-like opening for connection with the intermediate terminals 12 ahead of the terminals 14. More specifically, as shown in Figs. 16 and 17, a retaining claw 70 is formed on the inner lower side of the cover member 6A. As the cover member 6A is lightly pressed onto the printed circuit board 5 from the upper side thereof, the lower surface of the printed circuit board 5 is brought into engagement with the retaining claw 70 so that the cover member 6A is secured to the printed circuit board 5. Then, the bottom plate 6B is fitted from the lower side of the cover member 6A so that small resilient tabs 71 provided on the periphery of the bottom plate 6B are received by retaining recesses 72 formed in the walls of the cover member 6A near the lower edges thereof, slot that the bottom plate 6B is held securely to extend in parallel with the printed wiring board 5 in the vicinity of the latter so as to close the lower opening of the cover member 6A. Thus, the printed circuit board 5 is housed by the housing member 6 such that the upper and lateral sides of the function parts 22 and the terminals 14 are covered by the cover member 6A and that the lower side thereof is also closed by the bottom plate 6B. In the described construction for containment of the printed circuit board 5, the position or posture of the printed circuit board 5 is stabilized by means of a locking pin 29 which is extended through the attaching hole 24 in the printed circuit board 5 and fixes the base portion to the boss 28 of the cover member 6A. At the same time, a retainer tab 72 is formed at the front side of the cover member 6A. The arrangement is such that, as the housing member 6 accomodating the printed circuit board 5 is mounted in the recess 4 in the casing member 2, the housing member 6 is locked through mutual engagement between the upper edge of the front wall 4′ of the recess 4 and a locking claw 72′ on the lower end of the retainer tab 72. On the other hand, two pairs of holding tabs 30A,30B and 31A,31B, the tabs of each pair being spaced vertically, are formed on the inner surfaces of the side walls of the recess 4. These tabs are formed as protrusions having certain lengths in the back and forth directions and to extend substantially in parallel with the wiring board 1. In addition, engaging protrusions 73A and 73B are formed on the outer surfaces of both side walls of the cover member 6A so as to extend in the direction parallel to the plane of the printed circuit board 5 received in the cover member 6A. These engaging protrusions are introduced into the gaps between the holding tabs 30A and 30B and 31A and 31B of the corresponding pair. A notch 74 for loosely receiving a holding tab 31A is formed between the engaging protrusions 73A and 73B. In assembly, the housing member 6 accomodating the printed circuit board 5 is inserted to the rear portion of the recess 4 from the upper side of the latter as illustrated by broken lines in Fig. 18 with the holding tab 31A loosely received by the notch 74 and is then slid slightly in the forward direction as indicated by an arrow E so as to introduce the engaging protrusions 73A and 73B into the gaps between the holding tabs 30A and 30b and between 31A and 31B thereby to attain a close fit therebetween. Then, the printed circuit board 5 is moved on the wiring board 1 in parallel with the latter thereby to complete the mounting of the printed circuit board 5. As a result of the forward sliding movement of the printed circuit board 5, the tab-like contactors 14' of the terminals 14 are inserted into the receptacle-like contactors 13A of the intermediate terminals 12 so that the functional part circuits on the printed circuit board 5 are connected to corresponding branching circuits formed on the wiring board by the bus bars 3. By taking the reverse procedure, the printed circuit board 5 can easily be demounted from the recess 4 in the wiring board 1 and detached from the housing member 6 for maintenance or inspection purpose. In the housing member 6 explained hereinabove, the cover member 6A is provided at its front inner side thereof with a resistance bearing mechanism for bearing the force required to overcome resistance encountered during connecting and disconnecting the terminals 14 and the intermediate terminals 12 to and from each other, as well as a guide mechanism, in order to attain a smooth connecting and disconnecting operation. More specifically, the cover member 6A is provided at the inner side of the front portion thereof with a resistance bearing portion 64 and a guide tab 67 suspended therefrom. The resistance bearing portion 64 is provided at its lower end with bearing holes 65 which receive engaging tabs 66 protruded from the terminals 14. At the same time, the printed circuit board 5 is movable slightly in the back and forth directions within the cover member 6A by, for example, a loose fit of the lock pin 29 in the attaching hole 24. The force which is generated to overcome the frictional resistance when the terminals 14 are brought into and out of engagement with the intermediate terminals 12 is born by the resistance bearing portion 64 so that no substantial force is applied to the weak legs 14″ of the terminals nor to the printed circuit board 5 itself. The aforementioned guide tab 67 provided on the front inner side of the cover member 6A contacts the upper edge of the intermediate terminal 12 when the printed circuit board 5 is correctly positioned in the wiring board 1. The guide tab 67 is provided at its front lower side with a curved edge 68 which contacts, if the intermediate terminal beforehand mounted is floated for any reason, the intermediate terminal 12 to correct its position when the printed circuit board 5 is slid to the mounting position, thereby to ensure smooth connection and disconnection between the terminals. As has been described, in the fourth embodiment of the electrical junction system of the invention, the printed circuit board arranged at its one side with terminals is contained by a housing member and is mounted on the wiring board through the medium of the housing member. Therefore, the terminals are required to share only the electrical connecting function but are not required to possess physical strength for attaining mechanical stability of mounting. This advantageously permits a single printed circuit board to carry quite a large number of terminals. In consequence, it becomes possible to arrange on, for example a single printed circuit board, all of the functional parts necessitated by the branching circuits of the wire harness in a concentrated manner at a high density, thereby to save the installation space considerably. Accordingly, it is possible to produce an electrical junction system of an extremely small size, well meeting the requirements such as increase in the number of the function parts, upgrading and complication of the branching circuits and so forth to cope with the current demand for upgrading of automobiles, while satisfying the requirement from the restriction in the installation space. It is to be noted also that the electrical junction system of the invention having a simple construction promotes a diversification of the production process and the adoption of automation, which in turn improves the productivity considerably. Furthermore, it is possible to attain a highly smooth repetitional connection and disconnection of terminals resulting in a stable long-lasting electric function of the functional parts, thanks to the use of the housing member which is provided with a guide mechanism for guiding the terminals during connecting and disconnecting operation, as well as the resistance bearing mechanism which bears the force generated by the friction between the terminals when they are connected and disconnected to and from each other. The terminals, functioning parts and printed conductors on the printed circuit are generally weak mechanically and, hence are liable to be damaged or distorted as a result of contact with other parts, when the printed circuit board is shifted transported or handled as a new part for replacement. This problem can be overcome satisfactorily because the housing member conceals the terminals, functional parts and printed conductors on the printed circuit board to permit the latter to be treated as a protected unit part, which is a great advantage in practical use.

Claims: An electrical junction system having a wiring board (1) provided with branching conductors formed by a plurality of bus bars (3) on an insulation plate, said plurality of bus bars (3) being connectable to a plurality of printed conductors (23) carried on a printed circuit board (5) and to electric wires (18) in a wiring harness to form branching electric circuits, said printed circuit board (5) being detachably mounted on said wiring board (1) and carrying a multiplicity of functional parts (22), said printed conductors (23) being provided with terminals (14) arrayed on one side edge of said printed circuit board (5), and said bus bars (3) being provided at one end with contactors (7) by which they are connected to said terminals (14) thereby to attain the electrical connection between said bus bars and said printed conductors (23) provided for said functional parts (22) such that the electrical connection between said terminals (14) on said printed circuit board (5) and said contactors (7) of said bus bars (3) is achieved by moving said printed circuit board (5) parallel to said wiring board (1), characterized in that the contactors (7) are tab-like contactors extending upwardly from the wiring board and are provided with intermediate terminals (12) which are L-shaped female terminals having a central portion (12') curved through 90° and having receptacle-like contactors (13A, 13B) on respective sides of the central portion (12').

Inventors: INOUE, NORI, MORIAI, YASUHARU, SAKATANI, ATUSHI, YOSHIDA, NORIYUKI
Applicants: SUMITOMO ELECTRIC INDUSTRIES LIMITED, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1983
Main classification: H01R9
IPC codes: H05K3, H05K5, H01R12, H05K7