ELECTRICAL CONNECTORS

Abstract: A printed circuit board connector in which contacts of the connector are self-cleaning as the board is inserted into or extracted from the connector.

Description: ELECTRICAL CONNECTORS This invention is concerned with electrical connectors. In the telecommunications field, especially in the private sector where telephone circuits are provided for continuous use, there is a requirement for accessing and testing these circuits without interrupting them so that they can remain in service and in use while testing takes place. These private telephone circuits, or lines, are not part of the public dial-up network and therefore require specialised testing equipment as is provided, for example, by the Hewlett-Packard HP37100 series remote access testing system. It is a primary requirement that the test equipment must be installed in a circuit so that it can be disconnect¬ ed from or connected into that circuit without breaking transmission in that circuit. To achieve this, the test equipment typically comprises a number of "access cards" which can be connected into the circuit to be tested, each access card having mounted thereon a plurality of relays, the relays operating in a manner such as to maintain continuity of circuit, and to switch the circuit to the test equipment as hereinafter described. Each access card is essentially a printed circuit board having conductive traces thereon leading to and from relays mounted on the board and extending to an edge of the board on both surfaces thereof. The traces thus provide edge connectors along the edge of the board, which edge connectors are arranged to be held in electrically-conductive spring clips which provide normally contacting jaws when the board is not urged therebetween and can be forced apart by the edge of the board when the test equipment is connected in circuit. Figure 1 is a schematic circuit diagram which illustrates the principle of interconnection of an access card in a -single circuit line, of which in practice there are many. The line 100 includes a spring clip indicated by the box 102, the clip comprising jaws indicated by the two arrowheads 104, 106. As illustrated in Figure 1, the jaws 104, 106 are sprung apart and make contact with edge connectors 110, 112 on opposite surfaces of a circuit board, the ' connectors being electrically connected to relays RLl, RL2 mounted on the board. Provided that the jaws 104, 106 make good electrical contact with the connectors 110, 112 continuity is maintained in the line 100 via the closed contact 115 of the relay RLl, while the contacts of the relay RL2 remain ..open. When it is desired to test the circuit, the contacts of the relay RL2 are closed and those of the relay RLl are opened to divert the circuit through an access bus 116 to test equipment provided at a remote location. In normal operation, the circuit is maintained through the contact 115 of the relay RLl and only for occasional intervals is the circuit switched through the relay RL2 to the remote test equipment. Occasionally, a component, e.g. a relay, of an access card can fail and at that point in time it is necessary to withdraw the access card from use. At this point the access card is physically moved so that the edge connectors thereof are withdrawn from between the jaws of the spring clip, the design of the spring clip being such that the jaws make contact with each other before becoming disconnected from the connectors, thereby preserving circuit continuity. However, with current spring clip design, it is possible that dirt can collect on * the jaws of the spring clip and prevent closing of the circuit, thereby disruptin flow of information therethrough. This problem will becom more clear from reference to Figures 2, 3a-3c, 4a-4c and 5a, 5b which illustrate an element of a typical prior art sprin clip and the potential problem that may arise due to ingress of dirt or due to corrosion on the jaws of the clip. The prior art clip comprises two elements 300 such as are shown in Figure 2, the two elements being mounted in face-to-face relationship, as indicated in side elevation in Figure 3a. Each element is made of electrically-conductive material, and the two elements are mounted a distance apart from each other on an insulating base 302 such that the shortest distance between opposed arched portions 304 of the elements is less than the thickness of a printed circuit board 306 to be inserted therebetween, and such that the two leaf-spring portions 308 of the opposed elements are urged against each other adjacent their extremities 310. As the edge portion of a circuit board is inserted into the spring clip, the elements of the clip flex apart as shown in Figures 3b and 3c, until the board is located between the elements. Insertion of the board can be considered as a two-stage process, in the first stage of which, as the board is urged between the arched portions 304, continuity of the circuit is maintained through the leaf-spring portions 308 which remain in contact and through the closed contact of relay RLl of Figure 1. In the second stage, continuity of circuit is transferred entirely to the contact of relay RLl. The reverse is true when the board is withdrawn from the clip. It will be seen from Figure 2 that the geometry of each element is symmetrical about the line A-A and from Figure 3a it can also be seen that the geometry of the clip is also symmetrical about the plane B-B normal to the paper. The symmetry of this arrangement can cause a number of different problems, all of which can adversely affect continuity of circuit. When the printed circuit board is removed, circuit integrity relies on only one contact from each side of the make-before-break connector provided by the clip, i.e., the leaf-spring portion 308 of each connector. This means that if any dirt or detritus, such as glass fibre from the printed circuit board or corrosion products, becomes trapped between the contacts provided by the leaf-spring portions 308, the circuit will not close and will remain open. In a private circuit telephone line, used for transmission of data from one computer installation to another, such an open circuit may remain open until detected with consequent loss of valuable data. The second problem which can arise with such an arrangement as is provided by the prior art, is that as the clip is sprung, the extremities 310 of the leaf-spring portions 308 will roll against each other, as shown in exaggerated form in Figures 4a and 4b. There will be no self-cleaning between these end portions and particles may even become trapped between them to be ground into the surfaces thereof. The third problem that can occur is also a result of the environment in which access to a circuit line is available. If a printed circuit board has been mounted in a plurality of clips for a sufficient period of time in an industrial environment, it is very possible that corrosion products may form on the leaf-spring portions 308 or that dirt deposits may build up between the board 306 and the leaf-spring portions. Whilst this may be satisfactory whilst the board is in situ and will not adversely affect the quality of electrical contact, as soon as the board is removed, there may be a tendency for the board to drag the deposits from a position in which they may do no harm onto the face of the actual contact area so that the deposits are exactly where they should not be when the board is removed. Furthermore, corrosion products may build-up at the end of conductive trace on the board where the material of th trace is exposed. This may lead, on withdrawal of th board, to the corrosion products being dislodged an becoming trapped between the ends of the leaf-sprin portions, thus preventing the leaf-spring portions fro coming into contact. These effects are shown in Figures 5 and 5b. The present invention provides an electrically-conduct ive connector element suitable for use with a like element, when mounted in face-to-face relationship therewith, i providing a connector for electrical connection to a printe circuit board, the element comprising a bridge portion and first and second resiliently-flexible elongate portions i side-by-side relationship and integrally-formed with said bridge portion, the first elongate portion being formed as leaf-spring to electrically contact the opposed element, and the element further comprising a laterally-extending portio arranged to face the other element so that a printed circuit board can be inserted between the two elements firstly to conductively engage the laterally-extending portions with conductive traces on opposite sides of the circuit board and urge them apart while electrical contact is maintained between the two elements, and so that the circuit board can be further inserted to separate the leaf-springs from electrical contact with the opposed element and to establish electrical contact between the leaf-spring and said conductive traces, the element being characterized in that the second elongate portion thereof comprises a mounting portion, and the leaf-spring is of a length and shape such that as the laterally-extending portions of the two elements of a connector are urged apart or flex together, the end portion of each leaf-spring wipes against surface portions of the opposed element to provide self-cleaning of the contacting surfaces. In an element as set forth in the last preceding paragraph, it is preferred that the second elongate portion includes said laterally-extending portion/ said laterally- extending portion being provided adjacent the bridge portion. Alternatively, the laterally-extending portion may be provided by the bridge portion. In an element as set forth in either one of the last two immediately preceding paragraphs, it is preferred that the leaf-spring thereof is adapted, when the element is mounted in opposed relationship to a like element, to electrically contact the second elongate portion of the like element, whereby two separate electrical connections are made between the elements. In an element as set forth in any one of the last three immediately preceding paragraphs, it' is preferred that the second elongate portion also comprises a curved portion bowed in the same direction as the laterally-extending portion and provided between the laterally-extending portion and the mounting portion. In an element as set forth in the last preceding paragraph, it is preferred that the end portion of the leaf- spring is adapted to bear against the curved portion of an opposed element. The present invention also provides a connector for electrical attachment to a printed circuit board and com¬ prising a pair of electrically-conductive resiliently-flex- ible elements arranged to be mounted in face-to-face relationship, each element comprising a bridge portion and first and second elongate portions in side-by-side rela- tionship and integrally-formed with said bridge portion, the first elongate portion being formed as a leaf-spring arranged to electrically contact the opposed element, and each element further comprising a laterally-extending portion facing the other element so that a printed circuit board can be inserted between the two elements firstly to conductively engage the laterally-extending portions wit conductive traces on opposite sides of the circuit board an urge them apart while electrical contact is maintaine between the two elements, and so that the circuit board ca be further inserted to separate the leaf-springs fro electrical contact with the opposed element and to establis electrical contact between the leaf-springs and conductiv traces, the connector being characterized in that eac second elongate portion comprises a mounting portion, an each leaf-spring is of a length and shape such that as th laterally-extending portions are urged apart or fle together, the end portion of each leaf-spring wipes agains surface portions of the opposed element to provid selfcleaning of the contacting surface. The present invention also provides means for connect ing circuit means to components on a printed circuit board said means comprising a plurality of connectors as set fort in the last preceding paragraph and arranged in a linea array for receiving and making electrical contact wit conductive traces provided along an edge portion of th circuit board and electrically connected with sai components. The present invention further provides a connector fo electrical attachment to a circuit board and comprising pair of opposed, electrically-conductive, resiliently-flex ible conductor elements, each element comprising a firs portion arranged to make electrical contact with a conduct ive trace on a respective surface of the board when th board is initially inserted into the connector, a secon portion whereby the element can be mounted in opposed space relationship to the opposite element on an insulating moun and a third, leaf-spring, portion arranged to bear agains and make electrical contact with the second portion of the opposite element, the first, second and third portions of each element being integrally formed, and the connector 8 being characterized in that each element is asymmetrical and in that an end portion of each leaf-spring portion is wipable against a respective opposed second portion as the two opposed elements are urged apart by insertion of a circuit board therebetween and is separable from the opposed second portion by further insertion of the board to make contact with said conductive traces. The invention also provides an electrically-conductive element suitable for use with a like element to provide a connector clip for electrical attachment to a circuit board, the element comprising a mounting portion, an arched portion and a leaf-spring portion integrally formed of a resiliently flexible material, the element being characterized in that the element is asymmetrical and further comprises an integrally-formed curved leaf-spring portion located so that when the element is mounted in proper spaced face-to-face relationship relative to a like element, the leaf-spring portion of each element is in opposed relationship to. the arched portion and the curved portion of the other with an ' end portion of each leaf-spring portion urged against the curved portion of the other, such that a circuit board can be inserted between the two elements to urge * the arched portions apart while maintaining electrical contact therewith and such that the circuit board can be further inserted between the two elements to urge the leaf-spring portions apart while maintaining electrical contact therewith, the action of the end portion being to wipe against the opposed curved portions to clean the contacting surfaces thereof as the element is flexed during insertion or withdrawal of the circuit board. The invention also provides an electrically-conductive connector element suitable for use with a like element to provide a connector clip for electrical attachment to a circuit board, the element being formed of a resiliently flexible material and comprising first and second elongate portions and an arched portion, the elongate portions bein integrally joined in side-by-side relationship, the firs elongate portion providing a leaf-spring and the secon elongate portion being integrally formed with a mountin portion, the free end portion of the leaf-spring, and th arched portion being arranged to bear against electrica contacts of a circuit board so that electrical contact i made between the connector and the circuit board, an electrical contact is maintained between the two element until the circuit board is fully inserted into the connect or, the element being characterized in that, when it is use in face-to-face relationship with a like element, the en portion of each leaf-spring has a wiping, self-cleanin action against the second elongate portion of the other element, when the elements are flexed by insertio therebetween and/or removal therefrom of a circuit board. There now follows a detailed description which is to be read with reference to Figures 6 to 12 of the accompanyin drawings of an element and connector according to the invention; it is to be clearly understood that the element and the connector have been selected for description to illustrate the invention by way of example and not by way of limitation. Figure 6 is a perspective view of an element according to the invention; Figure 7 is a side view of a connector according to the invention in a first, relaxed, condition; Figure 8 is a side view of the connector of Figure 6 partially extended by an edge portions of a printed circuit board; Figures 9 and 10 are exaggerated views illustrating a characteristic feature of the present invention: Figure 11 is a side view, similar to Figure 8, of the connector, showing the connector in fully expanded condition with a printed circuit board inserted therein; and Figure 12 is a perspective view of a further elemen according to the invention. The element shown in Figure 6 is formed of metal o metal-coated plastics material, which is resilientl flexible. It comprises two elongate portions indicate generally at 600 and 610 which are integral with a bridg portion 620. The elongate portion 600 comprises a first arched, portion 630, a second flat spacer portion 640, further, arched, portion 650 and a planar, mounting portio 660. In the relaxed condition shown in Figure 6, th bridge portion 620 and the mounting portion 660 ar coplanar. The arched portion 630 is " more pronounced tha the arched portion 650. The elongate portion 610 is formed as a curved lea spring curving from the bridge portion 620 in the sam direction as the arched portions 630, 650 away from th plane defined by the portions 620 and 660. The leaf-sprin portion 610 terminates as a shoe portion 670 and is of length such that, if bent flat, the shoe portion would li adjacent the lower portion of the arched portion 650. In use, the element shown in Figure 6 is mounted on base 680 in face-to-face, opposed relationship with a lik element to provide a connector as shown in Figure 7, wit the mounting portions • also providing terminal pads fo connection of the circuit board connected in a transmissio line. The two elements provide the jaws 104, 106 of th spring clip 102 shown in Figure 1. The two elements are so mounted that the elongat portion 600, 600' of each is in face-to-face relationshi with the leaf-spring portion 610', 610 respectively of th other, and the separation of the mounting portions 660, 660 is such that the shoe portion 670, 670* of each bear positively against the curved, arched portion 650', 650 o the other so that electrical contact is achieved therebet ween, providing two contact areas as opposed to the singl contact area achieved by the prior art (see Figure 3a) . The distance of separation of the arched portions 630, 630' is less than the thickness of a printed, circuit board to be inserted therebetween. The edge portion of a printed circuit board 690 is inserted between the two elements and forces them to flex or bend outwardly as the arched portions 630, 630' are urged apart. This movement of separation causes the shoe portion 670, 670' of each element to slide along the surface of each shallower arched portion 650', 650 respectively, in the direction of the arrow C shown in Figure 8. In the illustrated construction, the movement of separation of the arched portions 630, 630* is substantially arcuate, and is the result of flexing of the curved portions 650, 650' about the junction of these portions with the mounting portions 660, 660' of the portions .640, 640' and of movement of the arched portions 630, 630' relative to the portions 640, 640'. Thus, as the upper extremities, viewing Figure 8, of the arched portions 630, 630* move apart, the shoe portions of the leaf-spring portions will follow the movement and be drawn along the surfaces of the curved portions, due to the change in attitude of the leaf-spring portions. The effective movement of the shoe portions 670, 670' along the surfaces is shown by the illustration in exaggerated form in Figures 9 and 10 of the movement of the shoe portion 670 against the curved portion 650*, Figure 9 showing the relationship when the connector is in its relaxed state (that of Figure 6) and Figure 10 showing the relationship when the elements of the connector are urged apart as in Figure 7. Between these two positions, each shoe portion will effect a sliding, scraping motion against the curved portion while changing its attitude so as to effect a self-wiping action between mutually self-contacting portions of the shoe portion and the surface of the curved portion. As the edge portion of the printed circuit board is urged between the arched portions 630, 630', the arched portions make electrical contact with electrically-conduct¬ ive traces on the board whilst the shoe portions maintain contact with the curved portions 650', 650 respectively. Continuity of circuit is thus maintained through both the leaf-spring"portions contacting the opposed elements and the normally-closed contact of the relay on the board which is equivalent to the relay RLl of Figure 1. When the edge portion of the board is urged further into engagement with the spring clip connector, as shown in Figure 11, the leaf-spring portions 610, 610' are themselves sprung apart and make electrical contact with the traces on each side of the board, so that continuity of the circuit is transferred to the circuit board, specifically through the relay RLl. The self-wiping facility of the elements of the connector is of great . significance when, for whatever reason, it is desired to withdraw the board from the connector, e.g., to replace a defective relay.. At this stage it is critical that, when the board is partially withdrawn from the Figure 11 position to the Figure 8 position, the leaf-spring portions 610, 610* make good electrical contact with the opposite curved portions 650*, 650 respectively for otherwise, when the circuit board is fully withdrawn from the connector, the circuit will be broken. As will be seen by reference again to Figures 9 and 10, aggregation of dirt or corrosion can be removed by the scraping motion of the shoe portions 670, 670' of each leaf- spring portion along the surface of the curved portion, as the shoe portion moves from the position shown in Figure 10, which is the position adopted immediately the leaf-spring portions have been released from engagement with the printed circuit board, to the position shown in Figure 9. An alternative embodiment of an element according t the invention is shown in Figure 12 where the arched portio of the previous embodiment itself provides a bridge portio 700 between an elongate mounting portion 710 and leaf-sprin portion 720. In this embodiment, no curved portion, corresponding to the curved portion 650 shown in Figure 6, is provided', although it may be if desired. It is believed that the curvature of the curved portion of each element provides for a more variable geometry thus allowing for a larger surface area of each shoe portion to be cleaned. Obviously, the geometry of the portions of the individual elements can be varied according to requirements. What is considered to be important, however, is the asymmetry of the individual elements whereby a sliding movement of contacting portions of the opposed elements can be obtained.

Claims: CLAIMS 1. An electrically-conductive connector element suitable for use with a like element, when mounted in face- to-face relationship therewith, in providing a connector for electrical connection to a printed circuit board, the element comprising a bridge portion (620) and first and second resiliently-flexible elongate portions (610,600) in side-by-side relationship and integrally-formed with said bridge portion, the first elongate portion being formed as a leaf-spring (610) to electrically contact the opposed element, and the element further comprising a laterally- extending portion (630) arranged to face the other element so that a printed circuit board can be inserted between the two elements firstly to conductively engage the laterally- extending portions with conductive traces on opposite sides of the circuit board and urge them apart while electrical contact is maintained between the the two elements, and so that the circuit board can be further inserted to separate the leaf-springs (610) from electrical contact with the opposed element and to establish electrical contact between the leaf-springs and said conductive traces, the element being characterized in that the second elongate portion (600) thereof comprises a mounting portion (660), and the leaf-spring (610) is of a length and shape such that as the laterally-extending portions (630) of the two elements of a connector are urged apart or flex together, the end portion (670) of each leaf-spring wipes against surface portions of the opposed element to provide sel-fcleaning of the contacting surface. 2. An element according to claim 1 characterized in that the second elongate portion (600) includes said laterally-extending portion (630), said laterally-extending portion being provided adjacent the bridge portion (620). 3. An element according to claim 1 characterized i that the laterally-extending portion is provided by th bridge portion. 4. An element according to any one of the precedin claims characterized in that the leaf-spring (610) thereof is adapted, when the element is mounted in opposed relation¬ ship to a like element, to electrically contact the second elongate portion (600) of the like element, whereby two separate electrical connections are made between the elements. 5. An element according to any one of the preceding claims characterized in that the second elongate portion (600) also comprises a curved portion (650) bowed in the same direction as the laterally-extending portion (630) and provided between the laterally-extending portion and the mounting portion (660). 6. An element according to claim 5 as appended to claim 4 characterized in that the end portion of the leaf- spring (610) is adapted to bear against the curved portion (650) of an opposed element. 7. A connector for electrical attachment to a printed circuit board and comprising a pair of electrically-con¬ ductive resiliently-flexible elements arranged to be mounted in face-to-face relationship, each element comprising a bridge portion (620) and first and second elongate portions (610, 600) in side-by-side relationship and integrally- formed with said bridge portion, the first elongate portion being formed as a leaf-spring (610) arranged to electrically contact the opposed element, and each element further comprising a laterally-extending portion (630) facing the other element so that a printed circuit board can be inserted between the two elements firstly to conductively engage the laterally-extending portions with conductive traces on opposite sides of the circuit board and urge them apart while electrical contact is maintained between the two 5 elements, and so that the circuit board can be further inserted to separate the leaf-springs (610) from electrical contact with the opposed element and to establish electrical contact between the leaf-springs and said conductive traces, the connector being characterized in that 10 each second elongate portion (600) comprises a mounting portion (660) , and each leaf-spring (610) is of a length and shape such that as the laterally-extending portions (630) are urged apart or flex together, the end portion (670) of each 15 leaf-spring wipes against surface portions of the opposed element to provide self-cleaning of the contacting surfaces. 8. Means for connecting circuit means to .components on a printed, circuit board, said means comprising a 20.plurality of connectors as set forth in claim 7 and arranged in a linear array for receiving and making electrical contact with conductive traces provided along an edge portion of the circuit board and electrically connected with said components. 25 30 35

Inventors: CRAWFORD GREGAN FREDERICK, CRAWFORD, GREGAN, FREDERICK
Applicants: HEWLETT PACKARD LTD, HEWLETT-PACKARD LIMITED
Application year: 1985
Main classification: H01R23
IPC codes: H01R12, H01R13, H01R29