GB2210210A - Plugboard switching system - Google Patents

Abstract

A plugboard system, having a plurality of hairpin shaped contact wires (12, 14, 16) disposed in parallel sets between pairs of stacked, parallel insulation plates (18) containing arrays of aligned through holes (26) for the reception of shorting plugs (10), each hairpin contact wire (12, 14, 16) projecting from two opposite sides of the stack and being located longitudinally relative to the stacked insulation plates (18) by mechanically coupling together the two projecting legs of the hairpin contact wire at the two opposite sides of the stack, respectively. In addition to the two projecting legs of each individual hairpin being mechanically coupled at the two sides of the stack, all of the contact wires in a given set may be mechanically coupled together by strips (30a, 30b) at the two sides of the stack, respectively. <IMAGE>

Description

DESCRIPTION IMPROVED PLUGBOARD SWITCHING SYSTEM The present invention relates to plugboard switching systems of the type shown in our earlier GB Patent No 1081171.

As illustrated in Figs 1,2,3 and 4 of the accompanying drawings, our existing plugboard shown in GB Patent No 1081171 comprises plural sets of parallel contact wires 12,14,16, arranged in layers, sandwiched between stacked plates of insulation 18 containing arrays of aligned holes 26. The wires 14 of one layer lie in a direction perpendicular to those of adjacent layers 12,16, and are such that at one end they project from the insulation to form respective solder tags 20. By this structure, a signal on one contact wire in one layer can be selectively routed to a contact wire in another layer by the insertion of a shorting plug 10 inserted into a selected set of the aligned holes 26.

The number of layers may be extended to twelve or more, allowing six or more signals to be switched by a single shorting plug. In such a situation, a multiple pin plug is used, the number of pins and the length of each pin depending on how many interconnections are required.

Fig 3 shows in plan view one of the insulating plates 18. The upper surface of the plate 18 as viewed in Fig 3 is formed with a plurality of upstanding circular studs 22 disposed in perpendicular rows and columns. Disposed between each pair of studs in adjacent rows are two smaller upstanding pips 24a,24b. Disposed between each adjacent pair of pips 24 is a respective through hole 26 in the plate; these being the holes through which the pins 10 can be passed for forming the electrical connections between the contact wires.

The arrangement of the studs 22, pips 24a,24b and holes 26 is shown to a much enlarged scale in Fig 4.

This figure also shows the means by which the contact wries 14 are normally anchored to the insulation plates 18 in our known device. Each contact wire 14 is bent in the general form of a hairpin, with the bends forming the solder tags 20 which extend laterally from the stack of plates 18 as shown in Figs 1 and 2. As shown in Fig 4, the two legs 14a,14b of the hairpin contact wires each contain a double kink which engages resiliently between one of the studs 22 and the adjacent pair of pips 24a,24b so as to resist longitudinal displacement of the contact wire from its operational position shown, in which the two legs 14a,14b lie over two diametrically opposite regions of all the holes 26 in a given row thereof, whereby pins 10 inserted into any of the latter holes 22 are resiliently engaged on two opoosite sides by the two legs of that contact wire.

The latter system works very well. However, problems are occasionally associated with the known design as follows.

Firstly, it has been encountered that one or both of the pips 24a,24b have sheared off after a period of use so that the hairpin contact wire can then move longitudinally from its intended operational position.

Secondly, as will be apparent from Fig 4, the portions of the hairpin contact wires adjacent to the kinked region, which locate the contact wire by engagement with the studs and pips, are distorted compared to straight portions of the wires further away from the kinked region. Thus, in the case of the two holes marked 26 in Fig 4 the portions of the hairpin contact wires which cross these holes are bent and are tending to extend away from these holes. This can be compared to the situation at the left hand hole (marked 26a) in the case of which the relevant portions of the contact wire are straight and parallel. The result is that the spring contact pressure of the legs of the contact wires with pins 10 inserted in the holes 26 is less reliable in the case of holes close to the kinked portions than in the case of the other holes which are remote from the kinked portions.

It would thus be advantageous to have an alternative means of fixing the contact wires in their operational positions which avoids the necessity for having kinked portions and which does not rely on engagement of the contact wires with the pips 24.

In accordance with the present invention, in a plugboard system of the type described, having a plurality of hairpin shaped contact wires disposed in parallel sets between pairs of stacked, parallel insulation plates containing arrays of aligned through holes for the reception of shorting plugs, each hairpin contact wire projecting from two opposite sides of the stack and being located longitudinally relative to the stacked insulation plates by mechanically coupling together the two projecting legs of the hairpin contact wire at the two opposite sides of the stack, respectively.

In one embodiment, in addition to the two projecting legs of each individual hairpin being mechanically coupled at the two sides of the stack, all of the contact wires in a given set are mechanically coupled together at both sides of the stack, respectively.

Preferably, the mechanical coupling of the individual legs is achieved by soldering the respective two legs together.

Preferably, the mechanical coupling of the set of wires is achieved by the use of a strip of an insulating material, such as glass-loaded epoxy.

Preferably, the strip contains flexible portions disposed respectively between adjacent pairs of the contact wires so that mutual relative displacement of the wires is accommodated by the flexibility of the strip.

In another embodiment, the mechanical coupling of the individual legs and also the mechanical coupling of the set of contact wires is achieved by the use of printed circuit board strips having holes through which the legs of the contact wires extend, the boards having respective conductive areas which interconnect the individual pairs of legs in the case of each contact wire and which provide a conductive region for the reception of additional circuit connections.

In another embodiment the individual pairs of contact wire legs are interconnected by respective clamping elements having the shape of spade type connector sockets.

In a still further embodiment, the individual pairs of contact wire legs are interconnected by positioning around the pairs of legs projecting from the stack a respective miniature helical coil spring which is soldered to the legs such as to leave an unsoldered resilient portion between the soldered portion and the adjacent face of the stack, whereby each hairpin contact wire is capable of some longitudinal movement relative to the stack against the resilient compression of the unsoldered portions of the springs.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which: Fig 1 is a perspective view of part of our known plugboard switching system; Fig 2 is a perspective, cut-away view of the plugboard device of Fig 1; Fig 3 is a plan view of one of the insulating plates forming the plugboard device of Figs 1 and 2; Fig 4 shows a detail of the known plugboard device of Figs 1 to 3; Fig 5 is a front view of an insulating strip used in a first embodiment of the present invention; Fig 6 is a plan view of a plugboard utilising the strip of Fig 5 for securing the contact wires; Fig 7 is a plan view of a plugboard incorporating a second means in accordance with the present invention for securing the contact wires;; Fig 8 is an end view illustrating the use of a metal clip to secure the contact wires in accordance with a further embodiment of this invention; Fig 9 is a plan view of a plugboard utilising metal clips of the form shown in Fig 8; Fig 10 is a plan view of a plugboard utilising printed circuit boards to secure the contact wires in accordance with a still further embodiment of the invention; Fig 11 is a front view, to a larger scale, of one of the printed circuit boards of the embodiment of Fig 10; and Fig 12 is a section on line A-A in Fig 11.

In the embodiment of Figs 5 and 6, the metal contact wires 20 in a given plane are secured in their operational positions in the plugboard using a pair of glass loaded epoxy strips 30a 30b. As shown in Fig 5, each strip 30 has a plurality of pairs of through-holes 32, the spacing between the holes of each pair corresponding to the lateral separation of the two legs of the hairpin-shaped contact wires 20.

At a region intermediate each pair of holes 32, the strip 30 has a respective narrowed portion allowing some flexibility between the adjacent portions of the strip containing the holes 32. As indicated in Fig 6, each hairpin contact wire 20 is fitted through a respective pair of apertures 32 in the first strip 30a and then between a pair of adjacent plugboard insulation panels 18 in the usual way. The second strip 30b is applied over the free ends of that contact wire extending from the opposite side of the plugboard. Solder is applied at 34a,34b in order to prevent the contact wire from being withdrawn longitudinally from the plugboard, although leaving small gaps 36a,36b to allow a small amount of longitudinal freedom for the wires 20.

It will be understood that it is no longer necessary with this construction to make use of the pips 24 for the purposes of securing the contact wires, those pips then serving only to maintain the lateral separation between the two legs of the hairpin wire. Thus, the legs of the hairpin wire can remain straight and parallel over their whole length whereby to subject the contact pins to a uniform pressure right across the plugboard.

Fig 7 shows an alternative structure for achieving the same effect. In this case, there is positioned on the two ends of the hairpin contact wires projecting from the plugboard block a respective metal coil spring 38a,38b, the outer end of which is in each case soldered to the contact wire 20. The size of the coil springs 38 is chosen so as to leave a small clearance between its inner end and the adjacent face of the plugboard so that a small amount of longitudinal movement of the contact wire can occur before the spring 38a or 38b engages the plugboard body. Any further longitudinal movement of the contact wire then compresses the spring 38a or 38b depending upon the direction of movement. Thus, this arrangement provides longitudinal spring-loading of the contact wires such that movement of one contact wire 20 can occur without affecting any other contact wire.

Fig 8 shows a further alternative which uses metal clips 40a,40b to secure the two opposite ends of the hairpin contact wires 20 at the two sides of the plugboard body, respectively. As shown in Fig 8, each clip comprises a metal plate (of similar shape to a conventional spade terminal socket) which is clamped around the two legs of the wire as shown.

A still further alternative is shown in Figs 11 and 12. This is similar to the embodiment of Figs 5 and 6 but replaces the glass loaded epoxy strips of that embodiment with printed circuit board type strips 42a,42b. One such strip 42 is shown in more detail in Figs 11 and 12 and comprises a strip of printed circuit board 44 having printed on its one surface a plurality of conductive, solderable areas 46 which include a pair of through-holes 48a,48b for receiving the two legs of a hairpin contact wire therethrough and a second through-hole 50 serving as a connection hole for receiving one or more circuit leads. As shown in Fig 12, it is preferred for the holes 48a,48b to be through-plated. However, the overflow of through plating onto the undersurface of the printed circuit board 44 should be as small as possible.

Claims (10)

1. A plugboard system, having a plurality of hairpin shaped contact wires disposed in parallel sets between pairs of stacked, parallel insulation plates containing arrays of aligned through holes for the reception of shorting plugs, each hairpin contact wire projecting from two opposite sides of the stack and being located longitudinally relative to the stacked insulation plates by mechanically coupling together the two projecting legs of the hairpin contact wire at the two opposite sides of the stack, respectively.

2. A plugboard system as claimed in claim 1, wherein the mechanical coupling of the individual legs is achieved by soldering the respective two legs together.

3 A plugboard system as claimed in claim 1 or 2, wherein, in addition to the two projecting legs of each individual hairpin being mechanically coupled at the two sides of the stack, all of the contact wires in a given set are mechanically coupled together at both sides of the stack, respectively.

14. A plugboard system as claimed in claim 3, wherein the mechanical coupling of the set of wires is achieved by the use of a strip of an insulating material.

5. A plugboard system as claimed in claim 14, wherein said insulating material is a glass-loaded epoxy.

6. A plugboard system as claimed in claim 4 or 5, wherein the strip contains flexible portions disposed respectively between adjacent pairs of the contact wires so that mutual relative displacement of the wires is accommodated by the flexibility of the strip.

7. A plugboard system as claimed in claim 3, wherein the mechanical coupling of the individual legs and a]so the mechanical coupling of the set of contact wires is achieved by the use of printed circuit board strips having holes through which the legs of the contact wires extend, the boards having respective conductive areas which interconnect the individual pairs of legs in the case of each contact wire and which provide a conductive region for the reception of additional circuit connections.

8. A plugboard system as claimed in claim 1, wherein the individual pairs of contact wire legs are interconnected by respective clamping elements having the shape of spade type connector sockets.

9. A plugboard system as claimed in claim 1, wherein the individual pairs of contact wire legs are interconnected by positioning around the pairs of legs projecting from the stack a respective miniature helical coil spring which is soldered to the legs such as to leave an unsoldered resilient portion between the soldered portion and the adjacent face of the stack, whereby each hairpin contact wire is capable of some longitudinal movement relative to the stack against the resilient compression of the unsoldered portions of the springs.

10. A plugboard system substantially as hereinbefore described with reference to and as illustrated in any of Figs. 5 to 12 of the accompanying drawings.