EP0083862B1

EP0083862B1 - Improvements in and relating to printed-circuit board edge connectors

Info

Publication number: EP0083862B1
Application number: EP19820306849
Authority: EP
Inventors: John Angus Robertson
Original assignee: Unisys Corp
Current assignee: Unisys Corp
Priority date: 1981-12-22
Filing date: 1982-12-21
Publication date: 1988-10-19
Also published as: DE3279143D1; GB2113018B; EP0083862A2; EP0083862A3; GB2113018A

Description

The present invention relates to connectors for providing a plurality of simultaneous electrical connections to a printed circuit board by the insertion therein of an edge of the printed circuit board.
It is well known to employ an edge connector for providing plural simultaneous electrical connections to a printed-circuit board.
The edge of the board is provided with an array comprising a plurality of spaced contact pad areas. The areas are in general gold plated or plated with any other corrosion-resistant substance which is suitable for providing electrical connection. The connector comprises a correspondingly spaced array of spring contacts. The edge of the board is inserted into the connector to compress the spring contacts and bring each one of the contact pads into sliding engagement with a corresponding one of the spring contacts. The spring contacts are in general also plated with gold or any other corrosion resistant electrical conductor.
The spring contacts on the connector are generally arranged in opposed pairs such that one spring contact in each pair opposes the other through the thickness of the board. The pairs are regularly spaced along the length of the edge of the board. When the board is not therebetween the opposed members of each pair, being in a non-compressed condition, approach one another closely but do not touch. Even when non-compressed there is generally some residual force pushing each spring contact against stops in their housing such that it requires a definite starting force to initiate the separation of a pair.
In order to insert the board between the pairs it is necessary first to separate the pairs without damage thereto. To this end the board is generally provided with chamfers on its insertable edge. The contact pads reach right to the edge of the chamfers. By the time the spring contacts have been separated by the chamfers they are in contact with the leading edges of the pads and are also exerting maximum restoring force. High attritional wear therefore occurs where the pads meet the chamfers. Having been inserted to the ends of the chamfers the board is further introduced between the pairs of spring contacts until each spring contact lies centrally on a corresponding one of the connector pads on the board. During this further introduction the pairs exert maximum restoring opposing forces against one another causing considerable and undesirable attritional wear as each spring contact slides against its pad. Plastic flow of the non-corrosive electrically conducting layer can also occur.
The attrition of the surfaces of both the spring contacts and the pads causes the exposure to air of the underlying non-noble substrata which then become liable to atmospheric oxidation bringing about a degradation of the electrical conductivity of the spring contact to pad interface.
The plastic flow of the non-corrosive layers renders their thickness less along the path of sliding engagement between each spring contact and its corresponding pad. The layers are therefore subject to a greater susceptibility to disappearance by attrition.
In the presence of possible oxidation the reliability of an edge connector decreases rapidly. When there are plural sets of contacts the chances of all sets simultaneously providing satisfactory operation is unacceptably small.
It has been one solution to the above problem to offset the effects of oxidation by arranging that the force between opposing pairs of spring contacts is very large indeed so that any oxide layer is broken up and the heat generated by friction causes small areas of air-excluding spring-to-pad welds. This approach causes the insertion force of a board into a connector to be extremely large and the withdrawal force correspondingly great. The rate of wear on the spring contacts and pads is enormous so that only a limited number of insertions and withdrawals is possible before a board and connector combination has to be discarded. The boards and connector housings must be unnecessarily mechanically strong to withstand the forced exerted thereon.
It has been another approach to provide that separate means is provided for lowering the spring contacts onto the board by the use of manually operable levers and the like. This approach relieves attritional wear but substitutes complexity and high cost, the connectors themselves taking up much space. Consequently, although successful, this approach is reserved for test equipment for testing boards.
It is therefore desirable to provide an edge connector of simple construction and small size for the insertion therein of a board for the establishing of electrical connection therebetween with substantially no sliding between spring contacts in the connector and contact°pad areas on the board.
European Patent Application 0,030,222 discloses a non-attritional printed circuit board edge connector which requires the inclusion of.a resilient arm. The present invention seeks to provide an improvement thereover by eliminating the need for a resilient arm, the resilient arm being instead a rigid arm and the spring connector designed to engage the margin of the printed circuit board also acting to move the arm over the entire extent of its motion during insertion or retraction of a printed circuit board.
German Patent Application 2,341,770 discloses a non-attritional printed circuit board edge connector wherein a pair of opposed arms having protrusions at their distal ends for engaging the edge of a printed circuit board and moving spring contacts apart to allow attrition-free entry of the printed circuit board therebetween and thereafter for entering an aperture in the printed circuit board to allow the spring contacts to engage opposite faces of the margin of the printed circuit board are urged together by a U-shaped spring. The present invention seeks to provide improvement thereover by eliminating the U-shaped spring and allowing the spring contacts themselves to urge the arms together over the full extent of their range of movement.
United States Patent 3,858,857, Figs. 5 to 8 thereof disclose an attrition-free printed circuit board edge connector wherein first and second opposed resilient arms are urged apart by protrusions at their distal ends engaging the leading edge of a printed circuit board in turn to urge apart spring contacts for the spring contacts to stand clear of the opposite faces of the printed circuit board until the protrusions enter a hole in the printed circuit board allowing the spring contacts to engage the opposite faces of the printed circuit board. The present invention seeks to provide improvement thereover by arranging that the arms are rigid and are provided with elastic force urging them together over the full extent of their range of movement by the spring contacts themselves.
United Stated Patent 3,594,699 discloses an attrition-free printed circuit board edge connector wherein first and second opposed protrusions proximate to the distal ends of first and second opposed arms are first forced apart by the edge of an entering printed circuit board for first and second spring contacts to clear opposite faces of the printed circuit board and thereafter enter a hole in the printed circuit board to allow the spring contacts to engage their respective faces of the printed circuit board. The present invention seeks to provide improvement thereover by arranging that the spring contacts urge together the two arms over the full extent of their range of movement.
United States Patent 3,710,303 discloses yet another attrition-free printed circuit board edge connector where forced-apart protrusions at the distal ends of resilient arms move first and second spring contacts away from the first and second faces of the printed circuit board and thereafter enter a hole in the printed circuit board to allow the spring contacts to engage their respective faces of the printed circuit board. Once again the present invention seeks to provide -improvement thereover by obviating the necessity for resilient arms allowing the use of rigid arms elastically urged towards one another over the full extent of their range of movement by the spring contacts themselves.
United States Patent 2,811,700 discloses a printed circuit board edge connector wherein a plurality of spaced spring contacts bear against a fixed housing. A leading edge of a printed circuit board displaces rollers which move bars pulling apart all of the spring contacts to clear the edge of the board. After the board has been inserted a predetermined distance the rollers fall into notches in the circuit board along the spring contacts to engage contact pads on either face of the board. The present invention seeks to provide improvement thereover by providing means whereby the spring contacts are not required to engage a fixed housing and are instead supported on rigid arms.
The present invention consists in a system wherein a connector provides electrical connection to a margin of a printed circuit board; wherein first and second opposed protrusions respectively provided at the distal ends of first and second opposed rigid arms pivotal with respect to a base member are operative to be engaged by a leading edge of the printed circuit board and to move first and second opposed spring contacts respectively away from a first connecting pad on a first face of the printed circuit board and a second connecting pad on a second face of the printed circuit board; and wherein, said edge of the printed circuit board having been inserted a predetermined distance between said protrusions, said first and second protrusions are operative to enter a hole in the printed circuit board to allow said first and second spring contacts respectively to engage said first and second contact pads; said system being characterised by said arms being urged towards one another only by said spring contacts.
In a preferred embodiment first and second lever arms are rigid and pivoted at their ends remote from the direction of entry of a board into the connector. First and second spring contacts are preferably associated with the first and second lever arms respectively. The spring contacts preferably urge the lever arms together. The spring contacts preferably engage the lever arms by means of catches near to the end wherefrom a board enters the connector. The first and second lever arms comprise first and second cutaways respectively to form a common void. The first and second lever arms comprise first and second protrusions respectively at the end wherefrom a board is inserted into the connector and, when urged together by the spring contacts, the protrusions meet to press against one another. The first and second spring contacts preferably comprise first and second contact sections. The contact sections preferably protrude into the common void. When both the first and second lever arms are urged together by the spring contacts, the contact sections are preferably non- contiguously proximate to one another in the void. The first and second protrusions preferably comprise first and second entry ramps which co-operate to force the lever arms apart when the edge of a board is introduced thereto. The protrusions preferably comprise a bearing surface for pushing against one another and for pushing against a board. The first and second protrusions preferably comprise first and second exit ramps for pushing the protrusions apart whenever a board which has been inserted into the connector is withdrawn therefrom.
In the preferred embodiment the printed-circuit board comprises a leading edge. The leading edge is preferably unchamfered. A plurality of contact pads are preferably provided along the leading edge. The contact pads are preferably evenly spaced along the leading edge. Each end of the leading edge is preferably provided with a tab sharing an end portion of the leading edge. The tab preferably extends backwards from the leading edge for a distance a little less than the extent of the common void. Behind the tab there is preferably provided a gap large enough for the protrusions to touch one another therethrough.
The connector of the preferred embodiment preferably comprises first and second members comprising first and second contact-spacing bars respectively. The contact separating bars preferably run the length of the connector. Each contact-spring bar preferably comprises a lever arm at each end so that the entire connector comprises two opposed contact separating bars and four lever arms. The spring contacts preferably engage the rear of the contact-spacing bars. When the lever arms are separated the contact bars preferably move all of spring contacts on their respective sides of the connector together.
In the operation of the preferred embodiment the leading edge of the board is preferably intro-- duced to the first and second entry ramps of the closed first and second lever arms respectively, and forced therebetween to push the protrusions apart. The board is thereafter insertable therebeyond. In being pushed apart, the first and second lever arms pull the first and second contact sections of the first and second spring contacts respectively far enough apart to avoid contact with a board as it is inserted into the connector. The board is preferably insertable until the leading edge engages the remote boundary of the common void. As the board engages the remote edge of the common void, the first and second protrusions fall behind the tab into the gap allowing the first and second lever arms to come together and allowing the plurality of contact sections of the plurality of spring contacts on both sides of the board along the length of the contact-spacing bars to oppose one another on opposite sides of the board for each spring contact to connect with a corresponding contact pad.
In the preferred embodiment the connector preferably comprises a common housing for the protection of the spring contacts. In a first pre- . ferred manner of mounting for the lever arms, the first lever arm is preferably affixed to the second lever arm by means of a pivot. The second lever arm is preferably a little longer than the first lever arm and is preferably affixed within the housing leaving only the second lever arm free to move within the housing. The housing is preferably U-shaped being open in the direction of insertion of a board.
In a second preferred manner of mounting for the lever arms both the first and second lever arms are provided with pegs which fit loosely into corresponding recesses in the housing and allow a degree of rotation of each lever arm relatively to the housing
In the preferred embodiment whenever an inserted board is to be withdrawn from the connector the rear of the tab or the edge of the hole in the board engages the exit ramps on the first and second lever arms forcing them apart with progressive withdrawal of the board and thereby disengaging the contact sections of the spring contacts from the pads on the board. Thereafter the board is withdrawable from between the lever arms without any engagement with the spring contacts, the lever arms closing behind the leading edge of the board as the leading edge of the board is removed from the entry ramps.
The present invention is further explained, by way of an example, by the following description read in conjunction with the appended drawings, in which:

Figure 1 shows a cross sectional view of the active members of the connector of the preferred embodiment.
Figure 2 shows a plan view of the printed-circuit board of the preferred embodiment.
Figures 3A to 3C show three successive stages in the insertion of a board according to figure 2 into the connector according to figure 1.
Figure 4 shows the connector of figure 1 in its housing.
Figure 5 shows a first manner of mounting the connector of figure 1 in its housing.
Figure 6 shows a second manner of mounting the connector of figure 1 in its housing.
Figure 1 shows a cross sectional view of the active members of the connector of the preferred embodiment.

The active assembly 8 comprises a first lever arm 10 and a second lever arm 12. The first and second lever arms 10, 12 are pivoted about their basal ends 13 in a manner to be described later so that they can swing apart from one another at their non-basal ends.
The first lever arm 10 comprises a first protrusion 14 extending towards the second lever arm 12. The second lever arm 12 comprises a second protrusion 16 extending towards the first lever arm 10. Both the first protrusion 14 and the second protrusion 16 are proximate to the non-basal ends of the first lever arm 10 and the second lever arm 12 respectively.
The first protrusion 14 comprises a first entry ramp 18 extending diagonally from the tip of the first lever arm 10 towards the second lever arm 12. The second protrusion 16 has a second entry ramp 20 extending from the tip of the second lever arm 12 towards the first lever arm 10 in a complementary manner to the first entry ramp 18 so that together they form a concave wedge symmetrical about the line of contiguity between the first and second lever arms 10, 12.
A common void 22 is formed by the provision of complementary cutaway sections in the first and second lever arms 10, 12 to the basal side of the first and second protrusions 14, 16 respectively.
The basal boundary of the first protrusion 14 with the common void 22 is provided in the form of a first exit ramp 24 which extends diagonally towards the second lever arm 12 in the general direction of its tip. The basal boundary of the second protrusion 16 with the common void 22 is provided in the form of a second exit ramp 26 which extends diagonally towards the first lever arm 10 in the general direction of its tip and which is complementary to the first exit ramp 24 such that together they form a concave wedge, when viewed from their basal ends, which is symmetrical about the line of contiguity between the first and second lever arms 10, 12.
A first spring contact 28 is provided in association with the first lever arm 10 and a second spring contact 30 is provided in association with the second lever arm 12. The first spring contact 28 as illustrated is in fact representative of a plurality of spring contacts stretching across the width of a connector in a manner which will be made clear in later description. The second spring contact 30 is similarly representative of a plurality of such contacts.
The first spring contact 28 comprises a first contact section 32 extending towards the second lever arm 12 in the area of the common void 22. The second spring contact 30 comprises a second contact section 34 extending towards the first lever arm 10 in the area of the common void. When the first and second lever arms 10, 12 are closed together the first and second protrusions 14,16 meet preventing closer approach of the first and second lever arms 10, 12 in which position the first and second contact sections 32, 34 fail to meet by a distance less than the thickness of a board.
The first lever arm 10 is provided with a first contact spacing bar 36. The first spacing bar 36 extends across the entire width of a connector in a manner which will become clear on reading later description. The first spring contact 28 engages the side of the first spacing bar 36 remote from the second lever arm 12 to urge the first lever arm 10 towards the second lever arm 12.
The second lever arm 12 is provided with a second contact spacing bar 38 which is extensive across the entire width of a connector in the same manner as the first contact spacing bar 36. The second spring contact 30 engages the side of the second contact spacing bar 38 remote from the first lever arm 10 to urge the second lever arm 12 towards the first lever arm 10.
It is to be appreciated that the engaging of the first contact spacing bar 36 by the first spring contact 28 is representative of such engagement by a plurality of similar spring contacts across the width of a connector and that the engaging of the second contact spacing bar 38 by the second spring contact 30 is representative of such engagement by a plurality of such spring contacts across the width of a connector.
Figure 2 shows the board of the preferred embodiment.
A printed circuit board 40 for the construction thereon of electrical or electronic circuits comprises a leading edge 42 for insertion into an electrical connector for the provision of electrical contacts to the board 40.
A plurality of contact pad areas 44 are provided adjacent to the leading edge 42. The areas 44 need not necessarily be contiguous with the leading edge 42. The areas 44 are arranged with a regular spacing along the leading edge 42, and are on both faces of the board 40.
At either end of the leading edge 42 the board 40 is provided with a tab 46. The tab 46 is rectangular and shares one of its edges with the leading edge 42. The tab 46 extends backwards from the leading edge 42 by a distance which would allow the tab 46 to rest within the common void 22 of figure 1.
To the rear of the tab 46 the board 40 is provided with a gap 48. The width and disposition of the gap 48 is such that, if the tab 46 is resting within the common void 22, the first and second protrusions 14,16 are able to meet within the gap 48.
Figure 3A shows the first stage of the insertion of a board 40 into the active assembly 8 of figure 1.
On the board 40 is inserted in the direction of the insertion arrow 50. The leading edge 42 of the board 40 engages the first and second entry ramps 18, 20 to separate the first and second protrusions 14, 16 which move apart to allow the entry of the tab 46 therebetween.
Figure 3B shows the second stage of the insertion of a board 40 into the active assembly 8 of figure 1.
In forcing apart the first and second protrusions 14, 16 the entering board 40 also forces apart the first and second lever arms 10, 12 which carry with them the first and second contact sections 32, 34 respectively which separate by a distance greater than the thickness of a board 40 to allow the insertion of the tab 46 between the first and second protrusions 14, 16 into the common void without abrasion between the contact sections 32, 34 and the pads 44.
Figure 3C shows the last stage in the insertion of a board 40 into the active assembly 8 of figure 1.
The tab 46 has passed entirely into the common void 22. The first and second protrusions 14, 16 have then been able to come together through the gap 48 allowing the restoration of the previous positions of the first and second second lever arms 10, 12. The contact sections 32, 34 are thereby allowed to impinge onto the board 40 to engage the pads 44 without significant sliding therebetween.
When it is desired to remove the board 40 the first and second exit ramps 24, 26 behave towards the edge of the tab 46 remote from the leading edge 42 of the board in the same way that the entry ramps 18, 20 behave towards the leading edge 42. The tab 46 causes the separation of the first and second protrusions 14,16 and the consequent separation of the first and second lever arms 10, 12 and of the first and second spring sections 32, 34 to allow the removal of the board 40 without abrasion between the contact sections 32, 34 and the pads 44.
It is to be appreciated that by suitable choice of elastic constant for the spring contacts 28, 30 and suitable choice of pretension when the lever arms 10, 12 are open and choice of the separation of the contact sections 32, 34 when the lever arms 10, 12 are closed without a board 40 therebetween, the contact sections 32, 34 can be caused to exert any desired pressure on the pads 44.
It is also to be appreciated that, although the leading edge 42 of the board is here shown as being unchamfered, there is nothing to prevent its being chamfered nor is there any reason why the edge of the tab 46 remote from the leading edge 42 should not be chamfered.
The tab 46 and the gap 48 are here shown as being substantially rectangular. It is to be appreciated that any other shape will suffice for them 46, 48 which allows for the mutual interaction of board 40 and active assembly 8 as described with relation to figures 3A, 3B and 3C.
The spring contacts 28, 30 and the pads 44 will in general be coated with an oxidation-resistant -layer of a noble metal such as gold.
The entry ramps 18, 20 and the exit ramps 24, 26 are here shown as planar. It is to be appreciated that many other shapes will suffice for these surfaces, the only requirement placed thereon being that the pair of entry ramps 18, 20 can co-operate to open the lever arms 10, 12 in response to the insertion of a board 14 and that the pair of exit ramps 24, 26 can co-operate to separate the lever arms 10, 12 in response to the withdrawal of a board 40. Whilst the two pairs 18, 20 and 24, 26 are here shown with reflective symmetry about the line of contiguity between the lever arms 10, 12, those skilled in the art will readily appreciate that the invention will function without such symmetry with modifications which will be apparant.
The invention is here described showing two sets of spring contacts 28, 20. It is to be appreciated that an active assembly 8 comprising only one set of spring contacts 28 can be provided for making contact with pads 44 on just one side of a board 40, in which case there is a necessity for just one pivotable lever arm 10, the other lever arm 12 being replaceable by an inert bearing surface, the inert surface being provided with a protrusion 16 as an optional feature.
Figure 4 shows the active assembly 8 of figure 1 in a protective housing.
The active assembly 8 is housed within a U-shaped protective housing 60. The active assembly 8 and the housing 60 together make up a connector. The housing 60 is in the form of a rectilinear, rectangular-cross-section U-shaped trough with the basal end 13 of the active assembly 8 attached to the base section 61 of the trough and the protrusions 14, 16 proximate to the open face of the trough such that a board 40 can be inserted through the open face of the trough into the active assembly 8 as described.
The active assembly 8 runs the entire length of the housing 60 by means of the contact spacing bars 36, 38 only one of which is clearly visible in figure 4. The spring contacts 28, 30 are regularly spaced along the contact spacing bars 36, 38 across the full width of the housing 60. A set of lever arms 10, 12 is provided at either end of the contact spacing bars 36, 38 and the two sets of lever arms 10, 12 co-operate on the insertion of a board in a manner which will be apparent to separate they contact spacing bars 36, 38 in the manner described.
Figure 5 shows a first manner of attaching the active assembly 8 in the housing 60.
The first and second lever arms 10, 12 are provided on their basal ends with first and second pegs 62, 64 respectively which provide a loose fit in first and second apertures 66, 68 in the base 61 of the housing 60. The pegs 62, 64 are so shaped with enlargements at their distal ends that they are not free to disengage the base 61. Being of a loose fit, the pegs 62, 64 allow for the mutual pivoting between the first and second lever arms 10, 12 required for the operation of the present invention.
There is of course no reason why the pegs 62, 24 should not entirely through-penetrate the base 61 of the housing 60.
The spring contacts 28, 30 pass right through the housing 60 and can be soldered to on the exterior of the housing.
Figure 6 shows a second manner of affixing the active assembly 8 within the housing 60.
The first lever arm 10 is attached to the second lever arm 12 by means of a pivot 70. The pivot 70 can range in complexity from a simple dimple-and-socket arrangement at either end of a pair of mouldings where a first moulding consists in a first lever arm 10 provided at either end of a first contact-spacing bar 36 and the second moulding consists in a second lever arm 12 provided at either end of a second contact spacing bar 38, one moulding snap-fitting inside the other, to a full hinge stretching the entire length of a connector. The second lever arm 12 is slightly longer than the first lever arm 10 and is-solidly and inflexibly affixed to the base 61 of the housing 60 to hold the first lever arm 10 a short distance clear of the base 61 for the first lever arm 10 to be free to pivot relative to the now unpivotable second lever arm 12. The second lever arm 12 can be affixed within the housing 60 in any suitable manner ranging from being an integral part of the housing (60) moulding by incorporation with its base (61) or one of its walls (71) to being pegged or glued into or onto the base (61). Once again the spring contacts (28, 30) through-penetrate the base (61) for soldering to external conductors outwith the housing, it being appreciated that connecting means other than those soldering are possible.
Those skilled in the art will appreciate that the manner of mounting shown in Fig. 6 can readily be adapted to do away with the housing (60) by the attachment of the basal end of the second lever arm (12) to any rigid support, the second lever arm (12) acting as the support for the first lever arm (10).
Whereas the present invention has been described with reference to the uses of a printed-circuit board (40) having a substantially straight leading edge (42) it is to be appreciated that with modifications which will be clear to those skilled in the art the invention can be made to function with leading edges of varied and different shapes. It will also be apparent that the printed-circuit board can be replaced by numerous other electrical component carriers, and one area of particular interest for the present invention is the provision of pluggable connections to very large scale integrated circuits up to the dimensions of an entire wafer.
The tabs (46) has so far been described as being of the same uniform thickness as the rest of the board (40). It is to be appreciated that the tabs (46) can be made with greater or lesser thickness than the board (40) to accommodate greater or lesser opening requirements for the arms (10, 12, 72, 74).
It is lastly to be appreciated that whereas the gaps (48) have been depicted as passing right through the board (40), the same function can equally be served by depressions that do not penetrate right through.

Claims

1. A system wherein a connector (10, 12, 32, 34, 60, 61, 14, 16) provides electrical connection to a margin of a printed circuit board (40); wherein first and second opposed protrusions (14, 16) respectively provided at the distal ends of first and second opposed rigid arms (10, 12) pivotal (62,64,70) with respect to a base member (60) are operative to be engaged by a leading edge (42) of the printed circuit board (40) and to move first and second opposed spring contacts (28, 30, 32, 34) respectively away from a first connecting pad (44, 96) on a first face of the printed circuit board (40) and a second connecting pad (44, 96) on a second face of the printed circuit board (40); and wherein, said edge (42) of the printed circuit board (40) having been inserted a predetermined distance between said protrusions (14, 16), said first and second protrusions (14, 16) are operative to enter a hole (48, 94) in the printed circuit board (40) to allow said first and second spring contacts (32, 34) respectively to engage said first and second contact pads (44, 96); said system being characterised by said arms (10, 12) being urged towards one another only by said spring contacts (32, 34).

2. A system according to Claim 1 further characterised by said second arm (12) being fixed in rigid relationship to said base member (61), and by said first arm (10) being affixed by a pivot (70) to said second arm (12) to rotate about a point proximate to the base of said second arm (12).

3. A system according to Claim 1 further characterised by said first arm (10) being attached to said base member (61) by a first peg (62) loosely fitting in a first aperture (66) in the base member (61) and allowing said first arm (10) a range of pivotal movement sufficient for insertion and withdrawal of the printed circuit board (40); and by said second arm (12) being attached to said base member (61) by a second peg (64) loosely fitting in a second aperture (68) in the base member (61) and allowing said second arm (12) a range of pivotal movement sufficient for inserted and withdrawal of the printed circuit board (40).

4. A system according to any of the preceding Claims wherein said base member (61) is a portion of a housing (60) incorporating walls (71) for protecting said first and second spring contacts (32, 34).

5. A system according to any of the preceding Claims wherein said connector comprises a third arm spaced along said connector from said first arm (10); wherein said connector comprises a fourth arm, opposed to said third arm; wherein a first contact spacer bar (36) is provided between said first (10) and third arms; wherein a second contact spacer bar (38) is provided between said second (12) and said fourth arms; wherein said first spring contact (28, 32) is one of a plurality of first spring contacts (28, 32) spaced along said connector, each of said plurality of first spring contacts (28, 32) being in engagement with said first contact spacer bar (36); and wherein said second spring contact (30, 34) is one of a plurality of second spring contacts (30, 34) spaced along said connector, each of said plurality of second spring contacts (30, 34) being in engagement with said second contact spacer bar (38).