ZERO INSERTION FORCE ELECTRICAL CONNECTOR

Abstract: The connector has an insulating housing (10) having a channel (18) for receiving a circuit board (not shown). A cam follower (14) is movable by a cam (12) between a first position in which contact springs (50) of terminals (16) in the housing (10) are in an open position in which the circuit board can be inserted into the channel (18) with substantially zero insertion force and a second position in which the contact springs (50) are in a closed position so as to engage the circuit board. To ensure that the cam follower (14) is positively returned to its second position and is not subject to unintended move­ ment therefrom, e.g. as a result of vibration, the cam follower (14) has a hooked extension (40) which is engageable by the cam (12) to return the cam follower (14) and to secure it in its second position.

Description: Zero insertion force electrical connector. We have described in EP-A1-78300558.0, a zero insertion force circuit board edge electrical connector, comprising an insulating housing having an elongate opening for receiving a circuit board along a board insertion path; at least one row of electrical terminals positioned beside the opening and extending in the longitudinal direction thereof, each terminal having a resilient contact portion for engaging the circuit board when such has been inserted into the opening along the insertion path; a groove formed in the bottom of the opening and extending longitudinally thereof; an elongate cam mounted for rotation about its longitudinal axis in the groove and extending longitudinally thereof; and a cam follower having a first surface engaging the cam, the cam follower being displaceable normally of the base of the groove by rotation of the cam, to cause the cam follower to move between a first position in which it displaces the contact portions from the insertion path and a second position in which the cam follower is retracted to allow the contact portions to intersect the insertion path. The use of a rotary cam as opposed to a linear action cam has the advantages that no space is required to accommodate reciprocating movement of the cam and that the cam can be of very simple construction, being for example of oblong or of substantially eliptical, cross-section. However, in this known connector, the cam follower is returned from its first to its second position by virtue of the resilience of the contact portions of the terminals, which resilience also serves tO maintain the cam follower in its second position. It s been found, that their exercise of this return function tends to cause the contact portions to loose resilience with the result that the cam follower, after an extended period of use of the Qannestar, can no longer be fully returned to its second position so that the connector becomes inoperative, or the cam follower is readily displaced from its second position Especially where the connector is subjected to vibration whilst in use or is mounted so that the return of the cam follower is not assisted by gravity, this latter disadvantage will result in intermittent impairment of the integrity of the electrical connections between the contact portions and the conductors of the circuit board. According to the present invention therefore a connector as defined in the first paragraph of this specification is characterised in that the cam follower has a second surface spaced from the first surface towards the base of the groove and which is engageable by the cam, as the cam is rotated to cause the cam follower to move from its first to its second position1 so that the cam positively drives the cam follower to its second position, in which position the second surface engages the side of the cam nearest to the base of the groove so that the cam follower is secured in its second position by the cam, against unintended movement. Although DE-A-2,707,122 discloses a zero insertion force electrical connector, in which a cam follower acting upon the contact portions of the terminals of the connector is positively driven by means of a cam, the cam is a linear action cam, and the cam follower could not be positively driven by ##a#s of a rotary cam. US-A-3,596,230, US-A-3,899,234, US-A-4,047,782 an# US-A-4,069,403 are also representative of the current general state of the art. tor a better understanding of the invention an embodiment thereof will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 is a perspective sectional view of 4 #ero in#ertion force circuit board edge electrical connector; Figure 2 is a longitudinal, vertical sectional view through an end portion of the connector; Figure 3 is an enlarged perspective, sectional view of a cam and a cam follower of the connector; and Figures a to 4 are cross-sectional views of the connector illustrating the operation thereof. The connector comprises an insulating housing 10 a cam 12, a cam follower 14 and a plurality of electrical terminals 16. The housing 10 defines an elongate central opening for receiving an edge portion of a circuit board 20 tri sure long a board insertion path A, a row of spacer members 22 on each side of the opening 18 defining recesses 24 each receiving a terminal 16 extending through a passage 26 in the base 27 of the housing lOr which passage communicates with the recess 24. The opening 18 communicates with a groove 28 formed in the base 27, which defines the bottom of the opening 18, the groove 28 extending longitudinally thereof The groove 28 receives the cam 12 for free rotation therein. At each end thereof the housing 10 has a mounting lug 30 (only one is shown) with a screw hole 32. The cam follower 14 (best seen in Figure 3), which is channel-shaped, comprises a base 34 having parallel side walls 36 and 38, extending in the same direction from the base 34, a wall 40 extending from a flat, cam engagement surface 35 of the base 34, in alignment with, and in the opposite direction to, the side wall 36 and terminating in an inwardly directed flange 42 having a flat, inner abutment surface 43 parallel to, and overlapping the base 34. The base 29 of the groove 28 has therein a longitudinal recess 44 dimensioned to receive the flange 42. The base 34 of the cam follower 14 is disposed in the groove 28 so that the surface 35 of the base 34 is engaged by the cam 12, the wall 40 protruding into the groove 28 beside the cam 12. The cam 12, which is elongate in the direction of the groove 28 and which can be rotated from outside the housing 10 as shown in Figure 2, is of elongate cross-section having parallel major sides 45 and convex minor sides 47. The surface 35 of the base 34 is spaced from the surface 43 of the flange 42 by a distance slightly exceeding that between the major sides 45 of the cam 12, the flange 42 overlapping-the base 34 by a distance which does not exceed that between the sides 45. The terminals 16 are in the form of metal strips having looped resilient contact portions 50 within the housing, free end portions 52 of the contact portions 50 engaging chamfered outer sides of the free longitudinal edges of the side walls 36 and 38 of the cam follower 14. The terminals have locking tongues 54 on.post portions 56 thereof, which portions extend through the passages 26, the tongues 54 serving to retain the terminals 16 in the housing 10. Figure 4 shows the cam follower 14 in a first position in which it has been advanced normally of the base 29 of the groove 28, by the cam 12 so that the side walls 36 and 38 of the cam follower have spread apart the contact portions 50, displacing them from the insertion path A, to allow entry of the board 20 into the opening 18 along such path, with substant zero insertion force. So to advance the cam follower 14, the cam 12 was rotated in an anticlockwise (as seen in Figures 4 to 6) sense, to an extent limited by a stop 58 on the left hand (as seen in Figures 4 to 6) side of the groove 28. As the cam 12 is rotated in the opposite sense, to retract the cam follower 14 in the groove 28, normally of the base thereof, to a second position, so as to allow the contact portions 50 to close so as to intersect the path A of the board 20 (which is not shown in Figures 4 to 6), one major side 45 of the cam 12 engages the flange 42, as shown in Figure 5, to drive the cam follower 14 positively towards the base of the groove 28, until, as shown in Figure 6, the flange 42 is fully received in the recess 44 and the major sides 45 of the cam 12 are in full surface to surface engagement with surface 35 of the cam follower 14 and with the base 29 of the groove 2 respectively1 one convex minor side of the cam 12 being received between the base 34 and the flange 42. In the second position of the cam follower 14, the surface 43 of the flange 42 engages the side 45 of the cam 12, nearest to the base 29 of the groove 28 r as shown in Figure 6, so that the cam follower 14 is locked in its second position by the cam 12. Since the cam follower 14 is positively driven by the cam 128 in the event that the contact portions 50 should loose resilience through use, they are nevertheless returned fully to their closed positions so as to apply the required contact force against the conductors of the board 20, even in the event that the connector is mounted in an orientation in which the return of the cam follower is not assisted by gravity. By virtue of the engagement of the cam 12 against the surface 43 of the flange 42, in the second position of the cam follower 14, the cam follower 14 is secured in its fully retracted position so that it cannot be unintentionally moved under the action of vibration for example, so as to impair the integrity of the electrical connections between the contact portions 50 and the conductors of the circuit board 20. For making connection to only one side of a circuit board, the connector may have only one row of terminals, one side of the cam follower being omitted and the base thereof on that side being arranged to slide against a blank wall of the housing.

Claims: Claims: 1. A zero insertion force circuit board edge electrical connector, comprising an insulating housing (10) having an elongate opening (18) for receiving a circuit board (20) along a board insertion path (A); at least one row of electrical terminals (16) positioned beside the opening (18) and extending in the longitudinal direction thereof, each terminal (16) having a resilient contact portion (50) for engaging the circuit board (20) when such has been inserted into the opening (18) along the insertion path (A); a groove (28) formed in the bottom (27) of the opening (18) and extending longitudinally thereof; an elongate cam (12) mounted for rotation about its longitudinal axis in the groove (28) and extending longitudinally thereof; and a cam follower (14) having a first surface (35) engaging the cam, the cam follower (14) being displaceable normally of the base (29) of the groove (28), by rotation of the cam (12), to cause the cam follower (14) to move between a first position in which it displaces the contact portions (50) from the insertion path (A) and a second position in which the cam follower (14) is retracted to allow the contact portions (50) to intersect the insertion path (A); characterised in that the cam follower (14) has a second surface (43) spaced from the first surface (35), towards the base (29) of the groove (28) and which is engageable by the cam (12), as the cam (12) is rotated to cause the cam follower (14) to move from its first to its second position, so that the cam (12) positively drives the cam follower (14) to its second position, in which position the second surface (43) engages the side of the cam (12) nearest to the base (29) of the groove (28) so that the cam follower (14) is secured in its second position by the cam (12), against unintended movement. 2. A connector according to Claim 1, characterised in that the cam follower (14) comprises a first wall (36) extending from a base (34) for engagement with the contact portions (50), and a second wall (40) extending from the base (34) in the Opposite direction to the first wall (36), the second surface 5) being provided on a flange (42) on the second wall (40) the flange (42) overlapping the base (34) and being spaced therefrom. 3. A connector according to Claim 2, characterised in that the cam (12) is of elongate cross-section having a pair of parallel major sides (45) and a pair of convex minor sides (47), the base (34) of the cam follower (14) being spaced from the flange (42) by a distance slightly exceeding that between the minor side of the cam (12), the length of the flange (42) r as seen in cross-section through the cam follower (14), being such that one minor side (47) of the cam (12) is received between the base (34) and the flange (42) in the second position of the cam follower (14) 4. A connector according to Claim 2 or 3, characteris-ed in that a recess (44) formed in the base (29) of the groove (28) is -adapted to receive the flange (42) in the second position of the cam follower (14). A A connector according to any one of the preceding claims, characterised in that one side wall of the groove (28) is provided with a stop (58) to prevent tether rotation of the cam (12) in the same sense after it has moved the cam follower (14) from its second to its first position. A connector according to any one of the preceding claims, characterised in that the first (35) and second (43) surfaces of the cam follower (14) are flat and are parallel to one another. 7. A connector according to Claim 1, in which the cam follower (14) comprises a channel-shaped insulating member comprising a base (34) from one side of which a pair of parallel side walls (36 and 38) extend in the same direction, the other side (35) of the base (34) being flat; characterised in that a single further wall (40) extends from the other side of the base (34) of the cam follower (14) in alignment with one (36) of the side walls (36 and 38) but in the opposite direction thereto, the further wall (40) terminating in a flange (42) extending substantially normally. of the further wall (40) and overlapping the base (34) by a distance which does not exceed that between the flange (42) and the base (34), the flange (34) presenting towards the base a flat surface (43) which is parallel to the other side (35) of the base (34).

Inventors: SHOWMAN, ROBERT LINN, WEBER, ROBERT NEY
Applicants: AMP INCORPORATED
Application year: 1981
Main classification: H01R13
IPC codes: H01R24, H01R12