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(11) | EP 0 002 114 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Zero insertion force printed circuit board edge connector |
| (57) The connector comprises a housing (12) containing a row of electrical contacts (18),
a cam (60) being rotatable about its own axis to raise a contact driving member (16)
to cam the contacts (18) away from a printed circuit board receiving channel (28)
formed in the housing (12) to allow the insertion of a printed circuit board into
the channel (28) without the board engaging the contacts (18), and to permit ready
removal of the board from the channel (28). To ensure that the contacts (18) are disengaged from the board only sequentially in groups, the contact driving member (16) is formed with relatively stepped, contact engaging, surfaces (47). |
[0001] We have disclosed in each of our United States Patent Specifications Numbers 3,899,234 and 4,077,688 a zero insertion force printed circuit board edge connector, comprising an insulating housing having a channel therein for receiving a printed circuit board along a board insertion path, a row of electrical contacts positioned beside the channel each having a contact surface for engaging the printed circuit board when such has been inserted into the channel, and a cam member movable to displace a contact driving member normally of the base of the channel to move each contact between a board receiving first position in which the contact surface of the contact is withdrawn from the board insertion path and a board engaging second position in which such contact surface intersects the board insertion path.
[0002] Such connectors, which are commonly used in electronic logic systems for the interconnection of circuitry thereof have the advantage that since the printed circuit board is inserted into the channel with the contacts in their first position, friction between the board conductors and the contact surfaces of the contacts, which surfaces will normally be gold plated, is avoided. In these known connectors all the contacts are moved by the contact driving member simultaneously between their first and second positions.
[0003] The invention proceeds from the realisation that there are many cases in which it is either desirable or necessary, or both, for different circuits such as power, ground and signal circuits to be broken sequentially, for mechanical or electrical reasons. For example, where bi-polar logic devices, which have both positive or negative power supplies are employed, the latter being referenced to ground, it may occur if the ground circuit is first broken, that supply voltages will "add" across an individual gate element and so destroy it. In digital electronic systems, for example, the generation of spurious transients leading to data falsification may result from the removal of a printed circuit board from a connector.
[0004] Although such effects may be avoided by various known expedients, for example by current sensing and limiting means, the provision of permanently grounded contacts on the connector or by appropriately choosing the type of logic elements employed, these expedients are usually inconvenient or unduly expensive.
[0005] According to the present invention, a zero insertion force printed circuit edge connector as defined in the first paragraph of this specification, is accordingly characterised in that the contact driving member is formed with relatively stepped surfaces succeeding one another in the longitudinal direction of the channel for sequential engagement with the contacts of the row, to move them sequentially between their first and second positions, in response to the movement of the cam member.
[0006] Each stepped surface may be conveniently dimensioned to engage a group of contacts connected to a respective circuit, for example a power circuit, a ground circuit or a signal circuit, whereby these circuits are made and broken sequentially.
[0007] Although there is disclosed in United States Patent Specification No. 3,648,221 a zero insertion force connector which can be programmed by varying the number of contact engaging projections on a cam member of the connector, there is no suggestion in this prior patent secification that the cam member can be arranged sequentially to displace the contacts.
[0008] According to United States Patent Specification No 3,475,717 two rows of contacts of a zero insertion force printed circuit edge connector may be independently driven between board engaging and board disengaging positions. However, all the contacts of each row can be driven only simultaneously between such positions.
[0009] The state of the art at this time is further exemplified by United States Patent Specifications Numbers 2,770,788, 3,037,181, 3,366,916, 3,541,490, 3,576,515, 3,744,805, 3,793,609, 3,897,991, 3,982,807, 4,047,782, and 4,076,362.
[0010] For a better understanding of the invention reference will now be made by way of example to the accompanying drawings, in which:-
Figure 1 is a perspective view of a sequentially actuable zero insertion force printed circuit board edge connector which embodies the invention, the connector being shown in a board engaging condition;
Figure 2 is a longitudinal vertical section through the connector of Figure 1;
Figure 3 is a top plan view of the connector shown partly in horizontal section, the connector being shown in an intermediate condition;
Figure 4 is a transverse vertical section through the connector with contacts thereof in a closed, position;
Figure 5 is a partial transverse vertical section, through the connector with the contacts in an open, board receiving position; and
Figure 6 is a foreshortened perspective view of a contact driving member of the connector.
[0011] The connector comprises four primary components, namely, an elongate insulating housing 12, a cam member 14, a contact driving member 16, and a plurality of spring electrical contacts 18.
[0012] The housing 12 has mounting flanges 20 and 22 at the opposite ends thereof for securing the connector to a mother printed circuit board 24 by means of fasteners 26 (Figure 2). The housing 12 has formed therein an elongate central guide channel 28 for receiving a daughter circuit board 30, the longitudinal side walls 2 of the housing 12 being formed with spaced ribs 22 projecting inwardly from the side walls 2 and defining recesses 34. Each recess 34, which communicates with the channel 28, receives a respective contact 18. A passage 36 extends from the lower (as seen in Figure 4) end of each recess 34 through a base 38 of the housing 12. The base of the channel 28 is formed with a central longitudinal groove 40 which communicates with a slot 41 in one end of the housing 12 and with an opening 39 in the other end thereof, opposed recesses 42 being formed in the upper (as seen in Figure 1) portions of the side walls of the slot 41 and opening into the upper surface of the housing 12.
[0013] The contact driving member 16, which lies in the channel 28 is, as best seen in Figure 6, channel shaped, having a base 44 and parallel side walls 46 and 48, the free longitudinal edges of the side walls 46 and 48 being formed, as best seen in Figure 6, with steps 49 so that the height of the free longitudinal edges of these side walls increases from right to left, as seen in Figures 2 and 6. These free longitudinal edges have chamfered outer faces 47 constituting at least two relatively stepped surfaces succeeding one another in the longitudinal direction of the channel 28. The ends of the base 44 have bevelled surfaces 50 and 52. As shown in Figures 2, 4 and 5, the outer or lower surface of the base 44 faces the mouth of the groove 40.
[0014] The cam member 14 comprises an elongate cam portion 60 and a resilient, loop-shaped, handle 62. The cam portion 60, which is slidably and rotatably received in the groove 40, is shaped, as seen in cross-section (Figures 4 and 5), as an elongate quadrilateral having parallel sides joined by radii. The handle 62, which has a free end portion 64, extends from the cam portion 60 externally of the housing 12, for rotating the cam portion 60 about its longitudinal axis and for sliding the cam portion 60 longitudinally of the groove 40.
[0015] The contacts 18 may be formed for example by stamping and forming metal strips, or by rolling and forming wire. Each contact 18 has a resilient, inwardly bowed, board engaging, contact surface 54 and a terminal portion 56 which extends through one of the passages 36 for mechanical and electrical connection to a printed conductor 58 (Figure 2) on the mother board 24 and to further conductors (not shown) and thus to electrical circuits (not shown) by wire wrap collections (not shown), for example. Each contact 18 is retained against withdrawal from the housing by means, for example, of a locking lance (not shown) or by the flow of the housing material during manufacture of the connector, into an aperture (not shown) in the contact 18.
[0016] The free end portion 64 of the handle 62 is receivable in the recesses 42 of the housing, for the avoidance unintended rotation of, and removal, in the direction of the arrow B in Figure 1, from the connector of, the cam member 14.
[0017] The connector is assembled by inserting the cam portion 60 of the member 14 into the groove 40 and the contact driving member 16 into the channel 28, aided by the bevelled surfaces 50 or 52.
[0018] When the cam portion 60 is positioned as shown in Figures 1, 2 and 4 so that its broader sides 61 lie parallel to the base of the groove 40 and to the base 44 of the driving member 16, the driving member 16 takes up a retracted position so that all the surfaces 54 of the contacts 18 are in a board engaging position, in which they project into the insertion path of the board 30 into the channel 28, as best seen in Figure 4.
[0019] As the handle 62 is rotated in the direction of the arrow A in Figure 3, the cam portion 60 is rotated about its longitudinal axis towards the position of Figure 5 in which the broader sides 61 of the portion 60 extend normally of the base of the groove 40 and of the outer surface of the base 44.
[0020] During such rotation of the handle 62, the driving member 16 is progressively forced by the cam portion 60 in a direction normal to the base of the groove 40 and thus of the base of the channel 28, and away therefrom, so that the chamfered faces 47 of the free longitudinal edges of the side walls 46 and 48 of the driving member 16 sequentially engage respective groups of the contacts 18 to move the contact surfaces 54 thereof outwardly into the recesses 34 and thus into their board receiving positions shown in Figure 5, in which the contact surfaces 54 are withdrawn from the insertion path of the board 30. As shown in Figure 3, the leftward group of contact surfaces, 54a, are first driven into their board receiving positions followed by the next adjacent group of contact surfaces, 54b, and so on in predetermined sequence.
[0021] When all the groups of contact surfaces 54 have thus been moved into their board receiving positions, the daughter board 30 is inserted into the channel 28 and the handle 62 is rotated back to its position of Figure 1, to move the groups of surfaces 54 sequentially back into their board engaging positions. The handle 62 is then pushed rightwardly, i.e. in the opposite direction to that of the arrow B, towards its position of Figure 2 and the free end portion 64 of the handle 62 is resiliently introduced in the recesses 42 so that the contact surfaces 54 are secured in their engagement with the daughter board 30. The daughter board 30 can be subsequently released from the connector by again rotating the handle 62 in the direction indicated by the arrow A, after removing the free end portion 64 of the handle 62 from the recesses 42 and withdrawing the handle 62 in the direction of the arrow B in Figure 1. The groups of contacts 18 are thereby released sequentially so that damage to the circuits to which the contacts 18 are connected and which might arise if the contacts 18 were simultaneously disconnected from the conductors of the board 30, can be avoided.
[0022] There are many cases in which it is either desirable or necessary, or both, for power, ground and signal circuits to be broken sequentially, for mechanical or electrical reasons. For example, where bi-polar logic devices, which have both positive and negative power supplier are employed, the latter being referenced to ground, it may occur if the ground circuit is first broken, that supply voltages will "add" across an individual gate element and so destroy it. In digital electronic systems, for example, the generation, by removal of the daughter board, of spurious transients leading to data falsification can be avoided by arranging for the power circuit to be first broken.
1. A zero insertion force, printed circuit board odqe connector, comprising an insulating
housing (12) having a channel (28) therein for receiving a printed circuit board (30)
along a board insertion path, a row of electrical contacts (18) positioned beside
the channel (28) each having a contact surface (54) for engaging the printed circuit
board (30) when such has been inserted into the channel (28), and a cam member (60)
movable to displace a contact driving member (16) normally of the channel (28) to
move each contact (18) between a board receiving first position in which the contact
surface (54) of the contact (18) is withdrawn from the board insertion path and a
board engaging second position in which such contact surface (54) intersects the board
insertion path, characterised in that the contact driving member (16) is formed with
relatively stepped surfaces (47) succeeding one another in the longitudinal direction
of the channel (28) for sequential engagement with the contacts (18) of the row, to
move them sequentially between their first and second positions, in response to the
movement of the cam member (60).
2. A connector according to Claim 1, characterised in that each stepped surface (47)
is dimensioned to engage a group of the contacts (18) simultaneously.
3. A connector according to Claim 1 or 2, characterised in that the contact driving
member (GO) is channel shaped, comprising a base (44) from opposite edges of which
extend side walls (46 and 48), the stepped surfaces (47) being formed in at least
one of the side walls (46 and 48).
4. A connector according to any one of the preceding claims, characterised is that
the cam member (60) has a handle (62) which extends exteriorly of the housing (12)
and is intertable in a recess (42) therein, to secure the cam member (60) to the housing
(12) and to restrain rotation of the cam member (60) relative to the housing (12),
when the contacts (18) are in their second position.
5. A connector according to Claim 4, characterised in that the cam member (60) is
slidable in the longitudinal direction of the channel (28) to move the handle (62)
towards and away from the housing (12).
6. A connector according to Claim 1, 2 or 3, characterised in that the can member
(60) has a handle (62) which extends exteriorly of the housing and (12) by means of
which the cam member (60) can be rotated relative to the housing (12), the handle
(62) having a free end portion (64) which can be moved relative to the housing (12)
to allow the free end portion (64) of the handle (62) to be lodged in a recess (42)
in the housing (12).