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(11) | EP 1 180 821 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Housing suitable for use in an electrical connector and substrate comprising such a housing |
| (57) The invention pertains to a housing suitable for use in an electrical connector,
which housing is attachable to a plurality of pins which are part of or inserted into
a substrate and comprises a base provided with a plurality of through-holes for receiving
the pins, and a plurality of locking elements, which, during attachment of the housing
to the pins, slide over the pins and are pushed into the through-holes thus establishing
interference between the housing and the pins. The locking elements are an integral
part of the housing and connected thereto by means of a connection which fails during
the said attachment of the housing to the pins. |
[0001] The invention pertains to a housing suitable for use in an electrical connector, which housing is attachable to a plurality of pins which are part of or inserted into a substrate, such as a printed circuit board used as a back-plane in a telephone exchange unit, and comprises a base provided with a plurality of through-holes for receiving the pins, and a plurality of locking elements, which, during attachment of the housing to the pins, slide over the pins and subseqently are pushed into the through-holes thus establishing interference between the housing and the pins.
[0002] Such a housing is known, e.g. from European patent application 0 578 487, which is directed to a pin field inserted in a printed circuit board (PCB), with back-to-back headers positioned on opposite sides of the PCB. The pins are electrically connected to circuit traces in the PCB by way of a press-fit portion. Pin portions extend in opposite directions from the press-fit portion and are profiled for mating with complimentary terminals in a complimentary connector. Housings are positioned over the pins on opposite sides of the PCB to form a complete connector assembly.
[0003] It is explained in EP 0 578 487 that PCBs may have through-holes having a diameter as small as 0.55 mm and that the pins on one side of the press-fit portion are provided with an enlarged barb which is larger than the nominal width of the pins and which is profiled for a (permanent) interference fit within a first housing. The other side of the pins may not comprise a barb, as it would not fit through the said through-holes. Therefore, this side of the pins has a constant width of e.g. 0.50 mm.
[0004] A second housing has passageways with which it can be attached to this side of the pins by means of interference fit. Two drawbacks of this technique are identified. First, as the housings are inserted over the pin field, the housings interfere with the pin field and leave some of the plastic on the pins which could lead to an unstable contact. Second, as many housings are made of a glass filled material, the glass particles in the housing could actually skive through the gold plating on the contacts, again leading to an ineffective contact system. Not mentioned in EP 0 578 487 is a third drawback, namely that the passageways are often permanently deformed by irregularities on the pins, such as local bulges, thus destroying or reducing interference fit.
[0005] These problems are overcome by means of a locking plate which includes a plurality of lead-in openings for easy placement of the locking plate over a pin field. The locking plate is further provided with gripping arms which are fitted into the through-holes of the housing. During the attachment of the housing to the pins, the through-holes of the housing are pushed over the gripping arms, thus urging the gripping arms against the pins and causing interference fit between these components.
[0006] Although the combination of the housing and the locking plate in accordance with EP 0 578 487 avoids damage to the pins, it requires a complicated and expensive manufacturing process.
[0008] To this end, the housing according to the opening paragraph is characterised in that the locking elements are an integral part of the housing and are connected to the base by means of a connection which fails during the said attachment of the housing to the pins.
[0009] Thus, the housing and the locking elements can be manufactured in the same process, for instance by means of injection moulding. Further, a pre-assembly step for placing the locking elements in the through-holes is no longer required.
[0010] It is preferred that the thickness of the connection is less than (preferably less than two thirds of) the thickness of the wall of the through-holes and of the locking elements. At any rate, the strength of the connection between the locking elements and the respective through-holes should such as to fail upon attaching the housing to the pins.
[0011] It is further preferred that the inner diameter(s) of the passageway for accommodating a pin in (each of) the locking elements is (are) larger than or equal to the diameter(s) of the pin so as to substantially avoid friction and interference prior to failure of the connections of the locking elements.
[0012] The invention also pertains to a substrate, such as a printed circuit board, comprising one or more pin fields, wherein a housing as described above is attached to at least one of the pin fields.
[0013] The invention will now be explained in more detail with reference to the drawings in which a preferred housing in accordance with the present invention is schematically shown.
[0014] Figure 1 shows a cross-section of a housing in accordance with the present invention as well as a side view of a back-plane and a pin field.
[0018] Figures 3 and 3A show a housing in accordance with the present invention after attachment to a back-plane.
[0019] Figure 1 shows a section of a back-plane 1 of e.g. a telephone exchange unit, provided with a pin field 2 comprising a plurality of pins 3. In this particular example, the pins 3 are arranged in seven columns of three pins each, i.e. the pin field 2 comprises a total of 21 pins. A housing or shroud 4 according to the present invention is positioned just above the pin field 2. The shroud 4 comprises a substantially flat base 5 and two side walls 6 which together define a cavity for accommodating a complementary connector part, such as a receptacle, which could either be shielded or not shielded.
[0020] The base plate 5 comprises first through-holes 7 for accommodating the pins 3 in the outer columns without interference and second through-holes 8 for accommodating the pins 3 in the five inner columns. The second through-holes 8 are each provided with a locking element, in this case a locking cylinder 9.
[0021] The enlargements in figures 1A and 1B, i.e. a cross along line A-A and a top view of the shroud 4, show the connection 10 between the locking cylinder 9 and the lower rim of the through-holes 8 in more detail. The connection 10 extends over approximately two thirds of the said lower rim and is relatively thin in comparison with the surrounding wall 11 of the locking cylinder 9 and the wall 12 of the through-holes 8, thus ensuring that the connection 10 will fail upon attaching the shroud 4 to the pin field 2. In general, the strength of the connection between the locking elements and the base of the housing can be influenced inter alia by the area of contact, which is mainly determined by the circumference of the connection, the local thickness of the material and the position of the upper rim of the locking element with respect to the lower rim of the through-hole, and by the presence of grooves, perforations and other structural features. The said strength can also be influenced by e.g. the process conditions during the manufacture of the housing.
[0022] Each of the locking cylinders 9 is rendered resilient in radial direction by means of at least two longitudinal slots 13 that are evenly distributed over the circumference of the locking cylinders 9. In this particular example, the locking cylinders 9 comprise two diametrically opposed longitudinal slots 13, which are preferably open at the end nearest the through-holes 8. Thus, upon failure of the connection 10, the ends of the walls of the locking cylinder 9 are released and can be pushed more easily towards a pin 3 by means of the wall 12 of the through-holes 8.
[0023] It is further preferred that the base 5 of the shroud 4 is provided with a rim 14 on its lower surface, which faces the back-plane 1 so as to provide room for the lower part of the locking cylinders 9, where the longitudinal slots 13 end, and avoid obstruction. The rim 14 may also be employed to ensure that the top surface of the base 5 is on a preselected level with respect to the top surface of the back-plane 1.
[0024] Figures 2 to 3A show how the locking cylinders 9 of the shroud 4 are slid over the pins 3 until the low rims of the cylinders 9 abut the upper surface of the back plane 1. Next, sufficient force is applied to the shroud 4 (substantially parallel to the pins 3) to break the connections 10, push the trough-holes 8 over the cylinders 9 and thus cause interference between these cylinders 9 and the pins 3 and effectively establish a header 15.
[0025] The interference of the locking cylinders 9 on the pins 3 results in a locking force of the shroud 4 (determined substantially parallel to the central axes of the through-holes and, accordingly, to the pins) typically ranges from e.g. 3 to 7 N per pin. However, it should be noted that the said range may vary considerably depending on the materials, shape and dimensions of the components as well as on a latching force that is necessary for a stable connection of the shroud to a complementary counterpart.
[0026] The shroud 4 can be manufactured by e.g. injection moulding a polymer such as a polyamide or a glass filled liquid crystalline polymer. The mould should be designed such that the shroud 4 can be easily removed upon solidification of the polymer. In case of a mould which separates along the bottom side of the base plate 5, it is preferred that the through-holes 7, 8 are slightly divergent towards the top of the base plate 5. Similarly, the locking cylinders 9 are slightly divergent towards the base plate 5. In general, it is preferred that the effective outer diameter halfway the locking cylinders 9, is greater than the effective inner diameter halfway the through-holes 8, because interference will in that case occur over a relatively large longitudinal section of the pins 3. The divergence of the through-holes 8 and that of the locking cylinders 9 can be readily selected to obtain this effect.
1. Housing (4) suitable for use in an electrical connector, which housing (4) is attachable
to a plurality of pins (3) which are part of or inserted into a substrate (1) and
comprises a base (5) provided with a plurality of through-holes (7, 8) for receiving
the pins (3), and a plurality of locking elements (9), which, during attachment of
the housing (4) to the pins (3), slide over the pins (3) and are pushed into the through-holes
(8) thus establishing interference between the housing (4) and the pins (3), characterised in that the locking elements (9) are an integral part of the housing (4) and connected to
the base (5) by means of a connection (10) which fails during the said attachment
of the housing (4) to the pins (3).
2. Housing (4) according to claim 1, wherein the thickness of the connection (10) is
less than the thickness of the wall (12) of the through-holes (8) and of the wall
(13) of the locking elements (9).
3. Housing (4) according to claim 1 or 2, wherein the inner diameter(s) of the passageway
(8') for accommodating a pin (3) in (each of) the locking elements (9) is (are) larger
than or equal to the outer diameter(s) of the pin (3).
4. Housing (4) according to any one of the preceding claims, wherein the effective outer
diameter halfway the locking elements (9) is greater than the effective inner diameter
halfway the through-holes (8).
5. Housing (4) according to any one of the preceding claims, wherein at least some of
the locking elements (9) comprise at least one longitudinal slot (13).
6. Housing (4) according to claim 5, wherein the locking elements (9) comprise at least
two longitudinal slots (13) that are evenly distributed over the circumference of
the locking elements (9).
7. Housing (4) according to claim 6, wherein the longitudinal slots (13) are open on
the end of the locking elements (9) nearest the base (5).
8. Housing (4) according to any one of the preceding claims, wherein the through-holes
(7, 8) are arranged in rows and columns.
9. Housing (4) according to claim 8, wherein the locking elements (9) are only provided
for the through-holes (8) in the inner rows and/or columns.
10. Substrate, such as a printed circuit board (1), comprising one or more pin fields
(2), wherein a housing (4) according to any one of the preceding claims is attached
to at least one of the pin fields (2).