The present invention relates to a shroud retention wafer.
Typical prior art shrouds have designed interference with a mating pin. In the application process the shroud is placed on the pin tip and, with some sort of toe and press, is pushed down the pin against the rear side of a back panel.
One of the difficulties associated with such a procedure is knowing if the shroud is properly aligned with the pins. That is, kowing if the shroud is misplaced by perhaps one position. Another problem is that the shroud needs to be held on the pin tips while a tool is placed within it and it is placed into a press. It is also found that as pressure is applied to the shroud, the pin may have a tendency to bend since the load is being placed on a long slender column.
As is disclosed in European Patent Application No. 578 487 A, it is known to provide a structure known as a locking plate or retention wafer between the shroud or housing and the circuit board or back panel. The arms fit in passageways in the base of. the housing and these passageways include a camming surface for urging the gripping arms into contact with the pins. The disadvantage to the above arrangement described in European Patent Application No. 578 487 A is that the interacting protuberance and camming surfaces require the gripping arms or cylindrical members to be displaced from each other at a relatively large distance.
US 5 522 730 discloses a spacer plate with locking arms to be inserted into passage ways of a housing member. The arms have thickened portions at approximale and portion of said arms, the thickened portion fully surrounding said arms.
US 4 749 373 discloses a crimp snap retention system. Here, respectively two tine members are mounted in an adjacent manner. The tine members are reinforced by vertical ribs.
It is the object of the invention to provide a shroud retention waver providing better retention than known shrouds.
This object is accomplished in accordance with the features of claim 1. Dependent claims are directed on preferred embodiments of the invention.
The insulative shroud retention wafer of this invention includes a planar base member having a first and a second side. There are also first, second, third and fourth cylindrical members each having an axial pin receiving aperture and an axial center line extending said pin receiving aperture. These cylindrical members extend form the first side of the planar base member, and these cylindrical members are positioned in an arrangement such that a first longitudinal center line extends through the axial center line of the first and second cylindrical members. A second longitudinal center line extends in parallel spaced retention to the first longitudinal center line through the axial center lines of the third and fourth cylindrical members. A first transverse center line extends through the centerlines of the first and third cylindrical members. A second traverse center line extends through the center line of the second and fourth cylindrical members. A protuberance is peripherally positioned on the first cylinder at least in part at a position between the first longitudinal center line and the first transverse center line.
The present invention is further described with reference to the accompanying in which:
The shroud retention wafer of the present invention is an improvement on the insulative plate with integral insulative sleeves which are shown respectively at numerals 57 and 56, PCT International Application No. WO 96/31922 published October 10, 1996. The contents of this application are incorporated herein by reference.
The wafer is composed of a thin molded base with cylindrical member on its top. Although 30 cylindrical members are shown in the disclosed embodiment, different numbers of cylindrical members may be used in various other situations. The inside coring of the 20 central cores has an odd shaped hole in it and two areas of added material on two opposing sides of the tower. The outside 5 cores on each end of the wafer are not pertinent to the wafers function. It will be appreciated that while the cores do not serve for pin retention they do serve for insulation and guidance. As pressure is applied to the opposing areas of added material, hereafter referred to as "protuberances", the cylindrical member will start to collapse, since there will preferably be approximately 8 mils of plastic on the cylindrical portion 90 degrees from the protuberances.
This wafer is used in conjunction with a die cast housing which has a matching grid of holes similar to the wafer. In practice, the wafer is placed by hand into the bottom of the casting and pushed to a specified depth. This piece is then supplied to a user as a shroud which is placed on the rear side of a back panel by hand. The shroud can be placed over the pins protruding from the rear side of the back panel and pushed down to the board until the wafer contacts the board. As this point the casting is not against the back panel. A piece of tooling is placed inside the casting, the back panel supported, and the casting is fully inserted over the wafer. The wafer, which was already pushed against the back panel, cannot move as the casting is pressed over it. This causes the bumps to be pushed toward the center of the core and the plastic core itself to press against the pin. This action causes the shroud to be securely fixed to the back panel.
Referring to the drawings the insulative shroud retention wafer of the present invention includes a planar base section 10 which has a first upper side 12 and a second lower side 14. Extending upwardly from the upward side there is a first lateral row of cylindrical members shown generally at numeral 16 which is comprised of members 18, 20, 22, 24 and 26. There is also an opposed lateral row of cylindrical members made up of members 30, 32, 34, 36 and 38. Interposed between these lateral rows there are four medial rows shown generally at 40, 42, 44 and 46. The array of cylindrical members is also defined by a number of transverse rows shown generally at numerals 48, 50, 52, 54 and 56. Each of the medial rows has a center line as, for example, center line 58 of medial row 40 and center line 60 of medial row 42. Similarily, each of the transverse rows has a center line as, for example, center line 62 of row 48 and center line 64 of row 50. The medial rows include, for example, first cylinder 66 and second cylinder 68 in medial row 40 and third cylinder 70 and fourth cylinder 72 in medial row 42. Each of the cylindrical members in the medial row has a axial center line as, for example, first axial center line 74 in cylindrical member 66, second axial center line 76 and second cylindrical member 68, third axial center line 78 in third cylindrical member 70 and fourth axial center line 80 in fourth cylindrical member 74. Each of the cylindrical members in the lateral rows such as cylindrical member 30 includes a peripheral base 82, a central body 84 and a central pin receiving aperture 86. While these lateral row pin receiving apertures allow for insulation of the pins they do not serve a gripping function. Each of the cylindrical members in the medial row as, for example, cylindrical member 66 has a peripheral base 88, and a central body 90. Its central pin receiving aperture through which the first axial center line 74 extends includes an elongated slot 92 and lateral recesses 94 and 96 which extend from the elongated 92 at a medial position in opposed directions. It will be seen that the lateral recesses 94 and 96 are triangularly shaped to receive a cross sectionally square pin. A semi-circular shape for these recesses would be used for a round pin. Each of the cylindrical members in the medial rows also includes a pair of opposed protuberances 98 and 100. These protuberances have respectively center lines 102 and 104. It will be seen that these protuberances 98 and 100 are radially aligned respectively with the opposed lateral recesses 94 and 96 in the pin receiving aperture. The protuberance center lines 102 and 104 are also displaced from the first longitudinal center line 58 and the first transverse center line 62 by an angle of 45 degrees. The protuberances 98 and 100 also include vertical wall sections 106 and 108 respectively which overly the outer periphery of cylindrical member 66. These walls each cover about 90 degrees of the periphery of the cylindrical member 66. These walls have a arcuate upper sections 110 and 112 respectively which curve inwardly toward the cylinder member to form a cam surface. The wall also has upper edge 114 and 116 respectively which slope laterally and downwardly toward the base from their center lines. It will be understood that all the cylindrical members in the medial rows are essentially identical to cylindrical member 66 and the protuberances in these rows are similarily positioned on the cylindrical members and have the same relatively positions to the longitudinal and traverse center lines.
The shroud retention wafer described above may be fixed to a header prior to shipment of that header thus saving considerable time and effort during the placement of the header on a back panel or circuit board. It will also be appreciated that the positioning of the protuberances as described above on the cylindrical members allows for efficient use of space on the wafer.
While the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. Therefore, the present invention should not be limited to any single embodiment, but rather construed in breadth and scope in accordance with the recitation of the appended claims.