This invention relates to the field of terminal clips and blocks, and connecting block assemblies thereof, used in telephone and data transmission interconnect assemblies. More particularly, this invention relates to a material reduced and transmission enhanced clip and block for clips of the type generally referred to in the art as 66 type clips. This invention also relates to a novel method of manufacturing such terminal clips.
Clip and block assemblies for 66 type clips are well known in the art and have been in use for many years. See, e.g., U.S. Pat. Nos. 3,112,147 and 3,518,618 to Pferd et al and to Swanson et al, respectively. These assemblies include a dielectric block or housing in which are located an ordered array of terminal clips. The clips are located in a series of openings in the block, and the top, or interconnect, end of each clip projects through the opening to extend above the upper surface of the central portion of the block. The bottom or base portion of each clip is retained within the body of the block by a combination of interaction with the block and a retainer plate which connects to the bottom of the block and retains the clips in position in the block.
Recently, a requirement has arisen for a small 66 type clip that will be both (a) less expensive, because of reduced volume of material present in the clip, and (b) suitable for and capable of functioning in and for the same applications for which the previous 66 type clips have been used.
One attempt at a smaller and less expensive 66 type clip, and a block therefore, is disclosed in U.S. Pat. No. 5,127,845 to Ayer et al. According to the '845 patent, the thickness of the clip is reduced relative to a previous 66 type clip of U.S. Pat. No. 3,112,147, the upper portion of the clip is unchanged in configuration relative to that previous clip, and the base is reduced in size relative to that previous clip, so that the overall height of the clip is about three-fourths that of the previous clip and the clip requires about two thirds of the material of that previous clip. The '845 patent is the closest prior art to this invention known to the inventors of the subject matter of this application.
An important feature of the Ayer et al '845 patent is that the lower part of the clip has a downwardly divergent aperture (76) between the base and that portion of the clip which holds the wire, and that aperture is flanked by arm portions (78,80) of constant width. The aperture (76) is triangular in shape, and the opposed inner and outer surfaces of the arm portions (78 and 80) are parallel.
As with prior art patents, most notably the Swanson '618 patent, the terminal block assembly described by the Ayer et al '845 patent consists of a block body that positions clips at a constant spacing and a slidably engageable retaining plate designed to captivate the clips in said block body. An important limitation of these and other prior art patents is that the regular clip spacing causes uniform capacitive coupling between adjacent rows of clips such that, when used with twisted-pair wires, the capacitive coupling between "tip" and "ring" wires that constitute a pair is equal to that of adjacent conductors from different pairs. Since crosstalk performance is determined by the capacitive imbalance between pairs (i.e., the difference in capacitive coupling between each conductor of a pair and a conductor of another pair), the constant spacing between rows poses a limitation in terms of crosstalk performance between adjacent circuits.
While it is appreciated that crosstalk performance may be improved by simply increasing the constant spatial separation between rows, such an approach has limitations and trade-offs in terms of diminished insertion loss and return loss performance caused by increased separation between tip and ring conductors of a pair, as well as limited compatibility with tools, adapters and other devices designed to plug directly into selected groups of clips on the connecting block assembly. Examples of such tools and plug-on devices are disclosed in U.S. Pat. Nos. 4,194,256, 4,585,290, 4,820,195, 4,883,430, 4,924,345 and 4,944,698, all of which are assigned to the assignee hereof.
All prior art blocks of this type are also limited by their height and the amount of material used to manufacture the connecting block body. The heights of the Pferd and Swanson blocks are determined by the height of the clip whereas the height of the Ayer et al block is determined by the combined height of the clip and that of the retainer ribs that support the clips. The disadvantage of these designs is that they are more limiting than other popular connecting block designs, such as the well known 110-series blocks disclosed in U.S. Pat. No. 4,964,812 (also assigned to the assignee hereof), in terms of the vertical clearance required for the block assembly when it is installed in telecommunications cabinets or other shallow telecommunications distribution facilities. The relatively greater height of the prior art block designs also requires more plastic material, which poses other limitations in terms of manufacturing cost and shipping weight.