In electrical devices it is known to provide terminals using a screw or like member to clamp the bared or insulation-stripped end of a conductor for connection to another electrical unit. Terminal strips of this type can accommodate a large number of conductors, e.g. 32, 48, 64 or 96, and can be provided for many purposes. For example, they are used in the electric-power field for the connection of conductors to circuit-breaker or fuse blocks or panels, for the connection of a plurality of lines to a single supply line, and for electric-current distribution in apparatuses of all types. In the electronics industry, such terminals may be used to connect wire conductors to block or jack systems, to the edge conductors of circuit boards or, in general, for current or signal distribution or collection in conjunction with a multiplicity of lines.
Terminal strips of the aforedescribed type have been provided in a variety of forms heretofore, some of which will be discussed below to the extent that they are relevant to the present invention. In general, it may be mentioned that practically all such systems comprise an insulating body previously formed with conductive elements in spaced-apart relation, the conductors previously stripped of insulation, being connected to these elements so as to form a good electrical contact therewith. Good electrical contact is important in the power field so as to avoid potential drops and contact heating and in the electronic and information-processing field to avoid noise and perturbations of the various signals. Good electrical contact is associated with an adequate pressure between the conductive element and the barred end of the wire and an effective surface contact between the two.
Terminal strips have been provided heretofore in the form of insulating blocks into which screws were threaded to form all or part of the conductive element at each station, the blocks being also provided with passages running at right angles to the screw into which the end of the wire could be inserted. When the screw is tightened, it presses the wire against a surface juxtaposed with the tip of the screw, thereby clamping the wire in place and generating the necessary contact pressure and surface contact for effective conduction. Thus, in such conventional terminal strips, the passage for insertion of the wire and the chamber for passage in which the screw is disposed and displaced lie at right angles to one another.
Such systems have been found to require a relatively large space since the conductors or wires must be inserted from the side and even if they are bent at right angles to reduce the lateral space requirements, the systems occupy a considerable volume when viewed in terms of the space required for insertion and removal of the wires and the space occupied by the terminal strip itself. Frequently, a terminal strip must be disposed along an edge of a housing, e.g. a circuit breaker box, and lateral space is therefore at a premium. Even the manipulation of such terminal strips may be fraught with difficulty if large numbers of wires must be inserted laterally in a minimum of space.
It has been proposed to avoid some of these disadvantages, especially where a large number of conductors must be attached in a limited area, i.e. in a system of having high conductor density, by the use of other types of terminals.
For example, the aforementioned conductive elements of the terminal strips may be posts about which the bared end of the wire is coiled by the so-called wire-wrap process. This system uses a tool for twisting the end of the wire in a multiplicity of turns tightly around the post. The pressure is a result of the tightness of the coiling operation and the large number of turns ensures an adequate contact surface. In another such system, referred to as the TERMI-point system, the wire, as in the wire-wrap system can lie practically parallel to the conductive element. Both of these systems have the advantage that practically no lateral space is required in addition to that occupied by the terminal strip.
However, these systems have a disadvantage in that the space occupied by each post and the associated wire can be relatively large and this may make manipulation (i.e. connection and disconnection) difficult where a high-conductor density is required.
Mention may also be made of systems in which the screw and the wire are substantially parallel to one another in terminal blocks, strips or devices. These systems, however, also have the disadvantage that they are not always suitable for use when a high terminal density is desirable and also occupy considerable space. As a result, such systems have not found widespread usage in practice.