A METHOD FOR CONNECTING ELECTRICAL CABLES TO ELECTRICAL EQUIPMENT

Abstract: A method for connecting an electrical cable (1) to an electrical equipment (2), the electrical cable being run to and mechanically connected to a cable attachment (5), is characterized in that the electrical equipment (2) and the cable attachment (5) are mechanically interconnected such that an electrically conductive member (6) forming part of the electrical equipment is caused to generate a force directed against a bared part (3) of the cable (1) running to the attachment, thereby to establish electric contact between the electrically conductive member (6) and the bared part (3).

Description: A METHOD FOR CONNECTING ELECTRICAL CABLES TO ELECTRICAL EQUIPMENT The present invention relates to a method for connecting an electrical cable to an electrical equip¬ ment, the electrical cable being run to and mechani¬ cally connected to a cable attachment separable from the electrical equipment. At present, it is customary to connect cables to electrical equipment via a terminal block which is mechanically and electrically connected to said equipment. As a rule, the equipment which may comprise, for example, one or more circuit cards, is placed in a housing or box of insulating material or metal, the terminal block constituting the lid or the bottom of the box. For connection of the cables themselves, bared cable parts can be inserted between two plates, whereupon a screw is tightened such that the upper plate is pressed against the bared cable part and the lower plate. This type of connection has the ad¬ vantage that a high and exact contact pressure can be achieved, and furthermore the same contact pressure is obtainable for all connections if the screws are tightened by means of a torque wrench. However, difficulties arise when the electrical equipment must be repaired or replaced. Then, all screws must be loosened and the cables detached before the electrical equipment can be removed from its hous¬ ing. This is time-consuming and difficult work, and efforts are being made to eliminate this problem. One proposed solution is to make the terminal block and the electrical equipment separable in some simple manner. For example, the block may constitute a bottom part to which the cables are permanently attached. The electrical equipment is then mechani¬ cally and electrically connected to the terminal block by means of plugs. Although this construction certainly makes the electrical equipment readily accessible for repairs and replacement, another problem has risen instead. The terminals oxidise fairly quickly, and a high contact pressure is required to prevent the contact resistances from becoming too high. However, a high contact pressure makes is difficult to detach the sensitive electrical equipment from the terminal box without damage to the equipment or the cables. To obviate this new prob¬ lem, use may be made of gold-plated terminals which do not oxidise, but since gold is a highly expensive metal, this is not a commercially satisfactory solu¬ tion. Consequently, it still remains to solve the prob¬ lem of connecting electrical cables to electrical equipment in a manner which makes the equipment readily accessible. It therefore is the object of this invention to provide a novel method of connecting electrical cables to electrical equipment so that the equipment, if necessary, can be readily disconnected from the cables. This object is achieved by means of a method which comprises the steps mentioned by way of intro¬ duction and which is characterised in that the electri¬ cal equipment and the cable attachment are mechanically interconnected such that an electrically conductive member forming part of the electrical equipment is caused to generate a force directed against a bared part of the cable running to the attachment, thereby to establish electric contact between the electrically conductive member and the bared part. This connection technique has many advantages and, in fact, combines the advantages of the two above- mentioned connection techniques. Thus, a sufficiently high and exact contact pressure can be obtained since the electrical connection is established directly between the bared cable part and the electrical equip¬ ment. Still, the equipment is readily accessible and replaceable since the mechanical separation also occurs directly between the bared cable parts and the electri¬ cal equipment. Furthermore, this connection technique is advantageous from the viewpoint of production en¬ gineering since the customer can acquire the standard attachments before the electrical equipment and there- fore can wire the entire cable system prior to installa¬ tion of the equipment. Embodiments of the invention will be described below, reference being had to the accompanying draw¬ ings. Fig. 1 is a cross-sectional view illustrating a method of making the connection according to the invention. Fig. 2 illustrates another method of making the connection according to the invention. Thus, Fig. 1 illustrates how a cable 1 is connected to an electrical equipment 2 identified hereinafter as the apparatus. The bared end 3 of the cable 1 is secured in an attachment member 4 on the upper side of an attachment 5. When the apparatus 2 is to be connected electrically to the cable 1, it is mounted mechanically on the upper side of the attachment 5. Mounting is carried out in such a manner that an electri¬ cally conductive member 6, for example a plate, which is secured to the underside of the apparatus 2, is contacted with the bared end 3 of the cable 1. After that, a screw 7 is used for urging " the plate 6 against the bared part 3 of the cable, whereby the desired contact pressure is established. The screw 7 may either extend through the plate 6 and down into the cable attachment 5 , thus contributing to the mechanical mounting of the apparatus 2 on the attachment 5, or it may only act upon the plate 6 from above, in which case the mechanical mounting must be accomplished for example by means of other screws (not shown). The Figure merely shows the connection of one cable to the electrical equipment, and it will be appreciated that in most practical instances a plurality of cables are connected in parallel to the illustrated cable 1 and on the opposite side of the cable attach¬ ment 5. When the electrical equipment must be made access¬ ible for repairs or replacement, the screw 7 (and any mounting screws) is loosened, and the apparatus 2 is removed from the attachment 5. The cable will then be retained by the attachment member 4, and when the repair or replacement has been carried out, one merely has to secure the apparatus again. Another embodiment of the connection according to the invention is shown in Fig. 2 in which the com¬ ponent parts illustrated in Fig. 1 are identified by like numerals. In this embodiment, the cable 1 is placed in a slit 9 and its end is introduced into an attachment member 4. Furthermore, the electrically conductive member 6 has a bulge which, when the appa¬ ratus 2 is mounted on the attachment 5 , extends down into the slit 9 and urges a bared part 3 of the cable against a plate 8. To prevent wear of the bared part, this may be provided with an electrically conductive contact safety device (not shown) which may consist of, for example, a U-shaped part which is secured over the bared part and against which the electrically conductive member 6 is urged when the apparatus is mounted on the attach- ment. The method according to the invention may, of course, also be applied to many other connection designs. For example, the attachment 5 may constitute instead a lid, to the underside of which the cable 1 is attached and the apparatus is mounted. Furthermore, the electri¬ cally conductive member 6 of the apparatus, as well as the attachment member 4, may be designed in different ways, and the cable can be attached by pushing it down into and at right angles to the upper side of the attachment.

Claims: CLAIMS 1. A method of connecting an electrical cable (1) to an electrical equipment (2), the electrical cable being run to and mechanically connected to a cable attachment (5) separable from the electrical equipment, c h a r a c t e r i s e d in that the electrical equipment (2) and the cable attachment (5) are mechanically interconnected such that an elec¬ trically conductive member (6) forming part of the electrical equipment is caused to generate a force directed against a bared part (3) of the cable (1) running to the attachment, thereby to establish electric contact between the electrically conductive member (6 ) and the bared part (3 ) . 2. A method as claimed in claim 1, c h a r a c - t e r i s ed in that the electrically conductive " member (6) is placed in direct contact with the bared part (3 ) . 3. A method as claimed in claim 1, c h a r a c ¬ t e r i s e d in that the electrically conductive member (6) is placed in contact with a contact safety device which is in direct contact with said bared part (3).

Inventors: BRAKL PETER, BRAKL, PETER
Applicants: INOR INSTRUMENT, INSTRUMENTFIRMAN INOR AB
Application year: 1986
Main classification: H01R4
IPC codes: H01R4, H01R13