Technical Field

The present invention relates to a piercing terminal system for providing electrical current taps in electrical wiring in buildings, and having a power cable in form of a flat cable having a plurality of conductors embedded in an insulation, and wherein the piercing terminal system comprises a plurality of piercing members essentially arranged and movable in a plane perpendicular to the flat cable, each said member having two legs, each leg being provided with a cutting edge intended to penetrate the insulation of the flat cable, and enclosing a slot which may receive one of the conductors of the flat cable, and wherein a terminal means is provided for each piercing member, said means either being directly or via additional conducting devices connected to an electrical cable or to an electrical wire to supply power to an electrical device.

Background Art

It is known from low voltage systems and inter alia from US PS 4,784,613 to connect the conductors in a flat cable with the conductors on a print card by means of piercing members penetrating the insulation around the conductor in the flat cable. A cable connector for flat cables and having piercing members of a similar type is described in EP-A1-0212.356. However, this connector is also intended for low voltage systems.

Connectors for insulated, low voltage flat cables are, moreover, described in Finnish publication No. 59.509 and EP-Al-0.385.770. EP-B 1-0.100.602 discloses a system for connecting flat cables acting as buses in an electrical system.

Disclosure of the Invention

The object of the present invention is to provide a stable, electrically conducting

connection between two conductors for use in electrical installations in buildings by means of a flexible piercing terminal system of the type stated in the introduction. It is thus particularly important to obtain and maintain a constant contact pressure on the conductor for a long term of years, whereby a good and reliable electrical connection is ensured continuously, and it should be easy for an electrician to connect the conductors and also easy to alter the connection at a later stage, if necessary.

The object is obtained by means of a piercing terminal system of the type stated in the introduction being characterised in that each piercing member is intended to pass through a slot in a bar extending essentially transversely of the conductors in the flat cable and being in a plane essentially parallel to the plane of the flat cable, the length of the slot being less than the width of the piercing member.

As a result, the slot in the bar is used to receive and directionally stabilize the piercing member during its downward movement about a conductor inside the flat cable. The slot also contributes to keeping the two legs of the piercing member joined so that they clamp the conductor being enclosed by the two legs, and thereby maintaining the desired contact pressure. Consequently, the mechanical stress arising between the legs of the piercing member and the ends of the slot is utilized to ensure a sufficient contact pressure between the piercing member and the conductor in the flat cable as well as between the piercing member and the bar preferably also acting as the terminal means. The invention is particularly advantageous in that the contact pressure is independent of plastic.

Brief Description of the Drawings

The invention is described in greater detail in the following with reference to the particularly preferred embodiments and accompanying drawings, in which

Fig. 1 illustrates an embodiment according to the invention of a piercing member between a conductor and a bar or terminal,

Fig. 2 illustrates the embodiment of Fig. 1 applied to a flat cable,

Fig. 3 illustrates the embodiment of Fig. 1 with the bar being arranged above the conductor,

Fig. 4 illustrates the embodiment of Fig. 3 applied to a flat cable,

Fig. 5 illustrates the embodiment of Fig. 1 with bars arranged above as well as below the conductor,

Fig. 6 shows the same as Fig. 5, although applied to a flat cable,

Fig. 7 shows an embodiment of a terminal blocks seen inclined in a top view,

Fig. 8 the same seen inclined from below,

Fig. 9 shows the same terminal blocks mounted on a flat cable,

Fig. 10 is an example of a connection of a phase with the embodiment of a connec¬ tion block shown disassembled,

Fig. 11a shows the same in another embodiment,

Fig. lib shows the same in an assembled state,

Fig. 12 is an example of connection of three phase by means of screw terminals,

Fig. 13 shown the same as Fig. 12 with sockets for receiving a mains plug,

Fig. 14 is an example of an embodiment of a lower part of a piercing block, seen from below,

Fig. 15 shows a carrier, and a piercing member in enlarged scale, and

Fig. 16 is a sectional view through an embodiment of an insulation piercing connect¬ ing assembly.

Best Mode for carrying out the invention

Fig. 1 shows the principle of the present invention. An electrical connection between a conductor 12 and conductor bar 16 is made by means of a U-shaped piercing member 13 pressed over the conductor 12 so that the conductor 12 is wedged in a slot 15 between the two legs 14a, 14b of the U-shaped piercing member 13 in turn being wedged in a defined slot 17 in the connected conducting bar and terminal 16.

The length of the slot 17 is adapted in such a manner to the width of the piercing member 13 that the two legs 14a, 14b are pressed slightly together in the slot, whereby the legs 14a, 14b are forced to press so heavily against the conductor 12 that a sufficient contact pressure between the conductor 12 and the piercing member 13 is obtained. By the structure according to the invention, a sufficient contact pressure between the piercing member 13 and the bar or the terminal 16 is also obtained. Considering the physical forces in the piercing member 13, it appears that the moment of force on the conductor 12 is to be balanced by the moment of force on the bar 16.

Naturally, the conductor 12, the piercing member 13, and the bar 16 are prepared from an electrically well-condμcting material, preferably copper or copper alloys. As an example, the piercing member 13 may have a thickness of approximately 1 - 2 mm and may be silver-plated in order to obtain good electrical contact with the adjacent parts, viz. the conductor 12 and the bar 16. It is particularly advantageous to silver-plate the contact areas of the inner and outer surfaces of the legs 14a, 14b.

Fig. 2 illustrates the principle of Fig. 1 used on a flat cable 20. The piercing member 13 is preferably mounted in an insulated carrier 21 guided by a surrounding

housing (not shown). The carrier 21 is used to force the piercing member 13 down through a plastic insulation 19 and further down over a conductor 12 in a flat cable 20. A bar 16 having a non- visible slot 17 is arranged below the flat cable.

Preferably, at least one weak recess, inwards curve or indentation 18 is provided on the outer edge of each leg 14a, 14b. As a result, the piercing member 13 is more securely retained in the bar 16. If desired, the end portions of the legs 14a, 14b may be tapered or bevelled, possibly with a cutting edge so as to easily cut through the insulation 19 around the conductor 12 in the flat cable 20.

Fig. 3 and 4 show a second embodiment, in which the bar 16 is arranged over the flat cable. Also in this embodiment, the limited slot 17 ensures that the legs squeez- ingly abut the conductor 12, and the clamped conductor ensures that a sufficient contact pressure is obtained between the piercing member 13 and the bar 16.

A comparison of the two embodiments in Figs. 1 and 2 and Figs. 3 and 4 shows that the force creating the contact pressure on the conductor 12 in Fig. 1 is slightly stronger than the corresponding force on the bar 16 in Fig. 1, the moment of the former force is slightly shorter than the moment of the latter force. The opposite being the case in Fig. 3 and 4.

Figs. 5 and 6 show a third embodiment, in which a bar is arranged below as well as above the flat cable. Such an embodiment may be advantageous, where branching is desired.

As shown in Figs. 4 and 6, the piercing member 13 may be provided with two (and possibly several) indentations or slightly inwards curves 18 co-acting with the locking means, i.e. the bar 16, for retaining the piercing member 13.

Figs. 7, 8, and 9 show an example of an embodiment having a terminal block 24 made of copper. The terminal block is provided with three curves 26,27,28 match¬ ing three insulated conductors 12 in a flat cable 20. The terminal block 24 is

provided with bores 29,30 to receive a conductor, which is to be connected, and with transverse, threaded bores 31,32 to receive screws for fixing the conductor in a known manner.

The terminal block 24 may be arranged below or above the flat cable 20 and optionally in both positions. The particular shape of the terminal block ensures that it abuts the flat cable in a stable manner, whereby it is easy to insert the tips of the legs 14a, 14b into a slot 17, when a piercing member 13 is pressed through the insulation 19 of the flat cable. By means of the terminal block 24, contact is obtained to any chosen phase conductor in the flat cable 20. Moreover, it is possible to change the installation at a later stage. A piercing member 13 may for instance be removed from the flat cable and subsequently inserted in one of the other phase conductors in the same flat cable and in the same terminal block. A particularly flexible electrical connection system has thus been provided.

In yet another advantageous embodiment shown in Fig. 10, a piercing block 40, which may receive and retain a cable, for instance a five- wire cable 20, and compri¬ ses a lower part 42 and an upper part 44 assembled and held together for instance by means of locking projections 46,47,48 engaging corresponding indentations 56,57, projections 58, openings or recesses. The upper face of the lower part 42 and the lower face of the upper part 44, i.e. the sides of said parts facing each other, are provided with recesses 43,45 corresponding to the shape of a predetermined flat cable. The piercing block is made of an insulating material and in a preferred embodiment it is moulded in plastic.

Figs. 11A and 11B show the same piercing block in another embodiment. As it appears from the drawing, the locking projections 46,47 and the corresponding openings 56,57 are designed in a slightly differing manner.

As it appears from Fig. 16, a set of bars 16 are arranged slightly spaced apart from the cable and just above or below cable, said Fig. giving a sectional view through the piercing block 40 with a piercing member 13 in its indented position.

For the sake of clarity, the bars are not shown in Fig. 10. The position and action of the bars is as shown in Figs. 1 to 6 and as described above.

Moreover, the piercing block 40 is provided with a number of predetermined openings 50,51,52 to receive a number of piercing members 13, each being retained in a separate carrier 21 described in detail below.

The carrier 21 is shown in Figs. 10, 11A, 11B, 12, and 13, and in an enlarged scale in Fig. 15. The carrier is made of an insulating material and moulded in plastic in a preferred embodiment. It is essentially cubical with a plane back 61 and plane side walls 62,63, having no a front, but an inner face 64 partially enclosing a circular cylindrical cavity. On the upper face 66, a circular, upright rim 67 is provided surrounding a hole for a screw (not shown). The collar 67 is intended to receive the head of the screw. The plane back is double-walled and enclosing a plane cavity intended to receive approximately the upper third of the piercing member, i.e. a contact-providing piercing member 13, as shown in Fig. 15.

The piercing member 13 has two legs 14 and an intermediary, downwardly open slot 15. The free end portions of the two legs are provided with cutting edges. Furthermore, in a preferred embodiment, the piercing member has two closed slots 23, one in each leg 13, whereby the piercing member has double spring effect. Each of the legs may be slightly yielding, on the outer face (where it is in contact with the inner face of the slot 17 in the bar 16), and on the inner face (where it is contact with the conductor 12). Such slots 23 cause the edges of the piercing member to yield slight, when the piercing member is pressed downwards over a conductor 12 inside the flat cable 20.

The openings 50, 51, 52 in the block 40 are formed so as to be complementary to the form of the carrier, i.e. they are intended to receive the carrier 21 being designed as described above. The openings 50,51,52 may thus guide the carrier 21, when the piercing member 13 is pressed into a thick cable. A slot is formed in the bottom of each opening, the length and width thereof matching accurately to the

cross-section of the piercing member 13, i.e. its width and thickness, and just therebelow the bars 16 with corresponding slots 17 are arranged. Preferably, the bars 16 form the terminal means or - in other words - the outlets from the connec¬ tion.

When mounting a carrier 21 with a piercing member 13 in an opening 50,51,52 in a piercing block 40, the carrier is inserted into the opening, the lowermost point of the piercing member 13 being guided down into the slot 17 (in Fig. 1) at the bottom of the opening. Subsequent thereto, the preferably self-cutting screw 65 is screwed into the hole 59 in the piercing block 40. The carrier with screw ensures that the piercing member is guided accurately down towards the flat cable being equally accurately fixed in the block 40 by means of the recesses 43,45. As a result, after having cut through the cable insulation, the piercing member engages the position of conductor precisely, whereby one leg of the piercing member slides downwards on one side of the conductor and the other leg of the piercing member slides downwards on the other side of the conductor. The width of the slot 15 between the legs of the piercing member 13 is to match the diameter of the conductor 12 so that the legs presses tightly on the conductor 12 and creates the desired contact pressure. The conductor 12 is preferably of solid copper and of an area of 2.5 or 1.5 mm ² . The slot 17 in the bar 16 slightly spaced apart from the cable, either just above or just below the cable, ensures that the legs of the piercing member is retained in a direction perpendicular to the cable, while being pressed through the insulation.

The guidance of the piercing member is particular important, when cables with strong insulation are use, for instance freely exposed cables with operative insulation (heavy insulation) and halogen-free cable types, as the hard and thick insulation in such cables may only be cut through by particular strong, rigid piercing member. However, the present invention may also be used in connection with softer and thinner cable types, and in such cases it may be advantageous to insert liners supporting such thin cables, when they are placed in the piercing block 40.

The length of the slot 17 ensures that the legs of the piercing member are interspac-

ed with such a distance that a sufficient contact pressure is maintained between the legs 14 and the conductor 12 in the flat cable 20. It is a particular advantages of the present invention that the contact pressure is maintained independent of plastic and only dependent on the metallic parts, viz. the piercing member 13, the conductor 12, and the bar 16. The surrounding carrier 21 and the piercing block 40, preferably being of plastic, do not affect the maintenance of the contact pressure.

Figs. 10, 11 A, and 11B illustrate a typical one-phased connection, in which it is possible to select any of the phases LI, L2 and L3. Moreover, an earth wire and a neutral conductor 50,51,52 are provided. It is advantageous to arrange the phase connections 50 very close to each other, as this piercing block is intended for the connection of only one phase of the three optional phases. At reference numeral 16 in Fig. 11 A, an embodiment is shown of a bar for optional connection of one of the three phases accessible through the openings 50.

In a preferred embodiment, three parallel bars are provided extending close to the edge of the block. The bars are bent 90° downwards and continue in three end portions or legs which may be inserted into the lower part and passed through a narrow portion therefrom, said narrow portion preferably being in form of a socket in which a plug 71 having an outlet cable 30 may be inserted, for instance as shown in Fig. 10.

Fig. 12 shows a piercing terminal system with five piercing members, each being mounted in a carrier 21 formed as a screw terminal 25. In this embodiment, the block 40 is also designed for a five- wire cable 20, and the upper part 44 is provided with five openings which are not visible, as each of the openings is covered by a carrier 21 having a piercing member and screw terminal 25.

Fig. 13 shows a similar piercing block 40 deviating from the block shown in Fig. 12 in that each carrier 21 is combined with a socket which may receive a pin on a five-legged plug 60 on an outlet cable 30. The piercing member 13 may thus be combined with a screw terminal or a slot for a pin which may be flat as shown, or

may be a slot or rather an opening for a circular pin as in a conventional socket. In a similar manner, the carrier may be combined with an embedded fuse-carrier with a fuse.

Fig. 14 shows an example of an embodiment of a lower part of a piercing block 40, seen from below. It is advantageous to provide reinforcing ribs 80 in two direction being perpendicular to one another in order to make the piercing block more rigid.

It is obvious that the invention may be modified in many ways within the scope of the attached claims. The upper part and lower part of the piercing block may thus be hinged to one another. Moreover, the phases may have built-in fuses. The piercing blocks shown on the drawings may be surrounded by one or more covers and cable clamps may be provided with the covers.