The present invention relates to a bus bar arrangement, of the type comprising at least one electrically conducting bus bar for supplying electrical power and at least one printed circuit layer overlaid on the bus bar.

In such arrangements, bus bars are used to conduct strong currents at high voltages, and printed circuit layers are adapted for transmitting and/or processing signals representing data, namely data related to the bus bars or electrical components electrically connected thereto. EP 1 229 767 Al describes a bus bar arrangement of this type, comprising a printed circuit board.

Nevertheless, the increasing use of bus bar arrangements in electrical power supply systems has shown that bus bar arrangements with a printed circuit board are unpractical as far as design of such systems is concerned. An object of the invention is to propose a bus bar arrangement which enables to make the design of electrical power supply systems comprising bus bar arrangements easier.

To this end, the invention proposes a bus bar arrangement of the above- mentioned type, characterised in that the printed circuit layer is a flexible printed circuit.

According to other embodiments of the invention, the bus bar arrangement comprises one or several of the following features, to be taken alone or in conjunction when technically possible:

- the at least one bus bar has at least one curved portion, whereby the flexible printed circuit covers said curved portion with following the three- dimensional shape of the at least one bus bar.

- the at least one bus bar is made of metal.

- it comprises at least one electrically insulating coating interposed between the at least one bus bar and the flexible printed circuit. - it comprises electrically insulating coatings covering each sides of the at least one bus bar.

- it comprises at least one electromagnetically screening layer located between at least one bus bar and the at least one flexible printed circuit. - it comprises means for connecting the at least one bus bar to at least one electrically conducting track printed on at least one flexible printed circuit.

- it comprises at least two bus bars located on the same side or one opposite sides of the at least one flexible printed circuit. The invention will be better understood from the reading of the following description, given only by way of example, and made with reference to the drawings, in which:

Figure 1 is an exploded perspective view of a bus bar arrangement according to the invention;

Figure 2 is a perspective view of the assembled bus bar arrangement of Figure l;

Figure 3 is a cross-sectional view of the bus bar arrangement of Figure 2 taken along line IH-III; Figure 4 to 6 are views similar to that of Figure 3 illustrating alternate embodiments of bus bar arrangements according the invention.

Referring to Figure 1, the bus bar arrangement 2 is made of a stacking of several overlaid layers comprising successively from top to bottom on figure 1 : an electrically insulating coating 4, an electrically conducting bus bar 6, electrically insulating coating 8 and 10, a flexible printed circuit (FPC) 12 and an electrically insulating coating 14.

The layers are substantially similar in shape and generally rectangular. Each insulating coating is made of a thin flexible sheet of electrically insulating material, such as Polyethylene Terephtalate (PET), Polyethylene Naphthalate (PEN), or Polyimide. The thickness of each insulating layer is for example of between 0,1 mm and 0,23 mm.

The bar 6 is substantially rigid, and is made for example of a sheet of metal having a thickness for example of between 0,31 mm and 20 mm. Such a sheet can also be made of several individual layers, superimposed, each of those individual layer having a thickness of between 0,1 mm and 1 mm.

The bar 6 has a curved portion 15 curved along a line 16 parallel to one of the small edges 18 of bar 6. The curved portion 15 confers to bar 6 a three-dimensional shape.

The bar 6 has several holes 20, for example six in number, extending therethrough for connecting electrical components (not shown) such as resistors, transistors, capacities, conductors... to the bar 6, as it will be explained later.

The bar 6 also comprises two connection tabs 22 projecting outwardly from one of the small edges 18, each tab 22 having a hole therethrough for connection to another electrical component or an electrical power source (not shown). The coatings 4 and 8 are designed to cover opposed faces 6a, 6b of the bar 6, except from the tabs 22. FPC 12 is a flexible printed circuit of a know type, comprising a flexible electrically insulating support 24 and electrically conducting tracks 26 printed thereon.

The support 24 is made of a thin film, for example of polymeric material such as a resin, which is easily flexible, namely more flexible than the bar 6, so that the FPC 12 can be bent very easily to conform to the three-dimensional shape of the bar 6 during assembly of the bus bar arrangement 2.

The tracks 26 enable to transmit electrical signals representing data. Optionally, in a known manner, the FPC 12 includes processing means for processing said data.

The support 24 comprises connection tabs 28 projecting outwardly from the support 24.

Only ends portions of the tracks 26 extending on the tabs 28 have been represented on figure 1 for the sake of clarity. The insulating coatings 10 and 14 are shaped to cover opposed faces 24a, 24b of the support 24.

Each of the coatings 4, 8, 10 and 14 and the FPC 12 are provided with holes 30 and cut-outs 32 extending inwardly from a peripheral edge, each being aligned with a hole 20 of the bar 6 so as to enable connection of electrical components to bar 6 through the coatings 4, 8, 10 and 14 and the FPC 12.

Referring to Figure 2, once the arrangement 2 is assembled, bar 6 is covered by coatings 4 and 8 and only the tabs 22 and connection areas 35 aligned with the holes 30 and cut-outs 32 of the other layers are apparent. The tabs 28 also protrude from the stacking. Due to their flexibility, the insulating coatings 4, 8, 10 and 14 and the FCB 12 conform themselves to the three-dimensional shape of the bar 6. Therefore, with the bus bar arrangement 2 of the invention, it is possible to design bus bars with complex three-dimensional shapes and which are curved in one or several regions, for example to facilitate the insertion of the bus bar arrangement into a housing and/or to facilitate the connection of numerous electrical components to the bus bar in an electrical power supply system. The design of the bus bars is thus facilitated.

Each of coatings 4 and 8 preferably has dimensions slightly larger than that of bar 6 and, as illustrated on Figure 3, the confronting marginal portions 37 of layers 4 and 8 are bounded together so as to cover the edges of bar 6 and conveniently isolate bar 6.

Electric connection of electrical components to bar 6 can be made in a known manner via metal sleeves, one sleeve 38 being shown of figure 3, inserted through holes 20 so as to be in contact with the edges of said hole 20. The sleeves 38 are adapted to accommodate fixing means such as a threaded shank of a screw.

As illustrated in dash-dotted line on figure 3, optionally the bar 6 is electrically connected to the FPC 12, for example to provide electrical power to the FCB 12 or to transmit and/or process data such as a voltage of bar 6 or a current running through bar 6.

To this end, the bar 6 comprises for example a connecting tab 40 free of insulating coating and extending outwardly from the bar 6 and bent so as to be in contact with the end portion of at least one track 26 extending over a tab 28. As illustrated on figure 4, in an alternate embodiment, the bus bar arrangement 2 further comprises an electromagnetic screening layer 42 interposed between a coating 8 covering bar 6 and the FPC 12. The screening layer 42 is made for example of a plain or perforated metal sheet, or a metal mesh.

The layer 42 is for example connected to an electrical mass. The electromagnetic perturbations of FPC 12 originating from bar 6 are thus avoided.

An alternate embodiment illustrated on Figure 5 differs from that of Figure 1 in that the insulating coating covering the faces 24a of FPC 12 confronting the bar 6 is omitted, whereby only the coating 8 is interposed between bar 6 and FPC 12.

In an alternate embodiment illustrated on Figure 6, the arrangement comprises a second bus bar 44. The bar 44 is covered on opposed faces by electrically insulating coatings 45, 46.

For example, the bar 44 is overlaid on FPC 12 opposite to the bar 6, whereby FPC 12 is located between the two bars 6 and 44. Alternatively, the two bars 6 and 44 are located on the same side of FPC 12. As shown in Figure 6, the bar 44 has a hole 48 to allow the sleeve 38 to pass therethrough without contacting bar 44.

The bars 6 and 44 are at the same voltage, or preferably at two different voltages, whereby bars 6 and 44 can be used to supply electrical power to electrical components connected thereto. Insulating coatings 45 and 46 covering bar 44 are preferably bounded together through the hole 48 to cover the edges of said hole 48 and avoid electric arcs between sleeve 38 and bar 44.

It is possible to combine the different alternative embodiments of figures 3 to 6 to provide one or several bars, on the same or opposite sides of the FPC, with on or several insulating layer between the FPC and a bar or between two bars, and with or without a screen layer between the FPC and the bus bar(s).

The bus bar arrangement is usable is electrical power supply systems, for example for electrical motors of trains or cars.