IE47298B1 - Busbar and production method therefor - Google Patents

Abstract

The busbar comprises at least one conductor bar constituted by at least two strip conductors (1, 2) glued to an interposed insulating tape (3) and potted in a covering of resin (6). The method consists in glueing the conductor 5 to the tube and then immersing the assembly in a bath of resin powder after preheating the assembly whereby the powder adheres to it. After cooling the assembly is placed between the plates of a press and reheated to polymerise the resin and provide a desired resin thickness.

Description

BUSBAR AKD PRODUCTION METHOD THEREFOR The invention relates to busbars intended to distribute power to electrical equipment lodged in racks and to a method of producing the busbars. The manufacturing industries concerned are those producing electrical, information processing/transmission, automation, and telecommunication equipments. The invention is preferentially applicable in the production of busbars distributing supply voltages to telecommunication rack shelves and printed circuit boards.

The busbars used in printed circuit equipment racks are of several types, namely horizontal, distributing power to all PCB's in a shelf, vertical, distributing power to the shelves, and minibus bars providing connections between the connection pins of one and the same PCB.

These bars are produced in ihe form of conductors, each being a straight metal strip carrying a number of connection tabs. The conductors are usually separated by insulating tape.

These bars vary in shape, size, ar.d number of conductors, but are frequently produced by the same method and with the same tooling.

It is common practice to protect the external faces of the bars with two adhesive tapes so placed as to have their respective edges touching and closely moulding the roots of the connection studs: this method does not provide very moisture-proof protection. Another method consists in providing a coat of moulded material, but involves a number of difficulties in application, particularly in preventing the material from running, forming bubbles, and shrinkage liable to distort long busbars. Horizontal busses are usually produced in the form of too bars mounted on a support. To support the bars, it is known practice to provide a bakelite strip between the bars, to which they are held by clips. A disadvantage of this method, is that the double bars so produced are not very rigid, which is not good for the production of automatically wrapped connections.

The aim of invention is a method applicable to the various types qf bar for turning out a moisture-proof product which can be quite rigid if required. A subsidiary aim of the invention is the production of various bars from a limited number of basic components.

The present invention provides a method of producing electrical power busbars comprising at least two conductors separated by an insulator, each having input connections &nd distribution connections for various potentials, the method consisting in: - gluing the strip conductors to a central insulating strip to form a naked bar; - immersing the bars obtained in a bath of resin, using the fluidizing process; - positioning the resin-coated bar in a press providing determination of thickness; and - heating the assembly to equalize the coat of resin during its softening phase, and then to polymerize it.

The invention also provides busbars made according to the above method and comprising at least two strip conductors glued to a central insulating strip and coated with a heat shrinkable insulating resin entirely enveloping said bar.

An embodiment of the invention is described in the following aa a non-restrictive example intended to assist understanding of the invention, with reference to the accompanying drawings v/liich are: - figure 1: an exploded perspective view of the two conductors and their insulation; - figure 2: an elevation and cut-away of two assembled conductors; - figure 3: a cross-section along III-III in figure 2, representing a resin -coated busbar; - figure 4: an elevation view of two bars on a support; - figure 5-’ a cross-section along V-V in figure 4; - figures 6 and 7s perspective views of the fixture for mounting of the support ln the rack; - figure 8: an elevation of a busbar variant; - figure 9! a cross-section along IX-IX in figure 8; - figure 10: the underside of the bar· shown in figure 9· As shown in figure 1, the two strip conductors 1 and 2 are assembled by adhesion to insulating strip 3.

In the case of horizontal bars (figure l), wiring to the PCB connectors is wrapped, and connections to the general power supply busses (the verticals) are of the plug-in type, known in trade as Faston.

A conductor 1 has a number of pilla-r for 4 wrapped connections, and tabs 5 for plugs of the Faston type, frequently situated at the two ends. jq To produce a two-conductor bar, the conductors are applied on a strip impregnated on both sides with a hot polymerized glue.

The strip used is polyester tape of the type commonly known as ’inylar. The conductors are pressed against the strip by devices applythe appropriate pressure·, and the assembly is baked for three hours at 15 170%, for example.

A certain minimum capacitance between the conductors of horizontal bars must be ensured, for the purpose of absorbing unwanted voltages. The capacitance to be obtained is for example 39 pF/cm^ with .strip .025 ®m thick.

Connection pillars are arranged in staggered formation, in such a way as to situate the pillars of one conductor between the pillar.'; of the other, after assanbly (figures 1, 2, 4). The tips of the pillars of both conductors must lie in the same plane after asssmbly; for this, the pillars are .'lightly cambered, and this may be done by the cutting tool (see cros -section in figure 3)« With the conductor production technique which consists in stamping out the conductors in sheet with a press, there is a rounded edge on the cutter entry side, and a burr on the other. The sharn edges of the burr · can cut through mylar type and short-circuit the conductors. In 3° a method in accordance with the invention, the pillars are cambered on the cutter entry side, the rounded edges on the two conductors therefore facing each other, and the sharp edges not in contact with the mylar. External protection of the two-conductor bar is a coating of epoxy resin applied by the process referred to as fluidizing.

According to this process, the item to be coated is preheated, and plunged into a bath of resin powder. Preheat temperature is such, that the powder does not melt, but adheres fo the metal, while the part is mechanically agitated to ensure uniform coating. The part is then baked, the rise in temperature softening the resin , then hardening it by polymerization. Excellent hardness is oDtained by baking for three hours at 120°C, for example.

Application of the fluidizing" process in the production of busbars consists in inserting the bars into t.he powder up to the roots of the connection pillars, the latter pointing upwards. The resin softening phase is used to regularize surface finish and coating thickness, and possibly for the stamping of characters in the resin eoat.

For this, the resin -coated bar is cooled ard placed between two plates, applied to both sides by springs applying pressure to discs, which at end-of-travel determine a specified distance between plates.

This assembly i3 then baked: during the softening phase, press action equalizes the resin coat 6 at the selected thickness, surplus material coating the edges of the bar and the roots of the pillars, as shown in figure 3.

The various bars used normally have identical ends, connection pillars being symmetrically arranged in relation to a section normal to the bar. Thia is used in the process according to the invention to produce bars with two conductors from only one type of part. It can be seen (figure l), that the bar represented is obtained with two identical parts 1 and 2, positioned with their identical ends pointing in opposite directions. 4- or 6-conduccor horizontal bars (figures 4 and 5) are obtained by assembling two bars on a metal strip δ acting as support. In accordance with the invention, the bars are glued to the strip with a resin-based adhesive, such as the resin having the trade name Araldite.

To produce busbars of various thicknesses, only one type of supporting strip is used (figure 5)·’ metal plates are added to strip 8 on either side, for example at each end, and in the center. These plates 9 may be spot-welded to the strip. The bars are then glued to plates 9· Figures 4 and 5 represent a double, 4-eonductor bar in which strip 8 has widening plates 9, and in which rack mounting is by excenter studs 12. This type of mounting is necessary in certain racks.

Mounting of the busbars on a rack is either by means of bushes 11 at each end (figure 6), or by threaded studs 12 (figure 5) situated >47298 on the underside of the bars, that is to say, on the side opposite the connection pillars. These hushes or studs are welded to supporting strip 8. Figure 7 shows a stud 15 fixed by welding with its diameter on the longest center-line of strip 8.

The process is also applicable to vertical bars. These are composed of several strip conductors, separated by mylar tape. Connection tabs are of the Faston type. Tabs 14 (figure 8) of the conductors 15 are regularly staggered to facilitate the positioning of connection wires (figure 10). The resin l6 is deposited by fluidizing and pro10 vides good protection of all faces and corners of the bar, as shown in the cross-section in figure 9» , The process may be applied to producing various typos of parts, even such parts as possess connection pillars on bnth sides, and at both ends. In this case, certain pillars are necessarily immersed in the resin- bath. These pillars are previously coated with silicon grease, so that when the part is removed from the bath, these pillars are covered by a sleeve of weakly adhering resin , which can be cut away.

The process is also of interest for the production of small bars referred to as minibus bars on FOB'S. These bars do not have pillars for connection purposes, but pins, which are inserted in the same way as descrete components equipping the FOB. Resin coating gives these minibus bars the same appearance and the same protection as the FCB's.

J-conductor bars can also obtained (figure ll) by placing one conductor 1 of the full length of the bar, on one side, and two conductors of half the length, end-to-end on the other side. In accordance with the invention, identical conductors are used on each side, but one has a part cut out from its center. The center part of the bar after coating is shown as seen from above in figure 11, in which the three conductors 1, 17, and l8 may he distinguished. Cutting out the central portion does away with one of the connection tabs. For the sake of clarity, these tabs are shown un-cajabered in figure 11.

Claims (9)

1./ A method of producing electrical power busbars comprising at least two conductors separated by an insulator, each having input connections and distribution connections for various potentials, the method consisting in: - gluing the strip conductors to a central insulating strip to fore: a naked bar; - immersing the bars obtained in a bath of resin, using the fluidizing process; - positioning the resin-coated bar in a press providing determination of thickness; and - heating the assembly to equalize the coat of resin during its softening phase, and then to polymerize it.

2. / A method according to claim 1, in which the conductors are produced by stamping metal sheet with connection pillars, wherein said connection pillars are cambered in such a way as said pillars of the two conductors constituting the busbar are in the same plane, and that the chamber is produced on the cutting tool entry side of the metal sheet.

3. / A method according to claim 2, for producing a bar including a first conductor on one side throughout its length, and two second conductors arranged on the other side each opposite to a corresponding part of the first conductor, wherein said second conductors are produced by cutting a conductor identical to the first into portions. Al A method according to any preceding claim for producing a bar with connections on at least two sides, wherein one of the sides at which connections are to be made and which will come into contact with the resin bath is previously coated with a product that reduces the adherence of the resin, so that the sleeve of resin formed around said coated portions of conductor can subsequently be cut away.

4. 5/ A busbar produced by a method according to any preceeding claim, wherein the busbar has at least one conductor bar composed of at least two strip conductors glued to a central insulating strip and 47398 coated with a heat shrinkable insulating resin entirely enveloping said bar.

5. 6/ A busbar according to claim 5, constituted by two conducting bars arranged in parallel on a supporting strip to which said bars are glued, said supporting strip being equipped with fixtures for mounting $ of the assembly in a rack.

6. 7/ A busbar according to claim 6, wherein its support is a flat metal strip on which metal plates are fixed on either side, the power supply bars.being glued to said plates.

7. 8/ A busbar according to claim 5, wherein said mounting fixtures are 10 bushes welded to the ends of the supporting strip.

8. 9/ A busbar according to claim G, wherein said mounting fixtures are threaded studs welded to the edge of the supporting strip.

9. 10/ A busbar substantially as herein described with reference to and as illustrated in the accompanying drawings.