WO1988003700A1

WO1988003700A1 - Method for producing capacitors and respective resin-bonded explosion-preventing capacitor with terminal board and external means of attachment

Info

Publication number: WO1988003700A1
Application number: PCT/IT1987/000031
Authority: WO
Inventors: Lucio Venturini
Original assignee: Ducati Energia SpA
Current assignee: Ducati Energia SpA
Priority date: 1986-11-14
Filing date: 1987-04-09
Publication date: 1988-05-19
Anticipated expiration: 1989-05-14
Also published as: IT1201826B; IT8683439A0; AU7302487A

Abstract

Method for producing capacitors and respective capacitor of the type having a casing in plastic material (4) containing the capacitive body (7) in solidified resin (6), and having a means of attachment to a support (4''') at the base and means of connection to a terminal board with tangs (10) at the top, in which: the resin-bonding of the capacitive body is carried out separately, realizing a preassembly having an inside container constituted of material which is flexible, yielding and compressible in thickness (5); the containing casing is realized by welding two half shells of semicylindrical shape (4) which become the semi-cover (4'') and the semi-base (4''') thus realizing, by welding, a complete means of closure having said means of attachment to a support (4''') at the base and having means of fixed fastening and containing (4'') at the top of the respective terminal board tangs (10) as the half shells are internally equipped with corresponding semicircular ribs (4'); a diaphragm with explosion-preventing function (3) which is enclosed and fixed internally between said half shells (4) by means of said semicircular ribs (4'), realizing an explosion-preventing chamber which is sealed by internal pressure (c) on the containing side of the resin-bonded capacitive body casing and above it, and a counter chamber on the other side which is not sealed (c').

Description

Method for producing capacitors and respective resin-bonded explosion-preventing capacitor with terminal board and external means of attachment

The present invention relates to a method for producing capacitors and respective resin-bonded explosion-preventing capacitor with terminal board and eaxternal means of attachment.

The necessity is known, at the present state of art, to realize capacitors which are equipped with explosion-preventing device, according to the above-mentioned characteristics.

It is also known that the respective explosion-preventing devices fall mainly into two categories:

- the first type which is used only in capacitors having a metal shell of which the upper part of the metal shell has^' bellows-type wrinkles so that it can stretch upon increase of pressure, thus allowing the upper cover to move away. As the upper cover has the respective electric connection wires rigidly fixed to it, this movement tears them away and breaks the

circuit;

- the second type foresees instead a p rt which bends towards the outside (generally a respective cover) which has the respective electric connections fi ed to its centre in such a „ay that its respective bending obtains the said Jerk.

The second solution is less complicated and less expensive and n^s it possible to realize the capacitors with a casing- entirely in plastic. Therefore the cost is even .ore conta.ned, and the capacitors are of excellent ,uality and certainly better insulated from the outside.

However, the difficulties in realizing both a terminal board and an explosion-prevention device in a space which hardly exists in the portion of cover are known.

The necessities of supplying the capacitors with opportune means of attachment to means of support are also known, and it is also known that such means of attachment must be realized externally (generally on the base) and it is therefore even more difficult to find a space for a corresponding explosion-preventing device.

The necessity of being able to have capacitors with high quality characteristics is also known, and they must therefore have maximum insulation by immersing the capacitive body in solidified resin.

It is also known that when capacitive bodies covered in solidified resin are used and a short circuit occurs in them which is particularly distant from the explosion-preventing device, it is extremely difficult that the device will be activated for the simple reason that the increase of pressure will find its way obstacled by the surrounding solidified resin. The consequence will therefore be an inevitable explosion with breakage of the covering shell in the area near the short circuit zone.

It is also known that in order to remedy these inconveniences it has been suggested to equip the capacitors with an opportune air chamber between the respective shell and the capacitive body so as to favour the transmission of the pressure increase to the explosion-preventing device, thus avoiding deflagration.

However, the last solution makes it impossible to resin-bond the capacitive body unless another containing shell is realized, except that a second containing shell becomes in any case an obstacle to the propagation of the pressure increase and the advantage of the hollow space such as the suggested air chamber becomes ineffective.

The scope of the invention is to eliminate the above-mentioned inconveniences and to conceive a capacitor which ^'possesses all the optimal requisites for this specific use.

According to the characteristics given in the attached claims, the present invention solves the problem by realizing a capacitor of the type having a shell in plastic material containing the capacitive body in solidified resin, ' having means of attachment to a support at the base and means of connection to a terminal board at the top, in which: the resin-bonding of the capacitive body is actuated separately, realizing a preassembly which has an inside container composed of flexible, yielding material which can be compressed in its thickness; - the casing shell is realized by welding two half shells of semicylindrical shape composed of a semi-base and a semi-cover thus realizing, by welding, a complete means of closure with said means of attachment to a support at the base and means of fixing and containing of the respective terminal board tangs at the top as the half shells are equipped internally with a corresponding semicircular rib;

- a diaphragm with explosion-preventing function which is included and fixed internally between said half shells by means of the said semicircular ribs, thus realizing an explosion-preventing chamber sealed by internal pressure on the containing side of the resin-bonded capacitive body and a counter chamber on the other side which is not sealed. This solution has the advantage of not having mobile parts on the outside as the explosion-preventing device is totally included in the capacitor casing shell, with the further advantage that air chambers are unnecessary as the resin covering carries out this function. The use of two half shells simplifies the constructive system and makes it possible to realize different types of capacitors thus permitting adptation to widely differing uses.

According to the invention the said internal casing shell of the capacitive body with the solidified resin is conveniently coc posed of an interspace.

The important advantage of being able to better transmit the increase in pressure to the explosion-preventing chamber is obtained in this way.

Said diaphragm advantageously presents a bell shape with a deflecting, central portion which, on the capacitive body side, has a sliding means of coupling for at least one electric connection wire welded to the capacitive body and the respective connection wires are clamped and rigidly welded to the outside of this area during the welding of the half shells through the union line between the respective fixing rib for the said diaphragm.

The important advantage of increasing the traction of the wire for the jerk in respect to the course of bending towards the outside of the diaphragm's bending portion is thus obtained, reducing the dimensions and the spaces inside the capacitor for the explosion-preventing device. Said diaphragm is conveniently equipped with juts directed towards the capacitive body.

The advantage of keeping the capacitive body fixed in its respective containing chamber is thus obtained.

The invention is hereafter explained in more detail with the help of the drawings showing one of the preferential realization solutions, the execution details of which are not to be held as limiting but only as examples.

Figure 1 shows an axial section on the union plane for welding of the respective half shells of a capacitor as per the invention with a sole capacitive body incorporated in it;

Figure 2 shows a top view of a cross section X - X above the diaphragm (3) of the version of the capacitor according to the previous figure;

Figure 3 shows an enlarged section of a portion of the covering material of the capacitive body and of the plastic covering sheath realized by welding the half shells.

As can be noted from the above-mentioned figures, the capacitor consists of a capacitive body (7) immersed in solidified resin (6) in an air chamber (5¹) made of a container of thin, flexible plastic material (5) to be inserted in a second container or external shell realized by welding two half shells in plastic material (4) so that the transmission of the overpressure due to short circuiting in the upper explosion-preventing chamber (C) is not obstacled. The chamber (C) bears the explosion-preventing device realized by a diaphragm of yielding, plastic material (3) with a central part which deflects towards the outside (3') and is able to drag by means of a passing hole (3'") at least one respective wire (1) with it and thus break the circuit. It will be noted that the air bubbles (5¹) of the first covering (5) determine an air chamber for points (8) between the outside surface of the resin container (5) and the outside containing shell (4). The . transmission of the increase in pressure to the explosion-preventing chamber (c) is thus favoured.

It will be noted that the counter chamber (c¹) need not necessarily be sealed as it has the sole function of space for the bending of the diaphragm and to contain the terminal board connections.

According to the invention, at the clamping position the wires (1,2) have the covering sheath gripped between corresponding ribs (4' ) which keep it in a fixed position during the respective welding phase of the half shells and then along the respective union and welding line (s) of the half shells (4). The said welding of the half shells is also able to weld the respective covering sheath of the electric wires (1,2). It will be noted that the same internal rib (4* ) of the half shells (4) which grips the wires (1,2) also fixes the respective explosion-preventing diaphragm (3) thus realizing the seal in the respective circular fixing seat (4¹). An explosion-preventing chamber (c) will then ob obtained at the side of the capacitive body (7) and an unsealed counter chamber (c¹) on the opposite side, under the corresponding terminal board (4", 10).

It will be further noted that a flange with opposed fins

(4"') is obtained tinder the capacitor as a means of fixing for lateral insertion on a respective support to fasten the capacitor. This means of fastening is conveniently obtained by molding directly on the respective half shells (4) with evident economy both of a separate production of the same and of a succesive assembly to the base.

According to the invention, the terminal board seat (4") is obtained directly by molding on the respective half shells (4) so that the structure shown in the figures is obtained upon assembly.

The terminal tangs of the terminal board (10) are clamped in the apposite fixing seats foreseen in the respective semi-seat of the terminal board (4") of a corresponding half shell (4) and similar fixing seats for the welded wires are foreseen with inside fins (i).

The construction procedure according to the invention is substantially as follows:

- the respective semicylindrical half shells in thermoplastic material (4) are separately molded with respective semicircular ribs (4') in order to fix the diaphragm (3) with a notch to seat the wires (1,2), a semi-cover with semi-seat for the terminal board (4") and a semi-base with means of fastening (4'");

- the respective discoid,bell-shaped diaphragm (3) is separately molded in flexible and/or yielding plastic material equipped with an anular edge with female fixing notch, and a central portion which deflects towards the outside (3' ) having beneath it a hole or hook (3") which receives one or more wires which are torn out during the deflecting movement by the respective contact of a capacitive body (7);

- the respective capacitive bodies (7) with welded electric wires (1,2) are produced separately; - a preassembly is realized which consists of: the capacitive body immersed in liquid resin (6) contained in an initial sheath of thin, flexible plastic material (^'5) of air bubbles (5') and left to polymerize while solidifying, it having been foreseen that the free ends of the wires are spot-welded to the respective tangs of the terminal board (10) with the expedient ^~ that the wire of the upper connection (1) is passed through the corresponding means of clamping (3") of the deflectible portion (3¹) of said diaphragm (3);

- this preassembly is clamped between the half shells (4) and care is taken to fix in the corresponding notches the respective terminal board tangs (10) and the corresponding wires to be locked (1,2) in the fixing rib (4') which will also clamp the respective diaphragm (3) by anular fixing;

- lastly, the two half shells are ultra-sonic welded.

The finished capacitor is thus realized, complete with all the accessories rigidly fastened internally and without mobile parts on the outside.

It is to be noted that said diaphragm (3) is conveniently equipped with juts pointing towards the capacitive body (3"') so as to fasten it and prevent eventual mobility.

The execution details may naturally be varied without altering the invention's field of protection defined by the characteristics laid out in the attached claims.

Claims

CLAIMS 1. Method for producing a capacitor and respective capacitor of the type having a shell in plastic material (4) containing the capacitive body (7) in solidified resin and bearing means of 5 connection to a terminal board with tangs (10), characterized by the fact that:

- the resin-bonding of the capacitive body is carried out separately by realizing a preassembly consisting of an internal container composed of flexible, yielding material which is

10 compressible in thickness (5); the containing shell is realized by welding the two semicylindrical half shells (4) composing a semi-cover (4") and a semi-base (4'") which upon welding realize a complete means of closure, having said means of fastening to a support (4'") at

15 the base and means of fixing and containing (4") at the top of the respective terminal board tangs (10) as the half shells are- internally equipped with a corresponding semicircular rib (4');

- a diaphragm with explosion-preventing function (3) which is internally enclosed and fixed between the said half shells (4)

20 by the said semicircular ribs (4') thus realizing an explosion-preventing chamber sealed by internal pressure (c) on the containing side of and above the resin-bonded capacitive body with a counter chamber on the other side (c');

252. Method for producing capacitors accordin to claim 1, characterized in that it includes the following phases:

- the respective capacitive bodies (7) with the welded electric wires (1,2) are produced separately;

- a preassembly is realized which comprises: the capacitive 0 body which is immersed in liquid resin (6) and contained in an initial sheath of flexible, plastic material (5) having a thickness which is compressible and spongy or with air bubbles (5') and left to polymerize while solidifying, it having been foreseen that the respective terminal board tangs (10) are welded to the free ends of the wires (1,2) with the expedient, that at least the wire of the upper connection (1) is passed through the corresponding means of clamping (3") of the deflecting portion (3') of said diaphragm (3);

- this preassembly is clamped between the half shells (4) taking care to fix in the corresponding notches the respective terminal board tangs (10) and the corresponding wire to be locked (1,2) in the fixing rib (4') which will also clamp the respective diaphragm (3) by anular fixing;

- the two half shells are spot-welded, closing the preassembly with the respective terminal board tangs (10) which come out of a respective end.

3. Capacitor of the type bearing an electric connection terminal board on its head (10) and means of fastening to a support on the base (4"' ) , also equipped with explosion-preventing means according to claim 1, characterized in that it comprises an external shell in plastic material obtained by welding the two semicylindrical half shells (4). These two half shells have the following features realized directly at molding:

- a terminal board semi-seat ( '") on the top

- a semi-flange with fins (4'") on the base, and — a semi-annular clamping rib (4') internally; which serves to obtain upon welding of two half shells:

- the formation of respective means of support for the capacitor (4'" ) on the base;

- the upper fixing of the terminal board tangs (10), the containing of said tangs and upper closing (4");

- the internal clamping of:

- a respective preassembly consisting of capacitive means (7) contained in solidified resin (6) in a container (5) having a. yielding thickness (5');

- a diaphragm in plastic material (3) having a bending- movement for the function of preventing explosions through 5 overpressure at the deflecting central portion (3¹) and means of central hooking of a respective wire (1), with clamping of the respective wires (1,2) in an intermediate position by welding said internal semi-anular ribs (4').

104. A capacitor according to claim 1, characterized in that said internal container of the resin (5) comprises a multitude of air bubbles (5') between two thin sheets of spot-welded plastic material.

5 5. A capacitor according to claim 1, characterized in that said diaphragm (3) has a bell shape with a central deflecting portion (3') where there is a means of fastening (3") on the capacitive body side (7) for the sliding of at least one electric connection wire welded to the capacitive body (1) and the 0 respective connection wires (1,2) are clamped and rigidly welded to the outside of this area during the welding of the half shells by the line of union between the respective fixing ribs (4') for the said diaphragm (3).

5 6. A capacitor according to claim 1, characterized in that said diaphragm (3) is equipped with juts pointed towards the capacitive body (3'") and in contact with it (7).

7. A capacitor according to claim 1, characterized in that 0 notches are cut in each respective terminal board seat (4") on each half shell (4) to fix the respective terminal board tangs of the corresponding electric connections (10).

8. A capacitor according to claim 1, characterized in that the respective covering is removed in the respective clamping zone of the wires.