GB2066572A

GB2066572A - Pleated metallized film capacitors with sprayed edge terminations

Info

Publication number: GB2066572A
Application number: GB8013604A
Authority: GB
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 1977-07-12
Filing date: 1979-07-12
Publication date: 1981-07-08
Also published as: MX144868A; BR7804182A; IT1096938B; GB2067016A; CA1093166A; JPS5441453A; FR2397708A1; DE2830423A1; GB2001199B; GB2066572B; IT7825481A0; NL7807154A; GB2067016B; GB2001199A

Abstract

An electrical capacitor comprises a dielectric strip 12 with metallisation 14; 20, 22 on both surfaces and folded along lines 30, 32, 34, 36, 38 to longitudinal edges and to the eventual contact ends of the capacitor body. One surface has two metal-free longitudinal edges 16, 18 while the other has a parallel central metal free zone 24. The strip is folded 5 + 4n times with one fold 40 extending beyond its neighbours along one side and the free edges 48, 50 extending beyond the folds at the other. The metal-free central zone is on the inside of the extending fold. The assembly, or a plurality thereof superimposed, may be wound into a roll before applying end-contact coatings. <IMAGE>

Description

SPECIFICATION Pleated metallized film capacitors with sprayed edge terminations An electrical capacitor according to this invention is built up of capacitor segments by winding or pleating, or consists of a single segment as defined below.

An electrical capacitor segment according to the present invention comprises at least one group of pleated layers comprising a dielectric layer, a first metallized electrode layer applied to one side of said dielectric layer so that an unmetallized margin area extends along each edge of a pair of parallel edges of said dielectric layer, a pair of metallized electrode layers on the other side of said dielectric layer, and at least one unmetallized strip that runs between said metallized layers on the other side of said dielectric layer, said dielectric layer being pleated M' number of times, where M' = 3 + (N)2 and N may be zero or any positive integer, in such a manner that at least one first pleat of said pleated dielectric layer extends along one end of said segment beyond at least one other pleat that extends along the same edge as first pleat or pleats, with all of said first pleats having unmetallized strips behind them along their length, while said margin areas extend along the opposite end of said segment beyond the other pleat or pleats that extend along the same end of said margin areas.

The present invention is illustrated by reference to the drawings in which: Figure 1 is a perspective view of a portion of a metallized dielectric layer which may be used in the construction of a capacitor in accordance with the present invention; Figure 2 is a perspective view of a segment constituted by a partially pleated metallized dielectric layer in accordinace with Figure 1, having five pleat lines; Figure 3 is a perspective view of a fully pleated metallized dielectric layer in accordance with Figure 1; Figure 4 is a perspective view of a fully pleated metallized dielectric layer of Figure 3 which, in addition, shows a winding mandrel and an unmetallized dielectric instert; Figure 5 is a diagrammatic showing of the winding of a capacitor in accordance with the construction of Figure 4;; Figure 6 is an end view of a capacitor before lead attachment, that is wound in accordance with the showing of Figures 4 and 5.

Figure 7 is an end view of the wound capacitor of Figure 6 after it has been pressed into an oval shape; Figure 8 is a side view of a completed capacitor following the attachment of axial leads; Figure 9 is a side view of a completed capacitor following attachment of radial leads; Figure 10 is a perspective view of an alternative version of a capacitor constructed in accordance with the present invention; Figure 11 is a perspective view of another alternative embodiment; and Figure 12 is a perspective view of a further alternative embodiment; Technical Description of the Invention A portion of a metallized dielectric strip which may be unwound from a reel, that is suitable for the making of a capacitor in accordance with the present invention, is shown in Figure 1.The metallized dielectric strip is formed with a dielectric layer 12 of a thin film dielectric material, such as polyester, polypropylene, polstyrene, polycarbonate or other suitable material. A thin metallized electrode layer 14 is applied to the upper surface of the dielectric layer 12 in such a fashion that unmetallized margin areas 1 6, 1 8 extend along the longitudinal edges of the strip 10. Two thin metallized electrode areas 20, 22 are applied to the lower surface of the dielectric layer 12 so that the metallized layer 20 extends to the left hand margin of the layer as shown in Figure 1, while the metallized layer 22 extends to the right hand margin of the layer. A central unmetallized strip 24 lies between the metallized electrode areas 20,22.

In the embodiment shown in Figure 1, the longitudinal dimension of the metallized strip 10 is shown along the arrows 26 while the narrow transverse dimension is shown along the arrows 28. The strip is pleated along the imaginary line 30 which extends through the length of the unmetallized central strip 24. This invention, however, is not limited to making by pleating along longitudinal lines, since a capacitor could be made by pleating along transverse lines if the appropriate corresponding metallized and unmetallized areas were provided.

A partially pleated capacitor segment is shown in Figure 2 wherein one pleat occurs along the longitudinal centre line 30 and other pleats occur along longitudinal pleat lines 32, 34, 36 and 38. It is to be noted that lines 32, 34, 36 and 38 are spaced so that the centre pleat 40 (Figure 3) extends beyond the other pleats 42, 44 that run along the right hand longitudinal edge of the capacitor segment of Figure 3, and that the inside of the pleat 40 in the area 46 is unmetallized. The extension of the centre pleat 40 beyond the pleats 42, 44 is preferably at least 0.020 inches.In addition, it is to be noted that the pleats are positioned so that the longitudinal ends 48, 50 of the metallized strip 10 are aligned with each other but so that they extend beyond the pleats 52, 54 that run along the left hand longitudinal edge of the capacitor segment. Again, the extension of the ends 48, 50 beyond the pleats 52, 54 is preferably at least 0.020 inches. The unmetallized margin 16, therefore, faces upwards while the unmetallized margin 18 faces downwards when the capacitor segment has been fully pleated as shown in Figure 3.

It will be noted from the foregoing description that the number of pleats that may be used to form a capacitor segment in accordance with the previously described embodiment of the present invention is M where M = 5 + (N)4 and N may be O or any positive integer. The number of pleats M in a capacitor segment made in accordance with this embodiment, therefore, will always be an odd number.

After the strip has been processed to form the capacitor segment shown in Figure 3, a number of different additional processing steps may be undertaken. For example, the pleated capacitor segment of Figure 3 could be used to form a capacitor merely by spraying the right and left hand longitudinal edges of the segment with a metallized spray, such as babbitt or other suitable metal, in accordance with conventional practice, and then electrical leads could be secured to them, for example, by soldering.Alternatively, the capacitor segment of Figure 3 could be cut along a transverse line, such as the line 43, and a number of such segments could be stacked upon each other, with the terminal end 50 of one capacitor segment being adjacent to and aligned with the terminal end 48' of the capacitor segment that is positioned immediately below it, as shown diagrammatically by the dotted line representation of Figure 3, and then their ends could be sprayed with a metallized spray and leads could then be secured to the stacked array of such segments. In conjunction with the presently preferred embodiment of the present invention, however, Figure 3 is to be understood as representing two capacitor segments formed by winding of the dielectric strip along the longitudinal dimension of the strip 10, as shown in Figures 4 and 5, to form a wound capacitor.Another version of this capacitor could be achieved, however, by pleating the structure of Figure 3 a number of times transversely along transverse fold lines parallel to the line 43, or alternatively pleating several times, and then completing the capacitor by winding the remainder of the length of the dielectric strip.

The winding of the structure of Figure 3 onto a wound capacitor may be achieved with various winding techniques, including the use of a removable split mandrel such as the mandrel 56 of Figures 4 and 5. An unmetallized dielectric strip 58 is desirably initially wound around the mandrel to protect the metallized electrode areas of the metallized strip 10. Near the completion of winding, an additional unmetallized dielectric strip 60 is desirably wound into the structure to form an outer protective coating. The dielectric strip 60 may also be heat-sealed to itself to enclose the capacitor 61 which is shown in Figure 6. The removal of the mandrel 56 from the capacitor 61 leaves an opening 62 in the unit.The opening 62 may be closed by applying prassure, or pressure and heat, in accordance with the type of dielectric used and conventional manufacturing techniques, to the capacitor 61 so that it assumes an oval shape as shown in Figure 7.

Once the capacitor has been wound, a metallized spray may then be directed against the longitudinal edges of the unit in accordance with conventional processing techniques to interconnect the electrode layers along these edges and to provide for the connection of electrical leads to the unit. The metallized spray will penetrate into the open area between the ends 48 and 50 on the left hand longitudinal edge of the capacitor as shown diagrammatically in Figure 3, to a depth such as that indicated by the plane 65. The plane 65 indicates the maximum depth that any high velocity spray particles will penetrate and it may thus be located at any place between the ends 48 and 50 of the metallized strip 10 and the edges of the pleats 52, 54.

Accordingly, the metallized spray material will extend into the left hand opening of the capacitor between the ends 48, 50 far enough to make contact to the two facing metallized electrode areas 20, 22 but not so far that it will penetrate through the dielectric material at the pleats 52, 54, nor as far as to touch the edges of the electrode layer 14. The configuration of the present invention thus provides for reliable lead termination at the left hand longitudinal edge of the capacitor segment of Figure 3 without the necessity of providing unmetallized longitudinal strips along the inside of the pleats 52, 54, thereby saving considerable processing expenses in the manufacture of completed capacitors of this type.

Termination to the right hand longitudinal edge of the capacitor of Figure 3 is similarly provided by a metallized spray which extends over the protruding centre pleat 40 to a depth, such as that indicated by the plane 67, which is sufficient to allow the metallized spray to make good contact to the electrode area 14, but which will prevent the penetration of the spray metallic particles through the dielectric at the pleats 42, 44. The location of the plane 67 may be anywhere between the edges of the pleats 42, 44 and the edge of the pleat 40 as long as there is sufficient depth of spray to provide adequate contact termination to the electrode area 14.Again, a considerable cost saving is achieved by the present invention since the pleats 42, 44, like the pleats 52, 54, do not have to be provided with their own unmetallized strips. It will be noted that only one unmetallized strip 24 is required in the centre of the metallized strip 10, and, thus, the same general pattern may be used for various pleat configurations and a separate individually configured metallized strip is not required for each pleat pattern.

Once the metallic spray has been applied to tbe edges of the capacitor of Figure 7, either radial or axial leads may be applied to it. For example, axial leads 70, 72 with conventional spiral "pig-tail" ends (not shown) may be soldered, arc-welded 6r connected by other means to the sprayed edge termination layers 66, 68 at the ends of the wound film capacitor segment 61, as shown in Figure 8. Alternatively, radial leads 74, 76 may be soldered, arc-welded or connected by other methods to the sprayed metallized layers 66, 68 if a radial leaded capacitor is desired, as shown in Figure 9.

Other alternative versions of the present invention are shown in Figures 10-12. In Figure 10 the pleated capacitor segment is formed so that the end pleats 42, 44 have unmetallized strips 48' behind these pleats while the centre 40 does not. The two end pleats 42, 44 extend beyond the recessed centre pleat 40. This version is less desirable, however, than the version of Figure 3 because it requires an additional strip.

Another alternative embodiment is shown in Figure 11 wherein only one of the end pleats 42 extends beyond the centre pleat 40 and the other of the end pleats 44. In this version only one unmetallized strip 46" is required behind the extending end pleat 42, but the charging path is longer for this configuration than that of Figure 3.

Still another alternative embodiment is shown in Figure 12, which differs from the version shown in Figure 3 in that intermediate dielectric layers 69, 69' are inserted between alternating groups 71, 73 of pleated layers with the centre pleat extended, as in Figure 3, but with alternating groups 71, 73 facing in opposite directions. If the capacitor of Figure 12 is to be a wound embodiment, the alternating groups 71,73 of pleated layers which face in opposite directions may be supplied from a different pleated segment supply. Also, it is apparent that the groups of pleated layers shown in Figures 10 and 11 could be employed to form a capacitor in accordance with the teaching of Figure 1 2 by facing alternating groups of these layers in opposite directions and by separating these alternating groups with dielectric material.

Considering all the above embodiments, and noting Figure 11, it can be stated that the number of pleats that may be used to form a capacitor segment in accordance with the present invention is M' where M' = 3 + (N)2 and N may be O or any positive integer.

Claims

1. An electrical capacitor segment comprising at least one group of pleated layers comprising a dielectric layer, a first metallized electrode layer applied to one side of said dielectric layer so that an unmetallized margin area extends along each edge of a pair of parallel edges of said dielectric layer, a pair of metallized electrode layers on the other side of said dielectric layer, and at least one unmetallized strip that runs between said metallized layers on the other side of said dielectric layer, said dielectric layer being pleated M' number of times, where M' = 3 + (N)2 and N may be zero or any positive integer, in such a manner that at least one first pleat of said pleated dielectric layer extends along one end of said segment beyond at least one other pleat that extends along the same edge as said first pleat or pleats, with all of said first pleats having unmetallized strips behind them along their length, while said margin areas extend along the opposite end of said segment beyond the other pleat or pleats that extend along the same end as said margin areas.

2. An electrical capacitor segment as claimed in claim 1, wherein said dielectric layer is pleated M number of times, where M = 5 + (N)4 and N may be zero or any positive integer.

3. An electrical capacitor comprising a plurality of capacitor segments as claimed in claim 1 or claim 2, and stacked upon each other, and metallized spray material which has been sprayed against both ends of said segments, but without penetration of said spray through any of said pleats other than said first pleat or pleats.

4. An electrical capacitor as claimed in claim 3, wherein said dielectric layer is an elongated layer and said capacitor segments have been wound along the elongated dimension of said layers subsequent to said pleating along longitudinal pleat lines, and said metallized sprayed material has been applied to the ends of said capacitor after said winding has been completed.

5. An electrical capacitor as claimed in claim 3, wherein said dielectric layer is an elongated layer and said capacitor segments have been pleated along lines transverse to the elongated dimension of said layer subsequent to said pleating along longitudinal pleat lines and said metallized sprayed material has been applied to the ends of said capacitor after said transverse pleating has been completed.

6. An electrical capacitor as claimed in claim 3, wherein alternating ones of said plurality of capacitor segments face in opposite directions and are separated from their neighbouring segments by dielectric material.

7. An electrical capacitor as claimed in any of claims 3 to 6, wherein a lead is secured to each of said metallized sprayed ends of said capacitor segments.

8. An electrical capacitor as claimed in claim 2, substantially as described with reference to Figures 1 to 3, Figure 10, Figure 11 or Figure 12 of the accompanying drawings.

8. An electrical capacitor segment as claimed in claim 1, substantially as described with reference to Figures 1 to 3, Figure 10, or Figure 11 of the accompanying drawings.

9. An electrical capacitor as claimed in claim 3, substantially as described with reference to Figures 1 to 3, Figure 10, Figure 11 or Figure 12 of the accompanying drawings.

New claims or amendments to claims fiied on 29-1-81.

Superseded claims.

New or amended claims

1. An electrical capacitor segment comprising at least one group of pleated layers comprising a dielectric layer, a first metallized electrode layer applied to one side of said dielectric layer so that an unmetallized margin area extends along each edge of a pair of parallel edges of said dielectric layer, a pair of metallized electrode layers on the other side of said dielectric layer, and at least one unmetallized strip that runs between said metallized layers on the other side of said dielectric layer, said dielectric layer being pleated M number of times, where M = 5 + (N)4 and N may be zero or any positive integer, in such a manner that at least one first pleat of said pleated dielectric layer extends along one end of said segment beyond at least one other pleat that extends along the same edge as said first pleat or pleats, with all of said first pleats having unmetallized strips behind them along their length, while said margin areas extend along the opposite end of said segment beyond the other pleat or pleats that extend along the same end as said margin areas.

2. An electrical capacitor comprising a plurality of capacitor segments as claimed in claim 1, and stacked upon each other, and metallized spray material which has been sprayed against both ends of said segments, but without penetration of said spray through any of said pleats other than said first pleat or pleats.

3. An electrical capacitor as claimed in claim 2, wherein said dielectric layer is an elongated layer and said capacitor segments have been wound along the elongated dimension of said layers subsequent to said pleating along longitudinal pleat lines, and said metallized sprayed material has been applied to the ends of said capacitor after said winding has been completed.

4. An electrical capacitor as claimed in claim 2, wherein said dielectric layer is an elongated layer and said capacitor segments have been pleated along lines transverse to the elongated dimension of said layer subsequent to said pleating along longitudinal pleat lines and said metallized sprayed material has been applied to the ends of said capacitor after said transverse pleating has been completed.

5. An electrical capacitor as claimed in claim 2, wherein alternating ones of said plurality of capacitor segments face in opposite directions and are separated from their neighbouring segments by dielectric material.

6. An electrical capacitor as claimed in any of claims 2 to 5, wherein a lead is secured to each of said metallized sprayed ends of said capacitor segments.

7. An electrical capacitor segment as claimed in claim 1, substantially as described with reference to Figures 1 to 3, Figure 10, or Figure 11 of the accompanying drawings.