GB2067016A

GB2067016A - Pleated metallized film capacitors with sprayed edge terminations

Info

Publication number: GB2067016A
Application number: GB8013611A
Authority: GB
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 1977-07-12
Filing date: 1978-07-12
Publication date: 1981-07-15
Also published as: CA1093166A; IT1096938B; MX144868A; BR7804182A; JPS5441453A; FR2397708A1; GB2001199A; GB2066572A; GB2001199B; GB2066572B; IT7825481A0; NL7807154A; GB2067016B; DE2830423A1

Abstract

An electrical capacitor comprises a dielectric strip 12 with metallisation 14; 20, 22 on both surfaces and folded along a line 30 parallel 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 once, off-centre so that one longitudinal edge 48 extends beyond the other. The metal- free central zone is on the inside of the fold 40. The assembly, or a plurality thereof superimposed, may be wound into a roll before applying end-contact coatings. <IMAGE>

Description

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GB2067016A 1

SPECIFICATION

Pleated metallized film capacitors with sprayed edge terminations

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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.

10 - An electrical capacitor segment according to the present invention comprises a dielectric layer having centre line, a first metallized electrode layer applied to one side of said dielectric layer so that an unmetallized mar-15 gin area extends along each edge of a pair of parallel edges of said dielectric layer, a second metallized electrode layer applied to the other side of said dielectric layer so that a further unmetallized area is located adjacent 20 said second metallized electrode layer, said dielectric layer being pleated once along said further unmetallized area off of said centre line so that one edge of said margin areas extends beyond the other of said edges 25 along the same end of said capacitor segment.

The present invention is illustrated by reference to the drawings in which:-

Figure 1 is a perspective view of a por-30 tion 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 single 35 pleated dielectric layer in accordance with Fig. 1;

Figure 3 is a perspective view of the fully pleated dielectric layer of Fig. 2 which, in addition, shows a winding mandrel and an 40 unmetallized dielectric insert.

Figure 4 is a diagrammatic showing of the winding of a capacitor segment in accordance with the construction of Fig. 3.

Figure 5 is an end view of a capacitor 45 segment, before lead attachment, that is wound in accordance with the showing of Figs. 3 and 4.

Figure 6 is an end view of the wound capacitor segment of Fig. 5 after it has been 50 pressed into an oval shape;

Figure 7 is a side view of a completed capacitor following the attachment of axial * leads; and

Figure 8 is a side view of a completed 55 capacitor following attachment of radial leads.

A portion of a metallized dielectric strip which may be unwound from a reel, that is suitable for making of a capacitor in accordance with the present invention is shown in 60 Fig. 1. This metallized dielectric strip is formed with a dielectric layer 12 of a thin film dielectric material, such as polyester, polypropylene, polystyrene, polycarbonate or other suitable material. A thin metallized electrode 65 layer 14 is applied to the upper surface of the dielectric layer 12 in such a fashion that unmetallized margin areas 1 6, 18 extend along the longitudinal edges of the strip 10. Two thin metallized electrode areas 20, 22 70 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 Fig. 1, while the metallized layer 22 extends to the right hand margin of the layer. 75 A central unmetallized strip 24 lies between the metallized electrode areas 20, 22.

In the embodiment shown in Fig. 1, the longitudinal dimensions of the metallized strip 10 is shown along the arrows 26 while the 80 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 85 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.

90 A capacitor segment with a single pleat line 30 is shown in Fig. 2 which is slightly off of the centre line 31 of the metallized strip 10, with the inside of the pleat 40 in the area being unmetallized. The longitudinal ends 48, 95 50 of the metallized strip 10 are arranged in a staggered pattern so that one end 48 extends beyond the other end 50 along the left hand longitudinal edge of the metallized strip because of the off-centre pleat of the dielectric 100 layer. The extension of the end 48 beyond the end 50 is preferably at least 0.020 inches. The unmetallized margin 1 6 faces upwards while the unmetallized margin 18 faces downwards when the capacitor segment has been 105 placed as shown in Fig. 2.

After the strip has been processed to form the capacitor segment shown in Fig. 2, a number of different additional processing steps may be undertaken. For example, the 110 pleated capacitor segment of Fig. 2 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 115 with conventional practice, and then electrical leads could be secured to them, for example by soldering. Alternatively, the capacitor segment of Fig. 2 could be cut along a transverse line parallel to the line 43, and a number of 120 such segments could be stacked upon each other, with the terminal end 50 of one capacitor segment being adjacent to but not extending as far as the terminal end 48' of the capacitor segment that is positioned immedi-125 ately below it, as shown diagrammatically by the dotted line representation on Fig. 2, and then their ends could be sprayed with a metallized spray and leads could then be secured to the stacked array of such seg-1 30 ments. In conjunction with the presently pre

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ferred embodiment of the present invention, however. Fig. 2 is to be understood as representing two capacitor segments formed by winding of the dielectric strip about the longi-5 tudinal dimension of the strip 10, as shown in Figs. 3 and 4, to from a wound capacitor. Another version of this capacitor could be achieved, however, by pleating the structure of Fig. 2 a number of times transversely along 10 transverse fold lines parallel to the line 43, or alternatively, pleating several tims and then completing the capacitor by winding the remainder of the length of the dielectric strip.

The winding of the structure of Fig. 2 into a 1 5 wound capacitor may be achieved with various winding techniques, including the use of a split mandrel such as the mandrel 56 of Figs. 3 and 4, which is removed from the capacitor after it has been wound. An unme-20 tallized dielectric strip 58 is desirably initially wound around the mandrel to protect the metallized electrode areas of the metallized strip 10. The winding of the capacitor segment then continues until it is almost com-25 pleted, at which time an additional unmetallized dielectric strip 60 is then desirably wound into the structure to form an outer protective coating. The dielectric strip 60 may also be heatsealed to itself to enclose the 30 capacitor in the manner shown in Figs. 7 and 8. The removal of the mandrel 56 from the wound capacitor leaves an opening in the unit. This opening may be closed by applying pressure, or pressure and heat in accordance 35 with the type of dielectric layer used and conventional manufacturing techniques to the capacitor so that it assumes an oval shape as shown in Fig. 6.

Once the capacitor has been wound, a 40 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 45 connection of electrical leads to the unit. The metallized spray will penetrate into the open area resulting from the staggering of the ends 48 and 50 on the left hand longitudinal edge of the capacitor, so that the inner electrode 50 provided by the unmetallized areas 20, 22, is contacted by the sprayed metal particles, but so that the electrode layer 14 is not contacted by such particles, as indicated by the imagin-ery plane 65 which represents the maximum 55 depth of penetration of the spray particles. The configuration of the present invention thus provides for reliable lead termination at the left hand longitudinal edges of the capacitor segment of Fig. 2 in a manner such that 60 the metallized end terminations may be employed with a single pleat metallized capaci- • tor. Termination to the right hand longitudinal edge of the capacitor segment of Fig. 2 is similarly provided by a metallized spray which 65 extends over the protruding centre pleat 40 to a depth which is sufficient to allow the metallized spray to make good contact to the electrode area 14.

Once the metallic spray has been applied to the edges of the capacitor segment, either axial or radial leads 70, 72 or 74, 76 may be applied to it as shown in Figs. 7 and 8.

Claims

1. An electrical capacitor segment comprising a dielectric layer having a centre line, 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 second metallized electrode layer applied to the other side of said dielectric layer so that a further unmetallized area is located adjacent said second metallized electrode layer, said dielectric layer being pleated once along said further unmetallized area off of said centre line so that one edge of said margin areas extends beyond the other of said edges along the same end of said capacitor segment.

2. An electrical capacitor segment comprising a dielectric layer having a centre line,

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, second and third metallized electrode areas applied to the other side of said dielectric layer so that a centrally located unmetallized strip runs between said metallized areas, said dielectric layer being pleated once along said unmetallized strip slightly off of said centre line so that one edge of said margin areas extends beyond the other of said edges being along the same end of said capacitor segment.

3. An electrical capacitor comprising a plurality of capacitor segments as claimed in claim 1, stacked upon each other, and metallized spray material in contact with said second electrode layer, wherein said metallized end spray has been applied to said capacitor segments after they have been stacked upon each other.

4. An electrical capacitor comprising a plurality of capacitor segments as claimed in claim 2, stacked upon each other, and metallized spray material in contact with at least one of said second and third electrode areas, wherein said metallized end spray has been applied to said capacitor segments after they have been stacked upon each other. ,

5. An electrical capacitor as claimed in claim 3 or claim 4, 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 of said layers, and said metallized sprayed material has been applied to the ends of said capacitor after said winding has been completed.

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6. An electrical capacitor segment as claimed in claim 2, substantially as described with reference to Figs. 1 to 3 of the accompa-70 nying drawings.

Printed for Her Majesty's Stationery Qffice by Burgess & Son (Abingdon) Ltd.—1981.

Published at The Patent Office, 25 Southampton Buildings,

London, WC2A 1AY, from which copies may be obtained.

6. An electrical capacitor as claimed in claim 3 or claim 4, wherein said dielectric layer is an elongated layer and said capacitor segments have been pleated along lines trans-

5 yerse to 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 transverse pleating has 10 been completed.

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.

15 8. An electrical capacitor segment as claimed in claim 2, substantially as described with reference to Figs. 1 to 3 of the accompanying drawings.

20 CLAIMS (29 Jan 1981)

1. An electrical capacitor segment comprising a dielectric layer having a centre line,

a first metallized electrode layer applied to one side of said dielectric layer so that an unmetal-25 lized margin area extends along each edge of a pair of parallel edges of said dielectric layer, second and third metallized electrode areas applied to the other side of said dielectric layer so that a centrally located unmetallized 30 strip runs between said metallized areas, said dielectric layer being pleated once along said unmetallized strip slightly off of said centre line so that one edge of said margin areas extends beyond the other of said edges along 35 the same end of said capacitor segment.

2. An electrical capacitor comprising a plurality of capacitor segments as claimed in claim 1, stacked upon each other, and metallized spray material in contact with at least

40 one of said second and third electrode areas, wherein said metallized end spray has been applied to said capacitor segments after they have been stacked upon each other.

3. An electrical capacitor as claimed in 45 claim 2 or claim 4, 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 of said layers, and said metal-50 lized 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 or claim 4, wherein said dielectric

55 layer is an elongated layer and said capacitor segments have been pleated along lines transverse to the elongated dimension of said layers subsequent to said pleating along longitudinal pleat lines, and said metallized sprayed 60 material has been applied to the ends of said capacitor after said transverse pleating has been completed.

5. An electrical capacitor as claimed in any of claims 2 to 4, wherein a lead is

65 secured to each of said metallized sprayed ends of said capacitor.