GB1567718A

GB1567718A - Cylindrical shaped capacitor

Info

Publication number: GB1567718A
Application number: GB33678A
Authority: GB
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 1977-01-11
Filing date: 1978-01-05
Publication date: 1980-05-21
Also published as: DE2801079A1; FR2375702A1; FR2375702B1

Description

(54) CYLINDRICAL SHAPED CAPACITOR (71) We, MURATA MANUFACTURING Co., LTD., a Japanese Body Corporate, of 16 Nishijin-cho, Kaiden, Nagaokakyo-shi, Kyoto-fu, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a capacitor, and more particularly, to a cylindrical shaped capacitor element of comparatively small size with high capacitance capable of receiving high voltages such as 50 to 500 volts, and having lead wires extending outwardly and coaxially in alignment with the axis of the cylindrical shaped body for the external connection therewith.

Conventionally, there have been proposed various types of cylindrical shaped capacitors in which one example shown in Fig. 1 ineludes a pipe shaped cylindrical body a made of dielectric material with opposite ends thereof opened. First and second electrodes b and c are laminated approximately on the inner and outer surface of the cylindrical body a, in such a manner that the first electrode b provided on the inner surface of the cylindrical body a extends from an intermediate portion of the inner surface preoccupying a clearance d between one end face of the cylindrical body and the edge of first electrode b, towards the other end face of the body and further onto the outer surface of the body a to terminate at position adjacent said other end face, while the second electrode c is provided on the outer surface of the body a with a predetermined clearance e provided between the first and the second electrodes.

The capacitor of the conventional type as described above further includes first and second cap elements f and g mounted on opposite end portions of the cylindrical body for the connection with the first and second electrodes, respectively. Each of the cap elements is provided with lead wire extending therefrom towards outside the body and serving as terminal members for the external connection therewith.

According to such conventional type of capacitor, there are such disadvantages that the dielectric material forming the cylindrical body a must be prepared in a thickness having enough durability against various shocks and pressures such as pressure applied when mounting the cap element on opposite ends of the body, and that since the increase in thickness of the dielectric material decreases the capacitance of the capacitor, it has been quite difficult to obtain small size capacitors having large capacitance.

Furthermore, positioning of the electrodes, particularly, the first electrode b, requires elaborate procedure in the manufacturing step thereof, while the application of the two cap elements results in high manufacturing cost, since such cap elements are comparatively expensive with respect to the manufacturing cost required for each of the capacitors.

Another type of conventional capacitor (not shown) includes pipe shaped cylindrical body with first and second electrodes being laminated entirely on the outer and inner surface of the cylindrical body, respectively, and one cap element mounted on one end of the cylindrical body for the connection with the electrode provided on the outer surface.

The electrode provided on the inner surface of the body is connected directly to the lead wire, the one end of which is partly inserted into the cylindrical body and is connected to the electrode provided on the inner surface of the body through application of solder.

However, this type of capacitor has difficulty not only in soldering the lead wire onto the electrode provided on the inner surface of the body, but also in positioning the lead wire coaxially with the axis of the cylindrical body.

Accordingly, a primary object of the present invention is to provide an improved capacitor of cylindrical shape of comparatively small size which has high capacitance.

Another object of the present invention is to provide a capacitor of the above described type which has sufficient resistance against shocks applied thereto.

Yet another object of the present invention is to provide a capacitor of the above des cribed type which is simple in construction and stable in functioning and can readily be manufactured at low cost.

In order to accomplish these and other objects, according to the present invention, the capacitor comprises a cylindrical body of dielectric material having an opening formed at one end face thereof, in which the opening extends through the cylindrical body and terminating therein adjacent the other end face of the body for forming a hollow portion in the body. In other words, the cylindrical body has one end opened and the other end closed. First and second electrodes are laminated on the outer and inner surface of the body, respectively, and are insulated from each other at the open end of the body.

With such structure as described above, it is understood that capacitance is produced between the first and second electrodes. Since the cylindrical body is closed at said other end, side wall of the cylindrical body is reinforced. Accordingly, it is possible to make the thickness of the cylindrical body comparatively thin, and thus the capacitance is increased. Furthermore, the increase in area between the first and second electrode obtained by the additional dielectric material provided to close said other end of the cylindrical body further increases the capacitance therebetween.

In order to facilitate the connection of the second electrode provided on the inner surface of the body with a terminal member such as lead wire provided for the external connection, the terminal member includes at the end portion thereof which is to be inserted into the hollow, various contacting members which readily contact the surface of the second electrode upon insertion of the terminal member.

These and other objects and features of the present invention will become apparent from the following descriptions taken in conjunction with preferred embodiment thereof with reference to the accompanying drawings, in which; Fig. 1 is a drawing already referred to in the foregoing description, and particularly showing cross sectional view of the capacitor of the conventional type; Fig. 2 is a perspective view of a capacitor of the present invention; Fig. 3 is a cross sectional view taken along a line III-III shown in Fig. 2; Figs. 4 and 5 are similar views to Fig. 3, but particularly showing modifications thereof; Fig. 6 is a similar view to Fig. 2, but particularly showing modification thereof; Fig. 7 is a perspective view of a cap element;; Figs. 8a and 8b are perspective and side views of a cap element which is a modification of the cap element shown in Fig. 7; Fig. 9 is a cross sectional view of the capacitor of the present invention, particularly showing modification of the terminal member; Fig. 10 is a perspective view of the capacitor of the present invention, particularly showing modification of the hollow formed in the body; Figs. 11 and 12 are similar views to Fig. 3, but particularly showing modifications of the terminal member; Figs. 13a, 13b and 13c are side views of the terminal member showing various modifications; Figs. 14 and 15 are similar views to Fig. 3, but particularly showing modifications thereof; Figs. 16a, 16b and 16c are perspective views of the terminal members particularly showing patterns of grooves to be formed thereon;; Figs. 17a and 17b are cross sectional views of the terminal members showing modifications thereof; and Figs. 18, 19, 20, 21, 22 and 23 are similar views to Fig. 3, but particularly showing modifications thereof.

Before the description of the present invention proceeds, it should be noted that like parts are designated by like reference numerals throughout the accompanying drawings.

Referring to Fig. 2, a capacitor 2 of the present invention comprises a cylindrical body 4 of dielectric material having an opening or bore 6 formed at one end face 8a thereof. The opening 6 extends through the cylindrical body 4 and terminating inwardly adjacent the other end face 8b of the body for forming a hollow portion 10 in the body 4, as best shown in Fig. 3. According to the embodiment shown in Fig. 3, the length of the cylindrical body 4 between the opposite end faces is comparatively small, for example, being 5 mm. A first electrode 12 is provided entirely on the outer surface of the cylindrical body 4, except on the end face 8a formed with the opening 6. Such first electrode 12 may, for example, be of a film of electrically conductive material, such as copper, laminated on said outer surface. A second electrode 14 also made of film of electrically conductive material, is laminated on the inner surface of the body 4 which corresponds to the surface forming said hollow 10. It is to be noted that the first and the second electrodes 12 and 14 are separated from each other at the end face 8a of the body.

The arrangement as described above constructs a fundamental portion of the capacitor 2, in which the electric energy can be accumulated between the first and the second electrodes, that is, substantially in the dielectric body 4.

In order to constitute the structure as described above, first the cylindrical body having the length between the opposite ends 8a and 8b slightly longer than the required length is laminated completely on the outer and inner surface thereof with the film of copper through a suitable laminating means, for example, immersion of the body in the molten copper or deposition of the copper.

Then, the end face 8a formed with the opening 6 is ground to remove the film of the copper and to adjust the length of the cylindrical body to the required length.

The capacitor 2 of the present invention further comprises first and second terminal members 16 and 18 connected to the first and second electrodes 12 and 14, respectively. The first terminal member 16 includes a cap element 20 of electrically conductive material which is fitted over the one end portion of the cylindrical body 4 for covering the end face 8b of the body 4, and a lead wire 22 extending outward from the center of the cap element 20 coaxially in alignment with the axis of the cylindrical body 4.The second terminal member 18 includes a lead wire 24 having one end inserted into the hollow portion 10 through the opening 6 for the electrical connection with the second electrode 14, and the other end extending outwardly from the opening 6 coaxially in alignment with the axis of the cylindrical body 4 for the external connection.

The electrical connection between the lead wire 24 and the second electrode 14 is effected by soldering in such a manner that the end portion of the lead wire 24 is bent substantially into "L" shape, while a bead of solder 26 rigidly connects the lead wire 24 and the second electrode 14.

A cover member 30 of electrically nonconductive material, such as synthetic resin, is provided around said body 4 and cap element 20 in an air tight relation thereto, while the lead wires 22 and 24 extend outwardly from openings formed in the cover member 30. Such cover member 30 is provided for the protection of the capacitor 2 from environmental conditions such as moisture and external forces which may injure the second electrode 14, and for supporting the lead wire, particularly the lead wire 24, in position coaxially aligned with the axis of the cylindrical body 4. It is to be noted that the cover member 30 may be formed by a heat shrinkable tube.

According to the capacitor 2 of the present invention, the thickness of the dielectric material forming the side wall ofthe cylindrical body 4 can be made comparatively thin, since the end wall containing the end face 8b reinforces the side walll of the cylindrical body 4. Furthermore, the effective surface for forming capacitor between the two electrodes extends not only over the side wall of the body 4, but also on over end wall thereof.

Therefore, it is possible to obtain higher capacitance between the two electrodes.

The description hereinbelow is directed to various modifications and arrangements of the capacitor 2 described above for the purpose of improvement.

Referring to Fig. 4, there is shown a capacitor 2a, which is a modification of the capacitor 2 shown in Fig. 3. The capacitor 2a has the cylindrical body 4a formed with a flanged portion 32 around the edge of the end face 8a for forming the outer diameter at the end face 8a substantially equal to the same of the cap element 20. With such arrangement, the constructed capacitor 2a is further reinforced at the end face 8b, while at the same time, the capacitor 2a will be stable when placed on a plane.

Referring to Fig. 5, there is shown a capacitor 2b, which is another modification of the capacitor 2 shown in Fig. 3. In this modification the cylindrical body 4b has the hollow portion 10b defined by a tapered wall.

In other words, the diameter of the hollow portion 10b is greatest at the end face 8a of the body 4b where the opening 6 is formed and is gradually narrowed towards the end of the hollow portion 10b which terminals adjacent the other end face 8b. Such hollow portion 10b presents the thickness of the side wall of the cylindrical body 4b to gradually increase toward the end face 8b, so that the body 4b itself is reinforced at the end portion including the end face 8b. Such reinforced end portion prevents the body 4b from being cracked particularly when the cap element 20 is forcibly mounted on the end portion.

Referring to Fig. 6, there is shown a capacitor 2c, which is a further modification of the capacitor 2 shown in Fig. 3. In this modification, the cap element 20e is substantially presented in a cylindrical shape having one end opened for the insertion ofthe body 4 and the other end closed for the contact with the end face 8b. The length of the cylindrical part of the cap element 20c is longer than half the length of the cylindrical body 4, while shorter than the full length of the cylindrical body 4. Such long cap element 20c ensures the connection between the first terminal member 16 and the first electrode 12, while at the same time, protects the cylindrical body 4. The connection between the cap element 20c and the first electrode 12 may be effected by deposition of electric conductive bonding agent such as solder.In order to spread the solder evenly and thorougly between the cap element and the first electrode, the surface of the first electrode and/or the inner surface of the cap element is formed with numbers of grooves in which the molten solder is spread. Instead of forming such grooves, an elongated opening or openings may be formed in the cap element 20c as is described hereinbelow.

Referring to Fig. 7, the cap element 20d is formed with two elongated openings 36a and 36b which will be filled with solder after inserting the body 4 into the cap element 20d.

Such openings 36a and 36b can be extended entirely along the side of the cylindrical cap element 20d, as shown in Figs. 8a and 8b, for substantially dividing the cylindrical cap element 20d into first and second covering elements 38a and 38b. Such separation of the cylindrical element into two covering elements facilitates the insertion of the body 4 therein.

It is to be noted that the two covering elements 38a and 38b may be connected to each other by means of connecting bar 39 extending therebetween. The connecting bar 39 preferably has some degree of elasticity for urging the two covering elements 38a and 38b towards each other when they are forced to be further separated apart form each other. Such urging force temporarily holds the body 4 in the inserted position. For securing the connection of the covering elements with the body 4, solder may be filled in the clearance between the two covering elements.

Referring to Figs. 9 and 10, there is shown a second terminal member 18e which is a modification of the second terminal member 18 described above. The second terminal member 1 8e has a rectangular plate 40 rigidly connected or integrally formed at the end of the lead wire 24 which contacts the second electrode 14. The rectangular plate 40 is formed by a conductive material such as copper and may be either comparatively thin for producing some degree of flexibility, or comparatively thick for presenting rigid structure. In either case, the four edges of the rectangular plate 40 is rounded for preventing the second electrode 14 from being undesirably scratched.In the case where the plate 40 is flexible, the width of the plate 40 is preferably equal to or slightly larger than the diameter of the cylindrical hollow portion 10 such as shown in Fig. 10, so that the plate 40 is slidingly inserted into the hollow portion 10. However, in the case where the plate 40 is of rigid type, the width of the plate 40 is preferably equal to or slightly smaller than the hollow portion 10. When the hollow portion is of the tapered type as shown in Fig. 9, the width of the plate 40 of the flexible and rigid type may be slightly smaller than the opening 6. In order to effect soldering, if necessary, between the plate 40 and the second electrode 14, the plate 40 may carry a bead of solder (not shown) which is melted, by the application of heat through the lead wire 24, after the insertion of the plate 40 into the hollow portion.In order to increase the contacting face between the plate 40 and the second electrode 14, the hollow portion is preferably formed such that the cross sectional shape thereof is substantially elliptical throughout the entire length of the hollow portion, as shown in Fig. 10.

Referring to Fig. 11, there is shown a second terminal member 1 8f which is another modification of the terminal member 18 shown in Fig. 3. The terminal member 1 8f has the lead wire 24 presented in a zigzag form at the end portion where the lead wire 24 is inserted into the body 4. The distance between the peaks of the zigzag portion is approximately equal to the diameter of the hollow portion 10, so that the respective peaks of the lead wire 24 comes into contact with the second electrode 14. For effecting the soldering between the lead wire 24 and the second electrode 14, the zigzag part of the lead wire 24 is previously coated or laminated with solder which is melted, by the application of heat through the lead wire 24, after the insertion of the lead wire 24 into the body 4.

Referring to Figs. 12 and 13a, there is shown a second terminal member 1 8g which is a further modification of the terminal member 18 shown in Fig. 3. The terminal member 1 8g includes a contact member 42 made of electrically conductive material in a flange-like shape provided at the end of the lead wire 24. Upon insertion of the wire 24 into the hollow portion 10, the contact member 42 slidingly contacts the surface of the second electrode 14 so as to connect the second electrode 14 with the lead wire 24.

The terminal member 1 8g further includes a support member 44 in a form of collar integrally connected to or rigidly mounted on the lead wire 24 in a spaced relation to the contact member 42 so that when the lead wire 24 is inserted into the hollow portion 10, the support member 44 locates inside the hollow portion 10 and adjacent the opening 6.

The outer diameter of the support member 44 is slightly smaller than the inner diameter of the cylindrical body 4 so that the insertion of the support member 44 can be easily effected.

The support member 44 thus inserted supports the lead wire 24 approximately in alignment with the axial direction of the cylindrical body 4. Since the wire 24 is already connected with the second electrode 14 through the contact member 42, it is not necessary to obtain any electrical connection between the support member 44 and the second electrode 14. Therefore, the support member 44 can be either metallic material or non-metallic material such as synthetic resin.

Instead of forming the support member 44 in the form of the collar, it can be formed with two or more projections 44a extending radially from the lead wire 24, as shown in Fig. 13b.

Likewise, the contact member 42 can be formed with two or more projections 42a radially extending from the lead wire 24, as shown in Fig. 13c.

According to the terminal members described above in connection with Figs. 9 to 13c, the face which contacts the second electrode 14 is comparatively small, so that the application of the solder may be by a small amount. Therefore, the second electrode 14 will not be damaged by the shrinkage of the solder which might otherwise peel off the second electrode.

Referring to Fig. 14, there is shown a second terminal member 1 8h which is a yet further modification of the second terminal member 18 shown in Fig. 3. The terminal member 1 8h includes a hollow cylindrical contact member 46 which has one end opened and the other end closed. The center of the closed end of the contact member 46 is integrally formed or fixedly connected with the lead wire 24. The cylindrical contact member 46 is fitly inserted into the hollow portion 10 formed in the body 4 for the connection between the lead wire 24 and the second electrode 14.In order to protect the side wall of the cylindrical body 10 from being cracked, as is most likely to be caused by an external force applied on the lead wire 24, it is preferable to extend the cap element 20 to cover the cylindrical body entirely therearound, as shown in Fig. 15.

For the purpose of rigid connection between the contact member 46 and the second electrode 14, it is preferable to effect soldering between the faces which are in contact with each other. For spreading the solder evenly and thoroughly between the faces, the surface of the contact member 46 and/or the surface of the second electrode 14 is formed with numbers of grooves, for example, in the forms shown in Figs. 16a, 16b and 16c for the contact member 46.

The hollow cylindrical contact member 46 can be rearranged in different forms, such as shown in Figs. 17a and 17b, in which Fig. 17a shows a cylindrical contact member 46a having the lead wire 24 inserted into the hollow portion formed in the contact member 46a, while the Fig. 1 7b shows a cylindrical contact member 46b having opposite ends being closed.

It is to be noted that the lead wire connected to any one of the cylindrical contact member 46 is in alignment with the axial direction of the respective cylindrical contact member 46, so that the lead wire is substantially in alignment with the cylindrical body 4.

Referring to Fig. 18, the capacitor 2 further comprises a shielding member 50 of non-conductive material such as synthetic resin which is provided to cover the hollow portion 10 and to support the lead wire 24, and also to reinforce the body 4 at the end face 8a of the body 4. The shielding member 50 shown in Fig. 18, as well as those shown in Figs. 19 and 20, is formed by a deposition of synthetic resin on and around the end face 8a. Although it is preferable to fill up the hollow portion with such synthetic resin, it is difficult to have the synthetic resin flow into the hollow portion, since the hollow portion is so small while the surface tension of the synthetic resin is comparatively high. However, it is found that the deposition of the synthetic resin at the end face 8a would sufficiently support the lead wire and reinforce the body 4.

In order to secure the deposition of such synthetic resin at the end face 8a, it is preferable to increase the surface which contacts the resin, and also to increase the edges which engage with the resin. For this purpose, the second terminal member 18, particularly provided with the cylindrical contact member 46 is positioned such that the contact member 46 slightly projecting outwardly from the opening 6, while the cap element is prepared in such a length that the edge thereof locates adjacent the end face 8a of the cylindrical body 4, as shown in Fig. 19, or otherwise in opposite relation, as shown in Fig. 20, in which the cylindrical contact member 46 is positioned inwardly adjacent the end face 8a of the body 4, while the edge of the cap element locates at the position further projected from the end face 8a.

Referring to Fig. 21, there is shown a shielding member 50k which is a modification of the shielding member 50 shown in Fig. 18.

The shielding member 50k of non-conductive material such as synthetic resin is previously formed through molding or other known method in a cylindrical shape having flange portion 52 at one end thereof and a through hole 54 in the axial direction thereof. In order to accommodate the shielding member 50k onto the body 4, the lead wire 24 is first inserted into the through hole 54, and then the body thereof is fitly inserted into the hollow portion 10 until the flange portion 52 engages the end face of the body 4.For securing the position of the shielding member 50k, a suitable bonding agent, such as thermoset resin may be provided between the faces which contact with each other, or otherwise, the cap element having the cylindrical portion thereof may be provided to be longer than that of the body 4 for tightly clamping the flange 52 of the shielding member 50k against the end face 8a, as shown in Fig. 22.

Referring to Fig. 23, there is shown a shielding member 50m which is a modification of the shielding member 50k shown in Fig. 21.

The shielding member 50m in this modification has the cylindrical body thereof prepared in a length slightly smaller than the length of the hollow portion formed in the body 4. The lead wire 24 is inserted into the through hole 54 formed in the shielding member 50m, while the tip end of the lead wire 24 projects slightly outwardly from the through hole 54, so that the tip end of the lead wire comes into contact with the second electrode 14 when the shielding member 50m is inserted into the hollow portion 10 formed in the body 4.

As is apparent from the foregoing des cription, the capacitor of the present invention can present high capacitance regardless of its small size, while the electrodes thereof can be applied thereto through simple procedures. Furthermore, the application of cover member 30 as well as the shielding member 50 prevents the capacitor from being damaged by the shocks and environmental conditions.

Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the scope of the present invention, they should be construed as included therein.

WHAT WE CLAIM IS 1. A capacitor which comprises: a cylindrical body, of dielectric material, which body has at one end an opening, which extends to a hollow portion formed in said body, and is closed at its other end, such that the cylindrical body includes an outer surface around the body and an inner surface around said hollow portion; a first electrode film made of electrically conductive material, said first electrode film laminated on the outer surface of the body; a second electrode film made of electrically conductive material, said second electrode film laminated on the inner surface of the body, and said first and second electrode films being insulated from each other at said opening formed in the body;; a cap element of electrically conductive material mounted on the body through the first electrode film, said cap element having a lead wire extending therefrom for an external electric connection thereto; an insert element of electrically conductive material having one end inserted into the hollow portion for the electrical and mechanical connection with the second electrode film and the other end extending outwardly from said hollow portion through said opening for external electric connection thereto; a cover member of electrically non-conductive material provided around said body and cap element in an air tight relation thereto, said cover member having two openings for the projection of said lead wire and said insert element, respectively.

2. A capacitor which comprises: a cylindrical body of dielectric material having an opening formed at one end face thereof, said opening extending through the cylindrical body and terminating inwardly adjacent the other end face of the body for forming a hollow portion in the body, so that the cylindrical body includes an outer surface around the body and an inner surface around said hollow portion; a first electrode film made of electrically conductive material, said first electrode film laminated on the outer surface of the body; a second electrode Im made of electrically conductive material, said second electrode film laminated on the inner surface of the body, and said first and second electrode films being insulated from each other at said opening formed in the body;; a cap element of electrically conductive material mounted, through the first electrode film, on the body at said other end face thereof, said cap element having a lead wire extending therefrom in a direction in alignment with an axis of said body, for an external electric connection thereto an insert element of electrically conductive material having one end portion inserted into the hollow portion for the electrical and mechanical connection with the second electrode film, and the other end extending outwardly in the direction in alignment with the axis of said body, from said hollow portion through said opening for external electric connection thereto; a cover member of electrically non-conductive material provided around said body and cap element in an air tight relation thereto, said cover member having two openings for the projection of said lead wire and said insert element, respectively.

3. A capacitor as claimed in Claim 2, wherein said cylindrical body is provided with a flange portion around said one end face thereof.

4. A capacitor as claimed in Claim 2, wherein said hollow portion formed in the cylindrical body is tapered to reduce the diameter as the hollow portion extends towards the other end face of the cylindrical body.

5. A capacitor as claimed in Claim 2, wherein said cap element is presented in a form of cylinder with one end opened and the other end closed to cover more than half the length of the cylindrical body.

6. A capacitor as claimed in Claim 5, wherein said cap element has at least one opening formed in the cylinder thereof for deposition of bonding agent.

7. A capacitor as claimed in Claim 5, wherein said cap element has a groove formed in parallel relation to the axis of the cylinder so as to substantially separate the cylinder into a first half cylinder and a second half cylinder, said cylindrical body provided between the first and second half cylinders.

8. A capacitor as claimed in Claim 5, wherein at least one surface of said first electrode film and surface of cap element which comes into contact with the first electrode film is formed with a number of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. cription, the capacitor of the present invention can present high capacitance regardless of its small size, while the electrodes thereof can be applied thereto through simple procedures. Furthermore, the application of cover member 30 as well as the shielding member 50 prevents the capacitor from being damaged by the shocks and environmental conditions. Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the scope of the present invention, they should be construed as included therein. WHAT WE CLAIM IS

1. A capacitor which comprises: a cylindrical body, of dielectric material, which body has at one end an opening, which extends to a hollow portion formed in said body, and is closed at its other end, such that the cylindrical body includes an outer surface around the body and an inner surface around said hollow portion; a first electrode film made of electrically conductive material, said first electrode film laminated on the outer surface of the body; a second electrode film made of electrically conductive material, said second electrode film laminated on the inner surface of the body, and said first and second electrode films being insulated from each other at said opening formed in the body;; a cap element of electrically conductive material mounted on the body through the first electrode film, said cap element having a lead wire extending therefrom for an external electric connection thereto; an insert element of electrically conductive material having one end inserted into the hollow portion for the electrical and mechanical connection with the second electrode film and the other end extending outwardly from said hollow portion through said opening for external electric connection thereto; a cover member of electrically non-conductive material provided around said body and cap element in an air tight relation thereto, said cover member having two openings for the projection of said lead wire and said insert element, respectively.

grooves for spreading solder on respective surfaces.

9. A capacitor as claimed in Claim 2, wherein said insert element is a lead wire having said one end portion bent at the tip thereof for the contact with the second electrode film, said one end secured on the second electrode by deposition of solder.

10. A capacitor as claimed in Claim 2, wherein said insert element comprises a lead wire and a prde member of conductive material connected to said one end of the lead wire, said plate member positioned in parallel relation to the axis of the cylindrical body for contacting the edge of the plate member with the second electrode film.

11. A capacitor as claimed in Claim 2, wherein said insert element comprises a lead wire having said one end being formed into zigzag portion for connecting the peak of the zigzag portion with the second electrode film.

12. A capacitor as claimed in Claim 2, wherein said insert element comprises a lead wire, a support element mounted on the lead wire for supporting said lead wire in the hollow portion, and a contact member of conductive material provided at the end of the lead wire, said contact member being formed in curved plate extended approximately in perpendicular relation to the axis of the cylindrical body for slidingly contacting the edge of the curved plate with the surface of the second electrode film.

13. A capacitor as claimed in Claim 2, wherein said insert element comprises a lead wire and a drum shaped member of conductive material provided at the end of the lead wire said drum shaped member fittingly inserted into the hollow portion for the contact between the drum shaped member and the second electrode film.

14. A capacitor as claimed in Claim 13, wherein said drum shaped member is secured in position by deposition of solder between a surface of the drum and the second electrode film.

15. A capacitor as claimed in Claim 14, wherein at least one surface of said drum and the second electrode film is formed with number of grooves for spreading solder on respective surfaces.

16. A capacitor as claimed in Claim 2 further comprises a shielding member mounted on said one end face of the cylindrical body for shielding the opened end of the cylindrical body to close the hollow portion in an air tight relation for preventing the second electrode film and the insert element from being injured by environmental conditions.

17. A capacitor as claimed in Claim 16, wherein said shielding member is a deposition of synthetic resin.

18. A capacitor as claimed in Claim 16, wherein said shielding member includes a cylindrical portion and a flange portion provided at the end of the cylindrical portion, said cylindrical portion being formed with through hole for inserting therein said insert element, said cylindrical portion fittingly inserted into the hollow portion formed in the body with said flange portion being engaged with said one end of the cylindrical body.

19. A capacitor as claimed in Claim 18, wherein said cylindrical portion is slightly shorter than the length of said hollow portion for contacting a tip end of the insert element with indented end of the second electrode upon insertion of the shielding member into the hollow portion.

20. A capacitor as claimed in Claim 18, wherein said cap element engages with said flange portion of the shielding member for securing the shielding member tightly against one end face of the cylindrical body.

21. A capacitor as claimed in Claim 18, wherein said flange portion and the one end face of the cylindrical body is bonded together by a thermoset resin.

22. A capacitor as claimed in Claim 2, wherein said cover member is formed by a heat shrinkable tube.

23. A method of manufacturing a capacitor comprises the steps of: a) preparing a cylindrical body of dielectric material having an opening formed at one end face thereof, said opening extending through the cylindrical body and terminating inwardly adjacent the other end face of the body for forming a hollow portion in the body, so that the cylindrical body includes an outer surface around the body and an inner surface around the hollow portion; b) laminating entirely on the outer and inner surface of the body with film of electric conductive material; c) removing said film of electric conductive material provided on the end face having opening for presenting a first electrode on the outer surface and a second electrode on the inner surface of the cylindrical body; ; d) grinding said cylindrical body at said end face for reducing the length of the cylindrical body to a predetermined length which produces predetermined amount of capacitance between the first and second electrodes; e) mounting a cap element on said other end face of the cylindrical body, said cap element provided with lead wire extending from the center thereof in alignment with the axis of the cylindrical body for the external connection of the first electrode; f) inserting one end portion of an insert element of electrically conductive material into the hollow portion for the electrical and mechanical connection with the second electrode, other end of the insert element extending outwardly in a direction in alignment with the axis of the body from the hollow portion through said opening for the external electric connection thereto; and g) covering said body and cap element in an air tight relation thereto with a cover member of electrically non-conductive material, said lead wires projecting from said cover member.

24. A capacitor as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.