GB2154062A

GB2154062A - Anchoring electrical devices

Info

Publication number: GB2154062A
Application number: GB08502635A
Authority: GB
Inventors: William J Evans; John D Shaw
Original assignee: Emhart Industries Inc
Current assignee: Emhart Industries Inc
Priority date: 1984-02-06
Filing date: 1985-02-01
Publication date: 1985-08-29
Also published as: DE3447851A1; JPS60171711A; GB8502635D0

Abstract

In an electrical device of a type including a housing (12) having an open end (42) for receiving an electrical component (14) such as a capacitor, and a bottom wall (58) providing a closed end (40), the housing (12) includes an anchoring spike (60) forming an integral part of the bottom wall (58) to align and secure the electrical component (14) within the housing (12). The anchoring spike (60) extends axially upwardly and includes a distal end (64) for engaging the electrical component (14) to laterally position the electrical component (14) along the bottom wall (58). The anchoring spike (60) further includes a threaded bore (66) opening outwardly for engaging a fastening device (68) to mount the electrical device to a base member (70). The bottom wall (58) including the anchoring spike (60) is constructed of a heat conductive material whereby the bottom wall (58), anchoring spike (60), fastening device, (68) and base member (70) provide a heat sink for dissipating heat from the electrical component (14). <IMAGE>

Description

SPECIFICATION Anchoring electrical devices The present invention relates to electrical devices of the type which includes a housing containing an electrical component.

Many electrical devices include an electrical component enclosed within a housing. An A-C electrolytic capacitor is an example of such an electrical device. Conventional dry-type electrolytic capacitors are formed by winding two sheets of metallic foil into a cylindrical shape.

The foil sheets are separated by a suitable insulative material impregnated with an electrolyte. The foil and insulative materials cooperate to form the capacitor body or cartridge.

Electrical devices such as capacitors are known to deteriorate in at least two different ways. Mechanical and thermal shock can cause serious damage to electrical components, in particular, to the delicate foil sheets of a capacitor. In applications where capacitors are exposed to mechanical shock or vibrations, it is important that the capacitor body not move in relation to the housing. Such movement can significantly impair proper electrical functioning of the capacitor. In addition, capacitors are frequently exposed to thermal shock when used in filter circuits to smooth the output voltage of a rectifier. The DC output of a bridge rectifier circuit is characterised by residual pulsation called "ripple" current. A large ripple current generates heat within the capacitor body which causes a significant reduction in capacitor life.

One of the earliest ways of anchoring the capacitor or electrical component within the housing to minimize mechanical shock was to place tar or asphalt in the bottom of the housing around the electrical component.

However, it was found that the tar or asphalt is not adequate to prevent harmful movement in applications involving great amounts of mechanical vibration. Accordingly, many anchoring devices have been developed in an effort to secure the electrical component within the housing.

Known anchoring devices include pieceparts that are separate and distinct from the capacitor housing. One type of anchoring device has been constructed only to engage the upper portion of a capacitor body while another type is designed to engage and support the lower end of the capacitor body.

Typically, an anchor device of the first type is either moulded into the inwardly facing surface of the detachable top cover of the housing or interposed between the capacitor body and the top cover to engage the axially upper end face of the capacitor body. Further, known anchor devices of the second type are inserted to the housing on the bottom wall to engage and support the axially lower end face of the capacitor body.

An anchor device of the second type for engaging and supporting the axially lower end face of a capacitor body is disclosed in U.S.

Patent No. 4,339,786 and is shown to include a centrally extending spike and radially extending members which abut the side and distal end of the housing. Neither the spike nor the radially extending members is formed to be an integral feature of the capacitor housing. The spike includes a proximal end fixed to the radially extending members and a distal end extending axially upwardly in the housing. The distal end is generally sized to engage a central axial core of the capacitor body. During assembly, the anchoring device is "dropped" into the otherwise empty capacitor housing and positioned along the bottom wall prior to insertion of the capacitor body into the housing.

While, in many instances, anchoring devices of the types described above are sufficient to protect a capacitor from unwanted mechanical shock, such conventional means do not mitigate the effect of thermal shock on filter-type capacitor caused by excessive ripple current. In point of fact these conventional anchor devices are many times constructed of materials that are not good thermal conductors e.g. glass fibre, reinforced nylon and polypropylene. Further, such anchoring devices are piece-parts separate from the housing. Thus, an additional manufacturing step is required to produce the generally plastic anchoring device and additional assembly steps are required to insert the anchoring device in its place within the capacitor housing.

The present invention envisages an improved anchoring means which is an integral feature of the bottom wall of the electrical device housing and not a discrete part. This novel means for anchoring the lower portion of a capacitor body reduces the number of costly and time consuming manufacturing and assembly steps necessary to produce the electrical device and further helps to improve the dissipation of heat within the capacitor body since the improved anchoring means is easily and inexpensively fabricated from the same heat conductive material used to form the housing.

Accordingly, the present invention provides an electrical device comprising an electrical component such as a capacitor and a housing for containing the electrical component. The housing has an open end for receiving the component. The electrical component is suitably formed to include a central axial core.

The housing also includes a bottom wall which faces the open end of the housing. The bottom wall includes anchoring means for engaging the electrical component, e.g. the axial core, to align and secure the component within the housing.

In the illustrative embodiment, hereinafter described in detail, the anchoring means in cludes means for receiving and engaging a fastening element to mount the housing to a chassis such as a printed circuit board or other base member, said means comprising a spike formed, as by extrusion, to be an integral part of the electrical component housing.

The spike includes a proximal portion forming a part of the bottom wall and a distal portion projecting in the direction of the open end of the housing. The spike extends axially upwardly in the housing so that it may easily engage the axial core of the electrical component. A truncated hole or bore is formed in the spike along its longitudinal axis. The truncated hole has a single opening which is located in the exterior face of the bottom wall of the capacitor housing. Thus, the hole opens outwardly from the bottom wall. The hole is preferably tapped to provided means for receiving a threaded fastening element such as a bolt so that the housing can be securely fixed to the chassis.

A preferred embodiment of the present invention includes a spike integrally formed in the bottom wall of the housing. 8uch an integral spike is easily extruded and provides two distinct advantages. The spike serves the dual purpose of aligning and securing the capacitor body within the housing to diminish the effect of mechanical shock or vibration and also of dissipating heat generated therein to the chassis or base member by conduction away from the electrical component in the housing. Dissipation of the heat is achieved by the fact that the spike engages the core of the capacitor body and is constructed of the same material as the housing i.e. metal, which is a good conductor of heat. The spike in combination with the base member serves as a heat sink.Further. a separately manufactured and installed element, such as a conventional plastic anchoring device of the type described above, is no longer required to be interposed between the lower end of the capacitor body and bottom wall of the housing.

Thus, manufacturing and assembly costs are reduced.

Another feature of the preferred embodiment of the present invention is that the anchoring means includes means for receiving a fastening element. Conventional electrical device mounting techniques include cumbersome strap and clamp means. A feature of this preferred embodiment is the provision of a central mass of material in the bottom wall of the housing in which a hole is tapped to accept a threaded fastening element. Such an advantage is not attainable in conventional electrical device housings due to the use of separate plastic anchoring devices of the type described above.

A further advantage of the present invention relates to the elimination of heat-insulating conventional anchoring devices along the bottom wall of the housing. In the present invention, the body of the electrical component, e.g. capacitor, sets directly on the bottom wall to provide a greater contact surface area than possible in conventional electrical devices.

Conduction heat transfer occurs through the bottom wall of the housing. Improved heat dissipation significantly prolongs the life of a capacitor. particularly, the fastening element of the preferred embodiment of the present invention can be tightened to cause the exterior portion of the bottom wall or closed end of the housing to be snugly drawn against the chassis or base member. Such close contact significantly improves conduction heat transfer between the component, e.g. capacitor, housing and the adjacent chassis to better dissipate heat generated in the capacitor body due to ripple current.

Yet another feature of the preferred embodiment of the present invention is the engagement of the spike in the axial core of the capacitor body. The novel spike is integrally coupled to the closed end of the housing and fabricated out of the same heat conductive material as used to form the housing. Thus, means are advantageously provided for conducting heat generated by the capacitor body from a point some distance within the interior of the housing to the surroundings outside of the housing. In particular, excess heat is conducted through the spike and fastening element to the chassis on which the electrical device is mounted to further prolong the life of a capacitor exposed to excessive ripple current or the like.

Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description, to be read with reference to the accompanying drawing, of one embodiment thereof, described by way of example.

The accompanying drawing is a view, partly in section, of an electrical device embodying the invention.

In the illustrative embodiment, the present invention provides an electrical device 10 having a container or housing 12 for receiving a conventional capacitor body 14. The capacitor body 14 includes a central core 16 along its longitudinal axis as shown in the drawing.

The capacitor body 14 is formed by a plurality of conductive and insulative sheets which are sandwiched together and typically wound around a mandrel (not shown). When the mandrel is removed, a hollow central core 16 typically remains.

An axially upper anchoring device 20 is shown which includes a central hub portion 22. The central hub portion 22 includes an axially downwardly extending top spike 24 which is adapted for engaging an electrical component, in this case, the rolled foil plates of the capacitor body 14. The top spike 24 includes a conically shaped end portion 26 which engages the central mandrel opening or core 16 common to such capacitors. The upper anchoring device 20 also includes at least two radially extending arms 28. The arms 28 terminate with radially extending ends 30. The ends 30 are rounded by an arc nominally having a radial centre at the centre of the upper anchoring device 20. Spacer means 32 are located in proximity to the radially extending ends 30. The spacer means 32 extend axially in the opposite direction from the top spike 24.Arms 28 of the top anchoring device 20 are resilient to adapt them for deflection to create a biasing force.

Any suitable semi-rigid masterial may be used for fabricating the upper anchoring device 20.

Examples of such materials are glass fibre, reinforced nylon and polypropylene.

The upper anchoring device 20 is shown in functional relationship with the electrical device 10. The container or housing 12 of the electrical device has a closed end 40 and an open end 42. The housing 12 is generally cylindrical in shape and may be fabricated from any suitable material such as a metal or metal alloy like aluminium or thermally conductive thermoplastic material. Housing 12 includes an inwardly extending flange 44 located in proximity to the open end 42. The flange 44 has an inwardly facing surface area 46. The surface area 46 faces towards the closed end 40 and away from the open end 42.

A rigid sealing member 50 closes the open end 42 of the housing 12. The rigid sealing member 50 is intended to abut the inwardly extending flange 44. The sealing member 50 may be fabricated from any suitable insulating material, and in one form phenolic resin is used. A pair of electrical connectors 52 are mounted in the sealing member 50 by rivets 54. A pair of connecting wires or risers 56 are used to connect the electrical connectors 52 to conductive sheets in the capacitor body 14.

The capacitor body 14 is held in position by the upper anchoring device 20 and the novel lower anchoring means 48 of the present invention. Thus, the lower end of the capacitor body 14 is engaged by the lower anchoring means 48. The lower anchoring means 48 is integrally formed in the bottom wall 58 of the closed end 40 and generally includes a central axially upwardly extending spike 60 for engaging the central core opening 16. In the illustrative embodiment the bottom spike 60 is extruded in the bottom wall 58 to provide a unitary closed end 40. The bottom spike 60 is thus fabricated out of the same thermaliy-conductive material used to fabricate the housing 12.

The bottom spike 60 includes a proximal portion 62 extending angularly upwardly from the bottom wall 58 and a distal portion 64 projecting in the direction of the open end 42 of the housing 12 to engage the core 16 of the capacitor body 14. Thus, the integral bottom spike 60 provides means for engaging the capacitor body 14 to laterally position the capacitor body 14 along the bottom wall 58 and align and secure the body 14 within the housing 12.

The distal portion 64 of the bottom spike 60 is shaped to provide a rounded or arcuate "nose". Further, the bottom spike 60 is tapered along its length such that the proximal portion 62 has the broadest cross-sectional area. Thus spike 60 is generally frustoconical in shape. For example, the base of the spike 60 is 3/8" in diameter and length varies between 1 /2" and 3/4" depending on the length of the housing 12. The bottom spike 60 is very easy to extrude because of its particular tapered shape. For example, impact extrusion would be an appropriate technique in manufacturing the housing and integral spike of the present invention. Further, the rounded nose of the distal portion 64 protects the layers of paper and foil in the capacitor body 14 from being torn during assembly of the electrical device 10.

A truncated hole 66 is bored and tapped in the exterior face of the closed end 40 as shown in the drawing. Thus, the bottom spike 60 includes means for receiving and engaging a fastening element 68 such as a bolt or other threaded member. It will be understood that any appropriate fastening element could be used without departing from the spirit of the present invention. The hole 66 opens outwardly towards the chassis 70 or other similar surface upon which the electrical device 10 is to be mounted. Appropriate chassis 70 would include a printed circuit board, metal plate, or an L-shaped metal bracket mounted on either the PC board or the plate.

The electrical device 10 is assembled by inserting the capacitor body 14 into the housing 12 so that the bottom spike 60 penetrates the core 16 of the capacitor body 14. Thus, the lower portion of the inserted capacitor body 14 is properly aligned and secured within the housing 12. The lower end face of the capacitor body 14 contacts the bottom wall 58 to support the capacitor body 14 within the housing 12. Next, the upper anchoring device 20 is positioned within the housing 12 between the inserted capacitor 14 and the rigid sealing member 50. A space 72 is left between the capacitor 14 and the sealing member 50 for allowing the resilient deflection of the upper anchoring device 20.

As positioned, the central spike 24 of the upper anchoring device 20 acts as a means for abutting the capacitor 14 in the area of the central core 16. The sides of the top spike 24 forcibly engage the inside wall of the core 16. Also, as positioned, the axially extending spacer means 32 extends in the direction of the sealing member 50 and abuts against the sealing member 50 to apply a biasing force to the upper anchoring device 20. In this manner, the central hub 22 and the spacer means 32 cause the radially extending arms 28 to concavely resiliently deflect into the housing 12 when the upper anchoring device 20 is installed between the capacitor 14 and the sealing member 50. Such deflection causes a biasing force to be set up between the capacitor 14 and the rigid member 50.

During installation of the capacitor 14 the flexibility of the upper anchoring device 20 allows the radially extending arms 28 to concavely deflect to allow the radially extending ends 30 to be installed through the open end 42 and past the flange 44 to engage the flange surface 46. After such engagement is attained, the radially extending arms 28 remain concavely deflected to produce the axial biasing force to hold the capacitor 14 against the bottom wall 58 of the housing 12. The bottom spike 60 of the lower anchoring means 48 aligns the capacitor 14 within the housing to dampen vibration and mechanical shock. Further, the bottom spike 60 conducts heat generated within the capacitor body from a point some distance within the interior of the housing to the chassis or base member 70.The lower anchoring means 48 and chassis 70 provide a heat sink for heat generated in the capacitor body 14.

The housing 12 is mounted on a chassis 70 by passing a fastening element 68 though an aperture in the chassis 70 for engagement with the tapped hole 66 in the bottom spike 60. The fastening element 68 is tightened to draw the exterior face of the closed end 40 into close contact with the chassis 70 whereby heat generated in the capacitor body 14 as a result of ripple current or the like will be conducted to the chassis 70 via the closed end 40 and the fastening element 58 for dissipation to the surroundings. Thus, the present invention provides means for dissipating excess heat to minimize the debilitating effect of thermal shock on the electrical device 10.

Although the invention has been described in detail with reference to a preferred embodiment, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.

Claims

1. An electrical device comprising a housing having an open end for receiving an electrical component, a bottom wall providing a closed end, and anchoring means, forming an integral part of the bottom wall, for aligning and securing the electrical component within the housing.

2. An electrical device according to claim 1 wherein the anchoring means includes means for engaging a fastening element to mount the electrical device to a base member.

3. An electrical device according to claim 2 wherein the bottom wall of the housing is constructed of a heat conductive material to allow heat generated in the electrical component to be transferred through the anchoring means to the base member.

4. An electrical device according to any one of claims 1 to 3 wherein the electrical component is a capacitor.

5. An electrical device comprising a housing having an open end for receiving an electrical component, a bottom wall providing a closed end, the bottom wall including an integral anchoring means, the anchoring means including first engaging means for engaging the electrical component to laterally position the electrical component along the bottom wall, the anchoring means further including second engaging means for engaging a fastening element to mount the electrical device to a base member, the bottom wall including the anchoring means being constructed of a heat conductive material whereby the bottom wall, anchoring means, fastening means, and base member provide a heat sink for dissipating heat from the electrical component.

6. An electrical device according to claim 5 wherein the anchoring means is a spike extruded from the bottom wall, which spike has a distal end projecting in the direction of the open end of the housing providing the first engaging means for engaging the electrical component.

7. An electrical device according to claim 6 wherein the spike has a frustoconical shape and includes means providing a truncated threaded bore for engaging a fastening element, the bore opening outwardly from the bottom wall of the housing.

8. An electrical device according to any one of claims 5 to 7 wherein the electrical component is a capacitor.

9. An electrical device comprising a housing having an open end for receiving an electrical component, a bottom wall providing a closed end, and an axially upwardly extending spike extruded from the bottom wall for engaging the electrical component, the spike including means providing a truncated bore opening outwardly from the bottom wall for engaging a fastening element to mount the electrical device on a base member.

10. An electrical device according to claim 9 wherein the bottom wall and the spike are fabricated out of a heat conductive material whereby heat from the electrical component is dissipated through the bottom wall and spike to the base member.

11. An electrical device having an electrical component comprising a housing having an open end for receiving the electrical component, a bottom wall, and a side wall, and heat transfer means for transferring heat from the electrical component inside the hous ing through one of the housing walls to the surroundings outside the housing.

12. An electrical device according to claim 11 wherein the heat transfer means includes means providing a truncated bore for engaging a fastening element to mount the electrical device to a base member to provide a heat sink for the heat transferred from the electrical component.

13. An electrical device constructed, arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawing.