WO2001006817A1

WO2001006817A1 - A ballast noise reduction scheme

Info

Publication number: WO2001006817A1
Application number: PCT/EP2000/006629
Authority: WO
Inventors: Frans Jansen; Allan J. Reinken; George Wozniczka
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 1999-07-16
Filing date: 2000-07-12
Publication date: 2001-01-25

Abstract

A ballast having a housing with an open bottom and a plate secured to the housing and covering at least the open bottom. A plurality of components positioned within the housing are surrounded by a potting material. The plate is substantially flat except for a plurality of protrusions extending into the housing. The potting material is displaced by the protrusions so as to substantially eliminate any gaps between the potting material and the plate. The protrusions decrease the volume of the potting material by displacing the latter. There is far less chance of any gap existing between the potting material and the plate since the potting material spreads more evenly/uniformly. Ballast vibrations due to the plate being able to move about during ballast operation are substantially lessened. A substantial reduction in undesirable and distinctive humming sounds result.

Description

A ballast noise reduction scheme.

This invention relates generally to the noise generated by a ballast and, more particularly, to a scheme for reducing this noise.

Ballasts in transforming electrical energy into magnetic energy produce mechanical energy. The mechanical energy causes the ballast can (i.e. housing) to vibrate. The typical sound level of these vibrations is about 43 dB. A ballast can with a relatively loose plate, however, can generate a distinctive and undesirable humming sound as high as about 70 dB. Occasionally, as much as 10% of the ballast cans produced may have these relatively loose plates commonly referred to as "outliers" or "flyers".

In order to diminish such hum, a conventional ballast, such as disclosed in German application no. DE-A 41 08 736, includes a pair of warts on either side of a ballast plate rib. The mechanical rigidity achieved by these pair of warts, however, does not substantially reduce the plate movement/rattle during ballast operation.

It is therefore desirable to provide an improved ballast construction which substantially eliminates production of a ballast can having an undesirable humming sound when in operation. The improved ballast construction should substantially reduce the number of ballast cans having a sound level near or at 70dB. In particular, the ballast construction should substantially reduce the amount of movement/rattle of the plate during ballast operation.

In accordance with a first aspect of the invention, a ballast having a housing with an open bottom and a plate secured to the housing and covering at least the open bottom, includes a plurality of components positioned within the housing and surrounded by a potting material such as, but not limited to, liquid asphalt. The plate is substantially flat except for a plurality of protrusions extending into the housing so as to displace the potting material. The plurality of protrusions displace the potting material so as to substantially eliminate any gaps between the potting material and the plate. The protrusions represent at least about 2% of the surface area of the plate covering the potting material. Preferably, the protrusions displace at least about .07 cubic inches of potting material. By displacing the potting material, the protrusions decrease the material volume of the potted ballast. There is far less chance of any gap existing between the potting material and the plate since the potting material spreads more evenly/uniformly. That is, a decrease in volume of potting material results due to the protrusions. Ballast can vibrations due to the plate being able to move about during ballast operation are substantially lessened. There is less room for the plate to rattle about and resonate since there is little, if any, gap/voids between the potting material and plate. A substantial reduction in undesirable and distinctive humming sounds result.

It is a feature of the invention that the protrusions are in the form of dimples having a substantially circular perimeter. The dimples typically form an asymmetrical pattern.

In accordance with a second aspect of the invention, a method of ballast construction, comprises the steps of positioning the ballast components through an open end of a ballast housing; filling the ballast housing with potting material; and securing a substantially flat plate to the housing so as to cover the open end. The plate includes a plurality of protrusions extending into the housing which displace the potting material so as to substantially avoid any gaps between the potting material and the plate.

It is a feature of this second aspect of the invention that the plurality of protrusions represent at least about 2% of the surface area of the plate covering the potting material. This method of ballast construction typically includes displacing at least about .07 cubic inches of the potting material.

Accordingly, it is an object of the invention to provide an improved ballast construction which reduces the likelihood of producing a ballast having an undesirable humming sound. It is another object of the invention to provide an improved ballast construction in which the number of ballast cans having a sound level near or at 70 dB is substantially reduced.

It is still another object of the invention to provide an improved ballast construction in which the amount of movement/rattle of the plate during ballast operation is substantially reduced. Still other objects and advantages of the invention will, in part, be obvious and will, in part, be apparent from the specification.

The invention accordingly comprises several steps in the relation of one or more such steps with respect to each of the others, and a device embodying features of construction, combination of elements, and arrangements of parts which are adapted to effect such steps, all is exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a top plan view of a ballast can in accordance with the invention.; and

FIG. 2 is a side elevational view, in cross section, along lines 2-2 of FIG. 1.

Components and materials have been sized in the figures for illustrative purposes only and are not sized in true proportion or in relation to each other. Referring now to FIGS. 1 and 2 , a ballast 10 includes an open ended can (i.e. housing) 13 covered by a plate 16. Plate 16 is secured to and encloses can 13 and is relatively flat except for a plurality of protrusions 17. Protrusions 17 are generally in the form of dimples having a substantially circular perimeter. Positioned within can 13 is an insulator 19 for electrically isolating can 13 from electrical components therein. A magnetic core 22 with coils 25 and 28 wound therearound is positioned between insulator 19 and plate 16. A power factor correction capacitor 31 is coupled (not shown) to coils 25 and 28. As can be readily appreciated, ballast 10 includes a plurality of other components not shown. An additional electrical insulator 34 is positioned between coils 25 and 28 and plate 16. An adhesive 37 is positioned between insulator 34 and plate 16 for securing insulator 34 to plate 16.

In assembling ballast 10, prior to attaching plate 16 to can 13, ballast 10 is filled with a potting material 40 such as, but not limited to, liquid asphalt the latter of which is subsequently cooled. Insulation 34 is placed on top of potting material 40. Adhesive 37 is placed on insulation 34 for securing and preventing movement of insulation 34 relative to plate 16. Plate 16 is then mounted and secured to can 13.

Gaps (i.e. voids) directly and indirectly between plate 16 and potting material 40 are substantially eliminated by protrusions 17 extending into housing 13 so as to displace potting material 40. Protrusions 17 represent at least about 2% of the surface area of plate 16 covering potting material 40. Typically, the protrusions displace at least about .07 cubic inches of potting material 40.

By displacing potting material 40, protrusions 17 decrease the volume of potting material 40. There is far less chance of any gap existing between potting material 40 and plate 16 since potting material 40 spreads more evenly/uniformly near plate 16. That is, a decrease in the volume of potting material 40 results due to protrusions 17 . Ballast can vibrations due to plate 16 being able to move about during ballast operation are substantially lessened. There is less room for plate 16 to rattle about and resonate since there is little, if any, gap/voids between potting material 40 and plate 16. A substantial reduction in the undesirable and distinctive humming sounds result.

As particularly, shown in FIG. 1 , protrusions 17 can form an asymmetrical pattern. The pattern of protrusions need not be limited to the pattern shown and can take any pattern which substantially eliminates any gap/void between potting material 40 and plate 16.

As can now be readily appreciated, the construction of ballast 10 will substantially reduce the undesirable humming sound associated with conventional ballasts. The improved ballast construction substantially reduces the number of ballast cans having a sound level near or at 70 dB. In particular, the improved ballast construction substantially reduces the amount of movement/rattle of plate 16 during ballast operation.

It will thus be seen that the objects set forth above and those made apparent from the preceding description are efficiently attained and since certain changes can be made in the above construction without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims

CLAIMS:

1. A ballast (10) can having a housing (13) with an open bottom and a plate (16) secured to the housing and covering at least the open bottom, comprising: a plurality of components (31,22,25,28) positioned within the housing (13) and surrounded by a potting material (40); the plate (16) being substantially flat except for a plurality of protrusions (17) extending into the housing wherein the potting material is displaced so as to substantially eliminate any gaps between the potting material and the plate.

2. The ballast (10) can of claim 1 , wherein the plurality of protrusions (17) represent at least about 2% of the surface area of the plate covering the potting material.

3. The ballast (10) can of claim 1, wherein the protrusions (17) displace at least about .07 cubic inches of potting material.

4. The ballast (10) can of claim 1, wherein the protrusions (17) are in the form of dimples having a substantially circular perimeter.

5. The ballast (10) can of claim 1 , wherein the protrusions form an asymmetrical pattern.

6. A method of ballast construction, comprising the steps of: positioning the ballast components (22,25,28,3 l)through an open end of a ballast housing (10); filling the ballast housing with potting material (40); and securing a substantially flat plate (16) to the housing so as to cover the open end; wherein the plate includes a plurality of protrusions (17) extending into the housing which displace the potting material so as to substantially avoid any gaps between the potting material (40) and the plate.

7. The method of claim 6, wherein the plurality of protrusions (17) represent at least about 2% of the surface area of the plate covering the potting material.

8. The method of claim 6, further including displacing at least about .07 cubic inches of the potting material.