EP0240737B1 - Ballast coil, especially for gas discharge lamps - Google Patents

Description

The invention relates to a ballast, in particular for gas discharge lamps, with a winding-supporting, sheet-iron layered core in jacket design, which is assembled from U- or E-shaped and T- or I-shaped core parts, with at least one optionally between the core parts an air gap containing a non-magnetic air gap insert of a defined size is arranged.

Examples of series chokes of this type are described in DE-OS 1946 885. The T- or I-shaped core sheets lie between the correspondingly elongated outer legs of E-shaped core sheets, on the middle leg of which the winding is placed. The outer legs of the E-shaped core part are pressed tightly against the opposite end faces of the T- or I-shaped core part by clamping rails in order to exclude as far as possible the formation of an air gap at these points. The operating air gap required with regard to the impedance of the choke is arranged in the region of the middle leg of the E-shaped core part. It contains an air gap insert made of non-magnetic material that defines the size of the air gap. If higher demands are placed on the accuracy of the impedance values of such a choke, for example by these values having to be within a tolerance range of 1.5-2% of a target value, the air gap often has to be readjusted after assembly. This is done in such a way that the I-shaped or T-shaped core part is pressed against the middle leg of the E-shaped core part, the air gap insert giving way to the (small) required extent and being compressed.

In order to keep the air gap exactly at the size adjusted in this way and to avoid humming phenomena, relatively complex clamping rails or metal housing sheathing are required. In addition, the correct insertion of the air gap insert in the mass production of such throttle assembly involves certain difficulties.

The object of the invention is therefore to provide a series choke which allows the impedance value to be precisely adjusted in a simple manner after assembly without compressing an air gap insert, and at the same time there is no need for complex additional clamping or tensioning devices for the magnetic core.

To achieve this object, the series choke mentioned at the outset is characterized according to the invention in that in the closing circuit of the magnetic lines of force there is at least one air gap, in the area of which the core parts are positively locked by at least one narrow tongue which crosses this air gap and engages in a groove on the opposite core part and are adjustably connected to each other.

The tongue crossing the air gap is so narrow that it is saturated by the small portion of the magnetic flux running over it, so that the magnetic resistance on the closing circuit of the magnetic lines of force remains essentially determined by the size of the air gap. However, since the tongue, on the other hand, is mechanically stable enough to hold the core parts delimiting and thus defining the air gap on both sides precisely at the adjusted distance, there is no need to use a separate air gap insert in the area of this air gap. At the same time, complex clamping or tensioning devices, for example in the form of metallic housing sheaths of the magnetic core, are also unnecessary. In addition, the size of the air gap can be adjusted very simply by pressing the core parts delimiting the air gap against each other to the required extent; the narrow tongue is deformed to the required small extent or pressed deeper into the groove and, as mentioned, permanently fixes the value of the air gap once it has been adjusted.

Because of the known saturation phenomena, the tongue lying in the closing circuit of a small portion of the magnetic flux can lead to an increase in the harmonic portion in the Drossse current, which is irrelevant for a number of applications. However, if, for example, according to VDE 0712, the harmonic component in the current has to be kept below certain limit values, this can be done in a simple manner by designing the choke, in which there is at least one further air gap in the closing circuit of the magnetic lines of force, it then being advantageous if the air gap containing the tongue is smaller than this further air gap. The division can expediently be such that the air gap containing the tongue accounts for about a third of the total air gap lying in the magnetic closing circuit.

In a preferred embodiment, the arrangement is such that the tongue or groove is formed in the region of the free end face of the middle leg of the T- or E-shaped core part and an opposite surface of the other core part, and that between the cross leg of the T-shaped Core part or the I-shaped core part and opposite surfaces of the extended outer legs of the other core part further air gaps are arranged. This embodiment has the advantage that when the air gap containing the tongue is adjusted, the size of the further air gaps present between the outer legs of the U-shaped or E-shaped core part and the adjacent end faces of the T-shaped or I-shaped core part remains essentially unchanged.

A further simplification, in particular during assembly, and a reduction in the individual parts of the inductor required in the manufacture can be achieved if these further air gaps each contain parts of an insulation film surrounding the winding as an air gap insert. These insulation parts protruding from the winding coil come to lie and define in the further air gaps when the coil is attached to the center leg of the E- or T-shaped core parts thus exactly their size. Since the film thickness is tolerated relatively closely and the exact adjustment of the resulting air gap takes place anyway via the air gap containing the tongue, no additional measures are required during assembly in the area of these further air gaps.

Finally, with a view to facilitating the adjustment of the air gap size, it is advantageous if the groove depth is greater than the tongue length, so that the press-in depth of the tongue in the groove can be varied during the adjustment. The tongue and the groove can moreover be designed with parallel flanks or V-shaped, the tongue being designed with oversizes with respect to the groove.

Finally, it should be noted that in U- / T- and E- / T-core sheet metal cuts for transformers, it is known to provide a narrow, possibly dovetail-shaped, tab-like tongue on the free end face of the central leg of the T-shaped core parts (DE-OS 1638 944, DE-OS 2139 010), which engages in a groove on the opposite surface of the other core part. However, the arrangement is such that the effects of the "residual air gaps" at the separation points of the core parts are eliminated as far as possible, i.e. the core parts firmly pressed together at the parting lines are fixed against each other and held taut.

• Fig. 1 - 3 eine Vorschaltdrossel gemäß der Erfindung, in drei verschiedenen Ausführungsformen, jeweils im Querschnitt und in schematischer Darstellung,
• Fig. 4 die am Mittelschenkel einer der Vorschaltdrosseln nach den Fig. 1 - 3 vorgesehene Zunge mit zugehöriger Nut in einer abgewandelten Ausführungsform, in einer Seitenansicht sowie in einer Teildarstellung und in einem anderen Maßstab,
• Fig. 5 die Vorschaltdrossel nach Fig. 8, geschnitten längs der Linie V-V der Fig. 8, in einer Seitenansicht,
• Fig. 6 die Vorschaltdrossel nach Fig. 1, in einer betriebsfähigen vollständigen Ausführungsform, in einer Draufsicht,
• Fig. 7 die Vorschaltdrossel nach Fig. 6, geschnitten längs der Linie VII-VII der Fig. 8, in einer Draufsicht,
• Fig. 9 die Vorschaltdrossel nach Fig. 6, in einer Draufsicht, bei abgenommenem Gehäusedeckel,
• Fig. 10 die Vorschaltdrossel nach Fig. 6, geschnitten längs der Linie X-X der Fig. 9,
• Fig. 11 die Vorschaltdrossel nach Fig. 1, in in eine Leuchte eingebautem Zustand, in einer Seitenansicht, teilweise im Schnitt, und
• Fig. 12 das Stanzbild der Kernteile der Vorschaltdrossel nach den Fig. 1 und 6.

Exemplary embodiments of the subject matter of the invention are shown in the drawing. Show it:

• 1-3 a series choke according to the invention, in three different embodiments, each in cross section and in a schematic representation,
• 4 the tongue provided on the center leg of one of the series chokes according to FIGS. 1-3 with associated groove in a modified embodiment, in a side view and in a partial representation and on a different scale,
• 5 shows the ballast choke according to FIG. 8, cut along the line VV of FIG. 8, in a side view,
• 6, the ballast choke according to FIG. 1, in a fully operational embodiment, in a plan view,
• 7, the ballast choke according to FIG. 6, cut along the line VII-VII of FIG. 8, in a plan view,
• 9, the ballast choke of FIG. 6, in a plan view, with the housing cover removed,
• 10 shows the ballast choke according to FIG. 6, cut along the line XX of FIG. 9,
• Fig. 11, the ballast according to Fig. 1, in the installed state in a lamp, in a side view, partly in section, and
• 12 shows the punching pattern of the core parts of the ballast choke according to FIGS. 1 and 6.

The ballast reactors shown schematically in FIGS. 1-3 each have a core of jacket-type construction which is cross-layered from sheet iron, which in the embodiment according to FIG. 1 is composed of U-shaped core parts 1 and T-shaped core parts 2.

In the embodiments according to FIGS. 2, 3, the core consists of E-shaped core parts 1 a and 1-shaped core parts 2 a or likewise T-shaped core parts 2 (FIG. 3).

The T- or I-shaped core parts 2 and 2a are inserted in the manner shown in the figures between the correspondingly elongated outer legs 3 of the other core parts 1 and 1a, so that their end faces face the inside of these outer legs 3. The winding indicated at 4, possibly comprising several coils, is on the middle leg 5 of the T-shaped core parts 2 (FIG. 1) or the middle leg 5a of the E-shaped core parts 1a (FIG. 2) or on the middle legs 5a, 5 of the E-shaped and the T-shaped core parts 1 a, 2 (Fig. 3) pushed, as is known per se with such core cuts.

In the area of the free end face 6 of the middle leg 5 of the T-shaped core part 2 of the ballast choke according to FIG. 1, a parallel, narrow, continuous, narrow groove is arranged, into which a pin-like tongue 8 engages, which on the opposite surface 9 of the middle leg 10 of the U-shaped core part 1 is cut.

The tongue 8 crosses an air gap 11 delimited between the opposing surfaces 6, 9, which lies in the magnetic closing circuit of the magnetic lines of force interlinked with the winding 4 and the size of which is chosen with regard to the required impedance value of the ballast choke.

The tongue 8, which is oversized with respect to the groove 7, is pressed into the groove 7; it thus holds the two surfaces 6, 9 at a precisely predetermined distance, i.e. the air gap 11 to an exact size without the need for air gap inserts etc.

The size of the air gap 11 can be adjusted during assembly by correspondingly pressing the T-shaped core part 2 in the direction of the surface 9 until the desired impedance value is reached. The narrow tongue 8 is deformed accordingly.

The arrangement can also be chosen according to FIG. 4, from which it can be seen that the effective tongue length lying in the groove 7 is greater than the groove depth, so that when the air gap 11 is adjusted, only the press-in depth of the tongue 8 in the groove 7 changes becomes. The groove 7 and the tongue 8 are here essentially V-shaped, while in the described embodiment according to FIG. 1 they are essentially parallel-flanked. In principle, other suitable cross-sectional shapes for the groove 7 and the tongue 8 are also conceivable.

The width of the tongue 8 crossing the air gap 11 is chosen so small in comparison to the width of the middle leg 5 that the magnetic resistance effective in the closing circle of the magnetic lines of force remains essentially determined by the air gap 11. The small portion of the magnetic force extending over the tongue 8 Because of its small width, the tongue quickly saturates.

The embodiments according to FIGS. 2, 3 basically correspond to those according to FIG. 1. The only difference is in the somewhat different position of the air gap 11 arranged in the region of the middle leg 5 or 5 a, with regard to the design and dimensioning of the narrow tongue 8 and Groove 7 and the adjustment of the air gap 11, the above remarks apply to the same extent; corresponding parts are provided with the same reference numerals.

In principle, it would also be conceivable to provide several, for example two, such narrow tongues 8 with associated grooves 7 instead of a narrow tongue 8 in the area of the air gap 11, or to move the air gap 11 to another location in the closing circuit of the magnetic lines of force. Such a possibility is indicated in dashed lines in FIG. 3, where the air gap 11 a is laid in the region of the outer legs 3 of the E-shaped core part 1 a. The associated narrow tongues crossing the two air gaps 11a and their associated grooves are designated 8a and 7a. Of course, in this embodiment, the cross leg of the T-shaped core part is extended to the outer sides of the two outer legs 3 of the other core part 1 a.

In order to reduce the harmonic influence on the current flowing through the choke from the small part of the main magnetic flux passing through the narrow tongues 8 rapidly saturating, an additional area of increased magnetic resistance can be provided in the closing circuit of the magnetic lines of force extending over the tongue 8 be, which is expediently formed by a further air gap.

In the embodiments according to FIGS. 1-3, this is realized in such a way that the cross legs of the T-shaped or I-shaped core parts 2 and 2a have been somewhat shortened, such that such further air gaps 12 lying in the closing circle of the magnetic lines of force are formed between the free end faces of the transverse legs of the T-shaped core parts 2 or I-shaped core parts 2a and the opposite surfaces on the inside of the outer legs 3 of the other core parts 1 and 1a. In this air gap 12, an air gap insert made of non-magnetic material is inserted, which simply consists in the manner shown in FIGS. 1-3 from a part 14 of the insulation film 13 surrounding the winding 4 and protruding from the winding 4. When wrapping the coil legs with the insulating film 13, the outer part 14 is no longer folded over, but is left in the extension of the coil outer sides, such that it comes to rest in one of the air gaps 12 during assembly. The thickness of this insulation film is, for example, 0.125 mm.

Since the core parts 1, 1a and 2 or 2a are fixed against each other by the narrow tongues 8 pressed into the respective groove 7 and positively locked therein, in particular if the throttle is cast with synthetic resin after assembly, additional clamping or tensioning devices can be used to be dispensed with. Without the potting mentioned, it is often sufficient if, as in FIG. 1, a fastening rail 15 is provided which braces the two outer legs 3 against one another.

The size of the air gap 11 is smaller than that of an air gap 12. It is, for example, only 1/3 of the air gap 12, so that the main part of the magnetic resistance lies in a closing circuit at the air gap 12 and the air gap 11 is only a smaller one used for adjustment Share provides.

The described design of the series choke not only permits simple adjustment of the impedance value without the use of deformable air gap inserts, but also a very flat design of the series choke with stable mutual fixing of the core parts. At the same time, the core sheets can be punched out with little waste.

A practical embodiment of such a series choke is illustrated in FIGS. 5 to 11:

The ballast with the core parts 1, 2 is arranged in a flat, cylindrical, can-like housing 20 made of insulating material and potted in this with a synthetic resin. At the end, insulating material molded parts 21 are placed on the core parts 1, 2, which are adapted to the circular shape of the housing 20 and by which the winding heads 22 of the winding 4 are held and insulated from the core. The winding connections are connected to two contact pins 23, which are arranged above in the region of the end faces of the housing 20. As can be seen from Fig. 11, two connection parts 24, 25 are placed on the housing 20 on both sides, of which the connection part 24 carries a lamp base 26, while the connection part 25 is provided with a lamp socket 27 into which a small fluorescent lamp 28 with its Socket 29 is inserted. The small fluorescent lamp 28 is shielded from the outside by a lamp glass 290 which is fastened to the connecting part 27 at 30 by means of a bayonet lock. In the connecting parts 24, 25 there are contacts not shown, which are in engagement with the contact pins 23 and a connecting bridge 300 (FIGS. 8, 9) and thus establish an electrical connection between the contacts of the lamp base 26 and those of the lamp base 29.

The compact, flat structure of the ballast choke and the elimination of complex, space-consuming clamping and tensioning devices for their core parts 1, 2 clearly allows a particularly simple and space-saving structure of the entire ballast.

The sheets forming the core parts 1, 2 or 1 a, 2 a can be punched with little waste, as can be seen from FIG. 12. A U-shaped sheet 1 encloses a T-shaped sheet 2 and two outer legs of the opposite U-shaped sheets 1 and the middle leg 5 of an opposite T-shaped sheet 2. The hatched parts 35 indicate the result of the small air gaps 11 ( also small) stamping waste. The grooves 7 and the cut tongues 8 who punched out independently of one another and can therefore be produced in any width, design and depth.

Claims (7)

1. Ballast coil, especially for gas-discharge lamps, comprising a laminate iron core of jacket design carrying the winding, said core being comprised of U- or E-shaped and T- or I-shaped core parts joined together, at least one air gap of a defined size possibly containing a non-magnetic air gap insert being arranged between said core parts, characterized in that at least one air gap (11) is present in the closure circuit of the magnetic lines of force, said core parts (1, 2; 1 a, 2a) being positively and adjustably connected to one another in the region of said air gap by at least one narrow tongue (8) crossing this air gap (11) and engaging a groove (7) on the opposite core part.

2. Ballast coil as defined in claim 1, characterized in that at least one further air gap (12) is located in said closure circuit of said magnetic lines of force.

3. Ballast coil as defined in claim 2, characterized in that said air gap (11) containing said tongue (8) is smaller than said further air gap (12).

4. Ballast coil as defined in one of the preceding claims, characterized in that said tongue (8) or said groove (7) is formed in the region of the free end face of the center leg (5; 5a) of said T- or E-shaped core part (2; 1 a) and an opposite surface of said other core part (1; 2a), and in that further air gaps (12) are arranged between the transverse legs of said T-shaped core part (2) or said I-shaped core part (2a) and opposite surfaces of the prolonged outer legs (3) of said other core part.

5. Ballast coil as defined in claim 4, characterized in that said further air gaps (12) contain parts (14) of an insulating foil (13) surrounding said winding (4) as non-magnetic air gap insert.

6. Ballast coil as defined in one of the preceding claims, characterized in that said tongue (8) and said groove (7) are of parallel-sided or V-shaped design and said tongue (8) is overdimensioned with respect to said groove (7).

7. Ballast coil as defined in one of the preceding claims, characterized in that the depth of said groove is larger than the effective length of said tongue.

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