EP1405322B1 - Swinging choke - Google Patents

Abstract

An oscillating inductor has a symmetrical double-E core, which has two geometrically identical core windows, a cuboid center limb and two cuboid outer limbs. The double-E core is designed such that a longitudinal cross sectional area of the center limb is greater than 90 mm<SUP>2</SUP>, with a longitudinal cross section being regarded as a cross section which would separate the double-E core into two single E-cores, and the cross section being at right angles to the longitudinal cross section such that the double-E can be identified in the cross section, with the double-E core being located in a component volume of less than 26.5 mmx26.5 mmx15 mm (widthxdepthxheight).

Description

The invention relates to vibration throttles, which are used in electrical engineering.

In electronic ballasts for igniting and operating fluorescent tubes, it is preferred today to use conventional standard construction kits of the E-core and RM series, as are described, for example, in US Pat. in the catalog "Inductive Components" of VOGT electronic AG from the year 2000 on pages 61-01 to 61-06. Also, the z. As the US 4,352,080 A known.

The voltage increase for igniting the fluorescent lamps is achieved by means of a series resonant circuit of an LC combination. This is described, for example, in the already mentioned catalog of VOGT electronic AG on pages 60-04 and 60-05. Voltages of up to 4 kV _SS are generated at the coils, and currents of up to 3.5 A must be processed, or even more.

These operating conditions for the ignition coil or voice coil lead according to the required performances to air gaps up to a maximum of 8 mm, depending on the kit. Air gaps of this magnitude, caused by the stray field of the core, lead to high eddy current losses in the copper windings. The low AL (permeability times form factor) caused by the large air gap requires relatively high numbers of turns, which inevitably leads to high copper losses (P _V = I ² .R). Necessarily, the use of strands is inevitable in such oscillating chokes also because of the high eddy current losses. These stranded structures have some disadvantages compared to solid wires. They are more expensive to supply, their temperature properties and mechanical properties are somewhat weaker than the normal copper enameled wires, strands are more difficult to wind than normal copper enameled wires, and finally strands cause difficulties in applying the wires to pins due to the broom effect.

To reduce the eddy current losses, today some coils are padded, i. the distance of the winding to the core is artificially increased by introducing insulating films or by injecting thick wall thicknesses in the bobbin in the region of the air gap. This measure inevitably leads again to a larger volume of the overall component or smaller available changing rooms.

In the case of oscillating inductors in general, the voltage which occurs between the individual winding layers, the so-called layer voltage, should be as low as possible. The lacquer layer of the wires must prevent a flashover within individual layers, which would be possible due to the corresponding potential difference. For this are also among others small chamber width w necessary to keep the tension between the individual layers as small as possible. In the related core and bobbin concept known from the prior art, the so-called concept of the lying core, as illustrated schematically in FIG. 8, for example, the winding window height b must be subdivided by three additional space-receiving chamber walls to accommodate relatively small chamber widths w to reach. This creates four chambers to realize the necessary dielectric strength can.

The invention has for its object to provide a swing throttle constructed as simple as possible, which makes it possible to be miniaturized stronger than the known from the prior art vibration chokes, without suffering substantial losses in the electrical, magnetic and thermal data.

This object is achieved by a swing throttle according to claim 1.

In the oscillating reactor according to the invention according to claim 1, the stray field is minimized due to the maximization of the magnetic cross section. This results in the swing throttle according to the invention according to claim 1 from the particular absolute dimensions of the core in the swing throttle. Furthermore, the height is minimized by rotation of the magnetic axis from horizontal (prior art) to vertical. Due to the large magnetic surfaces optimum magnetic and electrical shielding is achieved in the direction of the outfield. Furthermore, the eddy current losses in the surrounding, close-fitting housing of electronic ballasts are reduced by placing the air gap in the middle of the room. The large back surfaces of the cores in the oscillating choke according to the invention according to claim 1 give the oscillation choke according to the invention good cooling possibilities, both in the direction of the circuit board, as well as towards the housing.

Due to the smoothness of the surfaces of the symmetrical double E-core in the oscillating choke according to the invention according to claim 1 or the respective corresponding inventive oscillation choke can be automatically sucked or gripped, so that it is suitable for fully automatic assembly process.

Advantageous and preferred embodiments of the oscillating throttle according to claim 1 are the subject of claims 2 to 22.

In the preferred embodiment of the oscillating choke according to the invention according to claim 19 eliminates the strand, which in turn leads to the elimination of the disadvantages described above with respect to strands. The strand can be omitted due to the minimal stray field in the air gap region and because of the resulting due to the large effective magnetic cross-section low number of turns. In this embodiment, due to the higher filling factor of solid wires more copper than in Litzenbewicklung in the changing room are introduced. This results in a reduction of ohmic losses, which compensates for the unwanted frequency losses of solid wires, such as eddy current losses (due to the small air gap and the small number of turns relatively low), skin effects and Proximityeffekt in total to a large extent.

Fig. 1

ein Ausführungsbeispiel einer erfindungsgemäßen Schwingdrossel,

Fig. 2

eine Hälfte eines symmetrischen Doppel-E-Kerns aus der Schwingdrossel von Fig. 1,

Fig. 3

schematisch eine mit einem Lochraster versehene, kundenspezifisch vorgegebene Platine, auf die ein Ausführungsbeispiel einer erfindungsgemäßen Schwingdrossel montiert werden soll,

Fig. 4

schematisch eine zu der Platine von Fig. 3 gehörende kundenspezifische Höhenvorgabe für das Ausführungsbeispiel der erfindungsgemäßen Schwingdrossel,

Fig. 5

schematisch ein Ausführungsbeispiel einer auf die Platine von Fig. 3 aufgesetzten erfindungsgemäßen Schwingdrossel in Draufsicht,

Fig. 6

schematisch in Seitenansicht einen zur Höhenvorgabe von Fig.4 gehörenden Doppel-E-Kern der erfindungsgemäßen Schwingdrossel von Fig. 5, und

Fig. 7

schematisch eine aus dem Stand der Technik bekannte Schwingdrossel mit stehendem E-Kern, und

Fig. 8

schematisch eine aus dem Stand der Technik bekannte Schwingdrossel mit liegendem E-Kern.

Embodiments of the invention are explained below with reference to figures. It shows:

Fig. 1

an embodiment of a vibration throttle according to the invention,

Fig. 2

one half of a symmetrical double E-core from the oscillation choke of Fig. 1,

Fig. 3

schematically a provided with a breadboard, customer-specified board on which an embodiment of a swing throttle according to the invention to be mounted,

Fig. 4

3 schematically shows a specific height specification for the exemplary embodiment of the oscillating throttle according to the invention belonging to the circuit board of FIG.

Fig. 5

1 is a schematic plan view of an exemplary embodiment of a vibration damper according to the invention placed on the circuit board of FIG. 3, FIG.

Fig. 6

schematically in side view a belonging to the height specification of Figure 4 double E-core of the invention oscillation choke of Fig. 5, and

Fig. 7

schematically a known from the prior art oscillation choke with a standing E-core, and

Fig. 8

schematically a known from the prior art oscillation choke with lying E-core.

In principle, the following explanations are preceded by the following: Although the following explanations essentially relate to the description of exemplary embodiments with a double E core or with a double EQ core, the explanations apply correspondingly also to EI Cores and even generally for core shapes with a middle leg 17 and two outer thighs 18, 19. The In fact, according to the task demanded oscillating inductor properties can be achieved with such general core solutions. Only the criteria defined in the individual independent patent claims are decisive.

The basic structure of oscillating inductors according to the invention with a symmetrical double E-core, which has two geometrically identical core windows, a cuboid center leg 17 and two cuboid outer legs 18, 19, is from a synopsis of FIGS. 1, 2, 5, 6 and 7 readily apparent.

a -

Gesamtbreite des Doppel-E-Kerns,

b -

Breite eines Kernfensters,

h -

Gesamthöhe des Doppel-E-Kerns,

i -

Breite des Mittelschenkels 17,

t -

Tiefe des Doppel-E-Kerns

l_w -

mittlere Windungslänge.

Fig. 1 shows an embodiment of a swing throttle according to the invention, and in Fig. 2, a half of the symmetrical double-E core of the swing throttle of Fig. 1 is shown. The letters in Fig. 2 denote the following lengths:

a -

Total width of the double E-core,

b -

Width of a core window,

H -

Total height of the double E-core,

i -

Width of the middle leg 17,

t -

Depth of the double E-core

l _w -

mean turn length.

In the embodiment of the invention shown in FIGS. 1 and 2, both outer legs 18, 19 of the symmetrical double E-core law in the specified tolerances are each half as wide as its center leg 17, and the height of each of the two back plates 22 (FIGS. see also FIGS. 6 and 7) of the double E-core is in each case half as large as the width (i) of its center leg 17.

Specifically specified by the customer is provided with a perforated grid board 21, on which an embodiment of a swing throttle according to the invention is to be mounted. An example of such a printed circuit board 21 with a perforated grid is shown in FIG. 3, and FIG. 4 shows a customer-specific height specification for the embodiment of the oscillating choke according to the invention belonging to the board 21 of FIG.

mittel:7,3mm $\mathit{l}\mathit{=}\mathit{7}\mathit{,}{\mathit{5}}_{\mathit{-}\mathit{0}\mathit{,}\mathit{4}}^{\mathit{0}}$

mittel:7,3mm $\mathit{t}\mathit{=}\mathit{15}\mathit{,}{\mathit{25}}_{\mathit{-}\mathit{0}\mathit{,}\mathit{5}}^{\mathit{0}}$

mittel:15,0mm $\mathit{t}\mathit{=}\mathit{17}\mathit{,}{\mathit{5}}_{\mathit{-}\mathit{0}\mathit{,}\mathit{5}}^{\mathit{0}}$

mittel:17,25mm $\mathit{h}\mathit{=}\mathit{13}\mathit{,}{\mathit{8}}_{\mathit{-}\mathit{0}\mathit{,}\mathit{4}}^{\mathit{0}}$

mittel:13,6mm $\mathit{h}\mathit{=}\mathit{13}\mathit{,}{\mathit{8}}_{\mathit{-}\mathit{0}\mathit{,}\mathit{4}}^{\mathit{0}}$

mittel:13,6mm $\mathit{a}\mathit{=}\mathit{25}\mathit{,}{\mathit{0}}_{\mathit{-}\mathit{0}\mathit{,}\mathit{7}}^{\mathit{0}\mathit{,}\mathit{8}}$

mittel: 25,0mm $\mathit{a}\mathit{=}\mathit{25}\mathit{,}{\mathit{0}}_{\mathit{-}\mathit{0}\mathit{,}\mathit{7}}^{\mathit{0}\mathit{,}\mathit{8}}$

mittel: 25,0mm $\mathit{b}\mathit{=}\mathit{5}\mathit{,}{\mathit{3}}_{\mathit{-}\mathit{0}\mathit{,}\mathit{3}}^{\mathit{0}\mathit{,}\mathit{3}}$

mittel:5,3mm $\mathit{b}\mathit{=}\mathit{5}\mathit{,}{\mathit{3}}_{\mathit{-}\mathit{0}\mathit{,}\mathit{3}}^{\mathit{0}\mathit{,}\mathit{3}}$

mittel;5,3mm Damit ergibt sich die mittlere Längsschnittfläche des Mittelschenkels zu $\mathrm{i}\cdot \mathrm{t}=7,3\mathrm{\hspace{0.17em}}\mathrm{mm}\cdot 15,0$

$\mathrm{mm}=\mathit{109}\mathit{,}{\mathit{5}}_{\mathit{-}\mathit{4}\mathit{,}\mathit{8}}^{\mathit{4}\mathit{,}\mathit{9}}\mathrm{\hspace{0.17em}}{\mathrm{mm}}^2.$

Die mittlere Querschnittsfläche eines Kernfensters beträgt $\mathrm{b}\cdot (\mathrm{h}-\mathrm{i}/2-$

$\mathrm{i}/2)=5,3\mathrm{\hspace{0.17em}}\mathrm{mm}\cdot 6,3\mathrm{\hspace{0.17em}}\mathrm{mm}=\mathit{33}\mathit{,}{\mathit{4}}_{\mathit{-}\mathit{3}\mathit{,}\mathit{9}}^{\mathit{4}\mathit{,}\mathit{1}}\mathrm{\hspace{0.17em}}{\mathrm{mm}}^2.$

Dabei ist als Längsschnitt der Schnitt anzusehen, der den Doppel-E-Kern in zwei einfache E-Kerne trennen würde. Der Querschnitt steht zum Längsschnitt derart senkrecht, dass im Querschnitt das Doppel-E erkennbar ist.For example, there are two customer-specific variants with the following specific dimensions: 1st variant in mm: 2nd variant in mm $\mathit{l}\mathit{=}\mathit{7}\mathit{.}{\mathit{5}}_{\mathit{-}\mathit{0}\mathit{.}\mathit{4}}^{\mathit{0}}$

medium: 7.3mm $\mathit{l}\mathit{=}\mathit{7}\mathit{.}{\mathit{5}}_{\mathit{-}\mathit{0}\mathit{.}\mathit{4}}^{\mathit{0}}$

medium: 7.3mm $\mathit{t}\mathit{=}\mathit{15}\mathit{.}{\mathit{25}}_{\mathit{-}\mathit{0}\mathit{.}\mathit{5}}^{\mathit{0}}$

Intermediate: 15.0 mm $\mathit{t}\mathit{=}\mathit{17}\mathit{.}{\mathit{5}}_{\mathit{-}\mathit{0}\mathit{.}\mathit{5}}^{\mathit{0}}$

medium: 17,25mm $\mathit{H}\mathit{=}\mathit{13}\mathit{.}{\mathit{8th}}_{\mathit{-}\mathit{0}\mathit{.}\mathit{4}}^{\mathit{0}}$

Intermediate: 13.6 mm $\mathit{H}\mathit{=}\mathit{13}\mathit{.}{\mathit{8th}}_{\mathit{-}\mathit{0}\mathit{.}\mathit{4}}^{\mathit{0}}$

Intermediate: 13.6 mm $\mathit{a}\mathit{=}\mathit{25}\mathit{.}{\mathit{0}}_{\mathit{-}\mathit{0}\mathit{.}\mathit{7}}^{\mathit{0}\mathit{.}\mathit{8th}}$

medium: 25.0mm $\mathit{a}\mathit{=}\mathit{25}\mathit{.}{\mathit{0}}_{\mathit{-}\mathit{0}\mathit{.}\mathit{7}}^{\mathit{0}\mathit{.}\mathit{8th}}$

medium: 25.0mm $\mathit{b}\mathit{=}\mathit{5}\mathit{.}{\mathit{3}}_{\mathit{-}\mathit{0}\mathit{.}\mathit{3}}^{\mathit{0}\mathit{.}\mathit{3}}$

medium: 5.3mm $\mathit{b}\mathit{=}\mathit{5}\mathit{.}{\mathit{3}}_{\mathit{-}\mathit{0}\mathit{.}\mathit{3}}^{\mathit{0}\mathit{.}\mathit{3}}$

medium; 5,3mm This results in the average longitudinal sectional area of the middle leg $\mathrm{i}\cdot \mathrm{t}=7.3\mathrm{}\mathrm{mm}\cdot 15.0$

$\mathrm{mm}=\mathit{109}\mathit{.}{\mathit{5}}_{\mathit{-}\mathit{4}\mathit{.}\mathit{8th}}^{\mathit{4}\mathit{.}\mathit{9}}\mathrm{}{\mathrm{<figure-callout\; id="2"\; label="mm"\; filenames="imgf0001.png"\; state="\{\{state\}\}">mm</figure-callout>}}^2,$

The average cross-sectional area of a core window is $\mathrm{b}\cdot (\mathrm{H}-\mathrm{i}/2-$

$\mathrm{i}/2)=5.3\mathrm{}\mathrm{mm}\cdot 6.3\mathrm{}\mathrm{mm}=\mathit{33}\mathit{.}{\mathit{4}}_{\mathit{-}\mathit{3}\mathit{.}\mathit{9}}^{\mathit{4}\mathit{.}\mathit{1}}\mathrm{}{\mathrm{<figure-callout\; id="2"\; label="mm"\; filenames="imgf0001.png"\; state="\{\{state\}\}">mm</figure-callout>}}^2,$

The longitudinal section is the section that would separate the double E-core into two simple E-cores. The cross-section is perpendicular to the longitudinal section such that in cross-section the double-E can be seen.

FIG. 5 schematically shows an embodiment of such a swivel throttle according to the invention placed on the board 21 of FIG. 3 in plan view, and FIG. 6 shows schematically in side view a double E core belonging to the height specification of FIG. 4 of the embodiment of the swivel throttle according to the invention of Fig. 5

In the latter embodiment of the oscillating choke according to the invention, the average quotient of the longitudinal sectional area of the central limb 17 and the cross-sectional area of a core window of the double-E core is 3.3. Taking into account the tolerances one obtains 2.8 - 3.9. In other embodiments of the oscillating choke according to the invention, this ratio is greater or less, e.g. in variant 2 with 3.7. Taking into account the tolerances, the value obtained for the 2nd variant is 3.2 - 4.5, but in any case it is greater than 2.3.

In many embodiments of the oscillation choke according to the invention, the width i of the center leg 17 of the symmetrical double E core is in the range from 6.0 mm to 8.0 mm, but in other embodiments of the oscillation choke according to the invention also smaller or larger widths i of the center leg 17th of the symmetric double E-core are possible.

Also with regard to the depth t of the symmetrical double E-core, there is a whole series of different embodiments of the oscillating choke according to the invention. Thus, the depth t of the symmetric double E-nucleus may be e.g. be greater than 13 mm or even greater than 18 mm, in the range between 13 mm and 18.0 mm or in other embodiments of the swing throttle according to the invention also have other values.

In many embodiments of the oscillating choke according to the invention, the height h of the symmetrical double E-core is less than 15.25 mm and is in the range of 13 mm to 15 mm. However, other embodiments of the oscillating choke according to the invention also have others, i. greater or smaller heights h of the symmetrical double E-core.

In many embodiments of the oscillating choke according to the invention, the total width a of the symmetrical double E-core is less than 26.5 mm and is in the range of 24 mm to 26 mm. However, there are also embodiments of the oscillating choke according to the invention, in which the width a of the symmetrical double-E core is greater than 26.5 mm or smaller than 24 mm.

In the embodiment of the oscillating choke according to the invention shown in FIG. 1, the symmetrical double-E core consists of a manganese-zinc power ferrite.

In addition to the above-described embodiments of oscillating inductors according to the invention with a symmetrical double E-core, there are also corresponding embodiments of inventive oscillating inductors with a symmetrical double EQ core. In various embodiments, the double E core or the double EQ core have two geometrically identical winding windows, a cuboid center leg or a round center leg and two parallelepiped outer limbs or two outer limbs concavely curved on the inside.

In many embodiments of the present invention, the width of the middle limb of the E-core or the EQ core is in the range of 6.0 mm to 8.0 mm, but in other embodiments of inventive swing chokes also smaller or larger widths of the center leg are possible.

Also with regard to the depth of the symmetrical E-core or EQ-core, there are quite a number of different embodiments of inventive vibration throttles. Thus, e.g. the depth of the symmetrical double E-core or the symmetrical double EQ core should be greater than 13 mm or even greater than 18 mm.

In many embodiments of oscillating chokes according to the invention, the height of the symmetrical double E core or of the symmetrical double EQ core is smaller than 15.25 mm and is in the range of 13 mm to 15 mm. However, other embodiments of oscillating chokes according to the invention also have other, that is, larger or smaller heights of the symmetrical double E-core or the symmetrical double EQ-core.

In many embodiments of oscillating chokes according to the invention, the total width of the symmetrical double E core or of the symmetrical double EQ core is smaller than 26.5 mm and is in the range of 24 to 26 mm. However, there are also embodiments of inventive oscillation chokes, in which the width of the symmetrical double E-core or the symmetrical double EQ core is greater than 26.5 mm or smaller than 24 mm.

Fig. 7 schematically illustrates an embodiment of a swing damper according to the invention with a standing E-core. In this concept of the stationary core, the core rests with one of its broad sides 22 on the board 21 (see FIG. A related corner pin or pin 20 for insertion into the board 21 can be seen in the bottom left in Fig. 7.

If one compares the exemplary embodiment of an oscillating choke according to the invention with a standing E core schematically illustrated in FIG. 8, which is known from the prior art, with a lying E core, the difference already indicated above becomes visible. Due to the small core lensterbreite b of the stationary E-core concept (Fig. 7), the winding window width b _f must be divided only by a chamber wall to achieve a relatively small chamber width w and thus small layer tensions. This creates two chambers. At the old one On the other hand, the winding window width b _f must be subdivided by three additional chamber walls receiving winding space in order to achieve relatively small chamber widths w. This creates four chambers to realize the necessary dielectric strength can. The special feature of the new, stationary E-core concept is that due to the design, only one chamber wall and thus only two chambers are required in order to keep the layer tension between the individual layers sufficiently small. In addition one loses with a chamber wall less changing room.

As already explained above, at the beginning of the explanation of the embodiments, the above explanations for embodiments of oscillating chokes with double E-core or with double EQ core completely corresponding to embodiments of oscillating chokes with other core forms, the one Center leg and two outer legs have transferred. The legs can be designed in a very different way. The middle leg can be, for example, rectangular, rectangular with rounded corners, elliptical or circular. The outer legs are usually shaped so that the outer winding contour, which is determined by the shape of the middle leg, is modeled. In addition to double-core solutions, there are also plate-core solutions.

Such a plate-core solution is e.g. An embodiment of a vibration throttle according to the invention with E-I core. The E-I core solution consists of an E-core with longer legs, combined with a plate, with the air gap located exclusively in the E-core directly below the plate. The above-mentioned embodiment of the oscillating inductor according to the invention with E-I core corresponds to the basic dimensions of the above described in detail double E-core solution.

Claims (22)

1. Swinging choke with a core with a centre limb (17) and two outer limbs (18, 19), characterised in that the core is constructed such that the longitudinal sectional area of the centre limb is greater than 90 mm², wherein the section which extends parallel to the base area (22) of the core, on which the limbs (17, 18, 19) are seated, is to be considered as the longitudinal section, and the cross section is perpendicular to the longitudinal section such that an at least approximately E-like shape, formed from the above-mentioned base area (22) as E-back area and the three limbs (17, 18, 19), can be seen in cross section, wherein the core is located in a component volume which is less than 26.5 mm x 26.5 mm x 15 mm (width x depth x height).
2. Swinging choke according to Claim 1, characterised in that the core has two geometrically identical core windows.
3. Swinging choke according to Claim 1 or Claim 2, characterised in that the centre limb (17) is rectangular or rectangular with rounded corners or elliptical or circular.
4. Swinging choke according to Claim 3, characterised by a double core consisting geometrically of two cores which face one another by way of their limbs (17, 18, 19).
5. Swinging choke according to Claim 4, characterised in that the core is formed as a symmetrical double-E core.
6. Swinging choke according to Claim 5, characterised in that the outer limbs (18, 19) are cuboid.
7. Swinging choke according to Claim 4, characterised in that the core is formed as a symmetrical double-EQ core.
8. Swinging choke according to Claim 7, characterised in that the outer limbs (18, 19) are curved in a concave manner on the inside.
9. Swinging choke according to Claim 3, characterised by a core of the above-mentioned type above whose limbs a plate is disposed, this extending substantially parallel to the above-mentioned base area.
10. Swinging choke according to Claim 3, characterised in that the core is formed as an E-I core.
11. Swinging choke according to Claim 3, characterised in that the outer limbs are shaped such that they emulate the outer winding contour, which is defined by the shape of the centre limb.
12. Swinging choke according to Claim 1, characterised in that the longitudinal sectional area of the centre limb (17) is greater than 100 mm².
13. Swinging choke according to Claim 12, characterised in that the longitudinal sectional area of the centre limb (17) is greater than 110 mm².
14. Swinging choke according to Claim 13, characterised in that the longitudinal sectional area of the centre limb (17) is greater than 120 mm².
15. Swinging choke according to Claim 5, characterised in that the width (i) of the centre limb (17) of the symmetrical double-E core lies in the range from 6.0 mm to 8 mm.
16. Swinging choke according to any one of the preceding Claims, characterised in that the depth (t) of the respective core is greater than or equal to 14.5 mm.
17. Swinging choke according to any one of the preceding Claims, characterised in that the width (a) of the respective core is less than 26.5 mm.
18. Swinging choke according to Claim 17, characterised in that the width (a) of the core is in the range from 24 mm to 26 mm.
19. Swinging choke according to any one of the preceding Claims, characterised in that the respective core is wound with solid wire.
20. Swinging choke according to any one of the preceding Claims, characterised in that the respective core is a ferrite core.
21. Swinging choke according to Claim 20, characterised in that the core consists of a manganese-zinc power ferrite.
22. Swinging choke according to any one of the preceding Claims, characterised in that the respective core is mounted on a board (21) such that it lies by way of one of its broadsides (22) flatly on the board (21).

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