EP2960921B1 - Self-centring assembly for a vacuum tube and vacuum tube - Google Patents

Description

TECHNICAL AREA

The invention relates to the field of vacuum bulbs and more specifically to the field of assembly of these vacuum bulbs.

STATE OF THE PRIOR ART

A vacuum bulb is generally of axial symmetry and comprises a substantially cylindrical bulb body. The axis of symmetry of the bulb body thus defines the axis of symmetry of the vacuum bulb.

In order to limit the risk of arcing and to obtain a good distribution of the electromagnetic field in the bulb, the components of such vacuum bulbs, such as contacts, the screen or even the lids of the bulb must respect a relative concentricity vis-à-vis the axis of symmetry of the body. This problem of concentricity of the elements of the bulb and the bulb body is particularly present in the case where the vacuum bulb is intended to be overmoulded for a circuit breaker. Indeed, in such a configuration, the concentric nature or not of the bulb will define the thickness of the insulating overmoulding which directly affects the dielectric performance of the circuit breaker.

This concentricity remains difficult to guarantee during the manufacture of a vacuum bulb. Indeed, the assembly of a vacuum bulb may require temperature rise cycles, particularly with regard to the brazing steps. However, the thermal expansion of these bulb elements during these rise in temperature can cause misalignment vis-à-vis the axis of symmetry.

For these reasons, it is difficult to provide a good concentricity between the elements of the bulb and the body of the bulb without drastically increasing the cost of manufacturing a vacuum bulb.

To overcome this drawback, it is known to equip the bulb elements of centering systems which are adapted to center said vacuum bulb elements relative to the axis of the body of the bulb they equip. Each bulb element thus forms with such a centering system an autocentered assembly for a vacuum bulb.

These centering systems can take the form of either elastic lamellae or bosses which are distributed around the outer periphery of the element so that these lamellae or bosses are interposed between the element and the bulb body thus allowing to center the element. Thus such centering systems bearing on the bulb body can hold the elements in place during assembly of the bulb and in particular during the temperature rise cycles.

The document " DE10151105 C1 "discloses an autocentered assembly for a vacuum interrupter according to the preamble of claim 1.

Such systems, if they make it possible to provide a centering of the vacuum bulb elements, are not entirely satisfactory.

Regarding the use of lamellae, these can cause a decrease in the dielectric strength of the bulb because of their shape, the latter forming a triple point, and the opening they can leave in the case where they are formed in the element by a punching process. Such lamellae, when attached to the centering bulb element, generally require an expensive step, such as brazing, to be installed on said element. In addition, the positioning of these slats must be precise to ensure the conformity of the centering of the elements to be centered.

As regards the embossings, they do not have the elastic properties of the slats. It is therefore necessary that their shape is precisely adjusted to allow a centering "hot" to absorb deformations related to thermal expansion. In addition to these drastic engineering and adjustment constraints, the non-maintenance of the elements in the "cold" bulb body is particularly problematic for all transport operations before the heating cycles have been carried out. will ensure centering. Indeed, the less shock during these transport operations may result in decentering which will not always be corrected by the thermal expansion of the embossments.

For all these reasons, regardless of the type of centering system chosen among the elastic lamellae and the bossings, these do not make it possible to guarantee that the vacuum interrupters assembled with self-centering assemblies comprising these centering systems have the concentric configuration. required. It is therefore necessary, despite the use of these centering systems, to sort to eliminate non-compliant vacuum bulbs.

STATEMENT OF THE INVENTION

The invention aims to remedy at least partially the above problems and more particularly to provide a self-centering assembly whose centering system allows a centering of the element "cold" as "hot" and n ' unlike the lamella-based centering systems, it does not reduce the dielectric strength of the bulb fitted by the assembly.

It is understood above and in the remainder of this document by centering "cold" and "hot" that the centering is obtained at a respective temperature of the order of the ambient, that is to say between 10 and 50 ° C, and at a temperature above 400 ° C and preferably of the order of 800 ° C-850 ° C.

• un élément d'ampoule à vide destiné à être centré par rapport à l'axe d'au moins une partie de corps d'ampoule lors de son montage dans ladite partie de corps d'ampoule,
• un système de centrage adapté pour centrer l'élément d'ampoule à vide par rapport à l'axe du corps d'ampoule,

le système comprenant au moins un ressort à spires dont les spires sont distribuées le long d'une ligne directrice du ressort, le ressort et sa ligne directrice étant adaptés de manière à ce que lors du montage de l'élément d'ampoule dans la partie de corps d'ampoule plusieurs spires du ressort s'interposent entre l'élément d'ampoule et le corps de l'ampoule en étant en contact à la fois avec l'élément d'ampoule et avec la partie de corps d'ampouleTo this end, the invention relates to an autocentered assembly for a vacuum interrupter comprising:

• a vacuum bulb element for centering with respect to the axis of at least one bulb body portion when mounted in said bulb body portion,
• a centering system adapted to center the vacuum bulb element with respect to the axis of the bulb body,

the system comprising at least one coil spring whose turns are distributed along a guide line of the spring, the spring and its guide line being adapted so that during assembly of the bulb element in the part of bulb body several turns of the spring interpose between the bulb element and the body of the bulb by being in contact with both the bulb element and the bulb body portion

Such an autocentered assembly benefits from the inherent elasticity of a coil spring and thus allows an assembly of a bulb with the element centered with respect to the bulb body both "cold" and "with hot ". This centering of the bulb element is moreover relatively robust, since it is provided at several points by the turns interposing between the bulb element and the body. In this way, the assembly of a vacuum bulb with such an autocentered assembly does not present any particular risk during the transport operations that they are carried out before or after the cycles of temperature rise. In addition, because of the shape of a coil spring, any problem related to the triple points is avoided and a bulb comprising such a self-centering assembly does not have a reduction in the dielectric strength associated with the centering system.

In addition, due to the elasticity of the spring and the fact that the centering is obtained along the spring, it is possible to reduce the tolerances vis-à-vis the deviation from the average radius of the element. Indeed, such a spring will allow, due to the multiplicity of points of contact with the bulb element and the bulb body that are offered by the turns, to compensate for these axial symmetry defects. This possibility of relaxation vis-à-vis manufacturing constraints of the vacuum bulb elements and reduces the cost of manufacturing a vacuum bulb.

Above and in the remainder of this document, the expression "spring coil" of a coil spring means a length of the spring on which the spring spirals, that is to say the length of spring included between two consecutive locations of the spring for which the spring has the same angular dimension vis-à-vis its guideline. More generally, such a turn corresponds to a spring loop.

The guideline may be an arc of a circle, preferably a circle so as to form an annular spring.

With such a guideline, the spring is particularly adapted to be interposed between two axially symmetrical elements such as the bulb body and the bulb element so as to make them concentric.

Above is meant in the remainder of this document, by "arc of circle" an arc of circle whose arc angle is between 10 ° and 360 °, it can in particular take the following values: °, 45 °, 60 °, 90 °, 120 °, 150 ° and 180 °.

The turns can be disjointed.

With such a characteristic of the turns, the turns can deform independently of each other so as to better distribute the forces between them and thus better absorb any differences in concentricity between the bulb element and the bulb body.

The spring may be a helical spring inclined angle of inclination turns θ .

Such inclination of the turns makes it possible to absorb part of the stresses to which the spring is subjected by a modification of the inclination of the bulb. In this way, the spring is likely to allow a good centering of the bulb element vis-vis the bulb body even with large concentricity differences.

avec c l'amplitude d'inclinaison (distance axiale de laquelle le sommet d'une spire est décalé par rapport à un ressort hélicoïdal) et d le diamètre de la spire.Above, and in the remainder of this document, the term "angle of inclination" of an inclined helical spring is understood to mean the angle θ formed between a turn and a plane perpendicular to the axis of the spring. Geometrically, the inclination of a turn is defined by the straight line passing through the median of the two ends of a turn and the midpoint of this turn, that is to say the vertex of the turn opposite the two ends. . This angle of inclination is also defined for those skilled in the art by the following equation: $$\theta ={\tan }^{-1}\left(\frac{\mathrm{vs}}{d}\right)$$

with c the amplitude of inclination (axial distance from which the top of a turn is offset relative to a helical spring) and d the diameter of the turn.

The vacuum interrupter element may comprise a holding system configured to hold the spring in place when it interposes between the bulb element and the bulb body portion, said retention system being preferably a receiving groove of the spring which is arranged in the bulb element.

Thus, such an assembly has a reduced risk of movement of the spring during assembly of the bulb, the risk of decentering that could cause such a movement of the spring being also reduced.

The bulb element can be selected from the group consisting of fixed vacuum bulb screens, movable vacuum bulb screens and vacuum bulb covers.

The autocentered assembly may further comprise independent parts forming screens for triple points.

The spring may be made of a material having a melting temperature lower than that of the bulb member material, whereby the spring may be used as a feed material during a soldering step of the bulb member with the bulb body portion when mounting the bulb element in the bulb body portion, the spring being preferably made of a copper-silver alloy

Such a centering system is particularly advantageous since it offers both a centering function and a fixing function of the element in the bulb body.

The spring may be made of a material selected from the group comprising iron, stainless steel, copper, silver and an alloy comprising at least one of these metals, the spring being preferably made of silver copper alloy .

The invention also relates to a vacuum interrupter comprising at least one bulb body part and which is characterized in that it comprises an autocentered assembly according to the invention.

Such a bulb can easily be assembled since at least part of the elements that compose it can be centered during its assembly by means of a centering system according to the principle of the invention

The bulb body may include a holding system configured to hold the spring in place when the spring is inserted between the bulb element. and the bulb body portion, said retention system preferably being a spring receiving groove which is provided in the bulb member.

• fourniture de l'élément d'ampoule à centrer,
• fourniture d'un ressort à spires pour former avec l'élément d'ampoule un ensemble autocentré,
• fourniture d'au moins une partie de corps d'ampoule,
• montage de l'ensemble autocentré dans l'au moins une partie de corps l'élément d'ampoule avec l'élément d'ampoule qui est centré par rapport à ladite partie de corps d'ampoule par le ressort.

The invention also relates to a method of centering a bulb element in a bulb body comprising the following steps:

• supply of the bulb element to be centered,
• providing a coil spring for forming a self-centering assembly with the bulb element,
• supplying at least a portion of bulb body,
• mounting the self-centering assembly in the at least one body portion the bulb member with the bulb member which is centered with respect to said bulb body portion by the spring.

Such a method allows an assembly of an ampoule with at least a portion of the elements that are perfectly centered, their centering having been made according to the principle of the invention.

The invention also relates to a method of manufacturing a vacuum interrupter comprising a step according to the method of centering a bulb element in a bulb body according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 illustre schématiquement et en vue en coupe d'un exemple d'ampoule à vide comportant plusieurs ensembles autocentrés selon l'invention,
• la figure 2 illustre le principe de centrage selon l'invention,
• la figure 3 illustre une portion de ressort à spires de type hélicoïdal particulièrement adapté pour former un système de centrage selon l'invention,
• la figure 4 illustre une vue rapprochée extraite de la figure 1 qui illustre l'agencement d'un ressort de centrage vis-à-vis d'un écran de l'ampoule et d'un corps d'ampoule.

The present invention will be better understood on reading the description of exemplary embodiments, given purely by way of indication and in no way limiting, with reference to the appended drawings in which:

• the figure 1 illustrates schematically and in cross-sectional view an example of a vacuum interrupter comprising a plurality of autocentered assemblies according to the invention,
• the figure 2 illustrates the centering principle according to the invention,
• the figure 3 illustrates a coil spring portion of helical type particularly adapted to form a centering system according to the invention,
• the figure 4 illustrates a close-up view taken from the figure 1 which illustrates the arrangement of a centering spring vis-à-vis a screen of the bulb and a bulb body.

Identical, similar or equivalent parts of the different figures bear the same numerical references so as to facilitate the passage from one figure to another.

The different parts shown in the figures are not necessarily in a uniform scale, to make the figures more readable.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

The figure 1 illustrates a vacuum bulb 1 comprising three self-centering assemblies 20, 30, 40 according to the invention of different types.

• un corps d'ampoule 10 comprenant une première et deuxième partie 11, 12 de corps d'ampoule,
• un premier et un deuxième couvercle 31, 41 monté chacun sur l'une des deux parties 11, 12 de corps d'ampoule (ici, chacun des couvercles inclut un écran du point triple situé entre la céramique et le couvercle) et
• un premier et un deuxième contact 15, 16 montés mobiles l'un relativement à l'autre entre une position ouverte dans laquelle ils sont à distance et une position fermée dans laquelle ils sont en contact électrique,
• un écran 21.

Such a vacuum interrupter 1 comprises:

• a bulb body 10 comprising a first and second part 11, 12 of bulb body,
• a first and a second cover 31, 41 each mounted on one of the two bulb body portions 11, 12 (here, each of the covers includes a triple point screen located between the ceramic and the cover) and
• a first and a second contact 15, 16 movably mounted relative to one another between an open position in which they are at a distance and a closed position in which they are in electrical contact,
• a screen 21.

The vacuum interrupter 1 has axial symmetry around a bulb axis which is also the axis 14 of the bulb body 10. Such symmetry is provided by a substantially cylindrical bulb body 10 and components of the bulb body 10. bulb 31, 32, 15, 16, 21 also of axial symmetry and concentric with the bulb body 10.

The bulb body 10 is formed by the two bulb body portions 11, 12. Each of the bulb body portions 11, 12 is made of insulating material such as ceramic, said bulb body 10 thus being generally known as "ceramic". The bulb body portions 11, 12 have the general shape of a hollow right cylinder with open bases. The body portions 11, 12 are circular so as to form a closed volume when assembled for forming the vacuum bottle 1 and closed by the covers 31, 41. The two parts 11, 12 of bulb body are concentric and share the same axis 14 of symmetry which is the axis of symmetry of the body.

The first and second contacts 15, 16 are mounted, as illustrated on the figure 1 respectively on the first and second covers 31, 41.

The provision of the movable mounting of the contacts 15, 16 relatively to one another is carried out by an integral mounting of the first contact 15 on the first cover 31 and a movable mounting in translation of the second contact 16 with respect to the second cover 41.

The vacuum bottle 1 also comprises, so as to form the self-centering assemblies 20, 30, 40 according to the invention, springs 25, 35, 45 each associated with one of the bulb elements 21, 31, 41 respectively. are the screen 21, the first cover 31 and the second cover 41.

Each spring 25, 35, 45 is a coil spring with its turns which are distributed, according to the same principle as that illustrated on FIG. figure 2 , according to a guideline. These springs 25, 35, 45 are adapted to allow a centering of the bulb element 21, 31, 41 corresponding and thus form a centering system.

The principle of such an adaptation is illustrated in figure 2 . This figure 2 thus shows the centering of an element 221 to center vis-à-vis an outer envelope 222, such as the bulb body 10 or one of the parts 11, 12 of the bulb body, this by means of a spring 225 according to the invention.

We can see on the figure 2 that the element 221 to be centered is equipped with the spring 225 so as to form a self-centering assembly 220 according to the invention. The spring 225 is therefore, according to the principle of the invention, a coil spring with the turns which extend along the line of direction 226.

Conventionally the spring 225 illustrated on the figure 2 has circular turns of identical dimensions. Nevertheless, the spring 225 may also comprise turns other than circular, such as ellipsoidal turns, and / or of variable dimensions without departing from the invention.

According to an advantageous possibility of the invention illustrated on the figure 2 , the guide line 226 of the spring 225 follows a circle, the spring 225 thus being an annular helical spring.

In order to ensure the centering of the element 221 to be centered, the spring is disposed along the periphery of said element extending in a plane substantially perpendicular to the axis of symmetry of the element. To allow the spring 225 to remain in place when it is placed on the element 221, the element 221 to be centered may comprise a receiving groove 222 configured to receive the spring 225. The receiving groove 222 extends around the periphery outside a plane substantially perpendicular to the axis of symmetry of the element 221.

Such a receiving groove 222 forms a holding system configured to hold the spring in place when it is inserted between the element 221 and the casing 210.

The spring 220 as illustrated on the figure 2 and according to a particularly advantageous possibility of the invention is an inclined coil spring whose turns are disjoint. According to this possibility of the invention, the inclination of the turns is preferably chosen so that this inclination is, when the autocentered assembly 220 is mounted in the envelope 210, defined with respect to the plane containing the axis of symmetry. and which goes through the center of the turn. Thus, in a configuration of the spring 225 in which the spring guideline is a circle or an arc, the inclination is then defined with respect to the plane containing the axis of symmetry of the circle corresponding to the guideline and which passes by the center of the turn.

The spring 225, therefore its dimensional characteristics, and its directional line 226 are adapted to allow a good centering of the element 221 with respect to the casing 210.

Thus, in a usual configuration of the invention, the diameter of the turns d of the spring is of the same order as the space between the element 211 and the envelope 210.

avec d le diamètre des spires, θ l'angle d'inclinaison des spires et gap_moy l'espace minimum entre l'élément 221 et l'enveloppe 210 lorsqu'ils sont concentriques.More specifically, for a helical spring 225 inclined at an angle θ and having a diameter d as illustrated in FIG. figure 3 , it is preferable that the diameter d and the angle θ of the turns of the spring 225 comply with the following equation: $$d>\frac{{\mathit{gap}}_{\mathit{Avg}}}{\cos \left(\theta \right)}$$

with d the diameter of the turns, θ the angle of inclination of the turns and gap _moy the minimum space between the element 221 and the envelope 210 when they are concentric.

avec d le diamètre des spires, θ l'angle d'inclinaison des spires et gap_max l'espace maximum entre l'élément 221 et l'enveloppe 210 lorsqu'ils sont concentriques. En effet, avec un tel dimensionnement l'ensemble des spires est en contact avec à la fois l'élément 221 à centrer et l'enveloppe 210 comme cela est montré sur la figure 2.In addition, for this same dimensioning, it is particularly advantageous for the diameter and the angle θ of the turns of the turns of the spring 225 to also respect the following equation: $$d\ge \frac{{\mathit{gap}}_{\mathit{max}}-0,5\mathit{mm}}{\cos \left(\theta \right)}$$

with d the diameter of the turns, θ the angle of inclination of the turns and gap _max the maximum space between the element 221 and the envelope 210 when they are concentric. Indeed, with such a dimensioning all the turns is in contact with both the element 221 to center and the envelope 210 as shown on the figure 2 .

avec d le diamètre des spires, θ et θ ₂ les angles d'inclinaison respectifs des spires au repos et de l'une des spires lorsque le ressort s'intercale entre l'élément et l'enveloppe, et gap_min l'espace minimal entre l'élément 221 et l'enveloppe 210 lorsqu'ils sont concentriques. En effet, avec un tel dimensionnement une majorité des spires est en contact avec à la fois l'élément 221 à centrer et l'enveloppe 210 comme cela est montré sur la figure 2. La répartition des efforts qui résulte de ce contact tend à augmenter l'angle d'inclinaison de chaque spire. Bien entendu lorsque l'une des spires n'est pas en contact avec l'un ou l'autre de l'élément 221 et l'enveloppe 210, elle n'est pas soumise aux efforts et elle conserve son inclinaison. Ainsi, dans ce dernier cas, θ₂= θ.Thus during the establishment of the element 221 in the casing 210 with the spring which is interposed between them, the arrangement of the turns along the guide line including a change in their angle of inclination. It follows that with a spring according to equations (2) and (3) that each of the turns has an angle of inclination θ ₂ greater than or equal to θ and which respects the following equation: $$\theta \le {\theta }_2\le {\cos }^{-1}\left(\frac{{\mathit{gap}}_{\min }}{d}\right)$$

with d the diameter of the turns, θ and θ ₂ the respective angles of inclination of the turns at rest and one of the turns when the spring is inserted between the element and the envelope, and gap _min the minimum space between the element 221 and the envelope 210 when they are concentric. Indeed, with such a dimensioning a majority of turns is in contact with both the element 221 to center and the envelope 210 as shown on the figure 2 . The distribution of effort resulting from this contact tends to increase the angle of inclination of each turn. Of course when one of the turns is not in contact with one or other of the element 221 and the envelope 210, it is not subject to the forces and it retains its inclination. Thus, in the latter case, θ ₂ = θ .

In addition during a heat-up cycle, such as that performed for a stirring during the final step of assembling a vacuum bottle, the thermal expansion of the envelope, the element and the spring causes an increase in the forces applied to the spring which causes an additional inclination θ ₃ with: θ ₃ ≥ θ ₂ .

Thus, the centering is provided both "hot" and "cold".

Likewise the diameter, the pitch p of the turns and the angle of inclination θ (see figure 3 ) can be adapted according to the irregularities and the variations of the space between the element and the envelope when they are concentric. Indeed, a space between the element and the envelope with a large variation can be compensated by a tilt spring between 15 ° and 30 °, and a pitch p between the major turns. Such a pitch, combined with an average angle of inclination, allows a large variation in the inclination of the turns along the spring and thus makes it possible to compensate for the large variation of space between the element 221 and the envelope 210.

The spring 225 is made of a material selected from the group consisting of iron, steels, stainless steels, copper, silver and metal alloys having any of these materials.

So, as illustrated on the figure 2 according to the principle of the invention, the element 221 and the spring 225 form an autocentered assembly. When assembling a light bulb, exemplified in the figure 2 by mounting the element 221 in the casing 210, the spring 225 is previously placed on the element 221. This implementation is performed so that the spring 225 extends over the periphery of the element, its turns in contact with the element 221. The self-centering assembly, thus arranged, is then inserted into the casing 210. The elastic deformation of the spring 225 distributes the forces over its entire length, the element 221 thus being brought back, during this insertion, in a position in which it is concentric with the casing 210. With such an arrangement of the element vis-à-vis the casing 210, any expansion related to a possible cycle of rise in temperature does not change the distribution of efforts along spring but only changes the intensity of the latter. Thus the centering is carried out both "hot" and "cold".

When the spring 225 is interposed between the element 221 and the casing 210, the spring 225 works in compression in a direction substantially perpendicular to the axis of symmetry of the casing 221 and with respect to its guide line 226 so as to maintain the element 221 and the envelope 210 concentric.

It is therefore the principle explained above which is implemented in the bulb 1 illustrated on the figure 1 to center the screen 21 and the covers 31, 41 of the bulb 1. The other bulb elements that are the two contacts 15, 16 of the bulb 1 benefit from this centering due to their mounting on the covers 31 , 41. The figure 4 also shows that, according to the principle already described above, the bulb element to be centered, here the screen 21, may comprise a receiving groove 22 for receiving the spring 25.

• fourniture de l'élément d'ampoule 21, 31, 41 à centrer,
• fourniture du ressort 25, 35, 45 à spires pour former avec l'élément d'ampoule 21, 31, 41 un ensemble autocentré 20, 30, 40,
• fourniture d'au moins la partie 1112 de corps d'ampoule,
• montage de l'ensemble autocentré 20, 30, 40 dans l'au moins une partie 11, 12 de corps l'élément d'ampoule avec l'élément d'ampoule 21, 31, 41 qui est centré par rapport à ladite partie 11, 12 de corps d'ampoule par le ressort 25, 35, 45.

When assembling a bulb 1 such as that illustrated on the figure 1 , the placement of an autocentered element, such as the screen 21 or one of the covers 31, 41 is carried out according to a centering method comprising the following steps:

• supplying the bulb element 21, 31, 41 to be centered,
• supplying the spring 25, 35, 45 with turns to form with the bulb element 21, 31, 41 an autocentered assembly 20, 30, 40,
• supplying at least the bulb body portion 1112,
• mounting the self-centering assembly 20, 30, 40 in the at least one body portion 11, 12 of the bulb member with the bulb member 21, 31, 41 which is centered with respect to said portion 11 , 12 of bulb body by the spring 25, 35, 45.

According to an advantageous variant of the invention, the spring 25, 35, 45 may be formed of a material suitable for soldering such as a copper-silver alloy. Such an adaptation is provided by a melting temperature of said material which is lower than that of the material of the bulb element 21, 31, 41.

With such a variant of the invention, the spring acts both as a centering system and a material for brazing. Thus according to this variant, the fixing of a bulb element can be provided by a simple rise cycle. temperature for brazing the bulb element on the bulb body. Of course, in order to ensure a good attachment of the bulb element to the bulb body, additional material may be provided. The centering element can then be made to disappear after ensuring its centering function: melted, it occupies the interstices between the parts to be centered. The dielectric performance of the vacuum bulb is then optimized.

Examples of embodiment of the invention:

The tables below represent two examples of implementation of the invention. The first relates to a bulb comprising a self-centering assembly whose bulb element is a fixed screen of the same type as that illustrated in FIGS. figures 1 and 3 . The second example relates to a vacuum interrupter comprising an autocentered assembly whose bulb element is a mobile screen. In both cases, the spring of the self-centering assembly is identical with a turn diameter of 2.1 mm and an angle θ ₁ of inclination of 15 °. Fixed screen Ø int bulb body (mm) Ø outside screen (mm) Δ radius (mm) Gap (mm) θ 2 spring (deg) Ø spring Gap after installation (mm) Status Last name 81.4 79.3 0.85 1 62 2.1 0 Well Low 80.65 78.9 0.875 1 62 2.1 0 Well Max 82.15 79.7 1,225 1.2 55 2.1 0 Well Mobile Screen Ø int bulb body (mm) Ø outside screen (mm) Δ radius (mm) Gap (mm) θ ₂ spring (deg) Ø spring (mm) Gap after installation (mm) Status Last name 81.4 77.0 2 2 18 2.1 0 Well Low 80.65 76.6 2,025 2 18 2.1 0 Well Max 82.15 77.4 2,375 2.5 0 2.1 0.4 Well

The nomenclature in the tables above is as follows: "Ø int bulb body" corresponds to the inside diameter of the bulb body, "Ø ext screen" corresponds to the outside diameter of the screen, "Δ radius" corresponds to the difference between the inner radius of the bulb body and the outer radius of the screen, "Gap" corresponds to the space between the inside of the body of bulb and the outside of the screen when the screen is in place in the bulb without the spring, " θ ₂ spring" corresponds to the inclination θ of the turns of the spring when the spring is in place, "spring Ø" corresponds to the diameter of turns of the spring, "Gap after installation" corresponds to the space left free by the spring between the interior of the bulb body and the outside of the screen, and "status" corresponds to the control of the good quality of the centering of the element, it being considered, for the dimensions present in these tables, good if the Gap after installation is less than 0.5 mm. The lines "Name", "Min" and "Max" correspond respectively to the nominal, minimum and maximum values.

These two examples of implementation of the invention make it possible to illustrate two different configurations of the invention with, in the case of the fixed screen, that is to say the case exemplified by the first table, the set coils which are placed in compression and which are interposed between the bulb element and the bulb body, and in the case of the movable screen, that is to say the second array, only a part turns that are put in compression and are interposed between the bulb element and the bulb body, the other turns being at "rest".

Thus in the case of the fixed screen, the distance between the screen and the bulb body is relatively small, less than 1.2 mm, vis-à-vis the diameter of the turns which is 2.1 mm. A simple inclination of the turns, related to the compression of the latter, allows a good distribution of the spring forces on the fixed screen to center the latter vis-à-vis the bulb body.

Regarding the case of the mobile screen, because of the mobile nature of the latter, the distance between the screen and the bulb body is of the same order of magnitude as the diameter of the turns of 2.1 mm or higher: by places, this one can exceed 2,3mm. The inclination of the turns therefore does not compensate for the distance between the screen and the body over its entire range of variation. Thus, as shown by the Gap value after installation which can be non-zero in places, a part of the turns of the spring does not interconnect between the screen and the bulb body. These last turns are therefore not in contact with both the bulb element and the body.

Nevertheless, as shown by the Gap values obtained after installation and the proper centering status, it is only necessary that some of the turns be adapted to constrain the moving screen to a position in which it is concentric with the body. of bulb to provide a self-centering element.

Of course if in the embodiment described above the spring is a helical spring inclined disjoint turns, the invention covers any type of coil spring as long as its turns are distributed along a guide line of the spring with the spring and its guideline which are adapted so that, when assembling an ampoule, several turns of the spring are interposed between the bulb element and the body of the bulb. Thus, the spring may be a coil spring non-helical, may not include inclined turns or may have contiguous turns, without departing from the scope of the invention.

Similarly, if in the embodiment described above, the spring has a guide line in the form of a circle, the latter may also be in the form of a circular arc without departing from the scope of the invention. According to this same possibility, when the spring has an arcuate arc angle guideline of less than 360 °, the centering system may comprise one or more other coil springs having an arcuate guideline this without that we leave the scope of the invention.

According to the latter possibility, the total sum of the arcuate angles of the guidelines of the springs forming the centering system is preferably substantially equal to 360 °.

In addition, if in the embodiment described above, the springs illustrated are springs with substantially circular turns, it is also conceivable as already indicated, that the springs comprise turns of another shape. Thus, the turns may, for example, have an ellipsoidal shape without departing from the invention. According to this latter possibility, the parameter d in equations (1) to (3) represents the dimension of the turns in a direction which is substantially perpendicular to the axis of the bulb body when the spring equips the vacuum bulb.

Similarly, if in the embodiment described above, the bulb element has a receiving groove as a holding system, the bulb element and / or the bulb body may have another type. maintenance system or not to include without departing from the scope of the invention. Thus, according to a variant of the invention, the receiving groove can be arranged on the bulb body portion so as to lock the spring in position during placement of the element in the bulb body. According to another variant of the invention, the bulb element and / or the bulb body may comprise a projection serving as a stop to hold the spring in place.

Claims (11)

1. A self-centered assembly (20, 30, 40) for a vacuum bulb (1) including:

   - a bulb element (21, 31, 41) intended to be centered with respect to the axis of at least one bulb body part (11, 12) upon mounting the former in said bulb body part (11, 12),

   - a centering system suitable for centering the bulb element (21, 31, 41) with respect to the axis (14) of the bulb body part (11, 12),

   the self-centered assembly (20, 30, 40) being characterized in that the centering system comprises at least one coil spring (25, 35, 45) the coils of which are distributed along a central line of the spring (25, 35, 45), the spring (25, 35, 45) and its central line being suitable such that upon mounting the bulb element (21, 31, 41) in the bulb body part (11, 12), several coils of the spring (25, 35, 45) are interleaved between the bulb element (21, 31, 41) and the bulb body part (11, 12) by being in contact with both the bulb element (25, 35, 45) and the bulb body part (11, 12).
2. The self-centered assembly (20, 30, 40) according to claim 1, wherein the central line is an arc of circle, preferentially a circle so as to form a ring spring.
3. The self-centered assembly (20, 30, 40) according to claim 2, wherein the coils are disjoined.
4. The self-centered assembly (20, 30, 40) according to claim 3, wherein the spring (25, 35, 45) is a tilted helical spring having a tilt angle θ of the coils.
5. The self-centered assembly (20, 30, 40) according to one of claims 1 to 4, wherein the vacuum bulb element (21, 31, 41) includes a holding system configured to hold the spring (25, 35, 45) in place when the same is interleaved between the bulb element (21, 31, 41) and the bulb body part (11, 12), the holding system being preferentially a spring receiving groove (22) which is provided in the bulb element (21, 31, 41).
6. The self-centered assembly (20, 30, 40) according to any of claims 1 to 5, wherein the bulb element (21, 31, 41) is selected from the group including the stationary vacuum bulb shields (21), mobile vacuum bulb shields and vacuum bulb covers (31, 41).
7. The self-centered assembly (20, 30, 40) according to claim 6, further comprising independent pieces forming triple point shields.
8. The self-centered assembly (20, 30, 40) according to any of claims 1 to 7, wherein the spring (25, 35, 45) is made of a material having a melting temperature lower than that of the material of the bulb element, thus the spring can be used as a filler material during a step of soldering the bulb element with the bulb body part upon mounting the bulb element (21, 31, 41) in the bulb body part (11, 12), the spring (25, 35, 45) being preferentially made of a copper-silver alloy.
9. A vacuum bulb (1) including at least one bulb body part and which is characterized in that it includes a self-centered assembly according to any of claims 1 to 8.
10. The vacuum bulb (1) according to claim 9, wherein the bulb body (10) includes a holding system configured to hold the spring (25, 35, 45) in place when the same is interleaved between the bulb element (21, 31, 41) and the bulb body part (11, 12), said holding system being preferentially a spring receiving groove (22) which is provided in the bulb element (21, 31, 41).
11. A method for centering a bulb element (21, 31, 41) in a bulb body (10) including the following steps of:

    - providing the bulb element (21, 31, 41) to be centered,

    - providing a coil spring (25, 35, 45) to form together with the bulb element (21, 31, 41) a self-centered assembly (20, 30, 40),

    - providing at least one bulb body part (1112),

    - mounting the self-centered assembly (20, 30, 40) in the at least one bulb body part (11, 12) with the bulb element (21, 31, 41) which is centered with respect to the bulb body part (11, 12) by the spring (25, 35, 45).

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