Vacuum switching device

Abstract

Vacuum switching device (1), comprising a housing (2,3,8) at one end of which a fixed contact (4,5) is arranged, and a bellows (11) with lamellae, which is attached on one side to a flange (8) at the other end of the housing (2,3,8) and on the other side to a movable contact (6,7), and a guide bearing (14) for the movable contact (6,7), which is attached to the flange (8) and guides the movable contact (6,7) in a sliding manner, wherein a spacer means (10) is designed to minimize abrasion of the bellows (11) when the movable contact (6,7) is moved, when the housing (2,3,8) is subjected to overpressure. characterized by the fact that the spacer means (10) has a sliding sleeve (10) arranged between the movable contact (7) and the bellows (11), which is positioned by means of a first spring device (17) when the movable contact (7) is moved such that it supports the lamellae in an expected buckling area (30), and that a second spring device (21) is arranged at the end of the sliding sleeve (10) facing away from the guide bearing (14).

Description

[0001] The present invention relates to a vacuum switching device according to the preamble of claim 1.

[0002] From the operating instructions for "3TM Vacuum Contactor 7.2 kV - 15 kV, 3-pole, 4.15 kV - 6.9 kV, 1-pole", order no.: 9229 0106 100 0, Siemens AG 2020, a switching device for medium voltage is known that has a vacuum switching device with an electromagnetic drive. The magnetic drive can exert a magnetic force on a so-called armature plate and attract it. The movement of the armature plate is mechanically translated into a movement for pressing a movable contact against a fixed contact within the vacuum switching device.

[0003] A vacuum switching device according to the invention comprises, for example, a fluid-tight housing in which a vacuum prevails (or an extremely low gas pressure below 0.1% atmospheric pressure). Typically, the housing is partially formed as a ceramic insulating body made of aluminum oxide, which is connected to other components of the housing via a metallic flange. If a movable contact is quickly pulled away from the fixed contact, for example by means of a spring force, any resulting arc is rapidly extinguished, among other reasons because there is hardly any ionizable medium present for current flow. Vacuum switching devices are particularly well suited for switching alternating current because an arc always breaks at the zero crossing of the voltage.

[0004] The movable contact is guided out of the vacuum via a flexible bellows. A guide bearing, preferably made of plastic, is used to stabilize and center the moving contact rod; this bearing is attached to the flange of the moving contact.

[0005] The guide bearing is often attached via a separate component, a bearing cap. The bearing cap is soldered to the flange of the moving contact during the soldering process and serves as a receptacle for the bearing. After the plastic bearing is inserted, the upper edge of the bearing cap is folded over, for example, to secure the bearing. Solutions are also known in which a type of nozzle is pulled out of the flange to secure the bearing. Furthermore, bearings are known that snap into a locked position during assembly. For this purpose, the plastic bearing is designed to include locking hooks that engage with the flange opening.

[0006] Operating vacuum switching devices or vacuum interrupters in an elevated pressure environment, e.g., when used inside a container filled with an electrical insulating gas under overpressure (e.g., above 1.3 bar absolute pressure) (e.g., in a gas-insulated switchgear), can reduce the mechanical service life of the vacuum interrupter. The service life of a metal bellows depends not only on geometric factors but also on environmental factors such as pressure and temperature.

[0007] Under increased pressure, the bellows' service life is further reduced by so-called "column buckling." This means that the lamellarly raised metal sheet of the bellows buckles under pressure, for example, inwards towards the movable metal contact rod, and rubs against it mechanically during switching. Within the scope of the invention, the term "lamellar" refers to a design in which a sheet has several so-called "bellows waves," i.e., in the case of a cylindrical bellows, wave-like distortions propagating between an outer and an inner diameter of the bellows. A lamella denotes a single bellows wave.

[0008] In designs with a cylindrical sleeve (e.g., coated with Teflon), friction occurs between the sleeve and the bellows. This results in one-sided contact and thus continuous abrasion until eventual failure due to leakage. A further problem is that the aforementioned sleeve is freely movable along the contact rod and shorter than the finned section of the bellows. Because the sleeve moves along with the contact rod during switching, its circular edge can collide with the bellows.

[0009] Depending on certain technical parameters, a critical pressure P can be determined through measurements. KIt must be determined at what pressure a bellows will buckle when subjected to this pressure. Typically, when pressurized above 1.3 bar, it cannot be reliably guaranteed that the bellows will not buckle over time. Therefore, for higher pressures, it is advisable to look for particularly pressure-resistant designs to ensure a long service life.

[0010] As a solution, the publication DE 10 2017 222 406 A1 proposes to use a cylindrical sleeve that is longer than previous designs, is fixed on the movable contact rod, supports the lamella-equipped area of ​​the bellows along its entire length against the contact rod and also extends between the contact rod and the guide bearing.

[0011] Furthermore, US patent 4,585,913 discloses a bellows that has segments with lamellae along its longitudinal axis, the lamellae being made of a thicker sheet metal than the statutory segments with lamellae. This stabilizes the bellows against buckling inward toward the moving contact. A bellows is also disclosed that consists of two segments, each attached on one side to a sleeve that slides freely on the contact bar.

[0012] Furthermore, vacuum switching devices are known from publications DE1750257A and US3196236A.

[0013] Based on existing vacuum switching devices, the invention aims to provide a vacuum switching device that enables a long operating time even at comparatively high ambient pressures.

[0014] The invention solves this problem by means of a vacuum switching device according to claim 1.

[0015] The housing, for example, has a metallic lid and a metallic cover connected to a cylindrical ceramic insulating body (e.g., made of aluminum oxide). The interior of the housing is evacuated.

[0016] A bellows is a component that is coiled in a wave-like, accordion-like manner, allowing it to be compressed and released with low mechanical resistance while simultaneously being fluid-tight and durable. A bellows is manufactured, for example, from a thin sheet metal component forming lamellae. A lamella, as defined in the invention, is, for example, a ring-shaped, rotating shaft with a diameter that decreases and then increases again within the cylindrically shaped sheet metal of the bellows. According to the invention, the bellows is attached to the movable contact either directly or indirectly via an intermediate component such as a bellows cap. In the latter case, the bellows is, for example, fluid-tightly attached to the bellows cap, which in turn is fluid-tightly attached to the movable contact.

[0017] A flange is typically a metallic connecting part.

[0018] A guide bearing is a component used to guide the movable contact through the housing. The movable contact is typically bolt-shaped, so the guide bearing provides an elongated hollow cylinder to accommodate the bolt. For cost reasons, guide bearings are often made of plastic and are formed, for example, by injection molding or machining. The plastic guide bearing is attached to the flange, for example, with a metal plate that is bent radially inwards for fixation.

[0019] In the context of the invention, the term "slidingly displaceable" refers to the property that a body is not fixed in place but can be displaced along an axis against another body with low frictional resistance. For example, a material with a low coefficient of friction for static and / or kinetic friction slides relatively easily on the moving metallic contact, i.e., it causes little wear. For example, polytetrafluoroethylene (trade name: Teflon) has a low coefficient of friction and can therefore be used to coat slidingly displaceable components.

[0020] A significant advantage is that the spacer provides particularly reliable support for the lamellae. This further reduces abrasion and extends service life compared to conventional vacuum switching devices. Furthermore, it allows for exceptionally high ambient pressures, such as those encountered during use within an encapsulated gas-insulated switchgear.

[0021] Another advantage is that the vacuum switching device does not undergo any external changes for adapting to higher pressures, which would need to be taken into account when connecting or integrating it into a switching device.

[0022] Furthermore, it is an advantage over the vacuum switching device known from the prior art with a sliding sleeve extended between the guide bearing and the contact rod that, in the vacuum switching device according to the invention, the sleeve for stabilizing the lamellae cannot fall out during assembly or be accidentally removed.

[0023] In a preferred embodiment of the vacuum switching device according to the invention, the overpressure is a pressure of at least 1.25 bar absolute. The term "bar absolute" refers to an absolutely measurable gas pressure and not a relative gas pressure; that is, 1.25 bar absolute corresponds to an internal overpressure within an encapsulated housing of 0.25 bar relative to atmospheric pressure. This configuration is advantageous because 1.3 bar absolute is typically used as the gas pressure in some gas-insulated switchgear.

[0024] Even more preferred is an overpressure between 1.25 bar absolute and 2.5 bar absolute. Equally preferred is a particularly pressure-resistant design for pressures between 2.5 bar absolute and 10 bar absolute.

[0025] In a further preferred embodiment of the vacuum switching device according to the invention, the spacer means has a sliding sleeve arranged between the movable contact and the bellows, which supports all the lamellae on their inner surface adjacent to the movable contact, with the sliding sleeve and the guide bearing being fixed to one another. This is advantageous because an unsupported area between the sliding sleeve and the movable contact is avoided. Furthermore, it simplifies manufacturing.

[0026] In a further preferred embodiment of the vacuum switching device according to the invention, the vacuum switching device encompasses A bellows cap secures the bellows at its end fixed to the movable contact, with a cavity formed between the bellows cap and the movable contact to accommodate the sliding sleeve. This is advantageous because the comparatively elongated sliding sleeve can slide into the cavity when the contacts open, i.e., when the bellows is compressed. If the movable contact is essentially round, the cavity can, for example, have a cylindrical shape to accommodate a cylindrically shaped sliding sleeve.

[0027] In this embodiment and the following embodiments, the length of the cavity for receiving the sliding sleeve can be adjusted to the maximum stroke of the movable contact such that the sleeve can slide into the cavity without impact during normal operation. If the normal stroke is, for example, 10 mm for a switching operation, a length of 12 mm can be provided for the cavity as a safety margin, preferably a length of 16 mm.

[0028] In a further preferred embodiment of the vacuum switching device according to the invention, the sliding sleeve and the guide bearing are formed in one piece. This is advantageous because it simplifies manufacturing. For example, the sliding sleeve and guide bearing can be manufactured in one piece by injection molding from plastic or by machining.

[0029] The spacer has a sliding sleeve located between the movable contact and the bellows. This sleeve is positioned by a first spring mechanism when the movable contact moves, such that it supports the lamellae in an expected buckling zone. For example, a spring mechanism with a coil spring can be used, which encircles the movable contact. An expected buckling zone is, for example, a centrally located longitudinal section on the bellows, where experience has shown that buckling with significant abrasion of the movable contact is typically likely to occur. Outside the buckling zone, for example at an edge of the bellows, the spring mechanism provides at least some protection against buckling and abrasion.

[0030] The forced positioning by means of the spring device is advantageous because, on the one hand, the bellows' lamellae are supported, and on the other hand, the spring device can accommodate the resulting shortening of length when the contacts open. In this embodiment, the previously described cavity for the sliding sleeve can therefore be omitted.

[0031] In a further preferred embodiment of the vacuum switching device according to the invention, the first spring assembly is arranged at the end of the sliding sleeve facing the guide bearing.

[0032] In a further preferred embodiment of the vacuum switching device according to the invention, the first spring assembly is arranged between the guide bearing and the movable contact. This is advantageous because the spring assembly can be fixed particularly easily in the space between the guide bearing and the contact.

[0033] A second spring assembly is arranged at the end of the sliding sleeve facing away from the guide bearing. This is advantageous because the second spring assembly, particularly in interaction with the first, ensures exceptionally good forced positioning of the sliding sleeve.

[0034] In a further preferred embodiment of the vacuum switching device according to the invention, the spacer means has a sliding sleeve arranged between the movable contact and the bellows, which supports all lamellae on their inner side associated with the movable contact, and a bellows cap surrounds the bellows at its end fixed to the movable contact, wherein a cavity for receiving the sliding sleeve is formed between the bellows cap and the movable contact, and A cavity for receiving the sliding sleeve is formed between the guide bearing and the movable contact.

[0035] In a further preferred embodiment of the vacuum switching device according to the invention, the spacer means has two sliding sleeves arranged between the movable contact and the bellows, which are designed to be slidable into one another in an overlap area and are fixed at their respective ends facing away from the overlap area.

[0036] In a further preferred embodiment of the vacuum switching device according to the invention, the spacer means has two sliding sleeves arranged between the movable contact and the bellows, which are designed to be slidable into one another in an overlap area, wherein a third spring device is assigned to the overlap area, which pushes the two sliding sleeves apart.

[0037] In a further preferred embodiment of the vacuum switching device according to the invention, at least one sliding sleeve has a tapered area at at least one end, so that a chamfer is formed in the cross-section of the tapered area in the direction of the movable contact.

[0038] In a further preferred embodiment of the vacuum switching device according to the invention, the spacer means includes sealing elements that seal an evacuated cavity between the bellows and the movable contact. In this embodiment, unlike the other embodiments of the invention, the evacuated area is located "inside," i.e., between the bellows and the contact. This design is based on the surprising observation from measurement series that a bellows subjected to a higher pressure on the outside than on the inside is more stable (i.e., less prone to buckling). In this design, the bellows is no longer fixed to the movable contact at its end facing away from the guide bearing, but rather fixed to the housing. However, at the end of the bellows facing the guide bearing, it is fixed to the movable contact.To further improve the design, a sliding sleeve can be provided which, unlike before, is not located between the bellows and the movable contact, but between the bellows and the bellows cap.

[0039] In a further preferred embodiment of the vacuum switching device according to the invention, the guide bearing has an anti-rotation device that prevents a cylindrically shaped movable contact from rotating. This is a significant advantage of the invention over the design known from German patent application DE 10 2017 222 406 A1, in which the sliding sleeve extends between the guide bearing and the contact, and thus no anti-rotation device can be provided because the guide bearing and the contact do not directly touch. For example, the anti-rotation device can have at least one projection on the inner surface of the guide bearing facing the contact, which engages in at least one complementarily shaped recess in the contact. For example, the recess can be provided as a longitudinal groove or slot in the movable contact.

[0040] In a preferred embodiment of the vacuum switching device according to the invention, the vacuum switching device is designed for medium voltage. Medium voltage, as defined in the invention, is characterized by an electrical voltage between 1 kV and 52 kV.

[0041] In a preferred embodiment of the vacuum switching device according to the invention, the vacuum switching device is designed for high voltage. High voltage, as defined in the invention, is characterized by an electrical voltage above 52 kV.

[0042] To better illustrate the invention, the following are shown in a highly simplified and schematic representation: Fig. 1 a first embodiment of the invention, and Fig. 2 a second embodiment of the invention, and Fig. 3 a third embodiment of the invention, and Fig. 4 a fourth embodiment of the invention, and Fig. 5 a fifth embodiment of the invention, and Fig. 6 a sixth embodiment of the invention.

[0043] The Fig. Figure 1 shows a vacuum switching device 1 according to the invention, comprising a cylindrical ceramic housing 2, which is closed with a base or flange 3 and a flange 8 or cover. An evacuated area 9 is located inside the housing 2, 3, 8. A fixed contact 4, 5 with a contact rod 4 and a contact disc 5 is provided on the flange 3.

[0044] A movable contact 6, 7 with a contact disc 6 and a contact rod 7 is slidably guided outwards through the housing 2, 3, 8. To ensure fluid tightness, a metal bellows 11 with lamellae is provided, which is attached on one side to the flange 8 and on the other side to a shield 13, also referred to as a bellows cap 13. The bellows cap 13 establishes a fluid-tight connection with the contact rod 7. In this case, the metal bellows 11 is not directly fixed to the slidably movable contact rod 7, but indirectly via the bellows cap 13. However, within the scope of the invention, this corresponds to an attachment to the movable contact 7; that is, an indirect attachment is always implied when the invention states that the metal bellows 11 is attached to the movable contact 6, 7.

[0045] To guide the movable contact rod 7 for sliding movement, a guide bearing 14 is provided outside the housing 2, 3, 8 on the flange 8. According to the invention, this guide bearing is extended in the direction of the fixed contact 4, 5 such that a spacer 10 is formed in which the movable contact rod 7 is guided for sliding movement. In this embodiment, the spacer 10 and the guide bearing 14 are manufactured in one piece from plastic. To prevent the bellows from being compressed when a separation or switching path is formed, i.e., when the movable contact 6, 7 is withdrawn from the housing, a cavity 12 is provided between the movable contact rod 7 and the bellows cap 13 to accommodate the spacer 10 or the sliding sleeve.

[0046] The design according to the invention ensures that all lamellae of the metal bellows 11 are supported by the spacer 10 and cannot press against the movable contact rod 7. This is guaranteed even when the vacuum switching device 1 is operated in a situation where it is subjected to an external overpressure of at least 1.25 bar. In this example, the spacer 10 is designed as a sliding sleeve 10 arranged between the movable contact rod 7 and the bellows 11, which is fixed to the guide bearing 14.

[0047] The Fig. Figure 2 shows another embodiment of a spacer 10 according to the invention, which, as in Figure 2, Fig. 1 is formed in one piece with the guide bearing 14, but has a tapered area 15 at its end facing the movable contact, so that a chamfer in the direction of the movable contact is formed in the tapered area 15 in cross-section.

[0048] The Fig. Figure 3 shows a third embodiment of the invention, wherein in this figure and in the subsequent figures only a detailed section of the vacuum switching device 1 is shown. The movable contact rod 7 is indicated, and all elements shown in cross-section can also be considered mirror images of each other on the other side of the movable contact rod 7.

[0049] The illustrated embodiment differs from the one in the Fig. In the first embodiment shown in Figure 1, the guide bearing 14 and the spacer 10, or the sliding sleeve 10, are designed in two parts. In addition to the cavity 12 between the bellows cap 13 and the movable contact rod 7, a second cavity 31 is also formed in the area of ​​the guide bearing 14 between the guide bearing 14 and the movable contact rod 7. The two cavities 12 and 31 serve to receive the sliding sleeve 10 when switching the vacuum switching device 1 to the open state.

[0050] The Fig. Figure 4 shows a fourth embodiment in which a first spring device 17 is arranged in the cavity 16 between the guide bearing 14 and the movable contact 7. This spring device presses the sliding sleeve 10 towards the fixed contact onto the bellows cap 13. As a result, when the movable contact rod 7 is moved, the sliding sleeve 10 is positioned such that it supports the lamellae in an expected buckling zone 30. The expected buckling zone 30 is an area in which, based on experience, buckling of the metal bellows 11 towards the movable contact rod 7 is particularly likely to occur.

[0051] The Fig. Figure 5 shows a fifth embodiment, in which, unlike in Fig. 4. A second spring assembly 21 is also arranged in a cavity 20 between the bellows cap 13 and the movable contact rod 7. This embodiment represents a further improved forced positioning of the sliding sleeve 10 by means of the first and second spring assemblies 17, 21. The two spring assemblies 17, 21 also ensure that the metal bellows 11 cannot buckle in the direction of the movable contact rod 7, thereby causing unacceptable wear.

[0052] The Fig. Figure 6 shows a sixth embodiment of a vacuum switching device 1 according to the invention, in which, in contrast to all other embodiments according to the Fig. 1 to 5 The area between the housing 2 and the metal bellows 10 is not evacuated, but is partially filled with a gas 26 at ambient gas pressure. In contrast, the area between the movable contact 7 and the metal bellows 11 is sealed fluid-tight by means of sealing agents 25, 28, so that this area can be kept evacuated. In this design, the bellows 11 is fixed to the housing at one end facing the fixed contact and to the movable contact 7 at the other end facing away from the fixed contact. When the switching device is opened, the movable contact 7 is pulled out of the housing and the bellows 11 is stretched, whereby the spring bellows, which is fixed to the sealing agent 15, can be carried along towards the guide bearing 14, which in the Fig. 6 is indicated by the arrow 29.

Claims

[1] Vacuum switching device (1), comprising a housing (2,3,8), at one end of which a fixed contact (4,5) is arranged, and a bellows (11) with lamellae, which is fastened on the one hand to a flange (8) at the other end of the housing (2, 3, 8) and on the other hand to a movable contact (6, 7), and a guide bearing (14) for the movable contact (6, 7), which is fastened to the flange (8) and guides the movable contact (6, 7) in a sliding manner, wherein a spacing means (10) is designed to minimize abrasion of the bellows (11) when the housing (2, 3, 8) is subjected to an overpressure when the movable contact (6, 7) moves. characterized by , that the spacing means (10) comprises a sliding sleeve (10) arranged between the movable contact (7) and the bellows (11), which is placed by means of a first spring device (17) during movement of the movable contact (7) in such a way that it supports the lamellae in an expected buckling region (30), and that a second spring device (21) is arranged at the end of the sliding sleeve (10) facing away from the guide bearing (14). [2] Vacuum switching device (1) according to claim 1, characterized by that the overpressure is a pressure of at least 1.25 bar absolute. [3] Vacuum switching device (1) according to claim 1 or 2, characterized by that the spacing means (10) has a sliding sleeve (10) arranged between the movable contact (7) and the bellows (11), which supports all the lamellae on their inner side associated with the movable contact (6, 7), wherein the sliding sleeve (10) and the guide bearing (14) are fixed to one another. [4] Vacuum switching device (1) according to claim 3, characterized by that a bellows cap (13) encompasses the bellows (11) at its end fixed to the movable contact (7), wherein a cavity (12) for receiving the sliding sleeve (10) is formed between the bellows cap (13) and the movable contact (7). [5] Vacuum switching device (1) according to claim 3 or 4, characterized by that the sliding sleeve (10) and the guide bearing (14) are formed in one piece. [6] Vacuum switching device (1) according to claim 1, characterized by that the first spring device (17) is arranged at the end of the sliding sleeve (10) facing the guide bearing (14). [7] Vacuum switching device (1) according to claim 6, characterized by that the first spring device (17) is arranged between the guide bearing (14) and the movable contact (7). [8] Vacuum switching device (1) according to claim 1 or 2, characterized bythat the spacing means (10) has a sliding sleeve (10) arranged between the movable contact (7) and the bellows (11), which supports all the lamellae on their inner side assigned to the movable contact (11), and that a bellows cap (13) engages around the bellows (11) at its end fixed to the movable contact (7), wherein a cavity for receiving the sliding sleeve (10) is formed between the bellows cap (13) and the movable contact (7), and that a cavity for receiving the sliding sleeve (10) is formed between the guide bearing (14) and the movable contact (7). [9] Vacuum switching device (1) according to claim 1 or 2, characterized by that the spacing means comprises two sliding sleeves arranged between the movable contact and the bellows, which are designed to be slidable into one another in an overlapping region and are fixed at their respective ends facing away from the overlapping region. [10] Vacuum switching device (1) according to claim 1 or 2, characterized by that the spacing means comprises two sliding sleeves arranged between the movable contact and the bellows, which are designed to be slidable into one another in an overlapping region, wherein a third spring device is assigned to the overlapping region, which presses the two sliding sleeves apart. [11] Vacuum switching device (1) according to one of claims 3 to 10, characterized by that at least one sliding sleeve (10) has at least one end a region (15) tapering towards the end, so that in the tapered region (15) a bevel in the direction of the movable contact is formed in cross section. [12] Vacuum switching device (1) according to claim 1 or 2, characterized by that the spacing means comprises sealing means (25,28) which seal an evacuated cavity between the bellows (11) and the movable contact (7). [13] Vacuum switching device (1) according to one of the preceding claims, characterized by that the guide bearing has an anti-rotation device which prevents rotation of a cylindrical movable contact.

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