Switching device

Abstract

The invention relates to a switching device having a housing with a front wall, a rear wall, a top wall, a bottom wall and two side walls, in which an air channel is formed parallel to the side walls and having a clear width D, and having a rotational axis, the rotating shaft extends from the front wall to the rear wall and is rotatably mounted in the front wall with a first end section and in the rear wall with a second end section, the rotating shaft carries a rotating device at the end of the first end section, and the rotating device is connected with the rotating shaft in a rotationally fixed manner and can be accessed from the outer side of the front wall; the rotary shaft carries a coupling device, which is connected to the rotary shaft in a rotationally fixed manner, at the end of the second end section, by means of which the switchgear can be fastened to the respective receiving device, and the bottom wall and the top wall each have at least one ventilation opening such that an air flow in the air channel flows from the bottom wall to the ventilation opening of the top wall, the rotating shaft has an intermediate section located between the first and second end sections, which intermediate section has an outer diameter d and is located in the air channel, and the rotating shaft is designed as a hollow shaft with a ratio D / d greater than 1.5.

Description

Technical Field

[0001] The present invention relates to a switching device and a method for manufacturing a rotating shaft for the switching device. Background Technology

[0002] The Siemens SIMATIC ET 200SP motor starter, a switching device for starting and stopping motors, is assembled on a corresponding, fully wired assembly base (“BaseUnit”) by first turning the mechanical rotary lock of the motor starter to the assembly / disassembly position. Figure 1 ), and then guide the motor starter to the assembly base ( Figure 1 Finally, rotate the rotary lock clockwise to the running position. Figure 2 and Figure 3 The motor starter is securely locked in the assembly base and all electrical contacts are connected. See: Chapter 6.14.2 "Assembling / Removing Motor Starters" in the System Handbook "SIMATIC ET 200SP Distributed Peripheral Systems", 02 / 2018 edition, A5E03576848-AH, Siemens AG, Division Digital Factory, Nürnberg, Germany.

[0003] Here, the mechanical rotary lock is designed as a solid shaft made of plastic ( Figure 5 Solid shafts are respectively mounted in the front and rear walls of the motor starter housing. One end protruding from the front wall carries a knob for manual operation, and the other end protruding from the rear wall has a stop nose that can engage with a corresponding groove in the assembly base in a bayonet-like manner. Figure 6 Here, the solid shaft has a relatively large diameter to ensure the necessary torsional stiffness: when the knob is operated, torques can sometimes reach up to 2 Nm.

[0004] However, due to its large diameter, the solid shaft obstructs the flow of cooling air through the motor starter to dissipate the heat generated within it. For this reason, a continuous air passage transverse to its longitudinal axis is incorporated within the solid shaft. Figure 7 This improves air convection.

[0005] In modern motor starters with high-power electronics, high currents, such as >>50 A motor starting current, can occur, lasting for several seconds. These periodic short-duration currents, as well as long-duration continuous currents, generate relatively high heat losses. If air convection in the switching equipment is obstructed by a large, solid shaft, problems may arise in dissipating such a large amount of heat from the motor starter or (more generally) the switching equipment. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to change the mechanical rotary lock of the switching device so as to improve the heat dissipation from the switching device.

[0007] According to the present invention, the above-mentioned technical problems are solved by a switching device having the features of the present invention and a method having the features of the present invention.

[0008] The switching device according to the invention has a housing. The housing has a front wall and a rear wall opposite to the front wall, a top wall and a bottom wall opposite to the top wall, and two opposing side walls. The front wall is the wall on the front side of the housing, on which an operator can make inputs, such as test buttons and reset buttons, and obtain outputs, such as LEDs for status and error indication. The rear wall is the wall on the rear side of the housing. The bottom wall is the wall of the housing facing the ground.

[0009] Here, an air passage is formed within the housing, extending parallel to the sidewall. The air passage has a net width D measured in the direction transverse to the sidewall.

[0010] The switching device according to the invention has a rotating shaft extending from the front wall through the housing to the rear wall. The rotating shaft has a first end section rotatably mounted in the front wall. The rotating shaft also has a second end section rotatably mounted in the rear wall. Here, the end of its first end section carries a rotating device, such as a rotary knob, which is torsionally connected to the rotating shaft and is accessible from the outside of the front wall. Furthermore, the end of its second end section carries a coupling device, which is torsionally connected to the rotating shaft and is accessible from the outside of the rear wall. By means of the coupling device, the switching device can be fastened to a corresponding receiving device. Therefore, the rotating shaft is also referred to as a "coupler shaft".

[0011] The bottom and top walls each have at least one vent, allowing airflow to pass from the bottom vent to the top vent within the air passage. The airflow direction through the air passage is from the bottom wall to the top wall because the air absorbs heat from the heated electronic components inside the housing and is therefore hotter than the surrounding environment; thus, the heated air rises from bottom to top due to natural convection within the air passage. If more heat removal is desired through convection, a fan can also be used to generate forced convection through the air passage. At low flow rates, heat removal through free convection is usually sufficient; at high flow rates, a fan is used additionally.

[0012] The rotating shaft has an intermediate section located between the first end section and the second end section. The intermediate section is situated within an air passage and has an outer diameter d. Here, the dimensional ratio D / d, i.e., the quotient of the net width D of the passage and the outer diameter of the intermediate section of the rotating shaft located in the air passage, is greater than 1.5. Furthermore, the rotating shaft is designed to be a hollow shaft.

[0013] According to the present invention, the above-mentioned technical problem is also solved by a method for manufacturing a rotating shaft of a switching device according to the present invention. Here, in the injection molding process, a metal center part is supplied to the injection molding machine as an insert, and plastic end parts are respectively injection molded at both ends of the center part.

[0014] This invention is based on the understanding that hollow shafts have a significant advantage in torsional stiffness compared to solid shafts. The following example from the website https: / / technikdoku.com / torsion / (accessed July 24, 2023 at 3:00 PM CEST) illustrates this: a comparison of solid and hollow shafts. The solid shaft has a diameter Dm = 40 mm (cross-sectional area A1 = 1256 mm²). 2 The hollow shaft has an outer diameter Dm = 70 mm and an inner diameter dm = 57 mm (cross-sectional area A2 = 1297 mm). 2 Therefore, the cross-sectional areas of the two shafts are basically the same (difference of only 3%). Each shaft is subjected to a torsional moment M_t = 700 Nm. Although the cross-sectional areas of the shafts are not significantly different, the torsional stress τ_t occurring in the shafts is quite different: for a solid shaft, the formula τt = (16 M_t) / (π Dm) is used. 3 Calculations show that the torsional stress τt = 56 N / mm². 2 In the case of a hollow shaft, the formula τt = (16D M_t) / (π(Dm)) is used. 4 -dm 4 The calculated torsional stress τt = 19 N / mm² 2Therefore, this example illustrates that, for the same weight, a hollow shaft can transmit a much greater torsional moment (torque) than a solid shaft. Or, in other words: a hollow shaft capable of withstanding the same torsional moment as a solid shaft has a smaller outer diameter.

[0015] In this invention, the recognition that hollow shafts have a significant advantage over solid shafts in terms of torsional stiffness is utilized to advance in a completely new direction regarding rotating shafts, differing from previous strategies. Until now, rotating shafts designed as solid shafts have the largest possible diameter to achieve sufficiently high torsional stiffness; attempts have been made to compensate as well as possible for air passage blockage caused by the large rotating shaft through through-holes in the shaft. According to this invention, rotating shafts designed as hollow shafts are now used, and the outer diameter of the rotating shaft is as small as possible. Therefore, hollow shaft rotating shafts can block only a much smaller area of ​​air passage than conventional solid shaft rotating shafts; additionally, the smaller outer diameter allows for lateral flow of the rotating shaft, i.e., airflow can pass through the control device almost unimpeded.

[0016] By reducing the diameter of the rotating shaft, primarily by saving structural space in the middle section of the rotating shaft, the switching device can be constructed to be smaller, or a larger heat sink for electronic components can be used within the same structural space.

[0017] Furthermore, planar flow resistance, which is absent in the form of blind holes in conventional rotating shafts, is avoided. Therefore, cooling air can flow unimpeded through the rotating shaft according to the invention from the outside, because the smaller outer diameter of the rotating shaft, combined with its position in the switching device, results in a significantly smaller negative impact of the rotating shaft on the cooling performance of the cooling channels.

[0018] To couple the front knob to the rear assembly base, large-diameter rotating shafts designed as solid shafts with ventilation channels and blind hole-shaped material cutouts have been used to date. Due to the central location of the switchgear, ventilation of the switchgear is limited by these previous rotating shafts. This invention replaces the existing rotating shaft with a tubular rotating shaft. This satisfies the manufacturing requirement for thin and uniform wall thickness and, additionally, significantly reduces the outer diameter. Despite the effective reduction in outer diameter, the mechanical stress caused by torsion of the rotating shaft remains sufficiently small because it is designed as a hollow shaft.

[0019] Because of the smaller diameter of the rotating shaft, material cutouts are no longer required. This results in a uniform, smooth, circular surface that does not, in flow technology, create a surface that relatively resists airflow. The reduced outer diameter also means that the rotating shaft no longer plays a significant role in terms of flow resistance within the air passage.

[0020] The present invention also provides advantageous design solutions and extensions.

[0021] According to a preferred design of the invention, the ratio D / d is between 1.8 and 2.2. Therefore, the rotating shaft is only in the airflow at half of the air passage; thus, very good lateral circulation of the rotating shaft can be achieved technically.

[0022] According to a preferred design of the invention, the air channel is defined on one hand by a first circuit board arranged parallel to the first of the two sidewalls in the housing, on which electronic components and a heat sink are arranged, and on the other hand by a second plate arranged parallel to the second of the two sidewalls, wherein the net width D of the air channel is defined by the distance between the first and second circuit boards. For larger currents, heat sinks are used, typically made of aluminum; they are thermally connected to the electronic components. With the rotating shaft of the invention having a reduced outer diameter, there is no substantial structural flow resistance in the effective line of "inlet (fan) => heated electronic components (e.g., semiconductors) => heat sink => outlet".

[0023] Heat loss from electronic components must be dissipated to prevent overheating and damage. Adequate heat dissipation from electronic components becomes crucial, especially given their compact size and the increased current they carry, such as during motor starting. Power semiconductors installed in switching equipment are the largest heat sources. Temperature variations occurring during continuous operation or motor start-up are decisive for further design of electronic and mechanical components and for classification based on operating conditions (rated current, starting current, permissible ambient temperature, etc.).

[0024] The switching device according to the invention has at least one electronic component. In electrical engineering and electronics, a component, or simply electronic component, is understood as the smallest indivisible unit in a circuit (DIN 40150:1979-10 rule for functional and structural units), such as a resistor. Electronic components can be passive electronic components, such as resistors, coils, or capacitors. Electronic components can also be active electronic components, such as transistors (IGBTs, FETs, MOSFETs, etc.), diodes, rectifiers, processors / ICs (integrated circuits), and LEDs. Electronic components can also be components of power electronic devices. Electronic components can be, for example, two-terminal triac switches (DIACs), three-terminal triac switches (Triacs), transistors, MOSFETs, IGBTs, thyristors, diodes, capacitors, etc., in power electronic devices, as well as components in control electronic devices, such as controllers, voltage regulators, resistors, coils, etc. Electronic components can particularly be power semiconductors or power semiconductor modules.

[0025] According to a preferred embodiment of the present invention, the second plate is an insulating plate that electrically insulates the first circuit board from the second circuit board disposed between the second plate and the second sidewall.

[0026] According to a preferred design of the present invention, the wall thickness of the rotating shaft formed as a hollow shaft is in the range of 0.5 to 5 mm, more preferably in the range of 1 to 4 mm, and even more preferably in the range of 2 to 3 mm.

[0027] According to a preferred design of the invention, the rotating shaft is composed of two or more independent components in the axial direction. The rotating shaft is divided into two or more independent components, which are preferably made of plastic. Different variations of the rotating shaft with different lengths can be manufactured with relatively low overhead using interchangeable inserts in manufacturing tools (e.g., injection molding molds). Therefore, the desire for variability in the length of the rotating shaft can be met.

[0028] According to a preferred design of the invention, the rotating shaft consists of two or more independent components that are interlocked with each other.

[0029] According to a preferred design of the invention, the rotating shaft consists of a metal central member and two plastic end members. The rotating shaft is divided into three or more independent components, with the two end members made of plastic and the central member made of steel. Variable length can be controlled by varying the length of the central member. This metal central member absorbs most of the torsional stress.

[0030] According to a preferred embodiment of the invention, the center member is a round steel bar with toothed ends. The center member can be made of round steel bar with toothed ends so that it can be firmly pressed onto the end member and prevent rotation.

[0031] According to a preferred design of the invention, the center member is designed as a square rod loosely inserted into the end member.

[0032] According to a preferred design of the present invention, during the injection molding process, a metal part is inserted into an injection mold and injection molded, thus forming a metal-plastic hybrid part. Attached Figure Description

[0033] The invention will now be explained with reference to the accompanying drawings. The drawings are schematic, not to scale:

[0034] Figure 1 The first step for assembling a conventional motor starter on an assembly base is shown;

[0035] Figure 2 The second step for assembling a conventional motor starter on an assembly base is shown;

[0036] Figure 3A cross-section of a conventional motor starter assembled on an assembly base is shown;

[0037] Figure 4 The steps for removing a conventional motor starter from the assembly base are shown;

[0038] Figure 5 A conventional rotating shaft is shown;

[0039] Figure 6 A cross-section of a conventional motor starter parallel to the sidewall is shown;

[0040] Figure 7 The cross sections AA and BB of a conventional motor starter parallel to the front wall are shown;

[0041] Figure 8 A cross-section of a conventional switchgear parallel to the front wall is shown;

[0042] Figure 9 A first cross-section of the switching device according to the invention, parallel to the front wall, is shown;

[0043] Figure 10 A second cross-section of the switching device according to the invention, parallel to the front wall, is shown;

[0044] Figure 11 Three views of the two-piece rotating shaft of the switching device according to the present invention are shown; and

[0045] Figure 12 Two views of a three-piece rotating shaft of a switching device according to the present invention are shown. Detailed Implementation

[0046] Figures 1 to 4 A conventional switching device, namely the SIMATIC ET 200SP motor starter, is shown, which is assembled on a corresponding fully wired mounting base, as described in the background section of the specification.

[0047] The switchgear 10 has a housing 2, which has a front wall 20, a rear wall 22 opposite to the front wall 20, a top wall 24, and a bottom wall 26 opposite to the top wall 24, as well as two opposing side walls 28L and 28R. An air passage 4 extending parallel to the side walls 28L and 28R is formed in the housing 2, having a net width D measured in a direction transverse to the side walls 28L and 28R. Here, the top wall 24 and the bottom wall 26 have vents 24.1 and 26.1, respectively.

[0048] The switching device 10 has a rotating shaft 6, which is rotatably mounted in the front wall 20, and its end extending beyond the housing 2 carries a rotating device 62 that is anti-torsionally connected to the rotating shaft 6. In this exemplary embodiment, the rotating device 62 is designed as a rotary knob, accessible from the outside of the front wall 20 to an operator wishing to assemble the motor starter 10 onto a corresponding mounting base. The rotating shaft 6 is also rotatably mounted in the rear wall 22, and its end extending beyond the housing 2 carries a coupling device 64 that is anti-torsionally connected to the rotating shaft 6. With the aid of the coupling device 64, the housing 2 of the switching device 10 can be secured to a corresponding receiving device BU, also referred to as a mounting base.

[0049] Figure 1 The first step of assembling the motor starter on the assembly base BU is shown. First, the rotation shaft 6 of the motor starter 10 is rotated to the assembly / disassembly position by means of the rotation knob 62 of the rotation shaft 6, as shown by arrow 40. Thereafter, as shown by arrow 42, the motor starter 10 is guided onto the assembly base BU.

[0050] Figure 2 The second step is shown, in which the rotating shaft 6 of the motor starter 10 is rotated to the READY position: in this position, the motor starter 10 is securely locked in the assembly base BU and all electrical contacts are connected.

[0051] Figure 3 It shows Figure 2 Section III-III, parallel to the sidewalls 28L and 28R, is shown in the diagram. Inside the housing 10, a rotating shaft 6 can be seen; this shaft is used to lock the motor starter 10 into the assembly base BU.

[0052] Figure 4 The disassembly steps are illustrated, in which the motor starter 10 is removed from the assembly base BU again, as indicated by arrow 44. To do this, the rotating shaft 6 of the motor starter 10 is rotated back to the assembly / disassembly position, thereby pushing the motor starter 10 out of the assembly base BU, and then pulling the motor starter 10 out of the assembly base BU. When the rotating shaft rotates, a torque, sometimes up to 2 Nm, can be applied to the rotating shaft by operating the rotary knob, resulting in mechanical stress in the rotating shaft.

[0053] Figure 5A conventional rotating shaft 6 is shown. The rotating shaft 6 has a first end section 6F, which is rotatably mounted in the front wall 20 of the motor starter 10. The rotating shaft 6 has a second end section 6R, which is rotatably mounted in the rear wall 22 of the motor starter 10. Here, the rotating shaft 6 may carry a rotating device 62 at the end of its first end section 6F. This rotating device 62 is torsionally connected to the rotating shaft 6 and is accessible to the operator of the switching device 10 from the outside of the front wall 20. The rotating device 62 may be designed as a rotary knob.

[0054] Furthermore, the rotating shaft 6 can carry a coupling device 64, which is torsionally connected to the rotating shaft 6, at the end of its second end section 6R. With the aid of this coupling device 64, the switching device 10 can be fastened to the corresponding receiving device BU. Here, the coupling device 64 can be designed as a stop nose, which can engage with the corresponding groove in the assembly base in a bayonet-like manner.

[0055] The rotating shaft 6 has an intermediate section 6M located between the first end section 6F and the second end section 6R, the intermediate section 6M having an outer diameter d. When the rotating shaft 6 is assembled in the housing 2 of the switching device 10, the intermediate section 6M is located in the air passage 4 of the switching device 10.

[0056] During operation of the rotating device 62, such as rotating a knob, torques as high as 2 Nm can sometimes occur, resulting in mechanical stress in the rotating shaft 6. The rotating shaft 6 must be designed to not be damaged during operation.

[0057] Due to the relatively large distance (>10cm) between the front and rear walls of the basic unit, the axis of rotation is twisted. This twist should be kept as small as possible to ensure functional safety.

[0058] The rotating shaft must not be conductive and must have functional surfaces / functional profiles at its ends (a bayonet-type closure stop nose on the shaft that engages in a corresponding slot in the assembly base; a driven pin; a connector, etc.). Therefore, plastic is a suitable material.

[0059] Due to structural reasons, conventional rotary shafts exhibit the following characteristics: to ensure strength and torsional stiffness, they have the largest possible diameter due to their length (>10cm). However, the relatively large diameter of the rotary shaft clogs the cooling channels and prevents cooling air from flowing properly through the housing.

[0060] To improve the flow of cooling air through the housing, the rotating shaft has through openings 66. However, these through openings 66 reduce the torsional stiffness of the rotating shaft because they significantly weaken the ideal cylindrical profile. This weakening is compensated for by further increasing the diameter of the rotating shaft 6, thereby greatly limiting the space available for cooling airflow through the air passages, see [reference needed]. Figure 7 .

[0061] In addition to the through opening 66, the conventional rotary shaft 6 also has blind holes 68: these grooves are used to reduce material thickness. This aims to maintain the shortest possible cycle time during the plastic injection molding of the rotary shaft 6. The through opening 66 can only be implemented alternately with the blind holes 68, which in turn severely restricts airflow through the air channels.

[0062] In addition to the vertical view (left) of rotation axis 6, Figure 5 An oblique view (right) of the rotation axis 6 is also shown, as well as two sections of the rotation axis 6 transverse to its longitudinal axis: section AA and section BB, the positions of which are indicated in the vertical view of the rotation axis 6.

[0063] Figure 6 and Figure 7 A cross-section of a conventional motor starter is shown. Figure 6 The cross-section shown extends parallel to the sidewall. Figure 7 The cross-section shown extends parallel to the front wall. Here, the air passage 4 is defined on one hand by a first circuit board 8, which is arranged in the housing parallel to the first sidewall 28L of the two sidewalls 28L and 28R, and on the first circuit board 8 are arranged electronic components 16, such as power semiconductors, and cooling bodies 18 arranged on the electronic components 16. On the other hand, the air passage 4 is defined by a second plate 12, which is arranged parallel to the second sidewall 28R of the two sidewalls 28L and 28R. Here, the second plate 12 is an insulating plate that electrically insulates the first circuit board 8 from the second circuit board 14 arranged between the second plate 12 and the second sidewall 28R. Here, the net width D of the air passage is defined by the distance between the first circuit board 8 and the second plate 12.

[0064] When using a thyristor, heat dissipation from the thyristor via the first circuit board (circuit board cooling) is sufficient to achieve a certain starting current (e.g., 50 A for 6 seconds). For example, heat generation during continuous current is limited by bypassing a low-resistance relay. Therefore, an additional cooling element can be omitted. Thus, sufficient space is provided inside the housing for a rotating shaft with a large diameter and a large through-hole 66, see [reference needed]. Figure 6 .

[0065] Therefore, sufficient space is provided inside the housing for the rotating shaft with a large diameter and a large through opening 66, because no further large-volume heat sink is required. See [reference needed] Figure 6 .

[0066] Therefore, in an attempt to obtain the largest possible diameter d of the rotating shaft 6, the rotating shaft 6 is equipped with the largest possible through opening 66. This means that the rotating shaft is completely within the airflow A, but the airflow can only reach the opposite side of the rotating shaft through the through opening 66. Due to manufacturing reasons, the through opening 66 alternates with blind holes 68, resulting in completely different flow characteristics, such as... Figure 7 The cross-section is shown. Figure 7 The left side shows the basis Figure 5 The cross-section in plane AA of the axis of rotation is shown on the right side according to Figure 5 The cross-section is shown in plane BB of the axis of rotation. The left cross-section shows the rotational position of the axis of rotation 6, in which a relatively small amount of airflow can pass through the axis of rotation 6. The right cross-section shows the rotational position of the axis of rotation 6, in which the airflow through the axis of rotation 6 is completely blocked.

[0067] The large rotating shaft further limits the available structural space. The possibility of using a heat sink is greatly restricted.

[0068] In the case of low flow rate with low heat release, heat removal by free convection is sufficient; in the case of higher flow rate with increased heat release, a fan 30 that causes forced convection is additionally used.

[0069] Figure 8 A cross-section of a conventional switching device 10, parallel to the front wall of the housing of the motor starter 10, is shown. Here, the net width D of the air passage is defined by the distance between the first circuit board 8 and the second board 12. A rotating shaft 6, formed as a solid shaft and having an outer diameter d, extends in the middle of the air passage 4. The ratio D / d is approximately 1.3. The rotating shaft 6 has one or more through openings 66 through which a portion of the airflow A entering through the vent 26.1 in the bottom wall, driven by the fan 30, can flow under the influence of the airflow A. Another portion of the airflow A passes between the outside of the rotating shaft 6 and the walls 8, 12 defining the air passage 4. In general, a relatively large portion of the airflow A is blocked by the rotating shaft 6.

[0070] Figure 9 A first cross-section of the switching device 10 according to the invention, parallel to the front wall of the housing of the motor starter 10, is shown. Here, the net width D of the air passage 4 is defined by the distance between the first circuit board 8 and the second plate 12. Extending in the middle of the air passage 4 is a rotating shaft 6 formed as a hollow shaft with an outer diameter d, the outer diameter d being substantially smaller than... Figure 8The outer diameter d of the conventional rotating shaft is shown. The ratio D / d is approximately 2. A large portion, approximately 50%, of the airflow A entering the air passage 4 through the vent 26.1 on the bottom wall driven by the fan 30 can pass between the outside of the rotating shaft 6 and the walls 8, 12 defining the air passage 4. In general, a relatively small portion of the airflow A is blocked by the rotating shaft 6.

[0071] Figure 10 A second cross-section of the switching device 10 according to the invention, parallel to the front wall, is shown. The switching device 10 has a housing 2, which has a top wall 24 and a bottom wall 26 opposite to the top wall 24, and two opposing side walls 28L, 28R. Here, the top wall 24 and the bottom wall 26 respectively have vents 24.1, 26.1, through which airflow A generated by the fan 30 can enter or exit. An air passage 4 extending parallel to the side walls 28L, 28R is formed in the housing 2, having a net width D measured transversely to the side walls 28L, 28R.

[0072] The air passage 4 is defined on one side by a first circuit board 8, which is arranged in the housing parallel to the first sidewall 28L of the two sidewalls 28L and 28R, on which electronic components 16 and a cooling element 18 are arranged. On the other side, it is defined by a second plate 12, which is arranged parallel to the second sidewall 28R of the two sidewalls 28L and 28R. The net width D of the air passage 4 is defined by the distance between the first circuit board 8 and the second plate 12. The second plate 12 is an insulating plate that electrically insulates the first circuit board from the second circuit board arranged between the second plate and the second sidewall.

[0073] The switchgear 10 has a rotating shaft 6 rotatably mounted in the front wall 20. In addition, the rotating shaft 6 can also be rotatably mounted in the rear wall 22.

[0074] Figure 11 Three views of a two-piece rotating shaft 6 of the switching device according to the present invention are shown. The rotating shaft 6 is divided into two independent parts 6.1 and 6.2, which are designed as hollow shafts and made of plastic. Different variations with different lengths can be achieved with relatively low overhead by means of interchangeable inserts in the injection molding mold. Therefore, the expectation of length variability can be met.

[0075] Figure 12 Two views of a three-piece rotating shaft 6 of the switching device according to the present invention are shown. The rotating shaft 6 is divided into three independent parts 6.1, 6.2, and 6.3: the two end parts 6.1 and 6.3 are made of plastic, and the middle intermediate part 6.2 is made of a plastic-metal hybrid (=composite material=composite). Here, the intermediate part is also referred to as the center part. Here, the metal intermediate part is provided to the injection molding machine as an insert during the injection molding process.

[0076] In another implementation, the intermediate member 6.2 is made of steel. The intermediate member 6.2 can be made of, for example, round steel with toothed ends, so that it is firmly pressed against the end members in a torsion-resistant manner. Alternatively, the intermediate member 6.2 can be designed as a square steel pin, loosely inserted into the end members 6.1, 6.3. Length variability can be controlled by varying the length of the intermediate member 6.2.

[0077] The intermediate component 6.2 may have a metal pin 6.4, which is encased in a plastic sheath.

Claims

1. A switch device (10) having - a housing (2), the housing (2) having a front wall (20), a rear wall (22) opposite to the front wall, a top wall (24) and a bottom wall (26) opposite to the top wall (24), and two opposite side walls (28L, 28R), wherein an air channel (4) extending parallel to the side walls (28L, 28R) is formed in the housing (2), the air channel (4) having a clear width D measured in a direction transverse to the side walls (28L, 28R), - a rotational axis (6), which extends from the front wall (20) through the housing to the rear wall (22) and is rotatably mounted in the front wall (20) with a first end section (6F) and in the rear wall (22) with a second end section (6R), wherein the rotational axis (6) carries a rotation device (62) at the end of its first end section (6F), the rotation device (62) being connected to the rotational axis (6) in a rotationally fixed manner and being accessible from the outside of the front wall (20), and wherein the rotational axis (6) carries a coupling device (64) at the end of its second end section (6R), the coupling device (64) being connected to the rotational axis (6) in a rotationally fixed manner, by means of which the switching device can be fastened to a corresponding receiving device (BU), - wherein the bottom wall (26) and the top wall (24) each have at least one ventilation opening (26.1, 24.1), so that the airflow (A) can flow from the ventilation opening (26.1) of the bottom wall (26) to the ventilation opening (24.1) of the top wall (24) in the air channel (4), - wherein the rotating shaft (6) has a middle section (6M) between the first end section (6F) and the second end section (6R), the middle section (6M) having an outer diameter d, the middle section (6M) being located in the air channel (4), and It is characterized in that The rotating shaft is designed as a hollow shaft and the ratio D / d is greater than 1.

5.

2. The switchgear (10) according to claim 1, wherein the ratio D / d is between 1.8 and 2.

2.

3. A switchgear according to any one of the preceding claims, wherein: The air channel is defined on one side by a first circuit board (8), which is arranged in the housing in parallel to a first side wall (28L) of the two side walls (28L, 28R), on which electronic components (16) and a heat sink (18) are arranged, and on the other side by a second board (12), which is arranged in parallel to a second side wall (28R) of the two side walls (28L, 28R), wherein a net width D of the air channel (4) is defined by a distance between the first circuit board (8) and the second board (12).

4. The switchgear according to claim 3, wherein: The second plate (12) is an insulating plate which electrically insulates the first circuit board from a second circuit board arranged between the second plate and the second side wall.

5. The switchgear according to any one of the preceding claims, wherein: The wall thickness (Δ) of the rotating shaft is in the value range of 2 to 3 mm.

6. A switchgear according to any one of the preceding claims, wherein: The rotating shaft (6) is composed of two or more independent parts (6.1, 6.2, 6.3) in the axial direction.

7. A switchgear according to any one of the preceding claims, wherein: The rotating shaft is composed of two or more independent parts (6.1, 6.2, 6.3), and the independent parts are locked together.

8. A switchgear according to any one of the preceding claims, wherein: The rotating shaft consists of a metal center piece (6.2) and two plastic end pieces (6.1, 6.3).

9. The switchgear according to claim 8, wherein: The center piece (6.2) is a round steel with toothed ends.

10. A method for producing a rotary shaft of a switchgear device (10) according to any one of the preceding claims, wherein: A metal center piece is provided to an injection molding machine as an insert piece during the injection molding process, and plastic end pieces are injection molded at both ends of the center piece, respectively.

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