Supporting frame for a radiation shield

Abstract

The invention relates to a supporting frame for holding a radiation shield (2, 110) for a high-temperature furnace (100), wherein the supporting frame (1) is designed to connect the radiation shield (2, 110) to a wall (3, 120) of the high-temperature furnace and to space the radiation shield (2, 110) from the wall (3, 120) at a normal distance (n), and the supporting frame (1) has at least one holding element (4) which is inclined in relation to a normal distance direction (N) at an angle (α) at least in sections between the radiation shield (2, 110) and wall (3, 120) and is designed to be rotatable and / or flexible at least in sections in such a way that a lateral expansion of the radiation shield (2, 110) brings about an increase in the angle (α) and therefore a reduction in the normal distance (n).

Description

[0001]Support frame for a radiation shield. The present invention relates to a support frame for a radiation shield for a high-temperature furnace, having the features of the preamble of claim 1. In the context of this application, a high-temperature furnace refers, in particular, to a metallic high-temperature furnace. A metallic high-temperature furnace comprises an outer furnace wall, which is usually designed as a steel shell ("vessel"). The steel shell is generally water-cooled. Furthermore, it comprises a process or charging chamber into which a charging material can be introduced. Heating devices for heating the charging material are located in the process chamber.In metallic high-temperature furnaces, the thermal insulation of a process chamber from the outer furnace wall is usually achieved by a so-called radiation shield. This shield is formed by radiant plates made of metal, in particular refractory metal, especially tungsten, molybdenum, or their alloys, arranged essentially parallel to one another and held apart by spacers. Furthermore, insulation for high-temperature furnaces based on graphite and ceramic, as well as hybrid solutions, are known. An assembly of a shield together with heating conductors is referred to as a heating insert (hot zone). The design of a heating insert in a high-temperature furnace is crucial for the temperature distribution, purity, and energy consumption of high-temperature processes. A typical design of a metallic high-temperature furnace can be found, for example, in EP0303420 (A1) and WO 2020 / 120147 (A1).A common design for metallic high-temperature furnaces consists of an essentially cylindrical furnace shell with a radiation shield formed along its circumference, known as a side shield. The end faces are closed by covers. These covers also have radiation shielding. This shielding is called the cover shield or, if the cover is designed as a door, also called the door shield. Typically, the support frame of the side shield is connected to the cylindrical part of the vessel wall, and the support frame of the cover shield is connected to the vessel lid. The same applies, analogously, to polygonal, for example, rectangular, heating inserts. In a discontinuously operated high-temperature furnace, the charge chamber must be loaded and unloaded after each process cycle.For this reason, the heating insert usually has one or two covers (doors) that are opened and closed before and after each kiln run. In horizontal kilns with a cylindrical or cuboid-shaped usable space, a cover shield is often attached to a pivoting door of the outer steel vessel. For loading and unloading, the door with the shielding cover is opened, giving the user free access to the charge chamber. When the door is closed, the shielding cover is positioned relative to the side shielding so that the charge chamber is effectively shielded against heat loss. The aim is to ensure that the gap between the cover and side shields is as small as possible during operation, but without direct contact, i.e. a collision between the respective shields, as this could cause damage or deformation to the shields.According to current construction, the lid shield is attached to a support frame by several steel bolts welded to the water-cooled door in a circular line, using threaded mounting bolts. The correct distance between the side shield and lid shield is adjusted evenly around the circumference to a specified gap when cold using the threaded bolts. This gap is determined by assuming or calculating the thermal expansion of the various components of the heating element when the furnace is heated to its maximum target temperature. The desired remaining gap during operation is a few millimeters (4 to 6 mm) to minimize collision between the components.A support frame for suspending (attaching) the lid shield to the boiler lid must fulfill various functions and requirements: - Supporting the weight of the shield - Positioning the shield - Adjusting the gap between the lid and side shields - Resistance to deformation at high temperatures and cyclic thermal stress - Cost-effective design. A particular challenge is the thermal expansion that occurs during the thermal cycles of the high-temperature furnace. The side shield, often fixed in the center of the boiler, expands lengthwise as the temperature increases, thus reducing the gap between the side shield and lid shield. The lid shield, attached to the boiler lid, expands in a similar (but much smaller) manner, further reducing the gap.Consequently, the gap is adjusted in the cold state so that it has the optimal size at a specific reference target temperature. During heating and cooling, and at temperatures deviating from the maximum target temperature, the gap is therefore larger or smaller than the optimum. The weaknesses of current designs are as follows: Deficit 1: As described, the gap size changes depending on the operating temperature. A gap that is too large leads to additional energy losses and thermal stress on support frame components. A large gap causes other disadvantages besides heat loss. In furnaces with a gas atmosphere and in furnaces with rapid gas cooling, a gap represents a gas leak with a correspondingly negative impact on temperature and atmosphere uniformity as well as cooling performance. Deficit 2: Today's suspension devices and support frame modules are designed to be massive and rigid.The damage caused by contact with sensitive and brittle components such as molybdenum shielding plates and bolts is correspondingly severe. A closed gap (i.e. contact between the cover and side shielding) must therefore be avoided at all costs to prevent damage to the shielding. Deficiency 3: Nowadays, the support frame of the cover shielding is usually attached to the boiler cover by bolts that are rigidly and permanently connected to the boiler cover, usually welded. When the temperature rises, the cover shielding expands significantly, while the boiler door itself remains cool due to the water cooling. Accordingly, bending stresses arise in the suspension bolts, which can lead to deformation and, over time, to the fracture of the bolts in brittle materials. In addition, due to its rigid fixation by bolts, the cover shielding is subjected to considerable forces during heating and cooling.Deficiency 4: To prevent undesirable deformations and the resulting lack of functionality of the cover shield due to the stress described in Deficiency 3 over the course of its service life, the support frame is designed to be very rigid and expensive. In addition to the high manufacturing costs, the material-intensive construction leads to high energy requirements and thermal inertia due to the heating of the correspondingly high masses. The object of the present invention is to eliminate or at least mitigate the previously described deficiencies. This object is achieved by a support frame for holding a cover shield with the features of claim 1. Preferred developments are defined in the dependent claims.According to the invention, the support frame is designed to connect a cover shield to a boiler cover of a high-temperature furnace and to space the cover shield from the boiler cover at a standard distance, and the support frame has at least one holding element which is inclined at an angle at least in sections with respect to a standard spacing direction between the cover shield and the boiler cover and is designed to be rotatable and / or flexible at least in sections such that a lateral expansion of the cover shield causes an increase in the angle and thus a reduction in the standard distance, it is achieved that a change in a gap dimension between the cover shield and an expanding side shield is at least partially compensated.The inventive design of the support frame ensures forced guidance of the cover shield such that it is brought closer to the boiler cover upon expansion. This allows, for example, a gap between the cover shield and an adjacent side shield in an assembly to be narrower in a cold state than with a conventional connection of a cover shield to the boiler cover via rigid bolts. The invention makes it possible, for example, and preferably, to keep the gap between the cover shield and an adjacent side shield constant over wide temperature ranges. The deficiencies described above are eliminated by the invention. The gap between the cover and side shield remains virtually constant despite changing temperatures.This is achieved by the cover shield being displaced towards the vessel cover by the support frame according to the invention as the temperature rises. This displacement preferably corresponds to the thermal displacement of the front edge of the side shield, where the gap exists relative to the cover shield, towards the cover shield. During the cooling process, the cover moves accordingly towards the side shield, while the front edge of the side shield moves in the same direction and keeps the gap constant. In addition to the constant gap width during heating and cooling, the gap size is always the same and optimally adjusted at different holding temperatures. A high-temperature furnace equipped in this way is therefore not only optimally designed for a single operating temperature.Eliminating the problem of changing gap sizes leads to reduced energy losses, the best possible temperature and atmosphere uniformity, and high process stability under a wide range of operating conditions. The cover shield is attached to the boiler cover or boiler door using flexible and / or pivoting retaining elements, which significantly reduces mechanical stress compared to rigid bolts. This prevents wear and breakage of the retaining elements and ensures consistently consistent functionality over time. This is achieved by defined lengths and angles between the components, in particular by slanting the suspension elements relative to the boiler door and door shield. By preferably flexible suspension of the cover shield using elastically deflectable retaining elements, the support frame can be designed to be less rigid and less complex without causing undesirable deformation.The new, simplified design can be manufactured cost-effectively, and the mass savings lead to a reduction in energy consumption during heating and allow faster temperature changes. In operation of a high-temperature furnace, the invention results in the following advantages over the prior art: • Increased energy efficiency • Avoidance of leakage flows • Avoidance of damage • Lightweight design of the support frame The invention can be applied both to new designs of high-temperature furnaces and to the replacement of a heating insert in an existing high-temperature furnace. The invention is by no means limited to all-metallic heating inserts. The invention is equally suitable for graphitic heating inserts or for hybrid solutions with a combination of metallic shields and graphitic and / or ceramic insulation layers.When replacing an existing cover shield with a solution according to the invention, the geometries of the holding elements can be adapted to the specified conditions or additional fastening adapters can be used. The holding elements of the cover shield on the boiler cover are usually made of steel. They can also be made of another temperature-resistant material. If designed as flexibly deflectable holding elements, the holding elements must be sufficiently elastically deflectable to absorb the displacements without plastic deformation. However, the holding elements must be dimensioned such that the dead weight of the door shield can be supported safely and precisely. The expert can meet these requirements in the design by selecting a suitable material, dimensions, material thicknesses and number of holding elements.Further advantages of the invention include: Increased energy efficiency The inventive design allows gaps in shields to be dimensioned more tightly, which leads to an increase in energy efficiency. The increased efficiency results from improved shielding due to lower radiation losses through gaps. This increased efficiency reduces operating costs through energy savings. In addition, a reduction in acquisition costs can be expected, since the power supply can be dimensioned smaller due to the lower power requirement. Avoidance of leakage flows The gas flow in the heating insert is more controlled thanks to the narrower gaps, and leakage flows through gaps are reduced. Due to the reduced losses, the cooling gas is better directed to the charge, which leads to an increase in cooling efficiency.Avoiding damage If the gap between the door and side shields is set too small or the heating insert is operated at too high a temperature, this can lead to a collision between the door and side shields. Even here, the invention offers an advantage over a conventional design, as the support frame according to the invention is designed to be more flexible and thus damage can be kept to a minimum even in the event of an unwanted collision. The geometry and flexibility of the support frame according to the invention also avoid problematic bending stresses in the suspension elements, which have previously often led to plastic deformation and even material fractures. Lightweight design of the support frame In the conventional solution, the expansion of the door shield (especially the support frame) leads to high bending stresses in the bolts and correspondingly high stresses in the door shield.To prevent damage and unwanted deformation in the door shield, the support frame is conventionally designed to be very rigid and solid. The suspension according to the invention, using at least partially rotatable and / or flexible holding elements, allows the support frame to be made significantly less complex and lighter. This results in cost advantages in manufacturing, permanently deformation-free operation, and advantages in the furnace process, as less mass needs to be heated and cooled. In a design comparison by the applicant, the elimination of tangential stiffeners and expensive welded joints resulted in cost savings of approximately 20% compared to the conventional design. Typical dimensions of furnace types for which the invention can be particularly advantageously used are 30 cm to 3 m in diameter for the cover shield. The furnace length is typically between 30 cm and 5 m.The invention can also be used in rectangular furnaces. Of course, the invention can also be used for smaller furnaces, for example laboratory furnaces. The savings are correspondingly lower. Preferred developments of the invention are described in more detail below: The angle between the normal spacing direction and the at least partially inclined profile of the holding element is preferably between 5° and 85°. More preferably, the angle lies in a range between 10° and 80°. Even more preferably, the angle lies in a range between 15° and 75°. In particular, the angle lies in a range between 40° and 50°. The angle is defined between the holding element and the normal spacing direction, with zero degrees corresponding to an orientation parallel to the normal spacing direction.If a support element is not designed as a straight strut, but for example has a curved shape at least in sections, the angle formed between an imaginary straight connection of the attachment points on the cover shield and the boiler cover and the normal spacing direction can be used to determine the average inclination of a support element. If there are several support elements, it is not absolutely necessary for all to form the same angle to the normal spacing direction. However, in the interests of a modular design using identical parts, it is preferable for all support elements to form the same angle to the normal spacing direction. If the support elements are positioned too steeply (corresponding to a small angle), this may lead to undesirably high axial stiffness.If the holding elements are positioned too flat (corresponding to a large angle), overcompensation may occur, which corresponds to an undesirable gap enlargement. The angle must be adjusted to the length of the side shield. It is preferably provided that at least two holding elements are designed with an inclined profile, at least in sections. As a rule, there are considerably more, for example four to ten holding elements, depending on the size of the cover shield. Advantageously, the holding elements are evenly spaced along a circumference of the cover shield. It is preferably provided that holding elements which are arranged opposite one another with respect to a central axis running normal to the cover shield have a profile which is inclined in the opposite direction to the normal spacing.The "opposite" arrangement of the retaining elements means and is intended to ensure that the (tensile) forces induced in the retaining elements by the expansion of the cover shield, in particular the radial component of these forces, cancel each other out. This prevents any lateral displacement of the cover shield or any tilting of the same. The axial component of the forces induced in the retaining elements leads to the described effect that as the cover shield expands, it moves closer towards the boiler cover. "Opposite" does not necessarily mean that the retaining elements are mirror-symmetrical with respect to a central axis. Rather, the aim is for the radial components of the forces in the retaining elements (i.e. those perpendicular to the normal spacing direction) to cancel each other out. As the cover shield expands, it then performs a translational movement towards the boiler cover.It can be provided that the attachment points of a holding element on the cover shield and the boiler cover do not lie in the same plane containing the central axis. This configuration can be imagined as the cover shield and the boiler cover being rotated relative to one another about the central axis. When expanded, the cover shield then performs a translational movement towards the boiler cover and additionally a rotation around the central axis. Preferably, the attachment points of the holding elements arranged around a central axis are located radially further outwards on the side of the cover shield and run radially further inwards towards the boiler cover. It is preferably provided that the holding element or a plurality of holding elements is rotatably mounted relative to the cover shield and / or the boiler cover via a joint.The holding element can, for example, be designed as a strut which is connected to the lid shield and / or the boiler lid via simple hinges, such as pins, and is rotatably mounted. The joint allows the inclination of the holding elements to be changed when the lid shield expands. Alternatively or additionally, it can be provided that one or more holding elements are designed to be elastically deflectable. In this design, the inclination of the holding elements can be changed when the lid shield expands by elastic deflection of the holding elements. It can be provided that the support frame has a guide element that is movable along a direction of movement. In particular, the direction of movement of the guide element corresponds to the normal spacing direction. A guide element designed in this way can, if necessary, achieve improved guidance of the movement of the lid shield towards the lid.The guide element can, for example, be designed as a telescopic guide for movable cylinders. Interlocking profiles that can be moved relative to one another and form a type of telescopic rail are also conceivable. Protection is also sought for an arrangement comprising a cover shield for a high-temperature furnace with a support frame according to the invention, as well as for a high-temperature furnace with a support frame according to the invention. The invention is particularly directed at applications with process temperatures above 900°C. Since radiation losses increase exponentially with temperature, the advantages of the invention are particularly noticeable at high temperatures. The invention is particularly intended for metallic shields. Metallic shields consist of a substantially parallel arrangement of spaced-apart radiant plates. These are preferably made of refractory metal, in particular tungsten or molybdenum, and alloys thereof.High-temperature furnaces of this design are used primarily for heat treatments above 900°C. The invention is particularly intended for high-temperature furnaces designed for a target temperature of > 1,200°C, in particular > 1,500°C, up to target temperatures in the range of 2,500°C. Such high-temperature furnaces are used, for example, for sintering refractory metals, particularly molybdenum- or tungsten-based materials, for growing sapphire single crystals for LED production, for soldering, for heat treatment of turbine components, etc. By implementing the insulation in the form of metallic shields, particularly clean process conditions can be achieved. Depending on the design, operation under a protective gas atmosphere or vacuum is possible.Protection is sought for a support frame for holding a cover shield for a high-temperature furnace, wherein the support frame is designed to connect the cover shield to a cover of the high-temperature furnace and to space the cover shield from the cover at a standard distance, and the support frame has at least one holding element which runs at least partially inclined at an angle with respect to a standard spacing direction between the cover shield and the cover and is designed to be rotatable and / or flexible at least partially such that a lateral expansion of the cover shield causes an increase in the angle and thus a reduction in the standard distance. It is preferably provided that the angle between the standard spacing direction and the at least partially inclined course of the holding element is between 5° and 85°.It is preferably provided that at least two holding elements are designed with an inclined profile, at least in sections. It is preferably provided that holding elements which are arranged opposite one another with respect to a central axis running normal to the cover shield have a profile which is inclined in the opposite direction with respect to the normal spacing direction. It is preferably provided that at least one holding element is rotatably mounted relative to the cover shield and / or the cover via a joint. It is preferably provided that at least one holding element is designed to be elastically deflectable. It is preferably provided that the support frame has a guide element which is axially movable along the normal spacing direction. Protection is also sought for an arrangement comprising a cover for a high-temperature furnace with a support frame as described above, and for a high-temperature furnace with a support frame as described above.As already explained, radiation shielding for a high-temperature furnace typically includes a lid shield and a side shield. The above explanations for the support frame for holding a lid shield also apply, where applicable, to side shields.Analogous to the support frame for holding a cover shield, protection is sought for a support frame for holding a side shield, wherein the support frame is designed to connect the side shield to a wall of a high-temperature furnace and to space the side shield from the wall at a standard distance, and the support frame has at least one holding element which runs at an angle, at least in sections, relative to a standard spacing direction between the side shield and the wall and is designed to be rotatable and / or flexible, at least in sections, such that a lateral expansion of the side shield causes an increase in the angle and thus a reduction in the standard distance. By applying it to side shields, a gap between adjacent side shields can be designed to be smaller when cold and is not only closed by thermal expansion.Analogous to the application on cover shields, the thermal expansion of side shields in the circumferential direction (more precisely, the thermal expansion in the direction of a secant of the polygon spanned by the side shields) is translated here into a movement in the radial direction. This deflection in the radial direction ensures that the gap between the segments is kept approximately constant. Further advantages and usefulness of the invention will become apparent from the following description of exemplary embodiments with reference to the attached figures. The figures show: Fig. 1a and 1b: schematically a high-temperature furnace according to the prior art Fig. 2: an arrangement with a support frame according to the invention Fig. 3: a support frame according to the invention in a first exemplary embodiment Fig. 4: a further exemplary embodiment of the invention Fig. 5: a further exemplary embodiment of the invention Fig.6: another embodiment of the invention. Fig. 7: an example of a side shield. Fig. 8: an example of a side shield with compensation of the gap size due to thermal expansion. For basic orientation, Figures 1a and 1b schematically show a high-temperature furnace 100 according to the prior art, with Figure 1a showing a schematic longitudinal section and Figure 1b a schematic cross-section. This example shows a cylindrical furnace shape in a horizontal design. The high-temperature furnace 100 comprises a furnace shell 120, also called a vessel, which is generally designed as a steel shell and is usually water-cooled. The high-temperature furnace 100 can be closed at the end faces by covers 3. The high-temperature furnace 100 comprises a process chamber 140, which is insulated from the furnace shell 120 by a side shield 110. Cover shields 2 on the covers 3 insulate the process chamber 140.For illustrative purposes, the cover 3 of the right-hand end is shown spaced apart from the high-temperature furnace 100 in this illustration. The cover 3 can, for example, be designed as a pivoting door. The high-temperature furnace 100 is designed, in particular, as a metallic furnace. The shields 2, 110 are usually designed as packages of spaced-apart sheets. In particular, the shields are made of refractory metals, in particular molybdenum or tungsten or alloys thereof. As shown in Figure 1b, the side shield 110 is formed as a circular cylinder around the process chamber 140; however, the side shield can also consist of a polygonal line made up of several interconnected shielding modules. In the example shown, an approximately circular cross-section is realized. Alternatively, a rectangular cross-section could also be formed, for example, by shielding modules arranged perpendicular to one another.The shields 2, 110 shown in Figure 1a are suspended via bolts 130 welded to the cover 3 and the furnace shell 120, respectively. In this conventional design, the cover shield 2 is firmly screwed to bolts 130, which in turn are firmly welded to the cover 3 (here designed as a vessel door). Similarly, the side shield 110 is connected to the furnace shell 120 via bolts 130. The thermal expansion of the shields 2, 110 is blocked at least in sections by the rigid fastening and causes high bending stresses in the bolts 130. When the process chamber 140 heats up, the side shield 110 lengthens (represented by block arrow d1) as a result of the thermal expansion. The cover shield 2 expands predominantly in the lateral direction illustrated by block arrow d2.In addition to the thermal expansion along the shields 2, 110 in the direction of the respective planes, the bolts 130 supporting the shields 2, 110 also experience thermal expansion – to a lesser extent. In particular, the thermal expansion of the side shield 110 along the direction of block arrow d1 and (to a lesser extent) the thermal expansion of the bolts supporting the cover shield 2 result in a change in the gap dimension – s – between the cover shield 2 and the side shield 110. The gap dimension – s – is adjusted in a cold state so that it has the optimal size at a certain maximum target temperature. During heating and cooling, and at temperatures deviating from the maximum target temperature, the gap dimension – s – is therefore larger or smaller than the optimum. This results in the disadvantages discussed above.Figure 2 schematically shows a support frame 1 according to the invention for holding a cover shield 2, here in an assembly with a side shield 110 of a high-temperature furnace 100, shown in detail. The support frame 1 connects the cover shield 2 to the cover 3 and spaces it apart from the side shield 110 by a gap dimension - s -. The support frame 1 has at least one holding element 4, which extends between the cover 3 and the cover shield 2. There is a normal distance - n - between the side shield 110 and the cover shield 2 along a normal distance direction N. In the support frame 1 according to the invention, the holding element 4 has a course that is angled at an angle D with respect to the normal distance direction N, wherein the angle D is not equal to zero. The angle D is preferably in a range between 5° and 85°. More preferably, the angle D is in a range between 10° and 80°.Even more preferably, the angle D lies in a range between 15° and 75°. In particular, the angle D lies in a range between 40° and 50°. If, due to heating, thermal expansion of the side shield 110 occurs along the direction indicated by block arrow d1, then in a conventional design of a suspension of the cover shield 2 via a rigid bolt connection along the normal distance N, the gap dimension - s - would decrease, as already described for Figure 1a. However, since according to the invention the support frame 1 has a holding element 4 with an angled profile relative to the normal distance direction N and the holding element 4 is designed to be rotatable and / or flexible at least in sections, the occurring lateral thermal expansion of the cover shield 2 (along block arrow d2) can advantageously be used to compensate for the change in the gap dimension - s.To facilitate understanding of the displacements occurring, the fixed points F with respect to the cover 3 and the bolts 130 for the side shield 110 can be assumed as fixed points with respect to the x-axis shown here as an aid. The thermal expansion of the cover shield 2 causes a displacement v1 of the cover shield 2 in the (negative) x-direction due to the support frame 1 designed according to the invention. The extent of the displacement v1 of the cover shield 2 results from the lateral displacement v2 of the cover shield 2 as well as the dimensions of the holding elements 4 and the angle D according to the angular function. The change in the gap dimension – s – results from the displacement v1 of the cover shield 2 in the (negative) x-direction and the extent of the expansion of the side shield 110 along the expansion direction – d1 – of the side shield 110.The geometric relationships are chosen so that the gap dimension – s – remains as constant as possible for all operating temperatures and in the ideal order of magnitude of a few mm, particularly at very high furnace temperatures, in order to keep radiation losses low. The mode of operation is explained in more detail with reference to Figure 3. Figure 3 illustrates the kinematics of the support frame 1 according to the invention according to a first exemplary embodiment. The support frame 1 carries a cover shield 2 for a high-temperature furnace (high-temperature furnace not shown) via holding elements 4 and connects the cover shield 2 to a cover 3. The view according to Figure 3 shows two holding elements 4. Depending on the design and size, several holding elements 4 can also be provided. For example, in the case of a circular cover 3, at least three holding elements 4 can be formed.Two positions of the support frame 1 are shown: - with solid lines, the position at a temperature T1 - with dashed lines, the position at a temperature T2, with temperature T2 greater than temperature T1. For example, temperature T1 is room temperature and temperature T2 is the operating temperature of a high-temperature furnace. At temperature T1, the cover shield 2 is spaced from the cover 3 by a first normal distance n1. A holding element 4 forms a first angle D1 with respect to a normal distance direction - N - between the cover shield 2 and the cover 3. In other words, the holding element 4 does not run normal (perpendicular) to the cover shield 2 and the cover 3, as is the case with bolts known from the prior art, but has an inclined course, at least in sections. The normal distance direction - N - in this example is a normal to the cover shield 2 and the cover 3.If the shape of the cover shield 2 and / or cover 3 deviates from a flat shape, the direction of a local shortest connection can be assumed as the normal spacing direction N. In the present example, two holding elements 4 are shown, which are arranged opposite one another with respect to a central axis - S. In the present case and advantageously, the two holding elements 4 are arranged symmetrically to the central axis - S. The opposing holding elements 4 each assume a first angle D1 with the normal spacing direction - N - which, in this exemplary embodiment, has the same value, but the inclination of the holding elements 4 is opposite. When the temperature rises from temperature T1 to temperature T2, the lateral thermal expansion of the cover shield 2 (along block arrow d2) causes an increase in the deflection of the two holding elements 4 in this illustration.At temperature T2, the holding elements 4 each form a second angle D2 with respect to the normal spacing direction - N -, wherein the magnitude of the second angle D2 is greater than the magnitude of the first angle D1. The lateral extension of the cover shield 2 refers to the extension transverse to a plane normal of the cover shield 2. Since the holding elements 4 are designed to be rotatable and / or flexible at least in sections, the holding elements 4 allow a lateral expansion of the cover shield 2 and guide it - unlike rigid bolts - into a second position, shown in dashed lines as cover shield 2'. At temperature T2, the cover shield 2' is spaced from the cover 3 by a second normal distance n2, wherein the second normal distance n2 is smaller than the first normal distance n1.In the present exemplary embodiment, the holding elements 4 are movably connected to the shield 2 or the cover 3 via shield-side joints 5 and cover-side joints 6. The support frame 1 according to the invention ensures that, upon heating and the associated thermal expansion of the cover shield 2, the cover shield moves closer to the cover 3. A change in the gap dimension compared to a side shield (not shown here) expanding in the direction of the cover shield 2 can thereby be at least partially compensated. In other words, the support frame 1 comprising at least one holding element 4 inclined with respect to the normal spacing direction N is designed such that the forces induced by the thermal expansion of the cover shield 2 cause an increased deflection of the at least one holding element 4.Since – in this exemplary embodiment – ​​free movement of the holding element 4 is blocked by an opposite holding element 4 with the opposite inclination, the normal distance is reduced without the cover shield 2 being displaced relative to the central axis – S. As the temperature rises, the cover shield 2 therefore preferably undergoes a parallel displacement towards the cover 3. In the preferred case, the support frame 1 is designed such that the gap remains constant over a temperature range between room temperature and the operating temperature of a high-temperature furnace. For this purpose, a person skilled in the art can design the holding elements 4 with the aid of numerical simulation of the thermal expansion and tests. It is understood that the holding elements 4 are also subject to thermal expansion. However, this is small compared to the lateral expansion of the cover shield 2 and in no way negates the effect of the arrangement according to the invention.In an upright design of a high-temperature furnace, i.e., a horizontal arrangement of the cover shield 2, the holding elements 4 are equally subject to gravity. A design of the holding elements 4 is recommended in which the holding elements 4 are arranged evenly along a circumference relative to the central axis S. In a horizontal design of a high-temperature furnace, it can be advantageous to arrange the holding elements 4 relative to the central axis S in such a way that the influence of gravity does not lead to a lowering of the cover shield 2 relative to the central axis S. The lowering of the cover shield 2 can also be avoided by clever dimensioning of the holding elements 4. Figure 4 shows a further embodiment of the support frame 1. The reference numerals introduced for Figure 3 will not be described again.The illustration uses the explanations of the various positions of the holding elements 4 depending on the temperature from Figure 3. The design of the holding elements 4 has remained unchanged compared to Figure 3. In addition, however, a guide element 7 is provided which is axially displaceable in the direction of the central axis - S - and rigid transversely thereto. The central axis - S - is here and preferably parallel to the normal spacing direction N. The guide element 7 can, for example, be formed telescopically from an arrangement of a hollow cylinder with a cylinder displaceably mounted therein. In the present example, a cylinder is formed on the side of the cover 3, which cylinder extends into a hollow cylinder fixed on the side of the cover shield 2. In this exemplary embodiment, the guide element 7 prevents the cover shield 2 from moving away from the central axis - S -.In this way, only one inclined holding element 4 would be required to achieve the inventive effect of the support frame 1. In practice, several holding elements 4 along a circumference of the cover shield 2 are preferable solely because of the desired uniform introduction of force. Figure 5 shows a further exemplary embodiment of the invention. For the basic principle and the reference numerals, reference is made to Figure 3. Here, the deflection of the holding elements 4 upon expansion of the cover shield 2 is realized in that the holding elements 4 are designed to be flexible. The function of the pivot points is taken over by folds in the holding elements 4, which thereby have a spring effect. The holding elements 4 can, for example, be designed as folded sheet metal strips, which are fixed, for example, to the cover shield 2 and to the cover 3 via a rivet, screw, or welded connection.It goes without saying that the variants shown in the exemplary embodiments can be freely combined with one another. For example, flexible holding elements 4 can be combined with articulated holding elements 4 on a support frame 1. It is also conceivable to additionally equip flexible holding elements 4 with joints 6. Furthermore, one or more guide elements 7 can be provided. Figure 6 shows a further exemplary embodiment of the invention. Shown is a perspective view of a support frame 1 with a cover shield 2 and an adjacent side shield 110. The illustration corresponds to an arrangement for a cylindrical furnace type in the horizontal design shown here. Eight holding elements 4 are arranged at equal intervals along a circumference of the cover shield 2. With respect to the central axis - S - opposite holding elements 4 run in opposite directions.The holding elements 4 run at an angle from the cover shield 2 towards the cover (not shown) with respect to the central axis S. If there is a non-even number of holding elements 4, the holding elements 4 are naturally not mirror-symmetrical with respect to the central axis S. As already explained, opposing holding elements 4 have an opposite course. In the present example, the holding elements 4 run from further out on the cover shield 2 further inwards towards the cover (not shown). The ends of the holding elements 4 facing away from the cover shield 2 are designed for fixing to a cover (not shown). In this case, the holding elements 4 are designed to be flexible and as folded sheet metal strips. For stiffening and force transmission, a support frame 8 with (here eight) radially extending struts 9 is provided. The holding elements 4 engage radially on the outside of the struts 9 of the support frame.Another advantage of the design of the holding elements 4 as flexible sheet metal strips is that they can be deflected like leaf springs, but are rigid transverse to the intended direction of movement. This ensures rigid support of the cover shield 2. The design principle of the support frame 1 comprising a support frame 8 is generally suitable for the implementation of the invention. In an assembly, the cover shield 2 would be connected to a cover and the side shield 110 to a furnace shell. When the side shield 110 expands with a temperature increase, the gap dimension - s - between the side shield 110 and the cover shield 2 remains constant thanks to the support frame 1 according to the invention. The configurations of the present exemplary embodiment can be combined with the previously discussed variants and are by no means limited to this exemplary embodiment.Figure 7 shows an example of a side shield 110 constructed from individual shielding modules. The side shield 110 is connected to a furnace shell 120 (only indicated) via bolts 130. Figure 8 shows an application of the support frame previously described for cover shields to side shields 110 of a high-temperature furnace 100 in a cross-section normal to a longitudinal axis of the high-temperature furnace 100. In the present case, an arrangement of four flat side shields 110 is shown, which surround a process chamber 140 with a square cross-section. The side shields 110 are connected to a furnace shell 120 via a support frame 1. Instead of a direct connection to the furnace shell 120, a support structure could be provided, to which the support frame 1 is attached.As already described above, the support frame 1 comprises holding elements 4, which connect a side shield 110 to the furnace shell 120 and space the side shield 110 from the furnace shell 120 at a standard distance n. The holding elements 4 extend at an angle, at least in sections, relative to a respective standard spacing direction N, such that a lateral expansion of the side shields 110 causes an increase in the angle D and thus a reduction in the standard distance n. In the present arrangement, the support frame 1 designed in this way ensures that a gap between adjacent side shields 110 is kept essentially constant during thermal expansion of the side shields 110.In conventional rigid suspensions of side shields, e.g. via rigid bolts, a gap size is selected for the cold state so large that it is only closed by thermal expansion, provided that the side shields do not collide. Thanks to the support frame 1, a narrow gap can be selected even in the cold state. This reduces thermal losses. Two positions of the support frame 1 are shown: - with solid lines the position at a temperature T1 - with dashed lines the position at a temperature T2, with temperature T2 higher than temperature T1. For example, temperature T1 is room temperature and temperature T2 is an operating temperature of a high-temperature furnace. When heated, the side shields 110 (position at temperature T1) experience lateral expansion, represented by the side shields 110' at temperature T2.The expansion causes the holding elements 4 to deflect from a first angle D1 (at temperature T1) to a second angle D2 (temperature T2). As can be seen, the gap between adjacent side shields 110 remains constant due to the support frame 1 thus formed. Previous explanations for the support frame on the cover shield 2 also apply, where applicable, to the side shields 110.

Claims

Claims 1. A support frame for holding a radiation shield (2, 110) for a high-temperature furnace (100), wherein the support frame (1) is designed to connect the radiation shield (2, 110) to a wall (3, 120) of the high-temperature furnace and to space the radiation shield (2, 110) from the wall (3, 120) at a standard distance (n), and the support frame (1) has at least one holding element (4) which, with respect to a standard distance direction (N) between the radiation shield (2, 110) and the wall (3, 120), is inclined at least in sections at an angle (D) and is designed to be rotatable and / or flexible at least in sections, such that a lateral expansion of the radiation shield (2, 110) causes an increase in the angle (D) and thus a reduction in the standard distance (n). 2.Support frame (1) according to claim 1, wherein the angle (D) between the normal spacing direction (N) and the at least partially inclined course of the holding element (4) is between 5° and 85°.

3. Support frame (1) according to claim 1 or 2, wherein at least two holding elements (4) are designed with an at least partially inclined course.

4. Support frame (1) according to one of the preceding claims, wherein holding elements (4) which are arranged opposite one another with respect to a central axis (S) running normal to the radiation shield (2, 110) have a course which is inclined in the opposite direction with respect to the normal spacing direction (N).

5. Support frame (1) according to one of the preceding claims, wherein at least one holding element (4) is inclined relative to the radiation shield. (2, 110) and / or the wall (3, 120) via a joint (5, 6).

6. Support frame (1) according to one of the preceding claims, wherein at least one holding element (4) is designed to be elastically deflectable.

7. Support frame (1) according to one of the preceding claims, wherein the support frame (1) has a guide element (7) that is axially movable along the normal spacing direction (N).

8. Arrangement comprising a cover (3) for a high-temperature furnace (100) with a support frame (1) according to one of the preceding claims.

9. Arrangement comprising a side wall (120) for a high-temperature furnace (100) with a support frame (1) according to one of the preceding claims 1-7.

10. High-temperature furnace (100) with a support frame (1) according to one of the preceding claims 1-7.

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