Mounting a ceramic roller in a roller hearth furnace

Abstract

The invention relates to a sleeve (3) for mounting a ceramic roller (2) in a roller hearth furnace (1), the sleeve (3) having a receptacle (4) for one end (5) of the ceramic roller (2), the receptacle (4) being surrounded by a cylinder wall (6), the cylinder wall (6) having, in the axial direction, a waist portion (7) and a clamping portion (8) located therein. The wall thickness (d) of the cylinder wall (6) in the waist portion (7) is smaller than in the vicinity of the waist portion (7), and a cross-sectional area of the receptacle (4) in the clamping portion (8) is smaller than in the vicinity of the clamping portion (8). A ceramic roller (2) can be mounted particularly reliably in a roller hearth furnace by means of the sleeve (3), even at high temperature. To achieve this, during production the sleeve (3) is provided with a reduced cross-sectional area in the clamping portion (8). When the sleeve (3) is pressed axially onto the end (5) of a ceramic roller (2), the reduced cross-sectional area in the clamping portion (8) produces an elastic force, by means of which the sleeve (3) is held on the ceramic roller (2).

Description

[0001] The invention relates to a sleeve for storing a ceramic roller in a roller hearth furnace, and to a method for mounting such a sleeve on a ceramic roller.

[0002] It is known to heat components, especially those made of steel, in a roller hearth furnace. For this purpose, the components can be moved through the furnace by means of a multitude of rollers. These rollers are often made of ceramic to withstand the high temperatures in the roller hearth furnace.

[0003] Several methods exist for mounting the rollers of a roller hearth furnace. A common problem is the connection between the ceramic roller and a steel bearing element. Since steel has a significantly higher coefficient of thermal expansion than ceramic, the interference fit of a friction-fit connection is reduced at the high operating temperature of such a roller hearth furnace if the metal sleeve is mounted externally on the ceramic. Consequently, the preload is reduced, thus impairing the ability to transmit the drive torque.

[0004] Methods for storing rolls in roll hearth ovens are known, for example, from DE 690 08 091 T2, DE 20 2015 100 449 U1, DE 695 13 848 T2, US 4 247 000 A and US 4,330,268.

[0005] The object of the present invention is to provide, starting from the described prior art, a sleeve with which a ceramic roller can be mounted in a roller hearth furnace with sufficient force-fit even at high temperatures. Furthermore, a method for mounting such a sleeve onto a ceramic roller is to be presented.

[0006] These tasks are solved by the subject matter of the independent claims. Further advantageous embodiments are specified in the dependent claims. The features described in the claims and in the description can be combined with one another in any technologically meaningful way.

[0007] According to the invention, a sleeve according to claim 1 is presented.

[0008] The sleeve is designed and configured to hold a ceramic roller in a roller hearth furnace. The ceramic roller is preferably one of many ceramic rollers arranged in the roller hearth furnace and intended for transporting components through the furnace. Components, particularly those made of steel, can be thermally treated in the roller hearth furnace, for example, for press hardening. The roller hearth furnace is preferably designed for the thermal treatment of components, especially for motor vehicles.

[0009] The ceramic roller can be supported in the roller hearth furnace by means of two sleeves. Preferably, the ceramic roller is supported at both ends by a sleeve. These two sleeves are preferably identical. To support the ceramic roller, the ends of the roller are inserted into the respective receptacles of the sleeves. During operation, the sleeve is frictionally connected to the ceramic roller. The sleeve is preferably positively connected to a drive and bearing assembly, for example, via a hexagonal fit. The part of the drive and bearing assembly connected to the sleeve is rotatably held in the remaining part of the drive and bearing assembly. This remaining part is stationary. The sleeve thus acts as an adapter between the drive and bearing assembly on the one hand and the ceramic roller on the other.The sleeve provides the ceramic roller with a connection through which the ceramic roller can be connected to the drive and bearing unit.

[0010] To describe the sleeve, two axial sections of the outer wall are defined: the waist section and the clamping section. The clamping section lies within the waist section. This means that the clamping section neither projects beyond the waist section on one or both sides nor coincides with it. In addition to the waist section and the clamping section, the outer wall preferably has further axial sections. It is particularly preferred that the waist section is spaced apart from the end faces of the receptacle. The waist section and the clamping section are defined by the conditions described below. Furthermore, it is not necessary for the waist section and the clamping section to be identifiable as such.In particular, it is possible that different sections can be identified as waist sections and / or that different sections can be identified as clamp sections. It is sufficient that one section can be identified as a waist section and that one section can be identified as a clamp section – alternative possible classifications of the sections are irrelevant.

[0011] The waist section is defined by the fact that the wall thickness of the shell is smaller within this section than in the surrounding area. This means that the wall thickness of the shell is reduced in the waist section. While this is preferred, the wall thickness of the shell need not be constant in the waist section. Outside the waist section, it is also preferred, but not necessary, for the wall thickness of the shell to be constant. In both statements, the term "constant" refers to the fact that the wall thickness remains unchanged when viewed along the axial direction.

[0012] Since the waist section is defined axially, the "neighborhood of the waist section" refers to the sections of the shell wall that adjoin the waist section axially. The wall thickness of the shell wall does not need to be constant in these sections either. The wall thickness of the shell wall in the "neighborhood of the waist section" is defined as the wall thickness at the edges of the waist section. These edges are not considered part of the waist section.

[0013] When viewed circumferentially, the wall thickness is preferably constant, which applies particularly to the entire shell wall. If the wall thickness varies circumferentially, any axial section of the shell wall qualifies as a waist section, provided that, over at least a portion of the shell wall's circumference, the wall thickness in this section is smaller than in the surrounding area. Preferably, the condition is met over the entire circumference of the waist section that the wall thickness in the waist section is smaller than in the surrounding area. Since an axial section is being considered, the "surrounding area of ​​this section" is also defined axially. Therefore, only the area surrounding the section at the respective location in the circumferential direction is relevant.

[0014] In the waist section, the wall thickness of the shell is preferably in the range of 0.5 to 1.0 mm. In the vicinity of the waist section, the wall thickness of the shell is preferably in the range of 1 to 2 mm.

[0015] The clamping section is defined by the fact that the cross-sectional area of ​​the receptacle is smaller within it than in the surrounding area. The cross-sectional area of ​​the receptacle represents the area of ​​the two-dimensional extent of the receptacle when viewed perpendicular to its axis. The receptacle is the space enclosed by the shell wall. Therefore, the cross-sectional area of ​​the receptacle, viewed perpendicular to the axis of the shell wall, is the area bounded by the inner surface of the shell wall. The fact that the cross-sectional area of ​​the receptacle is smaller within the clamping section than in its surrounding area means that the cross-sectional area of ​​the receptacle is reduced within the clamping section. While this is preferred, the cross-sectional area of ​​the receptacle need not be constant within the clamping section. It is also preferred, but not necessary, for the cross-sectional area of ​​the receptacle to be constant outside the clamping section.In both statements, the term "constant" refers to the fact that the cross-sectional area remains unchanged when viewed along the axial direction.

[0016] Since the clamping section is defined axially, the "surroundings of the clamping section" refer to the sections of the casing wall that connect axially to the clamping section. The cross-sectional area of ​​the receptacle need not be constant in these sections either. The relevant cross-sectional area of ​​the receptacle in the "surroundings of the clamping section" is the cross-sectional area of ​​the receptacle at the edges of the clamping section. These edges are not considered part of the clamping section.

[0017] If the receptacle is cylindrical, its diameter in the clamping section is smaller than in the surrounding area. However, it is not necessary for the receptacle to be perfectly cylindrical. In fact, it is preferred that the receptacle be deformed relative to a cylindrical shape, at least in the clamping section. To emphasize this possibility, the term "diameter"—which, according to its mathematical definition, refers to a circular cross-section—is not used for such a deformed receptacle. Instead, the distance from the inner surface of the cylindrical wall to the axis of the cylindrical wall is considered. This distance corresponds to the radius of a cylindrical receptacle.The requirement that the cross-sectional area of ​​the clamping section is smaller than in the vicinity of the clamping section can be fulfilled in particular by the fact that the distance of the inside of the shell wall from the axis of the shell wall in the clamping section is smaller than in the vicinity of the clamping section.

[0018] When viewed circumferentially, the distance of the inner surface of the shell wall from its axis need not be constant. In this respect, the shell wall can deviate from a rotationally symmetrical shape. If the distance of the inner surface of the shell wall from its axis varies circumferentially, any axial section of the shell wall can be considered a clamping section, provided that the distance of the inner surface of the shell wall from its axis is smaller than in the vicinity of that section. The "mean" here refers to a plane perpendicular to the axis of the shell wall. Preferably, the clamping section must meet the condition over its entire circumference that the distance of the inner surface of the shell wall from its axis is smaller in the clamping section than in the vicinity of the clamping section. Since an axial section is being considered, the "nearby section" is also defined in the axial direction.Therefore, only the area surrounding the section at the respective point in the circumferential direction is relevant.

[0019] The distance between the inner surface of the casing wall and its axis is preferably in the range of 24 to 100 mm in the vicinity of the clamping section. Preferably, this distance is 0.15 to 1.00 mm smaller in the clamping section than in the surrounding area. Therefore, a comparatively very small deformation of the casing wall is sufficient.

[0020] The sleeve allows for particularly reliable mounting of a ceramic roller in a roller hearth furnace, even at high temperatures. The plastic deformation of the clamping section during sleeve manufacturing results in a reduced cross-sectional area. During sleeve assembly, this cross-sectional area is elastically expanded so that the minimum distance between the inner surface of the sleeve wall and the axis of the sleeve wall in the clamping section corresponds to the resulting cross-sectional area of ​​the ceramic roller. The resulting radial force between the ceramic roller and the sleeve is sufficient to transmit a drive torque to the ceramic roller via the sleeve. It is preferred that the radial force is not higher than the value that the ceramic roller must withstand.It has been found that the radial force, due to the described design of the sleeve, is sufficiently high for a force-fit connection between the sleeve and the ceramic roller, even at high temperatures and despite the reduced interference resulting from the different coefficients of thermal expansion of the sleeve and the ceramic roller. The elasticity of the clamping section is preferably designed such that no permanent, i.e., plastic, deformation of the clamping section occurs under any operating conditions.

[0021] The outer wall is preferably closed in the circumferential direction. This applies at least to an axial section, in particular at least to the waist section and / or the clamping section. It is especially preferred that the outer wall is completely closed. Openings at the end faces are not considered openings in the outer wall. In particular, the outer wall has no axial slots. Such a design could be provided to compensate for the different expansion of the ceramic roller and the sleeve by means of a spring effect achievable thereby. However, since the stiffness of the sleeve is very limited in this design, the required preload can only be maintained within a very limited range. Due to the design, particularly with the waist section and the clamping section, such slots are not necessary.Consequently, the slots can be omitted, thus increasing the stability of the sleeve and the connection to the ceramic roller. Furthermore, manufacturing is simplified because no slots need to be created, eliminating a production step.

[0022] In a preferred embodiment of the sleeve, the wall thickness of the sleeve wall in the waist section is 20 to 60% of the wall thickness of the sleeve wall in the vicinity of the waist section.

[0023] It has been shown that this achieves the described advantage of reduced wall thickness and that, on the other hand, the shell wall is sufficiently stable even in the waist section.

[0024] In another preferred embodiment of the sleeve, the cross-sectional area of ​​the receptacle in the clamping section is 0.03 to 0.3% smaller than in the vicinity of the clamping section.

[0025] It has been found that this allows the described advantage of a reduced cross-sectional area to be achieved on the one hand, and on the other hand, that the sleeve can be pressed onto the ceramic roller without damaging the ceramic roller.

[0026] In another preferred embodiment of the sleeve, the axial extent of the clamping section is at least 70% of the axial extent of the waist section.

[0027] In particular, it is preferred that the axial extent of the clamping section is between 70% and 90% of the axial extent of the waist section.

[0028] In another preferred embodiment of the sleeve, the waist section has an axial extent in the range of 40 to 80% of the axial extent of the receptacle.

[0029] It has been shown that this achieves the described advantage of reduced wall thickness on the one hand, and that on the other hand the shell wall is sufficiently stable.

[0030] The described special advantages and design features of the sleeve can be applied and transferred to a set, and vice versa. In the set, the sleeve is not pressed onto the ceramic roller. However, the sleeve is designed and configured to be pressed onto the ceramic roller. Preferably, the set comprises two sleeves. In this case, one of the sleeves can be pressed onto each end of the ceramic roller.

[0031] The cross-sectional area of ​​the receptacle is smaller within the clamping section than in the surrounding area, such that the cross-sectional area of ​​the receptacle is smaller than the cross-sectional area of ​​the end of the ceramic roller only within the clamping section. The cross-sectional area of ​​the end of the ceramic roller is the area covered by the outer surface of the ceramic roller when viewed perpendicular to its axis. The end of the ceramic roller is the portion of the roller that is held by the sleeve. If the cross-sectional area of ​​the ceramic roller at its end is not constant, an average is used. Outside the clamping section, the cross-sectional area of ​​the receptacle is therefore equal to or greater than the cross-sectional area of ​​the end of the ceramic roller. When the sleeve is pressed onto the ceramic roller, it is held against the roller, particularly via the clamping section.This is a clamp connection, which explains the designation clamping section.

[0032] As a further aspect of the invention, a method according to claim 6 is presented.

[0033] The described special advantages and design features of the sleeve are applicable and transferable to the process, and vice versa. The described sleeve is obtained by step a) of the process. After step a), the sleeve is designed as described. Step b) of the process is carried out accordingly with the described sleeve. Step b) is preferably carried out with a device for axially pressing the sleeve onto the end of the ceramic roll. The device preferably has a hydraulic drive to apply the force required for the axial pressing. The process is preferably carried out twice for each ceramic roll by pressing a respective sleeve onto each end of the ceramic roll.

[0034] In a preferred embodiment of the method, the cross-sectional area of ​​the receiving area in the clamping section is made smaller by step a) than the cross-sectional area of ​​the end of the ceramic roller.

[0035] The receptacle initially has a cross-sectional area that is greater than or equal to the cross-sectional area of ​​the end of the ceramic roller. Preferably, the cross-sectional area of ​​the receptacle is constant throughout its entire length. In particular, the cross-section of the receptacle is preferably circular throughout its entire length. The same applies to the end of the roller. The radial pressing in step a) reduces the cross-sectional area of ​​the receptacle in the clamping section, making it smaller than the cross-sectional area of ​​the end of the ceramic roller. Outside the clamping section, however, the cross-sectional area of ​​the receptacle remains greater than or equal to the cross-sectional area of ​​the end of the ceramic roller.

[0036] In a further preferred embodiment of the method, the sleeve is pressed in step a) with at least three press jaws, which each extend circumferentially over an angular range of 10 to 60° of the shell wall and / or which each extend axially over at least 80% of the waist section of the shell wall.

[0037] Preferably, exactly three pressing jaws are used. Each pressing jaw can exert a radially inward force on the shell wall. The pressing jaws are preferably shaped to fit the shell wall. The pressing jaws, preferably evenly distributed around the circumference of the shell wall, deform the shell wall, for example, starting from a cylindrical shape.

[0038] Preferably, in step a) the sleeve is pressed with at least three pressing jaws, which each extend circumferentially over an angular range of 10 to 60° of the shell wall and which each extend axially over at least 80% of the waist section of the shell wall.

[0039] The invention is explained in more detail below with reference to the figures. The figures show a particularly preferred embodiment, to which, however, the invention is not limited. They show: Fig. 1: a schematic sectional view of a roller hearth furnace with a ceramic roller mounted on two sleeves according to the invention, Fig. 2: a schematic enlargement of a part of Fig. 1 , Fig. 3: a sectional view of the sleeve made of Fig. 2 , Fig. 4: a side view of the sleeve made of Fig. 2 and 3 , Fig. 5: a cross-sectional view of the sleeve made of Figs. 2 to 4, Fig. 6: a cross-sectional view of part of a sleeve before radial pressing with a press jaw.

[0040] Fig. 1 Figure 1 shows a roller hearth furnace 1 with a plurality of ceramic rollers 2, one of which is visible. The ceramic roller 2 is connected at both ends 5 via a respective sleeve 3 according to the invention to a respective (only indicated) drive and bearing device 10 and is thus supported by the sleeves 3. The dashed line shows the part of Fig. 1 , who in Fig. 2 shown enlarged.

[0041] To Fig. 2It can be seen that the end of the ceramic roller 2 is inserted into a receptacle 4 of the sleeve 3. The receptacle 4 is surrounded by a shell wall 6. This is shown here in a simplified manner with constant inner and outer radii. A gap is shown between the ceramic roller 2 and the sleeve 3. This serves only to clarify the illustration. In reality, the ceramic roller is in contact with at least part of the shell wall 6. Fig. 2 The drive and bearing device 10 is indicated.

[0042] Fig. 3 shows a detailed and true-to-scale sectional view of sleeve 3 from Figs. 1 and 2 before assembly on the ceramic roller 2. This can be recognized by Fig. 3that the receptacle 4 is surrounded by a shell wall 6, the shell wall 6 having a waist section 7 and a clamping section 8 located therein in the axial direction. The wall thickness d of the shell wall 6 is smaller in the waist section 7 than in the vicinity of the waist section 7. The cross-sectional area of ​​the receptacle 4 is smaller in the clamping section 8 than in the vicinity of the clamping section 8. However, this deviation is too small to be shown in the representation of the Fig. 3 to be able to be recognized. The reduced cross-sectional area was achieved by step a) of the inventive method, according to which the sleeve 3 is radially pressed in the clamping section 8, whereby a radially inwardly directed force is applied to the shell wall 6 at at least three points on the shell wall 6.

[0043] The sleeve 3 will be mounted on the ceramic roller 2 in step b) of the inventive method in order to be placed in the roller hearth furnace 1. Figs. 1 and 2to be inserted. For this purpose, the sleeve 3 is pressed axially onto the end 5 of the ceramic roller 2 and thus connected to the ceramic roller 2 in a force-fit manner.

[0044] Also shown are an axial extension l T of the waist section 7 and an axial extension l K of the clamping section 8. In addition, an axial extension l A of the receptacle 4 is shown.

[0045] Furthermore, an internal hexagon socket 11 can be seen, via which the sleeve 3 can be positively connected to the drive and bearing device 10.

[0046] Fig. 4 shows a side view of the in the Fig. 2 and 3 shown sleeve 3. Fig. 5 shows a cross-sectional view of this sleeve 3.

[0047] Fig. 6 Figure 1 shows a cross-sectional view of part of a sleeve 3 before radial pressing according to step a). By radial pressing, the sleeve 3 shown can be formed from the sleeve 3 shown. Figs. 2 to 5The following are obtained: Before radial pressing, the shell wall 6 has a cylindrical shape. The radial pressing slightly deforms the shell wall 6. Ri,1 and Ri,2 are two distances of the inside of the shell wall 6 from the (outside the cutout of the) Fig. 6 The axis of the mantle wall 6 (lying) is denoted. Furthermore, Ra is the distance between the outer surface of the mantle wall 6 and the (outside the cutout of the) Fig. 6The axis of the sleeve wall 6 is denoted by the horizontal axis. In the situation shown before radial pressing, Ri,1 = Ri,2. The radial pressing can be carried out, among other things, with a pressing jaw 9. Preferably, the pressing is carried out with at least three pressing jaws, which are designed like the pressing jaw 9 shown and which are arranged evenly distributed around the circumference of the sleeve 3. Due to the arrangement of the pressing jaw 9, Ri,2 is more strongly affected by the radial pressing than Ri,1. The wall thickness remains unchanged during radial pressing. The sleeve 3 allows a ceramic roller 2 to be reliably mounted in a roller hearth furnace 1, even at high temperatures. This is possible by giving the sleeve 3 a reduced cross-sectional area in the clamping section 8 during manufacturing.When the sleeve 3 is pressed axially onto the end 5 of a ceramic roller 2, the reduced cross-sectional area in the clamping section 8 causes an elastic force by which the sleeve 3 is held on the ceramic roller 2. Reference symbol list

[0048] 1 Roller hearth oven 2 Ceramic roller 3 Sleeve 4 Mounting 5 End 6 Shell wall 7 Waist section 8 Clamping section 9 Press jaw 10 Drive and bearing device 11 Hex socket dWall thickness lT axial extension of the waist section lK axial extension of the clamping section lA axial extension of the receptacle Ri,1 inner distance before radial pressing Ri,2 inner distance before radial pressing Ra outer distance before radial pressing

Claims

1. Sleeve (3) configured to support one end (5) of a ceramic roller (2) in a roller hearth furnace (1) via the sleeve (3), wherein the sleeve (3) has a receptacle (4) for the end (5) of the ceramic roller (2), wherein the receptacle (4) is surrounded by a lateral wall (6), wherein, in an axial direction, the lateral wall (6) has a waist section (7) and has a clamping section (8) which is situated therein and which does not extend in the axial direction beyond the waist section (7) either on one side or on both sides and which also does not correspond to the waist section (7), wherein a wall thickness (d) of the lateral wall (6) is smaller in the waist section (7) than in the surroundings of the waist section (7), wherein the surroundings of the waist section (7) is to be understood as meaning sections of the lateral wall (6) that axially adjoin the waist section (7), wherein a cross-sectional area of the receptacle (4) is smaller in the clamping section (8) than in the surroundings of the clamping section (8), wherein the surroundings of the clamping section is to be understood as meaning sections of the lateral wall (6) that axially adjoin the clamping section (8), and wherein the cross-sectional area of the receptacle (4) is delimited by an inner side of the lateral wall (6).

2. Sleeve (3) according to Claim 1, wherein the wall thickness (d) of the lateral wall (6) in the waist section (7) is 20 to 60% of the wall thickness (d) of the lateral wall (6) in the surroundings of the waist section (7).

3. Sleeve (3) according to either of the preceding claims, wherein the cross-sectional area of the receptacle (4) is 0.03 to 0.3% smaller in the clamping section (8) than in the surroundings of the clamping section (8).

4. Sleeve (3) according to one of the preceding claims, wherein an axial extent (lK) of the clamping section (8) is at least 70% of an axial extent (lT) of the waist section (7).

5. Sleeve (3) according to one of the preceding claims, wherein the waist section (7) has an axial extent (lT) ranging from 40 to 80% of an axial extent (lA) of the receptacle (4).

6. Method for mounting a sleeve (3) on a ceramic roller (2) for a roller hearth furnace (1), wherein the sleeve (3) is configured for supporting the ceramic roller (2) in the roller hearth furnace (1), wherein the sleeve (3) has a receptacle (4) for one end (5) of the ceramic roller (2), wherein the receptacle (4) is surrounded by a lateral wall (6), wherein, in an axial direction, the lateral wall (6) has a waist section (7), wherein a wall thickness (d) of the lateral wall (6) is smaller in the waist section (7) than in the surroundings of the waist section (7), wherein the surroundings of the waist section (7) is to be understood as meaning sections of the lateral wall (6) that axially adjoin the waist section (7), and wherein the method comprises: a) radially pressing the sleeve (3) in a clamping section (8), which is also situated in the waist section (7), wherein, at at least three points on the lateral wall (6), the lateral wall (6) is acted on by a respective radially inwardly directed force, b) axially pressing the sleeve (3) onto the end (5) of the ceramic roller (2), wherein, after step a), the sleeve (3) is designed according to one of Claims 1 to 5.

7. Method according to Claim 6, wherein, by way of step a), the cross-sectional area of the receptacle (4) in the clamping section (8) becomes smaller than the cross-sectional area of the end (5) of the ceramic roller (2).

8. Method according to Claim 6 or 7, wherein, in step a), the sleeve (3) is pressed by at least three pressing jaws (9) which extend circumfentially, in each case over an angle range of 10 to 60° of the lateral wall (6), and / or which extend axially, in each case over at least 80% of the waist section (7) of the lateral wall (6).

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