Telescopic rail

Abstract

The present invention relates to a telescopic rail for a microwave oven with at least a first rail element and a second rail element made of an electrically conductive material, wherein the first and the second rail element are slidably mounted to one another in such a way that the second rail element is slidable relative to the first rail element between a retraction position and an extension position in and against an extension direction.It is proposed to design such a telescopic rail in such a way that at least at one front end of the second rail element in the extension direction, a spacer element made of an electrically insulating material is arranged, wherein the spacer element extends from the second rail element in the extension direction, or a spacer element made of an electrically insulating material is arranged between the front end of the second rail element in the extension direction and a front end of the first rail element in the extension direction, wherein the spacer element is arranged in such a way that, in the retracted position of the second rail element, the spacer element defines a distance between the front end of the second rail element and the front end of the first rail element.

Description

[0001] The present invention relates to a telescopic rail for a microwave oven with at least a first rail element and a second rail element made of an electrically conductive material, wherein the first and the second rail element are slidably mounted relative to one another such that the second rail element is slidable relative to the first rail element between a retraction position and an extension position in and against an extension direction, wherein a spacer element made of an electrically insulating ceramic material is arranged at a front end of the second rail element in the extension direction and wherein the spacer element extends from the second rail element in the extension direction.

[0002] Telescopic slides with at least two slide elements and optionally a rolling element cage containing rolling elements to reduce friction between the slide elements during extension are known in various embodiments from the prior art. They are used in various household appliances, as well as in automotive engineering and many other applications.

[0003] EP 2 690 367 A1 discloses a telescopic rail with a first and at least one further rail element, wherein the first rail element, when the telescopic rail is fixed in a household appliance, can be pulled out of the appliance and has a tab at its end facing the opening of the household appliance, which extends perpendicular to the extension direction of the telescopic rail. To provide a telescopic rail that does not pose a risk of burns during handling, or reduces the risk of burns, it is proposed that the tab have a cover on at least one surface facing the opening of the household appliance, the cover being made of a material with a lower thermal conductivity than the material of the tab.

[0004] WO 2019 / 179956 A1 discloses a drawer guide for a microwave oven or an industrial heating oven. The drawer guide comprises a cabinet rail and a running rail that is movable relative to it for holding a support. The drawer guide also includes means for electrically connecting the running rail to the cabinet rail.

[0005] EP 3 484 247 A1 also discloses a telescopic rail with at least one first rail element and a second rail element, wherein the rail elements each have two running surfaces, wherein rolling elements received in a rolling element cage are arranged on the running surfaces of the first rail element and rolling elements received in a rolling element cage are arranged on the two running surfaces of the second rail element, and wherein the rail elements are movable relative to each other between a retraction position and an extension position.EP 3 484 247 A1 further provides for the design of such a telescopic rail for use in a microwave oven in such a way that the rail elements each have at least one electrically conductive contact element, wherein the contact elements are designed and arranged on the rail elements such that in the retracted position either the contact elements are directly engaged with each other or that the contact element of the first rail element and the contact element of the second rail element are each engaged with an electrically conductive guide element moving with the rolling element cage, so that in the retracted position there is an electrically conductive connection between the first and the second rail element and that in at least one position other than the retracted position the electrically conductive connection is interrupted.

[0006] While many applications can already be addressed with conventional telescopic rails, telescopic rails have not yet become established in microwave ovens. If a telescopic rail is used whose rail elements are made of an electrically conductive material, particularly a metal sheet, the microwave radiation incident on the telescopic rail during operation leads to a local charge on the rail elements. With a sufficiently large potential difference between the individual rail elements and the surroundings, this results in a spark discharge between the telescopic rail elements and a component of the microwave oven, such as the door. This can lead to the destruction or at least damage of a part of the microwave oven.

[0007] Therefore, there is a need for a telescopic rail that effectively prevents spark discharge between the telescopic rail and a part of the microwave oven.

[0008] According to the invention, it is proposed to design a telescopic rail of the type mentioned above for a microwave oven in such a way that a spacer element made of an electrically insulating ceramic material is arranged between the front end of the second rail element in the extension direction and a front end of the first rail element in the extension direction, wherein the spacer element is arranged such that, in the retracted position of the second rail element, the spacer element defines a distance between the front end of the second rail element and the front end of the first rail element, wherein the spacer element extends at least 3 mm in the extension direction from the electrically conductive material of the second rail element and the spacer element extends at least 3 mm in the extension direction between the front end of the second rail element and the first end of the first rail element.

[0009] The present invention is based on the idea of ​​ensuring, by means of an electrically non-conductive spacer element between the front end of the second rail element and the door of the microwave oven, a sufficiently large distance between the metallic, i.e., electrically conductive, elements of the telescopic rail and the door of the microwave oven is always, i.e., necessarily, ensured, such that a spark discharge is not possible or at least the probability of a spark discharge is reduced, and by means of an electrically non-conductive spacer element between the front end of the second rail element and the front end of the first rail element, a sufficiently large distance between the front ends of the first and second rail elements is always, i.e., necessarily, ensured, such that a spark discharge is not possible or at least the probability of a spark discharge between the rail elements is reduced.

[0010] The leading end of the first rail element, in the extension direction, is the end that, when the telescopic rail is installed, points towards the opening of the microwave oven's oven cavity. Furthermore, the leading end of the second rail element, in the extension direction, is the end that, when the telescopic rail is installed, points towards the opening of the microwave oven's oven cavity. For the purposes of this application, the retracted position is understood to be the position of the first and second rail elements relative to each other, in which the telescopic rail is fully retracted. Typically, the retracted position is characterized by reaching an end stop.

[0011] When the term "telescopic rail" is used in the context of this application, it is to be understood in such a general way as to include not only rails in which the first rail element and the second rail element are approximately the same length, but also linear guides in which the second rail element is significantly shorter than the first rail element.

[0012] The fact that the telescopic rail according to the invention has a first rail element and a second rail element does not preclude the telescopic rail from comprising further rail elements, in particular for providing a full extension.

[0013] In one embodiment of the invention, the first and second rail elements each have two running surfaces, wherein rolling elements received in a roller cage are arranged on the two running surfaces of the first rail element and rolling elements received in a roller cage are arranged on the two running surfaces of the second rail element.

[0014] A rolling element within the meaning of the present application is understood to be a rotating body which, as an element of a guide, significantly reduces the friction between the various rail elements and thus facilitates the relative movement of two rails to each other. Rolling elements include, for example, balls, rollers, barrels, needles, or cones. In particular, in one embodiment of the invention, the rolling elements can be made of an electrically conductive material, for example, steel.

[0015] In one embodiment of the present invention, the rolling elements are spheres. It is understood that in this case the rolling element cage is a spherical cage.

[0016] In one embodiment of the invention, at least the second rail element is made of a material selected from the group consisting of sheet steel, aluminized sheet steel, and stainless steel. In another embodiment of the invention, the first and second rail elements, and in particular all rail elements of the telescopic rail, are made of such an electrically conductive material.

[0017] The electrically insulating material of the spacer element and the distance element consists of a ceramic material.

[0018] In one embodiment of the invention, the electrically insulating material is a high-temperature resistant material, in particular a material that can withstand temperatures of 200°C or more, preferably 300°C or more, and most preferably 500°C or more, without damage or material change. The advantage of such a material is that it can be used in a microwave oven with a pyrolytic cleaning function for the pyrolytic self-cleaning of the microwave oven.

[0019] In one embodiment of the invention, the ceramic material comprises a metal oxide ceramic, preferably at least an aluminum oxide ceramic or a zirconium oxide ceramic. In another embodiment, the ceramic material is a mixture of an aluminum oxide ceramic and a zirconium oxide ceramic. In a further embodiment, the aluminum oxide ceramic content of such a mixture is between 20% and 80%.

[0020] Spacers and spacers made of metal oxide ceramics, particularly aluminum oxide ceramics and / or zirconium oxide ceramics, can be manufactured in many different shapes using ceramic injection molding. The material has the advantage of being resistant to sudden mechanical stress and possessing a sufficiently smooth surface to prevent damage when it comes into contact with the microwave oven door. The latter is particularly advantageous when the spacer engages with the door during closing and then, due to the geometry of the single-hinged door, slides across its surface.

[0021] The spacer element extends at least 3 mm, preferably at least 5 mm, from the electrically conductive material of the second rail element in the extension direction. This extension of the spacer element determines the minimum distance that must be maintained between the rail elements and the microwave oven door. A distance of at least 3 mm between the microwave oven door and the electrically conductive material of the second rail element effectively reduces the probability of a spark discharge between these elements. With a distance of at least 5 mm, such a spark discharge is largely eliminated for most microwave ovens.

[0022] The spacer element extends at least 3 mm, preferably at least 5 mm, between the first end of the second rail element and the first end of the first rail element in the extension direction. This extension of the spacer element determines the minimum distance that must be maintained between the first and second rail elements. A distance of at least 3 mm between the conductive edges of the first and second rail elements effectively reduces the probability of a spark discharge between these elements. With a distance of at least 5 mm, such a spark discharge is largely eliminated for most microwave ovens.

[0023] There are several, partly alternative, embodiments for the realization of the distance element and / or the spacing element.

[0024] In one embodiment of the invention, the telescopic rail comprises both a spacer element and a distance element. In another embodiment, the spacer element and the distance element are formed in one piece. In such an embodiment, a single molded body forms both the spacer element and the distance element.

[0025] Telescopic rails for ovens, especially microwave ovens, usually have tabs at the front end in the extension direction, i.e., pointing towards the oven opening. These tabs form a front end to the telescopic rail and also extend vertically beyond it, so that the tab acts as a stop for a cooking support placed on the telescopic rail. This allows the telescopic rail to be pulled out of the oven by grasping the cooking support, for example a baking tray, as the cooking support engages behind the tab.

[0026] In one embodiment of the invention, the spacer element and / or the distance element is an end cap made of electrically insulating material, wherein the end cap is connected to the second rail element at its leading end in the extension direction. In this embodiment, the end cap made of electrically insulating material replaces the tab made of electrically conductive material as provided in the prior art. In one embodiment, the end cap extends from the leading end of the second rail element also against the extension direction, so that the end cap forms the spacer element. In one embodiment of the invention, the end cap made of electrically insulating material forms both the spacer element and the distance element.

[0027] For the purposes of this application, the vertical direction is understood to be a direction perpendicular to the extension direction, which, in the installed state, extends essentially parallel to the wall of the furnace muffle to which the telescopic rail is connected.

[0028] In one embodiment of the invention, the end cap, acting as a spacer and / or distance element, has a dimension in the vertical direction of the telescopic rail that is greater than the dimension of the second rail element in the vertical direction. In this way, the spacer element projects beyond the second rail element in the vertical direction.

[0029] In further embodiments of the present invention, the spacer element is arranged in addition to a tab, preferably electrically conductive, at the front end of the second rail element, wherein the spacer element extends from the tab in the extension direction so that it can fulfill its spacer function vis-à-vis the door.

[0030] In such an embodiment, the extension of the spacer element in the extension direction is at least 3 mm, preferably at least 5 mm, measured against the front surface of the tab made of electrically conductive material that points towards the opening of the oven.

[0031] In an embodiment of the present invention, the spacer element is arranged at the front end of the second rail element in addition to a tab, preferably electrically conductive, wherein the spacer element extends from the tab in the opposite direction of extension, so that it can fulfill its spacer function relative to the first rail element.

[0032] In such an embodiment, the extension of the spacer element from the tab against the direction of pull-out is at least 3 mm, preferably at least 5 mm, measured against the rear surface of the tab made of electrically conductive material, which points away from the opening of the oven.

[0033] In one embodiment of the invention, the tab has a front surface pointing in the extension direction, with the spacer element completely covering the front surface. Such complete coverage results in a dielectric being provided entirely between the oven door and the rail element, which makes spark discharge less likely.

[0034] In one embodiment, the spacer element covers only a portion of the front surface. Even partial coverage significantly reduces the probability of a spark discharge due to the spacer element's spacing function. Furthermore, partial coverage of the tab's front surface reduces the amount of material required for the spacer element.

[0035] Particularly with a spacer element and / or a distance element made of a ceramic material, it is only possible to create arbitrary shapes for the spacer element and / or the distance element to a limited extent. Preferably, the spacer element and / or the distance element, especially if it is made of a ceramic material, has rotational symmetry, for example, a cylindrical basic shape. Such shapes exhibit high stability and are also easy to produce from ceramic material using ceramic injection molding.

[0036] In one embodiment of the invention, the spacer element and / or the distance element is connected to the respective rail element, in particular to the tab of the second rail element, by means of a force-fit, a form-fit or a material-fit connection, or by means of a combination of a force-fit, a form-fit or a material-fit connection.

[0037] In one embodiment of the invention, the spacer element and / or the distance element is glued onto the tab made of the electrically conductive material or glued into a recess in the tab.

[0038] In one embodiment of the invention, the spacer element has a formed external thread, wherein the external thread is screwed into an internal thread provided in the tab. An external thread can be formed on a spacer element such that the thread is made of the same material as the rest of the spacer element, i.e., the thread is an integral part of the spacer element. Such a spacer element with an external thread can be produced, in particular, from a ceramic material by injection molding. In one embodiment of the invention, the external thread of the spacer element extends through the tab such that the section of material with the external thread forms a spacer element as defined in the present application.

[0039] In one embodiment of the invention, the spacer element and / or the distance element has an opening, in particular a hole, wherein a fastening means, for example a screw, extends through the opening and engages with the tab, preferably a thread of the tab.

[0040] In a further embodiment of the invention, the tab made of the electrically conductive material has at least one locking lug, and the spacer element and / or the distance element has at least one locking recess, wherein the locking lug and the locking recess are arranged such that the locking lug engages in the locking recess. In one embodiment of the invention, the spacer element and / or the distance element has a cylindrical section which engages in an opening in the tab made of the electrically conductive material, wherein the locking recess on the cylindrical section is formed in the form of a circumferentially extending groove. The locking lug is then a projection provided circumferentially on the side walls of the opening in the tab made of the electrically conductive material. This projection engages in the groove as a locking lug.In one embodiment of the invention, the tab has a plurality of locking lugs, for example three or four locking lugs.

[0041] In a further embodiment of the present invention, the spacer element surrounds the tab made of the electrically conductive material at least partially in the manner of a cover cap.

[0042] In one embodiment of the present invention, the first rail element has at least one electrically conductive contact element and the second rail element also has an electrically conductive contact element, wherein the contact element of the first rail element and the contact element of the second rail element are configured and arranged on the rail elements such that in the retraction position either the contact element of the first rail element and the contact element of the second rail element are in engagement with each other or that the contact element of the first rail element and the contact element of the second rail element are each in engagement with an electrically conductive guide element moved along with a rolling element cage.such that in the retracted position there is an electrically conductive connection between the first and second rail elements, and that in at least one position other than the retracted position the contact element of the first rail element and the contact element of the second rail element are not in contact with each other, or at least the contact element of the first rail element or the contact element of the second rail element is not in contact with the guide element, so that in the at least one other position the electrically conductive connection is interrupted. An electrically conductive connection between the first and second rail elements in the retracted position ensures potential equalization in the event of a possible charging of the second rail element by the electromagnetic radiation of the microwave oven and thus reduces the probability of a spark discharge.

[0043] In such an embodiment, the spacer element causes a forced displacement of the second rail element relative to the first rail element into the retracted position, thus forcibly establishing electrical contact between the first and second rail elements for potential equalization.

[0044] This embodiment is based on the idea that mechanical engagement, and thus a direct electrically conductive connection between the contact elements of the first and second rail elements, is required in the retracted state, i.e., the extended position. Microwave ovens can generally only be operated, meaning that the electromagnetic microwave radiation can only act on the telescopic rail, when the oven door is closed. However, closing the door requires that the rail elements of the telescopic rail no longer protrude beyond the oven cavity.

[0045] The contact elements do not provide an electrically conductive connection in any position other than the insertion position; that is, the electrically conductive connection is then interrupted.

[0046] For the purposes of this application, an engagement between the contact element of the first rail element and the contact element of the second rail element is understood to mean a direct mechanical contact of their surfaces, which is such that an electric current can flow between the contact elements and via the engagement point, i.e., via the point of contact between the two contact elements.

[0047] Surprisingly, it has been shown that such contact elements in the retracted position can not only effectively prevent sparking between the edges and tips of adjacent rail elements, but also prevent localized current flow across the rolling elements of the telescopic rail. The latter proves particularly advantageous because localized currents flowing across the contact points of the rolling elements with the running surfaces of the rail elements can damage both the rolling elements and the running surfaces, and can also be destroyed by thermal influences on lubricants in the vicinity of the rolling elements.

[0048] To realize the advantages of the present invention, it is necessary to effect potential equalization of at least one rail element exposed to microwave radiation. It is initially irrelevant whether the resulting local charges dissipate to an immediately adjacent rail element or to another rail element. In the case of a full extension with three rail elements, the charges can alternatively dissipate to the middle rail element or to the inner rail element.

[0049] It is understood that the contact elements are electrically connected to the rail elements in order to provide equipotential bonding. In one embodiment, at least one of the contact elements is formed integrally with the respective rail element.

[0050] In one embodiment, at least one of the contact elements is formed by a projection on the first or second rail element. It is advantageous if the projection has a greater extent in the extension direction than in a direction perpendicular to the extension direction. A greater extent of the projection in the extension direction than in a direction perpendicular to the extension direction ensures the function of the contact elements even when the telescopic rail is not fully retracted, i.e., in the retracted position.

[0051] This is particularly advantageous if, in one embodiment of the invention, the length of the telescopic rail in the extension direction is dimensioned such that, even after closing the door of a household appliance in which the telescopic rail is installed, the telescopic rail is not fixed in exactly one position, but rather the two rail elements can be arranged relative to each other within a range of positions. In this case, it is necessary to ensure electrical contact between the two rail elements across this range.

[0052] Such an elongated projection extending in the direction of extension can, particularly in the case of a full extension, also be arranged on a central rail element, which in the area of ​​its connecting section only allows for a small size of the projection.

[0053] In one embodiment of the invention, the projection is formed as an indentation of sheet metal material in the respective rail element. Such grooves can be produced simply and cost-effectively.

[0054] In a further embodiment of the invention, the contact element of the first rail element is formed by a projection and the contact element of the second rail element is formed by a projection, wherein the projection on the first rail element has a larger extent in the extension direction than in a direction perpendicular to the extension direction and wherein the projection on the second rail element has a smaller extent in the extension direction than in the direction perpendicular to the extension direction.

[0055] Elongated projections arranged in such a crossed manner on the two rail elements, acting as contact elements, are able to compensate for the tolerances of the profiles of the rail elements and the assembly. In one embodiment, the tolerance chain to be considered also includes the dimensions of the installation space of a household appliance, in particular the cavity of a microwave oven, as well as the door that closes it.

[0056] In one embodiment of the invention, the telescopic rail provides a full extension, wherein the telescopic rail has two outer rail elements and a middle rail element, and wherein the projection with the extension being greater in the extension direction than the extension in the direction perpendicular to the extension direction is provided on the middle rail element.

[0057] In one embodiment of the invention, the contact elements are engaged exclusively in the retraction position, i.e., when reaching the end stop, either with each other or both with the guide element.

[0058] In a further embodiment, the contact elements in the retracted position and over a partially extended area in the vicinity of the retracted position are engaged with each other or both with the guide element, wherein the length of the area in the extension direction over which the contact elements are engaged with each other in the partially extended state is determined by an extension and / or a position of the contact elements on the rail elements in the extension direction.

[0059] This ensures that potential equalization between the rail elements also takes place when the telescopic rail is almost, but not fully, retracted.

[0060] In addition to embodiments of the present invention in which the contact elements of the first and second rail elements are directly electrically conductive in the retracted position, the solution according to the invention also includes embodiments in which each of the contact elements of the first or second rail element engages with an electrically conductive guide element that moves with the rolling element cage, but is not in direct engagement with each other. Such an embodiment has the advantage that the material of the guide element can be made thinner and thus more flexible than the material of the rail elements themselves. This optimizes the electrical contact between the contact elements of the rail elements and the guide element, and thus between the first and second rail elements. In one embodiment of the invention, the guide element is formed by the rolling element cage itself.

[0061] At least one of the aforementioned tasks is also solved by a microwave oven with a telescopic rail in embodiments as previously described. In one embodiment, the microwave oven has a source of microwave radiation with a frequency of approximately 2.4 GHz.

[0062] For the purposes of this invention, a microwave oven is understood to be any oven or cooking appliance that has a source of microwave radiation. For example, a combination oven with a microwave function is a microwave oven within the meaning of this invention.

[0063] In particular, at least one of the aforementioned problems is also solved by a microwave oven with pyrolysis for self-cleaning. In one embodiment, the microwave oven therefore has a heating device for heating the oven cavity to a temperature of 200°C or more, preferably 300°C or more, and particularly preferably 500°C or more.

[0064] In one embodiment of the invention, the lengths of the telescopic rail elements in the extension direction and the extent of the spacer element in the extension direction are selected such that the telescopic rail is in the retracted position or in a partially extended position when the microwave oven door is closed. In this way, closing the microwave oven door ensures a sufficiently large distance, provided by the spacer element, between the electrically conductive second rail element and the microwave oven door. In one embodiment of the invention, this selection of dimensions in the extension direction also ensures electrically conductive contact between the contact elements and thus potential equalization between the rail elements.

[0065] In one embodiment of the invention, the microwave oven has an oven cavity and a door for closing the oven cavity, the door being movable between a closing position and a releasing position. The telescopic rail is installed in the oven cavity such that when the door is in the releasing position, the second rail element can be moved into the extended position, so that the second rail element protrudes from the oven cavity.

[0066] In one embodiment of the invention, a door-side spacer element made of electrically insulating material is provided on the door. This door-side spacer element is arranged such that, after the door is closed, it extends between the door material and the front end of the second rail element. This door-side spacer element can be provided as an alternative or additional element to the spacer element at the front end of the second rail element.

[0067] Furthermore, in one embodiment, at least a length of the first rail element or a length of the second rail element in the extension direction and the extent of the spacer element at the front end of the second rail element and / or the extent of the door-side spacer element in the extension direction are selected such that when the door is in the position closing the oven muffle, the telescopic rail is necessarily in the retracted position.

[0068] Further advantages, features, and applications of the present invention will become clear with reference to the following description of one embodiment and the accompanying figures. In the figures, identical elements are designated by the same reference numerals. Figure 1 is a partially cropped isometric front view of a first embodiment of the spacer element. Figure 2 is a partially cropped isometric rear view of the spacer element.Figure 1 Figure 3 is a partially cropped isometric view from the front of another embodiment of the spacer element. Figure 4 is a partially cropped isometric view from the rear of the spacer element. Figure 3 Figure 5 is a cropped isometric front view of another embodiment of the spacer element. Figure 6 is a cross-sectional view in the extension direction of the spacer element. Figure 5 Figure 7 is a partially cropped isometric view from the front of another embodiment of the spacer element. Figure 8 is a partially cropped isometric view from the rear of the spacer element. Figure 7 Figure 9 is a partially cropped isometric front view of another embodiment of the spacer element. Figure 10 is a partially cropped sectional view of the spacer element. Figure 9Figure 11 is a schematic top view of a microwave oven with one embodiment of the telescopic rail. Figure 12 is a partially cutaway isometric view of one embodiment of the telescopic rail. Figure 13 is a partially cutaway side view of the telescopic rail. Figure 12 Figure 14 is a partially cutaway isometric view of another embodiment of the telescopic rail. Figure 15 is a partially cutaway side view of the telescopic rail made of Figure 14 .

[0069] In all specific embodiments described with reference to the figures, the spacer element 4 is made of a ceramic material, namely an aluminum oxide ceramic with a zirconium content of 15%. Such a ceramic material can be produced by ceramic injection molding in a variety of shapes and has a smooth surface with a low coefficient of friction.

[0070] The telescopic rail 3 is shown in all representations of the Figures 1 to 10 Each of the telescopic rails 3 is shown broken away. Each of the telescopic rails forms a full extension with three rail elements 1, 2, 7. The stationary rail element connected or connectable to the furnace muffle is referred to as the first rail element 1. The rail element that can be fully extended from the furnace muffle is referred to, for the purposes of this application, as the second rail element 2. In a full extension, there is also a third, middle rail element 7, which is only shown in the schematic top view. Figure 11 as can be seen. In addition, ball cages with bearing balls arranged inside them (not shown in the figures) are arranged between the rail elements 1, 2, 7 of the telescopic rails 3, which serve to guide the individual rail elements 1, 2, 7 relative to each other.

[0071] Figure 11Figure 1 shows a microwave oven 13 with two telescopic rails 3 according to the invention, each connected to a side wall 14 of the muffle 15 of the oven 13. During operation of the microwave oven 13, the telescopic rails 3, and in particular the inner, second rail elements 2, are exposed to the microwave radiation of the oven. This electromagnetic radiation leads to a local electrostatic charge in the rail elements 2. This charge, in turn, can lead to a spark discharge between the rail elements 1, 2, 7 and the door 12' when closed, if a sufficient distance between the rail elements 1, 2, 7 and the door 12' is not ensured.

[0072] With the door 12 open, the rail elements 2, 7 can be pulled out of the muffle 15 through the opening. However, the microwave oven 13 can only be operated with the door 12' closed. In other words, electrostatic charging of the rail elements 1, 2, 7 can only occur with the door 12' closed.

[0073] Therefore, in all the Figures 1 to 11 In the embodiments shown, the lengths of the rail elements 1, 2, 7 in the extension direction 5 and the extent E of the spacer element 4 in the extension direction 5 are dimensioned such that when the door 12' is closed, the rail elements are essentially in the retracted position.

[0074] In order to reduce the local electrostatic charge, especially of the rail element 2, the telescopic rails 3 also provide an electrically conductive connection between the first and second rail elements when the telescopic rail 3 is in the retracted position.

[0075] In the embodiment of the Figures 1 and 2 The spacer element 4 is designed in the form of an end cap at the front end 6 of the second rail element 2 of the telescopic rail 3 in the extension direction 5.

[0076] The end cap 4 has an extension E in the extension direction 5, such that the minimum distance between an end face 11 of the second rail element and the door 12,12' of the microwave oven 13 is 5 mm.

[0077] The end cap 4 replaces the tab provided in the prior art at the front end 6 of the second rail element 2 in the extension direction 5. The end cap 4 has a projection U in the vertical direction 10 relative to an upper edge of the second rail element 2. The spacer element 4 thus also acts as a stop for a cooking tray placed on the second rail element 2.

[0078] The end cap 4 has a fastening section 9 on the rail side, which has an excess in the vertical direction 10, so that the fastening section 9 is clamped forcefully between the running surfaces 8 of the second rail element 2.

[0079] In the embodiment of the Figures 1 and 2 The spacer element 4 completely replaces the metal tab otherwise provided on the second rail element. In contrast, all other embodiments shown here of the Figures 3 to 10A metal tab 17 is provided at the front end 6 of the second rail element 2. This tab is bent away from the material of the rail back 6 of the second rail element 2. The tab 17 provides a projection beyond the upper edge of the second rail element 2 to form a boundary for the cooking carrier placed on the second rail element 2.

[0080] The extension of the spacer element in the extension direction starting from the second rail element 2 is described in the embodiments of the Figures 3 to 10 measured from a front surface 19 of the tab 17. In all embodiments, the extent of the ceramic spacer element 4 from the front surface 19 of the tab 17 is 5 mm.

[0081] In the embodiment of the Figures 3 and 4 The spacer element 4 is a cuboid that is glued into a groove 18 in the tab 17 of the second rail element 2.

[0082] The embodiments of Figures 5 to 10 What they have in common is that the spacer element 4 has an essentially cylindrical basic shape. Such cylindrical basic shapes can be produced easily and inexpensively using ceramic injection molding. Furthermore, such ceramic components are extremely stable, even under point loads.

[0083] The other embodiments of the Figures 5 to 10 compared to the material-bonded connection of the spacer element 4 with the tab 17 from the Figures 3 and 4 a positive-locking connection between the spacer element 4 and the tab 17.

[0084] In the embodiment of the Figures 5 and 6The spacer element 4 has a cylindrical receiving section 20 with an external thread 21 formed therein. The spacer element 4 with the cylindrical receiving section 20 is manufactured entirely and in one piece from the ceramic material. The external thread 21 is screwed into an internal thread 22 located in a hole in the tab 17.

[0085] In the embodiment of the Figures 7 and 8The cylindrical surface 24 of the spacer element 4 has a detent in the form of a circumferential groove running around the surface 24 of the spacer element 4. The cylindrical body of the spacer element 4 is inserted into a hole 26 in the tab 17. The wall of the hole has four detent lugs 27 that extend radially, such that the hole in this area is smaller than the outer diameter of the surface 24 of the spacer element 4. The detent lugs 27 therefore engage positively in the groove 25 in the surface 24 of the spacer element 4 and effectively hold the spacer element 4 against the tab 17.

[0086] While the embodiments of Figures 5 and 6 on the one hand, and the Figures 7 and 8 On the other hand, both can manage without an additional fastening means, as is the case in the embodiment of the Figures 9 and 10A fastening element in the form of a screw 23 is provided. This screw 23 passes through a hole 28 in the spacer element 4. The screw is screwed into an internal thread 22 of the tab 17.

[0087] The embodiments of Figures 12 to 15 These embodiments differ from the previously described embodiments in that they all have a spacer element 29 in addition to the spacer element 4. Like the spacer element 4, the spacer element 29 is made of an electrically insulating ceramic material. The spacer element 29 serves to provide sufficient distance between the metallic tab 17 arranged at the front end 6 of the second rail element 2 and the front end 30 of the first rail element 1. Due to the spacer element 29, the probability of a spark discharge between the tab 17 and the front end 30 of the first rail element 1 is significantly reduced.

[0088] Out of Figure 13It is evident that the spacer element 29 is provided in addition to a spacer element 4 between the tab 17 and the closed door 12 of the oven muffle. The function of the spacer element 4 is the same as previously described for the embodiments of the Figures 1 to 11 described. In the embodiment of the Figures 12 and 13 Both the spacer element 29 and the distance element 4 are glued to the tab 17, i.e., materially bonded to it.

[0089] While in the embodiments of the Figures 12 to 15Since the spacer element 29 is provided in addition to the spacer element 4, embodiments are conceivable in which the telescopic rail 3 has only a spacer element 29, but not a spacer element 4. Furthermore, it is also conceivable that the spacer element 4 is arranged on the door 12 of the oven muffle instead of on the front end 6 of the second rail element. Finally, embodiments are conceivable in which the spacer element is realized from a first spacer element 4, which is mounted on the front end 6 of the second rail element 2, and a door-side spacer element (not shown in the figures), which is attached to the door 12 of the oven muffle.

[0090] In contrast, the Figures 14 and 15 An embodiment in which the spacer element 4 and the distance element 29 are integrally formed as a single molded body made of ceramic material. In this embodiment, the Figures 14 and 15the spacer element 4 the tab 17. The spacer element 4 is inserted or clamped into the second rail element 2 by means of a clamping block, whereby this clamping block also forms the spacer element 29.

[0091] For the purposes of the original disclosure, it is pointed out that all features as they can be deduced by a person skilled in the art from the present description, the drawings, and the claims, even if they are specifically described only in connection with certain other features, can be combined individually or in any combination with other features or groups of features disclosed herein, unless this has been expressly excluded or technical circumstances render such combinations impossible or pointless. A comprehensive, explicit description of all conceivable combinations of features is omitted here solely for the sake of brevity and readability.

[0092] While the invention has been illustrated and described in detail in the drawings and the preceding description, this illustration and description are merely exemplary and are not intended to limit the scope of protection as defined by the claims. The invention is not limited to the disclosed embodiments.

[0093] Variations of the disclosed embodiments are obvious to a person skilled in the art from the drawings, the description, and the accompanying claims. In the claims, the word "have" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude multiple features. The mere fact that certain features are claimed in different claims does not preclude their combination. Reference numerals in the claims are not intended to limit the scope of protection. Reference symbol list

[0094] 1. First rail element 2. Second rail element 3. Telescopic rail 4. Spacer 5. Extension direction 6. Front end of the second rail element 7. Third (middle) rail element 8. Running surfaces of the second rail element 2 9. Mounting section of the spacer 4 10. Vertical direction 11. End face of the second rail element 2 12. Door 13. Microwave oven 14. Side wall 15. Sleeve 16. Rail back 17. Tab 18. Groove 19. Front face of the tab 17 20. Mounting section 21. External thread 22. Internal thread 23. Screw 24. Sleeve surface 15. Groove 26. Hole in the tab 17 27. Detent 28. Hole in the spacer 4 29. Spacer 30. Front end of the first rail element E. Extension of the spacer in the direction of withdrawal

Claims

1. A telescopic rail (3) for a microwave oven (13) comprising at least a first rail element (1) and a second rail element (2) made of an electrically conductive material, wherein the first and second rail elements (1, 2) are mounted on each other in such a way that the second rail element (2) can be moved relative to the first rail element (1) between a retracted position and an extended position in and against a pull-out direction (5), wherein a distance element (4) made of an electrically insulating ceramic material is positioned at a front end (6) of the second rail element (2) in the pull-out direction (5), wherein the distance element (4) extends from the second rail element (2) in the pull-out direction (5), characterised in that a spacer element (29) made of an electrically insulating ceramic material is positioned between the front end (6) of the second rail element in the pull-out direction (5) and a front end (30) of the first rail element (1) in the pull-out direction (5), wherein the spacer element (29) is positioned in such a way that the spacer element (29) defines a distance between the front end (6) of the second rail element (2) and the front end (30) of the first rail element (1) in the retracted position of the second rail element (2), wherein the distance element (4) extends from the electrically conductive material of the second rail element (2) and extends at least 3 mm in the pull-out direction (5), and the spacer element (29) extends at least 3 mm in the pull-out direction (5) between the front end (6) of the second rail element (2) and the first end (30) of the first rail element (1).

2. The telescopic rail (3) according to any one of the previous claims, wherein the ceramic material is a metal oxide ceramic, preferably a metal oxide ceramic comprising a mixture of an aluminium oxide ceramic and a zirconium oxide ceramic.

3. The telescopic rail (3) according to any one of the previous claims, wherein at least the distance element (4) extends from the electrically conductive material of the second rail element (2) by at least 5 mm in the pull-out direction (5) or the spacer element (29) extends between the front end (6) of the second rail element (2) and the front end (30) of the first rail element (1) by at least 5 mm in the pull-out direction (5).

4. The telescopic rail (3) according to any one of the previous claims, wherein the distance element (4) and / or the spacer element (29) is an end cap made of electrically insulating material, wherein the end cap is joined to the second rail element (2) at the front end (6) in the pull-out direction (5).

5. The telescopic rail (3) according to any one of the previous claims, wherein the second rail element (2) comprises a tab (17) made of an electrically conductive material at the front end (6), wherein the distance element (4) extends from the tab (17) in the pull-out direction (5) and / or the spacer element (29) extends from the tab (17) in the opposite direction to the pull-out direction (5).

6. The telescopic rail (3) according to claim 5, wherein the tab (17) made of electrically conductive material comprises a front surface (19) facing in the pull-out direction (5), wherein the distance element (4) covers the front surface (19) only partially.

7. The telescopic rail (3) according to claim 5 or 6, wherein the distance element (4) and / or the spacer element (29) comprises an external thread (21) formed from the material of the spacer element, wherein the external thread (21) is screwed into an internal thread (22) formed in the tab (17) made of electrically conductive material.

8. The telescopic rail (3) according to claim 5 or 6, wherein the distance element (4) and / or the spacer element (29) comprises an aperture (28), wherein a fastening means, preferably a screw (23), passes through the aperture (28) and engages with the tab (17) made of electrically conductive material, preferably an internal thread (22) of the tab (17).

9. The telescopic rail (3) according to claim 5 or 6, wherein the tab (17) made of electrically conductive material comprises a locking lug (27) and the distance element (4) and / or the spacer element (29) comprises a locking recess (25), wherein the locking lug (27) and the locking recess (25) are positioned such that the locking lug (27) is locked into the locking recess (25).

10. The telescopic rail (3) according to any one of the previous claims, wherein the distance element (4) and the spacer element (29) are integrally formed.

11. The telescopic rail (3) according to claim 5, wherein the distance element (4) surrounds the tab (17) made of electrically conductive material at least in sections in the manner of a cover cap.

12. A microwave oven (13) comprising a telescopic rail (3) according to any one of the previous claims, wherein the microwave oven (13) comprises an oven muffle (15) and a door (12, 12') for closing the oven muffle (15), wherein the telescopic rail (3) is installed in the oven muffle (15) in such a way that when the door (12) is in a position that exposes the oven muffle (15), the second rail element (2) can be moved into the extended position so that the second rail element (2) protrudes from the oven muffle (15).

13. The microwave oven (13) according to claim 12, wherein a door-side spacer element made of electrically insulating material is provided on the door (12, 12'), and wherein the door-side spacer element is positioned such that the door-side spacer element extends between the door (12, 12') and the front end (6) of the second rail element (2) when the door (12, 12') is in a position closing the oven muffle (15).

14. The microwave oven (13) according to claim 12 or 13, wherein the microwave oven (13) comprises an oven muffle (15) and a door (12, 12') for closing the oven muffle (15), wherein the telescopic rail (3) comprises the oven muffle (15) in such a way that when the door (12) is in a position exposing the oven muffle (15), the second rail element (2) can be moved into the extended position so that the second rail element (2) protrudes out of the oven muffle (15), wherein the first rail element (1) and the second rail element (2) are arranged and at least the distance element (4) at the front end (6) of the second rail element (2) or the door-side distance element is positioned and designed in such a way that when the door (12') is in a position closing the oven muffle (15), the telescopic rail (3) is forcibly in the retracted position.

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