Pull-out system for household appliance

0001The invention relates to an extension system for a household appliance, in particular cooking appliance having at least one stationary holding rail and a movable pull-out rail for holding a food support, of which at least a first rail is coated with a first layer having a lubricant.

0002Out <patcit id="pcit0001" dnum="EP0994309A2"><text>EP 0 994 309 A2</text></patcit> a generic extension device is known, which partially has a cooking chamber pull-out rails. These are slidably guided in stationary guides. The rails and / or the guides are provided at least on their sliding surfaces with a sliding material.

0003Out <patcit id="pcit0002" dnum="DE10211470A1"><text>DE 102 11 470 A1</text></patcit> a generic pull-out system is known which has a stationary inner rail, a movable intermediate rail and a movable outer rail. The rails are provided with an easy-to-clean PTFE-based coating. Depending on the accessibility of the rails or components for food and / or the user different coating qualities are provided. Thus, component areas that point downwards can be equipped with a lower coating quality with regard to cleanability and / or abrasion resistance than component areas facing upwards, which are exposed directly to product spills.

0004Out <patcit id="pcit0003" dnum="DE19949239A1"><text>DE 199 49 239 A1</text></patcit> is a pull-out device, in particular telescopic extension device, known, are guided in the rails by means of ball bearings or roller bearings on stationary guides. The balls of the ball bearings or the rollers of the roller bearings consist at least on their surface of a self-lubricating material.

0005Out <patcit id="pcit0004" dnum="DE3815440"><text>DE 38 15 440</text></patcit> a telescopic insertion device is known, which is designed as a telescopic extension with a stationary inner rail, a rollable middle rail and a rollable outer rail for the food support. At the middle rail two rollers are each mounted by bolts. In the bolt grooves are formed, which serve to accommodate high-temperature-resistant grease or lubricating paste.

0006Out <patcit id="pcit0005" dnum="DE10241683A1"><text>DE 102 41 683 A1</text></patcit> a rail extension for horizontal or vertical extension of an element is known, with at least one outer rail of bent sheet metal and a partially encompassing and slidably guided on this by a rolling bearing guided slide made of bent sheet metal, having a connected to the outer rail and this stiffening additional outer rail and / or one associated with the slide and this stiffening additional rail.

0007Out <patcit id="pcit0006" dnum="DE19949239A1"><text>DE 199 49 239 A1</text></patcit> a pull-out device, in particular telescopic pull-out device, is known for at least one food support in a cooking chamber of a cooking oven, with rails guided in or on guides by means of ball bearings or roller bearings and at least partially extractable from the cooking chamber, on or to which at least one food support can be placed or fastened, wherein the balls of the ball bearings or the rollers of the roller bearings consist at least on their surface of a self-lubricating material.

0008The object of the invention is to provide a drawer system for a household appliance, which permanently has good running or sliding properties.

0009The object of the invention is achieved with a household appliance having the features of patent claim 1. According to claim 1 is a pull-out system for a household appliance, in particular cooking appliance having a stationary support rail, a movable intermediate rail and a balls movably mounted pull-out rail for holding a food support, wherein the intermediate rail is mounted on balls between the pull-out rail and the support rail and of which at least the intermediate rail is coated with a first layer having a lubricant, wherein at least one of the other rails is coated with a second layer or is uncoated, wherein<ul><li>the lubricant layer comprises a binder that holds the lubricant to the rail; and</li><li>from the lubricant layer due to the rotation of the balls rubbed lubricant particles in the extraction system also due to the rotation of the balls reach running or sliding surfaces which are not in contact with a lubricant layer. According to the invention, it has been recognized that it suffices for a sufficient lubrication of the entire extension system, only to provide one of the rails with a lubricant layer. Lubricant particles rubbed off from the lubricant layer can also reach running or sliding surfaces in the pull-out system according to the invention which are not in contact with a lubricant layer. This is sufficient in order to maintain a smooth running of the extraction system.</li></ul>

0010Next arise according to claim 1 for the rails different surface properties. As a result, the running or sliding behavior of the extension system can be significantly increased. The running or sliding behavior improves in particular when the rails are coated with layers of different surface hardness. In view of a favorable production, it is preferred if at least one of the rails is uncoated, ie has a metallic surface.

0011It is particularly preferred if the lubricant is an inorganic solid lubricant. Such a lubricant, in contrast to many other lubricants, such as liquid lubricants of oil or fat, even at high temperatures physiologically harmless.

0012It is advantageous if the lubricant is chemically resistant, in particular alkali-resistant, to enable cleaning in a dishwasher. In this case, the extraction system can also be exposed to chemically aggressive media, for example alkalis in a dishwashing machine.

0013Inorganic solid lubricants are particularly easy to detach from a layer structure. Distributing the inorganic solid lubricant to components that are not coated with the solid lubricant is therefore particularly easy. Squeaking noises or a stiffness of the extension system are therefore reliably prevented.

0014According to the invention it may be advantageous if the lubricant is resistant to high temperatures. For this purpose, all lubricants come into question, which are up to maximum cooking temperatures of up to 300 ° C and optionally up to 500 ° to 600 ° C in the pyrolysis resistant. It is particularly preferred if graphite is used as the solid lubricant. Graphite can be used even at very high temperatures as well as chemically resistant and cost-effective. Furthermore, molybdenum disulfide can be used as the solid lubricant. In this case, however, at very high temperatures, because of the generation of S₂ be problematic. If the manufacturing costs are only of secondary importance, as a solid lubricant and boron nitride is conceivable that is resistant and physiologically harmless in all temperature ranges. The same applies to tungsten disulfide.

0015It is advantageous if the lubricant layer has a binder that holds the lubricant to the rail. The binder provides improved bonding of the lubricant to the rail surface. In contrast, such a connection does not exist if the lubricant only finds support in a roughened rail surface. It is particularly advantageous with regard to a lubricant layer having a uniform layer thickness and uniform surface properties when the binder is a lacquer. This can be sprayed for example on the rail, resulting in a uniform layer thickness. Subsequently, the paint applied to the rail can be burned into the rail together with the lubricant. Advantageously, the lubricant is suspended in the paint.

0016In order to adjust the abrasion resistance of the rail coating or its layer quality to the requirements, combinations of the abovementioned solid lubricants made of graphite, molybdenum disulfide (MoS₂), Boron nitride or tungsten disulfide conceivable.

0017Compared to a plain bearing, with a roller bearing in the extension system an improved pull-out behavior can be achieved. In contrast to a sliding bearing, no frictional force is generated between the movable components, but instead roll the movable components against each other via rolling elements. As a result, in a drawer system with plain bearing significantly less lubricant is required. It is therefore also possible to use a lubricant layer with lower quality requirements.

0018According to the invention, the lubrication of the extraction system can be achieved via a lubricant layer provided only on the intermediate rail. Other components in the extension system, such as rails, rolling elements or Wälzkörperkäfige must therefore take no lubricating function. The rolling elements and / or their Wälzkörperkäfige can therefore be specially designed as limit stops. This occurring loads could not withstand, for example on carbon-based Wälzkörperkäfige (so-called. PEEK cages).

0019In terms of manufacturing technology, it is preferred if the intermediate rail is completely coated with the lubricant. Compared to a partial coating of the intermediate rail thus the coating process can be significantly simplified.

0020Plays the production cost for applying the lubricant layer on the rail only a minor role, it is conceivable to apply several lubricant layers with different properties. In this case, a lowermost layer layer may have a large proportion of binders and correspondingly less solid lubricant. As a result, an abrasion-resistant mounting of the lubricant is secured to the rail. On the other hand, an uppermost layer can have little binder and, for that, a high proportion of solid lubricant. As a result, the lubricating property of the intermediate rail is increased.

0021In addition, the lubricant-containing layer may contain further fillers, such as ceramic, to adjust its layer quality or abrasion resistance.

0022According to a further embodiment, the extension system may be removably mounted in the cooking appliance. In this case, on the one hand, a simple cleaning of the pull-out system outside of the cooking appliance is achieved. On the other hand, for example, in a pyrolysis operation in the cooking appliance, the extraction system can be removed so as not to expose it to high temperatures in pyrolysis operation.

0023Preferably, the extraction system can be designed such that the coated with the lubricant layer rail is protected from contamination. For example, the holding rail and / or the pull-out rail define a cavity in which the intermediate layer coated with the lubricant layer is arranged. In this case, the intermediate rail is inserted at least in the cooking mode in the cavity formed by the retaining rail / pull-out rail. A contamination of the intermediate rail by cooking liquid or by vapors is thereby substantially reduced. This makes it possible that the lubricant layer has an inorganic solid lubricant. Such a lubricant layer has excellent lubricating properties, but is difficult to clean. This is due to the physical properties of inorganic solid lubricants. The poor cleanability, however, plays only a minor role when the, the lubricant layer having rail is largely protected from contamination.

0024In the following, two embodiments of the invention will be described with reference to the attached figures. Show it:<dl id="dl0001"><dt>FIG. 1</dt><dd>according to the first embodiment, an extension system in a cooking appliance;</dd><dt>FIG. 2</dt><dd>in a sectional view of the extension system of the cooking appliance;</dd><dt>FIG. 3</dt><dd>a ball cage of the extension system; and</dd><dt>FIG. 4</dt><dd>according to a second embodiment, an extension system in a cooking appliance.</dd></dl>

0025In the <figref idref="f0001">FIG. 1</figref> is shown in the first embodiment, a cooking appliance with a cooking appliance muffle 1, which limits a cooking chamber. The cooking appliance has a hinged door 3 for closing a front-side muffle opening 5. In the<figref idref="f0001">FIG. 1</figref> the swing door 3 is shown in an open state. On opposite side walls 9 of the cooking appliance muffle 1 are corresponding lateral guide rods 11 and a pull-out system, consisting of two opposite telescopic extensions 13, supported. The telescopic extensions 13 are removably supported in a top of four horizontal Garraumebenen. In the underlying three Garraumebenen each of the corresponding guide rods 11 are removably supported. On the two corresponding lowermost guide rods 11, a baking sheet 13 is supported, which is partially pushed out of the cooking appliance muffle 1. The guide rods 11 are muffelfrontseitig each inserted in a bearing bush 15. This is mounted in a mounting opening of the muffle side wall 9. The telescopic extensions 13 are formed with a holding plate 14 which is mounted in each case in an annular groove 16 of the bearing bush 15. In the area of ​​a muffle rear wall 17, the guide rods 11 and the telescopic extensions 13 are each mounted in a mounting opening 19. Both the guide rods 11 and the telescopic extensions 13 are tool-free by a user from the muffle 1 to solve.

0026In the present case, the extension system 13 is designed as a telescopic extension. The telescopic extension 13 is according to the<figref idref="f0002">FIG. 2</figref> in one in the <figref idref="f0001">FIG. 1</figref> shown viewing direction I shown in cross section. The telescopic extension 13 has a lower holding rail 23, which is held on the holding plate 14 fixed to the muffle side wall 9.

0027Both the retaining plate 14 and the bearing bush 15 are in the <figref idref="f0002">FIG. 2</figref> shown with dashed lines. In addition to the stationary support rail 23, the telescopic extension 13 consists of a movable intermediate rail 25 and a likewise movable pull-out rail 27. The intermediate rail 25 is mounted on balls 29 between the pull-out rail 27 and the stationary support rail 23.

0028The configuration of the rails 23, 25, 27 is not limited to the present embodiment. Thus, the retaining rail 23 may also be formed like a round rod 11. On the support rail 23, the pull-out rail can be guided sliding or mounted on other rolling elements. The design of the pull-out rail 27 is not limited to the present embodiment. Rather, the pull-out rail 27 may also be designed as a slide, a runner or another pull-out element. Between the extension element 27 and the support rail 23 can also be dispensed with the arrangement of the intermediate rail 25.

0029The support rail 23 and the extension rail 27 are made according to the <figref idref="f0002">FIG. 2</figref> from mutually identically formed U-profile parts of an uncoated sheet steel. The two rails 23, 27 are arranged facing each other with their open sides. They define a substantially closed cavity 31, in which the intermediate rail 25 is arranged. This means that at least in the retracted state of the telescopic extension 13, the intermediate rail 25 is almost completely enclosed by the pull-out rail 27 and the support rail 23. Splashes of grease, dirt or the like are therefore kept away from the balls 29 and from the intermediate rail 25.

0030In order to allow a smooth pulling and pushing together of the extension system, the intermediate rail 25 is coated with a lubricant layer 33. The lubricant layer 33 is in the<figref idref="f0002">FIG. 2</figref> shown in exaggerated layer thickness. The layer thickness is realistically in a range between 10 and 20 microns. In contrast to the intermediate rail 25, both the balls 29 and the support rail 23 and the pull-out rail 27 are not coated with the lubricant layer 33, but uncoated. As a result, the balls 29 run on the one hand on the lubricant layer 33 of the intermediate rail 25 and on the other hand on the uncoated running surfaces of the support rail 23 and the pull-out rail 27th

0031The surface properties of the metal surface of the balls 29, the support rail 23 and the pull-out rail 27 on the one hand and the lubricant layer 33 on the other hand are different. Due to these different surface properties results in a particularly good rolling behavior of the balls 29 and thus good running properties of the extension system.

0032Alternatively, the holding rail 23 and / or the pull-out rail 27 may be coated with a second layer, as shown in the <figref idref="f0002">FIG. 2</figref> is indicated by the reference numeral 34 with a dashed line. The two different layers 33 and 34 have different surface properties. In particular, the rolling behavior of the ball 29 can be improved with a different surface hardness. The second layer 34 may be formed as a corrosion resistant layer, for example.

0033In the present case, the lubricant layer 33 comprises particles of an inorganic solid lubricant, such as graphite. To produce the lubricant layer 33, a powder of the inorganic solid lubricant is first suspended in a lacquer solution and then the intermediate rail 25 is subsequently coated. In a further step, the paint solution is baked in the intermediate rail 25. This results in an extremely high mechanical abrasion resistance of the coating 33 and a good chemical resistance to aggressive media, such as detergents. In addition to this cost-effective coating method, other methods, such as a PVD coating (Physical Vapor Deposition) or a CVD coating (Chemical Vapor Deposition) for producing the lubricant layer 33 are conceivable.

0034The lubricant layer 33 of the intermediate rail 25 is sufficient to introduce enough lubricant between the balls 29 and the pull-out rail 27 or the holding rail 23. The in the<figref idref="f0002">FIG. 2</figref> illustrated U-shaped rails 23, 27 are particularly well suited to protect the intermediate rail 33 from contamination. In the in the<figref idref="f0002">FIG. 2</figref> it is sufficient to adapt the lubricant layer 33 only with regard to its lubricating properties. Of subordinate importance in this case is the cleanability of the lubricant layer 33. The protection against contamination of the lubricant layer 33 is namely taken over by the U-shaped retaining rail 23 or the pull-out rail 27. These act at least in the inserted state as cover with respect to the intermediate rail 25. An contamination of the intermediate rail 25 is therefore largely reduced.

0035Only such a protection of the intermediate rail 25 from contamination therefore makes it possible to suitably coat the intermediate rail 25 with the inorganic solid lubricant layer 33. Namely, such a layer is very difficult to clean compared with, for example, a PTFE-based layer.

0036According to the <figref idref="f0002">FIG. 2</figref> the balls 29 are arranged in two opposing ball cages 37. The balls 29 are rotatably supported in the ball cages 37. One of the ball cages 37 in the<figref idref="f0003">FIG. 3</figref> shown. The ball cage 37 consists of a thin sheet steel, which is formed into an angular part with three trapezoidally arranged in profile sides 39. In each of the sides 39 recesses 41 are cut out. The recesses 41 are arranged on each side 39 in two consecutive rows. The two rows are spaced apart by a central portion 43 of the ball cage 37. Each recess 41 is partially bounded by an angled embossing edge 45 which holds the ball 29 in the recess 41.

0037The in the <figref idref="f0002">Figures 2</figref> and <figref idref="f0003">3</figref> shown ball cages 37 are additionally coated with the lubricant layer 33. In the<figref idref="f0002">FIG. 2</figref> the applied on the ball cage 37 lubricant layer 33 is indicated by dashed line. In the<figref idref="f0003">FIG. 3</figref> is the applied on the ball cage 37 lubricant layer 33 indicated in hatching. As a result, due to the rotation of the balls 29 on the angled embossing edge 45, a slight lubricant abrasion can be generated. The abrasion is distributed by the adjusting movement of the telescopic extension 13 along the running surfaces of the rails 25, 23, 27. As a result, the pull-out behavior of the extension system is permanently improved. Furthermore, squeaking noises or sluggishness in the operation of the telescopic extension are effectively reduced. The application of the lubricant layer 33 on the ball cage 37 takes place here as the application of the lubricant layer 33 to the respective rail.

0038The ball cages 37 are freely movable between the rails 23, 25, 27 in the longitudinal direction. The end faces 47 of each ball cage 37 are used in the in the<figref idref="f0002">FIG. 2</figref> shown telescopic extension 13 as stops that limit a longitudinal movement of the rails 23, 25, 27. The telescopic extension 13 can therefore be pulled apart until the end faces 47 of the ball cage 37 come into contact with corresponding rail stops, not shown.

0039In the <figref idref="f0004">FIG. 4</figref> is shown according to the second embodiment, a cooking appliance, which corresponds to the cooking appliance of the first embodiment. The only difference to the first embodiment is that the telescopic rails 13 of the extension system consists of the stationary support rail 23 and the pull-out rail 25 mounted directly thereon. On the intermediate rail 25 is omitted. In this case, the pull-out rail 25 is mounted, as in the first embodiment, on balls 29, which are held in the ball cages 37.

0040According to the <figref idref="f0004">FIG. 4</figref> the movable pull-out rail 27 is coated with the lubricant layer 33. By an adjusting movement of the pull-out rail 27, the lubricant is distributed in sufficient quantity in the extension system. In contrast, the stationary support rail 23 is uncoated. The balls 29 therefore roll between rolling surfaces with different surface properties, resulting in a particularly good rolling behavior of the balls 29 and thus good running properties of the extension system.