DE102013105878A1 - Surface-coated telescopic rail - Google Patents

Abstract

Process for coating surfaces of rail elements made of metal or metal alloys for telescopic rails, wherein the rail elements have at least one raceway, in which a) the surface of the rail elements, including the surface of the raceways, is provided with a surface coating and then b) the surface coating on the The surface of the raceways is removed from the surface of the raceways by heating the coating material with laser beams, and the rail element produced by this method.

Description

Subject of the invention

The present invention relates to a method for producing ball-bearing or roller-mounted telescopic rails with surface-coated rail elements.

Background of the invention

Telescopic rails are used, inter alia, in ovens for holding and for easy retraction and extension of food supports. In addition to the aspects of ease of movement, the noise occurring, the feel and stability, in particular in the oven area requirements are still made on the food safety and cleanability of the telescopic slides.

a) sliding behavior / lubricant

Telescopic rails consist of two or more elongated rail elements which are mounted so as to be displaceable in the longitudinal direction. One distinguishes between ball-bearing or roller-mounted telescopic rails on the one hand and slide rails on the other. Ball or roller mounted telescopic rails usually offer a quieter and easier common running behavior and high stability. In order to ensure a smooth and quiet as possible movement of the rail elements, the ball or roller bearings and the corresponding running surfaces are provided on the rail elements with lubricants. The lubricants are introduced in the manufacture of the telescopic rails in the ball or roller bearings and should usually survive the entire life of the telescopic rails, without relubrication is required. In particular, in telescopic rails, which are used in ovens, the lubricant must meet high demands on food safety and heat resistance. Lubricants for conventional ovens must withstand temperatures of up to 300 ° C and maintain their lubricating properties. In modern ovens with pyrolysis, the rails for cleaning the oven are regularly exposed to temperatures up to about 500 ° C for periods of one to three hours. Only a few lubricants can withstand temperatures of up to 300 ° C and at the same time meet the requirements of food safety and health safety.

b) contamination / discoloration / cleanability

Telescopic rails for ovens are usually made of steel. A disadvantage of steel telescopic rails in the oven area is the oxidation or scale formation on the surfaces of the rail elements or even the balls or rollers at high temperatures. This discoloration of the surfaces of the steel rails occur, which are undesirable in the visible range of the rail elements for aesthetic reasons. These problems occur especially in telescopic rails in pyrolysis ovens due to the very high temperatures used for cleaning purposes up to 500 ° C on.

In addition, the surfaces of the steel-made rail elements in the oven area pollute very easily. During operation, fats and other substances from the food to be cooked are deposited on the rail elements and are burned into the material over the course of time so that they can only be removed with difficulty or not at all. In addition, the surfaces of the rail elements in the oven area scratch very easily, as here often sharp-edged areas of other metal objects, such. B. the food support, come into contact with the rail elements.

It is known to provide the rail elements of telescopic rails with a surface coating to improve resistance to oxidation and scale formation, pyrolysis resistance, resistance to soiling, scratch resistance and cleanability. Examples are coatings of chrome, enamel, PTFE, high-temperature coatings, ceramics, etc.

Many of the known coatings provide protection of the rail surfaces against oxidation and scale formation at high temperatures and allow a good cleaning of the surfaces of contaminants or prevent the stoving of the contaminants.

The DE-A-10 2005 002 315 describes telescopic rails for the food industry and for use in ovens where the steel or stainless steel rail elements are improved with a coating of enamel to improve resistance to soiling and improve cleanability be provided. The DE-A-10 2004 027 717 and the DE-A-102 11 470 describe telescopic rails for ovens with a coating of PTFE.

c) Production of coated rail elements

The coatings described above provide the rail elements of telescopic rails with many advantageous properties in terms of resistance to oxidation and scale formation, pyrolysis resistance, resistance to contamination, scratch resistance and cleanability. However, in the field of raceways in which the balls or rollers are rolled, the coatings can significantly affect the running properties of the telescopic rails. In addition, some of the known coatings are not sufficiently resistant to the strong mechanical stresses exerted by the balls or rollers on the raceways. In particular, by bullets very high point loads are applied to the treads. As a result of these stresses, the coatings may detach from the surface of the raceways over time and the running properties of the telescopic rails may additionally be impaired by the detached coating fragments.

In order to keep the tracks free of the coating applied to the rail elements, they can be covered during the coating process or the coating is applied so targeted that it does not cover the raceways. Both variants are associated with considerable expense and therefore high costs, since coatings are usually applied most easily to the entire surface of rail elements, for example by immersing the rail elements in corresponding coating dip or the like.

task

There is therefore a need for a simple and comparatively cost-effective method for producing ball-bearing or roller-mounted telescopic rails with surface-coated rail elements, in which the raceways of the rail elements are substantially free of the surface coating.

Description of the invention

• a) die Oberfläche der Schienenelemente, einschließlich der Oberfläche der Laufbahnen, mit einer Oberflächenbeschichtung versieht und anschließend
• b) die Oberflächenbeschichtung auf der Oberfläche der Laufbahnen durch Erhitzen des Beschichtungsmaterials mittels Laserstrahlen von der Oberfläche der Laufbahnen entfernt.

This object is achieved by a method for coating surfaces of rail elements of metal or metal alloys for telescopic rails, wherein the rail elements have at least one career, in which one

• a) provides the surface of the rail elements, including the surface of the raceways, with a surface coating and then
• b) the surface coating on the surface of the raceways by heating the coating material by means of laser beams away from the surface of the raceways.

By this method, a rail element is obtained, on the one hand has a desired coating that gives the rail element protection against oxidation, scale formation, etc. and an attractive appearance and at the same time has at least one career, on which no or only a thin coating is applied and their Running characteristics are comparable to those of uncoated rail elements. In addition, it has been found that the thus treated track a rail element of a metal or a metal alloy less prone to discoloration when exposed to very high temperatures of up to 500 ° C, as comparable rail elements that were not coated and not treated with laser.

In the process, the coating is evaporated and / or blasted off by heating by means of laser beams. The term "laser beams" in the sense of this invention essentially comprises the laser radiation generated by a source, wherein the use of several laser sources is also included. The laser beams are generated in a device which is also commonly referred to as a laser head.

By "removal of the coating" in the sense of this invention is meant that the coating is completely or partially removed.

Typical rail elements of telescopic rails have at least two raceways. In one embodiment, the removal of the coating in step b) takes place simultaneously of two raceways of a Rail element. Preferably, two separate laser sources are used for this, but they may have a common control.

In a preferred embodiment, at least 70%, preferably at least 80%, and up to 99% are removed from the coating material applied to the track. There remains a structured surface, wherein the structuring is generated by the movement of the laser beams over the surface of the track. A partial removal of the coating material is on the one hand due to the fact that in the inventive method preferably the laser beams are guided substantially only once over the surface, and thereby a removal takes place, not completely up to the surface of the track of the rail element of a metal or a On the other hand, the laser beams are guided in tracks over the surface of the track, wherein the paths of the laser beams in certain embodiments, only partially or not overlap, so that a rough surface due to burrs remaining coating results. The term "substantially only once over the surface" includes the fact that the laser beams are guided in paths over the surface, which do not overlap, but can intersect.

It has been shown that, despite remaining coating residues, good running properties are achieved with rail elements treated in this way by ball-bearing or roller-mounted telescopic rails, and in addition there are no problems with the lubricants usually used for telescopic rails. This is especially true for the lubricants that are used even at high temperatures, including graphite. Both the remaining coating material on the surface of the raceways and the coating at the edges of the raceways are stable and there is no flaking or cracking of the coating in these areas when one or more balls or rollers stress the raceway.

In a preferred embodiment, the rail members are made of a material selected from the group consisting of steel, austenitic and ferritic stainless steel, aluminum and aluminum alloys, and mixtures thereof. These materials have proven to be particularly advantageous when used in telescopic rails, which are used in particular in heatable devices, such as ovens, ovens, steamer, etc.

Austenitic stainless steel has a high alloying addition, that is to say high proportions of Ni, Cr, etc., while ferritic stainless steel has fewer alloying components. Austenitic stainless steel is usually more corrosion resistant, especially at welds. In certain embodiments, austenitic and ferritic stainless steels known to those skilled in the art are used, including stainless steel with the material number 1.4301 (X5CrNi18-10), also with AISI 304 and the stainless steel with the material number 1.4016 (X6Cr17), also with AISI 430 designated. However, there are also other stainless steels used, which are particularly suitable for high temperature stresses.

Aluminum is characterized by its low weight and by the fact that this material in addition to or instead of a coating also anodization of the surface is possible, which also allows a uniform appearance, temperature resistance and easy cleaning. An anodized surface of this type, which optionally also has an additional coating, can be removed in the described method by means of laser beams. The person skilled in the known processes for anodization of aluminum.

In a preferred embodiment, the surface coating is selected from the group consisting of enamels, high temperature paints, PTFE, plastics, siloxanes, metal oxides, and mixtures thereof, or the surface coating is a surface modification of the material of which the rail members consist. The coatings may be applied as such or in coating compositions wherein, in certain embodiments, in the coating compositions, in an intermediate step, prior to removal of the coating by laser, a solvent is stripped and / or the coating is fired or cured. For the application of the coating methods known in the art are suitable, which also include that before the application of a coating, a pretreatment of the rail element. Known pretreatments are mechanical treatment by brushing or sandblasting, cleaning by acetone, ultrasonic cleaning, cleaning by perchlorethylene and / or degreasing by alkaline boiling and electropolishing and combinations thereof. Preferably, no further pretreatment for the coating with enamel and a pretreatment by sand blasting for a coating of PTFE.

In one embodiment, a laser with a power of 50 to 600 watts, preferably 100 to 400 watts, and particularly preferably 100 to 300 watts is used for the generation of the laser beams in b). Such a powerful laser makes it possible to remove a coating on the surface of the track of a rail element substantially without residue, so that the running property of the track is not impaired. In a preferred embodiment, a laser with a pulse frequency between 5 and 80 kHz, preferably between 10 and 50 kHz, preferably between 10 and 15 kHz, is used for the generation of the laser beams in b). It has been found that a pulsed laser with the specified pulse frequency is particularly suitable for the removal of a coating from a rail element made of metal or a metal alloy.

In one embodiment, the coating is removed in b) at a temperature in the range of 10 ° C to 38 ° C, preferably in a range of 15 ° C to 25 ° C, preferably at a temperature of about 20 ° C.

In one embodiment, as the coating is removed, the laser beams are zig-zagged, meandered, serrated, squared, or looped over the surface of the track. The movement of the laser beams is composed here of an advancing movement, which takes place along a longitudinal extent of the track, and a movement, which takes place essentially transversely to the longitudinal extent of the track, of periodically repeating motion, from which a zigzag, sawtooth, rectangular Meander or loop pattern results. The loop pattern in one embodiment is composed of a series of shapes similar to the number 8. In one embodiment, the advancing movement is effected by a movement of the rail element, while the periodically repeating movement is generated by a movement of the laser beams extending substantially transversely to the longitudinal extent of the rail element. It has been found that, despite the corrugation of the surface of the track occurring transversely to the longitudinal extent of the rail element and thus also transversely to the longitudinal extent of the track, a low-noise and uniform displacement of rail elements of a telescopic rail, which has at least one rail element machined in this way, is possible.

In one embodiment, the laser beams are guided in a loop movement or a zigzag movement over the surface of the track, wherein the movement, with which the laser beams are guided over the track, from a uniform or uniform rectilinear feed movement parallel to the longitudinal extent of the Rail element and extending substantially transversely to the longitudinal extent of the rails movement in the form of the number 8 or in the form of straight lines which extend alternately in opposite directions, composed. This results in an efficient removal of coating material, wherein, despite remaining remnants of coating material on the track, a silent and uniform against each other method of rail elements of a telescopic rail with at least one so machined rail element is possible.

Preferably, the transverse to the longitudinal extent of the rail element extending movements extend substantially over the entire width of the track. The width of the raceway is the extension extending transversely or perpendicular to the longitudinal extension of the raceway in the plane of the raceway, the raceways of rail elements of telescopic rails usually having a curvature whose axis of curvature lies parallel to the longitudinal extension of the raceway. The uniform linear feed movement can be effected by a movement of the laser beam generating laser head or by a movement of the rail element.

In one embodiment, the distance between a laser head of the laser beam generating laser to the surface of the track in the removal of the coating in b) in the range of 80 mm to 120 mm. The focal length of the laser is adjusted accordingly or a laser with such a focal length is used. With such a focal length, effective removal of a coating from a metallic or metallic alloy rail member is possible.

In one embodiment, during and / or after the removal of the coating material in b), the removed coating is sucked off or blown out. When removing a coating by means of laser beams, the coating is vaporized or blown off, whereby both processes can take place simultaneously. For coatings that are mainly removed by evaporation, a suction of the coating is possible. For coatings that are mainly blasted off, the remaining residues can be removed from the track by means of compressed air. Preferably, in one embodiment, suction of the removed coating material occurs during removal of the coating material in stage b). By sucking off during the removal, both the resulting vapors as well as particles and debris of the coating can be immediately removed and thereby not reach the environment or into the environment.

The invention also includes a rail member made by a method as described above, and a telescopic rail having at least one rail member made by a method as described above. The telescopic rails are ball-bearing or roller-mounted telescopic rails. Such telescopic rails and rail elements can be used in many areas, but they are designed according to the invention especially for a food support system or as part of a Gargutträgersystems in an oven or oven. However, they are also advantageous for use in refrigerators and freezers and other appliances and in furniture.

A telescopic rail according to the invention can be designed as a full extension rail or partial extension rail with inner, outer and optionally one or more middle rails. In a partial extension rail, the inner rail and the outer rail are expediently designed as substantially C-shaped profiles, wherein the end portions or legs of the C-shaped profile of the outer rail engage around the inner rail or vice versa.

Further advantages, features and design options of the present invention will become apparent from the figures and examples described below.

characters

Show it:

1 : A schematic representation of a structure for the removal of a coating from a track with laser beams and

2a ) and 2 B ): a schematic representation of different tracks describing the laser beams on the track.

In a method according to the invention, first rail elements are completely provided with a coating by a coating material. Subsequently, the removal of the coating material from a track of the rail element takes place. In 1 is shown schematically a structure with which the removal of the coating takes place. The representation is purely schematic and does not reflect the actual proportions and details. For the removal of coating material on a track becomes a completely coated rail element 1 provided that a career 2 having. The rail element is on a support 6 stored and fixed on this. The edition 6 may be fixed or, in particular, movable relative to a laser device. With the help of a laser head 4 Laser beams are generated. The laser used in the examples described below is a Nd: YAG solid state laser. The arrow A indicates the direction of the longitudinal extent of the rail element 1 at. During removal, the laser beams move in a periodically repeating motion transverse to the longitudinal extent over the surface of the raceway 2 guided, at the same time a feed movement in the direction of arrow A takes place. The feed movement comes either by a movement of the laser head 4 in the direction of arrow A or by a movement of the pad 6 with the rail element fixed thereon 1 in the opposite direction of the arrow A state. Upon removal, the coating material is completely or partially removed from the raceway, with a treated surface 3 the career 2 which, when the coating is partially removed, has a structuring which is conditioned by the path which describes the movement of the laser beams across the surface.

2 schematically illustrates examples of webs that describe the laser beams in the removal of coating material from a track of a rail element on the track. It is in both illustrated tracks in the 2a ) and 2 B ) each around periodically repeating shapes, the webs being composed by a periodic repeating movement substantially transverse to the longitudinal extent of the raceway from which the coating is removed and an advancing movement in the direction of the longitudinal extent of the raceway. The longitudinal extent of the track runs in the illustrated tracks parallel to the direction of the arrow B.

In the 2a ) consists of several rectilinear motion, which is substantially transverse to the longitudinal extent of the track and alternately in opposite directions run, and from a uniform rectilinear motion in the direction of the longitudinal extent together. The uniform or uniform rectilinear movement in the direction of the longitudinal extent can be achieved by a movement of the laser beams in the direction of the arrow B or by a movement of the support on which the rail element is fixed, in the opposite direction. The movement taking place essentially transversely to the longitudinal extent of the raceways can extend essentially over the entire width of the raceway of the rail element.

In 2 B ) is shown a web which is composed of a substantially transverse to the longitudinal extent of the rail element extending movement in the form of the number 8 and a uniform or uniform rectilinear movement in the direction of the longitudinal extent of the rail element. The uniform or uniform rectilinear movement in the direction of the longitudinal extension can be achieved by a movement of the laser beams in the direction of the arrow B or by an opposite movement of the support on which the rail element is fixed. The movement taking place essentially transversely to the longitudinal extent of the raceways can extend essentially over the entire width of the raceway of the rail element.

In both in 2 Lanes shown schematically result in gaps within the trajectory that lead to the removal of coating material to burrs that remain on the surface of the track. This results in a structured surface, in the form of a corrugation, which runs essentially transversely to the longitudinal extension of the track or of the rail element. Despite this corrugation so machined rail elements provide satisfactory running properties.

Examples

In order to investigate the running properties and temperature resistance of rail elements treated by a method according to the invention, in each case a partial pull-out rail (outer and inner rail) was provided with different coatings and the coating of the raceways of the individual rail elements was removed with laser beams. The properties of the thus treated rail elements or telescopic rails composed thereof were compared with those of an uncoated telescopic rail.

Example 1: Machining of rail elements with different coatings

The rail elements used for the tests were (a) coated with an air-drying, high-temperature resistant solvent-based paint, (b) with PTFE or (c) with enamel. There was no pretreatment of the rail elements before applying the paint and enamel coatings and a pre-treatment by sandblasting before applying the coating with PTFE. The rail elements of the telescopic rails were individually coated and then removed the coating on the tracks with laser beams. Only then were the telescopic rails assembled.

The removal of the coating on the running surfaces of the rail elements was carried out for all coated rail elements with a diode-pumped class 4 Nd: YAG laser with a system power of 150 watts to 600 watts, with laser powers in the range of 150 to 300 watts were set. A pulsed laser was used with a pulse frequency in the range between 10 and 50 kHz. The path of the laser described on the track corresponded to that in 2 B ) shown schematically. On the tracks of the rail elements treated in this way, after removal of the coating with laser, a clear structure was seen which corresponded to the path described by the laser beams on the raceway.

Example 2: Endurance test and checking the temperature resistance

In order to determine whether comparable running properties can be achieved with a telescopic rail having such machined rail elements as with non-coated rail elements, the rail elements obtained in Example 1 and a telescopic rail with rail elements, in which no coating was applied, were subjected to an endurance test with heat , For this purpose, a partial extension telescopic rail was assembled from the rail elements treated as described above. The composite telescopic rails were loaded perpendicular to their longitudinal extent or running direction with 10 kg and 8 treatment cycles, each with 10 pyrolysis operations and each subjected to 3000 inputs and Ausfahrvorgängen. In the pyrolysis operations, the telescopic rails were exposed to a temperature of 500 ° C. Telescopic rails having PTFE coated rail elements were exposed to a temperature of only 280 ° C. The entry and exit processes are relative movements the rail elements of a telescopic rail against each other, wherein a telescopic rail was completely pulled out and completely pushed together again.

It has been found that the telescopic rails, in which a coating has been applied to the tracks of the rail elements and subsequently removed with laser beams, achieved satisfactory running properties both before and after the test described above.

–

deutliche Beeinträchtigung bei den Laufeigenschaften

±

zufriedenstellende Laufeigenschaft

+

hervorragende Laufeigenschaft

Bearbeitung der Schienenelemente Laufeigenschaft vor Test Laufeigenschaften nach Test Beispiel 1a) Hochtemperaturlack ± ± Beispiel 1b) PTFE ± ± Beispiel 1c) Emaille ± ± Vergleichsbeispiel ohne Beschichtung + + The results of the tests are shown in Table 1. The details of the assessments have the following meaning:

-

significant impairment in the running properties

±

satisfactory running characteristic

+

excellent runnability

Processing the rail elements Run property before test Running properties after test Example 1a) High-temperature varnish ± ± Example 1b) PTFE ± ± Example 1c) enamel ± ± Comparative example without coating + +

After the test described above, the rails were examined for external changes. It has been shown that the telescopic rails not only have the usual pyrolysis for coated rails pyrolysis, but also no discoloration of the metal or the metal alloy occurs in the partially freed from the coating tracks, in contrast to the telescopic rail, in which no coating had been applied. It has also been shown that both the remaining coating material on the surface of the raceways and the coating at the edges of the raceways at the selected temperatures and loads are stable and no further flaking or jumping off of the coating in these areas.

For purposes of the original disclosure, it is to be understood that all such features as will become apparent to those skilled in the art from the present description, drawings, examples and dependent claims, even though they have been specifically described in connection with certain further features, both individually or in any combination with others of the features or feature groups disclosed herein are combinable, unless this has been expressly excluded or technical conditions make such combinations impossible or pointless. On the comprehensive, explicit representation of all conceivable combinations of features and the emphasis on the independence of the individual characteristics of each other is omitted here only for the sake of brevity and readability of the description.

While the invention has been illustrated and described in detail in the drawings and examples and the foregoing description, such illustration and description is exemplary only and is not intended to limit the scope of the protection as defined by the claims. The invention is not limited to the disclosed embodiments.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102005002315 A [0008]
• DE 102004027717 A [0008]
• DE 10211470 A [0008]

Cited non-patent literature

• AISI 304 [0020]
• AISI 430 [0020]

Claims (11)

Method for coating surfaces of rail elements made of metal or metal alloys for telescopic rails, wherein the rail elements have at least one track, in which one a) provides the surface of the rail elements, including the surface of the raceways, with a surface coating and then b) the surface coating on the surface of the raceways by heating the coating material by means of laser beams away from the surface of the raceways. Method according to claim 1, characterized in that at least 70%, preferably at least 80%, and up to 99% are removed from the coating material applied to the track. Method according to one of the preceding claims, characterized in that the rail elements consist of a material selected from the group consisting of steel, austenitic and ferritic stainless steel, aluminum and aluminum alloys and mixtures thereof. Method according to one of the preceding claims, characterized in that the surface coating is selected from the group consisting of enamel, high temperature paints, PTFE, plastics, siloxanes, metal oxides and mixtures thereof, or a surface modification of the material of which the rail elements consist. Method according to one of the preceding claims, characterized in that for the generation of the laser beams in b) a laser with a power of 50 to 600 watts, preferably 100 to 450 watts, and particularly preferably 100 to 300 watts is used and / or for the Generation of the laser beams in b) a laser with a pulse frequency between 5 and 80 kHz, preferably between 10 and 50 kHz, preferably between 10 and 15 kHz, is used. Method according to one of the preceding claims, characterized in that the laser beams are guided on removal of the coating in zig-zag movements, meandering, sawtooth, rectangular or loop movements over the surface of the track. A method according to claim 6, characterized in that the laser beams are guided in a loop movement or zig-zag movement over the surface of the track, wherein the movement, with which the laser beams are guided over the track, from a uniform rectilinear feed motion parallel to the longitudinal extent of the rail element and a substantially transverse to the longitudinal extent of the rail element extending movement in the form of the number 8 or in the form of straight lines which extend alternately in the opposite direction, composed. Method according to one of the preceding claims, characterized in that the distance between a laser head of the laser generating laser to the surface of the raceways in the removal of the coating in b) in the range of 80 mm to 120 mm. Method according to one of the preceding claims, characterized in that during and / or after the removal of the coating material in b), the removed coating is sucked off or blown out. Rail element produced by a method according to one of the preceding claims. Telescopic rail having at least one rail element according to claim 10.

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