EP2338003B1 - Drawer slide for household appliances - Google Patents

Description

The present invention relates to a drawer slide, in particular for a baking oven, with at least two rails which can be moved relative to one another and which are guided against one another via roller bodies.

In the area of the pull-out guide with the application in the higher temperature range, many of the known lubricants reach the limits of material load capacity. Many of the known liquid lubricants, such as, for example, polyfluorinated compounds, can no longer be used despite their excellent lubricating and lubricating properties in the higher temperature range.

Therefore, it is a technical challenge to create a corresponding fitting, in particular a pullout guide, which always has consistently good lubricating and sliding properties below room temperature as well as at temperatures up to 600 ° C. Furthermore, a chemical resistance of the coating and a cost-effective production and application of the same is required.

The EP 1589291 A1 discloses a generic drawer slide, which has rolling elements which are mounted in a rolling cage. In this case, the Wälzkörperkäfig on a smear layer, which, inter alia, the inclusion of boron nitride in a paint provides. The coating extends over the entire surface of the Wälzkörperkäfigs. Since boron nitride is used only for reasons of cost in areas in which its special material properties are absolutely necessary, when using this compound, the most cost-effective application is required. A large area coating like in EP 1589291 A1 is therefore not useful.

The DE 35 37 479 A1 discloses a corrosion inhibitor with simultaneous lubricating effect, which can be used for high temperature applications.

Object of the present invention is to provide a drawer guide that allows for the use of low as well as the use of high temperatures over a long period of smooth running of the rails.

This object is achieved by a pullout guide with the features of claim 1.

The inventive solution, the boron nitride and graphite lubricant is applied to the much smaller areas of the raceways at least partially. This allows a targeted lubrication with less material consumption.

Hexagonal boron nitride has proven to be an optimal lubricating and lubricating agent in the range of higher temperatures. It is chemically inert and oxidation resistant, with the exception of alkaline melts and basic solutions. The structure of the boron nitride is similar to that of graphite and from a temperature of 900 ° C, boron nitride converts to cubic β-boron nitride.

The application of the lubricant takes place according to the invention as a sliding paste. This allows the lubricant to be used for industrial series production. In addition, this form of application enables a very exact selection and coating of the application surfaces.

The lubricant mixture is according to a preferred embodiment, a mixture of boron nitride, graphite and high temperature fat, with a mass fraction w (boron nitride) between 5% to 30%, preferably a mass fraction w (boron nitride) between 10% to 20%. Both the use of the relatively inexpensive graphite as a further lubricant component and high-temperature fat as matrix and carrier additionally support the lubricating and lubricating action of boron nitride. However, while graphite emits embedded water molecules at longer heating times, which reduces its lubricating effect for a short time, it remains with boron nitride even at high temperatures, in particular over 200 ° C.

Furthermore, the lubricant may advantageously contain as polysiloxane preferably a silicone paste, a silicone grease and / or a silicone oil, which does not burn at temperatures above 300 ° C, so for example in the pyrolysis of ovens. The consistency between these designs can be varied by mixing.

The lubricant mixture according to claims 8-9 to support the sliding molybdenum sulfide and polytetrafluoroethylene especially in applications below 300 ° C included.

Post-treatment after application of the lubricant by vibratory grinding allows better distribution and maintenance of the lubricant on the metallic substrate.

In an advantageous embodiment, the lubricant has a temperature resistance of over 600 ° C, which allows, for example, an application in the range of cooking ovens and their purification by pyrolysis.

It is also advantageous if the lubricant has a thixotropy, which decreases in these pastes under mechanical action whose viscosity and the original viscosity sets only after prolonged standing again. As a result, the pastes can be relatively easily distributed on the surface of the drawer guides under pressure load. This is the case with BNC pastes, for example.

The viscosity of a lubricant without the addition of solids is advantageously in the range between 50-1500 mm ² / s, preferably 100-1000 mm ² / s, whereby a discharge of the low to medium viscosity mass can be carried out without the lubricant at the ends the lanes can flow out.

It is also advantageous if the lubricant is so hydrophobic that a bacterial or fungal attack of the lubricant is excluded.

The low surface tension in conjunction with a pronounced surface activity at 25 ° C. of 20-22 mN / m, preferably 20.9-21.2 mN / m, allows full wetting of a large surface under application despite the high viscosity of a lubricant.

Depending on the carrier substance, it is decomposed predominantly into water and carbon dioxide during the pyrolysis. By operating the pullout guide during use by the user, the boron nitride and graphite content in the lubricant mixture was uniformly distributed in the tracks of the pullout guide with the aid of the carrier material. After decomposition of the carrier substance during the pyrolysis, at least the boron nitride remains in the tracks of the pullout guide and enables a smooth operation of the pullout guide, thus it is still lubricated. Due to the mechanical load prior to pyrolysis, the boron nitride / graphite content in the mixture is incorporated into the raceways of the pullout guide.

The lubricant according to the invention is particularly suitable for the lubrication of fittings in household appliances such as e.g. Ovens or refrigerators, due to its operating range of approx. - 50 ° C to approx. 600 ° C. For other areas, the application of the lubricant is conceivable, especially in areas where a food suitability is required. In addition to pullout guides, hinges, flap fittings or other moving parts, in particular on household appliances, can also be lubricated with the lubricant according to the invention.

In order to meet all requirements for the carrier substance for their suitability for foodstuffs, lubricants are preferably used which comply with the FDA 21 CFR 178.3570 (US Food and Drug Administration).

In addition, the lubricants should be registered by the NSF (National Sanitation Foundation) in the Hl category. Reference is also made to ISO 21469.

In the US, the approval of the US-DA (United States Department 30 of Agriculture) to US-DA-H. It should be noted that the relevant regulation is to become Directive 21 CFR 178.3570.

The lubricants used preferably also meet the hygiene requirements according to the German version DIN EN ISO 21469: 2006.

Figur 1

eine perspektivische Ansicht einer Auszugsführung in der eingefahrenen Position;

Figur 2

eine perspektivische Ansicht der Auszugsführung der Figur 1 in der ausgefahrenen Position;

Figur 3

eine Explosionsdarstellung der Auszugsführung der Figur1;

Figur 4

eine Schnittansicht der Auszugsführung der Figur 1, und

Figur 5

eine Schnittansicht der Auszugsführung der Figur 1.

Figur 6

ein Diagramm zur Darstellung des erfindungsbedingten Effekt auf die Auszugsführungen

The invention will be explained in more detail using an exemplary embodiment with reference to the accompanying drawings. Show it:

FIG. 1

a perspective view of a pullout guide in the retracted position;

FIG. 2

a perspective view of the pullout guide the FIG. 1 in the extended position;

FIG. 3

an exploded view of the pullout guide of Figur1 ;

FIG. 4

a sectional view of the pullout guide of FIG. 1 , and

FIG. 5

a sectional view of the pullout guide of FIG. 1 ,

FIG. 6

a diagram illustrating the invention-related effect on the pullout guides

A pullout guide 1 comprises a guide rail 2 and a running rail 3 movable relative to the guide rail. The guide rail 2 and the running rail 3 are made of a bent sheet steel.

The guide rail 2 can be fixed to a side wall of a baking oven and on the running rail 3, a food support can be placed accordingly. The running rail 3 is mounted on rolling elements 4 movable on the guide rail 2. For this purpose, the guide rail 2 in the longitudinal direction of a plurality of raceways 6 for the spherical rolling elements 4, which are held in a rolling element cage 5.

In order to ensure smooth running of the running rail 3, a lubricant 7 is applied to a portion of the raceways 6 each. By rolling the rolling elements 4 on the sections with the lubricant 7, this is distributed over the entire track 6 on the guide rail 2 and on the raceways 8, which are formed on the running rail 3.

In the illustrated embodiment, a pullout guide with a running rail 3 and a guide rail 2 is described. It is of course also possible to form the pullout guide as a full extension and to provide a center rail between the guide rail 2 and the running rail 3.

• Beschichten der Laufbahnen mit einem Bornitrid Gleitlack
• Auftragen des Bornitrid als Gleitpaste oder Suspension
• Auftragen des Bornitrids in Pulverform durch Gleitschleifen
• Mischungen aus Bornitrid und Hochtemperaturfett, wobei nach der Pyrolyse das Bornitrid als Festschmiermittel in den Laufbahnen zurückbleibt
• Mischungen aus Bornitrid mit Molybdänsulfid, Graphit und PTFE sind denkbar
• Mischungen aus Bornitrid mit einem Polysiloxan
• Mischungen aus Graphit, Polysiloxan und Wasser
• Mischungen aus Graphit mit einem Polysiloxan
• Mischungen aus Graphit, Bornitrid und einem Polysiloxan

The application of a lubricant with boron nitride and / or graphite can be carried out in the following ways:

• Coating the raceways with a boron nitride lubricating varnish
• Apply the boron nitride as a sliding paste or suspension
• Applying the boron nitride in powder form by vibratory grinding
• Mixtures of boron nitride and high-temperature grease, wherein after pyrolysis, the boron nitride remains as a solid lubricant in the raceways
• Mixtures of boron nitride with molybdenum sulfide, graphite and PTFE are conceivable
• Mixtures of boron nitride with a polysiloxane
• Blends of graphite, polysiloxane and water
• Blends of graphite with a polysiloxane
• Blends of graphite, boron nitride and a polysiloxane

Lubricants and lubricants are, for example, boron nitride and graphite, which are relatively easily distributed by friction on a surface due to their hexagonal structure and then prevent friction.

The mixture of powder of boron nitride BN and graphite C in the mass ratio of 10% BN / 90% C to 80% BN / 20% C leads to a powder with different gray levels. The mixture BNC has tribological and other physical and chemical properties that make it possible to use them as dry lubricants with hygroscopic properties in household waste products.

The powder has sufficient sliding properties after high temperature stress as it can occur in pyrolysis (self-cleaning process in the oven at 600 ° C), as well as at minus temperatures in freezers. The temperature stress has a different influence on the mixed substances at common temperatures in the oven, the sliding friction of both substances is taken. With the vesicle-containing range up to 100 ° C, as well as with high air humidity, the main lubricating effect of graphite, which unfolds its lubricating effect in the presence of moisture best. In the low temperature range and temperatures above 400 ° C, the lubricating effect is mainly at BN.

The BNC mixture can also be further processed with different methods. As the method of application, inflation onto the surface as powder with or without carrier gas, spraying with a wet carrier, brushing with a brush and wet carrier, mixing by means of drum technique or dipping in a wet carrier into consideration. Furthermore, a spraying process via nozzles, even with pasty consistency of the mixture, conceivable.

If the BNC powder is mixed with a wet carrier such as water, alcohol or food oils, fats together, then depending on the Nassträger a suspension (heterogeneous solid / liquid mixture), a dispersion (homogeneous solid / liquid mixture) or an emulsion (heterogeneous liquid / liquid mixture). The subsequent mixture can consist of solid / liquid or liquid / liquid or gaseous / liquid substances, which are then further processed in the above-mentioned processes.

Both boron nitride and carbon have hexagonal and cubic modifications of their crystal structure, with hexagonal carbon modification widely known as graphite and cubic modification as diamond. Similar to the graphite, the hexagonal boron nitride has a layer structure, whereby the overlapping layers shift relative to each other relatively easily let and thus cause a lubricating and lubricating effect. These synergies between graphite and boron nitride allow for mixing in the ratios mentioned.

The performance of the BNC-Si lubricants used is based on a physical and tribochemical effect for use in extracts and hinges. This occurs particularly advantageous in the range of -50 to + 220 ° C. With a consistently high mechanical load, you will get an almost constant viscosity within the specified temperature range. The viscosity of BNC-Si lubricant - is in the range between 100-1000 mm ² / s, is determined at 25 ° C according to DIN 51562 and classifies the BNC-Si lubricant in the category of low to medium viscosity substances , Due to the high hydrophobicity of the lubricants form a corrosion protection, which leads neither to bleeding in the temperature range, nor to oil secretions, even over long periods of time. The viscosity data refer to the lubricant without added solids.

• der Viskositätstemperaturkoeffizient liegt zwischen 0,5-0,7, vorzugsweise zwischen 0,60-0,62;
• die Verdampfungswärme liegt bis 200°C zwischen 150-300 J/g, vorzugsweise zwischen 220-240 J/g;
• der Siedepunkt bei 0,5 mbar liegt zwischen 100-300°C, vorzugsweise zwischen 150-230°C;
• der Stockpunkt gemäß DIN 51583 liegt zwischen -50-10°C, vorzugsweise zischen -30 - -10°C;
• der Flammpunkt liegt nach DIN 51376 zwischen 230-370°C, vorzugsweise 275-321°C
• der Zündpunkt liegt nach DIN 51794 über 400°C, vorzugsweise über 420°C
• der Tropfpunkt liegt nach ASTM-D-445 zwischen -80°C - -30°C, vorzugsweise zwischen -65°C und -50°C.

In connection with the temperature resistance of the BNC-Si, the following properties can be mentioned:

• the viscosity temperature coefficient is between 0.5-0.7, preferably between 0.60-0.62;
• the heat of vaporization is up to 200 ° C between 150-300 J / g, preferably between 220-240 J / g;
• the boiling point at 0.5 mbar is between 100-300 ° C, preferably between 150-230 ° C;
• the pour point according to DIN 51583 is between -50-10 ° C, preferably hiss -30 - -10 ° C;
• the flash point is according to DIN 51376 between 230-370 ° C, preferably 275-321 ° C.
• the ignition point is in accordance with DIN 51794 over 400 ° C, preferably above 420 ° C.
• the dropping point according to ASTM-D-445 is between -80 ° C - -30 ° C, preferably between -65 ° C and -50 ° C.

Additional disturbing noises, such as squeaking, do not occur when using BNC-Si lubricants. Here, a high pressure absorption capability comes into play. For example, a pull-out guide provided with BNC silicone lubricants will have consistently good sliding properties even under high mass load, for example due to food carriers.

After the pyrolysis treatment of the BNC paste, a lubricating film remains, which provides the functionality of the extracts.

The BNC-Si lubricant can be applied with silicone pastes, silicone greases and silicone oils. The low surface tension in conjunction with a pronounced surface activity at 25 ° C. of 20-22 mN / m, preferably 20.9-21.2 mN / m, allows complete wetting of a large surface area during application. In order to make the viscosities of BNC-Si lubricants variable, other solvents can be added to the lubricant.

A BNC-Si-Scmiermittelschicht is highly water-repellent and chemically inert to vegetable oils, mineral oils, gases, dilute acids and alkalis and most aqueous solutions. Due to its highly hydrophobic properties also a bacterial or fungal attack of the lubricant is excluded. In addition, BNC-Si lubricants are radiation resistant, oxidation resistant, non-toxic, non-flammable and physiologically inert and odorless.

The color of the lubricant is adjustable by the BNC ratio.

All ingredients of the BNC-Si lubricant comply with the USDA and FDA regulations and are therefore suitable for use in the food industry.

In addition, according to the Foodstuffs and Commodities Act (§5, para. 1 no. 1 of 15.08.1974 BGBL.IS 1945), there are no concerns for the use of silicone carriers and phenylmethylsilicone oils with a viscosity of ≥ 100 mm ² / s at 20 ° C, in the food sector.

In FIG. 6 Measurements are shown in the form of a diagram, which can be described the properties of a BNC-Si paste, which was applied as a lubricant on an electrodeposited aluminum surface.

1. a) Kraftaufwand beim Ausziehen der Auszugsführung (Fa) in N
2. b) Kraftaufwand beim Einfahren der Auszugsführung (Fe) in N
3. c) Laufgüte, beurteilt durch eine geschulte Prüfperson mittels Ordinalskala
4. d) Geräusche, beurteilt durch eine geschulte Prüfperson mittels Ordinalskala

In the test test, the results of which are shown in the diagram, a pull-out guide equipped with the BNC-Si paste was tested for frequent use of the pull-out guide for the following properties:

1. a) force when pulling out the pullout guide (Fa) in N
2. b) force when retracting the pullout guide (Fe) in N
3. c) running quality, assessed by a trained examiner using ordinal scale
4. d) noises, assessed by a trained examiner using ordinal scale

In the experiment, the pullout guide with 15000 double strokes, ie a extension and retraction of the pullout guide, was tested for wear.
At the beginning of the measurement, the pull-out rail was subjected several times to pyrolysis cycles of 500 ° C., which were repeated once in each case after 750 double strokes. This serves to simulate the conditions to which the drawer runner is exposed in pyrolysis furnaces.

The pullout guide was loaded during this experiment with a mass of 11 kg and subjected to a total of 100 pyrolysis runs.

The forces which were used to pull out the pullout guide were in the range between 3.5 and 6.5 N, the fluctuations being relatively constant around a mean value of 5.0 N and observed no increase or decrease in the force on average is.

Similar observations can be made with the forces that must be applied to retract the drawer rail. Here, in a range from 1.5 to 4.0 N, comparably high fluctuations occur around a mean value of 2.3 N.

The measurement results show a consistent runnability with quiet running with little effort (classification 1-7, where 1 of the highest running quality, with smooth running, and 7 of the lowest running quality, with blocking and halting run, corresponds).

The measurement results also show a constant mobility with quietly pounding barrel (classification 1-7, where 1 is defined as discreet noise and 7 as disturbing, booming noise).

From material trials, the following picture emerged: test number lubrication composition double strokes pyrolysis test result test result 1 BN: C: NO paste 25:25:50 BNC: oil 17500 60 Gi staining of the surface Running test went trouble-free 2 BN: C: Si paste series state degreased 25:25:50 15000 40 Gray coloration of the surface Running test was trouble-free 3 BN: C: NO paste degreased series 48: 48: 4 15000 44 Gray coloration of the surface Running test was trouble-free 4 C: Si: H ₂ O paste series state degreased 36: 2: 62 15000 18 Gray coloration of the surface Running test was trouble-free 5 BN: C: PFPE 25:25:50 15000 40 Graying the surface Running test was trouble-free 6 BN: C: Si paste series state degreased 25:25:50 15000 100 Gi staining of the surface Running test was trouble-free

The compositions which are listed in the table refer in each case to percentage mass fractions. With Si, the percentage mass fractions of silicone oils or silicone pastes were characterized. NO was used to denote the percentage by weight of native oils. PFPE was used to denote the percentage by weight of perfluoroethyloxide oil.

The composition under test number 2 or 6 is particularly preferred. Thus, even after 100 cleaning cycles, according to test number 6, this formulation shows no change in the running properties or runnability.

The silicone oil used in this exemplary composition consists essentially of polydimethylsiloxane, moreover, the particle size of the hexagonal boron nitride used is about 5 microns and the particle size of the graphite used also about 5 microns. A particle size of about 5 microns shows a particularly good lubricating property. Investigated were investigated particle size in the range of 0.1 microns to 8 microns.

Due to the particle size and the roughness of the friction partners, the boron nitride and graphite particles roll into the surface. The rolled-in BNC particles can not be removed from the pull-out guides in the dishwasher after only 100 double strokes. After 25 cleaning applications in the intensive cleaning program, the drawer slides are still fully functional. Thus, a dishwasher resistance is achieved. Household and industrial dishwashers were used to investigate dishwasher safety.

Both the particle size of the boron nitride and of the graphite are subject to a certain fluctuation range. In addition, depending on the composition of the mixtures, the particle size can vary between 0.1-500 μm.

Use of synthetic graphite has proven to be advantageous as it is more uniform in structure and grain size distribution. Preferably, the fraction was used with a particle size of about 5 microns.

As a result, several possibilities for compositions of lubricants in the high-temperature range (in parts by weight w) are stirred up:
1.Mischung: graphite 20-50%, preferably 30-40% silicone oil 0.5-5%, preferably 1-3% water 45-79.5%, preferably 57-69%
2.Mischung: boron nitride 10-40%, preferably 20-30% graphite 10-40%, preferably 20-30% silicone oil 20-80%, preferably 40-60% (reached viscosity is 1000 mm ² / s)
3.Mischung: boron nitride 10-40%, preferably 20-30% graphite 10-40%, preferably 20-30% Perfluorethyloxidöl 20-80%, preferably 40-60%
4.Mischung: boron nitride 10-40%, preferably 20-30% graphite 10-40%, preferably 20-30% olive oil 20-80%, preferably 40-60% (reached viscosity is 100 mm ² / s)
5.Mischung: boron nitride 30-70%, preferably 40-60% graphite 30-70%, preferably 40-60% olive oil 1-10%, preferably 1-5%
6. mixture: boron nitride 15-35%, preferably 20-30% graphite 15-35%, preferably 20-30% Perfluorethyloxidöl 30-70%, preferably 40-60%
7. mixture: graphite 30-70%, preferably 40-60% silicone oil 30-70%, preferably 40-60%
8. mixture: boron nitride 30-70%, preferably 40-60% Perfluorethyloxidöl 30-70%, preferably 40-60%
9. mixture: boron nitride 30-70%, preferably 40-60% silicone oil 30-70%, preferably 40-60%

As an alternative to olive oils, other oils with a high content of unsaturated fatty acids and other native oils can also be used.

The viscosity of the liquid lubricants can be varied without departing from the scope of the inventive concept.

Other greases that meet US Food and Drug Administration FDA purity requirements under 21 CFR 178.3570 can also be used. The same applies to greases that have been registered by the NSF (National Sanitary Foundation) in category H1 - in this case, reference is additionally made to ISO 21469.
Thus, the lubricant meets the testing standards of DIN 21469: 2006 as a food grade lubricant.

LIST OF REFERENCE NUMBERS

1

pull-out guide

2

guide rail

3

runner

4

rolling elements

5

Rolling Element

6

career

7

lubricant

8th

career

Claims (10)

1. A drawer slide (1), especially for an oven, comprising at least two rails (2, 3) that can move relative to one another and are guided on each other by way of bearing elements (4), characterized in that the tracks (6, 8) of the bearing elements (4) are lubricated at the rails (2, 3) at least in areas by way of a lubricant (7), wherein the lubricant (7) contains a mixture of boron nitride and graphite and is applied as a sliding paste.
2. A drawer slide according to claim 1, characterized in that the lubricant (7) contains a polysiloxane.
3. A drawer slide according to claim 1 or 2, characterized in that boron nitride is contained in a mass fraction w (boron nitride) of between 5% and 30%, preferably a mass fraction w (boron nitride) of between 10% and 20%.
4. A drawer slide according to one of the claims 1 to 3, characterized in that the lubricant (7) contains a food-grade grease.
5. A drawer slide according to one of the claims 1 to 4, characterized in that the lubricant (7) contains a silicone compound as a silicone paste, silicone grease and/or silicone oil.
6. A drawer slide according to one of the claims 1 to 5, characterized in that the lubricant (7) contains molybdenum sulphide.
7. A drawer slide according to one of the claims 1 to 6, characterized in that the lubricant (7) has a temperature resistance of over 600°C.
8. A drawer slide according to one of the claims 1 to 7, characterized in that the lubricant (7) is thixotropic.
9. A drawer slide according to one of the claims 1 to 8, characterized in that the lubricant (7) has a viscosity of 50 to 1500 mm²/s, preferably 100 to 1000 mm²/s.
10. A drawer slide according to one of the claims 1 to 9, characterized in that the lubricant (7) has a surface tension of 20 to 22 mN/m, preferably 20.9 to 21.2 mN/m, at 25°C.

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