EP2338003A1 - Fitting for household appliances and lubricant - Google Patents

Abstract

The invention relates to a fitting, for example a drawer slide for household appliances, comprising two rails that can move relative to one another and that are slid toward one another by way of rolling elements. In the process, the tracks (6, 8) of the rolling element (4) are lubricated at the rails (2, 3) at least in areas by way of a lubricant (7) comprising a boronitride and/or polysiloxane. This facilitates an efficient use of lubricant (7), which is also stable at high temperatures. The invention further relates to a lubricant, in particular for fittings in household appliances, that is stable at temperatures of over 600°C and can be used in wet and humid areas.

Description

 Hardware for household appliances and lubricants

The present invention relates to a fitting, for example a pull-out guide, 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 rolling elements

Lubricant.

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 loading 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 drawer guide, which always has consistently good lubricating and sliding properties below room temperature as well as at temperatures up to 600 ⁰ C. Furthermore, a chemical resistance of the coating and a cost-effective production and application of the same is required.

EP 1589291 A1 discloses a generic pull-out guide which has rolling elements mounted in a rolling cage. In this case, the Wälzkörperkäfig on a lubricating layer, which u.a. the inclusion of boron nitride in a paint provides. The coating extends over the entire surface of the rolling element cage. 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 as in EP 1589291 A l is therefore not useful.

The object of the present invention is to provide a fitting, in particular a pull-out guide, and a lubricant which, even when using rigens and when using high temperatures over a long period of time a smooth running of the rails allows.

This object is achieved by a drawer slide with the features of claim 1, a lubricant with the features of claim 16 and a

Fitting solved with the features of claim 27.

By means of the solution according to the invention, the lubricant contained in the boron nitride and / or polysiloxane is applied to the significantly smaller areas of the raceways at least in regions. 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 ⁰ C, boron nitride converts to cubic ß-boron nitride.

The application of the lubricant is preferably carried out as a lubricating paste, suspension or in powder form. This allows the lubricant to be used for industrial series production. In addition, these application forms enable 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 grease, 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 further lubricant component and high-temperature fat as matrix and carrier additionally support the sliding and lubricating effect of boron nitride. While graphite stored at longer heating times

Water molecules gives off, which reduces its lubricating effect for a short time, this remains with boron nitride even at high temperatures, in particular over 200 ⁰ C. Furthermore, the lubricant may advantageously contain as polysiloxane preferably a Siükonpaste, a silicone grease and / or a silicone oil which does not burn at temperatures above 300 ⁰ C, so for example in the pyrolysis of ovens. The consistency between these embodiments 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 ⁰ C.

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

In an advantageous embodiment, the lubricant has a temperature resistance of above 600 ⁰ 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 mmVs, whereby an application of the low to medium viscosity mass can be carried out without the lubricant flowing out at the ends of the webs can.

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 from 20.9 to 21 _s, 2 mN / m allows the complete wetting of a large-area substrate upon application despite a 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 with the help of the carrier material, the boron nitride and graphite content in the lubricant mixture evenly into the

Runways of the pullout guide distributed. 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 stress before the pyrolysis of the boron nitride / graphite content is incorporated in the mixture in the tracks of the statement leadership.

The lubricant according to the invention is particularly suitable for the lubrication of fittings in household appliances such as ovens or refrigerators, through its range of use of about - 5O ⁰ C to about 600 ⁰ C. Also for other areas is the

Application of the lubricant 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 l become necessary. 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.

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

Figure 1 is a perspective view of a pullout guide in the retracted

Position;

Figure 2 is a perspective view of the pullout guide of Figure 1 in the extended position;

Figure 3 is an exploded view of the pullout guide of Figure 1;

Figure 4 is a sectional view of the pullout guide of Figure 1, and

FIG. 5 is a sectional view of the pullout guide of FIG. 1.

Figure 6 is a diagram illustrating the erfmdungsbedingten 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

Runways 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.

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

Applying the boron nitride as a sliding paste or suspension

• Application of the boron nitride in powder form by vibratory grinding

• Mixtures of boron nitride and high-temperature grease, leaving the boron nitride as a solid lubricant in the raceways after pyrolysis • Mixtures of boron nitride with molybdenum sulfide, graphite and PTFE are conceivable

Blends 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 ° / oC to 80% BN / 20% C leads to a powder with different gray levels. The mixture BNC has tribological and other physical properties. metallic and chemical properties, which makes it possible to use them as dry lubricants with hygroscopic properties in the household appliance sector.

The powder has sufficient sliding properties after high temperature stress as in the pyrolysis operation (self-cleaning method in the oven to

600 ⁰ C) can occur, 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 wrasenhaltigen range up to 100 ⁰ C, as well as with high air humidity the main lubricating effect lies with the graphite, which its

Lubricating effect in the presence of moisture best unfolded. In the low temperature range and temperatures above 400 ⁰ 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 together with a wet carrier such as water, alcohol or food oils and fats, a suspension (heterogeneous solid / liquid mixture), a dispersion (homogeneous solid / liquid mixture) or an emulsion (depending on the wet carrier) results 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 as well as cubic

Modifications of their crystal structure, wherein the hexagonal modification of the carbon is widely known as graphite and the 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 + 22O ⁰ 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 mm7s, 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 lubricants without added solids.

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 ⁰ 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 ⁰ C;

• the pour point according to DIN 51583 is between -50- 10 ⁰ C, preferably -30 hiss - -1 O ⁰ C;

• The flash point is according to DIN 51376 between 230-370 ⁰ C, preferably 275-321 ⁰ C.

• the ignition point is in accordance with DIN 51794 over 400 ⁰ C, preferably about 42O ⁰ C.

• the dropping point is in accordance with ASTM-D-445 of between -80 ⁰ C - -3O ⁰ C, preferably between -65 ⁰ C and -50 ⁰ C. Additional disturbing noises, such as squeaking, do not occur when using BNC-Si lubricants. Here, a high pressure absorption capability comes into play. Thus, a provided with BNC silicone lubricant drawer slide even under high mass load, for example by Gargutträger, consistently good sliding properties.

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 for the application of a complete wetting of a large area underlay. In order to make the viscosities of BNC-Si lubricants variable, other solvents can be added to the lubricant.

A BNC-Si lubricant layer is highly water-repellent and chemically inert to vegetable oils, mineral oils, gases, dilute acids and alkalis as well as most aqueous solutions. Due to its highly hydrophobic properties, bacterial or fungal attack of the lubricant is also ruled out. 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 the

FD A regulations and are therefore suitable for use in the food industry.

In addition, according to the Food and Consumer Goods Act consist (§5, par. 1 no. 1 from 15.08.1974 BGBL.lS 1945) no concern for the use of silicone carriers and Phenylmethylsilikonölen, having a viscosity of> 100 MMCs at 20 ⁰ C, in the food industry. FIG. 6 shows measured values in the form of a diagram, which can be used to describe the properties of a BNC-Si paste which has been applied as a lubricant to an electrodeposited aluminum surface.

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:

a) force when pulling out the pullout guide (Fa) in N b) force when retracting the pullout guide (Fe) in N c) running quality, assessed by a trained inspector ordinal scale d) noise, assessed by a trained inspector by means Ordinalskala

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 repeatedly subjected to pyrolysis cycles of 500 ^° C., which were each repeated once 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 1 1 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 of 1.5 to 4.0 N, comparably high fluctuations occur around a mean value of 2.3 N. The measurement results show a consistent running quality with quiet running with little effort (classification 1-7, where Ider the highest running quality, with smooth running, and 7 the lowest running quality, with blocking and halting run, corresponds).

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

From material trials, the following picture emerged:

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 is in this exemplary composition in

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 .mu.m, a particle size of about 5 microns shows a particularly good lubricating property. Investigated were investigated particle sizes 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 surfaces. 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 intensive care

Cleaning program, the pullout guides are still fully functional. Thus, a dishwasher resistance is achieved. Household and industrial dishwashers were used to investigate dishwasher safety.

Both the particle sizes 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 sizes may vary between 0.1-1.500 μm.

Use of synthetic graphite has proven to be advantageous as it is more uniform in structure and grain size distribution. Preference was given to

Fraction having a particle size of about 5 microns used.

In the following, several possibilities for compositions of lubricants in the high temperature range (in mass fractions w) are listed:

1, mixture:

Graphite 20-50%, preferably 30-40%

Silicone oil 0.5-5%, preferably 1 -3%

Water 45-79.5%, preferably 57-69% 2. Mixture: boron nitride 10-40%, preferably 20-30% graphite 10-40%, preferably 20-30% silicone oil 20-80%, preferably 40-60%

(reached viscosity is 1000 mnWs)

3. Mixture: boron nitride 10-40%, preferably 20-30%

Graphite 10-40%, preferably 20-30% Perfluoroethyloxide oil 20-80%, preferably 40-60%

4. Mixture: 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)

S.Mixture: 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%

Perfluoroethyloxide oil 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%

Perfluoroethyloxide oil 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 lubricant can be varied without departing from the scope of the inventive concept.

Other greases meeting US FDA purity requirements. Food and Drug Administration according to Directive 21 CFR 178.3570 can also be used. The same applies to greases that have been registered by the NSF (National Sanitary Foundation) in the category Hl - 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 pullout guide

2 guide rail

3 track

4 rolling elements

5 rolling element cage

6 career

7 lubricants

8 career

Claims

claims 1. pullout guide (1), in particular for a baking oven, with at least two relatively movable rails (2, 3) which are guided on one another via rolling elements (4), characterized in that the raceways (6, 8) of Rolling elements (4) on the rails (2, 3) at least partially lubricated by a boron nitride and / or a polysiloxane containing lubricant (7). 2. pullout guide according to claim 1, characterized in that the Lubricant (7) is applied as a sliding paste, dispersion or suspension. 3. pullout guide according to claim 1, characterized in that the lubricant (7) is powdery. 4. pullout guide according to one of claims 1 to 3, characterized in that the lubricant (7) contains a mixture of boron nitride and graphite. 5. pullout guide according to claim 4, characterized in that boron nitride in a mass fraction w (boron nitride) between 5% to 30%, preferably a mass fraction w (boron nitride) between 10% to 20% is included. 6. pullout guide according to one of claims 1 to 5, characterized marked, that the lubricant (7) contains a high-temperature grease. 7. pullout guide according to one of claims 1 to ό, characterized in that the lubricant (7) contains a food fat. 8. pullout guide according to one of claims 1 to 7, characterized in that the lubricant (7) contains a silicone compound as a silicone paste, a silicone grease and / or a silicone oil. 9. pullout guide according to one of claims 1 to 8, characterized in that the lubricant (7) contains molybdenum sulfide 10. pullout guide according to one of claims 1 to 9, marked thereby, that the lubricant (7) contains polytetrafluoroethylene (PTFE) 1 1. pullout guide according to one of claims 1 to 10, characterized in that the lubricant (7) is incorporated by vibratory grinding, 12. pullout guide according to one of claims 1 to 1 1, characterized in that the lubricant (7) has a temperature resistance of about 600 ⁰ C. 13. pullout guide according to one of claims 1 to 12, characterized in that the lubricant (7) is thixotropic. 14. pullout guide according to one of claims 1 to 13, characterized in that the lubricant (7) has a viscosity of 50-1500 mm Vs, preferably 100-1000 mmVs. 15. pullout guide according to one of claims 1 to 14, characterized in that the lubricant (7) has a surface tension at 25 ° C of 20-22 mN / m, preferably 20.9-21, 2 mN / ra. 16. lubricant, in particular for fittings in household appliances, characterized in that the lubricant (7) contains boron nitride and / or a polysiloxane and a temperature resistance of - 5O ⁰ C to about 600 ⁰ C has. 17. A lubricant according to claim 16, characterized in that the Lubricant (7) is powdery. 18. A lubricant according to claim 16, characterized in that the Lubricant (7) is applied as a sliding paste, dispersion or suspension. 19. A lubricant according to any one of claims 16 to 18, characterized in that the lubricant (7) contains a mixture of boron nitride and graphite. 20. A lubricant according to any one of claims 16 to 19, characterized in that boron nitride in a mass fraction w (boron nitride) between 5% to 30%, preferably a mass fraction w (boron nitride) is contained between 10% to 20%. 21. Lubricant according to one of claims 16 to 20, characterized in that the lubricant (7) contains a silicone compound as a silicone paste, a silicone grease and / or a silicone oil. 22. Lubricant according to one of claims 16 to 21, characterized in that the lubricant (7) contains polydimethylsiloxane. 23. Lubricant according to one of claims 16 to 22, characterized in that the lubricant boron nitride and / or graphite particles, in the size range 0.1 microns to 8 microns. 24. Lubricant according to one of claims 16 to 23, characterized in that the lubricant is essentially a mixture of boron nitride, graphite and silicone oil and / or silicone paste and / or silicone grease 25. A lubricant according to claim 24, characterized in that boron nitride in a mass fraction w (boron nitride) between 20% to 30%, preferably a mass fraction w (boron nitride) of 25%, graphite in a mass fraction w (graphite) between 20% to 30 %, preferably a mass fraction w (graphite) of 25%, and silicone oil in a mass fraction w (silicone oil) of between 45% to 55%, preferably a mass fraction w (silicone oil) of 50%. 26. A lubricant according to any one of claims 23 to 25, characterized in that the boron nitride and / or graphite particles, after incorporation of these Particles in the surfaces of the friction partners, household and indus- trial dishwashers are resistant. 27. Fitting, in particular for household appliances, characterized in that the fitting with a lubricant (7) contains the boron nitride and / or a polysiloxane and a temperature resistance of - 50 ⁰ C has over 600 ⁰ C has been lubricated. 28. Fitting according to claim 27, characterized in that the fitting with a lubricant (7) is lubricated according to one of claims 16 to 26. 29. Fitting according to claims 27 to 28, characterized in that the Fitting is a hinge, for example, for a household appliance door. 30. Fitting according to claims 27 to 28, characterized in that the Fitting is a flap fitting, for example, for a household appliance flap. 31. Fitting according to claims 27 to 28, characterized in that the fitting is a pullout guide, for example, for food support in food preparation equipment or for extracts in food storage equipment.