The present invention concerns a lubrication capsule and a machine element comprising at least one such lubrication capsule. The present invention also concerns a method for 5 lubricating a machine element using at least one such lubrication capsule.

BACKGROUND OF THE INVENTION

An automatic lubrication system, often referred to as a centralized lubrication system, generally comprises a controller or timer, a pump and lubricant reservoir, metering valves 10 and fittings, and supply and feed lines, typically delivers a controlled amount of lubricant, such as grease or oil, to one or more specific locations in a machine while the machine is operating, at specific times from a central location.

The term grease, in the context of lubrication, is used to describe a semi-solid lubricant 15 consisting of a thickener, typically a soap, emulsified with mineral or vegetable oil and/or other fluid lubricant. Grease possesses a high initial viscosity, which upon the application of shear, drops to give the effect of oil lubrication of approximately the same viscosity as the base oil used in the grease. Greases are applied to machine elements that can only be lubricated infrequently and where a lubricating oil would not stay in position.

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Grease also protects the machine elements that it lubricates against corrosion and wear, it helps to dissipate heat, seal out solid and liquid contamination, and reduces noise. Adequate lubrication allows for smooth continuous operation of equipment, with only mild wear, and without excessive stresses or seizures at components such as bearings. When 25 lubrication fails, components can rub destructively over each other, causing damage, heat, and failure. Lubrication failure can be caused by insufficient lubricant quantity or viscosity, deterioration due to prolonged service without replenishment, excessive temperatures, contamination with foreign matter, the use of an incorrect grease for a particular application and/or over-lubricating.

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To ensure that a machine element is correctly lubricated, the grease used has to be precisely selected for the particular application and applied in the right amount, at the right frequency and to the right place(s) in the machine elements. Factors influencing the choice of grease for a bearing application for example, include the bearing's rotational speed, service temperature range, running noise requirements, re-lubrication intervals, sealing, starting torque, load and running conditions and environmental influences. Over time, the grease may leak, evapourate and/or harden. Oil may be depleted from the grease leaving a thick waxy substance with little or no ability to lubricate. New grease may be applied, however, to prevent premature wear and damage, manufacturers recommend that old grease is removed and replaced with new grease on a periodic basis, which can be a complex and time consuming process since it often requires equipment to be dismantled and carefully cleaned.

SUMMARY OF THE INVENTION

An object of the invention is to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

At least one of these objects is achieved by a capsule containing at least one component of a lubricant for a machine element, whereby the capsule comprises an external wall comprising a first substance that is arranged to perish (i.e. to become at least partly destroyed or ruined whereby the contents of the capsule will no longer be encapsulated therein) during the use of the machine element when the capsule is placed in and/or around the machine element and/or into lubricant being used to lubricate the machine element. Such a capsule may for example contain a liquid, semi-liquid or solid lubricant (such as a dry powder) and/or lubricant part (such as the liquid lubricant part of a grease) and/or a lubricant additive. The capsule may for example be in the form of a pellet, tablet or spheroid and/or may have a hard or soft external wall, such as an external wall made from an aqueous solution of a gelling agent such as animal protein (gelatin), a plant polysaccharide or its derivative, such as a carrageenan and/or a modified form of starch and cellulose. The external wall may comprise a plasticizer such as glycerin and/or sorbital. The external wall itself may comprise said at least one component of a lubricant. The capsule may be of any suitable size and shape, depending on the application, ranging from a few mm in maximum transverse dimension to a few centimeters in maximum transverse dimension. According to an embodiment of the invention the capsule comprises at least one inner encapsulating wall comprising a second substance that is arranged to perish during the use of the machine element when subjected to a first condition. A capsule may namely comprise one or more inner encapsulating walls comprising (i.e. containing and/or comprising) the same, or a different at least one component of a lubricant.

According to another embodiment of the invention the first substance and/or said second substance is/are oil-soluble, is/are arranged to dissolve on contact with a liquid at a predetermined temperature and/or predetermined pressure, and/or is/are arranged be mechanically destroyed by the machine element.

At least one capsule may namely be added to the lubricant lubricating a machine element and/or placed in and/or around the machine element. The at least one capsule is arranged to perish if/when needed. For example, when a machine element's lubricant that contains or consists of oil reaches a predetermined temperature, an oil-soluble external wall of the at least one capsule may be arranged to perish by dissolving in oil at that temperature. If a capsule comprises at least one inner encapsulating wall comprising a second substance, the second substance may be arranged to dissolve in oil at a different temperature. A capsule may comprise one smaller capsule, or a plurality of smaller capsules of the same size or of a different size, which small capsule(s) is/are arranged to perish under different conditions than the external wall and/or at least one other inner encapsulating wall.

Additionally, or alternatively, a capsule may be arranged to perish by being crushed by the machine element it is lubricating. For example, at least one capsule may be provided in and/or around the machine element (such as between a rolling element bearing's rolling elements and outer ring) before it is put into use so that the machine element will be lubricated once it is put into use, i.e. the lubricant will fill the spaces in the machine element not already occupied by lubricant. Additionally, or alternatively at least one capsule may be supplied to a machine element during its use to lubricate/re-lubricate the machine element or to add at least one component of a lubricant, such as an additive, to the lubricant lubricating the machine element.

According to a further embodiment of the invention the capsule comprises a plurality of inner encapsulating walls and a number of the plurality of inner encapsulating walls comprises the second substance that is arranged to perish when subjected to a first condition, and a number of the plurality of inner encapsulating walls comprises a third substance that is arranged to perish when subjected to a second condition. The external wall of a capsule may be arranged to have a first thickness and at least one inner encapsulating wall of a capsule may be arranged to have a second thickness, whereby the second thickness may be the same as or different to the first thickness. The thickness and/or composition of an external wall and/or an inner encapsulating wall need not necessarily be uniform.

According to an embodiment of the invention the capsule comprises a fluid lubricant, such as mineral oil, synthetic oil and/or vegetable oil, a polvalphaolefin. an ester, a polvether. If grease is used as to lubricate a machine element, re-lubricating the machine element is simplified since old grease does not have to be removed from a machine element and the amount of waste grease is reduced since the grease's thickener is re-used.

According to another embodiment of the invention the capsule comprises at least one of the following: a polymeric thickener, polypropylene, polyethylene, polyalkylene glycol, polyethylene glycol, polyolefin phenol, lanolin, lanoline polyethylene glycol, polyoxyethylene lanolin, silicon oil, ionic soap, urea soap, metal organic soap.

According to a further embodiment of the invention the capsule comprises at least one of the following: a tackifier, an elastomer, an anti-wear additive, an anti-corrosion additive, an EP additive, an anti-oxidant. Some greases are labeled "EP", which indicates "extreme pressure". Under high pressure or shock loading, normal grease can be compressed to the extent that the greased parts come into physical contact, causing friction and wear. EP grease contains solid lubricants, usually graphite and/or molybdenum disulfide, to provide protection under heavy loadings. The solid lubricants bond to the surface of metal components, and prevent metal-to-metal contact and the resulting friction and wear when the lubricant film gets too thin.

Teflon may for example be added to improve the lubricating properties of the lubricant. Glycerol and sorbitan esters may be added to lubricant that is intended to be used in low temperature conditions. Copper may be added to lubricant intended for a high pressure applications. According to an embodiment of the invention the lubricant comprises a thickener comprising at least one polvolefin component, for example comprising polyethylene or polypropylene or mixtures of these substances, at least one fluid lubricant component such as mineral oil, vegetable oil, synthetic oil-like polvalphaolefins. esters or polvethers. and at least one additive component which is selected from the group antioxidants, corrosion inhibitors, anti-wear agents or extreme pressure/load carrying capacity increasing additives. The content of the thickener component(s) may be between 5% and 30% by weight, preferably between 9 and 15% bv weight, the content of the fluid lubricant(s) is between 60% and 90% by weight and the additive component(s) by weight between 0.2 and 15%. preferably between 1 and 8% bv weight- According to an embodiment of the invention the lubricant comprises a high molecular weight component and a low molecular weight component. For example, the thickener may comprise a mixture of a) a (co- or homo-)polvmer of propylene with a weight average molecular weight greater than 200.000 and (b) a (co- or homo-)polvmer of propylene with a weight average molecular weight less than 100,000. The ratio between the high molecular weight component and the low molecular weight component may be 1 :40 - 1 :5. preferably 1 :25 - 1 :15, more preferably 1 :19. The low molecular weight component may be a polypropylene homopolvmer. The low molecular weight component may have an average molecular weight between 50.000 and 100.000 with a melt flow rate (ASTM D- 1238) of 500-1000. preferably 750-850. The high molecular weight component may be a polypropylene homopolvmer or a propylene/ethylene-copolvmer. The high molecular weight component may have an average molecular weight of 200.000-250.000 and a melt flow rate (ASTM D-1238) of 1.5-15. preferably 1.5-7.

According to another embodiment of the invention the lubricant comprises a mineral oil, at least one of the following: a thickening agent, oil-soluble polypropylene, oil-soluble propylene or mineral, metal soaps (soap-salt thickener), oil-soluble polypropylene, oil- soluble propylene or amorphous polvolefine polymers or semicrvstalline polvolefine polymers e.g. isotactic or atactic polvolefin polymers.

Esters can effect solubility and boost oil-solubility of additives and thickening agents like polymers. Esters may be derived from carboxylic acids, branched, unbranched. straight or with cyclic alkyl goup. aryl. alkaryl or aralkyl group group with 1 - 30 carbons, cyclic fatty esters, alkyl esters, saturated and unsaturated esters, diesters (from dicarboxylic organic compounds), disebacic acide esters, polvol esters, synthetic esters, phthalate esters, carboxylic acid esters .Alkylated napthlenes may be used as a synthetic fluid lubricant.

According to an embodiment of the invention the lubricant may comprise a paraffin based wax of a carbon chain length up to C40, either in pure form or in mixtures of different alkenes. or mixed with other polvolefin polymers (polyethylene) or ester waxes like cetyl myristoleate esters or cetyl palmitate esters. Waxes are natural, organic compounds that characteristically consist of long alkyl chains. The present invention also concerns a machine element containing at least one capsule according to any of the embodiments of the invention. The machine element is at least part of a one of the following: a shaft, coupling, key, spline, gear, fastener, spring, seal, belt, clutch, brake, chain, or a bearing element, such as a ball bearing, a roller bearing, a needle bearing, a tapered roller bearing, a spherical roller bearing, a toroidal roller bearing, a ball thrust bearing, a roller thrust bearing, a tapered roller thrust bearing, a wheel bearing, a hub bearing unit, a slewing bearing, a ball screw, or a component for an application in which it is subjected to alternating Hertzian stresses, such as rolling contact or combined rolling and sliding and/or an application that requires high wear resistance and/or increased fatigue and tensile strength.

The present invention also concerns a method for lubricating a machine element, which comprises the steps of placing at least one capsule that comprises an external wall comprising a first substance that is arranged to perish during the use of the machine element when the capsule is placed in and/or around the machine element and/or into lubricant being used to lubricate the machine element, in and/or around the machine element and/or into lubricant being used to lubricate the machine element. The at least one capsule may be placed in and/or around the machine element and/or into lubricant being used to lubricate the machine element before and/or during and/or after (i.e. during a pause in operation or a maintenance/repair stop for example) the use of the machine element.

Further embodiments of the method according to the present invention are recited in the dependent method claims. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be further explained by means of non-limiting examples with reference to the appended figures where; Figure 1 shows a bearing that is lubricated and/or re-lubricated using at least one capsule according to an embodiment of the invention, and

Figures 2 & 3 show capsules according to embodiments of the invention. It should be noted that the drawings have not been drawn to scale and that the dimensions of certain features have been exaggerated for the sake of clarity.

DETAILED DESCRIPTION OF EMBODIMENTS

Figure 1 schematically shows an example of a bearing 10, namely a rolling element bearing, that may range in size from 10 mm in diameter to a few metres in diameter and have a load-carrying capacity from a few tens of grams to many thousands of tonnes. The bearing element 10 may namely be of any size and have any load-carrying capacity. The bearing element 10 has an inner ring 12, an outer ring 14 and a set of rolling elements 16. Prior to the use of the bearing 10, a suitable lubricant, such as grease, is applied between the rolling elements 16 and the innner ring 12 and outer ring 14 to lubricate the bearing 10. The grease may for example comprise a thickener, such as at least one of the following: a polymeric thickener, polypropylene, polyethylene, polyalkylene glycol, polyethylene glycol, polyolefin phenol, lanolin, lanoline polyethylene glycol, polyoxyethylene lanolin, silicon oil, ionic soap, urea soap, metal organic soap. The thickener may for example comprise polypropylene having both molecules of a high molecular weight and molecules of a low molecular weight. The grease may also comprise a fluid lubricant comprising at least one of the following: mineral oil, synthetic oil and/or vegetable oil. The grease may for example comprise 60-90% of the fluid lubricant. For example, the optimum grease for the application in which the rolling element bearing 10 is to be used comprises 85% mineral oil and 15% soap.

At least one capsule 18 according to an embodiment of the invention may be used to lubricate and/or re-lubricate the bearing 10. At least one capsule 18 may namely be placed between the inner ring 12 and the outer ring 14 of the bearing 10 before, during and/or after (during a pause in operation or a maintenance/repair stop for example) the use of the bearing 10. During the use of the bearing 10, analysis means may for example be used to determine which component of the grease that is being used to lubricate the bearing 10 has been depleted. For example, one or more sensors of an analysis means may determine that the grease composition in or around the bearing 10 has changed during the use of the bearing and for example comprises 70% mineral oil and 30% soap, i.e. mineral oil has been depleted. One or more capsules containing an amount of mineral oil to return the lubricant to its original composition (85% mineral oil and 15% soap) may then be added to the lubricant lubricating the machine element and/or be placed in/around the machine element. Furthermore, a sensor of the analysis means may also be arranged to determine whether there is an increased amount of iron in the lubricant being used to lubricate the machine element, indicative of rust in some part of the machine comprising the machine element. One or more capsules comprising an anti-corrosion additive may then be added to the lubricant lubricating the machine element and/or be placed in/around the machine element. Figure 2 shows a capsule 18 containing at least one component 20 of a lubricant for a machine element, the at least one component 20 may for example be mineral oil containing an anti-corrosion additive. The capsule 18 comprises an external wall 22 comprising a substance that is arranged to perish during the use of the machine element when the capsule 18 is placed in and/or around the machine element and/or into lubricant being used to lubricate the machine element, and/or when the capsule 18 has been subjected to a particular condition.

In the illustrated embodiment the capsule 18 also comprises an inner encapsulating wall 24 comprising a second substance that is arranged to perish during the use of the machine element when subjected to a first condition. The inner encapsulating wall 24 may contain and/or comprise another component 26 of a lubricant such as mineral oil of a different composition to that contained immediately inside the capsule's external wall 22. The first substance and the second substance may be oil-soluble and arranged to dissolve on contact with oil at a pre-determined temperature and/or predetermined pressure for example. For example, the external wall 22 may be arranged to dissolve in oil at 50°C and the inner encapsulating wall may be arranged to dissolve in oil at 100°C. A capsule 18 according to the present invention may comprise any number of inner capsules placed one inside the other. Figure 3 shows a capsule 18 that comprises an external wall 22 comprising a first substance that is arranged to perish when subjected to a particular condition and a plurality of inner encapsulating walls 24 each encapsulating at least one component 26 of a lubricant. The capsule 18 may comprise at least two different types of inner encapsulating walls: a type comprising a second substance that is arranged to perish when subjected to a first condition, and a type comprising a third substance that is arranged to perish when subjected to a second condition.

Further modifications of the invention within the scope of the claims will be apparent to a skilled person.