ROLLER BEARING

Abstract: In rolling bearings the phenomena "breathing", i.e. in­ crease and decrease of damp volume inside the bearing mainly due to temperature circumstances, is wellknown. In view of this phenomena the lip-seal (9′) of the (mechanical) seal (9) will slightly but regular be pushed from its support i.e. the bearing innerring (2), which leads to escape of lubricant. To effectively avoid this leakage a second seal (5) having magnetic properties is added to the (mechanical) seal (9). This magnetic seal (5) is provided with grooves (6) and pro­ jections (7) adjacent the sealing side of the seal arrangement (5,9). Mainly between said projections (7) magnetic fluid (8) is applied and fixed thereto due to the magnetic properties of the seal arrangement. Breathing inside the bearing (1, 2, 3) will now be resiliently received by said magnetic seal arrangement (5), without influencing the function of the seal­ lip (9), thus preventing leakage of the lubricant.

Description: The invention concerns a rolling bearing comprising an outer race and an inner race situated coaxially therein, and a row of rolling members situated in the annular space between these races and a seal for sealing the annular space between the races from the surroundings on one side of the rolling members, to prevent a lubricant present in this space from escaping to the outside and, on the other hand, to prevent foreign matter such as dust particles, water or similar impurities from penetrating into the annular space from outside, which seal is generally annular and is fixed relative to one of the races whereby the annular seal has an end portion at a short distance from the other race, and the slot-shaped annular space thus formed between the seal and the said race contains a quantity of magnetic fluid, where means forming a magnetic field are present, and whereby such fluid is held within the slot-shaped annular space. Such a rolling bearing is disclosed by the US-A-4.531.846. In rolling bearings of this type the problem still arises that penetration of impurities from the outside into the annular space may occur, which may be detrimental to a good sealing effect of such fluid. The object of the invention is to procure a rolling bearing of the type mentioned wherein the above described disadvantage does not appear. This object is accomplished in that in the rolling bearing pursuant to the invention to said sealing means a second seal is arranged outside and adjacent said first sealing means whereby said second seal comprises a sealing lip which rests against said inner bearing race. In a rolling bearing designed in this way the seal obtained by the magnetic fluid withstands any difference in vapor pressure between the inner side of the bearing and the surroundings, so that the sealing lip always remains in sealing contact with the race concerned, and, on the other hand, the magnetic fluid is protected against penetration into it from the outside of impurities which may be detrimental to a good sealing effect of such fluid. By this means, therefore, leakage due to "breathing" of the bearing is no longer possible. The bearing may be further improved in that the second seal is made of a self-lubricating elastomeric material in order to obtain very little friction between said sealing lip and the inner bearing race. Since in a bearing pursuant to the invention a complete seal from the surroundings is obtained, where periodic exchanges of air or vapor between the surroundings and the inner side of the bearing are thus unable to occur, the annular space between the races, in addition to the lubricant, may advantageously contain an inert gas instead of air, whereby oxidation of the lubricant and components of the bearing is prevented. A magnetic fluid is known per se and consists of a colloidal suspension of extremely small particles, in the order of magnitude of 7-10 µm, of a material having paramagnetic properties, usually magnetized, in a fluid consisting mostly of a hydrocarbon, these particles being clad with a thin layer of a material that prevents flocculation of the particles. The particles normally move constantly in the fluid as a result of thermal agitation and Brownian movement, but when such a magnetic fluid is located in a magnetic field the particles orient themselves in essentially one direction, whereby the fluid acts like soft iron. It is noted further that US-A-4043612 discloses that a magnetic lubricant may be used in a bearing design where such lubricant is placed under pressure during rotation by a pumping action obtained by means of grooves, and such lubricant, upon stanstill of the bearing, is held within the bearing by means of a magnetic field. The invention is described in detail with reference to the drawing, wherein a portion of the rolling bearing pursuant to the invention is shown in axial cross section. As illustrated in the drawing, the rolling bearing comprises an outer race 1 and an inner race 2 situated coaxially therein, and a row of rolling members 3 situated in the annular space between these races, which are kept apart by a cage 4. The annular space between the races 1 and 2 is sealed off from the surroundings by the sealing rings 5 which are designed as magnets with the north and south poles indicated. In the end portion of the sealing ring 5 directed toward the inner race 2 is provided a plurality of grooves, so that between these grooves are formed ridges 7 which lie at a short distance from the inner race 2. The slot-shaped annular spaces thus formed between the sealing ring 5 and the inner race 2 contain a quantity of magnetic fluid 8, which fluid is held in these slot-shaped spaces by the magnetic field formed by the sealing ring 5, the lines of force of said magnetic field being indicated by the arrows A. To the sealing ring 5 is attached a seal 9 having a sealing lip 9′, which lip 9′ rests springily against the outer race 1. The seal 9 is preferably formed of a self-lubricating elastomeric material so that only very little friction will occur between the sealing lip 9′ and the inner race 2 upon rotation of one of the races 1, 2.

Claims: 1. A rolling bearing comprising an outer race (1) and an inner race (2) situated coaxially therein, and a row of rolling members (3) situated in the annular space between these races and a seal (5) for sealing the annular space between the races from the surroundings on one side of the rolling members, to prevent a lubricant present in this space from escaping to the outside and, on the other hand, to prevent foreign matter such as dust particles, water or similar impurities from penetrating into the annular space from outside, which seal is generally annular and is fixed relative to one of the races (1) whereby the annular seal (5) has an end portion at a short distance from the other race (2), and the slot-shaped annular space thus formed between the seal (5) and the said race (2) contains a quantity of magnetic fluid (8), where means (5) forming a magnetic field are present, and whereby such fluid (8) is held within the slot-shaped annular space, characterized in that to said sealing means (5) a second seal (9) is arranged outside and adjacent said first sealing means (5) whereby said second seal (9) comprises a sealing lip (9′) which rests against said inner race (2). 2. Rolling bearing according to claim 1, characterized in that the seal (9) is made of a self-lubricating elastomeric material in order to obtain very little friction between said sealing lip (9′) and said inner race (2). 3. Rolling bearing according to claim 1 or 2, characterized in that the (annular) space between said races (1, 2) and sealing means (5, 9) contains an inert gas in addition to the lubricant.

Inventors: GABELLI, ANTONIO
Applicants: SKF INDUSTRIAL TRADING & DEVELOPMENT COMPANY B.V.
Application year: 1987
Main classification: F16C33
IPC codes: F16C33, F16J15