Rolling element bearing system comprising a filtering seal

Abstract: A rolling element bearing system comprises at least one rolling element bearing (1;34;65 and 66) with an outer race (2;21;51;57) and an inner race (5;20;50;58;69) which enclose a space containing rolling elements (7;23;52;59 and 60), which space is confined to the outside by means of sealing rings (9;24 and 25;28 and 29;35;54 and 55). At least one of the sealing rings and/or one of the races (57) is provided with flow generating means (12;27;31;54-56;61) for feeding a lubricant into said space, as well as filtering means (19;26;30;36;53;64;71) for preventing the ingress of contaminations into said space with said lubricant. Preferably at least one of the sealing rings at its edge which slidably contacts one of the races has a shape which promotes the outflow out of said space towards the outside of said sealing ring during relative movement of said sealing ring and race.

Description: The invention relates to a rolling element bearing system comprising at least one rolling element bearing with an outer race and an inner race which enclose a space containing rolling elements, which space is confined to the outside by means of sealing rings, the rolling element bearing system further comprising filtering means for preventing the ingress of contaminations into said space with a lubricant. Such a rolling element bearing is known from DE-U-9002218. Said known bearing element is provided with discs, which by means of centrifugal forces are able to throw outside lubricant or oil onto a filter element which is in connection with the bearing space. The lubricant thus applied onto the filter element would subsequently enter said bearing space. Although in this way it is possible to apply the lubricant reliably onto the filter element, the subsequent entering of the lubrication into the bearing space is more difficult. For instance, in case an overpressure occurs in the bearing space, it is not likely that any lubricant will penetrate therein. The object of the invention is therefore to provide a rolling element bearing providing a reliable lubricant of oil feed into its bearing space. This object is achieved in that at least one of said sealing rings and/or one of the races is provided with flow generating means for pumping said lubricant out of said space, thereby generating an underpressure in said space which causes lubricant to flow from the outside through the filtering means into said space. Having regard to the underpressure which prevails in the bearing space, the lubricant which is available on the outside will always be drawn through the filter element. Subsequently, the pumping means expel the lubricant from the bearing space, thus providing a reliable lubricant circulation through the bearing. The porosity of the filtering means can be selected according to the nature of the contaminations to which the bearing will be exposed in service, as well as on the basis of the optimum life and lubrication performance of the bearing. The flow generating means together with the filtering means may be provided in any suitable place. For instance, the flow generating means themselves may be situated in a location remote from the bearing system. and be connected thereto via a flowline. The underpressure will promote the inflow of lubricant into the bearing space, through the filtering membrane. Thereby, a constant refreshment of the lubricant is guaranteed. Also, any contaminations produced inside the bearing will be discharged from the bearing space together with the flow of lubricant thus generated. According to a preferred embodiment at least one of the sealing rings is provided with an opening covered by a filtering membrane. Such sealing rings can be installed relatively easy on any kind of bearing. In order to achieve the desired lubricant supply, at least one of the sealing rings at its edge which slidably contacts one of the races has a shape which promotes the outflow from the said space towards the outside of said sealing ring during relative movement of said sealing ring and race. Such shape may for instance be provided by said edge having a lip the inside surface of which encloses a relatively small angle with the race surface lying inwards with respect to the sealing ring, and the outside surface of which enclosing a relatively large angle with respect to the race surface lying outwards with respect to the sealing ring. The specific shape of the lip generates an outward flow when said lip and the opposite surface are moving relative to each other. Of course. further flow generating means may be provided on the lip, such as specific profiles in its surface. In a first embodiment, at least one of the sealing rings is provided both with an opening covered by a filtering membrane as well as with a sliding edge promoting the outflow out of said space, which opening is situated at a distance from said sliding edge. In a second embodiment, one of the sealing rings is provided with an opening covered by a filtering membrane, and the other sealing ring is provided with a sliding edge promoting the outflow out of said space. In a third embodiment, both races at least at one of their sides are provided with rings which extend into the direction of the other race, both rings partly overlapping each other and delimiting a narrow radially oriented gap for generating a radially outward flow upon relative rotation of both races. In a fourth embodiment, the system comprises at least one rolling element bearing having two rows of rollers and an outer race with a common spherical raceway, whereby the raceway is provided with at least one opening situated between the two rows of rollers for discharging lubricant under the influence of centrifugal forces upon rotation of the outer race. The underpressure thus generated within the enclosed bearing space leads to an inflow of lubricant through the filtering means. The rolling element bearing system may also comprise two axially aligned rolling element bearings, the outer races and/or the inner races of which are mutually connected by a ring of filtering material. Preferably, the sealing rings consist of an elastomeric material. Thereby, a proper elastic pressure between the ring and the corresponding surface of the opposite, relatively movable race is obtained which is favourable for the pumping action sought. The invention will now be described further with reference to several embodiments as shown in the figures. Figure 1 shows a ball bearing with a sealing element according to the invention. Figure 2 shows a bearing with another set of sealing rings according to the invention. Figure 3 shows a third embodiment. Figure 4 shows a fourth embodiment. Figure 5 shows a fifth embodiment. Figure 6 shows a sixth embodiment. In figure 1, a ball bearing 1 is shown, the outer ring 2 of which is connected to a machine element 3 which is rotatable with respect to a housing 4, onto which the inner ring 5 of the bearing is connected. The housing 4 contains an oil bath 6, the oil of which, by the rotative movements of the machine elements is splashed onto the outside of the bearing. The bearing 1 furthermore contains balls 7 and a cage 8. On the inner surface of race 2, a sealing element according to the invention 9 is clamped with its outer edge 10. The inner edge 11 of the sealing ring has a U-shaped cross section containing a sealing lip 11. The top 13 of this lip 12 contacts the outer surface of the race 5. Moreover, the inner wall 14 of lip 12 makes a relatively small angle with respect to the outer surface of race 5, whereas the outer wall 15 of the lip 12 makes a relatively large angle with that surface. As a consequence of this form of lip 12 an outward flow, as indicated by the arrows, is generated in the fluid next to said lip, when race 5, and thereby surface 16, is rotated with respect to lip 12. Thereby an underpressure is created in the internal bearing space 17, delimited by the races 2 and 5, and the sealing lips 9 on both sides. The sealing lip 9 is furthermore provided with a hole 18, covered with a filtering membrane 19. Thereby the oil which splashes onto the membrane, can enter the space 17 via said membrane 19. The inflow of the oil is furthermore promoted by the underpressure generated by a relative movement of lip 12 and race 5. Any contaminations present in the splash oil are collected on the outside of the membrane 19, which means that only clean oil is entering the internal space 17. Once the oil has entered said space 17, it spreads over the balls 7 and the cage 9, as well as the raceways of the races 2 and 5. Figure 2 shows a second embodiment of the invention, in which different sealing rings are applied. Between the inner race 20 and the outer race 21 there is an internal space 22, which contains rolling elements 23. Said space is furthermore confined by sealing ring 24 and sealing ring 25. Sealing ring 25 contains an opening provided with a filtering membrane 26. It may be connected to either one of the races 20 or 21 and be slidable with the respect to the other race. Sealing ring 25 however is clamped onto the race 20, and has an outer edge containing a lip 27 which has the same shape as the one discussed with reference to figure 1. Thereby, the lip 27 generates an underpressure in the internal space 22, upon rotation of race 21 with respect to race 20. Also, oil is sucked into the space 22 via filtering membrane 26. Figure 3 shows a third embodiment, containing sealing rings 28 and 29. Both the sealing ring 28 and sealing ring 29 contain a filtering membrane 30. as well as a lip 31 which offers a pumping action. Thereby, oil is fed into the internal space 21 and pumped therefrom at both sides of the bearing. The rolling element bearing shown in figure 4 comprises an inner race 50 and an outer race 51, supported by means of balls 52. Onto the inner race a ring of filtering material 53 has been connected. This ring 53 carries a ring 54 which is oriented radially outwardly, into the direction of the outer race 51, and delimits a narrow gap with respect to said outer race 51. Onto the outer race 51 a further ring 55 is connected, which is oriented radially inwardly, and which delimits a narrow gap with respect to the filter ring 53 of sealing material. Also, rings 54 and 55 delimit a narrow, radially oriented gap 56. Upon rotation of ring 55 with respect to ring 54, a radially outwardly oriented flow from the bearing space delimited by the races 50. 51 and rings 54, 55 on either side of the bearing is generated. Thereby, an underpressure is created in said bearing space. Any splash oil which hits the ring of filtering material 53 is thereby sucked into the bearing space, where it is finally deposited on races 50. 51 and the balls 52. The embodiment of figure 5 contains a spherical bearing with an outer race 57 and an inner race 58. Furthermore, there are two rows of rolling elements 59, 60. For the embodiment in which the outer race 57 is rotating, said race 57 is provided with at least one opening 61. Upon rotation of the outer race 57, centrifugal forces are generated which force an outflow through said opening 61. Of course, the element 62 which is connected to said outer race 57 should contain a bore 63, which is aligned with opening 61 in the outer race 57 and which allows the discharge from the bearing space. On both sides of the spherical bearing, filtering rings 64 have been provided which allow the inflow of splash oil particles into the bearing space.

Claims: Rolling element bearing system comprising at least one rolling element bearing (1) with an outer race (2, 21, 51, 57) and an inner race (5, 20, 50, 58) which enclose a space containing rolling elements, which space is confined to the outside by means of sealing rings (9, 24, 25, 28, 29, 54, 55), the rolling element bearing system further comprising filtering means (19, 26, 30, 53, 64, 71) for preventing the ingress of contaminations into said space with a lubricant, characterized in that at least one of said sealing rings and/or one of the races is provided with flow generating means (12, 14, 15, 54, 55, 56) for pumping said lubricant out of said space, thereby generating an underpressure in said space which causes lubricant to flow from the outside through the filtering means (19, 26, 30, 53, 64, 71) into said space. System according to claim 1, whereby at least one of the sealing rings (9, 24, 28, 29, 54) is provided with an opening covered by a filtering membrane (19, 26, 30, 53, 64). System according to claim 2, whereby at least one of the sealing rings (9, 24, 8, 29) at its edge which slidably contacts one of the races (5, 21) has a shape which promotes the outflow of lubricant out of said space towards the outside of said sealing ring during relative movement of said sealing ring and race. System according to claim 3, whereby said edge has a lip (12, 27, 31) the inside surface (14) of which encloses a relatively small angle with the race surface (16) lying inwards with respect to the sealing ring (9), and the outside surface (15) of which encloses a relatively large angle with respect to the race surface (16) lying outwards with respect to the sealing ring (9). System according to claim 3 or 4, whereby at least one of the sealing rings (9, 28, 29) is provided both with an opening covered by a filtering membrane (18, 30) as well as with a sliding edge promoting the outflow of lubricant from said space, which opening is situated at a distance from said sliding edge. System according to claim 3 or 4, whereby one of the sealing rings (24) is provided with an opening covered by a filtering membrane (26), and the other sealing ring (25) is provided with a sliding edge (27) promoting the outflow of lubricant out of said space. System according to claim 1, whereby both races (50, 51) at least at one of their sides are provided with rings (54, 55) which extend into the direction of the other race, both rings partly overlapping each other and delimiting a narrow radially oriented gap (56) for generating a radially outward flow of lubricant upon relative rotation of both races. System according to claim 7, whereby one of the races (50) is provided with a layer (53) of filtering material, onto which layer (53) one of the rings (54) is connected and the other ring (55) extending up to said (53) layer without touching same. System according to claim 1 or 2, comprising at least one rolling element bearing with an outer race (57) having two rows of rollers (59, 60) and a common spherical raceway, whereby the raceway is provided with at least one opening (61) situated between the two rows of rollers for discharging lubricant under the influence of centrifugal forces upon rotation of the outer race (57). System according to one of the preceding claims, whereby two axially aligned rolling element bearings (65, 66) are provided, the outer races and/or the inner races of which are mutually connected by a ring (71) of filtering material. System according to one of the preceding claims, whereby the sealing rings consist of an elastomeric material.

Inventors: DE VRIES GERARDUS, GABELLI ANTONIO, POLL GERHARD, DE VRIES, GERARDUS, GABELLI, ANTONIO, POLL, GERHARD
Applicants: SKF IND TRADING & DEV, SKF INDUSTRIAL TRADING & DEVELOPMENT CO, B.V.
Application year: 1993
Main classification: F16C33
IPC codes: F16C33, F16C23