CAGE FOR A BALL BEARING, AND BALL BEARING COMPRISING SUCH CAGE

Abstract: A cage for a ball bearing comprises a ring-shaped element (1) provided with prongs (2, 3) which extend with respect to the ring-shaped element, cage pockets (4) being enclosed between adjacent pairs of prongs (2, 3), and said pairs of prongs each defining an opening (5) through which a ball element (6) may be accommodated in the cage pocket (4) by snapping in in the axial direction with respect to the ring-shaped element (1). In the circumferential direction of the ring-shaped element (1), at least one cage pocket (4) has an elongated shape.

Description: 1 Cage for a ball bearing, and ball bearing comprising such cage The invention is related to a cage for a ball bearing, comprising a ring-shaped element provided with prongs which extend with respect to the ring-shaped element, cage pockets being enclosed between adjacent pairs of prongs, and said pairs of prongs each defining an opening through which a ball may be accommodated in the cage pocket by snapping in in the axial direction with respect to the ring-shaped element Such cage, which is generally known, and the balls assembled by pressing them together, such that said balls all at the same time snap into the respective pockets The pockets are shaped in such a way that the cage is fully supported by the balls, which means that no direct contact between the cage and the inner ring or outei ring of the bearing exists By means of the cage, the balls are held at predetermined intervals. As a result of the engagement of the cage with all balls, the cage is subjected to varying load Said loads are caused by the conditions to which the bearing as a whole is subjected, i.e. misalignment and the loads on the (rotating) inner ring such as thrust load and acceleration These conditions lead to the development of a pattern of contact forces between the cage, in particular the cage pockets, and the associated balls The contact forces are caused by the external conditions imposed on the bearing, and the behaviour of the balls in the cage pockets Each ball is accommodated with some play in the corresponding cage pocket, which play leads to a relative forwarαVbackward movement of ball and cage pocket in the circumferential bearing direction Thus, the highest contact forces appear at the front and the back of the pocket However, also any misalignment of the inner ring with respect to the outei ring of the bearing plays a role in this respect Such misalignment imposes a non- symmetπcal loading pattern on the balls and pockets, which in combination with the backward and forward movements of the balls with respect to the cage lead to high contact forces These forces lead to excessive wear of the cage material and earliei fatigue failure, as well as an instable running behaviour of the bearing as a whole In high speed running conditions, these phenomena are aggravated The object of the invention is to provide a solution to this pioblem This 2 object is achieved in that in the circumferential direction of the ring-shaped element, at least one cage pocket has an elongated shape. The elongated shape of the cage pocket(s) leads to a reduction of the contact forces. Thereby, advantages are obtained concerning the running properties of the bearing, improved wear life etc. The elongated shape of the cage pockets can be obtained in several ways. However, said shape should also guarantee the required supporting function with respect to the balls. According to the invention therefore, said at least one cage pocket comprises two symmetrical cage pocket halves which each have a spherically shaped inner surface, the spacing of which cage pocket halves is larger than the sphere diameter of said inner surfaces. Preferably, the spherically shaped, symmetrical cage pocket halves enclose an intermediate cage pocket piece. Other shapes are also possible, as long as a proper guidance of the ball in question is ensured. A proper guidance back and forth in circumferential direction of the ball elements is obtained in case the intermediate cage pocket piece has an inner surface which is curved according to a torus the axis of which corresponds to the axis of the ring-shaped element. In particular, the inner surface of the intermediate cage piece, and the inner surfaces of the adjoining cage pocket halves at their junction are identically curved in a plane through the axis of the ring-shaped element for providing a smooth transition between said surfaces. According to a preferred embodiment, the prongs each extend from an intermediate prong body, said intermediate prong bodies being situated between two adjacent cage pockets each. The intermediate prong bodies constitute the separation between consecutive cage pockets, and provide the required holding stiffness of the prongs, in combination with the flexibility necessary for snapping in of the balls in the cage pockets. Each intermediate prong body is connected to the roots of two adjoining prongs. The cage pockets may be regularly spaced; alternatively, irregular spacings are also possible. Preferably, in the circumferential direction of the ring-shaped element, all cage pockets have an elongated shape. The invention is also related to a ball bearing, comprising an inner ring and an 3 outer ring which each comprise a raceway, and a ring-shaped element provided with prongs which extend with respect to the ring-shaped element, cage pockets being enclosed between adjacent pairs of prongs, and said pairs of prongs each defining an opening through which a ball element is accommodated in the cage pocket by snapping in in the axial direction with respect to the ring-shaped element, in such a way that said cage is supported by the ball elements. According to the invention, in the circumferential direction of the ring-shaped element, at least one cage pocket has an elongated shape. In the bearing according to the invention, the cage is fully supported by the balls. Although said cage is subjected to varying loads as a consequence of the engagement with the balls, nevertheless a favourable pattern of contact forces and a smooth running behaviour is obtained as a result of the particular elongated shape of the cage pockets. The invention will now be described with reference to the embodiments shown in the figures. Figure 1 shows a view in perspective of the cage according to the invention. Figure 2 shows a developed top view of the cage according to figure 1. Figure 3 shows a detail of a cage pocket on an enlarged scale. The cage shown in figures 1 and 2 comprises a ring-shaped element 1, carrying prongs 2, 3 which extend with respect to said ring-shaped element 1. The pairs of prongs 2, 3 each enclose a cage pocket 4, and define an opening 5 which provides access to the respective cage pocket 4. As shown in figure 2, which is a developed view, balls 6 can be accommodated in the cage pockets 5. To that end, a series of balls 6 and the cage are assembled by snapping in in the axial direction of the ring-shaped element. The balls 6 enter the corresponding cage pocket 4 via the openings 5 defined between the pairs of prongs 2, 3. The ring-shaped element 1 and the prongs 2, are deformed in this process, and once the balls 6 have been snapped in, they are held in the respective cage pockets 4 in a reliable way. As shown in figure 2, the shape of all cage pockets in the circumferential direction of the ring-shaped element 1 is somewhat elongated. Thereby, each ball 6 has some play, in the forward and backward direction, seen in the circumferential direction of the ring-shaped element. According to the invention, not all cage pockets 4 need to have an elongated shape. However, at least one of said cage pockets must have such elongated shape. The play thus obtained has a positive influence on the running behaviour and the loadings between the balls 6 and the opposing walls 7, 8 of each cage pocket. Moreover, the internal walls, in particular the parts 7, 8, of the cage pockets may be conformed somewhat to the ball shape of the ball 6. At the side of the ring-shaped element, which faces away from the prongs 2, 3, recesses 12 have been provided for manufacturing purposes. As is clear from the embodiment in figures 1 and 2, the prongs 2, 3 of adjoining cage pockets 4 are accommodated on a common intermediate prong body 9. These prong bodies 9 extend over a certain distance in the axial direction of the ring-shaped element 1. The prongs 2, 3, in particular the roots 10 thereof, are connected to these prong bodies 9. The face 12 of the prong bodies 9, onto which the roots 10 of the prongs 2, 3 are connected, is at a distance from the bottom 1 1 of the cage pockets 4. Thus, the prongs 2, 3 are relatively short, but together with the rest of the cage provide sufficient flexibility for snapping in of the balls 6 in the corresponding cage pockets 4, while still maintaining an adequate holding capability. As shown on an exaggerated scale in figure 3, each cage pocket 4 comprises two symmetrical and spherically shaped cage pocket halves 13, 14, which enclose an intermediate cage pocket piece 15. The intermediate cage pocket piece 15 has an inner surface which is shaped according to a torus 19 which is indicated as well. Said inner surface smoothly merges into the spherically shaped inner surfaces of the cage pocket halves 13, 14, through (imaginary) junction lines 17, 18. As a result of the interposed cage pocket piece 15, the spacing (or maximum mutual distance in the circumferential direction of the ring-shaped element 1) of the surfaces of the adjoining cage pocket halves 13, 14 is greater than the diameter of the sphere which defines the shape of said inner surfaces of the adjoining cage pocket halves 13, 14. Said cage pocket piece 15 has an inner surface which is curved according to a torus, the axis of which corresponds to the axis of the ring-shaped element. As a result, the balls 6 are reliably held between the prongs 2, 3 and the curved parts of the cage pockets 4.

Claims: 5 Claims 1. Cage for a ball bearing, comprising a ring-shaped element (1) provided with prongs (2, 3) which extend with respect to the ring-shaped element (1), cage pockets (4) being enclosed between adjacent pairs of prongs (2, 3), and said pairs of prongs (2, 3) each defining an opening (5) through which a ball element (6) may be accommodated in the cage pocket by snapping in in the axial direction with respect to the ring-shaped element (1), characterized in that, in the circumferential direction of the ring-shaped element (1), at least one cage pocket (4) has an elongated shape. 2. Cage according to claim 1, wherein said at least one cage pocket (4) comprises two symmetrical cage pocket halves (13, 14) which each have a spherically shaped inner surface, the spacing of which cage pocket halves is larger than the sphere diameter of said inner surfaces. 3. Cage according to claim 2, wherein the spherically shaped, symmetrical cage pocket halves (13, 14) enclose an intermediate cage pocket piece (15). 4. Cage according to claim 3, wherein the intermediate cage pocket piece (15) has an inner surface which is curved according to a torus (19) the axis of which corresponds to the axis of the ring-shaped element (1). 5. Cage according to claim 4, wherein the inner surface of the intermediate cage piece (15), and the inner surfaces of the adjoining cage pocket halves (13, 14) at their junction (17, 18) are identically curved (16) in a plane through the axis of the ring-shaped element for providing a smooth transition between said surfaces. 6. Cage according to any of the preceding claims, wherein the prongs (2, 3) each extend from an intermediate prong body (9), said intermediate prong bodies (9) being situated between two adjacent cage pockets (4) each. 7. Cage according to claim 6, wherein each intermediate prong body (9) is connected to the roots (10) of two adjoining prongs (2, 3). 6 8. Cage according to claim 7, wherein, in axial direction, the root (10) of each prong (2, 3) is at a distance from the bottom (1 1) of the cage pockets (4), said bottom (1 1) lying opposite the opening (5) defined by the prongs (2, 3). 9. Cage according to any of the preceding claims, wherein, in the circumferential direction of the ring-shaped element (11), all cage pockets (4) have an elongated shape. 10. Ball bearing, comprising an inner ring and an outer ring which each comprise a raceway, ball elements (6) which are in contact with the raceways of the rings, and a cage comprising a ring-shaped element (1) provided with prongs (2, 3) which extend with respect to the ring-shaped element (1), cage pockets (4) being enclosed between adjacent pairs of prongs (2, 3), and said pairs of prongs (2, 3) each defining an opening (5) through which a ball element (6) is accommodated in the cage pocket by snapping in in the axial direction with respect to the ring-shaped element (1), in such a way that said cage (1) is supported by the ball elements (6) characterized in that, in the circumferential direction of the ring-shaped element (1), at least one cage pocket (4) has an elongated shape. 1 1. Ball bearing according to claim 10, wherein said at least one cage pocket (4) comprises two symmetrical cage pocket halves (13, 14) which each have a spherically shaped inner surface, the spacing of which cage pocket halve, is larger than the sphere diameter of said inner surfaces. 12. Ball bearing according to claim 1 1, wherein the spherically shaped, symmetrical cage pocket halves (13, 14) enclose an intermediate cage pocket piece (15). 13. Ball bearing according to claim 12, wherein the intermediate cage pocket piece (15) has an inner surface which is curved according to a torus (19) the axis of which corresponds to the axis of the ring-shaped element (1). 14. Ball bearing according to claim 13, wherein the inner surface of the 7 intermediate cage piece (15), and the inner surfaces of the adjoining cage pocket halves (13, 14) at their junction (17, 18) are identically curved (16) in a plane through the axis of the ring-shaped element for providing a smooth transition between said surfaces. 15. Ball bearing according to any of claims 10-14, wherein the prongs (2, 3) each extend from an intermediate prong body (9), said intermediate prong bodies (9) being situated between two adjacent cage pockets (4) each. 16. Ball bearing according to claim 15, wherein each intermediate prong body (9) is connected to the roots (10) of two adjoining prongs (2, 3). 17. Ball bearing according to claim 16, wherein, in axial direction, the root (10) of each prong (2, 3) is at a distance from the bottom (11) of the cage pockets (4), said bottom (11) lying opposite the opening (5) defined by the prongs (2, 3). 18. Ball bearing according to any of claims 10-17, wherein, in the circumferential direction of the ring-shaped element (11), all cage pockets (4) have an elongated shape.

Inventors: FIERLING YANNINCK PIERRE HUBER, RYDELL BENGT ERIK LENNART, STACKE LARS-ERIK, FIERLING, YANNINCK, PIERRE, HUBERT, RYDELL, BENGT, ERIK, LENNART, STACKE, LARS-ERIK
Applicants: FIERLING YANNINCK PIERRE HUBER, RYDELL BENGT ERIK LENNART, SKF ENG & RES CENTRE BV, STACKE LARS ERIK, FIERLING, YANNINCK, PIERRE, HUBERT, RYDELL, BENGT, ERIK, LENNART, SKF ENGINEERING & RESEARCH CENTRE B.V., STACKE, LARS-ERIK
Application year: 1999
Main classification: F16C33
IPC codes: F16C33