GB2053380A

GB2053380A - Three-point ball bearing

Info

Publication number: GB2053380A
Application number: GB8007633A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-03-12
Filing date: 1980-03-06
Publication date: 1981-02-04
Also published as: DE2909658A1; JPS55123016A; FR2451497A1; DE2909658C2

Abstract

The invention relates to a three- point ball bearing having a first bearing part (10, 12, 15) which forms a rolling surface (14) parallel to the axis and two essentially radial rolling surfaces (11, 13), and a second bearing part (17) which is rotationally mobile relative to the first bearing part and forms two rolling surfaces (18, 19) which are in each case located opposite the two abovementioned rolling surfaces and are inclined in opposite directions. According to the invention, the rolling surface (14) parallel to the axis is formed by a ring (15) which is elastically yielding in the radial direction. The result is that the bearing can work substantially without play at differing temperatures and can nevertheless absorb axial and tilting forces on the rigid rolling surfaces (11, 13), while remaining essentially rigid. <IMAGE>

Description

SPECIFICATION Three-point ball bearing The invention relates to a three-point ball bearing having a first bearing part which forms a rolling surface parallel to the axis and two essentially radial rolling surfaces, and a second bearing part which is rotationally mobile relative to the first bearing part and forms two rolling surfaces which are in each case located opposite the two abovementioned rolling surfaces and are inclined in opposite directions.

In a known ball bearing (German Offenlegungsschrift 2,728,186, Figure 5), one bearing part has two parallel radial rolling surfaces and, in between, a rolling surface parallel to the axis, whilst the other bearing part comprises two rolling surfaces inclined in opposite directions.

Depending on the state of loading, the rolling surfaces parallel to the axis interact on the one hand with a radial rolling surface and, in the manner of a three-point ball bearing, with the inclined rolling surface located opposite this pair of rolling surfaces. This arrangement has great advantages because of its simply defined rolling surfaces and its ability not only to absorb radial forces but also high axial and tilting forces.

Moreover, it can easily be manufactured without play. At the same time, however, it has the disadvantage - like all roller bearings composed of rigid parts - that problems are unavoidable in those applications in which different temperatures occur on the two bearing rings. If the expansion of the inner ring is greater than that of the outer ring, large additional forces arise between the rolling surfaces and the balls, and these forces can lead to premature failure of the bearing. If the outer ring is hotter than the inner ring, additional play occurs with a corresponding reduction in the number of load-bearing roller bodies and a corresponding increase in the specific forces which can likewise cause damage to the bearing.

Such expansions can be taken into account beforehand in the design, by allowing a corresponding initial play or corresponding pretension, only if they arise at a constant defined level. This condition, however, is not always met.

Grooved ball bearings are known (French Patent Specification 516,502, U.S. Patent Specification 1,305,131) in which this disadvantage is avoided by a design in which one or both rolling surfaces are elastically yielding since they consist of thin shells which are supported on rigid components on either side of the ball track and are therefore capable of flexing between these supports. Since this flexing is connected with a reduction of the radius of curvature (measured in axial section) and the radius of curvature must not become smaller than the ball radius, it is envisaged in these known grooved ball bearings that the rolling surfaces in the normal state have a considerably larger radius of curvature than the balls, and this has the consequence that these bearings are suitable only for the transmission of radial forces, but not of axial forces.

In order to match the geometrical conditions of a grooved ball bearing, in spite of the use of a yielding rolling surface, more closely to the otherwise customary form of bearings which is also suitable for the transmission of certain axial forces, it is also known (U.S. Patent Specification 3,749,460) to assemble one of the two bearing rings from two thin, elastically yielding split rings which are mutually offset axially and which each form one axial half of the rolling surface associated with this bearing ring and, since they can yield independently of one another, can be more steeply inclined in their rolling zones and can therefore absorb greater axial forces than the grooved ball bearings illustrated above, but the axial loading capacity is still very limited and, additionally, the disadvantage arises that the bearing yields elastically to a rather great extent under an axial load.

Finally, it is known (German Offenlegungsschrift 2,728,186, Figures 9 and 11) to combine several three-point ball bearings, in which at least one radial rolling surface is designed to be resiliently yielding, in an arrangement without play. Evidently, however, the formation of a radial rolling surface has the same disadvantage as the grooved ball bearings described, with respect to the absorption of axial forces, namely that the bearing arrangement yields excessively under axial forces. Moreover, it would not be possible to design such an arrangement of a twin three-point ball bearing, of the generic type to which the invention relates, to be free from play at different temperatures, since the yielding radial rolling surface is unable to compensate for any differences of diameter in the radial direction.

It is therefore the object of the invention to design a three-point ball bearing of the type initially set forth in such a way that it is able to work without play at varying temperatures and can also absorb considerable axial and tilting forces while remaining essentially rigid.

According to the invention, the object is achieved when the rolling surface parallel to the axis is formed by a ring which is elastically yielding in the radial direction.

Since the radially extending rolling surfaces are rigid, the bearing can absorb high axial tilting forces without a significant deformation. A compensation for radial differences in the diameter of the bearing parts, due to differential thermal expansion, is readily possible. The bearing according to the invention therefore displays substantially more advantageous properties than the ball bearings of a different design, discussed above, in which either all the rolling surfaces of a bearing part or at least the radial rolling surface are designed to be elastically yielding.

Preferably, the first bearing part which comprises the rigid radial rolling surfaces and the yielding rolling surface parallel to the axis, is arranged to be stationary in order to prevent imbalance in the rotating bearing part.

In the following text, the invention is explained in more detail by reference to the drawing in which a longitudinal section through an illustrative embodiment is represented in a figure.

The ball bearing shown comprises a ball 9, an outer ring which is composed of an angular ring 10 in order to form a first radial rolling surface 11, a side ring 12 in order to form a second radial rolling surface 13 and a thin yielding ring 1 5 in order to form a rolling surface 14 parallel to the axis, the foot 1 6 of the yielding ring 1 5 being firmly clamped in between the rings 10 and 12, and on the other hand an inner ring 1 7 with two rolling surfaces 1 8 and 1 9 which are concavely inclined towards one another. The diameter of the ball 9 corresponds to the clear distance between the rolling surfaces 11 and 13. Moreover, the balls are in contact with the two rolling surfaces 1 8 and 1 9 and with the rolling surface 14.Thus, since the ring 1 5 is yielding, the bearing can be assembled without play at least in the radial direction. It can absorb not only radial forces but also, in particular, axial forces in both directions. In every load case, it acts as a three-point bearing, and the rolling tracks marked with reference numerals in the lower half of the drawing interact in the following manner when the forces indicated by arrows in the middle of the drawing act on the inner ring: Axial force 25: rolling tracks 20, 22, 23.

Axial force 26: rolling tracks 20, 21, 24.

Radial force 27: rolling tracks 20, 23, 24.

Tilting force 28: rolling tracks 20, 22, 23 below, and 20,21,24 above.

A three-point bearing in the sense of the invention is preferably to be understood as a bearing in which the tangent to the balls at the bearing point provided on one bearing part intersects in the axis of rotation of the bearing with the line connecting the bearing points present in the other bearing part. This has the consequence that ideal rolling conditions prevail under all circumstances.

Although only a single rolling surface out of a total of five rolling surfaces present is designed to be elastically yielding, the arrangement according to the invention has the advantage that the elasticity of this one rolling surface is effective for all load cases in which mutually alternating rolling surfaces participate. This makes it possible to design four of the five rolling surfaces present to be rigid, as a result of which the complete bearing arrangement is provided with relatively rigid characteristics and nevertheless retains the advantages of freedom from play even under varying temperature conditions.Finally, it should be pointed out that the arrangement according to the invention, in which one rolling surface parallel to the axis is formed by an elastic ring, is different in principle from those arrangements in which a radial rolling surface is designed to be elastic.

Whilst the latter arrangement displays characteristics obeying Hooke's law over wide ranges and therefore yields to large forces correspondingly more than to small forces, the elastic arrangement according to the invention does not obey Hooke's law. The reason is that the portions, shown in section in the drawing, of the elastic ring are not freely deflectable but are supported by those portions of this ring which are offset thereto by 900. In contrast to other bearing arrangements, a resilient softness of the bearing thus need not be feared, in particular since it is possible to avoid an excessive deformation of the yielding ring by providing, at a small distance from the latter, a rigid ring which acts as a stop. It can be seen in the representation that the yielding ring 20 is arranged with a relatively small play 32 (shown exaggerated in the drawing) relative to the surrounding rigid ring part 33. When a certain degree of deformation is exceeded, the yielding ring makes contact with the rigid ring and is protected in this manner from excessive deformation.

Claims

1. Three-point ball bearing having a first bearing part which forms a rolling surface parallel to the axis and two essentially radial rolling surfaces, and a second bearing part which is rotationally mobile relative to the first bearing part and forms two rolling surfaces which are in each case located opposite the two abovementioned rolling surfaces and are inclined in opposite directions, characterised in that the rolling surface (14) parallel to the axis is formed by a ring (15) which is elastically yielding in the radial direction.

2. Ball bearing according to Claim 1, characterised in that the first bearing part (10, 12, 15) is arranged to be stationary.

3. Three-point ball bearing substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.