TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a pedestal bearing housing for accommodating a bearing, and to a bearing assembly including such a pedestal bearing housing and a bearing accommodated in the pedestal bearing housing.

BACKGROUND ART

[0002] Bearing assemblies for guiding a shaft usually include a bearing received in a housing. The bearing can be of any type, e.g. a plain bearing or a roller bearing with rolling bodies of various shapes, including balls, needles, cylindrical rollers, barrel rollers, tapered rollers and spherical rollers. The pedestal bearing housing is an intermediate stationary part, which supports the rotating part and can be fixed to a support structure, e.g. a planar base. The pedestal bearing housings can be subjected to relatively high dynamic stress at frequencies that can vary considerably with the rotation speed of the shaft. These stresses should be not result in vibration of the pedestal bearing housing, which would be transmitted to the bearing and to the shaft or to the base. Hence, the pedestal bearing housing should have a high stiffness. However, the pedestal bearing housing should simultaneously minimise the amount of material used. [0003] In order to meet both requirements, it has be proposed in WO 2013/085448 to provide a pedestal bearing housing comprising a substantially cylindrical bearing seat configured to receive a bearing, and a foot member adapted to support said bearing seat and having a generally planar lower surface formed by end surfaces of outer and inner supporting walls configured to be connected to an external support structure, wherein the inner supporting walls extend between the outer supporting walls forming cavities there between, wherein at least one of the inner supporting walls comprises at least one protrusion along its axial extension. By providing at least one protrusion on at least one of the inner supporting walls, the contact surface to the external support structure may be increased. Hereby, the pedestal bearing housing may have an increased stiffness and thereby being able to distribute the forces emanating from the bearing during use in a more suitable manner. However, substantial deformations of the bearing seat and high stress zones in some parts of the pedestal bearing housing are still experienced, in particular when a radial load is applied in a direction at an angle with the plane of symmetry of the pedestal bearing housing.

SUMMARY OF THE INVENTION

[0004] The invention aims to provide an improved pedestal housing structure that avoids or limits stress concentrations and weak points so that the pedestal bearing housing can sustain higher loads. [0005] According to a first aspect of the invention, there is provided a pedestal bearing housing comprising a bearing seat, two attachment flange portions extending between the bearing seat and a support plane, the two attachment flange portions protruding on opposite sides of a median longitudinal plane perpendicular to the support plane, each of the two attachment flange portions including an upper flange wall protruding away from the median longitudinal plane, an outer longitudinal supporting wall and an inner longitudinal supporting wall extending in a direction parallel to the median longitudinal plane, and two outer transverse supporting walls each extending from the outer longitudinal supporting wall to the inner longitudinal supporting wall, the outer longitudinal supporting wall, inner longitudinal supporting wall and outer transverse walls extending from the upper flange wall towards the support plane and having edges that lie in the support plane to form at least part of a planar support surface of the pedestal bearing housing, a flange cavity being provided between the upper flange wall, outer longitudinal supporting wall, inner longitudinal supporting wall, outer transverse walls and support plane, the upper flange wall being provided with at least one through hole which opens into the flange cavity, wherein the pedestal bearing housing further comprises two transverse ribs each extending at least from the bearing seat to the inner longitudinal supporting wall of a respective one of the two flange portions, in a common transversal reference plane perpendicular to the median longitudinal plane and to the support plane and located between the two outer transverse supporting walls of each of the two flange portions. Each of the transverse ribs transfers part of the load from the bearing seat to the associated inner longitudinal supporting wall so that the stress field in the region of the upper flange wall is less critical.

[0006] According to a preferred embodiment, the bearing seat defines a surface of revolution about a revolution axis, parallel to the support plane and contained in the median longitudinal plane, to receive a bearing.

[0007] According to a preferred embodiment, each of the two transverse ribs has a lower free edge that lies at a distance from the support plane. Preferably, the lower free edge of each of the two transverse ribs has a concave cross-section in the transversal reference plane. The transverse ribs operate like arch-buttresses between the bearing seat and the inner longitudinal supporting walls.

[0008] According to a preferred embodiment, the pedestal bearing housing further comprises an intermediate portion that extends between the bearing seat and the support plane and between the two flange portions. The intermediate portion includes at least a median foot protruding from the bearing seat towards the support plane and having a median support surface that lies in the support plane and is part of the planar support surface, and each of the two ribs extends from the inner longitudinal supporting wall of the respective one of the two flange portions to the median foot. The median foot supports a substantial part of the radial load on the pedestal bearing housing. Moreover, part of the load transmitted by the bearing seat to the ribs is transferred to the median foot, which further limits the stress in the flange portions.

[0009] According to a preferred embodiment, the lower free edge of each of the two transverse ribs has a convex intermediate portion, a concave end portion between the convex intermediate portion and the median foot and a concave end portion between the convex intermediate portion and the inner longitudinal supporting wall of the respective one of the two flange portions. The concave end portion between the convex intermediate portion and the inner longitudinal supporting wall is preferably at an angle of between 35° and 50° to the median longitudinal plane. The concave end portion between the convex intermediate portion and the median foot is preferably at an angle of between 3° and 10° to the median longitudinal plane. Preferably,

D ₁

3 <— < 7

D ₂ where:

Dl is the maximal distance Dl between the from the support plane (300) and the concave end portion between the convex intermediate portion and the inner longitudinal supporting wall (54),

- D2 is the minimal distance between the support plane (300) and the convex intermediate portion, in a transition area between the convex intermediate portion and the concave end portion between the convex intermediate portion and the median foot (48).

[0010] According to one embodiment, the intermediate portion further includes two intermediate outer transverse walls each extending from one of the flange portions to the other of the two flange portions. The intermediate outer transverse walls interconnect the two flange portions to avoid undesired deformation of the housing. Each of the two intermediate transverse walls can be parallel to, and preferably coplanar with, one of the two outer transverse walls of each of the two flange portions. The median foot lies between the two intermediate outer transverse walls. One or more intermediate cavities are provided between the intermediate outer transverse walls, and the inner longitudinal wall of each of the two flange portions. The pedestal of the housing is essentially hollow, which is particularly advantageous in terms of weight and quantity of material. The two intermediate outer transverse walls reinforce the overall structure of the pedestal and connect the two flange portions with one another. Preferably, the two intermediate outer transverse walls extend from the bearing seat towards the support plane and have edges that lie in the support plane to form part of the planar support surface of the pedestal. The two intermediate outer transverse walls contribute to the transfer of the load to the base on which the pedestal housing is fixed. [0011] According to one embodiment, the intermediate portion further includes at least two inner reinforcing walls each extending from one of the two intermediate outer transverse walls to the median foot. This limits bending of the intermediate outer transverse walls. Preferably, the at least two inner reinforcing walls extend from the bearing seat towards the support plane and have edges that lie in the support plane to form part of the planar support surface of the pedestal. The two inner reinforcing walls contribute to the transfer of the load to the base on which the pedestal housing is fixed.

[0012] According to one embodiment, the at least two inner reinforcing walls include at least two walls perpendicular to the outer intermediate transverse walls. According to another embodiment, the at least two inner reinforcing walls include at least two slanted inner reinforcing walls each at an angle of between 30° and 60° to the outer intermediate transverse walls. Preferably, the at least two inner reinforcing walls include at least four slanted inner reinforcing walls each at an angle of between 30° and 60° to the outer intermediate transverse walls and forming a cross. The cross between the intermediate outer transverse walls, combined with the inner and outer longitudinal walls, provides a very stiff structure.

[0013] According to one embodiment, the bearing seat has two axial ends, located on each side and at equal distance of the transversal reference plane. In most applications, the dynamic load applied to the bearing seat is maximal in a central part of the bearing seat and the deformations are also potentially greater in this region, and it particularly advantageous to provide the reinforcement of the ribs in this region. According to one embodiment, the transversal reference plane is closer to a first geometrical plane containing one of the two outer transverse walls of each of the two flange portions than to a second geometrical plane containing another one of the two outer transverse walls of each of the two flange portions.

[0014] Preferably, the pedestal bearing housing is made of ductile cast iron.

[0015] Preferably, the pedestal bearing housing comprises a cap and a pedestal, which comprises the pedestal flange portions, the cap and pedestal being fixed to one another, preferably by removable fastening elements such as bolts, the bearing seat formed by walls of the cap and pedestal.

[0016] According to another aspect of the invention, there is provided a bearing assembly comprising a pedestal bearing housing as described hereinbefore and at least one outer bearing ring fitted into the bearing seat. According to one embodiment, the outer bearing ring has a spherical race having a centre located in the transversal reference plane. Preferably the outer bearing ring has two end walls perpendicular at equal distance from the transversal reference plane.

BRIEF DESCRIPTION OF THE FIGURES

[0017] Other advantages and features of the invention will then become more clearly apparent from the following description of a specific embodiment of the invention given as non-restrictive examples only and represented in the accompanying drawings in which:

- Figure 1 is a longitudinal cross section of a bearing assembly according an embodiment of the invention, cut by the plane I-I of Fig. 2;

- Figure 2 is a cross section of a pedestal bearing housing of the bearing assembly of figure 1 cut by the plane 11 - 11 of Fig. 1;

- Figure 3 is a view from below of the pedestal bearing housing of Fig. 2;

- Figure 4 is an isometric view of the pedestal bearing housing of Fig. 2; - Figure 5 is view from below of a pedestal bearing housing according to another embodiment of the invention.

[0018] Corresponding reference numerals refer to the same or corresponding parts in each of the figures.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0019] With reference to Figs. 1 to 4, a bearing assembly 10 for guiding a rotating shaft 12 in rotation about a rotation axis 100 includes a bearing 14 fitted onto the shaft 12 and a pedestal bearing housing 16 for affixing the bearing assembly 1 to a planar surface of a base (not shown).

[0020] The bearing 14 illustrated in the drawings is a spherical roller bearing which consists of a single outer ring 18 provided with a single spherical raceway 20, a single inner ring 22 provided with two spherical raceways 24, two rows of rolling bodies 26, in this case spherical rollers, and one or two cages 27 for guiding the rolling bodies 26. The inner ring 22 has a tapered inner face and is force-fitted onto the shaft 12 by means of a slit tapered sleeve 28 and of a nut 29. In the illustrated embodiment, the outer ring 18 has two end faces 30 at equal distance of a centre of rotation O of the bearing and an external cylindrical face 32, which is press-fitted into a cylindrical bearing seat 34 provided in the pedestal bearing housing 16. The axial position of the outer ring 18 can be secured by one or two spacer rings 36, each inserted between one of the end faces 30 and an end shoulder 38 of the bearing seat 34.The revolution axis 200 defined by the cylindrical bearing seat will be a reference axis for the entire description. As is well known in the art, the spherical roller bearing 14 allows a degree of rotation of the rotation axis 100 of the shaft about the centre of rotation O and the particular position illustrated in Fig. 1, with the rotation axis 100 aligned with the revolution axis 200, is only one particular position. The section plane II-II of Fig. 2 is perpendicular to the revolution axis 200 and contains the centre of rotation O of the bearing. This transversal reference plane II-II is at equal distance from the two end faces 30 of the outer ring 18 and at equal distance of the shoulders 38 of the bearing seat 34.

[0021] The pedestal bearing housing 16 is preferably made of ductile cast iron and consists of two parts, namely a cap 40 and a pedestal 42 fixed to one another by any convenient means, preferably by detachable fixing elements such as bolts 44. The bearing seat 34 is defined by internal surfaces of the cap 40 and pedestal 42. The pedestal 42 has a planar support surface 46, which lies in a support plane 300 parallel to the revolution axis, and is intended to rest on a planar face of a base or foundation. The median longitudinal plane I-I, which contains the revolution axis 200 and is perpendicular to the support plane 300, is a plane of symmetry of the bearing seat 34. [0022] The pedestal 42 comprises two attachment flange portions 48 protruding on opposite sides of the median longitudinal plane I-I. As shown in particular in Fig. 3, each of the two attachment flange portions 48 includes an upper flange wall 50 protruding away from the median longitudinal plane I-I and substantially perpendicular to the median longitudinal plane I-I, an outer longitudinal supporting wall 52 and an inner longitudinal supporting wall 54 extending in a direction parallel to the median longitudinal plane I-I, and two outer transverse supporting walls 56 each extending between the outer longitudinal supporting wall 52 to the inner longitudinal supporting wall 54. The outer longitudinal supporting wall 52, inner longitudinal supporting wall 54 and outer transverse walls 56 extend from the upper flange wall 50 towards the support plane 300 and have edges that lie in the support plane to form parts of the planar support surface 46 of the pedestal. A flange cavity 58 is provided between the outer longitudinal supporting wall 52, upper flange wall 50, inner longitudinal supporting wall 54, outer transverse walls 56 and support plane 300. The upper flange wall 50 is provided with two through holes 60, which open into the flange cavity 58, each with a hole axis perpendicular to the support plane 300. These through holes 60 are suitable intended for inserting bolts or other fixing elements (not shown) for securing the bearing assembly 10 to a base or foundation. [0023] The pedestal further includes an intermediate portion 62 between the two flange portions 48. The intermediate portion 62 includes two intermediate outer transverse walls 64 each parallel or substantially coplanar with one of the two outer transverse walls 56 of each of the two flange portions 48, and four inner reinforcing walls 66 each extending from one of the two intermediate outer transverse walls 64 to a common median foot 68 to form a cross. The median foot is located at the intersection between the longitudinal median plane II-II and the transversal reference plane I-I, i.e. directly below the centre of rotation O of the bearing. The median foot 68 protrudes towards the support plane 300 and has a median support face that lies in the support plane and is part of the planar support surface 46. The four slanted inner reinforcing walls 66 are each at an angle of between 30° and 60° to the outer intermediate transverse walls 64 (i.e. two adjacent inner reinforcing walls 66 are at an angle of between 60° and 120° with one another). The intermediate outer transverse walls 64 and inner reinforcing walls 66 extend from the bearing seat 34 towards the support plane 300 and have edges that lie in the support plane 300 to form part of the planar support surface 46 of the pedestal 42. Intermediate cavities 70 are formed between the intermediate outer transverse walls 64, the inner longitudinal wall 54 of each of the two flange portions 48, and the inner reinforcing walls 66.

[0024] Because of the nut 29 received within the pedestal bearing housing 16 for fixing the inner ring 22 of the bearing 14 onto the shaft 12, the bearing 14 is slightly offset in the axial direction with respect to the bearing housing. In other words, the transversal reference plane II-II is offset with respect to the pedestal, i.e. it is closer to one of the two outer transverse walls 56 of each of the two flange portions 48 than to the other one of the two outer transverse walls 56 of each of the two flange portions 48.

[0025] The pedestal bearing housing 16 further comprises two transverse ribs 72 each extending in the transversal reference plane II-II from the bearing seat 34 to the inner longitudinal supporting wall 54 of a respective one of the two flange portions 48. More specifically, each of the two ribs 72 extends from the inner longitudinal supporting wall 54 of the respective one of the two flange portions 48 to the median foot 68. Each of the two transverse ribs 72 has a lower free edge 74 that lies at a distance from the support plane 300. As shown in Fig. 2, the lower free edge 74 of each of the two transverse ribs has a curved cross-section in the transversal reference plane II-II with a convex intermediate portion 74.1 between to concave end 74.2, 74.3 portions, which reach the support plane 300 preferably at an angle of more than 45°. The maximal distance Dl between the support plane 300 and the free edge 74 is found in the concave portion 74.2. The minimal distance D2 between the convex intermediate portion 74.1 and the support plane 300 is found in a transition zone between the convex intermediate portion 74.1 and the concave end portion 74.3. Depending on the size of the pedestal bearing housing, the ration D1/D2 is between 3 and 7. The two transverse ribs 72 are effective to transfer load from the bearing seat 34 to the inner longitudinal walls 54, without substantially increasing the stress in the region of the upper flange wall 50 and of the through holes 60. Hence, the stress, which would be too high in the region of the upper flange wall 50 without the transverse ribs 72, lies within limits that ensure an indefinite operating life to the pedestal housing. Each transverse rib 72 spans an angle Al, measured in the transversal reference plane II-II from the median longitudinal plane I-I to the inner longitudinal supporting wall 54, of preferably more than 35° and less than 55°, in the present case of approximately 43°. The median foot 68 on the other hand spans and angle A2, measured in the transversal reference plane II-II from the median longitudinal plane I-I to the inner longitudinal beginning of the transverse rib 72, of preferably more than 3° but less than 10°, in the illustrated embodiment about 3,5°. The median longitudinal plane I-I is a plane of symmetry for the planar support surface 46 of the pedestal 42 and for the transverse ribs 72, and preferably for the outer longitudinal supporting walls 52, inner longitudinal supporting walls 54, upper flange walls 50 and preferably for the outer transverse walls 56, intermediate outer transverse walls 64 and inner reinforcing walls 66. [0026] In the variant of Fig. 5, the slanted inner reinforcing walls are omitted and the arched transverse ribs 72 extend from the bearing seat 34 to the inner longitudinal supporting wall 54 of the respective one of the two flange portions 48 and to the median foot 68, which protrudes towards the support plane 300 and has a median support surface that lies in the support plane and is part of the planar support surface 46.

[0027] Experimental results show that the ribs have a significant influence on the rigidity and deformation in particular when radial load is applied in a direction globally in the transverse reference plane II, but significantly offset with respect to a 0° direction defined as the radial direction towards the median foot 68, e.g. in a radial direction towards one of the inner longitudinal supporting walls 54.

[0028] A number of other variants are contemplated within the scope of the claims. In particular, the transverse reference plane II-II can be at mid-distance of the two outer transverse walls 56 of each flange portions 48. The intermediate outer transverse walls 64 can be dispensed with, or can have a free edge that remains at a distance from the support plane 300, in which case they operate like bridges between the two flange portions 48 without transmitting load to the base to which the pedestal is fixed. The bearing housing 16 can be made in one piece, or in more than two parts, in any suitable material, including e.g. grey cast iron, ductile cast iron, or cast aluminium.

[0029] The bearing 14 can be of any type, including spherical and non-spherical bearings, plain bearings and rolling bearings with rolling bodies 26 of any kind, including tapered, cylindrical, barrel or spherical rollers, balls and needles or combinations thereof, with one or more rows of rolling bodies, one or more outer rings and one or more inner rings. The inner ring can be force-fitted or otherwise fixed onto the shaft by any means. The outer ring can be omitted, in which case the bearing seat 34 is a bearing raceway or, if the bearing is a slide bearing, a slide bearing surface. Similarly, the inner ring can be omitted, and the inner raceway (in the case of a roller bearing) or inner slide bearing surface (in the case of a plain bearing) can be formed directly on the shaft. The bearing seat 34 can have a cylindrical shape, a stepped cylindrical shape, a conical shape, with or without splines.