GB2374854A

GB2374854A - Pivot bearing sealing arrangement

Info

Publication number: GB2374854A
Application number: GB0204769A
Authority: GB
Inventors: Jurgen Appel
Original assignee: Demag Mobile Cranes GmbH and Co KG
Current assignee: Demag Mobile Cranes GmbH and Co KG
Priority date: 2001-03-08
Filing date: 2002-02-28
Publication date: 2002-10-30
Also published as: GB0204769D0; DE20202463U1

Abstract

A large-dimension pivot bearing arrangement with rolling elements (4, 5) between a first annular bearing component (1) and a second annular bearing component (2) rotatable relative thereto about a bearing axis (3). The bearing components (1, 2) are connectable respectively to a first or second structural component of a large-scale apparatus, for example the upper and lower carriages of mobile cranes, excavators, turret cranes, cargo cranes, concrete mixing vehicles or other large-scale apparatus with high axial loads and load moments perpendicular to the bearing axis. Circularly circumferential running surfaces (6a, b; 7a, b), which in each case form running surface pairs, are provided respectively on the two bearing components (1, 2) for at least two rows of rolling elements (4, 5), by means of which compressive and tensile forces directed parallel to the bearing axis (3) may be transmitted. Circularly circumferential bearing surfaces (15a, b) can be provided respectively on the two bearing components (1, 2) for the transmission of radial forces. One (1) of the two bearing components (1, 2) is of divided construction and the two bearing components (1, 2) are each provided with a plurality of through-holes (10, 11) for fastening screws distributed circularly and extending parallel to the bearing axis (3). The gap between the two bearing components (1, 2) is covered externally by a casing-like seal (12), which covers the through-holes (11) in the second bearing component (2) in such a way that the heads or nuts of fastening screws inserted into the through-holes (11) are enclosed by the seal (12). The seal (12) is preferably an annular metal portion (12a) with sealing lip (12c) meeting annular portion (12b).

Description

Large-dimension pivot bearing arrangement The invention relates to a large-dimension pivot bearing arrangement.

Large-dimension pivot bearing arrangements have been-known for many years and are deemed standard components. They serve to connect large structural components, which need to be capable of rotation relative to one another. Typical applications are the connection of upper and lower carriages of mobile cranes, excavators, turret cranes or cargo cranes. Concrete mixing vehicles or similar large pieces of apparatus also require such bearing arrangements, since they are capable of absorbing high axial loads and load moments perpendicular to the bearing axis.

A standard large-dimension pivot bearing suitable for such applications is known from company brochure"Rothe Erde Large-Diameter Antifriction Bearings (Hoesch Rothe Erde GmbH, 8.97/2. 0, page 161)".

This large-dimension pivot bearing comprises a first bearing component and a second bearing component, which components are each provided with circularly circumferential bearing or running surfaces for two rows of cylindrical rolling elements with horizontal axes of rotation, wherein the running surfaces on the two bearing components each form running surface pairs. On the first bearing component, the two running surfaces for the two rows of rolling elements are located respectively on the top and bottom of a supporting ring, which projects from an annularly shaped base member. On the opposite side of this base member, the first bearing component has circumferential toothing which allows rotary driving of this first bearing component. This standard bearing is

obtainable in two versions, namely with internal toothing or with external toothing, such that the supporting ring is arranged either radially externally or radially internally on the base member of the first bearing component. The second bearing component is divided horizontally, i. e. perpendicularly to the bearing axis, and consists of an annular upper part and an annular lower part. To provide running surfaces for the rolling elements, the upper and lower parts are each provided with circumferentj recesses, which encompass the supporting ring of the first bearing component at a vertical distance from the upper and lower parts of the second bearing component when these are assembled. The vertical distance corresponds in each case to the diameter of the rolling elements, which are each arranged between the running surfaces of a pair of running surfaces. Forces which act in the direction of the vertical bearing axis (upwards or downwards) may be reliably transmitted via these rolling elements. To absorb radial forces, the magnitude of which is substantially less than the expected vertical forces, a third row of rolling elements is provided which comprise a vertical axis of rotation and may be described as radial guide rollers.

These guide rollers are supported on cylinder jacket-shaped bearing surfaces, which are in each case incorporated into end faces in the area of the circumferential supporting ring or at the upper part of the second bearing component.

In order to be able to connect the two bearing components with the structural components of the large-scale apparatus which are to be rotatably mounted relative to one another, a plurality of through-holes are provided in the two bearing components parallel to the bearing axis. These through-holes are designed to accommodate screws, with which the bearing components are each connected firmly to the structural components, for example with the upper carriage or the lower carriage of a mobile crane. The upper and lower parts of the second bearing component are held securely together by the screws. The two-part construction of he second bearing component is necessary, in order to

be able to position the rolling elements in the space between the respective associated running surface pair.

A mobile crane is known from US 5 664 692, in which the upper carriage is connected with the lower carriage by such a bearing. In addition, however, the first bearing component is of horizontally divided construction, wherein the two components may be coupled together via a bayonet joint type coupler in the manner of a rapid action coupling.

The through holes for the screws are arranged in two circles which exhibit a marked difference in diameter so that the screw heads or the associated nuts and the necessary seals for protecting the rolling elements may be accommodated in trouble-free manner. In the area between the two circles there are arranged the rolling elements for transmitting the vertical and also radial forces. In the event of the transmission of vertical forces acting from top to bottom (i. e. including the weight for example of the upper carriage of a mobile crane), considerable bending moments arise in the area of the supporting ring. In order reliably to control these, a solid construction of the pivot bearing is necessary. Due to the large diameter of such a bearing, this leads to considerable bearing weights, which take up a corresponding proportion of the admissible total weight, for example of a mobile crane.

An object of the present invention is to improve a largedimension pivot bearing arrangement of the above-described type so that the tare weight of the large-dimension pivot bearing is reduced but its load-bearing capacity remains the same.

A large-dimension pivot bearing arrangement comprising a first annular bearing component and a second annular bearing component rotatable relative thereto about a bearing axis, the bearing components being connectable

respectively to a first and second structural component of a large-scale apparatus, running surfaces provided on the two bearing components which form a running surface pair for each of at least two rows of rolling elements for transmitting compressive and tensile forces directed parallel to the bearing axis, and bearing surfaces provided on the two bearing components for the transmission of radial forces, wherein one of the two bearing components is of divided construction and the two bearing components are each provided with a plurality of through-holes in a circular distribution around and extending parallel to the bearing axis, and wherein the gap between the two bearing components is covered externally by a casing-like seal, which covers the through-holes in the second bearing component in such a way that the heads or nuts of fastening screws inserted into the through-holes in the second bearing component are enclosed by the seal.

In order to protect the rolling elements and the associated running surfaces from increased wear caused by the penetration of dirt, it is necessary to cover the gap between the first and second bearing components by a circumferential seal. According to the invention, the seal is constructed in such a way that it covers in the manner of a casing the screw connections (screw heads or nuts) for securing the second bearing component to a structural unit (e. g. the lower carriage of a mobile crane). This makes it possible to move these screw connections very close to the first bearing component, since the space no longer has to remain free to accommodate the seal. In this way, an altogether markedly more compact construction is achieved.

The associated effect of weight reduction is increased further in that the bending moments arising during force transmission between the two bearing components become smaller due to the fact that the securing points of the first and second bearing components are located closer together, such that the bearing components may be designed for smaller loads and thus be lighter.

The seal is preferably formed as a sheet metal casing, consisting of two sheet metal parts. A first sheet metal part of a flat, circular ring shape is connected tightly with the first bearing component and a second sheet metal part in the shape of a cylindrical jacket is connected tightly with the second bearing component in such a way that only a narrow, annular seal gap exists between the two sheet metal parts, which seal gap is covered by a circumferential resilient sealing lip, which is attached to the one sheet metal part and rests sealingly against the other sheet metal part.

In a preferred embodiment, rolling elements in the form of radial guide rollers are provided between the bearing surfaces, which serve to transmit radial bearing forces.

However, these bearing surfaces are not accommodated in conventional manner in the structural space which exists between the running surface pairs for transmitting axial bearing forces, but rather they are located outside this structural space, preferably beneath the lower most running surface pair in the case of a vertical bearing axis. In this way, a further reduction is possible in the difference in diameter between the two circles in which the fastening screws are arranged and so also a reduction in the bending moments arising.

A similar effect is achieved if, to transmit radial bearing forces, the bearing surfaces are constructed as plain bearings, in particular in the form of embedded plain bearing rings, instead of the hitherto conventional radial guide rollers.

In a further preferred embodiment, the through-holes through the first bearing component pass through only one of the two parts thereof. The one part of the first bearing component is then of solid construction, while the other part of the first bearing component takes the form of a

flat, hardened annular member with a substantially rectangular cross section, which surrounds the one part.

This flat annular member is not suited to transmitting relatively large bending moments, but it is suited to transmitting large compressive forces. On its flat underside, it comprises the running surface for one row of rolling elements, while its flat upper side forms a supporting surface for the first structural component of the large-scale apparatus (e. g. upper carriage of a mobile crane) when the large-dimension pivot bearing arrangement is in use.

The rolling elements recommended for use for the axial bearing forces are those of cylindrical or slightly tapered shape, rather than spherical or barrel-shaped rolling elements. The running surfaces for these rolling elements are appropriately perpendicular to the bearing axis.

It is advisable to make at least a proportion of the running surfaces for the rolling elements of embedded, hardened, annular, in particular segmentally assembled, arcuate strips. In this way, the effort involved in hardening the running surfaces may be reduced considerably.

In order to be able to rotate the bearing-mounted components relative to one another, it is expedient to provide one of the two bearing components radially internally or externally with circumferential toothing, in which a pinion or worm may engage.

In a particularly preferred embodiment, provision is made for the second bearing component to be provided with toothing and to be attached as a fixed bearing component to the lower carriage of a mobile crane in an horizontal orientation by means of screw connections.

The invention will now be described in more detail by way of example with reference to Figures 1 and 2, which each

illustrate different embodiments of a bearing arrangement of the invention in axial longitudinal section.

The large-dimension pivot bearing arrangement illustrated in Figure 1 comprises a first bearing component 1 and a second bearing component 2 mounted rotatably about the bearing axis 3. The first bearing component 1 is of divided construction and consists of a solid first part 8a and a light, flat, circular ring-shaped part 8b, which surrounds the first part 8a externally in the upper area. Distributed over the circumference of the first part 8a of the annular first bearing part 1 and parallel to the bearing axis 3 are through-holes 10, by means of which the first bearing component 1 may be fastened to a component (not shown, e. g. an upper carriage of a mobile crane) by means of screws, not shown. The second bearing component 2 radially externally comprises circumferential toothing 9, in which a pinion or worm, not shown, may engage for rotary drive. The second bearing component 2 is also provided with throughholes 11, which extend parallel to the bearing axis 3 and are distributed over the circumference of the likewise annular bearing component 2. Due to the through-holes 11, the second bearing component 2 may be fastened, e. g. to the lower carriage of a mobile crane, by means of screws, not shown. The two rows of rolling elements 4 and 5 serve to transmit axial bearing forces. The rolling elements 4,5 are oriented with their axes of rotation in each case perpendicular to the bearing axis 3 and are therefore suited only to the transmission of axial forces. The rolling elements 4 run in a pair of circularly circumferential running surfaces, of which the running surface 6a is arranged on the underside of the annular part 8b, exhibiting a rectangular cross section, of the first bearing component 1, while the running surface 6b is arranged at the base of a cylindrical recess in the area of the inner periphery of the annular second bearing component 2. Two circularly circumferential running surfaces 7a, 7b are associated with the rolling elements 5, which are

likewise arranged with their axes of rotation perpendicular to the bearing axis 3. The running surface 7a is arranged at the base of a cylindrical recess in the lateral surface area of the part 8a of the first bearing component 1, while the running surface 7b is incorporated likewise cylindrically into the area of the inner periphery of the second bearing component 2, in the lower half thereof. The rolling elements 4,5 are each cylindrical. Radial bearing forces may be transmitted via rolling elements 14 serving as radial guide rollers, which rolling elements 14 are arranged between cylindrical bearing surfaces 15a, 15b, which are provided beneath the lower row of rolling elements 5, i. e. not between the two running surface pairs 6a, 6b and 7a, 7b. The rolling elements 14 are retained by a cover plate 13.

To prevent the penetration of dirt into the area of the running surfaces 6a, 6b and 7a, 7b, a casing-like seal 12 is provided which covers the gap between the two bearing components 1,2 moving relative to one another. This seal 12 comprises a flat, circular, first sheet metal part 12a, which is connected in sealed manner with the flat second part 8b of the first bearing component 1 and is positioned radially relative to the bearing axis 3. A second sheet metal part 12b cooperates with the first sheet metal part 12a and is cylinder jacket-shaped and connected tightly with the second bearing component 2. The sheet metal part 12b starts close to the foot of the toothing 9 and extends coaxially to the bearing axis 3 as far as the flat sheet metal part 12a, such that only a narrow seal gap remains between the two. This seal gap is covered by a resilient circumferential sealing lip 12c attached to the sheet metal part 12a, which sealing lip 12c lies in externally sealing manner against the outer surface of the second sheet metal part 12b. In this way, the seal 12 covers the entire structural space for accommodating the screw heads or nuts of the fastening screws to be introduced into the throughholes 11. A separate free space between the rolling

elements 4 and the through-holes 11 for accommodating the seal is therefore no longer necessary. The partial circles for the through-holes 10,11 may therefore be moved markedly closer together. The effective lever arm is thereby correspondingly reduced in the case of the transmission of bearing forces parallel to the bearing axis 3 and the load caused by bending moments is markedly reduced.

Figure 2 shows a functionally substantially identical variant of the arrangement of Figure 1. It differs merely in that a plain bearing is provided instead of the rolling elements 14 for the transmission of radial bearing forces.

To this end, the bearing surfaces 15a, b, which are arranged in the area between the two running surface pairs 6a, 6b and 7a, 7b, take the form of plain bearing surfaces.

This is preferably achieved in the form of an embedded plain bearing ring on at least one bearing surface 15a, 15b. The plain bearing rings may be composed segmentally of curved, batten-like flat strips.

Claims

Claims: 1. A large-dimension pivot bearing arrangement comprising a first annular bearing component and a second annular bearing component rotatable relative thereto about a bearing axis, the bearing components being connectable respectively to a first and second structural component of a large-scale apparatus, running surfaces provided on the two bearing components which form a running surface pair for each of at least two rows of rolling elements for transmitting compressive and tensile forces directed parallel to the bearing axis, and bearing surfaces provided on the two bearing components for the transmission of radial forces, wherein one of the two bearing components is of divided construction and the two bearing components are each provided with a plurality of through-holes in a circular distribution around and extending parallel to the bearing axis, and wherein the gap between the two bearing components is covered externally by a casing-like seal, which covers the through-holes in the second bearing component in such a way that the heads or nuts of fastening screws inserted into the through-holes in the second bearing component are enclosed by the seal.
2. A large-dimension pivot bearing arrangement according to claim 1, wherein the seal comprises a ring-shaped first sheet metal part connected tightly with the first bearing component and a cylindrical jacket-form second sheet metal part connected tightly with the second bearing component, such that an annular seal gap is formed between sheet metal parts.
3. A large-dimension pivot bearing arrangement according to claim 2, wherein the seal gap is covered by a resilient sealing lip.

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4. A large-dimension pivot bearing arrangement according to any preceding claim, wherein the bearing surfaces comprise plain bearings.
5. A large-dimension pivot bearing arrangement according to claim 4, wherein the bearing surfaces comprise plain bearing rings.
6. A large-dimension pivot bearing arrangement according to any preceding claim, wherein rolling elements in the form of radial guide rollers are arranged between the bearing surfaces and the bearing surfaces are located outside the structural space enclosed between at least the two running surface pairs.
7. A large-dimension pivot bearing arrangement according to claim 6, wherein the bearing surfaces are located beneath the lowermost running surface pair.
8. A large-dimension pivot bearing arrangement according to any preceding claim, wherein the through-holes in the first bearing component extend only through a first part of the first bearing component and the second part of the first bearing component takes the form of a flat, annular member of substantially rectangular cross section which surrounds the first part, has a running surface for the rolling elements on its underside and, in use, forms a supporting surface for the first structural component of the large-scale apparatus.
9. A large-dimension pivot bearing arrangement according to any preceding claim, wherein the rolling elements are of cylindrical construction.
10. A large-dimension pivot bearing arrangement according to claim 9, wherein the running surfaces extend perpendicularly to the bearing axis.

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11. A large-dimension pivot bearing arrangement according to any preceding claim, wherein at least a proportion of the running surfaces take the form of embedded, hardened, annular strips.
12. A large-dimension pivot bearing arrangement according to claim 11, wherein the strips are segmentally divided.
13. A large-dimension pivot bearing arrangement according to any preceding claim, wherein one of the two bearing components has circumferential toothing internally or externally.
14. A large-dimension pivot bearing arrangement substantially as hereinbefore described and illustrated in accompanying drawings.