GB2123497A

GB2123497A - Spring assembly for resiliently supporting a bearing

Info

Publication number: GB2123497A
Application number: GB08317887A
Authority: GB
Inventors: Ken Mitsubori; Kazuo Watanuki
Original assignee: Ishikawajima Harima Heavy Industries Co Ltd; IHI Corp
Current assignee: IHI Corp
Priority date: 1982-07-12
Filing date: 1983-07-01
Publication date: 1984-02-01
Also published as: DE3322522A1; FR2529975A1; GB8317887D0; GB2123497B; JPS5910520U

Abstract

A spring assembly for resiliently supporting a bearing comprises a plurality of nested coaxial cylindrical plates 4 of spring material. Each of the plates is punched to form cuts defining a plurality of resilient integral spring tongues 4a spaced apart in the peripheral direction. <IMAGE>

Description

SPECIFICATION Spring assembly for resiliently supporting a bearing The present invention relates to a spring assembly for resiliently supporting a bearing, in particular a journal bearing of a high speed machine, and to a bearing supported by such an assembly.

One known such spring assembly for resiliently supporting a bearing which in turn supports a rotary shaft of a machine, such as a marine turbocharger or a centrifugal compressor, rotating at high speed, and the method of making it is illustrated in Figure 1. The spring assembly is fabricated by punching a multiplicity of small holes 102, seen in Figure 1(b), in a metal sheet 101 and then forming the metal sheet into the shape of a cylinder, as shown by the solid line in Figure 1(a).

When loaded, this spring assembly is deformed as indicated by the broken line in Figure 1(a). In practice, a plurality of such cylindrical springs fabricated in the manner described above are nested within each other as shown diagrammatically in axial section in Figure 1(c).

However, a satisfactory spring action is not obtained. Especially if the shaft to be supported is a heavy one, the lower side 103 of the spring assembly sinks as indicated in Figure 1 (d) so that satisfactory oil films cannot be formed and maintained between the cylindrical spring members and consequently fretting tends frequently to occur. In Figure 1(d), reference numeral 104 denotes the upper side of the spring assembly and 105 a load acting on the shaft.

It is an object of the present invention to provide a spring assembly for resiliently supporting a bearing which substantially overcomes the problems referred to above and which can reduce the vibrations of a rotary shaft supported by the bearing to a minimum, can increase the operational range in which safe and stable rotation of the shaft is ensured and can also increase the operating life of the bearing.

According to the present invention a spring assembly for resiliently supporting a bearing comprises a plurality of overlying plates together formed into an annular shape, at least some of the plates affording a plurality of resilient integral spring tongues. The radius of curvature of the spring tongues preferably differs from that of the plates with which they are integral, e.g. each spring tongue may be substantially planar.

Further features and details of the present invention will be apparent from the following description of certain specific embodiments which is given by way of example with reference to Figures 2 to 5 of the accompanying diagrammatic drawings, in which: Figure 2 is an axial sectional view of a first embodiment of the present invention resiliently supporting a bearing which in turn supports a rotary shaft; Figure 3(a) is an end view of the spring assembly of Figure 2; Figure 3(b) is a side view of the spring assembly; Figure 4(a) is a scrap plan view of a single tongue-shaped spring portion punched in a metal sheet or the like in accordance with the present invention; Figure 4(b) is a view illustrating the spring action produced by the tongue-shaped spring portion shown in Figure 4(a);; Figures 5(a), 5(b) and 5(d) show alternative shapes and dispositions of the tongue-shaped spring portions; and Figure 5(c) is an axial view of a single spring member.

Figure 2 shows a rotary shaft 1 supported by a bearing 2 within an outer bearing bushing 3 which in turn is supported by a spring assembly 4 in accordance with the present invention within a casing 5.

The spring assembly 4 comprises a plurality of cylindrical spring members of metal or other spring material nested coaxially within one another, as shown in Figure 3(a). Each spring member is provided with a longitudinal array of tongue-shaped spring portions or spring tongues 4a spaced apart from each other by a small distance in the peripheral direction, as seen in Figure 3(b). The tongue-shaped spring portions 4a can be formed by a conventional punching or rolling operation to form a plurality of apertures or cuts each of which defines a spring tongue integrally connected to its plate along a line extending in the axial direction.

In the free state, that is to say when no load is exerted on a spring member, it has a radius of curvature r1 as shown in Figure 4(b) but a radius of curvature r2 as indicated by the broken line when assembled with other spring members and subjected to a load. However, the spring portions 4a tend to spring back so as to assume their initial position, i.e. to have the initial radius r.

A plurality of spring members, each with a plurality of punched tongue-shaped spring portions 4a, are formed into a stack and then bent into a cylindrical or annular shape. The resultant spring assembly 4 is snugly fitted over the bushing 3 which in turn is snugly fitted over the bearing 2 as shown in Figure 2. The spring assembly 4 can produce a spring action over its whole circumference as shown in Figure 5(c).

Alternatively, a spring assembly may be formed by making a stack of spring members with punched tongue-shaped spring portions 4a according to the present invention alternating with conventional spring members of the type illustrated in Figure 1 (b) with holes punched therein and then forming the stack into a cylindrical or ring shape.

The spring members of the spring assembly 4 can produce a spring action over their whole circumference so that satisfactory oil films can be maintained due to the surface tension of the oil between the spring members. As a result, an adequate damping action can be achieved.

The tongue-shaped spring portions 4a can be clearly defined so that it is simple to provide a spring assembly with a desired spring constant.

The tongue-shaped spring portions 4a have been described as having a predetermined radius of curvature ra, but it is to be understood that the punched spring portions 4a may have no radius of curvature, that is to say they may be planar.

As shown in Figure 5(a), the spring portions 4a may be disposed in two or more peripheral lines and they may all be directed in the same peripheral direction or they may be disposed in pairs in back-to-back relationship as shown in Figure 5(b). The tongue-shaped spring portions 4a may be square or rectangular, as shown in Figures 3(b), 4(a), 5(a) and 5(b) or they may have other shapes, e.g. hexagonal as shown in Figure 5(d).

The features and advantages of the present invention may be summarised as follows: In order to ensure a stable support and rotation of a rotary shaft, an optimum spring constant as well as an optimum damping coefficient must be selected. In a spring assembly according to the present invention, an optimum spring constant can be selected by suitably selecting the width A, the length B and the thickness t of the spring portions, as shown in Figure 4(a).

The spring portions are preferably uniformly distributed along the circumference or periphery of each spring member so that non-uniform characteristics of the spring assembly 4 can be avoided and consequently a high degree of concentricity can be attained. A stable rotation of the rotary shaft can thus be ensured even at high speeds. Vibration of the rotary shaft can be reduced to a minimum so that the vibratory load exerted on the bearing can be reduced to a minimum and consequently the operating life of the bearing can be considerably increased.

Oil films can be positively maintained between the spring members so that fretting may be suppressed.

Claims

1. A spring assembly for resiliently supporting a bearing comprising a plurality of overlying plates together formed into an annular shape, and at least some of the plates affording a plurality of resilient, integral spring tongues.

2. An assembly as claimed in Claim 1 in which the radius of curvature of the spring tongues differs from that of the plates with which they are integral.

3. An assembly as claimed in Claim 2 in which the spring tongues are substantially planar.

4. An assembly as claimed in any one of the preceding claims in which each spring tongue is integrally connected to its associated plate along a single line extending substantially in the axial direction.

5. A spring assembly for resiliently supporting a bearing substantially as specifically herein described with reference to any one of Figures 3(b), 4(a), 5(a), 5(b) and 5(d).

6. A bearing surrounded and resiliently supported by a spring assembly as claimed in any one of the preceding claims.