GB2054766A

GB2054766A - Shaft bearing

Info

Publication number: GB2054766A
Application number: GB8013618A
Authority: GB
Original assignee: Union Sils Van de Loo and Co GmbH
Current assignee: Union Sils Van de Loo and Co GmbH
Priority date: 1979-04-26
Filing date: 1980-04-24
Publication date: 1981-02-18
Also published as: FR2455207A1; DE2916798A1; NL8002445A; FR2455207B3; DE2916798C2

Abstract

In a bearing for fast running shafts, for example the rotor shaft of a bicycle dynamo, a plastics bearing bush axially insertable and rotationally securable in a bearing housing comprises hollow spaces (25, 25'; 26, 26') forming lubricant chambers extending around bearing surface 15, this surface being provided with lubricant grooves (21, 22) which each communicate with a lubricant chamber. <IMAGE>

Description

SPECIFICATION Shaft bearing The present invention relates to a plastics material bearing, which is particuiarly suitable for use as for the rotor shaft of a bicycle dynamo.

The journalling of shafts with the use of bearing bushes of plastics material is generally known.

Difficulties which have not yet been satisfactorily solved, have arisen in the use of plastics material bearings for shafts which run extremely fast, for example, the rotor shafts of bicycle dynamos.

Although trials of plastics material bearings journalling rotor shafts of bicycle dynamos have already been undertaken, these trials have not been successful, because at the high rotational speeds which may arise, such bearings are damaged after unacceptably short running times and eventually become unusable.

In view of the fact that substantial cost advantages would be achieved by the use of plastics material bearings for fast-running shafts, which is of particular importance in the field of the bicycle accessories such as dynamos, there is a need for a longer-lifed plastics material bearing.

According to the present invention there is provided a high-speed shaft bearing of plastics material, the bearing comprising a substantially cylindrical sleeve, the interior wall of which defines a bearing surface provided with a plurality of lubricant channels, and means defining a plurality of lubricant chambers which extend around the bearing surface and each communicate with at least one of the channels.

With such a bearing, the communication of the lubricant channels grooves with the lubricant chambers enable a flow through the channels of a cooling lubricant and thereby heat removal from the bearing, which keeps the temperature loading of the bearing surface within acceptable limits.

Investigations have confirmed that the earlier trials with plastics material bearings in the particular field of interest have been unsuccessful because the bearings, due to inadequate removal of heat at rotational speeds in the order of, for example, 10,000 r.p.m., were destroyed by overheating. By contrast, a bearing construction which withstands high temperature loading and may be economic to manufacture is provided by a bearing embodying the invention.

Preferably the bearing comprises two substantially cylindrical and concentric sleeves with a gap therebetween, the gap being divided into regions which form the lubricant chambers.

Expediently, the lubricant channels each extend from an end of the bearing over about half the length of the bearing surface and project beyond a radial web arranged in a plane transverse to the bearing axis, each of the channels being connected to a respective lubricant chamber, which is arranged in the region of the axial half of the bearing remote from the respective channel.

For preference, a respective web, interconnecting the sleeves in the region of each lubricant channel, extends axially between the radial web and the respective end of the bearing; the lubricant chambers divided by the radial web are then also divided in circumferential direction into separate compartments so that it is possible to associate a separate lubricant compartment with each lubricant channel. Preferably, the bearing comprises an injection-rmoulded part manufactured from a temperature-resistant plastics material, for example by a slideless tool.

An embodiment of the invention will now be more particularly described by way of example with reference to the accompanying drawings in which: Fig. 1 is a partly sectioned schematic elevation of a bicycle dynamo housing with a rotor shaft of the dynamo journalled in a bearing embodying the invention; Fig. 2 is a plan view of the bearing of Fig. 1; Fig. 3 is a longitudinal section on the line Ill-Ill offing.2; Fig. 4 is a longitudinal section on the line IV--IV of Fig. 2; Fig. 5 is a longitudinal section on the line V-V of Fig. 3, the section being displaced through 900 relative to the section of Fig. 3; and Fig. 6 is an inverted plan view of the bearing.

Referring now to the drawings, in Fig. 1 there is shown a bicycle dynamo rotor shaft 10 with a knurled wheel 11 mounted on the shaft to be rotatable therewith, the shaft being journalled in a bearing 13 retained in a dynamo housing 12.

The bearing 13, illustrated by itself in Figs. 2 to 6, is injection-moulded from temperature-resistant plastics material in a slideless tool and comprises two thin-walled sleeves 14 and 15, the sleeves being arranged substantially concentrically but at a radial spacing. The sleeves are connected by a radial web 17, which is arranged in a plane transversely intersecting the axis 1 6 of the bearing and which divides the annular gap between the sleeves into hollow spaces each open towards one end face of the bearing. These spaces are further divided by four radial webs, which extend in the axial direction of the bearings and are explained in more detail below.

Arranged at one end of the outer sleeve 14 is an encircling flange 18, which extends radially beyond the sleeve and which, when the bearing is mounted in the housing 12, rests on an end face 1 9 of the housing, the cylindrical part of the sleeve being received in a cylindrical recess of the housing.

The inner sleeve 1 5 defines a bearing surface 20, which is provided with a respective pair of lubricant grooves 21,21 or 22, 22' extending from each end face of the bearing beyond the radial web 1 7. The grooves of each pair are arranged to be diametrically opposite and adjacent grooves disposed in axial halves remote from each other are displaced through ninety degrees relative to each other. A respective pair of webs 23, 23' or 24, 24', which interconnect the sleeves 14 and 1 5 and subdivide the hollow spaces communicating with one of the end faces of the bearing into a pair of chambers 25, 25' or 26, 26', extends in axial direction between each end face of the bearing and the radial web 1 7.These chambers form lubricant pockets and each of the lubricant grooves, which extends along a respective one of the webs 23,23', 24 and 24' at the interior of the bearing, communicates through a respective one of four channels 27,27', 28 and 28' with a respective one of the lubricant pockets arranged in the axial half of the bearing remote from the particular end face of the bearing from which that groove extends. In addition, two radially extending lubricant grooves 29 and 29' are arranged in the region of the end face of the bearing provided with the radial flange 1 8.

In use of the bearing as illustrated in Fig. 1 , the lubricant pockets 25, 25' or 26,26' are filled with a suitable lubricant of viscous consistency and a throughflow of the lubricant grooves 21, 21' or 22, 22' by lubricant via the channels 27, 27' or 28, 28' takes place in operation of the dynamo so that heat arising in the region of the bearing is conducted away. ln view of the thin-walled construction of the inner sleeve 1 5 forming the bearing surface 20, in conjunction with heat removal from the bearing due to the throughflow by cooling lubricant, a build-up of heat in the bearing is prevented and the life of the bearing meets the particular requirements of use in journalling a relatively high-speed shaft.

Claims

1. A high-speed shaft bearing of plastics material, the bearing comprising a substantially cylindrical sleeve, the interior wall of which define a bearing surface provided with a plurality of lubricant channels, and means defining a plurality of lubricant chambers which extend around the bearing surface and each communicate with at least one of the channels.

2. A bearing as claimed in claim 1, comprising a further sleeve concentrically surrounding the firstmentioned sleeve with an annular space therebetween, the sleeves being interconnected by a radial web which is arranged in a plane extending transversely to the axis of the sleeves and which divides the annular space.

3. A bearing as claimed in claim 2, wherein each of the channels extends over approximately half the axial length of the first-mentioned sleeve from an end thereof to a point past the radial web and communicates with a lubricant chamber disposed in the half of the sleeve remote from that end.

4. A bearing as claimed in either claim 2 or claim 3, wherein the channels are arranged at substantially uniform spacings around the bearing surface.

5. A bearing as claimed in any one of claims 2 to 4, wherein the sleeves are further interconnected by a respective plurality of axial webs extending in the axial direction of the sleeves from the radial web to each pair of adjacent ends of the sleeves.

6. A bearing as claimed in claim 5, wherein each of the axial webs is arranged in the region of a respective one of the channels.

7. A bearing as claimed in any one of the preceding claims, the bearing being an injection moulding from temperature-resistant plastics material.

8. A high-speed shaft bearing substantially as hereinbefore described with reference to the accompanying drawings.

9. A bicycle dynamo comprising a housing, a bearing as claimed in any one of the preceding claims mounted in the housing to be stationary relative thereto, and a rotor drive shaft rotatably journalled in the bearing.