GB2067438A

GB2067438A - Washers for electric motors

Info

Publication number: GB2067438A
Application number: GB8100815A
Authority: GB
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1980-01-17
Filing date: 1981-01-12
Publication date: 1981-07-30
Also published as: FR2474249B1; DE3001481A1; BE886391A; DE3001481C2; GB2067438B; FR2474249A1

Abstract

A washer for limitation of the axial freedom of movement of the rotor of a small motor, consisting of a hollow cylinder 2 of rubber, in the end face of which is embedded a running ring 1 of hardened steel, with a running surface 5 extending in the radial direction. The hollow cylinder 2 and the running ring 1 are vulcanised together, and the hollow cylinder has a projection 4, which extends inside the running ring 1 as far as the running surface 5 of the latter. <IMAGE>

Description

SPECIFICATION Washers The invention relates to washers for limitation of the axial freedom of movement of the rotor of a small motor, the washers consisting of a hollow cylinder of rubber, in the end face of which is embedded a running ring of hardened steel, with running surface extending in the radial direction.

The advertising leaflet Ringsdorff-MK Sintermetall-Larger, 1977 issured by Ringsdorff Werke GmbH, 5300 Bonn-Bad Godesberg, Germany, relates to washers of the kind defined above. The washers in the leaflet consisted of a hollow cylinder of rubber with a circumferential recess in the shape of an angle and open inwards, in which the actual running ring of hardened steel was secured by adhesive. The internal diameter of the running ring was slightly greater than the external diameter of the associated shaft, the internal diameter of the hollow cylinder slightly smaller than the shaft. The anchoring between the shaft and the washer occurred from the elastic enlargement of the hollow cylinder during assembly.By this elastic enlargement, however, damage, to the adhesive connection between the two components of the washer could be caused, which has a disadvantageous effect with respect to the later reliability in use.

The objective underlying the invention is to develop a washer of this kind in such a way that, in addition to the possibility of manufacture simply and economically, an exceptional reliability in use in ensured.

This objective is solved according to the improvement in that the hollow cylinder and the running ring are vulcanised together, and that the hollow cylinder has a projection, which extends inside the running ring as far as the running surface of the iatter.

The security of the connection between the two components can additionally be improved by employment of an adhesive coating in the zone of the co-operating contact surfaces. In this connection it is preferred to use an epoxy resin, and the blank is provided with this before carrying out the vulcanisation process, at least on the back surface and on the radially inwardly facing surface of the running ring.

The running ring is inserted in a vulcanisation tool, while its concentric position is determined by the external diameter and projections of the tool associated with it, and the elastomeric material is deformed to fit by injection or pressing, and is vulcanised on. A further subsequent treatment is thus not necessary after cooling, but the washer can be taken out of the tool in a condition ready to be installed.

What is decisive for the anchoring of the washer on a shaft is, just as in the state of the art, the matching of the internal diameter of the hollow cylinder to the external diameter of the associated shaft.

A significant distinctive feature however consists in the fact that the actual zone of support in the washer according to the invention is displaced into the area of the projection. This projection, after installation of the washer, is supported in the radial direction from within by the shaft and in the radial direction from without by the internal periphery of the running ring. Relaxation phenomena of the elastomeric material can therefore not become apparent in a disadvantageous manner, even after a long time, and a particularly high-quality anchorage of the washer is ensured. The contact surfaces between the running ring and the hollow cylinder are fully relieved of mechanical pre-stresses, and hence, even in this zone, no loosening is to be feared even after long operation. The overall reliability achieved in use can consequently-be significantly improved.

The projection of the hollow cylinder, particularly with small dimensions of the washer, is suitably constituted as a circumferential bead, in general rectangular cross-sections of bead are preferred.

However, in the neighbourhood of the internal periphery, half-round cross-sections are also possible, and they are suitable if the zone of the hollow cylinder which, in the axial direction, is behind the running ring, has shape departing from a rectangular cross-section for improvement of the axial resilient behaviour. The anchoring of the washer to the shaft is in these cases produced exclusively by the zone lying radially within the running ring, while the remaining part of the hollow cylinder can possible have an internal diameter which is greater than the external diameter of the shaft. The cross-section of the hollow cylinder in this zone can for example be bulged outwards like a membrane, and then enclose internally an annular space.According to further constructions it is possible to form the relevant zone like a bellows, and possible to reinforce it with additional resilient reinforcing elements of metal.

Such elements are for example annular coil springs or dish springs. These can individually be either loosely installed, or directly vulcanised in.

According to a development, the projection is divided by grooves distributed uniformly around the circumference, into segments extending parallel to the axis of rotation. Such a construction commends itself particularly in relation to the formation of washers for large shaft diameters of for example more than 15 mm. It permits easier assembly.

The width of the segments is in itself as desired, but it amounts preferably to no more than three times the radial thickness. In the neighbourhood of the internal diameter, the segments can be rounded.

The number of segments uniformly distributed around the circumference is as desired, numbers divisible by three are preferred however with reference to a rotationally symmetrical arrangement of the washer on the shaft.

With reference to the attainment of the desired reliable anchoring, it is desirable that the ratio between the axial length and the radial width of the projection lies in a range of 0.9 to 1.5. The radial width of the projection preferably has a value in the range of 0.03 to 0.5 times the internal diameter of the hollow cylinder, but is at least 0.2 mm.

In the above calculation, the internal diameter of the hollow cylinder can be taken as approximately equal to the external diameter of the associated shaft. The stability of the anchoring of the washer to the shaft, for all shaft diameters, is found to be exceptional if the proportions mentioned above are used.

In the accompanying drawings are shown two embodiments of washers according to the invention by way of example, in half-sectioned view.

Figure 1 shows a washer with a retangular crosssection with a running ring vulcanised in on one side.

Figure 2 shows a washer on which a running ring is vulcanised in on both end faces, and where the hollow cylinder has circumferential recesses on the external and internal peripheries between the two running rings, for attainment of a better elasticity in the axial direction.

The washer according to Figure 1 includes a hollow cylinder 2 of an elastomeric material, preferably of rubber. This cylinder is vulcanised on directly onto the running ring 1, which has a running surface 5 extending in the radial direction. The anchorage on the associated shaft, not shown, is effected principally in the neighbourhood of the projection 4, where the elastomeric material after assembly is compressed between the internal periphery of the running ring and the external periphery of the associated shaft. If the projection 4 is made circumferentially continuous, it is sufficient if the internal diameter 3 of the hollow cylinder is only slightly smaller than the external diameter of the associated shaft. If, however, the projection 4 is sub-divided into a plurality of segments by grooves extending in the axial direction, then the relevant difference in dimensions must be larger.

In Figure 2 is shown a washer in which a running ring 1 isvulcanised in into each of the two end surfaces opposed to one another. The hollow cylinder 2 is weakened in its cross section in the zone between the two running rings, by circumferential grooves in the external and internal peripheries, so that the cylinder has an X-shaped formation in cross section. As regards the anchoring on the associated shaft, the remarks above with reference to Figure 1 hold good. The resilient elasticity in the axial direction is substantially improved by the particular shape of cross section of the hollow cylinder.

Claims

1. Awasherfor limitation of the axial freedom of movement of the rotor of a small motor, consisting of a hollow cylinder of rubber, in the end face of which is embedded a running ring of hardened steel, with a running surface extending in the radial direction, characterised in that the hollow cylinder and the running ring are vulcanised together, and that the hollow cylinder has a projection, which extends inside the running ring as far as the running surface of the latter.

2. Awasher according to claim 1, characterised in that the projection is constituted as a circumferential bead.

3. A washer according to claim 1 or claim 2, characterised in that the projection is divided, by grooves distributed uniformly around the circumference, into segments extending parallel to the axis of rotation.

4. Awasher according to claim 3, characterised in that the number of segements is divisible by three.

5. Awasheraccording to any of claims I to 4, characterised in that the radial width of the projection has a value in the range of 0.03 to 0.5 times the internal diameter of the hollow cylinder, but is at least 0.2 mm.

6. Awasher according to any of claims 1 to 5, characterised in that the ratio between the axial length and the radial width of the projection lies in a range of 0.9 to 1.5.