GB2223827A - Hub and bush assembly - Google Patents

Description

HUB AND BUSH ASSEMBLV The present invention relates to a hub and bush assembly for a rotary component.

Exchangeable slide bushes or bushes subject to wear must be inserted into hubs as free of play as Possible and must be secured against axial displacement and against rotation relative to the hub after the insertion. This securing is usually effected by means of a fitted key or another suitable locking element. The use of several keys or the like at the circumference is generally not possible, because the grooves in bush and hub would not be in alignment. The axial fastening of the bush in the hub for the reception of the thrust forces takes place by way of collars.

Another possibility of securing consists in shrinking the bush in place. For this purpose, the bushing receives an excess dimension at its outer diameter and, after supercooling by nitrogen, is inserted into the hub.

A further possibility of a securing can be achieved by serrated toothings, splined shafts or similar. Performance of this mode of securing, however, is very laborious and correspondingly expensive.

In the case of components with extremely large dimensions, for example cable sheaves for mine shaft conveyor plant, it is not possible at all, because processing machines cannot handle components with a diameter of several metres.

Bronzes, gun metal and so forth are used as material for cable sheave bushes. The moduli of elasticity for such materials are only half as great as in the case of steel, and to that extent the bush is twice as elastic as the hub material (steel). When the load is rotating, the axle rolls along on the bush inner circ-umference with the required play. This process is equivalent to the rolling of a wheel on a resilient substrate or to the rolling of a rolling pin on dough. A bead of resilient material forms in front of the wheel in the rolling direction, i.e. the wheel quasi entrains material.

Transferred to the example of the cable sheave, this means that the bush will tend to rotate. When this bead of material jumps over a fitted key, the key is stressed at high pressure in its groove-in the bush. In the course of time, this groove is beaten out in the-more solid and less compressible hub material. In the case of the aforementioned cable sheave, this effect is enhanced by constant changes in rotational direction. The exchange of bushes, particularly in the mentioned components, is time-consuming and costly.

A similar wear process is observable in shrunk bushes. Due to the constant filling, the shrinkage stresses suffer fatigue and the bush becomes loose and turns in the hub. Since lubrication takes place through the hub, the lubrication bores are no longer in alignment after rotation of the bush and the bush is destroyed in a short time.

There is therefore a need for securing, in simple mode and without additional cost, of a bush in a hub such that an almost stepless support of the bush may be achievable.

According to the present invention there is provided a hub and bush assembly for a rotary component, the assembly comprising a hub provided with an internal toothing, a bush provided with an external toothing and arranged in the hub with the toothings disposed at a spacing from each other, and a resin casting mass filling the space between the hub and the bush.

In such an assembly, the bush can be secured over its entire circumference against rotation in the hub. The fulling action, which is damaging in the securing of bushes by means of a fitted key, or the rotation of the bush in the hub on stress relaxation in the case of shrink fitting, cannot arise.

An axial fixing of the bush by means of a fit an an inner collar is not required if sufficient space is present in this region for the introduction of casting resin.

Such a hub and bush assembly is particularly suitable as a cable sheave for a multi-cable pit conveyor in the mining industry. Use of the assembly is not, however, restricted to components of that kind, but can be utilised for other components such as hubs mounted in sliding bushings with slowly rotating loads.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a cross-section of a hub and bush assembly embodying the invention; Fig. 2 is a sectional view, along the line A-B of Fig. 1, of one connection arrangement in the assembly; and Fig. 3 is a sectional view similar to Fig. 2, but of an alternat ive connection arrangement.

Referring now to the drawings, there is shown in Figs. 1 and 2 a hub and bush assembly of two conveyor cable sheaves of a four-cable pit shaft conveyor, the assembly comprising a bush 1 arranged within a hub 2. A cable sheave of that kind, with a diameter of about 6 metres, is constructed in two parts. The connection of the sheave halves is effected by way of screws. The cable sheave axle is borne in radially self-aligning roller bearings. In the case of a cable sheave for a multi-cable conveyor, one sheave is secured to a common axle 3 and the remaining sheaves are free on the axle.

Web plates 4, at which arms (not shown) with tread are arranged, are mounted on the hub 2.

As shown in Fig. 1, the hub 2 is provided with an internal toothing 5 and the bush 1 with an external toothing 6. It can be seen that the toothings are not interengaging and thus are independent of tolerance.

A positioning screw 12 serves as an assembly aid for fixing the position of the toothings of the hub and bush bushing relative to each other.

To fix the bush relative to the hub, liquid casting resin 8 is poured by way of a bore 7 into the intermediate space between the hub and the bush. A commercially available phenol resin, epoxide resin or unsaturated polyester can inter alia be used as the casting resin.

The toothing 6 of the bush 1, as shown in Fig. 2, has an encircling groove 9 by means of which the formation of air bubbles in the lower region is avoided during filling with resin.

After the setting of the resin, the bush is secured around its entire circumference against rotation.

A particular advantage of filling of the intermediate space between hub and bush with casting resin for the purpose of securing against relative rotation is that the load carrying capacity of the component is increased or the pressure per unit area reduced, since the middle bush part can particiDate in the carrying.

A fit at an inner collar is not necessary for axial fixing of the component. If sufficient space is present there, the fixing can take place at the same time during the filling of the intermediate space between hub and bushing by casting resin, as illustrated in Fig. 3.

By contrast, and merely by way of example, Fig. 2 shows a fitted-in collar.

A lubricating tube 10, indicated in Fig.1 , is sheathed by a permanently resilient filling mass, for example silicone putty, in order that elastic deformations cannot shear off the lubricant tube.

Claims (6)

- CLAIMS

1. A hub and bush assembly for a rotary component, the assembly comprising a hub provided with an internal toothing, a bush provided with an external toothing and arranged in the hub with the toothings disposed at a spacing from each other, and a resin casting mass filling the space between the hub and the bush.

2. An assembly as claimed in claim 1, wherein the hub is provided at its circumference with positioning means for positioning the bush relative thereto.

3. An assembly as claimed in either claim 1 or claim 2, wherein the toothing of the bush is provided with an encircling ventilation groove.

4. An assembly as claimed in any one of the preceding claims, comprising a lubricant pipe for supply of lubricant to the bush, the pipe being sheathed by a resilient filling mass.

5. A hub and bush assembly substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.

6. A hub and bush assembly substantially as hereinbefore described with reference to Figs. 1 and 3 of the accompanying drawings.