WO1993010373A1

WO1993010373A1 - Belt or pulley drive arrangements

Info

Publication number: WO1993010373A1
Application number: PCT/GB1992/002099
Authority: WO
Inventors: Kevin Granville
Original assignee: Kevin Granville
Priority date: 1991-11-13
Filing date: 1992-11-12
Publication date: 1993-05-27
Also published as: GB9124123D0

Abstract

A belt or pulley drive arrangement comprises a reaction strut mounted between two rotary shafts which are coupled by the belt or pulley. The strut comprises an elongate tube (10) having bearings (12, 14) screw-threaded to its opposite ends. In use, the bearings mount the respective rotary shafts at a fixed distance parallel to each other.

Description

Belt or Pulley Drive Arrangements

This invention relates to belt or pulley drive arrangements.

Belt or pulley drives are used extensively in industrial machinery, either to transmit drive between shafts or for timing the rotation of one shaft relative to another, or for a combination of these purposes. The use of belt or pulley drives provides many advantages over other forms of drive. However, the tension in the belt or pulley causes considerable stress to be placed on the rotary shafts and the support structure for these shafts. This can make it difficult to maintain the necessary constant tension in the belt or pulley and can prohibit the use of belt drives in applications which would otherwise benefit from their advantages.

I have now devised belt or pulley drive arrangements which overcome these problems.

In accordance with this invention, there is provided a belt or pulley drive arrangement which comprises a reaction strut mounted between two rotary shafts which are coupled by the belt or pulley. The reaction strut includes a bearing at each end for the respective rotary shafts. Preferably the reaction strut mounts the two rotary shafts at a fixed distance parallel to each other. The reaction strut is adjustable in length, so that it can be adjusted to preset the tension in the drive belt or pulley (so that the tension will remain constant) .

The reaction strut opposes the tension in the belt and effectively contains the action and reaction forces between the two shafts with little or no stress being transmitted elsewhere. The stresses in the shafts are confined to a shear load which is of low value.

Preferably two reaction struts are employed with each drive belt, the two struts being positioned either side of the drive belt and close to it. Alternatively a single strut may be employed with each drive belt, the strut being positioned inside the belt.

Embodiments of this invention will now be described by way of examples only and with reference to the accompanying drawings, in which:

FIGURE 1 is a side view of an embodiment of a reaction strut for a belt drive with some parts shown cut away; FIGURE 2 is a schematic view of a belt drive in which two such reaction struts are employed between two rotary shafts;

FIGURE 3 is a schematic view of a belt drive in which drive is transmitted from one shaft to another via an intermediate shaft, and in which reaction struts are mounted between the adjacent pairs of shafts; and

FIGURE 4 is a sectional view through an alternative embodiment of a single reaction strut mounted to a rotary shaft; Referring to Figure l of the drawings there is shown a reaction strut for use in a belt or pulley drive. The reaction strut comprises an elongate section e.g. a tube 10 having bearings 12, 14 fixed to its opposite ends by means of screw threads 11, 13 which are of opposite hand. The bearings 12, 14 are intended to receive two parallel shafts and the screw- threaded mounting of the bearings 12, 14 to the tube 10 enables the strut to be expanded in length by turning the tube 10, to preset the tension in the drive belt. Locknuts e.g. 16 are provided to lock the tube 10 against turning after the tension has been set.

Referring to Figure 2, preferably two reaction struts

20, 21 (each as shown in Figure 1) are used, one either side of a belt 22 which is trained about pulley wheels 23, 24 keyed at 27, 28 onto respective rotary shafts 25, 26. The reaction struts are positioned close to the opposite sides of the belt.

Referring to Figure 3, the reaction struts can be used in an arrangement which transmits drive from one shaft 30 to another shaft 32 via an intermediate shaft 31 and in which the shafts 30 and 32 can be moved relative to each other in

transverse directions x and y. Thus, in the example shown, two reaction struts 36, 37 are mounted between the shafts 31 and

32 either side of a drive belt 38 which couples these two shafts. It will be appreciated that the shafts 30 and 32 can be moved relative to each other (with consequent movement of the intermediate shaft 31) in the x and y directions, whilst maintaining the drive and keeping a constant tension in each of the drive belts.

Referring to Figure 4 there is shown an alternative embodiment of reaction strut in which like parts are given like reference numerals. A clevis 40 is screw-threaded to opposite ends of the tube 10. The clevis 40 comprises a U-shaped element having an aperture extending through its opposite sides for receiving a rotary shaft e.g 41. Two bearings 43, 46 are mounted in the apertures formed in the clevis 40. A motor 45 having a shaft 41 is mounted adjacent the clevis so that its shaft 41 extends axially along the aperture. A sleeve 44 fits onto the shaft 41 to connect the shaft 41 to the bearings 43, 46. A pulley wheel 42 is mounted to the shaft 41 inside the clevis 40. A similar arrangement is preferably provided at the opposite end of the tube 10 so that a single strut may be used to mount a belt or pulley around the pulley wheels on opposite ends of the strut.

Claims

1) A belt or pulley drive arrangement which comprises a reaction strut mounted between two rotary shafts which are coupled by the belt or pulley.

2) A belt or pulley drive arrangement as claimed in claim 1 comprising a bearing at each end for the respective rotary shafts.

3) A belt or pulley drive arrangement as claimed in claim 1 or 2 in which the reaction strut mounts the two rotary shafts at a fixed distance parallel to each other.

4) A belt or pulley drive arrangement as claimed in any preceding claim in which the reaction is adjustable in length.

5) A belt or pulley drive arrangement as claimed in any preceding claim in which two reaction struts are employed with each drive belt, the two struts being positioned either side of the drive belt.

6) A belt or pulley drive arrangement as claimed in any of claims 1 to 4 in which a single reaction strut is employed with each drive belt, the strut being positioned inside the belt.