GB2214266A

GB2214266A - Belt and pulley drive

Info

Publication number: GB2214266A
Application number: GB8800721A
Authority: GB
Inventors: Peter Hadlow
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1988-01-13
Filing date: 1988-01-13
Publication date: 1989-08-31
Also published as: GB8800721D0

Abstract

A drive apparatus comprises a drive belt (3) entrained about a pulley (1). The pulley (1) has a flange (6) to restrain the belt from moving laterally. The flange (6) is arcuate and has a relieved portion in the form of a flat (6a) which enables the pulley to be located at a minimum radial distance from a fixed restraint, such as a second pulley (2) about which the drive belt is also entrained, without trapping the belt. By rotating the pulley (1) until the flat (6a) is adjacent the second pulley (2), the belt can be removed from the area between the pulleys (1 and 2) for servicing or repair purposes. <IMAGE>

Description

Belt and Pullev Drive This invention relates to a drive apparatus comprising a pulley and a drive belt entrained about the pulley.

It is very well known in the art to transmit drive to a rotatable shaft via a pulley mounted on the shaft, and a drive belt entrained about the pulley. The belt may rely merely on friction to drive the pulley or the belt and pulley may both be toothed to provide more positive interaction.

It is also well known to provide the pulley with an annular flange on one or both sides thereof to restrain lateral movement of the belt and hence control belt tracking.

However, if the pulley is located in a radial direction close to a restriction, the flange can give rise to increased space requirement than would otherwise be necessary. This is obviously a drawback where compactness is sought. Thus, if the pulley is located close (radially) to a fixed part of the drive apparatus such as the housing, the flange of the pulley must be spaced apart from the housing by at least the thickness of the belt in order that the belt can be removed for servicing and repair purposes. Similarly, if the drive apparatus has two closely located pulleys driven by the same belt, the spacing between the pulleys has to be increased if either pulley has such a belt-tracking flange on its outboard side, that is to say on the side from which it is required to remove the belt for servicing or repair.

According to the present invention there is provided a drive apparatus comprising a pulley, and a drive belt entrained about the pulley, the pulley having on its outboard side an arcuate flange adjacent the bearing surface thereof to check lateral movement of the belt, the flange extending around a major arcuate portion but not the whole of the circumference of the pulley bearing surface.

A drive apparatus in accordance with the invention has the advantage that the pulley is provided with a flange for belt tracking but without affecting the minimum radial separation of the pulley from a fixed restriction. In other words the provision of an arcuate flange on the pulley means that the pulley may be located just as close to a restriction as if the flange were absent. This is especially advantageous for a compact drive apparatus. In order to remove the belt, e.g. for servicing or repair purposes, it is then necessary merely to rotate the pulley until the non-flanged portion is aligned with the restriction. The belt can then be removed from the gap between the pulley bearing surface and the restriction.

To enable minimal radial space in between the pulley and the restriction it is preferable if the chord joining the ends of the arcuate flange is tangential to the circumference of the pulley or, for more clearance, if the aforementioned chord intersects the circumference of the pulley.

In a particular embodiment the drive apparatus comprises a further pulley about which the belt is also entrained in such manner that the belt extends about the two pulleys in a substantially 'S'-shaped configuration. In this case the radial distance between the arcuate flange and the bearing surface of the further pulley may be less than the thickness of the belt.

The minimum spacing is when the respective bearing surfaces of the two pulleys are at a distance substantially equal to the thickness of the belt.

Although a flange may be provided on both the outboard and inboard sides of each pulley, a preferred arrangement is where each pulley has only a single flange on opposite sides respectively, with the arcuate flange on the outboard side of one pulley and the other pulley having on its inboard side an annular flange extending around the whole circumference of that pulley.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: The single Figure is an elevation of the salient part of a drive apparatus in accordance with the invention.

The drive apparatus in the Figure comprises a first pulley 1 and a second pulley 2 and a drive belt 3 entrained about the two pulleys 1 and 2 in a substantially 'S'-shaped configuration. The drive belt 3 may be a an endless belt driven in known manner by a motor (not shown). The belt may be driven in either direction, depending on the desired rotation of the pulleys 1 and 2, but in either case, as will be evident from the drawing, the pulleys 1 and 2 are rotated in mutually opposite senses. The drive belt 3 may be a flat, high-friction belt or may be provided with teeth on both its bearing surfaces to engage corresponding teeth on the bearing surfaces of the pulleys 1 and 2. Pulley 1 drives an integral drive shaft 4 and pulley 2 drives an integral drive shaft 5.These drive shafts 4 and 5 may, for example, be associated respectively with the developer roll and toner distributing auger of a conventional electrostatographic copying machine, which have to be closely located.

Pulley 1 is provided with a single flange 6 on its outboard side that is to say the side which would be accessed for servicing and repair purposes; and pulley 2 has a single flange on the opposite, inboard side. This pair of flanges 6 and 7 on the opposite sides of pulleys 1 and 2 respectively act to restrain the belt 3 from moving laterally and so control belt tracking. The flange 7 extends around the full circumference of pulley 2, whereas the flange 6 extends around a major arcuate portion, but not the whole, of the circumference of the bearing surface of pulley 1. Thus the flange 6 is effectively provided with a relieved portion in the form of a flat 6a which is defined by the chord joining the two ends of the arc defining the outline of the flange 6. The flat 6a may be substantially tangential with the circumference of the bearing surface of pulley 1.Alternatively the plane in which flat 6a lies may intersect the circumference of the bearing surface of pulley I. Thus the flange 6 is essentially relieved at least as far as the bearing surface of pulley 1 so that the belt 3 can easily be removed from between the pulleys I and 2 by rotating pulley 1, for example manually, until the flat 6a is aligned between the two pulleys at right angles to a line joining the centres of the two pulleys 1 and 2. In this way the pulleys 1 and 2 can be located at the same minimum radial spacing as if the pulleys were flangeless. In other words, the pulleys 1 and 2 may be so close that the distance between their bearing surfaces is substantially equal to, or only a little in excess of the thickness of the drive belt.

In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention. For example, a flange having a circular outline may be provided on the inboard side of pulley 1 either in addition to or as an alternative to the inboard flange 7 on pulley 2. Also, an outboard flange may be provided on pulley 2, and this may provided with a flat analagous to the flange 6 on pulley 1 so that the two flats could be aligned to help release the belt more easily. Also, it is noted here that a drive apparatus in accordance with the invention may comprise only a single pulley. The fixed restriction constituted by the second pulley 2 in the above embodiment may be constituted by some other fixed member such as the housing of the drive apparatus.

Claims

Claims:

1. A drive apparatus comprising a pulley, and a drive belt entrained about the pulley, the pulley having on its outboard side an arcuate flange adjacent the bearing surface thereof to check lateral movement of the belt, the flange extending around a major arcuate portion but not the whole of the circumference of the pulley bearing surface.

2. A drive apparatus as claimed in claim 1, wherein the chord joining the ends of the arc defining the flange is substantially tangential to the circumference of the bearing surface of the pulley.

3. A drive apparatus as claimed in claim 1, wherein the chord joining the ends of the arc defining the flange intersects the circumference of the bearing surface of the pulley.

4. A drive apparatus as claimed in any of the preceding claims, comprising a further pulley about which the belt is also entrained in such manner that the belt extends about the two pulleys in a substantially 'S'-shaped configuration, the radial distance between the arcuate flange and the bearing surface of the further pulley being less than the thickness of the belt.

5. A drive apparatus as claimed in claim 4, wherein the further pulley has on the inboard side a flange extending around the whole circumference thereof.

6. A drive apparatus substantially as herein described with reference to the accompanying drawing.