AU772441B2

AU772441B2 - Tracking of belts and webs

Info

Publication number: AU772441B2
Application number: AU64486/99A
Authority: AU
Inventors: John Pear Cumberledge
Original assignee: Tru Trac Rollers Pty Ltd
Current assignee: TRU-TRAC ROLLERS Pty Ltd
Priority date: 1999-12-13
Filing date: 1999-12-13
Publication date: 2004-04-29
Anticipated expiration: 2019-12-13
Also published as: AU6448699A

Description

P/00/01i1 Regulation 3.2 AUSTRALI1A Patents Act 1990

ORIGINAL

COMPLETE* SPECIFICATION STANDARD PATENT a Invention Title: 'Tracking of belts and webs' The following statement is a full description of this invention, including the best method of performing it known to us: FNPSYT)CRWNATP32W99U7022.1 SCQ98334X)2.9 1 Tracking of Belts and Webs Field of the invention This invention relates to a tracking roller of the type adapted to track the alignment of belts and webs.

Background of the invention Tracking rollers are known and one roller which has proved to particularly effective in practice is that described in Australian patent no. 95/35584. The specification of that patent is incorporated herein by way of reference. The tracking roller described in patent no. 95/35584 has proved to be particularly effective for tracking conveyor belts and other belts where the belt is reasonably heavy.

The tracking roller described in patent no. 95/35584 can, it has been found, be used to track lighter belts and webs and this specification is directed to that invention. It is also found that wrapping the belt around the web to some extent can improve the tracking action.

Summary of the invention S: 15 According to the invention there is provided a method of tracking a belt web or the like, the method comprising the steps of: mounting a tracking roller adjacent the web so that the web travels over the tracking roller in use, the roller having a shaft and a drum coaxially rotatable relative to the shaft, the drum being pivotable relative to the shaft about a pivot axis; 20 aligning the web so that it wraps around the drum of the roller through a selected angle of wrap, the web being held under tension to ensure that a load is placed on the drum by the web; and allowing the drum to pivot on its pivot axis relative to the shaft when the web moves off its central position, the drum thereby steering the web back to its central position.

Preferably the pivot axis is perpendicular to the plane of the web at the point where the web leaves the surface of the roller. The angle of the pivot relative to the web may be varied so as to better track the web.

It is found that by aligning the pivot axis forward of perpendicular at the point where the web leaves the roller a very sensitive tracking action can be achieved.

C098334(H)2.9, 2 The invention will be described below in more detail with reference to the accompanying drawings. The specific features shown in the drawings should not be construed as limited on the invention.

Brief description of the drawings Figure 1 shows a tracking arrangement according to the invention; Figure 2 shows a side view of the arrangement depicted in Figure 1; and Figure 3 shows diagrammatically the manner in which the pivot axis and angle of wrap can be varied for different applications.

Detailed description of the embodiments 10 As shown in Figure 1 of the drawings a roller 10 for tracking a light weight web 12 includes a shaft 14 which in use will be mounted in a support frame or the like (not shown). The roller is similar to that described in the specification of Australian patent no. 95/35584. It will be noted that the roller includes an internal central pivot pin 16 which defines a pivot axis 18 about which the drum 15 is able to pivot relative to the shaft 14. Bearing assemblies 20 which are 15 spaced apart on either side of the pin 16 provide the facility for rotating the drum 15 relative to the shaft 14.

S Each edge region 22 of drum is tapered in a convergent direction away from the centre of the roller for the reasons set forth in patent no. 95/35584. However, in this particular application tapered edge regions are not necessarily required although it is found that if there is a taper the 20 sensitivity of the tracking action is improved.

The arrangement shown is particularly suitable for tracking light webs. The web 12, it will be noted, is wrapped around the drum of the roller through an angle a of approximately 90' The web travels in the direction of arrow 24 and the pivot axis 18 is substantially perpendicular to the web at the point where the web leaves the roller. The arrangement is best seen in Figure 2 of the drawings. As shown in Figure 2, the angle of wrap is shown as angle cx which in this particular instance is approximately 900. Figure 3 shows an angle of wrap which is less than The wrap of the web 12 around the roller imparts a load to the roller in the direction of arrow 26. This load, when it is eccentric to one or other side of the pivot axis 18 will cause the drum .CQ98334(X)29 3 to pivot to the shaft 14 and steer the web back to its centre position. The steering effect, as mentioned above, is enhanced where the edge regions 22 of the drum are tapered, but it is not essential that the tapers are provided since the eccentric load will, in any event, cause pivoting of the drum relative to the shaft 14.

The greater the wrap angle a the more positive will be the tracking angle. Figure 3 show a wrap angle a of less than 900. Obviously it will be possible to have a wrap angle of greater than It is found that the best tracking action is provided when the pivot axis 18 is substantially perpendicular to the web 12 at the point where the web 12 leaves the drum 15. It is also found that highly effective and sensitive tracking can be achieved where the pivot axis 18 is forward 10 of perpendicular at the point where the web leaves the drum 15. Figure 3 shows three different S'positions of the pivot axis 18. Position is where the pivot axis 18 is forward of the perpendicular, position shows the axis perpendicular, and position shows the pivot axis rearward of this perpendicular position. By adjusting the pivot angle (which is achieved by

S.

rotating the shaft 14 through a small angle relative to its mounting arrangement on the frame) a 15 greater of lesser degree of accuracy and sensitivity of tracking action can be achieved. By adjusting this angle the optimum tracking effect for a particular application can be achieved.

It is found that in the position the web may drift cyclically from side to side as it travels over the roller. This is because the roller will tend to overcorrect when the web travels to one side with the result that the web travels first to one side of the drum and then to the opposite side of 20 the drum. In certain applications, side to side tracking of the web is advantageous and by adjusting the pivot angle in the manner described this advantageous tracking effect can be achieved.

It will be appreciated that the simple manner in which the tracking sensitivity can be adjusted will be a considerable advantage in many applications.

Dated this 13th day of December 1999 Tru-Trac Rollers (Pty) Ltd by its attorneys Freehills Patent Attorneys

Claims

2. A method according to claim 1 wherein the pivot axis is substantially perpendicular to *:fe the plane of the web at the point where the web leaves the surface of the roller
3. A method according to claim 1 wherein the pivot axis forward of perpendicular at the point where the web leaves the roller.
4. A method substantially as hereinbefore described with reference to the accompanying drawings. i 0