GB2030465A

GB2030465A - Intermittently advancing an endless filter belt

Info

Publication number: GB2030465A
Application number: GB7837738A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-09-22
Filing date: 1978-09-22
Publication date: 1980-04-10
Also published as: DE2937599A1; DE2937599C2; GB2030465B

Abstract

An endless belt filter 20 is provided wherein an operative run of the belt 21 can be intermittently advanced by a horizontally reciprocating main drive roller 22 adjacent a downstream end thereof and wherein a secondary drive arrangement 24-29 is provided adjacent the upstream end of the operative run, the secondary drive arrangement including a one-way device 24 (e.g. a ratchet or friction drive) arranged to prevent the main drive roller moving the inoperative run of the belt backwards and a movable secondary drive roller 27 supported by a bight of the belt and acting to apply tension thereto. Rollers 25 and 26 are fixed support rollers, and belt tracking devices 29 track the belt. Roller 27 may be hollow with weights disposed therein and may slide in guides between a raised position (shown dotted) which corresponds to the advancing position of roller 22 and a lower position when it has taken up slack occurring upon retraction of ram 23 and roller 22. <IMAGE>

Description

SPECIFICATION Belt filter This invention relates to a belt filter particularly a horizontal belt filter similar to that described in British Patent No. 1434211.

As described in that Patent, the upper operative run of a belt filter 10 (see Figure 1) can be advanced by a displaceable roller 11. The slack belt produced being returned to the infeed end of the filter 10 by means of a pneumatic motor 12 driving rollers 13 and absorbed at the infeed end by a gravityinfluenced tension roller 14. The condition of the filter 10 after the displaceable roller 11 has travelled to the left in Figure 1 is shown in dotted lines. The belt is typically tracked by pneumatic trackers 15.

This belt filter 21 has some serious disadvantages.

Firstly, it requires a motor to drive the belt. Secondly, the angle of contact at the trackers 15 changes with different lengths of filter. Thirdly, on long filters the counterweightforthe roller 14 has to be ofsubstantial size, because it has to overcome not only the pull of the wet cloth, but also the weight of roller 14 and friction at its guides and at the pulley. An object of the present invention is to provide an improved belt filter which does not have the above disadvantages.

Accordingly the invention provides a belt filter wherein an operative run of the belt can be advanced by a movable main drive roller adjacent a downstream end of the operative run of the belt, a secondary belt drive arrangement being provided adjacent the upstream end of the belt and comprising a one-way device arranged to prevent the main drive roller moving the inoperative run when the main drive roller moves to advance the operative run, and, between the one-way device and the upstream end of the operative run, a secondary drive roller supported by a bight of the belt and acting to apply thereto, by its own weight, tension to draw in slack in the inoperative run open retraction of the main drive roller.

The one-way device can comprise one or a pair of rollers engaging the belt and associated with a ratchet device. Alternatively a one-way friction device can be used. Preferably the said bight of belt extends between an upstream deflection roller of the filter and a second, fixed, support roller disposed below and downstream of the deflection roller of the filter and a second, fixed, support roller disposed below and downstream of the deflection roller. The secondary drive roller can have its ends provided with slides which engage guides fixed in a frame of the filter. Belt tracking devices can be mounted to engage the belt between the second fixed support roller and the one-way device.

The secondary drive roller can have sufficient weight by virtue of its construction, or can be hollow and have weights placed inside it. In cases where neither of these possibilities provides sufficient weight (it is envisaged that these would be extremely rare) weights can be attached to the ends of the secondary drive roller.

The invention will be described further, by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a schematic side elevation of a known filter; Figure 2 is a similar view of a preferred filter of the invention; and Figure 3 is an elevation of a tension arrangement of an actual filter conforming to the invention.

Referring firstly to Figure 1, which shows a known arrangement, it will be seen that the upper operative run of a belt filter 10 (see Figure 1) can be advanced by a displaceable roller 11. The slack belt produced being returned to the infeed end of the filter 10 by means of an electric motor 12 driving rollers 13 and absorbed at the infeed end by a gravity-influenced tension roller 14. The condition of the filter 10 after the displaceable roller 11 has travelled to the left in Figure 1 is shown in dotted lines. The belt is typically tracked by pneumatic trackers 15. This belt filter 10 has some serious disadvantages. Firstly, it requires a motor to drive the belt. Secondly the angle of contact at the trackers 15 changes with different lengths of filter, which means that the trackers 15 have to be positioned differently for each different length of filter.Thirdly, on long filters the counterweight for rollers 14 has to be of substantial size, because it has to overcome not only the pull of the wet cloth, but also the weight of roller 14 and friction at its guides and at the pulley.

A preferred filter 20 of the present invention (Figures 2 and 3) has a belt 22 and a main drive roller 22 at the downstream end of the upper, operative, run of the belt 21. The roller 22 can be extended to the left in Figure 2 by means of fluid actuated rams 23. Adjacent the upstream end of the operative run of the belt 21 is a secondary belt drive arrangement (best seen in Figure 3) which takes in the slack produced in the inoperative run of the belt 21 when the roller 22 is retracted. The secondary belt drive arrangement includes a one-way device in the form of a pair of friction rollers 24 which are allowed to pass the belt only from left to right in the figures by a ratchet (not shown). Between the rollers 24 and a fixed end infeed roller 25 is disposed a second fixed support roller 26.A bight of the belt 21 between rollers 26 and 25 supports a secondary drive roller 27, whose ends have slides engaging guides 28. Belt tracking devices 29 of conventional form, act on the belt 21 between the rollers 24 and roller 25.

In operation suction is normally applied to a chamber or chambers (not shown) beneath the operative run of the belt 21 and liquid is thereby drawn through the belt 21. Whilst the suction is applied, the belt 21 is held so tightly against the filter tray that the roller 22 would not move it. Accordingly, when the belt 21 is removed, the application of suction is suspended and the rams 23 extend to move rollers 22 to the left in the figure. The one-way device (rollers 24 and their ratchet) prevent this movement causing right-to-left movement of the inoperative run. The right-to-left movement of the operative run raises roller 27. When the rams 23 begin to retract they start to create slack which is drawn along the inoperative run by the weight of roller 27.

The invention is not limited to the precise details of the foregoing and variations can be made thereto.

For example, the one-way device does not have to incorporate a ratchet and can be a one-way friction device. The roller 27 can have sufficient weight by virtue of its construction or be hollow and have weights disposed therein. In rare occasions additional weights could be added to the ends of the roller 27 outside the width of the belt 21.

Claims

1. A belt filter wherein an operative run of the belt can be advanced by a movable main drive roller adjacent a downstream end of the operative run of the belt, a secondary belt drive arrangement being provided adjacent the upstream end of the belt and comprising a one-way device arranged to prevent the main drive roller moving the inoperative run when the main drive roller moves to advance the operative run, and, between the one-way device and the upstream end of the operative run, a secondary drive roller supported by a bight of the belt and acting to apply thereto tension to draw in slack in the inoperative run open retraction of the main drive roller.

2. Afilterasclaimedinclaim 1, wherein the oneway device comprises one or a pair of rollers engaging the belt and associated with a ratchet device.

3. A filter as claimed in claim 1, wherein the one-way device is a friction device.

4. A belt as claimed in claim 1,2 or 3, wherein the said bight of the belt extends between an upstream deflection roller of the filter and a second, fixed, support roller disposed below and downstream of the deflection rollers.

5. A filter as claimed in any preceding claim, wherein the secondary drive roller has its ends provided with slides which engage guides fixed in a frame of the filter.

6. Afilter as claimed in any preceding claim wherein belt tracking devices are mounted to engage the belt between the second fixed support roller and the one-way device.

7. A filter as claimed in any preceding claim, wherein the secondary drive roller has sufficient weight by virtue of its construction.

8. A filter as claimed in any of claims 1 to 6, wherein the secondary drive roller is hollow and has weights placed inside it.

9. A filter as claimed in any of claims 1 to 6, wherein weights are attached to the ends of the secondary drive roller.

10. A belt filter substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.