WO1992001616A1

WO1992001616A1 - Conveyor

Info

Publication number: WO1992001616A1
Application number: PCT/GB1991/001245
Authority: WO
Inventors: George Terah Gough; Andrew Terah Gough; John Stuart Francis; Eric +Di Whitehurst
Original assignee: Gough Holdings (Engineering) Ltd.; Whitehurst, Freda +Hf
Priority date: 1990-07-25
Filing date: 1991-07-25
Publication date: 1992-02-06
Also published as: AU8237891A; GB9016274D0; ZA915854B

Abstract

A conveyor for conveying materials comprises a plurality of containers (10), at least one endless drive member (12) for driving the containers in an endless circuit, the endless circuit including a filling (26) and a discharge (28) zone, each container being attached to the or each drive member so as to be rotatable relative thereto; means (18, 20) for driving the or each endless member around the endless circuit, a first guide formation (63), and a second complementary guide formation (40, 110). The first and second guide formations are arranged to engage in a region between the filling and discharge zones to maintain each respective container upright in that region, whereby spillage of the container contents in that region can be prevented.

Description

CONVEYOR This invention relates to a conveyor for conveying materials.

A known conveyor comprises a plurality of containers attached to an endless chain and driven on that chain in an endless circuit so as to convey particulate material between a filling zone, where material is loaded into the containers, and a discharge zone, where the material is unloaded from the containers by inverting the containers. The containers are pivotally mounted on the chain. A fixed lip is provided on each container, and the containers are arranged by a system of pivoting links to be moved closer to each other in the region of the filling zone so that the lip on each container overlaps an adjacent container. This prevents material falling between the containers while they are being loaded.

However, the known conveyor suffers from a number of drawbacks. Firstly, since the containers are free to pivot they are liable to spill their contents or collide witir adjacent containers, especially if they have been fille - unevenly. Satisfactory discharge of the container contents can also be difficult. Secondly, the mechanism required to move the containers closer together in the region of the filling zone is complex, and is thus expensive to manufacture and maintain.

Another conventional conveyor is a belt and bucket or chain and bucket dredging type elevator, in which the buckets are fixedly attached to the belt or chain so that they cannot pivot relative thereto. Discharge is achieved purely by centrifugal forces. The containers are filled in the normal way. Material which has been spilt during filling or discharge is "dredged up" by the containers on their return run prior to reaching the filling zone.

This type of conveyor is expensive to maintain because of the wear caused by the dredging action, and has a low capacity because of inaccuracies in the filling process and because of spillage between the filling and discharge zones.

According to the present invention, there is provided a conveyor for conveying materials, comprising a plurality of containers; at least one endless drive member for driving the containers in an endless circuit, the endless circuit including a filling and a discharge zone, each container being attached to the or each drive member so as to be rotatable relative thereto; means for driving the or each endless member around the endless circuit; a first stationary guide formation; and a complementary second guide formation on each container for engagement with the first guide formation; the first and second guide formations being arranged to engage in a region between the filling and discharge zones to maintain each respective container upright in that region, whereby spillage of the container contents in that region can be prevented, As used herein, the term "conveyor" includes the term "elevator", and "upright" connotes orientations of the container at which spillage of the container's contents is substantially prevented, as opposed to orientations at which the container contents will discharge. By use of the cooperating first and second guide formations in a region between the filling and discharge zones much greater control of the containers is achievable in that region, so that content spillage and container collision can be prevented. The containers are most usually containers of a conventional shape such as are used in conveyors such as centrifugal belt and bucket conveyors, and are most conveniently spaced regularly along the or each endless member so that the gaps between the containers and their adjacent containers which may form large clearances are roughly identical. The endless member may be a chain supporting the containers, the chain being driven round two or more sprockets, or it may be a belt or the like. The conveyor of the present invention may conveniently be of the elevator type, in which materials are elevated from a lower filling zone to a higher discharge zone.

Often, the first and second guide formations would be arranged to engage over the entire region between the filling and discharge zone. The region of their engagement suitably includes a region where the containers are driven on an incline, and more preferably a region where the containers are driven vertically or near vertically, since use of the guide formations is then particularly advantageous.

The first and second guide formations may engage interlockingly together, but would more normally be some form of cam and cam follower arrangement. In this case, preferably each container is attached to the or each endless member such that the weight of the container is arranged to bias the respective second guide formation against the first guide formation in said region. This is a particularly simple manner of ensuring that the two guide formations engage.

Alternatively or additionally, the conveyor may further comprise a biassing device for biassing the respective second guide formation against the first guide formation in said region. This biassing device preferably comprises a respective resilient member for each container arranged to cause a biassing torque between the respective container and a respective endless member.

In one preferred embodiment, each container is resiliently attached to the respective endless member via its respective resilient member, so that the attachment does not involve any frictional bearing. This can reduce the number of parts required in the conveyor and ensure that there is no wear at the attachment between container and endless member. Preferably, the conveyor further comprises a first control formation on each container engageable with a second complementary control formation on an adjacent container to limit rotation of said container relative to said adjacent container. The complementary control formations can thus be utilised to provide an additional way of controlling container rotation.

Preferably, one of the control formations includes cover means for covering at least part of the gap between said container and said adjacent container. By using the control formation for a second purpose, the number of parts in the conveyor can thus be reduced. The other of the control formations may suitably be a portion of the container itself (typically one of its edges) .

In one preferred embodiment, the cover means is mounted fixedly on its respective container.

In another preferred embodiment, the conveyor further comprises cover means mounted on each said container and movable relative thereto between a deployed position in which it covers at least part of the gap between itself and an adjacent container, and a retracted position, and trigger means to move the cover means between its deployed and retracted positions. The cover means and complementary trigger means enable the gap between adjacent containers to be covered in a manner which is mechanically simpler than that adopted in the known conveyor. Further, since the cover means can be moved to a retracted position, movement of one container relative to another may be permitted without the cover means interfering with this movement, so that, for instance, the containers can be moved from a horizontal portion of the circuit to an upstanding or even vertical portion.

Although the cover means may not cover the gap between each container and the relevant adjacent container completely when it is in its deployed position, it is preferable that the coverage is such as to prevent material falling between the containers in the filling zone. The cover means on each said container may suitably be mounted adjacent the leading edge of that container, although there is no reason why it should not be mounted adjacent its trailing edge.

Preferably, the cover means on each said container includes a cover which is shaped to direct material into either said container or the relevant adjacent container. This ensures satisfactory filling of the containers at the filling zone. The cover may suitably have an arcuate cross- section. Preferably, the cover means on each said container includes a cam, and the trigger means includes a stationary cam follower (conveniently in the form of an unlatch or relatch ramp) , each cam cooperating with the cam follower during operation of the conveyor to move the cover means between its deployed and retracted positions. This arrangement is preferred because it is mechanically simple, and particularly because movement of the cover means is effected by movement of the containers themselves rather than by some other type of actuator. Again, for mechanical simplicity, it is preferred that the cover is fixed to the cam and both the cam and the cover are pivotable relative to their respective container.

Preferably, the cover means on each said container forms a close fit with said adjacent container in its deployed position (to prevent material passing between the cover means and the adjacent container) , but does not interfere with the movement of said adjacent container in its retracted position. This is important if, for instance, the containers are directed from a horizontal portion of the circuit to an upstanding portion (or vice versa) so that they move relatively to each other.

Thus, the drive means may be arranged to drive each said container upright along a generally horizontal portion of the circuit so that it can be filled, and then to elevate it whilst maintaining it upright, and, if so, the trigger means is preferably arranged so that the cover means on each said container is deployed during filling but retracted before each said container has been elevated significantly. Preferably, after elevating each said container the drive means is arranged to drive it generally horizontally, and the trigger means is arranged so that the cover means is retracted during the final portion of the elevation. This ensures that the transition between an upstanding portion of the circuit and the horizontal is effected without the cover means interfering with the relative movement of each said container and its relevant adjacent container.

Preferably, the cover means on each said container is arranged to cooperate, in its deployed position, with said adjacent container to limit movement of said container and said adjacent container relative to each other. The cover means can thus be used to control the relative orientation or position of the containers. It will be appreciated that this feature may in fact be completely independent of the feature that the cover means covers the gaps between adjacent containers. The cooperation between the cover means on each said container and said adjacent container is suitably achieved by the cover itself bearing on or latching with the adjacent container.

In one preferred embodiment, the cover means on each container is arranged to limit pivotal movement of said adjacent container between discharge and subsequent filling of each container. Thus the cover means may support one end of the container during its return run. This arrangement is advantageous because the drive means does not have to control the orientation, but only the position, of each container. It will be understood that between the discharge and subsequent filling of each container it is not necessary that the container be upright.

Preferably, the cover means on each said container is biassed towards the deployed position.

In broad terms, the invention provides generally a drive means which maintains each container upright not only during filling but also during its elevation (or other subsequent travel) , to prevent spillage. It is preferred that it achieves this by supporting it at two vertically separated locations. This may suitably be achieved by providing each container not only with a pivot connection to the drive means but also with a control arm, one end of which is fixed to the container and the other end of which is arranged (possibly by means of a roller) to be guided over a ramp. In this way the orientation of the container can be precisely controlled.

Preferred embodiments of conveyor will now be described, by way of example, by reference to the accompanying drawings, in which: Figure 1 is a side elevational view of a conveyor according to the present invention, with a main frame removed and upper and lower sprockets removed (but shown chain dotted) to reveal hidden detail; Figure 2 is a view, similar to that shown in Figure 1, of an alternative layout for the top portion of the conveyor;

Figure 3 is an exploded view of a container for use on the conveyor; Figure 4 is a cross-sectional view of a part of the container taken in the direction of the arrows X-X' shown in Figure 6;

Figure 5 is a cross-sectional view of the conveyor mounted in the main frame taken in the direction of the arrows Y-Y' shown in Figure 1;

Figure 6 is a detailed side elevational view of part of the conveyor showing the operation of an unlatch ramp;

Figure 7 is a detailed side elevational view of part of the conveyor showing a filling zone; Figure 8 is a detailed side elevational view of part of the conveyor in the region of the unlatch ramp;

Figure 9 is a detailed side elevational view of part of the conveyor in the region of a relatch ramp;

Figure 10 is a diagrammatic side elevational view of an alternative embodiment of conveyor according to the present invention;

Figure 11 is a detailed side elevational view of a container mounted on the conveyor chain of the second embodiment; Figure 12 is a detailed plan view of the container; and

Figure 13 is a detailed front elevational view of the container.

In the various embodiments, the same parts are represented by the same reference numerals.

Referring to Figure 1, a first embodiment of conveyor comprises generally a plurality of containers 10 mounted between two endless chains 12, only one of which is visible

8

in Figure 1. The chains 12 pass around upper sprockets 14 and lower sprockets 16. Again, although two upper and two lower sprockets are provided, only one of each is visible in Figure 1. A drive motor 18 is connected to each upper sprocket 14 by a drive chain and sprocket assembly 20 so as to drive each chain 12 in the direction shown in Figure 1. Each lower sprocket 16 is arranged to be tensioned by a tensioner 22 which enables the tension in each chain 12 to be adjusted. Clearly, other drive and tensioning arrangements may alternatively be adopted. Intermediate the upper and lower sprockets 16 and 20 the chains 12 are arranged to run in a path defined by chain tracks 24 (not shown in Figure 1) which are described in more detail below. As shown in Figure 1, the conveyor is configured to be filled at a filling zone 26 and to be discharged at a discharge zone 28.

It will be appreciated that, by altering the shape of the chain tracks 24 or by adding additional sprockets, different layouts to the layout shown in Figure 1 can be produced. As an example. Figure 2 shows such' an alternative layout in which, by the addition of additional sprocket 30 and changing the geometry of the chain track 24, the top section of the conveyor has been extended in the horizontal plane so as to distance horizontally the discharge zone 28 further from the filling zone 26.

The design of the containers 10 will now be described in greater detail with reference^* to Figures 3 and 4. Each container 10 comprises generally a container body 32, which is of the standard type, a U-shaped support plate 34 bolted to the container body 32, and a lip cam assembly 36 mounted on the support plate 34 for limited pivotal movement relative thereto. A control arm 38 depends from one end only of the U-shaped support plate 34, and is rigidly affixed thereto. A lower roller 40 is affixed to the depending end of the arm 38. Although only one control arm and lower roller is provided on just one side of the container, it will be appreciated that control arms and lower rollers could be provided on both sides. This would indeed be preferable for long containers.

The lip cam assembly 36 consists of a lip cover 42 extending between two lip cams 44. The lip cam assembly 36, support plate 34 and chains 12 are joined together by means of pivot pins 46, washers 48, spacers 50, and tapped bushes 52 for receiving the pivot pins. The lip cam assembly, as seen in Figure 3, is biassed anticlockwise by spring 54.

As can be seen from Figure 3, the chains 12 may be of two types. The type shown on the left-hand side of the figure consists of alternate pairs of inner and outer links 56 and 58 separated by chain rollers 60 for rolling on the chain track 24. The other type, shown on the right-hand side of the figure, is a plastic chain having in this embodiment no rollers, although of course, rollers could be utilised where appropriate. It will be appreciated that normally only one type of chain would be used with any particular conveyor.

Referring now to Figure 5, the conveyor is housed within an approximately square cross-section main frame 62 to which are attached the chain tracks 24 over which the chains 12 roll or otherwise move.

As shown in Figure l, the containers 10 are kept substantially upright between the filling zone 26 and the discharge zone 28, to prevent premature discharge of their contents. This is achieved by guiding the lower roller 40 on each container over a ramp 63 which extends between, and feeds onto, upper guide wheel 64 and lower guide wheel 65 which are mounted so as to rotate with their respective upper and lower sprockets 14 and 16. Thus in the region where the ramp 63 is provided, each container 10 is effectively supported at two separate locations so that it cannot pivot, namely at the pivot pins 46 (supported by the chain rollers 60 moving on the chain tracks 24) and at the lower roller 40 (which moves on the ramp 63) . This arrangement serves to maintain the containers upright between the filling zone 26 and discharge zone 28. However, a ramp is not provided in the conveyor run from the discharge zone 28 to the filling zone 26 so that the 10

containers 10 are only supported on the chain tracks 24. As explained later, in this region the containers are prevented from pivoting by the action of their respective lip covers. It will be appreciated that a lower roller is not essential to the operation of the invention. For example, the control arm 38 could slide over the ramp 63.

Pairs of unlatch ramps 66 and relatch ramps 68 are provided, located as shown in Figure 1 (only one unlatch and relatch ramp being visible) . These ramps are located to cooperate with the lip cams 44 on each container 10 so as to unlatch or relatch the lip cam assembly.

The operation of the unlatch ramps is now described with reference to Figure 6, in which three particular containers 10 are designated "A", "B" and "C". Container A is shown with the lip cam assembly 36 in its normal deployed position, that is with the lip cover 42 bearing against the top of the trailing edge of its leading container (Container B) , by virtue of the anticlockwise bias provided by springs 54. In this normal position, the gap between the neighbouring edges of neighbouring containers is covered by the lip cover 42 so that during loading of the containers material cannot fall between the containers.

As Container B approaches the pair of unlatch ramps 66, the lip cams 44 on the lip cam assembly 36 of Container B engage with the ramps, and the forward motion of the container rotates the lip cam assembly clockwise away from the trailing edge of its leading container (Container C) . The leading container (Container C) is thus free to move relative to its neighbour (Container B) . It will be appreciated that the operation of the pair of relatch ramps 68 (shown, for example, in Figure 9) is essentially the reverse of the operation of the pair of unlatch ramps 66 described above.

The main stages of operation of the first embodiment of conveyor will now be described with reference to Figures 7 to 9. Figure 7 shows in anticlockwise progression first the containers 10 on part of their return run between the discharge zone 28 and the filling zone 26 with their respective lip cam assemblies 36 in their normal deployed position. The bias provided by each lip cover 42 on its leading container by the spring 54 keeps the containers in a fixed orientation relative to each other, as shown also in Figure 1. Without this bias, they would pivot, since at this point they are only supported by the pivot pins 46. Next, the chains 12 feed onto the sprockets 16 whilst the lower roller 40 feeds onto the lower guide wheel 65. On the lead-off from the lower sprockets the containers are supported both on the chain tracks 24 and, via the lower roller 40, on the ramp 63. In this embodiment, the containers 10 are then filled at the filling zone 26; it will, however, be appreciated that the filling zone could be at other locations in relation to the lower sprockets 16. Figure 8 shows, in progression from right to left, first each container 10 approaching the unlatch ramps 66, which causes the lip cam assembly 36 on each container to be released from the trailing edge of its leading container. Containers which have been unlatched then travel in a direction steeply angled to the horizontal whilst remaining upright. The container edges remain unlatched until the relatch ramps 68 are reached at the upper level of the conveyor.

Figure 9 shows in anticlockwise progression first, as the containers reach the top of the conveyor, the lip cams 44 engaging the relatch ramps 68. The relatch ramps move the lip cam assembly on each container from its deployed to its retracted position, thus allowing the lip cover 42 on one container to engage the trailing edge of its leading container as the container reaches the end of the relatch ramps 68. Meanwhile, the chains 12 have fed onto the upper sprockets 14 and the lower roller 40 has been guided onto an arcuate portion of the ramp 63 so that the containers have started to move in a direction increasingly aligned with the horizontal. Next, during their exit from the upper sprockets 14, the containers begin moving in a generally downwards direction as the lower roller 40 feeds onto the upper guide wheel 64. In the region of the discharge zone 28 the containers are pointing at such an angle that their contents are discharged. The containers finally embark on their return run to the filling zone 26 where another circuit begins. The second embodiment of conveyor illustrated in Figures 10 to 13 shares generally the same features as the first embodiment illustrated in Figures 1 to 9. The main distinctions lie firstly in the method of attachment of the containers 10 to the chains 12, secondly in the manner in which the gap between successive containers is covered, and thirdly in the manner in which the containers are guided over the ramp 63. These three features are now considered in more detail.

In the second embodiment, each container 10 is resiliently attached to the chains 12, instead of the arrangement of pivot pins 46, washers 48, spacers 50 and tapped bushes 52 employed in the first embodiment. The resilient attachment comprises a resilient rubber plate 102 bolted to each container, a cross arm 104 formed from relatively rigid metal plate and riveted to the plate 102, and brackets 106 welded to each end of the cross arm and bolted to a special link 107 of the chain 12 fitted with a bracket portion as shown in the figures. Thus, when the container is freely suspended, its entire weight is borne by the chains via the resilient plate 102. By this arrangement, each container (as seen in Figures 10 and 11) can rotate anticlockwise against the resilience of the plate 102, and has its clockwise rotation limited by abutment of the plate 102 against the front panel of the adjacent container. It will thus be appreciated that the attachment between container and chain is simpler than that in the first embodiment because it involves fewer parts, and no moving parts such as bearings.

It will be understood that alternative resilient attachments could be used. As an example, the resilient plate 102 could be replaced by a resilient elongate moulding having a rectangular cross-section hole extending its entire length. A relatively rigid bar of matching cross-section would be inserted through the hole and attached (e.g. by bolting) at each end to the chains. This arrangement would have the advantage that the container (including resilient moulding) could be replaced merely by sliding it off the bar.

Concerning the second feature of distinction (the manner in which the gap between successive containers is covered) , in the second embodiment each container has a fixed lip cover 108 extending from its trailing edge and adapted to cover the gap between adjacent buckets in the filling zone 26 (see Figure 10) . Apart from acting as a cover, each fixed lip cover 108 also assists in controlling rotation of its respective container in the filling and discharge zones 26 and 28. By abutting with the leading edge of the adjacent trailing container, each lip cover limits clockwise rotation of its respective container relative to the adjacent trailing container (see Figure 10) . This ensures that the containers are upright during the filling and discharge zones. Whereas in the first embodiment the lip cover is mounted on the leading edge of each container 10, in the second embodiment the lip cover is mounted on the trailing edge. In the first embodiment, each lip cover limits anticlockwise rotation of its respective container (as seen in Figure 1) , and thus controls its respective container between the discharge and filling zones 28 and 26 (that is, on its return run) . The lip cover needs to be retractable to ensure satisfactory engagement and disengagement of adjacent containers. In the second embodiment, each fixed lip cover limits clockwise rotation of its respective container (as seen in Figure 10) , and thus controls its respective container particularly at the filling and discharge zones 26 and 28, but not on its return run. In the second embodiment, rotation of each container during its return run is limited by the resilience of the resilient plate 102.

Concerning the third feature of distinction (the manner in which the containers are guided over the ramp 63) , in the second embodiment the control arm and roller assembly of the first embodiment is replaced by a crook-shaped guide arm 110, which is shown in detail in Figures 11 to 13 and is attached to the front panel of its respective container. The crook of the guide arm is arranged to engage the ramp to maintain its container upright between the filling and discharge zones 26 and 28. The guide arm has the advantage over the control arm and roller arrangement of the first embodiment of having no moving parts. In an alternative embodiment (not illustrated) the container 10 itself engages directly with the ramp 63, thus obviating the need for a separate guide formation.

The operation of the second embodiment of conveyor is now described with particular reference to Figure 10. A circuit of a typical container is considered. At the filling zone 26, the container is maintained upright both by engagement of the guide arm 110 with the ramp and also by engagement of the lip cover 108 with the adjacent container. It will be appreciated that only one of these methods of controlling the container orientation is strictly necessary, and, in fact, in an alternative embodiment the ramp is omitted in the filling zone. The resilient plate 102 is somewhat flexed at this location from its unstressed position and thus biases (together with the weight of the container itself) the guide arm against the ramp.

At a location midway between the filling and discharge zones 26 and 28 the containers are carried vertically upwardly. Each is maintained upright by engagement of the guide arm against the ramp under the bias of the resilient plate. The lip cover performs no control function at this position.

At the discharge zone 28 the containers are controlled in the same way as at the filling zone 26. In an alternative embodiment, the ramp is omitted in the discharge zone, so that control is effected purely by engagement of the lip cover 108 with the adjacent container. Just beyond the discharge zone the change of direction of the chain flips each container over to empty its contents. Excessive rotation of the container is prevented by the resilience of the resilient plate 102. During tipping rotation of the container is only controlled by the resilience of the resilient plate, and not by the guide arm or lip cover. Just after the discharge zone 28 the guide arm 110 on each container engages with a second portion of the ramp 63 to control the container rotation so as to prevent collision of adjacent containers. During the remainder of the return run, rotation of the container is only controlled by the resilience of the resilient plate, and not by the guide arm or lip cover. It will be appreciated that portions of ramp may be used at other locations on the conveyor circuit to effect container control as desired.

It will be appreciated that the conveyor in general, and particularly the containers and chains, may be made of any suitable material. For instance, if the conveyor is to be deployed in arduous or heavy duty operations, standard commercial steel roller chains can be used. As another example, the conveyor chains and even the containers themselves may be made of plastics material if it is intended to use the conveyor in the food, chemical or pharmaceutical industries.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

16CLAIMS

1. A conveyor for conveying materials, comprising a plurality of containers; at least one endless drive member for driving the containers in an endless circuit, the endless circuit including a filling and a discharge zone, each container being attached to the or each drive member so as to be rotatable relative thereto; means for driving the or each endless member around the endless circuit; a first stationary guide formation; and a complementary second guide formation on each container for engagement with the first guide formation; the first and second guide formations being arranged to engage in a region between the filling and discharge zones to maintain each respective container upright in that region, whereby spillage of the container contents in that region can be prevented.

2. A conveyor according to Claim 1 wherein said region includes a region where the containers are driven on an incline.

3. A conveyor according to Claim 2 wherein said region includes a region where the containers are driven vertically or near vertically.

4. A conveyor according to any of the preceding claims wherein each container is attached to the or each endless member such that the weight of the container is arranged to bias the respective second guide formation against the first guide formation in said region.

5. A conveyor according to any of the preceding claims further comprising a biassing device for biassing the respective second guide formation against the first guide formation in said region.

6. A conveyor according to Claim 5 wherein the biassing device comprises a respective resilient member for each container arranged to cause a biassing torque between the respective container and a respective endless member.

7. A conveyor according to Claim 6 wherein each container is resiliently attached to the respective endless member via its respective resilient member.

8. A conveyor according to any of the preceding claims further comprising a first control formation on each container engageable with a second complementary control formation on an adjacent container to limit rotation of said container relative to said adjacent container.

9. A conveyor according to Claim 8 wherein one of the control formations includes cover means for covering at least part of the gap between said container and said adjacent container.

10. A conveyor according to Claim 9 wherein the cover means is mounted fixedly on its respective container.

11. A conveyor according to any Claims 1 to 7 further comprising cover means mounted on each said container and movable relative thereto between a deployed position in which it covers at least part of the gap between itself and an adjacent container, and a retracted position, and trigger means to move the cover me- s between its deployed and retracted positions.

12. A conveyor according to Claim 11 wherein the cover means on each said container includes a cover which is shaped to direct material into either said container or said adjacent container.

13. A conveyor according to Claim 11 or 12 wherein the cover means on each said container includes a cam, and the trigger means includes a stationary cam follower, each cam cooperating with the cam follower during operation of the conveyor to move the cover means between its deployed and retracted positions.

14. A conveyor according to Claim 13 when dependent on Claim 12 wherein the cover is fixed to the cam and both the cam and the cover are pivotable relative to their respective container.

15. A conveyor according to any of Claims 11 to . therein the cover means on each said container forms a close fit with said adjacent container in its deployed position but does not interfere with the movement thereof in its retracted position.

16. A conveyor according to any of Claims 11 to 15 wherein the drive means is arranged to drive each said container upright along a generally horizontal portion of the circuit so that it can be filled, and then to elevate it whilst maintaining it upright, and the trigger means is arranged so that the cover means on each said container is deployed during filling but retracted before each said container has been elevated significantly.

17. A conveyor according to Claim 16 wherein after elevating each said container the drive means is arranged to drive it generally horizontally, and the trigger means is arranged so that the cover means is retracted during the- final portion of the elevation.

18. A conveyor according to any of Claims 11 to 17 wherein the cover means on each container is arranged to limit pivotal movement of said adjacent container between discharge and subsequent filling of each container.

19. A conveyor according to any of the Claims 11 to 18 wherein the cover means on each said container is biassed towards the deployed position.

20. A conveyor substantially as hereinbefore described with reference to Figures 1 to 9 or 10 to 13 of the accompanying drawings.