GB2379433A

GB2379433A - Self-cleaning grid

Info

Publication number: GB2379433A
Application number: GB0215450A
Authority: GB
Inventors: Robin Clive Travis; Philip Richmond
Original assignee: RENBY Ltd
Current assignee: RENBY Ltd
Priority date: 2001-07-23
Filing date: 2002-07-04
Publication date: 2003-03-12
Anticipated expiration: 2022-07-04
Also published as: GB0117818D0; GB0215450D0; GB2379433B

Abstract

A self-cleaning grid arrangement 11, 19 for use in the quarry, chemical, waste or recycling industries during the conveyance of particulate material prevents the passage of oversize particles or foreign objects to the destination of the particulate material. The grid arrangement 11 is formed of a first set bars 12 disposed substantially parallel with each other, the bars 12 extend between and are supported in holes 14, 21 in the sides 13, 22 of a chute 10 in which the bars 12 are free to rotate. As a result of such rotation, if particulate material does stick to a bar 12, there will be a lesser tendency for any material to bridge to an adjacent bar 12 and an increased the tendency for the particulate material to fall from the bars 12. The bars 12 are curved along their length and have a radius of curvature greater than the length of the bars 12 between the sides 13. Each bar 12 has one end 16 depending from the remainder of the bar 12 in the direction away from the centre of curvature of the bar 12. A second set of bars 20 that are substantially parallel with each other, is disposed substantially at right angles to the first set of bars 12. The bars 12, 20 may be inclined, and bars (26, fig. 7) may be tapered towards their lower ends. In a further embodiment, the wall of the chute 10 may be fitted with a flap (25, fig 6) through which oversized debris may be discharged.

Description

GRID ARRANGEMENT This invention relates to a grid arrangement, and in particular to a grid arrangement for use in the conveyance of particulate material. One particular application is in the filling of bags with particulate material using a chute from a hopper containing the material.

Grid arrangements are used in the quarry, chemical, food, waste and recycling industries during the conveyance of particulate material for preventing the passage of oversize particles or foreign objects to the destination of the particulate material Typical materials for which such grid arrangements are used are fluorspar, sand, rubber crumb and the like. Such grid arrangements usually comprise a parallel arrangement of bars disposed across a chute or other form of passageway down or through which the particulate material is passed. A second parallel arrangement of bars disposed at right angles to the first arrangement may be provided such that the two arrangements form a lattice. Alternatively a wire mesh arrangement may be used. The spacing of the bars or mesh size dictates the size of the particles or objects retained by the grid arrangement. The bars or mesh may be welded or the bars screwed into side plates to form an integral structure that may be removed from the chute or passageway for cleaning purposes. However, many of the materials for which such grid arrangements are used tend to stick to the bars or mesh, particularly when the materials are damp. This often results in bridging of the bars or mesh by the particulate material, thereby preventing further passage of the material through the bars or mesh. In consequence, frequent cleaning may be required if the passage of the particulate material is to proceed satisfactorily. This is an undesirable task, and can result in considerable downtime of the process equipment.

It is an object of the present invention to provide a grid arrangement that minimises the above problem of the requirement for frequent cleaning.

The invention provides a grid arrangement comprising a plurality of bars disposed substantially parallel with each other, the bars extending between and being mounted in a support structure, wherein the bars are free to rotate in the support structure.

The support structure may comprise opposed side plates. The bars may pass through holes in the support structure that are oversize relative to the cross-sectional dimensions of the bars. The bars may be curved along their length, having a radius of curvature greater than the length of the bars between the support structure. The radius of curvature may be at least six times the length of the bars between the support structure. Each bar may have a bend in

the region of one end thereof to form an end region that in use depends from the remainder of the bar. The end region may depend in the direction away from the centre of curvature of the bar. An actuator may be coupled to at least some of the bars to rotate them, preferably to at least alternate bars.

The grid arrangement may comprise a second plurality of bars disposed substantially parallel with each other and substantially at right angles to the first plurality of bars. In this case, each plurality of bars may be supported in respective holes disposed along a line that is substantially parallel with the bars of the other plurality of bars. If the bars are curved, each plurality of bars may be supported in respective holes disposed along a curved line that is substantially parallel with the curved bars of the other plurality of bars.

The bars may be disposed to extend horizontally between the support structure. Altematively, the bars may be inclined. An access opening to the lower end of the bars may be provided in the support structure. Alternatively. the bars may be tapered towards their iower ends. The grid arrangement may comprise separate receptacles for particles passing between the bars at the upper and lower ends thereof. Each bar may have a circular cross-section, or at least between the side plates may have a wedge section. The bars may be of stainless steel.

The invention will now be described with reference to the accompanying drawings in which: Fig. 1 : s a cross-section of a chute with a first embodiment of grid arrangement, Fig. 2 is an underplan of the embodiment of Fig. 1, Fig. 3 is a cross-section of a chute with a second embodiment of grid arrangement, Fig. 4 is an underplan of the embodiment of Fig. 3, Fig 5 is a cross-section through an alternative bar Fig. 6 is a cross-section of a chute with a third embodiment of grid arrangement, and Fig. 7 is a plan view of a fourth embodiment.

Referring now to Figs. 1 and 2, there is shown a passageway in the form of a chute 10 down which particulate material is passed from a hopper (not shown) to a destination (not shown). The destination may be, for example, a bag to be filled with the particulate material or a vehicle to transport the material to another location. To prevent the passage of oversize particles or foreign bodies, a grid arrangement 11 is installed in the chute 10, which forms a support structure for the grid arrangement 11. The grid arrangement consists of an array of bars 12 in parallel disposition extending across the chute 10. The bars 12 extend between side plates 13, which in the embodiment shown are part of the chute 10. However, the plates 13 may be a separate support structure attached to the walls of the chute 10 if preferred. The

bars 12 are of stainless steel to inhibit rusting and to minimise the tendency of the particulate material to stick to the bars 12. However, the bars 12 may be of other suitable wear resistant materials, for example corrosion protected mild steel, dependent on the particulate material involved, if preferred. The bars 12 are of circular cross-section and pass through holes 14 that are oversize relative to the diameter of the bars 12 so that the bars 12 are free to rotate In the plates 13. In consequence, if particulate material does stick to a bar 12, there will be a tendency for that bar to rotate, thereby breaking any tendency for the material to bridge to an adjacent bar 12 and increasing the tendency for the particulate material to fall from the bars 12. This tendency for the bars 12 to rotate is enhanced by two factors. Firstly, each bar 12 is curved along its length, at least along that length extending across the chute 10 between the side plates 13. The radius of curvature is greater than the length of the bars 12 between the side plates 13, and preferably is about six times that length. Thus, if a bar 12 is displaced from the disposition shown in Fig. 1, it will tend to rotate back to that disposition due to the offset weight of the centre portion of the bar 12. Secondly, each bar 12 has a bend 15 in the region of one end to form an end region 16 that will tend to hang vertically downwards due to its weight. The end region 16 extends in the direction away from the centre of curvature of the bar 12 so that the curvature of the bar 12 and the depending end region 16 create the same disposition restoring effect to the bar 12. As an alternative, or in addition, the bars 12 may be readily agitated by hand using the end regions 16 as a"handle", or an actuator 17 may be coupled by an actuating rod 18 (both shown in dotted lines) to the end regions 16 of all of, or at least alternate, bars 12 to agitate or rotate those bars 12 to dislodge particularly sticky material. The actuator 17 may be a motor or an electrical, pneumatic or hydraulic actuator.

Referring now to Figs. 3 and 4, there is shown an alternative grid arrangement 19. Many of the parts shown in Figs. 3 and 4 are identical with the corresponding parts of the grid arrangement 11 and are identified by the same reference numerals. In this second embodiment, there is provided a second array of bars 20 that extend parallel with each other across the chute 10 at right angles to the bars 12. This provides a mesh type of arrangement of the bars 12,20 when viewed in underplan as in Fig. 4. To maintain a substantially constant spacing between the bars 20 and the bars 12, the centres of the holes 21 in side plates 22 in which the bars 20 are supported lie on a line that is curved to the same curvature as that of the bars 12. Similarly, the centres of the holes 14 lie on a line that is curved to the same curvature as that of the bars 20.

As an alternative to the bars 12 being disposed horizontally across the chute 10, they may be inclined as shown in Fig 6. With such an arrangement, oversize particles may roll or slide to

the lower end of the bars 12. These oversize particles may then be removed through an access opening 25. Particle size or product separation may also be achieved by an arrangement as shown in Fig. 7. In this case, the bars 26 are tapered towards their lower ends so that the gap between them increases towards their lower ends. By this means, larger particles may pass between the bars 26 only at their lower ends down an auxiliary chute 27 separate from the main lower part 28 of the chute 10. The bars 12,20, 26 may be of noncircular cross-section, at least in the part extending across the chute 10, such as the wedge shape of the bar 23 shown in Fig. 5. Such a section will have an enhanced effect of breaking coagulated or oversize particles and any particles adhering to the sides 24 of the bar 23 will cause rotation to the bar 23 to inhibit bridging of the material to an adjacent bar 23. Other sections of bar such as elliptical or polygonal may be used if preferred.

Individual bars 12,20, 23,26 may be readily removed from the chute 10 if necessary for cleaning or replacement when worn, thereby avoiding the need to open the chute 10 or remove and possibly replace the entire grid arrangement 11, 19-Thus cleaning, which is required less frequently with the grid arrangement 11 or 19, due to its self-cleaning effect, than was the case with prior known grid arrangements, is less onerous and involves less downtime than was previously the case. Also replacement of a single bar 12,20, 23,26 if worn or damaged is less costly than replacement of an entire grid arrangement of previously known type. In the figures, the grid arrangements 11,19 are shown at a location below the top of the chute 10. However, in appropriate circumstances, the grid arrangement may be disposed at either the top or the bottom of the chute or on top of a receiving hopper or the like.

Claims

CLAIMS 1. A grid arrangement comprising a plurality of bars disposed substantially parallel with each other, the bars extending between and being supported by a support structure, wherein the bars are free to rotate in the support structure.
2. A grid arrangement according to claim 1, wherein the support structure comprises opposed side plates.
3. A grid arrangement according to claim 1 or claim 2, wherein the bars pass through holes in the support structure that are oversize relative to the cross-sectional dimensions of the bars.
4. A grid arrangement according to claim 3, wherein the bars are curved along their length.
5. A grid arrangement according to claim 4, wherein the bars have a radius of curvature greater than the length of the bars between the support structure.
6. A grid arrangement according to claim 5, wherein the radius of curvature is at least six times the length of the bars between the support structure.
7. A grid arrangement according to any one of claims 1 to 6, wherein each bar has a bend in the region of one end thereof to form an end region that in use depends from the remainder of the bar.
8. A grid arrangement according to claim 7, wherein the bars are curved along their length and the end region depends in the direction away from the centre of curvature of the bar
9. A grid arrangement according to claim 7, wherein an actuator is coupled to at least some of the bars to rotate them.
10. A grid arrangement according to claim 9, wherein an actuator is coupled to at least the alternate bars to rotate them.

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11. A grid arrangement according to any one of claims 1 to 10, comprising a second plurality of bars disposed substantially parallel with each other and substantially at right angles to the first plurality of bars.
12. A gnd arrangement according to claim 11, wherein each plurality of bars is supported in respective holes disposed along a line that is substantially parallel with the bars of the other plurality of bars.
13 A grid arrangement according to claim 12, wherein the bars are curved along their length and each plurality of bars is supported in respective holes disposed along a curved line that is substantially parallel with the curved bars of the other plurality of bars.
14. A grid arrangement according to any one of claims 1 to 13, wherein the bars are disposed to extend horizontally between the support structure.
15 A grid arrangement according to any one of claims 1 to 13, wherein the bars are inclined.
16. A grid arrangement according to claim 15, wherein an access opening to the lower end of the bars is provided in the support structure.
17. A gnd arrangement according to claim 15, wherein the bars are tapered towards their lower ends.
18. A grid arrangement according to claim 15 or claim 17, comprising separate receptacles for particles passing between the bars at the upper and lower ends thereof.
19. A grid arrangement according to any one of claims 1 to 18, wherein each bar has a circular cross-section.
20. A grid arrangement according to any one of claims 1 to 18, wherein each bar has a wedge section at least between the support structure.
21. A grid arrangement according to any one of claims 1 to 20, wherein the bars are of stainless steel.

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22. A grid arrangement according to any one of claims 1 to 20, wherein the bars are of corrosion protected mild steel.
23. A grid arrangement substantially as hereinbefore described with reference to and as illustrated in Figs 1 and 2, or Figs 3 and 4, or Fig. 6 or Fig. 7 of the accompanying drawings.