WO1991006491A1

WO1991006491A1 - Material feeding apparatus

Info

Publication number: WO1991006491A1
Application number: PCT/GB1990/001662
Authority: WO
Inventors: Ernest Chambers
Original assignee: Hq Engineers Ltd.
Priority date: 1989-11-01
Filing date: 1990-10-31
Publication date: 1991-05-16
Also published as: GB8924564D0

Abstract

Material feeding apparatus (10) comprising a hopper (14) tapering inwardly and downwardly into a horizontal cylindrical tube (16) leading to an outlet (12). A material conveying screw (18) is rotatably mounted in the tube (16). An open wire mesh agitator (24) is provided within the hopper (14) and has a substantially corresponding shape thereto. The agitator (24) and screw (18) are driven by a motor (20) to agitate material in the hopper (14) and to move material along the length of the tube (16).

Description

Material Feeding Apparatus

This invention concerns improvements in or relating to material feeding apparatus and part icularly but not exclusively to apparatus for feeding part iculate material.

When processing particulate materials, it is

generally preferable to provide a constant flow of

materials of consistent density. Material is normally stored in, or supplied to, a bin which may be in the form of a silo or hopper, from which is obtained the flow of material. The bin is generally of a shape which tapers towards its base to direct the material to a delivery point.

In practice, the rate of discharge from this

delivery point can vary considerably which is undesirable. As a result , there have been provided material conveying screws to move material from the base of the bin to an outlet , but for this to work efficient ly the material must consistently fill the screw and not be unduly compacted. One problem often encountered is that in cohesive

materials a bridge of material forms across the hopper at the base, thus reducing the flow of material and when the bridge does break erratic flow of mate rial at the delivery point may occur. A problem encountered with highly aerated materials is that they tend to 'flush', i.e.

behave as a non viscous liquid. It has been found that agitation of the material causes deaeration, thus

improving the flow properties thereof.

A number of bin discharge aids have thus been devised in order to attempt, to regulate the discharge, but have not been totally successful. A further problem encountered with bin discharge aids is that they often make the bin difficult to clean.

According to the present invention there is provided material feeding apparatus comprising a container for the material, means within the container for agitating

material therein and means for providing a flow of

material out. of the container.

The agitating means preferably comprises an assembly which is movable with a rocking motion, desirably at a frequency of between 0.1 and 3 Hz. The assembly may have a relatively open structure, preferably in the form of a grid, and the shape of the grid may substantially

correspond to the internal profile of the container, whereby to be normally cquispaced from the sides thereof.

The means for providing a flow of material

preferably comprises a material conveying rotating screw extending across an open lower end of the container and outwardly of an outlet side thereof. The pitch of the length of the screw in the container may increase towards the outlet, side thereof.

A common drive may be provided for the screw and the agitating means, and the speed of movement of the screw and/or agitating means may be variable.

A lower part of the container is preferably

removable to permit access internally of the container, for example at the location of the screw, to permit cleaning.

The agitating means may comprise a plurality of assemblies in a single container and a corresponding number of screws and outlets may also be provided.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:-

Fig. 1 is a partially cut away diagrammatic side view of a material feeding apparatus; and

Fig. 2 is a partially cut away diagrammatic end view of the apparatus of fig. 1. The drawings show a material feeding apparatus 10 suitable for providing a substantially constant feed of particulate material from an outlet 12. The apparatus 10 comprises a hopper 14 of substantially rectangular cross section with one pair of opposed sides tapering inwardly and downwardly to an open base from which a cylindrical tube 16 extends horizontally and outwardly from one end to the outlet 12.

Rotatably mounted in the tube 16 to extend across the base of the hopper 14 is a material conveying screw 18. Outwardly of the other end of the hopper 12 the screw 18 is directly connected to an electric motor 20 (not shown in fig. 2 for clarity). On the length of the screw 18 extending across the base of the hopper 14, the pitch of the thread increases at a constant rate away from the motor 20, the thread being of constant size over the lengt h o f t he sc rew 1 8 i n t he t ube 1 6 . A l owe r pa rt 22 o f t he hopper 14 is releasably connected to the remainder of the hopper and can therefore be readily removed to permit cleaning especially of the area around the screw 18. The inner surface 15 of the remainder of the hopper downwardly overlays the part 22 to prevent leakage of material through the connection therebetween.

An agitator 24 is mounted within the hopper 14 and has a W shaped cross section with relatively long side limbs which have the same relative inclination as the tapering sides of the hopper 14. The agitator 24 is mounted on a shaft 26 extending horizontally across the hopper 14 via a spaced relation to the base whereby the side limbs of the agitator are normally parallel to, but spaced from, the respective side wall of the hopper 14. The agitator 24 is principally made of an open wire mesh.

The shaft 26 extends outwardly of the same end of the hopper 14 as the motor 20, and is supported on a casing of the latter in spaced bearings 28. An outer end of the shaft 26 is connected to a radially extending arm 30A which in turn is connected at an outer end to an arm 30B extending radially from a drive shaft of the motor 20. The arms 30A, 30B are so rotatively interconnected in a 'cranked' relation that driving the motor 20 causes the agitator 24 to rock between the positions shown by dotted lines in fig. 2. The motor 20 may be of variable speed and is set such that the agitator 24 generally rocks at a frequency of between 0.1 and 3 Hz. In particular

situations, especially with small quantities of material, higher frequencies may be necessary.

There is thus described a material feeding apparatus suitable for use with a wide range of particulate materials which has a number of advantageous features.

The motion of the agitator 24 maintains the material in the hopper in motion and thus prevents the formation of bridges or other large masses of material, while a low frequency oscillation rather than a high frequency

vibration also helps prevent compaction. With highly aerated materials the agitator causes deaertion thus improving their flow characteristics. The open mesh of the agitator 24 prevents compaction of the material and is easy to clean, while the removable lower portion also facilitates cleaning. The variation in screw thread along the length of the hopper provides for uptake of material from along the length of the hopper rather than the material all being taken up at the motor end of the screw.

The apparatus is of relatively simple construction and thus can be inexpensively and robustly manufactured. In tests a repeatability of one to three percent of flow rate was obtained. The use of a single power supply reduces the power uptake of the machine.

Various modifications may be made without departing from the scope of the invention. For example the agitator may be differently constructed and a different arrangement could be used to provide the rocking motion. The screw and agitator could also be driven by separate motors, and movement of material away from the hopper may be achieved by other than a screw.

If the apparatus is to be used, for example, with a large bin, it may be appropriate to provide two or more agitators in the bin, each connecting with a respective screw and outlet.

Claims

C laims

1. Material feeding apparatus (10) comprising a

container (14) for the material, characterised in that there is provided means (24) within the container (14) for agitating material therein and means (18) for providing a flow of material out of the container (14).

2. Apparatus according to claim 1, characterised in that the agitating means (24) comprises an assembly (24) which is movable with a rocking motion.

3. Apparatus according to claim 2, characterised in that the assembly (24) is moveable at a frequency of between 0.1 and 3 Hz.

4. Apparatus according to claim 2 or claim 3,

characterised in that the assembly (24) has a relatively open structure.

5. Apparatus according to claim 4, characterised in that the assembly (24) is in the form of a grid (24).

6. Apparatus according to claim 5, characterised in that the shape of the grid (24) substantially corresponds to the internal profile of the container (14), whereby to be normally equispaced from the sides thereof.

7. Apparatus according to any of the preceding claims, characterised in that the means (18) for providing a flow of material comprises a material conveying rotating screw (18) extending across an open lower end of the container (14) and outwardly of an outlet side (12) thereof.

8. Apparatus according to claim 7, characterised in that the pitch of the length of the screw (18) in the container increases towards the outlet side (12) thereof.

9. Apparatus according to claim 7 or claim 8,

characterised in that a common drive (20) is provided for the screw (18) and the agitating means (24).

10. Apparatus according to any of claims 7 to 9, characterised in that the speed of movement of the screw (18) and/or agitating means (24) is variable.

11. Apparatus according to any of the preceding claims, characterised in that a lower part (22) of the container is removable to permit access internally of the container to permit cleaning.

12. Apparatus according to any of the preceding claims, characterised in that the agitating means (24) comprises a plurality of assemblies (24) in a single container (14).

13. Apparatus according to claim 12 when dependent on claim 7, characterised in that a number of screws and outlets corresponding to the number of assemblies (24) are provided.