GB2258172A

GB2258172A - Improvements relating to separating apparatus

Info

Publication number: GB2258172A
Application number: GB9215279A
Authority: GB
Inventors: Christopher Philip Morris
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-07-31
Filing date: 1992-07-17
Publication date: 1993-02-03
Also published as: GB9215279D0; GB9116436D0

Abstract

The separation chamber (23, Fig 1, not shown) has an upper outlet (25, Fig 1) and a lower outlet (27). The lower portion of the chamber has a pair of plates (26) which are inclined downwardly towards the lower outlet and which have apertures arranged in zones. The apertures in adjacent zones are angled in opposite directions, one set being inclined to the surface of the plate in a direction away from the lower outlet and the apertures in an adjacent set being inclined in the opposite direction. The lower outlet (27) has a side wall (33) with a number of apertures inclined upwardly at an angle of 70 DEG to the axis of the outlet. Air is fed through these apertures from plenum chambers to create a venturi effect negative pressure below the lower outlet, resulting in a zero pressure area in the outlet. This enables the heavier material to fall from the chamber under gravity. The apparatus can be used to separate tobacco leaf and stem, tea, cereal. <IMAGE>

Description

Title: Improvements Relations to Searatins Apparatus The present invention relates to separating apparatus.

There are a number of known forms of apparatus which are used for the conveying and/or separation of materials such as, for example, tobacco leaf and stem, tea, cereal and other bulk material using an airstream.

GB-A-2240079 describes an apparatus for separating different grades of material. The separating apparatus has a separation chamber having upper and lower outlets and a pair of apertured plates in the lower portion of the chamber inclining downwardly towards the lower outlet. The apertures are arranged in zones with apertures in one series of zones being inclined to the surface of the plate in a direction away from the lower outlet and apertures in a second series of zones being inclined to the surface of the plate in the opposite direction. As a result of this, material disposed above the plates is fluidised and by controlling the rate of flow of air through the holes the heavier material can be allowed to drop through the lower outlet whilst light material is discharged through the upper outlet.

The present invention seeks to provide an improved separation chamber for a separating apparatus.

Accordingly, the present invention provides a separation chamber for an apparatus for separating different grades of material, the separation chamber comprising: an upper outlet and a lower outlet; a pair of plates in a lower portion of the chamber, said plates inclining downwardly towards the lower outlet; a plurality of apertures in said plates, the apertures in each plate being arranged in a first series of spaced zones along the length of the plate from the lower outlet, a further apertured zone being located between each adjacent pair of said zones wherein said further apertured zones form a second series of zones and the apertures in the first series of zones are inclined to the surface of the plate in a direction away from the lower outlet and the apertures in the second series of zones are inclined to the surface of the plate in the opposite direction; and wherein said lower outlet comprises a side wall having a plurality of apertures inclined upwardly at a predetermined angle or angles to the axis of the outlet for directing fluid flow therethrough into the separation chamber to create a balanced pressure zone in said chamber.

Preferably the balanced pressure zone is a zone at substantially atmospheric pressure.

The present invention is further described hereinafter, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side elevation of a separating apparatus in accordance with the present invention; and Figure 2 is a sectional view of part of the apparatus of Figure 1.

Referring to the drawings there is shown a separating apparatus 10 having a separation chamber 23 to which material such as for example, tobacco leaf and stem can be supplied by means of a belt or other feed conveyor 24. An upper portion of the chamber communicates with an outlet duct 25 and the lower wall of the chamber has a pair of inclined distribution plates 26 (Figure 2) which are spaced at their lower ends to define an outlet 27 beneath which is arranged a conveyor. The side walls of the outlet are formed by plates 33 respectively in which are formed apertures or holes which incline upwardly, at substantially 700 to the plate surface or aperture axis. Air under pressure is supplied through the holes in the plates 33 from plenum chambers 34.The distribution plates 26 are also provided with holes through which air can flow into the separation chamber from plenum chambers 29 respectively. The air is supplied to the plenum chambers 29, 34 through a conduit 30 by means of a fan 31 which draws air from the outlet duct 25 and returns it to the plenum chambers, air circulating in the direction A in Figure 1.

The conduit 30 leads into a diffuser section 35 which incorporates baffles to provide the desired air flow to the plenum chambers 29 and 34.

The distribution plates 26 are provided with holes in the same manner as the plates disclosed in GB-A-2240079 and reference is directed to that specification for a full description. The air flowing through the holes in the plates 26 forms two upwardly flowing outer air streams the velocity of which can be controlled, for example by controlling the speed of the fan 31, and the air flowing through the holes in the plates 33 forms a central upwardly flowing air stream. The velocity of the air streams is adjusted in such a manner that the components of the material which have a so called lower terminal velocity than the velocity of the air stream, are discharged through the outlet duct 25. The components of the material having a higher terminal velocity fall through the outlet 27 onto the conveyor.In some cases, it is desired to modify the upward flow of air in the separation chamber and this can be achieved by providing valvecontrolled by pass ducts 29A which connect the plenum chambers 29 respectively to the outlet duct 25. By adjusting the valves the upward vertical air flow in the separation chamber can be modified.

The air in the apparatus is recirculated by the fan 31 and a discharge unit 32 is provided in the outlet duct 25. This collects those components of the material fed into the separation zone which have the lower terminal velocity. The collected material is led away from the discharge unit 32 by means of a conveyor which can be a belt conveyor or a conveyor of the type disclosed in GB-A-2240079. The discharge unit 32 will not retain fine dust and this will be recirculated by the fan 31. In order to prevent build up of the dust a proportion of the air delivered by the fan 31 is removed by an extractor unit which filters the air. The air which is withdrawn has to be replaced and this is conveniently introduced at the entrance of conveyor 24.Thus, by careful control of the extractor unit there is no need to provide an air lock at the entrance of the conveyor 24 into the separation chamber.

Normally, in the closed system of the apparatus there is only one point of zero (i.e. atmospheric) pressure created. This is in the separation chamber 23 where positive air pressure generated by the fan 31 progressively changes to negative pressure towards the fan inlet in the direction of air flow. The point of zero pressure is normally just prior an "open" entry to the system, which in this case, is at the feed conveyor 24, described above.

In the separation chamber of the apparatus disclosed in GB-A-2240079 the plates 26 are positioned at substantially 450 with holes at substantially 700 to the surface of the plates, some of the holes being directed upwardly and others being directed in the reverse direction. As a result, the air flow in the lower part 40 of the separation chamber 23 is substantially vertical and at positive pressure. The air flow in the chamber produced by the holes which are directed upwardly.would, without the provision of the holes extending in the opposite direction, progressively incline towards the plates, in other words towards the sides of the separation chamber 23.

Referring now to Figure 2, the arrangement of the separating plates 26 and of the holes and their angles in the plates is similar to that of the apparatus described in GB-A-2240079.

However, the vertical plates 33 in the described embodiment of the present invention are provided with holes which are angled upwardly as seen in Figure 2 at substantially 700 to the surface of the plates 33. The angles may be in the range 500 to 850, preferably 650 to 850.

This produces a venturi effect of negative pressure below the outlet 27 which opposes and balances the positive air pressure in the lower section of the air chamber 23, creating a zero pressure (atmospheric) area between the vertical walls of the plates 33, as a result of which there is little or no resultant air pressure on the heavier material in the lower part of the separation chamber, which can therefore fall out of the chamber under gravity. This provides a more efficient and effective way of separating the heavier material from the lighter material as the former is not subject to any pressure differential tending to assist or prevent its fall under gravity from the separation chamber 23.

As will be appreciated, the angles of the holes in the plates 33 may be varied as may the angle of the holes in the plates 26, provided the end result is to provide a balanced pressure zone in the chamber 23.

Claims

1. A separation chamber for an apparatus for separating different grades of material, the separation chamber comprising: an upper outlet and a lower outlet; a pair of plates in a lower portion of the chamber, said plates inclining downwardly towards the lower outlet; a plurality of apertures in said plates, the apertures in each plate being arranged in a first series of spaced zones along the length of the plate from the lower outlet, a further apertured zone being located between each adjacent pair of said zones wherein said further apertured zones form a second series of zones and the apertures in the first series of zones are inclined to the surface of the plate in a direction away from the lower outlet and the apertures in the second series of zones are inclined to the surface of the plate in the opposite direction; and wherein said lower outlet comprises a side wall having a plurality of apertures inclined upwardly at a predetermined angle or angles to the axis of the outlet for directing fluid flow therethrough into the separation chamber to create a balanced pressure zone in said chamber.

2. A separation chamber as claimed in claim 1 wherein said side wall serves as a venturi for creating a negative air pressure at or adjacent said lower outlet and said balanced pressure zone is at atmospheric pressure.

3. A separation chamber as claimed in claim 1 or 2 wherein said predetermined angle is in the range 500 to 850.

4. A separation chamber as claimed in claim 3 wherein said predetermined angle is in the range 650 to 85 .

5. A separation chamber as claimed in claim 4 wherein said predetermined angle is substantially 700.

6. A separation chamber as claimed in any of claims 1 to 5 having separate plenum chambers for supplying fluid under pressure to the apertured plates respectively and said side wall so as to obtain said balanced pressure zone.

7. A separating apparatus for separating different grades of material having a separation chamber as claimed in claim 6 and having a fan having an inlet connected to the upper outlet and an outlet connected to said plenum chambers by way of a diffuser section.

8. An apparatus as claimed in claim 7, including valve controlled by-pass ducts through which fluid from the plenum chambers associated with said pair of plates can flow to an outlet duct connected to the upper outlet.

9. An apparatus according to claim 7 or 8, including an extractor for removing part of the fluid delivered by the fan to prevent a build up of dust within the apparatus and a further fan for replenishing the fluid extracted.

10. A separation chamber for an apparatus for separating different grades of material, substantially as hereinbefore described with reference to the accompanying drawings.