GB2055308A - Material grading apparatus - Google Patents

Abstract

Apparatus for separating "longs" from bulk material, e.g. unwanted rod-like lengths of extruded plastics in the production of uniformly pelleted plastics or straws and twigs from grain or seeds, uses a vibratory feed trough (10) having longitudinal ridges defining a series of valleys (13) in which the longs will be aligned for endwise movement. Lugs or projections (14) may be added, staggered across the width to turn the longs into the valleys. A gap (16) is defined between a downstream end of the trough and a receiving section 11 which the aligned longs will cross while remaining material is separated by dropping through the gap. <IMAGE>

Description

SPECIFICATION Material grading This invention relates to the grading of bulk dry materials in the sense of separating articles or particles having a length which is substantially greater than their width, diameter or girth (hereinafter referred to as "longs") from the same or different material in pelleted, granular and/or powder form whose individual particles do not have said length, but are of the same or greater diameter.

While the invention may have various applications in circumstances where sorting, grading and/or purification of these types of material is desired e.g. to separate longs in the form of twigs or straws from loose grain, seeds or like natural produce; the invention is particularly applicable to the grading of pelleted polystyrene or other plastics material.

In the manufacture of pelleted plastics a small proportion of longs, that is rod-like lengths of the extruded plastics considerably longer than the desired pellets, arise and are troublesome to separate as they tend to curl upend and pass through the apertures of perforated screens or to hook themselves into the same apertures of perforated screens, eventually working through so that in either manner the good product is still contaminated. It is not practical or economical to maintain a continuous watch on the screening process or close it down at intervals to remove lodged longs.

The object of the invention is to provide simple and easily operated apparatus which will separate longs reliably.

According to the invention there is provided apparatus for separating longs (as hereinbefore defined) in pelleted, granular or powdered material including an upstream section operable to advance a stream of the material including longs therealong in the form of a vibratory feed trough provided with alignment formations which cause the longs to be aligned longitudinally of said trough during vibration thereof, and a downstream receiving section separated from the upstream section by a gap whereby the longs so aligned will cross said gap and pass to the receiving section while other material falls through the gap.

Preferably the receiving section has an edge formation which is below the level of the upstream section and spaced forwardly therefrom to define said gap. Both sections may form part of a common vibratory feed device.

The alignment formations may take the form of longitudinal grooves or valleys in the floor of the upstream section and may further include upstanding projections, possibly staggered longitudinally, on the upstream section to assist in turning the longs into longitudinal alignment with the grooves of valleys.

One way of carrying out the invention is now described in detail with reference to the accompanying drawings illustrating a specific embodiment, in which: Figure 1 is a plan view of a vibratory separator, Figure 2 is an end elevation, and Figure 3 is a side elevation thereof.

The apparatus comprises conveying means in the form of a vibratory feed device divided into an upstream section 10 and a downstream receiving section 11. Spaced below this device is a conventional perforated plate screen 1 2. In this construction both sections 10, 11 and screen 1 2 are mounted for vibration in common by a conventional vibratory drive unit though it is possible that, in some applications, these elements could be separately vibrated.

The overall length of the apparatus shown is about 2 meters and the general width is about 450 mm. The floor of upstream section 10 is formed as a series of longitudinal ridges and V section valleys 1 3. The crests of the ridges are about 25 mm apart and the valleys are about 15-20 mm deep. The dimensions and proportions can, of course, be different depending on the desired throughput and the physical qualities of the material to be handled.

A series of upwardly projecting lugs 1 4 are mounted on the crests of the ridges in a chevron or other staggered formation across the width of section 10 and in the upstream half thereof.

The floor of downstream section 11 is flat and is arranged with its rearward edge spaced forwardly of and below section 10 to define a gap 16. Means is provided for selectively adjusting the relationship between the two sctions so as to vary their relative levels in a range of about 6-25 mm and to vary their horizontal relationship (i.e. width of gap 1 6 in plan view) though about the same range.

This apparatus handles pelleted polystyrene, the required pellet size being about 3 mm diameter X 3 mm length. The longs to be separated from this material may have lengths from 1 2 mm up to 1 50 mm, or bigger.

The vibratory movement carries the flow of material downstream (from right to left as viewed in Figs. 1 and 3) and, as it passes along upstream section 10 the longs will drop into valleys 1 3 so that they are aligned longitudinally of said section. Some longs (depending on their dimensions) may initially arrange themselves transversely across the tops of the ridges but one end or other of them will be caught by the staggered upward projections 14 so that they are turned longitudinally.

When the flow of material reaches gap 1 6 the now longitudinally aligned longs are projected end on across the gap their leading ends dropping to be caught by the floor of downstream section 11 and transferred ther eto. The much shorter pellets drop straight through the gap onto screen 1 2 which further grades them as the first step in any conventional screening process to remove dust and small particles and/or "doubles". The longs do not reach screen 12, thus the nuisance of them upending or lodging in passing through screen apertures is entirely avoided.

Gap 1 6 is adjusted to suit the material being handled, the speed of vibration, and the desired product throughput for most effective operation.

In alternative constructions screen 1 2 may be dispensed with (e.g. the pellets may drop straight into a container or onto some other form of conveyor) and/or the downstream receiving section may be a non-vibratory conveyor (e.g. a belt or gravity slide or chute) or even a static formation such as a simple dividing wall whose upper edge is aligned to define said gap, the longs falling down the downstream side thereof, or a receiving bin or hopper.

Claims (11)

1. Apparatus for separating longs (as hereinbefore defined) in pelleted, granular or powdered material including an upstream section operable to advance a stream of the material including longs therealong in the form of a vibratory feed trough provided with alignment formations which cause the longs to be aligned longitudinally of said trough during vibration thereof, and a downstream receiving section separated from the upstream section by a gap whereby the longs so aligned will cross said gap and pass to the receiving section while other material falls through the gap.

2. Apparatus as in Claim 1 wherein the receiving section has an edge formation which is below the level of the upstream section and spaced forwardly therefrom to define said gap.

3. Apparatus as in claim 1 or 2 wherein the relationship between the sections can be selectively adjusted to vary the dimensions of the gap.

4. Apparatus as in claim 1, 2 or 3 wherein the receiving section is also a vibratory feed trough.

5. Apparatus as in claim 4 wherein both sections are part of a common vibratory fee device.

6. Apparatus as in any one preceding claim including a screen below the sections to receive the material which falls through the gap.

7. Apparatus as in claim 6 wherein the screen is vibrated together with the upstream section.

8. Apparatus as in any one preceding claim wherein the floor of the upstream section is formed as a series of longitudinally extending ridges defining grooves or valleys therebetween and constituting the alignment formations.

9. Apparatus as in any one preceding claim wherein the alignment formations include upstanding projections on the floor of the upstream section.

1 0. Apparatus as in claim 9 wherein the projections are staggered across the width of said floor.

11. Apparatus for separating longs substantially as hereinbefore described with reference to and as shown in the accompanying drawings.