GB1558523A - Thickness sorting - Google Patents

Description

(54) THICKNESS SORTING (71) We, BRITISH STEEL CORPORATION, a Corporation incorporated and existing under the Iron and Steel Act 1967 whose principal office is at 33 Grosvenor Place, London, S.W.1 do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to apparatus for sorting material by reference to its thickness.

When plate iron from a plating pit is broken up prior to being fed via a continuous charging system to an electric arc furnace it is important that the material has a fairly uniform size characteristic. It should not be larger than about 200 mm, in any dimension, but should exclude "fines" (say 2.5 mm). The material can be broken down by dropping a weight on it in a pit and then further reduced in size in a hammer mill. To prevent damage to the hammer mill it is desirable to exclude the thickest pieces, and to prevent undue production of fines it is desirable to exclude the smallest pieces. Thus there is a requirement for a device to sort over-thick, standard and undersized material.

The invention provides apparatus for sorting material by size characteristics, and having a vibratable tray forming a path between a reception area and a discharge area, a gate member extending across the tray in the path of the material and inclined at an angle with respect to that path, there being a gap between the gate member and the tray which progressively increases across the path to be largest where the gate member is furthest from the reception area such that material passing through the gap at different points across the path reaches different parts of the discharge area, so to sort out over-thick material which cannot pass through the gap, said tray being inclined to a horizontal plane such that material placed on the reception area of the tray is biased into movement towards the gate member, and including a fiddle along at least the edge of the tray at which the size of the gap is smallest.

It is preferred that the gate is perpendicular to the tray.

It is further preferred that the gate is planar and the edge of the gate closest to the tray is bevelled away from the reception area.

Conveniently the tray has a bias such that material is biased into movement towards the fiddle.

In one form of the invention it is preferred that a part of the tray on the other side of the gate from the reception area is perforated to permit some but not all of the pieces of material passing under the gate to drop through the perforations.

The apparatus of the invention may be used in combination with the second similar such apparatus arranged to run in series therewith.

The invention includes apparatus as specified above in combination with means to vibrate the tray.

Two specific embodiments of the invention will now be described by way of the example with reference to the accompanying drawings in which: Figure 1 is an isometric view of a plate iron thickness sorter.

Figures 2, 3 and 4 are respectively a side view, end view and plan of another plate iron thickness sorter; Figure 5 is a block diagram showing two plate iron thickness sorters in series, and Figure 6 is a block layout showing a plant incorporating a plate iron thickness sorter.

The apparatus shown in Figure 1 has a tray (10), supported on resilient mountings (Il) for vibration by a motor (12) in the sense of the arrow ("X"). Along one side of the tray there is a fiddle (14), and there is a gate (15) extending across the tray at an angle of C" to the fiddle. Between the gate (15) and the top surface of the tray there is a gap which widens at an angle of D". On the side of the gate away from the material reception area there is a perforated section (16) in the tray and at the end of the tray away from the material reception area there is a discharge space (17) for oversized material to pass off the tray. The tray is tilted at an angle of A" relative to its longer side, and at an angle of B" relative to its shorter side.The tilt of the tray biases material thereon to move towards the gate 15 when vibration is applied.

Depending on the size and characteristics of the material being sorted the angle A may vary up to 50 and the angle B may vary up to 20 , and the angle D between the gate and the tray may vary from 1-3".

In operation material of variable size is deposited on the reception area at an upper level of the tray. Vibration is applied, and the material moves according to the bias of the tray towards the gate (16). Oversized material cannot pass under the gate, and so moves along the gate until it reaches the discharge area (17) where it drops off the tray (together with any misrouted under-thick material). Undersized material passes beneath the gate and then either drops through the perforations (16) to fall onto a diverter (18) leading to a collection device, or if it is too large to drop through perforations, falls on the diverter (19) for subsequent collection.

While it would be appreciated that size sorting is possible with many configurations of gate it has been found convenient to angle the gate relative to the fiddle with an angle C of between 20-50".

A second embodiment of a plate thickness sorter is shown in Figures 2, 3 and 4, in which like items are designated with like numerals to those used on Figure 1. the most obvious differences between the embodiments are that the second embodiment has two 3 hp motors 12a, a second fiddle 21 on the 'high' side of the tray 10, and an extension 22 to the gate 15.

The motors 1 2a are arranged to vibrate material on the plane shown, so to move it along the tray. The second fiddle 21 allows an overload to be carried by the tray without falling off the side. The optional extension 22 (also at angle DO) prolongs the period allowed for undersized material to reach the area 17.

Figure 5 shows how two sorters 24 and 25 can be arranged in series. The sorting efficiency of each stage is to some extent a function of the throughput rate at that stage. A mixture of 2000 kg under-thick and 1000 kg over-thick material was processed, the primary sorter receiving material at 60 t/h. This was sorted at an efficiency of 85% of the under-thick material (1700 kg) being recovered from the mixture. The remainder of the under-thick material, together with all the over-thick material, then passed to the secondary sorter where the lower feed rate 26 t/h gave a higher efficiency of 93.5%. Thus a further 280.5 kg were recovered, giving a total recovery of 1980.5 kg and an overall efficiency of 99%.

A typical plant, to prepare plate iron for feeding to a continuously charged electric arc furnace, is shown in Figure 6. A loading magnet 30 feeds material onto a screen 31 from which undersize material travels directly to a magnetic separator 32.

Oversize material passes over the screen onto the reception area of the tray 10 of a sorter. Under-thick material passes to a plate iron breaker 33, while over-thick material is rejected at 34. Comminuted material 35 passes onto a screen 36 from which undersize material passes to the magnetic separator 32. Oversize material 37 is returned to the plate iron breaker 33. In this way over-thick material is rejected, and suitably sized material is passed to the magnetic separator for use in an electric arc furnace after non-ferrous fragments have been separated.

WHAT WE CLAIM IS: 1. Apparatus for sorting material by size characteristics, having a vibratable tray forming a path between a reception area and a discharge area, a gate member extending across the tray in the path of the material and inclined at an angle with respect to that path, there being a gap between the gate member and the tray which progressively increases across the path to be largest where the gate member is furthest from the reception area, such that material passing through the gap at different points across the path reaches different parts of the discharge area so as to separate out over-thick material which cannot pass through the gap, said tray being inclined to a horizontal plane such that material placed on the reception area of the tray is biased into movement towards the gate member, and including a fiddle along at least the edge of the tray at which the size of the gap is the smallest.

2. Apparatus as claimed in claim 1 in which the gate is perpendicular to the tray.

3. Apparatus as claimed in any preceding claim in which the gate is planar and the edge of the gate closest to the tray is bevelled away from the reception area.

4. Apparatus as claimed in any preceding claim in which the tray has a bias such

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. (Il) for vibration by a motor (12) in the sense of the arrow ("X"). Along one side of the tray there is a fiddle (14), and there is a gate (15) extending across the tray at an angle of C" to the fiddle. Between the gate (15) and the top surface of the tray there is a gap which widens at an angle of D". On the side of the gate away from the material reception area there is a perforated section (16) in the tray and at the end of the tray away from the material reception area there is a discharge space (17) for oversized material to pass off the tray. The tray is tilted at an angle of A" relative to its longer side, and at an angle of B" relative to its shorter side.The tilt of the tray biases material thereon to move towards the gate 15 when vibration is applied. Depending on the size and characteristics of the material being sorted the angle A may vary up to 50 and the angle B may vary up to 20 , and the angle D between the gate and the tray may vary from 1-3". In operation material of variable size is deposited on the reception area at an upper level of the tray. Vibration is applied, and the material moves according to the bias of the tray towards the gate (16). Oversized material cannot pass under the gate, and so moves along the gate until it reaches the discharge area (17) where it drops off the tray (together with any misrouted under-thick material). Undersized material passes beneath the gate and then either drops through the perforations (16) to fall onto a diverter (18) leading to a collection device, or if it is too large to drop through perforations, falls on the diverter (19) for subsequent collection. While it would be appreciated that size sorting is possible with many configurations of gate it has been found convenient to angle the gate relative to the fiddle with an angle C of between 20-50". A second embodiment of a plate thickness sorter is shown in Figures 2, 3 and 4, in which like items are designated with like numerals to those used on Figure 1. the most obvious differences between the embodiments are that the second embodiment has two 3 hp motors 12a, a second fiddle 21 on the 'high' side of the tray 10, and an extension 22 to the gate 15. The motors 1 2a are arranged to vibrate material on the plane shown, so to move it along the tray. The second fiddle 21 allows an overload to be carried by the tray without falling off the side. The optional extension 22 (also at angle DO) prolongs the period allowed for undersized material to reach the area 17. Figure 5 shows how two sorters 24 and 25 can be arranged in series. The sorting efficiency of each stage is to some extent a function of the throughput rate at that stage. A mixture of 2000 kg under-thick and 1000 kg over-thick material was processed, the primary sorter receiving material at 60 t/h. This was sorted at an efficiency of 85% of the under-thick material (1700 kg) being recovered from the mixture. The remainder of the under-thick material, together with all the over-thick material, then passed to the secondary sorter where the lower feed rate 26 t/h gave a higher efficiency of 93.5%. Thus a further 280.5 kg were recovered, giving a total recovery of 1980.5 kg and an overall efficiency of 99%. A typical plant, to prepare plate iron for feeding to a continuously charged electric arc furnace, is shown in Figure 6. A loading magnet 30 feeds material onto a screen 31 from which undersize material travels directly to a magnetic separator 32. Oversize material passes over the screen onto the reception area of the tray 10 of a sorter. Under-thick material passes to a plate iron breaker 33, while over-thick material is rejected at 34. Comminuted material 35 passes onto a screen 36 from which undersize material passes to the magnetic separator 32. Oversize material 37 is returned to the plate iron breaker 33. In this way over-thick material is rejected, and suitably sized material is passed to the magnetic separator for use in an electric arc furnace after non-ferrous fragments have been separated. WHAT WE CLAIM IS:

1. Apparatus for sorting material by size characteristics, having a vibratable tray forming a path between a reception area and a discharge area, a gate member extending across the tray in the path of the material and inclined at an angle with respect to that path, there being a gap between the gate member and the tray which progressively increases across the path to be largest where the gate member is furthest from the reception area, such that material passing through the gap at different points across the path reaches different parts of the discharge area so as to separate out over-thick material which cannot pass through the gap, said tray being inclined to a horizontal plane such that material placed on the reception area of the tray is biased into movement towards the gate member, and including a fiddle along at least the edge of the tray at which the size of the gap is the smallest.

2. Apparatus as claimed in claim 1 in which the gate is perpendicular to the tray.

3. Apparatus as claimed in any preceding claim in which the gate is planar and the edge of the gate closest to the tray is bevelled away from the reception area.

4. Apparatus as claimed in any preceding claim in which the tray has a bias such

that material on it tends to move towards the fiddle.

5. Apparatus as claimed in any preceding claim in which a part of the tray on the other side of the gate from the reception area is perforated to permit some, but not all of the pieces of material passing under the gate to drop through the perforations.

6. Apparatus as claimed in any preceding claim arranged in series with a second similar such apparatus.

7. Apparatus as claimed in any preceding claim including means for vibrating the tray.

8. Apparatus for sorting material by size characteristics as hereinbefore described with reference to and as shown in the accompanying drawings.