WO2001060531A1

WO2001060531A1 - Screening plant

Info

Publication number: WO2001060531A1
Application number: PCT/GB2001/000623
Authority: WO
Inventors: Patrick Joseph Douglas
Original assignee: Douglas Patrick J
Priority date: 2000-02-18
Filing date: 2001-02-15
Publication date: 2001-08-23
Also published as: WO2001060531B1; WO2001060531A9; GB0003786D0

Abstract

A multi-deck screening plant (10) which comprises: a chassis (11); upper and lower screen decks (12, 13) mounted on the chassis (11), one above the other, and each sloping downwardly from an upper receiving end (14, 15) to a lower discharge end (16, 17) from which over-sized material can be discharged, such material being too large to pass through the screening apertures of each deck (12, 13); an upper frame arranged to support the upper deck (12) and including longitudinal support beams (19) extending from the upper end (14) to the lower end (16) of the upper deck (12) and underlying the upper deck (12); and a lower frame arranged to support the lower deck (13) at a level in which the plane of the deck (13) is located at or close to the level of the underside of the support beams (19) of the upper frame.

Description

SCREENING PLANT

This invention relates to a multi-deck screening plant of the type in which a bulk supply of screenable material can be applied first to an upper deck which carries out a preliminary screening operation, and a lower deck is arranged to receive screened material from the upper deck and to carry out a further screening operation.

In a multi-deck screening plant, it is usual for the decks to be arranged one above the other, and generally parallel to each other, and with a downward slope from an upper receiving end of the plant to a lower discharge end at which over-sized material (relative to the screen deck concerned) can be discharged.

The supply of bulk material to the receiving end of the plant can be e.g. via conveyor, or by discharge from an excavator bucket or loading shovel, and material of a size in excess of the size of the screening apertures of the upper deck can be discharged under gravity action to the lower end of the upper deck, whereas material which is able to pass downwardly through the screening apertures of the upper deck can fall under gravity onto the lower deck where the further screening action takes place.

Material which is too large to pass through the screening apertures of the lower deck can be discharged under gravity action from the lower discharge end of the lower deck, whereas the material which passes through the screening apertures can be collected and then discharged to a required deposition site.

Therefore, with a two deck screening plant, a supply of bulk material can be separated into three screened size ranges.

In order to improve the screening efficiency, it is also known to provide an input of vibrational energy to the screen decks.

Evidently, in the assembly of two screen decks into a screening plant, it is necessary to provide a supporting frame for each deck, and typically this comprises generally rectangular frames which underlie each deck. Depending upon the size of each deck, it may be supported by one or more underlying rectangular frame. Thus, for a large area screen deck, it may be necessary to have two or more rectangular frames spaced apart transversely of the slope of the deck, and also two or more rectangular frames spaced apart lengthwise of the slope of the deck. The frame of a screening plant usually also has a pair of side plates, and which must be held together in a rigid assembly by transversely extending support beams or plates.

Also, bearing in mind that heavy loads of material will be dumped onto the upper deck, and then screened while vibratory motion is applied to the deck, it is necessary to provide framework assemblies to maintain rigidity to the overall structure of the screening plant, and to minimize risk of any stress-induced failures arising over a period of time.

However, in current designs of screening plant, the inevitable presence of substantial support frameworks (usually involving longitudinal and transverse support beams) can have an adverse effect on screening efficiency, in that the frameworks necessarily will impede flow of screened material through the upper deck to the lower deck; over the lower deck to a discharge end; and through the lower deck to a further discharge position.

Furthermore, in existing screening plants, there is usually substantial overall height of the plant, by reason at least of the current arrangements in which the two decks are of substantial depth, to accommodate the respective supporting frameworks, i.e. the upper deck is located at an appreciable height above the lower deck, and this can cause difficulties in loading the upper deck with screenable material using some types of excavator bucket or loading shovel, of which the lifting height is limited.

The present invention therefore seeks to provide an improved support frame for the screening decks of a multi-deck screening plant, with a view to improving the screening efficiency of the screen decks.

According to the invention there is provided a multi-deck screening plant which comprises: a chassis; upper and lower screen decks mounted on the chassis, one above the other, and each sloping downwardly from an upper receiving end to a lower discharge end from which over-sized material can be discharged, such material being too large to pass through the screen apertures of each deck; an upper frame arranged to support the upper deck and including support beams extending from the upper end to the lower end of the upper deck and underlying the upper deck; and a lower frame arranged to support the lower deck at a level in which the plane of the deck is located at or close to the level of the underside of said support beams of the upper frame.

Therefore, by reason of the arrangement of the upper and lower frames as defined above, there are the following advantages; 1) oversized material can readily be discharged from the lower discharge ends of the screen decks without being impeded by the frames; and 2) the depth of the upper and lower screen decks i.e. the height of the upper deck above the lower deck can be maintained substantially equal to the depth of the support beams of the upper frame, and therefore the overall height of the plant can be reduced compared with known arrangements, and which means that discharge from overhead via loading buckets or loading shovels can be facilitated.

The upper frame may comprise an assembly of longitudinal support beams extending parallel to each other, and one or more transverse support beam interconnects the longitudinal beams.

The lower frame which supports the lower deck preferably comprises transversely extending support beams, and which also hold side frame plates of the chassis together to give rigidity to the assembly.

Relatively massive transverse support beams may support the upper and lower ends of the lower deck, whereas lightweight intermediate transverse support beams may also be provided.

To give additional rigidity to the chassis assembly, the massive upper transverse support beam of the lower frame may be rigidly fastened to an upper transverse support beam of the upper frame.

A shaft-driven vibratory mechanism is preferably coupled with the screen decks, directly, or indirectly via the chassis, to impart vibrational energy to the decks and thereby improve the screening operation. The screening plant may comprise a trailed wheeled unit, which can readily be transported from one position to another on a construction site, or can readily be transported from one site to another.

A preferred embodiment of multi-deck screening plant according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a view from one side of a screening plant according to the invention, viewed from a discharge end thereof;

Figure 2 is an end view of the plant;

Figure 3 is a plan view of the plant:

Figure 4 is a further end view, to an enlarged scale to illustrate more detail of the construction of the support frame assemblies of the screen decks;

Figure 5 is a further end view to an enlarged scale;

Figure 6 is a further plan view of the plant, but to an enlarged scale: and

Figure 7 is a detailed view, to an enlarged scale, from the discharge end side of the plant.

Referring now to the drawings, a preferred embodiment of multi-deck screening plant according to the invention is designated generally by reference 10, and comprises a chassis 11 on which upper and lower screen decks 12 and 13 are mounted, one above the other, and each sloping downwardly from an upper receiving end to a lower discharge end. This can be seen in particular from Figure 4, in which screens 12 and 13 have upper material receiving ends 14 and 15 respectively, and lower discharge ends 16 and 17 respectively.

Bulk material to be screened is loaded onto the upper deck 12, preferably at or near its upper end 14, and oversized material, which is too large to pass through the screening apertures of the upper deck 12, is discharged under gravity action towards the lower discharge end 16 from which the material is discharged onto the ground, or to a discharge conveyor (not shown). Material which can pass downwardly through the screening apertures of the screening deck 12 then falls under gravity onto the lower deck 13, where it undergoes a further screening action. Oversized material i.e. material which too large to pass through the screening apertures of the lower deck 13 is discharged under gravity action towards the lower discharge end 17, for discharge from the screening plant. Screenable material is able to pass downwardly through the screening apertures of the lower deck 13 to be collected and then transferred to a suitable discharge point e.g. by a discharge conveyor.

An upper frame is arranged to support the upper deck 12, and comprises a transverse support beam 18 at the upper receiving end of the upper deck 12, and a number of support beams 19 which extend from the upper end 14 to the lower end 16 of the upper deck 12, and underlying the upper deck. Preferably, the beams 19 extend parallel to each other, and longitudinally with respect to the axis of the upper deck 12.

A lower frame is arranged to support the lower deck 13 at a level in which the plane of the deck is located at or close to the level of the underside of the transverse beam 18 and the longitudinal beams 19 of the upper frame i.e. substantially coplanar with the lower flanges of the beams.

Therefore, by reason of the arrangement of the upper and lower frames, there is the advantage that oversized material can readily be discharged from the lower discharge ends 16 and 17 of the screen decks 12 and 13, without being impeded by the frame components. Furthermore, in that the depth of the upper and lower screen deck assembly is small i.e. the height of the upper deck 12 above the lower deck 13 can be maintained substantially equal to the depth of the transverse beam 18 and longitudinal beams 19 of the upper frame, the overall height of the plant 10 can be reduced compared with known arrangements. This means that discharge from overhead via loading buckets or loading shovels can be facilitated.

The lower frame which supports the lower deck 13 comprises transversely extending support beams, and which also hold the side frame plates 1 la of the chassis 11 together to give rigidity to the assembly.

Relatively massive transverse support beams 20 and 21 support the upper and lower ends 15 and 17 of the lower deck 13 respectively. In addition, lightweight intermediate transverse support beams 22 also form part of the lower frame structure supporting the lower deck 13. A shaft-driven vibrating mechanism, designated generally by reference 23, is coupled with the screen decks 12 and 13, indirectly via the chassis 11, to impart vibrational energy to the decks 12 and 13 and thereby improve the screening operation.

As can be seen from Figure 1, the screening plant 10 is a trailed wheeled unit, and which can be readily transported from one position to another on a construction or demolition site, or from one site to another.

Claims

Claims:

1. A multi-deck screening plant (10) which comprises: a chassis (11); upper and lower screen decks (12, 13) mounted on the chassis (11), one above the other, and each sloping downwardly from an upper receiving end (14, 15) to a lower discharge end (16, 17) from which over-sized material can be discharged, such material being too large to pass through the screening apertures of each deck (12, 13); an upper frame arranged to support the upper deck (12) and including support beams (19) extending from the upper end (14) to the lower end (16) of the upper deck (12) and underlying the upper deck (12); and a lower frame arranged to support the lower deck (13) at a level in which the plane of the deck (13) is located at or close to the level of the underside of the support beams (19) of the upper frame.

2. A screening plant according to claim 1, in which the support beams (19) extend parallel to each other, and to the longitudinal axis of the upper screen deck (12).

3. A screening plant according to claim 1 or 2, in which the upper frame includes a transverse support beam (18) at the upper receiving end (14) of the upper deck (12), and the plane of the lower deck (13) is also at or close to the underside of the transverse beam (18).

4. A screening plant according to any one of claims 1 to 3, in which the lower frame which supports the lower deck (13) comprises transversely extending support beams (20, 21) which also hold the side frame plates (11a) of the chassis (11) together, to give rigidity to the assembly.

5. A screening plant according to claim 4, in which massive transverse support beams (20, 21) support the upper and lower ends (15, 17) of the lower deck (13), and lightweight intermediate transverse support beams (22) also form part of the lower frame.

6. A screening plant according to claim 5, in which the massive upper transverse support beam (20) of the lower frame is rigidly fastened to the upper transverse support beam (18) of the upper frame.

7. A screening plant according to anyone of the preceding claims, in which a shaft- driven vibrating mechanism (23) is coupled with the screen-decks (12, 13), to impart vibrational energy to the decks and thereby improve the screening operation.

8. A screening plant according to anyone of the preceding claims, and comprising a trailed wheeled unit.