IES67147B2 - A washing plant - Google Patents

Abstract

A washing plant 3 for use with a material screening apparatus has a chassis (20, Fig 2) carrying two screen decks 27, the first (lower) having an inlet path (21, Fig 2) for accepting aggregate material into a first washing area 11, wherein sand and fines are washed from the aggregate. The outlet path 13 from 11 feeds material to recirculating conveyors 5 and 7. From the top of conveyor 7 washed material enters another inlet path (24, Fig 2) for delivery to a second washing area 15. The second screen deck is disposed over the first screen deck so that the sand and fines washed from the second (upper) screen deck are rinsed through to the lower screen deck and out of the washing stations. The sand is collected and the water recycled. Each washing area 11, 15 of the first and second screen decks 27 has a plurality of washing stations (30, Fig 2) comprising water jets, and an air jet (39, Fig 2) is provided at the first inlet path (21, Fig 2) to separate the raw aggregate material. The outlet path 16 of the second screen deck feeds washed aggregate material to a conveyor 9, and thence to further grading means G.

Description

A WASHING PLANT The present invention relates to a washing plant for use with a material screening apparatus and more particularly to a combined washing and material screening apparatus which cleans and grades aggregate material such as gravel, sand, stone and the like.

Material to be graded is usually a mixture of gravel and pebble sizes which are mixed with sand and dust (or fines). Known washing plants are often extremely inefficient and require relatively large quantities of water. Additionally, valuable material may be lost during the washing process.

It is an object of the present invention to provide a washing plant for use with material screening apparatus to clean and grade material efficiently and without significant waste.

Accordingly, the present invention provides a washing plant for use with a material screening apparatus, the washing plant having a chassis carrying: a first screen deck having a recirculating means, an inlet path for directing aggregate material into a first washing area and an outlet path to feed material passing therethrough to the recirculating means to provide material for recirculation through the plant; and a second screen deck having an inlet path for directing the recirculated material into a second washing area and an outlet path for feeding the material to further processing stations, wherein each washing area of the first and second screen decks has a plurality of washing stations comprising water jets and the second screen deck is disposed over the first screen deck so that water and fine particulate material washed from the aggregate and recirculated material are directed through the screens for removal.

Preferably, the input path to the first washing area includes a water jet for wetting and agitating the aggregate material, a deflector plate for redirecting the flow of the wet aggregate material and an air jet for moving the material from the edge of the deflecting plate to impact it against the chassis of the washing plant.

Each screen deck vibrates to direct the material from the inlet path to the outlet path and to separate sand and fines from the material to be processed.

The present invention further provides a screening apparatus comprising a hopper for receiving and subsequently dispensing raw unprocessed material, a first conveyor for conveying the raw material to a first washing area which includes a screen deck for removing sand and fines from the raw material, a chute for retrieving the washed material which is subsequently transferred by a belt-feeder to a second conveyor which feeds the material to a second washing area which includes a screen deck where the material is washed again before subsequent grading, wherein the second washing area is disposed over the first washing area so that sand and fines are removed from the raw material in two successive operations for optimal processing.

The washing plant comprises an inclined tray having a pair of vibrating screen decks. Raw aggregate material is - 3 conveyed to a first inlet where the aggregate is washed I and directed over an edge facing rearwardly with respect to the direction of travel of the material. As the material is falling over the edge, air is blasted through the aggregate to separate it by impacting the aggregate against a rear wall of the tray. The material then falls under the vibratory action of the first screen through a first series of washing stations.

The screen is provided with a mesh of a size to pass only sand and fines which are taken away to a blender from which water may be extracted. The material, without sand and fines, is recirculated to a second inlet of the washing plant where it is washed at a second series of washing stations over a second vibrating screen, again provided with a mesh of a size to allow only sand and fines to be extracted. The sand and fines extracted from the second series of washing stations are carried with the water into the area of the first series of washing stations where they are removed to the blender.

The washed material is then dispensed to a delivery chute which deposits the material on a conveyor belt to a grader where the material can be graded to various sizes as required.

Each washing station comprises a pipe for carrying water under pressure, disposed transversely to the direction of travel of the material. The pipes have a plurality of jets which produce a spray capable of removing sand and fines from the raw material. Air is blasted through the aggregate material from a pipe transversely disposed to the direction of travel of the material. Jets are provided along the length of the pipe to deliver air under sufficient pressure to carry falling material and impact - 4 it against the rear wall of the tray.

The invention will now be described more particularly with reference to the accompanying drawings which show, by way of example only, one embodiment of washing plant for use with a material screening apparatus according to the invention. In the drawings: Figure 1 is a schematic side elevation of the material 1 0 screening apparatus in use; Figure 2 is a detailed side sectional view of the washing plant; and Figure 3 is a plan view of the washing plant.

Referring to the drawings and initially to Figure 1, the screening apparatus comprises a main hopper H for storing raw aggregate material, a first conveyor 1 for feeding material to the washing plant 3 of the invention, a belt-feeder 5 for recirculating material to a second conveyor 7 for a second pass through the washing plant 3 and a third conveyor 9 for transferring the washed material to a grader G. The hopper H is provided with a rejection grid (not shown) to ensure large stones or oversized pieces of debris are not accepted for processing. The stored raw material is dispensed onto the first conveyor 1 which carries the material into a first washing area 11 of the washing plant 3 for a first pass. The material is collected in a chute 13 which delivers the washed material onto the belt-feeder 5. The second conveyor 7 carries the washed material back to the washing plant 3 for a second pass in a second washing area 15. The cleaned material falls along a delivery chute 16 to the third conveyor 9 which transfers the material to the grader G.

The washing plant, as shown in detail in Figures 2 and 3, comprises a tray-shaped chassis 20 having an inlet 21 to the first washing area 11 and a corresponding outlet 22.

A second inlet 24 is provided to allow material pass to the second washing area 15, which is disposed directly above the first washing area 11, and has an outlet 25 leading to the delivery chute 16. Each washing area 11,15 has a vibrating screen 27 at its base over which the material passes. The screens 27 are graded to allow only sand and fines to pass therethrough. A set of four washing stations 30 are provided in each washing area.

Each washing station 30 comprises a pipe disposed transversely to the direction of travel of the material and has a number of jets which spray water onto the material below. Water, sand and fines falling through the screen 27 of the second area 15 fall into the first area 11. The water, sand and fines from the first area 11 fall through the corresponding screen 27 and are carried from the base of the chassis 20 to a sand blender (not shown) where they are separated.

The first inlet 21 includes a water pipe 32 which sprays the raw aggregate material as it enters the washing plant 3. An air wash station comprising a hollow pipe 35 having a series of jets along its length blasts the aggregate material to break up conglomerations of the material. Deflector plates 36,37 direct the material into the washing area 11.

In use, raw material is applied into the main hopper H which includes a screen to prevent overly large rocks being processed by the apparatus. The material is metered out from the base of the hopper to the first conveyor 1. - 6 This raw aggregate material falls from the conveyor 1 and is washed by the pressurised water pipe 32 having jets which direct the material into a forwardly inclined plate 36. As the material falls under gravity from the plate 36 5 towards a rearwardly facing edge 39 on the second plate 37, it is blasted by air jets from the air pipe 35 as it falls over the edge 39, rearwardly to impinge against the rear 40 of the chassis tray 20. The aggregate material is broken up by the successive actions of the water jets, the air jets and being forced against the rear 40 of the tray 20. The material is then passed under the first series of washing stations 30 by the vibratory action of the first screen 27 which is provided with a mesh of a size to allow only sand and fines to fall therethrough. A mesh size of 2-5 mm^ £g typically used. All material over a predetermined size passes over the vibrating screen 27 and is collected in the chute 13 which delivers the material onto the belt-feeder 5 to recirculate the material. The sand and fines which are collected in the tray 20 together with the water used for cleaning the material is directed to a sand blender which may separate the sand, fines and the water for use. Any material which cannot be used is directed to a tailings pond.

The recirculated material from the chute 13 is transferred to the second conveyor 7 which is disposed parallel to the first conveyor 1. The recirculated material is carried to the second inlet 24 of the washing plant 3 where it passes through the second washing area 15 through four washing stations 30 which produce high pressure water jets. Any remaining sand or fines is carried through the mesh of the vibrating screen 27 into the first washing area 11 and on to the sand blender. The now twice-washed material is directed down the delivery chute 16 onto the third conveyor 9 which brings the material to a grader G, typically having five successive grading series to separate the various sizes of material required.

It will of course be understood that the invention is not 5 limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the appended claims.

Claims (5)

CLAIMS :

1. A washing plant for use with a material screening apparatus, the washing plant having a chassis carrying: a first screen deck having a recirculating means, an inlet path for directing aggregate material into a first washing area and an outlet path to feed material passing therethrough to the recirculating means to provide material for recirculation through the plant; and a second screen deck having an inlet path for directing the recirculated material into a second washing area and an outlet path for feeding the material to further processing stations, wherein each washing area of the first and second screen decks has a plurality of washing stations comprising water jets and the second screen deck is disposed over the first screen deck so that water and fine particulate material washed from the aggregate and recirculated material are directed through the screens for removal.

2. A washing plant as claimed in claim 1, in which the input path to the first washing area includes a water jet for wetting and agitating the aggregate material, a deflector plate for redirecting the flow of the wet aggregate material and an air jet for moving the material from the edge of the deflecting plate to impact it against the chassis of the washing plant.

3. A washing plant as claimed in either claim 1 or claim 2, which includes an inclined tray having a pair of vibrating screen decks to which raw aggregate material is conveyed via a first inlet where the aggregate is washed - 9 and directed over an edge facing rearwardly with respect to the direction of travel of the material so that as the material is falling over the edge, air is blasted through the aggregate material to impact it against a rear wall of 5 the tray, the material falling under the vibratory action of the first screen through a first series of washing stations to an outlet to be recirculated to the second inlet of the washing plant where it is washed at a second series of washing stations over a second vibrating screen 10 and subsequently dispensed via a delivery chute to a conveyor belt to carry the washed material to a grader where it can be graded to various sizes as required, and in which each washing station comprises a pipe for 15 carrying water under pressure, disposed transversely to the direction of travel of the material, each pipe having a plurality of jets which produce a spray capable of removing sand and fines from the raw aggregate material, and the air is delivered from a pipe, transversely 20 disposed to the direction of the travel of the material, each pipe having jets to carry falling material and impact it against the rear wall of the tray.

4. A screening apparatus comprising a hopper for 25 receiving and subsequently dispensing raw unprocessed material, a first conveyor for conveying the raw material to a first washing area which includes a screen deck for removing sand and fines from the raw material, a chute for retrieving the washed material which is subsequently 30 transferred by a belt-feeder to a second conveyor which feeds the material to a second washing area which includes a screen deck where the material is washed again before subsequent grading, wherein the second washing area is disposed over the first washing area so that sand and 35 fines are removed from the raw material in two successive operations for optimal processing.

5. A washing plant for a screening apparatus or a screening apparatus comprising such a plant substantially 5 as herein described with reference to and as shown in the accompanying drawings.