GB2302514A

GB2302514A - A transportable rock screening plant

Info

Publication number: GB2302514A
Application number: GB9613062A
Authority: GB
Inventors: Peter Cooper
Original assignee: Hydraplant Equipment Pty Ltd
Current assignee: Hydraplant Equipment Pty Ltd
Priority date: 1995-06-23
Filing date: 1996-06-21
Publication date: 1997-01-22
Anticipated expiration: 2016-06-21
Also published as: GB2302514B; AUPN375495A0; GB9613062D0

Abstract

The present invention relates to a transportable rock screening plant (10) comprising a primary screen, a secondary screen, and a tertiary screen shown generally as (12, 14, 16) respectively. The screens (12, 14, 16) are mounted on a chassis (18). The transportable screening plant (10) further comprises a rock feeder (20) also mounted on the chassis (18). The rock feeder (20) has a feeder tray (22). The transportable plant (10) further comprises a hopper (24) surrounding and located immediately above the rock feeder (20). The screening plant (10) is designed to receive relatively large rocks of usually not greater than 1.5 metres in diameter. The rock screening plant (10) in operation classifies relatively large rocks and/or stones into at least four size distributions.

Description

A TRANSPORTABLE ROCK SCREENING PLANT FIELD OF TEE INVENTION The present invention relates generally to a transportable rock screening plant and relates particularly, though not exclusively, to a rock screening plant that is transportable as a semi-trailer or transportable on a skid base or track-mounted.

BACKGROUND To THE INVENTION Screening machines used to size rock and/or stone particles into various size distributions are used in mines, quarries, refuse areas, and other materials handling applications. Screening machines are divided into five main classes including: grizzly screens, revolving screens, shaking screens, vibrating screens, and oscillating screens.

Rock and/or stone screening plants mounted on a semitrailer have been designed with a view to overcoming costs associated with fixed installation screening plants.

However, largely because of size limitations, the amount of screening equipment that can be mounted on a semi-trailer is somewhat restricted. Furthermore, the chassis of the semi-trailer must be adequately supported on the ground while the plant is in use and the weight of screening equipment may be constrained by vibrational and weight forces present while the screening plant is classifying rock.

These known screening plants are also restricted to rocks and/or stones of a relatively small size. Typically the screening plants handle rocks and/or stones of a size less than approximately 350 mm in diameter. Although the screening plant can size rock and/or stone of a slightly larger size, the screening plant then requires frequent maintenance and repair.

A known rock screening plant mounted as a semi-trailer produces rock and/or stone of three (3) size distributions using a stationary grizzly screen located above a vibrating grizzly screen. In use, the stationary grizzly retains oversize rock and undersize rock passing through the stationary grizzly passes to the vibrating grizzly.

Intermediate rock is retained on the vibrating grizzly and undersize stone passed through the vibrating grizzly.

Further size classification of at least the undersize stone may then be performed by transporting said stone to another screening plant.

SUMMARY OF THE INVENTION An intention of the present invention is to provide a transportable rock screening plant which classifies relatively large rocks into at least four (4) size distributions.

According to the present invention there is provided a transportable rock screening plant comprising: a primary screen adapted to receive relatively large rocks to be screened, the primary screen having a plurality of first openings through which first undersize rock is passed and first oversize rock remains; a secondary screen operatively communicating with the primary screen, adapted to receive the first undersize rock, said secondary screen having a plurality of second openings through which second undersize rock is passed and second oversize rock remains; and a tertiary screen operatively communicating with the secondary screen, adapted to receive said second undersize rock, said tertiary screen having a plurality of third openings through which third undersize rock is passed and third oversize rock remains whereby, in use, relatively large rocks received on the primary screen are sized through the screening plant to provide first, second, and third oversize rocks, and third undersize rock each of a size distribution depending on the predetermined size of the first, second, and/or third openings.

Typically, the primary, and secondary screens are each grizzly screens having a plurality of first and second spaced parallel bars, respectively, between which the first and second openings are defined. Furthermore, the tertiary screen typically comprises a mesh structure having third openings. Alternatively, the tertiary screen is also a grizzly screen having third spaced parallel bars between which third openings are defined.

Preferably, at least one of the primary, secondary, or tertiary screens comprises a primary, secondary, or tertiary frame, respectively, to which each of said plurality of spaced first, second, or third parallel bars are adjustably coupled so that, in use, adjacent bars can be moved and then fixed at a predetermined separation relative to each other so as to control the size distribution of said first, second, and third oversize rock, and the third undersize rock.

Typically, the first, second, and/or third spaced parallel bars are tapered longitudinally. Alternatively the bars are oriented relative to each other so that the first, second, and/or third openings are tapered longitudinally.

Typically, the transportable rock screening plant further comprises a rock feeder operatively communicating with the primary screen so as to move the first undersize rock to the secondary screen located adjacent the rock feeder.

Preferably, the rock feeder comprises a feeder tray located beneath the primary screen and inclined away from the primary screen toward the secondary screen.

Typically, the transportable rock screening plant further comprises a feeder motor assembly operatively coupled to the feeder tray to provide vibrational movement to the feeder tray so that, in use, the feeder motor assembly effects vibration of the feeder tray and thus conveys first undersize rock to the secondary screen. Preferably, the feeder motor assembly can in operation be adjusted to vary the frequency and/or amplitude at which the feeder tray vibrates. The frequency and/or amplitude at which the feeder tray vibrates is substantially proportional to the speed and/or weight, respectively, of rock which is conveyed to the secondary screen.

Typically, the transportable rock screening plant further comprises a screen motor assembly operatively coupled to both the secondary and tertiary screens so that, in use, the screen motor assembly effects vibration of the secondary and tertiary screens and thus movement of oversize rock relative to each of said screens, and promotes movement of undersize rock passing through each of said screens. Preferably, the secondary and tertiary screens are inclined from a horizontal plane so that, in use, movement of oversize rock relative to each of said screens is promoted by gravity acting on said oversize rock. The screen motor assembly has variable frequency and/or amplitude wherein the speed and/or weight, respectively, of rock vibrated along the secondary and tertiary screens can be controlled.

Typically, the transportable rock screening plant further comprises a hopper located between the primary screen and the rock feeder so that, in use, the hopper channels first undersize rock from the primary screen to the rock feeder.

Preferably, at least a portion of an internal surface of the hopper is lined with a wear resistant material.

Preferably, the plant further comprises feeder skirts connected adjacent and protruding from a bottom edge of the hopper.

Typically, the transportable rock screening plant further comprises an oversize conveyor system operatively communicating with the tertiary screen so that, in use, third oversize rock from the tertiary screen is carried from the plant via the oversize conveyor system. In another embodiment the screening plant further comprises an undersize conveyor system operatively communicating with the tertiary screen so that, in use, third undersize rock from the tertiary screen is transported from the plant via the undersize conveyor system.

Typically, the transportable rock screening plant further comprises a base frame to which the primary, secondary, and tertiary screens, and feeder are operatively coupled. In a preferred example the base frame is a chassis of a semitrailer.

Advantageously, the primary screen is movably coupled to the chassis of the semi-trailer so that, in use, first oversize rock retained on the primary screen can be removed therefrom by tipping the primary screen. Preferably, the primary screen is pivotally connected to the hopper. In one example, movement of the primary screen to remove first oversize rock retained on said screen is effected by a remote control unit. In a further embodiment, the primary screen is designed to be removed from the hopper for transportation purposes. In this example the primary screen is designed to locate on a forward section of the chassis, the primary screen being oriented relative to the chassis so that it consumes minimum road-space.

It is to be generally understood that relatively large rocks includes rocks or stones of a size greater than approximately 300 mm in diameter.

BRIEF DESCRIPTION OF THE DRAWINGS In order to achieve a better understanding of the nature of the present invention a preferred embodiment of a transportable rock screening plant will now be described in some detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side elevational view of a transportable rock screening plant mounted on a semitrailer; and Figure 2 is a rear elevational view of the transportable rock screening plant shown in Figure 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT As illustrated in both figures 1 and 2 there is a transportable rock screening plant shown generally as 10 comprising a primary screen, a secondary screen, and a tertiary screen shown generally as 12, 14, 16, respectively. The screens 12, 14, 16 are mounted directly or indirectly on a chassis 18. The transportable screening plant 10 further comprises a rock feeder, in this example a vibrating rock feeder 20, also mounted on the chassis 18.

The vibrating rock feeder 20 includes a feeder tray floor 22.

The transportable plant 10 further comprises a hopper 24 surrounding and located immediately above the vibrating rock feeder 20. The hopper 24 is supported above the chassis 18 via a hopper support structure shown generally as 26. Feeder skirts 28 are connected to and protrude from a bottom edge of the hopper 24. In this example, the hopper 24 is lined with a plurality of wear resistant tiles constructed of a high wear-resistant BISALLOY grade steel.

The feeder skirts 28 are also constructed of a high wearresistant BISALLOY grade steel.

The transportable screening plant 10 further comprises a twin vibrating motor assembly 30 connected to the vibrating rock feeder 20. In this example, the vibrating rock feeder 20 is mounted to the chassis 18 via a series of feeder mounting springs 32. The twin vibrating motor assembly 30 can be vibrated at a variable frequency and/or amplitude.

Control instrumentation for the twin vibrating motor assembly 30 is provided in a demountable control cabinet (not shown) positioned on the chassis 18. The travel of rock across the feeder tray floor 22 can thus be controlled from the control cabinet by adjusting the frequency and/or amplitude of the twin vibrating motor assembly 30.

A screen vibrator motor assembly 34 having twin motors is mounted to a grizzly screen box 36. The screen vibrator motor assembly 34 is also electrically connected to the control cabinet, and the amplitude of the screen vibrator motor assembly 34 can be adjusted.

The primary screen 12, in this example, is a grizzly screen having a plurality of first spaced parallel bars 38. The parallel bars 38 extend substantially parallel to the chassis 18. The first bars 38 are movably connected to a bottom frame 40 mounted within the primary screen 12. Each of the bars is constructed of a high wear-resistant BISALLOY grade steel tapered longitudinally. The space or opening defined between adjacent first bars 38 can be varied by sliding the first bars 38 relative to the bottom frame 40 so as to adjust the opening between adjacent first bars 38. Typically, the first parallel bars 38 are spaced at 600 mm centres relative to each other with a nominal aperture or first opening of approximately 400 mm.

The primary screen 12 further comprises a three (3) sided primary bin 42 connected to the bottom frame 40. The primary bin 42 is pivotally connected to a pair of rear legs 44 connected to and extending vertically from the chassis 18.

Two telescopic hydraulic rams 46 connected between the primary bin 42 and a pedestal 48, mounted inside the hopper 24, can be actuated to effect pivotal movement of the primary bin 42 relative to the hopper 24. In one example, the telescopic hydraulic rams 46 can be operated via a remote control unit (not shown) which can be carried by a loader operator.

The secondary screen 14, in this example, is a grizzly screen having a plurality of second spaced parallel bars 50. The tertiary screen 16 comprises a fixed aperture mesh. The secondary and tertiary screens 14, 16 are mounted within the grizzly screen box 36.

The secondary and/or tertiary screens 14, 16 are in the form of a cartridge which can be selected depending on the size distribution of rock and/or stone required.

In this example, the second spaced grizzly bars 50 are typically located at approximately 100 mm centres relative to each other. The tertiary screen 16, in this example, is a mesh having openings of between 20 to 100 mm. The grizzly screen box 36 is connected to the chassis 18 via a second set of springs 52. The grizzly screen box 36 is located next to and immediately below the feeder tray floor 22. In this example, the secondary and tertiary screens 14, 16 are inclined at approximately 150 to a horizontal plane. The feeder tray 24 is inclined at approximately 20 to a horizontal plane. An oversize chute 54 is connected to the chassis 18 adjacent an end of the secondary grizzly screen 14.

The transportable rock screening plant 10 further comprises an oversize conveyor system shown generally as 56 connected to the chassis 18 adjacent a lower end of the tertiary grizzly screen 16. As shown in figure 2, the oversize conveyor system 56 comprises an endless conveyor belt 58 operatively connected at opposite ends around a tail drum 60, and a head drum 62, respectively. A series of idler rollers 64 support an upper surface of the conveyor belt 58. The tail drum 60, head drum 62, and idler rollers 64 are rotatably coupled to a foldable conveyor frame 66 connected to the chassis 18. In this example, the endless conveyor belt 58 extends at right angles to the chassis 18, and is inclined in an upward direction at an angle of approximately 100.

The transportable screening plant 10 also comprises an undersize conveyor system comprising a second and third conveyor belt 68,70 respectively (see figure 1). Each of the second and third conveyor belts 68, 70 has a head drum and a tail drum, with an upper surface of the conveyor belt supported by a series of idler rollers. The second conveyor belt 68 is located beneath the tertiary screen 16 and extends in an upward direction at an angle of approximately 150. The third conveyor belt 70 is at a lower end located beneath an upper end of the second conveyor belt 68, and extends at right angles to the second conveyor belt 68. The third conveyor belt 70 is inclined at from between approximately 5 to 150 to the horizontal.

The third conveyor belt 70 is foldably connected to the chassis 18. Each of the conveyor belts 58, 68, 70 is driven either electrically or hydraulically.

The semi-trailer in this example is a triple axle arrangement, with each axle having wheels 72. Two pairs of opposing jack legs 74 are connected to the chassis 18 on opposite sides of the axles. Each pair of jack legs 74 comprises two hydraulic jack-up rams each having a control valve.

Operation of the transportable rock screening plant 10 described above will now be explained in some detail. In this example, the screening plant 10 is designed to receive relatively large rocks of usually not greater than approximately 1.5 m in diameter.

The semi-trailer is transported to site using a suitable prime mover. During transportation the primary bin 42 and primary grizzly screen 12 can be removed from the hopper 24 and fitted on a forward section of the chassis 18. The primary bin 42 extends longitudinally along the chassis 18 for relatively safe transportation, and to reduce the overall height of the transportable plant 10. Furthermore, a head section of each of the first and third conveyor belts 58, 70 is designed to fold for transportation purposes.

With the primary bin 42 located on the hopper 24, as shown by the solid lines in figure 1, rock is loaded into the primary bin 42 using a front-end loader (not shown). First undersize rock then passes between the spaces defined between adjacent first grizzly bars 38, and oversize rock is retained on the primary grizzly screen 12.

The first undersize rock passing through the primary grizzly screen 12 falls to the feeder tray floor 22 located beneath the hopper 24. The feeder tray floor 22 is being vibrated at a predetermined variable frequency and variable amplitude via the feeder vibrating motor assembly 30. The first undersize rock then moves along an upper surface of the feeder tray floor 22 at a rate determined both by the inclination of the feeder tray floor 22, and the frequency and amplitude at which the feeder tray floor 22 is vibrated.

The first undersize rock then passes across an upper surface of the secondary grizzly screen 14 of which second undersize rock passes between the second spaced grizzly bars 50. Second oversize rock passes along the secondary grizzly screen 14 and is directed from the screening plant 10 via the chute 54.

The second undersize rock then falls to the tertiary screen 16 of which third oversize rock passes along the tertiary screen 16 to the oversize conveyor system 56. Third undersize rock passes through apertures in the mesh of the tertiary screen 16 and falls onto an upper surface of the second conveyor belt 68. The third undersize rock is conveyed up the second conveyor belt 68 and then falls to the third conveyor belt 70 located beneath an upper end of the second conveyor belt 68.

In this example, the size distribution of the four (4) products produced from the transportable screening plant 10 is as follows: (1) first oversize rock - usually greater than between 300 to 500 mm in diameter; (2) second oversize rock - from between approximately 75 mm to 1.00 m in diameter; (3) third oversize rock - from between approximately 25 to 200 mm in diameter; and (4) third undersize rock - less than approximately 25 to 100 mm in diameter.

The size distribution of the four (4) products produced from the above described plant 10 can be varied by adjusting the separation between adjacent grizzly bars 38, of the primary screen 12 and/or selecting a secondary or tertiary screen 14, 16 with predetermined second or third openings, respectively.

During operation of the screening plant 10 the screen vibrator motor assembly 34 is vibrated at a predetermined amplitude which together with the vibration of the feeder tray floor 22 determines the transportable plant 10 rock and/or stone throughput.

The primary bin 42, when it is full of first oversize rock, can be tipped or pivotally hinged relative to the hopper 24. When the primary bin 42 is tipped first oversize rock is tipped into an empty bucket of the front-end loader or onto the ground. An operator of the loader can tip the primary bin 42 using a remote control device without having to leave the loader.

Now that a preferred embodiment of the present invention has been described in some detail it would be apparent to those skilled in the relevant arts that the transportable screening plant has at least the following advantages over the admitted prior art: (i) a rock screening plant is provided which classifies relatively large rocks and/or stones into at least four (4) size distributions, the plant being relatively compact and thus transportable; and (ii) a transportable rock screening plant is provided which can handle relatively large rocks and be adjusted to produce rocks and/or stones of a predetermined size distribution at a predetermined throughput.

It will be apparent to persons skilled in the relevant arts that numerous variations and modifications can be made to the transportable rock screening plant in addition to those already mentioned above, without departing from the basic inventive concepts of the present invention. For example, the primary, secondary, and/or tertiary screens described herein are not limited to grizzly or mesh screens. In particular, the tertiary screen may comprise bars or mesh or a piano wire arrangement for the size classification of finer stones. The configuration and relative arrangement of parts on the chassis may vary so long as three screens produce four products of various size distributions. The conveyor belts described herein are not essential to the invention and are merely indicative of ways of transporting sized rock or stone away from the transportable plant. The vibrator motors of the vibrating feeder, secondary/tertiary screen assembly, and .conveyor drives may be powered via diesel/hydraulic, electric/hydraulic, diesel/electric, mains electric, or other power systems. The transportable rock screening plant may also be mounted on a skid base or may be track-mounted. All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A transportable rock screening plant comprising: a primary screen adapted to receive relatively large rocks to be screened, the primary screen having a plurality of first openings through which first undersize rock is passed and first oversize rock remains; a secondary screen operatively communicating with the primary screen, adapted to receive the first undersize rock, said secondary screen having a plurality of second openings through which second undersize rock is passed and second oversize rock remains; and a tertiary screen operatively communicating with the secondary screen, adapted to receive said second undersize rock, said tertiary screen having a plurality of third openings through which third undersize rock is passed and third oversize rock remains whereby, in use, relatively large rocks received on the primary screen are sized through the screening plant to provide first, second, and third oversize rocks, and third undersize rock each of a size distribution depending on the predetermined size of the first, second, and/or third openings.

2. A transportable rock screening plant as defined in claim 1 wherein the primary, and secondary screens are each grizzly screens having a plurality of first and second spaced parallel bars, respectively, between which the first and second openings are defined.

3. A transportable rock screening plant as defined in either claim 1 or 2 wherein the tertiary screen typically comprises a mesh structure having third openings.

4. A transportable rock screening plant as defined in either claim 1 or 2 wherein the tertiary screen is a grizzly screen having third spaced parallel bars between which third openings are defined.

5. A transportable rock screening plant as defined in claim 4 wherein at least one of the primary, secondary, or tertiary screens comprises a primary, secondary, or tertiary frame, respectively, to which each of said plurality of spaced first, second, or third parallel bars are adjustably coupled so that, in use, adjacent bars can be moved and then fixed at a predetermined separation relative to each other so as to control the size distribution of said first, second, and third oversize rock, and the third undersize rock.

6. A transportable rock screening plant as defined in either claim 4 or 5 wherein the first, second, and/or third spaced parallel bars are tapered longitudinally.

7. A transportable rock screening plant as defined in any one of the preceding claims further comprising a rock feeder operatively communicating with the primary screen so as to move the first undersize rock to the secondary screen located adjacent the rock feeder.

8. A transportable rock screening plant as defined in claim 7 wherein the rock feeder comprises a feeder tray located beneath the primary screen and inclined away from the primary screen toward the secondary screen.

9. A transportable rock screening plant as defined in claim 8 further comprising a feeder motor assembly operatively coupled to the feeder tray to provide vibrational movement to the feeder tray so that, in use, the feeder motor assembly effects vibration of the feeder tray and thus conveys first undersize rock to the secondary screen.

10. A transportable rock screening plant as defined in any one of the preceding claims further comprising a screen motor assembly operatively coupled to both the secondary and tertiary screens so that, in use, the screen motor assembly effects vibration of the secondary and tertiary screens and thus movement of oversize rock relative to each of said screens, and promotes movement of undersize rock passing through each of said screens.

11. A transportable rock screening plant as defined in any one of the preceding claims further comprising a hopper located between the primary screen and the rock feeder so that, in use, the hopper channels first undersize rock from the primary screen to the rock feeder.

12. A transportable rock screening plant as defined in any one of the preceding claims further comprising an oversize conveyor system operatively communicating with the tertiary screen so that, in use, third oversize rock from the tertiary screen is carried from the plant via the oversize conveyor system.

13. A transportable rock screening plant as defined in any one of the preceding claims further comprising an undersize conveyor system operatively communicating with the tertiary screen so that, in use, third undersize rock from the tertiary screen is transported from the plant via the undersize conveyor system.

14. A transportable rock screening plant as defined in any one of the preceding claims further comprising a base frame to which the primary, secondary, and tertiary screens, and feeder are operatively coupled.

15. A transportable rock screening plant as defined in claim 14 wherein the primary screen is movably coupled to the base frame so that, in use, first oversize rock retained on the primary screen can be removed therefrom by tipping the primary screen.

16. A transportable rock screening plant as defined in claim 15 wherein the primary screen is detachably coupled to the base frame so that the primary screen can be repositioned on the base frame for transportation purposes.

17. A transportable rock screening plant substantially as herein described with reference to and as illustrated in the accompanying drawings.