GB2048124A - Screen assembly - Google Patents

Description

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GB 2 048 124 A 1

SPECIFICATION Rock screen assembly

This invention relates to a rock screen assembly.

A rock screen assembly is used, for example, in quarries and in screening plant over a hopper mouth. The screen serves to reject rock over a predetermined size, the rejected rock falling from the screen onto the ground. One serious problem associated with existing screens which comprise a series of spaced apart parallel steel bars is that rock marginally greater than the acceptable rock size tends to jam between the spaced apart bars, and as a further load is dumped onto the screen the jammed rock is further pushed between the bars to lodge itself more firmly or to deform the bars in a permanent manner.

Accordingly, the present invention provides a rock screen assembly comprising a plurality of substantially parallel bars each pivotally mounted at one end for sideways deflection under load and mounted at the other end in a manner providing a restoring force which returns the bar substantially to its undeflected position after removal of the load.

Preferably, at the said one end each bar is bent back under itself and inserted in a locating aperture in a support member extending transversely beneath the bars, whereby the sideways deflection of the bar is achieved by rotation of the bent-under portion of the bar in the locating aperture.

Furthermore, at the said other end each bar is preferably angled into a pair of spaced locating apertures in a further support member extending transversely of the bars.

The rock screen assembly is preferably arranged in use with its bars upwardly inclined from their said one ends to their said other ends.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:

Figure 1 is a perspective view of an embodiment of rock screen assembly according to the invention, and

Figure 2 is a detailed side view of the mounting arrangement for each bar.

Referring now to the drawings, a rock screen assembly generally indicated at 10 comprises a plurality of substantially parallel inclined steel bars 13 mounted at opposite ends in respective transverse support members 14 and 15. The members 14 and 1 5 are themselves bolted between side panels 16, and the whole assembly is mounted on a hopper 11 and supporting structure 12.

At its lower end 20 each bar 13 is pivotally mounted for sideways deflection under load. For this purpose, at the lower end each bar is bent back under itself through approximately 180° and inserted in a respective single one of a series of locating holes 1 7 in the transverse support member 15 which extends beneath the bars. Thus the sideways deflection of the bar 13 is achieved by rotation of the bent-under portion 18 of the bar in its locating hole 17. The distance R (Figure 2) is the radius of the rotational motion of the lower end of the bar about the hole 17 during sideways deflection, and the distance d is clearance distance to permit such deflection to occur.

At its upper end 21 each bar 13 is angled into a respective aligned pair of spaced locating holes 19 in the transverse support member 14. This ensures that the upper end of the bar is held fairly rigidly so far as any sideways movement is concerned and thus gives directional control to the bar, since when the lower end of the bar is subjected to a sideways deflection under load a degree of torsion is introducted into the bar such that when the load is removed the bar is returned substantially to its original undeflected position.

By appropriately selecting the amount of bending of the bar 13 at the upper end where it is angled into the member 14, a measure of control can be given to the degree of sideways flexibility of the working portions of the bars at the lower end. The correct degree of sideways flexibility of the bars allows stones and rocks which are marginally greater than the spacing between the undeflected bars to go through whereupon the bars spring back to the original setting. This prevents or at least substantially reduces the incidence of blinding of the rock screen.

The vertical shock load on the hopper 11 and supporting structure 12 is also reduced by virtue of the bending flexibility of the bars.

Claims (6)

1. A rock screen assembly comprising a plurality of substantially parallel bars each pivotally mounted at one end for sideways deflection under load and mounted at the other end in a manner providing a restoring force which returns the bar substantially to its undeflected position after removal of the load.

2. A rock screen assembly as claimed in Claim

1, wherein at the said one end each bar is bent over and inserted in a locating aperture in a support means extending transversely with respect to the bars, whereby the sideways deflection of the bar is achieved by rotation of the bent-over portion of the bar in the locating aperture.

3. A rock screen assembly as claimed in Claim

2, wherein at the said one end each bar is bent under itself through approximately 180°, the said support means extending transversely beneath the bars.

4. A rock screen assembly as claimed in Claim

1, 2 or 3, wherein at the said other end each bar is angled into a pair of spaced locating apertures in a further support means extending transversely with ■ respect to the bars.

5. A rock screen assembly as claimed in Claim

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GB 2 048 124 A

1, 2, 3 or 4, wherein the bars are upwardly

6. A rock screen assembly substantially as inclined from their said one ends to their said 5 described with reference to the accompanying other ends. drawing.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1980. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.