GB2227992A - Conveyor belt scraper - Google Patents

Abstract

An elongate blade (1) for a conveyor belt scraper, has at least one scraping edge (10, 11) that is convex or cambered. The blade is preferably made of polyurethane cast over a mild steel bar. The blade may have 2, 3 or 4 scraping edges equiangularly spaced, so that when one edge wears a fresh edge can be brought into use. The blade is mounted on a circular mounting plate at each end and is angularly adjustable and urged against the belt to be scraped by a torsion tube, or a circular leaf spring. <IMAGE>

Description

BLADE AND CONVEYOR BELT SCRAPER ETC.

This invention relates to a blade for a conveyor belt scraper, and also to a scraper incorporating such a blade which, in use, is adapted to be engaged with a materialconveying surface of a return run of a belt of a belt conveyor, to clean that surface of adhesive residue e.g., of coal, iron ore, sand, after the conveyor has discharged the bulk of the material being conveyed at a delivery end of the conveyor. Known scrapers incorporate a blades e.g., of polyurethane, which is pressed against the surface to be cleaned by the means of a spring loaded lever arrangement mounted on the conveyor support structure.

Known blades c om p r i se an elongate strip of polyurethane, usually with a metallic reinforcing/mounting insert and of oblong cross section, to provide two, parallel long edges, being in use an upper edge that is resiliently urged into engagement with the belt surface to be cleaned, and after progressive wear of that edge, the blade is rotated through 1800 to present the opposite, unused edge of the belt surface.

However, it has been found in practice that the blade edge does not wear evenly, due to the preponderance of residue adhering to the belt surface always being over the middle area of the belt, hence greater wear occurs over the centre area of the blade than at the outer edges, and the resulting concave wear profile results in a considerable loss of scraping/cleaning efficiency over this middle area. Hence, contrary to reduced scraping efficiency over this middle area, an enhanced scraping effect is in fact desired for effective removal of the greater quantity of residue present in this area.

The result is that the blade of the first aspect of the invention provides additional material in the camber, principally over the centre area of the blade and even when this additional material has worn away e.g., to the extent that the blade then has a straight rather than cambered edge, the straight edge exhibits scraping properties as good as the (straight edges) prior art blades.

The blade has of course an axial length approximating to the belt width, and preferably the blade is of cast polyurethane, casting being over a centre mild steel bar, and a camber may be readily cast onto the scraping edge of the scraper blade. As indicated previously this compensates for the first problem by allowing more polyurethane to be worn away without impeding scraping efficiency. Also the camber acts against the tension, necessarily applied to the belt, over the entire section of the blade, to increase scraper edge pressure and thus the scraping efficiency over this area.

The blade is preferably provided with at least two scraping edges. If two edges part are provided, then after wear of the first blade part beyond its effective service life, the blade is simply rotated through 1800 to bring the unused edge into use. Again the blade may be provided with three edges 1200 apart or four edges 900 apart. The centre bar is preferably of shallow "C"-section.

According to a second aspect of the invention, there is provided a conveyor belt scraper incorporating a blade in accordance with the first apect.

According to a third aspect of the invention, there is provided a belt conveyor with a scraper in accordance with the second aspect, in engagement with the surface of the return run of the belt beyond the delivery discharge end of the conveyor.

The scraper is preferably provided at each end with a circular mounting plate having a centre hole, an array of through holes around a pitch circle, and a co-axial quadrant plate.

The mounting plate is also bent through 900 at one side into a mounting bracket provided with bolt holes for fastening the mounting bracket (and thus the s c r a pe r ) to the conventionally provided, channel section conveyor support structure and also for locking the scraper in its working position in conjunction with the quadrant plate. For this purpose the quadrant plate is provided with through holes on the same pitch circle as the holes of the mounting plate and is adapted to be rotatable with respect to the mounting plate, being attached at its centre to a torsion tube by which the scraper blade is urged against the surface of belt to be cleaned. When the scraper is then secured in position by locating a peg in selected, aligned holes in both the quadrant plate and the mounting plate.

The mild steel bar is supported at each opposite end by a carrying arm comprising one long and one short arm secured together by one bolt to form the pivot of a scissor like arrangement at the opening ends of which a circular leaf spring is attached which together with the offset mounting of the torsion bar forms a spring-loaded lever arrangement.

The various aspects of the invention will now be described in greater detail, by way of example with reference to the accompanying drawings in which: Figure 1 is a transverse view of a conventional prior art scraper blade with the wear pattern illustrated; Figure 2 corresponds to Figure 1 but shows a scraper blade in accordance with the first aspect of the invention; Figure 3 is a side elevation of a blade in accordance with the first aspect, a scraper in accordance with the second aspect, and a conveyor in accordance with the third aspect; Figure 4 is a plan view of Figure 3; Figure 5 is an enlarged view of a portion of Figures 3 and 4 showing the spring arrangement in an untensioned condition; Figure 6 corresponds to Figure 5 but shows a tensioned condition;; Figures 7 and 8 are to a larger scale, an end elevation and plan of blade clamping and adj ustment possibilities.

In the drawings, is illustrated an elongate blade 1 e.g., of polyurethane attached to a mounting bar 2 e.g., of mild steel, the blade 1 being adapted to scrape residue adhering to a material carrying surface 3 of a conveyor belt 4, after the latter has passed around a delivery drum 5 (Figure 3) and hence being transformed from a conveying run 6 into a return run 7. Both the prior art blade illustrated in Figure 1, and the blade in accordance with the invention approximate in length to the width of the conveyor.

The prior art blade of Figure 1 has parallel upper and lower longitudinal scraper edges 8 and 9. In use, the scraping edge is worn away unevenly to the concave position 8A, and during this progressive wear, scraping efficiency is reduced and more residue adherance to the belt than is desirable, resulting in increased driving power than would otherwise be the case, and undesirable detachment of residue over the entire length of the conveyor as a result of vibration etc.

In accordance with the invention, the scraper blade of Figure 2 has convex or cambered profile scraping edges 1 and 11, and in use, the greater wear over the centre area of the blade than at the edges of the blade results in blade wear to position 1BA, but during this progresive wear, no loss of scraping efficiency occurs as the straight edge 1BA is equally as efficient as an unworn prior art edge 8. After wear to position 1A, the blade of the invention is unclamped and rotated through 1800 to present edge 11 to the surface 3.

The convex or cambered profiles of the scraping edges 1 and 11 of the blade 1 in accordance with the invention can be readily produced during casting of the polyurethane around the bar 2. The latter is of shallow "C"section with ends 12 extending beyond the length of the blade 1 by which ends the blade is secured, in an angularly adjustable manner to the ends of support arms 13. Angular adjustment with respect to the belt surface 3 is by clamping bolts 14 engaging the concave face 15 of the ends 12, which ends 12 are located in an arcuate slot 16 in an end piece 17 of each support arm 13, with the concave face 18 of the ends 12 frictionally engaging the convex face 19 of the slot 16.

At their other ends, each support arm 13 is attached to one end 2 of a circular spring 21, the other end 22 of which is attached to a short bar 23 attached by a pivot bolt 24 to its arm 13. A square section torsion tube 25 is attached to the short bar 23, and extends laterally, through an aperture 26 in circular mounting plate 27 provided with a plurality of through holes 28 around a pitch circle and bent through 900 at one side into a mounting bracket 29 provided with bolt holes 3 by which the mounting plate is attachable to channel section conveyor support structures 31.A quadrant plate 32, co-axial with the mounting plate 27, is attached by welds 33 to the torsion tube 25 and extends downwardly where, on the same pitch circle as the holes 28 of the mounting plate 27, it is provided with three holes 34, a selected one of which is alignable with one hole 28 for insertion of a peg (not shown).

The torsion tube 25 extends beyond the quadrant plate 32 to a manually operable adjustment lever 35 to apply selective torque to the tube 25, and hence selective angular rotation of the short bar 23 and consequently displacement of one end of the spring 21, whereupon the other end of the spring reacts to displace the adjacent end of the support arm 13 to cause resilient loading of the blade against the surface 3 via the spring 21. Hence, when the adjustment lever 35 has been moved to its desired setting position, the quadrant plate 32 moving with the torsion tube 25, at least one hole 34 is aligned with a hole 28 so that a peg (not shown) is inserted into aligned holes to retain the scraper in this position, with blade 1 resiliently loaded against the belt surface 3. After wear on the edge 1, re-adjustment is periodically necessary by removing the peg, suitably rotating the adjustment lever 35, and re-inserting the peg in freshly selected holes 34 and 28.

Claims (19)

1. An elongate blade for a conveyor belt scraper, having at least one scraping edge that is convex or cambered.

2. A blade as claimed in Claim 1, of cast polyurethane.

3. A blade as claimed in Claim 2, wherein the polyurethane is cast over a mild steel bar.

4. A blade as claimed in Claim 2 or Claim 3, wherein the camber is cast onto the scraping edge(s) of the blade.

5. A blade as claimed in any preceding Claim, provided with two scraping edges, 1800 apart.

6. A blade as claimed in any one of Claims 1 to 4, provided with three scraping edges, 1200 apart.

7. A blade as claimed in any one of Claims 1 to 4, provided with four scraping edges, 900 apart.

8. A blade as claimed in any one of Claims 3 to 7, wherein the centre bar is of shallow "C" section.

9. An elongate blade for a conveyor belt and scraper substantially as hereinbefore described with reference to Figures 2 to 4 of the accompanying drawings.

113. A conveyor belt scraper incorporating a blade as defined in any preceding Claim.

11. A scraper as claimed in Claim 1 provided at each end with a circular mounting plate having a centre hole and a co-axial retaining quadrant.

12. A scraper as claimed in Claim 11, wherein the mounting plate is provided with a mounting bracket.

13. A scraper as claimed in Claim 12, wherein the clamping quadrant is adapted to be rotatable with respect to the mounting plate and carries through its centre a torsion tube by which the scraper blade is urged against the surface of belt to be cleaned, and when the scraper has been tensioned against that surface, the clamping quadrant is then secured in position by a peg engaging aligned holes in both the quadrant plate and the mounting plate.

14. A scraper as claimed in any one of Claims 18 to 13, wherein the blade is supported at each opposite end by a carrying arm.

15. A scraper as claimed in Clain 14, wherein each carrying arm is conencted to one end of a circular leaf spring the other end of which is attached to a short bar pivotally mounted at its other end to its carrying arm.

16. A scraper as claimed in any one of Claims 1 to 15, wherein the blade is angularly adjustable with respect to the belt surface to be scraped by clamping bolts engaging ends of the centre bar.

17. A conveyor belt scraper substantially as hereinbefore described with reference to Figures 2 to 6 of the accompanying drawings.

18. A belt conveyor having a scraper as defined in any one of Claims 18 to 17 in engagement with the surface of the return run of the belt beyond the delivery discharge end of the conveyor.

19. A belt conveyor substantially as hereinbefore described with reference to Figures 2 to 6 of the accompanying drawings.