Abstract:
A torsion unit ( 14 ) for use with a conveyor belt scraper ( 12 ) which includes a tubular component ( 36 ), an extension member ( 38 ) which is located at least partly inside the tubular component ( 36 ), at least one resiliently deformable torsion element inside the tubular component which acts between opposed surfaces of the tubular component and the extension member, and a flange on the tubular component.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to scraper arrangements for conveyor belts and particularly is concerned with apparatus for biasing scrapers into contact with a conveyor belt surface at a location which is adjacent, near or on a head pulley. 
     A primary belt scraper or, more generally, a scraper at a head pulley of a conveyor belt, may be called upon to exert a substantial scraping action. To achieve this objective the scraper must be biased into scraping engagement with the conveyor belt surface which is to be cleaned, with a fair amount of force but in such a way that the scraper is deflectable, away from the belt, by significant obstructions on the belt. 
     The biasing arrangement which is adopted should be capable of being reset, from time to time, to compensate for wear on the scraper due to use. It is also desirable to be able to mount the scraper in different orientations to take account of different operative requirements 
     U.S. Pat. No. 5,992,614 relates to a tensioning device which enables an adjustable force to be exerted on a shaft which supports a scraper blade. A spring is used to provide a resilient force applying mechanism. 
     The spring is not self-dampening and is exposed and hence is subject to corrosion. Another factor is that a scraper blade is mounted directly to the shaft in a fixed orientation. A variation of this arrangement is shown in PCT/ZA98/19863. 
     EPO 583 731 shows a basic arrangement, which has a similar effect to the device of U.S. Pat. No. 5,992,614, but wherein the biasing force is generated by twisting a resilient tube about its axis. Different mounting configurations are shown, but there is no positional adjustment facility. EPO 497 324 shows a similar arrangement. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention there is provided a scraper arrangement for use with a conveyor belt which includes an elongate member to which at least one scraper blade is mounted, a support for the elongate member which allows at least limited rotation of the elongate member relatively to the conveyor belt with the scraper blade in scraping engagement with the belt, a tubular component which is mounted for at least limited rotation relatively to the elongate member, at least one resiliently deformable torsion element, at least partly inside the tubular component, means for retaining the tubular component at a selected angular orientation with the torsion element in a deformed state characterised therein that the tubular component has an angular inner surface, an angular extension member is located at least partly inside the tubular component and the torsion element acts between the angular inner surface and the extension member. 
     The torsion element may be located at least partly inside the tubular component bearing against a surface or surfaces of the extension member which are within the tubular component. 
     The scraper arrangement may include four torsion elements respectively positioned at four inner corners of the tubular component, bearing respectively against four outer sides of the extension member. 
     In one form of the invention the scraper arrangement includes a clamp engaged with the elongate member, which permits at least limited rotational adjustment of the scraper blade relatively to the tubular component. 
     The scraper arrangement may include a mounting bracket whereto the tubular component is mounted for limited sliding adjusting movement relatively to the bracket. 
     The invention also provides a torsion unit for use with a conveyor belt scraper which includes a tubular component, an extension member which is located at least partly inside the tubular component, at least one resiliently deformable torsion element inside the tubular component, and a flange on the tubular component, characterised therein that the tubular component has an angular inner surface, the extension member is angular and the torsion element acts between opposed surfaces of the angular inner surface and the extension member. 
     The flange may be located at an end of the tubular component and the extension member may project from the tubular component at this end. 
     The torsion unit may be provided in combination with a scraper which has an elongate member, at least one scraper blade mounted to the elongate member, and mounting means to fix the elongate member to support structure so that the elongate member is rotatable at least to a limited extent relatively to the support structure, the extension member of the torsion unit being engaged with the elongate member and the combination including means for securing the flange of the torsion unit to the mounting means with the torsion element in a desired state of deformation. 
     The torsion unit may include a clamp which permits at least limited rotational adjustment of the scraper blade relatively to the torsion unit and the torsion unit may also include a bracket to which the tubular component is mounted so that the tubular component is slidably movable, to a limited extent, relatively to the bracket. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is further described by way of examples with reference to the accompanying drawings in which: 
     FIG. 1 is an end view of a scraper arrangement according to the invention, 
     FIG. 2 is a side view of the arrangement shown in FIG. 1, 
     FIG. 3 shows a different type of scraper arrangement, with a height adjustment mechanism, 
     FIGS. 4 and 5 show a scraper blade which is mounted to an arm, in different orientations, 
     FIG. 6 shows another scraper blade type, also on an arm, with height adjustment, and 
     FIG. 7 is a side view of a mounting or bias system which is particularly suited for the arrangements of FIGS. 4 to  6  wherein the scrapers are mounted to arms. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 of the accompanying drawings illustrate a scraper arrangement  10  according to the invention which includes a conveyor belt scraper  12  and a torsion unit  14 . 
     The conveyor scraper  12  includes an elongate tubular support shaft  16 , which is square in cross-section, and which has a tapered channel section  18  secured to an upper surface. A plurality of scraper blades  20  are engaged with the channel section. 
     The shaft  16  is mounted to conventional fixed support structure  22 , shown in dotted outline in FIG. 1, adjacent a conveyor head pulley  24 . A conveyor belt  26  passes over the pulley. 
     At one end the shaft  16  is supported by a bearing  28  which is mounted to a support plate  30  which, in turn, is fixed to the structure  22 . 
     At an opposing end the scraper shaft  16  is supported by a bearing  32  which is fixed to a mounting bracket  34 . The mounting bracket is fixed to the support structure  22  in any suitable manner. 
     The torsion unit  14  includes an outer torsion tube  36  and an inner torsion bar  38 . The tube  36  is square in profile, see FIG.  2 . The torsion bar  38  is also square in profile but is angularly displaced relatively to the tube  36  through 45°. As is evident from FIG. 1 the torsion bar extends from the torsion tube  36  into the interior of the tubular support shaft  16 . The extended torsion bar has two relatively small pieces  40  of rectangular steel bar fixed to it on opposing sides. The pieces  40  fit snugly inside the tubular scraper shaft and effectively link the torsion bar to the scraper shaft in such a way that rotation of the scraper shaft imparts rotational movement to the torsion bar, and vice versa. On the other hand it is relatively easy to engage the torsion bar with the scraper shaft for this is effected merely by sliding the torsion bar and the steel pieces  40  into the tubular interior of the scraper shaft. 
     The bearing  32  is in a housing  42  which is directly fixed, on one side, by means of a flange  43  to the mounting bracket  34 . A flange  44  is fixed to an opposing side of the bearing housing. 
     A second flange  46  is fixed to the torsion tube  36 . The flange  46  has a number of holes  48  formed through it, at spaced intervals, see FIG.  2 . The flange  44  has a series of holes formed in it. If the flanges  46  and  44  are rotated relatively to one another then different holes  48  are progressively brought into alignment with one of the holes in the flange  44 . A bolt or pin can be passed through the holes which are in alignment and in this way the angular orientation of the flange  46 , relatively to the flange  44 , can be adjusted, within reason, and the flange  46  can then be locked in position. The holes  48  are spaced fairly close to one another and in practice permit the angular orientation of the flange  46  to be adjusted, relatively to the flange  44 , in increments of 2½°. 
     Four torsion elements  50  are positioned inside the torssion tube  36 . Each torsion element is made from round rubber and, when compressed, has a substantially triangular cross-section. As is shown in FIG. 2 each torsion element is located at an inner corner of the tube  36  and is in contact with a flat outer side of the torsion bar  38 . 
     The angular position of the torsion bar  38  relatively to the shaft  16  is fixed through the medium of the steel pieces  40  which prevent relative rotation of the torsion bar and the scraper shaft. The shaft  16  is however rotatable, at least to a limited extent, about the bearings  28  and  32 . The torsion tube  36 , apart from the flange  46 , is fixed to the torsion bar  38  only through the medium of the torsion elements  50 . 
     If a rotational force is exerted on the torsion tube  36 , using a suitable lever such as a spanner which is engaged with the torsion tube  36 , then the resulting force is transmitted to the torsion bar via the rubber torsion elements  50 . There is a tendency for the scraper a shaft  16  to rotate in the same direction and in this way the scraper blades  20  can be urged into scraping engagement with an outer surface of the conveyor belt  26  with a force which is dependent on the level of torque applied to the torsion tube  36 . 
     The scraper blades  20  can thus be urged into scraping contact with the conveyor belt with a scraping force which is controllable depending on the extent to which the torsion tube  36  is rotated relatively to the fixed structure  22 . When the torsion tube  36  is rotated the flange  46  rotates relatively to the adjacent flange  44 , which it is to be noted, is not movable relatively to the fixed structure  22 . A pin  45  is then inserted through the hole  48  which is in register with the locating hole in the flange  44  and the assembly can be locked in position. 
     If an obstruction on the belt  26  exerts substantial force on one or more of the scraper blades  20  then such blades are capable of deflecting in that the resulting force, generated by the obstruction, causes the scraper shaft  16  to rotate about its elongate axis X against the action of the torsion elements  50  which are further deformed to allow such deflecting movement to take place. 
     If scraping edges of the scraper blades become worn then the force which is exerted by the scraper blades on the conveyor belt surface is reduced. The force can be increased simply by rotating the torsion tube relatively to the fixed structure in a direction which compensates for the wear whereafter the two flanges  44  and  46  are again fixed to one another. 
     FIGS. 3 to  6  illustrate variations of the invention which is shown in FIGS. 1 and 2 and, where applicable, components which are the same in the various embodiments bear similar reference numerals. 
     FIG. 3 shows an arrangement wherein the support shaft  12  and the torsion unit  14  are mounted to brackets  60  an opposing sides of the conveyor belt  26 . The brackets are substantially identical and only one bracket is shown in FIG.  3 . 
     The bracket  60  includes two uprights  62  and  64  which are formed with respective elongate vertically extending slots  66  and  68 . The flange  43  of the torsion unit  14  is attached to the bracket by means of bolts which pass through holes  69  in the flange and which are engaged with the slots. 
     It is apparent from an inspection of FIG. 3 that the torsion unit and the belt scraper  12  are movable, in unison, upwards or downwards, according to requirement, in order to bring one or more scraper blades  20 A into engagement with an outer surface of the conveyor belt  26 . When the scraper arrangement is at a desired position the bolts are tightened thereby to lock the flange  43  to the bracket  60 . 
     The opposing side of the scraper arrangement, not shown in the drawing, is adjusted in a corresponding manner. 
     The scraper blade  20 A may be attached to a support shaft  16 A in a similar way to what has been described in connection with FIG. 2, or in any other way. 
     The arrangement of FIG. 3, viewed from the side, is generally as is shown in FIG.  7 . The construction is substantially the same as what is shown in FIG. 1 and, as before, if the torsion tube  36  is rotated relatively to the inner torsion bar  38  the torsion elements  50  between the tube and the torsion bar are distorted and thereby exert a resilient biassing force on the scraper blade  20 A which urges the blade into resilient engagement with the conveyor belt  26 . 
     In the arrangements of FIGS. 1,  2  and  3  the scraper blade or blades extend directly from the support shaft  16  which is co-axial with the torsion unit  14 . In the arrangement shown in FIGS. 4,  5  and  6  the torsion units are displaced from the support shafts. FIG. 4 illustrates an arrangement wherein the torsion unit  14  is mounted to a bracket  60  in a similar manner to what has been described in connection with FIG.  3 . An arm  70  (refer to FIG. 7 as well) extends from the torsion unit. The arm terminates in a clamp section  72  which has an inner semi-circular formation  74 . A similar clamp section  76 , also with an inner semi-circular formation  78 , is engageable with the clamp section  72 . The two sections can be fixed tightly together by means of bolts  80 . 
     The support shaft  16 , as before, has scraper blades  20 A attached to it. This is done in any appropriate way. A mounting bush  82  is fitted over the support shaft. The bush is round in outline and is formed with a square hole  84  which is complementary in size and shape to the outer surface of the support shaft  16 . Thus the bush can be threaded onto the shaft and moved to a desired position at which the bush is enclosed by the clamp sections  72  and  76 . 
     The arrangement is such that when the clamp sections  72  and  76  are loose the scraper blades and the support shaft  16  can be rotated, in unison, to a desired angular orientation relatively to the arm  70 . At this stage the bolts  80  are tightened and the scraper blades are then held in the desired orientation. 
     The configuration shown in FIG. 4 thus permits sliding adjustment of the torsion unit and rotational adjustment of the scraper blades relatively to the belt which is to be cleaned. This is in addition to the adjustable bias which is provided by the torsion unit which has already been described. 
     In FIG. 4 the scraper blades are at a leading outer surface of the conveyor belt directly opposite to the head pulley. FIG. 5 shows an arrangement, which uses similar components to what is shown in FIG. 4, wherein the torsion unit is lower than the position shown in FIG.  4  and the orientation is such that the scraper blades  20 A extend upwardly and outwardly with what may be referred to as inner surfaces  86  in scraping engagement with the conveyor belt. This is in contrast to what is shown in FIG. 4 which shows what is referred to as outer surfaces  88  of the blades in scraping engagement with the conveyor belt. 
     FIG. 6 shows another embodiment with scraper blades  20 B replacing the blades  20 A shown in FIGS. 4 and 5. The arm  70  is substantially horizontal and the scraper blades  20 B are positioned to extend vertically upwardly into engagement with an undersurface of the belt  26 . The blades can be adjusted vertically by sliding movement relatively to the bracket  60 , and rotationally by means of the clamp sections. 
     With each of the embodiments it is to be understood that, apart from the sliding and rotational adjustments of the scraper blades it is possible to vary the torsion force which is exerted by the torsion unit. The holes in the torsion unit flange are fairly close to one another and for example are spaced angularly apart by about 2½°. This makes it possible to vary the resilient torsion force in relatively small increments. Another possibility in this regard is to replace the torsion elements  50  with rubber of a different hardness. The lengths of the torsion elements which are inserted into the torsion tube  36  can also be altered. Another variable is the cross section of the torsion bar  38  and of the torsion tube  36 . 
     The torsion unit operates through the bearing  32 . The bearing is protected for it is fully enclosed and it is therefore not exposed to corrosive effects. The same applies to the torsion elements which are protected inside the torsion tube. 
     With the arrangement shown in FIGS. 2 and 3 only one torsion unit will be required. If the scraper arrangement includes an arm  70  of the kind shown in FIGS. 4,  5  and  6  then, due to the leverage which is exerted by the arm, it may be necessary to have more substantial support on opposed sides of the scraper blade. For example it may be necessary, depending on the requirements, to make use of two torsion units, on respective opposed sides of the conveyor belt, instead of making use of a single torsion unit, as is shown in FIG.  1 .