Primary belt cleaners and blades

Abstract: A primary conveyor belt cleaner includes an elongated support (24) extending across but spaced from a conveyor belt of width W and includes a stiff guide extending for approximately the full length of the support; a scraper blade (136) of resilient elastomer resin is mounted on the support and engages the conveyor belt surface. The scraper blade has a short base wall (151) removably mounted on the support by a reinforcement that interfits with the guide; the blade has two longer curved side walls (155 and 156), an inner wall (156) concave toward the belt and an outer wall (155) convex away from the belt. The two side walls come together to form a scraping edge (137). The belt cleaner includes a torsion bias mechanism that resiliently maintains the belt scraping edge in continuous engagement with the belt. Two or more primary cleaners may be incorporated in one system. Flexure of the blade permits passage of a mechanical splice in the belt without appreciable damage to the blade or the splice.

Description: The invention relates to a conveyor belt cleaner for cleaning the outer surface of a conveyor belt comprising the features included in the preamble of claim 1 and known from EP-A-0 497 324. Single-blade and multi-blade belt scrapers or cleaners are frequently used with belt conveyors in mining and mineral storage operations and in a wide variety of other applications. Single-blade cleaners (the blade may be formed of a plurality of abutting segments) are usually used in primary cleaners, scraping conveyed material from a part of the conveyor belt backed up by the head pulley. These conveyor belt cleaners usually operate in an invironment that can only be described as hostile. The working conditions are frequently wet, dirty, and even corrosive. Continuing maintenance activity is a necessity due to inevitable wear on the cleaner blades, but is often rendered difficult by limited access space and the aforementioned adverse working conditions. In excessively wet or corrosive environments, maintenance is made more difficult by corrosion of metal mounting bolts, clamps, and the like. All of these difficulties are likely to be present in mining operations and also in industrial applications. The conveyor belt cleaner as known from already mentioned EP-A-0 497 324 comprises a plurality of scraper blades mounted on cantilever arms disposed in mutual distance along a support member extending across the belt. Each blade has a short base wall including mounting means for connection to the support member, and two curved side wall extending from said base wall and converging into a small angle forming the scraping edge. Such small-angled scraping edge, however, tends to excessive wear because the blade at its end area is quite thin. On the other hand, replacement of belt cleaner blades is quite troublesome in most cases for the reasons outlined above. EP-A-0 573 688, state of the art according to Art. 54(3) EPC, discloses a scraper blade having an outer configuration similar to that of EP-A-0 497 324 with the upper end of the tip portion being formed so as to have a short transition wall acting as a leading face against which the belt moves and forming a scraper edge with the curved wall facing the belt, but the blade of EP-A-0 573 688 being configured as a two-part blade consisting of a frustroconincal base portion connected to a support member, and of a tip portion fitted to the base portion so as to be replacable after being worn. The interconnection between the tip member and the base member includes three projections extending from the lower portion of the tip member into three correspondingly formed holes provided in the upper face of the base member whereby those two faces are in contact with each other and a pin being pushed through a bore extending traversely through the holes and extensions so as to hold the tip portion firmly to the base portion. In this way, replacement of only the tip portion will be readily possible without need of replacing the hole scraper blade. From EP-A-0 393 866 a conveyor belt cleaner for removing residue from the surface of a conveyor belt is disclosed which cleaner is radially adjustable through connection with a rotatable support member positioned generally transverse to the direction of the conveyor belt travel. The conveyer belt cleaner includes a scraping blade having a curvilinear scraping surface. One edge of such surface is in contact with the conveyor belt. The curvilinear scraping surface is configured in a way such that the cleaning angle formed between a first line, tangent to the curvilinear scraping surface and extending through a point where the scraping surface edge is in contact with the conveyor belt, and a second line, either tangent or parallel to the surface of the conveyor belt and extending through the same point where the scraping surface edge contacts the conveyor belt, will remain constant as the conveyor belt cleaner is radially adjusted to compensate for wear to the scraping blade. In a primary belt cleaner the scraper blade must accommodate mechanical belt joints and heavy, clinging, localized accumulations. The primary cleaner blade should afford an effective, consistent scraping action despite extensive wear and continuing movement of belt joints (splices) through the cleaner. Corrosion should be precluded, along with effective shock protection for individual blades. Moreover, overly compliant or excessively stiff blades should be avoided to preclude excessive vibration. It is an object of the invention, therefore, to provide a new and improved construction for conveyor belt cleaners, in particular for cleaner blades usable in either primary or secondary belt cleaners, that effectively eliminate or minimize the problems discussed briefly above while providing for extended operating life in a belt cleaner of minimum cost. This object is solved by the features of claim 1. Flexure of the scraper blade, adjacent the belt scraping edge, as well as cross-sectional configuration, flexibility and resilience permit a mechanical splice in the conveyor belt to pass through the belt cleaner with no appreciable damage to the splice, the belt, or the blade. Particular embodiments of the invention are defined in the subclaims. In an embodiment the invention relates to a primary conveyor belt cleaner system according to the features of claim 5. Use of two primary belt cleaners on one pulley is advantageous for a number of reasons. The presence of two belt cleaners on the head pulley could be expected to clean the belt somewhat better than only one belt cleaner. The point, however, is that the prior art constructions, with thicker blade configurations, made it very difficult and in some instances impossible to put two primary belt cleaners on a single head pulley. The new blade configuration is more compact. Further, its curvature makes it possible to put two primary belt cleaners on one head pulley in installations where this formerly could ot be done. The end result is that it is now possible to eliminate a secondary belt cleaner on the return path of the conveyor belt. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front elevation view of a primary conveyor belt cleaner constructed in accordance with one embodiment of the invention; Fig. 2 is a side elevation view, partly in cross-section, taken approximately as indicated by line 2-2 in Fig. 1; Fig. 2A is an enlarged view of the encircled portion of Fig. 2; Fig. 3A-3D illustrate, in a partial, cross-sectional view, successive positions of the belt cleaner blade and its scraping edge during passage of a mechanical belt joint or splice; and Fig. 4 is a partly schematic side elevation view of a dual primary conveyor belt cleaner system constructed in accordance with another embodiment of this invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figs. 1, 2 and 2A illustrate a primary conveyor belt cleaner 120 for cleaning a conveyor belt 21 of width W. Belt 21 is driven in the direction of arrow A, Figs. 1 and 2, around the longitudinal axis L, Fig. 1, on the surface of a head pulley 70. Belt cleaner 120 comprises two shafts 22A and 22B that are aligned with each other and that are joined by an elongated support 24. Support 24 preferably comprises a rigid metal sleeve that extends transversely of belt 21 in spaced relation to the outer surface to be cleaned. Support 24 has a length L1 approximately equal to the belt width W; they are shown equal in Fig. 1. The left-hand end of shaft 22A, Fig. 1, is journalled in a bearing 25 supported by a fixed frame (not shown). Inwardly from bearing 25, shaft 22A is affixed to the elongated sleeve or support 24 by suitable means (not shown). If desired, the shaft segments 22A, 22B may be a continuous shaft through the interior of support sleeve 24. The right-hand portion of shaft 22B, Fig. 1, extends through another bearing 28 mounted in the fixed frame (not shown) that affords general support for primary conveyor cleaner 120. Bearing 28 is connected to a flange 29 on a torsion tube 31 that is part of a torsion bias mechanism 30. Another flange 32 on the other end of torsion tube 31 is connected to a collar 33. Collar 33 is connectable to the outer end of shaft 22A through an angularly adjustable connection comprising a shear pin 34. As shown in Fig. 2, there is an inverted T-shaped mounting member or guide 42, shown as formed by two angle irons, affixed to support sleeve 24. Mounting member 42 preferably extends for the full length of sleeve 24. Guide 42 is also a blade reinforcement, as described hereinafter. Guide 42 may be welded or otherwise firmly secured to transverse support 24. Moreover, guide 42 may be continuous or intermittent along sleeve 24, depending on the blade construction employed. In primary belt cleaner 120, a single, unitary scraper or cleaner blade 136 is mounted directly on support 24. As shown in Fig. 1, blade 136 may have a length approximately equal to the length L1 of support member 24 and the width W of belt 21. Alternatively, a plurality of blade segments (not shown) may be utilized, abutting each other, with the same overall length. Scraper blade 136 has a short base wall 151 and two substantially longer side walls 155 and 156; see Fig. 2. Thus, blade 136 is generally triangular in cross-sectional configuration. Walls 155 and 156, however, are curved, in the same direction, and blade 136 is mounted on support 24 so that the one side wall 156 of the blade that faces belt 21 and head pulley 70 is concave toward the belt and pulley. With that alignment the other wall 155 of blade 136 is concave outwardly of pulley 70 and belt 21. In the preferred construction for primary blade 136, the outer (concave) wall 155 of blade 136 projects inwardly toward wall 156 from a break line 157 (Figs. 2 and 2A). Break line 157 is preferably somewhat rounded, affording a smooth corner which joins the convex wall 155 to a second, short transition wall surface 158 that extends to the upper edge of the concave wall 156. The intersection of transition surface 158 of wall 155 with the inner concave wall 156 defines the scraping edge 137 of blade 136. That is, surface 158 affords a truncated or curtailed transition of wall 155 to wall 156 in blade 136. With this blade configuration, the outer end or tip portion 138 of blade 136 is thicker than would have been the case if the wall 155 did not have the break line 157 ending in the inwardly directed transition surface 158. As explained below, the tip portion 138 in a new, unworn scraper blade provides a significant improvement during inception of blade operation, particularly during movement of a mechanical belt splice past cleaner 120. Primary blade 136 has a rigid metal reinforcement 139 molded into the base wall 151 of the blade. Reinforcement 139 is of inverted U-shaped configuration, affording a receptacle 153 facing outwardly of the base wall 151 of the blade. Receptacle 153 receives the upwardly projecting portion of guide 42, so that the guide serves as a reinforcement for the base portion of blade 136 in addition to providing a guide to align the blade on support 24. Inasmuch as primary cleaner 120 works on the surface of belt 21 in that part of the belt that is in contact with head pulley 70, there is no need to provide for varying angular configurations other than an incremental and instantaneous adjustment in angular position of the blade which is absorbed by the torsion bias mechanism 30, as explained below. On the other hand, support 24 is provided with a torsion bias device such as the device 30, Fig. 1, to bias support member 24 in the direction of the arrow X, Figs. 1 and 2. Thus, the shape of blade 136, with its converging curved walls 155 and 156 and the thickened tip portion 138 in an unworn blade, provides a resilient spring back feature when the blade end section 138 and scraping edge 137 undergo stresses which arise from debris adhered to the belt or from a mechanical belt joint. This feature continues to play a role in blade operation even after substantial blade wear, in part because a relatively soft, more resilient resin can be and is used in molding blade 136. This can be quite important for any belt 21 on which debris has adhered and which is especially difficult to scrape and for any belt 21 that employs mechanical splices. Figs. 3A-3D are similar to Fig. 2; they afford a cross-section view of belt 21, head pulley 70, and blade 136 as a mechanical joint 180 in belt 21 moves past the scraping edge 137 of blade 136. The belt splice 180 comprises an inner plate 182 and an outer plate 184 located on opposite sides of two segments 21X and 21Y of conveyor belt 21. The two segments 21X and 21Y of belt 21 are joined by the mechanical joint 180 to provide a part of the endless belt used in the conveyor. There may be several such mechanical joints 180 in belt 21; the number of splices depends to some extent on the length of the conveyor belt. Plates 182 and 184 are secured to each other by pins or rivets 186 between the plates; pins 186 also go through the ends of belt segments 21X and 21Y. Thus, plates 182 and 184 of mechanical joint 180 sandwich the two ends of the belt 21 between them to retain the belt ends together. Figs. 3A-3D show successive intervals of time which mechanical joint 180 passes the scraping edge 137 of a newly installed, unworn blade 136. Of course, the duration of those time intervals depends upon the speed of movement in the direction of arrow A and hence cannot be stated precisely. This particular example, that of a mechanical joint meeting the scraping edge of the resilient blade, is used because it occurs at least once and usually several times for each revolution of belt 21 around the conveyor. However, operating principles featured in the discussion of mechanical joint 180 are equally applicable in the case of adhered debris or any other anomaly which may occur in the smoothness or flatness of belt 21. Fig. 3A shows the position of a new blade 136 and its scraping edge 137 as joint 180 first contacts the scraping edge 137 of the blade. The outer surface of belt 21 is displaced away from the outer surface of head pulley 70 to accommodate the increased thickness of belt 21 caused by splice 180. Because of the resilience of the blade material, scraping edge 137 and a local portion of the blade tip 138 are first bent toward the left, outwardly from the normal blade position, Fig. 2. At this point (Fig. 3A) the main body of the blade 136 has moved a short angular distance against the tension, in direction X, from the torsion bias mechanism 30 (Fig. 1). The angular displacement of the support 24 relative to a normal or index position, line P', is indicated as angle a in this and the succeeding views (Figs. 3B-3D). Angle a indicates the difference in angular position of support 24 from that normal or index position, Fig. 2. In Fig. 3A, angle a is approximately 10°. In a preferred actual installation, the scraping edge 137 would contact the head pulley 70 some small distance e.g., 5 cm below the plane P (Fig . 2 ). Plane P' is parallel to plane P. Accordingly, the contact point of the scraping edge 137 and belt 21 on head pulley 70 occurs beyond the point where the belt 21 has begun to return toward the right in the direction of rotation A. Fig. 3B illustrates the next instant of the belt cleaner operation; joint 180 has rotated to a point just a short distance lower than that shown in Fig. 3A. Because of the elasticity of the material of blade 136, and due to the shape and dimensions of blade 136, the scraping edge 137 of the blade maintains its position relative to the outer plate 184 of joint 180. As the outer plate 184 of joint 180 rotates with the head pulley in the direction A, the scraping edge 137 of blade 136 is compressed downwardly; the main body of blade 136 does not come under tension and is not thrust radially outwardly from its position relative to the surface of the head pulley 70 to any appreciable extent. Rather, blade 136 bends slightly. Thus, in Fig. 3B the angle a changes only infinitesimally; it is approximately 10°1'. Fig. 3C illustrates the instant when the resiliency of blade 136 causes its scraping edge 137 to be released by the edge of the upper joint plate 184 and to spring back to an extended position. The configuration of the main body of blade 136 is bent as it returns toward its normal, non-stressed configuration. At this point belt 21 is greater in thickness, at joint 180, due to the presence of plates 182 and 184. This greater thickness causes blade 136 to rotate somewhat farther against the angular force X applied by the torsion bias mechanism, in order to compensate for the difference in angular position. However, the main body of blade 136 has not yet experienced the effects of the outward motion of the blade end section 138. Thus, the base of the blade 136 maintains the "bowed out" position (Fig. 3B); angle a in Fig. 3C is approximately 11°8'. Fig. 3D illustrates the relationship of the belt cleaner components as the mechanical position of the joint 180 continues its movement past the scraper blade edge 137. In this figure, blade 136, and especially the base, experiences the full effect of the sudden release of compressive tension which was caused by the downward displacement of the end section 138. Thus, the base of the blade 136 indicates only a slight angular displacement because the base of the blade is undergoing the overreaction of the resilient springing force of the blade with the release of tension compressive force on scraping edge 137, which is suddenly set free. Accordingly, although the end section 138 of blade 136 is angularly displaced more than normal, angle a is back to about 10°1', as in Fig. 3B. Once splice 180 clears scraping edge 137, blade 136 and support 24 return to their initial positions, Fig. 2. Figs. 3A-3D illustrate a significant feature and distinct advantage of the inventive blade. The combination of a relatively "soft" resilient material as the constituent material for blade 136 and the configuration and placement of blade 136 and its support mechanism, together with the continuous resilient bias X from mechanism 30, provide an ability to maintain the scraping edge 137 of the blade 136 flush against the surface of the belt 21 even when encountering anomalies, such as joint 180, in the belt surface. Moreover, the transition blade surface 158 is angled relative to walls 155 and 156 of blade 136 so that any material engaging surface 158 is deflected from blade 136. Thus the shape, dimensions and configuration of the blade, the support and the head pulley provide a most efficient scraping function for the cleaning system, and withstand mechanical splices and other anomalies without damage to the scraper blade. Fig. 4 illustrates another embodiment of the cleaning system of this invention. The system shown in Fig. 4 includes a primary cleaner 120, as described above, with its support 24 biased in direction X, and blade 136 with its edge 137 engaging a conveyor belt 21 passing over a head pulley 70. There is no secondary cleaner of the conventional kind. Instead, the system of Fig. 4 comprises a second primary cleaner 120' having a blade 136' with its tip edge 137' engaging belt 21. The components 136', 137', and 24' of cleaner 120' may have the same length, shape and dimensions identical of the corresponding components of belt cleaner 120. Indeed, belt cleaner mechanism 120' is preferably a duplicate of cleaner 120. The blade 136' of the second primary cleaner 120' is positioned further along the path of the belt 21, beyond blade 136 of cleaner 120, in the direction A of conveyor belt movement. For an unworn blade 136, the preferable distance from plane P down to the contact point of the blade scraping edge 137 with belt 21 is approximately 5 cm. The second scraper 120' may be mounted to contact belt 21 quite close to cleaner 120. For a blade height of 15 cm (six inches), therefore, the distance between plane P and the contact point of scraping edge 137' of the secondary cleaner blade 136' may be approximately 20 cm (eight inches). Of course, substantial variation is permissible, depending in part on the diameter of head pulley 70. The close relative positions of blades 136 and 136' (Fig. 4) provides for a more efficient belt cleaning function than usual with a more conventional primary and secondary belt cleaner configuration. The uppermost blade 136 usually has an angle of incidence which approximates a vertical tangent to the cylindrical surface of the head pulley. Even after blade 136 has become worn to a degree where the transition surface 158 is no longer on the blade the angle between the head pulley 70 and the inner blade wall 155 remains an obtuse angle. Moreover, the inwardly curved concave configuration of the outer blade wall 156, relative to the base wall 151, permits blade support 24 to be disposed close to the head pulley 70 without interfering with operation of the conveyor. This is advantageous because it enables the blade to maintain an obtuse angle between its outer wall 156 and the head pulley and belt surface even after considerable wear of the blade; Referring again to Fig. 4 because the blade 136' of the second primary cleaner 120' is disposed at a point further along the path of arrow A in which the belt 21 is driven, that blade 136' is disposed at an even greater angle to the vertical than is blade 136. Thus, if any debris continues to adhere to belt 21 after it has passed blade 136, the secondary cleaner comprising blade 136' will be more apt to dislodge and remove the debris because of the added force resulting from gravitational pull at the point of engagement of edge 137' with the surface of belt 21. Blade 136', which cleans the outer surface of the belt across its whole width, provides an efficient second cleaning capacity for the system. In particularly adverse applications conveying material that adheres strongly to belt 21, a blade 136' may be used in conjunction with a secondary cleaning system of the kind described in U.S. Patent No. 5 222 588 issued June 29, 1993. For blades 136, polyurethane is the preferred resin, though other resilient resins can be used. Polyurethane in a durometer range of 75 to 85 Shore A is preferred. For the rigid elements (support 24, guide 42, etc.), metal is preferred, though rigid resin or laminate members could be employed in some instances, as for reinforcements 42 and 139. In all of the embodiments described above, blade 136 is shown as one integral, continuous member having a length L1 approximately equal to belt width W. It should be understood, however, that the blade 136 may be assembled as a sequence of shorter blade segments, as shown in the applicant's earlier patent No. 4 533 036. Reference to a blade in the appended claims is intended to include such an assembly of shorter blade segments.

Claims: A conveyor belt cleaner (120) for cleaning the outer surface of a conveyor belt (21), comprising: an elongated support (24) extending transversely of a conveyor belt (21) of given width W, in spaced relation to a belt surface to be cleaned, the support having a length (L1); at least one scraper blade (136) of molded flexible, resilient resin, having a length (L2), mounted on the support and engageable with the conveyor belt surface to be cleaned, the blade having a short base wall (151) and two longer curved inner and outer side walls (155 and 156), respectively, extending away from the base wall (151) and both curved in the same direction toward the belt and converging from said base wall to a belt scraping edge (137), with L2≈L1≈W; the inner blade side wall (156), facing the belt conveyor, being concave toward the belt conveyor; the outer blade side wall (155), facing away from the belt conveyor, being convex away from the belt conveyor; the scraper blade (136) being removably mounted in the belt cleaner with the belt scraping edge (137) of the blade engaging the belt conveyor surface to be cleaned and the blade base wall (151) engaging and being supported by said support member (24); torsion bias means (30) resiliently urging the support (24) toward rotation in a direction (X) to maintain the belt scraping edge (137) of the blade (136) in continuous engagement with the conveyor belt surface to be cleaned; said support member (24) including an elongated, stiff guide (42) of predetermined cross-sectional configuration extending along approximately the full length of the support member; and the scraper blade including an elongated, stiff reinforcement member (139) molded into its base wall (151), which reinforcement member interfits with the guide (42) to mount the blade (136) on the support member (24); characterized in that : said scraper blade (136) has a cross-sectional configuration in which the outer blade side wall (155) near its convergence with the non-parallel thereto extending inner blade side wall (156) terminates in a short transition wall (158) that extends to the inner blade side wall (156) in the form of a leading face against which said belt moves such that the intersection of said transition wall (158) with said inner blade side wall (156) defines the scraping edge (137), said scraber blade (136) is formed as only one part between its reinforcement member (139) and its transition wall (158), and in that the flexibility and the resilience of said scraper blade (136) are selected so as to allow damage-free flexure of the scraper blade, adjacent its belt scraping edge (137), away from a rigid mechanical splice (180) in the conveyor belt (21) passing the belt cleaner (120). A conveyor belt cleaner according to Claim 1, in which the transition wall (158) of said scraper blade (136) is flat. A conveyor belt cleaner according to claim 1 or 2, characterized in that said scraper blade (136) is of a molded, resilient elastomeric resin. A conveyor belt cleaner according to Claim 4, in which said elastomeric resin is resilient molded polyurethane in a Shore A durometer range of 75 to 85. A conveyor belt cleaner according to one of the preceding claims, characterized by a double arrangement system wherein each of the conveyor belt cleaners (120,120') of the system is a primary belt cleaner and the scraper blades (136, 136') of the belt cleaners engage and clean the outer surface of the conveyor belt (21), sequentially, as that belt traverses a single head pulley (70), the blades both being located below the head pulley axis (L).

Inventors: GORDON JAMES R, GORDON, JAMES R.
Applicants: GORDON BELT SCRAPERS INC, GORDON BELT SCRAPERS, INC.
Application year: 1993
Main classification: B65G45
IPC codes: B65G45