BRIDGE SCRAPER

Abstract: A bridge scraper has a harrow with a base beam (22) supported by wheels (20a), which run along a bridge rail (28) that is pivotal about a longitudinal axis. To accommodate mutual deflections, whilst allowing free running of the wheels along the rail, the wheels are mounted in a bogie (2l) which is universally pivoted to the beam (22), except that relative pivoting about an axis parallel to the rail (28) is restricted by a bracket (26) which is carried by the bogie and has surfaces (27) engageable with sides of the beam (22).

Description: The invention relates to a bridge scraper (hereinafter referred to as of the kind described) for raking material from a detached bulk material heap, the bridge scraper comprising a bridge, which extends, in use, substantially horizontally along the base of a sloping heap face; and a harrow of triangular lattice construction and having a base, which is movable to and fro along the bridge; the harrow being supported partly by wheel sets mounted at respective ends of the harrow base and travelling on a rail which is pivotally mounted about an axis parallel to its length on, and parallel to, the bridge and partly by a wire extending from the harrow apex over a sheave, at the top of a tower in the middle of the bridge, to a winch for adjusting the inclination of the harrow; and each wheel set cooperating with the profile of the rail to inhibit relative pivoting of the wheel set relatively to the rail about an axis in the plane of the harrow and perpendicular to the rail. Each supporting wheel set normally comprises one or more wheels positioned in a bracket on the harrow base, the wheel axes lying in a plane perpendicular to the base and their treads engaging, and cooperating with the profile of, the rail to guide the harrow along the rail. The rail is pivotably mounted on the bridge, allowing it to turn and thus ensuring full engagement between the wheel treads and the rail when the inclination of the harrow is adjusted to the slope of the material heap face to be raked. To make the harrow light the triangular construction is comparatively slender. Consequently, the sides of the triangular harrow construction will be bent more or less out of the plane of the harrow owing to the influences of gravity and the force exerted on the harrow during operation. The wheels are mounted on the harrow base so as to travel along the straight rail parallel to the base, but, when the harrow base is bent, the direction of travel of the wheels will deviate from the direction of the rail, and the wheels will tend to roll off the rail. If the wheels are forced to follow the rail their movement will be a combined rolling and sliding, causing heavy wear on the wheels as well as on the rail. It is an object of the invention to provide a support for the harrow by which these drawbacks are avoided. This is achieved when, in accordance with the invention, each wheel set of a bridge scraper of the kind described comprises at least one pair of wheels, which are mutually spaced in the direction of the rail, the wheels being mounted in a bogie, which is mounted on the harrow by a joint permitting comparatively free pivotal movements between the harrow and the bogie except about an axis parallel to the rail. If a joint permitting full universal free pivotal movement is established between the harrow and the bogie there may be a risk that the bogie will tilt and the harrow fall down. Therefore the degrees of freedom involving a risk of tilting are restricted by using wheel sets with pairs of wheels spaced in the direction of the rail, and inhibiting the relative movement of the harrow and the bogie about an axis parallel to the rail. The joint between the harrow and the bogie may be a universal joint, such as a ball joint, coupled between brackets on the harrow base and on the bogie. The joint may be substantially locked against relative pivotal movements of the harrow and the bogie about an axis parallel to the rail because the harrow base is a beam with a rectangular profile and a bracket on the bogie has a narrow bearing surface immediately adajacent to, and engageable with, two adjacent side walls of that beam along lines perpendicular to its length. Alternatively, the bogie may be encompassed by a housing on the harrow adjacent to where the joint is positioned between the housing and the bogie, and narrow bearing surfaces of the housing are immediately adjacent to, and engageable with, the sides of the bogie along lines in a central plane of the bogie perpendicular to the rail. The examples of bridge scraper in accordance with the invention are illustrated in the accompanying drawings, in which:- Figure l shows schematically a bridge scraper with a raking harrow travelling to and fro; Figure 2 shows one example of bogie mounted on the harrow; Figure 3 is a side view of the bogie of Figure 2; Figure 4 shows partly in section another example of a bogie mounted on a harrow; and, Figure 5 is a view in the direction A-A of the bogie according to Figure 4. In Figure l the bridge scraper is shown raking material from the sloping front face l of a material heap 2. A bridge 3 extends along the base of the head front face and a rail 4 is mounted parallel to the bridge 3 in brackets 5, which allow the rail to pivot about an axis parallel to its length. A triangular harrow 6 is carried by a wheel set 7 and 7′ at each end of the harrow base, and a wire 8 which passes from the harrow apex g over a sheave l0 at the top of a tower (not shown) to a winch ll, by which the inclination of the harrow 6 may be adjusted to make the harrow plane parallel to the heap front face. Figures 2 and 3 show a construction of a wheel set bogie lg, which has two pairs of spaced wheels 20a, 20b, each pair engaging a side of a pivotally suspended rail 28 corresponding to the rail 4 in Figure l. Between two brackets 2l mounted on a base beam 22 of the harrow is a shaft 23 carrying a ball 24 of a ball joint, a ball cup 25 of which is mounted in a bracket 26 on the bogie l9. The bracket 26 has a claw-shaped extension with two surfaces 27 almost engaging two adjacent sides of the rectangular harrow base beam 22. In this way all kinds of pivotally adjusting movements between the harrow and the bogie may take place through movements about the ball joint, except pivotal movements about an axis parallel to the rail 4. Such pivotal movements due to changes in the harrow inclination take place about the axis determined by the pivotal suspensions of the rail 4. Figures 4 and 5 show another harrow support. A bogie 40 has the wheel set comprising a pair of spaced wheels 4la and 4lb, both wheels having a profiled tread engaging a corresponding profiled tread of a pivotally suspended rail 42. Through a ball joint 43 the bogie 40 is suspended from a housing 44 which is rigidly mounted on a base beam 47 of the harrow through a bracket 45. The pivotal movement about the ball joint has three degress of freedom, but one of these is eliminated through locking of the pivoting about an axis parallel to the rail. This locking is obtained by the provision of narrow bearing strips 46 at the inner side of the housing enclosing the bogie. Only a small gap is left between these strips and outer side walls of the bogie, and the strips are mounted along the lines of intersection between a symmetry plane of the bogie through the ball joint and the side walls of the housing enclosing the bogie.

Claims: 1. A bridge scraper for raking material from a detached bulk material heap, the bridge scraper comprising a bridge (3), which extends, in use, substantially horizontally along the base of a sloping heap face (l); and a harrow (6) of triangular lattice construction and having a base (22; 47), which is movable to and fro along the bridge; the harrow being supported partly by wheel sets (7; 20a,20b; 4la,4lb) mounted at respective ends of the harrow base and travelling on a rail (4; 28; 42) which is pivotally mounted about an axis parallel to its length on, and parallel to, the bridge and partly by a wire (8) extending from the harrow apex (9) over a sheave (l0), at the top of a tower in the middle of the bridge, to a winch (ll) for adjusting the inclination of the harrow; and each wheel set (7; 20a,20b; 4la,4lb) cooperating with the profile of the rail (4; 28; 42) to inhibit relative pivoting of the wheel set relatively to the rail about an axis in the plane of the harrow and perpendicular of the rail; characterized in that each wheel set comprises at least one pair of wheels (20a,20b; 4la,4lb), which are mutually spaced in the direction of the rail, the wheels being mounted in a bogie (l9,40), which is mounted on the harrow by a joint (24,25; 43) permitting comparatively free pivotal movements between the harrow and the bogie except about an axis parallel to the rail. 2. A bridge scraper according to claim l, characterized in that the joint between the harrow (6) and the bogie (l9) is a ball joint (24,25; 43) coupled between brackets (2l,26; 40,45) on the harrow base and on the bogie. 3. A bridge scraper according to claim l or 2, characterized in that the joint (24,25) is substantially locked against relative pivotal movements of the harrow and the bogie about an axis parallel to the rail (28) because the harrow base is a beam (22) with a rectangular profile and a bracket (26) on the bogie has a narrow bearing surface (27) immediately adajacent to, and engageable with, two adjacent side walls of that beam along lines perpendicular to its length. 4. A bridge scraper according to claim l or 2, characterized in that the bogie (40) is encompassed by a housing (44) on the harrow adjacent to where the joint (43) is positioned between the housing and the bogie, and narrow bearing surfaces (46) of the housing are immediately adjacent to, and engageable with, the sides of the bogie along lines in a central plane of the bogie perpendicular to the rail (42).

Inventors: HOFFMEYER, HENDRIK STRANGE
Applicants: F.L. SMIDTH & CO. A/S
Application year: 1987
Main classification: B65G65
IPC codes: B65G65