Sizer tooth

Abstract

A sizer tooth assembly for a mineral sizer is described. The tooth assembly includes a horn protrusion extending from a rotatable support, the horn protrusion having a pair of opposed front and rear faces; and a shell structure encapsulating the horn protrusion and defining the outer shape of the sizer tooth; wherein the shell structure comprises exactly two cover formations which are non-releasably secured to one another but not to the horn protrusion, to define when so secured a unitary tooth assembly. Each of the two cover formations seats upon and presents an inward engagement face to a respective one of the pair of opposed front and rear faces of the horn protrusion; and each such engagement face of a cover formation and its corresponding face of the horn protrusion are provided with a complementary arrangement of projections and recesses configured such that when the two cover formations are non-releasably secured to one another the shell structure is releasably connected upon the horn protrusion. A mineral sizer including such tooth assemblies and a method of constructing such a tooth assembly and especially of constructing a replacement for repair are also described.

Claims

1. A sizer tooth assembly for a mineral sizer, the sizer tooth assembly comprising: a horn protrusion extending from a rotatable support, the horn protrusion having a pair of opposed front and rear faces; a shell structure encapsulating the horn protrusion and defining an outer shape of the sizer tooth assembly; wherein the shell structure consists of a first cover formation and a second cover formation, the first cover formation and the second cover formation being non-releasably secured to one another but not to the horn protrusion, wherein each of the first cover formation and the second cover formation is a singular integral structure; wherein each of the first and second cover formations seats upon and presents an inward engagement face to a respective one of the pair of opposed front and rear faces of the horn protrusion; and wherein each such inward engagement face of the first and second cover formations and its corresponding face of the horn protrusion are provided with a complementary arrangement of projections and recesses configured to secure the first and second cover formations to the horn protrusion.

2. The sizer tooth assembly in accordance with claim 1, wherein the first and second cover formations are non-releasably secured to one another by a welded joint.

3. The sizer tooth assembly in accordance with claim 1, wherein the first and second cover formations are non-releasably secured to one another by a welded joint on one or more mutually adjacent surfaces.

4. The sizer tooth assembly in accordance with claim 1, wherein a releasable connection is provided by at least one projection, extending from an engagement face of at least one of the first and second cover formations and a corresponding face of the horn protrusion, receivable within at least one complementary recess provided in the adjacent engagement face of at least one of the first and second cover formations and corresponding face of the horn protrusion.

5. The sizer tooth assembly in accordance with claim 4, wherein each cover formation of the first and second cover formations engages upon the horn protrusion in that the projections and recesses are configured such that one or more faces of the respective projections and recesses engage against one another.

6. The sizer tooth assembly in accordance with claim 5, wherein the projections and recesses are configured such that the one or more faces of the respective projections and recesses engage against one another in intimate face to face contact.

7. The sizer tooth assembly in accordance with claim 4, wherein the projections and recesses are configured to engage to create an interference fit.

8. The sizer tooth assembly in accordance with claim 1, wherein the horn protrusion has a pair of opposed side faces and the shell structure as assembled in situ is adapted to overlie at least partly the opposed side faces of the horn protrusion.

9. The sizer tooth assembly in accordance with claim 1, wherein the first cover formation comprises a major part of the shell structure and the second cover formation comprises a minor part of the shell structure.

10. The sizer tooth assembly in accordance with claim 1, wherein the first and second cover formations are provided with joining surfaces configured to be positioned adjacently face to face when each respective cover formation is in position on the horn protrusion.

11. The sizer tooth assembly in accordance with claim 10, wherein the joining surfaces comprise one or more sites for weld seams between and joining the first and second cover formations.

12. The sizer tooth assembly in accordance with claim 1, wherein the first cover formation is configured to receive the second cover formation.

13. A mineral sizer or breaker including a tooth assembly in accordance with claim 1.

14. A drum assembly for a mineral sizer or breaker, the drum assembly including a plurality of toothed annuli mounted on a drive shaft, each annulus having a plurality of tooth assemblies according to claim 1 spaced about its circumference.

15. A mineral sizer or breaker including a drum assembly in accordance with claim 14.

16. A method of assembling a sizer tooth for a mineral sizer or breaker, the method comprising: providing a horn protrusion extending from a rotatable support, the horn protrusion being shaped to define a pair of opposed front and rear faces; providing a shell structure consisting of a first cover formation and a second cover formation, the first cover formation and the second cover formation are configured to be non-releasably secured to one another but not to the horn protrusion to define a unitary sizer tooth assembly, wherein each of the first cover formation and the second cover formation is a singular integral structure; defining on each of the first and second cover formations an inward engagement face which is presented to a respective one of the pair of opposed front and rear faces of the horn protrusion when each of the first and second cover formations seats thereupon, wherein each such engagement face of a cover formation and its corresponding face of the horn protrusion are provided with a complementary arrangement of projections and recesses; and engaging each of the first and second cover formations onto the horn protrusion via the projections and recesses; and non releasably securing first and second cover formations to one another such that the first and second cover formations are secured to the horn protrusion.

17. The method of assembling a sizer tooth in accordance with claim 16, wherein the first and second cover formations are non-releasably secured to one another by welding.

18. The method of assembling a sizer tooth in accordance with claim 17, wherein the first and second cover formations are non-releasably secured to one another by welding one or more mutually adjacent surfaces.

19. The method of assembling a sizer tooth in accordance with claim 16, wherein: the first cover formation is urged into contact with a first end surface of the horn protrusion via clamping; the second cover formation is urged into contact with a second end surface of the horn protrusion via clamping; and the first and second cover formations are non-releasably secured to one another by a welded joint.

20. A method of replacement of a shell structure of a tooth assembly fabricated, the method comprising: destructively removing a welded joint between the first and second cover portions; providing replacement first and second cover formations; and performing the steps of the method of claim 16 to attach the replacement first and second cover formations in-situ on the horn protrusion.

Description

(1) Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a part perspective view of a prior art drum annulus and horn protrusion;

(3) FIG. 2 is a perspective view of a drum annulus with horn protrusions and associated shell structures according to an embodiment of the present invention, shown partly disassembled;

(4) FIG. 3 is an end elevation of a shell structure as illustrated in FIG. 2 to exemplify the location of a welded connection between the first and second cover formations of the shell structure;

(5) FIG. 4 is a cross-section through A-A of FIG. 3 illustrating three shell structures in position on three horn protrusions of a drum annulus in accordance with an embodiment of the invention;

(6) FIG. 5 is a partly disassembled perspective view of an alternative embodiment of the invention;

(7) FIG. 6 is a partly disassembled perspective view of an alternative embodiment of the invention.

(8) Referring initially to FIG. 1, there is illustrated a known drum annulus 10 having an annular boss 11 from which a plurality of horn protrusions 12 project radially. The annulus 10 is illustrated as having four horn protrusions 12 spaced about its circumference (one of the horns not being shown). It is envisaged that the number of horn protrusions 12 may be greater or less than four; typically the number of horn protrusions 12 would be in the range of three to eight.

(9) The horn protrusions 12 have a width in the axial direction which is less than the axial width of the annular boss 11 and are centrally located relative to the axial end faces 14, 16 of the boss 11. Accordingly, on both sides of the row of horns 12 the boss 11 defines an annular shoulder 20. Each horn protrusion is provided with a rear face 31, a front face 32, side faces 33, 34 and a top face 51.

(10) The drum annulus 10 includes a through bore 15 which, in use, enables the annulus 10 to be slid onto a drive shaft. To construct a drum assembly for a mineral breaker, several drum annuli 10 are slid onto a drive shaft and each annulus 10 is fixedly secured to the shaft so as to be rotatable therewith.

(11) Each annulus 10 can be secured to the draft shaft by welding. This is conveniently achieved by exposing a portion of the shaft between adjacent annuli and welding the annuli to the exposed portion of the shaft. Preferably the exposed portions of the shaft are defined by axially spacing opposed end faces 14, 16 of adjacent annuli and filling the resultant gap with weld. The annulus 10 may be forged in one piece from a suitable metal such that the boss 11 and horn protrusions 12 are integrally formed.

(12) FIGS. 2 to 4 illustrate a first embodiment in accordance with the present invention.

(13) In the illustrated embodiment, a drum annulus 110 is provided with three circumferentially spaced horn protrusions 112, each of which is covered by a shell comprising two permanently connected cover formations.

(14) FIG. 2 illustrates in perspective view this embodiment of the invention in which two of the three shell structures 125 have been assembled in-situ, and a third is shown prior to assembly on the horn protrusion 112, comprising a first cover formation 121 and a second cover formation 123. Each horn protrusion 112 has recesses 130, 131 formed in its front and rear faces which are shaped to define outwardly extending lips 140, 141. Complementarily shaped projections 150, 151 are respectively provided on inwardly facing surfaces of the two cover formations.

(15) In the illustrated embodiment, the first cover formation 121 makes up a major part of the shell structure defining the tooth surface when assembled, including a top formation 162 with forwardly projecting breaking tip formation 161, side faces 163 and a forward face 164 that together cover corresponding top, side and forward faces of the horn protrusion 112. Additionally, a rear portion 165 of the first cover formation 121 partly extends across a rear face of the horn protrusion 112. The second cover formation 123 is shaped to slot into engagement with and complete closure of the rear face as illustrated in the figures.

(16) The shell structure may be attached to the horn protrusion 112 in the following manner. First, the first cover formation 121 is brought over to seat upon the major part of the horn protrusion 112, in particular so that the projection 150 is received in the recess 130. Second, the second cover formation 123 is slotted into place at the back of the first cover formation, in particular so that the projection 151 is received into the slot 131. Suitably, a clamping force may be applied to bringing each projection and recess into suitably close and for example intimate contact. In a convenient embodiment, each of the lip surface 140, 141 on the horn protrusion may be brought directly into intimate face to face contact with the corresponding detent surfaces 152, 153 of the protrusions 150, 151 on the two cover formations. There may then be a small clearance provided to other surfaces of the protrusion/recess arrangement.

(17) Adjacent faces of the two cover formations 121, 123 may then be welded together. In this manner, a stable but passive contact and engagement is effected between the assembled shell structure and the horn protrusion, which can be released by removal of the weld structures between the two cover portions 121, 123.

(18) FIG. 3 is an end elevation of a shell structure as illustrated in FIG. 2 to exemplify the location of a welded connection between the first and second cover formations of the shell structure.

(19) The first cover formation 121 comprises a major part of the assembled shell structure 125 and the second cover formation 123 comprises a minor part. In this embodiment second cover formation comprises a part of a first, rearward end cover portion, and the first cover formation comprises the remainder of the shell structure including the remainder of that end cover portion, first and second side cover portions, a top portion including a tooth formation as above described, and the second, forward end cover portion. The part of the first, rearward end cover portion defined by the first cover formation 125 defines a three-sided trapezoidal slot into which the second cover formation 123 receivingly seats, so that adjacent faces on these three sides of the slot define sites for weld seams 170. The first and second cover formations are thereby non-releasably secured together so as to locate onto the horn protrusion 112 and effect a secure but passive engagement to the horn protrusion by means of the respective projections and recesses.

(20) An assembled drum annulus with three tooth structures is shown in FIG. 4 as a cross-section through A-A of FIG. 3.

(21) It is an essential feature of the invention that each of the first and second cover formations 121, 123 comprise single integral structures when they are assembled in-situ on the horn protrusion 112, and as a result merely need to be disassembled from each other to remove the shell structure from the horn protrusion for replacement. Conveniently, this may be achieved in that each of the two cover formations comprises a one-piece casting. Similarly, the drum annulus 110 including horn protrusions 112 may comprise a single one-piece casting.

(22) However, other methods of fabricating each of the two cover formations into a single integral whole prior to their assembly onto the horn protrusion may be considered.

(23) This allows appropriate material selection for the different components, and in particular allows the use of a hard and wear resistant material for the components making up the shell structure 125, but of a more resilient material for the horn protrusions 112, in a manner which will be familiar to the skilled person from known horn/shell tooth assemblies.

(24) The above arrangement produces a breaker tooth in which a horn protrusion 112 is completely enclosed by the fabricated shell assembly 125 by welding or otherwise non-removably fixing the two and only two cover formations to one another. The shell structure formed by the two cover formations when so assembled together is not non-removably fixed, for example by welding, to the horn protrusion itself. Only the two cover portions are non-removably fixed and for example welded together. The arrangement provides a stably attached breaker tooth shell construction which is securely but passively fixed to the horn protrusion so as to be readily releasable therefrom for replacement in the event of wear or damage. It is only necessary to destructively remove the joint between the two cover portions, for example by gouging the weld surfaces, in order to disassemble the shell structure and release it from the horn for replacement. Removal and replacement times are greatly reduced compared with prior art systems either where the shell structure is welded directly to the horn or where multiple welds between multiple modules of a shell structure need to be gouged.

(25) FIG. 5 illustrates in partly disassembled perspective view an alternative embodiment of the invention. In accordance with FIG. 5, the horn protrusion 212 again receives a first cover portion 221 comprising the bulk of the shell structure, and a second cover portion 223 which slots into and is welded to the first to complete the shell structure, and thereby effect a secure but passive engagement to the horn protrusion by means of respective projections and recesses in similar manner to that illustrated for the first embodiment. The embodiment differs in that the second cover portion 223 seats in and completes the forward part of the shell structure.

(26) FIG. 6 illustrates an alternative arrangement to that of FIG. 5 in which a horn protrusion 312 receives a first cover formation 321 and a second cover formation 323 which again slots into the forward face of the horn protrusion, but in this case includes a second breaking tip structure 324 that complements the primary breaking tip structure 351 on the first cover formation 321.

(27) Modifications or improvements may be made to the foregoing without departing from the scope of the present invention.