MILL DISCHARGE GRATE HAVING DYNAMIC VARIABLE SIEVE OPENINGS

A discharge grate (200) for an internal discharge end (3) of a mill (1) may be characterized in that it has at least one dynamic variable sieve opening (206) defined between two adjacent floating screen bars (202). The floating screen bars (202) may be configured to a least temporarily move with respect to one another and/or with respect to a holding frame (201) receiving the floating screen bars (202). Temporary expansion of the at least one dynamic variable sieve opening (206) may permit undersized media to pass to the discharge chute (8) and reduce or eliminate pegging.

FIELD OF THE INVENTION

The present invention relates to a unique discharge grate200for use within a discharge end3of a mill1. The discharge grate200comprises a number of movable (i.e., “floating”) screen bars202, which enable dynamic variable sieve openings206of the discharge grate200to dynamically expand and contract as necessary to accommodate passage of media4and pulverized material5to a discharge chute8whilst discouraging occurrences of pegging.

BACKGROUND TO THE INVENTION

Reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge in the arts.

Turning toFIGS.1-5, discharge grates2have been known to be used within discharge ends3of mills1(e.g., SAG mills, ball mills, rod mills) for decades. During comminution operations, undersized media4can become stuck in fixed sieve openings6. Due to heat, pressure, and/or force, the media4can become wedged or welded into sieve openings6(as suggested inFIG.4). The lodged media4reduces the overall open area of the discharge grate2defined by the fixed sieve openings, thus leading to further occlusion of the fixed sieve openings by pulverized material. Eventually, the open area of the discharge grates2can become so reduced that the discharge grates2must be removed and replaced. It is thus, a long-felt need to provide a more robust and pegging-resistant mill discharge grate2design.

FIG.1depicts a discharge end3of a mill1shortly after re-commissioning (photo taken from inside the mill1), wherein conventional discharge grates2have been recently replaced. It can be seen from this figure that very little pegging and/or occlusion is present at discharge grates2, and that flow of pulverized material5is quite free to flow through fixed sieve openings6.

FIG.2depicts a discharge end3of a mill1shortly after de-commissioning (photo taken from inside the mill1), wherein conventional discharge grates2have experienced pegging/occlusion and need replacing. In particular, one of the discharge grates2and lifter bars9have been removed from a mount7, thus exposing a discharge channel8below. It can be seen from this figure that a significant amount of pegging by media4and/or occlusion by pulverized material5is present at discharge grates2. Thus, a flow of pulverized material5through discharge grates2and into discharge chute is significantly hindered due to reduced open area of fixed sieve openings6.FIG.3shows a close-up portion ofFIG.3.

The present invention aims to improve upon existing mill discharge grate devices by incorporating movable i.e., “floating” screen bars that can temporarily expand to allow passage of media4and/or pulverized material5, in turn, leading to improved performance, reduced pegging, increased flexibility, and modularity.

OBJECTS OF THE INVENTION

It is an aim of embodiments of the invention to provide an improved discharge grate2for a mill1which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful alternative to conventional discharge grate apparatus.

A particular aim of embodiments is to provide a discharge grate2which exhibits better wear life, reduced pegging occurrences, reduced sieve opening occlusion rate, and improved screening performance over conventional discharge grates2.

Other preferred objects of the present invention will become apparent from the following description.

SUMMARY OF INVENTION

Embodiments of a dynamic variable opening discharge gate (200) are disclosed.

A discharge grate (200) for an internal discharge end (3) of a mill (1) may comprise open surface area for passing pulverized material (5) from the inside of the mill (1) to a discharge chute (8). The discharge grate (200) may further comprise closed area for discouraging passage of grinding media (4) from the mill (1). The closed area may help maintain the grinding media (4) and unpulverized material within the mill (1). The discharge grate (200) may be characterised in that it may further comprise at least one dynamic variable sieve opening (206). The dynamic variable sieve opening (206) may be defined between two adjacent floating screen bars (202). The floating screen bars (202) may be configured to a least temporarily move with respect to one another and/or with respect to a holding frame (201) receiving the floating screen bars (202).

According to some embodiments, the discharge grate (200) may comprise a resilient member (213). The resilient member may be positioned between each of the floating screen bars (202) and the holding frame (201), without limitation. The resilient member (213) may comprise a material which is configured to elastically deform. For example, the material of the resilient member (213) may comprise a polymeric material, without limitation.

According to some embodiments, the holding frame (201) may comprise receiving openings (214). The receiving openings (214) may be configured for receiving floating screen bars (202). For example, a floating screen bar (202) may be received within a respective receiving opening (214). Receiving openings (214) may be sized larger than the floating screening bars (202). In addition to a floating screen bar (202) a receiving opening (214) may be configured for receiving a resilient member (213), without limitation.

According to some embodiments, each (or at least one) of the receiving openings (214) may comprise a first cutout (214d) and a second cutout (214e). The second cutout (214) may be positioned across from the first cutout (214d).

According to some embodiments, each (or at least one) of the floating screen bars (202) may comprise a first cutout (202d) and a second cutout (202e) positioned opposite the first cutout (202d). The at least one dynamic variable sieve opening (206) may, in some embodiments, be defined between a first cutout (202d) of a floating screen bar (202) and a first cutout (214d) of a receiving opening (214), without limitation.

According to some embodiments, a lifter (203) may be provided to the discharge grate (200). The discharge grate (200) may comprise a channel (211) (e.g., in its base (204)), for receiving a protrusion (218) of the lifter (203), without limitation.

According to some embodiments, the discharge grate (200) may comprise at least one transverse securing bar (205). The at least one transverse securing bar (205) may extend across one or more floating screen bars (202). For example, a transverse securing bar (205) may extend generally orthogonally across a plurality of screen bars (202). A lower surface of a transverse securing bar (205) may be positioned above an upper surface of a floating screen bar (202).

The at least one transverse securing bar (205) may be secured by two side supports (212). The side supports (212) may extend from and/or form an integral portion with a base (204). In some embodiments, the discharge grate (200) may comprise a baseplate (207). The baseplate (207) may provide a backing portion of the base (204), without limitation. The baseplate (207) may comprise a large pass-through aperture (215). The large pass-through aperture (215) may be positioned below the floating screen bars (202). Edge portions of the large pass-through aperture (215) may optionally support surfaces of one or more floating screen bars (202).

In some embodiments, the discharge grate (200) may comprise a recessed support lip (210). For example, two recessed support lips (210) may be provided to opposing sides of a base (204) portion. A recessed support lip (210) may be configured for supporting a lifter (203) or portion thereof, without limitation.

A method of lining an internal discharge end (3) surface of a mill (1) suitable for comminuting ore is further disclosed. The method, according to some embodiments, may comprise the step of providing a discharge grate (200) as described above. The method may further comprise the step of mounting the discharge grate (200) over a discharge chute (8) of the mill (1). The method may further comprise the step of securing the discharge grate (200) to a mount (7) provided at the discharge end (3), without limitation.

A method of comminuting ore is also disclosed. The method may comprise the step of providing a mill (1) suitable for comminuting ore and having a discharge grate (200) as described above. The discharge grate (200) may be, for example, provided to an internal discharge end (3) surface of the mill (1). The discharge grate (200) may be secured to a mount (7) and extending over a discharge chute (8): The method of comminuting ore may comprise the step of filling the mill (1) with media (4) and material to be pulverized. The method of comminuting ore may further comprise the step of operating the mill (1) by rotating a portion thereof containing the media (4) and material to be pulverized. The method of comminuting ore may further comprise the step of allowing the at least one dynamic variable sieve opening (206) of the discharge grate (200) to expand, thus allowing pulverized material (5) and/or undersized media (4) to pass therethrough.

DETAILED DESCRIPTION OF THE DRAWINGS

As shown inFIGS.1-4, conventional discharge grates2are prone to pegging and occlusion by pulverized material. Embodiments described herein aim to improve the overall lifespan and effectiveness of conventional discharge grates2and address the shortcomings of state-of-the art mill discharge grate devices.

A mill1configured for comminuting ore, such as a ball mill, semi-autogenous grinding (SAG) mill, rod mill, or the like may comprise a number of dynamic variable opening discharge grates200as shown and described herein. Each dynamic variable opening discharge grate200may be secured to a mount7within a mill1, and extend over a discharge chute8as conventionally done. Collectively, the dynamic variable opening discharge grates200may form an internal surface portion of mill discharge end3of a mill1.

The dynamic variable opening discharge grate200described and illustrated herein are provided merely as examples to which the invention of the claims may be applied. The specification does not suggest that the invention of the claims is limited to or applies only to the particular dynamic variable opening discharge grate200shown and described herein.

Turning now toFIGS.6-15, a dynamic variable opening discharge grate200according to embodiments of the invention may comprise one or more holding frames201. Each holding frame201may be configured to receive a number of floating screen bars202. The floating screen bars202may each be received within a respective receiving opening214of the holding frame201as depicted. Each receiving opening214may comprise a first end214aand a second end214b. As depicted, according to some non-limiting embodiments a receiving opening214may further comprise a middle portion214c, a first cutout214d, a second cutout214e, a third cutout214f, and/or a fourth cutout214g, without limitation. Cutouts214d-214gmay each form portions of dynamic (i.e., expanding/contracting) variable sieve openings206as will be described in further detail below.

Each floating screen bar202may comprise a first end202aand a second end202b. As best depicted inFIG.11, a floating screen bar202may be bone-shaped, wherein the first202aand/or second202bends are wider or larger in a transverse direction than central portions of the floating screen bar202, without limitation. In some embodiments, as depicted, a middle portion202cof the floating screen bar202may also be widened as the first202aand second202bends are, without limitation. If this is the case, a floating screen bar202according to embodiments of the invention may comprise a first cutout202d, a second cutout202e, a third cutout202f, and a fourth cutout202g, without limitation. These cutouts202d,202e,202f,202gmay form portions of a dynamic (i.e., expanding/contracting) variable sieve opening206of the dynamic variable opening discharge grate200.

The dynamic variable opening discharge grate200may further comprise a lifter203extending across its central portion as illustrated. The lifter203, as best seen inFIG.13, may comprise one or more fastening bores216for securing the lifter203to a mount7or other components of the dynamic variable opening discharge grate200. Lifter203may also comprise one or more lifting features217(e.g., hook eye) for safety and ease of installation/removal from a dynamic variable opening discharge grate200and/or from the discharge end3of mill1. Lifter203may comprise a lower protrusion218extending along a portion or entirety of its length for being complimentarily received in a channel211of the dynamic variable opening discharge grate200as best depicted inFIGS.6&7.

As best depicted inFIG.12, one or more transverse securing bars205may be provided to extend over the floating screen bars202and hold them captive. As shown, a plurality of (i.e., two) transverse securing bars205extend over two adjacent rows of floating screen bars202. The transverse securing bars205may further serve as wear members similar to lifter bar203. The transverse securing bars205may be received in channels defined by side supports212of a base204. Side supports212are most clearly depicted inFIG.14.

A baseplate207may be provided below the floating screen bars202as suggested inFIG.12. The baseplate207may serve to stiffen base204, and provide a rigid mounting surface for mounting the dynamic variable opening discharge grate200to a mount7, without limitation. Baseplate207may serve to prevent flexing of base204over discharge chutes8upon impacts within a mill1, without limitation. The baseplate207may serve to support end portions (i.e., first202aand second202bends of floating screen bars202), without limitation. The baseplate207may comprise a number of baseplate mounting holes208for receiving fasteners. The fasteners received by baseplate mounting holes208may be the same fasteners extending through fastening bores216of lifter203, without limitation.

The baseplate207may be shaped so as to be complimentary with base204, and thus, it may have an outer peripheral shape or profile that matches or approximates an outer peripheral shape or profile of base204as depicted. The baseplate207may comprise one or more large pass-through apertures215as shown. Each large pass-through aperture215may extend across an area of the baseplate207beneath/under floating screen bars202. An edge portion of the large pass-through apertures215may optionally serve to support first202aand/or second202bends of screening bars202. In such embodiments, a width of a large pass-through aperture215may be sized so as to be less than an overall length of one or more floating screen bars202extending between ends202a,202b. In some embodiments, as depicted inFIG.15, a screen bar support219portion of base204may support a screen bar202, without limitation.

The base204of the dynamic variable opening discharge grate200may comprise a polymer, such as hard polyurethane. The base204may be formed in a mold, e.g., by virtue of over-moulding one or more of the other components within the dynamic variable opening discharge grate200. A peripheral portion of the base204may comprise one or more mounting hole portions209. Each mounting hole portion209may be formed within a portion of a recessed support lip210. Recessed support lips210may extend outwardly along opposing side portions of base204as shown. When placed adjacent to the recessed support lip210of an adjacent base204of another dynamic variable opening discharge grate200, a structure similar to channel211may be formed between adjacent dynamic variable opening discharge grates200. A lifter203, such as the one depicted inFIG.13may be received by a channel (similar to channel11) formed by two adjacent recessed support lips210. The mounting hole portions209may, align with mounting holes within channel211so that a lifter203may be equally placed within channel211or received by a channel formed by two adjacent recessed support lips210. Fasteners (not shown) may extend through mounting hole portions209to connect a lifter203to a mount7and secure two adjacent bases204to the mount7.

A portion of the base204may comprise a resilient buffer213. The resilient buffer213may comprise a soft rubber, elastomeric material, or other polymer which is designed to elastically, rather than plastically deform. The entire base204may be formed of the same material as resilient buffer213, or the resilient buffer213may be formed of a softer or lower durometer polymer than a polymer used for other portions of base204, without limitation. Portions of floating screen bars202may be over-moulded with resilient buffer213.

During operation, as undersized media4within a mill1impacts between two adjacent floating screen bars202, the resilient buffer213may be configured to allow the two adjacent floating screen bars202to temporarily separate from one another, thus providing a dynamic (i.e., expanding/contracting) variable sieve opening206between adjacent floating screen bars202.

Upon temporary expansion of the dynamic variable sieve opening206, the undersized media4may be allowed to pass through the dynamic variable opening discharge grate200and into the discharge chute8; or, the undersized media4may be allowed to return to the mill1without permanently lodging itself between floating screen bars202. Accordingly, resilient buffer213may be adequately configured to absorb kinetic energy and impact shocks caused by media4, thus mitigating the potential for pegging/spot welding of undersized media4within openings206which is known to occur with conventional discharge grates2.

In this specification, adjectives such as first and second, and the like may be used solely to distinguish one element or action from another element or action without necessarily requiring or implying any actual such relationship or order. Where the context permits, reference to an integer or a component or step (or the like) is not to be interpreted as being limited to only one of that integer, component, or step, but rather could be one or more of that integer, component, or step etc.

In this specification, the terms ‘comprises’, ‘comprising’, ‘includes’, ‘including’, or similar terms are intended to mean a non-exclusive inclusion, such that a method, system or apparatus that comprises a list of elements does not include those elements solely, but may well include other elements not listed.

LIST OF REFERENCE IDENTIFIERS