Patent Publication Number: US-2019184403-A1

Title: Rotatable feed distributor

Description:
FIELD OF INVENTION 
     The present invention relates to a rotatable feed distributor for a crusher, and in particular although not exclusively, to a feed distributor for a gyratory crusher configured to manipulate a feeding supply of crushable material into an inlet region of the crusher. 
     BACKGROUND ART 
     Generally, a belt conveyor or feeder delivers rocks and stones into a crusher. The rocks ride up the conveyor, whose end is located above the input of the crusher and then fall under gravity into the crusher where they are broken to a predetermined size. Typically, the uncrushed rocks pass initially through a feed distributor, which assists in dispensing the rocks into the crusher. 
     Since rocks fed into the crusher are not always of the same size and shape, they will not necessarily be reduced to a final desired and uniform size. However, it is preferable to obtain the crushed rocks within a relative size range, otherwise the material may require further processing. Furthermore, the final crushed rock product should preferably have a uniform size and shape gradation, rather than having a batch of stones that may contain very fine dust as a product and another batch that only contains larger rocks. Such rock segregation is disadvantageous as it can lead to a less saleable end product. 
     A variety of different feed distributors have been proposed with examples described in U.S. Pat. No. 7,040,562; U.S. Pat. No. 6,227,472; U.S. Pat. No. 4,106,707; and U.S. Pat. No. 3,212,720. However premature wear of specific parts of existing feed distributors is a continuous problem. In particular, when rocks fall upon the distributor and in particular a distributor chute, the impact tends to wear and erode specific components. Additionally, the rock crushing environment creates excess and abrasive dust which can also cause premature wear of certain machine elements, such as bearings. As a result feed distributor components require regular replacement and maintenance, which increases downtime of the crushing system and consequently reduces the efficiency of the overall system. 
     U.S. Pat. No. 7,040,562 and U.S. Pat. No. 8,056,847 describe rotating feed distributors that provide improved resistance to the impacting forces and abrasive dust resulting from the transfer of the crushable material. However, the problems of excessive wear due to dust and particulate contamination within the internal region of the distributor remains problematic. Accordingly, there is a need for a feed distributor that addresses these problems. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a feed distributor for a crusher and in particular a gyratory crusher that is effective to distribute and dispense a flow of crushable material into a crusher so as to optimise the distribution of material fed into the crushing zone whilst providing a distributor that is effectively robust against the dust and debris laden environment within which the distributor is typically operative. It is a further specific objective to provide a distributor that requires reduced maintenance and is configured to protect internal component, in particular moving parts and surfaces, so as to extend the longevity of the distributor working parts and in turn minimise system downtime. 
     The objectives are achieved by providing a feed distributor having a rotatable chute operating and mounted at a housing such that dust, debris or other particulate matter is prevented from being entrained into the housing (from the region of the chute) that would otherwise contaminate the internal working part zone within the housing and within which the various drive and bearing components are located to drive and stabilise the rotating motion of the chute. 
     In particular, and according to one aspect, a feed distributor is provided comprising at least one seal ring or a plurality of seal rings located at one or a plurality of regions between the chute and parts of the housing. The seal rings provide an effective physical barrier to the ingress of particulates at specific locations between the chute and housing. According to further aspects, a feed distributor is provided that is capable of creating a positive pressure within the working part zone (defined by the housing) such that dust and debris ingress into the working part zone is inhibited or preferably prevented by an exhaust air flow stream flowing from the region of the working part zone to exhaust from between selected regions of the rotatable chute and housing. In certain aspects, a distributor is provided with a combination of at least one sealing ring and an air feed assembly (communicating with and providing the positive pressure at the working part zone) such that dust and debris ingress into the working part zone is prevented by a combination of such seals and the positive pressure (air flow and exhaust). 
     Preferably, the present feed distributor is intended to sit beneath the top end or output end of a conveyor or feeder used in conjunction with a rock crusher. The conveyor or feeder is capable of delivering rocks from a supply source to the distributor that is positioned over the crusher. The present feed distributor is configured to receive the rocks onto a feed platform, where the rocks travel from the feed platform into a feed chute comprising an inlet and an outlet. Optionally, the feed chute may have an outer tube and an inner tube, with the outer tube configured to rotate and the inner tube being relatively stationary. The outer tube may be driven by a motor coupled to a gear mechanism. The use of two tubes reduces the wear on the feed distributor as the rotating outer tube allows the rocks to be evenly distributed into the crusher which in turn minimises rock size segregation, which improves the crusher efficiency and reduces operating costs. 
     The present feed distributor provides for an even distribution of the rocks before entering the crusher, thereby minimizing uneven rock build-up within the crusher and further minimizing the need for recycling or re-crushing of rocks that are not crushed within predetermined size limitations. The present feed distributor is configured specifically via the at least one seal ring and/or positive pressure within the working part zone to protect a power means, a support means and drive system (encompassing bearings, bearing surfaces, drive belts, belt surfaces, pulleys, gears and other working components and surfaces) from abrasive dust and other rock particles, thereby reducing the overall wear on the feed distributor. The arrangement of the seal ring and/or positive air pressure protected working part zone provides for a reliable and low maintenance drive and chute support system. 
     Optionally, the feed distributor comprises a sheave coupled around the rotating outer tube (chute). The sheave may comprise a flange and a face, the flange and face being perpendicular to one another. The sheave structure may be supported on its flange by a plurality of thrust bearings mounted to the feed distributor housing. Accordingly the rotating outer tube is preferably supported by the thrust bearings. The sheave is configured to receive one or more drive belts driven by a power means, such as a motor and gear reducer assembly. A distance between the power means and rotating outer tube may be maintained by a plurality of roller bearings circumferentially arranged about the sheave. 
     According to a first aspect of the present invention there is provided a rotating feed distributor for a crusher comprising: a housing defining an internal working part zone; a rotatable chute to receive crushable material to be fed to a crusher, the chute defining at least part of an internal bore provided with an inlet and an outlet; a sheave provided externally at and rotatably coupled with the chute; a power means and drive transmission mounted within the working part zone, at least part of the drive transmission coupled to the sheave to provide rotation of the chute relative to the housing; characterised by: at least one seal ring provided at the chute to at least partially close a gap region between the chute and a part of the housing and inhibit ingress of dust into the working part zone. 
     Preferably, the housing comprises an inlet aperture and an outlet aperture in fluid communication with the working part zone to allow the crushable material to pass through the housing and into the internal bore, the chute projecting trough at least the outlet aperture and at least partially into the working part zone. 
     Preferably, at least a first seal ring is provided between the inlet of the chute and a part of the housing that defines the inlet aperture. Optionally, the first seal ring is positioned within the working part zone and is positioned against an internal facing surface of the housing that defines the working part zone. Optionally, at least a second seal ring is provided between the chute and a part of the housing that defines the outlet aperture. Optionally, the second seal ring is positioned externally to the working part zone and against an external facing surface of the housing relative to the working part zone. The seal rings may be positioned directly or indirectly (via an intermediate gasket) against the housing. 
     Within this specification reference to the chute and housing having a respective inlet and outlet is with regard to a flow of crushable material through the distributor as the distributor supplies material to the crusher. 
     Preferably, a first seal ring is provided at a first region of the chute to provide at least partial closure of a first gap region between the first region of the chute and a first part of the housing that is internal facing relative to the working part zone. Preferably, a second seal ring provided at a second region of the chute to provide at least partial closure of a second gap region between the second region of the chute and a second part of the housing that is external facing relative to the working part zone. 
     Preferably, the first seal ring is positioned at or towards the inlet of the chute and the second seal ring is spatially separated from the first seal ring and is positioned between the first seal ring and the outlet of the chute. 
     Preferably, the at least one seal ring comprises an annular main body and a flexible annular flange projecting from the main body. Preferably, the at least one seal ring comprise a V-ring seal. 
     Preferably, the distributor comprises at least one clamp to radially compress against the at least one seal ring and secure the seal ring at an external facing surface of the chute such that the seal ring is rotatably coupled to the chute. 
     Optionally, the chute comprises a radially outward projecting shoulder to abut the seal ring or comprises a radially inward projecting groove at an outward facing surface of the chute to at least partially receive the seal ring. The groove or shoulder is configured to assist the clamp (secured around the seal ring), maintain the desired position of the seal ring at the outward facing surface of the chute. Where the chute comprises a shoulder to help seat the seal ring, the shoulder does not project radially outward from the outward facing surface to an extent that would other inhibit or prevent the seal ring from being axially slid over the outward facing surface from the chute outlet towards the chute inlet. 
     Preferably, the distributor comprises an air feed assembly coupled in fluid communication with the working part zone to provide a supply of air into the working part zone. Preferably, the air feed assembly comprises ducting and any one of a fan, a compressor or pneumatic system to generate an air flow stream through the ducting and into the working part zone. 
     According to a second aspect of the present invention there is provided a rotating feed distributor for a crusher comprising: a housing defining an internal working part zone; a rotatable chute to receive crushable material to be fed to a crusher, the chute defining at least part of an internal bore provide with an inlet and an outlet; a sheave provided externally at and rotatably coupled with the chute; a power means and drive transmission mounted within the working part zone, at least part of the drive transmission coupled to the sheave to provide rotation of the chute relative to the housing; characterised by: an air feed assembly coupled in fluid communication with the working part zone to provide a supply of air into the working part zone, the air capable of exhausting from the working part zone from at least a region between the chute and the housing to inhibit ingress of dust into the working part zone. 
     According to a third aspect of the present invention there is a provided a gyratory crusher comprising a feed distributor as described and claimed herein. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: 
         FIG. 1  is a side view of the present invention in combination with a rock crusher and a feed conveyor; 
         FIG. 2  is a perspective view of the present invention; 
         FIG. 3  is a bottom plan view of the present invention; 
         FIG. 4  is a sectional side view of the present invention taken along line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a partial cut away sectional side view; 
         FIG. 6  is another partial cut away section side view; 
         FIGS. 7 and 8  are sectional side views of the present invention, feedbox and rocks; 
         FIG. 9  is overhead view of a crusher used in connection with the present invention; 
         FIG. 10  is a cross sectional perspective view through the chute section of the distributor; 
         FIG. 11  is an underside cross sectional perspective view of the distributor of  FIG. 10 ; 
         FIG. 12  is a cross sectional perspective view of a first seal ring mounted between the chute and housing of  FIG. 11 ; 
         FIG. 13  is a cross sectional perspective view of a second seal ring mounted between the chute and housing of the distributor of  FIG. 11 ; 
         FIG. 14  is a further cross sectional perspective view of the feed distributor. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION 
       FIG. 1  shows a side view of a rock crushing system  10  employing the present invention. A plurality of rocks  12  is fed upwards on a conveyor  14 . The conveyor  14  delivers the rocks  12  through a feedbox  16  and into an improved feed distributor  18 , which is the focus of the present invention. The feed distributor  18  is designed for  360  degree rotation and delivers the rocks  12  uniformly to the crusher  20 . The distributor  18  may be mounted to the crusher  20 , the conveyor  14 , or may be mounted independently. A frame or mount  19  holds the feed distributor  18  in place over the crusher  20 . The frame  19  can encompass a wide range of shapes and sizes that will adequately mount the distributor  18  over the crusher  20 . The feedbox  16  should be considered a stand-alone feature that is not part of the present invention. The feed distributor  18  passes the rocks  12  into the crusher  20 , which rotates or gyrates and crushes the rocks  12 . The crushed rocks  12  exit below the crusher  20 , possibly onto a second conveyor  22 , which will then take the crushed rocks  12  away to be used, further sorted, or to be recycled and reprocessed in the rock crushing system  10 . 
       FIG. 2  shows a perspective view of the improved feed distributor  18 . A power means, such as electric motor  24  of any sufficient design or size that will adequately allow the distributor  18  to operate powers the feed distributor  18 . The output of the motor  24  is rotationally coupled to a gear reducer  241   a , which in turn drives the rotating components of the feed distributor  18 . 
     The feed distributor  18  has three main areas that the rocks will encounter when proceeding towards the crusher  20 : a feed platform or box  26 , an inlet  28 , and an outlet  30 . The inlet  28  and the outlet  30  generally are opposing sections of a tubular chute  32  containing a coextensive bore within the chute  32 , which will be described in more detail with respect to the subsequent figures. When rocks  12  enter into the distributor  18 , as shown in  FIG. 1 , the rocks  12  fill up the feed platform  26  and some of them drop into the inlet  28 . After enough rocks have accumulated on the platform  26 , all of the rocks  12  will pass into the inlet  28 , further traveling through to the outlet  30 , where they will eventually end up in the crusher  20 . The inlet  28  includes a reinforced lip  34 , which helps to extend the life of the inlet  28 . Similarly, a second lip  36  is located around the outlet  30  to also extend the life of the outlet  30  (see  FIG. 2 ). The lips  34  and  36  may be designed in any fashion, such as from a metal rod or similar material that may be welded to the inlet  28  and the outlet  30 , which will reduce wear on the inlet  28  and outlet  30 . 
     Again referring to  FIG. 2 , the feed distributor  18  comprises a housing  38 , which prevents dust and other debris from interfering with mechanical components of the feed distributor  18 . The housing  38  may be of any shape that will efficiently protect the internal components and not interfere with the functions of the distributor  18 . Preferably, the housing  38  is designed so that it substantially seals off the inner parts of the distributor  18  from the outside elements. A plurality of brackets  40  is provided on the outside of the housing  38 . The brackets  40  provide an area for the distributor  18  to be mounted onto the frame  19  over the crusher  20  (see  FIG. 1 ). The brackets  40  should be understood to encompass any mounting means that will sufficiently secure the distributor  18  to the crusher  20 . Similarly, the brackets  40  together with the frame  19  may be of any design. For instance, the distributor  18  does not necessarily need to be firmly bolted down, but may be held in place with stop blocks (not shown). 
     The inlet  28  and the outlet  30  comprise the tubular chute  32 . Located within the inlet  28  is an optional stationary tube or wear sleeve  62 . The stationary tube or wear sleeve  62  preferably extends a distance above the inlet  28  and also a distance below the inlet  28 . The reinforced lip  34  formed along the upper edge of the wear sleeve  62  helps to extend the life of the inlet  28 . When the wear sleeve  62  is employed in the feed distributor  18 , the previously described lip  34  is located at the top of the wear sleeve  62 . While the wear sleeve  62  may be secured to the inlet  28 , it preferably rests upon the feed platform  26 . A laterally extending flange  64  assists in the wear sleeve  62  resting on the feed platform  26 . When it becomes worn down, the wear sleeve  62  may be easily removed and replaced with a new sleeve. 
       FIG. 3  shows a bottom view of the improved feed distributor  18 . The output shaft  72  of gear reducer  24   a  (shown in phantom) is coupled to one or more drive wheels, sheaves, or pulleys  50 , which is connected to one or more drive belts  52 . Drive belts  52  are engaged with sheave  50  and with sheave structure  54 . An air feed assembly indicated generally by reference  83  is mounted at housing  38  so as to be provided in fluid communication with an internal region of housing  38  referred to herein as a working part zone  29  (that is defined by housing  38  and in which the various drive transmission components  241   a ,  50 ,  52 ,  54 ,  100  etc., are housed. Further details of the air feed assembly  83  is described with reference to  FIG. 14  below. 
     As shown in  FIG. 4 , the sheave structure  54  is attached to the tubular chute  32 . The drive belts  52  are received into belt receiving grooves  56  on the sheave structure  54 . The drive belts  52  are preferably V-belts. The drive belts  52  are tightened by adjusting the distance between the sheave  50  and the sheave structure  54 . Once the position of the tubular chute  32  is set (as described below) belt tightening is accomplished by means of slotted openings  59  being formed in the mounting for the gear reducer  24   a  and motor  24  assembly. 
     As also shown in  FIG. 3 , the force exerted by the belts  52  about the sheave structure  54  and tubular chute  32  is countered by a pair of idler wheel assemblies  80 . Each idler wheel assembly  80  is mounted to the underside of feed platform  26 . An idler wheel  86  is rotationally supported by an axle between upper and lower idler brackets. A fastener  92  passes through an offset opening in each of the idler brackets and the feed platform  26  to allow the assemblies  80  to pivot on the feed platform about the axis of the fastener  92 . Once the tubular chute  32  is properly positioned within the feed distributor  18 , each idler wheel assembly  80  is pivoted such that its idler wheel  86  comes into contact with the face  55  of the sheave structure  54  which is in turn coupled to the tubular chute  32 . While not required, a cover  94  may extend about each idler wheel  86  to prevent the build-up of dust and other materials that may adversely affect the performance of the rollers  86  and their bearings  88 . 
     Tubular chute  32  is vertically supported by at least three thrust bearings  100 . Each bearing  100  has a bearing surface  102  formed from a composite material commercially known as PEEK. Bearing surfaces  102  support the flange  58  formed on the sheave structure  54  that is coupled to the tubular chute  32 . 
     The platform  26 , as shown in  FIG. 4 , preferably has a square shape, with the inlet  28  and the wear sleeve  62  centered within the platform  26 . The height of the platform  26  is shown as being approximately the same height that the wear sleeve  62  extends upwardly from the inlet  28 . However, any height that will allow the platform  26  to operate as a rock bed for the feed distributor  18  will suffice. 
     Further in  FIG. 4 , the outlet  30  has a base  66 , an open side  68 , and at least one closed side  70 . The open side  68  and the closed side or sides  70  extend laterally upward from the base  66 . Preferably, the closed side  70  has a curvilinear shape (see  FIGS. 2 and 3 ), which prevents rocks from unnecessarily building up in the comers of the outlet  30 . However, the outlet  30  may have straight sides  70 , forming such other geometric shapes, and still fall within the scope of the invention. The outlet  30  is relatively large, thereby increasing throughput capacity of the distributor  18 . Referring further to  FIG. 4 , the motor  24  and the gear reducer  24   a  are shown connected to the output shaft  72 , which drives the drive wheel or sheave  50 . The drive wheel  50  rotates the drive belts  52 , which pass around the sheave structure  54  coupled to the tubular chute  32 , causing the chute  32  to rotate. As the chute  32  rotates, the wear sleeve  62  preferably remains stationary, which contributes to even wear of the sleeve  62 , thereby extending the life of the wear sleeve  62 . 
       FIG. 5  is a cross-sectional view depicting the relationship between the stationary housing  38 , rotating tubular chute  32 , sheave structure  54  and a thrust bearing  100  in greater detail. As shown, the sheave structure  54  includes two grooves  56  for receiving the drive belts  52  that rotate the chute  32 . The drive belts  52  are preferably v-belts. Sheave structure  54  also includes a horizontal flange portion  58 . The sheave structure  54  is coupled to the chute  32  utilizing fasteners  60  as shown. The flange portion  58  has a smooth underside surface that is supported on thrust bearings  100  at bearing surfaces  102 . Each thrust bearing  100  is supported on a bearing block or support  104 . The bearing blocks  104  are affixed to housing  38 . A lubricant line  106  supplies a lubricant, such as grease to the thrust bearing surface  102 . Fittings, such as grease fittings  108  are mounted outside the housing  38  so that the thrust bearings  100  can be periodically lubricated without having to remove any components from the feed distributor  18 . 
     While it has been found that the presence of lubricant reduces an audible hum from the feed distributor during operation, it is not necessary to supply lubricant to any of the thrust bearings  100  during operation of the feed distributor  18 . In other words, the performance of the feed distributor remains the same with or without the presence of lubricant at the interface of the flange portion  58  and thrust bearing surface  102 . 
     Housing  38  comprises a first mouth or aperture  11  provided at the region of platform or feedbox  26 . Aperture  11  is generally circular and comprises a diameter being larger than an external diameter of sleeve  62  such that sleeve  62 , having a generally cylindrical configuration, is capable of extending through aperture  11  and into a part of the working part zone  29  defined by housing  38 . Sleeve  62  comprises an inlet  15  and an outlet  17  such that feed material is capable of flowing into the generally cylindrical sleeve  62  through inlet  15  and to exit via outlet  17 . Sleeve  16  is mounted at feedbox  26  so as to have a degree of lateral play (in a radial direction relative to a central axis  79  of sleeve  62  and rotatable chute  32 ). Housing  38  also comprises a second mouth or aperture  13  positioned generally vertically below first aperture  11  and is generally co-aligned with first aperture  11  to be centered on axis  79 . Second aperture  13  is generally circular and provides a means of receiving and mounting rotatable chute  32  at the feed distributor. In particular, an uppermost axial end of chute  32  is received and extends beyond second aperture  13  so as to sit within a part of the working part zone  29 . As will be appreciated, a small radial gap is provided between an external facing surface  24  of chute  32  and aperture  13  so as to allow chute  32  to rotate relative to housing  38 . Chute  32  comprises a corresponding inlet  21  mounted within working part zone  29  (and immediately under feedbox  26 ) and a corresponding outlet  23  that corresponds to the feed distributor outlet  30 . Accordingly, feed material is capable of flowing through sleeve  62  and into a bore  47  defined by an internal facing surface of rotatable chute  32  and then to exit from the feed distributor via chute outlet  23 . 
     So as to prevent ingress of dust and particulate matter into working part zone  29 , feed distributor  18  comprises a first seal ring  35  and a second seal ring  37  positioned respectively between a region of chute  32  and respective regions or parts of housing  38  Within this specification, reference to the housing  38  encompasses the feedbox  26  and its surfaces and components. In particular, each of the first and second seal rings  35 ,  37  is rotatably coupled to chute  32  and are respectively secured against an external facing surface of chute  32  at an axial upper half of chute  32  closest to chute inlet  21 . 
       FIG. 6  is an enlarged cross-sectional view of the relationship between idler wheel assembly  80  and the sheave structure  54 . Each idler wheel assembly  80  is mounted to the underside of feed platform  26  (see also  FIG. 3 ). Each assembly  80  includes a lower idler bracket  82 , an upper idler bracket  84 , an idler wheel  86 , a pair of ball bearing assemblies  88 , an axle  90  and a fastener  92 . The idler wheel  86  is rotationally supported by the axle  90  between the upper and lower idler brackets  84 ,  82 . The fastener  92  passes through an offset opening in the idler bracket  82  and is fastened to the idler bracket  84  through a threaded hole to allow the assemblies  80  to pivot on the base platform about the axis of the fastener  92 . Once the tubular chute  32  is properly positioned with respect to the stationary tube  64  and within the feed distributor  18 , each idler wheel assembly  80  is pivoted such that its idler wheel  86  comes into contact with the face  55  of the sheave structure  64  coupled to the tubular chute  32 . While not required, a cover  94  may extend about each idler wheel  86 . 
     As further shown in  FIG. 6 , idler wheel  86  makes contact with the vertical face  55  of sheave structure  54  to maintain the predetermined distance between sheave  50  and rotating chute  32  so that the chute is properly centered in the housing  38  and proper tension is maintained by the drive belts  52 . It can also be seen that the face  55  of sheave structure  54  is substantially orthogonal to the flange  58  of sheave structure  54 . 
       FIG. 7  shows a side view of the feed distributor  18  after rocks  12  have been fed into the feedbox  16 . As previously shown in  FIG. 1 , the feedbox  16  is located directly over the platform  26 . The feedbox  16  securely fits onto the platform  26  in a way that will contribute to the platform  26  acting as an accumulator or ‘dead bed’  74  for the feed distributor  18 . The dead bed  74  decreases wear on the feed distributor  18 , the chute  32 , and the wear sleeve  62 . Because the rocks  12  build-up on the platform  26  as opposed to constantly falling down upon the chute  32  and the wear sleeve  62 , the wear will be reduced, as there is rock on rock sliding, as opposed to rock on distributor sliding. 
       FIG. 8  shows the distributor  18  of  FIG. 7  after more rocks  12  have been fed into the distributor  18 . A second dead bed  76  is formed in the outlet  30 , defined by the base  66  and the closed side  70 . The second dead bed  76  further reduces wear on the chute  32  and the base  66 . Furthermore, the sloped shape of the dead bed  76  allows the rocks  12  to easily exit the outlet  30  without unnecessary wear on the chute  32 . However, the rotation of the chute  32  still provides that the rocks  12  are evenly distributed. 
       FIG. 9  shows an overhead view of the crusher  20  and the chute  32 . Because of the arrangement of the present design, the rocks  12  are evenly distributed throughout the crusher  20 . Because the rocks  12  are fed into the crusher  20  with less size segregation and more uniformity, the crusher  20  will more efficiently crush the rocks  12 . Likewise, it is advantageous that the chute  32  is centered over the crusher  20  for further uniformity of the fed rocks  12 . 
     Referring to  FIGS. 10 and 11 , according to the specific implementation, sleeve  62  comprises a first upper cylindrical portion  62   a  and a second lower cylindrical portion  62   b  with portions  62   a ,  62   b  separated by a radially outward projecting annular flange  49  configured to abut against a lower or base region of feedbox  26 . The uppermost region of chute  32  (at the region of chute inlet  21 ) is positioned concentrically with and surrounds the sleeve axially lower portion  62   b . Accordingly, an external facing surface  61  of sleeve portion  62   b  is positioned opposed to an internal facing surface  25  of chute  32  that define internal bore  47 . Accordingly, sleeve outlet  17  extends into chute bore  47  beyond chute inlet  21 . 
     Chute  32  comprises a radially outward projecting flange  43  extending from an outward facing surface  24  of chute  32  immediately below chute inlet  21 . Flange  43  is separated from chute inlet  21  by a short axial distance. Flange  43  comprises a annular downward facing surface  51  configured for positioning against an annular upward facing surface  53  of sheave structure  54 . Accordingly, chute  32  is mounted to rest upon sheave  54  and is secured via fasteners  60  as illustrated referring to  FIG. 5 . First seal ring  35  is mounted to extend around the uppermost end of chute  32  immediately below chute inlet  21 . In particular, first seal ring  35  is configured to sit upon an upward facing surface  81  of flange  43  and against chute outward facing surface  27 . An upper portion of seal ring  35  is also positioned opposed to a region of an inward facing surface  31  that defines housing working part zone  29 . Seal ring  35  is positioned at housing internal facing surface  31  at a region immediately surrounding first aperture  11 . A thin plate-like annular gasket  39  is mounted at housing inward facing surface  31  immediately around aperture  11  with first seal ring  35  positioned against gasket  39 . Seal ring  35  is secured so as to be rotatably coupled to chute  32  via an annular clamp ring (not shown). Accordingly, seal ring  35  provides an appropriate seal between chute outward facing surface  27  and the housing internal facing surface  31  at the region of first aperture  11 . Accordingly, a gap region between chute inlet  21  and the working part zone  29  is sealed by seal ring  35  so as to prevent the ingress of dust and debris into the working part zone from the region of bore  47 . In particular, the axial overlap of the sleeve lower portion  62   b  and the upper region of chute  32  is configured to inhibit larger particulates from passing between the region of the chute inlet  21  and housing  38 , with finer entrained particles (dust) being blocked from entering working part zone  29  by the first seal ring  35 . 
     The protection of the working part zone  29  and in particular the internal drive components described with reference to  FIGS. 3 to 6  (including in particular bearing  100  and associated bearing surfaces) is enhanced by the provision of the second lower seal ring  37 . Second seal ring  37  is a mirror image of first seal ring  35  and is mounted at and in close proximity to second aperture  13  so as to provide a dust seal arrangement at the region between chute external facing surface  27  and second aperture  13 . According to the specific implementation, a second annular gasket  45  is mounted to extend around chute external facing surface  27  so as to provide a mount for second seal ring  37  which is similarly clamped onto chute  32  via a clamp ring (not shown). A third annular plate-like gasket  41  is mounted immediately around second aperture  13  at a region of an external facing surface  33  of housing  38 . Accordingly, a part of second seal ring  37  is mounted in touching contact against third gasket  41  so as to provide an appropriate seal between the chute external facing surface  27  and second aperture  13 . 
     According to the specific implementation, the first and second seal rings  35 ,  37  are coaxially located at the external facing surface  27  of chute  32  and provide a dual sealing arrangement to prevent the ingress of dust into the working part zone  29  at two separate regions of housing  38  corresponding to the first and second apertures  11 ,  13 . As will be appreciated, the first seal ring  35  is configured to prevent the ingress of dust or particulates flowing between the sleeve inlet  15  to chute outlet  23  whilst the second seal ring  37  is configured to prevent the ingress of dust into working part zone  29  resulting from the general dust laden environment immediately above the crusher and surrounding the feet distributor  18 . As the chute  32  extends from an external region of the housing  38  (and the working part zone  29 ) and into the housing  38  (and the working part zone  29 ), the present seal rings  35 ,  37  are positioned to seal against both the external and internal facing surfaces  33 ,  31  of the housing to provide a secure seal to prevent dust ingress into the working part zone  29 . 
     Referring to  FIGS. 12 and 13 , each of the first and second seal rings  35 ,  37  comprises a V-ring seal. In particular, each ring  35 ,  37  comprises an annular main body  65  having a generally square cross sectional profile. A part conical flange  63  projects upwardly from main body  65  and is aligned transverse to central axis  79  about which each ring  35 ,  37  is centered. In particular, flange  63  of the first upper seal ring  35  is inclined such that an uppermost annular tip  71  of flange  63  is positioned closest to axis  79  relative to a base part of flange  63  positioned at main body  65 . Conversely, the corresponding flange  63  of second seal ring  37  is declined such that the annular end tip  71  is positioned radially furthest from central axis  79  relative to a respective base part positioned at main body  65 . Each seal ring main body  65  comprises an annular groove  67  formed in an outward facing surface of main body  65  to receive a clamp ring (not shown) so as to secure each ring  35 ,  37  in position about the chute external facing surface  27 . The use of V-ring seals  35 ,  37  is advantageous in that flexible flanges  63  are configured to be urged against the respective sealing gaskets  39 ,  41  positioned at the respective regions of housing  38  (in close proximity to the first and second apertures  11 ,  13 ). Moreover, the flanges  63  are flexible which is advantageous to reduce wear of the seal rings  35 ,  37  as they rotate with chute  32  and against the respective gaskets  39 ,  41 . Preferably, the material of each seal ring  35 ,  37  comprises a polymeric material such as a polyurethane. 
     Referring to  FIG. 14 , the present feed distributor  18  is further advantageous to reduce dust ingress into the working part zone  29  by the creation and continuation of a positive pressure within the working part zone  29 . Such a configuration is achieved via the air feed assembly  83  mounted at housing  38  and provided in fluid communication with the working part zone  29 . According to the specific implementation, air feed assembly  83  comprises ducting  73  mounted at housing external facing surface  33  via a mount boss  75 . A fan, compressor or other pneumatic drive (not shown) of conventional design is mounted within or coupled to ducting  73  so as to force a flow of air through ducting  73  and into the working part zone  29  via an aperture (not shown) with a wall of housing  38  (defined between the internal and external facing surfaces  31 ,  33 ). The air feed assembly  38  is compatible for use with a feed distributor  18  comprising first and second seal rings  35 ,  37  and also with a corresponding distributor  18  that does not comprise respective seal rings  35 ,  37 . That is, where the distributor  18  comprises seal rings  35 ,  37 , the positive air pressure created within working part zone  29  may be modest so as to provide a modest ‘back pressure’ against the respective flanges  63  of the seal rings  35 ,  37 . The prevention of dust ingress is accordingly provided by a combination of the positive air pressure and the seal rings  35 ,  37 . Such an embodiment may involve providing a small (1 to 5 mm) gap between the respective flanges  63  and the respective gaskets  39 ,  41  so as to allow a low to modest exhaust air flow to exit working part zone  29  at the two regions of the housing apertures  11 ,  13 . As will be appreciated, such an exhaust air flow at the region between chute  32  and each respective housing aperture  11 ,  13  is effective to prevent dust ingress that would otherwise need to flow in the opposite flow direction, against the exhaust air flow. However, the combination of the air feed assembly  83  and seal rings  35 ,  37  is also compatible with no gap between the respective seal rings  35 ,  37  and gaskets  39 ,  41 . As will be appreciated, appropriate control units may be coupled to the air flow drive (fan, compressor etc.,) so as to regulate and control the magnitude of the positive pressure within the working part zone  29  and accordingly the flow speed of the exhaust air stream from housing apertures  11 ,  13 .