"Improvements in flight bars" Cross-Reference to Related Applications

The present application claims priority from Australian Provisional Patent Application No 2005906814 filed on 5 December 2005, the content of which is incorporated herein by reference.

Field of the Invention

This invention relates to improvements in flight bars.

Background of the Invention

In longwall coal mining, a coal cutter traverses back and forth across a coal face depositing coal cut from the coal face into a conveyor including a steel trough/pan disposed behind the coal cutter. The coal is pushed along the trough/conveyor to the end of the coalface and onto another conveyor for carrying the coal out of the mine, by means of flight bars. These are clamped to either one, two or three stands of continuous chain. Two strands are most typically used currently. Flight bars are clamped every six, eight or ten links, depending on the requirements of the installation, and extend transversely to the length of the chains. Sprockets and power transmission systems are disposed at each end of the coal face/trough for driving the chains. The chain is driven to drag the chains and flight bars through the conveyor pan/trough and the flight bars push the coal along the conveyor to the end of the face and onto the other conveyor.

It is a problem with flight bars that they wear relatively quickly, particularly the base of the bar and the tips at each lateral end of the flight bar where they contact the sides and base of the conveyor pan. The replacement cost of flight bars is relatively high.

Flight bars are commonly one piece and define recesses to which the chains may be clamped. Two piece flight bar designs have been proposed to allow for the clamping of the chains between the two bars using fasteners. However, these designs have not proved to be commercially successful due to the fasteners extending normally to the chains resulting in little clamping force and a resultant tendency for the chains to work loose over time. Wear is also a problem with two piece designs.

AU 763637 discloses a number of two piece flight bar designs in one of which the clamping force may horizontal, rather than vertical. Although this design has advantages over earlier designs, wear remains a problem and also the flight bars are uni-directional and may only be pulled one way.

The present invention seeks to address at least some of the problems of the prior art as discussed above.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Summary of the Invention

In a first broad aspect, the present invention provides a two part flight bar in which all the components of the flight bar which wear significantly in use are defined on one of the two components.

Typically the wear parts comprise the base and the tips at the ends of the base and these both are provided in a cradle component connectable in use to a top or upper component.

More specifically, the present invention provides a flight bar defining a longitudinal axis and configured to be driven in use along a conveyor pan by a pair of drive chains extending generally transverse to the longitudinal axis, the flight bar being separable into two parts comprising; a first part or cradle part comprising a base and solid walls extending upwardly and away from the base to define tips and means for receiving at least part of a one or more strands of continuous chain; and an upper part connectable to the cradle part with one or more chain links sandwiched therebetween, the upper part defining lateral edges, the configuration of the upper part and cradle being such that when connected together for use, the lateral edges of the upper part are generally enclosed within the cradle thereby protecting the side edges of the top part from wear.

All the parts of the flight bar which suffer major wear, are included in the cradle and hence, when the flight bar conveyors using flight bars embodying the present invention are overhauled, only the cradle needs to be replaced and the upper part which wears very little, can be salvaged and attached to a new cradle. The cradle may be manufactured from less material than a typical one piece flight bar and this results in cost savings in terms of material used.

It is preferred that the weight of the upper part is at least 40%, more preferably at least 50% of the weight of the bar when assembled, and may be at least 60% of the weight of the assembled bar.

Preferably, the walls of the cradle have a length of at least 10mm measured in the direction of the longitudinal axis of the flight bar more preferably a length of at least 5cm, and typically at least 10cm

In a preferred feature the components are configured such that one component partly overlaps an area of the other component in the direction of travel of the flight bar in use, so that the components may be clamped together, by bolts or the like, aligned with the direction of travel. One or more overlapping areas may be provided. The overlaps may be offset both forwards and rearwards to allow for bi-directional pulling of the flight bars.

In a preferred aspect the overlapping is provided by an elongate groove or rebate in a face of the upper component or cradle and a mating elongate projection in the face of the cradle or upper component which locates in the groove.

Brief Description of the Drawings

A specific embodiment of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which;- Figure 1 shows a top plan view of a flight bar, assembled from upper and lower components, embodying the present invention attached to a pair of chains;

Figure 2 shows a side view of the flight bar of Figure 1 in a conveyor pan, showing hidden detail in dashed lines;

Figure 3 shows a top plan view of the upper component of the flight bar of Figure 1;

Figure 4 is a side view of the upper component shown in Figure 3, showing hidden detail in dashed lines;

Figure 5 is a sectional view on lines v-v of Figure 4; Figure 6 is a sectional view on lines vi-vi of Figure 4; Figure 7 is a sectional view on lines vii-vii of Figure 4;

Figure 8 shows a top plan view of the lower component of the flight bar of Figure 1, showing hidden detail in dashed lines;

Figure 9 is a side view of the upper component shown in Figure 8; Figure 10 is a sectional view on lines x-x of Figure 9; Figure 11 is a sectional view on lines xi-xi of Figure 9; and

Figure 12 is a sectional view on lines xii-xii of Figure 9;

Detailed Description of Preferred Embodiments.

Referring to the drawings, a flight bar assembly 10 comprises a lower bar or cradle 12 and an upper bar 14. As shown, the cradle has a generally planar base 15 and side arms 16 and 18 that extend upwardly and diverge outwardly from the base 14 defining tip portions 20 and 22. The central portion of the upper surface of the cradle defines a generally planar portion 22. Near each end of the central portion 22 there is a generally vertically extending aperture 24 for receiving a bolt 26. Spaced apart in between the holes 24 there are four recesses 28 for receiving links of chains 30 and 32 which in use extend parallel to one another and perpendicular to the bar for pulling the flight bar along a conveyor pan 100 (see Fig. 2) dragging coal or the like therealong. As can be seen from Figure 2, the assembled flight bar 10 is sized and shaped to be a close fit in the conveyor pan, the pan having a flat base and side walls which diverge outwards at an angle of about 120° and an inwardly extending overhang portions 104 which overlaps the side arms 16, 18 and the ends of the upper bar 14. As best seen in Figures 3 to 7, the upper bar 14, defines a generally planar lower surface 30 which defines indents 28a which comprise part of the recesses 28 and a top surface which comprises a central generally horizontal portion 32 and two downwardly sloping wings 34 which terminate at distal ends 36. As can be seen from Figure 1, the distal ends 36 are covered by the side portions 16 and 18 of the cradle portion 12. The side portions 16, 18 should have a minimum thickness or length L of 10mm measured along the elongate axis X of the bar to protect the ends 36 of the upper component allowing for wear, but more typically will have a length L of about 10cm.

With reference to Figure 9, the cradle defines two upwardly extending diagonally opposed lugs 40, 41 which are located in correspondingly shaped and located recesses 42 (hidden and shown in dashed outline), 43 defined in the upper bar best seen in Figure 4. Co-axial apertures extend through the lugs and recesses and bolts 44 secure the cradle to the upper bar The lugs and recess transmit forces in the direction of the axial forces on the chain. In use one lug is forward (on the front of the bar) and one lug trails (on the rear of the bar) to allow for bi-directional pulling of the flight bars. The ability for bi-directional use, eliminates replacement bolt costs when the chain is turned, and reduces labour costs and time delays when the chain is turned.

Bi-directional pulling is also enabled by the provision of a rebate or groove 50 which extends along the length of the lower surface of the upper component. A mating projection 52 is extends along the upper surface of the cradle and slots into the groove. In use a flight conveyor is assembled from two chains clamped between a plurality of flight bar assemblies 10. As the flight bars 10 are dragged through a trough

containing coal for the purposes for pushing the coal to the end of the trough and onto another conveyor, the significant areas of wear occur at the tips 20 and 22 and the base 14 of the bar.

All the parts which suffer major wear, are included in the cradle and hence, when the flight bar conveyors using flight bars embodying the present invention are overhauled, only the cradle 14 needs to be replaced and the upper flight bar 12 which wears very little, can be salvaged and attached to a new cradle.

The cross-sectional area and volume of material which makes up the cradle 14 is less than that of a one piece bar to suit the same sized conveyor pan. Hence, the replacement cost of the cradle is less than that of the one piece bar as less raw material is required to manufacture the cradle. Typically at least 40 to 50% of the weight of the bar is contained in the upper bar and is saved and re-used when the cradle is replaced. For a bar weighing 80Kg up to 40Kg or even 50 Kg (about 60% by weight of the assembled bar) may be saved and reused. Since the major cost of the cradle bar is the amount of material (typically steel) used this results in a significant cost saving.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.