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FIELD OF THE INVENTION 
     The invention relates to a driving and guide arrangement for a mining machine which travels along a scraper chain conveyor, in particular for a drum cutter machine, with a guide rail arranged on the trough sections of the scraper chain conveyor above the level of the trough sections, and bounding a chain channel for a chain allowing the machine to haul itself along the mining face, with the horizontal links of the chain resting on support elements arranged within the chain channel, the latter being provided with openings underneath the chain to allow fines to fall through. 
     BACKGROUND OF THE INVENTION 
     An arrangement of this kind is known from DE-OS 4423925. In this arrangement the support elements for the horizontal links of a pin drive chain consist of support ledges extending over the length of the conveyor trough sections, with the vertical links of the pin drive chain engaging in, and practically entirely occupying, the slot-form space between the stowing-side and face-side ledges. The discharge openings for the fines in this known arrangement are open towards the gob or stowing side of the conveyor. 
     It has been found that the discharge of fines from the chain channel does not always function satisfactorily in the known construction. In most cases this is because the continuous support ledges and the vertical chain-links engaging in the space between them leave relatively little clearance for eg. coal dust etc. to fall through on its way to the fines discharge openings. Consequently, caking of fines on the pin drive chain in the chain channel is a frequent occurrence. As a result, a correct engagement of the chain-wheel in the pin drive chain is no longer assured, and there may even be damage to chain-wheel and guide. 
     It is the object of the invention to provide a particularly simple and inexpensive arrangement of the above-mentioned kind in which accumulations of fines in the chain channel accommodating the pin drive chain can be more reliably avoided, and an easier discharge of fines from the openings underneath the drive chain is obtained. 
     SUMMARY OF THE INVENTION 
     To achieve this object the support elements are formed as rest elements spaced apart from one other and engaging the horizontal chain-links from below, the individual rest elements having a limited dimension in the direction of travel of the mining machine, and the openings for discharge of fines are provided both on the stowing side of the chain channel and on its working front-facing side. 
     Utilizing only spaced elements that are themselves short or narrow in the travel direction of the mining machine as supports for the chain-links, fines which get into the chain channel have sufficient clearance between any two adjacent support elements on either side of the vertical chain-links to be able to fall to the bottom of the chain channel, whence they can re-emerge on the working side as well as on the gob side. This arrangement largely eliminates the risk of accumulations of fines and caking or clogging in the chain channel. 
     In a preferred form of the invention, the chain channel is made as a welded construction bounded on its working, front-facing side by the guide rail and on its rear, gob side 
     by a rear wall, and welded connecting plates interconnect the rear wall and the guide rail. This configuration as a welded construction yields considerable cost and weight benefits. A particularly convenient arrangement is obtained by forming the connecting plates as support elements for the horizontal chain-links and providing them with recesses for the vertical chain-links. The connecting plates then perform a dual role, as they not only provide the bridge between the guide rail and rear wall components which bound the chain channel, but simultaneously serve as support elements for the chain-links. The lower region of the rear wall may be bent towards the guide rail, so as to bound the chain channel at the bottom as well as at the rear. 
     The guide rail preferably consists essentially of a rolled or extruded section, which can have smaller dimensions and weights in comparison with the cast section that is still often used, and to which the connecting plates can be welded without any problem. The smaller dimensions and weights and the good weldability of the components can result in quite considerable cost advantages in relation to known designs. The fines discharge openings can consist basically of cutouts in the rear wall and/or guide rail, located between the connecting plates, preferably of trapezium form with the wider parallel side at the base. A particularly advantageous configuration is obtained by locating the guide rail a certain distance above the bottom boundary of the chain channel on the front side of the chain channel, thus forming between the guide rail and the bottom boundary of the chain channel a front fines discharge opening which can then conveniently extend over the whole length of the conveyor trough sections and/or of the chain channel itself. In this case, a guide shoe may be arranged on the mining machine so as to project through the front discharge opening to the conveyor trough and underneath the guide rail. This guide shoe not only serves to guide the drum cutter machine or its equivalent correctly on the guide arrangement, but additionally may be formed as a kind of scraper which rakes out any fines which have not already emerged from the chain channel through the discharge opening. 
     The upper part of the guide rail may have a rail profile for a slide block and/or for one or more running wheels of the mining machine. In this case it is particularly advantageous for the rail profile to be approximately semicircular, engaging in a matching groove in the periphery of a running wheel. With this configuration, the mining machine is guided in a positive manner transversely with respect to its direction of travel. It is convenient to provide the guide rail with a projection in the region of the rail profile or of the lower edge of the rail, which overhangs a derailment preventer arranged on the mining machine. This will ensure that the running wheel or slide block of the mining machine cannot be derailed. 
     The guide rail is conveniently provided, in a manner known in itself, with ledge-like projections which protrude into the chain channel and overhang the face-side shanks of the horizontal chain-links inside the chain channel. These projections prevent the drive chain from being lifted out of the chain channel. In a similar fashion, retaining bars can also be releasably attached on the stowing side of the chain channel after the chain has been inserted, so that these bars overhang the stowing-side shanks of the horizontal chain-links. After the retaining bars have been removed, the drive chain can be laid in the chain channel from above, or removed from above when replacement is necessary. 
     The bottom boundary of the chain channel may be given a ridged, somewhat roof-like form, in which the ridge may be located approximately in the longitudinal centre plane of the chain channel and chute surfaces for the fines falling away on either side of the ridge to the fines discharge openings. The provision of such sloping chute surfaces assists the unhindered discharge of the fines which have entered the chain channel. 
     Further features and advantages of the invention will be apparent from the description which follows and from the drawings, in which preferred embodiments of the invention are described in detail with reference to some examples. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an end view, partly in section, showing an individual trough section of a scraper chain conveyor with a pin drive and guide arrangement according to the invention mounted on the gob side of the conveyor trough; 
     FIG. 2 is an enlarged sectional view of the pin drive and guide arrangement mounted on the conveyor trough shown in FIG. 1; 
     FIG. 3 is a view of the region shown in FIG. 2, as seen in the direction of the arrow III; 
     FIG. 4 shows a second embodiment of a pin drive and guide arrangement according to the invention, in a similar view to FIG. 2; 
     FIG. 5 is a view of the region in FIG. 4, as seen in the direction of the arrow V; and 
     FIG. 6 shows, in cross-section, a third embodiment of an arrangement according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The scraper chain conveyor used as a longwall face conveyor in underground mining normally consists of individual trough sections which are joined to one another with no longitudinal play, but with limited angular play; a single such trough section  10  together with its mountings is shown in the drawing in FIG.  1 . The drum cutter machine  11 , which straddles the scraper chain conveyor and travels along it for coal getting, is merely indicated in the drawing by chain-dotted lines. The trough sections  10  which together form the conveyor trough of the scraper chain conveyor consist, in a manner known in itself, of side-profiles  12  and  13  which are disposed symmetrically with respect to each other and are connected to each other by the conveyor deck  14 . An endless scraper chain loop, which in the illustrated example consists of a double centre endless chain loop  16 , with scraper flights  15  attached, runs in the troughs of the trough sections  10  bounded by the side-profiles and the conveyor deck. A running track  17  upon which the cutter machine is supported and guided by working-side track rollers  18  is mounted at the foot of the working-side profile  12  of the trough sections  10 . The drum cutter machine, which straddles the scraper chain conveyor, is guided on the gob side on guide rails  19  which are secured above the trough sections  10  and the gob-side side profiles  13  and which form part of a pin drive and guide arrangement  20 , the subject of the present invention. 
     The pin drive and guide arrangement  20  essentially comprises for each conveyor trough section  10  an angle section  21  or profile member extending over the entire length of the trough section and the guide rail  19  likewise extending over the length of the trough section. The angle section  21  and the guide rail  19  are joined to one other by a plurality of connecting plates  22  which are welded to them at intervals, thus forming a chain channel  23  to receive a pin drive chain  24 . This chain channel  23  is bounded on the gob side by a rear wall  25  formed by the angle section  21 , on the working side by the guide rail  19 , and on the underside by a bottom chain channel boundary enclosure  26  formed by the second leg of the angle section  21 . 
     The pin drive chain  24  lies with its horizontal chain-links  27  resting firstly on narrow rest bars  28  protruding a short way into the chain channel from the rear wall and from the guide rail, and partly on the narrow connecting plates  22  located between every two rest bars, the connecting plates  22  being provided for this purpose with recesses  29  which the vertical chain-links  30  can enter. 
     The chain channel  23  has fines discharge openings  31 ,  32  both on the gob side and on the working side, between the chain channel bottom boundary  26  on the one hand and rear wall  25  or guide rail  19  on the other hand. The rearward discharge openings  31  in the rear wall  25  are each located between two adjacent connecting plates  22 , and each has the shape of a trapezium with the wider parallel side at the chain channel bottom boundary  26 . In the embodiments shown in FIGS. 1,  2 ,  3  and  6 , the working side fines discharge openings  32  are formed as a continuous discharge channel  33  which extends over the entire length of the individual trough sections  10 . In order to form this discharge channel  33 , the feet  34  of the guide rails  19  are not placed on the chain channel bottom boundary  26 , but are welded to the connecting plates  22  to lie some distance above the bottom boundary. 
     In the embodiments shown in FIGS. 1,  2 ,  3  and  6 , the guide rails  19  are also provided with additional discharge openings  35 , approximately oval in shape, immediately below the rest bars  28 . 
     In the embodiment of the invention shown in FIGS. 1 to  3 , the guide rails have at the top a profile  36  with an approximately semicircular cross-section  36  which engages in a matching groove  27  in a running wheel  38  of the cutter machine  11 . The running wheel  38  is provided on its gob-side outer face  39  with the pin drive sprocket  40 , the teeth  41  of which engage between adjacent vertical links  30  of the pin drive chain  24  lying in the chain channel and thus with rotation of the running wheel  38  haul the cutter machine  11  along the conveyor. To prevent the running wheel  38  from lifting off the guide rail  19 , the drum cutter machine is provided with a derailment preventer  42  which projects under the foot  34  of the guide rail  19  into the discharge channel  33 . This arrangement ensures that the cutter machine is not only guided transversely with respect to the running direction of the machine because of the interlocking forms of the running wheel and rail profile cross-sections, but also that it cannot be accidentally derailed. 
     The same applies to the embodiment according to FIGS. 4 and 5, in which the guide rail is provided with an additional projection  43  which overhangs the derailment preventer  42  arranged on the getting machine  11 . 
     In the pin drive and guide arrangements which have been described and illustrated, fines, such as coal dust or the like, entering the chain channel  23  from above descend between—and largely unhindered by—the connecting plates  22  and rest bars  28 , since these have a limited extent in the travel direction, and can be discharged through the fines discharge openings  31 ,  32 ,  33  and  35  both towards the gob side and towards the working side. Because the cross-sections of the discharge openings are relatively large and because there are sufficiently large gaps between the connecting plates  22  and the rest bars  28 , there is no tendency for the fines to cake and clog the chain channel. With the embodiment shown in FIG. 2, an additional chain channel cleaning action can be obtained by constructing the derailment preventer  42  engaging in the discharge channel as a scraper which scrapes the chain channel as it moves along the foot  34  of the guide rail, at least as far as the connecting plates, and rakes out the fines through the discharge channel  33  and/or towards the rear fines discharge openings  31 . 
     In the embodiment shown in FIG. 6, the discharge of fines is additionally assisted by giving the bottom boundary  26  of the chain channel  23  a convex or roof-shaped form, with a ridge  44  extending approximately along the chain channel  23  in the longitudinal centre plane of the channel, and with chute surfaces  45  for the fines falling away on either side of the ridge  44  to the fines discharge openings  31 ,  32 . In this embodiment, fines dropping through the chain channel from above fall on the sloping chute surfaces and are at once led down the slopes and out through the discharge openings. 
     The rail profile  36  illustrated in this embodiment has a flat upper surface  46  for a running wheel (not shown in the drawing) which has no special profile on its periphery. 
     To prevent the chain from being unintentionally lifted out of the chain channel while the machine is in operation, projections  47  which overhang the working side shanks  48  of the horizontal chain-links  27  in the chain channel, are formed by the guide rail in all the illustrated embodiments, in the region of its rail profile  36 . The gob-side shanks  49  are similarly retained in the chain channel by releasably attaching a retaining bar  50  or the like to the working side of the rear wall  25 , as indicated in FIG.  1 . This retaining bar together with the shoulders  47  on the rail profile keeps the pin drive chain on the rest bars  28  and connecting plates  22 , and prevents it from creeping out of the chain channel, which is open at the top. With the retaining bar  50  removed, the pin drive chain  24  can, with a slight twist, be laid in the chain channel of the conveyor trough sections from above, or lifted out of the chain channel again when chain replacement is necessary.

Summary:
In the driving and guide arrangement according to the invention, the drive chain in a chain channel bounded by a guide rail and a rear wall is supported only on series of spaced, narrow support elements at least some of which may form connecting plates welded between the rear wall and the guide rail. As the narrow support elements are spaced apart from one another, fines getting into the chain channel from above readily drop between them, and emerge freely through face side and gob-side discharge openings in the chain channel. Caking of fines in the chain channel is largely prevented in the arrangements, which are fabricated as welded constructions and are therefore particularly economical to produce.