EP0003843B1 - Grate surface for a mechanically operated stepped fire grate for large furnaces - Google Patents

Description

The invention relates to a grate covering for mechanically moving step-shaped grates of large combustion systems, in which in the individual stages there are several grate bars which are relatively movable relative to one another and which are clamped in the transverse direction by projecting stops which are passed through openings in the outer ribs of the adjacent bars and on fit the inside of the outer rib.

In a known grate covering of this type (DE-C-911 317) a laterally protruding hook is provided on an outer rib of a grate bar, which after insertion through a special insertion opening during the relative stroke is guided in a longitudinal slot of the outer rib of the adjacent grate bar and thereby its hook part slides along the inner wall of the outer rib. With the help of this bracketing, the mutual distances between adjacent grate bars cannot be set exactly, since the inside of the cast outer rib is unprocessed and the hook is also cast or forged, so that dimensional tolerances and, as a result, gaps between the grate bars occur. During the relative displacement of adjacent bars, the unprocessed hook slides on an unprocessed rib surface, which can result in large frictional forces acting on a narrow, for example 20 mm wide hook, so that it wears out relatively quickly, which increases the gap. The consequence of this is that with increasing operating time, increasingly larger parts can penetrate into the widening gaps, which can impair the relative stroke and even lead to jamming. If such jamming is present in many places, the driving force for the movement of the grate bars in the relative stroke, i. H. for the relative displacement of the grate bars, so high that the drive mechanism of the grate stops. Since in the known embodiment the stapling takes place from one bar to the respective neighboring bar, the frictional force and thus the force for executing a relative stroke is doubled when jamming occurs on both flanks of a grate bar. Jamming between grate bars can be caused by stones and slag as well as by penetrated iron parts, as can be the case with a refuse furnace.

The object of the invention is to design a grate covering of the type described in the introduction in such a way that the distance between the individual grate bars or the gaps between the grate bars can be kept smaller and the frictional forces during the relative displacement and the associated wear are reduced.

This object is achieved in that two stops are arranged at the ends of a clamp bolt and together form a clamp, the clamp bolt with mirror gripping through a longitudinal slot corresponding to the relative displacement of the grate bar of a grate bar movable relative to its neighboring bars and with its stops in each case interacts with the grate bars provided on both sides of the movable grate bar and fixed within the respective grate level.

Since, due to the design according to the invention, the stops rest on the inner sides of the outer ribs of such grate bars, which are fixed during the relative stroke, there is no displacement between the stops and these outer ribs and therefore no wear on the ribs and the stops. The grate bar movable during the relative stroke is now moved between two grate bars which are stationary during the relative stroke and which have a constant distance due to the clamp. The movable grate bar is thus displaced relative to the unit consisting of the two adjacent bars and the fixed bracket, the bracket gripping through the movable grate bar with play.

If there is talk of movable and fixed grate bars, this relates in each case to the relative stroke, in which the grate bars which are suspended to a limited extent on the support frame are displaced relative to grate bars which are firmly attached to the support frame. This relative stroke occurs in both movable and fixed grate levels.

Since the clamp no longer slides along the outer ribs, there is no longer any unavoidable movement due to dimensional tolerances. Due to the fixed arrangement of the clamp on fixed grate bars, the gap widths can be reduced to less than 1 mm. This avoids that larger parts can penetrate between relatively movable grate bars. If there is still jamming due to many small parts, the resulting force causes the movable grate bar to be pressed against a fixed grate bar and, under the effect of this force, to slide its flank along the flank of the fixed grate bar during the relative displacement.

Since the flanks of the grate bars are precisely machined by means of farallel grinding and thus have a smooth surface, correspondingly low frictional forces occur during the relative displacement. The reduction in the frictional forces or the forces required for the relative displacement is therefore due to the fact that, on the one hand, only small parts can penetrate into the relatively narrow gaps, which do not lead to the strong jamming can lead, as can be the case with large parts, and also in such a case, large ground surfaces slide on each other, whereby the wear on the surfaces is low. In the known embodiment, the forces resulting from the jamming have an effect on the very small area of the hook, which is also still unprocessed, which increases wear.

Another significant advantage is that the resistance to displacement of the movable grate bar due to jamming remains constant, regardless of whether the jam occurs in one or both gaps between the movable grate bar and the two fixed grate bars held together by a clamp. In the known embodiment, however, the displacement resistance is doubled when jamming occurs in both columns on both sides of the movable grate bar, since the clasps on both sides of the movable grate bar are independent of one another, so that the forces building up on the hooks add up.

If the stops are integrally formed on the ends of the clamp bar, the gap width between the adjacent grate bars depends on the manufacturing accuracy in the manufacture of the grate bars and the bracket, which cannot be increased arbitrarily for economic reasons. In order to be able to achieve the smallest possible gap widths at the start of operation, on the one hand, and to be able to correct these gap widths even after a long period of operation, after which a certain amount of wear will occur, the effective length of the clamp can be adjusted according to a development of the invention adjustable.

According to the invention, a first possibility of making the clamp adjustable and readjustable is that an adjusting screw is provided on at least one of the stops, which can be made in one piece with the clamp bolt, which engages on the inside of the outer rib.

Another design option, which leads to an adjustable and adjustable clamp, is that the stops are designed as transverse to the clamp bolt by means of adjusting screws arranged at the ends thereof, which at one end have conical projections which, in the operating position, also have on the inside of the outer ribs arranged to interact. The clip therefore consists of a simple, straight clamp bolt, which has threaded bores at the ends essentially transversely to its longitudinal axis, into which the set screws are screwed. Since both the set screws and the inside of the outer ribs have inclined surfaces that are in contact with each other, the desired distances can be adjusted and adjusted.

A simple setting option also results from the fact that the stops are formed by nuts that can be screwed onto the ends of the clamp bolt.

In order to be able to assemble the grate covering, insertion openings for the stops are provided at least in the outer ribs of the fixed grate bars. If these stops are firmly connected to the clamp bolts, the movable grate bars also have corresponding openings. So that the connection cannot come loose during operation, the clips are locked after insertion. This can be done according to the invention in that the clamp is rotated in the operating position relative to the insertion position.

If the clamp bolt is made of a round material, there is a possibility that it will turn back during operation.

To exclude this with certainty, the clamp bolt can have sliding blocks on which the movable grate bar is slidably guided. It is advantageous if the sliding blocks have a shape that deviates from the circular shape, so that they in turn cannot be subject to any rotational movement. The arrangement of sliding blocks on the clamp bolt also has the advantage that wear-resistant materials can be used, because despite the movement play in the longitudinal slot, it cannot be ruled out that a relative movement perpendicular to the grate bars between adjacent grate bars occurs during the stoking movements Grind the movable grate bars along the stacks! The sliding blocks reduce wear without it being necessary to manufacture the entire bracket from a particularly wear-resistant material.

Another possibility of locking the clamp in its operating position is that locking bolts are provided on the underside of the clamp bolt, which can be inserted into the insertion openings after insertion of the stops and the clamp is displaced in relation to the insertion position and thus can hold locked position. The locking bolts can be secured in their locking position against unintentional shifting.

In the case of clamps with set screws arranged at the ends, the clamp can be locked in a simple manner in that the insertion openings for the set screws serving as stops in the outer ribs are assigned to that side of the clamp bolt which is opposite the conical projections. The set screws are brought into a position for insertion, in which the conical projections are located essentially within the clamp bolt and are then re-adjusted inserted through the outer rib into an operating position in which the conical projections protrude beyond the clamp bolt. However, since the insertion openings are provided on the side opposite the conical projections, the clamp can no longer be released from the fixed grate bars.

In the described brackets, two fixed grate bars and one movable grate bar of one step are combined to form a unit, it being entirely possible for five or seven or a higher odd number of grate bars to be combined to form one unit. Then only the distance between the two outer grate bars of a unit is defined. The distances between the individual grate bars of this unit can vary within the unit. The grating bars of a unit are thus held at a certain maximum distance from one another by the clamping.

A gap formation can occur not only between the grate bars, but also between the edge bar of a step and the boundary plates. In order to prevent the edge bar of fixed steps from migrating from the boundary plates, the edge bars of the one grating side of the fixed grate steps can be held at the lateral boundary plates of the grate by clamps at a fixed, adjustable and adjustable distance. This prevents the formation of edge gaps between the edge bars and the boundary plates, which can no longer be compensated for by other compensation devices. This is the case when parts are inserted between the edge bar, which is immovable relative to the boundary plates, and the latter. Such parts can widen the marginal gap, whereby increasingly larger parts can penetrate. There is no self-cleaning effect due to the lack of relative movement between the edge bar and the boundary plates in the fixed steps. The invention solves the problem of edge gap formation in fixed steps.

So that the edge bars can also follow possible pumping movements of the grate step in which the grate bars move essentially perpendicular to their surface, the clamps can be held on the boundary plates so as to be displaceable perpendicular to the grate bar surface. Details and advantageous developments of the brackets for the edge rods result from the subclaims.

• Fig. 1 einen Längsschnitt durch einen Rostbelag nach der Erfindung;
• Fig.2 einen Querschnitt nach der Linie II-II in Fig. 1;
• Fig. 3 einen Teilschnitt in Längsrichtung des Rostbelages einer anderen Ausführungsform;
• Fig. 4 einen Schnitt nach der Linie IV-IV in Fig. 3;
• Fig. eine Unteransicht der Darstellung in Fig. 4;
• Fig. 6 eine gegenüber Fig.4 abgeänderte Einzelheit;
• Fig. 7 einen Teilschnitt in Längsrichtung durch den Rostbelag im Bereich der Verklammerung, entlang der Linie VII-VII in Fig. 9;
• Fig. 8 eine Seitenansicht der Außenrippe des feststehenden Roststabes;
• Fig. einen Schnitt nach der Linie IX-IX in Fig. 7;
• Fig. 10 einen der Fig. 9 ähnlichen Schnitt durch eine weitere Ausführungsform;
• Fig. 11 eine Seitenansicht nach der Linie XI-XI in Fig. 10;
• Fig. 12 einen Schnitt nach der Linie XII-XII in Fig. 10;
• Fig. 13 einen Teilschnitt durch einen Randstab im Bereich seiner Anlagestelle an eine Begrenzungsplatte des Feuerungsrostes;
• Fig. 14 einen Schnitt nach der Linie XIV-XIV in Fig. 13;
• Fig. 15 einen der Darstellung in Fig. 13 ähnlichen Schnitt durch eine abgeänderte Ausführungsform;
• Fig. 16 einen Schnitt nach der Linie XVI-XVI in Fig. 15 und
• Fig. 17 einen Schnitt nach der Linie XVII-XVII in Fig. 16.

The invention is shown in the drawing, for example. In this shows

• 1 shows a longitudinal section through a grate covering according to the invention.
• 2 shows a cross section along the line II-II in Fig. 1;
• 3 shows a partial section in the longitudinal direction of the grate covering of another embodiment;
• Fig. 4 is a section along the line IV-IV in Fig. 3;
• FIG. 4 shows a bottom view of the illustration in FIG. 4; FIG.
• 6 shows a detail modified compared to FIG. 4;
• 7 shows a partial section in the longitudinal direction through the grate covering in the area of the clamp, along the line VII-VII in FIG. 9;
• Fig. 8 is a side view of the outer rib of the fixed grate bar;
• Fig. A section along the line IX-IX in Fig. 7;
• 10 shows a section similar to FIG. 9 through a further embodiment;
• FIG. 11 is a side view along the line XI-XI in FIG. 10;
• Figure 12 is a section along the line XII-XII in Fig. 10 .;
• 13 shows a partial section through an edge bar in the region of its contact point on a boundary plate of the firing grate;
• 14 shows a section along the line XIV-XIV in FIG. 13;
• FIG. 15 shows a section similar to the illustration in FIG. 13 through a modified embodiment; FIG.
• Fig. 16 is a section along the line XVI-XVI in Fig. 15 and
• 17 shows a section along the line XVII-XVII in FIG. 16.

In all of the grate coverings shown in the drawing, grate levels consisting of grate bars 1 fixed during the relative stroke and grate bars 2 movable for this purpose during the relative stroke are provided, which are located either on movable support frames 3 in the case of movable steps or on fixed support frames 4 in the case of fixed steps. The respective fixed grate bars 1 are suspended essentially without play at their hanging end 5 on a hanging rail 6 or 7 of the support frame 3 or 4, while the grate bars 2 movable relative to these grate bars with a longitudinal play on the support frame of the movable or fixed Rest level.

In all of the embodiments shown in FIGS. 1 to 12, two grate bars 1 which are fixed with respect to their supporting frame are held at a fixed distance from one another by means of a clamp, and the grate bar 2 which is displaceable relative to these fixed grate bars not only moves relative to its adjacent grate bars 1 and the suspension rail 6 or 7, but also with respect to the clamp, which prevents its neighboring bars from being removed from one another.

In the embodiment shown in FIGS. 1 and 2, the bracket which holds the fixed grate bars 1 together is designated by 8 and comprises a bracket bolt 9 as well as hook-like projections 10 formed at their ends, which are integral with the bracket row gel are formed and protrude transversely to the clamp bolt 9 on both sides. In order to be able to combine two fixed and one movable grate bar with each other, the inner ribs 11 and the outer ribs 12 of the movable grate bar 2 and the outer ribs 13 of the fixed grate bars 1 have insertion openings 14 and 15, respectively. The insertion openings 15 in the outer rib 13 of the fixed grate bar 1 are adapted to the shape of the hook-like extension 10 and run perpendicular to the back surface of the grate bar 1.

So that the clamp 8 can hold the fixed grate bars 1 at a certain distance from one another, or so that the stops 10 can no longer slide out through the insertion openings 15 of the fixed grate bar 1 during operation, the clip 8 is rotated by means of a key 16 which is attached to one Lever 17 engages, which is firmly connected to the clamp bolt 9. The key 16 has at its front end a pocket 18 with two stops 19 in which the lever 17 is received, the stops 19 alternately engaging the lever 17 while the clamp 8 is being rotated.

The movable grate bar 2 has a longitudinal slot 20 which is connected to the insertion opening 14 and is dimensioned such that the movable grate bar 2 can move with play 21 relative to the clamp bolt 9 of the clamp 8 in accordance with its relative displacement with respect to the fixed grate bars 1.

In order to be able to ensure a constant gap 22 between all grate bars when installing the grate covering despite manufacturing tolerances in the manufacture of the clamp, and to be able to return the gap 22 to its original size after wear on the flanks 23 and 24, according to FIG 3 to 6, an adjustable clamp 25 is provided which has a clamp bolt 26 and two hook-like stops 27. One of the stops 27 is provided with a threaded bore 28 into which a set screw 29 can be screwed, which bears against the inside of the outer rib 13 of one of the two grate bars 1 connected by the clamp 25 and thus the mutual distance between the two fixed grate bars 1 and thus allowed to set the gap widths 22.

In this embodiment shown in FIGS. 3 to 6, an insertion opening 30 is provided in each outer rib 13 of a fixed grate bar 1, the width of which is essentially adapted to the width of the clamp bolt 26, which is rectangular in cross section, and the height of which corresponds to the height of the stop 27, increased by a certain movement game, corresponds. Provided in the movable grate bar 2 is a longitudinal slot 31 which is connected to the insertion opening 30 and which has a height which also corresponds to the height of the stop 27, so that the clamp 25 can be passed through the movable grate bar 2. A special insertion opening as in the embodiment according to FIGS. 1 and 2 is not required here with the movable grate bar. So that the clamp 25 can be locked in its operating position after insertion, two locking bolts 32 are slidably held on the underside of the clamp bolt 26, which correspond in width to the width of the clamp bolt 26 and in height to the protrusion of the hook-like stop 27. The fixed grate bars 1 are then raised so far that the respective stop 27 can be inserted through the insertion opening 30, whereupon the grate bars 1 are lowered, whereby the stops 27 engage behind the outer ribs 13 of the fixed grate bars.

Each locking bolt 32 has a longitudinal slot 33 through which a bolt, which is fixed on the clamping bolt 26, extends and which holds the respective locking bolt 32 on the underside of the clamp bolt 26 with a head 34. A double-armed flap 35, which is pivotably mounted on the underside of the clamp bolt 26 and is connected to the locking bolts 32 in an articulated manner by its ends by means of pivot pins 36, is used to move the locking bolts 32. The pivot pins 36 protrude from the locking bolt 32 and can engage with their projecting ends in locking holes 37 in the clamp bolt 26 when the locking bolts 32 are in the locking position shown in FIG. 4, in which the fixed grate bars can no longer be raised, since the insertion opening 30 is filled by the clamp bolt 26 and the locking bolt 32, so that a movement of the grate bar 1 with respect to the clamp bolt is no longer possible. So that the pivot ends 36 can be pivoted past the clamp bolt 26 with their projecting ends in order to get into the latching bores 37, the pivoting tab is lowered by means of a screw 38 holding it, which serves as a pivot axis for the tab 35. After the locking bolts 32 are in their locking position, the screw 38 is tightened again and the pivot pins 36 engage in the locking bore 37.

In order to avoid actuating the screw 38, according to the configuration according to FIG. 6, the tab 35 can be loaded by means of a compression spring 39, so that the tab 35 can move away from the clamp bolt 26 against the action of the compression spring 39, so that the pivot pin 36 do not hit the clamp bolt 26 when pivoting. If the pivot pins 36 engage in the locking holes 37 after pivoting of the tab 35, the tab is held in this position by the compression spring 39, so that the locking bolts 32 are secured in their locking position.

In the embodiment according to FIGS. 7 to 9 a clamp 40 is provided with a round clamp bolt 41, at the ends of which hook-shaped stops 42 are fastened, of which one stop carries an adjusting screw 43. The design corresponds to that of FIG. 4 except for the round design of the clamp bolt 41. The clamp 40 is locked by rotating the latter after the stops 42 have been pushed through a correspondingly adapted insertion opening 44. As can be seen from FIG. 8, the stop is located 42 after rotation by means of a lever 45 fastened to the clamp bolt 41 in a position in which the stop no longer aligns with the insertion opening 44, so that the fixed grate bars 1 can no longer be removed from one another. The ribs 11 and 12 of the movable grate bar 2 each have a longitudinal slot 46 'and 46, wherein in each case a sliding block 47 is arranged in the longitudinal slots 46, which sits on the clamp bolt 41. The sliding block 47 has a rectangular shape and can therefore not be rotated in the longitudinal slot 46, even if two forces act on the sliding block 47 when the movable grate bar is displaced. For this reason, the bracket 40 can not be rotated, so that the locking that has been achieved by twisting can no longer be automatically reversed.

10 to 12 show a further embodiment of the clip. This configuration is particularly simple, since the clamp designated overall by 48 has a simple straight clamp bolt 49 with a preferably rectangular cross section, which is provided at its ends with threaded bores 50 into which set screws 51 can be screwed. As shown, the set screws can have a hexagon socket for their actuation. At the opposite end they have conical projections 53 which, in the installed state of the clamp 48, interact with inclined surfaces 54 on the inside of the outer rib 13 of the respective fixed grate bar. As can be seen from FIG. 10, the distance between the two fixed grate bars 1 can be shortened by screwing in the set screws 51 more, or increased by unscrewing the set screws. The clamp bolt 49, which has a rectangular cross-section in the example shown, is passed through a longitudinal slot 56 in the movable grate bar 2 which is essentially the same as the thickness of the clamp bolt when installing the grate covering without the set screws 51. The length of the longitudinal slot 56 corresponds to the size of the maximum relative displacement of adjacent grate bars. The set screws 51 are screwed in for installation only so far that the conical projections 53 are flush with the top of the clamp bolt 49, as can be seen from the illustration at the left end of the clamp bolt in FIG. 10. In this position, the clamp bolt with the adjusting screw 51 can be inserted into an insertion opening 55 provided in the outer rib 13, which corresponds to the cross section of the clamp bolt 49 and the set screw 51 projecting downward. If the adjusting screw 51 is then turned upward so that the conical projection 53 comes to rest against the inclined surface 54, the stop can no longer be pulled out of the insertion opening 55. The clamp 48 is thus locked in its operating position.

13 and 14 one of the possible embodiments of a clamp for a fixed edge bar 1 'of a fixed grating step is shown. With 78 a boundary plate of a fire grate is designated, which is assigned to the edge bar 1 '. On this boundary plate 78, a retaining tab 80 is fastened, which has a guide slot 57 which is oriented perpendicular to the grate bars of the edge bar 1 '. In this guide slot 57, a guide pin 58 is guided, which carries a bracket 59 which is substantially U-shaped and comprises a base part 60 and two legs 61 and 62. In the legs 61 and 62, which run parallel to the grate bar, set screws 63 are screwed in, which correspond to the set screws 51 of the embodiment according to FIG. 11. With their conical projections 64, the set screws 63 rest on inclined surfaces 65 and 66 of the outer rib 13 'of the edge bar 1'. If the set screws are screwed further up, the gap 67 between the edge bar 1 'and the limiting plate 78 is reduced. The arrangement of the guide slot 57 and the guide pin 58, which is connected to the bracket 59 by holding eyes 79 arranged on the base part 60, the edge bar 1 'can execute movements which are perpendicular to its bar surface. So that the clip 59 does not come free on the outer rib 13 ', the upper leg 61 is inserted into an insertion opening 68, which is comparable to the insertion opening 55 in the embodiment according to FIG. 11, because this insertion opening 68 is adapted to the upper leg 61 and points In the lower area there is a recess 69, which is provided for the passage of the adjusting screw 63 when it is in its lower position, in which the conical extension 64 does not protrude beyond the leg 61.

In the embodiment according to FIGS. 15 to 17, the bracket used to hold the fixed edge bar 1 'of a fixed grate step, according to the example shown, consists of an angle piece, one leg 71 of which passes through an insertion opening 72 in the outer rib 13' of the edge bar 1 ' is, while the other leg 73 is slidably supported by a bracket 74 which is attached to the boundary plate 78. The sliding bracket is provided so that the grate bar is vertical can move to its bar surface and thus follow the movements of the remaining grate bars of the grate step if this should perform vertical movements. The outer end of the leg 71 is designed as a threaded bolt 75, onto which a nut 76 can be screwed, which together with a washer 77 serves as a stop which bears against the inside of the outer rib 13 '. By turning the nut 76, the edge gap 67 between the edge bar 1 'and the boundary plate 78 can be adjusted.

Claims (14)

1. Grate covering for mechanically moved stepshaped furnace grates of large furnaces, in which several grate bars (2) lie movably relative to one another in the individual stages and are cottered together in transverse direction by projecting abutments (10; 27; 42; 51), which are led through openigs (14; 15; 30; 44) in the outside ribs of the neighbouring bars and bear against the inside of the outside rib, characterised thereby, that two abutments (10; 27; 42; 51) are arranged at each of the ends of a cotter pin (9; 26; 41; 49) and together with this form a clasp (8; 25; 40; 48), wherein the cotter pin passes through an elongate slot (20; 31; 46; 56), appropriate to the relative displacement of the grate bar (2), of a grate bar (2) movable relatively to its neighbouring bars (2) and by its abutments (10; 27; 42; 51) respectively co-operates with the grate bars (1) which are provided to both sides of the movable grate bars (2) and stationary within the respective grate stage.

2. Grate covering according to claim 1, characterised thereby, that the abutments (10, 27; 42) at the ends of the cotter pin (9; 26; 41) are integrally shaped on to or firmly connected with this and that the outside ribs (13) of the stationary grate bars (1) display entry openings (15; 30; 44) adapted to the abutments.

3. Grate covering according to claim 1 or 2, characterised thereby, that the effective length of the clasp (25; 40; 48) is setable and readjustable.

4. Grate covering according to one of the claims 1 to 3, characterised thereby, that a setscrew (29; 43) is provided on at least one of the abutments (27; 42).

5. Grate covering according to claim 1 or 3, characterised thereby, that the abutments are constructed as setscrews (51; 63), which are arranged substantially transversely to the cotter pin (49; 61; 62) through at the ends of the same-and which at their one ends carry conical projections (53; 64), which in the operative setting co-operate with ramp surfaces (54; 65; 66) arranged at the insides of the outside ribs (13; 13').

6. Grate covering according to claim 1 or 3, characterised thereby, that the abutments are formed by nuts (76) threadable onto the ends (75) of the cotter pin (71).

7. Grate covering according to one of the claims 1 to 4, characterised thereby, that the clasp (8; 25) in the operative setting is turned relative to the entry setting.

8. Grate covering according to one of the claims 1 to 7, characterised thereby, that the cotter pin (41) displays slide rings (47), on which the movable grate bar (2) is slidably guided.

9. Grate covering according to one of the claims 1 to 8, characterised thereby, that locking bolts (32), which after the introduction of the abutments (27) into the entry openings (30) are likewise insertable into these and hold the clasp (25) in a setting displaced relative to the entry setting and thereby locked, are provided at the underside of the cotter pin (26).

10. Grate covering according to claim 5, characterised thereby, that the entry openings (55) for the setscrew (51) serving as abutments are associated in the outside ribs (13) with that side of the cotter pin (59), which lie opposite the conical projections (53).

11. Grate covering for mechanically moved stepshaped furnace grates of large furnaces, in which the individual stages are devised alterna- tivly stationary and movable and are arranged between lateral boundary plates, characterised thereby, that the edge bars (1') of the one grate covering side of the stationary grate stages are held at a fixed, settable and re-adjustable spacing (67) by clasps (59; 70) on the lateral boundary plates (78) of the furnace grate.

12. Grate covering according to claim 11, characterised thereby, that the clasps (59; 70) are held on the boundary plates (78) to be displaceable perpendicularly to the grate bar surface.

13. Grate covering according to claim 11 or 12, characterised thereby, that the clasp (59) is constructed to be substantially U-shaped with a base part (60) and two limbs (61, 62), that both limbs in the operative setting lie substantially parallel to the grate bar back and carry setscrews (63), serving as abutments and estending parallel to the outside rib (13') of the grate bar (1'), with conical projections (64), which bear against corresponding ramp surfaces (65, 66) at the inside of the outside rib (13') and that the base part (60) displays retaining eyelets (79), which carry a guide bolt (58), which is guided in an elongate slots (57) of a retaining strap (80) firmly connected with a boundary plate (78).

14. Grate covering according to claim 11 or 12, characterised thereby, that the clasp (70) consists of an angle member, the one limb (71) of which by an abutment (76) engages through the outside rib (13') of the grate bar (1') and the other limb (73) of which is guided in a retaining bracket (74) fastened to a boundary plate (78) to be displaceable perpendicularly to the grate bar back.

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