Furnace grate structure

A furnace grate structure for a furnace or incinerator on which solid fuel advances in an advancing direction has at least two parallel grate beams extending substantially transversely to the advancing direction, the beams being mounted on a substructure and forming upwardly facing support structures. The grate beams form grate beam sections with gaps formed between the end surfaces of adjacent grate beam sections. The gaps are covered by a covering device and a recess is provided in the end surfaces of the grate beam sections to receive the covering device.

BACKGROUND OF THE INVENTION 
The present invention relates to a furnace grate structure over which solid 
fuel advances in a direction of conveyance as the fuel is combusted, and 
more particularly to a furnace grate structure having a plurality of grate 
beams extending substantially parallel to one another and substantially 
transversely to the direction of conveyance, with the grate beams being 
supported on a substructure. 
At least one bank of elongated grate bars of the furnace grate structure 
extend substantially parallel to the direction of conveyance in spaced 
relation to each other. Upwardly facing support surfaces of the grate bars 
are inclined downwardly in said direction of conveyance for conveying the 
solid fuel. Each of the bars is supported at each end thereof on a 
mounting surface of a respective grate beam, such that some of grate bars 
are reciprocatingly movable in a substantially horizontal direction and 
the other grate bars are stationary. 
By means of the fact that several banks of grate bars can be arranged one 
behind the other like steps, the grate structure is thereby subdivided. A 
particularly beneficial and adaptable stirring effect is achieved when 
some of the grate bars are moved back and forth in a substantially 
horizontal direction. By regulating the grate movement in the individual 
banks of grate bars, inclined grate structures of this type can be adapted 
to the characteristics of various fuels. 
Because of the high thermal loads to which such inclined grate structures 
are subjected, the grate beams serve primarily as a framework to support 
the grate bars on the substructure which is made of steel and cannot 
withstand the thermal loads. For this reason, the grate beams generally 
consist of a grey cast iron that can withstand the thermal loads. 
A furnace grate structure of this type is described in U.S. Pat. No. 
4,638,905, assigned to the same assignee as the present invention, where 
at least one of the grate beams comprises a plurality of grate beam 
sections, which are arranged end to end on said substructure to form a 
grate beam having gaps between adjacent grate beam sections. 
According to the U.S. Pat. No. 4,638,905, keyed engagement means are 
provided on said grate beam sections for guiding and laterally positioning 
the reciprocatingly movable and said stationary grate bars such that each 
of the gaps between the adjacent ends of said grate beam sections are 
covered by preferably stationary grate bars. 
In the preferred embodiment of the afore-mentioned patent, the gaps between 
the adjacent grate beam sections are covered by stationary grate bars in 
which each of the shortest grate beam sections supports two stationary 
grate bars partly for covering the gap between the adjacent grate beam 
sections and between the stationary grate bars one grate bar being 
reciprocatingly movable parallel to the direction of conveyance. 
In said known inclined grate, the lateral arrangement o the grate bars 
mounted on the grate beams is fixed because the separating gaps between 
the adjacent grate beam sections must be covered by the stationarily 
mounted grate bars. 
Furthermore, in the known inclined grate, every grate beam section must be 
capable of supporting two stationary grate bars partly and between them at 
least one reciprocating grate bar, thus limiting the shortest length of 
each grate beam section and the flexibility of the furnace grate 
structure. 
Finally, because of the displaced arrangement of the grate bars on the 
grate beam sections in the known inclined grate, special and different end 
sections for abutment against the side walls of the furnace chamber are 
necessary, so that it is always necessary to provide three different 
shapes of grate beam sections for a variable-length grate beam. 
SUMMARY AND OBJECTS OF THE INVENTION 
In view of the foregoing limitations and shortcomings of the prior art 
devices, as well as other disadvantages not specifically mentioned above, 
it should be apparent that there exists a need in the art for an improved 
furnace grate structure. It is, therefore a primary object of this 
invention to fulfill that need by providing a furnace grate structure in 
which the length of the grate beam sections is independent of the grate 
bars so that grate bar sections of an optionally short length are 
possible. 
More particularly, it is an object of this invention to provide a covering 
of the gaps between the adjacent ends of the grate beam sections 
independently from the grate bars. 
It is another object of the invention to provide a recess in at least one 
endface of at least one grate beam section for receiving a covering means 
for covering the adjacent gaps. 
Briefly described, the aforementioned objects are accomplished according to 
the invention by providing a projection of an adjacent grate beam section 
or a separate strip to cover the gap between adjacent sections. This has 
the advantage over the known inclined grate, which has grate beam sections 
that support the horizontally movable as well as the stationarily mounted 
grate beams, that the separating gaps no longer need to be covered by the 
stationarily mounted grate bars, so that the grate bars mounted on the 
grate beams can be arranged in any desired manner laterally to the 
direction of conveyance. Accordingly, it is also possible to select an 
arrangement in which each grate beam section supports only one grate bar, 
or in which one grate bar is mounted on several adjacent grate beam 
sections. In this manner the smallest possible units of identical grate 
beam sections can be realized, which, when lined up, form grate beams 
whose lengths can be optimally adapted for installation in whatever 
furnace chamber is provided. 
In this manner it can also be achieved that, in contrast to the known 
inclined grate, every second grate bar mounted on the grate beam no longer 
need be capable of reciprocating horizontally, but rather that, depending 
on the individual circumstances of use, grate bars that can be moved on 
the grate beam and those that are stationarily mounted can be lined up 
together in any desired manner. Accordingly, for example, a row of 
adjacent grate bars can be provided on the grate beam in which only every 
third grate bar is stationarily mounted. 
The recesses to receive the covering means can be upwardly open. It is also 
possible for a grate beam section to have a recess in each of its two end 
surfaces. In this manner it can be provided that these recesses are 
arranged at the same elevation in the two end surfaces of each grate beam 
section, so that facing end surfaces of grate beam sections of this type 
form a channel, which can be upwardly either closed or open, serving to 
receive a strip serving as the covering means. This has the advantage that 
a particularly suitable material, such as a ceramic, can be used for the 
strip, which does not have to be the same material as that used for the 
grate beam sections. In case of a material defect, the strips are 
especially easy to replace, without it being necessary to disassemble the 
inclined grate, because the strips can simply be set or slid into place 
and can be removed just as easily. 
Because of the displaced arrangement of the grate bars on the grate beam 
sections in the known inclined grate, special and different end sections 
for abutment against the side walls of the furnace chamber are necessary, 
so that there are always necessary three different shapes of grate beam 
sections for a variable-length grate beam. In the inclined grate according 
to the invention, in which the recesses are provided at the same elevation 
in both end surfaces of the grate beam section, the grate beam 
cross-section is symmetrical relative to its center plane running parallel 
and vertical to the direction of conveyance. This has the advantage that 
special end sections facing the side walls of the furnace chamber are 
unnecessary, so that different lengths of grate beams can be assembled 
from completely identical grate beam sections. 
Detachable securing devices, such as screw connections or the like, can be 
provided to connect the covering devices with the grate beam sections. 
However, the securing devices can also be formed by an interlock bar 
provided on the covering means, which interlock bar prevents a relative 
horizontal shifting movement between the covering means and the grate beam 
not connected with the securing device. 
If upwardly open recesses are provided in the two end surfaces of a grate 
beam section, projections from respective adjacent grate beam sections, 
each of which has an interlock bar as a securing device which engages in 
the adjacent grate beam section, can engage in these recesses. The shape 
of these projections is adapted to that of the recesses and the 
projections serve as covering means. With this arrangement, the grate beam 
sections lying between the grate beam sections having the upwardly open 
recesses, can easily be set down into place and secured against horizontal 
shifting by means of the securing device. 
In addition, for the mounting of the horizontally movable or fixed grate 
bars on the grate beam sections, the covering means can form ribs on the 
upper side of the grate beam sections, which ribs engage in cutouts in the 
grate bars, so that the covering means and the ribs form a single 
structural element. 
With grate beam sections having two mounting surfaces successively arranged 
in the direction of conveyance for the mounting of the grate bars, the 
mounting surfaces lying downstream in the direction of conveyance are 
arranged lower than the mounting surfaces lying upstream. 
In this manner it can be provided that at least one end surface of at least 
one grate beam section includes two recesses to receive covering means 
which are arranged at different elevations and extend in such a manner 
that the covering means engaging therein cover the gap between the grate 
beam sections, whereby the recesses, which can also be upwardly open, 
border the mounting surfaces. 
With the foregoing and other objects, advantages and features of the 
invention that will become hereinafter apparent, the nature of the 
invention may be more clearly understood by reference to the following 
detailed description of the invention, the appended claims and to the 
several views illustrated in the attached drawings.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring now in detail to the drawings, the known inclined grate 
illustrated in FIG. 1, which is arranged in a furnace chamber illustrated 
in section, includes a lower frame, designated generally with numeral 3, 
having support rails 2 arranged in pairs. A grate beam 4 is mounted on 
each pair of support rails 2, which grate beam 4 extends essentially 
horizontally and perpendicular to the conveyance direction of the fuel 
(not illustrated) indicated in FIG. 1 by the arrow 1. The ends 11, 12 of 
horizontally movable grate bars 5 and solid grate bars 6 which are not 
visible in FIG. 1 are mounted on the grate beams 4. 
As can be seen from FIG. 2, the grate beam 4 in the first exemplary 
embodiment made in accordance with the invention is illustrated as having 
four grate beam sections 7, which are arranged in a straight line with 
abutting end surfaces 30. Each grate beam section is essentially the same 
length as the width of a grate bar 5 or 6. 
Each of the grate beam sections 7 illustrated in FIG. 2 has two mounting 
surfaces 8b and 8a successively arranged in the direction of conveyance, 
and these mounting surfaces 8b and 8a serve for the mounting of the ends 
11 and 12 of the grate beams 5 or 6 arranged upstream or downstram in the 
direction of conveyance. The mounting surfaces 8a lying downstream in the 
direction of conveyance lie lower than the mounting surfaces 8b. Ribs 9a 
and 9b, which extend parallel to the direction of conveyance over the 
entire width of the respective guide surfaces 8a and 8b are provided to 
guide and hold the horizontally movable and stationarily mounted grate 
bars 5, 6 on the mounting surface. Accordingly, as can be seen in FIG. 3, 
the grate bar 6 is rigidly connected with the grate beam section 7. For 
this purpose, the higher end 12 of the stationary grate bar 6, which end 
points opposite to the direction of conveyance, extends into a hollow 
chamber 14 of the grate beam section 7 through an opening 13 provided for 
this end 12 of the grate bar 6. The hollow chamber 14 is connected to the 
outside air for ventilation by means of a lower opening 15 and a rear slot 
16, whereby outer and inner cooling ribs 17 and 18 are provided for the 
cooling of the grate beam section 7. The lower opening 15 is laterally 
bounded by two side walls 21 running parallel to the direction of 
conveyance (FIG. 4). The outer sides of these side walls 21 opposite the 
lower opening 15 lie in a plane with the two end surfaces 30 of the grate 
beam section 7. 
To lock the upstream ends 12 of the fixed grate bars 6 together with the 
grate beam sections 7, hook-like projections 19 are provided on the grate 
beam sections 7 into which corresponding pins 20 of the fixed grate bars 6 
engage (FIG. 3). These pins 20 are absent in the horizontally movable 
grate bars 5. 
To lock the downstream ends 11 of the fixed grate bars 6, a rod 25 (FIG. 3) 
engages beneath a lug 26 on the grate beam section 7, so that the ends 11 
of the fixed grate bars 6 supported on the mounting surface 8b of the 
grate beam sections 7 cannot lift away from the grate beam sections 7. In 
a known manner, (not shown) the movable grate bars 5 are connected with 
the immediately adjacent fixed grate bars 6 in a vertical plane parallel 
to the direction of conveyance in such a manner as to be essentially 
capable of horizontal movement but incapable of being lifted away. 
In a known manner as shown in FIG. 1, the horizontally movable grate bars 5 
are driven by one or more drive means 35 and/or 36 by means of carriers 33 
and 34. 
As can be seen particularly in FIGS. 2 and 4, grate beams 4 of any desired 
length can be assembled from the grate beam sections 7. To do so, one need 
only line up the desired number of grate beam sections 7. 
As shown particularly in FIG. 4, the abutting end surfaces 30 of the grate 
beam sections 7 form gaps 27. In order to prevent hot fuel particles from 
falling onto the lower frame 3 through the respective gaps 27, it is 
provided, as shown in FIG. 4, that a horizontally running covering means 
extending over the entire width of the grate beam section 7 and formed on 
one end surface 30 of the grate beam section 7 as a projection 32 engages 
into the cut-out 34 formed in an adjoining end surface 30 of the adjacent 
grate beam section 7. This cut-out 34 is essentially adapted to the shape 
of the projection 32. 
As can be seen in FIG. 4, in the first exemplary embodiment with an 
extended series of grate beams sections 7, in order to adapt the grate 
beam 4 to the inner size of the furnace chamber, the projection 32 shown 
at the left side in FIG. 4 abuts the side wall of the furnace chamber. 
However, if it is desired the fuel particles should rest on this 
projection 32, since the projection 32 is not covered by a grate bar 5 or 
6, then a separate end section (not shown) must be provided on the left 
side of the arrangement according to FIG. 4 viewed in the direction of 
conveyance, which end section has no projection 32 on its left end surface 
30. The left end surface of this end section, as viewed in the direction 
of conveyance, together with the left side surface of the grate bar 
mounted thereon, abuts the side wall of the furnace chamber. 
In an embodiment that is slightly modified from the first exemplary 
embodiment, the side walls of the furnace chamber are formed in such a 
manner that in an arrangement according to FIG. 4, the left side wall of 
the furnace chamber, viewed in the direction of conveyance, has a cut-out 
34 which is adapted to the projection 32 of the extreme left grate beam 
section 7, while the right side wall of the furnace chamber, viewed in the 
direction of conveyance, has a projection adapted to the cut-out 34 of the 
extreme right grate beam section 7. The left and right end surfaces 30 of 
the extreme left and right grate beam sections 7 of the grate beam 4 
thereby abut the side walls of the furnace chamber. 
In order to secure the grate beam sections 7 against undesired horizontal 
shifting relative to the lower frame 3, it is provided that the grate beam 
sections 7 are connected to the support rails 2 by four screws 28 (FIG. 
2), which engage in bores 29 (FIG. 3). In the first exemplary embodiment, 
the projection 32, which extends horizontally over the entire width of the 
grate beam 7, can be provided on both end surfaces 30 of the grate beam 
section 7. In this version of the first exemplary embodiment, however, it 
is necessary that the two end surfaces 30 of adjacent grate beam sections 
7 have cut-outs 34 adapted to the shape of the projections 32. In this 
version of the first exemplary embodiment, special end sections or 
adaptations of the side walls of the furnace chamber can be completely 
eliminated, if the grate beam sections 7 having the cut-outs 34 form the 
extreme right and left grate beam sections 7 abutting the side walls of 
the furnace chamber. 
In the illustrations of the following exemplary embodiments in FIGS. 5 
through 13, the elements corresponding to the first exemplary embodiment 
according to FIGS. 1 through 4, are designated with reference numerals 
increased by 100, so that by the use of these reference numerals, 
reference can be made to the description of the exemplary embodiment 
according to FIGS. 1 through 4. 
In the exemplary embodiments shown in FIGS. 5 through 9, the horizontal 
recesses extending over the entire width of the grate beam sections on 
both end surfaces of each grate beam section are provided at the same 
elevation and are upwardly closed. If the end surfaces abut each other in 
grate beam sections of this type, the adjacent recesses form a channel 
that is upwardly closed and is provided for the reception of a strip 
serving as a covering means. A particularly suitable material, such as a 
ceramic or the like, is used for this strip. In order to prevent the 
strips from sliding out of the channels, the strips have detachable 
holding devices for connecting the strips with the grate beam sections. 
In the second exemplary embodiment shown in FIGS. 5 and 6, the strip 132 
has a flange element 140 at one of its ends as a holding device. This 
flange element 140 is connected with the two side surfaces of the grate 
beam sections 107 by means of a screw connection. 
In the third exemplary embodiment shown in FIG. 7, as a holding device, the 
strip 232 has at each end a downwardly extending projection to form an 
interlock bar 237. Each pair of interlock bars 237 produced in this manner 
form, on the facing sides thereof, stop surfaces 238, which, when the 
strip 232 is placed in the channel, rest against the side surfaces of two 
adjacent grate beam sections 207 with a degree of play. In order to be 
able to slide such a strip 232 into or out of the channel, it is provided 
that the vertical height H of the channel is somewhat larger than the 
vertical total height h of the combined strip 232 and interlock bar 237. 
In the fourth exemplary embodiment illustrated in FIG. 8, the strip 332 has 
as a holding device an interlock bar 337 on one of its side surfaces. When 
the strip 332 is pushed into the channel, this interlock bar 337 
form-fittingly engages in a cut-out 339 which is adapted to the shape of 
the interlock bar 337 and is arranged on one side surface of the recess 
344. Also in the fourth exemplary embodiment it is necessary for the 
installation and removal of the strip 332, that the channel has an 
adequate height, as described above relative to the third exemplary 
embodiment. In addition, the horizontal width B of the portion of the 
channel in which the strip 332 is inserted or removed must be at least as 
large as the horizontal width b of the combined strip 332 and interlock 
bar 337. 
In the fifth exemplary embodiment illustrated in FIG. 9, the interlock ba 
437 which serves as the holding device is arranged on a lower side surface 
of the strip 432. This interlock bar 437, when the strip 432 is pushed 
into the channel, engages in a cut-out 439 adapted to its shape, which 
cut-out 439 is provided in a lower side surface of the recess 434. 
In the sixth exemplary embodiment illustrated in FIGS. 10, 11 and 12, the 
two end surfaces of the outer grate beam sections 607 each have two 
upwardly open recesses 634a and 634b, which, as viewed from above, 
overlappingly extend over the entire width of the grate beam 604 at 
different elevations (FIGS. 10 and 11). The recesses 634a and 634b extend 
horizontally over the entire width of the mounting surfaces 608a and 608b. 
Projections 632a and 632b of the grate beam section 607 are adapted to the 
shape and height elevation of these recesses and engage in these recesses 
of the grate beam section 607 lying therebetween. As shown in FIG. 10, the 
two outer grate beam sections 607 are connected with the lower frame 603 
by means of the above-described screw connections 628. The center grate 
beam section 607 is only suspended between the adjacent grate beam 
sections 607. In order to hold the center grate beam section 607 so that 
it essentially cannot move horizontally between the adjacent grate beam 
sections 607, respective interlock bars 637 are provided on the ends of 
the projections 632 for abutment against the opposing side surfaces of the 
adjacent grate beam sections 607. 
In a modified embodiment (not shown) of the sixth exemplary embodiment, two 
upwardly open recesses are provided on the two end surfaces of each grate 
beam section, which recesses, as described above with regard to the sixth 
exemplary embodiment, are provided at different elevations and extend over 
the entire width of the grate beam when viewed from above. 
Aligned grate beam sections of this type form upwardly open channels. To 
cover the gaps between the grate beam sections, strips adapted to the 
shape of these channels are placed therein in such a manner that their 
upper side surfaces lie in a horizontal plane with the mounting surfaces 
of the grate beam sections. The embodiments of strips shown in the 
exemplary embodiments 2 through 5, for example, can be used for this 
purpose. 
All embodiments of the first through fifth exemplary embodiments can also 
be used in the sixth exemplary embodiment, if the recesses in the grate 
beam sections are closed upwardly, rather than open. 
In the seventh exemplary embodiment illustrated in FIG. 13, the downstream 
lower-lying side surface of each grate beam section 707 has a half 719a 
and 719b of the hook-like projection 719 next to its two end surfaces, and 
the upstream higher-lying side surfaces thereof each has a half 726a and 
726b of the nub 726 next to its two end surfaces 730. If the grate beam 
sections 706 in an assembled grate beam 704 abut each other, then the 
adjacent halves form the hook-like projections 719 and the nubs 726. The 
two end surfaces 730 of each grate beam section 707 each have two upwardly 
open recesses 734a and 734b, which, as viewed from above, overlappingly 
extend over the entire width of the grate beam 707 at different elevations 
(FIG. 13). In the assembled grate beam 704, the adjacent recesses 734a and 
734b form two channels arranged one behind the other in the direction of 
conveyance. Strips 732a and 732b engage in these channels as covering 
means, which strips project above the mounting surfaces 708a and 708 b and 
form ribs to hold or guide the grate bars 706 and 705. 
The strips 732a and 732b thereby are connected with the grate beam sections 
707 in a manner described relative to the previous exemplary embodiments, 
for example by means of screws. 
All of the exemplary embodiments described above can also be realized in 
grate beam sections having only one instead of two mounting surfaces. 
Grate beam sections of this type having only one mounting surface also are 
appropriate at the two ends of an inclined grate when the inclined grate 
has only two grate beams and one row of grate beams lying therebetween. 
In addition, the recesses and the associated covering means in all of the 
exemplary embodiments do not need to run precisely horizontally. The 
decisive factor is that they cover the gaps and thus prevent hot fuel from 
falling onto the lower frame. 
Although only preferred embodiments are specifically illustrated and 
described herein, it will be appreciated that many modifications and 
variations of the present invention are possible in light of the above 
teachings and within the purview of the appended claims without departing 
from the spirit and intended scope of the invention.