Note: Descriptions are shown in the official language in which they were submitted.
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Hydraulic drive for a sliding combustion grate
[0001] The invention pertains to a drive for water-cooled sliding combustion
grate
for refuse incineration plants which are especially suitable for burning of
refuse
and waste with high heating value. Such sliding combustion grates have fixed
and
movable grate stages made of grate plates or made of a row of grate bars in
which the grate plates are laid out on top of each other in a stairway
formation.
These combustion feed grates can be installed in such a way that the
combustion
lo bed basically lies horizontally or else inclined, whereby slopes of 20
angular
degrees or more are common. Grate plates are preferably made of steel sheets
and they form board-shaped hollow bodies which extend over the complete width
of the grate run. Water is channelled through these as a cooling medium. Every
second grate plate is movable and can therefore execute a sliding or feeding
stroke. When it concerns the feed grate, the movable grate plates can push the
incinerator charge to the next underlying grate plate with their rear side. On
the
other hand, a reverse feed grate forms a virtually inverted, integrated,
inclined
staircase with overlapping steps. In the case of a reverse feed grate, the
front
sides of the movable grate plates carry the incinerator charge lying behind
them
back, after which this is again milled downwards in the direction of the slope
of the
grate. The movable grate plates, i.e. the respective grate plates located
between
two fixed grate plates, are moved to and from in the drop direction of their
slope.
This ensures that the refuse burning on the grate is constantly relocated with
a
high retention time of 45 to 120 minutes and is equally distributed on the
grate.
[0002] European patent document, EP-0 621 449, discloses a water-cooled
sliding combustion grate. This grate has grate plates which stretch over the
complete width of the grate run and do not consist of multiple grate bars per
grate
stage. Like the stationary grate plates, the movable grate plates are fixed at
the
back to crossbars which collectively move forwards and backwards during
operation and hence move the movable grate plates. European patent document,
EP 0 874 195, shows a special construction of such a grate with individual
drives
for every single movable grate stage. Here the movable grate plates roll on
the
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steel rolls and are also laterally guided on the horizontal rolls along the
lateral end
planks. The drive is implemented with every hydraulic piston-cylinder unit
which
impinges on the grate plates approximately at the centre and which is located
directly under the grate plate.
[0003] The present drive construction is located under the grate, which means
the
associated hydraulic piston-cylinder units are also located underneath the
grate.
They are difficult to access there and are not accessible particularly during
the
operation of the grate due to the prevailing temperatures and due to possible
slag
falling through the grate.
[0004] The object of the present invention is therefore to create a hydraulic
drive
for a water-cooled sliding combustion grate which is particularly safe to
operate,
can be manufactured cost-effectively and can be easily mounted. Moreover, this
drive should be easier to maintain, in that it is accessible during the
combustion
operation and the hydraulic piston-cylinder units of the individual drives of
the
grate plates can be replaced without the need for interrupting the operation
of the
grate.
[0005] The objective is achieved by a hydraulic drive for a water-cooled
sliding
combustion grate in which every movable grate stage of the grate construction
is
connected to at least one connection rod supported at the other end thereof on
a
crank, wherein the associated crankshaft is supported in a bushing penetrating
the side wall of the grate construction and a crank connected to the piston of
a
hydraulic cylinder-piston unit is seated on the other side of the crankshaft.
[0006] First a sliding combustion grate with a conventional hydraulic drive is
illustrated in the drawings and then this special hydraulic drive is presented
here.
The drive and its functions are further described below with the help of these
drawings.
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It shows:
Figure 1: A sliding combustion grate in perspective view with partially
removed
grate plates;
Figure 2 A longitudinal section through the grate run, with a view
perpendicular to the grate run and the conventional hydraulic drive
integrated under it;
Figure 3: A cross-section through the framework of the grate and the
substructure of the grate without the grate plates, i.e. the grate as
shown in Figure 1 seen from the front;
Figure 4: The support members for integration between the two hollow profiles
along the grate, seen from front;
Figure 5: A movable grate plate seen from below;
Figure 6: A perspective, schematic representation of the hydraulic drive for
an
individual, movable grate plate according to the invention, seen
diagonally from above;
Figure 7: A cross-section through a grate run with this hydraulic drive
outside
the side wall for the grate plates located to the left in the figure;
Figure 8: A cross-section through two adjacent grate runs with the hydraulic
drive covered by means of the sheet metal casing as a protective
cover for the grate plates located on the left in the figure.
[0007] The basic construction of a sliding combustion grate with its important
members, how it is presented during the construction, where the individual
grate
plates are still missing and the view of the substructure are evident from
Figure 1.
Here it concerns a grate inclined downwards in the direction of flow. Two
vertical,
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lateral steel walls 1,2, parallel to one another, are connected stably to one
another
with distancing bars 3,4. These distancing bars 3,4 run perpendicular to the
grate
and extend across the inside width between the two vertical steel walls 1,2 at
two
different levels. Both the steel walls 1,2 to the left and right of the grate
can
thereby consist of multiple steel sheets or parts which are screwed to one
another
in a suitable manner. Distancing bars 3,4, threaded at both ends, penetrate
the
two vertical steel walls 1, 2 and are screwed tightly to the vertical steel
walls 1,2
by means of tapered ends and nuts. The top level of distancing bars or
crossbars
3 also serve as supporting rods for the stationary grate plates 5 lying on top
of
them. The front edge of the bottom stationary grate plate 5 abuts against a
discharge lip 7 welded in place between vertical steel walls 1,2, while its
rear
section is suspended over the first top distancing bar or crossbar 3. Next in
line is
a movable grate plate 6, the front bottom edge of which rests on the first
stationary grate plate 5 below. The front bottom edge of the next highest
stationary grate plate 5 rests in turn on movable grate plate 6 and so on. The
sloped front side of the individual grate plates 5,6 is perforated by primary
air slots
8, through which the primary air for the combustion is blown from below into
the
incinerator charge. Along the upper edge of steel walls 1,2 are two square
tubes
9,10 disposed on top of each other in a slightly offset manner, the lower ends
of
which are sealed by welding, in that they are welded there. These square tubes
9,10 constitute the side panels of the grate run and restrict the sides of the
incinerator charge bed when the grate is in operation. They are water-cooled
and
are forcibly flooded with water from bottom to top so that their insides are
always
completely filled with water. The individual grate plates 5,6 are made from
sheet
steel and are designed as hollow bodies that are forcibly flooded with water
so
that their insides are always completely filled with water and no air bubbles
can be
present inside. Alternatively, they consist of a support framework in which a
free-
flowing hollow body is inserted as a cooling body whereby this can then be
covered by a wear plate which is interlocked with the support framework and
the
cooling body to ensure good heat transfer. All the sheet steel parts of the
grate,
whether square tubes 8,9 or grate plates 5,6, that come into contact with the
incinerator charge are, therefore, continuously covered with water on the back
side of the steel sheet or at least cooled by a water-cooled heat sink. Hence
all
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the parts in contact with the fire are cooled continuously and kept at a
stable
temperature so that practically no dilatation occurs. This eliminates the need
to
provide compensating elements of any kind to the sides of the grate plates.
The
stability of the grate construction is essentially achieved by the distancing
bars or
crossbars 3,4, which strut and brace the two outer steel walls 1,2 on two
parallel
levels as already described. Between these two levels of crossbars 3,4,
running
along the grate on both sides of its centre are two other hollow profiles in
the form
of square tubes 11,12, which are connected at the bottom and at the top at
some
points to the crossbars 3,4, running perpendicular to them. One of the square
tubes, namely square tube 11, feeds the cooling water from bottom to top for
grate
plates 5,6, while the other square tube 12 supplies flushing and cooling air
for the
hydraulic components of the drive of the movable grate plates 6. Support
members 13 are installed for movable grate plates 6 between these two parallel-
running square tubes 11,12. These support members 13 are fixed to the square
tubes by two bolts that run through the two square tubes 11,12. For this
purpose,
the square tubes or hollow profiles 11,12 have welded-in crossbars with an
inside
diameter designed to accommodate the retaining bolts for the support members
13. The support members 13 themselves each have steel roll 16 disposed
parallel
to the corresponding grate plate plane, as well as a steel roll 17,18 to the
left and
right acting in the vertical plane. The movable grate plate 6 rolls off the
last and
the horizontal steel roll 16 serves as a lateral guide at the rear side of the
grate
plate 6. At the planks, i.e. at the square tubes 9,10, two horizontal steel
rolls 19,20
are constructed for every movable grate plate 6 and these rolls are laterally
guided into the plates from outside.
[0008] Figure 2 shows an area of the grate with the conventional drive of the
movable grate plate 6 as a longitudinal section seen from the side. The
hydraulic
cylinder 21, whose piston rods 22 reach the interior of the movable grate
stage 6,
can be recognised and the hydraulic cylinder 21 is hinged to a support member
13
with its rear side. At the rear, the grate plate 6 rolls off on the rolls 17
of the
support member 13 which is fixed to the square tubes 11,12 by means of both
bolts 14,15. Each of these support members 13 can be tilted backwards by
removing the rear bolt 14 after which the pivot point of the hydraulic
cylinder 21 is
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accessible and this can be readily dismantled. That can however take place
only
after decommissioning of the grate. The square tube 10 can be recognised
behind
the grate plates 5,6 which forms the lateral plank and below the side wall 2
with
the crossbars 4.
[0009] In the case of constructions till now, the hydraulic drive is located
directly
under the grate plates as shown in Figure 2 and that is now eliminated to
eliminate any fire hazard under the grate. The hydraulic cylinder 21 with
piston rod
22 is newly replaced by a mechanical connection rod which is hinged to a crank
and the associated crankshaft is inserted externally through one of the side
walls
1,2, so that the hydraulic components are completely obstructed outside the
grate
construction as illustrated subsequently.
[0010] Figure 3 shows a cross-section through the grate framework and the
grate
substructure without grate plates as shown in Figure 1, seen from the front.
The
side walls 1,2, the planks in the form of square tubes 9,10 as well as the
crossbars 3,4 and the square tubes 11,12 in the middle extending along the
grate
can be recognised here. A single support member 13 as seen from the front is
illustrated in Figure 4 with the horizontal steel roll 16 for the horizontal
guidance of
the movable grate plate 6 as well as with the vertical steel rolls 17,18 for
the
carrying the movable grate plate 6.
[0011] Figure 5 shows a single grate plate 6 or a support framework seen from
below. The horizontal steel roll 16 lies in the recess 23 at the support
member 13.
The inside width of the recess 23 is chosen in such a way that it is slightly
larger
than the diameter of the horizontal steel roll 16 through which the grate
plate is
guided adequately in a transverse direction from the roll 16 to the grate run.
The
steel rolls 19,20 (Figure 1) located at the planks 9,10 serve to guide the
front side
of the movable grate plate. The movable grate plate 6 has such recesses 24,25
at
the bottom of its front side that it has a guiding area 26,27 on each of its
sides,
which runs parallel to the lateral surface of the grate plate 6, but it is
repositioned
against this surface. These steel rolls 19,20 roll off along this guiding area
during
inside and outside movement. Thereby every movable grate plate 6 effectively
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has a three-point bearing. At the centre back where the drive is located, the
grate
plate 6 is guided horizontally and vertically by the corresponding steel rolls
16,17,18 and at the front it is guided laterally to the left and right of the
steel rolls
19,20 when the front bottom edge of the grate rests on the next stationary
grate
plate 5 that is lower and slides on it when moved back and forth.
[0012] The hydraulic cylinder 21 and its hydraulic lines are present directly
underneath the grate according to the construction as per the Figures 1 and 2
as
described previously and all parts are exposed to the downdraught which can
have an abrasive effect over the years. The aim of the drive construction
presented subsequently is to specify an alternative construction in which only
heavy mechanical parts of the drive construction, which themselves do not have
any other parts, are exposed to the abrasive effect of the downdraught and
simultaneously locate drive parts that are sensitive to it outside the grate.
[0012] Figure 6 shows this hydraulic drive for an individual movable grate
plate 6
illustrated schematically as seen diagonally from above. The hydraulic
cylinder
under the grate plate is replaced by only a connection rod 30 which is hinged
to a
crank 31 which in turn sits on a crankshaft 32. The crank 31 has a slotted
hole 38
in which the bolts 39 of the connection rod 30 are mounted because the
connection rod 30 must move back and forth linearly in the direction of its
course
as shown with a double arrow when the crank 31 pivots back and forth angularly
and consequently its end does not carry out a linear motion. The crankshaft 32
is
supported in a bushing 33 which penetrates the side wall 2 of the grate
construction and is stably welded or screwed to this. On the outside of the
grate
construction, the crankshaft 32 is equipped with another crank 34 which is
hinged
to the end of a piston rod 35 of a hydraulic cylinder 36.
The cranks 31,34 can be simply plugged in at the crankshaft ends and can be
secured with a lock nut. With its other end, the hydraulic cylinder 36 is
hinged to a
retaining bracket 37 which is fixed to the outside of the side wall 2 of the
grate
construction. The axle of the bushing 33 runs at a right angle to the
direction of
motion of the movable grate plate 6 and the crank 31 for the connection rod 30
at
the crankshaft 32 can be mounted to the crank 34 at the other end of the
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crankshaft 32 by turning and swivelling by approx. 1200 to 180 . When the
crank
34 is actuated at this other end of the crankshaft 32 and the crankshaft 32 is
turned correspondingly, the movable grate plate 6 is accordingly moved forward
and backwards as with the forward and backward movements of the piston 35 by
means of the hydraulic cylinder-piston unit 36. The crankshaft 32 can be
turned by
0 to approx 60 by means of systematic controlling of the hydraulic piston-
cylinder
unit 35,36 so that the degree of thrust of the movable plate 6 can be
continuously
varied.
[0013] The hydraulic components are situated further away from the grate with
this drive construction and are no more directly beneath the grate. Every
single
movable grate stage can be operated individually in this way via its own
hydraulic
cylinder-piston unit which is fixed to its side wall 2 on the outside of the
grate
construction.
[0014] A cross-section through the grate run with a view of the rear in the
direction
of motion of the movable grate plate 6 is shown in Figure 7. A connection rod
30 is
hinged to a recess at the bottom of the grate plate 6. The connection rod 30
is
flexibly connected to the crank 31 which is at the bottom of the crankshaft 32
via
the bolts 39. The crankshaft 32 is supported in the bushing 33 by means of the
replaceable slide bearing 40. The bushing is stably connected to the side wall
1 of
the grate construction 2 via the vane struts 41. These vane struts 41 are
integrated with the corresponding recesses in the side wall 1 or 2 of the
grate
construction and are welded to them. The drive is present on the other side,
of
which the crank 34 and the piston rod 35 are illustrated in a section here.
[0014] Figure 8 shows a solution for a drive when multiple grate runs 28,29
are
located next to each other. The water supply lines for the grate plates 6
should
therefore be indicated with 43 and the water discharge pipes of the grate
plate
marked on the right side should be indicated with 44. The hydraulic cylinder
36 of
this drive described above is located completely outside the first grate run
28, but
however lies under the grate plate 6 of the grate run 29 connected on this
side of
the grate. In this case it is however ensured that the hydraulic cylinder 36
is
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located further away from the grate plates 6 than the solution described
previously
and in the beginning. Moreover, the hydraulic cylinder 36 and its hydraulic
feed
and drainage pipes are surrounded by a steel casing 42 so that it is
completely
covered from above and only its piston rod protrudes at the side from a hole
in the
sheet-metal case 42. So it protrudes backwards from the sheet-metal case in
Figure 8 and consequently actuates the crank 34.
[0015] It is clear that such a drive, as shown for every single, movable grate
plate
6, can be provided in duplicate execution and with a piston-cylinder unit at
every
side of the grate run. It is further possible to design all the grate plates
of a grate
as movable plates. The piston-cylinder units can also eventually be located in
another mounting direction according to the space conditions. The individual
hydraulic cylinders can also be arranged in a staircase manner over one
another
and mounted on the outside of the side wall. In the case of vertically
arranged
cylinders, the cranks at the crankshaft must be rotated by 900. In the case of
cylinders tilted at an angle of 45 , they should correspondingly be rotated by
45
opposite to the execution shown in the figures. To gain some space, multiple
alignments can also be chosen interchangeably.
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