Abstrict An owl-mill crusher with stationary grinding rollers (6) inside
a housing (1) that roll over a grinding bowl (3) resting on a rotating
grinding-bowl support (5). An air box (8) is provided below the
grinding bowl (3). A circular-conical disk (17) is secured to the
grinding-bowl support (5) with its outer edge pointing down. A stationary
cleanout arm (24) is positioned above the disk (17) with one end
extending into the extraction shaft (20) of the removal container
(21), which is mounted on the side of the housing. Several blades
(25) are secured to the bottom of the disk.
Claims We claim:
1. A bowl-mill crusher comprising: a housing having a top and a
bottom; stationary grinding rollers inside said housing; a grinding
bowl inside said housing, said grinding rollers rolling over said
grinding bowl; a rotating grinding bowl support for supporting said
grinding bowl; an air box at the bottom of said housing and beneath
said grinding bowl; an extraction shaft extending laterally from
said air box; a removal container coupled to said extraction shaft;
cleanout means coupled to said grinding bowl support and comprising:
a circular-conical disk secured to said grinding bowl support and
having an outer edge pointing downwardly, and a stationary cleanout
arm positioned above said disk and having an end extending into
said extraction shaft coupled to said removal container.
2. A bowl-mill crusher as defined in claim 1 including a plurality
of blades secured to the bottom of said circular-conical disk and
having inner ends preceding outer ends of said blades along a direction
of rotation of said grinding bowl and said grinding bowl support.
3. A bowl-mill crusher as defined in claim 1 including a barrier-air
housing surrounding said grinding-bowl support; and exit means from
said barrier-air housing in said air box and below said circular-conical
disk.
4. A bowl-mill crusher as defined in claim 3 wherein said air
box has a bottom, barrier air flowing out of said barrier-air housing
and combining with a stream of air genrated by said blades to produce
a stream cooling the bottom of said air box.
Description BACKGROUND OF THE INVENTION
The cleanout mechanism in a known bowl-mill crusher (Au-fbereitungs-Technik
12 [1971], 9 542-43) consists of two arms secured to the grinding-bowl
support that sweep over the horizontal bottom of the air box at
each revolution. Coarse material that arrives in the air box from
the grinding area by way of the nozzle ring is emptied into the
removal container through an extraction opening in the bottom of
the air box. To protect the cleanout arms from damage or destruction
by coarse particles, the arms are loosely articulated to the grinding-bowl
support and can roll over the particles. An articulation of this
type is subject to malfunction. Furthermore, larger quantities of
ground material arrive in the air box from the grinding area when
the supply of air to the grinder is suddenly discontinued in the
event of an emergency turnoff. The known cleanout arms, which sweep
the horizontal bottom of the air box, are then no longer able to
remove the ground material out of the air box rapidly enough.
SUMMARY OF THE INVENTION
The object of the invention is to improve the cleanout mechanism
of the generic bowl-mill crusher to the extent that it will be less
subject to malfunction and that the material will be removed from
the air box more rapidly.
According to the present invention circular-conical disk diverts
the material that arrives in the air box from the grinding area
through the nozzle ring outward by centrifugal force, whence it
is conveyed farther on into the extraction shaft outside of the
bowl housing and into the removal container by way of the cleanout
arms. This system ensures rapid cleanout of the air box. Eliminating
the free articulation of the arms makes it less subject to malfunction.
The bottom of the bowl is simultaneously protected by the disk against
the impact of hot air and is accordingly less thermally stressed
because the space between the disk and the bottom is subjected to
barrier air.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be specified with reference
to the drawing, wherein
FIG. 1 is a longitudinal section through a bowl-mill crusher,
FIG. 2 illustrates the detail Z in FIG. 1 and
FIG. 3 is a section along the line III--III in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The bowl-mill crusher has a housing 1 through which extends a
riser 2 that supplies crude coal. Inside housing 1 is a rotating
horizontal grinding bowl 3 that is driven by an unillustrated motor
by way of a transmission 4. Grinding bowl 3 which is composed of
several segments although it can also be in one piece, is connected
to transmission 4 by way of a grinding-bowl support 5. Rigidly mounted
grinding rollers 6 roll over grinding bowl 3. Grinding rollers 6
are supported on a frame 26 that is resiliently tensioned against
the base 27 of the crusher by way of rods 7. This tensioning mechanism
resiliently forces grinding rollers 6 against grinding bowl 3.
At the bottom of housing 1 and below grinding bowl 3 is an air
box 8 that is provided with an air-supply connection 9. The bottom
of air box 8 is closed off by a horizontal bottom 10 and communicates
with a grinding area 13 inside housing 1 through a nozzle ring 14.
Mounted on housing 1 is a separator 15 into which there extends
a dust-exit line 16. A drying and conveying gas in the form of hot
air is introduced into air box 8 through air-supply connection 9.
The air flows through nozzle ring 14 and into grinding area 13
picks up the coal dust produced by grinding rollers 6 against grinding
bowl 3 and conveys it out by way of separator 15 and dust-exit
line 16.
Material that cannot be ground, foreign bodies for example, can
enter air box 8 through nozzle ring 14 and must be removed therefrom.
When the grinder must be shut down in the event of an emergency
due to a sudden interruption in the supply of air, some of the coal
dust in grinding area 13 will drop into air box 8. Since air box
8 is hot from the hot air, there is a risk of the coal dust igniting
if it is not removed rapidly enough.
The cleanout mechanism that will now be specified will remove foreign
bodies and, if necessary, coal dust. Secured to grinding-bowl support
5 and below grinding bowl 3 is a circular-conical disk 17 the outer
edge of which points down and extends almost to the wall of housing
1. Circular-conical disk 17 rotates with grinding-bowl support 5
in the direction indicated by arrow 18. At the level of circular-conical
disk 17 housing 1 is provided with an extraction opening 19 the
lower surface of which merges into the bottom 10 of air box 8. Extending
out of extraction opening 19 is an extraction shaft 20 that rests
on a preferably cylindrical removal container 21. Removal container
21 has a slide 22 at its entrance and an extraction opening 23
which can be closed off, at the bottom.
Above circular-conical disk 17 is a stationary cleanout arm 24
one end of which extends into extraction shaft 20 and is secured
to the wall of extraction shaft 20. The inner end of stationary
cleanout arm 24 points opposite the direction that circular-conical
disk 17 rotates in. The lower edge of stationary cleanout arm 24
slopes along with circular-conical disk 17 and faces it at a variable
distance.
Secured to the bottom of disk 17 are several blades 25. The outer
edge of blades 25 extends beyond the outer margin of disk 17. The
inner end of blades 25 precedes the outer end along the direction
that disk 17 rotates in. During one rotation of disk 17 blades
25 generate an outward flow of air that cools the bottom 10 of air
box 8.
The material that arrives in air box 8 from grinding area 13 through
nozzle ring 14 slides down and out due to the sloping surface and
to the centrifugal force and is scraped off disk 17 and diverted
into extraction shaft 20 by cleanout arm 24. The portion of material
that arrives on the bottom 10 of air box 8 by way of the margin
of disk I7 is picked up by blades 25 and also conveyed into extraction
shaft 20.
The rotating grinding-bowl support 5 is sealed off from the stationary
air box 8 by a barrier-air housing -2 provided with a barrier-air
connection 11. Barrier-air housing 12 is secured to the bottom 10
of air box 8 and surrounds grinding-bowl support 5 creating a barrier-air
chamber. The barrier air that is supplied to the barrier-air chamber
through barrier-air connection 11 enters air box 8 below disk 17
and is forced outward by the air box. This intentional outflow of
barrier air supports the flow of air generated by blades 25 to cool
bottom 10.
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