Note: Descriptions are shown in the official language in which they were submitted.
~0~3394
This invention relates to an apparatus for depositing
loose particulate solid material in a pile comprisin~ a dis-
charge pipe having an outlet end the position of which is var-
iable, e.g. in a vertical and/or lateral sense, by means of a
positioning device.
On unloading loose particulate solid material, such
as coal, ores, stones, etc. one usually encounters great diffi-
culties as the material generates clouds of dust, and one has
sometimes tried to solve these problems with the aid of tele-
10 scoping discharge pipes through which the loose particulate '
material is conducted from e.g. the discharge end of a conveyor
belt to a pile located below said end. The telescoping discharge
pipe is usually shortened according as the height of the pile
increases. Problems may be encountered with this type of un-
loading apparatus, especially if the amount of material fed
per unit of time to the upper inflow end of the discharge pipe
varies and especially if it is not possible or desired for some
reason to stop the feed device, for instance a conveyor belt,
or lower the speed thereof. It has therefore been necessary to
give the discharge pipe excessive dimensions so that it can re-
ceive the largest amount of material calculated per unit of time.
In normal operation the discharge pipe will therefore be only
incompletely filled with particulate material, which sometimes
results in an increased dust formation at the discharge end.
Dust formation at the discharge end may also arise iE the inflow
end of the discharge pipe should be full, namely in the event
that the particulate material in a lower part of the discharge
pipe moves downwards in free fall and thus by its acceleration
sucks air into the discharge pipe.
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It is an object of the present invention to diminish
the dust formation problems in prior art apparatuses.
According to the present invention there is provided an~
apparatus for depositing loose particulate solid material by
positive discharge into a pile in a manner to diminish dust for-
mation problems, comprising a substantially ~ertically directed
discharge pipe having an outlet end, positioning means for vary-
ing the position of the outlet end according to pressure in the
discharge pipe, the positioning means including a drive motor,
positive discharge means arranged at the outlet end of the dis-
charge pipe for forcing the discharge of the material through
the outlet end under pressure into the pile, the positive dis-
charge means including a drive motor; and pressure sensing means
for sensing the pressure of the material at the outlet end and
regulating the drive motor of the positioning means in dependence
on the pressure to vary the position of the outlet end.
By so sensing the pressure at the outlet end the driv~
motor of the positioning means can be controlled and caused to
change the position of the outlet end to keep the pressure of
the positive discharge means on the supply of material relative-
ly cons-tant and thereby, e.g., ensure that the particulate mat-
erial is forced out below the surface level of the pile in order
that the material already in the supply shall serve as a "dust
trap".
It is particularly advantageous if the positive discharge
means is a screw conveyor. This will make it easy to regulate
the discharge speed by regulation of the speed of rotation of
the screw conveyor.
The pressure sensing means adapted to sense the pressure
of the material a-t the outlet end of the discharge pipe may be a
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load sensing device according to Swedish Patent 366 178 or Swedish
Printed Patent Application 7506483 2 (Pub]. No. 390,589) said de-
vice being adap ted to sense the load of the motor of the posi-
tive discharge means, since said load is a measure of the pres-
sure of the material, that is to say, a high pressure of mater-
ial and, as a consequence, a high resistance to the discharge
gives a high load on the motor of the positive discharge means.
The pressure sensing means can also be provided in the positive
discharge means in the vicinity of the outlet end and may e.g.
10 comprise a diaphragm mounted in the wall of the discharge pipe
and a microswitch disposed outside the diaphragm and connected in
the con trol circuit for the motor of the positioning means.
A level sensing means is preferably mounted in the inflow
end of the discharge pipe for sensing the level of material in
said end pipe, said level sensing means being connected to a con-
trol circuit for controlling the level of material in the dis-
charge pipe. Such a level sensing means may preferably be a cap-
acitive transmitter, that is, a transmitter the capacitance of
which is influenced by the surrounding material and is related
20 -to how long an extension of the transmi tter is surrounded by
the material. However, the level sensing means can also be of
the type having a rotary shaft penetrating into the material and -
being rotated at a constant speed by a short circuited AC-motor,
the motor lead of which is sensed by a load sensing device ac-
cording to Swedish Patent 366 178 or Swedish Printed Patent
Application No. 7506483-2 (Publ. No. 390,589), the mo-tor load
sensed by the load sensing device being a measure of how large
a part of the rotary shaft is surrounded by the particulate mat-
erial and is exposed to friction against the material. Irres-
30 pectively of whether the level sensing means is of the capacitive
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type or of the friction measuring type, the level sensing means
has a transmitter section for transmitting a control signal to
the control circuit controlling the level of material in the in-
flow end of the discharge.pipe. The control circuit preferably
controls the motor of the positive discharge means and contains
a thyristor rectifier controlling such motor, in which case the
motor is designed as a DC-motor of variable speed.
However, the level sensing means at the inflow end of the
discharge pipe in a preferred embodiment of the invention can al-
so be used for controlling the feed rate of a feed device, serv-
ing to supply the particulate material -to the inflow end of the
discharge pipe, in dependence on the level of materlal in the in-
flow end of the discharge pipe. Such a level sensing means can
also be utilized as an overfill protection device which prevents
overfilling of the discharge pipe with material.
If the length of the discharge pipe between the inflow
and outflow ends of the discharge pipe is variable, that is, if
the discharge pipe is of telescoping or bellows-like construction,
the positioning means is preferably a hoist.
According to an advantageous embodiment of the invention,
it is suitable, if the discharge pipe is of constant length, for
the discharge pipe to be pivotally connected to a feed conveyor
for feeding the particulate material to the inflow end of the
discharge pipe, the discharge pipe and -the Eeed conveyor being
pivotally interconnected in form of a raisable and lowerable and
possibly also swingable system simllar to a crane arm.
The invention will appear morer~adily from the following
description of embodiments thereof reference being made -to the
accompanying drawings, in which:-
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Fig. 1 schematically shows an embodiment of an unload-
in~ apparatus according to the invention, in which only the
lower end of the discharge pipe is shown;
Fig. 2 schema-tically shows a section on line II-II in
Fig. l;
Fig. 3 shows another embodiment of the invention in
which the discharge pipe is united with a feed conveyor to form
a system similar to a crane arm;
Fig~ 4 shows still another embodiment of the invention in
which the discharge pipe is of telescoping design;
Fig. 5 (which appears on the same sheet as Fig. 3)
schematically shows a detail and a pressure sensing means for
sensing the pressure of the material;
Fig. 6 (which appears on t~le same sheet as Fig. 3)
schematically shows a further embodiment of the invention and
a preferred way of arranging the motor of the positive discharge
device.
The unloading apparatus shown in Figs. 1 and 2 aomprises
a discharge pipe 10. The discharge pipe has at its lower end a
positive discharge device 16 with an outlet end 17. The dis-
charge device 16 has an inner conveyor screw 18 the shaft 19
of which is mounted in a suitable manner. Said conveyor screw
18 is driven by a drive motor 20 which is secured to a bracket
21 on the discharge device 16. As will appear from Fig. 2/ the
upper portion of the discharge device is formed as a "breeches
pipe" having breeches 16a, 16b, which divide the flow of material
from the discharge pipe into two streams and conduct them on
either side of a wedge-shaped space 45 which is defined by the
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.:
inner walls 46 of the breeches 16a, l~b. The motor 20 secured to
the bracket 21 is drivably connected to the shaft 19 of the
conveyer screw by a V-belt and pulley arrangement 47.
The motor 20 has a load sensing means 35 which is adapted
to sense the load of the motor and w~ich preferably ls designed
in conformlty with that disclosed in 5wedish Patent 366 178 or
Swedish Printed Patent Application 7506483-2 ~Publ. No..390,589).
The load of the motor of the positlve discharge device in fact
is a measure of the pressure of the material at the outlet end
17 of the positive discharge device, that is to say, a high
pressure of material and, as a consequence, a high resistance
to the discharge gives a high load on the motor of the
positive discharge device. The pressure sensing me.ans 35
is connected via a conductor 36 to a motor 25, 25a, 25b, 25c,
which is adapted to alter the vertical or lateral position of
the outlet end 17 of the positive discharge device.
The above-described unloading apparatus functions
in the ollowing manner. When the apparatus is started and the
dlscharge pipe 10 is empty,the feed of the matexial is initiated,
preferably while the positive discharge device 16 is at stand~
still. When the level of material has risen somewhat in the dis-
charge pipe~the positive discharge device is initiated so that
the material in the discharge pipe will be positively discharged
downwards into a supply 39. Since the material is positively dis-
charged from the discharge pipe lO~the positive discharge device
16 will constantly rest on and exert pressure against the top of
the supply 39. In principle, the positive discharge device could
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; 1~73394
of its own accord "climb" the ever increasing supply 39, but
said device would thus take up a varyin~ load in dependence of
how much material is contalned in the discharge pipe 10, As the
pressure in the outlet end 17 is sensed by senslng of the loa~
on the motor 20 of the positive discharge device, the motor 25,
25a, 25b, 2Sc for positioning the outlet end 17 of the devic~
can be so regulated that the pressure of the device against the
supply 39 is kept reasonably constant, the partlculate material
being forced out below the sur~ace level of the supply 39 so
that the material in said supply will serve as a "dust trap".
Positioning can thus take place by raising or lowering the out-
let end 17 in dependence on whether the pressure oE the material
in the positive discharge device is too high or ~oo low. However,
positionlng can also be carried out as a lateral displacement
so that the outlet end 17 projects o~er parts of the supply
39 lying at lower levels. ~egulatlon of the positioning motor
25, 25a, 25b, 25c thus takes place ln such a manner that the
pressure of the material in the outlet end 17 is kept as constant
: as posslble.
Fig. 3 ~how~ how the dlscharge pipe 10 with its positive
di~charge device 16 is mounted on a crane structure, the discharge
pipe 10 belng connected at its upper inflow end via a dust proof
transitlon housing 50 to a feed conveyer 51 which at its opposite
end ls plvoted to a gantry crane 52. The gantry crane 52 has a
hoist motor 25 wlth a wire rope drum (not shown~ for a wire rope
53 which passes o~er a return pulley 54 and ls connected to the
transltlon housing 50. The dlscharge pipe 10 could be freely
30 .
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swingable with regard to the feed conveyer 51 but, as shown, is
preferably connected to said conveyer by a piston and cylinder
unit 25b by means of which the angle enclosed between the feed
conveyer 51 and the discharge pipe 10 can be regulated. The
gantry crane 52 further has a drive motor 25a by means of which
the gantry crane can be driven along tracks (not shown). The
tower of the gantry crane can be disposed on a turntable
assembly 56 for swinging of the entire arm system. The drive
motor for this swinging movement has been schematically illu-
strated in Fig. 3 at 25c. In this embodiment the pressure ofthe material sensed at the outlet end 17 of the positive dis-
charge device 16 can be utilized for controlling any of or any
combinatlon of the motors 25, 25a, 25b, 25c.
In Fig. 4 ~here is shown a further embodiment of the in-
vention in which the discharge pipe 10 comprises various tele-
scoping parts 11-14. Mounted at the upper end of the discharge
plpe is an inflow hopper 15 and at the lower end of the discharge
pipe a positive discharge device 16 which in this embodiment has
an outlet cone 17' Xn this embodiment there is provided inside
the posltlve discharge device 16 a transverse beam or a spider
22 which carries a hearing device (not shown) for the conveyer
screw 18 and which besides serves as an anchorage for a hoist
wire rope 23 which extends inside the discharge pipe 10 and is
windahle onto a wire rope drum 24. The drum 24 is driven by a
drive motor 25~. By controlling the drive mo~or 25' the length
of the discharge pipe 10 can thus be increased and reduced.
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The motor ~5' is mounted to a bracket 26 in a frame 27
which ts formed as a dust proof houstng. ~ level sPnsing means
29 is arranged on another bracket 28. Saicl level sensing means
in the illustrated embodiment has a rotary shaft 30 which extends
downwards in the inflow hopper 15 and is rotated at constant speed
by a short circuited AC-motor, the motor load of whlch is sensed
in conformity with what is stated in Swedish Printed Patent
Application 7506~83-2 (Publ. No. 390,589) or Swedish Patent
36S 178. The load on the motor is a measure of how large a por-
tion of the shaft 30 is surrounded by the particulate materialand exposed to friction against it. Therefore, the load is a
measure of the level of -the material in the inflow hopper. The
level sensing means 29 is connected by a conductor 31 to a
transmitter 32 which in turn is connected by a conductor 33 to
a thyristor rectifier 34 which is connected into the control
circuit of the drive motor 20 of the positive discharge device
16.
In this embodiment, the pressure sensing means 35' is
arranged in the outlet cone 17' of the positive discharge
device 16. In this case the pressure sensing device, as will
appear from Fig. 5, can comprise a diaphragm 60 provided in the
wall of the outlet cone 17 and a microswitch 61 disposed outside
said diaphragm and connected by the conductor 36 to the hoist or
drive motor 25' to control it, said microswitch being influenced by
the pressure of the material in the outlet cone 17'. The micro- -~
switch ls disposed in the interior of an envelope 62 which is
screwed by screws 63 to the outlet cone 17 opposite a hole 64
therein.
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As will appear from Fig. 4, a conveyer belt 37 terminatcs
above the inflow hopper 15. The particulate material 38 is con-
veyed on said conveyer belt 37 to the dischar~e pipe 10. At
least the discharye end of the conveyer belt is enclosed in the
dust proof housing 27 to reduce dusting and whirling of the ~ate-
rial.
The unloading apparatus accordin~ to the embodiment shown
in Fig. 4 functions in the following manner. When the apparatus
is started and the discharge pipe 10 is empty, the feed of the
material 38 is initiated, while the positive discharge device
16 is at standstill, the level of the material in the discharge
pipe rislng until the pipe is finally entirely full. The,level
of the material in the discharge pipe should be kept at a de-
termined mean level 40, but may be allowed to vary from a maxi-
mum at the level 41 to a preferred minimum at the level 42.
When the level of the material has risen to the level range 41-42
the sensing shaft 30 of the level sensing means 29 will be
partlally immersed in the material in the discharge pipe. The
level sensing means senses the level of the material and the
transmitter 32 of the sensing means transmits a control signal
to the ~yristor switch 34 to control the speed of the motor 20
and thus the speed of the positive discharge device 16. If the
level in the inflow hopper 15 should vary, said level variation
ls thus sensed by the level sensing means 29. Should the level
sink and should thus the control voltage applied by the level sens-
in~ means to the thyristor switch 34 sink, the speed of the motor
20 is reduced so that the conveyer screw 18 of the positive
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discharge device will no longer disch~rge the same amoun~ of
material to the supply 39 located below the discharge pipe 10.
The result is that the level of the material in the inflow hopper
15 again rises. Should, on the other hand, the level of the
material in the inflow hopper rise unusually much and approach
the upper maximum limit at the level 41, the level sensing means
will -~hrough its transmitter 32 transmit a higher voltage to the
th~istor switch, the speed of the motor 20 being increased so
that the positive discharge device will carry away the material
more rapidly from the telescoping discharge pipe 10 so that the
level of the material in -the inflow hopper 15 again sinks to
the mean level 40. It is thus obvious that a variation of the
amount of material 39 supplied per unit of time frvm the con-
veyer belt 37 can be compensated for, in that these variations are
reflected by level variations in ~he inflow hopper 15, the level
sensing means 29 controlling the conveyer screw 18 in such a
manner that said screw tends to keep the level at the desired
me~n level 40.
As the material is positively discharged from the discharge
pipe 10 also in the embodiment according to Fig. 4, the positive
discharge device 16 will constantly rest on and exert pressure
agalnst the top of the supply 39. ~n principle, the positive
discharge device could of its own accord "climb" the ever in-
creasing supply 39 but in so doing the posi~ive discharge device
would have to take up an ever larger load because the different
dlscharge pipe members 11-13 will successlvely rest on the trans-
: verse beam or spider 22 in the interior of ~he positive discharge
. . .
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10~339~
- device. By the pressure in the outlet cone 17 beiny sensed anu
the hoist motor 25 or 25' being caused to raise the dis~ha~ge;device
16 the pr~essure of the discharge device on the supply 39 can
be kept also in this case reasonably constant, the particulate
material being forced out below the surface level of the su~ply
39 so that the material already in the supply will serve as
a "dust trap".
In the described embodiments of the invention the successive
elevation or altered positivn of ~he positive discharge device
16 is controlled with the aid of the pressure sensing n~ans 35' or 35
which either is disposed in the outlet cone 17' (Fig. 4) or is
a sensing means for sensing the load on the motor of the positive
discharge device 16 (Fig. 1). Said pressure senslng means thus
senses -the pressure in the outlet end 17 or 17' and when said pressure
rises over a given set maximum value the pressure sensing means
35 or 35' transmits a starting signal to the motor 25, 25a, 25b, 25c of
the positioning device, said motor being started and the mouth
of the positive discharge device 16 being caused to change posi-
tion. In the embodiment shown in Fig. 4 the motor 25' of the
hoist means is thus started and the wire rope 23 is wound onto
the wire rope drum 24. The winding of the wire rope 23 onto the
drum 24 will result in the positive discharge device 16 being
raised somewhat until the pressure sensing means 35'senses a pre-
determined permissible minimum pressure, the pressure sensing means ~ r
35 transmitting a stop signal to the motor 25 ~whereby the
raising of the positive discharge device 16 is arrested. Simi-
larly, a control of the position of the outlet en~ 17 vertically
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10~33~
.
or laterally takes place when the positive discharge device is
arranged at the lower end of a rigid pipe 10 of non-variable ~i
length~ although the discharge pipe is designed for raising and
lowering and possibly also for lateral displacement in conformity
with what i, shown in Fig. 3.
It will thus be realized that ~he above-described unlcad-
ing apparatuses each provide a pressurized contlnuous
discharge of the particulate material, the ac~ual dust formation
having been restricted to the area about the inflow end of the
discharge pipe 10, that is, to the area about the dischar~e end
of the conveyer belt 37 above the inflow hopper 15 in Fig. 4 and
to the loading station of the feed conveyer 51 twhich preferably
ls a screw conveyer) in Fig. 3. However, this portion o~ the un-
loading apparatus can readily be encapsulated in a dust proo~
manner. No dust formation arises at the outlet end o the positive
discharge device 16, since said device is constantly caused to
discharge the particulate material below the surface of the supply
39. Besides, if care is taken - as contemplated in the embodiment
shown ln Fig. 4 - that the particles 38 are not allowed in normal
operation of the apparatus to fall freely through the discharge
pipe 10, a further reduction of the dust formation is attained.
The system of course includes bypass connections so that
the positive discharge device 16 can be caused entirely to empty
the discharge pipe 10. A prerequisite herefor is that the level
sensing means 29 is bypassed since said means will o~erwise stop the
motor 20 when the level of the material in the discharge pipe 10
; falls below the set minimum level 40. Moreover, the apparatus of
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course contains s~lch bypass connections that the ~5 or 25' ~ be
driven independently of the pressure sensed by the pressure sens-
ing means 35or 35' as othe~wise an entirely empty unloading apparatus
could not be raised from the supply 39 when this is needed.
Further, the apparatus preferably colltains means which shut off
the feed de~ices upstream of the discharge pipe, particularly the
conveyer belt 38 when the maximum level permissible in the in-
flow hopper 15 ls exceeded so that overflowing of the inflow
hopper 15 is avoided. A level sensing means can also be exploited
in the embodiment of the invention where the discharge pipe 10
is of constant length. Thus, a level sensing means can be arranged
in the area of the transition housing 50 in Fig. 3, and said
level sensing means may be designed in the same manner as the
level sensing means 29 in the embodiment according to Fig. 4.
The level sensing means can serve as an overfill protection
means and shut down feed devices upstream of the discharge pipe
10, particularly the feed conveyer 51 so that overfilling or the
discharge pipe 10 and the transition housing 50 is avoided. As
a safety measure the unloading apparatus suitably also has a
safety circuit which prevents a downward movement of the outlet
end 17 when the motor of the positive discharge device is at
standstill.
In the embodiments lllustrated the positive discharye device
16 is designed as a screw conveyer having a stationary tubular
shell but the positive discharge device can also be designed
in accordance with the disclosure of Swedish Patent 352 600
which relates to a screw conveyer in which both the screw proper
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~ 3394
ana the tubular shcll rotate, but in opposite directions
Fig. 4 very schematically shows the transmission of power
from the motor 20 to the shaft l9 of the conveyer screw. Purely
technically, the problem of power transmission can be solved in
the same manner as in Fig. 2, in which the upper part of the
tubular shell of the positive discharge device has been designed
as a breeches pipe, the shaft l9 of the conveyer screw extendlng
tllrough the breeches pipe walls and carrying in the free space
45 between the breeches a belt pulley 47 which is connected by
means of a drive belt to a pulley mounted on the shaft of the
motor 20. Another possi~ility of solving this problem of power
transmission is to mount the drive motor 20 at the lower end
of the conveyer scxew shaft l9 in the outlet cone 17, in whlch case
the drive motor 20 and the lower bearing of the shaft 19 are pro-
tected in a suitable way, for instance by a conical partition,
from getting in contact with the material discharged through the ;~
discharge device. A third possibllity of arranging the trans-
mlssion of power from the motor of the positive discharge device
to the conveyer screw shaft l9 is shown in Fig. 6. In this erl~o-
diment the lower end of the discharge pipe 10 has a slanting
pipe length 60, ~hich opens into the side of the upper end of the
posltive discharge device 16 so that it has been possible to
mount the motor 20 beside the discharge pipe lO for direct connec-
tion to the shaft l9 of the conveyer screw~ This embodiment of
the power transmission between the motor 20 and the conveyer
screw shaft 19 can be exploited in all of the foregoing embodi-
ments of the unloading apparatus. If use should be made of the
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arrangement shown in Fig, 6 for a telescoping discharge pip~ lO
a fixation 61 for the hoist wire rope 23 can be provided on the
slanti.ng pipe length 60 so that the hoist wire rope neecl not
extend through the interior of the discharge pipe lO and
to the wearing eEfect of the discharg~d partieulate material.
Also in the embodiment according to Fig. 4 the hoist wire rope
23 can thus be placed outside the discharge pipe lO, and natural-
ly nothing prevents utilizing more than one hoist wire rope.
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