DE202007011767U1 - Fütter-screw machine - Google Patents

Abstract

Feed screw machine for conveying powdered bulk material,
With a housing (2),
- With at least one bore (3, 4), the
A bore wall (36, 37),
With a feed opening (9) for the pulverulent material arranged at one end of the housing (2),
- With one in each case in the at least one bore (3, 4) arranged screw (7, 8)
- With a vacuum housing portion (19, 19 ', 19'') in at least one bore wall 36, 37, which has a gas-permeable porous wall portion (20, 20', 20 '') of sintered material having a plurality of channels, and
With a drive (14) for the at least one worm (7, 8),
characterized,
In that the gas-permeable wall section (20, 20 ', 20'') has an inner wall (35, 35', 35 '') delimiting the at least one bore (3, 4), which faces the bore wall ( 36, 37) is set back with the formation of a gap (40, 40 ', 40'') with a partial circular ring cross-section and ...

Description

The The invention relates to a feed screw machine according to the preamble of claim 1.

From the DE 32 20 916 A1 Such a feed screw machine is known, which is used to feed a roll press. The roller press is used for the compression of powdery or fine-crystalline bulk material. The screw machine has a housing, in the bore of a screw is arranged. In the screw wall receiving bore wall, a vacuum housing section is arranged, through which a suction opening for the air released in front of the nip by compaction of the powdery bulk material is formed. The constant suction of the air immediately before the rolls of the roller press creates the conditions for the desired high compression of the bulk material in the nip. In the feed screw machine, therefore, there is a pre-compression of the powdered bulk material and a supply under pressure to the nip. The feed screw machine is completely filled with bulk material during operation.

From the DE 1 729 395 B For example, an extruder is known in the feed zone of which a normal sieve or filter of sintered material is provided as a vacuum housing section to effect venting of the bulk bulk material to be treated. The porous wall portion may be formed flat and arranged at a significant distance from the holes in the housing. Alternatively, this porous wall portion may be disposed in alignment with the bore walls. It has been found that in the latter case, the wall facing the bore of the porous wall portion was added by anplastifiziert plastic and thus the desired effect of the venting was nullified. In the former case, the vent has been largely prevented.

Another extruder is from the DE 195 16 082 A1 known. There, it is assumed that the basic problem is that the entry of powdered bulk material into an extruder is difficult. In order to avoid the use of precompressive feeders, e.g. As stuffing screws, are in the feed zone or solid-feed zone openings of such large diameter formed that can emerge from them by applied negative pressure in the range of 0 to 50% gas and solid and should. The only purpose of this negative pressure is the degassing of the bulk material. This should also be avoided that a backward degassing takes place via the feed opening, which also hinders the bulk material supply. Furthermore, pressure can already be built up in the intake zone. Another advantage is that in the area of the gas and material outlet openings serving an increase in the coefficient of friction takes place on the housing. The disadvantage is that in addition to gas and a part of the powdery solid is withdrawn through the openings. Thus, a sufficient reliability and cost-effectiveness is not guaranteed.

Out the publication of "The Japan Steel Works, Ltd., Plastics Processing Technology News Letter, "De - Gassing Cylinder" DGC "- is an extruder of the generic assumed Art known as the gas-permeable wall section a filter is used, through the air, but also large Quantities of process gases, such as B. Water vapor in ABS and wood flour, should be deducted. Again, a part of the solid is through removed the filter openings. Otherwise exists also the risk of clogging the filter openings the powdered bulk material.

Of the Invention is based on the object, a feeding screw machine the generic type so that in the promotion of powdered and in particular dusty bulk material even in a production operation with partial filling a trouble-free operation with high throughput is achieved.

These Task is according to the invention in the feed screw machine of the generic type by the features in Identification part of claim 1 solved. As a result of that at the gas-permeable wall section by negative pressure a Layer of uniform thickness of powdered Bulk material is produced without being powdered Bulk material is sucked to the outside, are no additional process steps such as the gas-solid separation and return of the bulk material due undesirable bulk material discharge necessary. By the bulk material layer significantly increases the wall friction, so that the promotion of bulk material essential is improved. The degassing of the partially filled Holes as solids conveyed bulk material takes place in the usual way. So there is no significant Degassing through the gas-permeable wall section. Surprisingly it has been shown that clogging of the bore facing Wall of the porous wall section by compaction of Bulk material does not take place. On the other hand, there is no active Suction of air through the porous wall section during the entire promotion, so that clogging of the porous Wall section practically does not occur. By an adapted This can be influenced by choosing the sinter material.

The dependent claims give advantageous again.

Further Features, details and advantages of the invention will become apparent the following description of an embodiment. It shows

1 an extruder plant with a feed screw machine in vertical longitudinal section,

2 the feed auger machine behind 1 in horizontal longitudinal section,

3 a partial presentation 1 on an enlarged scale,

4 a cross-section through the feed-screw machine with a first possible embodiment of a gas-permeable wall section, and

5 a cross section through the feed-screw machine with a second embodiment possibility for a gas-permeable wall section.

The feed auger machine shown in the drawing 1 has a housing 2 in, in the eight-shaped interlocking holes 3 . 4 are formed, whose axes 5 . 6 parallel to each other. In the housing holes 3 . 4 are two snails 7 . 8th arranged. At one - in 1 and 2 left - end opens a feed funnel 9 into the holes 3 . 4 one. The snails 7 . 8th are designed as co-rotating, tightly meshing augers. In the area of the snail peaks 10 . 11 is a housing outlet 12 formed in a downstream extruder 13 In the means of the feed screw machine 1 be prepared material, in particular powdered material, polymer or additives, are entered.

The drive of the slugs 7 . 8th done by means of an electric motor 14 that has a clutch 15 with a reduction and distribution gearbox 16 is drivingly connected. To the transmission 16 are again the snails 7 . 8th coupled in the usual way.

Above the feed funnel 9 is a dosing device 17 arranged, which is designed for example as a gravimetric metering screw. It is powered by an electric motor 18 driven.

At a short distance behind the feed funnel 9 shows the case 2 a vacuum housing section 19 on, the one inside, the holes 3 . 4 partially delimiting porous wall section 20 has. The latter consists of sintered material in which unrecognizable channels are formed in the drawing, so that this porous wall section 20 is gas permeable. On its outside closes to the porous wall section 20 a vacuum room 21 on, of course - outward through a wall 22 is completed. Through this wall 22 opens a vacuum line 23 in the vacuum room 21 , The vacuum line 23 is at a vacuum source 24 , For example, a water ring pump connected.

According to 1 to 4 can such vacuum housing sections 19 the horizontal holes 3 . 4 limit above. The respective vacuum housing section 19 So each is approximately parallel to the through the axes 5 . 6 arranged spanned plane. In the embodiment according to 1 to 4 so both holes 3 . 4 together over just one upper porous wall section 20 subjected to a vacuum.

In the embodiment according to 5 Finally, each is a vacuum housing section 19 ' . 19 '' with porous wall sections 20 ' and 20 '' side of the holes 3 respectively. 4 arranged, namely left and right, that is, the porous wall sections 20 ' and 20 '' lie in the through the axes 5 . 6 spanned level. The rest in 5 contained parts of the vacuum housing sections 19 ' . 19 '' which correspond to the comparable parts or areas in the 1 to 4 are denoted by the same reference numerals, each with an insignificant stroke or two superscripts.

In the vacuum line 23 is a vacuum control valve 25 appropriate. Furthermore, between the vacuum source 24 and the valve 25 a pressure measuring device 26 arranged. Furthermore, every vacuum room 21 by means of a pressure-flushing line 27 with a compressed gas source 28 connected, being in the line 27 a flushing valve 29 is installed. The pressure measuring device 26 gives over a signal line 30 Measuring signals corresponding to each in the vacuum line 23 measured pressure correspond to a central control 31 , From the central control 31 in turn will be the vacuum control valve 25 via a vacuum control line 32 driven. Furthermore, by the controller 31 over a line 33 the purge valve 29 driven. Finally, from the controller 31 also the drive motor 18 the dosing device 17 , the drive motor 14 and a drive motor 34 the vacuum source 24 driven.

It is essential that the respective bore 3 . 4 delimiting porous interior wall 35 . 35 ' . 35 '' the porous wall sections 20 . 20 ' . 20 '' has a partial annular cross-section and opposite the respective bore wall 36 respectively. 37 zurückver is set so that R3 = R4 <R35 (or R35 'or R35''). Here, R3 and R4 are the radii of the holes 3 respectively. 4 and R35, R35 'and R35''are the radii of the porous inner walls 35 respectively. 35 ' respectively. 35 '' , in each case measured from the corresponding axis 5 respectively. 6 , This configuration is thus - compared to the game 38 between the respective comb 39 the corresponding snail 7 respectively. 8th and the hole wall 36 respectively. 37 - An enlarged gap 40 respectively. 40 ' respectively. 40 '' between the respective comb 39 the snails 7 respectively. 8th opposite the interior wall 35 respectively. 35 ' respectively. 35 '' produced. This gap 40 respectively. 40 ' respectively. 40 '' Thus, in the radial direction has a constant thickness D for which applies: D = R35 (or R35 'or R35'') - R4 (or R3), where: 2.0 mm ≤ D ≤ 30 mm. The larger R3 or R4 is, that is, the larger the feed screw machine 1 is, the larger becomes also D.

Like that 3 to 5 can also be removed in the vacuum housing sections 19 . 19 ' . 19 '' and the porous wall sections 20 . 20 ' . 20 '' Cooling channels 41 be formed, their supply of coolant via a coolant supply line 42 and a coolant discharge line 43 he follows.

The operation is as follows:
About the dosing device 17 Powdered or dusting bulk material is added. This powdered bulk material may be a polymer, but also any bulk material to be processed on extruders. The addition of the bulk material and the speed of the screws 7 . 8th are tuned so that the feed-screw machine 1 operated with partial filling. The vacuum housing or sections 19 be acted upon with such, referred to here as vacuum negative pressure, that the powdery bulk material in this area with a layer in the game 38 between the snail's crest 39 and the inside wall 35 the wall sections 20 corresponding thickness of the or the porous wall sections 20 is held. This increases the friction between the bulk material to be conveyed and the inner wall 35 , which in turn leads to an increase in the bulk material promotion. As in the porous wall sections 20 trained, not visible in the drawing channels are smaller than the grain size of the bulk material to be conveyed, the latter is not in the porous wall sections 20 drawn; So there is no clogging of these porous wall sections 20 , Generally, the width of the channels in the porous wall sections 20 is below or within the range of grain size distribution of the bulk material. The grain size distribution of the bulk material regularly extends over a certain range from extremely fine to less fine grain size. Also in the porous wall sections 20 trained channels have a width extending over a certain area. It has been found that clogging of these channels can be effectively avoided as the diameter region of the channels in the porous wall sections 20 within or below the described particle size distribution. With a particle size distribution between D10 = 30 microns and D90 = 160 microns z. B. channel widths of 15 to 90 microns sufficient. The lower diameter specification D10 indicates that at most 10% of the powdery bulk material has a smaller or the same diameter than the specified, ie 30 microns. Under D90 is to be understood that at least 90% of the bulk particles have a diameter which is less than or equal to the specified value of 160 microns. In the present case: D50 = 75 μm. With such a distribution, it is ensured that a sufficient number of particles (grains) of the bulk material upon application of the vacuum from the screw side against the channel openings, so that a clogging of the channels does not or at least not take place to any significant extent.

Through the porous, ie gas-permeable wall sections 20 only as much gas, usually so air or nitrogen, withdrawn, as is necessary for the generation of the bulk material layer by negative pressure. When in steady state operation of the screw machine 1 on the respective interior wall 35 the porous wall sections 20 If a dense or compacted bulk material layer has formed, air or gas is drawn off only to a very small extent, without the desired positive effect on the promotion suffers. The negative pressure in the gap 40 only serves the powdery material in this gap 40 to keep.

The compaction of the bulk material in the area of the inner wall 35 leads to a reduction in the density of the bulk material in the area of the screw core 44 , In this area, air entrained with the bulk material can pass to the feed hopper 9 flow back and escape through this. The bulk material is therefore largely vented and correspondingly pre-compressed by the housing outlet 12 out and into the downstream extruder 13 into promoted.

Due to the gap 40 There is no danger of getting the porous wall section 20 or its inner wall 35 unintentionally added by Anplastifizeren a polymer to be promoted. If something like this happened, there would be no vacuum on the inside wall 35 be generated. This danger is - as I said - excluded. As has been surprisingly found, plasticizing a polymer on the inner wall 35 of the vacuum housing section 19 through the enlarged gap 40 effectively prevented. This is done by the Cooling in the area of the porous wall sections 20 positively influenced. As is apparent from the embodiments described above, it is sufficient, the vacuum only over a portion of the circumference of the holes 3 . 4 apply and only over a short section of the holes 3 . 4 ,

If only the porous wall sections 20 be added by dusty bulk material, this is the pressure-measuring device 26 displayed, which in turn from the controller 31 a closing of the vacuum control valve 25 and opening the purge valve 29 is triggered, so via the pressure-purge line 27 a pressurized gas flushing of the porous wall sections 24 takes place in the form of a pressure surge.

Under Vacuum in the sense of this application is not an absolute vacuum in the physical sense, but a very low Pressure of, for example, 0.02 to 0.2 bar, so a vacuum of 98 up to 80%.

It may be advantageous in individual cases, if the housing 2 Coolable is what happens through cooling channels 45 can be realized.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3220916 A1 [0002]
• - DE 1729395 B [0003]
• DE 19516082 A1 [0004]

Claims (10)

Feed screw machine for conveying powdered bulk material, - with a housing ( 2 ), - with at least one bore ( 3 . 4 ) - a bore wall ( 36 . 37 ), with one at one end of the housing ( 2 ) arranged feed opening ( 9 ) for the powdery material, - in each case one in the at least one bore ( 3 . 4 ) arranged snail ( 7 . 8th ) - with a vacuum housing section ( 19 . 19 ' . 19 '' ) in at least one bore wall 36 . 37 containing a gas permeable porous wall section ( 20 . 20 ' . 20 '' ) of sintered material having a plurality of channels, and - with a drive ( 14 ) for the at least one screw ( 7 . 8th ), characterized in that - the gas-permeable wall section ( 20 . 20 ' . 20 '' ) one the at least one bore ( 3 . 4 ) bounding inner wall ( 35 . 35 ' . 35 '' ) facing the bore wall ( 36 . 37 ) forming a gap ( 40 . 40 ' . 40 '' ) is set back with a partial circular ring cross section and - that the gas-permeable wall section ( 20 . 20 ' . 20 '' ) by means of a pressure-flushing line ( 27 ) to a compressed gas source ( 28 ) connected. Feed screw machine according to claim 1, characterized in that the gap ( 40 . 40 ' . 40 '' ) has a uniform thickness D, where: 2.0 mm ≤ D ≤ 30 mm. Feed-screw machine according to claim 1 or 2, characterized in that the channels in the gas-permeable porous wall section ( 20 . 20 ' . 20 '' ), in particular in the area of the inner wall ( 41 ), have a width which is smaller than or equal to the mean grain size of the powdery bulk material. Feed screw machine according to one of claims 1 to 3, characterized in that the vacuum housing section ( 19 . 19 ' . 19 '' ) with cooling channels ( 41 ) is provided. Feed screw machine according to one of claims 1 to 4, characterized in that the vacuum housing section ( 19 ) above the at least one bore ( 3 . 4 ) is arranged. Feed screw machine according to one of claims 1 to 4, characterized in that the side of the at least one bore ( 3 . 4 ) a vacuum housing section ( 19 ' . 19 '' ) is provided. Feed screw machine according to one of claims 1 to 6, characterized in that in the housing ( 2 ) at least two parallel to each other partially penetrating holes ( 3 . 4 ) are formed. Feed-screw machine according to claim 6 and 7, characterized in that each side of each bore ( 3 . 4 ) a vacuum housing section ( 19 ' . 19 '' ) is provided. Feed screw machine according to one of claims 1 to 8, characterized in that the feed opening ( 9 ) a dosing device ( 17 ) is arranged upstream of the feeding of the powdery bulk material, which is designed such that the feed screw machine ( 1 ) is operated with partial filling. Feed-screw machine according to one of claims 1 to 9, characterized in that it is fed into an extruder ( 13 ).