DE2520244C3 - Loading device for a screw extruder - Google Patents

Description

45

The invention relates to a charging device for a screw extruder for plasticizing, Kneading and homogenizing of pourable material, in particular of plasticizable ceramic masses and plastics, with at least one in an associated housing bore rotatably arranged screw, wherein the at least one housing bore an evacuable and feed container connected in a gastight manner to the housing is arranged upstream, and wherein a material feed controlling level sensor is provided in the feed container.

Such a loading device for a screw extruder is known from US Pat. No. 3,036,335. The material supply takes place via a filling-Leiiung in which a controlled by the level sensor valve is provided, due to the vacuum in the supply container, being sucked in with the material flow I.lift into the container, which in turn via a vacuum pump upstream ^'1 S Filter is sucked off. Particularly when using powder-shaped material, part of this material is entrained during evacuation and, after a relatively short operating time, leads to clogging of the filters, which then have to be cleaned. Furthermore, it cannot be ruled out that this material could get through the filter into the vacuum pump and lead to signs of wear there. Finally, if any significant amount of air gets into the feed container, it cannot be ruled out that the air will get into the screw extruder, albeit to a small extent, despite the presence of the vacuum pump. However, this is in turn disadvantageous in that such evacuable charging devices are only used on screw extruders, which in turn operate under partial vacuum so that the material plasticized or melted in the screw extruder remains or becomes free of volatile constituents.

From the magazine "Gummi-Asbest-Kunststoffe", 1970, issue 11, pages 1222 and 1224 is one Feeding device for a screw extruder known, in which a feed container with the Housing of the screw extruder is connected, and via a vacuum lock with the housing bore the screw extruder is connected. To allow material to pass into the vacuum pump prevent, dust filters are provided, which are, however, so far when using fine or powdery Material can clog quickly and lead to operational disruptions. Besides, this is not the case either prevent material from getting into the vacuum pump and damaging it.

From US-PS 27 85 455 designed as vacuum locks rotary valve are known. From the DE-OS 18 02 694 rotary feeders are known as metering devices.

From DEAS 15 29 822 it is known in a feed screw for a screw extruder upstream task container to provide an agitator, by means of its bridges and thus Disturbances in the material feed to the feed screw are prevented.

The invention is based on the object of providing a loading device of the type described at the beginning Kind of designed so that an air inlet into the feed container with the continuous addition of Materia! is largely excluded in the feed container.

According to the invention, this object is achieved by the combination of the following features:

a) A vacuum lock for material supply is connected upstream of the feed container;

b) the vacuum lock is preceded by a metering device;

c) the level sensor is coupled to the motor of the metering device;

d) there is a control device for the vacuum lock depending on the volume flow of the Dosing device is provided which controls the motor of the vacuum lock in such a way that the respective Total delivery volume of the vacuum lock per unit of time roughly equal to that of the metering device supplied volume flow is.

By these measures it is achieved that any air supply / to feed container practically completely is prevented because the vacuum lock is independent of the amount of material to be supplied per unit of time is always completely filled with material, so that there is no air together with the material in the Can transport feed containers, as it is with a

Working the vacuum lock with partial filling the case were. You practically no air in the feed container can reach, practically no air needs to be sucked off / ground. so that corresponding one Filters connected upstream of the vacuum pump cannot become clogged. As a rule, these filters can even completely omitted. In addition, the material cannot get into the vacuum pump and there is no signs of wear and tear to lead. After all, there can be no air here either - even if only in the finest Distribution - attach to the material and, despite the presence of a vacuum pump, into the screw extruder reach.

If a metering scale, for example a belt scale, is provided as the metering device. then '5 According to a further advantageous feature of the invention, the control device has a multiplier stage / assigned to setting the specific bulk density of the material. This is so practical a conversion of the weight of the weight fed into the vacuum lock by the metering device per unit of time Material on its volume. A known rotary valve is expediently used as the vacuum lock intended. Weilerhin it is advantageous if an agitator is provided in the feed container. This ensures that the material in the feed container does not form bridges that came in Prevent the material from flowing out of the feed hopper into the housing bore. As the material itself in the feed container as a practically gas-tight shut-off of the inlet opening in the housing against the vacuum zone in If the screw extruder is used, it is advantageous to always maintain a constant fill level echo.

The invention is in the following description of an exemplary embodiment with reference to the drawing, which a vertical longitudinal section through a screw extruder with an upstream feeding device and a downstream degassing device, explained in more detail.

In a housing 1 there is arranged a worm 2 which consists of a worm shaft 3 on which helically extending worm windings 4 are attached, between which worm flights 5 are located. The worm 2 is arranged in a housing bore 6 of the housing 1 in such a way that the screw corner windings 4 have only a small amount of running play relative to the wall of the housing bore 6. The housing 1 consists of individual sections 1 ', 1 ", 1'" and 1 "", which are each screwed together in alignment by means of associated flanges 7, only two of which are shown. The sections I ′ to 1 ″ ″ of the housing I are arranged between frontal support plates 8 and 9, which are supported on a foundation 10. The worm shaft 3 is passed through the support plate 8 and is driven from this side by a motor 11 with the interposition of a reduction gear 12 and a clutch 13. The outlet end 14 of the housing 1 is arranged behind the support plate 9. Baffle disks 15 are attached to the screw shaft 3, in which the material to be treated is kneaded particularly intensively. Such baffle disks are known from DT-PS 9 40 109 (corresponding to US-PS 28 14 472 and GB-PS 7 55 069). In the vicinity of the support plate 8 is a Beschickungsvorrich- ^(> 5 tung 16 is provided. This essentially consists of a funnel-shaped dispensing container 17, the gas-tight above a connected to the housing bore 6 feed opening 18 of the housing 1 and is connected to the housing 1. A motor 20 is arranged on an upper lid-like closure 19 of the feed container 17, on whose cantilevered shaft 21, which is likewise gas-tight through the closure 19, is attached This prevents material from building up in this area with bridging, thus ensuring that the pulverulent or granular material in the feed container 17 flows through the inlet opening 18 into the inlet zone A of the screw extruder.

On a horizontal shoulder 24 of the cover-like closure 19 is a rotary valve designed as a rotary valve. Commercially available vacuum lock 25, which can be driven by a motor 26, is attached. According to her Function as a vacuum lock, the cellular wheel 27 is sealed gas-tight from its housing 28 The outlet side 29 of the vacuum lock 25 opens into the feed container 17. The vacuum lock is the inlet port 25 upstream of a feed hopper 30, which is connected to a Vent 31 is provided. In the feed hopper A metering device 32 opens out at 30. about the handling in dtr screw extruder / u '.' powder or granular material into the feed hopper 30 of the vacuum lock 25 is entered. The metering device 32 is a Vorralsbunker 33 for this material upstream. The metering device 32 is driven by means of a motor 34.

In the upper area of the gully-like part 23 of the Dispensing container 17, a commercially available level sensor 35 is attached, each of which emits a signal when the Matcrialspicgcl 36 in the task hall 17 falls below a predetermined value or above a specified value increases.

This material level 36 is in every case below the outlet side 29 of the vacuum lock 25. If one of these two signals is given by the level sensor 35, it is fed via a multi-core line 37 a signal processing device 37 '. The motor 34 is controlled by this signal processing device 37 ' the metering device 32 either when a signal indicating the maximum fill level is present lower speed or when a signal representing the minimum level is present higher speed switched, d. H. from the storage bunker 33 into the feed hopper 30 of the vacuum lock The amount of material entered per unit of time is reduced or increased. In the case of the metering device 32 it can be a commercially available dosing scale or a volumetric dosing device Act. A commercially available belt scale is shown schematically in the drawing.

) e according to the registered by the metering device 32, The amount of material fed to the feed hopper 30 is controlled via a corresponding speed controller 48 of the Motor 26 and thus the cellular wheel 27 are driven in such a way that the metering device 32 /".guided material volume always equal to the total throughput volume the vacuum lock is; d. H. the speed of the cell wheel is readjusted in this way. dall the total volume of the bucket wheel 27 is always multiplied by the speed of the bucket wheel 27 per unit of time is approximately equal to the volume of material supplied by the metering device 32 per unit of time. If the

Dosing device 32 - as in the case of the one in the drawing Rill shown - “Is the weigh feeder works, so that continuous material weight registered per unit of time, the speed controller 48 is another Miiltipli / icrsiufc 38 connected upstream of the Registriersliife 39 of the dosing device 32 coming signals with the bulk weight (specific Multiply the weight) of the material! Signals corresponding to the painting volume come to the speed controller 48. Through these measures will ensures that practically no uifi with the Material can pass through the vacuum lock 25 into the feed container 17.

At the upper lid-like end 19 of the Aufgabcbohälters 17, a line 40 connected to its interior is attached via which the interior of the Feed container 17 can be largely evacuated by means of a vacuum pump 41.

The housing bore 6 extends through the support plate 8 in the area where the worm shaft 3 passes through gastight shaft seals 42, for example commercially available Simmerrings, sealed.

The feed zone A in the housing 1 is followed by a Drueaufbau- and plasticizing zone B. which is a kneading zone C formed by the baffle plates 15 is after-sonicated. Subsequent to this, a l-lnispanmings / onc D. ii is provided, which is conveyed in the l-conveying direction 43 through the housing i and in the meantime plasticized or blown up material is degassed. A hood 45 is connected to the housing 1 in a gas-tight manner via a corresponding venting bore 4 ', from which a line 46 leads to a vacuum pump 4i. If the degassing device formed by the degassing bore 44, the hood 45, the line 46 and the vacuum pump 4j is omitted, then only the vacuum pump 41, which partially evacuates the feeding device, serves as the degassing device, which in many cases is already sufficient

, _{5 is} unity.

The materials to be treated are ceramic powders, e.g. B. catalyst carrier, or plastic powder or plastic granulate into consideration.

In a practically realized crease, there was unity Powdery Kalalysalortträgerstoff with a grain size of 5 to 50 μm in the Aufgabebehälicr 17 entered with a filling level height of 50 to 60 cn above the intake opening 18 of the housing I eim sufficient gas-tight barrier against the vacuum

2 <i zone was reached.

1 sheet of drawings

Claims (4)

Patent claims: ί. Feeding device for a screw extruder for plasticizing, kneading and homogenizing of material added in a free-flowing state, in particular of plasticizable ceramic masses and plastics, with at least one in an assigned housing bore rotatably arranged screw, the mineslens a housing bore that can be evacuated and is connected to the housing in a gas-tight manner The feed container is arranged upstream, and a level sensor controlling the material supply in the feed container provided, is characterized by the combination of the following features: a) The feed container (17) is preceded by a vacuum lock (25) for material supply; b) the vacuum lock (25) is a metering device (32) upstream; c) the level sensor (35) is coupled to the motor (34) of the metering device (32); d) there is a control device for the vacuum lock (25) as a function of the volume flow the metering device (32) is provided, which drives the motor (26) of the vacuum lock controls such that the respective total delivery volume the vacuum lock per unit of time is approximately equal to the volume flow supplied by the metering device. 2. Loading device according to claim 1 with a weigh feeder, characterized in that the control device has a multiplier (38) for setting the specific Schütlgewichls of the Material is assigned. 3. Loading device according to claim 1, characterized in that as a vacuum lock (25) a rotary valve is provided. 4. Loading device according to claim 1, characterized in that in the feed container (17) an agitator is provided.