DE2520244B2 - FEEDING DEVICE FOR A SCREW EXTRUSION PRESS - 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 assigned 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 fill level sensor is provided in the feed container.

A loading device of this type for a screw extruder is disclosed in US Pat. No. 3,036,335 known. The material is supplied via a filling line, in which one of the level sensor controlled valve is provided, due to the vacuum in the feed container, with the flow of material Air is sucked into the container, which in turn is connected to an upstream vacuum pump Filtering is sucked off. Especially when using powder !! Material becomes part during evacuation this material is carried away and leads to clogging of the filters after a relatively short operating time, which then have to be cleaned. Furthermore, it cannot be ruled out that this material will get through the filter passes through into the vacuum pump and leads to signs of wear there. Finally, then if any significant amount of air gets into the feed container, despite the presence of the Vacuum pump can not be excluded that the air - albeit to a small extent - in the Screw extruder arrives. However, this is in turn disadvantageous as such evacuable charging devices can only be used on screw extrusion presses, which in turn are under Working partial vacuum, so that the plasticized or melted material in the screw extruder is released of volatile constituents remains or becomes.

From the magazine "Gummi-Asbest-Kunststoffe", 1970, No. 11, pages 1222 and 1224 is a loading device for a screw extruder known, in which a feed container is connected to the housing of the screw extruder, and which is connected to the housing bore of the screw extruder via a vacuum lock. To the Dust filters are provided to prevent material from entering the vacuum pump in this respect, when using fine or powdery material, they clog quickly and lead to operational disruptions being able to lead. In addition, the possibility of material entering the vacuum pump cannot be ruled out here either and damage it.

Cell wheel locks designed as vacuum locks are known from US Pat. No. 2,785,455. From the DT-OS 18 02 694 rotary feeders are known as metering devices.

From DT-AS 15 29 822 it is known in one to provide an agitator upstream of a feed screw for a screw extruder, by means of its bridging and thus disruptions in the material supply to the feed screw be 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 Material in the feed container is largely excluded.

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

a) The feed hopper is preceded by a vacuum lock for material supply:

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 the feed container is practically completely is prevented because the vacuum lock is independent of the amount of material to be fed in 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. Since practically no air can get into the feed container, practically no air is needed to be sucked off, so that corresponding filters upstream of a vacuum pump them! ' do not clog can. As a rule, these filters can even be omitted entirely. Besides, the material cannot get into the vacuum pump and there are no Vcr wear phenomena 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 According to a further advantageous feature of the invention, the control device has a multiplier stage assigned to set the specific bulk density of the material. So this is done in practice 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. It is also advantageous if an agitator is provided in the feed container. This ensures that the material in the feed container cannot form bridges that cause a 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 obtain.

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 t in such a way that the worm windings 4 have only a slight running clearance with respect to the wall of the housing bore 6. The housing 1 consists of individual sections Γ, 1 ″, V ″ and 1 ″ ″, each screwed together in alignment by means of associated flanges 7, only two of which are shown. The sections 1 'to I "" of the housing 1 are arranged between end-face support plates 8 and 9, which are supported on a foundation IO. 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 exit cable end 14 of the housing 1 is arranged behind the support plate 9. On the screw shaft 3 there are baffle plates 15 in which the material to be treated is kneaded particularly intensively. Such baffles are known from DT-PS 9 40 109 (corresponding to US-PS 28 14 472 and GB-PS 7 55 069). A loading device 16 is provided in the vicinity of the support plate 8. This consists essentially of a funnel-shaped feed container 17, which is arranged in a gas-tight manner above an intake opening 18 of the housing 1 connected to the housing bore 6 and connected to the housing 1. On an upper lid-like closure 19 of the feed container 17, a motor 20 is arranged, on whose cantilevered shaft 21, which is also passed through the closure 19 in a gas-tight manner, frame-like stirring elements 22 are attached, which form the inner wall of the lower funnel-like part 23 of the container 17 paint over it, which prevents material from building up in this area and forming bridges. This ensures that the powdery or granular material located in the feed container 17 continues to flow through the feed opening 18 into the feed 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 Functioning as a vacuum lock, the cellular wheel 27 is sealed gas-tight from its housing 28. the The outlet side 29 of the vacuum lock 25 opens into the feed container 17. The inlet side is the vacuum lock se 25 is preceded by a feeder 30 which is provided with a vent opening 31. In the feed hopper 30 a metering device 32 opens, via which the to be treated in the screw extruder powder or granular material is entered into the feed hopper 30 of the vacuum lock 25. The metering device 32 is preceded by a storage bin 33 for this material. The drive of the dosing device 32 takes place by means of a motor 34.

In the upper area of the funnel-like part 23 of the feed container 17 is a commercially available level sensor 35 attached, each of which emits a signal when the material level 36 in the feed container 17 falls below decreases a predetermined value or rises above a predetermined value.

This material level 36 is in any 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 '. From this signal processing device 37 ', the motor 34 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 dosing 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 the volume of material supplied is always equal to the total throughput volume of the vacuum lock; d. H. the The speed of the cell wheel is readjusted so that the total volume of the cell wheel 27 is multiplied by the speed of the cell wheel 27 per unit of time is always approximately the same as that of the metering device per unit of time 32 supplied volume of material is. If the

DosicrcinrichUing 32 - as with the one in the drawing case shown - works as a weigh feeder, i.e. registers the quantity of material passing through per unit of time, the speed controller 48 is preceded by a Multiplierstufc 38, which is from the Regislrierslufe 39 of the dosing device 32 coming signals with the bulk weight (specific Weight) of the material is multiplied so that the amount conveyed through the metering device per unit of time Signals corresponding to the material volume come to the speed controller 48. Through these measures will ensures that virtually no air with the material through the vacuum lock 25 in the Feed container 17 can reach.

At the upper lid-like closure 19 of the feed container 17 is connected to its interior Line 40 attached, via which the interior of the feed hopper 17 by means of a vacuum pump 41 can be largely evacuated.

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 pressure build-up and plasticizing zone B. which is followed by a kneading zone C formed by the sluice disks 15. Subsequent to this, a relaxation zone D is provided, in which the material conveyed through the housing 1 in the conveying direction 43 and now plasticized or melted on is degassed. For this purpose, a hood 45 is connected to the housing 1 in a gas-tight manner via a corresponding degassing bore 44, from which a line 46 leads to a vacuum pump 47. When the through the degassing bore 44, the

ίο hood 45, line 46 and vacuum pump 47 The degassing device formed is omitted, then the feed container 17 is used exclusively partially evacuating vacuum pump 41 as an evacuation device, which in many cases is already sufficient is.

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 case, a powdery catalyst carrier mass with a grain size was used from 5 to 50 μιη entered into the feed container 17, wherein at a level of 50 to 60 cm above the intake opening 18 of the housing 1 a sufficient gas-tight barrier against the vacuum

zone has been reached.

1 sheet of drawings

Claims (4)

Patent claims: 1. Feeding device for a screw extruder for plasticizing, kneading and homogenizing Sneezing of pourable material, especially plasticizable material ceramic masses and plastics, with at least one in an assigned housing bore rotatably arranged screw, wherein the at least one housing bore an evacuable and upstream of the feed container connected to the housing in a gas-tight manner, and wherein a die Material supply controlling fill level sensor is provided in the feed hopper, is marked by combining 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 controls the motor (26) of the vacuum lock in such a way 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 I with a weigh feeder, characterized in that the control device has a multiplier (38) for setting the specific bulk density 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.