DE1756497A1 - Method and device for the metered conveyance of pulverulent substances which tend to form bridges and lumps - Google Patents

Description

the 2't. May 1968 " D.Ph.Schm / rai 5737 = Gm 836

Method and device for the metered delivery of powdery substances that tend to form bridges and lumps

The subject of the invention is a method and a device for the metered delivery of bridges and clusters dung-prone powdery substance eij such as dyes, milk powder and powdery polymer.

When processing powdery substances that -for Tend to build bridges, difficulties and disturbances often arise due to insufficient flowability. It is coming for the formation of bridges and clumps in the storage container, which disrupts or interrupts metered removal from this will.

These disturbances make the ver rar-r very special Processing of powdery polymers, including in the following: PVC, low-pressure polyethylene and, above all, polytetrafluoroethylene should be understood, noticeable after the various extrusion and molding processes. In addition to the

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Pw 573? * Om β} 6

Bridging prevents frequent clumping the even distribution of the powder Ie Verkseug, a necessary prerequisite for the manufacture of parts that should be uniform in dimensions, Qeffce and OrHAe *

For the dosing of the aforementioned powdery substances Withdrawal and storage containers are already a series of devices such as dosing screws, cell locks, plate feeders, Vibrating chutes, vibrating augers and VibratioftS bunkers known. Bs lit also known in the storage container or feed hopper a stirring device with propeller and / or P auger to use. Such devices are expensive and maintenance-intensive. For example, polytetrafluoroethylene is used with a soft grain of powder through a central agitator, E.g. metered with Ruhrann and discharge screw, the occurring shear forces destroy the grain structure. Bi comes to Agglomerations and for the formation of coherent structures that no longer allow further funding. By »her fine-grained Powder with a grain radius of about 20 .mu.m and smaller on average is conveyed with such devices not possible anymore.

To avoid the difficulties outlined above, a method for the metered delivery of pulverulent substances with a tendency to bridge and jtlumpeii- W formation is proposed, which is characterized according to the invention in that pulverulent substances are whirled up by gas and sucked in and conveyed by a pump, preferably an air jet pump . I.

Depending on whether continuous or cycle-continuous conveyance is required, the suction power or the pumping time the pump varies.

The inventive method is suitable in principle for Promotion of all for the formation of bridges and clumps p

Fw 5737 - β »

powdery substances. In particular, it is suitable for promotion of powdered polytetrafluoroethylene, at de » since then there have been considerable difficulties in this regard

A suitable device for carrying out the invention The method consists of a known VirbelgefKQ and a pump connected to its fluidized bed, in particular an air jet pump. To dose the zu conveying material, a time-controlled valve and a throttle valve can be built into the gas inlet pipe.

X has proven itself in practice. Swirl the foot and the air jet pump to feed from the same gas line The amount of gas required for the pump can be adjusted using a throttle valve be regulated.

The difficulties identified at the beginning will be caused by the Method and device gamKA of the invention completely eliminated. At the same time, the invention automatically Processing of especially very fine-grained polytetrafluorethylene powder enables.

An example device according to the invention is shown schematically in the figure. It consists of the gas inlet 1, a controllable valve 2 which can be regulated by a control device 3 which can optionally be provided with a timer for the cycle time 3a and the metering time 3b, a distributor 4, a throttle valve 5t * · ■ Virbelgef & ß 6 with sieve plate 7, the air jet pump 8 and the delivery line 9 to the consumer. The distributor k and the throttle valve 5 are omitted if separate gas lines are used for the virgin and pumping. With continuous metering, the controllable valve 2 remains during the Dosing process opened.

• the

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BATH

Fv 5737 * βη 8) 6

Example It

In the metering device according to FIG. 1, compressed air from 10 atU initiated. AIa Virbelgefäß serves · «in commercial · Vessel and a laboratory water jet purape as an air jet pump.

The throttle valve 5 was set so that polytetrafluoroethylene powder with a larger grain size of kO .um was whirled up to about 3 times the volume. The powder was fed continuously in portions of 2 g to a Ram extruder. With a working cycle of β seconds for the Ram extruder, the dosing time was 0.5 seconds.

Example 2s

With the metering device described in Example 1, pulverulent polytetrafluoroethylene with a medium grain size was produced of 4OO yun with compressed air of 7 atU continuously in metered in a screw extruder. The dosage took place in portions of 5 g, for which a dosage of 1 second was sufficient. During an 8 hour run time of the extruder there were no difficulties with dosing »

BAD ORiGiNAL

009815/0360

Claims (1)

Pw 5737 - β » Claim «! β * Process for the metered delivery of powdery substances with a tendency to bridge * and lump formation, characterized in that the powdery substances are whirled up by Qa «and sucked in and conveyed by a pump. . ^ The method according to claim 1, characterized in that the metered delivery with continuous delivery is regulated by varying the suction power of the pump •) _v Method according to claim 1, characterized in that the metered delivery is regulated by varying the pumping time in the case of continuous-cycle delivery » . ^ j Method according to claim 1, characterized in that Dye, milk, PVC, low-pressure polyethylene or polytetrafluoroethylene powder is promoted. Device for carrying out the method according to claims 1-4, characterized in that the device consists of a vortex vessel known per se and a pump connected to its fluidized bed. Ä Device according to Claim 5, characterized in that the vortex vessel and the pump are connected to a common gas line connected and in which a timed valve (2) is arranged. 009815/0360 L e r s e i t e