DE102004051196A1 - Controled filling and emptying of granulate hoppers for feeding extruder involves filling storage hopper with part of hourly material requirement which is completely emptied into weighing hopper before refilling - Google Patents

Abstract

The hopper system comprises a storage hopper(7) and a weighing hopper(4) with computer controled output to an extruder below. The amount(8) of granulate material in the storage hopper forms a fraction of the hourly usage for each component. At each filling stage the fraction in the storage hopper is completely emptied into the weighing hopper and a further similar fraction is then delivered to the empty storage hopper. Amounts(8) of granulate in the storage hopper can be freely chosen and are programmable. The percentage of granules in the storage hopper relative to the hourly throughput in an extrusion plant is almost the same for each component. At the start of a particular production run the amount added to the storage hopper can be relatively large, but decreases towards the end of the run. Determination of individual amounts added to the storage hopper can be made by calculating the filled level(10) in the hopper and controling with an ultrasonic sensor(9) on the hopper. For determination of material weight added to the storage hopper the latter is mounted on a weighing cell which allows the filling level to be measured. Filling ends when the correct weight is reached. Alternatively the level of material during filling can be determined by a level sensor. Sensor positions can be set as required by a servomotor and height setter. After setting the filling amount all further stages are automatically controled by a computer.

Description

The The invention relates to a method for controlled filling and Emptying granule funnels, e.g. at production change, which is often associated with material changes, a short changeover time to achieve and optimize the use of materials in which the funnels not in addition must be emptied.

at In modern extrusion plants, the funnel system consists of 2 one above the other arranged funnels that over a slide valve are connected to each other. The upper funnel is the storage hopper, from which the lower hopper is filled. Of the lower hopper is the weighing hopper, it hangs freely on a load cell, The almost continuous consumption of granules through the weight reduction determined and so u. the screw speed of the extruder on the prescribed consumption regulates. If a minimum weight is reached at the weighing hopper, it opens the sliding valve and the weighing hopper are almost completely filled. The Granulated material escaped from the storage hopper then immediately becomes refilled again by means of granulate conveyor. The is called, In this system, often both funnels are almost completely filled, and the entire capacity hangs in the essentially from the two funnel volumes. At production change then the entire amount has to be added, mostly by hand, be emptied. You can also premature the granules conveyor but this is for coextrusion systems with multiple extruders (up to 7) and up to 15-20 Funnels barely overlooked, Errors are not excluded.

The The present invention seeks to eliminate these fill operations from hopper volumes dependent to do, but exclusively on the consumption of the individual funnel systems. Has e.g. at a 7-layer system with 7 extruders each extruder still 3 hopper systems, 21 hopper systems are to be controlled. The operating staff is overwhelmed. The modern extrusion lines are controlled by computer, thus also the throughput of each component and thus each Hopper system. Thus lies for Each funnel system requires the required throughput in kg / h.

The The present invention now divides the hourly flow rate for each component in almost equal percentages which simultaneously determines the filling cycle times. For example, e.g. with a distribution of the quantity power to 4 times 1/4 the performance of the filling cycle every 15 minutes.

at A hopper system with a capacity of 100 kg / h is the filling quantity per filling cycle 25 kg, with a capacity of 40 kg / h equal to 10 kg per filling cycle. This is the maximum amount of granules in each funnel system between 15 and 30 minutes, depending on the current level.

Based the attached Drawings may be closer to the invention to be discribed.

It demonstrate

1 a hopper system with conventional filling system

2 a filling system with a solution according to the invention with an ultrasonic sensor for determining the level of the storage hopper

3 a filling system with a solution according to the invention with a storage hopper with load cell for determining the optimum filling weight.

4 a filling system with a solution according to the invention with a Fülistandssensor for determining the level of the storage hopper

5 shows the sequence of a work cycle

1 shows a normal arrangement of a funnel system with the extruder 1 and the filler housing 2 connected is. The weighing funnel 4 is with granules 3 filled. The funnel 4 hangs on a load cell 6 , which is almost continuously the weight of the weigh hopper 4 measures and calculates the throughput per hour from the weight change and compares it with the specified value and, if necessary, corrects the screw speed.

Above it is the storage funnel 7 arranged by the granule conveyor 11 over the filler neck 12 is supplied with granules. In this case, the filling process takes until the storage hopper is completely filled. The slide valve 6 is closed, preventing granules from falling out of the storage hopper. Will about the load cell 6 found that the weighing hopper 4 is almost empty, the slide valve is opened and the weigh hopper is filled until the maximum weight is reached and the slide valve 6 is closed. During the filling process, the weight measurement is interrupted. The storage hopper 7 will now again on the granule conveyor 11 completely filled. In this funnel system, both funnels are used with as large a volume as possible. This provides the greatest possible safety with respect to idling in the case of faults, but has the disadvantage that all hopper systems are replaced when changing the product and thus changing the granules must be completely emptied. This is relatively expensive.

The solution according to the invention avoids this disadvantage by specifying a delivery cycle for each component and thus each funnel system and which can also be selected, which results exclusively from the quantity output of each individual funnel system. For example, you can choose a delivery cycle of 6 or 12 minutes, then one tenth of the hourly demand will be charged every 6 minutes or one fifth at 12 minutes. This means, per cycle, the reservoir is filled according to the area code with, for example, a tenth or a fifth of the hourly demand. 2 shows such a situation.

The storage tank 7 is filled with granulate according to the instructions until the desired weight is reached. This is controlled by calculating the fluid level from the computer based on physical conditions and the level 10 via eg an ultrasonic sensor 9 is determined and on reaching the relevant level height promotion via the granule conveyor 11 is switched off. Has the weighing funnel 4 reached its minimum weight, the sliding valve 6 opened and the predetermined subset is introduced into the weighing hopper and thereby completely emptied. When the level sensor 20 no more granules is detected, the sliding valve 6 closed and the granule conveyor 11 begins with the filling of the storage hopper until the fill level 10 is reached. After that, the process repeats itself. The advantage of this solution lies in the fact that the complete funnel system never contains more than twice the specified filling quantity and thus the system never contains more granules than required for twice the cycle time. This means that in the case of granule changes, after a short time the system has emptied itself through the normal granule consumption and only the suction tube of the granulate conveyor 11 is introduced into the container with the new granules. Thus, every cost-intensive emptying of the hopper system with the accompanying circumstances such as manual hopper emptying, granule contamination in the extrusion area and residual granulate storage or disposal. Since the filling quantity per delivery cycle can be chosen freely and always based on the granulate consumption of each component, this advantage applies to all components, so that all granules can be changed almost simultaneously when changing products, regardless of the volumes of the individual funnel systems. Sets the level sensor 19 at the bottom of the storage hopper 7 notice that the funnel 7 is empty, the sliding valve becomes 6 closed and the granule conveyor 11 starts with a new filling process.

3 shows another solution for determining the predetermined capacity. In this case, the storage hopper also depends 7 on a load cell 14 , As soon as the filling weight has been reached, the pumping will stop. Since modern systems are always computer-controlled systems, all the values required for automation are available.

4 shows another solution for determining the amount in the hopper. Here, a level sensor ensures 15 upon reaching the predetermined filling quantity for the shutdown of the filling. The level sensor 18 is via a servomotor 16 and, for example, set a thread guide to the required height.

Theoretically, it is also possible to use the level sensor 18 To push by hand in the necessary position, but this is very complicated in several extruders with multiple funnel systems.

5 shows the sequence of a filling cycle. In 5.1. Both funnels are filled, the bottom feeds the extruder, the top one is ready for emptying. In 5.2. the bottom funnel has reached its minimum weight, so that the next moment the slide valve opens and the upper funnel is completely emptied, 5.3. , Subsequently, the slide valve is closed, the granules filled again to the predetermined capacity ( 5.4 ) It is important that the upper funnel is always emptied completely so that no mixing of the granules takes place when the material changes.

If the set filling quantity is greater than the available funnel volumes, the filling cycle will change automatically, since upon reaching the minimum weight of the weighing funnel 4 automatically the slide valve 6 is opened and granules fall after, and at empty storage hopper 7 whose filling begins again.

In general it can be said that by pre-determining the fill levels to a percentage of, for example, 20% of the hourly consumption, the quantities of granules in each component take the same time until the system has emptied on change of product. The operator can in such a case (20%) about 12 minutes before the end of the product fill the suction tube of the granular conveyor between the conveyor cycles in the granules with the new granules, so that when re-aspirating the granules is filled in the then empty storage hopper. If the weighing hopper is almost empty (minimum weight), the new granules fall onto the remainder of the old one without mixing with it. The operator then has the option of using other products during the rinsing phase (rinsing old with the new granules) make adjustments. Thus, there is no additional hopper emptying and Granulatrestmengen. When determining the optimum filling quantity, one therefore essentially assumes how much time is needed for a product changeover.

By the data available in the control computer is also possible during one large part the current production the filling quantities relatively big too and only at the end of the product to change to smaller quantities, which the Accelerated granule change,

1

extruder

2

Einfüllgehäuse

3

amount of granules in the weighing funnel

4

weighing hoppers

5

Load cell

6

slide valve

7

hopper

8th

granules in the storage hopper

9

ultrasonic sensor

10

distance to the ultrasonic sensor = filling limit

11

granulate conveyor

12

filler pipe

13

suction tube

14

Load cell at the storage hopper

15

screw

16

stepper motor

17

Granulatansaugrichtung

18

level sensor

19

weight limit

20

level sensor at the bottom of the storage funnel

Claims (8)

Method for filling hopper systems, consisting of storage hopper 7 and the weighing hopper below 4 , which are used to feed, for example, extruders and their throughputs are controlled by appropriate computer systems, characterized in that the capacity 8th for each granule component is a subset of the hourly consumption and each subset of this subset in the weighing hopper 4 by completely emptying the storage hopper 7 is filled and then the storage hopper 7 with the same subset refills. A method according to claim 1, characterized in that the quantities 8th are freely selectable and programmable. A method according to claim 1 and 2, characterized in that the percentage of the quantities 8th the hourly throughput within an extrusion line for all components is almost the same. Method according to claims 1-3, characterized that the fill quantities to be relatively large at the beginning of the order can and get smaller at the end of the order. A method according to claims 1-4, characterized in that for determining the individual quantities 8th the filling level 10 in the storage hopper 7 calculated by a funnel-mounted ultrasonic sensor 9 which also finishes the filling process on each cycle. A method according to claim 5, characterized in that for determining the filling weight 8.1 the storage hopper 7 on a load cell 14 is mounted, with which the filling level 19 is measured and stops the filling after reaching the capacity. A method according to claim 5, characterized in that the filling level via a level sensor 18 is determined and calculated the position of the level sensor and a servomotor 16 and a height adjustment 15 is set. 8, Method according to claim 5, characterized in that any other suitable measuring device for determining the filling quantity 8th or the filling level 10 can be used. Method according to claims 1-7, characterized that after setting the filling Percentage of all further operations be controlled by a computer and essentially automatically expire.