DE19723218A1 - Weighing bulk goods from silo - Google Patents

Abstract

The method involves periodically operating a silo closure member (13), to release a variable amount of goods into a container (16). To compensate for the afterflow of bulk goods between the closure member and the container after closure of the member, the amount of goods for the next dispensing process is adjusted. A correction value is calculated from the difference between the set amount and the weighed actual amount, and the amount is weighted by a weighting factor (K1,K2). The weighting factor is set differently for sequential dispensing processes.

Description

The invention relates to a method for weighing a bulk goods, where the goods from a silo through periodically actuating a closure arranged on the silo elementes in the form of successive individual fillings with adjustable bulk quantity in a container poured and the respective bulk quantity is weighed where to compensate for a between the closed Ver closing element and the container still trailing wake  the bulk quantity for the subsequent pouring process is made by using the difference between a target Amount and the weighed respective bulk amount Weighting with a factor a correction value for readjustment of the target overrun quantity to be set in each case becomes.

The invention further relates to a weighing device of a pourable good, in which the pourable good consists of a silo by periodically actuating one on the silo arranged closure element in the form of successive Individual fillings with adjustable bulk quantities in poured a container and dispensed the respective bulk amount is weighed, with a compensation between the closed closure element and the container still after a post-flow control for readjustment the bulk quantity for the subsequent pouring process see and the wake control from the difference between a target bulk quantity and the weighed resp corrected bulk quantity by weighting with a factor value to adjust the target values to be set in each case Overrun quantity determined.

Weighing machines for weighing pourable materials are known Use goods such as this for filling dry, powdery, granular, small pieces or bulky Filling goods at the same weight quantities are always required.

Weighing machines of this type can be constructed purely mechanically be, however, have become electromechani over time and electronic-mechanical weighing machines more and more enforced. With modern electronic-mechanical weighing The actual weighing process is machined using sensors carried out with an associated evaluation electronics in Connect.  

To operate these weighing machines, the bulk material to be weighed is poured from a silo into a container, a closure element, for example a closure flap or the like, being provided at the silo outlet. By periodically actuating the closure element, a predetermined amount can be filled into the container. There are two different methods:
With the abbreviation "SWA", which is common in the professional world, a weighing machine is referred to in which the goods are portioned in order to provide a large number of predetermined individual portions. In this case one also speaks of a bagging scale. A typical application example is the filling of single bags with e.g. B. dog food, plastic granules or other pourable goods or food.

In contrast to this is the usual in the professional world The abbreviation "SWT" denotes a weighing machine with a lot Number of individual weighings totaled to a total weighing becomes. If e.g. B. a large container or a truck or the like with a very large amount of a pourable Good things should be loaded, so this happens with one such weighing machine in that a predetermined number of Individual weighings are carried out and then the total weight Adding up is totalized.

In known weighing machines had to be used for these two weighers different measuring systems or evaluations systems are used.

An essential problem with weighing machines is the exact one Dosage of each poured and then weighed individual bulk amount. If the pourable good at open closure element under the influence of gravity in the  Container falls and then the closure element to a pre is closed again at the given time on the path between the closure element and the Container still a certain amount of wake in free flight, which has not yet been detected by the weighing sensors on the container. This "wake" or "wake" represents a system table errors in known weighing machines.

To minimize this error, it is known the mass divide the flow from the silo into the container into two phases, namely a coarse feed in which a coarse quantity in the Container arrives during a subsequent fine feed the final weight is filled in the container. In this case, the wake or wake only occurs in the Phase of the fine feed, i.e. during a mass flow of lower throughput per time, so that already there by reducing the error. However, the lead division of the mass flow into a rough feed and a fine lead to an extension of the weighing process because only a small mass during the fine feeding phase current can be adjusted.

It is also known to be the wake or wake to be taken into account by a so-called post-flow controller. Such post-flow controllers are also purely mechanical or electrical or electronic embodiment known. In principle, a wake controller causes the ver closing element at the exit of the silo at one time is closed, for which the weighing sensors have not yet display the full amount, so that only when the Afterflow into the container the full predetermined bulk amount is achieved.  

Weighing machines are therefore known in which the weight the individual bulk quantity is recorded electronically, the The target bulk quantity can also be specified for each individual fill is like a target follow-up quantity. The target overrun quantity is pre-selected by the user of the weighing machine based on experience give. It depends e.g. B. from the consistency of the pourable Good and the design of the machine, especially the Ver final element and the wake controller.

In this context, it is known after every single weigh the actual bulk quantity, the difference to Determine target bulk quantity and the resulting differences limit to adjust the target overrun quantity. To For this purpose, the difference is determined with a wich factor, which is usually less than 0.3. If so z. B. when weighing a certain individual bulk quantity it is found that 100 g were poured too little (compared to the target bulk quantity), so for the next correct the pouring process of the post-flow regulator by 30 g, with the result that the shortage at the next single filling is lower. The weighting of the determined There is also a difference with a factor of less than 0.3 the sense that mistakes in pouring are only appropriate have a dampened effect, for example if the door is open Closure element a large lump of the pourable goods falls into the container and consequently with this single the bulk weight compared to the target bulk quantity is significantly higher. By the described proportional The pouring error is thus regulated over a plurality of Single pouring processes gradually settled.

In these known weighing machines or the one used Weighing is disadvantageous in that for newly set up Pouring processes it takes a whole time before  e.g. B. in the SWA process explained above, individual fillings be achieved within a given tolerance lie, while in the SWT process the initially occurs tendency to either falsify the totalized end result or avoid this error must be eliminated in advance.

This problem occurs particularly with automated Filling systems with appropriate weighing machines on which different varieties of Bulk goods must be filled and thus weighed.

The invention is therefore based on the object of a method of the type mentioned to further develop that even if the type of bulk goods changes quickly half-shortest time single deliveries within a pre given tolerance are carried out, d. that is, the night current errors largely eliminated in the shortest possible time is regulated.

In a method of the type mentioned at the beginning, this is Problem solved according to the invention in that the factor for successive pouring processes differ is set.

In a device of the type mentioned that Invention underlying problem solved in that the Different factors for different pouring processes is adjustable.

This task is solved in particular by the following steps:

• a) Specifying a target bulk quantity and one first target overrun quantity;
• b) pouring a first quantity into the Container with specification of the target bulk quantity and the first target overrun quantity;
• c) weighing the first bulk quantity;
• d) comparing the weighed first bulk quantity with the target bulk quantity and forming one first quantity difference;
• e) Weighing the first quantity difference with a first factor, which is between 0.8 and 1.0;
• f) forming the difference of the first target caster quantity and the weight determined in step e) quantity difference as the second target-after run quantity;
• g) pouring a second quantity into the Container with specification of the target bulk quantity and the second target overrun quantity;
• h) weighing the second bulk quantity;
• i) Compare the weighed second bulk quantity with the target bulk quantity and formation a second difference in quantity;  
• j) Weights of the second quantity difference with a second factor, which is between 0.1 and 0.5 lies;
• k) forming the difference of the second target after run quantity and the one determined in step j) weighted quantity difference as the third target Run-on quantity;
• l) Pour a third quantity into the Container with specification of the target bulk quantity and the third target overrun quantity;
• m) repeating steps h) to l), the Bulk amount of the umpteenth pouring process below Specification of the target bulk quantity and the xth Target overrun quantity is set.

It is particularly preferred if the first factor is 1.0 is set.

Furthermore, it has already been mentioned that the pourable good choice wise for weighing individual quantities or totalized can be weighed. In the method according to the invention, this is in a simple way by switching between the two Operating modes possible without measuring modules or the like should be exchanged.

Further advantages result from the description and the attached drawing.

It is understood that the above and the following standing features to be explained not only in the  combination specified in each case, but also in other com binations or alone can be used without the To leave the scope of the present invention.

An embodiment of the invention is in the drawing shown and is described in more detail in the following description explained. Show it:

Fig. 1 is an extremely schematic view of an example of a Ausfüh approximately device according to the invention, on which the inventive method can be carried out;

Fig. 2 is a diagram for explaining the time sequence of individual bulk quantities;

Fig. 3 is a diagram, similar to FIG. 2, but for the illustration of individual target follow-up quantities.

In FIG. 1, 10 denotes a silo for a bulk material 11 of the type described in the introduction. The bottom of the silo 10 runs into a hopper 12 . In the funnel 12 there is a closure element 13 , for example a closure flap. The closure element 13 can be actuated by means of an actuating device 14 so that individual quantities of the bulk material 10 can fall down through the funnel 12 , as indicated by an arrow 17 .

Below the funnel 12 there is a fixed weighing table 15 , on which an upwardly open container 16 is located. The bulk material 11 falling in the direction of arrow 17 thus falls into the container 16 . The container 16 can be individually emptied or replaced, as indicated by an arrow 18 . Here too, the representation is only to be understood schematically. The container 16 can in practice, for. B. be designed as a bucket-like weighing vessel, which is provided with a bottom flap, the weight being measured laterally in the suspension of the weighing vessel.

A sensor 20 is located in the weighing table 15 in order to measure the quantity or the weight of the individual quantity of bulk material 11 which has fallen into the container 16 . The sensor 20 is connected to a control unit 21 , which at the same time controls the actuating device 14 . The control unit 21 has a keyboard 22 for entering setpoints and also a switch 23 with which, for. B. can be switched between the explained operating modes SWA and SWT.

The mode of operation of the device according to FIG. 1 is to be explained using the diagrams of FIGS. 2 and 3:

If with the device a new type of bulk material 11 is to be weighed in individual portions according to the SWA method explained, the predetermined bulk quantity M _SS of z. B. 10.0 kg. The user of the system also determines a first target overrun quantity M _NS1 on the basis of empirical values or corresponding tables. This target _overflow quantity M _NS1 is the estimated quantity of bulk material 11 which is still in free fall along the arrow 17 to the container 16 after the closure element 13 has been closed. The target trailing amount M _NS1 is determined based on the construction of the system, the closure element 13 with the actuating device 14 , but in particular also with regard to the respective type of bulk material 11 . It is, for example, 0.5 kg in the embodiment described here.

In a further step b), a first bulk quantity M _S1 is now poured into the container 16 , specifying the two values M _SS and M _{NS1 mentioned} .

This first bulk quantity M _S1 is now weighed in a further step c). It turns z. B. out that the amount actually poured M _{S1 is} only 9.7 kg. This is shown schematically in FIG. 2.

In a further step d), the target bulk quantity M _{SS is} compared with the weighed first bulk quantity M _S1 and a first quantity difference Δ ₁ M _{S is} formed. The difference in quantity Δ ₁ M _S in the example is 10.0-9.7 = 0.3 kg.

In a next step e), this first quantity difference Δ ₁ M _{S is} weighted with a first factor K ₁ . The first factor K ₁ is preferably between 0.8 and 1.0, a value of 1.0 is particularly preferred. So the weighting is 1.0 0.3 = 0.3 kg.

In a subsequent step f), the difference between the first target overrun quantity M _NS1 and the weighted quantity difference K ₁ .Δ ₁ M _S determined in step e) is determined as the second target overrun quantity M _NS2 . In the example, this is 0.5-0.3 = 0.2 kg. This means that the target overrun quantity is now reduced from the originally set value of 0.5 kg to 0.2 kg, because it has been found that the overrun is obviously much smaller than expected, with the result that the only 9.7 instead of 10.0 kg were poured in the first filling.

In a subsequent step g), a second bulk quantity M _S2 is now poured into the container 16 , specifying the target bulk quantity M _SS and the second target overflow quantity M _NS2 .

In a subsequent step h), this second bulk quantity M _{S2 is} now weighed out. It turns z. B. out that M _S2 = 10.05 kg, the target bulk quantity M _SS of 10.0 kg was therefore slightly exceeded.

In a next step i), the target bulk quantity M _{SS is} compared with the weighed second bulk quantity M _S2 and the corresponding second quantity difference Δ ₂ M _{S is formed} , which in the example is 10.0-10.05 = -0.05 kg .

In the next step j), the second quantity difference Δ ₂ M _{S is} weighted with a second factor K ₂ . This second factor K ₂ is preferably between 0.1 and 0.5, for example 0.3.

The weighting is therefore 0.3. (- 0.05) = -0.015 kg.

In the next step k), the difference between the second target follow-up quantities M _NS2 and the weighted quantity difference K ₂ .Δ ₂ M _S determined in step j) is formed as the third target follow-up quantity M _NS3 . In the example, this is 0.2 - (- 0.15) = 0.215 kg.

It can thus be seen that the target overrun quantity is from the out current value of 0.5 kg over the first corrected value 0.2 kg has now changed to 0.215 kg, so slowly on one Full value settles.

In step l), a further filling follows, and further corresponding calculation and correction processes follow, the fourth target _{overflow quantity} M _NS4 consequently following the equation in the following process:

M _NS4 = M _NS3 - (M _SS -M _S3 ) .K ₂

is determined, generally expressed:

M _NSx = M _{NS (x-1)} - (M _SS -M _{S (x-1} ) .K ₂ .

From Fig. 2 and 3, where these values are roughly shown schematically, it follows that a first substantial com pensation takes place after the first bed because the first correction factor K _{1 is set} at 1.0. Ideally, the entire error is compensated for at the first correction, so that usable pouring results are available from the second fill. Therefore, you have to eliminate the first fill in a SWA measurement if you have been too wrong in determining the first target _overflow quantity M _NS1 . With totalizing weighing according to SWT, it may not be necessary to discard the first batch because the error occurs only once during the first batch and therefore no longer has a significant impact on the totalization of a large number of batches.

Claims (7)

1. A method for weighing a pourable good ( 11 ), in which the good ( 11 ) from a silo ( 10 ) by periodically pressing a silo ( 10 ) arranged Ver closing element ( 13 ) in the form of successive individual fillings, each with an adjustable bulk quantity poured into a container ( 16 ) and the respective bulk quantity is weighed, the bulk quantity for the subsequent pouring process being readjusted in order to compensate for a wake flowing between the closed closure element ( 13 ) and the container ( 16 ), in which the difference between a target / bulk quantity (M _SS ) and the weighed respective bulk quantity (M _Sx ) is determined by weighting with a factor (K ₁ , K ₂ ), a correction _value for adjusting the set target quantity to be set (M _NSx ), characterized in that the factor (K ₁ , K ₂ ) is set differently for successive pouring operations . 2. The method according to claim 1, characterized by the steps:

• a) Specifying a target bulk quantity (M _SS ) and a first target trailing quantity (M _NS1 );
• b) pouring a first bulk quantity (M _S1 ) into the container, specifying the target bulk quantity (M _SS ) and the first target overflow quantity (M _NS1 );
• c) weighing the first bulk quantity (M _S1 );
• d) comparing the target bulk quantity (M _SS ) with the weighed first bulk quantity (M _S1 ) and forming a first quantity difference (Δ ₁ M _S );
• e) weighting the first quantity difference (ΔM _{1 S} ) with a first factor (K ₁ ) which is between 0.8 and 1.0;
• f) forming the difference between the first target overrun quantity (M _NS1 ) and the weighted quantity difference (K ₁ .ΔM _S ) determined in step e) as the second target overrun quantity (M _NS2 );
• g) pouring a second bulk quantity (M _S2 ) into the container, specifying the target bulk quantity (M _SS ) and the second target overflow quantity (M _NS2 );
• h) weighing the second bulk quantity (M _S2 );
• i) comparing the target bulk quantity (M _SS ) with the weighed second bulk quantity (M _S2 ) and forming a second quantity difference (Δ ₂ M _S );
• j) weighting the second quantity difference (Δ ₂ M _S ) with a second factor (K ₂ ) which is between 0.1 and 0.5;
• k) forming the difference between the second target overrun quantity (M _NS2 ) and the weighted quantity difference (K ₂ .Δ ₂ M _S ) determined in step j) as the third target overrun quantity (M _NS3 );
• l) pouring a third bulk quantity (M _S3 ) into the container, specifying the target bulk quantity (M _SS ) and the third target overflow quantity (M _NS3 );
• m) repeating steps h) to l), the bulk quantity (M _Sn ) of the x-th bulk process being set by specifying the target bulk quantity (M _SS ) and the x-th target trailing _quantity (M _NSx ), where
  M _NSx = M _{NS (x-1)} - (M _SS - (M _{S (x-1)} ) K ₂
  is.

3. The method according to claim 2, characterized in that the first factor (K ₁ ) is set to 1.0. 4. The method according to one or more of claims 1 to 3, characterized in that the pourable material ( 11 ) is weighed either for weighing individual quantities (SWA) or totalizing (SWT). 5. Apparatus for weighing a pourable good ( 11 ), in which the pourable good ( 11 ) from a silo ( 10 ) by periodically actuating a on the silo ( 10 ) arranged closure element ( 13 ) in the form of successive individual fillings with each setting cash bulk quantity poured into a container ( 16 ) and the respective bulk quantity is weighed, a post-flow control for adjusting the bulk quantity for the subsequent pouring process being pre-compensated for a compensation flow between the closed closure element ( 13 ) and the container ( 16 ) can be seen and the night current control determines a correction _value from the difference between a target bulk quantity (M _SS ) and the weighed respective bulk quantity by weighting with a factor (K ₁ , K ₂ ) for adjusting the target _{flow quantity} to be set (M _NSx ), characterized in that the factor (K ₁ , K ₂ ) for different Sc can be set differently. 6. The device according to claim 5, characterized in that a first factor (K ₁ ) for determining the target wake quantity (M _NS2 ) for the second pouring process between 0.8 and 1.0 and other factors (K ₂ ) for determination the target _{overflow quantity} (M _NS3 , M _NS4 , _... M _NSx ) for the subsequent pouring operations is set between 0.1 and 0.5. 7. The device according to claim 6, characterized in that the first factor is set to 1.0.