RU2029249C1 - Method of constant weight batching of material - Google Patents

Abstract

FIELD: measuring equipment. SUBSTANCE: one makes each discrete batch of material constant by weight. The cycles of charging of the discrete batches are unchangeable. In each cycle, time interval between the instant corresponding to the top given magnitude of the level of the oil product in a hopper and instant corresponding to the lower given level and time interval from the instant corresponding to lower given value of the level up to the beginning of the hopper charging in the next cycle are measured and volume flow rate of a source is set depending on sign and magnitude of difference between the first time interval and time of discharging of material from the top to the bottom level. EFFECT: enhanced accuracy. 1 dwg

Description

 The invention relates to methods of weight dosing and can be used in various technological processes.

 Known methods for continuous weight dosing, for example, using the weighting of a portion of a conveyor belt of a conveyor scale [1]. The main disadvantage of this method is the low metrological characteristics of continuous weight dosing.

 The closest in technical essence to the invention is the method described in [2], in which the continuous storage hopper is loaded with discrete doses of material and a constant predetermined mass rate of material discharge from the hopper is established.

 The disadvantages of the known method adopted for the prototype are low accuracy and complexity of implementation. These disadvantages are due to the following main reasons: the weight of the hopper due to the presence of motors, cables, etc. significantly exceeds the mass of material in it; mass estimation is carried out in dynamics by its change in fixed periods of time.

 The aim of the invention is to increase the accuracy of dosing and simplify the implementation of the method.

The goal is achieved in that the mass of each discrete dose is set constant, the loading of discrete doses is performed with a constant cycle providing a given average weighted performance, in each cycle of loading the hopper-feeder, the time interval t ₁ from the moment corresponding to the upper specified value of the product level in the hopper is measured, until a predetermined value corresponding to the lower level, and the interval from the time t ₂ corresponding to the lower preset level, prior to loading hopper next qi le and set the volumetric capacity feeder continuous depending on the sign and magnitude of the difference between the interval t ₁ and t setpoint _of - time discharging the material from the upper to the lower level, which varies depending on the value of t _2, if the latter is out of range.

 The drawing schematically shows a device for implementing a method of continuous weight dosing of material.

 The device comprises a discrete weighing batcher 1, a hopper 2 with a continuous feeder 3. The bunker is equipped with two signaling devices of level 4, 5 and in internal volume does not exceed two, three times the volume of the discrete dose. In the region of levels B and C (at the places of setting level signaling devices), the hopper is, as a rule, cylindrical with a diameter slightly exceeding the critical diameter of the compilation of bulk material. To reduce the diameter of the arch formation and increase the accuracy of fixing levels, you can impose vibration effects on the hopper.

 The method of continuous weight dosing of the material is implemented as follows.

 A discrete weighing batcher with a constant cycle loads discrete doses of constant weight material into the hopper 2, and a feeder 3 with an adjustable capacity performs continuous unloading of the hopper 2.

 Consider the operation of the device, taking as the beginning of the cycle a signal to load a discrete dose of material into the hopper 2.

 After loading a discrete dose, the material level in hopper 2 is maximum (level A). Subsequently, due to unloading of the hopper 2, the level in it decreases and reaches the upper preset value B, which is fixed by the level 4 indicator. With a further decrease in the level of the material, the lower predetermined level C is reached, which is fixed by the signaling device 5, and then the minimum level D is reached (by the time the signal is issued for loading the next discrete dose). This is followed by loading another dose of the mass of material and the cycle repeats.

During the cycle, the time t _{1 is} measured from the moment corresponding to the upper predetermined level B of the material to the moment corresponding to the lower predetermined level C of the material, and the time t ₂ from the moment corresponding to the lower predetermined level C of the material until the hopper starts loading.

In addition, before the start of measurements of time t ₁ and t ₂ , the time t _{o of} unloading the material from the upper to the lower level and the time interval t from the moment corresponding to the lower level C of the material in the hopper to its loading into the hopper in the next cycle are set, and material is unloaded from the hopper at a fixed speed.

The measured values of time t ₁ and t _{2 are} compared with t _o and t, respectively, and if mismatch t ₁ ct _o change the fixed speed of unloading, and if the mismatch t ₂ ct correct t _o . The value of t _o for this material is set at startup.

где S - площадь поперечного сечения бункера-накопителя;
h - разность уровней В и С;
γ- средняя насыпная плотность сыпучего материала;
G - массовая скорость выгрузки материала из бункера-накопителя.The value of t _o is determined by the formula
t _o =

where S is the cross-sectional area of the storage hopper;
h is the difference in levels B and C;
γ is the average bulk density of the bulk material;
G is the mass rate of discharge of material from the storage hopper.

The need to adjust the value of t _o is explained as follows. The dispenser control system first of all ensures that t ₁ corresponds to t _o in order to maintain a given mass productivity. However, the mass productivity is equal to the set value only if the bulk density of the bulk material is constant and equal to its average value. Otherwise, an error accumulates, which, in particular, leads to a change in t ₂ . If t ₂ has become less than the smallest limit value (equal to zero in the limit), then the bulk density has decreased and as a result the levels A and D have unacceptably increased, therefore it is necessary to reduce the set point t _o by a discrete value Δ t _o , while t ₁ immediately will become more than the new value of t _o and the control system will increase the volumetric capacity of the continuous feeder, thereby compensating for the decrease in the density of the bulk product, and accordingly, levels A and D will begin to decrease. If after adjusting t _{o the} value of t ₂ is still less than the limit value, the set point t _{o is} again reduced by Δ t _o , etc., until t ₂ falls within the established tolerance. If the level D drops below a predetermined value (t ₂ has become greater than the highest limit value), then levels A and D are unacceptably lowered and it is necessary to increase the setpoint t _o and, all things being equal, the control system will be forced to reduce volumetric performance, returning the system to its nominal state.

This system guarantees with high accuracy the average mass productivity, and the deviation of the instantaneous mass productivity from the average depends on the step of changing the set point and the limits of variation of t ₂ .

An example of a specific implementation of the method of continuous weight dosing of the material (indicative data). Cycle time, t _c , s 20 Setting value, t _o , s 12 Step of changing the set point, Δ t _o , s 0.1 Limits of change t: largest t _2max , c 5.5 smallest t _2min , c 4.5
At a certain point in the functioning of the system, the time intervals are: t ₁ = 12.1 s; t ₂ = 4.6 s.

In accordance with the value of the difference t ₁ -t _o = 0.1 s, the volumetric productivity of the continuous feeder is increased, for example, by 1% (the performance of the feeder is adjusted over a period of time corresponding to a change in the material level from level C to level D). The value of the setting t _o do not change, since t _2min <t ₂ <t _2max .

Suppose that in the next cycle of the system’s functioning, the results t ₁ = 12.1 s were obtained; t ₂ = 4.3 s.

In accordance with the value of t ₁ -t _o = 0.1 s, the capacity of the feeder is increased at the end of the cycle, for example, by 1%. After reaching level D, the value of the set point t _{o is} changed (it is reduced by Δ t _o ), since t ₂ <t _2min
t _o = 12-0.1 = 11.9 s
We assume that as a result, in the next cycle, the values t ₁ = 12 s are obtained; t ₂ = 4.4 s.

In accordance with the value of t ₁ -t _o = 0.1 s, the capacity of the feeder is increased by another 1%, after reaching the level D, the setting is again reduced by Δ t _o , since t ₂ <t _2min
t _o = 11.9-0.1 = 11.8 s
In the next cycle, t ₁ = 11.8 s; t ₂ = 4.6 s.

Since t ₁ -t _o = 0, the volumetric capacity of the dispenser is not changed. The value of the setting also does not change, since t _2min <t ₂ <t _2max .

This method guarantees high accuracy of the average mass productivity by loading the dispenser with discrete doses of a product with a constant cycle, and the deviation of the instantaneous mass productivity from the average value is set depending on the step of changing the set point t _o and the limit of the time interval t ₂ .

Claims (1)

 METHOD OF CONTINUOUS WEIGHT DOSING OF "RINT" MATERIAL. The method of continuous weight dosing of material, which consists in loading the material into the hopper and then unloading it at a fixed speed, characterized in that the upper and lower levels of the material in the hopper are set, the time setting t _{0 for} unloading the material from the upper to the lower level, time interval t from the moment corresponding to the lower level of the material in the hopper, before it starts to be loaded into the hopper in the next cycle, and the material is loaded into the hopper with a fixed mass dose, and during the unloading process, time t _{1 is} measured from the moment corresponding to the upper level of the material, until the moment corresponding to the lower level of the material, and the time t ₂ from the moment corresponding to the lower level of the material, before loading the hopper, and compare them with t ₀ and t respectively and if the mismatch t ₁ with t ₀ change the fixed speed unloading, and if mismatch t ₂ with t adjust t ₀ .

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