JPH039223A - Conveyor type flowmeter - Google Patents

Abstract

PURPOSE:To measure an instantaneous flow rate with high accuracy by supporting screw conveyors at a necessary position and measuring the weight of a granule in the conveyors by a weight sensor, and calculating the granule flow rate from the rotating speed of the conveyor. CONSTITUTION:A conveyor case 2 which has upper-stage and lower-stage screw conveyors 11 and 12 is supported by a supporting part 20 right below a granule feed opening 13, the weight of the case 2 is measured by a load cell 21 to measure the weight of the granule in the conveyors, and the measurement result is outputted from a load cell amplifier 22. Then an arithmetic controller 23 where the speed of revolution of a motor 19 for conveyor driving is applied performs multiplication to determine the granule flow rate and the speed of revolution of the motor 19 is controlled through a speed varying device 24 so that the weight of the granule in the conveyors becomes constant. In this constitution, the flow rate of the granule varies without being affected by a shock, etc., by a fed granule to move the center of gravity of the conveyors, the accurate instantaneous flow rate is measured with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a conveyor-type flowmeter that measures the flow rate of powder using a conveyor.

(Prior Art) Conventionally, various methods for measuring the flow rate of powder and granular materials are known. For example, a batch-type flowmeter measures a part of continuously flowing powder or granular material by temporarily retaining it in a container, and then repeatedly flowing it downstream after metering, thereby measuring the flow rate. When this flowmeter is used, the flow of powder and granules is intermittent, making it impossible to measure the instantaneous flow rate.

Therefore, when it is desired to measure the instantaneous flow rate without interrupting the flow of powder or granular material, a conveyor type flowmeter such as a belt conveyor type flowmeter or a screw conveyor type flowmeter is used. This type of flow meter measures the flow rate by measuring the weight of the powder on the conveyor while conveying the powder on a belt conveyor or screw conveyor, and can measure the flow rate continuously with little vibration. Can you do it,
The problem is that it is relatively large and requires a considerable amount of installation space. In addition, the impact of transferring the powder to the -H belt conveyor or screw conveyor and the impact of sudden fluctuations in flow rate affect the measurement, making accurate measurement impossible. There is a problem with that.

On the other hand, with conventional conveyor-type flowmeters, the weight of the powder and granules being conveyed by the conveyor is converted into a flow rate and measured while keeping the conveyance speed of the powder and granules constant. When the flow rate fluctuates, the center of gravity of the entire conveyor moves, resulting in measurement errors, which again poses a problem with accuracy.

(Object and Structure of the Invention) The present invention has been made in view of the above points, and an object thereof is to provide a flow meter that can accurately measure instantaneous flow rate without stopping the flow of powder or granular material. In order to achieve this objective, firstly, a fulcrum for supporting the entire screw conveyor is provided at a position directly below the powder or granular material inlet provided in the screw conveyor. The second configuration is such that the rotational speed of the conveyor drive motor is controlled so that the weight of the granular material in the conveyor is approximately constant, whether it is a belt conveyor or a screw conveyor.

(Example) The present invention will be explained below based on the drawings.

A screw conveyor will be described as an example of a flowmeter according to the present invention. Prior to explaining the embodiments, the conveyance capacity of the screw conveyor will be explained first.

Now, the diameter of the blades of the screw conveyor is D, the diameter of the shaft is d, the pitch of the blades is P, the number of blades is n, the rotation speed of the blades is N (rpm), the apparent specific gravity of the powder is γ, the screw conveyor When the filling rate of the powder and granular material in the screw conveyor is φ, the powder and granular material conveying capacity Q (Kg/h) of the screw conveyor can be expressed by the following formula.

Q=-(D2-d")・γ・φ・P-Nx60...(
1) The weight W (kg) of the granular material in the screw conveyor at a certain moment is W=-(D2-d2)・γ・φ・cross...
...It can be expressed as (2).

On the other hand, the pitch P of the blades, the length of the conveyor, and the number n of blades
There is a relationship between P=seen/n (3).

From these equations (1), (2), and (3), the conveying capacity Q (Kg/h) is determined as follows.

Q;-・N・50...(4) That is, in a screw conveyor of a certain length, if the weight W of the powder or granular material in the conveyor, the number n of blades, and the rotation speed N are known, the conveyance amount can be calculated. Since the number n of blades of the screw conveyor does not change, the conveyance amount Q can be calculated by measuring the weight W and the rotation speed N.

The weight W is measured using a weight sensor such as a load cell,
The rotation speed N of the screw conveyor is calculated directly from a rotation meter or the rotation speed of the conveyor drive motor. When calculating the amount of conveyance, the amount of staying in the conveyor can be any amount depending on the size of N, so if you keep that amount constant, the center of gravity position will not change and the distance between the sensor and the center of gravity will change. This prevents changes in the moment due to this, allowing for more accurate weight measurement.

FIG. 1 shows an embodiment of a screw conveyor flowmeter as an example of a conveyor flowmeter according to the present invention.

The screw conveyor flowmeter 1 consists of screw conveyors 11 and 12 that are housed in two stages, upper and lower, in a case 2 and communicated at one end (the left end in the figure), and the upper screw conveyor 11 is connected to the other end (the right end in the figure). ) is connected to an input port 13 for powder and granular material, and a discharge port 14 for powder and granular material is connected to the input port 13 at the other end of the lower screw conveyor 12.
are connected in the same position.

Inside the upper screw conveyor 11, screw conveyor blades 15 are provided fixedly to the shaft 15a, and inside the lower screw conveyor 12, screw conveyor blades 16 are provided fixedly to the shaft 16a. are gears 1 that fit together
It is designed to be rotated by a motor 19 via 7 and 18.

The case 2 of the screw conveyors 11 and 12 is supported with respect to the stationary system as a fulcrum by a support member 20 between the two conveyors 11 and 12 at the position of the granular material input port 13 and the discharge port 14 at one end thereof. , the other end (the left end in the figure) is coupled to the load cell 21.

The load cell 21 outputs a signal corresponding to the weight of the powder inside the screw conveyors 11 and 12.

22 is a load cell amplifier that amplifies the weight signal output from the load cell 21; 23 is a load cell amplifier 22 that calculates the flow rate of the powder according to the above formula (4) based on the rotation speed N of the screw conveyor caused by the rotation of the motor 19; 24 is a variable speed device that outputs an AC speed control signal in accordance with the control signal from the arithmetic and control device 23.

Now, in this flowmeter, when the motor 19 is rotated to rotate the screw conveyors 11 and 12, and powder and granules are introduced from the powder and granule inlet 13, the powder and granules are transferred to the upper screw conveyor 11 at the left end in the direction of the arrow. The paper is conveyed to the left end, transferred to the lower screw conveyor 12, and then transported in the direction of the arrow to the right end, and discharged from the discharge port 14 at the right end. When starting, set the motor rotation speed to the maximum (
In other words, the conveying capacity is set to maximum) and the powder and granular material begins to flow.

In this state where a steady flow of powder and granular material is created in the screw conveyor 11.12, the weight W of the powder and granular material filling the screw conveyor 11.12 is measured by the load cell 21 as a weight signal. It is being output. This weight signal is amplified by the load cell amplifier 22 and sent to the arithmetic and control unit 23.

The arithmetic and control unit 23 calculates the weight of the powder and granular material according to equation (4) from the weight signal (representing the weight W) amplified by the load cell amplifier 22 and the rotation speed N of the blades of the screw conveyor 11, 12 determined from the rotation speed of the motor 19. The conveying capacity Q, that is, the flow rate is calculated and output.

By the way, when the flow rate of the powder and granular material input from the powder and granular material input port 13 changes, the arithmetic and control unit 23 detects the change by a change in the weight signal, and changes the rotation speed of the motor 19 to cancel the change in weight. A control signal is output to the variable speed device 24. In other words, the flow rate of the powder decreases and the load cell 2
When the weight detected by 1 decreases, the number of rotations of the motor 19 is reduced to increase the amount of powder staying in the screw conveyor 11, 12, thereby suppressing the decrease in weight and increasing the flow rate of the powder. When the weight increases, the number of rotations of the motor 19 is increased to reduce the amount of powder remaining in the screw conveyor 11, 12, thereby suppressing the increase in weight. By doing this, the weight of the powder and granular material in the screw conveyor 11, 12 is always kept constant, and the flow rate is calculated and displayed from the weight W and the rotational speed N at that time. At this time, the amount retained in the conveyor is kept constant regardless of the size of the inflow, so the center of gravity of the flowmeter is kept almost constant, and the moment does not change due to changes in the position of the weight sensor and the center of gravity, making it accurate. A flow rate calculation will appear.

In addition, the impact when the powder or granular material is introduced from the input port 13 is
Since the input port 13 and the discharge port 14 are located on the same vertical axis, and the conveyor case 2 is supported by the support member 20 on the same axis, the impact may affect the flow rate measurement. It can't be affected.

In the above embodiments, a two-stage screw conveyor flowmeter is illustrated, but the present invention is not limited to a two-stage flowmeter, and can of course be applied to a single-stage conveyor flowmeter.

(Effects of the Invention) As explained above, in the present invention, the screw conveyors are arranged one above the other, and the entire screw conveyor is supported as a fulcrum at a position directly below the powder/granular material inlet provided in the upper screw conveyor. Because of this structure, it is possible to measure the flow rate continuously without interrupting the flow of powder or granules, and it is also possible to eliminate the impact of impact when introducing powder or granules, without having any negative effect on flow measurement. Accurate flow measurement is possible. In addition, the number of revolutions of the conveyor drive motor is controlled so that the weight of the powder on the conveyor remains constant, and the flow rate is calculated based on the number of revolutions. Even if the flow rate fluctuates and the center of gravity of the entire conveyor moves, the flow rate calculation will not be affected in any way and accurate flow rate measurements can be made. In addition, by providing the powder inlet and outlet at the same vertical position,
The influence of upper and lower negative pressures generated in the powder transport path can be avoided, and application to closed systems is also possible. It can also be easily installed by inserting it in the middle of existing piping.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a conveyor type flowmeter according to the present invention. 1...Flowmeter, 2...Conveyor case, 11...
Upper screw conveyor, 12...Lower screw conveyor, 13...Powder material inlet, 14...Powder material discharge port, 15.16...Screw conveyor, 17゜1
8... Gear, 19... Motor, 21... Load cell, 220-Tocell amplifier, 23... Arithmetic control unit,
24...Variable speed device

Claims (3)

[Claims] (1) A support member provided near one end of the screw conveyor that supports the position of the powder/granular material input port as a fulcrum, and a weight sensor that measures the weight of the powder/granular material in the screw conveyor by supporting the entire screw conveyor. and a calculation means for calculating the flow rate of the powder or granule based on the weight of the powder or granule measured by the weight sensor and the rotation speed of the screw conveyor. (2) The screw conveyor type flowmeter according to claim 1, wherein the screw conveyor is comprised of conveyors arranged one above the other, and the lower screw conveyor has a powder outlet directly below the powder input port of the upper screw conveyor. . (3) A conveyor support member provided near one end of the conveyor, a weight sensor that measures the weight of the granular material in the conveyor by supporting the conveyor, and the weight of the granular material measured by the weight sensor. and calculation means for calculating the flow rate of the powder and granular material based on the rotation speed of the conveyor drive motor, and the calculation means calculates the weight of the powder and granular material in the conveyor based on the output from the weight sensor. A conveyor-type flowmeter characterized by having a function of controlling the rotation speed of a conveyor drive motor so that it is almost constant.