JP3129604B2 - Constant air volume control device used for pneumatic transportation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant air volume control device used in a multi-pipe air transport system, and more particularly to a constant air volume control device provided at a predetermined position of each branch pipe (transport pipe) of a collecting pipe air transport system. It relates to an apparatus (a constant air volume valve).

[0002]

2. Description of the Related Art Since a multipipe air transport system has a large number of air transport pipes (branches), when a load fluctuation occurs in each transport pipe, the air volume balance of each transport pipe is lost. Therefore, the set air volume of each transport pipe is previously set to an air volume considerably larger than the air volume required for actual steady air transport.

[0003] For this reason, the applicant of the present invention can set the set air volume low without breaking the air volume balance of each transport pipe even if a load change occurs, and thus can reduce the air volume and the power, and thus can reduce the air volume and the power. And Japanese Patent Publication No. 1-17967 discloses a pneumatic transportation method for controlling such a pneumatic transportation system to operate at an economic wind speed.

[0004] The multi-pipe air transport system 80 disclosed herein.
Is, for example, as shown in FIG.
And a main pipe (collecting pipe) L, and the main pipe L
Many branch pipes (transport pipes) L₁, L_Two, ..., L_nBranch to
And each branch pipe L₁, L_Two, ..., L_nIs set to
Air volume control device (hereinafter referred to as constant air volume valve)
V₁, V_Two, ..., V_nAnd cyclone C₁, C_Two,
..., C_nAnd the mixer M₁, M_Two, ..., M_nAnd
Is provided. Also, in this multi-pipe air transport system 80,
Is the mixer M₁, M_Two, ..., M_nSuitable for powder
The air mixed each time is supplied to each mixer by the fan 12.
M₁, M_Two, ..., M_nFrom each branch pipe L₁, L_Two, ...
・, L_nCyclone C₁, C_Two, ...
・ 、 C_nIs separated by the filter 14 and the filter 14
Dust is removed and exhausted. Here, the constant air volume valve V ₁,
.., V_nIs the constant air volume control, that is, the air volume in each branch pipe
It serves to keep the constant.

FIG. 7 shows such a multi-pipe air transport system 80.
Of constant air volume valve V _1, ···, it is used as V _n,
1 shows a schematic cross-sectional view of an example of a conventional constant air volume valve according to the disclosure of the present applicant. The constant air volume valve 60 shown in the figure has a venturi-type housing 64 having a throttle portion 62,
A cone 66 as a flow rate adjusting member is installed near the throttle portion of the housing 64 so as to be movable in the axial direction of the housing 64, that is, in the direction of air flow. A single linear compression coil spring 74 is attached to the cone 66 and is urged in the upstream direction of the air flow (the direction opposite to the arrow in the figure). The reference position of the cone 66 is controlled by operating the air volume setting means 68 to move the shaft 70 in the axial direction so that the flow rate adjustment reference value (set air volume value) can be adjusted in accordance with the transported amount of the granular material. It can be adjusted by moving it. Here, reference numeral 72 denotes a spring receiver fixed to the tip of the shaft 70 and receiving the compression coil spring 74.

In the constant air volume valve 60, the cone 66
When the wind speed of the air flow as indicated by an arrow in the housing 64 increases around the reference position corresponding to the flow rate adjustment reference value, that is, when the wind pressure of the air increases, the spring 74
Is compressed and moves in the downstream direction (the direction of the arrow in the figure) as shown by the solid line, and the gap between the cone 66 and the housing 64 is narrowed, that is, the cross-sectional area of the flow path in the throttle portion 62 is reduced to reduce the flow resistance. It acts to increase air flow and reduce air volume.
Conversely, when the wind speed in the housing 64 decreases and the wind pressure decreases, the spring 74 expands and moves the cone 66 in the upstream direction (the direction opposite to the arrow in the drawing) as indicated by the dotted line, and the gap with the housing 64 is reduced. It increases the cross-sectional area of the flow path in the throttle section 62 to reduce the flow resistance and increase the air volume.

As described above, the constant air volume valve 60 shown in FIG.
In the multipipe air transport system 80 shown in FIG.
Branch pipe L₁, L_Two, L_Three, ..., L_nConstant air volume adjustment equipment
Place V ₁, V_Two, V_Three, ..., V_nThis is provided as
With this, the air volume of each transport pipe is transported for each transport branch pipe.
Constant according to the physical properties and transport volume of
Air volume Q₁, Q_Two, Q_Three, ..., Q_nAutomatic to be
It can be adjusted dynamically.

However, the conventional constant air volume valve 6 shown in FIG.
At 0, the constant air volume range (differential pressure range of the constant air volume valve) that can be automatically adjusted to a constant value is limited, and as shown in the graph of the constant air volume valve characteristic shown in FIG.
The limit is about mAq, and when it is 300 mmAq or more, the accuracy of the constant air volume deteriorates remarkably. On a transportation line where the flow rate of the granular material stock fluctuates greatly, the constant air volume range is 300 mmA.
There is a problem that q is insufficient, but in order to extend the constant air volume range, it is necessary to improve the durability in order to function without trouble for a long time on the high pressure side. The accuracy of the constant air volume is preferably within a range of ± 5% of the set air volume value. Similarly, as shown in the characteristic graph of the conventional constant air volume valve 60 in FIG. The constant air volume accuracy of 60 is about ± 10%, and there is a problem that the air volume varies, and therefore, the transportation becomes unstable.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a low cost,
High accuracy of constant air volume, wide constant air volume area, provided at a predetermined location of each transport branch pipe of the multi-pipe air transport system, each branch even if the flow rate of the granular material stock of each branch pipe fluctuates A pneumatic transport system that can maintain the air flow rate of the pipe at a predetermined ratio and can perform stable pneumatic transport with a smaller air volume and therefore with less power without breaking the pneumatic transport balance of each transport branch pipe. It is an object of the present invention to provide a constant air volume control device used for a vehicle.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present inventors have improved the constant air volume characteristics of a constant air volume adjusting device, particularly, expanded the constant air volume range and improved the accuracy of the constant air volume. After examining in detail and conducting research, the constant air volume characteristics of the constant air volume valve were determined by the characteristics of the spring inside the cone, the shape of the cone and the surface properties from the problems of the venturi shape and the adhesion of the passing granular material and durability. And the constituent materials, etc., and we consider that the major influencing factor is the characteristics of the spring.

For this reason, the present inventors attached a displacement transducer for measuring the axial displacement of the cone and a load transducer for measuring the load (wind pressure) applied to the cone to the cone in the constant air volume valve, The load (kgf) and the displacement (mm) were measured over the operating pressure range (differential pressure range before and after the cone, ie, the air volume range) 50 to 700 mmAq (water column), and FIG.
As a result of plotting as shown in (a), it was found that the load (kgf) applied to the cone and the displacement (mm) of the cone were not linear but non-linear. Based on this knowledge, in order for the constant air volume valve to obtain a high constant air volume accuracy in the operation range of 50 to 700 mmAq, the constant air volume valve must be configured as shown in FIG.
A compression spring exhibiting a non-linear load-displacement characteristic shown in (a) may be used.
The inventors have found that the approximation can be made by combining two compression springs, or that the approximation can be made with one non-linear compression spring, leading to the present invention.

That is, the present invention is provided at a predetermined position in each branch pipe in a system for transporting powdery material by flowing air through a number of branch pipes communicating with the main pipe, and controlling the air flow rate of each branch pipe to a predetermined value. A constant-air-volume adjusting device for controlling the air flow so as to maintain the ratio, a venturi-type housing having a throttle, a flow adjusting member installed near the throttle in the housing and movable in an axial direction of the housing, Urging means for urging the member in the upstream direction of the air flow, and urging means having a non-linear relationship between the urging force and the amount of displacement, and the urging means moves the flow rate adjusting member from the reference position to the air flow. It provides a constant air volume control device used in an air transportation system, which is configured to automatically move according to a flow velocity and to adjust an air flow rate to be constant by increasing or decreasing a cross-sectional area of a flow path. is there.

Further, it is preferable that the biasing means comprises at least two compression springs having different lengths. further,
Preferably, the biasing means comprises a single compression spring having a non-linear spring constant. In addition, it is preferable that the reference position of the flow rate adjusting member is movable so as to be a reference value corresponding to the set transport amount of the granular material.

[0014]

The constant air volume adjusting device (constant air volume valve) used in the pneumatic transportation system of the present invention is provided in each of the branch pipes where the air and the powder appropriately mixed by the suction by the fan are branched from the collecting main pipe. In the air transport system for transporting air, the wind speed of the air flow flowing through each branch pipe is provided on the outlet side of the cyclone from which the granular material is separated, and is set based on a preset reference value of the wind speed of the air flow. Is faster, the airflow is reduced, while the airflow that flows through each branch pipe is slower than this reference value, and the airflow is increased so that the airflow in each branch pipe is always kept constant in a certain constant airflow range. The amount of movement of a flow control member (cone) that moves in the axial direction in the vicinity of the throttle portion in the Venturi-type housing to adjust the flow rate (air volume) of air flowing through the housing is determined by the flow rate adjustment. The relationship between the urging force of the urging means (compression spring) and the amount of displacement, which urges the member in the upstream direction of the air flow and adjusts it in accordance with the wind speed (wind pressure) received by the flow rate adjusting member, is, for example, the length of each other. By using at least two different compression springs or by using one non-linear compression spring, it is possible to make the air flow non-linear so as to make the air flow constant over a wide constant air volume range, that is, a wind pressure (operating pressure) range.

Therefore, according to the constant air volume adjusting device used in the pneumatic transportation system of the present invention, not only can the air volume in each branch pipe be kept constant, but also the constant air volume region can be widened at low cost, and It is possible to improve the constant air volume accuracy.
That is, according to the constant air volume adjusting device used in the pneumatic transportation system of the present invention, even in a transportation line in which the flow rate of the granular material in each transportation tube fluctuates drastically, the air volume balance of each transportation tube is extremely rarely broken. The amount of transport varies very little. As a result, according to the constant air volume adjusting device of the present invention,
Even when used in an air transport system in which the flow rate of the granular material in each transport pipe (branch pipe) fluctuates greatly, the set wind speed of each branch pipe can be set to a lower economic wind speed, and therefore, the pneumatic transport system requires less power. Driving is possible, and reduced transportation costs can be used.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a pneumatic conveying system according to the present invention.

FIG. 1 is a schematic cross-sectional view of an embodiment of a constant air volume adjusting device (hereinafter, referred to as a constant air volume valve) used in the pneumatic transportation system of the present invention. FIG. 2 is a schematic system diagram of an embodiment of an air transportation system using the constant air volume valve of the present invention. Prior to the description of the constant air volume valve 20 of the present invention shown in FIG. 1, a pneumatic transport system 10 using the same will be described with reference to FIG.

As shown in FIG. 2, the constant air flow valve of the present invention
The pneumatic transportation system 10 using the main pipe L includes a main pipe L and a main pipe L.
A fan 12 for sucking fluid (air) in the fan,
And a bag filter 14 provided downstream of the main pipe L.
A main valve 16 provided immediately before the
Branch pipes L branching from₁, L_Two, ..., L_nWhen,
Branch pipe L₁, L_Two, ..., L_nThe present invention provided in
Air flow valve (20) V _C1, V_C2, ..., V_CnAnd the rhino
Clon C₁, C_Two, ..., C_nAnd cyclone C₁,
C_Two, ..., C_nRotary valve provided in the lower part of
RV₁, RV_Two, ..., RV_nAnd mixing section M₁,
M_Two, ..., M_nAnd mixing section M₁, M_Two, ..., M
_nRoll-type crusher (roll)
Mill) RM₁, RM_Two, ..., RM_nAnd each
Branch pipe L₁, L_Two, ..., L_nCyclone of
C₁, C_Two, ..., C_nAnd mixing part M₁, M_Two, ...
・ 、 M_nRoll mill RM between₁, RM_Two, ...
・ 、 RM_nPipe TL for powder and granules crushed by₁,
TL_Two, ..., TL_nIs composed. Mixing part M₁,
M_Two, ..., M_nThen, air inlet I from outside₁, I
_Two..., I_nAir from outside and roll mill RM₁, R
M_Two, ..., RM_nCrushed material with air from
Tube TL₁, TL_Two, ..., TL_nMixed in.

In such a pneumatic transport system 10, 1
Each branch pipe L by two fans 12₁, L_Two, ..., L
_nAir inlet I₁, I_Two..., I_nAir is sucked from
And mixed part M₁, M_Two, ..., M_nBy roll
Mill RM₁, RM_Two, ..., RM_nPowder supplied from
Granules at an appropriate mixing ratio according to their type, characteristics and amount
Mix and pneumatic transport tube TL₁, TL_Two, ..., TL_nInside
The air transport. Transport tube TL₁, TL_Two, ..., TL
_nThe pulverized material transported in the air is cyclone C ₁,
C_Two, ..., C_nSeparated from suction air for transportation in
And the rotary valve RV₁, RV_Two, ..., RV_nTo
(Not shown) and supplied to downstream equipment such as a shifter.
It is.

On the other hand, cyclone C₁, C_Two, ..., C
_nThe suction air separated from the granular material by the
Luv V_C1, V_C2, ..., V_CnAfter passing through the main
Tube) L, passes through the main valve 16 and passes through the fan 12
After passing through, cyclone C with bag filter 14₁, C_Two,
..., C_nRemove particles that could not be completely separated by
After being dusted, it is exhausted to the atmosphere. Where the constant air volume
Bu V_C1, V_C2, ..., V_CnAs shown in Figure 1
A quantity valve 20 is used to evacuate the granular material as shown in FIG.
Roll mill RM for pneumatic transportation ₁, RM_Two, ..., RM_n
Each air transfer of the lower multi-tube (multi-tube suction type) air transport system 10
Transmission TL₁, TL_Two, ..., TL_nBranch pipe L
₁, L_Two, ..., L_nAttached in the middle of each air
Transport tube TL₁, TL_Two, ..., TL_nGranules in
Each air transport pipe TL₁, TL_Two,
.., TL_nEach branch pipe L to maintain the transport balance of₁,
L_Two, ..., L_nAirflow value set for each airflow
To keep it constant.

Originally, as shown in FIG.
The transmission system 10 has a constant air volume valve V_C1, V _C2, ..., V_CnBut
If not, each transport pipe TL₁, TL_Two,
..., TL_n, Load fluctuation occurs in each pipe
When each transport pipe TL₁, TL_Two, ..., TL_n,
That is, each branch pipe L₁, L_Two, ..., L_nAirflow balun
Collapse, for example, if the transport volume of a certain transport pipe increases,
Due to the increased resistance, air escapes to other transport pipes,
The air volume in the transport pipes of
It will not be sucked. When this gets worse, cho
Cause the system to be unable to operate, resulting in a major failure.
If you do not use a constant air volume valve,
To prevent choke, each transport branch L₁, L_Two, ...
・, L_nSet a large air volume for
Need to increase the fan power requirements.
This is as described above.

Each of the pneumatic transport systems 10 is used to transport
Tube TL₁, TL_Two, ..., TL_nEliminate load fluctuations
That is usually not possible. At the start of operation or when grinding raw materials
Even if there is a load fluctuation that inevitably occurs when switching
Each transport pipe TL₁, TL_Two, ..., TL_nAirflow balun
Constant air flow valve V so as not to break_C1, V_C2, ...,
V_CnThe use of causes the pressure loss of the constant air volume valve
Not only to prevent choke, etc., but also to
L₁, TL_Two, ..., TL_nRequired air volume, and
It is necessary to reduce the required air volume and required power of the fan.
You. In addition, the required air volume can be saved by the transportation system (transportation tube TL).₁,
TL_Two, ..., TL_n, Cyclone C ₁, C_Two, ...
・ 、 C_nTo reduce the pressure loss of the bag filter 14)
This greatly increases the mixing ratio and reduces the required power.
ing.

The constant air volume valves V _C1 , V _C2 ,..., V _Cn have the functions described above, and are used in a multi-tube suction type pneumatic transport system such as the pneumatic transport system 10 shown in FIG. Although applied, the applied pneumatic transport system is not limited to the illustrated example, and can be applied to any pneumatic transport system as long as it is a multi-tube system. The specific structure of one embodiment of the constant air volume valve 20 of the present invention applied as the constant air volume valves V _C1 , V _C2 ,..., V _Cn of the air transport system 10 shown in FIG.
Shown in

As shown in FIG.
A venturi-type housing 24 having a right circular tube portion 21 and a throttle portion 22 formed of a venturi tube;
A cone 26 which is a flow rate adjusting member disposed near the throttle (venturi) portion 22 in the inside 4, and a cone which is disposed in the cone 26 and urges the cone 26 upstream against the wind pressure received by the cone 26. In order to set the air flow rate to an air flow rate corresponding to the transport amount of the pneumatically conveyed granular material, that is, a flow rate adjustment reference value, the reference position of the cone 26 is set to a flow rate adjustment reference value (set constant air volume value). ) Is provided at a position corresponding to the constant air volume setting device 28.

The end of the housing 24 on the side of the throttle section 22 formed of a Venturi pipe is connected to the downstream side (suction source side) of the branch pipe, and the other end of the housing 24 on the side of the straight pipe section 21 is located on the upstream side of the branch pipe ( Flanges 24a and 24b are provided at both ends so as to be connected to the air transport pipe side (that is, the cyclone side). The throttle unit 22 is formed of a Venturi tube, and an appropriate shape and length (dimension) may be appropriately selected according to the shape of the cone 26 described later and the movement amount (stroke) of the cone 26.

Here, the cone 26 is made of, for example, aluminum and has a spherical front portion receiving wind pressure, a cone (conical) surface rear portion, and an opening in the center of the front portion. Shaft 30 inserted through resin bearing
Accordingly, the housing 24 is movably supported in an axial direction (hereinafter, simply referred to as an axial direction). A spring receiver 32 is fixed to the tip of the shaft 30, and an urging means 27 is disposed inside the cone 26 between the spring receiver 32 and a spring support 33 at the center of the front surface of the cone. The urging means 27 includes three types of coiled compression springs 34 and 36 having different lengths from each other.
And 38, these compression springs 34, 36, 3
8 are all attached to the spring support 33.
The longest compression coil spring 34 among these compression coil springs has the other end engaged with the spring receiver 32.

The shaft 30 movably supporting the cone 26 is movably supported in the axial direction at the center of the housing 24 by shaft support fittings 23a and 23b fixed in the straight pipe portion 21 of the housing 24. . In the middle of the shaft 30, a vertically protruding shaft pin 29 is provided.
Is attached.

The constant air volume setting device 28 is for setting a constant air flow (constant air volume) to be adjusted by the constant air volume adjusting device 20 of the present invention, that is, a flow control standard value. The housing 2
4 is provided in the straight pipe section 21, and is located in the axial direction of the shaft 30, that is, the cone 26 in the venturi section 22.
It functions as a position adjusting means for adjusting and setting the reference position (in the axial direction of the housing 24). Such a constant air volume setting device 28 includes a casing 40 fixed to the outer periphery of the straight pipe portion 21 and columns 42 at both ends of the casing 40 in the axial direction.
a, a ball screw 44 rotatably supported by 42b;
An air volume setting dial 46 attached to one end of the ball screw 44, a moving nut 48 screwed into the ball screw 44 and an intermediate position in the axial direction thereof, a pin 49 fixed to the moving nut 48 and protruding vertically, A fulcrum pin 43 provided on a bottom plate 41 of a casing 40 fixed to the main pipe portion 21 of the housing 24 is rotatably engaged, and both ends thereof are U-shaped.
It has a U-shaped concave portion, and has a dial frame 50 that engages with the shaft pin 29 of the shaft 30 and the projecting pin 49 of the ball screw 44 by this concave portion.

In the constant air volume setting device 28, the set air determined according to the type and amount of the powder and granules transported through the air transport pipe of the multi-pipe air transport system using the constant air volume valve 20 of the present invention. The air volume setting dial 46 is rotated to a scale indicating the flow rate (air volume). The rotation of the air volume setting dial 46 rotates the ball screw 44, and the moving nut 48 screwed to the ball screw 44 moves in the axial direction. Moving nut 4
8 is fixed to the moving nut 48 by the movement of the pin 49.
The shaft 30 on which one end is engaged rotates around the fulcrum pin 43 and the shaft pin 29 which engages with the other end of the dial frame 50 is fixed.
Is moved in the axial direction, and the cone 26 movably engaged with the tip of the shaft 30 is moved to a predetermined reference position corresponding to the set airflow.

In this manner, the cone 26 is set at the reference position corresponding to the set air volume, and the cone 26 moves in the axial direction about the reference position according to the wind pressure received by the cone, and contacts the inner wall of the venturi portion 22 of the housing 24 with the inner wall. The gap between the cone 26 and the cone 26 is appropriately adjusted, and the amount of air passing through the gap is kept constant (constant air volume) irrespective of fluctuations in wind pressure. That is, when the shaft 30 is set at the predetermined reference position corresponding to the constant air volume value to be set by the air volume setting device 28, the cone 26 is disposed at the set reference position in the state where the wind pressure is not received in the venturi section 22. You.

Here, when the cone 26 is not subjected to wind pressure, the springs 34, 36, 38 are arranged in an extended state. However, when the cone 26 is subjected to wind pressure, the cone 26 is first compressed according to the pressure. The spring 34 contracts, and the cone 26 moves in the direction of the arrow (rightward) in the figure, narrowing the gap between the cone 26 and the inner wall of the housing 24 in the venturi section 22, and passing the predetermined air volume. The cone 26 will move to a position where is possible. In addition, corn 26
When the wind pressure received by the spring increases, the spring 34 contracts and the spring 36
The tip of the spring abuts against the spring receiver 32, the wind pressure received by the cone 26 is received by the two springs 34 and 36, and when the wind pressure further increases, the springs 34 and 36 contract, and the tip of the spring 38 abuts against the spring receiver 32. And the wind pressure received by the cone 26 is 3
The cone 26 is received by the springs 34, 36, and 38 and moves to a position where the amount of air passing therethrough has the predetermined value described above. Thus, the cone 26 automatically moves in accordance with the wind pressure, and regulates the passage of the air flow rate (air volume) to a constant value.

As described above, according to the study of the present inventors, in the constant air volume valve 10 having a certain size shown in FIG.
It has been found that the relationship with the change position is indicated by dots in FIG. The load applied to the cone 26 was measured by a load transducer, and the displacement position was measured by a displacement transducer. The measurement was performed in an operating pressure range, that is, in an air volume range of 50 to 700 mmAq.

Further, the present inventors modeled the constant air volume valve as shown in FIG. 4 and performed a theoretical analysis to obtain a displacement-load characteristic curve shown in FIG. 3B, supporting that the above findings were correct. Was. In the theoretical analysis, it is assumed that the cone is spherical as shown in FIG. 4, and the force acting on the cone and the weight of the cone are balanced with the pressure and frictional force, and the following equation is established.

[0034]

(Equation 1)

Here, F is the force applied to the cone, P ₁ is the pressure at the lower part of the cone (upstream side), and P ₃ is the upper part of the cone (downstream side).
Pressure, D _f cone maximum diameter, A _f is the center cross-sectional area of the cone ^{_{(πD f 2/4),}} F f is the frictional force exerted per cone unit length, F _s is incoming air into the gap of the cone and venturi M, the weight of the cone, g is the gravitational acceleration, Q is the air volume (air flow), A is the area of the gap between the cone and the venturi (πH (D _f + H), H is the gap between the gap), γ
Is the density of air.

In the illustrated example, the non-linear spring characteristics required for the urging means (compression spring) 27 of the constant air volume valve 20 supported by such a theoretical analysis are shown in FIG. The linear spring characteristics are defined by the linear spring constants K1 and K
This is realized by combining three linear springs 34, 36 and 38 having K2 and K3. By combining the three compression springs 34, 36, 38 with the constant air volume valve 20 in this manner, the urging means 27 having a variable spring constant
By using a cone 26 having, for example, transport tube TL ₁ air transport system 10 shown in FIG. 2, even when variations in wind pressure (load) of the cone 26 due to load change · · · TL _n, Accordingly, the gap between the cone 26 and the venturi section 22 is appropriately and automatically adjusted.
The air flow passing through 0 can be kept constant at a set value in a wide air flow range of 30 to 700 mmAq. Therefore, the urging means 27 having such a spring characteristic is used.
To provide a constant air volume characteristic, that is, a constant air volume valve 2 having a wide constant air volume range and high constant air volume accuracy.
It can be set to 0.

Here, in FIG. 3A, in the load range shown in FIG. 3A, the cone 26 is supported only by the compression spring 34, and the spring constant in this range is the spring constant K1 of the compression spring 34. Similarly, in the load range shown in (B),
The cone 26 is supported by the compression springs 34 and 36, and the spring constant in this range is the sum K1 + K2 of the spring constants of the compression springs 34 and 36. Further, in the load range shown in (C), the cone 26 is supported by the compression springs 34, 36, and 38, and the spring constant in this range is
The sum of the spring constants of 4, 36 and 38 is K1 + K2 + K3. Note that the number of compression springs used in the constant air volume valve 20 used in the pneumatic transportation system of the present invention is not limited to three in the illustrated example. For example, two or four compression springs may be used. Any number of springs may be used as long as the spring characteristics of the urging means 27 having a necessary non-linear spring constant can be approximated using at least two compression springs having different lengths.
Here, at least two compression springs used as the urging means 27 may have the same spring constant or may have different spring constants. Further, FIG.
The biasing means 27 exhibiting the non-linear load-displacement characteristic shown in (a) or (b) is not limited to a combination of at least two compression springs having different lengths. May be a single non-linear compression spring. From the viewpoint of cost, it is preferable to obtain nonlinear characteristics by combining two or more linear springs, rather than using a non-linear compression spring having a variable spring constant.

The constant air volume valve 20 constructed as described above
Prior to the start of operation of the pneumatic transport system 10, the dial 46 is rotated to determine the amount of air flowing through the transport pipe, that is, the amount of air to be flown through the constant air volume valve 20, in accordance with the type, characteristics, and amount of the granular material to be pneumatically transported. The position is determined by determining the positions of the shaft 30 and the cone 26. When the operation is started, the fan 12 is driven, the suction of air is started, and a wind pressure is applied to the cone 26 of the constant air volume valve 20,
First, the compression spring 34 inside the cone 26 is compressed, and the cone 26 moves downstream in the axial direction in the venturi section 22 and stops at a flow adjustment reference position corresponding to the set airflow in a stable steady flow. Here, depending on the set air volume, not only the compression spring 34 but also the compression spring 36, and further the compression spring 3
8, the position of the compressed cone 26 becomes the flow rate adjustment reference position.

The cone 26 moves in the venturi 22 in accordance with the wind pressure, that is, the flow velocity, about the reference position corresponding to the air volume set in this way, and adjusts the gap between the cone 26 and the venturi 22. To maintain a constant air flow. That is, when the flow rate of the airflow flowing through the constant air volume valve 20 becomes lower than the steady value, the load on the cone 26 is reduced, so that the cone 26 is pushed back by the urging means 27 and moves from the reference position to the downstream side. The gap between the Venturi portion 24 and the cone 26 is widened to compensate for the decrease in the airflow due to the decrease in the flow velocity, and keep the passing airflow constant. Conversely, when the flow velocity of the airflow increases from the steady value, the action of the cone 26 is completely reversed, the gap is narrowed, the increase in the airflow due to the increase in the flow velocity is suppressed, and the passing airflow is kept constant. Even when the set air volume is changed during operation, the cone 26 moves in the same manner in the venturi unit 22 to a reference position that matches the set air volume and wind speed, and the cone 26 moves around the reference position according to a load change. It can be moved to maintain a constant flow rate.

FIG. 5 shows the constant air volume characteristic of the constant air volume valve 20 shown in FIG. 1 using three compression springs 34, 36, and 38 having the spring characteristics of FIG. As is clear from FIG. 5, the constant air volume valve 20 of the present invention has a constant air volume characteristic shown in FIG.
It can be seen that a wide constant air volume range over 00 mmAq and a high constant air volume accuracy of about ± 5% can be achieved. Therefore, the constant air volume valve 20 of the present invention is capable of maintaining the air volume of each transport pipe constant at each set air volume even in a multi-pipe air transport system in a transport line in which the flow rate fluctuation of the granular material and the load fluctuation are large or severe, that is, for example, In the graph shown in FIG. 5, the accuracy of the constant air volume can be set to about ± 5% at the maximum with respect to the set air volume value, and the variation of the transport amount of the granular material in each transport pipe can be reduced.

Since the stroke amount of the cone 26 (the range in which the cone 26 moves from the reference position as a starting point) becomes long in order to widen the constant air volume region, the venturi portion 22 of the venturi-type housing 24 is made long. Is good.
In addition, if the constant air volume region is widened, the load applied to the cone 26 increases. Therefore, it is preferable to improve the durability in order to function at a high wind pressure for a long time without any trouble. For example, the diameter of the shaft 30 inserted into the cone 26 to support the cone 26 may be increased,
It is preferable to use a resin bearing at the insertion port of the shaft 30 to reduce wear of the tube and the piston in the cone 26, and to increase the thickness of the cone 26. In order to improve the constant air volume characteristics, it is preferable to prevent the adhesion of the granular material to the cone 26. For preventing the adhesion of the granular material, for example, buffing is performed on the front of the cone 26, It is preferable to adopt a shape that eliminates the step at the rear. In the present invention, the buffing is applied to the front of the cone 26 to reduce the amount of adhesion by 35% as compared with the conventional amount of the granular material adhering to the cone 26. By removing the shape, the amount of adhesion can be reduced by 25%.

[0042]

As described in detail above, according to the present invention, not only can the air volume be kept constant, but also the constant air volume range can be widened at low cost and the accuracy of the constant air volume can be improved. it can. That is, according to the present invention, even in a transportation line in which the flow rate of the granular material fluctuates drastically, for example, in a multi-pipe air transportation system, it can be used without any problem, and not only can the variation in the transport amount be reduced, but also the multi-pipe The set wind speed of each branch pipe (transport pipe) of the pneumatic transport system can be set to a lower economic wind speed, the flow rate of the suction air flow by the fan can be reduced, and the power of the fan can be reduced, and therefore, the pneumatic transport The system can be operated with less power. For this reason, by using the constant air volume valve of the present invention, the transportation cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of a constant air volume valve used in a pneumatic transportation system according to the present invention.

FIG. 2 is a schematic system diagram of one embodiment of a multi-tube suction air transport system using the constant air volume valve of the present invention.

3 (a) and 3 (b) are graphs showing spring characteristics (relation between load and displacement) of the urging means of the constant air volume valve of the present invention, where (a) is the measured value and (b) ) Are theoretical analysis values.

FIG. 4 is a diagram showing a theoretical analysis model of the constant air volume valve of the present invention.

FIG. 5 is an example graph showing characteristics of a constant air volume valve used in the pneumatic transportation system of the present invention.

FIG. 6 is a schematic system diagram of an example of a pneumatic transportation system.

FIG. 7 is a schematic cross-sectional view of a constant air volume valve used in a conventional pneumatic transportation system.

FIG. 8 is a graph showing characteristics of a constant air volume valve used in a conventional pneumatic transportation system.

[Explanation of symbols]

L main _{L 1, L 2, ···,} L n branch _{TL 1, TL 2, ···,} TL n air transport tube _{RM 1, RM 2, ···,} RM n roll mill M _1, M _2, · · ·, M _n aeration unit _{C 1, C 2, ···,} C n cyclone _{RV 1, RV 2, ···,} RV n rotary valve _{I 1, I 2, ···,} I n the air suction port _{V c1, V c2, ···,} V cn constant air volume valve (constant air volume regulating device) 10 air transport system 12 fan 14 bag filter 16 the main valve 20 constant air volume valve (constant air volume regulating device) 21 straight pipe 22 throttle portion (Venturi part) 23a, 23b Shaft support fitting 24 Venturi type housing 24a, 24b Flange 26 Cone (flow rate adjusting member) 27 Energizing means 28 Air volume setting unit 29 Shaft pin 30 Shaft 32 Spring receiver 33 Spring support 34, 36, 38 compression Spring 40 Casing 41 Bottom plate 42a, 42b Support column 43 Support pin 44 Ball screw 46 Air flow setting dial 48 Moving nut 49 Pin 50 Dial frame

Claims (4)

(57) [Claims] 1. A system in which air flows through a large number of branch pipes communicating with a main pipe to transport a granular material is provided at a predetermined position of each branch pipe so that an air flow rate of each branch pipe is maintained at a predetermined ratio. A venturi-type housing having a throttle, a flow control member installed near the throttle in the housing and movable in the axial direction of the housing, and an air flow control device. Urging means in the upstream direction, the urging means having a non-linear relationship between the urging force and the displacement amount, and the urging means moves the flow rate adjusting member from a reference position in accordance with the flow rate of the air flow. A constant air volume adjusting device used in an air transportation system, wherein the air volume is adjusted automatically by moving automatically and increasing or decreasing the cross-sectional area of the flow path. 2. The constant air volume adjusting device according to claim 1, wherein said urging means comprises at least two compression springs having different lengths. 3. The apparatus according to claim 1, wherein said urging means has a non-linear spring constant.
The constant air volume adjusting device according to claim 1, comprising a plurality of compression springs. 4. The constant according to claim 1, wherein the reference position of the flow rate adjusting member is movable to a reference value corresponding to the set transport amount of the granular material. Air flow control device.