JP2702550B2 - Parent-child screw feeder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a parent-child screw feeder used as a feeder for quantitative measurement of a particulate material.

[Prior art] Quantitative weighing of powders and granules is generally performed by supplying powders and granules from a feeder to a weighing container placed on a weighing machine, and stopping the supply when the weighing of the weighing machine reaches a target value. A powder having a desired weight is obtained.

Conventionally, as this weighing machine, a twin-screw screw feeder shown in FIG. 9 (Japanese Patent Application Laid-Open No. 61-174019) or a parent-child screw feeder shown in FIG. 10 (Japanese Patent Application Laid-Open No. 61-23032) is known.

The twin-screw feeder (1) shown in FIG. 9 is designed to reduce the cost by driving two screws (3) and (3) with one speed reducer (2). In this screw feeder, a power transmission mechanism (4) also serving as a bearing is arranged on the opposite side of the speed reducer (2), and a supply chamber (5) for powder and granular material is provided.
A stirring blade (6) that rotates integrally with the output shaft of the speed reducer (2).

The parent-child screw feeder (1) shown in FIG. 10 uses a large-diameter screw feeder (8) and a small-diameter screw feeder (9) to shorten the supply time while ensuring the measurement accuracy. . That is, when the current weighing value reaches a value smaller than the target value by the maximum error of the supply of the screw feeder of a large diameter, the supply is switched to the supply of only the small diameter screw feeder (9) and the remaining amount is accurately supplied. It is assumed that.

[Problems to be solved by the invention]

2. Description of the Related Art Recently, powders used in the fields of chemistry, foods, plastics, fine ceramics, etc., are ultra-fine powders and have many properties of low fluidity and high adhesion. For this reason, it is difficult for the conventional screw feeders (1) and (7) shown in FIGS. 9 and 10 to supply smoothly.

In the twin-screw screw feeder (1) shown in FIG. 9, even if the stirring is performed by the stirring blade (6), it is difficult for the powdery material to be sent from the bottom of the supply chamber (5) to the screws (3) and (3). Easily remain on the surface. A parent-child screw feeder (7) shown in FIG.
Does not have a stirring blade, so that the granular material is not smoothly fed to both screws.

In the parent-child screw feeder (7) shown in FIG. 10, the absolute error at the end of the measurement is determined by the supply speed of the small-diameter screw feeder (9) that ensures the measurement accuracy. For this reason, with respect to the weighing accuracy determined as a percentage of the total weighed value, if the weighed value is small, the weighing accuracy cannot be maintained. Further, if a small-diameter screw feeder with a small supply speed is used to avoid this, a problem arises in that the measurement time becomes too long for a large measurement value.

Further, a parent-child screw feeder (7) shown in FIG.
However, even if the accuracy is guaranteed by the small-diameter screw feeder (9), the lump of the granular material remaining at the outlet of the large-diameter screw feeder (8) stopped by the external vibration immediately before the end of the measurement is obtained. May fall and cause a large weighing error.

Therefore, the present invention has a poor fluidity like ultra-fine powder, can be smoothly supplied even with a powder having high adhesiveness, weighing weight, required accuracy over a wide range of weighing in one device, The purpose is to provide something that can be performed at high speed and with high accuracy.

[Means for solving the problem]

The present invention is a parent-child screw feeder in which a large-diameter screw feeder and a small-diameter screw feeder are vertically arranged in parallel, a constant-speed motor that drives a large-diameter screw feeder, and a variable-speed motor that drives a small-diameter screw feeder. Provided separately is a blade provided with a stirring blade that is provided coaxially with the large-diameter screw feeder, with the blade tip approaching the screw of the small-diameter screw feeder, and that rotates in conjunction with the small-diameter screw feeder in the opposite direction.

In this basic configuration, the discharge port is provided with a high-speed cut gate common to the large-diameter screw feeder and the small-diameter screw feeder, and when the large-diameter screw feeder stops, it moves below the discharge port of the feeder and falls from the feeder. With a cup for receiving powder and granules, and a small-diameter screw feeder that stops the large-diameter screw feeder and switches to operation with only the small-diameter screw feeder, and rotation of the small-diameter screw feeder during small-volume feed It has a control data table that stores speeds corresponding to the target weight and weighing accuracy of weighing, and has a control device that controls the constant-speed motor and the variable-speed motor according to the set target weight and weighing accuracy. And provide.

[Action]

The parent-child screw feeder is a large-diameter screw feeder that supplies most of the measured values at high speed. And
The remaining amount is supplied with high precision using a small-diameter screw feeder. At the time of this supply, the stirring blade stirs the powder and granules around the large-diameter and small-diameter screw feeders, thereby facilitating the supply. In particular, when only a small-diameter screw feeder is operated at a low speed, the stirring blades rotate at a high speed in the opposite direction to supply the powder to the screw stably.

The cup provided on the large-diameter screw feeder is
In the case of high-precision feeding using only a small-diameter screw feeder, it is possible to prevent a lump of granular material from dropping from a stopped large-diameter screw feeder.

The control device refers to the control data table and optimally controls the stop timing of the large-diameter and small-diameter screw feeders and the operation speed of the small-diameter screw feeders according to the target measured value and the required accuracy. And it achieves high speed and high accuracy for a wide range of weighing from large to small.

〔Example〕

1 to 3 show the overall configuration of a parent-child screw feeder (10) according to an embodiment of the present invention, and its main parts are shown in FIGS.
This is shown in the figure and will be described below.

In FIGS. 1 to 3, reference numeral (11) denotes a base, on which a variable speed motor (12) is mounted, and a supply chamber (13) below the hopper and a gear box (14) are mounted and fixed on a top surface thereof. doing.

A hopper (15) for supplying the granular material to the supply chamber (13) is provided with an air knocker (16) for improving the fluidity of the granular material.

(17) is a large-diameter screw feeder, (18) is a small-diameter screw feeder. Two cylindrical cylinders (17a) and (18a) are mounted in parallel on one side of the supply chamber (13). It is constituted by passing the screws (17b) (18b) from the supply chamber to the respective cylindrical cylinders (17a) (18a). The shape of each screw (17b) (18b) is as shown in FIG. 4 (a) (b) and FIG.
Each drive shaft (17c) (18) supported by the gearbox (14)
c) is fixed.

The bottom of the supply chamber (13) is a small-diameter screw (18
It has a cylindrical shape along the rotation trajectory of the outer circumference of b).

(19) Large and small diameter screw feeders (1
7) With the common discharge pipe of (18), the cylindrical cylinder (17a)
(18a). A high-speed cut gate (20) is attached to a lower discharge port of the discharge pipe (19), and a semi-cylindrical cup (see FIG. 7) is provided at a position facing the large-diameter screw (17b). 21) is installed. The cup (21) is moved by the actuator (22) so that the center of the shaft is aligned with the large-diameter screw (17a).
Rotate at an 80 ° pitch to take up or down position.

(23) Large-diameter screw (17a) in the supply chamber (13)
And a stirring blade mounted so as to match the center of rotation.
FIGS. 7A and 7B are enlarged views. This stirring blade (23)
A cylindrical shaft (23a) fitted to the outside of the output shaft (17c) of a large-diameter screw (17b) via a bearing (not shown)
Mounted on

(24) is a constant speed motor fixed to the gear box (14) via a bracket (25).
It is connected to the output shaft (17c) of b) by the joint (24a).

(26) is a sprocket wheel attached to the output shaft of the variable speed motor (12), (27) is a chain belt,
(28) is a sprocket wheel to which the drive shaft (18c) of the small diameter screw feeder (18) is attached, and transmits the rotation of the variable speed motor (12) to the small diameter screw (18c). (29) and (30) are gears fixed to the drive shaft (18c) of the small-diameter screw feeder and the drive shaft (23a) of the stirring blade (23), respectively, and mesh with each other.

(31) is a control device, based on a target weighing value and a weighing accuracy setting unit (32), a storage unit of a control data table (33), and a discharge weight of a granular material output from a weighing machine (not shown).
Constant speed motor (24) while referring to the control data table
And a control circuit (34) for controlling the variable speed motor (12).

The above-mentioned control data table defines the small-quantity supply start weight and the rotation speed of the small-diameter screw feeder at the time of small-quantity supply that enable high-speed weighing while ensuring weighing accuracy, against the target weighing value and weighing accuracy. And has a value as shown in Table 1 for example.

This table shows typical values, and data is actually created for even smaller steps of the target weighing value.

The operation of the parent-child screw feeder (10) will be described below with reference to the flowchart shown in FIG.

First, the setting of the target weighing value and the setting of the required weighing accuracy are performed in the setting unit (32) of the control device (31). Thereby, the control device (31) reads control data corresponding to the set value from the recording unit (33). For example, if the target weighing value is 2000 g and the weighing accuracy is 0.5% or ± 10 g, the small supply start weight is
100 g, (2000-100 = 1900 g based on weighing machine output), and the inverter frequency (rotation speed) is 45 Hz. When the operation enters the standby state and the metering start switch (not shown) is pressed, the high-speed cut gate (20) provided in the discharge pipe (19) is opened, and the cup (21) is opened downward by the actuator (22). Then, the control circuit (34) starts the operation of the constant speed motor (24) and the variable speed motor (12). In this case, the variable speed motor (12) is operated at the highest speed. By starting operation of the motor, large and small diameter screws (17
b) (18b) rotates and feeds from the hopper (15) to the supply chamber (13)
The powder and granules which have fallen into the container are put into a measuring container placed on a measuring machine through a discharge pipe (19). When the small-diameter screw rotates, the rotation of the drive shaft (18c) of the small-diameter screw feeder (18) is transmitted to the drive shaft (23a) of the stirring blade (23) by the gears (29) and (30). The stirring blade also rotates in the opposite direction. By the rotation of the stirring blade (23), the granular material is smoothly supplied to the large-diameter and small-diameter screws (17b) (18b). In particular, the stirring blade (23) is provided in the supply chamber (13).
Since it moves so as to approach the small-diameter screw (18b) arranged at the bottom of the screw, any granular material can be reliably supplied to this screw.

Such large and small diameter screw feeders (1
7) By the operation of (18), the supply of the granular material is continued, and when the signal input from the weighing machine reaches the standard of the small amount supply start weight, for example, (2000-100 = 1900g), the large-diameter screw feeder is used. Only the operation of (17) is stopped, and at the same time, the cup (21) is rotated 180 ° by the actuator (22) to take the lower position. As a result, even when external vibration is applied, the granular material does not drop from near the outlet of the large-diameter screw feeder (18). Further, the variable speed motor (12) switches to a low speed operation in which the rotation speed initially read from the storage unit (33), for example, the inverter frequency is 45 Hz.

As a result, only the small-diameter screw feeder (18) and the stirring blade (23) are rotated, and the powder is discharged into the measuring container in small quantities.

By continuing this operation, the output of the weighing machine reaches the target weighing value. At the same time as closing the high-speed cut gate (20), the variable speed motor (12) is stopped. This completes the weighing.

In the above description, the case where the target weighing value of the granular material is relatively large as 2000 g is taken as an example, so that the large-diameter and small-diameter screw feeders (17) and (18) are operated at the start of operation. However, when the target weighing value is as small as 20 g, as shown in the first table, the small amount starting weight is 20 g.
Therefore, the supply is performed only by the small-diameter screw feeder (18) without rotating the large-diameter screw feeder (17).

The variable speed motor (12) can use a DC motor whose speed can be controlled, in addition to the inverter motor.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, a large diameter can be smoothly supplied by the small diameter screw by the effect | action of the stirring blade which has a specific mounting structure, such as an ultrafine powder, which has poor supply characteristics.

Further, the cup provided at the outlet of the large-diameter screw feeder prevents an error caused by a large amount of powder particles falling during small-quantity supply, and ensures high-precision weighing.

The control device of the present invention refers to the control data table, controls the operation / stop of the large-diameter screw feeder and performs variable speed control of the small-diameter screw feeder, and performs measurement with a wide range of measurement values and required accuracy. Enables high-speed, high-precision operation with a single feeder.

[Brief description of the drawings]

1 to 3 show the overall configuration of a parent-child screw feeder according to an embodiment of the present invention. FIG. 1 is a front view, FIG. 2 is a plan view, and FIG. 3 is a left side view. 4 to 7 show main parts used in the parent-child screw feeder of the present invention. FIGS. 4 (a) and (b) are a front view and a side view of a large-diameter screw feeder, and FIG. 5 (a). (B) is a side view and a front view of the stirring blade, FIG. 6 is a front view of a small-diameter screw feeder, and FIG. 7 is a perspective view of a cup. FIG. 8 is a flowchart showing an operation procedure in one embodiment of the parent-child screw feeder of the present invention. 9 and 10 show a conventional example, FIG. 9 is a sectional view of a biaxial screw feeder, and FIG. 10 is a sectional view of a parent-child screw feeder. (10) Parent-child screw feeder (12) Variable speed motor (13) Supply chamber (17) Large screw feeder (18) Small screw feeder (20) ) High-speed cut gate, (21) cup, (23) stirring blade, (24) constant-speed electric motor, (31) control device, (33) storage unit.

Claims (3)

(57) [Claims] 1. A constant-speed motor for driving a large-diameter screw feeder, and a variable-speed motor for driving a small-diameter screw feeder in a parent-child screw feeder in which a large-diameter screw feeder and a small-diameter screw feeder are vertically arranged in parallel. A motor is provided separately, the blade tip is brought close to the screw of the small-diameter screw feeder, and the stirring blade is provided coaxially with the large-diameter screw feeder and rotates in conjunction with the small-diameter screw feeder in the opposite direction. Parent and child screw feeder. 2. A discharge port having a high-speed cut gate common to a large-diameter screw feeder and a small-diameter screw feeder. When the large-diameter screw feeder is stopped, the powder that moves below the discharge port of the feeder and drops from the feeder. The parent-child screw feeder according to claim 1, further comprising a cup for receiving the granules. 3. Stopping the large diameter screw feeder,
It has a control data table that stores the small-amount feed start weight to switch to the operation of only the small-diameter screw feeder, and the rotation speed of the small-diameter screw feeder at the time of the small-amount supply in accordance with the target weight and the measurement accuracy of the measurement. The parent-child screw feeder according to claim 1 or 2, further comprising a control device that controls the constant speed motor and the variable speed motor according to the set target weight and weighing accuracy.