JPH0122021B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic separation device that uses static electricity to separate desired materials from undesired materials. ) from the remaining leaf veins (hereinafter referred to as midribs) from which the lamina has been peeled off, using an electrostatic separation device.

Generally, in the cigarette manufacturing process, raw tobacco leaves are first unraveled one by one, then softened with water and steam in a humidifier, and then separated into lamina and backbone in a deboning machine. A separator separates it into lamina and back bone.

Conventional separators of this type mainly used an air flow method, but this method not only has high running costs, but also separates by using the difference in air resistance coefficient and area weight. However, there has been a problem in that it is difficult to separate the lamina from bones with little difference in their characteristic values, for example, where the lamina has not been completely peeled off and the lamina remains partially.

Therefore, attention is being focused on a separation method using static electricity, which is advantageous in terms of running cost and utilizes the difference in dielectric constant. FIG. 1 shows an example of a conventionally known electrostatic separator. In the figure, metal pulley 1,
2 are provided at upper and lower positions, and a conductive endless belt 4 covered with an insulating coating 3 is stretched over these belts, and the metal pulley 1 is driven in the direction of arrow M to move the belt. The material to be separated is supplied by a conveyor 5 and charged in a corona electric field by a corona discharge electrode 6.

As described above, the material charged by the corona discharge electrode on the surface of the pulley 1 receives the action of electrostatic force between it and the pulley 1, and the attraction force to the pulley 1 is exerted.
The attraction force differs depending on the magnitude of the charge, and the material is separated by utilizing the fact that the trajectory of the material ejected from the belt 4 differs depending on the material.

However, in the conventional device described above, the material is charged at the pulley immediately before being discharged, so if the material bounces on the belt 4 before reaching the pulley, some of the material may be on the belt 4. Some substances are released before they reach a sufficiently stable state. For this reason, it is no longer ejected with a uniform force, and even if there is a difference in charge, stable material separation cannot be performed. In particular, the above-mentioned problem becomes noticeable in belts that move at high speeds.

The present invention has been made to solve the problems of the conventional devices described above, and its purpose is to provide an electrostatic separation device that can perform stable separation at high speed.

The apparatus according to the present invention, which has been made to achieve the above object, comprises: a spreading means for spreading the raw material to be separated in the width direction and the traveling direction; a belt conveyor for receiving and transporting the raw material spread by the spreading means;
discharge field generating means for charging the raw material being transferred by the conveyor and applying an electric field to the charged raw material discharged from the conveyor; Each of the head rollers at the discharge end is made of metal, and the discharge field generating means uses a receiving plate provided on the back surface of the flat part of the conveyor belt and the head roller as receiving electrodes, and a discharge electrode to which a high voltage is applied between them. It is characterized by having the following.

Embodiments of the present invention will be described below based on the drawings.

Figure 2 shows a mixed raw material of deboned tobacco mesophyll (hereinafter referred to as lamina) and leaf veins (hereinafter referred to as backbone, which includes the backbone to which the lamina is attached), which is an embodiment of the present invention. The lamina/middle bone separator that separates each is shown. In the figure, reference numeral 10 denotes a raw material spreading device consisting of a vibrating conveyor, which spreads the raw material thinly in the width direction and the traveling direction and supplies it onto a conveyor belt 12a of a belt conveyor 12. The conveyor belt 12 is stretched around a pair of metal rollers 14 and 16, and is moved in the direction of the arrow by an electric motor 18 connected to the roller 16.The conveyor belt 12 may be made of an insulating material in principle, but preferably polyester, Nylon type is good. The speed of the conveyor belt 12 is a high speed of 100 to 300 m/min, so that the raw material is further stretched thinly on the conveyor belt 12 in the direction of movement.

20a, 20b, and 20c are corona discharge electrodes that may be wire electrodes or needle electrodes, and the discharge electrode 20a is a flat receiving electrode 22 arranged on the back side of the flat part of the conveyor belt 12a near the discharge end of the conveyor 12. The high voltage applied during this period causes corona discharge to charge the raw material on the flat surface of the conveyor belt 12a. The discharge electrode 20b performs corona discharge by applying a high voltage between the plate-shaped receiving electrode 22, which extends to just before the discharge end of the conveyor 12, and the metal pulley 14, which serves as the receiving electrode, to discharge the raw material just before it is discharged. It becomes more electrically charged. Further, the discharge electrode 20c faces the head roller 14 of the conveyor at an angle of about 45 degrees in the discharge direction, and applies an electric field to the raw material immediately after discharge.

As described above, the raw material on the conveyor belt 12a is charged when passing between the electrodes constituted by the discharge electrodes 20a to 20c and the receiving electrodes 22 and 14. This charged state is maintained because the conveyor belt 12a is made of an insulating material. The plate-shaped receiving electrode 22 also serves as a receiving plate for the conveyor belt 12a, and is grounded together with the receiving plate 26 in a portion where corona discharge is not performed.

In addition, 30 is a high voltage source that supplies a discharge voltage to the discharge electrodes 20a to 20c, 32 is a brush roller that scrapes off the raw material adhering to the belt 12a, 34 is a static elimination brush that eliminates static electricity from the belt 12a, 36a is a lamina storage box, 36b is a lamina/backbone mixture storage box, 36c is a backbone storage box, and 38 is a storage box 36a~
This is an adjustable partition wall provided between 36c.

As described above, the charged lamina and backbone are carried to the discharge end while being attracted to the conveyor belt 12a, and are discharged at the discharge end in substantially the same direction in the traveling direction of the conveyor belt 12a. The discharged lamina and back bone are transferred to the discharge electrode 20c and the conveyor head roller 1.
The lamina receives a Coulomb force within the electric field formed between the lamina and the lamina, and the lamina having a large amount of charge per unit area weight is attracted to the head roller 14 side and falls near the head roller 14 or adheres to the conveyor belt 12a. The attached lamina is scraped off by the brush roller 32 and collected in the lamina storage box 36a.

On the other hand, the backbones with a small amount of electric charge per unit area weight have a discharge force greater than the force due to the electric field, so they fall far from the conveyor 12 in the traveling direction and are collected in the backbone storage box 36c. Most of the lamina and backbone are separated as described above, but there are some lamina and backbone that fall between them, and these are collected in the lamina/backbone storage box 36b. Then, separation is performed again using a similar separator, and the separated lamina and backbone are combined with the contents of the storage boxes 36a and 36c.

In the above-described embodiment, the conveyor 12 is horizontal, but it may be inclined within a range of 0 to 30 degrees. In this case, in order to prevent the material from slipping on the conveyor belt 12a, the height should be 5 mm or less, preferably 2 mm.
It is recommended to provide a horizontal bar of ~3 mm or less.

Moreover, although the polarity of the discharge electrodes 20a to 20c may be either, it is preferable to do so in order to increase the discharge current.

Incidentally, the speed of the conveyor belt 12a influences the amount of air resistance experienced when the raw material is discharged, and the faster the belt speed is, the greater the air resistance is experienced. On the other hand, the higher the belt speed, the shorter the time it takes to pass through the separation electric field, and the smaller the impulse received from the electric field. Therefore, there will be a belt speed at which the separation efficiency is maximum when the voltage is held constant. However, this varies depending on the type of raw material, and 200 m/min is optimal for separating the back bone and lamina.

The higher the voltage applied to the discharge electrodes 20a to 20c, the greater the amount of charge and the strength of the separation electric field, and the greater the force acting on the raw material. The relationship between voltage and separation efficiency when the belt speed is 200 m/min is that the higher the voltage, the higher the separation efficiency, but the optimum value varies depending on the raw material, and for the separation of backbone and lamina, 80KV
That's about it.

The relationship between raw material flow rate and separation efficiency is that the lower the flow rate, that is, the lower the amount of raw material per unit area on the belt, the higher the separation efficiency. It's much larger than that.

As explained above, the present invention utilizes the electrostatic force received in an electric field in proportion to the amount of charge applied to the raw material, and the air resistance that the raw material receives when released into the air from a conveyor belt. However, in the present invention, in particular, the receiving plate of the conveyor belt is used as the receiving electrode to generate electric discharge on the flat part of the belt to charge the raw material, so that the raw material remains stable until the discharge end of the conveyor belt. The separation performance is significantly improved without causing any variation in the discharge direction of the raw materials.

[Brief explanation of drawings]

FIG. 1 is a simplified diagram showing an example of a conventional electrostatic separator, and FIG. 2 is a side view showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 10... Raw material spreading device, 12... Belt conveyor, 12a... Conveyor belt, 14... Head roller, 20a-20c... Discharge electrode, 22... Receiving plate.

Claims (1)

[Claims] 1. A spreading means for spreading the raw material to be separated in the width direction and the traveling direction, a belt conveyor for receiving and transferring the raw material spread by the spreading means, and electrifying the raw material being transferred by the conveyor, and a discharge field generating means for applying an electric field to the charged raw material discharged from the conveyor, the belt conveyor having a conveyor belt made of an insulating material,
Each of the head rollers at the raw material discharge end is made of metal, and the discharge field generating means uses a receiving plate provided on the back surface of the flat part of the conveyor belt and the head roller as receiving electrodes, and a discharge field generating means with a high voltage applied between them. An electrostatic separator characterized by comprising an electrode.