JPH05228923A - Method and device for granulating plastic - Google Patents

Abstract

PURPOSE:To control optimum pushing pressure automatically by taking the hot-water head pressure of a cutter case, in which a cutter knife is incorporated, and the number of revolution of a cutter driving shaft into a controller, and controlling pushing pressure through each pressure regulating valve. CONSTITUTION:The pressure of a pressure medium fed into air gap chambers 56, 57 constituted between a sleeve 52 and a housing 15 is regulated by a controller 20, and pushing pressure pushing a cutter knife 11 against a die surface 3a is controlled freely. Consequently, the effect of thrust FA generated by the revolution of a cutter driving shaft 12 is computed and predicted previously, thus automatically regulating the pressure of the pressure medium fed into the air gap chambers 56, 57 every time the number of revolution No of the driving shaft 12 is deflected, then pushing the cutter knife by proper force. The head pressure PW of hot water 4a filled into a cutter case 4 can also be predicted, and the pressure of the pressure medium supplied to the air gap chambers 56, 57 can also be controlled automatically. Even when the maximum pressure of a pressure medium source 69 is lowered by an elastic body 203 mounted into the air gap chamber 57, the proper pushing force of the knife 11 is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for granulating plastics, and more particularly to a new improvement for automatically controlling an optimum pressing pressure of a cutter knife against a die surface by a control device. is there.

[0002]

2. Description of the Related Art As a conventional method of controlling the pressing of a cutter knife of a molten plastics granulating apparatus of this type, it is generally adjusted on site each time. As a thing, the structure shown in FIG. 3 can be mentioned. That is, what is indicated by reference numeral 1 in FIG. 3 is a granulator, and this granulator 1 has a manifold 2 for circumferentially distributing molten resin extruded from an extruder (not shown), and a manifold 2 for distributing the molten resin. It comprises a die 3 which is attached in close contact with the manifold 2, a cutter case 4 which is attached to the die surface 3a side of the die 3, and a cutter 5 which is provided in the cutter case 4. The die 3 has a disc shape, and a ring-shaped region surrounding the center of the die 3 has a large number of nozzles 6 penetrating in the axial direction.
6 are provided in communication with the resin passage 2a.
One end of the nozzle 6 is opened to the resin passage 2a of the manifold 2, and the other end is opened to the inside of the cutter case 4.

The cutter case 4 is configured to be detachably attached to the surface of the die 3 by a bolt 7. The cutter case 4 is provided with a hot water inlet 8 and a hot water outlet 9 so that the inside of the cutter case 4 is always warm water 4.
It is designed to be filled with a. The cutter 5 has a structure in which a plurality of cutter knives 11, 11, ... Are radially fixed and supported on the outer periphery of the end surface of the cutter holder 10 facing the die 3, and each cutter knife 11 has a die surface of the die 3. 3a, that is, it is arranged so as to face the surface of the ring-shaped region where the nozzles 6, 6, ... Are provided. A rotational force is transmitted to the cutter holder 10 by a cutter drive shaft 12 arranged on the central axis of the cutter holder 10. The cutter holder 10 is attached to and detached from the cutter drive shaft 12 via a bolt 10a and a key groove 10b. It is provided freely.

At one end of the cutter case 4, a housing 15 having a sleeve 52 that is axially movable via an O-ring 50 and a plurality of packings 51 is attached via a bolt 53. Sleeve 52
The cutter drive shaft 12 is coaxially and rotatably provided therein through a pair of shaft sealing devices 54 and a pair of bearings 55. The cutter drive shaft 12 is axially (longitudinal direction) relative to the sleeve 52. ) Is relatively immovable.

A first cavity 58 and a second cavity 57 are formed between the rear portion 52a of the sleeve 52 and the rear portion 15a of the housing 15, and the first cavity 58 has a first hole 58. Are communicated with each other, and the second void chamber 57 is formed.
A second hole 59 is formed to communicate therewith. The cutter drive shaft 12, the sleeve 52, and the housing 15 constitute a cutter knife axial sliding mechanism 100.

A key 60, which is radially implanted in the rear portion 52a of the sleeve 52, penetrates through a through groove 61 formed in the rear portion 15a of the housing 15 and protrudes to the outside. The detection rod 62a of the detection means 62 formed of a dial gauge or the like provided on the outer surface 15b of the housing 15 is in contact. The housing 1
5 at the rear end 15c. A ring-shaped rear lid 63 is attached via a bolt 64, and a stopper portion 66 having an operating lever 65 is screwed to a screwing portion 63a formed on the rear lid 63.

The stopper 66 is in contact with an adapter 67 connected to the rear end 52c of the sleeve 52,
By rotating the stopper 66 to move it in the axial direction, the stopper operation in the axial direction of the sleeve 52 can be obtained. Further, a first switching valve 70 connected to a pressure medium source 69 having a pressure medium such as compressed air or pressure oil via a first pressure regulating valve 68 is connected to the first hole 58, and Second hole 5
A second switching valve 72 is connected to 9 via a second pressure adjusting valve 71. In addition, the first hole 58 and the second hole 59.
A pressure gauge 73 is connected to each of the pressure adjusting valves 68 and 71 in order to monitor the pressure of the pressure medium supplied to.

The conventional plastics granulating apparatus is constructed as described above, and the granulating method will be described below. First, when the second pressure adjusting valve 71 is fully opened, the sleeve 52 moves to the die 3 side in the housing 15 by the action of the pressure medium supplied to the second void chamber 57 in the same manner as the piston, and the die surface 3a. A cutter knife 1
1 is pressed, and in this state, the detecting means 62 sets the current state to zero.

When the cutter driving shaft 12 is rotated by a driving means (not shown) in the above-mentioned state, the cutter knife 11 rotates at a high speed, and molten plastics (not shown) discharged from the nozzle 6 is moved by each cutter knife 11. The pellets that have been finely cut are solidified with hot water or cold water in the cutter case 4, sent together with this hot water or cold water from a hot water outlet 9 to a treatment unit (not shown), and dried to be manufactured as plastics grains. It

[0010]

Since the conventional plastics granulating apparatus is constructed as described above, the following problems exist. That is, when the cutter drive shaft 12 is rotated by the driving means (not shown), a thrust is generated by the rotation of the cutter knife 11, and this thrust increases as the rotation speed of the cutter knife 11 increases, and the thrust speed increases in the normal rotation speed range. Then, it becomes significantly large. This thrust moves the cutter knife 11 in the forward direction and presses it against the die 3, which causes wear and plugging of the cutter knife 11. Therefore, the rotation speed of the cutter drive shaft 12 is detected, and the rotation speed signal is detected. First manually based on
It was necessary to adjust the pressure adjusting valve 68 each time to control the pressure medium in the first void chamber 56 and keep the contact state between the cutter knife 11 and the die surface 3a optimal. Further, in this type of granulating apparatus, as shown in FIG. 4, the hot water in the tank 110 is supplied to the cutter case 4 by the pump 111, and the plastic pellets cut by the cutter knife 11 are cooled and the dehydrator 112 and the dryer are dried. It is carried to machine 113,
The transport pipe 11 to the dehydrator 112 and the dryer 113
No. 4 requires an inclination in order to prevent the pellets from sticking to each other, so that the height H is generally 15 to 25.
The height H is often a meter, and this height H may be a head pressure of 35 mH ₂ O depending on the distance to and the arrangement of the dehydrator 112 and the dryer 113. Therefore, since the sleeve 52 is pushed by the head pressure of the hot water 4a, it is necessary to manually adjust the pressure adjusting valves 68 and 71. Also, the cutter knife 11 is
It is necessary to move forward and backward, and this is realized by the movement allowance of the first void chamber 56 and the second void chamber 57 of the sleeve 52, but at this time, a force greater than the frictional force is required, and the first pressure regulating valve 6
8 and the setting of the second pressure adjusting valve 71 had to be manually adjusted so as to correspond to a force equal to or greater than this frictional force. In this case, when it is necessary to operate the cutter knife 11 at a relatively low rotational speed, it is necessary to handle a case where a differential pressure between the first pressure adjusting valve 68 and the second pressure adjusting valve 71 exceeding the medium supply pressure source is required. Since it cannot be done, lower the set pressure of the first pressure adjusting valve 68,
It was necessary to deal with it by increasing the differential pressure. Therefore, the first pressure adjusting valve 68 and the second pressure adjusting valve 71 are manually adjusted each time based on the number of revolutions of the cutter knife 11 and the head pressure of the hot water 4a to keep the contact state between the cutter knife 11 and the die surface 3a. I had to keep it optimal.

The present invention has been made to solve the above problems, and in particular, provides a method and an apparatus for granulating plastics in which an optimum pressing pressure is automatically controlled by a controller. The purpose is to do.

[0012]

The method for granulating plastics according to the present invention comprises a cutter knife which rotates in water while contacting the die surface along the die surface of the die,
While obtaining plastics particles by cutting the molten resin extruded from the die, in the plastics granulation method, the pressing pressure of the cutter knife against the die surface is controlled by a plurality of pressure adjusting valves, In this method, the rotational speed of the cutter drive shaft of the cutter knife and the head pressure of hot water in the cutter case containing the cutter knife are taken into a control device, and the pressing pressure is controlled via the pressure adjusting valves.

More specifically, it is a method of constantly energizing the cutter drive shaft via an elastic body to obtain the required pressing pressure even when the maximum pressure of the pressure medium source is low.

Further, the plastics granulating apparatus according to the present invention comprises a cutter holder having a cutter knife which is rotationally driven along the die surface of the die, and a housing which houses a cutter drive shaft for rotationally driving the cutter holder. In a granulating apparatus for molten plastics, which is obtained by cutting the molten resin extruded from the die with the cutter knife, to obtain plastics particles.
A sleeve that holds the cutter drive shaft coaxially and rotatably in the housing, and first and second pressures for supplying a pressure medium to first and second void chambers formed between the sleeve and the housing. A regulating valve and first and second switching valves,
A controller for calculating the pressure of the pressure medium in each of the cavity chambers by detecting the rotational speed of the cutter drive shaft and the head pressure of hot water in the cutter case, and automatically controlling the pressure of the pressure medium in each of the cavity chambers. And the pressing pressure of the cutter knife against the die surface is controlled.

More specifically, an elastic body for constantly urging the cutter drive shaft is provided in the second void chamber.

[0016]

In the method and apparatus for granulating plastics according to the present invention, the force for pressing the cutter knife against the die surface is adjusted by adjusting the pressure of the pressure medium supplied into each of the void chambers formed between the sleeve and the housing. Since the influence of the thrust generated by the rotation of the cutter drive shaft can be calculated and predicted in advance, each time the rotation speed of the cutter drive shaft is changed, it is supplied into the space defined between the sleeve and the housing. The pressure of the pressure medium can be automatically adjusted by the control device, and the cutter knife can be pressed against the die surface with an appropriate pressing pressure. Further, when the cutter housing is filled with hot water and different head pressures are generated for each plant, the pressure medium supplied to the space between the sleeve and the housing is calculated by predicting and predicting the head pressure. The pressure can be automatically adjusted by the control device, and the cutter knife can be pressed against the die surface with an appropriate pressing pressure. Further, by providing a spring in the space defined between the sleeve and the housing, an appropriate pressing pressure of the cutter knife can be obtained at a desired cutter knife rotation speed even when the maximum pressure of the pressure medium source is low. In addition, by changing the setting of the pressure of the pressure medium to be supplied to the cavity chamber when the cutter drive shaft moves forward and backward and the pressure of the pressure medium required to press the cutter knife, and instructing the output, the die surface of the cutter knife is It is possible to widen the range of the rotational speed of the cutter drive shaft that can appropriately adjust the pressing pressure of.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the method and apparatus for granulating plastics according to the present invention will be described in detail below with reference to the drawings. It should be noted that the same or equivalent portions as those of the conventional example are designated by the same reference numerals and described. FIG. 1 is a configuration diagram showing an overall configuration of a main part of a plastics granulating apparatus according to the present invention.
FIG. 2 is a characteristic diagram.

In the figure, the reference numeral 1 designates a granulator, which is attached to a manifold 2 connected to an extruder (not shown), and a die 3 which is attached in a state of being in close contact with the manifold 3. It is mainly composed of a cutter case 4 attached to the die 3 and a cutter 5 provided in the cutter case 4, and the inside of the cutter case 4 is constantly filled with hot water 4a supplied from a hot water inlet 8 to a hot water outlet 9. The molten plastic extruded from the die 3 in the state of being cut is cut.

The cutter 5 has a structure in which a plurality of cutter knives 11 are radially fixed and supported on the outer circumference of the end face of the die 3 facing the cutter holder 10 and facing the die surface 3a. The cutter holder 10 is mounted via bolts 10a. And is detachably attached to the cutter drive shaft 12. At one end of the cutter case 4, a housing 15 having a sleeve 52 movably in the axial direction is provided with a fixing bolt 53.
The cutter drive shaft 12 is attached by
It is held so as to be movable relative to the sleeve 52.

At the rear of the sleeve 52, a first void chamber 56 and a second void chamber 5 are provided between the sleeve 52 and the rear of the housing 15.
7 is formed, the cutter drive shaft 12 moves in the direction opposite to the die 3 when pressure is applied to the first void chamber 56, and the cutter drive shaft 12 moves in the die 3 direction when pressure is applied to the second void chamber 57. It has a structure.

A first pressure regulating valve 68 and a first switching valve 70 are connected to the first void chamber 56 via a first hole 58, and a second pressure chamber 57 is connected to a second void chamber 57 via a second hole 59. Pressure control valve 7
1 and the second switching valve 72 are connected to each other, and each pressure medium source 6
The configuration is such that the pressure medium is supplied from 9.

The pressing medium supply device 200 includes the first pressure adjusting valve 68 and the first switching valve 70, the second pressure adjusting valve 71 and the second switching valve 72, the first pressure adjusting valve 68 and the second pressure adjusting valve 68. A control device 201 that outputs a pressure setting signal to the adjusting valve 71 and a signal converter 202 that outputs a rotation speed Nc of the cutter drive shaft 12 (this signal is also replaced by a control signal of a cutter drive motor (not shown)). (Possible) and a pressure transmitter 162 provided in the cutter case 4 for detecting the head pressure Pw of the hot water 4a in the cutter case 4.

Next, in the above-mentioned configuration, the control device 201 of the pressing medium supply device 200 is actually used to
A case where the pressing pressure of the cutter knife 11 against the die surface 3a is controlled to a suitable state will be described. First, the thrust Fs generated by the rotation speed Nc of the cutter 5 is as shown in FIG.
It can be estimated in advance as shown in. Fs = f (Nc) On the other hand, the force Ff required to move the cutter drive shaft 12 to the pushing (advancing) side is set to the second pressure adjusting valve 71 as the set value Pf by the control device 201, and then pulled ( The force Fb required to move to the (reverse) side is the first pressure adjusting valve 6
8 is set as a set value Pb by the control device 201.

Further, the head pressure Pw of the hot water 4a obtained from the pressure transmitter 162 provided in the cutter case 4 exerts a force Fw for moving the sleeve 52 toward the pulling (retracting) side. Therefore, the force (pressing pressure) P with which the cutter knife 11 is pressed against the die surface 3a is calculated by P = Ff + Fs-Fb-Fw-Fr. (However, Ff is the force required to move to the push (forward) side above the pressure of the pressure medium source 69, Ff
s is thrust, Fb is force necessary to move to the pull (reverse) side, Fw is force to move to the pull (reverse) side, F
r is the sliding resistance of the sleeve 52. )

Since the thrust Fs is determined by the rotation speed Nc of the cutter drive shaft 12, the desired optimum pressing pressure P can be set in advance by the set pressure of the second pressure adjusting valve 71, and therefore the rotation speed of the cutter 5 is convenient for production. It can be set automatically even when changes occur.

Further, the force Fb required to move to the pulling (retracting) side can be freely set by the first pressure adjusting valve 68.
When the pressure of the pressure medium source 69 is low and the force Ff required to move to the pushing (advancing) side that is equal to or higher than the pressure of the pressure medium source 69 is required, it is necessary to move to the pulling (retracting) side. This effect can be enhanced by reducing the force Fb to be set, and further by providing the elastic body 203 made of a spring or the like so as to work on the push side in the second void chamber 57. In addition,
The elastic body 203 can be provided not only in the second void chamber 57 but also in another place to obtain the same effect.

Therefore, by controlling the pressure of the pressure medium supplied into the void chambers 56 and 57 formed between the sleeve 52 and the housing 15 by the control device 201, the cutter knife 11 is moved to the die surface 3a. Since the pressing pressure applied to the cutter can be adjusted freely, the cutter drive shaft 1
By preliminarily calculating and predicting the influence of the thrust force Fs generated by the rotation of 2, the pressure of the pressure medium supplied into each of the void chambers 56 and 57 is automatically set every time the rotation speed Nc of the cutter drive shaft 12 is changed. The cutter knife 11 can be adjusted and pressed against the die surface 3a with an appropriate force.

Further, when the cutter case 4 is filled with the hot water 4a and the head pressure Pw which is different for each plant is calculated and predicted in advance by the control device 201, the pressure to be supplied into each of the void chambers 56 and 57. It is possible to automatically control the pressure of the medium and press the cutter knife 11 against the die surface 3a with an appropriate force.

Further, since the elastic body 203 is provided in the second void chamber 57 or in another portion,
Even if the maximum pressure of the pressure medium source 69 is low, each void chamber 56 required when the cutter drive shaft 12 is moved forward and backward so that an appropriate pressing pressure of the cutter knife 11 can be obtained at the desired rotation speed Nc of the cutter knife 11. , 57, and the pressure medium required for pressing the cutter knife is changed by the control device 201 to instruct the output, so that the cutter knife 11 is appropriately pressed against the die surface 3a. The range of the rotational speed Nc of the cutter drive shaft 12 that can be adjusted to a wide range can be widened.

[0030]

Since the method and apparatus for granulating plastics according to the present invention are configured as described above, the following effects can be obtained. (1) Even if the number of rotations of the cutter changes, the supply pressure of the pressure medium can be automatically controlled according to the generated thrust, so the contact state between the cutter knife and die surface is optimized and Efficient granulation and longer life of cutter knife and die can be achieved. (2) Since this can also be calculated for the head pressure of hot water in the cutter case depending on the equipment layout of each plant, the optimum conditions for granulation operation can be obtained. (3) Since the supply pressure of the pressure medium can be freely controlled on the pushing (forward) side and the pulling (backward) side, it is possible to avoid being restricted by the maximum pressure of the pressure medium source. (4) Conventionally, the efficiency of granulation depends largely on the skill of the driver, but since the optimum pressing force can be obtained by calculation, the required skill level can be reduced, and the labor shortage can be resolved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of a main part of a plastics granulating apparatus according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between rotation speed and thrust.

FIG. 3 is a configuration diagram showing a conventional plastics granulating apparatus.

FIG. 4 is a configuration diagram showing a conventional plastics granulating apparatus.

[Explanation of symbols]

 3 dice 3a die surface 4 cutter case 4a hot water 11 cutter knife 12 cutter drive shaft 15 housing Nc rotation speed 52 sleeve 56 first void chamber 57 second void chamber 68 first pressure regulating valve 69 pressure medium source 70 first switching valve 71 Second pressure regulating valve 72 Second switching valve Pw Head pressure 201 Control device

(72) Inventor Takaaki Okita 1-6-1, Funakoshi-minami, Aki-ku, Hiroshima-shi, Hiroshima, Japan Steel Works, Ltd. (72) Inventor Shigeyoshi Kinomoto 1-6 Funakoshi-minami, Aki-ku, Hiroshima-shi, Hiroshima No. 1 Japan Steel Works, Ltd.

Claims (4)

[Claims] 1. A cutter knife which rotates in water while being in contact with the die surface (3a) along the die surface (3a) of the die (3).
(11), by obtaining a plastics grain by cutting the molten resin extruded from the die (3), the pressing pressure of the cutter knife (11) against the die surface (3a) is a plurality of pressure control valves. In the method of granulating plastics controlled by (68, 71), the cutter knife
The rotation speed (Nc) of the cutter drive shaft (12) of (11) and the head pressure (Pw) of the hot water (4a) of the cutter case (4) containing the cutter knife (11) are taken into the control device (201). A granulation method for plastics, characterized in that the pressing pressure is controlled via the pressure regulating valves (68, 71). 2. The cutter drive shaft (12) is constantly urged via an elastic body (203) to obtain the required pressing pressure even when the maximum pressure of the pressure medium source (69) is low. The method for granulating plastics according to claim 1. 3. A cutter holder (10) having a cutter knife (11) which is rotationally driven along a die surface (3a) of the die (3).
And a cutter drive shaft for rotationally driving the cutter holder (10)
And a housing (15) containing (12) therein,
(3) In a granulating device for molten plastics obtained by cutting the molten resin extruded from the cutter knife (11) with the cutter knife (11), in the housing (15) the cutter drive shaft ( Sleeve (52) for holding 12) coaxially and rotatably, and said sleeve
First and second void chambers formed between the (52) and the housing (15)
Rotation of the cutter drive shaft (12) and the first and second pressure regulating valves (68,71) and the first and second switching valves (70,72) for supplying the pressure medium to the (56,57) The number (Nc) and the head pressure (Pw) of the hot water (4a) in the cutter case (4) are detected to detect the void chambers (56, 57).
With a control device (201) for calculating the pressure of the pressure medium inside, automatically controlling the pressure of the pressure medium in each of the void chambers (56, 57), a cutter knife for the die surface (3a) ( 11)
An apparatus for granulating molten plastics, which is configured to control the pressing pressure of. 4. The elastic body (203) for constantly urging the cutter drive shaft (12) is provided in the second void chamber (57). Item 3. A molten plastics granulating apparatus according to Item 3.