JPH0139062B2 - - Google Patents

Description

Detailed Description of the Invention The present invention is based on an automatic magnification measuring method for automatically detecting fluctuations in the expansion magnification of expandable thermoplastic resin particles pre-foamed in a pre-foaming machine, and an automatic magnification measuring method based on the measuring method. This invention relates to a method for controlling the expansion ratio in a pre-foaming machine.

Before forming styrene foam using the bead method in a mold using a molding machine, the raw material styrene foam beads are expanded to the required apparent specific gravity to form beads with the required expansion ratio, which is commonly known as pre-foaming. ing.

For this pre-foaming, raw resin particles such as the expanded styrene beads are generally continuously fed from the bottom into a foaming tank equipped with a stirrer, heated and foamed with a heating medium such as water vapor, and the pre-foamed particles are A continuous method that takes out the foam continuously from the top of the foaming tank,
There are two methods: a batch method, in which the raw resin particles are fed into the foaming tank equipped with a stirrer in a fixed amount in batches, the resin particles are foamed with a heating medium, and then the pre-expanded particles are taken out in batches; Both methods are used, but in the case of the former, there is a difference in the circumferential speed of the stirring blade near the wall and the center of the foaming tank, uneven temperature distribution, and even unevenness caused by the stirring operation. There is considerable variation in the expansion ratio of the pre-expanded particles, and on the other hand, the expansion ratio of the pre-expanded particles is
It is practically difficult to evenly and evenly stir the foaming tank from top to bottom, and there is a difference in the foaming ratio between the top and bottom of the tank, resulting in an uneven foaming ratio.

Such variations in the expansion ratio of pre-expanded particles naturally lead to variations in the quality of foamed molded products, and not only can it not be expected to produce high-quality molded products, but also in the modern era where high quality is required. This trend has become a bottleneck in the production of mechanical structural parts.

Therefore, some attempts have been made to automatically control the expansion ratio from the viewpoint of the uniformity of pre-expanded particles and the stability of the average expansion ratio. This is a batch-type manual control method, in which the pre-foamed particles discharged from the pre-foaming machine are sampled in a container such as a bucket, the volume is made to a constant volume, the weight is measured, and the apparent specific gravity is calculated. , compare it with the set specific gravity, and if there is a deviation between the two, either manually adjust the steam supply amount by opening and closing the manual valve, or manually adjust the rotation speed of the motor with a transmission. The feed rate of raw material particles is adjusted to maintain a predetermined expansion ratio.

However, the expansion ratio of the pre-expanded particles is a major factor that determines the quality of the molded product produced by the molding machine, and also accounts for a large proportion of the cost, so the operation of adjusting the expansion ratio is a very important operation.

Therefore, in the manual control method described above, a dedicated operator is required for the pre-foaming operation, and this operator measures the pre-foamed particles at intervals of 15 to 30 minutes.
The situation is that adjustments are being made.

However, this control method not only has problems in terms of effective utilization of personnel, but also measurement control at 15 to 30 minute intervals is not necessarily sufficient to ensure uniformity and stability of pre-expanded particles. It does not necessarily meet the demands of the times.

The present invention addresses the above-mentioned circumstances and aims to provide a novel method for measuring and controlling the expansion ratio of pre-expanded particles that is compatible with the trends of the times.

That is, in the present invention, pre-foamed thermoplastic resin particles foamed by a pre-foaming machine are continuously introduced into a cylindrical container, and a weighing device installed in the container allows the pre-foamed particles to be weighed in a fluidized state. The foaming ratio can be manipulated by automatically and continuously measuring a certain volume at a certain volume and converting it into a foaming ratio.The steam supply amount or raw material particle supply amount, or both, can be automatically controlled to always maintain a predetermined foaming ratio. This is the method.

To describe this more specifically, first, the first aspect of the present invention
The invention introduces pre-expanded particles into a vertical cylindrical container,
While flowing downward in the container, a meter installed in the container automatically measures a certain volume of the pre-expanded particles under the flow, and detects the expansion ratio of the pre-expanded particles. The second
In the invention, pre-foamed particles discharged from a pre-foaming machine are guided into a vertical cylindrical container, and while flowing downward within the container, a weighing device installed in the cylindrical container is used to collect the pre-expanded particles in the flowing state. A certain volume of foamed particles is automatically weighed one after another, the measured weight value is taken out by an electrical signal and input into a control device, and the control device responds to the deviation between the measured value and a preset setting value. In this method, a control signal is transmitted, and either or both of the amount of heating medium supplied or the amount of raw material supplied into the pre-foaming machine is automatically controlled by this transmitted signal.

Hereinafter, specific embodiments of the method of the present invention will be explained with reference to the accompanying drawings.

FIG. 1 is an outline of a continuous system pre-foaming device for expandable thermoplastic resin particles to which the method of the present invention is applied. Raw material particles such as pre-expanded styrene particles supplied to a hopper 8 are rotated by a motor 4 with a transmission. The driven screw feeder 7 continuously feeds into the pre-foaming machine 5.
While being stirred by a stirring member 11 inside, the particles are heated and foamed by a heating medium such as steam introduced from a steam supply line 9, and are discharged from an upper pre-expanded particle discharge chute 6 at a desired expansion ratio.

The structure of this pre-foaming machine 5 is a known structure, and various types of pre-foaming machines known or improved can be adopted and used, but the pre-foaming machine 5 is shown by the reference numeral 1 provided directly below the discharge chute 6. The foaming ratio measuring device is a continuous automatic measuring device that occupies the main part of the measuring method that constitutes the first aspect of the present invention, and examples of its configuration are shown in detail in FIGS. 2 to 4.

That is, FIG. 2 shows an example of such a measuring device, in which a screen 22 and an umbrella-shaped distribution plate 25 on the upper surface having a rhombic cross section are provided in two stages above a cylindrical container 21. The middle part of the plate is constricted to form a narrow passage 23, and an overflow hole 24 is provided at the open end of the passage for overflowing the excess pre-foamed particles supplied to the cylindrical container 21. The upper limit of the number of pre-expanded particles that can be filled and housed within the container is regulated.

Here, the upper limit of the pre-expanded particles is based on the angle of repose measurement method that is widely used to measure the mechanical and mechanical properties of powder, and for the cylindrical container 21 shown in FIG. 2, it is indicated by a dotted line. This is the intersection (apex) of the angle of repose starting from the intersection between the lower side of the overflow hole 24 and the outside of the cylindrical container 21, and is located at the center of the cylindrical container.

The angle of repose is the inclination angle at which the pre-expanded particles form a constant inclination angle with respect to the horizontal plane, and this angle varies depending on the particle size of the particles, but is usually in the range of 40 to 30 degrees.

On the other hand, a pre-expanded particle discharge port 26 is formed at the lower part of the cylindrical container 21, and a funnel-shaped cover support member 27 for weight measurement is provided adjacent to the lower opening of the pre-expanded particle outlet 26, and a part of the upright wall of the cover support member 27 is attached to the lower part of the cylindrical container 21. It is provided in an overlapping state around the outer periphery of the opening, and a cover 28 for weight measurement is mounted inside the cover 28 with its sloped surface overlapping the sloped surface of the funnel-shaped member. The weight measuring cover 28 and the support member 27 are connected to the cylindrical container bottom support stand 3 via the hollow cylindrical receiving part 29 on the bottom surface thereof.
The strain gauge 35 is supported by the upper end of a support bolt 30 that is screwed through the upper support stand 34 of the strain gauge 35 disposed on the top of the strain gauge 6 , and is supported by the upper end of the support bolt 30 screwed on. Then, there is a discharge passage 32 for guiding and discharging the measured pre-expanded particles to a discharge hole 37 provided below the cylindrical container 21.
is formed.

The discharge passage 32 is connected to the weight measuring cover support member 2.
a cylindrical wall surrounding the outer periphery of the communication opening in the lower central part of 7 with a slight gap; an upper partitioning member having a slanted wall that extends continuously toward the discharge hole 37; and the slanted wall. The support bolt 3 is partitioned by a lower partition member having a chevron-shaped wall surface 33 formed by an inclined wall parallel to the
A guide tube 31 is installed around the 0, passing through the upper and lower partition members with a slight gap between them.

Support bolts 3 that support the weight measurement cover 28 and the support member 27 inside the cylindrical container 21
0, the strain gauge 35 including the upper and lower partition members is integrally constructed, and is arranged in the cylindrical container 21 to constitute a removable weighing device, and the weight measurement device forming the measurement surface The lower limit of the pre-expanded particles below is regulated by the cover 28 surface.

In this way, the capacity of the pre-expanded particles measured by the weighing device is a constant volume regulated by the upper and lower limits, and the pre-expanded particles always flow from the top to the bottom while maintaining a constant volume of the pre-expanded particles. By keeping the foam on the measurement surface, it is possible to check the fluctuations in the foaming ratio using a weighing device.

Therefore, a method for automatically and continuously measuring the expansion ratio of pre-expanded particles according to the present invention as shown in FIG. 1 using the scale disposed in the cylindrical container 21 will be described below. The pre-expanded particles are usually solid spherical particles with a diameter of 2 to 5 mm, but since some of them are large clumps that are fused together, they are first introduced into the measuring device through a screen 22 to prevent them from entering the measuring device.

The measuring device is formed of the cylindrical container 21 as described above, and may be either cylindrical or prismatic.
The pre-foamed particles that are continuously discharged and supplied from the pre-foaming machine to the upper part of the cylinder pass between the circumferential edge of the upper distribution plate 25 and the cylinder wall and flow into the weight measurement section below. descend. At this time, the function of the upper distribution plate 25 is to always maintain a constant volume of the pre-expanded particles in the weight measuring section, together with the overflow hole that regulates the upper limit, and to prevent the pre-expanded particles that have entered the upper part of the cylinder. It also has the role of a friction plate so as not to be affected by variations in the head of the particles, and it is preferable that the top surface of the pre-expanded particle packed bed is brought into slight pressure contact with the bottom surface of the distribution plate.

Usually, the range to be measured by the weight of the pre-expanded particles in the present invention is the weight measurement cover 28 inside the cylindrical container.
The pre-expanded particles present on the distribution plate 25 closest to this are measured.

Therefore, if the distance between the weight measurement cover 28 and the distribution plate 25 is increased, the measurement range will be increased.
Generally, the measurement accuracy improves as the measured weight value increases.

However, on the other hand, if the same distance increases, the measuring device becomes larger, which creates a contradiction in that handling and cost of the measuring device become higher. Therefore, although FIGS. 3 and 4, which will be described later, show that the distribution plate may have one stage 44, 63, in any case, the bottom surface of the distribution plate should be brought into slight pressure contact with the top surface of the pre-expanded particle packed bed. This is effective in keeping the amount of pre-expanded particles in the weight measurement section constant, that is, in preventing it from being affected by fluctuations in the head of the pre-expanded particles in the weight measurement section.

On the other hand, in the weight measurement section, the pre-expanded particles pass through the pre-expanded particle discharge port 26, flow along the upper surface of the weight measurement cover 28, and are discharged out of the measuring device system through the discharge hole 37. Then, the amount of pre-expanded particles filled into the measurement system is maintained at a constant amount regardless of their flow, while matching the supply above the cylindrical container 21 with the amount of discharge from the bottom of the measurement device. While doing so, measure the weight sequentially.

If the expansion ratio of the pre-expanded particles is uniform, the weight at the time of this measurement is a constant volume and should not fluctuate, but if the expansion ratio in the pre-expanding machine is uneven, There is a change in the measured value, and from this it is possible to confirm the uniformity of the pre-expanded particles heated and expanded in the pre-expander.

FIG. 3 shows another embodiment of the measuring device used in the method of the present invention, in which a cylindrical container 41 and a screen 4 on the surface are shown.
2, and has an upper distribution plate 44, an overflow hole 43, and a throttle passage 45 in the cylindrical container 41, which is the same structure as in the case of FIG. The structure is simplified, and a strain gauge 51 is arranged at the bottom of the pre-expanded particle discharge port 46, and a weight measurement cover 47, which forms a measurement surface, is supported by an erected support rod 50 together with a lower orifice 48 on the bottom surface of the strain gauge 51. are doing. Note that 49 is a guide, and 5
2 is a lower discharge hole, and 53 is a strain gauge support plate.

On the other hand, FIG. 4 shows still another example of the method of the present invention.
This is another example of a measuring device, and like each of the above examples, a weighing device is disposed at the bottom of a cylindrical container 61, and a screen 62, a distribution plate 63, and an overflow hole 66 are provided above. ing. The weighing device is constructed by supporting a measurement cover 67 forming a measurement surface by an upright rod 68 of a strain gauge 69 installed on a strain gauge support plate 70 at the lower part of the pre-expanded particle discharge port 64. A guide 65 is disposed outside the strain gauge 69 by fitting its tip into the bottom of the measurement cover 67. A discharge hole restriction plate 72 is rotatably attached to the bottom surface of the strain gauge support plate 70 by a fixing bolt 74, and a discharge restriction hole 73 that continues to the pre-expanded particle discharge hole 71 is formed on one side thereof.

In the case of the measuring devices shown in FIGS. 3 and 4, the method of measuring the pre-expanded particles is the same as in the case of FIG. The weight of pre-expanded particles of a certain volume, the upper limit of which is regulated as shown by the dotted lines, and the lower limit of which is regulated by the measuring cover surface, can be automatically and sequentially measured in a fluidized state.

In these measurements, it is preferable that the lower end of the pre-expanded particle outlet, that is, directly above the measurement cover, be an opening with the largest possible diameter, so that more accurate measured values can be obtained.

The above is related to the automatic weighing of the method of the present invention. By determining in advance the relationship with the electrical signal obtained from the signal, continuous automatic measurement can be easily performed and its fluctuations can be known.

In this measurement, the guide 65 in the measuring device serves to prevent pre-expanded particles, moisture, etc. from flowing into the strain gauge.
In addition, the inflow amount of pre-expanded particles can be adjusted by changing the amount of discharge from the lower pre-expanded particle discharge hole.
It can be changed at any time.

The measuring device is usually made of plastic or metal, and various means such as adhesives, bolts, welding, etc. can be used to fix each component.

Next, using the automatic measurement method using the measurement device,
An automatic control method for controlling the expansion ratio of pre-expanded particles in a continuous pre-expanding machine will be explained with reference to FIG.

That is, as shown in FIG.
The weight of the pre-expanded particles is successively measured by the measuring method described above, and the weight of the pre-expanded particles of the constant volume measured at this time is taken out as an electrical signal by the strain gauge. , is input to the foaming ratio control device 2 which is provided separately from the measuring device 1.

This control device 2 is inputted by flowing known pre-expanded particles into the measurement device in advance to determine the relationship between the pre-expanded particles and the electrical signal obtained from the strain gauge, and determining the set value in advance. By comparing it with the set value, a control operation signal corresponding to the deviation value between the two is transmitted. As shown in FIG. 1, this control device 2 is connected to a steam supply line 9 via an automatic steam amount control valve 3, and is also configured to be connected to rotation control of a motor 4 with a transmission. Therefore, by transmitting the control operation signal, the automatic steam amount control valve 3 is actuated to change the amount of supplied steam to adjust it to a predetermined foaming ratio, or the motor 4 with a transmission is actuated. The amount of raw material particles supplied to the pre-foaming machine is adjusted to achieve a predetermined foaming ratio.

In this way, the expansion ratio of the continuously pre-foamed particles can be continuously controlled without interrupting the pre-foaming operation, and pre-foamed particles having a uniform expansion ratio can be obtained.

In order to supply the pre-expanded particles to the automatic expansion ratio measuring device 1, it is possible to directly supply them using the discharge chute 6 as shown in FIG. It may also be supplied.

As described above, the present invention is based on one method of continuously weighing pre-expanded particles discharged from a pre-expanding machine to a fixed volume under a fluidized state, and further based on the weighing results, This is a method that stably controls the expansion ratio of pre-foaming in a pre-foaming machine to a predetermined ratio, and is more accurate and can be obtained continuously compared to the conventional batch-type measurement of expansion ratio that was performed manually. This makes it possible to measure all of the pre-expanded particles, which has a remarkable effect on improving the uniformity and stability of the expansion ratio.It also eliminates the need for full-time operators, which was previously required, and is useful for streamlining work. fulfill a role.

Moreover, by combining a measuring device and a control device, it is possible to automatically control the magnification of pre-expanded particles using electrical signals, which increases the homogeneity of pre-expanded particles, enables the production of molded products of uniform quality, and the production of high-quality products such as mechanical structural parts. It contributes to the production of required products and is a promising method for industrial development.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the pre-foaming device in the present invention;
2 to 4 are schematic sectional views showing each embodiment of the measuring device used in the method of the present invention. 1... Foaming ratio measuring device, 2... Control device, 5
...Pre-foaming machine, 21,41,61...Cylindrical container, 35,51,59...Strain gauge.

Claims (1)

[Scope of Claims] 1 Pre-expanded particles are guided into a vertical cylindrical container, and while flowing downward within the container, a weighing device installed in the container measures the pre-expanded particles under the flow. 1. An automatic magnification measuring method for pre-expanded particles, which is characterized in that the expansion magnification of pre-expanded particles is detected by automatically weighing a constant volume one after another. 2. The pre-foamed particles discharged from the pre-foaming machine are guided into a vertical cylindrical container, and while flowing downward within the container, the pre-foamed particles under the flow are measured by a weighing device installed in the cylindrical container. Automatically weighs a certain amount of water one after another in succession, extracts this weight measurement value as an electrical signal and inputs it into a control device, and the control device controls according to the deviation between the measured value and a preset setting value. Pre-foaming characterized by transmitting a signal and automatically controlling the amount of heating medium supplied or the amount of raw material supplied into the pre-foaming machine based on the transmitted signal, or automatically controlling both the amount of heating medium and raw material supplied Automatic magnification control method for particles.