JPS62214905A - Pre-expanding device and method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention is directed to a pre-expansion chamber for expandable polymer beads.

BACKGROUND OF THE INVENTION Prior to feeding expandable polymer beads into molds for making lightweight products, such as pots, the polymer beads are heated for pre-expansion. Conventionally, the beads are temporarily held in a hopper before being sent to a mold for final expansion.

The bead (generally polystyrene) contains a hydrocarbon blowing agent that reaches its boiling point while it is in the pre-expansion chamber. The blowing agent evaporates and exerts pressure within the heat-softened walls of the bead, causing it to expand in a process known in the art as a pre-expansion process.

Various types of pre-inflation chambers are known. Continuous or batch steam preexpansion chambers are known, but both devices require at least a four-hour aging period to stabilize the pressure within the bead before being used to form the bead. It has some disadvantages. This device provides direct contact between the steam heating medium and the expandable beads. Because of the maturation time required, steam-type bead production requires a large hopper that can hold the beads during maturation.

An alternative pre-expansion chamber is a device known as a dry pre-expansion type. In this device, the expandable beads are pre-expanded not in direct contact with the heating medium, but in indirect contact with the heating medium by using a heated cylindrical wall. An advantage of this equipment is that there is no need to age the beads before forming. Devices of this type are disclosed in U.S. Pat. Nos. 4,060,354 and 3,577.
It is described in No. 360. The devices described in the two aforementioned patents use a closed heated cylinder in which the beads remain for a period of time. In these devices, the temperature of the heating medium and the mass of the bead "shot" introduced into the pre-expansion chamber are consistent.

The final density cannot be adjusted accurately during the fixed time period during which the Y-biased expansion is performed. The main reason why it is not possible to obtain a pre-expanded bead of a density similar to that of the devices of the two prior art patents mentioned above is that the unexpanded D-bead itself is inconsistent. First, the age of the blowing agent within the bead can vary from bead to bead due to irregularities during manufacturing or loss of blowing agent after manufacturing. Second, and more specifically,
There are variations in the size of polymer beads in certain containers;
Third, the beads within a particular container can be separated by size.

Due to the non-negativity mentioned above, the pre-expanded beads do not dry satisfactorily for a period of time. These non-intrinsics can cause the final product mass to vary by around 20% from the desired mass.

OBJECTIVE OF THE INVENTION 1 The main objective of the invention is to provide a pre-expansion chamber for producing beads of uniform density.

SUMMARY OF THE INVENTION According to one aspect of the invention, a heated pre-expansion chamber for receiving unexpanded beads, a means for heating the pre-expansion chamber, an agitator in the pre-expansion chamber, and a stirrer are provided. an electric motor for driving the machine; and means for detecting an increase in motor power requirements as the beads expand and provide increased resistance to movement of the agitator; and for ejecting the pre-expanded beads from said pre-expansion chamber. and means for ejecting the pre-expanded beads from the pre-expansion chamber by actuating the ejecting means when the detecting means detects an increase in the power requirement a of a predetermined magnitude. A pre-expansion chamber is provided for the polymer beads.

Preferably, the current flowing to the motor is monitored by a relay, such as a contact that is activated when the current flowing through the coil increases to a predetermined level.

The pre-expansion chamber includes a cylindrical body arranged such that its axis is horizontal, and the agitator is arranged coaxially with the cylindrical body.
a shaft and a radial arm extending outwardly from the shaft, and a stirring element can be provided at the outer end of the arm.

The cylinder may be heated by a steam coil, an electric heating element or a steam jacket and may be provided with a temperature control device to maintain the temperature of the cylinder at a desired level.

The pre-expansion chamber further includes a chamber for holding a predetermined number of unexpanded beads, means for delivering lubricant to the pre-expansion chamber, and means for discharging the mixed beads and lubricant from said holding chamber to said pre-expansion chamber. and may include.

The means for delivering said lubricant to the holding chamber may consist of a container of II lubricant and a worm driven by an electric motor.

A hopper may be provided for receiving the pre-expanded beads from the pre-expansion chamber and includes a level sensor for detecting when the beads therein exceed a predetermined level.

The pre-expansion chamber may include means for charging unexpanded beads into the pre-expansion chamber, and the level sensor is connected to the charging means to ensure that the level of the pre-expanded beads in the hopper is at a predetermined level. is detected, and operation of the charging means is interrupted when the level of pre-expanded beads in the hopper exceeds the predetermined level.

The pre-expansion means further includes unexpanded peas 1 in the holding chamber.
and a second sensor that detects the presence of unexpanded beads in a path along which the unexpanded beads flow from the holding chamber to the pre-expansion chamber.

According to another aspect of the invention, the beads are sent to a pre-expansion chamber, the pre-expansion chamber is heated, the beads within the pre-expansion chamber are agitated, and the power requirements of the agitator are monitored to ensure that the beads are as desired. A method of pre-expanding a polymer is provided that includes detecting when it has pre-expanded to an extent.

For a better understanding of the invention, and for illustrating how the invention may be carried out, reference will now be made, by way of example, to the accompanying drawings, in which: FIG.

DETAILED DESCRIPTION OF THE DRAWINGS Referring first to FIGS. 1 and 2, the illustrated pre-expansion chamber includes a hopper 10, and above the hopper is an automatic system that keeps the hopper full with unexpanded polymer beads. Loader 1
2 is provided. Below the hopper 10 is a vertical tube 14 containing a shutoff valve 16. The tube extends downward into the holding chamber 18. Reference numeral 20 designates a mechanism by which the depth of penetration of the tube 14 into the holding chamber 18 can be adjusted. As will be seen in more detail below, the depth of penetration of the tube 14 into the holding chamber 18 controls the size of the "shot" of unexpanded pellets to be processed within the pre-expansion chamber.

Automatic loader 12 may include a suction hose (not shown) for sucking beads from a drum, cardboard or other source and placing them onto hopper 1o.

In order to control the operation of the self-help loader 12, the hopper 1o is provided with a level sensor (not shown).

The outlet from the holding chamber 18 is at its lower end and is indicated at 22, which outlet 22 leads downwardly to a valve 24. The valve 24 controls the flow of beads into the expansion chamber 26.
! 1, and includes a continuously open inlet at its top, to which the outlet 22 is connected. The valve also includes an outlet communicating with the expansion chamber, 26, and a valve head that normally opens the valve outlet. The valve head has an air supply device. The valve head is attached to an actuation rod.

Expansion chamber 26 is shown in more detail in FIG. The expansion chamber is in the form of a horizontal cylinder including a cylindrical wall and two end plates. Said cylindrical wall is surrounded by a jacket 28, inside which is provided an electric heating element or, as shown, a steam pipe 30.

In an alternative, steam is supplied directly to jacket 28.

The agitator shaft 32 is in coaxial relationship with the cylindrical wall of the expansion chamber 26, the shaft 32 passing through one end wall of the expansion chamber and connecting the gearbox 34.1 and the drive bell 1-36.
It is connected to an electric motor 34 (see FIG. 2) which rotates continuously.

An arm 38 extends radially outwardly from the shaft 32 and has a stirring blade 4 at its radially outer end.
There is 0. The stirring blade 40 is close to the inner surface of the cylindrical wall of the expansion chamber. More than one set of arms 38 and more than one blade 40 can be provided as desired. Alternatively, a single arm located intermediate between the end plates of the expansion chamber can be provided with stirring blades 40 projecting axially in both directions of the arm.

An outlet vibe 42 extends from a point proximate the bottom of the expansion chamber 26 and then extends upwardly into a storage hopper 44 .

The hopper 44 includes a level sensor 46 that detects the level of pre-expanded beads stored therein. Communication between the expansion chamber 26 and the pipe 42 is provided by a valve 48.

Referring to FIG. 3, a container designated at 50 serves to store particulate lubricant. Chamber 18 that holds the lubricant used
It is generally zinc stearate with a 0.05 to 0.1% lubricant mass added to the beads within. Specifically, electric motor 52 drives a worm 54 that expels lubricant from container 50 into an upwardly open funnel 56 .

The lower end of the funnel communicates with a via 58 and there is a venturi 60 in the pipe. A pipe 58 is connected to the throat of the venturi so that as air is blown through the venturi into the holding chamber 18, a low pressure is created in the pipe 58, which in the funnel 56 draws lubricant into the venturi and then Then, it is sucked into the holding chamber 18.

In FIG. 1, 62, 64 and 66 indicate timers, and 68 indicates a temperature control device. The timer 62 is the valve 16
and 24, and a valve for controlling air supply to the venturi 60 (indicated by ■ in FIG. 4 only) and a motor 52.
connected to.

Timers 64 and 66 are interlocked as described in more detail below. Humidity control device 68 is set so that the temperature of the cylindrical wall of expansion chamber 26 does not rise above the desired level.

The current flowing through motor 34 is monitored by a trip current relay 70 (FIG. 4) whose contacts 72 are connected between timers 64 and 66.

In the pre-expansion chamber, the expandable beads fall from the hopper 10 into the holding chamber 18. The holding chamber 18 is filled until the unexpanded beads that are being deposited in the chamber effectively close the lower end of the tube 14. Typically, valve 16 is opened to allow beads to fall into chamber 18 and valve 24 is opened to allow beads to fall into chamber 18.
is closed to prevent the beads from reaching the expansion chamber 26. It will be understood that the charging of the holding chamber 18 with "the next shot of the bead to be expanded" takes place while the pre-expansion of the previous shot of the bead is taking place.

To begin the charging cycle, timer 62 closes valve 16 and moves the head of valve 24 to close said chambers 18 and 26.
and communicate with each other. Air is supplied through the valve head so that the pellet is swept away by the air flowing through the valve into the expansion chamber 26. At the same time, valve v1 opens to allow air to flow to venturi 60 and motor 5.
2 starts. The motor 52 operates for a period of time equal to the charge of unexpanded beads delivered to the holding chamber 18 .

After the motor 52 has been operated for the required time, e.g. 3 seconds, after a predetermined amount of zinc stearate has been delivered to the funnel 56 and drawn into the chamber 18, an attached timer T (FIG. 4) is activated.
causes the motor 52 to stop. Timing by timer T starts when timer 62 operates motor 52. Air continues to flow to the venturi 60, forcing all the beads into the expansion chamber 2.
6, timer 62 opens and closes air supply valve VI, opens valve 16, opens and closes valve 24, and stops the air supply to valve 24.

The agitator shaft 32 is continuously driven by a motor 34 and the current flowing to the motor is monitored by a relay 70. A scraper blade 40 lifts the bead from the bottom of the expansion chamber 26, smoothes it over the walls of the expansion chamber, and then drops it back to the bottom of the expansion chamber. The gas emerging from the bead is extracted via a valve designated 26.1 in FIG. 2, and low pressure air is supplied to the expansion chamber 26 to flush it during pre-inflation.

Timer 64 begins its timing cycle when timer 62 closes valve 24 and opens valve 16, etc. This means that the bead charge has entered pre-expansion. If the required inflation rt@ is known to be, for example, 5 minutes, timer 64 is then set to 10 minutes. As the bead expands, it eventually fills approximately 90% of the volume of the expansion chamber, increasing the resistance to rotational movement of arm 38 and blade 40. Therefore, the current flowing through the motor 34 increases.

Relay 70 is set to operate when the motor lid rises above a predetermined level. As soon as relay 70 is actuated, a timing cycle begins, which is timed till tll by timer 66. The operation of timer 64 is stopped. The valve 48 is opened and the inside of the expansion chamber 26 is communicated with the hopper 44, and the vent valve 26.1 is opened and closed (not shown in FIGS. 1 and 2, but shown as ■2 in FIG. 4). )
Another valve supplies pressurized purging air to the expansion chamber 26, which traps the pre-expanded beads into the hopper 44.
carry it to

Timer 66 maintains this condition for 25 seconds, for example, sufficient to convey all pre-expanded beads to hopper 44. At the end of this time, the supply of bead-entrained air to the expansion chamber 26 ceases as valve 2 opens, valve 48 opens and vent valve 26.1 reopens.

At the same time, timer 62 is activated to begin a new bead charge cycle if it does not overlap with the signal from sensor 46 indicating that hopper 44 is full.

If the level sensor 46 indicates that there are enough fully pre-expanded beads in the hopper 44, the timer 62 will be deactivated, i.e. the valve 16 will not open and the expansion chamber 26 will be filled with unexpanded beads. This means that it has not been entered. However, timers 64 and 66 continue their normal cycles.

However, since no bead is inserted into the expansion chamber, it is clear that contact 72 will not close because the current flowing through the motor will not increase. As a result, the timer 64 will run for the set amount of time, which will then cause the valve 48 to open and the source of purging air through the expansion chamber 26 to also be emptied.

Assuming that the previously described sequence of operations then continues and the level of pre-expanded beads in hopper 44 has been sufficiently reduced,
The cycle is automatically repeated, but this time the expansion chamber is loaded with beads.

Adjustment of the bead density is accomplished by increasing or decreasing the charge of polymer beads fed into the expansion chamber. The lower the charge a, the more the bead needs to expand before the agitator motor 34 is overloaded. Thus, the final density will be lower. If you put a human bead into the expansion chamber,
Expansion of the bead should be modest until the bead occupies approximately 90% of the volume of the expansion chamber and causes a detectable overload condition on the motor 34.

The upper portion of the hopper 44 can include a wire mesh and agitation device to sieve and then break up beads that adhere to each other during pre-leak expansion.

When a shot of beads is first charged into the expansion chamber 26, it causes a temporary but significant periodic increase in the current flowing through the motor 34. This is due to the fact that the blade 40 periodically advances into the unexpanded "heavy" bead at the bottom of the expansion chamber 26, and the movement of the blade is resisted.

This causes a peak in the current flowing through the motor. Once the bead expands to some extent, the motor current will drop to a stable level. Monitoring of the current may begin only after a suitable delay to prevent the current increase due to actuation of relay 70 and energization of contact 72. For example, if the pre-inflation time is approximately 4 minutes, the current monitor may be 217
It can be started after 2 minutes.

As the beads are agitated, a small amount of water can be injected into the expansion chamber 26 to prevent static charge from building up. This "water vapor" atmosphere prevents static charge build-up. A water injection device is shown schematically at 74 in FIG.
A water supply hose is shown at 76 which carries the injector.

Valve 24 is replaced by a gated chute in an alternative construction. It is this gate that is backed off by timer 62 and begins the bead charging cycle. Air is blown into the chute as desired to facilitate the flow of pellets from the holding chamber 18 down the chute and into the expansion chamber 26. It is also possible to blow air down this chute into the expansion chamber 26 during bead evacuation. Such air acts to blow the pre-expanded pellets, which may be present in the inlet defined by the chute, towards the outlet of the expansion chamber 26.

In another modification, funnel 56, pipe 58 and venturi 60 are omitted and screw 54 delivers lubricant directly to holding chamber 18. Screw 54 and holding chamber 1
There is a valve in the passage between 8 and 8. When the second valve 16 opens,
The beads forcefully enter the holding chamber 18. Although the holding chamber 18 is not airtight, it is sufficiently sealed to allow the incoming beads to increase the pressure within the holding chamber 18. Only after a sufficient time has elapsed for this overpressure to dissipate, the valve between the screw 54 and the holding chamber 18 is open and the screw 54 is driven. After the time set in timer T has elapsed, the valve is restarted and the screw 54 is stopped.

It is possible to omit the level sensor in the hopper 10 and replace it with a level sensor in the holding chamber 18. In that case,
A sensor detects that the desired shot of unexpanded beads is within the holding chamber.

The sensor moves vertically with the tube 14. Another sensor can be provided between the holding chamber 18 and the valve 24. This sensor is located in the path along which the unexpanded pods flow from the holding chamber 18 to the pre-expansion chamber 26 . The other sensor detects that no unexpanded beads are present in the passageway after the shot is loaded into the pre-expansion chamber 26. If a bead is present in the passage at this point, it will indicate that the pre-expansion chamber 26 has been partially filled with peed.

[Brief explanation of drawings]

FIG. 1 is a schematic front view of the interior of the pre-expansion chamber for preparing expandable polymer for molding; FIG. 2 is a side view of the interior of the pre-expansion chamber shown in FIG. 1; FIG. Schematic diagram of part of the pre-inflation chamber shown in figure and:
and FIG. 4 is a layout diagram of the control device. In the figure,

Claims (11)

[Claims] (1) In a pre-expansion device for pre-expandable beads,
A pre-expansion device comprising a pre-expansion chamber for receiving unexpanded beads, means for heating the pre-expansion chamber, a stirring device in the pre-expansion chamber, and an electric motor for driving the stirring device, the pre-expansion device comprising: a pre-expansion chamber for receiving unexpanded beads; expands, and the stirring device (32, 38
, 40) as the resistance to the movement of the motor (34) increases.
means (70) for detecting an increase in the power requirements of the pre-expanded beads; and means (48) for ejecting the pre-expanded beads from said pre-expanded chamber.
and wherein said detection means (70), upon detecting an increase in power requirements of a predetermined magnitude, actuates said ejection means such that the pre-expanded beads are ejected from the pre-expansion chamber (26). A pre-expansion device characterized by: (2) A pre-inflation device according to claim 1, characterized in that said detection means (70) monitors the current flowing through said motor. (3) In the apparatus according to claim 1 or 2, the pre-expansion chamber includes a cylindrical body arranged with its axis in a horizontal direction, and the stirring device is coaxial with the cylindrical body. A reserve characterized in that it comprises an associated shaft (32) and a radial arm (38) extending outwardly from said shaft, the outer end of said arm being provided with a scraper element (40). Expansion device. (4) The apparatus according to any one of claims 1, 2, or 3, including a holding chamber (18) for holding a predetermined amount of unexpanded beads, and a lubricating chamber for the holding chamber. Pre-expansion characterized in that it comprises means (52, 54, 56, 58, 60) for delivering a lubricant and bead mixture from said holding chamber to said pre-expansion chamber. Device. (5) The device according to claim 4, wherein the means for feeding lubricant into the holding chamber (18) is driven by a lubricant container (50) and an electric motor (52). A pre-inflation device characterized in that it includes a worm (54). (6) The apparatus according to claim 4 or 5, further comprising: a first sensor that detects the presence of unexpanded beads in the holding chamber; and a first sensor that detects the presence of unexpanded beads in the holding chamber; a second sensor for detecting the presence of unexpanded beads in the passageway along which they flow. (7) The apparatus according to any one of claims 1 to 6, including a hopper (44) for receiving pre-expanded beads from the pre-expansion chamber (26), wherein the hopper , comprising means (46) for detecting when a bead therein exceeds a predetermined level. (8) An apparatus according to claim 7, with means (16) for charging unexpanded beads into the pre-expansion device.
), said level sensor (46) is connected to said charging means so that upon detecting that the level of pre-expanded beads in said hopper exceeds a predetermined level, said level sensor (46) A pre-expansion device, characterized in that the operation of the charging means is cut off until the level falls below the predetermined level. (9) A pre-expansion device according to any one of claims 1 to 8, characterized in that the device includes means for injecting water into the pre-expansion chamber. (10) In the device according to any one of claims 1 to 9, after charging the unexpanded beads into the pre-expansion chamber, the power detection means (70) is timed. 1. A pre-inflation device, characterized in that it includes timing means for inactivating the pre-inflation device for a certain amount of time. (11) Charge the beads into the pre-expansion chamber, heat the pre-expansion chamber, stir the beads in the pre-expansion chamber, and monitor the power requirements of the agitator until the beads are pre-expanded to the desired degree. A method of pre-expanding a polymer bead comprising detecting when.