JPH0479294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a parison wall thickness control device in a blow molding device.

[Conventional technology]

In recent years, many plastic blow-molded products having flat shapes, such as heat collecting plates and pallets for solar water heaters, have been seen. An example of a conventional blow molding apparatus for molding this type of molded product is shown in FIGS. 6 and 7.

That is, a nozzle 2 having an opening similar to the hollow part of the head body 1 is attached to the lower end of the parison head body 1 formed into a hollow flat shape, and is connected to a parison control cylinder 3 installed above the head body 1. At the lower end of the mandrel shaft 4, a sheet-like passage 5a is arranged between the nozzle 2 and the lower part of the head body 1, and a merging passage 5b is formed between the nozzle 2 and the lower part of the head body 1.
and the nozzle 2 to form a flat annular passage 5c.
A mandrel 6 extending in the width direction (horizontal direction in FIG. 7) of the opening is attached, and by operating the parison control cylinder 3, the mandrel 6 is raised and lowered via the mandrel shaft 4 to adjust the width of the outlet slit 7 at the lower end of the passage 5c. It is designed to be adjustable.

Further, inside the head body 1, the head body 1
A flat partition wall 8 extending in the width direction of the inner hollow part,
8 are erected on the mandrel 6 so as to sandwich the mandrel shaft 4, and resin accumulation chambers 15, 15 are formed between the respective partition walls 8 and the inner wall of the head main body 1. , flat plate plungers 10, 10 are inserted vertically slidably to be connected to injection cylinders 9, 9 installed above the head main body 1.
16 is a guide key when the plunger 10 slides.

The plunger 10 has, on its outer surface, a vertical groove 12 of a required length extending in the vertical direction so as to communicate with the resin inlet 11 provided on the upper side of the head main body 1, and a width direction ( A distribution groove 13 (in the lateral direction) is carved therein, and the outer surface located below the distribution groove 13 is carved in the upper part of the distribution groove 13 so as to form a throttle passage 14 between the head body 1 and the inner wall of the head body 1. A step is formed to make the wall thinner than the outer surface where it is located.

Further, in the opening surface of the nozzle 2, two yoke bars 18, 18 are buried facing each other along the width direction, and each yoke bar 18 is connected to an adjustment bolt 19 screwed onto the nozzle 2, so that each yoke bar 18 has a flat annular shape. It is configured so that it can go in and out of the passage 5c.

Now, in a state in which each plunger 10 is raised by the required amount by operating the injection cylinder 9 and a predetermined accumulation chamber 15, 15 is formed at the bottom of each plunger 10, the molten resin is extruded from an extruder (not shown). , the resin enters the head body 1, passes through the longitudinal grooves 12 of each plunger 10, and further passes through the distribution grooves 1 in the width direction.
Flows within 3. The resin that has flowed into the distribution groove 13 of each plunger 10 is further pushed and flows into the storage chamber 15, but at this time, the flow rate is adjusted when passing through the throttle passage 14, and the flow rate is uniform in the width direction within each storage chamber 15. stored in When the resin in each storage chamber 15 reaches the required amount, each injection cylinder 9 is operated to lower each plunger 10. Then, due to the pressure, the resin in each accumulation chamber 15 passes through the sheet-like passage 5a, the merging passage 5b, and the flat annular passage 5c, and becomes an integrated flat annular parison 20 before being extruded from the outlet slit 7. forced out. The extruded parison 20 is then sandwiched between molds and blow molded.

[Problem that the invention seeks to solve]

However, in the conventional blow molding apparatus described above, the flow rate of the resin is adjusted by operating the adjustment bolts 19 to move each cheese bar 18 in and out of the flat annular passage 5c. Although it is possible to obtain a flat-shaped product, there has been no means for accurately controlling the thickness of the parison 20 in the longitudinal direction (longitudinal cross-sectional direction).

The present invention makes it possible to control the thickness of the parison in the longitudinal direction with high precision.

[Means for solving problems]

In the present invention, a hollow flat nozzle is attached to the lower end of a parison head body provided with a flat plate plunger, a mandrel is disposed within the nozzle, and an exit slit is formed between the mandrel and the nozzle, and the A required recess is provided in the inner corner of the lower end of the nozzle, and a flexible plate for adjusting the width of the exit slit is attached to the recess, and the flexible plate is operated by a drive device. In the blow molding apparatus, the blow molding apparatus includes: a thickness gauge for measuring the wall thickness of the parison extruded from the exit slit; a comparator for comparing the signal from the thickness gauge with a set signal; and the comparator. A controller that sends a command to the drive device based on a signal from the drive device.

[Effect]

Therefore, the measured parison thickness is compared with a set value and the width of the exit slit is controlled based on that value.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. 1, 3, and 4 show embodiments of the present invention. In FIG. 1, reference numeral 21 is an ultrasonic thickness gauge for measuring the thickness of the parison 20, which is held by an air cylinder 23 and inserted through the slit 7. The signal from the detection head 22 disposed at the outlet of the sensor is processed and displayed on a digital display 24, for example. 25 is a signal from the thickness gauge 21 and a controller 2;
This is a comparator that compares the setting signal from 6 and sends the signal obtained by comparison to the controller 26. The controller 26 is configured to drive the servo valve 40 based on the signal from the comparator 25 and operate the control cylinder 37.
Moreover, the control cylinder 37 and the injection cylinder 9
are provided with position detectors 29 and 39, respectively, and detection signals are sent to the controller 26.
In FIG. 1, numeral 30 indicates an air unit, and numeral 31 indicates a hydraulic unit.

The thickness gauge measures the time T between the echo S reflected on the surface of the object to be measured (parison 20 in this case) and the echo B ₁ reflected on the back surface of the object, as shown in Figure 2 A and B. , multiplied by 1/2 as the one-way value,
Furthermore, the thickness D is obtained by multiplying by a preset sound velocity value V of the object to be measured as D=T×1/2×V. 17 is a transducer, and 31 is a delay material.

In FIG. 1, the same reference numerals as in FIG. 6 indicate the same parts.

In this configuration, when each plunger 10 is gradually lowered by the operation of the injection cylinder 9, the parison 20 is pushed out from the slit 7 between the mandrel 6 and the flexible plate 36. When the parison 20 is pushed out, the air cylinder 23 is operated to bring the detection head 22 into light contact with the surface of the parison 20, the thickness of the parison 20 is determined by the total thickness 21, and the signal is sent to the comparator 25 as a setting signal. compare. Note that this setting signal corresponds to the positions of the flexible plate 36 and the plunger 10 detected by the detectors 29 and 39. If there is a difference between the signals compared by the comparator 25, the controller 26
A drive signal is sent from the servo valve 27 to the control cylinder 37 and the flexible plate 36 is actuated.
The width of the slit 7 is adjusted by moving in and out.

In the blow molding apparatus shown in the conventional example, when the shape of the molded product has unevenness, the parison control in the vertical direction by raising and lowering the mandrel 6 alone could not correspond to the shape and could not control the parison in the cross section. In the embodiment, the thickness of the parison in the cross-sectional direction can be changed arbitrarily in accordance with the uneven shape of the molded product, and the thickness can also be controlled with high precision.

That is, as shown in FIG. 5, if a part of the molded product 32 has a convex portion 33, the wall thickness of the molded product 32 becomes thinner, so when the mandrel 6 is lowered to compensate for the wall pressure, the opposite side The wall thickness in the same circumferential direction including the part indicated by 33' increases, and on the other hand, the molded product 3
If there is a recess 34 in a part of the molded product 32, the wall thickness of the molded product 32 will increase, so in order to reduce the wall thickness, when the mandrel 6 is raised, the recess 34 on the opposite side
There was a problem that the wall thickness in the same circumferential direction including the portion indicated by 4' became thinner.

According to the present invention, in the blow molding apparatus shown in FIG. A flexible plate 36 for adjusting the slit width is attached, and a hydraulic cylinder 37 is installed on the outside of the nozzle 2, and its rod 38 is passed through the nozzle 2 and connected to the back side of the flexible plate 36. This is what I did.

As shown in detail in FIG. 4, the flexible plate 36 is attached by having a cylindrical shaft portion 36a at the upper end, and attaching the shaft portion 36a to the correspondingly shaped nozzle 2 side from the axial direction. The flexible plate 36 is made to be able to move freely by sliding between the shaft portion 36a and the nozzle 2 side.

In FIGS. 1, 3, and 4, the same reference numerals as in FIG. 6 indicate the same parts. However, the thickness gauges 21 and their detection heads 22 are arranged in parallel corresponding to the number of cylinders 37 shown in FIG.

Now, according to a command from the controller 26, the servo valve 40
is driven, actuating the cylinder 37 to release each rod 3.
When 8 is moved in and out with controlled strokes,
The flexible plate 36 is pushed or pulled to widen or narrow the exit slit 7. This control is
Parison 20 of each part determined by each thickness gauge 21
This can be achieved by moving the flexible plate 36 to a desired position based on the thickness of the flexible plate 36.

Therefore, the flat annular parison 20 becomes thicker as the width of the exit slit 7 becomes wider, and becomes thinner as the width becomes narrower. In particular, the thickness of the flat annular parison 20 in the cross-sectional direction can be freely controlled. Further, at this time, by using the parison control in the vertical direction by vertically moving the mandrel 6, it becomes possible to perform even more detailed control. In addition to the blow molding apparatus described above that molds the flat annular parison 20, the present invention can naturally be applied to a blow molding apparatus that controls the wall thickness of the annular parison in the cross-sectional direction.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be applied not only to single-layer but also to multi-layer blow molding machines such as two-layer, three-layer, etc., and other gist of the present invention. Of course, various changes can be made without departing from the above.

〔Effect of the invention〕

As explained above, according to the wall thickness control device for the blow molding apparatus of the present invention, the slit width is controlled based on the signal from the thickness gauge, so the wall thickness in the longitudinal direction of the parison can be controlled with high precision. It is possible to achieve excellent effects in that it is possible to control the

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the parison wall thickness control device in the blow molding apparatus of the present invention, and Fig. 2 shows the measurement principle of the ultrasonic thickness meter. FIG. 3 is a view taken from the - arrow in FIG. 1, FIG. 4 is a partially enlarged view of FIG. 1, FIG. 5 is an explanatory diagram of a conventional molded product, and FIG. 6 is a conventional blow molding device. Fig. 7 is an explanatory diagram of - of Fig. 6.
It is an arrow view. 1 is the head body, 2 is the nozzle, 3 is the parison control cylinder, 6 is the mandrel, 7 is the exit slit, 21 is the ultrasonic thickness gauge, 25 is the comparator,
26 is a controller, 35 is a recess, 36 is a flexible plate, 37
indicates a cylinder.

Claims (1)

[Claims] 1. A hollow flat nozzle is attached to the lower end of a parison head body having a flat plate plunger, and a mandrel is disposed within the nozzle to form an exit slit between the mandrel and the nozzle, and an outlet slit is formed between the mandrel and the nozzle, and the inside of the lower end of the nozzle is A required recess is provided in the corner portion, a flexible plate for adjusting the width of the exit slit is attached to the recess, and the flexible plate is driven by one or more drive devices. one or more thickness gauges for measuring the wall thickness of the parison extruded from the exit slit in a blow molding apparatus adapted to be operated; and a comparison for comparing signals from the thickness gauges with a set signal. A device for controlling the wall thickness of a parison in a blow molding machine, comprising: a comparator; and a controller that sends a command to the drive device based on a signal from the comparator.