JPH0455096B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a blow molding method for obtaining hollow bodies such as blow bottles for foods, medical products, etc. or tanks for various liquids.
The present invention relates to a blow molding method for obtaining a hollow body free of undissolved matter, burnt material, carbonization, stains, etc.

[Conventional technology]

Conventionally, in the hollow molding method to obtain a hollow body free of the above-mentioned foreign objects, the above-mentioned foreign objects are detected with the naked eye after the hollow body is formed, but such work can cause eye strain for the operator if it continues for a long time. This method has the disadvantage of increasing the number of detection errors, and there is also a limit to the throughput of visual detection by humans, so high-speed inspection cannot be expected. In view of the labor and inaccuracy of visual inspection, it has been proposed to use a television camera instead of the human eye.

In addition, the technology for detecting foreign objects using a television camera is disclosed in Japanese Patent Application Laid-Open No. 55-50144, and Japanese Patent Application Laid-Open No. 59-59.
This is shown in Publication No. 31437.

[Problem that the invention seeks to solve]

By the way, when analyzing images with a TV camera,
It is necessary to keep the subject stationary while the shutter of the television camera is open. Generally, a television camera takes 16.7 milliseconds to form one screen, so if the subject is not stopped for at least this time, the imaging data obtained during this time will be inaccurate. Therefore, in the former technique mentioned above, when the hollow object that is the subject passes in front of the TV camera, the movement of the hollow object itself is stopped mechanically, or the image of the hollow object is stopped optically using a strobe. However, when stopping the transport of a hollow body mechanically, the transport method is extremely complicated and intermittent transport at high speed is virtually impossible.Also, when stopping optically using a strobe, the light of the strobe This has the disadvantage of causing malfunctions and lowering accuracy.

Furthermore, the latter technique has a drawback in that there is a limit to the size of foreign matter or undissolved matter that can be detected by a television camera, and that foreign matter of a size actually required for molding cannot be detected. The parison, which is a preform before blow molding, turns into a very large foreign object when it is molded and appears on the surface of the hollow body, so even if it is a small foreign object or is not melted, it becomes a very large object when it is formed and appears on the surface of the hollow body. Therefore, it is necessary to detect more precise objects than detecting the hollow body. However, television cameras have the disadvantage that they cannot be detected.

[Means and actions for solving problems]

The present invention was made in view of the above, and involves placing a preformed body of thermoplastic synthetic resin between molds, then tightening the mold and injecting pressurized fluid into the preformed body to form an intermediate molded body. In the method of blow molding a hollow body, in which a hollow body is obtained by cutting off the excess portion of the hollow body, a preform or an intermediate body is irradiated with a laser while repeatedly changing the incident angle, and the transmitted laser beam is transmitted through the preform or intermediate body. The gist of this method is a hollow forming method that detects and ejects foreign matter from a hollow body through changes in the energy of the body, thereby obtaining a hollow body free of foreign matter. , undissolved matter, burnt, carbonized, dirt, etc. can be detected accurately over a wide range, and since the laser is applied directly to preforms or intermediate molds that are continuously placed under constant conditions, these can be detected accurately. Preformed bodies or intermediate formed bodies can be easily and continuously detected without any positional restriction.

〔Example〕

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

In the figure, 1 is a rotary blow molding machine which is an example of a continuous blow molding machine for molding the intermediate molded product a, and 2 is a surplus portion of the intermediate molded product a, which is disposed adjacent to the rotary blow molding machine 1. A burr removing machine 3 is a conveying machine that conveys the hollow body a from which the burrs b have been removed.

The rotary blow molding machine 1 is a known device, and a large number of sets of split molds 10 each consisting of a main body 10a and a lid 10b that can be opened and closed are mounted on the outer periphery of a rotating disk 11 that rotates around a rotating shaft 12. It is attached facing the rotation direction, and as the rotary disk 11 rotates, the lid body 10b opens and closes using the side of the rotation direction of the rotary disk 11 as a pivot point, and is supplied into the split mold 10 at the end of the opening section. The formed tubular preform 15 is sandwiched between closed lids, hollow-molded in the closed lid section, and the intermediate molded body a is taken out at the starting end of the open lid section. At this time, the intermediate molded bodies a are connected by burrs b and are taken out in a continuous state.

Tubular preform 1 fed into split mold 10
5 is obtained by extruding a thermoplastic synthetic resin kneaded and melted in an extruder (not shown) into a tubular shape through an extrusion head 14. At an upper position parallel to the extrusion head 14, there is a laser projector 16 that projects a laser beam generated by He-Ne gas. into the tubular preform 15, and the tubular preform 15
After passing through the interior, the light beam is disposed so as to proceed to a light receiver 18 fixed above the main body 10a by appropriate means. This vibrating mirror 17 changes its direction by a minute angle while maintaining the incident angle of the laser, so that the laser penetrating into the tubular preform 15 is oriented relative to the longitudinal direction of the tubular preform 15. The laser returns to its original state by scanning in a transverse manner and shaking the vibrating mirror 17, and this is repeated by vibrating the vibrating mirror 17. The vibrating mirror 17 can be vibrated at high speed by a known method such as using magnetic force.

The burr removal machine 2 is the rotary blow molding machine 1 described above.
It is arranged adjacent to the intermediate molded body take-out part, and transmits the rotational power of the drive part 23 to the rotating disk through the rotating shaft 22, and a hollow body is placed on the outer peripheral surface of the rotating disk.
Separation mold 20 for separating and removing a′ and burr b
is attached at the same pitch as the attachment pitch of the split mold 10 of the rotary blow molding machine 1.

The conveying machine 3 is arranged adjacent to the discharge part of the hollow body a' of the deburring machine 2, and includes a conveyor 30 that receives and conveys the hollow body a', and a conveyor 30 located on the side of this conveyor 30. It has an ejector 31 having means for ejecting the upper hollow body a' from above the conveyor 30, and a phototube 32 that is located near the upstream side of the conveyor 30 of the ejector 31 and detects the hollow body a' passing over the conveyor 30. (See Figures 1 and 2).

The molding method of this example will be explained one by one.

A transparent or natural-colored tubular preform 15 mainly made of polyethylene is extruded from the extrusion head 14.
A laser beam generated by He-Ne gas is emitted from a laser projector 16 located parallel to the extrusion head 14 in a direction parallel to the extrusion direction of the tubular preform 15.
This laser beam is reflected at right angles by a vibrating mirror 17 and transmitted through the tubular preform 15 at right angles.

The laser beam diameter at this time was φ1 mm,
It traverses the inside of the tubular body with a diameter of 10 mm by vibrating the vibrating mirror 17. The width of the beam beam of this laser is preferably about 12 mm for the tubular preform 15 having a diameter of 10 mm. A laser beam with a beam diameter of 1 mm passes through the oscillating mirror 17 between this 12 mm beam width.
It reciprocates in response to the vibrations of the The surface of the tubular preform 15 is covered by a laser that is transmitted transversely to the tubular preform 15 that is successively extruded.

The electrical flow at this time is as shown in FIGS. 2 and 3. The laser that has passed through the tubular preform 15 is detected by the light receiver 18, amplified by the light receiving amplifier, and then set by the level setting and comparator. It detects the energy of the sensed laser and outputs this energy as a voltage. At this time, if foreign matter is included in the tubular preform 15, part of the laser is cut off, the output voltage to be sensed decreases, and whether or not it is acceptable is determined by level setting and a comparator.

The tubular preform 15 through which the laser has passed is placed on a split mold on the outer peripheral surface of the rotating disk 11 which is rotated at a constant rotational speed by the drive unit 13,
The tubular preformed body 15 is sequentially clamped, and as the rotation progresses, blowing, cooling, and discharge of the blown fluid are performed in sequence, and finally the mold is opened to obtain an intermediate molded body a connected by burrs b. and deburr them with deburring machine 2.
Connect to. With the burr removal machine 2, the intermediate molded body a
The burr b is separated and removed to obtain a hollow body a', which is conveyed to a predetermined position by a conveyor 3. If the tubular preform 15 contains foreign matter, the transmitted laser will be blocked, and the voltage detected by the receiver 18 will drop, and if it falls below a preset level, the rotary blow molding machine 1 and burr removal will be removed. The hollow body passes in front of the ejector 31 due to the rotational speed from the drive parts 13 and 23 of the machine 2 and the photocell 32.
Based on the information of the number a', a counter resolves the time lag, and the ejector 31 ejects the hollow body a' containing foreign matter. In this way, a hollow body free of foreign matter is obtained.

Defects such as foreign matter, undissolved matter, burnt matter, carbide, dirt, etc. are removed from the tubular preform 15 in an extremely small state.
However, since the laser beam diameter is extremely small as in this example, even if the foreign matter contained in the tubular preform is small and difficult to detect visually. Through accurate detection, hollow bodies containing foreign matter can be properly excluded, and only hollow bodies containing no foreign matter can be obtained.

Furthermore, even when the tubular preform is extruded into an endless length at high speed as in the rotary blow molding machine of this embodiment, the vibration of the vibrating mirror 17 can be made extremely fast by using magnetism or the like. The entire preform can be effectively penetrated and judged.

FIG. 4 shows another embodiment.

In the figure, reference numeral 4 denotes a corrugated type blow molding machine for molding the intermediate molded body c, and numeral 5 denotes a burr installed adjacent to this corrugated type blow molding machine to remove the burr d, which is the surplus portion of the intermediate molded body c. The remover 6 is a laser detector which is a feature of the present invention.

This laser detector 6 uses a plurality of lasers, and in this embodiment, two laser projectors 61, 61, vibrating mirrors 62, 62,
It is composed of light receivers 63, 63, and the laser projectors 61, 61 are provided at an angle of 90° with respect to the intermediate molded body c.

The flow of this embodiment will be explained in order.

The corrugated blow molding machine 4 has divided molds 42a and 42b that move like a caterpillar and repeat separation.
A tubular preformed body 41 of thermoplastic synthetic resin is placed between them and the molds are successively clamped. The clamped tubular preform 41 is molded into the shape of a hollow molded body to be formed inside using split molds 42a and 42b by jetting pressure fluid into the inside thereof. After cooling and releasing the pressure fluid inside the intermediate molded body c, the split molds 42a and 42b are opened to obtain an intermediate molded body c connected at the surplus portion of the burr d. When this intermediate molded body c passes in front of the laser detector 6, the laser repeatedly crosses the surface of the intermediate molded body c in the direction perpendicular to the moving direction due to the action of the vibrating mirror, as in the previous embodiment. Together with the movement of the molded body c, the entire intermediate molded body c is traversed. As shown in FIGS. 4 and 5, two laser projectors 61, 61, vibrating mirrors 62, 62 and light receivers 63, 63
The laser beam irradiates the intermediate molded body c from directions orthogonal to each other to detect foreign matter.

After passing through a laser detector 6 to detect the presence or absence of foreign matter, the burr d on both ends of the intermediate formed body c is cut and removed by a burr removal machine 5, and the intermediate formed body c is separated one by one. Obtain a hollow body c′. When the laser detector 6 detects foreign matter in the intermediate molded body c, the ejector 7 located downstream of the burr remover 5 in the moving direction discharges the hollow body c' containing the foreign matter and makes it hollow. Finish molding.

In this embodiment, since the intermediate molded body c can pass through the laser detector 6 while connected to the burr d, its position can be regulated in a fixed direction without rotating, and even the smallest foreign matter can be detected. By detecting and eliminating foreign matter, it is possible to easily obtain a hollow body that does not contain any foreign matter, even if it is minute. Furthermore, since the intermediate molded bodies c are connected to each other by the burrs d, the position of the hollow body c' can be stably held and removed from the blow molding machine without using a holding jig to hold the hollow body c'. After being taken out, it has the characteristic that it can be maintained in that state without blocking the transmission of the laser in any way.

By the way, as shown in Fig. 5, P ₁ Q ₁ , P ₂ Q ₂ ,
The laser that passes through the edges of the intermediate molded body c shown by P ₃ Q ₃ and P ₄ Q ₄ has a longer transmission distance than other parts, so the energy of the laser that disappears is also large, causing the generation of foreign matter. The laser energy will be lost to the area where there is no.

The laser detector 6 determines the presence or absence of foreign matter based on the degree of energy dissipation when passing through the intermediate compact c, and the degree of dissipation is defined by the level setting shown in the block diagram of FIG. , according to the conditions such as the material and wall thickness of the intermediate molded body c,
This set level is compared with the energy level of the laser that reaches the receiver to detect the presence of foreign objects. Therefore, the above P ₁ Q ₁ , P ₂ Q ₂ ,
The transmission laser between P ₃ Q ₃ and P ₄ Q ₄ needs to have a low setting level for its disappearance, and in order to accurately detect this part, it is necessary to lower the overall setting level, which is extremely Only clear foreign objects etc. can be detected. Therefore, the laser is transmitted through the width shown by Q ₁ Q ₂ and Q ₃ Q ₄ in Fig. 5, and the above-mentioned P ₁ Q ₁ and P ₂
If you remove Q ₂ , P ₃ Q ₃ , P ₄ Q ₄ , the above drawback will disappear and the setting level can be increased, so
Even the smallest foreign matter can be detected. the above
The transmitted portions of the lasers denoted P ₁ Q ₁ , P ₂ Q ₂ , P ₃ Q ₃ , and P ₄ Q ₄ are each complemented by mutual laser beams that are at an angle of 90° to each other.

In the above embodiment, two lasers were used because the intermediate molded body was a simple cylinder, but it is preferable to decide the number of lasers to be used depending on the shape of the intermediate molded body or the preformed body.

FIG. 6 shows the third embodiment, 81,8
1 is a split mold and has a blowing means (not shown) in the mold. Above the split molds 81, 81, heating means 84, 84 are provided.
A sheet-like preformed body 83 is supplied in between.

At the lower end of this heating means 84, a laser detector consisting of a laser projector 85 and a light receiver 86 is arranged. This laser projector 85 has a mechanism that swings its direction in the horizontal direction, and traverses the sheet-like preform 83 and transmits light across its entire width.

To explain the flow of this embodiment step by step, by rotating a drum 82, a sheet preform 83 wound up into a roll is heated to a heating means 83.
It is placed between 4 and 84. Sheet-like preformed body 8
3 is heated by the heating means 84, 84 to a moldable temperature, the drum 82 is rotated between the divided molds 81, 81 and fed at a constant speed. At this time, a laser detector provided at the lower end of the heating means 84, 84 detects the presence or absence of foreign matter. The sheet-like preform 83 in which foreign matter has been detected is cut off by a cutting means (not shown), and only the sheet-like preform without thermal deterioration is subjected to molding.
1 and 81 are closed and pressurized fluid is blown between the sheet-like preforms to form a hollow body.

According to this embodiment, the sheet-like preform 83,
Since a light receiver 86 is inserted between 83 and the laser beam transmitted through only one sheet-like preform is detected, foreign matter and deterioration of the sheet-like preform can be detected extremely accurately. At this time, if the laser detector and the drum are electrically connected, and when the cutting means is used, the drum is rotated to replenish the preform in an amount to compensate for the cut part, which is stable and economical. A preformed body is obtained which is heated to . In addition, since a laser is used, even if the sheet-like preform is placed rapidly, it can be sufficiently transmitted.
There is no need to reduce the speed of placement of the preform for detection, and as a result, the sheet-like preform does not cool and solidify.

〔Effect of the invention〕

According to the present invention, a laser is applied to the preformed body or the intermediate formed body while repeatedly changing the incident angle, and foreign matter in the hollow body is detected by the change in the energy of the transmitted laser.
Continuously without stopping the preform or intermediate mold, it is possible to accurately detect foreign objects over a wide range of the preform or intermediate mold, such as foreign objects, undissolved matter, burnt material, carbonization, dirt, etc. It is possible to easily obtain a hollow body having no .

[Brief explanation of the drawing]

1 to 3 show a first embodiment of the present invention, FIG. 1 is an explanatory diagram showing an apparatus used for implementation, FIG. 2 is a plan view of FIG. 1, and FIG. The block diagram of the laser detector, FIGS. 4 and 5, shows the second embodiment. FIG. 4 is an explanatory diagram showing the apparatus used for the implementation, and FIG. The side view and FIG. 6 are conceptual diagrams for explaining the third embodiment. 15... Tubular preformed body, 16... Laser projector, 18... Light receiver, 31... Ejector.

Claims (1)

[Claims] After placing a preformed body of thermoplastic synthetic resin between two molds, the molds are tightened and pressure fluid is blown into the preformed body to form an intermediate molded body, and the excess portion of the intermediate molded body is cut off to form a hollow body. In the method of blow molding a hollow body to obtain a hollow body, a laser is applied to the preform or intermediate body while repeatedly changing the angle of incidence, and the laser passes through the body, and foreign objects in the hollow body are detected by changes in the energy of the transmitted laser. A hollow molding method that produces a hollow body free of foreign matter.