WO2020119002A1

WO2020119002A1 - Axial bidirectional positioning stretching and hollow blow molding method

Info

Publication number: WO2020119002A1
Application number: PCT/CN2019/083557
Authority: WO
Inventors: 谢国基; 姜晓平; 胡青春; 卢佳; 梁炎均
Original assignee: 广东星联精密机械有限公司
Priority date: 2018-12-13
Filing date: 2019-04-20
Publication date: 2020-06-18
Also published as: CN109454851A; CN109454851B

Abstract

Provided is an axial bidirectional positioning stretching and hollow blow molding method. A bearing device for temporarily bearing the bottom of a bottle preform is provided in a mold cavity. The container blow molding method comprises the following steps: step 1: heating a bottle preform to a stretching temperature, and performing pre-blow molding while stretching same; step 2: when the bottle preform is stretched to the position of the bearing device, the bearing device bearing the center of the bottom of the bottle preform that has been gradually stretched and expanded, wherein the stretching speed is slowed down or the stretching is paused at the position of the born point at the bottom of the bottle preform, and the periphery of the born point is continuously stretched under the action of air pressure and the inertia of its own material; and step 3: after a cone bottom is pre-formed, the bearing device retracting or moving with a stretching rod, the stretching rod continuing to stretch, air pressure being injected, and then performing cooling to form a blow-molded container. By means of the bearing in step 2, the material at the bottom of the bottle preform is fully stretched and more evenly distributed at the bottom of the bottle, so that better cooling and molding can be achieved.

Description

Axial bidirectional positioning and stretching hollow blow molding method

Technical field

The invention relates to the technical field of blow molding container molding, in particular to an axial bidirectional positioning and stretching hollow blow molding method.

Background technique

At present, in the process of blow molding containers, especially in the two-step injection molding blow molding method, the axial stretching of the preform basically touches the inner bottom of the preform through a stretching rod (round steel rod) The preform is stretched to the bottom of the cavity at one time. During the stretching process of the stretching rod, compressed air is injected at the same time, and the preform is inflated by the compressed air, so that it is closely attached to the cavity wall of the mold, and the hollow plastic product is obtained by cooling and shaping. When the preform is stretched into contact with the metal at the bottom of the mold cavity, the bottom of the preform cools relatively quickly, and the material with limited stretching space is difficult to fully stretch. The bottom of the container forms an accumulation, resulting in waste of material and the resulting concentration of stress. The bottom of the container is easy to crack, especially in large-capacity containers (above 5L). In addition, when the vertical stretch size of the preform is large, the stretching rod is prone to unstable speed, insufficient rigidity, and eccentricity at the bottom of the preform, which leads to uneven wall thickness of the blow molded container and affects the overall strength of the container.

Summary of the invention

The invention provides an axial bidirectional positioning and stretching hollow blow molding method for achieving uniform material distribution and reducing the weight of the bottom material.

The technical solutions adopted by the present invention to solve its technical problems are:

An axial bidirectional positioning and stretching hollow blow molding method, characterized in that: a supporting device for temporarily supporting the bottom of the preform is provided in the mold cavity, and the blow molding container molding includes the following steps:

Step 1: Heat the preform to the stretching temperature, and then put it into the blow molding cavity for axial stretching by means of the stretching rod, and at the same time, inject compressed air at the mouth of the preform, and pre-blow molding while stretching;

Step 2: When stretching to the position of the supporting device, the supporting device holds the center of the bottom of the preform that has been gradually stretched and expanded, and the position of the supported point at the bottom of the preform slows down the stretching speed or pauses the stretching , The periphery of the supported point is continuously stretched under the influence of air pressure and its own material inertia, so that the bottom of the preform forms a cone bottom with the supported point high and the periphery low;

Step 3: After the cone bottom is formed in advance, the supporting device retracts or moves with the stretching rod. The stretching rod continues to stretch and inject air pressure to expand the preform and adhere to the inner wall of the mold cavity, and then cool to form a blow molded container.

In the present invention, in step three, for a bottle with a large height-to-diameter ratio, the supporting device performs the retracting movement in several times.

In the present invention, the supporting device includes a supporting rod provided at the bottom of the mold cavity and a driving mechanism I that drives the supporting rod to perform telescopic movement.

In the present invention, the supporting device includes a jack arranged in the middle of the mold cavity and a driving mechanism II for driving the jack to move up and down.

In the present invention, the supporting device includes an arc-shaped hook provided on the side wall of the mold cavity and a driving mechanism III for driving the arc-shaped hook to rotate.

In the present invention, the supporting device includes a negative pressure port provided at the top of the stretching rod and a pneumatic device that communicates with the negative pressure port and generates negative pressure.

The advantage of the present invention is that the material in the bottom of the preform is fully stretched through the support of step two, and is more evenly distributed on the bottom of the bottle, and better cooling and setting can be obtained. Due to sufficient stretching, not only can the internal stress of the bottom of the bottle be reduced and the probability of bursting can be reduced, but also the weight of the bottom material can be reduced to achieve the effect of reducing the weight. The method used in the present invention is not only aimed at carbonated bottles and large-capacity plastic bottles, but also applied to glass bottles.

Further, the bottom of the bottle directly falls to the center of the bottom of the cavity through the guidance of the supporting device. Even if the speed of the stretching rod is unstable and the rigidity of the stretching rod is insufficient, there will be no eccentricity of the bottom of the preform and the radial circumferential material distribution of the preform The uneven phenomenon ensures that the wall thickness of the blow molded container is uniform and enhances the overall strength of the container.

BRIEF DESCRIPTION

The utility model is further described below with reference to the drawings and embodiments:

Figure 1 is a schematic diagram of the first embodiment;

2 is a schematic diagram of the second embodiment;

FIG. 3 is a schematic diagram of Embodiment 3;

4 is a schematic diagram of the fourth embodiment;

5 is a schematic diagram of the fifth embodiment;

6 is a schematic diagram of the sixth embodiment.

detailed description

To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of the embodiments of the present invention, but not all the embodiments.

Example one:

Referring to FIG. 1, this embodiment discloses an axial bidirectional positioning and stretch hollow blow molding method, which is realized by using a supporting device provided with a short supporting preform 2 bottom in the mold cavity 1, The supporting device includes a supporting rod 3 disposed at the center of the bottom of the mold cavity 1 and a driving mechanism I8 for driving the supporting rod 3 to perform a telescopic movement. The top of the supporting rod 3 does not puncture the bottom of the preform 2 In the form of a platform, the driving mechanism I8 is a pneumatic cylinder or a hydraulic cylinder.

The blow molding container molding includes the following steps:

Step 1: Heat the preform 2 to the stretching temperature, and then put it into the blow mold cavity 1 to perform the axial stretching by means of the stretching rod 4; at the same time, inject low air pressure at the mouth of the preform 2 and pre-blow molding while stretching , This step is basically the same as the traditional stretch blow molding method;

Step 2: When stretching to the position of the supporting device, the supporting rod 3 has extended from the bottom of the mold cavity and holds the center of the bottom of the preform that has been gradually stretched and expanded, the stretching rod 4 and the supporting rod 3 Separate at least one layer of container wall thickness to avoid piercing the bottom. The position of the supported point at the bottom of the preform slows down the stretching speed or pauses the stretching. In this embodiment, it is to pause the stretching. The pause time is 0.1 to 0.3 seconds. The periphery of the supported point is under the air pressure and its own material. Continue to stretch under the action of inertia, so that the bottom of the preform has a cone bottom with a high support point and a low periphery;

Step 3: After the cone bottom is formed in advance, the stretching rod 4 and the supporting rod 3 are simultaneously stretched downward and continue to be injected with air pressure. The supporting rod 3 guides the bottom of the preform directly to the center of the bottom of the mold cavity 1, and the preform expands And close to the inner wall of the mold cavity 1, and then cool to form a blow molded container, after completion, the stretching rod 4 exits and returns to the original position.

In step two, the top of the support rod 3 is located at the lower part of the middle of the mold cavity 1. This position should not be too high. The excessive position may cause deformation during the process of lowering the cone bottom, but the position should not be too low. Too low a position makes the periphery of the supported point not stretched enough to achieve the desired effect.

Example 2:

Referring to FIG. 2, the method adopted in this embodiment is basically the same as that in Embodiment 1, and the only difference is that the supporting device is different. The supporting device includes a jack 5 provided in the middle of the mold cavity 1 and a driving mechanism II 6 for driving the jack 5 to move up and down. Both sides of the jack 5 are mounted on the inner side wall of the mold cavity 1, the drive mechanism Ⅱ6 is a pneumatic cylinder, a hydraulic cylinder or a motor and drives the jack 5 to move up and down. The forming steps of the blow molded container of this embodiment are basically the same as those of the first embodiment.

Example three:

Referring to FIG. 3, the method used in this embodiment is the same as the principle of Embodiment 2, except that the driving mechanism II6 is different. In this embodiment, the driving mechanism II6 is an electromagnet with a variable magnetic pole. The upper end is a magnetic substance with an N pole and the lower end is an S pole. The magnetic substance is light and heavy to avoid turning over when ascending. By changing the magnetic pole of the electromagnet, the purpose of controlling the up and down movement of the jack 5 can be achieved.

In the second step of forming the blow molded container, when it is stretched to the position of the supporting device, the top rod 5 has been suspended in the middle under the action of the electromagnet, and holds the center of the bottom of the preform that has been gradually stretched and expanded. At this time, the stretching rod 4 slows the stretching speed or pauses the stretching, and the periphery of the supported point continues to stretch under the action of air pressure and its own material inertia, so that the bottom of the preform is pre-formed with a high supported point and a low peripheral Cone bottom; step three, after the cone bottom is formed in advance, the stretch rod 4 continues to stretch down and inject air pressure, at this time, the change of the magnetic pole of the electromagnet drives the top rod 5 to fall back.

Here, it is not limited to the combination of the electromagnet and the magnetic substance, and any other method of matching by field force is within the protection scope of the present invention.

Example 4:

Referring to FIG. 4, the method used in this embodiment is basically the same as that in

Embodiments

1 and 2, and the difference is that the supporting device is different. The supporting device includes an arc-shaped hook 7 provided on the side wall of the mold cavity 1 and a driving mechanism III for driving the arc-shaped hook 7 to rotate. The top of the arc-shaped hook 7 is not to puncture the bottom of the preform 2 Platform-shaped, here, the arc-shaped hook 7 can also be a "∟" hook, which has the same technical effect. The blow molding container forming step of this embodiment is different from the

steps

2 and 3 in the first embodiment.

In step two of this embodiment, when drawing to the position of the supporting device, the curved hook 7 has protruded from the side wall of the mold cavity and holds the center of the bottom of the preform that has been gradually stretched and expanded. The position of the supported point is temporarily suspended, and the periphery of the supported point is continuously stretched under the action of air pressure and its own material inertia, so that the bottom of the preform has a cone bottom with a high supported point and a low periphery;

In step three of this embodiment, after the cone bottom is formed in advance, the arc-shaped hook 7 is retracted from the side, the stretching rod 4 is stretched downward and the air pressure is continuously injected, the preform expands and clings to the inner wall of the mold cavity 1, and then cools to form a blow Plastic container.

Example 5:

Referring to FIG. 5, the supporting device and the blow molding container forming steps used in this embodiment are different from the first embodiment. The supporting device includes a negative pressure port 9 provided at the top of the stretching rod 4 and a communicating negative pressure port 9. An air pressure device 10 that generates negative pressure. The air pressure device may be a vacuum pump or the like.

The blow molding container molding includes the following steps:

Step 1: Heat the preform 2 to the stretching temperature, and then put it into the blow mold cavity 1 to perform axial stretching by means of the stretch rod 4; at the same time, inject compressed air at the mouth of the preform 2 to pre-blow while stretching , This step is basically the same as the traditional stretch blow molding method;

Step 2: At the stretching setting position, the negative pressure port 9 of the stretching rod 4 generates negative pressure and sucks the center of the bottom of the preform. At this time, the stretching rod 4 slows down the stretching speed or pauses the stretching. At the same time, the preform At the same time, the sucked point on the bottom also slows down or pauses the stretching. The periphery of the sucked point continues to stretch under the action of air pressure and its own material inertia, so that the bottom of the preform is preformed with a high supporting point and a low peripheral edge. Cone bottom

Step 3: After the cone bottom is formed in advance, the negative pressure of the negative pressure port 9 can be closed. The stretching rod 4 continues to stretch downward and inject air pressure. During the downward stretching process, the preform expands and clings to the mold cavity 1 The inner wall is then cooled to form a blow molded container.

Example 6:

Referring to FIG. 6, the structure of this embodiment is the same as that of Embodiment 1, and the forming steps are different, mainly for bottles with a large height-to-diameter ratio, especially for the depth of the bottom of the bottle that is too deep, that is, the aspect ratio (H/W >0.4) Large bottle. In step three, after the cone bottom is formed in advance, the stretching rod 4 and the supporting rod 3 are simultaneously drawn down and continue to inject air pressure, and the supporting rod 3 guides the bottom of the preform directly to the center of the bottom of the mold cavity 1, at When the stretching rod 4 and the supporting rod 3 move to the highest point of the bottom of the inner wall of the mold cavity 1 and the bottom of the preform contacts the lowest end of the bottom of the inner wall of the mold cavity, the supporting rod 3 moves upward again so that the supporting point is higher than the cavity 1 At the highest point of the bottom, the support rod 3 is then reset and retracted, and then cooled to form a blow molded container. The number of times of reciprocating retraction of the support rod 3 may be multiple times, the higher the height, the more the number of reciprocating times, and the amplitude of its reciprocating gradually decreases with the number of times. Through this reciprocating retraction movement, the bottom material can be prevented from fitting into the mold cavity, resulting in poor plastic deformation of the material after cooling and poor bottom molding, such as blushing.

The above is only the preferred embodiment of the present invention, as long as the technical solutions for achieving the object of the present invention by basically the same means fall within the protection scope of the present invention.

Claims

An axial bidirectional positioning and stretching hollow blow molding method, characterized in that: a supporting device for temporarily supporting the bottom of the preform is provided in the mold cavity, and the blow molding container molding includes the following steps:

Step one: Heat the preform to the stretching temperature, and then put it into the blow molding cavity for axial stretching by means of the stretch rod, and at the same time inject low air pressure at the mouth of the preform, pre-blow molding while stretching;

Step 2: When stretching to the position of the supporting device, the supporting device holds the center of the bottom of the preform that has been gradually stretched and expanded, and the position of the supported point at the bottom of the preform slows down the stretching speed or pauses the stretching , The periphery of the supported point is continuously stretched under the influence of air pressure and its own material inertia, so that the bottom of the preform forms a cone bottom with the supported point high and the periphery low;

Step 3: After the cone bottom is formed in advance, the supporting device retracts or moves with the stretching rod. The stretching rod continues to stretch and inject air pressure to expand the preform and adhere to the inner wall of the mold cavity, and then cool to form a blow molded container.
The method of axial bidirectional positioning and stretching hollow blow molding according to claim 1, characterized in that: in step three, for a bottle with a large height-to-diameter ratio, the supporting device performs the retracting movement in several times.
The axial bidirectional positioning and stretching hollow blow molding method according to claim 1, characterized in that: the supporting device includes a supporting rod provided at the bottom of the mold cavity and a driving supporting rod for telescopic movement Drive mechanism Ⅰ.
The axial bidirectional positioning and stretching hollow blow molding method according to claim 1, characterized in that the supporting device comprises a jack arranged in the middle of the mold cavity and a driving mechanism for driving the jack to move up and down Ⅱ.
The axial bidirectional positioning and stretching hollow blow molding method according to claim 1, characterized in that the supporting device comprises an arc-shaped hook provided on the side wall of the mold cavity and drives the arc-shaped hook to rotate Driving mechanism Ⅲ.
The axial bidirectional positioning stretch hollow blow molding method according to claim 1, wherein the supporting device includes a negative pressure port provided at the top of the stretching rod and a negative pressure port communicating with the negative pressure port and generating a negative pressure Air pressure device.