NL193213C - Device for orientation blowing of objects. - Google Patents

Description

1 193213

Device for orientation blowing of objects

The invention relates to a device for manufacturing biaxially oriented hollow objects from preforms which are made of a crystalline thermoplastic plastic and are closed at one end, comprising: a heating chamber provided with heating elements for heating the preforms to a desired temperature lower than its crystalline melting point; transport means for transporting the preforms through the heating chamber; a molding device adapted to axially stretch the heated preform to its final length, and then to radially stretch the preform by means of gas under elevated pressure; and a loading means for transferring the heated preforms from the heating chamber to the former.

In a known method of forming a bottle-shaped plastic container by orientation blowing, a preform with a substantially cylindrical shape, which is closed at one end, is first made. The plastic used can be, for example, polyethylene terephthalate. This preform is heated to a predetermined temperature. Then the heated preforms are first axially stretched to their final length using a push arm, and then they are radially stretched by introducing gas under increased pressure into the now axially stretched preform. An apparatus of the above-mentioned type for carrying out that method is known from United States Patent Specification 4,036,925.

When performing the said process, it is important that the preforms are heated uniformly and uniformly and that the temperature of the preform is kept within certain limits suitable for orientation molding to ensure that the molded containers have good strength properties , have toughness and transparency and are of uniform quality. The object of the invention is to provide means for achieving these objectives.

To this end, the device of the above-mentioned type according to the invention is characterized in that the heating chamber comprises several heating chamber sections, each section being individually controlled to have a specific temperature range; that the transporting means is arranged to transport the preforms through said heating chamber sections while they are rotated about their body axis; that the heating elements of the heating chamber are elongated heating elements, part of which is arranged vertically oriented along one side of the advance path of the preforms, and another part of which is arranged horizontally oriented along the other side of the advance path of the preforms; and that a shield plate is disposed at the exit of the heating chamber, which shield plate has radial fins rotated synchronously with the transfer of the preform from the heating chamber to the loading member.

It is noted that in prior Dutch patent application 7909368 a device is described for manufacturing biaxially oriented hollow objects from preforms which are made of a crystalline thermoplastic plastic and are closed at one end, comprising: a heating element provided with heating elements. heating chamber for heating the preforms to a desired temperature below its crystalline melting point; transport means for transporting the preforms through the heating chamber; a molding device adapted to axially stretch the heated preform to its final length, and then to radially stretch the preform by means of gas under elevated pressure; and a loading means for transferring the heated preforms from the heating chamber to the former; the heating chamber comprising multiple heating chamber sections, each section being individually controlled to have a specific temperature range; the transporting means being arranged to transport the preforms through said 45 heating chamber sections while they are rotated about their body axis; the heating elements of the heating chamber being elongated heating elements, part of which is arranged vertically oriented along one side of the advance path of the preforms, and another part of which is arranged horizontally oriented along the other side of the advance path of the preforms. However, this non-prepublished patent application does not disclose the presence of a radial-fin shield plate disposed at the exit of the heating chamber.

The invention will be further elucidated by description of a preferred embodiment with reference to the drawing, in which: figure 1A is a side view of a preform; Fig. 1B is a perspective view of a container made from the preform; Figure 2 is a partially broken away top view of a blow molding device for forming the container; and Figure 3 is a more detailed longitudinal section of a heating device for use with the blow molding device.

In the orientation blow molding apparatus according to the invention, a preform 10 in the form of a cylinder 5 with a closed end, which preform 10 is prepared by a previous injection molding step, is cooled and placed upside down on a carrier, which is mounted on a conveyor 11. Subsequently, the carrier with the preform 10 is placed by a transfer device 12 on a metal core, which is circulated in a heating chamber 13. In the heating chamber 13, the preform 10 is heated to a temperature lower than the crystalline melting point of polyethylene terephthalate to prevent irregular temperature distribution. At the exit of the heating chamber 13, to prevent the heated preform 10 from being cooled locally, the preform 10 is rotated through the metal core and while it is rotated, placed by a loading device in a blow mold of an orientation blow molding device 15 Immediately after the blow mold is closed, an orienting means (core shaft) is extended axially of the preform for longitudinally orienting the preform, and then compressed air is blown into the preform for radially orienting it laterally. Thereafter, the mold is opened and the carrier, which holds the then biaxially oriented container, is taken out of the mold by a take-out device 16. The carrier and the container are then transferred to the conveyor 11, where the shaped container 20 of the carrier is is unloaded. The carrier thus released is returned to the conveyor 11 and is ready to take on a new preform.

The preform 10 is an intermediate that is cooled to ambient temperature after it has been manufactured in an injection molding machine (not shown). As illustrated in Figure 1A, the preform 10 has a round bottom 17 and an annular protrusion 19 at the top end for later attaching a lid of the container, which protrusion 19 extends near the neck opening 18. Furthermore, the preform 10 has a body portion 21, the diameter of which gradually decreases from the neck opening 18 to the bottom 17.

Apparatus for orientation blow molding.

As can be seen from Figure 2, which shows the whole of the device in top view, the blow-molding device according to the invention is composed of a conveyor 11, a transfer device 12, a heating chamber 13, loading equipment 14, an orientation blow-molding machine 15 and a removal device. 16.

The conveyor 11 is provided with an endless chain 22, equipped with a number of fastening hooks 23 which are equidistant and substantially in the shape of a rectangular U. These fasteners carry a mandrel of a support 25 which will be described later. . The preform 10 mentioned above is placed on a carrier 25 of the conveyor 11. That is, the preform 10 is held in the inverted position so that the neck opening 18 thereof is located at a neck support of the wearer 25.

The carrier 25 on which the preform 10 is placed is fed on the conveyor 11 to the transfer device 12.

40 The transfer device 12 is equipped with an arm 40 which has a hook at the front end for holding the carrier 25 and which is rotated about a pivot 41. Within the path of the angular movement, a curved guide rail 42 is provided with a magnet for giving the carrier 25 a slight rotational movement while it is being moved so that it engages and is held by a metal core 44 in the heating chamber 13.

45 The metal core 44 includes a hollow holder attached to a rotating disk 45, and a hollow shaft held by the holder 46 through a pair of bearings.

At the bottom end! a pinion 54 is provided of said hollow shaft, engaging a gear 53, as shown in figure 3. Thus, when the gear 53 is rotated, the pinion 54 is also rotated, whereby the metal core 44 and hence the carrier 25 with the preform 10 are rotated 50.

Heating chamber

As shown in Figure 2, the heating chamber 13 includes a rotating disk 45, to which a plurality of metal cores 44 are mounted along its peripheral edge with a cover 61 disposed thereover. The heating chamber 13 is divided into a number of heating zones, for example four zones, I, II, III and IV, along the path of the metal cores 44 covered by the cover 61. The four zones can be controlled separately so that the preform, which is a support 25 is attached, under optimal conditions for the subsequent orientation process to be heated.

In each heating zone, various (two, each at an up and down position) rod-shaped heating elements are provided with infrared heating tubes 62, which are arranged horizontally on the inside of the web of the metal cores 44. On the outside of this web is a number of infrared heating tubes 63 placed in vertical position. Also, a heat-dissipating damping unit 64 is provided on the top of the cover 61 at each heating zone. That is, a set of two heat-dissipating shafts is provided and a damper 66 is pivotally mounted in each shaft on a shaft 67 connected to a driving device 68. The temperature of each heating zone heating zone is measured by a thermocouple 69, such as shown in Figure 3, which is electrically connected to a control unit 70. The control unit 70 instructs the actuator 68 to open and close each damper 66, depending on the measured temperature, so that the temperature in the respective heating zone is at a preselected value is adjusted.

For example, the following temperatures can be set in the various zones of the heating chamber:

15 zone 140 ° C-160 ° C

zone II 160 ° C-180 ° C

zone III 180 ° C-220 ° C

zone IV 160 ° C-200 ° C

As shown in Figure 3, the metal core 44 is held at the peripheral portion of the disk 45.

As described above, the pinion 54 at the lower end of the carrier 25 engages the gear 53. Thus, if the disk 45 rotates, the gear 53 is rotated and the metal core 44 is rotated and also in a circular path moved.

Screen plate 25 As shown in Figure 2, a screen plate 71 is provided at the exit of the heating chamber 13.

The shield plate has radial blades rotated in synchronism with the movement of core 44 to prevent the atmosphere near the exit from the heating chamber 13 from being suddenly disturbed. The preform 10, which has been moved to the exit of the heating chamber 13 while it is being rotated, is now moved, thereby being shielded by the blades; its rotation is interrupted. The blades serve to prevent local heating of the preform 10.

After the shield plate 71, at the exit of the heating chamber 13, a braking device 73 is provided for interrupting the rotation of the metal core 44.

Loading device 35 As can be seen from the middle part of figure 2, the loading device 14 is provided with a mechanical manipulator with four rotating arms. That is, four arms 76 are mounted on a rotatable shaft 75. Each arm 76 is equipped at the free end with a pair of retaining means 77. Also, each arm 76 has a cam follower 79, which contacts the rotation of the rotatable shaft 75 with a cam 78 for extending or contracting the arm 76 and for opening or closing the retaining means 77, depending on the configuration of the cam 78.

In a position slightly further from the exit of the heating chamber 13, the retaining means 77 is closed and the support 25 is removed from the metal core 44 and the arm 76 is contracted toward the shaft 75. Then, the arm 76 is contracted into the initial length while rotating in the direction of the arrow 80. A curved guide rail 81 for guiding the rotation 45 of the retaining means 77 is provided at the circumference of the semicircle described by the free end of the arm 76. A magnet is mounted on the inner surface of the guide rail 81 to attract and retain the carrier 25 so that the carrier 25 is rotated and local cooling of the preform 10 during rotation of the arm 76 is prevented. The preform 10 with the carrier 25, held by the free end of the arm 76, is placed in the mold 72, where the carrier 25 is released from the retaining means T1 and slid into the cavity 87 of the mold 72. From this position, where the preform 10 is slid into the mold 72 via the circumference of the semicircle, opposite the guide rail 81, to the other position, where the brakes are applied and the stalled carrier 25 is started, the holding means 77 on the arm 76 in their opened state. When the carrier 25, started by the holding means, has been pulled towards the shaft 75, the 55 preform 10, held by the opposite arm, is placed in the mold.

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Exploratory blow molding machine

The orientation blow molding machine 15 is one of the rotary station type, with a mold 72 disposed at eight stations on a turntable 82. However, it should be noted that the number of stations need not necessarily be limited to eight, as in the illustrated embodiment, but ten or more stations may also be present.

The mold 72 includes two mold halves 83 and 84 which are longitudinally separated, as well as an upper mold element 85. One mold half 83 is fixed, while the other mold half 84 is pivotable about a pivot axis 86 shown in Figure 2. Mold 72 opens at the first and eighth stations and is closed from the second to seventh stations. The top mold element 85 is moved up and down correspondingly to the opening and closing of the mold 72.

Mold 72 is opened at the eighth station of the blow molding machine, where the carrier 25 holding the biaxially oriented container is released. Subsequently, the doom of the thus released carrier 25 is started by a pair of retaining means 90 of the unloader 16, provided with two rotating arms, and the carrier is released from the mold 72. The unloader 16 has two arms 92 which extend diametrically opposite each other from an element mounted on the rotary shaft 89, and the retaining means 90 which can be opened and closed are mounted on the free ends of the arms 92. carrier 25 taken out of mold 72 at the eighth station is held by the holding means 90 and moved in the direction of the arrow 93 until the carrier is started by said hook 23 of the conveyor 11, the holder 20 of the carrier 25 is removed.

20

Operation

The operation of the device according to the invention is as follows. First, an empty carrier 25 is transferred by the conveyor 11, shown in Figure 2, to the mounting position, where an injection molded preform 10 is mounted on the carrier 25, as shown in Figure 1A, in the inverted position. The preform 10 is placed on the support 25 with its neck portion 18 under the influence of gravity.

With a swinging movement of the arm 40, the transfer device 12 places the carrier 25 with the preform 10 on the metal core 44.

The metal core 44 moves through the heating chamber 13 and is thereby rotated by the rim wheel 53 and the pinion 54.

After entering the heating chamber 13, the carrier 25 is advanced from the entrance near the transfer device 12 to the exit of the chamber 13, while it is rotated by the rotation of the metal core 44. in the heating chamber 13, the preform 10 which is the carrier 25 is mounted, heated in a sequence of heating zones and thus kept at optimum temperature for the subsequent orientation molding process. As noted above, two or three heating tubes 62 are arranged horizontally on the inside of each heating zone, while several vertical heating tubes 63 are arranged on the outside. This is necessary because a vertical wave distribution of the preform 10 would result from the use of lateral heating tubes only, while a chevron-like distribution of the temperature with the tip in the longitudinal center of the object and gradually decreasing temperatures upwards and down would result from using only vertical heating tubes. Thus, in the blow molding apparatus according to the invention, a combination of vertical and horizontal heating tubes is used to ensure an even and uniform temperature distribution over the entire object. The heating tubes 62 and 63 are mounted in an array 95 of moldings and screws such that their mounting can be accurately adjusted 45 both sideways and longitudinally and both vertically and horizontally. The temperature in the heating chamber 13, heated by the vertical and horizontal heating tubes 62 and 63, is adjusted using the heat sink damper 66 on the top of the lid. That is, the temperature of each zone of the heating chamber 13 is determined by the thermocouple 69 (see Figure 3) connected to a control unit 70. The drive device 68 is operated depending on signals from the control unit 50 70 for opening and closing the damper 66, for correspondingly controlling the temperature of the heating zone.

The object 10, which is heated uniformly in the heating chamber 13, is advanced to the exit of chamber 13 while it is being rotated.

Figure 1B shows a container 20 as a product of the device according to the invention. As shown in Figure 1B, the holder 20 has a neck opening 18, a cylindrical body 20b of approximately the same diameter along its entire length, and a shoulder portion 20a extending between the neck opening 18 and the body portion 20b, while from the top to the top. bottom the diameter gradually decreases. As described above,

Claims (2)

193213, the container is manufactured by heating an injection molded article and orienting this article first in the longitudinal direction and then in the lateral direction. The body portion has an almost equal wall thickness and the container has an improved light transmittance and excellent impact properties due to the biaxial orientation. As described in detail above, such plastic containers have improved strength, toughness and transparency as a result of the uniform heating of the preform formed by, for example, injection molds in the orienting blow molding device according to the invention and by the precise orientation both in longitudinal and transverse directions. Since the heating chamber is divided into several heating zones, the preform can also be heated to temperatures that can be controlled stepwise, and the heating is done under optimal temperature conditions for the subsequent orientation movement. Furthermore, since the preform is rotated on the support in the heating chamber, uniform and uniform heating is ensured, while the shield plate at the end of the heating chamber prevents local heating from occurring, while the preform passing through the loading device into the orientation blow molding device 15 rotating station type, can be accurately formed, the preform retaining the heating temperature up to the orientation and forming operations. 20 An apparatus for manufacturing biaxially oriented hollow articles from preforms made of a crystalline thermoplastic plastic and closed at one end, comprising: a heating chamber provided with heating elements for heating the preforms to a desired temperature lower than the crystalline melting point thereof; Transport means for transporting the preforms through the heating chamber; a molding device adapted to axially stretch the heated preform to its final length, and then to radially stretch the preform by means of gas under elevated pressure; and a loading means for transferring the heated preforms from the heating chamber to the former; characterized in that the heating chamber (13) comprises a plurality of heating chamber sections (I, II, III, IV), each section being individually controlled to have a specific temperature range; that the transport means (25, 44) are arranged to transport the preforms (10) through said heating chamber sections while they are rotated about their body axis; that the heating elements of the heating chamber (10) are elongated heating elements (62, 63), part (63) of which is oriented vertically along one side of the advance path of the preforms (10), and another part (62) of which is horizontal oriented along the other side of the advance path of the preforms (10); 40 and that a shield plate (71) is disposed at the exit of the heating chamber (13), which shield plate (71) has radial fins synchronous with the transfer of the preform (10) from the heating chamber (13) to the loading member (14 ) rotated. Device according to claim 1, characterized in that elongated infrared heating tubes are arranged in each heating section of the chamber, two or three tubes being arranged horizontally and 45 several tubes being arranged vertically in each section. Hereby 2 sheets drawing