Method and apparatus for cooling a preform

Abstract: This invention relates to a method and apparatus of cooling and solidifying a preform comprising: introducing a preform (5) ina heated state released from an injection mold into a cooling tube (3) having a bottom opening and an upper opening through which cooling air flows from said bottom opening to said upper opening, said bottom opening being provided with turning means (6) for cooling air, and inserting a cooling core (4) into the preform (5) to place said cooling core in close contact therewith, said preform being forcibly cooled from interior and exterior thereof by cooling air flowing in a turning state between said preform and said cooling tube and a coolant supplied to said cooling core.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a method and apparatus for cooling a preform, in which an injection molded preform is released from an injection mold while the preform is in a heated state, and the preform is then transferred to the other area to cool and solidify it. Prior Art In molding of a bottle in which an injection molded preform is cooled and solidified, and the preform is then re-heated later to orientation blow mold it into a bottle-like container, a large amount of preforms are required. Therefore, when a preform is cooled and solified by the injection mold as in conventional injection molding, it takes time for cooling, resulting in a very poor productivity. It has been desired therefore that cooling time is shortened by some means to shorten a molding cycle and improve the productivity of the preform. One means has been partly proposed in which on the basis of the fact that in the state wherein even if the interior is in a molten state, a shape of a preform is maintained by a skin layer formed on the surface, the preform can be released, the preform is released in such a state as described, the preform is then immediately transferred to a cooling device at the other position for forced cooling whereby cooling time of the preform is shortened. As the cooling means after release, quenching using a refrigerator or contacting with a cooling tube set to a low temperature have been employed. The cooling by way of a refrigerator poses a problem in that a preform is materially contracted by cooling to impair the molding accuracy. On the other hand, in the cooling by way of contact, since the contact with the cooling tube is effected by pressure of air blown into a preform, a wall thickness of the preform becomes thinner than a desin dimension. The contraction and formation of thiner wall thickness of the preform during the process of cooling do not occur uniformly but the location thereof differs with the injection molding state of a preform. These locations give rise to unevenness of temperature of a preform after being reheated, making it technically difficult to perform orientation blow molding a preform into a container. It has been proposed also to cool a parison by supplying cooling air from both sides of inner surface and outer surface of parison, the parison being inserted into a cooling chamber and cooling air being introduced into the chamber (Patent Abstracts of JAPAN, vol. 10, no. 307 (M-527) (2363). The pending invention aims at providing an improved method and apparatus for cooling a preform, internally and externally. SUMMARY OF THE INVENTION This invention has been achieved in order to solve the aforementioned conventional problems. It is an object of this invention to provide a new method capable of performing cooling in a short time without bringing forth a change in thickness and shape of a preform and an apparatus capable of adjusting flow rate of cooling air. For achieving the aforesaid object, a method of cooling a preform is as defined in claim 1. Further, an apparatus of cooling a preform is as defined in claim 2. Furthermore an apparatus of cooling a preform according to a preferred embodiment is characterized in that an inner wall surface of the bottom of the cooling tube is formed to have a tapered surface which is wider toward an opening, a guide member for cooling air of which outer periphery has the same tapered surface as said inner wall surface and formed with a recess in its upper surface is provided in a central portion of the upper fixed fan, so that the flow rate of cooling air can be regulated by a change in spacing with a relative positional change between two tapered surfaces caused by upward and downward movement of said fixed fan. With the aforementioned arrangement, the preform is cooled from the interior thereof by the cooling core inserted into and placed in close contact with the preform, and contraction of the preform resulting from cooling by the cooling core is prevented. The preform is also cooled from the exterior thereof by cooling air which flows around the exterior, and the preform is cooled to a predetermined temperature in a short time and solidified by said both internal and external cooling. Moreover, the cooling air is turned between the preform and the cooling tube by the fixed fan at the bottom opening and flows out toward the upper opening, and therefore, cooling of the side of the preform is uniformly carried out. With the aforementioned arrangement, a plurality of preforms can be simultaneously cooled in a short period of time without occurrence of one-sided wall thickness and deformation one by one every cooling tube. In addition, since the molding accuracy is maintained even after cooling, orientation blow molding after reheating becomes easy to reduce a loss of molding and further improve the productivity. Furthermore, it will suffice that the cooling tube having a fan mounted on the bottom opening is provided on the opening portion of the cooling chamber, and the cooling core is disposed movably up and down at the upper portion of the cooling tube. The apparatus is simple. Cooling air is merely supplied into the cooling tube from the cooling chamber without requiring special adjustment. The present invention will be described in detail by way of an embodiment shown in the drawings. BRIEF DESCRIPTION OF THE DRAWINGS The drawings schematically show one embodiment capable of performing a method of cooling a preform according to this invention. Fig. 1 is a longitudinal sectional view. Fig. 2 is a sectional view taken on line II-II of Fig. 1. MODE OF PREFERRED EMBODIMENT In the drawings, reference numeral 1 designates a cooling chamber, 2 a cooling pipe therein, 3 a cooling tube having a bottom portion secured to an opening of the cooling chamber 1, 4 a cooling core into which a coolant is supplied, and 5 a closed-end preform formed of polyethyleneterephtalate or the like subjected to injection molding. The cooling tube 3 has an inside diameter larger than the preform 5. An upper portion and a bottom portion of the cooling tube 3 are opened, and an inner wall surface 3b at the bottom portion thereof is formed to have a tapered surface which is wider toward the opening side. A cooling air turning means 6 is mounted from the bottom portion to the opening 3a. The turning means 6 has upper and lower fixed fans 6a and 6b connected by a threaded shaft 7. The fixed fans 6a and 6b are provided with blades inclined at a predetermined angle at four corners of cores 6c and 6d and integrally connected by the threaded shaft 7 provided over the cores 6c and 6d. On the core of the upper fixed fan 6a is integrally provided a frustonical guide member 8 having an outer peripheral portion formed to have the same tapered surface as the inner wall surface and an upper surface formed into a recess in the form of a concave curve along the bottom surface of the preform. The guide member 8 guides cooling air from the bottom opening to the peripheral portion of the preform and protects the bottom surface of the preform from cooling air. In the turning means 6 composed of the upper and lower fixed fans 6a and 6b as described above, the lower fixed fan 6b is secured to the cooling tube so that the upper fixed fan 6a is moved up and down together with the guide member along the guide groove 3c on the cooling tube side by the rotation of the threaded shaft 7 and provided within the bottom, whereby cooling air 9 from the cooling chamber 1 flows into the upper opening in the turning state within the cooling tube. Cooling of the preform 5 by the aforementioned apparatus will be described hereinbelow. The preform 5 in the aformentioned state released from an injection mold (not shown) is transferred upwardly of the cooling tube 3 with a neck portion thereof held on a neck mold 10. When the preform 5 assumes a position above the cooling tube as the transfer means stops, the preform 5 moves down together with the neck mold 10, and the bottom surface thereof is inserted into the cooling tube till it comes close to the guide member 8 and a portion lower than the neck portion is introduced into the cooling tube. The cooling core 4, which is slightly smaller in outside diameter than inside diameter of a preform and through which coolant flows, is inserted into the preform through the neck mold 10. In insertion of the cooling core 4, cooling air has been already fed from the cooling chamber 1 into the cooling tube at a predetermined flow velocity. A flow of cooling air is turned into a turning flow by inclination of blades provided on the upper and lower fixed fans 6a and 6b, during passage through the latter, and flows into the cooling tube. For this reason, the preform 5 is cooled from interior and exterior thereof by both coolant of the cooling core and the cooling air, and slight contraction of the preform 5 caused by the cooling causes the inner wall surface of the preform 5 to contact with the cooling core 4. Thereby, the preform 5 is prevented from contraction due to further cooling to prevent the loss of molding accuracy of the preform 5 caused by the contraction. The cooling air 9 entered in the cooling tube 3 flows into the upper opening while turning along the cooling tube 3 avoiding the bottom surface of the preform 5 to be covered by the guide member 8. For this reason, the bottom surface is not excessively cooled but cooling from the exterior is applied uniformly to the preform 5 and a difference in contraction resulting from unevenness of cooling is hard to occur. The adjustment of flow rate of the cooling air 9 is easily carried out by changing a spacing due to a relative positional change between the two tapered surfaces as a result of upward and downward movement of the upper fixed fan 6a caused by the rotation of the threaded shaft 7. Therefore, cooling according to the design of the preform 5 can be always carried out. The above-described embodiment, a single cooling tube has been used. However, a plurality of cooling tubes can be similarly provided in the cooling chamber and at the same time a plurality of preforms can be cooled and processed by similar means. Therefore, this invention is not limited to cooling of a single preform.

Claims: A method for cooling a preform internally and externally, comprising: introducing the preform (5) in a heated state released from an injection mold into a cooling tube (3) and introducing cooling air into said cooling tube, characterized in that said cooling air is flowed from a bottom opening to an upper opening of said cooling tube, in that said bottom opening is provided with turning means (6) for cooling air, and in that a cooling core (4) is inserted into the preform (5) to be in close contact therewith, and a coolant is supplied to said cooling core. An apparatus for cooling a preform, comprising a cooling tube (3) for receiving the preform and means for introducing cooling air into the cooling tube, characterized in that said cooling tube (3) has bottom and upper portions which are opened, said bottom opening being located at an opening portion of a cooling chamber (1), and a cooling core (4) disposed movably up and down at the upper portion of said cooling tube, said cooling tube being provided with turning means (6) for cooling air in which upper and lower fixed fans (6a,6b) are connected by a threaded shaft (7) within the bottom, said fixed fans being mounted on the side of the cooling tube (3) so that the upper fixed fan (6a) is moved up and down by rotation of the central threaded shaft (7) to regulate flow rate of cooling air. An apparatus for cooling a preform according to claim 2, wherein an inner wall surface (3b) of the bottom of the cooling tube (3) is formed to have a tapered surface which is wider toward an opening (3a), a guide member (8) for cooling air of which outer periphery has the same tapered surface as said inner wall surface and formed with a recess in its upper surface is provided in a central portion of the upper fixed fan (6a), so that the flow rate of cooling air can be regulated by a change in spacing with a relative positional change between two tapered surfaces caused by upward and downward movement of said fixed fan.

Inventors: FUKAI HIDEHIKO, FUKAI, HIDEHIKO
Applicants: NISSEI ASB MACHINE CO LTD, NISSEI ASB MACHINE CO., LTD.
Application year: 1991
Main classification: B29B13
IPC codes: B29C49, B29B11, B29B13, B29L22, B29C35, B29C45