Device for temperature adjustment of an object

Details Device for temperature adjustment of an object Device for temperature adjustment of an object

2001-05-11

2002-07-23

Davis, Robert (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Female mold and means to shape parison directly by internal...

With heating or cooling means

C264S237000, C425S445000, C425S547000

Reexamination Certificate

active

06422855

ABSTRACT:

INTRODUCTION
The present invention relates to a device and a method for temperature adjustment of an object, especially a device and a method for temperature adjustment of a molded object after removal from a mold cavity of an injection molding machine.
In order to improve the productivity of injection molding equipment, it has been known to reduce the cycle time for molding an object by removing the molded object from the mold cavity while it is still at high temperature. The molded object has thus to be cooled in a subsequent step in order to reduce the temperature of the molded object below its crystallization temperature range.
Two different approaches have been found for removing and subsequently cooling the molded objects.
In conventional molding machines, a carrying plate. with water-cooled tubes is positioned between the opened mold parts and the molded objects are transferred into the tubes of said carrying plate. The plate is then removed from between the mold parts so that the following molding cycle can start. During the next molding cycle the outer surface of the molded objects is cooled in the water-cooled tubes of the carrying. Such a device is disclosed in U.S. Pat. No. 4,729,732. In order to also cool the inner surface of hollow objects, a blowing nozzle can be introduced into the hollow object and a cooling fluid may be blown onto the inner surface of said hollow object.
Turret style injection machines comprise a rotatable turret block with a plurality of movable mold halves and a stationary mold half and platen. Each of the movable mold halves includes a set of mold cores adapted for engagement with a set of mold cavities located in stationary mold half and platen. After a set of objects has been formed on the mold cores of the first movable mold halve, the turret block rotates to a second position, in which the second movable mold halve is positioned for engagement with the stationary mold half. The set of objects remains on the mold cores of the first movable mold and is cooled by a cooling fluid, which is blown onto the exterior surface of the object. U.S. Pat. No. 4,449,913 discloses such a rotary injection turret for use in making preforms. The patent teaches a turret block rotatable on a vertical axis, which block uses two of the turret, block positions for post mold treatment of preforms while the preforms are still on mold cores. Accordingly, after injection, hold and some cooling at a first station, the turret block rotates to a second position where cooling fluid is blown onto the exterior surface of the preforms in order to cool the preforms. At a third position, the preforms are inserted into a conditioning mold from the turret block where the gate vestige is trimmed and further temperature conditioning is performed.
According to U.S. Pat. No. 4,449,913, the cooling of the performs at the second position is executed by means of a cooling unit comprising a plurality of nozzles for blowing a cooling gas onto the preforms. The nozzles are equal in number to the cores and are positioned in accordance with the arrangement of the cores so that, after alignment of the preforms with the nozzles, air is separately blown on each of the preforms. The nozzles are carried by a manifold to which there is connected a supply line. At the third station, a conditioning mold comprising a plurality of conditioning cavities receives the partially cooled preforms. Each conditioning cavity is oversized as compared to the preform so that conditioning gas (air) may be circulated along the preform.
An embodiment of a conditioning cavity is disclosed in U.S. Pat. No. 3,882,213. This conditioning cavity comprises a cooling tube for receiving a molded object that is to be cooled. The inner diameter of the cooling tube is larger than the outer diameter of the object, so that a flow passage having a generally annular section is formed between the cooling tube and the object. The inner walls of the cooling tube are provided with interior fluid directing fins in the form of an internal spiral for directing airflow in an axial and peripheral spiral path around the exterior of the object. It follows, that the flow path of a cooling fluid under pressure, which is introduced into the flow passage, will be substantially longer that in cooling tube with straight flow path. Accordingly, the heat exchange between the object and the cooling fluid in this conditioning cavity will be higher than in a cooling tube with smooth inner walls.
Although the cooling tube of U.S. Pat. No. 3,882,213 enhances the heat exchange between the object and the cooling fluid with respect to a smooth cooling tube, it is believed that the cooling rate of this device is still not sufficient. Furthermore, the manufacture of the fluid directing ribs in the form of an internal spiral is considered to be rather expensive.
OBJECT OF THE INVENTION
The primary object of the present invention is to provide an improved device and method for cooling a molded object.
A further object of the present invention is to provide an inexpensive post mold cooling device which exhibits increased cooling capacity.
GENERAL DESCRIPTION OF THE INVENTION
This object is generally achieved by a device for temperature adjustment of an object, comprising means for providing a flow of a conditioning fluid, said flow of conditioning fluid being directed along a surface of said object, and at least one fin directed towards said surface of said object. According to the invention said at least one fin is arranged in the immediate vicinity of said surface of said object so that an edge of said fin extends substantially normally with respect to said flow of said conditioning fluid, said conditioning fluid passing between said surface of said object and said edge of said fin.
Since the fin ends in the immediate vicinity of the surface of the object, the flow of conditioning fluid along the surface of the object is squeezed in the passage between the surface of the object and said fin. This means that the speed of flow increases in this region, so that the flow of conditioning fluid is highly turbulent in this region. It follows that the heat transfer between the conditioning fluid and the surface of the object in the region of the fin is very high.
After passing between the fin and the surface of the object, the conditioning fluid expands and accordingly the flow of conditioning fluid slows down again. This creates further turbulences, so that the heat transfer between the conditioning fluid and the surface of the object is also increased in a region adjacent to the fin.
With the present invention, the creation of a laminar flow of conditioning fluid along the surface of the object, i.e. a flow configuration with reduced heat exchange inside the flow and between different layers of the flow, is effectively prevented. Hence, the heat exchange between the surface of the object and the conditioning fluid is highly increased compared to prior art devices.
It has to be noted that the conditioning fluid can be either a cooling fluid, as e.g. compressed air, for cooling a warm object or a heat carrier for heating the object. The improved conditioning result is independent from the type of conditioning.
Depending on the embodiment of the invention, the at least one fin may be arranged substantially normal to said surface of said object or be inclined with respect to a normal of said surface of said object.
In a preferred embodiment of the invention, the fin ends in the vicinity of the surface of the object, so that a small gap is formed between the object and the edge of the fin. In this case the fin can be formed of an elastic or rigid material. In an alternative embodiment the edge of the fin abuts against said surface of said object if no conditioning fluid passes between said surface of said object and said edge of said fin. In this embodiment, the fin should be formed of an elastic material, so that the flow of conditioning fluid can displace the edge of the fin from the surface of the object. It follows that in this case, the gap between the edge of

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