Device for cooling and granulating molten thermoplastic strands

Details Device for cooling and granulating molten thermoplastic strands Device for cooling and granulating molten thermoplastic strands

1994-04-01

1995-08-15

Mackey, James P.

Plastic article or earthenware shaping or treating: apparatus

Including means advancing continuous length work through...

264178F, 425301, 425308, B29C 4788

Patent

active

054413940

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a device for cooling and granulating molten thermoplastic strands, which emerge from dies and which either drop along the falling line starting at the dies or are guided in an operating position through a coolant bath, freely stressed between guide rollers, arranged in said bath and then are fed into granulator, where a precooling device, which carries the strands emerging from the dies and takes them to the coolant bath, is arranged in the region between the dies and the coolant bath.
Such a device is known from the DE-PS 11 76 346. In this device between the dies and the coolant bath there are cooling rollers, into which the strands coming from the dies have to be threaded, in order to be guided thereafter through the coolant bath. In the coolant bath the strands travel through two pairs of deflecting rollers, which provide that the strands are guided reliably through the coolant bath. After leaving the coolant bath, the strands are then carried by a revolving conveyor belt, in order to then travel into the inlet of the granulator. In this device the strands must be threaded by hand, as customary with the use of such coolant baths, in the region between the dies and the granulator into the organs guiding and carrying the strands. This work is not only time-consuming, but it is also a dangerous operation, since the responsible personnel for monitoring such a device must reach into the hot strands. This is difficult, above all, when a larger number of strands, e.g. 50 strands and more, has been produced due to the width of the space that the strands occupy. At every startup of the device one has to wait until a qualitatively perfect material emerges from the dies, a state which, according to experience, takes some time following startup, during which the strands are guided first along their falling line next to the device into a waste container. If the operating personnel determines the quality of the emerging strands to be flawless, then a knife-like tool has to be slid by hand over the dies, in order to produce a break in the strands, after which then the newly emerging strands are guided into the coolant bath. The more strands issue from the dies, the more difficult this operation is, so that with this manual manipulation only one portion of the dies can be stripped off in the described manner, so that the strands emerging from the other dies continue to fall into the waste container.
In addition, a device for cooling molten thermoplastic strands emerging from dies is known from the DE-AS 22 30 187; in said device the strands are guided to a pair of conveyor belts, by means of which the strands and the conveyor belts are guided in a meandering guide through a coolant bath.
Furthermore, it is known from the DE-AS 12 95 176 to cool the strands emerging from the dies in a coolant bath, in which the strands are caught by a collecting pan, before the strands are fed into a granulator. The collecting pan is slid along a slideway, whereby the strands are supposed to catch apparently in an intercepting slot of the collecting pan. They are taken along by the displaced collecting pan and thus pulled out of the coolant until they get to the granulator. To thread the granulator, the strands are cut off upstream of the collecting pan, so that a quantity of plastic, guided beforehand into the collecting pan, remains first in said pan and has to be removed for the next working step.
The invention is based on the problem of automating the threading operation of the strands in such a manner that it is ensured that the entire number of delivered strands can always enter with their forward ends simultaneously into the granulator.
This problem is solved according to the invention by disposing behind the precooling device for a clamping grasp of the forward ends of the strands a gripping device, which guides the forward ends of the strands--after the strands have been jointly separated by means of a separator moveable through the falling line of the strands--along a guid

REFERENCES:
patent: 2838800 (1958-06-01), Hertz
patent: 3518722 (1970-07-01), Ryan et al.
patent: 3837781 (1974-09-01), Lambertus
patent: 3942933 (1976-03-01), Svendsen
patent: 4528157 (1985-07-01), Lettner et al.
Patent Abstracts of Japan, vol. II, No. 71 (M-567) 2518, 4 Mar. 1987 & JP, A, 61 227 014 (Mitsubishi Metal Corp.) 9 Oct. 1986, see Abstract.

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