Extrusion die for plastic material

Details Extrusion die for plastic material Extrusion die for plastic material

1987-01-12

1988-05-03

Chiesa, Richard L.

Plastic article or earthenware shaping or treating: apparatus

Stock pressurizing means operably associated with downstream...

Centripetal elastic melt extruder type

74479, 425466, B29C 4716

Patent

active

047416866

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to a flat or circular extrusion die fitted with lips which define an extrusion slit, at least one of said lips being flexible such that they can be moved towards or away from one another. The flexible lip is operated by a series of independent thrust members, which are placed parallel and very close to one another.


DISCUSSION OF THE PRIOR ART

Until now these thrust members have been made in the form of a series of screws, placed side by side parallel to one another and operated manually. Unfortunately this type of operation requires the continual presence of a skilled worker and is therefore very costly and unreliable in practice.
Automatic actuation has also been applied. This solution foresees a whole series of gudgeon pins acting on the flexible lip. These pins are lengthened or shortened by heating them by means of an electric heater. This type of coupling allows the thrust members to be placed very close to one another, but does not provide for timely intervention, that is, the part of the lip which is to be displaced cannot be acted on in real time. A further drawback is the fact that, since the length of the gudgeon pin varies as a function of its own temperature, this system, as well as being slow, also depends on the ambient temperature and the working temperature of the extrusion die. This leads to a high degree of imprecision or to a very complicated arrangement of circuits, if all these variables are to be taken into account.
U.S. Pat. No. 3,427,889 is also known wherein a connection between a regulating means for the flow and an operating device is described. No offset positioning of the operating devices is foreseen, so that it becomes necessary to place the devices at such a distance that they do not interfere with one another.
The U.S. Pat. No. 4,125,350 describes an adjusting screw which acts on the thickness regulating lip. The screw is fitted at one end with a gear which can be selectively engaged by two toothed pawls. The latter temporarily hold the screw fast with an operating means which is unique for all the screws. Therefore a simultaneous working working of the screws is impossible. The thickness tolerance of the finished product must thus compulsively be of some tenths of mm.


OBJECT OF THE INVENTION

Object of the present invention is thus to carry out an extrusion die fitted with a series of extremely precise adjusting devices, independent from the temperature and such that they can be operated automatically in real time, one independently from the other.
The above-said object has been achieved as specified in the enclosed claims .


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail on the basis of an exemplary embodiment which is shown in the accompanying drawings, in which:
FIG. 1 is a side view partially sectioned of an extrusion die according to the invention;
FIG. 2 is an axonometric scrap view of said die.


DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, it can be seen that 10 indicates the rigid lip of the flat extrusion die. On the other hand, 11 indicates the flexible lip, which is connected to the body by means of thin portion 15, the latter flexing when acted on by a series of thrust members 13, which in the example are in the form of screws 13A, 13B, 13C, 13D. Each screw is connected to the flexible lip 11 by means of a fastening 14, which may be of any known kind. Each screw is made integral with one link 20A, 20B, 20C or 20D, which mechanically connects said screw to the respective actuating means M1, M2, M3 or M4, in this example provided in the form of a stepping motor. Each link 20A, 20B, 20C and 20D is telescopic and articulated or flexible, such that each respective actuating means M1, M2, M3 and M4 can be staggered with respect to the neighbouring means.
In particular, as can be seen in FIGS. 1 and 2, the motors are arranged on two support surfaces P1 and P2, placed at an angle to one another. Motor M1 is situated at the front on top, on surface P1

REFERENCES:
patent: 2880832 (1959-04-01), Apel
patent: 2926544 (1960-03-01), Carmichael, Jr.
patent: 3195183 (1965-07-01), Phillips
patent: 3427889 (1969-02-01), Baum
patent: 3680997 (1972-08-01), Dukert et al.
patent: 3940221 (1976-02-01), Nissel
patent: 3963051 (1976-06-01), Kuhlmann
patent: 4124342 (1978-11-01), Akatsuka et al.
patent: 4125350 (1978-11-01), Brown
patent: 4514348 (1985-04-01), Iguchi et al.
patent: 4627786 (1986-12-01), Minematsu et al.

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