Device for adjusting a gap

Details Device for adjusting a gap Device for adjusting a gap

2001-07-10

2004-10-05

Davis, Robert (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Control means responsive to or actuated by means sensing or...

Control means responsive to product weight or dimension

C425S19200R, C425S381000, C425S465000, C425S466000

Reexamination Certificate

active

06799961

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a device for adjusting the gap of a die arrangement using a thermopin (
1
), in which the thermopin is connected to the die lip (
10
) without any play.
In the production of films, tapes, sheets and similar two-dimensional, continuously shaped extrudates of thermoplastics, a plastic melt is generally extruded through a slot die to give a surface having a rectangular cross section. It is important here to set a controlled thickness profile of the extrudate by adjusting the die gap. The thickness profile is important for subsequent process steps, such as, for example, the stacking of sheets, the winding of film webs or, for example, the stretching of films, the thermoforming of sheets, etc. For stretched films in particular, a uniform thickness profile of the final film over the entire width depends on the thickness profile of the precursor film.
It is known to adjust the height of the die gap or its profile by bending the die lip. The fine adjustment is frequently carried out by means of so-called thermopins. These thermopins expand on heating and exert a mechanical force on the die lip, causing the latter to deform. Conversely, the thermopin contracts on cooling, causing tension on the die lip at the corresponding point and thus an increase in the die gap.
For precise adjustment of the die gap by means of thermopins, it is important that the thermopin is connected to the die lip without any play. If there is excessive play, the heating or cooling of the thermopin in some cases does not result in deformation of the lip, but instead the change in the length of the thermopin is partly lost in the play of the arrangement and has no effect. Thermopins therefore have to act on the die lip as directly as possible and without any play.
Known play-free die arrangements with thermopins are afflicted by the disadvantage that they do not facilitate simple exchange of individual thermopins. DE 38 34 719 describes a device which has a bore in a die projection, this die projection being an integral part of the die. This connection mechanism may be damaged in operation and may wear. Deficiencies of this type cannot be eliminated since the die projection is an integral part of the die lip. The known device results in premature unusability of the entire die. Furthermore, die deformation by means of a connection mechanism of this type is not sufficiently precise, since the integral die projection results in a stiffening of the die lip.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention was therefore to provide a device for adjusting the gap of a die using thermopins which ensures easy removability of individual thermopins and a play-free connection between the thermopins and the die lip and facilitates precise deformation of the die lip using thermopins.
This object is achieved in accordance with the invention by a device for adjusting the gap of a die arrangement using a thermopin, in which the thermopin is connected to the die lip (
10
) without any play and this play-free fixing of the thermopin (
1
) to the die lip (
10
) is effected by means of a clamp-type socket (
7
), where the clamp-type socket (
7
) engages on the one hand in a lip nose (
11
) and on the other hand in a groove (
5
) of the thermopin (
1
), where the lip nose (
11
) is an integral part of the die lip (
10
) and the clamp-type socket (
7
) has a bore (
8
) and the thermopin (
1
) has a bore (
4
) and a fixing means is passed through the bores (
8
) and (
4
).


REFERENCES:
patent: 4753587 (1988-06-01), Djordjevic et al.
patent: 4781562 (1988-11-01), Sano et al.
patent: 5020984 (1991-06-01), Cloeren et al.
patent: 5259747 (1993-11-01), Cloeren
patent: 5626888 (1997-05-01), Sanze et al.
patent: 6019924 (2000-02-01), Montalbano
patent: 37 31961 A 1 (1989-04-01), None
patent: 38 34719 A 1 (1990-04-01), None

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