DD141237A3 - FLEXIBLE PRESS FOR ISOSTATIC PRESSING - Google Patents

Description

Rudolf Y / asner WP B 28 B / 197 491

Dieter Pelikan P 556 ·

Hans-Dieter Krämer. December 6, 1979

Hans-Ulrich Rauscher Horst disc

Title of the invention

Flexible mold for isostatic pressing

Field of application of the invention;

The invention relates to a flexible mold sum isostatic pressing of bodies with complicated shape, such as electrical screen insulators of powdered ceramic mass. The isostatic shaping gives a very uniform compression of the material and thus correspondingly homogeneous combustion and strength behavior. It is desirable that o.a. To obtain complicated molds in a single operation without rework, the molds used must also have sufficient dimensional stability and high flexibility in terms of demolding.

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Characteristic of the most known tec hnical solutions

In known flexible molds these contradictory requirements have always been met with a fairly thin-walled (1. "2 mm or even smaller wall thickness in the manner of a balloon) Preßhülle made of soft rubber, which was given by various measures shape and strength. A particular problem was always the required Entformungsmöglicblceit.

Thus divisible rigid molds are known, which completely or largely enclose and support the flexible mold (DL-PS 7I.O7I and 86.771). The disadvantage here is the high cost of making the molds and the fact: that is limited to a workpiece shape that allows removal from the s_tarren mold.

This deficiency has been avoided in a further flexible mold, the support body consists of a Schäumstoffkörper with interconnected pores (DL-PS 86c772) "This has the disadvantage that two different, but precisely matched .formen for Plerstellung the Preßhülle and the. Foam body are required and that very easily inhomogeneities in the structure of the foam occur, which naturally have inhomogeneities in the pressure distribution and thus in the formation of the compact result.

Finally, even such a mold is known in the foam body rigid supports are embedded, which serve the removal in the pressure vessel by means of electromechanical drives for each support (DL-PS 120.615). Here is the need for separate drives for demolding disadvantageous

It is the object of the invention to make the isostatic shaping and the creation of the associated production equipment, in particular for electrical screen isators, simpler and more economical.

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Explanation of the essence of the invention

The invention has for its object to provide producible in a single piece and a single operation flexible molds for isö- etatisches pressing, which allow by a slight demolding while maintaining a high degree of freedom.

According to the invention, this object is achieved in a mold with planar, the shape-related projections of the mold shell connecting struts in a radial arrangement and a Einspannflansch in the same amount with the bottom closure that embedded in the dimensionally stable mold shell, the same aias, thick-walled material and with this a unit forming support struts are preferably arranged at a distance of 45 ° and the mold has a separate sealing flange with annular bead.

By mounted in the production of thick-walled mold cover flexible support struts a very high stability of the entire mold is achieved. The support struts are arranged according to the required support functions on the mold.

In addition, the flexible struts allow a very easy demolding the thick-walled, designed with complicated geometry dies. The expansion effect occurs even when a slight negative pressure is applied. Without the flexible support struts widening of the mold by means of vacuum is not possible.

Advantageously, the use of thick-walled molds, combined with flexible support struts, considered a stability, Ausformgenauigkeit, reproducibility and

results and without additional aids

(e.g., sponge rubber or metal jackets) allow low vacuum removal.

In order to avoid the penetration of granules between the clamping flanges and the whereabouts of this granulate after pressing in the mold (risk of cutting the mold when re-pressing on sharp edges), the lower clamping

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Here, it is advantageous that the mold cover is designed to be closed at the lower part and, in addition to avoiding the vertical pressure build-up during isostatic pressing, a clamping flange is provided for fastening in a steel support frame.

In order to avoid the ingress of granules between the upper chuck flanges and the creation of permanent sharp edges leading to the cutting of the mold, the mold is extended beyond the upper chucking flanges .. By appropriate design of the extension, eg round bead, the mold simultaneously becomes Seal the top closure used.

It is advantageous here that the mold is extended beyond the clamping flanges and that this extension is used with appropriate design (for example round ring bead) as sealing.

For the sake of brevity

As an embodiment, the design of a mold for the isostatic pressing of high voltage insulators is selected.

The mold is made by casting from latex rubber. As a mold, a ß'ipsform is used. The wall thickness of the mold shell (6) is approximately '10 mm. To support the umbrella contour of the molds, 45 flexible support struts (7) are cast together with the mold shell (6) at intervals of 45 each. These struts (7) are firmly connected to the mold shell (6). To avoid the formation and remaining of press residues between the clamping plates (9, 10), the bottom of the mold (6) is closed at the lower clamping flange (8).

At the upper clamping plates (4, 5), the formation of the pressing residues is avoided by lengthening the mold

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elongated form at the end of a torus (2). By this annular bead (2), the sealing of the upper closure (1) is made possible. As a result, the usual seal of the closure (1) can be omitted.

To avoid a pressing pressure in the longitudinal axis, the mold is installed via the clamping plates (4, 5, 9, 10) in a steel stand (11) having holes for passing the molding liquid.

During pressing, the mold shell (6) is compressed, whereby the support struts (7) fixed to the mold shell exert no resistance to the pressing process and the migration of the flexible mold material due to their flexibility. Rather, the flexible support struts act on the entire filling and pressing stabilizing.

During the pressing process, the flexible mold shell (6) is widened by generating negative pressure either in the recipient or in a vacuum pot intended for this purpose. The flexible support struts (7) cause a uniform expansion of the flexible mold (6). By their flexibility, the support struts (7) adapt to the expansion process even at moderate vacuum ideal and pulling away the flexible mold shell (6) to one side, which makes demolding impossible, is avoided.

Claims (1)

-6-1 07 49 8 P 556 invention claim Flexible mold for isostatic pressing of bodies of complicated shape, such as electric umbrella insulators, with planar, the shape-related projections of the Pormenhülle connecting struts in radial arrangement with a Einspannflansch the same height with the 'bottom closure, characterized in that in the dimensionally stable mold shell (6 ) embedded, consisting of the same, thick-walled material and with this unit forming support struts (7) are preferably arranged at a distance of 45 and the "mold has a separate sealing flange (3) with annular bead (2). For this 1 page drawings