Valve unit

Abstract

The invention relates to a valve unit, comprising a valve housing (1) having a process pressure input line (31), a process pressure output line (32), and a process guide shaft (10). Furthermore, an operating piston (2) for closing the valve, a first and a second control line (50, 60), and a first and a second control room (40, 41) for controlling the operating piston (2) are provided. The operating piston (2) can be displaced in the axial direction within the process guide shaft (10) in a sealed manner by means of a dynamic process seal. The operating piston has a closing ring, which in the closed state of the connection sealingly abuts a valve seat (700) of the valve housing (1). The closing ring is designed as a circumferential sealing edge (250), wherein the valve seat (700) is made ofa softer and more elastic material than the sealing edge (250) abutting valve seat. The circumferential sealing edge (250) has a diameter, which corresponds to a guide diameter of the dynamic processseal. The valve unit according to the invention has low axial forces, and thus makes a long service life with a high number of cycles of operation possible.

Description

technical field [0001] The invention relates to a valve unit, in particular for pneumatic switching in a blow molding process. The valve unit is particularly suitable for use in extrusion blow molding machines or stretch blow molding machines for producing hollow bodies made of plastic. Background technique [0002] For the manufacture of plastic bottles, especially PP or PET bottles (PP=polypropylene; PET=polyethylene terephthalate), blanks or preforms are processed in a blow molding machine, especially an extrusion blow molding machine or Blow molded into its final shape in a stretch blow molding machine. For this purpose, the blank is held in the blow mold with its bottle head, which already has its final shape, and is connected to a compressed air system. By blowing compressed air through the bottle head, the blank is blown and brought into its final shape. [0003] The blow molding process is usually carried out in a two-stage process, wherein in the first stage, com...

AI Technical Summary

Problems solved by technology

This results in a large control volume, which in turn contradicts the requirements for rapidly switching valves, since the large control volume must be filled and emptied again quickly enough

To ensure sufficiently fast filling and emptying, pilot valves with a relatively large nominal width are therefore used, which however switch over more slowly than pilot valves with a smaller nominal width

Also, the pilot valve is expensive and requires more space

The resulting high sealing and acceleration forces limit the switching time and also minimize the number of switching cycles and also the service life of the valve unit

In principle it applies that the higher the sealing force and the kinetic energy in the valve unit, the lower the number of switching cycles to be achieved and the shorter the service life of the valve unit

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