DE4138849A1 - Intrusion mould filling for thermoplastic blanks - uses timed filling in sequence with reduced pressure in final filling stage from continuous extruder - Google Patents

Abstract

The assembly to produce blanks of thermoplastics, from a continuously operating extruder, uses intrusion moulding in a static assembly with at least two moulds which are filled in succession from a continuous flow of melted material. Before the end of a filling operation of a mould the next mould filling action starts for the next mould, in the time sequence, by release of the molten flow and the remainder of the filling is at a reduced pressure. Pref. the filling pressure is maintained at the mould for the whole filling and cooling phases, with a short interruption for emptying. The moulded blanks are ejected by the pressure of steam formed by the coolant water injected at the heated zone, and/or by compressed air. The moulded blank can also be ejected by the subsequent molten pressure, where the mould and feed closure acts through holding the moulded blank to be ejected. ADVANTAGE - The final filling of the mould is slowed down to avoid a pressure shock. In operation all the feed slides are open until a short closing time in each mould for emptying, the residual pressure remains for the filling time at each mould in the whole array, so that the hollow zone shrinkage is minimised to give uninterrupted extruder working.

Description

The invention relates to a mold filling machine for thermo plastic plastics, especially mixed waste art fabrics. It refers to a filling mechanism, the one Filling of several forms with continuously running extrusion which allows, the arrangement of the forms is stationary and the final filling pressure of each individual mold under control remains.

In contrast to injection molding machines, only with high pressure filling (Screw piston up to 2000 bar) and accordingly expensive Mold tools can work on intrusion machines known design relatively light tools are used, because the mold filling takes place much more slowly and therefore lower filling pressures up to about 100 bar occur.

A disadvantage of known systems is the batch filling of the forms and the resulting idle times of the Ex truders and the uncontrolled pressure surges when reached of the full state.

Another disadvantage arises from the fact that after filling one Single shape uncontrolled cavity due to core shrinkage education occurs and that the individual forms mechanically or have to be moved by hand.

With the device according to the invention, these disadvantages can be avoided be eliminated. By opening the filling valve prematurely the shape that follows the shape when it is filled the rest of the mold filling slows down and thereby ver a pressure surge avoided. Since all inlet valves are open in the operating state, except for a short shutter speed one form for emptying of the molded part, the emphasis remains on the filling time of the whole Mold battery insist on each individual mold, reducing the shrinkage cavities are minimized and uninterrupted work of the Extruder is made possible.

The function of the inventive device will now be described and explained with reference to the drawings, FIG. 1 and FIG. 2.

When starting up, an extruder 1 , FIG. 1 conveys thermoplastic melt via a distributor head 2 and channels 3 arranged in a star shape in mold filling nozzles 4.1-4.8 ( FIG. 2). Each form filling nozzle is equipped with a slider or other melt closure element 6.1 - 6.8 .

The system parts 2 - 6 are located in a thermally adjustable heating chamber 5 ( Fig. 1).

In the present embodiment there are eight shapes at the distribution star. This number can vary from a minimum of two to be varied to a variety.

After filling the distributor star 2 , 3 , 4 melt flows through the inlet slide 6.1 , which is in the open position when starting the device, in the form 7 , which can be provided with a cooling jacket. As the mold filling progresses, the mold wall heats up in the direction of the mold exit 8 . Before full filling, a signal for opening the slide 6.2 is given by the rising temperature via a thermal sensor 9 . This process is repeated from 6.2 to 6.3 etc. to 6.8. In this state, the extruder conveys the rest to full filling through the slide 6.7 and the last of the eight molds through the slide 6.8 . In this state, the slide is open on all molds.

While the slide 6.1 - 6.8 are set from the closed position to the opening when the mold battery is filled for the first time, during further operation the slide 6.1 must be closed before the remaining mold 7.8 is filled and during the closing time the molded part after the flap 8 has been opened by steam, Press air or the pressure of the subsequent melt can be ejected. After the mold has been emptied, the flap 8 is closed again and the filling slide 6.1 is opened. The ejection process must be completed from before the remaining filling of 7.8 has taken place.

This switching sequence after the first emptying process corresponds to the normal operating state. The period of time from the temperature signal on the mold wall (beginning of the remaining filling) to the end of the remaining filling is determined experimentally and, if necessary, selected by moving the temperature sensor 9 in the direction of the longitudinal axis of the mold so that the emptying, closing and reopening process of the filling slide is completed before the The rest of the mold has been filled in the previous form.

If the emptying process is carried out by the pressure of the subsequent melt, the flaps 8 are omitted, since the form closure is achieved by length-adjustable mechanical stops for the mold parts. The chamber opening after a filling cycle of the entire molded battery is then done by releasing the mechanical stop or an equivalent clamping device.

The mold battery is firmly anchored on the frame 10 , with easy replacement of the individual molds by means of quick-release fasteners ensuring good variability of the device. Since all molded parts are installed stationary, the lengths of the individual molds are not tied to the machine dimensions.

Claims (4)

1. Apparatus for the production of molded parts from thermoplastic materials by intrusion, characterized by a stationary arrangement of a mold battery with at least two molds, which are filled in succession by a continuous melt flow, the respective subsequent mold filling by releasing the mold before the end of the filling process The melt feed begins and the remaining filling takes place under reduced pressure. 2. Device according to claim 1, characterized in that the filling pressure on all forms over the whole filling and Cooling phase with a short break to the molded part emptying remains intact. 3. Device according to claim 1 and 2, characterized in that that the molding output by the pressure of the cooling water injected in the hot area and / or Compressed air takes place. 4. The device according to claim 1 and 2, characterized in that the molding output through the subsequent melt pressure takes place, the form and inlet closure through the molded part to be ejected is stopped.