| 摘要 |
In a hot-runner injection moulding device with a fixed needle, an injection part with an injection nozzle is separated from the mould plate by an insulating air gap; a nozzle seal with an internal bore extends through the air gap around the injection opening. A hot-runner extends from a hot-runner block through the injection part at an angle and into the nozzle seal. The heat-conducting, fixed needle is centred in the injection part in alignment with the nozzle seal and with the injection opening and projects directly upstream from the injection opening, at an acute angle, from the injection part into the hot-runner in a position in which the tapered end runs in the nozzle seal towards the injection opening. The size of the tapered end and the axial position of the needle are chosen such that the ratio of the surface area of the injection opening to the smallest area of the annulus between the inner wall of the nozzle seal and the outer surface of the tapered end of the needle, through which the melt flows, is 2:1 to 1:2. The heat supply to the hot-runner takes place principally from the exterior, from the injection part, however also from the injection part, via the fixed needle, as far as the tapered end thereof, by means of which additional heat is supplied in the region of the injection opening and the melt is held at a more uniform temperature with the reduction of streaking. <IMAGE>
|
