| 摘要 |
<p>A simultaneous biaxial stretching machine comprises two chain conveyor paths, each of the chain conveyors carrying clamps which grip the edge of the foil and pull it forwards while stretching it sideways and forwards. The conveyor paths initially run parallel, then diverge in the biaxial stretching zone, then again run parallel. Each path has two guide rails, in which the rollers at the articulations of the chain conveyors run; these guide rails run parallel initially, then converge so that the zig-zag form of the chain links becomes stretched so that the chain advances rapidly stretching the sheet forward, then again run parallel in the last parallel zone. In the diverging stretching zone an endless conveyor belt fitted with permanent magnets runs parallel to the chain guide track; the links of the chain carry magnetic material which is attracted by these magnets and therefore the links are pulled towards the conveyor belt. The speed of advance of the conveyor belt is greater than the speed of the foil. Pref. the magnetic facing on the links is of a hysteresis material or of a copper plate having a magnetically soft material facing. The effect of the conveyor belt with its magnets is to flatten the zig-zag form of the links of the chain, i.e. to promote the convergence of these links, which considerably reduces the friction forces and prevents jamming of the chain and excessive wear in the guide rails.</p> |
