| 摘要 |
<p>The invention relates to a novel valve unit for air expulsion devices which are composed primarily of components which are detachably connected to one another, the elements, namely the piston and cylinder, which are subject to particularly strong stresses being constructed according to the invention in such a way that for example the two basic faces of the cylinder which are stressed by the piston constitute circular rings which do not overlap. Consequently, the wear of the piston which is of completely symmetrical construction also takes place on circular ring faces which do not overlap. After the occurrence of relatively large wear phenomena, a piston of the kind proposed according to the invention can be re-used like a completely new piston by rotating it through 180 DEG . When using special material combinations for piston and cylinder, the valve unit can also be used at high operating temperatures and operated in an oil-free manner and then also used to eliminate flowing problems for bulk food materials.</p> |
