| 摘要 |
<p>Safety value for pressure cookers consists of a counterbalanced relief valve having a ball held in its seat by a weight. Above this is an actuating knob. The valve can be lodged open by pulling up the knob and rotating it. The knob has a hollow short shaft which slides around a short shaft extending from the top of the weight. A bar runs through the outer shaft and a slot in the inner one. When the knob is pulled, the bar lifts the weight and opens the valve. If the knob is pressed, it does not exert extra pressure on the valve seat because of the slot, and thus the valve always relieves at the set pressure. Used on pressure cookers and autoclaves esp. for rapid cooking of food. The problem with conventional values is that if pressure is applied to the knob on top, this increases the pressure inside the vessel and can damage it, also causing accidents and injury to the person using it. The valve described cannot be held down in this way.</p> |
