| 摘要 |
<p>A low flow indicator for monitoring the flow of air or breathable gas to the breathing zone 30 of a respirator helmet 10. The flow indicator has a member 40 with a restricted orifice 44 through which all or part of the air or gas flows, so as to create a pressure differential across the orifice. A pressure sensing device 50 alerts the wearer of the respirator if the pressure differential falls below a predetermined value corresponding to a predetermined flow rate. The indicator can be calibrated by adjusting the size of the orifice 44. The pressure sensing device consists of a vertical tube 52 positioned in the breathing zone 30, open at its top and connected at its lower end to the orifice member 40, so that the pressure differential creates a flow of air or gas through the tube. A float 54, normally seated on a support 56 in the tube 52, is lifted off the support by the flow of air or gas as long as the pressure differential exceeds the predetermined value. The tube 52 is positioned in the field of view of the wearer, so that dropping of the float 54 gives a visual warning that the flow rate of gas or air to the respirator has fallen below the predetermined value. The float 54 may also operate an electrical switch 58 connected to a device 60 providing a visual or audible warning. Operation of the flow indicator is independent of the pressure inside the respirator, so that the indicator can be calibrated and tested before being fitted to the respirator. <IMAGE></p> |
