Abstract: An inflator for an airbag system has a target mounted in the pressurized gas contained in the inflator. An ultrasonic transducer is mounted on an external surface of the inflator in alignment with the target. The transducer generates and receives reflected ultrasonic signals from the target. The time-of-flight of the signals which are dependent on the gas pressure are used to determine the gas pressure in the inflator. Temperature compensation is provided by fabricating the target of bimetallic material which changes the spacing of the target from the transducer with temperature or providing a temperature sensitive element, e.g. a thermocouple to electrically provide temperature compensation.

Abstract: A low pressure sensing device for sensing pressure changes in a pressurized gas storage bottle of an inflater. At least one wire is wrapped around the vessel to sense the expansion or contraction of the vessel due to pressure changes in the vessel. The wire has a first end and a second end. The first end of the wire is secured to the vessel and the remainder of the wire is free to move circumferentially relative to the vessel in response to the expansion and contraction of the vessel. This relative movement can be monitored to determine if a pressure change has occurred in the vessel.

Abstract: A hybrid inflator has porous substrate coated with a heat-producing, essentially non gas-producing composition for heating pressurized inflation gases in the inflator.