Inflatable seat belt having defined shape

An inflatable seat belt for restraining movement of an occupant in a vehicle, comprising:

• a webbing attached to the vehicle and extending for restraining movement of the occupant;
• an inflatable portion fixed to the webbing and contacting the occupant when the webbing is worn, said inflatable portion including an elastic inflatable tube having an elongated shape and heat resistance, and fixed to the webbing;
• a knitted member in a flat form and connected at both longitudinal ends to the webbing to entirely cover the inflatable tube, said knitted member having elasticity in a direction perpendicular to a longitudinal direction of the webbing and non-elasticity in the longitudinal direction of the webbing;
• and a non-expandable cover for substantially completely covering the knitted member and having a joining portion extending along the longitudinal direction of the webbing without connecting to the knitted member, said joining portion having a first part corresponding to a chest of the occupant and at least one second part situated adjacent to the first part, said first part being weaker than the second part in strength;
• a tongue fixed to the inflatable portion and having a gas flow path therein;
• and
• a buckle attached to the vehicle and engagable to the tongue, said buckle having a port to supply a gas to the inflatable portion through the gas flow path of the tongue so that when the inflatable tube is inflated by the gas, the knitted member expands laterally at the portion corresponding to the first part while breaking the first part, expansion of the knitted member being restricted by the second part.