Inflatable seat belt unit

An inflatable seat belt unit, comprising:

• an elongated belt for restraining an occupant in a vehicle;
• at least a portion of said elongated belt being formed in a bag-shape;
• said bag-shape portion being maintained, in a normal case, in a generally flat shape;
• gas generating means for inflating said bag-shape portion in an emergency;
• a tongue connected to an end of said elongated belt;
• a buckle unit capable of being fixed to the vehicle;
• said tongue being removably insertable and engageable with said buckle unit;
• said buckle unit is provided with a buckle side gas flow hole which communicates with said gas generating means;
• said tongue is provided with a tongue side gas flow hole which communicates with said bag-shape portion;
• when said tongue is in an inserted and engaged state with said buckle unit said buckle side gas flow hole and said tongue side gas flow hole communicate with each other and a gas flowing passage is formed which communicates said gas generating means with said bag-shape portion of said belt;
• wherein said buckle unit is provided with a buckle side cap which is constructed to close said buckle side gas flow hole during said normal case and which is constructed to open said buckle side gas flow hole in an emergency after being ruptured by gas released from said gas generating means, and further said tongue is provided with a tongue side cap which is constructed to close said tongue side gas flow hole during said normal case and which is constructed to open said tongue side flow hole in an emergency after being ruptured by said gas;
• and
• wherein a filter is provided in said tongue side gas flow hole, said filter preventing intrusion of foreign objects into said bag-shape portion of said belt.