Air-bag and a method of controlling pressure within an air-bag

An air-bag comprising:

• a first vent aperture defined by the air-bag, the first vent aperture being substantially closed by a membrane;
• and
• a second vent aperture defined by the membrane, the second vent aperture having a smaller diameter than the first vent aperture, the membrane being formed of an elastic material;
• wherein the membrane is formed of a silicone rubber material with a minimum percentage of elongation of at least approximately 450% to maintain a constant maximum pressure inside the air-bag under various impact conditions.

A method of controlling pressure within an air-bag, the method comprising:

• providing the air-bag with a fabric defining a first vent aperture;
• securing a membrane to the air-bag such that the membrane extends across and substantially seals the first vent aperture, the membrane defining a second vent aperture and being formed of an elastic material having a minimum percentage elongation of at least approximately 450%;
• and
• enlarging the second vent aperture of the membrane as a function of pressure within the air-bag to substantially maintain a constant maximum pressure within the air-bag.