Tensioning device for a gas bag

[0002] The invention concerns a tensioning device for a head protection restraining system in vehicles, comprising an inflatable gas bag extending between the A-column and the C-column of the vehicle, one end of which is fastened to the A-column and the other to the C-column.

[0003] In its inflated state, the gas bag in such a head protection restraining system is tensioned between the A and C columns, since the increase in volume during the inflation process implies a simultaneous contraction in length. In its tensioned state the gas bag ensures lateral support even with burst windowpanes. As a result of unavoidable leakage losses and/or an intentional gas discharge to dissipate impact energy, the gas bag then relaxes so that it regains its original length and its lower edge hangs down loosely.

[0004] The invention provides a tensioning device for a gas bag of the type described, which ensures that the gas bag remains tensioned between the A and C columns of the vehicle even in its vented state.

[0005] In accordance with the invention, a tensioned spring is arranged between at least one end of the gas bag and its adjacent column. When the length contraction of the gas bag reduces during the venting process, the tensioned spring accordingly relaxes and automatically compensates for the corresponding increase in length of the gas bag to the required amount, in order to maintain the tension of the lower gas bag edge.

[0006] Further features of the invention will become apparent from the attached claims, and from the following description, with reference to the attached drawings, in which:

[0007] FIG. 1 shows a schematic representation of a head protection restraint system in its non-activated state;

[0008] FIG. 2 shows the restraining device in the activated state, and

[0009] FIG. 3 is a schematic representation of a tensioning device with a tensioned spring received within a tube.

[0010] The head protection gas bag module shown in its deactivated condition in FIG. 1 is curved over its entire length and extends between the A and C columns of the vehicle. The attachment points at the gas bag ends are marked A and C, correspondingly. The end of the gas bag adjoining the C-column is not attached directly to the column, but by means of the tensioning device shown in FIG. 3. This tensioning device consists of a cylindrical tube 10, one end of which is pivotally attached to the C-column by means of a bolt 12, a tensioned spring 14 hooked at one end over the bolt 12, and a piston 16 which is movably received in the tube 10 and to which is hooked the other end of the tensioned spring 14. The adjoining end of the gas bag is connected to the piston 16 by means of a traction band 18. The piston 16 is provided with a reverse stroke inhibiting means in the form of two roller bodies 20, arranged between each of the inclined surfaces of the piston and the inner surface of the tube 10.

[0011] When the gas bag is in the state shown in FIG. 1, the tension spring 14 is taut, since the folded gas bag as a whole is fitted to follow a curved shape. Even when the gas bag is in its activated state, as shown in FIG. 2, the tension spring 14 is taut, since the lower edge of the gas bag is shortened on account of the length contraction resulting from the increase in volume of the gas bag.

[0012] As the gas bag is subsequently vented, the lower bag edge, however, progressively regains its original length, but as the tensioned spring 14 shortens at the same rate, the gas bag remains tensioned between the fixing points A and C even after it has become completely vented. The reverse stroke inhibiting means at the piston 16 ensures that the tensioned gas bag, also when under load, provides an effective support and head protection, even in its vented state.