Air bag restraint systems

Claim 2

An air bag restraint system comprising an air bag module (20) adapted to be located centrally of a steering wheel (10) and secured with respect thereto by at least one fastening means (54), said air bag module (20) including an inflator (23) and screw means (38) for arming said inflator (23), characterised in that interlock means (45, 55) is associated with said screw means (38) which will, prevent release of said fastening means (54) until the inflator (23) has been disarmed and provide an indication of whether the inflator (23) is armed or not.

Claim 3

An air bag restraint system according to Claim 1 characterised in that said interlock means (45, 55) comprises a slide (45) which is movable between a first position in which it is clear of said fastening means (54) and a second position in which it prevents release of said fastening means (54).

Claim 4

An air bag restraint system according to Claim 2 characterised in that in said second position, the slide (45) overlays said fastening means (54).

Claim 5

An air bag restraint system according to Claim 2 or 3 characterised in that the slide (45) is resiliently loaded from its first position to its second position.

Claim 6

An air bag restraint system according to any one of Claims 2 to 4 characterised in that a first formation (55) on said screw means (38) engages a complimentary formation (62) on the slide (45) to lock the slide (45) in its second position when the inflator (23) is armed.

Claim 7

An air bag restraint system according to Claim 5 characterised in that a second formation (56) on said screw means (38) engages a complimentary formation (60) on the slide to hold the slide (45) in its first position, when the inflator (23) is disarmed.

Claim 8

An air bag restraint system according to Claim 6 characterised in that said first and second formations (62, 60) on the slide (45) and the complimentary formations (55, 56) on said screw means (38) are arranged to engage sequentially as said screw means (38) is screwed up to arm the inflator (23), there being an intermediate position at which neither formation (62, 60) engages its complimentary formation (55, 56) when the slide (45) is free to move from its first to its second position.

Claim 9

8 . An air bag restraint system according to any one of Claims 5 to 7 characterised in that the slide (45) is free to move from its second position to its first position when said screw means (38) is fully unscrewed and the inflator disarmed (23).

Claim 10

An air bag restraint system according to any one of Claims 5 to 8 characterised in that the slide (45) is arranged to move transverse to the axis of said screw means (38), said slide (45) having a longitudinal flange formation (52), a collar formation (56) on said screw means (38) being adapted to engage a portion (60) of the flange formation (52) of reduced height, when the slide (45) is in its first position and the inflator (23) is disarmed; and an enlarged diameter portion (55) of said screw means (38) being adapted to engage in a part circular recess (62) in the flange formation (52) when the slide (45) is in its second position and the inflator (23) is armed, a circumferential groove (57) being provided between the collar (56) and enlarged diameter portion (55) of said screw means (38), said groove (57) permitting movement of the flange formation (52) past said screw means (38) as said screw means is screwed to arm the inflator (23).

Claim 11

An air bag restraint system according to any one of the preceding Claims characterised in that a cover plate (65) is provided to prevent access to said screw means (38) when the inflator (23) is armed.

Claim 12

An air bag restraint system according to Claim 10 characterised in that a formation (66) on said cover plate (65) engages said screw means (38) when the inflator (23) is disarmed, in order to prevent closure of the cover plate (65).