Inertia switch device

An inertia switch device comprising:

• an inertia mass (4) which is movable from a rest position when the device is subjected to an applied acceleration exceeding a threshold value;
• spaced electrical contact means (16 and 17, and 31 and 32);
• a hinge-like assembly (8) which is mounted independently of the inertia mass (4) and in which two parts (9 and 10) are connected for movement between two over-centre positions on opposite sides of a centre position in which the two parts (9 and 10) are aligned with a common plane, in response to movement of the inertia mass (4) when subjected to said applied acceleration;
• and
• movable electrical contact means (14 and 15) on at least part of the hinge-like assembly (8) and arranged to engage the spaced electrical contact means (16 and 17, and 31 and 32) when the hinge-like assembly (8) is in one of the over-centre positions;
• characterized in that:
• the spaced electrical contact means (16 and 17, and 31 and 32) comprise two first contacts (16 and 17);
• the movable electrical contact means comprise two electrically connected movable contacts (14 and 15);
• the hinge-like assembly (8) is mounted independently of the spaced electrical contact means (16 and 17, and 31 and 32) so that the movable contacts (14 and 15) are respectively movable into and out of contact with the two first contacts (16 and 17) so as to bridge the first two contacts (16 and 17);
• and
• resilient biasing means (26 or 41) are operable, on said movement of the inertia mass (4), to move the hinge-like assembly (8) from said one of the overcentre positions, in which the movable electrical contacts (14 and 15) engage the first electrical contacts (16 and 17, and 31 and 32), to the other of the over-centre positions, and are operable to releasably hold the hinge-like assembly (8) in said other of the over-centre positions.