Electrically controlled tripping mechanism

A detent mechanism comprising

• a support member having a fixed seating member comprising opposite sides:
• a first spring for exerting a first spring force, disposed between one side of the fixed seating member and a first slidable seating member, further comprising
• a second spring member exerting a second spring force less than said first spring force, disposed between the other side of said fixed seating member and a second slidable seating member, whereby the forces of the springs are directed to operate on said first and second slidable members in opposite directions,
• means for applying an external force to the first slidable seating member to move the first slidable seating member from a first position relative to the fixed seating member to a second position against the action of said first spring force, and
• means-for releasably connecting the first slidable seating member to said second slidable seating member when said first sliding member is in its second position and said second slidable member is in a first position, such that when said members are not acted on by said external force, said first slidable member returns towards its first position and said second slidable member is constrained to move with said first slidable member to a second position, the resultant force on both said slidable members in the direction of said first spring force being the difference between said first spring force and said second spring force characterised in that the releasably connecting means
• comprises an electromechanical arrangement carried by one of said suitable seating members, which arrangement includes a detent and an electrically energised device for controlling the movement of said detent.