Subsea electric actuators and latches for them

A subsea electric actuator comprising:

• an electric motor;
• an operating member;
• a drive unit;
• a telescopic drive connection from said motor to said drive unit, which can be moved to and fro and converts rotary motion of said connection to linear motion of said operating member;
• a return spring operable on said drive unit to urge said operating member towards a datum state;
• and
• a latch which is operative when set to maintain said drive unit in a predetermined position so as to decouple the action of said return spring, whereby the operating member can be advanced and retracted relative to the drive unit free from the action of said return spring, and is operative on release to allow said return spring to operate on said drive unit to return said operating member to said datum state;
• wherein said latch comprises:
• a bracket pivoted to said drive unit, the bracket carrying a first roller and a second roller for engagement with said first roller;
• means for biasing said bracket to an angular position wherein a force of said return spring on said drive unit is transmitted to said fixed member when said drive unit is in the predetermined position;
• and
• a hammer which is disposed to be held against the force of an operating spring by an electromagnet and is moveable by said operating spring on de-energization of the electromagnet to strike said bracket to rotate said bracket, the rotation of said bracket causing relative rolling movement of said rollers and disengagement thereof.