Patent Number: 
Section: claims

1. A gripper mechanism for moving an object having a surface cavity, the gripper mechanism comprising:an actuation end moveable in an axial direction;a rotary body;a first mechanism configured such that movement of the actuation end in an axial direction rotates the rotary body;a gripper moveable between an engaged position and a disengaged position, wherein in the engaged position the gripper is capable of engaging an object and in the disengaged position the gripper is capable of being received into and removed from a cavity of an object,wherein the gripper is connected to the rotary body by a second mechanism configured such that rotary motion of the body moves the gripper between the engaged position and the disengaged position; anda latching arrangement comprising an internal latch enclosed within the gripper mechanism, wherein:the latching arrangement is configured to prevent the gripper moving from the engaged to the disengaged position before the actuation end is moved by a predetermined distance; andthe latching arrangement is configured such that axial movement of the actuation end in a direction opposite to a desired direction of motion of the gripper mechanism at least partially unlatches the latching arrangement. 2. The gripper mechanism according to claim 1 comprising a linear actuator, wherein the actuation end is defined at one end of the linear actuator. 3. The gripper mechanism according to claim 2, wherein the first mechanism is provided between the linear actuator and the rotary body. 4. The gripper mechanism according to claim 1 wherein the internal latch is configured such that axial movement of the actuation end in the direction opposite to the desired direction of motion of the gripper mechanism unlatches the internal latch. 5. The gripper mechanism according to claim 1 wherein the first mechanism comprises a pin and a curved pathway, the pin being arranged to move along the curved pathway. 6. The gripper mechanism according to claim 5, wherein the curved pathway has a tick shape arranged so that when the gripper is in the engaged position the pin is at a tip of the tick, and arranged such that axially downward movement of the actuation end by a predetermined distance is required before the pin and actuation end can move axially upward. 7. The gripper mechanism according to claim 1 wherein the latching arrangement comprises an external latch, and wherein at least a portion of the external latch is positioned external to a volume defined by a remainder of the gripper mechanism such that the latch can be actuated by a component external to the gripper mechanism. 8. The gripper mechanism according to claim 1, wherein a biasing element is arranged to resist axial movement of the actuation end. 9. The gripper mechanism according to claim 1, wherein the gripper is configured such that in the engaged position at least a portion of the gripper is positioned more radially outward from a central longitudinal axis of the gripper mechanism than in the disengaged position. 10. The gripper mechanism according to claim 1 comprising an indicator configured to indicate the position of the gripper. 11. The gripper mechanism according to claim 1, wherein the gripper mechanism is a nuclear fuel rod gripper mechanism, and in the engaged position the gripper is capable of engaging a cavity in a plug end of a fuel rod and in the disengaged position the gripper is capable of being received into and removed from a cavity in a plug end of a fuel rod. 12. A gripper mechanism for moving an object having a surface cavity, the gripper mechanism comprising:an actuation end moveable in an axial direction;a rotary body;a first mechanism configured such that movement of the actuation end in an axial direction rotates the rotary body;a gripper moveable between an engaged position and a disengaged position, wherein in the engaged position the gripper is capable of engaging an object and in the disengaged position the gripper is capable of being received into and removed from a cavity of an object,wherein the gripper is connected to the rotary body by a second mechanism configured such that rotary motion of the body moves the gripper between the engaged position and the disengaged position;a latching arrangement configured to prevent the gripper moving from the engaged to the disengaged position before the actuation end is moved by a predetermined distance,wherein the latching arrangement comprises an external latch and at least a portion of the external latch is positioned external to a volume defined by a remainder of the gripper mechanism such that the latch can be actuated by a component external to the gripper mechanism; anda housing wherein the external latch comprises one or more latch arms engageable with the housing. 13. The gripper mechanism according to claim 12, wherein the latch arms comprise one or more engagement features and the housing comprises one or more complimentary engagement features. 14. The gripper mechanism according to claim 13, wherein the engagement feature of the housing comprises circumferential grooves provided at two axial locations on the housing; a first groove corresponding to a position where the gripper is in the disengaged position and a second groove corresponding to a position where the gripper is in the engaged position. 15. The gripper mechanism according to claim 12, wherein the latch arms are biased to a position of engagement with the housing. 16. The gripper mechanism according to claim 12, wherein the gripper mechanism is a nuclear fuel rod gripper mechanism, and in the engaged position the gripper is capable of engaging a cavity in a plug end of a fuel rod and in the disengaged position the gripper is capable of being received into and removed from a cavity in a plug end of a fuel rod. 17. The gripper mechanism according to claim 12, wherein the latching arrangement comprises an internal latch enclosed within the gripper mechanism. 18. A gripper mechanism for moving an object having a surface cavity, the gripper mechanism comprising:an actuation end moveable in an axial direction;a rotary body;a first mechanism configured such that movement of the actuation end in an axial direction rotates the rotary body;a gripper moveable between an engaged position and a disengaged position, wherein in the engaged position the gripper is capable of engaging an object and in the disengaged position the gripper is capable of being received into and removed from a cavity of an object,wherein the gripper is connected to the rotary body by a second mechanism configured such that rotary motion of the body moves the gripper between the engaged position and the disengaged position, and the gripper is configured such that in the engaged position at least a portion of the gripper is positioned more radially outward from a central longitudinal axis of the gripper mechanism than in the disengaged position; anda guide plate at a position axially beneath the gripper, wherein the guide plate is configured to guide the gripper between the engaged and the disengaged position. 19. The gripper mechanism according to claim 18, wherein the gripper mechanism is a nuclear fuel rod gripper mechanism, and in the engaged position the gripper is capable of engaging a cavity in a plug end of a fuel rod and in the disengaged position the gripper is capable of being received into and removed from a cavity in a plug end of a fuel rod.