Patent Number: 054904188
Section: claims

1. A device for measuring a force which would be exerted by a spring of a supporting grid on a fuel rod of set diameter passing through the grid, comprising: an elongate body; a pair of flexible blades parallel to the direction of elongation and connecting the body to a pair of respective beams insertable in a cell, a force sensor connected to at least one of the beams for contact against the spring; a unit slidable in and along the body between a position in which it moves the beams apart while keeping them parallel to give them a spacing that corresponds to said set diameter, and a position in which it allows the flexible blades to move the beams towards each other; and means moving said movable unit at will between said two positions. 2. A device according to claim 1, wherein said unit comprises a longitudinally displaceable connecting rod connected to the beams by arms that make up a virtual deformable parallelogram. 3. A device according to claim 1, wherein said unit comprises at least two sets of ramps co-operating with cams provided on the beams. 4. A device according to claim 1, wherein said displacement means have adjustment elements limiting a stroke thereof and limiting an extent by which the beams may spread apart to an amount equal to said set diameter. 5. A device according to claim 4, wherein the adjustment elements comprise a stop-forming bush longitudinally displaceable and limiting the amount of displacement away from a rest position of an assembly belonging to the moving unit and comprising a piston and a piston rod, and a wedge for bearing against the bush and enabling the longitudinal position thereof to be adjusted. 6. A device according to claim 1, for measuring a force exerted by a double spring having two active branches, one on either side of a common cell wall, said device comprising two sets each having one said pair of beams and one said pair of flexible blades, carried by a common housing. 7. A device according to claim 6, wherein the two sets are independently mounted on the common housing by means enabling them to pivot about an axis parallel to a direction along which the beams can spread apart. 8. A device according to claim 6, wherein an outer one of said blades in each set is less flexible than an inner one of said blades thereof and said inner blade is designed to bear against the double spring.