Patent Number: 
Section: claims

1. Fuel elements gripping device comprising:a main carriage oriented along a longitudinal axis,a clamp coupled to the main carriage and adapted to grip a head of fuel elements,a secondary carriage oriented along the longitudinal axis and comprising attachment means for attaching the secondary carriage to a lifting/pushing chain, wherein the main carriage and the secondary carriage are coupled to each other by force transmission means, said force transmission means transmitting forces applied to the attachment means when the device is lifted and when the device is pushed horizontally, the force transmission means forming a dismountable connection between the main carriage and the secondary carriage, wherein the main carriage and the secondary carriage are adapted to be uncoupled from each other in a blocked position of the secondary carriage in which the secondary carriage is attached at its attachment means to the lifting/pushing chain, by dismounting the dismountable connection of formed by the force transmission means between the carriages, the connection being dismounted by only applying a pulling force and a pushing force to the main carriage, the pulling force being applied towards the secondary carriage. 2. Gripping device according to claim 1, in which recoupling between the main carriage and the secondary carriage is done, in a blocked position of the secondary carriage in which the secondary carriage is attached at its attachment means to the lifting/pushing chain, by reassembling the connection formed by the force transmission means between the carriages, the connection being reassembled by only applying a pulling force and a pushing force to the main carriage, the pulling force being applied towards the secondary carriage. 3. Gripping device according to claim 1, in which the force transmission means forming a dismountable connection between the main carriage and the secondary carriage comprise:a first key, mounted on the main carriage, the first key being tippable transverse to the longitudinal axis and being in abutment against the secondary carriage to enable forces applied to the attachment means to be transmitted when the pushing force is applied,a second key, mounted on the main carriage, pivotable orthogonally to the longitudinal axis and being in abutment against the secondary carriage to enable forces applied to the attachment means to be transmitted during lifting;wherein the pulling force applied to the main carriage enables tipping of the first key, the relative movement of the main carriage towards the secondary carriage and then pivoting of the second key, until the first tipped key and the second pivoted key each remaining in a position free from abutment with the secondary carriage. 4. Gripping device according to claim 1, in which the main carriage comprises two rigid parts connected to each other by a flexible connection, in which:one rigid part is coupled with the clamp and comprises an electronic weigh-scale to electrically test tension or compression forces applied to said rigid part supporting the clamp;the other rigid part comprises a so-called head carriage which is coupled with the secondary carriage in an assembled state of the fuel elements gripping device, the other rigid part also comprising a gripping socket to which the pulling force and the pushing force for uncoupling the dismountable connection are applied. 5. Gripping device according to claim 1, in which the main carriage comprises:an electric motor,a main carriage body,a hollow shaft mounted in translation on the main carriage body, one of hollow shaft ends being fitted with a screw/nut type drive engaged with the electric motor, and the other of the hollow shaft ends bearing on part of the clamp gripping arms, actuation of the electric motor causing translation of the shaft in one direction and simultaneously moving the gripping arms of the clamp towards or away from each other by tipping orthogonally to the axis. 6. Gripping device according to claim 5, comprising a coupling lever fixed to the main carriage and arranged to form a lever arm to translate the hollow shaft and uncouple it from the clamp, the lever arm being adapted so that it can be manipulated by remote operated means. 7. Gripping device according to claim 6, in whichthe main carriage comprises pins mounted free to tip orthogonally to the longitudinal axis;the clamp body comprises a wall with steps;the hollow shaft comprises relief fixed to its periphery; coupling between the clamp and the shaft being made by the relief tipping the pins and by the tipped pins bearing in contact with the steps in the clamp body. 8. Gripping device according to claim 7, comprising, a peg forming locking means for coupling the main carriage body and the clamp, a the peg being inserted inside the wall of the clamp body transverse to the longitudinal axis of the main carriage body to block one in translation relative to the other, the peg being designed so that it can be removed by remote-operated means. 9. Gripping device according to claim 7, in which:the hollow shaft comprises a projection that extends transverse to the axis forming a shaft flag,the main carriage comprises a first and a second position detector each arranged so as to be facing the flag in a respective given translated position of the hollow shaft to electrically detect a respective given translated position of the relief and therefore detect whether or not the pins are tipped. 10. Gripping device according to claim 9, in which:the clamp body comprises a projection that extends transverse to the axis forming a clamp flag,the main carriage comprises a third position detector arranged to be facing the clamp flag when the clamp is coupled with the main carriage, and thus arranged to electrically detect the presence of the clamp. 11. Gripping device according to claim 5, in which:the clamp comprises a body on which the gripping arms are installed free to tilt and on which a clamp rod is installed free to slide along the axis between the arms,the hollow shaft comprises a rod fixed inside it, the rod of the hollow shaft bearing in contact with the clamp rod, the length of the clamp rod being such that in the near or the far extreme position of the clamp gripping arms corresponding to the gripping position of the fuel element head, there is a direct contact between the fuel element head and the clamp rod. 12. Gripping device according to claim 11, in which:the hollow shaft comprises a projection that extends transverse to the axis forming a shaft flag,the main carriage comprises a first position detector arranged so as to be facing the flag so that it electrically detects direct contact between the fuel elements head and the clamp rod. 13. Fuel elements handling system comprising:a tipping crane comprising a drum in which carriages of the fuel elements gripping device are installed, having:a main carriage oriented along a longitudinal axis,a clamp coupled to the main carriage and adapted to grip a head of fuel elements,a secondary carriage oriented along the longitudinal axis and comprising attachment means for attaching the secondary carriage to a lifting/pushing chain, wherein the main carriage and the secondary carriage are coupled to each other by force transmission means, said force transmission means transmitting forces applied to the attachment means when the device is lifted and when the device is pushed horizontally, the force transmission means forming a dismountable connection between the main carriage and the secondary carriage, wherein the main carriage and the secondary carriage are adapted to be uncoupled from each other in a blocked position of the secondary carriage in which the secondary carriage is attached at its attachment means to the lifting/pushing chain, by dismounting the dismountable connection formed by the force transmission means between the carriages, the connection being dismounted by only applying a pulling force and a pushing force to the main carriage, the pulling force being applied towards the secondary carriage;a handling chain comprising a lifting/pushing chain, wherein part of the lifting/pushing chain is fixed to the attachment means of the secondary carriage of the gripping device, the lifting/pushing chain being adapted to roll the fuel elements gripping device out of the tipping crane drum, when the fuel elements gripping device is in an horizontal position. 14. A method for handling fuel elements with a fuel elements gripping device, wherein if a failure occurs during a handling operation:part of the fuel elements gripping device is attached to mechanical intervention handling means,part of the fuel elements gripping device attached to the mechanical intervention means is uncoupled from the remaining of the fuel elements gripping device attached to a mechanical operational handling means using remote-operated means,said fuel elements gripping device comprising:a main carriage oriented along a longitudinal axis,a clamp coupled to the main carriage and adapted to grip a head of fuel elements,a secondary carriage oriented along the longitudinal axis and comprising attachment means for attaching the secondary carriage to a lifting/pushing chain, wherein the main carriage and the secondary carriage are coupled to each other by force transmission means, said force transmission means transmitting forces applied to the attachment means when the device is lifted and when the device is pushed horizontally, the force transmission means forming a dismountable connection between the main carriage and the secondary carriage, wherein the main carriage and the secondary carriage are adapted to be uncoupled from each other in a blocked position of the secondary carriage in which the secondary carriage is attached at its attachment means to the lifting/pushing chain, by dismounting the dismountable connection formed by the force transmission means between the carriages, the connection being dismounted by only applying a pulling force and a pushing force to the main carriage,the pulling force being applied towards the secondary carriage. 15. Handling method according to claim 14, in which the handling operation is either lifting, or horizontal tipping or horizontal pushing. 16. Method according to claim 14, according to which the actuation of the remote-operated means advantageously applies a pulling force and a pushing force to the main carriage for separating the part of the fuel elements gripping device attached to the mechanical intervention means from the remaining of the fuel elements gripping device.