Patent Number: 
Section: claims

1. A drilling instrument for machining tubes in tube sheets of heat exchangers in a radioactive environment, comprising:a support device;a transport device having retaining elements; anda drilling device having retaining fingers and a resting plate;wherein the transport device, and the drilling device are located proximate to each other and are each connected to the support device, such that the retaining elements and the retaining fingers are arranged on a common first side of the transport device and of the drilling device,wherein the support device has a support plate and wherein the resting plate is located proximate to and supported by the support plate,wherein the support plate is connected to the resting plate by at least one connecting element that is movable between a first position and a second position,wherein the resting plate is fixed in position relative to the support plate when the at least one connecting element is in the first position, andwherein the resting plate is movable relative to the support plate when the at least one connecting element is in the second position. 2. The drilling instrument as claimed in claim 1, wherein the transport device has at least four retaining elements on the first side which are subdivided into two groups, wherein each group is controllable separately, wherein a first group of the two groups is capable of pivoting with respect to the second group, and wherein at least one of the two groups is displaceable with a linear movement. 3. The drilling instrument as claimed in claim 2, wherein the drilling device has at least two retaining fingers, and wherein the retaining elements of the transport device and the at least two retaining fingers are movable in a direction perpendicular to the first side. 4. The drilling instrument as claimed in claim 1, wherein the drilling device has at least two retaining fingers, and wherein the retaining elements of the transport device and the at least two retaining fingers are movable in a direction perpendicular to the first side. 5. The drilling instrument as claimed in claim 4, wherein the support plate or the resting plate has at least one limiting element which is arranged in a recess, and in that the shape of the recess allows play in the second position of the connecting element. 6. The drilling instrument as claimed in claim 5, wherein the support plate or the resting plate has at least one approximately conical or frustoconical centering element that is configured to cause the support plate and the resting plate to be arranged in a predefined position with respect to one another when the connecting element is positioned in the first position. 7. The drilling instrument as claimed in claim 4, wherein the support plate or the resting plate has at least one approximately conical or frustoconical centering element that is configured to cause the support plate and the resting plate arranged in a predefined position with respect to one another when the connecting element is positioned in the first position. 8. The drilling instrument as claimed in claim 7, wherein the connecting element has a pneumatic or hydraulic drive device that is configured to cause the connecting element to be movable selectively into the first position or the second position. 9. The drilling instrument as claimed in claim 1, wherein the connecting element has a pneumatic or hydraulic drive device that is configured to cause the connecting element to be movable selectively into the first position or the second position. 10. The drilling instrument as claimed in claim 9, wherein the drive device contains a biasing spring that is configured to cause the resting plate to be held with the support plate in the second position when the drive device is switched off. 11. The drilling instrument as claimed in claim 9, wherein the drive device has a hydraulic or pneumatic drive mechanism configured to apply an opposing force to that of the biasing spring such that the connecting element is movable into the first position by a predefined distance perpendicular to the first side. 12. The drilling instrument as claimed in claim 11, wherein a peg or pin is arranged on the support plate and is operable to apply a lifting force to the resting plate such that the resting plate is capable of being moved a predefined distance in the direction of the second position. 13. The drilling instrument as claimed in claim 9, wherein a peg or pin is arranged on the support plate and is operable to apply a lifting force to the resting plate such that the resting plate is capable of being moved a predefined distance in the direction of the second position. 14. The drilling instrument as claimed in claim 13, wherein the peg or pin applies the lifting force to the resting plate in a location on the surface of the resting plate that is colinear with the center of gravity of the drilling device. 15. The drilling instrument as claimed in claim 14, wherein the lifting force is no more than 10% higher than is necessary to offset the opposing weight force of the drilling device. 16. The drilling instrument as claimed in claim 15, wherein the functions of one or more of the transport device, the drilling device, and the retaining element are controllable by a control device. 17. The drilling instrument as claimed in claim 1, wherein the functions of one or more of the transport device, the drilling device, and the retaining element are controllable by a control device. 18. The drilling instrument as claimed in claim 1, wherein the support plate or the resting plate has at least one limiting element which is arranged in a recess, and in that the shape of the recess allows play in the second position of the connecting element. 19. The drilling instrument as claimed in claim 1, wherein the support plate or the resting plate has at least one approximately conical or frustoconical centering element that is configured to cause the support plate and the resting plate to be arranged in a predefined position with respect to one another when the connecting element is positioned in the first position.