Patent ID: 8235240

Claim:
A fuel tank comprising an inner tank ( 3 ), of flat design, which is surrounded by an outer tank ( 1 ) and serves to hold a cryogenic liquid, the inner tank comprises: (a) a longitudinally extending, single-piece basic body ( 4 ) having a top wall ( 5 ) and a base wall ( 6 ) which are connected by means of likewise longitudinally extending side walls ( 7 ), and having at least two longitudinally running, substantially straight webs ( 9 ) which connect the base wall ( 6 ) to the top wall ( 5 ) so as to form at least one longitudinally extending chamber ( 10 ) which is arranged between the webs and which extends over the entire length of the basic body ( 4 ) and in each case from the base wall ( 6 ) to the top wall ( 5 ), with the longitudinally extending chamber having a predetermined width between the webs, (b) at least two caps ( 11 ) which sealingly close off the two open ends of the basic body ( 4 ) in each case at the periphery, and (c) with at least one of the top wall and base wall having, in each case with respect to a planar reference top wall and reference base wall, a bulge with a spacing, measured centrally between the webs, in each case between the inner contour of the top wall and base wall and the planar reference top wall and reference base wall, of less than 30% of the width of the chamber, wherein the webs have a cutout ( 30 ) in the region of the fastening of the caps ( 31 ) to at least one of the base wall and top wall, and wherein the caps are fastened by means of an encircling weld seam, to the basic body, and the webs have the cutout ( 30 ) in each case in the region of the weld seam, between the caps and the basic body.