Patent Number: 
Section: description

Referring now in detail to the figures of the drawings, which show embodiment examples that relate to spacers with longitudinal webs and transverse webs that form rectangular meshes, and first, particularly, to FIG. 1 thereof, there is seen a longitudinal web 1 and transverse webs 2, 3 and 4 crossing it. The webs form a left-hand mesh in which no spring has as yet been inserted, whereas in a right-hand mesh, a spring 5 protrudes out from the center of the transverse web 2. In this embodiment, a domed, resilient or sprung central part 6 merges at the top and the bottom through a convex curvature 7 into a respective upper end strip 8 and lower end strip 9. A center line of a fuel rod to be inserted in the web is designated by reference symbol Axe2x80x94A. In an operating position, the center line Axe2x80x94A is located in the center between the webs 2 and 4. A profiled section is seated parallel to the center line Axe2x80x94A, on each rim of the two end strips 8, 9 of the spring 5. The spring therefore has four profiled sections of which only an upper front profiled section 10 and a lower front profiled section 11 are visible in FIG. 1. Corresponding rear profiled sections 10xe2x80x2, 11xe2x80x2 are covered and are therefore not shown in the drawing. In addition, the longitudinal web 1 in the right-hand part of FIG. 1 likewise carries a spring. However, that spring protrudes into a mesh located behind the longitudinal web 1 so that FIG. 1 only shows those parts of that spring (otherwise covered) which protrude through openings 12, 13, 14, 15 or are visible through these openings. The visible parts of the (otherwise covered) spring are two end strips 16, 17 and profiled sections 18, 19, 20, 21 seated on their lateral rims. The openings 12, 13, 14, 15 are repeated in the longitudinal web in the left-hand part of FIG. 1. Each of the openings 12, 13, 14, 15 contains a slot-shaped opening part 22, 23, 24, 25 extending in the same direction (namely to the left) transverse to the center line Axe2x80x94A. The profiled sections 18, 19, 20, 21 are seated on ends of the opening parts 22, 23, 24, 25. These profiled sections touch lateral end edges 26, 27, 28, 29 of the slots 22, 23, 24, 25. Each opening part 22, 23, 24, 25 ends in an enlarged opening part 30, 31, 32, 33. In the right-hand part of FIG. 1 it may be seen that the profiled sections 18, 19, 20, 21, which protrude through the slot-shaped opening parts 22, 23, 24, 25 in the operating position of the corresponding spring, can be removed from the openings 12, 13, 14, 15 if they are displaced along the slot-shaped opening parts 22, 23, 24, 25 to the right as far as the enlarged opening parts 30, 31, 32, 33. This displaced position corresponds to an assembly position of the spring. The slot-shaped parts of the assembly openings 12, 13, 14, 15 have a length which practically corresponds to half a distance between the profiled rims of the springs (i.e. practically half the spring width). The enlarged cross-sectional areas 30, 31 therefore come to rest in the center between the end edges 26, 28 and 27, 29 of the slots. The idea of this dimensioning is clear from FIG. 2. When a fuel rod 35 is inserted into the mesh, it presses the resilient central part 6 of the spring 5, with the connected convex curvatures 7, 8, into enlarged cross-sectional openings or snap-in openings 36, 37, which are increased in such a way that their upper edge and lower edges protrude beyond upper and lower dimensions of the spring 5. Therefore, in this way, the convex curvatures 7, 8 are used in order to fix the spring 5 when it is loaded by a fuel rod 35 and presses the fuel rod onto corresponding holding elements (for example knobs or protuberances 38, 39 on a side of the mesh opposite to the spring). Although springs with a C-shape are preferred, other spring shapes, provided they produce the desired spring force, can be combined with the fastening according to the invention. This is shown in FIGS. 3 to 5 using a spring 40 with a hat-shaped or plate-shaped central part 41. FIG. 4, in particular, shows rims 42, 43, 44, 45 on two end parts 46, 47 connected to the central part 41. These rims carry profiled sections 48, 49, 50, 51 which are in contact with respective inner parts 53, 53xe2x80x2 on an inside surface 55 of a wall 56 (represented by interrupted lines). Outer parts 52, 52xe2x80x2 of these profiled sections 48, 49, 50, 51 protrude through the non-illustrated assembly opening and encompass its opening rim. These assembly openings 60, 61, 62, 63 are represented more precisely in FIG. 6. In that figure, end edges of slot-shaped opening parts 70, 71, 72, 73 are designated by reference numerals 65, 66, 67, 68. The profiled sections 48, 49, 50, 51 touch these end edges in the operating position of the spring. In this case, the slot-shaped opening parts 70, 71, 72, 73 do not extend at right angles to the center line of the fuel rod but instead at a certain angle, so the spring must be compressed when it has to be displaced from the operating position into the assembly position. This is only possible while the spring is not loaded by a fuel rod (see FIG. 2) so that, in the loaded condition, the spring is locked in the operating position. In this case as well, the slot-shaped opening parts 70, 71, 72, 73 end in enlarged cross-sectional areas 75, 76, 77, 78. Arrows 79 indicate the width of the springs (the distance between outer side edges of the profiled sections), which correspond to a corresponding width 79 in FIG. 4. A cross section through a different spring, corresponding to FIG. 5, is shown in FIG. 7. This spring is inserted through an enlarged opening area 12xe2x80x2 of an assembly opening provided in a web 1xe2x80x2 through the use of profiled rims of its end strips 8xe2x80x2. The spring is then displaced in the direction of an arrow 79xe2x80x2 along a slot-shaped part 22xe2x80x2 of the assembly opening, sufficiently far for it to butt onto an end edge 26xe2x80x2 of that slot-shaped part. Since the profiled rims determine the size of the opening area 12xe2x80x2, these rims are initially bent toward one another. In this way, upper profiled sections (or all four profiled sections under certain circumstances) can be inserted in the common opening area 12xe2x80x2. In addition, this provides an improvement of a contact surface, through the use of which inner profiled section parts 53a are supported on an inner surface 2xe2x80x2 of the web. Whereas an outer profiled section part 53b encompasses an edge of the web 1xe2x80x2 at a rim of the slot 22xe2x80x2 which is only above and below the plane of the drawing, another rim 53c carries a protuberance which, in this case, is configured in the shape of a barb. In this way, the spring is locked in a snap-in opening 23xe2x80x2 of the web as soon as the operating position is taken up. In an embodiment example shown in FIG. 8, a central part 81 of a spring 80 likewise merges into end strips which extend approximately parallel to the center line of the fuel rod and which have lateral rims 82, 83, 84, 85 that are bent away from the fuel rod and pass through corresponding assembly openings 86, 87. Outer profiled section parts 91, 92, 93, 94, which protrude on the back of a web are, in this case (in a manner similar to FIG. 5), again bent around and spread in order to encompass edges of the openings 86, 87 with a larger surface. However, as a departure from FIGS. 1 to 7, only two slot-shaped opening parts are provided in this case. The upper slot-shaped opening part 86 is associated with the upper profiled section pair 91, 92 and the lower opening part 87 is associated with the lower profiled section pair 93, 94. Enlarged cross-sectional areas 88, 89 connected to the opening parts 86, 87 are located, in this embodiment example, at a position at which one longitudinal wall is crossed by a transverse wall. The spring is therefore inserted in the corresponding webs before the spacer is welded. Although this prevents a damaged spring, for example, from being subsequently changed, it reliably prevents a spring from becoming unintentionally loose if a rod is removed from the fuel assembly during inspection work. In order to fix the spring in the operating position, each end strip 95, 96 carries a locking knob or protuberance 97, 98 which engages in a corresponding locking window 97xe2x80x2, 98xe2x80x2 in the web. The spring can therefore only be removed from the operating position if the corresponding end strips are bent sufficiently far away from the web. In addition, the end strips of FIG. 8 carry further knobs or protuberances 99, 99xe2x80x2 which point in the direction toward the resilient central part and act as a stop that limits the deflection of the resilient central part during loading of the spring. This can prevent the spring from being overstrained and damaged when the corresponding fuel rod is inserted in the mesh. Generally speaking, it suffices if the outer profiled section parts, on the rims of the end strips, which are bent away from the fuel rod and protrude through the assembly openings, are only profiled in one direction, i.e. are configured as support webs which pass through the web in the assembly opening approximately at right angles and extend approximately parallel to the center line of the fuel rod. A bottom of such a first spring 100 is shown on the left in FIG. 9. A central part 101 is substantially covered by end strips 102 and 103 with snap-in knobs or protuberances 104, 105. Four profiled sections 106, 107, 108, 109, which form lateral rims of the end strips 102 and 103 as flat support webs, can be seen. A top of a second spring 110 with a central part 111 and end strips 112, 113 that are covered (and therefore only indicated by interrupted lines) are shown on the right. In this position of the two springs 100 and 110, the two springs are symmetrically placed relative to one another to the extent that the bottom of the first spring 100 points to the bottom of the second spring 110. FIG. 10 shows two parallel webs 120, 121 of the spacer. The spring 100 is inserted from the left into the web 120 and the spring 110 is inserted from the right into the web 121. Profiled sections 106, 116 and 107, 117 on the rims of the two springs 100, 110 differ somewhat in this case. One outer profiled section part 123 of the profiled section 106, which is initially pushed through a non-illustrated assembly opening and protrudes through a slot of the web 120, has a recess 124 with a width b, which is not necessary for the profiled section 116. The width b corresponds approximately to the width of the profiled section 116 at a position where this profiled section 116 merges into an end strip 112. In addition, the spring 110 also differs from the spring 100, as is shown in FIG. 9, by the fact that inner surfaces of web-type rims 116, 118 of the spring 110 are at a distance from each other which is equal to or slightly larger than a distance axe2x80x2 between outer surfaces of web-type rims 106, 108 of the spring 100. The following is achieved, as is shown in FIG. 9, by this profiling: The two springs are already shown in such a way that their central parts point to opposite sides. If the spring 100 is, for example, displaced to the right, this makes it possible for the rims of the spring 100 to be inserted from the left into the corresponding rims of the spring 110, which are rims that point to the left. The two springs can therefore be simultaneously fastened to a common wall in such a way that their end strips are opposite to one another, as is shown in FIG. 11 through the use of a wall 130. The spring 100 is therefore inserted from the left, corresponding to an arrow 131, and the spring 110 is inserted from the right, corresponding an arrow 132, into a widened opening in the wall 130. The springs are displaced in the opening until, at the upper end strips 102 and 112, the profiled sections 106 and 116 of both springs, or the profiled sections 108 and 118, respectively, form a mutually engaging profiled section pair. At the lower end strips 103, 113, a profiled section pair is correspondingly formed from the profiled sections 107 and 117 and a second pair of mutually engaging profiled sections is formed from the profiled sections 109, 119. FIG. 12 shows the wall 130 with an enlarged cross-sectional area before the springs 100 and 110 are inserted in directions corresponding to the arrows 131 and 132 into corresponding assembly openings 134, through the use of their profiled section parts. The profiled sections of the two springs then finally engage in one another and the spring pair can then be displaced laterally along the edge of a slot-shaped opening part into the operating position. FIG. 13 shows a corresponding cross section of the fully assembled spring pair. The cross-sectional plane selected for FIG. 13 is indicated by numerals XIIIxe2x80x94XIII in FIG. 11. FIG. 14 shows the bottom of a spring 150 which represents a combination of the two-springs 100 and 110 from FIG. 9 to the extent that lateral rims 151, 152 of an upper end strip 150xe2x80x2 are formed corresponding to the rims 106, 108 of the end strip 102 of the spring 100. Corresponding lower rims 153, 154 are formed corresponding to the lower rims 117, 119 of the spring 110. If the spring 150 is pivoted about its transverse center line CC, the left-hand spring 150 of FIG. 14 becomes a right-hand spring 160. These two springs 150, 160 can now be combined to form a spring pair in the same manner as has been presented in FIGS. 12 and 13. This embodiment, therefore, only necessitates a single spring type. In a spring 170 of FIGS. 15 and 16, a right-hand upper rim 173 of an upper end strip 171 and a left-hand lower rim 174 of a lower end strip 172 are formed corresponding to the web-type rims of the spring 100. However, a left-hand upper rim 176 and a right-hand lower rim differ from the rim of the spring 100 to the extent that outer profiled section parts 176xe2x80x2, 177xe2x80x2 protruding beyond the web are bent outward over the rim of the slot-shaped opening part. The spring 170 therefore presents a combination of the spring 150 and the spring shown in FIG. 8. In addition, the profiled sections 174, 176 of the spring 170 can also be combined to provide a single profiled section which can be used for all four rims 181, 182, 183, 184 of the spring, as is shown by a spring 180 of FIG. 17. In this embodiment, one profiled section part 185 corresponds to the profiled section part 176xe2x80x2 and another profiled section part 186 corresponds to the profiled section part 174. It may therefore be seen that the fastening according to the invention opens many variation possibilities. In a spacer, such as is shown as a portion of a pressurized water reactor, for example, in FIG. 18, webs 200, 201, 202, 203, etc. generally form square meshes in which two adjacent mesh sides each carry a spring in the center protruding into the mesh. The spring presses the fuel rod of this mesh (the fuel rods are omitted for the sake of clarity) against opposite knobs or protuberances 205. Two individual knobs or protuberances are usually located opposite a spring. The knobs or protuberances are disposed one above the other and respectively above and below the plane in which the spring presses against the fuel rod. In general, each two adjacent meshes (for example meshes 206, 207) form a pair. The springs (for example the springs 110 and 100) which protrude into the meshes of a pair from a common wall separating the meshes of the pair, can be fastened as shown in FIGS. 10 to 17. Since pressurized water fuel assemblies also have some meshes which contain a guide tube 204 on which the spacer is fastened, instead of a fuel rod, there can be deviations in the configuration in pairs of the meshes, so that unpaired springs (for example the spring 5) can also be necessary. Similar relationships can also be caused by water pipes, such as are used in many boiling water fuel assemblies, replacing some fuel rods. FIG. 19 shows a longitudinal section through a part of the meshes 206 and 207 with springs 210, 110 and 100 supported on the webs 200 and 203. An assembly opening can be recognized in a wall 200. The assembly opening is necessary for inserting the spring 210 or a spring pair of which, apart from the first spring 210, only an outer profiled section part is visible, which is respectively formed on side rims of end strips of a second spring. The assembly opening, which in this case is formed of two slot-shaped opening parts 220 and 230, has a widened opening area 221 which is laterally offset relative to the position in which the spring 210 (or the spring pair mentioned above) is located. This widened opening area is advantageously applied at the position of the web at which this web crosses another web 203 in the finally assembled fuel assembly. Therefore, this widened opening area is blocked when the webs are joined together to form a grid-shaped spacer after the insertion of the springs. In accordance with FIGS. 12 and 13, the spring 210 is inserted through the use of the profiled section parts of its end strips from the front of the web shown in FIG. 19. Only inner profiled section parts 250, 251, 252, 253 of the spring 210 remain in the mesh while outer profiled section parts, which are not visible in FIG. 19, protrude into the adjacent mesh. Outer profiled section parts 240, 241, 242, 243 of the other spring are correspondingly pushed from the adjacent mesh (i.e. the back of the wall 200) through an opening area 220xe2x80x3 and the two springs are joined together in such a way that one profiled section pair 240, 250 or 241, 251 or 242, 252 or 243, 253 results in each case. If the widened opening area is to be used to insert corresponding springs in both a position D and in a position E, slot-shaped opening parts (220, 220xe2x80x2, 230, 230xe2x80x2) symmetrically emerge from this opening area toward both sides. These slot-shaped opening parts have edges 221, 222 and 231, 232 at the top and at the bottom, which act as a guide for the profiled section pairs when these profiled section pairs are displaced laterally from the assembly position into the operating position D. In this operating position, two profiled section pairs, namely the profiled section pair 240, 250 and the profiled section pair 241, 251 then touch the end edges 225, 235, located one above the other, of the slot-shaped opening parts 220, 230. Apart from the extremely small material requirement for the fastening of the spring and the great freedom of choice for the shape of the spring itself, the invention has the great advantage of permitting two springs protruding into adjacent meshes to be seated in the same assembly opening in the center of a mesh wall. The principle which is used can be briefly stated by using the spring 5 of FIG. 18 as an example: The spring, of which only an upper end 301 is visible in FIG. 18, has one rim 302, 303 for each of the sides at this upper end. That rim is bent out of the mesh 206 around the center line of the fuel assembly in such a way that it penetrates through an assembly opening 304 into the web 201. These two rims (302, 303) each carry a profiled section which approximately form-lockingly encompasses one edge of the assembly opening 304. The lower end of the spring also has one rim that is correspondingly bent outward on both sides with a profiled section form-lockingly encompassing an edge of the assembly opening. As is shown in the figures, generally each spring (FIGS. 1 through 8) or each pair of springs (FIGS. 11 through 19) is associated with one assembly opening area and at least one snap-in opening in a web. The snap-in opening (e.g. 97xe2x80x2 or 98xe2x80x2 in FIG. 8 and the opening for the snap-in knob or protuberence 98 or 105 in FIG. 10) may be separated from the assembly opening area, but it may as well be integrated into that assembly opening area, especially in the enlarged parts of that area. That is shown in FIG. 1, where the convex curvature 7 snaps in the enlarged part 30 of the assembly opening area, or in FIG. 6, where a concave protrusion 40xe2x80x2 (FIG. 3) of spring 40 snaps in the enlarged part 75. Each assembly opening area is formed of several parts which may be joined into one window or separated from each other. In FIG. 1, for instance, the assembly opening area is formed of four enlarged opening parts 30, 31, 32, 33 and four slot-shaped opening parts 22, 23, 24, 25, each slot-shaped opening part ending in an enlarged opening part. On the other hand, FIG. 8 shows only two slot-shaped opening parts 86, 87 and only two enlarged opening parts (enlarged cross-sectional areas 88, 89) forming one assembly opening area.