SK121696A3 - Spacer with hexagonal interstices - Google Patents

Abstract

The hexagonal interstices (1) of the spacer proposed are formed by plate-metal strips (3) with two free ends (4, 5), most of the strips extending round several sides (2a, 2b, 2c) of an interstice, the free ends of the strips being welded to the bend lines (6, 7) in other strips (8, 9) of the same kind. The bend lines in the metal strips form the corners of the spacer.

Description

Spacer with hexagonal eyes

Technical field

The invention relates to a spacer for approximately parallel rods which are mounted in the meshes of the lattice, wherein at least the inner meshes of the spacer have a hexagonal cross-section.

BACKGROUND OF THE INVENTION

In Soviet-type reactors, fuel cells are used, the fuel rods of which are embedded in lattices with hexagonal meshes. Also, set reactors and planned reactor types, in which the ratio between the volume of fuel mass and moderator mass are almost the same, have such an arrangement. Depending on the type of fuel cells, some fuel positions can be replaced by tubes equipped with apparatuses, guide tubes for absorbent rods, tubes filled with water or other rod links. The spacer has operative elements, e.g. springs or cams so that the fuel rods can be supported on the stirrups of the lattice spacer if several rods, e.g. guide tubes do not need such supports because they can serve, for example, as a stop to determine the axial position of the fuel cells. It has also been proposed not to use such grids to support the rods, but as a support for mixing elements, for example on flag wings in the form of flags located on the upper edges which spread the coolant flowing between the fuel rods.

If, in the case of rectangular meshes, such spacers are formed by stirrups which extend practically over the entire cross-section and intersect with each other, such through and intersecting yokes are not possible with hexagonal spacers, because in the corners of three meshes each mesh separates from each other. It is therefore the object of the invention to find an inexpensive structure that meets the needs and requirements of the fuel cell.

The known fuel elements of the Soviet construction are formed by first being made of a bent sheet metal strip, the two free ends of which are welded together in a hexagonal sleeve. These sleeves are then welded flat with their hexagonal sides together to form double-walled yokes, which separate the meshes from each other. If water enters the double wall, corrosion may occur in the gap, and the corrosion layers then need to increase in volume. There are tensions in the gap, surface bulging and rupture that compromise the stability of the spacer. The sheet metal strips must be formed relatively thick, so that the double walls are disadvantageous both with regard to narrowing the flow cross section and also to reduce neutron flux through the spacers.

Z pat. EP-A-0 433 493 discloses a spacer for fuel cells, in which a hexagonal sleeve is also produced first by welding the free ends of the bent sheet metal strip.

The upper edges and the lower edges of the tape are not side shims which are bent outward at the corners of the hexagon and are welded to another housing by their free ends. This results in joint welded joints above and below the sleeves, which delimit the adjacent sleeve eyes. Although corrosion in the gap is prevented, these jointly welded calipers have little stability if the material used, i.e. the amount of neutron absorbing material, remains limited. This construction also requires a large number of welds and hence increased costs for the careful production of the grid.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to find another design principle for manufacturing a hexagonal spacer which is advantageous to manufacture and which can be adapted to particular needs by material cost, flow resistance under operating conditions of fuel element usage, amount of neutron absorbing material and other requirements. fuel cell. The invention is based on a grid with meshes which are separated from one another by yokes. The stirrups form the edge of the inner meshes, which are surrounded by edge meshes at the edge of the lattice. While the shape of the meshes at the edge is dependent on how the outer belt surrounding the lattice is shaped from the outside, and under certain conditions the outer belt may be omitted, whereas the peripheral meshes may remain open on the sides, the inner meshes have a polygonal cross-section. denoted by those structural members which extend from one corner of the inner eye to the next corner, or alternatively from the edge meshes to the point at the edge of the lattice and form the sides of the meshes. Each corner of the inner eye is formed by the bent edge of the sheet metal strip, but the free ends of such sheet metal strip do not weld, as mentioned in the production of hexagonal shells, but both free ends of the sheet metal strip are fastened to the bent edges of another sheet metal strip.

By means of this construction, it is usually possible to produce a lattice whose yokes are arranged approximately on a flat surface. In this plane, the sheet strips have only two free ends. Other loose ends as they arise in the construction according to Pat. EP-A-0 433 493 by bending side-by-side inserts are therefore not present. As a result, the stirrups consist essentially of exactly the same portions of sheet metal strips arranged in a plane at a high edge and can all have virtually the same height and the same stability. Thus, it is not excluded that the upper edges or lower edges of the sheet metal strips do not yet have shrink wings fitted, or e.g. shaped projections on said guide tubes.

SUMMARY OF THE INVENTION

Starting from the aforementioned construction, the invention provides for approximately parallel rods, which are embedded in the meshes of the lattice, with the following features on the corresponding spacer:

the inner meshes, i.e. the meshes surrounded by six other meshes, have six corners, if the edge meshes located at the edge of the lattice have at least four sides, the sides of the interconnecting sheet metal strip are each formed with two free ends and each corner of the inner mesh is formed one bent edge of a sheet metal tape, on which one free end of another sheet metal tape is fixed,

In this case, it is usually possible not to use double walls to form the meshes, that is, each side of the inner eye is formed by one side surface of the sheet metal tape, as long as one side surface forms the opposite side surface on the other side of the sheet metal tape of the adjacent eye.

Advantageously, no yoke is made up of welded parts by a plurality of sheet metal strips, but each side of the eye consists of a single transitional piece of a single tape, with just a plurality of sides being formed by one piece strips that extend on multiple sides.

In this case, it is generally advantageous that all the metal strips which form the sides of the inner meshes are welded to each other so that only a weld that extends perpendicularly to the rods is formed. These welds always connect the free end of one sheet metal strip to the bent edge of another sheet metal part, which is equally integral and extends on several sides of the eye.

Starting from the grids described above, it may also first only be required not to use double walls. This then leads to a structure characterized by the above-mentioned features, in which case the metal strips each have at least one pair of mutually opposed side faces, one side surface of which is the side of the inner eye and the other side surface of the side of the adjacent eye.

Each yoke can be formed from a single sheet metal tape in its entirety, which has two free ends and which extends over the entire width of the side of the eye and in many cases forms more yokes. In this case, one end of the sheet metal strip lies either at the edge of the spacer or is connected to the bent edge of another sheet metal strip. These bent edges are then the corners of the meshes. If all the loose ends of the metal strips that form the lattice clamps are always attached to such bent edges, then a hexagonal structure is obtained in which three stirrups each contact each other at each corner of the inner eye, one of these yokes contacting each other at each the corner is formed by the first sheet metal tape, while the two second mutually interconnecting yokes are formed by the second sheet metal tape, which is correspondingly bent at each corner, and the free end of the first sheet metal band is fastened to its bent edge.

A relatively small number of welds is sufficient. Basically, only one type of bent sheet metal tape is required. However, there may also be variations of this type of sheet metal tape due to the formation of edge meshes, support elements such as springs and fuel rod cams, and due to meshes, for example, carrying guide tubes and no such support elements.

Overview of the figures in the drawing

The invention and its preferred development will be explained in more detail below by means of the seven embodiments shown in the seventeen figures.

In FIG. 1 shows the principle of the invention in a first example of a spacer.

In FIG. 2 is a side view and plan view of a sheet metal tape for this first embodiment.

In FIG. 3 shows an embodiment of a spacer according to the invention.

In FIG. 4 shows the type of sheet metal tape in two positions as used for the third embodiment.

In FIG. 5, this third embodiment is shown.

In FIG. 6 shows a section of a spacer according to a fourth embodiment of the invention.

In FIG. 7 shows a type of sheet metal tape according to a fifth embodiment.

In FIG. 8 shows a variation of the basic type of FIG. 7 on the brackets that are held on the guide tubes.

In FIG. 9 shows a spacer according to this fifth embodiment, FIG. 9a the left half, FIG. 9b right half.

In FIG. 10 shows a variation of the basic type of sheet metal tape to the edge walls.

In FIG. 11 shows the structure of the central eye, the adjacent meshes and the sector of the sixth spacer.

In FIG. 12 shows the basic type of sheet metal tape in the sixth and seventh exemplary embodiments.

In FIG. 13 shows the yokes required for the central eye of the seventh exemplary embodiment.

In FIG. 14 shows a variation of these yokes as used for meshes lying on diagonals or containing guide tubes.

In FIG. 15 shows an edge yoke of this seventh embodiment.

In FIG. 16 shows the structure of the central eye, the central region and the spacer sector of this seventh embodiment.

In FIG. 17 shows a complete seventh embodiment, FIG. 17a the left half, FIG. 17b right half.

Examples of the invention

According to the first embodiment of FIG. 1 starts from sheet metal strips which extend over each of the three adjacent sides of the hexagonal inner eye, that is to say, through the three sides 2a, 2b and 2c of the inner eye 1 and thus define the half of the lattice eye. Thus, the sheet metal strip 2 first consists of three stirrups, one side of which represents the sides 2a, 2b, 2c of the inner eye 1, while the opposite sides 2a, 2b, 2c are always the sides of the adjacent eye. Arrows 21, 22 indicate the positions of any operating elements, for example springs or cams.

The sheet metal strip 2 has free ends 4 and 5 which are welded in the direction of the arrow to the corresponding folded edges 6 and 7 of the other sheet metal strips 8 and 9. These additional sheet metal strips 8 and 2 have free ends 10 and 11 by which they are fitted edges of another sheet metal tape 13.

In this way, all the sides of the inner eye 1 are formed from a sheet metal strip which extends over three yokes, here three sides of the individual eye. The free ends 14 and 15 of the metal strips 8, 9 and 13 end at the edge of the spacer.

If the resulting grid is only used as a support structure for the mixing wings (not shown) at the upper edges of the metal strips, the edge of the spacer, indicated by a dashed line, may remain open. These calipers then do not need any operating elements for the fuel rods, the highest safety stop, to maintain a minimum distance of the fuel rods from each other from the sea and from the calipers and their mixing wings.

Fig. 2 shows the most common case where the spacer carries the operative elements, i. cams 20, 21 and springs 22 for supporting fuel rods. These springs 22, which bear with their central c-shaped part on the fuel rods, can be suspended by their resilient ends in the slots 23. Not to mention these cuts, which cannot affect the stability of the calipers, all calipers have the same height. Their upper edges and lower edges each lie in a plane that is perpendicular to the fuel rods (not shown). However, other types of springs may also be used, for example, springs springed out, ie punched out of the yoke itself. It is also possible in many cases to hold the fuel rods only by springs or only by cams.

In order to be able to fasten the free ends of the sheet metal strips to the bent edges, the corresponding free ends have protrusions 24 which engage corresponding grooves 25 which are arranged on the bent edges of the sheet metal strips. By means of the welds which are guided along these bent edges, and thus the bent edges strengthen and extend approximately parallel to the fuel rods, all the metal strips are thus joined to each other, thereby ensuring the mechanical stiffness of all the yokes.

In FIG. 3, the embodiment shown has only inner meshes which are alternately folded on both sides by a bent sheet metal strip 30 and by connecting brackets 31 which consist of a one-piece sheet metal part extending over a single bar bracket, shown only briefly in order to recognize the weld spot for fastening the metal brackets together. With their ends 32, 33 they are fastened to the bent edges 34, 35 of the longer sheet metal strips 30. The sheet metal strips 30 are held by their free ends 36 on the outer yoke 37 extending externally around the spacer.

The spacer includes support members 38 for supporting the fuel rods 39.

If the free ends of these sheet metal strips 30, 31 are welded to the bent edges 34, 35 of other sheet metal strips, the inner eyelets 1, which do not differ in any way from the inner meshes made according to FIG. First

The sheet metal strips of FIG. 4 stretch like the type of FIG. 1, through three yokes, but not U-shaped, only the shape of the letter Z, the arrow 43 indicates the position of the support spring on yoke 40. This yoke connects the two yokes 41 and 42 to each other, carrying the cams 44.

Fig. 4 further shows that by rotating the sheet metal tape 45, the sheet metal tape reaches position 46, with positions 44 and 45 for cams and springs.

In FIG. 5, again to better illustrate the free ends of the sheet metal strips 45, 46 are shown in abbreviated form so that the position of the welds by which the free ends are fastened to the corresponding bent edges 47 is visible.

While the inner meshes 1, which serve to support the fuel rods (not shown), have such support elements 43,

44. 5 shows the eye with which the spacer is held on the guide tube 48. The yokes of this eye carrying the guide tube 48 thus have no cams and springs directed inwardly of the eye. Two metal strips with corresponding cams without cams and one metal stripe without suspended springs must be used for each such eye.

A similar variation of the sheet metal type shown in FIG. 4 is also envisaged for edge meshes, and FIG. 5 shows a peripheral strip 50 on which the free ends of the metal strips involved in forming the edge meshes are fastened.

In addition, it is shown that the free ends 51 of several loose sheet metal strips shown in dotted lines extend beyond the edge of the spacer and are shortened. Otherwise, however, the spacer consists of FIG. 5, similar to FIG. 1, of completely identical sheet metal strips that extend over the three yokes, unless they participate in the formation of the edge meshes and until they are correspondingly shortened.

The same applies to the spacer according to FIG. 6, the sheet metal strips of which correspond to the corresponding sheet metal strips of FIG. 1 differ only in the arrangement of springs and cams.

The basic type of sheet metal tape shown in FIG. 7 from the types according to FIG. 1 and 6 also differ only in the arrangement of the cams and springs. This basic type of sheet metal tape 70 with its free ends 71, 52 and bent edges 73, 74 is only arranged when calipers 75, 76 and 77 are required with cams 78, 79 or springs 80 to support the fuel rods 81, 82. However, if the stirrups formed by the sheet metal tape are to rest against the guide tubes 85, 86, as shown in FIG. 8, the corresponding positions 78, 79 and 80 of cams 78, 79 and springs 80 are not occupied. Thus, a plurality of strands 81, 82 of special shapes are provided to form such meshes.

Consequently, the construction principle of the spacer according to FIG. 9 shown in FIG. 1. Here, although the guide tube eyes are shown on which the metal strips 70 are of the basic type, as well as the metal strips 81 and 82 of special shapes, and which carry the guide tubes 85, 86, they are only in the normal inner eyes 1 which are formed. only from the basic type of sheet metal tape 70, wherein fuel rods are omitted for added clarity.

Further, FIG. 9, it is assumed that the spacer is surrounded by the circumferential zone 91 at the sides. 8 of the sheet metal strips 81 of the special free end shape shown in position 78. then, a sheet metal tape 90 of a further special shape, as shown in FIG. 10. This special shape is used when the free ends 71 of the basic type 70 metal strip, which are necessary to form the edge meshes, are to be fixed to the peripheral bracket 90 and simultaneously supported by corresponding cams 92 of the particular type of fuel rod in the edge. sts.

In FIG. 10, two such sheet metal strips 90, 90 of this particular shape are shown side by side, which can be secured with their free ends to the edge bracket 91. Instead of a sheet metal strand 90 formed by shortening the sheet metal strand 81, yoke, alternately avoided on the opposite side, eg. FIG. 15, the so-called zig-zag shape, which can then be welded by several of its bent edges to the outer bracket 90. This edge structure is only necessary in the shown in FIG. 9a as well as the hexagonal circuit. In another part shown in FIG. 9b, the sheet metal strips 70 of the basic type already contact the corresponding outer strip with their bent edges and can be welded there.

one half of the spacers, only two sides here

In this embodiment according to FIG. 9, the springs in all eyes are directed in the same direction. Tire may be given a preferred direction when it comes to mechanical load and hydromechanics. Conversely, in the case of a hexagonal spacer, such a favorable direction can be avoided if it is formed by rotating in accordance with its symmetry of 60 °

This can be achieved with the types of sheet metal strips of FIG. 7 to 10 and FIG. 12 to 15, as explained by FIG. 11 shows a central inner eye 93 which lies at the intersection of lines 94a, 94b and 94c, which connect the hexagonal edge of the spacer to each other. The sides of the inner eyelet 93 are formed by six sheet metal strips 95 which extend only over two mesh tents. Starting from this central eye are all calipers that intersect with the diagonals 94a, 94b and 94c. formed by such shorter metal strips.

Fig. 11 further shows that the inner meshes, which lie entirely in one sector between the diagonals 94a and 95b, are formed by sheet metal strips 100 that extend along the length of three yokes, thus in this embodiment form three sides of the inner eyelet 1.

The sheet metal strips of FIG. 11 correspond to the mirror positions of the sheet metal tape 70 of the basic type of FIG. 7. In FIG. 12 are shown once again. Since the springs can be suspended in the calipers without disturbing the cams 103 which are opposed from the caliper relative to the springs, the additional springs are hinged on the sides of the sheet metal strip 100 facing the diagonals 94a. In FIG. 2, the recesses 23 shown can be arranged on each surface forming the yoke. In FIG. 11 shows the construction of the sector between the diagonals

94a and 94b with inner eyelets 1 and sheet metal tape, it can also continue to rotate through 60 ° to adjacent sectors between dagals 94a, 94c or 94e, 94c and further rotate to the remaining sectors. The resulting spacer according to the sixth embodiment is rotationally symmetrical with angle. 60 ° symmetry.

Said springs 96 additionally suspended in a plurality of sheet metal strips 100 can also be placed in a sine orientation in the meshes lying on the diagonals. A corresponding embodiment example is shown in FIG. 13 to 17.

This embodiment also starts from the sheet metal strip 100 of the basic type in FIG. 12. For the construction of the central eye 111 (FIG. 15), in which a guide tube, instrument tube, water tube or other rod element which does not need a support element is accommodated, the metal strips 101 and 102 of FIG. 13. If the free end 101 of the sheet metal tape 101 is welded to the corresponding bent edge 108, the formation thus formed corresponds to two welded metal sheets 95 on the central eye 93 in FIG. 11, but the cams and springs are now otherwise arranged. As shown in FIG. inner eye 111 of three sheet metal strips 102.

15, thus forming a tape 101 and three

Starting from this central eye 111 ', on the diagonal 120 the sheet metal strips 106 and 107 (FIG. 14), which, like the metal strip 95 in FIG. 11 only extend over two yokes, namely two sides of the inner meshes lying on the diagonal.

Fig. 16, which as FIG. 11 also shows the construction of the sector of the hexagonal spacer, further showing that in the vicinity of the meshes 113, which, like the central eye 111, do not contain any support rod, other metal strips 102 and 112 of a special type are used.

On the edge of the hexagonal spacer, one edge bracket according to FIG. 15. The spacers of FIG. 17, in which, in addition to six identical edge brackets, a total of sixty sheet metal parts 100 of the basic type, twenty-one sheet metal parts 102 of the special type and twelve sheet metal parts 112 of the special type are used near the guide tubes as well as . On the diagonals further lie three sheet metal strips 101 of a special type, six sheet metal strips 107 of a special type, whereby cams are missing due to guide tubes mounted on the diagonals, and twenty-four sheet metal strips 106 of a special type.

As already mentioned, only springs can be used as supporting elements. It is advantageous to use at least one spring in the eyes which support the fuel rod. It is further preferred to provide cams at least two sides of each eye carrying the fuel rod. By way of example, it can be seen that the springs or cams are usually distributed at equal distances from each other around the periphery of the meshes, with each yoke having a cam projecting into the eye having such adjacent yokes having no cams or springs projecting into this inner eye, but at most have such cams or springs that point into the adjacent eye.

According to the embodiment of FIG. 3 and 15, it may be advantageous if the inner eyelets comprise sheet metal parts that extend over only one yoke. In all embodiments, however, at most, the yokes defining the inner meshes are sheet metal parts that extend over more than two yokes. This reduces the number of welds.

More important than the number of welds and the types of sheet metal tapes used, however, is that the spacer can be welded with high precision in production machines. Sheet metal strips, which have a simple geometry, can accurately bend in mass production and their free ends are already held in the gaps on the bent edges when welding, so that identical, regular meshes from straight stirrups are obtained from one unit without the free ends sheeting tapes usually had to be carefully aligned during welding.

Claims (23)

Spacer with hexagonal meshes on mutually approximately parallel bars which are embedded in the meshes of the lattice, characterized in that the inner meshes (1) have six corners with six sides (2a, 2b, 2c), edge meshes of at least four sides, on the sides (2a, 2b, 2c), the metal strips (3) run with two free ends (4, 5) each, and each corner of the inner eye is formed by a bent edge (6, 7) of the metal strips (3), one free end (4, 5) of another sheet metal tape (8, 9). Spacer according to claim 1, characterized in that each side (2a) of the inner eye (1) is formed by a side surface of the sheet metal strip (3), which on its other side (2a) carries a side surface which forms the side of the adjacent eye. Spacer according to claim 1 or 2, characterized in that each side (2a) is entirely formed by one single sheet metal strip (3), wherein a plurality of sides of the metal strips (3, 8, 9) are formed which extend over a plurality of pages (2a, 2b, 2c). Spacer according to one of the preceding claims 1 to 3, characterized in that all the metal strips (3, only perpendicular) 8, 9) are so welded to each other that they are formed by the rods running through the welds. Spacer according to any one of the preceding claims 1 to 4, for parallel bars which are mounted in lattice meshes, characterized in that the inner meshes (1) have six corners with six sides (2a, 2b, 2c), edge meshes at least four sides, wherein on the sides of the running sheet metal strip (3, 8, 9) they have two free ends, each sheet metal strip (3, 8, 9) having at least one pair of opposed faces, one side surface forming one side (2a) the inner eye (1) and the other side surface forms the side (2a) of the adjacent eye, with a plurality of metal strips (1) each free end of the metal strip is fastened to the bent edge (6, 7) of another metal strip (8, 9); With the metal strips (8, 9), each free end (10, 11, 14, 15) of the metal strips lies either at the edge of the spacer or is always fixed to the bent edge of another metal strips. Spacer according to claim 5, characterized in that each side (2a, 2b, 2c) is formed from a single one-piece sheet metal strip. Spacer according to any one of the preceding claims 1 to 6, characterized in that all the sheet metal strips (3, 8, 9) are arranged on a high edge in a single flat surface side by side and their side surfaces all or at least more than half all of their lateral surfaces have the same height. Spacer according to any one of the preceding claims 1 to 7, characterized in that at least the sides of the plurality of inner meshes (1) are formed by sheet metal parts (3) which extend in each case over the three sides of the inner meshes. Spacer according to one of the preceding claims 1 to 8, characterized in that it has a hexagonal cross-section in which all the inner meshes between the two line lines (94a, 94b, 94c) of opposite corners each have three sides over which they always extend. core sheet metal tape (100). A spreader according to claim 9, characterized in that a metal strip (95, 107) extends over several sides of the adjacent eye is connected to the bent edges of said sheet metal strips (100) extending over three sides. Spacer according to claim 9 or 10, characterized in that a central eye (111) is provided in the center of the spacer, in which three sides are formed by three metal strips (101) extending one over each side. Spacer according to any one of the preceding claims 1 to 11, characterized in that it has a hexagonal cross-section with a central eye (111) located in the center of the spacer, with the highest except for sheet metal parts (101) between the central eye and adjacent inner eyes. are all sides of the inner meshes formed by sheet strips (102) extending over at least two sides. A spacer according to claim 12, characterized in that all the inner meshes of each sector of the six sectors that lie between the connecting lines (94a, 94b, 94c) of the opposite corners of the spacer have only sides formed by longer sheet metal strips (112) wherein the longer sheet metal strips extend over the three tents of meshes lying within the corresponding sector, or extend over at least two sides of the edge meshes or meshes lying on the connecting lines. Spacer according to one of the preceding claims 1 to 13, characterized in that the at least several inner meshes each have at least one sheet metal strip (31) which extends only over one side of the inner meshes and its free ends (32, 33). are attached to the bent edges of two further sheet metal parts (10) having at least two bent edges and extending over at least three sides of adjacent meshes. Spacer according to one of the preceding claims 1 to 10, characterized in that the sheet metal strips (3) are drawn over all sides of the inner meshes (1), which always extend over at least two sides of the inner meshes. Spacer according to any one of the preceding claims 1 to 15, characterized in that at least in the plurality of inner eyes there are at least two sides of the cam (20, 21) which extend inwardly of the inner eye and are designed as a fuel rod storage location. Spacer according to claim 16, characterized in that the two cam-bearing sides are connected to each other by means of at least one non-cam sheet metal strip, or at most one cam (20, 21) or more cams facing adjacent OK. Spacer according to claim 16 or 17, characterized in that the sheet metal tape, which on one side of the inner eye carries one or more cams (20, 21), on its side face opposite to this side has no cams. Spacer according to any one of the preceding claims 1 to 18, characterized in that at least a plurality of inner eyes one side carries a spring (22) which is designed as a bearing on the fuel rod. Spacer according to claim 19 in combination with one of claims 16 to 18, characterized in that all the inner eyes comprising the fuel rod have a spring (22) on one side and a cam (20, 21) on two sides, the spring and the cams are distributed at equal distances from each other around the periphery of the eye. Spacer according to claim 20, characterized in that all the springs (22) project parallel to the interior of the respective eye. A spacer according to claim 20, characterized in that the spacer has a hexagonal cross-section with one central eye and six sectors which are bounded by the connecting lines (120, 121) of opposite corners of the spacer, all except the central inner eye (111) all within In the sector of the eye, the loops carry springs which project parallel to one another in the inner eye and the two adjacent sectors are always offset by 60 ° to each other (Fig. 16). 23. A lattice with meshes separated from one another by yokes, characterized in that the yokes extend between the inner meshes which are each surrounded by six meshes and edge meshes at the edge of the lattice, the inner meshes having a polygonal cross-section, each yoke extending from one corner of the inner eye up to the next corner or to a point on the edge of the lattice, the stirrups are arranged in one flat surface and are formed by metal strips (3, 8, 9) with two free ends (4, 5) and each corner of the inner eye is formed by a bent edge (6, 7) of a sheet metal strip (3, 8, 9) on which one free end (6, 7) of another sheet metal strip (3, 8, 9) is fixed.