US 3929569 A
Grid for the retaining or laterally supporting of primarily nuclear fuel rods, comprising plate springs that exert a retaining force remaining constant, irrespective of the degree of compression. A spring may be spotwelded to the grid, snapped into place in a hole in the grid wall, or both.
Description (OCR text may contain errors)
United States Patent Piepers et al.
[ Dec. 30, 1975  PLATE SPRING OR RETAINING GRID FOR 3,646,994 3/1972 Pie ers et al. 176/78 A BUNCH CYLINDRIC L ELEMENTS 3,679,546 7/1972 Nluellner et al. 176/78 ENGAGED IN A H EXCHANGE 3,769,159 10/1973 Zmn et a1. 176/78 PROCESS FOREIGN PATENTS OR APPLICATIONS  lnvemors F Gerhard E 346,144 4 1931 United Kingdom 267/164 1-1e1loo; Leonard Hendrik Vons, 631,061 11/1961 Canada 267/164 Bergen, both of Netherlands  Assignee: g i :ederland The Primary Examiner-Verlin R. Pendegrass ague et er an S Attorney, Agent, or FirmCushman, Darby &  Filed: June 27, 1973 Cushman  Appl. No.: 374,065
' 57 ABSTRACT  Foreign Application Priority Data July 10, 1972 Germany 2233904 Grid for the retaining or laterally supporting of primarily nuclear fuel rods, comprising plate springs that  US. CL... 176/78; 165/69 exert a retaining force remaining constant, irrespec-  Int. Cl. G2lc 3/18; G210 3/34 tive of the degree of compression. A spring may be  Field of Search 176/78; 267/164; 165/69 spotwelded to the grid, snapped into place in a hole in the grid wall, or both.
 References Cited UNITED STATES PATENTS 3 Claims, 10 Drawing Figures 3,379,617 4/1968 Andrews et a1 176/78 0T s 2 s K 95 1, Z 96 98 g 92 Z 90 a1 99 27 III-11- 4 m 4 6 15 e1 93 -s1 US. Patent Dec.30, 1975 Sheet10f8 3,929,569
Sheet 3 of 8 III/ll amt Dec. 30, 1975 Sheet4 0f8 3,92 5
., amt Dec.30, 1975 SheetS 0f8 392956 Fig. 6
US. Patent Dec. 30, 1975 Sheet 6 of8 3329 569 Fig. 8
Dec. 30, 1975 Sheet 7 of 8 3,9256
. atem Fig.9
PLATE SPRING OR RETAINING GRID FOR A BUNCH CYLINDRICAL ELEMENTS ENGAGED IN A HEAT EXCHANGE PROCESS The invention relates to a retaining grid or supporting grid for laterally supporting a bunch of cylindrical elements engaged in a heat exchange process, the supporting grid being made up of strip material in such a way that a plurality of compartments is formed.
One of the objects of the invention is to indicate a structure for a grid of this kind in which a plate spring is introduced at least at one position into aside wall of a compartment. The plate spring extends in two directions and, when released, shows an arched form in one direction in its principal middle part, whilst the outer ends of the plate spring are in rigid connection with fixing points of the said side wall, between which fixing points and a span of distance near at least one end of the plate spring a smaller section is similarly arched in the form of a plate spring.
The said cylindrical elements may consist, for instance, of rods or bars of fissile or breeding material which are introduced into the core of a nuclear reactor. The same set-up, however, may also be used for a heat exchanger. In that case the cylindrical compartments consist of pipes around which there is a flow of media to be cooled or heated.
Lastly, it is also possible to use a set-up mounted inside the cylindrical elements.
The said plate springs have a non-linear spring characteristic. The pressure increase with the degree of compression according to the dimensional conditions ruling at any moment, but remains constant or decreases within a certain range. Consequently, it is possible within certain limits to apply an equal pressure to all the cylindrical elements, independently of manufacturing and assembling tolerances and temperature effects. This is of particular importance in cases where the pressure and spring tensions may not exceed certain permissible maximum values. It is not necessary to give the spring a symmetrical shaping in the longitudinal direction. Thus, it is quite possible to use a plate spring having only one curved section in connection with the arched span. In this embodiment the plate spring is shorter, which is advantageous to the flow of medium around it.
his a further object of the invention to use a plate spring having only on one side a curved section in connection with the arched span. The advantage of this form of spring is that the spring becomes shorter and can therefore be manufactured in a more simple and hence less expensive manner.
According to a further embodiment of the invention a plate spring is used which shows at least on one side of the large archlike convexity smaller convex spring portions which are outwardly curved towards the opposite side of the large convexity. In this way a form of spring is obtained which is characterized in that it can be produced in a very easy manner if these small convexities of the spring are formed at both ends. By giving the plate spring a suitable shaping it is now possible with these slight spring convexities to make the plate spring rest in holes provided in the wall of the grid. With suitable shaping it is even possible in this embodiment to bring about a so-called snap connection. In that case the plate spring is brought into position by being pushed through the apertures until the two convexities snap through this aperture, whereupon the spring is fixed in the grid. For greater security it is always possible to fix the ends of this spring through the grid additionally by means of spot welds. Should such a spot weld become detached, this spring is still unable to move out of the grid as it is kept locked in position by the snap joint.
The same holes in the grid wall which are used for fixing the plate spring may also be utilized for fixing the rod holder in the same way. This rod holder, which is situated in the other compartment of the grid, serves to provide a firm point of support for the fissile rod by means of a few projecting parts.
According to a further variant of the invention the springs used consist of an assembly of two or more springs mounted one above the other. In the case where two springs are used, these two springs are connected at least to each others ends. The assembly of plate springs formed in this way is connected at its ends to the grid by means of so-called backing strips (rod holders). The advantage of this is that each spring individually shows a lower stress level than a replacement spring whose total length corresponds to the sum of the thickness of the individual springs stacked upon each other. This lowered stress level is of particular importance because the degree of stress relaxation is a function also of the magnitude of this stress level. By the use of this assembly of composite springs it is possible to keep the stress relexation under control in such a manner that the spring tension can be maintained for a much longer time than was formerly the case. The result is thus achieved that, in spite of the often very high working temperature, springs made in this way can perform their function in a reliable manner for a long period.
Typical embodiments of the invention will be elucidated below by reference to the accompanying drawmgs:
FIG. 1: shows these spring characteristics.
FIG. 2; shows a longitudinal section II-II taken through the retainning grid according to FIG. 4.
FIG. 3: represents a longitudinal section III III taken through the retaining grid according to FIG. 4. FIG. 4 gives a top plan view of the retaining grid.
FIG. 5: gives a top plan view of a non-symmetrical plate spring.
FIG. 6: is a front elevation of a cross-shaped rodshielding element.
FIG. 7: gives a side view of a non-symmetrical plate spring according to FIG. 5.
FIG. 8: shows, in an elevation according to VIII, a rod holder as used in FIG. 9.
FIG. 9: discloses a vertical cross-section of a grid element in which the plate springs used show an amended form of construction.
FIG. 10: shows a side elevation of a doubly constructed non-symmetrical spring.
FIG. 1 shows the spring characteristics of plate spring of the kind described.
The force K by which the plate is compressed in plotted along the vertical axis (see also FIG. 3).
The spring deformation f is represented by the horizontal axes. This spring deformation is measured in the middle 27 of the plate spring (see FIG. 3).
The characteristics b and c in particular are of importance for the purpose concerned here. Characteristic b shows a trend which ensures a constant resiliency K between the limits d and e.
Characteristic b shows that it is also possible to make the resiliency K diminish according as the deformation increases. Springs with this characteristic as well as springs with characteristic b are suitable for intercepting the vibration of pipes or fuel rods. Such vibrations, which may be due to variations of pressure in the cooling medium, have hitherto frequently been a source of difficulty, as they are liable to cause fatigue fractures.
FIG. 4 shows, in a top plan view of a supporting grid 1, how a plurality of rods 2 of fissile material are supported in this grid. The grid consists of a plurality of strips 3, 4, 5 and 6 which are permanently connected with each other at points 14, 15, 16 and 17, at which intersecting strips interlock. In this .way a plurality of grid compartments 7 is formed. For one of these sections the figure shows in detail how these rods 2 of fissile material are supported by a plate spring 8 together with a rod holder having two bends 78 and 79 each of which shows a protrusion 81, 82.
FIG. 3 shows, in a longitudinal section of the element of fissile material depicted in FIG. 4, how the plate springs used are shaped. According to FIG. 3 each plate spring shows an arched middle part which merges at its two ends into smaller plate spring parts 16 with an arching similar to that of the middle part 15.
At points 23 each end of the plate spring is rigidly fixed, e.g. by means of spot welds, to a side wall portion 5 of a compartment 7.
For the sake of clarity this is again shown in FIG. 3 in a longitudinal section III III of the grid. It can furthermore be seen from the figure that in the middle of the larger wall portion a protrusion 27 is provided which is adjacent to the adjoining surface of the fissile rod 2.
FIGS. 5 and 7 show a modified form in which a plate spring is shaped non-symmetrically with only one arched part.
If a rectangular set-up of the fissile rods is to be provided, the FIG. 4 construction offers a simple and inexpensive mode of solution. According to FIG. 4. vertical strips 5 and 6 are connected by means of soldered or plasma-welded joints 14, 15, 16 and 17.
The plate springs 8 are fixed to the transverse strips 5 and 7 respectively. These springs may be of the kind shown as spring 8 in FIG. 2 or as springs in FIGS. 5 and 7.
Rod holders 76 and 77 give the fissile rod 2 a firm hold at points and 46. FIG. 6 gives a top plan view of a rod holder 77. The curved clamps 81 and 82 provide a firm hold. These clamps are the opposite ends of the cross-beam or strip of the cross-shaped part 77. The longitudinal strip 85 is used for spot welds at points 86 and 87.
FIG. 2 is a front elevation of the plate spring 8 used in FIG. 3. It distinctly shows the positions 23 at which a spot weld has been made.
FIG. 9 shows in common with FIG. 3 a vertical crosssection of the grid, in which, however, a variant upon the letter figure is depicted. In this embodiment two apertures 90 and 91 respectively are provided in the grid walls 6 and 5 respectively. Since there are corresponding apertures 92 and 93 respectively in the backing strip or rod holder 95, the plate spring portions 96 and 97 which are bent over with small archings can be pushed through these apertures. During this action the spring 25 is supported by its end 98, bent over practically at right angles, in the edges 99 of the apertures. Although this is not shown in FIG. 9, this construction can without difficulty be made in such a way that when the plate spring is pushed through apertures 90 and 91 a snap effect is brought about, so that the spring is not only fixed in the apertures but can as it were be locked in them.
FIG. 8 shows the view according to VIII on the rear side of the retaining plate 95. This plate is provided with bent-over edges 100 and 101 by means of which the retaining plate is fixed upon the edges 102 and 103 of apertures 92 and 93. As shown in FIG. 8, spot welds may furthermore be provided at the positions 23.
In FIG. 10 a construction is depicted partly in crosssection and partly in side elevation, in which a spring 104 and a spring 105 are superimposed upon each other and fixed by means of spot welds 106 and 107. If desired, a few other spot welds may be provided over the length of the spring, for example at 108. Spring 105 has for the sake of clarity been given a different shade of colour from spring 104. From FIG. 10 it can also be seen that the retaining plate 109 is in this case provided with two protrusions 110 and 111 which pass through apertures 112 and 113 so as to come into contact with the underside of 105, where they are fixed with the same spot weld by means of which the spring portions themselves are joined to each other.
1. A supporting grid for supporting a plurality of elements engaged in a heat exchange process against sideways shifting comprising: a plurality of grid strips connected together to form the sidewalls of a plurality of compartments having parallel axes; a plate spring extending longitudinally in each compartment, said plate spring having a continuous surface facing the sidewall of the respective compartment, said spring having a central arch-like bend projecting toward the center of the respective compartment for engaging an element therein and having at each end of the arch-like bend a smaller bend facing in the opposite direction, said spring further having straight end portions which engage the sidewall of the respective sidewall, each end portion extending longitudinally outwardly from the respective smaller bend so that the surface of the end portion engaging the sidewall is part of said continuous surface, each of said smaller bends projecting through I an aperture in the adjacent sidewall and engaging only that edge of the respective aperture which is adjacent the straight end portions of the plate spring to thereby fasten said plate spring to said adjacent sidewall; and an element holder in each compartment engaging the sidewall opposite the respective plate spring and having a portion projecting toward the center of the compartment for engaging an element therein on the opposite side from the respective plate spring.
2. A grid as in claim 1 wherein said element holder includes a plate portion engaging the compartment sidewall, said plate portion being provided with two apertures each of which coincides with one of said apertures in the compartment sidewall, an edge of each aperture in the plate portion being bent into a lip which grasps the edge of the corresponding aperture in the compartment sidewall.
3. A grid as in claim 1 wherein said element holder includes a plate portion engaging the compartment sidewall and wherein the projecting portion of said element holder includes two curved clamps projecting toward the center of the respective compartment.