GB1566635A

GB1566635A - Wieghing apparatus

Info

Publication number: GB1566635A
Application number: GB18139/77A
Authority: GB
Original assignee: Alkem GmbH
Current assignee: Alkem GmbH
Priority date: 1976-05-20
Filing date: 1977-04-29
Publication date: 1980-05-08
Also published as: BE854730A; JPS52143063A; BR7703190A; IT1074514B; FR2393282A1; DE2622586A1; FR2393282B1; DE2622586B2; SE7705548L; ES458971A1

Description

(54) WEIGHING APPARATUS (71) We, ALKEM GMBH, a German company, of 6450 Hanau 11, Germany (Fed.

Rep.), do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a weighing apparatus.

More particularly, but not exclusively, the invention is concerned with a weighing apparatus which operates in accordance with the principle of a spring balance for elongate and, where necessary, unevely distributed loads, more particularly for fuel rods of fuel elements of nuclear reactors. The weighing of elongate objects such as, for example, fuel rods of fuel elements which may have a length of about 4 m is always attended by relatively great difficulties. These are due to the fact that, on the one hand, the weight distribution is not constant over the whole length of the rods and on the other hand such objects must be made to weigh on the balance at the level of the centre of gravity of the object, which is a very laborious procedure. It has been substantially impossible to introduce such a weighing technique, for example, into a production line.

Not only is it necessary to keep a very accurate account of the consumption of nuclear fuels employed in nuclear reactor technology because of the valuable nature of the material involved, such as UO2 or PuO2 and even carbides, but it is essential also because of the so-called nuclear fuel surveillance which is required in accordance with international regulations to prevent misuse.

The requirement has therefore arisen to find for weighing such long component parts an apparatus which can be installed in a production line and which supplies measured values of very high accuracy independently of the position of the centre of gravity of the objects concerned.

According to the present invention there is provided a weighing apparatus for weighing elongate articles, which apparatus comprises (i) two bearer members, which bearer members are spaced apart from one another and are each provided with a support in the form of a parallelogram which is biased to a predetermined position; (ii) a beam for receiving an elongate article to be weighed, which beam connects the two bearer members; and (iii) means for measuring the change in the position of the bearer members which is produced by the application to the beam of an article to be weighed, whereby the weight of the article can be determined.

Preferably, at least one of the joints of each support is provided with a resilient mounting. The or each resilient mounting may be fixedly clamped in upright portions of the support. Preferably, the resilient mountings are located at each joint of the support, the mountings being in the form of leaf springs which form the lateral parts of the support.

The mid-portions of the leaf springs are preferably thickened so as to be resistant to bending.

Preferably, the bearer members are movable towards and away from one another.

The beam connecting the bearer members may be of lightweight construction and have high bending strength.

The bearer members of the weighing apparatus may be so arranged that the parts to be weighed, for example such as the fuel rods from a preceding processing station, are rolled or pushed onto them. It is immaterial whether or not the fuel rods lie symmetrically in relation to the bearer members.

An essential requirement, however, is that the application of pressure to the dial gauge or to the pressure sensors always takes place vertically, because otherwise the desired indicating accuracy cannot be expected. For this purpose, the bearer members are mounted on a parallelogram arrangement which is suitable in known manner to ensure that the movement which takes place is always vertical. This parallelogram mounting may be in the present case combined with spring elements to provide the biasing, upon the spring force of which the loading capacity of the weighing apparatus depends. However, since maximum accuracy is required of this weighing apparatus, frictional forces must as far as possible be completely avoided in the mecha nism.

For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 shows a side elevation of one embodiment of a parallelogram mounting for a bearer member in which joints of a nature known per se are provided and friction is therefore present; Figure 2 shows a side elevation another embodiment of a parallelogram mounting; and Figure 3 is a front elevation of the weighing apparatus with the two bearer members and a bearing beam which connects them.

The figures show an object to be weighed 9, for example a nuclear reactor fuel rod, which lies on two bearer members 7. Each bearer member 7 is connected to a bearing arm 2 of a parallelogram mounting, which arm 2 is connected at its lower end to a pressure sensor 5 for measuring the vertical displacement of the bearing arm and hence the weight of the fuel rod 9.

The parallelogram mounting shown in Figure 1 comprises a post 1, fixedly arranged in parallel relationship to the bearing arm 2, and arms 3 and 4 of equal length, which arms are connected by means ofjoints 21 and 24 to the bearing arm 2 and by means ofjoints 13 and 14 to the post 1. The resilient counterforce required for the weighing is here supplied by springs provided in the joints 13 and 14. This arrangement thus constitutes, in a manner of speaking, a spring balance whose length of movement is ascertained by means of a dial gauge or pressure-measuring cell 5. Instead of this measuring arrangement, there could of course be employed in the conventional manner a pointer system having a corresponding scale and actuated by way of a corresponding transmission means.The latter system, however, would have the disadvantage of relatively poor accessibility and in addition would be attended by internal friction which might impair the measuring accuracy.

In the embodiment shown in Figure 2, the springs in the joints 13 and 14 have been replaced in the form of construction according to Figure 2 by the end sections of two leaf springs 31 and 41 which are rigidly clamped in the bearing arm 2 and in the part 1. The mid-portion of the leaf springs is stiffened by, for example, channel sections 32 and 42, so that a completely parallel guiding between the bearing arm 2 and the post 1 is again achieved in this construction. The spring force required for the weighing is here supplied by the non-reinforced ends of the leaf springs 31 and 32. The dash-dotted extension of the bearer member 7, denoted by 91, indicates an area over which the fuel rod 9 to be weighed passes to the weighing apparatus.

Figure 3 illustrates the arrangement of Figure 2 in front elevation. The weighing apparatus consists of two spaced-apart bearer members 7 each having a parallelogram mounting. If the fuel rod 9 to be weighed were directly laid upon the two bearer members 7, it would undergo a very considerable deflection by reason of its great length, for example 4 m, and might thereby suffer damage. In order to avoid this danger, the fuel rod is laid upon a bearing beam 8 which forms part of the weighing apparatus.

The beam is of lightweight construction because its weight must, of course, be included in the weighing. It lies directly and therefore rigidly upon the left-hand bearer member 7, but on the right-hand bearer member 7 with the interposition of a roller 71. This ensures that, while a longitudinal expansion of this component part by temperature influences is possible, no lateral pressure component can be applied to the righthand bearer member 2. The bearing beam 8 may have a box section disposed on edge, and it will be made of material of minimum weight and could even be constructed in the form of a lattice girder as diagrammatically illustrated in the drawing. Of course, other lightweight forms of construction having high bending strength, for example such as the sandwich form of construction, would also be possible.

In order to give a better idea of the order of the size of such a weighing apparatus, it may be mentioned that the parallelogram parts 3 and 4 have a length of substantially 120 mm and a spacing of about 70 mm. The distance betwen the two bearer members in Figure 3 is then about 3 m. The vertical length of movement of the bearer members 7 is of the order of magnitude of 0.5 to 1 mm. For a total measuring range of6 kg and a weight of the bearing beam of 4 kg, a weighing accuracy with the use of two pressuremeasuring cells 5 of +0.1 gram per 5 kg has been obtained. This high measuring accuracy is independent of whether or not the fuel rod 9 is placed symmetrically in relation to the two bearer members 7. Any other inequality of load distribution on the bearer members also does not affect the measuring accuracy, and this means that other component parts having unequal internal weight distribution can be tested on such a weighing apparatus. This is because the indicating values of the dial gauges or of the pressuremeasuring cells, which may operate in a manner known per se in accordance with the inductive or capacitive principle, are added together in the indicating instrument (not shown). Of course, it is possible to record this value in a conventional manner and hence to ensure that it is assigned to the respective weighed fuel rod.

Since temperature influences might affect the spring characteristics and might in some cases influence the amplifiers and other electronic component parts connected to the pressure-measuring cells 5, it is desirable to keep available a weight standard in order that the calibration of the weighing apparatus may be checked and where necessary adjusted at any time.

Thus, the illustrated embodiments of the present invention provide an apparatus in which there are provided to receive the load two bearer members having a parallelogram mounting, wherein spring elements are provided in the joints of the mounting, and wherein there are employed for the measuremen of the change in the position of the bearer members which is produced by the application of the load, means known per se, such as dial gauges, pressure sensors and the like. The object to be weighed is therefore laid upon a beam supported by two spacedapart bearer members, in each of which bearer members there is situated a pressuremesuring system. The sum of the indicated values of these instruments then gives the weight of the applied load.

WHAT WE CLAIM IS: 1. A weighing apparatus for weighing elongate articles, which apparatus comprises (i) two bearer members, which bearer members are spaced apart from one another and are each provided with a support in the form of a parallelogram which is biased to a predetermined position; (ii) a beam for receiving an elongate article to be weighed, which beam connects the two bearer members; and (iii) means for measuring the change in the position of the bearer members which is produced by the application to the beam of an article to be weighed, whereby the weight of the article can be determined.

2. An apparatus as claimed in claim 1, wherein at least one of the joints of each support is provided with a resilient mounting.

3. An apparatus as claimed in claim 2, wherein the or each resilient mounting is fixedly clamped in upright portions of the support.

4. An apparatus as claimed in claim 3, wherein the resilient mountings are located at each joint of the support, the mountings being in the form of leaf springs which form the lateral parts of the support.

5. An apparatus as claimed in claim 4, wherein the mid-portions of the leaf springs are thickened so as to be resistant to bending.

6. An apparatus as claimed in any preceding claim, wherein the bearer members are movable towards and away from one another.

7. An apparatus as claimed in any preceding claim, wherein the beam is of lightweight construction and has high bending strength.

8. A weighing apparatus as claimed in claim 1 and substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

9. A weighing apparatus substantially as hereinbefore described with reference to, and as shown in, Figures 2 and 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. weighed fuel rod. Since temperature influences might affect the spring characteristics and might in some cases influence the amplifiers and other electronic component parts connected to the pressure-measuring cells 5, it is desirable to keep available a weight standard in order that the calibration of the weighing apparatus may be checked and where necessary adjusted at any time. Thus, the illustrated embodiments of the present invention provide an apparatus in which there are provided to receive the load two bearer members having a parallelogram mounting, wherein spring elements are provided in the joints of the mounting, and wherein there are employed for the measuremen of the change in the position of the bearer members which is produced by the application of the load, means known per se, such as dial gauges, pressure sensors and the like. The object to be weighed is therefore laid upon a beam supported by two spacedapart bearer members, in each of which bearer members there is situated a pressuremesuring system. The sum of the indicated values of these instruments then gives the weight of the applied load. WHAT WE CLAIM IS:

1. A weighing apparatus for weighing elongate articles, which apparatus comprises (i) two bearer members, which bearer members are spaced apart from one another and are each provided with a support in the form of a parallelogram which is biased to a predetermined position; (ii) a beam for receiving an elongate article to be weighed, which beam connects the two bearer members; and (iii) means for measuring the change in the position of the bearer members which is produced by the application to the beam of an article to be weighed, whereby the weight of the article can be determined.