GB2286357A

GB2286357A - Tool for fitting the knives of a shear

Info

Publication number: GB2286357A
Application number: GB9501943A
Authority: GB
Inventors: Jean-Paul Jusseau; Serge Sauvadon
Original assignee: Commissariat a lEnergie Atomique CEA; Compagnie Generale des Matieres Nucleaires SA
Current assignee: Orano Cycle SA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 1994-02-14
Filing date: 1995-02-01
Publication date: 1995-08-16
Anticipated expiration: 2015-02-01
Also published as: GB2286357B; FR2716132B1; FR2716132A1; JPH0862383A; GB9501943D0

Abstract

Tool for fitting knives (3a - 3e) in the form of blocks to the cutting edges on a blade holder (1) by means of lock screws or setscrews (41, 42a - d, 45) in order to apply the blades (3a - 3e) to the bottom of indentations defined by three planar surfaces. This leads to a good alignment of the cutting edges. The tool has been especially designed for remote manipulation work maintaining shears for cutting up nuclear fuel needles. <IMAGE>

Description

Tool for fitting the knives of a shear.

DESCRIPTION The invention relates to a tool for fitting the blades of a shear.

A shear for which the invention is intended serves to cut up nuclear fuel assemblies constituted by a bundle of needles filled with fissile material and grids connecting the said needles and it has an edge fitted with detachable cutting knives, which are in the form of blocks at the cutting edges and screwed and located in indentations defined by three planar surfaces perpendicular to the carrying part and referred to as a blade holder. The knives are stepped in staircase-like manner along the edge in such a way that they partly overlap and the cutting of the assembly is progressive, having the advantage of a more progressive, reduced force.

It could be assumed that the relatively light knives would be replaced by others on the blade holder when worn, but this cannot be achieved in practice through the incorrect positioning of the knives in their indentations. Thus, in practice the blade holder is replaced at the same time as the knives after making the assembly outside the enclosure, which produces a large volume of contaminated waste. However, if the knives were fitted incorrectly, i.e. with clearance between them and the bottom of their indentations, there would either by movements of the knives during the application of the cutting forces and the jagging of the friction surfaces, or cutting debris would be introduced between the knives and the blade holder, which would mark their surfaces and would produce essentially the same damage.

The aim of the tool according to the invention is therefore to make it possible to easily and correctly replace worn knives on a blade holder, without the latter having to be replaced or removed from the enclosure. The essential elements of this tool are used for immobilizing the blade holder and maintaining the knives to be fitted at the bottom of the indentations, after which they can be screwed down.

In its most general definition, the invention relates to a tool for fitting knives in indentations, defined by three planar surfaces, of a blade holder to which they are screwed according to an arrangement in which the knives are arranged in staircase-like manner, partly overlap and form recesses between consecutive knives, and the tool is characterized in that it has a cage for retaining the blade holder, means for fixing the blade holder in the cage and fitting screws directed towards the knives and having an arrangement and number so as to push back the knives over all the planar surfaces of their indentations.

It is advantageous for the rotary shank fitting screws to be fitted on an arm of the rotary frame towards the knives about a joint perpendicular to the rotary shank screws, in order to free the indentations prior to the introduction of the knives.

An advantageous distribution of the fitting screws consists in that the rotary shank screws are of the same number as there are recesses and are directed towards a respective recess and that the fitting screws incorporate two screws directed in coplanar directions to the rotary shank screws, towards perpendicular surfaces of two end knives and in convergent directions.

Screws directed in directions perpendicular to the rotary shank screws are advantageously combined with other fitting screws in order to maintain the knives in a fitting plane prior to the actual fitting. It is then possible to turn the cage with the advantage that the screwing down of the knives can take place more easily, without said knives dropping beforehand.

It was also considered that the means for fixing the blade holder to the tool could seize or jam, particularly if they consisted of screws. It is therefore recommended that the fixing screws are engaged in detachable structural components of the tool so that they can be withdrawn.

The invention is described in greater detail hereinafter relative to the drawings, wherein show: Fig. 1 an overall view of the blade holder in the operating position.

Fig. 2 a view of the blade holder mounted in the tool.

Fig. 3 the rotary nuts of certain screws.

Fig. 4 the tool seen from the right in fig. 2.

Fig. 5 like fig. 4 but in the form of a diagrammatic section.

Fig. 6 a lateral sectional view of the knives of the blade holder.

Fig. 7 a partial front view of the blade holder.

Fig. 8 a sectional view along line VIII-VIII of fig. 2.

The actual blade holder 1 is in the form of a plate having a trapezoidal cross-section and having on the larger straight face longitudinal channels 6, as can be seen in fig. 1.

The opposite face carries on one edge knives 3 in the form of parallelepipedic blocks (five in this embodiment and designated 3a to 3e) having cutting edges retained by screws 4, whose heads 5 are flush with the opposite surface, eitner at the bottom of the channels 6, or at the surface of rectangular section crests 2 separating them, but without projecting because they occupy receptacles hollowed out of said face.

There is a pair of screws 4 for each knife 3 and they are spaced in the cutting direction. The screws 4 traverse openings in the blade holder 1 which must be sufficiently wide not to disturb their introduction and which cannot contribute to the putting into position of the knives 3. Instead of this, each of the knives 3 is located in an indentation formed in the blade holder 1 and constituted by three planar, perpendicular surfaces on which it must bear, namely a bottom surface 7 common to all the knives 3, a lateral surface 8 and an upper surface 9, so that the surfaces 8 and 9 of all the knives 3 succeed one another in alternating manner and have a general broken line profile. The knives partly overlap in the lateral direction, so that their overall arrangement is in the form of a staircase, the overlapping faces of consecutive blocks being spaced by a very small clearance. Therefore shearing consists of advancing the blade holder 1 through a bundle of nuclear fuel needles 10 which is advanced to a blade holder 11 between each cutting movement, so that the knives 3 pass in front of the counterblade 11 with only a limited spacing and the end of the needles is cut on each occasion in order to become what is called a shell. The shells are then introduced into a nuclear waste processing operation and in particular are dissolved in hot nitric acid.

The cutting edges of the knives 3 consequently include the lower edge 13 (oriented towards the bundle 10) and the bottom of the laterally outer blade 14 opposite to the bottom surface 7.

The blade holder 1 is located in a trapezoidal indentation 16 of a blade holder carriage 15 in which it is held, whilst passing out of the same by one end carrying knives 3, which are thus well freed from the carriage 15. The blade holder 1 slides in the trapezoidal section indentation 16 (vertical with the representation of fig. 1), but abutment means are provided in order to prevent it from falling. The crests 2 on the blade holder 1 are chosen in such a way that the blade holder 1 is wedged at the top of the trapezoidal indentation 16 by driving it into the carriage 15. It is then firmly wedged during shearing. Thus, displacement takes place of a key 17 through the trapezoidal indentation 16 and said key 17 has a bevelled face, which bears on the also bevelled, rear face of the crests 2 in order to force downwards the blade holder 1 into the wedging position.

The tool according to the invention is illustrated by figs.

2 to 8. According to fig. 2 it has a base 20 placed on the ground and a frame 21 rotating on the base 20 by means of journals 22. A stop pin 58 is provided on one of the sides of the base 20 in order to retain the frame 21 in rotation.

It is terminated by a shank 59, which penetrates a hole 60 in a flange 25 of the frame 21 close to one of the journals 22. The shank 59 can rotate in a bush 61 fixed through the base 20 by manipulating a handle 62 at the rear of the shank 59 and a lug 63 of the shank 59 in order to maintain the latter locked in the bush 61 and simultaneously engaged in the hole 60. However, when the lug 63 is freed, a compressed spring 64 between the shank 59 and the bush 61 can expand and withdraws the latter freeing the hole 60. It is then possible to incline the frame 21. There are in fact three holes 60 distributed over the flange 25 and in which the shank 59 can be engaged. The holes 60 are positioned in such a way that the frame is placed in a vertical position illustrated by fig. 2 and in two opposite horizontal positions. Two abutment lugs 24 on the flange 25 abut against the base 20 when the horizontal positions are exceeded.

The other side of the base 20 which is clearly visible in fig. 4 carries a stop screw 23, whose end can penetrate a hole 65 made in a lateral plate 52 of the frame 21 in order to bring about a stoppage, which offers a security against untimely manipulations of the stop pin 58.

The frame 21 is essentially constituted by a cage 26 formed from metal sections and plates enclosing a cavity into which the blade holder 1 can be introduced with a little clearance.

The cage 26 in particular has a rear plate 50, two lateral plates 51,52, a front plate 53 and a bottom plate 54 in order to retain and guide the blade holder 1. Its trapezoidal section is identical to that of the blade holder 1, as can be seen in fig. 8. The lateral plates 51,52 in each case carry an already mentioned flange 25 or 66 equipped with one of the journals 22.

The blade holder 1 is engaged by the top of the cage and shackles 27 of the frame 21 can prevent the removal thereof.

There are two of them articulated to the cage 26 by one of their ends 28. Their other end can be placed in front of the opening of the cage 26 and setscrews 29 located at said other ends are rotated in order to weigh on the rear end of the blade holder 1, which passes beyond the cage 26, so as to maintain the blade holder 1 at the bottom of the cage 26.

Another essential part of the tool is a rotary arm 30 connected by one end to the bottom of the cage 26 by an articulation or joint 31 and whose other end can be locked against another part of the cage 26 by introducing a stud 32 into an opening of said other end and by screwing down a nut 33 onto the stud 32 so as to lock the rotary arm 30. The stud 32 is articulated to the cage 26 so that it can be correctly oriented. In the position shown in fig. 2, the knives 3 are positioned horizontally, the lateral faces 8 of the indentations receiving the knives 3 being located thereon, the knife 3e being positioned to the rear of the others in the shearing direction and is placed against the joint 31, the opposite knife 3a by which shearing commences now projecting over the others and extending close to the stud 32. The cage 26 is left open so as to render visible the knives 3, as well as the heads 5 of their screws and its front 53 and rear 50 plates are consequently notched, but the front plate 53 has heads 34 (fig. 2) above the junctions of the lateral and upper surfaces 8,9 of the indentations, in which are engaged setscrews 35, clearly visible in fig. 5, each of which can thus press one corner of the knives 3 against the bottom surface 7 of its indentation. There are other setscrews 36 screwed onto the rotary arm 30 in order to press the respective knives 3 onto the bottom surface 7 by their opposite corners. As the rotary arm 30 does not cover any part of the knives 3, but instead extends in front of them, the locking is not obtained by the shank of the screws 36, as for the screws 25, but instead by a collar 37 placed underneath the head of the screws 36. When new knives 3 have to be fitted, the first operation consists, with the rotary arm 3 freed from the stud 32, of sliding the knives 3 to their respective position below the front plate 53 of the cage 26, raising the rotary arm 30 and fixing it by locking the nut 33 and then the screws 35 and 36. During these operations the frame 21 is horizontal and the knives 3 rest on the bottom surfaces 7 of the blade holder 1.

A horizontal screw 41 (cf. fig. 7) is engaged through the lateral plate 52 of the cage 26, close to the rotary stud 32 and is then screwed down so that its end reaches the knife 3a in front of which it is located and then forces it back against its upper face 9 (at present lateral).

This is followed by the successive tightening of the four other screws 42 located on the rotary arm 30. Each of them is rotary, because it is engaged in a cylindrical nut 43 rotating about an axis parallel to that of the rotary arm 30 (also visible in fig. 3). wne end of the screw 42a manipulated first then reaches both the knife 3a and its neighbour 3b whilst abutting in the recess which they form and forces the knife 3a against its lateral surface 8 (at the present top) and the knife 3b against its upper surface 9. The end 44 of the screws 42 is rounded so as to be able to slide on the surfaces of the knives and abut against the recesses.

When this operation is completed, the knife 3 is perfectly applied in the three surfaces 7,8 and 9 of its indentation and one then passes to the screw 42b, which faces the adjacent recess formed by the knife 3b and its lower neighbour 3c. As previously screwing makes it possible to press the top knife 3b against its lateral surface 8 and the bottom knife 3c against its upper surface 9, so that the situation shown in fig. 7 is obtained.

The procedure is the same for the two other screws 42c,42d facing the two last recesses and it is then merely necessary to tighten a vertical orientation screw 45 engaged in the base plate 54 of the cage 26 and adjacent to the joint 31.

This screw presses the final knife 3e against the lateral surface 8. The fitting of the knives 3 in the blade holder 1 is then perfect and the screws 4 can be tightened without any risk of disturbing the layout. For this purpose it is advisable to tilt the frame 21 in order to place its rear plate 50 at the top. The screws 4 are then engaged in openings of the blade holder 1 and tightened by an impact wrench to the desired torque. When the knives 3 are joined to the blade holder 1, all the screws 35,36,41,42 and 45 are loosened and the blade holder 1 removed. The latter operations take place after restraightening the frame 21. The operations for removing worn blades 3 from the blade holder 1 consist, after placing the latter in the frame 21, retaining the knives 3 by the screws 35,36 and then removing the screws 4.

The base plate 54 can carry a fixing screw 46 (figs. 6 and 7), whose end is inserted in a cap of the bottom of the blade holder 1. The shackles 27 are then unnecessary. This fixing screw 46 can be jammed and therefore as a precaution it does not directly traverse the base plate 54, but instead passes through a plate 47 located in a cutout thereof and two other screws 48 join the same. In case of need, it is then merely necessary to remove the screws 48 and raise the blade holder 1 in order to pull out the plate 47 with the blade holder 1. With regards to the pressure fixing screws 29 they could be removed, if they were seized in the shackles 27, after dismantling the joints at the ends 28 of the shackles 27.

These joints can be in the form of journals assembled with the front and rear plates 50,53 by bolts.

Claims

1. Tool for fitting knives (3) in indentations, defined by three planar surfaces (7,8,9), of a blade holder (1) to which they are screwed according to an arrangement in which the knives (3) are arranged in staircase-like manner, partly overlap and form recesses between consecutive knives, and the tool is characterized in that it has a cage for retaining the blade holder (1), means (27,46) for fixing the blade holder in the cage and fitting screws (35,36,41,42,45) directed towards the knives (3) and having an arrangement and number so as to push back the knives (3) over all the planar surfaces (7,8,9) of their indentations.

2. Fitting tool according to claim 1, characterized in that certain (42) of the fitting screws are directed towards the recesses of the knives, are connected to the frame (21) by rotary nuts (43) and have rotary shanks in front of the recesses.

3. Fitting tool according to claim 2, characterized in that the rotary shank fitting screws (42) are fitted to an arm (30) of the frame (21) rotating towards the knives about a joint (31) perpendicular to said rotary shank screws.

4. Fitting tool according to claim 2, characterized in that the rotary shank screws (42) are present in the same number as the recesses and are directed towards a respective recess and the fitting screws comprise two screws (41,45) directed in directions coplanar to the rotary shank screws (42) and towards perpendicular surfaces of two extreme knives (3a,3e) and in convergent directions.

5. Fitting tool according to claim 3, characterized in that the fitting screws comprise screws (35,36) directed in directions perpendicular to the rotary shank screws (42).

6. Fitting tool according to claim 5, characterized in that there are two screws (35,36) perpendicular to the rotary shank screws (42) for each of the knives (3) one (35) being integral with a cage (26) of the frame (21) in which the blade holder is held and the other (36) is integral with the rotary arm (30).

7. Fitting tool according to claim 1, characterized in that it has shackles (27) articulated to the frame (21) and able to occupy a position of closing an opening of the frame (21) by which the blade holder (1) is introduced and removed.

8. Fitting tool according to to claim 7, characterized in that the shackles (27) carry the fixing means (29) of the blade holder (1).

9. Fitting tool according to claim 1, characterized in that the blade holder fixing means comprise screws (48) engaged in detachable structural elements (47) of the frame (21).

10. Fitting tool according to claim 1, characterized in that the frame (21) and the fitting screws rotate on a fixed base (20).