Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B30—PRESSES
  • B30B—PRESSES IN GENERAL
  • B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
  • B30B15/06—Platens or press rams
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B30—PRESSES
  • B30B—PRESSES IN GENERAL
  • B30B11/00—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses
  • B30B11/02—Presses specially adapted for forming shaped articles from material in particulate or plastic state, e.g. briquetting presses, tabletting presses using a ram exerting pressure on the material in a moulding space
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B30—PRESSES
  • B30B—PRESSES IN GENERAL
  • B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
  • B30B15/06—Platens or press rams
  • B30B15/065—Press rams
  • B30B15/067—Press rams with means for equalizing the pressure exerted by a plurality of press rams

Definitions

• the present invention relates to a press providing improved maintenance, for example a press intended for the manufacture of nuclear fuel pellets.
• a press for the manufacture of nuclear fuel pellets comprises a table in which molding dies are made for pressing the nuclear fuel powder between two punches, a lower punch and an upper punch.
• the upper punch moves in the die during pressing while the lower punch remains stationary.
• the powder is for example formed from a mixture of plutonium oxide and uranium oxide.
• the table has a plurality of dies etched simultaneously by a plurality of punches.
• Each upper punch is carried by a compensator, itself mounted in a common support which is moved relative to the table by means of a jack.
• the support is called "compensator housing”.
• a compensator forms a piston, sealingly movable in a bore formed in the compensator housing. Pressurized oil is injected between the bottom of the piston and the bottom of the bore so as to urge the piston bearing the punch outwardly of the compensator housing.
• the bores are interconnected, and the compensators are used to balance the oil pressure on the different punches.
• Each compensator has a large diameter portion on which the oil pressure is applied, and a small diameter portion of which a free end carries the punch.
• the large diameter portion has on its periphery seals.
• the compensator is guided in the bore by a bushing surrounding the small diameter part.
• the sleeve is itself held in the bore by a nut which is screwed into the bore of the compensator.
• the bushing also, has seals on its outer periphery and on its inner periphery.
• Reliable sealing of the compensator assembly is required to prevent contamination of the dies and the nuclear fuel powder. It is recalled that, for security reasons, the press is in a glove box; therefore, any intervention on it is long and tedious. In addition, a pollution of the powder causes discarding of the pellets.
• the seals are then monitored regularly, which requires disassembly of the compensators. For this, the retaining nut is unscrewed, then the guide sleeve is removed and finally the compensator is extracted from its bore. It may happen that the guide sleeve remains stuck in the bore, it is then necessary to exert a tensile force on the sleeve, which can damage the bushing and the inside of the bore. In addition, this area is difficult to access, and in all cases the intervention is through a round of glove. The application of this important effort is carried out at arm's length. In addition, when reassembling the sleeve, it may appear damage to joints.
• a guide sleeve and retaining nut assembly secured to one another axially, while providing axial play and radial clearance between the guide sleeve and the retaining nut so that to allow a self-centering of the sleeve in the bore and around the compensator, during the assembly, to avoid deterioration of the joints.
• the bushing is free to rotate relative to the nut.
• the present invention therefore relates to a guiding and holding assembly for a press compensator comprising: a guide bushing of the compensator in its bore, said guide sleeve being intended to be mounted around the compensator,
• the guide sleeve being between a shoulder of the compensator and the retaining nut
• the guide sleeve is surrounded by the retaining nut over part of its length
• the securing means comprise at least two radial fingers housed in radial bores (made in the retaining nut and one of which radially inner end opens into an annular groove formed in the outer periphery of the guide sleeve, a radial clearance being provided between the radially inner end of the radial fingers and a radial bottom of the groove and an axial play being provided between side edges the radially inner end of the radial fingers and the lateral edges of the groove.
• the radial fingers are held in position in the radial housings by means of pressure screws.
• the pressure screws can be immobilized axially for example by means of a needle punch or a threadlock.
• the end radially inner fingers advantageously has a reduced diameter.
• the radial fingers are preferably three in number arranged at 120 ° from each other.
• the guide sleeve may comprise in its inner periphery a guide segment of the compensator.
• the retaining nut comprises, in a transverse face opposite to that in contact with the guiding bush, indentations intended to cooperate with indentations carried by a tool for exerting a tightening or loosening force on the holding nut.
• the present invention also relates to a press comprising:
• a punch holder adapted to be moved by a jack to bring the punches of the molding dies in a longitudinal direction
• each compensator having a longitudinal axis and being sealingly mounted in a bore of the support, and having a first longitudinal end intended to undergo a pressure of hydraulic fluid and a second longitudinal end bearing the punch, said bores being in fluid communication with each other, and - Compensating guide and maintenance assemblies according to the present invention mounted in each of the bores.
• the press forms, for example, a press for manufacturing nuclear fuel pellets.
• a tool for mounting and dismounting the press compensator guiding and holding assembly according to the present invention, for clamping and loosening the compensator retaining nuts may have a longitudinal axis and has a central cavity open to a first end for receiving the second end of the compensator, said open end being bordered by an annular surface provided with indentations or protrusions corresponding to recesses protruding or recessed respectively to the housing of the nut, and a second end means for exerting a rotational force on the tool about its longitudinal axis.
• the tool may have protruding indentations and the nut may have indentations.
• the means for exerting a rotational force to the tool are formed for example by a fingerprint for the mounting and the angular immobilization of a lever on the tool, for example an imprint of polygonal shape recessed or protruding.
• the side wall of the central housing is perforated.
• the depth of the housing corresponds substantially to the length of the portion of the compensator projecting from the nut, or the length of the assembly formed by the portion of the compensator projecting from the nut and the punch.
• FIG. 1 is a diagrammatic representation of a nuclear fuel pellet manufacturing press to which the present invention can be applied
• FIG. 2 is a partial sectional view of a compensator casing provided with upper punches, adapted to the press of FIG. 1;
• FIG. 3 is an enlarged view of a detail of FIG. 2;
• FIG. 4A is a longitudinal sectional view of a mounting bushing and guide nut assembly represented alone, in a plane of section different from that of FIG. FIG. 3
• FIG. 4B is a detail view of FIG. 4A
• FIG. 4C is a cross-sectional view along the plane A-A of FIG. 4A.
• FIGS. 5A and 5B are longitudinal sectional views of embodiments of tools for disassembly of the guide sleeve assembly and retaining nut.
• the present invention applies to any type of hydraulic press and is not limited to the nuclear field. It is particularly advantageous in the areas where cleanliness is an important criterion, but also in all areas implementing presses, because of its simplified maintenance.
• the press of FIG. 1 is housed in a confined enclosure 2, type glove box. It comprises a table 4 carrying the molding dies 6, mounted mobile along guide columns 8, a lower jack Vi to move the table 4, a fixed support 12 of lower punches 14 and a movable support 15 of upper punches 16 and displaceable by an upper cylinder Vs.
• the support 15 forms the compensator casing and carries the compensators (not shown) and the upper punches 16.
• the cylinders pass tightly through the walls of the enclosure 2.
• FIG. 2 a detail view of the compensator housing 15 can be seen and in FIG. 3, a compensator alone can be seen mounted in its bore.
• the compensator housing 15 is formed by a plate in which are machined bores 18, of longitudinal axis X, each of them receiving a compensator 20.
• the bores 18 are through and are closed at one end, opposite to that by which the compensator leaves, by a plug 22.
• Each bore 18 has a first portion of smaller diameter 18.1 and a second portion of larger diameter 18.2 connecting to the portion of smaller diameter 18.1 by an annular bearing surface 18.3.
• the compensator 20 has a first portion of larger diameter 20.1 and a second portion of smaller diameter 20.2 connecting to the larger diameter portion by a shoulder 20.3.
• the larger diameter portion 20.1 is received in the smaller diameter portion 18.1 of the bore 18.
• the larger diameter portion 20.1 of the compensator 20 has a groove 24 receiving a seal 26 and two grooves 28 located on either side of the groove 24 and receiving guide rings 30.
• the bottom of the larger diameter portion 20.1 of the compensator 20 comprises two bores 29 receiving two anti-rotation rods 31 fixed in the bottom of the bore 18.
• each bore defines with the bottom of the compensator that it contains a chamber 19 to be filled with oil under pressure.
• the chambers 19 of all the bores are in fluid communication with each other to allow the flow of oil between the chambers 19 and ensure the balancing of the pressures on the punches during the pressing step.
• Pits 19 ( Figure 2) made in front of the compensator housing allow the filling of the bores.
• a guide sleeve 32 is mounted in the larger diameter portion 18.2 of the bore 18 and abuts against the annular bearing surface 18.3.
• the bushing 32 surrounds the smaller diameter portion 20.2 of the compensator 20.
• the bushing has a large outer diameter portion 32.1 and a small outer diameter portion 32.2 connected by a shoulder 32.3.
• the guide sleeve 32 has on its outer periphery two seals 34 and on its inner periphery two axially offset sealing means 35 and a guide segment 36 of the compensator.
• the guide segment is mounted in the small outer diameter portion 32.2.
• the sealing means 35 each comprise an O-ring mounted radially at the bottom of the groove and a sealing ring at the outlet of the groove and rubbing on the compensator. The ring is then pressed onto the compensator by the O-ring and the pressurized oil.
• a retaining nut 38 is mounted in the larger diameter portion 18.2 of the bore 18 and bears against the shoulder 32.3 of the guide sleeve 32.
• the retaining nut 38 has a large inner diameter portion 38.1 and a small inner diameter portion 38.2.
• the retaining nut 38 is mounted around the sleeve 32 so that its large-diameter inner portion 38.1 surrounds the small outer diameter portion 32.2 of the guide sleeve 32.
• the retaining nut 38 has a thread 40 on its outer periphery cooperating with a tapping of the portion of larger diameter 18.2.
• the retaining nut carries on its inner periphery a seal 42, for example of the lip seal type rubbing on the smaller diameter portion 20.2 of the compensator.
• a clearance is provided between the inner diameter of the large diameter portion 38.1 of the nut and the outer diameter of the small diameter portion of the bushing 32, so that the bushing is not forced into the nut.
• FIG. 4A a sectional view of the guide sleeve assembly 32 and the retaining nut 38, represented alone along a plane of section different from that of FIG. 3, can be seen.
• the bushing 32 and the nut are secured axially and radially to one another, while leaving an axial and radial clearance between the parts.
• Solidarity means 44 with clearance are then provided between the sleeve 32 and the nut 38.
• the solidarity means 44 comprise three radial holes 46 arranged at 120 ° from each other formed in the nut, made in the small inner diameter portion and opening in a groove 48 made in the periphery of small outer diameter portion 32.2 of the sleeve 32 and fingers 50, housed in the housing 46 and penetrating the groove 48.
• the outer dimensions of the fingers and the dimensions of the groove 48 are chosen so that a radial clearance and axial play are assured.
• the fingers 50 are slidably mounted in the housings 46.
• the solidarity means may comprise two fingers, however the implementation of three fingers reduces the risk of biasing the nut relative to the sleeve.
• the groove 48 avoids the need to angularly orient the nut relative to the sleeve.
• the sleeve is not integral in rotation with the nut. Thus, during the tightening and loosening of the nut, the sleeve 32 does not rotate with the nut, which avoids soliciting the seals.
• the transverse position of the fingers and thus the radial clearance are adjusted by pressure screws.
• This piece offers the possibility of improving axial play.
• the rotation of the pressure screws 52 is blocked in order to ensure a fixed position of the fingers over time, for example by means of the threadlocker or by means of a needle punch at the level tapping.
• This definitive fixation makes it possible to fix the games permanently and in a very simple manner. This is made possible because during the life of the press, the bushing and the nut do not need to be separated.
• the end of the fingers 50 penetrating into the annular groove 48 has an end having a reduced diameter section, which makes it possible to limit the size of the annular groove 48 and avoids inducing weak spots in the bushing 32.
• This end With reduced diameter section provides non-binding guidance for the seals of the sleeve 32 during the introduction of the sleeve assembly 32 and nut 38 in the bore of the compensator housing. In the locked position, the clamping force is taken up by the surfaces in contact with the parts 32 and 38 at the bearing surface 57 in FIG. 4A.
• an axial clearance between the sleeve 38 and the nut 37 is between 0.045 mm and 0.355 mm is provided.
• the clamping is adjusted to keep a radial clearance between 0.05 mm and 0.139 mm.
• FIGS. 5A and 5B tools specially adapted for tightening / loosening of the retaining nut 38 can be seen.
• the tool 54 is adapted to tighten / loosen the retaining nut 38 when the punch is not mounted on the compensator 20.
• the tool 54 comprises means for rotating the nut in a direction of tightening or loosening.
• the tool 54 comprises, at a first longitudinal end, an annular face 56 provided with three fingers 58 projecting and extending longitudinally.
• the fingers 58 are intended to penetrate into three corresponding housings 59 formed in one face of the retaining nut 38 oriented towards the outside of the bore 18.
• the fingers 58 are for example formed by pins mounted in bores made in the transverse face 56.
• the tool comprises at least two fingers and preferably at least three.
• the tool 54 also comprises a central cavity 60 bordered by the annular face 56; the cavity 60 is intended to receive the projecting end of the compensator 20.
• the tool 54 comprises, at a longitudinal end opposite to that carrying the fingers, a recess 62 for mounting a lever forming tool capable of exerting a torque on the tool about the longitudinal axis.
• the cavity is projecting 62 and has a hexagonal shape and the tool is of the ratchet type.
• the recess is recessed and has a hexagonal, square section ..., the lever is then immobilized angularly on the tool 54 and the application of a torque on it causes the rotation of the tool.
• the side wall of the central cavity 60 is perforated to reduce the mass of the tool 54. Indeed, this tool is held at arm's length during assembly and disassembly operations.
• the retaining nut has protruding pins and that the tool has corresponding indentations.
• the tool 54 ' is similar to the tool 54; however, it is adapted to the tightening / loosening of the retaining nut 38 when the punch is mounted on the compensator 20.
• the central cavity 60 has a greater depth to accommodate the compensator and the punch.
• the tool 54 is mounted around the punch and is oriented so that the fingers 58 are opposite the housing of the nut. The tool is then moved axially close to the nut and the fingers penetrate into the housing. A torque is exerted on the tool 54 in the loosening direction of the nut 38. The nut 38 turns on itself and unscrews itself. Almost simultaneously, the sleeve 32 is driven in rotation and axially by the nut 38, the displacement of the sleeve 32 has a slight delay due to axial and radial play.
• the nut 38 and the sleeve 32 are removed. Then, the compensator 20 is extracted from the bore 18 by exerting a tensile force thereon.
• the seals are checked and replaced if necessary.
• the compensator 20 is introduced into the bore 18, preferably by means of a jacket (not shown).
• the compensator is oriented so that the anti-rotation rod mounted in the bottom of the bore enters the bore of the compensator.
• the sleeve assembly 32 and nut 38 is introduced into the bore 18 and mounted around the compensator.
• the mounting of the sleeve 32 is made with particular care not to damage the seals.
• the nut 38 is then screwed into the bore, which moves the sleeve 32 axially until it abuts against the annular bearing surface of the bore. Because of the radial clearance and the axial play, the sleeve 38 can be positioned on the compensator 20 and in the bore 18 without damaging the seals.
• the present invention simplifies the maintenance of the presses, more particularly the maintenance of the compensators by providing a simplified disassembly of the guide sleeve and a mounting of the sleeve protecting the seals.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Automatic Assembly (AREA)
• Presses And Accessory Devices Thereof (AREA)
• Press Drives And Press Lines (AREA)

Applications Claiming Priority (2)

Publications (2)

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• 2011
  • 2011-03-23 FR FR1152412A patent/FR2972957B1/fr not_active Expired - Fee Related
• 2012
  • 2012-03-21 JP JP2014500361A patent/JP5950134B2/ja active Active
  • 2012-03-21 RU RU2013147167/02A patent/RU2591921C2/ru not_active IP Right Cessation
  • 2012-03-21 WO PCT/EP2012/054954 patent/WO2012126930A1/fr active Application Filing
  • 2012-03-21 EP EP12711140.9A patent/EP2688741B1/de active Active
  • 2012-03-21 US US14/006,382 patent/US9114584B2/en not_active Expired - Fee Related
  • 2012-03-21 CN CN201280014732.5A patent/CN103442885B/zh active Active

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