EP0077468A2 - Pressing device for the manufacture of compacts for nuclear fuel - Google Patents

Abstract

Press device for producing compacts from powdered starting material, in particular powdered nuclear reactor fuel, with a die which is located in a die table and which has a die hole assigned to a press ram for receiving powdery starting material, and with a movable arm which can be moved over the die table filling shoe on the die table for pouring powdered starting material into the die hole, which has an outlet opening facing the die table with a filling aid device and is more softly connected with a hose to a storage container for powdered starting material provided with a metering device. It is provided that a passing wheel (16) is arranged in the outlet opening (20) of the filling shoe (14) as a filling auxiliary device, that a pipe (6) is connected between the hose (12) and the storage container as a metering device, in which a pipe (6) coaxial feed screw (9) is that the reservoir is a base part (22) with a can-like attachment part (23) and with in the bottom with respect to the longitudinal axis (23a) of the can-like attachment part (23) arranged eccentrically to the tube (6) with the Conveying screw (9) leading outlet bore (22a) has that at the opening (23b) of the can-like attachment part (23) sits a coupling part (24), which with an opening (23b) of the can-like attachment part (23), eccentric to the longitudinal axis (23a) of the can-like attachment part (23) arranged through hole (24a) is provided and to which a cover part (25) located between base part (22) and coupling part (24) is assigned, which also has an eccentric ch to the longitudinal axis (23a) of the can-like attachment part (23) arranged passage opening (25a) is provided, and that the coupling part (24) and the cover part (25) relative to each other about the longitudinal axis (23a) of the can-like attachment part (23) in one position are rotatable, in which the passage opening (25a) in the cover part (25) and the outlet bore (22a) in the base part (22) are aligned.

Description

The invention relates to a pressing device for producing compacts from powdery starting material, in particular powdered nuclear reactor fuel, with a die which is located in a die table and which has a die hole associated with a press ram for receiving powdery starting material, and with a die attached to a movable arm, Filling shoe, which can be moved over the die table and is in contact with the die table, for filling powdered starting material into the die hole, which has an outlet opening facing the die table with a filling aid device and which is connected with a hose to a storage container for powdered starting material provided with a metering device.

Such a pressing device is already on the market. A vibrating grid is arranged in the filling shoe of this commercially available pressing device, which supports the filling of the powdered starting material into the die hole as a filling auxiliary device. Furthermore, the storage container for powdered starting material is an open funnel with a flat slide as a metering device for metering the powdered starting material supplied to the filling shoe.

The vibrating grid in the filling shoe of this pressing device ver However, causes the leakage of substantial amounts of powdery starting material at the seal, which the filling shoe has towards the die table. Furthermore, the transfer of powdered starting material from a storage or transport can into the open funnel causes a strong dust development, which also leads to losses of powdered starting material. Such losses also occur on the slide with which the open funnel is equipped for metering the powdery starting material fed to the filling shoe. _'

The losses mentioned are particularly important when processing powdered nuclear reactor fuel such as U0 ₂ or UO ₂ / PuO ₂ powder, since these powdered nuclear reactor fuels are not only very expensive, but also toxic and radioactive.

This applies in particular to powdered nuclear reactor fuels containing plutonium, which are generally processed in so-called glove boxes to avoid toxic and radioactive contamination of the operating personnel, the interior of which is dust-tight from the outside environment.

Since the press device on the market shows a dust development and a powder discharge on the filling shoe, which are too large for the processing of powdered nuclear fuels, this pressing device causes considerable cleaning work in this glove box during installation and operation in a glove box, which regularly recur and the z. B. when processing plutonium-containing powdered nuclear reactor fuels can lead to high radiation exposure - the operating personnel.

The invention is based on the object, remedy here to create and largely avoid dust and powder losses on the pressing device when producing compacts from powdered starting material.

To achieve this object, a pressing device of the type mentioned at the outset is characterized in that a passing wheel is arranged in the outlet opening of the filling shoe as a filling auxiliary device, that a tube is connected between the hose and the storage container as a metering device, in which there is a screw which is coaxial to the tube that the storage container has a base part with a can-like attachment part and with an outlet hole that is arranged eccentrically in the floor with respect to the longitudinal axis of the can-like attachment part and leads to the tube with the screw, that a coupling part sits at the opening of the can-like attachment part, which has a coupling part for opening the can-like attachment part leading, eccentrically arranged to the longitudinal axis of the can-like attachment part is provided and which is assigned a cover part located between the base part and coupling part, which also has an eccentric to the longitudinal axis of the do Sen-like attachment part arranged passage opening is provided, and that the coupling part and the cover part are rotatable relative to each other about the longitudinal axis of the can-like attachment part in a position in which the through hole in the coupling part with the through opening in the cover part and the outlet bore in the base part are aligned.

The impeller can, for example, be provided with bristles on its circumference, with which it, when it is rotating, passes the powdered starting material into the die hole in the outlet opening of the filling shoe. This prevents vibrations in the filling shoe, which can lead to losses due to the escape of powdered starting material between the filling shoe and matrix table occur.

The tube with coaxial feed screw connected as a dosing device between the hose and the storage container completely covers this coaxial feed screw and thus also prevents losses of powdered starting material from occurring on the dosing device.

The can-like attachment part can be, for example, a hollow cylindrical transport or storage box for powdery starting material with a screw cap. After unscrewing the screw cap, the coupling part is screwed onto the box and closed with the cover part. Then the box with the coupling and the lid part is placed on the base part. If the through-hole in the coupling part, the through-hole in the cover part and the outlet hole in the base part are aligned, powdered starting material can get from the transport or storage box into the tube with the coaxial screw to this conveyor screw without the formation of dust and thus without loss of powdery starting material .

This pressing device also has the advantage that the impeller can be driven without vibrations, so that a renewal of the seal, which is located on the filling shoe towards the die table, is only very rarely required. Furthermore, the impeller and its bearings are subject to much less wear than guides for vibrating grids, so that time-consuming and expensive repair work, which can be associated with a high radiation exposure for the operating personnel, can be avoided with this pressing device.

It is advantageous if the impeller is an impeller that has an axis of rotation that coincides with that of the outlet opening certain plane forms an angle of 90 ° or at least approximately 90 °. Such an impeller smashes powder bridges which form in the outlet opening of the filling shoe on the die table and can lead to the die bore not being filled uniformly with powdered starting material.

• Fig. 1 zeigt einen Ausschnitt aus einer erfindungsgemäßen Preßvorrichtungmit zum Teil in Längsrichtung geschnittenen Einzelteilen.
• Fig. 2 zeigt die Draufsicht auf ein Einzelteil nach Fig. 1.

The invention and its advantages are explained in more detail with reference to the drawing using an exemplary embodiment:

• Fig. 1 shows a section of a pressing device according to the invention with parts cut partly in the longitudinal direction.
• FIG. 2 shows the top view of an individual part according to FIG. 1.

1 has a die table 2 and a stand 3. In the die table 2 there is a die 4 with an open die hole 5 perpendicular to the die table 2.

On the stand 3 eini ^is horizontally disposed tube 6 supported on a frame 7 with screws. 8 In this tube 6 there is a coaxial screw 9, with which the tube 6 forms a dosing device. At one end of this screw 9, a flexible shaft 10 is connected, which is coupled to the shaft of an electric motor, not shown.

At one end, the tube 6 is provided with an attachment part 30, into which the interior of the tube 6 opens and which has a vertically downwardly directed pipe socket 11. On this pipe socket 11 sits one end of a deformable hose 12 made of polyvinyl chloride, the other end of which sits on a pipe socket 13 of a filling shoe 14.

This filling shoe 14 rests on the die table 2 and is attached to a two-part arm 15, with which it can be moved over the die table 2 in FIG. 1 from right to left and left to right, i.e. H. back and forth, can be moved.

The filling shoe 14 has a frustoconical interior, which tapers towards an outlet opening 20, which is directed towards the die table 2. The nozzle 13 of the filling shoe 14 opens into this interior. An impeller 16 with an axis of rotation is arranged in the outlet opening 20 as a passing wheel, which forms an angle of 90 ° with the plane defined by the outlet opening 20. The edges of the impeller 16 facing the die table 2 are flat and flat and lie in the same plane with the flat and flat contact surfaces 14a with which the filling shoe 14 rests on the die table 2. The outlet opening 20 is enclosed by an annular felt seal 17 which is embedded in the likewise annular contact surface 14a. The impeller 16 is connected to a flexible shaft 18 which is coupled to the shaft of an electric motor, not shown.

On the other end of the tube 6 with the flexible shaft 10 sits a sleeve 21, the cross section of which has a rectangular outer circumference. The jacket of this sleeve 21 is provided on the top with a bushing 21a, which is aligned with a bushing 6a in the jacket of the tube 6, which leads to the conveying path of the screw 9. On the outside of the sleeve 21 sits at the top a base 22 of a storage container for powdered starting material with a can-like attachment part 23 belonging to the storage container the sleeve 21 and 6a in the casing of the tube 6 are aligned.

At the opening 23b of the can-like attachment part 23, a hollow cylindrical coupling part 24 is screwed to the attachment part 23, which tapers in the shape of a funnel to a passage bore 24a, which is arranged eccentrically to the longitudinal axis 23a of the can-like attachment part 23 on the bottom of the coupling part 24.

Between the coupling part 24 and the base part 22 there is a pot-like cover part 25, which in its bottom also has a passage opening 25a arranged eccentrically to the longitudinal axis 23a of the can-like attachment part 23.

The cover part 25 closes the through bore 24a in the coupling part 24, as long as the can-like attachment part 23 is not placed on the base part 22.

Appropriate guiding and locking devices, such as punctures, axially directed grooves and associated pins on the base part 22, on the cover part 25 and on the coupling part 24, can achieve that the can-like attachment part 23 can only be placed on the base part 22 such that the outlet bore 22a in the base part 22 is aligned with the passage opening 25a in the cover part 25. The locking devices ensure that the can-like attachment part 23 with the coupling part 24 can only be rotated about the longitudinal axis 23a of the can-like attachment part 23 relative to the cover part 25a to such an extent that the outlet bore 24a in the base part 24 is aligned with the passage opening 25a and the outlet bore 22a, when the coupling part 24 with the cover part 25 is placed on the base part 22.

Above the die hole 5 in the die 4 in the die table 2, an upper press ram 31 is indicated in FIG. 1, with the one being filled in the die hole 5 powdery starting material is compacted into a compact.

1 and 2, a can-like attachment part 23, which contains, for example, UO ₂ / PuO ₂ powder, is opened with the opening 23 b directed vertically upwards. The coupling part 24, on which the cover part 25 is located, is hereby screwed tightly onto the opening 23b. Here, the outlet bore 24a in the coupling part 24 is closed by the cover part 25.

Then the can-like attachment part 23 with the vertically downward opening 23b and the coupling part 24 together with the cover part 25 is placed on the base part 22, so that the passage opening 25a in the cover part 25 is aligned with the outlet bore 22a in the base part 22. By rotating the can-like attachment part 23 with the coupling part 24 about the longitudinal axis 23a of the can-like attachment part 23 with respect to the cover part 25, the through hole 24a in the coupling part 24 is brought into alignment with the passage opening 25a in the cover part 25. As a result, the U0 ₂ / Pu0 ₂ powder flows loss-free from the can-like attachment part 23 to the feed screw 9 in the tube 6, through which it is also conveyed to the attachment part 30 without loss. From the attachment part 30, the powder again flows loss-free through the hose 12 into the interior of the filling shoe 14 located above the die hole 5, from where it is passed into the die hole 5 with the help of the impeller 16 which is rotating.

Then the filling shoe 14 with the arm 15 in FIG. 1 on the die table 2 is pushed to the right, ie to the rear, so that the die hole 5, which is filled to the top with powdery starting material, is released Then, the upper press ram 31 is pushed into the die bore 5 and the powder in the die bore 5 is pressed to form a compact against a lower press ram, not shown in FIG. 1, located in the die bore 5. After retracting the upper ram 31 into its initial position shown in FIG. 1, the compact formed in the matrix bore 5 is ejected from the latter onto the die table 2 by a relative movement between the die 4 and the lower ram located in the die bore 5, from which die it is pushed into a storage container, not shown, by the filling shoe 14, which is moved again from right to left, ie from the back to the front, in FIG. 1 on the die table 2. In the end position of this movement from right to left, ie from the back to the front, the filling shoe 14 is again above the die hole 5, which is filled again with UO ₂ / PuO ₂ powder.

A particularly favorable passing effect is achieved if the blades on the circumference of the impeller 16 form an angle of inclination which is not equal to 90 ° with the plane determined by the outlet opening 15 of the filling shoe 14 and thus also with the plane determined by the die table 2.

It is advantageous if the filling level of the U0 ₂ / Pu0 ₂ powder in the filling shoe 14 is always the same, so that the filling quantity of powder in the die bore 5 always has the same value. It is thereby achieved that the height and weight of all compacts, which are compacted to a uniform density by the upper punch 30, are always the same. It is therefore advantageous if an electrical capacitor electrode is arranged in the filling shoe 14. Such an electrical capacitor electrode is advantageously the metal bearing 19 of the impeller 16 located in the interior of the filling shoe 14, which is in contact with the metals NEN die table 2 forms a capacitive level indicator as a counter electrode. This capacitive level indicator can be connected as a sensor to a controller, not shown, with which the speed of the electric motor, which is also not shown and which is coupled to the flexible shaft 10 of the feed screw 9, is regulated.

To avoid metallic abrasion that could get into the powdered starting material and possibly interfere there, it is advantageous if the tube 6 and the hose 12 made of plastic, for. B. polyethylene, while the screw 6 located in the tube 9 is made of stainless steel.

Also to avoid metallic abrasion and to facilitate the formation of a capacitive level indicator, it is advantageous if the housing of the filling shoe 14 is also made of plastic, preferably polyethylene.

The filling shoe 14 is pneumatically pressed against the die table 2 by means of a lever 32 articulated on the arm 15 with a constant contact pressure. As a result, uniform wear of the felt seal 17 in the filling shoe 14 is achieved without any manual adjustment of this seal 17. It is expedient if the filling shoe 14 is mounted on the movable arm 15 via ball bearings 28 about an axis of rotation 29 transversely to its direction of displacement on the die table 2. As a result, the filler shoe 14 can better follow the oscillating movements of the die table 2, so that the felt seal 17 in the filler shoe 14 fits well on the die table even during such swinging movements 2 is present and any losses of powdered starting material which penetrates this seal 17 can be avoided.

Claims (7)

1. Press device for producing compacts from powdered starting material, in particular powdered nuclear reactor fuel, with a die, which is located in a die table and which has a die hole assigned to a press ram for receiving powdery starting material, and with an attached to a movable arm, over the Filler shoe which can be moved and is in contact with the die table for filling powdered starting material into the die hole, which has an outlet opening facing the die table with a filling aid device and which is connected with a hose to a storage container for powdered starting material provided with a metering device, characterized in that in the Outlet opening (20) of the filling shoe (14) as a filling aid, a passing wheel (16) is arranged that a tube (6) is connected between the hose (12) and the reservoir as a metering device, i n to which there is a coaxial feed screw (9) for the tube (6), that the storage container has a base part (22) with a can-like attachment part (23) and with an eccentrically arranged in the bottom with respect to the longitudinal axis (23a) of the can-like attachment part (23) Pipe (6) with the delivery screw (9) leading outlet bore (22a) has that at the opening (23b) of the can-like attachment part (23) sits a coupling part (24) which is connected to the opening (23b) of the can-like attachment part (23 ) leading, eccentrically to the longitudinal axis (23a) of the can-like attachment part (23) arranged through bore (24a) and to which a cover part (25) located between the base part (22) and coupling part (24) is assigned, which also has an eccentric to the longitudinal axis (23a) of the can-like attachment part (23) arranged through opening (25a) is provided, and that the coupling part (24) and the cover part (25) can be rotated relative to one another about the longitudinal axis (23a) of the can-like attachment part (23) into a position in which the through bore (24a) in the coupling part (24), the through opening (25a) in Align the cover part (25) and the outlet bore (22a) in the base part (22). 2. Press device according to claim 1, characterized in that the impeller (16) is an impeller which has an axis of rotation which forms an angle of 90 ° or at least approximately 90 ° with the plane determined by the outlet opening (20). 3. Press device according to claim 2, characterized in that the wings on the circumference of the impeller with the plane determined by the outlet opening (20) form an inclination angle which is not equal to 90 °. 4. Press device according to claim 1, characterized in that an electrical capacitor electrode (19) is arranged in the filling shoe (14), which forms a capacitive level indicator with the die table (2) as a counter electrode. 5. Press device according to claim 1, characterized in that the tube (6) connected between the hose (12) and the storage container is made of plastic, preferably polyethylene, and the feed screw (9) located in the tube (6) consists of stainless steel. 6. Press device according to claim 1, characterized in that the housing of the filling shoe (14) consists of plastic, preferably polyethylene. 7. Press device according to claim 1, characterized in that the filling shoe (14) on ball bearings (28) about an axis of rotation (29) is rotatably mounted transversely to its shear direction on the movable arm (15).

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