US 3654970 A
A device for automatically supplying successive charges of powder to the die of a press, comprises a spoon carried by a flexible strip fitted with a strain gage associated with an apparatus for continuous weighing of the spoon and a vibratory feeder for pouring the powdered material progressively into the spoon. When the total weight of the powder and spoon attains a predetermined value, the flow of powder into the spoon is stopped and the spoon is moved forward and inverted so as to discharge its contents into the die chamber.
Claims available in
Description (OCR text may contain errors)
United States Patent Teboul [451 Apr. 11, 1972  DEVICE FOR FEEDING POWDERED  References Cited MATE L UNITED STATES PATENTS  Lapalud France 2,892,225 6/1959 Buhrer et al 164/336  Assignee: Commissariat A LEnergie Atomique, 3,537,156 11/1970 Glass Paris, France Primary Examiner-Houston S. Bell, Jr.  1970 Attorney-Cameron, Kerkam & Sutton  Appl. No.: 32,178
[ ABSTRACT  Foreign Application P i it D n; A device for automatically supplying successive charges of powder to the die of a press, comprises a spoon carried by a Apr. 30, 1969 France ..69l3828 flexible Strip fitted with a strain gage associated wiih an ap paratus for continuous weighing of the spoon and a vibratory  U.S. Cl ..l41/284, 164/ 155, 164/336, f d f pouring h Powdered material progressively into 177/62 177/108 222/77 222/363 the spoon. When the total weight of the powder and spoon at- [5 1] Int. Cl ..B67c 3/26, B67d 5/00 i a predetermined value, the fl f powder into the spoon Field of Search 141/73-81, 83, is stopped and the Spoon is moved f d and inverted so as 141/94, 102, 250-284; 164/1551 1 0 8 2 2 /}I77 g 6 3 to discharge its contents into the die chamber.
6 Claims, 7 Drawing Figures PATENTEUAPR 11 I972 3, 654,970
sum 2 [1F 3 PATENTEDAPR 1 1 I972 SHEET 3 [1F 3 DEVICE FOR FEEDING POWDERED MATERIAL This invention is concerned with a device for supplying powdered material to the die of a press, said device being intended to effect the automatic delivery of successive charges having a constant weight of powder.
In powder metallurgy, the technique involving fabrication of pellets by press-forming is frequently employed: in general, the powder is poured into the die chamber of the press until it takes up a constant and predetermined volume, whereupon said powder is compressed between two punches.
This method entails the need for virtually hydrostatic flow of the powder and for ensuring that the die chamber is filled with powder in a uniform and reproducible manner. However, on completion of the chemical process employed in the preparation of starting materials in the powdered state, there are some materials which exhibit poor flowability" and thus fail to satisfy the conditions mentioned above this is especially true in the case of single or mixed dioxides of actinides (U PuO (U, Pu) 0 etc.) as obtained by calcination of compounds such as diuranates and oxalates. In this case, it is necessary to pass through a long and costly intermediate operation known as granulation which is intended to convert the starting powder to granules having better flowability, with the result that charges of constant volume can be obtained in a reproducible manner.
The complexity of the granulation process can be illustrated by one example in connection with the fabrication of nuclear fuels having a mixed uranium and plutonium oxide base. The oxide powder is pressed to form compacts which are then crushed and granulated the granules are screened and the undersize and oversize fragments are rejected and recycled to the feed end of the process.
The primary object of the invention is to provide a device for automatically supplying powdered material to a press in charges of constant weight so that said material can occupy a variable volume within the die chamber in the event that it should have poor flowability.
To this end, the invention proposes a device comprising means for progressively pouring the powdered material into a container which is weighed continuously during the pouring operation and means for stopping the flow of powder into the container, automatically inverting said container so as to discharge its contents into the die chamber when the weight of powder added to the weight of the container attains a predetermined value and automatically renewing the same cycle at a frequency which corresponds to the rate of operation of the press.
This device makes it possible to employ any powder irrespective of its flowability and to ensure that the properties and especially the raw state density of the end product are more reproducible than has been the case heretofore by virtue of the fact that the operation is carried out with charges of constant weight and not of constant volume.
A better understanding of the invention will be gained from the following description of a device constituting one embodiment which is given by way of example without any limitation being implied, reference being made in the description to the accompanying drawings, in which:
FIGS. 1 and 2 are respectively a view in elevation and a top view showing the mechanical components of the device FIGS. 3, 4, 5, 6 and 7 are diagrammatic views of the device and ancillary components as shown during the successive stages of operation.
The device which is illustrated in FIGS. 1 and 2 comprises a stationary support 10, said support being secured to the press frame 12 which is shown diagrammatically in chaindotted lines. The frame is adapted to carry the body 14 of an operating jack 13 which is placed in such a manner as to ensure that the jack-piston rod 16 carries out a movement of displacement in parallel relation to the frame 12 of the press towards and away from the die chamber 18 (shown in chain-dotted lines in FIG. 1). The rod 16 of the jack is coupled to a moving system comprising an end-plate 20 which is attached to the rod 16 and to traction rods 22 which are guided in parallel relation to the rod 16 by the stirrup-piece 24 which carries the jack body 14. Said traction rods 22 are attached to a head 26 which is adapted to carry a lug 28 for controlling limiting switches 30 and 32 whose function will become apparent hereinafter. There is rotatably mounted on the head 26 a sleeve 34 fitted with a guide pin 36 which is slidably engaged in a skew groove 38, said groove being formed for this purpose in a cylinder 40 which constitutes an extension of the jack body.
There is attached to the sleeve 34 a flexible strip 42, the extremity of which is adapted to carry a spoon 44. The strip 42 is parallel to the axis of displacement of the moving system over the major part of its length and has an elbowed end portion in order that the edge of the spoon 44 should be located at the level of the axis of the jack 14. Thus, when the sleeve 34 rotates, the spoon is progressively inverted as it pivots about a diameter in the plane of its edge.
There is also slidably mounted in the head 26 a pin 46 which is guided parallel to the axis of the jack 13 by means of a bore formed in the stirrup-piece 24 (FIG. 2). A spring 48 is adapted to thrust the pin towards the position which is illustrated in FIG. 2 and which is determined by the application of a flange 50 of the pin against the head 26. The extremity of the pin 46 carries a funnel 52 by means of an electromagnetic vibrating mechanism 54. When the pin 46 is free and the spring 48 maintains the flange 50 abuttingly applied against the head 26, the funnel 52 and the spoon 44 take up relative positions as illustrated in FIG. I and 2. The pin 46 also carries a connecting funnel 56 (shown in FIG. 1) which is intended to connect the vibrating funnel 52 to the die chamber 18 when these elements are in aligned relation.
The pin 46 is also provided with an annular boss 58 (as shown in FIG. 2) which is intended to come into contact with a stop 60 carried by the support plate 10 when the jack 13 produces the forward displacement of the head 26. Any forward displacement of the head 26 which takes place when the annular boss 58 is in contact with the stop 60 is evidently accompanied by compression of the spring 48 whilst the pin 46 remains stationary. During this additional displacement, the spoon 44 moves with respect to the vibrating funnel 52. Thus, in the embodiment which is illustrated in FIGS. 1 and 2, provision is made for a relative displacement over a distance L corresponding to that portion of the travel of the sleeve 34 which produces pivotal motion of the spoon 44.
As shown in FIGS. 1 and 2, a strain gage 62 is carried by the strip 42 near the point of attachment of this latter to the sleeve 34 and constitutes the sensitive element of a device for weighing the spoon 44 as shown diagrammatically in FIG. 3. This device comprises a measuring instrument 64 and a trip relay 66 which delivers a signal when the weight of the spoon attains a predetermined value which is adjustable by means of a selector switch 68. In the embodiment which is illustrated in FIG. 3, the measuring instrument 64 is associated with a stripchart recorder 70 which, though not an essential element, does facilitate checking of correct operation.
When it is operated, the relay 66 trips the excitation mechanism of a vibrating distributor 74, said distributor being intended to discharge powder into the spoon 44 when this latter is in the position illustrated in FIGS. 1, 2 and 3, the powder being supplied from a hopper 76.
Provision is also made for a programming or timing system 72 which is of conventional type and will therefore not be described but serves to carry out the required sequence of operations in an automatic and repetitive manner in synchronism with the operation of the press which is associated therewith and the essential components of which are illustrated diagrammatically in FIG. 3. These components comprise a die 78 which defines the cylindrical die chamber 18, punches 82 and 84 being intended to engage within said chamber in a movement of vertical displacement.
Since the operation of the device will have become apparent from the foregoing description, only one cycle of operation will now be discussed briefly with reference to FIGS. 3 to 7. FIG. 3 shows the components in their initial positional arrangement, the punches 82 and 84 being thus located at the end of the range of travel resulting in compression of the pellet 80 which is contained within the chamber 18. The vibrating distributor 74 is excited and the powder contained in the hopper 76 is discharged into the spoon 44 which is maintained by the jack in the rear end position (namely in the extreme right-hand position shown in the figures). The measuring instrument 74 provides a continuous determination of the weight of powder contained in the spoon, said weight being marked on the recorder 70.
At the moment when the weight which is preselected by means of the switch 68 is attained, the relay 66 operates, trips the vibrating distributor 74 and actuates an electromagnetic valve 86 (shown in FIG. 3) by means of the system 72. Said valve supplies the jack so as to cause the forward motion of the moving system which comprises the head 26 and the spoon 44 During the forward motion of the moving system in the direction indicated by the arrow f in FIG. 4, the punches 82 and 84 must move so as to extract the pellet of powder which has just been compressed within the die chamber. To this end, the punch 82 moves upwards and is followed by the punch 84 which comes level with the top face of the die and ejects the pellet 80.
The displacement of the moving system continues in the direction of the arrow f and brings the connecting funnel 56 opposite to the die chamber by causing said funnel to slide over the top face of this latter. At the same time, the pellet which has just been formed is thrust aside by means of a small pin 88 which is carried by said funnel. The punch 84 then returns downwards to a bottom position in which it again closes the lower end of the chamber 18 of the die 78.
This relative arrangement is illustrated in FIG. 5 and corresponds to a displacement of the moving system from its starting position such that the annular boss 58 comes into contact with the stop 60. From this moment, the head 26 and the spoon 44 are capable of displacement only with respect to the pin 46 while compressing the spring 48.
During this final stage of forward motion of the head 26 from the position shown in FIG. 5 to the position shown in FIG. 6, the spoon 44 advances over the distance L while carrying out a pivotal movement, the sleeve 34 being driven in rotation by means of the skew groove 38. When the head 26 reaches the end of travel, the lug 28 closes the switch 30 (shown in FIG. 1) which initiates the operation of the vibrator of the funnel 52 and stopping of the jack. The duration of this vibration (while all the other components remain stationary) is established by the timing or programming circuit 72 of conventional type. At the end of this cycle, the circuit 72 reverses the electrovalve 86 and initiates the operation of the jack 13 in a direction corresponding to the movement of withdrawal of the head 26. Said head returns from the position shown in FIG. 6 to the initial charging position (as shown by the arrow j in FIG. 7). At the same time, the upper punch 82 begins to move downwards towards the die chamber 78. The spoon returns to the charging position as illustrated in FIG. 3, the lug closes the switch 32 and thereby automatically initiates a further cycle.
A device of the type described above has been constructed for the purpose of fabricating pellets of uranium oxide or mixed uranium and plutonium oxide, said pellets being intended to be employed as nuclear fuel. The weights specified were maintained with a degree of precision which was higher than 1 percent and the rate of production was seven pellets per minute. Much higher rates can be obtained if necessary by increasing the number of die chambers and correlatively the number of feed spoons.
It is therefore evident that the invention makes it possible to solve the problems associated with the use of materials provided in the form of powder which exhibits poor flowability while entailing only relatively simple arrangements and rugged means. Moreover, the device according to the invention can be perfectly integrated with a fully automatic, continuousproduction line and can in fact be controlled by the displacement of the press punches.
1. A device for automatically supplying successive charges of powdered material of constant weight to the die of a press, comprising a spoon carried by a substantially horizontal resilient strip provided with a strain gage which constitutes the detection element of a device for continuous weighing of the spoon, feeder means for pouring said powdered material progressively into the spoon and means for automatically stopping the flow of powder into the spoon, automatically rotating the spoon about a horizontal axis so as to discharge its contents into the die chamber when the weight of powder added to the weight of said spoon attains a predetermined value, and automatically renewing the same cycle at a frequency determined by the rate of operation of the press.
2. A device for automatically supplying successive charges of powdered material to a press die and the like, comprising a spoon carried by a resilient strip, means for continuously measuring the weight of said spoon comprising a strain gauge operatively associated with said strip, feeder means for pouring a flow of said powdered material into said spoon and control means actuated by said first named means in response to the weight of said spoon attaining a predetermined value for stopping said flow, impressing a rotating movement to said spoon whereby it is emptied into said press die, and bringing back said spoon into initial condition whereby initiating a new cycle.
3. A device according to claim 2, having a stationary horizontal cylinder, a sleeve slidable on said cylinder, a jack for reciprocating said sleeve along said cylinder, said sleeve carrying said strip and being operatively associated with said cylinder by guiding means which cause the sleeve to rotate about said cylinder in response to axial movement of said sleeve along said cylinder.
4. A device according to claim 3, wherein said guiding means comprises a pin secured to said sleeve and engaging a skew groove formed in said cylinder.
5. A device according to claim 3, additionally comprising a funnel connected by resilient means to said jack for axial movement and stationary abutment means for retaining the funnel above the die and between said die and spoon upon actuation of the jack.
6. A device according to claim 2, wherein said control means comprises means for manually adjusting said predetermined value and a trip relay adapted to delivers a signal which deactivates a vibratory feeder constituting said feeder means.