JPS6017640B2 - Monitoring analysis method and device for double platen press operation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and method for monitoring and controlling the operation of a double platen press.

In particular, the present invention is useful when producing nuclear fuel pellets using a double platen press. This is because slight variations in press operation during nuclear fuel pellet production can exceed undesirable variations in fuel pellet density and thus have a detrimental effect on fuel pellet integrity. BACKGROUND OF THE INVENTION Instruments for obtaining visual indicators or electrical signals representative of the displacement of a single press platen are known in the art.

However, such conventional platen displacement indicating plates have been found to have limited utility when used in conjunction with dual platen presses. This is because information regarding the relative displacement and velocity of the press platens is required to properly monitor and control the operation of a dual platen press. A device for obtaining a visual indication of the relative displacement of the platens of a double platen press was also available in the related art. However, generally speaking, such counterfeits merely provided a pair of visual indicators that moved simultaneously on a vertical scale. The usefulness of this type of device is limited because in order to obtain information regarding the relative displacement of the platen, the observer has no choice but to compare the relative displacement of the two indicators. Furthermore, this type of device does not provide an indication of the relative speed of the press plate. Accordingly, there is a widespread need in the dual platen press industry for an apparatus that accurately records the platen displacement of each double platen press and provides an indication of the relative displacement and velocity of the press platens.
In the production of nuclear fuel, fuel in the form of U02 powder is suitably pressed into a pellet shape.

Such pellets are then phosphorized and then laid within a tubular cladding to form a complete fuel element. In that case, for reasons related to the design of the nuclear reactor and for the purpose of protecting the integrity of the fuel pellet, it is essential that the fuel pellet has a uniform, known density. If the density of the pellet in front of the scale varies, the fuel pellet may crack after the scale or after long-term use in a nuclear reactor. Therefore, when producing nuclear fuel pellets using a dual platen press, there is a critical need for a device that accurately indicates the relative displacement and velocity of the platen press. If such a device were available, continuous or periodic monitoring of press operation would result in maximum yield of qualified fuel pellets. Hydraulically operated double platen vertical presses are commonly used in the production of nuclear fuel pellets.

This is because such a press allows a large number of operating variables to be varied over a wide range, whereas various U02 fuel powders require different pressurization conditions. Hydraulically operated dual platen compression presses are known to have the ability to vary compression speed, ejection speed, relative movement between upper and lower platens, compression pressure and ejection retention force.
However, experience has shown that it is extremely difficult to determine the appropriate operating variables for a given U02 powder and then precisely adjust the compression press to meet those requirements. Even if the appropriate working variables are known for a given U02 powder, it is often extremely difficult to reproduce those variables during compaction pressing. Thus, the techniques involved in determining and/or reproducing appropriate press maintenance conditions for producing qualified nuclear fuel pellets from a given type of U02 powder with maximum yield. relied on operator skill rather than scientifically repeatable procedures. As a result, a need has arisen for a system that accurately relates various work variables to the measured displacement of the platen, the relative displacement of the platen, and the relative velocity of the platen. If such a device were available, the press operator could analyze the operation of the press to determine good press maintenance and
This should help in reproducing the press maintenance conditions for the two powders. In dual platen or single platen presses, each portion of the press cycle is generally stopped and started by displacement of the press platen actuating various microswitches.

However, the present invention seeks to provide a method and mechanism for generating signals useful for stopping and starting parts of a press cycle without the use of microswitches. Briefly, the invention is implemented by drawing a Lissajous figure based on the platen displacement of a dual platen press.

The sajous figure thus drawn represents the amount of movement and relative speed of the press platen. Note that the term "travel amount" used in this specification includes the actually measured displacement of the press platen. According to the invention, the displacement of both platens of a double platen press is measured. If these displacements are then applied on orthogonal axes so that they simultaneously control the motion of a single point, that point will draw a Lissajous figure. Thereafter, when the Sajous figure drawn in this way is superimposed on the second Lissajous figure representing the desired platen movement amount and relative velocity, the Sajous figure and the second Lissajous figure are drawn based on the actually measured displacement of the platen. Any deviation from this will indicate a deviation from the desired press operation. The slope of each portion of the first Lissajous diagram, drawn based on the measured displacement of the platen, indicates the relative velocity of the press platen during the portion of the press cycle under consideration. The actual displacement of the press platen can be directly measured from each part of the Lissajous figure, and the relative displacement of the platen can be determined by comparing those parts. In this way, the press operator can analyze the operation of the press simply by using the first Lissajous figure. Also, by detecting and using the completion of a predetermined portion of the Lissajous figure, each part of the press cycle can be analyzed. A press control method is also provided, such as stopping and starting parts.Furthermore, mechanical, optical and electrical devices are provided for drawing a Lissajous figure based on the transformation of both platens of a double platen press. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more clearly understood from the following description taken in conjunction with the accompanying drawings.

Referring first to FIG. 1, a hydraulic dual platen press is shown.

This press includes an upper and a lower hydraulic actuator 1.2,
They control the movement of the upper and lower pressure solders 3, 4, respectively. In the area between the upper and lower platens 3, 4 there is a die table 6 with a plurality of die cavities 7. Each of the upper and lower platens 3, 4 supports a plurality of cylindrical rams 8, 9, each of which is associated with a single die capacitance. The hydraulically actuated platens 3, 4 move the rams 8.9 vertically into and out of the die cavity, thereby compressing the U02 powder placed therein and compressing the compressed fuel pellet thus formed. Perform the protrusion. The normal working sequence begins with positioning the lower platen 4 so that the lower ram 9 is level with the surface 10 of the die table 6.

The lower platen is then moved downward and the die cavity is then filled with U02 powder to the desired depth. Thereafter, the upper die plate 3 is moved downward so that the upper ram 8 is aligned with the upper surface 10 of the die table 6. The U02 powder is then compacted by moving the upper and lower platens simultaneously and by exactly the same amount. Thereafter, the upper and lower platens move upward, thereby ejecting the compressed fuel pellet from the top of the die cavity. During the ejection portion of the press cycle, a ram 8 associated with the upper platen remains in contact with the compressed fuel pellet for the purpose of exerting a holding force on the pellet. In order to obtain such a protrusion holding force, spring techniques or pressure generated in the upper hydraulic actuator 1 may be used. When spring pressure is used to generate an ejection holding force, such a press is typically referred to as being in a standard ejection cycle.

During a standard ejection cycle, the hydraulic pressure in the upper hydraulic actuator 1 is released immediately after the completion of the compression portion of the press cycle, allowing the spring 11 to form the gap 12. As the lower ram pushes the fuel pellet out of the upper part of the die cavity as the ejection cycle progresses, the spring 11 provides a relatively constant holding force due to the formation of the gap 12. In order to vary the holding force during the standard ejection cycle to correspond to different press maintenance conditions, the spring preload may be varied by adjusting the spring gap 12 or a different spring 11 may be used instead of the spring 11. You can use another spring with a similar constant. Holding forces generated by hydraulic pressure are generally used when a holding force greater than that which can be generated by spring pressure is required for a pressing operation.

The hydraulic holding force is generated by manipulating the pressure in the internal chambers 13 and 14 above and below the piston 15 of the upper hydraulic actuator 1. The pressure above the piston is commonly referred to as back pressure, and the pressure below the piston is commonly referred to as weight control pressure. Hydraulic holding force can be generated by the use of back pressure alone or by the combination of back pressure and weight control pressure set at the beginning of the ejection cycle. If the holding force is generated hydraulically,
The spring gap 12 is closed. According to the invention, a method for monitoring, analyzing and controlling the operation of the above-described dual platen press is also provided.

This method consists of the following steps. The displacements of the upper and lower platens 3, 4 are measured and optical, mechanical or electrical signals representative of these displacements are generated. If these signals are then applied on orthogonal axes such that the displacement of both press platens simultaneously controls the motion of a point, that point will form a planar curve (in our case a Lissajous figure). draw. A Lissajous figure is generally known as a plane curve drawn by points that make two independent chord movements along orthogonal directions. A Lissajous figure drawn according to the method of the invention can be used directly by a press operator or in combination with a second Lissajous figure representing the desired platen displacement. In the first case, the operator uses the Lissajous diagram directly as a basis for monitoring and analyzing the operation of the press.
In the latter case, in order for the operator to monitor and analyze the operation of the press using the present invention, a first Lissajous diagram drawn based on the measured displacement of the platen is required for the type of press operation to be performed. It may be superimposed on a second Lissage figure which serves as a reference. In that case, the deviation between the first Lissajous figure and the second Lissajous figure indicates a deviation from the desired pressing operation. Whether or not used in combination with a second Lissajous figure, the first Lissajous figure provides an important diagnostic tool for press operators to monitor and analyze press operation. The slope of each portion of the first Lissajous figure indicates the relative speed of the press platen during the considered portion of the press cycle. The displacement of the press platen can be measured directly from each part of the first Lissajous figure, and the relative displacement of the platen can be determined by comparing the parts. Thus, the use of sajous shapes drawn in accordance with the method of the present invention allows press operators to monitor and analyze press operation and adjust various work variables to reproduce good press maintenance conditions. Alternatively, it can be helpful in initially determining a good press maintenance condition. The present invention also provides a method that eliminates the various microswitches typically used to detect platen displacement to stop and start portions of the press cycle. To perform this function, a predetermined portion of the first Lissajous figure may be detected and the next pressing operation may be triggered accordingly. Referring primarily to Figures 2 and 2b, a typical press cycle for a double platen press used in the production of nuclear fuel pellets will now be described in detail.

Figure 2a represents the displacement over time graph for the upper platen, and Figure 2b represents the displacement over time graph for the lower platen. Line segments on each graph are shown in uppercase letters. When the platens are in their initial positions, as represented by lines A and G, both platens are stationary. Meanwhile, U02 powder is placed on the die table above the die cavity. In position A, the upper platen 3 and ram 8 are completely separated from the die cavity. Further, at position G, the lower platen 4 is arranged so that the ram 9 is at the same height as the upper surface 10 of the die table 6. Next, if we move the lower platen downward as represented by the line segment, we get
U02 powder enters the die cavity. The upper platen then moves first rapidly downward, as represented by line segment B, and then more slowly, as represented by line segment B', once the ram 8 is one inch closer to the top of the die table 6. At the end of line segment B, ram 8 is placed on top surface 1.
Align with 0. Then, as represented by line segments C and J, the two platens are moved opposite each other at the same speed and by exactly the same amount. Thereby, the powder disposed within the die capacity is compressed to form a fuel pellet. In the next part of the press cycle, as represented by lines D and K, the lower platen continues to move upwards while the upper platen reverses direction. As a result, both platens move upward at the same speed. This is commonly referred to as the protrusion portion of the press cycle. The upper platen then rises away from the pellet, as represented by line segment E, and then retreats more rapidly, as represented by line segment 8'. On the other hand, the lower platen reaches the upper surface of the die table and stops moving as represented by line segment L. The press cycle is now complete, and both platens are now in position to begin the next press cycle.

The first and third examples are simple mechanical and optical rhombuses that correspond to the displacement of both pressure plates and draw a sajous figure as described above.
As shown in the figure.

This diamond layer consists of two plates 16 and 17 mounted on the sides of the press, overlapping each other.
The plate 16 is connected to the upper platen 3 by a filler 18, while the plate 17 is connected to the lower platen 4 by a filler 19. These plates have orthogonal slots 20 and 21 arranged overlappingly at right angles to each other. Case in point, each slot forms a 45 degree angle to the vertical. According to one embodiment of the invention, a light source 22 is arranged behind these plates, and the light source 22 from which the light source reaches the hawk hole 2
It will pass through the intersection 23 of 0 and 21. According to other embodiments of the invention, pens or heat markers can also be attached to the intersections of the slots. As the platen moves according to the cycle illustrated in Figures 2a and 2b, the intersection 23 of the two slots 20 and 21 moves in a pattern. Such a pattern is shown in FIG. 4, which is a Lissajous diagram of the press operation illustrated in FIGS. 2a and 2b. In Fig. 4, in order to show which part of the Lissajous figure corresponds to which part of the line segment in Figs. 2a and 2b,
The same symbols used to identify the line segments in figure b are used in combination. For example, part AH is created by the downward movement of the lower platen while the upper platen is stationary, and the intersection of the slots traces a straight line at a 45 degree angle to the vertical line. . Another example is the horizontal section denoted CJ.
Here, the two platens and therefore the two plates are moved by exactly the same amount in opposite directions. The result is a horizontal movement from right to left from the intersection of the slots. If the platens did not move synchronously at the same speed, the slope of line segment CJ would change.
A further example is section DK, where both platens move upwards together so that the intersection of the slots describes a straight line extending vertically.

The gradual rise of the upper ram while the lower ram is stationary is indicated by diagonal lines EL and E'L. In this way, a complete sajous diagram representing the displacement and relative velocity of the press platen is drawn. For monitoring purposes, a transparent plate 25 with a desired Lissajous figure 26 drawn thereon may be attached in front of the two plates 16 and 17.

In that case, when the two plates 16 and 17 move according to the press cycle, as long as the light passing through the intersection 23 of the two slots is written on the transparent plate 25 or moves along the sag figure 26, the press is confirmed to be working correctly. In embodiments of the invention in which a pen or heat marker is attached to the intersection of the slots, a suitable drawing surface is provided for marking the Lissajous figure resulting from the operation of the press. When a Lissajous figure is drawn using a moving light beam, means can be provided for detecting a predetermined portion of the Lissajous figure and initiating the next pressing operation thereon.

FIG. 5 shows a simple light-activated trip circuit that can be used with the apparatus of the invention shown in FIG. This type of circuit is known to those skilled in the electrical industry;
It can be generally described as a Schmitt trigger.
The collector of phototransistor 30 is connected to bias voltage Vcc. The emitter of phototransistor 301 is connected to the base of output transistor 31 and grounded via resistor 33. The outside of the output transistor 31 is connected to the output trigger line 38 and is also connected to the bias voltage Vcc via a resistor 32. The emitter of the output transistor 31 is grounded. Note that the base of the phototransistor 30 is arranged to receive the light beam 34 from the light source 22. An illustrative example of a circuit of the type of FIG. 5 suitable for use with the present invention includes phototransistor 30 being a Fairchild FRT1 31, output transistor 31 being any 2N222 transistor, and resistors 32 and 33, respectively. 3. Aki○ and lkQ.

In operation of such a circuit, the phototransistor 30
When the phototransistor 34 hits the photosensitive surface of the phototransistor 30, the phototransistor 30 becomes conductive, so that a voltage is applied to the base of the output transistor 31. Output transistor 31 then becomes conductive, thus providing an output force trigger on line 38. The output trigger line 38 can be connected in any suitable manner to stop or start operation of the press. Referring again to FIG. 3, a plurality of such photovoltaic trip circuits are typically provided.

In that case, phototransistor 30 is mounted on transparent plate 25 at points 40-46. Outside these phototransis, as mentioned above, the intersection point 2 of the slots 20 and 21
The arrangement is such that the completion of a predetermined portion of the Lissajous figure drawn by the movement of 3 is detected. When the light beam that draws the Lissajous figure hits the photosensitive surface of one of the phototransistors mounted at points 40 to 46 on the transparent plate 25, it is pressed by using the output power of the circuit shown in FIG. The next part of the cycle begins. In this way, the microswitches typically used to stop and start parts of the press cycle are eliminated. Although the above-described embodiments have been described, modifications can be made without departing from the spirit of the invention.

For example, plates 16 and 17 can be mechanically and hydraulically connected to the mura. A hydraulic connection between the above-described device and the press platen allows the device to be installed far away from the press. It may also be desirable to utilize only a portion of the Lissajous figure to obtain only the most important sections corresponding to the compression and extrusion portions of the press cycle, respectively. In that case, it is only necessary to equip devices that operate only in those compartments. Referring now to FIG. 6, an electrical implementation of such a device is shown.

The dual platen press 50 shown in FIG. 6 is of the same type as the press shown in FIG. 1, and like components have been given the same reference numerals. In such an electrical embodiment, linear variable differential transformers (LVDTs) 51 and 52 are provided for the upper and lower platens 3, 4, respectively.
is installed. The LVDT unit is a staple of those skilled in the fin industry, and the unit used herein serves to convert linear motion into a linear DC electrical signal. Electric power is supplied to the LVDT units 51 and 52 from electric wires 53 and 54, respectively.

Output signals V and V2 from LVDT units 51 and 52 are connected to X and Y terminals 57 and 58 of recorder 55, thereby drawing a Lissajous figure 56 on graph paper 59 representing the operation of the press. Recorder 55
can be any of the commonly available electrical recording devices. For example, recorder 55 may be a cathode ray tube, and the signals provided at terminals 57 and 58 may be used to drive the cathode ray tube's X and Y deflection circuits (see, e.g., FIG. 7). sea bream). An example of such an electrical implementation is that the LVDT unit 51 is a Shaevitz unit. 500
The additional DC-B and the LVDT unit 52 are connected to the shift unit M. It's 1B out of 200.

These LVDT units convert linear motion into linear DC electrical signals of ~10y. Power supplies 53 and 54 are Schevit M. This is a 15V DC power supply for Kamo M120. In addition, the recorder 55 is a Hewlett-Packard
ttPackard) 703 $ type X-Y recorder.
Referring now to FIG. 7, a different type of apparatus is shown for displaying a Lissajous figure representing the operation of a press and for detecting completion of a predetermined portion of the Lissajous figure.

Here, cathode ray tubes (CRTs) 70 and 71 are LV
The DT units 5 are connected to receive electrical signals V and V2 from 1 and 52, respectively. CR
T71 provides a visual display that allows operators to monitor and analyze press operations and also (
Alternatively) a comparison can be made with a reference Lissajous figure representing the desired platen displacement. On the other hand, CRT
Reference numeral 70 is provided as a means for detecting the completion of a predetermined portion of a sajous figure drawn based on the measured displacement of the platen. A mask 72 is fixed to the front surface of the CRT 70 with screws 73 or the like. On the mask 72, C
A plurality of phototransistors 74 are mounted to receive light from the Sajous figure drawn by RT 70. Each of the phototransistors 74 is actually part of a light guide tripping circuit as shown in FIG. can be used to stop and start parts of the press cycle. FIG. 8 shows a simple voltage comparator circuit that generates an 8-bit digital control word from the LVDT signals V and V2.

Circuits of this type are known to those skilled in the electrical industry. The signals from LVDT units 51 and 52 are 8
Bit analog-to-digital converters 60 and 61 are applied, respectively, where the signals V and V2 are converted into binary codes. Analog-digital converter 6
0 and 61 are stored in private storage devices 62 and 6 by the usual arrangement considering the most significant and least significant bits.
Connected to 3. Dedicated storage devices 62 and 6
Combining the outputs of 3 provides an 8-bit control word to be used to control the next press operation.

Analog-to-digital converters 60 and 61 and name-only storage devices 62 and 63 may be readily available commercially. By way of example, the analog-to-digital converters 60 and 61 may be ADC Models distributed by Ahalog Devices, Inc. (IM). In addition, Intel Corporation (lnt
el, Inc. 231 Jasei OM sold by ) is suitable. In operation of such a circuit, the analog signals V and V from the LVDT units 51 and 52 are
2 is converted to an 8-bit digital control word that can be used directly to stop and start parts of the press cycle, or to generate a series of programmatic responses. It may also be supplied to a digital processing device. In this way, the mechanically actuated microswitch typically used to trigger the next part of the press cycle can be eliminated. 9th
Figures a to 9i show various resjus obtained from the above-mentioned apparatus.
Figures are illustrated.

In the following description, using these Lissajous figures it will be explained how the Lissajous figures drawn according to the invention can be analyzed from the point of view of the pressing operation. In order to identify the series of press operations, each part of the press cycle is given the same symbol as in FIG. 4. The Nori-Sajous figures in Figures 4 and 9 differ only in the orientation of the orthogonal axis that applies the displacement of the base plate. Line segment AH represents lowering of the lower platen to fill the die cavity. line segment BI
and B'1 represents the downward movement of the upper platen. Curve CJ represents the compaction of the powder in the die cavity, and curve DK represents the extrusion of the compacted nuclear fuel pellet. And lines EL and EL represent the raising of the upper platen at the end of the press cycle. 9th a
Each of Figures 9i-9i represents various press setup conditions for producing a 0.5 inch tall nuclear fuel pellet from a 1.0 inch die capacitance fill depth.

Figure GA illustrates the Sajou figure observed based on the press maintenance condition judged to be "good" by an operator skilled in the maintenance of a hydraulic double platen press for manufacturing nuclear fuel pellets. In the figure, a solid curve 80 is drawn based on the actually measured displacement of the foundation and represents a sajous figure. Curve 80 is superimposed on an ideal sag figure 81 (arrows and dashed lines) to show the deviation of the press operation. A standard ejection cycle was used in this breather cycle. That is, the holding force exerted by the upper ram during the protruding portion of the press cycle was generated by the panes rather than by hydraulic pressure. For this kind of press work,
Assuming equal compression from the upper and lower platens, the Y component of the protruding portion of the curve should ideally be three times as large as the Y component of the compressed portion of the curve. It is shown. This becomes clear from the dimensional analysis of the compaction operation. To obtain a 0.5 inch height pellet from a 1.0 inch fill depth, both rams and therefore both platens must move 0.25 inch during the compression portion of the press cycle.

As a result, the bottom of the pellet will be located a distance of 0.75 inch from the top of the die tee pull, so both the upper and lower rams will need to move 0.75 inch to complete ejection of the pellet. It will have to be done. Therefore, the ratio of the Y components of the protruding portion and the compressed portion is 0.75:0.25 or 3:1. 9th
A comparison of the Sajiyu figure depicted in Figure a with the reference symbols (x and 2X) in Figure 9a shows that the ratio is less than 3:1. Therefore, even though this press maintenance condition was considered to be "good", it can be seen that the compression by the lower platen was greater than desired. Also, the 9th
Projected part DK and compressed part C of Lissajous figure in a
Since the slope of J is essentially 45 degrees, it can be seen that the speeds of the upper and lower platens were the same during the ejection and compression portions of the press cycle. number 8
2, the slight horizontal movement at the beginning of the ejection portion of the press cycle indicates that the upper ram has moved away from the pellet at the beginning of the ejection cycle. In this respect, the speed of the upper platen was exceeded because the lower ram had to overcome the initial friction of the pellet in the die cavity at the same time as the spring pressure weakened during the formation of the spring gap. The change in slope at the end of the ejection cycle, as indicated by number 83, indicates that the speed of the lower platen has increased during the ejection cycle, which probably results in the closing of the spring gap at the end of the ejection cycle. It should have been. The press maintenance condition, which was judged to be ``good'' by an operator who is skilled in the maintenance of double platen presses for producing nuclear fuel pellets but who does not benefit from the present invention, produced such a misaligned Lissajous figure. The fact that the present invention allows for improved analysis of press operations is shown. FIG. 9b illustrates a Lissajous diagram representing a press cycle in which compression by the upper platen is excessive.

A standard ejection cycle was also used in this case. Looking at the ratio of the Y component of the protruding portion and the compressed portion of the curve (approximately 9:1), it can be seen that the upper platen compressed approximately three times as much as the lower platen. This is because the lower platen was activated too late during the compression portion of the press cycle. This is because the slope of J in the protruding portion DK and the compressed portion of the Lissajous figure is basically 45 degrees, which indicates that the platen speeds were consistent. The overall shape of the protruding portion of this Lissajous figure is the same as in Figure 9a, since only the pressing position during the die cavity has changed. FIG. 9c illustrates a Lissajous diagram relating to a press cycle in which the amount of compression by the lower platen is excessive.

A standard ejection cycle was also used in this case. Looking at the ratio (1.6:1) of the Y component of the protruding portion DK and compressed portion CJ of the Lissajous figure, it can be seen that the amount of compression by the lower platen was excessive. The problem of too much compression by the lower platen is one of those rare cases that can be easily diagnosed by the operator. This is because at the beginning of the compression portion of the press cycle, there is a visible indication that powder is being forced out of the top of the die cavity before the top ram closes the top of the die cavity. 9th
Figure d illustrates a Lissajous diagram for a press cycle in which the speed of the lower platen is reduced.

A standard ejection cycle was also used in this case. The slopes of the protruding portions DJ of the Lissajous figure were all less than 45 degrees with respect to the horizontal line, indicating that the speed of the upper platen was greater than the speed of the lower platen. Looking at the ratio of the Y component of the protruding and compressed parts of the Lissajous figure, it can be seen that the compression amounts by both platens were the same, but the speeds were different. The speed of the upper platen during the ejection cycle greatly exceeded the speed of the lower platen, so that the holding force was completely lost during the ejection cycle. Looking at the change in slope during the compression cycle, it can be seen that the velocity of the upper platen was initially greater than the velocity of the lower platen, but as the compression pressure increased, the upper platen experienced a deceleration. Figure 9e is an illustration of a Lissajous figure for a press operation using hydraulic holding forces.

In the case of this press operation, the handling force was generated only by back pressure; no weight control pressure was set. If you look at this Lissajous figure, you can see that the amount of compression by the upper and lower platens was the same, but the speeds were initially different (the lower platen was slower). The horizontal portion (eg 82 in FIG. 9a) which is usually present at the beginning of the protruding portion of the Lissajous figure has been eliminated, so that it can be seen that the upper ram has begun to retract at the same time as the lower ram. The non-linear slope of the protruding portion of the Lissajous figure is believed to be indicative of pressure build-up on the underside of the piston within the upper hydraulic actuator. Figure 9f illustrates a Lissajous diagram for a press operation using hydraulic holding forces generated by manipulating both weight control pressure and back pressure.

This curve shows that the amount of compression by the upper and lower platens is equal, so it can be seen that the amount of compression is not dependent on the weight control pressure. The weight control pressure was set at the beginning of the ejection portion of the press cycle, resulting in the upper platen retracting at a faster rate than the lower platen. This can be seen from the fact that the initial slope during the ejection cycle is less than 45 degrees to the horizontal. It is believed that this occurs because only a few microseconds of time are available to perform the vacuum, set the weight control pressure, and then set the backpressure. The reason why the speed of the upper platen is faster in the initial stage is that sufficient back pressure cannot be set at the beginning of the L ejection cycle. This pressing operation was carried out again in Figure 9g with holding pressure applied. Holding pressure at the maximum compression point of the ram is carried out when the powder to be compressed has poor compression properties. Comparing the glue shapes in Figures 9g and 9f obtained with and without holding pressure, respectively, it can be seen that the normal operation of the press is not affected by holding pressure. 9th h and 9th
Diagram i illustrates the Lissajous diagram for a press operation using a hydraulic holding force generated using weight control pressure and back pressure.

Figure 9i represents a press cycle that produces a qualified pellet. However, Figure 9h shows the result of increasing the back pressure until the pellet collapses. This curve shows that the amount of compression by the upper and lower platens is equal. The pressure profile of the bullet during the ejection cycle can be seen from the fact that the slope becomes vertical at the end of the ejection portion DK of the sajous figure in Figure 9h, as indicated by numeral 84. The increase in backpressure is evidenced by the angle of curve 85 just before the compression point mirroring more than 45 degrees. The increase in backpressure is also evidenced by comparing the protrusions of the sajous shapes in Figures 9h and 9i. That is, the low horizontal movement (and therefore the low speed of the upper platen) ensures that the upper platen is prevented from accelerating more than the lower platen due to increased back pressure. Looking at the results of analyzing the various Lissajous figures shown in FIG. 9 from the viewpoint of press operation, it can be seen that the Lissajous figure drawn according to the present invention is an excellent diagnostic tool for the operation of a double platen press, as well as an excellent diagnostic tool for press operation. It becomes clear that a monitoring method is provided.

With such a new means of analyzing the press operation and relating it to the quality of the nuclear fuel pellet, it is possible to more quickly determine the appropriate operating parameters for a given type of U02 powder. As a result, the problem of obtaining good press maintenance conditions for UC2 powders, which require a known Lissajous figure according to known operating conditions, is reduced to adjusting the press so that the appropriate Lissajous figure is reproduced. Also, as long as the sajous figure drawn based on the measured displacement of the platen is created based on the desired platen displacement and matches the sajous figure, it is guaranteed that the press will continue to operate under the desired working variables. That is why it is done. Although the invention is particularly advantageous when applied to presses used for the production of nuclear fuel pellets, the invention also monitors any type of production operation in which dual platen presses are used, It should be understood that it can also be used advantageously to analyze press cycles and control press operations.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of a hydraulic double platen press that constitutes the single shelf embodiment of the present invention; FIGS. 2a and 2b are typical displacement hourly graphs for the two platens of the double platen press; FIG. 4 is a partial side view of the device of FIG. 1 taken along line 3--3; FIG. 4 is a Lissajous figure drawn by the device of FIG. 6 is a schematic front view of a hydraulic double platen press constituting another embodiment of the present invention; FIG. 7 is a counterfeit of FIG. 6; 8 is a schematic diagram of a rumor pressure comparator circuit that can be used with the device of FIG. 6, and FIG.
The figure is an illustration of a sajous figure drawn in accordance with the present invention. In the figure, 1' is the upper hydraulic actuator, 2 is the lower hydraulic actuator, and 3 is the upper hydraulic actuator.
is an upper platen, 4 is a lower platen, 6 is a die table, 7 is a die cavity, 8 is an upper ram, 9 is a lower ram, 11 is a spring, 16 and 17 are plates, 20 and 21 are slots, 22
is a light source, 23 is the intersection of the hawk holes, 25 is a transparent plate, 51 and 52 are linear variable transformers, 53 and 54 are power sources, 55
Recorder, 70 and 71 are cathode ray tube display discs, and 7
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Claims (1)

[Claims] 1. Measure the displacement of the first platen and measure the displacement of the second platen, and apply these two displacements on orthogonal axes so that both simultaneously move one point. try to control it,
A method for monitoring and analyzing the operation of a double platen press, characterized in that the points draw a first Lissage figure representing the displacement and relative velocity of the first and second platens. 2. The step of measuring said displacement comprises generating a first electrical signal representing the displacement of a first platen and generating a second electrical signal representing the displacement of a second platen. The method described in Scope 1. 3. The method according to claim 1, which is used in the production of nuclear fuel pellets. 4. Measuring the displacement of the first platen and measuring the displacement of the second platen, applying these two displacements on orthogonal axes so that they both simultaneously control the movement of one point,
Draw a first Lissage figure representing the movement amount and relative speed of the first and second platens using the points, and represent the desired platen movement amount and relative speed on the orthogonal axis on this first Lissage figure. It is characterized in that the second Lissage figure is superimposed to facilitate comparison between the first Lissage figure and the second Lissage figure. A method for monitoring and analyzing the operation of a double platen press. 5. Measuring the displacement of the first platen and measuring the displacement of the second platen, applying these two displacements on orthogonal axes so that they both simultaneously control the movement of one point, A first Lissage figure representing the movement amount and relative speed of the first and second platens is drawn using the points, completion of a predetermined portion of the first Lissage figure is detected, and a predetermined portion of the first Lissage figure is drawn. initiating the next pressing motion in response to detection of completion of the portion;
A method for monitoring and analyzing the operation of a double platen press. 6. A device for monitoring and analyzing the operation of a double platen press having a first and a second platen, the device comprising:
a first plate fixed to the first platen for measuring the displacement of the platen and having a slot arranged obliquely with respect to the direction of movement of the first platen; and the second platen. a second plate fixed to the second platen and having slots orthogonal to the slots in the first plate; and means for projecting a beam of light through an intersection point to draw a first Lissage figure representing the amount of movement and relative velocity of the first and second platens. 7. A device for monitoring and analyzing the operation of a double platen press having a first and a second platen, the device comprising:
a first linear variable differential transformer coupled to the first platen for measuring the displacement of the platen; and a second linear variable differential transformer coupled to the second platen for measuring the displacement of the second platen. a linear variable differential transformer, and having X and Y inputs connected to the first and second linear variable differential transformers, respectively, the two displacements of the first and second platens are orthogonally and a device for drawing a first Lissage figure representing the amount of movement and relative speed of the first and second platens by applying an electric voltage on an axis. 8. The device for drawing the first Lissage figure is an X-Y recorder. An apparatus according to claim 7. 9. The device for drawing the first Lissage figure is a cathode ray tube having X and Y deflection circuits connected to the first and second linear variable differential transformers, respectively. An apparatus according to claim 7.