GB2098758A

GB2098758A - Method and system for continuously monitoring and controlling a set of filling posts for gas bottles

Info

Publication number: GB2098758A
Application number: GB8211366A
Authority: GB
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 1981-04-22
Filing date: 1982-04-20
Publication date: 1982-11-24
Also published as: DK174282A; ES511526A0; ES8306242A1; DE3214629C2; DK162616B; GB2098758B; FR2504650A1; DK162616C; FR2504650B1; DE3214629A1

Abstract

The system comprises a carrousel (200) carrying a plurality of individual filling posts (210), a bottle-entry and data-recording device (100), a weighing device (400), an ejection device (500), and control, calculating and display means (600). It allows, by means of a comparison made subsequently between the actual weight of a filled bottle and the desired weight, on the one hand the follow-up control of each filling post and on the other hand the ejection of those bottles which are empty or under-filled. Furthermore, the measurements given by the weighing device are stored and subsequently reproduced in order to find the total production of each filling post and the production of the set of filling posts. Application to monitoring and control of the filling of bottles for compressed or liquefied gas. The weight is determined before the weigher reaches equilibrium from instantaneous measurements made at intervals of e.g. 100 ms. <IMAGE>

Description

SPECIFICATION Method and system for continuously monitoring and controlling a set of filling posts for gas bottles The present invention relates to a method for continuously monitoring and controlling a set of filling posts for gas bottles, and a system for carrying out this method.

Various systems are known for filling bottles with compressed or liquefied gas. Most frequently efforts are concentrated on the most advanced automation. However, notwithstanding the increased filling rate afforded by this automation it remains essentail to check individually the content of each bottle after filling in order to reject under-filled bottles. Furthermore this check makes it possible to ascertain systematic over- or under-filling. It should be possible to correct these differences by controlling the filling operation. However, such checking becomes very difficult if use is made of a carrousel comprising a number of filling posts for a single line of bottles.Checking downstream of the filling location, where it is not possible to identify what filling post has filled the bottle under inspection, only makes it possible to establish the deficit or excess of the set of filling posts as a whole. In order to control each post individually it is essential to perform this control immediately after filling, before the bottle is ejected from its filling post. Such a control cannot be carried out systematically for each bottle without the risk of unduly reducing the speed of the carrousel. The precision of control is accordingly reduced as is the speed at which the follow-up correction is effected.

In order to remedy this drawback, the present invention envisages a method for continuously monitoring and controlling each of a set of filling posts on the basis of measurements taken subsequently, downstream of each filling post, as well as a system for carrying out this method.

The method according to the invention comprises conducting a bottle to the vicinity of a data-recording device situated upstream of a filling post, which device records the tare data on said bottle, admitting the bottle to the filling post the number of which is recorded beforehand, filling the bottle, transferring the filled bottle to a cleared weighing device situated downstream of the filling post, weighing the bottle, reproducing the data on the tare and post number recorded upstream of the filling post, comprising the actual weight of the bottle with the desired weight in order to determine any over-or underfilling, determining, on the basis of a series of measurements on bottles filled by a given filling post, the average error for each filling post considered, and finally controlling each filling post in order to correct the systematic error thus revealed.

In addition, the measurements given by the weighing device can be stored and subsequently reproduced in order to find the total production of each filling post and the total production of the set of filling posts forming the carrousel.

A characteristic feature of the invention resides in determining the weight of the bottle in advance, on the basis of a series of instantaneous measurements before the weighing device has reached equilibrium, by determining the average of the resulting values. In this way it is possible to evaluate the bottle weight in a very short time, compatible with the rapid movement of the bottles along the filling line.

Another characteristic feature of the method according to the invention is the periodical measuring of the error caused by the weighing device and so adjusting the weighing operation as to eliminate the effect of that error.

To carry out the above method the invention proposes a system comprising a carrousel carrying a plurality of individual filling posts, a device for admitting bottles to the carrousel, a device for ejecting bottles from the carrousel, and a weighing device situated downstream of the ejection device, characterized in that the system further comprises: a data-recording post situated upstream of the filling posts and allowing the weight of an empty bottle to be recorded, means for reading and storing the number of the filling post to which the bottle has been admitted, calculating means, display means, and control means for the filling posts.

Preferably, the weighing device comprises a strain gauge scale from which a balance is suspended which receives the bottle to be weighed and comprising the counterweight which is integral with the balance when no bottle is present.

Finally, the system may also comprise means for ejecting empty or insufficiently filled bottles so that those bottles which have a gas load below a preset value are put aside.

Other characteristics and advantages of the invention will become apparent from the following detailed description, which is given with reference to the accompanying drawings wherein: Figure 1 is a diagram of the system showing the sequence of the various steps of the method and the arrangementofthe means for carrying out the method.

Figure 2 is a view of the weighing device, Figure 3 is a graph showing the instantaneous value of the weight of the bottle as may result from the measurement by the weighing device.

Figure 1 represents bottle entry and data-recording means 100, a carrousel 200 which carries a set of filling posts one of which is represented by 210, a device 300 for ejecting bottles from the carrousel, a weighing device 400, a device for ejecting empty or underfilled bottles 500, as well as a calculating, control and display unit 600, which may for example be a micro-processor of the type "micral S".

The bottle entry and data-recording means 100 comprises an entry conveyor 101, a data-recording device 102 and pushing means 103. The filling post 210 comprises a filling head 211 supplied with compressed or liquefied gas by a control device 212 which allows a larger or smaller quantity of gas into a bottle 213. A sensor 214 enables the filling post to be identified and its number to be transmitted. The ejection device 300 comprises pushing means 310 for pushing a bottle 302 onto a transfer conveyor 303 which passes the bottle to the weighing device 400. Downstream of this weighing device the empty bottle ejection device 500 comprises ejection pushing means 501, a lateral ejection conveyor 502 situated opposite the pushing means 501, and a discharge conveyor 503.Finally, the control and calculating unit 600 is connected on the one hand to the data-recording device 102, to the sensor 214 and to the weighing device 400 from which it receives the data, and on the other hand to the filling control device 212 and to the ejection pushing means 501, both of which are controlled by the said unit 600. A display panel 601 allows the display of a certain number of parameters relating to the operation of the filling line, and a printing unit 602 allows the storage of data supplied by the control and calculating unit 600.

An empty bottle arriving from the entry conveyor 101 is brought to a halt in position 104. Here the weight of the empty bottle is read, either automatically by coding information on the bottle or by an operator reading the information on a label arranged at the top of the bottle. This information is transmitted to the data-recording device 102 and subsequently to the control and calculating unit 600 where it is stored. The pushing means 103 is then activated to push the bottle onto the carrousel 200 where it is fixed, for example in the position 213, on one of the filling posts 210. It is here filled with a quantity of gas predetermined by the control device 212 on the basis of the data supplied by the control and calculating unit 600. During the filling operation the carrousel 200 makes one rotation in the direction indicated by the arrows 201 and 202.When the filling is completed the bottle occupies the position 302, where it is ejected from the carrousel by the action of the pushing means 301. The bottle is subsequently passed to the weighing device 400. After weighing the bottle arrives at position 504. If its weight as determined at the weighing post 400 is insufficient, the control and calculating unit 600 activates pushing means 501 which pushes the bottle onto the empty bottle ejection conveyor 502 for a subsequent treatment to determine the reason for underfilling.

If the weight is correct the bottle proceeds along the discharge conveyor 503.

Figure 2 represents the weighing device 400. A scale 401, which receives on its tray 402 a bottle 403 to be weighed, is suspended from a balance 404 integral with a frame 405. The device used may be of the "ISP2" type strain gauge. A device of this type automatically converts the weight measured into a digital signal which can be directly used by the control and calculating unit 600. The lower part of the tray 402 may be made integral with a weight 406 which rests on a fixed support 407 by means of a connecting device 408.

In the absence of a bottle the tray 402 occupies a high position so that the device 408 is in connection with the weight 406 and lifts the latter from the support 407. A counterweight is thus effected by the weight 406 if no bottle is present. When a bottle is placed on the scale the tray 402 descends, the weight 406 rests on the support 407 and the device 408 disconnects the weight from the tray. The counterweight, thus disengaged in the presence of a bottle, allows excessively large vertical oscillations of the scale to be avoided.

Preferably the counterweight also serves to determine the error produced by the weighing device, by periodical comparison of the actual weight of the counterweight and the measurement given by the weighing device when there is no bottle on the scale. The error, in terms of over- or under-weight thus estimated, is transmitted to the control and calculating unit 600 which deducts it from or adds it to the weight of the bottle indicated by the device for all subsequent measurements, thereby eliminating this systematic error.

Figure 3 represents the weight measurement given by the balance 404. The abscissa shows the time, the ordinate the weight in kg. This measurement, which is the apparent weight of the bottle, varies according to curve 700, which is depicted as a broken line. This measurement is not constant as the result of parasitic oscillations of the scale resulting from loading of the bottle. The apparent weight tends to stabilize around the value 701 after a prolonged period of time owing to the inertia of the mechanical combination balance-scale. This time is too long in view of the rapid passage of the bottles. It is therefore necessary to be able to evaluate this final value in advance, without having to wait for definitive stabilization of the unit. To this end the ISP2 balance provides a series of measuring points 710,711,712 etc. at regular intervals of 100 milliseconds.This series of instantaneous values is transmitted to the control and calculating unit 600 which evaluates the average value, represented in the Figure by the value 720 which is therefore an approximation of the exact value 701. The number of measuring points is invariably the same; it is so chosen that the total sum: loading time of the bottle on the tray + measuring time (number of measuring points x per interval between two points) + the time required for disengaging the tray, remains on average smaller than the passage time of the bottles along the filling line. In orderto improve the measurement accuracy, recording of the measurement points is not begun before the error between the highest measurement and the lowest measurement remains below a pre-determined value. If, in the example of Figure 3, this maximum admissible error is for example 80 g, as represented by the arrow 730, it can be seen that the points 710 and 711 will be disregarded since their error (120 g) is too large, whereas points 712,713,714 etc. will be considered since they remain within the accepted limits.

Alternatively, a calculation of the average can be envisaged by a process not numeric as in the example described but analogical, where the damping of the curve 700 will be effected for example by integrator circuits.

The value 720, an estimation of the weight 701 of the bottle, is subsequently compared by the control and calculating unit 600 with the desired value, which equals the weight of the empty bottle + the standard gas load. The difference thus determined is stored at the same time as the data on the number of the post already transmitted by the sensor 214 at filling. When a sufficiently large number of such differences is known for one post the average is determined, which provides an indication of the deviation produced by the filling post 210. As a result, the latter can then be immediately and continuously readjusted such that the error found is eliminated.

It should be understood that the above specification is not limited to one particular embodiment of the invention, and that a large number of variants may be envisaged without departing from the scope of the present invention.

Claims

1. A method for continuously monitoring and controlling a set of filling posts for bottles for compressed or liquefied gas, characterized in that the method comprises: conducting a bottle to the vicinity of a data-recording device (100) situated upstream of a filling post (210) and recording the tare data on the said bottle, admitting the bottle to the filling post (210) the number of which is recorded beforehand, filling the bottle, transferring the filled bottle to a cleared weighing device (400) situated downstream of the filling post, weighing the bottle, reproducing the data on the tare and post number recorded upstream of the filling post, comparing the actual weight of the bottle with the desired weight in order to determine any over- or under-filling, determining, on the basis of a series of measurements on bottles filled by a given filling post, the average error for each filling post considered, and finally, controlling each filling post in order to correct the systematic error thus revealed.

2. A method as claimed in claim 1, characterized in that determination of the weight of the bottle after filling is effected in advance, on the basis of a series of instantaneous measurements made from the moment the bottle is admitted to the weighing device and before the latter has reached equilibrium, by determining the average of the values of said measurements, and providing that the difference between the maximum value and the minimum value of the series of values is below a predetermined quantity.

3. A method as claimed in claim 1 or 2, characterized in that it also comprises periodical measurement of the error caused by the weighing device, the value of which measurement serves to so adjust the weighing operation as to eliminate the effect of that error.

4. A method as claimed in any one of claims 1 to 3, characterized in that the measurements given by the weighing device are stored and subsequently reproduced in order to find the total production of each filling post and the production of the set of filling posts.

5. A system for use in the method as claimed in any one of claims 1 to 4, comprising: A A carrousel (200) carrying a plurality of individual filling posts (210), a a device (100) for admitting bottles to the carrousel, a a device (300) for ejecting bottles from the carrousel, and a a weighing device (400) situated downstream of the ejection device, characterised in that the system further comprises: - a data-recording post (102) situated upstream of the filling posts (210) and allowing the weight of an empty bottle to be recorded, - means (214) for reading and storing the number of the filling post to which the bottle has been admitted, calculating means (600), display means (601), and control means (212) for the filling posts.

6. A system as claimed in claim 5, characterized in that the weighing means (400) comprise a strain gauge balance (404) from which a scale (401) is suspended which receives the bottle to be weighed (403).

7. A system as claimed in claim 6, characterized in that the weighing device comprises a counter-weight (406) which is integral with the scale of the weighing device when no bottle is present, and disengaged when the bottle is admitted.

8. A system as claimed in claim 7, characterized in that the counterweight also serves to determine the error produced by the weighing device, by periodical comparison of the actual weight of the counterweight and the measurement given by the weighing device when there is no bottle on the scale.

9. A system as claimed in any one of claims 5 to 8, characterized in that it also comprises means (500) for ejecting empty or underfilled bottles, which means co-operate with the weighing device, so that those bottles which have a gas load below a preset value are put aside.

10. A method for continuously monitoring and controlling a set of filling posts for bottles for compressed or liquefied gas, substantially as described with particular reference to the accompanying drawings.

11. A system for use in the method as claimed in claim 10, substantially as described with particular reference to the accompanying drawings.