HK1010112B - Method of testing a container, test device, use - Google Patents

Description

The present invention relates to a process as defined in claim 1, a test order as defined in claim 14, and a use of the process or order as defined in claim 24.

The present invention relates to a test procedure as known from US-PS-5 029 464 and EP-A-0 313 678 and EP-A-0 432 143 respectively.

This shows that for the test of the tightness of containers, a pressure differential between a pressure inside the container and a pressure in its surroundings can be calculated and the behaviour of one of the pressures can be used to determine whether the container under test meets the specified pressure or volume conditions.

The pressure difference is calculated by placing the container to be tested in a sealing chamber connected to a pressure medium or suction source and, as a starting condition, by pre-switching a pressure value of the container environment to a reference pressure chamber, a differential pressure sensor, and comparing it with subsequent pressure values of the container environment.

The disadvantage of this method is that a differential pressure sensor must be provided with highly precise control valves to ensure that even the smallest leakage or slightest deviation of the container volume from a SOLL volume is detected.

It is known from DE-B-1 031 030 that the leakage of components is tested by first exposing them to a pressure difference, after which the output signal of a vacuum meter acting as a sensor is stored on a condenser, and the input of a gas discharge tube acting as a unit of comparison is charged after a period of about 1 second with the difference between the output signal of the vacuum meter and the signal on the condenser.

The present invention, based on a procedure or test procedure of the latter type, is intended to provide a defined signal at the output of the comparison unit at the beginning of the difference evaluation.

This is achieved by the procedure or test procedure of the said type, performed or implemented according to the characteristics of claims 1 and 14.

The pressure of interest is recorded by means of a relative pressure sensor, converted into an electrical signal, which is recorded at a given time during the leakage test and compared with at least one subsequent value recorded by the same sensor. A pressure value is specified and stored as a basis for comparison during the volume test, thus eliminating sensitive aggregates of a known arrangement, namely the differential pressure sensor and in particular the control valves which are particularly demanding in terms of characteristics.

The method of the invention is specified in preferred embodiments in claims 2 to 13.

Preferably, this is done according to the wording of claim 3 or claim 6 respectively, by connecting both the source connection for pressurising or suction media and the sensor input, either to the container interior or to the container environment.

The pressure difference can be calculated in various ways, which are quite familiar to the professional, for example by using a given load or suction capacity to construct the pressure difference over a given period of time and then evaluate both the pressure value achieved and its course.

The pressure relief can also be achieved, as is known from the above documents, by precharging a pre-chamber to a specified pressure and then discharging the said chamber into the container or into its surroundings formed by a sealed chamber.

In the volume test, a volume dependent on the volume of the container, whether its internal volume itself or its differential volume to a test chamber, may be loaded with a specified amount of pressurised medium or a specified amount of gas may be removed from that volume and the resulting pressure is then applied to the volume of the container.

Of course, the measured values are compared with SOLL values or SOLL trends, as is also known from the above-mentioned literature.

Preferably, according to the wording of claim 7, the storage is done by releasing an analogue/digital converter to convert the sensor output signal at a controlled time and then using the stationary output signal of that analogue/digital converter as a reference for subsequent evaluation of the sensor output signal, either by switching another analogue/digital converter to the sensor output and then comparing the output signal of the last selected converter with that of the storage A/D converter, or, preferably, by switching a D/A converter to the analogue/digital converter and then directly accessing the analogue signal and returning it to the analogue signal as a reference, so that the analogue signal is also stored and returned to the analogue signal, which is also readily comparable to the digital signal.

In the following, and following the wording of claim 9, a zero-matching is preferably done by essentially recording at the comparison unit during the value storage whether an output signal of the order is at least close to zero; if a signal differs from zero or a specified minimum value, it is used as a zero-matching signal.

Preferred embodiments of the arrangement of the invention are specified in claims 15 to 23.

The invention is then explained, for example, by means of figures.

It shows: Figure 1 schematically, an arrangement according to the invention in which the pressure relief or suction source and the pressure sensor are connected to the container environment;Figure 2 as schematically as Figure 1, a section of the apparatus according to Figure 1, in a further embodiment;Figure 3 in an analogue representation to Figure 2 the section in a third embodiment;Figure 4 in an analogue representation to Figure 2, the section in a further preferred embodiment;Figure 5 a functional block diagram of an apparatus according to the invention for performing a test procedure according to the invention;Figure 6 illustrates the flow of a measurement curve.

Figure 1 shows a diagram of a closed container 1 to be tested for leakage or volume, which may be already filled and is located inside a test chamber 3, for example, the chamber 3 is sealed by means of an insert lid 5 over a controlled valve 7 the test volume, here the difference volume between chamber 3 and container 1 is pressurised by means of a suction or pressure source 9 such that a pressure gradient 1 is created over the wall of the container.

The electrical output signal el of the sensor 11 is directed via a memory control circuit, as shown in S, to a control signal s given by a time control unit (not shown), which is stored in a memory unit 13. The output signal el of the memory 13 is fed to one of the comparator units 15 as a reference pressure.

The leakage test is considered first: if the tank 1 is closed and storage in tank 13 is not carried out until any pressure difference-related shape changes in tank 1 have been attenuated, the sensor output signal el will remain at the closed value elo.

In the case of leakage in tank 1 the signal value will change according to the direction of the pressure gradient over the tank wall, the higher the rate of change, the greater the leakage.

Comparison of the output signal of the comparator unit 15 with (not shown) SOLL values gives information on whether a leak is present and also on its extent.

If the leakage in tank 1 is large, no pressure difference will build up over the wall of tank 1 at all: the pressures between the tank interior and its surroundings will quickly equalize over the leakage, but then a zero signal would appear at the starting point of the comparator 15, as in the case of a sealed tank, and lead to test errors.

Therefore, preferably after storing the value elo in the storage tank 13, as shown in brackets, this stored value is compared at another comparator unit 17 with a reference value ref. The output signal of the further comparator unit 17 indicates whether or not a large leak is present.

For the volume test, a given volume of pressure medium is injected into chamber 3 or a given volume of gas is withdrawn. The reservoir 13 is used as a reference value storage, as shown in ref1 with dashes, where reference values corresponding to the SOLL volumes of the test vessels are pre-stored. By comparing the mentioned volume reference values ref1 and the actual pressure value corresponding to el in the differential volume in chamber 3, i.e. the output signal of the comparator unit 15, which depends on the internal volume of vessel 1, it is determined whether the vessel has or does not have a volume of 1 SOLL or whether the volume difference is as large as the IST/SOLL volume difference.

In the embodiment of Fig. 2, where the same parts are used for the same reference marks as in Fig. 1, only source 9 enters chamber 3. Through a tight closure 19 the sensor 11 is connected to the inside of the container 1 which is open here.

In Figure 3 an even more variation is shown, similar to Figure 2, in which the arrangements of source 9 and sensor 11 are replaced with reference to Figure 2.

In the arrangement shown in Fig. 4, the source 9 enters a container 1 via the sealing connector 19 and the input of the sensor 11 is connected to the container 1 inside. Here again the evaluation electronics shown in Fig. 1 are provided, with the sensor 11 connected.

In Fig. 5 a block diagram shows a preferred implementation of the output unit I, which is partially edged in Fig. 1. The output signal of sensor 11 is fed to the preferred embodiment of a converter stage 21 which initially comprises an analogue/digital converter, 21a, followed immediately by a digital/analogue converter 21b, the output of digital/analogue converter 21b is fed to a differential amplifier unit 23 built in a familiar way, as is the output signal of sensor 11.

The converter unit 21 and the memory unit 27 are controlled by a timing control 29 which operates as follows:

In order to store the value elo as shown in Fig. 1, the time control unit 29 releases a conversion cycle at the converter unit 21, whereupon the signal value elo appears at one of the inputs of the differential amplifier unit 23. Preferably at essentially the same time, the time control unit 29 controls the memory unit 27, returning the output signal value of the amplifier 25 as a zero-value matching signal to its input signal. If the output signal of the amplifier 25 is not zero when the input is stored, this signal value is used as a zero-compensation signal via the memory unit elo 27.

The detection of large leaks, as shown in Figure 1, can be carried out in various ways, for example by passing the output signal value of the transducer unit 21 to another (not shown) comparator, where it is compared with the reference signal value ref as shown in Figure 1, or by, as shown in S1 in parenthesis, immediately before or after setting the storage unit 27, preferably after setting it, switching the differential amplifier otherwise connected to the sensor 11 to an input reference potential, such as mass, and then starting the amplifier unit 25 from the value of ref directly to see whether it has reached a reference value of ref as shown in Figure 1 or not.

In contrast to the preferred embodiment shown, it is quite possible to omit the second converter stage, namely the digital/analogue converter 21b, and to provide for an analogue/digital converter, as shown in brackets in 22b, and then to process both signals, i.e. elo and el digital.

For the volume test, either the volume reference values 21 as shown in brackets at ref1 are pre-entered at the intended converter unit or another digital storage unit is directly connected to the digital/analog converter 21b to convert the input digital volume reference values into corresponding analog signals and then to use the displayed arrangement to also perform the volume measurement.

The apparatus shown is particularly suitable for in-line testing of containers such as a carousel conveyor, e.g. bottles, plastic bottles, etc.

In principle, it is also possible, after a specified test pressure has been reached, to compare the electrical output of the sensor with this or several preset values, which can be done, for example, on a computer where the sensor output is read.

Claims (25)

1. A method for testing a container (1), in which a differential pressure is built up between a pressure in the interior of the container and a pressure in the vicinity thereof, and conclusions are drawn from the behaviour of one of the pressures as to whether the container meets given testing conditions or not, and the electrical output signal of a pressure sensor (11) is stored for this purpose and then the electrical output signal of the sensor is compared with the stored signal value in a comparison unit (15), characterised in that the stored signal and the output signal of the sensor prevailing at the time of storage are applied to the inputs of the comparison unit (15) and a zero reference signal is produced therewith.
2. A method according to Claim 1, characterised in that the electrical output signal of the sensor (11) is compared with one or more pre-entered values.
3. A method according to one of Claims 1 or 2, characterised in that in order to build up the pressure difference the pressure in the interior of the container is increased or reduced and the internal container pressure is measured with the sensor.
4. A method according to one of Claims 1 or 2, characterised in that in order to build up the pressure difference the pressure in the interior of the container is increased or reduced and the pressure in the vicinity of the container is measured with the sensor.
5. A method according to one of Claims 1 or 2, characterised in that in order to build up the pressure difference the pressure in the vicinity of the container is increased or reduced and the internal container pressure is measured with the sensor.
6. A method according to one of Claims 1 or 2, characterised in that in order to build up the pressure difference the pressure in the vicinity of the container is increased or reduced and the ambient container pressure is measured with the sensor.
7. A method according to one of Claims 1 to 6, characterised in that the storage is effected by means of an analog-to-digital converter (21a) succeeding the sensor (11) and released for conversion at a given time.
8. A method according to Claim 7, characterised in that the analog-to-digital converter (21a) is succeeded by a digital-to-analog converter (21b) and the signals are supplied in analog form to the comparison unit.
9. A method according to one of Claims 1 to 8, characterised in that when supplying the stored signal value and the momentarily prevailing output signal of the sensor to the comparison unit the output signal of the comparison unit is detected and is stored as zero balance signal.
10. A method according to Claim 9, characterised in that the stored zero balance signal is taken into account for the subsequent signal comparison by returning it via at least one amplifier stage (25).
11. A method according to one of Claims 1 to 10, characterised in that after establishing the pressure difference the storage is effected after a given time period.
12. A method according to Claim 11, characterised in that the output signal of the sensor in the time period passes through a maximum point.
13. A method according to Claim 12, characterised in that a maximum point which has been passed through is detected by re-achieving a pressure value which had already occurred when building up the pressure difference.
14. A test arrangement for containers, with a pressure or suction source (9) which can be brought into active connection in terms of its internal and/or external pressure with a container (1) to be tested, having at least one pressure sensor (11) which emits an electrical output signal, and a storage unit (13, 21, 17) succeeding the pressure sensor output and a comparison unit (15) to which the output signal of the pressure sensor and the output signal of the storage unit are supplied, characterised in that when the sensor output signal is stored in the storage unit the output signal thereof and the output signal of the sensor are actively connected to the comparison unit.
15. A test arrangement according to Claim 14, characterised in that a container connection (19) with sensor pressure input (11) and source connection (9) is provided, which can be applied in sealing manner to a container opening (1).
16. A test arrangement according to Claim 14, characterised in that a container connection (19) with sensor input (11) is provided which can be applied in sealing manner to a container opening (1), and a chamber (3) which can be sealed closed for receiving the container (1), into which chamber the source (9) opens.
17. A test arrangement according to Claim 14, characterised in that a container connection (19) is provided with the source connection (9), which can be applied in sealing manner to a container opening (1), and a chamber (3) which can be sealed closed for receiving the container (1), on or in which the sensor input (11) is provided.
18. A test arrangement according to Claim 14, characterised in that a chamber (3) which can be sealed closed is provided for receiving the container (1), on or in which both the sensor input (11) and the source connection (9) are provided.
19. A test arrangement according to one of Claims 14 to 18, characterised in that the storage unit comprises an analog-to-digital converter, to the analog input of which the output of the sensor is actively connected.
20. A test arrangement according to Claim 19, characterised in that the analog-to-digital converter is succeeded by a digital-to-analog converter, the output of which is actively connected to the comparison unit.
21. A test arrangement according to one of Claims 14 to 20, characterised in that the comparison unit has at least one amplifier stage, the output of which is actively connected to the input of an additional storage unit.
22. A test arrangement according to Claim 21, characterised in that the storage unit and the additional storage unit are activated substantially simultaneously to store their respective input signals.
23. A test arrangement according to Claim 22, characterised in that the output of the additional storage unit is returned to an input of an amplifier stage at the comparison unit.
24. The use of the method according to one of Claims 1 to 13 and/or the arrangement according to one of Claims 14 to 23 for testing a container for leaks.
25. The use according to Claim 24 for testing a closed container for leaks.