EP2311773B1 - Method and device for applying screw caps to containers, in particular bottles - Google Patents

Description

The invention relates to a method and a device for screw-closing vessels, in particular bottles, according to the preamble of claim 1 or 11.

Screw caps of vessels, such as bottles, are known to be closed in rotary machines with several circumferentially arranged and rotating about a common axis Verschließstationen, the caps are held in Verschließköpfen and these are both rotated after placement on the respective bottle mouth and the thread pitch lowered accordingly , Alternatively, the bottles can be raised accordingly during the rotation of the cap.

It is from the published patent application DE 10 2007 057 857 A1 Known to accomplish both the stroke and the rotation of a capping head when closing a vessel via a combined linear rotary drive.

From the publication DE 10 2007 047 742 A1 It is also a method and a device for screwing of vessels, in particular bottles, according to the preamble of claim 1 or 11 known, wherein the torque or the power consumption of a motor for rotating the shutter is measured in particular when applying a closure strip provided on the guarantee To set and control the maximum torque when applying the guarantee band and finally tightening the closure separately.

However, there is still a need to be able to close vessels both with a lower error rate and, if appropriate, to be able to discharge incorrectly closed vessels with a low error rate from a continuous product stream, in particular using a capping head with a linear rotary drive.

It is an object of the invention to provide an improved in this regard method for closing vessels and a corresponding device.

This object is achieved by a method in which the power consumption of the linear drive system of the closure head in a pick phase for receiving the respective closure cap and / or in a screwing phase for screwing on the closure cap is measured and compared with at least one characteristic value of the power consumption in order to prevent an impending or Failure to recognize. The power consumption of the linear drive system can be used as a measure of the contact pressure of the capping head and thus give a direct inference about the contact between the capping head and the cap or the cap and the vessel mouth. Depending on the specification or selection of the characteristic value, individual phases of picking up and screwing on the closure cap can be specifically controlled. A characteristic value here is to be understood as meaning a single value, such as a threshold value, or a current profile, such as a positive or negative current peak, which serves as a reference value in a specific time segment of the method in order to be able to decide whether the closing process is correct or incorrect. The term power consumption is used as a representative of all electrical variables that correlate directly or indirectly with the applied engine power, in particular as a measure of an applied contact pressure of the capping head or the cap.

Preferably, the position of the closing head is also determined with respect to the linear axis of the linear drive system. As a result, it is possible to assign a position of the capping head to individual measured values of the power consumption. Accordingly, it can be checked whether or not a current value is allowed at a certain position, thus improving the reliability of error detection. Likewise, it can be concluded from a specific course of the power consumption to a possible change in position of the capping head along the linear axis.

Preferably, the characteristic value is an upper threshold of power consumption in the pick phase. When the upper threshold value is exceeded, it is possible to conclude that an inadmissibly high contact pressure force is applied, and thus to recognize or decide whether or that the closure cap is deformed and / or is not screwed on correctly. As a result, an impending false closure can be detected or a miscarriage can be avoided.

Preferably, the characteristic value is a lower threshold of power consumption in the pick phase. If the lower threshold value is undershot, it is possible to infer an impermissibly low contact force and thereby recognize or decide whether or not the closure cap or a guarantee band of the closure cap is missing. As a result, an impending false closure can be detected or a miscarriage can be avoided.

Preferably, the characteristic value is a characteristic peak of the current consumption in the pick phase, and it is checked whether the characteristic peak occurs in the pick phase. Overcoming a mechanical resistance when the cap engages in the capping head produces a momentary increase in power consumption. It can therefore be recognized or decided upon occurrence of the characteristic current peak, whether or that the cap was correctly received by the capping. This makes it possible to make a statement that a cap can be screwed on with a particularly high probability correctly. In particular, in combination with a comparison of the power consumption and the travel of the linear axis with at least one threshold, the validity of the review can be further increased and improve quality assurance.

Preferably, the characteristic value is an upper threshold of power consumption in the screw phase. If the upper threshold value is exceeded, an increased mechanical resistance during screwing on can be deduced, as arises, for example, when a guarantee strip starts up at the bottle mouth. Thus it can be recognized or decided whether or that a guarantee band has been correctly attached. This ensures the quality of the closure.

Preferably, the characteristic value is a characteristic peak of the power consumption in the screwing phase, in particular during a rotation against the closing direction, and a starting position of the closing head at the beginning of the thread formed by the closure cap and the vessel mouth is determined on the basis of the characteristic tip. This makes it possible to determine a reference value for an absolute position determination of the bottle mouth. Such a determination is largely independent of tolerances of individual closing stations and therefore particularly accurate.

Preferably, based on the starting position at the beginning of the thread, a lower target end position of the capping head is calculated, and the power consumption when reaching the target end position is compared with a further characteristic value of the power consumption. As a result, the screw connection can be checked at a defined end point of the screwing phase. This allows a final inspection of the screwing process.

Preferably, the further characteristic value is a lower threshold of power consumption in the screwing phase. If the lower threshold value is undershot, it can be recognized or decided whether or not the closure cap is unscrewed correctly or that the vascular muzzle is missing. As a result, a false closure can be detected.

The vessels are preferably supplied as a continuous product stream, and vessels that are recognized as being incorrectly sealed are discharged from the product stream. This can ensure that only properly sealed bottles are processed.

The technical problem is further solved by a device for screw-capping vessels, in which a measuring device is provided for measuring the power consumption of the linear drive system, and an evaluation device for comparing the measured during recording and / or screwing the cap power consumption with a characteristic value of power consumption, to detect impending misclosure or mishap. With the measuring device, a measure of the contact pressure of the capping head can be determined and thus directly on the contact between the capping head and the cap or the cap and the vessel mouth are deduced.

A particularly advantageous embodiment further comprises a control device for determining the position of the capping head with respect to the linear axis. As a result, it is possible to assign a position of the capping head to individual measured values of the power consumption. Accordingly, it can be checked whether or not a current value is allowed at a certain position, thus improving the reliability of error detection. Likewise, it can be concluded from a specific course of the power consumption to a possible change in position of the capping head along the linear axis.

A favorable embodiment further comprises a discharge device for discharging incorrectly closed vessels. This can ensure that only properly closed vessels are processed.

Preferably, the device according to the invention further comprises a control device that can control the linear drive system and the rotation drive system so that only caps for which no imminent miscorriage was recognized, are screwed.

It is also possible by the current consumption of the linear axis when screwing on the mouth to influence the speed of the axis of rotation, for example, the System to adapt to changed gradients and / or heights of the mouth / closure. Here it would be conceivable to create a kind of self-learning system in which only start and end angle and characteristic thresholds affect the system.

Figur 1

eine schematische Darstellung einer erfindungsgemäßen Vorrichtung;

Figur 2

ein schematisches Ort-Zeit-Diagramm des Verschließkopfs während des Auf- nehmens einer Verschlusskappe und ein zugehöriger Strom-Zeit-Verlauf ei- nes Linearantriebssystems des Verschließkopfs

Figur 3

ein schematisches Ort-Zeit-Diagramm des Verschließkopfs während des, Aufsetzens, Aufschraubens und Festziehens einer Verschlusskappe auf einer Gefäßmündung sowie zugehörige Strom-Zeit-Verläufe eines Linearantriebs- systems und eines Rotationsantriebssystems des Verschließkopfs.

A preferred embodiment of the invention is shown in the drawing. Show it:

FIG. 1

a schematic representation of a device according to the invention;

FIG. 2

a schematic location-time diagram of the capping head during the recording of a cap and an associated current-time course of a linear drive system of the capping

FIG. 3

a schematic location-time diagram of the capping head during the placement, screwing and tightening a cap on a vessel mouth and associated current-time courses of a linear drive system and a rotational drive system of the capping.

As Fig. 1 can recognize, is an inventive embodiment of the device 1 for closing bottles 2 or the like vessels designed as a rotary with a plurality of circumferentially uniformly on the device 1 Verschließköpfen 3 for receiving and holding each a screw cap 4, each of which a motor 5, for example a servo motor , for lifting or lowering the capping head 3 by means of a linear drive system L and for rotating the capping head 3 by means of a rotary drive system R is assigned (drive systems L, R not shown separately). The motors 5 could also be stepper motors or any linear motors, wherein the drive systems L, R need not necessarily be combined in one motor or housing. Devices for introducing and discharging the bottles 2 are known in the art and therefore not shown.

For the sake of simplicity only schematically indicated for the right-hand motor 5 are electrical supply lines with ammeters 7 for measuring the electrical currents I _L and I _R flowing through the drive systems L, _R and a control device 9 for determining the position y of the closing head 3 with respect to the linear axis L For example, the control device 9 could be part of a servo drive system. The axis of rotation R 'is also indicated for the sake of completeness, the systems L, R driving the closing head 3 via a common shaft.

In combination with a neck star 10 for holding the bottles 2 to be closed on their collars 2a, the closing heads 3 form closing stations 11 over a certain machine angle range, as in FIG FIG. 1 indicated on the right. In order to keep in particular PET bottles 2 against rotation in the neck star 10, elevations or spikes are provided in this, which can be brought into engagement with corresponding recesses in the bottle collars 2 a (not shown in detail). Instead, glass bottles or reusable PET bottles could be held against rotation in a known manner, for example via a belt clamp.

On the left side of the FIG. 1 shown is a picking station 12, which is formed by the Verschließköpfen 3 with a pick wheel 13 and a supply 14 for the screw caps 4. Here, the closure caps 4 are provided on the pick wheel 13 in synchronization with the Verschließköpfen 3 and picked up by these by lowering over the respective cap 4 or picked. For this purpose, a centering and clamping device 3a for the closure cap 4 is preferably provided in the closing head 3, for example in the form of spring-mounted circumferential balls.

The caps 4 are received and screwed on as follows and the process monitored by measuring the currents I _L , I _R and the linear position y of the capping head. Typical measuring curves are in FIG. 2 and 3 illustrated, wherein the currents I _L and I _{R are} always shown as positive values regardless of their respective drive direction for the sake of simplicity.

Accordingly, the closing head 3 for picking up or picking a closure cap 4 is first lowered to a position y ₀ just above the closure cap 4. As in FIG. 2 schematically illustrated, the current I _L increases from a base value l ₀ for holding the capping head 3 against gravity to a substantially constant value during the lowering. In a substantially central position over the cap 4, the closing head 3 is then lowered a second time in a picking phase P ₁ , wherein a lower target position y ₁ at the end of the picking phase P ₁ from the known coordinates of the capping head 3, the cap 4 and the Picking wheel 13 with respect to the linear axis L 'can be determined.

During a majority of the picking phase P ₁ , a substantially constant current I _{L flows} . However, the engagement of the closure cap 4 into the closure head 3 or the overcoming of a mechanical resistance in the centering and clamping device 3a by a brief increase in the current I _L in the form of a current peak S ₁ noticeable. Typically, the current peak S _{1 is} within a time period T _S1 , which is preferably no longer than one-fifth, in particular not more than one-tenth of the duration T _{P1 of} the picking phase P ₁ . The current peak S ₁ is typical for a correct locking of the cap 4 and serves as a characteristic comparison value, the occurrence of which expresses a normal behavior of the current I _L. Thus, a correct picking of the cap 4 can be detected on the basis of the course of the current I _L in the picking phase P ₁ .

The current I _L remains at correct picking the cap 4 in the picking phase P _1, at least with the exception of the short-term current fluctuation S ₁ within a certain range of measurement. Thus, an upper and a lower threshold value I ₁ and I ₂ can be defined, in the case of which an error is exceeded or fallen short of. For example, a faulty closure cap 4 with asymmetrical cross-section can only be pressed into the closure head 3 with an increased mechanical resistance or not at all, as a result of which the current I _L rises above the upper threshold value I ₁ . In the absence of cap 4, however, the current I _L remains below the lower threshold I ₂ . The threshold values I ₁ and I ₂ are thus characteristic comparison values whose exceeding or falling below expresses an abnormal behavior of the current I _L. If necessary, separate frequency components of the current signal I _{L could be} compared with the characteristic values S ₁ and I ₁ or I ₂ by suitable filtering in order to avoid misinterpretations. This also applies to the comparison with further characteristic values described below.

Falling below the lower threshold value I ₂ can also be observed at least at the beginning of the picking phase P ₁ if a guarantee strip 4 a on the closure cap 4 is missing, since in this case the total height of the closure cap 4 is less than with the guarantee strip 4 a and the closing head 3 the cap 4 is touched late when lowering. In this case, the measurement of the current I _L can be compared with a simultaneous registration of the linear position y of the capping head 3 in order to increase the hit probability and / or accuracy of the error determination.

Thus, in the picking station 12, by monitoring the current I _L in the picking phase P _1, damage or lack of the cap 4 can be detected and a subsequent mishandling in the capping station 11 avoided by, for example, unscrewing a damaged cap 4 onto an associated bottle 2 becomes. The fitting, screwing and tightening of the caps 4 in the closing station 11 is based on the phases P ₂ and P ₃ in FIG. 3 indicated by way of example. Accordingly, the closure caps 4 are lowered in the Verschließköpfen 3 at the beginning of Aufschraubphase P ₂ under specification of a desired stroke of the linear drive system L, wherein the current I _L in the section P _2a in particular when placing the cap 4 on the bottle mouth 2b increases.

By the stroke of the bottle collar 2a is pressed onto the spikes of the neck star 10. In this case, it is both possible to rotate the closure cap 4 at the beginning P _{2a of} the unscrewing phase P ₂ in the closing direction or against the closing direction, as well as in FIG FIG. 3 hinted not to turn.

In FIG. 3 the cap 4 is rotated after pressing on the spikes in the section P _2b against the closing direction. The seated on the thread of the bottle mouth 2b cap 4 is moved by this rotational movement initially as when opening the shutter of the bottle mouth 2b away, causing the contact pressure of the cap 4 and as a result of the current I _L continue to increase until the pressed together or sliding Screw threads of the cap 4 and the bottle mouth 2b at a time t _P2 or threading.

Turning against the closing direction in the section P _2b is not absolutely necessary, but has the advantage that the closure cap 4 locks abruptly and immediately after reaching a relative upper maximum position y _{3 of} the closing head 3. Associated with this is a characteristic current peak S ₂ , in particular a transient drop in the current I _L due to the momentarily lower contact pressure during latching. For detecting the current peak S ₂ , an associated time window T _S2 (not shown) can be defined within the screwing phase P ₂ . The characteristic current fluctuation S ₂ can be used to determine a defined upper starting position y ₃ for the subsequent section P _2c , in which the closure cap 4 is screwed on in the closing direction. From the upper starting position y ₃ , in turn, a desired value for a lower end position y ₄ can be calculated when the cap 4 is completely screwed on to check the screwing operation.

In section P _2c , the closing head 3 is continuously pulled down by the thread. Therefore, the contact pressure of the closing head 3 and thus the current I _L in this phase is smaller than immediately before the engagement or threading of the sliding on each other Thread. The current I _L is the smaller the smaller the difference between the stroke of the capping head 3 and the predetermined by the rotational speed about the rotation axis R 'and the thread pitch movement of the cap 4 along the linear axis L' is.

In section P _2c , a characteristic current peak S ₃ in the current I _L may additionally occur when starting the guarantee strip 4 a via the so-called Pilferproof ring (not shown), which is provided on the bottle mouth 2 b for fastening the guarantee strip 4 a. Accordingly, a tip S ₃ in the operating current I _R of the rotary drive system R occur, wherein the current consumption I _R of the rotary drive system R is a measure of the torque or torque of the closing head. 3 Thus, the application of the guarantee band 4a can be monitored by registering the current I _L or I _R , the current peaks S ₃ and S _{3 'representing} characteristic comparison values, in the absence of which an abnormal behavior of the current I _L or I _R can be closed, caused by a missing or incorrectly applied guarantee strip 4a. Conversely, when the current peak S ₃ or S _{3 'is} detected, a correctly applied guarantee strip 4 a can be closed.

In particular, given the specification of a suitable time window T _S3 in the section P _2c, it is also possible to check whether the current I _L or I _R rises above a threshold value I ₃ or I _{3 '} . In this case, the threshold value I ₃ or I _{3 'is} a characteristic comparison value, which can be inferred if it exceeds or falls permanently below a correctly or incorrectly attached guarantee strip 4a.

The Aufschraubphase P ₂ ends with the complete screwing the cap 4, essentially as soon as the lower target end position y _{4 of} the capping head 3 is reached. Since a mechanical resistance must occur at the target end position y ₄ when the cap 4 is screwed on correctly, the current I _L at the end position y _{4 must} not be below a characteristic threshold I ₄ . Thus, the threshold value I _{4 can be used} as a characteristic comparison variable for the current I _L , when exceeding or falling below in the section 2c a correct or incorrect fit of the cap 4 or a closure of the bottle 2 can be detected. In addition, the current I _R can also be compared here with an associated threshold value (not shown).

The tightening phase P ₃ subsequent to the Schraubphase P _2, in which the closure of the rotary drive unit R is tightened in known manner by a certain tightening torque by a metered raising the current I _R, the current I _L of the linear drive unit L is set so that a sufficient contact pressure of the capping head 3 is ensured.

Subsequently, the closing head 3 is withdrawn from the closure cap 4 or the closed bottle 2. The capping head 3 moves into an ejector position, upon reaching which a cap 4, which may not be screwed on, is inserted in the capping head 3, is removed from the capping head and is then moved back into a starting position with respect to the picking station 12.

The evaluation of the current measurements for error detection or determination of a correct picking and closing takes place in an evaluation unit (not shown) by comparing the measured current I _L or I _R with at least one characteristic comparison value, wherein the above-described threshold values and current peaks arbitrarily as characteristic comparison values can be combined. Error messages can occur via suitable output units (not shown), for example with the aid of acoustic and / or optical signals. Likewise, it is possible to specifically control the production on the basis of the current measurements with the aid of a control unit (not shown) in the case of a detected faulty closure and / or a recognized impending faulty closure.

For example, improperly sealed bottles 2 may be removed by a discharging device (not shown) after the closing device, e.g. a pusher, to be selectively discharged from the product stream by activating the discharge device via signals issued by the control unit. As a result, a higher production quality can be achieved overall.

In this case, the current measurement offers a variable possibility of recognizing the sequence of closing in different phases of operation as being correct or incorrect with only a small amount of equipment.

Claims (14)

1. Method for screw capping containers (2), in particular bottles, wherein screw caps (4) are screwed to a container (2) to be capped by means of a capping head (3) coupled to a motor-driven linear drive system (L) and a motor-driven rotational drive system (R), characterised in that the power consumption (I_L) of the linear drive system (L) is measured in a pick phase (P₁) for picking the respective screw cap (4) and/or in a screw phase (P₂) for screwing on the screw cap (4) and is compared with at least one characteristic value of the power consumption of the linear drive system (L), in order to detect an impending or actual faulty capping operation.
2. Method according to Claim 1, characterised in that additionally the position (y) of the capping head (3) is determined with respect to the linear axis (L') of the linear drive system (L).
3. Method according to Claim 1 or 2, characterised in that the characteristic value is an upper threshold value (I₁) of the power consumption (I_L) in the pick phase (P₁).
4. Method according to at least one of the preceding claims, characterised in that the characteristic value is a lower threshold value (I₂) of the power consumption (I_L) in the pick phase (P₁).
5. Method according to at least one of the preceding claims, characterised in that the characteristic value is a characteristic peak (S₁) of the power consumption (I_L) in the pick phase (P₁), and in that it is checked whether the characteristic peak (S₁) occurs in the pick phase (P₁).
6. Method according to at least one of the preceding claims, characterised in that the characteristic value is an upper threshold value (I₃) of the power consumption (I_L) in the screw phase (P₂).
7. Method according to at least one of the preceding claims, characterised in that the characteristic value is a characteristic peak (S₂) of the power consumption (I_L) in the screw phase (P₂), in particular during a rotation against the capping direction, and in that on the basis of the characteristic peak (S₂) a start position (y₃) of the capping head (3) is determined at the start of the thread formed by the screw cap (4) and the container opening (2b).
8. Method according to Claim 7, characterised in that on the basis of the starting position (y₃) at the start of the thread a lower target end position (y₄) of the capping head (3) is calculated, and in that when the target end position (y₄) is reached the power consumption (I_L) is compared with a further characteristic value of the power consumption (I_L).
9. Method according to Claim 8, characterised in that the further characteristic value is a lower threshold value (I₄) of the power consumption (I_L) in the screw phase (P₂).
10. Method according to at least one of the preceding claims, characterised in that the containers (2) are fed as a continuous product flow, and in that containers (2) detected as having been incorrectly capped are diverted from the product flow.
11. Apparatus (1) for screw capping containers (2), in particular bottles, having:

    - at least one capping head (3) for picking and screwing a screw cap (4) onto a container (2);

    - a motor-driven linear drive system (L) for lifting and lowering the capping head (3) along a linear axis (L') and

    - a motor-driven rotational drive system (R) for rotating the capping head (3) about a rotational axis (R'),

    characterised by a measuring device (7) for measuring the power consumption (I_L) of the linear drive system (L); and an evaluation device for comparing the power consumption (I_L) of the linear drive system (L), measured when picking and/or screwing on the screw cap (4), with a characteristic value of the power consumption (I_L) of the linear drive system (L), in order to detect an impending incorrect capping operation or an incorrect capping operation.
12. Apparatus according to Claim 11, further characterised by a monitoring device (9) for determining the position (y) of the capping head (3) with respect to the linear axis (L').
13. Apparatus according to Claim 11 or 12, further characterised by a removing device for removing incorrectly capped containers (2).
14. Apparatus according to at least one of Claims 11 to 13, further characterised by a control device which can control the linear drive system (L) and the rotational drive system (R) in such a way that only screw caps (4) are screwed on for which no impending incorrect capping operation has been detected.

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