System and method for synchronization of a container forming machine and a container processing machine in a container processing plant

A synchronization system for a container-processing plant, including a container-forming machine configured to form a container, the container-forming machine having a first rotating wheel for rotating the container about a first rotation axis; a container-filling machine operatively coupled to the container-forming machine and configured to fill the container, the container-filling machine having a second rotating wheel for rotating the container about a second rotation axis; and at least one electric motor configured to cause the first rotating wheel and the second rotating wheel to rotate, the synchronization system comprising: a position sensor provided in the container-forming machine and configured to detect a rotating position of the first rotating wheel and to generate a position detection signal; at least one control unit configured to: receive information associated with the position detection signal; synchronize the rotation of the second rotating wheel to the rotation of the first rotating wheel based on the information associated with the position detection signal; and synchronize the rotation of the container-forming machine and container-filling machine from a zero speed up to a full operating speed of the container forming machine at which processing operations are designed to be performed.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of European Application No. 17305654.0, filed Jun. 2, 2017. The entire contents of the above-referenced application are expressly incorporated herein by reference

TECHNICAL FIELD

The present invention relates to a system and method for synchronization of a container forming machine and a container processing machine in a container processing plant.

In particular, the following discussion will make explicit reference, without this implying any loss of generality, to a combined bottling plant for packaging fluid products in bottles or similar containers, and to the synchronization of rotating motions of at least two machines of the combined bottling plant, in particular a blowing (or blow moulding) machine used for the formation of containers, by stretch blow moulding of preforms made e.g. of thermoplastic material, and a filling machine for filling the formed containers with a fluid product, e.g. a food product.

BACKGROUND

A combined bottling plant includes a number of cooperating processing machines, performing a number of corresponding operations, such as (but not limited to) forming, filling, sterilising, labelling and capping of containers, for example plastic bottles.

Each machine generally includes a main rotating wheel (or carousel), carrying along its periphery a number of processing units performing processing operations on a respective number of containers.

The various processing machines are arranged in a desired operating sequence, at a close distance one with respect to the other, and conveying or transfer assemblies, each including a number of transfer star wheels or analogous conveying elements, allow transfer of the containers between the various processing machines, through the required operating sequence.

During regular operation, it is required to achieve synchronization between the rotary motions of two or more machines in the processing plant, e.g. the blowing and filling machines, meaning that the machines are operatively coupled to operate in synchronization with respect to their rotary position around a respective axis of rotation and the speed of rotation expressed as number of containers processed per unit time.

A known solution for achieving synchronization is diagrammatically depicted inFIG. 1, which shows a container-processing plant1including: a container-forming machine, e.g. a blowing machine2; and a processing machine, e.g. a filling machine4, operatively coupled to the blowing machine2to fill containers that have been previously formed by the same blowing machine2.

Blowing and filling machines2,4include: a respective main rotating wheel (or carousel)5, carrying (in a manner not shown) a number of processing units designed to perform processing operations on a corresponding number of containers; a respective electric motor6, in particular an asynchronous electric motor, designed to cause rotation of the respective rotating wheel5via a rotating shaft7; and a respective control unit8, including a PLC (Programmable Logic Controller)9or similar computing unit, operatively coupled to the respective electric motor6and providing suitable control and power supply signals thereto, in order to control the rotary motion of the respective rotating wheel5.

In particular, for synchronization of their rotating motion, blowing and filling machines2,4further include: a respective sensing wheel10, having a toothed rim, arranged below the rotating wheel5and coupled to the same rotating shaft7so as to rotate therewith; and a respective synchronization optical sensor11, in particular a photocell sensor, operatively coupled to the sensing wheel10.

The synchronization optical sensors11of the blowing and filling machines2,4are configured to generate a respective pulse-train synchronization signal S1, S2, wherein each pulse corresponds to detection, by the respective sensor, of a tooth of the respective sensing wheel10during rotation of the same sensing wheel10.

The synchronization signals S1, S2are received by a synchronization module12of the control unit8of the filling machine4, which is programmed to process the same synchronization signals S1, S2and to control the respective electric motor6to achieve synchronization with the motion of the blowing machine2. In particular, the synchronization module12suitably modifies the speed of the rotary motion of the respective rotating wheel5, until the pulses in the synchronization signals S1, S2are synchronized (i.e. until the edges, e.g. the rising edges, of corresponding pulses of the synchronization signals S1, S2occur substantially at a same instant of time).

According to this solution, the synchronization process requires motion of both machines, blowing and filling machines2,4, at a synchronization speed, whose value is suitably set so as to achieve a sufficient resolution of the synchronization optical sensors10; this synchronization speed is lower than a full operating speed of the rotating wheels5, at which the blowing and filling machines2,4are configured to perform the respective forming and filling operations on the preforms/containers.

The present Applicant has realized that the above synchronization solution has some drawbacks, which do not allow to fully exploit its advantages, in particular in case of faults in the container-processing plant1. Faults that may occur during operation are e.g. formation of defective containers, or destroying of containers due to an excessive pressure applied during the filling operations or due to defects in the formation of the same containers.

In the event of a fault occurring in the processing plant1, operation of the blowing and/or filling machine2,4is interrupted, in order to address and solve the issue. Once the fault is removed, operation of the blowing and/or filling machine2,4is resumed and synchronization between the same blowing and/or filling machine2,4has to be once again achieved.

The present Applicant has realized that using the above discussed solution entails a rather long time for achieving synchronization, in particular due to the fact that: if the filling machine4is stopped, at the restart of the operation, the blowing machine2has to slow down to the synchronization speed, at which synchronization may be achieved, before the speed ramps up to the full operating speed for both blowing and filling machines2,4; conversely, if the blowing machine2is stopped, also the filling machine4is stopped, and, at the restart of the operation, both the filling and the blowing machines2,4have to reach the synchronization speed, so as to achieve synchronization, before the speed may ramp up to the full operating speed for both machines.

The need is therefore felt for a synchronization solution allowing to achieve a more efficient synchronization between the machines in the container-processing plant, in particular allowing to decrease the time needed for the synchronization process, particularly at restart of the processing operations after a fault has occurred.

BRIEF SUMMARY

The aim of the present invention is consequently to address the above need, and in particular to provide an improved solution for synchronizing the rotary motions of different machines in a container-processing plant.

According to the present invention, a synchronization system and method are provided, as defined in the annexed claims.

DETAILED DESCRIPTION

FIG. 2schematically shows a combined container-processing plant20, including a container-forming machine22, in particular a blowing machine22, which receives at its input preforms and provides at its output formed containers, e.g. bottles; and at least one container-processing machine, in particular a filling machine24, which receives at its input the formed containers from the blowing machine22, fills the containers with a liquid product according to a desired filling recipe, and outputs the filled containers making them available for successive processing steps (e.g. for sterilizing, labelling and/or capping operations by respective further processing machines of the same container-processing plant20).

The blowing machine22comprises: a main rotating wheel (carousel)25, defining a circular processing path P1for the preforms/containers being processed; a main electric motor26, for example an asynchronous motor, which is coupled to the main rotating wheel25via a physical shaft and is controlled to drive the rotating motion of the same main rotating wheel around a first axis A; and a main control unit28, including a PLC (Programmable Logic Controller) or similar computing unit, programmed to control the main electric motor26to cause the rotation of the main rotating wheel25and to control the container-forming operations.

The blowing machine22further comprises a number of transfer wheels (or star wheels)29, each rotating around a respective axis of rotation and carrying the articles (preforms/formed containers) to be transferred along their periphery (at respective seats, in a known manner, here not discussed in details); in a manner not shown, the blowing machine22may instead include a combination of star wheels and linear conveyors, e.g. belt, air or chain conveyors. Each star wheel29may be provided with a respective electric motor, to drive its rotary motion, being controlled by the main control unit28or by a local control unit (here not shown) suitably coupled to the same main control unit28.

A number of input transfer wheels29define an inlet conveyor assembly30, receiving preforms from an input line31; and a number of output transfer wheels29define an outlet conveyor assembly32, for transferring the formed containers from the upstream blowing machine22to the downstream filling machine24. In a manner here not shown, inlet and outlet conveyor assemblies30,32may also be selectively configurable in order to define alternative paths for the articles to be transferred to and/or from accumulation reservoirs or discharge paths (in a known manner, here not shown in detail).

The blowing machine22further includes a position sensor34, in particular a position encoder34, more particularly an absolute position encoder, arranged and configured to detect position information indicative of the rotating motion of the same blowing machine22(in particular of the main rotating wheel25thereof), generating a corresponding position detection signal S. The position sensor34may be coupled to the main rotating wheel25, or, as in the shown embodiment, to one of the transfer wheels29, in the example to a transfer wheel29of the outlet conveyor assembly32; in particular, the position sensor34may be coupled to a brushless electric motor of this transfer wheel29of the outlet conveyor assembly32.

Detection signal S may be provided to the main control unit28of the blowing machine22, in order to implement a position feedback control of the operation of the electric motor26.

FIG. 3shows the detection signal S generated by the position sensor34, in the example including a plurality of linear-increasing ramps, each corresponding to a complete rotation of the main rotating wheel25from an initial position around the first axis A (0°) and a final position around the same first axis A (360°); the value of the detection signal S is at any time indicative of the rotating position of the main rotating wheel25around the first axis A, while the slope of the linear ramp of the same detection signal S is indicative of the speed of rotation of the same main rotating wheel25.

In a substantially corresponding manner, filling machine24comprises: a respective main rotating wheel35, defining a respective circular processing path P2for the containers being processed and carrying along its periphery a number of processing units (here not shown), each performing processing (i.e. filling) operations on a respective container; a main electric motor36, in particular a brushless motor, which is coupled to the main rotating wheel35and is controlled to drive the rotating motion of the same main rotating wheel35; and a control unit38, including a PLC (Programmable Logic Controller) or similar computing unit, operatively coupled to the main electric motor36and programmed to control the container-processing operations, according to the desired plan or recipe.

The filling machine24further comprises a number of transfer wheels (or star wheels)39, each rotating around a respective axis of rotation and carrying the containers to be transferred along their periphery. Each star wheel39may be provided with a respective electric motor, in particular a brushless motor, to drive its rotary motion, being controlled by the main control unit38or by a local control unit (here not shown), coupled to the same main control unit38.

In particular, a number of input transfer wheels39define an inlet conveyor assembly40, receiving the formed containers from the blowing machine22; and a number of output transfer wheels39define an outlet conveyor assembly42, for transferring the filled containers to an outlet line43(and possibly to downstream processing machines, here not shown, such as a capping machine or a labelling machine).

According to an aspect of the present solution, the main control unit38of the filling machine24is coupled to the main control unit28of the blowing machine22, according to a master/slave relation (the main control unit28of the blowing machine22acting as the “master” and the main control unit38of the filling machine24acting as the “slave”), via a digital communication bus46, for example a field bus, operating with an Ethernet protocol, e.g. the Powerlink protocol, arranged and configured to transfer digital signals between the blower machine22and the filler machine24.

In particular, the main control unit38of the filling machine24is configured to receive information about the rotating position and speed of the main rotating wheel25of the same blowing machine22, as detected by the position sensor34, the position information being related to the position detection signal S generated by the same position sensor34; in a possible embodiment, main control unit38of the filling machine24may directly receive the position detection signal S.

The main control unit38of the filling machine24is configured to generate a virtual rotation axis V, around which to control the rotation of the main rotating wheel35of the same filling machine24; the physical axes of rotation of the main rotating wheel35and transfer wheels39of the filling machine24being coupled and tracking this virtual rotation axis V.

According to an aspect of the present solution, the virtual rotation axis V may be associated to the position sensor34, i.e. being generated by the main control unit38based on the information about the rotating position of the main rotating wheel25of the blowing machine22provided by the same position sensor34.

In particular, the main control unit38of the filling machine24is programmed and configured to implement a first, so called standalone, operating mode, whereby the operation of the same filling machine24is controlled and run independently from the blowing machine22, so that the main control unit38of the filling machine24manages directly operation start/stop commands and speed references, controlling the main electric motor36, without considering (or disregarding) the information about the rotating position of the main rotating wheel25of the blowing machine22provided by position sensor34.

In this first operating mode, the filler virtual axis V is generated by the main control unit38of the filling machine24independently from the rotating motion of the blowing machine22(i.e. independently of the position information associated to the detection signal S generated by position sensor34).

According to a particular aspect of the present solution, the main control unit38of the filling machine24is further programmed and configured to implement a second, so called coupled, operating mode, whereby operation of the same filling machine24(acting as “slave”) is synchronized with the operation of the blowing machine22(acting as “master”). In this operating mode, the blowing machine22manages the operation start/stop commands and speed references, and suitable position/speed information are transmitted to the main control unit38of the filling machine24via the digital communication bus46; in particular these information are associated to the detection signal S generated by position sensor34and are used by the main control unit38of the filling machine24to obtain an indication of the rotating position and speed of the main rotating wheel25of the blowing machine22around the first axis A.

In this coupled mode, the filler virtual axis V is generated by the main control unit38of the filling machine24so as to be coupled to the rotating motion of the blowing machine22(as indicated by the dashed line inFIG. 2), using the information associated to the detection signal S generated by position sensor34.

Moreover, the transfer wheels39driven by the main control unit38of the filling machine24can thus be moved coupled to the main rotating wheel35of the same filling machine24; coupled to the main rotating wheel25of the blowing machine22; or can be stopped in a safe mode. In particular, thanks to the possibility of having independent safety areas, the blowing and filling machines22,24can even be cleaned, changed-over or subjected to other maintenance operations at a same time.

According to a particular aspect of the present solution, thanks to the above discussed arrangement, synchronization of the blowing and filling machines22,24can be achieved at any speed, from (and including) zero speed, up to full processing speed (i.e. the high speed at which processing, formation or filling, operations are designed to be performed); in particular, it is possible to achieve motion synchronization even when one or both machines are still (i.e. at zero speed), and/or when one or both machines are at the full processing speed. In other words, synchronization does not require operating the machines at a specific synchronization speed, having a value that is lower than the processing speed.

In particular, the position sensor34maintains the position information detected at the stopping of the blowing machine22, so that the control unit38of the filling machine24is able to synchronize with respect to the blowing machine22based on the maintained information even at zero speed of the same blowing machine22; moreover, position sensor34is able to accurately detect the rotating position even at high speed, so that the control unit38of the filling machine24is able to synchronize with respect to the blowing machine22also at full processing speed.

In particular, synchronization at zero speed allows the possibility to synchronize the filling machine24to the blowing machine22, without moving the same blowing machine22; this in turn allows, as will be readily appreciated to a person skilled in the field, the two machines to run synchronized with operator's protection open for testing purposes (so called “jog run”). This feature allows to access the container transfer zone between the machines with operator's protection open and the machines running synchronized, to check and easily set-up the container transfer parameters.

Moreover, synchronization of the filling machine24to the blowing machine22at zero or at high speed (e.g. at the full operating speed) allows an improved management of the restart of processing operations after a fault has occurred in one of the blowing and filling machines22,24.

In this respect,FIG. 4shows an exemplary synchronization algorithm for synchronization of the filling machine24to the blowing machine22at high speed, after a fault in the filling machine24, causing a stop of the rotating motion of the same filling machine24, has occurred, step50.

After the fault is detected, main control unit24of the blowing machine22controls discharge of the preforms and containers from the main rotating wheel25, at step52. It is indeed known that, once the plant restarts after an operating fault, the preforms present in the blowing machine22are no longer suitable for subsequent processing, e.g. due to the fact that they were subjected to temporary cooling or being kept too long in a heating device of the same machine, and therefore must be discharged and disposed of, or recycled.

The main control unit24does not, however, commands a stop or a slowing down of the main rotating wheel25, at a speed lower than the full operating speed (in other word, the blowing machine22continues its run at full processing speed).

After the fault in the filling machine24has been suitably taken care of, the main control unit38of the same filling machine24signals the availability for restart of the operations and for synchronization, at step54.

Accordingly, preforms are loaded again in the main rotating wheel25of the blowing machine22(that is still running at the full operating speed), at step56, and the filling machine24restarts its rotating motion.

In particular, the main control unit38of the filling machine24then controls, step58, the synchronization at high speed, i.e. at the full operating speed, to the motion of the blowing machine22, using the information associated to the position detection signal S coming from the position sensor34of the same blowing machine22to determine the rotating position and speed of the main rotating wheel25of the blowing machine22around the first axis A. In particular, the filler virtual axis V is generated based on these information, and the rotating motions of the main rotating wheel35and the transfer wheels39of the filling machine24is coupled to the same virtual axis V, to achieve synchronization of filling machine24to the blowing machine22.

Tests performed by the present Applicant have shown the possibility to save time, e.g. up to 100 s, using the discussed algorithm, with respect to traditional solutions, that would instead envisage synchronization at a low synchronization speed, and thus first slowing down of the blowing machine22to the required low synchronization speed and then subsequent ramp-up of the speed of the same blowing machine22to the full operating speed.

FIG. 5shows a further synchronization algorithm, again for synchronization of the filling machine24to the blowing machine22at high speed, this time after a fault in the blowing machine22, causing a stop of the rotating motion of the same blowing machine22, has occurred, at step60.

After the fault has been detected, main control unit38of the filling machine24controls discharge of the containers present on the main rotating wheel35, at step62.

Afterwards, the same main control unit38of the filling machine24commands a stop of the rotating motion of the main rotating wheel35, at step64.

After the fault in the blowing machine22has been suitably taken care of, the main control unit38of the filling machine24controls, at step66, the synchronization to the motion of the blowing machine22, at zero speed of the main rotating wheel25of the same blowing machine22.

The main control units28,38of the blowing and filling machines22,24then control restart of the respective rotating motions and ramp-up to the full operating speed, at step68; blowing and filling machines22,24thus reach the full operating speed in a synchronized state, again without the need to first reach a lower synchronization speed.

Also in this case, tests performed by the present Applicant have shown the possibility to save time, e.g. up to 30 s, using the discussed algorithm, with respect to traditional solutions, that would envisage synchronization at a low synchronization speed, and then subsequent ramp-up of the speed of the blowing machine22and filling machine24to the full operating speed.

The advantages that the described solution allows to achieve are clear from the foregoing description.

In particular, it is again underlined that this solution allows to achieve improved and more efficient synchronization between different machines in a container-processing plant (e.g. between a blowing and a filling machine), particularly allowing to decrease the time needed for the synchronization process, especially at the restart of the operations after a fault has occurred in at least one of the machines.

The synchronization solution thus allows to improve the throughput of the container-processing plant.

Finally it is clear that modifications and variations may be applied to the system described and shown, without departing from the scope defined by the appended claims.

In particular, it is underlined that the discussed synchronization solution may be applied also in the case where a greater number of machines are to be synchronized, e.g. in a container-processing plant including further processing machines, such as a sterilizing machine, a labelling machine and/or a capping machine, in addition to, or substitution of, the blower and filler machines.

In general, the described synchronization system and method may be advantageously employed in any case where two, or more, rotating machines are to be synchronized in a processing plant.

Moreover, the type and configuration of the elementary parts of the bottling plant, previously shown and discussed, are to be considered only as exemplary: e.g. the electric motors could be of a different kind, so as the position sensors, that could include any kind of sensor able to track the position of a corresponding rotating wheel with respect to the respective rotating axis.