Blow moulding machine with compressed air recycling

An apparatus for shaping plastic preforms into plastic containers, including a plurality of blow molding stations which each have a cavity in which the plastic preforms can be shaped into plastic containers. The blow molding stations are arranged on a movable carrier and each have a stretching rod which stretches the plastic containers in their longitudinal direction by a movement in a stretching direction. A fluid-actuated drive device is provided for driving the stretching rod in the stretching direction. The apparatus includes a guide cam which is arranged in a stationary manner and by means of which the stretching rod can be moved counter to the stretching direction as a function of a movement of the blow molding station. At least one portion of the guide cam is adjustable and, for example, by virtue of this adjustment a dependency of the movement of the stretching rod on the movement of the blow molding station can be varied.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of German Patent Application No. 10 2010 024 277.2, filed Jun. 18, 2010, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a blow moulding machine for shaping plastic preforms into plastic containers.

BACKGROUND

Blow moulding machines for shaping plastic preforms into plastic containers are known from the prior art. Usually, such blow moulding machines comprise a plurality of blow moulding stations, within which cavities are formed in which plastic preforms can be shaped into plastic containers by applying compressed air. It is also known that such blow moulding stations comprise stretching rods which stretch the plastic preforms in their longitudinal direction during the expansion process. A wide range of drive concepts are known for these stretching rods. For instance, it is conceivable that the stretching rods are controlled by means of electric motor drives or by means of cams. It is also known for these stretching rods to be actuated by pneumatic drives. To this end, both an extending of the stretching rod, which stretches the plastic preform, and a retracting of the stretching rod are pneumatically driven.

In the prior art, however, such blow moulding machines have a relatively high energy consumption, wherein the drive devices for actuating the stretching rod are also noticeable in the energy balance.

It may therefore be desirable to improve the energy balance of such blow moulding machines.

SUMMARY

According to various aspects of the disclosure, an apparatus for shaping plastic preforms into plastic containers comprises a plurality of blow moulding stations which each have a cavity in which the plastic preforms can be shaped into plastic containers. These blow moulding stations are arranged on a movable carrier and each have a stretching rod which stretches the plastic containers in their longitudinal direction by a movement of the stretching rod in a stretching direction. A drive device is provided for driving the stretching rod in the stretching direction.

According to the disclosure, the apparatus comprises a guide cam which is arranged in a stationary manner and by means of which the stretching rod can be moved counter to the stretching direction as a function of a movement of the blow moulding station, wherein at least one portion of this guide cam is adjustable and, for example, by virtue of this adjustment the dependency of the movement of the stretching rod (in particular counter to the stretching direction) on the movement of the blow moulding station can be varied. Varying the dependency of the movement of the stretching rod on the movement of the blow moulding station is understood to mean that, for a given stretching rod, the relationship between the position thereof and the position of the blow moulding station to which this stretching rod is assigned is at least partially varied. By virtue of the adjusting of a geometric position of the guide cam relative to a movement path of the individual blow moulding stations this relationship is changed. For example, a position changes in a direction perpendicular to a movement plane of the blow moulding stations.

It is therefore proposed according to the disclosure that the movement of the stretching rod counter to the stretching direction, i.e. from a fully extended position to a retracted position, is brought about by the guide cam. For example, the stretching rod may have a stretching carriage with a guide roller, wherein this guide roller is movable relative to the guide cam and in this way a retracting movement of the stretching rod is achieved during a movement of the blow moulding station. Advantageously, therefore, a movement of the stretching rod in the stretching direction is driven by a pneumatic and/or electric drive device and the movement counter to the stretching direction is achieved by means of the guide cam.

This guide cam will also be referred to below as the run-up segment. Such run-up segments can be used to bring the stretching rod or the cam-controlled stretching carriage including the stretching rod from the lower end position, i.e. in the stretching stop, back into the upper end position, i.e. the starting position.

The position of this guide cam is dependent for example on the length of the containers to be produced. If long containers are used, a lower position of the run-up segment is required; if short bottles are to be produced, a correspondingly higher position is required. It is therefore helpful if the position of the run-up segment or of the guide device can be varied when changing the type of container.

In an exemplary embodiment, at least one drive device is and, for example, all the drive devices are fluid-actuated and in particular pneumatically actuated drive devices. In a further exemplary embodiment, at least one drive device is an electrically operated drive device and comprises in particular an electric motor. This electric motor may be either a linear motor or a rotary drive. By returning the stretching rod counter to the stretching direction, such an electric motor can act as a generator and in this way can generate electrical energy.

In an exemplary embodiment, the (pneumatic) drive devices of at least two blow moulding stations are at least at times in fluid communication (in particular compressed air communication) with one another. For instance, it is conceivable that, during the return of the stretching rod to its starting position, the compressed air can be discharged to a further blow moulding station, as a result of which in this further blow moulding station the stretching rod can in turn be moved downwards.

In some aspects, the apparatus comprises a reservoir for the fluid for actuating the drive devices, and this reservoir is in flow communication with all the drive devices for actuating the stretching rod. All the drive devices may for instance be pneumatic drives which are supplied with compressed air from a common annular channel. When the guide cam pushes a stretching rod back into the starting position, the resulting compressed air can be fed into the annular channel and, due to the resulting positive pressure, a further stretching rod can in turn be moved downwards.

In some aspects, the fluid or the air in the exemplary reservoir is at a positive pressure, which is, for example, also maintained in the operating mode of the apparatus.

In this way, a recycling of compressed air is possible when using the guide cam.

In some aspects, the apparatus comprises an actuation element for adjusting the portion of the guide cam, and a movement of this actuation element is coupled to a movement of the portion of the guide cam.

In principle, it would also be possible that the run-up segment is screwed onto a carrier by screw devices, such as hexagon screws for example, and an adjustment takes place by loosening these screws and then displacing the guide cam. In this case, however, the accessibility of these screws and the possibility of precise adjustment may be problematic. By providing an actuation element, such as for example a rotary spindle or a rotary lever, it can be ensured that a very precise adjustment of the guide cam or of the run-up segment is possible. A movement of this actuation lever is coupled to the movement of the run-up segment in a predefined manner, for example by using a rotary spindle.

In some aspects, the guide cam is arranged on a holding device in such a way as to be displaceable along a predefined displacement travel. This holding device may be for example a so-called catch cam, which is known from the prior art. This catch cam may in turn have an elongate hole, in which the guide cam is displaceably arranged. This elongate hole also predefines a clearly defined displacement travel for the guide cam. The guide cam is, for example, arranged on the catch cam in such a way that these merge geometrically into one another, i.e. in such a way that a guide roller moving along the guide cam transitions smoothly and without disruption into the catch cam.

In an exemplary embodiment, the guide cam can be arrested relative to the holding device. For example, it would be possible that the guide cam is arrested relative to the holding device by means of screw connections. However, it would also be possible that clamping cylinders are used to hold the guide cam. This will be explained in more detail below with reference to the figures.

In an exemplary embodiment, the guide cam is adjustable along a movement path of the blow moulding stations. This means that the blow moulding stations move along a predefined movement path, for example along a circular path when arranged on a blow moulding wheel, and the guide cam is adjustable along this path or along a path concentric thereto.

In an exemplary embodiment, the apparatus comprises a display device for outputting information characteristic of a position of the guide cam. For example, a scale may be provided in the region of the actuation element. However, it would also be possible that an appropriate display device or scale is provided on the holding device or also on the guide cam, by means of which the exact geometric position of the guide cam can be determined.

In an exemplary embodiment, the holding device is a further guide cam which serves at least at times for moving the stretching rod. In the prior art, this so-called catch cam may also be used when, for certain reasons, a return movement of the stretching rod does not take place, for example because the associated pneumatic cylinder is defective. In this case, it must nevertheless be ensured that the stretching rod is pulled back since, if the stretching rod remains in the container and the latter is then removed from the blow mould, this could result in serious damage to the installation.

In an exemplary embodiment, an arresting of the guide cam relative to the holding device is controlled by a valve device.

It is also possible that the guide cam (particularly even when the arresting is released) is biased towards the holding device. By virtue of this biasing, even if the clamping is inadvertently relaxed, there is still sufficient friction so that inadvertent movement during operation is ruled out even after the actual arresting has been released.

The guide cam may be advantageously curved, that is to say in particular not only has a curved edge along which a cam roller can move, but rather is also curved in a direction extending perpendicular to the course of the edge. This curvature may be adapted to the curvature of a movement path of the individual blow moulding stations. In other words, the guide cam here is curved and is movable radially relative to the centre of the blow moulding machine along the curved cam.

The present disclosure also relates to a method for operating an apparatus for shaping plastic preforms into plastic containers, wherein the apparatus comprises a plurality of blow moulding stations which each have a cavity in which the plastic preforms are shaped into plastic containers. These blow moulding stations are arranged on a movable carrier and each have a stretching rod which stretches the plastic containers in their longitudinal direction by a movement in a stretching direction. The stretching rods are driven in the stretching direction by a drive device, and the apparatus can be converted for different containers and, when converting the machine, at least a bottom mould of a blow moulding station, which serves for producing the plastic containers, is replaced by a different bottom mould.

According to the disclosure, the apparatus comprises a guide cam which is arranged in a stationary manner and by means of which the stretching rod is moved counter to the stretching direction as a function of a movement of the blow moulding station, and this guide cam is adjusted during the conversion of the machine. By virtue of this conversion, the apparatus can be converted in particular to different heights of the containers to be produced, but optionally also to different heights of the plastic preforms used.

In some aspects, the guide cam is adjusted as a function of a height of the bottom mould. The bottom mould is in this case advantageously part of a blow mould which may additionally also comprise two side parts. These side parts and the bottom mould, or the respective inner surfaces thereof, may form the abovementioned cavity and the plastic preforms are expanded against this inner wall to form the plastic containers.

Further exemplary embodiments and advantages may be evident from the accompanying drawings.

DETAILED DESCRIPTION

FIGS. 1aand1bshow two diagrams of an apparatus100for shaping plastic preforms into plastic containers. A rotatable blow moulding wheel106is provided, on which a plurality of blow moulding stations108are arranged (only one blow moulding station108is shown here). This blow moulding wheel106rotates together with the individual blow moulding stations108. During the rotation, the plastic preforms120, which are fed to the blow moulding wheel106and the blow moulding stations108by means of a feed wheel122, are shaped into plastic containers. These plastic containers130are discharged again from the apparatus via a discharge wheel132.

Reference14inFIG. 1ashows a drive device which serves for actuating the stretching rod112, i.e. for moving the stretching rod112in the stretching direction D1. Reference116denotes a carrier, on which the stretching rod arrangement is arranged. Reference L1denotes a longitudinal direction of the container, along which the stretching rod112also moves. Reference108adenotes a side part carrier of the blow moulding station, on which a side part (not shown) of the associated blow mould is arranged, and reference108bdenotes a bottom part carrier, on which a bottom mould (not shown) of the blow mould is arranged.

FIG. 2shows a first diagram to illustrate the exemplary aspects of the disclosure. Shown here is a guide cam20which is adjustable. The guide cam20is arranged in its entirety on a holding device80and is movable relative to this holding device. The holding device itself is arranged in a stationary manner, so that the individual blow moulding stations8move relative to this holding device80and thus also relative to the guide cam20. The holding device may itself serve as a catch cam.

Reference104denotes a cavity which is formed inside the individual blow moulding stations in order to expand therein plastic preforms into plastic containers. Reference15denotes a spindle which is rotatable by means of an actuation element16in order in this way to displace an end section96or a holding element96in the longitudinal direction L of this spindle. Also arranged on this holding element96is the guide cam or the run-up segment20in order in this way to be able likewise to displace the latter (relative to the holding device).

It can be seen in particular inFIG. 2that the guide cam or the run-up segment20has two portions20aand20bwith a different inclination. The portion20aof the run-up segment20has a greater inclination than the portion20b. The portion20bis in any case matched in its end section to an inclination of the holding device80. The guide roller24is configured here in such a way that it can roll both on the holding device80and also on the guide cam or run-up segment20. In particular, by means of the holding device, the cam roller and thus the stretching carriage with the stretching rod can be brought into the upper stop position. The holding device80or the further cam can also continue further in the horizontal direction in order to keep the stretching rod in the upper position.

FIG. 3shows a side view of the apparatus shown inFIG. 2. It can be seen that the spindle15is articulated on the holding device96and is therefore pivotable relative to the latter. Reference82denotes an elongate hole which is formed in the holding device80and relative to which the run-up segment can move. This elongate hole82runs parallel to an upper edge84of the holding device, which acts here as a further guide cam.

FIGS. 4 and 5show a further diagram of the arrangement shown inFIG. 2. It is also possible to see here the guide roller24which is indirectly connected to the stretching rod112and which is arranged on a stretching carriage132in order to move the latter. As mentioned above, the actuation of the stretching rod112in the direction D1takes place via the pneumatic drive device14. As shown inFIG. 5, the adjustment of the run-up segment takes place via the threaded spindle15, which is adjustable when the clamping between the run-up segment20and the holding device80is loosened. In order to ensure a reproducible setting, a position indicator or counter is fitted. The operating elements, i.e. the actuation element16, is located to the side of the machine and is thus easily visible and accessible. The elongate hole82runs parallel to the course of the cam.

FIGS. 6a-6cshow a further diagram of the actuation device according to the disclosure. It is possible to see a clamping jaw7which is arranged on the run-up segment20by means of screw devices41and in this way brings about a clamping relative to the holding device80. Reference39denotes a bolt. Reference95shown inFIG. 6cdenotes a clamping cylinder which serves for drawing the clamping jaw7against the holding device or catch cam80. These clamping cylinders are biased by plate springs on the piston rod side and an autonomous adjustment of the run-up segment20is thus not possible even in the pressureless state. In the operating state of the machine, the clamping cylinders95are additionally acted upon and thus the ultimately required clamping force (spring+compressed air) is produced. Friction linings97are arranged on the run-up segment20. These friction linings, for example, three friction linings, prevent any displacement of the run-up segment20in the operating state. In order to release the clamping, a button17is actuated, a valve acts upon the cylinder95on the piston side and the clamping is released. This valve is denoted by reference93. Reference25denotes a position indicator which indicates a position of the hand wheel16. Reference98denotes a vibration sensor, by means of which the correct setting of the run-up segment20is monitored in the operating state. If the vibrations measured by this vibration sensor are too high, this indicates that the cam roller24has been placed too roughly onto the run-up segment20.

In the case of automated adjustment, it is possible to replace the hand wheel16by an actuating drive as the actuation element. This can be integrated in the control system of the machine and can be automatically adjusted when changing the type of container. In this way, setting errors and thus disruptions or damage to the machine can be avoided.

It will be apparent to those skilled in the art that various modifications and variations can be made to the blow moulding machine with compressed air recycling of the present disclosure without departing from the scope of the invention. Throughout the disclosure, use of the terms “a,” “an,” and “the” may include one or more of the elements to which they refer. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only.