DEVICE FOR MANUFACTURING CONTAINERS FROM THERMALLY CONDITIONED PREFORMS MADE OF THERMOPLASTIC MATERIAL

Description

[0001] The invention relates to a device for producing containers from thermally conditioned preforms made of thermoplastic material.

[0002] Preforms made of thermoplastic material are used to manufacture containers. These preforms are first thermally conditioned and then formed into containers in molds using a stretch blow molding process. This involves, among other things, inserting a stretch rod into the preform, which stretches the preform along its longitudinal axis. In the axial direction, shaping is carried out using a blowing gas, which expands the preform within the mold, so that the preform is pressed against the inner walls of the mold. After molding, the containers still retain residual heat from the thermal conditioning of the preforms. Due to this residual heat, the container material is not yet stable and the containers cannot yet hold their shape. Therefore, the molds or the molded containers are cooled after the containers have been molded in order to dissipate this residual heat from the container material.

[0003] To assist in the dissipation of residual heat, EP 2 040 905 B1 discloses directing a cooling gas from the stretching rod toward the bottom of the formed container after the preform has expanded. The gas can be, for example, blowing gas, which is introduced into the container after the pressure has been reduced to absorb the residual heat from the container material.

[0004] A blow molding system is known from WO 2011 / 079917 A1. The blow molding system comprises a blow mold housing defining a mold cavity. The blow molding system also comprises a stretch rod movable within the mold cavity. The stretch rod comprises a first stretch rod component defining a first fluid flow path. The stretch rod also comprises a first valve coupled to the first stretch rod component and adapted to selectively provide a fluid communication path between the first fluid flow path and the mold cavity.

[0005] Furthermore, DE 10 2011 009 889 A1 discloses a method and a device for producing filled containers. A preform made of a thermoplastic material is first subjected to thermal conditioning along a transport path in the area of ​​a heating section. The preform is then formed into the container within a mold by applying pressure. A filling medium, which is to be poured into the container, is used as the fluid for forming the container. The preform is guided into the container at least temporarily during its forming process.

[0006] US 2020 / 346390 A1 discloses a method for manufacturing a liquid container, in which a nozzle unit comprises a blowing nozzle with a supply opening and a spare supply hose with a spare supply opening at its lower end. The method includes an air discharge step for discharging the air in the preform to the outside by supplying a liquid into the preform from the spare supply opening located at a lower portion of the preform; a liquid blow molding step for molding the preform into a liquid container by supplying a pressurized liquid from the supply opening into the preform; and a headspace forming step for forming a headspace by discharging the liquid from the interior of the liquid container.

[0007] The object of the invention is to provide a device for producing containers from thermally conditioned preforms made of thermoplastic material, which has a further increased cooling potential and improved efficiency.

[0008] The problem is solved by the features of the independent claims. Advantageous further developments are the subject of the dependent claims and the following description.

[0009] In a device for producing containers from thermally conditioned preforms made of thermoplastic material, wherein the device has at least one mold for forming the container from a preform, and at least one stretching rod which can be inserted into the mold for stretching a preform placed in the mold, wherein the stretching rod has, at least at an end section which can be inserted into the preform, a fluid line which can be connected in a fluid-communicating manner to a purge gas reservoir, the invention provides that the stretching rod has an injector valve which controls the fluid line and is used to generate purge gas pulses, wherein the injector valve is arranged at the end section.

[0010] The invention thus provides a device for producing containers in which the injector valve is arranged at the end section of the stretch rod. The injector valve is thus arranged relatively close to the elements to be cooled, in particular the bottom of the recently produced container to be cooled. The purge gas flows from the purge gas reservoir via the fluid line through the stretch rod to the injector valve, which is arranged at the end section of the stretch rod. During the stretching process, the end section of the stretch rod is arranged in the bottom region of the produced container. The injector valve can release purge gas with the provided purge gas directly at the end section, i.e. also directly at the bottom region of the container. The purge gas can be released in pulsed fashion, so that the injector valve generates purge gas pulses.By arranging the injector valve at the end section of the stretch rod, dead space for the purge gas is avoided downstream of the injector valve. By eliminating the dead space, the delay with which the purge gas is fed into the container after the injector valve opens is reduced. The injector valve thus enables short purge gas pulses to be realized, avoiding inertia effects caused by the purge gas located in the dead space. The invention increases the cooling efficiency while maintaining the same process time. This increases the cooling potential. Furthermore, the invention reduces purge gas consumption and increases the output of the container manufacturing device.

[0011] The purge gas reservoir can, for example, be a blowing air reservoir or a blowing gas source of a blow molding machine for producing containers.

[0012] According to the invention, the injector valve is switchable and connected to a control device via at least one signal connection.

[0013] This allows the purge gas pulses to be adjusted by the control device to the individual properties of the containers produced.

[0014] It is conceivable that the signal connection is, for example, a wireless signal connection.

[0015] In particular, no cables are required running in or on the stretching rod. Due to the installation space constraints, there is very little room on or in the stretching rod for laying cables. This saves material and reduces the effort involved in manufacturing the device for producing containers.

[0016] Furthermore, the signal connection can comprise, for example, an electrical line that is connected to the injector valve and arranged on the stretch rod.

[0017] The electrical power can be used to improve the reliability and susceptibility to interference of the signal connection.

[0018] In a further example, the stretch rod has a taper in the end section, wherein the injector valve is arranged immediately adjacent to the taper.

[0019] It is also conceivable that the taper is arranged between the injector valve and a tip of the stretch rod.

[0020] The tapered end section of the stretch rod may be required for the stretching process. The injector valve is thus positioned as close as possible to the tip of the stretch rod. This further reduces the dead space downstream of the injector valve and further increases the efficiency of the device.

[0021] Furthermore, the injector valve can be arranged, for example, within the stretch rod.

[0022] When the injector valve is positioned inside the stretch rod, the outer diameter of the stretch rod is not affected by the injector valve. This allows installation space requirements for the stretch rod to be met regardless of the injector valve's location, and protects the injector valve from external influences.

[0023] The invention is described below using an exemplary embodiment with reference to the accompanying drawings. They show: Figure 1 is a schematic representation of an apparatus for producing containers, and Figure 2 is a schematic cross-sectional representation of a mold for forming the container from a preform.

[0024] The device for producing containers is designated in its entirety by the reference numeral 10, as in Figure 1 shown.

[0025] The device 10 is designed to produce containers from thermoplastic material. For this purpose, preforms are first provided, which are thermally conditioned. The device 10 has at least one mold 12 for producing the containers, into which a thermally conditioned preform can be inserted. In the example according to Figure 1 the device 10 is shown as a rotary machine with a blowing wheel and has a plurality of molds 12 so that it can form a plurality of containers from preforms in rapid succession.

[0026] The mold 12 has a cavity that has the outer shape of a container to be manufactured. The mold 12 further includes a bottom mold 18 that forms the bottom of the container within the cavity. The cavity may have vent outlets (not shown) that open into the environment. Air displaced from the cavity during the expansion of a preform can escape from the cavity through the vent outlets.

[0027] A stretching rod 14 can be inserted into the mold 12. When the stretching rod 14 is inserted into the mold 12 and a preform is inserted into the mold 12, the stretching rod 14 stretches the preform along its longitudinal axis into the area of ​​the bottom mold 18. The stretching is assisted by the thermal conditioning of the thermoplastic material of the preform.

[0028] A fluid line 16 can be used to introduce a blowing gas into the preform placed in the mold 12. This increases the pressure within the preform. The pressure increase stretches the preform, among other things, radially along its longitudinal axis and presses it against the walls of the cavity of the mold 12. The preform now takes on the shape of the container to be produced.

[0029] The container material still contains residual heat from thermal conditioning. This residual heat can be reduced by a cooling unit 20.

[0030] Figure 2shows a cross-sectional view of the mold 12 with the cooling unit 20. The preform has already been formed into a container 34, and the stretch rod 14 is still arranged in the mold 12. The blowing gas was introduced into the preform via the fluid line 16 through a blowing gas valve 22. The blowing gas is preferably admitted into the preform laterally past the stretch rod 14. The pressurized blowing gas can be released from the produced container 34 through a discharge opening 38 via a discharge valve 36 in order to reduce the pressure in the container 34.

[0031] At the beginning of the pressure reduction in the container 34 or after a predefined period of time thereafter, the bottom 30 of the container 34 is cooled. For this purpose, the stretch rod 14 can be hollow. The interior of the stretch rod 14 can be fluidly connected to the fluid line 16, which in turn is fluidly connected to a purge gas reservoir. Furthermore, a section of the fluid line 16 can extend through the hollow stretch rod 14 to an end section 26 of the stretch rod 14. The end section 26 is arranged at a free end at a tip 29 of the stretch rod 14. The tip 29 is arranged closest to the bottom of the container 34 when the stretch rod 14 is fully inserted.

[0032] At the end section 26 of the stretch rod 14, an injector valve 20 controlling the fluid line 16 is also arranged.

[0033] In this example, the injector valve 20 can be arranged inside the stretch rod 14. However, this does not preclude the possibility that the injector valve 20 can also be arranged outside the stretch rod 14.

[0034] By means of the injector valve 20, purge gas from the purge gas reservoir can be introduced into the mold 12 via the fluid line 16 through an outlet 28 on the stretch rod 14.

[0035] The purge gas may be the blow gas used to produce the container 34 from the preform in the mold 12. In this case, the purge gas reservoir is also the blow gas reservoir or blow gas source.

[0036] Alternatively, the purge gas can be another gas stored in a separate purge gas reservoir.

[0037] The injector valve 20 may be configured to generate purge gas pulses that are directed into the container 34 produced in the mold 12. The purge gas pulses may be directed from the end portion 26 toward the bottom of the container.

[0038] The at least one outlet 28 is arranged such that it is directed toward the base 30 and can be configured as an expansion nozzle. From the at least one outlet 28, the purge gas is introduced onto the base 30 by means of a plurality of purge gas pulses in order to cool the base 30. Cooling occurs when the purge gas is discharged from the container 34, while the pressure of the purge gas in the container 34 is reduced.

[0039] Due to the arrangement of the injector valve 20 at the end section 26, only a small purge gas volume is present between the injector valve 20 and the at least one outlet 28. This small purge gas volume can therefore only cause minor, generally negligible, inertia effects on the purge gas pulses. The purge gas pulses generated by the injector valve 20 thus reach the at least one outlet 28 without significant influence from the purge gas in the dead space.

[0040] The purge gas pulses can be timed so that no continuous purge gas flow is introduced through the at least one outlet 28 onto the bottom 30 throughout the entire cooling period. Cooling occurs primarily through the expansion of the purge gas after exiting the outlet 28. This results in an adiabatic expansion of the purge gas, during which the purge gas cools. The cooled purge gas then hits the bottom 30 of the container 34 and can absorb the residual heat at the bottom 30 of the container 34.

[0041] With each purge gas pulse, the pressure in the container 34 is initially increased and then drops again after the purge gas pulse ends. For this purpose, for example, the drain valve 36 can remain open throughout the entire cooling period to achieve pressure equalization via the drain opening 38.

[0042] Furthermore, the timing of the purge gas pulses is designed such that a purge gas pulse only begins when pressure equalization has occurred after the previous purge gas pulse. At the start of each purge gas pulse, a maximum possible pressure difference is created between the pressure of the purge gas and the contents of container 34, given these boundary conditions. This maximizes the expansion of the purge gas, thus achieving maximum cooling.

[0043] The end portion 26 may further comprise a taper 32, wherein the end portion 26 tapers toward the tip 29 of the stretch rod 14. The injector valve 20 may be arranged downstream of the purge gas flow direction, upstream of the taper 32, so that the taper 32 is arranged between the injector valve 20 and the tip of the stretch rod 14.

[0044] The stretch rod 14 can be manufactured by hollow drilling. It can also have an outer diameter of 14 mm, with the hollow bore having a diameter of 9 mm. After the taper 32, the bore in the stretch rod 14 can have a diameter of 3 mm. In this example, the injector valve 20 is arranged immediately upstream of the taper 32 in the area with the 9 mm diameter.

[0045] To generate the purge gas pulses, the injector valve 20 can be switchable. The switching of the injector valve 20 can be controlled by a control device 40. For this purpose, the injector valve 20 can be connected to the control device 40 via a signal connection 24.

[0046] The signal connection 24 can be wireless or routed via an electrical cable. The electrical cable can be arranged inside or outside the horizontal bar 14. List of reference symbols

[0047] 10 Device for producing containers 12 Mold 14 Stretch rod 16 Fluid line 18 Bottom mold 20 Injector valve 22 Blow gas valve 24 Signal connection 26 End section 28 Outlet 29 Tip 30 Bottom 32 Taper 34 Container 36 Drain valve 38 Drain opening 40 Control device

Claims

1. Device for producing containers from thermally conditioned preforms of thermoplastic material, the device (10) having at least one mould (12) for shaping the container from a preform, and at least one stretching rod (14) which can be introduced into the mould (12) for stretching a preform inserted into the mould (12), the stretching rod (14) having a fluid line (16) at least at an end section (26) which can be introduced into the preform, which can be connected to a flushing gas reservoir in a fluid-communicating manner, characterised in that the stretching rod (14) has an injector valve (20) controlling the fluid line for generating flushing gas pulses, the injector valve (20) being arranged on the end section (26), the injector valve (20) being switchable and connected to a control device (40) via at least one signal connection (24).

2. Device according to claim 1, characterised in that the signal connection (24) is a wireless signal connection.

3. Device according to claim 1 or 2, characterised in that the signal connection (24) comprises an electrical line which is connected to the injector valve (20) and is arranged on the stretching rod (14).

4. Device according to one of claims 1 to 3, characterised in that the stretching rod (14) has a taper (32) in the end section (26), wherein the injector valve (20) is arranged directly adjacent to the taper (32).

5. Device according to claim 4, characterised in that the taper is arranged between the injector valve (20) and a tip (29) of the stretching rod (14).

6. Device according to one of claims 1 to 5, characterised in that the injector valve (20) is arranged inside the stretching rod (14).