DE202005020679U1 - Blow molding method for bottles comprises blowing premolds in, low pressure and high pressure stage, some of air used being recycled after blow molding via recirculation valve whose outlet is connected to low pressure air tank - Google Patents

Abstract

Blow molding method for bottles (2) comprises blowing premolds in a first, low pressure stage followed by a second, high pressure stage. The air used in each stage is controlled by a valve (44, 45). Some of the air is recycled after blow molding via a recirculation valve (47) connected in parallel to the other valves whose outlet (50) is connected to the low pressure air tank (42). An independent claim is included for apparatus as described for carrying out the method.

Description

The The invention relates to a device for the blow molding of containers, the at least one blowing station with a blow mold arranged on a blowing wheel and at least one stretch rod and at the blowing station both to a low pressure supply to provide a first blowing pressure as well as to a high pressure supply to provide a relative higher for the first blowing pressure second blower pressure is connected, as well as a blown air return for after a container molding the blowing station emanating High-pressure blowing air is used in the Niederduckversorgung.

at a container molding by blowing pressure are preforms of a thermoplastic Material, for example PET preforms (polyethylene terephthalate), within a blow molding machine different processing stations fed. Typically, such a blow molding machine has a heating device and a blowing device, in the region of which previously tempered Preform expanded by biaxial orientation to a container becomes. The expansion takes place with the help of compressed air, which in the is initiated to expander preform. The procedural process in such an expansion of the preform is in DE-OS 43 40 291 explained. The introductory mentioned Introduction of the pressurized gas also includes the pressurized gas introduction into the developing container bubble and the introduction of compressed gas into the preform at the beginning of the blowing process.

Of the fundamental Construction of a blowing station for container molding is described in DE-OS 42 12 583. Possibilities for tempering The preforms are described in DE-OS 23 52 926.

Within the blow molding apparatus, the preforms and the blown containers transported by means of different handling devices become. proven In particular, the use of transport thorns, to which the preforms are attached. But the preforms can be handled with other support devices. The usage grippers for handling preforms and use of expanding mandrels for mounting in a mouth region of the preform insertable are, belong also available Constructions.

A Handling of containers using transfer wheels For example, in DE-OS 199 06 438 in an arrangement of the transfer wheel between a blowing wheel and an output path.

The already explained Handling of the preforms takes place on the one hand in the so-called two-stage process, where the preforms initially in an injection molding process produced, then stored and later conditioned in temperature and inflated to a container become. On the other hand, an application in the so-called one-step process, in which the preforms immediately after their injection molding Manufacture and sufficient solidification suitable tempered and subsequently be inflated.

in the With regard to the blowing stations used are different embodiments known. At blow stations, which are arranged on rotating transport wheels are, a book-like Aufklappbarkeit the mold carriers are frequently encountered. But it is also possible to use relatively displaceable or differently guided mold carriers. at fixed blow molding stations, which are particularly suitable for multiple cavities for container molding are typically arranged parallel to each other Plates as mold carriers used.

The recirculation of spent blast air from a high pressure region to a low pressure region is already described in US-A 4,488,863. A device implementation for multiple use of blowing air is in the DE 43 40 291 A1 explained.

The Hitherto known devices are not yet sufficient wise for that suitable to achieve an optimization of the blown air return in such a way that both one possible size Recirculation rate guaranteed as also an invalid pressure increase is avoided in the low pressure range.

task It is the object of the present invention to provide a device mentioned type to construct such that an optimized blown air return is supported.

These Task is inventively characterized solved, that the Blowing air return Recirculation valve having, in a parallel to a blowing pressure valve extending Return branch is arranged that a Valve output of the return valve the low pressure supply is connected and that one input a compressor with the pre-compressed compressed air providing Low pressure supply is connected.

By using a return valve arranged in a separate return branch, it is possible to realize the blowing air return irrespective of a circuit of the blowing pressure valve ren, wherein the blown air valve is preferably used for supplying the Niederdruckblasluft. In particular, such a use of a separate return valve supports the realization of a pressure limitation in the low pressure range, without a discharge of compressed air to avoid an excessive pressure increase is required.

to Specification of a flow direction in the return branch exclusively from the blowing station towards the low pressure supply suggested that the Recirculation valve in series with a check valve is switched.

A Optimization of the blown air return is supported thereby, that the Pressure in the range of low pressure supply is measured.

Especially it proves to be advantageous that at least one of the valves depending on controlled pressure is controlled.

One typical high pressure level is realized that in the area the high pressure supply a pressure of about 40 bar provided becomes.

to execution a Vorblasphase, it proves appropriate that in the field of low pressure supply a pressure of about 20 bar is provided.

A Further optimization of the blown air return can be done by that at least a part of the compressed air in the low pressure supply controllable is traceable to a working air area.

According to one typical embodiment is thought that in the Working air range a pressure of about 10 bar is provided.

A further embodiment to optimize the compressed air return exists in that at least a part of the compressed air from the low pressure range controlled as Form is returned to a high pressure compressor.

A further homogenization of the Pressure levels is supported by a volume accumulator for the low pressure air is used.

In The drawings are exemplary embodiments of the invention shown schematically. Show it:

1 A perspective view of a blowing station for the production of containers from preforms,

2 a longitudinal section through a blow mold, in which a preform is stretched and expanded,

3 a sketch to illustrate a basic structure of a device for blow molding containers,

4 a modified heating section with increased heating capacity,

5 a block diagram illustrating the pneumatic functional components in the blown air return,

6 one opposite the representation in 5 modified embodiment in which a reducing distributor station is arranged for the lower pressure on the blowing wheel,

7 one opposite 6 modified embodiment with additional control in the area of the Reduzier-Verteilstation for the lower pressure and

8th a further modified embodiment in which only a high pressure supply of the blowing wheel is provided and the lower pressure control technology in the field of blowing wheel is generated.

The basic structure of a device for forming preforms ( 1 ) in containers ( 2 ) is in 1 and in 2 shown.

The device for forming the container ( 2 ) consists essentially of a blowing station ( 3 ), which are blown ( 4 ) into which a preform ( 1 ) can be used. The preform ( 1 ) may be an injection-molded part of polyethylene terephthalate. To enable insertion of the preform ( 1 ) in the blow mold ( 4 ) and to allow removal of the finished container ( 2 ) the blow mold ( 4 ) from mold halves ( 5 . 6 ) and a bottom part ( 7 ), which by a lifting device ( 8th ) is positionable. The preform ( 1 ) in the area of the blowing station ( 3 ) of a transport mandrel ( 9 ), which together with the preform ( 1 ) passes through a plurality of treatment stations within the device. But it is also possible to use the preform ( 1 ), for example via pliers or other handling means directly into the blow mold ( 4 ).

To enable a compressed air supply line is below the transport mandrel ( 9 ) a connecting piston ( 10 ) disposed of the preform ( 1 ) Supplies compressed air and at the same time a seal relative to the transport mandrel ( 9 ). In a modified construction, it is basically also conceivable to use solid compressed air supply lines.

A stretching of the preform ( 1 ) takes place in this embodiment by means of a stretch rod ( 11 ), by a cylinder ( 12 ) is positioned. According to another embodiment, a mechanical positioning of the stretch rod ( 11 ) carried out over curve segments which are acted upon by Abgriff. The use of curve segments is particularly useful when a plurality of blow molding stations ( 3 ) are arranged on a rotating blowing wheel 1 illustrated embodiment, the stretching system is designed such that a tandem arrangement of two cylinders ( 12 ). From a primary cylinder ( 13 ), the stretch rod ( 11 ) first before the beginning of the actual stretching process into the area of a soil ( 14 ) of the preform ( 1 ) hazards. During the actual stretching process, the primary cylinder ( 13 ) with extended stretch rod together with a primary cylinder ( 13 ) carrying carriages ( 15 ) from a secondary cylinder ( 16 ) or via a cam control. In particular, the secondary cylinder ( 16 ) such a cam-controlled use that of a leadership role ( 17 ), which slides along a curved path during the execution of the stretching process, a current stretching position is specified. The leadership role ( 17 ) is from the secondary cylinder ( 16 ) pressed against the guideway. The sled ( 15 ) slides along two guide elements ( eighteen ).

After closing in the range of girders ( 19 . 20 ) arranged mold halves ( 5 . 6 ) there is a locking of the carrier ( 19 . 20 ) relative to each other by means of a locking device ( 20 ).

For adaptation to different shapes of a mouth section ( 21 ) of the preform ( 1 ) is according to 2 the use of separate thread inserts ( 22 ) in the area of the blow mold ( 4 ) intended.

2 shows in addition to the blown container ( 2 ) also shown in dashed lines the preform ( 1 ) and schematically a developing container bubble ( 23 ).

3 shows the basic structure of a blow molding machine with a heating line ( 24 ) and a rotating blowing wheel ( 25 ) is provided. Starting from a preform input ( 26 ), the preforms ( 1 ) of transfer wheels ( 27 . 28 . 29 ) in the area of the heating section ( 24 ). Along the heating route ( 24 ) are radiant heaters ( 30 ) as well as blowers ( 31 ) arranged to the preforms ( 1 ) to temper. After a sufficient temperature of the preforms ( 1 ) these are to the blowing wheel ( 25 ), in whose area the blowing stations ( 3 ) are arranged. The finished blown containers ( 2 ) are provided by further transfer wheels of a delivery line ( 32 ).

To get a preform ( 1 ) into a container ( 2 ) that the container ( 2 ) Has material properties which have a long useful life from inside the container ( 2 ), in particular beverages, special process steps in the heating and orientation of the preforms ( 1 ) be respected. In addition, advantageous effects can be achieved by adhering to special dimensioning regulations.

When thermoplastic material can different plastics are used. Can be used for example PET, PEN or PP.

The expansion of the preform ( 1 ) during the orientation process is carried out by compressed air supply. The compressed air supply is in a Vorblasphase in which gas, for example, compressed air, is supplied at a low pressure level and divided into a subsequent Hauptblasphase in which gas is supplied at a higher pressure level. During the pre-blowing phase, compressed air with a pressure in the interval of 10 bar to 25 bar is typically used and during the main blowing phase compressed air is supplied at a pressure in the interval of 25 bar to 40 bar.

Out 3 is also apparent that in the illustrated embodiment, the heating section ( 24 ) from a plurality of circulating transport elements ( 33 ) is formed, the chain-like strung together and along deflection wheels ( 34 ) are guided. In particular, it is envisaged to open a substantially rectangular basic contour by the chain-like arrangement. In the illustrated embodiment, in the region of the transfer wheel ( 29 ) and an input wheel ( 35 ) facing the extent of the heating section ( 24 ) a single relatively large-sized deflection ( 34 ) and in the region of adjacent deflections two comparatively smaller dimensioned deflection wheels ( 36 ) used. In principle, however, any other guides are conceivable.

To enable a dense arrangement of the transfer wheel ( 29 ) and the input wheel ( 35 ) relative to each other, the arrangement shown to be particularly useful, since in the region of the corresponding extent of the heating section ( 24 ) three deflection wheels ( 34 . 36 ), in each case the smaller deflection wheels ( 36 ) in the area of the transition to the linear curves of the heating section ( 24 ) and the larger deflection wheel ( 34 ) in the immediate transfer area to the transfer wheel ( 29 ) and to the input wheel ( 35 ). Alternatively to the use of chain-like transport le menten ( 33 For example, it is also possible to use a rotating heating wheel.

After a finished blowing of the container ( 2 ), these are picked up by a picking wheel ( 37 ) from the field of blowing stations ( 3 ) and via the transfer wheel ( 28 ) and an output wheel ( 38 ) to the output section ( 32 ).

In the in 4 illustrated modified heating section ( 24 ) can by the larger number of radiant heaters ( 30 ) a larger amount of preforms ( 1 ) are tempered per unit time. The blowers ( 31 ) direct cooling air into the area of cooling air ducts ( 39 ), which the associated radiant heaters ( 30 ) in each case opposite and deliver the cooling air via outflow openings. Due to the arrangement of the outflow directions, a flow direction for the cooling air is substantially transverse to a transport direction of the preforms ( 1 ) realized. The cooling air channels ( 39 ) in the area of the radiant heaters ( 30 ) opposite surfaces provide reflectors for the heating radiation, it is also possible on the discharged cooling air and a cooling of the radiant heater ( 30 ) to realize.

5 schematically shows a block diagram of the compressed gas supply. The drawn container ( 2 ) was also representative of the preform ( 1 ) and the container bladder ( 23 ). Via a high pressure compressor ( 40 ) Pressure of an output pressure level, for example, above 40 bar, provided. Via one or more pressure transducers ( 41 . 61 ) takes place in the illustrated embodiment, a pressure reduction to two different supply pressure levels. The higher pressure level is about 40 bar, the lower pressure level about 20 bar. The pressure transducer ( 41 . 61 ) are designed as reducing distribution stations and with silencers ( 62 . 63 ) for discharged into the environment compressed air. The silencer ( 63 ) is via a vent valve ( 64 ) with the pressure transducer ( 61 ) connected.

About boiler ( 42 . 43 ), a storage volume for the respective pressures is provided, so that even with a clocked pressure removal, the respective pressure level is maintained at least approximately upright. The controlled supply of compressed gas is carried out using valves ( 44 . 45 ). The valves ( 44 . 45 ) are connected to a controller ( 46 ), the respective switching times of the valves ( 44 . 45 ) coordinates.

Parallel to the valve ( 44 ) for the supply of the lower blowing pressure is a return valve ( 47 ) arranged in series with a check valve ( 48 ) is switched. A valve inlet ( 49 ) of the return valve ( 47 ) is with the blowing station ( 3 ), a valve outlet ( 50 ) of the return valve ( 47 ) is connected to the check valve ( 48 ) connected. The check valve ( 48 ) allows only a flow from the blowing station ( 3 ) through the return valve ( 47 ) through in the direction of the low pressure supply. For venting the interior of the container ( 2 ) to an environment, a vent valve ( 51 ) used with a silencer ( 52 ) is coupled. Preferably, the controllable valves ( 47 . 51 ) to the controller ( 46 ) connected.

According to an extended embodiment, an additional working air compressor ( 53 ), which provides working air in a pressure range of about 10 bar. For storing the working air, a working air boiler ( 54 ) used. Via a control unit ( 55 ), it is possible, after a corresponding reduction in pressure, to transfer compressed air from the region of the low-pressure supply into the area of the working air supply. The control unit ( 55 ) is each formed as a Reduzier-Verteilerstation.

By using the control unit ( 55 ), it is possible to make a compressed air transfer into the working air range when reaching a maximum allowable upper pressure level in the region of low pressure supply. The performance of the working air compressor ( 53 ) can be reduced thereby.

According to a further alternative or supplementary embodiment, it is also possible, the working air boiler ( 54 ) or the boiler ( 42 ) for the low-pressure blowing air via a control unit ( 56 ) to the entrance of the high pressure compressor ( 40 ). The high pressure compressor ( 40 ) This would not be supplied air at an ambient pressure level, but already precompressed compressed air. By such a mode of operation, the performance of the high-pressure compressor ( 40 ) and thus energy can be saved. An advantage of these cascaded embodiments is to minimize the total amount of energy for operating the device. The control units ( 55 . 56 ) are each equipped with a silencer ( 65 . 66 ) provided for venting.

When using the compressed air supply according to 5 for a blowing machine with a rotating blowing wheel ( 25 ) are in a mobile area ( 57 ) drawn device components on the rotating blowing wheel ( 25 ) and the other components are stationary installed on the machine bed. For coupling the stationary area with the mobile area ( 57 ) are rotary entrances ( 58 . 59 ) used. The rotary entrances ( 58 . 59 ) can, for example, in the region of a coaxial relative to a rotation axis construct be summarized rotary coupling.

According to a typical procedure, first after opening the valve ( 44 ) blowing the container ( 2 ) with the lower blowing pressure and then after closing the valve ( 44 ) and opening the valve ( 45 ) a finished blowing with the higher blowing pressure. After achieving sufficient stability of the container ( 2 ) within the blow mold ( 4 ) opens the return valve ( 47 ) after a previous closure of the valve ( 45 ) and there is a return from the container ( 2 ) blowing air into the area of low pressure supply. After completion of the regeneration process, the vent valve opens ( 51 ) and the internal pressure in the container ( 2 ) is lowered to an ambient pressure.

From the area of a blowing station ( 3 ) in the region of the low-pressure supply flowing back blown air is passed through the valve ( 44 ) is used again in a blowing station following in the course of the process. Depending on the amount of return and the amount of consumption, the area of the boiler ( 42 ) a varying within a tolerance band pressure curve. In order to optimize the amount of recirculation and to reduce the fluctuation range of the pressure in the region of the low-pressure supply, the already described forwarding of compressed air in the range of working air supply or the use of as a return amount as a form for the high-pressure compressor ( 40 ) respectively.

According to a preferred mode of operation, it is possible in the region of the low-pressure supply, a pressure sensor ( 60 ) and to the controller ( 46 ). The control ( 46 ) can thereby optimize the switching times for the return valve ( 47 ) and the vent valve ( 51 ).

6 shows one opposite the representation in 5 modified embodiment. The pressure transducer ( 61 ) for the lower pressure here is not stationary outside the mobile area ( 57 ), but in the mobile area ( 57 ) Installed. There is thus an arrangement of the pressure transducer ( 61 ) in the region of the rotating blowing wheel ( 25 ). The pressure control is carried out thereby in local proximity to the boiler ( 42 ), so that a more accurate pressure control is supported.

According to the embodiment in FIG 7 the compressed air return via the return valve ( 47 ) first into the area of a cache ( 67 ) having a pressure level between the lower pressure P1 and the higher pressure P2. A typical print for the cache ( 67 ) is about 30 bar. The cache ( 67 ) is in addition to the rotary joint ( 58 ) connected. In addition, the rotary joint ( 58 ) and the cache ( 67 ) together to the input of the pressure transducer ( 61 ) for the lower pressure. The input of the pressure transducer ( 61 ) is also via a check valve ( 68 ) with the boiler ( 43 ) connected. The check valve ( 68 ) is from a control unit ( 69 ), to which a pressure sensor ( 70 ) for detecting an input pressure of the pressure transducer ( 61 ) connected. About the rotary joint ( 58 ) takes place both in the embodiment according to 6 as well as in the embodiment according to 7 only a discharge of compressed air from the mobile area ( 57 ) into the area of the working air boiler ( 54 ). In the embodiment according to 5 via the rotary joint ( 58 ) also a power supply of the mobile unit ( 57 ) with the lower pressure.

According to the embodiment in FIG 7 will the pressure transducer ( 61 ) so long with compressed air from the area of the buffer ( 67 ), as here is a sufficient pressure level. Additional compressed air can be supplied via the check valve ( 68 ) are provided from the high pressure circuit. The compressed air return duct to the inlet of the pressure transducer ( 61 ) has the advantage that pressure fluctuations in the area of the boiler ( 42 ) are minimized.

According to the embodiment in FIG 8th is on the second rotary joint ( 58 ) waived. The mobile area ( 57 ) is only via the rotary joint ( 59 ) fed with high pressure. All further pressure conversions take place within the mobile area ( 57 ). Shown is in 8th a compressed air return similar to 5 and 6 , Basically, however, in this embodiment, a compressed air return to the input of the pressure transducer ( 61 ) corresponding 7 possible.

Claims (7)

Apparatus for blow molding containers having at least one blowing station having at least one blow mold and at least one stretching rod arranged on a blowing wheel and at which the blowing station is connected to a low pressure supply for providing a first blow pressure and to a high pressure supply for providing a second blow pressure higher relative to the first blow pressure is connected and in which a blown air return is used for after a container forming the blow station escaping high pressure blowing air into the low pressure supply, characterized in that the blown air return a return valve ( 47 ), which in a parallel to a blow-pressure valve ( 44 . 45 ) is arranged return branch, that a valve outlet ( 50 ) of the return valve ( 47 ) is connected to the low pressure supply and that an input of a compressor ( 40 . 53 ) is connected to the vorkompri mized compressed air providing low pressure supply. Apparatus according to claim 1, characterized in that the return valve ( 47 ) in series with a check valve ( 48 ) is designed. Apparatus according to claim 1 or 2, characterized in that in the region of the low pressure supply at least one pressure sensor ( 60 ) is arranged. Device according to one of claims 1 to 3, characterized in that at least one of the valves ( 44 . 45 . 47 ) to a controller ( 46 ) for controlling in dependence on the measuring signal of the pressure sensor ( 60 ) connected. Device according to one of claims 1 to 4, characterized that the High pressure supply has an operating pressure of about 40 bar. Device according to one of claims 1 to 5, characterized that the Low pressure supply has an operating pressure of about 20 bar. Device according to one of claims 1 to 6, characterized in that the low-pressure supply via a control unit ( 50 ) is connected to a working air area for pressure feedback.