Blowing apparatus for expanding a preformed hollow body, stretch-blow-moulding machine and method for expanding a hollow body

Abstract

The invention relates to a blowing apparatus (102) for expanding a preformed hollow body (113) with a fluid, comprising a moulding tool (101) with a receiving device for the preformed hollow body (113) and a main blowing nozzle (123) which is positioned so as to be displaceable in a blowing direction (C) on the blowing apparatus (102) and which, in a first operating state of the blowing apparatus (102) in which the preformed hollow body (113) expands by means of a predefined maximum pressure of the fluid to form a shaped hollow body (127), is connected in an insufflation position fluid-tightly to a mouth opening (125) in the preformed hollow body (113), wherein the blowing apparatus (102) is configured and designed in such a way that the main blowing nozzle (123), in response to a second operating state of the blowing apparatus (102) in which the preformed hollow body (113) has been expanded to form the shaped hollow body (127) and a predefined internal pressure in the shaped hollow body (127) has been fallen below, is transferred into a venting position by means of a displacement device.

Description

Blowing device for expanding a preformed hollow body, stretch blow molding machine and method for expanding a hollow body

[0001] The invention relates to a blow molding device for expanding a preformed hollow body, a stretch blow molding machine and a method for expanding a hollow body.

[0002] Blow molding machines for producing hollow bodies, particularly plastic containers made of thermoplastics such as PET, PVC, or PP, are known in the prior art. Stretch blow molding machines are also known. The blow molding process is used in particular for the production of bottles. Preforms (preformed hollow bodies, also called preforms) are heated in a first process step, in particular to a processing temperature of approximately 100°C - 120°C, and expanded in a second step. Additionally or alternatively, the preforms can be stretched in the second process step. The expansion and, if necessary, stretching is achieved in particular by plastic deformation of the preform material. The molded preform accordingly represents the hollow body to be produced.

[0003] For stretching, a stretching rod is inserted into an opening of the pre-formed hollow body and the latter is mechanically expanded in the longitudinal direction by further inserting the stretching rod in the direction of the bottle bottom.

[0004] The expansion is achieved by introducing a process gas and thus applying pressure to the inner wall of the preform. Valves are used to introduce the process gas. The molding process can be carried out in a single stage by introducing the process gas until a maximum pressure is reached. Blowing devices are known that feature multi-stage process gas introduction. For example, a first gas line with a first valve can establish a first pressure level of the process gas in the preform to be molded, and a second gas line with a second valve can establish a second pressure level of the process gas in the preform to be molded.

[0005] After the molding process is completed, an exhaust valve is opened, allowing the air to flow out of the molded hollow body due to pressure equalization with the ambient air. Blowing devices are known that have sound-damping devices to dampen exhaust air noise. Blowing devices are also known that have a further exhaust air valve, through which the pressurized process gas is discharged from the hollow body in a third process step and fed back into the first gas line and / or second gas line before the exhaust valve is opened in a fourth process step.

[0006] Stretch blow molding processes have a very long cycle time. The time required to vent the hollow body is comparatively long with conventional venting processes, particularly due to the valve actuation time and / or the hose cross-section through which the process gas must pass, which inhibits venting. This effect is particularly evident in large hollow bodies. Consequently, there is a need for improved venting of a molded hollow body.

[0007] EP 4 082 750 A1 discloses a device of a blow molding device for forming hollow bodies, in particular a stretch blow molding machine with a housing block with a through-bore, at least one valve with a movable piston and with a valve chamber, a first channel which is in Housing block and connects the valve chamber with the through hole, a second channel that connects the valve chamber with an external line and a cover for attaching the valve to the housing block.

[0008] US 7,927,093 B2 discloses a control arrangement for fluid flow in a container blow-molding machine, comprising: a blow pin, a plurality of lines for the circulation of a blowing fluid, which allow the blowing fluid to flow between at least one blowing fluid source, at least one fluid outlet, and the aforementioned blow pin; and valves that can control the flow of the blowing fluid within the plurality of fluid circulation lines. The valves are all arranged at the front of a body that accommodates the blow pin, and on the opposite side of the housing block, a second housing is arranged, in which all supply channels and the vent channel for the process air run. The second housing connects such external lines and the channels running in the housing block.

[0009] WO 002019 025 551 A1 discloses a device for forming plastic preforms into plastic containers, comprising a blow-molding device which has at least two side parts and a base mold, which form a cavity within which the plastic preforms are formed into the plastic containers, wherein the device has a changing device which is suitable and intended to remove either the complete blow-molding device or only parts of the blow-molding device from its blow-molding carriers and / or to arrange them on the blow-molding carriers, wherein the base mold is arranged on a base holder and the base mold can be connected to the base holder or separated from the base holder in an alternating operation by a lifting movement and in particular a raising and / or lowering of the base holder, and between the base holder and the base mold at least one first A separable media connection is provided, through which a flowable medium can be supplied to the base mold and / or through which the flowable medium can be removed from the base mold. Thus, by raising and / or lowering the base support, the media connection between the base support and the base mold can also be established and / or severed.

[0010] The object of the invention is to improve the state of the art.

[0011] The object is achieved by a blowing device for expanding a preformed hollow body with a fluid, comprising a molding tool with a receiving device for the preformed hollow body and a main blowing nozzle arranged on the blowing device so as to be displaceable in a blowing direction, which in a first operating state of the blowing device, in which the preformed hollow body expands by means of a predefined maximum pressure of the fluid into a formed hollow body, is connected in a blowing-in position in a fluid-tight manner to an opening of the preformed hollow body, wherein the blowing device is set up and designed such that the main blowing nozzle, in response to a second operating state of the blowing device, in which the preformed hollow body has expanded into the formed hollow body and a predefined internal pressure in the formed hollow body has fallen below,is transferred into a venting position by means of a displacement device.

[0012] Advantageous embodiments arise from the subclaims.

[0013] The venting position thus enables rapid venting of the hollow body. The gaseous fluid escapes from the formed hollow body through the gap between the support ring and the preformed hollow body more quickly than through a valve.

[0014] A key concept of the invention is that rapid pressure equalization from the molded hollow body is achieved by creating a physical gap. This requires no additional components. Furthermore, the technical solution is low-maintenance and robust.

[0015] The following terminology is explained:

[0016] A "blowing device" is understood, in particular, to be a device for expanding a preformed hollow body with a first volume into a predefined, molded hollow body with a second volume that is larger than the first volume. The blowing device can be a stretch blow molding machine or a sub-element of a stretch blow molding machine or a beverage filling system. The blowing device has at least one holding device for the preformed hollow body, a molding tool (blow mold), which can be one-part or multi-part, at least one main blow nozzle, also called a blow nozzle, and a fluid, e.g., process gas, as well as corresponding control devices.The blow molding device is in particular set up and designed to expand a particularly pre-tempered, pre-formed hollow body into a container by blowing in, also referred to as introducing, the fluid, preferably compressed air, until an outer wall of the pre-formed hollow body rests against an inner wall of the mold. The main blow nozzle connects in particular the pre-formed hollow body to a pressure line system for the fluid. To control the process, the stretch blow molding machine can have a control system and / or an evaluation system with corresponding communication devices and / or sensors, in particular sensors which detect parameters for determining a process status, and / or can be manually controlled. The stretch blow molding machine can have a housing. The housing can have recesses at suitable positions so that escaping fluid. Fluid is advantageously drained from an interior of the stretch blow molding machine.

[0017] A “preformed hollow body” is understood in particular to mean a preform which is produced in a first production step, in particular from a molten material, and which, due to its respective geometry and wall thickness, is suitable for forming a predefined hollow body. The preformed hollow body has, in particular, a neck with an outlet opening, wherein the neck has, in particular, a first partial region adjoining the outlet opening, said neck having an external thread, and a second partial region with a support. The support has, in particular, a top side and a bottom side. The preformed hollow body can comprise a thermoplastic material, such as, for example, PET, PVC or PP. The preformed hollow body is advantageously suitable for being expanded in a device, e.g., a blow molding machine, by means of a fluid to form a shaped hollow body, also called a container or bottle.

[0018] A "fluid" can be a gaseous fluid, in particular a process gas, such as compressed air. Furthermore, a fluid can be a liquid, in particular a liquid with which the molded hollow body is filled. To expand the preformed hollow body with a liquid as the fluid, the expansion pressure of the liquid can be additionally increased, in particular by means of a gaseous fluid. The liquid can be a beverage.

[0019] "Expanding" refers, in particular, to the expansion of the preformed hollow body. During expansion, the wall thickness of the preformed hollow body is reduced and the volume of the preformed hollow body is increased.

[0020] A "molding tool" is understood, in particular, to be a blow mold having an opening into which the preformed hollow body, in particular a neck of the preformed hollow body, is inserted. The molding tool may be made of steel. The molding tool may be multi-part. Channels, valves, cooling and / or heating elements, ejectors, or other elements may be arranged in the molding tool.

[0021] A "receiving device" is understood to mean, in particular, a round region of the molding tool that is designed to receive the preformed hollow body. The receiving device can have seals. Additionally or alternatively, the receiving device can have a predefined contact surface for the preformed hollow body. Finally, the receiving device can have a first position for receiving a preformed hollow body and a second position for securing a received preformed hollow body.

[0022] The “blowing direction” is in particular the direction in which the preformed hollow body is expanded by blowing in the fluid.

[0023] A "main blow nozzle" is understood, in particular, to be a fluid outlet through which the fluid is directed into the preformed hollow body. The main blow nozzle can be a valve. The main blow nozzle can be arranged on the blowing device so that it can be displaced in a blowing direction. Additionally or alternatively, a second main blow nozzle or a plurality of further blow nozzles can be arranged on the blowing device. A main blow nozzle or a plurality of blow nozzles can be arranged additionally or alternatively on a stretching rod of the blowing device, in particular on a peripheral surface of the stretching rod and / or on an end of the stretching rod projecting into the preformed hollow body.

[0024] In a “first operating state” of the blowing device, the main blowing nozzle can have an injection position, wherein the injection position is characterized in that the main blowing nozzle is directly or indirectly connected in a fluid-tight manner to an orifice of the preformed hollow body.

[0025] The "first operating state" of the blow molding device occurs, in particular, during expansion of the preformed hollow body into a molded hollow body by means of an expansion pressure of the fluid until the predefined maximum pressure of the fluid in the molded hollow body is reached. During expansion, the expansion pressure in the hollow body can increase from an initial pressure linearly, in stages, and / or taking pressure plateaus into account until a maximum pressure is reached. The maximum pressure can be maintained for a predefined period in order to advantageously realize complete expansion.

[0026] Fluid tightness exists in particular when the fluid does not leak out or only leaks out to a small extent. Fluid tightness can be achieved, for example, by means of a frictional connection or contact pressure and / or a seal and / or a positive connection.

[0027] The “second operating state” of the blowing device is characterized in particular in that the pre-formed hollow body has expanded to form the formed hollow body and a predefined internal pressure in the formed hollow body has fallen below.

[0028] In a second operating state of the blowing device, the main blowing nozzle can have a venting position, wherein the venting position is characterized by a distance between the main blowing nozzle and the mouth opening of the formed hollow body. The main blowing nozzle is moved in particular by means of a displacement device from the injection position to the venting position and vice versa. The displacement device can be a rail, a threaded rod, a pneumatic cylinder, or similar. The displacement of the main blowing nozzle occurs in particular in response to the reaching of the second operating state. In the second operating state, the expansion fluid can advantageously flow out of the molded hollow body through the gap between the main blowing nozzle and the outlet opening, essentially until pressure equalization occurs between the interior of the molded hollow body and the ambient pressure.

[0029] A "third operating state" of the blow molding device is characterized in particular by the fact that the preformed hollow body has expanded to form the formed hollow body, and a second predefined internal pressure, also called reduced pressure, in the formed hollow body corresponds to the predefined maximum pressure, wherein the second predefined internal pressure is greater than the predefined internal pressure. The third operating state can occur prior to the second operating state.

[0030] The “predefined internal pressure”, also called first predefined internal pressure, is a pressure ratio in the hollow body and can be 20 percent to 80 percent, in particular 40 percent to 60 percent, of the predefined maximum pressure of the fluid in the formed hollow body. In other words, at a first point in time, the first operating state is present with an initial pressure in the hollow body to be formed, which is increased, if necessary in stages, also called pre-blowing, up to the maximum pressure, also called finished blowing. In a third operating state, which follows in particular after the first operating state, the maximum pressure is reduced, for example, until the predefined internal pressure is reached. Finally, in a second operating state, which immediately follows in particular after the third operating state, In particular, the essentially complete venting of the molded hollow body. At the transitions between the operating states, these can correspond to one another and / or occur simultaneously. The predefined internal pressure is defined in such a way that, advantageously, easy opening of the molded hollow body is possible. Easy opening can be achieved by applying low forces to the mechanical elements and / or require little or no effort to absorb the pressure forces.

[0031] The predefined maximum pressure can be between 15 bar and 40 bar. The expansion pressure can be varied over time. The expansion pressure can be controlled according to a predefined pressure curve and / or, in particular, a stepped pressure profile. The selected predefined maximum pressure advantageously leads to an optimally formed hollow body, although a significantly excessive predefined maximum pressure should be avoided for efficiency reasons.

[0032] The reduction of the pressure of the fluid in the molded hollow body from the predefined maximum pressure to the predefined internal pressure, in other words during the third operating state of the blowing device, can be achieved by means of a valve, in particular a vent valve, also called an outlet valve. The vent valve can be arranged on the main blowing nozzle. The vent valve can be switchable. By using a vent valve, standard industrial components can be advantageously used and, furthermore, an adjustable pressure reduction can be advantageously realized.

[0033] The duration of pressure equalization in the formed hollow body, in particular the pressure equalization from the predefined maximum pressure to an ambient pressure, can be 0.01 seconds to 0.5 seconds. Duration is advantageously as short as possible in order to achieve the shortest possible production time.

[0034] To advantageously reduce noise emissions during pressure release and thus protect workers, one embodiment of the blowing device includes a silencer. The silencer can be arranged such that the fluid used to expand the preform is directed through the silencer after escaping from the molded hollow body, in particular after flowing out of the molded hollow body, thus reducing noise.

[0035] In one embodiment, a fluid conducting device can also be arranged on the blowing device. The fluid conducting device is particularly designed to conduct expansion cooling, which is produced by the fluid flowing out of the molded hollow body, to, in particular, at least one side wall of the molded hollow body. This advantageously increases the efficiency, in particular the energy efficiency, of the process, since the resulting process energy is reused and no new energy, in this case, cooling energy, needs to be supplied.

[0036] The fluid guidance device can, in particular, have a first cross-section at an outflow area of the fluid from the molded hollow body and a second cross-section, which is larger than the first cross-section, at a distance from the outflow area. By increasing the flow cross-section and thus the expansion potential of the fluid, the generation of process cooling is advantageously further supported.

[0037] Additionally or alternatively, the fluid guiding device may have an air outlet or a plurality of air outlets at a ventilation area on the side wall of the molded hollow body. In other words, The fluid-guiding device can be configured to cool the walls of the molded hollow body, which are at a process temperature during the molding process. Additionally or supplementarily, a blow mold base and / or another portion of the blow molding device can be cooled using the fluid-guiding device. Particularly advantageously, the air flow of the expanding fluid enables the easy utilization of energy introduced into the production process, which particularly serves the goal of sustainable production processes. The fluid-guiding device can be made of metal, plastic, and / or sheet metal.

[0038] In one embodiment, the blowing device further comprises a blowing attachment, which is arranged displaceably in the blowing direction by means of a first guide device of the blowing device, and a hold-down device, which is arranged on the blowing attachment and is displaceable in the blowing direction by means of a second guide device arranged on the blowing attachment, and on which, in particular, the main blowing nozzle is arranged. The aforementioned arrangement advantageously realizes a production process that is optimized both in terms of time and process at high cycle rates.

[0039] The blowing device can be designed and configured such that a bottom side of a support ring of the preformed hollow body inserted into the blowing device rests fluid-tight against an opening of the mold in a second blowing position, and the hold-down device rests fluid-tight against an upper side of the support ring of the preformed hollow body. Thus, by pressing the support ring by means of the hold-down device, possibly also in cooperation with the main blowing nozzle, a particularly fluid-tightly sealed cavity is advantageously produced in the preform and / or a particularly fluid-tightly sealed cavity is produced in the preform and the hold-down device interior, which cavity can be opened by simply lifting the main blowing nozzle while the hold-down device is pressed on and / or by Can be partially expanded by lifting the hold-down device when the blower attachment is lowered and / or can be opened by lifting the blower attachment. The respective positions of the elements and the times of their position change can advantageously simplify and / or accelerate an expansion process and / or a subsequent production process, e.g. filling. Additionally or alternatively, the blowing device can be set up and designed such that the hold-down device, in a second venting position, is at a distance, in particular a distance of 1 mm to 5 mm, from the support ring of the molded hollow body, so that the fluid escapes through the distance between the hold-down device and the support ring in the second operating state.

[0040] In one embodiment, the distance between the hold-down device and the support in the second venting position is 1 mm to 5 mm, in particular 2 mm to 4 mm. The distance between the hold-down device and the support in the second venting position advantageously realizes efficient pressure equalization to achieve high production results at high cycle times.

[0041] A "blowing attachment" is understood to be an element that can be moved vertically in the blowing direction, which is placed on the mold and covers the opening. The blowing attachment thus temporarily closes the mold, particularly for the duration of the expansion of the preformed hollow body. After expansion, the blowing attachment is moved vertically against the blowing direction, so that the opening of the mold is now open again.

[0042] A seal can be arranged on the blowing attachment, which creates a fluid-tight seal between the mold and the blowing attachment. The blowing attachment can in particular be made of steel. Additionally or alternatively, A fluid line system mentioned above can be arranged on the blower attachment. The advantages already mentioned also apply to this.

[0043] In particular, a hold-down device is arranged on the blowing attachment, which can be displaced in the blowing direction by means of the second guide device. In other words, the displaceability of the blowing attachment and the hold-down device is realized by means of the first or second guide device. A "guide device" is understood in particular to mean a movable connection of a first element with respect to a second element, wherein the movement is in particular a relative movement predefined by the guide device. The guide device is, for example, a rail, a threaded rod, or the like. The first and / or second guide device can additionally or alternatively be the displacement device.

[0044] A "hold-down device" is understood in particular to be an essentially hollow-cylindrical element which presses the pre-formed hollow body against the mold in a second blow-in position in a fluid-tight manner. The hold-down device can have a seal. The "second blow-in position" is characterized in particular by a position of the hold-down device in which a volume, which comprises at least an internal volume of the molded hollow body, is fluid-tightly sealed from the surroundings. In order to be able to apply a process-related expansion pressure to the pre-formed hollow body, a high degree of fluid tightness must be achieved. Additionally or alternatively, the volume should ideally not be significantly larger than the internal volume of the molded hollow body. In particular, the volume is at most 2 percent to 10 percent larger than the internal volume of the molded hollow body.

[0045] In the second blow-in position, the hold-down device can rest on the support ring of the preformed hollow body. The hold-down device can correspond to a shape of the preformed hollow body, in particular to the shape of the upper side of the support ring of the preformed hollow body. The hold-down device has, in particular, a seal at the contact area. In the second blow-in position, the hold-down device can be pressed against the support ring with a predefined pressure.

[0046] By moving the hold-down device against the blowing direction to a second venting position, a gap is created between the support ring and the hold-down device. In other words, in the second venting position, the fluid can escape from the molded hollow body into the blowing attachment and from there into the environment of the blowing device.

[0047] Additionally or alternatively, a stretch rod can be arranged on the blowing attachment, which can be displaced in the blowing direction. A fluid line system can be arranged in an interior space of the stretch rod. The stretch rod can be arranged on a further guide device. The stretch rod can be used in particular for plastically deforming the preformed hollow body. The stretch rod can be displaceable in a longitudinal direction of the preformed hollow body. A main blowing nozzle or additional blowing nozzles can be arranged on the stretching rod and / or integrated into the stretching rod.

[0048] The inner diameter of the neck of the preformed hollow body is, in particular, larger than the outer diameter of the stretch rod of the blow molding device. This advantageously allows the fluid to escape between the stretch rod and the inner wall of the neck of the preformed hollow body without the stretch rod having to be removed from the neck of the molded hollow body. The inner diameter of the neck is, in particular, 2 mm to 5 mm larger than the outer diameter of the stretch rod.

[0049] In a further aspect, the object is achieved by a stretch blow molding machine having a blow molding device for expanding a preformed hollow body. A stretch blow molding machine may, in particular, have a heating area and / or an expansion area and / or a treatment area, such as a filling area and / or a closing area and / or a labeling area.

[0050] In a third aspect, the problem is solved by a method for expanding a hollow body. Essentially the same advantages and definitions apply to the second and third aspects as previously explained, which is why reference is made to the above explanations to avoid repetition.

[0051] The invention will be explained in more detail below using exemplary embodiments. Figure 1 is a schematic representation of a blowing device with a main blowing nozzle, Figure 2 is a schematic representation of a blowing device with an air guiding device, Figure 3 is a schematic representation of a blowing device with a hold-down device and Figure 4 is a flow chart of a process for expanding a hollow body.

[0052] A first blow molding device 102' has a blow mold 101 and a main blow nozzle 123. The blow mold 101 forms the contour for a bottle 127 to be expanded. The bottle 127 is formed from a preform 113 as a preformed hollow body. The preform 113 has a hollow body, a support ring 115 and a bottle opening 125. The preform 113 is rotationally symmetrical and is inserted into an opening of the blow mold 101 such that an underside of the support ring 115 rests fluid-tight against the blow mold 101. The main base nozzle 123 is moved towards the bottle opening 125 by means of a vertical movement in the blowing direction C and closes it fluid-tight in an injection position of the main blowing nozzle 123 (Fig. 1) while compressed air flows from the main blowing nozzle 123 into the preform 113. After the preform 113 has been formed into a bottle 127 with a maximum expansion pressure of 30 bar, the compressed air is vented from the bottle 127 until the internal pressure in the bottle is 80 percent of the maximum expansion pressure.The main blowing nozzle 123 is then moved opposite to the blowing direction C and by means of the compressed air flowing out through the gap between the main blowing nozzle 123 and the bottle opening 125, a complete pressure equalization between the ambient pressure and the interior of the bottle 127 is achieved.

[0053] A second blow molding device 102" has a blow mold 101, a main blow nozzle 123, and an air guide device 131. The preform 113 has already expanded. An underside of the support ring 115 of the bottle 127 rests fluid-tight against the blow mold 101. In a venting position of the main blow nozzle 123 (Fig. 2), the air guide device 131 covers an annular gap between the main blow nozzle 123 and the bottle opening 125. The cross-section of the air guide device 131 increases as the air guide device 125 extends further and directs compressed air flowing out of the bottle 127 to ventilation openings 133, which are arranged on the side walls of the bottle 127 and distributed over the height and circumference. The bottle 127 is thus cooled by expansion cooling.

[0054] A third blowing device 102'" has a blow mold 101, a blowing attachment 103, a stretching rod 107 and a hold-down device 105. The third blowing device 102'" is capable of exchanging sensor data via a Data output 119 is connected to a control unit 117. The control unit 117 is programmed to control the third blow molding device 102'". The blow mold 101 forms the contour for a bottle 127 to be expanded. The bottle 127 is formed from a preform 113. The preform 113 has a support ring 115. The support ring 115 is arranged at the lower end of a thread of the preform 113. The support 115 has a bottom side A and a top side B. The preform 113 is rotationally symmetrical. To hold the preform 113, the blow mold 101 has an opening on an upper side of the blow mold 101, against which the support ring 115 of the preform 113 rests during an expansion process.

[0055] The blow attachment 103 closes the opening of the blow mold 101 in a blowing-in position of the blow attachment 102 (Fig. 3) in a fluid-open manner and has a distance from the blow mold 101 in a setup position (not shown) so that a preform 113 can be inserted into the blow mold 101 or a bottle 127 can be demolded from the blow mold 101.

[0056] The movement of the blower attachment 103 is implemented by a servo motor with a threaded rod, which is controlled by the control unit 117. For control, the servo motor is connected to the control unit 117 via a first data line 121A via the data output 119. The stretch rod 107 is arranged centrally on the blower attachment 103 and can be moved in a blowing direction by means of a threaded rod with a motor (not shown). The motor is connected to the control unit 117 via the data output 119 via a third data cable 121C, exchanging sensor data, and is controlled by the control unit 117.

[0057] A first blowing nozzle 109 as the main blowing nozzle and a second blowing nozzle 111 are arranged on a lateral surface of the stretching rod 107. The first blowing nozzle 109 and the second blowing nozzle 111 are connected to a compressed air system (not shown), which can be pressurized with an adjustable pressure. The compressed air application is controlled by the control unit 117. The hold-down device 105, which can be moved in the blowing direction by means of a gas pressure cylinder (not shown), is arranged on an inner wall of the blowing attachment 103. The gas pressure cylinder is connected to the control unit 117, which controls the gas pressure cylinder, by means of a second data cable 121B via the data output 119, in such a way that sensor data can be exchanged. When the hold-down device 105 is in an inflating position (Fig. 3), the hold-down device 105 rests fluid-tight against the upper side B of the support ring 115 and, when the hold-down device 105 is in a venting position (not shown), is spaced from the upper side B of the support ring 115.

[0058] To expand a preform 113 into a bottle 127, the preform 113 is inserted into the opening of the blow mold 101 so that the support ring 115 rests with its underside A against a supporting surface surrounding the opening of the blow mold 101. By means of a first control command from the control unit 117, the blow attachment 103 is placed on the blow mold 101, and the stretch rod 107 is guided into the preform 113 by means of a second control command from the control unit 117. Subsequently, the hold-down device 105 is moved to the upper side B of the support ring 115 of the preform 113 by means of a third control command of the control unit 117, so that a first fluid tightness is established between the blow mold 101 and the underside A of the support ring 115 and a second fluid tightness is established between the upper side B of the support ring 115 of the preform 113 and the hold-down device 105.

[0059] The preform 113 is stretched by vertically displacing the stretching rod 107 in the blowing direction C into the preform 113, which is initiated by a fifth control command of the control unit 117. During this process or subsequently, compressed air is directed into the preform 113 via the first blowing nozzle 109 and the second blowing nozzle 111, initiated by a sixth control command of the control unit 117, so that the Side walls of the preform 113 are formed onto the inner wall of the blow mold 101 and the bottom wall of the preform 113 is formed onto a bottom of the blow mold 101 and the preform 113 is formed into the bottle 127 at the end of the expansion.

[0060] After the molding process, the internal pressure from the bottle 127 is reduced by 40 percent by means of a vent valve (not shown) and then the hold-down device 105 is moved in the vertical direction against the blowing direction C of the preform 113 by means of a seventh control command of the control unit 117, so that a gap is created between the upper side B of the support ring 115 of the preform 113 and the hold-down device 105 and the compressed air escapes completely from the bottle 127.

[0061] Figure 4 shows the steps of the method for expanding a preform into a bottle using compressed air. First, the preform is arranged 100 in a stretch blow molding machine such that the underside of a support ring of the preform rests against the opening of an injection mold. A main blow nozzle is then placed 200 on a mouth opening of the preform so that the main blow nozzle rests fluid-tight against the mouth of the preform. The preform is formed into a bottle 300 using compressed air, which is fed into the preform via the main blow nozzle, until a predefined maximum pressure is reached in the bottle. The bottle is vented 400 using a vent valve until a reduced internal pressure of 50 percent of the maximum pressure is reached. Finally, the main blow nozzle is moved to a venting position 500 to completely vent the bottle. List of reference symbols 101 Blow mold 102' first blowing device 102" second blowing device 102'“ third blowing device 103 Blow attachment 105 hold-down clamps 107 horizontal bar 109 first blow nozzle 111 second blow nozzle 113 Preform 115 Support ring 117 Control unit 119 Data output 121 A first data line 121 B second data line 121C third data line 123 Main blow nozzle 125 bottle opening 127 bottles 131 Air guiding device 133 Ventilation opening A bottom B Top C Blowing direction 100 Arranging the preform in the stretch blow molding machine 200 Attaching the main blow nozzle 300 Forming the preform into a bottle 400 First venting of the bottle 500 Moving the blowing nozzle

Claims

Patent claims:

1. Blowing device (102) for expanding a preformed hollow body (113) with a fluid, comprising a molding tool (101) with a receiving device for the preformed hollow body (113) and a main blowing nozzle (123) arranged on the blowing device (102) so as to be displaceable in a blowing direction (C), which in a first operating state of the blowing device (102), in which the preformed hollow body (113) expands by means of a predefined maximum pressure of the fluid to form a formed hollow body (127), is fluid-tightly connected in an injection position to an opening (125) of the preformed hollow body (113), characterized in that the blowing device (102) is set up and designed such that the main blowing nozzle (123), in response to a second operating state of the blowing device (102),in which the preformed hollow body (113) has expanded to form the formed hollow body (127) and a predefined internal pressure in the formed hollow body (127) has fallen below, is transferred into a venting position by means of a displacement device.

2. Blowing device (102) according to one of the preceding claims, wherein the predefined internal pressure is 20 percent to 80 percent, in particular 40 percent to 60 percent, of the predefined maximum pressure of the fluid with which the preformed hollow body (113) is expanded to the formed hollow body (127).

3. Blowing device (102) according to one of the preceding claims, wherein the predefined maximum pressure is 15 bar to 40 bar.

4. Blowing device (102) according to one of the preceding claims, wherein the blowing device (102) is arranged and designed such that the duration of a pressure equalization in a venting position of the main blowing nozzle (109, 111) is 0.01 seconds to 0.5 seconds.

5. Blowing device (102) according to one of the preceding claims, wherein the blowing device (102) further comprises a vent valve and the blowing device (102) is set up and designed such that, in response to a third operating state of the blowing device (102), in which the pre-formed hollow body (113) has expanded to form the formed hollow body (127) and a second internal pressure in the formed hollow body (127) corresponds to the maximum pressure, the fluid escapes from the formed hollow body (127) by means of the vent valve until the second operating state of the blowing device (102) is reached.

6. Blowing device (102) according to one of the preceding claims, wherein a silencer is further arranged on the blowing device (102) such that the fluid is guided through the silencer after the fluid has flowed out of the shaped hollow body (127).

7. Blowing device (102) according to one of the preceding claims, wherein a fluid guiding device (131) is further arranged on the blowing device (102), wherein the fluid guiding device (131) is designed to guide an expansion cold, which has been cooled by the outflow of the fluid from the shaped hollow body (127), in particular to at least one side wall of the shaped hollow body (127).

8. Blowing device (102) according to one of the preceding claims, wherein the blowing device (102) further comprises a blowing attachment (103) which is arranged displaceably in the blowing direction (C) by means of a first guide device of the blowing device (102), with a hold-down device (105) which is arranged displaceably in the blowing direction on the blowing attachment (103) by means of a second guide device arranged on the blowing attachment (103), on which hold-down device the main blowing nozzle (123) is arranged, wherein the blowing device (102) is arranged and designed such that in a second blowing-in position, an underside (A) of a support ring (115) of the preformed hollow body (113) inserted into the blowing device (102) rests fluid-tight against an opening of the molding tool (101), and the hold-down device (105) rests fluid-tight against an upper side (B) of the support ring (115) of the preformed hollow body (113) and the hold-down device (105) in a second venting position has a distance in particular a distance of 1 mm to 5 mm, from the support ring (115) of the shaped hollow body (127).

9. Blowing device (102) according to the preceding claim, wherein a stretching rod (107) which is displaceable in the blowing direction (C) and has at least the main blowing nozzle (109, 111, 123) is further arranged on the blowing device (102), wherein the blowing device (102) is set up and designed such that a second distance, in particular a distance of 2 mm to 5 mm, is present between an outer diameter of the stretching rod (107) and an inner neck diameter of the preformed hollow body (113), so that the fluid can escape between the stretching rod (107) and the inner neck diameter during venting.

10. Blowing device (102) according to one of the preceding claims, wherein the fluid is a gas and / or a liquid.

11. Stretch blow molding machine comprising a blow molding device (102) according to claims 1-10.

12. A method for expanding a preformed hollow body with a fluid using a stretch blow molding machine according to claim 11, comprising the steps: • Arranging (100) a preformed hollow body (113) in the stretch blow molding machine, • Placing (200) the main blowing nozzle (109, 111, 123) on an opening (125) of the preformed hollow body (113) so that the main blowing nozzle (109, 111, 123) lies fluid-tight against the opening (125), • Shaping (300) the preformed hollow body (113) by means of at least one pressure of the fluid which is passed through the main blowing nozzle (109, 111, 123) into the preformed hollow body (113) until the predefined maximum pressure in the formed hollow body (127) is reached • First venting (400) of the formed hollow body (127) by means of a venting valve until a predefined internal pressure, which is 20 percent to 80 percent, in particular 40 percent to 60 percent, of the predefined maximum pressure of the fluid in the shaped hollow body (127) and • Moving (500) the main blowing nozzle (109, 111, 123) into a venting position to completely vent the formed hollow body (127).

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