DEVICE FOR BLOW SHAPING OF CONTAINERS

Description

[0001] The present invention relates to a device for blow-molding containers. Such devices have long been known in the art. Typically, heated plastic preforms are subjected to compressed air to form plastic containers. Such devices for forming the plastic preforms into plastic containers typically comprise a blowing wheel on which a plurality of blowing stations are arranged. These blowing stations, in turn, form cavities within which the plastic preforms are expanded.

[0002] Compressed air is typically applied to the plastic preforms using blowing nozzles. The blowing pressure required to expand the plastic preforms is typically provided by valve blocks. Various designs of these valve blocks or valve mechanisms are known from the prior art.

[0003] EP 1 328 396 B1 describes a blow molding machine with a control valve attached to the blow molding device for controlling the blowing air. A valve body is provided that surrounds the blow nozzle in a ring-like manner over at least part of its height. A low-pressure valve, a high-pressure valve, and a vent valve are arranged distributed around the circumference of the valve carrier and connected to the blow nozzle through bores in the valve carrier.

[0004] From EP 1 271 029 B1, which discloses the preamble of claim 1, a device for blow molding containers is known. This device has a device for pneumatically controlling the blowing pressure, and this device has a control piston guided in a cylinder, which is mounted along a longitudinal axis. This control piston is formed, at least in part, from a plastic material. By forming the control piston in some regions from plastic, metallic contact with the cylinder wall is avoided. In this way, separate guide bands can be avoided. In addition, this control piston made of plastic also has a lower weight and reduced mass inertia.

[0005] Although this device works satisfactorily, it has been shown that the control pistons manufactured in this way are sometimes subject to increased wear.

[0006] The present invention therefore aims to provide a device for blow-molding containers that has an increased service life. This is achieved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

[0007] In a first embodiment, the device according to the invention, which is defined in claim 1, has blow molding stations arranged on a blow molding wheel for blow molding containers from a thermoplastic material. Furthermore, the device has a device for pneumatically controlling a blow molding pressure, wherein the pneumatic control device has a control piston guided in a cylinder, which is mounted displaceably in the direction of a piston longitudinal axis and through which a main flow path, which can be closed by the control piston, runs. Furthermore, the control piston is provided with a control surface that faces a control chamber of the cylinder and is designed to transmit a control force to the control piston.

[0008] A peripheral wall of the control piston blocks the main flow path in at least one position of the control piston. In other words, in particular, the main flow path is blocked by a peripheral wall of the control piston when the device is closed.

[0009] While in the prior art, usually only the end faces of the control piston block the main flow path for the blowing air, it is proposed here that at least the peripheral wall also blocks the main flow path. The containers are, in particular, plastic preforms or the plastic containers to be formed from them. Blocking is understood to mean that the said peripheral wall obstructs the main flow path. The peripheral wall does not necessarily have to seal the main flow path. Rather, it is possible for the seal to be created via an end face of the control piston or a portion of this end face.

[0010] Advantageously, an inlet for the compressed air is arranged in a circumferential wall of the cylinder. Advantageously, an inlet for the blast air or compressed air is offset from the outlet in the longitudinal direction of the control piston, i.e. offset in height. In the prior art, both the inlet for the compressed air and the outlet for the compressed air are usually covered or blocked by an end face of the control piston. Within the scope of the present disclosure, it is proposed that at least either the inlet for the blast air or the outlet for the blast air, preferably the inlet for the blast air, is blocked or (at least partially) obstructed by a circumferential wall of the control piston when the device or valve is in the closed state. The advantage of this embodiment is that it enables a more uniform flow to the control piston in its circumferential direction.

[0011] A further embodiment of a disclosed device comprises blow molding stations arranged on a blow molding wheel for blow molding containers from a thermoplastic material. Furthermore, the device comprises a device for pneumatically controlling a blow molding pressure. The pneumatic control device comprises a control piston guided in a cylinder, which is mounted for displacement in the direction of a piston longitudinal axis, and in which a main flow path, which can be closed by the control piston, extends through the cylinder. Furthermore, the control piston is provided with a control surface facing a control chamber of the cylinder and designed to transmit a control force to the control piston.

[0012] The control piston is made of a metal or ceramic, at least in part.

[0013] It is therefore proposed to provide a pneumatically controlled valve whose control piston is partially made of a metal or ceramic. By constructing the control piston from metal or ceramic, the resistance of the control piston and thus of a movable valve element can be increased, thus also extending the service life of the device, i.e., the valve as a whole.

[0014] Preferably, the main flow path is arranged such that, when the control pressure decreases, the control piston is displaced in the direction of the piston's longitudinal axis by the acting high pressure. However, it would also be possible for the control piston to be displaced not under the influence of the high pressure or blowing pressure, but in another way, such as through an additional pilot valve, a spring, magnetic forces, or the like.

[0015] Advantageously, the individual blow molding stations each have blow molds within which plastic preforms can be expanded to form plastic containers.

[0016] In a further advantageous embodiment, the cylinder has guide surfaces made at least partially of a plastic for guiding the control piston. This prevents metallic contact with the control piston.

[0017] In a further advantageous embodiment, the main flow path is arranged in the cylinder. While in the case of EP 1 271 029 the main flow path is arranged below the piston, here it is proposed that the main flow path be located in the cylinder or a peripheral wall of the cylinder itself. Therefore, in this embodiment, said main flow path is not covered or sealed by a bottom surface of the control piston, but by the outer circumference of the control piston.

[0018] According to a further advantageous embodiment, the pneumatic control device has a sealing surface for closing the main flow path, and this sealing surface is arranged on an outer circumference of the cylinder. The end face of the piston is not understood as the outer circumference. It is therefore proposed that the control piston be designed as an at least partially metallic or ceramic piston, and preferably as a metal piston or ceramic piston, which is preferably guided in a plastic bushing, wherein the said sealing surfaces are advantageously also integrated into this plastic bushing. The sealing surface and the said guide for the control piston are preferably designed in two parts.

[0019] In a further advantageous embodiment, the control piston is made entirely of metal. Advantageously, the control piston is made of aluminum.

[0020] According to the invention, the control piston has a hollow space. This hollow space is formed inside the control piston. In other words, the piston can be hollow inside, for example, machined, to reduce weight.

[0021] In a further advantageous embodiment, at least one sealing device is arranged in the cylinder to seal the movement of the control piston (along its longitudinal direction). More precisely, these are sealing surfaces designed to seal the movement of the control piston.

[0022] In a further advantageous embodiment, the device has an admission chamber surrounding the control piston in its circumferential direction (or around its direction of movement), which chamber can be pressurized with blast air. This means that, in contrast to the prior art, the control piston is not pressurized exclusively in its longitudinal direction, but rather completely circumferentially from the side. In this way, a symmetrical flow to the control piston is possible. Advantageously, the device has at least two, preferably at least three, and preferably a plurality of air openings arranged evenly around the circumference of the control piston. When the device or valve is closed, these air openings are advantageously closed by the outer circumference of the control piston.

[0023] In a further advantageous embodiment, the control piston has a pressure surface which, when pressurised with compressed air - in particular in the radial direction of the control piston, i.e. a direction perpendicular to the longitudinal direction of the control piston - displaces the control piston along the piston's longitudinal axis. In the prior art, the control piston can be displaced directly by the air impinging on it in the longitudinal direction. Since, as mentioned above, in the embodiment shown here the air does not impinge on the control piston in a longitudinal direction but rather sideways, the aforementioned pressure surface is advantageously provided. This can, for example, be an inclined surface arranged on the piston end which, when pressurised with compressed air in a radial direction or perpendicular to the direction of movement of the control piston, causes the control piston as a whole to move.In addition, said thrust surface can be arranged on an outer circumference of the control piston. This will be explained in more detail with reference to the figures.

[0024] In a further preferred embodiment, the control piston is constructed in several parts, particularly two parts. One of these multiple parts or both parts of the control piston can be made, for example, of metal and the other of plastic.

[0025] In a further advantageous embodiment, a stop means, such as a stop screw, is arranged on the control piston. This stop screw serves both as a stop and, advantageously, as a cover for reducing the control air dead space volume.

[0026] In a preferred embodiment, the control piston is made of a material selected from a group including metals, ceramics, magnesium, hard rubber, and the like. The guide or guide cylinder, as mentioned above, is advantageously made of a plastic.

[0027] However, it would also be possible for the guide cylinder to be made of metal or ceramic. It would also be possible for the guide cylinder to be constructed in several parts, for example, with a plastic guide body for guiding the control piston and a base body that supports this guide body. This base body can also form the control chamber.

[0028] In a further advantageous embodiment, the control piston has a plastic element. This makes it possible for the control piston to be composed of a metal component and a plastic component. For example, it would be possible for a plastic segment to be housed in a cavity of the control piston. It would also be possible for a sealing surface at the end of the control piston to be made of plastic. It would also be possible for a plastic element to be incorporated into a control piston otherwise made of metal.

[0029] Further advantages and embodiments can be seen from the attached drawings: Showing:

[0030] Fig. 1a schematic representation of a device for blow molding containers; Fig. 2aa valve block according to the prior art; Fig. 2ba detailed representation of the valve block from Figur 2a ; Fig. 3 shows a representation of a device according to the invention for pneumatically controlling the blowing pressure; Fig. 4 shows a further representation of a device; Fig. 5a shows a detailed representation of a device; Fig. 5b shows a further detailed representation of a device; Figs. 6a - 6c show three possible variants for control pistons; Figs. 7a - 7b show two partial views of a device; Figs. 8a - 8d show four representations of an advantageous embodiment of a valve which is not part of the claimed invention; Fig. 9a shows a further representation of a device form for pneumatic control; Fig. 9b shows a further representation of a device for controlling the blowing pressure; Fig. 10 shows a further representation of a device for controlling the blowing pressure; Figs. 11a, 11b show two representations of an aseptic pilot valve.

[0031] Fig. 1 shows a roughly schematic representation of a device 1 for forming containers. This device has a rotatable support, such as a blowing wheel 2, on which a plurality of blowing stations 4 are arranged. These blowing stations 4 each serve to form plastic preforms 10 into plastic containers. For this purpose, the individual blowing stations each have blow molds that form a cavity inside them that serves to expand the plastic preforms 10. Preferably, the individual blowing stations also have stretching rods that stretch the plastic preforms in their longitudinal direction, so that the device is a stretch blow molding machine.

[0032] Fig. 2a shows a valve block according to the prior art. This valve block has a blowing nozzle 72, which is applied to the plastic preforms 10 to pressurize them with compressed air to expand them. Reference numeral 110 refers to a housing of the valve block, which is designated as a whole by 120. Reference numeral 118 denotes a silencer.

[0033] Fig. 2b shows a more detailed representation of a valve block according to the prior art. It can be seen that supply channels 104 are present here, through which the blowing air can be supplied to the plastic preform 10. Reference numeral 106 refers to a movable piston, which can be moved along the double arrow P, for example, using guide curves or the like. The blowing air for expanding the plastic preforms 10 can be supplied via an annular space 102 by means of a valve (not shown).

[0034] Fig. 3 shows a representation of a device 20 according to the invention for pneumatically controlling the blowing pressure or a control block 20. This control block has a control piston 14 which is displaceably mounted along the longitudinal axis L. In detail, this control piston 14 is displaceably mounted in a cylinder 12 or a guide body 12.

[0035] The control piston 14 is formed at least in sections from a metal and in particular it is formed from a metal on its outer circumference 14a. The cylinder or the guide cylinder 12 is formed from a plastic. Guide surfaces 42 and 44, which are also made of plastic, are also integrated into this cylinder 12. The reference numeral 28 designates a sealing device, which is also arranged in a circumferential groove 23 of the cylinder 12. The reference numeral 16 designates a main flow path which, when the valve is open (in Fig. 3 the closed position is shown) from a pressurization chamber 30 to an outlet 31. Along this main flow path 16, the blowing air reaches the plastic preforms (not shown).

[0036] Reference numeral 32 denotes openings, which here are evenly distributed in the circumferential direction of the control piston 14 and are arranged in particular in the cylinder 12. A surface 17 arranged on the outer circumference 14a of the control piston 14 lies opposite the individual openings 32 when the valve is closed.

[0037] The reference number 46 refers to a sealing surface of the control piston 14, which seals the outlet channel 31 in the Fig. 3 shown position. Thus, the sealing surface 46 also seals the main flow path 16. More precisely, in a closed state of the valve, the control piston rests against a sealing body 36, which is formed here at the left end of the cylinder 12. Advantageously, this sealing body 36 is formed integrally with the cylinder 36. This is explained with reference to the Figuren 8a - 8d explained in more detail.

[0038] At the Fig. 3 In the illustration shown, this sealing surface 46 is arranged on the control piston 14; more precisely, a section of the end face of the control piston forms the said sealing surface 46. The control piston 14, which is designed here as a metal piston (but can also be made of ceramic), is thus guided in an additional guide cylinder, i.e. the cylinder 12, which is made of plastic here. The cylinder simultaneously serves to seal the end face of the control piston 14 against the metallic valve block. If the control piston 14 is made of ceramic, the additional guide cylinder 12 can be dispensed with. The guide cylinder, in turn, can be accommodated in a receiving body such as a sleeve (not shown).

[0039] The control piston 14 is mounted directly on the guide points or fitting diameters 42, 44 integrated into the cylinder 12. To save weight, the guide piston has a cavity 52 within it, or is machined hollow inside. Reference numeral 34 denotes a stop screw. This stop screw 34 serves, on the one hand, to form a stop for the backward movement of the control piston 14. On the other hand, this stop screw 34 also serves as a cover to reduce the control air / dead volume, since the cavity 52 is covered by this stop screw 34. The air openings 32 are arranged evenly around the circumference of the control piston 14 and thus ensure that the compressed air flows symmetrically against the piston.

[0040] The reference numeral 15 refers to a pressure surface designed as an inclined surface, which is arranged at the lower end of the control piston 14. This pressure surface or inclined surface 15, which is designed to be circumferential here, also serves as a pressure surface. A pressure surface is understood to be a surface or a section which, due to its (particularly geometric) arrangement, is suitable for generating a force when acted upon by a gaseous medium, which force acts in the longitudinal direction of the control piston. The pressure surface thus preferentially deflects a force acting on it. As soon as the space 30 surrounding the control piston 14 is pressurized with compressed air, this pressure also acts on this pressure surface 15 and thus causes the control piston 14 to Fig. 3 is pushed back to the right.

[0041] However, the device 20 is designed so that when a control pressure of, for example, 10 bar is present in the control chamber 26, the control piston 14 is in the Fig. 3 shown, left position. Only when the control pressure in the control chamber 26 is no longer present, the control piston 14 can move into the Fig. 3 to the right. The control pressure acts on the control surface 24 of the control piston 14

[0042] Fig. 4 shows another illustration of a device 20. In this embodiment, sealing against the outlet 31 is achieved by means of a plastic disc 50, which has equal areas A1, A2 on the pressure sides. This results in equal areas during sealing.

[0043] The control piston 14 is mounted on guide bands 62, 64, which are inserted in the cylinder 12. Here, too, a cavity 52 is provided to save weight, as well as the Fig. 3 stop screw shown. As in the case of Fig. 3 Here, too, a symmetrical flow to the control piston 12 is achieved through the openings 32 arranged uniformly around the circumference.

[0044] The control piston can be made of metal, ceramic, or even magnesium or hard rubber. The cylinder or guide is preferably made of metal or ceramic.

[0045] Fig. 5a shows a further embodiment to illustrate the guide. Here, a seal 29 is provided on the control piston 14, which serves to seal the 10 bar pressure chamber. Another seal 28 is arranged in the cylinder 12. The control piston 14 is guided exclusively on the small diameter D1 of the cylinder 12. The reference numerals 42 and 44 again refer to the respective guide surfaces.

[0046] Fig. 5b shows another illustration of a device. In this case, a seal 29 is also provided in the control piston 12, as well as a seal 28 in the cylinder 12. However, the piston is guided here on both the small diameter D1 and the large diameter D2 of the control piston 12. Reference numerals 42 and 45 refer to the respective guide surfaces.

[0047] Preferably, in all representations, the guide surfaces are designed in such a way that purely metallic contact of the guide surfaces is avoided, so that, for example, the guidance takes place between a plastic surface and a metal surface or between two plastic surfaces.

[0048] The Figuren 6a bis 6c show three possible designs of a control piston 14. In these illustrations, the piston is made up of two components. Specifically, the piston has a base body 14b. Fig. 6a In the embodiment shown, a sealing surface 25 made of plastic is arranged on the base body 14b. Fig. 6b In the variant shown, a sealing surface 27 is provided, which engages behind a portion of the base body 14b. This sealing surface 27 is vulcanized onto the base body 14b.

[0049] At the Fig. 6c In the illustration shown, the sealing surface 25 is also made of plastic and is vulcanized into the base body 14b with a base section 21.

[0050] Fig. 7a shows a detailed view illustrating the sealing surfaces. Here, too, a peripheral wall 14a of the control piston 14 blocks the main flow path 16. However, the control piston has a recess 18 here so that the supplied blast air flows completely against the control piston. Sealing is achieved here via the two surfaces A1 and A2. More precisely, a plastic disc 50 is also provided here, against which the control piston 14 rests via surface A1 for the purpose of sealing. In the illustrations shown, it is therefore not necessary for the control piston to touch the plastic guide over its entire circumference. Fig. 7a The illustration shown ensures that a metallic or ceramic surface seals against a plastic surface. Here, too, the two surfaces A1 and A2 are preferably the same size.

[0051] Fig. 7b shows a further illustration of the seal. Here, too, two sealing surfaces A1 and A2 are provided, via which the seal is achieved. The control piston 14 here again has a recess 19, which is, however, designed as a circumferential groove. In both illustrations, the reference numeral 46 refers to the sealing surface formed on the control piston 14. The two surfaces A1 and A2 are preferably parallel to one another and particularly preferably offset from one another in the longitudinal direction of the control piston 14.

[0052] The Figuren 8a - 8d show different representations of the cylinder 12, partly with the control piston 14 arranged therein. In Figur 8a one can see that a sealing body 36 is formed on the cylinder 12. More precisely, this sealing body 36 is arranged in one piece on the cylinder 12. The (in Fig. 8a The inner surface (not shown) of the sealing body 36 serves to seal the valve when a corresponding end face of the control piston 14 rests against it. The sealing body 36 is arranged on the base body of the cylinder 12 by means of webs 38, and the individual openings 32, through which the blowing air can enter, are formed between these.

[0053] Fig. 8b shows a representation of the Fig 8a shown cylinder 12 and the control piston 14 to be movably arranged therein. It can be seen that the control piston 14 is designed in two parts and, more precisely, has a stop screw 34, which is screwed into a corresponding cavity of the control piston. The reference numeral 48 refers to a circumferential projection, which is arranged on the cylinder 12. Furthermore, the pressure surface 15 can be seen here again, which, when pressurized with compressed air, causes the control piston to move in Fig. 8b moved to the left relative to cylinder 12.

[0054] Fig. 8c shows a sectional view of the cylinder 12 with the control piston 14 arranged therein. It can be seen that the circumferential projection 48 can penetrate into a recess 49 formed in the control piston 14. The reference numeral 36a designates the above-mentioned inner surface of the sealing body 36, which, together with the end face 14c of the control piston 14 (or a part of this end face 14c, in particular an annular part), serves to seal the valve. Fig. 8d shows a further sectional view, in which in particular the end face 14c of the control piston 14 is visible

[0055] Fig. 9a shows another possible representation of a device. In this embodiment, the control piston 14 does not have the Fig. 3 und 4 shown inclined surfaces 15. Therefore, the transverse flow originating from the annular space 30 does not cause any axial force on the control piston 14, because the pressure is not applied to the front side of the piston. For this reason, a further (positive) control is provided by means of two additional valves 82 and 84, which function here as pilot valves. By means of a first pilot valve 82, it is possible to apply control air to an annular surface 86 in order to thereby move the control piston 14 into Fig. 7 along the arrow P1 into its rear position (ie to the right). In this position, the working compressed air can flow into the plastic preform. The movement of the control piston 14 can be achieved by a second pilot valve 84, which in turn pressurizes the control chamber 26 with compressed air and thus causes the control piston 14 to move in Fig. 7 to the left, ie opposite to the direction of arrow P1.

[0056] At the Fig. 9b In the illustration shown, a combination of an additional piston and an air spring is used. This system pressure of 10 bar acts in the control chamber 26 and causes the control piston to be pushed into the forward position, thus closing the "P1" valve. By means of the pilot valve 82, the annular surface 86 is pressurized with control air, allowing the control piston 14 to be moved to the rear position, thus allowing the working compressed air to flow into the plastic preform.

[0057] At the Fig. 10 In the illustration shown, the device has an additional piston. In this embodiment, the working compressed air (e.g., at 40 bar) permanently acts on the annular surface 86, so that the control piston 14 is pushed into the rear position, thus opening the valve (i.e., the working compressed air can flow into the plastic preform).

[0058] By means of a pilot valve 84, the circular surface or control surface 24 is pressurized with control air, thereby moving the control piston 14 to the forward position, thus closing the valve. However, it would also be possible for the valve to be reset in another way, such as by a spring. An electromagnet could also be provided, which moves the control piston 14 to the right in the figures or opens the valve.

[0059] In an advantageous embodiment, the device or devices for pneumatically controlling the blowing pressure comprise pressure sensors. Such pressure sensors typically contain the pressure sensor itself and the evaluation electronics in one housing. To allow the pressure sensor to be positioned closer to the process, it is proposed here to construct the pressure sensor in two parts and, in particular, to provide the evaluation electronics at a distance from the actual pressure sensor. Therefore, the evaluation electronics and the pressure sensor themselves are advantageously designed as different components and, in particular, separately from one another.

[0060] The present invention is therefore further directed to a device according to the preamble of claim 1, wherein, according to the invention, this device comprises a pressure sensor for determining at least one pressure occurring in the device, and wherein evaluation electronics for this pressure sensor are arranged separately from the actual pressure sensor. The pressure sensor is preferably arranged directly on the unit for pneumatically controlling the blowing pressure.

[0061] In other words, the pressure sensor can be positioned directly in the pressure chamber, for example, the annular chamber 30 pressurized by the blowing pressure, and the evaluation electronics can be positioned outside. This allows the control block to be constructed more compactly overall.

[0062] In a further advantageous embodiment, which can also be used independently of the invention described above, the venting of the valves, such as the pilot valves 82 and 84, takes place through air channels (not shown) in the control block. In this way, it is possible to Fig. 2a The silencer 118 shown in the figure is to be arranged in a non-aseptic area. This procedure is particularly suitable for an aseptic design of the control block.

[0063] In a further advantageous embodiment, the pneumatic control device has two pilot valves, and the control block also has two exhaust valves. However, these valves are provided redundantly and are intended, in particular, or only, for the safe opening of the device in the event of a pilot valve failure. It would be possible to install two (redundant) pilot valves on one exhaust valve, which is advantageous for a space-saving solution for safe opening.

[0064] Fig. 11a und 11b show two possible designs of an aseptic pilot valve 90. The reference numerals 92 and 94 each refer to a signal connection, in Fig. 10b the two openings 96 and 98 refer to working connections, the reference numeral 95 refers to a connection for a silencer and the reference numeral 93 refers to a supply connection (in particular for air). It would also be possible to design one or more of the pilot valves shown in the previous figures as a single unit and to encapsulate them in plastic, for example. The signal connection 92 and 94 can be designed, for example, as an IP67-suitable plug or as a gap-free, encapsulated cable. The air connections (for air supply and silencer) can be designed separately for each pilot valve or can be used together. Bezugszeichenliste

[0065] 1 Device 2 Blowing wheel 4 Blowing stations 10 Plastic preforms 12 (Guide) cylinder, guide body 14 Control piston 14a Outer circumference of the control piston 14b Base body 14c End face of the control piston 15 Pressure surface 16 Main flow path 17 Surface of the control piston 18 Recess 19 Groove-shaped recess 20 Control block, device 21 Base section 23 Groove 24 Control surface 25 Sealing surface 26 Control chamber 27 Sealing surface 28 Sealing device 29 Seal 30 Pressurization chamber, annular space 31 Outlet, outlet channel 32 Openings 34 Stop screw 36 Sealing body 36a Inner surface of the sealing body 38 Webs 42, 44, 45 Guide surfaces, fitting diameter 46 Sealing surface 48(annular) projection 49Recess 52Cavity 62First pilot valve 62, 64Guide bands 72Blow nozzle 82, 84(Pilot) valves 86Annular surface 90Aseptic pilot valve 92, 94Signal connection 93Supply connection 95Connection for silencer 96,98Working connections 102Annular space (state of the art) 104Feed channels (state of the art) 106Movable piston (state of the art) 110Housing 118Silencer 120Valve block (state of the art) A1, A2Large surfaces D1Small diameter D2Large diameter LLongitudinal axis PDouble arrow P1Arrow P2Arrow direction,

Claims

1. Apparatus (1) with blow stations (4) arranged on a blow wheel (2) for blow moulding containers (10) from a thermoplastic material, having a device (20) for pneumatic control of a blow pressure, wherein the device (20) for pneumatic control has a control piston (14) which is guided in a cylinder (12) and is mounted so as to be movable in the direction of a longitudinal axis (L) of the piston, and wherein a main flow path (16) which can be closed by the control piston (14) extends through the cylinder (12), and wherein the control piston (14) is provided with a control surface (24) which faces a control chamber (26) of the cylinder (12) and is designed to transmit a control force to the control piston (14), wherein the control piston (14) is constructed at least in some regions from a metal or a ceramic, characterized in that the control piston (14) has a cavity (52) which is executed in the interior of the control piston.

2. Apparatus according to claim 1, characterized in that the cylinder(12) has guide surfaces (42, 44) made from plastic for guiding the control piston (14).

3. Apparatus according to claim 1, characterized in that the main flow path (16) is arranged in such a way that, when the control pressure is lowered, the control piston (14) is displaced by the acting high pressure in the direction of the longitudinal axis (L) of the piston.

4. Apparatus (1) according to at least one of the preceding claims, characterized in that the control piston (14) is made completely from a metal or from ceramic.

5. Apparatus (1) according to at least one of the preceding claims, characterized in that at least one sealing unit (28) is arranged in the cylinder (12) in order to seal the movement of the control piston (14).

6. Apparatus (1) according to at least one of the preceding claims, characterized in that the apparatus (1) has an application chamber (30) which surrounds the control piston (14) in the circumferential direction thereof and can be applied with blow air.

7. Apparatus (1) according to at least one of the preceding claims, characterized in that the control piston (14) has a displacement surface (15) which is designed to move the control piston (14) along the longitudinal axis (L) of the piston by applying compressed air.

8. Apparatus (1) according to at least one of the preceding claims, characterized in that the control piston (14) is of multi-part and in particular two-part construction.

9. Apparatus (1) according to at least one of the preceding claims, characterized in that the control piston (14) has a stop screw (34).

10. Apparatus (1) according to at least one of the preceding claims, characterized in that the control piston (14) has a plastic element (25, 27).