Device for producing hollow bodies

Abstract

The invention relates to a device for producing hollow bodies from a thermoplastic material in a blow molding process, comprising a hollow profile having at least two molded parts (2, 2a), the at least two molded parts (2, 2a) being movable relative to each other; a bearing device (6) on which the at least one molded part (2) is movably mounted; and a first drive device (7) for moving the at least one molded part on the support device (6) such that the two molded parts (2, 2a) are brought close to each other or away from each other in the direction of movement (18), a second drive device (7) being designed for applying a closing force acting substantially in the direction of movement (18).

Description

[0001] The present invention relates to a device for manufacturing a hollow body from a thermoplastic plastic material in a blow molding method, the device comprising a hollow profile having two molded parts, wherein the two molded parts are movable relative to each other; a supporting device, at least one molded part is movably supported on the supporting device; and a first drive device for moving at least one molded part on the supporting device so that the two molded parts approach each other or move away from each other along the moving direction.

[0002] The aforementioned type of equipment is also called extrusion blow molding machine, which is designed to produce hollow plastic products by extruding a tube formed in the head, which is inflated under pressure between at least two closed mold parts or mold halves. The finished plastic container is then produced by cooling, demoulding and removing the excess tube.

[0003] A key step in the production process is the opening and closing of the two molded parts to form the outer contour of the product. The molded parts are usually mounted on a so-called closing plate, which allows linear opening and closing. When the plastic container is inflated in the molded part, the internal pressure is usually 10 bar, so a corresponding counterpressure must be applied to the molded part by the closing mechanism to prevent the molded part from opening during the blow molding process. In addition, the head or end of the hose is usually squeezed out of the molded part by the closing force. During the demoulding process, the molded parts must be sufficiently spaced, i.e. opened, so that the blown article can preferably be removed from one side between these molded parts. Therefore, the opening distance usually depends on the molded part thickness or the product diameter.

[0004] There are already various solutions in the prior art that can reliably move the molded parts in order to open and close the device and to exert the necessary closing force on the two molded parts during the blow molding process.

[0005] Document DE 1 814 883 A1 discloses an extrusion blow-molding machine, in which a drive is provided for moving the molding halves in order to apply the force generated by the blowing pressure. The drive is provided by a hydraulic cylinder with a piston, which is connected to a crank lever. The middle joint of the crank lever is connected to a vertically acting piston that can move the cylinder horizontally. When the molding halves are closed, the drive piston extends the crank lever until the crank lever is extended and the middle joint of the crank lever comes to rest on a fixed support. The crank lever is held in the extended position by the pressure of the vertically acting piston. Therefore, when closing, the force generated by the blowing pressure is transmitted to the vertical rod of the machine frame via the piston and the extended crank lever. In order to relieve the load on the hydraulic piston-cylinder drive, the piston can be locked in the closed position of the hollow molding, and the locking device transmits the force generated by the blowing pressure directly to the frame provided as a supporting device. Therefore, the fixing or locking of hydraulic drives for absorbing pressure during the blow molding process is known in the prior art. However, it is disadvantageous that the force of the displacement and closing pressure is carried out by the same drive.

[0006] Document EP 1 598 165 B1 also discloses a drive device for producing molded parts such as containers, such as bottles, from plastic materials. The device has a drive unit consisting of a main drive device and an auxiliary drive device, wherein the main drive device is electric and the auxiliary drive device is mechanical. The electric motor drives two rocker arms, which connect the half shells to two respective arms, wherein at least one arm consists of an adjustment cylinder. The two arms are articulated on one side to an articulated connection and on the other side to a rocker arm. Therefore, the drive device is not conducive to the rotation of a relatively complex rocker arm device.

[0007] Document WO 2018 / 216361 A1 also discloses a mold clamping machine with an electric servo motor, which moves a pair of movable plates in a closing direction via a ball screw, and the molding halves are connected to the movable plates so as to close the molding halves. The mold clamping machine is also equipped with a hydraulic cylinder, which is connected to one of the plates and applies pressure to the plate in the closing direction. When the distance between the molding halves reaches a predetermined size, the electric servo motor and the hydraulic cylinder are started simultaneously. This means that two different, parallel-acting drive devices need to be provided, so the energy consumption is high.

[0008] The technical problem to be solved by the present invention is to alleviate and eliminate at least one disadvantage of the prior art. In particular, the technical problem to be solved by the present invention is to provide an efficient device, wherein the drive device used has high efficiency.

[0009] The technical problem is solved by a device of the aforementioned type, wherein the second drive device applies the closing force mainly in the direction of movement. The solution according to the invention is based on the recognition that in order to be able to remove the plastic container produced by the blow molding process from the molded part, there are very different requirements for the movement of the molded part and the force applied to the molded part during the blowing process. On the one hand, when moving at least one molded part in the opening / closing movement, if the molded part moves at a faster speed, it is beneficial to shorten the cycle time. On the other hand, the necessary closing force must be applied by the molded part during the blowing process, which force usually exceeds 500 kN. Using a single drive device can only meet these two different requirements in an inefficient way. On the other hand, in the known hydraulic clamping system, only a single hydraulic cylinder is used for the closing movement and the generation of the closing force. However, to apply the necessary closing pressure, especially a pressure of more than 500 kN, a piston of correspondingly large diameter is required. However, the relevant large cross-section hydraulic cylinder requires a large amount of hydraulic oil, so the energy consumption is high and the speed of the opening / closing movement is limited. According to the invention, a second drive is provided which is designed to exert a closing force substantially in the direction of movement, so that two different drives can be selected for generating the movement and the closing force in the opening / closing movement, thereby using different, efficiently operating drives to meet very different requirements. In principle, it is sufficient to move only one profile between the opening and closing positions. Typically, the movement of at least two profiles is synchronized by a synchronization device (known in the prior art), so that the at least two profiles are moved in the opening / closing movement and the two profiles move closer to each other in the closing movement and move away from each other in the opening movement.

[0010] With regard to a structurally simple design, it is advantageous for displacing the at least one shaped part during the opening and closing movement to provide a crank lever for displacing the at least one shaped part, the crank lever having a first and a second lever element which are connected to one another via a joint.

[0011] The first drive is arranged on a fixing element fixedly connected to the bearing device and also on a pivotably mounted first lever element of the crank lever, whereby a force can be transferred from the first drive to the at least one shaped part via the crank lever in a simple and effective manner. The piston of the first drive preferably meshes with the crank lever, so that during the extension process the crank lever is stretched so that the at least one shaped part approaches the second shaped part.

[0012] Advantageously, a linear drive, in particular a hydraulic cylinder with a piston rod or an electric drive is provided as the first drive. Thus, the closing movement can be carried out in an efficient manner by means of a hydraulic cylinder or an electric drive with a relatively small diameter, such as a roller with an electric drive. In addition, the electric drive can also be designed as a rotary drive with a gearbox and a crank. In the case of an electric design, the braking energy can be fed back to the intermediate circuit, thereby achieving further energy savings.

[0013] Advantageously, a linear drive, in particular a hydraulic cylinder with a piston rod, is provided as the second drive. The second drive is provided for generating a closing force or applying a power stroke, and the second drive has a much shorter stroke than the first drive. However, since the force applied by the second drive, i.e. the closing force of the two molded parts during the blowing process, is much greater, the second drive is preferably more powerful than the first drive.

[0014] The second drive is fastened to the second lever element, preferably to the freely projecting end of the second lever element, so that the second drive moves in a simple manner following the movement of the second lever element initiated by the first drive. In this way, the second drive and the at least one movably mounted shaped part can be brought close to the second shaped part in a simple manner, so that in the end position of the first drive, the second drive only has to perform a relatively small stroke, the so-called power stroke, to transfer the at least one shaped part into its closed position.

[0015] Advantageously, at least one movably supported profile and the second drive are fixed to a moving element, which is movably supported on the support. In order to make the movement of the at least one profile simple and efficient, it is very advantageous to arrange the profile on a moving element, such as a slide. The slide is preferably supported on the base plate side, wherein the profile is preferably fixed to the opposite end of the upper side of the slide, i.e., to a support on the base plate side, via a closing plate. The moving element is especially designed in the form of a slide, which can be movably supported on a linear guide, in particular a rail element.

[0016] Preferably, the hydraulic cylinder and / or the piston rod of the hydraulic cylinder provided as the second drive device has radially opposite guide supports on the side for connecting elements between the hydraulic cylinder and / or the piston rod and the moving element. The guide supports are used to withstand the lateral forces generated by the closing movement on the crank lever. Therefore, the piston rod / hydraulic cylinder does not bear or only bears a small lateral force load and bending stress, thereby greatly reducing the wear of seals and the like.

[0017] In the closed position of the at least two molded parts, the crank lever is arranged in a slightly overextended position, wherein the two lever elements preferably form an angle of 0.5° to 3°, particularly preferably substantially 1°, in the overextended position, so that the crank lever can be fixed in this position in a simple manner. Preferably, a stop is provided, against which the crank lever, preferably the first lever element, abuts in the closed position of the at least two molded parts. As a result, the crank lever can be fixed in the closed position of the at least two molded parts so that it is in a substantially extended, i.e. slightly overextended, position when considerable forces are applied during the blowing process.

[0018] Preferably, the second drive is designed to move at least one molding half by a maximum of 700 mm, preferably a maximum of 500 mm. Thus, a displacement stroke of several hundred millimeters, for example 200 mm to 400 mm, is achieved only by the second drive, so that the second drive can be designed for a relatively short displacement and a high force transmission. If the stroke is several hundred millimeters, different molding thicknesses can also be used.

[0019] Unlike the second drive, the first drive is designed to move the movably supported molded part to a greater extent in order to remove the blow molded product laterally in the open position. The first drive is therefore advantageously designed to move at least one molded part by a maximum of 0.7 m to 2 m. Advantageously, the first drive is designed to move at least one mold half by a movement path that is substantially 2 to 10 times, preferably 2 to 5 times, the movement path carried out by the second drive.

[0020] In order to ensure that the two molded parts are securely closed even during the blowing process, it is advantageous if the second drive device exerts a closing force of more than 200 kN, preferably more than 500 kN, on the at least two molded parts in their closed position.

[0021] The present invention is described in detail below in conjunction with the preferred embodiments shown in the accompanying drawings, but the embodiments shall in no way limit the protection scope of the present invention.

[0022] Figure 1 A schematic side view of a device for producing hollow bodies from thermoplastic plastic material using the blow molding method in an open position,

[0023] Figure 2 Show Figure 1 A schematic side view of the device shown in the closed position,

[0024] Figure 3 A schematic diagram showing an intermediate position in which the piston of the second drive device is retracted,

[0025] Figure 4A top view showing the connection between the second drive device and the connecting element,

[0026] Figure 5 Shown along Figure 4 A sectional view taken along line VV in FIG.

[0027] Figure 1 A device 1 for producing hollow bodies from thermoplastic plastic material using the blow molding method, a so-called extrusion blow molding machine, is schematically shown. Figure 1 In the position shown, the two molded parts or mold halves 2, 2a are in an open position. In the open position, the two molded parts 2, 2a are arranged at a distance from one another, wherein during operation of the machine, the two molded parts 2, 2a are moved into the open position, in particular for the lateral removal of finished plastic containers during the blow molding process. Figure 2 The closed position shown and Figure 1 The two molded parts 2 , 2 a can be easily moved between the shown open positions, in which the two molded parts 2 , 2 a form a mold cavity in which the object to be produced is blow-molded, and in which the two molded parts 2 , 2 a are movably supported.

[0028] The two shaped parts 2, 2a are fixed to the closing plates 3, 3a, respectively, and the closing plates 3, 3a are fixed to the force distributors 4, 4a, respectively. The force distributors 4, 4a are respectively mounted on the moving devices 5, 5a, which stand on the ground in the manner of a trolley on a support device 6, especially a base plate. The two moving devices 5, 5a are moved between the open and closed positions, and the two driving devices 7, 16 act indirectly on the moving devices 5, and the moving devices 5a are connected to the moving devices 5 by known synchronization devices, so that when the driving devices 7, 16 are activated, the two shaped parts 2, 2a are moved closer to each other in the closing movement or away from each other in the opening movement.

[0029] In order to facilitate the movement between the closed position and the open position, the profile 2 fixed to the displacement position 5 is slidably supported on the support device 6 and can be moved on the support device 6 by the first drive device 7. The first drive device 7, more precisely the cylinder 8 of the drive device 7, is fixed to the fixed element or column 6a on the base plate 6. On the rear side of the fixed element 6a, that is, on the side facing away from the movable profile half, a bending support 9 is fixed, which is connected to another bending support 9a via a tie rod 10, and the other bending support 9a is arranged on the rear side of the force distributor 4a.

[0030] The piston 8a of the drive device is connected to the first lever element 11 of the crank lever 13, which has two lever elements 11, 12. The first lever element 11 is pivotally supported on the fixed element 6a. The lever element 12 is pivotally connected to the first lever element 11 via a pivot bearing 13a and is connected to a connecting element 15 via a further bearing 14, which is fixed to the force distributor 4.

[0031] The connecting element 15 is used in particular to connect the second drive 16 and the force distributor 4, thereby indirectly connecting the movably supported mold half 2. The piston rod 16a of the hydraulic cylinder of the second drive has a radially opposite guide bearing 17 for the connecting element 15 on the side to prevent the transmission of transverse forces to the hydraulic cylinder, thereby protecting the seal of the second drive 16 in particular.

[0032] In order to move the movably mounted shaped parts 2, 2a from Figure 1 The open position shown moves to Figure 2 In the closed position shown, the piston 8a is first moved to its extended position; then the molded halves 2, 2a are arranged in an intermediate position close to the open position, as shown in FIG. Figure 3 As shown, the crank lever 13 is moved to the basic extended position, and the two movably supported molded parts 2, 2a are moved relative to each other. In the example shown in the figure, the crank lever 13 is moved to a slightly overextended position, so that the two lever elements form an angle of about 1°. In this slightly overextended position, the lever element 11 abuts against the upper stop 6b of the fixed element 6a, so that during the blowing process, the first drive device 7 does not need to actively keep the crank lever in the slightly overextended position.

[0033] By activating the first drive 7, the moving device 5, 5a and the molded part 2, 2a are moved on the support device, and thus most of the closing movement in the displacement direction 18 is completed by the relatively low-power but high-speed drive, i.e., by the so-called fast stroke, after which the second drive 16 is activated in order to move the molded half from Figure 3 The intermediate position shown is shifted to Figure 2 The closed position shown. This more powerful drive 16 allows a smaller displacement of the molding half 2, preferably about 200 mm to 400 mm, the so-called power stroke. A more powerful second drive 16 can generate a closing force of more than 500 kN between the molding halves 2, 2a.

[0034] exist Figure 4 and Figure 5 Detailed representation is given in FIG. 2 of the connection between the second drive 16 and the connecting element 15 of the force distributor 4 carrying the closing plate 3 .

[0035] In the connecting section between the cylinder as the second drive 16, the so-called power stroke cylinder, and the lever element 12, guide supports 17 are provided on the opposite outer sides. The guide supports 17 preferably each have a roller frame 19 in which a guide rail 15a of the connecting element 15 is movably mounted, which serves to guide the cylinder as the second drive 16. As a result, the transverse forces generated by the crank lever 13 during the closing movement are absorbed and transferred to the displacement element 5, so that the lever element 12 and the drive 16 are substantially free from transverse force loads and bending stresses, thereby reducing the wear of the seals in particular.

[0036] The two drives 7 and 16 meet very different requirements, so that a fast and efficient opening and closing of the two molded parts 2, 2a is achieved by these two drives. In the example shown, the first drive 7 is preferably an electric cylinder with an electrically driven roller shaft. Alternatively, the electric drive can also be designed as a rotary drive with a gearbox and a crank. However, a hydraulic cylinder can also be used as the first drive 7, in which case the hydraulic cylinder diameter of the first drive 7 is significantly smaller than the hydraulic cylinder diameter of the second drive 16.

Claims

1. A device for producing hollow bodies from thermoplastic plastic material in a blow molding process, the device comprising A hollow profile having at least two shaped parts (2, 2a), wherein: The at least two shaped parts (2, 2a) are movable relative to each other, a support device (6) on which at least one shaped part (2) is movably supported, and A first drive device (7) is used to move at least one molded part on the support device (6) so that the two molded parts (2, 2a) move closer to each other or farther away from each other along a moving direction (18), It is characterized in that a second drive device (16) is provided for applying a closing force acting substantially in the displacement direction (18).

2. The device according to claim 1, characterized in that A crank lever (13) having a first and a second lever element (12) is provided for moving the at least one molded part (2), wherein the first and the second lever element are connected to each other via a joint.

3. The device according to claim 2, characterized in that The first drive device (7) is arranged on a fixing element (6a) fixedly connected to the bearing device (6) and also on a pivotably supported first lever element (12) of the crank lever (13).

4. The device according to any one of claims 1 to 3, characterized in that A linear drive, in particular a hydraulic cylinder or an electric drive with a piston rod (8) is provided as the first drive (7), or a rotary drive is provided as the first drive (7).

5. The device according to any one of claims 1 to 3, characterized in that A linear drive, in particular a hydraulic cylinder with a piston rod (16a) is provided as a second drive (16), wherein the second drive (16) is preferably more powerful than the first drive (7).

6. The device according to any one of claims 3 to 5, characterized in that The second drive device (16) is fastened to the second lever element (12), preferably to the freely protruding end of the second lever element (12).

7. The device according to any one of claims 1 to 6, characterized in that At least one movably supported molded part (2) and a second drive device (16) are fixed to a displacement element (5), which is movably supported on the support device (6).

8. The device according to claim 7, characterized in that The hydraulic cylinder and / or the piston rod (16a) of the hydraulic cylinder provided as the second drive device (16) has radially opposite guide supports on the side for the connecting element (15) between the hydraulic cylinder and / or the piston rod (16a) and the displacement element.

9. The device according to any one of claims 1 to 8, characterized in that In the closed position of the at least two molded parts (2, 2a), the crank lever (13) is arranged in a slightly overextended position, wherein the two lever elements (12) preferably form an angle of 0.5° to 3° in the overextended position.

10. The device according to claim 9, characterized in that A stop is provided, against which the crank lever (13), preferably the first lever element (12), comes into contact in the closed position of the at least two molded parts (2, 2a).

11. The device according to any one of claims 1 to 10, characterized in that The second drive device (16) is designed to move at least one mold half (2) by a maximum of 700 mm, preferably by a maximum of 500 mm, particularly preferably by 200 mm to 400 mm.

12. The device according to any one of claims 1 to 11, characterized in that The first drive device (7) is designed to move at least one molded part by a maximum of 0.7 m to 2 m.

13. The device according to any one of claims 1 to 12, characterized in that The first drive (7) is designed to cause at least one mold half (2) to execute a displacement path which is substantially equal to 2 to 10 times, preferably 2 to 5 times, the displacement path executed by the second drive (16).

14. The device according to any one of claims 1 to 13, characterized in that The second drive device (16) exerts a closing force of more than 200 kN, preferably more than 500 kN, on the at least two molded parts (2a) in the closed position of the at least two molded parts.

Images