Pelletizer

Abstract

To provide a pelletizer that achieves rigid, energy-efficient axial adjustment in a cutter head without having to sacrifice a compact design or require a specially designed main driving part.SOLUTION: A pelletizer includes: a cutter head that is rotationally drivable and connected to a drive motor via a drive shaft to split a material strand output from a die head into pellets; and a feed device for axial adjustment of the cutter head relative to the die head in the direction of the axis of rotation. A spindle element of a spindle drive stage of the feed device is constructed as a spindle sleeve that is rigidly mounted in the axial direction on the rotating drive shaft between the drive motor and the cutter head. The drive shaft is axially fixed and non-rotatably connected to the cutter head and transmits the axial movement of the spindle sleeve to the cutter head.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pelletizer having a rotatably drivable cutter head for dividing a material strand output from a die head into pellets, the cutter head being drivingly connected to a drive motor via a drive shaft, and a feeder for axially adjusting the cutter head relative to the die head in the direction of the axis of rotation of the cutter head. [Background technology]

[0002] Such pelletizers are known in various designs, for example for pelletizing plastics, in which molten strands of polymeric material output from nozzle-shaped orifices or through-holes in a die plate are cut off and pelletized by blades in a cutter head, which are then carried past the die plate by a rotating cutter head. Pelletizers can operate wet, but in underwater pelletizers, for example, the cutter head runs through a cutting chamber through which process water or liquid flows to prevent the cut pellets from sticking and solidifying and transport them from the cutting chamber. Water ring pelletizers also operate wet, but the blades do not run through a water bath, but are surrounded at their periphery by an annular flow of water flowing past them, which attracts and transports the cut pellets and cools them in a process that leads to solidification. The rotating blades cut off the dry molten strand output from the die plate at the front and discharge the still-hot molten pellets into a rotating water ring. As in the case of underwater pelletizers, water does not necessarily have to be used as the processing liquid, although it is possible, but also water containing other liquids or mixtures or additives.

[0003] However, such pelletizers can also operate dry, in which the hot die plate is dry, for example in the case of air or cooled air pelletizers, and here too rotating blades can run along the die plate to cut off the molten strands output from the channel mouths. The hot cut off pellets are transported forward and cooled by the air flow, which takes longer due to the lower thermal conductivity of air compared to water.

[0004] The die plate that outputs the molten strand does not necessarily have to be in the form of a flat plate, but can also have a tapered or curved profile, although plate-shaped die plates are advantageous for many applications. Regardless of this, pelletizers do not necessarily have to granulate plastic melts, but can also pelletize other pasty material strands, for example in the food sector or into pasty masses of active pharmaceutical ingredients.

[0005] In pelletizing processes, the axial position of the cutter head relative to the die plate is important for several reasons. Typically, the blade must be pressed or clamped against the cutting surface of the die plate with a predetermined set force so that the blade scrapes precisely across the cutting surface. Restoring forces that arise during cutting, which can vary depending on the blade angle setting, must be absorbed.

[0006] For example, with different applications of pelletizing materials or with different cutterheads or blades, the axial position and / or feed force may need to be changed to suit each application or cutterhead used. Also, as blades wear, the cutterhead may need to be readjusted due to wear.

[0007] The axial adjustment of the cutter head relative to the die plate in the direction of the axis of rotation can be achieved in various ways. For example, it is known to use mechanical, hydraulic or pneumatic spring devices to drive the cutter head relative to the cutting surface of the die plate, in which, for example, the cutter head is axially adjustable via a splined shaft profile or a similar axially adjustable torque-transmitting connection mounted on a drive shaft, which may be hollow, for example, in order to press a spring-loaded movement rod against the cutter head (see, for example, DE 19647396 or DE 29624638).

[0008] However, it is also known that the axial adjustment of the cutterhead can be achieved by motor drive. For example, EP 2067591 shows an underwater pelletizer whose drive shaft is mounted on an axially adjustable bearing connected to an adjustable rack by a pinion. The pinion is driven by a pneumatic cylinder via a gear stage. While the above-mentioned patent document guarantees low fluctuations in the holding torque from the pneumatic drive in a static state, the pneumatic cylinder causes considerable efficiency losses, especially when operating at the high pressures required to sufficiently securely fix the cutterhead. Furthermore, the actuation forces are introduced to one side via the rack and pinion configuration, which causes stresses in the bearing arrangement, leading to losses in stiffness and efficiency.

[0009] Further known from the patent document EP 1286811 is a pelletizer whose cutter head is axially adjustable by a servomotor. The servomotor rotates a threaded sleeve via a worm gear stage, and its rotational movement axially adjusts a threaded spindle threadedly engaged therewith. The axial movement of the threaded spindle is transmitted via a cross bolt to a bearing sleeve, to which the drive shaft is axially fixed and rotatably mounted. However, due to the cross bolt, the actuation force is applied exclusively and eccentrically to the bearing sleeve of the drive shaft, which also results in bearing stress and losses in stiffness and efficiency. Furthermore, the eccentric and laterally spaced arrangement of the spindle drive stage and the associated worm gear stage results in a large drive train between the servomotor and the bearing sleeve, sacrificing the self-locking effect ensured by the multiple gear stage design.

[0010] Furthermore, an underwater pelletizer is known from the patent document EP 2 442 954, which also adjusts the cutter head by a motor drive. The variable displacement motor is arranged adjacent to the main drive shaft but laterally spaced apart and drives a spindle drive stage via a belt. The spindle drive stage is arranged coaxially with the main drive shaft and via the hollow main drive shaft, a movement rod acting on the cutter head can be axially adjusted. In this case, the spindle drive stage is arranged on the rear side of the main drive motor, i.e., facing away from the cutter head, and the movement rod passes through the main drive motor so that it can be connected to the movement rod. This requires a specially designed main drive motor with a hollow drive shaft extending over both ends, resulting in a very long axial structure. Summary of the Invention

[0011] On this basis, it is the object of the present invention to provide an improved pelletizer of the above-mentioned kind, avoiding the disadvantages of the prior art and developing the latter in an advantageous manner, in particular to achieve a rigid and energy-efficient axial adjustment of the cutter head without having to sacrifice a compact design for this purpose or requiring a specially designed main drive.

[0012] According to the present invention, the above-mentioned problem is solved by a pelletizer according to claim 1. Preferred embodiments of the invention are the subject matter of the dependent claims.

[0013] Therefore, it is proposed to arrange a spindle drive stage directly on the drive shaft between the main drive motor and the cutter head for axial adjustment of the cutter head, thereby adjusting the rotating drive shaft itself axially. This eliminates the need for a moving rod passing through the entire drive train and the need for the main drive to be a hollow shaft motor. In this invention, the spindle element of the spindle drive stage of the feeder is configured as a spindle sleeve rigidly mounted axially on the rotating drive shaft between the drive motor and the cutter head, and the drive shaft is connected to the cutter head in an axially fixed and non-rotatable manner, transmitting the axial movement of the spindle sleeve to the cutter head. Unlike the prior art, the axial positioning movement of the spindle element is not introduced timely from the eccentric spindle drive via a cross bolt or transmitted to the cutter head via a separate moving rod from the rear of the main drive, but is transmitted directly to the rotatably drivable drive shaft, resulting in good power flow and therefore high rigidity and energy efficiency of the feeder. At the same time, a compact design is realized, eliminating the need for an axial extension of the drive train beyond the main drive motor. At the same time, special configurations of the main drive, in particular hollow shaft motors, can be dispensed with, although of course such motors can still be used.

[0014] In a further embodiment of the invention, the above-mentioned tube nut of the spindle drive stage, which is also mounted coaxially above the drive shaft, is rotatably but axially fixedly mounted to a housing and / or chassis assembly which may be provided around or adjacent to the drive shaft, for example between the drive motor and the cutter head.

[0015] A spindle element designed as a spindle sleeve may also be mounted to the housing assembly and / or chassis assembly described above, but independently of this, the spindle element is mounted in an axially adjustable but non-rotatable manner, such that rotational movement of the tube nut is translated into axial movement of the spindle element.

[0016] In a further advantageous embodiment of the invention, the above-mentioned spindle element is axially fixed relative to the drive shaft but is rotatably held so that the drive shaft can rotate away below the spindle sleeve but accurately follow the axial movement of the spindle sleeve.

[0017] In order to achieve a thin construction transverse to the rotation axis, an advantageous further development of the invention can provide for an axially offset arrangement of the bearing assemblies for the tube nut on the one hand and the spindle element on the other hand. In particular, the bearing assembly for rotatably and axially fixedly mounting the tube nut can be arranged axially offset and / or non-overlapping when viewed in the radial direction and / or spaced apart from the bearing assembly for rotatably and axially fixedly mounting the spindle element on the drive shaft. Alternatively or additionally, the above-mentioned bearing assembly for rotatably mounting the tube nut in an axially fixed manner can also be axially offset and / or non-overlapping and / or spaced apart from the bearing assembly for axially adjustable but non-rotatably mounting the above-mentioned spindle element, in particular in the above-mentioned housing assembly and / or chassis assembly.

[0018] Independently of the above-mentioned offset of the tube nut bearing assembly, the bearings between the spindle element and the drive shaft on the one hand, and between the spindle element and the housing assembly and / or chassis assembly on the other hand, can be provided overlapping one another and / or at approximately the same axial position, thereby enabling radial support of the drive shaft via the spindle sleeve.

[0019] The spindle drive stage can basically be configured in various ways to convert the rotational movement of the tube nut into an axial movement of the spindle element. In order to precisely position the cutter head even at high operating forces while at the same time maintaining a compact design, the spindle drive stage can, in an advantageous further development of the invention, be configured as a planetary screw drive with planetary screw rollers provided between the tube nut and the spindle element to convert the rotational movement of the tube nut into an axial movement of the spindle element.

[0020] Alternatively, in an advantageous further development of the invention, the spindle drive stage can also be configured as a ball screw drive, in which instead of the planetary screw rollers specified for converting the rotational movement of the tube nut into an axial movement of the spindle element, balls can be provided between the tube nut and the spindle element. Such a ball screw drive allows the tube nut to be configured very short, which, even at higher adjustment speeds, runs very smoothly and does not transmit vibrations to the drive shaft.

[0021] Alternatively, however, the spindle drive stage can also be configured as a threaded drive, in which case no rolling elements are provided between the tube nut and the spindle element, but instead an internal thread on the tube nut directly engages with an external thread on the spindle element, which allows for a particularly thin configuration of the spindle drive stage.

[0022] Independently of the specific design of the spindle drive stage, the tube nut can be rotationally driven by a servo motor, in which case a chain or belt drive stage is provided between the servo motor and the tube nut, and in a simple manner the servo motor can be positioned laterally spaced adjacent to the drive shaft or eccentrically relative to the main drive train, and the servo motor can be positioned so that its motor axis is parallel to the axis of rotation of the cutter head.

[0023] In a further development of the invention, the chain or belt of the aforementioned chain or belt drive stage can drive a drive pinion that can be non-rotatably attached to the end face of the tube nut. Thus, the chain or belt extends around a drive shaft, or an axially adjustable drive shaft extends through the belt drive stage. By arranging the drive pinion on the end face of the tube nut, simple assembly of the spindle drive stage and the belt drive stage can be achieved. At the same time, the tube nut can be stably supported in the center in the area where the actuating force is transmitted to the spindle element.

[0024] However, it may in principle also be possible to drive the tube nut via a spur gear stage instead of a chain or belt stage, which allows for efficient driving of the spindle drive stage with a thinner design and greater freedom in positioning the servo motor, while at the same time allowing for quieter operation.

[0025] Alternatively or additionally, the gear stage between the servo motor and the tube nut can also be contactless and / or include a magnetic gear stage and / or a clutch stage. For example, a magnetic gear stage can be provided, which has a permanent magnet non-rotatably connected to the tube nut on the one hand and a permanent magnet connected to a drum element arranged coaxially therewith on the other hand. However, in particular, such magnetic gear stage and / or clutch stage can be configured to operate electrodynamically and transmit drive motion via eddy currents. Such electrodynamically operated magnetic gear stages and / or clutch stages are known, for example, as retarders or eddy current brakes or are similar in function to electric motors. The advantages of such magnetic gear stages are, in particular, their excellent results in terms of wear-free and smooth operation.

[0026] When a chain or belt stage is provided, the servomotor can essentially drive the drive pinion directly with its motor shaft, which drives the chain or belt of the chain or belt stage. However, in an alternative further development of the invention, a further gear stage can be provided between the servomotor and the drive pinion to drive the chain or belt that may be located between the servomotor and the drive pinion. In particular, such a further gear stage between the drive pinion and the servomotor can be integrated into the servomotor or into a common motor and gearbox housing. Advantageously, the above-mentioned further gear stage can be arranged coaxially with the motor shaft of the servomotor or can have a gear input shaft and an output shaft, both of which are arranged coaxially with the shaft of the servomotor.

[0027] In order to be able to stably maintain the axial position of the cutter head moved by the servo motor and / or the feed force of the cutter head brought about by the servo motor, in a further development of the invention, a locking brake can be provided which can lock, fix or fix the relevant part of the adjustment drive train between the spindle drive stage and the servo motor.

[0028] For example, the locking brake described above can be provided or designed to rotationally lock or hold the tube nut of the spindle drive and / or axially lock or hold the spindle element in the form of a spindle sleeve. By locking the tube nut and / or the spindle element, yielding or elasticity in the further drive train between the tube nut and the servo motor is avoided or no longer plays a role, allowing the cutter head to be particularly tightly clamped in the position set by the servo motor.

[0029] Alternatively or additionally, the locking brake can also lock a drive element closer to the servomotor, taking advantage of the transmission ratio to ensure that the feed device can be locked with a smaller holding force. For example, the drive pinion for driving the chain and / or belt of the chain or belt stage and / or the gear element of the gear stage between the drive pinion and the servomotor and / or the servomotor shaft itself can be acted upon and held in place by the locking brake.

[0030] The bearings of the drive shaft, which are axially adjustable in addition to its main rotational movement between the spindle drive stage and the cutter head, can be of various designs depending on the design of the pelletizer, and in particular if the pelletizer is operated wet, for example if designed as an underwater pelletizer, seals can be provided instead of or in addition to bearings.

[0031] In a further embodiment of the invention, the above-mentioned axially adjustable and rotatably drivable drive shaft may be axially adjustable and rotatably mounted in a cutting chamber housing that surrounds the cutting chamber that receives the cutterhead.

[0032] Depending on the connection of the cutter head, this does not have to be the drive shaft itself, but in an advantageous further development can also be a cutter head receptacle attached to the cutting chamber housing in the manner described above and connected to the drive shaft so as to be axially fixed and non-rotatable.

[0033] In particular, a bearing assembly between the cutting chamber housing and the drive shaft or cutterhead receptacle can radially support the drive shaft / cutterhead receptacle in the cutting chamber housing.

[0034] Independently therefrom, a sealing assembly can be provided between the cutting chamber housing and the drive shaft or cutterhead receptacle to seal the cutting chamber in the area between the cutting chamber housing and the drive shaft / cutterhead receptacle, and in an advantageous further development of the invention, the above-mentioned sealing assembly can be designed to allow axial and rotational movement of the drive shaft and cutterhead receptacle.

[0035] In particular, a guide bushing may be provided between the cutting chamber housing and the cutterhead receptacle / drive shaft, on which the cutterhead receptacle and / or drive shaft are radially supported by at least one radial bearing in the form of a rolling bearing and / or a plain bearing.

[0036] Thereby, the guide bush can be advantageously guided in an axially adjustable manner in the cutting chamber housing, in particular by means of one or more plain bearings, and at the same time, the guide bush can be sealed against the cutting chamber housing by means of at least one seal, which can be in the form of a sealing ring, for example an elastic O-ring.

[0037] To seal between the guide bushing and the cutterhead receptacle or drive shaft, a sliding ring seal may be provided, which may be mounted on the cutterhead receptacle and / or the drive shaft connected thereto.

[0038] In particular, the cutterhead receptacle can be radially mounted and sealed in the above-mentioned guide bush, and in an advantageous further development of the invention, the cutterhead receptacle can be mounted in the guide bush by means of two ball bearings or other rolling bearings. For sealing, a sliding ring seal can be provided on the cutterhead receptacle, which together with the sealing receptacle can seal the cutterhead receptacle against the guide bush.

[0039] The present invention will now be described in more detail with reference to preferred embodiments and associated drawings. [Brief explanation of the drawings]

[0040] [Figure 1] FIG. 1 is a perspective view of an underwater pelletizer showing the cutterhead drive and process water connections for running in the cutting chamber. [Figure 2] FIG. 2 is a longitudinal section through a drive train for rotating the cutter head of the pelletizer of FIG. 1, showing a feeder for axial adjustment of the cutter head, in which a spindle drive stage nested on a rotating drive shaft is configured as a planetary screw drive. [Figure 3] FIG. 3 shows a longitudinal section of a drive train similar to FIG. 2, in which the spindle drive stage of the feeder for the axial adjustment of the cutter head is configured as a screw drive. [Figure 4] FIG. 4 is a longitudinal cross-sectional view of the drive train bearing and seal arrangement within the cutting chamber housing of the pelletizer of the previous figures. DETAILED DESCRIPTION OF THE INVENTION

[0041] As shown in Fig. 1, the pelletizer 1 is designed as an underwater pelletizer and includes a cutting chamber housing 22 provided with a cutting chamber 23 (see Fig. 4) in which a cutter head 2 having a blade is housed. The molten plastic material is supplied to a die plate 3 including a nozzle-like melt channel via a melt supply head 31 that can be connected to a melt supply device (not shown), for example including an extruder, so that a molten strand can be forced through or output from the die plate 3. The melt channel of the die plate 3 forms a cutting surface and can be located within the cutting chamber 23 facing the cutter head 2 or can be open at its end face adjacent to the cutting chamber 23.

[0042] The cutting chamber 23 can be flushed with process water, which can be fed to the cutting chamber 23 via an inlet 32 ​​and discharged together with the pellets via an outlet 33 in the form of a mixture of pellets and process water.

[0043] The cutter head 2 may be driven in rotation by a main drive 34 about a cutter head axis of rotation 12, which may extend, for example, perpendicular to the die plate 3. The main drive 34 may include a drive motor 5, for example in the form of an electric motor, which drives the cutter head 2 in rotation via a drive shaft 4 (see Figure 1).

[0044] In addition to the main drive 34, a feed device 6 including a servo motor 10 is provided for the axial adjustment of the cutter head 2 relative to the die plate 3 (see Figures 2 and 3).

[0045] The above-mentioned feed device 6 comprises a spindle drive stage 7 mounted on the drive shaft 4 between the drive motor 5 and the cutter head 2 so that the rotatably drivable drive shaft 4 itself can be adjusted in the axial direction. The drive shaft 4 is connected to the cutter head 2 in an axially fixed but non-rotatable manner, so that the axial adjustment movement of the drive shaft 4 results in the advancement of the cutter head 2 in the axial direction.

[0046] The spindle drive stage 7 includes a tube nut 8 and a spindle element 9 mounted on the tube nut 8. The aforementioned spindle element 9 is configured as a spindle sleeve mounted on the drive shaft 4 (see FIG. 2).

[0047] As shown in FIG. 2, the spindle drive stage 7 can be configured as a planetary screw drive having planets in the form of planetary screw rollers provided between the tube nut 8 and the spindle element 9 to convert rotational movement of the tube nut 8 into axial movement of the spindle element 9.

[0048] However, as FIG. 3 shows, the spindle drive stage 7 can also be configured as a thread drive in which there is no planetary arrangement between the tube nut 8 and the spindle element 9, but instead the internal thread of the tube nut 8 is in threaded engagement with the external thread of the spindle element 9.

[0049] 2 and 3, the tube nut 8 may be rotatably but axially fixedly mounted to the housing assembly and / or chassis assembly 13, for example, by a bearing assembly 16 between the tube nut 8 and the housing assembly and / or chassis assembly 13, which may include one or more rolling bearings in the form of, for example, a tapered roller bearing pair or a radial / axial bearing pair. However, plain bearings are also possible for rotatably and axially fixedly mounting the tube nut 8, if desired.

[0050] The above-mentioned spindle element 9 is mounted on the one hand on the drive shaft 4, and the bearing 15 provided for this purpose can be designed to be axially fixed but rotatable, so as to transmit the axial movement of the spindle element 9 directly to the drive shaft 4, while the latter can rotate within the spindle sleeve 9. The above-mentioned axially fixed and rotatably mounted bearing assembly 15 between the drive shaft 4 and the spindle element 9 can comprise, for example, two rolling and / or plain bearings which can be arranged on opposite sides of the shaft lug 35, the rolling bearings used being, for example, tapered roller and / or ball and / or cylindrical bearings.

[0051] The above-mentioned axially fixed bearing assembly 15 between the drive shaft 4 and the spindle element 9 may be located outside the tube nut 8 or may be axially offset from the bearing assembly 16 for the tube nut 8 (see Figures 2 and 3).

[0052] The spindle element 9 is radially supported between the drive shaft 4 and the tube nut 8 or, if applicable, the intermediate planetary section 14. In order to hold the spindle element 9 non-rotatably but axially adjustable, a further bearing assembly 17 configured to be axially adjustable but non-rotatable can be provided between the spindle element 9 and the housing assembly and / or chassis assembly 13. This can be, for example, a splined shaft profile or a pin guide in the extension of the spindle element 9.

[0053] A servo motor 10 is provided for rotationally driving the tube nut 8 of the spindle drive stage 7 and may be positioned so that its motor axis is aligned parallel to the rotation axis 13 of the cutter head 2 or drive shaft 4 and is laterally offset adjacent to the drive shaft 4 (see Figures 2 and 3).

[0054] To compensate for the lateral offset between the servo motor 10 and the tube nut 8, a belt stage 18 can be provided, the belt 36 of which can drive a drive pinion 19 that can be attached to the end face of the tube nut 8 and non-rotatably connected thereto. The drive pinion 19 is configured as a ring gear through which the drive shaft 4 passes.

[0055] On the other hand, the above-mentioned belt 36 of the belt stage 18 is driven by a drive pinion 37 which can be driven to rotate by the servo motor 10 .

[0056] Advantageously, a further gear stage 20 can be provided between the servo motor 10 and the above-mentioned drive pinion 37, the gear input and output shafts of which can be arranged coaxially with the motor shaft of the servo motor 10 and in particular can be integrated into a common motor / gear housing (see Figure 2).

[0057] The axial adjustment of the cutter head 2 involves the following force flow: the servo motor 10 drives the belt stage 18 via the gear stage 20, which drives its drive belt 36 via the drive pinion 19. The rotational movement of the axially fixed tube nut 8 is converted into the axial movement of the spindle element 9 via the planetary section 14 in FIG. 2 or the threaded engagement in FIG. 3. The axial movement of the spindle element 9, which is axially fixed to the drive shaft 4, is transmitted to the aforementioned drive shaft 4, which is then coupled to the cutter head 2 in an axially fixed but non-rotatable manner, allowing the cutter head 2 to move towards or away from the plate 3.

[0058] The rotational drive motion from the drive motor 5 can be transmitted to the drive shaft 4 by a coupling 38 which is configured to be non-rotatable but axially movable and which can include, for example, a splined shaft profile 38 or a toothed profile or the like.

[0059] As FIG. 4 shows, the drive train may be sealed towards the cutting chamber 23 or may be radially supported or mounted in the cutting chamber housing 22.

[0060] The bearing arrangement of the drive shaft 4, which is axially adjustable in addition to its main rotational movement between the spindle drive stage 7 and the cutter head 2, can be of various designs depending on the design of the pelletizer 1, and in particular if the pelletizer 1 is operated wet, for example if it is designed as an underwater pelletizer, seals can be provided in addition to the bearing arrangement.

[0061] In this case, the above-mentioned axially adjustable and rotatably drivable drive shaft 4 can itself be mounted axially displaceably and rotatably in a cutting chamber housing 22 which surrounds the cutting chamber 23 .

[0062] Depending on the cutter head connection, this does not have to be the drive shaft 4 itself, but in an advantageous further development can also be a cutter head receptacle attached and sealed to the cutting chamber housing 22 in the manner described above and connected to the drive shaft 4 so as to be axially fixed and non-rotatable.

[0063] In particular, a bearing assembly 24 between the cutting chamber housing 22 and the drive shaft or cutterhead receptacle may radially support the drive shaft / cutterhead receptacle in the cutting chamber housing 22.

[0064] Independently, sealing assemblies 29, 30 may be provided between the cutting chamber housing 22 and the drive shaft / cutterhead receptacle to seal the cutting chamber 23 in the area between the cutting chamber housing 22 and the drive shaft / cutterhead receptacle, the sealing assemblies 29, 30 allowing axial and rotational movement of the drive shaft and cutterhead receptacle.

[0065] In particular, a guide bushing 26 may be provided between the cutting chamber housing 22 and the cutterhead receptacle / drive shaft, on which the cutterhead receptacle and / or drive shaft are radially supported by at least one radial bearing 24 in the form of a rolling bearing and / or a plain bearing (see Figure 4).

[0066] Thereby, the above-mentioned guide bush 26 is guided axially displaceably in the cutting chamber housing 22, in particular by means of one or more plain bearings 28, and at the same time the above-mentioned guide bush 26 can be sealed relative to the cutting chamber housing by means of at least one seal 29 (see FIG. 4 ). The above-mentioned seal 29 can be in the form of a sealing ring, for example in the form of an elastic O-ring.

[0067] To seal between the guide bushing 26 and the cutterhead receptacle or drive shaft, a sliding ring seal 30 may be provided, which may be mounted on the cutterhead receptacle and / or the drive shaft connected thereto.

[0068] In particular, the cutterhead receptacle can be radially mounted and sealed in the above-mentioned guide bush 26, and in an advantageous further development of the invention, the cutterhead receptacle can be mounted in the guide bush 26 by means of two ball bearings or other rolling bearings. For sealing purposes, a sliding ring seal 30 can be provided in the cutterhead receptacle, which together with the sealing receptacle can seal the cutterhead receptacle against the guide bush 26.

[0069] As can be seen from the above, the pelletizer 1 is characterized in particular by the following features and properties:

[0070] The assembly described allows for axial displacement of a shaft 4 driven by an external motor 5 .

[0071] The assembly can apply tension or compression to a shaft 4 driven by an external motor 5 .

[0072] The assembly holds the sliding shaft 4 in place and allows it to be subjected to external tension or compression forces.

[0073] By adjusting the rotational torque of the servo motor 10, the feed force can be adjusted continuously and independently in both directions of movement.

[0074] By adjusting the speed of the servo motor 10, the speed of movement can be adjusted continuously in both directions and independently of each other.

[0075] A locking brake 21 can be used to maintain the position of the movement rod even when an external force is applied.

[0076] An integrated absolute encoder allows the position of the moving rod to be measured and monitored during operation.

[0077] By means of a suitable, in particular electronic, control device 40, automatic processing sequences can be set up, e.g. Automatic cutter head position adjustment Adaptation of the blade travel to the current wear height of the cutting surface Die plate wear / cutter wear measurement -Feed force according to recipe Coupling and uncoupling of the cutting chamber without the feed force of the cutter head -Various operation settings are possible, such as manual blade movement, feeding via torque from the main motor, feeding via torque from a servo motor (=feed force specification), and feeding based on the amount of movement per time, making maintenance and installation work easier.

[0078] The main drive can use a standard motor, allowing for easy control of position and feed force.

Claims

1. a rotationally drivable cutter head (2) for dividing a material strand output from a die plate (3) into pellets, the cutter head (2) being drivingly connected to a drive motor (5) via a drive shaft (4); and a feeder (6) for axially adjusting the cutter head (2) relative to the die plate (3) in the direction of a rotation axis (12) of the cutter head, the feeder (6) comprising a spindle drive stage (7), a tube nut (8) of which is rotatably adjustable by a servo motor (10) via a gear stage (11), and a spindle element (9) operably connected in a geared manner to the tube nut (8) being axially adjustable; the spindle element (9) is configured as a spindle sleeve axially fixed to the rotating drive shaft (4) between the drive motor (5) and the cutter head (2), the spindle sleeve being able to move the drive shaft in the axial direction towards and away from the die plate based on the geared connection with the tube nut (8), the spindle drive stage being configured to convert the rotational movement of the tube nut (8) into an axial movement of the spindle element (9) and to apply tension and compression forces to the drive shaft, the drive shaft is axially fixed and non-rotatably connected to the cutter head (5) and transmits the axial movement of the spindle sleeve to the cutter head (2); The servo motor (10) is positioned laterally offset from the drive shaft (4) and / or is aligned so that its axis is parallel to the drive shaft (4).

2. 2. The pelletizer of claim 1, wherein the tube nut (8) is rotatably but axially fixedly mounted to a housing assembly and / or chassis assembly (13), the spindle element (9) is axially adjustable but non-rotatably mounted to the housing assembly and / or chassis assembly (13), and the drive shaft (4) is axially fixed but rotatably held on the spindle element (9).

3. 3. A pelletizer according to claim 1 or 2, wherein the bearing assembly (16) for rotatably and axially fixedly mounting the tube nut (8) is spaced axially apart in the direction of the cutter head rotation axis (12) from the bearing assembly (15) for rotatably and axially fixedly mounting the spindle element (9) on the drive shaft (4) and / or from the bearing assembly (17) for non-rotatably and axially adjustably mounting the spindle element.

4. 2. The pelletizer according to claim 1, wherein the spindle drive stage (7) is configured as a planetary screw drive in which planetary screw rolls (14) are provided between the tube nut (8) and the spindle element (9) to convert the rotational movement of the tube nut (8) into an axial movement of the spindle element (9).

5. 2. The pelletizer according to claim 1, wherein the spindle drive stage (7) is configured as a ball screw drive in which balls are provided between the tube nut (8) and the spindle element (9) to convert a rotational movement of the tube nut (8) into an axial movement of the spindle element (9).

6. 2. The pelletizer according to claim 1, wherein the spindle drive stage (7) is configured as a threaded drive in which an internal thread on the tube nut (8) engages with an external thread on the spindle element (9).

7. 2. The pelletizer according to claim 1, wherein the gear stage (11) between the servo motor (10) and the tube nut (8) comprises a chain or belt stage (18), in particular a toothed belt stage.

8. 8. A pelletizer according to claim 7, wherein the chain or belt stage (18) has a drive pinion (19) non-rotatably connected to the tube nut (8) at the end face of the tube nut (8).

9. 9. A pelletizer according to claim 7 or 8, wherein a further gear stage (20) is provided between the chain or belt stage (18) and the servo motor (10) and is integrated in the servo motor (10).

10. 2. The pelletizer according to claim 1, wherein the gear stage (11) between the servo motor (10) and the tube nut (8) comprises a contactless operating magnetic gear stage and / or a clutch stage for transmitting rotational torque and driving motion from the servo motor (10) to the tube nut (8).

11. The pelletizer of claim 10 , wherein the magnetic gear stage and / or the clutch stage are configured to operate electrodynamically with eddy currents.

12. 2. A pelletizer according to claim 1, wherein a locking brake (21) is provided for rotationally locking the tube nut (8) and / or for axially locking the spindle element (9).

13. 13. The pelletizer according to claim 12, wherein the locking brake (21) is configured to lock the servo motor (10).

14. 2. The pelletizer according to claim 1, wherein the axially adjustable and rotatably drivable drive shaft (4) and / or the cutter head receptacle connected thereto are axially displaceably and rotatably mounted in a cutting chamber housing (22) surrounding a cutting chamber (23) that receives the cutter head (2).

15. 15. The pelletizer of claim 14, wherein a bearing assembly (24) between the cutting chamber housing (22) on the one hand and the cutter head receptacle and / or the drive shaft (4) on the other hand radially supports the cutter head receptacle and / or the drive shaft (4) in the cutting chamber housing (22).

16. 16. A pelletizer according to claim 14 or 15, wherein a sealing assembly (25) is provided between the cutterhead receptacle and / or the drive shaft (4) on the one hand and the cutting chamber housing (22) on the other hand to seal the cutting chamber (23) in the area between the cutterhead receptacle and / or the drive shaft (4) on the one hand and the cutting chamber housing (22) on the other hand, the sealing assembly (25) being configured to allow axial and rotational movement of the cutterhead receptacle and / or the drive shaft (4).

17. 15. The pelletizer according to claim 14, wherein a guide bush (26) is provided between the cutting chamber housing (22) on the one hand and the cutter head receptacle and / or the drive shaft (4) on the other hand, on which the cutter head receptacle and / or the drive shaft (4) are radially supported by at least one radial bearing (24) in the form of a rolling bearing and / or a plain bearing, and the guide bush (26) is guided axially adjustably in the cutting chamber housing (22), in particular is mounted axially adjustably by a plain bearing (28), and is sealed against the cutting chamber housing (22) by at least one seal (29), in particular in the form of a sealing ring.

18. 18. The pelletizer according to claim 17, wherein a sliding ring seal (30) is provided between the guide bush (26) on the one hand and the cutter head receptacle and / or the drive shaft (4) on the other hand.

19. 19. The pelletizer of claim 18, wherein the sliding ring seal (30) is mounted on the cutter head receptacle non-rotatably connected to the drive shaft (4).

20. 2. The pelletizer of claim 1, wherein the feeding device (6) comprises a control device (40) for controlling the servo motor (10) according to at least one process parameter and / or one system parameter.

21. 21. The pelletizer according to claim 20, wherein the control device (40) has an automatic mode for automatically adjusting the position of the cutter head (2) relative to the die plate (3) according to the at least one process parameter and / or one system parameter, in particular for automatically moving the cutter head (2) onto the die plate (3) or moving it away from the die plate (3).

22. 21. The pelletizer of claim 20, wherein the control device (40) has setting means for setting the feed force of the cutter head (2) relative to the die plate (3), and the setting means has an automatic mode in which the servo motor (10) is controlled to set the feed force in accordance with a manual input and / or a sensor-sensed recipe signal characterizing a recipe of the material to be pelletized.

23. 21. The pelletizer according to claim 20, wherein the control device (40) is configured to automatically control the feed of the cutter head (2) by driving the servo motor (10) according to at least one of the parameters being the rotational torque of the drive motor (5), the rotational torque of the servo motor (10), the feed speed and / or the feed in movement / time.

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