Patent Publication Number: US-2020298450-A1

Title: Die assembly with pressure regulating device, and a pelletizing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority to German patent application no. 10 2019 107 140.2, filed Mar. 20, 2019, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein. 
     BACKGROUND 
     The invention relates to a die assembly for a pelletizing apparatus, with a pressure regulating device coupled to the die member, the pressure regulating device comprising a base member having a fluid inlet side and a fluid outlet side, a flow channel formed in the base member to provide a fluid-conducting connection between the fluid inlet side and the fluid outlet side, and an annular channel section connected to the flow channel in a fluid-conducting manner and formed in the region of the fluid outlet side. 
     Such die assemblies are known from the prior art and are used in pelletizing apparatus, for example. They are used to extrude molten pelletizing material, such as thermoplastics, by means of a die plate into the form of a plurality of melt strands, in most cases. In the “underwater pelletizing” process, the individual melt strands are then divided by a cutting device into strand sections which are cooled to form pellet grains when they come into contact with a coolant, such as water. The underwater pelletizing process allows a high throughput of pelletizing material while requiring a small installation space for such a device and producing low emissions in the form of dust or noise. 
     In the die assemblies known from the prior art, melt is fed on an inlet side into a die member. The melt is guided through the die member by many flow channels and reaches a die plate. The die plate typically has a large number of die orifices to provide a high a level of productivity and, depending on the melt to be processed, a desired pelletizing result, i.e., high throughputs and/or small pellet grains. The disadvantage of classic die assemblies known from the prior art is that the die members and die plates, in particular, are designed for specific throughputs and viscosities of plastic melts. This means that each material or melt must typically be processed with advantageous process parameters, for example a specified pressure, to ensure that the melt strands exit the die plate in a desired manner. In die assemblies known from the prior art, changes of material typically involve replacing the entire die assembly and providing different die assemblies for each material to be processed, or for different categories of material at least. If different materials are to be processed, this ties up a large amount of capital, as it is necessary to provide a large number of die assemblies. Furthermore, replacing a die assembly is typically time-consuming, with the result that changing the material to be processed is associated with high set-up costs. 
     Using pressure regulating devices to allow different materials with different viscosities to be processed with a single die assembly is known from the prior art. DE 20 2006 018 456 U1, for example, relates to a die head of a plastic strand pelletizing plant. The die head in question has a melt inlet opening for receiving melt from an extruder, and a melt distributor for distributing melt from the melt inlet opening to a plurality of melt channels with orifices opening toward one end for discharging molten plastic strands, the die head having a plurality of constrictions for the flow of melt, which are arranged between the melt inlet opening and the orifices and which are variable and individually adjustable in cross-section. 
     However, the disadvantage of such a solution is that the manufacturing and maintenance costs of such an arrangement increase significantly due to its high complexity compared to the classic die assemblies known from the prior art. Although such a device avoids having to provide a large number of die assemblies in order to process different materials having different viscosities, the potential cost benefit that results cannot be exploited in the best possible way due to the high complexity of the proposed device. 
     SUMMARY 
     Given this background, the object of the invention is to develop a die assembly of the kind initially specified in such a way that the disadvantages found in the prior art are eliminated as far as possible. More specifically, a die assembly was to be specified which can be used for a large number of different materials, material throughputs and viscosities, while at the same time being inexpensive, functionally reliable and easy to maintain. 
     In a die assembly of kind initially specified, the object is achieved, according to the invention, by a flow cross-section regulating element for influencing a flow cross-section of the annular channel section, said element being movable relative to the annular channel section and/or the flow channel. 
     The invention makes use of the discovery that the motion of a single component or of an assembly with narrow limits to its number of components can be used to modify the free cross-section of flow of a respective annular channel section of a die assembly in such a targeted manner that different materials with different throughputs and viscosities can be processed with such a die assembly. 
     Such a flow cross-section regulating element can be used, in particular, to influence the free cross-section of flow in an annular channel section that, for example, supplies a large number of flow channels with melt. Alternatively, or additionally, the flow cross-section regulating element may be movable relative to a flow channel. Thus, a single flow cross-section regulating element can be used to indirectly influence the melt pressure in an entire die assembly. Furthermore, the free flow cross-section and the melt pressure are influenced in the immediate proximity of the die plate from which the melt strands exit. The melt pressure can thus be adjusted very precisely on the whole, while at the same time the device according to the invention is of low component complexity and easy to maintain. Compared to the pressure regulating devices known from the prior art, the cost efficiency can be significantly increased by using the pressure regulating device according to the invention. 
     The invention is developed by arranging the regulating element in the annular channel section. Melt preferably flows around the regulating element. The regulating element can now be used to influence the gap between the regulating element and the annular channel section, and thus the free cross-section of flow, by moving the regulating element relative to the annular channel section. This provides the advantage that the free cross-section of flow, and thus indirectly the pressure conditions in the melt, can be influenced in a very finely metered manner. Such an arrangement also ensures that any adverse impacts on the flow of melt are minimized as far as possible, in particular that strong turbulence is reliably prevented. 
     According to a preferred embodiment, the regulating element has a regulating ring and a retaining ring connected to the regulating ring. Such a two-part structure allows the regulating ring to be easily replaced and adapted to different materials, throughputs or viscosities, for example, as required. The individual components can also be easily replaced in the event of wear. The regulating ring and the retaining ring can be connected in many different ways, for example by means of a screw connection, a heat-resistant adhesive bond, or a form-fit connection. 
     The invention is developed by making the regulating ring wedge-shaped. A wedge shape of the regulating ring has proved to be particularly favorable for influencing the free cross-section of flow, without the melt flow being adversely affected by turbulence, for example. According to an alternative embodiment, the regulating ring may have concave and/or convex sections for influencing the flow in a targeted manner, or it may be formed in some other streamlined form. 
     According to a preferred development of the invention, the regulating ring has pins which extend at least in sections into the annular channel section, depending on the position of the regulating ring. The additional use of such pins, also referred to as pressure regulating pins, allows the free cross-section of flow to be additionally constricted in certain regions so that the pressure of the melt can be additionally influenced by means of such pins. Alternatively or additionally, the pins may be dimensioned in such a way that they extend into the flow channels formed in the die member. This allows the pressure control region to be moved closer to the die plate. By this means, the quality of the melt strands can be positively influenced, depending on the melt throughput being used or depending on the material throughput that is desired. 
     It is further preferred that the die assembly has at least one actuator, operatively connected to the regulating element, for moving the regulating element relative to the annular channel section, in particular translationally in the direction of a longitudinal axis of the base member. In this regard, the die assembly preferably has three or more such actuators to ensure that the regulating element in the region of the annular channel is at as constant a distance as possible from the lateral boundaries of the annular channel along the course of the annular channel. It is necessary, at all events, to ensure that the regulating element is prevented from tilting, which would indirectly result in melt exiting unevenly from the die plate. 
     According to an alternative embodiment, the actuator is formed as a fluid-operated actuator, in particular as a pneumatic actuator or hydraulic actuator. Embodying the actuator as a fluid-operated actuator has been found to be advantageous for applications in which the number of mechanical components is to be reduced and a low-wear actuator is to be used at the same time. 
     The fluid-operated actuator preferably has a cylinder with at least one pressurized fluid inlet/outlet, wherein the cylinder and the at least one pressurized fluid inlet/outlet are formed in the base member. Forming the cylinder in the base member allows a further reduction in the number of components required. It is preferable that a piston be arranged in the cylinder, the piston being sealed against the cylinder by means of a bellows. This ensures a durable tight seal. 
     The actuator is preferably designed such that it has a stub which is connected to the retaining ring and which is operatively connected to a translationally movable plunger. The assembly described allows the position of the retaining ring or regulating element to be finely adjusted while at the same time being of simple design. 
     It is further preferred that the base member has at least one mounting bore for mounting the plunger and for guiding the plunger to an outer side of the base member. This mounting bore preferably has a seal to prevent any melt from leaking from the housing. It is further preferred that the plunger has an actuating element, in particular a nut or a gear wheel arranged outside the base member, which nut or gear wheel preferably matches an external thread of the plunger. Such an actuating element arranged outside the housing allows the regulating element to be actuated easily and ensures that melt cannot leak from the housing. The type of actuating element used can be freely selected on the whole and will depend in particular on how it is to be controlled. For example, the actuating element may have devices for manual actuation, or machine elements such as nuts or gears. 
     The invention is further developed by a coupling means for coupling the actuating elements of at least two actuators. The coupling means is preferably configured as an internal gear in engagement with the actuating elements, in particular the gear wheels, of the plurality of actuating elements, such that actuation of the internal gear causes actuation of the plurality of actuating elements. This is based on the principle that actuation of a single coupling means synchronously actuates several actuators of a die assembly. In alternative embodiments, the actuators themselves, or a group of actuators which may be coupled in any way, can be actuated individually or in groups by means of a motor drive, a pneumatic drive, an electric drive or a linear drive. 
     According to a preferred embodiment, the actuating elements or the coupling means have a drive means and/or a hand lever. An electric motor, a pneumatic drive or a linear drive can be used as the drive means. A hand lever is a particularly inexpensive way of actuating, but requires direct interaction by an operator. Actuating the coupling means by a drive means allows the die assembly to be automated with regard to actuation of the regulating element. 
     According to an alternative embodiment, the regulating element is formed as a sleeve which surrounds the base member at least in sections and is translationally movable in the direction of the longitudinal axis of the base member, wherein a regulating section adapted to influence the free cross-section of flow in the annular channel section is formed on the regulating element. Designing the regulating element as a sleeve or sleeve-shaped member has also been found suitable for influencing the free cross-section of flow in the annular channel section in a targeted manner. This alternative embodiment involves a further reduction in the number of components and, due to the regulating element being structurally formed as a sleeve, it is possible for large forces to be applied to the regulating section of the regulating element. 
     In a preferred embodiment, the sleeve is moved translationally by means of a bolt inserted into the base member. The sleeve has a matching receptacle for the bolt, the receptacle having a recess for inserting an actuating nut which can be screwed onto the bolt. The actuating nut is limited in both actuating directions of the sleeve, such that any rotation of the nut causes the sleeve to move translationally in the direction of the longitudinal axis of the base member or in the respective opposite direction. Preferably, at least three such actuating bolts are arranged in the base member. 
     The regulating section is preferably wedge-shaped. In alternative embodiments, however, the regulating section may also have concave or convex sections, or a combination of these and straight sections. In particular, the shape of the regulating section can be adapted to the material to be processed, its viscosity and the desired throughput. 
     According to a preferred embodiment, the regulating section also has pins which extend at least in sections into the annular channel section, depending on the position of the regulating section. In yet another alternative embodiment, the regulating element has pins which extend at least in sections into the annular channel section, depending on the position of the regulating element. As already mentioned, the pins enable the free cross-section of flow to be further narrowed and thus indirectly enable the pressure on the melt to be increased in a specific region. 
     In different embodiments, the pins may have different lengths and shapes. According to a first embodiment, the pins extend substantially into the annular channel section and, particularly in the state in which the pins are moved in the direction of the die plate, an additional further amount into at least a portion of the flow channels of the die unit. In a further embodiment, slightly longer pins are used, which likewise extend into the annular channel section and into a larger portion of the flow channels of the die unit. This allows the pressure conditions in the immediate vicinity of the die plate to be adjusted in a targeted manner according to the melt to be processed (viscosity, throughput). 
     In a preferred embodiment, the pins taper toward the die plate. In an alternative embodiment, the pins have two sections, namely a first section of constant diameter and a second pin section which tapers toward the die plate. The pin ends facing the die plate are designed as tips or roundings. 
     According to one embodiment, the pins also have an external thread on the side facing away from the die plate, which matches an internal thread provided in the regulating section or the regulating element. The pins can thus be screwed preferably into the regulating section or the regulating element. In an alternative embodiment, the regulating section and the regulating element have bores into which the pins can be inserted. 
     In an alternative embodiment, the number of pins arranged at the regulating section or the regulating element is variable. By precisely selecting the number of pins to be inserted, the pressure conditions in the annular channel section or in the flow channel of the die unit can be influenced in a targeted manner. 
     According to an alternative embodiment, the flow cross-section regulating element is formed as a cone which is translationally movable relative to a longitudinal axis of the base member. 
     Using a cone which can be moved translationally has proved to be particularly suitable for fine regulation of the flow rate and also reduces turbulence in the fluid. 
     An actuator for translational movement of the cone is preferably assigned to the cone. 
     According to a preferred embodiment, the actuator is configured as a fluid-operated actuator, particularly preferably as a pneumatic actuator or hydraulic actuator. 
     According to an alternative embodiment, the actuator is configured as a mechanical actuator. Designing it in this way is preferable whenever no pressurizing medium is available in a production environment. 
     The invention is developed by the mechanical actuator having a set screw which is engagable with an internal thread arranged in the cone for translational movement of the cone. In this way, the position of the cone can be finely adjusted by rotary movement of the set screw and using standard components. According to an alternative embodiment, the mechanical actuator has an adjusting pin which is operatively connected to a rotating member via a gear, and wherein the rotating member is operatively connected to the cone by means of a thread. Such an arrangement allows the transfer of strong restoring forces, so such a die assembly can be used for a variety of operating pressures. 
     The translationally movable cone is preferably guided relative to and sealed against the base member and/or the die plate by means of a cone guide. This ensures that the cone is guided evenly and centered in relation to the base member and/or the die plate. 
     According to another preferred embodiment, the cone has a trapezoidal section on its side facing the annular channel section, for influencing the cross-section of flow in the annular channel section. The cone is thus adapted to exert direct influence, via the trapezoidal section, on the flow conditions in the region of the annular channel section. 
     According to another alternative embodiment, the translationally movable cone is sealed against the base member and/or the die plate by means of a bellows, the bellows being adapted to influence the cross-section of flow in the annular channel section. In a first operating position of the cone, the bellows preferably rests tightly against the outer circumference of the cone, whereas in a second position of the cone, the bellows has a curvature which is suitable for influencing the flow conditions in the annular channel section. 
     The invention is further developed by coupling the pressure regulating device to a die member. The pressure regulating device and the die member thus form a die unit. 
     According to an alternative embodiment, the pressure regulating device is formed in a die member. The advantage here is that a more compact arrangement of the pressure regulating device and die member can be achieved. 
     According to an alternative preferred embodiment, the die member has a guide assembly for guiding the flow cross-section regulating element relative to the die member. By means of the guide assembly, the flow cross-section regulating element is aligned and guided concentrically relative to the die member. The guide assembly preferably comprises a plurality of guide plates, in particular three such guide plates, arranged concentrically on the die member, which guide the flow cross-section regulating element, in particular at its inner radius or outer radius. 
     According to another alternative preferred embodiment, the flow cross-section regulating element has at least one guide element for guiding the flow cross-section regulating element relative to the die member, and the die member has at least one guide groove in which the at least one guide element is movably accommodated. This again provides alignment and guidance of the flow cross-section regulating element relative to the die member. 
     According to another alternative preferred embodiment, the flow cross-section regulating element has throttle pins, the throttle pins being guided and received in radially outwardly extending guides in the die member and extending at least in sections into the annular channel section. The throttle pins can preferably be inserted so far into the annular channel section that the latter is almost completely blocked. It is also preferred that the throttle pins can be moved into a further position in which they do not protrude into the annular channel section and thus exert little or no influence over the free cross-section of flow in the annular channel section. 
     It is preferred, alternatively, that the flow cross-section regulating element has at least one slider element with at least one slider bore, wherein the slider element can be brought into a position in which the slider bore is aligned with die member flow channels and into another position in which the slider bore is not or only partially aligned with the die member flow channels. 
     In this alternative embodiment, sliders with bores are used to influence the flow in the region of the die member flow channels. If the hole in the slider elements is aligned with the die member flow channels, the flow through the die member flow channels is unaffected. If the slider elements—and thus also the slider bores contained therein—are brought out of alignment, this will affect the flow conditions in the die member flow channels. 
     It is preferred in this regard that the slider elements are operatively connected to a slider rod which is guided and received in radially outwardly extending guides in the die member. This means the slider rods are easily accessible and operable from outside the die member. 
     According to an alternative embodiment, the slider elements are coupled to a rotationally movable slider adjustment means. This allows delicate positional variation of the slider elements. 
     According to an alternative embodiment, the flow cross-section regulating element is formed as a throttle element which can be pivoted selectively into the flow channel. The invention is further developed by mounting the throttle element so that it is pivotable about a pivot axis and is held in a pivoted position by an adjusting screw. Using such pivoting elements, which are typically pressed outwards by the fluid pressure and thus preferably against an adjusting screw, has proved to be particularly suitable for the fine adjustment of flow conditions. It is preferred that the throttle elements have wedge-shaped sections, concave or convex sections, or combinations thereof. The invention has been described above with reference to a die assembly. In another aspect of the invention, the invention relates to a pelletizing apparatus for producing pellets from a flow of melt by means of a die assembly. The invention achieves the initially specified object in respect of the pelletizing apparatus by the die assembly being formed according to one of the aspects described above. 
     In another aspect, the invention relates to a method for regulating the pressure of a flow of melt. The invention achieves the initially specified object by reference to a method comprising the following steps: Providing a flow of melt at a pressure regulating device, conducting the flow of melt to an annular channel section of the pressure regulating device, and regulating the free flow cross-section of the annular channel section. In an alternative embodiment, the free flow cross-section of a flow channel of a die unit is regulated in addition. 
     With regard to the advantages of such a pelletizing apparatus or such a method, reference is made to the statements above, which are incorporated here by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention ensue from the attached claims and the following description, in which embodiments are described in more detail with reference to schematic drawings. In the Figures, 
         FIG. 1  shows a perspective view of a first embodiment of a pelletizing apparatus according to the invention, comprising a die assembly according to the invention; 
         FIG. 2  shows a perspective view of the embodiment of the inventive die assembly shown in  FIG. 1 , comprising a die unit and a pressure regulating device; 
         FIG. 3  shows a perspective view of the embodiment of the inventive pressure regulating device shown in  FIG. 1 ; 
         FIGS. 4, 5  show cross-sectional views of the embodiment of the inventive die assembly shown in  FIG. 1 , in different operating states; 
         FIGS. 6, 7  show cross-sectional views of the embodiment of the inventive die assembly shown in  FIG. 1 , with pins for influencing the free cross-section of flow in different operating states; 
         FIG. 8  shows a perspective view of an alternative embodiment of a die assembly according to the invention; 
         FIG. 9  shows a cross-sectional view of the embodiment of the inventive die assembly shown in  FIG. 8 ; 
         FIGS. 10, 11  show cross-sectional views of the embodiment of the inventive die assembly shown in  FIG. 8 , in different operating states; 
         FIG. 12  shows a cross-sectional view of the embodiment of the inventive die assembly shown in  FIG. 8 , with pins for influencing the free cross-section of flow; 
         FIGS. 13, 14  show cross-sectional views of the embodiment of the inventive die assembly shown in  FIG. 8 , with pins for influencing the cross-section in different operating states; 
         FIG. 15  shows a perspective view of a third embodiment of a die assembly according to the invention; 
         FIG. 16  shows a cross-sectional view of the embodiment of the inventive die assembly shown in  FIG. 15 ; 
         FIGS. 17, 18  show the embodiment of the inventive die assembly shown in  FIG. 15 , in different operating states; 
         FIGS. 19, 20  show cross-sectional views of the embodiment of the inventive die assembly shown in  FIG. 15 , with an alternative embodiment of the pins for influencing free cross-section of flow in different operating states; 
         FIG. 21  shows a cross-sectional view of the first embodiment of the inventive pressure regulating device shown in  FIG. 1 , with an alternative embodiment of a die unit; 
         FIG. 22  shows a perspective view of another embodiment of a pressure regulating device according to the invention, with a die unit; 
         FIG. 23  shows a cross-sectional view of the embodiment of the inventive pressure regulating device shown in  FIG. 22 ; 
         FIG. 24  shows a cross-sectional view of the embodiment of the inventive pressure regulating device shown in  FIGS. 22-23 , while in an alternative operating position; 
         FIG. 25  shows an embodiment of an inventive pressure regulating device based on  FIG. 1 , with a concave regulating section; 
         FIG. 26  shows the embodiment of an inventive pressure regulating device with a concave regulating section as shown in  FIG. 25 , in an alternative operating position; 
         FIG. 27  shows another alternative embodiment of a pressure regulating device based on the embodiment shown in  FIG. 1 , with a convex regulating section; 
         FIG. 28  shows the embodiment of the inventive pressure regulating device shown in  FIG. 27 , in an alternative operating position; 
         FIG. 29  shows a cross-sectional view of an alternative embodiment of a pressure regulating device according to the invention and a die unit according to the invention; 
         FIG. 30  shows the embodiment of an inventive pressure regulating device and a die unit according to the invention as shown in  FIG. 29 , in an alternative operating position; 
         FIG. 31  shows a cross-sectional view of another alternative embodiment of a pressure regulating device according to the invention and a die unit according to the invention; 
         FIG. 32  shows the embodiment shown in  FIG. 31 , in an alternative operating position; 
         FIG. 33  shows a cross-sectional view of another alternative embodiment of a pressure regulating device according to the invention and a die unit; 
         FIG. 34  shows the embodiment shown in  FIG. 33 , in an alternative operating position; 
         FIG. 35  shows a cross-sectional view of another alternative embodiment of a pressure regulating device according to the invention and a die unit according to the invention; 
         FIG. 36  shows the embodiment shown in  FIG. 35 , in an alternative operating position; 
         FIG. 37  shows a cross-sectional view of another alternative embodiment of a pressure regulating device according to the invention and an alternative die unit; 
         FIG. 38  shows the embodiment shown in  FIG. 37 , in an alternative operating position; 
         FIG. 39  shows a perspective view of an alternative embodiment of a die unit according to the invention, with a pressure regulating device integrated therein; 
         FIGS. 40, 41  show partial cross-sectional views of the inventive die unit with pressure regulating device, in different operating positions; 
         FIG. 42  shows a perspective view of another alternative embodiment of a pressure regulating device according to the invention, integrated in a die unit; 
         FIGS. 43, 44  show the inventive die unit and pressure regulating device as shown in  FIG. 42 , in different operating positions; 
         FIG. 45  shows another cross-sectional view of the embodiment of the inventive pressure regulating device integrated in a die unit as shown in  FIGS. 42-44 ; 
         FIG. 46  shows a perspective view of another embodiment of a pressure regulating device according to the invention, with a die unit; 
         FIGS. 47, 48  show cross-sectional views of the embodiment of the inventive pressure regulating device shown in  FIG. 46 , in different operating positions; 
         FIGS. 49, 50  show the partial views of the embodiment shown in  FIGS. 46-48 , in different operating positions; 
         FIGS. 51, 52  show cross-sectional views of an alternative embodiment of a pressure regulating device according to the invention, in different operating positions; 
         FIG. 53  shows a perspective view of another embodiment of a die unit according to the invention, with a pressure regulating device integrated therein; 
         FIGS. 54, 56  show the embodiment of the inventive pressure regulating device shown in  FIG. 53 , in different cross-sectional views and operating positions; 
         FIG. 57  shows a cross-sectional view of another alternative embodiment of a pressure regulating device according to the invention, arranged a die unit; and 
         FIG. 58  shows by way of example a block diagram of a controller according to the invention, for operating a pressure regulating device. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a pelletizing apparatus  2 , which is configured here and preferably as an underwater pelletizing apparatus; the embodiments according to the invention can also be used in other pelletizing apparatus or methods, however. Pelletizing apparatus  2  has a driver  6  that provides driving power to an underwater pelletizer  14 . Pelletizing apparatus  2  also has a protective cover  16 . 
     Liquid plastic melt is typically fed to die assembly  4  by means of an extruder (not shown in the Figures). Die assembly  4  has a pressure regulating device  26  and a die unit  28 . The melt is fed to pressure regulating device  26  and regulated in respect of melt pressure, in particular, depending on the melt material, its viscosity and intended throughput, and fed to die unit  28 . Die unit  4  is heated electrically or by means of a heating fluid. Process water can also be introduced into die assembly  4  by means of a process water inlet  24  and can leave it via process water outlet  12 . During operation, the melt exits in the form of melt strands (not shown in  FIG. 1 ) from die assembly  4  or die unit  28  in the direction of the underwater pelletizer  14  and is first divided into strand sections by means of a cutting device (not shown); the cutting device is preferably designed with rotating cutting blades. These melt strand sections come into contact with a coolant, in particular water, in the underwater pelletizer  14  and are cooled abruptly. The melt strands are cut and form granules that are separated from the water as pellets later in the process. 
     Driver  6  is used to drive the cutting device which is provided for separating the melt strands into strand sections. The assembly comprising driver  6 , underwater pelletizer  14  and die assembly  4  with die unit  28  and pressure regulating device  26  is mounted on a machine baseplate  20 . The latter, for its part, is coupled by means of spacer elements  22  to a baseplate  18 , which for its part is connected to a housing  8 . Housing  8 , for its part, is mounted on a skid mount  10 , which has rollers, for example, for making it easier to position pelletizing apparatus  2 . 
       FIG. 2  shows die assembly  4  as shown in  FIG. 1 , but separated from pelletizing apparatus  2 . Die assembly  4  includes pressure regulating device  26  and die unit  28 . Die unit  28  contains a die member  38  and a die plate  40 . Die plate  40  has die orifices  42  from which melt strands exit die unit  28 . Pressure regulating device  26  is coupled to die unit  28 . Pressure regulating device  26  has a base member  30  and a housing section  31 . Melt enters base member  30  at fluid inlet side  32 .  FIG. 2  also shows actuators  34  which allow the free cross-section of flow in a section of pressure regulating device  26  to be influenced by means of actuating nuts  36 , and which thus allow the melt pressure to be influenced indirectly. 
     In  FIG. 3 , pressure regulating device  26  is now shown without die unit  28 , and the fluid outlet side  48  of pressure regulating device  26  can now be seen. A flow channel  46  is formed inside base member  30  of pressure regulating device  26 . In the present embodiment, the flow channel is defined in the region of fluid outlet side  48  by a sleeve  44  which can be moved translationally. By moving the sleeve  44 , it is possible, in combination with die unit  28  not shown here, to influence the free cross-section of flow in the region of fluid outlet side  48 , as shown in detail in the following Figures. 
       FIGS. 4 to 5  show sectional views of the die assembly shown in  FIG. 2 . As already mentioned, die assembly  4  comprises pressure regulating device  26  and die unit  28 . Here, die unit  28  consists here of a die member  38  into which die member flow channels are introduced. Die unit  28  consists of a die member  38  in which die member flow channels are introduced. A guide cone  58  is attached to die member  38 . The guide cone is centered by centering pin  54 , in particular, and coupled to die member  38  by means of a cone fastening screw  56 . A die plate  40 , which has die orifices  42  (see  FIG. 2 ) from which melt strands exit from the apparatus, is mounted on the outlet side of die member  38 . 
     Pressure regulating device  26  is coupled to die unit  28 . The pressure regulating device has a base member  30  in which a flow channel  46  is formed. Here, flow channel  46  is centered relative to the longitudinal axis in the middle of base member  30 . An annular channel  50  is formed in the outlet region of pressure regulating device  26  by the interaction of flow channel  46  with the guide cone  58  of die unit  28 . In order to influence the free cross-section of flow in this annular channel section  50 , a sleeve  44  with a regulating section  52  is arranged in the region thereof. Sleeve  44  is mounted translationally movably along the longitudinal axis of base member  30 . If sleeve  44  with regulating section  52  is moved in the direction of die member  38 , the free cross-section of flow in annular channel section  50  is narrowed. If, however, sleeve  44  is moved in the opposite direction away from die member  38 , the free cross-section of flow is increased, although the free cross-section of flow cannot become greater overall than the region of annular channel section  50  defined by the interaction of guide cone  58  and base member  30 . A housing section  31  is arranged on the fluid outlet side  48  of pressure regulating device  26  and extends substantially annularly around base member  30  and sleeve  44 . Housing section  31  is additionally connected to base member  30  by means of bolt  62 . Bolt  62  is screwed in sections into base member  30  at the end facing away from the bolt head and is fastened to base member  30  by means of fastening nut  66 . The preferred plurality of bolts  62  thus provide an additional connection between base member  30  and housing section  31 . 
     Bolts  62  are received in housing section  31  and are fastened to the housing section by means of fastening nuts  64 . Sleeve  44  has bores with a diameter that matches the diameter of bolt  62 . Sleeve  44  also has a recess for insertion of an actuating nut  36 . Sleeve  44  is slid onto bolts  62 , and nut  36  is screwed onto bolt  62 . Due to the shape of the section for receiving actuating nuts  36 , actuation of the actuating nuts  36  causes sleeve  44 , which is in contact with actuating nut  36 , to move translationally when actuating nut  36  is rotated, if housing section  31  is fixed in position relative to base member  30 . The position of sleeve  44  can thus be adjusted translationally by rotating the actuating nut  36  associated with an actuator  34 . The free cross-section of flow in annular channel section  50  can thus be influenced by interaction with regulating section  52  of sleeve  44 . The melt pressure is regulated indirectly by this adjustment of the free cross-section of flow in annular channel section  50 . The range of movement of sleeve  44  is limited by a first abutment shoulder  70  and a second abutment shoulder  72 . 
       FIG. 5  shows an operating state of die assembly  4 , in which sleeve  44  has been moved translationally in the direction of die member  38 . The free cross-section of flow  50  is now restricted at the direct transition to die member  38  of die unit  28 . 
     Such a restriction of the free cross-section of flow in annular channel section  50  can be used, for example, to increase the pressure of the melt compared to the state shown in  FIG. 4 . 
     The structure of die assembly  4  as shown in  FIGS. 6 to 7  is essentially based on the structure known from  FIGS. 4 and 5 . However, sleeve  44  or regulating section  52  of sleeve  44  has a number of pins  74 . In addition to positioning regulating section  52 , positioning pins  74  also offers a way of influencing the free cross-section of flow and thus indirectly the pressure conditions in annular channel section  50 , specifically, and also in die member flow channels  60 . Pins  74  may be screwed or glued to sleeve  44 , for example, or inserted into the sleeve by a press fit. Alternatively, pins  74  and sleeve  44  may be integrally formed. The total number of pins  74  is variable and may also be adapted to a material to be processed, to a respective viscosity or to a desired material throughput. 
       FIG. 6  shows the state in which sleeve  44 , including pins  74 , is in a position moved away from die member  38 . In this operating position, regulating section  52  does not restrict the free cross-section of flow in annular channel section  50 , but pins  74  are already inserted at least partially into annular channel section  50  and into die member flow channels  60 . In the state shown in  FIG. 7 , sleeve  44  has now been moved translationally in the direction of die member  38 . This results in regulating section  52  restricting the free cross-section of flow in the annular channel section  50 , while at the same time pins  74  restrict the free cross-section of flow in the region of annular channel section  50  and additionally in the region of die member flow channels  60 . 
     An alternative embodiment of a die assembly  104  is shown in  FIG. 8 . Die assembly  104  includes an alternative embodiment example of a pressure regulating device  126  as well as die unit  28  that is already known. Die unit  28  has a die member  38  and a die plate  40  with die orifices  42 . Pressure regulating device  126  is connected to die unit  28  and has a base member  130  to which a coupler  188  with a hand lever  182  is attached. Moving hand lever  182  along the circumference of base member  130  results in a change in the free cross-section of flow in annular channel section  150  or in die member flow channels  60 , as can be seen in detail from the following Figures. 
       FIG. 9 , for example, shows pressure regulating device  126 , which is mounted on die unit  28 . Pressure regulating device  126  has a base member  130  in which a flow channel  146  is arranged. In combination with guide cone  58  of die unit  28 , flow channel  146  forms a annular channel section  150 . A regulating ring  186  is arranged in said annular channel section  150 . The free flow cross section in annular channel section  150  can be influenced, specifically, by a translational movement of said regulating ring  186  in the direction of die unit  28  (or in the opposite direction). 
     A movement of regulating ring  186  in the direction of die unit  28  results in a reduction of the free cross-section of flow in annular channel section  150 . This allows indirect influence to be exerted on the pressure conditions of a melt in this region. Regulating ring  186  is arranged on a retaining ring  184 . The respective components may be glued together, for example, or screwed together or connected in some other way, and if necessary may also be integrally formed. An actuating element  176  is attached form-fittingly or force-fittingly to retaining ring  184 . A plurality of actuating elements  176  are typically attached to retaining ring  184 , although only one is shown here due to the sectional view. Actuating element  176  is connected, in turn, to a plunger  178 , which has a threaded portion at its end opposite retaining ring  184 , onto which threaded portion an actuating element  180  is placed. The range of movement of actuating element  180  is limited on one side by base member  130  and on the other side by a cap ring  190 . Translational movement of actuating element  180  is thus inhibited, with the consequence that rotation of actuating element  180  causes plunger  178  to move translationally in the direction of die member  38  or away from it. As regulating ring  186  is connected indirectly to plunger  178 , any rotation of actuating element  180  will cause a translational movement of regulating ring  186 , with which the free cross-section of flow in annular channel section  150  can then be regulated. 
     As already mentioned, pressure regulating device  126  preferably has a plurality of plungers  178 , in particular three. In order to facilitate a uniform translational movement of the plurality of plungers  178 , actuating elements  180  are preferably provided in the form of gear wheels that match a coupler  188  configured as an internal gear, in particular. Rotation of coupler  188  along the circumference of base member  130  results in uniform movement of the plurality of actuating elements  180 , thus ensuring that regulating ring  186  is moved uniformly and as purely translationally as possible in the direction of die member  38  or away from it. A hand lever  182  is provided on coupler  188  to facilitate manual operation of coupler  188 . 
       FIGS. 10 and 11  show different operating states of the die assembly  104  shown in  FIG. 9 .  FIG. 10  shows an operating state in which regulating ring  186  has been moved as far as possible in a direction away from die member  38 . The free cross section of flow in annular channel section  150  is thus maximized. In contrast,  FIG. 11  shows a state in which regulating ring  186  has been moved as far as possible toward die member  38 . In this operating state, the free flow cross section in annular channel section  150  is minimized. However, a certain free cross-section of flow always remains between regulating ring  186  and annular channel section  150 . 
       FIG. 12  shows the die assembly of  FIGS. 8 to 11 , but with pins  174  arranged on regulating ring  186  to influence the free cross-section in annular channel section  150  or in die member flow channels  60 . Pins  174  may be connected to retaining ring  184  or regulating ring  186  in different ways. The components can be screwed, glued, otherwise connected, or integrally formed, for example. The number of pins  174  is also variable, as are their geometry and length. Referring now to  FIG. 12 , any actuation of coupler  188  will now cause actuating element  180  to likewise rotate. As actuating element  180  is held in position by base member  130  and cap ring  190 , rotation of actuating element  180  will result in plunger  178  being moved translationally, either in the direction of die member  38  or away from it, depending on the direction of rotation. 
     As a plurality of pins  174  are arranged on retaining ring  184  or regulating ring  186 , these are moved in the direction of annular channel section  150  and in the direction of die member flow channels  60 , or away from them. Pins  174  specifically allow a further reduction of the free cross-section of flow in annular channel section  150  and in particular in die member flow channels  60 , so that the melt pressure in a region in the immediate vicinity of die plate  40  can be influenced in a targeted manner. The aforementioned operating states are illustrated in  FIGS. 13 and 14 . In  FIG. 13 , regulating ring  186  together with pin  174  has been moved away from die member  38 , whereas in  FIG. 14  the aforementioned components have been moved by the maximum amount in the direction of die member  38 . As can be seen from  FIG. 14 , in particular, pins  174  cause die member flow channels  60  to be filled almost completely by pins  174 , thus minimizing the remaining free cross-section of flow in die member flow channels  60 . 
     Another embodiment of a die assembly  204  is shown in  FIG. 15 . Die assembly  204  has a pressure regulating device  226  and a die unit  28 . Die unit  28  has a die member  38  and a die plate  40  with die orifices  42 . Pressure regulating device  226 , which has a retaining ring  292 , a connecting ring  294  and pins  274 , is mounted on said die unit  28 . The pressure regulating device also has an actuating nut  236 . A plurality of actuating nuts  236 , in particular three actuating nuts  236 , are preferably provided on pressure regulating device  226 . 
     The structure of pressure regulating device  226  can be seen from  FIGS. 16 to 20 . Pressure regulating device  226  has a base member  230  in which a flow channel  246  is formed. In a region between pressure regulating device  226  and die unit  28 , an annular channel section  250  is formed in conjunction with guide cone  58  of die unit  28 . A plurality of pins  274 , which can be moved translationally in the direction of die unit  28  or away from it, project into annular channel section  250 . Pins  274  are guided section-wise in base member  230  and are mounted with their head in a mounting ring  292 . A translational movement of mounting ring  292  thus results in a translational movement of pins  274  as well. Mounting ring  292  is connected to base member  230  and to the connecting ring  294  by one, preferably several, actuating nuts  236 . 
     Here, rotation of actuating nut  236  causes mounting ring  292  to move translationally in the direction of die unit  28  or away from it, depending on the direction of rotation. As pins  274  are accommodated in mounting ring  292 , they are moved analogously in a translational manner. By actuating or rotating actuating nuts  236 , it is thus possible to move pins  274  translationally into annular channel section  250  or into die member flow channels  60  and to move them back out of them. The different operating states of die assembly  204  can be seen from  FIGS. 17 to 18 . In the state shown in  FIG. 17 , pins  274  have been moved the maximum distance away from die member  38 . This means that pins  274  extend only into the region of annular channel section  250  and slightly into die member flow channels  60 . A larger free flow cross section remains in the region of annular channel section  250  and die member flow channels  60 . In the state shown in  FIG. 18 , pins  274  have been moved translationally in the direction of die member  38  by the maximum amount. As can be seen from  FIG. 18 , the remaining free cross-section of flow, especially in die member flow channels  60 , is now minimized. 
       FIGS. 19 and 20  show alternative embodiments with regard to the configuration of pins  296 , which are now longer compared to those in the previous embodiments. Depending on the operating state, pins  296  accordingly extend further into die member flow channels  60 , in particular, as a result of which the free cross-section of flow and thus indirectly the melt pressure in the immediate vicinity of die plate  40  can be influenced. 
       FIG. 21  shows a final embodiment of a die assembly  304 . Die assembly  304  comprises the pressure regulator  26  shown in  FIGS. 2 to 5 , with an alternative embodiment of a die unit  328 . A detailed description of pressure regulator  26  is dispensed with here, and reference is made to the embodiment above. The alternative embodiment of die unit  328  is characterized by a die member  338  in which die member flow channels  360  are formed in a known manner. There is also a guide cone  358  arranged on die member  338 , said guide cone being mounted by means of a cone fastening screw  356  to die member  338 . A heating ring  398  used to heat die unit  328  is arranged around die member  338 . It can be clearly seen here that pressure regulating device  26  can be combined with many different die units  328 . The die unit may be formed as a two-part die unit as described in  FIG. 21 , or as an integral die unit as described in  FIGS. 1 to 20 . The die unit can also be heated in many different ways, for example by means of an electric current, a heating fluid or by steam or the like. 
       FIG. 22  shows a die unit  428  and a pressure regulating device  426  mounted on the die unit. Pressure regulating device  426  has a fluid inlet side  432  where fluid can enter pressure regulating device  426  via flow channel  446 . Pressure regulating device  426  also has a base member  430  on which a first housing ring  488  and a second housing ring  490  are arranged. An inlet/outlet for pressurized fluid  484  is arranged in the first housing ring  488 . A second inlet/outlet for pressurized fluid  486  is arranged on the second housing ring  490 . 
     The functional principle is illustrated with reference to  FIGS. 23 and 24 . As can be seen from  FIG. 23 , the inlets and outlets for pressurized fluid  484 ,  486  are connected to a cylinder chamber  496  located in the second housing ring  490 . A piston  494  connected to pins  474  is also arranged in cylinder chamber  496 . A bellows  492  is used to seal piston  494 . If pressurized fluid is now introduced into cylinder chamber  496  via the inlet/outlet for pressurized fluid  486 , this causes piston  494  to be moved to the right in the plane of the drawing. Due to the direct coupling between piston  494  and pin  474 , this causes pin  474  or the plurality of pins  474  to be moved at least partially into die member flow channels  460 . Due to the positioning of pins  474  relative to cylinder chamber  496 , the flow cross-section in die member flow channels  460  and in annular channel section  450  is regulated. 
     As shown in  FIG. 23 , die member  438  has a die plate  440  and is connected to a guide cone  458  by means of a cone fastening screw  456  and a centering pin  454 . 
       FIG. 24  shows an operating state of pressure regulating device  426 , in which pins  474  are in a state that narrows annular channel section  450  less than in  FIG. 23 . Piston  494  can be moved to the left—in the drawing plane—by introducing pressurized fluid via an inlet/outlet for pressurized fluid  484  into the cylinder chamber  496  on the side of piston  494  facing away from bellows  492 . Provided that pressurized fluid can flow out of inlet/outlet  486 , introducing pressurized fluid via inlet/outlet  484  causes piston  494  to move to the left in the plane of the drawing, and pins  474  coupled to piston  494  to move to the left and thus at least partially out of annular channel section  450  and die member flow channels  460 . 
       FIGS. 25 and 26  show alternative embodiments of die assembly  4  already described with reference to  FIGS. 4 and 5 . The embodiment shown in  FIGS. 25 and 26  differs specifically from the one shown in  FIGS. 4-5  by the shape of regulating section  52   a , which is concave in  FIGS. 25 and 26 , and by the shape of die member  38   a , which has a convex flow channel in the region of annular channel section  50  in  FIGS. 25 and 26 . 
       FIGS. 27 and 28  show another alternative embodiment of a regulating section  52   b  and die member  28   b . In  FIGS. 27 and 28 , regulating section  52   b  is now convex in shape. In the region of regulating section  52   b , die member  38   b  is correspondingly concave in shape. For the rest, reference is made to the description of  FIGS. 4-5 . 
       FIGS. 29 and 30  show another alternative embodiment of a die unit  528 . Die unit  528  has a die member  538  which is connected to a further member  530 . In combination with an axially adjustable guide cone  558 , base member  530  forms an annular channel section  550 . The free cross-section of flow in annular channel  550  can be influenced by moving the axially adjustable guide cone  558  translationally relative to base member  530 . Guide cone  558  is axially adjusted as follows: The axially adjustable guide cone  558  is initially guided in a translationally movable manner relative to die member  538  by means of a conical guide  592 . Guide cone  558  is adjusted fluidically here. To that end, die member  538  is configured in such a way that it forms a first pressure chamber  580  in combination with a pressure chamber ring  590 . If pressurized fluid is introduced into the first pressure chamber  580 , the axially adjustable guide cone  558  is thus moved to the left in the plane of the drawing. 
     A second pressure chamber  582  which is sealed against a distributor section  854  by means of a sealing ring  586  is also formed in guide cone  558 . If pressurized fluid is now introduced into the second pressure chamber  582  by means of inlet/outlet  588 , this results in the axially adjustable guide cone  558  moving to the right in the plane of the drawing, and in the free cross-section of flow being reduced in the region of annular channel section  550 . In the same way, introducing pressurized fluid into the first pressure chamber  580  causes the axially adjustable guide cone  558  to move to the right in the plane of the drawing. The result is that the free cross-section of flow is increased in the region of annular channel section  550 . Cone  558  has a trapezoidal section  596  on its side facing annular channel section  550 , for influencing the cross-section of flow in annular channel section  550 . 
     An alternative embodiment of a die unit  528   a , which likewise implements the basic principle of an axially adjustable guide cone  558   a , is shown in  FIGS. 31 and 32 . A bellows  594  is arranged between the axially adjustable guide cone  558   a  and die unit  538   a . If the axially adjustable guide cone is in an extended state, as shown in  FIG. 31 , in which the axially adjustable guide cone  558   a  has been moved to the left in the plane of the drawing, bellows  594  rests tightly against a transition area between the axially adjustable guide cone  558   a  and die unit  538   a . This means that the free flow cross-section of annular channel section  550  is not constricted by bellows  594 . 
     In the state shown in  FIG. 32 , however, the axially adjustable guide cone  558   a  is in a retracted state, i.e., it is moved to the right in the plane of the drawing, in comparison with  FIG. 31 . If the axially adjustable guide cone  558   a  is in the respective state, bellows  594  is compressed, which causes it to arch into the region of the annular channel section. This in turn causes a reduction in the free cross-section of flow in the region of annular channel section  550 . 
     The free cross-section of flow in the region between base member  530  and the axially adjustable guide cone  558   a  is additionally adjusted by moving guide cone  558   a  translationally relative to base member  530 . 
     An alternative mechanical adjusting device for axially adjusting a guide cone  658  is shown in  FIGS. 33 and 34 . Guide cone  658  is initially guided in an axially adjustable manner inside die member  638 . In the region of its longitudinal axis, die member  638  has a bore into which a set screw  696  is inserted. Set screw  696  can be actuated from outside the device, in particular from the die plate  640  side. A nut  698  is fitted on set screw  696 . The axially adjustable guide cone  658  also has a bore arranged in the region of its longitudinal axis, which bore has an internal thread in which an external thread applied to set screw  696  can engage. Rotatability of the axially adjustable guide cone  658  is inhibited by a centering pin  654 , so any rotation of set screw  696  results in the axially adjustable guide cone undergoing a translational movement in the axial direction, depending on the direction of rotation. The flow cross-section between guide cone  658  and base member  630  is influenced by the axial position of guide cone  658 . 
       FIGS. 35 and 36  show a further embodiment in which mechanical axial adjustment of a guide cone  758  is likewise performed. However, the respective adjusting element or adjusting pin  796  is no longer in the region of a die plate  740 , but extends radially outwards from a die member  738 . To that end, valve pin  796  is arranged in a radial recess in die member  738 . On its inwardly facing side, adjusting pin  796  has a gear section  782 , in combination with a rotating body  798 . By means of gear section  782 , a rotational movement of valve pin  796  is transferred to rotating member  798  in such a way that the latter can now be rotated about an pivot axis that corresponds substantially to the longitudinal axis of die member  738 . Rotating member  798  is guided by means of a ball bearing  786 . The position of rotating member  798  on a receiving portion  784  of die member  738  is fixed, in addition, by a lock ring  788 . An external thread  780  which engages with a guide cone internal thread  778  is also provided on some regions of rotating member  798 . This has the effect that any rotational movement of rotating member  798  will change the axial position of the axially adjustable guide cone  758 . This change in position of the axially adjustable guide cone  758  will in turn cause a change in the flow cross-section between base member  730  and the axially adjustable guide cone  758 . 
     Another alternative embodiment of a guide cone  858  that is fluidically adjustable in the axial direction is shown in  FIGS. 37 and 38 . The axially adjustable guide cone  858  is mounted axially movably in a die member  838  and is axially adjustable by means of fluid which can be introduced into a first pressure chamber  880  and a second pressure chamber  882 . Axial adjustment of guide cone  858  causes a change in the flow channel between a base member  830  and the axially adjustable guide cone  858 . The free cross-section of flow in annular channel section  850  is not changed by axial adjustment of guide cone  858 . 
       FIG. 39  shows a die unit  928  which has a die member  938  in which throttle pins  996  extend radially inwards. A guide cone  958  is arranged on die member  938 .  FIGS. 40 and 41  show sectional views of a region in die member  938 . Die member flow channels  960  extend here through die member  938 . These channels conduct fluid from a flow channel  960  adjacent guide cone  958  to die plate  940 . Throttle pins  996  are arranged in die member  938  to regulate the free cross-section of flow in die member flow channels  960 . These throttle pins  996  can be actuated from outside die member  938  and restrict the free cross-section of flow of die member flow channels  960  depending on how far throttle pins  996  are inserted into die member flow channels  960 . In the state shown in  FIG. 40 , throttle pin  996  restricts die member flow channel  960  only partially. In the state shown in  FIG. 41 , throttle pin  996  is inserted almost completely into die member flow channel  960  and restricts it almost completely. 
     Another alternative embodiment of a die unit  1028  is shown in  FIG. 42 . Die unit  1028  again has a die member  1038  in which slider rods  1096  are inserted. A guide cone  1058  is also arranged on die member  1038 . 
     The manner of operation of die unit  1028  can be seen in  FIGS. 43-45 . As shown in  FIGS. 43 and 44 , slider rods  1096  are coupled to slider elements  1098 . These slider elements  1098  have slider bores  1084  and are movably arranged inside a slider chamber  1082 . In the operating state shown in  FIG. 43 , slider bores  1084  are arranged so that they overlap die member flow channels  1060 . This means that slider elements  1098  do not influence or only slightly influence the free cross-section of flow of die member flow channels  1060 . 
     In the state shown in  FIG. 44 , slider element  1098  has now been moved with the aid of slider rods  1096  in such a way that slider bores  1084  only partially overlap die member flow channels  1060 . The free cross-section of flow is thus influenced by positioning slider elements  1098 .  FIG. 45  shows the state shown in  FIG. 44  in an alternative cross-sectional plane. It can be seen here also that die member flow channels  1060  are locally restricted by the position of slider element  1098 , such that the free cross-section of flow is influenced. 
     Another alternative embodiment is shown in  FIGS. 46-50 . Referring now to  FIG. 46 , a die unit  1128  has a pressure regulating device  1126 . Die unit  1128  has a base member  1130 . Adjusting screws  1196  are inserted into pressure regulating device  1126 . 
       FIGS. 47 and 48  show sectional views of die unit  1128  in different operating states. Die member  1138  has die member flow channels  1160 . A guide cone  1158  is connected to die member  1138 . The connection is made by means of a centering pin  1154  and a cone fastening screw  1156 . Pressure regulating device  1126  is coupled to die member  1138 , which has a base member  1130  in which a flow channel  1146  is formed in combination with guide cone  1158  of die unit  1128 . 
     Throttle elements  1198  are arranged in the region of said flow channel  1146  between base member  1130  and guide cone  1158 . Throttle elements  1198  are rotatably arranged on pivot axis  1194 . By means of an adjusting screw  1196  that acts on throttle element  1198 , throttle element  1198  can be pivoted into the region of flow channel  1146  between guide cone  1158  and base member  1130 , thus restricting the free cross-section of flow in said region, depending on the position of throttle element  1198 . In the state of throttle element  1198  as shown in  FIG. 47 , flow channel  1146  is not or only very slightly restricted. 
     In the state shown in  FIG. 48 , however, throttle element  1198  extends almost completely into the flow channel formed between base member  1130  and guide cone  1158 . The effects of positioning throttle elements  1198  are illustrated additionally in  FIGS. 49 and 50 . However, the throttle elements  1198  shown in  FIGS. 49 and 50  do not have any rotational axes in comparison to the throttle elements shown in  FIGS. 47 and 48 . 
       FIGS. 51 and 52  show an alternative embodiment of a die unit  1228 . Die unit  1228  has a die member  1238 . A slider adjustment device  1296  is arranged about a longitudinal axis of die member  1238 . Slider adjustment device  1296  is rotatably mounted. Slider elements  1298  each having slider bores  1284  are coupled to slider adjustment device  1296 . In the operating state shown in  FIG. 51 , the slider bores  1284  of slider adjustment device  1296  are arranged such that they overlap and are thus in alignment with die member flow channels  1260 . Thus, in the operating state shown in  FIG. 51 , no significant influence is exerted on die member flow channels  1260 . 
     In the state shown in  FIG. 52 , however, slider elements  1298  are not aligned with die member flow channels  1260 . In this case, the positioning of slider elements  1298  causes a restriction of die member flow channels  1260  and reduces the free cross section of flow. The free cross-section of flow can be regulated by positioning the slider elements  1298  relative to die member flow channels  1260 . 
     Another alternative embodiment of a die unit  1328  is shown in  FIGS. 53-56 .  FIG. 53 , firstly, shows a die unit  1328  with a die member  1338 . A die plate  1340  having die orifices  1342  is arranged on die member  1338 . An adjusting head  1380  is also arranged in the region of die plate  1340 . 
     The structure of die unit  1328  can be seen in detail in  FIG. 54 . Die unit  1328  has a die member  1338  in which die member flow channels  1360  are arranged. A guide cone  1358  is arranged on die member  1338 . An adjusting element  1384  is also arranged in the region of a longitudinal axis of die member  1338 . 
     Adjusting element  1384  has an adjusting head  1380  on a first side. An adjusting disc  1382  is arranged on adjusting element  1384 . Adjusting disc  1382  has adjusting disc bores  1386 . The diameter of adjusting disc bores  1346  is approximately the same as the diameter of die member flow channels  1360 . Depending on their position, i.e., depending in particular on the angle of rotation of adjusting disc  1382  relative to die member flow channels  1360 , it is possible to vary the free cross-section of flow in the region of die member flow channels  1360 . 
     If die member flow channels  1360  are aligned with adjusting disc bores  1386 , there is no significant restriction or limitation of fluid flow through die member flow channels  1360 . However, if adjusting disc  1382  is rotated by means of adjusting head  1380  from the position shown in  FIG. 54 , in such a way that adjusting disc bore  1386  is no longer aligned with die member flow channels  1360 , flow in die member flow channels  1360  is restricted. 
     This is illustrated in  FIGS. 55 and 56 . In the state shown in  FIG. 55 , adjusting disc bores  1386  are aligned with die member flow channels  1360 , so there is no or no significant restriction of fluid flow through die member flow channels  1360 . 
     In the state shown in  FIG. 56 , however, adjusting disc bores  1386  are no longer aligned with die member flow channels  1360 , so the cross-section of flow through die member flow channels  1360  is restricted in the region of adjusting disc  1382 . 
     An alternative embodiment of a die assembly  1428  is shown in  FIG. 57 . Die unit  1428  has an adjusting disc  1482  which is mounted movably relative to a die member  1438 . Adjusting disc  1482  has adjusting disc bores  1490  which can be positioned in alignment relative to die member flow channels  1460  so that there is effectively no restriction of fluid flow through die member flow channels  1460 , or, as shown in  FIG. 57 , they can be brought into a non-aligned position relative to the flow channels so as to restrict the flow of fluid through die member flow channels  1460 . Adjusting disc  1482  has a threaded section  1484  for controlling adjusting disc  1482 . An adjusting element  1486  arranged in die member  1438  has a worm  1488  in the region of one of its ends. Worm  1488  matches threaded section  1484  in such a way that rotating the adjusting element  1486  having worm  1488  will cause adjusting disc  1482  to rotate. Adjusting element  1486  is guided in such a way that one of its ends can be actuated from outside die member  1438 . 
       FIG. 58  shows a control block diagram  1500  for controlling a pressure regulating device  1510 . The arrangement has a pressure sensor  1502 , which is in signal communication with a controller  1506 . Depending on the pressure value measured by pressure sensor  1502 , controller  1506  actuates an actuator  1508 , which in turn actuates a pressure regulating device  1510  according to the pressure value measured by pressure sensor  1502 . By means of controller  1506 , the pressure in a plastic melt stream  1504  in the region of a die plate  1540  can be influenced in the desired manner and by means of the technical means mentioned and described in the embodiments. 
     LIST OF REFERENCE SIGNS 
     
         
           2  Pelletizing apparatus 
           4  Die assembly 
           6  Driver 
           8  Housing 
           10  Skid mount 
           12  Process water outlet 
           14  Pelletizer 
           16  Protective cover 
           18  Baseplate 
           20  Machine baseplate 
           22  Spacer elements 
           24  Process water inlet 
           26  Pressure regulating device 
           28  Die unit 
           30  Base member 
           31  Housing section 
           32  Fluid inlet side 
           34  Actuator 
           36  Actuating nut 
           38 ,  38   a , Die member 
         
           38 
           b  
         
           40  Die plate 
           42  Die orifices 
           44  Sleeve 
           46  Flow channel 
           48  Fluid discharge side 
           50  Annular channel section 
           52  Regulating section 
           52   a  Concave regulating section 
           52   b  Convex regulating section 
           54  Centering pin 
           56  Cone fastening screw 
           58  Guide cone 
           60  Die member flow channels 
           62  Bolt 
           64 ,  66  Fastening nuts 
           68  Flat washer 
           70  First abutment shoulder 
           72  Second abutment shoulder 
           74  Pins 
           104  Die assembly 
           126  Pressure regulating device 
           130  Base member 
           146  Flow channel 
           150  Annular channel section 
           174  Pins 
           176  Actuating element 
           178  Plunger 
           180  Actuating element (gear wheel) 
           182  Hand lever 
           184  Retaining ring 
           186  Regulating ring 
           188  Coupler 
           190  Cap ring 
           204  Die assembly 
           226  Pressure regulating device 
           230  Base member 
           236  Actuating nut/screw 
           246  Flow channel 
           250  Annular channel section 
           274  Pins 
           292  Mounting ring 
           294  Connecting ring 
           296  Extended pins 
           304  Die assembly 
           328  Die unit 
           338  Die member 
           340  Die plate 
           356  Cone fastening screw 
           358  Guide cone 
           398  Heating ring 
           426  Pressure regulating device 
           428  Die unit 
           430  Base member 
           432  Fluid inlet side 
           438  Die member 
           440  Die plate 
           446  Flow channel 
           450  Annular channel section 
           454  Centering pin 
           456  Cone fastening screw 
           458  Guide cone 
           460  Die member flow channels 
           474  Pins 
           484  Inlet/outlet for pressurized fluid 
           486  Inlet/outlet for pressurized fluid 
           488  First housing ring 
           490  Second housing ring 
           492  Bellows 
           494  Piston 
           496  Cylinder chamber 
           528 ,  528   a  Die unit 
           530  Base member 
           538 ,  538   a  Die member 
           540  Die plate 
           550  Annular channel section 
           558 ,  558   a  Axially adjustable guide cone 
           560  Die member flow channels 
           580  First pressure chamber 
           582  Second pressure chamber 
           584  Distributor section 
           586  Sealing ring 
           588  Inlet/outlet for pressurized fluid 
           590  Pressure chamber ring 
           592  Cone guide 
           594  Bellows 
           596  Trapezoidal section 
           630  Base member 
           638  Die member 
           640  Die plate 
           650  Annular channel section 
           654  Centering pin 
           658  Axially adjustable guide cone 
           660  Die member flow channels 
           694  Set screw receiver 
           696  Set screw 
           698  Nut 
           730  Base member 
           738  Die member 
           740  Die plate 
           758  Axially adjustable guide cone 
           760  Die member flow channels 
           778  Guide cone female thread 
           780  Male thread 
           782  Gear section 
           784  Receiving portion 
           786  Ball bearing 
           788  Lock ring 
           796  Adjusting pin 
           798  Rotating member 
           830  Base member 
           838  Die member 
           840  Die plate 
           850  Annular channel section 
           858  Axially adjustable guide cone 
           860  Die member flow channels 
           880  First pressure chamber 
           882  Second pressure chamber 
           884  Distributor section 
           886  Sealing ring 
           888  Inlet/outlet for pressurized fluid 
           890  Pressure chamber ring 
           928  Die unit 
           938  Die member 
           940  Die plate 
           958  Guide cone 
           960  Die member flow channels 
           996  Throttle pins 
           1028  Die unit 
           1038  Die member 
           1040  Die plate 
           1050  Annular channel section 
           1058  Guide cone 
           1060  Die member flow channels 
           1082  Slider chamber 
           1084  Slider bores 
           1096  Slider rod 
           1098  Slider element 
           1126  Pressure regulating device 
           1128  Die unit 
           1130  Base member 
           1138  Die member 
           1140  Die plate 
           1146  Flow channel 
           1150  Annular channel section 
           1154  Centering pin 
           1156  Cone fastening screw 
           1158  Guide cone 
           1160  Die member flow channels 
           1194  Pivot axis 
           1196  Adjusting screw 
           1198  Throttle element 
           1228  Die unit 
           1238  Die member 
           1260  Die member flow channels 
           1284  Slider bores 
           1296  Slider adjustment device 
           1298  Slider element 
           1328  Die unit 
           1338  Die member 
           1340  Die plate 
           1342  Die orifices 
           1350  Annular channel section 
           1354  Centering pin 
           1358  Guide cone 
           1360  Die member flow channels 
           1380  Adjusting head 
           1382  Adjusting disc 
           1384  Adjusting element 
           1386  Adjusting disc bore 
           1428  Die unit 
           1438  Die member 
           1460  Die member flow channels 
           1482  Adjusting disc 
           1484  Threaded section 
           1486  Adjusting element 
           1488  Worm 
           1490  Adjusting disc bore 
           1500  Control block diagram 
           1502  Pressure sensor 
           1504  Hot-melt adhesive flow 
           1506  Controller 
           1508  Actuator 
           1510  Pressure regulating device 
           1540  Die plate