Patent Publication Number: US-6902384-B2

Title: Apparatus for melt spinning and cooling a group of filaments

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an apparatus for melt spinning and cooling a group of filaments. 
   When synthetic threads are melt-spun from a polymer melt using a spinneret with a plurality of nozzle bores, a plurality of strand-like filaments is extruded. The filament strands coming out of the spinnerets must be cooled before being taken up in the form of threads or thread bundles after further treatment. The cooling agent used is preferably air, which flows perpendicularly to the thread direction and is trained onto the filaments. The cooling air can penetrate the group of filaments from the exterior toward the interior or from the interior toward the exterior. German Laid Open Publication DE 36 29 731 A1, for example, discloses a prior-art device in which the cooling air stream penetrates a group of filaments from the interior toward the exterior as disclosed. 
   In the prior-art device the group of filaments is produced by an annular spinneret of a spinning device. A cooling device is provided below the spinning device and comprises a coolant dispersing head that is substantially centered relative to the spinneret. This coolant dispersing head is connected with a holder through which a cooling medium is introduced into the interior of the coolant dispersing head. The coolant dispersing head has a porous shell that is made, for instance, of a sintered material, such that the cooling air flowing into the interior of the coolant dispersing head exits radially therefrom and permeates the group of filaments. In this type of device, the coolant dispersing head can be displaced between an operating position and a standby position to permit startup of spinning the group of filaments at the beginning of the process. In standby position, the coolant dispersing head is guided completely out of the spinning area at a distance from the spinneret, such that particularly prolonged downtimes are inevitable if the process is interrupted. To enable the coolant dispersing head to be guided into its operating position after spinning startup, a strong radial air stream is produced at the free end of the coolant dispersing head by means of an additional annular gap that is formed at the end of the coolant dispersing head. Particularly when the coolant dispersing head is swiveled, a problem occurs wherein the filament strands that are blown away by the coolant dispersing head stick together. Another drawback is that an additional air stream must be guided to the annular gap by additional guiding means within the cooling dispersing head. When the operating position is reached, this additional air stream must be shut off by additional means. 
   Thus, there is a need in the art to equip an apparatus of the initially described type with a flexible cooling device, which enables the coolant dispersing head to be rapidly brought into its operating position after spinning startup without an additional supply of air. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention achieves this object by providing a guide tube that encloses the coolant dispersing head in the form of a jacket leaving a clearance. The guide tube is open at its end facing toward the spinning device (blowing end). The guide tube and the coolant dispersing head can be axially displaced relative to one another to produce an air stream at the blowing end of the guide tube. 
   The present invention is characterized in that the cooling air stream that radially exits through the coolant dispersing head can be used to keep the filaments away from the coolant dispersing head while the coolant dispersing head is brought into its operating position. The intensity of the air stream at the blowing end of the guide tube can be adjusted by the degree of overlap between the guide tube and the coolant dispersing head. If the guide tube extends over the entire length of the coolant dispersing head, an air stream that is oriented substantially in axial direction is produced by the guide tube at the end of the coolant dispersing head. This air stream is trained onto the spinning device such that the path for adjusting the coolant dispersing head is kept free. Since the coolant dispersing head and the guide tube can be axially displaced relative to one another, this overlap between the guide tube and the coolant dispersing head can be canceled in the operating position, such that the radial cooling air stream produced by the coolant dispersing head can exit freely to cool the filament strands. 
   An especially advantageous further development of the present invention makes it possible to adjust the overlap between the guide tube and the coolant dispersing head solely by moving the coolant dispersing head. To this end, the guide tube is fixed to the holder. Within the guide tube, the coolant dispersing head can be axially moved relative to the holder and relative to the guide tube between the operating position and the standby position. The overlap required to generate the air stream is thus greatest in the standby position of the coolant dispersing head and becomes smaller as the coolant dispersing head is adjusted in the direction toward the operating position. This further development has the advantage that as the overlap decreases between the coolant dispersing head and the guide tube, the air stream exiting from the blowing end of the guide tube converges with the air stream of the coolant dispersing head exiting radially outside the guide tube to form a combined air stream, so that the filament curtain flares out due to this combined air stream. 
   The advantageous further development of the present invention offers a particularly flexible cooling device in which the degree of overlap at the coolant dispersing head can be adjusted independently of the position of the coolant dispersing head. For this purpose, the guide tube is designed to be axially movable on the holder. 
   To enable a flaring out of the annular filament curtain after spinning startup, a preferred further development of the present invention proposes to provide the free end of the coolant dispersing head with a centering shoulder, which has a circumferential collar that protrudes over the diameter of the coolant dispersing head. This causes the air stream flowing out of the blowing end of the guide tube parallel to the coolant dispersing head to be deflected in radial direction. In addition, the collar of the centering shoulder can be configured in such a way that an annular air gap is produced between the blowing end and the collar. 
   To obtain the strongest possible axially directed air stream at the blowing end of the guide tube, an advantageous further development of the present invention provides that the end of the coolant dispersing head facing away from the holder be connected with a connecting piece that is guided in the guide tube so as to form a seal. 
   To increase the air stream exiting from the blowing end of the guide tube, the inventive apparatus is advantageously configured such that the air stream reaches the guide tube from the pressure chamber through a plurality of lateral openings of the guide tube and is guided between the coolant dispersing head and the guide tube toward the blowing end. 
   In a particularly advantageous further development of the present invention, the coolant dispersing head is axially adjustable relative to the holder between the operating position and the standby position by means of an actuator. In the operating position, the coolant dispersing head is held to the spinning device by the actuator. This ensures that the coolant dispersing head is securely guided and held in its operating position after each replacement. 
   This actuator can be formed by electric, pneumatic or hydraulic means. 
   To exchange the coolant dispersing head directly from the cooling device positioned below the spinning device, the coolant dispersing head is detachably connected with the holder according to an advantageous further development of the present invention. Thus, the coolant dispersing head is removed from the holder in standby position and after cleaning or exchange is reinstalled on the holder. The holder with the feed lines for the coolant can advantageously be kept stationary. 
   The holder of the cooling device is preferably used to receive a finishing device, which is mounted to the holder below the coolant dispersing head. This finishing device comprises a finishing ring, which is contacted by the group of filaments and applies a finishing agent to the filaments. 
   To obtain uniform wetting and distribution of the finishing agent along the surface of the finishing ring on the one hand and to ensure low wear and secure thread guidance on the other hand, the finishing ring is preferably formed by several ceramic disks. 
   The further development of the present invention wherein the holder is pivotable relative to the spinning device is particularly advantageous to allow the cooling device to be guided completely out of the spinning line. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
     Some exemplary embodiments of the device according to the invention will now be described in greater detail with reference to the attached drawings in which: 
       FIG. 1A  is a schematic view of the apparatus when it is in operation, according to a first embodiment of the present invention; 
       FIG. 1B  is a schematic view of the apparatus when it is not in operation, according to the first embodiment of the present invention; and 
       FIG. 2  is a schematic view of a second embodiment of the apparatus of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Unless specific reference is made to one of the figures, the following description applies to both. 
   The invention comprises a spinning device  1  and a cooling device  2  arranged below the spinning device  1 . On its underside spinning device  1  comprises an annular spinneret  4 , which is connected with a spin pump  6  via a melt distributor  5 . Spin pump  6  is connected with a melt generator (not depicted) via a melt line  7 . 
   The cooling device  2  below spinning device  1  is provided with a holder  10  and a coolant dispersing head  9  that is connected with holder  10 . The coolant dispersing head  9  has a porous shell, which can be made, for instance, of a nonwoven material, a foam, a wire gauze, or a sintered material. At its free end, the coolant dispersing head  9  is sealed by a centering shoulder  11 . With its opposite end, coolant dispersing head  9  is guided in a guide tube  13  via a connecting piece  12 . Connecting piece  12  and coolant dispersing head  9  are interconnected via a detachable conical seat  16 . 
   Guide tube  13  is fixed to the holder  10  concentrically to the coolant dispersing head  9 . The inside diameter of guide tube  13  is larger than the outside diameter of coolant dispersing head  9 . One end of guide tube  13  protrudes from holder  10 . This end of guide tube  13  is referred to as the blowing end and is identified by reference numeral  15 . With its opposite end, guide tube  13  projects into a pressure chamber  17  which is formed in the interior of holder  10 . 
   The cylindrical connecting piece  12  is slidingly guided within guide tube  13 . In the guidance portion of connecting piece  12  a seal  22  is provided along the circumference relative to the wall of guide tube  13 . Connecting piece  12  is configured as a hollow cylinder and is connected with pressure chamber  17  within holder  10  via the open end of guide tube  13 . Pressure chamber  17  within holder  10  is connected with a pressure source via feed inlet  21 . 
   Through the open end of guide tube  13 , connecting piece  12  is connected with an actuator  25 , which is preferably embodied as a piston-cylinder unit and is held within pressure chamber  17  on holder  10 . Through actuator  25 , the coolant dispersing head  9  can be moved between an operating position and a standby position and vice versa. 
   Along the circumference of holder  10 , a finishing device  18  is provided, which comprises a finishing ring  19  mounted to holder  10 . Finishing ring  19  is supplied with a finishing liquid from the inside, which is fed via a line  20 . 
     FIG. 1A  shows the apparatus in operation. For this purpose, the coolant dispersing head  9  is held in an operating position by actuator  25 . The centering shoulder  11  of coolant dispersing head  9  rests against a limit stop  8  of spinning device  1 . Limit stop  8  is arranged on the underside of spinning device  1  and is substantially centered relative to spinneret  4 . 
   In the operating position, a cooling agent, preferably cooling air, is supplied via feed inlet  21  and a pressure chamber  17 , which is formed within holder  10 . Via pressure chamber  17 , the coolant is guided into the interior of coolant dispersing head  9  via the open end of guide tube  13  and the hollow cylindrical connecting piece  12 . The coolant now passes uniformly through the shell of coolant dispersing head  9  to the outside and penetrates a group of filaments  3  produced by spinneret  4  from the interior toward the exterior. After the filaments of filament group  3  have been cooled, they are finished in finishing device  18 . For this purpose, a finishing agent is supplied to finishing ring  19  via line  20 . This finishing ring  19  can be made, for instance, of a porous material, such that the finishing agent is uniformly distributed in finishing ring  19  and exits along the surface for finishing the filaments. After finishing, the filament bundle is ready for further processing. For instance, the group of filaments could be guided to form threads, which are wound up, or be combined into a thread bundle and deposited in a can. 
     FIG. 1B  depicts the inventive apparatus when it is not in operation. The coolant dispersing head  9  of cooling device  2  is in a standby position at a distance from spinneret  4 . The coolant dispersing head  9  with connecting piece  12  is axially displaced in thread direction within guide tube  13  by actuator  25 , such that the centering shoulder  11  of coolant dispersing head  9  is detached from limit stop  8  of spinning device  1 . Coolant dispersing head  9  plunges into guide tube  13 , such that guide tube  13  encloses at least a partial area of coolant dispersing head  9  in the form of a jacket. 
   In standby position, coolant dispersing head  9  can be easily detached from its conical seat  16 , for instance to be replaced by a new coolant dispersing head. Advantageously, such a replacement can only be performed by an operator to minimize interruption of production due to coolant head replacement. At the same time, while the coolant dispersing head  9  is removed, the underside of spinneret  4  can be cleaned. Holder  10  of cooling device  2  can be kept stationary during this process. However, holder  10  can also be designed to be height adjustable and/or pivotable relative to spinning device  1 . The height adjustability of holder  10  is particularly advantageous for setting the finishing position while the apparatus is in operation. 
   Only after any possible process disturbance has been eliminated, the process can be resumed by spinning startup. To return the coolant dispersing head  9  from its standby position to the operating position, a cooling air stream is supplied to coolant dispersing head  9  via pressure chamber  17 . In the area of coolant dispersing head  9  which is covered by guide tube  13 , the air stream exiting radially from the shell of coolant dispersing head  9  is taken up by guide tube  13  and is blown out through open blowing end  15  of guide tube  13  as a substantially axially directed air stream. The air stream flowing parallel to coolant dispersing head  9  is trained onto spinning device  1 , so as to prevent filament strands from entering into the trajectory of coolant dispersing head  9 . In addition, the radial air stream produced by coolant dispersing head  9  outside guide tube  13  acts on the filament curtain, so that any contact between coolant dispersing head  9  and the filament strands is excluded. 
   To increase the air stream exiting at blowing end  15 , guide tube  13  can be provided with one or several lateral openings  14  in the area of pressure chamber  17  through which pressure chamber  17  directly communicates with the interior of guide tube  13  and directly reaches blowing end  15 . In  FIGS. 1A and 1B , lateral openings  14  are represented by dashed lines. 
   The connection between blowing end  15  and pressure chamber  17  is thus only given in the standby position of coolant dispersing head  9 . In this position, connecting piece  12  with seal  22  is located directly at the open end of guide tube  13  below lateral opening  14 . Only after coolant dispersing head  9  has been brought into its operating position, the connection between pressure chamber  17  and blowing end  15  is interrupted in pressure-tight manner by seal  22  which is provided along the circumference of connecting piece  12 . 
     FIG. 2  depicts a further embodiment of an apparatus according to the invention. The embodiment shown in  FIG. 2  is substantially identical to that of the preceding embodiment, so that only the significant differences are described below. Components with like functions carry identical reference numerals. 
   The embodiment depicted in  FIG. 2  is not in operation. Coolant dispersing head  9  is held on holder  10  in its standby position. Coolant dispersing head  9  is slidingly guided in guide tube  13  via connecting piece  12 . The movement of coolant dispersing head  9  is controlled by actuator  25 . Guide tube  13  is axially displaceable in holder  10 . To this end, blowing end  15  of guide tube  13  is provided with one or several radially projecting webs  24  with which one or more actuators  27  engage. Actuator  27  is mounted on holder  10 . Between the circumference of guide tube  13  and holder  10 , a seal  28  is provided by means of which pressure chamber  17  is outwardly sealed. 
   Coolant dispersing head  9  held in guide tube  13  has a centering shoulder  11  at its free end. Centering shoulder  11  is provided with a circumferential collar  26  whose outside diameter is larger than the outside diameter of coolant dispersing head  9 . 
   After spinning startup, cooling air is supplied to coolant dispersing head  9  via pressure chamber  17 . Due to the areas of coolant dispersing head  9  that are covered by guide tube  13 , the radially exiting air stream of coolant dispersing head  9  is diverted by guide tube  13  and guided to blowing end  15 . The air stream exiting from blowing end  15  flows substantially parallel to coolant dispersing head  9  and is deflected in radial direction by collar  26  at the free end of coolant dispersing head  9 , so that the filament curtain flares out. 
   To permit a partial air stream in axial direction, collar  26  of centering shoulder  11  can be provided with a plurality of openings, such that a portion of the air stream exiting from blowing end  15  of guide tube  13  flows axially against the spinning device. 
   To change the degree of overlap between guide tube  13  and coolant dispersing head  9  in the standby position, guide tube  13  can be displaced by actuator  27  in the direction toward the free end of coolant dispersing head  9 . This enlarges the degree of overlap, such that a stronger air stream can be produced at the blowing end  15 . 
   In addition, a circumferential gap can be formed between blowing end  15  of guide tube  13  and collar  26  to generate a radially directed air stream. 
   After coolant dispersing head  9  has reached its operating position below spinning device  1 , guide tube  13  is returned to a lower position by actuator  27 , such that there is no overlap between guide tube  13  and coolant dispersing head  1 . This causes coolant dispersing head  9  to be axially moved within guide tube  13  via connecting piece  12  and actuator  25 . 
   The embodiments shown in  FIGS. 1A and 2B  are given by way of example with respect to their construction and their type. The invention extends not only to the exemplary embodiments shown here but comprises any cooling device with which a person skilled in the art will be familiar and in which a relative motion can be executed between the coolant dispersing head and the holder in order to adjust the coolant dispersing head between an operating position and a standby position.