Patent Abstract:
The invention relates to a device for the compression crimping of a synthetic multifilament yarn, said device comprising a transport nozzle and a compression chamber. Said transport nozzle comprises a yarn channel by which means a yarn is guided to a compression chamber. Said compression chamber forms a section having a gas-permeable chamber wall, between a yarn inlet and an enmeshment outlet. According to the invention, the gas-permeable chamber wall comprises a friction surface consisting of material which is resistant to wear, on the inner side facing the yarn enmeshment. The constancy of the braking action produced by the friction on the yarn enmeshment can thus be significantly improved.

Full Description:
The invention relates to a device for the stuffer box crimping of a synthetic multifilament yarn. 
   The disclosure in German Patent Application 101 32 148.1 of Jul. 3, 2001 and PCT/EP02/07161 of Jun. 28, 2002 are incorporated herein by reference. 
   BACKGROUND OF INVENTION 
   An example of a device for the stuffer box crimping of a multifilament yarn is disclosed in EP 0 554 642 A1 and corresponding U.S. Pat. No. 5,351,374. The device comprises a conveying nozzle and a stuffer box arranged downstream from the conveying nozzle. The yarn is conveyed by means of the conveying nozzle into the stuffer box, compressed to a yarn plug and thereby stuffer box crimped. The conveying nozzle is loaded with a conveying medium, preferably a hot gas, which conveys the yarn within the yarn channel to the stuffer box. The yarn plug is formed inside the stuffer box. In doing so, the multifilament yarn deposits itself in loops on the surface of the yarn plug and is compressed by the conveying medium, which can discharge above the yarn plug out of the stuffer box. To do so, the chamber wall of the stuffer box comprises several slot-shaped openings on the perimeter through which the conveying medium can escape. In order to obtain uniform crimping of the yarn, plug formation must result with very high uniformity in the stuffer box. Thus, the friction forces caused by the relative motion of the yarn plug in the stuffer box have a substantial impact on the texturizing process. A counterbalance of forces exists between the conveying effect, or the dynamic pressure effect of the conveying medium flowing from the yarn channel of the conveying nozzle, and the braking action resulting from the friction forces on the yarn plug. Adjusting the conveying pressure, or adjusting additional suction of the conveying medium, essentially determines the conveying effect. In contrast, the braking action resulting from the friction between the yarn plug and the chamber wall essentially depends on the condition of the chamber wall. 
   In the device disclosed in EP 0 554 642 A1, only a slight number of friction surfaces exist due to the slot-shaped openings especially in the section with the gas-permeable wall. Therefore, wear marks are unavoidable in prolonged operation, which results in a change in the braking action. If the braking action decreases sufficiently, the yarn plug will be conveyed out of the stuffer box due to small frictional forces. The texturizing process then fails. On the other hand, as frictional forces increase, the yarn plug is no longer or no longer uniformly conveyed out of the stuffer box. Non-uniform stuffer box crimping occurs when a stick-slip effect begins in the stuffer box. These effects cannot be controlled with a dynamic medium opposing the conveying medium. 
   In contrast, one task of the present invention is to further improve a stuffer box crimping device for synthetic multifilament yarn in such a manner that uniform crimping is ensured in the yarn, even during very prolonged operation. 
   SUMMARY OF INVENTION 
   According to this invention, the task is solved by a device for compressing a synthetic, multifilament yarn, the device including a conveying nozzle and a stuffer box. The conveying nozzle includes a yarn channel for guiding and conveying the yarn. The stuffer box is arranged at the end of the yarn channel to form and collect a yarn plug. The stuffer box includes a yarn inlet, a plug outlet, and at least a section with a gas-permeable chamber wall between the yarn inlet and the plug outlet. The gas-permeable chamber wall includes a friction surface made of wear-resistant material on an inner side facing the yarn plug. 
   The friction surface of the section may be a coating applied to the surface of the gas-permeable chamber wall. Alternatively, the gas-permeable chamber wall is a ceramic material that forms the friction surface on the surface of chamber wall. 
   The gas-permeable chamber wall may be formed as a cylindrical body with elongated slots evenly distributed along the circumference. Alternatively, the gas-permeable chamber wall may be formed by a plurality of blades arranged in a ring-shape with little separation distance from each other. 
   The stuffer box may include an additional section downstream from the section with the gas-permeable chamber wall. The additional section includes an enclosed chamber wall. The enclosed chamber wall includes a contact surface made of wear-resistant material on the inner side facing the yarn plug. 
   As with the section, the friction surface of the additional section may be a coating applied to the surface of the enclosed chamber wall. Alternatively, the enclosed chamber wall is a ceramic material that forms the friction surface on the surface of chamber wall. 
   Further, the contact surfaces contacted by the yarn within the conveying nozzle may be at least partially formed from a wear-resistant material. The wear-resistant material may be in the form of a coating or a ceramic material. 
   The conveying nozzle may include a guide insert forming an inlet of the yarn channel. The guide insert includes an intake channel arranged as an extension of the yarn channel. Also, the conveying nozzle may include a second guide insert forming the outlet of the yarn channel. As with the guide insert, the second guide insert may be manufactured from a ceramic material or coated on its surface. Further, the conveying nozzle may include a third guide insert forming the air inlet into the yarn channel. The third guide insert forms a guide channel arranged as an extension of the yarn channel. The third guide insert forms an outlet channel arranged as an extension of the yarn channel. The guide inserts may be manufactured from a ceramic material or coated on its surface. 
   The third guide insert may further include an insert forming the inlet of the guide channel. The insert forms an intake channel arranged as an extension of guide channel. The inserts may be manufactured from a ceramic material or coated on its surface. 
   Any one of a conveying device, cooling device, and a conveying device in combination with a cooling device may be arranged downstream from the stuffer box in the yarn&#39;s direction of travel. The conveying device and the cooling device may include a coating on the contact surfaces contacted by the yarn plug. 
   The invention is based on the knowledge that depositing of the yarn on the yarn plug surface by self-shaping loops and coils significantly influences crimp uniformity. In order to maintain the yarn&#39;s point of impact on the yarn plug surface at an essentially unchanging height, the balance of forces between the conveying effect and the brake action at the yarn plug resulting from the friction must be held constant. This can be essentially achieved by the device according to this invention in that the gas-permeable chamber wall comprises a friction surface made of wear-resistant material on the inner side facing the yarn plug. Thereby, a change in the friction forces is not possible even in extended operation. Thus, the invention has the advantage that plug formation is solely controlled by controlling the conveying medium by, for example, means of pressure control. 
   The wear-resistant material on the surface of the chamber wall can be constructed essentially from two variants. In an initial especially preferred embodiment of the invention, the friction surface is formed by a coating applied to the chamber wall surface. This coating could consist, for example, of a ceramic material, a chrome oxide or a carbon coating. The possibility also exists to manufacture the chamber wall from aluminum in order to then form anti-wear protection by means of a hard oxide coating. 
   In another especially preferred embodiment of the invention, the friction surface is formed by a chamber wall manufactured from a ceramic material. To this end, the chamber wall can be manufactured out of ceramic materials such as zircon oxide, aluminum oxide or a combination of both. 
   The use of ceramic coatings, or ceramic materials, also achieves a corrosion-resistant gas-permeable wall and decreased fallibility to fouling. In particular, deposits caused by preparation residue may be avoided. Even after a maintenance period, the same friction specifications are achieved when operating the device as prior to shutting down the facility. 
   Regardless whether a coating or solid-ceramic is used to form the friction surface, the gas-permeable chamber wall can be designed as a cylindrical body with evenly distributed elongated slots along its circumference. 
   However, an especially preferred embodiment has a gas-permeable chamber wall with a plurality of blades that are arranged in a ring-shape with clearance from each other. Thus, it was observed in the use of ceramic blades that decreasing the friction coefficient subjects the yarn to less of a thermal and mechanical load. 
   In order to avoid wear inside the stuffer box on all sides contacting the yarn plug, an additional section with an enclosed chamber wall may be provided. In accordance with a preferred embodiment of this invention, the stuffer box includes an additional section with an enclosed chamber wall. The additional section is downstream from the section with the gas-permeable chamber wall. The enclosed chamber wall includes a contact surface comprised of a wear-resistant material on the inner side facing the yarn plug. 
   The contact surface could be formed by a coating applied to the surface of the chamber wall or by a chamber wall manufactured from ceramic material. 
   It was observed that when using a conveying nozzle with ceramic sides at least on parts of the surface contacting the yarn, that the yarn tension reduction in the conveying nozzle was reduced by the friction of the yarn on the side. In accordance with a preferred embodiment, the contact surfaces contacted by the yarn within the conveying nozzle are at least partially formed from a wear-resistant material in the form of a coating or a ceramic material. Thus, higher yarn tension can be achieved with the same conveying pressure, which results in higher operational uniformity of the texturizing process. On the other hand, yarn tension can be achieved with a lower pressure, whereby a lower conveying pressure results in less consumption of the conveying medium. The contact surface&#39;s wear-resistant material inside the conveying nozzle can be formed of coatings or ceramic base materials. Thus, the conveying nozzle can be preferentially manufactured entirely out of ceramics. 
   In another embodiment variant of the invention, the inlet of the yarn channel is formed by means of a guide insert in the conveying nozzle. The guide insert, which can be manufactured from a ceramic material or carry a coating on its surface, forms an intake channel as an extension of the yarn channel. Wear, in particular, at the yarn&#39;s entry into the conveying nozzle is thereby avoided. Using ceramic materials or ceramic coatings also enables a very low friction guidance of the yarn. 
   The conveying nozzle could also comprise a guide insert forming the yarn channel&#39;s outlet, which is also manufactured from a ceramic material or carries a coating on its surface. The yarn thereby leaves the conveying nozzle through the guide insert&#39;s outlet channel. 
   To convey the yarn, a conveying medium, preferentially hot air or a hot gas, is supplied. In order not to have any scouring in the yarn channel even at very high flow speeds, that may even lie in the range of the speed of sound, the air inlet into the yarn channel is formed by means of a guide insert, according to a preferred embodiment of the invention. Next to the air inlet, the guide insert comprises a guide channel that is arranged as an extension of the yarn channel. The guide insert is also made of a ceramic material or carries a coating on its surface. 
   Since the conveying medium flowing into the yarn channel results in a sudden dynamic load for the yarn, in a preferred embodiment of the invention, the third guide insert includes an additional insert forming the inlet of the guide channel. The additional insert forms an intake channel arranged as an extension of the guide channel. Also, the additional insert is either manufactured from a ceramic material or coated on its surface. The third guide insert in the area of the air inlet includes the additional insert in the inlet of the guide channel. In this manner, yarn guidance is stabilized and disturbances affecting the yarn are avoided. 
   To guide and condition the yarn plug, a cooling device is arranged downstream from the stuffer box at the plug outlet. In some cases a conveying device is provided between the cooling device and the stuffer box to guide the yarn plug. In order to avoid premature fouling and adhesion of preparation residue, in a preferred embodiment according to the present invention, the conveying device and the cooling device comprise a coating on the contact surfaces contacted by the yarn plug. 
   The invention is further described by means of several embodiments depicted in the attached illustrations. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  schematically depicts an initial embodiment of the device in accordance with this invention in a cross-sectional view; 
       FIG. 2  schematically depicts an additional embodiment of the device in accordance with this invention in a sectional cross-section; 
       FIG. 3.1  schematically depicts an embodiment of a conveying nozzle in a cross-sectional, exploded view; and 
       FIG. 3.2  schematically depicts an embodiment of a conveying nozzle in a cross-sectional view. 
   

   DETAILED DESCRIPTION 
     FIG. 1  schematically depicts a cross-sectional view of an initial embodiment of the device in accordance with this invention. The device consists of conveying nozzle  1  and stuffer box  2  arranged downstream from conveying nozzle  1 . Conveying nozzle  1  comprises yarn channel  3  that forms inlet  21  on one end and outlet  24  on the opposite end. Conveying nozzle  1  is connected to a pressure source (not depicted) by means of feed line  17 . Feed line  17  is connected to yarn channel  3  by air inlet  16  and pressure chamber  39 . Air inlet  16  is formed by several boreholes that supply a conveying medium in yarn travel direction, marked by an arrow, to yarn channel  3 . Yarn channel  3  merges into yarn channel  31  of stuffer box  2  by means of outlet  24 . 
   Stuffer box  2  is formed by section  7 . 1  facing conveying nozzle  1  having yarn inlet  5 , and section  7 . 2 , arranged downstream from section  7 . 1 , having a plug outlet  6 . In section  7 . 1 , plug channel  31  is formed by a gas-permeable chamber wall  8 . Gas-permeable chamber wall  8  comprises a multiplicity of blades  9  that are arranged in a ring in close proximity to each other. Blades  9  are held by blade holders  10 . 1  on the upper end of section  7 . 1  and by holder  10 . 2  on the lower end of section  7 . 1 . Blades  9  and holders  10 . 1  and  10 . 2  are arranged in housing  11 , whereby housing  11  is enclosed to the outside and connected to suction  12  by opening  32 . 
   On the side facing yarn plug  13 , blades  9  each comprise friction surface  14 . Blades  9  are made of a ceramic material so that friction surfaces  14  consist of a wear-resistant material. 
   Enclosed chamber wall  15  is provided below the gas-permeable chamber wall  8 , which forms plug channel  33 . Plug channel  33  is designed to have a larger diameter than the plug channel  31  in the area of the gas-permeable chamber wall  8 . At its end, plug channel  33  forms plug outlet  6 . 
   The embodiment of the device in accordance with this invention and depicted in  FIG. 1  is shown with a yarn course in order to clarify the device&#39;s function. Thus, yarn  4  is transported through conveying nozzle  1  into yarn channel  3  by means of a conveying medium supplied via air inlet  16 . Yarn  4  thereby enters into yarn channel  3  through inlet  21 . Hot air or a hot gas are preferentially used as conveying medium. The conveying medium flowing at high speed conveys yarn  4  at high speed to stuffer box  2 . In doing so, yarn plug  13  develops in plug channel  31 . Yarn  4 , comprised of a plurality of filaments, is deposited on the surface of yarn plug  13  in such a manner that the filaments form loops and coils. The conveying medium is suctioned off between and past blades  9  through opening  32 . Yarn plug  13  forming in plug channel  31  abuts on friction surfaces  14  of blades  9 . The friction forces and the conveying pressure of the conveying medium acting on yarn plug  13  are essentially counterbalanced so that the yarn plug height within the yarn channel  31  remains essentially the same. Since blades  9  are manufactured from a ceramic material, the counterbalancing forces acting on yarn plug  13  are essentially maintained by constant pressure of the conveying medium. After leaving plug channel  31 , yarn plug  13  enters into plug channel  33  that is formed by enclosed chamber wall  15 . Enclosed chamber wall  15  that could be constructed from a tube, for example, serves to feed yarn plug  13  to a downstream placed cooling device not depicted here. Plug channel  33  is designed larger than plug channel  31  so that only slight friction forces act on yarn plug  13 . Anti-wear protection is therefore unnecessary. 
     FIG. 2  schematically depicts an additional embodiment in a cross-sectional view. The embodiment is essentially identical in its design to the previous embodiment according to  FIG. 1 , so that hereafter only the essential differences will be pointed out. For clarity&#39;s sake, components having identical functions are identically labeled. 
   For additional acceleration of the conveying medium in yarn channel  3 , conveying nozzle  1  comprises its smallest diameter directly downstream from air inlet  16 . The conveying medium is thereby accelerated to a supersonic flow velocity. Yarn channel  3  merges into plug channel  31  that is formed by cylindrical body  18 . cylindrical body  18  is arranged in the first section  7 . 1  of stuffer box  2 . Cylindrical body  18  has distributed on its circumference several elongated slots  34 , whereby plug channel  31  is connected to the annulus  35  which is formed between the housing  11  and cylindrical body  18 . The annulus  35  is connected to suction  12  via the opening  32  in the housing  11 . On the side facing yarn plug  13 , cylindrical body  18  has a coating  19  which forms a friction surface  14  to guide a yarn plug. The coating  19  preferably consists of a ceramic material. However, metallic hard chrome layers or carbon compounds are also possible. Thus, cylindrical body  18  may also be manufactured from an aluminum material, which receives an aluminum oxide coating forming friction surface  14 . Elongated slots  34  extend at least over a portion of cylindrical body  18 . Elongated slots  34  extend at least over a portion of cylindrical body  18 . 
   The second section  7 . 2  of the stuffer box is formed by enclosed chamber wall  15  that comprises plug channel  33 . Plug channel  33  forms at its end plug outlet  6 . On the side facing yarn plug  13 , enclosed chamber wall  15  comprises contact surface  20  that also carries wear-resistant coating  35 . 
   Formed out of two opposing rollers, conveying device  29  is attached directly to stuffer box  2  at plug outlet  6 . Conveying device  29  guides the yarn plug  13  to a cooling device  30  arranged downstream from conveying device  29 . Cooling device  30  could be constructed from a cooling barrel on whose circumference the yarn plug is cooled. Both conveying device  29  and cooling device  30  are furnished with a coating on their contact surfaces  37  and  38 . 
   The function of the embodiment depicted in  FIG. 2  is essentially identical to the previous embodiment according to  FIG. 1 , so that depicting the yarn course was not repeated. However, yarn plug development can be also influenced by conveying device  29 . 
     FIGS. 3.1  and  3 . 2  schematically depict an embodiment of a conveying nozzle in a cross-sectional view as it might be used for example in the embodiment according to  FIG. 1  or the embodiment according to  FIG. 2 . The conveying nozzle is thus depicted in  FIG. 3.1  in a disassembled state and in  FIG. 3.2  in an assembled state. The following description applies for both illustrations, unless express reference is made to one of the illustrations. 
   Conveying nozzle  1  comprises in the areas of inlet  21 , air inlet  16 , outlet  24 , and grooves  36 . 1 ,  36 . 2 , and  36 . 3  respectively. 
   Grooves  36 . 1 ,  36 . 2 , and  36 . 3  are connected to each other by means of yarn channel  3 . Pressure chamber  39  is designed in conveying nozzle  1  between grooves  36 . 1  and  36 . 2 . Groove  36 . 1  in the intake section of conveying nozzle  1  serves to receive guide insert  22 . 1 . Guide insert  22 . 1  forms an intake channel  23  that is arranged as an extension of yarn channel  3 . Guide insert  22 . 1  is preferentially manufactured from ceramic material. However, it is also possible that guide insert  22 . 1  carries a coating in the area of the intake channel  23 . 
   Guide insert  22 . 2  is inserted into groove  36 . 2 . Guide insert  22 . 2  forms air inlet  16  through which the conveying medium is fed from pressure chamber  39  into guide channel  26  of guide insert  22 . 2 . Guide channel  26  of guide insert  22 . 2  is arranged as an extension of yarn channel  3 . Insert  27 , which forms intake channel  28 , is provided on the inlet side of guide insert  22 . 2 . Intake channel  28  has a smaller diameter than guide channel  26  located downstream. Insert  27  and guide insert  22 . 2  may also be preferentially manufactured from a ceramic material or furnished with a coating. 
   Guide insert  22 . 3  is embedded in groove  36 . 3  on the outlet side of conveying nozzle  1 . Guide insert  22 . 3  forms outlet channel  25  that is arranged as an extension of yarn channel  3  and forms outlet  24  of conveying nozzle  1 . Guide insert  22 . 3  is also preferentially manufactured from a ceramic material. 
   The conveying nozzle depicted in  FIGS. 3.1  and  3 . 2  consists of a wear-resistant material especially in the contact and friction areas heavily stressed by the yarn so that stable and uniform yarn guidance as well as yarn conveying are achieved. In addition, the friction coefficients between the yarn and the contact or friction points are substantially decreased. 
   In the device depicted in  FIGS. 1 to 3 , one should note that conveying nozzle  1  and stuffer box  2  are each preferentially formed out of two halves that are frictionally connected with each other during operation. However, it is also possible to basically provide one-piece conveying nozzles and stuffer boxes with corresponding ceramic inserts or coatings. Regardless of the device&#39;s design type, the possibility also exists, however, to manufacture each of the devices&#39; yarn-contacting areas from solid ceramics or a coated aluminum material. The device according to this invention thereby distinguishes itself especially by a high degree of wear-protection and thus stable friction behavior and non-sensitivity to yarn conditioning, as well as a substantial lengthening of the cleaning cycles due to the resistance to fouling. Using a device in accordance with this invention, the service life was increased 3- to 5-fold. When using the device in accordance with this invention, which was furnished with ceramic materials or ceramic material coatings, crimping of the yarn could be kept uniform over a substantially longer period than compared to conventional crimping devices. A significantly higher degree of production safety is thereby achieved. 
   Reference List 
   
       
         1  Conveying nozzle 
         2  Stuffer box 
         3  Yarn channel 
         4  Yarn 
         5  Yarn inlet 
         6  Plug outlet 
         7  Section 
         8  Gas-permeable chamber wall 
         9  Blade 
         10  Blade holder 
         11  Housing 
         12  Suction 
         13  Yarn plug 
         14  Friction surface 
         15  Enclosed chamber wall 
         16  Air inlet 
         17  Feed line 
         18  Cylindrical body 
         19  Coating 
         20  Contact surface 
         21  Inlet 
         22  Guide insert 
         23  Intake channel 
         24  Outlet 
         25  Outlet channel 
         26  Guide channel 
         27  Insert 
         28  Intake channel 
         29  Conveyance device 
         30  Cooling device 
         31  Plug channel 
         32  Opening 
         33  Plug channel 
         34  Elongated slot 
         35  Annulus 
         36  Groove 
         37  Contact surface 
         38  Contact surface 
         39  Pressure chamber 
     
  
   The disclosure in German Patent Application 101 32 148.1 of Jul. 3, 2001 and PCT/EP02/07161 of Jun. 28, 2002 are incorporated herein by reference. The German Patent Application and the PCT Application describe the invention described hereinabove and claimed in the claims appended hereinbelow and provided the basis for a claim of priority for the instant application. 
   While the invention has been illustrated and described as an embodiment of a device for compression crimping, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

Technology Classification (CPC): 3