Abstract:
A device and method for applying a liquid to at least one advancing yarn which is guided over a surface of a driven godet in contact therewith. A liquid is supplied through a plurality of capillaries to the surface. To this end, the pore-sized openings of the capillaries are evenly distributed on the godet surface being wetted.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a national phase application of PCT/EP 98,/06029, filed Sep. 22, 1998. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a godet for applying a liquid to an advancing yarn wherein the yarn is advanced over the outer surface of the godet as the godet rotates about its axis and wherein the liquid is applied in measured quantities to the surface of the godet so as to be applied to the yarn. 
     DE 29 08 404 discloses a method and an apparatus for applying a liquid to an advancing yarn. The apparatus is formed by a driven godet, which comprises radially peripheral surface areas that can be wetted. A metering device applies the liquid for lubricating the yarn in measured quantities to the surface of the godet. The yam advances over the wetted surfaces in contact therewith and thus receives its coating of the lubricant. 
     This known method has the disadvantage that the liquid made available on the surface for lubricating the yam decreases as the circumferential speed of the godet increases. Thus, a slowly advancing yarn is offered a relatively large quantity of liquid and a fast advancing yarn a relatively small quantity of liquid. Consequently, fast advancing yarns at a speed greater than 3,000 m/min can be lubricated by this method only inadequately. 
     DE 43 33 716 discloses a method and an apparatus, wherein the godet surface comprises a groove. In this groove, a liquid for lubricating a yarn is sprayed from the outside. For the lubrication, the advancing yarn is guided over the groove of the godet. Likewise, this method shows the tendency that a small amount of liquid is offered to a relatively fast advancing yarn for its lubrication. 
     It is therefore the object of the invention to improve a method and an apparatus of the initially described kind, so that they ensure a uniform lubrication of a yarn regardless of its speed. 
     SUMMARY OF THE INVENTION 
     The above and other objects and advantages of the present invention are achieved by the provision of a godet which defines a cylindrical outer surface, and which includes a plurality of substantially radially oriented capillaries formed in the godet and communicating with the outer surface so as to define openings on the outer surface which are distributed circumferentially thereabout. Also, a liquid supply device is connected to the capillaries for supplying a liquid to the capillaries and thus to the openings on the outer surface. 
     In use, the liquid is metered onto the outer surface of the godet through the capillaries and openings, and the openings are distributed over the surface of the godet. Thus, metering of the liquid is determined by the diameters of the capillaries, the number of the capillaries, as well as the rotational speed of the godet. By merely increasing the rotational speed of the godet and, thus, the surface speed, the quantity of the liquid emerging from the capillaries increases. With that, it is possible to use the method as well as the apparatus even at higher yarn speeds of more than 3,000 m/min without subjecting the lubrication effect to a change. 
     To lubricate one or more yarns, it is preferred to drive the godet by a motor. However, both the method and the apparatus of the present invention also offer the possibility of constructing the godet without a drive. In this instance, the yarn or yarns drive the godet. A speed control would here be possible, for example, by means of an adjustable brake. The metering is directly determined by the yarn speed. Thus, due to the centrifugal force at high yarn speeds and, with that, at high circumferential speeds of the godet, a larger quantity of liquid is present on the surface of the godet that is contacted by the yarn. 
     A further advantage of the invention lies in that the liquid emerging from the surface distributes very evenly over the surface. This permits metering the liquid that is applied to the yarn. 
     Likewise, the path of the advancing yarn never dries, since the liquid is constantly supplied to the yarn even from the bottom. 
     The method will be especially advantageous and efficient, when the liquid is supplied to the capillaries inside the godet. The liquid is guided without losses to the surface of the godet. The transfer into the capillaries occurs alone due to the centrifugal forces. 
     The capillaries extend in the surface areas that serve to lubricate the yarn. However, it will be especially advantageous, when the pore-sized openings of the capillaries are evenly distributed over the entire surface on the circumference of the godet. With that, it is possible to realize a very uniform lubrication in that the yarn loops about the godet several times. In particular, in the case of low yarn speeds, it will be possible to lubricate therewith several, parallel guided yarns at the same time. To this end, the yarns advance over the godet parallel with a multiple looping. 
     The variant of the method, wherein the capillaries are formed in a sleeve that is slipped over the godet casing distinguishes itself in particular in that a varied metering is to be realized in a simple manner irrespective of the rotational speed of the godet. In this connection, a sleeve slipped over the godet casing may be replaced with a second sleeve having differently configured capillaries. 
     To obtain a great evenness of the capillaries, it will be especially advantageous to make the sleeve of a sintered material. 
     To lubricate several yarns evenly with one godet, the variant of the method is especially advantageous, wherein the yarn advances with a partial looping on the godet circumference. To this end, in one embodiment of the apparatus according to the invention the pore-sized openings of the capillaries are evenly arranged within a plurality of parallel juxtaposed, radially peripheral surface areas of the godet casing or sleeve. Each of the surface areas forms a path for wetting a yarn. 
     In a particularly advantageous embodiment of the apparatus according to the invention, the liquid supply to the capillaries in the sleeve proceeds through a plurality of grooves arranged in the godet surface that is covered by the sleeve. In this connection, the grooves may be formed in the godet surface radially, axially or spirally. The grooves connect to the liquid supplying device, so that the liquid required for lubricating the yarn is continuously present within the groove. 
     The diameters of the capillaries, the number of capillaries, as well as the rotational speed of the godet determine the amount of liquid available on the surface for lubricating the yarn. The diameter of the capillaries that is selected as a function of the yarn denier is preferably in a range from 10 μm to 1,000 μm. In this connection, a number of capillaries are selected that covers from minimally 2% to maximally 75% of the surface. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Some of the objects and advantages of the present invention having been stated, others will appear as the description proceeds, when considered in conjunction with the accompanying drawings, in which 
     FIG. 1 shows an apparatus of the present invention for applying a liquid to a plurality of advancing yarns; 
     FIG. 2 is a schematic, cross sectional view of the casing of the godet of FIG. 1; 
     FIG. 3 shows an apparatus of the present invention for lubricating an advancing yarn; and 
     FIG. 4 is a schematic, cross sectional view of the casing of the godet of FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a first embodiment of an apparatus for applying a liquid to a plurality of advancing yarns. The apparatus consists of a godet  2  that connects to a drive shaft  4 . A godet drive  3  drives the shaft  4  in such a manner that the godet surface moves in the direction of the advancing yarn, as is indicated by an arrow. A sleeve  10  is securely slipped over the circumference of godet  2 . The sleeve  10  comprises a plurality of parallel juxtaposed, radially peripheral surface areas  5 . The surfaces  5  contain a plurality of substantially evenly distributed, pore-sized openings  8 , which are formed by a corresponding number of capillaries  6  that extend substantially radially into the sleeve  10 . 
     The godet  2  connects to a liquid supplying device  9 . FIG. 2 is a schematic, cross sectional view of the godet of FIG.  1 . The liquid supplying device  9  constructed as a tube extends into an axially directed annular groove  13  that is formed in godet casing  7 , and which is radially offset from the central axis of the godet. The annular groove  13  is arranged for rotation in godet casing  7 . The liquid supplying device comprises an outlet  14  at the end of the tube portion that extends into the annular groove  13 . The outlet  14  is arranged in the vicinity of the internal end of annular groove  13 . At the internal end of the annular groove  13  inside the godet casing  7 , a plurality of radial bores  12  arranged in a normal plane are provided. The bores  12  connect the annular groove  13  to a plurality of grooves  11  arranged in the surface of godet casing  7 . The sleeve  10  covers the grooves  11 . A plurality of capillaries  6  extend in the radial direction through the sleeve  10 . The capillaries  6  represent a connection between the grooves  11  and the surface  5  of sleeve  10 . Yarns  1  contact the surface  5 . 
     To lubricate yarns  1 , the godet is driven by godet drive  3 . In this connection, it is preferred to adjust the surface speed such that it is equal to the speed of the advancing yarn. However, it is also possible to generate a relative speed between the yarn  1  and the surface  5 . At the same time, the annular groove  13  receives via liquid supplying device  9  the liquid that is required for lubricating the yarn. From the annular groove  13 , the liquid flows due to the centrifugal force through bores  12  to the grooves  11 . Subsequently, the liquid enters from grooves  11  into the capillaries  6  of sleeve  10 , and reaches through capillaries  6  the surface  5 . On the surface  5 , the liquid is picked up by the yarn  1  respectively advancing thereover. Besides the rotational speed of the godet, the amount of liquid emerging from the surface  5  is dependent on the number of capillaries as well as their size. 
     In the apparatus shown in FIGS. 1 and 2, the sleeve  10  is exchangeable. By exchanging sleeves  10  with respectively differently shaped capillaries, it is possible to vary the metering of the liquid. 
     The surface areas contacted by the yarn have a roughness from Rz 2.4 to Rz 10, so that even higher loopings are possible for applying the liquid. 
     FIG. 3 shows an apparatus, wherein a yarn  1  is lubricated by looping several times about a godet  2 . In its construction, the apparatus of FIG. 3 is similar to that of FIG.  1 . To this extent, the description of FIGS. 1 and 2 is herewith incorporated by reference. 
     Unlike the embodiment of FIG. 1, FIG. 3 shows a godet  2 , wherein the pore-sized openings  8  of the capillaries  6  are evenly distributed over the entire surface  5  of godet casing  7 . As shown in FIG. 4, the capillaries  6  are directly provided in the godet casing  7 . In this embodiment, the capillaries  6  terminate in the annular groove  13  within godet casing  7 . The annular groove  13  in godet casing  7  connects again to the liquid supplying device  9 . Thus, the liquid arrives from the annular groove  13  through the capillaries  6  at the godet surface  5 . The godet surface  5  is therefore evenly wetted with the liquid over the entire area, thereby permitting a uniform lubrication of yarn  1 . 
     A sintered material may advantageously produce the capillaries in sleeve  10  as well as in godet casing  7 . However, it is also possible to use other porous, permeable materials for forming the capillaries in the godet casing. 
     A further possibility consists in working capillaries as bores into a metallic surface, for example, by laser beams.