Drafting device for fine spinning frame

Abstract: A three line type drafting device wherein first, second and third sets of drafting rollers (4 and 5, 6 and 7, and 13 and 16) are provided. The middle (second) set of rollers (6 and 7) are both constructed as apron rollers. In the back (third) set of rollers, the top roller (13) is constructed by an apron roller, while bottom roller (16) is constructed as a fluted roller. A guide plate (41) is arranged between the middle bottom and back bottom rollers (9a and 16) and is made to contact, at its top surface, with a lower side of the apron (14) of the back roller set. A desired control of floating fibers is obtained at a back drafting zone between the middle and back sets of rollers (6 and 7; and 13 and 16), while a desired total drafting ratio is obtained between the front and back set of rollers (4 and 5 and 13 and 16) without being influenced by inevitable variation in thickness of the apron (14) at the back roller set.

Description: DESCRIPTION OF THE INVENTION The present invention relates to a drafting device for a fine spinning frame of a sliver-to-yarn type. More particularly, the present invention relates to a three line type drafting device which is suitable for spinning at a high drafting ratio. Known in the prior art is a drafting device of a sliver-to-yarn type fine spinning frame, in which a spun yarn is obtained directly from a sliver. In such a sliver-to-yarn type fine spinning frame, a large value of a drafting ratio, which is a ratio, to a rotating speed of a roller at a inlet side (back roller), of a rotating speed of a roller at an outlet side (front roller) is used. In order to execute such a high draft operation, a drafting device of a four line type or a five line type has been proposed. In such a type of drafting device, a multiplicity of drafting zones are provided, which is advantageous in that a large value of a total drafting ratio is obtained. However, this type of the drafting device is disadvantageous in that it comprises an increased number of sets drafting rollers and drive elements for the rollers, which makes the construction complicated and increases the cost. Furthermore, complicated setting is required for various factors, such as spacing (roller gauges) and an allocation of draft ratios between the roller pairs, which makes maintenance of the system complicated. In view of the above difficulties when using the four line type or five line type drafting device, it has been, usual to use, in place of such a device, a three line type drafting device of double an apron type for a drafting device in the sliver-to-yarn fine spinning frame. Namely, in such a three line type drafting device, second or middle top and bottom rollers are constructed by apron rollers. The employment of the aproned, second rollers allows floating fibers to be controlled at the front drafting zone, so that a large drafting ratio can be obtained at the main drafting zone over the back drafting zone, even though the drafting ratio at the back drafting zone is relatively small, thereby obtaining a high total drafting ratio. However, such a "one sided" increase in a drafting ratio at the front drafting zone causes an allocation of the drafting ratios to be improper between the main and back drafting zones, thereby reducing yarn quality. In the aproned three line type drafting device an improvement can be conceived, wherein the back roller pair is, also, constructed by apron rollers. However, an employment of apron rollers also at the back rollers causes the speed of the sliver, as fed thereby, to vary due to an inevitable variation in the thickness of the aprons. Such a variation of the speed of the sliver fed by the back rollers causes the total drafting ratio between the back and front rollers to vary. Such a variation in the total drafting ratio causes the yarn thickness to largely vary, thereby causing the yarn quality to be worsened. It has also been proposed in GB 814 456 a three line drafting device in which the bottom roller of the back roller pair is an apron roller. This apron is below the sliver and has the point at which the fibers leave it lifted slightly above the plane of draft, producing the retention of the fibers necessary for carrying out the drawing. However, such a solution does not overcome the speed variation caused by the inevitable irregularities of the apron thickness. An object of the present invention is to provide a three line drafting device capable of increasing a drafting ratio at a back drafting zone, while preventing a variation in the total drafting ratio from being increased, thereby realizing a high drafting operation while preventing the yarn quality from being worsened. According to the present invention, a three line type drafting device is provided which comprises first and second pairs of top and bottom rollers, between which a main drafting zone is created, the top and bottom rollers in said second pair being constructed as apron rollers, and a third pair of top and bottom rollers comprising a third apron roller, a back drafting zone being created between said second and third pairs, an allocation of drafting amounts being adjustable between said main and back drafting zones, characterized in that said third, top roller is constructed as an apron roller, that the said third, bottom roller is constructed as a fluted roller, and that, between said third, bottom fluted roller and said second, bottom roller, a guide plate is arranged so that said guide plate is under a contacted condition with a lower surface of said apron of the third, top roller. In an operation of the present invention, the sliver is fed forwardly while being nipped between an outer peripheral surface of the fluted roller as a back, bottom roller and the apron of the back, top roller. The rotating movement of the fluted roller causes the apron of the top roller to be directly moved, so that the speed of the movement of the apron is always equalized to the peripheral speed of the fluted roller. As a result, the sliver nipped between the fluted roller and the apron is moved at the speed which is equal to the peripheral speed of the fluted roller. The fluted roller is directly driven by a rotating movement source, so that the rotating speed of the fluted roller is maintained unchanged irrespective of an inevitable variation in thickness of the apron. Thus, the speed of the movement of the sliver, which is in direct contact with the fluted roller, is also maintained unchanged, thereby preventing the total drafting ratio from being varied. Furthermore, the sliver fed from the fluted roller is moved in the back drafting zone, while being nipped between the guide plate and the apron of the top, back roller, thereby controlling floating fibers in the back drafting zone, which also serves to obtain an increased value of the drafting ratio at the back drafting zone over that in the prior art. The sliver, which is subjected to the drafting operation of a higher drafting ratio at the back drafting zone, is introduced into the main drafting zone, and is subjected to a drafting operation of a higher drafting ratio, thereby obtaining a highly increased drafting ratio. Now, an embodiment of the present invention will be explained with reference to attached drawings in which: Fig. 1 is a side cross-sectional view of a drafting device of a fine spinning frame according to the present invention. Fig. 2 is a cross sectional view of a back roller pair in Fig. 1. Fig. 3 is a front view of the back roller pair in Fig. 2. Fig. 4 is a cross sectional view of a back roller pair in a modification. Fig. 5 is a front view of the back roller pair in the modification in Fig. 4. Fig. 6 shows graphs illustrating yarn quality as obtained by the present invention in comparison with that as obtained by a prior art. Fig. 7 is a side cross-sectional view of a drafting device in a prior art. Now, an embodiment of a three line type drafting device for a fine spinning frame according to the present invention will be explained with reference to the attached drawings. In Fig. 1, reference numeral 1 denotes, generally, a spinning frame. The spinning frame 1 includes a three line type drafting device 2, which is constructed by three pairs of drafting rollers. Namely, the first pair at a front side of the frame is constructed by a front top roller 4 and a front bottom roller 5. The top roller 4 is formed at a rubber coated roller having an outer layer formed by a rubber material, while the bottom roller 5 is constructed as a fluted roller made of a steel material. The second pair at the middle of the frame is constructed by a top apron roller 6, which includes a top roller member 8a, a tensor 8b and an apron 8 looped between the top roller member 8a and the tensor 8b and by a bottom apron roller 7, which includes a bottom roller member 9a, tensors 9b and 9C urged downwardly moved by means of a lever 9d, an apron 9 looped between the bottom roller member 9a and the tensors 9b and 9C. Finally, the third pair at a back side of the frame is constructed by a back top apron roller 13, which includes a top roller member 14-1, a tensor member (cradle) 28 and a top apron 14 of the similar structure as that of the apron 8 of the middle top roller 6 and looped between the top roller member 14A and the tensor member 28, and by a back bottom roller 16 constructed as a fluted roller made of a steel material. In this three line type drafting device, two drafting zones are created, the zones being a main drafting zone 10 between the front pair including the top and bottom rollers 4 and 5 and the middle roller pair including the top and bottom apron rollers 6 and 7, and a back drafting zone 20 between this middle pair and the rear pair including the top apron roller 13 and the bottom fluted roller 16. In Fig. 1, the fine spinning frame includes a roller stand 3 for rotatably supporting the front bottom roller 5. Mounted horizontally slidably on the roller stand 3 is a middle bottom rotor supporting member 18, on which the bottom apron roller 7 is rotatably supported. Mounted, also, horizontally slidably on the roller stand 3 is a back bottom roller supporting member 19, on which the bottom back fluted roller 16 is rotatably supported. These front, middle and back bottom rollers 5, 7 and 16 are in connection with a drive train (not shown), which has gear wheels in meshed condition. A change in a gear ratio between the meshed gears wheels causes a ratio of rotational speeds between the gear wheels to be changed, which allows values of draft ratio to be changed between the main drafting zone 10 and the back drafting zone 20. The second slide member 18 and the back slide member 19 are mounted slidably adjustably on the roller stand 3, so that a spacing (gauge) of the pair of the middle rollers 6 and 7 from the pair of the front rollers 4 and 5 and a spacing (gauge) of the pair of the back rollers 13 and 16 from pair of the middle rollers 6 and 7 can be desirably adjusted. After the completion of the adjustment of the gages (spacing between the adjacent rollers), bolts 21 and 22 are tightened by means of nuts 21a and 22a, respectively, which allows the middle and back roller pairs to be located on fixed positions on the stand 3. In a well known manner, a top arm 25 is rotatable with respect to the roller stand 3 about an axis 25-1, and, in the top side of the drafting roller assembly, the front roller 4, the middle, apron roller 6 and the back, apron roller 13 are rotatably connected to the top arm 25. Also in a known manner, a lever 26 is provided for allowing the top arm 25 to be rocked between an operating position as shown in Fig. 1, where the front roller 4, the middle roller 6 and the back roller 13 on the top side are in contact with the front roller 5, the middle, apron roller 7 and the back, fluted roller on the bottom side, respectively, and a rest position, where the paired rollers are detached from each other. In Fig. 1, the apron 14 of the top, back roller 13 has a portion 14a looped around the tensor member 28 at an acute angle, so that the portion 14a is located at a location adjacent the second or middle pair of the rollers 6 and 7 as near as possible, which allows a supporting length of a sliver S to be increased to as long as possible between the apron 14 and a guide plate 41, which is located below the apron 14 and the construction of which will be in detail explained later, while the distance is reduced to as short as possible between a nipping point between the apron (back) roller 13 and the guide plate 41 and a nipping point between the middle (second) top and bottom apron rollers 6 and 7. In Fig. 1, at a location upstream from the pair of the back (third) top rollers 13 and the bottom (fluted) roller 16, a trumpet 29 is arranged for collecting a silver S supplied from a can. The trumpet 29 is mounted to a traverse bar 32 at its side wall, which is mounted slidably to a back slide 19 along the length of the machine frame. As explained above, between the fluted, bottom roller 16 of the back (third) roller pair and the apron roller 7 of the middle (second) roller pair, the guide plate 41 is located below a lower side of the apron 14 of the top roller 13 of the back roller pair. The guide plate 41 extends along the length of the machine frame and has a pair of ends tightened to the corresponding back slide members 19 at their upper walls by means of bolts (not shown). The guide plate 41 has, at its upper side, guide portions 41a opposite the aprons 14 of the top rollers 13 of the corresponding back (third) roller pair. Each of the guide portion 41a forms an upwardly curved guide surface, to which the lower surface of the apron 14 of the back, top roller 13 is in a press contacted condition. The guide plate 41 is, at both sides of the each of the guide portions 41a, formed with flat surface portions 41b which are lower than the guide portions 41a. Guide member 42, which are vertically displaceable, are arranged on both sides of each of the apron rollers 13 as shown in Figs. 2 and 3. Each of the guiding members 42 has a U-shaped end which is engaged with a shaft 13-1 of the roller 13. The tensor member 28 is connected to the guiding members 42 on both side of the roller 13. A spring (not shown) is provided for generating a spring force which causes the apron 14 to be in a press contacted condition with the faced curved guide surface 41a of the guide plate 41 flat surface portions 41b are guide plate 42. The guide member 42 has a downwardly directed projected portion 42a, which is press contacted with the flat lowered portion 41b of the guide plate 41, so that a predetermined relative vertical position of the top, apron roller 13 at the back roller pair is obtained, which allows the sliver S to be positively held under a desired force between the apron 14 and the guiding surface 41a. The guide plate 41 can be suitably made from a material with low friction including a metal or a synthetic resin. The projections 42a may be detachably connected to the guide plate. Figs. 4 and 5 show a modification of the cradle supporting means, wherein a pair of tensors 28 are supported by a guide member 42, which is arranged between the rollers 13 which are adjacent with each other. Namely, the guide member has a portion 42-1 extending forwardly, from which portion the tensors 28 extend transversely into the corresponding aprons 14. The portion 42-1 has an integral pin 42-2, to which a distance piece 44 is detachably snapped, so that a desired distance is obtained between the lower surface of the apron 14 and the upper surface 41a of the guide plate 41, when the guide member 42 is urged downwardly by means of a spring (not shown). It should be noted that the upper surface of the guide plate 41 facing the aprons is at the same vertical level with respect to the remaining parts. A collector 50 (Fig. 1) is arranged between the back (third) set of the rollers (13 and 16) and a middle (second) set of rollers (6 and 7). Now, an operation of the drafting device 1 according to the present invention will be explained. Prior to the spinning operation, an allocation of values of drafting ratio at the main drafting zone 10 between the middle roller pair (6 and 7) and the front roller pair (4 and 5) and at the back drafting zone 20 between the back roller pair (13 and 16) and the middle roller pair (6 and 7) is done while maintaining a predetermined total drafting ratio between the back roller pair (13 and 16) and the front roller pair (4 and 5). An operation of the driving motor (not shown) of the drafting device 1 causes the fluted roller 16 (back, bottom roller) at the back drafting zone 20 to be rotated, while the rotating movement of the fluted roller 16 is, under a frictional force, transmitted to the apron 14 of the back, top roller 13, so that the sliver S nipped between the fluted roller 16 and the apron 14 is moved and introduced into the back drafting zone 20 at a speed which is identical with the surface speed of the fluted roller 16. The sliver S introduced into the back drafting zone 20 is moved while being nipped between the apron 14 and the guide surface 41a of the guide plate 41. Due to such a movement while being nipped between the apron 14 and the guide plate 41, a positive control of a movement of floating fibers in the sliver S at the back drafting zone 20, which are not nipped by both of the back roller pair (14-1 and 16) and the middle roller pair (50 and 9a), is realized. Such a positive control of the movement of the floating fibers in the sliver allows the drafting ratio to be increased at the back drafting zone 20 when compared with that obtained in the prior art. As a result, a desired allocation of drafting ratios between the back drafting zone 20 and the main drafting zone 10 is obtained. The sliver thus passed through the back drafting zone 20 is, then, introduced into the main drafting zone 10, whereat the sliver S is subjected to a further drafting operation, thereby obtaining a predetermined thickness of a yarn Y. According to the present invention, as explained above, the feeding speed of the sliver S to the back drafting zone 20 is purely dependent on the rotating movement of the fluted roller 16. Furthermore, the front top and bottom rollers 4 and 5 in the front roller pair (4 and 5) for taking out the sliver are, also, not apron rollers. As a result, the existence of the aprons 8, 9 and 14 does not cause the speed of the sliver S to be changed at the inlet or the outlet sides of the drafting system. In short, the three line type drafting device 2 according to the present invention can obtain a constant value of a total drafting ratio irrespective of a fact that the apron roller 13 is used as a top roller of the back roller pair. In other words, a constant value of the total drafting ratio between the back roller pair and the front roller pair is obtained regardless a variation of a thickness of the apron of the apron roller 13, which otherwise would cause the quality of the yarns Y to be worsened. Fig. 7 shows a three line type drafting device 2A in a prior art, which includes a front set of top and bottom rollers 3 and 4, a middle set of top and bottom rollers 6 and 7 as apron rollers, and a back set of top and bottom rollers 13 and 16. In this prior art three line type drafting device, the back top roller 13 is a metal roller and not an apron roller unlike the present invention. In the construction of the prior art in Fig. 7, employment of the apron roller type middle rollers 6 and 7 allows movement of floating fibers in a sliver S to be positively controlled at a main drafting zone 10 between a middle pair of rollers (6 and 7) and the front pair of rollers 4 and 5, so that an increased drafting ratio as high as 200 can be obtained at the main drafting zone 10 over a back drafting zone 20 between the back pair of rollers 13 and 16 and the middle pair of rollers 6 and 7. However, at the back roller pair, both of the top and bottom rollers 13 and 16 are metal rollers, so that a drafting ratio at the back drafting zone 20A cannot be so high. As a result, an allocation of drafting ratios between the main and back drafting zones cannot be optimized, which may cause the yarn quality to be worsened. In the prior art three line drafting device in Fig. 7, in order to obviate this problem, both of the back rollers 13 and 16 may be constructed as apron rollers, which allows the drafting ratio at the back drafting zone 20A to be increased. However, the influence on a total drafting ratio when constructing the middle rollers 6 and 7 by apron rollers is different from the influence on a total drafting ratio when constructing, additionally, the back rollers 13 and 16 by apron rollers. Namely, a total drafting ratio is a ratio of the rotating speed of the front rollers 4 and 5, which corresponds to the speed of the yarn being spun to the rotating speed of the back rollers 13 and 16, which corresponds to the speed of a sliver fed to the back rollers. On the other hand, the apron of the bottom roller is looped around an outer periphery of the bottom roller member subjected to a rotating movement of a driving source, so that the rotating movement of the roller induces the movement of the apron. As a result, a variation in the surface speed of the apron occurs when there is a change in the thickness of the apron. In case where the aprons are employed only at the middle rollers as shown in Fig. 7, a variation in the thickness of the aprons causes the values of the drafting ratios to be changed at the back drafting zone 20A and the front drafting zone 10, respectively. The variation in the thickness of the aprons, however, does not cause the total drafting ratio to be changed, because the rotating speed ratio between the back rollers and front rollers is unchanged due to the fact that both of the back rollers 13 and 16 and the front rollers 4 and 5 are under a direct contact with the sliver S, i.e., without any intervention of apron means. As a result, the variation in the thickness of the aprons would not cause the yarn quality to be affected. Contrary to this, if the top and bottom back rollers 13 and 16 are modified so as to be provided with the aprons in the prior art drafting system as shown in Fig. 7, a variation of a surface speed of the apron looped around the back, bottom roller 16 and driven thereby would cause the speed change to be generated in the sliver S fed between the apron on the back, bottom roller 16 and the apron on the back, top roller 13 in a press contacted with the apron on the bottom roller 16 and entrained thereby, so that an amount of sliver being fed is correspondingly changed. Such a change in the sliver fed amount causes the total drafting ratio between the back rollers (13 and 16) and the front rollers (4 and 5) to be changed, thereby reducing the yarn quality as obtained. The present invention, wherein the back, top roller 13 is constructed by an apron roller, and the back, bottom roller 16 is a fluted roller as shown in Fig. 1, can overcome these problems since the speed of the sliver is only influenced by the bottom roller 16, as fully explained with reference to Fig. 1. Fig. 6 shows a result of a test by the inventors in view of relationships between a back drafting ratio and an average deviation in thickness of spun yarns Y, so called U-%, as obtained by the device according to the present invention in Fig. 1 and the prior art device as shown in Fig. 7, respectively. The test was done under a condition that the sliver S being fed is a 100% combed sliver, the thickness of the sliver is 350 grain per 6 yards, the total drafting ratio is 280 and a thickness of the yarn Y as produced is 25 grain per 120 yards, which is designated to obtain a yarn count of 40. In Fig. 6, a solid curve is the yarn thickness variation of the yarn obtained by the device 2 according to the present invention in Fig. 1, while a dotted curve is a yarn thickness variation of the yarn obtained by the device 2A in the prior art in Fig. 7. As will be easily understood from the curves in Fig. 6, according to the present invention, for the same value of the U-%, an increased value of the drafting ratio at the back drafting ratio at the back drafting zone is obtained over the prior art. In other words, the present invention makes it possible that a difference of the value of the drafting ratio at the back drafting zone 20 from that at the main drafting zone 10 can be reduced when compared with the prior art construction. It will be also understood from a comparison of the curves in Fig. 6 that the present invention makes it possible that, along a wide range of the values of the drafting ratio, a reduced value of the U-% of the produced yarn is obtained, i.e., an increased yarn quality is obtained when compared with the yarn as produced by the prior art device 2A in Fig. 7. In short, due to an employment of a direct feed construction of the sliver S by the fluted back, bottom roller 16 as well as of the nipping of the sliver S between the back apron 14 of the back roller and the guide plate 41 according to the present invention, an increased yarn quality is obtained.

Claims: A three line type drafting device comprising first (4,5) and second (8a,9a) pairs of top and bottom rollers, between which a main drafting zone is created, the top (8a) and bottom (9a) rollers in said second pair being constructed as apron rollers, and a third pair (13,16) of top and bottom rollers comprising a third apron roller, a back drafting zone being created between said second and third pairs, an allocation of drafting amounts being capable of being adjusted between said main and back drafting zones, characterized in that said third, top roller (13) is constructed as an apron roller, that the said third, bottom roller (16) is constructed as a fluted roller, and that, between said third, bottom fluted roller (16) and said second, bottom roller (9a), a guide plate (41) is arranged so that said guide plate (41) is under a contacted condition with a lower surface of said apron (14) of the third, top roller (13). A drafting device according to claim 1, wherein said third top roller (13) comprises a roller member (14-1), an apron (14), and a cradle (28) for obtaining a press contact of the apron (14) with said guide plate (41), said cradle (28) include guide members (42) arranged on both sides of the roller member and a tensor (28) extending between guide members (42), the guide members (42) having portions which are in contact with the guide plate (41). A drafting device according to claim 1, wherein each of said third top rollers (13) comprises a roller member (14a), an apron (14), and a cradle (28) for obtaining a press contact of the apron (14) with said guide plate (41), said cradle (28) includes a guide member (42) arranged between roller members which are adjacent with each other, tensor members (28) extend integrally from the guide member (42) toward respective aprons (14), and a spacer (44) is arranged between the guide member and the guide plate. A drafting device according to claim 1, wherein a spacer (44) is detachably connected to the guide plate (41), thereby adjusting the force for making the apron (14) and the guide plate (41) to be contacted via the sliver (S).

Inventors: ADACHI NORITAKA, KOGISO TAKASHI, ADACHI, NORITAKA, KOGISO, TAKASHI
Applicants: HOWA MACHINERY LTD, HOWA MACHINERY LIMITED
Application year: 1996
Main classification: D01H5
IPC codes: D01H5