EP2028300A2

EP2028300A2 - Device for controlling and reducing the tension pulsations in the feed of four-for-one twisting spindles

Info

Publication number: EP2028300A2
Application number: EP08160624A
Authority: EP
Inventors: Roberto Badiali; Fabio D'agnolo
Original assignee: Savio Macchine Tessili SpA
Current assignee: Savio Macchine Tessili SpA
Priority date: 2007-08-01
Filing date: 2008-07-17
Publication date: 2009-02-25
Also published as: ITMI20071578A1; CN101358393A; CN101358393B; EP2028300A3

Abstract

Device for controlling and stabilising the feed tension in four-for-one twisting spindles wherein a rotating unwinder rotates by following the unwinding of the feed yarn that re-ascends an internal axial cavity up to a deflecting bell-shaped transmission element, from which the inner balloon of the four-for-one twisting spindle begins, where the deflecting bell-shaped element is rendered idle with respect to the unwinder below.

Description

The present invention refers to a four-for-one twisting spindle for twister machines and in particular to a tension-regulating device of the yarn feeding to a four-for-one twisting spindle.
In order to better clarify the technical problems involved and appreciate the technical solution according to the present invention, reference is made here to the four-for-one twisting spindle diagram reported in figure 1 and to its functioning illustrated with its exploded view reported in figure 2, as a non-limiting example. The four-for-one twisting spindle illustrated here mirrors the mechanical diagram of the apparatus according to the patent application EP 1.726.693 by the same applicant. Reference can also be made to the four-for-one twisting spindle diagram according to the patent EP 1.007.773 . In such documents, greater details can be found on the functioning of such devices.
According to the diagram of figures 1 and 2, the twisting spindle for multiple twists of textile threads and yarns, comprises a basket support 10 for a feeding bobbin 11, which is maintained locked in place by using stationary magnets M, for example. Generally, the bobbin 11 is separately prepared with doubled yarns wound in a doubler machine on a package that is then brought to the twister.
The four-for-one twisting spindle also comprises two parts rotating in opposite directions, respectively an upper, more internal rotating part 15 and a lower rotating part 16, both arranged under the bobbin-holder basket 10, the rotating parts 15 and 16 being coaxial with each other and with respect to the spindle axis, and a transmission and unwinder element 20 arranged above the bobbin 11. The yarn F that is unwound from the bobbin first passes through an unwinder element 20, which terminates with the transmission element 21 arranged above the bobbin, then descends towards the internal, upper rotating part 15, defining an inner balloon B around the bobbin. It enters into said upper rotating part 15 with the radial duct 28, is deflected with the roller 29 and crosses an axial passage 30 made in said internal, upper rotating part 15. Once it reaches the exit of said passage 30, arranged on the spindle rotation axis, the yarn crosses a second transmission element 31, integral with the lower rotating part 16, and then a radial passage 32 made inside said lower rotating part 16; it exits from this and re-ascends, defining an outer balloon B', arriving at a final transmission 33 and finally is sent to collection means in an upper position. Such collection means, not shown in the figure for the sake of simplicity, draw at constant and predetermined speed - and collect in packages - the yarn that was worked in the four-for-one twisting spindle. In the run that follows from the upper transmission 21 to the final transmission 33, the yarn receives two twists for every revolution of each of the two rotating parts.
The lower rotating part 16 is supported by a stationary bearing 14 that sustains the entire four-for-one twisting spindle and is driven by external motion transmission means, for example by means of a pulley 17 coaxial with the spindle which receives the rotary motion with a transmission belt. The lower rotating part 16 in turn transmits the motion to the upper rotating part 15, for example through an epicycloidal transmission device 18, according to the mentioned patent application EP 1.726.693 by the same applicant, to which reference is made for more details. Such epicycloidal device 18 is contained within a fixed box part 19, also held locked in place with fixed magnets mounted on the bottom of the basket 10.
Above the feed bobbin 11, an unwinder device 20 is comprised which receives the doubled yarn F from the bobbin 11. Such unwinder 20 is mounted on the inner shaft 13 of the basket 10 with the interposition of a rolling bearing 22. The entire unwinder 20 is placed in rotation by the same doubled yarn F which unwinds as a spiral from the bobbin 11, passes into the terminal ring of the rotating arm 23 and enters inside the axial cavity 24 of the unwinder 20 which re-ascends the unwinder itself up to the bell-shaped transmission 21 at its top. The linear unwinding speed is determined by the draw of the collection unit placed downstream, which also determines the hourly quantity of twisted yarn production.
A yarn tensioning element 25 is placed inside the cavity 24. In the diagram of figures 1 and 2 - and also in greater scale in the following figure 4 - this consists of an elastic piston 26 with a spring at its interior that presses the doubled yarn F against two annular seats 27 placed at the two upper and lower rounded ends of the piston 26. Such tensioner 25 meets the need that both ends of the doubled yarn F arrive at the transmission 21 precisely parallel to each other and with a certain tension. In the undesired case that, in the preliminary doubling operation of the yarn F, one of the two ends results slack and in the twisting there is a slot of projecting yarn, this would be an unacceptable defect of the twisted yarn. The tensioner 25 is therefore an equaliser of the doubled yarn F in order to prevent going beyond a possible slack end present in the doubled yarns. One feature of the spindle consists of the fact that the yarn, for at least one part of its course, can form free balloons B and B' that are not externally delimited.
In order to better clarify the technical problems faced and resolved with the present invention, the twisting process is described with reference to figure 2 with reference to the actual speed during the spindle functioning.
The four-for-one twisting spindle receives its single drive from the axial shaft of the lower rotating part 16, for example by means of the pulley 17, and is driven for example at 10,000 rev/min. The epicycloidal transmission device 18 transmits the motion to the upper rotating part 15 with a speed of about 50%: the upper part rotates in turn, for example, at 5000 rev/min.
Since, as said above, during its run the yarn F receives two twists for every revolution of each of the two rotating parts, per every minute of work the doubled yarn that passes receives 10,000 revolutions, twice, from the rotating part 16 and 5,000 revolutions, twice, from the rotating part 15, i.e. 30,000 rev/min in total. If a twisting of 600 twists per linear meter is required for the yarn F, it is thus possible to work 50 meters of yarn F per minute in the four-for-one twisting spindle, actuating the device downstream of collection with a draw of 50 m/min.
For the structure and functioning of the twister, most of the tensions on the yarn are due to the centrifugal force of the balloons of the yarn which rotates at high speed. The technical problem of balloon stability derives not so much from the value of the yarn tension but from its irregularity due to the unwinding of the yarn F from the feeding bobbin 11.
Due to the draw of the pick-up device that is downstream, from the terminal ring of the rotating arm 23, the yarn F is pulled away from the bobbin 11 locked in its basket, from which unwinding takes place at 50 metres per minute, for example. At the start of the bobbin, the 50 m/min correspond to about 100 spirals wounded per minute: the yarn F rotates slowly around the bobbin with spiral progression. The resistance to the unwinding and the corresponding tension of the yarn F varies depending on the drawing point of the yarn with a pulsation that corresponds to the bobbin 11 traversing: it goes from a minimum value when the yarn is drawn from the highest part of the bobbin to a maximum value when the yarn is drawn from the lower part of the bobbin 11. Such pulsation is due both to the variation of the yarn section length, which extends from the bobbin drawing point to the ring of the rotating arm 23, and to the greater or lesser friction that the yarn sliding on the bobbin encounters. The variation of the unwinding tension between the upper part and the lower part of the bobbin essentially depends on the fact that the yarn that is unwound in ascending or descending direction encounters different resistance from the adjoining spirals.
When the bobbin 11 is close to finishing, the aforesaid 50 m/min of linear speed correspond with 400 spirals unwound per minute (the limit value is 500-600): the yarn F rotates quickly around the bobbin 11, always with spiral progression and with analogous tension pulsation, and with greater frequency.
Due to the increasing speed rotation of the yarn F unwound from the bobbin 11, also the unwinder 20 that draws the yarn F is driven by the drawing of the yarn itself in a rotation that is slow at first, at a speed of a few dozen rev/min, up to a faster rotation at several hundred revolutions per minute when the bobbin is finishing. The unwinding resistance is progressively increasing due to the greater rotation speed to transmit to the unwound yarn spiral F that extends from the bobbin 11 to the unwinder 20.
Such driving in rotation is transmitted through the rotating arm 23. Due to the resisting tension pulsation of the yarn F, also the arm 23 and the entire unwinder 20 rotate at pulsating speed and give an amplifying effect of the resisting tension pulsation of the yarn F during its unwinding. The variation of the resistance of the doubled yarn F at the drawing in fact leads to a periodic offset between the angular coordinates of the drawing point, where it is separated from the bobbin, and the rotating arm 23. Since the free length of the yarn F varies periodically, extending from the drawing point on the bobbin to the terminal ring of the rotating arm 23 and from such ring the yarn is instead drawn at substantially constant speed, the pulsation of said free length leads to a pulsation of the angular drawing and pulling speed that is exerted by the arm 23 on the yarn. In the reversal points of the yarn F unwinding from the feeding bobbin 11, there are angular accelerations/decelerations of the unwinder arm 23 with respect to the drawing point of the yarn from its winding. The unwinder 20 has a certain inertia proportional to its weight and structure; it is driven in rotation by the yarn F drawn upward and that is unwound from the bobbin 11. When the drawing direction is reversed at the upper edge of the bobbin, the yarn F suddenly increases its unwinding resistance and the displacement angle between the arm 23 and the drawing point of the yarn increases: the unwinder 20 goes beyond the drawing point of the yarn and there is a positive tension peak due to the increase of angular displacement, followed by a certain release, i.e. a "negative" tension peak. On the other hand, when the drawing direction is reversed at the edge of the bobbin 11, the yarn F decreases its unwinding resistance and the displacement angle between the arm 23 and the drawing point of the yarn decreases: the unwinder 20 has a certain inertia, but it then adapts and in the transition there is a certain release of tension due to the reduction of angular displacement. In other words, when the yarn is more resistant, it is tauter and the angular displacement is greater. The longer the section of yarn F between the drawing point and the ring, the more the yarn encounters friction; when such yarn is shortened, it resists less and the opposite occurs.
At the outlet of the upper transmission 21 of the unwinder 20, the yarn F re-descends, forming the inner balloon B. The progression over time of the instantaneous tension of the yarn during its re-ascending run towards the upper transmission 21 is shown as an example in the solid line TI of figure 3, from the start to the end of the bobbin 11. The progression of the average tension of the yarn is instead shown in the dashed-dotted line TM. The instantaneous tension is irregularly pulsing and on average increasing from start to finish. Such overall tension is the resultant of all the forces and resistances offered by the yarn and by the system in motion from the drawing point up to the inlet of the radial duct 28.
Unlike the outer balloon B', the inner balloon B does not have a compensating pulley due to the space unavailability and system geometry. For the above reasons, the yarn of the inner balloon B naturally has a pulsating tension that causes instability of the balloon itself. For this reason, the inner balloon B continuously varies its shape and size. The tension of the inner balloon B can neither be too high nor too low. Overly low tensions can cause interferences between the two balloons B and B', but the greatest danger lies in excess tension. Excess tension of the descending balloon B can reduce the winding of the reserve of the second balloon B' around the surface 36, bringing it to a condition of instability. Such excess can also diminish the radial size of the inner balloon B and cause the contact between the balloon itself, rotating at high speed, with the cylindrical surface of the fixed basket 10, with the consequent braking of the yarn. Upon contact, the yarn adheres to the basket and is wound thereon, being immediately torn.
The present invention is therefore directed towards an unwinder device that permits controlling the tension progression and values of the inner balloon B at the point in which the yarn drawn from the bobbin 11 arrives at the bell-shaped transmission 21 and starts to form said balloon.
The present invention is directed towards a new unwinder device for four-for-one twisting spindles that permits controlling the inner balloon B and the tension value of the yarn and overcomes the drawbacks described up to now. The present invention, in its most general meaning of the unwinder device employed by a twister, is defined in the first claim. Its preferred variants or embodiments are defined in the dependent claims 2 - 14.
The characteristics and advantages of the unwinder according to the present invention will be clearer from the following exemplifying and non-limiting description, referred to the attached schematic drawings in which:

Figure 1 reports the structure scheme of a four-for-one twisting spindle,
Figure 2 reports its exploded view illustrating its functioning,
Figure 3 shows the progression over time of the yarn tension in its re-ascending run towards the upper transmission in the spindles according to figures 1 and 2,
Figure 4 shows the scheme of the unwinder device according to the present invention,
Figure 5 shows the progression of the inner balloon B with respect to the bell-shaped element above the unwinder,
Figure 6 shows a preferred embodiment of the unwinder according to the present invention.
Figure 7 shows the progression over time of the tension of the yarn in its re-ascending run towards the upper transmission with the unwinder illustrated in figure 6.

The characteristics and advantages of the unwinder device according to the present invention are more evident from the description of a typical, exemplifying and non-limiting embodiment thereof, illustrated in figure 4.
With reference to figure 2, at the outlet of the axial duct 24 of the unwinder 20, the yarn F is deflected downward by the drawing of the upper rotating part 15 and begins to form the inner balloon B driven into rotation at high speed, for example 5,000 rev/min. The bell-shaped transmission device 21 of figures 1 and 2 is integral with the unwinder 20 that rotates at a reduced speed, from several dozen rev/min at the start of the bobbin 11 to several hundred rev/min. At the outlet of the bell-shaped element 21, the yarn not only slides on the bell-shaped element with a speed of dozens of metres/min in longitudinal direction, but also rotates by sliding on the bell-shaped element itself at nearly 5,000 rev/min.
Such sliding, for example at nearly 5,000 rev/min, causes considerable drawbacks. Due to the wear of the sliding yarn, one considerable drawback lies in the fact that such sliding causes a significant deflection of the yarn from the radial direction desirable for the inner balloon B. The balloon B thus tends to be arranged towards a direction tangential to the rotary motion, along a spiral that brings the free yarn section, constituting the inner balloon B, dangerously close to the fixed basket 10 of the bobbin 11. Another drawback is due to the tangential sliding with such rotation of the yarn F with respect to the bell-shaped element, which constitutes a significant component of the energy dissipated in the four-for-one twister and which contributes to the yarn tension.
The unwinder device 50 according to the present invention, illustrated in figure 4, is achieved according to the present description regarding its lower part, i.e. arm 23, the inner axial cavity 24 with tensioner 25 of the yarn F, which consists of an elastic piston 26 which presses the yarn against two annular seats 27 placed at the two upper and lower rounded ends of the piston 26.
Its upper part, which achieves the transmission 21 of figures 1 and 2, is instead made with bell-shaped deflector 51 rendered idle with respect to the unwinder 50 below. In the embodiment of figure 4, the rotary independence of the bell-shaped element 51 employs a ball bearing 52, fit at the top of the body 53 that contains the axial cavity 24. The external surface of the rotating bell-shaped element 51 is achieved with a moderate friction coefficient, so that the yarn F driven in rotation at the speed of the balloon B, for example at 5,000 rev/min, drives the bell-shaped element 51 therewith without the latter losing revs. It is necessary, in fact, to consider the fact that the longitudinal friction is negligible, and absorbs little power, since the sliding corresponds to the relatively limited drawing speed - generally on the order of 30 - 100 m/min - while the tangential sliding contributes to the energy dissipated in the four-for-one twister.
In order to obtain the best results, the yarn F must be capable of driving the bell-shaped element 51 therewith without the latter losing revs. The preferred friction coefficient values for the surface of the bell-shaped element 51 are in the range of 0.2 - 0.4.
With regard to the unwinders 20 provided with bell-shaped transmission integrally in rotation with the unwinder itself, available in the four-for-one twisting spindles according to the prior art, the unwinder 50 provided with idle bell-shaped element 51 according to the present invention offers considerable advantages.
With the technical solution according to the present invention, which provides the bell-shaped element 51 which substantially rotates at the same speed as the inner balloon B, it is obtained that, regarding the outlet direction of the yarn F from the idle rotating bell-shaped element 51, there is no significant deflection of the yarn from the radial direction. In figure 5, the progression of the inner balloon B is shown with respect to the bell-shaped element above the unwinder. In the left part of figure 5, the progression of the balloon B with respect to the shape of the basket 10 is seen in side view, where the dashed line on the left shows the progression of the balloon B with the rotating bell-shaped element 51 and the dotted line to the right shows the progression of the balloon B with the fixed bell-shaped element 21, given the same conditions. In the right part of figure 5, the progression of balloon B is shown in plan view, in its run on the upper transmission bell-shaped element, where the dashed line shows the progression of the balloon B with the rotating bell-shaped element 51 and the dotted line shows the progression of the balloon B with the fixed bell-shaped element 21, given the same conditions.
As shown in figure 5, due to the rotating bell-shaped element 51, the inner balloon B thus does not tend to be arranged towards a tangential direction and its spiral progression is significantly limited; it does not come as close to the fixed basket 10. In addition, the rotating bell-shaped element 51 permits reducing the inlet tension of the balloon itself to a significant value, allowing the balloon B to assume a more regular progression, far from the basket, such as for example indicated to the left in figure 5. The rotary sliding of the yarn against the bell-shaped element and the related wear are substantially eliminated.
According to an improvement and a preferred embodiment of the present invention, there is the object of regulating, with a brake, the rotation of the unwinder 20 in order to make such rotation as uniform as possible. This is done so as to eliminate, or at least reduce, the amplifying effect of the pulsation of the resisting tension of the yarn F during its unwinding exerted by the unwinder 20, limiting its angular speed pulsations and making the inlet tension of the inner balloon B more regular. This is described here below with reference to figure 6.
As said for the unwinder 20, the unwinder 50 is mounted on the inner shaft 13 of the fixed basket 10 with the interposition of a rolling bearing 22, the entire unwinder 20 being placed in rotation by the same doubled yarn F that is unwound from the fixed bobbin 11. A conductive material ring 60 is placed and fixed on the upper end of the fixed shaft 13. On the lower end of the rotating unwinder 50, one or more permanent magnets 61 are mounted, facing, with one of their polarities N-S, at an adjustable distance from the ring 60. Due to the rotation of the magnets 61 integral with the unwinder 50, the conductive material fixed ring 60 is thus subjected to a variable magnetic field, which induces eddy currents therein that generate a magnetic field opposing the magnets 61, with braking effect on the unwinder.
On the other hand, an alternative embodiment can be composed by placing the conductive material ring 60 on the lower end of the rotating unwinder 50 and placing the magnets 61 on the upper end of the fixed shaft 13.
Such conductive material ring 60 can be made with a continuous ring, as shown in the detail on the right, or with a ring with holes distributed on its surface, as shown in the detail on the left. The embodiment with continuous ring permits a more regular braking, but requires increased precision in the adjustment of the work distance.
The ring 60 is provided with a height adjustment device, so to be able to determine, at a desired value, its axial distance from the rim on which the magnets 61 lie as well as the exerted braking action. When yarns with fine counts are worked, or yarns that exert little resistance in unwinding, generating a reduced speed pulsation, the operator adjusts the braking distance at the start of the processing so as to exert a very light braking action: ring 60 and magnets 61 are kept quite far from each other. In the case of large counts, the disc 60 is brought closer to the magnets 61 in order to increase the braking action, which typically increases with the decrease in distance in a quadratic relationship.
In order regulate the braking action exerted between the ring 60 and the magnets 61, an adjustment device of their mutual distance is inserted on the fixed shaft 13. The exemplifying embodiment of figure 6 provides - for such purpose - the use of a threaded ring nut 64 that is screwed on a thread 65 made on the upper end of the fixed shaft 13. With a 1.5 mm pitch thread, it is possible to adjust - with six 60°-spaced positions - said distance with 0.25 mm pitches. Appropriate locking means are then provided of the ring nut's angular position.
Such braking system results unaffected by dirt and dust, can be easily regulated, doesn't depend on the rotation speed and is unaffected by the vibrations and sliding.
The effect obtainable from the braking device illustrated in figure 6 - with the unwinder 50 with rotating bell-shaped element 51 according to figure 4 combined with the effect of the magnetic brake 60,61 - is shown in figure 7 with the dashed-dotted line. Here it is seen how the instantaneous tension irregularities of the unwound yarn F are clearly reduced with respect to those of the preceding figure 3, reported with reference to the more solid line. The average tension values between start and finish of the bobbin 11 do not show differences between the two cases. On the other hand, the correct instantaneous tension values shown with the dashed-dotted line clearly show reduced pulsations, generally passing from tension pulsations with amplitude of 40% of the average value to a pulsation with halved amplitude. The more regular progression of the unwinding tension permits the balloon B to assume a more regular progression, far from the basket.

Claims

Device for controlling and stabilising the feed tension in four-for-one twisting spindles wherein a doubled feed yarn (F) of the four-for-one twisting spindles (10) is unwound from a fixed feeding bobbin (11) by means of a rotating unwinder (50) provided with a radial arm (23) and which rotates by following the unwinding of the feed yarn, characterised in that the rotating unwinder (50) has an inner axial cavity (24) for the re-ascending of the yarn (F) coming from the terminal ring of the rotating arm (23), follows said cavity up to a deflecting bell-shaped transmission element (51), from which the inner balloon (B) of the four-for-one twisting spindle (10) has its beginning, and in that such deflecting bell-shaped element (51) is rendered idle with respect to the unwinder (50) below.
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 1, characterised in that the rotary independence of the bell-shaped element (51) is obtained with a ball bearing (52), fit at the top of the body (53) which contains the axial cavity (24).
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 1, characterised in that the friction coefficient values for the surface of the bell-shaped element (51) are in the range of 0.2 - 0.4.
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 1, characterised in that, inside the cavity (24), a yarn tensioning element (25) is placed that ensures that both ends of the doubled yarn (F) arrive at the upper transmission taut and precisely parallel to each other.
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 1, characterised in that the unwinder (50) is mounted on an internal shaft (13) fixed to the four-for-one spindle (10), with the interposition of a rolling bearing (22)
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 1, characterised in that, on the fixed internal shaft (13) of the spindle (10), a magnetic brake is mounted for the rotation of the unwinder (50).
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 6, characterised in that the magnetic brake consists of a conductive material ring (60) opposing one or more permanent magnets (61), facing each other at an adjustable distance, one of the two elements being made integral with the fixed shaft (13) and the other made integral with the rotation of the unwinder (50).
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 7, characterised in that the conductive material ring (60) is fixed on the upper end of the shaft (13) while the magnets (61) are mounted on the lower end of the rotating unwinder (50).
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 7, characterised in that the conductive material ring (60) is fixed on the lower end of the rotating unwinder (50) while the magnets (61) are mounted on the upper end of the shaft (13).
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 7, characterised in that the conductive material ring (60) is made with a continuous ring.
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 7, characterised in that the conductive material ring (60) is made with holes distributed on its surface.
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 7, characterised in that, in order to adjust the braking action exerted between the ring (60) and the magnets (61), an adjustment device of their mutual distance is inserted on the fixed shaft (13).
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 12, characterised in that the adjustment of the distance between ring (60) and magnets (61) is made with a threaded ring nut (64) that is screwed on a thread (65) made on the upper end of the fixed shaft (13).
Device for controlling and stabilising the feed tension in four-for-one twisting spindles according to claim 12, characterised in that the threaded ring nut (64) is provided with locking means of its angular position.