Classifications

• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04B—KNITTING
  • D04B15/00—Details of, or auxiliary devices incorporated in, weft knitting machines, restricted to machines of this kind
  • D04B15/38—Devices for supplying, feeding, or guiding threads to needles
  • D04B15/48—Thread-feeding devices
  • D04B15/482—Thread-feeding devices comprising a rotatable or stationary intermediate storage drum from which the thread is axially and intermittently pulled off; Devices which can be switched between positive feed and intermittent feed

Definitions

• the present invention relates to a device for feeding thread or yarn to a textile machine in accordance with the introduction to the main claim.
• the invention also relates to a method for implementing the feed.
• Two main types of device are known for feeding a thread or yarn to a textile machine: a first device is the so-called accumulation or negative device, the second device being a continuous (positive) feed system without thread accumulation, and enabling the thread to be fed to the textile machine at constant tension or quantity.
• the first known device is, for example, described in DE1937059; it comprises a cylindrical element or rotary accumulator driven by its own motor and on which the thread to be fed to the textile machine is wound. The thread is autonomously withdrawn from the machine which unwinds it from the above cylindrical element. In other words, this cylindrical element or accumulator serves as a thread reservoir and unloads more or less depending on the machine particular production moment.
• This thread passes successively through a tensioning member (annular comb, annular brush or the like), the pressure of which (adjusted to fixed values or manually by interchangeable tensioning members) on the cylindrical element or accumulator transmits an uncontrolled and unregulated tension (not adjustable continuously on the basis of that stage of the textile process underway) to the thread via a closed regulator ring, to maintain it constant with time; this first device consequently operates under open loop.
• the tension is however maintained within an acceptable range of values related to the fact that the thread has been accumulated and unwinds from an accumulation drum or accumulator of predefined diameter.
• the tensioning member wears, the applied tension varies to an extent which cannot be compensated by the accumulator or drum and requires a new adjustment of the position of this member or its complete replacement.
• the variation in the tension of the yarn which accumulates on the drum (linked mainly to the variation in the spool diameter from full to empty or to simply changing the spool, this variation affecting the tension of the thread unwinding from it) varies with time and cannot be entirely compensated.
• Said first device enables the thread to be fed to the textile machine without undergoing jerking during its unwinding from the usual bobbin or spool located upstream of the rotary cylindrical element (such jerking could break the thread wound compactly on itself or could cause processing defects).
• this device it is impossible to maintain constant feed tension as it is the machine itself which withdraws the thread from the accumulator in known manner (for example by shuttle, water jet, needles, etc.).
• this known device is able to maintain correct thread feed only if a low thread tension is required (for example 1 g or 10 g). Again, if the type of yarn processed is changed, the type of tensioning member (for example annular brush) has to be replaced by one compatible with the fed yarn and the tensions required.
• the yarn cannot be fed under high tension (for example 50 or 100 g), neither can the tension of the fed yarn be varied on the basis of the stage of manufacture during the textile processing cycle (for example cuff; leg-foot of a stocking).
• a tensioning member in direct contact with the thread can damage and wear both the thread and itself very rapidly.
• Control means for example of photoelectric cell type
• vibration means also being present to separate the accumulated turns and to facilitate thread unwinding from this element.
• a device of the stated type is described in particular in US5509450 which forms the introduction to the main claim. This device is arranged to feed thread to a textile machine with which it cooperates in strict synchronism and comprises a thread accumulation drum which is fixed but on which a winder mechanism moves, driven by guide means.
• a gripper element positioned radially to the front of the fixed drum is driven by its own guide means and is associated with a shaft coaxial to the geometrical axis of the drum.
• the guide means for the winder mechanism and for the gripper element are positioned consecutively in the device.
• a thread retainer element is mainly described rotating relative to the drum, with which it is in point contact, to control the velocity profile of the thread in the various stages of insertion of the thread into a textile machine (weaving machine) so as to determine this insertion position
• This device has the same aforedescribed limits of similar accumulation devices of open loop operation.
• continuous feed devices or positive feed devices are interposed between the bobbin from which the thread is unwound and the textile machine, and comprise means for example to measure the thread tension and if necessary to intervene on this latter to adjust this tension and maintain it constant.
• these devices therefore present closed loop tension regulation means.
• the devices under examination are influenced by system inertia in response to the request for yarn by the machine, in particular when this operates discontinuously. It can hence happen that because of this inertia, a sudden request for thread gives rise to a tension peak in the thread while cooperating with such feed devices, with the result that a defect in the weaving process or a thread breakage occurs, with obvious drawbacks with regard to the operability of the textile machine.
• An object of the present invention is to provide a device and method for feeding thread or yarn to a textile machine which represent an improvement compared with said known feed devices operating in accordance with the aforesaid types.
• a particular object of the present invention is to provide a device and method of the stated type which combine in themselves both the aforesaid negative and positive types of thread feed, to overcome the drawbacks of the individual similar known devices and methods of the state of the art. Another object is to provide an improved device and method of the stated type which enable correct yarn feed to a discontinuously operating textile machine by which thread breakage is prevented, while at the same time maintaining constant thread tension and rapid response of the feed system following each stoppage and restart of the machine or sudden variation in thread or yarn absorption. Another object is to provide a device which in addition to feeding at constant tension also enables take-up at constant tension and accumulation of the thread taken up so that it can be returned when again withdrawn by the textile machine.
• a further object is to provide a method for feeding thread or yarn to a textile machine which uses the combined and controlled action of two separate actuators to multiply the acceleration and deceleration performance of the aforesaid device during this feed, in order to maintain the yarn tension constant.
• a further object is to provide a device of the stated type which is of small dimensions enabling it to be easily positioned on a textile machine.
• a further object is to provide a device and method for feeding a thread at constant tension which enables it to be freely unwound from an accumulation element in the case of sudden thread withdrawal by the textile machine without appreciable tension variation occurring such as to negatively affect the quality of the product obtained by said machine.
• Figure 1 is a perspective view of a device according to the invention
• Figure 2 is a view of the device of Figure 1 from above
• Figure 3 is a front view of the device of Figure 1
• Figure 4 is a section on the line 4-4 of Figure 3
• Figure 5 is a block scheme of the device of the invention.
• the device of the invention comprises a casing 1 defined by two portions 2, 3 removably fixed together by fixing screws 4. Both portions are hollow, at 5 and 6 respectively.
• the cavity 6 of the portion 3 partially contains an electric motor 9 (for example of brushless type) projecting from said cavity 6 to the front of the casing 1.
• Keyed onto an exit shaft 8 of the electric motor 9 there is a rotary element 7 positioned above that motor part 9 projecting from said cavity 6 and rotating above the motor about a longitudinal axis W of the casing 1.
• the element 7 presents an outer advantageously grooved surface 11 for supporting a thread or yarn 12 unwinding from a spool or bobbin 13 represented schematically in Figure 1.
• the thread 12 reaches the surface 11 via a thread guide 15 associated with the casing 1.
• a turn separator member 7K of adjustable inclination is present to space the turns. This adjustment enables the inclination of the member 7K to the element 7 to be modified by acting on a screw 7F present on the casing 1.
• the element 7 acts as a yarn accumulator.
• a large number of yarn turns can be accumulated on the surface 11, the number of these turns being controlled and programmable, for example in the manner described hereinafter.
• the motor 9 and its emerging shaft 8 are hollow, within them there being positioned another shaft 17 driven by a second electric motor 18 located in the cavity 5 of the portion 2 of the casing 1.
• the drive shaft 17 cooperates with a rotary element 20 positioned to the front of the casing 1 beyond the element or accumulator 7 along the path along which the thread moves towards a textile machine (not shown).
• the rotary member 20 is therefore independent of the accumulator 7 and can move both idly and as a result of the activation of the motor 18.
• the rotary element 20 is preferably in the shape of a solid of rotation, as a spherical or conical cap or paraboloid or ellipsoid tapering in the direction (indicated by the arrow G of Figure 1) of the thread 12 directed to the textile machine; this element 20 presents an outer free surface 21 along which the thread 12 originating from the accumulator 7 slides freely, the thread thus being able to reach a thread guide 23 and from there be directed to the textile machine.
• the fact that the thread can move freely on the outer surface of the element 20 enables the thread to freely unwind from the accumulator 7 in the case of sudden absorption of thread by the textile machine, even though the element 20 is under rotary movement.
• any knotting or thickening of the thread does not cause extra tension in the thread moving towards the textile machine, with consequent possible breakage or possible production of a defective article.
• a large-dimension aperture or eyelet 21 A can be provided in the rotary element 20, opening in proximity to an edge thereof and through which the thread passes. The purpose of this is to enable a predetermined quantity of thread to be fed to the textile machine.
• the thread guide 23 is defined by a ring 25 formed in a portion 26 of a bent angle bracket 27 fixed to the casing 1.
• the portion 26 of the angle bracket 27 supports a tension sensor 30 of known type connected to a yarn feed control unit 200 (see Figures 4 and 5) which also controls the operation of the electric motors 9 and 18 and controls the accumulation of the thread on the element 7.
• This control unit can be advantageously inserted into the device casing 1 , as shown in Figure 4.
• the device of the invention hence operates as a feed device with thread accumulation as a result of using the element 7 and as a positive constant- tension thread feed device by virtue of the tension control provided by the elements 20 and 7 controlled by the unit 200 on the basis of the tension measured by the sensor 30 and the desired value programmed for the precise processing stage which the machine is carrying out (closed loop regulation).
• the element 20 By virtue of its rotation, which is independent but combined with the element 7, the element 20 enables the acceleration and deceleration performance of the device to be multiplied, to hence maintain the tension of the thread 12 fed to the textile machine constant.
• the element 20 alone can if necessary take up this thread when the textile machine is of intermittent operation type (reciprocating motion) and hence subjected to thread withdrawal stages alternating with withdrawal stoppage stages with possible return of part of the fed thread.
• the rotary member 20 enables the thread already fed to the textile machine (during the stoppage stage) to be taken up and be rewound on the element 7.
• the thread would still be taken up by the element 20 because of the friction exerted between it (its profile or the fibres associated with it) and said thread without the need for any fixed retention element (such as the eyelet 21A) for the thread.
• the element 20 is always able to be controlled by the motor 18 or can remain free to rotate idly about said motor in order, for example, not to oppose a sudden request for yarn by the machine.
• the machine on which it is mounted can be made to vary the type of operation on the basis of the thread being processed and the actual process itself, without having to modify or replace the feed device for the thread to be processed.
• the only device function utilized is substantially that of feeder with constant thread accumulation (number of thread turns present thereon constant with time), the thread which unwinds from the spool 13 and directed towards the element 7 being wound on this latter and being constantly fed at constant tension to the textile machine under the said closed loop tension regulation.
• the element 20, controlled by the unit 200 and rotating in the same direction as the accumulation element 7 at a velocity equal to or less than that of this latter, allows the thread to slide along its surface (if said element 20 is without an eyelet, the preferred solution).
• both the rotary elements 7 and 20 intervene actively (independently of each other, but combined) during thread feed.
• the textile machine withdraws the thread 12 from the element 7 which rotates driven by its motor 9 and enables thread feed at constant tension (controlled by the sensor 30) to be maintained
• the motor 18 which operates the element 20 rotates in the same direction as the element 7 and the thread can move freely on the surface 21 of the element 20 towards the textile machine.
• the motor 9 which drives the element or accumulator 7 accelerates whereas the thread continues to unwind freely along the surface 21 of the element 20.
• the thread requirement by the machine can be so high as to exceed the acceleration dynamics of the motor 9, the machine can also withdraw part of the supply accumulated on the element 7. This happens without impediment and without increase in thread tension as the thread is free to slide along the surface 21 of the rotating element 20.
• the motor 9 then continues its operation even when the sudden thread absorption ceases, in order to recover and re-establish the thread supply accumulated on the element 7.
• the increase in acceleration of the motor 9 is determined by the closed control loop defined by the sensor 30, the unit 200 and the motor itself. Moreover, as the motor 9 accelerates the motor 18 also accelerates proportionally in consequence. In the case of a sudden absorption decrease, the motor decelerates or stops while the element 20, already rotating and maintained moving in the previous direction or rotation equal to that of the element 7, rewinds the thread onto the element 7 itself, enabling high deceleration capacity in the thread feed to the machine by taking up any excess thread overfeed.
• the motor 9 when the textile machine stops withdrawing thread from the element 7, the motor 9 is halted wile the motor 18 continues its rotation to rotate the element 20 about the axis W in the same direction as that of the previous rotation of the element 7.
• the element 20 consequently takes up thread from the textile machine by virtue of the friction exerted between it and said element (its profile or the fibres associated with it) without any fixed thread retention element (such as the eyelet 21A).
• the element 20 deposits this thread on the element 7 by rewinding it on this latter and maintaining the thread take-up tension at a constant programmed value, equal to or different from the programmed working tension at which the thread is fed.
• the number of new turns wound on this element is known from the number of revolutions of the element 20 about the axis W, for example known using usual control elements for the rotation of the motor 18 (Hall sensors, encoders, etc.).
• This machine again withdraws thread 12, with the motor 9 still at rest this machine again unwinds thread from the element 7, this thread being able to unwind freely and undisturbed by sliding on the surface 21 of the element 20. This happens in a like manner to the previously described case of sudden increase in thread absorption.
• the rotation of the motor 18 can be reversed to hence rotate the element 20 in the opposite direction to that prior to take-up, so allowing the thread previously withdrawn and accumulated (in known quantity as the number of wound turns is known) on the element 7 to be immediately returned at constant tension to said machine.
• the motor 9 is restarted to again feed the thread accumulated on the element 7 to the textile machine at constant tension, while at the same time again removing further thread from the spool 13 to maintain the number of turns accumulated on its surface 11 constant. This method of operation prevents jerking of the thread which could create processing defects or break it on resuming operation of the textile machine.
• the invention can prevent thread accumulation on the machine when it stops withdrawing thread from the spool, so dispensing with any mechanical, electromechanical or pneumatic thread take-up members currently used on machines, such as seamless and straight bar hosiery machines operating discontinuously.
• the element 20 takes up the thread by accumulating it on the element 7.
• a surplus of thread is formed on said element 7, so facilitating restart of the textile machine on restoring production of the article by maintaining the tension constant both during feed and during take-up of the yarn, hence without subjecting the thread to excessive tension which could cause a thread processing defect or breakage.
• the invention also prevents thread accumulating at the textile machine following a sudden deceleration thereof, even if the element 20 is provided with an eyelet 21A.
• deceleration is sensed (in known manner) by the control unit 200 via the tension measurement effected by the sensor 30 of the feed device connected or applied to the machine, this unit braking the operation of the motor 9 and rotating the element 20 in the take-up direction by operating the motor 18.
• the motor 18 is rotated in the opposite direction, so unloading the thread accumulated by the element 7 by passing through the eyelet 21A of the element 20, and enabling the textile machine to take from this later the thread accumulated thereon.
• the element 20 is provided with an eyelet 21 A, its intervention is very rapid as it acts on a thread presenting practically zero resistance (to traction by said element) both when the thread is taken up from the textile machine and returned freely to the feeder, and when it unwinds it from the element 7 (where it is accumulated by having been withdrawn from the machine or from the spool 13). Because of this absence of effort in withdrawing the thread from the element 7 by the machine, said withdrawal can also be achieved by simple "friction" between the thread and the surface 21 of the element 20 when provided with an eyelet 21A. The absence of effort hence enables the device performance to be not merely a simple addition to combine the effects of the two motors, but to be a multiplication of the performances as the motor 18 operates without effort.
• the device enables a constant number of turns to be maintained on the element 7. This is achieved totally automatically in the following manner.
• the number of turns on the element 7 is maintained constant by continuously recognizing (by the control unit 200 of the device) the number of rotations made by said element 7 about the axis W (by recognizing the number of rotations of the motor 9, for example by Hall sensors) and by the element 20 (by recognizing the number of rotations of its motor 18, for example by Hall sensors).
• the number of rotations of the motor 9 always increases the turns accumulated, whereas the number of rotations of the motor 18 can either increase or decrease this count.
• the control unit 200 of the device can always know (directly from the rotations of the motor if the motor 18 and the element 20 are at rest, or by the algebraic sum if the motor 9 and the motor 18 operate in opposite directions, or if only the motor 18 is operated to form turns on the element 7 with the thread taken up from the textile machine at rest) how many turns have been added from a predetermined number of turns controlled at the start of operation of the device under examination, in order to maintain this accumulation constant. In this manner a further closed control loop is achieved for the number of turns accumulated on the element 7, in order to maintain them constant at a programmable value.
• both the motors 9 and 18 are activated to rotate in the same direction so that the thread withdrawn from the spool 13 is wound onto the element 7.
• this thread is fed to the element 20 which contributes to distributing it on the surface 11 of the element 7 without withdrawing it from the textile machine.
• This unique action continues until the required number of turns (programmed or controlled) are formed on the element 7, the number being determined as aforedescribed.
• the device is hence ready to be used to feed the thread to the textile machine under constant feed (and possibly take-up) tension.
• Control of the number of turns hence utilizes intrinsic means of the device motors, without adding optical, mechanical or other sensors to measure the "filling" of the element or accumulator 7 where the element 20 is provided with an eyelet 21 A. Otherwise sensors are necessary for counting the unwinding thread (optical or equivalent), these being positioned between the element 20 and the thread guide 23 or the sensor 30, as stated below, to count the thread quantity unwound by the element 7 and passed freely by sliding on the surface 21 of the element 20.
• the device also enables the thread tension to be controlled.
• the simplest method to achieve this is to use the tension sensor 30 connected to the device control unit 200 which, on the basis of the measured tension, acts via independent closed control loops both on the motor 9 and on the motor 18 to regulate the rotation of the electric motors themselves.
• These control loops can be known control algorithms of PID (proportional-integral-derivative) type.
• the motor 9 can be accelerated while at the same time the motor 18 rotates the element 20 in the opposite direction to the element 7 (and hence in the thread unwinding direction), to make the movement of the thread from the element 7 to the thread guide 23 as precise and stable as possible by unwinding it from this element, so decreasing the tension to maintain it constant.
• the tension tends to decrease, the element 7 is decelerated while the element 20, rotating in the same direction, takes up part of the thread, this resulting in an increase in the thread tension in order to oppose the variation and maintain the tension constant.
• the motor 9 can be accelerated, the same occurring simultaneously for the motor 18 which drives the element 20 rotating in the same rotation direction as the element 7. If the acceleration increase of the motor 9 is not sufficient to maintain the tension within the control limits, these limits are maintained by increasing thread withdrawal from the supply present on the element 7, this withdrawal being achieved freely by the machine and without impediment by the element 20 on whose surface 21 the thread slides freely.
• the tension of the thread 12 can be identified and regulated.
• the element 20 is provided with an eyelet 21A, as the force exerted on the thread by this element is proportional to the thread tension and as this force is proportional to the torque applied by the motor 18 and hence to the current absorbed thereby, controlling the current absorption by the motor 18 enables the thread tension to be controlled.
• controlling the current absorption by the motor 18 enables the thread tension to be controlled.
• the absorbed current can be controlled by known means, for example by known shunt resistors for measuring the currents absorbed by the motor 18.
• known means for example by known shunt resistors for measuring the currents absorbed by the motor 18.
• a specific embodiment of the invention has been described in which three control loops implemented by the unit 200 are used: the first loop between the sensor 30 and the motor 9; the second loop between said sensor 30 and the motor 18; and finally the third loop between the number of turns (or thread quantity) accumulated on the element 7 by the motor 9 and the number of turns added to or subtracted from said element 7 (or thread quantity wound or unwound) by the motor 18 (see Figure 5).
• the element 20 can be provided with an edge having a plurality of flexible elements (for example an annular brush mounted on the element 20) with which the thread 12 cooperates, or with a sinusoidal pattern (with which the thread is always maintained in contact) to enable the thread to be released by the element 20 when its tension exceeds a predetermined value close to that which could lead to thread breakage or a processing defect.
• a plurality of flexible elements for example an annular brush mounted on the element 20
• a sinusoidal pattern with which the thread is always maintained in contact
• the fall in the thread tension (obtained by supplying more thread to the machine by increasing the rotation of the element 7 or unwinding more thread from it) again results in thread stabilization (by friction) on the element 20, enabling the required number of turns to be again restored on the accumulator 7 (by suitably rotating the element 20, as described, for the purpose of taking thread and rewinding it on the accumulator element 7).
• the unwound turns can, as already described, be counted by a further sensor, for example a photoelectric cell or equivalent, positioned between the element 20 and the thread guide 23 or the tension sensor 30.
• the tension sensor 30 can also be incorporated into the thread guide 23 and the actuator motors 9 and 18 can be identical, of the same type (for example brushless as described) or can be of different type to achieve different performance in measuring the thread quantity unwound.
• the described invention hence provides three main aspects which can be developed individually or in combination, i.e.:

Landscapes

• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Tension Adjustment In Filamentary Materials (AREA)
• Spinning Or Twisting Of Yarns (AREA)
• Looms (AREA)
• Preliminary Treatment Of Fibers (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

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• 2006
  • 2006-02-21 IT IT000311A patent/ITMI20060311A1/it unknown
• 2007
  • 2007-02-20 AT AT07705652T patent/ATE503049T1/de not_active IP Right Cessation
  • 2007-02-20 DE DE602007013364T patent/DE602007013364D1/de active Active
  • 2007-02-20 ES ES07705652T patent/ES2362239T3/es active Active
  • 2007-02-20 WO PCT/IB2007/000460 patent/WO2007096765A1/fr active Application Filing
  • 2007-02-20 EP EP07705652A patent/EP1991726B1/fr active Active

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